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32337 Publications
Source term calculation and validation for F-18 production with a cyclotron for medical applications at HZDR
Konheiser, J.; Müller, S. E.; Magin, A.; Naumann, B.; Ferrari, A.;
In this document we present the calculation and experimental validation of a source term for F-18 production with a cyclotron for medical applications operating at 18 MeV proton energy and 30 microA proton current. The Monte Carlo codes MCNP6 and FLUKA were used for the calculation of the source term. In addition, the radiation field around the O-18 enriched water target was simulated with the two codes. To validate the radiation field obtained in the simulation, an experimental program has been started using activation samples which are placed close to the water target during an F-18 production run of the cyclotron. After the irradiation, the samples are analyzed and the resulting activation is compared to Monte Carlo calculations of the expected sample activation. We and good agreement between simulations and experimental results, with most calculation to experiment (C/E) ratios well between 0.6 and 1.4.
Keywords: F-18, MCNP, FLUKA, Source Term, Cyclotron
Related publications
Source term calculation and validation for F-18 production … (Id 28964) HZDR-primary research data are used by this publication

Publ.-Id: 28971 - Permalink


Fast-neutron-induced fission cross section of Pu(242) measured at the neutron time-of-flight facility nELBE
Kögler, T.ORC

This dataset includes the processed data of the fast neutron-induced fission of Pu(242) experiement performed in November 2014 at the neutron time-of-flight facility nELBE which was published in T. Kögler et al., Phys. Rev. C 99, 024604

It contains the absolute (Pu242_nfis_Koegler_2019.csv) and relative (Pu242_U235_nfis_Koegler_2019.csv) cross section data ranging from 0.5 MeV to 10 MeV. The cross section data is given in comma separated ASCII files, as well as in a MS Excel-Sheet.

The columns of the tables are defined as follows:

  1. EN...neutron kinetic energy from the measured time of flight (ToF)
  2. EN-ERR...uncertainty of neutron kinetic energy = 0.5*(ToF bin width) = 1 ns
  3. DATA...cross section data
  4. ERR-S...statistical uncertainty of the cross section data
  5. ERR-SY...systematic uncertainty of the cross section data
  6. ERR-T...combined standard uncertainty of the cross section data
  7. ERR-0...relative uncertainty counting
  8. ERR-1...relative uncertainty normalization
  9. ERR-2...relative uncertainty reference cross section
  10. ERR-3...relative uncertainty FF detection inefficiency
  11. ERR-4...relative stat. uncertainty scattering correction H19
  12. ERR-5...relative sys. uncertainty scattering correction H19
  13. ERR-6...relative stat. uncertainty scattering correction PuFC
  14. ERR-7...relative sys. uncertainty scattering correction PuFC

Additionally, a root (see https://root.cern.ch/) file is supplied, including the determined cross sections and all nessessary data to reconstruct the experiment. This includes the measured quantities, reference data, correction factors, evaluated cross sections etc.

To have the whole functionality of the root file, additional libary files (libGo4UserAnalysis.rootmaplibGo4UserAnalysis.so and libGo4UserAnalysis_rdict.pcm) are also given here.

Keywords: neutron-induced fission; plutonium-242; cross section measurements; nuclear reactions; nucleon induced nuclear reactions; nELBE
Related publications
Fast-neutron-induced fission cross section of Pu(242) … (Id 28878) has used this publication of HZDR-primary research data
Die Bestimmung des neutroneninduzierten Spaltquerschnitts … (Id 26338) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-03-06
    DOI: 10.14278/rodare.117
    License: CC-BY-4.0

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Publ.-Id: 28970 - Permalink


Supplementary Data: Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration
Huebl, A.ORC; Rehwald, M.ORC; Obst-Huebl, L.ORC; Ziegler, T.ORC; Garten, M.ORC; Widera, R.ORC; Zeil, K.; Cowan, T. E.ORC; Bussmann, M.ORC; Schramm, U.ORC; Kluge, T.ORC

Supplementary materials for our paper "Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration".

Additional high-resolution, raw HDF5 files using the openPMD standard (DOI:10.5281/zenodo.1167843) increase simulation output data to 4.7 TByte and are available from the corresponding author upon reasonable request. 

Keywords: LPA; laser-ion acceleration; TNSA; multi-species; cryogenic target; particle-in-cell
Related publications
Spectral Control via Multi-Species Effects in PW-Class … (Id 28962) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-03-06
    DOI: 10.14278/rodare.115
    License: CC-BY-SA-4.0

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Publ.-Id: 28969 - Permalink


Understanding the size effects on the electronic structure of ThO2 nanoparticles
Amidani, L.; Plakhova, T. V.; Romanchuk, A. Y.; Gerber, E.; Weiss, S.; Efimenko, A.; Sahle, C. J.; Butorin, S. M.; Kalmykovc, S. N.; Kvashnina, K. O.;
Developing characterization techniques and analysis methods adapted to the investigation of nanoparticles (NPs) is of fundamental importance considering the role of these materials in many fields of research. The study of actinide based NPs, despite their environmental relevance, is still underdeveloped compared to that of NPs based on stable and lighter elements. We present here an investigation of ThO2 NPs performed with High-Energy Resolution Fluorescence Detected (HERFD) X-ray Absorption Near-Edge Structure (XANES) and with ab initio XANES simulations. Structural models of ThO2 NPs with sharp edges and corners reproduce the size effect observed in experimental data. Inspection of the simulations from Th atoms in the core and on the surface of the NP indeed demonstrates that the origin of the effect is the lowering of the number of coordinating atoms for Th at the surface of the NP. The sensitivity of HERFD XANES to the less coordinated atoms at the surface may be exploited to investigate surface interactions.

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  • Secondary publication expected from 29.04.2020

Publ.-Id: 28968 - Permalink


Ion irradiation driven changes of magnetic anisotropy in ultrathin Co films sandwiched between Au or Pt covers
Mazalski, P.; Kurant, Z.; Sveklo, I.; Dobrogowski, W.; Fassbender, J.ORC; Wawro, A.; Maziewski, A.
Modifications of magnetic anisotropy of 30 keV Ga + ion irradiated ultrathin Co films sandwiched between Au or Pt buffer and capping layers are investigated as a function of magnetic layer thickness, d Co , and the ion fluence, F. Maps (d Co , F) of saturation fields have been derived from local magnetooptical polar Kerr effect (PMOKE) measurements. The areas with increased remanent magnetization and/or saturation fields, which are directly related to the uniaxial anisotropy, adopt linear shapes for the two branches in the maps. They are very distinct, especially for the Pt/Co/Pt system irradiated at lower and higher fluence. Replacement of Pt with Au in the buffer layer results in minor influence on the magnetization properties of the irradiated trilayers. Au as a capping layer significantly decreases the anisotropy in the branch appearing at lower fluence. In the Au/Pt/Au sandwich, a severe reduction of induced anisotropy is observed in both branches. The proposed phenomenological model describing experimentally investigated magnetic anisotropies enables separation of surface and volume contributions to both branches of enhanced anisotropy.
Keywords: Chemical driving force demixing, Ion beam irradiation, Magnetooptics, Perpendicular magnetic anisotropy

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Publ.-Id: 28967 - Permalink


SPECT-Untersuchungen mit dem 123 I-markierten Dopamintransporter-Liganden FP-CIT (DaTSCAN):DGN-Handlungsempfehlung (S1-Leitlinie)
Tatsch, K.; Buchert, R.; Bartenstein, P.; Barthel, H.; Boecker, H.; Brust, P.; Drzezga, A.; La Fougère, C.; Gründer, G.; Grünwald, F.; Krause, B.-J.; Kuwert, T.; Langen, K.-J.; Rominger, A.; Sabri, O.; Schreckenberger, M.; Meyer, P. T.;
Die S1-Leitlinie soll bei der Indikationsstellung, Durchführung, Interpretation und Befundung von SPECT-Untersuchungen des Dopamintransporters (DAT) mit DaTSCANTM unterstützen.
Gegenüber der Vorgängerversion von 2007 berücksichtigt die vorliegende Aktualisierung und Überarbeitung die neuere wissenschaftliche Literatur, zwischenzeitlich veröffentlichte Guidelines der europäischen (EANM) und amerikanischen Fachgesellschaften (SNM), sowie die aktuelle Fassung der S3-Leitlinie „Idiopathisches Parkinson-Syndrom“ der Deutschen Gesellschaft für Neurologie. Zudem finden neue technische Möglichkeiten Berücksichtigung.
  • Nuklearmedizin 58(2019)1, 5-16

Publ.-Id: 28965 - Permalink


Source term calculation and validation for F-18 production with a cyclotron for medical applications at HZDR
Konheiser, J.; Mueller, S. E.ORC; Magin, A.; Naumann, B.; Ferrari, A.ORC

Data contained in Fig. 2 of the
publication

Keywords: Cyclotron; Source term; MCNP6; FLUKA
Related publications
Source term calculation and validation for F-18 production … (Id 28971) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-03-04
    DOI: 10.14278/rodare.113
    License: CC-BY-4.0

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Publ.-Id: 28964 - Permalink


CFD-based optimization of heat exchanger tube bundle arrangement for passive spent fuel pool cooling to ambient air
Unger, S.; Beyer, M.; Krepper, E.; Hampel, U.;
The storage of spent fuel in actively cooled water pools is common practice in nuclear power plants. One possibility to improve the reliability and the economy of spent fuel storage is the substitution of active cooling components by passive heat transfer systems. Thereby, ambient air should be the ultimate heat sink. A major drawback of natural convection heat transfer to ambient is the low heat transfer coefficient. Thus, bundle heat exchangers with finned tube are commonly employed. In one of our previous studies an optimum fin design was derived for such a heat exchanger. In the present investigation this tube bundle arrangement was numerical analysed with respect to optimal tube bundle configuration, tube shape, longitudinal tube pitch, transversal tube pitch and tube row number. We found highest heat transfer performance for oval shaped tubes with an axis ratio of 1:2.1 in a staggered configuration, having longitudinal tube pitch of 73 mm, a transversal tube pitch of 52 mm and 4 tube rows.
  • Contribution to proceedings
    50th Annual Meeting on Nuclear Technology, 07.-08.05.2019, Berlin, Deutschland
    Proceedings of the 50th Annual Meeting on Nuclear Technology

Publ.-Id: 28963 - Permalink


Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration
Huebl, A.ORC; Rehwald, M.ORC; Obst-Huebl, L.ORC; Ziegler, T.ORC; Garten, M.ORC; Widera, R.ORC; Zeil, K.; Cowan, T. E.ORC; Bussmann, M.ORC; Schramm, U.ORC; Kluge, T.ORC
Laser-ion acceleration with ultra-short pulse, PW-class lasers is dominated by non-thermal, intra-pulse plasma dynamics. The presence of multiple ion species or multiple charge states in targets leads to characteristic modulations and even mono-energetic features, depending on the choice of target material. As spectral signatures of generated ion beams are frequently used to characterize underlying acceleration mechanisms, thermal, multi-fluid descriptions require a revision for predictive capabilities and control in next-generation particle beam sources. We present an analytical model with explicit inter-species interactions, supported by extensive ab initio simulations. This enables us to derive important ensemble properties from the spectral distribution resulting from those multi-species effects for arbitrary mixtures. We further propose a potential experimental implementation with a novel cryogenic target, delivering jets with variable mixtures of hydrogen and deuterium. Free from contaminants and without strong influence of hardly controllable processes such as ionization dynamics, this would allow a systematic realization of our predictions for the multi-species effect.
Keywords: LPA, laser-ion acceleration, TNSA, multi-species, cryogenic target, particle-in-cell
Related publications
Supplementary Data: Spectral Control via Multi-Species … (Id 28969) HZDR-primary research data are used by this publication
  • Poster
    Laser-Plasma Accelerator Workshop 2019, 06.-10.05.2019, Split, Kroatien

Publ.-Id: 28962 - Permalink


Revealing the Nature of Photoluminescence Emission in Metal-Halide Double Perovskites
Zelewski, S. J.; Urban, J. M.; Surrente, A.; Maude, D. K.; Kuc, A.; Schade, L.; Johnson, R. D.; Dollmann, M.; Nayak, P. K.; Snaith, H. J.; Radaelli, P. G.; Kudrawiec, R.; Nicholas, R. J.; Plochocka, P.; Baranowski, M.;
Double perovskite crystals such as Cs2AgBiBr6 are expected to overcome the limitation of classic hybrid organic-inorganic perovskite crystals related to the presence of lead and the lack of structural stability. Perovskites are ionic crystals in which the carriers are expected to strongly couple to lattice vibrations. In this work we demonstrate that the photoluminescence (PL) emission in Cs2AgBiBr6 is strongly influenced by the strong electron-phonon coupling. Combining photoluminescence excitation (PLE) and Raman spectroscopy we show that the PL emission is related to a color center rather than a band-to-band transition. The broadening and the Stokes shift of the PL emission from Cs2AgBiBr6 is well explained using a Franck-Condon model with a Huang-Rhys factor of S=11.7 indicating a strong electron-phonon interaction in this material.

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  • Secondary publication expected from 19.06.2020

Publ.-Id: 28961 - Permalink


Effect of four lanthanides onto the viability of two mammalian kidney cell lines
Heller, A.; Barkleit, A.ORC; Bok, F.; Wober, J.
Exposure to lanthanides (Ln) poses a serious health risk to animals and humans. Since Ln are mainly excreted with the urine, we investigated the effect of La, Ce, Eu, and Yb exposure on renal rat NRK-52E and human HEK-293 cells for 8, 24 and 48 h in vitro. Cell viability studies using the XTT assay and microscopic investigations were combined with solubility and speciation studies using ICP-MS and TRLFS. Thermodynamic modeling was applied to predict the speciation of Ln in the cell culture medium. All Ln show a concentration- and time-dependent effect on both cell lines with Ce being the most potent element. In cell culture medium, the Ln are completely soluble and most probably complexed with proteins from fetal bovine serum. The results of this study underline the importance of combining biological, chemical, and spectroscopic methods in studying the effect of Ln on cells in vitro and may contribute to the improvement of the current risk assessment for Ln in the human body. Furthermore, they demonstrate that Ln seem to have no effect on renal cells in vitro at environmental trace concentrations. Nevertheless, especially Ce has the potential for harmful effects at elevated concentrations observed in mining and industrial areas.
Keywords: f-elements; renal cells; cytotoxicity; XTT; time-resolved laser-induced fluorescence spectroscopy; thermodynamic modeling

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  • Secondary publication expected from 22.02.2020

Publ.-Id: 28960 - Permalink


Improved axial plane distance and velocity determination for ultrafast electron beam X-ray computed tomography
Neumann, M.; Bieberle, M.ORC; Wagner, M.; Bieberle, A.; Hampel, U.
Ultrafast electron beam X-ray computed tomography (UFXCT) has in recent years become an indispensable tool for multiphase flow studies. An essential feature of this technique is fast cross-sectional imaging in two distinct planes. Both the spatial location of focal spot path and detectors as well as the angular scanning range in UFXCT differ from that of conventional X-ray CT systems. This brings in a spatial dependence in axial scanning position and resolution. In this paper, we present an analysis of this problem, which results in an improved description of the location and shape of the imaging regions, a more accurate map of the distance between the imaging planes and finally a higher precision in the determination of axial structure velocities. The benefit of this improved approach is exemplarily demonstrated for a two-phase pipe flow around an obstacle.
Keywords: ultrafast X-ray computed tomography, phase velocity measurement

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  • Secondary publication expected from 28.06.2020

Publ.-Id: 28958 - Permalink


Transparent Conductive Tantalum Doped Tin Oxide as Selectively Solar-Transmitting Coating for High Temperature Solar Thermal Applications
Lungwitz, F.; Escobar-Galindo, R.; Janke, D.; Schumann, E.; Wenisch, R.; Gemming, S.; Krause, M.ORC
The transparent conductive oxide (TCO) SnO2:Ta is developed as a selectively solar-transmitting coating for concentrated solar power (CSP) absorbers. Upon covering with an antireflective layer, a calculated absorptivity of 95 % and an emissivity of 30 % are achieved for the model configuration of SnO2:Ta on top of a perfect black body (BB). High-temperature stability of the developed TCO up to 1073 K is shown in situ by spectroscopic ellipsometry and Rutherford backscattering spectrometry. The universality of the concept is demonstrated by transforming silicon and glassy carbon from non-selective into solar-selective absorbers by depositing the TCO on top of them. Finally, the energy conversion efficiencies of SnO2:Ta on top of a BB and an ideal non-selective BB absorber are extensively compared as a function of solar concentration factor C and absorber temperature TH. Equal CSP efficiencies can be achieved by the TCO on BB configuration with approximately 50 % lower solar concentration. This improvement could be used to reduce the number of mirrors in a solar plant, and thus, the levelized costs of electricity for CSP technology.
Keywords: concentrated solar power, solar thermal electricity, solar-selective transmitter, transparent conductive oxide, high-temperature in situ characterization

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  • Secondary publication expected from 30.03.2020

Publ.-Id: 28957 - Permalink


Interstellar ⁶⁰Fe in Antarctica
Koll, D.; Korschinek, G.; Faestermann, T.; Gómez-Guzmán, J.; Kipfstuhl, S.; Merchel, S.ORC; Welch, J. M.
Earth is constantly bombarded with extraterrestrial dust containing invaluable information about extraterrestrial processes, e.g. structure formation by stellar explosions or nucleosynthesis, which could be traced back by long-lived radionuclides. Here, we report the very first detection of a recent ⁶⁰Fe influx on Earth by analyzing 500 kg of snow from Antarctica by Accelerator Mass Spectrometry. By the measurement of the cosmogenically produced radionuclide ⁵³Mn, an atomic ratio of ⁶⁰Fe/⁵³Mn=0.017 was found, significantly above cosmogenic production. After elimination of possible terrestrial sources, such as global fallout, the excess of ⁶⁰Fe could only be attributed to interstellar ⁶⁰Fe from the solar neighborhood.
Keywords: AMS, supernova, ⁶⁰Fe

Publ.-Id: 28955 - Permalink


Critical dynamics of the Kuramoto model on sparse random networks
Juhász, R.; Kelling, J.; Ódor, G.;
We consider the Kuramoto model on sparse random networks such as the Erdős-Rényi graph or its combination with a regular two-dimensional lattice and study the dynamical scaling behavior of the model at the synchronization transition by large-scale, massively parallel numerical integration. By this method, we obtain an estimate of critical coupling strength more accurate than obtained earlier by finite-size scaling of the stationary order parameter. Our results confirm the compatibility of the correlation-size and the temporal correlation-length exponent with the mean-field universality class. However, the scaling of the order parameter exhibits corrections much stronger than those of the Kuramoto model with all-to-all coupling, making thereby an accurate estimate of the order-parameter exponent hard. We find furthermore that, as a qualitative difference to the model with all-to-all coupling, the effective critical exponents involving the order-parameter exponent, such as the effective decay exponent characterizing the critical desynchronization dynamics show a non-monotonic approach toward the asymptotic value. In the light of these results, the technique of finite-size scaling of limited size data for the Kuramoto model on sparse graphs has to be treated cautiously.
Keywords: Networks, Kuramoto Model, Synchronization

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  • Secondary publication expected from 24.05.2020

Publ.-Id: 28954 - Permalink


Small-angle neutron scattering (SANS): Overview on principles and best practices
Bergner, F.ORC; Ulbricht, A.
This talk provides an introduction into the method of small-angle neutron scattering (SANS), elements of good practice for the application and analysis as well as selected applications in the field of nuclear materials.
  • Lecture (Conference)
    OECD/NEA Nuclear Science Committee Preparatory meeting: Best practices for nuclear materials characterisation techniques, 11.-12.02.2019, Boulogne-Billancourt, France

Publ.-Id: 28953 - Permalink


Desynchronization dynamics of the Kuramoto model on connectome graphs
Ódor, G.; Kelling, J.;
The time dependent behavior of the Kuramoto model, describing synchronization, has been studied numerically on small-world graphs. We determined the desynchronziation behavior, by solving this model via the 4th order Runge-Kutta algorithm on a large, weighted human connectome network and compared the results with those of a two-dimensional lattice, with additional random, long-range links. In the latter case a mean-field critical transition is expected and here we provide numerical results for the synchonization/desynchonization duration distributions. We find power-law tails, characterized by a critical exponent τd≃1.6(1). In case of the connectome we assumed a homeostatic state, by the application of normalized incoming weights. Since this graph has a topological dimension d<4 a real synchronization phase transition is not possible in the thermodynamic limit, still we could locate a transition between partially synchronized and desynchronized states. At this crossover point we observe power-law--tailed desynchronization durations, with τt≃1.2(1), away from experimental values for the brain. Additionally, we changed the signs of outgoing weights of 20% of randomly selected nodes, to mimic a model with inhibitory interactions. In this case the at the crossover point we found τt≃1.9(2), which is in the range of human brain experiments.
Keywords: networks, brain, synchronization, kuramoto model
Related publications
Kuramoto Model on KKI18 connectome (Id 29065) HZDR-primary research data are used by this publication

