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39007 Publications

Tungsten Oxide/Reduced Graphene Oxide Aerogel with Low-Content Platinum as High-Performance Electrocatalyst for Hydrogen Evolution Reaction

Li, Y.; Jiang, K.; Yang, J.; Zheng, Y.; Hübner, R.; Ou, Z.; Dong, X.; He, L.; Wang, H.; Li, J.; Sun, Y.; Lu, X.; Zhuang, X.; Zheng, Z.; Liu, W.

Designing cost-effective, highly active, and durable platinum (Pt)-based electrocatalysts is a crucial endeavor in electrochemical hydrogen evolution
reaction (HER). Herein, the low-content Pt (0.8 wt%)/tungsten oxide/reduced graphene oxide aerogel (LPWGA) electrocatalyst with excellent HER activity and durability is developed by employing a tungsten oxide/reduced graphene oxide aerogel (WGA) obtained from a facile solvothermal process as a support, followed by electrochemical deposition of Pt nanoparticles. The WGA support with abundant oxygen vacancies and hierarchical pores plays the roles of anchoring the Pt nanoparticles, supplying continuous mass transport and electron transfer channels, and modulating the surface electronic state of Pt, which endow the LPWGA with both high HER activity and durability. Even under a low loading of 0.81 μgPt cm-2, the LPWGA exhibits a high HER activity with an overpotential of 42 mV at 10 mA cm-2, an excellent stability under 10000-cycle cyclic voltammetry and 40 h chronopotentiometry at 10 mA cm-2, a low Tafel slope (30 mV dec-1), and a high turnover frequency of 29.05 s-1 at η = 50 mV, which is much superior to the commercial Pt/C and the low-content Pt/reduced graphene oxide aerogel. This work provides a new strategy to design high-performance Pt-based electrocatalysts with greatly reduced use of Pt.

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Permalink: https://www.hzdr.de/publications/Publ-33133
Publ.-Id: 33133


Development and preliminary evaluation of [18F]JHU94620-d8 for PET imaging of cannabinoid receptors type 2

Moldovan, R. P.

The development PET radioligands for imaging of the cannabinoid type 2 receptors (CB2R) has been intensively explored due to their upregulation in various pathological conditions [1]. Recently, we reported the development of [18F]JHU94620 [2], however, this radioligand suffered from low metabolic stability in vivo. Here, we describe the development of the deuterated analogues [18F]JHU94620-d4 and -d8 as well as their biological evaluation (Figure 1). The precursors for radiofluorination were obtained by coupling 4,5-dimethylthiazol-ylidene-2,2,3,3-tetramethylcyclopropane-1-carboxamide with either d4 or d8 1,4-butanediol-bistosylate and radiofluorinated in the presence of Kryptand K2.2.2. and K2CO3. [18F]JHU94620-d4 and -d8 were obtained in 10% radiochemical yield and >99% radiochemical purity. The fraction of radiometabolites was quantified in mice plasma, brain and spleen of CD1 mice at 30 min p.i. Both [18F]JHU94620-d4 and -d8 demonstrated an improved metabolic stability with 80% intact radioligand detected in the brain vs. 36% for [18F]JHU94620. The CB2 affinity and specificity of [18F]JHU94620-d8 was determined by in vitro binding experiments and a KD(rCB2) of 0.36 nM was determined. Additionally, we evaluated the [18F]JHU94620-d8 uptake by PET-studies into the spleen of healthy rats and in a rat model carrying an adeno-associated viral (AAV2/7) vector expressing hCB2R(D80N) at high densities in the right striatum (hCB2-rs) [3, 4]. Our PET study with [18F]JHU94620-d8 revealed a rCB2 specific uptake into the spleen (AUC0-30min = 33 vs. 17 SUV min after blocking with GW405833). In the hCB2-rs model we could show a target specific uptake of [18F]JHU94620-d8 with a constant SUV of 6.7±0.3 from 6 to 60 min p.i. and an SUVr (right striatum-to-cerebellum) of 43±7at 60 min p.i., as well as a reversible binding in displacement studies. Thus, [18F]JHU94620-d8 is a new PET tracer with improved metabolic stability and excellent ability to image the CB2 receptors in-vivo. Its further evaluation is underway.

  • Invited lecture (Conferences) (Online presentation)
    DPhG Annual Meeting 2021 Trends and Perspectives in Pharmaceutical Sciences, 30.09.2021, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-33132
Publ.-Id: 33132


X-ray Spectroscopies with increased resolution: principles and perspectives

Amidani, L.

