Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33407 Publications

None is like the other: the interaction of selected fungi with radionuclides

Raff, J.ORC; Wollenberg, A.; Traxler, L.; Schulz, W.; Freitag, L.; Günther, A.; Gupta, D.; Steinhauser, G.; Großmann, S.; Lehmann, F.; Köhler, M.; Walther, C.; Kothe, E.
Not only since Chernobyl and Fukushima is it well known that fungi can accumulate large amounts of heavy metals and radionuclides. Although there are many publications describing this phenomenon and naming transfer factors, almost nothing is known about the underlying molecular processes being responsible for the binding, uptake and accumulation in the cell or even transport inside the organism for elements like uranium, americium and other heavy radio-metals. However, knowing this is crucial if one wants to understand the influence of fungi on the migration behavior of radionuclides in the environment. It is all the more important to know the underlying biochemical processes and to know how environmental influences affect the radionuclide-cell interaction, if one considers using these extraordinary properties to biologically immobilize radionuclides in contaminated soil or even to remove radionuclides from it. As part of the BioVeStRa project, various fungi have been studied to determine their potential for precautionary radiation protection and the remediation of contaminated soils. Therefore, two fungi were selected based on published transfer factor and a known rapid growth on complex media, namely Schizophyllum commune and Leucoagaricus naucinus. Additionally, two further fungi metabolically related to S. commune or L. naucinus were included also in the studies to determine if similar fungi behave similarly or not. To study the fungi, a combination of growth and binding experiments, mass spectrometry, fluorescence spectroscopy and electron microscopy was used. In summary, it can be stated, that S. commune is not only the most robust fungus that prevails even in the test field against autochthonic soil microbes and fungi, but also shows the highest accumulation rates for uranium and europium, the latter as a substitute for trivalent actinides such as americium. Furthermore, it could be shown that fungi behave very differently depending on the investigated elements.
Keywords: fungi, radinuclides, spectroscopy, microscopy
  • Invited lecture (Conferences)
    18. Jenaer Sanierungskolloquium, 01.-02.10.2019, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29596
Publ.-Id: 29596


Carbon nanotubes for mechanical sensor applications

Wagner, C.ORC; Meszmer, P.ORC; Blaudeck, T.ORC; Böttger, S.ORC; Fuchs, F.ORC; Hermann, S.; Schuster, J.ORC; Wunderle, B.; Schulz, S. E.
This article features the evolution of carbon nanotubes as functional material in nano and microelectromechanical systems. Introducing materials morphologies for the CNTs in a homologue series (single CNTs - bundles, fibers, yarns - networks and thin films), different concepts for mechanical sensors based on the intrinsic and extrinsic properties of the CNT material are introduced (piezoresistive effect, strain-induced band bending, charge tunneling).
In a rigorous theoretical treatment, the limits of the achievable sensor performance (i.e., gauge factor) are derived and discussed in the context of applications. A careful literature survey shows that highest sensitivity is reached for devices exploiting the intrinsic transport properties of single CNTs. For reliability tests of such sensor systems made from nanomaterials and classical MEMS, a specimen-centered approach is introduced to give viable insights into the structure-property relationships and failure modes.
Keywords: carbon nanotubes (CNTs), sensors, micro- and nano electromechanical systems (MEMS, NEMS), strain, reliability

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Permalink: https://www.hzdr.de/publications/Publ-29595
Publ.-Id: 29595


Interlayer excitons in van-der-Waals heterostructures: MoS2 on GaSe

Wagner, C.ORC; Rahaman, M.; Zahn, D. R. T.; Gemming, S.
Hybrid van-der-Waals heterostructures of two-dimensional nanomaterials are a vibrant field of study: The (weak) electronic interaction between two layers is often reasonably described by a perturbation of the physical effects of the isolated layers, such as electrostatic doping and increased screening of intralayer excitons. However, it turns out that this picture of the weak interaction is not exhaustive in terms of all optical properties: the formation of bound excitons from electrons of one layer and holes from the other layer yields the formation of interlayer excitons. These mixed states are measured experimentally by photoluminescence and photocurrents and predicted by theory. Examples are of MoS2 or MoSe2 on WSe2, MoS2 or GaSe due to type-II band alignment [1-3].
The conditions for the formation of interlayer excitons are elucidated from a first-principles point of view. For this, first-principles studies of a minimal test system of MoS2 on GaSe is conducted [1].
This work envisions to predict the interlayer states as a function of the heterostack in order to specifically tailor efficient photon absorption.
Keywords: 2D materials, DFT, Bethe-Salpeter, Density-functional perturbation theory, MoS2, GaSe, bilayer, van-der-Waals heterostructure, interlayer exciton
  • Lecture (Conference)
    Chem2DMat, 03.-06.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29594
Publ.-Id: 29594


Order/disorder processes and electromechanical properties of monoclinic GdCa4O(BO3)3

Münchhalfen, M.; Schreuer, J.; Reuther, C.; Möckel, R.; Götze, J.; Mehner, E.; Stöcker, H.; Meyer, D.
Large single crystals of GdCa₄O(BO₃)₃ (space group Cm) were grown by the Czochralski method. Dielectric, piezoelectric and elastic coefficients at room temperature as well as specific heat capacity, thermal expansion and cation disorder were studied employing a variety of methods including resonant ultrasound spectroscopy, differential scanning calorimetry, dilatometry and X-ray diffraction techniques. The electromechanical parameters (4 dielectric, 10 piezoelectric and 13 elastic stiffness coefficients) obtained on different samples are in excellent agreement indicating high internal consistency of our approach, whereas the values reported in literature differ significantly. The elastic behaviour of GdCa₄O(BO₃)₃ resembles the one of structurally related fluorapatite, i.e. the elastic anisotropy is relatively small and the longitudinal effect of the deviations from Cauchy-relations exhibit a pronounced minimum along the direction of the dominating chains of cation polyhedra. GdCa₄O(BO₃)₃ exhibits a maximum longitudinal piezoelectric effect of 7.67 × 10−12 CN−10, a value in the order of that of langasite-type materials. Significant changes of the calcium/gadolinium distribution on the 3 independent cation sites accompanied by characteristic anomalies of heat capacity and thermal expansion suggest processes of nonconvergent cation ordering above about 900 K in GdCa₄O(BO₃)₃.
Keywords: elasticity; GdCa₄O(BO₃)₃; heat capacity; nonconvergent cation ordering; piezoelectricity; thermal expansion

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Permalink: https://www.hzdr.de/publications/Publ-29591
Publ.-Id: 29591


One-step radiosynthesis of the MCTs imaging agent [18F]FACH by aliphatic 18F-labelling of a methylsulfonate precursor containing an unprotected carboxylic acid group

Sadeghzadeh, M.ORC; Moldovan, R.-P.; Teodoro, R.ORC; Brust, P.ORC; Wenzel, B.ORC
Monocarboxylate transporters 1 and 4 (MCT1 and MCT4) are involved in tumour development and progression. Their level of expression is particularly upregulated in glycolytic cancer cells and accordingly MCTs are considered as promising drug targets for treatment of a variety of human cancers. The non-invasive imaging of these transporters in cancer patients via positron emission tomography (PET) is regarded to be valuable for the monitoring of therapeutic effects of MCT inhibitors. Recently, we developed the first 18F-radiolabelled MCT1/MCT4 inhibitor [18F]FACH and reported on a two-step one-pot radiosynthesis procedure. We herein describe now a unique one-step radiosynthesis of this radiotracer which is based on the approach of using a methylsulfonate (mesylate) precursor bearing an unprotected carboxylic acid function. With the new procedure unexpected high radiochemical yields of 43 ± 8% at the end of the radiosynthesis could be obtained in a strongly reduced total synthesis time. Moreover, the radiosynthesis was successfully transferred to a TRACERlab FX2 N synthesis module ready for future preclinical applications of [18F]FACH.
Keywords: monocarboxylate transporters (MCTs); [18F]FACH; PET; aliphatic nucleophilic 18F-labelling; unprotected precursor

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Permalink: https://www.hzdr.de/publications/Publ-29590
Publ.-Id: 29590


Sample preparation for AMS astrophysics projects – Size does (not) matter

Merchel, S.ORC; Child, D.; Faestermann, T.; Fröhlich, M.; Golser, R.; Hotchkis, M.; Koll, D.; Korschinek, G.; Pavetich, S.; Wallner, A.; a lot of more AMS colleagues
The determination of long-lived radionuclides by means of accelerator mass spectrometry (AMS) is usually outstandingly successful when an interdisciplinary team comes together. The “heart” of AMS research is of course an accelerator equipped with sophisticated ion sources, analytical tools and detectors run by experienced and ambitious physicists [e.g. 1-3]. Setting-up and further developing AMS systems is one of the most interesting and challenging topics. The reputation to be reached here is the greatest uniqueness of analysis possible, lowest detection levels, and/or most reliable data world-wide.
For sure, another primary pillar of AMS research is based on the questions addressed within fundamental and applied research. “How have supernovae explosions influenced Earth, our solar system and beyond?” [e.g. 4] or “How does the Earth’s surface and environment respond to earthquakes, climate change and anthropogenic influences?” [e.g. 5] are just two examples of high-quality studies.
However, somehow in-between there are groups of hidden figures like people developing software for data analysis or performing the required chemical sample preparation for AMS. These often unacknowledged individuals do crucial work for the overall outcome of the studies.
Chemists can spend weeks and months trying (and failing) on sample preparation before they find a “safe way” and start the actual work on the most valuable sample material, repeat all over again the same “recipe” for hundreds of samples, or train non-chemists the secrets of their successful recipes. Nevertheless, interdisciplinary AMS work can also be very exciting for a chemist: touching (and destroying) samples from outer space, the deep ocean or (currently) frozen places like Antarctica is quite thrilling. But at the end of the day, the whole AMS chemist’s work can be described as “reducing the sample matrix, other impurities and especially isobars to a level the AMS machine can handle while enriching the radionuclide of interest”.
Starting materials for applications such as astrophysical research can be “orders of magnitude” different: a neutron-irradiated sample of 1 g tungsten powder [6], over 40 g of clay-rich material from the Cretaceous–Tertiary (K-T) boundary, 100 g of ultra-pure sodium iodide, or 500 kg of snow from Antarctica [4] can cause totally different and sometimes unexpected problems in the chemistry lab. In general, smaller samples are not always easier to handle for example if they are chemically rather resistant or reactive. The cream of the crop of failure and success in a few AMS chemistry labs will be presented.

[1] P. Steier et al., Int. J. Mass Spectr. 444, 116175 (2019).
[2] G. Rugel et al., Nucl. Instr. Meth. B 370, 94 (2016).
[3] D. Koll et al., Nucl. Instr. Meth. B 438, 180 (2019).
[4] D. Koll et al., Phys. Rev. Lett. 123, 072701 (2019) and this meeting.
[5] W. Schwanghart et al., Science 351, 147 (2016).
[6] M. Martschini et al., this meeting.
Keywords: AMS, long-lived radionuclides
  • Lecture (Conference)
    Heavy Ion Accelerator Symposium on Fundamental and Applied Science (HIAS), 09.-13.09.2019, Canberra, Australia

Permalink: https://www.hzdr.de/publications/Publ-29588
Publ.-Id: 29588


Lanthanide–induced conformational change of methanol dehydrogenase involving coordination change of cofactor pyrroloquinoline quinone

Tsushima, S.ORC
There is emerging interests to the role of lanthanides as cofactor in XoxF-type methanol dehydrogenase (MHD). Here, classical molecular dynamics simulations combined with fragment molecular orbital calculations were employed to rationalize enzymatic activities of MHD (both XoxF- and MxaF- types) carrying different lanthanides. In XoxF–type MDH, lanthanide binding to cofactor pyrroloquinoline quinone was found to switch from tridentate to unidentate fashion as it switches from lighter to heavier lanthanide. This fact possibly plays crucial role to the enzymatic activity exclusive to XoxF–type MDH incorporating lighter lanthanides.
  • Physical Chemistry Chemical Physics 21(2019), 21979-21983
    DOI: 10.1039/C9CP03953H
  • Poster
    17th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (Migration 2019), 15.-20.09.2019, Kyoto, Japan

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Permalink: https://www.hzdr.de/publications/Publ-29587
Publ.-Id: 29587


A theranostic PSMA ligand for PET imaging and retargeting of T cells expressing the universal chimeric antigen receptor UniCAR

Arndt, C.; Feldmann, A.ORC; Koristka, S.; Schäfer, M.; Bergmann, R.ORC; Metwasi, N.; Berndt, N.; Bachmann, D.; Kegler, A.; Schmitz, M.; Puentes-Cala, E.; Soto, J. A.; Ehninger, G.; Pietzsch, J.; Liolios, C.; Wunderlich, G.; Kotzerke, J.; Kopka, K.ORC; Bachmann, M.ORC
Chimeric antigen receptor (CAR) T cells have shown impressive therapeutic potential. Due to the lack of direct control mechanisms, therapy-related adverse reactions including cytokine release- and tumor lysis syndrome can even become life-threatening. In case of target antigen expression on non-malignant cells, CAR T cells can also attack healthy tissues. To overcome such side effects, we have established a modular CAR platform termed UniCAR: UniCAR T cells per se are inert as they recognize a peptide epitope (UniCAR epitope) that is not accessible on the surface of living cells. Bifunctional adapter molecules termed target modules (TM) can cross-link UniCAR T cells with target cells. In the absence of TMs, UniCAR T cells automatically turn off. Until now, all UniCAR TMs were constructed by fusion of the UniCAR epitope to an antibody domain. To open up the wide field of low-molecular weight compounds for retargeting of UniCAR T cells to tumor cells, and to follow in parallel the progress of UniCAR T cell therapy by PET imaging we challenged the idea to convert a PET tracer into a UniCAR-TM. For proof of concept, we selected the clinically used PET tracer PSMA-11, which binds to the prostate-specific membrane antigen overexpressed in prostate carcinoma. Here we show that fusion of the UniCAR epitope to PSMA-11 results in a low-molecular weight theranostic compound that can be used for both retargeting of UniCAR T cells to tumor cells, and for non-invasive PET imaging and thus represents a member of a novel class of theranostics.
Keywords: PSMA ligand, UniCAR, prostate cancer, immunotherapy, PET imaging

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Permalink: https://www.hzdr.de/publications/Publ-29586
Publ.-Id: 29586


Interactions of halophilic microorganisms with radionuclides

Bader, M.
For the final storage of radioactive waste in a deep geological formation rock salt is a potential host rock. Indigenous microorganisms and its interactions with radionuclides have to be considered for the safety performance of the repository in terms of a worst case scenario, where radionuclides are potentially released from the storage site.
The kinetics of uranium bioassociation onto cells of the extreme halophilic archaeon Halobacterium noricense DSM 15987 and the moderate halophilic bacterium Brachybacterium sp. G1 were investigated in detail in batch experiments. For the understanding on a molecular level, a combination of spectroscopic, microscopic and molecular biological methods was used.
  • Invited lecture (Conferences)
    Jahrestagung der Fachgruppe Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29585
Publ.-Id: 29585


1,4,7-Triazacyclononane ligands as bifunctional radiocoppper chelating agents

Stephan, H.; Joshi, T.
design of tailor-made bifunctional chelating agents (BFCAs) for radioactive transition metals in view of nuclear medical applications as well as acquisition of reliable information about the biodistribution of different materials represents an intensive and rapidly developing field of research [1]. In this context, the tridentate macrocycle 1,4,7-triazacyclononane (TACN) is of special interest since it forms stable complexes with transition metal ions particularly with Cu(II) [2]. Further, the introduction of donor groups, such as pyridyl units, on the TACN scaffold, significantly enhances the thermodynamic stability as well as the kinetic inertness of the Cu(II) complexes formed. Furthermore, the ligand structure offers various possibilities to introduce biological vectors and suitable linkers for tuning the lipophilicity, overall charge and aqueous solubility of the final bioconjugates. For example, TACN ligands with two pyridylmethyl side-arms (DMPTACN derivatives) rapidly chelate copper(II) radionuclides under ambient conditions and the resulting complexes show high in vivo stability. One such derivative, 2-[4,7-bis(2-pyridylmethyl)-1,4,7-triazacyclononan-1-yl]acetic acid (DMPTACN-COOH), containing two coordinating picoline groups, not only exhibits excellent in vivo stability after 64Cu radiolabeling, but also allows for direct attachment of vector molecules as well as easy introduction of bioconjugatable functionalities (e.g., maleimide, isothiocyanate) via the carboxylate pendant. This makes DMPTACN-COOH and its derivatives promising BFCAs for radiocopper (DMPTACN-based BFCAs), facilitating the preparation of radiolabeled targeting molecules and bio(nano)materials.
Examples of target-specific peptides and bio(nano)materials equipped with DMPTACN ligands for labeling with 64Cu as an ideal positron emitter are discussed. This enables tumor imaging and the biodistribution of the materials to be studied over a period of days via positron emission tomography (PET).

