Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41709 Publications

Experimental investigations on two-phase flows in a vertical pipe using ultrafast electron-beam X-ray tomography

Banowski, M.; Lucas, D.; Beyer, M.; Szalinski, L.; Hampel, U.

Abstract

At the Institute of Fluid Dynamics in the Helmholtz-Zentrum Dresden-Rossendorf, two-phase flow experiments at a vertical pipe are performed using ultrafast X-ray tomography. In comprehensive experimental series, upward flows, counter-current flows as well as downward flows were investigated. In this compact, developed processing methods and selected results of these experiments are presented.

Keywords: two-phase flow; bubbles; TOPFLOW; vertical pipe

Involved research facilities

  • TOPFLOW Facility
  • Lecture (Conference)
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.2014, Frankfurt am Main, Deutschland
  • Contribution to proceedings
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.2014, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20229


Ga-reiche Schichten in Si – vom Supraleiter zum Isolator

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.

Involved research facilities

Related publications

  • Lecture (Conference)
    51. Treffen der Nutzergruppe Ionenimplantation, 03.04.2014, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20228


Supraleitende Schichten in Ge und Si – Einfluss der Ausheilbedingungen

Fiedler, J.; Heera, V.; Skrotzki, R.; Herrmannsdörfer, T.; Voelskow, M.; Hübner, R.; Schmidt, B.; Skorupa, W.; Helm, M.

Involved research facilities

Related publications

  • Lecture (Conference)
    35. Treffen der Nutzergruppe Heißprozesse und RTP, 02.04.2014, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20227


On the joint multi point simulation of discrete and continuous geometallurgical parameters

van den Boogaart, K. G.; Tolosana-Delgado, R.; Lehmann, M.; Mueller, U.

Abstract

Geometallurgical parameters are descriptions of the mineralogy and microstructure of the ore determining its mineralogical and microstructural characteristics. From a conditional geostatistical simulation of such properties, a processing model could compute recovery, equipment usage, processing costs, and thus the monetary value for mining and processing the block with certain processing parameters. This can be used for optimizing mining sequences or finding optimal processing parameters by solving the corresponding stochastic optimization problem.
The approach requires two properties of the simulation not provided by established geostatistical techniques:
1) Many relevant geometallurgical parameters are from non-Euclidean statistical scales like (mineral) compositions, (grain size) distribution, (grain) geometry, (stratigraphic type) categorical, etc., which might produce impossible values when simulated with standard geostatistical techniques.
2) Due to the nonlinearity of processing, the whole conditional distribution of the geometallurgical parameters is relevant and not only its mean and variance. The geostatistical simulation needs to reproduce the joint conditional distributions of all the geometallurgical parameters.
We have developed a multi-point conditional geostatistical simulation technique, which allows for jointly simulating dependent spatial variables from various sample spaces. The technique combines an MPS-type infill simulation with a new form of distributional regression to estimate conditional distributions of arbitrary scales from different information sources, including training images, training models and observed data. The distributional regression is based on a generalization of logistic regression and has some relation to both BME-type geostatistics and high order cumulants.
The method ensures simulated data to reside within the constrained sample space and honour the characteristics of the joint distribution to be reproduced. The computational effort is substantial, but affordable for a useful application with standard problems: from processing-aware block value prediction and block processing optimization as we show in the test application to a completely defined simulated model situation with a complex processing model.

Keywords: geostatistical simulation; non Euclidean scales; geometallurgy

  • Lecture (Conference)
    SMP 2014, Ore Body modelling and strategic mine planning, 24.-25.11.2014, Perth, Australia
  • Contribution to proceedings
    SMP 2014, Ore Body modelling and strategic mine planning, 24.-25.11.2014, Perth, Australia
    Orebody Modelling and Strategic Mine Planning, SMP 2014, Integrated mineral investment and supply chain optimisation, Charlton Victoria, Australia: Australasian Institute of Mining and Metallurgy, 987-1-925100-19-8, 379-388

Permalink: https://www.hzdr.de/publications/Publ-20226


Combined PET/MR: Where Are We Now? Summary Report of the Second International Workshop on PET/MR Imaging April 8–12, 2013, Tubingen, Germany

Bailey, D. L.; Barthel, H.; Beuthien-Baumann, B.; Beyer, T.; Bisdas, S.; Boellaard, R.; Czernin, J.; Drzezga, A.; Ernemann, U.; Franzius, C.; Gückel, B.; Handgretinger, R.; Hartenbach, M.; Hellwig, D.; Nadel, H.; Nekolla, S. G.; Pfluger, T.; Pichler, B. J.; Quick, H. H.; Sabri, O.; Sattler, B.; Schäfer, J.; Schick, F.; Siegel, B. A.; Schlemmer, H. P.; Schwenzer, N. F.; van den Hoff, J.; Veit-Haibach, P.; Wehrl, H. F.

Abstract

This workshop was held a year after the initial positron emission tomography/magnetic resonance (PET/MR) workshop in Tübingen, which was recently reported in this journal. The discussions at the 2013 workshop, however, differed substantially from those of the initial workshop, attesting to the progress of combined PET/MR as an innovative imaging modality. Discussions were focused on the search for truly novel, unique clinical and research applications as well as technical issues such as reliable and accurate approaches for attenuation and scatter correction of PET emission data. The workshop provided hands-on experience with PET and MR imaging. In addition, structured and moderated open discussion sessions, including six dialogue boards and two roundtable discussions, provided input from current and future PET/MR imaging users. This summary provides a snapshot of the current achievements and challenges for PET/MR.

Keywords: Combined imaging; Molecular imaging; PET/CT; PET/MR; Quantification; MRbased attenuation correction methods; Oncology; Paediatric oncology; Neurology; Cardiology

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-20225


High-Speed PIXE: Fast Elemental Analysis with a Colour X-Ray Camera

Buchriegler, J.; von Borany, J.; Hanf, D.; Merchel, S.; Munnik, F.; Nowak, S. H.; Renno, A. D.; Scharf, O.; Ziegenrücker, R.

Abstract

A new PIXE-beamline equipped with a full-field energy dispersive X-ray camera [1,2] has recently been put into operation at HZDR. This so-called SLcam® comprises poly-capillary optics guiding the proton-induced X-ray fluorescence radiation towards a 264×264 pixel pnCCD-chip, each with an energy resolution of 156 eV (@Mn Kα). Two X-ray optics are available, with a magnification of one and six, allowing a field of view of 12×12 mm² and 2×2 mm², respectively. Attached to a large sample analysis vacuum chamber containing a precision sample manipulator, high throughput of even large samples is feasible. Additionally, a beam broadening system ensures a homogeneous illumination of the detection area and an optical microscope allows correlative superimposition of the PIXE maps with optical images. The single CCD pixel size is 48×48 µm² leading to a lateral resolution better than 100 µm for the 1:1 optics. By using sub-pixel resolution algorithms imaging of single capillary channels (25 µm) is expected.
The new setup is mainly developed for the investigation of geological samples for resource technology research which comprises the analysis of grain composition and intergrowths as well as the determination of rare earth element distributions. The simultaneous measurement of a huge array of pixel enables a fast overview over a large region of the sample with first results becoming visible almost immediately. Together with the PIGE implementation at the classical micro-beamline at HZDR this new approach allows analysis of most of the elements of interest in mineralogy.
First results concerning lateral resolution and detection limits on geological samples are encouraging. Due to the low background in the PIXE spectra investigation of trace elements with concentrations below 0.1 at.% is achievable.

[1] O. Scharf et al., Anal. Chem., Vol. 83, pp. 2532-2538 (2011).
[2] I. Ordavo et al., NIM A, Vol. 654, pp. 250-257 (2011).

Keywords: High-Speed PIXE; SLcam; polycapillary optics; pnCCD; lateral resolution; resource technology; mineralogy; trace elements

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    14th International Conference on Nuclear Microprobe Technology and Applications, 06.-11.07.2014, Padova, Italy

Permalink: https://www.hzdr.de/publications/Publ-20224


A Baseline Model for Monodisperse Bubbly Flows

Rzehak, R.; Krepper, E.; Ziegenhein, T.; Lucas, D.

Abstract

For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. The quest for models with a broad range of applicability allowing predictive simulations is an ongoing venture. A set of closure relations for adiabatic bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. In order to allow predictive simulations the model must work for a certain range of applications without any adjustments. This is shown here for flows that allow to impose a fixed bubble size distribution which bypasses the need to model coalescence and breakup processes.

Keywords: Dispersed gas-liquid multiphase flow; Euler-Euler two-fluid model; closure relations; CFD simulation; model validation

Involved research facilities

  • TOPFLOW Facility
  • Contribution to proceedings
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norway
    Proceedings of CFD2014
  • Lecture (Conference)
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-20223


Monodisperse bubbly flows with ANSYS CFX and OpenFOAM: A comparison

Kriebitzsch, S.; Rzehak, R.; Lucas, D.

Abstract

Within the framework of two-fluid modelling, the interfacial transfer processes needs to be modelled by suitable closure relations. Based on previous experience with ANSYS CFX (e.g Rzehak and Krepper, 2013) a set of closure relations applicable for adiabatic bubbly flow has been implemented in OpenFOAM. Great effort has been made to match all details of the models so that the same results may be expected and residual differences should be only due to different numerical procedures.
In this work we compare simulation results for dispersed gas-liquid pipe flow with experimental data given by Liu (1998) as well as in-house data obtained with the MTLoop facility described in Lucas et al. (2005). Overall, the experimental data are reasonably well predicted and the predictions are competitive with the results computed with ANSYS CFX. However some differences can be observed, especially in the turbulent quantities in the near wall region

Keywords: Dispersed gas-liquid multiphase flow; two-fluid model; model validation; closure relations

  • Contribution to proceedings
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norwegen
    Proceedings of the 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries
  • Lecture (Conference)
    CFD2014: 10th International Conference on Computational Fluid Dynamics In the Oil & Gas, Metallurgical and Process Industries, 17.-19.06.2014, Trondheim, Norwegen

Permalink: https://www.hzdr.de/publications/Publ-20222


Analysis of EXAFS spectra with the aid of neural networks: Aqueous U(VI) complexes with aliphatic (hydroxy-) carboxylic acides

Rossberg, A.; Domaschke, K.; Lucks, C.; Tsushima, S.

Abstract

Sixty U LIII-edge EXAFS spectra from 13 structurally different aliphatic ((di-)hydroxy-) carboxylic acids (acetic, succinic, tartaric, lactic, 3-hydroxybutyric, citric, formic, malic, maleic, malonic, oxalic, propionic, and tricarballylic acid) were measured at different pH, uranium and ligand concentrations. Each of the ligands can form several metal complexes, which may coexist as mixtures depending on the physicochemical parameters (pH, concentration).. The ligands were chosen in such a way that they would allow a structural analysis of the complexes solely by using the exclusion principle, i.e. by comparing the spectra with respect to pH, concentration, presence/absence, number, position and the type of the functional group/s. Due to the high number of different constellations in this highly correlated system, simple inspection by eye and other conventional tools will possibly lead to different solutions and is therefore prone to misinterpretation. Artificial neural networks, such as self-organizing maps (SOM), are expected to be better adapted and more specialized for dealing with such highly complex systems. We show that the inclusion of the Beer-Lambert law, in the training period of SOM, leads to a new kind of supervised learning algorithm [1] which enables the determination of the spectra and fractions of the different U(VI) complexes. Moreover, we show that the new SOM algorithm allows the inclusion of available information such as the ligand structures and the physicochemical parameters so that latent relationships between them and the spectra of the complexes are revealed.

[1] Domaschke, K. et al. (2014) Proceedings of ESANN.

Keywords: EXAFS; metal complex; neural networks; self-organizing map

Involved research facilities

Related publications

  • Lecture (Conference)
    Actinide XAS 2014, 20.-22.05.2014, Villigen, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-20221


Formation and structure of polynuclear tetravalent actinide and lanthanide carboxylates in aqueous solution and solid state

Hennig, C.; Takao, K.; Takao, S.; Ikeda-Ohno, A.; Kraus, W.; Weiss, S.; Scheinost, A. C.

Abstract

Tetravalent actinides and lanthanides form strong complexes with carboxyl containing ligands. Such complexes play an important role in technological processes as well as in biological and environmental systems. So far, most of the thermodynamic data of actinide(IV) and lanthanide(IV) carboxylates are estimated by assuming mononuclear solution species [1]. We applied comprehensive studies with EXAFS, UV-Vis-NIR spectroscopy and X-ray diffraction on Th4+, U4+, Np4+ and Ce4+ carboxylates (RCOO–; R = H, CH3, CHR’NH2; R’ = H, CH3, CH2SH) in aqueous solution and solid state [2-5]. Our studies reveal that in all of the investigated systems hexanuclear complexes appear, which become predominant with increasing metal and ligand concentration and increasing pH, and dominate finally the species distribution. We present here their structure, stability constants, and the mechanisms of complex formation. The appearance of hexanuclear complexes in aqueous solution coincides with the onset of the An(IV) hydrolysis on the one hand, and the deprotonation of the carboxylic function on the other hand. This results in a competing reaction between hydrolysis and ligation. The hydrolysis induces a polymerization of the metal ions via oxo and hydroxo bonds, whereas 12 carboxylic ligands provide charge neutrality of the hexanuclear core and prevent further polymerization. Our studies indicate that future work on tetravalent actinide carboxylates in aqueous solution requires consideration of these hexanuclear species.

REFERENCES
[1] Casellato, U.; Vigato, P. A.; Vidali, M. Coord. Chem. Rev. 1978, 26, 85-159.
[2] Takao, S.; Takao, K.; Kraus, W.; Emmerling, F.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Eur. J. Inorg. Chem. 2009, 4771-4775.
[3] Takao, K.; Takao, S.; Scheinost, A.C.; Bernhard, G.; Hennig, C. Inorg. Chem. 2012, 51, 1336-1344.
[4] Hennig, C.; Takao, S.; Takao, K.; Weiss, S.; Kraus, W.; Emmerling, F.; Scheinost, A.C. Dalton Trans. 2012, 41, 12818-12823.
[5] Hennig, C.; Ikeda-Ohno, A.; Kraus, W.; Weiss, S.; Pattison, P.; Emerich, H.; Abdala, P.M.; Scheinost, A.C. Inorg. Chem. 2013, 52, 11734-11743.

Involved research facilities

Related publications

  • Lecture (Conference)
    Actinide XAS 2014, 20.-22.05.2014, Böttstein, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-20220


Investigations on in-vessel melt retention by external cooling for a generic VVER-1000 reactor

Tusheva, P.; Altstadt, E.; Willschütz, H.-G.; Fridman, E.; Weiß, F.-P.

Abstract

External or internal hazards, combined with multiple failures of components and safety systems or human errors can lead to a reactor core melt. In that case the reactor pressure vessel is the last barrier to keep the molten materials inside the reactor and to prevent further challenges to the nuclear power plant structures and consequently to the environment. In-vessel melt retention by external vessel cooling is a possible mitigative severe accident measure. Up to the moment it is not considered as a severe accident management strategy for VVER-1000 reactors. In this paper we analyse the possibility of in-vessel melt retention for a generic pressurized water VVER-1000 reactor during the late phase of a postulated station blackout scenario.

We developed a numerical model describing the thermal behaviour of a segregated molten pool situated in the lower plenum of the reactor pressure vessel and the thermo-mechanic behaviour of the vessel wall. The finite element code ANSYS® was used for the simulations.

The results show that the highest thermo-mechanical loads are observed in the vertical part of the vessel wall, which is in contact with the molten metal. Parameter studies on the thickness of the metal layer have also been performed. Without flooding, the vessel wall will fail, as the necessary temperature for a balanced heat release from the external surface via radiation is near to or above the melting point of the steel. However, the external flooding could help the retention of the corium within the reactor pressure vessel.

Keywords: corium; in-vessel melt retention; external flooding; segregated pool; heat transfer; finite element analysis

Permalink: https://www.hzdr.de/publications/Publ-20219


Spin-wave caustic formation by higher-harmonic radiation from a localized spinwave mode in a Heusler waveguide

Sebastian, T.; Pirro, P.; Brächer, T.; Kubota, T.; Serga, A. A.; Naganuma, H.; Oogane, M.; Ando, Y.; Hillebrands, B.

Abstract

Cobalt-based full Heusler compounds are very promising candidates for future magnon-spintronic devices as well as for the observation of novel phenomena in magnon transport in magnetic microstructures. The reason for the anticipated advantages is their decreased Gilbert damping in comparison with most conventional metallic 3d-ferromagnets and, in particular, in comparison with the widely used Ni81Fe19.

As shown recently, the decay length of propagating spin waves in spin-wave waveguides made of the Heusler compound Co2Mn0.6Fe0.4Si (CMFS) shows a significant increase in comparison with wave propagation Ni81Fe19. This observation reflects the decreased Gilbert damping of α=0.003 in CMFS with respect to the damping constant of α=0.008 in Ni81Fe19.

The decreased losses in CMFS not only lead to an increase of the decay length but also to the pronounced occurrence of nonlinear effects in the spin system. In this talk, we report the nonlinear emission of spin-wave beams with a well-defined propagation direction from the directly-excited spin-wave mode.

The overall process that led to our observation comprises three interesting phenomena of spin dynamics: the localization of a spin-wave mode due to a field gradient, higher harmonic generation, and the formation of spin-wave caustic beams. Even though, each of the constituent phenomena stimulated serious research efforts in the field of magnon spintronics on its own, their complex interplay was observed for the first time in a CMFS spin-wave waveguide just recently. This highlights the advantage of the Heusler material compared to the commonly used 3d-ferromagnets.

Subsequently, all three phenomena will be addressed in this talk. The localization of the directly-excited mode is described on the basis of a micromagnetic simulation as well as a dispersion calculation. This localized spin-wave mode can be identified as the source for the generation of the second and third harmonic. Finally, the radiation characteristics of the higher harmonics are described quantitatively by an analytical calculation based on the anisotropic dispersion relation of spin waves in magnetic thin films.

Keywords: spin Dynamics; magnetooptics; Heusler coumpounds; nonlinear

  • Poster
    IEEE International Magnetics Conference - INTERMAG 2014, 04.-08.05.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20218


Evaluating the Gilbert damping in individual Co2Mn0.6Fe0.4Si microstructures via parametric amplification

Sebastian, T.; Brächer, T.; Pirro, P.; Kawada, Y.; Naganuma, H.; Serga, A. A.; Oogane, M.; Ando, Y.; Hillebrands, B.

Abstract

Recent experiments on spin dynamics in microstructures made of the Heusler compound Co2Mn0.6Fe0.4Si (CMFS) yielded promising results in the linear and nonlinear regime. These results were attributed to the low Gilbert damping that was observed with standard ferromagnetic resonance (FMR) technique on homogeneous thin films. However, a quantitative analysis of the damping in CMFS microstructures is still lacking. We present an alternative method to evaluate the damping in individual CMFS microstructures using parametric amplification and show that the low damping is preserved on the microscale.

Keywords: spin dyanmics; magnetooptics; Gilbert damping; Heusler compounds

  • Poster
    DPG Frühjahrstagung 2014, 30.03.-04.04.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20217


Hydrodynamic modelling of an inclined rotating fixed bed reactor

Vaibhav, V.

Abstract

The hydrodynamics of a newly developed reactor concept with rotating fixed-bed were investigated using gamma-ray computed tomography. During these investigations, operational parameters like reactor inclination and rotation as well as flow rates, liquid and fixed-bed properties were varied.
In this work, hydrodynamic models from the literature have to be implemented, extended and parameterized for the new reactor concept.

Keywords: Inclined rotating fixed bed reactor; process intensification; modelling

  • Study thesis
    HZDR, 2014
    Mentor: Hans-Ulrich Härting
    32 Seiten

Permalink: https://www.hzdr.de/publications/Publ-20216


Experimentelle Untersuchung der Verweilzeitverteilung in einem geneigt rotierenden Festbettreaktor

Donath, T.

Abstract

Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus dessen Betriebsweise ergeben sich zusätzliche Freiheitsgrade zur Strömungsführung in Form von Neigung und Drehzahl und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist die Hydrodynamik im geneigt rotierenden Festbettreaktor mit den Schwerpunkten Verweilzeitverteilung und Phasenverteilung zu untersuchen. Die Ergebnisse sind mit denen des etablierten Rieselbettreaktors zu vergleichen.
Durch die im rotierenden Reaktor zusätzlich aufgeprägte transversale Strömungskomponente ist die Eignung des axialen Dispersionsmodells für das neue Reaktorkonzept zu untersuchen und es sind Möglichkeiten zur experimentellen Bestimmung der radialen Dispersion zu präsentieren.

Keywords: Inclined rotating fixed bed reactor; residence time distribution; process intensification

  • Diploma thesis
    Technische Universität Dresden, 2014
    Mentor: Prof. Rüdiger Lange, Hans-Ulrich Härting
    119 Seiten

Permalink: https://www.hzdr.de/publications/Publ-20215


Reaktionstechnische Untersuchungen an einem geneigt rotierenden Festtbettreaktor

Bischof, C.

