Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32449 Publications
Two types of axisymmetric helical magnetorotational instability in rotating flows with positive shear
Mamatsashvili, G.; Stefani, F.ORC; Hollerbach, R.; Rüdiger, G.
We reveal and investigate a type of linear axisymmetric helical magnetorotational instability which is capable of destabilizing viscous and resistive rotational flows with radially increasing angular velocity, or positive shear. This instability is double-diffusive by nature and is different from the more familiar helical magnetorotational instability, operating at positive shear above the Liu limit, in that it works instead for a wide range of the positive shear when (i) a combination of axial and azimuthal magnetic fields is applied and (ii) the magnetic Prandtl number is not too close to unity. We study this instability first with radially local Wentzel-Kramers-Brillouin (WKB) analysis, deriving the scaling properties of its growth rate with respect to Hartmann, Reynolds, and magnetic Prandtl numbers. Then we confirm its existence using a global stability analysis of the magnetized flow confined between two rotating coaxial cylinders with purely conducting or insulating boundaries and compare the results with those of the local analysis. From an experimental point of view, we also demonstrate the presence of this instability in a magnetized viscous and resistive Taylor-Couette flow with positive shear for such values of the flow parameters, which can be realized in upcoming experiments at the DRESDYN facility. Finally, this instability might have implications for the dynamics of the equatorial parts of the solar tachocline and dynamo action there, since the above two necessary conditions for the instability to take place are satisfied in this region. Our global stability calculations for the tachocline-like configuration, representing a thin rotating cylindrical layer with the appropriate boundary conditions—conducting inner and insulating outer cylinders—and the values of the flow parameters, indicate that it can indeed arise in this case with a characteristic growth time comparable to the solar cycle period.

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Permalink: https://www.hzdr.de/publications/Publ-29917
Publ.-Id: 29917


Antibacterial activity of selenium nanoparticles studied by calorimetry, flow cytometry and electron microscopy
Schäfer, S.; Fahmy, K.; Merroun, M. L.;
Nanoparticles (NPs) are of growing interest for various applications due to their unique properties, such as elevated surface-to-volume-ratio and variability of composition surface features and charge. Moreover, certain metal NPs possess antimicrobial activity and are therefore considered as an alternative to common antibiotics to overcome the recently emerging issue of bacterial resistance against common antibiotics [1].
Silver (Ag) NPs are well-studied concerning their antimicrobial activity and already applied in medicine and household products. However, cellular interaction mechanisms and consequent toxicity are not entirely elucidated. It is proposed, that NPs either interact with the cell membrane via intermolecular interactions, such as charge-charge interactions or intracellular accumulation. Once interacting with the cell extra- or intracellularly, NPs release reactive oxygen species and metal ions, which subsequently damage the cell membrane and affect enzymatic activity, ultimately leading to cell death. [1]
Besides AgNPs, selenium (Se) NPs exhibit prominent antimicrobial activity, without being studied into more detail [2,3]. In our approach, gram-positive and gram-negative bacterial strains are chosen their putatively differing response to the metal NPs based on differing cell wall compositions. Calorimetric studies of differentially-coated Se NPs exhibited a decrease in growth rate of the bacterial model strains, indicating their antimicrobial activity. To further investigate the cytotoxicity, the influence on reactive oxygen species and enzymatic activity, fluorescence-based flow cytometry is being performed. Furthermore, electron microscopy is exploited to localize the NPs and to elucidate putative metal ion release.

References:
[1] Brandelli et al. (2017) Springer Int Publ 337-363.
[2] Piacenza et al. (2017) Microb Biotechnol 10, 804-818.
[3] Srivastava & Mukhopadhyay (2015) Bioprocess Biosyst Eng 38, 1723-1730.
  • Open Access LogoLecture (Conference)
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29907
Publ.-Id: 29907


Antiferromagnetic domain wall control via surface spin flop in fully tunable synthetic antiferromagnets with perpendicular magnetic anisotropy
Böhm, B.; Fallarino, L.ORC; Pohl, D.; Rellinghaus, B.; Nielsch, K.; Kiselev, N. S.; Hellwig, O.
Antiferromagnetic (AF) domain walls have recently attracted revived attention, not only in the emerging field of AF spintronics, but also more specifically for offering fast domain wall velocities and dynamic excitations up to the terahertz frequency regime. Here, we introduce an approach to nucleate and stabilize an AF domain wall in a synthetic antiferromagnet (SAF). We present experimental and micromagnetic studies of the magnetization reversal in [(Co/Pt)X-1/Co/Ir]N-1(Co/Pt)X SAFs, where interface-induced perpendicular magnetic anisotropy (PMA) and AF interlayer exchange coupling (IEC) are completely controlled via the individual layer thicknesses within the multilayer stack. By combining strong PMA with even stronger AF-IEC, the SAF reveals a collective response to an external magnetic field applied normal to the surface, and we stabilize the characteristic surface spin-flop (SSF) state for an even number N of AF-coupled (Co/Pt)X-1/Co multilayer blocks. In the SSF state our system provides a well-controlled and fully tunable vertical AF domain wall, easy to integrate as no single-crystal substrates are required and with uniform two-dimensional magnetization in the film plane for further functionalization options, such as lateral patterning via lithography.

Permalink: https://www.hzdr.de/publications/Publ-29901
Publ.-Id: 29901


Nonsaturating extreme magnetoresistance and large electronic magnetostriction in LuAs
Juraszek, J.; Bochenek, L.; Rudenko, A.; Hosen, M. M.; Daszkiewicz, M.; Wang, Z.; Wosnitza, J.; Henkie, Z.; Samsel-Czekala, M.; Neupane, M.;
In the known topological semimetals, conventional charge carriers exist in addition to relativistic quasiparticles, and thus a disentangling of their conduction properties remains challenging. Here, we address an unsaturated extreme magnetoresistance (XMR) with a marked deviation from the semiclassical B2 behavior that is commonly credited to the presence of topologically protected electronic states. For the topologically trivial semimetal LuAs, we observe a nonsaturating XMR with a nonquadratic magnetic-field dependence gained up to nearly 60 T. Remarkably, this diamagnetic material exhibits a very large magnetostriction that provides solid evidence for a field-dependent variation of electron and hole concentrations. We show that an underlying strain-induced change in the charge-carrier densities can give rise to an unsaturated XMR even in a moderately imbalanced semimetal. Our finding is of importance as well for topological semimetals in which the number of conventional charge carriers can be continuously altered with increasing field, and hence some of their high-field properties may not necessarily reflect the presence of massless quasiparticles.

Permalink: https://www.hzdr.de/publications/Publ-29899
Publ.-Id: 29899


Bose-Einstein condensation of triplons close to the quantum critical point in the quasi-one-dimensional spin-1/2 antiferromagnet NaVOPO4
Mukharjee, P. K.; Ranjith, K. M.; Koo, B.; Sichelschmidt, J.; Baenitz, M.; Scurschii, I.; Inagaki, Y.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.;
Structural and magnetic properties of a quasi-one-dimensional spin-½ compound NaVOPO4 are explored by x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, electron spin resonance, and 31P nuclear magnetic resonance measurements, as well as complementary ab initio calculations. Whereas magnetic susceptibility of NaVOPO4 may be compatible with the gapless uniform spin chain model, detailed examination of the crystal structure reveals a weak alternation of the exchange couplings with the alternation ratio α 󠆪≃ 0.98 and the ensuing zero-field spin gap Δ0/kB ≃ 2.4 K directly probed by field-dependent magnetization measurements. No long-range order is observed down to 50 mK in zero field. However, applied fields above the critical field Hc1 ≃ 1.6 T give rise to a magnetic ordering transition with the phase boundary TN ∝ (H – Hc1) 1/φ, where φ ≃ 1.8 is close to the value expected for Bose-Einstein condensation of triplons.With its weak alternation of the exchange couplings and small spin gap, NaVOPO4 lies close to the quantum critical point.

Permalink: https://www.hzdr.de/publications/Publ-29898
Publ.-Id: 29898


Model Experiments for Flow Phenomena in Crystal Growth
Dadzis, K.; Pätzold, O.; Gerbeth, G.;
The concept of a physical model experiment is introduced and discussed in the context of melt and gas flows in bulk crystal growth processes. Such experiments allow one to "extract" selected physical phenomena from the full complexity of a real crystal growth process and “transfer” them to material systems with an easier access for experimental measurements. Model experiments for the main techniques of melt growth are summarized in a literature review, and the applicability of the results to real crystal growth systems is analyzed. Recent examples of model experiments for melt and gas flows in Czochralski growth of silicon are used to demonstrate the state of the art and show the potential of such experiments to improve the understanding of complex multi-physical multi-scale phenomena occurring in every crystal growth process. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords: crystal growth, melt flows, model experiments, numerical simulation

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Permalink: https://www.hzdr.de/publications/Publ-29894
Publ.-Id: 29894


Magnetocaloric effect and spin-strain coupling in the spin-nematic state of LiCuVO4
Gen, M.; Nomura, T.; Gorbunov, D.; Yasin, S.; Cong, P. T.; Dong, C.; Kohama, Y.; Green, E. L.; Law, J. M.; Henriques, M. S.; Wosnitza, J.; Zvyagin, A. A.; Cheranovskii, V. O.; Kremer, R. K.; Zherlitsyn, S.ORC
We report on the magnetocaloric effect and ultrasound studies of the frustrated quasi-one-dimensional spin-1/2 compound LiCuVO4, evidencing a spin-nematic state. The magnetic Grüneisen parameter diverges at the transition to the spin-nematic phase, μ0Hc3 ≈ 40 T, showing quantum criticality accompanied by entropy accumulation. The observed high-field anomalies in the acoustic properties clearly evidence a strong involvement of the lattice in the spin dynamics. The theoretical approach, based on exchange-striction coupling with dipolar and quadrupolar contributions, suggests that the spin-dipole-strain and quadrupole-strain interactions govern the
spin-nematicity in LiCuVO4.

Permalink: https://www.hzdr.de/publications/Publ-29892
Publ.-Id: 29892


Fermi surface of LaFe2P2—a detailed density functional study
Förster, T.; Kraft, I.; Sheikin, I.; Bianchi, A. D.; Wosnitza, J.; Rosner, H.;
Angular-dependent de Haas-van Alphen measurements allow the mapping of Fermi surfaces in great detail with high accuracy. Density functional electronic-structure calculations can be carried out with high precision, but depend crucially on the used structural information and the applied calculational approximations. We report in a detailed study the sensitivity of the calculated electronic band structure of the 122 compound LaFe2P2 on (i) the exact P position in the unit cell, parametrized by a so-called z parameter, and on (ii) the treatment of the La 4f states. Depending on the chosen exchange and correlation-potential approximation, the calculated z parameter varies slightly and corresponding small but distinctive differences in the calculated band structure and Fermi-surface topology appear. Similarly, topology changes appear when the energy of the mostly unoccupied La 4f states is corrected regarding their experimentally observed position. The calculated results are compared to experimental de Haas-van Alphen data. Our findings show a high sensitivity of the calculated band structure on the pnictide z position and the need for an accurate experimental determination of this parameter at low temperatures, and a particular need for a sophisticated treatment of the La 4f states. Thus, this is not only crucial for the special case of LaFe2P2 studied here, but of importance for the precise determination of the band structure of related 122 materials and La containing compounds in general.

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  • Secondary publication expected from 18.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29891
Publ.-Id: 29891


The Helmholtz Innovation Lab for ultra-short time annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC; Skorupa, W.
Der Vortrag stellt das Helmholtz Innovation Lab für Ultrakurzzeitausheilung vor. Im zweiten Teil werden experimentelle Ergebnisse bei der Kristallisation von dünnen amorphen Halbleiterschichten (Si, Ge, NiGe) mittels magnetron sputtering und Blitzlampenausheilung diskutiert.
Keywords: Helmholtz Innovation Lab, flash lamp annealung, ultra-short time annealing, magnetron sputtering, nickel germanide
  • Lecture (Conference)
    43. Nutzertreffen Heißprozesse und RTP, 23.10.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29890
Publ.-Id: 29890


Crystallization of thin Si, Ge and NiGe films on SiO2 by flash lamp annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC; Skorupa, W.
There is a broad palette of applications for thin Si and Ge films ranging from photovoltaics over various microelectronic devices to sensor applications. Both amorphous and polycrystalline thin films are of interest for thin film photovoltaics, and thin film poly-Si transistors are the heart piece for driving LCDs and OLEDs [1]. In addition, the ability to deposit SiO2 and Si layers in an alternating order and to process them allows to extend the device density without further downscaling [2]. Amorphous thin film deposition methods are the most cost-effective ones, the subsequent crystallization is the most critical process step with regard to microstructure, defect density, and electrical properties.

Potentially, flash lamp annealing (FLA) is a very suitable method due to the short process time, the qualification for temperature-sensible substrates and the possibility to take advantage of non-equilibrium crystallization modes [3]. In this work thin amorphous Si and Ge films have been deposited on SiO2 by DC-magnetron sputtering and crystallized by in-situ FLA in a new FLA sputter tool recently installed by the Rovak GmbH at HZDR (Fig. 1). The in-situ-processing suppresses the influence of surface oxidation effects after deposition prior to FLA. In order to investigate the crystallization behaviour, the thin films have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements. Based on these results and in combination with temperature simulations, a model for the crystallization of thin amorphous Si and Ge films is derived.
Keywords: flah lamp annealing; magnetron sputtering, nickel germanide, crystallization
  • Lecture (Conference)
    Gettering and Defect Engineering in Semiconductor Technology 2019, 22.-27.09.2019, Zeuthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29888
Publ.-Id: 29888


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a semi-circular constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data
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Hydrodynamic experimental benchmark data of bubbly … (Id 29886) has this publication as part
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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.195
    License: CC-BY-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29887
Publ.-Id: 29887


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a ring-shaped constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is part of this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29885) has this publication as part
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29882) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) has this publication as part
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.197
    License: CC-BY-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29886
Publ.-Id: 29886


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a semi-circular constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is supplemented by this publication
Hydrodynamic experimental benchmark data of bubbly … (Id 29886) is part of this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29882) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) is a supplement to this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.137
    License: CC-BY-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29885
Publ.-Id: 29885


Structural, Magnetocaloric, and Critical Behavior of La0.5Ca0.5Mn1−xVxO3 Manganites Prepared by High-Energy Ball Milling
Mansouri, M.; Fallarino, L.ORC; M'Nassri, R.; Cheikhrouhou-Koubaa, W.; Cheikhrouhou, A.
The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model.
Keywords: Critical exponents, High-energy ball milling, Magnetocaloric effect, Manganites

Permalink: https://www.hzdr.de/publications/Publ-29884
Publ.-Id: 29884


The formation of Ni germanides by magnetron sputtering and flash lamp annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC
Silicides have been widely used for CMOS devices in order to provide a stable Ohmic contact with a low contact resistivity. With the integration of Ge on Si the focus also shifted to germanides as a low resistivity contact material. In addition, ferromagnetic germanides may serve as spin injector materials for Ge-based spintronic devices. Usually, germanides have been fabricated by furnace or rapid thermal annealing in literature.