[1] E. Boros, A. B. Packard, Chem. Rev. 119 (2019) 870-901.
[2] T. Joshi, M. Kubeil, A. Nsubuga, G. Singh, G. Gasser, H. Stephan, ChemPlusChem 83 (2018) 554-564.
  • Lecture (Conference)
    19th International Conference on Biological Inorganic Chemistry, 11.-16.08.2019, Interlaken, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-29584
Publ.-Id: 29584


CMOS-compatible Single Si Quantum Dot fabrication in a SiO2 layer sandwiched in a Si nanopillar for a Room Temperature Single Electron Transistor

Heinig, K.-H.; Hlawacek, G.; Engelmann, H.-J.; Prüfer, T.; Xu, X.; Möller, W.; Bischoff, L.; Gharbi, A.; Tiron, R.; Rommel, M.; von Borany, J.
Abstract :
The transistor pathway predicts an evolution from lateral MOSFETs via FinFETs to vertical nanowire gate-all-around FETs (vNW GAA-FET). Aiming at low-power electronics we replace the channel of the vNW GAA-FET by a SiO2 layer with an embedded Si Quantum Dot (QD), thus manufacturing a Single Electron Transistor (SET). To achieve room temperature (RT) operation of the vNW GAA-SET, Si QDs of ~3 nm diameter and tunneling distances of < 1 nm have to be manufactured. This is far beyond the present possibilities of lithography.
The challenge of such tiny structures has been solved in the framework of our European project IONS4SET [1] by means of a controlled self-organization and self-alignment process. Nanopillars with diameters down to ~20nm have been fabricated from Si/SiO2/Si layer stacks by Electron Beam Lithography and Reactive Ion Etching (RIE), a further diameter reduction to ~10nm has been achieved by sacrificial plasma oxidation. Before RIE the SiO2 layer is transferred to SiOx by Si+ ion beam mixing, which allows a controlled self-organization of a Si QD during thermally activated phase separation using RTA. During phase separation the Si QD becomes also self-aligned with respect of the upper and lower Si, thus forming the tunnel distances of ~1nm.
[1] This work has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 688072 (www.ions4set.eu).
Keywords: Ion Irradiation, Single Electron Transistor, SiOx Phase Separation
  • Lecture (Conference)
    European Materials Research Society 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29583
Publ.-Id: 29583


Dramatic SiO2 Thickness Reduction by Reactive Ion Etching of Nanopillars from Si/SiO2/Si layer stacks

Heinig, K.-H.; Engelmann, H.-J.; Gharbi, A.; Tiron, R.; Prüfer, T.; von Borany, J.
Abstract :
The transistor pathway predicts an evolution from lateral MOSFETs via FinFETs to vertical nanowire gate-all-around FETs (vNW GAA-FET). Our European project IONS4SET [1] goes a step further: Aiming at low-power electronics, the principle of operation of transistors will be changed from field effects to single electron tunneling via a Si quantum dot (QD) in SiO2. Room temperature (RT) operation of Single Electron Transistors (SETs) requires Si QDs of ~3 nm and tunneling distances of < 1 nm. The SiO2 with the embedded Si QD has to be ~ 5nm thick. To fabricate vNW GAA-SETs, Si nanopillars with ~5nm SiO2 have to be fabricated by Electron Beam Lithography and Reactive Ion Etching (RIE).
Here we report on a dramatic SiO2 thickness reduction in the Si/SiO2/Si layer stack by RIE of nanopillars. It is strongly pillar diameter dependent: In 100 nm pillars the thickness remains almost unchanged, but for < 20nm it shrinks from 8nm to ~3nm as shown by Energy-Filtered Transmission Electron Beam Microscopy (EFTEM). Modeling, computer simulation and dedicated experiments reveal that it is due to a huge number of electric breakdowns during RIE. A breakdown forms a SiOx filament which emits O in SiO2. Each O atom of the SiO2 becomes many times an O interstitial, which in most cases recombines with an O vacancy. Depending on diameter, some O will emanate from the edge of the SiO2 disk leading to the dramatic oxide thinning.
[1] This work has received funding from the European Unions Horizon 2020 research and innovation programme under grant agreement No 688072 (www.ions4set.eu).
Keywords: Nanoelectronics, Ion Irradiation, Single Electron Transistor, Reactive Ion Etching
  • Open Access Logo Lecture (Conference)
    European Materials Research Society 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29582
Publ.-Id: 29582


PIConGPU simulation setup for L|PWFA simulation

Pausch, R.ORC; Steiniger, K.ORC; Debus, A.ORC

The input set of the L|PWFA simulation as used in the publication "Demonstration of a compact plasma wakefield accelerator powered by laser-accelerated electron beams" by T.Kurz et al. .
To run the simulation use PIConGPU 0.4.2 (see DOI: 10.5281/zenodo.1491926).           

  • Software in the HZDR data repository RODARE
    Publication date: 2019-08-19
    DOI: 10.14278/rodare.146
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-29581
Publ.-Id: 29581


Coherent control of qudit modes in SiC at room temperature

Astakhov, G. V.ORC
We present room-temperature coherent control of high-dimensional quantum bits, the so-called qudits, associated with vacancy-related spins in silicon carbide enriched with nuclear spin-free isotopes. In addition to the excitation of a spectrally narrow qudit mode at the pump frequency, several other modes are excited in the electron spin resonance spectra whose relative positions depend on the external magnetic field.
  • Invited lecture (Conferences)
    4th International Conference on Metamaterials and Nanophotonics METANANO 2019, Special Symposium QuantuMetanano, 14.-19.07.2019, Saint Petersburg, Russia

Permalink: https://www.hzdr.de/publications/Publ-29579
Publ.-Id: 29579


Coherent control of qudit modes in SiC

Astakhov, G. V.ORC
We demonstrated coherent manipulation of spin qudit modes in isotopically purified SiC at room temperature. We also developed a theory describing the excitation and detection of these modes in inhomgeneously broadened systems and showed that qudits are characterized by multiple relaxation times. These findings can lead to dipole-coupled networks, unconditional electron-nuclear spin registers and spectral selection of highly coherent individual spins, particularly in nanocrystals. Our results hence open new possibilities to improve the sensitivity of quantum sensors and execute nontrivial quantum protocols in dense spin ensembles.
  • Invited lecture (Conferences)
    Invited colloquium at TU Dortmund, 13.06.2019, Dortmund, Germany

Permalink: https://www.hzdr.de/publications/Publ-29578
Publ.-Id: 29578


Effect of irradiation on defect coherence properties in silicon carbide

Astakhov, G. V.ORC
We have thoroughly investigated the irradiation impact on the room-temperature spin coherence properties of silicon vacancies in SiC. We have measured the spin-lattice relaxation time and the spin coherence time depending on the irradiation particle (electron, neutron and proton), irradiation fluence and irradiation energy.
  • Invited lecture (Conferences)
    Ion Beam for future Technologies 2019, 01.-03.04.2019, Dubrovnik, Croatia

Permalink: https://www.hzdr.de/publications/Publ-29577
Publ.-Id: 29577


UFXCT data of silo discharge of hydrogel spheres

Bieberle, M.ORC; Barthel, F.; Sancho Martinez, D.; Stannarius, R.

The outflow of hydrogel spheres from a cylindrical storage container with narrow outlet of two different sizes is imaged by means of ultrafast X-ray computed tomography (UFXCT) at different heights above the outlet. Sequences of cross-sectional images were recorded over 30 s with a frame rate of 1000 fps in dual plane mode.

Keywords: ultrafast measurement; X-ray CT; silo discharge
Related publications
UFXCT data of silo discharge of airsoft balls (Id 29573) is a supplement to this publication
High-speed X-ray tomography of silo discharge (Id 29464) is supplemented by this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-16
    DOI: 10.14278/rodare.144

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Permalink: https://www.hzdr.de/publications/Publ-29575
Publ.-Id: 29575


UFXCT data of silo discharge of airsoft balls

Bieberle, M.ORC; Barthel, F.; Sancho Martinez, D.; Stannarius, R.

The outflow of airsoft bullets from a cylindrical storage container with narrow outlet is imaged by means of ultrafast X-ray computed tomography (UFXCT) at different heights above the outlet. Sequences of cross-sectional images were recorded over 30 s with a frame rate of 1000 fps in dual plane mode.

Keywords: ultrafast measurement; X-ray CT; silo discharge
Related publications
UFXCT data of silo discharge of hydrogel spheres (Id 29575) is supplemented by this publication
High-speed X-ray tomography of silo discharge (Id 29464) is supplemented by this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-16
    DOI: 10.14278/rodare.142

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Permalink: https://www.hzdr.de/publications/Publ-29573
Publ.-Id: 29573


Biomaterials in repairing rat femoral defects: in vivo insights from small animal positron emission tomography/computed tomography (PET/CT) studies

Neuber, C.; Schulze, S.; Förster, Y.; Hofheinz, F.; Wodke, J.; Möller, S.; Schnabelrauch, M.; Hintze, V.; Scharnweber, D.; Rammelt, S.; Pietzsch, J.ORC
Biomaterials coated with artificial extracellular matrices (aECM) are intended to support the healing of critical size bone defects. This pilot study investigated (i) the feasibility of dual tracer PET/CT imaging for functional characterization of biomaterial-assisted bone healing in a rat femoral defect model and (ii) the bone healing ability of polycaprolactone-co-lactide (PCL) scaffolds, coated with various aECM consisting of collagen type I (Col) and glycosaminoglycans (GAGs) such as chondroitin sulfate (CS) or polysulfated hyaluronan (sHA3). [18F]FDG and [18F]fluoride PET 4 and 8 weeks after implantation of aECM-coated PCL scaffolds, which provide an in vivo measure of cellular activation and bone mineralization, respectively, combined with CT imaging (in vivo/ex vivo) and histologic/immunohistochemical investigations (ex vivo) showed that coating with CS in particular is beneficial for bone healing. The possible involvement of COX-2 and TGase 2, key enzymes of inflammation and ECM remodeling, in these processes offers starting points for targeted adjuvant therapy in the course of various bone healing phases. Our investigations show the feasibility of the selected dual tracer approach for PET/CT imaging. In principle, this approach can be extended by further PET tracers for the functional characterization of physiological processes such as hypoxia/reperfusion or selected molecular players.
Keywords: Artificial extracellular matrices • bone healing • [18F]fluorodeoxyglucose • [18F]fluoride • glycosaminoglycans • inflammation • metabolism • molecular imaging • revascularization
  • Open Access Logo Clinical Hemorheology and Microcirculation 73(2019), 177-194
    DOI: 10.3233/CH-199208

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Permalink: https://www.hzdr.de/publications/Publ-29572
Publ.-Id: 29572


More than 15 Years of CW SRF Operation at ELBE

Arnold, A.; Freitag, M.; Lehnert, U.; Michel, P.; Murcek, P.; Schneider, C.; Teichert, J.; Xiang, R.
ELBE is a compact, accelerator-driven photon and particle source. Since 2001 it is operated as a user facility, providing more than 5500 hours of beam time each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in full CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. The first part of the talk will summarize our experiences of operating TESLA cavities in CW. In detail, this includes their performance and attempts to improve it, as well as investigations on limitations. Additionally, we will discuss several issues that are related to the high average RF as well as beam power and we will present appropriate measures to protect the machine. In this regard, a resonant ring for RF component tests up to 100 kW was set up. The second part of the talk will focus on the development and operation of our SRF guns that are designed to produce short bunches with high charges and repetition rates of 1 MHz and beyond. Recently, SRF gun II was successfully transferred into routine user operation and delivers now more than 200 pC at 100 kHz to the experiment. First convincing results will be presented.
Keywords: ELBE, electron accelerator, SRF, cryomodule, high RF power, high average current
  • Invited lecture (Conferences)
    19th International Conference on RF Superconductivity, SRF2019, 30.06.-05.07.2019, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-29571
Publ.-Id: 29571


Single bubble dynamics during nucleate flow boiling on a vertical heater: Experimental and theoretical analysis of the effect of surface wettability,roughness and bulk liquid velocity

Sarker, D.; Ding, W.; Schneider, C.; Hampel, U.
The present study reports the mutual effect of heater surface wettability, roughness and bulk liquid velocity on the bubble dynamics and departure in nucleate boiling. Boiling experiments were conducted at atmospheric pressure with degassed-deionized water at low subcooling (1.9 ± 0.25 K) for vertically oriented stainless steel heaters. Self-assembled monolayer (SAM) coating and wet-etching technique were used to alter the heater surface wettability and roughness. Liquid contact angle hysteresis ("θ" _"hys" ) and root mean square roughness (Sq) of the heater surfaces were adjusted between "42.32° "≤ "θ" _"hys" ≤ "68.56°" and roughness "0.01" µm≤"Sq"≤"0.549" µm. High resolution optical shadowgraphy has been used to record the bubble life cycle. Experimental results show that higher bulk liquid velocity yields smaller bubble departure diameters for all heater surface characteristics. Bubble departure diameters are greater for low wetting surfaces. The bubble growth rate and departure diameter were found maximum for an intermediate surface roughness Sq between 0.108 and 0.218 m. The corresponding roughness height is referred to as the ‘optimal roughness height’ in this study. Eventually, a bubble departure criterion was derived from the expressions of forces which act on a nucleating bubble throughout its growth cycle. 90% of the departing bubbles satisfy the bubble departure criterion with ± 25% deviation.
Keywords: Bubble growth, bubble departure, surface wettability, roughness, flow boiling

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  • Secondary publication expected from 24.07.2020

Permalink: https://www.hzdr.de/publications/Publ-29570
Publ.-Id: 29570


A Two-Parameter Model for Colloidal Particles with an Extended Magnetic Cap

Neumann, M.; Strobel, A.; Al-Saadawi, Y.; Steinbach, G.; Erbe, A.; Gemming, S.
Self-assembly of magnetic colloidal particles in solution has succesfully been simulated by hard- or soft-sphere models with a set of embedded magnetic point dipoles, and the position and orientation of each dipole are adapted to mimic the magnetization distribution. The present study introduces a conceptually simpler approach for magnetically capped colloidal particles, which replaces the set of dipoles by the magnetization distribution of a single conductive loop. Only two parameters are required to characterize the magnetization distribution: the diameter of the loop and its radial off-center shift within the sphere. This approach reflects the radial symmetry and the spatial extension of the magnetic cap. In the far-field and in the limit of very small loops the model exactly reproduces the magnetization distribution and the particle arrangements obtained with the single, radially shifted dipole model. For larger loop radii additional stable assembly patterns are obtained, which occur in experiments, but can not be simulated with a single shifted dipole model.
Keywords: colloids, colloidal suspensions, magnetic colloidal particles, 2D assembly, self-assembly, effective Hamiltonians, theory, mesoscopic materials, soft-sphere potential, shifted-dipole model

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Permalink: https://www.hzdr.de/publications/Publ-29568
Publ.-Id: 29568


A new particle-based approach to process modelling and diagnostics

Pereira, L.ORC; Khodadadzadeh, M.; Tolosana-Delgado, R.; Schach, E.; Hannula, J.; Fernandes, I.; Frenzel, M.
For a long time, the mining and minerals processing communities have developed process models based on the bulk chemical compositions of ores and processing products. Recently, the emergence of the geometallurgy field and the advent of new characterization techniques have shifted the focus to mineralogical composition and certain particle-based properties (e.g. mineral liberation). Automated mineralogy systems based on scanning electron microscope platforms, such as the Mineral Liberation Analyzer or TIMA-X, were essential for this advance. They are capable of producing large data sets with detailed information on the sizes, shapes and compositions of individual ore particles in a sample.
Methodologies that use this particle-based information to model the outcomes of a specific processing unit or an entire operation are summarized as “particle tracking”. This is a useful diagnostic technique for mineral separation processes. However, limitations in the statistical methods applied in existing approaches mean that users are required to summarize considerably the information contained in the particle datasets by pre-selecting explanatory variables (expert input) and binning particles. This means that a distinct recipe, including specific assumptions, is required for each new case. It also makes the resultant models liable to human bias.
This work describes a new method for particle tracking that combines automated mineralogy data with machine learning to automate the variable selection process and eliminate the need for particle binning. In doing so, it maximizes the utilization of detailed particle data, minimizes the effects of human input, and provides the flexibility to assess different cases with minimal prior adjustments. Its utility is demonstrated using data from both a flotation and a magnetic separation units of an operating niobium mine. In both cases, the method is able to accurately predict the mineralogical compositions of the concentrate and tailings streams. It clearly has the potential to be extended as a diagnostic tool for the optimization and operation of processing plants.
Keywords: Machine learning, predictive geometallurgy, particle tracking
  • Lecture (Conference)
    Procemin Geomet, 20.-22.11.2019, Santiago, Chile

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Permalink: https://www.hzdr.de/publications/Publ-29567
Publ.-Id: 29567


Effect of materials heterogeneities on microstructure and mechanical properties at irradiated state

Bergner, F.ORC; Viehrig, H.-W.
This talk summarizes the new insight accumulated in the work package 3 of the European Horizon 2020 project SOTERIA on the effects of materials heterogeneities on microstructure and mechanical properties at the irradiated state.
Keywords: Reactor pressure vessel steels, irradiation effects, microstructure, mechanical properties
  • Lecture (Conference)
    Open SOTERIA Final Workshop, 25.-27.06.2019, Miraflores de la Sierra, Spanien

Permalink: https://www.hzdr.de/publications/Publ-29565
Publ.-Id: 29565


Transient Characteristics of Interdigitated GaAs Photoconductive Semiconductor Switch at 1-kHz Excitation

Xu, M.; Liu, X.; Li, M.; Liu, K.; Qu, G.; Wang, V.; Hu, L.; Schneider, H.
To explore the stability of gallium arsenide (GaAs) photoconductive semiconductor switches (PCSSs) with avalanche multiplication mechanism, an interdigitated electrodestructure is presented at 1-kHz excitation by a femtosecond laser. The influences of optical excitation and bias electric field on switching characteristics are investigated. The transient current density and the distribution of electric field are demonstrated by the Monte Carlo simulation. The repetitive switching indicates that the avalanche multiplication mechanism could persist stably at 1-kHz repetition rate operation with this specific electrode structure.
Keywords: Gallium arsenide, GaAs, high gain, photoconductive semiconductor switch, avalanche multiplication, repetition rate

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Permalink: https://www.hzdr.de/publications/Publ-29564
Publ.-Id: 29564


Computer Modeling of Single-layer Nanocluster Formation in a Thin SiO2 Layer Buried in Si by Ion Mixing and Thermal Phase Decomposition

Prüfer, T.; Möller, W.; Heinig, K.-H.; Wolf, D.; Engelmann, H.-J.; Xu, X.; von Borany, J.
A single sheet of Si nanoclusters with an average diameter of about 2 nm has been formed in a 30 nm Si / 7 nm SiO2 / Si layer stack by 50 and 60 keV Si+ ion-beam mixing at room temperature and fluences between 8.51015 and 2.61016 ions/cm2, and subsequent thermal annealing at a temperature above 1000°C. Computer modelling of the process is accomplished by TRIDYN dynamic ballistic simulation of ion mixing and subsequent lattice kinetic Monte Carlo simulation of the phase decomposition of sub-stoichiometric silicon oxide into Si nanoclusters in a SiO2 matrix. The simulation algorithms are briefly described with special emphasis on the choice of governing parameters for the present system. In comparison to the experimental results it is concluded that the predicted ion mixing profiles overestimate the interface broadening. This discrepancy is attributed to the neglect of chemical driving forces in connection with thermal-spike induced diffusion, which tends to re-constitute the Si/SiO2 interfaces. With a corresponding correction and a suitable number of Monte Carlo steps, the experimentally obtained areal densities and average diameters of the nanoclusters are successfully reproduced.
Keywords: Ion Beam Mixing; SiO2; Silicon; Thermal Spikes

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Permalink: https://www.hzdr.de/publications/Publ-29563
Publ.-Id: 29563


Cancer Stem Cells and Radioresistance: DNA Repair and Beyond

Schulz, A.; Meyer, F.; Dubrovska, A.; Borgmann, K.
The current preclinical and clinical findings demonstrate that, in addition to the conventional clinical and pathological indicators that have a prognostic value in radiation oncology, the number of cancer stem cells (CSCs) and their inherent radioresistance are important Parameters for local control after radiotherapy. In this review, we discuss the molecular mechanisms of CSC radioresistance attributable to DNA repair mechanisms and the development of CSC-targeted therapies for Tumor radiosensitization. We also discuss the current challenges in preclinical and translational CSC research including the high inter- and intratumoral heterogeneity, plasticity of CSCs, and microenvironment-stimulated tumor cell reprogramming.
Keywords: cancer stem cells; DNA repair; radioresistance; 5Rs of radiation biology

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Permalink: https://www.hzdr.de/publications/Publ-29561
Publ.-Id: 29561


Interference of tumour mutational burden with outcome of patients with head and neck cancer treated with definitive chemoradiation: a multicentre retrospective study of the German Cancer Consortium Radiation Oncology Group

Eder, T.; Hess, A.; Konschak, R.; Stromberger, C.; Johrens, K.; Fleischer, V.; Hummel, M.; Balermpas, P.; von der Grun, J.; Linge, A.; Lohaus, F.; Krause, M.; Baumann, M.; Stuschke, M.; Zips, D.; Grosu, A.; Abdollahi, A.; Debus, J.; Belka, C.; Pigorsch, S.; Combs, E.; Budach, V.; Tinhofer, I.
Background: Tumour mutational burden (TMB) estimated from whole exome sequencing or comprehensive gene panels has previously been established as predictive factor of response to immune checkpoint inhibitors (ICIs).
Its predictive value for the efficacy of concurrent chemoradiation (cCRTX), a potential combination partner of ICI, remains unknown.
Methods: The accuracy of TMB estimation by an in-house 327-gene panel was established in the Cancer Genome Atlas (TCGA) head and neck squamous cell carcinoma (HNSCC) data set. Interference of TMB with outcome after cCRTX was determined in a multicentre cohort of patients with locally advanced HNSCC uniformly treated with cCRTX. Targeted next-generation sequencing was successfully applied in 101 formalin-fixed, paraffin-embedded pretreatment tumour samples. In a subset of cases (n = 40), tumour RNA was used for immune-related gene expression profiling by the nanoString platform. TMB was correlated with TP53 genotype, human papilloma virus (HPV) status, immune expression signatures and survival parameters. Results were validated in the TCGA HNSCC cohort.
Results: A high accuracy of TMB estimation by the 327-gene panel was established. High TMB was significantly associated with an increased prevalence of TP53 mutations and immune gene expression patterns unrelated to T cell-inflamed gene expression profiles. Kaplan-Meier analysis revealed significantly reduced overall survival in the patient group with high TMB (hazard ratio for death: 1.79, 95% confidence interval: 1.02-3.14; P = 0.042) which remained significant after correcting for confounding factors in the multivariate model. The prognostic value of TMB was confirmed in the TCGA HNSCC cohort.
Conclusion: High TMB identifies HNSCC patients with poor outcome after cCRTX who might preferentially benefit from CRTX-ICI combinations.