Abstract

Der geneigt rotierende Festbettreaktor stellt ein neues Reaktorkonzept mit dem Ziel der Prozessintensivierung durch periodische Betriebsweise dar. Aus der neuartigen Betriebsweise ergeben sich in Form von Neigung und Drehzahl zusätzliche Freiheitsgrade zur Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der interdisziplinären Projektarbeit ist die Reaktionsführung hinsichtlich der Raum-Zeit-Ausbeute einer Modellreaktion (Hydrierung von α-Methylstyrol zu Cumol) zu untersuchen. Dazu sind abschließende MSR Arbeiten an einer bestehenden Versuchsanlage durchzuführen sowie Lösungen für die einfache Bestimmung von reaktionstechnischen Kenngrößen aus den Versuchsdaten zu präsentieren. Die Ergebnisse des geneigt rotierenden Festbettreaktors sind mit denen des etablierten Rieselbettreaktors zu vergleichen.

Keywords: Inclined rotating fixed bed reactor; process intensification; multiphase reaction; heterogeneous catalysis

  • Study thesis
    Technische Universität Dresden, 2014
    Mentor: Prof. Rüdiger Lange, Hans-Ulrich Härting
    56 Seiten

Permalink: https://www.hzdr.de/publications/Publ-20214


Live, Interactive, In-Situ, In-GPU Visualization of Plasma Simulations Running on GPU Supercomputers

Pausch, R.; Schneider, B.; Hettmanczyk, D.; Burau, H.; Huebl, A.; Schmitt, F.; Widera, R.; Grottel, S.; Gumhold, S.; Bussmann, M.

Abstract

With GPUs large-scale plasma simulations can provide frames-per-second simulation speeds. We present interactive, in-GPU rendering of large-scale particle-in-cell simulations running on GPU clusters. The user can choose which data is visualized and change the direction of view while the simulation is running. A remote visualization client can connect to the running simulation, allowing for live visualization even when bandwidth is limited.

Keywords: PIConGPU; remote visualization; in-situ; live; interactive

  • Lecture (Conference)
    GPU Technology Conference, 24.-27.03.2014, San Jose, CA, United States of America

Permalink: https://www.hzdr.de/publications/Publ-20213


Follow the Light: Plasma Physics on 18,000 GPUs

Pausch, R.; Juckeland, G.; Burau, H.; Bussmann, M.; Cowan, T.; Debus, A.; Huebl, A.; Kluge, T.; Nagel, W.; Schmitt, F.; Schramm, U.; Schuchart, J.; Widera, R.

Abstract

We show that with todays largest supercomputers it is possible to follow the trajectories of billions of particles, computing a unique fingerprint of their dynamics. With the use of 18,000 GPUs we could compute a 'sky map' of the radiation emitted by individual electrons in a large-scale, turbulent plasma, providing unique insight into the relation between the plasma dynamics and observable radiation spectra.

Keywords: PIConGPU; Kelvin-Helmholtz instability; KHI; radiation spectra

  • Lecture (Conference)
    GPU Technology Conference, 24.-27.03.2014, San Jose, CA, United States of America

Permalink: https://www.hzdr.de/publications/Publ-20212


Spectrally resolved sky-map of electromagnetic radiation from the Kelvin-Helmholtz instability

Pausch, R.; Huebl, A.; Schmitt, F.; Burau, H.; Widera, R.; Pugmire, D.; Debus, A.; Juckeland, G.; Nagel, W.; Bussmann, M.

Abstract

The Kelvin-Helmholtz instability (KHI) occurs at the interface between two neutral streams of plasma flowing past one another with different velocities. This instability is expected to take place in active galactic nuclei or in the afterglow of gamma-ray bursts, where it is a possible mechanism for non-thermal radiation.
We present results of a KHI scenario with relativistic velocity shear obtained in a petaflop scale run on the TITAN cluster at Oakridge using our relativistic 3D3V particle-in-cell code PIConGPU. From the dynamics of billions of macroparticle, we calculated angularly and temporally resolved radiation spectra based on classical Liénard-Wiechert potentials including the full coherence properties. Thus, in addition to the incoherent synchrotron-type radiation arising from DC magnetic fields in the KHI, we found rich radiation signatures, which we match with the dynamics and electron density structure of the KHI. We present a simple model, which explains these spectral features and connects them to the main quantities of the KHI.

Keywords: PIConGPU; Kelvin-Helmholtz instability; KHI; radiation spectra

  • Lecture (Conference)
    78. DPG-Jahrestagung und Frühjahrstagung der Sektion AMOP, 17.-21.03.2014, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20211


Radiative particle-in-cell simulations - How synthetic diagnostics help to understand plasma structure and dynamics

Pausch, R.; Debus, A.; Huebl, A.; Steiniger, K.; Burau, H.; Widera, R.; Bussmann, M.

Abstract

We present recent results of plasma simulations performed with PIConGPU, a fully relativistic 3D particle-in-cell (PIC) code running on GPU clusters. We extended our code to compute the radiation spectra of all particles in the simulation based on classical Liénard-Wiechert potentials including full coherence and polarization properties. We discuss physics tests, scaling and show simulation results of laser-wakefield accelerator and astrophysical plasmas, for which we calculated angularly resolved spectra ranging from infrared to X-ray wavelengths. Such an extensive treatment of plasma radiation across billions of macro particles makes it possible to explore temporally resolved plasma radiation spectra on linear and logarithmic photon energy scales over large solid angles ("sky-maps").
This ability of obtaining quantitative spectral data in plasma simulations poses a unique tool for determining the phase space distribution of electrons. Since spectral information is readily accessible in experiments, our results can serve as a valuable input to new diagnostics.

Keywords: PIConGPU; radiation; angularly resolved spectra; diagnostics

  • Lecture (Conference)
    78. DPG-Jahrestagung und Frühjahrstagung der Sektion AMOP, 17.-21.03.2014, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20210


Ferromagnetism and impurity band in a magnetic semiconductor: InMnP

Khalid, M.; Weschke, E.; Skorupa, W.; Helm, M.; Zhou, S.

Abstract

We have synthesized ferromagnetic InMnP, a member of the III-Mn-V ferromagnetic semiconductor family, by Mn ion implantation and pulsed laser annealing. Clear ferromagnetic hysteresis loops and a perpendicular magnetic anisotropy are observed up to a Curie temperature of 42 K. Large values of negative magnetoresistance and magnetic circular dichroism as well as an anomalous Hall effect are further evidence of a ferromagnetic order in InMnP. An effort is made to understand the transport mechanism in InMnP using the theoretical models. We find that the valence band of InP does not merge with the impurity band of the heavily doped ferromagnetic InMnP. Our results suggest that impurity band conduction is a characteristic of Mn-doped III-V semiconductors which have deep Mn-acceptor levels.

Keywords: diluted magnetic semiconductor; III-V semiconductor

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-20209


Analyse von Artefakten in der MR-basierten Schwächungskorrektur am PET-MR

May, C.; Schramm, G.; Platzek, I.; Kotzerke, J.; Beuthien-Baumann, B.

Abstract

Ziel/Aim:

Ziel der Arbeit ist die Analyse von Artefakten in MR-basierten Schwächungsbildern (MRMaps) bei Patientenuntersuchungen am Philips Ingenuity TF PET/MR. Die Artefakte wurden auf Art und Häufigkeit untersucht.

Methodik/Methods:

Insgesamt wurden 723 PET/MR Untersuchungen des Körperstamms im Zeitraum 01.10.2012 bis 01.10.2013 ausgewertet. Fehlerhafte MRMaps wurden mit dem zugrundeliegenden Schwächungs-MRT parallel betrachtet. Die Segmentierungsfehler wurden in folgende Kategorien eingeteilt: 1. die Lunge wurde nicht erkannt, 2. die Lunge wies eine falsche Form auf, 3. durch Metallimplantate verursachte Artefakte (z. B. durch Hüft-/Knie-TEP, Sternalcerclagen, Ports oder Zahnfüllungen), 4. sonstige Artefakte.

Ergebnisse/Results:

Es wurden 52 MRMaps mit Segmentierungsfehlern gefunden, die nicht durch eine einfache Nachbearbeitung der MTRA korrigiert werden konnten. In 20 Fällen wurde die Lunge nicht erkannt. In 24 Fällen wurde die Form der Lunge falsch segmentiert, wobei die Form 5 mal zu klein und 19 mal zu groß war. 35 Artefakte fielen in die Kategorie Metallartefakte, 5 in die Kategorie sonstige Artefakte. Einzelne MRMaps wiesen eine Kombination von Segmentierungsfehlern auf. Zusätzliche PET Rekonstruktionen mit korrigierten MRMaps zeigten SUV Abweichungen von bis zu 50% in verschiedenen Körperarealen.

Schlussfolgerungen/Conclusions:

Aufgrund der beobachteten Artefakte und deren Auswirkungen sollten bei allen PET/MRT Untersuchungen die MRMap von der MTRA auf Fehler untersucht werden.Treten gröbere Artefakte in der MRMap auf, müssen diese korrigiert und das PET Bild neu rekonstruiert werden, um eine quantitativ korrekte Auswertung der PET-Daten zu gewährleisten.

Involved research facilities

  • PET-Center
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A102
    ISSN: 0029-5566
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20208


Asphericity as a measure of spatial heterogeneity is superior to SUVmax change as a predictor of therapy outcome in FDG-PET of patients with head and neck cancer

Hofheinz, F.; Zöphel, K.; Lougovski, A.; Oehme, L.; Beuthien-Baumann, B.; Maus, J.; Steffen, G.; Buchert, R.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.

Abstract

Ziel/Aim:

The prognostic value of SUV is unsatisfactory in head and neck carcinoma. The aim of the present study was to evaluate a new measure of spatial heterogeneity as prognostic factor in FDG PET investigations of this cancer type.

Methodik/Methods:

We define the asphericity of a lesion as ASP=[1/(36*pi)*S^3/V^2]^(1/3)-1 where S is the lesion's surface and V is it's volume. ASP is a dimensionless number having a simple interpretation: ASP represents the fractional increase of the surface of the lesion relative to the surface of a sphere possessing the same volume (i.e. ASP=0 for a spherical lesion). ASP was evaluated retrospectively in 36 FDG PETs of patients with head and neck squamous cell carcinoma prior to chemoradiotherapy. A second FDG PET/CT was performed one to two weeks after start of therapy. The baseline and interim FDG images of the primary tumor were segmented using the ROVER 3D segmentation tool. The change of SUVmax (dSUVmax) of the primary tumor was computed. ASP was computed in the baseline PET. Kaplan-Meier analysis with respect to overall survival (OAS) was performed for dSUVmax and ASP and were compared by log-rank tests.

Ergebnisse/Results:

Mean OAS was 20.7 month. ASP was prognostic for OAS (p=0.0001), as was dSUVmax but with distinctly lower significance (p=0.023). Higher tumor asphericity was associated with reduced survival. Patients with ASP>25% showed a 2-year OAS rate of 12% compared to 74% in patients with ASP < 25%.

Schlussfolgerungen/Conclusions:

ASP of the pretherapeutic FDG uptake pattern in the primary tumor is predictive for survival of patients with head-and-neck carcinoma. It is superior to changes of SUVmax during therapy. This is remarkable since ASP is derived from a single PET scan prior to therapy, while computation of dSUVmax requires at least two PET measurements. Further investigations are necessary to confirm these preliminary results.

Involved research facilities

  • PET-Center
  • Poster
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A85-A86
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20207


Dosimetrische Evaluation des therapeutischen Potentials von Hg-197m

Freudenberg, R.; Walther, M.; Wunderlich, G.; Kotzerke, J.

Abstract

Ziel/Aim:

Hg-197m emittiert beim Zerfall Photonen und Elektronen. Damit besitzt es Potential zur nuklearmedizinischen Anwendungen. Während die emittierte Gammastrahlung die Lokalisation ermöglicht, erfolgt durch Elektronen eine lokal begrenzte Dosisdeposition. In Abhängigkeit der Elektronenenergie können damit Läsionen mit Durchmessern bis zu einigen mm therapiert werden. Anhand theoretischer Betrachtungen zur Dosisdeposition erfolgt ein Vergleich mit dem Therapienuklid Lu-177.

Methodik/Methods:

Die Produktion von Hg-197m erfolgt durch Bestrahlung von Gold-Targets am Zyklotron über eine (p,n)-Reaktion. Hg-197m wandelt sich mit einer Halbwertszeit von 23,8 h im Wesentlichen über Hg-197 in stabiles Au-197 um. Die Bildgebungseigenschaften wurden an einer Philips „BrightView“ Gammakamera nachgewiesen, Emissionsspektren mit einem GeLi-Halbleiterdetektor gemessen. Durch Simulationen mit Geant4 wurden Dose-Point-Kernels (DPK) für Hg-197m, Hg-197 und Lu-177 generiert. Weiterhin erfolgten die Schätzung der Dosisdeposition in Läsionen verschiedener Größen sowie ein Vergleich mit MIRD S-Werten.

Ergebnisse/Results:

Die DPK zeigen für Hg-197m und Hg-197 bei einem radialen Abstand < 270 μm eine 10-fach höhere Dosisdeposition im Vergleich zu Lu-177 sowie einen 5-fach höheren Dosiseintrag > 1 mm infolge der intensiveren Photonenemission. Im Bereich dazwischen dominiert die β--Dosisdeposition durch Lu-177. Für eine Läsion mit 10 g resultiert eine 1,9-fach höhere Tumordosis durch Hg-197m bei gleicher Zerfallszahl, bei Komplettzerfall beträgt die zu erwartende Dosis 0,6 Gy/MBq für Hg-197m und 2 Gy/MBq für Lu‑177.

Schlussfolgerungen/Conclusions:

Die Eignung von Hg-197m für nuklearmedizinische Zwecke konnte gezeigt werden, die erreichbaren Dosen liegen in der Größenordnung von Lu-177. Die Synthese neuer Radiopharmaka kann vielversprechende neue Behandlungskonzepte ermöglichen. Zusätzlich ist infolge des hohen linearen Energietransfers der Auger-Elektronen von Hg-197 nach DNA-Bindung eine vermehrte Induktion von Doppelstrangbrüchen zu erwarten.

  • Poster
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A79
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20206


Radiopharmacology of an Anti-CEA Monoclonal Antibody-l-RNA / l-DNA Duplex Pretargeting System

Bergmann, R.; Schlesinger, J.; Koezle, I.; Förster, C.; Klussmann, S.; Vonhoff, S.; Pietzsch, H.-J.; Pietzsch, J.; Wüst, F.; Behrsin, O.; Micheel, B.; Steinbach, J.

Abstract

Ziel/Aim:

This current study is aimed at demonstrating of the applicability of l‑oligonucleotides as a novel recognition system for pretargeting using a radiolabeled 17mer l‑DNA and complementary l‑RNA bound to microspheres and an antibody as targeting vector.

Methodik/Methods:

Small animal PET, biodistribution and metabolite studies of Ga-68 and Y-86-labeled L-DNA were carried out in rats and mice. Hybridization in vivo was demonstrated through cl‑RNA-modified microspheres trapped in the lungs and injection of complementary Ga-68-labeled 17mer l‑DNA. Tumor accumulation and pharmocokinetics in the human colon carcinoma models LS174T (n=10) and LoVo (n=2) tumors on NMRI nu/nu mice were evaluated with a 17mer cl‑RNA modified anti CEACAM5 (CEA) antibody aCEA(IG1)D11-DG2 and Ga-68-L-DNA.

Ergebnisse/Results:

The Ga-68- and Y-86-labeled L-DNAs showed typical biodistributions pattern of hydrophylic compounds with fast renal elimination and displayed high metabolic stability in vivo. cl‑RNA-microspheres trapped in the lungs could be visualized (SUV=0.51), i.e. 1.5%ID of the Ga-68-labeled 17mer l‑DNA were hybridized with the cl‑RNA on the microspheres. The LS174T and LoVo tumors were clearly visible with SUVs (median, 25%; 75% percentile) of 0.20 (0.19; 0.31) and 0.18 (0.16; 0.19), respectively. The averaged tumor/muscle ratio was 5.4±0.4 by administering the DG2 immunoconjugate first and injection of radiolabeled L-DNA after a 24 h delay.

Schlussfolgerungen/Conclusions:

Preliminary results demonstrate that the recognition system has promising properties for pretargeting in vivo to improve molecular imaging and therapy of solid tumors.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A49
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20205


Incorporation of position dependent detection probability into a tube-of-response based model for system matrix calculation in 3D PET imagereconstruction

Lougovski, A.; Maus, J.; Hofheinz, F.; Schramm, G.; van den Hoff, J.

Abstract

Ziel/Aim:

We have presented previously a model for fast on-the-fly volume-of-intersection (VOI) system matrix calculation for PET image reconstruction. The model replaces cubic voxels by spheres and the usual line of response by a cylindrical tube of response (TOR) whose diameter matches the size of the detector crystals. We now present a refined model which takes into account solid angle effects and position dependent detection efficiency across the crystal surface by using a TOR with a position-variant density.

Methodik/Methods:

We model the detection efficiency across the crystal surface as a radially symmetric function (superposition of two error functions) which leads to a TOR with a variable radial density. Additionally accounting for the solid angle effects results in a further modification of the TOR density that also varies in the axial direction. Consequently, the density-weighted VOI between TOR and spherical voxel now depends not only on the distance between the center of spherical voxel and line of TOR but also on the axial position along the TOR. The new model was integrated into our Tube-Of-Response High Resolution OSEM Reconstruction (THOR) and evaluated using a cylindrical phantom with spherical inserts. We have investigated several figures of merit (reconstructed spatial resolution, noise level, extend of Gibbs artifacts) and compared them between the original and modified TOR models.

Ergebnisse/Results:

The modified model maintains the high spatial resolution already demonstrated for the original TOR approach while showing an improved noise characteristics and reduction of residual Gibbs artifacts. The improvement of image quality overall is only modest.

Schlussfolgerungen/Conclusions:

The proposed modification of the TOR model for on-the-fly system matrix computation allows more accurate modelling of the scanner geometry and event detection and leads to reduced noise levels and Gibbs artifacts in the reconstructed image. However, it noticeably increases reconstruction times in comparison to the original model.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A35-A36
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20204


Detektionraten von Skelettmetastasen neuroendokriner Tumore (NET) im F18-NaF-PET und MRT am PET/MR im Vergleich zur Somatostatin-Rezeptor-Szintigraphie (SSRS)

Beuthien-Baumann, B.; Platzek, I.; Strumpf, A.; Schramm, G.; Zessin, J.; van den Hoff, J.; Kotzerke, J.

Abstract

iel/Aim:

NET weisen in fortgeschrittenen Stadien häufig Skelettmetastasen auf. Die Skelettszintigraphie detektiert Metastasen die eine Alteration der Knochenmatrix ausgelöst haben; Knochenmarkmetastasen werden in der MRT frühzeitig erkannt. Erhöht die Kombination von NaF-PET und MRT bei NET die Detektionsrate ossärer Metastasen?

Methodik/Methods:

Untersucht wurden 15 Patienten (5w/ 10m; mittl. Alter 63 Jahre mit NET (n=12), medull. Schilddrüsen-Ca (n=1) und SSR-pos. Foll. Schilddrüsen-Ca (n=2) mittels F18-NaF-PET sowie MRT am sequenziellen PET/MR (Ingenuity PET/MR, Philips) im Vergleich zum „Goldstandard“ SSRS (Ga68 DOTATOC/ DOTATATE) am PET/CT (Biograph 16, Siemens). Die MRT-Sequenzen bestanden neben dem Schwächungs-MRT (T1 TFE) aus einer sag. Wirbelsäulenaufnahe (T1 TSE n=10), einer cor. Ganzkörperaufnahme (T1TFE n=9), einer DWIBS (n=3). Die Kombination mehrerer MR-Sequenzen wurde bei langen Untersuchungszeiten nicht von allen Patienten toleriert.

Ergebnisse/Results:

Ein Patient wies im SSRS und im NaF eine disseminierte Metastasierung auf. Bei 14 Pat. wurden mittels SSRS 200 Metastasen im Skelett detektiert. Im NaF-PET fanden sich 176 Matchbefunde (88%), in den MRT-Untersuchungen zeigten sich 116 Läsionen (58%). Bei der Betrachtung allein der Wirbelsäulenbefunde (n=105 im SSRS), wurden im NaF 87%, im MRT 63% der WS-Läsionen detektiert. Im MRT zeigten sich 10 WS-Läsionen, die im NaF nicht abgrenzbar waren. Die Zusammenschau von NaF-PET und MRT erleichterte die Differenzierung zwischen Metastase oder degenerativem Befund.

