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33403 Publications

Electron mobility and lifetime in GaAs/In𝑥Ga1−𝑥As core/shell nanowires studied by optical pump – THz probe spectroscopy

Fotev, I.; Balaghi, L.; Hübner, R.; Schmidt, J.; Hähnel, M.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, A.
We utilize ultrafast optical pump – terahertz probe spectroscopy in order to investigate charge carrier response of GaAs/In𝑥Ga1−𝑥As core/shell nanowires (NWs) produced by molecular beam epitaxy. The NWs were ≈2 𝜇m long. The GaAs core diameter was 25nm and the InGaAs shell thickness was 80 nm. We studied the shells with different compositions, from 𝑥 = 0.20 to 𝑥 = 0.44.
From the pump-probe measurements we extracted terahertz photoconductivity of NWs and used the localized surface plasmon model to fit the results. The charge carrier lifetimes were estimated to be around 80–100 ps while the extracted electron mobilities reach 3700 cm2V−1s−1 at room temperature. Even without a surface passivation shell, these values are higher than those in previously studied GaAs/AlGaAs core/shell nanowires, but still lower than the ones for bulk InGaAs. Possible reasons (sources of electron scattering) which affect the mobility will be discussed.
Keywords: nanowires; terahertz; mobility
  • Lecture (Conference)
    DPG Spring Meeting 2018, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27620
Publ.-Id: 27620


Nonlinear Plasmonic Response of Doped GaAs Nanowires Observed in sSNIM

Lang, D.; Balaghi, L.; Dimakis, E.; Hübner, R.; Kehr, S. C.; Eng, L. M.; Pashkin, A.; Winnerl, S.; Schneider, H.; Helm, M.
We present nanoscopic infrared-optical investigations on highly n-type doped GaAs-based nanowires, revealing interesting nonlinear phenomena such as a pronounced redshift of the plasma resonance by the strong THz fields of a free-electron laser.
Keywords: nanowires, nonlinear plasmonics, free-electron laser, terahertz, s-SNOM, nanoscopy
  • Contribution to proceedings
    Conference on Lasers and Electro-Optics (CLEO), 14.05.2018, San José, USA
    Conference on Lasers and Electro-Optics, JM2A.3
    DOI: 10.1364/CLEO_AT.2018.JM2A.3
  • Lecture (Conference)
    Conference on Lasers and Electro-Optics (CLEO), 14.-18.05.2018, San José, USA

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Permalink: https://www.hzdr.de/publications/Publ-27619
Publ.-Id: 27619


Stability of U(VI) doped calcium silicate hydrate phases in repository-relevant brines studied by leaching experiments and spectroscopy

Wolter, J.-M.; Schmeide, K.ORC; Weiss, S.; Bok, F.; Brendler, V.ORC; Stumpf, T.

The stability of U(VI) doped calcium silicate hydrate (CSH) phases was evaluated in claystone formation waters that possess high ionic strengths and carbonate contents. Such phases were synthesized by direct U(VI) incorporation and characterized with time-resolved laser-induced fluorescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The time-dependent release of Ca, Si and U from U(VI) doped CSH phases into brines that contained 2.5 M NaCl, 2.5 M NaCl/0.02 M Na2SO4, 2.5 M NaCl/0.02 M NaHCO3 or 0.02 M NaHCO3 was monitored for three calcium-to-silicon (C/S) ratios over 32 days. Subsequently, changes of the U(VI) speciation and CSH phase mineralogy caused by leaching were investigated with TRLFS, IR spectroscopy and XRD. Results indicated that composition and pH of the leaching solution as well as presence and solubility of secondary phases such as portlandite and calcite determine the U(VI) retention by CSH phases under high saline and alkaline conditions. At high ionic strengths, the Ca release from CSH and secondary phases like calcite is increased. Under hyperalkaline conditions only small amounts of U(VI) were release during leaching. A decrease of the pH due to the additional presence of carbonate was linked with an increased U(VI) release from CSH phases caused by the occurrence of a calcium uranyl carbonate in the supernatant solution.

Keywords: uranium, CSH, portlandite, carbonate, ionic strength, TRLFS
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-12-31
    DOI: 10.14278/rodare.37

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Permalink: https://www.hzdr.de/publications/Publ-27618
Publ.-Id: 27618


Enhancing the Magnetic Moment of Ferrimagnetic NiCo2O4 via Ion Irradiation driven Oxygen Vacancies

Pandey, P.; Bitla, Y.; Zschornak, M.; Wang, M.; Xu, C.; Grenzer, J.; Meyer, D. C.; Chin, Y. Y.; Lin, H. J.; Chen, C. T.; Gemming, S.; Helm, M.; Chu, Y. H.; Zhou, S.ORC
Ion irradiation has emerged as a powerful tool for the efficient control of uniaxial lattice expansion to fine tune and modulate the otherwise inaccessible complex correlated phases in oxide thin-films. We report the fine tuning of the magnetic moment, ferromagneticparamagnetic and metal-insulator transition temperatures in the NiCo2O4 inverse-spinel oxide by creating oxygen deficiencies, employing high energy He-ion irradiation. Tailoring of oxygen vacancies and consequently a uniaxial lattice expansion in the out-of-plane direction drives the system towards the increase of the magnetic moment by two-times in magnitude.
The magnetic moment increases with the He-ion irradiation fluence up to 2.5×1016/cm2 . Our results are corroborated well by spin-polarized electronic structure calculations with density functional theory and X-ray absorption spectroscopic data which show peak-height change and energy shift of Co-L2,3 and Ni-L2,3 edges driven by the oxygen vacancies. These results demonstrate a new pathway of tailoring oxygen vacancies via He-ion irradiation, useful for designing new functionalities in other complex oxide thin-films.

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Permalink: https://www.hzdr.de/publications/Publ-27617
Publ.-Id: 27617


Vergleich der Wirkung von Alpha- und Protonenstrahlung an Normal- und Tumorzellen

Maucksch, U.; Runge, R.; Wetzig, K.; Naumann, A.; Freudenberg, R.; Lühr, A.; Beyreuther, E.; von Neubeck, C.; Kotzerke, J.
Ziel:
Für Alpha-Strahler ist bekannt, dass diese aufgrund eines hohen linearer Energietransfers (LET) bei gleicher Dosis eine höhere relative biologische Wirksamkeit (RBE) im Vergleich zu Gammastrahlern zeigen. Als Ursache werden die hohe lokale Dosisdeposition sowie die erhöhte Wahrscheinlichkeit für DNA-Doppelstrangbrüche (DSB) angenommen. Für Protonenstrahlung ist eine RBE von 1,1 zu erwarten. Untersucht wurde die Wirksamkeit von 150 MeV Protonenbestrahlung im Vergleich zum Alpha-Emitter Ra-223 auf das verwendete Zellsystem.
Methodik:
Die Wirkung der Protonenbestrahlung und des Alpha-Emitters Ra-223 wurde durch Bestrahlung der Schilddrüsennormalgewebszelllinie FRTL-5 sowie der Tumorzelllinie FaDu überprüft. Die Protonenbestrahlung im Dosisbereich von 0,5 bis 10 Gy erfolgte mit 3 Gy/min am Protonenstrahl der Universitätsprotonentherapie Dresden. Um Dosispunkte zwischen 0,125 und 2 Gy des Alpha-Strahlers Ra-223 zu applizieren, wurden die Zellen mit verschiedene Aktivitätskonzentrationen über 24 h inkubiert. Das klonogene Zellüberleben und die Anzahl der residualen DNA-DSB (H2AX-Assay) wurden 24 h nach Bestrahlung untersucht.
Ergebnisse:
Aus den Dosiswirkungskurven des Koloniebildungsassays wurde die Dosis für 37 % Überleben (D37) für die Normalzelllinie FRTL-5 nach Protonenbestrahlung mit 2,96 Gy und für Ra-223 mit 0,35 Gy bestimmt. Die Tumorzelllinie FaDu zeigte nach Protonenbestrahlung eine D37 von 2,32 Gy und nach Inkubation von Ra-223 eine D37 von 0,31 Gy. Für beide Zelllinien war die Anzahl an residualen DNA-DSB (H2AX-Assay) nach Protonenbestrahlung signifikant geringer als bei Bestrahlung mit Ra-223.
Schlussfolgerung:
Der erhöhte LET des Alpha-Strahlers Ra-223 (max. 250 keV/µm) führt zu einem geringenen Zellüberleben und zu einer höheren Anzahl der residualen DNA-DSB im Vergleich zur Protonenbestrahlung (LET ca. 2 keV/µm).
  • Lecture (Conference)
    56. Jahrestagung der Deutschen gesellschaft für Nuklearmedizin, 18.-21.04.2018, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27616
Publ.-Id: 27616


Radiobiological characterization of laser driven particle beams – Dresden activities

Beyreuther, E.
The long-term aim of developing laser based particle acceleration towards clinical application requires not only substantial technological progress, but also new technical solutions for dose delivery and quality assurance as well as comprehensive research on the radiobiological consequences of ultra-short radiation pulses with high pulse dose.
During the last years the laser driven technology was developed at such a rate that cell samples and small animals can be irradiated. Within the joint research project “onCOOPtics” extensive in vitro studies with several human tumor and normal tissue cells were performed revealing comparable radiobiological effects of laser driven and conventional electron and proton beams1,2. Using the same cell lines, these results were substantiated comparing the radiobiological response to ultra-short pulsed electron bunches (pulse dose rates of ≤1012 Gy/min) and continuous electron delivery at the radiation source ELBE3.
In a second translational step, in vivo experiments were established. Although the experiments were motivated by future proton trials, first attempts were performed with electrons at the laser system JETI4, since the delivery of prescribed homogeneous doses to a 3D target volume is easier for electrons than for protons. A full scale animal experiment was realized for the HNSCC FaDu grown on nude mice ear. The radiation induced tumor growth delay was determined and compared to those obtained after similar treatment at a conventional clinical LINAC. Again, no significant difference in the radiation response to both radiation qualities was revealed, whereas the successful performance of such a comprehensive experiment campaign underlines the stability and reproducibility of all implemented methods and setup components.
During this experiment campaign several limitations of the model were identified which were in the following redressed by co-injection of LN229 glioblastoma tumour cells with Matrigel5. Results of this optimization process and the status of the experiments with laser driven protons at the laser system DRACO will be presented.
The work was supported by the German Government, Federal Ministry of Education and Research, grant nos. 03ZIK445 and 03Z1N511.
1Laschinsky L et al. (2012) J. Radiat. Res. 53(3): 395-403.
2Zeil K et al. (2012) Appl. Phys. B 110(4): 437-444.
3Beyreuther E et al. (2015) Int. J. Radiat. Biol. 91(8): 643-652.
4Oppelt M et al. (2015) Radiat. Environ. Biophys. 54(2): 155-166.
5Beyreuther E et al. (2017) PloS One 12.5 (2017): e0177428.
  • Contribution to proceedings
    44th European Radiation Research Congress, 21.-25.08.2018, Pecs, Hungary

Permalink: https://www.hzdr.de/publications/Publ-27615
Publ.-Id: 27615


Simple vertebrate model development for radiobiology research at ELI-ALPS on laser driven hadron beams

Szabo, E. R.; Tőkés, T.; Polanek, R.; Brunner, S.; Czifrus, S.; Fenyvesi, A.; Biró, B.; Beyreuther, E.; Pawelke, J.; Hideghéty, K.
Purpose/objective: High power lasers provide the basis of particle acceleration, but at the actual status of the development, low energy, limited size beams with special properties (ultrahigh dose rate, pulsed mode) are available under highly technical conditions for radiobiology experiments.
Our main aim was to introduce and validate a vertebrate system for in vivo experiments to investigate the biological effects of novel hadron beams. The endpoints at diverse dose levels were observed during a certain time frame in order to establish the most relevant factors for relative biological effectiveness (RBE) definition.
Material/methods: Series of zebrafish embryos in 24 hour post fertilization ages in different holders like tubes and 96 well plates varying the number (n) of embryos/well were prepared. For irradiation we used fission neutron (0, 1.25, 1.875, 2, 2.5 Gy), cyclotron-based neutron (0, 2, 4, 6.8, 8.12, 10.28 Gy) and proton (0, 5, 10, 15, 20 and 30 Gy) at two positions along the proton depth-dose curve (at the plateau and at the middle of Spread Out Bragg Peak), furthermore, with reference linear accelerator photon (0, 5, 10, 15, 20 Gy) beams (n=96 in each group), repeated several times (≥3). Thereafter, survival, any type of organ developmental disturbance (pericardial edema, spine curvature, shortening of the body length and micro-opthalmia) were detected each days up to 7 days post irradiation (dpi). Histological evaluation (size of the eye, brain necrosis, intestinal changes, liver vacuolization, hyper eosinophilic necrotic muscle-fibers) and molecular changes were evaluated with RT-PCR method at certain time points post irradiation.
Results: The RBE was highly sensitive in this system to time, dose and endpoints. The most robust result could be revealed by survival analysis with RBE of definition on the base of LD50- s at the 5th to 7th dpi: RBE between 10 and 4.8 for the fission and = 3.5 MeV cyclotron based neutrons and around 1.1-1.4 for protons, respectively. The morphological distortions and its severity exhibited a good agreement to the survival derived RBE with a narrow time and dose frame for the different type (i.e. pericardial edema: 3 dpi 20 Gy, spine curvature 4 dpi 15 and 20 Gy). The gravity of the histopathological changes on the basis of semi-quantitative analysis corresponded well to the macro morphological abnormalities (eye layer disorganization, degree of brain necrosis, increased numbers of the goblet cells in the gastrointestinal tract, and muscle fibrosis).
Conclusion: Numerous features of the zebrafish embryo model makes it amenable for large scale of radiobiological investigations. On the basis of our experimental series the optimal radiation setup, radiation dose and observation time points for assessment of the different biological endpoints could be established. This vertebrate model proved to be highly reproducible, reliable, and seems to be well applicable for RBE determination.

Acknowledgement: The ELI-ALPS project (GINOP-2.3.6-15-2015-00001) is supported by the European Union and co-financed by the European Regional Development Fund., The project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement no 654148 Laserlab-Europe and by the German BMBF, grant no. 03Z1N511.
  • Contribution to proceedings
    44th European Radiation Research Congress, 21.-25.08.2018, Pecs, Hungary

Permalink: https://www.hzdr.de/publications/Publ-27614
Publ.-Id: 27614


Radiation quality influence on normal tissue cell response

Beyreuther, E.
Objective: From the various factors that are known to influence the radiobiological response to therapeutic beams, the radiation type and beam energy or LET (linear energy transfer), and the beam pulsing and dose rate are object of comprehensive investigations. Alterations of these parameters might result in altered damage pattern and consequently in a different radiobiological effectiveness, for example for the FLASH, single pulse, irradiation regime [1] and the use of multiple, ultra-short laser driven particle pulses [2] where therapeutic relevant doses are administered within the fraction of a second, i.e. at high dose rate. To characterize the influence of radiation quality, i.e. beam energy, dose rate and pulsing, systematic in vitro studies performed at different accelerators will be summarized in the talk.
Methods and results: Two normal human cell lines were applied to study the response to photons in the range of 10 kV to 34 MV, to conventional and laser driven electrons, and to continuous and pulsed proton beams. By measurements of chromosomal aberrations and DNA double-strand breaks (DSB) the inverse correlation of photon energy and biological damage was revealed, whereas for the proton studies no clear influence of pulsing was found. Furthermore, no influence on clonogenic survival was observed comparing laser driven electrons of ultra-high dose rate (109 Gy/s, multiple electron pulses) and conventional, linac electrons (continuous dose rate 3 Gy/min). By contrast, a trend towards less effectiveness of pulsed laser driven electrons was revealed by measurements of residual DNA DSB. To investigate this finding in more detail, radiobiological experiments were performed at the superconducting research electron linac ELBE, which is able to provide electron beams with very variable pulse sequences and to mimic both laser driven and clinical linac electron beams. Thereby, the DSB studies were complemented by DSB repair kinetics.
Conclusion:
Comprehensive in vitro studies of the effects of various radiation qualities revealed the influence of beam energy and LET, but show no clear result with respect to pulse structure and dose rate.
References:
[1] Favaudon et al. Sci Transl Med. 2014;6(245):245ra93.
[2] Karsch et al. Acta Oncol. 2017;56(11):1359-1366.
  • Invited lecture (Conferences)
    44th European Radiation Research Congress, 21.-25.08.2018, Pecs, Hungary

Permalink: https://www.hzdr.de/publications/Publ-27613
Publ.-Id: 27613


Best Practices in Running Collaborative GPU Hackathons: Advancing Scientific Applications with a Sustained Impact

Chandrasekaran, S.ORC; Juckeland, G.ORC; Lin, M.ORC; Otten, M.ORC; Pleiter, D.ORC; Stone, J. E.; Lucio-Vega, J.; Zingale, M.ORC; Foertter, F.ORC
The OLCF GPU Hackathons are a one-week code-development/learning event to better enable attendees to utilize GPUs. It only took three years to grow from a ``Let's give this a try''-event to a repeatedly copied format with several spin-offs that inspired HPC centers around the world.
Sticking to a few fundamental principles---work on your own code, learn from your mentors just what you need and when you need it, stay flexible in achieving your goal---the week-long hackathon format created at Oak Ridge Leadership Computing Facility (OLCF) has been just the spark needed by many groups of scientists to light the fire of a wider GPU adoption in leading-edge as well as university-scale HPC environments. Most interestingly, the format enabled both ends of the experience spectrum---graduate students vs. postdoc fellows---the same kind of progress and chance of success.
Keywords: B.1.4.b Languages and compilers D.1 Programming Techniques M.12.0.b Case Studies in Scientific Applications

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Permalink: https://www.hzdr.de/publications/Publ-27612
Publ.-Id: 27612


Local probe of irradiation induced structural changes and orbital magnetism in Fe60Al40 thin films via order-disorder phase transition

La Torre, E.; Smekhova, A.; Schmitz-Antoniak, C.; Ollefs, K.; Eggert, B.; Cöster, B.; Walecki, D.; Wilhelm, F.; Rogalev, A.; Lindner, J.; Bali, R.; Banerjee, R.; Sanyal, B.; Wende, H.
Hard X-ray absorption and magnetic circular dichroism spectroscopy have been applied to study the consequential changes of the local environment around Fe atoms and their orbital polarizations in Fe60Al40 thin films of 40 nm thickness along the order-disorder (B2→A2) phase transition initiated by 20keV Ne+ ion-irradiation with fluences of (0.75 - 6) × 1014 ions cm-2. The analysis of the extended X-ray absorption fine structure spectra measured at the Fe K-edge at room temperature revealed an increased number of Fe-Fe nearest-neighbors from 3.47(7) to 5.0(1) and ~ 1% of volume expansion through the transition. The visualization of the Fe and Al nearest neighbors rearrangement in the first coordination shell of Fe absorbers via the transition was carried out by wavelet transformations. The obtained changes in Fe coordination are evidently reflected in the XMCD spectra which show an increased orbital magnetic moment of Fe atoms and a pronounced magnetic multi-electronic excitations peak at ~60 eV above the edge. The amplitudes of both peaks demonstrated similar dependencies on the irradiation fluence. The results of self-consistent DFT calculations on relaxed Fe60Al40 model structures for the ordered (B2) and the disordered (A2) phases are consistent with the experimental findings and point to the formation of Fe-rich regions in the films studied.
Keywords: Chemical disorder, ion-irradiation, magnetism, EXAFS, wavelet transform, XMCD, DFT

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Permalink: https://www.hzdr.de/publications/Publ-27611
Publ.-Id: 27611


Large-scale self-organized gold nanostructures with bidirectional plasmon resonances for SERS

Schreiber, B.; Gkogkou, D.; Dedelaite, L.; Kerbusch, J.; Hübner, R.; Sheremet, E.; Zahn, D. R. T.; Ramanavicius, A.; Facsko, S.; Rodriguez, R. D.
Efficient substrates for surface-enhanced Raman spectroscopy (SERS) are under constant development, since time-consuming and costly fabrication routines are often an issue for high-throughput spectroscopy applications. In this research, we use a two-step fabrication method to produce self- organized parallel-oriented plasmonic gold nanostructures. The fabrication routine is ready for wafer-scale production involving only low-energy ion beam irradiation and metal deposition. The optical spectroscopy features of the resulting structures show a successful bidirectional plasmonic response. The localized surface plasmon resonances (LSPRs) of each direction are independent from each other and can be tuned by the fabrication parameters. This ability to tune the LSPR characteristics allows the development of optimized plasmonic nanostructures to match different laser excitations and optical transitions for any arbitrary analyte. Moreover, in this study, we probe the polarization and wavelength dependence of such bidirectional plasmonic nanostructures by a complementary spectroscopic ellipsometry and Raman spectroscopy analysis. We observe a significant signal amplification by the SERS substrates and determine enhancement factors of over a thousand times. We also perform finite element method-based calculations of the electromagnetic enhancement for the SERS signal provided by the plasmonic nanostructures. The calculations are based on realistic models constructed using the same particle sizes and shapes experimentally determined by scanning electron microscopy. The spatial distribution of electric field enhancement shows some dispersion in the LSPR, which is a direct consequence of the semi-random distribution of hotspots. The signal enhancement is highly efficient, making our SERS substrates attractive candidates for high-throughput chemical sensing applications in which directionality, chemical stability, and large-scale fabrication are essential requirements.