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Permalink: https://www.hzdr.de/publications/Publ-29560
Publ.-Id: 29560


Cancer Stem Cells in Head and Neck Squamous Cell Carcinoma: Identification, Characterization and Clinical Implications

Peitzsch, C.; Nathansen, J.; Schniewind, S.; Schwarz, F.; Dubrovska, A.
Head and neck squamous cell carcinoma (HNSCC) is the sixth most commonly diagnosed cancer worldwide. Despite advances in the treatment management, locally advanced disease has a poor prognosis, with a 5-year survival rate of approximately 50%. The growth of HNSCC is maintained by a population of cancer stem cells (CSCs) which possess unlimited self-renewal potential and induce tumor regrowth if not completely eliminated by therapy. The population of CSCs is not only a promising target for tumor treatment, but also an important biomarker to identify the patients at risk for therapeutic failure and disease progression.
This review aims to provide an overview of the recent pre-clinical and clinical studies on the biology and potential therapeutic implications of HNSCC stem cells.
Keywords: head and neck squamous cell carcinoma; HNSCC; cancer stem cells; therapy resistance; biomarkers

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Permalink: https://www.hzdr.de/publications/Publ-29558
Publ.-Id: 29558


Mineral Precipitation in Fractures and Nanopores within Shale Imaged Using Time-Lapse X-ray Tomography

Da Assuncao Godinho, J. R.; Ma, L.; Chai, Y.; Storm, M.; Burnett, T. L.
Barite precipitation in fractures and nanopores within a shale sample is analysed in situ, in 3D, and over time. Diffusion of barium and sulphate from opposite sides of the sample creates a supersaturated zone where barium sulphate crystals precipitate. Time-lapse synchrotron-based computed tomography was used to track the growth of precipitates over time, even within the shale’s matrix where the nanopores are much smaller than the resolution of the technique. We observed that the kinetics of precipitation is limited by the type and size of the confinement where crystals are growing, i.e., nanopores and fractures. This has a major impact on the ion transport at the growth front, which determines the extent of precipitation within wider fractures (fast and localised precipitation), thinner fractures (non-localised and slowing precipitation) and nanopores (precipitation spread as a front moving at an approximately constant velocity of 10 ± 3 µm/h). A general sequence of events during precipitation in rocks containing pores and fractures of different sizes is proposed and its possible implications to earth sciences and subsurface engineering, e.g., fracking and mineral sequestration, are discussed.
Keywords: time-lapse imaging; 3D imaging; shale; barite; mineral precipitation; scale; formation damage; porous media; fracking

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Permalink: https://www.hzdr.de/publications/Publ-29557
Publ.-Id: 29557


Study of process water recirculation in a flotation plant by means of process simulation

Michaux, B.; Hannula, J.; Rudolph, M.; Reuter, M. A.
One of the biggest challenges with water in the mining industry is the need for water management systems that consider production-related issues when the quality of process water is subject to variations. Part of the work required to tackle this challenge is the development of simulation platforms that correlates the quality of the process water to the processing plant performance. In this paper, the application of a previously developed simulation-based approach to include the impact of process water chemistry on the performance of a flotation plant is presented. The water chemistry-dependent plant simulation is then used to investigate the implementation of a water-saving strategy to reduce fresh water requirements without impairing process performance, thus demonstrating the applicability of the previously developed approach for the simulation of large scale industrial plants.
Keywords: Flotation plant simulation, flotation kinetics, process water chemistry, water-saving strategies.

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  • Secondary publication expected from 20.01.2021

Permalink: https://www.hzdr.de/publications/Publ-29556
Publ.-Id: 29556


R as an environment for data mining of process mineralogy data: A case study of an industrial rougher flotation bank

Kupka, N.; Tolosana Delgado, R.; Schach, E.; Bachmann, K.; Heinig, T.; Rudolph, M.ORC
Through a series of in-house routines of R, an open source programming language for statistical computing, statistical analysis is applied to automated process mineralogy data in order to describe the performance of an industrial scheelite rougher flotation bank. These routines allow: 1) exploring all particles properties over residence time, not only particle size or surface liberation but also mineral association and a wealth of other particle properties, 2) to free the user from the limitations of the menu-driven built-in mineralogy software or spreadsheets, for calculation, data plotting or predictive model fitting, in particular for the parallel analysis of several streams; and 3) a more flexible manipulation of the data, both class and particle wise, for instance allowing for data mining across streams.

In an illustration case study, these functions are used to show the separation efficiency shift over residence time and over particle size; to indicate which associated minerals have a greater influence on the flotation of scheelite; to determine which gangue minerals are more impacted by entrainment; and finally to link said entrainment to particle shape. In general, the Helmholtz Institute Freiberg for Resource Technology intends to use such a programming platform on automated mineralogy data as a routine to understand processes better, as a potential diagnostic tool for process troubleshooting, and also for predictive model building within the frame of geometallurgy.
Keywords: rougher flotation, R, automated mineralogy, statistical analysis

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  • Secondary publication expected from 15.01.2021

Permalink: https://www.hzdr.de/publications/Publ-29555
Publ.-Id: 29555


Spin Hall magnetoresistance in heterostructures consisting of noncrystalline paramagnetic YIG and Pt

Lammel, M.; Schlitz, R.; Geishendorf, K.; Makarov, D.; Kosub, T.; Fabretti, S.; Reichlova, H.; Huebner, R.; Nielsch, K.; Thomas, A.; Goennenwein, S. T. B.
The spin Hall magnetoresistance (SMR) effect arises from spin-transfer processes across the interface between a spin Hall active metal and an insulating magnet. While the SMR response of ferrimagnetic and antiferromagnetic insulators has been studied extensively, the SMR of a paramagnetic spin ensemble is not well established. Thus, we investigate herein the magnetoresistive response of the as-deposited yttrium iron garnet/platinum thin film bilayers as a function of the orientation and the amplitude of an externally applied magnetic field. Structural and magnetic characterization shows no evidence for the crystalline order or spontaneous magnetization in the yttrium iron garnet layer. Nevertheless, we observe a clear magnetoresistance response with a dependence on the magnetic field orientation characteristic for the SMR. We propose two models for the origin of the SMR response in paramagnetic insulator/platinum heterostructures. The first model describes the SMR of an ensemble of noninteracting paramagnetic moments, while the second model describes the magnetoresistance arising by considering the total net moment. Interestingly, our experimental data are consistently described by the net moment picture, in contrast to the situation in compensated ferrimagnets or antiferromagnets.
Keywords: spin Hall magnetoresistance, antiferromagnetic insulators

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Permalink: https://www.hzdr.de/publications/Publ-29554
Publ.-Id: 29554


Exploring enhanced low-energy magnetic dipole strength in photon scattering

Schwengner, R.; Rusev, G.
Strengths of M1 transitions depopulating high-lying 1+ states and of subsequent transitions in cascades populating the first excited state were determined on the basis of large-scale shell-model calculations for the nuclide 54Fe. The results reveal that the spectra of primary M1 transitions from 1+ states only as well as the subsequent cascade M1 transitions show an enhancement of strength toward small energy, similar to that found for a huge number of transitions between states of a wide spin range as observed in light-ion induced reactions. This allows in principle the study of low-energy M1 strength using photon scattering. Based on these results, intensities of M1 transitions under experimental conditions are estimated.
Keywords: Strength functions, M1 transitions, shell model, photon scattering.

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Permalink: https://www.hzdr.de/publications/Publ-29553
Publ.-Id: 29553


Tuning the interactions in the spin-ice materials Dy2Ge2−xSixO7 by silicon substitution

Stöter, T.; Antlauf, M.; Opherden, L.; Gottschall, T.; Hornung, J.; Gronemann, J.; Herrmannsdörfer, T.; Granovsky, S.; Schwarz, M.; Doerr, M.
We report that the lattice constant of Dy2Ge2−xSixO7 (x = 0, 0.02, 0.08, 0.125) can be systematically reduced by substituting the nonmagnetic germanium ion in the cubic pyrochlore oxide with silicon. A multianvil high-pressure synthesis was performed up to 16 GPa and 1100 °C to obtain polycrystalline samples in a solid-state reaction. Measurements of magnetization, ac susceptibility, and heat capacity reveal the typical signatures of a spin-ice phase. From the temperature shift of the peaks, observed in the temperature-dependent heat capacity, we deduce an increase in the strength of the exchange interaction. In conclusion, the reduced lattice constant leads to a changed ratio of the competing exchange and dipolar interaction. This puts the new spin-ice compounds closer towards the phase boundary of a short-range spin-ice arrangement and antiferromagnetic long-range order consistent with an observed reduction in the energy scale of monopole excitations.

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Permalink: https://www.hzdr.de/publications/Publ-29552
Publ.-Id: 29552


Controlling Chiral Spin States of a Triangular-Lattice Magnet by Cooling in a Magnetic Field

Deng, S.; Fischer, G.; Uhlarz, M.; Wosnitza, J.; Bohnen, K.-P.; Heid, R.; Wang, C.; Sürgers, C.
Magnetic materials with a non-collinear and non-coplanar arrangement of magnetic moments hosting a nonzero scalar spin-chirality exhibit unique magnetic and spin-dependent electronic transport properties. The spin chirality often occurs in materials where competing exchange interactions lead to geometrical frustrations between magnetic moments and to a strong coupling between the crystal lattice and the magnetic structure. These characteristics are particularly strong in Mn-based antiperovskites where the interactions and chirality can be tuned by substitutional modifications of the crystalline lattice. This study presents evidence for the formation of two unequal chiral spin states in magnetically ordered Mn3.338Ni0.651N antiperovskite based on density functional theory calculations and supported by magnetization measurements after cooling in a magnetic field. The existence of two scalar spin-chiralities of opposite sign and different magnitude is demonstrated by a vertical shift of the magnetic-field dependent magnetization and Hall effect at low fields and from an asymmetrical magnetoresistivity when the applied magnetic field is oriented parallel or antiparallel to the direction of the cooling field. This opens up the possibility of manipulating the spin chirality for potential use in the emerging field of chiral spintronics.

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Permalink: https://www.hzdr.de/publications/Publ-29551
Publ.-Id: 29551


Evidence for the Single-Site Quadrupolar Kondo Effect in the Dilute Non-Kramers System Y1−xPrxIr2Zn20

Yanagisawa, T.; Hidaka, H.; Amitsuka, H.; Zherlitsyn, S.; Wosnitza, J.; Yamane, Y.; Onimaru, T.
Acoustic signatures of the single-site quadrupolar Kondo effect in Y0.966Pr0.034Ir2Zn20 are presented. The elastic constant (C11 − C12)/2, corresponding to the Γ3(E)-symmetry electric-quadrupolar response, reveals a logarithmic temperature dependence of the quadrupolar susceptibility in the low-magnetic-field region below ∼0.3 K. Furthermore, the Curie-type divergence of the elastic constant down to ∼1 K indicates that the Pr ions in this diluted system have a non-Kramers ground-state doublet. These observations evidence the single-site quadrupolar Kondo effect, as previously suggested based on specific-heat and electrical-resistivity data.

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Permalink: https://www.hzdr.de/publications/Publ-29550
Publ.-Id: 29550


High magnetic field phase diagram and failure of the magnetic Grüneisen scaling in LiFePO4

Werner, J.; Sauerland, S.; Koo, C.; Neef, C.; Pollithy, A.; Skourski, Y.; Klingeler, R.
We report the magnetic phase diagram of single-crystalline LiFePO4 in magnetic fields up to 58 T and present a detailed study of magnetoelastic coupling by means of high-resolution capacitance dilatometry. Large anomalies at TN in the thermal-expansion coefficient α imply pronounced magnetoelastic coupling. Quantitative analysis yields the magnetic Grüneisen parameter γmag = 6.7(5) × 10−7 mol/J. The positive hydrostatic pressure dependence dTN/dp = 1.46(11) K/GPa is dominated by uniaxial effects along the a axis. Failure of Grüneisen scaling below ≈40K, i.e., below the peak temperature in the magnetoelectric coupling coefficient [7], implies several competing degrees of freedom. A broad and strongly magnetic field dependent anomaly in α in this temperature regime highlights the relevance of structure changes. Upon application of the magnetic field B||b axis, a pronounced jump in the magnetization implies spin reorientation at BSF = 32 T as well as a precursing phase at 29 T and T = 1.5K. In a two-sublattice mean-field model, the saturation field Bsat,b = 64(2) T enables assessing the effective antiferromagnetic exchange interaction Jaf = 2.68(5)meV as well as anisotropies Db = −0.53(4)meV and Dc = 0.44(8)meV.

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Permalink: https://www.hzdr.de/publications/Publ-29549
Publ.-Id: 29549


High Temperature and Ion Implantation-Induced Phase Transformations in Novel Reduced Activation Si-Fe-V-Cr (-Mo) High Entropy Alloys

Gandy, A. S.; Jim, B.; Coe, G.; Patel, D.; Hardwick, L.; Akhmadaliev, S.; Reeves-Mclaren, N.; Goodall, R.
For fusion to be realized as a safe, sustainable source of power, new structural materials need to be developed which can withstand high temperatures and the unique fusion radiation environment. An attractive aspect of fusion is that no long-lived radioactive wastes will be produced, but to achieve this structural materials must comprise reduced activation elements. Compositionally complex alloys (CCAs) (also called high entropy alloys, HEAs) are promising candidates for use in extreme environments, including fusion, but few reported to date have low activation. To address these material challenges, we have produced novel, reduced activation, HEAs by arc-melting, and investigated their thermal stability, and radiation damage resistance using 5 MeV Au2+ ion implantation. Whilst the alloys were designed to form single phase BCC, using room temperature and non-ambient in situ X-ray diffraction we have revealed the thermodynamically stable structure of these alloys is in fact a sigma phase. We propose that a BCC phase is formed in these alloys, but at high temperatures (>1000°C). A BCC phase was also formed during heavy ion implantation, which we propose to be due to the rapid heating and cooling that occurs during the thermal spike, effectively freezing in the BCC phase produced by an implantation induced phase transformation. The BCC phase was found to have high hardness and a degree of ductility, making these new alloys attractive in the development of reduced activation HEAs for nuclear applications.
Keywords: high entropy alloy (HEA), reduced activation, phase transformation, ion implantation, thermal stability, nuclear, radiation damage

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Permalink: https://www.hzdr.de/publications/Publ-29548
Publ.-Id: 29548


Not all Neoproterozoic iron formations are glaciogenic: Sturtian-aged non-Rapitan exhalative iron formations from the Arabian–Nubian Shield

Abd El-Rahman, Y.; Gutzmer, J.; Li, X.-H.; Seifert, T.; Li, C.-F.; Ling, X.-X.; Li, J.
Neoproterozoic iron formations are exposed in the Wadi Hamama area (Egypt) in the northwestern part of the Arabian–Nubian Shield. Mafic and felsic volcanic and volcaniclastic rocks of an intra-oceanic island-arc setting host multiple, thin iron-formation units. Major element compositions of the iron formation confirm a low detrital input, whereas the rare-earth elements and Y data suggest deposition related to an influx of low-temperature hydrothermal fluids. Unlike most Neoproterozoic banded iron formations, but similar to other iron-formation occurrences from the Arabian–Nubian Shield, the Nd isotopic compositions of the Wadi Hamama iron formations are predominantly mantle-like. SIMS U–Pb zircon ages of the host volcaniclastic units indicate that the age of iron-formation deposition is ca. 695 Ma, which is within the Sturtian epoch that is presumed to be a glacial event of global extent. Nevertheless, there is no robust evidence of any influence of Sturtian glaciation in the Arabian–Nubian Shield. Our results rather suggest that the iron formations in the area may have formed as low-temperature exhalites on the floor of an island-arc basin. The iron formations were deposited during periods of volcanic quiescence, with metals having been derived during low-temperature pervasive hydrothermal alteration of volcanic and volcaniclastic rocks exposed at the seafloor–seawater interface. Precipitation took place due to mixing of metal-bearing hydrothermal fluids and cold, oxygenated seawater. There is no need to invoke possible effects of global glaciation to explain the origin of the Sturtian-aged iron formations in the shield. Our study thus suggests that not all Neoproterozoic iron formations are necessarily linked to glacial events as the Hamama deposit represents a non-Rapitan exhalative iron formation.
Keywords: Cryogenian, Exhalite, Hydrothermal, Iron formations, Island arc, Sturtian glaciation

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Permalink: https://www.hzdr.de/publications/Publ-29547
Publ.-Id: 29547


High temperature plasma immersion ion implantation using hollow cathode discharges in small diameter metal tubes

Ueda, M.; Silva, C.; de Souza, G. B.; Pichon, L.; Reuther, H.
High temperature nitrogen plasma immersion ion implantation (HT-NPIII) method was used to treat the internal walls of small diameter metal tubes made of SS304 and of Ti6-Al4-V (TAV). Using a lid in one side of the tubes was essential to reach high temperatures of 700-900 °C, necessary for high thermal diffusion of nitrogen in Ti alloy samples placed inside the metal tubes for monitoring the HT-NPIII process. The used metal tubes also reached such high temperatures. New phases of TiN and Ti2N were successfully attained in the TAV samples with the treated layer thickness of more than 1.3 μm for all the tested cases. For tubes made of SS304, HT-NPIII treatments resulted in redeposition of FeN thick layers with high hardness on the surfaces of the internal walls of the tubes and on the monitoring samples. Obtaining such HT-NPIII conditions in these small metallic tubes was possible by achieving high plasma density through hollow cathode discharges inside those tubes. These results were compared to the ones obtained on the nitrogen implantation treatments of TAV samples in moderate to high temperatures carried out previously in the laboratory which indicated the superior performance of the presently reported method of surface modification.

