Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33403 Publications

Efficient solution of 3D electromagnetic eddy-current problems within the finite volume framework of OpenFOAM

Beckstein, P.; Galindo, V.ORC; Vukcevic, V.
Eddy-current problems occur in a wide range of industrial and metallurgical applications where conducting material is processed inductively. Motivated by realising coupled multi-physics simulations, we present a new method for the solution of such problems in the finite volume framework of foam-extend, an extended version of the very popular OpenFOAM software. The numerical procedure involves a semi-coupled multi-mesh approach to solve Maxwell’s equations for non-magnetic materials by means of the Coulomb gauged magnetic vector potential A and the electric scalar potential φ. The concept is further extended on the basis of the mpressed and reduced magnetic vector potential and its usage in accordance with Biot-Savart’s law to achieve a very efficient overall modeling even for complex three-dimensional geometries. Moreover, we present a special discretisation scheme to account for possible discontinuities in the electrical conductivity. To complement our numerical method, an extensive validation is completing the paper, which provides insight into the behaviour and the potential of our approach.
Keywords: eddy-currents, induction processing, potential formulation, Maxwell’s equations, finite volume method, block-coupling, OpenFOAM, foam-extend

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Permalink: https://www.hzdr.de/publications/Publ-25312
Publ.-Id: 25312


Microfluidic experiments on enrichment of paramagnetic metal ions in aqueous solutions by applying inhomogeneous magnetic fields

Mutschke, G.; Yang, X.; Wojnicki, M.; Femerling, M.; Zabinski, P.
Magnetic separation is a well-established technology for separating magnetic particles from solutions. The magnetic gradient force scales with the magnetization density and the volume of the particle. The magnetic moment of paramagnetic metal ions in solution could be utilized as well for separating ions from solutions in strong magnetic fields of large spatial gradients. This idea dates back to early work of Noddack et al [1], where firstly separation effects were found for rare earth metal ions in aqueous solutions. However, the effect is limited, as the ratio of magnetic to thermal energy is small. Recently, distinct separation effects of paramagnetic ions in inhomogeneous magnetic fields were reported in gel [2] and in various aqueous solutions [3,4,5].
Triggered by these findings, microfluidic experiments were performed. The setup consists of a small reactor printed by 3D technology where a spiral pipe flow is exposed to an inhomogeneous magnetic field created by an iron wire, the spiral of which is close to the pipe, and which is magnetized in an external magnetic field, thus creating strong gradients near the pipe. Flow experiments were performed for different salt solutions. At the outflow, the flow volume was separated into a near-magnet and a far-magnet half, the concentrations of which were analyzed by UV/VIS spectrophotometry and by ICP-MS. The absorption spectrum of 0.1 M HoCl3 solution is shown in Fig.1. According to Beer-Lambert's law, the absorbance in selected peaks can be used as a measure of the ion concentration. The concentration difference from the two outlets of the reactor was measured, and the effects of the magnetic field gradient and the flow rate were studied.
Acknowledgement:
This work is supported by the German Federal Ministry of Education and Research, Grant No. 01DS16007.
References
[1] Noddack, W., Noddack, I. and Wicht, E., Berichte der Bunsengesellschaft für physikalische Chemie 62 (1958): 77-85.
[2] Franczak, A., Binnemans, K., & Fransaer, J., Phys. Chem. Chem. Phys. 18 (2016): 27342-27350.
[3] Kolczyk, K., Kutyla, D., Wojnicki, M., Cristofolini, A., Kowalik, R., & Zabinski, P., Magnetohydrodynamics 52 (2016): 541-547.
[4] Yang, X., Tschulik, K., Uhlemann, M., Odenbach, S., & Eckert, K., J. Phys. Chem. Lett. 3 (2012): 3559-3564.
[5] Bing, J., Ping, W., Han, R., Shiping, Z., Abdul, R., & Li, W., Chin. Phys. B 25 (2016) 074704.
  • Lecture (Conference)
    68th Annual Meeting of the International Society of Electrochemistry, 27.08.-01.09.2017, Providence, RI, USA

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Permalink: https://www.hzdr.de/publications/Publ-25311
Publ.-Id: 25311


Entropy Evolution in the Magnetic Phases of Partially Frustrated CePdAl

Lucas, S.; Grube, K.; Huang, C.-L.; Sakai, A.; Wunderlich, S.; Green, E. L.; Wosnitza, J.; Fritsch, V.; Gegenwart, P.; Stockert, O.; von Löhneysen, H.
In the heavy-fermion metal CePdAl, long-range antiferromagnetic order coexists with geometric frustration of one-third of the Ce moments. At low temperatures, the Kondo effect tends to screen the frustrated moments. We use magnetic fields B to suppress the Kondo screening and study the magnetic phase diagram and the evolution of the entropy with B employing thermodynamic probes. We estimate the frustration by introducing a definition of the frustration parameter based on the enhanced entropy, a fundamental feature of frustrated systems. In the field range where the Kondo screening is suppressed, the liberated moments tend to maximize the magnetic entropy and strongly enhance the frustration. Based on our experiments, this field range may be a promising candidate to search for a quantum spin liquid.

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Permalink: https://www.hzdr.de/publications/Publ-25310
Publ.-Id: 25310


Analytical balance-based Faraday magnetometer

Riminucci, A.; Uhlarz, M.; de Santis, R.; Herrmannsdörfer, T.
We introduce a Faraday magnetometer based on an analytical balance in which we were able to apply magnetic fields up to 0.14 T. We calibrated it with a 1mm Ni sphere previously characterized in a superconducting quantum interference device (SQUID) magnetometer. The proposed magnetometer reached a theoretical sensitivity of 3x 10-8 Am2. We demonstrated its operation on magnetic composite scaffolds made of poly(e-caprolactone)/iron-doped hydroxyapatite. To confirm the validity of the method, we measured the same scaffold properties in a SQUID magnetometer. The agreement between the two measurements was within 5% at 0.127 T and 12% at 24mT. With the addition, for a small cost, of a permanent magnet and computer controlled linear translators, we were thus able to assemble a Faraday magnetometer based on an analytical balance, which is a virtually ubiquitous instrument. This will make simple but effective magnetometry easily accessible to most laboratories, in particular, to life sciences ones, which are increasingly interested in magnetic materials.

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Permalink: https://www.hzdr.de/publications/Publ-25309
Publ.-Id: 25309


Predicting SAXS images beyond single scattering

Garten, M.ORC; Grund, A.; Huebl, A.; Burau, H.; Widera, R.; Kluge, T.; Fortmann-Grote, C.; Bussmann, M.
We present a scalable GPU-based software framework for simulating photon scattering processes of X-ray beams in matter using Monte-Carlo methods. These simulations enable us to predict SAXS signals for experiments at upcoming superlative research facilities like the European XFEL. Often the expected outcome of SAXS experiments is produced by a Fourier Transform of a static 2D electron density distribution. Our new framework provides the opportunity to simulate the probing of femtosecond timescale 3D3V electron dynamics with single and multiple scattering and is extendable by more complex physics processes like laser absorption, atomic excitation and de-excitation to further enhance its predictive capability. As a foundation we use libPMacc, a powerful particle-mesh accelerator library that is also used by PIConGPU, the reportedly fastest fully-relativistic 3D3V particle-in-cell code in the world.
Keywords: XFEL, scattering, SAXS, pump-probe, GPU, HPC, simulation
  • Lecture (Conference)
    DPG Frühjahrstagung Dresden 2017, 23.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25308
Publ.-Id: 25308


Enhancing atomic physics modeling in PIConGPU

Garten, M.ORC; Huebl, A.; Burau, H.; Grund, A.; Widera, R.; Zacharias, M.; Kluge, T.; Bussmann, M.
In laser-generated plasmas the free electron density is a crucial parameter for plasma dynamics. Therefore, to model its spatial and temporal evolution the adequate treatment of ionization is vital. This poster presents the work in progress on numerical field ionization methods implemented in the world's fastest 3D3V electromagnetic particle-in-cell code PIConGPU. Thus, computing a value for the systematic error via repeating simulations with varying ionization schemes is in reach. With high performance computing we can give a range of validity for predictions of pump-probe experiments with high power lasers and X-ray free electron lasers.
Keywords: laser-particle acceleration, field ionization, particle-in-cell, HPC
  • Poster
    DPG Frühjahrstagung 2017 Dresden, 22.03.2017, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-25307
Publ.-Id: 25307


A new wettability Parameter based on iGC to characterize the Flotation process for the Separation of fine Mineral particles

Rudolph, M.ORC; Babel, B.; Hartmann, R.; Leistner, T.; Graebe, K.
Flotation is a heterocoagulation based separation process for fine particles in aqueous dispersions (size range approx. 5 µm < x <200 µm). It is used in large extent and with billions of tons of particles processed per year in the mining industry to separate valuable mineral particles from worthless ones. The main principle of separation is the particles’ differences in wettability. This wettability is influenced by controlled selective adsorption of amphiphilic molecules rendering most typically the valuable containing minerals hydrophobic. Usually the particle property “wettability” is being quantified with a water contact angle. However, this value is not only difficult to assess for particles but furthermore through Young’s equation a function of the surface free energy, which is a complex parameter as a result of various interatomic/intermolecular interactions. Using iGC we are able to characterize these complex wettability properties of particles assessing the heterogeneity of disperse and acid base specific surface free energies. These complex values are used in accordance to an approach by van Oss to formulate a new wettability parameter for flotation which is the specific free energy of interaction between a particle and a gas bubble immersed in water. We are presenting the general approach and results from various mineral collector systems and give insights to the boundary conditions and the general calculation scheme.
Keywords: inverse gas chromatography, minerals, flotation, surface free energy, collectors, surfactants, separation
  • Invited lecture (Conferences)
    IGC Symposium 2017, 20.06.2017, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25306
Publ.-Id: 25306


Angular Distribution Measurement of Gamma Rays from Inelastic Neutron Scattering on Fe-56 at the nELBE Time-of-Flight Facility

Dietz, M.; Bemmerer, D.; Beyer, R.; Gohl, S.; Junghans, A. R.; Kögler, T.; Massarczyk, R.; Müller, S. E.; Schwengner, R.; Szücs, T.; Takacs, M. P.; Wagner, A.; Wagner, L.
Inelastic neutron scattering from 56 Fe was studied at the nELBE time-of-flight facility. The incoming neutron energy ranges from 100keV to 10MeV in the fast neutron spectrum, where high precision nuclear data are needed. A detector setup has been installed to investigate the γ-ray angular distributions. It contains five HPGe and five LaBr 3 detectors positioned at 30, 55, 90, 125 and 150 degrees relative to the beam axis. The intrinsic and the neutron induced background from the setup was subtracted by cyclical measurements with and without the natural Fe-target. Corrections for extended source efficiency and gamma-self-absorption, inside the target, were done using GEANT4 simulations.
The angular distributions measured with the HPGe detectors are compared with earlier data. High neutron energy resolution up to a few keV was obtained with the LaBr 3 detectors due to their much better time resolution.
Keywords: gamma-ray angular distribution, inelastic neutron scattering 56Fe(n,n'g)
  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology (ND2016), 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714611040

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Permalink: https://www.hzdr.de/publications/Publ-25305
Publ.-Id: 25305


Measurements with neutrons and photons at nELBE

Beyer, R.; Dietz, M.; Frotscher, A.; Görres, J.; Junghans, A. R.; Kögler, T.; Nolte, R.; Oberlack, U.; Pirovano, E.; Plompen, A.; Reifarth, R.; Schwengner, R.; Urlaß, S.; Wagner, A.
The neutron time-of-flight facility nELBE at Helmholtz-Zentrum Dresden-Rossendorf features the first photo-neutron source at a superconducting electron accelerator, which provides a very precise time structure, high repetition rate and favorable background conditions due to the low instantaneous flux and the absence of any moderating materials. The neutron energy spectrum ranges from about 100 keV up to 10 MeV. The resulting very flexible beam properties at nELBE enable a broad range of nuclear physics experiments. Examples for the versatility of nELBE will be presented: Total neutron cross section measurements to look for unknown nuclear levels relevant for the astrophysical s-process, determination of the photon angular distribution after inelastic neutron scattering, determination of the detector response of a Dark Matter detector based on liquid Xe, or determination of the neutron induced fission cross section of 242Pu.
Keywords: nELBE, neutron time-of-flight, neutron inelastic scattering, neutron transmission, neutron induced fission, dark matter, liquid Xe
  • Lecture (Conference)
    81. Jahrestagung der DPG und DPG-Frühjahrstagung, 27.-31.03.2017, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25304
Publ.-Id: 25304


Methods for investigating Australia's former nuclear test sites

Johansen, M. P.; Caffrey, E. A.; Child, D. P.; Collins, R. N.; Harrison, J. J.; Hotchkis, M. A. C.; Howard, D. L.; Howell, N.; Payne, T. E.; Mokhber Shahin, L.; Ikeda-Ohno, A.ORC; Thiruvoth, S.
The radiological residues at the former weapons testing sites in Australia at Maralinga, Emu and the Montebello Islands are of ongoing interest in terms of environmental fate, transport, and uptake into the biosphere1. The physical and chemical characteristics of these residues affect their mobility and availability for uptake into living organisms2. At the Taranaki site, Maralinga, substantial body burdens of Pu were observed in mammals, likely due to the presence of respirable particles. Actinides often occur in particulate forms that, for characterisation, require advanced techniques including Accelerator Mass Spectrometry (AMS)3, Scanning electron microscopy and synchrotron X-ray fluorescence microscopy (XFM). Many nuclear test site particles have core-shell, or inhomogenous structures where the surface is dominated by lighter elements sourced from local soils and the Pu concentrated in the interior4. Modelling results suggest that for respirable-sized Pu-containing particles (that can be inhaled and lodged in the lung), most of the alpha emissions escape the particle and are deposited in the surrounding tissue.4 For larger particles, (e.g. >7 µm), which typically do not lodge in the lung but could be ingested, most of the alpha emissions do not escape the particle, but are instead captured within the particle itself (self-shielding) therefore decreasing the effective dose. We are currently using advanced techniques to compare the radionuclide forms from the inland sites (Maralinga and Emu) with the marine site (Montebello Islands).
Keywords: Actinides, radionuclides, environmental radioactivity, radioecology, environmental science, nuclear tests
  • Lecture (Conference)
    Annual Congress of the Royal Australian Chemical Institute (RACI) 2017, 23.-28.07.2017, Melbourne, Australia

Permalink: https://www.hzdr.de/publications/Publ-25303
Publ.-Id: 25303


Radiation hard ceramic RPC development

Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kiselev, S.; Kotte, R.; Laso Garcia, A.; Malkevich, D.; Naumann, L.; Nedosekin, A.; Plotnikov, V.; Stach, D.; Sultanov, R.; Voloshin, K.
We report recent advances in R&D; on the Beam Fragmentation and T0 Counter (BFTC) for the CBM experiment, based on RPCs with floating electrodes made of resistive ceramic material. An optimal value of the ceramics bulk resistivity has been determined to be about 5·109 Ω·cm. RPCs with such electrodes show even characteristics and stable operation under particle fluxes of up to 150 kHz/cm2, with the detection efficiency above 90%.

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Permalink: https://www.hzdr.de/publications/Publ-25302
Publ.-Id: 25302


In situ RBS, Raman spectroscopy, and ellipsometry study of nickel-catalyzed graphitization of thin amorphous carbon films

Janke, D.; Wenisch, R.; Lungwitz, F.; Munnik, F.; Hulman, M.; Gemming, S.; Rafaja, D.; Krause, M.
Metal-induced crystallization (MIC) with and without layer exchange (LE) is a method to decrease the crystallization temperature of amorphous group 14 elements by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC and to improve existing models of this type of phase transformation. In this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
LE was observed independently of the initial stacking sequence, while transformation rate and temperature differ significantly. The positions of the G, D and 2D Raman lines as well as the I(D)/I(G) ratio changed during the LE process. These were assigned in agreement with the Three-Stage-Model [1], confirming the transformation of a-C to nc-graphite. In situ RBS measurements demonstrated an opposite shift of the C- and Ni- related backscattering energies, proving that LE and graphitization occur simultaneously.
[1] Ferrari et al., Phys. Rev. B 61 (2000) 14095
Keywords: Metal-induced crystallization in situ RBS in situ Raman spectroscopy
  • Poster
    International Winterschool on Electronic Properties of Novel Materials, 04.-11.03.2017, Kirchberg in Tirol, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25301
Publ.-Id: 25301


High-resolution study of the 113 Cd(n,γ γ) spectrum by statistical decay model with discrete levels and transitions

Belgya, T.; Szentmiklósi, L.; Massarczyk, R.; Schwengner, R.; Junghans, A. R.; Grosse, E.
The gamma-ray spectrum and the decay scheme of 114 Cd obtained from a radiative neutron capture experiment on 113 Cd samples are modelled in the framework of extreme statistical model. The unfolding of the experimental spectrum with proper normalization yields a total capture cross section of 21640 b and an average gamma-ray multiplicity of 4.1. Using the extreme statistical model the development of the low energy decay scheme of 114 Cd is in progress. In the model the constant-temperature level density is used, where the temperature parameter was very sensitive to the shape of the modelled gamma-ray spectrum. Using this sensitivity T=0.64 MeV was obtained with the constraint of good description of low energy level density and the level density at the binding energy. This is in full agreement with our earlier publication. For the description of the continuum shape of the unfolded spectrum the inclusion of low energy enhancement for the photon strength function was an important new addition.
Keywords: neutron radiative capture, 113Cd(n,gamma), capture gamma-ray spectrum, photon strength function
  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714605009

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Permalink: https://www.hzdr.de/publications/Publ-25300
Publ.-Id: 25300


Neutron Transmission Measurement for Natural W at nELBE

Song, T.-Y.; Kim, J. W.; Kim, H. I.; Yang, S.-C.; Lee, C. W.; Lee, Y.-O.; Junghans, A. R.; Beyer, R.; Kögler, T.; Schwengner, R.; Hannaske, R.; Wagner, L.; Leinhardt, T. P.; Takacs, M. P.; Massarczyk, R.; Müller, S.; Ferrari, A.; Schmidt, K.; Röder, M.; Bemmerer, D.; Szücs, T.; Wagner, A.
Korea has developed a Helium Cooled Ceramic Reflector Test Blanket Module (Ko HCCR TBM) related to the ITER project. Tungsten is considered as a prime candidate for the plasma facing materials in fusion reactors, and for the structure material of Ko HCCR TBM. KAERI (Korea Atomic Energy Research Institute) has been evaluating neutron cross sections of tungsten isotopes for neutron energy of up to 150 MeV based on nuclear reaction codes and available measurement data. New experimental data were measured at nELBE of HZDR (Helmholtz-Zentrum Dresden-Rossendorf) for a comparison with the evaluated and existing measurement data. The neutron source nELBE adopts a 40 MeV superconducting electron linac and a liquid Pb target for time-of-flight measurements. The nELBE neutron source uses no moderator and provides fast neutrons. An electron bunch length of 5 ps and a compact target provide a good neutron energy resolution with a relatively short flight length compared to other time-of-flight neutron sources. Transmission data of a natural tungsten sample were measured with a flight path length of 852.1 cm and a repetition rate of 101.56 kHz. The neutron total cross section of natural tungsten was obtained for an energy range of 100 keV to 10 MeV.
Keywords: neutron total cross section, W, fast neutron transmission measurement, nELBE time-of-flight facility
  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714611044

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Permalink: https://www.hzdr.de/publications/Publ-25299
Publ.-Id: 25299


FDG uptake in normal tissues assessed by PET during treatment has prognostic value for treatment results in head and neck squamous cell carcinomas undergoing radiochemotherapy

Zschaeck, S.; Löck, S.; Leger, S.; Haase, R.; Bandurska-Luque, A.; Appold, S.; Kotzerke, J.; Zips, D.; Richter, C.; Gudziol, V.; Schreiber, A.; Zöphel, K.; Baumann, M.; Krause, M.
Background and purpose: Pronounced early side effects have been suggested to be a positive prognostic factor in patients undergoing chemo-radio-therapy (CRT) for head and neck squamous cell carcinomas (HNSCC). We assessed the utility of positron emission tomography (PET) during treatment to analyze the correlation of 18F-fluorodeoxyglucose (FDG) uptake in off target structures within the irradiated volume with outcome.
Material and methods: Two independent cohorts of patients with locally advanced HNSCC, both treated within prospective clinical imaging trials with curatively intended CRT were retrospectively analyzed.
The exploratory cohort included 50, the independent validation cohort 26 patients. Uptake of FDG in mucosa and submucosal soft tissues (MST) as well as in other structures was assessed at week 4 during treatment. Considered endpoints were local tumor control (LC) and overall survival (OS). The prognostic value of FDG uptake on the endpoints was measured by the concordance index (ci) using univariate and multivariate Cox regression analyses based on the continuous variables of the exploratory cohort.
Results: In the exploratory cohort FDG uptake in MST was prognostic for LC (hazard ratio HR = 0.23, p = 0.025) and OS (HR = 0.30, p = 0.003) in univariate analyses. These findings remained significant upon multivariate testing (LC HR = 0.14, p = 0.011; OS HR = 0.20, p = 0.001) and were confirmed in the validation cohort for LC (HR = 0.15, p = 0.034) and OS (HR = 0.17, p = 0.003). Also the SUVmean threshold of MST that was generated within the exploratory cohort (2.375) yielded significant differences in OS (p = 0.006) and a statistical trend for LC (p = 0.078) when applied to the validation cohort.
Conclusions: FDG uptake in normal tissues within the irradiated volume measured by PET during treatment has significant prognostic value in HNSCC. This effect may potentially be of use for personalized treatment adaptation.

