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39109 Publications

Modelling electrochemistry and mass transfer in sodium-zinc liquid metal batteries - an overview

Duczek, C.

The presented poster was prepared for the doctoral seminar 2021 at HZDR. It gives a short overview about numerical modelling of sodium-zinc liquid metal batteries, which are investigated in the European Union's Horizon 2020 project "SOLSTICE".

  • Poster
    Doctoral Seminar 2021, 18.10.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33350
Publ.-Id: 33350


Data publication: Strong Binding of Noble Gases to [B₁₂X₁₁]⁻: a theoretical study

Wöhner, K.; Wulf, T.; Vankova, N.; Heine, T.

This dataset contains output files of DFT and DLPNO calculations of the investigated species. At the DFT level of theory full geometry optimizations and frequency analysis where done. At DLPNO level of theory single point calculations were done.

Keywords: Boron; Anions; Complexation; Cluster chemistry; Group 17 compounds

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Permalink: https://www.hzdr.de/publications/Publ-33348
Publ.-Id: 33348


Data publication: Development of fluorinated and methoxylated benzothiazole derivatives as highly potent and selective cannabinoid CB2 receptor ligands

Aly, M. W.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.; Abadi, A. H.; Moldovan, R.-P.; Osman, N. A.

Numerous studies have indicated the upregulation of the cannabinoid type 2 receptors (CB2 receptors) in neuroinflammation and cancer, and that their visualization with PET (Positron emission tomography) could provide a valuable diagnostic and/or therapy-monitoring tool in such disorders. However, the availability of reliable CB2-selective imaging probes is still lacking in clinical practice. Encouraged by promising CB2 affinity results obtained for a benzothiazole lead compound, 6a, further structural optimizations led to the development of a series of fluorinated and methoxylated benzothiazole derivatives, endowed with extremely high CB2 binding affinity and an exclusive selectivity to the CB2 receptor, along with structural sites suitable for radiolabeling. Compounds 20, 21, 24, 25, 29, 32 and 33 displayed subnanomolar CB2 Ki values (ranging from 0.16 nM to 0.68 nM) while lacked affinity to the CB1 receptor subtype. The fluorinated analogs, 21 and 29, were evaluated for their in vitro metabolic stability in mouse and human liver microsomes (MLM and HLM). Both 21 and 29 displayed an exceptionally high stability (98% and 91% intact compounds, respectively) after 60 min incubation with MLM. Contrastingly, compound 29 revealed an almost 2-fold greater metabolic stability after incubation with HLM for 60 min. Taken together, our data represent remarkably potent and selective CB2 ligands as credible leads that can be further exploited for 18F- or 11C-radiolabeling and utilization as PET tracers.

Keywords: Benzothiazole; Cannabinoid receptor type 2; CB2 ligands; Fluorine; Metabolic studies; PET

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Permalink: https://www.hzdr.de/publications/Publ-33347
Publ.-Id: 33347


Data publication: Design, radiosynthesis and preliminary biological evaluation in mice of a brain-penetrant 18F-labelled σ2 receptor ligand

Moldovan, R.-P.; Gündel, D.; Teodoro, R.; Ludwig, F.-A.; Fischer, S.; Toussaint, M.; Schepmann, D.; Wünsch, B.; Brust, P.; Deuther-Conrad, W.

The σ2 receptor (transmembrane protein 97), which is involved in cholesterol homeostasis, is of high relevance for neoplastic processes. The upregulated expression of σ2 receptors in cancer cells and tissue in combination with the antiproliferative potency of σ2 receptor ligands motivates the research in the field of 2 receptors for the diagnosis and therapy of different types of cancer. Starting from the well described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds, we synthesized a novel series of fluorinated derivatives, bearing the F-atom at the aromatic indole/azaindole subunit. RM273 (2-[4-(6-fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) was selected for labelling with 18F and evaluation regarding detection of σ2 receptors in the brain by positron emission tomography. Initial metabolism and biodistribution studies of [18F]RM273 in healthy mice revealed promising penetration of the radioligand into the brain. Preliminary in vitro autoradiography on brain cryosections of an orthotopic rat glioblastoma model proved the potential of the radioligand to detect the upregulation of σ2 receptor in glioblastoma cells compared to healthy brain. The results indicate that the herein developed σ2 receptor ligand [18F]RM273 has potential to assess by non-invasive molecular imaging the correlation between the availability of σ2 receptors with properties of brain tumors such as tumor proliferation or resistance towards particular therapies

Keywords: σ2 receptor; transmembrane protein 97; azaindoles; binding affinity; radiochemistry; fluorine-18 labeling; positron emission tomography (PET); brain-penetration; glioblastoma; orthotopic

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Permalink: https://www.hzdr.de/publications/Publ-33346
Publ.-Id: 33346


Effect of temperature and cell viability on uranium biomineralization by the uranium mine isolate Penicillium simplicissimum

Schaefer, S.; Steudtner, R.; Hübner, R.; Krawczyk-Bärsch, E.; Merroun, M. L.

Remediation of heavy-metal-contaminated sites represents a serious environmental problem worldwide. Currently, cost- and time-intensive chemical treatments are mainly performed. Bioremediation by heavy-metal-tolerant microorganisms is considered a more eco-friendly and comparatively cheap alternative. The fungus KS1 (Penicillium simplicissimum), isolated from the flooding water of a former uranium (U) mine in Germany, shows promising U bioremediation potential mainly through biomineralization. The adaption of KS1 to heavy-metal-contaminated sites is indicated by an increased U removal capacity of up to 550 mg U per g dry biomass compared to the non-heavy-metal-exposed P. simplicissimum reference strain DSM 62867 (200 mg U per g dry biomass). In addition, the effect of temperature and cell viability of KS1 on U biomineralization was investigated. While viable KS1 cells at 30 °C removed U mainly extracellularly via metabolism-dependent biomineralization, a decrease in temperature to 4 °C or implementation of dead-autoclaved KS1 cells at 30 °C revealed increased occurrence of passive biosorption and bioaccumulation, as observed by scanning transmission electron microscopy. The precipitated U species were assigned to uranyl phosphates with a structure similar to that of autunite via cryo-time-resolved laser fluorescence spectroscopy. The major involvement of phosphorus in U precipitation by the fungus KS1 was additionally supported by the observation of increased phosphatase activity for viable cells at 30 °C. Furthermore, viable KS1 cells actively secreted small molecules, most likely phosphorylated amino acids, which interacted with U in the supernatant and were not detected in experiments with dead-autoclaved cells. Our studies provide new insights into the influence of temperature and cell viability on U phosphate biomineralization by fungi and highlight the potential use of KS1 particularly for U bioremediation purposes.

Keywords: Biomineralization; Bioremediation; Fungal biomass; Uranium; Wastewater

Permalink: https://www.hzdr.de/publications/Publ-33342
Publ.-Id: 33342


Continuous-time movement modeling

Alston, J.; Simoes Silva, I. M.; Fleming, C. F.; Noonan, M. J.

In this workshop, we presented an introduction to continuous-time movement models for modeling animal movement

  • Lecture (Conference) (Online presentation)
    2021 The Wildlife Society Annual Meeting, 01.11.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33341
Publ.-Id: 33341


Movement ecology research at CASUS

Alston, J.; Calabrese, J.

In this presentation, we provided an introduction to the animal movement research we conduct at CASUS.

  • Open Access Logo Lecture (Conference) (Online presentation)
    2021 EuroBoar Annual Meeting, 25.10.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33340
Publ.-Id: 33340


State with spontaneously broken time-reversal symmetry above the superconducting phase transition

Grinenko, V.; Weston, D.; Caglieris, F.; Wuttke, C.; Hess, C.; Gottschall, T.; Maccari, I.; Gorbunov, D.; Zherlitsyn, S.; Wosnitza, J.; Rydh, A.; Kihou, K.; Lee, C.-H.; Sarkar, R.; Dengre, S.; Garaud, J.; Charnukha, A.; Hühne, R.; Nielsch, K.; Büchner, B.; Klauss, H.-H.; Babaev, E.

The most well-known example of an ordered quantum state—superconductivity—is caused by the formation and condensation of pairs of electrons. Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of pairs of electrons, leading to zero resistivity and diamagnetism. Here we report a set of experimental observations in hole-doped Ba1−xKxFe2As2. Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. This combined evidence indicates the existence of a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs.

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Permalink: https://www.hzdr.de/publications/Publ-33339
Publ.-Id: 33339


A two-sublattice model for extracting rare-earth anisotropy constants from measurements on (Nd,Ce)2(Fe,Co)14B single crystals

Gomez Eslava, G.; Fayyazi, B.; Skokov, K.; Scurschii, I.; Gorbunov, D.; Gutfleisch, O.; Dempsey, N. M.; Givord, D.

Anisotropy constants are obtained from an analysis of single crystal magnetization curves measured up to high fields. The anisotropy of the 3d transition metal sublattice is considered, as well as molecular exchange field coupling between the rare-earth (R) and transition metal sublattices (M). This procedure allows for non colinear R and M magnetic moments, meaning that their angles with respect to the easy axis are independent variables. With this approach we obtain anisotropy constants that are larger than those reported in the literature, which reflects the anisotropy of the isolated R sublattice. Results for Co and/or Ce doped Nd2Fe14B single crystals are presented, showing the influence of such substitutions on the magnetocrystalline anisotropy. These results indicate that the enhanced performance of NdFeB-based magnets co-doped with Ce and Co can be ascribed to an improvement in intrinsic properties.

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Permalink: https://www.hzdr.de/publications/Publ-33338
Publ.-Id: 33338


Data publication: Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

Scripts and notebooks to reproduce the results presented in the paper "Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural
Networks", Maddu et al., 2021

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

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  • Software in external data repository
    Publication year 2021
    Programming language: Python
    System requirements: python, numpy, scipy, sklearn, torch, matplotlib, seaborn, pandas
    License: MIT
    Hosted on GitHub: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33337
Publ.-Id: 33337


Antiferromagnetic resonance in the cubic iridium hexahalides (NH4)2IrCl6 and K2IrCl6

Bhaskaran, L.; Ponomaryov, O.; Wosnitza, J.; Khan, N.; Tsirlin, A. A.; Zhitomirsky, M. E.; Zvyagin, S.

We report on high-field electron spin resonance studies of two iridium hexahalide compounds (NH4)2IrCl6 and K2IrCl6. In the paramagnetic state, our measurements reveal isotropic g factors g = 1.79(1) for the Ir4+ ions, in agreement with their cubic symmetries. Most importantly, in the magnetically ordered state, we observe two magnon modes with zero-field gaps of 11.3 and 14.2 K for (NH4)2IrCl6 and K2IrCl6, respectively. Based on that and using linear spin-wave theory, we estimate the nearest-neighbor exchange couplings and anisotropic Kitaev interactions J1/kB = 10.3 K, K/kB = 0.7 K for (NH4)2IrCl6, and J1/kB = 13.8 K, K/k = 0.9 K for K2IrCl6, revealing the nearest-neighbor Heisenberg coupling as the leading interaction term, with only a weak Kitaev anisotropy.

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Permalink: https://www.hzdr.de/publications/Publ-33336
Publ.-Id: 33336


Inverse Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

We characterize and remedy a failure mode that may arise from multi-scale dynamics with scale imbalances during training of deep neural networks, such as Physics Informed Neural Networks (PINNs). PINNs are popular machine-learning templates that allow for seamless integration of physical equation models with data. Their training amounts to solving an optimization problem over a weighted sum of data-fidelity and equation-fidelity objectives. Conflicts between objectives can arise from scale imbalances, heteroscedasticity in the data, stiffness of the physical equation, or from catastrophic interference during sequential training. We explain the training pathology arising from this and propose a simple yet effective inverse-Dirichlet weighting strategy to alleviate the issue. We compare with Sobolev training of neural networks, providing the baseline of analytically epsilon-optimal training. We demonstrate the effectiveness of inverse-Dirichlet weighting in various applications, including a multi-scale model of active turbulence, where we show orders of magnitude improvement in accuracy and convergence over conventional PINN training. For inverse modeling using sequential training, we find that inverse-Dirichlet weighting protects a PINN against catastrophic forgetting.

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

Permalink: https://www.hzdr.de/publications/Publ-33335
Publ.-Id: 33335


Electric-field manipulation of the magnetocaloric effect in a Fe49Rh51/PZT composite

Amirov, A. A.; Gottschall, T.; Chirkova, A. M.; Aliev, A. M.; Baranov, N. V.; Skokov, K. P.; Gutfleisch, O.

By simultaneous measurements in a purpose-built setup, an electric-field manipulation of the magnetocaloric effect and strain in a Fe49Rh51/PZT composite with a sandwich-type connection was demonstrated. Using the strain measurements from two gauges attached to the opposite sides of the composite, as well as finite element modeling (FEM) simulations, it was shown that the deformation in the composite is of a bending type. Mechanical strain induced by the electric field does not exceed ∼500 ppm, which is four times smaller than the expansion of FeRh during the transition ∼2000 ppm. Applying an electric voltage to the PZT favors the transition, but the further expansion of FeRh is hindered and thus blocks the antiferromagnetic-ferromagnetic transition. Obtained experimental results and FEM simulations can be used in the design of new multicaloric composites with optimal ratio between PZT and multicaloric material.

Permalink: https://www.hzdr.de/publications/Publ-33334
Publ.-Id: 33334


Convection triggers local MR signal loss during proton beam irradiation of liquid water phantoms

Peter, J.; Gantz, S.; Karsch, L.; Pawelke, J.; Hoffmann, A. L.

MRI-based proton beam visualisation in water has proven feasible in exploratory irradiation experiments performed on a first research prototype in-beam MRI system. Beam-induced convection was hypothesised to be implicated into MR signal loss observed within the beam volume. In this study, this hypothesis was tested in liquid water-filled phantoms by suppression of convection-induced motion using mechanical barriers and temperature control of water expansivity. In absence of convection-induced motion, no beam-induced signal changes occurred, supporting the hypothesis that convection triggers local MR signal loss during proton beam irradiation. The elucidation of the exact mechanism of convection-induced signal loss requires further investigation.

  • Contribution to proceedings
    Joint Annual Meeting ISMRM-ESMRMB 2022, 07.-12.05.2022, London/online, United Kingdom
    Proceedings of the joint annual meeting ISMRM-ESMRMB 2022 & ISMRT Annual Meeting
  • Poster
    Joint Annual Meeting ISMRM-ESMRMB & ISMRT 31st Annual Meeting, 07.-12.05.2022, London, Vereinigtes Königreich

Permalink: https://www.hzdr.de/publications/Publ-33333
Publ.-Id: 33333


ILIAMS assisted AMS of ⁹⁰Sr at VERA

Marchhart, O.; Hanstorp, D.; Honda, M.; Lachner, J.; Martschini, M.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The long-lived fission product ⁹⁰Sr is produced in the nuclear fuel cycle or in nuclear weapon tests with a high yield of 4%. It is very mobile in the environment and due to its chemical similarities to calcium is easily incorporated in the body, e.g. in bones or in teeth, following ingestion or inhalation. With a half-life of T1⁄2=28.90 years [1] its uptake and retention in the human body poses potential health risks. ⁹⁰Sr also has significant potential as an environmental tracer.

The established method to measure ⁹⁰Sr is decay counting. However, this is time consuming, as the ingrowth of ⁹⁰Y over a period of two weeks is needed due to ⁹⁰Sr being a pure and low-energy beta emitter. The main challenge in ⁹⁰Sr detection with mass spectrometric methods is the interference of isobars, i.e. ⁹⁰Zr and ⁹⁰Y. Limits of detection of mass spectrometric methods such as ICP-MS, RIMS and conventional AMS are all above or close to the radiometric detection limit of 3 mBq.

The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique [2,3] at the Vienna Environmental Research Accelerator (VERA) overcomes the isobaric problem. ILIAMS achieves near complete suppression of isobars via element selective laser photodetachment in a gas-filled radio frequency quadrupole ion guide. The technique exploits differences in the electron affinities (EA) between the isotope of interest and its isobars by neutralizing anions with EAs below the photon energy while leaving anions with EAs above the photon energy unaffected. Additionally, chemical reactions with the buffer gas may enhance separation.

The Sr samples are produced as SrF₂ and mixed with PbF₂, which allows the extraction of an intense SrF₃⁻ ion beam [4]. Using a 532 nm continuous wave laser at 10 W and a He+O₂ mixture, with an oxygen content of 3%, as buffer gas, ILIAMS achieves a suppression of ZrF₃⁻ and YF₃⁻ vs. SrF₃⁻ of >10⁷ at 35% ⁹⁰Sr transmission through ILIAMS. Extraction of SrF₃⁻ from the ion source and elemental separation in an ionization chamber leads to an additional ⁹⁰Zr suppression of 10⁵. The overall ⁹⁰Sr detection efficiency is 0.4‰; a blank level of ⁹⁰Sr/Sr = (4.5±3.2)×10⁻¹⁵ is reached. This corresponds to a more than tenfold improved detection limit of <0.1 mBq, i.e. 10⁵ atoms of ⁹⁰Sr in a 1 mg Sr sample. Measurements of samples from an in-house dilution series with ⁹⁰Sr/Sr ratios ranging from 10⁻¹¹ to 10⁻¹⁴ prove the linearity of this technique. First tests on different environmental samples – from bone to soils – were successful, showing no influence on the detection limit on “real” samples.