In this contribution we investigate the formation process of Ni germanides using a combination of magnetron sputtering and flash lamp annealing (FLA). Three different types of Ge served as a substrate for the deposition of the transition metal: amorphous Ge made by magnetron-sputtering on a SiO2-Si substrate, polycrystalline Ge made by magnetron-sputtering followed by FLA, and monocrystalline Ge in the form of a (100) Ge wafer. After metal deposition samples are in-situ annealed by FLA without breaking the vacuum, which triggers the formation of germanides and prevents a possible, but unwanted oxidation. In order to investigate the crystallization behavior, the structures have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements.
Keywords: flash lamp annealing; magnetron sputtering; nickel germanide
  • Lecture (Conference)
    EMRS 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29883
Publ.-Id: 29883


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a ring-shaped constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is part of this publication
Hydrodynamic experimental benchmark data of bubbly … (Id 29886) is supplemented by this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29885) is part of this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) has this publication as part
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.139
    License: CC-BY-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29882
Publ.-Id: 29882


Measurement of f orbital hybridization in rare earths through electric dipole-octupole interference in X-ray Absorption Spectroscopy
Juhin, A.; Collins, S. P.; Joly, Y.; Diaz-Lopez, M.; Kvashnina, K.; Glatzel, P.; Brouder, C.; de Groot, F.;
This work provides a direct route to measure the degree of hybridization of f states in rare earths. The interference between electric dipole and octupole transitions is measured at the L1 edge of Gd in Gd3Ga5O12 using X-ray Natural Linear Dichroism (XNLD) and high energy resolution
fluorescence detection. The Gd 4f-6p admixture is quantiffed through the integral of the dipole-octupole XNLD using a new sum rule easily applicable to experimental data. The mixing of the Gd valence states with the O ligand orbitals, calculated from first-principles, reveals that despite their localized character, the Gd 4f orbitals mix with the O 2p and 2s orbitals with an antibonding and bonding character, respectively.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29881
Publ.-Id: 29881


Neuroprogressive character of sigma-1 receptor pathophysiology in unmedicated patients with acute major depressive disorder as investigated by (-)-[18F]Fluspidine PET
Meyer, P.; Strauss, M.; Becker, G.; Hesse, S.; Bednasch, K.; Ettrich, B.; Wilke, S.; Zientek, F.; Rullmann, M.; Luthardt, J.; Fischer, S.; Patt, M.; Wünsch, B.; Brust, P.ORC; Sabri, O.
Aim/Introduction:
We have previously shown that the sigma-1 receptor(Sig-1R) availability is increased in unmedicated acute MDD (MDD) using (-)-[18F]Fluspidine PET. In order to assess whether this pathophysiology is progressive, we investigated the relationship between Sig-1R availability and duration of disease (DD), number of depressive episodes (DE) and severity of acute depressive symptoms (Hamilton Depression Rating Scale, HAMD) in this now completed first-in-human (-)-[18F]Fluspidine PET trial.
Materials and Methods:
Patients with moderate to severe MDD (n=18; 32±12 years; 9 females; DD 6±8 years; DE 3±1 years; HAMD: 20±4) were studied using (-)-[18F]Fluspidine PET (300 MBq, ECAT Exact HR+) and compared with sex-/age-matched healthy controls (HC; n=16; 32±13ys [n.s.]; 9 females [n.s.]). VOI analyses were performed and regional distribution volumes (VT) were estimated by kinetic modeling (0-210 min p.i.; 2TCM; metabolite correction).
Results:
In MDD, compared with HC, VT was higher especially within the fronto-temporal, anterior cingulate and insular cortices, amygdala, striatum, thalamus and ncl. raphe (P<0.005). Positive correlations were found between HAMD and VT within the anterior and posterior cingulate and insular cortices, ncl. caudatus and thalamus (r=0.43 to 0.57, P<0.05, adjusted for DD, BMI).Negative correlations were found between DD and VT within the orbitofrontal cortex and hypothalamus (r=-0.40 to -0.47, P<0.05, adjusted for severity of MDD) and between DE and VT within the hypothalamus, orbitofrontal, temporo-parietal and cingulate cortices, striatum, thalamus and cerebellum (r=-0.42 to -0.60, P<0.05, adjusted for severity of MDD).
Conclusion:
Using (-)-[18F]Fluspidine PET, we showed for the first time increased cortico-(para-)limbic Sig-1R availability during the DE of MDD, as compared with HC, that was associated with the severity of acute depressive symptoms (HAMD). Remarkably, in MDD, there is a negative correlation between DE or DD and Sig1-R availability, especially within orbitofrontal cortices and hypothalamus as well as within various (sub)cortical-(para)limbic and cerebellar brain regions. Although verification by longitudinal (-)-[18F]Fluspidine PET studies is needed, our findings suggest a neuroprogressive character of Sig-1R pathophysiology in MDD.
Keywords: sigma-1 receptor, acute major depressive disorde, (-)-[18F]Fluspidine, PET
  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine, 12.-16.10.2019, Barcelona, Barcelona, Spain
    DOI: 10.1007/s00259-019-04486-2

Permalink: https://www.hzdr.de/publications/Publ-29877
Publ.-Id: 29877


Spektroskopische Methoden für die Endlagerforschung
Drobot, B.ORC
Spektroskopische Methoden generieren molekulares Prozessverständnis. Dies ist wichtig für die Erhöhung der Belastbarkeit von Risokoanalysen im Endlager-Kontext.
Keywords: Endlager, Spektroskopie
  • Invited lecture (Conferences)
    Kraftwerkstechnisches Kolloquium, 23.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29875
Publ.-Id: 29875


HZDR Data Management Strategy — Top-Level Architecture
Knodel, O.ORC; Gruber, T.ORC; Müller, S.ORC; Juckeland, G.ORC

Top-Level Architecture of the proposed HZDR Data Management Strategy

Keywords: data management
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-11-06
    DOI: 10.14278/rodare.193
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-29873
Publ.-Id: 29873


Hydrodynamic investigations of gas-liquid two-phase flow in centrifugal pumps - reconstructions (selected data)
Schaefer, T.; Bieberle, A.ORC; Hampel, U.ORC

This data repository contains reconstructed and quantitatively analyzed gas-liquid two-phase distributions obtained from a centrifugal pump mock-up whose geometry is related to a commercially available industrial centrifugal pump. As measurement system the ultrafast electron beam X-ray CT scanner (UFXCT) is applied with a frame rate of 2,500 Hz, single-plane mode and a total scanning interval of 5 seconds. The data repository contains:

  • Reconstructed raw data (FBP) sets for selected two-phase flow operating conditions at constant 1480 rpm with static and rotating impeller, respectively
  • Corresponding quantitative gas fraction data sets (for static impeller position)
  • Averaged gas fraction distributions
  • Standard deviations of the gas fraction mean values
  • Data evaluation scripts

Keywords: centrifugal pump; gas-liquid two-phase flow; ultrafast X-ray computed tomography
Related publications
Ultrafast X-ray CT imaging for hydrodynamic investigations … (Id 29455) is supplemented by this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-10-30
    DOI: 10.14278/rodare.189

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Permalink: https://www.hzdr.de/publications/Publ-29872
Publ.-Id: 29872


Cross section of α-induced reactions on 197Au at sub-Coulomb energies
Szücs, T.ORC; Mohr, P.; Gyürky, G.; Halász, Z.; Huszánk, R.; Kiss, G. G.; Szegedi, T. N.; Török, Z.; Fülöp, Z.
Statistical model calculations have to be used for the determination of reaction rates in large-scale reaction networks for heavy-element nucleosynthesis. A basic ingredient of such a calculation is the a-nucleus optical model potential. Several different parameter sets are available in literature, but their predictions of a-induced reaction rates vary widely, sometimes even exceeding one order of magnitude.
This paper presents the result of a-induced reaction cross-section measurements on gold which could be carried out for the first time very close to the astrophysically relevant energy region. The new experimental data are used to test statistical model predictions and to constrain the a-nucleus optical model potential.
For the measurements the activation technique was used. The cross section of the (a,n) and (a,2n) reactions was determined from g-ray counting, while that of the radiative capture was determined via X-ray counting.
The cross section of the reactions was measured below Ea=20.0~MeV. In the case of the 197Au(a,2n)199Tl reaction down to 17.5~MeV with 0.5-MeV steps, reaching closer to the reaction threshold than ever before. The cross section of 197Au(a,n)200Tl and 197Au(a,g)201Tl was measured down to Ea=13.6 and 14.0~MeV, respectively, with 0.5-MeV steps above the (a,2n) reaction threshold and with 1.0-MeV steps below that.
The new dataset is in agreement with the available values from the literature, but is more precise and extends towards lower energies. Two orders of magnitude lower cross sections were successfully measured than in previous experiments which used g-ray counting only, thus providing experimental data at lower energies than ever before. The new precision dataset allows us to find the best-fit a-nucleus optical model potential and to predict cross sections in the Gamow window with smaller uncertainties.
Keywords: Nuclear Astrophysiscs, Heavy element nucleosynthesis, Alpha induced reactions

Permalink: https://www.hzdr.de/publications/Publ-29871
Publ.-Id: 29871


Status and innovations in pre-treatment CT imaging for proton therapy
Wohlfahrt, P.; Richter, C.ORC
Pre-treatment CT imaging is a topic of growing importance in particle therapy. Improvements in the accuracy of stopping-power prediction are demanded to allow for a dose conformality that is not inferior to state-of-the-art image-guided photon therapy. Although range uncertainty has kept practically constant over the last decades, recent technological and methodological developments, like the clinical application of dualenergy CT, have been introduced or arise at least on the horizon to improve the accuracy and precision of range prediction. This review gives an overview of the current status, summarizes the innovations in dual-energy CT and its potential impact on the field as well as potential alternative technologies for SPR prediction.
Keywords: Dual-energy CT, range prediction, stopping-power ratio, stopping-power prediction, SPR, proton therapy

Permalink: https://www.hzdr.de/publications/Publ-29865
Publ.-Id: 29865


Plasmonic nonlinearity in GaAs/In0.20Ga0.80As core/shell nanowires
Rana, R.; Balaghi, L.ORC; Fotev, I.ORC; Schneider, H.ORC; Helm, M.; Dimakis, E.ORC; Pashkin, O.ORC
We have investigated the plasmonic response of GaAs/In0.20Ga0.80As core/shell nanowires driven resonantly by strong THz fields with the amplitude of few MV/cm. The plasmon mode exhibits a systematic redshift with the suppression of the spectral weight with the increase of the driving THz field. Interestingly, the scaling of the plasmon parameters does not follow the usual quadratic behavior, indicating an inhomogeneous intervalley electron scattering across the nanowire.
Keywords: Plasmons, Nanowires, Nonlinear optics
  • Contribution to proceedings
    44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 01.-06.09.2019, Paris, France
    2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), IEEE Xplore: IEEEE, 978-1-5386-8285-2
    DOI: 10.1109/IRMMW-THz.2019.8874085

Permalink: https://www.hzdr.de/publications/Publ-29861
Publ.-Id: 29861


Mobility of radionuclides enhanced by complexing agents used in a repository: Modeling sorption and transport
Karimzadeh, L.; Lippold, H.; Fischer, C.ORC
Among the organic inventory of a nuclear waste repository, aminopolycarboxylic acids, which are used as decontamination agents during operation, are of particular concern in view of their chelating capability and high persistence, but data regarding their impact on the mobility of radionuclides in geological barriers are missing so far. Migration in the host rock is controlled by sorption reactions on mineral surfaces, potentially affected by organic complexing ligands. As a case study, using 152Eu as a short-lived tracer analogue of actinides, we investigated sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of the complexant diethylenetriaminepentaacetic acid (DTPA). The transport behavior was studied in column experiments (up- and down-flooding) at neutral pH in order to detect possible inconsistencies between sorption in batch systems and retardation in dynamic systems.
The effect of DTPA on sorption of Eu(III) was found to be strongly dependent on pH. At neutral and alkaline conditions, sorption is considerably decreased, resulting in accelerated breakthrough and facilitated elution in column experiments. Sorption as a function of DTPA concentration and pH was completely described by surface complexation modeling based on the Diffuse Double Layer Model of Dzombak and Morel, using the speciation program PHREEQC coupled with the parameter estimation code PEST. Results of column experiments were simulated in 1D calculations by means of the obtained surface complexation parameters. Breakthrough and elution curves were perfectly reproduced without readjustments.
  • Poster
    Jahrestagung der GDCh, Fachgruppe Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29859
Publ.-Id: 29859


Produktion und Reinigung von n.c.a. 48V am Leipziger Zyklotron für Extraktionsstudien
Mansel, A.; Franke, K.;
Vanadium ist ein Bestandteil in Eisen-Chromschlacken und gilt als strategisches Wertmetall. Um effiziente Abtrennungsverfahren von fünfwertigem Vanadium vom dreiwertigen Chrom bzw. sechswertigem Chromat mit Hilfe der Ionenchromatographie zu entwickeln, wurde die Radiotracertechnik eingesetzt [48V; T1/2 = 15,97 d; E = 984 keV; 99,97 %]. Die Produktion dieses Radionuklides wurde am Leipziger Zyklotron CYCLONE 18/9® durch die Kernreaktion natTi(p,n)48V realisiert. Eine Titanfolie (natürliche Isotopenzusammensetzung; 140 mg) wurde mit Protonen der Energie 12 MeV bei einem Strom von 22 µA für zwei Stunden bestrahlt. Das bestrahlte Target wurde für einen Tag zum Abklingen des kurzlebigen Radionuklides 47V (T1/2 = 32,6 min) aufbewahrt und anschließend in konzentrierter Schwefelsäure und wenigen Tropfen Flußsäure in einem Teflonbecher aufgelöst. Nach dem Eindampfen wurde der Rückstand mit 3 g Natriumcarbonat / 80 mg Natriumnitrat in einem Platintiegel für 30 Minuten bei 800 °C aufgeschlossen. Durch mehrmaliges Anlösen mit Wasser wurde das 48V in Form von Natriumvanadat vom Targetmaterial Titandioxid herausgelöst. Spuren von Titan wurden mit Hilfe eines Kationenaustauschers (DOWEX 50 W X-8) bei pH 3 abgetrennt und das Vanadylion in Form von Vanadat mit 20 %igem Ammoniak eluiert. Die radiochemische Ausbeute betrug (95 ± 8) %. Die Aktivität betrug fünf Stunden nach Bestrahlungsende ~ 245 MBq und die Nachweisgrenze wurde zu 8 fM (~0,4 pg/L) für n.c.a. 48V ermittelt.
  • Poster
    GDCh Jahrestagung der Fachgruppe Nuklearchemie, 24.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29857
Publ.-Id: 29857


Combining trace element measurements with analytical uncertainties for a better characterization of plant geochemistry
Pospiech, S.; van den Boogaart, K. G.ORC; Tolosana Delgado, R.; Wiebke, F.
Trace element analysis in plants is often subject to a high measurement uncertainty and accordingly the variability of the geochemical composition of trace elements in plants is – especially close to the detection limit - very high. In this contribution we propose a method to estimate models respecting the uncertainty and capable of treating values below and around the detection limit. We suggest to use all measurement signals, but report it alongside with the individual uncertainties for each value. The standard descriptive and statistical analysis mainly ignores these uncertainties by simply reporting if a signal value is below the detection limit (BDL) or above. BDL-values are either ignored or replaced by an arbitrary small value. In both cases this can substantially distort the analysis. Our methodology could substantially reduce this bias.
In order to take into account the constraints of concentration data we use methods of compositional data analysis, i.e. represent population by their compositional expectation, typically represented in an log-ratio transform. The uncertainties are incorporated in statistical methods by estimating the reported value not by a simple mean, but by an estimation procedure using the model assumption that a signal observed in the geochemical analysis has two components of variability: i) A population spread that could e.g. be modeled by a compositional distribution, and ii) a signal variability to be modeled according to the measurement instrument, typically assuming additive normal or Poisson errors and calibration errors. The parameters for the model of the signal variability are estimated from blind values, duplicate analysis as well as precision and accuracy of repeatedly measured reference samples.
We will present the change of results produced by the methodology over a standard approach with reporting BDL-values by demonstrating the applicability of the methodology with simulated data and a dataset of rye, ryegrass, faba bean, triticale and amaranth from two agricultural test sites in Germany. All samples had been treated by a four-acid digestion and analyzed by ICP-MS and ICP-OES.
Keywords: plant geochemistry, compositional data, uncertainty, analytics, ICP-MS, ICP-OES, Bayesian statistics
  • Open Access LogoPoster
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29847
Publ.-Id: 29847


