Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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28275 Publications
Investigation of the superconducting gap structure in κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDT-TTF)2Cu[N(CN)2]Br by means of thermal-conductivity measurements
Kühlmorgen, S.; Schönemann, R.; Green, E. L.; Müller, J.; Wosnitza, J.
Corresponding author: Green, E. L. Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report temperature-dependent thermal-conductivity, κ, measurements on the layered quasi-two-dimensional organic superconductors κ-(BEDT-TTF)2Cu(NCS)2 and κ-(BEDTTTF)2Cu[N(CN)2]Br down to 160 mK. The results for κ-(BEDT-TTF)2Cu(NCS)2 may be consistent with a nodal superconducting (SC) gap structure as indicated by a nonnegligible remnant linear contribution when κ /T α T2 is extrapolated to T = 0. For κ-(BEDT-TTF)2Cu[N(CN)2]Br, contrary to expectations, higher κ values are observed in the superconducting regime as compared to the normal, high-field state evidencing a dominant phonon contribution to κ in the superconducting state. The strong increase of κ in the normal state below Tc for both samples indicates strong electron–phonon scattering. Our results highlight the need for thermal-conductivity measurements performed down to significantly lower temperatures to determine the symmetry of the SC gap.

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  • Secondary publication expected from 01.09.2018

Registration No. 26080 - Permalink


Quasi-two-dimensional Fermi surfaces with localized f electrons in the layered heavy-fermion compound CePt2In7
Götze, K.; Krupko, Y.; Bruin, J. A. N.; Klotz, J.; Hinlopen, R. D. H.; Ota, S.; Hirose, Y.; Harima, H.; Settai, R.; Mccollam, A.; Sheikin, I.
Corresponding author: Sheikin, I. Laboratoire National des Champs Magnétiques Intenses (LNCMI-EMFL), CNRS, UGA, Grenoble, France
Abstract: We report measurements of the de Haas–van Alphen effect in the layered heavy-fermion compound CePt2In7 in high magnetic fields up to 35 T. Above an angle-dependent threshold field, we observed several de Haas–van Alphen frequencies originating from almost ideally two-dimensional Fermi surfaces. The frequencies are similar to those previously observed to develop only above a much higher field of 45 T, where a clear anomaly was detected and proposed to originate from a change in the electronic structure [M. M. Altarawneh et al., Phys. Rev. B 83, 081103 (2011)]. Our experimental results are compared with band structure calculations performed for both CePt2In7 and LaPt2In7, and the comparison suggests localized f electrons in CePt2In7. This conclusion is further supported by comparing experimentally observed Fermi surfaces in CePt2In7 and PrPt2In7, which are found to be almost identical. The measured effective masses in CePt2In7 are only moderately enhanced above the bare electron mass m0, from 2m0 to 6m0.

Registration No. 26078 - Permalink


Novel Functionalized Calixarenes as Host Molecules for Complexation with Alkaline Earth Metals
Steinberg, J.; Gott, M.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.
Corresponding author: Mamat, C.
Abstract: Alpha-emitting radionuclides (e.g. radium-223, 224) are of high interest for cancer therapy, but currently, no stable complexing agent for radium is known. Moderate stability constants have been described for complexes of alkaline-earth metal ions with calixarenes, crown and aza crown ethers [2, 3]. By combining calixarenes with crown and aza crown ethers as well as functionalizing the remaining calixarene hydroxyl groups, higher stability constants may be achieved. In this study, we synthesized and evaluated new functionalized calixarenes as host molecules for radium. 1,3 single-bridged crowns were selectively introduced on the lower rim of 4-tert-Butylcalix[4]arene by alkylation with tosylated crown ethers or by acylation and sequential amination with aza crown ethers. The remaining phenolic hydroxyl groups were functionalized by acylation and sequential amination to prepare acetic acid amide and hydroxyl amide derivatives. The complexation was carried out by vortexing the ligand in chloroform with an aqueous BaCl2-solution as surrogate for Ra for 10 min. The barium complex was isolated from the organic layer and characterization was performed by NMR. The barium-133 and radium-224 calixcrowns were prepared similarly and stability studies performed by TLC and HPLC. 1,3-bridged crown and calix(aza)crown ethers were obtained in good yields (53 and 58%, respectively) and acetic acid amide and hydroxyl amide calixcrown derivatives were successfully prepared with yields of 66-82%. Barium was incorporated into the calixarene compounds, isolated by a two-phase extraction and the structure confirmed by NMR. Synthesis and stability of the radioactive complexes will be reported. Future studies will incorporate a targeting moiety on the upper ring. Several novel, functionalized calixarene compounds were prepared and initial complexation studies were performed with nonradioactive barium. The resulting complexes were checked by NMR and the procedure was transferred to radioactive barium-133 and radium-224. Complexation and stability was demonstrated by radiographic imaging of the developed TLC plates. These complexes show great promise for application to cancer therapy.
Keywords: Alpha-therapy, Radium, Calixarenes
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S488
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

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  • Secondary publication expected from 14.05.2018

Registration No. 26074 - Permalink


Detection of Auger Electron Induced Strand Breaks on Plasmid DNA Caused by Technetium-99m Labeled Pyrene Derivatives
Wunderlich, G.; Reissig, F.; Mamat, C.; Pietzsch, H.-J.; Kotzerke, J.; Steinbach, J.
Corresponding author: Wunderlich, G. UKD / TU Dresden
Abstract: Simultaneously with the known γ-emission, 99mTc causes radical-mediated DNA damage due to Auger electrons, which were also emitted. We have synthesized a series of new 99mTc-labeled pyrene derivatives (common DNA intercalators) with varied distances between the pyrene moiety and the radionuclide (Fig. 1). Plasmids (pUC 19) enable the investigation of the unprotected interactions between the labeled pyrene derivatives (3-15MBq) and DNA that results in single-strand breaks (SSB) or double-strand breaks (DSB) separated by gel electrophoresis in 1.4% agarose gel and quantified by fluorescent staining. We used the 99mTc(CO)3-core for pyrene labeling. 99mTc was tightly bound to the plasmid DNA and its damage is mainly dependent on the chain length between the pyrene residue and the Tc-core. It could not be completely prevented by DMSO, a known free radical scavenger. The effectiveness of the DNA-binding 99mTc-labeled pyrene derivatives was demonstrated by comparison to non-DNA-binding [99mTc]NaTcO4, since nearly all DNA damage caused by [99mTc]NaTcO4 was prevented by DMSO. We prepared a 99mTc-complex with an optimal distance between the [99mTc]Tc(CO)3-core and the pyrene residue to position the 99mTc in close proximity to the plasmid DNA to induce direct SSB and DSB. By increasing the distance between the DNA-intercalating moiety and the bonding moiety for 99mTc, we observed decrease of direct DNA damages. This distance dependence has not been reported for 99mTc until now. Clinical relevant Auger electron therapy is hampered by the prerequisite of DNA binding which is hindered by cell and nucleus membranes.
Keywords: 99mTc, Auger, DNA damage, Therapy
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences (ISRS 2017), Dresden, 14.-19.05.2017, Dresden, Deutschland
  • Open Access LogoJournal of Labelled Compounds and Radiopharmaceuticals 60(2017)S1, S365
    DOI-Link: http://dx.doi.org/10.1002/jlcr.3508

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  • Secondary publication expected from 14.05.2018

Registration No. 26072 - Permalink


New measurement of the 242Pu(n,γ) cross section at n_TOF-EAR1 for MOX fuels: Preliminary results in the RRR
Lerendegui-Marco, J.; Guerrero, C.; Cortés-Giraldo, M. A.; Quesada, J. M.; Mendoza, E.; Cano-Ott, D.; Eberhardt, K.; Junghans, A.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Colonna, N.; Cortés, G.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; Gómez-Hornillos, M. B.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lo Meo, S.; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec The N_Tof Collaboration, P.
Abstract: The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70's, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its “High Priority Request List” and its report WPEC-26 that the capture cross section of 242Pu should be measured with an accuracy of at least 7–12% in the neutron energy range between 500 eV and 500 keV. This work presents a brief description of the measurement performed at n_TOF-EAR1, the data reduction process and the first ToF capture measurement on this isotope in the last 40 years, providing preliminary individual resonance parameters beyond the current energy limits in the evaluations, as well as a preliminary set of average resonance parameters.
Keywords: 242Pu neutron capture, neutron time-of-flight measurement, CERN nTOF
  • Open Access LogoContribution to proceedings
    International Conference on Nuclear Data for Science and Technology (ND2016), 11.-16.09.16, Bruges, Belgium, 11.-16.09.16, Bruges, Belgium
    European Physical Journal Web of Conferences
    DOI-Link: http://dx.doi.org/10.1051/epjconf/201714611045

Registration No. 26065 - Permalink


High repetition rate, multi-MeV proton source from cryogenic hydrogen jets
Gauthier, M.; Curry, C. B.; Göde, S.; Brack, F.-E.; Kim, J. B.; Macdonald, M. J.; Metzkes, J.; Obst, L.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schumaker, W.; Schramm, U.; Zeil, K.; Glenzer, S. H.
Corresponding author: Gauthier, M. High Energy Density Science Division, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
Abstract: We report on a high repetition rate proton source produced by high-intensity laser irradiation of a continuously flowing, cryogenic hydrogen jet. The proton energy spectra are recorded at 1Hz for Draco laser powers of 6, 20, 40, and 100 TW. The source delivers ca. 10^13 protons/MeV/sr/min. We find that the average proton number over one minute, at energies sufficiently far from the cut-off energy, is robust to laser-target overlap and nearly constant. This work is therefore a first step towards pulsed laser-driven proton sources for time-resolved radiation damage studies and applications which require quasi-continuous doses at MeV energies.

Registration No. 26061 - Permalink


Nitrogen redistribution in annealed LaFeOxNy thin films investigated by FTIR spectroscopy and EELS mapping
Haye, E.; Pierron, V.; Barrat, S.; Capon, F.; Munnik, F.; Bruyère, S.
Corresponding author: Haye, E. Institut Jean Lamour (IJL), CNRS/Université de Lorraine, France
Abstract: LaFeOxNy thin films have been deposited by magnetron sputtering in Ar/O2/N2 gas mixture at 800°C. Such oxynitride perovskites present an uncommon infrared vibration mode position at 2040cm-1, due to presence of nitrogen, which disappears with heating in air. The evolution of this vibration mode with temperature has been studied and permit to determine an activation energy of thermal degradation of LaFeOxNy. The quantification of nitrogen by Elastic Recoil Detection Analysis (ERDA) before and after heating exhibits the same nitrogen content, indicating a redistribution of nitrogen. Such nitrogen redistribution is observed by Electron Energy Loss Spectroscopy (EELS) mapping, showing migration of nitrogen into grain boundaries, in association with film oxidation.
Keywords: Oxynitride perovskite, Thermal stability, EELS mapping, FTIR

Registration No. 26059 - Permalink


The costimulatory domain in chimeric antigen receptor modified T lymphocytes defines their resistance to immunosuppression by regulatory T cells
Kegler, A.; Koristka, S.; Bergmann, R.; Feldmann, A.; Arndt, C.; Aliperta, R.; Albert, S.; Ziller-Walter, P.; Ehninger, G.; Bornhäuser, M.; Schmitz, M.; Bachmann, M.
Keywords: tumor immunotherapy, CAR design, Treg suppression
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26058 - Permalink


Using the novel universal CAR platform technology “UniCAR” to target tumors overexpressing disialoganglioside (GD2)
Mitwasi, N.; Feldmann, A.; Bergmann, R.; Rössig, C.; Bachmann, M.
Keywords: CAR Technology, UniCAR T cells, GD2.
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26057 - Permalink


Retargeting of human T lymphocytes to EGFR-expressing cancer cells via nanobody-based target modules using the universal chimeric antigen receptor technology
Albert, S.; Bergmann, R.; Koristka, S.; Feldmann, A.; Arndt, C.; Aliperta, R.; Ehninger, A.; Cartellieri, M.; Ehninger, G.; Steinbach, J.; Bachmann, M.
Keywords: CAR T cell therapy, nanobodies, EGFR-targeting
  • Lecture (Conference)
    47th Annual Meeting of the German Society for Immunology, 12.09.2017, Erlangen, Germany

Registration No. 26056 - Permalink


Flüssigmetallbatterien als Option für elektrische Großspeicher
Nimtz, M.; Weber, N.; Weier, T.
Abstract: Übersicht über die Forschungsaktivitäten an Flüssigmetallbatterien am HZDR.
  • Poster
    3. Wissenschaftliches SCI-Treffen "Energiesystemintegration", 11.09.2017, Karlsruhe, Deutschland

Registration No. 26042 - Permalink


Selection of Gallium-binding peptides using Phage Display technology
Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.
Abstract: Gallium is used essentially in the semiconductor compounds GaAs, GaN or GaP for high-potential future technologies. The resulting rapidly growing demand for gallium shouldn't be exclusively met by the recovery from primary raw material sources.
Biosorptive recycling of gallium from waste waters of the semiconductor industry is a promising and innovative contribution for establishing an economic and clean zero waste technology.
Peptides are excellently suitable ligands for the biosorptive complexation of gallium ions in aqueous solutions due to their variability in their amino acid sequence and their robust properties.
A well-established method for the selection of highly specific peptide ligands in medicine and biotechnology is the phage display technology. Random, short peptide sequences are presented on the surface according to genetically modified bacteriophages. In a biopanning called process, a pool of different bacteriophages is selected against a particular target, thereby enriching specific binding clone variants (figure 1). A very effective method has been established for the selection of different phage display libraries. Gallium ions immobilized on a monolithic ion exchanger are made accessible for biopanning in an FPLC system. This chromatopanning allows the selective enrichment of gallium-binding clone variants under strictly controlled process conditions.
In the present study, we report about the enrichment, identification and characterization of several gallium-binding motifs. Some promising gallium binding bacteriophage clones are chosen for further binding studies. The corresponding peptide sequences can be synthesized and used in subsequent experiments to develop biosorptive materials for selective gallium recovery from industrial waste waters.
Keywords: Phage Surface Display, biopanning, immobilized metal ions, Gallium, metal binding peptides
  • Lecture (Conference)
    6th International Symposium on biosorption and biodegradation/bioremediation, 25.-29.06.2017, Prag, Czech republic

Registration No. 26041 - Permalink


Development of Metal Ion Binding Peptides Using Phage Surface Display Technology.
Schönberger, N.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.
Abstract: Phage surface display technology is a useful tool for the identification of biosorptive peptides. In this work it is used for the identification of cobalt, nickel and gallium binding peptides. We present methods for the enrichment of metal ion binding bacteriophage clones from two commercial phage display libraries. One of them presents cyclic heptamer peptides, in which two cysteins flanke the peptide loop (C7C), and a linear dodecapeptide library (D-12).Metal ion selective peptides are suitable to separate as well as concentrate cobalt and nickel from copper black shale leaching products (EcoMetals project) and gallium from industrial waste waters (EcoGaIn project). In contrast to common capture methods of specific binding phage for solid materials the ionic species have to be immobilized prior to the bio-panning procedure. This was realized by chemical complexation of the metal ions using commercial complexing agents on porous matrices. Moreover, an option to harvest non elutable strong binding phage is proposed.
Keywords: Phage Surface Display, biopanning, immobilized metal ions, nickel, gallium, cobalt, metal binding peptides
  • Contribution to proceedings
    22nd International Biohydrometallurgy Symposium, Solid State Phenomena, 24.-27.09.2017, Freiberg, Deutschland
    22nd International Biohydrometallurgy Symposium, Schweiz: Trans Tech Publications, ISSN: 1662-9779,, 591-595
    DOI-Link: http://dx.doi.org/10.4028/www.scientific.net/SSP.262.591

Registration No. 26040 - Permalink


Overview on Helmholtz Reactor Safety Research
Kliem, S.ORC; Tromm, W.; Reinecke, E.-A.
Abstract: The paper gives an overview on the research conducted within the topic "Reactor Safety" of the Helmholtz NUSAFE programme.
  • Lecture (Conference)
    2nd Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology, 12.-15.09.2017, Karlsruhe, Deutschland

Registration No. 26038 - Permalink


Hierarchical thermoplastic rippled nanostructures regulate Schwann Cell adhesion, morphology and spatial organization
Masciullo, C.; Dell'Anna, R.; Tonazzini, I.; Böttger, R.; Pepponi, G.; Cecchini, M.
Corresponding author: Cecchini, Marco NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, Piazza San Silvestro 12, 56127 Pisa, Italy;
Abstract: Periodic ripples are a variety of anisotropic nanostructures that can be realized by ion beam irradiation on a wide class of solid surfaces. Only few authors have investigated these surfaces for tuning the response of biological systems, probably because it is challenging to directly produce them in materials that well sustain long-term cellular cultures. Here, hierarchical rippled nanotopographies with lateral periodicity of ∽300 nm are produced from a gold-irradiated germanium mold in polyethylene terephthalate (PET), a biocompatible polymer approved by the US Food and Drug Administration for clinical applications, by a novel three-steps embossing process. The effects of nano-ripples on Schwann Cells (SCs) are studied in view of their possible use for nerve-repair applications. Data demonstrate that nano-ripples can enhance short-term SC adhesion and proliferation (3-24h from seeding), drive their actin cytoskeleton spatial organization and sustain long-term cell growth. Notably, SCs orient perpendicularly with respect to the nanopattern lines. These results provide information about the possible use of hierarchical nano-rippled elements for nerve-regeneration protocols.
Keywords: hierarchical nanostructures, self-organization, ion Irradiation, cell adhesion, nano-ripples

Registration No. 26037 - Permalink


Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties
Jia, Q.; Ou, X.; Langer, M.; Schreiber, B.; Grenzer, J.; Siles, P. F.; Rodriguez, R. D.; Huang, K.; Yuan, Y.; Heidarian, A.; Hübner, R.; You, T.; Yu, W.; Lenz, K.; Lindner, J.; Wang, X.; Facsko, S.
Corresponding author: Lenz, Kilian HZDR
Abstract: A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, III-V semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a “reverse epitaxy” process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays (Au, Fe, Ni, Co, FeAl alloy) are fabricated on these III-V templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances (LSPRs) of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine (CoPc) in surface-enhanced Raman scattering (SERS). Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.
Keywords: self-assembly, metallic nanowire array, reverse epitaxy, magnetic anisotropy, anisotropic dielectric function

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Registration No. 26036 - Permalink


Spin-transfer driven dynamics in hybrid structures
Fowley, C.; Rode, K.; Gallardo, R.; Thiyagarajah, N.; Lau, Y.-C.; Borisov, K.; Betto, D.; Atcheson, G.; Kampert, E.; Wang, Z.; Lindner, J.; Coey, M.; Stamenov, P.; Deac, A. M.
Abstract: Since the discovery of giant magnetoresistance, metal spintronics has seen unprecedented advances, from the realisation of ultra-high magnetoresistance ratios to substantial output power from both conventional spin transfer torque oscillators as well as spin-torque vortex oscillators [1]. The recently discovered of the fully compensated ferrimagnetic half-metal, manganese ruthenium gallium (MRG), due to its widely tunable magnetic properties [2], could enable spin torque oscillators which work in the range of hundreds of GHz. Being a ferrimagnet, MRG consists of two magnetic sublattices which are coupled antiferromagnetically to each other. It has been shown that in this material the magnetotransport is dominated by one magnetic sublattice whereas the overall magnetisation is determined by both sublattices [3]. This means that MRG behaves magnetically like an antiferromagnet and electrically like a highly spin polarised ferromagnet, implying that spin-transfer torque would act on one sublattice only, enabling efficient current induced excitations. Due to the different temperature dependences of the sublattice magnetisations, MRG displays a compensation temperature at which the total magnetic moment is zero and the magnetic state is impervious to external magnetic fields [4].
Here we conduct high-field magnetotransport measurements [5] on selected films of MRG with differing Ru concentration and, therefore, different compensation temperatures (Tc). Both the transverse Hall resistivity and longitudinal resistivity are recorded in magnetic fields up to 58T. MRG exhibits a large spontaneous Hall angle of ~2%, coercivity exceeding 1T at room temperature (and several Teslas close to Tc) and has very low net magnetisation of 25kA/m. Despite having a no net magnetic moment at the compensation temperature the magnitude of the Hall signal does not become zero, further indicating both the half-metallic nature of the material and that the magnetotransport is dominated by one sublattice only. An additional feature is observed in the transport data, which resembles a spin-flop transition. By comparison to analytical and mean-field calculations of the sublattice magnetisation directions we can estimate the both the sublattice anisotropy (Hk) and interlayer exchange coupling (Hex). The out-of-phase and in-phase magnetic resonance modes, therefore, lie in the range of 0.3THz and 4THz, respectively. This makes MRG a uniquely tuneable material as a free layer in spin-transfer oscillator applications [6].