[1] R.R. Kinsey et.al., The NUDAT/PCNUDAT Program for Nuclear Data, Data extracted from the NUDAT database, version 2.8
[2] M. Martschini et.al., The ILIAMS project – An RFQ ion beam cooler for selective laser photodetachment at VERA, Nucl. Instrum. Methods. Phys. Res. B, 456 (2019) 213-217
[3] M.Martschini, this meeting
[4] X.-L. Zhao. et. al., Studies of anions from sputtering I: Survey of MFn⁻, Nucl. Instrum. Methods. Phys. Res. B, 268 (2010) 807-811

  • Poster (Online presentation)
    15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33332
Publ.-Id: 33332


135Cs and 137Cs detection in environmental samples by AMS

Wieser, A.; Lachner, J.; Zok, D.; Martschini, M.; Steier, P.; Priller, A.; Golser, R.

The isotopic ratio ¹³⁵Cs/¹³⁷Cs can be used to assign sources of anthropogenic cesium input, as a geochemical tracer, or for modifying anthropogenic radionuclide dispersion models. The long-lived ¹³⁵Cs is also of interest in stellar nucleosynthesis models, where ¹³⁴Cs is an important s-process branching point, defining the ¹³⁴Ba/¹³⁶Ba ratio as both those nuclides are shielded from the r-process. ¹³⁵Cs is a pure beta-emitter with a low end-point energy and a long but not very well known half-life around 2.3 Ma. Therefore, ¹³⁵Cs is hard to detect via radiometric methods. Mass spectrometry on the other side has to deal with the isobaric interferences ¹³⁵Ba and ¹³⁷Ba for Cs detection.
The new method of Ion Laser InterAction Mass Spectrometry (ILIAMS) at the Vienna Environmental Research Accelerator (VERA) overcomes this problem by exploiting differences in the electron affinities of CsF₂⁻ and BaF₂⁻. There, the ion beam is cooled and overlapped with a 532 nm laser beam of 10W power in a He buffer gas filled radiofrequency quadrupole. Ions like BaF₂⁻ with a detachment energy lower than the photon energy of 2.33 eV are efficiently suppressed by photodetachment, while CsF₂⁻ ions with a detachment energy higher than the photon energy remain unaffected. With this approach an isobar suppression of more than 10⁶ was achieved for BaF₂⁻, while reaching a CsF₂⁻ transmission of 40% through the RFQ ion cooler. A ¹³³CsF₂⁻ current on the order of 50 nA from a mixed Cs₂SO₄ and PbF₂ – matrix is extracted from the MC-SNICS ion source and measured in the 3+ charge state on the high-energy side with an accelerator transmission of 30%. In order to improve the yield for CsF₂⁻ and keep cross-contamination in the ion source between samples low, we investigated and present the results of two sputtering processes: Rubidium sputtering and negative ion production without external sputter agent.
We achieved reproducible detection of ¹³⁵Cs and ¹³⁷Cs in an in-house reference material with an isotopic ratio of ¹³⁵Cs/¹³⁷Cs ≈ 2.5. Further, first environmental samples showing the ¹³⁵Cs/¹³⁷Cs signature of the nuclear accidents in Chernobyl and Fukushima were measured at VERA and compared to values obtained by ICP-QQQ-MS by Zok et al. [1] at the Leibniz University of Hannover. The ILIAMS assisted AMS measurements at VERA reach blank levels of ¹³⁵Cs/¹³³Cs ≈ 6∙10⁻¹² and ¹³⁷Cs/¹³³Cs ≈ 3∙10⁻¹² .
Monitoring mass 136 throughout a measurement, where only stable barium and cerium are present, shows that at these levels there is no contribution to the background from insufficient isobar suppression so that the limitation for the AMS blank level is cross contamination in the ion source. We aim to reduce this blank value by at least two orders of magnitude to perform measurements of environmental samples also far from directly contaminated sites.

[1] Zok et al., Determination of Characteristic vs Anomalous ¹³⁵Cs/¹³⁷Cs Isotopic Ratios in Radioactively Contaminated Environmental Samples, Environ. Sci. Technol. 2021, 55, 8, 4984–4991

  • Poster (Online presentation)
    15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33331
Publ.-Id: 33331


From the U-233/U-236 fingerprint towards an environmental tracer: Tracking down the sources of anthropogenic U-233

Hain, K.; Golser, R.; Hou, X.; Lachner, J.; Lin, M.; Meszar, M.; Qiao, J.; Sakaguchi, A.; Steier, P.; Wagreich, M.; Wallner, G.; Wiederin, A.; Wolf, J.

Recently, the atomic ²³³U/²³⁶U ratio was proposed as a superior oceanographic tracer as the ²³³U/²³⁶U signature allows to distinguish environmental emissions of civil nuclear industry from weapons fallout [1] and uranium (U) behaves conservatively in sea water. In this previous work, the ratios detected in representative compartments of the environment affected either by releases of nuclear power production or by weapons fallout differ by one order of magnitude and varied between 0.1·10-²and 3.7·10-². Significant amounts of ²³³U were only released in nuclear weapons fallout, either produced by fast neutron capture on ²³⁵U or directly by ²³³U fuelled devices. For tracer applications, a careful characterization of the principal sources of ²³³U including the contribution from natural production is required.

The ²³³U/²³⁶U ratios were analysed in samples from different locations, partly time-resolved or of well-known age to be able to narrow down the time span of the maximum ²³³U release. Samples comprised air filters from 1961-1965 collected in Austria, i.e. the period of maximum deposition of global fallout, two time-resolved sediment cores from the Baltic Sea and sediment from the urban layered archaeosphere in the underground of Vienna (Austria). In addition, a depth profile of ²³³U/²³⁶U in a water column located in the Northeast Pacific Ocean was also analysed. This sampling station is assumed to be less affected by tropospheric fallout from a suspected ²³³U fuelled device (Nevada Test Site, 1955). Whenever possible, the ²³³U/²³⁶U data were directly compared to other isotopic signatures and/or mono-isotopic makers, such as ²⁴⁰Pu/²³⁹Pu or ²⁴¹Am, respectively.

The Baltic Sea sediment core confirms a maximum deposition of ²³³U around 1954/1955 [2]. This finding is supported by the rather low ²³³U/²³⁶U ratios (below 0.5·10-²) on the air filters from Vienna indicating a comparatively low ²³³U deposition during global fallout maximum. Values of around 0.1 were measured for the maximum of the ²³³U/²³⁶U ratio in the Baltic Sea sediment. The isotope ratios including ²³³U/²³⁶U found in a layer of the Vienna underground material which was assigned to the 1960s, clearly point to atmospheric atomic bomb fallout. The ²³³U/²³⁶U ratios in the upper part of the Pacific water column showed very stable values of (1.33±0.13) ·10-² which are in good agreement with the published value for global fallout [1].

The new data confirms the previous result that the maximum releases of ²³³U happened before the global fallout maximum in 1963. The consistently high ratios found in the Pacific Ocean indicate at least a contribution from thermonuclear explosions to the global inventory of ²³³U. The unexpectedly high ²³³U/²³⁶U values in the Baltic Sea show the necessity to systematically identify the global and local ²³³U input sources. Nevertheless, our preliminary data indicate that the ²³³U/²³⁶U ratio serves as a potential marker for the on-set of the Anthropocene, even in the rather demanding urban environment.

References
[1] K. Hain, et al. Nat Commun 11(2020), 1275.
[2] M. Lin, et al. Environ. Sci. Technol. 55(2021), 13, 8918–8927

  • Invited lecture (Conferences) (Online presentation)
    15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33330
Publ.-Id: 33330


Data - CST Studio files used for "Modeling of the effective permittivity of open-cell ceramic foams inspired by Platonic solids"

Camacho Hernandez, J. N.

CST Studio files with the geometry of sintered and Platinic foams used for calculating their effective permittivity. The permittivity of the continuous medium and the skeleton can be changed in materials. To change the porosity of platinum foams, the diameter of the struts in the parameter list must be changed. These files were used for preparing the article "Modeling of the effective permittivity of open-cell ceramic foams inspired by Platonic solids"

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Permalink: https://www.hzdr.de/publications/Publ-33329
Publ.-Id: 33329


Ion Laser InterAction Mass Spectrometry – prospects for AMS without chemistry

Martschini, M.; Lachner, J.; Marchhart, O.; Merchel, S.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

Laser photodetachment and molecular dissociation processes of anions provide unprecedented isobar suppression factors of >10¹⁰ for several established AMS isotopes like ³⁶Cl [1] or ²⁶Al [2] and give access to new AMS isotopes like ⁹⁰Sr [3], ¹³⁵Cs [4] or ¹⁸²Hf [5] at environmental levels. Five years ago, a setup for Ion-Laser InterAction Mass Spectrometry (ILIAMS) was coupled to the Vienna Environmental Research Accelerator (VERA) five years ago. Its potential and applicability as a new means of isobar suppression in AMS has since been explored at this state-of-the-art 3 MV tandem facility [6]. Over this time, ILIAMS has been proven to meet AMS requirements regarding efficiency, reliability and robustness with a typical reproducibility of results of 3%.

The benefits of the ILIAMS technique are in principle helpful for any AMS machine, irrespective of attainable ion beam energy. ILIAMS exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas, although the possibility of reverse reactions may cause some plateau effect not observed with laser photodetachment. In order to achieve the required ion-laser interaction times or ion-gas collision energies, the anion beam is decelerated to almost thermal energies within a gas-filled radiofrequency quadrupole.

Since isobar suppression via ILIAMS is so efficient, there is often no need for any further element separation in the detection setup. Hence, highly-populated charge states can be selected after the accelerator, which in combination with 100% efficient ion detection in an ionization chamber more than compensates for transmission losses in ILIAMS, which are on the order of 20-50%. Thus, counting statistics with ILIAMS are typically similar or better than with conventional AMS means, e.g. 500 cts of ²⁶Al in a 10 min run on a sample with 26Al/Al = 10−¹².

Recent test measurements also demonstrated that, owing to the virtually complete suppression of isobars, ²⁶Al (extraction of AlO−) and ⁴¹Ca (extraction of CaF₃−), can be measured directly from stony meteorite samples as little as 1-2 mg without doing any chemical sample preparation [7]. There is also potential for ILIAMS measurements of terrestrial cosmogenic ²⁶Al in in-situ-dating quartz originating from high altitudes. Last but not least, ³⁶Cl may even become accessible without the need for sulfur reduction by chemical treatment and, maybe, without accelerator at all.

[1] Lachner et al., NIMB 92 (2019) 146.
[2] Lachner et al., IJMS 465 (2021) 116576.
[3] Marchhart et al., this meeting
[4] Wieser et al., this meeting
[5] Martschini et al., EPJ Web of Conferences 232 (2020) 02003.
[6] Martschini et al., NIMB 456 (2019) 213.
[7] Merchel et al., this meeting

  • Invited lecture (Conferences) (Online presentation)
    15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33328
Publ.-Id: 33328


Optimization of 10Be beam transport at DREAMS ( DREsden AMS)

Lachner, J.; Rugel, G.; Stübner, K.; Vivo Vilches, C.; Winkler, S.; Wallner, A.

¹⁰Be measurements at DREAMS take up a large fraction of the AMS beam times at the 6MV accelerator at the ion beam center of HZDR. Currently, they are undertaken at a terminal voltage of 4.5 MV [Rugel et al., NIMB 2016]. Here, we investigated potential benefits from a change in accelerator terminal voltage in order to increase the efficiency of ¹⁰Be counting.
Presently, after the stripping in Ar gas in the accelerator, Be2+ ions are directed towards a 1 μm thin SiN foil placed after the analysing magnet on the high-energy side that helps to suppress the ¹⁰B interference by differential energy loss and separation in an electrostatic analyser. After passage through the absorber foil the mean charge state of Be ions is increased and the 4+ charge state is selected and transported to the detector. In this mode of operation, losses of ¹⁰Be ion beam intensity on the way from the low-energy side of the system to the detector are dominated by these two charge exchange processes [Arnold et al., NIMB 2010].
However, there is only limited data for the recharge behaviour of Be in a stripper gas at energies relevant for the measurements at DREAMS [Hofmann et al., NIMB 1987; Niklaus et al., NIMB 1994]. For an argon gas stripper, Niklaus et al. [NIMB 1994], suggest lower terminal voltages for optimal transmission of ¹⁰Be2+. On the other hand, an increase of the overall energy of the Be2+ beam after the accelerator will certainly allow for a higher Be4+ yield after the passage through the absorber foil.
In contrast to the original data by Niklaus et al. [NIMB 1994], we found that increasing the terminal voltage to ≥ 5MV does not reduce the yield of the Be2+ charge state after the accelerator.

As a further recharge to the 4+ charge state is conducted in a foil after the analysing magnet it is desirable to hit the foil with the highest available energy/velocity to have optimal stripping of Be2+ to the naked ion. Thus, the efficiency of ¹⁰Be measurements can indeed be improved by increasing the terminal voltage, both at DREAMS and at other AMS facilities of a similar size that are using the absorber method with a charge exchange from 2+ to 4+ for isobar suppression.
We present data on the performance of the system at higher beam energies documenting an increase in overall detection efficiency by 25%. Under these conditions the interfering isobar ¹⁰B is still well separated, and no additional interferences (e.g. from nuclear reactions) appear in our spectra.

Related publications

  • Poster (Online presentation)
    15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33327
Publ.-Id: 33327


The performance of ²¹⁰Pb AMS for the radioassay of materials considered for the construction of ultra-low background experiments in Astroparticle Physics

Vivo Vilches, C.; Gornea, R.; Weiser, B.; Zhao, X.; Francisco, B. B. A.; Kieser, W. E.

One of the most important tasks in the design and construction of ultra-low background experiments is the radioassay of the materials used. This requires the selection of the materials and enables the calculation of expected detector background. The ASTREA project (Accelerator mass spectrometry Survey of Trace Radionuclides for Experiments in Astroparticle physics) addresses AMS radioassay challenges for a few rare event experiments. Some examples are nEXO, which is searching for neutrinoless double beta decay; and NEWS-G and DarkSide, which are attempting to directly detect dark matter. This project, led by the André E. Lalonde AMS Laboratory (AEL-AMS) at the University of Ottawa, is performed in collaboration with Carleton University, Queens University and University of Alberta.

The main focus of the project is screening Pb-210 in various detector construction materials, with emphasis on low background copper and high-performance polymers. We have studied the possibility of using 2 different materials for the AMS measurements: lead fluoride (PbF2) and lead oxide (PbO) targets, producing respectively (PbF3)- and (PbO2)- ions on the LE side. In both cases, the 210Pb/206Pb blank ratio is in the 1e-14–1e-13 range. Measurements on 1-2 g Kapton films have established upper limits in the range 850-2500 mBq/kg at 90% C.L.

Future ASTREA activities will focus on the Pb-210 assay in acrylic, which is considered for future low background dark matter detectors. Previous best results, obtained in 2014 by γ-counting 2 kg of acrylic, have established an upper limit for the Pb-210 concentration of 0.3 mBq/kg. Our proposed method, using AMS, should provide a limit of detection in the 0.01-0.1 mBq/kg range.

Other important study looks at the Pb-210 contamination in the electroformation process of the copper for the NEWS-G and nEXO detectors. For the Pb-210 concentration in the copper, we estimate a limit of detection in the 0.3-1.0 mBq/kg range.

Keywords: ²¹⁰Pb contamination; Accelerator mass spectrometry; Rare event searches; Astroparticle physics; Radiopurity

  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 19.11.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33325
Publ.-Id: 33325


Nanoindentation response of ion-irradiated Fe, Fe-Cr alloys and ferritic-martensitic steel Eurofer 97: The effect of ion energy

Das, A.; Altstadt, E.; Kaden, C.; Kapoor, G.; Akhmadaliev, S.; Bergner, F.

Nanoindentation of ion-irradiated nuclear structural materials and model alloys has received considerable interest in the published literature. In the reported studies, the materials were typically exposed to irradiations using a single ion energy varying from study to study from below 1 MeV to above 10 MeV. However, systematic investigations into the effect of ion energy are still missing, meaning that the possibilities to gain insight from systematic energy variations are not yet exhausted. We have exposed pure Fe, ferritic Fe-9Cr, martensitic Fe-9Cr and the ferritic-martensitic reduced-activation steel Eurofer 97 to ion irradiations at 300 °C using 1 MeV, 2 MeV and 5 MeV Fe2+ ions as well as 8 MeV Fe3+ ions and applied nanoindentation, using a Berkovich diamond indenter, to characterize as-irradiated samples and unirradiated references. The effect of the ion energy on the measured nanoindentation response is discussed for each material. Two versions of a primary-damage-informed model are applied to fit the measured irradiation-induced hardening. The models are critically compared with the experimental results also taking into account reported microstructural evidence. Related ion-neutron transferability issues are addressed.

Keywords: iron; Fe-Cr alloy; ferritic-martensitic steel; ion irradiation; displacement damage; nanoindentation; irradiation hardeníng; indentation size effect

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Permalink: https://www.hzdr.de/publications/Publ-33324
Publ.-Id: 33324


HELIPORT (HELmholtz ScIentific Project WORkflow PlaTform)

Knodel, O.; Voigt, M.; Ufer, R.; Pape, D.; Lokamani, M.; Müller, S.; Gruber, T.; Juckeland, G.

In this presentation we present how HELIPORT is targeted to bring together tools that help in handling data as part of experiments or simulations. As a result it can serve as the one platform for users to interact with the data generated as part of their measurement campaigns and also provide data provenance.