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Permalink: https://www.hzdr.de/publications/Publ-27608
Publ.-Id: 27608


Integrating a low-field open MR scanner with a static proton research beam line: proof of concept

Schellhammer, S. M.ORC; Hoffmann, A. L.; Gantz, S.; Smeets, J.; van der Kraaij, E.; Quets, S.; Pieck, S.; Karsch, L.; Pawelke, J.
On-line image guidance using magnetic resonance (MR) imaging is expected to improve the targeting accuracy of proton therapy. However, to date no combined system exists. In this study, for the first time a low-field open MR scanner was integrated with a static proton research beam line to test the feasibility of simultaneous irradiation and imaging. The field-of-view of the MR scanner was aligned with the beam by taking into account the Lorentz force induced beam deflection. Various imaging sequences for extremities were performed on a healthy volunteer and on a patient with a soft-tissue sarcoma of the upper arm, both with the proton beam line switched off. T 1 -weighted spin echo images of a tissue-mimicking phantom were acquired without beam, with energised beam line magnets and during proton irradiation. Beam profiles were acquired for the MR scanner’s static magnetic field alone and in combination with the dynamic gradient fields during the acquisition of different imaging sequences. It was shown that MR imaging is feasible in the electromagnetically contaminated environment of a proton therapy facility. The anatomical MR images showed sufficient quality for target volume identification and positioning. The tissue-mimicking phantom showed no visible beam-induced image degradation. The beam profiles depicted no influence due to the dynamic gradient fields of the imaging sequences. This study proves that simultaneous irradiation and in-beam MR imaging is technically feasible with a low-field MR scanner integrated with a static proton research beam line.
Keywords: proton therapy, magnetic resonance imaging, MR guidance, beam quality, image quality

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Permalink: https://www.hzdr.de/publications/Publ-27607
Publ.-Id: 27607


Strain engineering in lattice-mismatched core/shell nanowires: extending the properties of GaAs

Balaghi, L.; Bussone, G.; Grifone, R.; Hübner, R.; Grenzer, J.; Shan, S.; Fotev, I.; Pashkin, A.; Ghorbani-Asl, M.; Krasheninnikov, A.; Wolf, D.; Hlawacek, G.; Schneider, H.; Helm, M.; Dimakis, E.
Strain engineering in core/shell nanowires (NWs) can be an alternative route to tailor the properties of III-V semiconductors without changing their chemical composition. In particular, we demonstrate that the GaAs core in GaAs/InxGa1-xAs or GaAs/InxAl1-xAs core/shell NWs can sustain unusually large misfit strains that would have been impossible in equivalent thin-film heterostructures, and undergoes a significant modification of its electronic properties.
Self-catalyzed core/shell NWs were grown on SiOx/Si(111) by MBE (Fig. 1a). The growth conditions were optimized in order to minimize the bending of the NWs, a phenomenon that originates from the large misfit between the core and the shell. Synchrotron X-ray diffraction and Raman scattering measurements showed that for a given core diameter, the magnitude and the spatial distribution of the built-in misfit strain can be regulated via the composition and the thickness of the shell. Beyond a critical shell thickness (Fig. 1b), we obtain a heavily tensile-strained core and a strain-free shell. The tensile strain of the core exhibits a quasi-hydrostatic character and causes the reduction of the GaAs band gap energy in accordance with our theoretical predictions (deformation potential theory and first principle calculations), reaching the remarkable value of 40% (0.87 eV at 300 K) for 7% of strain (x = 0.54). Signatures of valence-band splitting were also identified in polarization-resolved photoluminescence measurements, as a result of the strain anisotropy in GaAs. Presuming a reduced effective mass of electrons in the tensile-strained core of GaAs/InxAl1-xAs NWs (core diameter = 22 nm, x = 0.39–0.49), the corresponding electron mobility was measured by optical-pump THz-probe spectroscopy to be in the range of 4000 cm2/V·s at 300 K. These values are the highest reported, even in comparison to GaAs/AlxGa1-xAs NWs with double the core thickness.
In conclusion, our results (unpublished) demonstrate the possibility to resemble to a large extent the fundamental properties of InxGa1-xAs alloys using strained GaAs NWs grown epitaxially on Si (Fig. 1c). This could open a new dimension in the design of nano-photonics and nano-electronics, surmounting issues with phase separation, surface segregation or alloy disorder that typically exist in ternary alloys and limit the device performance.
Keywords: optoelectronics, band gap reduction, InxGa1-xAs
  • Lecture (Conference)
    Nanowire Week, 11.-15.06.2018, Hamilton, Ontario, Canada

Permalink: https://www.hzdr.de/publications/Publ-27606
Publ.-Id: 27606


Implanting Germanium into Graphene

Tripathi, M.; Markevich, A.; Böttger, R.; Facsko, S.; Besley, E.; Kotakoski, J.; Susi, T.
Incorporating heteroatoms into the graphene lattice may be used to tailor its electronic, mechanical and chemical properties, although directly observed substitutions have thus far been limited to incidental Si impurities and P, N and B dopants introduced using low-energy ion implantation. We present here the heaviest impurity to date, namely 74Ge+ ions implanted into monolayer graphene. Although sample contamination remains an issue, atomic resolution scanning transmission electron microscopy imaging and quantitative image simulations show that Ge can either directly substitute single atoms, bonding to three carbon neighbors in a buckled out-of-plane configuration, or occupy an in-plane position in a divacancy. First-principles molecular dynamics provides further atomistic insight into the implantation process, revealing a strong chemical effect that enables implantation below the graphene displacement threshold energy. Our results demonstrate that heavy atoms can be implanted into the graphene lattice, pointing a way toward advanced applications such as single-atom catalysis with graphene as the template.
Keywords: heteroatom doping; ion implantation; molecular dynamics; scanning transmission electron microscopy

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Permalink: https://www.hzdr.de/publications/Publ-27605
Publ.-Id: 27605


Wechselwirkungs- und Transportuntersuchungen dreiwertiger Radiometalle in Ton unter Berücksichtigung des Einflusses von Fulvinsäure und erhöhten Salinitäten

Poetsch, M.
The storage of radioactive waste demands for evidence of security over a long period. Mainly because of its high sorption capacity as well as favourable geomechanical properties, clay is being explored as one of the potential host rocks for a final repository. This work contributes to the understanding of interactions between trivalent lanthanides (as analogues for trivalent actinides), fulvic acid and Opalinus clay regarding high ionic strength. High salinity and natural organic matter are both known to facilitate migration of toxic or radioactive metals in geochemical systems, but little is known on their combined effect.
The complex system was split into three binary systems with the following interactions: lanthanides (Tb, Eu) and Opalinus clay, lanthanides and fulvic acid, Opalinus clay and fulvic acid.
The binary systems were investigated at pH of 5 and 7 with variable amounts of NaCl, MgCl2 or CaCl2 within a range of 0 - 4 mol L-1. The sorption of the lanthanides and fulvic acid onto the Opalinus clay was investigated in batch experiments, employing 160Tb, 152Eu and 14C as radiotracers. For the investigation of the complexation behaviour of Tb(III) and Eu(III) with fulvic acid, time-resolved laser-induced fluorescence spectroscopy was used.
A combined Kd approach (Linear Additive Model) was tested for suitability in predicting solid-liquid distribution of metals in the presence of organic matter based on the interactions in the constituent subsystems. The metal-ion interactions with fulvic acid were modelled by using the NICA-Donnan approach. To reproduce the migration behaviour of lanthanides in clay, a diffusion-based process was modelled.
This study has shown that there is no synergism in the mobilising effects of fulvic acid and electrolytes at in-situ pH. On the contrary, a mitigating effect of ionic strength was evidenced, based on the fact that metal binding is suppressed while adsorption of humic matter is hardly influenced.
  • Doctoral thesis
    Universität Leipzig, 2018
    Mentor: Lippold, Holger
    106 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-27603
Publ.-Id: 27603


THz spectroscopy of solids with a free-electron laser

Helm, M.
I will start describing the Dresden free-electron laser FELBE as an intense, tunable, pulsed and narrowband source of infrared and THz radiation and the unique opportunities it offers for the spectroscopy of low-energy excitations in solids. In particular, the FEL can be used for nonlinear optical experiments, for time-resolved pump-probe studies, and also for near-field microscopy. I will mainly discuss nonlinear experiments on excitons in semiconductor quantum wells and pump-probe studies of the relaxation dynamics in graphene. If time permits, I will also introduce the new superradiant THz radiation source TELBE.
Keywords: free electron laser, terahertz, graphene
  • Lecture (others)
    Kolloquium am Max-Born-Institut Berlin, 13.06.2018, Berlin, Germany
  • Lecture (others)
    Vortrag am Paul-Drude-Institut, 23.07.2018, Berlin, Germany
  • Lecture (others)
    invited talk at CTFEL User Meeting, 14.10.2019, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-27602
Publ.-Id: 27602


Development of a selective and highly sensitive fluorescence assay for nucleoside triphosphate diphosphohydrolase1 (NTPDase1, CD39)

Lee, S.-Y.; Luo, X.; Namasivayam, V.; Geiss, J.; Mirza, S.; Pelletier, J.; Stephan, H.; Sevigny, J.; Müller, C. E.
Ecto-nucleoside triphosphate diphosphohydrolase1 (NTPDase1, CD39) is a major ectonucleotidase that hydrolyzes proinflammatory ATP to AMP, which is subsequently converted by ecto-5’-nucleotidase (CD73) to immunosuppressive adenosine. Activation of CD39 has potential for treating inflammatory diseases, while inhibition was suggested as a novel strategy for the immunotherapy of cancer. In the present study, we developed a selective and highly sensitive capillary electrophoresis (CE) assay using a novel fluorescent CD39 substrate, a fluorescein-labelled ATP (PSB-170621A) that is converted to its AMP derivative. To accelerate the assays, a two-directional (forward and reverse) CE system was implemented using 96-well plates, which is suitable for screening of compound libraries (Z’-factor: approx. 0.7). The detection limits for the forward and reverse operation were 11.7 and 2.00 pM, respectively, indicating a large enhancement in sensitivity as compared to previous methods (e.g. malachite-green assay: 1,000,000-fold, CE-UV assay: 500,000-fold, fluorescence polarization immunoassay: 12,500-fold). Enzyme kinetic studies at human CD39 revealed a Km value of 19.6 µM, and a kcat value of 119 x 10-3 s-1 for PSB-170621A, which shows similar substrate properties as ATP (11.4 µM and 165 x 10-3 s-1). The compound displayed similar substrate properties at rat and mouse CD39. Subsequent docking studies into a homology model of human CD39 revealed a hydrophobic pocket that accommodates the fluorescein tag. PSB-170621A was found to be preferably hydrolyzed by CD39 as compared to other ectonucleotidases. The new assay was validated by performing inhibition assays with several standard CD39 inhibitors yielding results that were consonant with data using the natural substrates.
Keywords: capillary electrophoresis / CD39 / ectonucleotidase / fluorescein / fluorescent enzyme assay / NTPDase1

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Permalink: https://www.hzdr.de/publications/Publ-27601
Publ.-Id: 27601


Isolated Proton Bunch Acceleration by a Petawatt Laser Pulse

Hilz, P.ORC; Ostermayr, T. M.ORC; Huebl, A.ORC; Bagnoud, V.; Borm, B.; Bussmann, M.ORC; Gallei, M.; Gebhard, J.; Haffa, D.; Hartmann, J.; Kluge, T.ORC; Lindner, F. H.; Neumayr, P.; Schaefer, C. G.; Schramm, U.ORC; Thirolf, P. G.; Rösch, T. F.; Wagner, F.; Zielbauer, B.; Schreiber, J.ORC
Often, the interpretation of experiments concerning the manipulation of the energy distribution of laser-accelerated ion bunches is complicated by the multitude of competing dynamic processes simultaneously contributing to recorded ion signals. Here we demonstrate experimentally the acceleration of a clean proton bunch. This was achieved with a microscopic and three-dimensionally confined near critical density plasma, which evolves from a 1μm diameter plastic sphere, which is levitated and positioned with micrometer precision in the focus of a Petawatt laser pulse. The emitted proton bunch is reproducibly observed with central energies between 20 and 40 MeV and narrow energy spread (down to 25%) showing almost no low-energetic background. Together with three-dimensional particle-in-cell simulations we track the complete acceleration process, evidencing the transition from organized acceleration to Coulomb repulsion. This reveals limitations of current high power lasers and viable paths to optimize laser-driven ion sources.
Keywords: laser-plasma interaction, laser-ion acceleration, accelerator research, paul trap, experiment, HPC, simulation, PIConGPU
  • Open Access Logo Nature Communications 9(2018)1, 423
    DOI: 10.1038/s41467-017-02663-1
  • Lecture (Conference)
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge (CO), United States of America

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Permalink: https://www.hzdr.de/publications/Publ-27599
Publ.-Id: 27599


Normal tissue reaction following proton irradiation of the mouse brain

Suckert, T.; Müller, J.; Beyreuther, E.; Gotz, M.; Tillner, F.; Schürer, M.; Dietrich, A.; Bütof, R.; Lühr, A.; von Neubeck, C.; Krause, M.
Objective: Radiotherapy leads to inactivation of tumor cells following radiation-induced DNA damage. Compared to conventional photon-based radiotherapy, proton therapy offers the potential of normal tissue sparring due to its favorable depth-dose distribution. However, acute or long-term side effects could still occur due to clinical safety margins and uncertainties about the relative biological effectiveness (RBE). While a variable RBE has been demonstrated in in vitro studies, especially at the end of the proton range, in clinical practice, a constant RBE value of 1.1 is applied. To elucidate the RBE issue based on in vivo experiments, proton irradiation of mouse brains was realized in Dresden.
Methods: Experiments were performed at the experimental beam line [1] of the University Proton Therapy Dresden. For beam characterization and dosimetry, a 2D scintillation detector, ionization chambers and radiochromic films [2] were used. A multi-modality mouse bed suitable for imaging, transportation and irradiation was developed in-house. Like clinical applications, the workflow includes computed tomography scans for treatment planning and X-ray images for refined positioning. By combining these images with proton radiographies [3] of the setup, it was possible to accurately locate the animals relative to the beam. To confirm positioning, DNA damage was visualized by immunofluorescent staining of gH2AX in the irradiated mouse brain.
Results and conclusion: Proton mouse brain irradiation was successfully performed. Distribution of DNA DSB via gH2AX revealed that the proton beam stopped in the beam facing brain hemisphere. The setup enables the comparison to corresponding photon experiments with SAIGRT [4] and clinically relevant long-term experiments, such as measuring cognitive functions and anomalies in imaging, to directly relate potential photon and proton side effects in brain radiotherapy.

[1] Helmbrecht et al. J Instrum 2016
[2] Beyreuther et al. IJPT 2018 (accepted)
[3] Müller et al. Acta Oncologica 2017
[4] Tillner et al. Phys Med Biol 2016
Keywords: normal tissue double-strand breaks proton therapy gH2AX small animal
  • Lecture (Conference)
    European Radiation Research Congress, 21.-25.08.2018, Budapest, Ungarn

Permalink: https://www.hzdr.de/publications/Publ-27598
Publ.-Id: 27598


Combining in-situ synchrotron X-ray techniques to study the dendritic growth in Ga–In alloys

Shevchenko, N.; Grenzer, J.; Keplinger, O.; Rack, A.; Hoppe, D.; Eckert, S.
The dendrite growth kinetics and morphology have been of great interest in the solidification science and casting industry. A detailed analysis of the particular solidification phenomena (coarsening, fragmentation etc.) requires X-ray techniques with a better spatial and temporal resolution. High resolution experimental data are also very important for the verification of the existing microstructural models. In this work, in-situ synchrotron X-ray radiography and diffraction methods have been combined to study the evolution of dendritic microstructures during the solidification of Ga - In alloys. The directional solidification experiments were performed at the ID19 and BM20 beamlines (ESRF, France) at a high spatial resolution of < 1 µm. The study is especially focused on the sidearm evolution, retraction and detachment, dendrite morphology and orientation. The sidearm evolution is quantified by an image analysis in a manner appropriated for comparison to simulations. Furthermore, we report on the reconstruction of crystallographic orientation of growing dendrites by using the CaRIne crystallography software. Our measurements show that the Indium dendrites grow along the <110> orientation, typically observed in body-centered metals. Our future work will include the systematic study of the evolution of dendritic morphologies at finite cooling rates and under the impact of melt flow.
Keywords: synchrotron X-ray imaging, Ga-In alloy, directional solidification, X-ray diffraction, dendrite evolution
  • Poster
    Materials Science and Engineering Congress (MSE2018); Symposia: "Tomographic and Radiographic Imaging with Synchrotron X-rays and Neutrons: Exploiting Contrast and Time", 26.-28.09.2018, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-27597
Publ.-Id: 27597


High resolution synchrotron imaging of dendritic coarsening in Ga – In alloys

Shevchenko, N.; Grenzer, J.; Keplinger, O.; Neumann-Heyme, H.; Rack, A.; Eckert, K.; Eckert, S.
The dendrite coarsening kinetics and dendrite morphology have been of great interest in the solidification science and casting industry. A detailed analysis of particular solidification phenomena (coalescence, fragmentation etc.) requires X-ray techniques with a high spatial and temporal resolution. High resolution experimental data are also very important for the verification of the existing microstructural models. The synchrotron radiography experiments with solidifying Ga - In alloys were performed at BM20 and ID19 (ESRF, Grenoble) at a spatial resolution of < 1 µm. The temporal dynamics of morphological transitions such as retraction, coalescence and pinch-off of the sidearms were studied in-situ. Recently, we showed that the combination of numerical modelling [1] and experiments [2,3] performed at the ESFR synchrotron X-ray source in Grenoble has allowed to improve the understanding of the pinch-off process of dendritic sidearms and to obtain material information that is relevant for quantitative modelling.
In this work, a Ga–In alloy was solidified in vertical direction starting from the top of the solidification cell at a controlled cooling rate of 0.002 K/s and at a vertical temperature gradient of ~2 K/mm. In general, all fragmentation events are located in the deceleration zone that is formed during the initial phase of solidification. Behind an advancing growth front, under slow growth conditions that are almost close to steady state conditions, the coarsening in the mushy zone does not involve a significant detachment of sidearms.
A detailed and advanced image analysis in combination with the high temporal and spatial resolution data of the experiment, allowed us to identify an additional migration process that is influenced by the existing temperature gradient. This Temperature Gradient Zone Melting (TGZM) process is characterized by a sidearm migration rate of 0.01 µm/s. Interestingly, the results of our analysis suggest that this process does not play a significant role for the sidearm detachment process itself.
References
1. H. Neumann-Heyme, et al. PHYS. REV. E, 92 (2015) 060401
2. Shevchenko et al., IOP Conf. Series: Mat. Sci. and Eng. 228 (2017), 012005
3. Neumann-Heyme, Shevchenko et al., Acta Mater. 146 (2018) 176
Keywords: solidification, dendrite morphology, coarsening, synchrotron radiography, temperature gradient, Ga-In alloy
  • Poster
    7th International Conference on Solidification and Gravity (SG’18), 03.-06.09.2018, Miskolc – Lillafüred, Hungary

Permalink: https://www.hzdr.de/publications/Publ-27596
Publ.-Id: 27596


Investigations of forced flow effects on dendritic solidification

Shevchenko, N.; Keplinger, O.; Eckert, S.
Many studies have demonstrated that the application of electromagnetic stirring enhances the area of equiaxed grains and reduces the mean grain size (see e.g. [1-2]). It is widely accepted that flow-induced grain refinement and the CET (columnar to equiaxed transition) in metallic alloys is triggered by the appearance of additional dendrite fragments originating from the columnar front. The mechanism for grain multiplication by melt convection is supposed to be complex and is not fully understood until now. The idea to apply electromagnetic stirring to control the defects arising from the action of natural convection is not straightforward too.
The X-ray radiography was used for an in-situ study of the effect of electromagnetic stirring during the directional bottom-up solidification of a Ga-25wt%In alloy in a Hele-Shaw cell [3]. The experimental setup was extended by a magnetic wheel, which allowed for controlled excitation of a melt flow in the liquid phase. The forced flow eliminates the solutal plumes and damps the local fluctuations of solute concentration. The induced redistribution of solute induces different effects on dendrite morphology, such as the uneven growth of primary trunks or lateral branches, remelting of single dendrites and also of lager dendrite ensembles, changes the inclination angle of the dendrites and leads to an increasing arm spacing. The uneven growth of primary dendrites at the beginning of the solidification experiment leads to the formation of Ga-rich zones near the solidification front which develop into distinct segregation freckles.
Another interesting effect can be observed during solidification experiment: the switching off the magnetic wheel leads to "repairing" of a segregation channel due to growth of equiaxed or fine dendrites in areas of Ga-rich pools. It has been demonstrated that the appearance of small equiaxed grains in the undercooled melt in the segregation pools is triggered by quick redistribution of solute after stopping the magnetic pump. A more detailed study of the "repairing" mechanisms of channels is the subject of ongoing work.