References:
[1] Baibich M.N. et al., Physical Review B, 61, 2472 (1988), Ikeda S. et al., Applied Physics Letters, 93 082508 (2008), Tsunegi S. et al., Applied Physics Letters, 109, 252402 (2016)
[2] Kurt H. et al., Physical Review Letters, 112, 027201 (2014)
[3] Borisov K. et al., Applied Physics Letters, 108, 192407 (2016)
[4] Betto D. et al., AIP Advances, 6, 055601 (2016)
[5] Fowley C. et al., Journal of Physics D : Applied Physics, 48, 164006 (2015)
[6] Awari N. et al., Applied Physics Letters, 109, 032403 (2016)
Keywords: magnetism, spin-transfer torque, wireless communication
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moscow, Russia

Registration No. 26032 - Permalink


Wissenschaftliche Software – Anspruch und Realität im Forschungsprozess
Konrad, U.ORC
Abstract: Wissenschaftliche Software ist heute unverzichtbares Werkzeug im Forschungsprozess, sie ist Voraussetzung für die Nachvollziehbarkeit der (publizierten) Ergebnisse und in vielen Fällen auch selbst ein Ergebnis, das publiziert, genutzt und langfristig bewahrt werden muss. Publikationen bestehen künftig häufig aus zitierfähigen Texten, Daten und Software und müssen entsprechend konsistent behandelt werden, dies ist eine Herausforderung auch für die Bibliotheken. Daraus ergeben sich eine Reihe von Fragestellungen und Aufgaben für die gute wissenschaftliche Praxis im Umfeld der „Offenen Wissenschaft“ (Open Science). Diese Fragen werden in dem Vortrag diskutiert.
Ausgangspunkt ist die Frage, welche Kategorien wissenschaftlicher Software es gibt und was für Rollen diese im Forschungsprozess spielen. Mit der voranschreitenden Digitalisierung von Forschung und Lehre steigt die Abhängigkeit von Software-Lösungen. Die grundlegenden Prinzipien der „guten wissenschaftliche Praxis“ wie Nachvollziehbarkeit, Reproduzierbarkeit, Transparenz und Qualitätssicherung müssen auch bei der Entwicklung und Nutzung von wissenschaftlicher Software angewandt werden. Allerdings gibt es eine Reihe von Besonderheiten für den Umgang mit Software, da diese im Vergleich zu Veröffentlichungen und Daten einem meist kontinuierlichen Entwicklungsprozess unterliegt und im Kontext spezifischer Entwicklungs- und Laufzeitumgebungen zu betrachten sind.
Darüber hinaus sind die Publikation, Nachnutzbarkeit und Verwertung von Software zentrale Herausforderungen. Die Zitation von Quellcode, die Open Source Software-Entwicklung, die Bereitstellung forschungsnaher Infrastrukturen für Entwicklung und Test sowie die Lizenzen und rechtliche Aspekte der Softwarenachnutzung sind noch nicht umfassend in der wissenschaftlichen Praxis realisiert. Darüber hinaus fehlen auch Anreizsysteme für eine nachhaltige Softwareentwicklung in der Forschung.
Für viele dieser Fragen gibt es Lösungsansätze und „best practice“ Beispiele, auf die eingegangen wird. Seit einiger Zeit gibt es dazu internationale und nationale Initiativen wie u.a. die Software Carpentry (1998, US), das Software Sustainability Institute (2008, GB) und sciforge (2014, D). Des Weiteren unterstützt die Deutsche Forschungsgemeinschaft (DFG) die Entwicklung dieses Gebietes u.a. mit dem Programm ”Research Software Sustainability”.
Keywords: Wissenschaftliche Software, Softwareentwicklung, Publikation, Repositorien, Infrastruktur, Bibliothek, Scientific software, software development, publication, repository, infrastructure
  • Lecture (Conference)
    Internationale Open Access Tage 2017, 11.-13.09.2017, Dresden, Deutschland

Registration No. 26025 - Permalink


Qualification tests of optical coatings in space environment
Pelizzo, M. G.; Corso, A. J.; Tessarolo, E.; Martucci, A.; Donazzan, A.; Böttger, R.; Hübner, R.; Napolitani, E.
Abstract: Optical components such as mirrors, filters and windows need to be tested and qualified to verify their resistance in space environments. Future space missions, such as ESA JUICE and SOLO, will operate in harsh environments, rich of ions and electrons. Experiments and development of appropriate protocols are needed to develop proper radiation-hard components and to qualify them.
Keywords: Ions, Coatings, Radiation effects, Nonhomogeneous media, Reflectivity, Optical filters, Protons

Registration No. 26017 - Permalink


Structural and optical studies of Pr implanted ZnO films subjected to a long-time or ultra-fast thermal annealing
Ratajczak, R.; Mieszczynski, C.; Prucnal, S.; Guziewicz, E.; Stachowicz, M.; Snigurenko, D.; Gaca, J.; Böttger, R.; Wojcik, M.; Heller, R.; Skorupa, W.; Borany, J. V.; Turos, A.
Corresponding author: Ratajczak, R. National Centre for Nuclear Research, A. Soltana 7, 05-400 Otwock, Swierk, Poland
Abstract: Epitaxial thin ZnO films grown by Atomic Layer Depositionwere implanted with 150 keV Pr ions to a fluence of 1 × 1015 at/cm2. Implanted samples were subjected to two different kinds of annealing: rapid thermal annealing (RTA) and millisecond-range flash lamp annealing (FLA). Structural properties of implanted and annealed ZnO and the optical response were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c), High-resolution X-ray diffraction and Photoluminescence Spectroscopy (PL), respectively. The results shown, that both annealing techniques lead to recrystallization of the ZnO lattice, that was damaged during the ion implantation. Upon RTA performed at 800 °C a return of Zn atoms from interstitial to their regular site positions is accompanied by rejection of primarily substitutional Pr atoms to the interstitial sites. Consequently, it leads to the out-diffusion and precipitation of Pr atoms on the surface. In contrast to RTA, the diffusion of implanted Pr during
a millisecond range FLA treatment is completely suppressed. Despite differences in location of Pr inside the ZnO matrix after FLA and RTA, both annealing techniques lead to the optical activation of Pr3+. Interestingly, our RBS/c study for as implanted layers also revealed the anomalous damage peak, called intermediate peak (IP) located between the expected surface and the bulk damage peak. The PL spectra clearly suggest, that the defect which forms the IP, can be assigned to Zn interstitials. The long-time annealing at 800 °C in oxygen atmosphere causes the complete removal of the IP.
Keywords: Zinc oxide Atomic layer deposition Rare-earth Ion implantation Praseodymium Rapid thermal annealing Flash lamp annealing Channeling Rutherford backscattering spectrometry High-resolution X-ray diffraction Photoluminescence

Registration No. 26016 - Permalink


Electrical behaviour of carbon nanotubes under low-energy proton irradiation
Abbe, E.; Schüler, T.; Klosz, S.; Starruß, E.; Pilz, W.; Böttger, R.; Kluge, O.; Schmiel, T.; Tajmar, M.
Corresponding author: Abbe, Elisabeth Institute of Aerospace Engineering, Technische Universität Dresden, Germany
Abstract: Several applications for carbon nanotubes (CNT) have been proposed for space applications in the last years. However, their behaviour in the harsh space environment is mostly unknown. Energetic particles such as protons can influence the material degradation in space. This material damage could result in a system failure of space systems. Therefore it is necessary to investigate the performance of new materials under proton irradiation.

Screen and jet printed disordered single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) and multi-walled carbon nanotubes/resin composites (ME) were exposed to 1 keV, 15 keV and 100 keV protons. The electrical behaviour of the CNT conductor paths was measured during the experiment. After this exposure, the CNTs were analyzed using Raman scattering and a scanning electron microscope (SEM).

Their is a clear evidence that proton radiation can destroy carbon nanotubes and influence their electrical performance.
Keywords: Mulltiwalled carbon nanotubes; Single walled carbon nanotubes; Irradation; Protons; Enviromental behaviour

Registration No. 26014 - Permalink


Inclusion of Incidental Radiation Dose to the Cardiac Atria and Ventricles Does Not Improve the Prediction of Radiation Pneumonitis in Advanced-Stage Non-Small Cell Lung Cancer Patients Treated With Intensity Modulated Radiation Therapy
Wijsman, R.; Dankers, F. J. W. M.; Troost, E. G. C.; Hoffmann, A. L.; van der Heijden, E. H. F. M.; de Geus-Oei, L.-F.; Bussink, J.
Corresponding author: Wijsman, R. UMCN
Abstract: Purpose: To evaluate if inclusion of incidental radiation dose to the cardiac atria and ventricles improves the prediction of Grade ≥3 radiation pneumonitis (RP) in advanced stage non-small cell lung cancer (AS-NSCLC) patients treated with intensity-modulated radiation therapy or volumetric-modulated arc therapy.
Material and methods: Using a bootstrap modelling approach, clinical parameters and dose-volume histogram (DVH) parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction in 188 AS-NSCLC patients.
Results: After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; p=0.004). The MLD showed the highest Spearman correlation coefficient (Rs) for RP (Rs=0.21; p<0.01). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters. After bootstrap modelling, the heart DVH parameters were seldom included in the model predicting Grade ≥3 RP. The optimal model for RP consisted of the parameters: MLD and cardiac comorbidity (area under the curve: 0.71).
Conclusion: Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of AS-NSCLC patients.
Keywords: Non-small cell lung cancer; Intensity-modulated radiation therapy; Volumetric-modulated arc therapy; radiation pneumonitis; cardiac exposure.

Registration No. 26009 - Permalink


Thermally induced magnetic switching in bit-patterned media
Pfau, B.; Günther, C. M.; Hauet, T.; Eisebitt, S.; Hellwig, O.
Corresponding author: Pfau, B. Max-Born-Institut, Max-Born-Str. 2A, 12489 Berlin, Germany
Abstract: We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an analytical model for the thermally activated switching of the islands, we are able to determine the intrinsic magnetic anisotropy of each island and, consequentially, a distribution of anisotropies for the island ensemble investigated. In the distribution, we identify a separated group of islands with a particularly small anisotropy. We attribute this group to islands containing misaligned grains triggering the magnetic reversal. At room temperature and slow field sweep rates, the observed thermal broadening of the switching-field distribution is small compared to the intrinsic broadening. However, we illustrate that thermal fluctuations play a crucial role at high sweep rates by extrapolating our results to technological relevant regimes.

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  • Secondary publication expected from 31.07.2018

Registration No. 26002 - Permalink


Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations
Banerjee, C.; Gruszecki, P.; Klos, J. W.; Hellwig, O.; Krawczyk, M.; Barman, A.
Corresponding author: Hellwig, O. Institute of Physics, Chemnitz University of Technology, Reichenhainer Straße 70, D-09107 Chemnitz, Germany and Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
Abstract: By combining Brillouin light scattering and micromagnetic simulations, we studied the spin-wave (SW) dynamics of a Co/Pd thin film multilayer, which features a stripe domain structure at remanence. The periodic up and down domains are separated by corkscrew type domain walls. The existence of these domains causes a scattering of the otherwise bulk and surface SW modes, which form mode families, similar to a one-dimensional magnonic crystal. The dispersion relation and mode profiles of SWs are measured for the transferred wave vector parallel and perpendicular to the domain axis.

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Registration No. 26001 - Permalink


Radiative and non-radiative de-excitation of slow highly charged ions transmitted through freestanding single layer graphene
Wilhelm, R. A.; Schwestka, J.; Gruber, E.; Heller, R.; Kozubek, R.; Schleberger, M.; Facsko, S.; Aumayr, F.
Abstract: Slow highly charged ions interacting with a solid surface undergo an ultrafast charge exchange combined with a rapid electronic de-excitation within less than 10 fs. These processes involve capture of some 10 electrons, emission of at least some 10 additional electrons from the surface and radiative as well as non-radiative de-excitation of the ion. To investigate the branching ratio of radiative vs. non-radiative de-excitation we measured x-ray emission of highly charged Ar ions with two, one or no K-shell hole(s) when they are transmitted through a freestanding single layer of graphene.
  • Lecture (Conference)
    Conference on Ion-Surface Interactions 2017 (ISI2017), 20.-25.08.2017, Moskau, Russland

Registration No. 25997 - Permalink


Oncoidal granular iron formation in the Mesoarchaean Pongola Supergroup, southern Africa: Textural and geochemical evidence for biological activity during iron deposition
Smith, A. J. B.; Beukes, N. J.; Gutzmer, J.; Czaja, A. D.; Johnson, C. M.; Nhleko, N.
Corresponding author: Smith, A. J. B. University of Johannesburg
Abstract: We document the discovery of the first granular iron formation (GIF) of Archaean age and present textural and geochemical results that suggest these formed through microbial iron oxidation. The GIF occurs in the Nconga Formation of the ca. 3.0–2.8 GacPongola Supergroup in South Africa and Swaziland. It is interbedded with oxide and silicate facies micritic iron formation (MIF). There is a strong textural control on iron mineralization in the GIF not observed in the associated MIF. The GIF is marked by oncoids with chert cores surrounded by magnetite and calcite rims. These rims show laminated domal textures, similar in appearance to microstromatolites. The GIF is enriched in silica and depleted in Fe relative to the interbedded MIF. Very low Al and trace element contents in the GIF indicate that chemically precipitated chert was reworked above wave base into granules in an environment devoid of siliciclastic input. Microbially mediated iron precipitation resulted in the formation of irregular, domal rims around the chert granules. During storm surges, oncoids were transported and deposited in deeper water environments. Textural features, along with positive δ56Fe values in magnetite, suggest that iron precipitation occurred through incomplete oxidation of hydrothermal Fe2+ by iron-oxidizing bacteria. The initial Fe3+-oxyhydroxide precipitates were then post-depositionally transformed to magnetite. Comparison of the Fe isotope compositions of the oncoidal GIF with those reported for the interbedded deeper water iron formation (IF) illustrates that the Fe2+ pathways and sources for these units were distinct. It is suggested that the deeper water IF was deposited from the evolved margin of a buoyant Fe2+aq-rich hydrothermal plume distal to its source. In contrast, oncolitic magnetite rims of chert granules were sourced from ambient Fe2+aq-depleted shallow ocean water beyond the plume.

Registration No. 25996 - Permalink


Imaging of magnetic skyrmions with the PolLux endstation of the Swiss Light Source
Finizio, S.; Wintz, S.; Watts, B.; Raabe, J.
Keywords: magnetism, x-ray microscopy, skyrmions
  • Poster
    Skymag 2017, 02.-05.05.2017, Paris, Frankreich

Registration No. 25992 - Permalink


Frequency- and Amplitude Modulation of Spin-Wave Signals generated in Topological Spin Textures
Wintz, S.; Finizio, S.; Schultheiss, K.; Liersch, V.; Kilibarda, F.; Warnatz, T.; Suszka, A. K.; Warnicke, P.; Wohlhüter, P.; Erbe, A.; Lindner, J.; Raabe, J.; Fassbender, J.ORC
Keywords: magnetism, spin waves, x-ray microscopy
  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Registration No. 25991 - Permalink


In-situ membrane bending setup for the investigation of magnetostrictive materials with XMCD-STXM imaging
Finizio, S.; Wintz, S.; Kirk, E.; Raabe, J.
Keywords: magnetism, magnetostriction, spin dynamics
  • Poster
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Irland

Registration No. 25990 - Permalink


Spin Wave Emission from Topological Spin Textures
Wintz, S.; Sluka, V.; Schneider, T.; Kakay, A.; Weigand, M.; Schultheiss, K.; Warnatz, T.; Mattheis, R.; Gallardo, R. A.; Roldan-Molina, A.; Landeros, P.; Tiberkevich, V.; Slavin, A.; Erbe, A.; Deac, A.; Lindner, J.; Fassbender, J.ORC; Raabe, J.
Keywords: magnetism, spin waves, x-ray microscopy
  • Invited lecture (Conferences)
    Moscow International Symposium on Magnetism, 01.-05.07.2017, Moskau, Russische Föderation

Registration No. 25988 - Permalink


Control of the magnetic vortex core dynamics in magnetostrictive microstructured elements through the Magneto-Elastic coupling
Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Raabe, J.
Keywords: magnetism, vortex, magneto elastic, spin dynamics
  • Lecture (Conference)
    IEEE International Magnetics Conference, 24.-28.04.2017, Dublin, Ireland

Registration No. 25986 - Permalink


Control of the gyration of magnetic vortices by the magneto-elastic effect
Finizio, S.; Wintz, S.; Kirk, E.; Suszka, A.; Gliga, S.; Wohlhüter, P.; Zeissler, K.; Raabe, J.
Corresponding author: Finizio, S. Paul Scherrer Institut
Abstract: The influence of a strain-induced uniaxial magnetoelastic anisotropy on the magnetic vortex core dynamics microstructured magnetostrictive Co40 Fe40 B20 elements was investigated with time-resolved scanning transmission x-ray microscopy. The measurements revealed a monotonically decreasing eigenfrequency of the vortex core gyration with the increasing magnetoelastic anisotropy, which follows closely the predictions from in micromagnetic modeling.
Keywords: magnetism, x-ray microscopy, vortex, spin dynamics

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Registration No. 25984 - Permalink


Holographic vector mesons in a dilaton background
Zöllner, R.; Kämpfer, B.
Abstract: Within a holographic framework, we consider vector mesons riding on a gravity-dilaton background. The latter one is determined directly from a Schr\"odinger equivalent potential which delivers a proper ρ meson Regge trajectory. The mapping on the dilaton potential yields a thermodynamic phase structure with a first-order transition.

Registration No. 25974 - Permalink


Individualized risk assessment in neuroblastoma: does the tumoral metabolic activity on 123I-MIBG SPECT predict the outcome?
Rogasch, J.; Hundsdoerfer, P.; Furth, C.; Wedel, F.; Hofheinz, F.; Krüger, P.; Lode, H.; Brenner, W.; Eggert, A.; Amthauer, H.; Schatka, I.
Corresponding author: Rogasch, J. Department of Nuclear Medicine, Charité - Universitätsmedizin Berlin, Berlin, Germany
Abstract: Purpose

Risk-adapted treatment in children with neuroblastoma (NB) is based on clinical and genetic factors. This study evaluated the metabolic tumour volume (MTV) and its asphericity (ASP) in pretherapeutic 123I-MIBG SPECT for individualized image-based prediction of outcome.

Methods

This retrospective study included 23 children (11 girls, 12 boys; median age 1.8 years, range 0.3–6.8 years) with newly diagnosed NB consecutively examined with pretherapeutic 123I-MIBG SPECT. Primary tumour MTV and ASP were defined using semiautomatic thresholds. Cox regression analysis, receiver operating characteristic analysis (cut-off determination) and Kaplan-Meier analysis with the log-rank test for event-free survival (EFS) were performed for ASP, MTV, laboratory parameters (including urinary homovanillic acid-to-creatinine ratio, HVA/C), and clinical (age, stage) and genetic factors. Predictive accuracy of the optimal multifactorial model was determined in terms of Harrell’s C and likelihood ratio χ2.

Results

Median follow-up was 36 months (range 7–107 months; eight patients showed disease progression/relapse, four patients died). The only significant predictors of EFS in the univariate Cox regression analysis were ASP (p = 0.029; hazard ratio, HR, 1.032 for a one unit increase), MTV (p = 0.038; HR 1.012) and MYCN amplification status (p = 0.047; HR 4.67). The mean EFS in patients with high ASP (>32.0%) and low ASP were 21 and 88 months, respectively (p = 0.013), and in those with high MTV (>46.7 ml) and low MTV were 22 and 87 months, respectively (p = 0.023). A combined risk model of either high ASP and high HVA/C or high MTV and high HVA/C best predicted EFS.