  • Invited lecture (Conferences) (Online presentation)
    Better Data for Better Science - Research Data Management Workshop, 28.-29.10.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33323
Publ.-Id: 33323


Modeling of the effective permittivity of open-cell ceramic foams inspired by Platonic solids

Hernandez, J. N. C.; Link, G.; Schubert, M.; Hampel, U.

Open-cell solid foams are rigid skeletons permeable to fluids, which are used as direct heaters or thermal dissipaters in many industrial applications. Using dielectric materials for the skeleton and exposing them to microwaves is an efficient way to heat these excellent susceptors. The heating performance depends on the permittivity of the skeleton. However, a rigorous description of the effective permittivity is challenging and requires an appropriate consideration of the complex skeletal foam morphology. In this contribution, we propose Platonic solids as building elements of the open-cell skeletal structures to describe their effective permittivity. The derived new simplistic geometrical relation is used along with electromagnetic wave propagation calculations in representatives of the real foam. A geometrical parameter-free relation was then obtained, which is only based on foam porosity and the material´s permittivity. The derived relation enables efficient and reliable estimation of the effective permittivity of open-cell foams over a large range of porosity.

Keywords: open-cell ceramic foams; microwave heating; effective permittivity; Platonic structures; complex permittivity

Permalink: https://www.hzdr.de/publications/Publ-33322
Publ.-Id: 33322


Water dissociation and association on mirror twin boundaries in two-dimensional MoSe 2 : insights from density functional theory calculations

Joseph, T.; Ghorbani Asl, M.; Batzill, M.; Krasheninnikov, A.

The adsorption and dissociation of water molecules on two-dimensional transition metal dichalcogenides(TMDs) is expected to be dominated by point defects, such as vacancies, and edges. At the same time, the role of grain boundaries, and particularly, mirror twinboundaries (MTBs), whose concentration in TMDs can be quite high, is not fully understood. Using density functional theory calculations, we investigate the interaction of water, hydroxyl groups, as well as oxygen and hydrogen molecules with MoSe2 monolayers when MTBs of various types are present. We show that the adsorption of all species on MTBs is energetically favorable as compared to that on the basal plane of pristine MoSe 2 , but the interaction with Se vacancies is stronger. We further assess the energetics of various surface chemical reactions involving oxygen and hydrogen atoms. Our results indicate that water dissociation on the basal plane should be dominated by vacancies even when MTBs are present, but they facilitate water clustering through hydroxyl groups at MTBs, which can anchor water molecules and give rise to the decoration of MTBs with water clusters. Also, the presence of MTBs affects oxygen reduction reaction(ORR) on the MoSe 2 monolayer. Unlike Se vacancies which inhibit ORR due to a high overpotential, it is found that the ORR process on MTBs is more efficient, indicating their important role in the catalytic activity of MoSe 2 monolayer and likely other TMDs.

Keywords: ORR; MTB; TMD; Water dissociation and association

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Permalink: https://www.hzdr.de/publications/Publ-33321
Publ.-Id: 33321


The foilstack method for 10Be analysis at iThemba LABS - first results and intercomparison for field samples

Winkler, S.; Mbele, V.; Khosa, R.; Corbett, L.; Bierman, P.; Hidy, A.; Brown, T.; Makhubela, T.; Kramers, J.; Tooth, S.

Beryllium-10 is an important isotope for the AMS system at iThemba LABS in Johannesburg because of demand for cosmogenic radionuclide dating methods in the national, regional, and international earth science and paleosciences community. Rather than being designed as one system, the AMS system at iThemba LABS has been set up over several phases based on an existing tandem accelerator, which usually poses challenges implementing the best measurement approach for any given isotope. The injector-side features an in-house built multi-sample cesium sputter ion source, similar to systems employed at CAMS/Lawrence Livermore National Laboratory and Purdue Rare Isotope Measurement Laboratory. The ion source is followed by an in-house built electro-static analyzer and an (in-house built) analyzing magnet, with NEC’s multi-beam switching electronics system applied to our own insulated magnet chamber. The accelerator is a pelletron-refurbished HVEC Model EN tandem, and the high-energy beam line is modified by addition of a switching magnet beam-line from a typical setup delivered by NEC for 5 MV tandem accelerators. Unfortunately using the gas absorber cell employing Havar windows (as was delivered) requires higher energies, usually requiring the 3+ charge state and relatively high terminal voltage, which, for the purpose of AMS operations, are not currently delivered reliably enough by our tandem accelerator. Recently it has been shown that low-stress silicon nitride membranes can be used as absorber foils for full stopping of Boron-10 with a particle energy as low as 6 MeV for the measurement of Beryllium-10 [Steier, et al., 2019]. This allows for the use of the 2+ charge state, avoiding the charge state losses of the post-stripping method used with accelerators capable of similar or lower terminal voltage elsewhere, albeit at the expense of allowing some background from nuclear reactions. We implemented this method in lieu of the gas absorber cell, thus utilizing from the efficiency gain from using the 2+ charge state. In order to investigate the impact of Boron-10 interference and to devise a background correction formalism we conducted experiments using our own ultra-low-Beryllium-10 phenakite-based carrier, and a dilution series of deliberately added Boron-10. We present data which demonstrate good performance of the system on standards and the dilution series samples, and 14 comparison measurements with results obtained at CAMS/LLNL, with all the comparison samples having been prepared at University of Vermont for a landscape evolution study in South Africa. The independent AMS measurements results from the two laboratories are in excellent agreement. A correlation analysis for the two data sets yields a Pearson’s r of 0.9993, with slope (1.009+/-0.017) and offset fully consistent with cross-calibration between the laboratories. The mean difference between the laboratories’ results for individual samples is just 1.7%.

Keywords: 10-Beryllium; AMS intercomparison; isobar separation

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33320
Publ.-Id: 33320


Data for "Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1"

Skouteris, G.; Parra Ramirez, M. A.; Reinecke, S.; Hampel, U.

Input files and simulation results for the related publication.

Keywords: Energy flexibility; Wastewater treatment plant; Benchmark simulation model 1

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Permalink: https://www.hzdr.de/publications/Publ-33317
Publ.-Id: 33317


Substitutional synthesis of sub-nanometer InGaN/GaN quantum wells with high indium content

Vasileiadis, I. G.; Lymperakis, L.; Adikimenakis, A.; Gkotinakos, A.; Devulapalli, V.; Liebscher, C. H.; Androulidaki, M.; Hübner, R.; Karakostas, T.; Georgakilas, A.; Komninou, P.; Dimakis, E.; Dimitrakopulos, G. P.

InGaN/GaN quantum wells (QWs) with sub-nanometer thickness can be employed in short-period superlattices for bandgap engineering of efficient optoelectronic devices, as well as for exploiting topological insulator behavior in III-nitride semiconductors. However, it had been argued that the highest indium content in such ultra-thin QWs is kinetically limited to a maximum of 33%, narrowing down the potential range of applications. Here, it is demonstrated that quasi two-dimensional (quasi-2D) QWs with thickness of one atomic monolayer can be deposited with indium contents far exceeding this limit, under certain growth conditions. Multi-QW heterostructures were grown by plasma-assisted molecular beam epitaxy, and their composition and strain were determined with monolayer-scale spatial resolution using quantitative scanning transmission electron microscopy in combination with atomistic calculations. Key findings such as the self-limited QW thickness and the non-monotonic dependence of the QW composition on the growth temperature under metal-rich growth conditions suggest the existence of a substitutional synthesis mechanism, involving the exchange between indium and gallium atoms at surface sites. The highest indium content in this work approached 50%, in agreement with photoluminescence measurements, surpassing by far the previously regarded compositional limit. The proposed synthesis mechanism can guide growth efforts towards binary InN/GaN quasi-2D QWs.

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Permalink: https://www.hzdr.de/publications/Publ-33316
Publ.-Id: 33316


Obvious phase transition status induced by He+-ions implantation in KTN crystal

Yang, Q.; Li, X.; Liu, H.; Zheng, D.; Akhmadaliev, S.; Zhou, S.; Wu, P.

We report on the formation of a critical ferroelectric state induced by the He+ ion implantation in potassium tantalate niobate crystal. Obvious phase change has been observed in the ion irradiated region, which is mostly related to the stable polarized nanometric regions formed during the ion implantation process. Under the irradiation of 2 MeV He+ ions, two distinguishable layers corresponding to different energy transfer modes (elastic nuclear collision and inelastic electronic collision, respectively) between the incident He+ ions and the intrinsic lattices have been formed beneath the irradiated surface. Lattice dynamics before and after the ion implantation process are investigated by the confocal μ-Raman system. And the variations of typical Raman-active vibrational modes demonstrate the presence of lattice distortion in the irradiated region. X-ray diffraction experiments further suggest the mostly uniform lattice elongation in this region. Piezo-response force characteristic measurements reveal the existence of stable polarized nanometric regions with more intense polarization and verify that the crystal with such a phase status possesses extraordinary microscopic disorders, which is different from the traditional ferroelectric or paraelectric phase. Optical transmission experiments demonstrate that the irradiated region possesses relatively low propagation loss. The ion implantation method provides a new approach to form a temperature-stable critical ferroelectric state in relaxor ferroelectric materials. Analyses of the modification on the lattice dynamics of the irradiated region can help us build a clear awareness of the physical essence of this critical state and the relaxor ferroelectricity. Also, with good optical transmittance, the irradiated region is capable of promising optical functional devices.

Keywords: Implantation/irradiation; Ferroelectric; Relaxor; Phase stability; Polarized nanometric regions

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Permalink: https://www.hzdr.de/publications/Publ-33315
Publ.-Id: 33315


Q-switched mode-locked laser generation by Au nanoparticles embedded in LiTaO3 crystals

Pang, C.; Li, R.; Li, Z.; Sun, X.; Dong, N.; Wang, J.; Zhou, S.; Chen, F.

Au nanoparticles (NPs) in lithium tantalate (LiTaO3) crystal were prepared by ion implantation technique. The microstructure of the formed Au NPs was observed by transmission electron microscope (TEM). The linear and non-linear optical response of the samples was investigated and Z-scan measured that the Au NPs embedded LiTaO3 has saturable absorption properties. Based on this, the sample was used as a saturable absorber (SA) embedded in a waveguide laser system to achieve a 1 μm Q-switched mode-locked laser with a pulse width of 90 ps and a repetition frequency of 6.54 GHz.

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Permalink: https://www.hzdr.de/publications/Publ-33314
Publ.-Id: 33314


An E/E approach to model subcooled boiling for a stable/semi-stable system

Ding, W.; Setoodeh, H.; Lucas, D.; Hampel, U.

In this work, we report on the development of a time-averaged Eulerian multiphase approach
applied in the wall boiling process especially in the forced convective boiling process. Recently, in order to
obtain accurate bubble dynamics and reduce case dependency, a single bubble model for nucleate boiling
based on known published models was developed. The model considers geometry change and dynamic contact
and inclination angles during bubble growth. The model has good agreement with experiments. However, the
predicted bubble dynamics is dependent on the wall superheat (cavity activation temperature). This single
bubble model requires an update of the current nucleation site activation and heat flux partitioning models in
time-averaged Eulerian multiphase approaches. In this presentation, we will introduce this implementation in detail.
Further, with help of the MUSIG (MUltiple SIze Group) model, a breakup and coalescence model and GENTOP concept, this approach could simulate the bubble size distribution and further flow pattern and partten transitian in a heated pipe. With thenecessary calibration of the nucleation site density, the comparisons between the calculation results and DEBORA experiments demonstrate the success of the implementation and the accuracy of this approach.

Keywords: WALL BOILING; HEAT PARTITIONING; FLOW PATTERN

  • Lecture (others) (Online presentation)
    DEBORA BENCHMARK MEETING, 05.-06.10.2021, Paris (Virtual), France

Permalink: https://www.hzdr.de/publications/Publ-33313
Publ.-Id: 33313


Study on bubble-induced turbulence in pipes and containers with Reynolds-stress models

Liao, Y.; Ma, T.

Bubbly flow still represents a challenge for large-scale numerical simulation. Among many others the understanding and modelling of bubble-induced turbulence (BIT) are far from being satisfactory even though continuous efforts have been made. In particular, the buoyancy of the bubbles generally introduces turbulence anisotropy in the flow, which can not be captured by the standard eddy viscosity models with specific source terms representing BIT. Recently, on the basis of bubble-resolving Direct Numerical Simulations data, a new Reynolds-stress model considering BIT were developed by Ma et al. (J. Fluid Mech., vol. 883, 2020, A9) within the Euler–Euler framework. The objective of the present work is to assess this model and compare its performance with other standard Reynolds-stress models using a systematic test strategy. We select the experimental data in the BIT dominated range and find that the new model leads to major improvements in the prediction of full Reynolds-stress components.

Keywords: Bubble-induced turbulence; Reynolds-stress turbulence model; Pipe flow; Euler-Euler two-fluid model

Permalink: https://www.hzdr.de/publications/Publ-33312
Publ.-Id: 33312


Data: Electrical Characterization of Germanium Nanowires Using a Symmetric Hall Bar Configuration: Size and Shape Dependence

Echresh, A.; Arora, H.; Fuchs, F.; Li, Z.; Hübner, R.; Prucnal, S.; Schuster, J.; Zahn, P.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

The uploaded data are related to electrical measurements including two- and four-probe, Hall effect, and temperature-dependent measurements. The simulation data is included as well.

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Permalink: https://www.hzdr.de/publications/Publ-33311
Publ.-Id: 33311


Electrical Characterization of Germanium Nanowires Using a Symmetric Hall Bar Configuration: Size and Shape Dependence

Echresh, A.; Arora, H.; Fuchs, F.; Li, Z.; Hübner, R.; Prucnal, S.; Schuster, J.; Zahn, P.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

The fabrication of individual nanowire-based devices and their comprehensive electrical characterization remains a major challenge. Here, we present a symmetric Hall bar configuration for highly p-type germanium nanowires (GeNWs), fabricated by a top-down approach using electron beam lithography and inductively coupled plasma reactive ion etching. The configuration allows two equivalent measurement sets to check the homogeneity of GeNWs in terms of resistivity and the Hall coefficient. The highest Hall mobility and carrier concentration of GeNWs at 5 K were in the order of 100 cm^2/(Vs) and 4×10^19 cm^-3, respectively. With a decreasing nanowire width, the resistivity increases and the carrier concentration decreases, which is attributed to carrier scattering
in the region near the surface. By comparing the measured data with simulations, one can conclude the existence of a depletion region, which decreases the effective cross-section of GeNWs. Moreover, the resistivity of thin GeNWs is strongly influenced by the cross-sectional shape.

Keywords: germanium nanowires; Hall bar configuration; Hall effect; electrical characterization

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Permalink: https://www.hzdr.de/publications/Publ-33310
Publ.-Id: 33310


How Can Drones Contribute to Mineral Exploration?

Booysen, R.; Lorenz, S.; Jackisch, R.; Gloaguen, R.; Madriz Diaz, Y. C.

Drones are getting more and more used to replace piloted platforms to reduce the costs and increase safety of activities such as monitoring, delivery or warfare. So far though, drones have barely been used as more than single-sensor platforms. In order to be used in mineral exploration we need to ensure that the data acquired by drones are versatile, accurate and adapted to the tasks but also that the platforms are robust and low-maintenance to ensure an operational use in remote locations. During the last years we developed and tested a series of workflows to rapidly provide relevant information to exploration teams. It starts with multi-source data acquisition, data integration and preprocessing. We then use machine learning to process the data and generate relevant geological information.

Keywords: Drones; UAS; UAV; Hyperspectral; Magnetics; Machine learning; Exploration

  • Invited lecture (Conferences) (Online presentation)
    IGARSS 2021 - 2021 IEEE International Geoscience and Remote Sensing Symposium, 16.07.2021, Brussels, Belgium
    DOI: 10.1109/IGARSS47720.2021.9554041

Permalink: https://www.hzdr.de/publications/Publ-33308
Publ.-Id: 33308


HELIPORT use case POLARIS: Integration of a High Intensity Laser in a complete data life cycle workflow

Knodel, O.; Hein, J.; Kessler, A.

In this presentation we show how we deploy HELIPORT at Helmholtz Institute Jena. The integration of the High Intensity Laser POLARIS in a complete data life cycle workflow is an important aspect in the HMC funded HELIPORT project.

Keywords: HELIPORT; Data Management; Workflows; POLARIS; Laser; Data life cycle

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Better Data for Better Science - Research Data Management Workshop, 28.-29.10.2021, online, online

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Permalink: https://www.hzdr.de/publications/Publ-33307
Publ.-Id: 33307


Accurate hyperspectral imaging of mineralised outcrops: An example from lithium-bearing pegmatites at Uis, Namibia

Booysen, R.; Lorenz, S.; Thiele, S. T.; Fuchsloch, W.; Marais, T.; Nex, P. A. M.; Gloaguen, R.

Efficient, socially acceptable and rapid methods of exploration are required to discover new deposits and enable the green energy transition. Sustainable exploration requires a combination of innovative thinking and new technologies. Hyperspectral imaging (HSI) is a rapidly developing technology and allows for fast and systematic mineral mapping, facilitating exploration of the Earth’s surface at various scales on a variety of platforms. Newly available sensors allow data capture over a wide spectral range, and provide information about the abundance and spatial location of ore and pathfinder minerals in drill-core, hand samples and outcrops with mm to cm precision. Conversely, the complex geometries of the imaged surfaces affect the spectral quality and signal-to-noise ratio (SnR) of HSI data at these very narrow spatial samplings. Additionally, the complex mineral assemblages found in hydrothermally altered ore deposits can make interpretation of spectral results a challenge. In this contribution, we propose an innovative approach that integrates multiple sensors and scales of data acquisition to help disentangle complex mineralogy associated with lithium and tin mineralisation in the Uis pegmatite complex, Namibia. We train this method using hand samples and finally produce a three-dimensional (3D) point cloud for mapping lithium mineralisation in the open pit. We were able to identify and map lithium-bearing cookeite and montebrasite at outcrop scale. The accuracy of the approach was validated by drill-core data, XRD analysis and LIBS measurements. This approach facilitates efficient mapping of complex terrains, as well as important monitoring and optimisation of ore extraction. Our method can easily be adapted to other minerals relevant to the mining industry.