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Permalink: https://www.hzdr.de/publications/Publ-29546
Publ.-Id: 29546


Structure–Affinity Relationships of Fluorinated Spirocyclic Sigma2 Receptor Ligands with an Exocyclic Benzylamino Moiety

Bergkemper, M.; Kronenberg, E.; Schepmann, D.; Ludwig, F.-A.; Brust, P.; Wünsch, B.
To identify a potent and selective σ2 receptor ligand appropriate for development as a positron emission tomography (PET) tracer, several fluorinated analogues of the spirocyclic lead compounds trans- and cis-6 (N-(2,4-dimethylbenzyl)-3-methoxy-3,4-dihydrospiro[[2]benzopyran-1,1′-cyclohexan]-4′-amine) were designed. In multistep syntheses, a fluorine atom was introduced directly or as a 2-fluoroethoxy moiety on the 2-benzopyran scaffold, on the dimethylbenzylamino moiety, or on the central amino moiety. The σ1 and σ2 receptor affinity was determined in receptor binding studies with radioligands. With respect to σ2 affinity and σ2/σ1 selectivity, cis-N-(2,4-dimethylbenzyl)-5-fluoro-3-methoxy-3,4-dihydrospiro[[2]benzopyran-1,1′-cyclohexan]-4′-amine (cis-15 c, Ki(σ2)=51 nm) and cis-N-[4-(fluoromethyl)-2-methylbenzyl]-3-methoxy-3,4-dihydrospiro[[2]benzopyran-1,1′-cyclohexan]-4′-amine (cis-28 e, Ki(σ2)=57 nm) are the most promising ligands. The combination of both structural elements in one molecule, cis-N-[4-(fluoromethyl)-2-methylbenzyl]-5-fluoro-3-methoxy-3,4-dihydrospiro[[2]benzopyran-1,1′-cyclohexan]-4′-amine (cis-28 c: Ki(σ2)=874 nm), resulted in decreased σ2 and σ1 affinity. Methylation of secondary amines led to three tertiary methylamines with moderate affinity for both σ receptor subtypes.
Keywords: cis–trans configuration, fluorinated PET tracers, receptor selectivity, spirocyclic ligands, structure–affinity relationships, σ receptors

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Mikroorganismen und deren Relevanz in einem Endlager

Matschiavelli, N.
Der Vortrag dient der Weiterbildung von Lehrkräften und gibt Einblicke in die Endlager-Problematik von hoch-radioaktiven Abfällen. Im speziellen soll hier die Relevanz von Mikroorganismen dargestellt und erleutert werden.
  • Lecture (others)
    Radioaktivität - Forschung, Schule, Praxis, 09.10.2019, Schülerlabor DeltaX, HZDR, Dresden, Deutschland

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Publ.-Id: 29544


Opportunities for measurements of astrophysical‐relevant alpha‐capture reaction rates at CRYRING@ESR

Forstner, O.; Bemmerer, D.; Cowan, T.; Dressler, R.; Junghans, A.ORC; Schumann, D.; Stöhlker, T.; Szücs, T.; Wagner, A.ORC; Zuber, K.
The heavy‐ion storage ring CRYRING@ESR has recently been installed and commissioned at GSI as one of the first installations of the upcoming Facility for Antiproton and Ion Research (FAIR). It is designed to store highly charged ions in the energy range between 300 keV/u and about 10 MeV/u. It will incorporate a gas‐jet target providing high‐density jets of, among other gases, hydrogen and helium. This will allow to study alpha‐capture reaction rates of astrophysical interest in the energy range of the Gamow window for core‐collapse supernovae. Special interest comes from the long‐lived radio‐isotope 44Ti (t1/2 = 58.9 years), which is supposed to be produced in the alpha‐rich freeze‐out during such an event. The nucleosynthesis of this isotope is of great interest, as the amount of material produced can be estimated by direct observation in remnants of recent supernovae. The disagreements between the observations and the estimations from astrophysical models show the need of more experimental data for the production and consumption reactions in the energy range of a core‐collapse supernova. In this article, we will describe the proposed method of injecting beams of 44Ti into CRYRING@ESR and performing the actual reaction rate measurements.
Keywords: 44Ti core-collapse supernova alpha-capture

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Deutschlands Ausstieg aus der Atomkraft - Was passiert mit dem Müll und welche Rolle spielen dabei Mikroorganismen

Matschiavelli, N.
Zur Zeit werden in Deutschland noch 7 Kernkraftwerke zur Stromerzeugung betrieben. Bis 2022 soll das letzte Kernkraftwerk abgeschaltet werden – Deutschlands Ausstieg aus der Atomkraft. Der Atomausstieg ist ein wichtiger Schritt für die Energiewende, nicht nur in Deutschland, sondern in vielen Ländern Europas. Ziel ist eine langfristige und vollständige Umstellung auf erneuerbare Energien wie z. B. Wasserkraft, Sonnen- und Windenergie.
Der Ausstieg aus der Kernenergie bringt auch einige Konsequenzen mit sich, für welche wir Verantwortung übernehmen müssen. Eine der größten Herausforderungen ist dabei die sichere und langfristige Lagerung des Atommülls. Allein in Deutschland entstanden im Jahr 2015 15 Tonnen an abgebrannten Brennelementen. Dieser Atommüll ist hoch radioaktiv und wird erst nach einer Dauer von etwa 200.000 bis 500.000 Jahren als „ungefährlich“ eingestuft. Das Endlager für die Brennelemente muss also über diesen langen Zeitraum stabil und sicher sein. Weltweit hat sich hierbei das Konzept einer tiefen-geologischen Lagerung – etwa 500 m bis 1000 m unter der Erde – durchgesetzt. Hierbei soll ein Multi-Barrieren-Konzept Anwendung finden, welches aus folgenden Elementen bestehen wird:

1) technische Barriere – Metall-Behälter, welcher die Brennelemente beherbergt (Gusseisen, Stahl, oder Kupfer)
2) geo-technische Barriere – Puffer- und Abdichtungsmaterial (Bentonit oder Salzgrus)
3) geologische Barriere – Wirtsgestein (Steinsalz, Granit oder Tongestein)

In Deutschland starten wir von einer „weißen Landkarte“. Die unterschiedlichen Materialien und Gesteine werden momentan auf ihre Eignung für das Endlager in Deutschland untersucht. Viele verschiedene Fachdisziplinen sind dafür relevant: Geologie, Mineralogie, (Radio-)Chemie, Physik, Mathematik, Materialwissenschaften, Architektur – um hier nur einige zu nennen. Interessanterweise spielt auch die Biologie bei der Planung des Endlagers eine Rolle. Lebewesen können auf verschiedene Art und Weise mit den hier verwendeten Materialien – sogar mit dem Atommüll selbst – interagieren. Zu den hauptsächlich hier betrachteten Lebewesen zählen Pflanzen, Pilze und Mikroorganismen (Bakterien, Archaeen). Mikroorganismen sind ubiquitär auf dem Planeten Erde verbreitet und werden auch im Endlager für Atommüll anwesend sein. Bedingt durch ihren Stoffwechsel, welcher sich von dem des Menschen zum Teil stark unterscheidet, sind Mikroorganismen in der Lage, Materialien und deren Eigenschaften zu verändern. Da die Lagerung des Atommülls sicher und langfristig sein muss, ist es wichtig zu erforschen, inwiefern Mikroorganismen hierfür genutzte Barriere-Materialien verändern und deren Eigenschaften beeinflussen können. Im ungünstigsten Fall könnte dadurch die langfristige Sicherheit des Endlagers stark reduziert werden.

Der Vortrag gibt einen Einblick in die faszinierende Welt der Mikroorganismen und zeigt zugleich deren Relevanz für die sichere und langfristige Lagerung des Atommülls.
Keywords: hoch-radioaktiver Abfall, Endlager, Mikroorganismen
  • Lecture (others)
    Veranstaltung der Dresdner Seniorenakademie, 08.10.2019, Deutsches Hygienemuseum, Deutschland

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Publ.-Id: 29542


Crystal structure and dehydration behaviour of Ag+-exchanged levyne

Cametti, G.; Churakov, S. V.; Scheinost, A.
Levyne is a natural zeolite Ca2.53Na0.72K0.23(Al6.26Si11.8O36)·17.58H2O with LEV framework type. The structure can be described by a sequence of single six-membered rings (S6R) and double six-membered rings (D6R) stacked along the c axis with AABCCABBCAA sequence [1,2]. This sequence originates columns along [001] of [496583] polyhedra (levyne cages) alternating with [4662] polyhedra (double six-rings). Two-dimensionally interconnected channels (free diameters 3.6 × 4.8 Å) confined by eight-membered rings run perpendicular to [001]. In this study we investigated the crystal structure and thermal stability of a Ag-exchanged levyne by using a multimethodological approach.
Keywords: zeolite levyne Ag-doping XAFS
  • Poster
    32nd European Crystallographic Meeting (ECM 32), 18.-23.08.2019, Wien, Austria

Permalink: https://www.hzdr.de/publications/Publ-29541
Publ.-Id: 29541


Magnetization Dynamics of an Individual Single-Crystalline Fe-Filled Carbon Nanotube

Lenz, K.ORC; Narkowicz, R.; Wagner, K.; Reiche, C. F.; Körner, J.; Schneider, T.; Kákay, A.; Schultheiss, H.; Suter, D.; Büchner, B.; Fassbender, J.; Mühl, T.; Lindner, J.
The magnetization dynamics of individual Fe-filled multiwall carbon-nanotubes (FeCNT), grown by chemical vapor deposition, are investigated by microresonator ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) microscopy and corroborated by micromagnetic simulations. Up to now, only static magnetometry measurements are available. They suggest that the FeCNTs consist of a single-crystalline Fe nanowire throughout the length. The number and structure of the FMR lines and the abrupt decay of the spin-wave transport seen in BLS indicate, however that the Fe filling is not a single straight piece along the length. Therefore a stepwise cutting procedure was applied in order to investigate the evolution of the ferromagnetic resonance lines as a function of the nanowire length. Our results show that the FeCNT is indeed not homogeneous along the full length but is built from 300-400 nm long single-crystalline segments. These segments consist of magnetically high quality Fe nanowires with almost the bulk values of Fe and with a similar small damping in relation to thin films, promoting the FeCNTs as appealing candidates for spin-wave transport in magnonic applications.
Keywords: ferromagnetic nanotubes, ferromagnetic resonance, carbon nanotubes, Brillouin light scattering, micromagnetism

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IAEA Photonuclear Data Library 2019

Kawano, T.; Cho, Y. S.; Dimitriou, P.; Filipescu, D.; Iwamoto, N.; Plujko, V.; Tao, X.; Utsunomiya, H.; Varlamov, V.; Xu, R.; Capote, R.; Gheorghe, I.; Gorbachenko, O.; Jin, Y. L.; Renström, T.; Stopani, K.; Tian, Y.; Tveten, G. M.; Wang, J. M.; Belgya, T.; Firestone, R.; Goriely, S.; Kopecky, J.; Krticka, M.; Schwengner, R.ORC; Siem, S.; Wiedeking, M.
Photo-induced reaction cross section data are of importance for a variety of current or emerging applications, such as radiation shielding design and radiation transport analyses, calculations of absorbed dose in the human body during radiotherapy, physics and technology of fission reactors (influence of photo-reactions on neutron balance) and fusion reactors (plasma diagnostics and shielding), activation analyses, safeguards and inspection technologies, nuclear waste transmutation, medical isotope production and astrophysical applications. To address these data needs the IAEA Photonuclear Data library was produced in 2000, containing evaluated photo-induced cross sections and neutron spectra for 164 nuclides which were deemed relevant for the applications. Since the release of the IAEA Photonuclear Data Library however, new experimental data as well as new methods to assess the reliability of experimental cross sections have become available. Theoretical models and input parameters used to evaluate photo-induced reactions have improved significantly over the years. In addition, new measurements of partial photoneutron cross sections using mono-energetic photon beams and advanced neutron detection systems have been performed allowing for the validation of the evaluations and assessments of the experimental data. Furthermore, technological advances have led to the construction of new and more powerful gamma-beam facilities, therefore new data needs are emerging.
We report our coordinated efforts to address these data needs and present the results of the new evaluations of more than 200 nuclides included in the new updated IAEA Photonuclear Data Library, where the photon energy goes up to 200 MeV. We discuss the new assessment method and make recommendations to the user community in cases where the experimental data are discrepant and the assessments disagree. In addition, in the absence of experimental data, we present model predictions for photo-induced reaction cross section on nuclides of potential interest to medical radioisotope production.
Keywords: Photonuclear reactions, cross sections, data library.

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Publ.-Id: 29539


Analysis of mass transport near a conically shaped electrode during electrodeposition assisted by a magnetic field

Marinaro, G.; Huang, M.; Yang, X.ORC; Mutschke, G.; Eckert, K.
By superimposing a magnetic field during electrodeposition of metals, alloys or composite coatings, the surface structure and the deposition rates could be changed. We used conical shaped copper electrodes coated with a thin layer of gold to study the effects of the magnetic field on mass transport during electrodeposition. The setup involves a metallic cone working as cathode, a platinum wire above as counterelectrode and a magnet below the cone.
In this case buoyancy force dominates the mass transport near the tip because the current density is high and the magnetic field is weak. On the other hand, in the region away from the tip and near the cone surface, the electric field is normal to the surface and has a component perpendicular to the magnetic field, where the Lorentz force dominates. In this work we measure in detail the convection of the electrolyte near the electrode during the electrodeposition process by particle tracking which is useful to understand how the deposition rate varies along the surface of the cone.
Keywords: nanostructured surface, electrodeposition, magnetic driven forces
Related publications
Numerical simulation of mass transfer and convectinon near … (Id 29536) is supplemented by this publication
  • Lecture (Conference)
    11th Pamir international conference, 01.-05.07.2019, Reims, France
  • Contribution to proceedings
    11th Pamir international conference, 01.-05.07.2019, Reims, France

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Publ.-Id: 29537


Numerical simulation of mass transfer and convectinon near conically shaped electrodes under the influence of a magnetic field

Huang, M.; Marinaro, G.; Yang, X.ORC; Eckert, K.; Mutschke, G.
Copper electrodeposition on a conically shaped copper or iron electrode was studied under the influence of a vertical magnetic field. Numerical simulations were conducted to provide understanding of the interaction between the magnetic forces and the buoyancy force involved in the deposition process. The secondary flow caused by the Lorentz force is directed downward towards the cone, which is counteracted by the buoyancy force as the cathode is placed at the bottom of the electrochemical cell. For the iron cone, the magnetic gradient force can perceptibly enhance the local downward flow and is thus supporting conical growth, which indicates potential benefits of using magnetic fields in electrodeposition processes.
Keywords: electrodeposition, magnetic field, natural convection, numerical simulation, surface-structured electrode
Related publications
Analysis of mass transport near a conically shaped … (Id 29537) is a supplement to this publication
  • Contribution to proceedings
    11th Pamir international conference, 01.-05.07.2019, Reims, France
  • Poster
    11th Pamir international conference, 01.-05.07.2019, Reims, France
  • Lecture (Conference)
    The 8th International Conference on Magneto-Science (ICMS 2019), 11.-14.10.2019, Hefei, China

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Publ.-Id: 29536


Study of mixing enhanced by a magnetic field in a microfluidic channel

Yang, X.; Wojnicki, M.; Zabinski, P.; Mutschke, G.
Mixing in a microfluidic environment is challenging due to the laminarity of flow. The idea of the present study is to apply a magnetic force to a stratified channel flow. Due to the different magnetic susceptibilities of the liquid layers, mixing might be triggered. The magnetic gradient force is generated simply by the application of permanent magnets. Fig. 1 shows the channel setup with two entries and two outflows. The upper entry is fed with water, whereas the lower entry is fed with 0.1 M HoCl3 solution. On top of the front part, the magnets are applied. Different flow rates and magnet configurations were studied. The degree of mixing is measured by determining the concentration of HoCl3 in the upper outlet by a spectrophotometer measuring the absorbance at a specific wavelength. Additional Micro-PIV measurements are performed to resolve the related flow pattern in detail. Numerical simulations are performed to complement the investigation.
Keywords: microfluidics, mixing, paramagnetic solution, magnetic field, Kelvin force
  • Poster
    11th International PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-29535
Publ.-Id: 29535


Study of the Marangoni effect during electrolytic gas evolution

Mutschke, G.; Massing, J.; Hossain, S. S.; Yang, X.; Baczyzmalski, D.; Cierpka, C.; Eckert, K.
lectrolytic gas evolution is a fundamental phenomenon occurring in a large number of industrial applications. Near the electrode, bubble growth is understood to appear due to mass flux of dissolved gas across the bubble interface from a supersaturated electrolyte. Because of related thermal, electrical or solutal effects, a gradient of the surface tension along the interface may exist. The resulting shear stress would cause convection at the interface (Marangoni effect), which may affect the mass transfer across the interface during growth and also the departure of the gas bubble. This Marangoni effect was unveilled only recently in an experimental study [1]. The present work aims to investigate the origin of the effect in more detail. Numerical simulations are performed including only the thermal Marangoni effect near a hydrogen gas bubble growing electrochemically at a microelectrode in an acidic electrolyte. The simulation results are compared with experimental data of the near-bubble convection obtained by Particle Tracking Velocimetry (PTV) and by temperature measurements. The comparison allows to conclude on a strong thermocapillary effect at the microelectrode [2]. The related force on the bubble is found to retard the release of the bubble.