Microresonator-integrated magnetic tunnel junctions allowing for thermal gradient sign reversal designed using COMSOL simulations
Cansever, H.; Lindner, J.; Huebner, T.; Niesen, A.; Reiss, G.; Fassbender, J.; Deac, A. M.;
In magnetic tunnel junctions (MTJs), it was theoretically predicted that magnetization dynamics can be induced by thermal gradients via thermal-spin transfer torques (T-STTs), similar to STTs induced by applied voltages[1]. We recently proposed an approach based on microresonators (µR) in order to detect T-STT terms acting on the free layer of an MTJ device by means of investigating the ferromagnetic response of an MTJ exposed to a cw laser in open-circuit conditions. The linewidth of the ferromagnetic signal is modified by the damping-like torque induced by thermal gradient, while the frequency is subject to changes induced by the field-like torque[2]. Here, we used COMSOL simulations to determine the temperature profile of Co2FeAl/MgO/CoFeB MTJs, when the MR structure is considered, see Fig 1. In this design, the structure is defined with laterally larger Co2FeAl (CFA) layer below CoFeB (CFB) layer. This allows for the laser beam to be focused on the CFA layer surface, in order to heat the bottom electrode of the MTJ rather than the top, as commonly investigated[3-6]. The temperature of both layers and temperature differences (ΔT) as a function of lateral width are shown in Fig 2. The temperature on the CFA layer decreases laterally about 25K towards to center of the structure and yields a ΔT over the barrier of about 680mK, if a gold pad is placed on the CFA layer, in the position where the laser is shined on (Fig 2). Without the gold pad and leaving the MgO on the CFA unpatterned, the ΔT over the barrier is reduced almost by factor of 2, and is estimated to be around 320mK and 270mK respectively. When both layers have gold contacts, ΔT drops to 20mK (Fig 2). Consequently, the magnitude and the sign of ΔT over the barrier can be engineered by appropriately designing the design of the device, which would allow for T-STTs induced by thermal gradients of different sign to be investigated experimentally in a single MTJ.

*Figure 1 2D sketch of an MTJ structure considered for COMSOL modelling, where the loop of µR was taken into account and only the bottom layer is exposed to the laser.

*Figure 2 Temperature profile of the MTJ versus lateral size, ΔT dependence on designed structure.
References
[1] Jia X, Xia K and Bauer G E W 2011 Phys. Rev. Lett.107 176603
[2] H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac, 2018 J. Phys. D: Appl. Phys. 51 22400
[3] N. Liebing, S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker, H. W. Schumacher, 2011, Phys. Rev. Lett. 107, 177201.
[4] J. C. Leutenantsmeyer, M. Walter, V. Zbarsky, M. Münzenberg, R. Gareev, K. Rott, A. Thomas, G. Reiss, P. Peretzki, H. Schuhmann, M. Seibt, M. Czerner, C. Heiliger, 2013, Spin 3, 1350002.
[5] A. Boehnke, M. Milnikel, M. Ehe, C. Franz, V. Zbarsky, M. Czerner, K. Rott, A. Thomas, C. Heiliger, G. Reiss, M. Münzenberg, 2015, Sci. Rep. 5, 8945.
[6] H. Cansever, J. Lindner, T. Huebner, A. Niesen, G. Reiss, J. Fassbender, A. M. Deac, 2019, IEEE Trans.Magn. 51(17) Early Access
Keywords: COMSOL, thermal spin-transfer torque, magnetic tunnel junction, microresonator
  • Open Access LogoLecture (Conference)
    Annual Conference on Magnetism and Magnetic Materials, MMM Las Vegas 2019, 04.-08.11.2019, Las Vegas, USA

Permalink: https://www.hzdr.de/publications/Publ-29846
Publ.-Id: 29846


Spectral Random Masking für PIV in Mehrphasenströmung
Anders, S.ORC; Noto, D.ORC; Eckert, S.ORC
Im vorliegenden Beitrag wird eine neuartige Maskierungsmethode für die Particle Image Velocimetry (PIV) von Mehrphasenströmungen vorgestellt. Mit diesem neuen Ansatz können Geschwindigkeitsfelder einer unmaskierten Partikelfraktion (z. B. PIV-Tracer) unabhängig von der Bewegung einer zweiten, maskierten Partikel-Fraktion (z. B. Blasen oder Feststoffpartikel) bestimmt werden.
Ausgehend von einer segmentierten Bilderserie in welcher die verschiedenen Partikelfraktionen für alle Einzelbilder detektiert wurden, werden verschiedene Maskierungsverfahren diskutiert. Hierbei werden die Probleme, welche durch Standardverfahren für den Fall dynamischer Maskierung unter realen Belichtungsbedingungen entstehen besonders hervorgehoben. Als entsprechende Lösung stellen wir unseren Ansatz des Spectral Random Masking (vgl. Anders et al. 2019) vor, bei welchem maskierte Bildbereiche durch spektral angepasste, zufällige Intensitätsverteilungen ersetzt werden. Damit sollen die maskierten Bereiche für eine anschließende PIV-Analyse “unsichtbar” gemacht werden. Die Vorteile dieser Methode gegenüber konventionellen Maskierungsverfahren werden anhand eines Modellexperimentes dargestellt, bei welchem wässrige Ammonium-Chlorid Lösungen (NH₄Cl(aq)) durch Unterkühlung erstarrt werden. Dabei treten unter anderem verschiedene Konvektionsströmungen zeitgleich mit kolumnarer und äquiaxialer Kristallisation von NH₄Cl auf.
Keywords: Bild Segmentierung, dynamische Bildmaskierung, Mehrphasenströmung, Particle Image Velocimetry
  • Open Access LogoContribution to proceedings
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland
    Spectral Random Masking für PIV in Mehrphasenströmung, 978-3-9816764-6-4, 20.1-20.7
  • Lecture (Conference)
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-29844
Publ.-Id: 29844


Comparative Study of Monosalen Complexes with Tetravalent Actinides
Radoske, T.ORC
Two series of tetravalent actinide complexes with the salen ligand were synthesized. The coordination sphere supports two labile positions for small neutral solvent molecules, which were filled with either methanol or acetonitrile molecules. Solid state characterization reveals additional interactions of U(IV) and Np(IV) with the organic ligands.
  • Poster
    Migration 2019, 15.-20.09.2019, Kyoto, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29842
Publ.-Id: 29842


Tetravalent Actinide N-Donor Affinity in Monosalen Complexes
Radoske, T.ORC
Complexes with a range of differently substituted pyridines were synthesized using tetravalent actinides. The affinity of actinides for N-donors is discussed.
  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29841
Publ.-Id: 29841


Tetravalent Actinide Complexes with Schiff bases: Comparison with Isostructural Transition Metal and 4f Element Compounds
Radoske, T.ORC
Isostructural complex series with tetravalent actinides were characterized and results are discussed for observable trends.
  • Lecture (others)
    FENABIUM Projekttreffen, 27.02.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29840
Publ.-Id: 29840


Amidinates as Versatile Ligands for Tetravalent Actinides
Schöne, S.ORC; März, J.ORC; Kaden, P.ORC
A summary of work based on the synthesis and characterization of tetravalent actinide amidinates is given. Structural features are compared in solid and in solution phase. Comprehensive quantum chemical calculations support the findings.
  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29839
Publ.-Id: 29839


Relative Stability of Actinide(IV) Bissalen Complexes
Radoske, T.ORC; Schöne, S.ORC; Kloditz, R.; März, J.ORC; Stumpf, T.; Ikeda-Ohno, A.ORC
Schiff bases of salen-type have a wide range of applications and have proven to be a versatile ligand system for the investigation of complexation behavior. In particular, due to its hetero N/O-donor coordination properties, the salen ligands are often considered as a simplified analog of naturally-occuring organic ligands, which have potential implications for the migration behavior of radionuclides under geochemical conditions We have investigated the complexation behavior of salen ligands (L, H2salen = N,N’-bis(salicyliden)ethylenediamine) towards tetravalent metal cations and synthesized a series of complexes of tetravalent actinides (Th, U, Np, and Pu) as well as analogous tetravalent metals (Zr, Ce, and Hf). In all cases, the ligand forms bissalen ML2 complexes (M = metal). When the ML2 compound is treated with an equimolar amount of the metal tetrachloride, some metals also form M:L = 1:1 complexes with additional two Cl- in the primary coordination shell to form MLCl2. Based on this observation, we assume a trilateral equilibrium between the starting materials of metal tetrachlorides, the 1:1, and the 1:2 complex (Scheme 1), being similar to the study by Calderazzo et al.[1] This equilibrium holds even if ML2 is insoluble in the reaction medium and, therefore, we can apply the exchange reactions to determine the relative stability of the An(IV)-bissalen complexes when more than one types of metal are used. The relative stability of the complexes can then be directly compared to the results from quantum chemical calculations based on DFT. Hence, this study aims to understand the reaction mechanism and stability of salen complexes with a series of tetravalent metals, in particular tetravalent actinides (An(IV)).
  • Lecture (Conference)
    Fachtagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29838
Publ.-Id: 29838


Tetravalent Actinide and Transition Metal Amidinates – Trends and Perspectives
Schöne, S.ORC
A series of tetravalent actinide amidinates with chiral (S)-HPEBA ligands is presented. The complexes are structurally characterized in solid state and in solution. Further reactivity is proved by reduction to trivalent homoleptic complexes.
  • Lecture (others)
    Challenges in f-element chemistry - Bilaterales Meeting HZDR/KIT, 10.01.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29837
Publ.-Id: 29837


Amidinates – Versatile Ligands for Tetravalent Actinides
Schöne, S.ORC; Kloditz, R.ORC; März, J.ORC; Kaden, P.ORC; Patzschke, M.ORC; Roesky, P. W.; Stumpf, T.
Amidinates, a group of heteroallylic nitrogen donor ligands of type [RC(NR‘)2]–, have been used in a widespread manner in coordination chemistry and organometallics. They usually coordinate in a N,N’-bidendate mode to almost all metals in the periodic table including lanthanides and early actinides. The steric and electronic properties can be easily tuned by varying the substituents R and R’ to make them a valuable class of spectator ligands.
We have expanded the rich chemistry of amidinates to the tetravalent transuranic elements Np and Pu and compared the results to the earlier actinides Th and U and other tetravalent analogues. The focus of our investigations lies in the comprehensive characterization of An(IV) complexes with amidinates, both in the solid state and in solution. A comparison within the series enables us to perform a detailed structural analysis, which is complemented by high-level quantum chemical calculations to gain deeper insight into the bonding properties of tetravalent actinides (An(IV)).
Several An(IV) amidinate complexes have been synthesized including a series of chiral complexes using the chiral benzamidine, (S,S)-N,N‘-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA) [1]. We obtained the first enantiopure amidinate complexes [AnIVCl((S)-PEBA)3] (An = Th, U, and Np) as well as the analogous Ce(IV) compound, a chemical analog of An(IV). The tris-amidinate complexes have been structurally characterized in solid state and in solution showing a comparable complex geometry.
The presence of one chloro ligand in addition to three stabilizing amidinate ligands in the An coordination sphere points to complex reactivity. This could indeed be demonstrated by reduction to homoleptic trivalent actinide amidinates [An((S)-PEBA)3] (An = U, Np) as well as halogen exchange with pseudo-halogenides (i.e. N3–).
  • Lecture (Conference)
    GdCh Fachgruppentagung Nuklearchemie, 25.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29836
Publ.-Id: 29836


La–Sr–Mn–Co–O Films for High Pulsed Magnetic Field Measurements at Cryogenic Temperatures
Rudokas, V.; Zurauskiene, N.; Lukose, R.; Kersulis, S.; Stankevic, V.; Pavilonis, D.; Balevicius, S.; Plausinaitiene, V.; Vagner, M.; Skapas, M.; Arsenijevic, S.;
The magnetoresistance of nanostructured La1−xSrx(Mn1−yCoy)zO3±δ (La–Sr–Mn–Co–O) films with substitution of Co for Mn with amount of Co/(La + Sr) = 0.12 and different Mn excess Mn/(La + Sr) = 1.05, 1.07, nd 1.11 was investigated at temperatures of 4–230 K in pulsed magnetic fields up to 60 T. It was found that the manganite–cobaltite films exhibit larger magnetoresistance in comparison with manganite films without Co doping. The largest magnetoresistance values and sensitivity to the magnetic field are obtained for La–Sr–Mn–Co–O films having Mn Content close to the stoichiometric ratio for manganites: Mn/(La + Sr) = 1.05. It was found that magnetoresistance at high fields (20–60 T) has a minimum at (50–80 K) and increases with the decrease of temperature. The possibility to use these films for magnetic field measurements at cryogenic temperatures is demonstrated.

Permalink: https://www.hzdr.de/publications/Publ-29835
Publ.-Id: 29835


Superconductivity of Organic Charge-Transfer Salts
Wosnitza, J.;
Forty years after the discovery of the first organic superconductor, the nature of the superconducting state in these materials is still not fully understood. Here, I present an overview on the historical developments and current knowledge on this topic for the quasi-one- and quasi-two-dimensional (2D) organic charge-transfer salts. Thereby, I focus on the prototype materials based on the donor molecules tetramethyltetraselenafulvalene (TMTSF) and bisethylenedithio-tetrathiafulvalene (BEDT-TTF or ET for short). 2D organic superconductors based on the latter molecule are found to show Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states at high magnetic fields and low temperatures. Thermodynamic and nuclear magnetic resonance data give robust evidence for the existence of this FFLO state with modulated order parameter.