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Permalink: https://www.hzdr.de/publications/Publ-25298
Publ.-Id: 25298


Breaking of axial symmetry in excited nuclei as identified in experimental data

Junghans, A.; Grosse, E.; Massarczyk, R.
A phenomenological prediction for radiative neutron capture is presented and compared to recent compilations of Maxwellian averaged cross sections and average radiative widths. Photon strength functions and nuclear level densities near the neutron separation energy are extracted from data without the assumption of axial symmetry – at variance to common usage. A satisfactory description is reached with a small number of global parameters when theoretical predictions on triaxiality (from constrained HFB calculations with the Gogny D1S interaction) are inserted into conventional calculations of radiative neutron capture. The photon strength is parametrized using the sum of three Lorentzians (TLO) in accordance to the dipole sum rule. The positions and widths are accounted for by the droplet model with surface dissipation without locally adjusted parameters. Level densities are influenced strongly by the significant collective enhancement based on the breaking of axial symmetry. With the less stringent requirement of invariance against rotation by 180° a global set of parameters which allows to describe the photon strength function and the level densities in the nuclear mass range from mass number 50 < A < 250 is found.
Keywords: nuclear structure, axial symmetry breaking, photon strength function, GDR, neutron capture
  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology 2016, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714605007

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Permalink: https://www.hzdr.de/publications/Publ-25297
Publ.-Id: 25297


THEREDA – Thermodynamic Reference Database

Moog, H. C.; Altmaier, M.; Bok, F.; Brendler, V.; Gaona, X.; Marquardt, C.; Montoya, V.; Richter, A.; Scharge, T.; Thoenen, T.; Voigt, W.; Yalçintaş, E.
Thermodynamic data are necessary for the estimation of the maximum likely solubility of hazardous contaminants such as radio nuclides in aqueous solutions. Such assessments are done within the frame of long term safety analysis for repositories of radioactive waste. For this purpose various databases exist in the world. But they are poorly comparable and furthermore reflect the needs of the respective national disposal programme.
Not only activities related to the identification of a suitable site for disposal, for the construction of a repository, its operation and finally its closure, but also the establishment of reliable thermodynamic data is a time-consuming, expensive and long-term effort which spans generations of scientists. It is necessary to store the results of many research projects, national and international, in a way that ensures internal consistency, allows for easy access, and allows for an easy application in thermodynamic equilibrium calculations with some of the most popular codes. Therefore, the establishment of such a database is a national task and an important part for a long-term knowledge management.
To meet this demand a project was launched in 2006 to create a common, mutually agreed and web-based Thermodynamic Reference Database – THEREDA (Moog et al. 2015). The database is run by the following institutions:
• GRS: Gesellschaft für Anlagen- und Reaktorsicherheit mbH, Abteilung Prozessanalyse, Theodor-Heuss-Straße 4, D-38122 Braunschweig, Germany
• KIT-INE: Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, P.O. Box 3640, D-76021 Karlsruhe, Germany
• HZDR-IRC: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, Bautzner Landstraße 400, D-01328 Dresden, Germany
• TU-BAF: Technische Universität Bergakademie Freiberg, Fakultät für Chemie und Physik, Institut für Anorganische Chemie, Leipziger Straße 29, 09596 Freiberg, Germany
• PSI-LES: Paul Scherrer Institut, Laboratory for Waste Management, Villigen, Switzerland
In the initial phase of the project the participating institutions agreed upon quality objectives:
• Transparency: all data should be traceable to a publicly available reference.
• Consistency: all data should be stored in a way which ensures internal consistency between data directly entered and other data, which are internally calculated from the former ones.
• Comprehensiveness: the database should cover the whole range of possible applications with regard to safety assessments for nuclear disposal sites. Where data are missing, appropriate estimates should be added.
• Uncertainties: wherever possible, uncertainties of data were to be captured.
• Data assessment: the referenced source, the data quality and the way in which every particular datum was derived should be captured in terms of pre-defined identifiers. Thus, data of poor quality and estimates, which were added to meet the objective "comprehensiveness", are marked accordingly for the user.
Criteria for the quality of thermodynamic data were largely adopted from a database established by OECD-NEA. However, provisions had to be met for additional parameters needed to cover the specific conditions in northern German deep geologic strata as they are likely to occur in clay or rock salt formations.
The development of recommended thermodynamic data follows an internal scheme for quality assurance. Additional documentation is available about the selection of data, but also about technical specifications of the databank to enable future users the maximum possible benefit of today’s work.
In technical terms stored data are managed in ways to keep them accessible as long as possible. This includes the use of open source rather than proprietary software. The data structure was designed to be flexible to cover potential future needs in safety assessment. Databases are issued in plain text files which can be processed as long as computers exist. Internal project communication as well as public access to the database is realized by a graphical user interface accessible over the world wide web: www.thereda.de.

Acknowledgements
This project was and is jointly funded by the Federal Ministry of Education and Reearch (BMBF) (GRS: 02C1426/02C1628, FZD: 02C1436, TU-BAF: 02C1446), the Federal Ministry of Economics and Technology (BMWi) (FZK/KIT: 02E10126/02E1067, FZD: 02E10136, GRS: 02E10146, TU-BAF: 02E10709), and the Federal Office for Radiation Protection (BfS ) with funds from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).

REFERENCES
H. C. Moog et al., Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55), 72-84 (2015). http://dx.doi.org/10.1016/j.apgeochem.2014.12.016
Keywords: THEREDA, Thermodynamische Referenzdatenbank, Thermodynamic Reference Database, Pitzer
  • Lecture (Conference)
    ENTRIA Conference, 26.-28.09.2017, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25296
Publ.-Id: 25296


Inductive measurement of the free surface of liquid metals

Zürner, T.; Ratajczak, M.; Wondrak, T.; Eckert, S.
A novel measurement system to determine the surface position and topology of liquid metals is presented. It is based on the induction of eddy currents by a time-harmonic magnetic field and the subsequent measurement of the resulting secondary magnetic field using gradiometric induction coils. The system is validated experimentally for static and dynamic surfaces of the low-melting liquid metal alloy gallium-indium-tin in a narrow vessel. It is shown that a precision below 1 mm and a time resolution of at least 20 Hz can be achieved.
Keywords: Inductive measurement, liquid metal, surface topology

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Permalink: https://www.hzdr.de/publications/Publ-25295
Publ.-Id: 25295


In-situ XAFS characterization of PtPd nanoparticles synthesized by galvanic replacement

Tymen, S.; Scheinost, A. C.; Friebe, C.; Schubert, U. S.
Platinum-palladium nanoparticles are synthesized and characterized with regard to their application in fuel cells due to their high (electro)catalytic activity. Different preparation times are applied leading to different structures, from Pd cubic to core-shell PtPd concave, and different chemical compositions. The resulting particles are studied via TEM and in-situ XAFS measurements. The latter allows the investigation of the oxygen reduction reaction following the variations with varying applied potentials by analysis using ITFA and the creation of a two-component system that consists of metallic Pt-Pd and the related oxide. With the used model, the different concentrations of the oxide are linked to the consecutive chemical steps of the oxygen reduction reaction.
Finally, the catalytic activity of the particles is determined via linear scanning voltammetry and reveals a dependence on the shape and the composition of the particles.
Keywords: Pt Pd nanoparticles catalysis EXAFS TEM fuel cell
  • Open Access Logo Advances in Nanoparticles 6(2017), 75-91
    DOI: 10.4236/anp.2017.62007
  • Invited lecture (Conferences)
    Ninth Joint BER II and BESSY II User Meeting, 13.-15.12.2017, Berlin, Germany

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Simple Formulas for Porosity and Specific Surface of the Cherry-Pit Model

Stoyan, D.; Hermann, H.; Elsner, A.
The cherry-pit or penetrable concentric-shell model is an important, very successful stochastic model for random porous media with open pores. It is based on a random system of hard spheres (the ‘pits’), which are dilated in order to get open pores. The exact determination of porosity _phi_ and specific surface s is a problem obviously too difficult for the contemporary mathematics. Already in the 1980ies approximations were found which are presented in the book by Torquato (2002). Since 2009 these formulas have been refined by the authors, by combination of simulation and ideas of stochastic geometry. This includes the study of the poly-disperse case of pits with random radii, which was mastered by means of correction factors. In the present paper the true nature of these factors is explained, which leads to simple and elegant formulas in which only the first three moments of the radius distribution appear.
Keywords: cherry-pit model; specific surface; sphere packings; stochastic geometry

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Publ.-Id: 25293


CT imaging during treatment improves radiomic predictions for patients with locally advanced head and neck cancer

Leger, L.; Zwanenburg, A.; Pilz, K.; Baumann, M.; Troost, E.; Richter, C.; Löck, S.
Introduction: Radiomics applies machine learning algorithms to characterize the tumor phenotype and to predict clinical outcome based on quantitative imaging data. It has been applied using pre-treatment computed tomography (CT) scans but only few studies have assessed radiomics on imaging acquired during radiotherapy. Therefore, we compared the performance of radiomic models based on the pre-treatment CT with that based on CT imaging during treatment.
Material/Methods: Two datasets of patients with advanced stage head and neck squamous cell carcinoma (HNSCC) were used as an exploratory and a validation cohort (47 and 30 patients, respectively). All patients received primary radio-chemotherapy (RCT) and underwent a non-contrast-enhanced CT scan pre-treatment and in week 2 (W2) of treatment. 1610 image features were extracted from the gross tumour volume, delineated on the baseline CT and the W2 CT. Radiomic models were built to predict loco-regional tumour control (LRC). Different feature selection methods (mutual information maximization (MIM), random forest variable importance (RFVI)) and learning algorithms (Cox regression (COX), random forest (RF)) were evaluated using the concordance index (CI) as performance measure.
Results: On the W2 CT both FS methods combined with the RF algorithm achieved a higher performance (CI=0.71) than on the baseline CT (CI<0.65), which was also observed using the Cox regression model (W2 CT: CI=0.66, baseline CT: CI=0.51).
Conclusions: CT scans from the second week of RCT for patients with locally advanced HNSCC improved the performance of radiomic prediction models compared to baseline CT scans. The incorporation of during-treatment imaging is a promising way to improve radiomic models for clinical treatment adaption.
  • Lecture (Conference)
    15th Acta Oncologica conference on biology-guided adaptive radiotherapy - BIGART 2017, 14.-16.06.2017, Aarhus, Danmark

Permalink: https://www.hzdr.de/publications/Publ-25292
Publ.-Id: 25292


Development of an experimental setup for the integration of multi-modality imaging and photon/proton irradiation for preclinical cancer research with small animals

Müller, J.; Neubert, C.; Lühr, A.; von Neubeck, C.; Schürer, M.; Beyreuther, E.; Tillner, F.; Krause, M.; Bütof, R.; Dietrich, A.
In this abstract, we present an experimental setup that allows for multi-modal, cross-platform imaging of small animals as well as image-guided proton- and photon irradiation under laboratory conditions.
The setup consists of two units: A primary bedding unit which holds the animal and which is equipped with a breathing mask for inhalation anesthesia, an inlet for warm air and a breathing sensor. The primary unit was designed to meet the demands of the various imaging (magnetic resonance imaging, positron emission tomography, computed tomography, proton radiography,) and treatment modalities (photon- and proton irradiation). The bedding unit can be mounted inside a container, which is designed to maintain pathogen-free conditions outside designated animal laboratory facilities.
The second, peripheral unit comprises a heating module, several sensors and read-out electronics to control and monitor temperature as well as vital signs. Moreover, it allows for remote emergency intervention (e.g. oxygen flush) during the animal’s anesthesia.
The setup has currently been tested for proton irradiation in an experimental area. A method was implemented to perform on-line position verification by proton radiography.
The presented setup features multiple advantages for combined, multi-modal treatment which is of special importance for the monitoring and treatment planning of experimental tumor models. In particular, orthotopic tumors which require accurate imaging – the modality of which can be chosen based upon tissue and treatment – and treatment planning. It satisfies the various modalities’ requirements, hence allowing for one combined workflow. Moreover, image analysis is strongly simplified as multi-modal images can be co-registered without sophisticated techniques.
Keywords: Preclinical research, cancer, proton therapy, imaging
  • Lecture (Conference)
    15th Acta Oncologica conference on biology-guided adaptive radiotherapy - BiGART 2017, 13.-16.06.2017, Aarhus, Dänemark

Permalink: https://www.hzdr.de/publications/Publ-25291
Publ.-Id: 25291


ATHLET model development for the passive pressure pulse transmitter as part of the passive safety systems of a nuclear reactor within the frame of the German EASY project

Sporn, M.; Neukam, N.; Schuster, C.; Hurtado, A.; Hampel, U.; Schäfer, F.
In nuclear power plants, various kinds of active safety systems are installed to control reactor power and to ensure safe and stable core cooling for a wide spectrum of transients and accidents. The safety concept is complemented by inherent safety features and, especially for new reactor designs, by innovative passive safety systems. These systems are based on a change in the thermodynamic equilibrium established at steady-state conditions, enabling them to function without electric power supply. An important part of the passive safety systems of the KERENA© reactor, an evolutionary boiling-water reactor concept jointly developed by AREVA and PreussenElectra (formerly E.ON), is the passive pressure pulse transmitter (PPPT). In case of an accident with decreasing reactor water level, the PPPT serves as an alternative trigger to activate reactor scram, containment isolation or automatic depressurization of the reactor cooling system. Investigations on the interaction of the various components of the KERENA© passive safety concept (e.g. PPPT, emergency condenser and containment cooling condenser) are being performed for the EASY project. Using the system code ATHLET an input deck of the PPPT has been developed and successfully validated. Additionally, an ATHLET input deck for the complete passive heat-removal system has been developed to simulate hypothetical accident transients, which will be experimentally investigated at the INKA test facility in Karlstein. In this paper, the results of the simulations for the PPPT and a simulation for a hypothetical loss-of-coolant accident are presented.
Keywords: Passive pressure pulse transmitter, passive systems, ATHLET, KERENA, INKA, EASY
  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China
  • Lecture (Conference)
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China

Permalink: https://www.hzdr.de/publications/Publ-25290
Publ.-Id: 25290


Does the UO2(CH3COO)3-complex really exist: a spectroscopic study

Brinkmann, H.; Moll, H.; Stumpf, T.
The coordination chemistry of radionuclides (RN) with organic components is of great interest since latter can affect the mobility as well as the sorption behavior adversely. Acetate (AcO-) can be a biotic or abiotic degradation product of organic material present in nuclear waste. Additionally it is often declared as model compound for more complex organic structures. A large number of studies is available which investigated the speciation of uranium(VI) in the presence of acetate under acidic conditions. From potentiometric titrations it seems to be very clear that three uranyl-acetate species are formed under acidic conditions: UO2AcO+ (1:1), UO2(AcO)2 (1:2) and UO2(AcO)3- (1:3).
Spectroscopic methods (e.g. IR and EXAFS) provide no certainty whether the 1:3 complex exists or not. TRLFS and UV-vis spectroscopy were mainly applied to characterize the formation of the 1:1 complex. In this study TRLFS, ATR-FT-IR and UV-vis spectroscopy were applied to determine the speciation of uranium(VI) in the presence of acetate and to fill the gap of missing spectroscopic data for the other formed species. Experimental conditions were chosen so that all three previous identified species should be formed. Data evaluation was performed on the basis of factor analysis resulting in single component spectra and stability constants. The findings led us to the conclusion that the 1:3 complex was not formed. In addition the detailed evaluation of ATR-FT-IR spectra show that an approximation used in potentiometric studies should be treated with caution. All these indications reinforce the doubts with respect to the existence of the UO2(AcO)3- species.
Keywords: Acetate, Uranyl, TRLFS, UV-vis, ATR-FT-IR
  • Poster
    GDCh-Wissenschaftsforum Chemie 2017, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25289
Publ.-Id: 25289


Canola cell (Brassica napus) responses to europium(III) exposure: a spectroscopic study

Moll, H.; Sachs, S.; Geipel, G.
Rare earth elements (REE, e.g. lanthanides) and radionuclides are released in the environment. Hence, detailed knowledge of the fate of these elements in the ecosphere including the food chain is required for a reliable assessment of the resulting risk potential for humans and wildlife. Our aim is to explore the complex processes of trivalent actinides with plant cells on a molecular level using europium(III) as an analogue for trivalent actinides. Callus cell cultures are suitable models for studying cell metabolism processes in plants. They retain the ability to form metabolites characteristic of intact tissues for an adaptation to stress conditions, in this case europium.
We studied the response of Brassica napus cells to europium(III) exposure (30 µM and 200 µM). Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used as direct speciation technique to explore the Eu(III) speciation on callus cells and cell compartments after cell fractionation. The possible release of plant cell metabolites (e.g. phenolic compounds) promoted due to the cell contact with Eu(III) was investigated.
After an exposure time of 42 days and at 200 µM Eu(III) the growth of the calli was inhibited by ca. 50 % compared to 30 µM Eu(III) and the control. This correlates with increased amounts of secreted phenolic compounds. Callus cells accumulated 7.2 to 100 µg Eu/gwhet cells depending on [Eu(III)]initial. Cell fractionation studies revealed that 98 % of the Eu(III) was located on large cell fragments and 2 % was found in the cytoplasm. TRLFS studies showed a different Eu(III) speciation on callus cells (active uptake) compared to those found on suspension cell cultures (bioassociation).
This knowledge contributes to an improved understanding of REE/radionuclide interactions with plants on a molecular level.
Keywords: plants, europium, metabolism, TRLFS
  • Contribution to proceedings
    Goldschmidt2017, 13.-18.08.2017, Paris, France
  • Lecture (Conference)
    Goldschmidt2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25288
Publ.-Id: 25288


Recent and present activities in THEREDA

Moog, H. C.; Altmaier, M.; Brendler, V.; Bok, F.; Gaona, X.; Marquardt, C.; Richter, A.; Scharge, T.; Thoenen, T.; Voigt, W.
INTRODUCTION
THEREDA is the acronym for “Thermodynamic Reference Database”, a multi-institutional, national joint project to create a mutually accepted database for the geochemical modeling of solubilities in the near field of an underground repository for high-level waste in a rock salt formation (Moog et al. 2015).
As of April 2010 THEREDA became operative in the world wide web, and since 30th of June 2011 ready-to-use parameterfiles for EQ3/6, Geochemist’s Workbench, PHREEQC, and ChemApp are released. During the following years the team issued altogether eleven data releases. Each release covers data for particular subsystems only.
RECENT ACTIVITIES
Data releases
During the last two years three data releases were issued. Each release was qualified and documented with test calculations. Apart from ChemApp the releases are accompanied by code-specific scripts which enable the user to reproduce our calculations.
R-09 covered the systems
• U(IV) – (Na, K) – HCO3 – H2O
• U(IV) – Na – Cl – H2O
• U(VI) – (Na, K, Ca) – Cl – H2O
R-10 covered the systems
• Na - Cl - Tc(IV) / Tc(VII) - OH,
• Mg - Cl - Tc(IV) - OH,
• Ca - Cl - Tc(IV) - OH
R-11 covered the systems
• Sr – (Na, K, Mg, Ca) – Cl – H2O
• Sr - Na – SO4 – H2O
R-10 was the first release to cover a redox reaction. Our efforts to produce parameter files for different codes which deliver the same result posed unexpected difficulties and revealed differences on how the different codes tackle redox transitions.
Extension of internal calculation
THEREDA features a system of internal calculations of dependent data from independent data (the latter ones directly entered). It has been extended to provide for temperature extrapolations from standard reaction data and for the calculation of the latter from temperature functions of equilibrium constants of standard molar Gibbs free enthalpies of reaction.
PRESENT ACTIVITIES
Data releases
The following data releases are in preparation and have priority for 2017.
• Solubility of oxygen in pure water and high saline solutions
• Na, K – Cl,SO4 – (PO43-, HPO42-, H2PO4-) –H2O (binary, ternary, and some quaternary systems tested)
• This will lead to an upgrade of R-09 covering uranium solubility in phosphate bearing solutions
• Merge of R-01 (Na, K, Mg, Ca – Cl, SO4 – H2O polythermal) and R-03 (Na, K, Mg, Ca – Cl, SO4 – HCO3/CO2(g) – H2O 298.15K only) with an upgrade of the latter for elevated temperatures.
As a side product, the release on the oxygen solubilities will lead to a re-evaluation of logK-values for the reactions
2H2O(l) ⇌ O2(aq) + 2H2(g)
2H2O(l) ⇌ O2(g) + 2H2(g)
REFERENCES
1. H. C. MOOG et al., Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55), 72-84 (2015). http://dx.doi.org/10.1016/j.apgeochem.2014.12.016
E. Yalçintaş et al., Thermodynamic description of Tc(IV) solubility and hydrolysis in dilute to concentrated NaCl, MgCl2 and CaCl2 solutions, Dalton Transactions (45), 8916-8936 (2016). -> [YAL/GAO2016]
2. J. B. Macaskill et al., Isopiestic measurements on aqueous Mixtures of Sodium Chloride and Strontium Chloride. J. Solution Chem. (7), 339-347 (1978). -> [MAC/WHI1978]
3. V. K. Filippov et al., Thermodynamics of phase equilibria in the potassium, strontium, sodium, chloride, water (K+,Sr2+|| Cl--H2O, Na+,Sr2+|| Cl--H2O and Na+,K+,Sr2+|| Cl--H2O) systems at 25°, Russ. J. Gen. Chem. (60), 427-431 (1990). -> [FIL/FED1990]
4. J. A. Rard and D. G. Miller, Isopiestic determination of the osmotic and activity coefficients of aqueous mixtures of sodium chloride and strontium chloride at 25° C, J. Chem. Eng. Data (27), 342-346 (1982). -> [RAR/MIL1982b]
5. S. L. Clegg et al., Isopiestic Determination of the Osmotic and Activity Coefficients of NaCl + SrCl2 + H2O at 298.15 K and Representation with an Extended Ion-Interaction Model, J. Chem. Eng. Data (50), 1162-1170 (2005). -> [CLE/RAR2005]
6. M. Kydynov et al., Solubility in the quaternary system consisting of lithium, sodium and strontium chlorides and water at 25 °C, J. Appl. Chem. (London) (4), 736-739 (1969). -> [KYD/LOM1969]
Keywords: THEREDA, Thermodynamic Reference Database, Pitzer
  • Lecture (Conference)
    Actinide Brine Chemistry (ABC-Salt V Workshop 2017), 26.-28.03.2017, Ruidoso, USA

Permalink: https://www.hzdr.de/publications/Publ-25287
Publ.-Id: 25287


60Fe and 244Pu in deep-sea archives - a link to nearby supernova activity and r–process sites

Wallner, A.; Kinoshita, N.; Feige, J.; Froehlich, M.; Hotchkis, M.; Fifield, L. K.; Golser, R.; Honda, M.; Linnemann, U.; Matsuzaki, H.; Merchel, S.; Paul, M.; Rugel, G.; Schumann, D.; Tims, S. G.; Steier, P.; Yamagata, T.; Winkler, S. R.
The Interstellar Medium (ISM) is continuously fed with new nucleosynthetic products. The solar system moves through the ISM and collects dust particles. Therefore, direct detection of freshly produced radionuclides on Earth, i.e. before decaying, provide insight into recent and nearby nucleosynthetic activities [1,2]. Indeed, a pioneering work at TU Munich [3,4], which applied the ultra-sensitive single atom counting technique of accelerator mass spectrometry (AMS) to an ocean crust-sample, showed an enhanced 60Fe signal possibly of extraterrestrial origin. Within an international collaboration [5-7] we have continued to search for ISM radionuclides incorporated in terrestrial archives. We have analyzed several deep-sea sediments, crusts and nodules for extraterrestrial 60Fe (t1/2=2.6 Myr), 26Al (t1/2=0.7 Myr) and 244Pu (t1/2=81 Myr) [5-8] which are complemented by independent work at TU Munich [9-11]. All the data demonstrate a clear global 60Fe influx that is interpreted as exposure of Earth to recent (≤10 Myr) supernova explosions. Furthermore, the low concentrations measured for 244Pu suggest an unexpectedly low abundance of interstellar 244Pu [5]. This finding signals a rarity of actinide r–process nucleosynthesis which is incompatible with the rate and expected yield of standard core collapse supernovae as the predominant actinide-producing sites. In this talk I will also present additional new results for 60Fe and 244Pu measured with unprecedented sensitivity. These data provide new insights into their concomitant influx and their ISM concentrations over a time period of the last 11 million years.
[1] J. Ellis et al., ApJ. 470, 1227 (1996).
[2] G. Korschinek et al., Radiocarbon 38, 68 (1996); abstract.
[3] K. Knie et al., Phys. Rev. Lett. 83, 18 (1999).
[4] K. Knie et al., Phys. Rev. Lett. 93, 171103 (2004).
[5] A. Wallner et al., Nature Comm. 6, 5956 (2015).
[6] J. Feige et al., EPJ Web of Conf. 63, 3003 (2013).
[7] A. Wallner et al., Nature 532, 69 (2016).
[8] M. Paul M. et al. Astrophys. J. Lett. 558, L133L135 (2001).
[9] C. Wallner et al. New Astron. Rev. 48, 145150 (2004).
[10] L. Fimiani et al., Phys. Rev. Lett. 116, 151104 (2016).
[11] P. Ludwig et al., PNAS 113, 9232 (2016).
Keywords: accelerator mass spectrometry, AMS, supernova
  • Lecture (Conference)
    Nuclear Physics in Astrophysics 8 (NPA8), 18.-23.06.2017, Catania, Italia

Permalink: https://www.hzdr.de/publications/Publ-25286
Publ.-Id: 25286


Entwicklung und Validierung von Bildauswertealgorithmen zur Charakterisierung der Gas-Flüssigkeits-Strömung in Anstaupackungen