Publ.-Id: 28952 - Permalink


Framework modifications and dehydration path of a Ag+-modified, STI-type zeolite
Cametti, G.; Scheinost, A. C.; Giordani, M.; Churakov, S. V.;
The effect of Ag+ incorporation into stellerite, a natural zeolite with STI framework type, was investigated by means of Single Crystal X-ray Diffraction (SC-XRD), Molecular Dynamics (MD) simulations and X-ray Absorption Fine Structure Spectroscopy (XAFS). At room temperature the complete exchange of the original extraframework ions with Ag+ provoked a distortion of the framework accompanied by symmetry reduction from orthorhombic Fmmm to monoclinic F2/m space group. Ag+ ions were strongly disordered, with occupancies ranging from 0.02 to 0.24, at partially-occupied sites within zeolitic cages. The combination of ab initio molecular dynamic simulations and XAFS spectroscopy suggested that Ag+ is coordinated by three water oxygens at 2.37 Å and by two framework oxygens at ca. 2.55 Å. The thermal stability was monitored in situ by SC-XRD (from 25 to 400°C) and by XAFS (from 25 to 650°C). Upon heating the structure transformed to three different topologies: B phase, D’ phase, observed here for the first time, and D phase. The unit-cell volume contracted from 4392.85(14) at room temperature to 3644.4(4) Å3, measured at 400°C. Possible Ag+ to Ag0 reduction could be excluded although the formation of Ag+-Ag+ clusters could not be unambiguously ruled out.
Keywords: zeolite molecular dynamics SC-XRD XAFS XANES Ag

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  • Secondary publication expected from 07.05.2020

Publ.-Id: 28951 - Permalink


Directed Evolution and Engineering of Gallium-Binding Phage Clones—A Preliminary Study
Schönberger, N.ORC; Zeitler, C.; Braun, R.ORC; Lederer, F.ORC; Matys, S.ORC; Pollmann, K.ORC
The phage surface display technology is a useful tool to screen and to extend the spectrum of metal-binding protein structures provided by nature. The directed evolution approach allows identifying specific peptide ligands for metals that are less abundant in the biosphere. Such peptides are attractive molecules in resource technology. For example, gallium-binding peptides could be applied to recover gallium from low concentrated industrial wastewater. In this study, we investigated the affinity and selectivity of five bacteriophage clones displaying different gallium-binding peptides towards gallium and arsenic in independent biosorption experiments. The displayed peptides were highly selective towards Ga3+ whereby long linear peptides showed a lower affinity and specificity than those with a more rigid structure. Cysteine scanning was performed to determine the relationship between secondary peptide structure and gallium sorption.
By site-directed mutagenesis, the amino acids of a preselected peptide sequence are systematically replaced by cysteines. The resulting disulphide bridge considerably reduces the flexibility of linear peptides. Subsequent biosorption experiments carried out with the mutants obtained from cysteine scanning demonstrated, depending on the position of the cysteines in the peptide, either a considerable increase in the affinity of gallium compared to arsenic or an increase in the affinity for arsenic compared to gallium. This study shows the impressive effect on peptide–target interaction based on peptide structure and amino acid position and composition via the newly established systematic cysteine scanning approach.
Keywords: phage surface display; gallium; metal–peptide interaction; site-directed mutagenesis; cysteine; peptide structure

Publ.-Id: 28950 - Permalink


Nuclear level densities and gamma-ray strength functions in samarium isotopes
Naqvi, F.; Simon, A.; Guttormsen, M.; Schwengner, R.; Frauendorf, S.; Reingold, C. S.; Burke, J. T.; Cooper, N.; Hughes, R. O.; Humby, P.; Koglin, J.; Ota, S.; Saastamoinen, A.;
The gamma-strength functions and level densities of in the quasi-continuum of 147,149Sm isotopes have been extracted from particle-gamma coincidences using the Oslo method. The nuclei of interest were populated via (p,d) reactions on pure 148,150Sm targets and the reaction products were recorded by the HYPERION array. An upbend in the gSF has been observed. The systematic analysis of the gSF for a range of Sm isotopes show that the scissors mode and the upbend compete with each other. Shell model calculations show a very good agreement with the experimental gSFs and confirm the competition between the upbend and scissors mode.
Keywords: Nuclear structure, light-ion reactions, gamma spectroscopy, level densities, strength functions, shell-model calculations.

Publ.-Id: 28949 - Permalink


In vitro and in vivo Human Metabolism of (S)-[18F]Fluspidine – a Radioligand for Imaging σ1 Receptors with Positron Emission Tomography (PET)
Ludwig, F.-A.; Fischer, S.; Houska, R.; Hoepping, A.; Deuther-Conrad, W.; Schepmann, D.; Patt, M.; Meyer, P.; Hesse, S.; Becker, G.-A.; Zientek, F. R.; Steinbach, J.; Wünsch, B.; Sabri, O.; Brust, P.;
(S)-[18F]fluspidine ((S)-[18F]1) has recently been explored for PET imaging of sigma-1 receptors in humans. In the current report, we have used plasma samples of healthy volunteers to investigate the radiometabolites of (S)-[18F]1 and elucidate their structures with LC-MS/MS. For the latter purpose additional in vitro studies were conducted by incubation of (S)-[18F]1 and (S)-1 with human liver microsomes (HLM). In vitro metabolites were characterized by interpretation of MS/MS fragmentation patterns from collision-induced dissociation or by use of reference compounds. Thereby, structures of corresponding radio-HPLC-detected radiometabolites, both in vitro and in vivo (human), could be identified. By incubation with HLM, mainly debenzylation and hydroxylation occurred, beside further mono- and di-oxygenations. The product hydroxylated at the fluoroethyl side chain was glucuronidated. Plasma samples (10, 20, 30 min p.i., n=5-6), obtained from human subjects receiving 250-300 MBq (S)-[18F]1 showed 97.2%, 95.4%, and 91.0% of unchanged radioligand, respectively. In urine samples (90 min p.i.) the fraction of unchanged radioligand was only 2.6% and three major radiometabolites were detected. The one with the highest percentage, also found in plasma, matched the glucuronide formed in vitro. Only a small amount of debenzylated metabolite was detected. In conclusion, our metabolic study, in particular the high fractions of unchanged radioligand in plasma, confirms the suitability of (S)-[18F]1 as PET radioligand for sigma-1 receptor imaging.
Keywords: Sigma-1 receptors (S1R), fluspidine, positron emission tomography (PET), radiometabolites, liquid chromatography-mass spectrometry (LC-MS), liver microsomes

Publ.-Id: 28946 - Permalink


Selective histone deacetylase inhibitors as prospective radiotracers for PET imaging
Clauß, O.; Scheunemann, M.; Hansen, F. K.; Brust, P.;
The class I histone deacetylases (HDACs) 1, 2 and 3 are overexpressed in several types of cancer, neurodegenerative diseases and inflammation. The catalyzed deacetylation of lysine residues on histones represents a key epigenetic modification that modulates the chromatin and thus influence the gene expression and transcription. Inhibition of zinc-dependent HDACs relaxes the chromatin structure and can result in transcriptional activation and anticancer effects, e.g. induction of apoptosis. Consequently, radiolabelled HDAC inhibitors have emerged as a potential tool for the diagnostic imaging of tumors by positron emission tomography (PET).
The aim of this work is the development of novel highly affine and selective fluorine containing derivatives of a class I selective HDAC inhibitor to obtain the corresponding 18-fluorine PET radiotracers with an ortho-aminoanilide as zinc-binding motif for targeting class I HDACs in tumors. A series of fluorinated reference compounds will be synthesized and the binding affinities and selectivities towards the HDAC isoforms 1, 2 and 3 will be determined. Our strategy is mainly focused on the medicinal chemistry of fluorine-containing derivatives, which are suitable for direct and indirect nucleophilic radiofluorination. For the most promising compounds, precursors for radiolabeling will be synthesized and a fully automated procedure will be established. The evaluation of physicochemical properties, e.g. stability and lipophilicity of the radiolabelled compounds will be assessed and further in vitro and in vivo investigations performed.
Keywords: Histone deacetylase inhibitors, Positron emission tomography, Fluorinated compounds
  • Poster
    NCT Retreat 2019, 09.-10.05.2019, Heidelberg, Deutschland

Publ.-Id: 28945 - Permalink


Instability of precession driven Kelvin modes: Evidence of a detuning effect
Herault, J.; Giesecke, A.; Gundrum, T.; Stefani, F.;
We report an experimental study of the instability of a nearly resonant Kelvin mode forced by precession in a cylindrical vessel. The instability is detected above a critical precession ratio via the appearance of peaks in the temporal power spectrum of pressure fluctuations measured at the end walls of the cylinder. The corresponding frequencies can be grouped into frequency sets satisfying resonance conditions with the forced Kelvin mode. We show that one set forms a triad that is associated with a parametric resonance of Kelvin modes. We observe a significant frequency variation of the unstable modes with the precession ratio, which can be explained by a detuning mechanism due to the slowdown of the background flow. By introducing a semianalytical model, we show that the departure of the flow from the solid body rotation leads to a modification of the dispersion relation of Kelvin modes and to a detuning of the resonance condition. The second frequency set includes a very low frequency and does not exhibit the properties of a parametric resonance between Kelvin modes. Interestingly, this frequency set always emerges before the occurrence of the triadic resonances, i.e., at a lower precession ratio, which implies that it may correspond to a different type of instability. We discuss the relevance of an instability of a geostrophic mode described by Kerswell [Kerswell, J. Fluid Mech. 382, 283 (1999)], although other mechanisms cannot be completely ruled out.
Keywords: Precession, Dynamo, DRESDYN

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Publ.-Id: 28944 - Permalink


Limited importance of EphrinA1–ligand, Src kinase, and focal adhesion kinase in EphA2-mediated regulation of metastasis in Mel-Juso and A375 human melanoma cells
Neuber, C.; Herwig, N.; Pietzsch, J.ORC; Belter, B.
EphA2 receptor tyrosine kinase fulfils various functions in the development of cancers. Here we analyzed how regulation of EphA2 receptor influences metastatic properties in human melanoma cells in vitro and lung metastasis in vivo. Further, we investigated whether the effects are mediated by Src kinase/focal adhesion kinase (FAK) signaling downstream of EphA2. Therefore, as model Mel-Juso and A375 melanoma cell lines showing different intrinsic EphA2 expression levels were used. To regulate EphA2 expression and activity, we used RNA interference, transgeneic EphA2 overexpression, and stimulation of EphA2 activity by adding EphrinA1. Adhesion to fibronectin was increased in EphA2-silenced cells and decreased in EphA2-overexpressing cells. Migration and planar motility were unaffected in Mel-Juso cells, but increased in EphA2-silenced A375 cells and decreased in EphA2-overexpressing A375 cells. Adhesion and migration were unaffected by EphrinA1-stimulation, indicating ligand-independent mechanisms. In vivo we detected increased lung metastasis in mice inoculated with EphA2-overexpressing Mel-Juso cells, substantiating the pro-metastatic effects of EphA2 in melanoma. Activity of Src kinase and FAK were unaffected in EphA2-silenced cells and in response to EphrinA1-stimulation. However, in EphA2-overexpressing A375 cells Src phosphorylation was increased, indicating enhanced Src activity. Together, these data suggest that EphA2 receptor promotes malignancy ligand-independently by mechanisms different from Src kinase/FAK signaling.
Keywords: Cellular adhesion; cellular migration; Eph receptor tyrosine kinases; Ephrins; malignant skin cancer; metastatic melanoma; RNA interference

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  • Secondary publication expected from 22.04.2020

Publ.-Id: 28943 - Permalink


Regulation of A375 melanoma cell adhesion and migration by EphB4 and EphrinB2 –insights from co-culture experiments
Neuber, C.; Laube, M.; Mamat, C.; Belter, B.; Pietzsch, J.ORC
BACKGROUND: Malignant melanoma is the most malignant skin neoplasm due to early metastasis and resistance to currently available therapies. Inflammatory tumor infiltrate, particularly macrophages, are of outstanding importance for melanoma progression and therapy response. EphB4 receptor and its preferred ligand EphrinB2 are also associated with melanoma progression, metastasis, and therapy resistance.
OBJECTIVE: The aim of our study was to systematically investigate the role of EphB4 for melanoma cell adhesion and migration, also in the presence of macrophages, considering experimental i) EphB4 overexpression, ii) EphB4 activation, iii) inhibition of EphB4 and EphrinB2 interaction, and iv) inhibition of EphB4 and downstream signaling.
RESULTS: Overexpression of EphB4 resulted in increased A375 melanoma cell adhesion showing EphrinB2 reverse signaling rather than EphB4 forward signaling being responsible. By contrast, A375 melanoma cell migration was not affected by EphB4 overexpression and effects due to modulation of EphB4/EphrinB2 signaling were inconsistent. In co-culture experiments macrophages (HL-60(M)) showed substantial influence on adhesion and migration of A375 cells. However, HL-60(M)-mediated effects could not be assigned to EphB4/EphrinB2 signaling but rather to cytokine signaling pathways.
CONCLUSIONS: Under the used experimental settings EphB4 is important for adhesion but not for the migration of A375 melanoma cells. Macrophages influenced adhesion and migration of melanoma cells but without significant involvement of EphB4/EphrinB2 signaling.
Keywords: Eph receptor tyrosine kinases; Ephrin ligands; malignant melanoma; metastasis; tumor microenvironment; tyrosine kinase inhibitors

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  • Secondary publication expected from 22.04.2020

Publ.-Id: 28942 - Permalink


Mass separated Focused Ion Beams from Liquid Metal Alloy Ion Sources
Bischoff, L.ORC; Mazarov, P.; Pilz, W.; Klingner, N.; Bauerdick, S.; Gierak, J.
Focused Ion Beam (FIB) processing has been developed into a well-established and still promising technique in nearly all fields of nano-technology in particular for direct patterning and proto-typing on the µm scale and well below. Beside new ion source developments based on gas field emission (GFIS), on ionic liquids (ILIS), on magneto-optical traps (MOTIS) or on ICP or ECR sources for Xe-FIB as well as the nearly exclusively used gallium Liquid Metal Ion Sources (LMIS), the replacement of Ga by alloys therein with an adapted FIB optics design can open bright field of new employments. Local ion implantation, ion beam mixing, ion beam synthesis or Focused Ion Beam Lithography (IBL) in the µm- or nm range can benefit from ion species purposely selected in parallel to gallium or noble gases. Therefore, exploring the Liquid Metal Alloy Ion Sources (LMAIS) potential represent a promising alternative to expand the global FIB application fields. Especially, IBL as direct, resistless and three-dimensional patterning enables a simultaneous in-situ process control by cross-sectioning and inspection. Thanks to this nearly half of the elements of the periodic table are made available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness and stable ion current. Recent developments could make these sources as an alternative technology feasible for nano patterning challenges e.g. to tune electrical, optical, magnetic or mechanic properties.
In this contribution the operation principle, the preparation and testing technology as well as prospective domains for modern FIB applications will be presented. As an example we will introduce a Ga35Bi60Li5 LMAIS in detail. It enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source.
L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Appl. Phys. Rev. 3, 021101 (2016).
Keywords: Liquid Metal Alloy Ion Source, Focused Ion Beam, Mass spectra, Cluster ions
  • Lecture (Conference)
    PicoFIB - The International Network for gas Ion Patterning and Microscopy, 13.02.2019, London, Great Britain

Publ.-Id: 28939 - Permalink


Compositional Multi-Point Geostatistics for Tailings Deposits - A Synthetic Case Study
Selia, S. R. R.; Tolosana-Delgado, R.; van den Boogaart, K. G.; Schaeben, H.;
Currently tailings deposits have become new resources that are challenging and valuable to exploit. To properly exploit them, we require a 3D spatial characterization of their mineral content. In a natural deposit, this is achieved by sampling at several locations and applying geostatistics to estimate block values. Certain characteristics of tailings deposits make them not amenable to conventional geostatistics. In particular, it is important to consider both valuable and gangue minerals, thus we need to take the compositional nature of our variables into account. In addition, the interplay of erosional and depositional processes creates structures with certain continuity patterns that cannot be modelled by conventional variogram-based methods such as kriging.
Therefore, we use a Multi-Point Geostatistics method, Direct Sampling (DS). DS is based on selecting the event from a training image, the conceptual spatial arrangement of a variable, with the shortest distance to the data event from the simulation domain. To account for the compositional nature of our variables, the Aitchison distance is calculated. We use numerical stratigraphic modelling to obtain a variety of training images, which we feed into a modified DS to deal with multiple training images at once.
We tested the proposal on a multi-source synthetic tailings deposit produced by numerical stratigraphic processes. Each grid of the model contains information about the content of several sediment species summing to 100%. Hard data are sampled on the model at certain locations and along with several unique training images we recreate the full 3D spatial distribution of the properties.
Keywords: Conditional simulation, Tailings Characterization, Remining
  • Lecture (Conference)
    5th International Young Earth Scientist Network (YES) Congress 2019, 09.-13.09.2019, Berlin, Germany

Publ.-Id: 28938 - Permalink


Radiochemical and radiopharmacological characterization of a 64Cu-labeled α-MSH analog conjugated with different chelators
Gao, F.; Sihver, W.ORC; Bergmann, R.; Walther, M.; Stephan, H.; Belter, B.; Neuber, C.; Haase-Kohn, C.; Bolzati, C.; Pietzsch, J.; Pietzsch, H.-J.
Radiolabeled α-melanocyte stimulating hormone (α-MSH) derivatives have a high potential for diagnosis and treatment of melanoma, due to high specificity and binding affinity to the melanocortin-1 receptor (MC1R). Hence, the α-MSH-derived peptide NAP-NS1 with a β-Ala linker (ε-Ahx-beta-Ala-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2) was conjugated to different chelators: either to NOTA (p-SCN-Bn-1,4,7-triazacyclononane-1,4,7-triacetic acid), to a hexadentate bispidine carbonate derivative (dimethyl-9-(((4-nitrophenoxy)carbonyl)oxy)-2,4-di(pyridin-2-yl)-3,7-bis(pyridin-2-ylmethyl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate) or to DMPTACN (p-SCN-Ph-bis(2-pyridyl-methyl)-1,4,7-triaza-cyclononane), labeled with 64Cu and investigated in terms of radiochemical and radiopharmacological properties.
For the three 64Cu-labeled conjugates negligible transchelation, suitable buffer and serum stability, as well as appropriate water solubility was determined. The three conjugates exhibited high binding affinity (low nanomolar range) in murine B16F10, human MeWo and human TXM13 cells. The Bmax values of [64Cu]Cu-bispidine-NAP-NS1 ([64Cu]Cu-2) and [64Cu]Cu-DMPTACN-NAP-NS1 ([64Cu]Cu-3) were higher than those of [64Cu]Cu-NOTA-NAP-NS1 ([64Cu]Cu-1), implying that different charged chelate units might have an impact on binding capacity. Preliminary in vivo biodistribution studies suggested the main excretion pathway of [64Cu]Cu-1 and [64Cu]Cu-3 to be renal, while that of [64Cu]Cu-2 seemed to be both renal and hepatobiliary. An initial moderate uptake in the kidney decreased clearly after 60 min. All three 64Cu-labeled conjugates should be considered for further in vivo investigations using a suitable xenograft mouse model.
Keywords: copper chelators, melanocortin-1 receptor, α-MSH, malignant melanoma, molecular imaging, radiopharmaceuticals, radiotracer, PET
  • Journal of Labelled Compounds and Radiopharmaceuticals 62(2019)8, 495-509
    DOI: 10.1002/jlcr.3728

Publ.-Id: 28937 - Permalink


Influence of calcium on uranium and neptunium sorption on clay minerals at (hyper)alkaline conditions
Philipp, T.; Schmeide, K.; Stumpf, T.;
Our previous experiments have shown that U(VI) is retained very strongly by Ca-bentonite in the pH range 10-12. Different spectroscopic techniques (site-selective TRLFS, EXAFS) have proven that the underlying retention mechanism under the given conditions was adsorption (not precipitation) despite the negative mineral surface charge and the anionic character of prevailing aqueous U(VI) species. It was hypothesized that attachment is facilitated by mediating calcium cations which are present in the solution. Therefore, the influence of calcium on the sorption of U(VI), Np(V) and Np(VI) at alkaline conditions was systematically studied. These radionuclides were selected as their aqueous speciation at high pH values is characterized by the predominance of anionic hydroxide species. Furthermore the adsorption of 45Ca on clay minerals and the resulting effect on the mineral surface charge was examined.
It was found that 45Ca adsorbed almost completely on Ca-bentonite between pH 8 and 13. Zeta potential measurements showed a partial compensation of the strongly negative surface charge of Ca-bentonite upon introduction of calcium. Hence, calcium is present at the surface, offering possible sorption sites for anionic uranium and neptunium species. Batch sorption experiments at different calcium concentrations revealed enormous effects on the retention of U(VI), Np(V) and Np(VI) between pH 10 and 13. Exemplarily shown for U(VI) in the figure below, the strong retention could not be observed in the experiment with kaolinite, where calcium was completely absent. Consequently, calcium is a crucial factor for the safety assessment of deep geological radioactive waste repositories, where (hyper)alkaline conditions evolve due to cement degradation.
Keywords: Calcium, U(VI), Np(V), Np(VI), adsorption, surface charge
  • Lecture (Conference)
    2nd International Conference on Radioanalytical and Nuclear Chemistry, 05.-10.05.2019, Budapest, Ungarn