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  • Secondary publication expected from 05.09.2020

Permalink: https://www.hzdr.de/publications/Publ-29831
Publ.-Id: 29831


A numerical simulator for modeling the coupling processes of subsurface fluid flow and reactive transport processes in fractured carbonate rocks
Yuan, T.ORC; Wei, C.; Zhang, C.-S.; Qin, G.
Water–rock interactions can alter rock properties through chemical reactions during subsurface transport processes like geological CO2 sequestration (GCS), matrix acidizing, and waterflooding in carbonate formations. Dynamic changes in rock properties cause a failure of waterflooding and GCS and could also dramatically affect the efficiency of the acidizing. Efficient numerical simulations are thus essential to the optimized design of those subsurface processes. In this paper, we develop a three-dimensional (3D) numerical model for simulating the coupled processes of fluid flow and chemical reactions in fractured carbonate formations. In the proposed model, we employ the Stokes–Brinkman equation for momentum balance, which is a single-domain formulation for modeling fluid flow in fractured porous media. We then couple the Stokes–Brinkman equation with reactive-transport equations. The model can be formulated to describe linear as well as radial flow. We employ a decoupling procedure that sequentially solves the Stokes–Brinkman equation and the reactive transport equations. Numerical experiments show that the proposed method can model the coupled processes of fluid flow, solute transport, chemical reactions, and alterations of rock properties in both linear and radial flow scenarios. The rock heterogeneity and the mineral volume fractions are two important factors that significantly affect the structure of conductive channels.
Keywords: reactive-transport; fracture evolution; mineral dissolution; fractured carbonate formations

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Permalink: https://www.hzdr.de/publications/Publ-29830
Publ.-Id: 29830


Population balance modelling of isothermal and non-isothermal bubbly flows
Liao, Y.;
In bubbly flows, bubble size may vary with time and space as the result of coalescence and breakage, shrinkage and growth due to mass and/or heat transfer as well as other dynamic and transport processes occurring at the interface. One major task and challenge in modelling of bubbly flows is to reconstruct these processes and trace the change of local bubble size, since it is crucial in affecting the rate of all interfacial transfers. The population balance equation provides the basis for the description of the dynamics of particulate systems. It has become of great interest in a number of scientific disciplines or application fields. Different forms of the population balance models have been presented, and they all allow one to take into account above bubble size change mechanisms through so-called kernels. Nevertheless, continuous efforts are needed in developing, calibrating and validating the kernels. In addition, reliable and efficient solution of the population balance equation is not trivial. The presentation will focus on the class method of population balance modelling, its coupling with the two-fluid-model and application to adiabatic air-water, condensing and evaporating steam-water bubbly flows as well as recent progresses in developing coalescence and breakup kernels.
Keywords: Bubbly flow, Coalescence and breakup, CFD-PBM coupled method, Phase change, Population balance model
  • Invited lecture (Conferences)
    NSFC-DEG International Workshop on Three-Phase Flow Modelling and Simulation, 23.-25.10.2019, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-29825
Publ.-Id: 29825


Ferromagnetic resonance detection in magnetic single objects via a novel microresonator and microantenna approach
Cansever, H.ORC; Lenz, K.ORC; Narkowicz, R.; Kowalska, E.ORC; Faßbender, J.ORC; Deac, A. M.; Lindner, J.
Ferromagnetic resonance has been commonly used as a spectroscopic technique investigating the fundamental properties of ferromagnetic materials, such as magnetization, g-factor, magnetic anisotropy and damping (relaxation) parameters [1-4].Conventionally, an FMR spectrometer is operating at a fixed microwave frequency to detect the microwave absorption of the magnetic object by sweeping an external magnetic field through the resonance. The sensitivity of this weak absorption process is typically enhanced by using a microwave bridge setup. However, for a reliable quantification of key magnetic parameters like the g-factor or spin relaxation times, the measurements should be performed within a broad range of frequencies. This is achieved by broadband FMR spectrometers which employ vector network analyzers (VNA) that detect the microwave transmission or reflection parameters of the sample [5-6]. However, neither conventional cavities nor broadband FMR spectrometers are able to detect signals of micro/nano size samples due to the tiny sample volume. To achieve optimal sensitivity for small objects, planar microresonators were introduced for electron paramagnetic resonance (EPR) experiments [7]. Microresonators have been used to investigate magnetization dynamics of magnetic object to understand uniform and spin wave modes [8], as well as the spin-Seebeck effect in magnetic tunnel junctions [9.] The microresonator approach allows producing rf magnetic fields homogeneously concentrated inside a metallic loop, thereby increasing the filling factor of the resonator. Here, we explain the novel microesonator approach in detail and introduce moreover a microantenna approach which allows to perform experiments in the range of 8-18 GHz employing a co-planar layout. We investigate magnetization dynamics within Permalloy (Ni80Fe20) wires by using both, microresonator and microantenna approach.

[1] P. E. Wigen, C.F. Kooi, M. R Shanaberger, T. R. Rosing, Phys. Rev. Lett. 9, 206, 1962.
[2] P. E. Wigen, Z. Zhang, Braz. J. Phys. 22, 267, 1992.
[3] M. Farle, “Rep. Prog. Phys. 61, 755, 1998.
[4] J. R. Fermin, A. Azevedo, F. M. Aguiar, B. Li, S. M. J. Rezende, Appl. Phys. 85, 7316, 1999.
[5] M. Vroubel, Y. Zhuang, B. Rejaei, J. N. Burghartz, J. Appl. Phys. 99, 08P506, 2006.
[6] C. Nistor, K. Sun, Z. Wang, M. Wu, C. Mathieu, M. Hadley Appl. Phys. Lett. 95, 012504, 2009.
[7] R. Narkowicz, D. Suter, I. Niemeyer, Rev. Sci. Instrum. 79, 084702, 2008.
[8] A Banholzer, R Narkowicz, C Hassel, R Meckenstock, S Stienen, O Posth, D Suter, M Farle, J Lindner, Nanotechnology, 22, 295713, 2011.
[9] H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac, J. Phys. D: Appl. Phys. 51, 22400, 2018.
Keywords: ferromagnetic resonance, microresonator, microantenna
  • Open Access LogoInvited lecture (Conferences)
    9th APMAS 2019 INTERNATIONAL ADVANCES IN APPLIED PHYSICS & MATERIALS SCIENCE CONGRESS & EXHIBITION, 20.-28.10.2019, Fethiye- Mugla, Turkey

Permalink: https://www.hzdr.de/publications/Publ-29814
Publ.-Id: 29814


Automated SEM Mineral Liberation Analysis (MLA) with Generically Labelled EDX Spectra in the Mineral Processing of Rare Earth Element Ores
Schulz, B.; Merker, G.; Gutzmer, J.ORC
Many rare earth element (REE) deposits have experienced multistage geological enrichment processes resulting in REE bearing mineral assemblages of considerable complexity and variability. Automated scanning electron microscopy (SEM) mineral liberation analysis of such REE ores is confronted by the difficult assignment of energy-dispersive X-ray (EDX) spectra to REE mineral names. To overcome and bypass this problem, a generic and reliable labelling of EDX reference spectra obtained from REE-bearing minerals based on their contents of Si, Ca, F and P in a bulk normalised analysis is proposed. The labelled spectra are then combined into groups of REE-P (similar to monazite), REE-Ca-Si-P (similar to britholite), REE-Ca-F (similar to synchysite) and REE-F (similar to bastnaesite, parisite, fluocerite). Mixed spectra with low counts for REE from minute REE mineral grains are combined into a separate group. This classification scheme is applied to automated SEM mineral liberation analysis (MLA) data from beneficiation products by comminution and multistage flotation of REE carbonatite ores. Mineral modes, mineral grain size distribution, mineral liberation, mineral locking and mineral grade versus recovery curves based on the analysis of >200,000 particles in a sample can be recognised and interpreted in virtual grain size fractions. The approach as proposed here will allow future process mineralogical studies of REE deposits to be robust and comparable.

Permalink: https://www.hzdr.de/publications/Publ-29796
Publ.-Id: 29796


Independent Geometrical Control of Spin and Charge Resistances in Curved Spintronics
Das, K. S.; Makarov, D.ORC; Gentile, P.; Cuoco, M.; van Wees, B. J.; Ortix, C.; Vera-Marun, I. J.
Spintronic devices operating with pure spin currents represent a new paradigm in nanoelectronics, with a higher energy efficiency and lower dissipation as compared to charge currents. This technology, however, will be viable only if the amount of spin current diffusing in a nanochannel can be tuned on demand while guaranteeing electrical compatibility with other device elements, to which it should be integrated in high-density three-dimensional architectures. Here, we address these two crucial milestones and demonstrate that pure spin currents can effectively propagate in metallic nanochannels with a three-dimensional curved geometry. Remarkably, the geometric design of the nanochannels can be used to reach an independent tuning of spin transport and charge transport characteristics. These results laid the foundation for the design of efficient pure spin current-based electronics, which can be integrated in complex three-dimensional architectures.
Keywords: curved nanoarchitectures, electrical and spin resistance, geometrical control, nonlocal spin valves, Spintronics

Permalink: https://www.hzdr.de/publications/Publ-29794
Publ.-Id: 29794


Effects of Magnetic Field on Hydrogen Bubble Detachment during Water Electrolysis
Yang, X.ORC; Mutschke, G.ORC; Margitta, U.; Eckert, K.ORC
Water electrolysis is a promising option for hydrogen production from renewable resources. One main challenge in making water electrolysis economically competitive is to raise its efficiency by decreasing the cell voltage. In this respect, electrode coverage by gas bubbles is one of the key sources which creates undesired overpotential.

Better understanding of the fundamentals of bubble nucleation, growth, and detachment in detail might bring new ideas in such effective manipulating of bubbles and substantially accelerate a way toward advanced electrolysis. Despite extensive efforts in the past, important aspects of bubble dynamics, such as the interaction/coalescence of bubbles significantly affecting their evolution or different growth modes of the bubbles themselves, are not yet fully understood. To provide that necessary information on the bubble shape profile, including the contact angle, the contact line the bubble forms with the electrode [1], the Marangoni convection[2], we use a micro electrode to produce single hydrogen bubbles. Water electrolysis was carried out under potentiostatic conditions in a 1 M H2SO4 solution in a small electrochemical cell ([2], [3], [4]). The behavior of a single hydrogen bubble evolving on a microelectrode (100 µm in diameter) was analyzed by measurements of the current transient as well as by microscopic high speed imaging. Tracer particles were additionally added to the solution to measure the flow in the vicinity of the bubble.

The contribution will present experimental results of the hydrogen bubble release size and the bubble growing mechanism at two different magnetic field orientations and at different field intensities. As shown in Fig.1, the bubble departure size decreased with increase of the magnetic field intensity when the magnetic field was applied parallel to the electrode surface. However, an increase of the departure size was observed when the field was applied perpendicular to the electrode surface. The effects were further explained by the MHD convection around the bubble. A comparison of the flow field by measurements and numerical simulation will be presented.
  • Lecture (Conference)
    The 8th International Conference on Magneto-Science, 10.-14.10.2019, Hefei, China

Permalink: https://www.hzdr.de/publications/Publ-29792
Publ.-Id: 29792


Engineering Self-Supported Noble Metal Foams Toward Electrocatalysis and Beyond
Du, R.; Jin, X.; Hübner, R.; Fan, X.; Hu, Y.; Eychmüller, A.;
Noble metals, despite their expensiveness, display irreplaceable roles in widespread fields. To acquire novel physicochemical properties and boost the performance-to-price ratio for practical applications, one core direction is to engineer noble metals into nanostructured porous networks. Noble metal foams (NMFs), featuring self-supported, 3D interconnected networks structured from noble-metal-based building blocks, have drawn tremendous attention in the last two decades. Inheriting structural traits of foams and physicochemical properties of noble metals, NMFs showcase a variety of interesting properties and impressive prospect in diverse fields, including electrocatalysis, heterogeneous catalysis, surface-enhanced Raman scattering, sensing and actuation, etc. A number of NMFs have been created and versatile synthetic approaches have been developed. However, because of the innate limitation of specific methods and the insufficient understanding of formation mechanisms, flexible manipulation of compositions, structures, and corresponding properties of NMFs are still challenging. Thus, the correlations between composition/structure and properties are seldom established, retarding material design/optimization for specific applications. This review is devoted to a comprehensive introduction of NMFs ranging from synthesis to applications, with an emphasis on electrocatalysis. Challenges and opportunities are also included to guide possible research directions in this field and promote the interest of interdisciplinary scientists.

Permalink: https://www.hzdr.de/publications/Publ-29789
Publ.-Id: 29789


Updates on the FLUKA geometry for the MU2E experiment
Müller, S.ORC; Ferrari, A.ORC; Rachamin, R.ORC
Presentation at Mu2e Collaboration Meeting 16.10.2019
Keywords: Mu2e, FLUKA, Monte Carlo, CLFV
  • Lecture (Conference)
    Mu2e Collaboration Meeting, 16.-19.10.2019, Fermilab, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29784
Publ.-Id: 29784


Synthesis and cyclooxygenase inhibition of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their potential prodrugs
Laube, M.ORC; Gassner, C.; Knieß, T.ORC; Pietzsch, J.ORC
Non-invasive imaging of cyclooxygenase-2 (COX-2) by radiolabeled ligands is attractive for the diagnosis of cancer and novel highly affine leads with optimized pharmacokinetic profile are of high interest for future developments. Recent findings have shown that methylsulfonyl-substituted (dihydro)pyrrolo[3,2,1-hi]indoles represent highly potent and selective COX-2 inhibitors but possess unsuitable pharmacokinetic properties for radiotracer applications. Based on these results, we herein present the development and evaluation of a second series of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their conversion into the respective more hydrophilic N-propionamide-substituted analogs. In comparison to the methylsulfonyl-substituted leads, COX inhibition potency and selectivity was retained in the sulfonamide-substituted compounds; however, the high lipophilicity might hinder their future use. The N-propionamide-substituted analogs showed a significantly decreased lipophilicity and, as expected, lower or no COX-inhibition potency. Hence, the N-(sulfonyl)propionamides can be regarded as potential prodrugs, which represents a potential approach for more sophisticated radiotracer developments.
Keywords: Cancer; Imaging; Inflammation; Lipophilicity; McMurry cyclization; Structure-Activity-Relationship

Permalink: https://www.hzdr.de/publications/Publ-29783
Publ.-Id: 29783


⁹⁹Tc immobilization by aluminum solids containing Fe(II) moieties
Mayordomo Herranz, N.ORC; Rodriguez Hernandez, D. M.; Molodtsov, K.; Johnstone, Erik V.; Roßberg, A.; Heim, K.; Foerstendorf, H.ORC; Schild, Dieter; Brendler, V.ORC; Müller, K.ORC
The immobilization of ⁹⁹Tc is predominantly mediated by the reduction of Tc(VII) to Tc(IV), primarily due to the fact that [Tc(VII)O₄] ⁻ interactions with solid interfaces are limited, whereas Tc(IV)O₂ is a hardly soluble solid [1]. Tc reduction is facilitated by Fe²⁺, particularly when it is present as a sorbed species or a constituent mineral phase [2].
The present work analyzes the ⁹⁹Tc aqueous removal by two aluminum solids containing Fe(II) moieties: γ-Al₂O₃ with sorbed Fe²⁺ and Fe(II)-Al(III) layered double hydroxide (LDH). Batch contact experiments demonstrate that both solids are effective Tc scavengers, yielding a complete removal for pH > 6.5 and from pH 3.5 to 10.5, respectively. Characterization via XPS, XAS, and in situ ATR FT-IR spectroscopy provided information of the Tc speciation and uptake mechanism. Secondary Fe-minerals (hematite, magnetite, ferrihydrite) formed in the reduction were also identified by Raman microscopy.