Conclusions

In this exploratory study, pretherapeutic image-derived and laboratory markers of tumoral metabolic activity in NB (ASP, MTV, urinary HVA/C) allowed the identification of children with a high and low risk of progression/relapse under current therapy.
Keywords: Neuroblastoma, Prognosis, 123I-MIBG, Asphericity, Metabolic tumour volume

Registration No. 25969 - Permalink


Specific Features of the Ion-Beam Synthesis of Ge Nanocrystals in SiO2 Thin Films
Tyschenko, I. E.; Cherkov, V. A.; Volodin, V. A.; Voelskow, M.
Corresponding author: Tyschenko, I. E. Rzanov Institut of Semiconductor Physics, Novosibirsk, Russia
Abstract: The systematic features of the formation of Ge nanocrystals in SiO2 thin films implanted with Ge ions and then subjected to high-temperature annealing (1130°C) are studied in relation to hydrostatic pressure. It is established that annealing at atmospheric pressure is accompanied by the diffusion of Ge atoms from the implantation region to the Si substrate and does not induce the formation of Ge nanocrystals. An increase in pressure during annealing yields a deceleration in the diffusion of germanium into silicon and is accompanied by the formation of twinned lamellae at the Si/SiO2 interface (at pressures of ~103 bar) or by the nucleation and growth of Ge nanocrystals (at pressures of ~104 bar) in the SiO2 film. The results are discussed on the basis of the concept of a change in the activation volume of the formation and migration of point defects under conditions of compression.
Keywords: Ion Beam Synthesis, nanocrystals, SiO2

Registration No. 25968 - Permalink


Dynamo action from a laminar non-linear flow in a precessing cylinder
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.
Abstract: Within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) a dynamo experiment is under development in which a precession driven flow of liquid sodium will be used to excite dynamo action. In my presentation I will address preparative numerical simulations and flow measurements conducted at a small model experiment filled with water. The results provide typical flow pattern and flow amplitudes in dependence of precession ratio and Reynolds number and are used for the setup of kinematic dynamo models in order to estimate whether the particular flow is able to drive a dynamo.

In the strongly non-linear regime the flow essentially consists of the directly forced Kelvin mode superimposed by standing inertial waves caused by non-linear self-interaction of the forced mode whereas time-dependent contributions in terms of randomly distributed small-scale noise remain negligible. Most remarkable feature is the occurrence of a resonant-like axisymmetric mode around a precession ratio of Omega_prec/Omega_cyl = 0.1. Only the combination of this axisymmetric mode and the forced m=1 Kelvin mode is capable of driving a dynamo. Our simulations yield a critical magnetic Reynolds number of Rm_c=430 which is well within the regime that will be achieved in the experiment. However, the occurrence of the axisymmetric mode slightly depends on the absolute rotation rate of the cylinder and future experiments are required to indicate whether this instability will persist at the extremely large Re that will be obtained in the large scale experiment.
Keywords: Dynamo Dresdyn
  • Poster
    MREP 2017, 11.-12.09.2017, Cambridge, Great Britain

Registration No. 25966 - Permalink


Horizon 2020 EuPRAXIA design study
Walker, P. A.; Alesini, P. D.; Alexandrova, A. S.; Anania, M. P.; Andreev, N. E.; Andriyash, I.; Aschikhin, A.; Assmann, R. W.; Audet, T.; Bacci, A.; Barna, I. F.; Beaton, A.; Beck, A.; Beluze, A.; Bernhard, A.; Bielawski, S.; Bisesto, F. G.; Boedewadt, J.; Brandi, F.; Bringer, O.; Brinkmann, R.; Bründermann, E.; Büscher, M.; Bussmann, M.; Bussolino, G. C.; Chance, A.; Chanteloup, J. C.; Chen, M.; Chiadroni, E.; Cianchi, A.; Clarke, J.; Cole, J.; Couprie, M. E.; Croia, M.; Cros, B.; Dale, J.; Dattoli, G.; Delerue, N.; Delferriere, O.; Delinikolas, P.; Dias, J.; Dorda, U.; Ertel, K.; Pousa, A. F.; Ferrario, M.; Filippi, F.; Fils, J.; Fiorito, R.; Fonseca, R. A.; Galimberti, M.; Gallo, A.; Garzella, D.; Gastinel, P.; Giove, D.; Giribono, A.; Gizzi, L. A.; Grüner, F. J.; Habib, A. F.; Haefner, L. C.; Heinemann, T.; Hidding, B.; Holzer, B. J.; Hooker, S. M.; Hosokai, T.; Irman, A.; Jaroszynski, D. A.; Jaster-Merz, S.; Joshi, C.; Kaluza, M. C.; Kando, M.; Karger, O. S.; Karsch, S.; Khazanov, E.; Khikhlukha, D.; Knetsch, A.; Kocon, D.; Koester, P.; Kononenko, O.; Korn, G.; Kostyukov, I.; Labate, L.; Lechner, C.; Leemans, W. P.; Lehrach, A.; Li, F. Y.; Li, X.; Libov, V.; Lifschitz, A.; Litvinenko, V.; Lu, W.; Maier, A. R.; Malka, V.; Manahan, G. G.; Mangles, S. P. D.; Marchetti, B.; Marocchino, A.; Ossa, A. M. D. L.; Martins, J. L.; Massimo, F.; Mathieu, F.; Maynard, G.; Mehrling, T. J.; Molodozhentsev, A. Y.; Mosnier, A.; Mostacci, A.; Mueller, A. S.; Najmudin, Z.; Nghiem, P. A. P.; Nguyen, F.; Niknejadi, P.; Osterhoff, J.; Papadopoulos, D.; Patrizi, B.; Pattathil, R.; Petrillo, V.; Pocsai, M. A.; Poder, K.; Pompili, R.; Pribyl, L.; Pugacheva, D.; Romeo, S.; Rossi, A. R.; Roussel, E.; Sahai, A. A.; Scherkl, P.; Schramm, U.; Schroeder, C. B.; Schwindling, J.; Scifo, J.; Serafini, L.; Sheng, Z. M.; Silva, L. O.; Silva, T.; Simon, C.; Sinha, U.; Specka, A.; Streeter, M. J. V.; Svystun, E. N.; Symes, D.; Szwaj, C.; Tauscher, G.; Thomas, A. G. R.; Thompson, N.; Toci, G.; T...
Corresponding author: Schramm, U. HZDR
Abstract: The Horizon 2020 Project EuPRAXIA ("European Plasma Research Accelerator with eXcellence In Applications") is preparing a conceptual design report of a highly compact and cost-effective European facility with multi-GeV electron beams using plasma as the acceleration medium. The accelerator facility will be based on a laser and/or a beam driven plasma acceleration approach and will be used for photon science, high-energy physics (HEP) detector tests, and other applications such as compact X-ray sources for medical imaging or material processing. EuPRAXIA started in November 2015 and will deliver the design report in October 2019. EuPRAXIA aims to be included on the ESFRI roadmap in 2020.
Keywords: Plasma accelerator

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Registration No. 25965 - Permalink


Engineering of optical and electrical properties of ZnO by non-equilibrium thermal processing: The role of zinc interstitials and zinc vacancies
Prucnal, S.; Wu, J.; Berencen, Y.; Liedke, M. O.; Wagner, A.; Liu, F.; Wang, M.; Rebohle, L.; Zhou, S.; Cai, H.; Skorupa, W.
Corresponding author: Prucnal, S.
Abstract: A controlled manipulation of defects in zinc oxide (ZnO) and the understanding of their electronic structure can be a key issue towards the fabrication of p-type ZnO. Zn vacancy (V-Zn), Zn interstitials (I-Zn), and O vacancy (V-O) are mainly native point defects, determining the optoelectronic properties of ZnO. The electronic structure of these defects still remains controversial. Here, we experimentally demonstrate that the green emission in ZnO comes from V-Zn-related deep acceptor and V-Zn-V-O clusters, which is accompanied by the radiative transition between the triplet and the ground singlet state with the excited singlet state located above the CB minimum. Moreover, the I-Zn is identified to be a shallow donor in ZnO, being mainly responsible for the n-type conductivity of non-intentionally doped ZnO.
Keywords: ZnO, flash lamp annealing, defects, photoluminescence, positron annihilation spectroscopy

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  • Secondary publication expected from 21.07.2018

Registration No. 25964 - Permalink


Detecting Threatening States in Laser Beams
Kelling, J.; Juckeland, G.
Abstract: This poster presents our approach to automatic detection of critical failure states in the pulsed Petawatt laser systems DRACO and PENELOPE, used for investigations of exotic states of matter and medical applications. The beam shape is controlled to avoid high destructive energy densities. However, randomly occurring states threatening the device must be detected between pulses and trigger an interlock in the device firing at 10Hz.

The states we are aiming to detect are rare; thus, training data for this category is scarce. To address this, we present two approaches: First, to identify regions of interest based on physical properties of the system and apply a convolutional neural network (CNN) to to identify true positives. Secondly, using CNN-based image segmentation to localize and classify regions of interest.
Keywords: image classification, deep learning, smart laser operation
  • Poster
    Deep Learning Bootcamp 2017, 21.-25.08.2017, Dresden, Deutschland

Registration No. 25962 - Permalink


Efficient Parallel Monte-Carlo Simulations for Large-Scale Studies of Surface Growth Processes
Kelling, J.; Ódor, G.; Weigel, M.; Gemming, G.
Abstract: Lattice Monte Carlo methods are used to investigate far from and out-of-equilibrium systems, including surface growth, spin systems and solid mixtures. Such studies require observations of large systems over long times scales, to allow structures to grow over orders of magnitude, which necessitates massively parallel simulations. This talk presents work done to address the problem of parallel processing introducing correlations in Monte Carlo updates. Studies of the effect of correlations on scaling and dynamical properties of surface growth systems and related lattice gases is investigated further by comparing results obtained by correlation-free and intrinsically correlated simulations. Where the latter, based on a stochastic cellular automaton approach, are of interest because of their high efficiency. The primary subject of study is the Kardar–Parisi–Zhang surface growth in (2+1) dimensions. Key physical insights about this universality class, like precise universal exponent values and exponent relations, obtained from large-scale simulations are presented.
At the end of the talk, I will also speak about my current work at the computational science group at HZDR, which includes problems like frameworkdevelopment, image analysis and related machine learning applications.
Keywords: Lattice Monte Carlo, GPU, Surface Growth, Kardar-Parisi-Zhang
  • Lecture (Conference)
    IHRS NanoNet Annual Workshop 2017, 16.-18.08.2017, Neuklingenberg, Deutschland

Registration No. 25961 - Permalink


Direct Measurement of the Magnetocaloric Effect in La(Fe,Si,Co)13 Compounds in Pulsed Magnetic Fields
Ghorbani Zavareh, M.; Skourski, Y.; Skokov, K. P.; Karpenkov, D. Y.; Zvyagina, L.; Waske, A.; Haskel, D.; Zhernenkov, M.; Wosnitza, J.; Gutfleisch, O.
Corresponding author: Skourski, Y. Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
Abstract: We report on magnetization, magnetostriction, and magnetocaloric-effect measurements of polycrystalline LaFe11.74Co0.13Si1.13 and LaFe11.21Co0.65Si1.11 performed in both pulsed and static magnetic fields. Although the two compounds behave rather differently at low fields (∼5 T), they show quite similar values of the magnetocaloric effect, namely a temperature increases of about 20 K at high fields (50–60 T). The magnetostriction and magnetization also reach very similar values here. We are able to quantify the magnetoelastic coupling and, based on that, apply the Bean-Rodbell criterion distinguishing first- and second-order transitions.

Registration No. 25960 - Permalink


Doubly dressed bosons: Exciton polaritons in a strong terahertz field
Piętka, B.; Bobrovska, N.; Stephan, D.; Teich, M.; Król, M.; Winnerl, S.; Pashkin, A.; Mirek, R.; Lekenta, K.; Morier-Genoud, F.; Schneider, H.; Deveaud, B.; Helm, M.; Matuszewski, M.; Szczytko, J.
Corresponding author: Piętka, B.
Abstract: We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.
Keywords: ultrastrong coupling regime, dressed states, exciton polaritons

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Registration No. 25959 - Permalink


Observation of Reactive Transport in Soil Columns with Positron Emission Tomography (GeoPET)
Kulenkampf, J.; Stoll, M.; Gründig, M.; Mansel, A.; Lippmann-Pipke, J.
Abstract: Here we investigate reactive transport in soils with GeoPET as quantitative spatiotemporal molecular imaging method. As PET directly yields tracer concentrations, the data can be utilised for parameterization and validation of reactive transport computer models.
Artificial soil columns (sand/silt/clay/Goethit, length 90 mm, diameter 40 mm) have been prepared under CO2-atmosphere. Four different experiments on one and the same soil column are shown as motion pictures from the GeoPET-observations:
1) Injection of water, labelled with [18F]KF, into the CO2-saturated column
2) Conservative transport of [18F]KF solution through the water-saturated column
3) Injection of the reactive tracer [64Cu]Cu(MCPA)2 into the unconditioned water-saturated column
4) Injection of the reactive tracer [64Cu]Cu(MCPA)2 into the preconditioned column.

The study was supported within the framework of the priority program “Biogeochemical Interfaces in Soil” by the German Science Foundation (DFG SPP 1315: KE508/19 and LI872/5).

References:
Kulenkampff, J., Zakhnini, A., Gründig, M., and Lippmann-Pipke, J.: Quantitative experimental monitoring of molecular diffusion in clay with positron emission tomography, Solid Earth, 7, 1207-1215, 2016.
Kulenkampff, J., Gründig, M., Zakhnini, A., Gerasch, R., and Lippmann-Pipke, J.: Process tomography of diffusion, using PET, to evaluate anisotropy and heterogeneity, Clay Miner., 50, 369–375, 2015.
Kulenkampff, J., Gründig, M., Zakhnini, A., and Lippmann-Pipke, J.: Geoscientific process monitoring with positron emission tomography (GeoPET), Solid Earth, 7, 1217–1231, 2016.
Zakhnini, A., Kulenkampff, J., Sauerzapf, S., Pietrzyk, U., and Lippmann-Pipke, J.: Monte Carlo simulations of GeoPET experiments: 3D images of tracer distributions (18F, 124I and 58Co) in Opalinus Clay, anhydrite and quartz, Comput. Geosci., 57, 183–196, 2013.
Lippmann-Pipke, J., Gerasch, R., Schikora, J., and Kulenkampff, J.: Benchmarking PET for geoscientific applications: 3D quantitative diffusion coefficient estimation in clay rock, Comput. Geosci. 101, 21-27, 2017.
Stoll, M., Kulenkampff, J., Gründig, M., Lippmann-Pipke, J., and Kersten, M.: Molecular positron emission tomography imaging of Cu mobility enhanced by the herbicide 4-chloro-2-methylphenoxy-acetic acid in a soil column, submitted
Lippold, H., Karimzadeh L., Kulenkampff, J. Wissmeier, L., Stuhlfauth, C., Stoll, M., Lippmann-Pipke, L.: Effect of pH on the mobility of the herbicide MCPA in a goethite-sand matrix: 1D and 2D reactive transport modelling, to be submitted
Keywords: PET, reactive transport, soil, tomography

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Registration No. 25957 - Permalink


Origin of perpendicular magnetic anisotropy in Co/Ni multilayers
Arora, M.; Hübner, R.; Suess, D.; Heinrich, B.; Girt, E.
Corresponding author: Arora, M. Simon Fraser University
Abstract: We studied the variation in perpendicular magnetic anisotropy of (111) textured Au/N×[Co/Ni]/Au films as a function of the number of bilayer repeats N. The ferromagnetic resonance and superconducting quantum interference device magnetometer measurements show that the perpendicular magnetic anisotropy of Co/Ni multilayers first increases with N for N≤10 and then moderately decreases for N>10. The model we propose reveals that the decrease of the anisotropy for N<10 is predominantly due to the reduction in the magnetoelastic and magnetocrystalline anisotropies. A moderate decrease in the perpendicular magnetic anisotropy for N>10 is due to the reduction in the magnetocrystalline and the surface anisotropies. To calculate the contribution of magnetoelastic anisotropy in the Co/Ni multilayers, in-plane and out-of-plane x-ray diffraction measurements are performed to determine the spacing between Co/Ni (111) and (220) planes. The magnetocrystalline bulk anisotropy is estimated from the difference in the perpendicular and parallel g factors of Co/Ni multilayers that are measured using the in-plane and out-of-plane ferromagnetic resonance measurements. Transmission electron microscopy has been used to estimate the multilayer film roughness. These values are used to calculate the roughness-induced surface and magnetocrystalline anisotropy coefficients as a function of N.

Registration No. 25956 - Permalink


Combining Absorption and Emission Spectroscopy for the Detection and Characterization of Rare Earth Elements
Jakob, S.; Fuchs, M.; Gloaguen, R.
Abstract: In the last decade, the fast development of technology and high-tech industry distinctly increased the demand of Rare Earth Elements (REEs). The combination with the globally strongly concentrated distribution of production sites classifies REEs as critical raw materials and raises the need for the exploration of complex deposits with lower concentrations or remote locations. Spectroscopic methods are the key for an advanced, fast and non-invasive approach to reduce the economic and ecologic costs of REE characterization, not only within exploration, but along the whole raw material value chain. 
Currently, the research of spectral detection and characterization of REEs is concentrated on absorption spectroscopy. Although a considerable amount of REEs can be detected by their characteristic reflectance spectrum, the commonly low intensity of characteristic absorption limits its applicability for robust detection and characterization to a few REEs, such as Neodymium and Samarium.
In the past decades, studies were conducted to characterize REE crystals by their fluorescence properties. In contrast to absorption spectroscopy, an emission is induced in the sample using a laser with a defined excitation wavelength to maximize the response that depends on the investigated material. With emission spectroscopy, a broad set of REEs can be characterized, but still, the attribution of emission features is challenging, as it depends on crystal structure and experimental parameters.
Hereby, we propose a new approach for combining absorption and emission spectroscopy to characterize REEs and overcome the limitations of the single method. For that, we first investigated single REE crystal standards with different bindings using absorption as well as emission spectroscopy. The results can be used to create a library or decision routine for the detection of REE using combined absorption and emission spectroscopy. We will then test the proposed method on natural REE bearing samples, which are additionally characterized chemically and mineralogically to provide a proper validation. Hereby, the influence of the mineral matrix, natural crystal structure and mixed REE composition can be estimated and overcome by using lasers with different stimulation wavelengths in the UV and visible range of the spectrum. Absorption spectroscopy is conducted by point measurements with a reflectance spectrometer as well as with hyperspectral cameras. We developed the tools for processing and the analysis of the spectral data to ensure a fast and robust interpretation of the spectral features.
First results show the detectability of Dy, Er, Ho, Nd, Pr, Sm, and Tm with absorption and the detection of Er, Eu, Ho, Nd, Pr, Tb, and Yb with emission spectroscopy. Additionally, for REEs having spectral signatures in both cases, absorption features overprint the emission spectra within the broad fluorescence signal of the mineral matrix. They coincide with known and measured absorption features of the specific REEs. This, the integration of both features remarkably increases the detectability and the robustness of detection for those elements.
  • Lecture (Conference)
    10th EARSeL SIG Imaging Spectroscopy Workshop, 19.-21.04.2017, Zürich, Switzerland

Registration No. 25955 - Permalink


Nanorattles with tailored electric field enhancement
Schnepf, M. J.; Mayer, M.; Kuttner, C.; Tebbe, M.; Wolf, D.; Dulle, M.; Altantzis, T.; Formanek, P.; Förster, S.; Bals, S.; König, T. A. F.; Fery, A.
Corresponding author: Fery, A.
Abstract: Nanorattles are metallic core-shell particles with core and shell separated by a dielectric spacer. These nanorattles have been identified as a promising class of nanoparticles, due to their extraordinary high electric-field enhancement inside the cavity. Limiting factors are reproducibility and loss of axial symmetry owing to the movable metal core; movement of the core results in fluctuation of the nanocavity dimensions and commensurate variations in enhancement factor. We present a novel synthetic approach for the robust fixation of the central gold rod within a well-defined box, which results in an axisymmetric nanorattle. We determine the structure of the resulting axisymmetric nanorattles by advanced transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Optical absorption and scattering cross-sections obtained from UV-vis-NIR spectroscopy quantitatively agree with finite-difference time-domain (FDTD) simulations based on the structural model derived from SAXS. The predictions of high and homogenous field enhancement are evidenced by scanning TEM electron energy loss spectroscopy (STEM-EELS) measurement on single-particle level. Thus, comprehensive understanding of structural and optical properties is achieved for this class of nanoparticles, paving the way for photonic applications where a defined and robust unit cell is crucial.