Publ.-Id: 28936 - Permalink


Plasmonic field guided patterning of ordered colloidal nanostructures
Huang, X.-P.; Chen, K.; Qi, M.-X.; Zhang, P.-F.; Li, Y.; Winnerl, S.; Schneider, H.; Yang, Y.; Zhang, S.;
Nano-patterned colloidal plasmonic metasurfaces are capable of manipulation of light at the subwavelength scale. However, achieving controllable lithography-free nano-patterning for colloidal metasurfaces still remains a major challenge, limiting their full potential in building advanced plasmonic devices. Here, we demonstrate plasmonic field guided patterning (PFGP) of ordered colloidal metallic nano-patterns using orthogonal laser standing evanescent wave (LSEW) fields. We achieved colloidal silver nano-patterns with a large area of 30 mm² in <10 min by using orthogonal LSEW fields with a non-focused ultralow fluence irradiation of 0.25 W cm⁻². The underlying mechanism of the formation of the nanopatterns is the light-induced polarization of the nanoparticles (NPs), which leads to a dipole-dipole interaction for stabilizing the nano-pattern formation, as confirmed by polarization-dependent surface-enhanced Raman spectroscopy. This optical field-directed self-assembly of NPs opens an avenue for designing and fabricating reconfigurable colloidal nano-patterned metasurfaces in large areas.
Keywords: ordered colloidal nanostructures, plasmonic field guided patterning, polarization stabilizing

Publ.-Id: 28934 - Permalink


Investigation of [18F]FESCH for PET imaging of the adenosine A2A receptor in a rotenone-based mouse model of Parkinson´s disease and development of a two-step one-pot radiolabeling strategy
Schröder, S.; Lai, T. H.; Kranz, M.; Toussaint, M.; Shang, Q.; Dukic-Stefanovic, S.; Pan-Montojo, F.; Brust, P.;
Objectives:
Rotenone-treated mice are regarded as a model for Parkinson´s disease (PD). Increased availability of the adenosine A2A receptor (A2AR) has been found in the striatum of patients with PD and dyskinesias [1]. The aim of this study was to investigate whether similar alterations are found in the mouse model of PD using small animal PET/MR imaging. For that purpose, [18F]FESCH [2] was the radiotracer of choice due to its high A2AR specificity and excellent PET imaging properties [2-5]. Furthermore, we intended to develop a simplified one-pot strategy for the radiosynthesis of [18F]FESCH.
Methods:
The published two-step procedures for the radiosynthesis of [18F]FESCH start with the nucleophilic 18F-labeling of ethane-1,2-diol bis(3,4-dibromobenzenesulfonate) [4] or ethane-1,2-diol bis(4-methylbenzenesulfonate) [2]. The respective [18F]fluoroethyl synthon is isolated either by semi-preparative HPLC [4] or cartridge [2] and, only then, reacted with the phenol precursor desmethyl SCH442416. In our novel one-pot approach, desmethyl SCH442416 was treated with 40% TBAOHaq. to generate the activated phenolate which was directly reacted with the non-isolated 2-[18F]fluoroethyl tosylate in MeCN at 120 °C for 10 min (see Figure 1). [18F]FESCH was purified by semi-preparative HPLC, concentrated using solid-phase extraction on a pre-conditioned RP cartridge and eluted with absolute EtOH. After evaporation of the solvent at 75 °C, the radiotracer was finally formulated in isotonic saline ready for injection. [18F]FESCH (5.0±1.8 MBq) was administered to C57BL/6JRj mice (control n=5, rotenone-treated n=7, 18 month, 28-35 g) and whole body scans were performed for 60 min in listmode with a Mediso nanoScan® PET/MR scanner followed by dynamic reconstruction. Time-activity curves (TACs) were generated for regions of interest such as striatum (Figure 1) and cerebellum as reference region.
Results:
The herein described one-pot strategy provided [18F]FESCH (Ki hA2A=0.6 nM) with an overall radiochemical yield of 16.1±1.5% (n=9, EOB), a radiochemical purity of ≥98% and compared to the published two-pot procedure with a notably increased molar activity of 116±18.5 GBq/µmol (n=7, EOS). The PET images over 60 min showed high uptake of [18F]FESCH in the striatum (Figure 1) which is consistent with the known A2AR distribution pattern in the brain. Although not significant, slightly higher striatal A2AR binding was found in rotenone-treated mice.
Conclusions:
The radiotracer [18F]FESCH proved to be suitable for in vivo imaging of the adenosine A2A receptor in the mouse brain. Since the increased A2AR availability appears to be related to dyskinesia, it has to be proven whether the investigated mouse model of PD reflects this aspect.
Acknowledgments:
The European Regional Development Fund (ERDF) and Sächsische Aufbaubank (SAB) are acknowledged for financial support (Project No. 100226753).
References:
[1] Ramlackhansingh et al., Neurology, 76, 2011
[2] Khanapur et al., J. Med. Chem., 57, 2014
[3] Shinkre et al., Bioorg. Med. Chem. Lett., 20, 2010
[4] Bhattacharjee et al., Nucl. Med. Biol., 38, 2011
[5] Khanapur et al., J. Nucl. Med., 58, 2017
  • Open Access LogoPoster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Beijing, China
    DOI: 10.1002/jlcr.3725

Publ.-Id: 28932 - Permalink


Entwicklung einer Eintopf-Radiosynthese von F-18-FESCH für die PET-Bildgebung des Adenosin-A2A-Rezeptors im Rotenon-basierten Parkinson-Mausmodel
Schröder, S.; Lai, T. H.; Deuther-Conrad, W.; Dukic-Stefanovic, S.; Kranz, M.; Toussaint, M.; Shang, Q.; Pan-Montojo, F.; Brust, P.;
Ziel:
Gegenstand der Studie ist es, das Expressionsmuster des Adenosin-A2A-Rezeptors im Gehirn von Wildtyp(WT)- und Parkinsonmodel-Mäusen mittels KleintierPET/MRT zu untersuchen. Zu diesem Zweck wurde F-18-FESCH (1) als geeigneter A2A-Radiotracer ausgewählt, wobei eine vereinfachte Methode zur Radiosynthese entwickelt werden sollte.
Methodik:
In der publizierten zweistufigen Radiosynthese von F-18-FESCH wird das verwendete F-18-Fluorethylsynthon mittels Festphasenextraktion (1) oder semi-präparativer HPLC (2) isoliert und erst dann mit dem Phenol-Präkursor umgesetzt. In der hier entwickelten Eintopf-Methode wurde der Phenol-Präkursor mittels TBAOHaq. deprotoniert und direkt zur Reaktionsmischung des F-18-Fluorethylsynthons zugegeben. Die F-18-Fluorethylierung erfolgte in MeCN bei 120°C für 10 min. F-18-FESCH wurde mittels semi-präparativer HPLC isoliert, über eine RP18-Kartusche konzentriert und in 0,9%iger NaClaq. formuliert. Der Radiotracer (4-8 MBq) wurde C57BL/6JRj-Mäusen (WT n=5, Rotenon-behandelt n=7, 18 Monate) appliziert und Ganzkörperscans mit einem Mediso nanoScan® PET/MRT aufgenommen.
Ergebnisse:
F-18-FESCH (Ki hA2A=0,6 nM) wurde mit einer radiochemischen Ausbeute von 16,1±1,5% (n=9, EOB), einer radiochemischen Reinheit von ≥98% und einer im Vergleich zur Literatur deutlich gesteigerten molaren Aktivität von 116±18,5 GBq/µmol (n=7, EOS) bereitgestellt. Die summierten PET-Bilder (1 h) zeigen eine erhöhte Anreicherung von F-18-FESCH im Striatum, wobei kein signifikanter Unterschied zwischen den WT- und Rotenon-behandelten Mäusen detektiert wurde.
Schlussfolgerungen:
F-18-FESCH ist zur PET-Bildgebung des A2A-Rezeptors im Maushirn geeignet. Die ersten Ergebnisse der PET-Studie im Parkinson-Mausmodel weisen auf keine veränderte A2A-Rezeptordichte hin.
Literatur:
(1) Khanapur et al., J. Med. Chem., 57, 2014
(2) Bhattacharjee et al., Nucl. Med. Biol., 38, 2011
  • Open Access LogoPoster
    57. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin e.V.(NuklearMedizin 2019), 03.-06.04.2019, Bremen, Deutschland

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Publ.-Id: 28931 - Permalink


Experimental and theoretical investigation of the boiling heat transfer in a low pressure natural circulation system
Viereckl, F.; Schleicher, E.; Schuster, C.; Lippmann, W.; Hurtado, A.;
The implementation of passive safety systems in nuclear reactors provide the opportunity to enhance the nuclear safety. On the other hand, an accurate and reliable prediction of the heat removal behavior is not ensured because the operating conditions of certain types of passive systems like containment cooling systems differ from the validity ranges of the established heat transfer correlations. Therefore, a generic and detailed investigation is still necessary for passive systems.
Against this background, the test facility GENEVA was erected at Technische Universität Dresden in 2012. Since the commissioning, generic experiments concerning the system and stability behavior of this facility, which emulates a low pressure and low flow (LPLF) natural circulation system, were provided. Nevertheless, the investigation of the heat transfer behavior remained an open issue. On this account, the instrumentation in the heat transfer region inside GENEVA was improved to gather the necessary temperature and void fraction profiles.
The performed experiments provide a generic and wide database concerning boiling in a LPLF natural circulation systems. Within this paper, the development of the wall and bulk fluid temperature as well as the axial and center line void fraction profile in a slightly inclined tube for different heat flow rates are discussed. Furthermore, flow patterns could be identified on behalf of the void fraction measurements. To conclude the experimental analysis, the development of the heat transfer coefficient was estimated.
These experimental data provide the basis for a simulation with the lumped-parameter thermal-hydraulic code ATHLET and serve as validation reference. However, the comparisons between the experimental and computational results show insufficient agreements. Mainly, the simulation misses the saturation point of the experiments, which leads to great differences of the void fraction values. Moreover, inaccuracies appear as well with the heat transfer coefficient.
The experimental and computational results that are discussed in this paper provide the basis for the advancement not only of heat transfer correlations but also of flow pattern maps within the range of low pressure natural circulation system. In summary, this investigation contributes to the general purpose to enhance nuclear safety by providing an accurate and reliable prediction of the heat removal capacity of passive systems.
Keywords: flow patterns, GENEVA, heat transfer coefficient, low pressure natural circulation, nuclear safety, passive systems

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  • Secondary publication expected from 06.07.2020

Publ.-Id: 28930 - Permalink


Deterministic field-free skyrmion nucleation at a nano-engineered injector device
Finizio, S.; Zeissler, K.; Wintz, S.; Mayr, S.; Weßels, T.; Huxtable, A. J.; Burnell, G.; Marrows, C. H.; Raabe, J.;
Magnetic skyrmions are topological solitons that exhibit an increased stability against annihilation [1, 2], and can be displaced with low current densities [3], making them a promising candidate as an information carrier [1]. In order to demonstrate a viable skyrmion-based memory device, it is necessary to reliably and reproducibly nucleate, displace, detect, and delete the magnetic skyrmions. While the skyrmion displacement [4–7] and detection [8, 9] have both been investigated in detail, much less attention has been dedicated to the study of the sub-ns dynamics of the skyrmion nucleation and deletion processes. Only limited studies on the statics [10, 11] and above-ns dynamics [12] have been performed, leaving still many open questions on the dynamics of the nucleation process. Furthermore, the vast majority of the presently existing studies focus on the nucleation from random natural pinning sites [10, 12], or from patterned constrictions in the magnetic material itself [10, 11], which limit the functionality of the skyrmion-based device. Those limitations can be overcome by the fabrication of a dedicated injector device on top of the magnetic material [13]. In this study, we investigate the nucleation of magnetic skyrmions from a dedicated nano-engineered injector, demonstrating the reliable magnetic skyrmion nucleation at the remnant state. The sub-ns dynamics of the skyrmion nucleation process were also investigated, allowing us to shine light on the physical processes driving the nucleation.
Keywords: skyrmion, nucleation, x-ray microscopy

Publ.-Id: 28928 - Permalink


Zero-field dynamics stabilized by in-plane shape anisotropy in MgO-based spin-torque oscillators
Kowalska, E.ORC; Kákay, A.ORC; Fowley, C.; Sluka, V.; Lindner, J.; Fassbender, J.ORC; Deac, A. M.
Here, we demonstrate numerically that shape anisotropy in MgO-based spin-torque nano-oscillators consisting of an out-of-plane magnetized free layer and an in-plane polarizer is necessary to stabilize out-of-plane magnetization precession without the need of external magnetic fields. As the in-plane anisotropy is increased, a gradual tilting of the magnetization towards the in-plane easy direction is introduced, favouring zero-field dynamics over static in-plane states. Above a critical value, zero-field dynamics are no longer observed. The optimum ratio of in-plane shape to out-of-plane uniaxial anisotropy, for which large angle out-of-plane zero-field dynamics occur within the widest current range, is reported.
Keywords: spin-torque nano-oscillator (STNO), MgO-based magnetic tunnel junctions, tunnel magnetoresistance (TMR), spin dynamics
Related publications
Tunnel magnetoresistance angular and bias dependence … (Id 27885) is supplemented by this publication

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Publ.-Id: 28927 - Permalink


Spectroelectrochemical studies of the Tc(VII) reduction in aqueous electrolyte media
Rodriguez, D.; Mayordomo, N.; Brendler, V.; Müller, K.; Stumpf, T.;
99Tc, a weak β-particle-emitter with a half-life of 2.13×105 years, is a strongly relevant fission product. Under repository conditions it has two main oxidation states: Tc(VII), as pertechnetate TcO4, a highly water-soluble anion not significantly sorbed on minerals or sediments, and Tc(IV), mostly found as TcO2, a solid with a low solubility product and, thus, a lower mobility [1].

However, in 2004 Lukens et. al. [2] reported the existence of non-pertechnetate species in the Hanford waste tanks and identified them as Tc(I) – carbonyl complexes. In further reports of the Pacific Northwest National Laboratory [3–7] the synthesis of Tc(I) carbonyl and nitrosyl complexes, relevant to the Hanford Site and their characterization by XAS and NMR is fully explained. More recently, Chatterjee et. al. [8] succeeded to stabilize Tc(VI) species to study them by spectroscopic methods (UV-vis, EPR and XPS). These works show the importance of extending the current knowledge of Tc fundamental chemistry and the need for more thermodynamic information on low-valent Tc oxidation states in order to determine the reduction mechanism from Tc(VII) to Tc(IV), which is not yet fully understood.

As a first approach, we have studied the reduction of 1 mM Tc(VII) in 1M HNO3 by applying a series of negative potentials (from -100 to -500 mV) to the solution for 30 minutes each. After this time, an aliquot was taken to measure the UV-vis spectra, as shown in figure 1. Additionally, after applying -550 mV, the solution was sealed and left at rest for 24 hours to evaluate the stability of the product formed.

Figure 1-A shows a peak around 265 nm that corresponds to Tc(VII) [9,10]. The intensity of the band decreases with decreasing the potential, which implies that Tc(VII) concentration in solution decreases due to its reduction, as expected for low potential values. The spectra of the solution after 24 hours shows that Tc(VII) is formed again, although the initial concentration is not reached.

Figure 1-B shows two signals that may correspond to the formation of other Tc oxidation states. According to Alliot et. al. [10], the peak around 500 nm could be assigned to the Tc(IV) formation, although it would not fully explain the increase of the signal 24 hours after the experiment. On the other hand, the three peaks formed around 370 nm after V = -350 mV most probably account for the reduction of the nitric acid, as they maintain their shape after 24 hours and, if they were non common Tc species like Tc(V) or Tc(VI), they should have disproportionated to Tc(VII) in a short time.

Even though these results are very interesting, it is necessary to combine spectroscopic and electrochemical methods and to carry out the measurements at the same time in order to obtain a clear understanding on the reduction. Moreover, in order to avoid the uncertainty due to the reaction of the electrolyte, a systematic selection of anions and cations must be done. Therefore, we have studied the reduction of Tc(VII) in 1 M of aqueous sodium nitrate (NaNO3), sodium perchlorate (NaClO4), sodium bicarbonate (NaHCO3) and sodium chloride (NaCl) by cyclic voltammetry and differential pulse voltammetry coupled with UV – vis.

This work has been developed in the frame of VESPA II project (02E11607B), supported by the German Federal Ministry for Economic Affairs and Energy (BMWi).



1 A. H. Meena and Y. Arai, Environ. Chem. Lett. 15, 241 (2017).
2 W. W. Lukens, D. K. Shuh, N. C. Schroeder and K. R. Ashley, Environ. Sci. Technol. 38, 229 (2004).
3 T. Levitskaia, A. Anderson, S. Chatterjee, H. Cho, B. M. Rapko, J. Peterson, E. D. Walter and N. M. Washton, Speciation and Oxidative Stability of Alkaline Soluble, Non-Pertechnetate Technetium, Richland, Washington, 2014.
4 T. Levitskaia, A. Andersen, S. Chatterjee, G. B. Hall, E. D. Walter and Was, Spectroscopic Properties of Tc(I) Tricarbonyl Species Relevant to the Hanford Tank Waste, Richland, Washington, 2015.
5 G. B. Hall, S. D. Chatterjee, T. G. Levitskaia, T. J. Martin, N. A. Wall and E. D. Walter, Synthesis and Characterization of Tc(I) Carbonyl Nitrosyl Species Relevant to the Hanford Tank Waste: FY 2016 Status Report, Richland, Washington, 2016.
6 R. J. Serne, J. V Crum, B. J. Riley and T. G. Levitskaia, Options for the Separation and Immobilization of Technetium, Richland, Washington, 2016.
7 S. Chatterjee, A. Andersen, Y. Du, M. H. Engelhard, G. B. Hall, T. G. Levitskaia, W. W. Lukens, V. Shutthanandan, E. D. Walter and N. M. Washton, Characterization of Non- Pertechnetate Species Relevant to the Hanford Tank Waste, Richland, Washington, 2017.
8 S. Chatterjee, G. B. Hall, I. E. Johnson, Y. Du, E. D. Walter, N. M. Washton and T. G. Levitskaia, Inorg. Chem. Front. 5, 2081 (2018).
9 J. Paquette and W. E. Lawrence, Can. J. Chem. 63, 2369 (1985).
10 I. Alliot, C. Alliot, P. Vitorge and M. Fattahi, Environ. Sci. Technol. 43, 9174 (2009).
Keywords: Electrochemical reduction, technetium, electrolytes, aqueous chemistry
  • Poster
    17th international conference on the chemistry and migration behavior of actinides and fission products in the geosphere, 15.-21.09.2019, Kyoto, Japan

Publ.-Id: 28926 - Permalink


Terahertz-Field-Induced Time Shifts in Atomic Photoemission
Schmid, G.; Schnorr, K.; Augustin, S.; Meister, S.; Lindenblatt, H.; Trost, F.; Liu, Y.; Stojanovic, N.; Al-Shemmary, A.; Golz, T.; Treusch, R.; Gensch, M.; Kübel, M.; Foucar, L.; Rudenko, A.; Ullrich, J.; Schröter, C. D.; Pfeifer, T.; Moshammer, R.;
Time delays for atomic photoemission obtained in streaking or reconstruction of attosecond bursts by interference of two-photon transitions experiments originate from a combination of the quantum mechanical Wigner time and the Coulomb-laser coupling. While the former was investigated intensively theoretically as well as experimentally, the latter attracted less interest in experiments and has mostly been subject to calculations. Here, we present a measurement of the Coulomb-laser coupling-induced time shifts in photoionization of neon at 59.4 eV using a terahertz (THz) streaking field (λ = 152 μm). Employing a reaction microscope at the THz beamline of the free-electron laser in Hamburg (FLASH), we have measured relative time shifts of up to 70 fs between the emission of 2p photoelectrons (∼38 eV) and lowenergetic (<1 eV) photoelectrons. A comparison with theoretical predictions on Coulomb-laser coupling reveals reasonably good agreement.

Publ.-Id: 28925 - Permalink


Singlet ground state in the alternating spin-1/2 chain compound NaVOAsO4
Arjun, U.; Ranjith, K. M.; Koo, B.; Sichelschmidt, J.; Skourski, Y.; Baenitz, M.; Tsirlin, A. A.; Nath, R.;
We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline NaVOAsO4 by means of x-ray diffraction, magnetization, electron spin resonance (ESR), and 75As nuclear magnetic resonance (NMR) measurements as well as density-functional band structure calculations. Temperature-dependent magnetic susceptibility, ESR intensity, and NMR line shift could be described well using an alternating spin-1/2 chain model with the exchange coupling J/kB ≃ 52 K and an alternation parameter α ≃ 0.65. From the high-field magnetization measured at T = 1.5 K, the critical field of the gap closing is found to be Hc ≃ 16 T, which corresponds to the zero-field spin gap of Δ0/kB ≃ 21.4 K. Both NMR shift and spin-lattice relaxation rate show an activated behavior at low temperatures, further confirming the singlet ground state. The spin chains do not coincide with the structural chains, whereas the couplings between the spin chains are frustrated. Because of a relatively small spin gap, NaVOAsO4 is a promising compound for further experimental studies under high magnetic fields.