In was only in the early 90s that the use of hard X-ray emission spectrometers to collect X-ray Absorption spectra was first suggested [1]. X-ray emission spectrometers based on Bragg’s law achieve resolutions below 2 eV, a huge improvement compared to solid-state detectors whose resolution is only 150 – 200 eV. With this technical improvement, the characteristic fluorescence of the excited atoms is collected with a resolution below the core-hole lifetime broadening, resulting in better-resolved XAS spectra [2]. Since then, the use of X-ray Spectroscopies with improved resolution exploded and dedicated synchrotron beamlines multiplied. Nowadays, these techniques are largely exploited in many diverse fields of science.
Lanthanides and actinides are among the elements that profit the most of the improved resolution because of their large core-hole lifetime broadenings. Indeed, the demonstration of principle was done on Dy L3 edge XANES [1]. For actinides, the resolution at L3 edge is largely improved, but the biggest boost was given to M4,5 edges, whose conventional XANES are almost featureless. These edges probe directly the 5f states. With better-resolved spectra, the oxidation state can be easily determined and the spectral features that were invisible before bring information about the local coordination and the charge exchange with ligands [3,4].
The information encrypted in these spectra is enormous. Improved resolution makes it more readily available by disclosing details and allowing smaller differences to be appreciated. However, the interpretation often represent the bottleneck to the extraction of relevant information. In this respect, theoretical simulations are fundamental. Nowadays, we have several user-friendly codes that interprets the spectra starting from different approaches, focusing on the intra-atomic interactions or favouring the multi-atomic picture of the system studied.
In this talk, I will briefly introduce some of the techniques exploiting the improved resolution and then focus on their application to actinide science. I will present few examples illustrating the high potential of these techniques and the approach we use in our group to interpret the data [5–7].

References:

[1] K. Hämäläinen et al., Phys. Rev. Lett. 67, 2850 (1991).
[2] P. Glatzel et al., J. Electron Spectrosc. Relat. Phenom. 188, 17 (2013).
[3] K. O. Kvashnina et al., Phys. Rev. Lett. 111, 253002 (2013).
[4] K. O. Kvashnina et al., J. Electron Spectrosc. Relat. Phenom. 194, 27 (2014).
[5] L. Amidani et al., Phys. Chem. Chem. Phys. 21, 10635 (2019).
[6] K. O. Kvashnina et al., Angew. Chem. Int. Ed. 58, 17558 (2019).
[7] A. S. Kuzenkova et al., Carbon 291 (2020).

  • Invited lecture (Conferences) (Online presentation)
    AVS 67, 24.-29.10.2021, Charlotte, USA

Permalink: https://www.hzdr.de/publications/Publ-33131
Publ.-Id: 33131


Instantaneous Frequency representation used for CPA laser simulation

Oksenhendler, T.; Bock, S.; Schramm, U.

We present a novel intuitive graphical method for the simulation of non-linear effects on stretched pulses characterized by a large time-bandwidth product. By way of example, it allows precise determination of effects occurring in CPA (chirped pulse amplification) laser chains, such as the pre-pulse generation by the non-linear Kerr effect. This method is not limited to first order dispersion and can handle all resulting distortions of the generated pre-pulse.

Keywords: ultra-short laser pulses; laser pulse contrast; high-power laser

Permalink: https://www.hzdr.de/publications/Publ-33130
Publ.-Id: 33130


Tests of the detector system for the Stopping Target Monitor of the MU2E experiment in a high flux pulsed gamma beam

Alvarez, C.; Chen, J.; Edmonds, A.; Ferrari, A.; Huang, S.; Keshavarzi, A.; Knodel, O.; Koltick, D.; Lancaster, M.; Miller, J. P.; Müller, S.; Popp, J. L.; Rachamin, R.; Simic, M.; Tickle, S.; Ufer, R.; Voigt, M.

This dataset contains data generated with LaBr and Nal detector (DSPEC and oszilloscope data) at the gELBE beam. The gELBE pulsed gamma beam to test the detector system for the Stopping Target Monitor of the MU2E experiment. The gELBE pulsed gamma beam with narrow pulses set to about 600 kHz repetition rate - the choice of the ELBE CW mode with micropulses at 406 kHz or 812.5 kHz is ideal in our case- is the unique facility in the world suited to study the performance of the Stopping Target Monitor detector of the Mu2e Experiment. The STM monitor has the crucial role to normalize the charged lepton flavor muon conversion rate in the Mu2e experiment. The ability to operate at high rate in presence of background is crucial. We have at ELBE the unique possibility to validate the final methodology that will be employed by the STM detector.

Keywords: dataset; detector; Stopping Target Monitor (STM); MU2E; gELBE; Data Management; DAQ; muon conversion

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Permalink: https://www.hzdr.de/publications/Publ-33129
Publ.-Id: 33129


Synthesis and Pharmacological Evaluation of 1,8-Naphythyridin-2(1H)-one-3-carboxamides Derivatives as Cannabinoid Receptor Type 2 (CB2R) Ligands

Kaur, S.