Schlussfolgerungen/Conclusions:

Ausgehend vom „Goldstandard SSRS“ zeigte sich eine hohe Detektionsrate der ossären Metastasen im NaF-PET. Die Detektionsrate mit den durchgeführten MRT-Sequenzen fiel geringer aus, hier wird eine Optimierung der MRT-Sequenzen angestrebt. Die Kombination NaF-PET und MRT erleichtert die Differenzierung zwischen Metastase und Degeneration.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A30
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20203


Compensation and evaluation of metal-implant-induced artifacts in MR-based attenuation correction

Schramm, G.; Maus, J.; Hofheinz, F.; Petr, J.; Lougovski, A.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.

Abstract

Ziel/Aim:

MR-based attenuation correction (MRAC) using tissue type segmentation suffers from metal-implant-induced artifacts (MAs) in the underlying MR scan. We propose an improved MRAC segmentation algorithm compensating MAs in MR-based attenuation maps (MRMaps) and evaluate the quantitative influence of these artifacts on the reconstructed PET images.

Methodik/Methods:

MA-based cavities in MRMaps are filled by the developed algorithm using a delineation of the patient's body contour that is derived from the PET emission image . PET emission data of 11 patients with MAs (endoprotheses, sternal cerlages) examined in a Philips Ingenuity PET/MR were reconstructed with the vendor-provided method for attenuation correction (MRMap1,PET1) and additionally with our MRAC algorithm (MRMap2,PET2). Both types of MRMaps were visually inspected for segmentation errors. The segmentation errors in MRMap1 were classified into four classes (L1 and L2 artifacts inside the lung, and B1 and B2 artifacts inside the remaining body depending on the assigned attenuation coefficients). The average relative SUV differences (eps_relav) between PET1 and PET2 in all regions showing erroneous attenuation coefficients in MRMap1 were calculated.

Ergebnisse/Results:

MRMap1 showed erroneous attenuation coefficients in regions near metal implants and inside the patient's lung in all 11 patients. In MRMap2, all MA regions were filled with the soft tissue attenuation coefficient and the lung was correctly segmented in all cases. MRMap2 showed small residual segmentation errors in 8 patients. eps_relav was (mean+-sd): (-57+-1)% in B1, (-43+-4)% in B2, (19+-19)% in L1 and (128+-50)% in L2 regions.

Schlussfolgerungen/Conclusions:

MAs severely disturb MR-based attenuation correction and SUV quantification in PET/MR. The developed algorithm is able to compensate for these artifacts, improves SUV quantification accuracy distinctly and is suitable for clinical application.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A29
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20202


Development of a novel class of spirocyclic σ1 receptor ligands − structure-affinity relationships and fluorine-18 radiolabeling

Xie, F.; Kniess, T.; Deuther-Conrad, W.; Bergmann, R.; Mamat, C.; Brust, P.; Pietzsch, J.; Steinbach, J.; Jia, H.

Abstract

Ziel/Aim:

Two subtypes of sigma (σ) receptors were confirmed. While the expression of σ1 is mainly altered in several brain disorders, both of them are expressed in a number of tumor entities. Some radioligands for imaging of σ1 and σ2 have been developed but most of them suffer from lipophilicity too high for tumor targeting. The aim of this study was to synthesize a series of novel spirocyclic σ1 receptor ligands, and to develop by analyzing structure-affinity relationships a suitable hydrophilic radiotracer with high affinity and selectivity for σ1.

Methodik/Methods:

A series of novel spirocyclic σ1 receptor ligands was designed, synthesized, and characterized. The affinity to σ1 and σ2 receptors was assessed and the most superior compound chosen for radiolabeling with fluorine-18. The logD value of the radiotracer, its stability in vitro and in vivo as well the biodistribution in rats were investigated.

Ergebnisse/Results:

Six spirocyclic derivatives have been synthesized; Ki values were determined to be in the range of 3.26 - 11.2 nM for σ1 and 164.4 - 312.4 nM for σ2. Compound 1 (8-[4-(2-fluoroethoxy)benzyl]-1,4-dioxa-8-azaspiro[4.5]decane; Ki σ1=5.38±0.43 nM, Ki σ2=164±20.4 nM, was selected for fluorine-18 radiolabeling. [18F]1 was prepared by fluoroethylation via a two-step automated procedure in 20% yield after column purification. The radiochemical purity was >99% as determined by HPLC analysis, the specific activity was in the range of 25 - 45 GBq/μmol. The logD value of [18F]1 was determined as 0.81±0.13. [18F]1 was stable in saline, ethanol, and human plasma in vitro for up to 2h. In preliminary experiments an uptake in mice brain of 2.6% ID at 5 min p.i. was detected.

Schlussfolgerungen/Conclusions:

We designed a potential spirocyclic σ1 receptor ligand with high affinity, selectivity, and excellent hydrophilicity. The biological evaluation of the corresponding radiotracer in brain and selected tumor models is ongoing.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Nuklearmedizinischen Gesellschaft (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A25
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20201


Radiosynthesis of 5-(2-[18F]fluoroethyl)-sunitinib, an inhibitor of VEGFR-2

Knieß, T.; Kuchar, M.; Pietzsch, J.; Steinbach, J.

Abstract

Ziel/Aim:

Sunitinib is a multi-tyrosine kinase inhibitor (TKI) targeting VEGFR, PDGFR and FLT-3. Radiolabeled sunitinib might be suitable probe for monitoring angiogenesis with PET and to facilitate the success of corresponding anti-angiogenic
chemotherapy for the individual patient. For this purpose we developed an fluorine-18 radiolabeled PET tracer, 5-(2-[18F]fluoroethyl)-sunitinib basing on the lead structure of sunitinib.
Methodik/Methods:
The reference compound 5-(2-fluoroethyl)-sunitinib was synthesized by Knoevenagel condensation of 5-(2-fluoroethyl)-indoline-2-one with N-[2-(diethylamino)ethyl]-2,4-dimethyl-5-formyl-1H-pyrrole-3-carboxamide. Two suitable precursors for radiolabeling were obtained by reacting 5-(2-bromoethyl)-substituted sunitinib with AgC7H7SO3 and AgCH3SO3, respectively. In a set of experiments for finding the optimal radiolabeling conditions 4 mg of each
precursor was reacted with [18F]fluoride at a scheduled temperature regime for 20 min in acetonitrile, DMF or DMSO.
Ergebnisse/Results:
In a competition binding assay against VEGFR-2 a Kd value of 9 nM for 5-(2-fluoroethyl)-sunitinib was determined. For radiolabeling with [18F]fluoride the methanesulfonyl-substituted precursor in acetonitrile gave radiochemical yields up to 8%. In large scale synthesis using a TracerLAB (GE) synthesiser 8mg of precursor were reacted with 10 GBq of [18F]fluoride in acetonitrile at 110°C for 12 min. After semi-preparative HPLC purification and SPE separation 115-135 MBq of 5-(2-[18F]fluoroethyl)-sunitinib could be obtained in radiochemical purity > 95% and in a specific activity of 38-62 GBq/[mu]mol.
Schlussfolgerungen/Conclusions:
The new VEGFR-2 targeted radiolabeled probe 5-(2-[18F]fluoroethyl)-sunitinib was successfully synthesized by radiofluorination of the corresponding methanesulfonyl-substituted precursor with [18F]fluoride. The radiotracer can be obtained in high chemical and radiochemical purity in 100 MBq scale.

Involved research facilities

  • PET-Center
  • Lecture (Conference)
    52. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin (DGN), 26.-29.03.2014, Hannover, Deutschland
  • Open Access Logo Abstract in refereed journal
    Nuklearmedizin 53(2014), A43-A44
    ISSN: 0029-5566

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Permalink: https://www.hzdr.de/publications/Publ-20200


Comparative investigation of the novel radiotracers (R)- and (S)-[18F]fluspidine for imaging of σ1 receptors by PET

Deuther-Conrad, W.; Becker, G.; Patt, M.; Donat, C. K.; Kranz, M.; Stittsworth, S.; Holl, K.; Habermann, B.; Fischer, S.; Wenzel, B.; Mishchenko, L.; Hesse, S.; Steinbach, J.; Wünsch, B.; Lever, S. Z.; Sabri, O.; Brust, P.

Abstract

Objectives
Sigma1 receptor (σ1), found in plasma, mitochondrial and endoplasmic reticular membranes and involved in many cellular functions of the endocrine, immune, and nervous systems, is a promising target for novel concepts in diagnostics and therapy of cancer and brain diseases. To support such research by molecular imaging of σ1, we have comparatively evaluated the 18F-labelled (R)- and (S)-enantiomers of the σ1 ligand fluspidine in pigs.

Methods
(R)- and (S)-[18F]fluspidine were synthesized from enantiopure tosylate precursors with high specific activities (650-870 GBq/µmol) and radiochemical purity (>99%). Brain pharmacokinetics were investigated by dynamic PET studies in anaesthetized pigs under baseline (n=3 per enantiomer) and blocking conditions (n=3 per enantiomer) using σ1 selective SA4503. SUVs were calculated for 24 MR-defined brain regions. One- and two-tissue compartment modeling was applied to calculate individual rate constants, total distribution volumes (VT) and binding potentials of (R)- and (S)-[18F]fluspidine. Furthermore, VT was estimated from graphical Logan plot analyses. Organ doses (ODs) and effective doses (ED) of both radiotracers were determined in CD-1 mice and an extended single dose toxicity study of (S)-fluspidine was performed in SPRD rats.

Results
(R)- and (S)-[18F]fluspidine displayed significantly different brain uptake kinetics. Although initial SUVs were similar (R)-[18F]fluspidine showed higher values (60-150%) at 120 min p.i. Brain distribution in pigs correlated with brain distribution in CD-1 mice (Fig. 1). SA4503 reduced SUVs and k3 of both radiotracers by ~65% and 70-95%, respectively, in almost all brain regions (Fig. 1B, C), while effects on k4 differed region-specific. VT values estimated by full nonlinear kinetic and Logan analyses correlated highly and revealed also a significant decrease in all brain regions for both radiotracers by SA4503. The expected EDs of (R)- and (S)-[18F]fluspidine to humans are 31 and 28 µSv/MBq, respectively, and up to 620 µg (S)-fluspidine/kg no test item related effects were observed in the toxicity study.

Conclusion
Both [18F]fluspidine enantiomers appear to be suitable for σ1 imaging in human brain. The different pharmacokinetics of (R)-[18F]fluspidine and (S)-[18F]fluspidine may be translated into diagnostic imaging of different pathological conditions such as degenerative as well as cancerous processes.

Fig. 1: Distribution of [18F]fluspidine binding sites in brain. (A) Ex vivo autoradiography of a sagittal rat brain slice obtained at 45 min after intravenous injection of [18F]fluspidine. (B, C) Sagittal brain PET images acquired as summed data from 0-20 min after intravenous injection of piglet with (S)-[18F]fluspidine under baseline conditions (B) or under blocking with SA4503 (C).

  • Poster
    The 10th International Symposium on Funktional NeuroReceptor Mapping of the Living Brain, 21.-24.05.2014, Amsterdam, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-20199


Implementation of a fast running full core pin power reconstruction method in DYN3D

Gomez, A.; Sanchez Espinosa, V. H.; Kliem, S.; Gommlich, A.

Abstract

This paper presents a substantial extension of the pin power reconstruction (PPR) method used in the reactor dynamics code DYN3D with the aim to better describe the heterogeneity within the fuel assembly during reactor simulations. The flexibility of the new implemented PPR permits the local spatial refinement of one fuel assembly, of a cluster of fuel assemblies, of a quarter or eight of a core or even of a whole core. The application of PPR in core regions of interest will pave the way for the coupling with sub-channel codes enabling the prediction of local safety parameters. One of the main advantages of considering regions and not only a hot fuel assembly (FA) is the fact that the cross flow within this region can be taken into account by the subchannel code. The implementation of the new PPR method has been tested analysing a rod ejection accident (REA) in a PWR minicore consisting of 3x3 FA. Finally, the new capabilities of DNY3D are demonstrated by the analysing a boron dilution transient in a PWR MOX core and the pin power of a VVER-1000 reactor at stationary conditions.

Keywords: pin power reconstruction; DYN3D; VVER; whole core pin power predictions; boron dilution; REA; PWR

Permalink: https://www.hzdr.de/publications/Publ-20198


Application of Sub-second Annealing for Diluted Ferromagnetic Semiconductors

Zhou, S.; Bürger, D.; Schmidt, H.

Abstract

The dilute ferromagnetic semiconductor GaMnAs provides a great promise for its application in spintronics, which combines two degrees of freedom: charge and spin. Mn ions which substitute Ga sublattice sites provide both local magnetic moments and itinerant holes. The magnetic properties of GaMnAs can be controlled by manipulating free carriers via electrical gating. However, the preparation of ferromagnetic GaMnAs presents a big challenge due to the low solubility of Mn in GaAs. To overcome the low solid solubility limit of transition metal dopants in semiconductors, one needs highly nonequilibrium methods to introduce enough dopants and a short-time annealing to activate them. Both ion implantation and pulsed-laser (or flash-lamp) annealing occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants. The subsequent short-time annealing deposits energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Such a nonequilibrium process maintains the supersaturation induced by ion implantation. In this chapter, we review the application of sub-second annealing in the activation of Mn implanted GaAs as well as GaP.

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  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 297-314
    DOI: 10.1007/978-3-319-03131-6_15

Permalink: https://www.hzdr.de/publications/Publ-20196


Sub-nanosecond Thermal Spike Induced Nanostructuring of Thin Solid Films Under Swift Heavy Ion (SHI) Irradiation

Ghosh, S.; Kumar, H.; Singh, S. P.; Srivastava, P.; Kabiraj, D.; Avasthi, D. K.; Bürger, D.; Zhou, S.; Mücklich, A.; Schmidt, H.; Stouquert, J. P.

Abstract

The interaction between swift heavy ions (SHI) and a solid has been identified as one of the important physical processes to generate or modify nanostructures in thin solid films. The large part of the energy which is deposited in the electronic subsystem of a material by SHI is known as electronic energy loss and gets coupled to the lattice subsystem in a complex way resulting in a transient (picoseconds to sub-nanosecond) thermal spike within a few nanometer diameter region of the thin solid film along the ion path. The temperature of this narrow zone may raise up to 1000 K or more during this time. This transient heating process is known as lattice thermal spike and can be used as a tool to engineer materials down to the nanoscale. Here we address two important consequences of lattice thermal spike; (i) elongation of metal nanoparticles embedded in dielectric thin films and (ii) generation of a-Si/c-Si nanostructures in a silicon nitride matrix.

(i) Metal nanoparticles embedded in a thin film matrix belong to a class of materials that has potential applications as optical and magnetic sensors, storage, memory devices, field emission display etc. The nanoparticle size and shape, orientation, inter-particle separation and dielectric constant of the surrounding matrix are the crucial parameters which control their properties. Thermal spike generated by SHI in these nanoparticles and surrounding matrix can be used as a unique tool to tailor the shape of the embedded nanoparticles, eventually modifying the physical properties of these materials. Metal nanoparticles, which are mostly spherical in shape in as grown films, get elongated along the direction of SHI due to thermal spike induced melting and stress. After a brief introduction of some fundamental aspects and synthesis of these films, a detailed discussion on elongation of nearly spherical Ni nanoparticles embedded in SiO2 thin film matrix under 120 MeV Au ion irradiation is made. Various physical parameters influencing the shape modification of nanoparticles under the framework of thermal spike model are discussed.

(ii) a-Si/c-Si nanostructures embedded in different Si-based dielectric matrix have attracted researchers because of their potential application in low-cost Si-based optoelectronic devices. We report here the response of in-situ formed Si-nanostructures embedded in a Si-rich hydrogenated amorphous silicon nitride matrix to 100 MeV Ni8+ ions irradiation. Si-rich a-SiN x :H films have been prepared by Hg-sensitized Photo Chemical Vapor Deposition. Presence of elemental Si was confirmed from X-ray photoelectron spectroscopy. Irradiation with a fluence of 5×1012 ions/cm2 under normal incidence at room temperature leads to dissolution of these Si-nanostructures. However, irradiation with a relatively higher fluence of 1×1014 ions/cm2 enhances the nucleation and leads to the formation of amorphous Si-nanostructures in the film. In addition, at the surface a novel effect i.e. partial crystallization of Si-nanostructures along the beam direction is observed. The results are explained on the basis of thermal spike model.

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  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 107-121
    DOI: 10.1007/978-3-319-03131-6_6
    Cited 1 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-20195


Nanonet Formation by Constitutional Supercooling of Pulsed Laser Annealed, Mn-Implanted Germanium

Bürger, D.; Zhou, S.; Höwler, M.; Ou, X.; Kovacs, G. J.; Reuther, H.; Mücklich, A.; Skorupa, W.; Schmidt, H.

Abstract

This subchapter presents interesting aspects of pulsed laser annealing. During this process, a laser pulse incorporates heat in the near surface region of a semiconductor or a metal. If the energy density is high enough, the system may melt near the surface. Because of the large temperature gradient, a very fast recrystallization may lead to novel physical material properties. Here we present interesting aspects of the formation of a Mn-rich nanonet in germanium. Important physical phenomena are explained in detail. The material has been fabricated by pulsed laser annealing of Mn implanted Ge wafers with a pulse duration of 300 ns. Due to a segregation instability during recrystallization, Mn segregates at the liquid-solid interface and an approximately 40 nm thick Ge:Mn surface layer is strongly enriched with Mn. Transmission electron microscopy plan-view images reveal a percolating Mn-rich nanonet after etching the top 10 nm surface layer. Hysteretic anomalous Hall effect has been observed up to 30 K, but it vanishes after etching away the 40 nm thick Mn-rich Ge:Mn layer. The nanonet seems to support the correlation between magnetization and hysteretic Hall resistance. Intrinsic charge carrier scattering in the threads or vertices of the Ge:Mn nanonet may lead to the observed anomalous Hall effect. In the outlook the nanonet formation is revealed for supercooled Mn-implanted Si.

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Related publications

  • Book chapter
    Wolfgang Skorupa, Heidemarie Schmidt: Subsecond Annealing of Advanced Materials: Annealing by Lasers, Flash Lamps and Swift Heavy Ions (Springer Series in Materials Science), Switzerland: Springer, 2014, 978-3-319-03130-9, 15-33
    DOI: 10.1007/978-3-319-03131-6_2
    Cited 1 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-20194


Protein Conformational Rearrangement induced by the modulation of vibrational modes

Lorincz, I. Z.; Schay, G.; Rauscher, A. A.; Kellermayer, M. S. Z.; Gensch, M.; Malnasi-Csizmadia, A.

Abstract

We succeeded to induce a specific conformational change in a protein by infrared laser excitation and proved that the reaction was a non-thermal effect. An alpha helical – beta sheet structural rearrangement of an intrinsically fluorescent protein, LSSmOrange was monitored through its fluorescence intensity change upon irradiation with a free electron IR laser. The picosecond timescale IR pulse caused a reversible structural rearrangement of LSSmOrange on the second timescale. We found that the structural rearrangement was induced by a single IR photon with a very low, less than 10-6 photon efficiency and the maximum effect was detected at 1033 cm-1 IR irradiation. The IR induced reaction is not a trivial thermal effect because 1. the IR pulse increases the fluorescence of LSSmOrange whereas temperature jump decreases it, 2. its magnitude depends on the wavelength of the IR pulse. Based on the Arrhenius plots of the IR induced conformational change and its relaxation, we found that the IR excitation increases the free energy of the alpha-helical structure dominated state by 12 kJ/mol. Since this energy shift is exactly equal to the energy of the IR photon, we concluded that there are highly efficient energy flow pathways between the vibrational modes in the protein as it is indicated by recent theoretical calculations. These results may open a new horizon towards the direct investigation of the functional role of vibrational modes in proteins.

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  • Lecture (Conference)
    PepCon 2014 - BIT's 7th Annual Protein and Peptide Conference, 25.-28.04.2014, Dalian, China

Permalink: https://www.hzdr.de/publications/Publ-20193


64Cu-markierte Upconversion-Nanopartikel und ihr Potenzial für die multimodale Bildgebung von Tumoren

Hesse, J.; Barreto, J. A.; Graham, B.; Geipel, G.; Spiccia, L.; Steinbach, J.; Stephan, H.