Publ.-Id: 28924 - Permalink


Gaussian and critical scalings in the magnetoconductivity fluctuations of Y3Ba5Cu8O18 superconductor
Dias, F. T.; Vieira, V. N.; Oliveira, C. P.; Silva, D. L.; Mesquita, F.; Lima, J. R.; Wolff-Fabris, F.; Kampert, E.; Pureur, P.;
We have studied the superconducting transition and the magnetoconductivity fluctuations in the polycrystalline Y3Ba5Cu8O18 (Y358) superconductor under magnetic fields upto 1 T. A two-step superconducting transition could be observed as a consequence of the granular structure of the sample, which is strongly affected by the applied magnetic field. Gaussian and genuine critical 3D-XY-E fluctuation regimes were identified. A critical scaling regime beyond 3D-XY was identified for magnetic fields upto 0.25 T, corresponding to the averaged exponent 0.19 and suggesting the occurrence of the weak first-order character of the superconducting transition. In the approximation to the zero resistance a power law regime could be observed, corresponding to the averaged exponent 2.37, which are smaller than previously reported for the Y358 system. Our results are discussed in terms of the Y358 and Yba2Cu3O7−δ (Y123) results in the literature.

Publ.-Id: 28923 - Permalink


Magnetization beyond the Ising limit of Ho2Ti2O7
Opherden, L.; Herrmannsdörfer, T.; Uhlarz, M.; Gorbunov, D. I.; Miyata, A.; Portugall, O.; Ishii, I.; Suzuki, T.; Kaneko, H.; Suzuki, H.; Wonsitza, J.;
We report that the local Ising anisotropy in pyrochlore oxides—the crucial requirement for realizing the spin-ice state—can be broken by means of high magnetic fields. For the case of the well-established classical spin-ice compound Ho2Ti2O7 the magnetization exceeds the angle-dependent saturation value of the Ising limit using ultrahigh fields up to 120 T. However, even under such extreme magnetic fields full saturation cannot be achieved. Crystal-electric-field calculations reveal that a level crossing for two of the four ion positions leads to magnetization steps at 55 and 100 T. In addition, we show that by using a field sweep rate in the range of the spin-relaxation time the dynamics of the spin system can be probed. Exclusively at 25 ns/T, a new peak of the susceptibility appears around 2 T. We argue, this signals the crossover between spin-ice and polarized correlations.

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Publ.-Id: 28922 - Permalink


Electronic band structure and proximity to magnetic ordering in the chiral cubic compound CrGe
Klotz, J.; Götze, K.; Förster, T.; Bruin, J. A. N.; Wosnitza, J.; Weber, K.; Schmidt, M.; Schnelle, W.; Geibel, C.; Rößler, U. K.; Rosner, H.;
CrGe belongs to the family of cubic B20 intermetallics. From experimental investigations by susceptibility and de Haas-van Alphen (dHvA) measurements and from calculations of its electronic band structure by densityfunctional theory (DFT), CrGe is found to form a metallic paramagnetic ground state. Combining dHvA and DFT data, a detailed picture of the Fermi surface of CrGe is provided. The proximity to a magnetic longrange ordering in CrGe is suggested from a prominent thermal magnetic susceptibility. The possibility to induce magnetic long-range order in CrGe is discussed based on calculated properties for CrGe substituting Ge by As or Sn, and from a comparison with MnGe and the alloy series Cr1−xMnxGe. Owing to the noncentrosymmetric and nonsymmorphic crystal structure of CrGe, in absence of broken time reversal symmetry, its band structure is marked by forced nodal lines at the Fermi edge. Moreover, this material hosts degenerate unconventional electronic quasiparticles. In particular, CrGe exhibits a sixfold degeneracy of fermions crossing within about 5 meV of the Fermi energy at the R point of the Brillouin zone.

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Publ.-Id: 28921 - Permalink


Magnetic phase diagram and crystal-field effects in the kagome-lattice antiferromagnet U3Ru4Al12
Gorbunov, D. I.; Ishii, I.; Nomura, T.; Henriques, M. S.; Andreev, A. V.; Uhlarz, M.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.;
We report on the magnetic phase diagram of the distorted kagome-lattice antiferromagnet U3Ru4Al12 determined through measurements of magnetic and elastic properties. For field applied along the [100] and [120] axes of the hexagonal crystal structure, we find pronounced anomalies in the magnetization and elastic moduli that signal the existence of unknown magnetic phases. Our crystal-electric-field (CEF) analysis evidences interlevel quadrupolar interactions between the ground-state singlet and the first excited doublet. These interactions lead to a large softening of the shear elastic modulus C44. The large number of phases and pronounced elastic
softening suggest that geometric frustrations and CEF effects play an important role in the physical properties of U3Ru4Al12.

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Publ.-Id: 28920 - Permalink


U2Ni2Sn and the origin of magnetic anisotropy in uranium compounds
Maskova, S.; Andreev, A. V.; Skourski, Y.; Yasin, S.; Gorbunov, D. I.; Zherlitsyn, S.; Nakotte, H.; Kothapalli, K.; Nasreen, F.; Cupp, C.; Cao, H. B.; Kolomiets, A.; Havela, L.;
U2Ni2Sn is a member of a large family of intermetallic compounds with the tetragonal Mo2FeB2 crystal structure. It orders antiferromagnetically at 25 K with propagation vector q = (0, 0, 1/2 ). Magnetization, magnetoacoustic, and neutron-diffraction experiments on a single crystal provide evidence that the uranium moments align parallel to the c axis with the anisotropy energy of ≈170 K, indicating that U2Ni2Sn can be classified as an Ising system. The results are at variance with previous studies on polycrystals, which indicated different magnetic structure, and which were incompatible with the 5 f -5 f two-ion anisotropy model dominant in most U band systems. High-field magnetization studies exhibit a weak linear response for fields along the basal plane up to the highest field applied (60 T), while the c-axis magnetization curve exhibits three metamagnetic transitions at approximately 30, 39, and 50 T. The U magnetic moments of 0.87μB, the low magnetic entropy, and the enhanced Sommerfeld coefficient γ = 187 mJ/mol f.u.K2 suggest that U2Ni2Sn can be classified as an itinerant antiferromagnet with strong electron-electron correlations.

Publ.-Id: 28919 - Permalink


LISEL@DREAMS - The future of Accelerator Mass Spectrometry
Forstner, O.; Merchel, S.ORC; Rugel, G.; Wendt, K.
LISEL (Low energy Isobar SEparation by Lasers) is a future project at the DREAMS (DREsden Accelerator Mass Spectrometry) facility to widen the applications of AMS by extending the range of measurable (radio-) nuclides. AMS has proven to be a versatile tool capable of detecting a large number of long-lived radionuclides at the ultra-trace level i.e. isotope ratios down to 1E-16. However, being a mass spectrometric method, it is limited by the presence of strong isobaric background. To overcome this limitation, we propose to remove the isobars already at the low-energy side by laser photodetachment. This method allows to selectively neutralize isobars by laser radiation, leaving the ions of interest intact. First studies were performed at the University of Vienna and gave promising results [1,2] for the easier to be measured low-mass AMS isotopes Al-26 and Cl-36. Within the LISEL project this method will be for the first time applied to an AMS facility based on a 6 MV tandem accelerator. The first isotopes to be addressed with the new method will be Mn-53 and Fe-60. Both are currently only measurable at AMS facilities with more than 10 MV terminal voltage (currently available only at the ANU in Canberra/Australia or the LMU and TU Munich in Garching/Germany). Further on we foresee to apply this method to other rare isotopes, making LISEL@DREAMS a versatile machine for all isotopes. This will subsequently widen the applications and also the user community.
[1] Forstner, O. et al., Nucl. Instr. And Meth. B 361 (2015) p. 217-221 [2] Martschini, M. et al., Int. J. Mass Spectrom., 415 (2017) p. 9-17
Keywords: laser, AMS, accelerator mass spectrometry
  • Lecture (Conference)
    PLATAN 2019, International Conference Merger of the Poznan Meeting on Lasers and Trapping Devices in Atomic Nuclei Research and the International Conference on Laser Probing, 19.-24.05.2019, Mainz, Deutschland
  • Lecture (Conference)
    Ion Beam Physics Workshop, 24.-26.06.2019, Dresden, Deutschland

Publ.-Id: 28918 - Permalink


Ultrasensitive (<1 mBq), cheap, and fast detection method for ⁷Be allowing high sample throughput
Rugel, G.; Tiessen, C. J.; Bemmerer, D.ORC; Querfeld, R.; Scharf, A.; Steinhauser, G.; Merchel, S.ORC
Beryllium-7 (T1/2 = 53.22 d), mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science [1]. For activities < 0.1 Bq and especially for samples also containing so longer-lived ¹⁰Be (T1/2 = 1.387 Ma), accelerator mass spectrometry (AMS) is the method-of-choice.
We demonstrate that ⁷Be and ¹⁰Be can be quantified at the DREsden AMS (DREAMS) facility [2,3] on the same prepared BeO. Detection limits (⁷Be) are as low as ~ 0.6 mBq, hence, one-to-two orders of magnitude better than “standard/ordinary” and “sophisticated” decay counting (e.g. in an underground laboratory). Uncertainties for small samples are usually 6-7 % for small samples. The method is validated by γ-counting of two larger rainwater samples showing an excellent agreement with the AMS result [4].
Samples as small as tens of millilitres of rainwater can be chemically processed (after acidification) within a few hours without expensive and time-consuming ion exchange. Isobar (⁷Li) suppression by chemistry and AMS is sufficient to guarantee an ultrasensitive, cheap, and fast detection method for ⁷Be allowing high sample throughput.
The DREAMS facility allows external user access free-of-charge via a proposal system. Further information can be found at www.hzdr.de/ibc or www.ionbeamcenters.eu.

Acknowledgments
Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association. We appreciate support of Dominik Güttler, René Ziegenrücker and the DREAMS operator team during AMS-measurements, of Gyürky György (Hungarian Academy of Sciences) for providing ⁷Be for the calibration material, and of BMBF (05K16MG1) and DAAD-RISE Professional (HZDRPH-456) for funding. It was a pleasure to discuss ⁷Be-AMS with Andrew Smith (ANSTO).

References
[1] R. Querfeld, S. Merchel, G. Steinhauser, J. Radioanal. Nucl. Chem. 314 (2017) 521-527.
[2] S. Akhmadaliev et al., Nucl. Instr. Meth. B 294 (2013) 5-10.
[3] G. Rugel et al., Nucl. Instr. Meth. B 370 (2016) 94-100.
[4] C. Tiessen et al., Accelerator mass spectrometry (AMS) for beryllium-7 measurements in smallest rainwater samples, J. Radioanal. Nucl. Chem, 2019, doi: 10.1007/s10967-018-6371-6.
Keywords: Be-7, Be-10, accelerator mass spectrometry (AMS), rainwater
  • Invited lecture (Conferences)
    2nd International Conference on Radioanalytical and Nuclear Chemistry (RANC 2019), 05.-10.05.2019, Budapest, Hungary

Publ.-Id: 28917 - Permalink


Viable and active microorganisms in the deep terrestrial biosphere
Lopez-Fernandez, M.; Simone, D.; Broman, E.; Turner, E.; Wu, X.; Bertilsson, S.; Dopson, M.;
Although the continental deep biosphere is estimated to contain 2 to 19% of the earth’s total biomass, it is still one of the least understood ecosystems on the planet. A key question for the terrestrial deep biosphere is the viability and activity of the large diversity of microorganisms present. This work shows that the microbial populations in aquifers with different chemistry and depth below the surface are viable and active and their diversity decreased with depth below the surface. Quantitative PCR and high throughput 16S rRNA gene sequencing revealed no significant differences in 16S rRNA gene abundances and microbial diversity between total and viable communities. This suggested that the populations were adapted to the prevailing oligotrophic conditions and that non-viable cells are rapidly degraded and recycled into new biomass. In addition, in situ fixed RNA transcripts aligned to the three domains of life, supporting activity within these communities. Many of the SSU rRNA transcripts grouped within recently described candidate phyla or could not be mapped to known branches on the tree of life, suggesting that a large portion of the active biota in the deep biosphere remains unexplored. Despite the extremely oligotrophic conditions, mRNA transcripts revealed a diverse range of metabolic strategies carried out by different taxa. These results emphasize the need to further investigate microbial activities in the deep biosphere and the importance of unclassified and candidate phyla in this environment.
  • Lecture (Conference)
    12th International Congress of Extremophiles, 16.-20.09.2018, Ischia, Italy

Publ.-Id: 28916 - Permalink


Depth and Dissolved Organic Carbon Shape Microbial Communities in Surface Influenced but Not Ancient Saline Terrestrial Aquifers
Lopez-Fernandez, M.; Åström, M.; Bertilsson, S.; Dopson, M.;
The continental deep biosphere is suggested to contain a substantial fraction of the earth’s total biomass and microorganisms inhabiting this environment likely have a substantial impact on biogeochemical cycles. However, the deep microbial community is still largely unknown and can be influenced by parameters such as temperature, pressure, water residence times, and chemistry of the waters. In this study, 21 boreholes representing a range of deep continental groundwaters from the Äspö Hard Rock Laboratory were subjected to high-throughput 16S rRNA gene sequencing to characterize how the different water types influence the microbial communities. Geochemical parameters showed the stability of the waters and allowed their classification into three groups. These were (i) waters influenced by infiltration from the Baltic Sea with a “modern marine (MM)” signature, (ii) a “thoroughly mixed (TM)” water containing groundwaters of several origins, and (iii) deep “old saline (OS)” waters. Decreasing microbial cell numbers positively correlated with depth. In addition, there was a stronger positive correlation between increased cell numbers and dissolved organic carbon for the MM compared to the OS waters. This supported that the MM waters depend on organic carbon infiltration from the Baltic Sea while the ancient saline waters were fed by “geogases” such as carbon dioxide and hydrogen. The 16S rRNA gene relative abundance of the studied groundwaters revealed different microbial community compositions. Interestingly, the TM water showed the highest dissimilarity compared to the other two water types, potentially due to the several contrasting water types contributing to this groundwater. The main identified microbial phyla in the groundwaters were Gammaproteobacteria, unclassified sequences, Campylobacterota (formerly Epsilonproteobacteria), Patescibacteria, Deltaproteobacteria, and Alphaproteobacteria. Many of these taxa are suggested to mediate ferric iron and nitrate reduction, especially in the MM waters. This indicated that nitrate reduction may be a neglected but important process in the deep continental biosphere. In addition to the high number of unclassified sequences, almost 50% of the identified phyla were archaeal or bacterial candidate phyla. The percentage of unknown and candidate phyla increased with depth, pointing to the importance and necessity of further studies to characterize deep biosphere microbial populations.
Keywords: 16S rRNA gene, amplicon sequencing, deep subsurface, groundwaters, chemistry, microbial diversity

Publ.-Id: 28915 - Permalink


Microbial Community and Metabolic Activity in Thiocyanate Degrading Low Temperature Microbial Fuel Cells
Ni, G.; Canizales, S.; Broman, E.; Simone, D.; Palwai, V. R.; Lundin, D.; Lopez-Fernandez, M.; Sleutels, T.; Dopson, M.;
Thiocyanate is a toxic compound produced by the mining and metallurgy industries that needs to be remediated prior to its release into the environment. If the industry is situated at high altitudes or near the poles, economic factors require a low temperature treatment process. Microbial fuel cells are a developing technology that have the benefits of both removing such toxic compounds while recovering electrical energy. In this study, simultaneous thiocyanate degradation and electrical current generation was demonstrated and it was suggested that extracellular electron transfer to the anode occurred. Investigation of the microbial community by 16S rRNA metatranscriptome reads supported that the anode attached and planktonic anolyte consortia were dominated by a Thiobacillus-like population. Metatranscriptomic sequencing also suggested thiocyanate degradation primarily occurred via the ‘cyanate’ degradation pathway. The generated sulfide was metabolized via sulfite and ultimately to sulfate mediated by reverse dissimilatory sulfite reductase, APS reductase, and sulfate adenylyltransferase and the released electrons were potentially transferred to the anode via soluble electron shuttles. Finally, the ammonium from thiocyanate degradation was assimilated to glutamate as nitrogen source and carbon dioxide was fixed as carbon source. This study is one of the first to demonstrate a low temperature inorganic sulfur utilizing microbial fuel cell and the first to provide evidence for pathways of thiocyanate degradation coupled to electron transfer.
Keywords: MFC, thiocyanate degradation, extracellular electron transfer, low temperature, metatranscriptomics

Publ.-Id: 28914 - Permalink


Metatranscriptomes Reveal That All Three Domains of Life Are Active but Are Dominated by Bacteria in the Fennoscandian Crystalline Granitic Continental Deep Biosphere
Lopez-Fernandez, M.; Simone, D.; Wu, X.; Soler, L.; Nilsson, E.; Holmfeldt, K.; Lantz, H.; Bertilsson, S.; Dopson, M.;
ABSTRACT The continental subsurface is suggested to contain a significant part of the earth’s total biomass. However, due to the difficulty of sampling, the deep subsurface is still one of the least understood ecosystems. Therefore, microorganisms inhabiting this environment might profoundly influence the global nutrient and energy cycles. In this study, in situ fixed RNA transcripts from two deep continental groundwaters from the Äspö Hard Rock Laboratory (a Baltic Sea-influenced water with a residence time of < 20 years, defined as “modern marine,” and an “old saline” groundwater with a residence time of thousands of years) were subjected to metatranscriptome sequencing. Although small subunit (SSU) rRNA gene and mRNA transcripts aligned to all three domains of life, supporting activity within these community subsets, the data also suggested that the groundwaters were dominated by bacteria. Many of the SSU rRNA transcripts grouped within newly described candidate phyla or could not be mapped to known branches on the tree of life, suggesting that a large portion of the active biota in the deep biosphere remains unexplored.
Despite the extremely oligotrophic conditions, mRNA transcripts revealed a diverse range of metabolic strategies that were carried out by multiple taxa in the modern marine water that is fed by organic carbon from the surface. In contrast, the carbon dioxide- and hydrogen-fed old saline water with a residence time of thousands of years predominantly showed the potential to carry out translation. This suggested these cells were active, but waiting until an energy source episodically becomes available.
IMPORTANCE A newly designed sampling apparatus was used to fix RNA under in situ conditions in the deep continental biosphere and benchmarks a strategy for deep biosphere metatranscriptomic sequencing. This apparatus enabled the identification of active community members and the processes they carry out in this extremely oligotrophic environment. This work presents for the first time evidence of eukaryotic, archaeal, and bacterial activity in two deep subsurface crystalline rock groundwaters from the Äspö Hard Rock Laboratory with different depths and geochemical characteristics. The findings highlight differences between organic carbon fed shallow communities and carbon dioxide- and hydrogen-fed old saline waters. In addition, the data reveal a large portion of uncharacterized microorganisms, as well as the important role of candidate phyla in the deep biosphere, but also the disparity in microbial diversity when using standard microbial 16S rRNA gene amplification versus the large unknown portion of the community identified with unbiased metatranscriptomes.
Keywords: metatranscriptomes, mRNA, rRNA, deep biosphere, groundwaters

Publ.-Id: 28913 - Permalink


Investigation of viable taxa in the deep terrestrial biosphere suggests high rates of nutrient recycling
Lopez-Fernandez, M.; Broman, E.; Turner, S.; Wu, X.; Bertilsson, S.; Dopson, M.;
The deep biosphere is the largest ‘bioreactor’ on earth, and microbes inhabiting this biome profoundly influence global nutrient and energy cycles. An important question for deep biosphere microbiology is whether or not specific populations are viable. To address this, we used quantitative PCR and high throughput 16S rRNA gene sequencing of total and viable cells (i.e. with an intact cellular membrane) from three groundwaters with different ages and chemical constituents. There were no statistically significant differences in 16S rRNA gene abundances and microbial diversity between total and viable communities. This suggests that populations were adapted to prevailing oligotrophic conditions and that non-viable cells are rapidly degraded and recycled into new biomass. With higher concentrations of organic carbon, the modern marine and undefined mixed waters hosted a community with a larger range of predicted growth strategies than the ultra-oligotrophic old saline water. These strategies included fermentative and potentially symbiotic lifestyles by candidate phyla that typically have streamlined genomes. In contrast, the old saline waters had more 16S rRNA gene sequences in previously cultured lineages able to oxidize hydrogen and fix carbon dioxide. This matches the paradigm of a hydrogen and carbon dioxide-fed chemolithoautotrophic deep biosphere.
Keywords: 16S rRNA gene; deep subsurface; fracture groundwaters; propidium monoazide; viable cells; candidate phyla radiation

Publ.-Id: 28912 - Permalink


Focused ion beams in biology: How the Helium Ion Microscope and FIB/SEMs help reveal nature’s tiniest structures
Wolff, A.ORC; Klingner, N.ORC; Thompson, W.; Zhou, Y.; Lin, J.; Peng, Y. Y.; Ramshaw, J. A. M.; Xiao, Y.
Focused Ion Beams such as the Helium Ion Microscope (HIM) as well as FIB/SEMs have sparked great interest within the biological sciences in recent years. The HIM allows high resolution imaging of uncoated non-conductive samples while the FIB/SEM (FIB/SEMs combine a focused ion beam with a Scanning Electron Microscope (SEM)) allows to prepare TEM lamellae, 3D reconstruct the sample or reveal sub surface structures with nanometre precision. FIB/SEMs have become the “go to” tool in the materials sciences and semiconductor industry. Despite these unique capabilities, it is not yet fully established in the biological sciences [1-5]. This is predominantly due to the heat-induced damage from the ion beam when processing soft materials including biological samples.