The primary aim of the present work was to develop fluorinated containing CB2R
ligands based on the lead compound 26 (Figure 10), reported by Lucchesi et al. with
a binding affinity of Ki(CB2R)< 0.67 nM and Ki(CB1R)>5140 nM [91]. Although the
lead compound 26 had a remarkable binding activity it has rather unfavorable
pharmacological properties (cLogP = 4.99 and MW = 459.52 g/mol). Most of the
compounds with cLogP>5 and MW >500 g/mol have poor absorption due to low
solubility and are also unable to cross BBB resulting in poor pharmacokinetics.
Therefore, this master thesis was aimed to synthesize new derivatives based on the
lead compound 26 with modifications to retain or further increase the CB2R binding
affinity and selectivity and improve the pharmacological properties by introducing
substituents containing electronegative atom (fluoro pyridine, fluoro alkoxy, etc) to
make them more polar and thereby also reducing their molecular weight. In general,
the research work was primarily aimed to variously functionalize at N-1 position. In
addition, the newly derivatized compounds should contain a fluorine atom at a
position that allows a facile incorporation of the 18F-label. The cLogP of the planned
derivatives was calculated (ChemDraw 19.0 software) to analyze the effect of
various substituents on the lipophilicity. The substitution of furyl group with a Br at
C-6 position was aimed to increase the hydrophilicity of the lead compound 26
leading to the bromo substituted derivatives with cLogP < 4.5. In order to further
decrease the lipophilicity of the lead compound (26), the replacement of the pfluorobenzyl
at N-1 position with pyridine (cLogP= 3.57) and alkoxy derivatives
(cLogP= 3.72) was planned to synthesize new derivatives (X= R1: furyl, R2:
fluoropyridine, fluoroalkoxy).

  • Master thesis
    Universität Leipzig, 2021
    Mentor: Prof. Bachmann
    78 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33128
Publ.-Id: 33128


Stress-induced modification of gyration dynamics in stacked double-vortex structures studied by micromagnetic simulations

Iurchuk, V.; Körber, L.; Deac, A. M.; Faßbender, J.; Lindner, J.; Kakay, A.

In this paper, using micromagnetic simulations, we investigate the stress-induced frequency tunability of double-vortex nano-oscillators comprising magnetostrictive and non-magnetostrictive ferromagnetic layers separated vertically by a non-magnetic spacer. We show that the relative orientations of the vortex core polarities p1 and p2 have a strong impact on the eigen-frequencies of the dynamic modes. When the two vortices with antiparallel polarities have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the single-frequency resonant gyration mode of the two vortex cores. Additionally, for the case of parallel polarities, we demonstrate that for sufficiently strong magnetostatic coupling, the magnetoelastic anisotropy leads to the coupled vortex gyration in the chaotic regime and to the lateral separation of the vortex core trajectories. These findings offer a path for achieving a fine control over gyration frequencies and trajectories in vortex-based oscillators via adjustable elastic stress, which can be easily generated and tuned electrically, mechanically or optically.

Keywords: Magnetic vortex; Magnetization dynamics; Magnetoelastic anisotropy; Micromagnetic modelling

Permalink: https://www.hzdr.de/publications/Publ-33127
Publ.-Id: 33127


The Relevance of Electronic Perturbations in the Warm Dense Electron Gas

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

Warm dense matter (WDM) has emerged as one of the frontiers of both experimental and theoretical physics and is challenging traditional concepts of plasma, atomic, and condensed-matter physics. While it has become common practice to model correlated electrons in WDM within the framework of Kohn-Sham density functional theory, quantitative benchmarks of exchange-correlation (XC) functionals under WDM conditions are yet incomplete. Here, we present the first assessment of common XC functionals against exact path-integral Monte Carlo calculations of the harmonically perturbed thermal electron gas. This system is directly related to the numerical modeling of X-Ray scattering experiments on warm dense samples. Our assessment yields the parameter space where common XC functionals are applicable. More importantly, we pinpoint where the tested XC functionals fail when perturbations on the electronic structure are imposed. We indicate the lack of XC functionals that take into account the needs of WDM physics in terms of perturbed electronic structures.

Keywords: density functional theory; quantum monte-carlo; electronic structures; exchange-correlation; warm dense matter

Permalink: https://www.hzdr.de/publications/Publ-33126
Publ.-Id: 33126


Terahertz pump-probe of liquid water at 12.3 THz

Novelli, F.; Hoberg, C.; Adams, E. M.; Klopf, J. M.; Havenith, M.