References
1. B. Willers et al, Materials Science and Engineering A 402 (2005) 55-65
2. T. Campanella et al, Metallurgical and Materials Transactions A 35 (2004) 3201-3210
3. N. Shevchenko et al, Journal of Crystal Growth 417 (2015) 1-8
Keywords: X-ray radiography, solidification, convection, Ga-In alloy, electromagnetic stirring
  • Lecture (Conference)
    7th International Conference on Solidification and Gravity (SG’18), 03.-06.09.2018, Miskolc – Lillafüred, Hungary

Permalink: https://www.hzdr.de/publications/Publ-27595
Publ.-Id: 27595


Radio-ecological research – recent results and their application

Raff, J.
Radionuclides occur in the environment naturally and by anthropogenic activities. Beside other processes, their interaction with the biosphere determines their fate in nature. Therefore, a detailed understanding of how organisms interact with radionuclides and how they influence the migration behavior of radionuclides in the environment is crucial for a reliable risk assessment. This presentation gives an overview of how selected microbes interact with radionuclides and their analogs. In addition, some examples will be given of how the results of radio-ecological research can be successfully transferred into the industry.
Keywords: Radio-ecology, microbes, radionuclides
  • Invited lecture (Conferences)
    BioGeo-Colloquium, 19.06.2018, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27594
Publ.-Id: 27594


Age estimates of groundwater in western Dead Sea catchment based on bomb peak environmental tracer data

Wilske, C.; Suckow, A.; Roediger, T.; Geyer, S.; Weise, S.; Merchel, S.; Rugel, G.; Pavetich, S.; Merkel, B.; Siebert, C.
The aquifer system of the western side of the Dead Sea is investigated on groundwater recharge, groundwater flow velocities and potential mixtures. The two main limestone aquifers are of Cretaceous age, exposed in the recharge area and show karst characteristics with high transmissivities and flow velocities. Discharge is into springs in the Lower Jordan Valley and Dead Sea region. We use a multi-environmental tracer approach, combining anthropogenic bomb-derived ³⁶Cl/Cl, Tritium and the anthropogenic gases SF₆, CFC-12 and CFC-11, CFC-113 to cover the recharge period from the 1950s to recent and to estimate components in the aquifer system that were recharged less than about 70 years ago. By application of lumped parameter models, we derived residence times in the unsaturated zone, tested several age distributions and verified young groundwater components from the last 10 to 30 years. The data can only be explained assuming also an admixture of an old groundwater component, older than about 70 years, which cannot be further quantified with our tracer data.
Keywords: AMS, groundwater
  • Lecture (Conference)
    8th German-Arab Scientific Forum for Environmental Studies, 08.-09.10.2018, Amman, Jordan
  • Lecture (Conference)
    Australian Geoscience Council Convention - Big Issues & Ideas in Geoscience, 14.-18.10.2018, Adelaide, Australia

Permalink: https://www.hzdr.de/publications/Publ-27593
Publ.-Id: 27593


Interactions of halophilic microorganisms with uranium

Cherkouk, A.; Bader, M.; Swanson, J. S.; Steudtner, R.; Drobot, B.; Müller, K.; Foerstendorf, H.; Schmidt, M.; Rossberg, A.; Ikeda-Ohno, A.; Stumpf, T.
Rock salt formations are considered as potential host rocks for the long-term storage of highly radioactive waste in a deep geological repository. Next to bacteria and fungi, extremely halophilic archaea, e.g. Halobacterium species, are predominantly present in this habitat. For long-term risk assessment it is of high interest to study how these microorganisms can interact with radionuclides if released from the waste repository. Therefore, the interactions of the extremely halophilic archaeon Halobacterium noricense DSM 15987T and the moderately halophilic bacterium Brachybacterium sp. G1 with uranium, one of the major radionuclides of concern in the geological repository of radioactive wastes, were investigated in detail in batch experiments. Furthermore, a multi-spectroscopic and -microscopic approach was used to reveal these interaction mechanisms on a molecular level. The two microorganisms exhibited different association characteristics with uranium. Brachybacterium sp. G1 cells sorbed uranium within a short time, whereas a multistage bioassociation process occurred with the archaeon. In situ attenuated total reflection Fourier-transform infrared spectroscopy, time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy were applied to elucidate the U(VI) bioassociation behavior. By using these spectroscopic tools the formation of U(VI) phosphate mineral, such as meta-autunite, by the Halobacterium species was demonstrated. These findings highlight the microbial life in deep geological hypersaline environments and offer new insights into the microbe-actinide interactions at highly saline conditions relevant to the disposal of nuclear waste.
  • Lecture (Conference)
    Uranium biogeochemistry - transformations, isotopes, and applications, 21.-26.10.2018, Monte Verita Ascona, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-27592
Publ.-Id: 27592


Joint simulation of compositional and categorical data via direct sampling technique – Application to improve mineral resource confidence

Talebi, H.; Mueller, U.; Tolosana-Delgado, R.
Ore deposits usually consist of ore materials with different discrete (e.g. rock and alteration types) and continuous (e.g. geochemical and mineral composition) features. Financial feasibility studies are highly dependent on the modelling of these features and their associated joint uncertainties. Few geostatistical techniques have been developed for the joint modelling of high-dimensional mixed data (continuous and categorical) or constrained data, such as compositional data. The compositional nature of the mineral and geochemical data induces several challenges for multivariate geostatistical techniques, because such data carry relative information and are known for spurious statistical and spatial correlation effects. This paper investigates the application of the direct sampling algorithm for joint modelling of compositional and categorical data. In some mining projects the amount of available data may be enormous in some parts of the deposit and if the density of measurements is sufficient, multivariate geospatial patterns can be derived from the that data and be simulated (without model inference) at other undersampled areas of the deposit with similar characteristics. In this context, the direct sampling multiple-point simulation method can be implemented for this reconstruction process. The compositional nature of the data is addressed via implementing an isometric log-ratio transformation. The approach is illustrated through two case studies, one synthetic and one real. The accuracy of the results is checked against a set of validation data, revealing the potential of the proposed methodology for joint modelling of compositional and categorical information. The direct sampling technique can be considered as a smart move to assess the future risk and uncertainty of a resource by making use of all the information hidden within the early data.
Keywords: Multiple-point statistics, Isometric log-ratio transformation, Uncertainty modelling, Multivariate resource modelling, Sustainable mining

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Permalink: https://www.hzdr.de/publications/Publ-27591
Publ.-Id: 27591


Preclinical imaging for establishment and comparison of orthotopic Non-Small Cell Lung Carcinoma: In search for models reflecting clinical scenarios

Aktar, R.; Dietrich, A.; Tillner, F.; Kotb, S.; Löck, S.; Willers, H.; Baumann, M.; Krause, M.; Bütof, R.
Objectives:
Clinically relevant animal models of non-small cell lung carcinoma (NSCLC) are required for the validation of novel treatments. We compared two different orthotopic transplantation techniques as well as imaging modalities to identify suitable mouse models mimicking clinical scenarios.
Methods:
We used three genomically diverse NSCLC cell lines (NCI-H1703 adenosquamous cell carcinoma, NCI-H23 adenocarcinoma and A549 adenocarcinoma) for implanting tumour cells either as spheroids or cell suspension into lung parenchyma. Bioluminescence imaging (BLI) and contrast-enhanced cone beam computed tomography (CBCT) were performed twice weekly to monitor tumour growth. Tumour histological data and microenvironmental parameters were determined.
Results:
Tumour development after spheroid-based transplantation differs probably due to the integrity of spheroids, as H1703 developed single localized nodules, whereas H23 showed diffuse metastatic spread starting early after transplantation. A549 transplantation as cell suspension with the help of a stereotactic system was associated with initial single localized tumour growth and eventual metastatic spread. Imaging techniques were successfully applied to monitor longitudinal tumour growth: BLI revealed highly sensitive qualitative data, whereas CBCT was associated with less sensitive quantitative data. Histology revealed significant model dependent heterogeneity in proliferation, hypoxia, perfusion and necrosis.
Conclusions:
Our developed orthotopic NSCLC tumours have similarity with biological growth behavior similar to that seen in the clinic and could therefore be used as attractive models to study tumour biology and evaluate new therapeutic strategies. The use of human cancer cell lines facilitates testing of different genomic tumor profiles that may affect treatment outcomes.
Advances in knowledge:
The combination of different imaging modalities and orthotopic transplantation techniques pave the way towards representative preclinical NSCLC models for experimental testing of novel therapeutic options in future studies.
Keywords: Non-small cell lung cancer, orthotopic model, transplantation technique, preclinical imaging, microenvironment

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Permalink: https://www.hzdr.de/publications/Publ-27590
Publ.-Id: 27590


Probing plutonium dioxide nanoparticles with synchrotron methods

Gerber, E.; Romanchuk, A.; Pidchenko, I.; Hennig, C.; Trigub, A.; Weiss, S.; Scheinost, A.; Kalmykov, S.; Kvashnina, K.
INTRODUCTION

Plutonium is a chemical element of significant environmental and toxicological concern. At nuclear legacy sites, previous research has demonstrated that plutonium can migrate in colloidal form in the subsurface environment across several kilometers [1-2]. Recent spectroscopic and microscopic investigations showed that so called “colloidal Pu(IV) polymers” are in fact aggregates of PuO2 nanoparticles with diameters ~ 2 nm [3-4]. The exact stoichiometry and structure of such nanoparticles remain, however, still questionable, especially with respect to surface hydration and hydroxylation, as well as the purity of the tetravalent oxidation state considering the existence of four different oxidation states (with relatively small energy barriers III, IV, V, and VI) under environmental conditions.

RESULTS

This contribution will show first results of plutonium oxide nanoparticle studies at the large-scale facility – The European Synchrotron (ESRF) by X-ray spectroscopy and X-ray diffraction methods. Pu oxide nanoparticles were prepared by rapid chemical precipitation using precursors in the different oxidation states (Pu(III), Pu(IV), Pu(V) and Pu(VI)). These precursors were obtained by chemical reduction or oxidation of Pu stock solution. The obtained nanoparticles were characterized at the Rossendorf Beamline (ROBL) at the ESRF, dedicated to actinide science. The recently upgraded ROBL beamline provides unique opportunities to study actinide materials by several experimental techniques: high energy resolution fluorescence detection (HERFD) [5], X-ray emission spectroscopy (XES), resonant inelastic x-ray scattering (RIXS) [6], extended X-ray absorption fine structure (EXAFS) spectroscopy and X-ray diffraction (XRD) simultaneously.
We will show how the detailed information about local and electronic structure and plutonium oxidation state in different nanoparticles can be obtained using the variety of methods.
Keywords: XAFS, nanoparticles, actinides, HERFD
  • Lecture (Conference)
    Plutonium Futures - The Science 2018, 09.-14.09.2018, San Diego, California, USA

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Permalink: https://www.hzdr.de/publications/Publ-27589
Publ.-Id: 27589


Ultrafast transient absorption spectroscopy of UO22+ and [UO2Cl]+

Haubitz, T.; Tsushima, S.; Steudtner, R.; Drobot, B.; Geipel, G.; Stumpf, T.; Kumke, M. U.
For the only water coordinated "free" uranyl(VI) aquo ion in perchlorate solution, we identified and assigned several different excited states and showed that the 3∆ state is the luminescent triplet state. With additional data from other spectroscopic methods (TRLFS, UV/Vis, and TAS), we generated a detailed Jabłoński diagram and determined rate constants for several state transitions, like the inner conversion rate constant from the 3Φ state to the 3∆ state transition to be 0.35 ps-1. In contrast to luminescence measurements, it was possible to observe the highly quenched uranyl(VI) ion in highly concentrated chloride solution by TAS and we were able to propose a dynamic quenching mechanism, where chloride complexation is followed by the charge transfer from the excited state uranyl(VI) to chloride. This proposed quenching route is supported by TD-DFT calculations.

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Permalink: https://www.hzdr.de/publications/Publ-27588
Publ.-Id: 27588


Experimental platform for the investigation of magnetized-reverse-shock dynamics in the context of POLAR

Albertazzi, B.; Falize, E.; Pelka, A.; Brack, F.; Kroll, F.; Yurchak, R.; Brambrink, E.; Mabey, P.; Ozaki, N.; Pikuz, S.; van Box Som, L.; Bonnet-Bidaud, J. M.; Cross, J. E.; Filippov, E.; Gregori, G.; Kodama, R.; Mouchet, M.; Morita, T.; Sakawa, Y.; Drake, R. P.; Kuranz, C. C.; Manuel, M. J.-E.; Li, C.; Tzeferacos, P.; Lamb, D.; Schramm, U.; Koenig, M.
The influence of a strong external magnetic field on the collimation of a high Mach number, plasma flow and its collision with a solid obstacle is investigated experimentally and numerically. The laser irradiation (I ∼ 2 × 1014 W cm−2) of a multilayer target generates a shock wave that produces a rear side plasma expanding flow. Immersed in a homogeneous 10 T external magnetic field, this plasma flow propagates in vacuum and impacts an obstacle located a few mm from the main target. A reverse shock is then formed with typical velocities of the order of 15–20 ± 5 km/s. The experimental results are compared with 2D radiative MHD simulations using the FLASH code. This platform allows investigating the dynamics of reverse shock, mimicking the processes occurring in a cataclysmic variable of polar type.
Keywords: accretion processes; high-power laser; hydrodynamics; laboratory astrophysics; polar; radiative shocks

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Permalink: https://www.hzdr.de/publications/Publ-27587
Publ.-Id: 27587


Recent experiments on plasma immersion ion implantation (and deposition) using discharges inside metal tubes

Ueda, M.; Silva, C.; Marcondes, A. R.; Reuther, H.; de Souza, G. B.
Plasma immersion ion implantation (PIII) of nitrogen inside metallic tubes of different diameters and configurations were attempted recently. PIII tests in practical size metallic tubes of SS304, ranging from 1.1 to 16 cm∅ and length of 20 cm, were carried out as a continued effort in our lab, to explore PIII inside tubes. Tubes in laying down positions and configurations including metallic lid in one side or both sides open were used, as well as, plane sample support placed 10 cm far from the tube mouth and without bias, taking advantage of plasma flowing out the tube. In particular, nitrogen and argon PIIIs were tested for tube inner wall sputtering and deposition studies, running the PIII system in the last configuration of sample support detached from the tube. During the nitrogen ion implantation runs in other cases, it was found that the final temperature of the tubes and the plasma turn-on voltages were both inversely proportional to the dimensions of the tubes, except for the smallest tube tested. High voltage glow and hollow cathode discharges were produced inside the tubes, either alternately, during the pulse or independently, depending on the tube geometry and pulser used (LIITS, a current controlled source or RUP-4, a voltage controlled one). In the case of smallest diameter of 1.1 cm∅, a suspended tube of SS304 was tested using lower power pulser (RUP-4), at its near maximum capability of 1.2 kW. In this case also, very bright plasmas were formed, mainly inside the tube and resulted in high temperature there (~700 °C). Nitrogen uptake was superior for higher temperature PIII treatments (>700 °C), combining ion implantation and thermal diffusion, which allowed the formation of TiN and Ti2N on the Ti alloy samples inside tubes with diameters ≤4 cm. In this paper, detailed discussion of results of above cited PIII tests with diversified tubes and configurations are presented, together with the analysis of the corresponding treated surfaces of the samples inside, outside and on the support detached from the tube.
Keywords: Plasma immersion ion implantation, Sputtering and deposition inside metallic tubes, TiN and Ti2N in high temperature PIII, Tubes with different dimensions and configurations

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Permalink: https://www.hzdr.de/publications/Publ-27586
Publ.-Id: 27586


cupla - C++ User interface for the Platform independent Library Alpaka

Widera, R.ORC
cupla [qχɑpˈlɑʔ] is a simple user interface for the platform independent parallel kernel acceleration library alpaka. It follows a similar concept as the NVIDIA® CUDA® API by providing a software layer to manage accelerator devices. alpaka is used as backend for cupla.
  • Software in the HZDR data repository RODARE
    Publication date: 2018-06-10
    DOI: 10.14278/rodare.29
    License: LGPL-3.0

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Permalink: https://www.hzdr.de/publications/Publ-27585
Publ.-Id: 27585


Commissioning of a 4D MRI phantom for use in MR-guided radiotherapy

Schneider, S.; Dolde, K.; Engler, J.; Hoffmann, A.; Pfaffenberger, A.
Purpose:
Systems for integrated magnetic resonance guided radiation therapy (MRgRT) provide real-time and on-line MRI guidance for unequalled targeting performance of moving tumors and organs at risk. The clinical introduction of such systems requires dedicated methods for commissioning and routine machine quality assurance (QA). The aim of the study was to develop a commissioning protocol and method for automatic quantification of target motion and geometric accuracy using a 4D MRI motion phantom.

Material and Methods:
The commissioning was performed on a clinically used 3T MR scanner. The phantom was positioned on a flat tabletop overlay using an in-house constructed base plate for a quick and reproducible setup. The torso-shaped phantom body, which was filled with mineral oil as signal generating medium, includes a 3D grid structure for image distortion analysis and a cylindrical thru-hole in which a software-controlled moving rod with a hypo-intense background gel and a decentralized hyper-intense target simulates 3D organ motion patterns. To allow for sequence optimization, MR relaxometry was performed to determine the longitudinal T1 and transverse T2 relaxation times of both target and background gel in the movable cylinder. The geometric image distortion was determined as the mean and maximum 3D Euclidean distance (∆mean, ∆max) of grid points determined by non-rigid registration of a 3D spoiled gradient echo MRI scan and a CT scan. Sinusoidal 1D/2D/3D motion trajectories, varying in amplitude and frequency, as well as an exemplary 1D MR-navigator diaphragm motion pattern extracted from a volunteer scan were scanned by means of 2D cine MRI. Target positions were automatically extracted from 2D cine MRI using an in-house developed software tool.

Results:
The base plate enabled a reproducible setup with a deviation of <1 mm in all directions. Relaxometry yielded T1/T2 values for target and background gel of 208.1±2.8 / 30.5±4.7 ms and 871 .36±36 / 13.4±1.3 ms respectively. The geometric distortion in the MRI scan increased with distance from the magnetic isocenter, with ∆mean=0.58±0.30 mm and ∆max=1.31 mm. The frequencies of the reconstructed motion patterns agreed with the pre-set values within 0.5%, whereas the reconstructed amplitudes showed a maximum deviation to the pre-set amplitudes of <0.4 mm in AP/LR direction and <0.2 mm in IS direction.