This presentation shows how the HIM as well as FIB/SEMs can be used in biological sciences to reveal nature’s tiniest structures (Figure 1). The presented work then focuses on the underlying ion-solid interactions and the effect of processing parameters on heating induced by ion beams. The work presented here deals with gallium ion solid interactions, however the broader results are applicable to any type of FIB including the helium ion microscope (HIM) and plasma FIBs. The interactions of gallium ions in skin were simulated using Monte Carlo methods. The program SRIM [6] was used to obtain theoretical results which permit estimation of the ion beam induced temperature increases, using the physical principles of Fourier’s law of conductive heat transfer. The model suggests that the ion beam induced increase in temperature can be reduced by:
1. Reducing the local dose rate (smaller aperture/ion beam current)
2. Reducing the local dose (smaller aperture/ion beam current, introducing beam blur, reducing the beam overlap)
The technique was tested on collagen, a soft biological material which is commonly used in biomedical applications. Collagen was chosen as a suitable test sample as it loses its fibrillary structure when denaturated by heat, permitting damage to easily be recognized. Cross-sections and TEM lamellas were prepared from non-embedded collagen with conventional FIB processing parameters (see Figure 2 left) as well as heat reducing FIB parameters (see Figure 1 right).
The results also show that heat damage can be prevented by reducing the local dose rate and area underneath the ion beam. A TEM comparison of a microtome prepared lamella and a FIB prepared lamella (using heat reducing parameters) shows that the fibrillar structures can be maintained, and heat damage avoided. The approach described here can be used to determine suitable parameters for other soft materials.

The authors acknowledge scientific and technical assistance of Peter Hines, Jamie Riches, Rachel Hancock, and Ning Liu and the facilities at the Australian Microscopy & Microanalysis Research Facility (AMMRF) at the Central Analytical Research Facility (CARF), Queensland University of Technology, Brisbane, Australia.

References:

[1] Drobne et al, ‘Surface Damage Induced by FIB Milling and Imaging of Biological Samples is Controllable’; Microscopy Research and Technique 70; 895-903 (2007)
[2] Earl et al, ‘Characterization of dentine structure in three dimensions using FIB-SEM’; Journal of Microscopy 240, Pt 1, 1-5 (2010)
[3] Schneider et al; ‘Serial FIB/SEM imaging for quantitative 3D assessment of the osteocyte lacuna-canalicular network’; Bone 49, 304-311 (2011)
[4] Stokes et al; ‘A New Approach to Study Biological and Soft Materials Using Focused Ion Beam Scanning Electron Microscopy (FIB/SEM)’; Journal of Physics: Conference Series 26; 50-53 (2006)
[5] Bandara et al.; ‘Bactericidal Effects of Natural Nanotopography of Dragonfly Wing on Escherichia coli’ ACS Applied Materials & Interfaces 2017 9 (8), 6746-6760
[6] Ziegler et al, www.srim.org
  • Invited lecture (Conferences)
    Microscience Microscopy Congress 2019, 01.-04.07.2019, Manchester, United Kingdom
  • Lecture (Conference)
    Microscopy & Microanalysis 2019, 04.-08.08.2019, Portland, United States of America
    DOI: 10.1017/S1431927619005051

Publ.-Id: 28911 - Permalink


Formation of heavy clusters in ion-irradiated compounds
Kavetskyy, T.; Liedke, M. O.; Butterling, M.; Wagner, A.; Krause-Rehberg, R.; Sausa, O.; Meshi, L.; Dahan, I.; Vacik, J.; Horak, P.; Fuks, D.; Mykytenko, N.; Kiv, A.;
Ion-irradiated U(Al,Si)3 intermetallide, as an example of compounds with significantly different atomic masses of constituting atoms, was studied by slow positron beam spectroscopy in order to clarify the nature of defects accompanying the process of the ion-induced disordering of this material. The studied compound was irradiated with different Ar+ ion fluences with energy 30 keV. The formation of so-called heavy clusters (Uranium in this case) has been revealed. Such clusters affect the reliability of materials in nuclear reactors. Ion-induced creation of heavy clusters can provide important properties of similar materials.
Keywords: Intermetallic alloys and compounds; ion beam technology; positron annihilation; heavy clusters

Publ.-Id: 28910 - Permalink


Probing dense baryon-rich matter with virtual photons
Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Kühn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K. N.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.;
Quantum chromodynamics (QCD) supports the existence of a novel state of strongly interacting matter with temperatures above kT = 50 MeV and densities several times higher than those in nuclei. Such matter can be created in the laboratory as a transient state by colliding heavy ions at relativistic energies. The thermal electromagnetic radiation emitted from the dense stage of these collisions has been used to probe microscopic properties of the produced medium. The spectral distribution of virtual photons – manifesting themselves as di-electron pairs – shows a nearly exponential shape which indeed points to an emitting source of temperature in excess of 70 MeV/k and to a strong modification of the properties of its constituents. Regarding bulk properties, this medium is similar to the dense matter formed in the final state of a neutron star merger, as apparent from its recent multi-messenger observation.

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  • Secondary publication expected from 29.01.2020

Publ.-Id: 28909 - Permalink


Pressure-tuning the quantum spin Hamiltonian of the triangular lattice antiferromagnet Cs2CuCl4
Zvyagin, S. A.; Graf, D.; Sakurai, T.; Kimura, S.; Nojiri, H.; Wosnitza, J.; Ohta, H.; Ono, T.; Tanaka, H.;
Quantum triangular-lattice antiferromagnets are important prototype systems to investigate phenomena of the geometrical frustration in condensed matter. Apart from highly unusual magnetic properties, they possess a rich phase diagram (ranging from an unfrustrated square lattice to a quantum spin liquid), yet to be confirmed experimentally. One major obstacle in this area of research is the lack of materials with appropriate (ideally tuned) magnetic parameters. Using Cs2CuCl4 as a model system, we demonstrate an alternative approach, where, instead of the chemical composition, the spin Hamiltonian is altered by hydrostatic pressure. The approach combines high pressure electron spin resonance and magnetization measurements, allowing us not only to quasi-continuously tune the exchange parameters, but also to accurately monitor them. Our experiments indicate a substantial increase of the exchange coupling ratio from 0.3 to 0.42 at a pressure of 1.8 GPa, revealing a number of emergent field-induced phases.

Publ.-Id: 28907 - Permalink


Effect of insertion layer on electrode properties in magnetic tunnel junctions with a zero-moment half-metal
Titova, A.; Fowley, C.; Clifford, E.; Lau, Y.-C.; Borisov, K.; Betto, D.; Atcheson, G.; Hübner, R.; Xu, C.; Stamenov, P.; Coey, M.; Rode, K.; Lindner, J.; Fassbender, J.; Deac, A. M.;
Due to its negligible spontaneous magnetization, high spin polarization and giant perpendicular magnetic anisotropy, Mn₂RuₓGa (MRG) is an ideal candidate as an oscillating layer in THz spin-transfer-torque nano-oscillators. Here, the effect of ultrathin Al and Ta diffusion barriers between MRG and MgO in perpendicular magnetic tunnel junctions is investigated and compared to devices with a bare MRG/MgO interface. Both the compensation temperature, Tcomp, of the electrode and the tunneling magnetoresistance (TMR) of the device are highly sensitive to the choice and thickness of the insertion layer used. High-resolution transmission electron microscopy, as well as analysis of the TMR, its bias dependence, and the resistance-area product allow us to compare the devices from a structural and electrical point of view. Al insertion leads to the formation of thicker effective barriers and gives the highest TMR, at the cost of a reduced Tcomp. Ta is the superior diffusion barrier which retains Tcomp, however, it also leads to a much lower TMR on account of the short spin diffusion length which reduces the tunneling spin polarization. The study shows that fine engineering of the Mn₂RuₓGa/barrier interface to improve the TMR amplitude is feasible.
Keywords: Tunneling Magnetoresistance, Half-Metal, Mn-based alloys, MRAM, Spin Polarisation, Heusler alloy, Ferrimagnetic, Perpendicular Magnetic Anisotropy

Publ.-Id: 28906 - Permalink


Equiatomic quinary rare-earth rich amorphous ribbons with excellent magnetocaloric performance
Li, L.; Xu, C.ORC; Yuan, Y.; Zhou, S.
The glass forming ability, microstructure, magnetism and magnetocaloric effect (MCE) in two quinary rare-earth rich amorphous ribbons of Tm20Ho20Gd20Co20Ni20 and Tm20Ho20Gd20Co20Cu20 are reported. Both amorphous ribbons exhibit excellent glass forming ability and a table-like MCE. In addition to large magnetic entropy change of ∼14.0 J/kg-K, an extremely high refrigerant capacity of ∼790 J/kg are achieved which can almost cover the temperature range from liquid hydrogen to liquid nitrogen for the magnetic field change of 0–7 T for both ribbons. Therefore, the quinary rare-earth rich amorphous ribbons can be proposed as a new class of promising magnetic refrigeration materials.

Publ.-Id: 28905 - Permalink


Comparison of the stability of U(VI) and Cm(III) doped calcium (aluminum) silicate hydrate (C-(A)-S-H) phases at saline conditions
Wolter, J.-M.; Schmeide, K.ORC; Huittinen, N.; Bok, F.; Weiss, S.; Brendler, V.; Stumpf, T.
Cementitious materials, used in a nuclear waste repository in the form of concrete or grout to ensure mechanical stability and sealing of disposal tunnels, constitute an important containment barrier for radionuclides in the event of water intrusion into a disposal site. The immobilization potential of hardened cement paste (HCP) as well as of calcium silicate hydrate (C-S-H), as main component of HCP, towards radionuclides such as Cm(III) or U(VI) has been demonstrated in a number of studies, e.g. [1-3]. To evaluate the retention potential of cementitious materials towards radionuclides at saline conditions, U(VI) and Cm(III) doped C-S-H phases were exposed to background electrolytes with salinities comparable to those reported for pore waters of North German clay formations, which are considered as potential host rocks.
U(VI) and Cm(III) doped C-S-H phases with calcium-to-silicon (C/S) ratios ranging from 2.0 to 1.0, representing a portlandite saturated C-S-H system as well as chemically degraded cement paste, were synthesized directly in presence of either U(VI) or Cm(III). These phases were characterized by time-resolved laser-induced luminescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). Batch leaching experiments were performed for U(VI) doped CSH phases applying 2.5 M NaCl, 2.5 M NaCl/0.02 M Na2SO4, 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 and for Cm(III) doped CSH phases applying 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3. The time-dependent release of Ca, Si, U or Cm from CSH phases into brines was followed up to 60 days. Leaching induced changes of the C-S-H structure and of the U(VI) or Cm(III) coordination environment were studied mainly with XRD and TRLFS or IR spectroscopy, respectively.
Generally, the high immobilization potential of C-S-H gel towards U(VI) and Cm(III), reported in the literature, was verified. In the presence of saline solutions, the C-S-H phases showed differences with regard to C-S-H stability and radionuclide release in dependence on the C/S ratio, the composition of the leaching solution and the immobilized radionuclide.
The leaching results for U(VI) doped C-S-H gel indicated that the U(VI) retention is maintained in the presence of NaCl rich solutions (2.5 M NaCl/0.02 M Na2SO4) due to the formation of a uranophane-like phase as detected by TRLFS [4]. The presence of carbonate (0.02 M) in the leaching solution, however, led in case of a C-S-H gel with a low C/S ratio (1.5, representing altered HCP) to some dissolution and thus, to a partial release of U(VI) whereby Ca2UO2(CO3)3(aq) is formed at moderate alkaline pH values. Part of the U(VI) is found to be retained in secondary CaCO3 phases after leaching. The release of U(VI) from C-S-H gel with a high C/S ratio (2.0, representing fresh HCP) due to carbonate was significantly smaller, only enhanced to a small extent due to the additional presence of 2.5 M NaCl.
The binding study of Cm(III) incorporated into C-S-H gel revealed at least two Cm(III) species: (i) Cm(III) substituted against Ca2+ from the C-S-H interlayer and (ii) Cm(III) incorporated in the polyhedral CaO plane of the C-S-H structure (c.f. Fig. 1a), which is in accordance with the literature [5]. The luminescence line narrowing effect observed in the site-selective TRLFS measurements (c.f. Fig. 1b) indicates the presence of numerous, chemically similar sorption sites for Cm(III), which can be attributed to the amorphous to semi-crystalline structure of the C-S-H gel. In addition, C-S-H gel with a C/S ratio of 2.0 showed a co-incorporation of Cm(III) into portlandite. Leaching experiments showed that Cm(III) is not mobilized by solutions with increased salinities [6]. Results obtained by XRD showed that due to contact with carbonate-containing solutions part of the C-S-H gel is converted into calcite and aragonite (C/S 1.0) or calcite and vaterite (C/S 2.0). Site-selective TRLFS showed that Cm(III) was still incorporated in C-S-H gel and portlandite and in addition, partially incorporated in secondary CaCO3 phases.
Currently, the mobilization potential of low molecular weight organic ligands, which can be released due to leaching processes from cementitious materials or might occur as degradation products of polymeric cement additives, towards radionuclides retained by C-S-H gel is studied.
The utilization of Al-bearing additives in modern concrete and the usage of tobermorite as an ion exchanger justify the study of Al-containing C-S-H gel and tobermorite with regard to radionuclide retention. Thus, we investigated the Al and U(VI) incorporation into C-S-H phases and tobermorite at different Al/Si ratios (0.025−0.2) and synthesis temperatures (25°C or 200°C) using Al additives such as Al2O3 and Al(NO3)3. The obtained phases were characterized with solid state 27Al and 29Si NMR spectroscopy, TRLFS, XRD, IR and Raman spectroscopy. Subsequently, the synthesized U(VI) and Al containing samples (tobermorite and C-S-H) were exposed to leaching solutions (2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3) for 30 days to determine the U(VI) and Al release under degradation conditions. First results indicated a preferred synthesis of tobermorite over C-S-H at hydrothermal conditions while Al was found to enter the silica chain, cross-link the sheets of tobermorite and somewhat reduce the U(VI) retention capabilities of tobermorite in the presence of carbonate.
Keywords: uranium(VI); curium(III); C-S-H; portlandite; calcite; site-selective TRLFS; luminescence line narrowing effect; high ionic strength
  • Poster
    Migration 2019 - 17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere, 15.-20.09.2019, Kyoto, Japan

Publ.-Id: 28903 - Permalink


Flow Rate Measurement in Flows with Asymmetric Velocity Profiles by Means of Distributed Thermal Anemometry
Arlit, M.; Schroth, C.; Schleicher, E.; Hampel, U.;
Flow rate in closed conduits is one of the most frequently measured parameters in industrial processes and in gas and water supply. For an accurate measurement, flow meters typically require a fully developed symmetric flow profile with preferably no radial or tangential velocity components.
This is commonly secured by mounting flow meters in a pipe at a sufficiently long distance downstream any change in cross-section or pipe direction. In this paper, we introduce a new approach for flow rate measurement of gases or liquids that employs a novel spatially resolving fluid velocity sensor basing on thermal anemometry. The new principle allows accurate flow rate measurements for non-axisymmetric velocity profiles, even directly after pipe bends, T-junctions or other alterations in the pipe geometry. This is exemplified for air flow in three different pipe bend configurations.
Keywords: Flow rate measurement; installation effects; thermal anemometry grid sensor

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  • Secondary publication expected from 16.05.2020

Publ.-Id: 28902 - Permalink


Reductive immobilization of 99Tc(VII) by different crystalline phases of iron sulfide (FeS2)
Rodriguez, D.; Mayordomo, N.; Brendler, V.; Müller, K.; Schild, D.; Stumpf, T.;
99Tc is a fission product with a long half-life of 2.14 × 105 years. Its migration behaviour and bioavailability strongly depends on its speciation in aqueous solution and on its oxidation state. Under aerobic conditions, Tc mainly exists as pertechnetate, TcO4, which is a highly water-soluble anion that does not significantly sorb on minerals or sediments, i.e. is considered inert and its groundwater migration is favoured. Under reducing conditions, Tc(VII) becomes Tc(IV), whose main species, TcO2, is a solid with a low solubility product and, thus, its mobility decreases.

As the presence of reductants like Fe2+ in the near-field of a nuclear waste repository is expected due to canister corrosion, several studies consider 99Tc reductive immobilization by mineral containing reductant moieties, such as magnetite (FeIIFe2IIIO4) or mackinawite (FeS) [1, 2], confirming the 99Tc(VII) reduction and subsequent 99Tc(IV) retention on the mineral surfaces.

Pyrite (cubic FeS2) is a redox sensitive sulfur mineral that has been identified as a good sorbent for Tc(VII) from soil and groundwater in both the absence [3] and presence [4] of humic substances. Under repository conditions, iron sulfide will be formed as both pyrite and marcasite (orthorhombic FeS2) as a result of corrosion processes and microbial action [5]. Moreover, iron sulfides are also accessory minerals in granitic and argillaceous rocks. Therefore, reliable data on 99Tc(VII) retention by both minerals and their mixtures is relevant for the safe disposal of nuclear waste.

We have studied the reductive immobilization of 99Tc(VII) by a synthetic mixture 60:40 marcasite – pyrite, finding that it removes almost 100% of 99Tc(VII) from solution within 7 days at pH = 6.5. This ability decreases linearly with increasing Tc concentration due to the saturation of the mineral, while an increase in the ionic strength has no significant effects. The isotherm plot has a slope of 0.5 suggesting a single reaction mechanism: sorption on one site, which would mean that the affinity of the mineral for the technetium is low [6], or precipitation of 99Tc(IV) most probably as TcO2 [7]. Figure 1 shows the SEM images of the mixture marcasite-pyrite before and after being in contact with 99Tc(VII) for 7 days at pH 6.5.

In comparison to the plain mineral, the micrographs of Tc reacted FeS2 at 2.00 μm clearly show erosion on the surface. Furthermore, the micrograph at 1.00 μm suggests deeper effects, not only the first layers of the mineral, as the morphology has obviously changed. The high surface dynamics may be induced by the incorporation of the radionuclei into the mineral. However, the flat surface of the FeS2 after the 99Tc(VII) uptake reminds to a coating that could be made of technetium polysulphides.

Although it is clear that this Tc retention is due to the reduction from 99Tc(VII) to 99Tc(IV), it has not been possible to determine so far if the 99Tc(IV) is sorbed on the mineral surface, incorporated in its structure or precipitated. As the FeS2 crystal phase as well as Tc oxidation state affect those retention mechanisms, we have also studied the immobilization of 99Tc(VII) by both pure pyrite and pure marcasite with the aim of analysing the crystal rearrangement effect and performing X-ray absorption spectroscopy for structural characterization.

This work has been developed in the frame of VESPA II project (02E11607B), supported by the German Federal Ministry of Economic Affairs and Energy (BMWi).



1 T. Kobayashi, A. C. Scheinost, D. Fellhauer, X. Gaona, M. Altmaier, Radiochim. Acta 101, 323 (2013).
2 F. R. Livens, M. J. Jones, A. J. Hynes, J. M. Charnock, J. F. W. Mosselmans, C. Hennig, H. Steele, D. Collison, D. J. Vaughan, R. A. D. Pattrick, W. A. Reed, L. N. Moyes, J. Environ. Radioact. 74, 211 (2004).
3 L. Huo, W. Xie, T. Qian, X. Guan, D. Zhao, Chemosphere 174, 456 (2017).
4 C. Bruggeman, A. Maes, J. Vancluysen, Phys. Chem. Earth 32, 573 (2007).
5 W. M. B. Roberts, A. L. Walker, A. S. Buchanan, Miner. Depos. 4, 18 (1969).
6 G. Limousin, J.-P. Gaudet, L. Charlet, S. Szenknect, V. Barthès, M. Krimissa, Appl. Geochemistry 22, 249 (2007).
7 R. Guillaumont, T. Fanghänel, V. Neck, J. Fuger, D. A. Palmer, I. Grenthe, M. A. Rand, UPDATE ON THE CHEMICAL THERMODYNAMICS OF URANIUM, NEPTUNIUM, PLUTONIUM,AMERICIUM AND TECHNETIUM, Elsevier, 2003.
Keywords: Technetium, retention, pyrite, marcasite
  • Poster
    17th international conference on the chemistry and migration behavior of actinides and fission products in the geosphere, 15.-21.09.2019, Kyoto, Japan

Publ.-Id: 28901 - Permalink


Spectroscopic characterization of curium(III) protein interactions
Moll, H.; Raff, J.; Stumpf, T.;
Proteins are important biomolecules in all living cells. They perform a large array of functions within organisms. To understand the speciation of actinides in living organisms, their interactions with proteins need to be explored on a molecular level.
Bacterial surface layers (S-layers) are common surface structures in many bacteria and archaea consisting of so-called surface-layer proteins (S-layer proteins) [1]. So far, we could show that S-layers proteins of Lysinibacillus sphaericus JG-A12 selectively bind several metals including U, Pd, Au, and Eu, partly with a high affinity [2]. In the present work we studied the interaction of Cm(III) with bacterial S-layer proteins of L. sphaericus JG-A12.
The formation of aqueous Cm(III) S-layer protein complexes was studied at room temperature by time-resolved laser-induced fluorescence spectroscopy (TRLFS) in 0.1 M NaCl solutions. The experiments were performed at a fixed total concentration for Cm(III) 0.88 µM and the S-layer protein of 5 g/L (39.6 µM) by varying the pH (2.0-9.0) and the type of S-layer. Based on their individual luminescence spectra and lifetimes, a specific and unspecific Cm(III) binding could be distinguished. The formation of the specific Cm3+-S-layer complex A and unspecific Cm3+-S-layer complex B depend on pH and the Ca2+ amount in the S-layer types. The influence of Ca2+ on the Cm3+ S-layer complexation was investigated by Ca2+ titration experiments. The specific Cm3+-S-layer complex A is characterized by a narrow emission band at 602.5 nm combined with a long lifetime of 310 µs. The spectroscopic EDTA titration of Cm3+-S-layer complex A showed an exchange of S-layer ligands by EDTA in the first coordination sphere of Cm(III) at EDTA concentrations of 40 µM and higher. This corresponds to a EDTA:S-layer protein ratio of 1:1.