The dynamical complexity of the hydrogen-bonded water network can be investigated with intense Terahertz (THz) spectroscopy, which can drive the liquid into the nonlinear response regime and probe anharmonicity effects. Here we report single-color and polarization-dependent pump-probe experiments at 12.3 THz on liquid water, exciting the librational mode. By comparing results obtained on a static sample and a free-flowing water jet, we are able to disentangle the distinct contributions by thermal, acoustic, and nonlinear optical effects. We show that the transient transmission by the static water layer on a time scale of hundreds of microseconds can be described by thermal (slow) and acoustic (temperature-dependent) effects. In addition, during pump probe overlap we observe an anisotropic nonlinear optical response. This nonlinear signal is more prominent in the liquid jet than in the static cell, where temperature and density perturbations are more pronounced. Our measurements confirm that the THz excitation resonates with the rotationally-damped motion of water molecules, resulting in enhanced transient anisotropy. This model can be used to explain the non-linear response of water in the frequency range between about 1 and 20 THz.

Keywords: Ultrafast Spectroscopy; THz; FEL

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Permalink: https://www.hzdr.de/publications/Publ-33125
Publ.-Id: 33125


Ginzburg effect in a dielectric medium with dispersion and dissipation

Lang, S.; Sauerbrey, R.; Schützhold, R.; Unruh, W.

As a quantum analog of Cherenkov radiation, an inertial photon detector moving through a medium with constant refractive index n may perceive the electromagnetic quantum fluctuations as real photons if its velocity v exceeds the medium speed of light c/n. For dispersive Hopfield type media, we find this Ginzburg effect to extend to much lower v because the phase velocity of light is very small near the medium resonance. In this regime, however, dissipation effects become important. Via an extended Hopfield model, we present a consistent treatment of quantum fluctuations in dispersive and dissipative media and derive the Ginzburg effect in such systems. Finally, we propose an experimental test.

Keywords: dielectric media; dispersion and dissipation; quantum vacuum phenomena; Ginzburg effect; inertial atom; spontaneous excitation

Permalink: https://www.hzdr.de/publications/Publ-33124
Publ.-Id: 33124


Quality Assessment of CFD Software Using Workflows and Decision Trees

Evdokimov, I.; Hänsch, S.

The present research focuses on the new efforts for leveraging so-called workflows for the management of dozens of CFD validation cases. Proposed workflows are meta-algorithms built on top of the free open-source Snakemake library. They allow manipulation of a growing database that currently contains 66 OpenFOAM cases representing various pipe and bubble column multiphase flows with supplied experimental data. The curated case set also provides documentation files. The proposed approach relies on the utilization of human-provided "keywords" for designing a featured dataset. We also use the method developed earlier for quantification of the fitness of simulated to experimental results. It leverages Fuzzy Logic for combining fitness metrics across various physical fields and produces single performance metric called "Goodness". By transforming metrics into a single crisp output value, the algorithm can assign then and additional categorized property to the simulation result of each individual case such that "degraded", "neutral" or "improved" with regard to available experimental data. At the top level, we demonstrate how successes and failures of case sets may be highlighted and analyzed with Decision Trees. The resulting tree is useful in the quality assessment of the CFD software in the final stages of solver development. Decision Trees provide a transparent way for analyzing diverse CFD validation case sets when investigating top-level CFD model changes (for example, applying a new turbulence model).

Keywords: CFD; OpenFOAM; Decision Trees; workflow

  • Contribution to proceedings
    Ivannikov ISPRAS Open Conference, 02.-03.12.2021, Москва, Россия
    Proceedings of Ivannikov ISPRAS Open Conference: IEEE, 978-1-6654-2330-4
    DOI: 10.1109/ISPRAS53967.2021.00027

Permalink: https://www.hzdr.de/publications/Publ-33123
Publ.-Id: 33123


LDOS/SNAP data for MALA: Aluminium at 298K and 933K

Ellis, J. A.; Fiedler, L.; Popoola, G. A.; Modine, N. A.; Stephens, J. A.; Thompson, A. P.; Cangi, A.; Rajamanickam, S.

LDOS/SNAP data for MALA: Aluminium at 298K and 933K (liquid+solid).

Code development was done jointly by the authors.

The calculations have mainly been performed by:
DFT-MD snapshots / DFT calculations (LDOS data): N. A. Modine (at SNL)

SNAP data generation: A. P. Thompson (at SNL)

Neural network training: J. A. Ellis (ORNL, formerly SNL), G. A. Popoola (SNL), L. Fiedler (HZDR)

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Permalink: https://www.hzdr.de/publications/Publ-33121
Publ.-Id: 33121


The H2020 McSAFER project: Main goals, technical work program, and status

Sanchez-Espinoza, V. H.; Gabriel, S.; Suikkanen, H.; Telkkä, J.; Valtavirta, V.; Bencik, M.; Kliem, S.; Queral, C.; Farda, A.; Abéeguilée, F.; Smith, P.; van Uffelen, P.; Ammirabile, L.; Seidl, M.; Schneidesch, C.; Grishchenko, D.; Lestani, H.