Bibliography
[1] Meena, A. H.; Arai, Y. Env. Chem Lett 2017, 15, 241–263.
[2] Cui, D.; Eriksen, T. E. Environ. Sci. Technol. 1996, 30 (7), 2259–2262.
  • Lecture (Conference)
    The 43th symposium on scientific basis for nuclear waste management, 21.-24.10.2019, Viena, Austria

Permalink: https://www.hzdr.de/publications/Publ-29778
Publ.-Id: 29778


Some microbial issues regarding the storage of high-level radioactive waste
Matschiavelli, N.ORC; Kluge, S.; Dressler, M.; Cherkouk, A.ORC
The talk summerizes bio-geochemical results regarding the potential geo-technical barrier bentonite in a repositors of high-level radioactive waste.
  • Lecture (others)
    18th bilateral meeting HZDR/IRE - PSI/LES, 28.-29.10.2019, HZDR, IRE, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29777
Publ.-Id: 29777


Nonstoichiometric Phases of Two-Dimensional Transition-Metal Dichalcogenides: From Chalcogen Vacancies to Pure Metal Membranes
Joseph, T.ORC; Ghorbani Asl, M.ORC; Kvashnin, A. G.ORC; Larionov, K. V.ORC; Popov, Z. I.; Sorokin, P. B.ORC; Krasheninnikov, A.ORC
Two-dimensional (2D) membranes consisting of a single layer of Mo atoms were recently manufactured [ Adv. Mater. 2018, 30, 1707281] from MoSe2 sheets by sputtering Se atoms using an electron beam in a transmission electron microscope. This is an unexpected result as formation of Mo clusters should energetically be more favorable. To get microscopic insights into the energetics of realistic Mo membranes and nonstoichiometric phases of transition-metal dichalcogenides (TMDs) MaXb, where M = Mo and W and X = S, Se, and Te, we carry out first-principles calculations and demonstrate that the membranes, which can be referred to as metallic quantum dots embedded into a semiconducting matrix, can be stabilized by charge transfer. We also show that an ideal neutral 2D Mo or W sheet is not flat but a corrugated structure, with a square lattice being the lowest-energy configuration. We further demonstrate that several intermediate nonstoichiometric phases of TMDs are possible as they have lower formation energies than pure metal membranes. Among them, the orthorhombic metallic 2D M4X4 phase is particularly stable. Finally, we study the properties of this phase in detail and discuss how it can be manufactured by the top-down approaches.
Keywords: 2D, non-stoichiometric phases, Transition-Metal Dichalcogenides, DFT, metal membrane

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  • Secondary publication expected from 07.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29776
Publ.-Id: 29776


M4F - Materials Modelling For Fusion and Fission Materials - Domain 1
Heintze, C.; Olsson, P.; Konstantinovic, M.; Caturla, M.-J.;
The talk provides on overview on the objectives, activities and first results of Domain 1 of the H2020/EU project M4F. It aims at providing a broader scientific motivation and background for the benefit of the PhD students and post-docs participating in the project.
  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29774
Publ.-Id: 29774


Behaviour of C, Ni, Si, P under ion irradiation at different doses in model FeCr(Ni, Si, P) alloys
Gueye, P.-M.; Gomez-Ferrer, B.; Heintze, C.; Pareige, C.;
Ferritic-martensitic steels with high chromium content are considered as promising candidates as structural materials in Gen-IV reactors because of their low swelling value for operating conditions and low ductile-brittle transition temperature (DBTT) shift under irradiation. Nevertheless, they tend to harden and embrittle under irradiation at low temperatures (350°C). Impurities as Ni, Si and P are known to increase hardening in these steels by creating solute-rich clusters (SRCs) [1-4].
In order to understand the role of each impurity on the formation of SRCs under irradiation, FeCr (NiSiP) alloys with different concentrations in Ni, Si and P have been ion irradiated with 5 MeV Fe2+ ions up to 0.1, 0.5 and 2.5 dpa at 300°C. The evolution of the solute distribution has been investigated by atom probe tomography (APT).
The results reveal the tendency to cluster of Ni, Si and P under irradiation from 0.1 dpa. Moreover, differences on the solutes distributions between materials containing one low-alloying element (Ni, Si or P) and the alloy containing Ni, Si and P, suggest a synergetic effect between these species. Results show the major role of P on the formation of the SRCs. The influence of C on the formation of SRCs will also be discussed.

References
[1] F. Garner, M. Toloczko, B. Sencer, J. Nucl. Mater. 276 (2000) 123.
[2] R. L. Klueh, A. T. Nelson, J. Nucl. Mater. 371 (2007) 37-52.
[3] A. Kohyama, A. Hishinuma, D. S. Gelles, R. L. Klueh, W. Dietz, K. Ehrlich, J. Nucl. Mater. 233-237 (1996) 138-147.
[4] B. Gomez-Ferrer, C. Heintze, C. Pareige, J. Nucl. Mater. 515 (2019) 35-44.
  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29773
Publ.-Id: 29773


On the role of Ni, Si and P on the nanostructural evolution of FeCr alloys under irradiation – link with hardening
Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Oñorbe, E.; Hernandez-Mayoral, M.; Desgardin, P.; Malerba, L.;
High-chromium ferritic-martensitic (F-M) steels are promising candidates for structural components in Gen-IV reactors because of their excellent swelling resistance and good thermal properties. However, the operating window of these steels is constrained by irradiation hardening at low temperature (<350°C). This issues has been addressed within the FP7/MatISSE project.
After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small invisible dislocation loops1. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, FeCr(SiNiP) alloys of different composition has been ion irradiated and characterized using transmission electron microscopy, atom probe tomography, positron annihilation and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the concentration of vacancy defects, formation of solute clusters and dislocation loops and to make the link with irradiation hardening.
  • Lecture (Conference)
    SMINS 5 - NEA International Workshop on Structural Materials for Innovative Nuclear Systems, 08.-11.07.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29772
Publ.-Id: 29772


Influence of impurities in microstructural evolution of FeCr alloys under ion irradiation – link with hardening
Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Onorbe, E.; Hernándet Mayoral, M.; Gueye, P.-M.; Malerba, L.;
After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small dislocation loops. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, FeCr(SiNiP) alloys of different composition have been ion irradiated and characterized using transmission electron microscopy, atom probe tomography and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the formation of solute clusters and dislocation loops and to make the link with irradiation hardening. Influence of C atoms on the nanostructure evolution will also be discussed.
  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29771
Publ.-Id: 29771


Neutron irradiated microstructure of FeCr alloys investigated by TEM
Hernández Mayoral, M.; Onorbe, E.; Gómez-Ferrer, B.; Heintze, C.; Malerba, L.; Gueye, P.-M.; Pareige, C.;
Different parameters have been observed to influence the nature and evolution of the neutron radiation induced features, which are responsible of the mechanical behavior of FeCr-based alloys. In this work, the experimental conditions were selected so as to focus on the effect of both, composition and irradiation temperature. The study has been performed in the framework of collaborative European funded projects, where a combination of advanced characterization techniques was applied to a set of alloys of varying composition and initial microstructure, which were irradiated together under different conditions of temperature, dose and also dose-rate. The characterization of dislocation loops has been performed on the basis of Transmission Electron Microscopy (TEM), while the solute redistribution has been studied by Atom Probe Tomography (APT). The results, that show how the involved variables affect the neutron irradiated microstructure, will be presented and discussed.
  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29770
Publ.-Id: 29770


Hyperspectral outcrop models for palaeoseismic studies
Kirsch, M.ORC; Lorenz, S.; Zimmermann, R.ORC; Andreani, L.ORC; Tusa, L.; Pospiech, S.; Jackisch, R.ORC; Unger, G.; Khodadadzadeh, M.; Ghamisi, P.; Middleton, M.; Ojala, A.; Mattila, J.; Nordbäck, N.; Palmu, J.-P.; Ruskeeniemi, T.; Sutinen, R.; Tiljander, M.; Heikkilä, P.; Gloaguen, R.ORC
The traditional study of palaeoseismic trenches, involving logging, stratigraphic and structural interpretation, can be time consuming and affected by biases and inaccuracies. To overcome these limitations, a new workflow is presented that integrates infrared hyperspectral and photogrammetric data to support field-based palaeoseismic observations. As a case study, this method is applied on two palaeoseismic trenches excavated across a post-glacial fault scarp in northern Finnish Lapland. The hyperspectral imagery (HSI) is geometrically and radiometrically corrected, processed using established image processing algorithms and machine learning approaches, and co-registered to a structure-from-motion point cloud. HSI-enhanced virtual outcrop models are a useful complement to palaeoseismic field studies as they not only provide an intuitive visualisation of the outcrop and a versatile data archive, but also enable an unbiased assessment of the mineralogical composition of lithologic units and a semi-automatic delineation of contacts and deformational structures in a 3D virtual environment.
Keywords: palaeoseismology, SfM photogrammetry, hyperspectral imaging, geology, remote sensing, outcrop models

Permalink: https://www.hzdr.de/publications/Publ-29768
Publ.-Id: 29768


Direct Synthesis of Large-Scale Multilayer TaSe2 on SiO2/Si Using Ion Beam Technology
Tsai, H.-S.; Liu, F.-W.; Liou, J.-W.; Chi, C.-C.; Tang, S.-Y.; Wang, C.ORC; Ouyang, H.; Chueh, Y.-L.; Liu, C.; Zhou, S.ORC; Woon, W.-Y.
The multilayer 1T-TaSe2 is successfully synthesized by annealing a Se-implanted Ta thin film on the SiO2/Si substrate. Material analyses confirm the 1T (octahedral) structure and the quasi-2D nature of the prepared TaSe2. Temperaturedependent resistivity reveals that the multilayer 1T-TaSe2 obtained by our method undergoes a commensurate charge-density wave (CCDW) transition at around 500 K. This synthesis process has been applied to synthesize MoSe2 and HfSe2 and expanded for synthesis of one more transition-metal dichalcogenide (TMD) material. In addition, the main issue of the process, that is, the excess metal capping on the TMD layers, is solved by the reduction of thickness of the as-deposited metal thin film in this work.
Keywords: TaSe2, charge-density wave, ion beam, synthesis

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Permalink: https://www.hzdr.de/publications/Publ-29766
Publ.-Id: 29766


Production of the amphiphilic siderophore Marinobactin for the application as froth flotation reagent. 
Schrader, S.; Kutschke, S.; Rudolph, M.ORC; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Lecture (Conference)
    23. International Biohydrometallurgy Symposium, 20.10.2019, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-29765
Publ.-Id: 29765


Amphiphilic Siderophores – A group of complexing surfactant bioreagents for the application in froth flotation separation
Schrader, S.; Kutschke, S.; Hartmann, S.; Pollmann, K.; Rudolph, M.ORC
The consumption of metallic raw materials is constantly increasing. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, new approaches will have to be developed, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in conventional froth flotation processes. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to selectively form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate functional groups, is responsible for the selective binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same and even more selective functional groups are highly potential as ecofriendly collector molecules for flotation and should generally be interesting for the surfactant industry. The molecule’s tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work includes also interaction studies and flotation experiments of different scales, including bubble pick-up tests, Halimond tube microflotation and batch lab flotation experiments of iron and copper bearing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Zerkleinern und Klassieren, Kristallisation und Grenzflächenbestimmte Systeme und Prozesse, 12.-13.03.2019, Bamberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29764
Publ.-Id: 29764


Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
Reschke, E.ORC; Konrad, U.ORC
Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien (https://www.go-fair.org/fair-principles/) zu unterstützen, wurde am HZDR ein integriertes Publikationsmanagement aufgebaut. Insbesondere Daten- und Softwarepublikationen erfordern die Entwicklung bedarfsgerechter organisatorischer und technischer Strukturen ergänzend zu bereits sehr gut funktionierenden Services im Publikationsmanagement. In der Zusammenarbeit mit Wissenschaftlern des HZDR und internationalen Partnern in ausgewählten Projekten wurde der Bedarf an Unterstützung im Forschungsdatenmanagement analysiert. Darauf aufbauend wurde schrittweise ein integriertes System von Infrastrukturen und Services entwickelt und bereitgestellt. In einer seit Mai 2018 gültigen Data Policy wurden die Rahmenbedingungen und Regelungen sowohl für wissenschaftliche Mitarbeiter als auch für externe Messgäste definiert. Im Vortrag wird auf die Erfahrungen im integrierten Publikationsmanagement für Artikel, Forschungsdaten und Forschungssoftware eingegangen und daraus resultierend werden die nächsten Aufgaben und Ziele entwickelt.
Keywords: Open Access, Research Data, Rodare, Robis, Research Infrastructure
  • Open Access LogoInvited lecture (Conferences)
    „Forschungsdaten in Sachsen: Planen – Organisieren – Nachnutzen“ – 1. sächsische FDM-Tagung, 19.09.2019, Dresden, Deutschland
    Published in the HZDR-Repository RODARE (Test)
    DOI 10.14278/rodare.353

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29763
Publ.-Id: 29763


Production of the amphiphilic siderophore marinobactin and the application as froth flotation reagent
Schrader, S.; Kutschke, S.; Rudolph, M.ORC; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Poster
    4th Green & Sustainable Chemistry Conference, 05.-08.05.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29762
Publ.-Id: 29762


Design and Evaluation of a STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment
Knodel, O.ORC
Overview and status of the STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment located Fermilab.
Keywords: Data Management; DAQ; FPGA; Mu2e
  • Invited lecture (Conferences)
    STM-Working Group Meeting, 09.10.2019, Batavia, United States

Permalink: https://www.hzdr.de/publications/Publ-29759
Publ.-Id: 29759


HZDR Data Management Strategy — An Overview
Knodel, O.ORC; Müller, S.ORC
Overview of the HZDR data management strategy, hosted services for collaborative work and a (planned) technical realization.
Keywords: Data Management
  • Invited lecture (Conferences)
    Meeting with the Scientific Computing Division at Fermilab, 08.10.2019, Batavia, United States

Permalink: https://www.hzdr.de/publications/Publ-29758
Publ.-Id: 29758


Recent progress in application of computational chemistry to actinide interaction with biomolecules
Tsushima, S.ORC
Thanks to rapid advancement in computing technology, computer chemistry is becoming increasingly important in the field of biology. This approach is nowadays a common tool for drug discovery or for studying diseases such as HIV. In this talk, I will present several examples in which computer chemistry was applied for studying potential health risk of accidental ingestion of actinides and lanthanides. The new approach called “fragment molecular orbital method” has been implemented to drastically reduce computing time, which made it possible to calculate interactions of actinide/lanthanide with large biological molecules such as DNA and protein using full quantum mechanical description. In one example, how uranium ingestion could damage DNA in a molecular scale will be presented.
  • Invited lecture (Conferences)
    Engineering Physics Seminar Series at the Department of Engineering Physics of the McMaster University, 04.10.2019, Hamilton, Canada

Permalink: https://www.hzdr.de/publications/Publ-29757
Publ.-Id: 29757


Crystallization of Anhydrous Proton from Acidic Aqueous Solution with Diamide Building Block
Kazama, H.; Tsushima, S.; Takao, K.;
Although H+ has the largest hydration enthalpy amongst all the monovalent cations, we have demonstrated that anhydrous H+ can be crystallized together with selected diamide building block (L) and NO3− even in acidic aqueous solutions, which were confirmed in 3 different structures. One of these anhydrous H+ adducts constitutes of H+-involved hydrogen bond polymers [L···H+]n, which are coupled with another H+ adduct [O2NO−···H+···O−NO2]− as a counteranion unit. The anhydrous H+ can also be trapped between L and NO3− to form heteroleptic O···H+···O hydrogen bonds observed in two different crystal structures. DFT calculations revealed that there is no energetic barrier in these O···H+···O hydrogen bonds, having so-called a single-well hydrogen bond.