References:

[1] M. Sára, U.B. Sleytr, J. Bacteriol. 2000, 182,859. [2] M.L. Merroun et al., Appl. Environ. Microbiol. 2005, 71,5532.
Keywords: curium; S-layer proteins; Lysinibacillus sphaericus; luminescence spectroscopy, speciation
  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie der GDCh 2019, 25.-27.09.2019, Dresden, Deutschland

Publ.-Id: 28900 - Permalink


Annual Report 2018 - Institute of Resource Ecology
Stumpf, T.; Foerstendorf, H.ORC; Bok, F.; Richter, A.
Annual Report 2018 of the scientific activities of the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden-Rossendorf
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-096 2019
    ISSN: 2191-8708

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Publ.-Id: 28898 - Permalink


Impact of temperature on the complexation of Eu(III) and Cm(III) with aqueous phosphates
Jordan, N.; Huittinen, N.; Jessat, I.; Réal, F.; Vallet, V.; Starke, S.; Demnitz, M.; Lösch, H.; Brendler, V.;
The incorporation of actinides in solid lanthanide phosphates crystallizing in the monazite structure has been intensely investigated in the past decades due to the relevance of these monazites as potential ceramic phases for the immobilization of specific high level radioactive waste (HLW) streams [1-3]. In recent years, understanding the incorporation behaviour of trivalent dopants in the LnPO4×nH2O rhabdophane structure, which is the hydrated phosphate precursor in the synthesis of monazites through precipitation routes and a potential secondary mineral controlling actinide solubility in dissolution and re-precipitation reactions of monazite host-phases, has been given more attention [4,5]. Despite the large interest in lanthanide phosphates and the interaction of actinides with these solids, very little data is available on the complexation of lanthanides and actinides with aqueous phosphates, even though these complexation reactions precede any aqueous synthesis of monazite ceramics and are expected to occur in natural waters as well as in the proximity of monazite-containing HLW repositories. It also suffers from an almost systematic absence of independent spectroscopic validation of the stoichiometry of the proposed complexes. Both from the perspective of aqueous rhabdophane synthesis, which is often carried out at elevated temperatures, and heat-generating HLW immobilization in monazites, the lanthanide and actinide complexation reactions with aqueous phosphates under ambient conditions should be complemented with data obtained at higher temperatures.

In the present work, laser-induced luminescence spectroscopy (LIL) was used to study the complexation of Eu(III) (5×10 6 M) and Cm(III) (5×10 7 or 1×10 8 M) as a function of total phosphate concentration (0-0.3 M ΣPO4) in the temperature regime 25-90°C, using NaClO4 as a background electrolyte (I = 0.5 to 3.1 M). These studies have, in a first step, been conducted in the acidic pH-range (pH = 1) to avoid precipitation of solid Eu or Cm rhabdophane. Both trivalent metal cations form a complex with the anionic H2PO4 species, i.e. EuH2PO42+ and CmH2PO42+. The conditional complexation constants were found to increase upon rising ionic strength and temperature. Extrapolation of the obtained complexation constants to infinite dilution at 25 °C was performed by applying the Specific Ion Interaction Theory (SIT) [6]. The obtained log β° values for EuH2PO42+ and CmH2PO42 were 0.89 ± 0.13 and 0.45 ± 0.19, respectively, for reaction 1 below:

Me3+ + H3PO4 ⇌ MeH2PO42+ + H+ (Me = Eu or Cm) (1)

The ion-ion interaction coefficients ε(EuH2PO42+;ClO4 ) = 0.20 ± 0.08 and ε(CmH2PO42+;ClO4 ) = 0.16 ± 0.12 were derived at 25 °C. Temperature-dependent conditional complexation constants for the identified species were obtained from the recorded luminescence emission spectra. They were subsequently extrapolated to I =0 M, assuming that the ion-ion interaction parameters obtained at 25 °C are not significantly impacted by the temperature increase from 25 °C to 90 °C [6]. Using the extended van´t Hoff equation, the molal enthalpy ΔRHm° and entropy of reaction ΔRSm° values were both found to be positive.
Exactly the same combination of batch, spectroscopic, and thermodynamic studies was used at lower H+ concentrations ( log[H+] = 2.52, 3.44, and 3.65). Our results clearly showed the presence of Eu(H2PO4)2+ and Cm(H2PO4)2+ species, so far never reported in the literature. In addition Eu(HPO4)+ and Cm(HPO4)+ species were identified. Conditional complexation constants for these species will be derived and extrapolated to infinite dilution using the SIT approach.
Finally, relativistic quantum chemical investigations will be performed to shed light on the observed differences in the complexation strength of Eu(III) and Cm(III) with aqueous phosphates. They will also provide insight on the role of spin-orbit coupling and serve to probe the character of the metal water and metal phosphate bonds.
Keywords: Lanthanide; Actinide; Complexation; Luminescence spectroscopy; SIT
  • Contribution to proceedings
    Migration 2019 - 17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere, 15.-20.09.2019, Kyoto, Japan
    Proceedings of Migration 2019

Publ.-Id: 28897 - Permalink


Solvent extraction and separation of rare earth elements by diamide type ligands and the complex structure of extracted species
Shimojo, K.; Sasanuki, T.; Schöne, S.ORC; Sugita, T.; Okamura, H.; Ikeda-Ohno, A.ORC
Solvent extraction of rare earth elements using a new type of diamide ligand, DODGAA, was performed to investigate the extractability and separability of the ligand for the separation of rare earth elements. Single crystals of the DODGAA complexes with some rare earth metals were also synthesised and structurally determined by single-crystal X-ray diffraction (SC-XRD) to understand the molecular structure of extracted species.
Keywords: Rare earth elements, separation, solvent extraction, structure determination, single-crystal X-ray diffraction
  • Lecture (Conference)
    The 84th Annual Meeting of the Society of Chemical Engineering, Japan, 13.-15.03.2019, Shibaura Institute of Technology, Toyosu, Tokyo, Japan

Publ.-Id: 28896 - Permalink


Coordination chemistry of f-block metal ions with ligands bearing bio-relevant functional groups
Götzke, L.; Schaper, G.; März, J.ORC; Kaden, P.ORC; Huittinen, N.ORC; Stumpf, T.; Kammerlander, K. K. K.; Brunner, E.; Hahn, P.; Mehnert, A.; Kersting, B.; Henle, T.; Lindoy, L. F.; Zanoni, G.; Weigand, J. J.
Over recent decades there has been a great deal of interest and associated research into aspects of the f-block (lanthanide and actinide) metal chemistry of naturally-occurring ligands, such as proteins, peptides, porphyrins and related tetraaza derivatives as well as synthetically modified natural ligands and solely synthetic ligand systems incorporating bio-relevant functional groups. In this review, we present a wide-ranging overview of published work spanning the above areas, with emphasis on selected biological, medical and environmental aspects. Systems capable of discriminating between metal ions from within, or between, the lanthanide and actinide groups are also discussed including the design and synthesis of biomimetic radionuclide chelators and radionuclide decorporation agents as well as solid adsorbent materials for the uptake of radionuclides from the environment and elsewhere. Thus, the interaction of the f-group elements with a range of biopolymers, including systems based on cellulose, chitin, chitosan, humic substances as well as a range of synthetic model systems is also presented. Other applications include the synthesis of new luminescent materials, including luminescent probes and luminescent metal coordination polymers exhibiting unusual photophysical properties as well as systems showing potential for use in the development of new MRI imaging agents.
Keywords: Lanthanides Actinides Maillard products Siderophores Calix[4]arenes Porphyrins Cellulose Chitin Chitosan Humic substances Peptides Proteins

Publ.-Id: 28895 - Permalink


Facile preparation of radium-doped, functionalized nanoparticles as carriers for targeted alpha therapy
Reissig, F.; Hübner, R.; Steinbach, J.; Pietzsch, H.-J.; Mamat, C.;
Although significant advances in the tailoring of BaSO4-based nanoparticles have been achieved, the synthesis of particles is strongly dependent on the use of templates, surfactants, and additives, especially when radiolabeled with 133Ba or 224Ra. Herein, direct facile preparation of radiolabeled alendronate-functionalized BaSO4 nanoparticles in an aqueous medium in a one-pot reaction is developed. Remarkably, the size of the formed BaSO4 nanoparticles can be controlled by the type of the organic solvent used. Upon the addition of alendronate, amine functionalities were introduced into the nanoparticles. Additionally, a fluorescence dye-containing alendronate was used to evidence the introduction of the alendronate during the formation of the nanoparticles. The variations in the functionalities were investigated by IR and the morphology of the resulting BASO4 nanoparticles are investigated in detail by transmission electron microscopy. DLS and TEM measurements provided an average diameter of the nanoparticles of approx. 140 nm. Radium-doped alendronate nanoparticles were successfully obtained in a one-pot labeling procedure from [224Ra]RaCl2, Na2SO4 Ba(NO3)2 and alendronate.
Keywords: Radium-223, nanoparticles, Barium sulfate, talpha-theraphy

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  • Secondary publication expected from 01.06.2020

Publ.-Id: 28892 - Permalink


Vacancy cluster in ZnO films grown by pulsed laser deposition
Wang, Z.; Luo, C.; Anwand, W.; Wagner, A.; Butterling, M.; Azizar Rahman, M.; Phillips, M. R.; Ton-That, C.; Younas, M.; Su, S.; Ling, F. C. C.;
Undoped and Ga-doped ZnO films were grown on c-sapphire using pulsed laser deposition (PLD) at the substrate temperature of 600 oC. Positron annihilation spectroscopy study (PAS) shows that the dominant VZn-related defect in the as-grown undoped ZnO grown with relative low oxygen pressure P(O2) is a vacancy cluster (most likely a VZn-nVO complex with n=2, 3) rather than the isolated VZn which has a lower formation energy. Annealing these samples at 900oC induces out-diffusion of Zn from the ZnO film into the sapphire creating the VZn, which favors the formation
of vacancy cluster containing relatively more VZn. Increasing the P(O2) during growth also lead to the formation of the vacancy cluster with relatively more VZn. For Ga-doped ZnO films, the oxygen pressure during growth has significant influence on the electron concentration and the microstructure of the VZn-related defect. Green luminescence (GL) and yellow luminescence (YL) were identified in the cathodoluminescence study (CL) study, and both emission bands were quenched after hydrogen plasma treatment.
Keywords: Vacancy cluster ZnO pulsed laser deposition positron annihilation spectroscopy photo luminescence

Publ.-Id: 28891 - Permalink


Two-Dimensional Kagome Lattices Made of Hetero Triangulenes Are Dirac Semimetals or Single-Band Semiconductors
Jing, Y.; Heine, T.ORC
Here we discuss, based on first-principles calculations, two-dimensional (2D) kagome lattices composed of polymerized heterotriangulene units, planar molecules with D3h point group containing a B, C, or N center atom and CH2, O, or CO bridges. We explore the design principles for a functional lattice made of 2D polymers, which involves control of π-conjugation and electronic structure of the knots. The former is achieved by the chemical potential of the bridge groups, while the latter is controlled by the heteroatom. The resulting 2D kagome polymers have a characteristic electronic structure with a Dirac band sandwiched by two flat bands and are either Dirac semimetals (C center), or single-band semiconductors—materials with either exclusively electrons (B center) or holes (N center) as charge carriers of very high mobility, reaching values of up to ∼8 × 103 cm2 V–1 s–1, which is comparable to crystalline silicon.
Keywords: DFT, kagome, 2D polymers, 2D COFs

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  • Secondary publication expected from 30.11.2020

Publ.-Id: 28890 - Permalink


Assessing robustness of radiomic features by image perturbation
Zwanenburg, A.; Leger, S.; Agolli, L.; Pilz, K.; Troost, E.; Richter, C.; Löck, S.;
Image features need to be robust against differences in positioning, acquisition and segmentation to ensure reproducibility. Radiomic models that only include robust features can be used to analyse new images, whereas models with non-robust features may fail to predict the outcome of interest accurately. Test-retest imaging is recommended to assess robustness, but may not be available for the phenotype of interest. We therefore investigated 18 combinations of image perturbations to determine feature robustness, based on noise addition (N), translation (T), rotation (R), volume growth/shrinkage (V) and supervoxel-based contour randomisation (C). Test-retest and perturbation robustness were compared for combined total of 4032 morphological, statistical and texture features that were computed from the gross tumour volume in two cohorts with computed tomography imaging: I) 31 non-small-cell lung cancer (NSCLC) patients; II): 19 head-and-neck squamous cell carcinoma (HNSCC) patients. Robustness was determined using the 95% confidence interval (CI) of the intraclass correlation coefficient (1, 1). Features with CI >= 0:90 were considered robust. The NTCV, TCV, RNCV and RCV perturbation chain produced similar results and identified the fewest false positive robust features (NSCLC: 0.2-0.9%; HNSCC: 1.7-1.9%). Thus, these perturbation chains may be used as an alternative to test-retest imaging to assess feature robustness.

Publ.-Id: 28889 - Permalink


Testing halophilic bacteria for their potential as pyrite biodepressants in Cu-Mo bioflotation
Luque Consuegra, G.;
Presentation outlining work up to June 2018 in the screening of halophilic bacteria as pyrite biodepressants in Cu-Mo bioflotation processes delivered in the BHT conference in TUBAF, Freiberg.
Keywords: Bioflotation, Pyrite, Halophilic bacteria, Adhesion, M.A.T.H
  • Lecture (Conference)
    BHT – Freiberger Universitätsforum, 08.06.2018, Freiberg, Deutschland

Publ.-Id: 28884 - Permalink


Time-Like Baryon Transitions studies with HADES
Ramstein, B.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepał, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gillitzer, A.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Himmelreich, M.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kämpfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Karavicheva, T.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyll, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kuboś, J.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Liu, M.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Müntz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Włoch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.; Zuschke, M.;
The HADES collaboration uses the e+e− production as a probe of the resonance matter produced in collisions at incident energies of 1-3.5 GeV/nucleon at GSI. Elementary reactions provide useful references for these studies and give information on resonance Dalitz decays (R→Ne+e−). Such processes are sensitive to the structure of time-like electromagnetic baryon transitions in a kinematic range where (off-shell) vector mesons play a crucial role. Results obtained in proton-proton reactions and in a commissioning pion-beam experiment are reported and prospects for future pion beam experiments and for first hyperon Dalitz decay measurements are described. The connection with the investigations of medium effects to be continued with HADES in the next years at SIS18 and SIS100 is also discussed.

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Publ.-Id: 28881 - Permalink


Natural occurring spore-forming sulfate reducers and their influence on the bentonite barrier
Matschiavelli, N.; Kluge, S.; Podlech, C.; Standhaft, D.; Grathoff, G.; Ikeda-Ohno, A.; Warr, L. N.; Chukharkina, A.; Arnold, T.; Cherkouk, A.;
To investigate the potential influence of natural occuring microorganisms within the bentonite on its minaralogical properties, we prepared anaerobic microcosm-experiments containing bentonite and a synthetic Opalinus Clay pore-water solution. Two different Bavarian bentonites (a natural and an industrial one) were incubated for one year at 30 °C and 60 °C and analyzed for bio-geochemical parameters and microbial diversity. For stimulation of microbial activity, some set ups were supplied with organics (acetate or lactate) or H2.
Only microcosms containing the industrial bentonite show striking effects. The presence of supplemented lactate or H2 led to the dominance (up to 81 %) of spore-forming Desulfosporosinus spp. – strictly anaerobic, sulfate-redung microorganisms. The respective microcosms show an increase of ferrous iron and a simoultaneous decrease of ferric iron as well as a decrease in sulfate-concentration. Concomitantly, the redoxpotential dropped and hydrogen-sulfide was fomed – leading very likely to the formation of the observed fractures and iron-sulfur precipitations. Furthermore, lactate-containing microcosms show the formation of acetate in the same amount as lactate was consumed. The here mentioned, microbial formed metabolites could affect the dissolution bahavior of minerals and ions within the bentonite and, thus, potentially change the sealant and adsorbent properties of the bentonite barrier.
  • Lecture (others)
    MIND Project Annual Meeting 2019, 07.-09.05.2019, Stockholm, Sweden

Publ.-Id: 28880 - Permalink


Characterization of Continuous Wave Laser-Induced Thermal Gradients in Magnetic Tunnel Junctions Integrated Into Microresonators via COMSOL Simulations
Cansever, H.; Lindner, J.; Huebner, T.; Niesen, A.; Reiss, G.; Faßbender, J.ORC; Deac, A. M.
Spin caloritronics investigates static and dynamic effects on magnetic structures due to spin-currents generated by thermalgradients. Here, we present COMSOL simulation results using a 2-D heat transfer module applied to Co2FeAl/MgO/CoFeB magnetictunnel junctions (MTJs) integrated into microcavity resonators. Microresonators are used in order to study the effects of temperaturegradients on single micro-/nano-objects. We find that the thermal conductivity of the insulating barrier (MgO) plays a crucialrole, influencing the overall temperature, as well as the thermal gradient over the barrier. Taking into account the microresonatorstructure around the MTJ, which is mainly made from copper, strongly affects the uniform heating of the overall stack. Nevertheless,the gradient over the barrier is relatively unaffected by the surrounding conditions. The simulation results provide insight intothe temperature profile of the whole structure and show how modifying the structure of the surrounding materials may tune andoptimize the thermal gradient magnitude and ultimately provide a path for quantifying spin-transfer torques induced by thermalgradients.
Keywords: COMSOL simulation, ferromagnetic resonance (FMR), magnetic tunnel junction (MTJ), microresonator

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  • Secondary publication expected from 05.02.2020

Publ.-Id: 28879 - Permalink


Fast-neutron-induced fission cross section of Pu(242) measured at the neutron time-of-flight facility nELBE
Kögler, T.ORC; Junghans, A. R.ORC; Beyer, R.ORC; Dietz, M.; Düllmann, C. E.ORC; Eberhardt, K.; Lorenz, C.; Müller, S. E.ORC; Nolte, R.; Reinhardt, T. P.; Schmidt, K.; Runke, J.; Schwengner, R.ORC; Takacs, M.; Vascon, A.; Wagner, A.ORC
The fast-neutron-induced fission cross section of ²⁴²Pu was measured at the neutron time-of-flight facility nELBE. A parallel-plate fission ionization chamber with novel, homogeneous, large-area ²⁴²Pu deposits on Si-wafer backings was used to determine this quantity relative to the IAEA neutron cross-section standard ²³²U(n, f ) in the energy range of 0.5 to 10 MeV. The number of target nuclei was determined from the measured spontaneous fission rate of ²⁴²Pu. This helps to reduce the influence of the fission fragment detection efficiency on the cross section. Neutron transport simulations performed with GEANT 4, MCNP 6, and FLUKA 2011 are used to correct the cross-section data for neutron scattering. In the reported energy range the systematic uncertainty is below 2.7% and on average the statistical uncertainty is 4.9%. The determined results show an agreement within 0.67(16)% to recently published data and a good accordance to current evaluated data sets.
Keywords: neutron-induced fission, plutonium, parallel plate fission ionization chambers, cross section measurements, neutron transport simulations, nuclear reactions, nucleon induced nuclear reactions, nELBE
Related publications
Fast-neutron-induced fission cross section of Pu(242) … (Id 28970) HZDR-primary research data are used by this publication