This paper describes the main objectives, the technical content and the status of the H2020 project entitled “High-performance advanced methods and experimental investigations for the safety evaluation of generic Small Modular Reactors (McSAFER)”. The main pillars of this project is are the combination of safety-relevant thermal hydraulic experiments and numerical simulations of different approaches for safety evaluations of Small Modular Reactors (SMR). It describes the goals and the consortium first. Then, the involved thermal hydraulic test facilities, e.g. COSMOS-H (KIT), HWAT (KTH), and MOTEL (LUT) including the experimental programs. It also outlines the different safety assessment methodologies applied to four different SMR-designs such as the CAREM (CNEA), SMART (KAERI), F-SMR (CEA) and NuScale e.g. the multiscale thermal hydraulic, conventional, low order and high fidelity neutron physical methods applied to demon-strate the inherent safety features of the SMR-core designs under postulated design-basis-accident conditions. Finally, the status of the investigations is shortly discussed followed by the dissemination activities and an outlook.

Keywords: SMR; Multi-physics; Multi-scale; High fidelity; safety evaluation; experiments

Permalink: https://www.hzdr.de/publications/Publ-33120
Publ.-Id: 33120


Implementing HZDR Interactive Baseline Closure Concept Using Fuzzy Logic and Snakemake Workflows

Evdokimov, I.; Hänsch, S.

Euler-Euler multiphase simulations imply numerical challenges and require taking into account many nuances. As pointed out by the authors of the Baseline concept [1], the successful framework for multiphase CFD should reflect a contemporary view on underlying physical phenomena and predict well arbitrary flow configurations. The Baseline methodology [1] specifies a particular meta-algorithm for proposing new sub-models and validating them on a large number of cases (re-interpretation of the original Baseline strategy [1] is shown on the Figure). Although original work presents a clear specification of methodology in general aspects, it lacks the most important definition of “overall improvement”.
The definition of overall improvements is not a single challenge. In addition, simultaneous evaluation of the whole case set becomes important when the number of cases approaches several dozen setups with at least 3 different plots per setup. Meanwhile, human evaluation of all generated plots may be viewed as a serious burden for the research of new better EE models at scale. To address both challenges we propose implementation of the Fuzzy Logic Controller (FLC) and the workflow architecture for scalable simulations and results evaluation of hundreds of cases (potentially).
FLC is applied universally for each case and it ensures that all requirements are fixed. It relies on two metrics calculated for each plot (i.e. void fraction or gas velocity). These are average relative error and Pearson coefficient serving as input crisp values. As an output value, FLC provides the Goodness value which is a crisp output and indicates badly fitting simulation data (with G=0) or perfectly fitting results (with G=1). It uses fuzzy sets “low”, “medium”, and “high” (similar to example in [2]) for each error and Pearson coefficient intervals and helps to achieve better flexibility and clarity than some artificially constructed function.
FLC is an important component of the post-processing Snakemake workflow(more details available in [3]). The combination allows improvements on many levels. Those are 1) explicit specification of the “improvement”, 2) productivity gain in a sense of aggregation of results in a single report, 3) extensible post-processing system which may help to analyze hundreds of cases simultaneously. The demonstrated approach may be also applied to other fields of study where multiparametric models must be tested against multiple simulation setups.

Keywords: fuzzy logic; workflow; CFD; multiphase

  • Open Access Logo Poster (Online presentation)
    Multiphase Flow Workshop 2021, 08.-10.11.2021, Online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-33119
Publ.-Id: 33119


[nat/89Zr][Zr(pypa)]: Thermodynamically Stable and Kinetically Inert Binary Nonadentate Complex for Radiopharmaceutical Applications

Southcott, L.; Li, L.; Brian, P.; Stephan, H.; de Guadalupe Jaraquemeda-Pelaez, M.; Orvig, C.

Abstract
H4pypa is a nonadentate nonmacrocyclic chelator which previously demonstrated high affinity for scandium-44, lutetium-177 and indium-111. Herein, we report the highly stable binary [Zr(pypa)] complex; the non-radioactive complex was synthesized and characterized in detail using high resolution
electrospray-ionization mass spectroscopy (HR-ESI-MS) and various nuclear magnetic resonance spectroscopies (NMR), which revealed a C2v-symmetry of the complex. The geometry of [Zr(pypa)] was further detailed via X-ray crystallography and compared to the structure of [Fe(Hpypa)]. Despite a slow complexation rate with an association half-life of 31.4 h at pH 2 and room temperature, the [Zr(pypa)] complex is thermodynamically stable (log KML = 38.92, pZr =39.4). Radiochemical studies demonstrated quantitative radiolabeling achieved at 10 µM chelatorconcentration within 2 h at 40°C and pH = 7, antibody-compatible conditions. Of utmost importance, [89Zr][Zr(pypa)] is highly kinetically inert upon challenge with excess EDTA and DFO ligands, superior to [89Zr][Zr(DFO)], and maintains inertness towards human serum.