Permalink: https://www.hzdr.de/publications/Publ-29756
Publ.-Id: 29756


Re-mining of mine wastes in Germany: Challenges and opportunities
Büttner, P.; Nühlen, J.; Meima, J.; Gutzmer, J.ORC
The Fraunhofer Institute for Environmental, Safety, and Energy Technology and the Helmholtz Institute Freiberg for Resource Technology (HIF) have together compiled a mine waste cadaster for Germany on behalf of the Federal Institute for Geosciences and Natural Resources (BGR). For this purpose, a wide variety of data sources was evaluated with the aim to create a national database able to provide an overview about the content of critical raw materials (CRM) in mine waste repositories in Germany. Yet, even though mine wastes containing economically significant amounts of CRM, re-mining these anthropogenic “ore bodies” faces considerable technical and non-technical challenges.

Mine wastes often create environmental problems, such as acid rock drainage with associated high sulfate and heavy metal concentrations. This creates societal pressure for remediation. Remediation, however, is usually achieved by covering the surface with a water impermeable layer, an approach that is not sustainable, because of the required follow-up care and the inaccessibility of the resources that remain contained in the mine wastes. Besides that, legislative barriers are in conflict with recovering CRM and other metals and minerals from historic mine wastes. Many sites have essentially been abandoned since mining ceased in the 20th century. High metal contents and acidity released during sulfide oxidation has facilitated the establishment of a very specific flora and fauna. Species on these sites are often rare and strictly protected by environmental legislation. Metal recovery is all but impossible from such sites, despite the fact that acid rock drainage from these sites leads to environmental degradation downstream from the mine waste site.

Another important aspect is the general lack of suitable beneficiation and metallurgical infrastructure in Germany. Large capital investment would thus be necessary to enable the recovery of strategic metals from historic mine waste. Even if high metal concentrations are present in some mine wastes, small volumes will render the set-up of large, stationary plants unfeasible. Instead, flexible and semi-mobile small-scale technologies need to be developed. Such technologies are, at present, not available on the market.

To work at the intersection of society, legislation, remediation and re-mining is the aim of the new rECOmine partnership. This partnership is funded by the Federal Ministry of Education and Research (BMBF) for the next five years within the WIR! Program. It will be coordinated by HIF and build up three test sites in Saxony to develop combined remediation and re-mining technologies under real conditions with local partners.
Keywords: Re-Mining, Mine Waste, Resource, Tailing, Feasilbility, MLA
  • Lecture (Conference)
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-29755
Publ.-Id: 29755


Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease
Palhaugen, L.; Selnes, P.; Tecelao, S.; Lysvik, E. K.; Ingala, S.; Petr, J.ORC; Bjornerud, A.; Mutsaerts, H. J.; Fladby, T.
Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease
  • Open Access LogoContribution to proceedings
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway
  • Open Access LogoPoster
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway

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Permalink: https://www.hzdr.de/publications/Publ-29751
Publ.-Id: 29751


Scalable particle-in-cell simulations on many-core hardware with the free and open source code PIConGPU
Steiniger, K.ORC; Bastrakov, S.ORC; Cowan, T.ORC; Debus, A.ORC; Garten, M.ORC; Göthel, I.; Hübl, A.ORC; Juckeland, G.ORC; Kelling, J.; Kluge, T.ORC; Koßagk, S.; Matthes, A.ORC; Pausch, R.ORC; Schramm, U.ORC; Starke, S.; Widera, R.ORC; Worpitz, B.; Bussmann, M.ORC
Exploring new regimes, optimizing experimental setups, or quantifying sensitivity of final beam parameters on experimental parameters, represent current challenges for simulations of laser plasma accelerators. Time-to-solution and scalability are key parameters for codes to minimize turnaround times in order to scan e.g. tens of parameters such as the laser leading edge, resolve solid density target physics and run full-scale start-to-end simulations. PIConGPU reaches unprecedented performance by accelerating 100% of its computations on many-core architectures and leveraging next-generation scalable I/O. High-resolution, full-geometry studies on top-ten listed supercomputers decisively enhance predictive capabilities. PIConGPU's design allows for utilizing various compute architectures, including modern X86 and ARM CPUs and GPUs with a single, adaptable code base. Users can now run PIConGPU on almost any machine, either by easy recompiling or using predefined Docker images, and everybody can download, use and contribute to the code without extensive knowledge in compute architectures. We highlight latest additions to PIConGPU such as scalable file I/O via a new openPMD-API including ADIOS2 support for on the fly loosely coupled data analysis, live visualization with particle and field rendering, non-standard Gaussian laser pulses via Laguerre modes, in-situ X-ray scattering image generation, and an pythonic simulation setup interface.
Keywords: PIConGPU, Manycore, Scalable I/O, Alpaka, openPMD
  • Open Access LogoLecture (Conference)
    4th European Advanced Accelerator Concepts Workshop (EAAC2019), 15.-20.09.2019, La Biodola Bay - 57037 Portoferraio Isola d’Elba, Repubblica Italiana

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29750
Publ.-Id: 29750


Origin of the butterfly magnetoresistance in a Dirac nodal-line system
Chiu, Y.-C.; Chen, K.-W.; Schönemann, R.; Quito, V. L.; Sur, S.; Zhou, Q.; Graf, D.; Kampert, W. A. G.; Förster, T.; Yang, K.; Mccandless, G. T.; Chan, J. Y.; Baumbach, R. E.; Johannes, M. D.; Balicas, L.;
We report a study on the magnetotransport properties and on the Fermi surfaces (FS) of ZrSi(Se,Te) semimetals. Density-functional theory (DFT) calculations, in absence of spin orbit coupling (SOC), reveal that both the Se and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level εF at symmorphic and nonsymmorphic positions, respectively. We find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe displays low residual resistivities, pronounced magnetoresistivity, high carrier mobilities, and a butterflylike angle-dependent magnetoresistivity (AMR), although its DNL is not protected against gap opening. As in Cd3As2, its transport lifetime is found to be 102 to 103 times larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays conventional transport properties. Our evaluation indicates that both compounds most likely are topologically trivial. Nearly angle-independent effective masses with strong angle-dependent quantum lifetimes lead to the butterfly AMR in ZrSiSe.

Permalink: https://www.hzdr.de/publications/Publ-29749
Publ.-Id: 29749


The tremendous influence of hydrogenation on magnetism of NdMnGe
Ovchenkova, I. A.; Tereshina, I. S.; Bogdanov, A. E.; Tereshina-Chitrova, E. A.; Paukov, M. A.; Gorbunov, D.; Nikitin, S. A.;
The hydride NdMnGeH with the tetragonal ZrSiCuAs-type of structure (P4/nmm, N129, tP8) was obtained by hydrogen absorption at 523 K and 1 MPa from the NdMnGe intermetallic compound with a the tetragonal CeFeSi crystal structure (P4/nmm, N129, tP6). Measurements of magnetization in high magnetic fields up to 60 T and heat capacity measurements reveal pronounced changes in the magnetic properties of NdMnGe after hydrogenation. The Nd sublattice changes its ordering type from ferromagnetic to the antiferromagnetic one with a more than twofold decrease of and its magnetic ordering temperature (from 199 to 84 K). We explain the observed effects by the altered exchange interactions within the Nd sublattice resulting from the changed Nd–Nd interplane distances by interstitial atoms. The results are compared with data obtained previously for the NdMn1- xTixGe compounds, where the Ti substitution also changes significantly the magnetic properties.

Permalink: https://www.hzdr.de/publications/Publ-29748
Publ.-Id: 29748


THz relaxation dynamics and nonlinear optics in graphene
Helm, M.;
Graphene, because of its peculiar linear band structure, shows some fascinating effects in the relaxation processes of excited electrons. Due to the zero band gap, many of those processes are best investigated at low energies, in the THz region. By linearly polarized pump-probe measurements we show that fast thermalization occurs only with respect to energy, but not to momentum, i.e. the electron distribution remains anisotropic for more than 5 ps (Phys. Rev. Lett. 117, 087401 (2016)). Applying a magnetic field splits the bands into non-equidistant Landau levels. This gives rise to a situation, where strong pumping of a Landau level actually leads to its depletion, due to strong Auger type electron-electron scattering (Nat. Phys. 11, 75 (2015)). In the same system, a large, resonant third-order optical nonlinearity is demonstrated via degenerate four-wave mixing (Nano Lett. 17, 2184 (2017)). All experiments were performed with a THz free-electron laser at frequencies around 20 THz, in collaboration with M. Mittendorff, J. König-Otto, S. Winnerl, A. Pashkin H. Schneider, with theory support by F. Wendler, T. Winzer, F. Kadi, E. Malic, A. Knorr, Y. Wang, A. Belyanin, and samples from W. de Heer and C. Berger.
Keywords: free electron laser, graphene, terahertz, relaxation, nonlinear optics
  • Invited lecture (Conferences)
    2D Materials 2019, 30.09.-04.10.2019, Sochi, Russia

Permalink: https://www.hzdr.de/publications/Publ-29745
Publ.-Id: 29745


Helium interactions with (Y, Ti, O) nanoclusters in bcc Fe
Vallinayagam, M.; Posselt, M.ORC; Faßbender, J.ORC
Nanometer size (Y, Ti, O) clusters in nanostructured ferritic/martensitic Fe-Cr alloys can act as sinks for the transmutation product helium. In this manner irradiation swelling can be retarded significantly. Many details of He storage in or near the clusters are still not understood. In this work interactions of He with (Y, Ti, O) clusters in bcc Fe are investigated by density functional theory (DFT) calculations. Four different cluster structures studied in our previous work [1] are considered: Cage-type clusters with (i) 6 O atoms, 9 vacancies (v) and 6 Y atoms, and (ii) with 7 O, 9 v, 3 Y, and 3 Ti, as well as clusters with O in the center containing (iii) 6 O, 9 v, 6 Y, and (iv) 7 O, 9 v, 3 Y, 3 Ti. It is found that the most stable position of He is in the center of the cluster, followed by the interfacial substitutional site and other interstitial positions between metal or oxygen atoms, and sites away from the cluster. This shows the He trapping may be nearly irrespective of cluster morphology and mainly depend on cluster composition. Adding a second He atom to the cluster structure is investigated for selected cases. Furthermore, barriers for possible jumps between different sites at the rim of the cluster and the center are determined. First results show that these barriers are higher if the cluster contains Ti and that there is a strong dependence on the particular position at the rim. For the discussion of the results also the DFT data obtained from studies on the interaction of He with single O, Y, and Ti atoms as well as with a single vacancy are used.

[1] Vallinayagam et.al. Investigation of structural models for O-Y and O-Y-Ti clusters in bcc Fe: A DFT study J. Phys.: Condens. Matter (2018) https://doi.org/10.1088/1361-648X/aaf9cd
Keywords: DFT ODS He storage
  • Lecture (Conference)
    EUROMAT-2019 Conference, 01.09.-04.10.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-29736
Publ.-Id: 29736


First principles calculations of the thermodynamic stability of Ba, Zr, and O vacancies in BaZrO3
Nadarajan, R.; Devaraj, M.; Satyanarayana, S. V. M.; Posselt, M.ORC
The temperature dependence of the stability of bulk BaZrO3 (BZO) and of the vacancies in this material is investigated by considering phonon contributions to the free energy. The stability diagram of BZO is determined for different chemical environments. With increasing temperature the stability region becomes smaller which is particularly caused by the strong temperature dependence of the chemical potential of gaseous oxygen. The free formation energy of Ba, Zr, and O vacancies in BZO is calculated for all possible charge states and for different atomic reservoirs. While the free formation energy of Zr vacancies is strongly influenced by temperature a weaker dependence is found for Ba and O vacancies. This has also an effect on the charge transition levels at different temperatures. Present results demonstrate that O poor reservoir conditions and a Fermi level close to the valence band maximum favour a high concentration of doubly positively charged O vacancies which is a prerequisite to get a large number of protonic defects and a good proton conductivity. In such a chemical environment the amount of Ba and Zr vacancies is low so that Ba and Zr deficiencies are not an important issue and BZO stays sufficiently stable.
Keywords: DFT, Barium Zirconate, thermodynamic stability, vacancies

Permalink: https://www.hzdr.de/publications/Publ-29734
Publ.-Id: 29734


Comparison of Eulerian QBMM and classical Eulerian – Eulerian method for the simulation of polydisperse bubbly flows
Li, D.; Marchisio, D.; Hasse, C.; Lucas, D.;
The spatial gas distribution of poly-disperse bubbly flows depends greatly on the bubble size. To reflect the resulting polycelerity, more than two momentum balance equations (typically for the gas and liquid phases) have to be considered, as done in the multifluid approach. The inhomogeneous multiple-size group model follows this approach, also combined with a population balance model. As an alternative, in a previous work, an Eulerian quadrature-based moments method (E-QBMM) was implemented in OpenFOAM; however, only the drag force was included. In this work, different nondrag forces (lift, wall lubrication, and turbulent dispersion) are added to enable more complex test cases to be simulated. Simulation results obtained using E-QBMM are compared with the classical E – E method and validated against experimental data for different test cases. The results show that there is good agreement between E-QBMM and E – E methods for mono-disperse cases, but E-QBMM can better simulate the separation and segregation of small and large bubbles.
Keywords: bubbly flow, E – E method, E-QBMM, non-drag forces, wall peak

Permalink: https://www.hzdr.de/publications/Publ-29733
Publ.-Id: 29733


Lift Forces on Solid Spherical Particles in Wall-bounded Flows
Shi, P.ORC; Rzehak, R.
The present work is concerned with the lift forces acting on particles immersed in a wall-bounded fluid. Conditions where the particle translates in a fluid at rest and in a linear shear flow are considered. Likewise, non-rotating particles and particles in free rotation driven solely by the flow are considered. Furthermore, situations where the wall lies in the inner region and in the outer region of the flow disturbance produced by the particle are distinguished. The focus is on solid spherical particles at Reynolds numbers up to O(〖10〗^2 ) which are relevant for particulate flows in chemical and minerals engineering. A comprehensive review of existing results from analytical, experimental, and direct numerical simulation studies is given. The available correlations are critically assessed by comparison to data from these studies. Based on the comparison recommendations are given which correlations to use, including some new proposals, and gaps in the data are identified.
Keywords: lift force, particles, wall-bounded flow, particle rotation, inner / outer region, correlation

Permalink: https://www.hzdr.de/publications/Publ-29729
Publ.-Id: 29729


Au incorporation into various ZnO crystallographic cuts realised by ion implantation – ZnO damage characterization
Mackova, A.; Malinsky, P.; Jagerova, A.; Miksova, R.; Nekvindova, P.; Cajzl, J.; Böttger, R.; Akhmadaliev, S.;
Non-polar surfaces, such as a-plane (11–20) and m-plane (10-10), for ZnO have become more attractive as numerous efforts have recently been made to grow non-polar ZnO facets for applications in nanoscale photonic devices. Noble-metal incorporation into transparent semiconductors such as ZnO has been investigated because of the non-linear optical response of such structures. This paper presents a study of defect evolution in various ZnO crystallographic cuts caused by Au implantation. The investigation has focused on ZnO structure characterisation, Au distribution and the interior morphology of the a-, m- and c-planes ZnO single crystals implanted with 400 keV Au+ ions at the ion fluences of 5 × 1014 and 1 × 1015 cm−2 and subsequently annealed at 600 °C in O2. The structure modification was studied using Rutherford backscattering spectrometry (RBS) in the channelling mode (RBS/C) and Raman spectroscopy. After the ion-implantation process, low surface damage was observed in all ZnO orientations unlike deep structural damage. Deep structural damage grew with increased Au-ion fluence and Au did not exhibit strong out-diffusion from the depth to the surface during the post-implantation annealing. Small but noticeable differences were observed between different ZnO orientations. RBS measurements during ion implantation revealed more progressive deep-damage formation in the c- and m-planes than in the a-plane ZnO. Simultaneously, the smallest Zn sub-lattice disorder deduced from RBS/C measurements was observed in the a-plane ZnO. During post-implantation annealing, a slight structure recovery (about 4%) was observed in all orientations. Raman spectroscopy confirmed the increasing structure disorder with the enhanced ion fluence for all as-implanted ZnO orientations and a partial reconstruction of the ZnO structure during annealing, when the intensity of E2 phonons was increased and that of longitudinal optical (LO) phonons was suppressed because of the disorder recovery. E2 (high) and E1(LO) Raman phonon modes connected with oxygen sub-lattice ordering/disordering have been investigated in detail – they show a significant modification mainly in the m-plane. The cause of the different behaviour of ZnO planes as well as the differences in the incorporation and movement of Au and Er atoms in the ZnO structure are discussed in the work.