Keywords: Outcrop sensing; Hyperspectral imaging; Li-bearing pegmatites; Mineral exploration

Permalink: https://www.hzdr.de/publications/Publ-33306
Publ.-Id: 33306


Investigation on pool-scrubbing hydrodynamics with VOF interface-capturing method

Liao, Y.; Li, J.; Lucas, D.

Pool scrubbing with bubble swarm generated by gas jet is an effective technique for aerosol retention at severe accidents, owing to large interfacial area and long residence time. Correct understanding of the process and thus enhancing its efficiency relies on analysis of the hydrodynamic behaviour of the gas, since it affects particle removal mechanisms directly. The objective of the present work is to explore the gas jet structure in detail by means of VOF interface-capturing method and additional techniques for tracking bubble characteristics and trajectories. The main findings are: a) The breakup of globules in the injection zone becomes significant at high gas flow rates and has a great contribution in particle removal; b) The increase of bubble size
and velocity with the injection velocity will promote the inertial and centrifugal deposition of aerosol particles; c) However, the coalescence probability of
rising bubbles is found to increase with the gas flow rate, which may influence particle retention by re-enclosing particles from liquid film and reducing surface area; d) Furthermore, the reduction in bubble residence time as they rise through the pool is unfavourable for particle removal. Nevertheless, liquid recirculation originated from violent interaction between the gas jet and the pool surface as well as swarm effects helps to prolong the residence of bubbles. The effect of gas flow rates on the decontamination factor is found to be associated with a variety of gas-liquid hydrodynamic phenomena. The
proposed numerical approach is capable of acquiring detailed local information that is required for model development. Both the time-averaged spatial distribution of void fraction and the instantaneous size/rise velocity of individual bubbles obtained from the simulation conform to the experimental data. In the next step it will be extended to include aerosol particles.

Keywords: Aerosol particle; Decontamination factor; OpenFOAM; Pool scrubbing; VOF interface-capturing

  • Nuclear Engineering and Design 390(2022), 111713
    DOI: 10.1016/j.nucengdes.2022.111713
  • Lecture (Conference) (Online presentation)
    18th Multiphase Flow Conference & Short Course (online), 08.-12.11.2021, Dresden, Germany

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  • Secondary publication expected from 11.03.2023

Permalink: https://www.hzdr.de/publications/Publ-33305
Publ.-Id: 33305


Investigation on swirl instability in a vane-type separator with tomographic PIV

Zhang, T.; Huang, G.; Yin, J.; Zhang, Z.; Wang, D.; Sun, Y.; Liao, Y.

The separation efficiency of a vane-type separator is greatly affected by swirl instability. The separator consists of a swirling vane, a recovery vane and a main pipe. Driven by centrifugal force, the bubbly flow tends to develop into stratified flow with a continuous gas core floating in the central axis of the separator and facilitating the separation. Yet, the straight gas core can turn into a double helix under some circumstances for example if the pressure difference across the orifices of recovery vane falls below the critical value, and swirl instability occurs. In order to reveal the underlying mechanism, a device with adjustable operating pres-sure was introduced to reproduce the dynamic process of gas core transform between stable and unstable. With the increase of pressure difference, the gas core morphology near the recovery vane will turn from double-helix to straight-line within several seconds. The whole process was investigated further by using the tomographic particle image velocimetry. Results show that the development of vorticity structures in the swirl flow gives rise to the evolution of gas core morphology and keeps it stable. Furthermore, the direction of axial velocity, which becomes negative by low pressure differences, is found to be crucial in controlling the formation of inner forced vortex and hence leading to the occurrence of swirl instability. In addition, the magnitude of positive axial velocity is identified to be of great significance in vorticity enhancement.

Keywords: gas core instability; swirl flow; Tomo-PIV

Permalink: https://www.hzdr.de/publications/Publ-33304
Publ.-Id: 33304


Super-SIMS @ DREAMS: status of a challenging initiative

Rugel, G.; Ziegenrücker, R.; Lachner, J.; Vivo Vilches, C.; Renno, A.; Wallner, A.; Wiedenbeck, M.

At the DREAMS (DREsden AMS) facility [1,2] we are implementing a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry) device [3] for specialized applications. The system combines the spatial resolution capability of a commercial SIMS (CAMECA IMS 7f-auto) with AMS capability, which should suppress molecular isobars in the ion beam allowing for the quantification of elemental abundances down to ~ E-9 – E-12. This would be more than an order of magnitude improvement over traditional dynamic SIMS (e.g. [4,5]). We aim to use this for the highly sensitive analysis of geological samples in the context of resource technology.

In the present setup, high efficiency transmission in the low-energy ion optics segment remains a challenge, as the beam needs to traverse two existing magnet chambers without deflection, where no steering or lens elements are available over a flight distance of 4 m. We have now improved the low-energy injection just after the ion beam exits the 7f-auto, upgrading the steerers directly after the SIMS and by adding a beam intensity attenuator. This provides both more stable conditions for instrument tuning and simplifies transition between measurements of the beam intensity in Faraday cups and the gas ionization chamber. Regarding the measurement of C, N and O in silicon, we found that a simple Wien-filter using permanent magnets for the primary Cs-sputter beam significantly reduces the background at the detector, as the 7f-auto uses a Cs₂CO₃ source – rather than metallic Cs – for the generation of the primary positive Cs beam.

Once the remaining issues associated with ion beam-path are fully addressed, we will still need to tackle the issue of establishing suitable, well characterized reference materials needed for our first suite of resource and geoscience applications (e.g., halides in naturally occurring sulphide minerals). We present ongoing developments and results, as well as plans for extending to other matrices and isotope systems.

[1] S. Akhmadaliev et al., NIMB 294 (2013) 5. [2] G. Rugel et al. NIMB 370 (2016) 94. [3] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316. [4] C. Maden, PhD thesis, ETH Zurich 2003. [5] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470.

Related publications

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33303
Publ.-Id: 33303


Holmium-166m measurements with AMS for the ECHo-project

Rugel, G.; Berndt, S.; Düllmann, C. E.; Dorrer, H.; Forstner, O.; Kieck, T.; Kneip, N.; Lachner, J.; Merchel, S.; Vivo Vilches, C.; Wallner, A.; Wendt, K.

The Electron Capture in ¹⁶³Ho experiment (ECHo) aims at measuring the mass of the electron neutrino by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T_1/2 = 4570 a) with a metallic magnetic calorimeter (MMC). For the determination of a reasonable upper limit for the neutrino mass it is mandatory to keep the contamination with the long-lived radionuclide ¹⁶⁶mHo (T_1/2 = 1132.6 a) nine orders of magnitude below the ¹⁶³Ho content. The ion-implantation of ultra-pure ¹⁶³Ho into a MMC for the experiment is carried out by the RISIKO (Resonance Ionization Spectroscopy in KOllinear geometry) mass separator. The separation from ¹⁶⁶mHo, however, cannot be guaranteed to such low levels as needed in this project, it can only be estimated. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). Of course, this requires the formation of negative ions, where we find the highest negative ion yield for the anion HoO₂−. For first tests, stable ¹⁶⁵Ho was implanted by RISIKO into various different metal foils and we studied the overall Ho detection efficiency for our setup. We will present first results and estimates of the expected detection limit for the ¹⁶⁶mHo/¹⁶³Ho isotope ratio.

Related publications

  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33302
Publ.-Id: 33302


High electron mobility in strained GaAs nanowires

Balaghi, L.; Shan, S.; Fotev, I.; Moebus, F.; Rana, R.; Venanzi, T.; Hübner, R.; Mikolajick, T.; Schneider, H.; Helm, M.; Pashkin, O.; Dimakis, E.

Novel transistor concepts based on semiconductor nanowires promise high performance, lower energy consumption and better integrability in various platforms in nanoscale dimensions. Concerning the intrinsic transport properties of electrons in nanowires, relatively high mobility values that approach those in bulk crystals have been obtained only in core/shell heterostructures, where electrons are spatially confined inside the core. Here, it is demonstrated that the strain in lattice-mismatched core/shell nanowires can affect the effective mass of electrons in a way that boosts their mobility to unprecedented levels. Specifically, electrons inside the hydrostatically tensile-strained gallium arsenide core of nanowires with a thick indium aluminium arsenide shell exhibit mobility values 30 – 50 % higher than in equivalent unstrained nanowires or bulk crystals, as measured at room temperature. With such an enhancement of electron mobility, strained gallium arsenide nanowires emerge as a unique means for the advancement of transistor technology.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33301
Publ.-Id: 33301


Data publication: Flow morphology of high-pressure steam condensation in an inclined tube at low inlet steam qualities

Boden, S.; Moonesi Shabestary, A.; Bieberle, A.; Pietruske, H.; Hampel, U.

This archive contains the processed X-ray data of the measurement campaign "Investigation of flow morphology and heat transfer in an inclined tube", which was conducted between June 2020 and June 2021 at the thermal hydraulic test facility COSMEA (COndenSation test rig for flow Morphology and hEAt transfer studies) at Helmholtz-Zentrum Dresden - Rossendorf (HZDR). The flow morphology of high-pressure (up to 65 bar) steam condensation in a slightly inclined tube at low inlet steam qualities (down to 2.8%) were are studied. Both X-ray computed tomography as well as X-ray radioscopy have been applied. The results include images of the local condensate distribution in selected cross-sections of the condenser tube as well as time resolved projections of the condensate distribution.

Keywords: steam condensation; two-phase flow; X-ray tomography; X-ray radioscopy

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Permalink: https://www.hzdr.de/publications/Publ-33300
Publ.-Id: 33300


Universal Liquid Metal Alloy Ion Sources for FIB nanofabrication

Richter, T.; Mazarov, P.; Meyer, F.; Pilz, W.; Bischoff, L.; Klingner, N.

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. In addition, nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution and stability [2].
Therefore, we have extended the technology towards a stable supply of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [3]. This LMAIS provides single and multiple charged ion species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are thus made available in the FIB technology because of continuous research in this area [4]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution, the operation principle, first results and prospective domains for modern FIB applications will be presented. As examples, we will introduce the AuGeSi and GaBiLi LMAIS [5, 6]. Both sources provide light and heavy ions available from a single source to tailor chemical and physical properties of resulting nanostructures. GaBiLi enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source.
[1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63, 1219 (2020).
[2] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017).
[3] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3, 021101 (2016).
[4] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018).
[5] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019).
[6] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, and L. Bischoff, Imaging and milling resolution of light ion beams from helium ion microscopy and FIBs driven by liquid metal alloy ion sources, Beilstein J. Nanotechnol. 11, 1742 (2020).

Keywords: Liquid Metal Alloy Ion Sources; FIB; nanofabrication

Related publications

  • Lecture (Conference) (Online presentation)
    34th International Microprocesses and Nanotechnology Conference (MNC 2021), 26.-29.10.2021, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-33299
Publ.-Id: 33299


Retention of redox-sensitive Tc(VII) and Se(IV) on Fe(II)/Fe(III) bearing clay minerals

Qian, Y.; Grangeon, S.; Scheinost, A. C.; Hoving, A.; Greneche, J. M.; Marques Fernandes, M.

Clay minerals, as main components of the engineered barrier in deep geological repositories, are not only highly effective sorbents for a wide range of (cationic) contaminants, but due to their structural iron content, they can also modify the mobility and (bio)availability of redox-sensitive elements by changing their oxidation state. Here we will systematically address the retention of the redox-sensitive fission products Tc and Se by FeII/FeIII containing clays. The mobility of Tc and Se strongly depends on their oxidation states. The specific chemical form of Tc and Se is governed by many factors, such as pH, redox potential (Eh), solubility, mineralogical and chemical composition of the environment, biological (microbial) interactions and (redox) reaction kinetics. The most considerable influence, however, is exerted by redox potential, pH and solubility.
Tc(VII) in its anionic form (TcO4-) is highly mobile whereas under reducing conditions the mobility of Tc is decreased when it is reduced to Tc(IV). A few studies have shown that TcVII can be reduced to TcIV by Fe-bearing minerals, mainly forming TcO2.nH2O surface precipitates[1]. Most of these studies, however, were carried out at rather high Tc loadings. The focus of this study is on low to very low Tc loadings, which are more environmentally relevant.
Selenate (SeO42−, Se(VI)) and selenite (SeO32−, Se(IV)) are favoured under oxidizing conditions. Selenate reduction is kinetically hindered and very slow (high activation energy). Hence, the study focuses on selenite. There is little data on the retention of Se(IV) by Fe(II) bearing clay minerals. Reductive precipitation of Se(IV) to nanoparticulate Se(0) was observed when dissolved Fe(II) is sorbed onto synthetic montmorillonite[2].
By combining Tc and Se sorption experiments on native and reduced smectite clay samples with different FeII/FeIII ratios with Tc/Se K-edge extended X-ray absorption fine structure (EXAFS), mediated oxidation and reduction experiments (MEO/MER), Mössbauer spectrometry and microscopy, we aim at discriminating the contributions of the different available Fe sources to the overall adsorption and reduction of Tc and Se and to identify the surface products. The ultimate aim is to correlate mineral properties with respect to their redox reactive iron content, the degree of Tc and Se reduction and the molecular scale surface speciation, in order to improve the understanding of the coupled adsorption and electron transfer reactions contributing to the retention of Tc and Se on FeII/FeIII bearing clay minerals, and thus to contribute to a more reliable prediction of the Tc and Se retention in nuclear waste repositories.

1. Jaisi, D.P., et al., Reduction and long-term immobilization of technetium by Fe(II) associated with clay mineral nontronite. Chemical Geology, 2009. 264(1): p. 127-138.
2. Charlet, L., et al., Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay. Geochimica et Cosmochimica Acta, 2007. 71(23): p. 5731–5749.

Keywords: Technetium; Selenium; Clay Minerals; Redox; XAFS

Related publications

  • Lecture (Conference)
    Clay Conference 2022, 13.-16.06.2022, Nancy, France
  • Poster
    EURADWASTE'22, 30.05.-03.06.2022, Lyon, France
  • Lecture (Conference)
    ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France
  • Invited lecture (Conferences)
    ROBL-Workshop, 25.01.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-33298
Publ.-Id: 33298


Redox-active iron in different types of clay minerals – mediated electrochemical characterization and reactivity towards Se(IV)

Hoving, A. L.; Qian, Y.; Marques Fernandes, J. M.; Griffioen, J.; Behrends, T.; Scheinost, A. C.

Clay minerals are ubiquitous in the environment and are an important reactant to pollutants including radionuclides. Besides their adsorptive capacity, clay minerals can also participate in redox reactions due to the presence of iron (Fe) in their structure and can thereby influence the mobility of redox-active compounds such as technetium, selenium and uranium. However, not all Fe(II) or Fe(III) in the structure of clay minerals may be accessible for redox reactions. The redox activity of Fe can depend on the quantity and coordination of Fe in the clay mineral structure. Research on the redox activity of structural Fe in clay minerals has mainly focused on smectites whereas other types of clay minerals have received less attention. In this study we measured redox-activity of a variety of clay minerals, i.e. illites, chlorites, glauconites and mixed-layered illite-smectites. The redox-activity of the clay minerals was investigated by mediated electrochemistry. To examine the relation between electrochemically active structural Fe(II) in these clay minerals and their reactivity towards radionuclides, batch experiments were performed with selenite, a redox-active, mobile, long-lived radionuclide in radioactive waste. Both pristine (oxidized) clay minerals and chemically reduced clay minerals were tested. Results from mediated electrochemical oxidation and reduction show that all clay minerals have electrochemically active Fe to some extent, but there is a large variation in the fractions of electrochemically-active Fe between the different clay minerals, e.g. around 100% redox-active Fe in smectites, <20% redox-active Fe for the tested illites. K-edge XAFS spectroscopy of these batch experiment samples reveals that these different types of chemically reduced clay minerals reduce selenite to elemental selenium.

Keywords: redox; clay minerals; Mediated Electrochemistry; XAFS; Selenium

Related publications

  • Lecture (Conference)
    Clay Conference 2022, 13.-16.06.2022, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-33297
Publ.-Id: 33297


Towards multiscale ab-initio simulations: size transferability of density functional theory surrogates

Fiedler, L.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damage in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost due to using machine learning methods. In order to successfully model on multiple length and time scales, these models have to be transferable with respect to their size. Here, we present results of such an investigation, by showing how models trained on small numbers of atoms (e.g., 128) can be used to accurately calculate energies of much larger simulation cells (e.g., 1024 atoms). The models are based upon the Materials Learning Algorithms (MALA) package and the LDOS-based machine-learning workflow implemented therein.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    8th International Symposium on Optics & its applications, 19.-22.10.2021, Rostock, Dresden

Permalink: https://www.hzdr.de/publications/Publ-33296
Publ.-Id: 33296


Investigation of transferability in LDOS based DFT surrogate models for multiscale simulations

Fiedler, L.; Cangi, A.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damages in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost by using machine learning methods. Yet, a lack of transferability of many approaches lead to repeated and costly training data generation procedures. Here, we present results of an investigation to transfer such machine learning DFT surrogate models between different simulation cell sizes, with the goal of reducing the overall amount of computational time for training data generation. The models are based upon the Materials Learning Algorithms (MALA) package [1] and the therein implemented LDOS based machine learning workflow [2].
[1]: https://github.com/mala-project
[2]: J. A. Ellis et al., Phys. Rev. B 104, 035120, 2021

Keywords: Machine Learning; Density Functional Theory; Surrogate Model

  • Lecture (Conference) (Online presentation)
    84. Jahrestagung der DPG und DPG-Tagung der Sektion Kondensierte Materie (SKM), 27.09.-01.10.2021, online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33295
Publ.-Id: 33295


Materials Learning Algorithms (MALA): An Efficient Surrogate for Ab-initio Simulations

Fiedler, L.