Litzka, A.
Am Helmholtz-Zentrum Dresden Rossendorf wird die Fluiddynamik von Anstaupackungen untersucht, einer neuen Form von Einbauten für Trennkolonnen. Für die Auswertung der Messungen mithilfe der ultraschnellen Röntgentomographie werden Algorithmen benötigt, welche die Ermittlung der Phasenverteilung in den Packungen ermöglichen.
In dieser Arbeit wurde untersucht, ob dies mithilfe von Bildsegmentierung erfolgen kann. Die Segmentierung muss in Gas, Flüssigkeit und Titanblech erfolgen. Es wurden geeignete Messphantome erstellt, anhand derer die Implementierung der Algorithmen erfolgte. Für die Validierung der Ergebnisse wurden Referenzmessungen mit Röntgen-Mikrotomographie eingesetzt.
Aufgrund der mangelnden Bildqualität der rekonstruierten Daten ist zunächst nur Identifikation der Gasphase in den Phantomen möglich. Der Ansatz die Feststoffstruktur mithilfe der Referenzmessung lokalisieren zu können, scheiterte an einer Verzerrung der abgebildeten Geometrien durch die ultraschnelle Röntgentomographie infolge der Bildrekonstruktion.
Des Weiteren wurde versucht mithilfe einer Dekonvolution die Bildqualität zu verbessern und so die Voraussetzung für eine Segmentierung in drei Phasen zu schaffen. Im entfalteten Bild ist es für eine der drei Strömungsformen möglich, in lokalen Bereichen Schwellwerte für eine Segmentierung in drei Phasen zu ermitteln. Offen ist, ob sich dies auf die anderen Strömungsformen übertragen lässt und eine Optimierung der Auswertealgorithmen eine ausreichende Genauigkeit der Anteilsbestimmung ermöglicht.
  • Study thesis
    TU Dresden, 2017
    Mentor: J. Sohr, M. Schubert, U. Hampel

Permalink: https://www.hzdr.de/publications/Publ-25285
Publ.-Id: 25285


Site-specific binding affinity of Eu(III) towards Ca-binding protein calmodulin: A combined spectroscopic and theoretical study

Tsushima, S.; Samsonov, S.; Drobot, B.; Raff, J.; Komeiji, Y.; Mochizuki, Y.
Molecular modelling of actinide interaction with large biomolecules by quantum chemical calculations is restricted by request for huge computational resources. We challenged this problem by applying Fragment Molecular Orbital (FMO) method. In FMO, the molecular system is partitioned into small fragments and each fragment and fragment pair is subjected to self-consistent field calculations which drastically reduces computational cost.1 We are upgrading FMO program Abinit-MP 2 to implement f orbitals. Here, interaction of Eu3+ with Ca-binding protein calmodulin (CaM) was studied. Calculations were performed in the following way. Using the crystal structure of Ca2+-bound CaM, all four Ca2+ ions were replaced by Eu3+, protonation state of Eu-CaM was adjusted, and 12 Na+ were added for neutralization. The structure was immersed in a TIP3P water bath of 8 Å thickness around Eu-CaM and submitted to 100 ns molecular dynamics (MD) run. Structure at each 1 ns was collected (100 samples), waters were stripped off to 4 Å coverage, and the structures were used in FMO calculations at MP2 level. The statistical average of inter-fragment interaction energy (IFIE) was calculated. Average coordination number of Eu in Eu-CaM during 100 ns MD run is between 8.9 and 9.1. Eu sits in the same binding site as Ca but with increased bidentate coordination. Additionally, increased water coordination is observed. In EF Hand 1, 2, and 4, there is an average of 1.7 to 1.9 coordinating waters to Eu whereas in Hand 3 there is an average of 2.9 waters. This result perfectly matches with previous spectroscopic findings where 2 waters was found at sites 1 and 2 and at either site 3 or site 4, with 3 waters at the remaining site.3 When we compare four metal-binding sites in Eu-CaM, the IFIE between Eu3+ and the corresponding binding site are overall similar among three of the four binding sites, namely EF Hand 1, 2, and 4. On the other hand the IFIE for Hand 3 is clearly smaller pointing to that Hand 3 is the weakest binding site. The reason for this is clear; EF Hand 3 carries only three negatively charged residues, whereas the other motifs have four of them. Consequently, Eu binding in EF Hand 3 exhibits relatively larger fluctuations compared to other binding sites which causes structural disorder to Eu-CaM. We also performed titration and Eu luminescence lifetime measurements which are found to be consistent with MD and FMO results.
  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-25284
Publ.-Id: 25284


Untersuchung heterogener Strömungsmuster in Anstaupackungen mittels ultraschneller Röntgentomographie: Methode und Validierung

Sohr, J.; Litzka, A.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.
Die Kombination von strukturierten Packungen unterschiedlicher geometrischer Oberflächen in Anstaupackungen (s. Abb. 1) führt zu einem axial verteilten Strömungsprofil bestehend aus Blasenströmung, Sprudelschicht und Filmströmung. Die Strömungsmorphologie variiert dabei in den einzelnen Strömungsbereichen sehr stark, sodass durch integrale Hold-up-Messungen kaum Rückschlüsse auf die individuellen Flüssigkeitsinhalte und Phasengrenzflächen gezogen werden können. Zeitlich und örtlich hochaufgelöste bildgebende Messverfahren, wie die ultraschnelle Röntgentomographie, können hier neue Erkenntnisse zur Fluiddynamik liefern [1].
Im Rahmen eines durch die DFG geförderten Projekts sind umfangreiche Fluiddynamikstudien mittels ultraschneller Röntgentomographie geplant. In einem ersten Schritt wird die ultraschnelle Röntgentomographie für die Untersuchung der unterschiedlichen Strömungsmorphologien validiert. Dazu werden mittels Micro-Computertomographie exakt charakterisierte statische Messphantome eingesetzt und Methoden zur Erfassung und Bewertung von Hold-up, Phasenverteilung und Phasengrenzflächen entwickelt. Die Validierung dieser Methoden ist Gegenstand dieses Beitrags.
[1] Janzen, A., Schubert, M., Barthel, F., Hampel, U., Kenig, E.Y., Chem. Eng. Process, (2013), 66, 20-26.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mechanische Flüssigkeitsabtrennung, Kristallisation, Phytoextrakte, Adsorption, Extraktion, Fluidverfahrenstechnik und Membrantechnik, 06.-10.03.2017, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25283
Publ.-Id: 25283


A highly-parallel Monte-Carlo-Simulation of X-Ray-Scattering using a Particle-Mesh-Code on GPUs

Grund, A.
Im Rahmen dieser Arbeit wurde eine Softwarelösung entwickelt, welche die Streuung von Röntgenstrahlung in Materie mit einem Monte-Carlo-Ansatz simuliert. Dazu wurde die Anwendung der Röntgen-Kleinwinkelstreuung (SAXS) zur Untersuchung der komplexen Prozesse bei der Interaktion intensiver kurzer Laserpulse mit Festkörpern als Motivation verwendet und beschrieben, wie Fouriertransformationen zur Näherung dieser Streuung verwendet werden können. Darauf aufbauend wurde einerseits die schnelle Fouriertransformation (FFT) als effiziente Implementierung für Computer vorgestellt und andererseits wurde auf die Limitierung dieses Ansatzes zur Beschreibung der Streuprozesse eingegangen. Um diese Limitierungen zu umgehen, wurde ein Modell entwickelt, das die Röntgenstrahlung mittels photonenähnlicher Teilchen beschreibt. Da für eine gute Abbildung der physikalischen Prozesse Milliarden solcher Teilchen benötigt werden, wurde die auf diesem Modell basierende Simulation von Anfang an auf die hoch parallele Struktur moderner Grafikprozessoren ausgelegt, welche es ermöglicht, sehr viele Teilchen gleichzeitig zu simulieren. Der implementierte Algorithmus wurde detailliert beschrieben, wobei gezielt auf die Besonderheiten von Grafikprozessoren eingegangen wurde. Da die richtige Wahl der Datentypen wesentlich für die Geschwindigkeit und Präzision des Algorithmus ist, wurde in einer umfassenden theoretischen Analyse und Tests der numerischen Genauigkeit der Implementation gezeigt, dass sogar mit Berechnungen in geringer Genauigkeit Ergebnisse erzielt werden, die keine wesentlichen Abweichungen von denen der exakten Berechnung aufzeigen. Dadurch können für typische Anwendungen kleinere Datentypen gewählt werden, was die Durchführung umfangreicherer Simulationen auf einer gegebenen Hardware erlaubt. Abschließend konnte die Korrektheit für ausgewählte Beispiele sowie eine gute Skalierbarkeit nachgewiesen werden.

English abstract:
In this thesis a software solution was developed that simulates the scattering of X-rays in matter using a Monte Carlo approach. The application of small-angle X-ray scattering in the studies of the complex processes occurring during the interaction of short intense laser pulses in solid matter provides the motivation for this work. Therefore this technique is described and it is shown how Fourier transformation can be used for approximating the scattering results. It is shown how they can be efficiently implemented in computers using the fast Fourier transform (FFT) and why this approach has limitations when describing scattering processes. To circumvent these, a model was developed that uses photon-like particles to describe the X-rays. Billions of such particles are required to provide a good approximation of the physical processes involved, which is why the simulation algorithm described in this work was designed from the ground up to support the massively parallel structure of modern graphic processing units (GPUs) allowing to simulate many particles at once. The implemented algorithm is described focusing on the special methods required to make the most use out of GPUs. As the choice of the appropriate data types is vital for the correctness and precision of the algorithm a comprehensive analysis and test of the numerical accuracy was deployed. It is shown that even reduced precision provides results that are accurate enough for a wide range of applications. Therefore, smaller data types can be used allowing to simulate much larger experiments on a given hardware. Finally the correctness and good scalability of the parallel algorithm are demonstrated.
Keywords: HPC, Exascale, Monte-Carlo, Photons, Scattering, SAXS
  • Diploma thesis
    TU Dresden, 2016
    Mentor: Prof. Dr. W. Nagel, Dr. T. Kluge, Dr. M. Bussmann, Dr. A. Knüpfer

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Publ.-Id: 25282


Holography at QCD-Tc

Zöllner, R.; Kämpfer, B.
Within an extended soft wall model, we study the temperature dependence of the lowest vector meson states. Scales are adjusted by using as input the ρ meson mass in vacuum and the velocity of sound from lattice QCD which displays a minimum at Tc. The melting of the ρ meson occurs at temperatures O(Tc).

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Publ.-Id: 25280


The photoluminescence response to structural changes of Yb implanted ZnO crystals subjected to non-equilibrium processing

Ratajczak, R.; Prucnal, S.; Guziewicz, E.; Mieszczynski, C.; Snigurenko, D.; Stachowicz, M.; Skorupa, W.; Turos, A.
In this paper, we present the detailed study of optical and structural properties of Yb implanted single ZnO crystals. Hydrothermally grown wurtzite (0001) ZnO crystals were implanted with 150 keV Yb ions to fluencies of 5e14 and 1e15 at/cm2. After ion implantation, two different types of annealing were performed: rapid thermal annealing (RTA) and millisecond range flash lamp annealing (FLA). Crystalline quality, damage recovery, and Yb lattice site location were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c). It is shown that independent of the used annealing technique, defects formed in ZnO during ion implantation can be removed. Upon RTA performed at the temperature higher than 800C, strong out-diffusion of implanted Yb atoms and precipitation on the surface takes place. Consequently, the degradation of the photoluminescence (PL) efficiency is observed. The diffusion of implanted Yb during millisecond range FLA does not occur for such experimental conditions. Moreover, FLA treatment for 20 ms leads to the formation of single crystalline ZnO layer with Yb incorporated in the substitutional lattice sites. According to RBS/c and PL data, Yb atoms substituted in the Zn sublattice are predominantly in the 2þ oxidation state. The most intensive PL has been observed after annealing at 800C for 20 min which is accompanied with the reduction of Yb substitutional fraction and formation of octahedron Yb-oxygen clusters within ZnO.
Keywords: ZnO, ion implantation, FLA, Yb, photoluminescence, RBS

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Publ.-Id: 25279


Application of a single wire-mesh sensor in a parabolic trough facility with direct steam generation

Hoffmann, A.; Schleicher, E.; Keller, L.; Leon Alonso, J.; Pitz-Paal, R.
The direct steam generation process can contribute to increase the cost-effectiveness of line-focused solar thermal power plants. The current research focuses on the once-through mode as very promising option for large-scale commercial plants. However, the existing pool of knowledge about the steam–water flow in the horizontal receiver pipes reveals knowledge gaps. The present contribution aims to experimentally investigate the two-phase flow in the receiver pipes of the DISS test facility at the Plataforma Solar de Almer´ıa, Spain, by an invasive measurement device for the first time. Therefore a conductance wire-mesh sensor is employed in the low-quality evaporation section of the DISS test facility. This measurement device measures the local instantaneous void fraction that is used to describe the prevailing flow pattern under different pressures and mass flow rates. The results show slug flow, roll waves, wavy flow, and stratified-wavy flow in the horizontal receiver pipes within pressures of 30 to 80 bar. The probability of slug flow or large-amplitude waves decreases with higher pressures. The findings provide a valuable knowledge about the flow structure within the receiver pipes and confirm the proof of function of the wire-mesh sensor under conditions of the direct steam generation process.
Keywords: Wire-mesh sensor, flow pattern, experiment, direct steam generation, parabolic trough, two-phase flow

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Accelerator based Light Source Activities in Germany

Michel, P.
Accelerator based light sources for investigation of matter and materials are highly interesting tools in basic research and applied science. Wavelength ranges from microwaves to hard Gamma rays with extremely high photon fluxes and high average beam power can be generated. In most cases, accelerator based light sources are tunable and provide extremely short and high intensity light pulses. For many applications accelerator based sources offer clear advantages in comparison with other light sources, and can also be synchronized to with external laser based sources. Sophisticated accelerator technologies, such as superconducting RF technology, has pushed this trend during the last decade.
In Germany, an extended program to develop new accelerator technologies has been established in the framework of the Helmholtz Association. More than 200 million Euro will be invested from 2016-2019 within this publicly funded program. Against this background, a number of accelerator projects have been realized or started, in particular for generating light beams for research. This talk will give an overview about the largest existing accelerator facilities and projects for light generation reaching from THz up to x-Rays.
Flash and XFEL at DESY, FLUTE and the former THz project TBONE at KIT Karlsruhe, BESSY VSR and bERLinPro at HZB Berlin and ELBE and a potential follow up project at HZDR will be presented.
Keywords: Accelerator, THz, X-rays, XFEL, FLUTE, FLASH, BESSY VSR, BERLINPRO, ELBE
  • Invited lecture (Conferences)
    IX International Workshop on Advanced Generation of THz and Compton X-rays (AGTaX) using Compact Electron Accelerators, 06.-07.03.2017, New Delhi, India

Permalink: https://www.hzdr.de/publications/Publ-25277
Publ.-Id: 25277


Brillant Light from Cutting Edge Technologies

Michel, P.
Coherent sources of light such as Free Electron Lasers (FELs) are now modern microscopes in science. With the help of the extremely brilliant light that FELs can produce over a wide range of wavelengths, some of the most elusive scientific questions can be effectively answered. These important questions cover matter and novel materials, artificial quantum structures, semiconductor devices, as well as organic and biological samples related to the environment or drug discovery. With special technologies like near field techniques it is possible to overcome fixed measuring limits such as the diffraction limit according to Abbe and to explore some of the smallest building blocks of the world. By means of hard X-rays from X-ray FELs, the chemical structure of complex molecules, e.g. Proteins, can be determined. With the extreme electric fields of long-wave THz rays, the electronic states of solids can be examined or altered, or, for example, the signals of nerves through the membranes of neurons can be investigated. Furthermore, the ultrashort pulses of FEL light can probe the dynamics of fundamental physical and chemical processes with unprecedented resolution. To this extent, accelerator research facilities play a decisive role in science. In addition, such advanced technologies as accelerator systems and free electron lasers provide many other benefits beyond the applications for basic scientific research these technologies and research facilities are the sources of knowledge and training for young students and scientists. Building an accelerator can also benefit the national and local industry. For example, the development of new technologies and methods often also lead to industrial applications and in the process, many personnel are trained. In Dresden-Rossendorf, an accelerator center was built after the reunification of Germany, and in 2001, the ELBE superconducting accelerator went into operation with a variety of secondary sources, including FELs. Today, ELBE is a globally recognized facility drawing scientists and engineers from around the world. More than 70 user groups carry out experiments annually in basic and applied research. Hundreds of publications and scientific contributions to conferences and workshops were held in many areas of science. ELBE is an extremely positive example of how the ambitious establishment of a complicated accelerator facility drives the success of a scientific research center.
Keywords: Brillant, FEL, Synchrotron, accelereator
  • Invited lecture (Conferences)
    IX International Workshop on Advanced Generation of THz and Compton X-rays (AGTaX) using Compact Electron Accelerators, 06.-07.03.2017, New Delhi, India

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Publ.-Id: 25276


Production and purification of no-carrier-added 89Zr at the Leipzig cyclotron for extraction studies with a calix[4]arene

Mansel, A.; Franke, K.
Zirconium is one of the main contaminants in important lanthanide ores. To study the separation of tetravalent zirconium from the trivalent lanthanides by means of calixarene liquid-liquid extraction, the radiotracer technique was used [89Zr (T1/2=78.4 h, Eγ=909 keV, 99%)]. The production of this radionuclide was performed at the Leipzig cyclotron CYCLONE 18/9® by using the nuclear reaction 89Y(p,n)89Zr. An yttrium foil (natural abundance 100% 89Y; 80 mg) was irradiated with 14 MeV protons at a current of 22 µA for one hour. The irradiated target was stored for one hour for the decay of the short-lived 89mZr (T1/2=4.2 min) and was then dissolved in conc. HNO3. After dissolution of the residue with 9 M HNO3, UTEVA-Spec® was used to adsorb 89Zr and elute Y3+ with 9 M HNO3 from the resin. 89Zr was washed from the resin by complexation with 0.1 M oxalic acid. The oxalic acid complex was decomposed by fuming with conc. H2SO4. The no-carrier-added 89Zr was dissolved in 1 M H2SO4 with a radiochemical yield of 101% ± 8%. An activity of ~400 MBq was achieved 5 hours after end of bombardment with a detection limit of 7 fM (0.6 pg/L) for no-carrier-added 89Zr.
Liquid-liquid extraction was performed with a calixarene/chloroform system from acidic aqueous solutions with pH values from 1 to 5. A calix[4]arene, exhibiting phosphonate ester and carboxylic groups, was used. A solution containing ~5 MBq/L 89Zr and 10 µM non-radioactive zirconium carrier was shaken with a tenfold excess of the calixarene at the desired pH for one hour. After separation of the organic and the aqueous phases, the content of 89Zr was measured by γ-counting in both phases. An extraction yield of >95% was reached for zirconium at pH 4. In previous studies with 152Eu, less than 5% of this lanthanide were extracted at pH 4, while >98% of the 152Eu were extracted at pH 8.
In future studies, 89Zr could be used for radiolabelling ZrO2-nanoparticles in environmental sciences as a surrogate for long-lived ThO2-nanoparticles.
Keywords: Zirconium; Cyclotron; Yttrium; Proton induced nuclear reaction; Calixarene; Solvent extraction
  • Lecture (Conference)
    5th International Nuclear Chemistry Congress - INCC, 27.08.-02.09.2017, Gothenburg, Sweden

Permalink: https://www.hzdr.de/publications/Publ-25275
Publ.-Id: 25275


Uranium (VI) complexation with aqueous silicates under elevated temperatures

Lösch, H.; Huittinen, N.; Stumpf, T.
For the safety assessment of high-level nuclear waste repositories in deep geological formations, a sound understanding on the migration behavior of mobilized radionuclides from the spent nuclear fuel (SNF) is required. In recent decades, the solution chemistry of actinides, including hydrolysis and complexation with inorganic ligands such as silicates and carbonates, as well as the interactions of actinides at interfaces present in the geo- and biosphere, have been intensely investigated. These studies are, however, often conducted at ambient temperatures (20-30°C), which hampers the prediction of actinide migration in the environment of heat generating high-level nuclear waste repositories. It is estimated that maximum temperatures in the near field of a SNF repository could reach 100°C, depending on the waste form and host rock under consideration. Thus, for a reliable safety assessment of future SNF repositories, already existing thermodynamic data at 25°C (logK(T), ΔrH, ΔrS, ΔrG) should be expanded to higher temperatures [1, 2].
Silicon is ubiquitous in natural waters as ionic or colloidal species, as a result of weathering of amorphous silica or silicate minerals. U(VI) complexation with silicates in solution has been already subject in previous studies, but only in the temperature range between 20-25°C. For the U(VI)-silicate complexation reaction presented below, a log10*K° between (-1.44) - (-2.65) has been reported [3-4].

UO22+ + Si(OH)4(aq) ↔ UO2SiO(OH)3+ + H+

In the present study, we investigate the complexation of U(VI) with aqueous silicates at temperatures between 0-60°C, thus, allowing the extraction of complexation constants at elevated temperatures as well as thermodynamic parameters for the identified species.
The complexation of U(VI) with dissolved silicates will be investigated as a function of temperature, silicate concentration and pH. The U(VI) concentration will be fixed at 5*10-6 M and the silicate concentration will be varied between 3*10-4 - 2*10-3 M. The complexation will be analyzed with a combination of time-resolved laser-induced fluorescence (TRLFS) and UV-vis absorption spectroscopy to extract the complexation constants at elevated temperatures and subsequent determination of thermodynamic constants (ΔH, ΔS, ΔG). Slope analysis is used to calculate the complex formation constants, which are recalculated to standard conditions with the van´t Hoff equation and the SIT model.
The complexation constants, thermodynamic data and potential solubility products will be included in a thermodynamic database. Thermodynamic speciation modelling of the U(VI) silicate complexation behavior will be done based on the experimental data. Here, comparisons using existing data for ambient conditions can be directly made to estimate the influence of elevated temperatures on the complexation behavior and phase equilibria of U(VI) in the presence of silicates.
Results from the U(VI)-silicate complexation study at elevated temperatures will be presented at the conference.