Conclusion:
A method and protocol for commissioning of a 4D MRI motion phantom on a 3T MR scanner for MRgRT was developed. High-contrast and geometrically reliable 2D cine MR images of the phantom’s moving target could be obtained. The pre-set motion parameters could be extracted with sufficient spatio-temporal accuracy from 2D cine MRI in all motion directions. The measured geometric image distortion of <1.31mm within the phantom grid confirms geometric accuracy of the clinically utilized 3D spoiled gradient echo sequence.
The method developed can be used for routine QA tests of spatio-temporally resolved MRI data in MRgRT.
Keywords: MRI, dynamic phantom, image-guided radiation therapy, commissioning

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Publ.-Id: 27584


Microstructural degradation and creep fracture behavior of conventionally and thermomechanically treated 9% Chromium Heat Resistant steel

Vivas, J.; Capdevila, C.; Altstadt, E.ORC; Houska, M.; Sabirov, I.; San-Martín, D.
The microstructural degradation and the creep fracture behavior of conventionally and thermomechanically treated Grade 91 steel were investigated after performing Small Punch Creep Tests. A remarkable reduction in creep ductility was observed for the samples thermomechanically treated in comparison to those conventionally treated under the tested conditions of load (200 N) and temperature (700 ºC). A change in the fracture mechanism from a ductile transgranular fracture to a brittle intergranular fracture was observed when changing from the conventionally treated to the thermomechanically treated processing condition, leading to this drop in creep ductility. The change in the fracture mechanism was associated to the localized concentration of creep deformation, close to coarse M23C6 carbides, at the vicinity of prior austenite grain boundaries (PAGB) in the thermomechanically treated samples. The preferential recovery experienced at the vicinity of PAGB produced the loss of the lath structure and the coarsening of the M23C6 precipitates. The electron microscopy images provided suggest that the creep cavities nucleate in these weak recovered areas, associated to the presence of coarse M23C6. After the coalescence of the cavities the propagation of the cracks was facilitated by the large prior austenite grain size produced during the austenitization which favors the propagation of the cracks along grain boundaries triggering the intergranular brittle fracture. This fracture mechanism limits the potential use of the proposed thermomechanical processing routes.
Keywords: Creep resistant steels; thermomechanical treatment; creep fracture behavior; microstructural degradation; small punch creep tests; ausforming

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Permalink: https://www.hzdr.de/publications/Publ-27583
Publ.-Id: 27583


The use of assay data as a foundation for a geometallurgical model – the case of the Thaba Chromite Mine, South Africa

Bachmann, K.; Menzel, P.; Tolosana-Delgado, R.; Schmidt, C.; Hill, M.; Gutzmer, J.
The Lower and Middle Group chromitites of the Bushveld Igneous Complex in South Africa are the source of a very large portion of the global chrome supply. The recovery of platinum group elements and base metals (Ni, Cu) as by-products has the potential to add value to these chrome resources. Yet, the effectiveness of chromite and platinum-group element beneficiation circuits is highly sensitive to variations in feed composition. Of particular relevance is the abundance of alteration silicates, which have a negative impact on recoveries and concentrate grade. The use of geochemical proxies, based on data acquired routinely during the exploration and mining process may provide a cost- and time-efficient alternative to more time-consuming and expensive mineralogical analyses. Such an approach is presented in this study, which focuses on the LG-6, LG-6A, MG-1 and MG-2 chromitite seams at the Thaba mine located on the western limb of the Bushveld Complex. An extensive assay data set comprising of data for Cr2O3, FeO, Al2O3, MgO, SiO2, CaO and P provided by the mine owner was evaluated and corrected for systematic bias between different sample batches. A statistical assessment was performed to discuss the variability within and between the chromitite seams and to separate the mine lease area into distinct geochemical clusters. The distribution of the samples belonging to the different geochemical clusters was then transposed onto the geology of the mine lease area. This allowed the definition of spatial domains. These spatial domains, recognized by the assessment of assay data only, are then validated by mineralogical attributes; implications for mineral beneficiation are critically assessed. According to this assessment, the chromitites of the Thaba mine area can be subdivided into three distinct domains, domains that constitute the suitable fundament for a geometallurgical model. An extensive supergene altered domain is distinguished from a domain affected by hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The third domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.
Keywords: Cluster analysis, Lower Group chromitites, Middle Group chromitites, chromite ore, chromite deposits, chromite beneficiation

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-27582
Publ.-Id: 27582


Explicit decay heat calculation in the nodal diffusion code DYN3D

Bilodid, Y.ORC; Fridman, E.ORC; Kotlyar, D.ORC; Shwageraus, E.ORC
The residual radioactive decay heat plays an important role in some accident scenarios and, therefore, needs to be accurately calculated when performing accident analyses. The current reactor simulation codes used for accident analysis account for the residual decay heat by means of simplified models. Typically, these models rely on semi-empirical correlations which are defined over a limited range of burnup and fuel types. Therefore, the applicability of such correlations is limited and any deviation from the definition range may lead to high uncertainties, which is detrimental in evaluating safety margins.
Reactor dynamic code DYN3D was originally developed for transient and accident analysis of LWRs. In DYN3D, the residual radioactive decay heat calculation is based on the German national standard DIN Norm 25463 model. The applicability of this model is limited to a low enriched uranium dioxide fuel for light water reactors.
This paper describes a new general decay heat calculation model implemented in DYN3D. The radioactive decay rate of each nuclide in each spatial node is calculated by recently implemented depletion module and the cumulative released heat is used to obtain the spatial distribution of the decay power for every time step. Such explicit approach is based on first principles and is free from approximations and, thus, can be applied to any reactor system (e.g. thermal and fast) and fuel type. The proposed method is verified against the reference Serpent 2 Monte Carlo solutions for a range of reactor types.
Keywords: DYN3D, Decay heat, Microdepletion

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Publ.-Id: 27581


Comparison of radionuclide association of fungi under laboratory and natural conditions

Wollenberg, A.; Großmann, S.; Günther, A.; Raff, J.; Stumpf, T.
The varied use of different radionuclides in medicine, industry and research and their disposal has repeat-edly led to the release of these radionuclides into the environment. Through leaching and migration, the anthropogenic released radionuclides can reach the groundwater, endangering the environment, animals and humans. However, the mobility and thus the migration behavior of radionuclides in the soil are influ-enced by the microorganisms living there.
Fungi play an important role in the microbial community of soil and can therefore have a major influence on radionuclide mobility, for example through sorption, accumulation or reduction processes. Therefore, the aim of this research is to investigate the influence of fungi on radionuclide migration in soil by using column and field experiments and to determine the potential of fungi for radiation protection precaution-ary methods or even remediation methods.
For the assessment of the suitability of fungi the first step is to investigate the molecular interactions with radionuclides under laboratory conditions to identify dominant interaction processes. Therefore binding experiments with different media were performed and the molecular binding form was investigated with time-resolved laser-induced fluorescence spectroscopy. In the next step, column experiments were carried out with soil and under natural conditions, in which the retention capacity of the fungi for radionuclide migration in the soil was investigated.
The experiments so far showed that the biochemistry of the fungi determines the metal interaction and not the surrounding environment. Furthermore, it was clearly demonstrated by column experiments, that fungi are able to retain radionuclides significantly.
Keywords: Fungi, Radionuclide, TRLFS, Column
  • Poster
    RCA-Workshop, 12.-14.06.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27580
Publ.-Id: 27580


C++ & Python API for Scientific I/O with openPMD

Koller, F.ORC; Pöschel, F.ORC; Hübl, A.ORC

openPMD is an open metadata format for open data workflows in open science. This library provides a common high-level API for openPMD writing and reading. It provides a common interface to I/O libraries and file formats such as HDF5 and ADIOS. Where supported, openPMD-api implements both serial and MPI parallel I/O capabilities.

Keywords: openPMD; Open Science; Open Data; HDF5; ADIOS; data; MPI; HPC; research; file-format; file-handling
  • Software in the HZDR data repository RODARE
    Publication date: 2019-11-15
    DOI: 10.14278/rodare.27
    License: LGPL-3.0

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Permalink: https://www.hzdr.de/publications/Publ-27579
Publ.-Id: 27579


99Tc retention on pyrite and alumina: the effect of Fe2+

Rodríguez, D.; Mayordomo, N.; Stumpf, T.; Mueller, K.
For the safety case of a nuclear waste repository, Tc is treated very conservatively, assuming no retention by the geotechnical and geological barriers. Tc(VII), pertechnetate (TcO4-), the most dominant species in oxidizing environment is considered to be inert, hardly interacting with minerals and highly mobile. In contrast, the reduced form Tc(IV) is mainly found as solid, TcO2, and its mobility is limited.
The presence of reductants in the near-field of a nuclear waste repository, e.g. Fe2+ is expected due to canister corrosion. Therefore, most of recent studies consider Tc reductive immobilization by mineral containing reductant moieties, such as magnetite (FeIIFe2IIIO4) or mackinawite (FeS) [1,2] or pre-sorbed reductants on mineral phases, like Fe2+ on corundum (a-Al2O3), diaspore (a-AlOOH), goethite (a-FeOOH), and hematite (a-Fe2O3)[3,4].
In this work, we compare the Tc immobilization by two systems: i) pyrite (FeS2) and ii) nano particular alumina in presence of Fe2+ (ternary system).
Pyrite is capable to remove almost 100% of Tc(VII) from solution within 7 days at pH = 6.5. In a further step, we study the effect of ionic strength on the Tc immobilization under different NaCl concentrations, as the retention mechanism could be affected by the change of Tc(IV) solubility, due to different degrees of salinity [4].
Alumina is capable to retain 6.5% of Tc in the absence of reducing Fe2+. However, in the ternary system Tc retention is 100% for pH > 6.5. In this case, the improvement on the Tc reduction is not only due to Fe2+ presence, but also to the surface properties of alumina, triggering heterogeneous reduction of Tc by high Fe2+ surface coverage or possible LDH formation.

This work has been developed in the frame of VESPA II project (02E11607B), supported by the German Federal Ministry of Economy and Energy (BMWi).
Keywords: Technetium, sorption, pyrite, alumina, iron
  • Lecture (Conference)
    The 10th International Symposium on Technetium and Rhenium – Science and Utilization, 03.-06.10.2018, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-27578
Publ.-Id: 27578


Amphiphilic Siderophore Marinobactin for Froth Flotation Process

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
This work includes on the one hand the biotechnological production of the marine siderophore marinobactin for the first time using a bioreactor and optimized conditions to make the production more efficient. On the other hand, the produced siderophore is tested in different froth flotation micro scale experiments like “Bubble-pick-up-test” and micro flotation in the Halimond Tube. These results show for the first time that amphiphilic siderophores are working in the froth flotation process and supply first concepts about the required concentration of siderophores in this processing process. In addition, the results also include interaction studies of different metals.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the bioflotation process. This will reduce the usage of other chemical agents. Moreover the specific metal binding of siderophores changes flotation in a more purposeful and efficient process.
Keywords: Bioflotation, Flotation, Siderophore, Marinobactin
  • Lecture (Conference)
    Applied Biotechnology in Mining, 25.-27.04.2018, Dnipro, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-27577
Publ.-Id: 27577


Re-irradiation of recurrent gliomas: pooled analysis and validation of an established prognostic score-report of the Radiation Oncology Group (ROG) of the German Cancer Consortium (DKTK)

Combs, S.; Niyazi, M.; Adeberg, S.; Bougatf, N.; Kaul, D.; Fleischmann, D.; Gruen, A.; Fokas, E.; Rodel, C.; Eckert, F.; Paulsen, F.; Oehlke, O.; Grosu, A.; Seidlitz, A.; Lattermann, A.; Krause, M.; Baumann, M.; Guberina, M.; Stuschke, M.; Budach, V.; Belka, C.; Debus, J.; Kessel, K.
The heterogeneity of high-grade glioma recurrences remains an ongoing challenge for the interdisciplinary neurooncology team. Response to re-irradiation (re-RT) is heterogeneous, and survival data depend on prognostic factors such as tumor volume, primary histology, age, the possibility of reresection, or time between primary diagnosis and initial RT and re-RT. in the present pooled analysis, we gathered data from radiooncology centers of the DKTK Consortium and used it to validate the established prognostic score by Combs et al. and its modification by Kessel et al. Data consisted of a large independent, multicenter cohort of 565 high-grade glioma patients treated with re-RT from 1997 to 2016 and a median dose of 36 Gy. Primary RT was between 1986 and 2015 with a median dose of 60 Gy. Median age was 54 years; median follow-up was 7.1 months. Median OS after re-RT was 7.5, 9.5, and 13.8 months for WHO IV, III, and I/II gliomas, respectively. All six prognostic factors were tested for their significance on OS. Aside from the time from primary RT to re-RT (P = 0.074) and the reresection status (P = 0.101), all factors (primary histology, age, KPS, and tumor volume) were significant. Both the original and new score showed a highly significant influence on survival with P < 0.001. Both prognostic scores successfully predict survival after re-RT and can easily be applied in the routine clinical workflow. Now, further prognostic features need to be found to even improve treatment decisions regarding neurooncological interventions for recurrent glioma patients.
Keywords: Outcome, prognostic score, recurrent glioma, re-irradiation

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Permalink: https://www.hzdr.de/publications/Publ-27576
Publ.-Id: 27576


A Timing RPC with low resistive ceramic electrodes

Sultanov, R.; Akindinov, A.; Beyer, R.; Dreyer, J.; Fan, X.; Greifenhagen, R.; Kämpfer, B.; Kotte, R.; Laso Garcia, A.; Malkevich, D.; Naumann, L.; Plotnikov, V.; Prokudin, M.; Shirinkin, S.; Stach, D.
For precise start time determination a Beam Fragmentation T0 Counter (BFTC) is under development for the Time-of-Flight Wall of the Compressed Baryonic Matter Spectrometer (CBM) at FAIR/Darmstadt. This detector will be located around the beam pipe, covering the front area of the Projectile Spectator Detector. The fluxes at this region are expected to exceed 10^5cm^{-2}s^{-1}.
Ceramic RPCs could be use because of their high rate capabilities and radiation hardness of material. Efficiency >/=97%, time resolution /=10^5cm^{-2}s^{-1} were confirmed during many tests with high beam fluxes of relativistic electrons. We confirm the stability of these characteristics with low resistive Si3N4/SiC floating electrodes for a prototype of eight small RPCs, where each of them contains six gas gaps. The active RPC size amounts 20x20 mm^2 produced on basis of Al3O2 and Si3N4/SiC ceramics. Recent test results obtained with relativistic electrons at the linear accelerator ELBE of the Helmholtz-Zentrum Dresden-Rossendorf with new PADI-10 Front-end electronic will be presented.
Keywords: RPC, ceramic composite electrodes, high rate capability, signal cross-talk

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  • Secondary publication expected from 03.09.2020

Permalink: https://www.hzdr.de/publications/Publ-27575
Publ.-Id: 27575


Platinum transport in chloride-bearing fluids and melts: Insights from in situ X-ray absorption spectroscopy and thermodynamic modeling

Tagirov, B. R.; Filimonova, O.; Trigub, A. L.; Akinfiev, N. N.; Nickolsky, M. S.; Kvashnina, K. O.; Chareev, D. A.; Zotov, A. V.
Hydrothermal chloride-rich fluids are identified at the late stages of the formation of platinum group element (PGE) deposits in giant layered intrusions, and are considered as the PGEs transport media in Cu(-Mo,Au) porphyry systems. In order to quantify the hydrothermal mobility of Pt we performed an investigation of the speciation of Pt in hydrothermal chloride-bearing fluids and dry melt by means of X-ray absorption spectroscopy (XAS). The experiments consisted in recording the Pt L-3-edge X-ray absorption near edge structure/extended X-ray absorption fine structure (XANES/EXAFS) spectra of Pt-bearing fluids obtained by dissolution of Pt metal in KCl/HCl and CsCl/HCl fluids in the temperature range from 450 to 575 degrees C at pressures from 0.5 to 5 kbar. A spectrum of Pt dissolved in dry CsCl/NaCl/KCl + K2S2O8 melt was recorded at 650 degrees C. The capillary method, when the experimental solution together with Pt((cr) )is sealed inside a silica glass capillary, was used. As was determined from the XANES spectra, in all the experimental systems Pt existed in the +2 oxidation state. Analysis of EXAFS spectra showed that Pt is coordinated by four Cl atoms with Rpt-cl = 2.31 +/- 0.01 angstrom independently of the T-P-compositional parameters. No evidence of the formation of complex with alkali metal cations in the second coordination sphere of Pt was found by the analysis of the EXAFS spectra of concentrated CsCl brines and melt. Our results imply that PtCl42- is the main Pt-Cl complex which predominates in hydrothermal fluids at t > 400 degrees C and fluid density d > 0.3 g.cm(-3). Experimental data obtained for dry melt of alkali metal chlorides suggest that Pt-Cl complexes can dominate Pt speciation in chloride-bearing aluminosilicate melts where Cl exhibits a salt-like atomic arrangement and ionic bonding. The literature data on the Pt solubility constant, Pt-(cr) + 2HCl((aq))degrees + 2Cl(-) = PtCl42- + H-2(aq), are compiled and fitted to the simple density model equation log K-s degrees (PtCl42- ) = 0.973 - 8202. T(K)(-1) - 5.505 . log d (w) + 2223 . log d(w) .T(K)(-1), where d(w) is the pure water density in g.cm(-3). The equation, combined with the extended Debye-Hiickel equation for activity coefficients, can be used to calculate the solubility of Pt up to 1000 degrees C/5 kbar. It accurately predicts the solubility of Pt in concentrated chloride brine (up to 50 wt% NaCl) at parameters of magmatic-hydrothermal transition (800 degrees C/1.4 kbar). At fluid/vapor density below 0.3 g.cm(-3) a neutral complex PtCl2 degrees((aq)) is suggested as the dominant Pt species. Our data demonstrate that Pt is highly mobile in high-temperature oxidized chloride-rich hydrothermal fluids. For example, at 800 degrees C/2 kbar the concentration of Pt can reach a few wt% in the 1 wt% HCl/50 wt% NaCl fluid which is in equilibrium with magnetite-hematite buffer. Once a Cl-reach fluid exsolves from alumuinosilicate melt, Pt follows Cl and enriches the fluid phase where it exists mostly in the form of PtCl42-. Decrease of temperature, acidity, and fluid chlorinity results in precipitation of Pt from the fluid phase.

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Publ.-Id: 27574


Towards the bottom of the periodic table

Kvashnina, K. O.
Actinide and lanthanide chemistry is currently experiencing a renaissance, due to the prospects of obtaining novel materials relevant for applications in chemical synthesis, electronics, materials science, nanotechnology, biology and medicine. Most of the fascinating properties of the lanthanide and actinide materials are related to the partially filled 4f/5f valence shell and in contrast to the rest of the periodic table, are poorly understood. This contribution will provide a brief overview of applications of advanced X-ray techniques that have recently become available for studying the electronic structure of actinide and lanthanide materials at The European Synchrotron (ESRF).
  • Invited lecture (Conferences)
    Les Midis Minatec, 08.06.2018, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-27573
Publ.-Id: 27573


Towards the surface hydroxyl species in CeO2 nanoparticles

Plakhova, T. V.; Romanchuk, A. Y.; Butorin, S. M.; Konyukhova, A. D.; Egorov, A. V.; Shiryaev, A. A.; Baranchikov, A. E.; Dorovatovskii, P. V.; Huthwelker, T.; Gerber, E.; Bauters, S.ORC; Sozarukova, M. M.; Scheinost, A.ORC; Ivanov, V.; Kalmykov, S. N.; Kvashnina, K.ORC
Understanding the complex chemistry of functional nanomaterials is of fundamental importance. Controlled synthesis and characterization at the atomic level is essential to gain deeper insight into the unique chemical reactivity exhibited by many nanomaterials. Cerium oxide nanoparticles have many industrial and commercial applications, resulting from very strong catalytic, pro- and anti-oxidant activity. However, the identity of the active species and the chemical mechanisms imparted by nanoceria remain elusive, impeding the further development of new applications. Here, we explore the behavior of cerium oxide nanoparticles of different sizes at different temperatures and trace the electronic structure changes by state-of-the-art soft and hard X-ray experiments combined with computational methods. We confirm the absence of the Ce(III) oxidation state at the surface of CeO2 nanoparticles, even for particles as small as 2 nm. Synchrotron X-ray absorption experiments at Ce L3 and M5 edges, combined with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and small angle X-ray scattering (SAXS) and theoretical calculations demonstrate that in addition to the nanoceria charge stability, the formation of hydroxyl groups at the surface profoundly affects the chemical performance of these nanomaterials.

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  • Secondary publication expected from 19.09.2020

Permalink: https://www.hzdr.de/publications/Publ-27572
Publ.-Id: 27572


Atomic scale reversible opto-structural switching of few atom luminescent silver clusters confined in LTA zeolites

Aghakhani, S.; Grandjean, D.; Baekelant, W.; Coutiño-Gonzalez, E.; Fron, E.; Kvashnina, K.; Roeffaers, M. B. J.; Hofkens, J.; Lievens, B. F.; Sels, P.
Luminescent silver clusters (AgCLs) stabilized inside partially Ag exchanged Na LTA zeolites show a remarkable reversible on–off switching of their green-yellowish luminescence that is easily tuned by a hydration and dehydration cycle, making them very promising materials for sensing applications. We have used a unique combination of photoluminescence (PL), UV-visible-NIR Diffuse Reflectance (DRS), X-ray absorption fine structure (XAFS), Fourier Transform-Infrared (FTIR) and electron spin resonance (ESR) spectroscopies to unravel the atomic-scale structural changes responsible for the reversible optical behavior of the confined AgCLs in LTA zeolites. Water coordinated, diamagnetic, tetrahedral AgCLs [Ag4(H2O)4]2+ with Ag atoms positioned along the axis of the sodalite six-membered rings are at the origin of the broad and intense green-yellowish luminescence in the hydrated sample. Upon dehydration, the luminescent [Ag4(H2O)4]2+ clusters are transformed into non-luminescent (dark), diamagnetic, octahedral AgCLs [Ag6(OF)14]2+ with Ag atoms interacting strongly with zeolite framework oxygen (OF) of the sodalite four-membered rings. This highly responsive on–off switching reveals that besides quantum confinement and molecular-size, coordinated water and framework oxygen ligands strongly affect the organization of AgCLs valence electrons and play a crucial role in the opto-structural properties of AgCLs.