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Publ.-Id: 28878 - Permalink


Impact of radiation, systemic therapy and Treatment sequencing on survival of patients with melanoma brain metastases
Rauschenberga, R.; Bruns, J.; Brüttinga, J.; Daubner, D.; Lohaus, F.; Zimmer, L.; Forschner, A.; Zips, D.; Hassel, J. C.; Berking, C.; Kaehler, K. C.; Utikal, J.; Gutzmer, R.; Terheyden, P.; Meiss, F.; Rafei-Shamsabadi, D.; Kiecker, F.; Debus, D.; Dabrowski, E.; Arnold, A.; Garzarolli, M.; Kuske, M.; Beissert, S.; Löck, S.; Linn, J.; Troost, E. G. C.; Meier, F.;
Background
Combining stereotactic radiosurgery (SRS) and active systemic therapies (STs) achieved favourable survival outcomes in patients with melanoma brain metastases (MBMs) in retrospective analyses. However, several aspects of this Treatment strategy remain poorly understood. We Report on the Overall survival (OS) of patients with MBM treated with a combination of radiotherapy (RT) and ST as well as the Impact of the v-Raf murine sarcoma viral oncogene homolog B (BRAF)-V600 Mutation (BRAFmut) status, types of RT and ST and their sequence. Patients and methods Data of 208 patients treated with SRS or whole brain Radiation therapy (WBRT) and either immunotherapy (IT) or targeted therapy (TT) within a 6-week- interval to RT were analysed retrospectively. OS was calculated from RT to death or last follow-up. Univariate- and multivariate Cox proportional hazard analyses were performed to determine prognostic Features associated with OS.
Results
The median follow-up was 7.3 months. 139 patients received IT, 67 received TT and 2 received IT and TT within 6 weeks to RT (WBRT 45%; SRS 55%). One-year Kaplan-Meier OS rates were 69%, 65%, 33% and 18% (P < .001) for SRS with IT, SRS with TT, WBRT with IT and WBRT with TT, respectively. Patients with a BRAF mut receiving IT combined with RT experienced higher OS rates (88%, 65%, 50% and 18%). TT following RT or started before and continued thereafter was associated with improved median OS compared with to TT solely before RT (12.2 [95% confidence interval {CI} 9.3–15.1]; 9.8 [95% CI 6.9–12.6] versus 5.1 [95% CI 2.7–7.5]; P = .03).
Conclusion
SRS and IT achieved the highest OS rates. A BRAFmut appears to be a favourable prognostic factor for OS. For the combination of RT and TT, the sequence appears to be crucial. Combinations of WBRT and ST achieved unprecedentedly high OS rates and Warrant further studies.
Keywords: Melanoma; Brain metastases; Stereotactic radiosurgery; Whole brain Radiation therapy; Immunotherapies; Targeted therapy; Immune checkpoint inhibitors; BRAF inhibitors

Publ.-Id: 28875 - Permalink


Carboranyl Analogues of Celecoxib with Potent Cytostatic Activity against Human Melanoma and Colon Cancer Cell Lines
Buzharevski, A.; Paskas, S.; Sárosi, M. B.; Laube, M.; Lönnecke, P.; Neumann, W.; Mijatovic, S.; Maksimovic-Ivanic, D.; Pietzsch, J.ORC; Hey-Hawkins, E.
Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most common way of treating inflammatory disorders. Their widespread use helped reveal their other modes of action as pharmaceuticals, such as a profound effect on various cancers. Celecoxib has proven to be a very prominent member of this group with cytostatic activities. On the other hand, the highly dynamic field of drug design is constantly searching for new ways of modifying known structures to obtain more powerful and less harmful drugs. A very interesting development is the implementation of carboranes in pharmacologically active structures, mostly as phenyl mimetics. Herein we report the synthesis of three carborane-containing derivatives of the COX-2-selective NSAID celecoxib. The new compounds proved to have promising cytostatic potential against various melanoma and colorectal adenocarcinoma cell lines. Inhibited proliferation accompanied by caspase-independent apoptotic cell death was found to be the main cause of decreased cell viability upon treatment with the most efficient celecoxib analogue, 3 b (4-[5-(1,7-dicarba-closo-dodecaboranyl)-3-trifluoromethyl-1H-pyrazol-1-yl]-1-methylsulfonylbenzene).
Keywords: cancer; carboranes; celecoxib; cytotoxicity; drug discovery

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Publ.-Id: 28874 - Permalink


Simulation of the Radiation Field at the University Proton Therapy Dresden (UPTD)
Lutz, B.; Swanson, R.; Fiedler, F.; Enghardt, W.;
Radiation therapy is one of the most used treatment modalities of cancer. While most patients receive photon-therapy, a growing number of patients are treated with particles, mainly protons. Protons offers a more localised dose deposition compared to photon-therapy. This allows to reduce the dose that is applied by the primary beam to the healthy tissue outside the target volume. At the same time, the use of protons leads to a change in the composition of the radiation field, when compared to photons. For example, the out-of-field dose is dominated by secondary neutrons. Additionally, the radiation quality of protons is a function of energy. Therefore, the biological effect depends not only on the physical dose, but also on the linear energy transfer (LET). The neutron field and the LET, like other scientifically interesting quantities, are challenging to measure experimentally. Hence, a simulation that can reproduce the radiation field of a radiation treatment facility is of great value for the study of various aspects of proton therapy.
This work describes the simulation of the University Proton Therapy Dresden (UPTD) beam delivery system and treatment room.
Keywords: simulation, proton therapy, Geant4, TOPAS, double scattering
  • Lecture (Conference)
    EURADOS Annual Meeting 2019, 11.-14.02.2019, Lodz, Poland

Publ.-Id: 28873 - Permalink


Fluorine-18 labeling of S100 proteins for small animal positron emission tomography
Laube, M.; Kniess, T.; Neuber, C.; Haase-Kohn, C.; Pietzsch, J.ORC
The interaction of S100 proteins (S100s), a multigenic family of Ca2+-binding and Ca2+-modulated proteins, with pattern recognition receptors, e.g., Toll-like receptors (TLRs), the receptor for advanced glycation end products (RAGE), or scavenger receptors (SR), is hypothesized to be of high relevance in the pathogenesis of various diseases. This includes chronic inflammatory conditions, atherosclerosis, cardiomyopathies, neurodegeneration, and progression of cancers. However, data concerning the role of circulating S100s in these pathologies are scarce. One reason for this is the shortage of suitable radiolabeling methods for direct assessment of the metabolic fate of circulating S100s in vivo. We report a radiotracer approach using radiolabeling of recombinant human S100s with the positron emitter fluorine-18 (18F) by conjugation with N-succinimidyl 4-[18F]fluorobenzoate ([18F]SFB). The methodological radiochemical part focuses on an optimized and automated synthesis of [18F]SFB comprising HPLC purification to achieve higher chemical purity. The respective radioligands, [18F]fluorobenzoylated S100s ([18F]FB-S100s), were obtained with appropriate radiochemical purities, yields, and effective molar activities. Biological applications comprise cell and tissue binding experiments in vitro, biodistribution and metabolite studies in rodents in vivo/ex vivo, and dynamic positron emission tomography studies using dedicated small animal PET systems. Radiolabeling of S100s with 18F and, particularly, the use of small animal PET provide novel probes to delineate both their metabolic fate and the functional expression of their specific receptors under normal and pathophysiological conditions in rodent models of disease.
Keywords: Bolton-Hunter-type reagent; in vivo imaging; radiopharmacological characterization; 18F building block; module-assisted radiosynthesis; S100 proteins; calcium; EF-hand

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  • Secondary publication expected from 02.02.2020

Publ.-Id: 28872 - Permalink


Modeling discontinuous potential distributions using the finite volume method, and application to liquid metal batteries
Weber, N.; Landgraf, S.; Mushtaq, K.; Nimtz, M.; Personnettaz, P.; Weier, T.; Zhao, J.; Sadoway, D.;
The electrical potential in a battery jumps at each electrode-electrolyte interface. We present a model for computing three-dimensional current and potential distributions, which accounts for such internal voltage jumps. Within the framework of the finite volume method we discretize the Laplace and gradient operators such that they account for internal jump boundary conditions. After implementing a simple battery model in OpenFOAM we validate it using an analytical test case, and show its capabilities by simulating the current distribution and discharge curve of a Li||Bi liquid metal battery.

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  • Secondary publication expected from 21.06.2020

Publ.-Id: 28871 - Permalink


The Inverse Trans Effect in Uranium complexes containing N-heterocyclic Carbenes
Köhler, L.; März, J.; Patzschke, M.; Kloditz, R.; Stumpf, T.;
Aim of this work was to investigate the inverse trans influence (ITI) in uranium complexes containing soft-donor ligands. Uranium(IV) and (V) complexes were synthesized by using the N-heterocylic carbene ligand iPrIm (L¹ ) and lithium bis(trimethylsilyl)amide (TMSA) as a base. The structural characterization by SC-XRD and geometry optimization of the resulting compounds [U(IV)(L¹ )₂(TMSA)Cl₃] (1) and (HL¹ )₂ [U(V)(TMSI)Cl₅] (2) (TMSI = trimethylsilylimide) confirmed the occurrence of an inverse trans influence (ITI) by means of the silylamido- or silylimido ligand.
Keywords: inverse trans influence, ITI, uranium complex, actinides
  • Lecture (others)
    Bilaterales Treffen mit AK Roesky (KIT), 10.-11.01.2019, Karlsruhe, Deutschland

Publ.-Id: 28869 - Permalink


Reversible adiabatic temperature change in the shape memory Heusler alloy NiMn0.8Ga: An effect of structural compatibility
Devi, P.; Ghorbani Zavareh, M.; Salazar Mejia, C.; Hofmann, K.; Albert, B.; Felser, C.; Nicklas, M.; Singh, S.;
The large magnetocaloric effect (MCE) observed in Ni-Mn based shape memory Heusler alloys put them forward to use in magnetic refrigeration technology. It is associated with a first-order magnetostructural (martensitic) phase transition.We conducted a comprehensive study of the MCE for the off-stoichiometric Heusler alloy Ni2.2Mn0.8Ga in the vicinity of its first-order magnetostructural phase transition. We found a reversible MCE under repeated magnetic field cycles. The reversible behavior can be attributed to the small thermal hysteresis of the martensitic phase transition. Based on the analysis of our detailed temperature dependent x-ray diffraction data, we demonstrate the geometric compatibility of the cubic austenite and tetragonal martensite phases. This finding directly relates the reversible MCE behavior to an improved geometric compatibility condition between cubic austenite and tetragonal martensite phases. The approach will help to design shape memory Heusler alloys with a large reversible MCE taking advantage of the first-order martensitic phase transition.

Publ.-Id: 28868 - Permalink


Effect of background electrolyte composition on the formation of Th(IV) nanoparticles on the muscovite (001) basal plane
Schmidt, M.ORC; Qiu, C.; Hellebrandt, S.; Eng, P. J.; Skanthakumar, S.; Steppert, M.; Soderholm, L.
Reliable long-term predictions regarding the safety of a nuclear waste disposal facility must be based on a sound understanding of the fundamental processes controlling radionuclide mobility in a subsurface environment. In particular, reactions at the water/mineral interface must be characterized on the molecular level.[1] Several actinides (An) show a tendency to form An-oxo-nanoparticles[2], which may be enhanced in the presence of mineral surfaces and even drive redox reactions.[3-6] As these reaction may, both, enhance and reduce the mobility of the actinides, it is of utmost importance to understand their mechanism and which parameters control the nanoparticle formation in environmental systems.
Recently, we have reported an unusual variability in the reactivity of ThIV on the basal plane of muscovite mica dependent on the composition of the background electrolyte.[7] In this study, based on surface X-ray diffraction [SXD; crystal truncation rod diffraction (CTR) and resonant anomalous X-ray reflectivity (RAXR)] and alpha spectrometry, it was observed that ThIV sorption from NaClO4 solution was significantly lower [< d.l. (~0.04 ThIV per area of the muscovite unit cell AUC)] than from NaCl solution (θNaCl = 0.4 Th/AUC) under otherwise identical conditions.[8] The study also revealed that the adsorbed quantity of ThIV was significantly higher in LiClO4 medium (θLiClO4 = 4.9 Th/AUC), than in NaClO4 with KClO4 intermediate between Li and Na (θKClO4 ~ 0.1 Th/AUC). In the case of LiClO4 it could be shown by RAXR, that sorption occurs in the form of small particles a few nm in size.
Here, we present a study using SXD in combination with alpha spectrometry and atomic force microscopy (AFM) aiming to identify the basis of the previously observed, unexpected effects. To probe whether anion and cation effect occur independently, ThIV sorption was studied in the presence of LiCl and KCl ([Th] = 0.1 mM, pH = 3.3, I = 0.1 M). ThIV uptake is strongest in the presence of LiCl (θLiCl = 8.8 Th/AUC), while sorption in the presence of KCl is weaker (θKCl = 3.6 Th/AUC) but still exceeds the surface occupancy previously found in NaCl media.[8] For all cations ThIV sorption is stronger when Cl- is the counterion compared to ClO4-, confirming that the cation effect is indeed independent of the background electrolyte’s anion. The influence of aqueous speciation on the sorption processes was determined using electro-spray-ionization time-of-flight mass spectrometry (ESI-TOF-MS), which finds a speciation dominated by the ThIV aquo ion in all media, indicating that any electrolyte effects must occur at the water/mineral interface. We investigated the influence of the presence of oligomers on the sorption process, by repeating experiments at higher initial [Th] = 3.0 mM. As expected ThIV sorption is significantly increased. ThIV adsorbs at a preferential height of ~6.5 Å, which can be identified as the preferred size of Th-nanochains on the mica basal plane by AFM (Fig. 1). Uptake from LiCl media is still larger than from NaCl, but only by ~32% compared to 2100% at the lower ThIV concentration. This suggests that the electrolyte cation influences the formation or aggregation of ThIV oligomers at the interface, and its influence is diminished when these are initially present.

Fig. 1. Total electron density and ThIV electron density as a function of distance from the mineral surface determined by SXD upon sorption from NaCl, KCl, and LiCl, respectively. Upper curves (grey, light blue, dark red) are total electron densities determined by CTR, lower curves (black, dark blue, light red) are ThIV electron density distributions from RAXR.

References
[1] H. Geckeis, et al., Chem. Rev., 113, 1016 (2013).
[2] K. E. Knope, et al., Chem. Rev., 113, 944 (2012).
[3] S. Hellebrandt, et al., Langmuir, 32, 10473 (2016).
[4] A. E. Hixon, et al., Environmental Science: Processes & Impacts, 20, 1306 (2018).
[5] M. Schmidt, et al., Env. Sci. Tech., 47, 14178 (2013).
[6] C. Walther, et al., Chem. Rev., 113, 995 (2013).
[7] M. Schmidt, et al., Geochim. Cosmochim. Acta, 165, 280 (2015).
[8] M. Schmidt, et al., Geochim. Cosmochim. Acta, 88, 66 (2012).
Keywords: Surface X-ray Diffraction, CTR, RAXR, AFM, Nucleation, Thorium, background electrolytes
  • Lecture (Conference)
    49èmes Journées des Actinides, 14.-17.04.2019, Erice, Italia

Publ.-Id: 28867 - Permalink


Focusing of multi-MeV, subnanosecond proton bunches from a laser-driven source
Jahn, D.; Schumacher, D.; Brabetz, C.; Kroll, F.; Brack, F.-E.; Ding, J.; Leonhardt, R.; Semmler, I.; Blazevic, A.; Schramm, U.; Roth, M.;
We report on our latest transverse focusing results of subnanosecond proton bunches achieved with a laser-driven multi-MeV ion beamline. In the frame of the LIGHT collaboration, a target normal sheath acceleration (TNSA) source based 6 m long beamline was installed. In the past years, the laser-driven proton beam was transported and shaped by this beamline. The particle beam is collimated with a pulsed high-field solenoid and rotated in longitudinal phase space with a radio-frequency cavity which leads to an energy compression with an energy spread of (2.7 +/- 1.7)% (Delta E/E-0 at FWHM) or a time compression to the subnanosecond regime. Highest peak intensities in the subnanosecond regime open up an interesting field for several applications, e.g., proton imaging, as injectors in conventional accelerators or precise stopping power measurements in a plasma. We report on achieving highest peak intensities using an installed second solenoid as a final focusing system in our beamline to achieve small focal spot sizes. We measured a focal spot size of 1.1 x 1.2 mm leading to 5.8 x 10(19) protons per s cm(2) at a central energy bin of (9.55 +/- 0.25) MeV, which can be combined with a bunch duration below 500 ps at FWHM.

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Publ.-Id: 28866 - Permalink


4He irradiation of zircon, ZrSiO4, using a micro-patterned, Si-based energy filter
Nasdala, L.; Akhmadaliev, S.; Chanmuang N., C.; Zowalla, A.; Csato, C.; Rüb, M.;
The quantitative evaluation of alpha-particle damage in the mineral zircon, ZrSiO4, using 4He irradiation experiments is difficult because the vast majority of atomic knock-ons in the target are concentrated in a narrow depth range near the ends of the He-ion trajectories. Here we present a new concept to overcome this problem, namely, tailoring the depth profile of damage by means of a micromechanically fabricated “energy filter”. Lamellae of 1.5 μm thickness, prepared from ZrSiO4 using the focused-ion-beam technique, were subjected to irradiation with 8.8 MeV 4He ions. Five irradiations with ion fluences in the range 2.5 × 1015–1 × 1017 cm-2 have resulted in mild to severe damage, as monitored by the broadening and downshift of SiO4-stretching Raman bands. Our results may provide a means for quantifying the contribution of alpha particles to the total self-irradiation damage in zircon.
Keywords: Radiation damage, Helium irradiation, Energy filter, Focused ion beam, Raman spectroscopy

Publ.-Id: 28865 - Permalink


Software in the context of luminescence dating: status, concepts and suggestions exemplified by the R package Luminescence
Kreutzer, S.; Burow, C.; Dietze, D.; Fuchs, M. C.; Fischer, M.; Schmidt, C.;
The relevance of luminescence dating is re- flected by the steadily growing quantity of published data. At the same time, the amount of data available for analysis has increased due to technological and methodological advances. Routinely, luminescence data are analysed using a mixture of commercially available soft- ware, self-written tools and specific solutions. Based on a luminescence dating literature screening we show how rarely articles report on the software used for the data analysis and we discuss potential problems arising from this. We explore the growing importance of the statistical programming language R in general and especially its reflection in recent software developments in the context of lu- minescence dating. Specifically, for the R package ‘Luminescence’ we show how the transparency, flexibility and reliability of tools used for the data analysis have been improved. We finally advocate for more transparency if unvalidated software solutions are used and we emphasise that more attention should be paid to the tools used for analysing the data.
Keywords: R, Software, Luminescence dating, Data analysis
  • Open Access LogoAncient TL 35(2017)2, 1-11

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Publ.-Id: 28863 - Permalink


Laser-induced fluorescence and hyperspectral imaging integrated in one sensor system - the inSPECtor project
Fuchs, M.; Lorenz, S.; Beyer, J.; Seidel, P.; Sharma, S. K.; Heitmann, J.; Gloaguen, R.;
Optical spectroscopy-based methods provide an immense potential for identifying rock compositions in a non-invasive and highly efficient manner, which is crucial for innovative, sustainable and acceptable technologies in raw material exploration. In principle, we employ two fundamental types from the set of light-material interactions light absorption used for hyperspectral imaging (HSI), and light emission used for laser-induced fluorescence (LiF) spectroscopy. The light spectra measured after illumination may be used as fingerprints of a sample’s composition, as long as the characteristic spectral features are known and distinguishable.
In the inSPECtor project, we develop an integrated sensor system that combines the two types of spectroscopy in order to increase the range of detectable materials and the robustness of results. HSI has already proven successful for the mapping of various minerals and also of some REEs such as Nd. However, the complexity of natural samples leads to mixed spectra with masked or only weak REE-related features complicating or even precluding a robust identification of many other REEs. Here, LiF spectroscopy provides a much more sensitive alternative as REEs show very distinct emission features characteristic transitions in REE3+ ions, as encountered in typical REE-containing minerals.
Here, we present how the inSPECtor project combines the potential of both HSI and LiF, especially for REE identification. We focus on the qualitative aspects of REE characterization in synthetic REE standards, in natural minerals and complex rocks from a range of typical REE-mineral deposits. Based on the characterization and successful identification of Nd3+, Pr3+, Sm3+, Eu3+, Yb3+, Ho3+, Dy3+, Er3+, Tb3+ and Tm3+ , we summarize required sensor specifications and illustrate needed data analyses routines.
Keywords: optical spectroscopy, spectroscopic sensors, hyperspectral imaging, laser-induced fluorescence, rare earth elements, raw material exploration
  • Poster
    9th Workshop on Hyperspectral Image and Signal Processing, 23.-26.09.2018, Amsterdam, Netherlands