Registration No. 25954 - Permalink


Magnetic flow control in growth and casting of photovoltaic silicon: Numerical and experimental results
Poklad, A.; Pal, J.; Galindo, V.ORC; Grants, I.; Heinze, V.; Meier, D.; Pätzold, O.; Stelter, M.; Gerbeth, G.
Corresponding author: Galindo, V. HZDR
Abstract: A novel, vertical Bridgman-type technique for growing multi-crystalline silicon ingots in an induction furnace is described. In contrast to conventional growth, a modified setup with a cone-shaped crucible and susceptor is used. A detailed numerical simulation of the setup is presented. It includes a global thermal simulation of the furnace and a local simulation of the melt, which aims at the influence of the melt flow on the temperature and concentration fields. Furthermore, seeded growth of cone-shaped Si ingots using either a monocrystalline seed or a seed layer formed by pieces of poly-Si is demonstrated and compared to growth without seeds. The influences of the seed material on the grain structure and the dislocation density of the ingots are discussed. The second part addresses model experiments for the Czochralski technique using the room temperature liquid metal GaInSn. The studies were focused on the influence of a rotating and a horizontally static magnetic field on the melt flow and the related heat transport in crucibles being heated from bottom and/or side, and cooled by a crystal model covering about 1/3 of the upper melt surface.
Keywords: Magnetic flow control, Crystall-Growth, Photovoltaic Silicon, Numerical Simulation

Registration No. 25951 - Permalink


The effect of the initial microstructure in terms of sink strength on the ion-irradiation-induced hardening of ODS alloys studied by nanoindentation
Duan, B.; Heintze, C.; Bergner, F.ORC; Ulbricht, A.; Akhmadaliev, S.; Oñorbe, E.; de Carlan, Y.; Wang, T.
Corresponding author: Bergner, F. HZDR
Abstract: Oxide dispersion strengthened (ODS) Fe-Cr alloys are promising candidates for structural components in nuclear energy production. The small grain size, high dislocation density and the presence of particle matrix interfaces may contribute to the improved irradiation resistance of this class of alloys by providing sinks and/or traps for irradiation-induced point defects. The extent to which these effects impede hardening is still a matter of debate. To address this problem, a set of alloys of different grain size, dislocation density and oxide particle distribution were selected. In this study, three-step Fe-ion irradiation at both 300 C and 500 C up to 10 dpa was used to introduce damage in five different materials including three 9Cr-ODS alloys, one 14Cr-ODS alloy and one 14Cr-non-ODS alloy. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), small angle neutron scattering (SANS), and nanoindentation testing were applied, the latter before and after irradiation. Significant hardening occurred for all materials and temperatures, but it is distinctly lower in the 14Cr alloys and also tends to be lower at the higher temperature. The possible contribution of Cr-rich alpha’-phase particles is addressed. The impact of grain size, dislocation density and particle distribution is demonstrated in terms of an empirical trend between total sink strength and hardening.
Keywords: Oxide dispersion strengthened alloys, Ion irradiation, Nanoindentation, Hardening, Sink strength

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  • Secondary publication expected from 15.08.2018

Registration No. 25950 - Permalink


Microstructure characterization and strengthening mechanisms of oxide dispersion strengthened (ODS) Fe-9%Cr and Fe-14%Cr extruded bars
Chauhan, A.; Bergner, F.ORC; Etienne, A.; Aktaa, J.; de Carlan, Y.; Heintze, C.; Litvinov, D.; Hernandez-Mayoral, M.; Oñorbe, E.; Radiguet, B.; Ulbricht, A.
Corresponding author: Bergner, F. HZDR
Abstract: The collaborative study is focused on the relationship between microstructure and yield stress for an ODS Fe-9%Cr-based transformable alloy and an ODS Fe-14%Cr-based ferritic alloy. The contributions to the total room temperature yield stress arising from various strengthening mechanisms are addressed on the basis of a comprehensive description of the microstructures uncovered by means of transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), small-angle neutron scattering (SANS) and atom probe tomography (APT). While these methods provide a high degree of complementarity, a reasonable agreement was found in cases of overlap of information. The derived set of microstructure parameters along with reported strengthening equations was used to calculate the room temperature yield stress. The estimates were critically compared with the measured yield stress for an extended set of alloys including data reported for Fe-Cr model alloys and steels thus covering one order of magnitude or more in grain size, dislocation density, particle density and yield stress. The comparison shows that particle strengthening, dislocation forest strengthening, and Hall-Petch strengthening are the major contributions and that a mixed superposition rule reproduces the measured yield stress within experimental scatter for the whole extended set of alloys. The wide variation of microstructures additionally underpins the conclusions and goes beyond previous work, in which one or few ODS steels and narrow microstructure variations were typically covered.
Keywords: ODS steel, Strengthening mechanisms, TEM, APT, SANS

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  • Secondary publication expected from 01.08.2018

Registration No. 25949 - Permalink


Modeling electromagnetically driven free-surface flows motivated by the Ribbon Growth on Substrate (RGS) process
Beckstein, P.; Galindo, V.ORC; Schönecker, A.; Gerbeth, G.
Corresponding author: Beckstein, Pascal HZDR
Abstract: The Ribbon Growth on Substrate (RGS) technology is a crystallization technique that allows direct casting of silicon wafers and sheets of advanced metal-silicide compounds. With the potential of reaching high crystallization rates, it promises a very efficient approach for future photo-voltaic silicon wafer production compared to well-established processes in industry. However, a number of remaining problems, like process stability and controllability, need to be addressed for the RGS technology to eventually become a competitor in the near future. In this regard, it is very desirable to gain detailed insights into the characteristic process dynamics. To comply with this demand, we have developed a new numerical tool based on OpenFOAM (foam-extend), capable of simulating the free-surface dynamics of the melt flow under the influence of an applied alternating magnetic field. Our corresponding model thereby resolves the interaction of hydrodynamic and magnetodynamic effects in three-dimensional space. Although we currently focus on the RGS process, the modeling itself has been formulated in a more general form, which may be used for the investigation of similar problems, too. Here we provide a brief overview of these developments.
Keywords: RGS process, OpenFOAM, electromagnetic driven flow, foam-extend, free-surface

Registration No. 25948 - Permalink


Validation of X-ray radiography for characterization of gas bubbles in liquid metals
Keplinger, O.; Shevchenko, N.; Eckert, S.
Corresponding author: Eckert, S.
Abstract: X-ray radiography has proved to be an efficient and powerful tool for the visualization of two-phase flows in non-transparent fluids, in particular in liquid metals. This paper presents a validation of the X-ray radiography by comparing measurements in water with corresponding results obtained by optical methods. For that purpose Ar bubbles were injected through a single orifice. The measurements results are compared in terms of bubble size, bubble shape and velocity. Furthermore, visualization experiments were performed in the eutectic alloy GaInSn where the image contrast between the liquid phase and the gas bubble is much stronger. Some obvious differences of the bubble dynamics in water and GaInSn are discussed.
Keywords: X-ray radiography, two-phase flows, GaInSn, water

Registration No. 25946 - Permalink


Spins in Formation
Schultheiss, H.
Abstract: Spinwellen sind kollektive Anregungen magnetischer Momente eines Festkörpers. Lokal lassen sie sich auf sehr kleinen Längenskalen lenken durch ein Drehen der Magnetisierung. Damit ist es möglich, den Fluss von Spinwellen gezielt zu steuern. Dieser Vorgang könnte in der Informationstechnologie als Logik- baustein Anwendung finden.
Keywords: Spintronic, Magnonic
  • Physik Journal 09(2017), 59

Registration No. 25945 - Permalink


THz Nonlinear Response of Landau-Quantized Graphene
König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.
Abstract: The third-order nonlinear susceptibility of Landau-quantized graphene is studied by degenerate time-integrated four-wave mixing in the THz regime. The revealed resonance behavior and the observed field dependencies are in agreement with our theoretical calculations.
Keywords: graphene, Landau-quantized graphene, nonlinear optics, carrier dynamics, spectroscopy
  • Lecture (Conference)
    CLEO, 14.-19.05.2017, San Jose, USA

Registration No. 25941 - Permalink


Influence of structural quality on the carrier dynamics in graphene
König-Otto, J. C.; Schneider, H.; Helm, M.; Winnerl, S.
Abstract: Production of large-scale high quality graphene is a challenging task. Therefore understanding how quality will influence the properties of graphene is crucial for industrial applications. In this work we focus on the influence of defects on the carrier dynamics. To this end areas of a multilayer epitaxial graphene sample with high structural quality [1] are irradiated with different doses of low energy carbon ions. The different areas with now varying graphene quality (see D-Peaks in Raman spectra in Figure 1) are studied by a pump-probe experiment utilizing low energetic photons from a free-electron laser (photon energy 75meV). In this regime carrier relaxation is particularly slow as compared to excitation with visible light since scattering with optical phonons (energy 200meV) is efficiently suppressed [2]. The change in transmission is depicted in Figure 2 for three different structural qualities. One can directly see that the relaxation in the damaged areas is significantly faster than in the pristine graphene. This might be an indication for the presence of the intensively discussed supercollisions in graphene [3].
References
[1] C. Berger et al., Science 312, 1191 (2006).
[2] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[3] J. C. W. Song et al., Phys. Rev. Lett. 109, 106602 (2012).
Keywords: graphene, defects, carrier dynamics
  • Poster
    Graphene2017, 28.-31.03.2017, Barcelona, Espana

Registration No. 25940 - Permalink


Landau-Quantized Graphene: A Tunable Nonlinear Optical Material in the THz Range
König-Otto, J. C.; Wang, Y.; Belyanin, A.; Berger, C.; de Heer, W. A.; Orlita, M.; Pashkin, A.; Schneider, H.; Helm, M.; Winnerl, S.
Abstract: Finding nonlinear optical materials for the THz and mid-infrared regimes is not straightforward. State-of-the-art devices with a high third-order optical susceptibility are often processed as complex multiquantum-well structures designed to feature one specific resonance frequency. In our work we study Landau-quantized graphene as a tunable and simple to produce nonlinear material. To this end we perform time-integrated degenerate four-wave mixing (FWM) experiments at a photon energy of 78 meV resonant to the transitions between the Landau levels LL−1, LL0 and LL1 at a magnetic field of roughly 4 T. We can recover expected scaling of the FWM-signal with the incident fields and the resonance behavior. The value of the third-order surface susceptibility in this material is in agreement with our calculations based on the density matrix formalism. We find the order of 𝜒(3) of Landau-quantized graphene to be competitive with more complex and elaborated solutions.
Keywords: graphene, Landau-quantized graphene, nonlinear optics, carrier dynamics, spectroscopy
  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Registration No. 25939 - Permalink


“Brothers in Arms” – HIF High-Speed PIXE and MEGA Spectrometer
Renno, A. D.ORC; Buchriegler, J.; Dreßler, S.; Hanf, D.; Munnik, F.; Scharf, O.; Ziegenrücker, R.
Abstract: In a fast growing world with increasing demand on resources like high-tech metals as In, Ga, Ge, or rare earth elements (REE), mineralogists and economic geologists need faster and automated analytical tools to explore mineral deposits, make them accessible and define necessary initial data for all subsequent processing steps. Next to the necessary knowledge in which phases the elements of interest, ecotoxical as well as deleterious elements are concentrated, it is important to determine structural parameters like grain sizes and possible intergrowths relations of these minerals. These are typical geometallurgical analytical tasks, which are so far routinely performed by electron beam based methods of automated mineralogy, like MLA (mineral liberation analysis) or QEMSCAN, with their advantages and disadvantages. The methodological problems of these type of methods are, for example, the necessary measurement time, insufficient limits of detection (no trace element detection) and high background (electron Bremsstrahlung).

Some of these hurdles can be overcome by using alternative excitation radiation, like ions, known as particle-induced X-ray emission (PIXE) or X-rays, known as X-ray fluorescence (XRF). Combining these with a full-field detection system, such as the so-called SLcam®[1], allows the determination of trace element distributions in reasonable time over a large field of view.

The SLcam® consists of a 12 x 12 mm², X-ray sensitive pnCCD chip with 69696 pixels. A high read-out speed of up to 1000 Hz, allows the acquisition of complete X-ray spectra (2-20 keV) on each pixel simultaneously, with an energy resolution of around 160 eV (@ Mn-K even for high photon fluxes. A poly-capillary lens is used to guide the X-rays from their point of origin on the sample to the corresponding pixel on the detector-chip. Usage of a straight 1:1 lens results in a lateral resolution better than 100 µm.

The MEGA spectrometer is equipped with a laboratory-scale X-ray tube. XRF is used for the determination of major and trace element data. It’s “small”, table-top like size would in principle allow to use the set-up directly at the mining site. The so called High-Speed PIXE[2] uses a broad proton beam to excite the fluorescence radiation. Samples with a total weight of up to 10 kg and a maximum size 25 x 25 x 2.5 cm³ can be mounted in a dedicated vacuum sample chamber. The instrument is installed at the Ion Beam Center at the Helmholtz-Zentrum Dresden-Rossendorf. The advantages and disadvantages of both instruments will be presented, as well as first results of combined qualitative studies of the distribution of trace elements in representative samples to demonstrate the importance of these innovative concepts for geometallurgical research.

[1] Scharf, O., et al. (2011). Compact pnCCD-Based X-ray Camera with High Spatial and Energy Resolution: A Color X-ray Camera. Analytical Chemistry, 83(7), 2532–2538.
[2] Hanf, D., et al. (2016). A new particle-induced X-ray emission set-up for laterally resolved analysis over wide areas. Nuclear Instruments and Methods in Physics Research B, 377, 7-24.
Keywords: PIXE, High-Speed PIXE, XRF, Trace Elemenet Analysis
  • Poster
    2nd International Conference on Applied Mineralogy & Advanced Materials and 13th International Conference on Applied Mineralogy, 05.-09.06.2017, Castellaneta Marina- Taranto, Italy

Registration No. 25937 - Permalink


Transglutaminase 2 als molekulares Target zur funktionellen Bildgebung von Tumoren ─ Untersuchungen zu Inhibitoren und fluorogenen Substraten
Wodtke, R.
Abstract: Die TGase 2 ist ein konstitutiv exprimiertes Enzym, dessen bekannteste Funktion in der posttranslationalen Modifizierung von Proteinen durch Ca2+-abhängige Transamidierung zwischen proteingebundenen Glutaminyl-Resten und verschiedenen primären Aminen liegt. Obwohl ursprünglich namensgebend, wird diese Quervernetzungsfunktion des Proteins erst in zellulären Stresssituationen wie der Apoptose oder der Wundheilung aktiviert. Folglich erscheint es nicht überraschend, dass der TGase 2 und vor allem der Glutamyltransferase-Aktivität auch in diversen pathophysiologischen Prozessen eine große Bedeutung zukommt. Für diese Arbeit stand die Beteiligung der TGase 2 in tumorassoziierten Prozessen im Fokus. So ist bekannt, dass eine gesteigerte Expression der TGase 2 einen entscheidenden Beitrag zum Überleben, zur Resistenz gegenüber Chemo- und Strahlentherapie sowie zum Metastasierungspotential neoplastischer Zellen liefert. Dabei wurde das Enzym als ein Schlüsselprotein für die Progression zahlreicher Krebsarten identifiziert. Somit stellt das Enzym ein interessantes Target für die funktionelle Bildgebung von Tumoren mittels Positronen-Emissions-Tomographie (PET) sowie der Therapie von Tumorerkrankungen dar.
Die Zielstellungen dieser Arbeit waren durch die Entwicklung von Radiotracern für die TGase 2 motiviert, um perspektivisch mit Hilfe der nicht-invasiven Bildgebungsmodalität PET Aufschlüsse über die Relevanz des Proteins, die Bedeutung von dessen Glutamyltransferase-Aktivität in Tumoren sowie dessen molekulare Adressierbarkeit in vivo (auch im Hinblick auf therapeutische Anwendungen) zu erhalten. Dementsprechend setzt sich die vorliegende Dissertation aus zwei inhaltlichen Schwerpunkten zusammen:
• Der erste Teil befasst sich mit der Etablierung eines fluorimetrischen TGase 2-Assays einschließlich der Synthese und kinetischen Charakterisierung fluorogener Substrate als Voraussetzung für die Identifizierung und Charakterisierung von Molekülen, die zur Adressierung der TGase 2 hinsichtlich molekularer Bildgebung und therapeutischer Hemmung bestimmt sind
• Der zweite Teil beinhaltet die Entwicklung sowie enzymkinetische Charakterisierung, einschließlich Struktur-Wirkungsbeziehungen, irreversibler TGase 2-Inhibitoren als potentielle Radiotracerkandidaten. Darüber hinaus sollte eine initiale pharmakokinetische Evaluierung der Verbindungen in vitro erfolgen.

Fluorimetrischer TGase 2-Assay

Der literaturbekannte Acyldonor 2a, der durch TGase 2-vermittelte Umsetzung das stark fluoreszierende 7-Hydroxycumarin freisetzt, ist ein attraktives Substrat für Untersuchungen zur TGase 2 mittels fluorimetrischen Assays. Allerdings weist 2a nur eine geringe Löslichkeit im wässrigen Milieu auf (<10 µM). Dies schränkt sowohl die detaillierte kinetische Untersuchung der Verbindung als auch darauf beruhende Anwendungen der Verbindung ein. Daher wurden Acyldonoren auf der Basis kleiner Glutamat enthaltender Peptide entwickelt, bei denen die freie Carboxylgruppe löslichkeitsvermittelnd wirken sollte. Die Synthese der Verbindungen erfolgte mit einer modularen Synthesestrategie an einem polymeren Träger (Festphasensynthese). Alle Verbindungen konnten in ausreichenden Ausbeuten und hohen Reinheiten dargestellt werden. Die Untersuchungen zur Löslichkeit zeigten, dass die Verbindungen bis zu Konzentrationen von 250 µM im wässrigen Milieu löslich sind. Diese erheblich verbesserte Wasserlöslichkeit erlaubte die ausführliche kinetische Charakterisierung der neuartigen fluorogenen Substrate hinsichtlich ihrer TGase 2-katalysierten Hydrolyse und Aminolyse. Z-Glu(HMC)-Gly-OH (5b) erwies sich dabei als Cumarinylester mit den günstigsten Substrateigenschaften gegenüber humaner TGase 2 und kann darüber hinaus auch zur Charakterisierung weiterer Isoformen der Transglutaminase-Familie genutzt werden. Die Eignung von 5b zur Charakterisierung irreversibler Inhibitoren wurde ebenfalls demonstriert. Somit liegt nun eine verlässliche Assay-Methode zur Bewertung des Hemmpotentials und der Selektivität von TGase 2-gerichteten Inhibitoren vor.