Permalink: https://www.hzdr.de/publications/Publ-29728
Publ.-Id: 29728


Entwicklung des Gesamtsystems - Stand der Modellierungs- und Simulationsarbeiten
Fogel, S.ORC
Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)
  • Lecture (others)
    5. Projekttreffen DELTA, 25.04.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29727
Publ.-Id: 29727


3. Zwischenbericht DELTA
Fogel, S.ORC
Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)
  • Other report
    Dresden: HZDR, 2019
    27 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29726
Publ.-Id: 29726


Single Cell and System Modeling of Tubular Proton Conducting Solid Oxide Steam Electrolyzers for Intermittent Operation
Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Due to the constantly growing utilization of wind and solar energy, the demand for technologies for temporal and spatial decoupling of energy provision and consumption is steadily increasing. The application of proton-conducting solid oxide electrolysis cells (H-SOEC) has been a main concern in recent research activities since they offer an environmentally friendly and efficient technique for the conversion of excess energy into hydrogen. As renewables occur intermittently, SOEC designs and all employed materials have to be capable of withstanding large electrical transients and therefore harsh operating conditions. Tubular cell designs of SOEC received increased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat, thermal cycling, thermal stresses and high-pressure application capabilities. Since the knowledge of the dynamic behavior of SOECs is key to their future application, this work aims to study the transient behavior of a single, proton conducting SOEC during rapid load variations and of multi-tubular stacks on a system scale under high-pressure operation. The use of different load variation speeds is discussed with respect to cell control.
Keywords: SOEC, load variation, transient operation, tubular cell, proton conduction
  • Lecture (Conference)
    12th European Congress of Chemical Engineering ECCE, 15.-19.09.2019, Florence, Italy

Permalink: https://www.hzdr.de/publications/Publ-29725
Publ.-Id: 29725


Transient behavior of tubular solid oxide electrolyzer cells under fast load variations
Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Solid oxide electrolyzer cells (SOEC) pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOEC under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conver-sion efficiency and application. As a consequence of the intermittent occurrence of renewables, SOEC designs and all employed materials have to be capable of with-standing harsh operating conditions, leading to strict demands regarding process control and the overall cell design. Tubular cell designs of SOECs received in-creased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat and thermal stresses. Further-more, tubular cells are characterized by significantly smaller sealing lengths in com-parison to planar cells, enabling a high-pressure application. Operating SOECs at elevated pressures poses beneficial opportunities for their future system application, since the produced hydrogen does not need to be compressed using a separate compressor stage or the electrolyzer can be combined with promising downstream synthesis units (e.g. methanol synthesis). Dynamic simulations can be used to de-termine the transient behavior of SOECs during operation with harsh load-transients. This simulation work aimed to study the transient behavior of a single, proton conducting SOEC during rapid load variations under high-pressure opera-tion. For this purpose, a two-dimensional model of a tubular SOEC was developed and different load steps and their influence on crucial operational parameters, such as temperature profiles, cell potential and species concentrations were investigated. The feasibility of the cell design regarding harsh transient load variations was stud-ied. Various load-pulse shapes and durations, different flow configurations and steam mass flow rates have been investigated and their influence on the short-term transient behavior of the cell were examined. With the aid of the aforementioned simulations, limiting operational states of the cell (e.g. steam starvation and tempera-ture hot-spots) as well as beneficial process parameter combinations for an im-proved cell operational behavior were ought to be identified with respect to advanc-es in cell control strategies.
Keywords: SOEC, dynamic operation, proton conduction
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 06.-07.03.2019, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29723
Publ.-Id: 29723


Synthesis, Structural Characterisation, and Cytotoxicity Studies of Bi, W, and Mo containing Homo- and Hetero-bimetallic Polyoxometalates
Senevirathna, D.; Werrett, M.; Kubeil, M.ORC; Stephan, H.ORC; Andrews, P.
Three new and different homo- and hetero-bimetallic polyoxometalate (POM) species have been synthesised by simple one-pot synthetic methods utilising naturally occurring bismite (Bi2O3) (or Bi(NO3)3·5H2O) and aryl sulfonic acids. The POM species isolated are {(NH4)14[Bi2W22O76]·14H2O} (1·14H2O), {NH4[Bi(DMSO)7][Mo8O26]·H2O} (2·H2O) and {[(NH4)4(Mo36O108(OH)4·16H2O)]·45H2O} (3·45H2O). The compounds have been characterised by X-ray crystallography, energy dispersive X-ray spectroscopy (EDX), powdered X-ray diffraction (PXRD), mass spectrometry (ESI-MS), Raman spectroscopy, thermogravimetric (TGA) and ICP analyis. In vitro cytoxicity and proliferation studies conducted on 1 and 3, highlight the low toxicity of these species.

Downloads:

  • Secondary publication expected from 01.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29719
Publ.-Id: 29719


Effect of nozzle geometry on pressure drop in submerged gas injection
Xiao, J.; Yan, H.-J.; Schubert, M.; Unger, S.; Liu, L.; Schleicher, E.; Hampel, U.ORC
Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths.
Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter AoL o −2 and on the modified Froude number gd o 5 Q−2 with the hydraulic diameter of the nozzle do as characteristic length.
Keywords: submerged gas injection; nozzle geometry; hydraulic diameter; pressure drop; modified Euler number

Permalink: https://www.hzdr.de/publications/Publ-29718
Publ.-Id: 29718


Effect of Bath Depth and Nozzle Geometry on Spout Height in Submerged Gas Injection at Bottom
Xiao, J.; Yan, H.; Liu, L.; Möller, F.; Hu, Z.; Unger, S.;
Spout height is a widely used parameter to quantitatively analyze the performance of the submerged gas injection in industrial applications. However, the effect of bath depth and nozzle geometry on spout height in submerged gas injection is still unclear. In this work, the effect of bath depth and nozzle geometry on spout height in submerged gas injection at bottom was experimentally investigated. Circular-shaped, three-leaf-shaped, four-leaf-shaped, and four-flower-shaped nozzles were used for this study. Spout height was extracted from the images captured by high-speed camera and analyzed by digital image processing. The results indicate that the effect of nozzle geometry on spout height is as important as gas flow rate and bath depth. Through dimensional analysis, predictive correlations of spout height from circular shape and four-leaf shape were developed with dimensionless bath depth and a modified Froude number using orifice perimeter and opening area as characteristic parameters. Experimental data were compared with the correlations from literature and good agreement was found.

Permalink: https://www.hzdr.de/publications/Publ-29717
Publ.-Id: 29717


Control and stimulation of three-magnon scattering in a magnetic vortex
Körber, L.ORC; Schultheiß, K.ORC; Hula, T.; Verba, R.ORC; Hache, T.ORC; Schultheiß, H.ORC
When applying a large enough RF field amplitude, spin waves in a magnetic vortex disk can decay into two other spin waves via three-magnon scattering. In order to reach the threshold of this process, the energy flux from the decay of the directly excited mode must overcome the internal losses of the secondary modes. The resulting scattering processes obey certain selection rules which result in the two output frequencies to be distinct from one another. Moreover, three-magnon scattering of the directly excited mode into multiple pairs of secondary modes is possible. However, typically one of these scattering channels has a lower threshold than the others which leads to this channel being activated first and limiting the energy flux in the other possible “silent” channels. Here, we show that three-magnon scattering in such a system can be stimulated below the usual instability threshold by additionaly pumping one of the secondary modes. This is achieved by coupling the magnetic vortex to an adjacent magnonic wave guide. The response to the stimulation is instantaneous and can be used to activate the silent three-magnon channels, as well.
Keywords: nonlinear, magnon, vortex, magnetism, magnonics
  • Lecture (Conference)
    Magnonics 2019, 28.07.-01.08.2019, Carovigno, Italien

Permalink: https://www.hzdr.de/publications/Publ-29716
Publ.-Id: 29716


Liquid metal battery research activities at HZDR
Weier, T.; Horstmann, G. M.ORC; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.
Liquid metal batteries are promising candidates for low-cost, large-scale stationary electricity storage. Different systems investigated at HZDR are discussed with a focus on fluid dynamic phenomena like interfacial wave interactions, mass transfer, and electro-vortex flows.
Keywords: liquid metal batteries, mass transfer, electro-vortex flows
  • Invited lecture (Conferences)
    Institutskolloquium Institut für Thermo- und Fluiddynamik TU Ilmenau, 12.09.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29715
Publ.-Id: 29715


Anisotropic temperature-field phase diagram of single crystalline β-Li2IrO3: Magnetization, specific heat, and 7Li NMR study
Majumder, M.; Freund, F.; Dey, T.; Prinz-Zwick, M.; Büttgen, N.; Scurschii, I.; Jesche, A.; Tsirlin, A. A.; Gegenwart, P.;
Detailed magnetization, specific heat, and 7Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyperhoneycomb Kitaev magnet β-Li2IrO3 are reported. At high temperatures, anisotropy of the magnetization is reflected by the different Curie-Weiss temperatures for different field directions, in agreement with the combination of a ferromagnetic Kitaev interaction (K) and a negative off-diagonal anisotropy (Γ) as two leading terms in the spin Hamiltonian. At low temperatures, magnetic fields applied along a or c have only a weak effect on the system and reduce the Néel temperature from 38 K at 0 T to about 35.5 K at 14 T, with no field-induced transitions observed up to 58 T on a powder sample. In contrast, the field applied along b causes a drastic reduction in the TN that vanishes around Hc = 2.8 T, giving way to a crossover toward a quantum paramagnetic state. Li NMR measurements in this field-induced state reveal a gradual line broadening and a continuous evolution of the line shift with temperature, suggesting the development of local magnetic fields. The spin-lattice relaxation rate shows a peak around the crossover temperature 40 K and follows power-law behavior below this temperature.

Permalink: https://www.hzdr.de/publications/Publ-29713
Publ.-Id: 29713


Microstructural Characterization of a VVER-440 type Reactor Pressure Vessel Steel by Electron Microscopy
Chekhonin, P.; Röder, F.; Müller, G.; Roßner, M.; Heintze, C.; Bergner, F.;
A microstructural investigation of a VVER400-type reactor pressure vessel (RPV) steel in the initial state (unirradiated) is presented. Key points include a detailed characterization by electron backscatter diffraction and an analysis of precipitates and inclusions performed by transmission as well as scanning electron microscopy.
Keywords: Microstructure, Reactor Pressure Vessel Steels, Electron Microscopy
  • Lecture (Conference)
    IGRDM-21 - 21st meeting of International Group on Radiation Damage Mechanism, 19.-24.05.2019, Gifu, Japan

Permalink: https://www.hzdr.de/publications/Publ-29711
Publ.-Id: 29711


Electronic properties of GaAs/InₓGa₁₋ₓAs and GaAs/InₓAl₁₋ₓAs core/shell nanowires studied by pump – probe THz spectroscopy
Fotev, I.ORC; Balaghi, L.ORC; Shan, S.; Hübner, R.; Schmidt, J.; Schneider, H.ORC; Helm, M.; Dimakis, E.ORC; Pashkin, A.ORC
We report terahertz response of photoexcited core/shell nanowires. The obtained parameters of the localized surface plasmon mode allow us to estimate electron mobilities, concentrations and recombination lifetimes. The extracted mobilities reach 4000 cm²/V·s at room temperature, while the carrier lifetimes range from 80 to 300 ps, depending on the shell composition and the photoexcitation level.
  • Lecture (Conference)
    French-German THz Conference 2019, 02.-05.04.2019, Kaiserslautern, Germany

Permalink: https://www.hzdr.de/publications/Publ-29709
Publ.-Id: 29709


Thz User Operation With 200 pC CW Beam Generated by the ELBE SRF Gun II
Arnold, A.; Awari, N.; Chen, M.; Deinert, J.-C.ORC; Evtushenko, P.; Green, B. W.ORC; Klopf, J. M.; Kovalev, S.; Lehnert, U.; Ma, S.; Murcek, P.; Michel, P.; Schaber, J.; Teichert, J.; Xiang, R.; Zwartek, P.
As a new electron source with higher brilliance, the second superconducting RF photoinjector (SRF Gun II) has been built at the ELBE radiation center for high power radiation sources. One of the main goals of SRF gun II is to achieve a higher bunch charge (>200 pC) and lower emittance (3 mm mrad) than the present ELBE thermionic DC gun. SRF Gun II features a 3.5-cell niobium cavity as well as a superconducting solenoid in the same cryomodule. With Mg photocathodes the gun is able to provide medium current beam with bunch charge of more than 200 pC and sub-ps bunch length at 100 kHz repetition rate. With this contribution we present convincing results from long-term user operation of SRF gun II in combination with the bunching concept of the ELBE accelerator in order to produce THz radiation with much higher stability and power than available using the existing thermionic gun.
Keywords: SRF Gun, THz, ELBE, electron source, photoinjector
  • Open Access LogoPoster
    63rd ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 15.-20.09.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29708
Publ.-Id: 29708


Developing multi-sensor drones for geological mapping and mineral exploration: setup and first results from the MULSEDRO project
Heincke, B.; Jackisch, R.ORC; Saartenoja, A.; Salmirinne, H.; Rapp, S.; Zimmermann, R.ORC; Pirttijärvi, M.; Vest Sörensen, E.; Gloaguen, R.ORC; Ek, L.; Bergström, J.; Karinen, A.; Salehi, S.; Madriz Diaz, Y. C.; Middleton, M.
The use of Unmanned Aerial Systems (UAS), also known as drones, is becoming increasingly important for geological applications. Thanks to lower operational costs and ease of use, UAS offer an alternative approach to aircraft-based and ground-based geoscientific measurements (Colomina & Molina 2014). Magnetic and hyperspectral UAS surveys hold particular promise for mineral exploration, and several groups have recently published studies of magnetic data collected by UAS for such applications (Malehmir et al. 2017; Cunningham et al. 2018), although equivalent studies using hyperspectral data are still rare (Kirsch et al. 2018). Combining both techniques is particularly useful. Magnetic measurements play an important role in mineral exploration, since magnetisation in rocks is mainly associated with magnetite and other iron minerals, which can be used in mapping and targeting of mineral deposits (Dentith & Mudge 2014). Hyperspectral imaging (HSI) is a powerful exploration and mapping technique in areas where the rock surface is well-exposed, and where geological units and mineral compositions can be estimated from spectral features of the electromagnetic spectrum in the visual and infrared range.
Keywords: Drones, Geological Mapping, Unmanned Aerial System, Hyperspectral imaging, Magnetic survey