Permalink: https://www.hzdr.de/publications/Publ-33118
Publ.-Id: 33118


Radionuclide transport modelling: The Smart Kd-concept in reactive transport codes

Stockmann, M.; Lu, R.; Gehrke, A.; Montoya, V.; Noseck, U.; Brendler, V.

A key component of performance assessment for radioactive waste repositories in deep geological formations is the long-term prediction of potential radionuclide transport to the geosphere over periods longer than 100,000 years. Radionuclide sorption on minerals (host rocks and geotechnical barriers) is one of the most important retardation process. One big challenge for radionuclide transport calculations with large-scale heterogeneous geochemical compartments is the integration of realistic physico-chemical models and their parameters at affordable computational costs.
In performance assessment, sorption is an important retardation process and typically considered by constant distribution coefficients (Kd) that can be easily included in transport codes. One of the advantage of this approximation is their computational efficiency, but it cannot reflect changes in geochemical conditions. On the other hand, mechanistic surface complexation models used for process understanding can be directly coupled to transport codes with geochemical solvers, but usually only at high computational costs. An effective alternative to the above mentioned approaches is provided by the smart Kd concept (www.smartkd-concept.de) [1, 2], specifically developed to describe variable radionuclide sorption in transport models as consequence of changing geochemical conditions in time.
The fundamental strategy of the smart Kd-concept is to firstly compute multidimensional matrices (namely look-up tables) of distribution coefficients based on surface complexation and cation exchange models. The smart Kd-values are computed for different radionuclides as a function of a wide range of geochemical parameters. Such parameters are typically pH, ionic strength, and dissolved ions, e. g. calcium, carbonate. The look-up table is generated using the geochemical code PhreeqC [3].
The information stored in the look-up table can then be accessed by reactive transport codes at each point in time and space. This approach was already implemented in the d3f++ code [4]. Here, an additional implementation and validation of the smart Kd-approach in OGS6 [5, 6] is demonstrated. For this purpose, three benchmark test were defined with increasing complexity. Complexity is mainly related to the number of components (radionuclides) included in the simulation. Results obtained with the OGS6 were compared with OGS6#PhreeqC3.5.0, PHAST [7] and d³f++.

  • Poster (Online presentation)
    TransRet2020 Workshop, 12.-13.10.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-33117
Publ.-Id: 33117


Data associated with the publication "The relevance of electronic perturbations in the warm dense electron gas"

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

This repository contains the Kohn-Sham density functional theory (KS-DFT) and path-integral Monte-Carlo (PIMC) data used in the journal publication "The relevance of electronic perturbations in the warm dense electron gas".

Keywords: Density Functional Theory; Path-Integral Monte-Carlo; Electronic Structure Theory

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Permalink: https://www.hzdr.de/publications/Publ-33115
Publ.-Id: 33115


Verification of the code DYN3D for calculations of neutron flux fluctuations

Viebach, M.; Lange, C.; Kliem, S.; Demaziere, C.; Rohde, U.; Hennig, D.; Hurtado, A.

Insufficiently explained magnitudes and patterns of flux fluctuation observed mainly in KWU PWRs are recently investigated
by various European institutions. Among the numerical tools used to investigate the neutron flux fluctuations is the time-domain
reactor dynamics code DYN3D. As DYN3D and comparable codes have not been developed with the primary intention to simulate
low-amplitude neutron flux fluctuations, their applicability in this field has to be verified.
In order to contribute to the verification of DYN3D for the simulation of neutron flux fluctuations, two special cases of perturbations
of the neutron flux (a localized absorber of variable/oscillatory strength and a travelling oscillatory perturbation) are considered
with DYN3D on the one hand and with the frequency-domain neutron noise tool CORE SIM as well as analytical frequency-domain
approaches, respectively, on the other hand. The obtained results are compared with respect to the distributions of the amplitude and
the phase of the induced neutron flux fluctuations. The comparisons are repeated with varied amplitudes and frequencies of the
perturbation.
The results agree well both qualitatively and quantitatively for each of the conducted calculations. The remaining deviations
between the DYN3D results and the reference results exhibit a dependence on the perturbation magnitude, which is attributed to the
neglect of higher-order terms (linear theory) of the perturbed quantities in the calculation of the reference solutions.

Keywords: neutron noise; deterministic reactor modeling; DYN3D; CORE SIM

Permalink: https://www.hzdr.de/publications/Publ-33114
Publ.-Id: 33114


Formation and time dynamics of hydrogen-induced vacancies in nickel

Chiari, L.; Kojima, K.; Endo, Y.; Teshigahara, H.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Fujinami, M.