Ab-initio simulations are crucial tools for many scientific applications, from materials science to drug discovery. This is due to powerful simulation techniques such as Density Functional Theory (DFT), that combine high accuracy with computational feasibility. Yet, there exist applications unattainable to even the most performant of DFT programs. A prominent example is the modeling of materials on multiple time and length scales, especially under ambient or extreme conditions. While these simulations hold the potential to both further our understanding of important physical phenomena such as planetary formation or radiation damages in fusion reactor wall, they evade traditional ab-initio approaches due to their size and complexity.
Surrogate models can mitigate these computational restrictions, by reproducing DFT-level results at a fraction of the cost. Here, were present the Materials Learning Algorithms (MALA) package, an open source python package for building neural network based surrogate models for materials science. MALA provides easy-to-use functions to process DFT data, build models and use these models to replace DFT calculations, as shown for simulations of Aluminium at both 298K and 933K, as well as Iron at 3000K. The source code for MALA is publicly available on Github and developed by the Center for Advanced Systems Understanding (CASUS), Sandia National Laboratories, and Oak Ridge National Laboratory.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    17th International Conference on the Physics of Non-Ideal Plasmas, 20.-24.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33294
Publ.-Id: 33294


Preliminary Results of Contactless Inductive Flow Tomography for Rayleigh- Bénard Convection Cell with an Aspect Ratio of 0.5

Mitra, R.; Sieger, M.; Galindo, V.; Schindler, F.; Vogt, T.; Stefani, F.; Eckert, S.; Wondrak, T.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

Keywords: Contactless inductive flow tomography; Rayleigh-Bénard convection; Liquid metal measurement

  • Contribution to proceedings
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, Online, Online
  • Lecture (Conference) (Online presentation)
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33293
Publ.-Id: 33293


Rapid Iron(III)-Fluoride Mediated Hydrogen Atom Transfer

Panda, C.; Doyle, L. M.; Gericke, R.; McDonald, A. R.

We anticipate high-valent metal fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H–F bond (in the product) that drives HAT oxidation. We prepared a dimeric Fe(III)(F)–F–Fe(III)(F) complex (1) by reacting Fe(II)(NCCH₃)₂(TPA) where X = F/OTf. 1 and 2 were characterised using NMR, EPR, UV-vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive Fe III reagent for oxidative C–H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive Fe III and Fe IV oxidants.

Keywords: high-valent oxidants; biomimetic; proton coupled electron transfer; fluoride oxidant

Permalink: https://www.hzdr.de/publications/Publ-33292
Publ.-Id: 33292


Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: Au(III)–Cl versus Au(III)–OH

Lovisari, M.; Gericke, R.; Twamley, B.; McDonald, A. R.

High-valent metal−halides have come to prominence as highly effective oxidants. A direct comparison of their efficacy against that of traditional metal−oxygen adducts is needed. AuIII(Cl)(terpy)](ClO₄)₂ (1; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O−H and C−H bonds via a hydrogen atom transfer mechanism. A direct comparison with [AuIII(OH)(terpy) showed that 1 was a kinetically superior oxidant with respect to 2 for all substrates tested. We ascribe this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand.

Keywords: Bond dissociation free energy; Hydrocarbons; Ligands; Gold; Oxidation

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Permalink: https://www.hzdr.de/publications/Publ-33291
Publ.-Id: 33291


Migration kinetics of surface ions in oxygen-deficient perovskite during topotactic transitions

Cao, L.; Petracic, O.; Wei, X.-K.; Zhang, H.; Duchoň, T.; Gunkel, F.; Koutsioubas, A.; Zhernenkov, K.; Rushchanskii, K. Z.; Hartmann, H.; Wilhelm, M.; Li, Z.; Xie, Y.; He, S.; Weber, M. L.; Veltruská, K.; Stellhorn, A.; Mayer, J.; Zhou, S.; Brückel, T.

Oxygen diffusivity and surface exchange kinetics underpin the ionic, electronic, and catalytic functionalities of complex multivalent oxides. Towards understanding and controlling the kinetics of oxygen transport in emerging technologies, it is highly desirable to reveal the underlying lattice dynamics and ionic activities related to oxygen variation. In this study, the evolution of oxygen content is identified in real-time during the progress of a topotactic phase transition in La0.7Sr0.3MnO3-δ epitaxial thin films, both at the surface and throughout the bulk. Using polarized neutron reflectometry, a quantitative depth profile of the oxygen content gradient is achieved, which, alongside atomic-resolution scanning transmission electron microscopy, uniquely reveals the formation of a novel structural phase near the surface. Surface-sensitive x-ray spectroscopies further confirm a significant change of the electronic structure accompanying the transition. The anisotropic features of this novel phase enable a distinct oxygen diffusion pathway in contrast to conventional observation of oxygen motion at moderate temperatures. The results provide insights furthering the design of solid oxygen ion conductors within the framework of topotactic phase transitions.

Keywords: oxygen vacancy ordering; topotactic transition; defect chemistry; polarized neutron reflectometry; X-ray absorption

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33290
Publ.-Id: 33290


Effects of torsion and curvature in antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

Antiferromagnets represent a wide class of technologically promising materials for spintronic and spinorbirtonic devices with multiple magnetic sublattices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2]. Here, we explore curvature effects in curvilinear antiferromagnets which are stemming from exchange interaction [3]. It is shown that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI. In contrast to ferromagnetic spin chains, the dipolar interaction leads to the hard-axis anisotropy. This allows to observe the effects of geometry even in chains with small curvature and torsion because of absence of other competing easy axis anisotropies except the geometry-induced one. The latter determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve. We note, that the anisotropy in curvilinear antiferromagnetic spin chains is an additional source of geometry-driven effects on magnetic textures [4].

Keywords: antiferromagnetism; curvilinear magnetism; spin chains

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33289
Publ.-Id: 33289


Parallel computation of 3D magnetic structures

Tomilo, A.; Pylypovskyi, O.; Yershov, K.; Sheka, D.

Intensive experimental and theoretical research for novel materials introduces new architectures for magnetic devices, where shape and topology plays a crucial role [1]. A powerful way to study them as well as confirm analytical predictions is to compute the corresponding equations of motion numerically. Here, we present a spin-lattice simulation suite SLaSi, which can address flexible magnetic one- and two- dimensional spin lattices. They can represent soft wires and ribbons, where the coupling between magnetic and mechanical subsystem results into spontaneous deformations and symmetry breaks [2]. The SLaSi is a C-written program, where exchange, single-ion anisotropy, Zeeman energy, dipolar interaction, and Dzyaloshinskii-Moriya interaction are taken into account for the description cubic, square, and triangular lattices. Dynamics of the mechanical sub-system is modelled by the overdamped Newton equations, while magnetic sub-system is modelled by LLG. Speedup of the computations is achieved by parallelization using MPI and CUDA frameworks.

Keywords: curvilinear magnetism; computations; CUDA; MPI

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33288
Publ.-Id: 33288


Nanoscale mechanics of antiferromagnetic domain walls in Cr2O3

Hedrich, N.; Wagner, K.; Lehmann, P.; Pylypovskyi, O.; Shields, B. J.; Kosub, T.; Sheka, D.; Makarov, D.; Maletinsky, P.

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds combined with electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale texture are paramount for device operation, as well as interesting from a fundamental point of view. E.g. spin-textures in such materials are theorized to carry an intrinsic magnetization [2]. Here we study a single crystal ‘textbook’ magneto-electric antiferromagnet, Cr2O3, by nanoscale imaging of its surface magnetization via magnetic stray field imaging by scanning nitrogen vacancy magnetometry [3]. This surface magnetization is directly linked to the bulk Neel vector of Cr2O3 and thereby allows for nanoscale imaging of antiferromagnet spin textures. After confirming magneto-electric poling [4], local electrodes are utilized to nucleate single domain walls, which we then study on the nanometer scale. Manipulation of the domain wall is demonstrated both by local laser heating [5], as well as the creation of an energy landscape for the domain wall via topographic structuring [3]. We analyze the interaction of the domain wall with topographic islands both experimentally and in simulations. This analysis yields information about the domain wall boundary conditions at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles.

We then observe bistable domain wall paths configurations and switching between them is demonstrated and imaged experimentally. This pinning and control of the domain wall position constitutes the main ingredients for logic devices based on domain walls in magneto-electric antiferromagnets and their fundamental study.

Keywords: antiferromagnetism; Cr2O3; mesa; NV magnetometry

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33287
Publ.-Id: 33287


Ground states of the antiferromagnetic spin rings in strong magnetic fields

Borysenko, Y.; Pylypovskyi, O.; Faßbender, J.; Sheka, D.; Makarov, D.

Antiferromagnetic (AFM) materials have distinct advances compared to ferromagnets, that allow to use them in variety of spintronic applications [1,2]. Antiferromagnetically coupled curvilinear spin chains are of fundamental interest as simplest systems possessing interplay between the geometry and magnetic subsystem [3].

In this work, we analyze the ground states of AFM ring-shaped spin chain with the nearest-neighbour Heisenberg exchange and single-ion anisotropy in presence of external magnetic field. The direction of magnetic field coincides with the symmetry axis of the ring. Collinear two-sublattice 1D curved AFM chain with even number of spins is considered, and the hard axis of anisotropy is oriented tangentially to the chain.

Within the classical continuum approach its magnetic state is described by two order parameters, the Néel and ferromagnetism vector fields. In the ground state, the Néel vector is oriented perpendicularly to the ring plane.

The magnetic field applied along the ring normal allows to observe spin-flop and spin-flip orientational phase transitions. We determine the dependency of spin-flop and spin-flip transition fields on the ring curvature and the critical curvature which separates two topologically different ground states above spin-flop transition. The first one with the Néel order parameter within the normal plane is mainly determined by the anisotropy at small curvatures. The second ground state at large curvatures is represented by onion ordering of the Néel vector. With the applied fields larger than critical spin-flip transition field Néel order parameter vanishes, which leads to ferromagnetic ground state. The phase diagram of AFM as a function of applied field intensity and the ring curvature is developed.

Keywords: antiferromagnetism; spin-flop; curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33286
Publ.-Id: 33286


Challenges Porting a C++ Template-Metaprogramming Abstraction Layer to Directive-based Offloading

Kelling, J.; Bastrakov, S.; Debus, A.; Kluge, T.; Leinhauser, M.; Pausch, R.; Steiniger, K.; Stephan, J.; Widera, R.; Young, J.; Bussmann, M.; Chandrasekaran, S.; Juckeland, G.

HPC systems employ a growing variety of compute accelerators with different architectures and from different vendors. Large scientific applications are required to run efficiently across these systems but need to retain a single code-base in order to not stifle development. Directive-based offloading programming models set out to provide the required portability, but, to existing codes, they themselves represent yet another API to port to. Here, we present our approach of porting the GPU-accelerated particle-in-cell code PIConGPU to OpenACC and OpenMP target by adding two new backends to its existing C++-template metaprogramming-based offloading abstraction layer alpaka and avoiding other modifications to the application code. We introduce our approach in the face of conflicts between requirements and available features in the standards as well as practical hurdles posed by immature compiler support.

Keywords: C++; OpenACC; OpenMP; Offloading

  • Contribution to WWW
    https://arxiv.org/abs/2110.08650
  • Lecture (Conference) (Online presentation)
    Eighth Workshop on Accelerator Programming Using Directives (WACCPD) @SC21, 14.11.2021, St. Louis, USA
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    SC21 - The International Conference for High Performance Computing, Networking, Storage, and Analysis: OpenMP Offloading and the 5.2 API Birds-of-a-Feather, 14.-19.11.2021, St. Louis, MO, USA
  • Contribution to proceedings
    8th International Workshop, WACCPD 2021, 14.11.2021, St. Louis, USA
    Accelerator Programming Using Directives, Cham: Springer, 978-3-030-97758-0
    DOI: 10.1007/978-3-030-97759-7

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Permalink: https://www.hzdr.de/publications/Publ-33285
Publ.-Id: 33285


Geometrical symmetry breaking in nanomagnets

Pylypovskyi, O.

Three-dimensional ferro- and antiferromagnetic nanoarchitectures possess a special interplay between their geometrical (topological) properties and the magnetic order parameter. The emergent chiral and anisotropic responses extend the intrinsic material properties and pave the way to novel functionalities of spintronic and spin-orbitronic devices.

Keywords: curvilinear magnetism; ferromagnets; antiferromagnets

  • Invited lecture (Conferences) (Online presentation)
    META 2021 The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics, 20.-23.07.2021, Warsaw (Online event), Poland

Permalink: https://www.hzdr.de/publications/Publ-33284
Publ.-Id: 33284


A community data mining approach for surface complexation database development

Zavarin, M.; Chang, E.; Wainwright, H.; Parham, N.; Kaukuntla, R.; Zouabe, J.; Deinhart, A.; Genetti, V.; Shipman, S.; Bok, F.; Brendler, V.

This paper presents a comprehensive data-to-model workflow, including a findable, accessible, interoperable, reusable (FAIR) community sorption database (newly developed LLNL Surface Complexation/Ion Exchange (L-SCIE) database) along with a data fitting workflow to efficiently optimize surface complexation reaction constants with multiple surface complexation model (SCM) constructs. This workflow serves as a universal framework to mine, compile, and analyze large numbers of published sorption data as well as to estimate reaction constants for parameterizing reactive transport models. The framework includes (1) data digitization from published papers, (2) data unification including unit conversions, and (3) data-model integration and reaction constant estimation using geochemical software PHREEQC coupled with the universal parameter estimation code PEST. We demonstrate our approach using an analysis of U(VI) sorption to quartz based on a first L-SCIE implementation, concluding that a multisite SCM construct with carbonate surface species yielded the best fit to community data. Surface complexation reaction constants extracted from this approach captured all available sorption data available in the literature and provided insight into previously published reaction constants and surface complexation model constructs. The L-SCIE sorption database presented herein allows for automating this approach across a wide range of metals and minerals and implementing novel machine learning approaches to reactive transport in the future.

Keywords: Surface Complexation Modelling; Database; Sorption; Data Mining; Raw Data

Permalink: https://www.hzdr.de/publications/Publ-33283
Publ.-Id: 33283


Prompt-gamma imaging for prostate cancer proton therapy: CNN-based detection of anatomical changes

Pietsch, J.; Nick, P.; Berthold, J.; Khamfongkhruea, C.; Thiele, J.; Hölscher, T.; Traneus, E.; Janssens, G.; Smeets, J.; Stützer, K.; Löck, S.; Richter, C.

Purpose & Objective
A clinical study (PRIMA) regarding the potential of range verification in proton therapy by prompt-gamma imaging (PGI) is carried out at our institution. As a step towards the automatic evaluation of the measured PGI data, we present an approach to detect anatomical changes in prostate cancer patients from realistically simulated PGI data using convolutional neural networks (CNNs).

Materials & Methods
In-room control CTs (cCTs) were acquired in treatment position before monitoring 146 field deliveries of 10 hypo-fractioned (3Gy/fraction) prostate cancer patients with a PGI slit camera (range: 8-18 fields/patient). After manual CT registration and dose recalculation, spot-wise shifts of integrated depth-dose (IDD) profiles between cCTs and planning CTs were extracted at the 80% distal falloff position and used for ground-truth classification. Treatment fields were considered to be affected by relevant anatomical changes of the patient if >0.1% of all spots (with at least 0.1% of the total monitor units per field) had absolute IDD shifts above 5 mm. These parameters lead to a field-wise IDD ground-truth classification in optimal agreement with a prior manual field-wise classification based on dose difference maps.
Based on the cCTs, we simulated realistic PGI profiles, including Poisson noise and a positioning uncertainty of the PGI slit camera, and extracted spot-wise range shifts by comparison with the expected reference profiles for the planning CT. Spots with reliable PGI information (inside field-of-view and >5E7 protons), were considered with their Bragg peak position for generating two independent 3D spatial maps of 161616 voxels (0.740.740.66 cm3): (1) The PGI-determined range shift in each voxel is the weighted average taking the spot-wise proton number into account. (2) The proton number in each voxel is summed over all respective spots and normalized per field (Fig. 1).
With these maps and the IDD classification, 3D-CNNs (6 convolutional & 2 downsampling layers) were trained using patient-wise 10-fold cross-validation on the binary task to detect anatomical changes.

Results
The CNNs achieved a mean training and validation accuracy of 0.85 (range: 0.77-0.91) and 0.83 (0.70-0.93), respectively (Fig. 2). Based on the validation results, anatomical changes were detected with a sensitivity of 0.88 and a specificity of 0.76.