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Permalink: https://www.hzdr.de/publications/Publ-27571
Publ.-Id: 27571


Flow Structures in a Weakly Turbulent Rayleigh-Bénard Convection affected by a Horizontal Magnetic Field

Vogt, T.; Yanagisawa, T.; Ishimi, W.; Tasaka, Y.; Eckert, S.
MHD Rayleigh-Bénard convection was studied experimentally using the eutectic metal alloy GaInSn inside a box having a square horizontal cross section and an aspect ratio of 5. Flow measurements were performed by means of ultrasound Doppler velocimetry that can capture time variations of instantaneous velocity profiles. Applying a horizontal magnetic field organizes the convective motion into a flow pattern of quasi-two dimensional rolls arranged parallel to the magnetic field [1], [2]. If the Rayleigh number (Ra) is increased over a certain threshold Ra/Q, whereby Q is the Chandrasekhar number, the flow undergoes a transition to turbulence. Besides the primary convection rolls the measurements reveal regular flow oscillations arising from 2D and 3D deformations of the rolls, Ekman-pumping induced flow as well as smaller side vortices that develop around the convection rolls [3]. Our findings demonstrate the importance to take 3D flow effects into account in order to explain the observed flow structures, which are often considered as quasi 2D. The comparison between the experiments and accompanying direct numerical simulations shows a very good agreement.
  • Lecture (Conference)
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands
  • Open Access Logo Contribution to proceedings
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-27570
Publ.-Id: 27570


Large-scale circulations of turbulent Rayleigh-Bénard convection in a finite liquid metal layer

Akashi, M.; Tasaka, Y.; Yanagisawa, T.; Vogt, T.; Murai, Y.; Eckert, S.
Large-scale circulations of Rayleigh-Bénard convection in a finite liquid metal layer were examined experimentally by means of ultrasonic Doppler velocimetry. The fluid layer with aspect ratio of five and L = 40 mm in height was filled with eutectic alloy of GaInSn (Prandtl number, Pr = 0.03), and multiple ultrasonic transducers for the velocimetry were mounted in the side wall of the vessel to capture 3D structures of the convection.
  • Lecture (Conference)
    International Conference on Rayleigh Bénard Turbulence, 14.-18.05.2018, Enschede, Netherlands
  • Open Access Logo Contribution to proceedings
    International Conference on Rayleigh Bénard Turbulence, 14.-18.05.2018, Enschede, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-27569
Publ.-Id: 27569


LSC Oscillations in a Liquid Metal

Vogt, T.; Horn, S.; Grannan, A.; Aurnou, J.
We present experimental results of liquid metal Rayleigh Bénard convection in a Gamma = D/H = 2 cylindrical tank. The tank is filled with liquid gallium that has a Prandtl-number Pr = 0.03. Ultrasound Doppler velocimetry is used in this study to measure the instantaneous velocity distribution along four different measuring lines. This technique is a useful tool to measure the velocities in opaque fluids, such as liquid metals non-invasively. Furthermore, a total number of 29 thermocouples is used to monitor the temperature in the experiment. Thus, the experimental set-up allows for a simultaneous analysis of the velocity and temperature field. We observed a strong oscillatory behaviour of the LSC in both, the velocity and temperature signal whose characteristic behaviour remains unchanged over the investigated range of 7x10^4 < Ra < 6x10^6. We analysed the three dimensional structure of the oscillation and compare the results to direct numerical simulation, which are in excellent agreement to the experimental observation.
  • Lecture (Conference)
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands
  • Open Access Logo Contribution to proceedings
    INTERNATIONAL CONFERENCE ON RAYLEIGH BÉNARD TURBULENCE, 14.-18.05.2018, Enschede, Netherlands

Permalink: https://www.hzdr.de/publications/Publ-27568
Publ.-Id: 27568


Controlling the lability of uranyl(VI) through intramolecular π-π Stacking

Mashita, T.; Tsushima, S.; Takao, K.
A reaction of UO22+ with cyclohexyldiphenylphosphine oxide (OPCyPh2) in ethanol resulted in a perchlorate salt of the 4-fold homoleptic complex, [UO2(OPCyPh2)4](ClO4)2·EtOH. X-ray structure determination revealed that UO2(OPCyPh2)42+ shows a highly symmetric molecular structure supported by the intramolecular π-π stacking interactions between phenyl groups of the neighbouring OPCyPh2 in the equatorial plane of UO22+. To clarify if the reactivity of UO22+ is affected by such a unique coordination structure, the ligand exchange kinetics of [UO2(OPCyPh2)4]2+ in non-coordinating solvents has been studied by NMR line-broadening method. In CD2Cl2 and CD3NO2 solutions, both signals of coordinated and free OPCyPh2 appeared distinctively even at 298 K, while 2D EXSY experiment provided an evidence that the chemical exchange between [UO2(OPCyPh2)4]2+ and free OPCyPh2 occurs in these systems. Thus, this ligand exchange reaction is quite slow in the NMR time-scale. The dependencies of the apparent first-order rate constant (kobs) on temperature and the free OPCyPh2 concentration suggested that this ligand exchange reaction involves associative and dissociative mechanisms both governed by large negative ΔS‡ terms predominantly. Compared with kinetic data of ligand exchange reactions of other UO22+ complexes reported so far, the lability of UO22+ in [UO2(OPCyPh2)4]2+ is found to be significantly suppressed due to the intramolecular π-π stacking interactions as observed in the crystal structure. The DFT calculations successfully reproduced the intramolecular π-π stacking in [UO2(OPCyPh2)4]2+ by considering the empirical dispersion corrections, and provided theoretical rationales to the A and D mechanisms of the ligand exchange reaction of [UO2(OPCyPh2)4]2+.

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Publ.-Id: 27567


Dynamic Imaging Based Structure Tracking with Ultrafast X-Ray Tomography

Windisch, D.ORC; Bieberle, M.; Bieberle, A.; Hampel, U.ORC
A common problem in experimental multiphase flow studies is the tracking of structures in the flow domain. Such may be for example particles, bubbles and waves. Ultrafast electron beam X-ray computed tomography (UFXRCT) is a fast cross-sectional imaging technique, which is applicable to opaque multiphase flows. However, as it is a 2D imaging technique, we can only obtain statistical information about properties of moving structures in the given axial planes so far. To progress towards tracking of structures we now devised a novel approach for dynamic imaging-based structure tracking. For that the tomography scanner follows the structure of interest by controlled positioning basing on real-time image data analysis. This approach is described in the following.
Keywords: ultrafast X-ray CT, structure tracking, real-time control
  • Open Access Logo Contribution to proceedings
    9th World Congress on Industrial Process Tomography (WCIPT9), 02.-06.09.2018, Bath, United Kingdom
  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography (WCIPT9), 03.09.2018, Bath, United Kingdom

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Cerebrovascular Reactivity during Prolonged Breath-Hold in Experienced Freedivers

Keil, V.; Eichhorn, L.; Mutsaerts, H.; Träber, F.; Block, W.; Mädler, B.; van de Ven, K.; Siero, J.; Macintosh, B.; Petr, J.; Fimmers, R.; Schild, H.; Hattingen, E.
BACKGROUND AND PURPOSE:
Experienced freedivers can endure prolonged breath-holds of up to eleven minutes despite severe hypoxemia and are therefore ideal subjects to study apnea-induced cerebrovascular reactivity (CVR). This multi-parametric study investigates CBF, the spatial coefficient of variation (ASL-sCoV), as a correlate of arterial transit time, and brain metabolism dynamics during prolonged apnea.

MATERIALS AND METHODS:
Fifteen male freedivers (median age: 36.0, CI 32.0–50.0, years; median previous prolonged breath-holds >2.5 mins.: 384, CI 24.0–4,536) underwent repetitive 3T pseudo-continuous arterial spin labeling and 31P-/1H-MR spectroscopy scans before, during and after a five-minute breath-hold (split into early and late phases) and gave temporally matching venous blood gas samples. CVR was temporally and regionally compared to blood gases and previous experience.

RESULTS:
ASL-sCoV decreased during the early breath-hold phase (-30.0%, P=.002), whereas CBF remained almost stable during this phase and increased in the late phase
(+51.8%; P<.0001). CVR differed between the anterior and the posterior circulation during all phases (e.g. late breath-hold: MCA 57.3±14.2 vs. PCA 42.7±10.8 mL/100 g/min.;
P=.001). There was an association between breath-hold experience and lower CBF (1,000 previous breath-holds reduced WM CBF by 0.6 mL/100 g/min.; CI 0.15 –1.1 mL/100 g/min., P=.01). While breath-hold caused peripheral lactate rise (+18.5 %) and hypoxemia (SpO2 -24.0%), cerebral lactate and ATP remained within physiological ranges, despite early signs of oxidative stress (-6.4% phosphocreatine/(ATP+ADP); P=.02).

CONCLUSIONS:
The CVR responses to prolonged apnea are complex, but guarantee the maintenance of a physiological brain metabolism in trained individuals for at least five minutes.

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Publ.-Id: 27565


Architecture and mineral potential of the Paleoproterozoic Karrat Group, West Greenland - Results of the 2017 Season

Rosa, D.; Bernstein, S.; Dewolfe, M. Y.; Dziggel, A.; Grocott, J.; Guarnieri, P.; Kolb, J.; Partin, C. A.; Sørensen, E.-V.; Zimmermann, R.
The main goal of the 2017 field season was to revise the geological maps of the southern area of Karrat Group exposures. This revision will encompass the 1:100 000 sheets of Maarmorilik 71V.2 Syd, Nuugaatsiaq 71V.2 Nord, Pannertooq 72V.2 Syd, and Svartenhuk 71V.1 Nord, originally compiled between 1980 and 1991. This third field season followed up on fieldwork carried out in 2015 and 2016 and, as the other two field seasons, was jointly financed by the Geological Survey of Denmark and Greenland (GEUS) and the Ministry of Mineral Resources of Greenland (MMR).
Within this framework, and since the focus of the first two seasons had been on the Paleo- proterozoic Karrat Group, the 2017 fieldwork targeted Archean rocks, namely in Panner- tooq (head of Ukkusissat Fjord), Upernivik Ø, Kigarsima/Tornit and the area south of Maarmorilik. This work led to the identification, in what was originally mapped as Archean orthogneiss, of significant paragneiss and quartzite sequences, of uncertain age. These supracrustal sequences often appear infolded with Archean orthogneiss, so some of them could possibly be unrelated to the stratigraphy of the Karrat Group. Similar infolding ob- served in the Qeqertarssuaq Formation, mapped in Kangilleq Fjord, suggests that this for- mation could possibly also be unrelated to the Karrat Group, as traditionally defined. Cor- roborating this interpretation is the fact that higher-P metamorphic assemblages, evi- denced by garnet amphibolite and kyanite micaschist, were documented in the Qeqertars- suaq Formation, but not in overlying formations. This contrasting metamorphic evolution can be interpreted as evidence for an early thermal event, prior to Qaarsukassak Formation deposition. Alternatively, the disparate metamorphic conditions could be accounted for by juxtaposition of different tectonic units during the Rinkian orogeny. T o further constrain the depositional ages of the paragneiss and quartzite (including those of the Qeqertarssuaq Formation), follow up detrital zircon geochronology is warranted. However, regardless of what the subsequent analytical work reveals, these findings appear to already imply signifi- cant revisions to the existing maps.
Within the Paleoproterozoic volcano-sedimentary succession, fieldwork allowed for the identification of the presence of the Qaarsukassak Formation (informal) in Kussinersuaq (Umiammakku Isbræ), Rinks Isbræ, Qingaarssuaq (Kangerlussuaq Fjord), Kigarsima/T ornit (Kangerluarsuk Fjord) and Kangerluarsuup Sermia. This formation hosts the stratabound mineralisation in the Rio Tinto Zinc (RTZ) Discovery area (Kangerluarsuk Fjord), where it was first defined. While no primary Zn mineralisation was observed at the defined localities, with only faint zinc zap responses obtained at Kussinersuaq, and other localities not tested for mineralisation, these findings significantly stretch the areal extent of the stratabound Zn- hosting Qaarsukassak Formation, and are therefore of economic significance. Detailed follow up photogeological mapping and interpretation of hyperspectral scenes of this min- eralisation host should consequently be carried out. Further work within the Paleoprotero- zoic Karrat Group, included the study of the mafic volcanic rocks of the Kangilleq Fm (in- formal), was aimed at recognising horizons with distinct geochemical signatures (alkaline vs. subalkaline), as identified in samples collected in previous seasons, in order to elucidate petrogenesis of the volcanic rocks.
The structural setting and metamorphism of the Prøven Igneous Complex (PIC) is key to understanding the geological evolution of the region and its lower contacts and some internal structures were studied. This work demonstrated that the PIC comprises one or more tabular intrusions. In the west, near Upernavik, the complex was emplaced close to the basement-cover contact. Farther to the east and south, it seems to have been emplaced at a higher stratigraphic position within the Paleoproterozoic sedimentary sequence. Subse- quently, the complex was displaced to the NW (north side of the PIC) and SE (south side of the PIC). Wherever it was studied, both North and South, this contact is a shear zone. The PIC contains abundant enclaves of meta-sedimentary rocks, particularly near the lower contact. The enclaves are most likely to be from a Paleoproterozoic sequence - the Karrat Group - although this assumption is unproven. In the instances where possible cross- cutting intrusive relations are found with meta-sedimentary rocks at the base of the PIC, the cross-cutting igneous rocks are late syn-tectonic biotite granite and leucogranites, rather than elements of the PIC proper. Earlier workers assumed that these late syn-tectonic granites and the PIC were part of the same magmatic event and were both late syn- tectonic. Our new field evidence from the northern contact of the PIC, consistent with re- cently published geochronology (Sanborn-Barrie et al. 2017), shows that the PIC was af- fected by intense fabric formation and folding and that its contacts with its host rocks, where we have seen them, are always concordant as a consequence of intense defor- mation. We conclude that the published interpretation that the PIC was emplaced relatively late during Rinkian orogenic evolution should be rejected (Grocott & Pulvertaft, 1990 and references therein).
  • Other report
    København, Danmark: Danmarks of Grønlands geologiske undersøgelse, 2018
    102 Seiten

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Publ.-Id: 27564


Analysis of flow patterns in high gravity equipment using gamma-ray computed tomography

Groß, K.; Bieberle, A.; Gladyszewski, K.; Schubert, M.; Hampel, U.; Skiborowski, M.; Górak, A.
The capacity of today’s gas-liquid contacting equipment such as tray or packed columns is limited by the gravitational-driven liquid flow. Intensified equipment applying centrifugal force offers great potential for enhancing the mass transfer and for reducing equipment size. Yet, detailed knowledge about the liquid flow inside rotating packings is scarce due to limited accessibility with conventional measurement systems. In this study, a gamma-ray computed tomography is employed to quantify the liquid hold-up and its distribution in the moving packing.
Keywords: Flow behavior, gas-liquid flow pattern, local liquid hold-up, non-invasive flow imaging, rotating packed bed

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Publ.-Id: 27563


Evaluation of liquid hold-up in a rotating packed bed for high gravity fluid separation using process-synchronized gamma-ray computed tomography

Groß, K.; Bieberle, A.; Gladyszewski, K.; Schubert, M.; Skiborowski, M.; Hampel, U.; Górak, A.; (Editors)
A Rotating Packed Bed (RPB) is a compact and flexible fluid separation equipment, which utilizes a centrifugal forces to achieve enhanced mass and energy transfer between a liquid and a vapour phase, brought in contact within a porous rotating packing. In order to perform a reliable design and scale-up of RPBs, detailed knowledge about the hydrodynamics and flow mechanisms within the equipment is strongly required. However, due to the non-transparent solid casing, such insight cannot be generated by common analytics. In the present study, liquid hold-up and gas-liquid phase distribution are determined in a porous metal foam packing of 450 mm diameter installed in a pilot-scale RPB using a high-energetic gamma-ray computed tomography (CT). The CT system consists of an isotopic source Cs 137 and an in-house developed radiation detector comprising 320 scintillation detector elements operated in photon counting mode in order to detect each single gamma photon. In particular, the liquid hold-up distribution and the lateral spreading behaviour is visualized and analysed relative to the motion of the rotating packing applying conventional CT scanning and a time-averaged angular-resolved CT scanning procedure, respectively.
Keywords: Fluid Separation, High Gravity Equipment, Rotating Packed Beds, Gamma-Ray Computed Tomography, Process-Synchronized Imaging
  • Contribution to proceedings
    World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
  • Lecture (Conference)
    World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK

Permalink: https://www.hzdr.de/publications/Publ-27562
Publ.-Id: 27562


Compact high energy x-ray spectrometer based on forward Compton scattering for high intensity laser plasma experiments

Singh, S.; Versaci, R.; Laso Garcia, A.; Morejon, L.; Ferrari, A.; Molodtsova, M.; Schwengner, R.; Kumar, D.; Cowan, T.
This article describes the design and presents recent results from testing and calibration of a forward Compton scattering gamma-ray spectrometer. The calibration was performed using a bremsstrahlung source on the photon scattering facility at the ELBE accelerator at Helmholtz-Zentrum Dresden-Rossendorf, which provides gamma-ray photons with energies up to 18 MeV. The calibration was conducted at different bremsstrahlung end point energies - 10.5, 13, 15 and 18 MeV. Experimental spectra show systematic increase in the maximum energy, photon temperature and flux. The spectrometer is effective for an energy range of 4 to 20 MeV with 20 to 30% energy resolution. The article also describes the design and shielding considerations which helped to achieve a dynamic range greater than 30 with this spectrometer. The comparison between experimental results and Monte Carlo simulations are also presented.
Keywords: bremsstrahlung, photon scattering, gamma rays, Compton spectrometer

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Publ.-Id: 27561


Modification of the perpendicular anisotropy in synthetic antiferromagnets by global and local ion beam irradiation

Lenz, M.; Koch, L.; Samad, F.; Arekapudi, P.; Fallarino, L.; Hellwig, O.
We investigate sputter deposited synthetic antiferromagnets consisting of Co/Pt multilayers with perpendicular anisotropy. Repeated multilayer-blocks are antiferromagnetically coupled to each other via Ru interlayers. This complex sample structure allows an exact tuning of the energy contributions perpendicular anisotropy, interlayer exchange and demagnetization: Varying repeats within the Co/Pt multilayers (X) or a different number of multilayer-blocks (N) lead to various magnetic phases and 3-dimensional textures [1].
By ion beam irradiation we can change the balance of these energy contributions due to an intermixing at the interfaces. With this we can realize various magnetic phases within one and the same sample and by local irradiation we can even achieve a lateral coexistence of different magnetic phases.
We will present our investigations of globally and locally irradiated synthetic antiferromagnet’s field reversal behaviour, using vibrating sample magnetometry and high resolution magnetic force microscopy.
[1] O. Hellwig et al., J. Magn. Magn. Mater. 319, 13 (2007)
  • Poster
    Joint European Magnetic Symposia (JEMS), 03.-07.09.2018, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27560
Publ.-Id: 27560


Parametric resonances in periodically perturbed dynamo models

Giesecke, A.; Stefani, F.
I present results on kinematic dynsamo models driven by an axisymmetric large scale flow impacted by periodic perturbations due to azimuthally propagating vortices. I found a strong impact on growth rates and frequencies with regimes of parametric resonances whenn the frequency of the perturbation is twice the frequency of the unperturbed case. These models behave similar to rotating mechanical systems subject to periodic distortions that are described by the Matthieu equation. A possible application are dynamo experiments like VKS dynamo in Cadarache or convection driven planetary dynamos that are influenced by tidal forces.
Keywords: dynamo DRESDYN
  • Lecture (Conference)
    Planetary-Stellar Connection: The Sun's Lesson, 07.-09.05.2018, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27559
Publ.-Id: 27559