Publ.-Id: 28862 - Permalink


News from the sandbox – from virtual sediment sections to full measurement models
Dietze, M.; Fuchs, M.; Kreutzer, S.;
Geomorphic concepts and hypotheses are usually formulated based on empiric data from the field or the laboratory (deduction). After translation into models they can be applied to case study scenarios (induction). However, the other way around - expressing hypotheses explicitly by models and test these by empiric data - is a rarely touched trail. There are several models tailored to investigate the boundary conditions and processes that generate, mobilise, route and eventually deposit sediment in a landscape. Thereby, the last part, sediment deposition, is usually omitted. Essentially, there is no model that explicitly focuses on mapping out the characteristics of sedimentary deposits - the material that is used by many disciplines to reconstruct landscape evolution. The R-package sandbox is a model framework that allows creating and analysing virtual sediment sections for exploratory, explanatory, forecasting and inverse research questions. sandbox is a probabilistic and rule-based model framework for a wide range of possible applications. It has been advanced and linked to another model to allow the full work flow of modelling luminescence measurements. This contribution introduces news about recent developments and shows a set of applications.
Keywords: R package, sandbox, sediments
  • Open Access LogoContribution to proceedings
    EGU General Assembly 2018, 04.-13.04.2018, Vienna, Austria
    News from the sandbox – from virtual sediment sections to full measurement models

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Publ.-Id: 28861 - Permalink


inSPECtor - integrated spectroscopy sensor system for laser-induced fluorescence and hyperspectral imaging
Fuchs, M.; Lorenz, S.; Beyer, J.; Seidel, P.; Sharma, S. K.; Gloaguen, R.; Heitmann, J.;
The raw material sector demands for fast and non-invasive exploration technologies to reduce economic and ecologic costs as well as increasing public acceptance. Within the inSPECtor project, we develop an integrated spectroscopic sensor system that uses the light spectrum measured after illumination of a target as fingerprint of a sample's composition. The idea is to integrate information from two basic types of light-material interactions, light absorption used for hyperspectral imaging (HSI), and light emission used for laser-induced fluorescence (LiF) spectroscopy. HSI has already proven successful for various mineral identification and also allows the mapping of REEs such as Nd, which may be used as pathfinder for other REEs. However, the complexity of natural samples leads to mixed spectra with masked or weak REE-related features complicating or even precluding a robust identification of many other REEs. Here, LiF spectroscopy provides a much more sensitive alternative as REEs show very distinct emission features characteristic of the f-f type electronic transitions in REE3+ ions, as encountered in typical REE-containing minerals. We present the potential of both HSI and LiF, especially for REE identification and for raw material exploration. We focus on the qualitative and quantitative aspects of REE characterization in synthetic REE standards and in natural minerals and complex rocks from a range of typical REE-mineral deposits.
Keywords: inSPECtor, spectroscopy, laser-induced fluorescence, hyperspectral imaging
  • Open Access LogoContribution to proceedings
    EGU General Assembly 2018, 04.-13.04.2018, Vienna, Austria
    Proceedings of EGU

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Publ.-Id: 28860 - Permalink


The Need for Multi-Source, Multi-Scale Hyperspectral Imaging to Boost Non-Invasive Mineral Exploration
Gloaguen, R.; Ghamisi, P.; Lorenz, S.; Kirsch, M.; Zimmermann, R.; Booysen, R.; Andreani, L.; Jackisch, R.; Hermann, E.; Tusa, L.; Unger, G.; Contreras, C.; Khodadadzadeh, M.; Fuchs, M.;
The high demand for raw materials in our post-industrial societies contrasts the increasing difficulties to find new mineral deposits. In Europe, accessible and high-grade deposits are mostly exhausted or currently mined. Hence, future exploration must focus on the remaining, more remote locations or penetrate much deeper into the Earth's crust. Sustaining mining activities in Europe would allow the development of key technologies but also sustainable and ethical production of technological metals. Thus, we suggest to focus research on advances in multi-scale and multi-sensor remote sensing-based Earth integration techniques. The scale should range from satellite to air- and drone-borne systems and include ground validation. Multi-sensor downscaling methods involving SAR and optical data are particularly promising. We demonstrate that the integration with other sensors and/or measures such as geophysical/geochemical data as well as non-conventional remote sensing features such as textures and geometries are of interest. Thus, ultimately, our objective is to boost the competitiveness, growth, sustainability and attractiveness of the raw material sector in Europe. While we focus on the raw material sector as it is currently of strategic importance, the required methods are transferable to most environmental studies.
Keywords: Hyperspectral Imaging, Mineral Exploration
  • Open Access LogoContribution to proceedings
    IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium, 22.-27.09.2018, Valencia, Spain
    Proceedings of IGARSS 2018

Publ.-Id: 28859 - Permalink


Heavy Metal Binding Peptides – Design and Construction of new Biosorbents
Braun, R.ORC; Schönberger, N.; Bachmann, S.; Matys, S.ORC; Lederer, F.ORC; Pollmann, K.ORC
Heavy metal contaminations in both industrial and environmental waters are widely occurring. However, removal is both challenging and cost-intensive. In this study, we identified metal-binding peptide sequences using phage surface display (PSD). Fusion proteins with PSD-derived sequences were construced for further recombinant production, future scale-up and as alternative to chemical synthesis. The construction of the fusion proteins included usage of inteins and affinity tags for simplified expression and purification. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used for further characterization of the peptide-metal interaction. The system developed in this study provides metal-binding peptides with high specificity and sensitivity. Being biodegradable, the constructed peptides can be used in multiple applications. The identified motifs can furthermore provide a deeper understanding of peptide-metal interaction, leading to the discovery of novel metal-interacting biomolecules and better prediction of involved amino acids.
  • Poster
    8th Peptide Engineering Meeting, 08.-10.11.2018, Berlin, Deutschland

Publ.-Id: 28858 - Permalink


Multivariate Data Assimilation for Resource Model Updating
Prior, A.; Benndorf, J.; Tolosana-Delgado, R.; van den Boogaart, K. G.;
This is just a presentation in the COSMO Day. I did not submit an abstract since I was invited speaker
  • Invited lecture (Conferences)
    COSMO Day 2018, 05.07.2018, Montreal, Canada

Publ.-Id: 28856 - Permalink


Multivariate Ensemble Based Sequential Update Of The Resource Model For Real Time Mine Settings
Prior, A.; Tolosana-Delgado, R.; Prior-Arce, A.;
Mining industry is continuously monitoring key performance indicators (KPI), and geo-metallurgical properties such as grade, fragmentation or tonnage and reconciling estimates to online capture production performance parameters. New technology is looking for monitoring also other properties as grain size.
Relevant information is obtained from sensors installed at different mining production process stages, as in a Block Evaluation or Schedule and Blending.
This study aims to develop an efficient updating framework based on Sequential Ensemble Filtering by using compositional data statistics that will be able to cope with the non-linearities of the system.
  • Poster
    POF Evaluation, 28.02.-02.03.2018, Dresden, Germany

Publ.-Id: 28855 - Permalink


Resource model updating for underground mining production settings
Prior, A.; Benndorf, J.; Mariz, C.;
This research is part of the European Union funded 'Real Time Mining' project, which aims to develop a new framework to reduce uncertainties during the extraction process in highly selective underground mining settings. A continuously self-updating resource/grade control model concept is presented and aims to improve the raw material quality control and process efficiency of any type of mining operation. Applications in underground mines include the improved control of different components of the mineralogy and geochemistry of the extracted ore utilizing available “big data” collected during production. The development of the methodology is based on two full scale case study, the copper-zinc mine Neves-Corvo in Portugal and Reiche-Zeche mine in Germany. These serve for both, for the definition of method requirements and also as a basis for defining a Virtual Asset Model (VAM), which serves for artificial sampling as benchmark for performance analysis. This contribution introduces to the updating concept, provides a brief description of the method, explains details of the test cases and demonstrates the value added by an illustrative case study.
Keywords: Underground Mining, Data Assimilation, Geostatistitcs
  • Open Access LogoContribution to proceedings
    REAL TIME MINING - Conference on Innovation on Raw Material Extraction Amsterdam 2017, 10.-11.10.2017, Amsterdam, The Netherlands

Publ.-Id: 28854 - Permalink


Tissue-type mapping of gliomas.
Raschke, F.; Barrick, T. R.; Jones, T.; Yang, G.; Ye, X.; Howe, F. A.;
PURPOSE:

To develop a statistical method of combining multimodal MRI (mMRI) of adult glial brain tumours to generate tissue heterogeneity maps that indicate tumour grade and infiltration margins.

MATERIALS AND METHODS:

We performed a retrospective analysis of mMRI from patients with histological diagnosis of glioma (n = 25). 1H Magnetic Resonance Spectroscopic Imaging (MRSI) was used to label regions of "pure" low- or high-grade tumour across image types. Normal brain and oedema characteristics were defined from healthy controls (n = 10) and brain metastasis patients (n = 10) respectively. Probability density distributions (PDD) for each tissue type were extracted from intensity normalised proton density and T2-weighted images, and p and q diffusion maps. Superpixel segmentation and Bayesian inference was used to produce whole-brain tissue-type maps.

RESULTS:

Total lesion volumes derived automatically from tissue-type maps correlated with those from manual delineation (p < 0.001, r = 0.87). Large high-grade volumes were determined in all grade III & IV (n = 16) tumours, in grade II gemistocytic rich astrocytomas (n = 3) and one astrocytoma with a histological diagnosis of grade II. For patients with known outcome (n = 20), patients with survival time < 2 years (3 grade II, 2 grade III and 10 grade IV) had a high-grade volume significantly greater than zero (Wilcoxon signed rank p < 0.0001) and also significantly greater high grade volume than the 5 grade II patients with survival >2 years (Mann Witney p = 0.0001). Regions classified from mMRI as oedema had non-tumour-like 1H MRS characteristics.

CONCLUSIONS:

1H MRSI can label tumour tissue types to enable development of a mMRI tissue type mapping algorithm, with potential to aid management of patients with glial tumours.
Keywords: Glioma; Magnetic resonance spectroscopy (MRS); Multimodal MRI; Nosologic imaging; Pattern recognition

Publ.-Id: 28845 - Permalink


Dynamics of the magnetoelastic phase transition and adiabatic temperature change in Mn1.3Fe0.7P0.5Si0.55
Fries, M.; Gottschall, T.; Scheibel, F.; Pfeuffer, L.; Skokov, K. P.; Skourski, I.; Acet, M.; Farle, M.; Wosnitza, J.; Gutfleisch, O.;
The adiabatic temperature change ΔTad of a Mn1.3Fe0.7P0.5Si0.55 Fe2P-type alloy was measured under different magnetic field-sweep rates from 0.93 Ts−1 to 2870 Ts−1. We find a field-sweep-rate independent magnetocaloric effect due to a partial alignment of magnetic moments in the paramagnetic region overlapping with the magnetocaloric effect of the first-order phase transition. Additionally, the first-order phase transition is not completed even in fields up to 20 T leading to a non-saturating behavior of ΔTad. Measurements in different pulsed fields reveal that the first-order phase transition cannot follow the fast field changes as previously assumed, resulting in a distinct field-dependent hysteresis in ΔTad.

Publ.-Id: 28844 - Permalink


Influence of pH, carbonate and calcium concentration on U(VI) retention by clay minerals at (hyper)alkaline conditions – A batch sorption and spectroscopy study
Philipp, T.; Schmeide, K.ORC; Rossberg, A.; Huittinen, N.; Stumpf, T.
Clays are considered as potential host rocks and backfill material for deep geological repositories for radioactive waste. Therefore, profound understanding of radionuclide retention processes at clay mineral surfaces is essential for a long-term safety assessment. As a result of the degradation of concrete within such a repository, hyperalkaline cement pore waters can evolve. Since the U(VI) sorption behavior at alkaline conditions is still poorly understood, batch experiments were combined with spectroscopic investigations in order to gain insight into the underlying retention processes on the molecular level.
U(VI) batch sorption experiments (pH 8-13) with various clay minerals at different carbonate concentrations (absence, 0.5 and 100 mM) showed a decreased U(VI) retention in the presence of carbonate up until a certain pH (pH 9.5 or pH 11, depending on [CO32-]) due to the formation of weakly sorbing uranyl carbonate complexes in aqueous solution, confirmed by time-resolved laser-induced fluorescence spectroscopy (TRLFS). This is in accordance with previous studies. However, also in the presence of carbonate, U(VI) retention is increased in even stronger alkaline solutions, which is attributed to the preferred formation of hydrolyzed U(VI) species.
In order to clarify the mechanisms responsible for the very strong U(VI) retention in the pH range 10-12 (absence and 0.5 mM CO32-), uranyl complexes on Ca-bentonite surfaces were examined directly, using site-selective TRLFS and extended X-ray absorption fine structure (EXAFS) spectroscopy (ESRF, Grenoble). Both techniques showed the presence of two different U(VI) surface complexes and no indication for U(VI) precipitation. Consequently, under the given conditions, adsorption is the dominant retention process despite the negative mineral surface charge and the anionic character of prevailing aqueous U(VI) species (i.e. UO2(OH)3-). The retention could be realized by mediating cations, which adsorb to the mineral surface in the first place, leading to a local compensation of negative surface charge. Experiments with different calcium concentrations confirmed that the presence of calcium significantly enhances the U(VI) retention between pH 10 an 12.
Keywords: uranium, Ca-bentonite, site-selective TRLFS, EXAFS, speciation, surface complexation, carbonate, calcium
  • Lecture (Conference)
    International Conference on Clay Science and Technology – EUROCLAY 2019, 01.-05.07.2019, Paris, France

Publ.-Id: 28843 - Permalink


Enzymes Immobilized on Carbon Nitride (C3N4) Cooperating with Metal Nanoparticles for Cascade Catalysis
Wang, Y.; Zhang, N.; Hübner, R.; Tan, D.; Löffler, M.; Facsko, S.; Zhang, E.; Ge, Y.; Qi, Z.; Wu, C.;
The exploration of effective platforms for immobilizing chemo- and biocatalysts to develop biohybrid catalysts is an attractive subject of practical interest. In this work, carbon nitride (C3N4) is used for the first time as a platform for the immobilization of metal catalyst (Pd nanoparticles) and biocatalyst (Candida antarctica lipase B, CalB) in a facile manner to prepare biohybrid catalyst. The optimal biohybrid catalyst inherits the intrinsic performance of both Pd nanoparticles and CalB, and shows high activity in the one-pot cascade reaction converting benzaldehyde to benzyl hexanoate at room temperature. With this proof of concept, it is expected that C3N4 can be utilized for immobilizing more types of chemo- and biocatalysts for perspective applications.
Keywords: biohybrid catalysts, CalB, carbon nitride, cascade reactions, Pd nanoparticles

Publ.-Id: 28842 - Permalink


Technical Note: Experimental verification of magnetic field-induced beam deflection and Bragg peak displacement for MR-integrated proton therapy.
Schellhammer, S. M.; Gantz, S.; Lühr, A.; Oborn, B. M.; Bussmann, M.; Hoffmann, A. L.;
Purpose: Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation.
Such an integration raises several challenges, as both systems mutually interact. The proton beam will experience quasi-continuous energy loss and energy-dependent electromagnetic deflection at the same time, giving rise to a deflected beam trajectory and an altered dose distribution with a displaced Bragg peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton beam trajectories and Bragg peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations.
Methods: Planar dose distributions of proton pencil beams (80–180 MeV) traversing the field of a 0.95 T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected beam trajectories and the Bragg peak displacement were extracted from the measured planar dose distributions and compared against the simulations.
Results: The lateral beam deflection was clearly visible on the EBT3 films and ranged from 1 to 10 mm for 80 to 180 MeV, respectively. Simulated and measured beam trajectories and Bragg peak displacement agreed within 0.8 mm for all studied proton energies.
Conclusions: These results prove that the magnetic field-induced Bragg peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95 T, and allows Monte Carlo simulations to be used as gold standard for proton beam trajectory prediction in similar frameworks for MR-integrated proton therapy.
Keywords: magnetic field induced Bragg peak displacement, Monte Carlo simulation, MR guidance, proton dosimetry, proton therapy

Publ.-Id: 28841 - Permalink


SDF-1/CXCR4 expression is an independent negative prognostic biomarker in patients with head and neck cancer after primary radiochemotherapy
De-Colle, C.; Menegakis, A.; Mönnich, D.; Welz, S.; Boeke, S.; Sipos, B.; Fend, F.; Mauz, P. S.; Tinhofer, I.; Budach, V.; Abu, J. J.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Belka, C.; Ganswindt, U.; Pigorsch, S.; Combs, S. E.; Lohaus, F.; Linge, A.; Krause, M.; Baumann, M.; Zips, D.;
Introduction: Preclinical and clinical data suggest that the chemokine pathway governed by SDF-1 and CXCR4 contributes to a resistant phenotype. This retrospective biomarker study aims to explore the specific prognostic value of SDF-1 and CXCR4 expression in locally advanced head and neck squamous cell carcinomas (HNSCC) treated with primary radiochemotherapy (RT-CT).
Material and methods: Biopsies from 141 HNSCC tumours of the oral cavity, oropharynx and hypopharynx were evaluated for SDF-1 and CXCR4 expression by immunofluorescence. SDF-1 and CXCR4 expression was correlated with clinico-pathological characteristics and outcome after RT-CT.
Results: Patients with tumours exhibiting overexpression of intracellular SDF-1 and CXCR4 have a higher risk for loco-regional relapse and a worse overall survival after RT-CT (multivariate analysis, hazard ratio 2.33, CI [1.18–4.62], p = 0.02 and hazard ratio 2.02, CI [1.13–3.59], p = 0.02, respectively). Similar results were observed when only the subgroup of HPV DNA negative patients were analysed (hazard ratio 2.23 and 2.16, p = 0.02 and p = 0.01, respectively).
Conclusions: Our data support the importance of SDF-1 and CXCR4 expression for loco-regional control and overall survival in HNSCC after primary radiochemotherapy. Prospective multivariate validation and further studies into CXCR4 inhibition to overcome radiation resistance are warranted.
Keywords: SDF-1 CXCR4 Head and neck cancer Prognostic Biomarker Primary radiochemotherapy

Publ.-Id: 28840 - Permalink


Improved effectiveness of stereotactic radiosurgery in large brain metastases by individualized isotoxic dose prescription: an in silico study
Zindler, J. D.; Schiffelers, J.; Lambin, P.; Hoffmann, A. L.;
Introduction In large brain metastases (BM) with a diameter of more than 2cm there is an increased risk of radionecrosis (RN) with standard stereotactic radiosurgery (SRS) dose prescription, while the normal tissue constraint is exceeded. The tumor control probability (TCP) with a single dose of 15Gy is only 42%. This in silico study tests the hypothesis that isotoxic dose prescription (IDP) can increase the therapeutic ratio (TCP/Risk of RN) of SRS in large BM.
Materials and methods A treatment-planning study with 8 perfectly spherical and 46 clinically realistic gross tumor volumes (GTV) was conducted. The effects of GTV size (0.5–4cm diameter), set-up margins (0, 1, and 2mm), and beam arrangements (coplanar vs non-coplanar) on the predicted TCP using IDP were assessed. For single-, three-, and five-fraction IDP dose–volume constraints of V12Gy = 10cm3, V19.2 Gy = 10cm3, and a V20Gy = 20cm3, respectively, were used to maintain a low risk of radionecrosis.
Results In BM of 4cm in diameter, the maximum achievable single-fraction IDP dose was 14Gy compared to 15Gy for standard SRS dose prescription, with respective TCPs of 32 and 42%. Fractionated SRS with IDP was needed to improve the TCP. For three- and five-fraction IDP, a maximum predicted TCP of 55 and 68% was achieved respectively (non-coplanar beams and a 1mm GTV-PTV margin).
Conclusions Using three-fraction or five-fraction IDP the predicted TCP can be increased safely to 55 and 68%, respectively, in large BM with a diameter of 4cm with a low risk of RN. Using IDP, the therapeutic ratio of SRS in large BM can be increased compared to current SRS dose prescription.
Keywords: Radiotherapy · Stereotactic · Dose prescription · Normal tissue tolerance · Large brain metastases

Publ.-Id: 28839 - Permalink


Electro-vortex flow in liquid metal batteries
Nore, C.; Ziebell Ramos, P.; Herreman, W.; Cappanera, L.; Guermond, J.-L.; Weber, N.;
We study the generation of rotational flows in electrically conducting fluids due to the Electro-Vortex-Flow (EVF) phenomenon, i.e. the interaction of a non-uniform current with the magnetic field it generates. We have been developing a so-called code SFEMaNS since 2001 [2] capable of simulating the nonlinear magnetohydrodynamic (MHD) equations in heterogeneous domains (with electrical conductivity or magnetic permeability jumps) in axisymmetric geometries and with several fluids [1]. Liquid Metal Batteries are composed of three layers of fluids (liquid metal electrode–electrolyte–liquid metal electrode) of different densities lying over each other and stabilized by gravity. These batteries are prone to magnetohydrodynamical instabilities (e.g. the Tayler instability [3], the Metal Pad Roll instability [4], etc) which may deform the electrode–electrolyte interfaces until the ultimate situation of short circuit when the two metals touch each other.
In this talk we first discuss the typical intensity and structure of the axisymmetric flow in a liquid metal column covered by many previous studies. After that, we focus on EVF in liquid metal batteries (see figure 1). We discuss the deformation of the electrolyte-liquid metal interfaces caused by EVF and we characterize how EVF helps in mixing the bottom alloy layer.
  • Lecture (Conference)
    17th European Turbulence Conference, 03.09.2019, Turin, Italien

Publ.-Id: 28838 - Permalink


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