Nε-Acryloyllysine als irreversible Inhibitoren der TGase 2

Für die Entwicklung potentieller Radiotracer wurden irreversible Inhibitoren der TGase 2 als geeigneter Ausgangspunkt erachtet. In diesem Zusammenhang wurde das Nε-Acryloyllysinpiperazid 8a in der Literatur beschrieben, das neben einem hohen inhibitorischen Potential eine ausgezeichnete Selektivität sowie vielversprechende pharmakokinetische Eigenschaften aufweist. Daher wurde dieser Inhibitor zur Leitverbindung für das Design von potentiellen Radiotracern bestimmt. Die geplanten Strukturvariationen sollten daher vor allem Funktionalisierungen mit Fluor beinhalten, die auch eine Synthese der entsprechenden Fluor-18-Analoga ermöglichen. Zusätzlich sollten Modifikationen durchgeführt werden, die das Aufdecken von Struktur-Wirkungsbeziehungen erlauben. Zu diesem Zweck wurde eine modulare Syntheseroute entworfen, die sich aus den folgenden Schritten zusammensetzt: Nε-Acryloylierung von Nα-Boc-Lysin, Amidknüpfung mit dem jeweiligen Piperazinbaustein, Boc-Entschützung und Nα-Acylierung. Die benötigten Piperazinbausteine wurden in wenigen Syntheseschritten synthetisiert oder waren kommerziell erhältlich. Mit dieser Syntheseroute konnten schließlich 56 neue Inhibitoren der TGase 2 in hohen Reinheiten hergestellt werden.
Die kinetische Charakterisierung der Verbindungen erfolgte mit dem zuvor etablierten fluorimetrischen TGase 2-Assay unter Nutzung des Acyldonors 5b. Die Charakterisierung des (R)-konfigurierten Enantiomers von 8a belegte zunächst den deutlichen Vorteil der (S)-Konfiguration am Cα-Atom des Lysyl-Restes hinsichtlich des inhibitorischen Potentials gegenüber TGase 2. Die systematisch durchgeführten Strukturvariationen ermöglichten die Aufdeckung verschiedener quantitativer Struktur-Wirkungsbeziehungen. Einige der Strukturvariationen führten sogar zu Inhibitoren mit größerem inhibitorischen Potential als das der Leitverbindung. Die beste Toleranz gegenüber der Einführung von Fluor wurde durch Substitution des H-Atoms in ortho-Position der Phenylacetylgruppe sowie der Methylgruppe am Pyridinring der Leitverbindung erreicht (Verbindungen 9b und 20).
Zur initialen pharmakokinetischen Einschätzung der TGase 2-Inhibitoren wurden die Permeabilitätseigenschaften aller Verbindungen mittels PAMPA-Methode untersucht. Dabei wurden unter anderem Inhibitoren identifiziert, die schlecht permeabel sind und somit wahrscheinlich ausschließlich die extrazelluläre TGase 2 adressieren können. Dies ist im Hinblick auf die differentielle Betrachtung von intra- und extrazellulärer TGase 2, vor allem mittels molekularer Bildgebung in vivo, von großer Bedeutung.
  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Prof. Dr. Jörg Steinbach, Dr. Reik Löser
    285 Seiten

Registration No. 25930 - Permalink


Simultaneous Excitation of a TE011- and a TM010-Mode in a 3.5 Cell SRF Gun Cavity
Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Ciovati, G.; Forehand, D.; Kneisel, P.; Turlington, L.
Abstract: For future linear CW accelerators, superconducting (SC) RF guns are discussed to be the most promising solution to fulfil the demands on high average current and high brightness at the same time. But in difference to the NCRF guns, the application of static magnetic fields near the cathode to compensate for space charge forces is not possible. Instead, magnetic fields of transverse electric (TE) modes excited in parallel to the accelerating mode were proposed. Experiments at the 1st Rossendorf SRF gun using the existing fundamental mode coupler in combination with a RF diplexer have shown that this is feasible. However, since the cavity was not designed for this purpose, the mode was strongly damped by HOM couplers and cavity beam tubes and thus only low field strength could be achieved. In this contribution we will present a modified cavity design that avoids these problems and provides a separate RF coupler for the TE mode. Additionally, we will report on the first vertical test that demonstrated the functionality of the whole RF setup as well as realized significant higher field of the excited TE011 mode in parallel to the TM010 mode.
Keywords: SRF gun, superconducting RF injector, ELBE, electron source, TE mode, RF focussing, emittance compensation
  • Poster
    18th International Conference on RF Superconductivity, 17.-21.07.2017, Lanzhou, China

Registration No. 25929 - Permalink


Beam Parameter Measurements of the 2nd 3.5 Cell SRF Gun for ELBE
Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.
Abstract: In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In this contribution we will report on the commissioning of the SRF gun by presenting detailed beam parameter measurements up to a bunch charge of 300 pC. Additionally, we will report the results of the first two user experiments (neutron and THz generation) that demonstrated the reliability of this gun concept.
Keywords: SRF gun, superconducting RF injector, ELBE, electron source
  • Poster
    The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 18.-23.06.2017, Genf, Schweiz

Registration No. 25928 - Permalink


The FLUKA Monte Carlo simulation package and its applications at the HZDR
Müller, S. E.
Abstract: Vorstellung der FLUKA Monte Carlo Simulations Software und deren Anwendungen am HZDR
Keywords: FLUKA, Radiation Transport, HZDR
  • Lecture (Conference)
    VKTA KS-Klausurberatung, 08.-09.08.2017, Lohmen, Germany

Registration No. 25927 - Permalink


Commissioning and RF Results of the Second 3.5 Cell Rossendorf SRF Gun
Arnold, A.; Freitag, M.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.; Kneisel, P.; Ciovati, G.; Turlington, L.
Abstract: In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In this contribution we will report on the commissioning of the SRF gun by presenting a full set of RF performance results.
Keywords: SRF gun, superconducting RF injector, ELBE, electron source
  • Poster
    The 59th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 18.-23.06.2017, Genf, Schweiz

Registration No. 25926 - Permalink


Development and characterization of human melanoma cell lines and xenograft models exhibiting different levels of transglutaminase 2
Hauser, S.; Aepler, J.; Pufe, J.; Wodtke, R.; Pietsch, M.; Löser, R.; Pietzsch, J.
Abstract: Tissue transglutaminase (TGase 2) is involved in the progression of many different tumor entities, including malignant melanoma, via antiapoptotic processes and mechanisms supporting cellular survival, adhesion, and epithelial-mesenchymal transition [1]. Accordingly, it has been shown that TGase 2 expression is higher in metastatic and chemoresistant tumors compared to primary tumors, underlining its role during tumor progression [2]. Therefore, TGase 2 represents an interesting target for the development of selective inhibitors for theranostics of progressive malignant melanoma. In order to evaluate potent candidate compounds in vitro and in vivo, suitable transgenic melanoma cell lines and xenograft models with different TGase 2 expression and activity were developed.
A375 and MeWo cells, two human malignant melanoma cell lines with high and very low TGase 2 expression, respectively, were stably transfected with a lentiviral pHATtrick-mCherry vector (mCherry control cells) and a lentiviral pHATtrick-TGase 2 vector (TGase 2 cells). The resulting cell lines differed in their TGase 2 expression and activity, as determined by Western Blotting and fluorescence anisotropy assay [3]. Transfection and overexpression of TGase 2 did not influence cell proliferation behavior. 5×106 cells of each cell line were injected subcutaneously in athymic nude mice (NMRI-Foxn1nu) to form tumor xenografts that differed in their growth characteristics as well as in their TGase 2 expression and activity. TGase 2 activity in tumors was evaluated ex vivo by incorporation of fluorescently labeled cadaverine derivatives, which could be inhibited by a selective TGase 2 inhibitor. These results indicate that the established tumor xenograft models provide the opportunity to evaluate potent candidate substances for diagnosis and therapy of melanoma on the one hand and to investigate pathophysiological processes associated with TGase 2 in detail on the other.

References:
[1] Huang, L et al. Am J Cancer Res. 2015, 5, 2756-2776
[2] Fok, JY et al. Mol Cancer Ther 2006, 5, 1493-1503
[3] Hauser, C et al. Amino Acids 2017, 49, 567–583
  • Poster
    Debrecen University Symposium "Transglutaminases in Medicine", 03.-05.08.2017, Debrecen, Ungarn

Registration No. 25924 - Permalink


Evaluation of defect formation in helium irradiated Y2O3 doped W-Ti alloys by positron annihilation and nanoindentation
Richter, A.; Anwand, W.; Chen, C.-L.; Böttger, R.
Corresponding author: Richter, Asta Department Engineering Physics, Technical University of Applied Sciences Wildau, Hochschulring 1, 15745 Wildau, Germany
Abstract: Helium implanted tungsten-titanium ODS alloys are investigated using positron annihilation spectroscopy and nanoindentation. Titanium reduces the brittleness of the tungsten alloy, which is manufactured by mechanical alloying. The addition of Y2O3 nanoparticles increases the mechanical properties at elevated temperature and enhances irradiation resistance. Helium ion implantation was applied to simulate irradiation effects on these materials. The irradiation was performed using a 500 kV He ion implanter at fluences around 5 × 1015 cm−2 for a series of samples both at room temperature and at 600 °C. The microstructure and mechanical properties of the pristine and irradiated W-Ti-ODS alloy are compared with respect to the titanium and Y2O3 content. Radiation damage is studied by positron annihilation spectroscopy analyzing the lifetime and the Doppler broadening. Three types of helium-vacancy defects were detected after helium irradiation in the W-Ti-ODS alloy: small defects with high helium-to-vacancy ratio (low S parameter) for room temperature irradiation, larger open volume defects with low helium-to-vacancy ratio (high S parameter) at the surface and He-vacancy complexes pinned at nanoparticles deeper in the material for implantation at 600 °C. Defect induced hardness was studied by nanoindentation. A drastic hardness increase is observed after He ion irradiation both for room temperature and elevated irradiation temperature of 600 °C. The Ti alloyed tungsten-ODS is more affected by the hardness increase after irradiation compared to the pure W-ODS alloy.
Keywords: W-Ti-ODS alloys; He implantation; Positron annihilation spectroscopy; Nanoindentation; Vacancy defects

Registration No. 25918 - Permalink


Kooperationsprozess und strategisches Management entwickeln
Joehnk, P.
Corresponding author: Joehnk, Peter
Abstract: Anforderungen an das künftige Verhältnis zwischen Zuwendungsgebern, Forschungseinrichtungen und den Rechnungshöfen - Mängel im öffentlichen Sektor am Beispiel des Bundesrechnungshofs beheben
  • Science Finance 1(2017), 25-31

Registration No. 25914 - Permalink


HZDR, ZA Technischer Service, Abt. Bau- und technisches Gebäudemanagement
Oelke, M.
  • Lecture (others)
    HGF Arbeitskreis - Facility Management 2017, 16.-17.05.2017, xxx, Deutschland

Registration No. 25913 - Permalink


Gebäudeautomation im HZDR - Erfahrungsbericht
Oelke, M.
  • Lecture (others)
    HGF Arbeitskreis Facility Management, 09.-10.05.2012, xxx, Deutschland

Registration No. 25912 - Permalink


Neubau Heizwerk und Nahwärmenetz
Oelke, M.
  • Lecture (Conference)
    HGF Arbeitskreis Facility Management – 36. Tagung, 15.-16.05.2013, Kiel, Deutschland

Registration No. 25911 - Permalink


Structure and energetics of Y-Ti-O nanoclusters in bcc Fe
Vallinayagam, M.; Posselt, M.; Faßbender, J.ORC
Abstract: Nanostructured Ferritic Alloys (NFA) are considered as promising candidates for the structural materials of future fusion and fission reactors [1]. They consist of a ferritic or ferritic/martensitic Fe-Cr matrix with a high dispersion of nanometer size yttria-based oxide particles. In this research project (started in November 2016) the nature of nanometer-size yttria-based oxide clusters in a bcc Fe matrix shall be investigated by DFT calculations. The main goal of these studies is the better understanding of the nucleation as well as the structure and composition of the nanoclusters. The investigations shall clarify the conditions for the formation of nonstoichiometric clusters that are coherent with the bcc lattice and for the formation of oxide phases (in particular Y2O3 and Y2Ti2O7). The energetics of the different structures shall be determined and compared. Furthermore, the interaction of the nanoparticles with intrinsic point defects and He atoms shall be studied. Preliminary studies and their results on structure and energetics of certain Y-Ti-O nanoclusters will be presented on the poster. Two models are considered: (i) clusters consisting of Y, Ti, and O atoms on substitutional or defect sites of the bcc lattice [2-4], and (ii) cluster consisting of parts of the bixbyite (Y2O3) or pyrochlore (Y2Ti2O7) structure embedded in bcc Fe [5].
[1] G. R. Odette, JOM-J. Min. Met. Mat. S. 66, 2427 (2014)
[2] D. Murali, B.K. Panigrahi, M.C. Valsakumar, S. Chandra, C.S. Sundar, B. Raj, J. Nucl. Mater. 403, 113 (2010)
[3] A. Claisse, P. Olsson, Nucl. Instr. Meth. B 303, 18 (2013)
[4] M. Posselt, D. Murali, B. K. Panigrahi, Model. Simul. Mater. Sc. 22, 085003 (2014)
[5] L. Barnard, G. R. Odette, I. Szlufarska, D. Morgan. Acta Mater. 60 (2012) 935 (2012)
Keywords: oxide nanoclusters, bcc Fe, nanoferritic alloy, DFT
  • Poster
    NSF/CECAM School on Computational Materials Science: From Basics to Applications, 17.-27.07.2017, Lausanne, Switzerland

Registration No. 25904 - Permalink


Influence of foreign atoms on the diffusion of oxygen in bcc Fe
Wang, X.; Posselt, M.; Faßbender, J.ORC
Abstract: In this research project (started in September 2016) the diffusion of foreign atoms in bcc Fe shall be investigated by first-principle methods and kinetic Monte Carlo simulations. The focus of the present work is on the diffusion of oxygen under the influence of other foreign atoms such as Al, Cr, Si, Ti, and Y. Oxygen plays e.g. an important role in the formation and evolution of nanoclusters in nanostructured ferritic Fe-Cr alloys which are considered as promising candidates for structural materials of future fusion and fission reactors [1]. In bcc Fe the most stable site of oxygen is the octahedral interstitial position and the tetrahedral interstitial position is the saddle point for the migration [2-5]. The presence of foreign atoms and intrinsic point defects modifies the migration path [5-7]. Using DFT calculations the binding energy between oxygen and a foreign atom is determined for different neighbor distances. Then the modified migration barriers are calculated, i.e. for the O jump between the first and the second neighbor of a foreign atom, etc. The results shall be used in kinetic Monte Carlo simulations of the whole diffusion process and for the determination of the corresponding diffusion coefficient in dependence on the concentration of foreign atoms. Finally, the calculated diffusion coefficient shall be compared with the few existing experimental data on oxygen diffusion in dilute iron alloys.
[1] G. R. Odette, JOM-J. Min. Met. Mat. S. 66, 2427 (2014)
[2] C.L. Fu, M. Krcmar, G.S. Painter, X.-Q. Chen, Phys. Rev. Lett. 99, 225502 (2007)
[3] D. Murali, B.K. Panigrahi, M.C. Valsakumar, S. Chandra, C.S. Sundar, B. Raj, J. Nucl. Mater. 403, 113 (2010)
[4] A. Claisse, P. Olsson, Nucl. Instr. Meth. B 303, 18 (2013)
[5] S.L. Shang, H.Z. Fang, J. Wang, C.P. Guo, Y. Wang, P.D. Jablonski, Y. Du, Z.K. Liu, Corrosion Sci. 83, 94 (2014)
[6] P. Liu, W. Xing, X. Cheng, D. Li, Y. Li, X.-Q. Chen, Phys. Rev. B 90, 024103 (2014)
[7] C. Barouh, T. Schuler, C.-C. Fu, T. Jourdan, Phys. Rev. B 92, 104102 (2015)
Keywords: diffusion, oxygen, bcc Fe, DFT, foreign atoms
  • Poster
    NSF/CECAM School on Computational Materials Science: From Basics to Applications, 17.-27.07.2017, Lausanne, Switzerland

Registration No. 25903 - Permalink


Selective mass enhancement close to the quantum critical point in BaFe2(As1−xPx)2
Grinenko, V.; Iida, K.; Kurth, F.; Efremov, D. V.; Drechsler, S.-L.; Cherniavskii, I.; Morozov, I.; Hänisch, J.; Förster, T.; Tarantini, C.; Jaroszynski, J.; Maiorov, B.; Jaime, M.; Yamamoto, A.; Nakamura, I.; Fujimoto, R.; Hatano, T.; Ikuta, H.; Hühne, R.
Corresponding author: Grinenko, V. Institute for Solid State Physics, TU Dresden & IFW Dresden, Dresden, Germany & Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Nagoya, Japan
Abstract: A quantum critical point (QCP) is currently being conjectured for the BaFe2(As1−xPx)2 system at the critical value xc ≈ 0.3. In the proximity of a QCP, all thermodynamic and transport properties are expected to scale with a single characteristic energy, given by the quantum fluctuations. Such a universal behavior has not, however, been found in the superconducting upper critical field Hc2. Here we report Hc2 data for epitaxial thin films extracted from the electrical resistance measured in very high magnetic fields up to 67 Tesla. Using a multi-band analysis we find that Hc2 is sensitive to the QCP, implying a significant charge carrier effective mass enhancement at the doping-induced QCP that is essentially band-dependent. Our results point to two qualitatively different groups of electrons in BaFe2(As1−xPx)2. The first one (possibly associated to hot spots or whole Fermi sheets) has a strong mass enhancement at the QCP, and the second one is insensitive to the QCP. The observed duality could also be present in many other quantum critical systems.

Registration No. 25893 - Permalink


A new degree of freedom for electron holography
Röder, F.; Lubk, A.; Houdellier, F.; Denneulin, T.; Snoeck, E.; Hÿtch, M. J.
Abstract: Off-Axis Electron Holography permits the direct reconstruction of amplitude and phase of electron waves elastically scattered by an object (see, e.g., [1]). The technique employs the Möllenstedt biprism to mutually incline an object modulat-ed wave and a plane reference wave to form an interference pattern at the detec-tor plane. Limited coherence of the electron beam in presence of aberrations at-tenuates high spatial frequencies of the object exit wave spectrum, which is de-scribed by the sideband envelope function. We explore an extension of the con-ventional electron holography set-up given by deliberately tilting the reference wave independent from the object wave. This allows the transfer of spatial fre-quencies beyond the conventional sideband information limit as predicted by a generalized transfer theory for Off-Axis Electron Holography [2]. This is based on the idea that a reference wave tilted by q0 compensates the wave aberration for the spatial frequency q0 of the object wave spectrum. Thus, an off-axis hologram series with varying reference wave tilt allows in principle a linear synthesis of an effective coherent aperture with a radius reaching out beyond the conventional information limit. Furthermore, an object-independent measurement of aberra-tions as well as strain measurements by dark-field electron holography can be realized using this setup. The experimental realization of an arbitrarily tilted refer-ence wave is challenging and could be realized for the first time at the Hitachi HF3300C I2TEM at CEMES Toulouse for one direction [3]. We used an additional biprism placed in the illumination system. Three condenser lenses were adjusted to provide a demagnified image of the condenser biprism at the sample plane under parallel illumination. The pre-specimen deflectors were adapted to maintain the incident wave vector of the object wave and to realize a tilt of the reference wave as a function of the condenser biprism voltage. Finally, we have experimen-tally shown that dark-field holography can be conducted with an object-independent reference alleviating the need for a uniform area of known structure.

[1] H. Lichte, M. Lehmann, Rep. Prog. Phys. 71 (2008) 016102.
[2] F. Röder, A. Lubk, Ultramicoscopy 152 (2015) 63-74.
[3] F. Röder, F. Houdellier,T. Denneulin, E. Snoeck, M.J. Hÿtch, Ultramicoscopy 161 (2016) 23–40.
Keywords: electron holography, tilted reference wave, aperture systhesis, dark-field
  • Invited lecture (Conferences)
    PICO 2017 - Forth Conference on Frontiers of Aberration Corrected Electron Microscopy, 30.04.-04.05.2017, Kasteel Valsbroek, The Netherlands

Registration No. 25889 - Permalink


Probing the Impact of the Initiator Layer on Grafted-from Polymer Brushes: A Positron Annihilation Spectroscopy Study
Panzarasa, G.; Aghion, S.; Marra, G.; Wagner, A.; Liedke, M. O.; Elsayed, M.; Krause-Rehberg, R.; Ferragut, R.; Consolati, G.
Abstract: Grafting-from is the technique of choice to obtain polymer brushes. It is based on the growth of polymer chains directly from an initiator-functionalized surface, and its development gained momentum thanks to recent advances in controlled polymerization techniques. However, despite the great amount of work that has been performed on this subject, the influence exerted by the initiator layer on the characteristics of the resulting brushes has been almost completely overlooked. Our group has already demonstrated that positron annihilation spectroscopy (PAS) is a valuable analytical tool for the study of polymer brushes. Here, we applied this technique to show that differences in the organization of the initiator layer dramatically reflect on the characteristics of polymer brushes. Brushes made by surface-initiated atom transfer radical polymerization (ATRP) of a pH-responsive polymer, poly(dimethylaminoethyl methacrylate) (PDMAEMA), were investigated also in terms of the effects of protonation and of the incorporation of silver nanoparticles inside the brushes, shining a new light on the internal structure of such complex, fascinating systems.
Keywords: Grafting-from polymer brushes positron annihilation spectroscopy surface-initiated atom transfer radical polymerization (ATRP)

Registration No. 25884 - Permalink


Electrical Characterization of sub-20 nm Silicon Nanowires Fabricated using Electron Beam Lithography and Inductively Coupled Plasma Etching
Khan, M. B.; Deb, D.; Georgiev, Y. M.; Fuchs, F.; Schuster, J.; Erbe, A.
Abstract: Scaling down of CMOS faces strong challenges due to which new materials, enhanced functionality and new device concepts have gained importance. These concepts include undoped silicon nanowire based reconfigurable devices which can be programmed as p-FET or n-FET by controlling the electrostatic potential applied across gate. In this work, electrical characterization of undoped sub-20 silicon nanowires (SiNWs) is reported. SiNWs are fabricated on intrinsic SOI substrates in <110> and <100> crystal directions by a top down approach. Hydrogen silsesquioxane (HSQ), a negative tone electron beam resist is used for nano- patterning as well as hard mask for etching. Nanowire etching process is optimized using an inductively coupled plasma (ICP) source and C4F8/SF6/O2 mixed gas recipe at 18 oC. These NWs are oxidized to form a SiO2 shell and subsequently silicidized. For silicidation the SiO2 shell is wet etched at pre-defined positions followed by Nickel(Ni) sputtering and diffusion which yield silicide-silicon(Schottky) junctions. Ni is used for silicidation to selectively control the charge carriers injection at the junctions. Different transport and silicidation progress was observed in <110> and <100> crystal directions.
Keywords: Silicon nanowire; etching; lithography; schottky barrier devices
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, 19.-24.03.2017, Dresden, Germany

Registration No. 25881 - Permalink


Development of structured reactors for transformation of biomass components to high-value products - green process industry
Salmi, T.; Shumilov, V. V.; Eränen, K.; Kumar, N.; Hupa, L.; Murzin, D.; Boden, S.; Schubert, M.; Hampel, U.; Sulman, E.
Abstract: Transformation of biomass components to high-value products used in industry over structured catalysts is the idea behind this project. Synthesis of 5-Methyl-1-Hydroxyethyl-2-Pyrrolidone by reductive amination of ethyl levulinate using 3-aminopropanol as the alkyl amine in the presence of hydrogen was performed. Reactor which uses porous ceramic monolith as a catalytic carrier was studied.