The formation and time dynamics of hydrogen-induced defects in nickel by room temperature aging was investigated by positron annihilation spectroscopy. Low temperature conventional positron annihilation lifetime spectroscopy and positron lifetime measurements using a high-flux positron beam evidenced the formation of a large number of monovacancy-level defects simply by hydrogen addition at room temperature. Low-temperature coincidence Doppler broadening measurements proved that hydrogen was trapped and bound to these vacancies during the hydrogen charge. Room temperature aging, i.e. below the stage III temperature in Ni, and the concomitant hydrogen desorption induced the agglomeration of those monovacancies into large vacancy clusters which remained even after all the hydrogen had desorbed and hydrides had disappeared. These results demonstrated that vacancy-hydrogen complexes were induced in Ni only by hydrogen charging and that hydrogen has a primary role in the formation and stabilization of vacancies even at room temperature.

Keywords: hydrogen; nickel; vacancies; positron annihilation spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-33113
Publ.-Id: 33113


Quantification of cerebral nicotinic α7 acetylcholine receptors (α7 nAChRs) under gastric stimulation of the vagus nerve in piglets

Rullmann, M.; Alexander Becker, G.; Antonov, A.; Sattler, B.; Sattler, T.; Deuther-Conrad, W.; Schimpf, S.; Patt, M.; Meyer, P. M.; Teodoro, R.; Wenzel, B.; Scheunemann, M.; Hesse, S.; Brust, P.; Leitzke, M.; Sabri, O.

Introduction
Electrical gastric vagus nerve stimulation (VNS) shifts the sympathetic-vagal balance toward a parasympathetic predominance (1). We aim to assess central changes in α7 nAChR-mediated transmission and hypothesize that VNS changes the parasympathetic tone by changing the α7 nAChR availability in the nucleus tractus solitarii (NTS) and distinct cortical and subcortical regions (2).

Material and Methods
Following a standard 35-frames, 120-min protocol for dynamic brain PET imaging, data from eight piglets (15.6 ± 3.2 kg, ~6 weeks) were acquired post injection of 194.8 ± 9.4 MBq of [18F]DBT-10 (3) followed by T1-MPRAGE MRI: three baseline, two with infusion of the acetylcholine esterase inhibitor physostigmine (0.04 mg/kg, 1 ml/min, at 10 min prior to tracer injection; 0.24 mg/kg, 1 ml/min, at tracer injection/scan start over 120 min) and three with VNS in repeated sequences of 0.5 Hz over 5 min, 5 min pause started at scan start. TACs were analyzed using a 2-tissue compartment model involving a metabolite-corrected arterial input function to generate individual total distribution volumes (VT) as receptor parameter.

Results
Compared to baseline, we observed an increase of the mean VT after physostigmine infusion (61 %) as well as after VNS (28 %) without major alterations of K1 in the NTS (Figure 1 and 2).

Conclusion
These initial data indicate blood-flow-independent changes under VNS as compared with baseline suggesting an increase in α7 nAChR availability although the changes appear more heterogeneous in VNS as compared with physostigmine. The finding is in contrast to our hypothesis expecting lower α7 nAChR-availability as a result of increased acetylcholine release following VNS. We speculate that higher VT under VNS may reflect an increase in affinity of the α7 nAChR or result in an upregulation of the α7 nAChR. Increase of VT following physostigmine administration could be related to a positive allosteric effect on the α7 nAChR. Furthermore, the results of this study allow sample size estimations for further preclinical and clinical studies.

  • Lecture (Conference) (Online presentation)
    NRM2021 - XIII International Symposium of Functional Neuroreceptor Mapping of the Living Brain, 14.-16.12.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33112
Publ.-Id: 33112


Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems (Raw Data)

Michaux, B.

Files are containing the raw data of the dissertation:

Title: Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems

Author: M.Sc. Bruno Benjamin Xavier Michaux

Faculty: Faculty of Mechanical, Process and Energy Engineering of the Technische Universität Bergakademie Freiberg

Year: 2021

It contains 3 Excel sheets:

  • One for the flotation kinetics data
  • One for the water composition data in flotation
  • One for the water composition data in the mill.

Furthermore it contains a student report from 2017 which is describing the preparation of the synthetic water by

Miaad Farhan Fadami
Research Intern
miaad.farhanfadami@mail.mcgill.ca

Keywords: Flotation; Mineral Processing; Mining; Water

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Permalink: https://www.hzdr.de/publications/Publ-33111
Publ.-Id: 33111


SIMS analytics of quartz

Renno, A.