Permalink: https://www.hzdr.de/publications/Publ-29707
Publ.-Id: 29707


Pump – Probe THz Spectroscopy Study of Electronic Properties of Semiconductor Nanowires
Fotev, I.ORC; Balaghi, L.ORC; Shan, S.; Hübner, R.; Schmidt, J.; Schneider, H.ORC; Helm, M.; Dimakis, E.ORC; Pashkin, O.ORC
THz radiation is a perfect tool for probing electrical properties of semiconductor nanostructures in a contactless way. When applied to semiconductor nanowires, THz probe pulses can drive the oscillations of photoexcited electrons and holes in the form of localized surface plasmon. We used optical pump – THz probe spectroscopy to study plasmonic response of charge carriers in GaAs/InₓGa₁₋ₓAs core/shell nanowires. The carrier lifetimes are about 80-100 ps, depending on the shell composition and the photoexcitation level, while the extracted mobilities reach 3700 cm²/V·s at room temperature.
Keywords: GaAs nanowires, terahertz spectroscopy, ultrafast dynamics, electron mobility, plasmon, carrier lifetime
  • Lecture (Conference)
    44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 01.-06.09.2019, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-29706
Publ.-Id: 29706


Current management of pheochromocytoma/paraganglioma: A guide for the practicing clinician in the era of precision medicine
Nölting, S.; Ullrich, M.ORC; Pietzsch, J.ORC; Ziegler, C. G.; Eisenhofer, G.; Grossman, A.; Pacak, K.
Pheochromocytomas and paragangliomas (PCC/PGLs) are rare, mostly catecholamine-producing neuroendocrine tumors of the adrenal gland (PCCs) or the extra-adrenal paraganglia (PGL). They can be separated into three different molecular clusters depending on their underlying gene mutations in any of the at least 20 known susceptibility genes: the pseudohypoxia-associated cluster 1, the kinase signaling-associated cluster 2, and the Wnt signaling-associated cluster 3. Besides tumor size, location (adrenal vs. extra-adrenal), age of first diagnosis, and presence of metastatic disease (including tumor burden), other decisive factors for best clinical management of PCC/PGL include the underlying germline mutation. The above factors can impact the choice of different biomarkers and imaging modalities for diagnosis, as well as screening for other neoplasms, staging, follow-up, and therapy options. This review provides a guide for practicing clinicians summarizing current management of PCC/PGL according to tumor size, location, age of first diagnosis, presence of metastases and especially underlying mutations in the era of precision medicine.
Keywords: pheochromocytoma, paraganglioma, guideline, genetics, diagnosis, imaging, follow-up, therapy, precision medicine

Permalink: https://www.hzdr.de/publications/Publ-29705
Publ.-Id: 29705


Migration of Actinide-Analogues visualized by Positron Emission Tomography GeoPET
Schymura, S.; Karimzadeh, L.; Mansel, A.; Franke, K.; Eichelbaum, S.; Frühwirt, T.; Zakhnini, A.; Jankovsky, F.; Zuna, M.; Molodtsov, K.; Kulenkampff, J.; Schmidt, M.ORC; Lippmann-Pipke, J.; Fischer, C.
The search of a final repository for nuclear wastes from energy and weapon production calls for knowledge of actinide migration from molecular to kilometer scales. The migration behaviour on the mm to centimetre scale bridges a crucial step for the up- scaling of molecular knowledge and the validation of models based thereupon. Using the positron-emitting analogue for trivalent actinides 86Y we visualized its migration behaviour in a fractured granite core using positron emission tomography.
A granite drill core was obtained from the Bukov underground research facility in the Czech Republic. An artificial fracture was induced into the core by a geomechanical shear test and the core was subsequently encased in a plexiglas column. Radiotracers 18F and 86Y were produced at the in-house cyclotron at the HZDR Research Site Leipzig. 18F was produced by proton irradiation of 18O enriched water via 18O(p,n)18F. 86Y was obtained by proton irradiation of 86Sr enriched SrCO3 via 86Sr(p,n)86Y. Positon emission tomography was performed using the GeoPET setup at the HZDR Research Site Leipzig.
A transport experiment consisting of two steps was performed. First, aqueous [18F]KF solution was injected into the core to establish the conservative flow path through the fracture. Second, an aqueous 10-5 M [86Y]Y(NO3)3 solution in 0.1 M NaCl at pH 7.5 was flown through the fracture, followed by the eluent. The transport behaviour of the actinide analogue was monitored for a throughput of several pore volumes. After the conclusion of the experiment the core was opened and the sorption pattern on the fracture surface was additionally imaged by autoradiography.
Under the chosen conditions most of the 86Y got sorbed in the area close to the inlet and only 1% got eluted. The sorption pattern follows the conservative flow path. More detailed investigations of the sorbed species by μTRLFS (using Eu as a luminescent probe) and a modelling of the experiment based on the extracted flow path from the GeoPET data are planned.
Keywords: Positronenemissionstomographie, Positron Emission Tomography Aktinide, Actinides
  • Poster
    GDCh Fachgruppentagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29700
Publ.-Id: 29700


Enhanced ion acceleration from a non-ideal laser pulse contrast
Garten, M.ORC; Huebl, A.; Widera, R.ORC; Göthel, I.; Obst-Huebl, L.; Ziegler, T.ORC; Zeil, K.; Cowan, T.ORC; Schramm, U.ORC; Bussmann, M.ORC; Kluge, T.ORC
The major challenges of compact proton sources driven by an ultrashort high-intensity laser are currently to establish precise control over proton beam parameters and shot-to-shot stability. Shooting ultrathin targets has shown to yield higher proton energies, which became recently accessible due to temporal laser pulse shape control using plasma-mirror techniques. We find that the intensity ramp, transmitted to the target by the plasma mirror during the last picosecond before the pulse peak, becomes significantly decisive for the subsequent acceleration performance. Reliable characterization of this ramp with modern laser diagnostics remains challenging and immense computational needs required to fully resolve the plasma kinetics leave it mostly unexplored in today's simulations of laser-solid interaction. We present the results of 3D large-scale simulations with PIConGPU, taking into account realistic contrast conditions, bridging the scales from picosecond pre-plasma formation over transient, non-equilibrium dynamics of the tens of femtosecond laser duration down to attosecond plasma oscillations. Adding to beneficial acceleration conditions presented by hybrid acceleration mechanisms and the onset of relativistic transparency, we show that the maximum proton energy can be optimized by a specific leading pulse edge via a combination of pre-thermal and thermal TNSA, surpassing the performance of the ideal diffraction-limited Gaussian pulse.
Keywords: laser-ion acceleration, TNSA, simulation, PIConGPU, CSCS, Piz Daint, PRACE, HPC
  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Italia

Permalink: https://www.hzdr.de/publications/Publ-29695
Publ.-Id: 29695


Conventional CARs versus modular CARs
Feldmann, A.; Arndt, C.; Koristka, S.; Berndt, N.; Bergmann, R.ORC; Bachmann, M.
The clinical application of immune effector cells genetically modified to express chimeric antigen receptors (CARs) has shown impressive results including complete remissions of certain malignant hematological diseases. However, their application can also cause severe side effects such as cytokine release syndrome (CRS) or tumor lysis syndrome (TLS). One limitation of currently applied CAR T cells is their lack of regulation. Especially, an emergency shutdown of CAR T cells in case of life-threatening side effects is missing. Moreover, targeting of tumor-associated antigens (TAAs) that are not only expressed on tumor cells but also on vital tissues requires the possibility of a switch allowing to repeatedly turn the activity of CAR T cells on and off. Here we summarize the development of a modular CAR variant termed universal CAR (UniCAR) system that promises to overcome these limitations of conventional CARs.
Keywords: Immunotherapy, Chimeric antigen receptor, T cells, UniCAR, BiTE, TIMO XIV

Permalink: https://www.hzdr.de/publications/Publ-29692
Publ.-Id: 29692


Nanoscale Ferromagnetism in Alloy Thin Film via Lattice Disordering
Bali, R.; Schmeink, A. H.ORC; Eggert, B.; Ehrler, J.; Liersch, V.; Semisalova, A.; Hlawacek, G.ORC; Potzger, K.; Faßbender, J.ORC; Thomson, T.; Wende, H.; Lindner, J.
Structural disorder in certain alloys leads to the onset of strong ferromagnetism. Disorder can be induced in desired locations, at the nanoscale, making such materials useful for magnetic nano-patterning. Examples of these alloys include Fe60Al40,[1] Fe50Rh50,[2] and Fe60V40. Disorder can be generated locally using focussed ion- as well as laser- beams,[1 - 3] inducing nanoscale ferromagnetism. Furthermore, the effect can be reversed via thermal re-ordering of the alloy, achieving re-writeable magnetic structures.
Insights into the mechanisms of the ferromagnetic onset in prototype systems, helps achieve a broader understanding of magneto-structural correlations in general. For instance, in paramagnetic B2-ordered Fe60Al40 as well as D8b-type Fe60V40, the ferromagnetic onset is caused by antisite defects i.e. site swapping of the Fe and Al (V) atoms, resulting in a transition to the bcc (A2) structure. An increase of antisite defects can cause the Ms of Fe60Al40 as well as Fe60V40 to increase from nearly-zero in the ordered structures to 780 and 660 kAm-1, in their respective disordered structures. In contrast, in B2 Fe50Rh50 the well-ordered film is antiferromagnetic, and static disordering may be sufficient to fully transform the alloy to the ferromagnetic phase, possessing an Ms of ~ 1250 kAm-1 at 300 K. Thus, whereas the Ms in the above alloys increases drastically with lattice disorder, the microscopic nature of the disordering varies.
Here we deploy ion-irradiation to sensitively induce lattice disorder in the above binary alloy systems, while tracing the manifested ferromagnetic onsets, thereby obtaining insights into the correlation between magnetic behaviour and the structure. Properties of magnetic arrays and magneto-transport devices produced using lattice disorder will be discussed.
References:
[1] “Printing Nearly-Discrete Magnetic Patterns Using Chemical Disorder Induced Ferromagnetism”, R. Bali et al., Nano Letters 14, 435 (2014).
[2] “Tuning the antiferromagnetic to ferromagnetic phase transition in FeRh thin films by means of low-energy/low fluence ion irradiation”, A. Heidarian et al., Nucl. Instrum. Methods Phys. Res. B 358, 251 (2015).
[3] “Laser-Rewriteable Ferromagnetism at Thin-Film Surfaces”, J. Ehrler et al., ACS Appl. Mater. Interfaces 10, 15232 (2018).
  • Invited lecture (Conferences)
    6th International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems (6th IC4N), 30.06.-03.07.2019, Corfu, Greece
  • Invited lecture (Conferences)
    Symposium „Spins, Waves and Interactions“, 03.-05.09.2019, Greifswald, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29691
Publ.-Id: 29691


Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets
Nord, M.; Semisalova, A.; Kákay, A.; Hlawacek, G.ORC; Maclaren, I.; Liersch, V.; Volkov, O.; Makarov, D.; Paterson, G. W.; Potzger, K.; Lindner, J.; Faßbender, J.ORC; Mcgrouther, D.; Bali, R.
Nanoscale modifications of strain and magnetic anisotropy can open pathways to engineering magnetic domains for device applications. A periodic magnetic domain structure can be stabilized in sub-200 nm wide linear as well as curved magnets, embedded within a flat non-ferromagnetic thin film. The nanomagnets are produced within a non-ferromagnetic B2-ordered Fe60Al40 thin film, where local irradiation by a focused ion beam causes the formation of disordered and strongly ferromagnetic regions of A2 Fe60Al40. An anisotropic lattice relaxation is observed, such that the in-plane lattice parameter is larger when measured parallel to the magnet short-axis as compared to its length. This in-plane structural anisotropy manifests a magnetic anisotropy contribution, generating an easy-axis parallel to the short axis. The competing effect of the strain and shape anisotropies stabilizes a periodic domain pattern, in linear as well as spiral nanomagnets, providing a versatile and geometrically controllable path to engineering the strain and thereby the magnetic anisotropy at the nanoscale.
Keywords: embedded nanomagnets, curved magnets, strain anisotropy, ion-induced patterning, magnetic domains

Permalink: https://www.hzdr.de/publications/Publ-29690
Publ.-Id: 29690


Filling the 5-10 THz gap using Ge-based photoconductive emitter
Singh, A.; Pashkin, O.ORC; Winnerl, S.; Helm, M.; Schneider, H.
We present here a Ge photoconductive emitter generating THz pulses with a spectrum up to 13 THz free from any absorption lines if detected with a proper detector. Ge is a centrosymmetric non-polar crystal and hence its phonons are not IR-active. Therefore, Ge shows high and almost uniform transmission of THz radiation up to frequencies more than 20 THz besides a weak two-phonon absorption band near 10 THz [1]. Ge also has high carrier mobility required for efficient THz emission. Bowtie-like electrode structures with 10 µm electrode gap are deposited on a pure Ge substrate to fabricate the photoconductive THz emitter. The carrier lifetime in pure Ge is of the order of µs, thus it requires a pump laser with pulse repetition rate less than a MHz. A Ti:sapphire amplified laser system operating at 800 nm wavelength, 250 kHz repetition rate and ~ 65 fs pulse width is used to pump the Ge emitter and probe the radiated THz pulse using the electro optic sampling technique.
[1] A. Singh, A. Pashkin, S. Winnerl, M. Helm and H. Schneider, “Gapless broadband terahertz emission from a germanium photoconductive emitter”, ACS Photonics 5, 2718−2723 (2018).
Keywords: terahertz emitter, germanium
  • Lecture (Conference)
    Conference on Lasers and Electro-Optics (CLEO), 06.-10.05.2019, San José, USA
  • Contribution to proceedings
    Conference on Lasers and Electro-Optics (CLEO), 05.-10.05.2019, San José, USA
    Conference on Lasers and Electro-Optics OSA Technical Digest (Optical Society of America, 2019), 345 E 47TH ST, NEW YORK, NY 10017 USA: IEEE, 978-1-943580-57-6
    DOI: 10.1364/CLEO_SI.2019.STu3F.3

Permalink: https://www.hzdr.de/publications/Publ-29688
Publ.-Id: 29688


Scalable Large-Area Terahertz Emitters with Improved Electrode Design
Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.;
We have systematically investigated the influence of electrode parameters on the emission efficiency of scalable large-area photoconductive THz emitters. We identify two contributions to THz emission, originating from the photoexcited carriers in the semiconductor and from the interdigitated metal electrodes acting as dipole antennae, respectively. Both contributions are optimized for maximum THz emission efficiency by varying the gap and stripe widths of the interdigitated metal electrodes. Using this approach we achieve a 50% improvement of the radiated THz electric field as compared to electrodes with equal stripe and gap widths.
Keywords: terahertz emitter, large-area emitter
  • Lecture (Conference)
    The 44th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz'2019), 01.-06.09.2019, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-29687
Publ.-Id: 29687


Linear and nonlinear THz spectroscopy at HZDR
Schneider, H.;
In this talk I have presented some experiments on linear and nonlinear THz spectroscopy at HZDR
Keywords: terahertz spectroscopy, free-electron laser
  • Lecture (others)
    Seminarvortrag, Harbin Institute of Technology, 22.07.2019, Harbin, China

Permalink: https://www.hzdr.de/publications/Publ-29686
Publ.-Id: 29686


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