For the development of a new catalytic system, alumina was chosen as a carrier material and sponge replica technique was used for its production. Porous ceramics with different pore types and sizes are widely applied in chemical industry. The unique properties of porous materials allow to carry out a spectrum of well-established and recent applications, such as molten metal filtration, catalysis, refractory and thermal insulation, hot gas filtration. Porous form is perfect for heterogeneous catalysis because of high surface area, which enables liquid (or gas) to contact the catalyst intensively.

Alpha-Alumina is a strong material the surface area of which is low and so to enlarge surface area covering of the foam with a layer of gamma-alumina which has a much bigger surface area was performed.

Two methods of gamma-alumina coating were performed. One of them is covering alpha-alumina frame with gamma-alumina slurry. This method is limited by the pore size, as the smallest pores will be blocked after slurry adding. The second method is a hot water solution deposition where sedimentation of gamma-alumina from its salt takes place.

Pt and Ru in the form of nanoparticles were successfully deposited on the surface of the porous structure. Catalysts were characterized by nitrogen desorption, SEM, EDXA, TEM and other methods. Reactor represents a tube with a diameter about 20 mm and length about 350 mm into which porous catalyst is placed.

Reductive amination of ethyl levulinate using 3-aminopropanol as the alkyl amine which was performed. Ethyl levulinate is a product of levulinic acid transformation. Levulinic acid is a well-known precursor for pharmaceuticals, plasticizers and other additives. It is a building block or starting material for a wide range of compounds.
  • Poster
    10th International Symposium on Catalysis in Multiphase Reactors and Multifunctional Reactors, 07.-10.07.2017, Qingdao, China

Registration No. 25875 - Permalink


Active targeting and in vivo multimodal imaging of renally excretable polymer nanoparticles
Pant, K.; Zarschler, K.; Neuber, C.; Pufe, J.; Pietzsch, J.; Steinbach, J.; Stephan, H.; Haag, R.
Abstract: Multimodal imaging represents a strategy to integrate multiple modalities on a single carrier molecule so as to increase the detection sensitivity and to obviate the need to administer compounds with different pharmacokinetics. In this regard, dendritic polyglycerols are highly biocompatible nanoscale scaffolds with multiple attachment sites, anti-fouling properties and small size (2-20 nm).1 The great versatility of the dendritic polyglycerols allows to fine tune physicochemical parameters such as the size, water solubility, surface charge that are relevant for the successful preparation of theranostic systems. Previous experiments showed that the dendritic polyglycerols (>10kDa) show a fast renal clearance with negligible uptake in the mononuclear phagocytic system (MPS) organs such as the liver and spleen.2-3 The purpose of this work to design a PET/OI dual modal construct based on dendritic polyglycerols for epidermal growth factor receptor (EGFR) targeting. In this regard, a one-pot strategy was employed for simultaneous attachment of fluorescent labels for optical imaging (cy3/cy7) and macrocyclic chelators based on a 1,4,7-triazacyclononane system for 64Cu (PET tracer) to thiol anchoring groups of the dPGs. A small camelid single-domain antibody (sdAb) representing a potential recognition agent for EGFR as targeting vector was attached (1). In parallel, a probe with similar surface characteristics but an EGFR unspecific sdAb (control) was synthesized (2). The conjugates were purified using affinity chromatography, which selectively separates the antibody-conjugated mul-timodal conjugates. In vitro and in vivo studies were conducted to assess its diagnostic potential. The in vitro results revealed a highly specific receptor mediate uptake of 1 in EGFR expressing A431 and FaDu cell lines using confocal microscopy and radio detection.
Intravenous injection of 1 and 2 on mouse xenografted models studies using PET and optical imaging revealed an overwhelming tumor accumulation of the EGFR-specific 1 in comparison to the EGFR-unspecific 2 and a minimum off-target accumulation of both conjugates. These results unveil the potential of dendritic polyglycerols as efficient multimodal platforms for theranostic applications.
Keywords: dendritic polyglycerols, cancer, biodistribution, radiolabeling, renal clearance, protein corona, biomedical applications.
  • Lecture (Conference)
    Nanotech France 2017, 28.-30.06.2017, PARIS, France

Registration No. 25865 - Permalink


NMR investigations of paramagnetic effects in metal-organic complexes of trivalent and tetravalent actinides with soft-donor ligands
Radoske, T.; Adam, C.; Schöne, S.; Patzschke, M.; März, J.; Kaden, P.ORC
Abstract: When NMR spectroscopy is applied to paramagnetic metal-organic complexes additional chemical shifts are observed on nuclei of the ligands that originate from electronic interactions between metal and ligand. The major two contributors to these paramagnetic chemical shifts are either due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals (Fermi contact shift, FCS), or due to distance- and angle-dependent dipolar coupling of electron spins through space (pseudo contact shift, PCS). However, mathematical models for the treatment of paramagnetic chemical shifts are not yet applicable to actinide compounds.
Covalence is assumed to be the reason for some soft-donor ligands selectivity for the complexation of trivalent actinides over lanthanide ions. This long-kept notion was recently substantiated by evaluation of paramagnetic chemical shifts of respective Am(III) complexes1,2. The mathematical separation of contributions in complexes of the trivalent actinides, however, is hampered by the lack of a reliable diamagnetic reference in the actinide series. Furthermore, all available theories behind mathematical disentangling of contributions to the paramagnetic chemical shift, even for the lanthanide series, omit the influence of spin-orbit effects that might have a sizeable contribution as well.
To assess the chemical bonding situation via the influences on paramagnetic chemical shifts we started to study metal-organic complexes of tetravalent actinides (An(IV)) with soft-donor ligands with Th(IV) as diamagnetic reference. With increasing number of unpaired electrons throughout the series additional effects to the observed chemical shift are expected. Herein we report the first results of investigations of N-donor ligand complexes of the An(IV) series.
References
1. C. Adam, P. Kaden, B. B. Beele, U. Müllich, S. Trumm, A. Geist, P. J. Panak, M. A. Denecke, “Evidence for covalence in a N-donor complex of americium(III)”, Dalton Trans., 42, 14068-14074 (2013).
2. C. Adam, B. B. Beele, A. Geist, U. Müllich, P. Kaden, P. J. Panak, “NMR and TRLFS studies of Ln(III) and An(III) C5-BPP complexes”, Chemical Science, 6, 1548-1561 (2015).
Keywords: NMR, paramagnetic, diamagnetic reference, covalence, Fermi contact, pseudo-contact, U(IV), Th(IV), Am(III)
  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan

Registration No. 25860 - Permalink


Increased FDG uptake on late-treatment PET in non-tumour-affected oesophagus is prognostic for pathological complete response and disease recurrence in patients undergoing neoadjuvant radiochemotherapy
Zschaeck, S.; Hofheinz, F.; Zöphel, K.; Bütof, R.; Jentsch, C.; Schmollack, J.; Löck, S.; Kotzerke, J.; Baretton, G.; Weitz, J.; Baumann, M.; Krause, M.
Corresponding author: Zschaeck, S.
Abstract: Purpose

Early side effects including oesophagitis are potential prognostic factors in patients undergoing radiochemotherapy (RCT) for locally advanced oesophageal cancer (LAEC). We assessed the prognostic value of 18F-fluorodeoxyglucose (FDG) uptake within irradiated non-tumour-affected oesophagus (NTO) during restaging positron emission tomography (PET) as a surrogate for inflammation/oesophagitis.
Methods

This retrospective evaluation included 64 patients with LAEC who had completed neoadjuvant RCT and had successful oncological resection. All patients underwent FDG PET/CT before and after RCT. In the restaging PET scan maximum and mean standardized uptake values (SUVmax, SUVmean) were determined in the tumour and NTO. Univariate Cox regression with respect to overall survival, local control, distant metastases and treatment failure was performed. Independence of clinically relevant parameters was tested in a multivariate Cox regression analysis.
Results

Increased FDG uptake, measured in terms of SUVmean in NTO during restaging was significantly associated with complete pathological remission (p = 0.002) and did not show a high correlation with FDG response of the tumour (rho < 0.3). In the univariate analysis, increased SUVmax and SUVmean in NTO was associated with improved overall survival (p = 0.011, p = 0.004), better local control (p = 0.051, p = 0.044), a lower rate of treatment failure (p < 0.001 for both) and development of distant metastases (p = 0.012, p = 0.001). In the multivariate analysis, SUVmax and SUVmean in NTO remained a significant prognostic factor for treatment failure (p < 0.001, p = 0.004) and distant metastases (p = 0.040, p = 0.011).
Conclusions

FDG uptake in irradiated normal tissues measured on restaging PET has significant prognostic value in patients undergoing neoadjuvant RCT for LAEC. This effect may potentially be of use in treatment personalization.
Keywords: Oesophageal cancer Radiochemotherapy Side effects Inflammation FDG pet

Registration No. 25857 - Permalink


Nonmodal and nonlinear dynamics of helical magnetorotational instability
Mamatsashvili, G.; Stefani, F.
Abstract: The helical magnetorotational instability (HMRI), a relative of standard MRI (SMRI), has become a subject of active research in recent years in connection with the experiments on magnetized cylindrical Taylor-Couette (TC) flows. It occurs in the presence of helical magnetic field, consisting of azimuthal and axial components and, like SMRI with only axial magnetic field, taps into the rotational energy of the flow. However, a main advantage of HMRI is that, being governed by the Reynolds (Re) and Hartmann (Ha) numbers, it persists even at very small magnetic Prandtl numbers typical to liquid metals, in contrast to SMRI. The linear development of HMRI has been widely studied theoretically using both classical modal and more recently by nonmodal stability analysis, where a fundamental connection between nonmodal dynamics and dissipation-induced (double-diffusive) modal instabilities, such as HMRI, has been demonstrated. A series of specially designed liquid metal TC experiments provided the first experimental evidence of HMRI and reproduced the main results of the linear theory, such as the stability threshold and propagation speed (frequency) of HMRI-wave. More importantly, these experiments revealed much richer dynamics of HMRI as a function of system parameters (Re, Ha, etc.) than that obtained from the linear analysis only. These results prompted further theoretical studies of the nonlinear development of HMRI, but detailed physics of its saturation and sustenance still remains missing, especially when comparison with the experiment is concerned.
Motivated by the existing experimental results, we investigate the evolution of HMRI, from its linear growth to nonlinear saturation using numerical simulations.
We show that depending on the Reynolds number, two regimes of saturation can be realized. At Re below a certain critical value (but higher than the instability threshold), the saturation energy linearly depends on Re and the corresponding energy spectrum is dominated by the most unstable mode and its multiple wavenumbers, while at larger Re, the energy increases with Re, but not linearly, and the related spectrum looks like turbulent spectrum, being much smoother over wavenumbers. The nonlinear state remains markedly axisymmetric (m = 0)
and at high Re can be viewed as a 2D turbulence, whose (spectral) properties are further examined.
Keywords: MHD, turbulence, nonmodal growth, instabilities, numerical simulations
  • Lecture (Conference)
    2nd Conference on Natural Dynamos, 25.06.-01.07.2017, Valtice Castle, Czech Republic

Registration No. 25856 - Permalink


Kinetic Modeling of the New σ1 Receptor Ligand (-)-[18F]Fluspidine in the Human Brain
Becker, G. A. F.; Meyer, P.; Patt, M.; Hesse, S.; Luthardt, J.; Patt, J.; Rullmann, M.; Fischer, S.; Kluge, A.; Steinbach, J.; Wünsch, B.; Brust, P.; Sabri, O.
Corresponding author: Becker, G. A. F. University of Leipzig, Department of Nuclear Medicine, Germany
Abstract: Objectives:
The σ1 receptor, a transmembrane protein located at the endoplasmatic reticulum is involved in a variety of neuropsychiatric diseases, e.g. depression, schizophrenia and drug addiction. The newly developed PET tracer (-)-[18F]Fluspidine was successfully applied to quantify σ1 receptors in the porcine brain [1]. Here we present the first PET quantification of σ1 receptors with (-)-[18F] Fluspidine in humans.
Methods:
After intravenous administration of 269.6±13.3 MBq (-)-[18F]Fluspidine PET brain imaging was performed in 10 healthy subjects (age 36.6±14.8 years; gender 5F/5M) using an ECAT EXACT HR+ system in 3D-acquisition mode. 26 frames were acquired from 0-210 min post injection and motion corrected with SPM2. Kinetic modeling using 1- and 2-tissue compartment models (1TCM, 2TCM) with metabolite corrected arterial input-function was applied to the volume of interest (VOI) based tissue time-activity curves (TACs) in 43 brain regions (anatomically defined via MRI co-registration). Time ranges from 0 to 90 and 0 to 210 min were investigated. Model-based receptor parameter was the total distribution volume VT (ml/cm-3), a linear function of receptor density.
Results:
TACs of all 43 regions could be described with the 1- and 2TCM. VT in all cortical regions could be reliably estimated from 90 min PET data already. In white matter longer measurements can be necessary. The distribution volume was highest in the cerebellar cortex (31.4±6.1), low in the centrum semiovale (17.7±7.1) and ranged in cortical structures between 20.9±3.9 in the orbitofrontal and 24.9±5.7 in the posterior cingulate cortex (pcc) (2TCM, 90 min). The distribution volumes computed from 210 min data were comparable to 90 min results, e.g. in pcc 25.7±5.9 (2TCM) and 25.7±6.0 (1TCM).
Conclusions:
σ1 receptor parameters in cortical structures can be estimated with a 1- or 2TCM from 90 min (-)-[18F]Fluspidine TACs. If a model derived receptor parameter is used in a classification problem, e.g., distinguishing patients with depression from healthy controls, the final model decision should be made on the basis of the PET data of both groups.
References:
P. Brust, ..., O. Sabri, Journal of Nuclear Medicine 2014, 55, 1730-1736

Registration No. 25855 - Permalink


Development of (S)-[18F]T1 as first PET tracer for imaging the α3β4 nicotinic acetylcholine receptor
Sarasamkan, J.; Fischer, S.; Deuther-Conrad, W.; Scheunemann, M.; Ludwig, F.-A.; Vajragupta, O.; Brust, P.
Corresponding author: Sarasamkan, J. Mahidol University, Faculty of Pharmacy, Pharmaceutical Chemistry, Bangkok, Thailand
Abstract: Objectives:
Neuronal nicotinic acetylcholine receptors (nAChRs) are composed of diverse subtypes which have different functional properties, distributions and pharmacological profiles. The α7, α3β4 and α4β2 nAChRs are well recognized as drug targets implicated in cognitive disorders and addiction. Therefore, to image nAChRs in vivo, subtype-selective radiotracers need to be developed.
Methods:
A novel PET radiotracer for imaging nAChRs was developed based on the design and synthesis of six racemates (T1-T6) and its enantiomers based on the structure of triazole-quinuclidine QND8. All R enantiomers were found to be selective to α7 nAChR while their S counterparts were selective to α3β4 nAChR. (S)-T1 binds selectively to α3β4 nAChR (Ki 3.09 nM) with very modest off-target binding to α1 receptor, dopamine receptors and serotonin receptors. Radiosynthesis of (S)-[18F]T1 was achieved by two-step reaction, starting with the preparation of 18F-alkyne synthon (1-ethynyl-4-[18F]fluorobenzene; [18F]2), followed by the click reaction between [18F]2 and (S)-azidoquinuclidine.
Results:
The radiosynthesis of (S)-[18F]T1 was achieved in 130 min with the overall isolated radiochemical yield of 4.3±1.3%, radiochemical purity > 99%, and molar radioactivity > 158 GBq/µmol at end of synthesis. The brain uptake and brain-to-blood ratio of this tracer in mice at 30 min after injection were 6.06% ID/g and 6.1, respectively. The tracer remained intact > 99% in brain homogenates. Only one major radiometabolite was detected in plasma and urine samples. In vitro autoradiography on pig brain slices revealed high binding of (S)-[18F]T1 to brain regions consistent with the α3β4 nAChR distribution. Selective binding of (S)-[18F]T1 was evidenced by (i) the reduction of percent labeling of this tracer in the presence of a selective α3β4 nAChR partial agonist, AT-1001 and (ii) the retention of the tracer in the presence of α7 nAChR-specific SSR180711.
Conclusions:
These findings suggest the potential of (S)-[18F]T1 for imaging the α3β4 nAChR in the brain as a promising tool for both diagnosis and therapy monitoring of neurodegenerative diseases and addiction.
Acknowledgement:
This work was supported by Thailand Research Fund (TRF) through the Royal Golden Jubilee Ph.D. Program (grant no. PHD/0272/2552) to J.S. and O.V.
References:
[1] K. Arunrungvichian, V. V. Fokin, O. Vajragupta, P. Taylor. ACS Chem Neurosci. 2015, 6, 1317-1330.
[2] J. Sarasamkan, M. Scheunemann, N. Apaijai, S. Palee, W. Parichatikanond, K. Arunrungvichian, et al. ACS Med. Chem. Lett. 2016, 7, 890- 895.