Conclusion
Our work shows that CNNs can reliably detect anatomical changes in prostate cancer patients from realistically simulated PGI data of clinical irradiations. While a validation on measured PGI data is the next step, this study highlights the potential of an automatic interpretation of PGI data, which is highly desired for routine clinical application and required for the inclusion of PGI in an automated feedback loop for online adaptive proton therapy.

Keywords: range verification; prompt gamma imaging; proton therapy; artificial intelligence; machine learning

  • Lecture (Conference)
    ESTRO 2022, 06.-10.05.2022, Kopenhagen, Dänemark
  • Abstract in refereed journal
    Radiotherapy and Oncology 170(2022)Supplement, 546-548
    DOI: 10.1016/S0167-8140(22)02642-1

Permalink: https://www.hzdr.de/publications/Publ-33282
Publ.-Id: 33282


Skin-conformal flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

Motion sensing is the primary task in numerous disciplines including industrial robotics, prosthetics, virtual and augmented reality appliances. In rigid electronics, rotations, displacements and vibrations are typically monitored using magnetic field sensors prepared on flat and rigid substrates. Extending 2D structures into 3D space relying on the flexible and printed electronics approaches allows to enrich conventional or to launch novel functionalities of spintronic-based devices by tailoring geometrical curvature and 3D shape. We developed shapeable magnetoelectronics [1] – namely, flexible, stretchable [2] and even printable [3] skin-conformal magnetosensitive elements. The technology platform relies on high-performance magnetoresistive and Hall effect sensors fabricated on ultrathin polymeric foils based on thin film technologies or printing methods. These mechanically shapeable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins, soft robotics and human-machine interfaces. With these activities, we extended the use of high quality magnetic thin films to new research and technology fields. This topic is gaining visibility in the interdisciplinary community of physicists, chemists, mechanical and electrical engineers working on the fabrication of 3D shaped magnetic functional membranes, develops methods for their characterisation and theoretical frameworks for their description as well as puts forth concepts for the technological implementation of shapeable magnetoelectronics in different application fields. Here, we will review technological platforms allowing to realize mechanically imperceptible electronic skins for interactive electronics, which enable perception of the geomagnetic field, but also enable sensitivities down to ultra-small fields of sub-50 nT. These devices allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactivity concepts for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game using omnidirectional magnetosensitive skins [2]. This concept was further extended by demonstrating a flexible magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [4]. This is crucial for smart home applications, interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly conformal integrated feedback system [5] as well as in medicine for physicians and surgeons. In 2019, we brought these research activities to the next level in the frame of the Helmholtz Innovation Lab FlexiSens. FlexiSens bridges fundamental and application-oriented activities with the focus on the transfer of the thin film fabricated sensor technologies for flexible and printable electronics to the market. For this purpose, together with Scia Systems GmbH, we establish a 300 mm grade production line (thin film deposition, lithography, chemical processing of 300 mm wafers) to bring the our sensor technologies to the industry-relevant scale. Flexible magnetic field sensors are offered to industry partners either directly via the HZDR or via the company HZDR Innovation GmbH and already bring financial benefit to the group. The fundamental and application-oriented aspects of this technology will be discussed in the presentation.

[1] D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt, Applied Physics Reviews, 2016, 3, 011101.
[2] G. S. Cañón Bermúdez, H. Fuchs, L. Bischoff, J. Fassbender, D. Makarov, Nature Electronics, 2018, 1, 589.
[3] M. Ha, G. S. Cañón Bermúdez, T. Kosub, I. Mönch, Y. Zabila, E. S. Oliveros Mata, R. Illing, Y. Wang, J. Fassbender, D. Makarov, Advanced Materials, 2021, 33, 2005521.
[4] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, D. Makarov, Nature Communications, 2019, 10, 4405.
[5] M. Ha, G. S. Cañón Bermúdez, J. A.-C. Liu, E. S. Oliveros Mata, B. A. Evans, J. B. Tracy, D. Makarov, Advanced Materials, 2021, 33, 2008751.

Keywords: flexible electronics; printed electronics; magnetic field sensing; human-machine interfaces; soft robotics

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Advanced Nanomaterials Congress, 24.-27.10.2021, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-33281
Publ.-Id: 33281


Effect of Nozzle Geometry on Centerline Gas Holdup in Submerged Gas Injection

Xiao, J.; Yan, H.; Schubert, M.; Liu, L.; Döß, A.; Schleicher, E.; Hampel, U.

Non-circular nozzle geometries are widely used in many industrial processes with submerged gas injection for altering the centerline gas holdup to intensify the reaction process. However, the effect of the nozzle geometry on the centerline gas holdup is rarely investigated. In this work, hollow circular-shaped, gear-shaped, four-flower-shaped and multi-hole-shaped nozzle geometries are utilized to investigate the centerline gas holdup by wire-mesh sensors and
digital image processing. The results reveal that the centerline gas holdup is influenced by nozzle geometry, axial distance and gas flow rate. The centerline gas holdup for hollow circular-shaped,four-flower-shaped and multi-hole-shaped nozzles is larger than that of the gear-shaped nozzle.
The correlations for the centerline gas holdup are obtained based on modified Froude number Frm and dimensionless axial distance o via regression analysis. The correlations for hollow circular-shaped nozzle geometry obtained in this study are validated with experimental data
from this study and the literature.

Permalink: https://www.hzdr.de/publications/Publ-33280
Publ.-Id: 33280


Block model of passive seismic shear velocity and airborne electromagnetic resistivity in the Geyer area, Erzgebirge, Germany

Ryberg, T.; Kirsch, M.; Haberland, C.; Tolosana Delgado, R.; Viezzoli, A.; Gloaguen, R.

As a means of investigating the structure of the geological subsurface and delineating Sn-W-Li greisen-hosted mineral deposits in the Geyer-Ehrenfriedersdorf area, Central Erzgebirge, Germany, we collected an ambient noise dataset which was supplemented and analysed together with airborne time-domain electromagnetic data. The here presented dataset is a combined three-dimensional block model containing the following parameters:

(X), (Y), (Z) – Coordinates of the block model center nodes in ETRS89 UTM33N coordinates.

(PS_vel) – Shear wave velocity based on ambient noise data from a dense "LARGE-N" network comprising 400 low-power, short-period seismic stations tomographically inverted based on Bayesian statistics.

(logVTEM_res) – Logarithm of resistivity based on airborne time-domain electromagnetic data acquired using the Geotech Versatile Time Domain (VTEM™ ET) system and inverted using a layered earth approach.

(class_K-means) – Class labels of a spatially constrained clustering using K-means with 26 immediate neighbours performed on the bivariate velocity-resistivity 3D dataset.

Keywords: Ambient seismic noise; Airborne electromagnetics; Mineral exploration

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Permalink: https://www.hzdr.de/publications/Publ-33279
Publ.-Id: 33279


Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier / supplementary data

Schoenig, J.; von Eynatten, H.; Tolosana Delgado, R.; Meinhold, G.

The database includes 13615 garnet compositions of eight oxides commonly analysed in lab routines: SiO2, TiO2, Al2O3, Cr2O3, FeOtotal, MnO, MgO, and CaO (in wt%). These are complemented by the following covariables:

setting and metamorphic facies class: code indicating the geologic/tectonic setting of the host rock

composition class: code indicating the compositional class of the host rock

author: authors of the original paper providing the data

journal: journal of the original paper

region: origin of the data, in the format "region, country"

sample name: sample ID in the original paper

Pavg(kbar): if available, indicated pressure

Tavg(°C): if available, indicated temperature

host-rock type and/or metamorphic facies: facies indication of host rock

lithology and/or protolith: composition indication of host rock

SiO2: wt%

TiO2: wt%

Al2O3: wt%

Cr2O3: wt%

FeOtotal: wt%

MnO: wt%

MgO: wt%

CaO: wt%

This research was funded by DFG grant EY 23/27-1.

Keywords: garnet major-element composition; host-rock discrimination

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Permalink: https://www.hzdr.de/publications/Publ-33278
Publ.-Id: 33278


Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1

Parra Ramirez, M. A.; Reinecke, S.; Skouteris, G.; Hampel, U.

Future energy systems must mainly generate electricity from renewable resources. To
deal with the fluctuating availability of wind and solar power, new versatile electricity markets and
sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated
the potential of energy flexibility achieved through demand-side response for the wastewater treat-
ment plant of the Benchmark Simulation Model 1. First, seven control strategies were simulated and
assessed. Next, the flexibility calls were identified, two energy flexibility scenarios were defined and
incorporated into the model, and the control strategies were evaluated anew. In this research, the
effluent ammonia concentration needed to be maintained within the limits for as long as possible.
Strategy 5, which controlled ammonia in Tank 5 at a low value and did not control any nitrate
in Tank 2, of Scenario 1, which was characterized by an undetermined on/off aeration cycle, was
then found to be the best. Although this control strategy led to high total energy consumption,
the percentage of time during which aeration was nearly suspended was one of the highest. This
work proposes a methodology that will be useful to plant operators who should soon reduce energy
consumption during spikes in electricity prices.

Keywords: Energy flexibility; Wastewater treatment plant; Benchmark Simulation Model 1; Control strategies; Aeration; Water quality

Permalink: https://www.hzdr.de/publications/Publ-33277
Publ.-Id: 33277


Intraindividual comparison of [68Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 in prostate cancer patients: a retrospective single-center analysis.

Hoberück, S.; Löck, S.; Borkowetz, A.; Sommer, U.; Winzer, R.; Zöphel, K.; Fedders, D.; Michler, E.; Kotzerke, J.; Kopka, K.; Hölscher, T.; Braune, A.

Background: The analysis aimed to compare the radiotracers [68Ga]-Ga-PSMA-11 and [18F]-F-PSMA-1007 intraindividually in terms of malignant lesions, mi(molecular-imaging)TNM staging and presumable unspecific lesions retrospectively as used in routine clinical practice.
Methods: A retrospective analysis of 46 prostate cancer patients (median age: 71 years) who underwent consecutive [68Ga]-Ga-PSMA-11- and [18F]-F-PSMA-1007-PET/CT or PET/MRI within a mean of 12 ± 8.0 days was performed. MiTNM staging was performed in both studies by two nuclear medicine physicians who were blinded to the results of the other tracer. After intradisciplinary and interdisciplinary consensus with two radiologists was reached, differences in both malignant and presumable nonspecific tracer accumulation were analyzed.
Results: Differences in terms of miTNM stages in both studies occurred in nine of the 46 patients (19.6%). The miT stages differed in five patients (10.9%), the miN stages differed in three patients (6.5%), and different miM stages occurred only in one patient who was upstaged in [18F]-F-PSMA-1007 PET. Concordant miTNM stages were obtained in 37 patients (80.4%). There was no significant difference between [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11 in the SUVmax locally (31.5 vs. 32.7; p = 0.658), in lymph node metastases (28.9 vs. 24.9; p = 0.30) or in bone metastases (22.9 vs. 27.6; p = 0.286). In [18F]-F-PSMA-1007 PET, more patients featured presumable unspecific uptake in the lymph nodes (52.2% vs. 28.3%; p: < 0.001), bones (71.7% vs. 23.9%; p < 0.001) and ganglia (71.7% vs. 43.5%; p < 0.001). Probable unspecific, exclusively [18F]-F-PSMA-1007-positive lesions mainly occurred in the ribs (58.7%), axillary lymph nodes (39.1%) and cervical ganglia (28.3%).
Conclusion: In terms of miTNM staging, both tracers appeared widely exchangeable, as no tracer relevantly outperformed the other. The differences between the two tracers were far more common in presumable unspecific lesions than in malignant spots. A routinely performed two-tracer study could not be shown to be superior. Since it seems at least challenging for most nuclear medicine departments to provide both [18F]-F-PSMA-1007 and [68Ga]-Ga-PSMA-11, it appears reasonable to choose the PSMA radiotracer depending on local availability with attention to the greater occurrence of nonspecific bone findings with [18F]-F-PSMA-1007.

Keywords: PET; PSMA; Prostate cancer; [18F]F-PSMA-1007; [68Ga]Ga-PSMA-11; miTNM

Permalink: https://www.hzdr.de/publications/Publ-33276
Publ.-Id: 33276


Fermi-surface reconstruction at the metamagnetic high-field transition in uranium mononitride

Hamann, S.; Förster, T.; Gorbunov, D.; König, M.; Uhlarz, M.; Wosnitza, J.; Helm, T.

We report on the electronic and thermodynamic properties of the antiferromagnetic metal uranium mononitride with a Néel temperature TN ≈ 53 K. The fabrication of microstructures from single crystals enables us to study the low-temperature metamagnetic transition at approximately 58 T by high-precision magnetotransport, Halleffect, and magnetic-torque measurements.We confirm the evolution of the high-field transition from a broad and complex behavior to a sharp first-order-like step, associated with a spin flop at low temperature. In the high-field state, the magnetic contribution to the temperature dependence of the resistivity is suppressed completely. It evolves into an almost quadratic dependence at low temperatures indicative of a metallic character. Our detailed investigation of the Hall effect provides evidence for a prominent Fermi-surface reconstruction as the system is pushed into the high-field state.

Permalink: https://www.hzdr.de/publications/Publ-33274
Publ.-Id: 33274


Underground measurements and simulations on the muon intensity and 12C-induced nuclear reactions at low energies

Ludwig, F.

The reaction 12C(α,γ)16O is of paramount importance for the nucleosynthesis of heavier elements in stars. It takes place during helium burning and determines the abundance of 12C and 16O at the end of this burning stage and therefore influences subsequent nuclear reactions. Currently the cross section at astrophysically relevant energies is not known with satisfactory precision.
Due to the low cross section of the reaction, low background, high beam intensities and target thicknesses are necessary for experiments. Therefore a new laboratory hosting a 5 MV ion accelerator, was built in the shallow-underground tunnels of Felsenkeller. The main background component in such laboratories was investigated with a muon telescope in this thesis. It was found, that the rock overburden of about 45 m vertical depth reduces the muons by a factor of about 40 compared to the surface. Furthermore the results of the measurements were compared to a simulation based on the geometry of the facility and showed good agreement.
In the next step the accelerator was put into operation. Since the experiment on 12C(α,γ)16O will be done in inverse kinematics, an intense carbon beam is necessary to reach sufficient statistics. For this, the creation and extraction of carbon ions in an external ion source was improved. The external source now provides steady currents of 12C− of above 100 μA.
In the following the transmission through the accelerator and the high-energy beamline was tested with a beam restricted in width. The pressure of the gas stripper in the centre of the accelerator and the parameters of different focusing elements after the accelerator were varied. It was found, that for a desired carbon beam energy of below 9 MeV, the 2+ charge state is suited best, where up to 35% of the inserted beam could be transmitted.
To ease the planning of future experiments and aid the analysis of the data, the target chamber and two different kinds of cluster detectors were modelled in Geant4. The low-energy region was verified by comparing the simulations to measurements with radioactive calibration sources. Deviations for the detectors were below 10% without target chamber, and up to 30% for individual germanium crystals of the Cluster Detectors with the target chamber.
A first test measurement was undertaken to investigate the capabilities of the new laboratory. Solid tantalum targets implanted with 4 He were prepared. An ERDA analysis of the used solid targets showed contaminations with carbon and oxygen. These led to beam-induced background in the region of interest during the irradiation.
Then the targets were irradiated with a carbon beam at two different energies. While no clear signal of 12C(α,γ)16O could be observed, the beam could be steered on the target for the whole duration of the beam time spanning five days. Problems during this test, like low beam current, were identified. These could be partly remedied in the scope of this thesis. Suggestions for improvements for a second test run were developed as well.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-116 2021
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-33273
Publ.-Id: 33273


The Future of Solar Neutrinos

Orebi Gann, G. D.; Zuber, K.; Bemmerer, D.; Serenelli, A.

In this article we review the current state of the field of solar neutrinos, including flavour oscillations, non-standard effects, solar models, cross section measurements, and the broad experimental program thus motivated and enabled. We discuss the historical discoveries that contributed to current knowledge, and define critical open questions to be addressed in the next decade. We discuss the state of the art of standard solar models, including uncertainties and problems related to the solar composition, and review experimental and model solar neutrino fluxes, including future prospects. We review the state of the art of the nuclear reaction data relevant for solar fusion in the proton-proton chain and carbon-nitrogen-oxygen cycle. Finally, we review the current and future experimental program that can address outstanding questions in this field.

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Permalink: https://www.hzdr.de/publications/Publ-33272
Publ.-Id: 33272


Direct Measurement of the 13C(α ,n)16O Cross Section into the s-Process Gamow Peak

Ciani, G. F.; Csedreki, L.; Rapagnani, D.; Aliotta, M.; Balibrea-Correa, J.; Barile, F.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Cavanna, F.; Chillery, T.; Colombetti, P.; Corvisiero, P.; Cristallo, S.; Davinson, T.; Depalo, R.; Di Leva, A.; Ferraro, F.; Fiore, E.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Lugaro, M.; Marigo, P.; Masha, E.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Piatti, D.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takacs, M. P.; Terrasi, F.; Vescovi, D.; Zavatarelli, S.; Elekes, Z.