[1] Warwick P., Hall A., Zhu J., Dimmock P.W., Robbins R., Carlsen L., Lassen P., (1997), Chemosphere, 35, 2471-2477
[2] Rao L., Jiang J., Zanonato P., Bernardo P., Bismondo A., Garnov A.Y., (2002), Radiochim. Acta, 90, 581-588
[3] Guillaumont, R., Fanghänel, T., Neck, V., Fuger, J., Palmer, D.A., Grenthe, I., Rand, M.H., (2003), “Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Chemical Thermodynamics 5”, Nuclear Energy Agency, Elsevier Science Publisher
[4] Moll H., Geipel G., Brendler V., Bernhard G. and Nitsche H., (1998), J. Alloys Compounds 271–273, 765–768.
Keywords: Uranium (VI), silicates, complexation, aqueous system, elevated temperatures
  • Poster
    Migration 2017, 10.-15.09.2017, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25274
Publ.-Id: 25274


Impact of dynamic geochemical conditions on plutonium and americium mobility at a legacy trench disposal site

Payne, T. E.; Kinsela, A. S.; Ikeda-Ohno, A.ORC; Vazquez-Campos, X.; Waite, T. D.; Harrison, J. J.; Bligh, M. W.; Johansen, M. P.; Thiruvoth, S.; Wilsher, K. L.
Low-level radioactive wastes were disposed by burial in closely-spaced unlined trenches in clay-rich surface layers at the Little Forest Site on the southern periphery of Sydney, Australia, between 1960 and 1968. A previous paper [1] gave a general description of the site and described the distribution of plutonium in soils and groundwaters. A process known as the ‘bath-tub’ effect, in which the former trenches become filled to the ground surface with water during intense periodic rainfall events, was implicated in the mobilisation and dispersion of actinides in the surface soils.
A follow-up study investigated the chemical speciation of Pu and Am in water obtained from a sampler within one of the former trenches. The presence of readily detected amounts of Pu and Am provided a unique opportunity to study their aqueous speciation in this environment. The predominant oxidation state of dissolved Pu species was found to be Pu(IV), however the pH-Eh conditions of the groundwater were very close to the transition with Pu (III), suggesting that small changes in chemical conditions could alter its oxidation state [2]. Large proportions of both Pu and Am were associated with mobile colloids in the submicron size range. However, it was clear from ongoing studies at the site that the distribution of dissolved, colloidal and particulate forms of actinides was very variable, and sensitively dependent on the preceding conditions. These included the interval elapsed since the most recent rainfall event at the time of sampling, the initial state of water-saturation of the site when significant rainfall occurred, the intensity of rainfall, and the length of time between rainfall events.
The geochemical form of plutonium was found to be strongly affected by the changes in the redox state and groundwater chemistry during influxes of rainfall-derived water. The cycling of iron, including its precipitation in response to redox changes, is of particular importance, given its potential role as an actinide-sorbing phase. Following rainfall events, the chemical forms of Pu and Am transition from a particle-associated phase immediately after the initial rainwater pulse, to a progressively more soluble form as reducing conditions become re-established.
The formation of strongly sorbing Fe-oxyhydroxide particles is therefore a key process in the cycling of actinides in the system. Simulations in the laboratory using trench-derived water samples showed that increasing concentrations of dissolved silicate progressively retarded Fe(II) oxidation kinetics in the relevant pH range. Furthermore, with increasing Si, the primary Fe(III) oxidation product transitioned from lepidocrocite to a ferrihydrite / silica-ferrihydrite composite [3]. It was inferred that the presence of silicate restricts Fe-polymerization and consequently inhibits Fe(III) solid-phase particle growth. The presence of silicate may therefore significantly retard Fe(II) oxidation rates and facilitate transport of trace concentrations of plutonium and americium, which would otherwise adsorb to the Fe(III) oxide resulting from Fe(II) oxidation.
Microbial analyses demonstrated that oxygen-laden rainwater rapidly altered the redox balance in the trench water, strongly impacting the speciation of radionuclides and microbial functioning. When water levels were lowest, more reducing conditions prevailed, with the microbial community exhibiting a higher representation of dissimilatory sulfate reduction and methanogenesis pathways [4]. When water levels are low in the trenches, the Fe is predominantly present in soluble reduced forms.
In summary, the behaviour of actinides at the site is strongly influenced by a number of hydrological, geochemical and microbial factors and has a strong cyclic variation triggered by episodic rainfall events. Our results have important implications for the ongoing management of this site and are of relevance to other near-surface environmental systems in which redox cycling occurs. In the case of near-surface legacy radioactive waste sites, consideration should be given to the major consequential impact of these fluctuations on the mobility of disposed actinides and other radionuclides.
[1] Payne, T.E., Harrison, J.J., Hughes, C.E., Johansen, M.P., Thiruvoth, S., Wilsher, K.L., Cendón, D.I., Hankin, S.I., Rowling, B. and Zawadzki, A. (2013). Trench ‘Bathtubbing’ and Surface Plutonium Contamination at a Legacy Radioactive Waste Site. Environmental Science & Technology, 47: 13284-13293.
[2] Ikeda-Ohno, A., Harrison, J.J., Thiruvoth, S., Wilsher, K., Wong, H.K.Y., Johansen, M.P., Waite, T.D. and Payne, T.E. (2014). Solution Speciation of Plutonium and Americium at an Australian Legacy Radioactive Waste Disposal Site. Environmental Science & Technology, 48: 10045-10053.
[3] Kinsela, A.S., Jones, A.M., Bligh, M.W., Pham, A.N., Collins, R.N., Harrison, J.J., Wilsher, K.L., Payne, T.E., and Waite, T.D (2016). Influence of Dissolved Silicate on Rates of Fe(II) Oxidation Environmental Science & Technology. 50: 11663−11671
[4] Vazquez-Campos, X, Kinsela, A.S., Bligh, M.W., Harrison, J.J., Payne, T.E., and Waite, T.D., Response of microbial community function to fluctuating geochemical conditions within a legacy radioactive waste trench environment. Submitted to Applied and Environmental Microbiology, 2017.
Keywords: actinides, plutonium. americium, migration, geochemistry, nuclear waste disposal, surface water, speciation, minerals
  • Lecture (Conference)
    Migration 2017, 10.-15.09.2017, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-25273
Publ.-Id: 25273


Chloride Ion Battery Review: Theoretical Calculations, State of the Art, Safety, Toxicity and an outlook towards future developments

Gschwind, F.; Euchner, H.; Rodriguez-Garcia, G.ORC
Batteries using chloride ions as shuttles have only been under investigation for a few years, but already several publications have dealt with this topic. In this review, we extensively report for the first time the state of the art, along with theoretical screening and calculations and an analysis of safety and toxicity. At the end, possible future approaches are evaluated.

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Publ.-Id: 25272


An Eulerian-Eulerian Computational Approach for Simulating Descending Gas-Liquid Flows in Reactors with Solid Foam Internals

Subramanian, K.; Zalucky, J.; Schubert, M.; Lucas, D.; Hampel, U.
Chemical reactors with new types of packings, such as metallic and ceramic open-pore foams, have become of subjects of scientific and engineering interest in the past decades. For so-called trickle bed reactors the new packing types provide favorable conditions, such as a high specific surface area and low pressure drop, which are believed to contribute to an intensification of mass and heat transfer. While a number of experimental studies have been recently been reported in literature, hydrodynamic modelling and simulation, particularly at the full reactor scale, is still in its infancy due to the complexity of two-phase flow in such non-regular packings.
In this work, an attempt has been made to model and predict flow pattern and liquid distribution in a trickle bed reactor with solid foams using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was adopted, where gas and liquid phases flow co-currently downwards through a reactor with SiSiC ceramic foams as internals. The influence of both mechanical and capillary dispersion is included and studied in detail for foams of two different pore densities. The simulation results are validated against experimental data. In particular, the effects of gas and liquid superficial velocities and pore density on liquid holdup and two-phase pressure drop were studied in detail.
Keywords: Computational fluid dynamics, liquid holdup, multiphase flow pattern, relative permeability concept, Solid foams

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Publ.-Id: 25271


Architecture and mineral potential of the Paleoproterozoic Karrat Group, West Greenland: Results of the 2016 Season

Rosa, D.; Dewolfe, M.; Guarnieri, P.; Kolb, J.; Laflamme, C.; Partin, C. A.; Salehi, S.; Sørensen, E. V.; Thaarup, S.; Thrane, K.; Zimmermann, R.
This report presents the preliminary results of the second field season of a joint project be- tween the Geological Survey of Denmark and Greenland (GEUS) and the Ministry of Min- eral Resources of Greenland (MMR) focusing on the Paleoproterozoic Karrat Group. The motivation for the expedition stems from an evaluation of the mineral potential along with understanding the stratigraphic architecture of the Karrat Group and aims to address stra- tigraphy, structure, and economic geology. Field work extended to northern Karrat Group outcrops, between Upernavik and Kullosuaq, and allowed further studies of the southern Karrat Group outcrops between Svartenhuk and Maarmorilik. The relationship between the Karrat Group and the Prøven Igneous Complex (PIC), emplaced between these two areas, was also assessed. The 2016 field season was aided by oblique aerial photography (“pho- toflying”), and hyperspectral techniques. Hyperspectral scenes were collected along cliff faces in the areas with the most prospective mineral potential, including Kangerluarsuk Fjord and Maarmorilik. These studies have built on the observations made in 2015, and have led either to the consolidation or to the revision of interpretations suggested after that season.
The exposed Karrat Group extends from ~71° to ~75°N and is composed of five formations: the Qeqertarssuaq (Lower Karrat Group), Qaarsukassak, Mârmorilik, Kangilleq, and Nûkavsak formations (Upper Karrat Group), of which the Qaarsukassak amd Kangilleq formations are informal. The lower and upper Karrat Group are separated by a regional erosional unconformity, which represents a revision to the Karrat stratigraphy established during the 2015 field season. The Karrat Group has not been differentiated north of Uper- navik due to the high metamorphic grade and polyphase deformation. Major goals of the field work included delineating contact relationships between units, documenting sedimen- tary structures that can define depositional environment(s), mapping the lateral extent and nature of extrusive mafic volcanism and volcaniclastic rocks in the upper Karrat Group (Kangilleq Formation), and determining the relative age relationships between units, which is elusive since several units are not in contact with one another. Integrated stratigraphy, sedimentology, volcanology, and ongoing geochronology will lead to a better understanding of the basin tectonic setting(s) in which the Karrat Group was deposited.
The deformation history of the area put forward after the 2015 season has been reviewed, and this succession is suggested: a NW-vergent D1 north of the Prøven Igneous Complex and channel flow in an orogen-scale NW-SE compression; D2 is characterised by E-W extension near Archean orthogneiss at Kangiusap Kuua and distal compression further to the E (previously assigned to D4); D3 is represented by structuring of the Kigarsima nappe overprinting all the other structures on Karrat Island and the peninsula to the SE (formerly described as D2); and, finally, a NW-SE compression, documented in the Maarmorilik area, is now relabeled as D4 (previously assigned to D3).
The time-stratigraphic horizon above and laterally to the Kangilleq Formation volcanism represents a period of VMS-formation on (or just below) the seafloor. Sampling of massive sulfides has yielded anomalous base metal concentrations (typically <0.3% Cu+Pb+Zn). However, because it is known that massive sulfide horizons can display zonations from low-grade to gold- and/or base metal-rich zones, these horizons potentially constitute tar- gets for future base metal and/or gold exploration in the Karrat region.
A Mississippi-Valley Type (MVT) origin is suggested for the Zn-Pb mineralisation in the Qaarsukassak Formation (RTZ Discovery), which might therefore have formed at the same time as the mineralisation in the Mârmorilik Formation. This is based on proximity of the Qaarsukassak Formation mineralisation to Archean rocks and the association of its distri- bution with marble and chert horizons. The possible role of evaporites and their diapirism in the mineralising process has been highlighted in the Mârmorilik Formation, by establishing the proximity of the known Lower Mârmorilik Formation showings to what can be interpret- ed to have been an evaporite horizon (now a “mottled pelite”). From this horizon, evaporites possibly ascended and were emplaced, as diapirs, within the Upper Mârmorilik Formation, underneath the pelites that would have acted as cap rock (where the Black Angel deposit is). Diapirism was likely triggered by deformation, during which evaporites flowed along thrust planes, as has been tentatively documented through the hyperspectral survey.
Possible silicate-silicate liquid immiscibility accompanied by silicate-sulfide immisciblity, occurred in a gabbro complex identified on the eastern side of Nutaarmiut island, to the southeast of Upernavik. The degree of PGE-Au enrichment in the sulfide has not been tested yet, but could potentially be of economic significance.
  • Other report
    København: GEUS Geological Survey of Denmark and Greenland, 2017
    112 Seiten

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Publ.-Id: 25270


Proton modulated arc therapy for the treatment of left-sided breast cancer

Delso, N.; Stützer, K.; Kirk, M.; Huang, S.; Sanchez-Parcerisa, D.; Lin, L.; Freedman, G.; Metz, J.; Abel, E.; Carabe, A.
Current proton techniques for left-sided breast cancer use an anterior or lateral anterior oblique (LAO) proton beam which places the distal edge of the beam immediately against the ipsilateral lung and the cardiac structures. Tangential proton modulated arc therapy (tPMAT) would place the distal edge within the target, reducing the dose and linear energy transfer (LET) to the lung, the heart or the left anterior descending (LAD) artery.

Six patients treated with a single LAO proton beam (sLAO), were re-planned using a tPMAT beam extending from the left lateral to the mediastinal side of the patient. The plans consisted of fifty mono-energetic beams, separated by 2o each. A custom wedge was devised for each patient to enable full target coverage. Dose and volume constraints for PTV, heart, lung, LAD in both treatment modalities were reported, and the statistical significance of their difference was determined using the t-test. LET distributions were calculated and reported for all patients. The robustness of both plan modalities were tested by calculating perturbed doses with isocenter shiftsof 3mm in all 6 principal directions and considering ±3.5% range uncertainty.

tPMAT showed equal or better capacity to cover the target with 95% of the dose while maintaining the dose below prescription for the organs at risk (OARs). The use of tPMAT reduces the LET in the OARs compared to the sLAO. tPMAT is also more robust to isocenter shifts and range uncertainties. A universal wedge can be used in tPMAT without changing the dosimetric or biophysical properties of the plan.

tPMAT provides robust dosimetric and biophysical benefits over the current sLAO technique. The possibility of using universal wedges indicates the possibility of doing tPMAT without altering the current fast turnaround of PBS planning and delivery.
Keywords: PMAT, breast cancer, uncertainty, proton therapy, LET
  • Lecture (Conference)
    Annual Meeting of the American Association for Physicists in Medicine 2017, 30.07.-03.08.2017, Denver, Colorado, USA

Permalink: https://www.hzdr.de/publications/Publ-25269
Publ.-Id: 25269


Thermoelectric Properties of Natural Chalcopyrite from Zacatecas, Mexico

Wyżga, P.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Mori, T.; Gumeniuk, R.
The phase and chemical compositions of the mineral chalcopyrite from the sulphide footwall vein in La Cantera (Zacatecas, Mexico) is examined by powder x-ray diffraction, energy dispersive x-ray spectroscopy and chemical ICP-OES analyses. The influence of the detected impurities on the thermoelectric parameters (i.e. thermopower, electrical and thermal conductivities) is discussed. Thermoelectric figure of merit ZT of the studied natural minerals is found to be of the same order of magnitude (~ 10-3) as reported for CuFeS2 synthesized in the laboratory.
Keywords: chalcopyrite, powder x-ray diffraction, energy dispersive x-ray spectroscopy, ICP-OES

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Permalink: https://www.hzdr.de/publications/Publ-25268
Publ.-Id: 25268


Surface charge and particle size determine the metabolic fate of dendritic polyglycerols

Pant, K.; Pufe, J.; Zarschler, K.; Bergmann, R.; Steinbach, J.; Reimann, S.; Haag, R.; Pietzsch, J.; Stephan, H.ORC
Dendritic polyglycerols (dPG) are water soluble, polyether-based nanomaterials which hold great potential in diagnostic as well as therapeutic applications. In order to translate them for in vivo applications, a systematic assessment regarding their cell and tissue interactions as well as their metabolic fate in vivo is a crucial step. Herein, we explore the structure-activity relationship of three different sizes (ca. 3, 5, and 10 nm) of neutral dendritic polyglycerol (dPG) and their corresponding negatively charged sulfate analogs (dPGS) on their in vitro and in vivo characteristics. Cellular metabolic activity was studied in A431 and HEK293 cells. Biomolecular corona formation was determined using electrophoretic mobility shift assay, which showed an increased protein binding of the dPGS even with serum concentrations as low as 20%. An in situ technique, microscale thermophoresis, was employed to address the binding affinities of these nanomaterials with serum proteins such as serum albumin, apo-transferrin, and fibrinogen. In addition, nanoparticle-cell interactions were studied in differentiated THP-1 cells which showed a charge dependent scavenger receptor-mediated uptake. In line with this data, detailed biodistribution and small animal PET imaging studies in Wistar rats using 68Ga-labeled dPG-/dPGS-NOTA conjugates showed that the neutral dPG-NOTA conjugates were quantitatively excreted via the kidneys with a subsequent hepatobiliary excretion with an increase in their size, whereas the polysulfated analogs (dPGS-NOTA) were sequestered preferentially in the liver and kidneys irrespective of their size. Taken together, this systematic study accentuates that the pharmacokinetics of dPGs is critically dependent on the overall size and charge and can be ‚fine-tuned’ for the intended requirements in nano-theranostics.

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Permalink: https://www.hzdr.de/publications/Publ-25267
Publ.-Id: 25267


Experimental Investigation of Two-Phase Pipe Flow with Ultrafast X-ray Tomography and comparison with state-of-the-art CFD simulation

Banowski, M.; Hampel, U.; Krepper, E.; Beyer, M.; Lucas, D.
In this paper, we report on experimental investigations of air/water two-phase flow in a vertical pipe, which is a benchmark experiment for the development and validation of two-phase CFD models and codes. We conducted experiments for co-current upward and downward flow as well as counter-current flow at ambient temperature and pressure conditions. As measurement technique, we employed ultrafast X-ray tomography, which gives two-dimensional cross-sectional images of the gas-liquid distribution in two planes up to 2500 Hz scanning speed. In this paper, we briefly explain this technique, introduce essential data processing steps and discuss the findings of the study.
Keywords: Two-phase flow, ultrafast X-ray tomography, pipe flow, gas holdup measurement, image processing, bubble size measurement, CFD code validation

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Permalink: https://www.hzdr.de/publications/Publ-25266
Publ.-Id: 25266


A novel fuzzy-logic based method for determination of individual bubble velocity and size from dual-plane ultrafast X-ray tomography data of two-phase flow

Banowski, M.; Patmonoaji, A.; Lucas, D.; Hampel, U.
Ultrafast X-ray tomography enables non-invasive imaging of gas-liquid flows with high spatial and temporal resolution. While it is relatively straightforward to extract e.g. gas fraction profiles from cross-sectional tomographic images, the extraction of bubble and gas-liquid interface information requires advanced image processing techniques. Thereby it is an important necessity to transform the temporal scale in the scanned sequences into a corresponding length scale for obtaining correct volumetric information. For bubbly flows this means that the velocity of the dispersed phase, i.e. the gas bubbles, has to be determined from dual-plane scans. A common and widely applied method to obtain gas phase velocities is cross-correlating the image sequences of the two scanning planes. This gives an averaged velocity for each position in the cross-section. In the present work, a new method is introduced, which determines the velocity of individual gas bubbles. This new method is termed as “bubble twinning method”, because it tries to identify twin-bubbles in both scanning planes. The developed algorithm compares essential bubble parameters, that is, volume, position and residence time in the slice, by applying a fuzzy-logic based membership function approach. The algorithm was tested for bubbly flow as well as slug flow conditions. Results are compared with established theoretical predictions as well as the cross-correlation method.
Keywords: Ultrafast X-ray tomography, image processing, bubbly flow, bubble velocity, bubble size

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Permalink: https://www.hzdr.de/publications/Publ-25265
Publ.-Id: 25265


The uranium citric acid system and its sorption onto hematite

Steudtner, R.; Müller, K.; Schmeide, K.; Brendler, V.
The determination and verification of thermodynamic and kinetic parameters of complexation, redox and sorption processes will improve the safety assessment of nuclear waste disposal sites. On one side, this study focusses on uranium complexation and redox reactions in aqueous citric acid solution as a function of reaction parameters (pH, c, T, atm.) and visible light irradiation. To evaluate the impact of these reaction parameters on the uranium – citric acid – water system i we used UV-Vis, ATR FT-IR and TRLF spectroscopy. In all systems the uranium citrate complexes were detected as dissolved species. We identified and characterized the formed complexes for uranium(VI) – (UO2)2(cit)22–, (UO2)2(cit)2(OH)3–, (UO2)2(cit)2(OH)24– and (UO2)3(cit)3(OH)55– as well as for uranium(IV) – U(H2cit)3+, U(Hcit)20 (aq.) and U(cit)22– and determined the corresponding complex formation constants. The determination and verification of thermodynamic and kinetic parameters of complexation and redox processes were consequently applied to the uranium sorption on hematite in the presence of citric acid.
The uranium reactions at the iron mineral − water interface were comprehensively investigated by in situ vibrational spectroscopy and classical batch sorption experiments. The uranium retention on hematite depends on pH value and citric acid concentration. By infrared spectroscopy, we observe a typical chemical binding of uranium by formation of an inner-sphere sorption complex in absence of citric acid. In presence of citric acid the sorption process is suppressed due to simultaneous complex formation in aqueous solution.
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2017, 11.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25264
Publ.-Id: 25264


Numerical Investigation of Passive Heat Transfer to Ambient for Cooling of Nuclear Spent Fuel Pools

Unger, S.; Oertel, R.; Hampel, U.
In current power plants is the storage of spent fuel in active cooled water pools standard practice. The reliability of nuclear power plants can be enhanced by substituting the active cooling components by passive heat transfer systems. A promising concept of such systems uses ambient air as an unlimited heat sink. However the major drawback of heat transfer towards air is a low heat transfer coefficients. To overcome this disadvantage a finned tube bundle heat exchanger, promote a natural convection cycle, is numerical investigated and thermohydraulic optimized. The most beneficial fin design on an oval shaped tube heat exchanger as well as a favourable chimney height could be established.
  • Contribution to proceedings
    48th Annual Meeting on Nuclear Technology, 16.-17.05.2017, Berlin, Deutschland
  • Lecture (Conference)
    48th Annual Meeting on Nuclear Technology, 16.-18.05.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25263
Publ.-Id: 25263


Validation and update of the baseline model for poly-disperse bubbly flows

Lucas, D.; Krepper, E.; Rzehak, R.; Ziegenhein, T.; Ma, T.; Liao, Y.
For the consolidation of CFD-methods basing on the multi-fluid approach a baseline model strategy has been developed. Following this strategy a baseline model for poly-disperse bubbly flows was recently defined. This model is presented and an overview on the status as well as selected examples for the validation are given. Furthermore new developments regarding bubble induced turbulence, lateral lift force and bubble coalescence and breakup modelling are presented.
Keywords: baseline model, bubbly flow, CFD, bubble induced turbulence, lateral lift force, coalescence, breakup
  • Lecture (Conference)
    28th Meeting of the German CFD Network of Competence, 07.03.2017, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25262
Publ.-Id: 25262


Ultrasonic Measurements in a Model Experiment for Continuous Casting of Round Blooms with Magnetic Stirring in the Submerged Entry Nozzle

Schurmann, D.ORC; Willers, B.; Eckert, S.
We present an experimental study about the influence of magnetic stirring in the submerged entry nozzle (SEN) for continuous casting of round blooms performed at the mini-LIMMCAST facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).
The experimental setup consists of a round mould with an inner diameter of 80 mm made of acrylic glass (PMMA), representing a mould used in industry. A magnetic field, employed by permanent magnets, rotates around the SEN with variable rotation frequencies. In our experiment we use a near eutectic alloy GaInSn under isothermal conditions as a model fluid, which is liquid at room temperature.
Measurements are carried out using ultrasonic velocity sensors by means of Ultrasound Doppler Velocimetry (UDV). The sensors are mounted directly at the SEN as well as on several positions along the mould, allowing us to have an insight into the effects by the magnetic stirring in the mould and in the SEN itself. We show a comparison of our results with measurements obtained at the same setup where the magnetic stirring in the SEN is replaced by electromagnetic stirring in the mould by means of a rotating magnetic field (RMF).
Keywords: MHD, magnetic stirring in the submerged entry nozzle (SEN), Ultrasonic Measurements (UDV) in GaInSn, Continuous Casting of Round Blooms
  • Contribution to proceedings
    9th ECCC "European Continuous Casting Conference", 26.-29.06.2017, Wien, Österreich
    Proceedings of the 9th ECCC
  • Lecture (Conference)
    9th ECCC "European Continuous Casting Conference", 29.06.2017, Wien, Österreich

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Permalink: https://www.hzdr.de/publications/Publ-25261
Publ.-Id: 25261


High-energy resolution X-ray spectroscopy studies of electron-electron interactions in actinide and lanthanide systems

Kvashnina, K. O.; Rossberg, A.; Exner, J.; Scheinost, A. C.
Two new synchrotron-based techniques, high energy resolution fluorescence detection (HERFD) X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS), can now provide unprecedented detailed information about the electronic structure of actinide and lanthanide bearing materials. This includes information on the electron-electron interactions, hybridization between molecular orbitals, the nature of their chemical bonding, and the occupation and the degree of the f-electron localization.

We have studied the electronic structure of cerium, lanthanum, praseodymium, uranium and thorium systems by means of HERFD and RIXS at The European Synchrotron (ESRF). The recently upgraded Rossendorf Beamline (ROBL) at ESRF dedicated to actinide science provides now a unique opportunity to measure HERFD and RIXS with a novel X-ray emission spectrometer with ground-breaking detection limits.