Registration No. 25854 - Permalink


ElectroHydroDynamic emitters developments for improving Focused Ion Beam machines
Gierak, J.; Bischoff, L.; Mazarov, P.; Bruchhaus, L.; Blanchard-Desce, M.; Vaultier, M.; Lozano, P.
Abstract: The patterning of samples using Focused Ion Beams (FIB) is very popular, widely used both for industrial [1] and emerging nanoscience prototyping applications [2]. This FIB technique allows 3D and direct patterning of target materials using a finely focused pencil of ions having speeds of several hundreds of km/seconds at impact with a penetration range of a few tens of nanometres. Thanks to this, local information and/or modifications can be obtained at the target surface. In what the ion nature is concerned, apart that many elements can be used in FIB technology as pure elements or in the form of alloys, gallium (Ga+ ions) is often preferred.
Traditionally for several decades FIB technology has been mainly based on gallium Liquid Metal Ion Sources (LMIS). LMIS are also known as electrohydrodynamically (EHD) driven ion emitters operating in a cone-jet mode. The very high brightness, long lifespan, small source size, and easy handling of this emitter remain its chief and most decisive advantages. On the other hand, some weaknesses are also well known that inhibit the resolution of EHD/LMIS-based FIBs. Therefore progress on ion sources operational characteristics still remains very desirable.
In this presentation we will first summarize our work aiming at understanding, optimizing and evaluating gallium LMIS “needle type” performances. In particular stable operation at lowest possible emission currents will be detailed. The gains in terms of patterning resolution and beam selectivity [3], we will evaluate, are firm evidence that progresses can still be expected from this mature technology.
We will then review and detail the advantages of Liquid Metal Alloy Ion Sources (LMAIS) that represent a promising alternative to expand the already remarkable application field and potential of FIB machines in the field of nanosciences. Indeed selecting the best suited elements transported in a focused ion beam can open new nanofabrication routes. In this presentation we will explain that nearly half of the elements of the periodic table can already be made available to the FIB technology as a result of a continuous research effort in this area [4] and how, in our opinion, nanofabrication shall now take benefit of these capabilities. Finally we will introduce our new addition to the arsenal of EHD driven devices: The Ionic Liquid Ion Sources (ILIS). ILIS are capable to produce ion beams through field-evaporation, also in the cone-jet mode, but from room temperature molten-salts [5]. The possibility of extracting both positive and negative ions at
emission current several orders of magnitude below LMIS standards is already a very appealing perspective in terms of source virtual source size and brightness. Then we will show that ILIS allows to access new ionic species thanks to the almost limitless chemical engineering latitude of molten salts. Moreover subsequent tuning can be achieved via selecting the tip polarity, the ion emission current and the ion landing energy. We will show the possibility to achieve a new kind of FIB patterning using a beam of chemically reactive ion radicals native in the transported beam. This represents a formidable perspective for FIB technology.
In conclusion we will summarize our vision on the future of FIB technology based on electrohydrodynamically (EHD) driven emitters operating in the conejet mode, both in terms of performances, versatility and on the science frontiers these might help to push.

[1] J. Orloff, Scientific American Oct. 1994, pp.74-79
[2] J. Gierak Nanofabrication 2014; Volume 1: pp. 35–52
[3] J. Gierak and R. Jede, Patent US8546768 B2, WO2010029270A1; Sept 2008
[4] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Appl. Phys. Rev. 2016; 3: pp. 021101
[5] C. Perez-Martinez, J. Gierak, and P. C. Lozano, P106 (Invited), EIPBN Conference, May 31-
June 3, 2016, Pittsburgh, PA
Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; Ionic Liquid Ion Source; FIB patterning
  • Lecture (Conference)
    Conference on ultracold ion and electron beams, 10.-12.07.2017, Eindhoven, The Netherlands
  • Lecture (Conference)
    61th International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication EIPBN-2017, 30.05.-02.06.2017, Orlando, USA

Registration No. 25853 - Permalink


Ion-Beam-Induced Atomic Mixing in Ge, Si, and SiGe, Studied by Means of Isotope Multilayer Structures
Bracht, H.; Radek, M.; Posselt, M.; Liedke, B.; Schmidt, B.; Voelskow, M.; Bischoff, L.; Böttger, R.; Prucnal, S.; Hansen, J. L.; Larsen, A. N.; Bougeard, D.
Abstract: Crystalline and preamorphized isotope multilayers are utilized to investigate the dependence of ion beam mixing in silicon (Si), germanium (Ge), and silicon germanium (SiGe) on the atomic structure of the sample, temperature, ion flux, and electrical doping by the implanted ions. The magnitude of mixing is determined by secondary ion mass spectrometry. Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy, and transmission electron microscopy provide information about the structural state after ion irradiation. Different temperature regimes with characteristic mixing properties are identified. A disparity in atomic mixing of Si and Ge becomes evident while SiGe shows an intermediate behavior. Overall, atomic mixing increases with temperature, and it is stronger in the amorphous than in the crystalline state. Ion-beam-induced mixing in Ge shows no dependence on doping by the implanted ions. In contrast, a doping effect is found in Si at higher temperature. Molecular dynamics simulations clearly show that ion beam mixing in Ge is mainly determined by the thermal spike mechanism. In the case of Si thermal spike, mixing prevails at low temperature whereas ion beam-induced enhanced self-diffusion dominates the atomic mixing at high temperature. The latter process is attributed to highly mobile Si di-interstitials formed under irradiation and during damage annealing.
Keywords: silicon; germanium; ion beam; atomic mixing; thermal spike; radiation enhanced diffusion; amorphization; recrystallization; molecular dynamics

Registration No. 25852 - Permalink


Modeling tumor control probability for spatially inhomogeneous risk of failure based on clinical outcome data
Lühr, A.; Löck, S.; Jakobi, A.; Stützer, K.; Bandurska-Luque, A.; Vogelius, I. R.; Enghardt, W.; Baumann, M.; Krause, M.
Corresponding author: Lühr, A. DKTK, OncoRay, DKFZ, HZDR
Abstract: Purpose

Objectives of this work are (1) to derive a general clinically relevant approach to model tumor control probability (TCP) for spatially variable risk of failure and (2) to demonstrate its applicability by estimating TCP for patients planned for photon and proton irradiation.
Methods and Materials

The approach divides the target volume into sub-volumes according to retrospectively observed spatial failure patterns. The product of all sub-volume TCPi values reproduces the observed TCP for the total tumor. The derived formalism provides for each target sub-volume i the tumor control dose (D50,i) and slope (γ50,i) parameters at 50% TCPi. For a simultaneous integrated boost (SIB) prescription for 45 advanced head and neck cancer patients, TCP values for photon and proton irradiation were calculated and compared. The target volume was divided into gross tumor volume (GTV), surrounding clinical target volume (CTV), and elective CTV (CTVE). The risk of a local failure in each of these sub-volumes was taken from the literature.
Results

Convenient expressions for D50,i and γ50,i were provided for the Poisson and the logistic model. Comparable TCP estimates were obtained for photon and proton plans of the 45 patients using the sub-volume model, despite notably higher dose levels (on average +4.9%) in the low-risk CTVE for photon irradiation. In contrast, assuming a homogeneous dose response in the entire target volume resulted in TCP estimates contradicting clinical experience (the highest failure rate in the low-risk CTVE) and differing substantially between photon and proton irradiation.
Conclusions

The presented method is of practical value for three reasons: It (a) is based on empirical clinical outcome data; (b) can be applied to non-uniform dose prescriptions as well as different tumor entities and dose-response models; and (c) is provided in a convenient compact form. The approach may be utilized to target spatial patterns of local failures observed in patient cohorts by prescribing different doses to different target regions. Its predictive power depends on the uncertainty of the employed established TCP parameters D50 and γ50 and to a smaller extent on that of the clinically observed pattern of failure risk.
Keywords: Radiotherapy, Dose–response modeling, TCP, Inhomogeneous dose, Head and neck cancer, Proton therapy

Registration No. 25851 - Permalink


Superconducting Ferromagnetic Nanodiamond
Zhang, G.; Samuely, T.; Xu, Z.; Jochum, J. K.; Volodin, A.; Zhou, S.; May, P. W.; Onufriienko, O.; Kačmarčík, J.; Steele, J. A.; Li, J.; Vanacken, J.; Vacík, J.; Szabó, P.; Yuan, H.; Roeffaers, M. B. J.; Cerbu, D.; Samuely, P.; Hofkens, J.; Moshchalkov, V. V.
Corresponding author: Zhang, G. INPAC-Insititute for Nanoscale Physics and Chemistry, KU Leuven, Celestijnenlaan 200D, Heverlee, Belgium
Abstract: Superconductivity and ferromagnetism are two mutually antagonistic states in condensed matter. Research on the interplay between these two competing orderings sheds light not only on the cause of various quantum phenomena in strongly correlated systems but also on the general mechanism of superconductivity. Here we report on the observation of the electronic entanglement between superconducting and ferromagnetic states in hydrogenated boron-doped nanodiamond films, which have a superconducting transition temperature Tc ∼ 3 K and a Curie temperature TCurie > 400 K. In spite of the high TCurie, our nanodiamond films demonstrate a decrease in the temperature dependence of magnetization below 100 K, in correspondence to an increase in the temperature dependence of resistivity. These anomalous magnetic and electrical transport properties reveal the presence of an intriguing precursor phase, in which spin fluctuations intervene as a result of the interplay between the two antagonistic states. Furthermore, the observations of high-temperature ferromagnetism, giant positive magnetoresistance, and anomalous Hall effect bring attention to the potential applications of our superconducting ferromagnetic nanodiamond films in magnetoelectronics, spintronics, and magnetic field sensing.
Keywords: anomalous Hall effect; giant positive magnetoresistance; nanodiamond; spin fluctuations; superconductivity and ferromagnetism

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  • Secondary publication expected from 16.05.2018

Registration No. 25850 - Permalink


Structural and optical properties of Gd implanted GaN with various crystallographic orientations
Macková, A.; Malinský, P.; Jagerová, A.; Sofer, Z.; Klímová, K.; Sedmidubský, D.; Pristovsek, M.; Mikulics, M.; Lorinčík, J.; Böttger, R.; Akhmadaliev, S.
Corresponding author: Macková, A. Nuclear Physics Institute of the Academy of Sciences of the Czech Republic, v. v. i., 250 68 Rez, Czech Republic
Abstract: Structure, morphology, and optical properties of Gd implanted GaN epitaxial layers were studied for (0001), (11 − 20), and (11 − 22) orientations. The GaN layers grown by MOVPE on sapphire were subsequently implanted with 200 keV Gd+ ions using fluences of 5 × 1015 and 5 × 1016 cm− 2. Dopant depth profiling was accomplished by Rutherford Back-Scattering spectrometry (RBS). Structural and optical changes during subsequent annealing were characterized by RBS, Raman spectroscopy, and photoluminescence measurements. Post-implantation annealing induced a structural reorganization of GaN structure in the buried layer depending on the introduced disorder level, i.e. depending on the implantation fluence and on crystallographic orientation. The defect density depth distribution was evaluated by RBS. The surface morphology and optical properties depend on particular crystallographic orientation.
Keywords: GaN implantation; RBS channelling; Optical properties of Gd implanted GaN

Registration No. 25849 - Permalink


Experimental and Numerical Modeling of Fluid Flow Processes in Continuous Casting: Results from the LIMMCAST-Project
Timmel, K.ORC; Kratzsch, C.; Asad, A.; Schurmann, D.; Schwarze, R.; Eckert, S.
Corresponding author: Eckert, S.
Abstract: The present paper reports about numerical simulations and model experiments concerned with the fluid flow in the continuous casting process of steel. This work was carried out in the LIMMCAST project in the framework of the Helmholtz alliance LIMTECH. A brief description of the LIMMCAST facilities used for the experimental modeling at HZDR is given here. Ultrasonic and inductive techniques and the X-ray radioscopy were employed for flow measurements or visualizations of two-phase flow regimes occurring in the submerged entry nozzle and the mold. Corresponding numerical simulations were performed at TUBAF taking into account the dimensions and properties of the model experiments. Numerical models were successfully validated using the experimental data base. The reasonable and in many cases excellent agreement of numerical with experimental data allows to extrapolate the models to real casting configurations. Exemplary results will be presented here showing the effect of electromagnetic brakes or electromagnetic stirrers on the flow in the mold or illustrating the properties of two-phase flows resulting from an Ar injection through the stopper rod.
Keywords: LIMTECH-alliance, Continuous Casting, numerical modeling, experimental modeling, liquid metal models, electromagnetic actuators, two-phase flow

Registration No. 25847 - Permalink


Theranostic mercury 197(m)Hg: comparing different Hg/Au separation methods
Wang, C.; Červenák, J.; Walther, M.; Lebeda, O.; Preusche, S.; Pietzsch, H. J.; Steinbach, J.
Abstract: Objectives: The access to no-carrier-added 197(m)Hg for imaging and therapy research based on proton or deuteron irradiation of gold was recently reported1,2. The development of a rapid, reliable method for Hg/Au separation represents an important prerequisite for increasing yields. Ideally would be, a reversible interaction at least of one of the two metal ions, allowing for the product elution into a small volume. Besides the liquid-liquid extraction with methyl isobutyl keton (MIBK)1, the solid phase extraction using LN resin (LaNthanides) containing di(2-ethylhexyl)orthophosphoric acid as extractant was examined for this application2.
Methods: The gold target was irradiated for 120 minutes with a 25 µA beam current of 10 MeV protons resulting in 200 MBq of 197(m)Hg or with 15.6 MeV deuteron beam at 7.8 µA beam current for 180 min resulting in ca 800 MBq of of 197(m)Hg (EOB). The irradiated gold foil was dissolved after 1 h in 700 µl of aqua regia (freshly prepared 1 h before EOB from 525 µl 30% HCl + 175 µl 65% HNO3) at room temperature. The column preparation was carried out directly before use by loading 3.6 g LN resin slurried with 10 ml of 6M HCl onto the column and rinsing with additional 30 ml of 6M HCl. After dilution of the 700 µl product solution with 300 µl 6M HCl, this mixture was loaded onto the column and eluted with 6M HCl in 1 ml aliquots.
Results: Comparing with the previously described liquid-liquid extraction1, the solid phase extraction using the LN resin showed shorter performance time. After loading the mixture of chloroauric acid and n.c.a. mercury chloride, the colored gold solution was observed to rapidly distribute in the upper part of the column and then slowly proceeds down during the stepwise elution with 6M HCl. After the addition of 5–6 ml of HCl, the yellow chloroauric acid extended roughly two thirds down the column and almost stopped to move, while over 90% of n.c.a. radiomercury chloride (higher than 60-80% extracted with 4×500 µl MIBK) eluted in the following 2 ml of HCl. The separated 197(m)Hg has excellent radionuclidic purity with no detectable traces of 198Au. It is massively produced in the deuteron activation of gold and acts as a very sensitive tracer of the separation process efficiency.
Conclusions: In contrast to the liquid-liquid extraction, LN resin based method is significantly more efficient and provides product of high radionuclidic purity. Another major advantages compared to the liquid-liquid extraction are obviously 1) better handling and easy automation that shorten the separation time and minimize radiation burden, 2) negligible product losses 3) open possibility to collect and recycle the target material.
  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland

Registration No. 25842 - Permalink


Liquid metal batteries - materials selection and fluid dynamics
Weier, T.; Bund, A.; El-Mofid, W.; Horstmann, G.; Lalau, C.-C.; Landgraf, S.; Nimtz, M.; Starace, M.; Stefani, F.; Weber, N.
Corresponding author: Weier, Tom
Abstract: Liquid metal batteries are possible candidates for massive and economically feasible large-scale stationary storage and as such could be key components of future energy systems based mainly or exclusively on intermittent renewable electricity sources. The completely liquid interior of liquid metal batteries and the high current densities give rise to a multitude of fluid flow phenomena that will primarily influence the operation of future large cells, but might be important for today’s smaller cells as well. The paper at hand starts with a discussion of the relative merits of using molten salts or ionic liquids as electrolytes for liquid metal cells and touches the choice of electrode materials. This excursus into electrochemistry is followed by an overview of investigations on magnetohydrodynamic instabilities in liquid metal batteries, namely the Tayler instability and electromagnetically excited gravity waves. A section on electro-vortex flows complements the discussion of flow phenomena. Focus of the flow related investigations lies on the integrity of the electrolyte layer and related critical parameters.
Keywords: liquid metal batteries, Tayler instability, metal pad role instability, electro-vortex flows

Registration No. 25841 - Permalink


Strategies for the radiosynthesis of potent fluorinated Nε-acryloyllysines as potential PET tracers for transglutaminase 2
Wodtke, R.; Jäckel, E.; Bauer, D.; Lohse, M.; Wong, A.; Pufe, J.; Ruiz-Gómez, G.; Hauser, C.; Hauser, S.; Steinbach, J.; Teresa Pisabarro, M. T.; Pietsch, M.; Pietzsch, J.; Löser, R.
Corresponding author: Wodtke, Robert
Abstract: Objectives: Various kinds of tumour entities are characterised by increased activity of transglutaminase 2 (TGase 2), which contributes to enhanced invasive potential of the tumour cells and their resistance to chemo- and radiotherapy. Therefore, this enzyme represents an interesting target for the development of PET tracers for functional imaging of tumours. Among the TGase 2 inhibitors described in the literature, Nε-acryloyllysine 1 [1] seems to be most suitable for radiotracer development as this compound exhibits both strong inhibitory potential and selectivity towards human TGase 2. Extensive structure-activity relationship studies by our group revealed some potent fluorinated analogues of 1, of which compounds 2 and 4 were identified as potential candidates for PET tracer development due to their great inhibitory potencies and promising pharmacokinetic properties.
Methods: Reference compounds 2 and 4 as well as the precursor 3 were synthesised in a modular synthetic route. For the radiosynthesis of [18F]2, thienyl and anisyl iodonium salts were envisaged as precursors for prosthetic labelling groups, which were synthesised starting from iodophenylacetates. The fluorination reactions using [18F]F- were performed under various conditions to maximise the radiochemical yield (RCY).
Results: Although a wide range of conditions for radiolabelling of the phenylacetic acid-derived iodonium salts were applied, no incorporation of [18F]F- could be observed. To identify possible reasons for this, the two other regioisomeric phenylacetic acid-derived iodonium salts were synthesised and subjected to labelling with [18F]F-. As a result of these efforts, the CH acidity of the benzylic methylene group was supposed to have a detrimental effect on the labelling reaction. In contrast to this, labelling of precursor 3 was successful with RCYs (non-isolated crude product) of up to 15%. Due to the difficult separation of 3 and [18F]4, the nitro group was reduced to the respective amino group by tin(II) chloride prior to purification by RP-HPLC.
Conclusions: After identifying fluorinated Nε-acryloyllysines as potential PET tracer candidates, strategies for their radiosynthesis were developed. While attempts for the incorporation of fluorine-18 at the non-activated phenylacetic acid moiety revealed inherent structural limitations, labelling at the 2-nitropyridine-derived precursor led to a promising PET tracer candidate.
References:
[1] J. Wityak et al. ACS Med. Chem. Lett. 2012, 3, 1024-1028

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  • Secondary publication expected from 12.05.2018

Registration No. 25836 - Permalink


Improving Stability of Cathepsin B Endopeptidase Substrates as Potential Cleavage Sites in Activatable Cell-Penetrating Peptides
Kuhne, K.; Behring, L.; Birgit Belter, B.; Wodtke, R.; Steinbach, J.; Pietzsch, J.; Löser, R.
Corresponding author: Löser, Reik
Abstract: Objectives: The cysteine protease cathepsin B, whose expression in tumors correlates with increased metastasis, therapy resistance, and a generally poor prognosis, represents an excellent target for molecular imaging using radiotracers [1]. We aim to develop a cathepsin B specific, substrate-based radiotracer derived from poly-d-arginine-based activatable cell penetrating peptides [2]. With in vivo application of peptides being often limited by short biological half-life, stabilization against proteolytic degradation is a key aspect in the development of this agent.
Methods: Octapeptide substrates containing the FRET pair aminobenzoyl/dinitrophenyl (Abz/Dnp) were synthesized by solid phase peptide synthesis in high purities and good yields, using non-proteinogenic and N-methylated amino acids (AA) for stabilization. All substrates were evaluated for cleavage efficiency by cathepsin B in orientation to [3]. In vitro stability studies were performed in human serum, with analysis by UPLC-ESI-MS, using the UV absorbance of Dnp (λ = 365 nm) for quantification and subsequent ESI-MS analysis for identification of degradation products.
Results: Rapid degradation has been observed for the endopeptidase substrate Abz-Gly-Ile-Val-Arg-Ala-Lys(Dnp)-Gly-Ser-NH2 in the in vitro serum stability assay (T1/2 = 3.7 min), which was due to cleavage at the P1-P1’ cleavage site (Arg-Ala) as indicated by LC-MS analysis. In a first step, arginine was substituted by citrulline to decrease susceptibility to trypsin-like serum proteases, which increased serum stability (T1/2 = 8.9 min). The non-proteinogenic AA homoarginine, homocitrulline and O-carboxybenzylserine are being tested as further potential substitutes for arginine. Secondary cleavage sites, identified at P4-P3 (Gly-Ile) and P2’-P3’ (Lys-Gly), were suppressed by insertion of Nα-methyl-isoleucine and Nα-methyl-glycine.
Conclusions: After the optimization of the endopeptidase substrate with regards to cathepsin B-specific cleavage, substrate stabilization against other proteases is a crucial step to a peptide-based radiotracer. We have demonstrated the potential for stabilization by introduction of citrulline, with further stabilization by insertion of N-methylated and non-proteinogenic amino acids ongoing, which will pave the way to the envisaged substrate-based imaging probes.
References:
1. Löser & Pietzsch, Front. Chem. 2015, 3, 37
2. Jiang et al., PNAS 2004, 101, 17867
3. Cotrin et al., Anal. Biochem. 2004, 335, 244

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  • Secondary publication expected from 12.05.2018

Registration No. 25835 - Permalink


Thermal convection of liquid metal in the titanium reduction reactor
Teimurazov, A.; Frick, P.; Stefani, F.
Corresponding author: Teimurazov, Andrei ICMM Perm, Russia
Abstract: The structure of the convective flow of molten magnesium in a metallothermic titanium reduction reactor has been studied numerically in a three-dimensional non-stationary formulation with conjugated heat transfer between liquid magnesium and solids (steel walls of the cavity and titanium block). A nonuniform computational mesh with a total of 3.7 million grid points was used. The Large Eddy Simulation technique was applied to take into account the turbulence in the liquid phase. The instantaneous and average characteristics of the process and the velocity and temperature pulsation fields are analyzed. The simulations have been performed for three specific heating regimes: with furnace heaters operating at full power, with furnace heaters switched on at the bottom of the vessel only, and with switched-off furnace heaters. It is shown that the localization of the cooling zone can completely reorganize the structure of the large-scale flow. Therefore, by changing heating regimes, it is possible to influence the flow structure for the purpose of creating the most favorable conditions for the reaction. It is also shown that the presence of the titanium block strongly affects the flow structure.