Abstract

Das Interesse an der medizinischen Nutzung von Nanomaterialien ist insbesondere auf deren einzigartigen, strukturbedingten Eigenschaften zurückzuführen. Basierend auf unterschiedlichen Materialien, wie Polymeren, anorganische oder organisch-anorganische Hybridsubstanzen, werden Nanoteilchen auf ihre Anwendbarkeit in komplexen biologischen Systemen untersucht. Upconversion(UC)-Nanopartikel zeigen hierbei ein vielversprechendes Potenzial und besitzen bei einer gut abgestimmten Dotierung des anorganisch, kristallinen Wirtsgitters mit ausgewählten Seltenerd-Metallen eine sehr effiziente Lumineszenz[1]. Damit eröffnet sich speziell deren Nutzung für die optische Bildgebung, welche die Aufklärung von Prozessen auf zellulärer Ebene gestattet. Gleichzeitig erlaubt die Oberflächenstruktur der Partikel eine Mehrfachfunktionalisierung mit Chelatoren für die Bindung von Radiometallnukliden für PET und SPECT und tumoraffinen Einheiten wie beispielsweise Peptiden.
Wir berichten über die Synthese und Fluoreszenz-eigenschaften von ultrakleinen (< 10 nm) UC-Nanopartikeln auf der Basis von NaYF4: Yb3+, Er3+ und deren Umhüllung mit verschiedenen Polymeren zur Erzeugung wasserlöslicher und biokompatibler Materialien. Diese Partikel wurden mit einem Picolyl-Derivat des makrocyclischen Liganden 1,4,7-Triazacyclononan funktionalisiert. Der Chelator dient zur Radiomarkierung der Partikel mit 64Cu2+, was die Anwendung eines zusätzlichen bildgebenden Verfahrens, der Positronen-Emissions-Tomographie (PET), er-möglicht. Es werden weiterhin Synthesestragien zur Einführung von tumoraffinen Einheiten auf der Oberfläche der UC-Nanopartikel vorgestellt, die eine Adressierung des auf vielen Tumoren überexprimierten Epidermal Growth Factor Receptors (EGFR) gestatten.
[1] Mader, H. S., Kele, P., Saleh, S. M., Wolfbeis, O. S., Curr. Opin. Chem. Biol. 2010, 14, 582-596

  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2013, 01.-04.09.2013, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20192


High-Speed PIXE: A spatially resolved PIXE setup at the 6 MV Tandem accelerator

Buchriegler, J.; von Borany, J.; Hanf, D.; Munnik, F.; Nowak, S. H.; Renno, A. D.; Scharf, O.; Ziegenrücker, R.

Keywords: High-Speed PIXE; SLcam; Colour X-Ray Camera

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  • Invited lecture (Conferences)
    SLcam(R) User Workshop, 16.01.2014, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20191


Cryo-Fluoreszenzspektroskopie – Eine innovative Technik für die Wissenschaft

Steudtner, R.; Großmann, K.

Abstract

Fluoreszenzmikroskopische und fluoreszenzspektroskopische Untersuchungen finden in der Biologie, Medizin, Materialprüfung sowie Geowissenschaften eine breite Anwendung. Dabei spielt die chemische Charakterisierung und die Lokalisierung der verschiedensten Analyte mittels analytischer und bildgebender Verfahren eine wichtige Rolle. Die Analyse von Schwermetallen insbesondere von Radionukliden und seltenen Erden in natürlichen Systemen soll an Hand einer verbesserten Fluoreszenzanalytik bei tiefen Temperaturen erweitert werden. Durch die Weiterentwicklung der Fluoreszenzspektroskopie bei tiefen Temperaturen werden am Helmholz-Zentrum Dresden-Rossendorf nicht nur umweltanalytisch relevante Fragestellung im Bereich der Ressourcenökologie sondern auch verschiedenste Aufgaben aus dem Bereich der medizinischen Forschung bearbeitet.
Durch die Unterstützung der Max-Buchner-Forschungsstiftung konnten wir drei entscheidende Ergebnisse erzielen, welche für zukünftige Projekte die nötige wissenschaftliche Grundlage bieten.
1. Aufbau eines dauerhaften spektroskopischen Tieftemperaturmessplatzes zum schnellen und sensitiven Nachweis von Uran in diversen Umweltproben (Wasser- und Bodenproben)
2. Unterstützung beim Aufbau eines mikroskopischen Tieftemperaturmess-platzes, der mikroskopische Untersuchungen bei -253°C mit bis zu 630 facher Vergrößerung erlaubt.
3. Erste erfolgreiche Messungen mit dem spektroskopischen und mikroskopischen Aufbau im Bereich der Umweltanalytik sowie an verschiedenen medizinisch relevanten Anwendungen.
Langfristig zielen die Arbeiten auf die direkte Visualisierung der Analyten bei tiefen Temperaturen in biologischen und medizinischen Medien in Kombination mit fluoreszenzspektroskopischen Daten, welche zusätzliche molekulare Informationen über die der Mikroumgebung der Chromophore liefern, ab.

  • Open Access Logo CITplus 10(2014), 60-62
  • Lecture (Conference)
    ProcessNet-Jahrestagung, 30.09.-02.10.2014, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20190


New insight into self-irradiation effects on local and long-range structure of uranium-americium mixed oxides (through XAS and XRD)

Lebreton, F.; Martin, P. M.; Horlait, D.; Bes, R.; Scheinost, A. C.; Rossberg, A.; Delahaye, T.; Blanchart, P.

Abstract

Uranium-americium mixed oxides could be used as transmutation targets to lower Am inventory in spent nuclear fuels. Due to 241Am activity, these materials are subjected to α-self-irradiation which provokes structural damages. Previous studies on U-Am mixed oxides gave first insight into α-radiation tolerance of these compounds, but have never been carried out for more than a year, whereas Am-bearing targets might be stored up to a few years between fabrication and irradiation. In this work, we study effects of self-irradiation on the structure of U1-xAmxO2± solid solutions (x = 0.15 and 0.2) aged of 3 to 4 years. Especially, X-ray diffraction and X-ray absorption spectroscopy are combined to observe these effects from both long-range and local perspectives. Obtained results show that the fluorite-type structure of U-Am mixed oxides withstands 241Am α-irradiation without major damage. Even though an increase of interatomic distance and structural disorder was observed during the first year of storage, the present results show that no further evolution occurs. Furthermore, comparison between long-range and local evolution suggests that α-self-irradiation-induced defects are mainly located in low-ordered domains. The major difference between samples was even found to be related to differences in fabrication conditions. Based on these results, no detrimental factors have been identified for several-year storage of U-Am transmutation targets before irradiation.

Keywords: nuclear fuel; transmutation; uranium; americium; EXAFS; XRD

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Permalink: https://www.hzdr.de/publications/Publ-20189


Sorption data: Ways from a plain collection to recommended values

Bok, F.; Richter, A.; Brendler, V.

Abstract

For geochemical modeling of scenarios for the disposal of hazardous radioactive and (chemo)toxic waste, comprehensive and consistent thermodynamic data are required as well as sorption data for the surrounding host rocks. Whereas there are several projects running world-wide to arrive at the comprehensive and consistent thermodynamic data base for the aqueous phase and forming solids, the situation is much worse concerning the reactions on the mineral-water interface. For important processes such as sorption, ion exchange or surface precipitation incompleteness and inconsistencies, restricted ranges of variation (temperature, density, pressure, ionic strength) are abundant leading to hardly comparable results in geochemical modeling.
RES³T – the Rossendorf Expert System for Surface and Sorption Thermodynamics (http://www.hzdr.de/res3t) – is a free-for-use digitized thermodynamic sorption database utilizing surface complexation models (SCM). It is mineral-specific and can therefore also be used for complex real systems such as rocks or soils. Data records comprise of mineral properties, specific surface area values, characteristics of surface binding sites and their protolysis, sorption ligand information, and surface complexation reactions. An extensive bibliography is included, providing links not only to the above listed data items, but also to the primary reference. Currently efforts started to combine RES³T with the thermodynamic database THEREDA (http://www.thereda.de) to provide a comprehensive and consistent database for a holistic geochemical modeling.
Sorption speciation calculations of radionuclides on mineral surfaces will be presented, showing the actual consequences of inconsistent and scattered sorption data that can be found in literature, as well as the possibilities of the RES³T database for calculating radionuclide sorption onto complex geologic formations, e.g. the overburden of a nuclear waste disposal. Generally, RES³T proved to be a powerful tool for identifying data gaps for combinations of minerals and sorbing radionuclide essential for the risk assessment of waste disposals or in accident analysis.

Keywords: RES³T; Rossendorf Expert System for Surface and Sorption Thermodynamics; database; THEREDA

  • Invited lecture (Conferences)
    248th ACS National Meeting, 10.-14.08.2014, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-20188


Search for a live supernova signature of 60Fe in deep-sea sediments and a new half-life measurements of 60Fe

Wallner, A.; Feige, J.; Fifield, L. K.; Golser, R.; Kutschera, W.; Merchel, S.; Rugel, G.; Schumann, D.; Tims, S.; Winkler, S.; Sterba, J.; Bichler, M.

Abstract

60Fe (2.6 My) is one of the most versatile nuclides in astrophysics. Live 60Fe was identified in the Galaxy. Its stellar production requires neutron densities available only in explosive Supernovae (SNe) or SuperAGB stars. 60Fe is also found in meteorites and indirectly via 60Ni anomalies. Fresh nucleosynthetic products may enter the Solar System (SS) trapped in cosmic dust. Hence, nearby SNe might deposit traces on Earth and since it has negligible terrestrial production, 60Fe is an ideal candidate to search for recent SNe. However, detection requires sensitivities of 60Fe/Fe~10-15 and 60Fe-AMS faces interference from stable 60Ni. So far only TU Munich, combining a MP tandem with a gas-filled magnet, measures 60Fe routinely as los as ~10-16. This group discovered live 60Fe in a deep-sea crust indicating that SNe-isotopes found their way to Earth 2-3 My ago [1]. Work is ongoing at TUM to validate this finding in other archives [2,3]. Further, Rugel et al. [4] measured a half-life substantially longer than previously recommended. We have started a similiar program at the ANU using the 14UD accelerator and a split-pole magnetic spectrograph converted into a gas-filled magnet. A substantial beamtime devoted to 60Fe has resulted in an exceptional sensitivity below 10-16. We have searched for a SN-signal in 3 deep-sea sediment cores (indian Ocean) [5]. We will present exciting new data for 60Fe with high time resolution and will relate it to potantial exposure of the SS to recent SNe. In addition, we re-measured in an independent approach the 60Fe half-life via AMS measurements of the 60 Fe/55Fe ratio.
[1] Knie et al. PRL93 (2004)
[2] Ludwig et al. this conf.
[3] Fimiani et al. LPSC 1659 (2012)
[4] Rugel et al. PRL103 (2009)
[5] Feige et al. this conf.

Keywords: accelerator mass spectrometry; supernova; radionuclide

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  • Lecture (Conference)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Permalink: https://www.hzdr.de/publications/Publ-20187


Paramagnetic Decoration of DNA origami Nanostructures by Eu3+ Coordination

Opherden, L.; Oertel, J.; Barkleit, A.; Fahmy, K.; Keller, K.

Abstract

The folding of DNA into arbitrary two- and three-dimensional shapes, called DNA origami, represents a powerful tool for the synthesis of functional nanostructures. Here, we present the first approach toward the paramagnetic functionalization of DNA origami nanostructures by utilizing post-assembly coordination with Eu3+ ions. In contrast to the usual formation of toroidal dsDNA condensates in the presence of trivalent cations, planar as well as rod-like DNA origami maintain their shape and monomeric state even under high loading with the trivalent lanthanide. Europium-coordination was demonstrated by the change in Eu3+ luminescence upon binding to the two DNA origami. Their natural circular dichroism in the Mg2+- and Eu3+-bound state was found to be very similar to that of genomic DNA, evidencing little influence of the DNA origami superstructure on the local chirality of the stacked base pairs. In contrast, the magnetic circular dichroism of the Mg2+-bound DNA origami deviates from that of genomic DNA. Furthermore, the lanthanide affects the magnetic properties of DNA in a superstructure-dependent fashion, indicative of the existence of superstructure-specific geometry of Eu3+ binding sites in the DNA origami that are not formed in genomic DNA. This simple approach lays the foundation for the generation of DNA origami with taylored lanthanide-specificity. Such systems do not require covalent modifications and can be used for the magnetic manipulation of DNA nanostructures or for the paramagnetic alignment of molecules in NMR spectroscopy.

Keywords: magnetic circular dichroism; molecular alignment; lanthanide; NMR spectroscopy

Permalink: https://www.hzdr.de/publications/Publ-20186


CFD based approach for modeling direct contact condensation heat transfer in two-phase turbulent stratified flows

Apanasevich, P.; Lucas, D.; Beyer, M.; Szalinski, L.

Abstract

This paper describes a CFD based strategy for the modeling of stratified two-phase flows with heat and mass transfer across a moving steam-water interface due to direct contact condensation. Such flows have been of major importance for example in connection with the analysis of nuclear reactor safety systems, in particular during two-phase Pressurized Thermal Shock (PTS) scenarios. The approach is based on the two-fluid phase-average model. The interfacial friction was modeled by using an Algebraic Interfacial Area Density (AIAD) framework where the drag coefficient is a function of the local flow characteristics. To show the impact of the modeling of interfacial friction the simulation with the AIAD model was compared with a simulation where a constant drag coefficient of 0.44 was used in the whole domain. For the modeling of interfacial heat and mass transfer two correlations for the water heat transfer coefficient based on the penetration theory were utilized. The CFD simulations were validated against a steady-state TOPFLOW-PTS steam-water experiment. In the experiment, very detailed temperature measurements were conducted using special thermocouple lances and infrared thermography. Total condensation rate was determined indirectly by using three different methods. The simulations have depicted that the results obtained with the AIAD model are considerably closer to the experimental observations than the results obtained with the constant drag coefficient. It was also shown that a correct prediction of condensation rates is very important for prediction of the temperature field. In general, the simulations of the TOPFLOW-PTS steam/water experiment with condensation have revealed that Reynolds Averaged Navier-Stokes method can be applied for the simulation of two-phase stratified flows with rather large free surfaces and interfacial heat transfer. However, the modeling of turbulent interfacial heat transfer should be improved.

Keywords: computational fluid dynamics; stratified two-phase flow; pressurized thermal shock; interfacial heat and mass transfer; direct contact condensation; TOPFLOW-PTS experiments

Involved research facilities

  • TOPFLOW Facility

Permalink: https://www.hzdr.de/publications/Publ-20185


Investigation of vertical gas-liquid pipe flows using ultrafast X-ray tomography – An overview of methods, measurement series and previous results

Banowski, M.; Lucas, D.; Beyer, M.; Szalinski, L.; Hoppe, D.; Hampel, U.

Abstract

In this presentation, methods, measurement series and previous results of upward, counter-current as well as downward gas-liquid flows at the vertical titanium pipe of the TOPFLOW test facility are shown.

Involved research facilities

  • TOPFLOW Facility
  • Lecture (Conference)
    German CFD Network of Competence, Workshop, 19.-20.03.2014, München-Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20184


Systematic investigation of terahertz-induced excitonic Rabi splitting

Teich, M.; Wagner, M.; Stehr, D.; Schneider, H.; Helm, M.; Böttge, C. N.; Klettke, A. C.; Chatterjee, S.; Kira, M.; Koch, S. W.; Khitrova, G.; Gibbs, H. M.

Abstract

Weak near-infrared and strong terahertz excitation are applied to study excitonic Rabi splitting in (GaIn)As/GaAs quantum wells. Pronounced anticrossing behavior of the split peaks is observed for different terahertz intensities and detunings relative to the intra-excitonic heavy-hole 1s–2p transition. At intermediate to high electric fields the splitting becomes highly asymmetric and exhibits significant broadening. A fully microscopic theory is needed to explain the experimental results. Comparisons with a two-level model reveal the increasing importance of higher excitonic states at elevated excitation levels.

Keywords: QW; FEL; Autler-Townes; THz

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Permalink: https://www.hzdr.de/publications/Publ-20183


One-Group Cross-Section Generation for Monte Carlo Burnup Codes: Multigroup Method Extension and Verification

Kotlyar, D.; Fridman, E.; Shwageraus, E.

Abstract

Allowing Monte Carlo (MC) codes to perform fuel cycle calculations requires coupling to a point depletion solver. In order to perform depletion calculations, one-group (1-g) cross sections must be provided in advance. This paper focuses on generating accurate 1-g cross section values using Monte Carlo transport codes.
The proposed method is an alternative to the conventional direct reaction rate tally approach, which requires substantial computational effort. The method presented here is based on the multi-group (MG) approach, in which pre-generated MG sets are collapsed with MC calculated flux. In our previous studies, we showed that generating accurate 1-g cross sections requires their tabulation against the background cross section (σ0) to account for the self-shielding effect in unresolved resonance energy range. However, in previous studies, the model used for calculation of σ0 was simplified by relying on user specified Bell and Dancoff factors.
This work demonstrates that 1-g values calculated under the previous simplified model assumptions may not always agree with the directly tallied values. More specifically, the assumption is not universally applicable to the analysis of wide spectrum of reactor systems and may be inaccurate when the number of energy groups is reduced (i.e. from tens of thousands to hundreds of groups). Therefore, the original background cross section model was extended by implicitly accounting for the Dancoff and Bell factors. The method developed here reconstructs the correct value of σ0 by utilizing statistical data generated within the MC transport calculation by default. The proposed method was implemented in BGCore code system. The 1-g cross section values generated by BGCore were compared with those tallied directly from the MCNP code. Very good agreement in the 1-g cross values was observed. The method does not carry any additional computational burden and it is universally applicable to the analysis of thermal as well as fast reactor systems. Adopting this MG methodology, which accounts for self-shielding, allows generating highly accurate cross sections even for significantly reduced number of energy groups (hundreds vs. tens of thousands). This reduction considerably improves the computational efficiency which makes feasible the analysis of large scale reactor problems.

Keywords: Coupled Monte Carlo codes; BGCore; Multi group; One-group cross sections; Background cross section

Permalink: https://www.hzdr.de/publications/Publ-20182


Experimente zu vertikalen Dampf-Wasser-Rohrströmungen mit ultraschneller Röntgentomographie

Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.

Abstract

Gas-Flüssigkeits-Zweiphasenströmungen in Rohrleitungen sind für die Entwicklung und Validierung neuer zweiphasiger CFD-Modelle ein geeigneter generischer Untersuchungsgegenstand. Der Grad an strömungsmorphologischer Komplexität ist relativ hoch, was sich insbesondere in der Ausprägung charakteristischer Strömungsregime mit ihren jeweils spezifischen Impulstransferbeziehungen an der Phasengrenze in Abhängigkeit von Leerrohrgeschwindigkeiten und Stoffwerten äußert. An der TOPFLOW-Versuchsanlage des HZDR werden gegenwärtig umfangreiche experimentelle Studien zu Zweiphasenströmungen in senkrechten Testsektionen für Wasser/Luft- und Wasser/Dampf-Strömungen bis 65 bar Druck durchgeführt. Diese Experimente dienen vordergründig der Erhebung von Messdaten für die CFD-Codeentwicklung. Als Messverfahren kommt in aktuellen Versuchen an einer vertikalen DN50 Testsektion die ultraschnelle Röntgentomographie zum Einsatz. Diese ermöglicht es, den Strömungsquerschnitt mit Bildraten von 2500 Bildern/Sekunde und einer räumlichen Auflösung von etwa 1 mm in zwei jeweils 10 mm entfernten Ebenen abzubilden. Verschiedene Strömungsregime werden durch Wahl der Leerohrgeschwindigkeiten für die Gas- und die Flüssigphase am Versuchsstand eingestellt. Neben der Aufklärung des Strömungsregimes und der Erfassung interessanter Detailstrukturen der Strömung können radiale Gasgehaltsprofile ebenso wie Gasphasengeschwindigkeiten durch automatisierte Auswerteroutinen extrahiert werden. Im Beitrag werden Ergebnisse von Dampf-Wasser-Experimenten zu auf- und abwärtsgerichteten Gleichströmungen bei verschiedenen Druckstufen vorgestellt.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.

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  • TOPFLOW Facility
  • Poster
    ProcessNet Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20181


Investigation of Scintillation Detectors for Prompt Gamma Imaging

Römer, K.; Petzoldt, J.; Berthel, M.; Dreyer, A.; Enghardt, W.; Golnik, C.; Hueso-González, F.; Kormoll, T.; Müller, A.; Pausch, G.; Rohling, H.; Schöne, S.; Weinberger, D.; Fiedler, F.

Abstract

Characterization of Scintillators with respect to their Application in Prompt Gamma Imaging Systems.

Keywords: Prompt Gamma Imaging; Scintillation Detectors

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  • Poster
    OncoRay Retreat 2014, 27.-28.03.2014, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20180


Experimentelle Untersuchung von aufwärtsgerichteten zweiphasigen Rohrströmungen mit ultraschneller Röntgentomographie

Banowski, M.; Lucas, D.; Beyer, M.; Hampel, U.