One of the main neutron sources for the astrophysical s process is the reaction C 13 (α ,n )O 16 , taking place in thermally pulsing asymptotic giant branch stars at temperatures around 90 MK. To model the nucleosynthesis during this process the reaction cross section needs to be known in the 150-230 keV energy window (Gamow peak). At these sub-Coulomb energies, cross section direct measurements are severely affected by the low event rate, making us rely on input from indirect methods and extrapolations from higher-energy direct data. This leads to an uncertainty in the cross section at the relevant energies too high to reliably constrain the nuclear physics input to s -process calculations. We present the results from a new deep-underground measurement of C 13 (α ,n )O 16 , covering the energy range 230-300 keV, with drastically reduced uncertainties over previous measurements and for the first time providing data directly inside the s -process Gamow peak. Selected stellar models have been computed to estimate the impact of our revised reaction rate. For stars of nearly solar composition, we find sizeable variations of some isotopes, whose production is influenced by the activation of close-by branching points that are sensitive to the neutron density, in particular, the two radioactive nuclei Fe 60 and Pb 205 , as well as Gd 152 .

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Permalink: https://www.hzdr.de/publications/Publ-33271
Publ.-Id: 33271


Low-energy resonances in the 18O(p,γ)19F reaction

Pantaleo, F. R.; Boeltzig, A.; Best, A.; Perrino, R.; Aliotta, M.; Balibrea-Correa, J.; Barile, F.; Bemmerer, D.; Broggini, C.; Bruno, C. G.; Buompane, R.; Caciolli, A.; Cavanna, F.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Deboer, R. J.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Masha, E.; Menegazzo, R.; Mossa, V.; Paticchio, V.; Piatti, D.; Prati, P.; Rapagnani, D.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Takács, M. P.; Trezzi, D.; Wiescher, M.; Zavatarelli, S.; Derasmo, G.

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed 18O/16O relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions 18O(p ,α )15N and 18O(p ,γ )19F in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the (p ,γ ) reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement.

Purpose: Our aim is the direct measurement of states in 19F as populated through the reaction 18O(p ,γ )19F to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of 19F.
Method: Branchings and resonance strengths were measured in the proton energy range Eplab=150 -400 keV , using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity.
Results: The uncertainty of the γ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the 334 keV resonance, and individual γ decays of the 215 keV resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through α emission were identified. The strengths of the observed resonances are generally in agreement with literature values.
Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the 18O(p ,γ )19F reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the 18O depletion observed in Group 2 oxygen-rich stardust grains.

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Publ.-Id: 33270


Gas permeability and selectivity of a porous WS₂ monolayer

Hassani, N.; Ghorbani Asl, M.; Radha, B.; Drndic, M.; Krasheninnikov, A.; Neek-Amal, M.

Atomically thin porous membranes display high selectivity for gas transport and separation. To create such systems, defect engineering of 2D materials, e.g., via ion irradiation, provides an efficient route. Here,first-principles calculations are used to study permeability of He, H₂, N₂, CO₂, and CH₄ molecules through WS₂ monolayers containing vacancy-type defects. We found that i) for most pores, regardless of the pore size, H₂ exhibits large permeability (~10⁵ GPU), ii) dissociation of H₂ molecules and edge saturation occurs when they approach the angstrom-size pores, iii) the 1W6S pore (one W and six S atoms are removed from WS₂ monolayer) can separate H₂ and N₂ gases with high selectivity, and iv) the 2W6S pore exhibits exceptionally high selectivity for separation of H2/CO2 (~10¹³) and H₂/CH₄ (~10⁹).

Keywords: selectivity; permeance; translocation energy barrier; interaction energy; porous monolayer WS2

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Permalink: https://www.hzdr.de/publications/Publ-33268
Publ.-Id: 33268


Real-time tracking of fast-moving objects using ultrafast electron beam X-ray computed tomography

Windisch, D.; Barthel, F.; Hampel, U.; Bieberle, A.

Ultrafast electron beam X-ray computed tomography (UFXCT) allows for non-invasive investigation of multi-phase flows with frame rates up to 8,000 slice images per second and a spatial resolution down to 1 mm (see Fig. 1). With the current detector electronics, however, the scanner is limited to offline image reconstruction after the data acquisition which limits its applicability. Nevertheless, especially real-time process and scanner control are of high interest in multi-phase flow investigations. For this, we redesigned the detector electronics firmware, enhanced data transfer, and implemented real-time image reconstruction and analysis. We finally conducted a demonstration experiment in which the position of a moving test object is dynamically controlled using the online analysis of UFXCT images.

Keywords: Image-based real-time process control; ultrafast computed tomography

  • Lecture (Conference) (Online presentation)
    World Congress on Industrial Process Tomography (WCIPT-10), 13.-16.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33266
Publ.-Id: 33266


Data for "Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung"

Parra Ramirez, M. A.; Ristau, F.; Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

Data set for the publication in the wwt modernisierung magazine with the tittle "Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung".

Keywords: Aeration; Bubble size; Dynamic operation

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Permalink: https://www.hzdr.de/publications/Publ-33265
Publ.-Id: 33265


Atomistic simulations on the relationship between solid-phase epitaxial recrystallization and self-diffusion in amorphous silicon

Posselt, M.; Bracht, H.; Radic, D.

Recent experimental results on self-diffusion (SD) in amorphous silicon (a-Si) [J. Kirschbaum et al. Phys. Rev. Lett. 120, 225902 (2018)] indicate that the atomic mechanism of this process is akin to that of solid-phase epitaxial recrystallization (SPER). In this work this relationship is investigated by classical molecular dynamics (MD) simulations using selected interatomic potentials. At the beginning an overview on the status of the present knowledge on SPER and SD is given. Then properties of a-Si are determined for Stillinger-Weber(SW)-type and Tersoff(T)-type potentials. In all cases a good or satisfactory agreement with structural data measured at room temperature is obtained, in particular with the experimental static structure factor. On the other hand, deviations are found for thermal properties. These studies are followed by extraordinarily extensive MD simulations of SPER and SD which reveal that the temperature dependence of those processes can be described by a simple Arrhenius relation. This corresponds to the results of the measurements. However a fully quantitative agreement cannot be found in the case of the interatomic potentials considered. On the other hand, for a given potential the activation enthalpies of both SPER and SD are rather equal. Therefore, the simulated atomic-level processes are obviously very similar. This is consistent with earlier qualitative discussions of results of SPER and SD experiments. The quantitative agreement with measured data for SPER and SD can be improved for certain SW-type potentials if for a-Si an increased value of the three-body parameter is used.

Keywords: Amorphous silicon; Solid phase epitaxial recrystallization; Self-diffusion; Atomistic simulation

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Permalink: https://www.hzdr.de/publications/Publ-33264
Publ.-Id: 33264


A multifunctional, theranostic approach for universal CAR T cell therapy, targeted alpha-therapy and imaging of prostate cancer

Arndt, C.; Bergmann, R.; Máthé, D.; Berndt, N.; Rodrigues Loureiro, L. R.; Szöllősi, D.; Kovács, N.; Hegedűs, N.; Kovács, T.; Feldmann, A.

Background
Chimeric antigen receptor (CAR) T-cells are living drugs successfully applied for treatment of patients with hematological malignancies. However, clinical translation towards solid tumor therapy faces several challenges and does not result in durable responses. In order to improve CAR T-cells´ therapeutic efficiency, combinations with other treatment and imaging modalities are intensively investigated.

Methods
For prostate cancer theranostics we developed a novel, multifunctional IgG4-based antibody construct directed against the prostate stem cell antigen (PSCA). Due to equipment with the UniCAR-tag E5B9 it can be used as a target module (TM) for the well-established UniCAR T-cell approach [1]. Functionality of the PSCA-IgG4 antibody was investigated in vitro by conducting co-cultivation assays with UniCAR T-cells and PSCApos/PSCAneg prostate cancer cells. After radiolabeling with copper-64 or actinium-225, imaging and radioimmunotherapeutic potential of the PSCA-IgG4 antibody were studied using NMRI Foxn1 nu/nu mice.

Results
UniCAR T-cells were specifically activated upon cross-linkage with PSCApos tumor cells via the novel PSCA-IgG4 antibody, which resulted in the secretion of pro-inflammatory cytokines and an efficient tumor cell lysis with EC50 values in the picomolar range. 64Cu- or 225Ac-labeled PSCA-IgG4 antibodies were successfully applied for PET imaging and radioimmunotherapy of prostate tumors in experimental mice. Antibodies specifically enriched at the tumor side whereby maximal tumor accumulation and optimal tumor-to-background ratios were reached after 31 hours. Treatment of tumor-bearing mice with 225Ac-labeled PSCA-IgG4 antibody further resulted in significant lower tumor sizes compared to the control group after 40 days.

Conclusions
We here present a novel, multifunctional PSCA-IgG4 antibody construct for prostate cancer theranostics that facilitates not only UniCAR T-cell immunotherapy, but is also a suitable tool for targeted alpha-therapy and imaging of prostate cancer. This opens the door for a combined radioimmunotherapeutic and imaging approach of prostate cancer that may help to overcome present hurdles in solid tumor therapy.

  • Poster (Online presentation)
    World Immunotherapy Council’s (WIC) 4th Young Investigators Symposium during 36th Annual Meeting & Pre-Conference Programs (SITC 2021), 10.11.2021, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-33263
Publ.-Id: 33263


Towards Scalable Reconfigurable Electronics: Fabrication of Schottky Barrier Field-Effect Transistors using Flash Lamp Annealing

Khan, M. B.; Ghosh, S.; Prucnal, S.; Hübner, R.; Erbe, A.; Georgiev, Y.

To complement the scaling down of complementary metal-oxide-semiconductor (CMOS), new device concepts have been introduced. One such concept is the reconfigurable field-effect transistor (RFET). In the most general case, an RFET is a silicon nanowire (SiNW) based device. The SiNW is silicided at both ends, which results in silicide-Si-silicide Schottky junctions. Typically, two distinct gate electrodes are placed on silicide-Si junctions. By controlling the electrostatic potential on the gate electrodes, the RFET is programmed to the p- or n- polarity. We report on the fabrication and electrical characterization of top-down fabricated SiNW based RFETs. Flash lamp annealing based silicidation process is developed, which enables control over the silicidation process. Uni-polar transfer characteristics are obtained using two top-gates. The effect of implementing various gate dielectric materials (SiO2, Al2O3 and hBN) is studied to enhance device electrostatics.

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  • Poster (Online presentation)
    84th Annual DPG Meeting, 27.09.2021, Virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33262
Publ.-Id: 33262


Data for: Bubble formation from sub-millimeter orifices: experimental analysis and modeling

Mohseni, E.; Eduarda Chiamulera, M.; Reinecke, S. F.; Hampel, U.

raw data and processed data for the publication.

Keywords: Bubble formation; Sub-millimeter orifice; Gas reservoir; Bubble dynamics; Modeling

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Permalink: https://www.hzdr.de/publications/Publ-33261
Publ.-Id: 33261


Analyzing the microbial influence on corrosion at the bentonite-canister interface in a repository of high-level radioactive waste

Matschiavelli, N.

The talk gives an overview about some microbiological-related experimental work in the FWOB-department. The talk focusses on the microbial influence on different barrier materials in a repository for high-level radioactie waste.

  • Lecture (others) (Online presentation)
    HIF-FWOB joint seminar, 02.12.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33260
Publ.-Id: 33260


Bubble formation from sub-millimeter orifices: experimental analysis and modeling

Mohseni, E.; Chiamulera, M.; Reinecke, S.; Hampel, U.

We developed a theoretical model that estimates the bubble size from sub-millimeter orifices under variable gas flow conditions. The model is successfully tested for orifices with diameters in the range of 0.2 mm to 1 mm under both quasi-static and dynamic bubbling regimes. The model is able to predict the final bubble radius with an accuracy better than 20% compared with the experimental results. Moreover, we explicitly look into the influence of the gas reservoir volume V_c upstream of the orifice on the gas reservoir pressure P_c by simultaneously monitoring the events, i.e. changes in the state of bubble, upstream and downstream of orifices. We found that, variations in P_c reduce as V_c increases. Analysis of the dynamics of the dominating forces acting on a bubble show that, enlarging V_c mainly amplifies the gas momentum force and the liquid inertia force. Hence, the bubble detachment mechanism may no longer be only buoyancy driven.

Keywords: Bubble formation; Sub-millimeter orifice; Gas reservoir; Bubble dynamics; Modeling

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  • Secondary publication expected from 12.02.2023

Permalink: https://www.hzdr.de/publications/Publ-33258
Publ.-Id: 33258


Sauerstoffeintragstechnologien für die biologische Abwasseraufbereitung

Parra Ramirez, M. A.; Ristau, F.; Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

In entwickelten Ländern ist die Abwasseraufbereitung für etwa 1 % des gesamten elektrischen Energieverbrauchs verantwortlich, wobei die biologische Behandlung in Belebungsbecken bis zu 80 % des gesamten Energieverbrauchs ausmacht. Zudem wird für die nahe Zukunft ein Anstieg des Energieverbrauchs im Wassersektor um 80 % prognostiziert. Ein wesentlicher Faktor dabei ist die Verwendung energieintensiver Druckbelüftungssysteme, um den für die biologische Aktivität notwendigen Sauerstoff bereitzustellen. Wissenschaftler des Helmholtz-Innovationslabors CLEWATER arbeiten daran, die Effizienz des Belüftungsprozesses deutlich zu steigern. In diesem Artikel werden die aktuellen Fortschritte bei zwei von CLEWATEC vorgeschlagenen Ansätzen zur effizienten Belüftung vorgestellt.

Keywords: Belüftung; Sauerstoffeintragseffizienz; Blasengröße; Dynamischer Betrieb

  • Contribution to external collection
    in: wwt Modernisierungsreport, Frankfurt am Main: Deutscher Fachverlag GmbH, 2021

Permalink: https://www.hzdr.de/publications/Publ-33256
Publ.-Id: 33256


Data publication: In-situ GISAXS observation of ion-induced nanoscale pattern formation on crystalline Ge(001) in the reverse epitaxy regime

Erb, D.; Myint, P.; Evans-Lutterodt, K.; Ludwig, K.; Facsko, S.

experimental raw data: in-situ Grazing Incidence Small Angle X-ray Scattering (GISAXS), ex-situ Atomic Force Microscopy (AFM); simulated raw data: surface topography (RIDO)

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Permalink: https://www.hzdr.de/publications/Publ-33255
Publ.-Id: 33255


Unvailing charge storage and degradation mechanisms of electrochemical energy storage systems via ex-situ and in-situ analyses

Lee, J.; Monrrabal, G.; Landgraf, S.; Weber, N.; Weier, T.

In recent decades, a wealth of new electrochemical energy storage systems have emerged as well as a variety of novel and advanced materials for conventional systems. Once new systems and materials are introduced, they are often challenged by performance degradation such as capacity loss and the increase in cell resistance. Since degradation processes could also raise safety issues such as gas evolution and short-circuiting events, understanding charge storage and degradation mechanisms plays a crucial role in further development. In this work, some of the progress on unvailing charge storage and degradation mechanisms for various electrochemical energy storage systems will be presented. In particular, relying on ex-situ and in-situ technologies, X-ray diffraction, scanning transmission electron microscopy, neutron radiography, degradation processes of advanced electrode materials such as layered nickel-rich cathodes [1-3] and MXene [4] in lithium-ion batteries will be discussed. Additionally, some of the critical limitations of in-situ technologies, such as the radiolysis process in transmission electron microscopy, will be introduced, including the simulation work based on the reaction-diffusion model. [5, 6] Finally, we introduce our recent work on understanding the charge storage mechanism of membrane-free alkali metal-iodide (A-AI) batteries relying on ex-situ neutron radiography.
Acknowledgement:
This project has received funding from the European Union’s Horizon 2020 research and innovation
programme under grant agreement No 963599.

References:

1. C. Xu, K. Marker, J. Lee, A. Mahadevegowda, P. J. Reeves, S. J. Day, M. F. Groh, S. P. Emge, C. Ducati, B. Layla Mehdi, C. C. Tang and C. P. Grey, Nat. Mater., 2021, 20, 84-92.
2. W. Li, I. Siachos, J. Lee, S. A. Corr, C. P. Grey, N. D. Browning and B. Layla Mehdi, Microsc. Microanal., 2021, 27, 1254-1255.
3. J. Lee, H. Amari, M. Bahri, Z. Shen, C. Xu, Z. Ruff, C. P. Grey, O. Ersen, A. Aguadero, N. D. Browning and B. L. Mehdi, Batteries & Supercaps, 2021, DOI: 10.1002/batt.202100110.
4. J. Lee, D. Spurling, O. Ronan, W. Li, I. Siachos, V. Nicolosi and B. Layla Mehdi, Microsc. Microanal., 2021, 27, 1976-1977.
5. J. Lee, D. Nicholls, N. D. Browning and B. L. Mehdi, Phys. Chem. Chem. Phys., 2021, 23, 17766-17773.
6. D. Nicholls, J. Lee, H. Amari, A. J. Stevens, B. L. Mehdi and N. D. Browning, Nanoscale, 2020, 12, 21248-21254.

  • Lecture (Conference)
    Europe-Korea Conference on Science and Technology 2021, 10.10.2021, BEW, Essen, Germany

Permalink: https://www.hzdr.de/publications/Publ-33254
Publ.-Id: 33254


Data publication: B₁₂X₁₁(H₂)⁻: Exploring the limits of isotopologue selectivity of hydrogen adsorption

Wulf, T.