Advanced correction algorithms for ultrafast X-ray computed tomography

Bieberle, M.; Wagner, M.; Gücker, F.; Neumann, M.; Hampel, U.
Ultrafast electron beam X-ray computed tomography is a unique imaging technique for the investigation of multiphase flows. It provides high-resolution cross-sectional images at rates of up to 4,000 fps from two tomography planes, which also allows axial velocities to be determined. As is typical for such complex measurement systems, there are several physical effects leading to deviations from the ideal imaging system. On the one hand, these are deviations associated to X-ray computed tomography (CT) in general, such as photon scattering and beam hardening. On the other hand, there are several effects originating from the electron beam deflection, which are in particular related to electron beam X-ray CT. For example, some uncertainties about the final size and position of the X-ray focal spot path on the target are remaining. This paper addresses effects and corresponding practical correction algorithms for both categories. Scattering and beam hardening as interlinked phenomena are treated by correction based on fast ray-tracing in-plane simulations. The topic of focal spot path uncertainties has been analysed in detail with respect to different parameters. The problem is tackled with two approaches. The first approach searches the correct angular positions of the X-ray focal spot on the target by maximizing the grey value variance in the resulting reconstructed images. The second approach evaluates the resulting distance map between the two imaging planes by combining simulated distributions with measured values.
Keywords: correction algorithms, image reconstruction, ultrafast, X-ray CT
  • Contribution to proceedings
    9th World Congress on Industrial Process Tomography (WCIPT9), 02.-06.09.2018, Bath, United Kingdom
    Proceedings of the 9th World Congress on Industrial Process Tomography
  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography (WCIPT9), 02.-06.09.2018, Bath, United Kingdom

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Publ.-Id: 27558


Local structural effects of Eu3+ incorporation into xenotime-type solid solutions with different host cations

Xiao, B.; Lösch, H.; Huittinen, N.ORC; Schmidt, M.ORC
In this study, the effect of host cations on the local structure around the dopant site of materials from the xenotime family is systematically studied on the molecular level. A series of six Eu3+-doped xenotime-type single crystals (Tb, Y, Ho, Er Yb, and LuPO4) have been grown and spectroscopically analyzed using polarization−dependent laser−induced luminescence spectroscopy (p−TRLFS). Our results demonstrate that the structural disorder changes in a non-linear manner with a structural break between Yb3+ and Lu3+. Despite adopting identical crystal structures, the solid solutions of these materials vary significantly, and differ from monazite solid solutions. Similar Eu3+ incorporation behavior with a strongly distorted dopant site is found for the early members of the xenotime family, while LuPO4 with the largest host vs. dopant radii mismatch is anomalous in that it contains the most symmetrical lattice site. This goes along with a significantly stronger crystal field, indicating a shorter Eu – O bond distance, as well as a strong vibronic coupling to external translational lattice vibrations. The p−TRLFS analysis confirms the breakdown of the crystallographic site symmetry from D2d to C1 in YPO4, whereas a small distortion of the crystallographic site in LuPO4 results in an S4 point symmetry for the Eu3+ cation. The lattice with the smallest cation host site is no longer sufficiently flexible to make room for Eu3+ and instead “forces” the guest ion to occupy a less distorted Lu3+ site.
Keywords: Xenotime, Incorporation, TRLFS, Luminescence, Eu3+

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Publ.-Id: 27557


Temporal Evolution of Calcite Surface Dissolution Kinetics

Bibi, I.; Arvidson, R. S.; Fischer, C.; Luttge, A.
This brief paper presents a rare dataset: a set of quantitative, topographic measurements of a dissolving calcite crystal over a relatively large and fixed field of view (~400 μm) and long total reaction time (>6h). Using a vertical scanning interferometer and patented fluid flow cell, surface height maps of a dissolving calcite crystal were produced by periodically and repetitively removing reactant fluid, rapidly acquiring a height dataset, and returning the sample to a wetted, reacting state. These reaction-measurement cycles were accomplished without changing the crystal surface position relative to the instrument’s optic axis, with an approximate frequency of one data acquisition per six minutes’ reaction (~10/h). In the standard fashion, computed differences in surface height over time yield a detailed velocity map of the retreating surface as a function of time. This dataset thus constitutes a near-continuous record of reaction, and can be used to both understand the relationship between changes in the overall dissolution rate of the surface and the morphology of the surface itself, particularly the relationship of a) large, persistent features (e.g., etch pits related to screw dislocations; b) small, short-lived features (e.g., so-called pancake pits probably related to point defects); c) complex features that reflect organization on a large scale over a long period of time (i.e., coalescent “super” steps), to surface normal retreat and stepwave formation. Although roughly similar in frequency of observation to anin situ AFM fluid cell, this VSI method reveals details of the interaction of surface features over a significantly larger scale, yielding insight into the role of various components in terms of their contribution to the cumulative dissolution rate as a function of space and time.

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Publ.-Id: 27556


Self-Diffusion in Amorphous Silicon by Local Bond Rearrangements

Kirschbaum, J.; Teuber, T.; Donner, A.; Radek, M.; Bougeard, D.; Lundsgaard Hansen, J.; Nylandsted Larsen, A.; Posselt, M.; Bracht, H.; Böttger, R.
Experiments on self-diffusion in amorphous silicon (Si) were performed at temperatures between 460 to 600° C. The amorphous structure was prepared by Si ion implantation of single crystalline Si isotope multilayers epitaxially grown on a silicon-on-insulator wafer. The Si isotope profiles before and after annealing were determined by means of secondary ion mass spectrometry. Isothermal diffusion experiments reveal that structural relaxation does not cause any significant intermixing of the isotope interfaces whereas self-diffusion is significant before the structure recrystallizes. The temperature dependence of self-diffusion is described by an Arrhenius law with an activation enthalpy Q =2.70 +- 0.11eV and preexponential factor D0=5.5(+11.1 -3.7) × 10−2 cm2 s−1. Remarkably, Q equals the activation enthalpy of hydrogen diffusion in amorphous Si, the migration of bond defects determining boron diffusion, and the activation enthalpy of solid phase epitaxial recrystallization reported in the literature. This close agreement provides strong evidence that self-diffusion is mediated by local bond rearrangements rather than by the migration of extended defects as suggested by Strauß et al. (Phys. Rev. Lett. 116, 025901 (2016)).
Keywords: amorphous Si, self-diffusion, isotope multilayers

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Publ.-Id: 27555


Local structural analyses of the uranium and zirconium in fuel debris containing boron at the Fukushima Daiichi NPP accident

Uehara, A.; Akiyama, D.; Numako, C.; Takeda, S.; Ikeda-Ohno, A.ORC; Terada, Y.; Nitta, K.; Ina, T.; Kirishima, A.; Sato, N.
Mixtures of UO2, ZrO2 and B4C, that are one possible phase of nuclear debris remaining in the damaged reactors at the Fukushima Dai-ichi Nuclear Power Plants, were prepared at high temperature between 1200 to 1600 C, and their solid state structure was characterised by X-ray absorption spectroscopy at both U LIII- and Zr K-edges, and powder X-ray diffraction. The data were further analysed by principal component analysis.
Keywords: Nuclear fuel debris, Fukushima Dai-ichi Nuclear Power Plants, solid state, characterisation, uranium, zirconium, boron, X-ray absorption spectroscopy, X-ray diffraction
  • Lecture (Conference)
    2018 Fall Meeting, Atomic Energy Society of Japan, 05.09.2018, Okayama University, Japan

Permalink: https://www.hzdr.de/publications/Publ-27554
Publ.-Id: 27554


Design, validation and testing of new receiver coatings for concentrated solar power

Krause, M.; Heras, I.; Lungwitz, F.; Wenisch, R.; Schumann, E.; Janke, D.; Guillén, E.; Munnik, F.; Azkona, I.; Gemming, S.; Escobar-Galindo, R.
Increasing central receiver solar plant’s operation temperature from 550°C to about 800°C would improve the energy conversion efficiency by 15 to 20%. Absorber coatings appropriate for such conditions have to outperform the state-of-the-art pigment paint Pyromark® that has an absorptivity α > 95% but a high emittance (ε ~ 80%). The development of environmentally stable solar-selective coatings (SSC) for these temperatures requires new concepts of design and thermal testing. Multilayer SSC based on [AlyTi1-y(OxN1-x)] absorbers were designed after an extensive microstructural characterization and optical simulations. Based on excellent simulation performance values of α = 88-94% and εRT = 4.8-13.6%, complete coating stacks were experimentally validated and tested in vacuum and in air up to temperatures of 800°C [1]. Thermal stability in vacuum up to 800°C is shown by in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry (SE) for individual layers as well as for complete SSC. Regarding in-air stability, the most stable SSC fulfilled the standard performance criterion PC ≤ 5% for 300 symmetric, 3 hours long cyclic tests between 300°C and 600°C. Another promising and simpler coating concept to be presented is based on a metal-doped transparent conductive oxide acting as solar-selective transmitter on top of a blackbody. The onset of the infrared reflectivity is tuneable by variation of the parameters during reactive magnetron sputtering deposition, thus matching the specific temperature requirements during solar applications. Thermal stability up to 800°C in vacuum is demonstrated by in situ RBS and SE.

Financial support by the EU, grant No. 645725, project FRIENDS2, and the HGF via the W3 program (S.G.) is gratefully acknowledged.

[1] I. Heras, et al. , Design of high-temperature solar-selective coatings based on aluminium titanium oxynitrides [AlyTi1-y(OxN1-x)]. Part 1: Advanced microstructural characterisation and optical simulation. Solar Energy Materials and Solar Cells 176 (2018) 81-92
Keywords: Solar selective coatings, oxynitrides, TCO's, thermosolar energy, in situ analysis, cluster tool
  • Invited lecture (Conferences)
    5th European Conference in Nanofilms (ECNF), 20.-22.03.2018, Cranfield, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-27553
Publ.-Id: 27553


Percolated Si:SiO2 Nanocomposites: Oven- vs. Millisecond Laser-induced Crystallization of SiOx Thin Films

Schumann, E.; Hübner, R.; Grenzer, J.; Gemming, S.; Krause, M.ORC
Three-dimensional nanocomposite networks consisting of percolated Si nanowires in a SiOx matrix, Si:SiO2, were studied. The structures were obtained by reactive ion beam sputter deposition of SiOx (x~0.6) thin films at 450 °C and subsequent crystallization using conventional oven as well as millisecond line focus laser annealing. Rutherford backscattering spectrometry, Raman spectroscopy, X-ray diffraction, cross-sectional and energy-filtered transmission electron microscopy were applied for sample characterization. While oven annealing resulted in a mean Si wire diameter of 10 nm and a crystallinity of 72 % within the Si volume, almost single-domain Si structures with 30 nm in diameter and almost free of amorphous Si were obtained by millisecond laser application. The structural differences are attributed to the different crystallization processes: Conventional oven tempering proceeds via solid state, millisecond laser application via liquid phase crystallization of Si. The 5 orders of magnitude larger diffusion constant in the liquid phase is responsible for the three times larger Si nanostructure diameter. In conclusion, laser annealing offers not only significantly shorter process times but moreover a superior structural order of nano-Si compared to conventional heating.
Keywords: silicon; nanostructures; percolated networks; nanocomposites; thin films; laser processing; phase separation; liquid phase crystallization

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Publ.-Id: 27552


Tiny but timely: Crystal surface reactivity constraints on diagenesis

Fischer, C.
Quantitative variability of diagenetic alteration is a major challenge for the development of predictive concepts. Here, we focus on the nano- and microscopic variability of crystal surface reactivity as a major constraint to fluid-solid reactions. While density and distribution of defect structures play a critical role, additional important impact is provided by the interaction of surfaces with nanoparticles and colloids during precipitation reactions. Quantitative data are available from multiple surface-sensitive methods that provide mechanistic insight via reaction rate maps and rate spectra and challenge the prevailing view that crystal dissolution is simply the inverse process of continuous crystal growth at crystal dislocations, e.g., during secondary porosity formation. Mechanistic insight is available from kinetic Monte Carlo methods, e.g., about inherited reactivity. The upscaling of such simulation results to the pore scale is a challenging task that requieres novel numerical approaches. Additionally to heterogeneities of the fluid flow field, reactive transport modeling approaches need to address ultimately the variability in surface reactivity in order to provide improved predictability.
  • Lecture (Conference)
    Goldschmidt-Conference, 12.-17.08.2018, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-27551
Publ.-Id: 27551


Pulsating dissolution of crystalline matter

Fischer, C.
The reaction of crystalline material with fluids is of relevance for natural and technical processes. A basic as¬sump-tion has been that the reaction products are continuously released from the crystal surface. New experimental and ana-lytical results show something fundamentally different: Material is released in a series of reaction pulses [1]. We present reaction rate maps that are derived from sequences of topography maps and quantify the spatial distribution of reaction rates across the crystal surface. The first (rate acceleration) and second (rate jerk) temporal derivative of the rate quantify the dynamic formation and loss of reactive surface sites. The resulting variability in nanoscale roughness is a key factor that controls kink-site distribution and density and therefore may help explain why laboratory (bulk) dissolution rates are so variable.
Applied and theoretical implications impact both the upscaling of crystal dissolution kinetics, and more importantly, the problem of how dissolution and growth are connected via the equilibrium state. These results challenge the prevailing view that crystal dissolution is simply the inverse process of continuous crystal growth at crystal dislocations. Consequently, we need to examine how macroscopic crystal equilibrium reflects continuous or discontinuous processes in the microscopic state.

[1] Fischer, C., Luttge, A., 2018. Pulsating dissolution of crystalline matter. PNAS 115, 897-902.
  • Invited lecture (Conferences)
    Goldschmidt-Conference, 12.-17.08.2018, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-27550
Publ.-Id: 27550


Synthesis and radiofluorination of a novel monocarboxylate transporter 1 inhibitor for tumor imaging by PET

Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Fischer, S.; Teodoro, R.; Ludwig, F.-A.; Gurrapu, S.; Drewes, L. R.; Brust, P.
Monocarboxylate transporter 1 (MCT1) is an integral plasma membrane protein that bi-directionally transports lactate and ketone bodies and is highly expressed in non-hypoxic regions of human colon, brain, breast, lung and other tumors. Accordingly, MCT1 inhibitors are regarded to be of potential clinical use. In the current study we developed a new 18F-labeled radioligand for in vivo imaging of MCT1-overexpressing brain tumors by PET.
A new fluorinated analogue of α-cyano-4-hydroxycinnamic acid (RM231) was synthesized from m-anisidine via alkylation, ortho formylation and Knoevenagel condensation in 50% overall yield. Its MCT1 inhibition activity was evaluated via [14C]lactate uptake assay on rat brain endothelial 4 cells. The mesylated precursor was similarly prepared in 52% overall yield. Radiosynthesis of [18F]RM231 was achieved by a two-step reaction, starting with the radiofluorination using [18F]-K2CO3-K222 complex followed by protective group removal via hydrolysis under optimized reaction conditions.
RM231 showed relatively high MCT1 inhibition activity (IC50 = 12 nM). The radiolabeled intermediate was obtained by an optimized procedure (acetonitrile, 5.5 mg of K222, 0.7 mg of K2CO3, 12-15 GBq of K18F, 100 ̊C, 8 min) with 44-50% yield determined by radio-HPLC analysis (N=3, non-isolated). The final product was obtained by hydrolysis with TFA in dry dichloromethane at room temperature for 10 minutes with 29% yield (radio-HPLC, non-isolated).[18F]RM231 could be obtained after separation using semi-preparative HPLC (RP C18 column; 30% ACN, 20 mM NH4CO2H). Currently, attempts are made to stabilize and formulate the final product appropriately for biological investigation. The newly developed MCT1 radioligand is anticipated to be a useful agent for imaging of the tumors with PET. Accordingly, animal studies on the new radiotracer are currently under investigation.
Keywords: Monocarboxylate transporter 1, α-Cyanocinnamic acid derivatives, Radiofluorination, Fluorine-18, Brain tumors.
  • Lecture (Conference)
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Czeck Republic

Permalink: https://www.hzdr.de/publications/Publ-27549
Publ.-Id: 27549


Effect of beam energy straggling on resonant yield in thin gas targets: The cases 22Ne(p,gamma)23Na and 14N(p, gamma)15O

Bemmerer, D.; Cavanna, F.; Depalo, R.; Aliotta, M.; Anders, M.; Boeltzig, A.; Broggini, C.; Bruno, C.; Caciolli, A.; Corvisiero, P.; Davinson, T.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Prati, P.; Scott, D. A.; Straniero, O.; Szücs, T.; Takács, M. P.; Trezzi, D.
When deriving resonance strengths using the thick-target yield approximation, for very narrow resonances it may be necessary to take beam energy straggling into account. This applies to gas targets of a few keV width, especially if there is some additional structure in target stoichiometry or detection efficiency. The correction for this effect is shown and tested on recent studies of narrow resonances in the 22Ne(p, γ)23Na and 14N(p, γ)15O reactions.

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Permalink: https://www.hzdr.de/publications/Publ-27548
Publ.-Id: 27548


Erratum: Three new low-energy resonances in the 22Ne(p,γ)23Na reaction

Cavanna, F.; Depalo, R.; Aliotta, M.; Anders, M.; Bemmerer, D.; Best, A.; Böltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Corvisiero, P.; Davinson, T.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Prati, P.; Scott, D. A.; Somorjai, E.; Straniero, O.; Strieder, F.; Szücs, T.; Takács, M. P.; Trezzi, D.
Reported strengths of newly discovered resonances in [F. Cavanna et al., Phys. Rev. Lett. 115, 252501 (2015)] were affected by an error in the analysis. The energy straggling of the ion beam was erroneously neglected. When taking this effect into account, 18-19% higher values are found for the resonance strengths. The astrophysical implications are unchanged.

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Permalink: https://www.hzdr.de/publications/Publ-27547
Publ.-Id: 27547


Phage Display Derived Short Peptides for the Recovery of Valuable Metal Ions from Water Streams

Matys, S.; Schönberger, N.; Braun, R.; Lehmann, F.; Flemming, K.; Lederer, F.; Pollmann, K.
Since several years, the phage surface display technique (PSD) has been successfully applied for the development of new receptor-ligand pairs for medical purposes, new pharmaceuticals or the elucidation of protein-protein interactions [1,2]. A comparatively new methodological approach is the use of this technique for bioremediation [3,4]. We established the PSD as novel biotechnological platform for the selective recovery of industrial relevant elements either in ionic form or as small particles. The commercially available bacteriophage libraries Ph.D.C7C and Ph.D.12 (New England Biolabs, Inc.) were used for isolation and identification of specific nickel, cobalt and gallium ion binding peptides. From a pool of 1,2 x 10⁹ different peptide motifs, 24 phage clones for nickel, 20 for cobalt and 108 for gallium were isolated in the iterative bio-panning process. The binding strength of these phages clones was compared with the one of unmodified wild type phages by performing adsorption tests onto metal loaded agarose beads. Cross binding tests revealed for most of the nickel binding phages also binding capacities for cobalt and vice versa.