The recorded experimental spectral features were evaluated using a variety of theoretical codes including the LDA+U approximation within DFT, atomic multiplet theory and full multiple scattering FEFF. We furthermore show that RIXS and HERFD can be used to assess the degree of the f-electron localization and the (rather unpredictable) covalent or ionic nature of the actinide and lanthanide bonds. The combined experimental and theoretical data provide a fundamental understanding of lanthanide and actinide chemistry significant for topics of high societal relevance.
  • Lecture (Conference)
    Migration 2017, 10.-15.09.2017, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-25260
Publ.-Id: 25260


High energy resolution X-ray spectroscopy studies of U intermetallics at the U M4,5 edges

Kvashnina, K.; Walker, H.; Magnani, N.; Lander, G.; Caciuffo, R.
This contribution will provide an overview of applications of high energy resolution X-ray spectroscopic techniques to the U intermetallic systems. We will show resonant inelastic X-ray scattering (RIXS) and high energy resolution X-ray fluorescence detection (HERFD) X-ray absorption spectroscopy data from the uranium intermetallics UPd3, USb, USn3, URu2Si2 and others at the U M4,5 edges3 and compare the data to those from the well-localized 5f2 semiconductor UO2. We have found a small energy shift between UO2 and UPd3, both known to have localized 5f2 configurations, which we ascribe to the effect of conduction electrons in UPd3. The spectra from UPd3 and URu2Si2 are similar, strongly suggesting a predominant 5f2 configuration for URu2Si2. The valence-band RIXS provides information on the transitions (at about 18 eV) between the U 5f and U 6p states, as well as transitions of between 3 and 7 eV from the valence band into the unoccupied 5f states. These transitions are primarily involving mixed ligand states (O 2p or Pd, Ru 4d) and U 5f states. Calculations are able to reproduce both these low-energy transitions reasonably well.
We will demonstrate that two new synchrotron-based techniques – HERFD and RIXS at the actinide M4,5 edges – can now provide unprecedented detailed information on processes such as the electron-electron interactions, hybridization between molecular orbitals, the nature of their chemical bonding, and the occupation and the degree of the f-electron localization.
  • Invited lecture (Conferences)
    International Conference on Strongly Correlated Electron Systems, SCES 2017, 16.-21.07.2017, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-25259
Publ.-Id: 25259


Homogeneous gas-liquid distribution for monolithic structures via a needle distributor

Meitzner, C.; Hilpmann, G.; Schäfer, T.; Haase, S.; Lange, M.; Hampel, U.
Structured catalysts are a widely discussed approach for process intensification of chemical multiphase reactors. But equal to common catalyst structures homogeneous educt distribution along the catalytic surface is mandatory for high reactor performance. Especially monolithic structures require a homogeneous initial fluid distribution. The current work presents a novel distribution concept for gas liquid flow through arbitrary channel matrices. It is based on the injection principle where gas and liquid are inserted directly into the channels. A prototype for different cell densities has been built and tested by using various measurement techniques: gravimetry, X-ray tomography and an optical fiber sensor. Additionally, the flow regime per channel has been detected as equal to single channel conditions.
Keywords: process intensification, multiphase reactions, phase distribution, structured catalysts, monolith

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Permalink: https://www.hzdr.de/publications/Publ-25258
Publ.-Id: 25258


Ultrafast X-ray tomography for two-phase flow analysis in centrifugal pumps

Schäfer, T.; Hampel, U.
The unsteady behavior of gas-liquid two-phase flow in a centrifugal pump impeller has been visualized, using ultrafast X-ray tomography. Based on the reconstructed tomographic images an evaluation and detailed analysis of the flow conditions has been done. Here, the high temporal resolution of the tomographic images offered the opportunity to get a deep insight into the flow to perform a detailed description of the transient gas-liquid phase distribution inside the impeller. Significant properties of the occurring two-phase flow and characteristic flow patterns have been disclosed. Furthermore, the effects of different air entrainment conditions have been investigated and typical phase distributions inside the impeller have been shown.
Keywords: centrifugal pump, gas entrainment, two-phase flow, ultrafast X-ray computed tomography
  • Lecture (Conference)
    48th Annual Meeting on Nuclear Technology (AMNT48), 16.-17.05.2017, Berlin, Deutschland
  • Contribution to proceedings
    48th Annual Meeting on Nuclear Technology (AMNT48), 16.-17.05.2017, Berlin, Deutschland
    Proceedings of 48th Annual Meeting on Nuclear Technology
  • atw - International Journal for Nuclear Power 62(2017)7, 474

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Permalink: https://www.hzdr.de/publications/Publ-25257
Publ.-Id: 25257


Annual Report 2016 - Institute of Ion Beam Physics and Materials Research

Faßbender, J.ORC; Heera, V.; Helm, M.; Zahn, P.
Content:
Preface
Selected publications
Statistics
(Publications and patents, Concluded scientific degrees; Appointments and honors; Invited conference contributions, colloquia, lectures and talks; Conferences, workshops, colloquia and seminars; Exchange of researchers; Projects)
Doctoral training programme
Experimental equipment
User facilities and services
Organization chart and personnel
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-078 2017

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Permalink: https://www.hzdr.de/publications/Publ-25256
Publ.-Id: 25256


The 2017 terahertz science and technology roadmap

Dhillon, S. S.; Vitiello, M. S.; Linfield, E. H.; Davies, A. G.; Hoffmann, M. C.; Booske, J.; Paoloni, C.; Gensch, M.; Weightman, P.; Williams, G. P.; Castro-Camus, E.; Cumming, D. R. S.; Simoens, F.; Escorcia-Carranza, I.; Grant, J.; Lucyszyn, S.; Kuwata-Gonokami, M.; Konishi, K.; Koch, M.; Schmuttenmaer, C. A.; Cocker, T. C.; Huber, R.; Markelz, A. G.; Taylor, Z. D.; Wallace, V. P.; Zeitler, J. A.; Sibik, J.; Korter, T. M.; Ellison, B.; Rea, S.; Goldsmith, P.; Cooper, K. B.; Appleby, R.; Pardo, D.; Huggard, P. G.; Krozer, V.; Shams, H.; Fice, M.; Renaud, C.; Seeds, A.; Stöhr, A.; Naftaly, M.; Ridler, N.; Clarke, R.; Cunningham, J. E.; Johnston, M. B.
Science and technologies based on terahertz frequency electromagnetic radiation (100 GHz–30 THz) have developed rapidly over the last 30 years. For most of the 20th Century, terahertz radiation, then referred to as sub-millimeter wave or far-infrared radiation, was mainly utilized by astronomers and some spectroscopists. Following the development of laser based terahertz time-domain spectroscopy in the 1980s and 1990s the field of THz science and technology expanded rapidly, to the extent that it now touches many areas from fundamental science to ‘real world’ applications. For example THz radiation is being used to optimize materials for new solar cells, and may also be a key technology for the next generation of airport security scanners. While the field was emerging it was possible to keep track of all new developments, however now the field has grown so much that it is increasingly difficult to follow the diverse range of new discoveries and applications that are appearing. At this point in time, when the field of THz science and technology is moving from an emerging to a more established and interdisciplinary field, it is apt to present a roadmap to help identify the breadth and future directions of the field. The aim of this roadmap is to present a snapshot of the present state of THz science and technology in 2017, and provide an opinion on the challenges and opportunities that the future holds. To be able to achieve this aim, we have invited a group of international experts to write 18 sections that cover most of the key areas of THz science and technology. We hope that The 2017 Roadmap on THz science and technology will prove to be a useful resource by providing a wide ranging introduction to the capabilities of THz radiation for those outside or just entering the field as well as providing perspective and breadth for those who are well established. We also feel that this review should serve as a useful guide for government and funding agencies.
Keywords: terahertz, time-domain spectroscopy, semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-25254
Publ.-Id: 25254


Radiomarkierung von Nanopartikeln

Franke, K.; Hildebrand, H.; Schymura, S.
Nanoskalige Materialien halten zunehmend Einzug in verschiedenen Bereichen des alltäglichen Lebens. Viele Industrie- und Endverbraucherprodukte enthalten Nanopartikel, das betrifft u.a. den Gesundheitssektor, die Energie- und Umwelttechnik, den IT-Sektor, die Textilindustrie, die Automobilindustrie, die Chemie, die Bauindustrie aber auch Konsumgüter aus dem Lebensmittel- und Kosmetikbereich. Begleitet wird der wachsende Einsatz von Nanopartikeln von umfangreichen Studien zur Risikobewertung von Nanomaterialien. Bis heute sind jedoch viele erforderliche Aspekte für eine umfassende Gefährdungsabschätzung nur unzureichend bekannt. Eine wesentliche Ursache dafür ist die oft schwierige Identifizierung und Quantifizierung von Nanopartikeln in relevanten Testmedien und Zielkompartimenten, wie Böden, Sedimenten, Pflanzen oder Klärschlämmen. Mit der Radiomarkierung von Nanopartikeln steht jedoch eine effektive Methode zum Nachweis von Nanopartikeln in komplexen Umweltproben zur Verfügung, mit der es gelingt, radiomarkierte nanopartikuläre Spezies selektiv bei umweltrelevanten Nanopartikelkonzentrationen von anderen elementgleichen Spezies zu unterscheiden.
Wir haben verschieden Methoden zur Radiomarkierung von Nanopartikeln entwickelt, die es gestatten, abhängig von der Art der Nanopartikel und des zu untersuchenden Prozesses, gezielt Radiotracer in die Nanopartikel einzuführen. Wesentlich ist dabei oft die Möglichkeit, industriell genutzte bzw. kommerziell verfügbare Nanopartikel einer Radiomarkierung zu erschließen. Es wurden für die Radiomarkierung verschiedene Verfahren, wie die Synthese von Nanopartikeln unter Einsatz von radioaktiven Ausgangsstoffen, der chemischen Bindung von Radiotracern an Nanopartikel, die Aktivierung durch die Bestrahlung mit Protonen, die Rückstoßmarkierung und Diffusionsverfahren genutzt. Es ist möglich, durch die Auswahl geeigneter Radionuklide (Halbwertszeit, Zerfallsart) und die Einstellung der Aktivitätskonzentration gezielt die Eigenschaften der radiomarkierten Nanopartikel für verschiedene Nachweisverfahren und experimentelle Rahmenbedingungen (z.B. Zeitskala) einzustellen. In unseren aktuellen Arbeiten werden folgende radiomarkierte Nanopartikel hergestellt: [105Ag]Ag, [110mAg]Ag, [44Ti]TiO2, [45Ti]TiO2, [48V]TiO2, [64Cu]CuS, [64Cu]SiO2, [65Zn]CdSe/ZnS, [124I]CNTs, [125I]CNTs, [131I]CNTs, [7Be]MWCNT, [139Ce]CeO2 und [194Au]Pt. Begleitet werden die Arbeiten zur Radiomarkierung durch die Validierung der für die experimentellen Untersuchungen wesentlichen Eigenschaften der Nanopartikel.
Die radiomarkierten Nanopartikel werden in vielfältigen Studien z.B. im Bereich Bioverfügbarkeit (Pflanzenaufnahme), Transportverhalten, Abwasserbehandlung und in Verwitterungsuntersuchungen eingesetzt, Nachweisgrenzen im unteren ng/L-Bereich werden erreicht.
Keywords: Nanopartikel Radiomarkierung
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2017 ─ Jubiläumskongress "GDCh - 150 Jahre", 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25253
Publ.-Id: 25253


U(VI) sorption by Ca-bentoniteunder alkaline and saline conditions as a function of pH and carbonate content

Philipp, T.; Schmeide, K.; Stumpf, T.
Bentonite is considered as buffer and backfill material within the geo-technical barrier of such a repository. Therefore, profound understanding of the uranium retention processes in bentonite under environmentally relevant conditions is essential for long-term safety assessment. As the pore water chemistry of North German clay formations is characterized by high ionic strengths, corrosion of concrete present in the repository, is promoted. Upon corrosion, hyperalkaline (10 < pH < 13) cement pore waters evolve [3], which can alter the retention potential of bentonite towards radionuclides. Batch sorption experiments as a function of pH, c(U), SLR and carbonate content were conducted in combination with spectroscopic techniques such as time-resolved laser-induced fluorescence spectroscopy (TRLFS) and attenuated total reflectance Fourier-transform infrared (ATR FT-IR) spectroscopy in order to gain insight into the underlying processes on the macroscopic as well as on the molecular level. Lower U(VI) sorption in the presence of carbonate in the solution up to pH 9.5 can be explained with the formation of only weakly adsorbing uranyl carbonate species. TRLFS spectra verify the prevalence of these complexes already at low carbonate concentrations in the solution. In the pH region 10 – 12, an almost complete retention of U(VI) was observed in the absence as well as at low carbonate concentrations. TRLFS measurements reveal an abrupt change in U(VI) speciation at pH 10.5, to uranyl hydroxo complexes even at low carbonate concentrations (experiments at ambient atmosphere). TRLFS spectra suggest that anionic uranyl hydroxo complexes prevail in the pH region 10.5 – 12. Beside the adsorption of those, also precipitation processes are considered as a possible cause for the removal. pH-dependent U(VI) solubility tests have shown that the U(VI) retention in this pH region is apparently a combination of adsorption and precipitation processes. By contrast, at higher carbonate concentrations the U(VI) retention in the pH region 9.5 – 11 is very low . Under these conditions uranyl-carbonate complexes dominate the speciation up to pH 11.5. Consequently, the U(VI) speciation and the resulting sorption behavior in the (hyper)alkaline environment is highly dependent on the amount of carbonate in the solution.
  • Poster
    MIGRATION (16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere), 10.-15.09.2017, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-25252
Publ.-Id: 25252


In-vivo Dosimetrie in der Partikeltherapie – eine Herausforderung für die öffentliche und industrielle Forschung

Pausch, G.ORC
Die Zerstörung bösartiger Tumoren mit hochenergetischen Ionenstrahlen ist mittlerweile ein klinisch etabliertes Verfahren der Radioonkologie. Allein in Deutschland gibt es sechs Zentren, in denen Patienten mit Protonen oder schwereren (Kohlenstoff-) Ionen bestrahlt werden können. Der entscheidende Vorteil gegenüber der klassischen Radiotherapie mit harter Röntgenstrahlung - die mögliche Schonung gesunden Gewebes in unmittelbarer Nachbarschaft des Zielgebiets, die bei Tumoren in der Nähe kritischer Organe überlebenswichtig sein kann – wird aber klinisch nicht voll ausgeschöpft, da die Vorhersage (Planung) der Reichweite von Ionenstrahlen mit Unsicherheiten behaftet ist. Die direkte und präzise Messung der Reichweite therapeutischer Partikelstrahlen im Körper (in vivo) ist ein Schlüsselproblem mit erheblichem Einfluss auf die Zukunft der Partikeltherapie, denn der hohe Aufwand muss sich am Ende in deutlich besseren Behandlungsergebnissen widerspiegeln.
Der Vortrag erläutert Ansätze und Erfolge bei der Entwicklung klinisch einsetzbarer Verfahren zur Reichweitemessung in der Partikeltherapie. Entsprechende Forschungsvorhaben profitieren von einer engen Zusammenarbeit der öffentlichen Forschung mit Industriepartnern. Der lange Weg von einer Idee über den Nachweis der Machbarkeit zum Prototypen eines Gerät und dem ersten Einsatz am Patienten kann wesentlich effektiver bewältigt werden, wenn komplementäre Kenntnisse, Erfahrungen, Herangehensweisen und Ressourcen in den verschiedenen Projektphasen abrufbar sind.
Keywords: Radioonkologie, radiooncology Partikeltherapie, particle therapy Reichweitemessung, range assessment
  • Invited lecture (Conferences)
    Jahrestagung der Deutschen Physikalischen Gesellschaft (DPG), AIW Industrietag, 30.03.2017, Münster, Deutschland

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Publ.-Id: 25251


Self-Organized Semiconductor Surface Patterning of Pure and Compound Semiconductors by Polyatomic Ion Irradiation

Bischoff, L.; Böttger, R.; Pilz, W.; Facsko, S.; Heinig, K.-H.
Irradiation of solids by heavy polyatomic ions (e.g. Aunm+ or Binm+) can cause localized melting at the ion impact point due to the enhanced energy density in the collision cascade of a polyatomic heavy ion impact [1,2]. Former studies demonstrated the formation of high aspect ratio, hexagonal dot patterns on Ge, Si or GaAs after high fluence, normal incidence irradiation using a mass separated FIB system choosing a suited combination of energy density deposition (i.e. poly- or monatomic ions) and substrate temperature, which facilitated transient melting of the ion collision cascade volume [2-5].
This study underscores the universality of this ion impact-melting-induced, self-organized pattern formation mechanism probing the compound semiconductor GaSb under polyatomic Aunm+ ion irradiation with various irradiation conditions in particular, ion species, fluence, energy/atom, temperature and angle of incidence.
Calculations of the needed melting energies per atom (Emelt) for different materials show, that among others GaSb is a preferring candidate for a successful surface patterning by mon- and polyatomic heavy ions whereas i.e. the surface of SiC remains stable under the given conditions.
HRSEM, AFM and EDX analysis of irradiated surfaces reveal that for compound semiconductors, additional superstructures are evolving on top of the regular semiconductor dot patterns, indicating superposition of a second dominant driving force for pattern self-organization.

[1] C. Anders et al., Phys. Rev. B 87 (2013) 245434.
[2] L. Bischoff et al., Nucl. Instr. Meth. Phys. Res. B 272 (2012) 198.
[3] R. Böttger et al., J. Vac. Sci Technol. B 30 (2012) 06FF12.
[4] R. Böttger et al., Phys. Stat. Sol. RRL 7 (2013) 501.
[5] L. Bischoff et al., Appl. Surf. Sci. 310 (2014) 154.
Keywords: Self-Organized Surface Patterning; Polyatomic Ion Irradiation; Focused ion Beam
  • Lecture (Conference)
    Raith-FIB- Workshop, 28.-30.03.2017, Dortmund, Germany

Permalink: https://www.hzdr.de/publications/Publ-25250
Publ.-Id: 25250


THEREDA –Thermodynamic Reference Database for the Nuclear Waste Disposal in Germany

Bok, F.; Moog, H. C.; Altmaier, M.; Voigt, W.; Thoenen, T.
The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the still pending decision about the repository host rock (salt, granite, or clay) the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential failure scenarios accurately and to make well-founded predictions about the long-term safety. Specific challenges are comprehensive datasets covering also high temperatures and salinities. Against this background, available databases do not suffice and are limited in their use, partly because of high restrictions and resulting incompleteness of reactions. Other databases rely on heterogeneous and therefore inconsistent data leading to incorrect model calculations. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany and Switzerland, was started in 2006.
THEREDA contains a relational databank whose structure has been designed in a way that promotes the internal consistency of thermodynamic data. Data considered cover the needs of Gibbs Energy Minimizers (ChemApp) and Law-of-Mass-Action programs (Geochemist’s Workbench, EQ3/6, PHREEQC) alike. Parameters for a variety of models describing interactions in mixed phases are included. Namely, the Pitzer parameters to describe activity coefficients of hydrated ions and molecules are considered. Both thermodynamic and interaction parameters can be described by temperature functions.
THEREDA offers evaluated thermodynamic data for many compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements relevant according to the present state of research. In particular, all oxidation states expected for disposal site conditions are covered.
Ready-to-use parameter files are created from the databank in a variety of formats (generic ASCII type, and formats required by the geochemical speciation codes) and offered to the users. They are also used for internal test calculations – one essential element of the quality assurance scheme. The results are documented and provided to the users.
THEREDA is accessible via internet through www.thereda.de. This is not only a portal to the database, but shall also serve as an information and discussion platform on issues concerning the database. Thus, we are confident to generate helpful feedback from the anticipated user community.
Keywords: THEREDA, Thermodynamic Reference Database
  • Lecture (Conference)
    21. European Conference on Thermophysical Properties, 03.-08.09.2017, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25249
Publ.-Id: 25249


Characterization of tetravalent actinide complexes with imine type ligands (salen and its derivative)

Radoske, T.; März, J.; Kaden, P.; Walter, O.; Stumpf, T.; Ikeda-Ohno, A.ORC
Although the geochemistry of uranium is typically dominated by uranium(VI) (as UO22+), tetravalent uranium (U(IV)) could also occur under the geochemical conditions relevant to uranium mines or geological repositories of radioactive wastes, particularly under anaerobic conditions. In this context, the geochemical behaviour of U(IV) should be fully understood for the reliable safety/environmental assessment of such nuclear-related activities. The complexation and speciation of metal ions in groundwater is affected not only by inorganic ligands, but also many other natural organic ligands with a wide variety of different functional groups. Among the functionalities of naturally occurring organic ligands, oxygen(O)- and nitrogen(N)-donor groups play the most significant role in interacting with metal ions. The interaction of U(IV) with O- and N-donor ligands is, therefore, one of the fundamental information to understand the geochemical behaviour of uranium. Given this fact, this study focuses on the complexation of U(IV), as well as another tetravalent actinide of Th(IV), with the imine ligand salen and its derivative (Figure 1), which possess both O- and N-donor groups in the structure, as simplified model of naturally relevant organic O-/N-donor ligands. The complex structure in the solid state was determined by single crystal X-ray diffraction (SC-XRD), while the complexation in solution was studies by NMR and UV-visible absorption spectroscopy.
A series of single crystals of the U(IV)-salen complexes were obtained as a function of M:L ratio and pH by a liquid-liquid diffusion method. SC-XRD measurements on the obtained crystals revealed the new crystal structures, all showing the eight-fold coordination of the U centre with a trigonal dodecahedral geometry with the ligand on the primary coordination sphere of U.
UV-visible absorption measurements of U(IV)-salen solution as a function of M:L ratio indicate the existence of two independent solution species in the system, assigning as the U(IV)-salen complexes with the M:L ratios of 1:1 and 1:2. 1H-NMR spectra of solution samples in which the complex [UIV(Le)2] was dissolved indicate that the protons on the bridging ethyl group between the two imine groups show a significant high-field shift due to the paramagnetic effect of uranium(IV). The spectra also indicate that the metal is positioned at the centre of the coordination polyhedron formed by the two ligand molecules.
Keywords: uranium, imine, ligands, complex, thorium
  • Lecture (Conference)
    Migration 2017, 10.-15.09.2017, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-25248
Publ.-Id: 25248


Universal CAR technology for redirection of human T cells to leukemic and solid tumor cells

Feldmann, A.; Bergmann, R.; Albert, S.; Arndt, C.; Aliperta, R.; Koristka, S.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Steinbach, J.; Bachmann, M.
In recent years, adoptively transferred autologous human T cells that are genetically modified with chimeric antigen receptors (CARs) have been very successfully used for treatment of different hematological malignancies. However, immunotherapy of solid tumors seems to be more challenging. Especially for this application it is of great interest to enhance the very promising CAR technology.
Conventional CARs consist of (I) an extracellular single-chain fragment variable (scFv) redirected to a tumor-associated antigen (TAA), (II) a transmembrane region and (III) intracellular activating motifs. Although these CAR-armed T cells showed impressive therapeutic effects in leukemia patients, some limitations have appeared. Most importantly, CAR-armed T cells can cause life-threatening side effects as a consequence of immoderate on-target, on-tumor reactions or aggressive on-target, off-tumor attack against healthy tissues. Furthermore, under the pressure of a monospecific CAR therapy the targeted antigen can be reduced on tumor cells. To overcome these problems we have recently described a novel modular universal CAR (UniCAR) platform that consists of two separate arms: (I) the universal effector arm and (II) the individual targeting arm. T cells that are genetically modified with UniCARs are redirected to the short peptide epitope E5B9 that is physiologically not presented on the surface of living cells. E5B9 is coupled to the anti-TAA scFv of the target module (TM). Consequently, UniCAR T cells can be cross-linked to tumor cells via the TM which results in antigen-specific tumor cell killing.
We recently described a series of monospecific and bispecific TMs against TAAs including PSCA, PSMA, CD33, CD123, and EGFR (1-3). Here we summarize both in vitro and in experimental mice that all these TMs can efficiently redirect UniCAR T cells against tumor cells in a strictly target-dependent and target-specific manner. Killing occurred at pM TM concentrations. The killing efficacy of UniCAR T cells was comparable to conventional CAR T cells. Redirected UniCAR T cells released pro-inflammatory cytokines as measured by ELISA and/or flow cytometry-based multiplex assays including for example TNF, IL-2 and IFN-γ but not IL-6. In agreement with the UniCAR concept, TMs were released from UniCAR TM complexes in a concentration-dependent manner as measured by dynamic PET analysis.
In summary, we demonstrate that the reactivity of UniCAR-armed T cells can be switched on and off in the presence or absence of a variety of TMs against a series of different TAAs and thus supporting its high flexibility. Moreover, UniCAR activity can be regulated in a dose-dependent manner and thus improve the safety of the CAR technology.