Sample ORCA 4.2.1 input files (TXT);
atomic coordinates and NEB paths (XYZ);
vibration files (7-column XYZ)

for publication

T. Wulf, J. Warneke, T. Heine: B₁₂X₁₁(H₂)⁻: exploring the limits of isotopologue selectivity of hydrogen adsorption. RSC Advances, 11:46 (2021), 28466–28475, doi:10.1039/d1ra06322g

Keywords: hydrogen adsorption,closo-dodecaborates,hydrogen isotopes,boron clusters

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Permalink: https://www.hzdr.de/publications/Publ-33253
Publ.-Id: 33253


Effect of Mechanical Stress on the Splitting of Spin Sublevels in 4H-SiC

Breev, I. D.; Likhachev, K. V.; Yakovleva, V. V.; Veishtort, I. P.; Skomorokhov, A. M.; Nagalyuk, S. S.; Mokhov, E. N.; Astakhov, G.; Baranov, P. G.; Anisimov, A. N.

The effect of static mechanical strain on the splitting of spin sublevels of color centers based on spin 3/2 silicon vacancies in silicon carbide at room temperature has been shown. The deformed heterointerface of the AlN/4H-SiC structure has been studied. Stresses near the heterointerface have been determined using con- focal Raman spectroscopy. The spin–strain coupling constants −0.1 GHz/strain and −0.8 GHz/strain for the V2 center in 4H-SiC have been experimentally determined for the first time using the optically detected magnetic resonance method. The results obtained can be used to control spin states in SiC by means of the controlled piezoelectric strain in AlN and to estimate the fine-structure parameter D of spin centers using Raman scattering. Such an estimate makes it possible to forecast magnetometric parameters of nanosensors based on SiC nanocrystals.

Permalink: https://www.hzdr.de/publications/Publ-33251
Publ.-Id: 33251


alpaka-group/alpaka: alpaka 0.7.0: Maximum Warp

Worpitz, B.; Bastrakov, S.; Ehrig, S.; Gruber, B. M.; Hübl, A.; Kelling, J.; Rogers, D. M.; Stephan, J.; Widera, R.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

Permalink: https://www.hzdr.de/publications/Publ-33250
Publ.-Id: 33250


Flow Feature Extraction with Contactless Inductive Flow Tomography in Presence of the Variable Magnetic Field of an Electromagnetic Brake

Glavinic, I.; Stefani, F.; Eckert, S.; Wondrak, T.

Continuous casting is the primary means of production of steel semi-products. It is of paramount importance to keep the quality of the produced stock constantly at a high level to meet the tight margins of the steel industry. Flow conditions in the mould, where the solidification process starts, significantly impact the quality of the end product. Unfortunately, the harsh industrial environment limits the applicable measurement methods to detect any undesired flow conditions, thus limiting the viable control strategies.Contactless Inductive Flow Tomography (CIFT) was previously proposed to identify flow features in the mould of a continuous caster. While the Electromagnetic Brake (EMBr) is a common way to influence the flow, it has a disturbing influence on CIFT measurements which, however, can be compensated. In this work, we introduce the experimental setup, measurement technique, and discuss the control strategy derived from the CIFT flow reconstruction.

Keywords: Contactless Inductive Flow Tomography; Continuous casting; Electromagnetic Brake

  • Lecture (Conference) (Online presentation)
    10th World Congress on Industrial Process Tomography, 13.09.2021, Tianjin, China
  • Contribution to proceedings
    10th World Congress on Industrial Process Tomography, 13.-16.09.2021, Tianjin, China

Permalink: https://www.hzdr.de/publications/Publ-33248
Publ.-Id: 33248


Resistivity contrast imaging in semiconductor structures using ultra-low energy scanning electron microscopy

Jozwik, I.; Jagielski, J.; Dumiszewska, E.; Kaminski, M.; Kentsch, U.

The damage-induced voltage alteration (DIVA) contrast mechanism in scanning electron microscope (SEM) has been studied in broad range of the primary electron beam energies, with a special emphasis on the ultra-low energy range. The SEM imaging contrast related to resistivity changes in the In(0.55)Al(0.45)P irradiated with He2+ ions of 600 keV was subjected to an analysis in a range of 10 keV down to 10 eV of primary electron energies. The problem of specimen charging in ultra-low energy range and its effect on the contrast in SEM images has been tackled for the first time. Contrary to expectations based on the classical total emission yield approach, the potentials formed at the highly resistive part of irradiated area led to dramatic increase in the intensity of registered signal for primary electron energies below E1, which can be explained as signal saturation due to potential on the specimen surface acting as repeller for primary electrons. Nevertheless, the experimental data presenting the influence of the beam energy on the potential formation on the surface of an insulating material under electron irradiation have been presented for the first time in ultra-low energy regime.

Keywords: Ion damage; Ion irradiation; Low-kV SEM; Semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-33247
Publ.-Id: 33247


Influence of Cr substitution on the reversibility of the magnetocaloric effect in Ni-Cr-Mn-In Heusler alloys

Salazar Mejia, C.; Devi, P.; Singh, S.; Felser, C.; Wosnitza, J.

We present the effect of substitution-induced pressure on the reversibility of the magnetocaloric effect (MCE) in Ni2CrxMn1.4−xIn0.6 (x = 0.1, 0.2, 0.3) alloys, through characterization in pulsed magnetic fields.We measured the adiabatic temperature change ΔTad directly during applied magnetic field pulses of 2 and 6 T. We paid special attention to the reversibility of ΔTad. The substitution of Mn by Cr in Ni2Mn1.4In0.6 leads to a negative pressure, as evidence by the increase of the lattice parameters, which shifts the martensitic transition towards lower temperatures and enhances the ferromagnetism of the martensite phase.We found a large value of ΔTad = −7 K at T = 270 K for the sample with x = 0.1 for a field change of 6 T. We discuss the reversibility of the MCE in these alloys in terms of the Clausius-Clapeyron equation.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-33244
Publ.-Id: 33244


Data publication: Structure and Thermodynamics of Eu(III) and Cm(III) Complexes with Glucuronic Acid

Reese, S.; Kaden, P.; Taylor, C. J.; Kloditz, R.; Schmidt, M.

TRLFS spectra; NMR spectra; QMMM data

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Permalink: https://www.hzdr.de/publications/Publ-33243
Publ.-Id: 33243


Planar triangular S = 3/2 magnet AgCrSe2: Magnetic frustration, short range correlations, and field-tuned anisotropic cycloidal magnetic order

Baenitz, M.; Piva, M. M.; Luther, S.; Sichelschmidt, J.; Ranjith, K. M.; Dawczak-Debicki, H.; Ajeesh, M. O.; Kim, S.-J.; Siemann, G.; Bigi, C.; Manuel, P.; Khalyavin, D.; Sokolov, D. A.; Mokhtari, P.; Zhang, H.; Yasuoka, H.; King, P. D. C.; Vinai, G.; Polewczyk, V.; Torelli, P.; Wosnitza, J.; Bukhardt, U.; Schmidt, B.; Rosner, H.; Wirth, S.; Kühne, H.; Nicklas, M.; Schmidt, M.

Single crystals of the hexagonal triangular lattice compound AgCrSe2 have been grown by chemical vapor transport. The crystals have been carefully characterized and studied by magnetic susceptibility, magnetization, specific heat, and thermal expansion. In addition, we used Cr-electron spin resonance and neutron diffraction to probe the Cr 3d3 magnetism microscopically. To obtain the electronic density of states, we employed x-ray absorption and resonant photoemission spectroscopy in combination with density functional theory calculations. Our studies evidence an anisotropic magnetic order below TN = 32 K. Susceptibility data in small fields of about 1 T reveal an antiferromagnetic (AFM) type of order for H ⊥ c, whereas for H II c the data are reminiscent of a field-induced ferromagnetic (FM) structure. At low temperatures and for H ⊥ c, the field-dependent magnetization and AC susceptibility data evidence a metamagnetic transition at H+ = 5 T, which is absent for H II c. We assign this to a transition from a planar cycloidal spin structure at low fields to a planar fanlike arrangement above H+. A fully ferromagnetically polarized state is obtained above the saturation field of H⊥S = 23.7 T at 2K with a magnetization of Ms = 2.8 μB/Cr. For H II c, M(H) monotonically increases and saturates at the same Ms value at HIIS = 25.1 T at 4.2 K. Above TN , the magnetic susceptibility and specific heat indicate signatures of two dimensional (2D) frustration related to the presence of planar ferromagnetic and antiferromagnetic exchange interactions. We found a pronounced nearly isotropic maximum in both properties at about T = 45 K, which is a clear fingerprint of short range correlations and emergent spin fluctuations. Calculations based on a planar 2D Heisenberg model support our experimental findings and suggest a predominant FM exchange among nearest and AFM exchange among third-nearest neighbors. Only a minor contribution might be assigned to the antisymmetric Dzyaloshinskii-Moriya interaction possibly related to the noncentrosymmetric polar space group R3m. Due to these competing interactions, the magnetism in AgCrSe2, in contrast to the oxygen-based delafossites, can be tuned by relatively small, experimentally accessible magnetic fields, allowing us to establish the complete anisotropic magnetic H-T phase diagram in detail.

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Permalink: https://www.hzdr.de/publications/Publ-33242
Publ.-Id: 33242


Structure and Thermodynamics of Eu(III) and Cm(III) Complexes with Glucuronic Acid

Reese, S.; Kaden, P.; Taylor, C. J.; Kloditz, R.; Schmidt, M.

Complexation by small organic ligands controls the bioavailability of contaminants and influences their mobility in the geosphere. We have studied the interactions of Cm3+, as a representative of the trivalent actinides, and Eu3+, as an inactive homologue, with glucuronic acid (GlcA) a simple sugar acid. Time-resolved laser-induced luminescence spectroscopy (TRLFS) shows that complexation at pH 5.0 occurs only at high ligand to
metal ratios in the form of 1:1 complexes with standard formation constants log β0 = 1.84 ± 0.22 for Eu3+ and log β0 = 2.39 ± 0.19 for Cm3+. A combination of NMR, QMMM, and TRLFS reveals the structure of the complex to be a half-sandwich structure wherein the ligand binds through its carboxylic group, the ring oxygen, and a hydroxyl group in addition to five to six water molecules. Surprisingly, Y3+, which was used as a diamagnetic reference in NMR, prefers a different coordination geometry with bonding through at least two hydroxyl groups on the opposite side of a distorted GlcA molecule. QMMM simulations indicate that the differences in stability among Cm, Eu, and Y are related to ring strain induced by smaller cations. At higher pH a stronger complex was detected, most likely due to deprotonation of a coordinating OH group.

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Permalink: https://www.hzdr.de/publications/Publ-33241
Publ.-Id: 33241


Microstructure-informed prediction and measurement of nanoindentation hardness of an Fe-9Cr alloy irradiated with Fe-ions of 1 and 5 MeV energy

Kapoor, G.; Chekhonin, P.; Kaden, C.; Vogel, K.; Bergner, F.

Hardening of Fe-9%Cr alloys exposed to irradiation with Fe²⁺ ions of two different energies, 1 and 5 MeV, is investigated using nanoindentation. The limited penetration depth of the ions causes steep damage gradients in the near-surface volumes of the irradiated samples. This damage gives rise to graded microstructures resulting in depth-dependent irradiation hardening. Nanoindentation integrates the depth-dependent hardness over the indentation plastic zone. Our study combines quantitative analysis of the ion-irradiated microstructures with the determination of the full depth dependence of irradiation hardening. The microstructure-informed model incorporates direct experimental evidence revealed by a former investigation using cross-sectional scanning transmission electron microscopy. For both ion energies, the observed microstructures consist of dislocation loops with band-like distributions and are concluded to be the dominant source of the measured irradiation-induced hardening. The model predictions are found to be in reasonable agreement with the as-measured nanoindentation response. The comparison of hardening predictions with different kinds of superposition rules of hardening contributions suggests linear superposition as the most appropriate selection under the present conditions. The possible transferability of these results to neutron irradiation is also discussed.

Keywords: Fe-Cr alloys; Ion irradiation; Scanning TEM; Dislocation loops; Nanoindentation; Irradiation hardening

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Permalink: https://www.hzdr.de/publications/Publ-33240
Publ.-Id: 33240


Contactless Inductive Flow Tomography for control of liquid metal flow with electromagnetic actuators

Glavinic, I.; Ratajczak, M.; Stefani, F.; Eckert, S.; Wondrak, T.

To achieve an optimal flow pattern in the mould of a continuous caster, it is desirable to use a tailored control of the flow using electromagnetic actuators (e.g. electromagnetic brakes or stirrers) based on the current flow condition in the mould. However, the rough environment provides a challenge. Contactless Inductive Flow Tomography (CIFT) is a technique that can provide information about the flow structure by visualizing the full velocity field in the mould. In order to reconstruct the flow, the perturbation of an applied magnetic field by the flow is measured. It is obvious that every change of the strength of the magnetic field of an electromagnetic brake influences the measured values. In this paper we cover the challenges of measuring the flow induced magnetic field in the range of nT in the presence of varying magnetic field of the electromagnetic actuators in the range of 100 mT.

Keywords: continuous casting; flow control; inductive measurement techniques; electromagnetic brake

  • Lecture (Conference) (Online presentation)
    TMS2021 Annual Meeting & Exhibition, 16.03.2021, Orlando, Florida, United States of America

Permalink: https://www.hzdr.de/publications/Publ-33239
Publ.-Id: 33239


Control of liquid metal flow in a laboratory model of a continuous caster with Electromagnetic Brake and Contactless Inductive Flow Tomography

Glavinic, I.; Eckert, S.; Stefani, F.; Wondrak, T.

The quality of steel produced by a continuous caster depends on the flow condition during initial solidification in the mould. While the understanding of the flow and its effects is highly desirable, high temperature, opaqueness of the liquid steel and harsh conditions during the production limit viable measurement methods. Contactless Inductive Flow Tomography (CIFT) can provide information about the dominant flow structure in the mould in real time. This information can be used in a control loop for the Electromagnetic Brake (EMBr). Due to the inductive nature of CIFT, every change of the magnetic field strength of the EMBr has a strong influence on the measurements. Changing the strength of the EMBr alters the magnetization vector in its ferromagnetic yoke, which, in turn, generates a signal up to a thousand times higher than the flow induced magnetic field.
In this paper, we present a way to compensate these effects of EMBr on CIFT by filling a database containing compensation values. We will also present the preliminary results of a controller that utilizes CIFT and EMBr to actively control the flow in the mould during casting. The experiments are conducted on the Mini-LIMMCAST facility, a laboratory model of the mould of a continuous caster with the rectangular cross-section of 300 × 30 mm2. It is operated with the eutectic ally GaInSn.

Keywords: continuous casting; flow control; inductive measurement techniques; electromagnetic brake

  • Lecture (Conference) (Online presentation)
    SteelSim2021, 06.10.2021, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-33238
Publ.-Id: 33238


alpaka-group/alpaka: Version 0.6.1: Fix CPU shared memory and rework OpenMP scheduler configuration

Worpitz, B.; Bastrakov, S.; Ehrig, S.; Gruber, B. M.; Hübl, A.; Kelling, J.; Krude, J.; Stephan, J.; Widera, R.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on https://github.com/alpaka-group/alpaka/tree/0.6.1: Link to location
    DOI: 10.5281/zenodo.5040809

Permalink: https://www.hzdr.de/publications/Publ-33237
Publ.-Id: 33237


alpaka-group/alpaka: Version 0.6.0: New Backends and Useability Improvements

Worpitz, B.; Widera, R.; Bastrakov, S.; Hübl, A.; Ehrig, S.; Gruber, B. M.; Kelling, J.; Krude, J.; Stephan, J.

The alpaka library is a header-only C++14 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction of the underlying levels of parallelism.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2021
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on https://github.com/alpaka-group/alpaka/tree/0.6.0: Link to location
    DOI: 10.5281/zenodo.4452636

Permalink: https://www.hzdr.de/publications/Publ-33236
Publ.-Id: 33236


Synthese von Bispidinen für die Radiomarkierung mit Quecksilber-197(m)

Krönke, T.

In der Nuklearmedizin werden Radionuklide für die Diagnose oder die Therapie von Tumoren verwendet. Das Quecksilberisotop 197Hg und das dazugehörige metastabile 197mHg wecken großes Interesse in diesem Gebiet. Ziel dieser Arbeit ist es daher, Moleküle, basierend auf einem Bispidingrundgerüst zu synthetisieren, die eine kovalente Bindung von Hg2+ über Phenylgruppen ermöglichen, um so eine Freisetzung und damit verbundene unspezifische Anreicherung des Quecksilbers in vivo zu verhindern. Der Schwerpunkt liegt dabei auf der Funktionalisierung eines spezifischen Bispidolderivates, um dieses an ein biologisches Molekül knüpfen zu können. Letztendlich soll eine Synthesestrategie erarbeitet werden, die eine Herstellung dieser Bispidole ermöglicht.

Keywords: Quecksilber-197(m); Bispidine; Diagnose; Theranostisches Konzept

  • Bachelor thesis
    TU Dresden / Fakultät Chemie und Lebensmittelchemie, 2021
    Mentor: Dr. Constantin Mamat
    59 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33235
Publ.-Id: 33235


On the Way to Radium-223- and Actinium-225-Radiopharmaceuticals for Targeted Alpha Therapy

Mamat, C.

This talk is fossued on current strategies and future perspectives using the alpha-emitters actinium-225 and radium-223/-224 for targeted alpha therapy.

Keywords: alpha therapy; actinium-225; radium-223; theranostic concept

  • Invited lecture (Conferences) (Online presentation)
    PiDD - Perspectives on interdisciplinary Drug Development | Promote Synergies! in the research landscape Leipzig/Dresden, 01.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33234
Publ.-Id: 33234


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