[1]. H.M.E. Azzazy, W.E. Highsmith Jr., Clinical Biochemistry. 2002, 35, 425-45:
[2] J. Pande, M.M. Szewczyk, A.K. Grover, Biotechnology Advances. 2010, 28, 849-58:
[3] S.B. Curtis, J. Hewitt, R.T.A. MacGillivray, W.S. Dunbar, Biotech. Bioeng. 2009, 102, 644-650:
[4] T. Hatanaka, A. Matsugami, T. Nonaka, H. Takagi, F. Hayashi, T. Tani, N. Ishida, Nature Comm. 2017, 8, 15670:
Keywords: phage surface display, biopanning, metal recovery
  • Poster
    4th International Conference on Bioinspired and Biobased Chemistry & Materials, 14.-17.10.2018, Nizza, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-27546
Publ.-Id: 27546


Modelling of condensation inside an inclined pipe

Moonesi Shabestary, A.; Bieberle, A.; Krepper, E.; Lucas, D.; Hampel, U.
Designs of future nuclear boiling water reactor concepts are usually equipped with a so-called emergency cooling system which is passively driven to remove heat from the core to the outside in case of an accident. The emergency cooling system consists of a bunch of slightly inclined horizontal pipes which are immersed in a tank of subcooled water. At normal operation conditions, the pipes are filled with water and no heat transfer to the secondary side of the condenser exists. In case of an accident during which the water level in the core is decreasing, steam enters the emergency pipes and due to the cold water around the pipe, the steam condenses at the inner wall of the pipes. Therefore, the emergency condenser removes the decay heat from the reactor core. In the current PANAS-project all the involved thermal hydraulic components are studied intensively. The focus of the current paper is on CFD modeling of the emergency condenser and validation of the models with data obtained from experiments performed at the TOPFLOW facility at a single condensation pipe at operating conditions close to reality, i.e. at high pressure and saturated steam.
In this paper, the inflow of the pipe is assumed as pure steam. Due to wall condensation a thin liquid film is generated near the wall leading to annular flow. The generated liquid film stays in direct contact with steam which is on saturation temperature causing direct contact condensation at the interface between steam and liquid. Because of the gravity force, the laminar liquid film is falling, gathering at the lower part of the pipe and finally a stratified flow occurs. Combining wall condensation, direct contact condensation and effects of the liquid film on the heat transfer coefficient is a major focus of this paper. Finally, the results of the simulations are validated with the experimental data.
  • Contribution to proceedings
    49th Annual Meeting on Nuclear Technology, 29.-30.05.2018, Berlin, Germany
    Modelling of condensation inside an inclined pipe

Permalink: https://www.hzdr.de/publications/Publ-27545
Publ.-Id: 27545


Complexation of europium with chondroitin sulfate

Barkleit, A.ORC; Patzschke, M.; Heim, K.; Seidler, D. G.
Glycosaminoglycans (GAGs) are linear polysaccharides and highly negatively charged. GAGs are part of proteoglycans which are major components of the extracellular matrix. They are involved in binding cations (such as sodium, potassium and calcium) and water, and also regulating the movement of molecules through the matrix. Individual functions of proteoglycans can be attributed to either the protein core or the attached GAG chain. The GAG family consists of heparin/heparan sulfate, chondroitin sulfate (CS) and dermatan sulfate (DS). CS is composed of the disaccharide unit N-acetylgalactosamine (D-GalNAc) and D-glucuronic acid which can be sulfated at the C4 and C6 of GalNAc (CS4S and CS6S). DS is defined by presence of L-iduronic acid residues and is always sulfated at C4 at the GalNAc. The ability of the lanthanide ions, like Europium (Eu), which show luminescence properties, allowed studying the binding behavior of GAGs.
The behavior of the complex formation of Eu3+/GAGs was analyzed under physiological conditions by several experimental methods such as time-resolved laser-induced fluorescence spectroscopy (TRLFS) and infrared spectroscopy (ATR-FT-IR), supplemented by theoretical calculations of the possible structures and resulting spectra.
All three GAGs (CS4S, CS6S and DS) caused an increase in luminescence intensity of the hypersensitive 7F2 emission band of Eu3+ due to complex formation, which was more pronounced for CS4S and DS compared to CS6S. The luminescence lifetimes increased with CS4S and DS up to 200-300 µs, corresponding to 2-4 remaining H2O molecules in the first coordination shell of Eu3+. With CS6S, the luminescence lifetime was even more prolonged up to ~650 µs (~1 remaining H2O).
FT-IR showed that the binding of GAGs to Eu3+ occurs not only via the carboxyl groups but also via the sulfate groups.
Even though the coordination behavior of GAGs towards Eu3+ is in general quite similar, particular differences could be identified: GAGs with C4 sulfation seem to be stronger ligands, whereas C6 sulfation seems to be sterically more ambitious since it can replace more H2O molecules from the first spherical coordination shell of Eu3+ than C4 sulfation.
  • Poster
    10th International Conference on f-Elements (ICFE-10), 03.-06.09.2018, Lausanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-27544
Publ.-Id: 27544


Magnetic coupling effects in curvilinear nanomagnets

Makarov, D.; Volkov, O.; Kakay, A.; Fassbender, J.
While conventionally magnetic films and structures are fabricated on flat surfaces, the topology of curved surfaces has only recently started to be explored and leads to new fundamental physics as well as applied device ideas [1]. In particular, novel effects occur when the magnetization is modulated by curvature providing a new degree of freedom that leads to new magnetization configurations and is predicted to have major implications on the spin dynamics due to topological constraints [2].
Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning. In addition to these rich physics, the application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics [3], spin-wave filters and high-speed racetrack memory devices. The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.

[1] R. Streubel, D. Makarov et al., J. Phys. D: Appl. Phys. 49, 363001 (2016).
[2] D. Sander, D. Makarov et al., J. Phys. D: Appl. Phys. 50, 363001 (2017).
[3] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
Keywords: curvature effects, magnetic thin films
  • Poster
    Joint European Magnetic Symposia 2018, 03.-07.09.2018, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-27542
Publ.-Id: 27542


Spintronics with magnetoelectric antiferromagnetic thin films

Makarov, D.
Thin film antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties and magnetoelectric responses of AF thin films with respect to their bulk counterparts. Considering grainy morphology of thin films, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be addressed.
Our approach is based on the electron transport characterization of magnetic responses of thin film metallic (IrMn) and insulating (α-Cr2O3) antiferromagnets [1-3]. To access minute uncompensated surface magnetization, we rely on zero-offset Hall magnetometry [2]. To build a reliable description of the material properties, the analysis of the transport data is backed up by structural characterization and real space imaging of AF domain patterns using NV microscopy [2].
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its AF order parameter all-electrically allowed us to put forth a new recording concept where a magnetoelectric memory cell is addressed without using a ferromagnet [1].
[1] T. Kosub et al., Nat. Commun. 8, 13985 (2017).
[2] T. Kosub et al., Phys. Rev. Lett. 115, 097201 (2015).
[3] R. Schlitz et al., Appl. Phys. Lett. 112, 132401 (2018).
Keywords: antiferromagnets, magnetoelectric effect
  • Invited lecture (Conferences)
    2018 International Colloquium on Magnetic Films and Surfaces (ICMFS), 22.-27.07.2018, Santa Cruz, USA

Permalink: https://www.hzdr.de/publications/Publ-27541
Publ.-Id: 27541


Spintronics of thin film granular antiferromagnets

Makarov, D.
Antiferromagnets have the potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. There are already great advances in the field especially when bulk antiferromagnets are considered. The application potential of antiferromagnets can be explored in full only if they will be prepared in the way to be compatible with a conventional microelectronic processing. This necessarily requires the use of (i) thin film antiferromagnets and (ii) discovery of methods to address the order parameter and its modifications all-electrically.
With respect to the first challenge it is necessary to understand modifications of the magnetic properties and magneto-electric responses of thin film antiferromagnets with respect to their bulk counterparts. Typically, thin films possess grainy morphology. Hence, to determine their application potential, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be answered. This topic will be illustrated on the specific example of thin film magnetoelectric collinear antiferromagnet α-Cr2O3 studied using zero-offset Hall magnetometry and NV microscopy [1].
To address the second challenge it is required to develop transport-based techniques to harness the responses of thin film antiferromagnets. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. I will outline our developments of zero-offset anomalous Hall magnetometry [2] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets.
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing field of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [1]. The key performance parameters of the Cr2O3 based AF-MERAM will be highlighted.
The essence of the AF-MERAM concept is that the read out is realized by acquiring Hall effect measurements from a thin metal layer (e.g., Pt) in proximity with the insulating Cr2O3. While this approach provides a convenient all-electric way to interface with the antiferromagnetic material, the underlying mechanism is debated to be based on either spin Hall magnetoresistance (SMR) or proximity effect. By carrying out temperature dependent anomalous Hall and magnetoresistance measurements, we found out that the signal is dominated by the SMR with a clear presence of an additional contribution. The origin of this contribution might be related to the proximity effect. These preliminary experimental results will be put forth for the discussion as well.
[1] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, and D. Makarov, “Purely antiferromagnetic magnetoelectric random access memory”. Nature Communications 8, 13985 (2017).
[2] T. Kosub, M. Kopte, F. Radu, O. G. Schmidt, and D. Makarov, “All-Electric access to the magnetic-field-invariant magnetization of antiferromagnets”. Phys. Rev. Lett. 115, 097201 (2015).
Keywords: antiferromagnets, spintronics
  • Invited lecture (Conferences)
    Joint European Magnetic Symposia 2018, 03.-07.09.2018, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-27540
Publ.-Id: 27540


Curvilinear nanomagnetism

Makarov, D.
While conventionally magnetic films and structures are fabricated on flat surfaces, the topology of curved surfaces has only recently started to be explored and leads to new fundamental physics as well as applied device ideas [1]. In particular, novel effects occur when the magnetization is modulated by curvature providing a new degree of freedom that leads to new magnetization configurations and is predicted to have major implications on the spin dynamics due to topological constraints [2].
Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films [3]. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [4]. In addition to these rich physics, the application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics [5], spin-wave filters and high-speed racetrack memory devices. The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.

[1] R. Streubel, D. Makarov et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Topical Review) 49, 363001 (2016).
[2] D. Sander, D. Makarov et al., The 2017 Magnetism Roadmap. J. Phys. D: Appl. Phys. (Topical Review) 50, 363001 (2017).
[3] R. Streubel, D. Makarov et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nat. Commun. 6, 7612 (2015).
[4] V. P. Kravchuk, D. Makarov et al., Multiplet of Skyrmion states on a curvilinear defect: Reconfigurable Skyrmion lattices. Phys. Rev. Lett. 120, 067201 (2018).
[5] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Focused Review) 3, 011101 (2016).
Keywords: curvature effects, magnetic thin films, shapeable magnetoelectronics
  • Invited lecture (Conferences)
    Invited talk at the Condensed Matter Theory seminar at the University of Utrecht, 20.06.2018, Utrecht, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-27539
Publ.-Id: 27539


Spintronics with thin film magnetoelectric antiferromagnets

Makarov, D.
In this talk I will Review our activities on thin film Cr2O3 films, which led to the realization of antiferromagnetic magnetoelectric RAM [1-3].
[1] T. Kosub, D. Makarov et al., Nat. Commun. 8, 13985 (2017).
[2] T. Kosub, D. Makarov et al., Phys. Rev. Lett. 115, 097201 (2015).
[3] R. Schlitz, D. Makarov et al., Appl. Phys. Lett. 112, 132401 (2018).
Keywords: antiferromagnets, spintronics
  • Invited lecture (Conferences)
    2018 Gordon Research Conference entitled Multiferroic and Magnetoelectric Materials – "Effects in Multiferroics Beyond the Coupling of Magnetic and Electric Order", 05.-10.08.2018, Lewiston, Maine, USA

Permalink: https://www.hzdr.de/publications/Publ-27538
Publ.-Id: 27538


Magnetic smart skins for augmented reality

Makarov, D.
Augmented reality gadgets are becoming common for our information intensive society assisting us to acquire and process the data. Although impressive in the realization and demonstrations, the obvious drawback of the state-of-the-art augmented and virtual reality devices relying on optical detection systems is their bulkiness, energy inefficiency and the stringent requirement for an operator to be at the line of sight of the device.
We envision that prospective augmented reality systems will strongly benefit from the recent developments in compliant on-skin electronics [1-3]. The fabrication of highly conformable gadgets requires the realization of the electronic replica of the exteroceptive sensory system of humans as well as calls for the acquiring new perception skills beyond those prescribed by the evolution. The representative example of the missing exteroceptive sense of humans is the magnetoception, which allows some of the mammals but not humans perceiving the location in space or directions based on the detection of magnetic fields. The first crucial step towards the realization of this vision was accomplished with the development of interactive magnetosensitive skins [4-6]. The key enabler for this technology is the shapeable [7] –namely, flexible [5,6], stretchable [8,9] and imperceptible [4]– magnetic field sensorics.
Here, we present the first on-skin gadgets, which replicate our natural proprioceptive sensory ability of detecting the motion. The technology is put forth to realize distributed arrays of magnetic field sensors on ultra-thin polymeric foils. Relying on this magnetically enabled electronic proprioception, we visualize the bodily motion and demonstrate the touchless manipulation of virtual objects for augmented reality systems.
Those highly conformable interactive devices possess great potential to extend the portfolio of tasks, which can be performed in virtual or augmented reality. The integration of gadgets in imperceptible electronic skins will open not only exciting possibilities for business or gaming industry but is also beneficial for safety and security applications, where the somatic manipulation of objects, e.g. turning regulation knobs located in a restricted environment is undesirable or even prohibited.

1. J. A. Rogers et al. Nature 477, 45 (2011).
2. S. Bauer et al., Adv. Mater. 26, 149 (2014).
3. M. Kaltenbrunner et al., Nature 499, 458 (2013).
4. M. Melzer et al., Nature Commun. 6, 6080 (2015).
5. M. Melzer et al., Adv. Mater. 27, 1274 (2015).
6. N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
7. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
8. M. Melzer et al., Nano Lett. 11, 2522 (2011).
9. M. Melzer et al., Adv. Mater. 27, 1333 (2015).
Keywords: flexible magnetic field sensors, shapeable magnetoelectronics, virtual reality
  • Invited lecture (Conferences)
    18th International Conference on Experimental Mechanics (ICEM 2018), 01.-05.07.2018, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-27537
Publ.-Id: 27537


Magnetism in curved geometries

Makarov, D.
While conventionally magnetic films and structures are fabricated on flat surfaces, the topology of curved surfaces has only recently started to be explored and leads to new fundamental physics as well as applied device ideas. In particular, novel effects occur when the magnetization is modulated by curvature that has major implications on the spin statics and dynamics due to topological constraints.
Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [1]. In addition to these rich physics, the application potential of 3D-shaped objects is currently being explored as spin filters, magnetic field sensorics and memory devices.
To this end, the initially fundamental topic of magnetism in curved geometries strongly benefited from the input of the application-oriented community, which among others explores the mechanical shapeability of curved magnetic thin films. These activities resulted in the development of shapeable magnetoelectronics [2] - spintronics on flexible, bendable and stretchable surfaces.
[1] Streubel et al., J. Phys. D: Appl. Phys. (Topical Review) 49, 363001 (2016).
[2] Makarov et al., Appl. Phys. Rev. (Focused Review) 3, 011101 (2016).
Keywords: curvature effects, magnetism, 3D shapes, magnetic thin films
  • Lecture (Conference)
    DPG Spring meeting, 11.-16.03.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-27536
Publ.-Id: 27536


Spintronics of thin film granular antiferromagnets

Makarov, D.
Antiferromagnets have the potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. Their application potential can be explored in full only if antiferromagnets will be prepared to be compatible with a conventional microelectronic processing. This necessarily requires the use of (i) thin film antiferromagnets and (ii) discovery of methods to address the order parameter and its modifications all-electrically.
With respect to the first challenge it is necessary to understand modifications of the magnetic properties and magneto-electric responses of thin film antiferromagnets with respect to their bulk counterparts. Typically, thin films possess grainy morphology. Hence, to determine their application potential, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be answered. This topic I will illustrate on the specific example of thin film magnetoelectric collinear antiferromagnet α-Cr2O3 studied using zero-offset Hall magnetometry and NV microscopy [1].
To address the second challenge it is required to develop transport-based techniques to harness the responses of thin film antiferromagnets. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. I will outline our developments of zero-offset anomalous Hall magnetometry [2] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets.
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing field of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [1].

[1] T. Kosub et al., Nature Communications 8, 13985 (2017).
[2] T. Kosub et al., Phys. Rev. Lett. 115, 097201 (2015).
Keywords: antiferromagnets, magnetoelectric effect, Hall measurement
  • Invited lecture (Conferences)
    International Workshop on Magneto-Electric Actuation, Magneto-ionicsand Related Phenomena in High-Surface Area Materials, 28.-30.05.2018, Gavà-Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-27535
Publ.-Id: 27535


Magnetic Functionalities for Flexible Interactive Electronics

Makarov, D.
Augmented reality gadgets are becoming common for our information intensive society assisting us to acquire and process the data. Although impressive in the realization and demonstrations, the obvious drawback of the state-of-the-art augmented and virtual reality devices relying on optical detection systems is their bulkiness, energy inefficiency and the stringent requirement for an operator to be at the line of sight of the device.
We envision that prospective augmented reality systems will strongly benefit from the recent developments in compliant on-skin electronics [1-3]. The fabrication of highly conformable gadgets requires the realization of the electronic replica of the exteroceptive sensory system of humans as well as calls for the acquiring new perception skills beyond those prescribed by the evolution. The representative example of the missing exteroceptive sense of humans is the magnetoception, which allows some of the mammals but not humans perceiving the location in space or directions based on the detection of magnetic fields. The first crucial step towards the realization of this vision was accomplished with the development of interactive magnetosensitive skins [4-6]. The key enabler for this technology is the shapeable magnetoelectronics [7] –namely, flexible [5,6], stretchable [8,9] and imperceptible [4,10]– magnetic field sensorics.
Here, we present the first on-skin gadgets, which replicate our natural proprioceptive sensory ability of detecting the motion [6, 7, 10]. The technology is put forth to realize distributed arrays of magnetic field sensors on ultra-thin polymeric foils. Relying on this magnetically enabled electronic proprioception, we visualize the bodily motion and demonstrate the touchless manipulation of virtual objects for augmented reality systems.
Those highly conformable interactive devices possess great potential to extend the portfolio of tasks, which can be performed in virtual or augmented reality. The integration of gadgets in imperceptible electronic skins will open not only exciting possibilities for business or gaming industry but is also beneficial for safety and security applications, where the somatic manipulation of objects, e.g. turning regulation knobs located in a restricted environment is undesirable or even prohibited.

References
1. J. A. Rogers et al., Nature 477, 45 (2011).
2. S. Bauer et al., Adv. Mater. 26, 149 (2014).
3. M. Kaltenbrunner et al., Nature 499, 458 (2013).
4. M. Melzer et al., Nature Commun. 6, 6080 (2015).
5. M. Melzer et al., Adv. Mater. 27, 1274 (2015).
6. N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
7. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
8. M. Melzer et al., Nano Lett. 11, 2522 (2011).
9. M. Melzer et al., Adv. Mater. 27, 1333 (2015).
10. G. S. Canon Bermudez et al., Science Advances 4, eaao2623 (2018).
Keywords: flexible electronics, magnetic field sensors, on-Skin electronics
  • Invited lecture (Conferences)
    6th International Conference on Superconductivity and Magnetism, 29.04.-04.05.2018, Antalya, Turkey

Permalink: https://www.hzdr.de/publications/Publ-27534
Publ.-Id: 27534


Efficient Parallel Monte-Carlo Simulations for Large-Scale Studies of Surface Growth Processes

Kelling, J.
Lattice Monte Carlo methods are used to investigate far from and out-of-equilibrium systems, including surface growth, spin systems and solid mixtures. Applications range from the determination of universal growth or aging behaviors to palpable systems, where coarsening of nanocomposites or self-organization of functional nanostructures are of interest. 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 work addresses the problem of parallel processing introducing correlations in Monte Carlo updates and proposes a virtually correlation-free domain decomposition scheme to solve it. 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 but highly efficient simulations using a stochastic cellular automaton (SCA). Efficient massively parallel implementations on graphics processing units (GPUs) were developed, which enable large-scale simulations leading to unprecedented precision in the final results.

The primary subject of study is the Kardar–Parisi–Zhang (KPZ) surface growth in (2 + 1) dimensions, which is simulated using a dimer lattice gas and the restricted solid-on-solid model (RSOS) model. Using extensive simulations, conjectures regarding growth, autocorrelation and autoresponse properties are tested and new precise numerical predictions for several universal parameters are made.
Keywords: lattice Monte Carlo, surface growth, ballistic deposition, physical aging, Kardar–Parisi–Zhang, lattice gas, parallel processing, domain decomposition, GPU
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Universality of (2+1)-dimensional restricted … (Id 23645) HZDR-primary research data are used by this publication
Aging of the (2+1)-dimensional Kardar-Parisi-Zhang model (Id 20253) HZDR-primary research data are used by this publication

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Permalink: https://www.hzdr.de/publications/Publ-27533
Publ.-Id: 27533


Inductive System for Reliable Magnesium Level Detection in a Titanium Reduction Reactor

Krauter, N.; Eckert, S.; Gundrum, T.; Stefani, F.; Wondrak, T.; Frick, P.; Khalilov, R.; Teimurazov, A.
The determination of the Magnesium level in a Titanium reduction retort by inductive methods is often hampered by the formation of Titanium sponge rings which disturb the propagation of electromagnetic signals between excitation and receiver coils. We present a new method for the reliable identification of the Magnesium level which explicitly takes into account the presence of sponge rings with unknown geometry and conductivity. The inverse problem is solved by a look-up-table method, based on the solution of the inductive forward problems for several tens of thousands parameter combinations.
Keywords: titanium, Kroll process, level detection, inductive measurements

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Permalink: https://www.hzdr.de/publications/Publ-27532
Publ.-Id: 27532


Contilisant, a Tetratarget Small Molecule for Alzheimer’s Disease Therapy Combining Cholinesterase, Monoamine Oxidase Inhibition and H3R Antagonism with Sigma 1R Agonism Profile

Bautista-Aguilera, O. M.; Budni, J.; Mina, F.; Medeiros, E. B.; Deuther-Conrad, W.; Entrena, J. M.; Moraleda, I.; Iriepa, I.; López-Muñoz, F.; Marco-Contelles, J.
Contilisant, a permeable, antioxidant and neuroprotectant agent, showing high nM affinity at H3R, excellent inhibition of the monoamine oxidases and cholinesterases, is an affine and selective S1R agonist in the nanomolar range, based on the binding affinity and functional experiment, a result confirmed by molecular modeling. In addition, Contilisant significantly restores the cognitive deficit induced by Aβ1-42 in the radial maze assay in an in vivo Alzheimer’s disease test, comparing very favorably with donepezil.
Keywords: Alzheimer’s disease, Aβ, ASS234, ChE inhibitor, Contilisant, Cognitive impairment, H3R antagonist, MAO inhibitor, Molecular modeling, Radial arm-maze test, hSigma 1R agonist, rVAChT modulator, Y-maze test.