[1] X. Yang et al, Phys. Chem. Chem. Phys., 20: 11542-11548. 2018.
[2] J. Massing et al., Electrochim. Acta. 2019. IN PRESS
Keywords: Electrolysis, gas evolution, hydrogen evolution, Marangoni, thermocapillary effect
  • Invited lecture (Conferences)
    11th International PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich
  • Lecture (others)
    Institutskolloquium, 22.08.2019, Ilmenau, Deutschland
  • Lecture (others)
    Eingeladener Vortrag am SIMaP Grenoble, 22.-23.10.2019, Grenoble, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-29534
Publ.-Id: 29534


A comparison between time domain and frequency domain calculations of stationary neutron fluctuations

Viebach, M.; Lange, C.; Kliem, S.ORC; Demaziere, C.; Rohde, U.; Henning, D.; Hurtado, A.
Unexplained neutron flux fluctuation patterns observed in some reactors were recently investigated by various European institutions. The time-domain code DYN3D is one of the tools used for simulating these fluctuations. Though, the applicability of time-domain codes for modelling small stationary fluctuations remains a discussed question. Aiming at a confirmation that these codes may be applied for neutron noise calculations, two special cases of neutron flux oscillations have been simulated with DYN3D and with CORE SIM, the latter one being validated for the context here. The comparison between the results of these two codes is the subject of this paper. This study demonstrates that time- and frequency-dependent calculations can give qualitatively equivalent results but substantial quantitative deviations may occur. Nevertheless, DYN3D may be considered as qualified for neutron-noise calculations as the deviations are smaller than 20 %. The optimization of the DYN3D setup is a matter of future research.
Keywords: neutron noise, DYN3D, CORE SIM
  • Contribution to proceedings
    International Conference on Mathematics and Computational Methods applied to Nuclear Science and Engineering (M&C 2019), 25.-30.08.2019, Portland, USA
    Proc. of the International Conference on Mathematics and Computational Methods applied to Nuclear Science and Engineering
  • Poster
    International Conference on Mathematics and Computational Methods applied to Nuclear Science and Engineering (M&C 2019), 25.-30.08.2019, Portland, USA

Permalink: https://www.hzdr.de/publications/Publ-29533
Publ.-Id: 29533


Feasibility assessment of using external neutron and gamma radiation measurements for monitoring the state of fuel assemblies in dry storage casks

Rachamin, R.; Hampel, U.
This study assesses the feasibility of using external neutron and gamma flux measurements to detect the state of spent fuel assemblies inside a sealed cask. Several Monte-Carlo simulations were performed to evaluate the neutron and gamma flux distribution outside the sidewall of a cask with all intact fuel assemblies and a cask with one damaged fuel assembly, mimicking a fuel assembly with expanded rods and fuel relocation. The evaluation was performed for different positions of the damaged fuel assembly and different storage times. The results show that in case the damaged fuel assembly is located near the inner wall of the cask, it can be detected by both of the radiation modes. The detection of the inner damaged fuel assemblies, however, can be feasible only by the external neutron flux.
Keywords: Monte-Carlo, dry storage cask, monitoring, neutron and gamma radiation

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Publ.-Id: 29532


FLUKA simulations with and without magnetic field

Müller, S.ORC
Presentation at Mu2e Simulation WG meting August 1, 2019
Keywords: Mu2e, FLUKA
  • Lecture (others)
    Mu2e Simulation WG meeting, 01.08.2019, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29531
Publ.-Id: 29531


Improved magnetostructural and magnetocaloric reversibility in magnetic Ni-Mn-In shape-memory Heusler alloy by optimizing the geometric compatibility condition

Devi, P.; Salazar Mejia, C.; Ghorbani Zavareh, M.; Dubey, K. K.; Kushwaha, P.; Skourski, Y.; Felser, C.; Nicklas, M.; Singh, S.
We report an improved reversibility of magnetostriction and inverse magnetocaloric effect (MCE) for the magnetic shape-memory Heusler alloy Ni1.8Mn1.8In0.4. We show that the magnetostriction and MCE crucially depends on the geometrical compatibility of the austenite and martensite phases. Detailed information on the compatibility of both phases has been obtained from the transformation matrix calculated from x-ray diffraction data. The uniqueness of the lattice parameters results in an improved reversibility of the magnetostriction and the MCE. In the thermal hysteresis region of the martensitic transformation, the maximum relative length change is 0.3% and the adiabatic temperature change Δad ≈ −10 K in pulsed magnetic fields. Our results reveal that the approach of geometric compatibility will allow one to design materials with reversible magnetostriction and reversible inverse MCE at a first-order magnetostructural phase transition in shape-memory Heusler alloys.

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Publ.-Id: 29530


Magnetic phase transitions, metastable states, and magnetic hysteresis in the antiferromagnetic compounds Fe0.5TiS2−ySey

Baranov, N. V.; Selezneva, N. V.; Sherokalova, E. M.; Baglaeva, Y. A.; Ovchinnikov, A. S.; Tereshchenko, A. A.; Gorbunov, D.; Volegov, A. S.; Sherstobitov, A. A.
The phase transitions and magnetization processes in the antiferromagnetic compounds Fe0.5TiS2−ySey [FeTi2(S,Se)4] with an ordered layered crystal structure of the CrS4 type have been studied by using x-ray diffraction, measurements of the specific heat, electrical resistivity, magnetoresistance, and the magnetization in steady and pulsed magnetic fields together with calculations within the Ising model accounting the magnetoelastic interactions. The change from the spin-flip to spin-flop type phase transition and a monotonic growth of the critical transition field from ∼50 kOe at y = 0 up to 470 kOe at y = 2 has been observed with the Se for S substitution in antiferromagnetic (AFM) compounds Fe0.5TiS2−ySey. In the selenium-poor compounds (y < 0.5), the field-induced AFM-FM phase transition at low temperatures is accompanied by ultrasharp changes in the magnetization and magnetoresistance and by huge magnetic hysteresis. The presence of remnant magnetoresistance in these compounds after the application of a magnetic field indicates the formation of a metastable field-induced FM state. Despite an AFM ground state, the Fe0.5TiS2−ySey compounds with y < 0.5 after application of a magnetic field behave at low temperatures as high-anisotropic Ising-type ferromagnets with the coercive field Hc up to ∼60 kOe. It has been shown, that magnetoelastic interactions may be responsible for the formation of the metastable field-induced high-coercive FM state in the Ising-type antiferromagnets.

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Publ.-Id: 29529


Tailoring the ferrimagnetic-to-ferromagnetic transition field by Interstitial and substitutional atoms in the R–Fe compounds

Tereshina, I. S.; Ivanov, L. A.; Tereshina-Chitrova, E. A.; Gorbunov, D. I.; Paukov, M. A.; Havela, L.; Drulis, H.; Granovsky, S. A.; Doerr, M.; Gaviko, V. S.; Andreev, A. V.
Fundamental characteristics of rare-earth (R) – iron intermetallics R2Fe14B are highly sensitive to the atomic substitutions and interstitial absorption of light elements. We studied a combined influence of the substitutions in the rare-earth sublattice and hydrogen absorption on the magnetization behavior in magnetic fields up to 60 T Er2Fe14B and Tm2Fe14B ferrimagnets chosen for the study showed that the substitution of Nd for Er or Tm increases the saturation magnetization as a result of ferromagnetic ordering of Nd and Fe moments. Under sufficiently high magnetic fields the magnetic moments rotate and the field-induced ferromagnetic state may be observed. The field at which a transition occurs is related to the strength of the inter-sublattice exchange interaction. The role of hydrogen is primarily to weaken the inter-sublattice ferrimagnetic coupling so that the reorientation becomes achievable at the available magnetic field strength (in hydrides Tm2Fe14BH5.5 and (Tm0.5Nd0.5)2Fe14BH5.5). We analyze the volume dependence of the R–Fe magnetic interaction in R2Fe14B and compare it with other R–Fe compounds.

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Publ.-Id: 29527


Shifts in bentonite bacterial community and mineralogy in response to uranium and glycerol-2-phosphate exposure

Povedano-Priego, C.; Jroundi, F.; Lopez Fernandez, M.; Sánchez-Castro, I.; Martin-Sánchez, I.; Huertas, F. J.; Merroun, M. L.
The multi-barrier deep geological repository system is currently considered as one of the safest option for the disposal of high-level radioactive wastes. Indigenous microorganisms of bentonites, may affect the structure and stability of these clays through Fe-containing minerals biotransformation and radionuclides mobilization.
The present work aimed to investigate the behavior of bentonite and its bacterial community in the case of a uranium leakage from the waste containers. Hence, bentonite microcosms were amended with uranyl nitrate (U) and glycerol-2-phosphate (G2P) and incubated aerobically for 6 months. Next generation 16S rRNA gene sequencing revealed that the bacterial populations of all treated microcosms were dominated by Actinobacteria and Proteobacteria, accounting for >50% of the community. Additionally, G2P and nitrate had a remarkable effect on the bacterial diversity of bentonites by the enrichment of bacteria involved in the nitrogen and carbon biogeochemical cycles (e.g. Azotobacter). A significant presence of sulfate-reducing bacteria such as Desulfonauticus and Desulfomicrobium were detected in the U-treated microcosms. The actinobacteria Amycolatopsis was enriched in G2P‑uranium amended bentonites. High Annular Angle Dark-Field Scanning Transmission Electron Microscopy analyses showed the capacity of Amycolatopsis and a bentonite consortium formed by Bradyrhizobium-Rhizobium and Pseudomonas to precipitate U as U phosphate mineral phases, probably due to the phosphatase activity. The different amendments did not affect the mineralogy of the bentonite pointing to a high structural stability. These results would help to predict the impact of microbial processes on the biogeochemical cycles of elements (N and U) within the bentonite barrier under repository relevant conditions and to determine the changes in the microbial community induced by a uranium release.
Keywords: Deep geological repository Bentonite Bacterial diversity Uranium Glycerol-2-phosphate Microscopy

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Permalink: https://www.hzdr.de/publications/Publ-29526
Publ.-Id: 29526


Statistical Analysis of Community RNA Transcripts between Organic Carbon and Geogas-Fed Continental Deep Biosphere Groundwaters

Lopez Fernandez, M.; Broman, E.; Simone, D.; Bertilsson, S.; Dopson, M.
Life in water-filled bedrock fissures in the continental deep biosphere is broadly constrained by energy and nutrient availability. Although these communities are alive, robust studies comparing active populations and metabolic processes across deep aquifers are lacking. This study analyzed three oligotrophic Fennoscandian Shield groundwaters, two “modern marine” waters that are replenished with organic carbon from the Baltic Sea and are likely less than 20 years old (171.3 and 415.4m below sea level) and an extremely oligotrophic “thoroughly mixed” water (448.8m below sea level) of unknown age that is composed of very old saline and marine waters. Cells were captured either using a sampling device that rapidly fixed RNA under in situ conditions or by filtering flowing groundwater over an extended period before fixation. Comparison of metatranscriptomes between the methods showed statistically similar transcript profiles for the respective water types, and they were analyzed as biological replicates. Study of the small subunit (SSU) rRNA confirmed active populations from all three domains of life, with many potentially novel unclassified populations present. Statistically supported differences between communities included heterotrophic sulfate-reducing bacteria in the modern marine water at 171.3m below sea level that has a higher organic carbon content than do largely autotrophic populations in the H2- and CO2-fed thoroughly mixed water. While this modern marine water had signatures of methanogenesis, syntrophic populations were predominantly in the thoroughly mixed water. The study provides a first statistical evaluation of differences in the active microbial communities in groundwaters differentially fed by organic carbon or “geogases.”
IMPORTANCE
Despite being separated from the photosynthesis-driven surface by both distance and time, the deep biosphere is an important driver for the earth’s carbon and energy cycles. However, due to the difficulties in gaining access and low cell numbers, robust statistical omics studies have not been carried out, and this limits the conclusions that can be drawn. This study benchmarks the use of two separate sampling systems and demonstrates that they provide statistically similar RNA transcript profiles, importantly validating several previously published studies. The generated data are analyzed to identify statistically valid differences in active microbial community members and metabolic processes. The results highlight contrasting taxa and growth strategies in the modern marine waters that are influenced by recent infiltration of Baltic Sea water versus the hydrogen- and carbon dioxide-fed, extremely oligotrophic, thoroughly mixed water.
Keywords: deep biosphere, groundwaters, metatranscriptomes, protein-coding RNA, rRNA

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Publ.-Id: 29525


¹⁸F-Labeled benzylpiperazine derivatives as highly selective ligands for imaging σ1 receptor with positron emission tomography

Ye, J.; Wang, L.; Deuther-Conrad, W.; Chen, Y.; Zhang, X.; Zhang, J.; Huang, Y.; Brust, P.; Jia, H.
We report the design, synthesis, and evaluation of a new series of benzylpiperazine derivatives as selective σ1 receptor ligands. All seven ligands possessed low nanomolar affinity for σ1 receptors (Ki(σ1) = 0.31-4.19 nM) and high subtype selectivity (Ki(σ2)/Ki(σ1) = 50-2448). The fluoroethoxy analogues also exhibited high selectivity toward the vesicular acetylcholine transporter (Ki(VAChT)/Ki(σ1) = 99-18252). The corresponding radiotracers [18F]13, [18F]14, and [18F]16 with high selectivity (Ki(σ2)/Ki(σ1) > 100, Ki(VAChT)/Ki(σ1) > 1000) were prepared in 42% to 55% radiochemical yields (corrected for decay), greater than 99% radiochemical purity (RCP), and molar activity of about 120 GBq/μmol at the end of synthesis (EOS). All three radiotracers showed high initial brain uptake in mouse (8.37-11.48% ID/g at 2 min), which was not affected by pretreatment with cyclosporine A, suggesting that they are not substrates for permeability-glycoprotein (P-gp). Pretreatment with SA4503 or haloperidol resulted in significantly reduced brain uptake (35%-62% decrease at 30 min). In particular, [18F]16 displayed high brain-to-blood ratios and high in vivo metabolic stability. Although it may not be an optimal neuroimaging agent because of its slow kinetics in the mouse brain, [18F]16 can serve as a lead compound for further structural modifications to explore new potential radiotracers for σ1 receptors.
  • Journal of Labelled Compounds and Radiopharmaceuticals 62(2019)8, 425-437
    DOI: 10.1002/jlcr.3738

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Publ.-Id: 29524


SLC3A2/CD98hc, autophagy and tumor radioresistance: a link confirmed

Digomann, D.; Linge, A.; Dubrovska, A.
SLC3A2/CD98hc (solute carrier family 3 member 2) and its light chain subunits constitute the heterodimeric transmembrane complexes that mediate amino acid transport and regulate MTOR and macroautophagy/autophagy. Despite the proven tumorigenic role of SLC3A2 in a number of cancers including head and neck squamous cell carcinomas (HNSCC), the link between SLC3A2, autophagy regulation and tumor radioresistance remained elusive. In a recently published study we demonstrated that low levels of SLC3A2 and SLC7A5/LAT1 protein expression significantly correlate with good clinical prognosis in locally advanced HNSCC treated with primary radiochemotherapy. The SLC3A2-deficient HNSCC cells show a higher radiosensitivity and increased autophagy levels. We found that autophagy activation is a tumor survival strategy to overcome nutrient stress by lack of SLC3A2 and to withstand radiation-mediated cell damage. Inhibition of the autophagy activation in SLC3A2 knockout HNSCC cells by knockdown of ATG5 expression or treatment with bafilomycin A1 results in radiosensitivity. Consequently, the expression levels of ATG5 correlates with overall survival in HNSCC patients, and autophagy inhibition in combination with SLC3A2-targeted therapy can be a promising strategy for HNSCC radiosensitization. Abbreviations: CD98hc: CD98 heavy chain CSC cancer stem cells; EAA: essential amino acids; GSH: glutathione; MTOR: mammalian target of rapamycin; HNSCC: head and neck squamous cell carcinoma; RCTx: primary radiochemotherapy; PORT-C: postoperative radiochemotherapy; ROS: reactive oxygen species; SLC3A2: solute carrier family 3 member 2; TCA cycle: tricarboxylic acid cycle.
Keywords: ATG5; autophagy; biomarkers; CD98hc; HNSCC; LAT1; MTOR; radiotherapy; xCT

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Permalink: https://www.hzdr.de/publications/Publ-29523
Publ.-Id: 29523


Haemodynamic impairments in asymptomatic unilateral carotid artery stenosis are most pronounced within individual watershed areas

Kaczmar, S.; Goettler, J.; Petr, J.; Hansen, M.; Kufer, J.; Hock, A.; Kufer, J.; Mouridsen, K.; Hyder, F.; Christine, P.
Objectives
Severe internal carotid-artery stenosis (ICAS) is a major public health issue, as it accounts for approximately 10% of all strokes.1 Despite several studies,2–5 mechanisms of related haemodynamic impairments are still not well understood, which limits the currently insufficient treatment guidelines6. To improve diagnostic significance, we propose a multimodal-MRI protocol to better characterise haemodynamic impairments in asymptomatic ICAS. Since perfusion impairments arise first in the highly variableborder zones7 between perfusion territories,8 we hypothesize to be most sensitive to ICAS-impairments within subject’s individual watershed areas (iWSAs)7.

Methods
Fifty-nine participants (29 asymptomatic, unilateral ICAS-patients, age = 70.1 ± 4.8y and 30 age-matched HC, age = 70.3 ± 7.3y) underwent MRI on a Philips 3T Ingenia with written informed consent. Imaging yielded maps of cerebrovascular reactivity (CVR)9 by breathhold-fMRI;10 cerebral blood flow (CBF) by pCASL;11 relative oxygen extraction fraction (rOEF) by multiparametric-quantitative BOLD (mq-BOLD);12 relative cerebral blood volume (rCBV), capillary transit-time heterogeneity (CTH), and oxygen extraction capacity (OEC) by parametric modeling13 of dynamic susceptibility contrast (DSC) data14 (Fig.1C-H). Based on DSC-derived time-to-peak (TTP) maps, iWSAs were defined for each participant (Fig.1A).7 Mean haemodynamic parameter values within each hemisphere were compared between ICAS-patients vs. HC and inside vs. outside iWSAs (Fig.1B) within GM and WM.

Results
We found statistically significant lateralisation of CBF, CVR, rCBV, CTH and OEC for ICAS-patients, whereas no significant rOEF lateralisation was found (Fig.1I). Inside iWSAs, lateralisation was significantly enhanced for CBF and CVR (t-test, p < 0.05), with a strong trend for rCBV. Overall, lateralisation was stronger within WM than GM (Fig.1I). Contrary, OEC and CTH were indeed lateralised, but comparable inside vs. outside iWSAs (Fig.1I). For HC, all parameters were symmetrical between hemispheres (data not shown).