Abstract

Die Entwicklung von CFD-Modellen zur Berechnung von Zweiphasenströmungen für industrielle Anwendungen in der Prozessindustrie stellt eine große Herausforderung dar. Zweiphasenströmungen in Reaktions- oder Trennapparaten sind infolge der auf mehreren Skalen ablaufenden Transportprozesse für Impuls, Stoff und Wärme inhärent hoch komplex. Zur Validierung von CFD-Codes sind daher experimentelle quantitative Daten solcher Strömungen mit hoher zeitlicher und räumlicher Auflösung erforderlich.
An der TOPFLOW-Versuchsanlage des HZDR werden auf diesem Gebiet umfangreiche Versuche an einer vertikalen DN50-Testsektion mit Luft-Wasser und Dampf-Wasser-Strömungen bis zu p = 65 bar und einer weiten Variation der Leerrohrgeschwindigkeiten für Wasser- und Gasphase durchgeführt. Unter Verwendung der am HZDR entwickelten ultraschnellen Röntgentomographie können Strömungsquerschnitte mit Bildraten von bis zu 2500 frames/s und einer räumlichen Auflösung von etwa 1 mm rückwirkungsfrei erfasst und visualisiert werden. Neben der Ermittlung von Strömungsregimen und weiterer charakteristischer Strömunsgkenngrößen dienen diese Untersuchungen dem Erkenntnisgewinn über Strömungsdetails, wie etwa Blasenkoaleszenz und –zerfall, radiale Gasgehaltsprofile, Strömungsverhalten von Kleinblasen in Abhängigkeit benachbarter Blasen sowie Geschwindigkeitsinformationen, in hochturbulenten Zweiphasenströmungen bei industriell relevanten Gasgehalten. Mit Hilfe von speziell entwickelten Bildauswertungsroutinen können diese Daten analysiert und für die Zweiphasen-CFD-Modellvalidierung aufbereitet werden. In diesem Beitrag wird ein Überblick über bisherige Versuche und deren Ergebnisse gegeben.
Diese Arbeit wird im Rahmen eines aktuellen Forschungsprojekts, welches vom Bundesministerium für Wirtschaft und Technologie unter der Projektnummer 150 1411 gefördert wird, durchgeführt.

Involved research facilities

  • TOPFLOW Facility
  • Poster
    ProcessNet Jahrestreffen der Fachgruppen Extraktion und Fluidverfahrenstechnik, 27.-28.03.2014, Fulda, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20179


Design, synthesis, characterisation and in vitro studies of hydrophilic, colloidally-stable, 64Cu(II)-labelled, ultra-small iron oxide nanoparticles in a range of human cell lines

Pombo Garcia, K.; Zarschler, K.; Barreto, J. A.; Spiccia, L.; Graham, B.; Stephan, H.

Abstract

The application of ultra-small super-paramagnetic iron oxide nanoparticles (USPIONs) as versatile diagnostic probes for multimodal imaging in biomedicine, including via magnetic resonance imaging (MRI) and positron emission tomography (PET), requires hydrophilic and biocompatible surface coatings. Herein, we describe the development of USPIONs stabilised by octylamine-modified polyacrylic acid (OPA) and the subsequent
conjugation of a 64Cu(II) chelator, N-(4-aminophenyl)-2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]- acetamide (amino-dmptacn), for radioactivity-based detection. Transmission electron microscopic analysis and dynamic light scattering measurements confirmed the monodispersity and stability of the OPA-USPIONs in aqueous media and revealed a hydrodynamic size of ca. 15 nm. Furthermore, the biocompatibility and cellular uptake efficiency of the functionalised USPIONs was investigated in a range of normal and tumour cell lines. The results clearly show a cell type- as well as time-dependent internalisation of the OPA-USPIONs via active energy-dependent pathways. Biocompatibility of OPA- USPIONs in the concentration range of 10–50 mg mL-1 was demonstrated, while impairment of cellular viability was observed for human umbilical vein endothelial cells at 100 mg mL-1. Upon exposure to human serum, several biomolecules cover the negatively-charged surface of the nanoparticles and a biomolecular corona is formed. Nonetheless, the nanoparticles represent a promising platform for the future development of a bimodal PET-MRI tumour-imaging agent.

References
1. K. Pombo-Garcia, K. Zarschler, J. A. Barreto, J. Hesse, L. Spiccia, B. Graham, H. Stephan, RSC Advances 2013, 3, 22443.
2. M. P. Monopoli, D. Walczyk, A. Campbell, G. Elia, I. Lynch, F. B. Bombelli and K. A. Dawson, J Am Chem Soc, 2011, 133, 2525-2534.

Acknowledgements: Helmholtz Initiative and Networking Fund (Functional nanomaterials for multimodality cancer imaging (NanoTracking), project ID: VH-VI-421). Australian Research Council Discovery Grant and a Discovery Outstanding Researcher Award and a Senior Research Award by the Humboldt Foundation are gratefully acknowledged by L.S.

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  • PET-Center
  • Poster
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy

Permalink: https://www.hzdr.de/publications/Publ-20177


Ultrasmall and radiolabelled upconverting nanophosphors – ready for challenge of multimodal cancer imaging

Hesse, J.; Graham, B.; Geipel, G.; Grenzer, J.; Spiccia, L.; Steinbach, J.; Stephan, H.

Abstract

The increasing interest in nanomaterials for medical applications is mainly attributed to their unique and structural properties. Based on different materials like polymers, inorganic or organic-inorganic hybrid substances such nanomaterials are investigated for applications in biological systems. Regarding this upconverting nanophosphors exhibit a high potential because of their bright luminescence. With their exceptional characteristic to convert near infrared to visible light (upconversion) these inorganic lanthanide-doped nanoparticles are very attractive as probes for optical imaging with the possibiliy for elucidation of even cellular processes[1]. In addition the surface of the nanoparticles offer the chance for rather multiple functionalisation such as radiometall chelates for PET and SPECT as well as for tumor affine units (peptides, aptamers, antibodies).
We want to present the synthesis and photophysical properties of ultrasmall (<10 nm) upconverting nanophosphors based on a host lattice of NaYF4: (Nd3+),Yb3+, Er3+/Tm3+ which are excited at 800 nm or 980 nm. To generate watersoluble biocompatible nanoparticles the material was coated with different polymers and afterwards functionalized with DMPTACN, a picolyl derivative of the macrocyclic ligand 1,4,7-triazacyclononane. An initial point for further investigations in vitro and in vivo was achieved by radiolabelling with the positron emitter Cu-64.

References
1. Cheng, L. , Wang, C. , Liu, Z. Nanoscale. 2013, 5, 23-37.

Acknowledgements: This work was funded by the Helmholtz Initiative and Networking Fund „Functional nanomaterials for multimodality cancer imaging“ (NanoTracking, project ID: VH-VI-421).

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  • PET-Center
  • Poster
    e-WISPOC: European-Winter School on Physical Organic Chemistry, 02.-07.02.2014, Bressanone, Italy

Permalink: https://www.hzdr.de/publications/Publ-20176


Emittance minimization at the ELBE superconducting electron gun

Möller, K.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

Abstract

The transverse emittance is one of the most important quantities which characterize the quality of an electron source. For high quality experiments low beam emittance is required. By means of theoretical considerations and simulation calculations we have studied how the emittance of the Rossendorf superconducting radio-frequency photoelectron source (SRF gun) can be minimized. It turned out that neither a solenoid magnet nor the effect of space charge forces is needed to create a pronounced emittance minimum. The minimum appears by just adjusting the starting phase of the electron bunch with respect to the RF phase of the gun in a suitable way. Investigation of various correlations between the properties of the beam particles led to an explanation on how the minimum comes about. It is shown that the basic mechanism of minimization is the fact that the longitudinal properties of the particles (energy) are strongly influenced by the starting phase. Due to the coupling of the longitudinal and transverse degrees of freedom by the relativistic equation of motion the transverse degrees of freedom and thereby the emittance can be strongly influenced by the starting phase as well. The results obtained in this study will be applied to minimize the emittance in the commissioning phase of the SRF gun.

Keywords: electron gun; SRF gun; superconducting radio frequency; electron injector; transverse emittance

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Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-050 2014
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-20175


Metastatic potential of B16-F10 melanoma cells is enhanced by extracellular S100A4 derived from RAW264.7 macrophages

Haase-Kohn, C.; Wolf, S.; Herwig, N.; Mosch, B.; Pietzsch, J.

Abstract

S100A4, synthesized and secreted from both tumor and stroma cells, modulates an aggressive tumor phenotype in various cancers by intracellular and extracellular interactions which are not completely understood. Because of the high content of tumor-associated macrophages in melanoma, here, a syngeneic model (coculture of mouse B16-F10 melanoma cells (Mel) and RAW264.7 macrophages (Mϕ); administration (i.v.) of Mel and Mϕ/Mel in NMRI nu/nu mice) was used to investigate synthesis and secretion of a) S100A4, b) S100A4-mediated signaling and activation of NFκB, and c) S100A4-mediated modulation of Mel invasiveness in vitro (transwell assay, transwell matrigel assay) and in vivo (metastatic lung colonization), respectively. In this model substantial S100A4 synthesis and secretion is demonstrated in Mϕ. Macrophage-derived S100A4 promotes Mel invasiveness in a paracrine manner in vitro, which is further substantiated in control experiments using recombinant human S100A4 and Mel stably transfected with mouse S100A4. Moreover, the participation of S100A4-mediated signaling, e.g., via the receptor for advanced glycation endproducts (RAGE), resulting in activation of NFκB was demonstrated in all experimental settings. Finally, we demonstrated that interaction of macrophage-derived S100A4 with Mel results in increased metastatic lung colonization in vivo.

Keywords: Melanoma metastasis; Receptor for advanced glycation; endproducts (RAGE); S100 proteins; Tumor-associated macrophages (TAM)

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-20174


Simultaneous Targeting of Prostate Stem Cell Antigen and Prostate-Specific Membrane Antigen Improves the Killing of Prostate Cancer Cells Using a Novel Modular T Cell-Retargeting System

Arndt, C.; Feldmann, A.; Koristka, S.; Cartellieri, M.; Dimmel, M.; Ehninger, A.; Ehninger, G.; Bachmann, M.

Abstract

BACKGROUND
Recently, we described a novel modular platform technology in which T cell-recruitment and tumor-targeting domains of conventional bispecific antibodies are split to independent components, a universal effector module (EM) and replaceable monospecific/monovalent target modules (TMs) that form highly efficient T cell-retargeting complexes. Theoretically, our unique strategy should allow us to simultaneously retarget T cells to different tumor antigens by combining the EM with two or more different monovalent/monospecific TMs or even with bivalent/bispecific TMs, thereby overcoming limitations of a monospecific treatment such as the selection of target-negative tumor escape variants.
METHODS
In order to advance our recently introduced prostate stem cell antigen (PSCA)-specific modular system for a dual-targeting of prostate cancer cells, two additional TMs were constructed: a monovalent/monospecific TM directed against the prostate-specific membrane antigen (PSMA) and a bivalent/bispecific TM (bsTM) with specificity for PSMA and PSCA. The functionality of the novel dual-targeting strategies was analyzed by performing T cell activation and chromium release assays.
RESULTS
Similar to the PSCA-specific modular system, the novel PSMA-specific modular system mediates an efficient target-dependent and -specific tumor cell lysis at low E:T ratios and picomolar Ab concentrations. Moreover, by combination of the EM with either the bispecific TM directed to PSMA and PSCA or both monospecifc TMs directed to either PSCA or PSMA, dual-specific targeting complexes were formed which allowed us to kill potential escape variants expressing only one or the other target antigen.
CONCLUSIONS
Overall, the novel modular system represents a promising tool for multiple tumor targeting.

Keywords: T cell redirection; dual-targeting; recombinant antibody; immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-20173


A novel ex vivo Isolation and Expansion Procedure for Chimeric Antigen Receptor Engrafted Human T Cells

Cartellieri, M.; Koristka, S.; Arndt, C.; Feldmann, A.; Stamova, S.; von Bonin, M.; Töpfer, K.; Krüger, T.; Geib, M.; Michalk, I.; Temme, A.; Bornhäuser, M.; Lindemann, D.; Ehninger, G.; Bachmann, M. P.

Abstract

Genetically engineered T lymphocytes are a promising option for cancer therapy. Prior to adoptive transfer they have to be expanded in vitro to reach therapeutically sufficient numbers. So far, no universal method exists for selective in vitro expansion of engineered T lymphocytes. In order to overcome this problem and for proof of concept we incorporated a novel unique peptide sequence of ten amino acids as epitope (ETag) into the binding domains of two novel chimeric antigen receptors (ECARs) directed against either prostate stem cell antigen (PSCA) for the treatment of prostate cancer (PCa) or CD33 for the treatment of acute myeloide leukemia (AML). The epitope tag then was utilized for expanding ECAR engrafted T cells by triggering the modified T cells via a monoclonal antibody directed against the E-Tag (Emab). Moreover, the E-Tag served as an efficient selection epitope for immunomagnetic isolation of modified T cells to high purity. ECAR engrafted T cells were fully functional and mediated profound anti-tumor effects in the respective models of PCa or AML both in vitro and in vivo. The method can be integrated straightforward into clinical protocols to improve therapeutic efficiency of tumor treatment with CAR modified T lymphocytes.

Keywords: adoptive transfer; genetically engineered T cells; chimeric antigen receptor; in vitro cultivation; tumor immunotherapy; Tumor; cancer; T cell; Genetic engineering

Permalink: https://www.hzdr.de/publications/Publ-20172


Oxygen depth profiling with subnanometre depth resolution

Kosmata, M.; Munnik, F.; Hanf, D.; Grötzschel, R.; Richter, S.; Möller, W.

Abstract

An High-depth Resolution Elastic Recoil Detection (HR-ERD) set-up using a magnetic spectrometer has been taken into operation at the Helmholtz-Zentrum Dresden-Rossendorf for the first time. This instrument allows the investigation of light elements in ultra thin layers and their interfaces with a depth resolution of less than 1 nm near the surface. As the depth resolution is highly influenced by the experimental measurement parameters, sophisticated optimisation procedures have been implemented. Effects of surface roughness and sample damage caused by high fluences need to be quantified for each kind of material. Also corrections are essential for non-equilibrium charge state distributions that exist very close to the surface. Using the example of an high-k multilayer SiO2/Si3N4Ox/SiO2/Si it is demonstrated that oxygen in ultra-thin films of a few nanometres thickness can be investigated by HR-ERD.

Keywords: high resolution depth profiling; ERD; high-k materials

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Permalink: https://www.hzdr.de/publications/Publ-20171


Characterization of a novel single-chain bispecific antibody for retargeting of T cells to tumor cells via the TCR co-receptor CD8

Michalk, I.; Feldmann, A.; Koristka, S.; Arndt, C.; Cartellieri, M.; Ehninger, A.; Ehninger, G.; Bachmann, M. P.

Abstract

There is currently growing interest in retargeting of effector T cells to tumor cells via bispecific antibodies (bsAbs). Usually, bsAbs are directed on the one hand to the CD3 complex of T cells and on the other hand to a molecule expressed on the surface of the target cell. A bsAb mediating cross-linkage via CD3 leads to an activation of CD8+ T cells and as a consequence to the killing of the target cells. In parallel, CD4+ T cells including TH1, Th2, TH17 cells and even regulatory T cells (Tregs) will also be activated. Cytokines produced by CD4+ T cells can contribute to severe side effects e. g. life-threatening cytokine storms and, thinking of the immunosupressive function of Tregs, can even be counterproductive. Therefore, we asked whether or not it is feasible to limit the retargeting to CD8+ T cells e. g. via targeting of the co-receptor CD8 instead of CD3. In order to test for proof of concept, a novel bsAb with specificity for CD8 and a tumor-associated surface antigen was constructed. Interestingly, we found that pre-activated (but not freshly isolated) T cells can be retargeted via CD8 leading to an efficient lysis of the target cells.

Keywords: tumor immunotherapy; tumor; cancer; T cell; bispecific antibodies

Permalink: https://www.hzdr.de/publications/Publ-20170


Letter to the editor: Cytotoxic response of human regulatory 1 T cells upon T cell receptor-mediated activation – a 2 matter of purity

Koristka, S.; Cartellieri, M.; Arndt, C.; Feldmann, A.; Töpfer, K.; Michalk, I.; Temme, A.; Ehninger, G.; Bachmann, M.

Permalink: https://www.hzdr.de/publications/Publ-20169


Concept for individualized patient allocation: ReCompare-remote comparison of particle and photon treatment plans

Lühr, A.; Löck, S.; Roth, K.; Helmbrecht, S.; Jakobi, A.; Petersen, J. B.; Just, U.; Krause, M.; Enghardt, W.; Baumann, M.

Abstract

Background: Identifying those patients who have a higher chance to be cured with fewer side effects by particle beam therapy than by state-of-the-art photon therapy is essential to guarantee a fair and sufficient access to specialized radiotherapy. The individualized identification requires initiatives by particle as well as non-particle radiotherapy centers to form networks, to establish procedures for the decision process, and to implement means for the remote exchange of relevant patient information. In this work, we want to contribute a practical concept that addresses these requirements.Methods: We proposed a concept for individualized patient allocation to photon or particle beam therapy at a non-particle radiotherapy institution that bases on remote treatment plan comparison. We translated this concept into the web-based software tool ReCompare (REmote COMparison of PARticlE and photon treatment plans).Results: We substantiated the feasibility of the proposed concept by demonstrating remote exchange of treatment plans between radiotherapy institutions and the direct comparison of photon and particle treatment plans in photon treatment planning systems. ReCompare worked with several tested standard treatment planning systems, ensured patient data protection, and integrated in the clinical workflow.Conclusions: Our concept supports non-particle radiotherapy institutions with the patient-specific treatment decision on the optimal irradiation modality by providing expertise from a particle therapy center. The software tool ReCompare may help to improve and standardize this personalized treatment decision. It will be available from our website when proton therapy is operational at our facility. © 2014 Lühr et al.; licensee BioMed Central Ltd.

Keywords: Particle therapy, Patient selection; Proton therapy; Treatment plan comparison

Permalink: https://www.hzdr.de/publications/Publ-20168


Visualizing inflammation activity in rheumatoid arthritis with Tc-99 m Anti-CD4-mAb fragment scintigraphy

Steinhoff, K.; Pierer, M.; Siegert, J.; Pigla, U.; Laub, R.; Hesse, S.; Seidel, W.; Sorger, D.; Seese, A.; Künstler, J.-U.; Pietzsch, H.-J.; Lincke, T.; Rullmann, M.; Emmrich, F.; Sabri, O.

Abstract

Purpose:

T-cell-located CD4 antigen represents one of the therapeutic targets in rheumatoid arthritis (RA). However, up to now there is no established imaging tool to visualize this target in vivo. The aim of our study was to assess the safety and tolerability of a technetium-99 m labelled murine anti-human CD4 IgG1-Fab fragment ([99mTc]-anti-CD4-Fab, [99mTc]-EP1645) in patients with active synovitis due to RA, and to evaluate its potential as a marker of disease activity.
Methods:
In the present phase I proof of principle study five patients with RA were examined. Planar scans of the whole body, hands, and feet were taken 30 min up to 24 h after application of 550 ± 150 MBq [99mTc]-anti-CD4-Fab, followed by visual analyses, comparison with clinical data in 68 joints per patient and semiquantitative analysis of hand and wrist joints.
Results:
Neither infusion related adverse events nor adverse events during follow up were observed. No increase in human anti-murine antibody titres was seen. All patients had positive scans in almost 70% of clinically affected joints. Positive scans were also found in 8% of joints without evidence of swelling or tenderness.
Conclusion:
Scintigraphy with [99mTc]-anti-CD4-Fab is a promising technique for evaluation of inflammatory activity in patients with RA, pre-therapeutical evaluation of CD4 status and therapy control. Tracer uptake in clinically inconspicuous joints strongly indicates diagnostic potential of [99mTc]-anti-CD4-Fab. Whether this technique is eligible as a prognostic factor in RA needs to be analysed in further studies as well as the pathophysiological background of clinically affected joints lacking tracer uptake.

Keywords: CD4; Monoclonal antibodies; Technetium-99 m scintigraphy; Rheumatoid arthritis; Molecular imaging

Permalink: https://www.hzdr.de/publications/Publ-20166


Influence of different chelators on the radiochemical properties of a 68-Gallium labelled bombesin analogue.

Asti, M.; Iori, M.; Capponi, P. C.; Atti, G.; Rubagotti, S.; Martin, R.; Brennauer, A.; Müller, M.; Bergmann, R.; Erba, P. A.; Versari, A.

Abstract

The radiolabelled bombesin analogue AMBA shows high potential for diagnosis and treatment of prostate and breast cancer, but the influence of different chelators, which differ in terms of radiochemical reactivity and stability, have not been explored so far. In order to find the best suitable chelator for labelling of AMBA, we synthesized AMBA analogues linked to the most commonly used chelators DOTA, NOTA and NODAGA and compared their reactivity and stability after labelling with 68-Gallium.

Keywords: 68Ga-labelling; AMBA-chelators; Bombesin analogues; 68Ga-NODAGA-AMBA; Gallium radionuclides

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  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-20165


Radiolabeled anti-EGFR-antibody improves local tumor control after external beam radiotherapy and offers theragnostic potential

Koi, L.; Bergmann, R.; Brüchner, K.; Pietzsch, J.; Pietzsch, H.-J.; Krause, M.; Steinbach, J.; Zips, D.; Baumann, M.