Registration No. 25832 - Permalink


Transitions in a magnetized quasi-laminar spherical Couette flow
Kasprzyk, C.; Kaplan, E.; Seilmayer, M.; Stefani, F.
Corresponding author: Stefani, Frank HZDR
Abstract: First results of a new spherical Couette experiment are presented. The liquid metal flow in a spherical shell is exposed to a homogeneous axial magnetic field. For a Reynolds number Re=1000, we study the effect of increasing Hartmann number Ha. The resulting flow structures are inspected by ultrasound Doppler velocimetry. With a weak applied magnetic field, we observe an equatorially antisymmetric jet instability with the azimuthal wave number m=3. As the magnetic field strength increases, this instability vanishes. When the field is increased further, an equatorially symmetric return flow instability arises. Our observations are shown to be in good agreement with linear stability analysis and non-linear flow simulations.
  • Magnetohydrodynamics 53(2017)2, 393-401

Downloads:

  • Secondary publication expected from 13.07.2018

Registration No. 25830 - Permalink


Comparison of MLAA-derived attenuation maps with and without utilisation of time-of-flight information in the attenuation estimation step
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: INTRODUCTION
As is well known, quantitative combined PET/MR imaging depends on accurate MR-based attenuation correction (MRAC). While a mostly satisfactory state of affairs has been reached today, problems persist regarding segmentation
errors including unsatisfactory bone identification and residual systematic differences in comparison to PET/CT. Alternative or complementary strategies for attenuation correction (AC), therefore, are of considerable relevance. In this context, Maximum Likelihood reconstruction of Attenuation and Activity (MLAA) is one of the most promising approaches. As A. Rezaei et al. have shown [1], Time-Of-Flight (TOF) image reconstruction is required to eliminate possible ”crosstalk” between the estimated activity and attenuation distribution. On the other hand, it is widely believed that use of the TOF information during attenuation estimation does not result in image quality improvement and thus is unnecessary, see for example ref. [2]. However, so far this assumption has never been thoroughly tested. We address this issue in the present investigation. To this end, we have compared TOF and non-TOF versions of the attenuation estimation algorithm as part of MLAA within the framework of our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [3].

METHODS
MLAA is an image reconstruction algorithm, which maximizes the Likelihood function by alternately updating activity distribution and attenuation map. Maximum-Likelihood Estimation-Maximization (MLEM) is normally used for the
activity estimation and Maximum-Likelihood Transmission Reconstruction (MLTR) for the attenuation estimation. In order to investigate the potential impact of using TOF-MLTR instead of nonTOF-MLTR in the MLAA workflow both of them were implemented as a part of our THOR application. List-mode MLEM algorithm was used for activity reconstruction and accelerated by utilizing ordered subsets. For scatter correction (SC), the time-of-flight extension of the Single Scatter Simulation algorithm (SSS) was used, see ref [4]. Attenuation map reconstruction was performed by ordered subsets accelerated list-mode version of MLTR, which is equivalent to the standard sinograms based MLTR in the non-TOF case. For the initial attenuation map estimate the MR-derived outline of the scanned object was uniformly filled with the attenuation coefficient of water. During reconstruction, attenuation map estimates were augmented by a pre-computed template of the patient bed. The main difference between TOF- and nonTOF-MLTR is the way how scatter and randoms corrections are handled. TOF information allows to individually compute this correction for each event (or TOF-bin) depending on event position along the LOR, while this correction is assumed to be the same for all the events within the LOR in the non-TOF algorithm. Consequently, any differences between both MLTR versions should be most pronounced for high contrast objects as is the case, e.g., if the bladder is within the field-of-view. Therefore, two different configurations of the whole body phantom L981602 were used. The phantom in configuration A has two cylindrical air-filled inserts and one cylindrical bone-like insert. This phantom allows to assess accuracy of the attenuation map estimate under low-contrast conditions. The phantom in configuration B comprises a large spherical ”bladder” insert with high target-to-background contrast and a small ”lesion” insert with lower contrast. The attenuation map is uniform in this case, which facilitates detection of scatter-related artifacts in the MLAA reconstructed attenuation image. Transmission scans of the phantoms with the Siemens HR+ scanner were performed and used as ground-truth for the attenuation maps.

RESULTS
The whole body phantom in both configurations was scanned with the Time-Of-Flight capable Philips Ingenuity-TF PET/MR scanner (TOF resolution (FWHM): ∼600 ps). Acquired data were reconstructed with THOR MLAA and TOF-MLTR and nonTOF-MLTR, respectively. In the case of configuration A (low activity contrast, high attenuation contrast) TOF-MLTR does not improve attenuation coefficients estimate significantly. Reconstructed attenuation values differ by less than 1% for bone and less than 15% for air. The situation is different for configuration B (high activity contrast, homogeneous attenuation). Due to presence of the large hot object in the field-of-view a massive artifact appears in the transaxial plane of the reconstructed attenuation map containing the ”bladder” insert. In the coronal view this artifact appears as a rather large area of apparently reduced attenuation in the middle of the phantom. The difference between the attenuation coefficient of the water background in the central and the peripheral zones depends on the reconstruction method used. Specifically, the use of TOF-MLTR instead of nonTOF-MLTR yields twofold decrease of the artifact. On the other hand, the attenuation coefficient inside the ”bladder” is about 12% higher than the reference value with TOF-MLTR compared to a 6% overestimate with nonTOF-MLTR (where this reduced deviation probably is due to the influence of the mentioned attenuation artifact).

CONCLUSION
Our preliminary results indicate that the use of TOF-MLTR within the MLAA framework provides only small improvements in terms of attenuation map accuracy if activity contrasts are modest. However, it can distinctly decrease scatter related artifacts in the presence of high activity contrast such as is frequently observed in the pelvis region. We hypothesize the advantages of TOF-MLTR will become even more apparent with increasing TOF resolution. A more detailed investigation of the benefits of TOF-MLTR usage within the MLAA workflow is under way.

REFERENCES
[1] A. Rezaei, M. Defrise, G. Bal, C. Michel, M. Conti, C. Watson, and J. Nuyts, “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on Medical Imaging, vol. 31, no. 12, pp. 2224–33, dec 2012.
[2] A. Rezaei and J. Nuyts, “Simultaneous reconstruction of the activity image and registration of the CT image in TOF-PET,” IEEE Nuclear Science Symposium Conference Record, vol. 1852, p. 1852, 2016.
[3] A. Lougovski, F. Hofheinz, J. Maus, G. Schramm, E. Will, J. van den Hoff, and J. van den Hoff, “A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction,” Physics in Medicine and Biology, vol. 59, no. 3, pp. 561–577, feb 2014.
[4] C. C. Watson, “Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET,” IEEE Transactions on Nuclear Science, vol. 54, no. 5, pp. 1679–1686, 2007.
Keywords: PET, TOF-PET, PET/MR, MLAA, MRAC, Attenuation Correction
  • Poster
    PSMR 2017 - 6th Conference on PET-MRI and SPECT-MRI, 29.-31.05.2017, Lisbon, Portugal

Registration No. 25829 - Permalink


Sun - Batteries - Sun
Stefani, F.; Galindo, V.; Giesecke, A.; Weber, N.; Weier, T.
Abstract: Liquid metal batteries (LMBs) are presently discussed as cheap means for the storage of wind and solar energy. Among other drivers of undesired fluid motion that could destroy the three-fluids stratification, the Tayler instability (TI) sets some upper limit for the upscalability of LMBs. We present the principles of the TI, its possible effects on LMBs, and some simple ways to suppress it. We focus on the peculiar saturation mechanism of the TI at low magnetic Prandtl numbers, which relies on the change of the hydrodynamic base state. We discuss the recently found helicity oscillations of the m=1 velocity field of the TI which, in turn, might have consequences for stellar dynamo models for which the TI had originally been discussed. We show that these helicity oscillations can be resonantly excited by certain m=2 perturbations which would result, e.g., from planetary tidal forces. It is this high sensitivity of the helicity oscillations that could empower those very weak tidal forces to synchronize the entire solar dynamo.
  • Lecture (Conference)
    International workshop on liquid metal battery fluid dynamics (LMBFD 2017), 16.-17.05.2017, Dresden, Germany

Registration No. 25828 - Permalink


The DRESDYN project: planned experiments and present status
Stefani, F.; Eckert, S.; Gerbeth, G.; Giesecke, A.; Gundrum, T.; Räbiger, D.; Seilmayer, M.; Weier, T.
Abstract: The Dresden sodium facility for dynamo and thermohydraulic studies (DRESDYN) is a platform for large-scale liquid sodium experiments devoted to fundamental geo- and astrophysical questions as well as to various applied problems related to the conversion and storage of energy. Its most ambitious part is a precession driven dynamo experiment, comprising 8 tons of liquid sodium supposed to rotate with up to 10 Hz and to precess with up to 1 Hz. Another large-scale set-up is a Tayler-Couette experiment with a gap width of 0.2 m and a height of 2 m, whose inner cylinder rotates with up to 20 Hz. Equipped with a coil system for the generation of an axial field of up to 120 mT and two different axial currents through the center and the liquid sodium, this experiment aims at studying various versions of the magnetorotational instability and their combinations with the Tayler instability. We discuss the physical background of these two experiments and delineate the present status of their technical realization. Other installations, such as a sodium loop and a test stand for In-Service-Inspection experiments, will also be sketched.
  • Lecture (Conference)
    88th GAMM Annual Meeting, 06.-10.03.2017, Weimar, Germany

Registration No. 25827 - Permalink


Ultrasound propagation in bond frustrated HgCr2S4 spinel in magnetic fields
Felea, V.; Prodan, L.; Stefanet, E.; Cong, P. T.; Zherlitsyn, S.; Tsurkan, V.
Corresponding author: Tsurkan, V. Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova & Experimental Physics V, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Augsburg, Germany
Abstract: Ultrasound and magnetization studies of bond frustrated spinel HgCr2S4 are performed as a function of temperature in static magnetic fields. Beside the anharmonic effect, the sound velocity shows pronounced anomaly at the antiferromagnetic (AFM) transition at TN = 23 K with an additional significant increase of the order of 0.5 % indicating a strong spin-lattice coupling. External magnetic fields enhance the ferromagnetic (FM) correlations and shift the anomalies to lower temperatures concomitantly with the reduction of the Néel temperature. The constructed H–T Phase diagram beside the long-range AFM states reveals the state with induced FM order and regimes with short-range AFM and FM correlations as well.

Registration No. 25826 - Permalink


Comparison of arterial spin labeling registration strategies in the multi-center GENetic frontotemporal dementia initiative (GENFI)
Mutsaerts, H. J. M. M.; Petr, J.; Thomas, D. L.; de Vita, E.; Cash, D. M.; van Osch, M. J. P.; Golay, X.; Groot, P. F. C.; Ourselin, S.; van Swieten, J.; Laforce, R.; Tagliavini, F.; Borroni, B.; Galimberti, D.; Rowe, J. B.; Graff, C.; D. Pizzini, F. B.; Finger, E.; Sorbi, S.; Castelo Branco, M.; Rohrer, J. D.; Masellis, M.; Macintosh, B. J.
Abstract: Purpose: To compare registration strategies to align arterial spin labeling (ASL) with 3D T1-weighted (T1w) images, with the goal of reducing the between-subject variability of cerebral blood flow (CBF) images.
Materials and Methods: Multi-center 3T ASL data were collected at eight sites with four different sequences in the multi-center GENetic Frontotemporal dementia Initiative (GENFI) study. In a total of 48 healthy controls, we compared the following image registration options: (I) which images to use for registration (perfusion-weighted images [PWI] to the segmented gray matter (GM) probability map (pGM) (CBF-pGM) or M0 to T1w (M0-T1w); (II) which transformation to use (rigid-body or non-rigid); and (III) whether to mask or not (no masking, M0-based FMRIB software library Brain Extraction Tool [BET] masking). In addition to visual comparison, we quantified image similarity using the Pearson correlation coefficient (CC), and used the Mann-Whitney U rank sum test.Results: CBF-pGM outperformed M0-T1w (CC improvement 47.2% 6 22.0%; P < 0.001), and the non-rigid transformation outperformed rigid-body (20.6% 6 5.3%; P < 0.001). Masking only improved the M0-T1w rigid-body registration (14.5% 6 15.5%; P 5 0.007).
Conclusion: The choice of image registration strategy impacts ASL group analyses. The non-rigid transformation is promising but requires validation. CBF-pGM rigid-body registration without masking can be used as a default strategy.
In patients with expansive perfusion deficits, M0-T1w may outperform CBF-pGM in sequences with high effective spatial resolution. BET-masking only improves M0-T1w registration when the M0 image has sufficient contrast.

Registration No. 25825 - Permalink


Scatter correction in TOF and non-TOF PET image reconstruction in THOR
Nikulin, P.ORC; Lougovski, A.; Hofheinz, F.; Maus, J.ORC; van den Hoff, J.
Abstract: INTRODUCTION
As is well known, quantitative combined PET/MR imaging depends on accurate MR-based attenuation correction (MRAC). While a mostly satisfactory state of affairs has been reached today, problems persist regarding segmentation errors including unsatisfactory bone identification and residual systematic differences in comparison to PET/CT. Alternative or complementary strategies for attenuation correction (AC), therefore, are of considerable relevance. In this context, Maximum Likelihood reconstruction of Attenuation and Activity (MLAA) is one of the most promising approaches but, as A. Rezaei et al. have shown [1], Time-Of-Flight (TOF) image reconstruction is then required to eliminate possible ”crosstalks” between the estimated activity and attenuation distribution. We are aiming at implementation of MLAA for the Philips Ingenuity-TF PET/MR scanner as part of our previously developed Tube of response High resolution OSEM Reconstruction (THOR), see ref [2]. As a prerequisite we are currently modifying THOR to make full use of the available TOF information. The most critical point in this context is accurate and computational efficient TOF Scatter Correction (TOF-SC). Here, we report on our approach to solving this issue and compare TOF-SC techniques with conventional non-TOF SC method.

METHODS
One possible implementation of TOF-SC uses a straight forward extension of Watson’s well-known Single Scatter Simulation (SSS) algorithm [3] but this approach results in about an order of magnitude increase of computational burden compared to standard SSS. Alternatively, one can use standard SSS to estimate the number of scattered events in each Line Of Response (LOR) and use an additional algorithm to estimate the shape of the time distribution of scattered events within each LOR (scatter mask). To integrate TOF-SC into our THOR reconstruction, four different approaches to scatter mask calculation have been investigated:
A. Simple scatter scaling
This approach assumes that scattered and unscattered events have identical time distribution within each single LOR.
B. Attenuation based SC
In this approach the object is modeled as a set of “scatter points” which are generated by SSS. Each scatter point is then also assumed to be a scatter source. For each detector pair and scatter point the geometric path difference from scatter source to both detectors is calculated and an effective position of the scattered event within the corresponding LOR is determined. By repeating this procedure for a large number of scatter points and post-processing the results by smoothing or using a TOF-binning technique one can compute the required scatter mask.
C. Attenuation and activity based SC
While approach B allows to properly handle the shape of the attenuating object it does not take into account the given activity distribution. To fix this issue scatter sources and scatter points should be separated. To do this in a simple and fast way we introduce a small set of “emission points” for approximation of the given activity distribution. The activity distribution/object is then described as superposition of suitable 3D Gaussian distributions around these emission
points. Calculation of the scatter masks is similar to the previous approach, but now scatter sources are determined as projections of emission points onto straight lines connecting selected scatter point and detectors. In this approach the intensity of each source is proportional to the intensity of corresponding emission point and decreases according to a Gaussian as a function of the distance between them.
D. TOF-SSS Time-Of-Flight extension of Single Scatter Simulation by Watson.

RESULTS
All four approaches have been integrated into THOR and tested in dedicated phantom and patient studies. Approach A does not yield quantitatively correct scatter distributions for big objects. Approach B is superior to A but notable artifacts remain in the presence of high-contrast. Approach C is able to eliminate part of these artifacts but requires more computation time. Approach D is the most accurate and computationally most expensive.

CONCLUSION
Our preliminary results indicate that attenuation based SC might be the best compromise between computation time and image quality for a wide range of applications.

REFERENCES
[1] A. Rezaei, M. Defrise, G. Bal, C. Michel, M. Conti, C. Watson, and J. Nuyts, “Simultaneous reconstruction of activity and attenuation in time-of-flight PET.” IEEE transactions on Medical Imaging, vol. 31, no. 12, pp. 2224–33, dec 2012.
[2] A. Lougovski, F. Hofheinz, J. Maus, G. Schramm, E. Will, J. van den Hoff, and J. van den Hoff, “A volume of intersection approach for on-the-fly system matrix calculation in 3D PET image reconstruction,” Physics in Medicine and Biology, vol. 59, no. 3, pp. 561–577, feb 2014.
[3] C. C. Watson, “Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET,” IEEE Transations on Nuclear Science, vol. 54, no. 5, pp. 1679–1686, 2007.
Keywords: PET, TOF-PET, Scatter Correction, TOF-SC, Single Scatter Simulation, SSS
  • Lecture (Conference)
    Seminar on PET image reconstruction, 28.-30.09.2016, Leuven, Belgium

Registration No. 25824 - Permalink


Effect of Brain Extraction of Low Resolution Arterial Spin Labeling (ASL) Fmri Images on Realignment and Coregistration
Liao, J.; Petr, J.; Lazar, R. M.; Marshall, R. S.; Asllani, I.
Abstract: ASL is an fMRI method that maps cerebral blood (CBF), which is a key parameter of brain physiology. In ASL, flow-weighted images are computed by subtracting a “labeled” image from a contiguously acquired unlabeled control image. The difference is then converted to a CBF image using partial volume (PV) maps obtained from the segmentation of the anatomical T1w image. It follows that the quality of ASL data is dependent on the quality of motion correction and coregistration of the high-resolution T1w image to the low-resolution ASL. We tested whether applying brain-extraction on the low-resolution ASL would improve both these processes. The test was performed on 8 patients with carotid occlusive disease. Improvement in motion realignment was defined as % change averaged over the 6 degrees of freedom and across patients; improvement in coregistration was assessed as a difference in the mutual information (MI) value between the T1w and extracted and original ASL, respectively. There was a noticeable effect of brain extraction on both realignment and coregistration.
Keywords: MR neuroimaging, Brain image analysis, Rigid-body image registration, ASL
  • Contribution to proceedings
    39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 11.-15.07.2017, Jeju Island, Korea
  • Poster
    39th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 11.07.2017, Jeju Island, Korea

Registration No. 25823 - Permalink


SUR: a superior alternative to SUV as a surrogate of tumor glucose metabolism
van den Hoff, J.
Abstract: kein Abstract verfügbar
  • Invited lecture (Conferences)
    Symposium Nuclear Medicine & Molecular Imaging, Katholieke Universiteit Leuven, 10.01.2017, Leuven, Belgien

Registration No. 25822 - Permalink


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