1_A. Feldmann, C. Arndt, R. Bergmann, S. Loff, M. Cartellieri, D. Bachmann, R. Aliperta, M. Hetzenecker, F. Ludwig, S. Albert, P. Ziller-Walter, A. Kegler, S. Koristka, S. Gärtner, M. Schmitz, A. Ehninger, G. Ehninger, J. Pietzsch, J. Steinbach and M. Bachmann. Retargeting of T lymphocytes to PSCA- or PSMA positive prostate cancer cells using the novel modular chimeric antigen receptor platform technology “UniCAR”. Oncotarget 2017, in press.

2_S. Albert, C. Arndt, A. Feldmann, R. Bergmann, D. Bachmann, S. Koristka, F. Ludwig, P. Ziller-Walter, A. Kegler, S. Gärtner, M. Schmitz, A. Ehninger, M. Cartellieri, G. Ehninger, H.-J. Pietzsch, J. Pietzsch, J. Steinbach and M. Bachmann. A novel nanobody-based target module for retargeting of T lymphocytes to EGFR-expressing cancer cells via the modular UniCAR platform. OncoImmunology 2017, in press.

3_M. Cartellieri, A. Feldmann, S. Koristka, C. Arndt, S. Loff, A. Ehninger, M. von Bonin, EP Bejestani, G Ehninger and MP Bachmann. Switching CAR T cells on and off: a novel modular platform for retargeting of T cells to AML blasts. Blood Cancer J. 2016 Aug 12;6(8):e458. doi: 10.1038/bcj.2016.61.
  • Lecture (Conference)
    Cellular Therapy 2017, 9th International Symposium Erlangen, 16.-17.03.2017, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25247
Publ.-Id: 25247


Antigen-specific redirection of human regulatory T cells via a universally applicable chimeric antigen receptor technology

Kegler, A.; Koristka, S.; Feldmann, A.; Arndt, C.; Aliperta, R.; Albert, S.; Ziller-Walter, P.; Ehninger, G.; Bornhäuser, M.; Schmitz, M.; Bachmann, M.
Regulatory T cells (Tregs) play a fundamental role in preventing inflammatory diseases and, therefore, their adoptive transfer emerged as a promising therapeutic strategy for the treatment of autoimmunity, graft rejection and Graft-versus-Host disease. However, preclinical animal models have already substantiated that the application of antigen-specific instead of polyclonal Tregs results in a far more efficient suppression of pathogenic immune reactions. Due to their low frequency in human peripheral blood, the isolation of Tregs with defined antigen specificity is a highly time-consuming and labour-intensive process that does not yet provide therapeutically relevant cell numbers. To overcome this obstacle, we equipped polyclonal Tregs with a novel modular chimeric antigen receptor (CAR) technology called UniCAR.
Unlike conventional CARs, the UniCAR binding domain does not directly recognize a target cell antigen but a small peptide epitope, which is a subunit of a separate target module (TM) providing antigen specificity. Hence, UniCAR-armed Tregs are silenced until they encounter the TM that mediates their cross-linkage with target cells. Therefore, this novel CAR technology not only allows for precise regulation of Treg activity between an “on” and “off” status but also enables their specific retargeting towards any desired antigen simply by replacing the TM.
To additionally compare the influence of different costimulatory signals on Treg properties and functionality, UniCARs were generated and introduced comprising either a CD3ζ, CD28-CD3ζ or CD137-CD3ζ signaling domain. For generation of UniCAR-expressing Tregs the CD45RA+ subpopulation was used, as these cells show the highest capacity in preserving Treg phenotype and functionality ex vivo.
Thus, highly pure, sorted CD4+CD25+CD127lowCD45RA+ Tregs were genetically modified by using a lentiviral gene transfer system resulting in an average of 80 % UniCAR+ Tregs. These UniCAR-armed Tregs maintain their phenotype (≥ 93 % FOXP3+) and expand approximately 150- to 200-fold already after 8 days of in vitro culture. In addition, in the presence of target cells and a respective TM the genetically modified Tregs are activated antigen-specifically as shown by CD69 and LAP upregulation as well as an increased FOXP3 expression level. Most importantly, upon TM-mediated restimulation via the UniCAR, Tregs efficiently suppress proliferation and overall expansion of bead-activated autologous T effector cells.
Taken together, our results underline the enormous clinical potential of UniCAR-armed Tregs as this technology facilitates an antigen-specific activation of polyclonal Tregs at the side of inflammation where they subsequently exert their suppressive capacity. In addition, the UniCAR system enables a precise control over Treg activity. Moreover, the UniCAR-equipped Tregs can be applied for treatment of a wide range of inflammation-related diseases as their antigen specificity can be easily modified just by exchanging the TM.
  • Poster
    Cellular Therapy 2017, 9th International Symposium Erlangen, 16.-17.03.2017, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25246
Publ.-Id: 25246


Scalable, multi-GPU photon tracing for in-situ X-ray radiation transport in solid density plasmas

Garten, M.ORC; Grund, A.; Huebl, A.; Burau, H.; Widera, R.; Kluge, T.; Fortmann-Grote, C.; Bussmann, M.
We present our scientific roadmap towards in-situ modeling of non-LTE interactions of XFEL type X-rays with solid density plasmas using a symbiosis of our performance portable, open source, 3D3V particle-in-cell (PIC) code PIConGPU and its X-ray tracing prototype ParaTAXIS. Treating radiation transport via various atomic processes will enable us to synthesize detector signals and gain predictive capabilities for upcoming pump-probe experiments at the European XFEL. With the world’s fastest particle-in-cell code PIConGPU and the raw computational power of the largest high performance computers we open up the possibility for large-scale case studies of unprecedented repeatability.
Keywords: ParaTAXIS, PIConGPU, radiation transport, plasma physics, atomic processes
  • Poster
    2017 Joint ICTP-IAEA School on Atomic Processes in Plasmas, 27.02.-03.03.2017, Trieste, Italia

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Publ.-Id: 25245


Circumventing the dephasing and depletion limits of laser-wakefield acceleration

Debus, A.; Pausch, R.; Huebl, A.; Steiniger, K.; Cowan, T. E.; Schramm, U.; Widera, R.; Bussmann, M.
Compact electron accelerators are paramount to next generation synchrotron light sources and free-electron lasers, as well as for advanced accelerators at the TeV energy frontier. Recent progress in laser-plasma driven accelerators (LPA) has extended their electron energies to the multi-GeV range and improved beam stability for insertion devices.
However, the sub-luminal group-velocity of plasma waves limits the final electron energy which can be achieved in a single LPA accelerator stage, also known as the dephasing limit.
Here we present the first laser-plasma driven electron accelerator concept without electrons outrunning the wakefield. Our scheme is robust against parasitic self-injection and self-phase modulation as well as drive-laser depletion and defocusing along the accelerated electron beam. It works for a broad range of plasma densities in gas targets.
This opens the way for scaling up electron energies towards TeV scale electron beams without the need for multiple laser-accelerator stages.
Keywords: Laser-produced plasmas, Plasma-based accelerators, Laser-wakefield acceleration, Traveling-wave electron acceleration, TWEAC
Related publications
PIConGPU simulation settings for TWEAC (Id 29625) documents this publication

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Publ.-Id: 25244


Offshore floating packed bed reactors: Key challenges and potential solutions

Dashliborun, A. M.; Larachi, F.; Schubert, M.
The influence of floating vessel motions on the hydrodynamic behavior of multiphase flows in porous media was studied. For elucidating their effects, laboratory-scale experiments were carried out using a hexapod ship motion emulator with six-degree-of-freedom motions with an embarked packed column operating in the co-current gas-liquid down-flow mode. The response of gas-liquid distribution, pressure drop, liquid saturation, and flow regime transition to column inclinations and roll motions was monitored and compared to those of the corresponding static vertical and inclined configurations. On-line visualization of two-phase flow patterns in terms of local liquid saturation distribution is performed by means of a capacitance wire-mesh sensor positioned firmly on the floating packed bed. The results revealed that the hydrodynamic performance of packed beds under roll motion deviates strongly from that of the static beds, indicating that the known characteristics of the conventional land-based trickle-bed reactors cannot be transposed on a one-to-one basis for design and scale-up of the floating reactor configurations.
Keywords: Offshore floating packed bed reactors; hydrodynamics; rolling motion; gas-liquid segregation; liquid saturation; flow regime transition

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Publ.-Id: 25243


Structural clarification of a tert-butyl-calix[4]arene-based 8-hydroxyquinoline complex with uranium(VI) in non-aqueous solution

Bauer, A.; März, J.; Barthen, R.; Jäschke, A.; Glasneck, F.; Schmeide, K.; Brendler, V.; Kersting, B.; Stumpf, T.
The actinides uranium and thorium are considered disturbing constituents in rare earth production. Thus they have to be removed, e.g. by extraction.[1] Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of uranium(VI).[2]
A new chalice-like tert-butyl-calix[4]arene-based 8-hydroxyquinoline ligand consisting of four phenolic units was synthesized. Tert-butyl substituents provide a hydrophobic character. Functionalizing of the phenolic hydroxyl groups by 8-hydroxyquinoline ensures the affinity to uranyl ions.[2]
For better process understanding we examined the mechanisms of uranyl complexation by the calix[4]arene derivative. The structure of the tert-butyl-calix[4]arene-based 8-hydroxyquinoline uranyl complex was unveiled by spectroscopy and isothermal titration calorimetry.
The complexation studies were performed in acetonitrile. Luminescence spectroscopic studies indicated the interaction of uranyl ions with the ligand. UV visible investigations evidenced the presence of a 1:1 and a 1:2 ligand uranyl complex with stability constants of log ß1:1 = 5.94 ± 0.02 and log ß1:2 = 6.33 ± 0.01. Isothermal titration calorimetry provided the thermodynamic characterization of the complexation.
Single crystal X-ray analysis of the 1:1 complex revealed the coordination of the uranyl ion via a N2O2 donor set (Fig. 1). The charge is compensated by an additional coordinated nitrate ion.
The application of electrospray ionization time-of-flight mass spectrometry affirmed the coordination of two hexavalent uranyl nitrate ions in acetonitrile.
In addition, to improve the understanding of the ligand complexation properties the interaction with thorium is studied.

References:

[1] Z. W. Zhu, Y. Pranolo, C.Y. Cheng, Miner Eng 2015, 77, 185.
[2] A. Jäschke, M. Kischel, A. Mansel, B. Kersting, Eur. J. Inorg. Chem. 2017, 894
Keywords: calix[4]arene, SE-FLECX, rare earth production, uranium, complexation studies
  • Poster
    GDCh - Wissenschaftsforum - Jahrestagung Fachgruppe Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25242
Publ.-Id: 25242


Big Bang 6Li nucleosynthesis studied deep underground

Trezzi, D.; Anders, M.; Aliotta, M.; Bellini, A.; Bemmerer, D.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Corvisiero, F. C. P.; Costantini, H.; Davinson, T.; Depalo, R.; Elekes, Z.; Erhard, M.; Ferraro, F.; Formicola, A.; Fülop, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Junker, M.; Lemut, A.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Mossa, V.; Pantaleo, F.; Prati, P.; Rossi Alvarez, C.; Scott, D. A.; Somorjai, E.; Straniero, O.; Szücs, T.; Takacs, M.
The correct prediction of the abundances of the light nuclides produced during the epoch of Big Bang Nucleosynthesis (BBN) is one of the main topics of modern cosmology. For many of the nuclear reactions that are relevant for this epoch, direct experimental cross section data are available, ushering the so-called “age of precision”. The present work addresses an exception to this current status: the 2 H( α,γ ) 6 Li reaction that controls 6 Li production in the Big Bang. Recent controversial observations of 6 Li in metal-poor stars have heightened the interest in understanding primordial 6 Li production. If confirmed, these observations would lead to a second cosmological lithium problem, in addition to the well-known 7 Li problem. In the present work, the direct experimental cross section data on 2 H( α,γ ) 6 Li in the BBN energy range are reported. The measurement has been performed deep underground at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator in the Laboratori Nazionali del Gran Sasso, Italy. The cross section has been directly measured at the energies of interest for Big Bang Nucleosynthesis for the first time, at Ecm= 80, 93, 120, and 133 keV. Based on the new data, the 2 H( α,γ ) 6 Li thermonuclear reaction rate has been derived. Our rate is even lower than previously reported, thus increasing the discrepancy between predicted Big Bang 6 Li abundance and the amount of primordial 6 Li inferred from observations.
Keywords: Big Bang Nucleosynthesis Nuclear Astrophysics Lithium problem

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Publ.-Id: 25241


Use of specific metal binding of self-assembling S-layer proteins for metal bioremediation and recycling

Vogel, M.; Matys, S.; Lehmann, F.; Drobot, B.; Günther, T.; Pollmann, K.; Raff, J.
Most bacteria and all archaea possess as outermost cell envelope so called surface-layers (S-layers). These S-layers are formed by self-assembling proteins having a number of interesting intrinsic properties, e.g. they mediate selective exchange of molecules and therefore function as molecular sieves. Furthermore, S-layers from bacterial isolates recovered from heavy metal contaminated environments have outstanding metal binding properties and are highly stable. Thus they selectively bind several metals with different affinity. For using S-layer proteins for metal bioremediation and recycling three aspects of the metal-interactions with S-layer proteins must be taken into account. First, S-layers possess different functionalities, e.g. carboxyl, phosphoryl groups, binding toxic metals and metalloids, like U and As, unspecifically depending on pH-value. Second, precious metals like Au and Pd are likewise unspecifically bound to functional groups, but presumably covalently, making the binding irreversible unless the S-layer protein is destroyed completely. Third, some metals are needed for native protein folding of the S-layer protein monomer, self-assembly, and the formation of highly-ordered lattices. These particular metals are specifically bound bivalent cations, e.g. Ca2+. Important is that these binding sites allow selective binding not only of Ca2+, but also of chemical-equal elements including the trivalent lanthanides (Eu3+, Tb3+), possessing comparable ionic radii. Thus the metal dependent binding behavior of the proteins not only contributes to the development of biohybrid materials for the separation, removal or recovery of strategic relevant metals regulated by pH and allowing a conceivably release, but also allows a biochemical and mechanistic understanding of the interaction of different metal ions with S-layer proteins .
Keywords: S-layer, bioremediation, recycling, self-assembly, metal
  • Poster
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland
  • Contribution to proceedings
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland
  • Open Access Logo Solid State Phenomena 262(2017), 389-393
    DOI: 10.4028/www.scientific.net/SSP.262.389

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Publ.-Id: 25240


The surface processes of Se(IV) on γ-alumina in the presence of carbonate. Evaluating competitive effects on the sorption behavior

Foerstendorf, H.ORC; Mayordomo, N.; Jordan, N.; Alonso, U.; Missana, T.; Schmeide, K.
The sorption and desorption processes of selenium(IV) onto γ-Al2O3 at different pH values and ionic strengths, as well as the impact of carbonate ions, have been studied by classical batch sorption experiments and in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy.

From recent X-ray absorption spectroscopic investigations the predominant surface complexes of Se(IV) on γ-alumina were identified as bidentate bridging complexes with AlO6 surface groups in the circumneutral pH range (pH 4 – 8) [1]. However, contributions of outer-sphere complexes were not completely ruled out. Thus, we performed batch sorption series and vibrational spectroscopic experiments at different ionic strengths to evaluate the fraction of prevailing outer-sphere complexation. It could be shown that Se(IV) sorption was independent of the ionic strength suggesting that outer-sphere complexation can be neglected under the prevailing conditions.

At more alkaline pH level, the sorption processes proceeded more reversibly than under acidic and neutral conditions, as it was derived from the IR spectroscopic experiments providing molecular information of the ongoing sorption and desorption processes in real time [2]. The enhanced release of the selenite from the alumina phase is due to modification of alumina surface properties at a higher pH level.

Carbonate ions were found to form outer-sphere monodentate complexes at the γ-Al2O3 surface, and hence, the respective sorption process was highly reversible. In the ternary sorption system, the Se(IV) adsorption onto alumina was found to be slightly reduced and an enhanced release of selenite subsequent to the sorption reaction was observed. A change of the speciation of selenite on the alumina surface in terms of structural alterations or different binding mechanism was not observed.

Our results strongly suggested that Se(IV) surface affinity towards γ-Al2O3 is higher than the one of carbonate ions. Nevertheless, the competing effect of carbonate ions might impact the migration of Se(IV) by reducing the number of available sorption sites on sorbing surfaces and by enhancing desorption processes. Consequently, this should be taken into account in predicting the environmental fate of Se(IV). Therefore, we performed Surface Complexation Model (SCM) calculations triggered by the spectroscopic findings and first results will be presented. The modelling of the surface speciation based on spectroscopic results has proven to be a strong tool to gain a sustainable description of the surface processes occurring in sorption systems relevant for the safety assessment of a future nuclear waste disposal site.

[1] E. J. Elzinga, et al., J. Colloid Interface Sci. 340, 153 (2009).
[2] H. Foerstendorf, et al., J. Colloid Interface Sci. 416, 133 (2014).
[3] M. J. Comarmond, et al., Environ. Sci. Technol. 50, 11610 (2016).
  • Poster
    Migration 2017 - 16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Espania

Permalink: https://www.hzdr.de/publications/Publ-25239
Publ.-Id: 25239


Interactions between U(VI) doped CSH phases and high saline brines

Wolter, J.-M.; Schmeide, K.; Stumpf, T.
Cementitious materials will be used for the geotechnical barrier of a deep geological repository where long-lived radioactive waste like used fuel rods will be stored [1]. Calcium silicate hydrate (CSH) phases, as main component of hardened cement paste, are known for their retention potential for radionuclides like U which is the main component of used fuel rods [2].

The formation water of North German clay stone formations is characterized by high ionic strengths [3], which potentially lead to a corrosion of concrete. Thus, with respect to long-term safety assessment of cement containing repositories chemical alteration processes at high saline conditions have to be studied. Therefore, the leaching of U(VI) doped CSH phases in high ionic strengths electrolyte solutions is studied in batch experiments in combination with spectroscopic methods.

The approach of this study is to get a molecular understanding of interactions between U(VI) doped CSH phases and high ionic strengths electrolyte solutions. For this, batch leaching experiments were performed in combination with spectroscopic methods.

The formation of CSH phases is confirmed by XRD and IR / Raman spectroscopy. The TRLFS spectra obtained for U(VI) doped CSH phases are comparable to those reported by Tits et al. [4]. Thus, an incorporation of U(VI) in the CSH phases is verified. The results of leaching experiments are exemplarily shown for Ca for the CSH phase with C/S ratio of 1.6 for in Figure. 1. In presence of NaCl and Na2SO4, Ca is released into the supernatant solution. This mainly can be attributed to a release of Ca from the interlayers of CSH phases. Simultaneously, the pH values of the supernatant solutions increase to values between 11.2 and 12, depending on the C/S ratio. In the presence of NaHCO3, the Ca concentration in solution is much lower due to precipitation of CaCO3. In this case, pH values between 11.4 and 10.1 are observed.

In the presence of NaCl and Na2SO4, the release of Si and U is minimal. In the presence of NaHCO3, however, the Si and U concentration in solution is increased. Since Si can only be released from the complex layers of CSH phases, the release of Si and simultaneously, the release of U can be related to a decomposition of the CSH phases in the presence of carbonate. Spectroscopic investigations also confirmed the decomposition of CSH phases and the release of U due to carbonate.
Keywords: CSH phases, uranium, North Germany, clay stone, cement, retention, leaching, PXRD, TRLFS, IR, RAMAN, saline, salt
  • Contribution to proceedings
    MIGRATION 2017, 10.-15.09.2017, Barcelona, España
    Interactions between U(VI) doped CSH phases and high saline brines
  • Contribution to proceedings
    ABC Salt V, 26.-28.03.2017, Ruidoso, New Mexico, USA
    Proceedings of ABC Salt V
  • Poster
    ABC Salt V Actinide and Brine Chemistry in a Salt Repository Workshop (V), 26.-28.03.2017, English, USA
  • Poster
    Migration 2017 16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barça, España

Permalink: https://www.hzdr.de/publications/Publ-25238
Publ.-Id: 25238


Comparative studie of two fungi and their molecular interactions with uranium(VI) and europium(III)

Wollenberg, A.; Günther, A.; Raff, J.; Stumpf, T.
Radionuclides are widely used in industry, medicine and research. By their use, disposal, but also by accidental release radionuclides may reach the environment. There, their mobility and their behaviour is influenced by interactions with abiotic and biotic matter. As fungi are one of the most common microorganisms in nature, they have to be taken into consideration in particular. They play an important role for preservation of the soil structure and protect plants and symbiotic partners from intoxication [1, 2]. Furthermore, they interact with radionuclides in different ways leading to an immobilization and thus a reduced toxicity and a reduced migration through the soil [3, 4, 5]. The aim of this study was to investigate the binding and the uptake of uraniumVI and europiumIII, the latter as surrogate for trivalent actinides, by the two fungi Leucoagaricus naucinus and Schizophyllum commune.