Abstract

PURPOSE:

The effect of radioimmunotherapy (RIT) using the therapeutic radionuclide Y-90 bound to the anti-EGFR antibody cetuximab combined with external beam irradiation (EBRT) (EBRIT) on permanent local tumor control in vivo was examined.
METHODS:
Growth delay was evaluated in three human squamous cell carcinoma models after RIT with [(90)Y]Y-(CHX-A''-DTPA)4-cetuximab (Y-90-cetuximab). The EBRT dose required to cure 50% of the tumors (TCD50) for EBRT alone or EBRIT was evaluated in one RIT-responder (FaDu) and one RIT-non-responder (UT-SCC-5). EGFR expression and microenvironmental parameters were evaluated in untreated tumors, bioavailability was visualized by PET using ([(86)Y]Y-(CHX-A''-DTPA)4-cetuximab (Y-86-cetuximab) and biodistribution using Y-90-cetuximab.
RESULTS:
In UT-SCC-8 and FaDu but not in UT-SCC-5 radiolabeled cetuximab led to significant tumor growth delay. TCD50 after EBRT was significantly decreased by EGFR-targeted RIT in FaDu but not in UT-SCC-5. In contrast to EGFR expression, parameters of the tumor micromilieu and in particular the Y-90-cetuximab biodistribution or Y-86-cetuximab visualization in PET correlated with the responsiveness to RIT or EBRIT.
CONCLUSION:
EGFR-targeted EBRIT can improve permanent local tumor control compared to EBRT alone. PET imaging of bioavailability of labeled cetuximab appears to be a suitable predictor for response to EBRIT. This theragnostic approach should be further explored for clinical translation.

Keywords: Cetuximab; Combined treatment; Epidermal growth factor receptor (EGFR) inhibition; Radioimmunotherapy; Radiotherapy

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-20164


Investigations on multi phase flow in inline separators using ultra fast X-ray tomography and wire mesh sensors

Schäfer, T.; Schleicher, E.; Hampel, U.

Abstract

The optimization of separation processes with respect to the capacity and efficiency and the decreasing of the required residence time for the separation is significant for production of raw materials for petrochemical industries and in numerous operations of process engineering. Compact inline separators with swirl elements provide a smart technology for fast and robust mechanical separation of gases and liquids. A significant advantage of these separators is their small size and their applicability directly in pipes. However, unfavorable operating states in terms of separation quality (selectivity) appearing under specific conditions, caused by flow instabilities. They are leading to gas and liquid carry over effects. For the here presented tomographic investigations, it was a main objective to analyze the fluid dynamics inside and in the surrounding area of these separators, to improve the quality and efficiency of these separators. Therefore, ultrafast X-ray tomography and wire mesh sensor technology were used. Applying these tomographic measurement techniques, hydrodynamic characteristics, like the local distribution of the phase fractions, can be captured with very high spatial and temporal resolution. Thus it was possible, to evaluate the separation quality as well as critical flow regimes. Additionally, the obtained data are a basis for the modeling of the separation processes and the effects occurring thereby. Based on this, CFD simulations of the processes can be executed more accurately and design modifications and optimizations of the inline separators can be derived.

Die Optimierung von Separationsverfahren hinsichtlich Leistungsstärke und Effizienz bei Verringerung der notwendigen Verweilzeiten für die Separation hat eine hohe Bedeutung für die Gewinnung von Rohstoffen für die petrochemische Industrie und in einer Vielzahl verfahrenstechnischer Prozesse. Kompakte Inline-Separatoren mit Drallelementen bieten dabei eine elegante Möglichkeit für eine schnelle und robuste mechanische Separation von Gasen und Flüssigkeiten. Ein wesentlicher Vorteil dieser Separatoren ist ihre geringe Größe und die Möglichkeit des direkten Einsatzes in Rohrleitungen. Dabei treten unter bestimmten Umständen jedoch auch ungünstige Zustände hinsichtlich der Qualität der Separation (Trennschärfe), verursacht durch Strömungsinstabilitäten, auf. Diese führen zu Gas- und Liquid-carry-over Effekten. Ein wesentliches Ziel der hier vorgestellten tomographischen Untersuchungen war es, die Strömungsdynamik in der Umgebung und innerhalb solcher Separatoren aufzuklären, um damit Qualität und Effizienz der Separation weiter zu verbessern. Für diese Untersuchungen wurde neben der ultraschnellen Röntgentomographie auch die Gittersensormesstechnik eingesetzt. Mit diesen beiden tomographischen Messtechniken können hydrodynamische Größen, wie die lokale Verteilung der einzelnen Phasenanteile, mit sehr hoher örtlicher und zeitlicher Auflösung gemessen werden. Mit diesen Messdaten war es möglich, die Separationsqualität zu beurteilen und kritische Strömungsregime zu erkennen. Die gewonnenen Daten bilden zudem die Grundlage für eine Modellierung des Separationsprozesses und dabei auftretender Effekte. Darauf aufbauend können genauere CFD-Simulationen der Prozesse durchgeführt werden und konstruktive Optimierungen für die Inline-Separatoren abgeleitet werden.

Keywords: multi phase flow; inline cyclonic separator; swirl element; x-ray tomography; wire mesh sensor

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  • TOPFLOW Facility
  • Poster
    Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland
  • Open Access Logo Contribution to proceedings
    Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland
    KURZFASSUNGEN - Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme– und Stoffübertragung: DECHEMA / VDI, 70-70

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Permalink: https://www.hzdr.de/publications/Publ-20163


Mean-field coefficients for helical flow fields

Giesecke, A.; Stefani, F.

Abstract

We have performed kinematic simulations of dynamo action driven by a small scale helical flow of a conducting fluid. We considered different Roberts-flow like configurations with and without a vertical mean flow in a periodic Cartesian domain. Mean field coefficients that allow a parameterization of induction effects of the small scale flow in terms of an alpha- and beta-effect are computed with the so-called test-field method. The validity of the test-field method is checked by comparing the numerical solutions obtained with a fully resolved velocity field and the solutions from a low resolution mean field model based on the corresponding alpha- and beta coefficients.

Below and slightly above the dynamo threshold our results show a good agreement in terms of growth-rates and vertical field wavenumber. In the strongly overcritical regime, however, field modes with a larger vertical wave number emerge and require a careful consideration of the scale dependence of the alpha-effect. As expected, the agreement between fully resolved models and mean field models is better for increasing scale separation, i.e., for smaller horizontal flow scales.

The behavior of the beta-effect, that essentially describes an enhancement of the magnetic diffusivity by the action of the small scale flow, is determined by the ratio of horizontal to vertical velocity components. For a small vertical flow amplitude, beta scales proportional to the square of the local magnetic Reynolds number whereas for a large relation between vertical and horizontal flow component, beta becomes proportional to the cube root of Rm. This behavior is in rough agreement with measurements of the turbulent beta-effect from Frick et al. (PRL 2010, 105 (18), 184502).

In models with mean flow we have also taken into account internal rods and/or walls that lie in the center of individual eddies and/or provide a separation of the eddies from each other. These flow guiding fixtures can be made of soft iron with a relative permeability much larger than one. The associated inhomogeneity significantly reduces the critical magnetic Reynolds number. However, the problem of modelling the induction effects caused by the non-uniform permeability distribution within the framework of mean field coefficients is yet to be solved.

Without additional effects of permeability, our results allow an easy extrapolation to arbitraryly large systems that consist of an extremely large number of individual helical eddies. Such flows cannot be resolved in direct simulations, but the corresponding mean field models allow to assess whether a certain configuration provides for dynamo action. Such estimations are indeed useful because the typical flow in the cores of fast reactors consists of a forced helical Motion around each individual fuel rod. The occurrence of dynamo action may cause a significant pressure drop in the system with unpredictable consequences for the cooling of the core.

Keywords: Dynamo; permeability; Mean-Field Dynamo Theory

  • Poster
    9th Pamir International Conference, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    9th Pamir International Conference, 16.-20.06.2014, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-20162


Numerical simulations for the DRESDYN precession dynamo

Giesecke, A.; Albrecht, T.; Gerbeth, G.; Gundrum, T.; Stefani, F.

Abstract

A fluid flow of liquid sodium in a cylindrical container, solely driven by precession, is considered as a source for magnetic field generation in the next generation dynamo experiment. The device is currently under development in the framework of the project DRESDYN at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR).

A preparatory small scale water experiment is already in operation in order to provide the hydrodynamic flow properties. First results show that the precessional forcing converts a rather large amount of kinetic energy from the exterior rotation into internal fluid flow. A further striking feature is the abrupt transition from a large scale, quasi-laminar flow to a more disordered turbulent state. In this state the dynamical pressure is reduced while the power required to maintain the rotation of the container is increased.

For slow precession rates, both the amplitude and the shape of the elementary inertial mode obtained from ultrasonic measurements could be well reproduced in hydrodynamic simulations. The simulations also show the presence of the second state at larger precession rates, however, the transition is less abrupt and the degree of turbulence remains much smaller than in the water experiment.

We have used the time-dependent velocity fields obtained from the numerical simulations as input data for kinematic simulations of the magnetic induction equation. So far, the resulting magnetic field growth rates remain below the dynamo threshold for magnetic Reynolds numbers up to Rm=2000 which is in contradiction with results presented by Nore et al (PRE, 84 (1), 016317). Further simulations are necessary in order to restrict the expedient parameter regime and to allow for an optimization of the experimental configuration.

Another possibility for dynamo action may result from the cyclonic vortices aligned parallel to the symmetry axis of the cylinder that have been observed by Mouhali et al (Exp. Fluids 2012, 53 (6), 1693). These vortices provide a efficient source for helicity but, so far, they have not been found in numerical simulations of precession driven flows. Future simulations of magnetic induction caused by precession driven flows will have to be based on analytical models of These vortices and their temporal behavior. This requires more detailed experimental measurements that are expected from the forthcoming upgrade of the water experiment with a 3d-PIV (Particle Image Velocimetry) system.

Keywords: Dynamo; Precession

  • Poster
    9th Pamir International Conference, 16.-20.06.2014, Riga, Latvia
  • Contribution to proceedings
    9th Pamir International Conference, 16.-20.06.2014, Riga, Latvia
  • Magnetohydrodynamics 51(2015)2, 293-302

Permalink: https://www.hzdr.de/publications/Publ-20161


Ion beam shaping of embedded metal nanoparticles by Si+ ion irradiation

Balaji, S.; Panigrahi, B. K.; Saravanan, K.; David, C.; Amirthapandian, S.; Kalavathi, S.; Nair, K. G. M.; Hübner, R.

Abstract

Fine Co and Pt nanoparticles are nucleated when a silica sample is implanted with 400 keV Co+ and 1370 keV Pt+ ions. At the implanted range, Co and Pt react to form small CoxPt(1-x) nanoparticles during Si+ ion irradiation at 300 °С. Thermal annealing of the pre-implanted silica substrate at 1000 °С results in the formation of spherical nanoparticles of various sizes. When irradiated with Si+ ions at 300 °С, particles in the size range of 5 - 17 nm undergo rod-like shape transformation with an elongation in the direction of the incident ion beam, while those particles in the size range of 17 - 26 nm turn into elliptical shape. Moreover, it is suspected that very big nanoparticles (size > 26 nm) decrease in size, while small nanoparticles (size < 5 nm) do not undergo any transformation. During Si+ ion irradiation, the crystalline nature of the nanoparticles is preserved. The results are discussed in the light of the thermal spike model.

Keywords: Ion beam shaping; CoxPt(1-x); Ion tracks; TEM

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Permalink: https://www.hzdr.de/publications/Publ-20160


High-field magnetization and magnetic phase diagrams in Nd2RhIn8 and Tb2RhIn8

Javorský, P.; Pajskr, K.; Klicpera, M.; Cermák, P.; Skourski, Y.; Andreev, A. V.

Abstract

We present magnetic phase diagrams of Nd2RhIn8 and Tb2RhIn8 determined by magnetization and magnetoresistivity measurements on single crystals, including high-field magnetization up to 60 T. Both compounds order antiferromagnetically with the c-axis as the easy magnetization axis. Their magnetic Phase diagrams are qualitatively rather similar. At low temperatures up to 1/2TN, when applying the field along the tetragonal c-axis, we observe first-order transition to another magnetic phase prior to transition to the ferromagnetic order. The magnetic phase diagrams resemble those of other R2RhIn8 or RRhIn5 compounds.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-20159


Experimental investigations on heat transfer and flow structure during high pressure steam condensation in a single near-horizontal pipe of a passive heat removal system

Geißler, T.

Abstract

Passive safety systems are a feature for improved accident control and mitigation in future nuclear power plants. One example of an advanced boiling water reactor with passive safety systems is the KERENA concept (Wagner u. a., 2011). In this concept a two-stage passive heat transfer chain between the reactor and a large water pool outside the containment is foreseen, which is passively activated in case of an accident. The first stage is an emergency condenser, which transfers the heat from the primary circuit to a core flooding pool in the containment. High-pressure steam condensation in the emergency condenser tubes leads to various complicated flow patterns with strong axial and azimuthal inhomogeneity of the flow. This has feed-back on the local heat transfer and is therefore a challenge for accurate prediction, e. g. by system codes. To investigate the details of flow and heat transfer in emergency condenser pipes the experimental facility COSMEA (Condensation teSt rig for flow Morphology and hEAt transfer studies) with extensive special instrumentation has been setup at HZDR’s TOPFLOW facility. Special attention was paid to obtain wall and fluid temperatures and resolve the local flow patterns during the condensation process. Special measurement techniques are a heat flux probe operated at high wall-differential pressure and X-ray tomography for flow scanning.

Keywords: high pressure condensation; COSMEA; TOPFLOW; passive safety system; heat transfer measurement; x-ray tomography; multiphase flow

Involved research facilities

  • TOPFLOW Facility
  • Lecture (Conference)
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.2014, Frankfurt am Main, Deutschland
  • Contribution to proceedings
    45th Annual Meeting on Nuclear Technology - Preserving Competence in Nuclear Technology, 06.-08.05.14, Frankfurt am Main, Deutschland
    Proceeding of 45th Annual Meeting on Nuclear Technology

Permalink: https://www.hzdr.de/publications/Publ-20158


High-field magnetization and magnetoelasticity of single crystalline HoFe5Al7

Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Skourski, Y.; Arnold, Z.; Zherlitsyn, S.; Wosnitza, J.

Abstract

Magnetization and ultrasound measurements have been performed in pulsed magnetic fields up to 60 T on a ferrimagnetic HoFe5Al7 single crystal (Curie temperature TC = 216 K, compensation point Tcomp = 65 K) with a tetragonal crystal structure of the ThMn12-type. The compound exhibits a high magnetic anisotropy of the easy-plane type. A large anisotropy is also observed within the basal plane having an easy-magnetization direction along the [110] axis with the spontaneous magnetic moment Ms = 2 μB/f.u. at T = 2 K. Along the easy axis, two first-order field-induced magnetic transitions are observed. At both transitions sharp anomalies in the acoustic properties are found. The critical fields of the transitions depend on temperature in a different manner. Within molecular-field theory and using the high-field magnetization data the Ho-Fe inter-sublattice exchange parameter has been determined to be nHoFe ≈ 4 T/μB. The magnetoelasticity has also been probed by magnetization measurements under hydrostatic pressure. TC decreases with a rate dTC/dp = −10 K/GPa, whereas Tcomp increases with dTcomp/dp = 3.5 K/GPa.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-20157


Strongly correlated one-dimensional magnetic behavior of NiTa 2O6

Law, J. M.; Koo, H.-J.; Whangbo, M.-H.; Brücher, E.; Pomjakushin, V.; Kremer, R. K.

Abstract

The magnetic properties of NiTa2O6 were investigated by magnetic susceptibility, specific heat, electron paramagnetic resonance, neutron powder diffraction, and pulse field magnetization measurements. Accompanying ab initio DFT calculations of the spin-exchange constants complemented and supported our experimental findings that NiTa2O6 must be described as a quasi-1D Heisenberg S=1 spin chain system with a nearest-neighbor only antiferromagnetic spin-exchange interaction of 18.92(2) K. Interchain coupling is by about two orders of magnitude smaller. Electron paramagnetic resonance measurements on Mg1-xNixTa2O6 (x≈1%) polycrystalline samples enabled us to estimate the single-ion zero-field splitting of the S=1 states which amounts to less than 4% of the nearest-neighbor spin-exchange interaction. At 0 T NiTa2O6 undergoes long-range antiferromagnetic ordering at 10.3(1) K evidenced by a λ-type anomaly in the specific heat capacity. On application of a magnetic field the specific heat anomaly is smeared out. We confirmed the magnetic structure by neutron powder diffraction measurements and at 2.00(1) K refined a magnetic moment of 1.93(5) μB per Ni2+ ion. Additionally, we followed the magnetic order parameter as a function of temperature. Last, we found saturation of the magnetic moment at 55.5(5) T with a g factor of 2.14(1), with an additional high field phase above 12.8(1) T. The onset of the new high field phase is not greatly affected by temperature, but rather smears out as one approaches the long-range ordering temperature.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

Permalink: https://www.hzdr.de/publications/Publ-20156


Signature of the topological surface state in the thermoelectric properties of Bi2Te3

Rittweger, F.; Hinsche, N. F.; Zahn, P.; Mertig, I.

Abstract

We present electronic structure calculations based on density functional theory for the thermoelectric properties of Bi2Te3 films. Conductivity and thermopower are computed in the diffusive limit of transport based on the Boltzmann equation. Bulk and surface contributions to the transport coefficients are separated by a special projection technique. As a result we show clear signatures of the topological surface state in the thermoelectric properties.

Keywords: PACS: 71.15.Mb; 73.50.Lw; 72.20.−i; 03.65.Vf

Permalink: https://www.hzdr.de/publications/Publ-20154


Building bridges from research to industry: Innovative resource technologies "Made in Germany"

Birtel, S.

Abstract

Tasks and structure of the Helmholtz Instiute Freiberg, Network, Options for colaboration, introduction of the opti-moly Project in Chile

Keywords: raw materials; strategic metals; Mo recovery

  • Invited lecture (Conferences)
    Länderworkshop und NEtworking Chile- Bergbauigant in der Andenregion, 19.-20.03.2014, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-20153


Local Ion Irradiation Induced Resistive Threshold and Memory Switching in Nb2O5/NbOx Films

Wylezich, H.; Mähne, H.; Rensberg, J.; Ronning, C.; Zahn, P.; Slesazeck, S.; Mikolajick, T.

Abstract

Summarizing, metal-insulator-metal devices consisting of one insulating Nb2O5 layer were irradiated with krypton ions to form a metallic NbOx sublayer in order to introduce threshold switching. Two effects were identified that induce this metallic NbOx layer: preferential sputtering at the sample surface and interface mixing at the bottom electrode. These krypton irradiated devices can be operated either as a pure threshold switch or as a combination of both, threshold switch and memory element. The presented fabrication method enables costefficient device manufacturing, since ion irradiation could be structured easily using well established lithography methods. Thus, the threshold switch can be formed in defined areas, e.g. the intersection of top and bottom electrode in cross bar arrays.

Keywords: resistive switching; threshold switching; niobium oxide; ion irradiation

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Permalink: https://www.hzdr.de/publications/Publ-20152


Search for supernova-produced 60Fe in Earth’s microfossil record

Ludwig, P.; Bishop, S.; Egli, R.; Chernenko, V.; Faestermann, T.; Famulok, N.; Fimiani, L.; Gomez-Guzman, J. M.; Hain, K.; Korschinek, G.; Hanzlik, M.; Merchel, S.; Rugel, G.; Frederichs, T.