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Permalink: https://www.hzdr.de/publications/Publ-27531
Publ.-Id: 27531


Laser schaltet Magnet an und aus

Ehrler, J.ORC; Kronast, F.; Zhigilei, L. V.; Bali, R.
Mit einem Laserstrahl in einer Legierung magnetische Strukturen zu erzeugen und anschließend wieder zu löschen – das gelang einer internationalen Kooperation unter Leitung des Helmholtz-Zentrums Dresden-Rossendorf (HZDR). Durch Laserpulse veränderte sie die Anordnung der Atome, was eine Veränderung der magnetischen Eigenschaften zur Folge hatte. Da Laser in der Industrie weit verbreitet sind, könnten sich für die Materialbearbeitung, für optische Technologien oder die Datenspeicherung neue Perspektiven eröffnen.
Related publications
Laser-Rewriteable Ferromagnetism at Thin Film Surfaces (Id 27198) is cited by this publication
  • Physik in unserer Zeit (2018)

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Permalink: https://www.hzdr.de/publications/Publ-27530
Publ.-Id: 27530


Environmental fate of fission products: a comprenhensive study

Mayordomo, N.; Rodríguez, D. M.; Müller, K.ORC
Assuring a safe long-term nuclear waste management implies extensive knowledge on the fundamental behaviour of fission products in the surroundings of the feasible repository. This includes the radionuclide speciation, their migration, and their possible interaction with compartments of the technical and geological barriers, and biota.
Fission products, although generated in low yield, posse radiotoxicity and their half-life can be high (10^5 years). Among them, Se and Tc are especially relevant because some of their species are assumed highly mobile in water, since their interaction with the barrier materials (like clay) is considered negligible, as they are mainly found as anionic species [1].
We carry out a comprehensive study to fill the existing gaps of knowledge about the thermodynamic parameters and the molecular level information related to Tc and Se interaction with minerals. Our approach consist on having a global view of the interaction by combining experiments and theoretical tools [2]. On one hand the experiments consists on batch sorption experiments (to obtain the trend of sorption with pH, ionic strength or time) and on spectroscopic experiments (to get the information of the interaction at a molecular level). On the other hand, the theoretical tool consists on developing complexation models that allow the prediction of fission product-mineral interaction under given conditions and that can be adapted to other environments.
In this talk we focus on the Tc(VII) interaction with alumina. Alumina has been selected not only for its model character for complex minerals, but also because of its high affinity for anions, as Se(IV) [2].

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

[1] K.H. Lieser, et al. Radiochim. Acta. 42 (1987) 205–213.
[2] N. Mayordomo, et al. Environ. Sci. Technol. (2018) 581–588.
Keywords: Technetium, alumina, retention
  • Invited lecture (Conferences)
    Goldschmidt 2018, 12.-17.08.2018, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-27529
Publ.-Id: 27529


The Feasibility of Studying 44Ti(α, p)47V Reaction at Astrophysical Energies

Al-Abdullah, T.; Bemmerer, D.; Elekes, Z.; Schumann, D.
The gamma-ray lines from the decay of 44Ti have been observed by space-based gamma-ray telescopes from two supernova remnants. It is believed that the 44Ti(α, p)47V reaction dominates the destruction of 44Ti. This work presents a possible technique to determine its reaction rate in forward kinematics at astrophysically relevant energies. Several online and offline measurements in parallel with Monte Carlo simulations were performed to illustrate the feasibility of performing this reaction. The results will be discussed.

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Permalink: https://www.hzdr.de/publications/Publ-27528
Publ.-Id: 27528


Thermally driven convection in Li||Bi liquid metal batteries

Personnettaz, P.; Beckstein, P.; Landgraf, S.; Köllner, T.; Nimtz, M.; Weber, N.; Weier, T.
Liquid Metal Batteries (LMBs) are a promising concept for cheap electrical energy storage at grid level. These are built as a stable density stratification of three liquid layers, with two liquid metals separated by a molten salt. In order to ensure a safe and efficient operation, the understanding of transport phenomena in LMBs is essential. With this motivation we study thermal convection induced by internal heat generation.
We consider the electrochemical nature of the cell in order to define the heat balance and the operating parameters. Moreover we develop a simple 1D heat conduction model as well as a fully 3D thermo-fluid dynamics model. The latter is implemented in the CFD library OpenFOAM, extending the volume of fluid solver, and validated against a pseudo-spectral code. Both models are used to study a rectangular 10×10 cm Li||Bi LMB cell at three different states of charge.
Keywords: liquid metal batteries, heat transfer, thermal convection, thermodynamics, OpenFOAM, volume of fluid, spurious currents

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Permalink: https://www.hzdr.de/publications/Publ-27527
Publ.-Id: 27527


Using FIB/SEM's to Investigate Biological Samples

Wolff, A.; Klingner, N.ORC; Thompson, W.; Zhou, Y.; Lin, J.; Peng, Y. Y.; Ramshaw, J. A. M.; Xiao, Y.
This study focuses on gallium ion-solid interactions and their simulations to derive sets of suitable operational parameters and a technique which prevents heat damage in soft materials.
The technique is successfully demonstrated on non-resin embedded collagen,a bio material which serves as a case study for other soft tissues.
  • Poster
    The 62nd International Conference on Electron, Ion, and Photon Beam Technology and Nanofabrication, 29.05.-01.06.2018, Puerto Rico, USA
  • Lecture (Conference)
    2nd international HeFIB conference on Helium and emerging Focused Ion Beams, 11.-13.06.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-27526
Publ.-Id: 27526


Radiopharmaceutical evaluation of novel bifunctional chelators and bioconjugates for tumor imaging and therapy

Stephan, H.
The development of multi-functional complexing agents for radiometal nuclides with a view of nuclear medical application represents a field of research that is intensively dealt with and has rapidly been developing. In this context, ligands that form highly stable metal complexes and additionally possess several different functional groups are of particular interest. This enables the simultaneous introduction of targeting, solubilizing and, for example, fluorescent units into the relevant metal complexes. In this perspective, bifunctional chelating agents (BFCAs) based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) and 1,4,7-triazacyclononane (TACN) are discussed. Examples of target-specific peptides and bio(nano)materials equipped with bispidine and TACN ligands for labeling with 64Cu as an ideal positron emitter are presented. This enables tumor imaging and the biodistribution of the materials to be studied over a period of days via positron emission tomography (PET). This lecture will also give an insight into the pre-targeting strategy using complementary oligonucleotides such as peptide nucleic acid (PNA) derivatives. The pre-targeting strategy allows for the rational use of long circulating, high affinity antibodies for both non-invasive cancer radioimmunodetection (RID) and –therapy (RIT).
  • Invited lecture (Conferences)
    IsoSiM Summer School 2018, Medical Isotope Production and Applications, 03.-07.06.2018, Harrison Hot Springs, Canada

Permalink: https://www.hzdr.de/publications/Publ-27525
Publ.-Id: 27525


An experimental investigation on the air-side heat transfer and flow resistance of finned short oval tubes at different tube tilt angles

Unger, S.; Beyer, M.; Arlit, M.; Stasch, P.; Hampel, U.
We experimentally studied the heat transfer and flow characteristics of finned oval tubes at different Reynolds numbers, fin spacing and tube orientation and compared results with correlations from literature. As assessment parameters we used the efficiency index, the performance evaluation criterion and the global performance criterion. For tubes in horizontal orientation (main flow direction perpendicular to the tube axis) we found an improvement of Nusselt number and a reduction of friction factor, when fin spacing increases. The efficiency index and the performance evaluation criterion improve with rising fin spacing and the global performance criterion remains almost constant. A substantial impact of tilt tube angle on Nusselt number and friction factor was observed. As the tube tilt angle rises from 0° to 40° Nusselt number and friction factor strongly increase. The horizontal tube orientation outperforms the tilted orientations in all performance parameters and at all Reynolds number. Thus, the performance is highest at 0° and worst at 40° tilt angle, since the increase in pressure drop dominates over the heat transfer enhancement. Based on the experimental outcome correlations between Nusselt number, friction factor and Reynolds number, fin spacing and tube tilt angle are recommended, which can be used to design finned oval tubes.
Keywords: Finned tube heat exchanger, Heat transfer, Flow resistance, Tube tilt angle, Thermal-flow performance, Heat transfer correlation

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Permalink: https://www.hzdr.de/publications/Publ-27523
Publ.-Id: 27523


Individual Response to Ionizing Radiation and Personalized Radiotherapy

Domina, E.; Philchenkov, A.; Dubrovska, A.
Radiation therapy remains one of the most effective cancer treatments. Nevertheless, biology driven personalized radiation therapy which enables to treat the patients according to the biological characteristics of the individual tumors and normal tissues still needs to be implemented into clinic. Understanding the mechanisms of radiation response in both tumors and normal tissues is necessary to develop reliable predictive biomarkers for tumor radioresistance and normal tissue toxicity as well as to exploit new therapeutic opportunities for tumor radiosensitization. In this paper, we review the mechanisms of tumor radiosensitivity, the early and late responses of normal tissues to therapeutic radiation exposure and discuss possible implementation of these mechanisms for biology-driven personalized radiation treatment.
Keywords: ionizing radiation, DNA damage, DNA repair, cell cycle checkpoints, radiosensitivity, cancer, cancer stem cells, radiotherapy, radioresistance, marker

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Permalink: https://www.hzdr.de/publications/Publ-27522
Publ.-Id: 27522


Untersuchungen zu den Wechselwirkungen zwischen unter Tage lebenden Mikroorganismen mit Uran und deren Einfluss auf das Migrationsverhalten von Uran in gefluteten Urangruben und Spektroskopische Bestimmung der Bindungsform (Speziation) trivalenter Actinide/Lanthanide in Biofluiden des menschlichen Gastrointestinaltraltes und im Blut

Arnold, T.; Barkleit, A.; Gerber, U.; Krawczyk-Bärsch, E.; Wilke, C.
Teil A:
Es wurde gezeigt, dass das Transportverhalten von Uran in der Umwelt und an den ehemaligen Uranabbaustätten stark von der Anwesenheit und Aktivität natürlich vorkommender Mikroorganismen abhängt. Die Untersuchungen zeigten, dass die Isolate eine hohe Toleranz gegenüber Uran aufweisen und in der Lage sind, relativ hohe Mengen an Uran zu immobilisieren und aus der umgebenden Lösung zu entfernen. Durch anaerobe Versuche konnte gezeigt werden, dass die mikrobielle Reduktion von Uran(VI) allein durch die Zugabe von 10 mM Glycerin bei zukünftigen Anwendungen als in situ Biosanierungsapplikationen genutzt werden könnte. Die Ergebnisse dieser Arbeit konnten die Wechselwirkungsmechanismen zwischen natürlich vorkommenden Mikroorganismen und Uran im Detail beschreiben und neue Zusammenhänge zwischen aktivem und inaktivem Stoffwechsel der Mikroorganismen zeigen. Zusammenfassend können diese einen wertvollen Beitrag zur Entwicklung von Biosanierungsansätzen für die Behandlung von Radionuklid-kontaminierten Standorten aus der ehemaligen Bergbauindustrie leisten.
Teil B:
Im Speichel dominiert neben einem kleinen Bindungsanteil an dem Enzym alpha-Amylase die Komplexierung mit anorganischen Liganden, im Magen dominiert aufgrund des sauren pH-Wertes das Eu- bzw. Cm-Aquo-Ion, und im Darm dominiert neben anorganischen Komplexen die Bindung der Metallionen an das Glycoprotein Mucin. Die starke Komplexfähigkeit von Mucin gegenüber dreiwertigen f-Elementen könnte die Absorption dieser im menschlichen Körper unterdrücken und deren Exkretion fördern. Die Ergebnisse dieser Arbeit geben neue Einblicke in das biochemische Verhalten dreiwertiger f-Elemente und können zudem zur Einschätzung von Gesundheitsrisiken nach der Inkorporation von Radionukliden und der Entwicklung von Dekontaminationstherapien beitragen.
Keywords: Mikroorganismen, Uran, Immobilisierung, U(VI)-Reduktion, dreiwertige f-Elemente, Speziation, Biofluide, Verdauungssystem, Laserfluoreszenzspektroskopie
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-098 2019
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-27521
Publ.-Id: 27521


From Point to Line Defects in Two-Dimensional Transition Metal Dichalcogenides: Insights from Transmission Electron Microscopy and First-Principles Calculations

Komsa, H.-P.; Krasheninnikov, A. V.ORC
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently received great deal of attention due to their unique properties associated with the reduced dimensionality of the system. The properties of these materials have been shown to be affected by atomic defects in the atomic network. The very structure of these materials which are composed from three atomic layers only, combined with dramatic improvements in microscopy techniques, made it possible to study the behavior of defects in these systems with unprecedented accuracy. Various point and line defects were identified, and their effects on the properties of the systems were accessed. It was demonstrated that point defects induced by electron beam irradiation coalesce in line defects, but their quasi-one dimensional atomic structure varies from member to member in the transition metal dichalcogenides family. In this review, we summarize recent experimental and theoretical findings in this area, discuss how the line structures appear due to the agglomeration of point defects, and dwell upon how line defects can be used to engineer properties of 2D TMDs. Finally, we address the challenges in this field and issues which still lack the explanation.
Keywords: 2D materials
  • Book chapter
    Vittorio Morandi, Luca Ottaviano: Carbon nanostructures book series (CARBON), EU: Springer, 2017, 71-85
    DOI: 10.1007/978-3-319-58134-7_6

Permalink: https://www.hzdr.de/publications/Publ-27520
Publ.-Id: 27520


Ring-like spatial distribution of laser accelerated protons in the ultra-high-contrast TNSA-regime

Becker, G. A.; Tietze, S.; Keppler, S.; Reislöhner, J.; Bin, J. H.; Bock, L.; Brack, F.-E.; Hein, J.; Hellwing, M.; Hilz, P.; Hornung, M.; Kessler, A.; Kraft, S. D.; Kuschel, S.; Liebetrau, H.; Ma, W.; Polz, J.; Schlenvoigt, H.-P.; Schorcht, F.; Schwab, M. B.; Seidel, A.; Zeil, K.; Schramm, U.; Zepf, M.; Schreiber, J.; Rykovanov, S.; Kaluza, M. C.
The spatial distribution of protons accelerated from submicron-thick plastic foil targets using multi-terawatt, frequency-doubled laser pulses with ultra-high temporal contrast has been investigated experimentally. A very stable, ring-like beam profile of the accelerated protons, oriented around the target's normal direction has been observed. The ring's opening angle has been found to decrease with increasing foil thicknesses. Two-dimensional particle-in-cell simulations reproduce our results indicating that the ring is formed during the expansion of the proton density distribution into the vacuum as described by the mechanism of target-normal sheath acceleration. Here - in addition to the longitudinal electric fields responsible for the forward acceleration of the protons - a lateral charge separation leads to transverse field components accelerating the protons in the lateral direction.
Keywords: laser-plasma interaction, proton acceleration, proton beam profile, target normal sheath acceleration

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Permalink: https://www.hzdr.de/publications/Publ-27519
Publ.-Id: 27519


Metal-organic complexes of tetravalent actinides with soft-donor ligands investigated by paramagnetic NMR spectroscopy

Schöne, S.ORC; Radoske, T.; Felsner, B.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
In NMR spectra of paramagnetic metal-organic complexes electronic interactions are the origin of additional NMR chemical shifts observed on resonances of nuclei of the ligand. The major two contributors to these hyperfine shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.
The paramagnetic contributions can be mathematical separated provided that a suitable diamagnetic reference is available (to subtract non-paramagnetic contributions). For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. 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.[1,2]
Comparing studies of isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allow for an estimation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.
We started to study paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)). Throughout the 5f-series additional effects to the observed chemical shift are expected with increasing number of unpaired electrons. Assessing the chemical bonding situation is possible via the influences on NMR chemical shifts (via FCS) and structural properties of the complexes (via PCS) can be compared to SC-XRD structures. Herein we report the first results of investigations of N- and N,O-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, Actinide, N-donor, FCS, PCS
  • Lecture (Conference)
    ISNSC - 10th International Symposium on Nano and Supramolecular Chemistry 2018, 09.-12.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27518
Publ.-Id: 27518


Paramagnetic NMR investigations in metal-organic complexes of tetravalent actinides with soft-donor ligands

Schöne, S.ORC; Radoske, T.; Felsner, B.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
Electronic interactions between metal and ligand are the origin of additional NMR chemical shifts observed on nuclei of the ligand in paramagnetic metal-organic complexes. The major two contributors to these paramagnetic chemical shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalisation of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.
The mathematical separation of paramagnetic contributions in complexes relies on the availability of a suitable diamagnetic reference to subtract non-paramagnetic contributions. For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. 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. [1,2]
Comparing isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allows for an estimation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.
To assess the chemical bonding situation via the influences on NMR chemical shifts (via FCS) we started to study paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)). With increasing number of unpaired electrons throughout the 5f-series additional effects to the observed chemical shift are expected. Structural properties of the complexes as derived from PCS contributions can be compared to single crystal X-ray diffraction structures. Herein we report the first results of investigations of N- and N,O-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, Actinide, N-donor, FCS, PCS, structure determination, solution
  • Lecture (Conference)
    18th Radiochemical Conference - RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
  • Contribution to proceedings
    18th Radiochemical Conference, 13.-18.05.2018, Mariánské Lázně, Tschechische Rupublik
    Czech Chemical Society Symposium Series 2

Permalink: https://www.hzdr.de/publications/Publ-27517
Publ.-Id: 27517


Nanohardening features in ion and neutron irradiated EUROFER97 and model alloys investigated with atom probe tomography

Gómez-Ferrer, B.; Heintze, C.; Dethloff, C.; Gaganidze, E.; Konstantinovic, M. J.; Malerba, L.; Pareige, P.; Pareige, C.
Among other effects, neutron irradiation hardens ferritic/martensitic (F/M) nuclear steels; this hardening is suspected to be due to the formation of dislocation loops, alpha' phase and solute-rich clusters (SRCs). In neutron irradiated FeCr model alloys the SRCs which are made of unavoidable impurities such as P are likely to be the main contributors to the yield strength increase, together with the presence of alpha' precipitates, if any [1,2]. Ion irradiation is an extended tool used to investigate the creation and evolution of radiation damage. Since the experiments are fast they offer the possibility to tune the parameters to design model-oriented experiments. Their use is also oriented to reproduce the effects of neutrons for nuclear applications. However, the characteristics of the nano-sized features (solute concentration, density, size and size distribution) are difficult to reproduce using ions with respect to neutrons, since the increase of the sink strength due to injecte d inters titials [3,4] and the high values of damage rate [5] influence defect production and evolution.
Atom probe tomography (APT) is used in the present work to investigate the hardening nanofeatures in irradiated materials. First, an Fe14CrNiSiP model alloy has been irradiated with both Fe+ ions and neutrons up to a dose of 0.1 dpa at 300°C. At such low doses some features, such as SRCs or Cr-rich regions, are formed, thus a direct comparison can be made to highlight differences and commonalities between the two kinds of irradiation; these results can also be used for the development of models. Second, a similar investigation has been made on neutron irradiated EUROFER97 up to 15 dpa at 300°C. The presence of radiation induced segregation (RIS) and radiation enhanced features can be correlated to the model alloy providing some insights on the nature of the hardening in F/M steels.
  • Lecture (Conference)
    E-MRS 2018 Spring Meeting, 18.-22.06.2018, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-27516
Publ.-Id: 27516


Critical heat flux as a mass flux dependent local or global phenomenon: Theoretical analysis and experimental confirmation

Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.
In this article, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity.
Keywords: boiling, critical heat flux, initiation mechanisms

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Permalink: https://www.hzdr.de/publications/Publ-27515
Publ.-Id: 27515


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