Discussion
The multimodal MRI-protocol is sensitive to haemodynamic impairments in unilateral-ICAS. Specificity was affirmed by symmetrical HC results. As hypothesized, impairments of CBF, CVR and rCBV were stronger within iWSAs (Fig.1I). Pronounced effects in WM-iWSA fit with the different blood supply in GM/WM. Ipsilaterally decreased CBF agrees with recent studies.2 Decreased CVR, along with increased rCBV, indicates chronic vasodilation.15 Consistent with current literature,2 no rOEF lateralisation was found on group level. Observed ΔCBF vs. ΔrOEF mismatch could imply variable oxygen diffusivity16– potentially moderated by CTH17,18. Increased CTH in ICAS agrees with previous studies.18 Interestingly, we found CTH and OEC lateralisation independent of iWSA-locations, which coincides with previous CTH and Tmax comparisons.19,20 This indicates different CTH and TTP sensitivities to macrovascular effects and microcapillary flow heterogeneity.18

Conclusion
We successfully analyzed haemodynamic impairments in unilateral-ICAS and found lateralisation in accordance with current literature. Application of iWSA confirmed increased sensitivity to CBF, CVR and rCBV changes. Interestingly, CTH and OEC increases are independent of iWSA-locations.
  • Contribution to proceedings
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan
  • Lecture (Conference)
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan

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Publ.-Id: 29522


Recovery of cerebrovascular reactivity after treatment of asymptomatic carotid artery stenosis is assessable by non-invasive breath-hold fMRI within global watershed areas

Kaczmar, S.; Goettler, J.; Sollmann, N.; Hock, A.; Sorg, C.; Zimmer, C.; Mouridsen, K.; Hyder, F.; Preibisch, C.; Petr, J.
Objectives
Accounting for approximately 10% of all strokes,1 severe internal carotid-artery stenosis (ICAS) is a major public health issue. The average 2-year mortality after the invasive treatment is very high with 32%,2 which creates the need for non-invasive methods to support treatment decisions and evaluate treatment efficacy.3,4 A highly promising biomarker of vascular health is cerebrovascular reactivity (CVR),3,4 however, commonly employed methods are either invasive acetazolamide injections or complicated gas applications.3-8 We therefore used an easily-applicable breath-hold fMRI (BH-fMRI) scheme for CVR measurements. To maximize sensitivity and ensure specificity, we evaluated CVR within global watershed areas (gWSAs) in ICAS-patients before and after treatment and in healthy controls (HC).9

Methods
Thirty-three participants (16 asymptomatic, unilateral ICAS-patients, age = 71.4 ± 5.8 y and 17 HC, age = 70.8 ± 5.3 y) underwent MRI on a 3 T Philips Ingenia with written informed consent. All participants were scanned twice, patients before and at least three months after treatment (by stenting or endarterectomy), HC with a similar follow-up delay. The BOLD-based BH-fMRI scheme comprised five breath-holds of 15 s, each. CVR-maps were calculated by data-driven analysis10 (Fig.1B,C). Artefact-affected CVR-maps were excluded based on visual ratings (CP,SK,JG). To investigate the role of chronic vasolidation,5 dynamic susceptibility contrast (DSC) MRI was additionally acquired in both scans to calculate relative cerebral blood volume (rCBV) maps11. Lateralization between hemispheres was calculated in MNI-space by mean parameter-values within GM of gWSAs for each participant (Fig.1A). ICAS-patients were evaluated within hemispheres ipsilateral and contralateral to the stenosis.

Results
Exemplary data of an ICAS-patient shows impaired CVR before treatment, which improves after treatment (see arrows in Fig.1B,C). On group level, CVR is significantly decreased in the ipsilateral hemisphere before treatment (Fig.1D, p = 0.0038). After treatment, CVR lateralization was significantly reduced (p = 0.0495) towards more symmetrical values between hemispheres (p = 0.25). Similarly, rCBV was ipsilaterally increased in ICAS before treatment and more symmetrical after treatment (data not shown). HC data was symmetrical between hemispheres at all scans (Fig.1E, p > 0.60).

Discussion
As hypothesized, BH-fMRI based evaluation of CVR lateralization within gWSAs was sensitive to subtle impairments in asymptomatic ICAS without compromising its specificity, as affirmed by symmetrical HC results (Fig.1E). Decreased CVR along with increased rCBV before treatment is associated with chronic vasodilation.5 Consistent with current literature, CVR recovery was detected after ICAS-treatment,4-8 demonstrating improved haemodynamic status. Compared to more accurate CVR-measurements with CO2 application and end-tidal gas analysis,3,12 breath-holds remain a viable alternative being much more tolerable and easily applicable at low costs within clinically feasible scan times.
  • Contribution to proceedings
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan
  • Poster
    The 29th International Symposium on Cerebral Blood Flow, Metabolism and Function, 04.07.2019, Yokohama, Japan

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Publ.-Id: 29521


Human exposure to uranium in South African gold mining areas using barber-based hair sampling

Winde, F.; Geipel, G.; Espina, C.; Schüz, J.
Uranium (U) measurements in water, soil, and food related to gold mining activities in populated areas in Gauteng Province, South Africa, suggest the possibility of exposure levels that may lead to adverse health consequences, including cancer. Theoretical considerations on pathways of human uptake of significant exposures are plausible, but few data on directly measured human exposure are available. A cross-sectional study was conducted using human measurements to compare U levels with other settings around the globe (based on literature review), to explore potential exposure variability within the province, and to test the feasibility of recruiting subjects partially coming from vulnerable and difficult-to-reach populations. Wards of potentially high (HE) and low exposure (LE) were identified. Composite hair samples representing the respective local populations were collected from regular customers of selected barber shops over a period of 1–2 months. A total of 70 U concentrations were determined in 27 composite samples from 1332 individuals. U concentrations ranged from 31 μg/kg to 2524 μg/kg, with an arithmetic mean of 192 μg/kg (standard deviation, 310 μg/kg) and a median of 122 μg/kg. Although HE wards collectively showed higher U levels than LE wards (184 vs 134 μg/kg), differences were smaller than expected. In conclusion, detected U levels were higher than those from most other surveys of the general public. The barber-based approach was an efficient hair collection approach. Composite hair samples are not recommended, due to technical challenges in measuring U, and individual hair samples are needed in follow-up studies to determine predictors of exposure.

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Permalink: https://www.hzdr.de/publications/Publ-29520
Publ.-Id: 29520


Phase Selectivity in Cr and N Co-Doped TiO2 Films by Modulated Sputter Growth and Post-Deposition Flash-Lamp-Annealing

Gago, R.; Prucnal, S.; Hübner, R.; Munnik, F.; Esteban-Mendoza, D.; Jiménez, I.; Palomares, J.
In this paper, we report on the phase selectivity in Cr and N co-doped TiO2 (TiO2:Cr,N) sputtered films by means of interface engineering. In particular, monolithic TiO2:Cr,N films produced by continuous growth conditions result in the formation of a mixed-phase oxide with dominant rutile character. On the contrary, modulated growth by starting with a single-phase anatase TiO2:N buffer layer, can be used to imprint the anatase structure to a subsequent TiO2:Cr,N layer. The robustness of the process with respect to the growth conditions has also been investigated, especially regarding the maximum Cr content (<5 at.%) for single-phase anatase formation. Furthermore, post-deposition flash-lamp-annealing (FLA) in modulated coatings was used to improve the as-grown anatase TiO2:Cr,N phase, as well as to induce dopant activation (N substitutional sites) and diffusion. In this way, Cr can be distributed through the whole film thickness from an initial modulated architecture while preserving the structural phase. Hence, the combination of interface engineering and millisecond-range-FLA opens new opportunities for tailoring the structure of TiO2-based functional materials.
Keywords: TiO2, flash lamp annealing, doping,

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Permalink: https://www.hzdr.de/publications/Publ-29519
Publ.-Id: 29519


P-N Junction-Based Si Biochips with Ring Electrodes for Novel Biosensing Applications

Kiani, M.; Du, N.; Vogel, M.ORC; Raff, J.ORC; Hübner, U.; Skorupa, I.; Bürger, D.; Schulz, S. E.; Schmidt, O. G.; Schmidt, H.
In this work, we report on the impedance of p-n junction-based Si biochips with gold ring top electrodes and unstructured platinum bottom electrodes which allows for counting target biomaterial in a liquid-filled ring top electrode region. The systematic experiments on p-n junction-based Si biochips fabricated by two different sets of implantation parameters (i.e. biochips PS5 and BS5) are studied, and the comparable significant change of impedance characteristics in the biochips in dependence on the number of bacteria suspension, i.e., Lysinibacillus sphaericus JG-A12, in Deionized water with an optical density at 600 nm from OD600 = 4–16 in the electrode ring region is demonstrated. Furthermore, with the help of the newly developed two-phase electrode structure, the modeled capacitance and resistance parameters of the electrical equivalent circuit describing the p-n junction-based biochips depend linearly on the number of bacteria in the ring top electrode region, which successfully proves the potential performance of p-n junction-based Si biochips in observing the bacterial suspension. The proposed p-n junction-based biochips reveal perspective applications in medicine and biology for diagnosis, monitoring, management, and treatment of diseases.
Keywords: Biochips, impedance spectroscopy, electrical equivalent circuit, biomaterial, Lysinibacillus sphaericus JG-A12

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Permalink: https://www.hzdr.de/publications/Publ-29518
Publ.-Id: 29518


Update on the FLUKA geometry modeling

Müller, S.ORC
Update on FLUKA geometry modeling
Keywords: FLUKA, Mu2e
  • Lecture (others)
    Mu2e Simulation Workinggroup Meeting, 18.07.2019, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29516
Publ.-Id: 29516


Update on FLUKA simulation activities for the Mu2e experiment

Müller, S.ORC
Update on the FLUKA simulation for the Mu2e experiment
Keywords: FLUKA, Mu2e
  • Lecture (others)
    Mu2e collaboration meeting, 26.06.2019, Minneapolis, USA

Permalink: https://www.hzdr.de/publications/Publ-29515
Publ.-Id: 29515


Electrovortex liquid metal flows in cells with localized current supply

Kolesnichenko, I.; Frick, P.; Stefani, F.; Eltischev, V.; Weber, N.; Mandrykin, S.; Ozernykh, V.; Khalilov, R.
The paper studies the flow of a liquid metal in a cylindrical cell caused by the action of electromagnetic force. An electric current passes through the metal. The current is locally supplied to the area at the bottom of the cell and discharged at the top. Force generates from the joint action of an electric current and its own magnetic field. The vorticity of the force is nonzero and an electro-vortex flow (EVF) arises. The characteristics of the intensity and oscillations of EVF are studied numerically and experimentally. Methods for contactless determination of the position of the liquid metal boundary have been developed. The possibility of manipulation of the intensity and shape of EVF was studied.
  • Lecture (Conference)
    11th PAMIR International Conference - Fundamental and Applied MHD, 01.07.2019, Reims, Frankreich
  • Contribution to proceedings
    11th PAMIR International Conference - Fundamental and Applied MHD, 01.07.2019, Reims, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-29514
Publ.-Id: 29514


Electro-vortex flow in a cylindrical container

Liu, K.; Li, B. W.; Stefani, F.; Weber, N.; Weier, T.
In a cylindrical container filled with the eutectic alloy GaInSn, an electro-vortex flow (EVF) is caused by the interaction of a non-uniform current with the magnetic field that it generates. In this paper, we investigate the EVF numerically and experimentally. First, based on a solver by Weber, we develop a more advanced one, in which the effect of Joule heating is considered. The magnetic field, which is the combination of the current induced magnetic field and the external geomagnetic field, is also taken into account. For getting a higher computational efficiency, the so-called parent-child mesh technique is applied in OpenFOAM. Second, we conduct an experiment corresponding to the numerical simulation, in which Ultrasound Doppler Velocimetry (UDV) is applied for flow measurements. The results of the experiment are in good agreement with those of the simulation.
Keywords: electro-vortex flow, Joule heating, parent-child mesh, OpenFOAM
  • Contribution to proceedings
    11th PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich
  • Poster
    11th PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-29513
Publ.-Id: 29513


Novel Thyristor-Based Pulsed Current Converter for a Medical Application - a Conceptual Introduction

Wettengel, S.; Lindenmueller, L.; Bernet, S.; Schramm, U.ORC; Kroll, F.ORC; Brack, F.-E.ORC; Pawelke, J.
A novel ion beam radiation therapy apparatus employing pulsed high magnetic field coils for transporting the ion beam has been proposed. In this paper a new pulsed current converter topology is introduced, which can be used as a pulsed power supply for the therapy apparatus. Thyristors are selected as the semiconductors used in the pulsed current converter. Since the planned operating point is outside of the typical range of the semiconductors, research has been done to predict their behavior during turn-off (the most critical phase of the pulse). A behavioral model has been derived and experimentally parametrized to predict the turn-off behavior and to optimize snubber design.
  • Contribution to proceedings
    PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 05.-07.06.2018, Nuremberg, Germany
    PCIM Europe 2018; International Exhibition and Conference for Power Electronics, Intelligent Motion, Renewable Energy and Energy Management, 978-3-8007-4646-0

Permalink: https://www.hzdr.de/publications/Publ-29512
Publ.-Id: 29512


A Statistical Approach for Analysis of Dissolution Rates Including Surface Morphology

Pedrosa, E. P.; Kurganskaya, I.; Fischer, C.; Luttge, A.
Understanding mineral dissolution is relevant for natural and industrial processes that involve the interaction of crystalline solids and fluids. The dissolution of slow dissolving minerals is typically surface controlled as opposed to diffusion/transport controlled. At these conditions, the dissolution rate is no longer constant in time or space, an outcome observed in rate maps and correspondent rate spectra. The contribution and statistical prevalence of different dissolution mechanisms is not known. Aiming to contribute to close this gap, we present a statistical analysis of the variability of calcite dissolution rates at the nano- to micrometer scale. A calcite-cemented sandstone was used to perform flow experiments. Dissolution of the calcite-filled rock pores was measured using vertical scanning interferometry. The resultant types of surface morphologies influenced the outcome of dissolution. We provide a statistical description of these morphologies and show their temporal evolution as an alternative to the lack of rate spatial variability in rate constants. Crystal size impacts dissolution rates most probably due to the contribution of the crystal edges. We propose a new methodology to analyze the highest rates (tales of rate spectra) that represent the formation of deeper etch pits. These results have application to the parametrization and upscaling of geochemical kinetic models, the characterization of industrial solid materials and the fundamental understanding of crystal dissolution.
Keywords: dissolution kinetics; calcite; surface morphology;

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Permalink: https://www.hzdr.de/publications/Publ-29511
Publ.-Id: 29511


Numerical simulation of electrovortex flows in cylindrical fluid layers and liquid metal batteries

Herreman, W.; Nore, C.; Ziebell Ramos, P.; Cappanera, L.; Guermond, J.-L.; Weber, N.
We use the multiphase magnetohydrodynamic code SFEMaNS to study the generation of electrovortex flows in liquid metal batteries. We first reproduce some well known results in a single-phase liquid metal column and then we characterize the electrovortex flow in layered multiphase fluid systems. A simple energy density balance argument accurately estimates the typical interface deformation caused by the electrovortex flow. When applied to Mg-Sb liquid metal batteries, we find that the electrovortex flows may have the capacity to cause short-circuits even in moderate size batteries with radii in the range [10, 20] cm.

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Permalink: https://www.hzdr.de/publications/Publ-29510
Publ.-Id: 29510


Exploring new materials for optical thermometric sensing

Sharma, S.ORC; Beyer, J.; Fuchs, M.; Gloaguen, R.; Heitmann, J.
The luminescence intensity ratio (LIR) of emission from two thermally coupled excited states is one of the most popular temperature sensing schemes, which has proven to be reliable due to its non-invasive nature, minimal dependence on the measurement conditions, and high temperature-spatial resolution. However, it requires a special design effort to obtain stable luminescence emission, which can be used for any practical application, for example, optical thermometric sensing. In this work, we present our results on the influence of excitation-emission processes on the dynamical behaviour of charges, and their temperature dependence in a wide temperature range (300-870 K), on a single crystal of EuPO4. The EuPO4 host which previously did not appear suitable for temperature sensing, was successfully converted to a highly sensitive optical temperature sensor, by following appropriate experimental strategy. The coupling of two excited states of Eu3+ showed a relative sensitivity of 2.00 %K-1, while, the coupling between two ground states of Eu3+ showed a relative sensitivity of 0.34 %K-1. The results suggest that by optimizing experimental parameters, highly sensitive optical thermometric sensors can be prepared, with ease.
  • Lecture (Conference)
    2019 Spring Meeting of the European Materials Research Society (E-MRS), 27.-31.05.2019, Nice, France

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Permalink: https://www.hzdr.de/publications/Publ-29509
Publ.-Id: 29509


A Machine Learning Framework for Drill-Core Mineral Mapping Using Hyperspectral and High-Resolution Mineralogical Data Fusion

Contreras Acosta, I. C.ORC; Khodadadzadeh, M.; Tusa, L.; Ghamisi, P.; Gloaguen, R.
Mining companies heavily rely on drill-core samples during exploration campaigns as they provide valuable geological information to target important ore accumulations. Traditional core logging techniques are time-consuming and subjective. Hyperspectral (HS) imaging, an emerging technique in the mining industry, is used to complement the analysis by rapidly characterizing large amounts of drill-cores in a nondestructive and noninvasive manner. As the accurate analysis of drill-core HS data is becoming more and more important, we explore the use of machine learning techniques to improve speed and accuracy, and help to discover underlying relations within large datasets. The use of supervised techniques for drill-core HS data represents a challenge since quantitative reference data is frequently not available. Hence, we propose an innovative procedure to fuse high-resolution mineralogical analysis and HS data. We use an automatic high-resolution mineralogical imaging system (i.e., scanning electron microscopy-mineral liberation analysis) for generating training labels. We then resample the MLA image to the resolution of the HS data and adopt a soft labeling strategy for mineral mapping. We define the labels for the classes as mixtures of geological interest and use the classifiers (random forest and support vector machines) to map the entire drill-core. We validate our framework qualitatively and quantitatively. Thus, we demonstrate the ability of the proposed technique to fuse and up-scale high-resolution mineralogical analysis with drill-core HS data.
Keywords: Data fusion, drill-cores, hyperspectral (HS) data, machine learning, mineral liberation analysis (MLA), random forest (RF), support vector machine (SVM)
  • IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (2020)
    Online First (2019) DOI: 10.1109/JSTARS.2019.2924292

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Permalink: https://www.hzdr.de/publications/Publ-29508
Publ.-Id: 29508


Characterization of the rotenone mouse model of Parkinson’s disease using radioligands for the adenosine A2A receptor ([18F]FESCH) and the nicotinic α4β2 receptor ((‐)‐[18F]Flubatine)