Abstract

INTRODUCTION
The radioisotope 60Fe (T1/2 = (2.62+0.04) Ma [1]) can be produced in copious amounts during different phases of evolution of massive stars. It is possible that 60Fe-rich supernova debris is deposited into solar system reservoirs [2]. Samples from Pacific Ocean sediment were chosen as sample material for this work. Considering an enrichment of the ocean water with 60Fe after deposition of SN material on Earth, all minerals being formed during that time in the sediment will incorporate 60Fe and preserve the original concentration of 60Fe/Fe, except for natural radioactive decay. One particularly interesting reservoir of in situ formed iron-bearing minerals are magnetosomes. Chains of these magnetite crystals are built up by magnetotactic bacteria, who use it similar to a compass needle for magnetotaxis. After cell death, the magnetosome chains can be preserved over geologically significant timescales and represent a very interesting sample material to look for a 60Fe isotope anomaly.
MATERIALS AND METHODS
As sample material for this project, two sediment cores from the Eastern Equatorial Pacific (ODP Leg 138, Sites 848 and 851) were chosen. In order to extract iron from 60Fe rich minerals, the chemical CBD extraction procedure was employed. It was carefully calibrated to only dissolve particles of 200 nm diameter. In this way, dilution of 60Fe from iron-bearing grains from other sources (wind, water), which are typically larger, is reduced. A thorough study of the magnetic properties of the samples was also performed [3]. The concentration of 60Fe/Fe was then measured using accelerator mass spectrometry (AMS) at the GAMS setup at the MLL. Its unique ability to separate isobaric background in a gas-filled magnet allows for sensitivities reaching down to 60Fe/Fe ~10-16 and even lower.
RESULTS AND OUTLOOK
At this point, AMS measurements on the smaller one of the two cores have been completed. Measurements of the larger core are underway and are expected to be completed in mid 2014. The 60Fe/Fe concentration determined in core 848 (smaller core) can be seen in Fig. 2. A total of 7 counts of 60Fe have been observed in a depth range corresponding to an age of 2.0 to 2.6 Ma. The signal is above the expected background. Both, this age and the observed average concentration in this range (60Fe/Fe ~1x10-15) agree well with earlier results from a ferromanganese crust [2]. In order to improve statistics and time resolution, the larger core has to be examined as well. In this larger core 851, a total of 12 counts of 60Fe have been detected so far, but measurements have not been completed yet. In addition to measurements of 60Fe, 10Be and 26Al are also currently being measured in the smaller core, to obtain an independent dating, at the DREAMS facility in Dresden.
REFERENCES
[1] G. Rugel et al., Phys. Rev. Lett., 103(2009) 072502
[2] K. Knie et al., Phys. Rev. Lett., 93(2004) 171103
[3] P. Ludwig et al., Global Planet. Change 110(2013) 321-339

Keywords: accelerator mass spectrometry; supernova; cosmogenic radionuclide

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Permalink: https://www.hzdr.de/publications/Publ-20151


Search for supernova produced 60Fe in Earth's microfossil record

Ludwig, P.; Bishop, S.; Egli, R.; Faestermann, T.; Famulok, N.; Fimiani, L.; Gómez Guzmán, J. M.; Hain, K.; Korschinek, G.; Hanzlik, M.; Merchel, S.; Rugel, G.

Abstract

Nucleosynthesis in massive stars can produce copious amounts of the radioisotope 60Fe (T(1/2)= 2.62 Ma). When those stars end their lives in a supernova, material enriched with nucleosynthesis products can be ejected into the interstellar medium. If such supernova debris is picked up by Earth, it can be incorporated into terrestrial reservoirs. After the discovery of live 60Fe atoms in 2-3 Myr old layers of a Pacific Ocean ferromanganese crust (K. Knie et al., Phys. Rev. Lett., 93(2004) 171103), a confirmation of this signal, as well as a mapping of the signal with high time-resolution is desirable. Another reservoir in which the 60Fe signature should have been incorporated in are the fossils of magnetotactic bacteria in ocean sediment. These bacteria form chains of small magnetite crystals for magnetotaxis. After cell death and sedimentation, these magnetic chains can be preserved even over geologically significant timescales. In order to extract iron from secondary, 60Fe bearing minerals only, a carefully tuned chemical leaching technique was employed. A novel technique to characterize this procedure using magnetic measurements was also developed applied to quantify secondary magnetite in our samples. As sample materials, two sediment cores from the Eastern Equatorial Pacific were obtained and processed. The concentration 60Fe/Fe was then measured with accelerator mass spectrometry at the GAMS setup in Garching. It features a gas-filled magnet, allowing for complete isobar suppression in the case of 60Fe and 60Ni, leading to a sensitivity which can reach even below 60Fe/Fe = 1E-16. Additionally, one of the sediment cores was also analyzed for 10Be and 26Al for independent dating of the samples at the DREAMS facility in Dresden.

Keywords: accelerator mass spectrometry; supernova; cosmogenic radionuclide

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  • Lecture (Conference)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Permalink: https://www.hzdr.de/publications/Publ-20150


Formation of a Eu(III) borate solid species from a weak Eu(III) borate complex in aqueous solution

Schott, J.; Kretzschmar, J.; Acker, M.; Eidner, S.; Kumke, M. U.; Drobot, B.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T.

Abstract

In the presence of polyborates (detected by 11B-NMR) a weak Eu(III) borate complex formation (lg beta ~ 2, estimated) was observed with time-resolved laser-induced fluorescence spectroscopy (TRLFS). This complex is a precursor for the formation of a solid Eu(III) borate species. The formation progress of this solid was investigated by TRLFS in dependence on the total boron concentration: The lower the total boron concentration the slower is the solid formation. The solid Eu(III) borate was characterized by IR spectroscopy, powder XRD, solid-state TRLFS. The determination of the europium to boron ratio portends the existence of pentaborate units in the amorphous solid.

Keywords: europium; borate; complexation; solid; TRLFS; NMR; IR; PARAFAC

Permalink: https://www.hzdr.de/publications/Publ-20149


Magnetization dynamics of magnetic domain wall imprinted magnetic films

Hamann, C.; Mattheis, R.; Mönch, I.; Fassbender, J.; Schultz, L.; McCord, J.

Abstract

The influence of micromagnetic objects on the dynamic magnetic excitation in magnetic thin films is studied by imprinting periodic domain wall patterns through selective ion irradiation in exchange biased Ni81Fe 19/IrMn structures. For high domain wall densities an increased precessional frequency is achieved. The zero field resonance of the domain wall state hereby depends directly on the stripe period, showing a pronounced increase with decrease of domain wall spacing. With the abrupt annihilation of magnetic domain walls with an applied bias field a jump-like decrease in precessional frequency takes place. The experimental data and micromagnetic simulations prove that the characteristic collective dynamic mode for the domain wall configurations is attributed to strongly coupled tilted magnetization structure. This is evidenced by an overlapping Néel wall structure for the narrowly spaced imprinted antiparallel unidirectional anisotropy state. The controlled introduction of high density frozen-in micromagnetic objects is a novel way to control the dynamic magnetic properties of continuous magnetic thin films.

Keywords: magnetism; dynamics; domain wall; ion irradiation

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Permalink: https://www.hzdr.de/publications/Publ-20148


3D microstructural model of freckle formation validated using in situ experiments

Karagadde, S.; Yuan, L.; Shevchenko, N.; Eckert, S.; Lee, P. D.

Abstract

A 3D model of freckle (solute channel) formation at a microstructural level was coupled with in situ x-ray radiography to investigate the mechanisms of freckle initiation and growth. The model predictions for solute partitioning, diffusion and convection were validated via in situ x-ray radiographic measurements in a Ga-25wt%In alloy, showing good agreement. Other key features, such as freckle channel width and critical Rayleigh number, also correlated well.
This validated model was used to investigate freckle formation under a range of solidification conditions. Two distinct stages of freckle onset were observed, identified via the dendrite tip growth and solute profiles. The first stage corresponds to lower flow velocities with large fluctuations; in the second state the velocities stabilize, with established recirculating flows forming solute channels. The influence of imperfections in dendritic morphology, such as grain boundaries and primary spacing variations, upon the critical Rayleigh number were simulated. It was found that that these features initiate freckles. Non-intuitively, converging grain boundaries were observed to have the greatest propensity for freckle formation.

Keywords: Freckle formation; microstructure; solidification defects; solute transport; chimney formation

Permalink: https://www.hzdr.de/publications/Publ-20147


Forced convection effects on dendritic growth and freckle formation

Shevchenko, N.; Roshchupkina, O.; Sokolova, O.; Eckert, S.

Abstract

A directional solidification of Ga–25wt%In alloy within a Hele-Shaw cell under the influence of electromagnetically forced melt convection was studied by X-ray radioscopy. The forced convection was produced by a rotating wheel with two parallel disks containing at their inner sides a set of permanent NdFeB magnets with alternating polarisation [1, 2]. The top part of the solidification cell was positioned in the gap between the disks. Rotation speeds of the magnetic wheel were chosen in the range of 30 – 80 revolutions per minute. The melt flows are almost perpendicular with respect to the growth direction of the dendrites (local flow velocities 0.5 - 1.5 mm/s).
The forced convection provoked a preferential growth of the secondary arms at the upstream side of the primary dendrite arms, whereas the high solute concentration at the downstream side of the dendrites inhibited the formation of secondary branches completely. The changes of secondary arm spacing depended on the melt flow conditions. The accelerated growth of the secondary arms towards the incoming flow blocked the growth of neighboring primary dendrites leading to a considerable increase in the spacing between the primary trunks. Moreover, the primary trunks show a slight inclination towards the inflow. The flow-induced redistribution of the solute concentration leads to the formation of spacious segregation pattern.

Keywords: forced convection; dendrites; melt flow; microstructure

  • Poster
    E-MRS 2014 Spring Meeting, Symposium V : Effect of natural and forced convection in materials crystallization, 26.-30.05.2014, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-20146


In situ observation of freckle formation in Ga - In alloys under the influence of melt convection

Shevchenko, N.; Gerbeth, G.; Eckert, S.

Abstract

The directional bottom-up solidification experiments were carried out using a Ga–25wt%In alloy. A visualization of the solidification process and the main convection pattern in solidifying alloys was obtained by using the X-ray imaging technique [1, 2]. Variations of the temperature gradients applied over the solidification cell induce modifications of the melt flow pattern, which lead to different segregation structures.
Solidifications carried out at low temperature gradients (up to 1 K/mm) revealed a considerable number of perturbations of the growing dendritic network. Stable chimneys occur mainly at positions with initial growth defects or grain boundaries; however, not every initial segregation channel evolves into a stable chimney. The long-term stability of these segregation channels is strongly influenced by the transient nature of the melt convection.
The situation at higher temperature gradients up to 2 K/mm is characterized by a converging flow ahead of the mushy zone coming from the side walls. This leads to a continuous accumulation of solute in the central part of the mushy zone followed by a remelting of the solid fraction and the occurrence of a sustaining chimney. This mechanism of chimney formation is different as compared to the case where the development of the segregation channel is linked with any initial growth defect.

Keywords: X-ray imaging; bottom-up solidification; segregation channels; melt convection

  • Invited lecture (Conferences)
    E-MRS 2014 Spring Meeting, Symposium V : Effect of natural and forced convection in materials crystallization, 26.-30.05.2014, Lille, France

Permalink: https://www.hzdr.de/publications/Publ-20145


Neuroimaging of sigma-1 receptors with positron emission tomography.

Brust, P.

Abstract

In view of the involvement of sigma-1 receptors in different pathways related to the pathogenesis of various neuropsychiatric diseases and considering the neuroprotective potential of drugs targeting sigma-1 receptors quantitative neuroimaging by positron emission tomography (PET) is regarded as an unique method to investigate sigma-1 receptors in the progress of disease and under therapy. Alterations of sigma-1 receptor densities have been found in psychiatric disorders, neurodegeneration and cancer. Molecular receptor imaging with PET may provide a significant contribution to the understanding of the cross-talk between these receptors and inter- and intracellular signalling systems in these diseases. However the applicability of this imaging approach is still hampered due to lack of suitable radiopharmaceuticals for routine use. Although [11C]SA4503 has been used in human studies for already 10 years its broad clinical applicability is limited. Recent efforts made to develop 18F-labelled PET radiotracers for targeting the sigma-1 receptors in the human brain are presented. The current status of the evaluation of the most favourable radiolabelled compounds, including [18F]fluspidine, in animal models and humans will be discussed. New insights into the function of sigma-1 receptors in human brain will allow a better diagnosis of brain and cancerous diseases and direct a rational development of new therapeutic concepts.

  • Abstract in refereed journal
    Journal of Neurochemistry 130(2014), 13
  • Invited lecture (Conferences)
    12th Meeting of The Asian-Pacific Society for Neurochemistry, 23.-26.08.2014, Kaohsiung, China-Taiwan

Permalink: https://www.hzdr.de/publications/Publ-20144


Multiple radionuclide study of a recent supernova event in deep-sea sediments with AMS

Feige, J.; Wallner, A.; Bourlès, D.; Fifield, K. L.; Korschinek, G.; Merchel, S.; Rugel, G.; Steier, P.; Tims, S.; Winkler, S. R.; Golser, R.

Abstract

Long-lived radionuclides such as 26Al, 53Mn, and 60Fe are generated in massive stars and ejected into space by stellar winds and explosions. If a star ends its life in a supernova (SN) explosion close to the solar system, a fraction of these elements might be deposited in terrestrial archives. Recent analysis of a ferromanganese crust [1], fossilized bacteria in deep-sea sediments [2] and lunar samples [3] evidence a 60Fe concentration enhancement ~2-3 Myr ago, suggesting to originate from one or more SNe [1].
We expanded this work to a comprehensive and detailed study of a full set of SN-related radionuclides. Detailed depth profiles of 10Be, 26Al, 53Mn and 60Fe concentrations were measured at three different AMS laboratories for ~100 individual samples from four deep-sea sediment cores from the Indian Ocean. In contrast to our 60Fe data, which shows a clear signal without terrestrial background, a possible 26Al signal from a SN event is hidden within a non-negligible terrestrial background production. The major source of 26Al is spallogenic production by cosmic-rays in the Earth's atmosphere.
We obtained isotope ratios 26Al/27Al of ~10-14 with regularly <10% statistical uncertainty [4]. This allowed us to generate for the first time a full history of precise 26Al data over a time period of 2 Myr for two sediment cores revealing an unexpected smooth depth dependence. We took advantage of it and applied the 26Al/27Al ratio as an independent and enhanced dating tool, comparable to 10Be/9Be but without needing stable isotope measurements. Comparative measurements of 10Be/9Be at the DREAMS and VERA facilities show a very good agreement (~5 %).
[1] Knie et al., Phys. Rev. Lett 93, 2004, [2] Ludwig et al., AMS-13, [3] Fimiani et al., LPSC 1659, 2012, [4] Feige et al., EPJWC,63 2013

Keywords: accelerator mass spectrometry; AMS; supernova; radionuclide

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  • Lecture (Conference)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Permalink: https://www.hzdr.de/publications/Publ-20143


The first three years of DREAMS: Routine operation and developments

Rugel, G.; Akhmadaliev, S.; Merchel, S.; Pavetich, S.; Ziegenrücker, R.

Abstract

The DREAMS (DREsden AMS) facility is based on a state-of-the-art 6 MV accelerator AMS-system [1]. Located at the ion beam centre, the accelerator is also used for ion beam analysis (IBA), material modifications and high-energy ion implantation. Though having no 24/7 availability for AMS, the advantage of a multi-purpose accelerator is the synergy effect with respect to joint technology development and µ-beam IBA for the in-situ identification of elements in problematic cathodes.
Most often measured nuclides are 10Be, 26Al and 36Cl. The majority of samples is prepared on-site [2], 36Cl in a dedicated laboratory for halide targets. About 600 10Be unknowns have been measured for different applications [3]. The mean ratio of processing blanks is as low as 3x10-15 10Be/9Be, even when measuring samples with ratios as high as 10-10–10-11. However, the mean machine blank is generally a factor of four lower. While analysing 150 26Al unknowns, machine blanks are as low as 3x10-15 26Al/27Al. Typical high-energy currents (Al3+) e.g. for the in-house standard are about 300 nA (mean / 1 h).
One of the original ion sources has been modified for reducing long-term memory for volatiles [4] and yet applied to ~100 unknowns of 36Cl [e.g. 5]. Measurements of 41Ca are mainly for nuclear decommissioning [6] and cosmochemistry [5] applications.
The high-energy setup is upgraded with a time-of-flight and energy detector system to perform actinide AMS and Super-SIMS [7].
[1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Merchel et al., AMS-13. [3] Feige et al., Ludwig et al., Ott et al., Rodrigues et al. & Smith et al., AMS-13. [4] Pavetich et al., NIMB, (2014) 10.1016/j.nimb.2014.02.130 & AMS-13. [5] Ott et al., MAPS, subm. [6] Hampe et al., JRNC 296 (2013) 617. [7] Rugel et al., AMS-13.

Keywords: accelerator mass spectrometry; AMS; radionuclide; SIMS; nuclear decommissioning

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    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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DREAMS come true: Dresden SIMS becomes Super-SIMS

Rugel, G.; Akhmadaliev, S.; Merchel, S.; Pavetich, S.; Renno, A. D.; Wiedenbeck, M.; Ziegenrücker, R.

Abstract

The DREAMS (DREsden AMS) facility [1,2] has been proven to be very suitable for several kinds of applications [3] based on lighter radionuclides. However, the range of applications shall be broaden by upgrading to a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry). Super-SIMS is a combination of trace element AMS (TEAMS) for the determination of stable elements and isotopes using the spatial-resolution - greater than 3 µm (x,y) and 5 nm (z) - of SIMS. Thus, this ultrasensitive analytical method is best-suited for analysing geological samples within our focus of resource technology.
To realize the DREAMS Super-SIMS, a commercial SIMS (CAMECA IMS 7f-Auto) is used as an ion source and connected to a 6 MV accelerator of highest energy stability. Additionally, the high-energy setup of DREAMS will be equipped with a time-of-flight detector and an energy detection system. By the complete destruction of molecules detection limits some orders of magnitude better than for traditional dynamic SIMS are expected, i.e. ~ 10-9 - 10-12 (see e.g. [4]). A dedicated housing around the source guarantees the requirements for stable ion source operation, i.e. stability of temperature (<1°C/h) and humidity (<10%/h). For reducing vibrations the ion source is installed on a cube shaped block made of gabbro (6.4 t weight; 1.4 m x 1.8 m x 0.86 m size). The whole ion source setup can be set on a negative potential of up to -30 kV to allow for higher transmission.
[1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Rugel et al. & Pavetich et al., AMS-13. [3] Feige et al., Ludwig et al., Ott et al., Rodrigues et al., Smith et al., AMS-13. [4] Maden, PhD thesis, ETH Zurich 2003.

Keywords: accelerator mass spectrometry; SIMS

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    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Experimental investigation of high pressure condensation and heat transfer in a single near-horizontal pipe

Geißler, T.; Beyer, M.; Hampel, U.

Abstract

Wärmeübertragungsvorgänge mit Phasenübergang können genutzt werden, um effizient große Energiemengen zu übertragen. Einen Spezialfall stellt die Kondensation in einem leicht geneigten Rohr dar. Bedingt durch den Einfluss der Gravitation stellt sich eine ausgeprägte azimutale Struktur der Strömung mit dem einhergehenden Wärmeübergang ein. Im Gegensatz zu Kondensationsvorgängen in vertikalen Strukturen existieren für den horizontalen Fall nur integrale Beschreibungsmodelle. Mittels hochaufgelösten Kondensationsexperimenten soll ein Beitrag zur Entwicklung von dreidimensionalen Kondensationsmodellen geleistet werden.

Heat-transfer processes with phase change can be used to efficiently transfer large amounts of energy. A special case is the condensation in a nearly-horizontal pipe. Due to the influence of gravity a pronounced azimuthal structure of the flow with the associated heat transfer occurs. In contrast to condensation processes in vertical structures exist for the horizontal case only integral models. The conducted high-resolution condensation experiments will contribute to the development of three-dimensional condensation models.

Keywords: heat transfer; TOPFLOW; condensation; NOKO; KERENA; x-ray tomography; experiment; high pressure

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  • TOPFLOW Facility
  • Poster
    Jahrestreffen der Fachgruppen Mehrphasenströmungen und Wärme- und Stoffübertragung, 24.-25.03.2014, Fulda, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20140


Studying the constancy of galactic cosmic rays using cosmogenic radionuclides and noble gases in iron meteorites

Smith, T.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.; Wallner, A.; Fifield, K.; Tims, S.; Korschinek, G.

Abstract

During their orbit in space, extraterrestrial bodies are exposed to cosmic rays. The interaction between these energetic particles and the meteoroides produce both stable and radioactive cosmogenic nuclides that can be used to study, e.g., the size of the meteorite before ablation in the Earth’s atmosphere and the time the object traveled before falling on Earth (exposure age). For a proper interpretation of such data, especially the ages, the temporal constancy of the cosmic ray intensity has to be proven. Doing so and being interested in timescales in the range of a few hundred million years, we have to rely on iron meteorites because their exposure ages range from a few million to a few billion years.
In this study, we systematically investigate the exposure ages of iron meteorites and search for periodic structures in the age distribution. So far, we have studied 28 iron meteorites for 10Be, 26Al, and 36Cl at the DREsden Accelerator Mass Spectrometry (DREAMS) facility [1] and for the noble gas isotopes of He, Ne, and Ar at the University of Bern. The first 53Mn and 60Fe measurements have already been performed at the Australian National University (ANU) and at the TUM (Munich). Finally, 41Ca measurements at DREAMS to identify long terrestrial residence times influencing the radionuclide concentrations are foreseen for the very near future.
The measurements of additional iron meteorites, which will help improving the statistics of the age distribution as well as extending the list of radionuclides and also extending the study to mineral separates from iron meteorites, are currently ongoing.
[1] Akhmadaliev, S. et al. (2013) NIMB 294, 5.

Keywords: accelerator mass spectrometry; cosmic radiation; meteorite

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    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Packaging for radiation resistant X-ray detectors

Lohse, T.; Oppermann, M.; Metasch, R.; Zerna, T.; Seilmayer, M.; Wolter, K.-J.