First batch experiments showed the binding of UVI and EuIII by fungi depends on initial conditions. Both fungi showed a biphasic binding of the metals and interact different depending on pH value (see figure 1). In contrast, the fungi showed increasing sorption capacities with higher initial metal concentrations and lower initial biomass. Moreover, changes of the concentration of different ions in the solution before and after incubation were investigated. Furthermore, the UVI-binding of the fungi was examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS). This studies were performed in dependence on metal concentration and pH value.
In General, obtained results provide first indication that the binding behavior of both fungi is due to different binding mechanisms.
  • Lecture (Conference)
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, España

Permalink: https://www.hzdr.de/publications/Publ-25237
Publ.-Id: 25237


Annual Report 2016 Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.ORC; Bok, F.; Richter, A.
The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden – Rossendorf (HZDR). The research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”...
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-079 2017
    ISSN: 2191-8708

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Synthesis and structural characterization of mixed iron-uranium compounds with bidentate N-donor ligands

Schöne, S.ORC; Radoske, T.; März, J.; Stumpf, T.; Ikeda-Ohno, A.ORC
The reliable assessment of geochemical behavior of uranium (U) is one of the most significant issues for uranium mining sites and geological disposals of radioactive wastes. In addition to the major chemical parameters of groundwater, such as pH, ionic strength, co-existence of anionic species, etc., the oxidation state is one of the fundamental parameters which determine the geochemical behavior of uranium in aquatic environments. Under natural aquatic conditions, the redox chemistry of uranium is dominated either by uranyl(VI) (UO22+) mainly under aerobic conditions or by uranium(IV) (U4+) under anaerobic conditions [1]. The redox behavior of uranium is affected not only by solution conditions, but also by the co-existence of other redox-active ions, such as manganese (Mn) and iron (Fe) [2] which are ubiquitous in the actual aquatic environment. The interaction of U species with other redox species complicates the redox behavior of U, eventually influencing the interaction of U species with other organic ligands and inorganic anions [3,4]. Hence, the understanding of the chemical behavior of U in the presence of other redox active metals is indispensable for the reliable prediction of the geochemical behavior of U.
Based on this background, we performed a systematic study of the reactivity of U(IV) and -(VI) with Fe(II) and -(III), some of the major redox active species abundant in groundwater, in the presence of 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) as representatives of naturally occurring N-donor organic ligands. Mixing U(IV)/U(VI) with Fe(II)/Fe(III) and bipy/phen in different solution conditions yielded a wide variety of single crystals of mixed Fe-U compounds, which were further characterized by single crystal / powder X-ray diffraction and other spectroscopic methods.
In the studied iron-uranium systems, the N-donor ligand (L) is always coordinating to Fe, forming [FeII(L)3]2+ or oxo-bridged [(FeIIIL2Cl)2(µ2-O)]2+ cationic units. Uranium is not directly interacting with the ligands, existing as the counter anionic unit of [UIVCl6]2- or [UVIO2Cl4]2- in the structures. This preferable coordination of the N-donor ligands towards iron is independent of the oxidation state of uranium. The interaction of Fe(III) (oxidant) with U(IV) (reductant) naturally resulted in the formation of Fe(II)-U(VI) mixed compounds. This redox reaction is not affected by the presence of the strong N-donor ligands.
These results provide us a molecular insight into the coordination and redox chemistry of the mixed iron-uranium systems in aqueous solutions, which has direct relevance to the geochemistry of uranium. The iron-uranium compounds characterized in this study are also rare examples of such mixed metal-uranium compounds with organic ligands.
  • Lecture (Conference)
    Migration 2017 - 16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission, 11.09.2017, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25235
Publ.-Id: 25235


µTRLFS: Spatially-resolved sorption studies of Eu(III) on Äspö granite with time-resolved laser fluorescence spectroscopy

Zesewitz, K.; Schmidt, M.
Finding a safe long-term repository for high-level nuclear waste is a highly relevant global issue. To that end, the interaction of radionuclides with mineral phases contained in possible host rocks and construction materials must be understood. On a time scale of up to a million years, especially the scenario of a water intrusion into the repository and thus dissolution of radionuclides has to be considered. To investigate the sorption behaviour of actinides (e.g. Cm(III) and U(VI)O22+) and lanthanides (e.g. Eu(III)), time-resolved laser fluorescence spectroscopy (TRLFS) is a widely used method, because of its trace concentration sensitivity and capability to distinguish multiple species in complex systems. On the one hand this method gives the spectral information of the emitted fluorescence light, which allows determining the symmetry and the grade of complexation of the sorbed Ln/An. On the other hand the lifetimes of the excited electronic states provide information about the surrounding quenchers, mainly water. Typically, TRLFS investigations will focus on the interaction of an actinide with one relevant mineral phase. For a real rock formation, e.g. granite, sorption will however be a competitive process involving multiple mineral phases at the same time.
In this study a new method called µTRLFS is introduced, which will add a spatial dimension to TRLFS. By doing so, it is possible to separate the multi-phase system into discrete single-phase systems and therefore to make a step beyond model systems by investigating, for example whole natural granite rock with TRLFS. Because of its advantageous fluorescence properties we use europium as an analogue for the trivalent actinides americium and curium. Spatially resolved sorption experiments with Eu(III) on granite samples from the underground laboratory in Äspö, Sweden are presented. These samples are excited by a focused laser beam at a wavelength of 394 nm, and scanned through the laser’s focal point by an XYZ-stage with a resolution of approximately 50 µm. Through this approach it becomes possible to characterize Eu(III) sorption on single grains of the complex material by mapping fluorescence intensity, F2/F1-band ratios, as well as fluorescence lifetimes.
A combination of Raman-microscopy and energy dispersive X-ray spectroscopy (EDX) is used to reveal the mineral phase composition in each point of measurement which can then be correlated to the µTRLFS maps. On top of that EDX provides impurity distributions of e.g. iron or manganese as additional quenchers. By doing so, µTRLFS mapping of sorption capacity, complexation strength and surrounding quenchers can be correlated to phase distribution mappings and thus provide information about the sorption behaviour of each phase within the complete multi-phase system. The µTRLFS data will then be directly compared to single phase TRLFS data of the granite components quartz, feldspar and mica. For verification, the Eu(III) distribution obtained from µTRLFS data will be matched to spatially-resolved X-ray absorption spectroscopy (µXAS).
Keywords: µTRLFS, TRLFS, µXAS, granite, Raman, EDX, sorption, europium
  • Poster
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25234
Publ.-Id: 25234


Verbundprojekt WASA-BOSS: Weiterentwicklung und Anwendung von Severe Accident Codes – Bewertung und Optimierung von Störfallmaßnahmen; Teilprojekt B: Druckwasserreaktor-Störfallanalysen unter Verwendung des Severe-Accident Code ATHLET-CD – Abschlussbericht

Jobst, M.; Kliem, S.; Kozmenkov, Y.; Wilhelm, P.
Innerhalb des Vorhabens wurde ein ATHLET-CD-Eingabedatensatz für einen generischen deutschen DWR vom Typ KONVOI entwickelt. Das ATHLET-CD-Modell wurde für die Simulation schwerer Störfälle aus den Störfallkategorien Station Blackout (SBO) und Kühlmittelverluststörfällen mit kleinen Lecks (SBLOCA) eingesetzt. Dabei ist die vollständige Störfalltransiente für den Zeitbereich zwischen dem einleitenden Ereignis bis zum Versagen des Reaktordruckbehälters (RDB) abgedeckt und alle wesentli-chen Phänomene schwerer Störfällen werden abgebildet: Beginn der Kernaufheizung, Spaltproduktfrei-setzung, Aufschmelzen von Brennstoff- und Absorbermaterialien, Oxidationsprozesse mit Freisetzung von Wasserstoff, Verlagerung von geschmolzenem Material, Verlagerung in das untere Plenum, Schä-digung und Versagen des RDB. Das Modell wurde für die Analyse möglicher präventiver und mitigativer Notfallmaßnahmen für SBO und SBLOCA angewandt. Dafür wurden die Notfallmaßnahmen primärseitige Druckentlastung (PDE), primärseitiges Einspeisen mit mobilen Pumpensystemen sowie für SBLOCA das verzögerte Einspeisen der kaltseitigen Druckspeicher untersucht und die Eigenschaften und Einleitekriterien der Maßnahmen variiert. Es wurden die Zeitverläufe der Unfallszenarien analysiert und die verbleibenden Zeitspannen für die Einleitung zusätzlicher Maßnahmen ermittelt. Für ein SBO-Szenario mit PDE wurde für die Frühphase der Transiente (bis zum Beginn der Kernschmelze) eine Unsicherheits- und Sensititvitätsanalyse durchgeführt. Zusätzlich wurde für ein SBLOCA-Szenario ein Code-zu-Code-Vergleich zwischen ATHLET-CD und dem Störfallcode MELCOR erarbeitet.
Keywords: Druckwasserreaktor, Schwere Störfälle, Notfallmaßnahmen, ATHLET-CD-Simulation, Pressurized Water Reactor, Severe accidents, Accident management measures, ATHLET-CD simulations
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-080 2017

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Publ.-Id: 25233


Retention Of An(III)/Ln(III) By Calcite: Influence Of Mineral Formation On Contaminant Speciation

Schmidt, M.; Hellebrandt, S. E.; Johnstone, E. V.; Hofmann, S.; Barkleit, A.; Jordan, N.; Cherkouk, A.; Stumpf, T.
Calcite has been intensively studied for its potential to structurally incorporate trivalent actinides and lanthanides. As calcite is both a ubiquitous mineral in many host rock formations, and an important weathering product of cementitious phases it may occur in a nuclear waste disposal site as both, a primary and a secondary phase. In addition, in the far-field of such a disposal site calcite can be formed by microbiota. In order to understand if the origin of the mineral will impact its capacity to incorporate trivalent cations, we will present and compare the speciation of Eu(III) and Cm(III) in calcite formed inorganically via co-precipitation[1] and co-precipitation/phase transformation[2] with calcite formed in a microbially-induced precipitation reaction[3] and calcite contacted with Eu(III) close to equilibrium.[4]
Investigations using site-selective TRLFS reveal that the speciation of M(III) co-precipitated with calcite formed inorganically consists of three species, labelled A, B, and C, respectively, independent of the formation mechanism. The species have been characterized as two incorporation species, differing in the degree of lattice distortion, and a sorption species in contact with the solution.[1] Contrary to this behaviour the speciation of Eu(III) in both, calcite formed in a microbially-induced reaction, and after reaction with calcite close to equilibrium conditions comes to be dominated by a different incorporation species, labelled γ.
Species γ is also Eu(III) incorporated into the crystal bulk, but shows a lower symmetry than observed previously, and does not match with any of the previous species. It can be shown that the rate of formation of γ depends heavily on the recrystallization rate of the calcite used in the reaction, and that its formation is accompanied by several other species, some of which had been identified previously.
The formation of species γ as the main mode of interaction in the microbial process is particularly interesting as the reaction proceeds via vaterite, the same metastable polymorph used in a previous abiotic study. The speciation in the intermediate vaterite phases does not differ, yet the speciation in the calcite product shows little similarity.
In summary, the results highlight the importance of molecular level understanding for accurately describing the interaction of dissolved cations with surrounding mineral phases.


*Present address: Department of Materials Science and Engineering, The University of Sheffield, Sheffield, United Kingdom, S10 2TN.
[1] Schmidt, M., T. Stumpf, M. Marques Fernandes, et al., Angew. Chem. Int. Ed., 47, 5846 (2008).
[2] Schmidt, M., T. Stumpf, C. Walther, et al., J. Colloid Int. Sci., 351, 50 (2010).
[3] Johnstone, E.V., S. Hofmann, A. Cherkouk, et al., Env. Sci. Tech., 50, 12411 (2016).
[4] Hellebrandt, S.E., S. Hofmann, N. Jordan, et al., Sci. Rep., 6, 33137 (2016).

Acknowledgments. This study is supported by the Helmholtz Gemeinschaft Deutscher Forschungszentren by funding the Helmholtz Young Investigator Group “Structures and reactivity at the aqueous/mineral interface” (VH-NG-942).
Keywords: Calcite, TRLFS, actinides, europium, curium, co-precipitation, solid solutions
  • Lecture (Conference)
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spanien
  • Poster
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25232
Publ.-Id: 25232


Probing ultra-fast processes with high dynamic range at 4th-generation light sources: arrival time and intensity binning at unprecedented repetition rates

Kovalev, S.; Green, B.; Golz, T.; Maehrlein, S.; Stojanovic, N.; Fisher, A. S.; Kampfrath, T.; Gensch, M.
Understanding dynamics on ultrafast timescales enables unique and new insights into important processes in the materials and life sciences. In this respect, the fundamental pump-probe approach based on ultra-short photon pulses aims at the creation of stroboscopic movies. Performing such experiments at one of the many recently established accelerator-based 4th-generation light sources such as free-electron lasers (FELs) or superradiant THz sources allows an enormous widening of the accessible parameter space for the excitation and/or probing light pulses. Compared to table-top devices, critical issues of this type of experiment are fluctuations of the timing between the accelerator and external laser systems and intensity instabilities of the accelerator-based photon sources. Existing solutions have so far been only demonstrated at low repetition rates and/or achieved a limited dynamic range in comparison to table-top experiments, while the 4th generation of accelerator-based light sources is based on superconducting radio-frequency (SRF) technology which enables operation at MHz or even GHz repetition rates. In this article, we present the successful demonstration of ultra-fast accelerator-laser pump-probe experiments performed at an unprecedentedly high repetition rate in the few-hundred-kHz regime and with a currently achievable optimal time resolution of 13 femtoseconds (fs) (rms). Our scheme, based on the pulse-resolved detection of multiple beam parameters relevant for the experiment, allows us to achieve an excellent sensitivity in real-world ultra-fast experiments, as demonstrated for the example of THz-field-driven coherent spin precession.
Keywords: ultra-fast, high field THz

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Publ.-Id: 25231


Produktion und Reinigung von n.c.a. 89Zr am Leipziger Zyklotron für Extraktionsstudien mit Calix[4]arenen

Mansel, A.; Franke, K.
Zirkonium ist eine der Hauptverunreinigungen in Lanthanidenerzen. Um effiziente Abtrennungsverfahren von vierwertigem Zirkonium von den dreiwertigen Lanthaniden mit Hilfe der Flüssig-Flüssig-Extraktion mit Calixarenen zu entwickeln, wurde die Radiotracertechnik eingesetzt [89Zr; T1/2 = 78,4 h; Eγ = 909 keV; 99 %]. Die Produktion dieses Radionuklides wurde am Leipziger Zyklotron CYCLONE 18/9® durch die Kernreaktion 89Y(p,n)89Zr realisiert. Eine Yttriumfolie (natürliche Isotopenzusammensetzung 100 % 89Y; 80 mg) wurde mit Protonen der Energie 14 MeV bei einem Strom von 22 µA für eine Stunde bestrahlt. Das bestrahlte Target wurde für eine Stunde zum Abklingen des kurzlebigen Radionuklides 89mZr (T1/2 = 4,2 min) aufbewahrt und anschließend in konzentrierter HNO3 aufgelöst. Nach dem Eindampfen wurde der Rückstand mit 9 M HNO3 aufgenommen. Die Trennung von 89Zr vom Targetmaterial Yttrium erfolgte mit dem Ionenaustauscher UTEVA-SPEC®, wobei Y3+ mit 9 M von dem Säulenmaterial eluiert wird. 89Zr4+ wurde vom Ionentauscher mit Hilfe von 0,1 M Oxalsäure gewaschen. Der Oxalsäurekomplex wurde durch Erhitzen mit konzentrierter H2SO4 zersetzt und das n.c.a. 89Zr wurde in 1 M H2SO4 aufgenommen. Die radiochemische Ausbeute betrug (101 ± 8) %. Die Aktivität betrug fünf Stunden nach Bestrahlungsende ~ 400 MBq und die Nachweisgrenze wurde zu 7 fM (0,6 pg/L) für n.c.a. 89Zr ermittelt.
Die Flüssig-Flüssig-Extraktion erfolgte in einem Calixaren/Chloroform-System, wobei in saurer Lösung zwischen pH 1 und 5 gearbeitet wurde. Das Calixaren weist sowohl eine Phosphonatester- als auch eine Carboxylsäurefunktion auf. Die wässrige Phase (~ 5 MBq/L 89Zr und 10 µM nicht-radioaktives Zr4+) wurde mit dem zehnfachen Überschuß an Calixaren in Chloroform eine Stunde geschüttelt. Nach der Phasenseparation wurden beide Phasen mittels γ-Spektrometrie vermessen. Eine maximale Extraktionsausbeute von 95 % wurde für Zirkonium bei pH 4 ermittelt. Somit ist die Trennung von Zr und Eu realisierbar, da Eu bei pH 8 zu 98 % extrahiert wurde, bei pH 4 nur zu < 5 %.
Keywords: Zirkonium; Zyklotron; Radionuklidproduktion; Separation; Calixaren; Extraktion; Lanthanide
  • Poster
    GDCh - Wissenschaftsforum - Jahrestagung Fachgruppe Nuklearchemie, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25230
Publ.-Id: 25230


Effect of pH on the mobility of the herbicide MCPA in an artificial soil matrix: Reactive transport modelling on the basis of 3D flow patterns visualized by Positron Emission Tomography

Lippold, H.; Karimzadeh, L.; Kulenkampff, J.; Stuhlfauth, C.; Lippmann-Pipke, J.
Adsorption and transport of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in a sand-goethite matrix were investigated as a function of pH. Compared to adsorbed amounts reported for freshly prepared goethite, adsorption onto the commercial product used in this study was found to be considerably lower. Under acidic conditions, transport of MCPA was, however, significantly retarded referring to [3H]H2O as a conservative tracer. Interaction as a function of pH was geochemically modelled using the charge distribution multisite complexation (CD-MUSIC) approach. Based on this calibrated surface complexation model, breakthrough curves were calculated according to the 1D advection-dispersion-reaction equation. Retardation was slightly underestimated at low pH.
As a new approach, this study demonstrates quantitatively that discrepancies between batch and column systems can be caused by peripheral flow, i.e., not necessarily by non-equilibrium conditions, which are commonly taken into account. By means of Positron Emission Tomography (PET) using [18F]F as a radiotracer, flow patterns in the sand-goethite matrix were visualized in 3D. A pseudo-3D flow and transport model was aligned to the images. The observed flow profile was successfully simulated by assuming a peripheral zone with increased permeability and porosity. With this flow model, reactive transport of MCPA was predicted more precisely compared to the 1D calculations with the same parameter values.
  • Poster
    Jahrestagung der GDCh-Fachgruppe Nuklearchemie, 12.-13.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25229
Publ.-Id: 25229


Novel Valdecoxib Derivates by Ruthenium-catalyzed 1,3-Dipolar Cycloaddition of Nitrile Oxides with Alkynes - Synthesis and COX-2 Inhibition Affinity.

Roscales, S.; Bechmann, N.; Weiss, D. H.; Köckerling, M.; Pietzsch, J.; Kniess, T.
Novel valdecoxib-based cyclooxygenase-2 inhibitors were synthesized in one step via 1,3-dipolar cycloaddition of nitrile oxides with a series of eleven, partly novel aryl alkynes. Application of Ru(II)-catalysis leads preferably to the formation of the 3,4-diaryl-substituted isoxazoles, while under thermal heating with base the 3,5-diaryl substitution pattern is favoured. The new the 3,4-diaryl-substituted isoxazoles possessing a small substituent (H and Me) displayed high COX-2 inhibition affinity (IC50=0.042–0.073 µM) and excellent selectivity (COX-2 SI > 2000). In contrast, the 3,5-diaryl-substituted compounds displayed almost no COX activity. The application of fluoro-substituted nitrile oxides resulted in enhanced COX-2 affinity, making these compounds together with the feasible one step reaction promising candidates for the development of fluorine-18 labelled radiotracers for positron emission tomography.

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ROBL-II: A dedicated actinide beamline for X-ray spectroscopy and scattering techniques

Scheinost, A. C.; Kvashnina, K.; Hennig, C.; Exner, J.; Rossberg, A.; Schmidt, M.; Stumpf, T.
The Rossendorf Beamline (ROBL) operates since 1999 as a single-branch, double-experiment, multi-purpose X-ray beamline for radiochemistry and materials sciences. After 13 years of successful operation, the optical components of ROBL were replaced by state-of-the-art equipment, including a LN2-cooled double-crystal/double-multilayer monochromator, and a 1.2-m double-toroid focusing mirror with Pt and Rh coatings and 1.0 µrad slope errors. Since 2015, both experimental stations belong to the Institute of Resource Ecology at HZDR and are dedicated to study actinides. In 2016, a major upgrade program started to provide additional or largely improved techniques:
(1) A five-crystal Johann-type spectrometer with variable Rowland circle of 0.5 to 1 m to measure high-energy-resolution fluorescence detection XANES, XES and RIXS [1].
(2) A new 6-circle diffractometer for powder diffraction, crystal truncation rod (CTR) and resonant anomalous X-ray reflectivity (RAXR) measurements.
(3) A large 2D detector will further support the structure analysis of materials (PXRD, single crystal diffraction, PDF analysis).
(4) A new Ge-based energy dispersive detection system with ultrafast electronics to obtain detection limits for bulk XAS near or even below 1 ppm, and automated sample feeders for room temperature and cryogenic (10 K) conditions to enable a high sample throughput.
All experiments will be available from 2020 on in a control area comprising two hutches connected by a common lock room, which allows an easy exchange of radioactive samples (alpha emitters with total activity below 185 MBq) between four experimental stations.
Furthermore, ROBL-II will significantly benefit from the new electron storage ring of the ESRF installed in 2019/2020. ROBL-II’s new source, a short bending magnet, will provide a photon flux of 1013 ph/s across a wide energy range (3 to 35 keV). The much lower vertical divergence will allow us to obtain a spot size of 30 x 70 µm2 with the toroid mirror, thereby raising the photon density by an order of magnitude as compared to the current storage ring.
The complete experimental portfolio of ROBL-II will be available to users from 2020 on, for more than 200 (24-h) days per year, establishing the key role of ROBL-II for synchrotron-based actinide chemistry, and additionally providing beamtime for fundamental chemistry, catalysis, materials and earth sciences.

[1] K. O. Kvashnina and A. C. Scheinost, Journal of Synchrotron Radiation 2016, 23, 836-841.
Keywords: synchrotron actinides XAFS XES XRD CTR RAXR
  • Invited lecture (Conferences)
    AnXAS 2017: 8th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, 10.-13.04.2017, Oxford, United Kingdom
  • Lecture (Conference)
    ATAS Workshop, 06.-09.11.2018, Nice, France
  • Poster
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-25227
Publ.-Id: 25227


Glutamine metabolism as a potential target for prostate cancer radiosensitization

Tyutyunnykova, A.; Peitzsch, C.; Telegeev, G.; Dubrovska, A.
Tumor relapse associated with increased chemo- and radioresistance is a major problem for prostate cancer patients. Our previous findings suggest that altered amino acid (in particular, glutamine) metabolism can be associated with radioresistance of prostate cancer. The main aim of our project is to investigate the role of glutamine metabolism in the development of prostate cancer radioresistance and to find novel biomarkers to predict radiation treatment outcome. We used isogenic radioresistant cell lines developed from standard prostate cancer cell lines DU145, PC3, 22RV1 and LNCaP and analyzed the following parameters: the differential expression of genes involved in glutamine metabolism, cells’ tumorigenicity, metabolites of Krebs cycle, the amount of reactive oxygen species (ROS) and glutathione in cells, radioresistance of cells and DNA damage after irradiation.
Our findings suggest that glutamine metabolism contributes to prostate tumor cell proliferation, stem cell marker expression, tumorigenicity, oxidative stress, radioresistance and epigenetic changes. The combination of irradiation with inhibition of glutamine metabolism may increase the cytotoxic effects of irradiation in prostate tumor cells. Expression of the proteins involved in glutamine metabolism can be used to predict clinical outcome of prostate cancer patients. The intracellular mechanisms of the differential tumor cell sensitivity to glutamine supplementation are in the focus of ongoing study.
  • Contribution to proceedings
    Keystone symposia: Tumor Metabolism: Mechanisms and Targets (X3), 05.-09.03.2017, Whistler, Canada

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Coordination polymers of tetravalent uranium and neptunium with aromatic polycarboxylate ligands

Martin, N. P.; März, J.; Volkringer, C.; Henry, N.; Hennig, C.ORC; Ikeda-Ohno, A.ORC; Loiseau, T.ORC
Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with organic (e.g. O- or N-donor) ligands. In the particular case of actinides (An), precedent studies have reported mainly the synthesis of solid networks bearing U(VI) or Th(IV), while trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of An, the tetravalent state has been investigated most actively and large polyoxo clusters have been isolated for U or Pu. In contrast, there are very few data concerning Np(IV) compounds. In 2012, Takao et al. reported the presence of a hexanuclear cluster of Np(IV) in an aqueous solution, which is the only polyoxo cluster reported for Np(IV) thus far. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids, or other organic pollutants (e.g. phthalates).
In the present work, we studied the crystallization of U(IV) and Np(IV) with various aromatic polycarboxylate ligands in different solvents and analysed their crystal structures. In an aqueous medium, an infinite chain of An2O2(H2O)2(1,2-bdc)2 (An = U, Np) were isolated in the presence of phthalate. This compound crystallizes as aggregates of green or orange plates for U and Np, respectively. With mellitic acid the oxidation of Np(IV) to Np(V) was observed and led to large green plates. Single-crystal XRD analysis revealed layers of {NpO7H2O0-2} units linked to each other via trans-dioxo neptunyl bonds. Similar coordination environments have been observed in other neptunium(V) compounds. To the contrary, the same synthesis procedure with U(IV) led to an U(IV)-based compound: U2(OH)2(H2O)2(mel), in which two uranium atoms are linked by hydroxo groups; mellitate ligands stabilize and connect these dinuclear units.
The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear moiety of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure. The corresponding structure reveals for the first time the isolation of the hexanuclear cluster An6O8 with Np(IV). These clusters are linked by the ligand creating tetrahedral and octahedral voids in the structure.
Keywords: actinides, uranium, neptunium, tetravalent, single-crystal X-ray diffraction, carboxylate, polymer, cluster
  • Lecture (Conference)
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (Migration 2017), 10.-15.09.2017, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-25225
Publ.-Id: 25225