Toussaint, M.; Kranz, M.; Schröder, S.; Lai, T. H.; Deuther-Conrad, W.; Dukic‐Stefanovic, S.; Shang, Q.; Patt, M.; Reichmann, H.; Funk, R.; Sabri, O.; Pan‐Montojo, F.; Brust, P.
Objectives
Rotenone-treated mice are regarded as a model for Parkinson´s disease (PD). Increased availability of the adenosine A2A receptor (A2AR) and decreased availability of the α4β2 nicotinic acetylcholine receptor (nAChR) have been found in the striatum and thalamus, respectively, of patients with PD [1,2]. Therefore, we evaluated the potential of [18F]FESCH (for A2AR) and (-)-[18F]Flubatine (for α4β2nAChR) to characterize similar receptor changes in the mouse model of PD with small animal PET/MR imaging.
Methods
Two groups of 18-months-old male C57BL/6JRj mice (28-35 g) (Janvier labs, France) were investigated: a control group (n=5) treated with a vehicle solution (2% carboxymethyl cellulose, 1.25% chloroform) and a PD group (n=7) treated with rotenone (Sigma-Aldrich, Germany) during 4 months (5 days/week, 5 mg/kg p.o.). [18F]FESCH (5.0±1.8 MBq; Am: 116±19 GBq/µmol, EOS) or (-)-[18F]Flubatine (6.5±2.4 MBq; Am: 1080±2156 GBq/µmol, EOS) were injected intravenously followed by 60 min dynamic PET scans (Mediso nanoScan®, PET/MRI 1T, Hungary). Time-activity curves from the striatum, cerebellum, and thalamus were analyzed (PMOD v3.9, PMOD Technologies LLC, Switzerland). The cerebellum was used as a reference tissue.
Results
PET scans revealed high uptake of (-)-[18F]Flubatine in thalamus (SUV ~3.5 at 40 min p.i.) and considerably lower uptake in cerebellum (SUV ~1.2 at 40 min p.i.). The SUV ratio (SUVR) thalamus/cerebellum, indicating specific radiotracer binding, is significantly decreased in the rotenone-treated group compared to the control (Figure 1A).
Also for [18F]FESCH much higher uptake was observed in striatum (SUV ~0.9 at 5 min p.i.) compared to cerebellum (SUV ~0.2 at 5 min p.i.). Although not significant for this rather small and highly variable data set, the SUVR striatum/cerebellum is increased in the rotenone-treated group compared to the control suggesting a higher specific binding in striatum (Figure 1B). These findings are in accordance with a recent publication [3].
Conclusion
We have established a concordance between clinical imaging findings in PD and small animal PET/MR in rotenone-treated mice. Thus, we assume the rotenone mouse model to be suitable for further investigation of molecular aspects of PD in particular related to A2AR and α4β2nAChR.
Acknowledgments
The European Regional Development Fund and Sächsische Aufbaubank are acknowledged for financial support (Project No. 100226753).
References
[1] Vuorimaa et al. Contrast Media Mol Imaging 2017; 6975841. [2] Meyer et al., Arch Gen Psych 2009, 66: 866-877. [3] Khanapur et al., J Nucl Med 2017; 58: 466–472.
Keywords: Parkinson disease; adenosine A2A receptor; α4β2 nicotinic acetylcholin receptor, rotenone model; [18F]FESCH; [18F]Flubatine
  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-29507
Publ.-Id: 29507


Landscape dynamics and human-environment interactions in the northern foothills of Cho Oyu and Mount Everest (southern Tibet) during the Late Pleistocene and Holocene

Meyer, M.; Gliganic, L. A.; May, J.-H.; Merchel, S.ORC; Rugel, G.; Schlütz, F.; Aldenderfer, M.; Krainer, K.
Here we present an integrated earth surface process and paleoenvironmental study from the Tingri graben and the archaeological site of Su-re, located on the southern rim of the Tibetan plateau, spanning the past ca. 30 ka. The study area is characterized by cold climate earth surface processes and aridity due to its altitude and location in the rain shadow of the Mount Everest–Cho Oyu massif and is thus sensitive to climatic and anthropogenic perturbations. During the global last glacial maximum (gLGM) glaciers from the main Himalaya range advanced into the Tingri graben and deposited massive hummocky moraines, while the zone of discontinuous permafrost was depressed by ~450 m relative to today, greatly intensifying permafrost and periglacial hillslope processes and leading to fluvial aggradation of the valley floors of ≥12 m. We observe formation of a thick (≥50 cm) pedo-complex starting at ca. 6.7 ka before present (BP) and erosional truncation at ca. 3.9 ka BP. Widespread landscape instability and erosion characterize the region subsequent to 3.9 ka and intensifies in the 15th century AD. Several lines of (geo)archaeological evidence, including the presence of pottery sherds, sling-shot projectiles and hammer stones within the sedimentary record, indicate human presence at Su-re since ca. 3.9 ka BP. Our data suggest that in the Su-re-Tingri area climatic conditions were warm and moist enough to allow vegetation expansion and soil formation only from ca. 6.7-3.9 ka, followed by weakening of the Indian summer monsoon (ISM) strength between ca. 3.9 and 4.2 ka, which is a prominent climatic event in the wider Asian monsoon region, and reflected in the investigation area by the 3.9 ka erosional boundary. Merging our Holocene landscape reconstruction with the geoarchaeological evidence, we speculate that the combined effect of Little Ice Age (LIA) cooling and an anthropogenic overuse of the landscape led to climatically induced landscape degradation and ultimately to an anthropogenically triggered ecological collapse in the 15th century. Such a scenario is in-line with regional historical data on declining monastery construction and migration of the ethnic group of the Sherpas. From an earth surface dynamics perspective, we find that short-term transient landscape processes on the southern rim of the Tibetan plateau are strongly linked to millennial scale changes in the ISM intensity and duration. We identify three types of unidirectional non-linear ISM-landscape interactions. Given that the Tibetan plateau is the largest high-altitude landmass on our planet and our limited understanding of several of the key earth surface processes on the plateau, we pinpoint the need for more long-term (Quaternary scale) empirical data particularly on permafrost and periglacial processes and human-environment interactions.
Keywords: Tibet; monsoon; periglacial; permafrost; optical methods; cosmogenic isotopes; landscape degradation; Holocene; Pleistocene

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Predicting in Vitro Cancer Cell Survival Based on Measurable Cell Characteristics

Oesten, H.; Neubeck, C. V.; Jakob, A.; Enghardt, W.; Krause, M.; Mcmahon, S. J.; Grassberger, C.; Paganetti, H.; Lühr, A.
Variation in cellular characteristics may determine tumor response and, consequently, patient survival in radiation therapy. However, patient-specific prediction of cellular radiation response is currently unavailable for treatment planning. Thus, the importance of developing a novel approach based on clinically accessible parameters prior to treatment (e.g., by biopsy) is high. The goal of this study was to predict in vitro cancer cell survival through the p53mutation status and the number of chromosomes (NoC). To predict cell survival, we modified a mechanistic radiation response model incorporating DNA repair and cell death, originally designed for normal human cells. Cell-specific parameters of 24 cell lines originating from two laboratories (OncoRay, Dresden, Germany and HIMAC, Chiba, Japan) were considered for modeling. In a first step, we obtained estimates of the only unknown model input parameter genome size (GS) by fitting cell survival simulations onto experimental data. We then analyzed measured and published input model parameters (NoC, p53-mutation status and cell-cycle distribution) to assess their impact on measured and simulated parameters (modeled GS, and measured α, β, SF2 and H2AX). The resulting data suggested a linear correlation between NoC and modeled GS (R2 > 0.93) allowing for estimating GS based on NoC. Applying the estimated GS resulted in predicted cell survival that matched measured data mostly within the experimental uncertainty. The measured radiobiological value β increased quadratically with the cell's modeled GS irrespective of other cell-specific parameters. The measured α and SF2 split into two groups, depending on the cells' p53-mutation status, both linearly increasing and decreasing, respectively, with modeled GS. Model predictions of foci numbers were, on average, in agreement with published H2AX measurement data. In conclusion, knowledge of clinically accessible parameters (p53-mutation status and NoC) may support patient stratification in radiotherapy based on cell-specific survival prediction testable in prospective clinical trials. © 2019 by Radiation Research Society. All rights of reproduction in any form reserved.

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Challenges and caveats of a multi-center retrospective radiomics study: An example of early treatment response assessment for NSCLC patients using FDG-PET/CT radiomics

van Timmeren, J.-E.; Carvalho, S.; Leijenaar, R. T. H.; Troost, E. G. C.; van Elmpt, W.; de Ruysscher, D.; Muratet, J. P.; Denis, F.; Schimek-Jasch, T.; Nestle, U.; Jochems, A.; Woodruff, H. C.; Oberije, C.; Lambin, P.
Background Prognostic models based on individual patient characteristics can improve treatment decisions and outcome in the future. In many (radiomic) studies, small size and heterogeneity of datasets is a challenge that often limits performance and potential clinical applicability of these models. The current study is example of a retrospective multi-centric study with challenges and caveats. To highlight common issues and emphasize potential pitfalls, we aimed for an extensive analysis of these multi-center pre-treatment datasets, with an additional 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/ CT) scan acquired during treatment. Methods The dataset consisted of 138 stage II-IV non-small cell lung cancer (NSCLC) patients from four different cohorts acquired from three different institutes. The differences between the cohorts were compared in terms of clinical characteristics and using the so-called ‘cohort differences model’ approach. Moreover, the potential prognostic performances for overall survival of radiomic features extracted from CT or FDG-PET, or relative or absolute differences between the scans at the two time points, were assessed using the LASSO regression method. Furthermore, the performances of five different classifiers were evaluated for all image sets. Results The individual cohorts substantially differed in terms of patient characteristics. Moreover, the cohort differences model indicated statistically significant differences between the cohorts. Neither LASSO nor any of the tested classifiers resulted in a clinical relevant prognostic model that could be validated on the available datasets. Conclusion The results imply that the study might have been influenced by a limited sample size, heterogeneous patient characteristics, and inconsistent imaging parameters. No prognostic performance of FDG-PET or CT based radiomics models can be reported. This study highlights the necessity of extensive evaluations of cohorts and of validation datasets, especially in retrospective multi-centric datasets.

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Magnetoelastic coupling across the field-induced transition of uranium mononitride

Gorbunov, D.; Nomura, T.; Zvyagin, A. A.; Henriques, M. S.; Andreev, A. V.; Skourski, Y.; Zvyagina, G. A.; Troc, R.; Zherlitsyn, S.; Wosnitza, J.
Uranium mononitride (UN) displays a spin-flop-like transition for magnetic field applied along all principal crystallographic directions just below 60 T. Here, we report on ultrasound and magnetocaloric-effect results for UN in pulsed magnetic fields up to 65 T. The field-induced phase transition causes a discontinuous temperature decrease, indicating a larger magnetic entropy above the transition. Furthermore, we find pronounced anomalies in the acoustic properties, which signals strong spin-lattice interactions. A further anomaly observed at fields slightly above the transition is likely related to the formation of magnetic domains. A model based on the exchange-striction coupling mechanism well reproduces the strong renormalization of the acoustic properties.

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Publ.-Id: 29502


Early and late side effects, dosimetric parameters and quality of life after proton beam therapy and IMRT for prostate cancer: a matched-pair analysis

Dutz, A.; Agolli, L.; Baumann, M.; Troost, E. G. C.; Krause, M.; Hölscher, T.; Löck, S.
Purpose: To compare early and late toxicities, dosimetric parameters and quality of life (QoL) between conventionally fractionated proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) in prostate cancer (PCA) patients. Methods: Eighty-eight patients with localized PCA treated between 2013 and 2017 with either definitive PBT (31) or IMRT (57) were matched using propensity score matching on PCA risk group, transurethral resection of the prostate, prostate volume, diabetes mellitus and administration of anticoagulants resulting in 29 matched pairs. Early and late genitourinary (GU) and gastrointestinal (GI) toxicities according to Common Terminology Criteria for Adverse Events (CTCAE) and QoL based on EORTC-QLQ-C30/PR25 questionnaires were collected prospectively until 12 months after radiotherapy (RT). Associations between toxicities and dose–volume parameters in corresponding organs at risk (OARs) were modeled by logistic regression. Results: There were no significant differences in GI and GU toxicities between both treatment groups except for late urinary urgency, which was significantly lower after PBT (IMRT: 25.0%, PBT: 0%, p =.047). Late GU toxicities and obstruction grade ≥2 were significantly associated with the relative volume of the anterior bladder wall receiving 70 Gy and the entire bladder receiving 60 Gy, respectively. The majority of patients in both groups reported high functioning and low symptom scores for the QoL questionnaires before and after RT. No or little changes were observed for most items between baseline and 3 or 12 months after RT, respectively. Global health status increased more at 12 months after IMRT (p =.040) compared to PBT, while the change of constipation was significantly better at 3 months after PBT compared to IMRT (p =.034). Conclusions: Overall, IMRT and PBT were well tolerated. Despite the superiority of PBT in early constipation and IMRT in late global health status compared to baseline, overall QoL and the risks of early and late GU and GI toxicities were similar for conventionally fractionated IMRT and PBT.

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Publ.-Id: 29501


Successive Trimming of a Permalloy Stripe to enhance the localized Edge Mode Spectrum probed by Ferromagnetic Resonance

Lenz, K.ORC; Schneider, T.; Hlawacek, G.; Narkowicz, R.; Stienen, S.; Lenz, M.; Lindner, J.
Finite-size effects in ultrathin magnetic films are a well-known feature. They usually play a role, when the surface and interface layers dominate over the volume contribution of the sample and have different properties, due to roughness, texture, hybridization, modified magnetic moment, or dipolar fields. For micro- and especially nanostructures these effects might be there as well—but at the side walls. Regarding the magnetization dynamics these effects lead to additional spin wave modes, e.g. localized spin wave modes (edge modes). It has been shown that these edge modes are influenced by the quality of the side walls, namely by angled side walls, edge roughness, beveled edges, or even magnetic dilution [1]. As these structures have to be prepared by means of lithography involving masks a certain edge roughness or even side wall slope are inevitable. Nevertheless, when it comes to micromagnetic simulations to corroborate or explain measurements these contributions are usually excluded from the model. Here we show, how successive trimming the sides of a 5 µm x 1 µm Permalloy stripe by a focused Ne ion beam improves the spin wave spectrum and enhances the edge mode spectrum as probed by ferromagnetic resonance (FMR). To achieve the sensitivity to detect the FMR of the weak edge modes of a single Permalloy stripe we use planar microresonator FMR [2,3]. The experimental results are corroborated by micromagnetic simulations. Including just edge roughness of ~4 nm (rms) in the simulations is enough to perfectly match the FMR experimental data. The residual edge roughness is in the order of the grain size of the polycrystalline permalloy. Although the focused ion beam and its motion are able to cut the side walls perfectly straight and vertical with sub-nm precision, the Ne ions penetrate the side wall up to 15 nm (called straggling). This is due to the collision cascade with the Ni and Fe atoms of the Permalloy causing possible lateral damage of the Permalloy lattice. Hence, we attribute the residual roughness to the ion induced damage by the lateral penetration during trimming of the side walls, and a small remaining edge roughness due to changes in sputter yield for differently oriented Permalloy grains.

[1] R.D. McMichael, B.B. Maranville, Phys. Rev. B 74,024424 (2006).
[2] A. Banholzer et al., Nanotechnology 22, 295713 (2011).
[3] R. Narkowicz et al., Rev. Sci. Instrum. 79, 084702 (2008).
Keywords: Magnetic nanostructures, ferromagnetic resonance, spin waves, edge modes, HIM
  • Poster
    International Conference on Magnetism ICM 2018, 15.-20.07.2018, San Francisco, United States of America
  • Poster
    9th Joint European Magnetic Symposia, JEMS 2018, 03.-07.09.2018, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29500
Publ.-Id: 29500


Turbulent Multiphase CFD Modelling: State-of-the-art applications in Nuclear Engineering

Höhne, T.
Two-phase flows occur in many industrial-relevant processes in power plants, chemical engineering, oil and gas industries and others.
Reliable predictions of the flow characteristics are important for the design of the facilities, the optimization of processes and safety analyses.
Experimental results are often hardly transferable to modified geometries, flow condition or scales.
Keywords: CFD, AIAD, GENTOP, Multiphase
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Permalink: https://www.hzdr.de/publications/Publ-29499
Publ.-Id: 29499


Colloidal Mercury-Doped CdSe Nanoplatelets with Dual Fluorescence

Galle, T.; Kazes, M.; Hübner, R.; Lox, J.; Khoshkhoo, M. S.; Sonntag, L.; Tietze, R.; Sayevich, V.; Oron, D.; Koitzsch, A.; Lesnyak, V.; Eychmüller, A.
Quasi-two-dimensional (2D) CdSe nanoplatelets (NPLs) are distinguished by their unique optical properties in comparison to classical semiconductor nanocrystals, such as extremely narrow emission line widths, reduced Auger recombination, and relatively high absorption cross sections. Inherent to their anisotropic 2D structure, however, is the loss of continuous tunability of their photoluminescence (PL) properties due to stepwise growth. On top of that, limited experimental availability of NPLs of different thicknesses and ultimately the bulk band gap of CdSe constrain the achievable PL wavelengths. Here, we report on the doping of CdSe NPLs with mercury, which gives rise to additional PL in the red region of the visible spectrum and in the near-infrared region. We employ a seeded-growth method with injection solutions containing cadmium, selenium, and mercury. The resulting NPLs retain their anisotropic structure, are uniform in size and shape, and present significantly altered spectroscopic characteristics due to the existence of additional energetic states. We conclude that doping takes place by employing elemental analysis in combination with PL excitation spectroscopy, X-ray photoelectron spectroscopy, and single-particle fluorescence spectroscopy, confirming single emitters being responsible for multiple distinct emission signals.

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Publ.-Id: 29498


Trimming of permalloy stripes to enhance the localized edge mode spectrum probed by ferromagnetic resonance

Lenz, K.ORC; Schneider, T.; Hlawacek, G.; Narkowicz, R.; Stienen, S.; Kákay, A.; Lenz, M.; Fassbender, J.; Lindner, J.
Finite-size effects in ultrathin magnetic films are a well-known feature, i.e., when the surface or interfaces dominate the volume of the sample due to different roughness, texture, hybridization, modified magnetic moment, or dipolar fields. For nanostructures these effects could arise at the side walls as well. This leads to localized spin wave modes (edge modes).
It has been shown that the quality of the side walls (angled side walls or roughness) influence these modes [1]. During preparation of samples by lithography a certain edge roughness and side wall slope are sometimes inevitable. Nevertheless, in micromagnetic simulations these contributions are usually excluded from the model. We show, how successive trimming the sides of a 5 μm x 1 μm Permalloy stripe by a focused Ne ion beam improves the spin wave spectrum and enhances the edge mode spectrum as probed by planar microresonator ferromagnetic resonance (FMR) [2,3] as depicted in Figure 1. Including an rms edge roughness of ~2 nm (within the order of the permalloy grain size) in the simulations is enough to match the FMR data. Hence, we attribute the residual roughness to the ion induced damage by the lateral penetration during trimming of the side walls, and a small remaining edge roughness due to changes in the sputter yield for differently oriented Permalloy grains.
Keywords: ferromagnetic resonance, nanostructures, trimming, HIM, FMR, edge modes, spin waves
  • Poster
    Magnonics 2019, 28.07.-01.08.2019, Carovigno, Italy

Permalink: https://www.hzdr.de/publications/Publ-29497
Publ.-Id: 29497


Direct measurements of the magneto-caloric effect of MnFe4Si3 in pulsed magnetic fields

Maraytta, N.; Skourski, Y.; Voigt, J.; Friese, K.; Herrmann, M. G.; Perßon, J.; Wosnitza, J.; Salman, S. M.; Brückel, T.
We have studied the magnetic and magnetocaloric response of MnFe4Si3 to pulsed and static magnetic fields up to 50 T. We determine the adiabatic temperature change ΔTad directly in pulsed fields and compare to the results of magnetization and specific heat measurements in static magnetic fields. The high ability of cycling even in fields μ0H = 50 T confirms the high structural stability of MnFe4Si3 against field changes, an important property for applications. The magnetic response to magnetic fields up to μ0H = 35 T shows that the anisotropy can be overcome by fields of approx. 4 T.