Abstract

Today non-destructive evaluation techniques become more and more important. Consequently, X-ray detectors are suitable tools to get information about specimens. In comparison to the already established scintillation principle, the direct converting method on the basis of semiconductor materials delivers several advantages. Hence, it is necessary to speed this measurement method and develop appropriate packages for these assemblies. In this paper the method of direct converting X-ray line detectors as well as their packaging and relevant aspects are introduced.

Keywords: X-ray detection; electronics packaging; silicon radiation detectors; measurement method; nondestructive evaluation techniques; radiation resistant X-ray detectors; scintillation principle; semiconductor materials; Absorption; Anodes; Detectors; Integrated circuits; Materials; Packaging; X-ray detectors

  • Contribution to proceedings
    33rd International Spring Seminar on Electronics Technology (ISSE 2010), 12.-16.05.2010, Odrębna 4 04-867 Warsaw, Poland
    33rd International Spring Seminar on Electronics Technology (ISSE 2010): Institute of Electrical and Electronics Engineers, 9781424478491, 138-142

Permalink: https://www.hzdr.de/publications/Publ-20138


Grundlagenuntersuchungen zur selektiven Trennung sehr feiner Partikelsysteme mittels Flüssig-Flüssig Flotation am System Magnetit-Quarz

Leistner, T.; Müller, M.; Rudolph, M.; Peuker, U. A.

Abstract

Die Vergrößerung des effizienten Anwendungsbereiches von Sortierprozessen in den Bereich feinster Partikelsysteme (0,1 bis 10 µm) stellt aufgrund der Bedeutung komplexer Partikel-Partikel Wechselwirkungen eine erhebliche Herausforderung für die Forschung dar. Einen möglichen Ansatz in diese Richtung stellt die Flüssig-Flüssig Flotation dar. Bei diesem Heterokoagulationsprozess (ähnlich der Flotation) werden anstelle von Luftblasen feine Tröpfchen einer mit Wasser nicht-mischbaren unpolaren Flüssigkeit zum selektiven Austrag von Feststoffpartikeln eingesetzt. In diesem Beitrag werden erste Ergebnisse einer Grundlagenforschungsstudie zur Anwendbarkeit der Flüssig-Flüssig Flotation für die selektive Trennung im Feinstbereich am Beispiel von Magnetit- und Quarzpartikel (< 10 µm) vorgestellt. Als unpolare Flüssigkeit wird Isooktan eingesetzt. Die selektive Anreicherung der Feststoffpartikel an der Isooktan/Wasser-Grenzfläche bzw. der Transfer in die Isooktan-Phase wird in Abhängigkeit von ausgewählten Prozessparametern, wie dem pH-Wert der wässrigen Suspension sowie der Zugabe von grenzflächenaktiven Substanzen, untersucht und quantitativ dargestellt.

  • Lecture (Conference)
    Jahrestagung 2013 "Aufbereitung und Recycling", 13.-14.11.2013, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-20137


Photo-neutron reaction cross section for nat-Zr in the end-point bremsstrahlung energies of 12 - 16 and 45 - 70 MeV

Naik, H.; Kim, G. N.; Schwengner, R.; Kim, K.; Zaman, M.; Yang, S. C.; Lee, M. W.; Shin, S. G.; Gey, Y.; Massarczyk, R.; John, R.; Junghans, A.; Wagner, A.; Goswamia, A.; Cho, M.-H.

Abstract

The natZr(γ, xn)89-86Zr reaction cross-sections were experimentally determined at the end-point bremsstrahlung energies of 12, 14, 16, 45, 50, 55, 60 and 70 MeV by activation and off-line γ-ray spectrometric technique using the 20 MeV electron linac (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany and 100 MeV electron linac at Pohang Accelerator Laboratory (PAL), Pohang, Korea. The natZr(γ, xn)89-86Zr reaction cross-sections as a function of photon energy were also calculated theoretically using TALYS 1.4 computer code. The flux-weighted average values at the end-point energies of 12-16 and 45-70 MeV were obtained from the literature and the TALYS data based on mono-energetic photon and are found to be in good agreement with the present dat. It was also found that the present data and the flux-weighted literature and theoretical values for the natZr (γ, xn)89-86Zr reaction cross-sections increase from the threshold values to a certain energy, where other reaction channels opens. This indicates the role of excitation energy. However, the increase trend of natZr(γ, xn)89,88Zr reaction cross-sections are sharper from the threshold value up to end-point bremsstrahlung energies of 17-22 MeV compared to the same for natZr(γ, xn)87,86Zr reactions. This is due to the Giant Dipole Resonance (GDR) effect besides the role of excitation energy. After a certain values, the individual natZr (γ, xn) reaction cross sections decrease with increase of bremsstrahlung energy due to opening of other reactions, which indicates portioning of energy in different channels.

Keywords: Photonuclear reactions; photoactivation; electron accelerators; bremsstrahlung; cross sections; statistical-model calculations

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From tip to toe – Improvements of the DREAMS facility for the determination of volatile and heavy radionuclides

Pavetich, S.; Akhmadaliev, S.; Arnold, M.; Aumaître, G.; Bourlès, D.; Buchriegler, J.; Fifield, K.; Golser, R.; Keddadouche, K.; Martschini, M.; Merchel, S.; Rugel, G.; Srncik, M.; Steier, P.; Wallner, A.; Ziegenrücker, R.

Abstract

Since the DREAMS (DREsden Accelerator Mass Spectrometry) facility [1] based on a HVE 6 MV Tandetron went operational in 2011, special effort was immediately devoted to upgrading the system for measurements of volatile elements e.g. Cl, I, and heavy elements e.g. actinides.
In the case of volatile elements, understanding and minimizing the ion source memory effect is a key issue for precise AMS-measurements [2,3]. For this purpose, one of the two original HVE sources was mechanically optimised. The new design has a more open geometry to improve the vacuum level and a modified target loading and positioning system, which allows exchanging the cathode aperture together with each target. To evaluate improvements of these modifications in comparison to other up-to-date AMS facilities [4], the long-term memory effect in the ion sources of VERA [5], ASTER [3] (Accélérateur pour les Sciences de la Terre, Environnement, Risques) and DREAMS [1] have been investigated by measuring samples of natural 35Cl/37Cl-ratio and samples containing highly enriched 35Cl (35Cl/37Cl ~1000). In these measurements the modified DREAMS ion source showed the lowest level of ion source memory effect and typically the fastest recovery [4].
To extend the measurement capabilities to actinides a time-of-flight system based on thin carbon foils and Micro Channel Plates was designed and constructed at DREAMS. For an optimal tuning of the system with low currents special beam diagnostic elements were manufactured. In cooperation with ANU first actinide samples were measured at DREAMS.

[1] S. Akhmadaliev et al., NIMB 294 (2013) 5.
[2] R. Finkel et al., NIMB 294 (2013) 121.
[3] M. Arnold et al., NIMB 294 (2013) 24.
[4] S. Pavetich et al., NIMB, accepted.
[5] M. Martschini et al., NIMB 269 (2011) 3188.

Keywords: Accelerator Mass Spectrometry; Cl-AMS; long-term memory effect; actinide AMS; Time-of-Flight; DREAMS

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    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Development of MMRPC prototype for the NeuLAND detector of the R3B collaboration

Datta Pramanik, U.; Chakraborty, S.; Basu, P.; Basu, J.; Banerjee, P.; Bemmerer, D.; Bose, S.; Chatterjee, S.; Elekes, Z.; Kempe, M.; Leifels, Y.; Panja, J.; Mukherjee, A.; Rahaman, A.; Roy, S.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.

Abstract

A prototype of Multi-strip Multi-gap Resistive Plate chamber (MMRPC) with active area 40 cm×20 cm has been developed at SINP, Kolkata as a new Time-Of-Flight (TOF) system with timing resolution σt<120ps and position resolution σx∼0.58cm. The intention is to use multilayers of this type together with converter materials as a high energy neutron (1GeV>En>200MeV) TOF system for the R3B collaboration at the FAIR facility. The design of the detector elements is as follows: a double stack MMRPC with float glass plates and two gas gaps of 0.3 mm per stack. The response of this MMRPC has been studied with cosmic muons and γ-raysγ-rays from a standard radioactive source (60Co) in coincidence with fast inorganic scintillators at SINP laboratory. Recently, response of developed MMRPC has been studied using pulsed electron beam at ELBE, FZD. The details of the MMRPC construction , experimental set-up for investigation of its response and first results are presented.

Keywords: Multi-strip Multi-gap Resistive Plate chamber high energy neutron R3B FAIR

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Permalink: https://www.hzdr.de/publications/Publ-20134


Establishment of two complementary in vitro assays for radiocopper complexes achieving reliable and comparable evaluation of in vivo stability

Zarschler, K.; Kubeil, M.; Stephan, H.

Abstract

The development of novel radiopharmaceuticals for imaging and therapy requires rapid and reproducible in vitro assays to estimate their in vivo stability and dissociation behaviour. In general, these assays should allow an assessment of dissociation of the radiometal from the radiopharmaceuticals. In the past, a series of chemical challenges has been widely used to estimate complex stability under non-physiological and non-radiotracer conditions providing limited information on the potential in vivo stability. In contrast, we herein present two independent in vitro methods to measure the stability of radiocopper complexes under physiologically relevant conditions. To quantify and compare the dissociation behaviour of six well-established 64Cu chelates (TETA, DOTA, NOTA, Cyclam, diamSar and EDTA), we combine a protein challenge experiment considering the stability of the chelates in the presence of human superoxide dismutase with a serum assay measuring the stability of the radiometal complexes against human serum. Unlike HPLC- and TLC-based analytical techniques, we describe the stability assessments by standard gel electrophoretic procedures, which allow a timesaving workflow as well as simultaneous processing and comparative analysis of a variety of copper-containing chelates and conjugates thereof. [64Cu]Cu-diamSar is the most kinetically stable ligand, whereas the acyclic chelate [64Cu]Cu-EDTA underwent an almost complete complex dissociation. Furthermore, kinetic stability studies in human serum carried out for [64Cu]Cu-diamSar revealed no substantial time-dependent influence under commonly used labelling conditions. Both described assays, the protein challenge experiment as well as the serum stability assay, are not restricted to radiocopper, but may be adopted for other radiometal containing chelates. © 2014 The Royal Society of Chemistry.

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  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-20133


Transverse wobbling: A collective mode in odd- A triaxial nuclei

Frauendorf, S.; Dönau, F.

Abstract

The wobbling motion of a triaxial rotor coupled to a high-j quasiparticle is treated semiclassically. Longitudinal and transverse coupling regimes can be distinguished depending on, respectively, whether the quasiparticle angular momentum is oriented parallel or perpendicular to the rotor axis with the largest moment of inertia.
Simple analytical expressions for the wobbling frequency and the electromagnetic E2 and M1 transition probabilities are derived assuming rigid alignment of the quasiparticle with one of the rotor axes and harmonic oscillations (HFA). Transverse wobbling is characterized by a decrease of the wobbling frequency with increasing angular momentum. Two examples for transverse wobbling, 163 Lu and 135 Pr, are studied in the framework of the full triaxial particle-rotor model and the HFA. The signature of transverse wobbling, decreasing wobbling frequency, and enhanced E2 interband transitions, is found in agreement with experiment.

Keywords: Nuclear structure; triaxial particle-rotor model; E2 transitions

Permalink: https://www.hzdr.de/publications/Publ-20132


Improving AMS-chemistry: Two steps forward, one step back

Merchel, S.; Bourlès, D. L.; Feige, J.; Ludwig, P.; Pavetich, S.; Ritter, A.; Rodrigues, D.; Rugel, G.; Smith, T.; Ziegenrücker, R.

Abstract

The DREAMS (DREsden AMS) facility consists of a sophisticated 6 MV accelerator system [1], but also provides two chemistry laboratories for external users. One lab is used for preparation of 10Be, 26Al, 41Ca, 53Mn and 60Fe targets. The other one is dedicated to halide targets (36Cl, 129I), thus, any use of Cl- or S-compounds such as HCl or H2SO4 is strictly prohibited.
Separation protocols are applied to calcite- and quartz-rich samples for in-situ projects [2-4]. Atmospheric 10Be has been leached from marine sediments and Mn-nodules for dating purposes [5] and chemistry refined for bigger samples and heavier nuclides (26Al, 53Mn, 60Fe) [6]. After adapting standard protocols [7] introducing simple Mn-separation by delayed hydroxide separation, higher isobar concentrations (53Cr) have been found asking for further cleaning by ion exchange. With intent to speed-up and simplify the separation procedures for ice and meteorite samples [8], difficulties have been arisen e.g. carryover of Ag+-ions into MnO2, and shortly after overcome. Another chemistry challenge probably mastered is the dissolution of meteoritic troilite (FeS) without losing natCl-carrier before equilibrium with 36Cl, plus suppression of massive isobar amounts. Remaining issues also influencing the quality of AMS-data, such as incorrectly measured stable isotope concentrations (9Be, 27Al), are usually underestimated and harder to tackle.
[1] Akhmadaliev et al., NIMB 294 (2013) 5. [2] Merchel et al., Quat. Geo. 22 (2014) 33. [3] Zech et al., Paleo3 369 (2013) 253. [4] Yildirim et al., Tectonics 32 (2013) 1107. [5] Feige et al., Ludwig et al. & Rodrigues et al., AMS-13. [6] Feige et al., EPJ Web Conf. 63 (2013) 03003. [7] Merchel & Herpers, RCA 84 (1999) 215. [8] Smith et al., AMS-13.

Keywords: accelerator mass spectrometry; cosmogenic radionuclides

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  • Lecture (Conference)
    13th International Conference on Accelerator Mass Spectrometry (AMS-13), 24.-29.08.2014, Aix-en-Provence, France

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Detectability of proton range shifts in heterogeneous targets with prompt gamma based range monitoring

Priegnitz, M.; Fiedler, F.; Helmbrecht, S.; Janssens, G.; Smeets, J.; Vander Stappen, F.; Enghardt, W.

Abstract

To make optimal use of the advantages of proton beams in tumor therapy a precise knowledge on their range is required. Recently, a slit camera has been developed using prompt gamma rays emitted during irradiation. First investigations in homogeneous media have shown that the position of the distal falloff of the prompt gamma ray profiles is closely correlated with the Bragg-peak position. Now, heterogeneous targets are under investigation and first results on detectability of range shift as well as range retrieval precision will be presented.

  • Lecture (Conference)
    Dreiländertagung Medizinische Physik - Joint Conference of the SGSMP, DGMP, ÖGMP, 07.-10.09.2014, Zürich, Schweiz
  • Contribution to proceedings
    Dreiländertagung Medizinische Physik - Joint Conference of the SSRMP, DGMP, ÖGMP, 07.-10.09.2014, Zürich, Schweiz
    Abstractbook, 987-3-9816508-5-3, 136-137

Permalink: https://www.hzdr.de/publications/Publ-20130


Surface speciation of dissolved radionuclides on mineral phases derived from vibrational spectroscopic data

Foerstendorf, H.; Jordan, N.; Heim, K.

Abstract

A detailed knowledge of the molecular reactions of radionuclides at the aqueous-mineral interface is required for a reliable assessment of their dissemination in the environment. Among numerous spectro-scopic approaches, in situ vibrational spectroscopy has been developed to a powerful tool for the study of surface complexes of heavy metal ions on solid phases. In particular from vibrational data, molecular in-formation can be derived which might be complementary to those obtained from other widely applied techniques, such as X-ray absorption spectroscopy. In this study, a survey of very recent results obtained from sorption reactions of radionuclides, namely U(VI) on iron(hydr)oxides and Se(VI) on metal oxides is given.
A significantly different surface complexation of U(VI) was found for two different iron bearing min-eral phases, that is ferrihydrite and maghemite. As in situ IR spectroscopy allows the investigation of sorption and desorption processes in real time under environmentally relevant conditions, the type of sur-face complexation can be identified by the extent of reversibility of the sorption reactions. Moreover, the evaluation of the formation of ternary U(VI)carbonato surface complexes provides further details of the sorption processes.
The selenate anion (SeVIO42−) preferentially shows relatively weak interactions (physisorption) with mineral phases in the circumneutral pH range. However, the electrostatic interactions of this ion with the mineral surfaces, referred to as outer-sphere complexation, might base on different types of surface com-plexes as shown by vibrational data from surface complexes on different minerals. With respect to the high selectivity of vibrational spectra to molecule symmetry, the results from Se(VI) sorption experiments on different mineral phases clearly demonstrate two different types of outer sphere complexes.

  • Invited lecture (Conferences)
    248th ACS National Meeting & Exposition, 10.-14.08.2014, San Francisco, U.S.A.

Permalink: https://www.hzdr.de/publications/Publ-20129


Post-irradiation annealing behaviour of neutron-irradiated FeCu, FeMnNi and FeMnNiCu model alloys investigated by means of small-angle neutron scattering

Bergner, F.; Ulbricht, A.; Lindner, P.; Keiderling, U.; Malerba, L.

Abstract

Neutron irradiation of reactor pressure vessel steels gives rise to the formation of thermodynamically stable and unstable nano-features. The present work is focused on the stability of Cu-, Mn- and Ni-containing solute clusters in model alloys exposed to post-irradiation annealing. Fe0.1Cu, Fe1.2Mn0.7Ni and Fe1.2Mn0.7Ni0.1Cu (wt%) model alloys irradiated up to neutron exposures of 0.1 and 0.19 dpa (displacements per atom) were annealed at stepwise increasing temperatures in the range from 300 °C (i.e. near irradiation temperature) to 500 °C and characterized by means of small-angle neutron scattering (SANS). We have found characteristic differences in the annealing behavior of the alloys. In particular, there is a non-trivial (synergistic-antagonistic) interplay of Mn/Ni and Cu.

Keywords: radiation effects; Fe-based model alloys; SANS; thermal treatment

Permalink: https://www.hzdr.de/publications/Publ-20128


SiΛvio: A trigger for Λ-hyperons

Münzer, R.; Berger, M.; Fabbietti, L.; Averbeck, R.; Andronic, A.; Barret, V.; Basrak, Z.; Bastid, N.; Benabderrahmane, M. L.; Buehler, P.; Cargnelli, M.; Čaplar, R.; Carevic, I.; Charviakova, V.; Crochet, P.; Deppner, I.; Dupieux, P.; Dželalija, M.; Fodor, Z.; Gasik, P.; Gašparić, I.; Grishkin, Y.; Hartmann, O. N.; Herrmann, N.; Hildenbrand, K. D.; Hong, B.; Kang, T. I.; Kecskemeti, J.; Kim, Y. J.; Kirejczyk, M.; Kiš, M.; Kienle, P.; Koczon, P.; Kotte, R.; Lebedev, A.; Leifels, Y.; Liu, J. L.; Lopez, X.; Manko, V.; Marton, J.; Matulewicz, T.; Petrovici, M.; Piasecki, K.; Rami, F.; Reischl, A.; Reisdorf, W.; Ryu, M. S.; Schmidt, P.; Schüttauf, A.; Seres, Z.; Sikora, B.; Sim, K. S.; Simion, V.; Siwek-Wilczyńska, K.; Smolyankin, V.; Suzuki, K.; Tyminski, Z.; Wagner, P.; Widmann, E.; Wiśniewski, K.; Xiao, Z. G.; Yamazaki, T.; Yushmanov, I.; Zhang, X. Y.; Zhilin, A.; Zinyuk, V.; Zmeskal, J.

Abstract

As online trigger for events containing Λ hyperons in p+p collisions at 3.1 GeV a silicon-based device has been designed and built. This system has been integrated close to the target region within the FOPI spectrometer at GSI and was also employed as a tracking device to improve the vertex reconstruction of secondary decays. The design of the detector components, read-out, the trigger capability as well as the tracking performance are presented. An enrichment factor of about 14 was achieved for events containing a Λ-hyperon candidate.

Keywords: Si Lambda vio; Lambda-hyperons

Permalink: https://www.hzdr.de/publications/Publ-20127


Amorphization and recrystallization of single-crystalline hydrogen titanate nanowires by N+ ion irradiation

Behera, A. K.; Facsko, S.; Bandyopadyay, M. K.; Das, S.; Chatterjee, S.

Abstract

We report the phase transformation of hydrogen titanate (H2Ti3O7) nanowires induced by 50 keV N+ ion irradiation at room temperature with fluencies of 1×1015 ions/cm2 and 1×1016 ions/cm2. By high resolution transmission electron microscopy the internal structure of the ion irradiated nanowires is analyzed. While at lower fluence a transformation from crystalline H2Ti3O7 to amorphous TiO2 is observed, at higher fluence a remarkable crystalline-amorphous TiO2 core-shell structure is formed. At this higher fluence the recrystallization occurs in the core of the nanowire and the outer layer remains amorphized. The phase transformation and formation of core-shell structure is explained using the thermal spike model and non-equilibrium thermodynamics. X-ray Photoelectron Spectroscopy and Raman Scattering reveale further insight into the structure of the nanowires before and after ion irradiation.

Keywords: Nanowires; core-shell structure; ion induced phase transformation

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Permalink: https://www.hzdr.de/publications/Publ-20126


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