Thermal Anemometry Grid Sensor

Arlit, M.; Schleicher, E.; Hampel, U.
A novel thermal anemometry grid sensor was developed for the simultaneous measurement of cross-sectional temperature and axial velocity distribution in a fluid flow. The sensor consists of a set of temperature resistors arranged in a regular grid. Each temperature resistor allows the simultaneous measurement of fluid temperature via electrical resistance and of flow velocity via constant voltage thermal anemometry. Cross-sectional measurement is enabled by applying a special multiplexing-excitation scheme. In this paper we report on the design and characterization of a prototypical sensor.
Keywords: Temperature measurement, thermal anemometry, grid sensor

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Permalink: https://www.hzdr.de/publications/Publ-25224
Publ.-Id: 25224


Thermofluiddynamische und konstruktive Auslegung sowie Aufbau und Inbetriebnahme eines Strömungskanals zur Untersuchung des konvektiven Wärmeübergangs an innovativen Rippenrohren

Stasch, P.
Im Rahmen dieser Diplomarbeit wird die thermofluiddynamische und konstruktive Auslegung eines Strömungskanals zur Untersuchung von innovativen Rippenrohrdesigns beschrieben. Die Kernmotivation stellt dabei die Verbesserung des luftseitigen Wärmeübergangs an berippten Rohren dar. Dieser ist der limitierende Faktor für die Leistungsfähigkeit von luftgekühlten Rippenrohrwärmeübertragern. Der luftseitige Wärmeübergang ist von mehreren Faktoren, wie dem Rippendesign, dem Rippenabstand oder dem Strömungsfeld zwischen den Rippen abhängig. Demzufolge ist der Einfluss von geometrischen Parametern auf Wärmeübergangs- und Druckverlustcharakteristika bereits seit Jahren Untersuchungsgegenstand zahlreicher Studien. Die vorgelegte Arbeit gibt einen Überblick über die bisher untersuchten Geometrieparameter und deren Einfluss auf den Wärmeübergang. Wie aus der Literaturrecherche hervorgeht, bleibt die Untersuchung des Einflusses der radialen Wärmeleitung innerhalb einer Rippe, des Rippenwirkungsgrades oder auch des Anströmwinkels bis dato weitestgehend unberücksichtigt. Diese Arbeit beschreibt die Auslegung und Konstruktion eines Strömungskanals zur experimentellen Untersuchung dieser Einflussgrößen. Zur Bestimmung der Abmessungen des Strömungskanals wurde ein Rippenrohr unter festgelegten Randbedingungen ausgelegt, um einen Rippenwirkungsgrad von 30% zu erreichen. Möglichst große Rippenhöhen ermöglichen eine Untersuchung der radialen Wärmeleitung innerhalb der Rippen. Ein Wärmestrom wird mithilfe elektrischer Heizstäbe im Inneren des Rohres erzeugt.Auf der Grundlage der Dimensionen desRippenrohres wurde die Querschnittsfläche des Strömungskanals festgelegt. Zur Gewährleistung eines homogenen Strömungsprofils am Eintritt in die Testsektion wurden geeignete Einbauten zur Strömungsgleichrichtung ausgewählt. Um den Einfluss des Anströmwinkels untersuchen zu können, bietet der Strömungskanal zudem die Möglichkeit Rippenrohre in unterschiedlichen Neigungswinkeln zu installieren. Des Weiteren wurde geeignete Messtechnik im Strömungskanal installiert, mit der es möglich ist, die zur Bestimmung des Wärmeübergangs notwendigen physikalischen Größen zu erfassen. Im letzten Abschnitt der Diplomarbeit wurden die durch die Messgeräte bedingten Unsicherheiten bei der Bestimmung der charakteristischen Größen zur Beschreibung des konvektiven Wärmeübergangs ermittelt. Der Strömungskanal bietet die Möglichkeit, Rippenrohre in einem homogenen Strömungsfeld unter verschiedenen Anströmwinkeln experimentell untersuchen zu können. Der Bau des Strömungskanals leistet einen Beitrag den luftseitigen Wärmeübergang an Rippenrohren besser verstehen zu können, um so die Effizienz luftgekühlter Rippenrohrwärmeübertrager mithilfe innovativer Rippendesigns weiter zu verbessern.
  • Diploma thesis
    TU Dresden, 2017
    Mentor: Sebastian Unger, Matthias Beyer
    150 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-25223
Publ.-Id: 25223


A novel nanobody-based target module for retargeting of T lymphocytes to EGFR-expressing cancer cells via the modular UniCAR platform

Albert, S.; Arndt, C.; Feldmann, A.; Bergmann, R.; Bachmann, D.; Koristka, S.; Ludwig, F.; Ziller-Walter, P.; Kegler, A.; Gärtner, S.; Schmitz, M.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Pietzsch, H.-J.; Pietzsch, J.; Steinbach, J.; Bachmann, M.
Recent treatments of leukemias with chimeric antigen receptor (CAR)-expressing T cells underline their impressive therapeutic potential. However, once adoptively transferred into patients, there is little scope left to shut them down after elimination of tumor cells or in case adverse side effects occur. This becomes of special relevance if they are directed against commonly expressed tumor associated antigens (TAAs) such as receptors of the ErbB family. To overcome this limitation, we recently established a modular CAR platform technology termed UniCAR. UniCARs are not directed against TAAs but instead against a unique peptide epitope on engineered recombinant targeting modules (TMs) which guide them to the target. In the absence of a TM UniCAR T cells are inactive. Thus an interruption of any UniCAR activity requires an elimination of unbound TM and the TM complexed with UniCAR T cells. Elimination of the latter one requires a disassembly of the UniCAR-TM complexes. Here we describe a first nanobody (nb)-based TM directed against EGFR. The novel TM efficiently retargets UniCAR T cells to EGFR positive tumors and mediates highly efficient target-specific and target-dependent tumor cell lysis both in vitro and in vivo. After radiolabeling of the novel TM with 64Cu and 68Ga we analyzed its biodistribution and clearance as well as the stability of the UniCAR-TM complexes. As expected unbound TM is rapidly eliminated while the elimination of the TM complexed with UniCAR T cells is delayed. Nonetheless, we show that UniCAR-TM complexes dissociates in vitro and in vivo in a concentration-dependent manner in line with the concept of a repeated stop and go retargeting of tumor cells via the UniCAR technology.
Keywords: CAR, EGFR, Retargeting, T cell, T cell therapy

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Publ.-Id: 25222


CFD-Simulation of boiling in a heated pipe including flow pattern transitions using the GENTOP concept

Höhne, T.; Krepper, E.; Lucas, D.; Montoya, G.
Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Finally the above mentioned boiling pipe is considered as demonstration case.
Keywords: CFD, GENTOP, multiphase flow, AIAD, boiling
  • Contribution to proceedings
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xian, China
  • Lecture (Conference)
    The 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xian, China
  • Open Access Logo Nuclear Engineering and Design 322(2017), 165-176
    DOI: 10.1016/j.nucengdes.2017.06.047

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Permalink: https://www.hzdr.de/publications/Publ-25221
Publ.-Id: 25221


Recent Developments in CFD Modeling of Multiphase Flows in Energy related Industrial Applications

Höhne, T.
Two-phase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a clear requirement for numerical tools. Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive. Since large scale applications are considered such as chemical reactors or components of the cooling system of a nuclear power plant the Euler-Euler two- or multi fluid model is the base for the development. Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our multiphase flow research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered. A second focus is to establish modelling frameworks as iMUSIG, AIAD and GENTOP to allow a proper consideration of the local physical phenomena. These activities will help to improve the CFD code capabilities in energy related industrial applications.
Keywords: CFD, iMUSIG, AIAD, GENTOP, multiphase flow
  • Contribution to proceedings
    The 7th International ENERGY Conference & Workshop - REMOO, 10.-12.05.2017, Venedig, Italien
  • Invited lecture (Conferences)
    The 7th International ENERGY Conference & Workshop - REMOO, 10.-12.05.2017, Venedig, Italien

Permalink: https://www.hzdr.de/publications/Publ-25220
Publ.-Id: 25220


CFD-simulation of boiling in a heated pipe including flow pattern transitions using a multi-field concept

Höhne, T.; Krepper, E.; Lucas, D.; Montoya, G.
Boiling flow inside a wall heated vertical pipe is simulated by a multi-field CFD approach. Sub-cooled water enters the pipe from the lower end and heats up first in the near wall region leading to the generation of small bubbles. Further along the pipe larger and larger bubbles are generated by coalescence and evaporation. This leads to transitions of the two-phase flow patterns from bubbly to churn-turbulent and annular flow. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach. It allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The paper presents the extension of the GENTOP model for phase transfer and discusses the sub-models used. Finally the above mentioned boiling pipe is considered as demonstration case.
Keywords: multi-phase, boiling, GENTOP, multi-scale, CFD
  • Contribution to proceedings
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 30.05.-01.06.2017, Trondheim, Norwegen
  • Lecture (Conference)
    12th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, 30.05.-01.06.2017, Trondheim, Norwegen

Permalink: https://www.hzdr.de/publications/Publ-25219
Publ.-Id: 25219


Application of computational fluid dynamics (CFD) codes for nuclear power plant design

Krause, M.; Smith, B.; Höhne, T.
The nuclear industry recognises that CFD codes have reached the desired level of maturity (at least for single-phase applications) to be used as part of the NPP design process, and it is the objective of this IAEA Coordinated Research Project (CRP) to assess their current capabilities in this regard, and contribute to the technology advance in respect to their verification and validation. Currently, this CRP is ongoing, with participation from 14 member states to address the issue, following a three-pronged approach:
1. Preparation of a Summary Document to put on record the use of CFD in the nuclear reactor design process;
2. Development of (four) detailed, NPP design-oriented CFD benchmark exercises; and
3. Documentation of participants’ CFD simulations of these benchmarks, including the use of best-practice recommendations.
This paper describes the structure of the CRP, the Summary Document, and two of the benchmarks launched. Both benchmarks are related to safety issues in PWRs and are based on completed, but not yet published, measured data from ROCOM facility tests: one related to pressurized thermal shock (PTS) and the other to boron dilution.
Keywords: IAEA, ROCOM, CFD, PTS, CRP, NPP
  • Contribution to proceedings
    IAEA International Conference on Topical Issues in Nuclear Installation Safety, 06.-09.06.2017, Wien, Österreich
  • Lecture (Conference)
    IAEA International Conference on Topical Issues in Nuclear Installation Safety, 06.-09.06.2017, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25218
Publ.-Id: 25218


A combined EXAFS spectroscopic and quantum chemical study on the complex formation of Americium(III) with formate

Froehlich, D. R.; Kremeleva, A.; Rossberg, A.; Skerencak-Frech, A.; Koke, C.; Krueger, S.; Panak, P. J.
The pH-dependent (pH 2 - 4) formation of aqueous Am(III) complexes with formate (Form) is studied by EXAFS, iterative target transformation factor analysis (ITFA) and by quantum chemical calculations [1]. According to thermodynamical calculations three complexes (aq. Am3+, AmForm2+, AmForm2+) coexist and change their fractions, so that EXAFS spectral mixtures occur. A maximal spectral change of only 9% is observed between the different Am LIII-edge EXAFS spectra, which rules out the direct use of conventional shell fit analysis for structural investigation prior to the decomposition of the spectra into the single spectral components by ITFA. By combining pH-speciation calculations with quantum chemistry, the pH-dependent number of coordinated water and formate molecules is calculated and used as constraint for a modified ITFA-approach. The decomposition results in the separate spectral contributions of the exchanged molecules, hence the signal of a coordinated water and a monodentate coordinated formate molecule for which the structural parameters are determined by shell-fitting and are compared with twelve complex structures gained by quantum chemical calculations. Methodologically consistent, the prevailing coordination numbers are 9, 9 and 8 for the aq. Am3+, AmForm2+ and AmForm2+ complexes, respectively [2]. Low concentrations of species with other coordination numbers and modes cannot be excluded, as energy differences obtained by our quantum chemical calculations are small [2].

This work shows the power of the proposed ITFA-framework in obtaining structural information for weak ligand systems like formate, where conventional EXAFS data analysis fails due to the lower spectroscopic resolution in analysing mixtures of metal species.


References
[1] Rossberg et al., Anal. Bioanal. Chem. 376, 631-638 (2003).
[2] Fröhlich et al., Inorg. Chem. submitted (2017).
Keywords: EXAFS, iterative target transformation factor analysis, ITFA, Americium
  • Lecture (Conference)
    8th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, 11.-13.04.2017, Oxford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-25217
Publ.-Id: 25217


Li, Co, Nd ... - Strategische Metalle für die Elektromobilität

Rudolph, M.ORC
Elektromobilität ist zurzeit in aller Munde; von eAutos, eBikes und Pedelecs hat jeder schon gehört. Die 32. Hochschultage Physik widmen sich dem gegenwärtigen Stand der Technik und der Zukunft dieses spannenden Forschungsgebietes. Vortragende aus Wissenschaft und Industrie greifen ein breites Spektrum an Aspekten auf, das sicherlich Anregungen für lebhafte Diskussionen bietet.
Die Veranstaltung richtet sich nicht nur an Lehrerinnen und Lehrer, sondern auch an die breite Öffentlichkeit, an Studierende und natürlich auch an die Mitglieder des Fachbereichs Physik.
  • Invited lecture (Conferences)
    32. Hochschultage Physik, 13.-14.02.2017, Marburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25216
Publ.-Id: 25216


Als Ingenieur in der Forschung - an der Grenzfläche von Wissenschaft, Gesellschaft und Anwendung

Rudolph, M.ORC
Ingenieure sind vielseitige Problemlöser und daher sehr gefragt in der Forschung, sowohl in Industrie wie auch in der Wissenschaft. Noch bis ins 19. Jahrhundert aber waren Ingenieure nicht wirklich geduldet als Wissenschaftler, nicht ohne Grund ist der Doktorgrad der Ingenieurwissenschaften in Deutschland seit dem als einziger nicht lateinisch und versehen mit einem Bindestrich, also Dr.-Ing. und nicht Dr. rer. tech. Der moderne Ingenieur ist aber schon längst ein angewandter Naturwissenschaftler und nicht nur geschickter Tüftler. Der Beitrag soll anhand der eigenen Erfahrungen des Vortragenden einen Einblick geben über die spannenden Themen eines Ingenieurs in der Forschung. Ganz speziell werden darüber hinaus die Felder der Grenzflächenverfahrenstechnik und der Ressourcentechnologie vorgestellt und aufgegriffen. Dabei soll auch das Spannungsfeld aus Wissenschaft, Gesellschaft und Anwendung beleuchtet werden.
  • Invited lecture (Conferences)
    VDI suj Freiberg - Stammtisch, 09.01.2017, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25215
Publ.-Id: 25215


Targeting stem cells in radiation oncology

Coppes, R.; Dubrovska, A.
At the annual conference of the Association for Radiation Research held in Oxford 26-28 June 2017, one session focused on the potential of targeting stem cells in radiation oncology. Cancer stem cells (CSCs) are highly tumorigenic cells capable to self-renew and to give rise to all other tumour cells. Emerging clinical evidence links CSCs to the risk of tumour relapse and suggests that therapeutic targeting of CSC populations in combination with radiotherapy might be a promising approach to improve local tumour control. This editorial outlines the concept of cancer stem cells in radiation biology and the main avenues for tumour radiosensitisation by anti-CSC therapies.
Keywords: Cancer stem cells, Radiotherapy, Biomarker, Prediction, Radiosensitisation

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Permalink: https://www.hzdr.de/publications/Publ-25214
Publ.-Id: 25214


Multistage bioassociation of uranium(VI) on a halophilic archaeum investigated with luminescence spectroscopic and microscopic techniques

Bader, M.; Steudtner, R.; Drobot, B.; Cherkouk, A.
Luminescence spectroscopy and microscopy are powerful tools to study the chemistry of f-elements (actinides – An, lanthanides – Ln) in trace concentration. Manifold operating modes (e.g. steady-state, time-resolved, laser-induced, site-selective, cryogenic, etc.) can be used to investigate the environmental behaviour of An/Ln in various geological and biological systems. In this study the halophilic archaeum Halobacterium noricense DSM-15987T, which commonly occurs in rock salt [1], a potential host rock formation for the deep geological disposal of radioactive waste, was used to characterize its interaction processes with uranium(VI). The bioassociation showed differences regarding initial uranium concentration (30 and 85 µM) and incubation time (up to two weeks). The lower uranium concentration caused a multistage association behaviour with a desorption phase after 5 h of exposure to uranium. A further difference provoked by uranium concentration was the cell agglomeration. This formation was pronounced at higher uranium(VI) concentration. For lower uranium(VI) concentration agglomerate formation took longer, but still occurred. To understand these processes on a molecular level, time-resolved laser-induced fluorescence spectroscopy at low temperature of 153 K (cryo-TRLFS) was applied. Changes detected in the batch experiments were confirmed with cryo TRLFS. The spectroscopic analyses showed the involvement of a polynuclear carboxylate species and the presence of a meta-autunite like uranium(VI) mineral phase [2]. A fraction analysis revealed that the biomineralization process (formation of meta-autunite) is more pronounced at lower uranium(VI) concentration. At the higher uranium(VI) concentration of 85 µM polynuclear carboxylate species were dominating. This could be explained with the higher toxicity of uranium(VI) and the accompanying cell agglomeration, which was more pronounced at higher uranium(VI) concentration. In combination with other spectroscopic (e.g. infrared spectroscopy) and microscopic tools (e.g. scanning electron microscopy) the applied luminescence methods were essential for a better understanding of the bioassociation process of uranium(VI) to cells of the halophilic archaeon.

[1] A. Gramain, Environ. Microbiol. 2011, 13, 2105-2121. [2] M. Bader, submitted to Environ. Sci. Technol. [3] S. Fröls, Biochem. Soc. Trans. 2013, 41, 393-398.
  • Poster
    ANAKON 2017, 03.-06.04.2017, Tübingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25213
Publ.-Id: 25213


Chemical speciation of trivalent lanthanides and actinides in body fluids

Barkleit, A.ORC; Wilke, C.
In case of incorporation into the human body, heavy metals and radionuclides potentially represent serious health risks due to their chemo- and radiotoxicity. In order to assess their toxicological behavior, such as transport, metabolism, deposition, and elimination from the human organisms, the understanding of their in vivo chemical speciation on a molecular level is crucial. In order to improve our understanding of the behavior of trivalent actinides (An(III)) and lanthanides (Ln(III)) in the human body, the present study focuses on the chemical speciation of An(III) and Ln(III) in the gastrointestinal tract. The human gastrointestinal system was simulated by using an in vitro digestion model, which is part of an international unified bioaccessibility method (UBM), developed by the Bioaccessibility Research Group of Europe (BARGE) [1]. To verify the model, natural human saliva samples were included in the speciation investigation [2].
The speciation of curium(III) (Cm(III)) and europium(III) (Eu(III)) in the gastrointestinal tract as well as in human natural saliva has been studied by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS). The standard model body fluids and the natural saliva samples were spiked in vitro with Cm(III) and Eu(III) in trace metal concentrations.
The dominant chemical species in the human saliva was identified by a comparison of the natural human sample spectra with reference spectra obtained for synthetic saliva and individual components of the body fluid. Linear combination fitting analysis on the sample spectra indicates the formation of 60-90% inorganic- and 10-40% organic species of Cm(III)/Eu(III) in the salivary media. Ternary M(III) complexes containing phosphate and carbonate anions with the additional counter-cation calcium are formed as the main inorganic species. Complexes with the digestive enzyme α-amylase and the protein mucin (to a minor extent) represent the major part of the organic species. When the M(III) reached the stomach, the metal complexes were dissociated due to the high acidic conditions. That is, Cm(III) and Eu(III) are mainly present as the aquo ion, and only a small part (about 20%) is coordinated by the protein pepsin. When entering the intestine the metal ions are strongly bound by the protective protein mucin (about 65%) and inorganic ligands (about 35%; mainly carbonate and phosphate).

References
[1] J. Wragg, M. Cave, H. Taylor, N. Basta, E. Brandon, S. Casteel, C. Gron, A. Oomen, T. van de Wiele, British Geological Survey Open Report OR/07/027, Keyworth, Nottingham (2009) 90 pp.
[2] A. Barkleit, C. Wilke, A. Heller, T. Stumpf, A. Ikeda-Ohno, Dalton Trans. 46 (2017), 1593-1605
  • Invited lecture (Conferences)
    2nd International Conference on Pollutant Toxic Ions and Molecules, PTIM2017, 06.-09.11.2017, Caparica, Portugal

Permalink: https://www.hzdr.de/publications/Publ-25212
Publ.-Id: 25212


Speziation trivalenter f-Elemente in den Biofluiden des Verdauungssystems

Barkleit, A.ORC; Wilke, C.
Im Falle einer Inkorporation radioaktiver Stoffe entstehen ernsthafte gesundheitliche Risiken durch deren Chemo- und Radiotoxizität. Um die möglichen toxischen Effekte besser abschätzen und letztendlich verhindern zu können, ist es notwendig, die Speziation dieser Elemente im menschlichen Organismus auf molekularer Ebene zu verstehen. Die Speziation beeinflusst die Aufnahme, den Transport, den Metabolismus, die Einlagerung und die Ausscheidung der Elemente.
Die Gefahr einer oralen Aufnahme von Radionukliden besteht durch kontaminierte Lebensmittel oder Trinkwasser. Deshalb haben wir die Speziation von ausgewählten dreiwertigen Actiniden und Lanthaniden (Cm(III) und Eu(III)) in den Biofluiden des Verdauungstraktes näher untersucht. Die Biofluide wurden nach einer international anerkannten Methode (Unified Bioaccessibility Method, UBM) der Bioaccessibility Research Group of Europe (BARGE) synthetisch hergestellt [1]. Parallel dazu wurden natürliche menschliche Speichelproben zum Vergleich in die Untersuchungen einbezogen [2].
Die Speziatonsuntersuchungen von Cm(III) und Eu(III) in den Verdauungsfluiden wurden mit Hilfe der zeitaufgelösten laserinduzierten Fluoreszenzspektroskopie (Time-Resolved Laser-induced Fluorescence Spectroscopy, TRLFS) durchgeführt. Für Speichel wurde ermittelt, dass sich zum größten Teil (60-90%) anorganische Komplexe bilden, darunter dominiert ein ternärer Komplex mit Phosphat und Carbonat als Liganden und Calcium als weiterem Kation zum Ladungsausgleich. Organische Komplexe, hauptsächlich mit dem Verdauungsenzym α-Amylase, wurden ebenfalls nachgewiesen. Wenn die Speichelmischung den Magen erreicht, findet aufgrund des niedrigen pH-Wertes im Magen (pH<2) eine Dissoziation der Komplexe statt, Cm(III) und Eu(III) liegen dann hauptsächlich in Form ihrer Aquo-Komplexe vor. Aber ein kleiner Teil der Metallionen (ca. 20%) bildet trotz des niedrigen pH-Wertes Komplexe mit dem Verdauungsenzym Pepsin. Im Dünndarm, wo die eigentliche Verdauung und die Absorption der (Nähr-, aber auch Gift-)Stoffe in den Blutkreislauf stattfindet, werden die Metallionen hauptsächlich (ca. 65%) von dem Protein Muzin komplexiert, welches Hauptbestandteil der schützenden Schleimhaut (Mucosa) ist, und ca. 35% liegen als anorganische Spezies mit Phosphat und Carbonat als Liganden vor.

Referenzen

[1] J. Wragg et al., British Geological Survey Open Report OR/07/027, Keyworth, Nottingham, 2009, 90 pp.
2] A. Barkleit et al., Dalton Trans. 46, 2017, 1593-1605.
  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2017, 10.-14.09.2017, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25211
Publ.-Id: 25211


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