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Publ.-Id: 29496


Magnetic structure and spin waves in the frustrated ferro-antiferromagnet Pb2VO(PO4)2

Bettler, S.; Landolt, F.; Aksoy, Ö. M.; Yan, Z.; Gvasaliya, S.; Qiu, Y.; Ressouche, E.; Beauvois, K.; Raymond, S.; Ponomaryov, A. N.; Zvyagin, S. A.; Zheludev, A.
Single crystal neutron diffraction, inelastic neutron scattering, and electron spin resonance experiments are used to study the magnetic structure and spin waves in Pb2VO(PO4)2, a prototypical layered S = 1/2 ferromagnet with frustrating next-nearest neighbor antiferromagnetic interactions. The observed excitation spectrum is found to be inconsistent with a simple square lattice model previously proposed for this material. At least four distinct exchange coupling constants are required to reproduce the measured spin wave dispersion. The degree of magnetic frustration is correspondingly revised and found to be substantially smaller than in all previous estimates.

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Publ.-Id: 29495


Numerical study of simultaneous heat and mass transfer in Liquid Metal Batteries

Personnettaz, P.; Weber, N.; Weier, T.
Liquid metal batteries (LMBs) are promising candidates for electrical energy storage. An LMB is a concentration cell made of three liquid layers, stably stratified by density. A molten salt acts as an electrolyte between two liquid metal electrodes. The simple chemistry and geometry, the liquid nature of the active layers and the presence of multi-physics phenomena have made the LMB an intriguing candidate for continuum mechanics investigations. Simultaneous transport of charge, heat, mass and momentum takes place in each liquid layer together with chemical reactions. The interfaces between layers are the places in which electrochemical reactions occur along with interfacial transport phenomena.
In our work we investigate heat and mass transport in LMBs with openFOAM libraries using a multi-region approach. We assign to each layer a numerical region and we design a procedure able to ensure the physical coupling between the different transport mechanisms through an iterative procedure. The heat and mass transfer equations are solved on a global mesh and in the positive electrode region respectively. Then we solve the Navier-Stokes equations in each fluid region. Appropriate boundary conditions were designed to ensure a consistent transport at the interfaces between different regions. Thanks to this procedure we can compute temperature and concentration distributions and the corresponding thermal and compositional convection. Therefore, we can investigate the interaction of different mechanisms and can give a prediction of the fluid flow in the interior of an LMB. The numerical procedure is introduced as well as the first results. Furthermore, the modeling limitations and the future developments are discussed.
Keywords: Liquid metal battery, openFOAM, mass transport, heat transfer, transport phenomena
  • Poster
    OpenFOAM Workshop 2019, 23.-26.07.2019, Duisburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29494
Publ.-Id: 29494


A semiconducting layered metal-organic framework magnet

Yang, C.; Dong, R.ORC; Wang, M.ORC; Petkov, P. S.ORC; Zhang, Z.ORC; Wang, M.; Han, P.ORC; Ballabio, M.; Bräuninger, S. A.; Liao, Z.; Zhang, J.ORC; Schwotzer, F.; Zschech, E.; Klauss, H.-H.; Cánovas, E.; Kaskel, S.ORC; Bonn, M.; Zhou, S.ORC; Heine, T.ORC; Feng, X.
The realization of ferromagnetism in semiconductors is an attractive avenue for the development of spintronic applications. Here, we report a semiconducting layered metal-organic framework (MOF), namely K3Fe2[(2,3,9,10,16,17,23,24-octahydroxy phthalocyaninato)Fe] (K3Fe2[PcFe-O8]) with spontaneous magnetization. This layered MOF features in-plane full π-d conjugation and exhibits semiconducting behavior with a room temperature carrier mobility of 15 ± 2 cm2 V−1 s−1 as determined by time-resolved Terahertz spectroscopy. Magnetization experiments and 57Fe Mössbauer spectroscopy demonstrate the presence of long-range magnetic correlations in K3Fe2[PcFe-O8] arising from the magnetic coupling between iron centers via delocalized π electrons. The sample exhibits superparamagnetic features due to a distribution of crystal size and possesses magnetic hysteresis up to 350 K. Our work sets the stage for the development of spintronic materials exploiting magnetic MOF semiconductors.

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Publ.-Id: 29493


Strain-induced perpendicular magnetic anisotropy and Gilbert damping of Tm3Fe5O12 thin films

Ciubotariu, O.; Semisalova, A.; Lenz, K.ORC; Albrecht, M.
In the attempt of implementing iron garnets with perpendicular magnetic anisotropy (PMA) in spintronics, the attention turned towards strain-grown iron garnets. One candidate is Tm3Fe5O12 (TmIG) which possesses an out-of-plane magnetic easy axis when grown under tensile strain. In this study, the effect of film thickness on the structural and magnetic properties of TmIG films including magnetic anisotropy, saturation magnetization, and Gilbert damping is investigated. TmIG films with thicknesses between 20 and 300 nm are epitaxially grown by pulsed laser deposition on substituted-Gd3Ga5O12(111) substrates. Structural characterization shows that films thinner than 200 nm show in-plane tensile strain, thus exhibiting PMA due to strain-induced magnetoelastic anisotropy. However, with increasing film thickness a relaxation of the unit cell is observed resulting in the rotation of the magnetic easy axis towards the sample plane due to the dominant shape anisotropy. Furthermore, the Gilbert damping parameter is found to be in the range of 0.02 ± 0.005.
Keywords: Thulium iron garnet, magnetic anisotropy, Gilbert damping
  • Open Access Logo Scientific Reports 9(2019), 17474
    DOI: 10.1038/s41598-019-53255-6
  • Poster
    Magnonics 2019, 28.07.-01.08.2019, Carovigno, Italy
  • Poster
    MMM 2019 - Annual Conference on Magnetism and Magnetic Materials, 04.-08.11.2019, Las Vegas, United States of America

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Publ.-Id: 29492


Theranostic CAR T cell targeting: A brief review

Arndt, C.; Bachmann, M.; Bergmann, R.; Berndt, N.; Feldmann, A.; Koristka, S.
More than 100 years ago Paul Ehrlich postulated that our immun system should be able to eliminate tumor cells. Just recently, the development of check point inhibitors, bispecific antibodies, and T cells genetically modified to express chimeric antigen receptors (CARs) underlines the true power of our immune system. T cells genetically modified with CARs can lead to complete remission of malignant hematologic diseases. However, they can also cause life-threatening side effects. In case of cytokine release syndrome, tumor lysis syndrome, or deadly side effects on the central nervous system, an emergency shut down of CAR T cells is needed. Targeting of tumor-associated antigens that are also expressed on vital tissues require a possibility to repeatedly switch the activity of CAR T cells on and off on demand and to follow the treatment by imaging. Theranostic, modular CARs such as the UniCAR system may help to overcome these problems.
Keywords: bispecific antibody, BiTE, chimeric antigen receptor, immunotherapy, T cells, UniCAR
  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 62(2019)8, 533-540
    DOI: 10.1002/jlcr.3727

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Permalink: https://www.hzdr.de/publications/Publ-29490
Publ.-Id: 29490


Electronic Properties of a New Family of Layered Materials from Groups 14-15: First-Principles Simulations

Ramzan, M. S.; Bacic, V.; Jing, Y.; Kuc, A.
Variaty of 2D layered materials has gain tremendous focus of materials scientists, physics, chemistry, and other fields of science. This is due to the fact that thin films of layered materials often exhibit superior (for a given application) properties than the parental bulk materials. Thus, in this work, we studied a new family of layered materials with a general composition of XY3 (where X and Y are elements from Group-14 and 15, respectively). Among the proposed materials, 3D bulk structures of layered GeP3 and SnP3 are stable, metallic, and already synthesized in the 1970s. We calculated cleavage energies of mono- and bilayers to be less than 1 J m-2, what indicates possibility of exfoliation from the bulk materials. Many of the investigated monolayers are mechanically and thermally stable. Electronic structure calculations indicate strong interlayer quantum confinement and consequently a metal-to-semiconductor transition when going from bulk to a mono- or bilayer. These electronic properties promise interesting applications in nanoelectronic devices.

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  • Secondary publication expected from 25.09.2020

Permalink: https://www.hzdr.de/publications/Publ-29488
Publ.-Id: 29488


Structural modifications and thermal stability of Cd2+ -exchanged stellerite, a zeolite with STI framework-type

Cametti, G.; Scheinost, A. C.; Churakov, S. V.
The structure and thermal stability of a Cd2+-exchanged zeolite with STI framework type was investigated by combining single crystal X-ray diffraction (SCXRD), ab initio molecular dynamic (MD) simulations and X-ray absorption fine structure spectroscopy (XAFS). The room temperature structure was found to be monoclinic, space group F2/m. The Cd2+ ions were disordered at partially occupied sites with maximum occupancy of 0.38(2). MD simulations and XAFS spectroscopy indicated that Cd forms Cd(H2O) 2+6 complexes distributed within the t-sti-1* cage running parallel to [100]. The dehydration was monitored in situ by SCXRD. Upon heating a new contracted phase was observed at 225 C. Compared to the pristine material, the Cd2+-exchanged
structure started collapsing already at 325 C, pointing out a reduced thermal stability.
Keywords: zeolite molecular dynamics EXAFS stellerite

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  • Secondary publication expected from 20.09.2020

Permalink: https://www.hzdr.de/publications/Publ-29487
Publ.-Id: 29487


Spatial solitons in KTaxNb1-xO3 waveguides produced by swift carbon ion irradiation and femtosecond laser ablation

He, S.; Zhang, Z.; Liu, H.; Akhmadaliev, S.; Zhou, S.; Wang, X.; Wu, P.
We report on the fabrication of planar waveguide and ridge waveguides in a KTN crystal by using swift heavy C5+ ions irradiation and femtosecond laser ablation. The reconstructed refractive index profile of the irradiated KTN waveguide illustrates an optical well and barrier distribution. The confocal Raman spectra suggest that the enhanced tetragonality and the lattice damage occurs in the waveguide region and the optical barrier area, respectively. The optical spatial solitons at 632.8 nm are observed from the planar waveguide and the ridge waveguides with a width of 60 μm and 20 μm, respectively, at room temperature.

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  • Secondary publication expected from 26.06.2020

Permalink: https://www.hzdr.de/publications/Publ-29486
Publ.-Id: 29486


Defect-induced magnetism in SiC

Zhou, S.ORC; Chen, X.
Defect-induced magnetism describes a magnetic phenomenon in materials containing neither unpaired 3d nor 4f  electrons. Therefore, it presents a challenge to the conventional understanding of magnetism and has remained under debate for over a decade. Different from graphite and oxides which are common research venues in defect-induced magnetism, SiC is commercially available at large scale and with high quality at the microelectronic grade. Therefore, SiC presents a suitable model system for studying defect-induced ferromagnetism and exploring possible applications. Understanding and controlling defect-induced magnetism in a semiconductor like SiC opens up the possibility for producing spintronic devices based on classical semiconductor technologies. Here, we review recent studies on defect-induced magnetism in SiC. We start with a brief description about defects in SiC. Then we summarize the experimental results on defect-induced magnetism in SiC, the microscopic origin of the magnetism and the magnetic coupling mechanism. We also propose several potential applications, particularly using magnetometry as a complementary method for quantitative characterization of defects in SiC. At the end, we list the challenges from our point of view, such as controlling defects in SiC regarding their charge states, distribution and local environment, and understanding defect-induced magnetism by local and elemental selective probe techniques.

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  • Secondary publication expected from 18.07.2020

Permalink: https://www.hzdr.de/publications/Publ-29485
Publ.-Id: 29485


Spectroscopic insights into U(IV) speciation in aqueous solution

Lehmann, S.ORC; Steudtner, R.; Gerber, U.ORC; Zimmermann, T.ORC; Brendler, V.ORC
This work is focused on uranium as the major component of the nuclear fuel cycle. It is important to predict its environmental behavior for, e.g., the safety assessment of a future repository or the remediation of the various legacies of uranium mining and milling. Typically, diluted to highly saline aquifer systems under reducing conditions with carbonates, silicates, phosphates, chlorides and sulfates as important complexing agents are to be considered. However, predictions for U(IV) speciation often suffer from a sparsely populated thermodynamic data base [1], often due to a missing spectroscopic evaluation of species stoichiometry and structure.
This work combines absorption and fluorescence spectroscopies to reveal the speciation of U(IV) in solution in concentrations down to 10⁻⁶ M uranium. The set-up for time-resolved laser-induced fluorescence was optimized to allow the determination of fluorescence decay times of U(IV) in perchloric as well as in chloric acid with 2.5 ± 0.4 ns at room temperature and 152 ± 8.3 ns at liquid nitrogen temperature. By decreasing the temperature we gained an improved fine structure with a band splitting of the main peak at 410 nm and a redshift could be observed.
By evaluation of UV-vis based titration series (pH = 0 2, [U] = 10⁻⁴-10⁻⁵ M, [SO4] from 0 to 1.9·10⁻⁵ M) in the U(IV) sulfate system, complex formation constants for USO₄²⁺ and U(SO₄)₂(aq) could be derived, yielding 6.9 ± 0.3 and 11.8 ± 0.5, respectively, when extrapolated to infinite dilution. This log K values for the 1:1 complex is close to the NEA recommendation of 6.58 whereas our value for the 1:2 complex is about one order of magnitude higher than that selected in [1]. The NEA recommendations are exclusively based on liquid-liquid extraction experiments, with higher ionic strengths (up to 2 M) and U(IV) concentrations (up to 0.1 M) as applied in this work.
The potential of direct U(IV) spectroscopy for speciation analysis at environmentally relevant uranium concentrations was proven in this study. Eventually, all acquired information will increase confidence in respective U(IV) reactive transport modelling.
The authors gratefully acknowledge funding by the German Federal Ministry of Economic Affairs and Energy under the grant 02E11334B.
[1] R. Guillaumont et al. (2003). "Update on the chemical thermodynamics of uranium, neptunium, plutonium, americium and technetium., vol. 5 of Chemical Thermodynamics." Elsevier: 960 pp.
Keywords: tetravalent uranium, photometry, thermodynamics,
  • Poster
    EGU General Assembly 2019, 07.-12.04.2019, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-29484
Publ.-Id: 29484


Formation of structured membranes by coacervation of xanthan gum with CnTAB surfactants

Keshavarzi, B.; Schwarzenberger, K.; Huang, M.; Javadi, A.; Eckert, K.
We present a novel approach for studying membrane formation by interaction of polymers and surfactants with opposite charge using a Hele-Shaw experimental setup. A solution of the anionic biopolymer xanthan gum is placed in direct contact with a CnTAB surfactant solution (n=10, 12, 14 and 16). Thereby, a polymer-surfactant membrane spontaneously forms between the two solutions due to the precipitation of polymer-surfactant complexes, which grows afterwards in direction of the polymer solution. The dynamics of the growth of the membrane thickness and the mass transfer of polymer are evaluated for different surfactant types and concentrations.
The experiments and supporting numerical calculations indicate that polymer mass transfer is driven by diffusion of the charged macromolecules along the concentration gradient which is coupled to the electric field induced by the faster diffusion of the more mobile counterions. The properties and structure of the formed membrane significantly depend on surfactant hydrophobicity and concentration. In addition, in a wide range of experiments, the formation of a porous structure in the membrane is observed whose characteristics can be tuned by the process parameters. A mechanism is proposed for the pore formation explaining it as an instability of the growing membrane surface in interaction with the supply of polymer across the depleted zone in the vicinity of the membrane front.
Keywords: Polymer-surfactant interaction, structure formation, Hele-Shaw, membrane

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Publ.-Id: 29483


Annual Report 2018 - Institute of Ion Beam Physics and Materials Research

Faßbender, J.ORC; Helm, M.; Zahn, P.
The Institute of Ion Beam Physics and Materials Research conducts materials research for future applications in, e.g., information technology. To this end, we make use of the various possibilities offered by our Ion Beam Center (IBC) for synthesis, modification, and analysis of thin films and nanostructures, as well as of the free-electron laser FELBE at HZDR for THz spectroscopy. The analyzed materials range from semiconductors and oxides to metals and magnetic materials. They are investigated with the goal to optimize their electronic, magnetic, optical as well as structural functionality. This research is embedded in the Helmholtz Association’s programme “From Matter to Materials and Life”. Six publications from last year are highlighted in this Annual Report to illustrate the wide scientific spectrum of our institute.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-097 2019

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Publ.-Id: 29482


Progress in the second-moment closure for bubbly flow based on direct numerical simulation data

Ma, T.; Lucas, D.ORC; Jakirlić, S.; Fröhlich, J.
Data from direct numerical simulations (DNS) of disperse bubbly flow in an upward vertical channel are used to develop a new second-moment closure for bubble-induced turbulence (BIT) in the Euler–Euler framework. The closure is an extension of a BIT model originally proposed by Ma et al. (Phys. Rev. Fluids, vol. 2, 2017, 034301) for two-equation eddy-viscosity models and focuses on the core region of the channel, where the interfacial term and dissipation term are in balance. Particular attention in this study is given to the treatment of the pressure–strain term for bubbly flows and the form of the interfacial term to account for BIT. For the latter, the concept of an effective BIT source is proposed, which leads to a significant simplification of the modelling work for both the pressure–strain correlation and the interfacial term itself. The anisotropy of bubbly flow is analysed with the aid of the anisotropy-invariant map obtained from the DNS data, and a parameter governing this issue is established. The complete second-moment closure is tested against reference data for different bubbly channel flows and a case of a bubble column. The agreement achieved with the DNS data is very good and the performance of the new model is better than obtained with the standard procedure. Furthermore, the model is shown to be robust and to fulfil the requirements of realizability.
Keywords: turbulence modelling, multiphase flow, Direct Numerical Simulation

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Publ.-Id: 29481


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