Secondary ion mass spectrometry (SIMS), as a high-precision, spatially resolved analytical method, is an alternative to the standard LA-ICP-MS and EPMA methods of quartz analysis. Quartz, with its "notoriously low" trace element contents, presented a welcome challenge from the beginning of the routine application of SIMS methods in mineralogy. In the course of instrument development, there has been an increasingly intensive instrumental differentiation of SIMS instruments. Today, it is possible to analyze almost all naturally occurring elements (H-U), isotope ratios as well as molecular ions and molecular fragments with resolutions from the millimeter to the nanometer range using SIMS. In principle, this allows its use in solving a variety of scientific problems closely related to quartz. Examples are the clarification of crystallochemical questions of the incorporation of different ions into the quartz lattice, questions of element diffusion (e.g. Li, Ti or H) in quartz, the determination of causes for certain spectroscopic features (e.g. CL or EPR), the reconstruction of formation conditions via isotope ratios (O, Si, Li or H), the application of geothermometers (e.g. TitaniQ), the mechanical behavior of quartz as a function of hydrogen content, provenance analyses for natural rocks but also archaeological artifacts, exploration-related questions for quartz deposits and in particular for deposits in which quartz occurs as a genetic-critical accompanying mineral, up to problems of quality testing and quality assurance of high-purity quartz and the engineering evaluation of processing technologies in particular flotation for quartz extraction.
The main limitation of SIMS is the extreme matrix dependence of secondary ion yield. This requires the use of meticulously characterized reference materials (Audétat et al., 2015). New promising developments in this field will be presented (Nachlas, 2016; Wu et al., 2019).
New instrumental developments such as the positive ion SIMS-SSAMS (Grabowski et al., 2019), the Super-SIMS (Rugel et al., 2016) or SIMS analysis in specially modified helium microscopes (Wirtz et al., 2019) and associated enhanced analytical capabilities of quartz will be presented.

References:

Audétat, A., Garbe-Schönberg, D., Kronz, A., Pettke, T., Rusk, B., Donovan, J.J. and Lowers, H.A. (2015) Characterisation of a Natural Quartz Crystal as a Reference Material for Microanalytical Determination of Ti, Al, Li, Fe, Mn, Ga and Ge. Geostandards and Geoanalytical Research 39, 171-184.
Grabowski, K.S., Groopman, E.E., Rock, B.Y. and Imam, M.A. (2019) Positive ion SIMS-SSAMS for trace analysis of materials. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 455, 158-164.
Nachlas, W.O. (2016) Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials. Geostandards and Geoanalytical Research 40, 505-516.
Rugel, G., Pavetich, S., Akhmadaliev, S., Baez, S.M.E., Scharf, A., Ziegenrucker, R. and Merchel, S. (2016) The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data. Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 370, 94-100.
Wirtz, T., Castro, O.D., Audinot, J.-N. and Philipp, P. (2019) Imaging and Analytics on the Helium Ion Microscope. Annual Review of Analytical Chemistry 12, 523-543.
Wu, H., Böttger, R., Couffignal, F., Gutzmer, J., Krause, J., Munnik, F., Renno, A.D., Hübner, R., Wiedenbeck, M. and Ziegenrücker, R. (2019) ‘Box-Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry. Geostandards and Geoanalytical Research 43, 531-541.

Keywords: SIMS; Mineralogy; Geochemistry; Quartz

Related publications

  • Lecture (Conference)
    QUARTZ2021 - International Symposium on Quartz, 05.-07.09.2021, Tønsberg, Norge

Permalink: https://www.hzdr.de/publications/Publ-33110
Publ.-Id: 33110


A systematic review on the use of quantitative imaging to detect cancer therapy adverse effects in normal-appearing brain tissue

Petr, J.; Hogeboom, L.; Nikulin, P.; Wiegers, E.; Schroyen, G.; Kallehauge, J.; Chmelik, M.; Clement, P.; Nechifor, R. E.; Fodor, L.-A.; de Witt Hamer, P.; Barkhof, F.; Pernet, C.; Lequin, M.; Deprez, S.; Jancalek, R.; Mutsaerts, H. J.; Pizzini, F. B.; Emblem, K. E.; Keil, V. C.

Cancer therapy for both central nervous system (CNS) and non-CNS tumors has been previously associated with transient and long-term cognitive deterioration, commonly referred to as ‘chemo fog’. This therapy-related damage to otherwise normal-appearing brain tissue is reported using post-mortem neuropathological analysis. Although the literature on monitoring therapy effects on structural magnetic resonance imaging (MRI) is well-established, such macroscopic structural changes appear relatively late and irreversible. Early quantitative MRI biomarkers of therapy-induced damage would potentially allow to take these treatment side-effects into account and pave the way towards a more personalized treatment planning.
This systematic review (PROSPERO number 224196) provides an overview of quantitative tomographic imaging methods, potentially identifying the adverse side-effects of cancer therapy
in normal-appearing brain tissue. Sixty-six studies were obtained from the MEDLINE and Web of Science databases. Studies reporting changes in normal-appearing brain tissue using MRI, PET, or SPECT quantitative biomarkers, related to radio-, chemo-, immuno-, or hormone therapy for any kind of solid, cystic, or liquid tumor were included. The reviewed studies were assessed for risk of bias using a modified QUADAS-2 tool, of which findings were summarized. For each imaging method, this review provides the methodological background, and the benefits and shortcomings of each method from the imaging perspective. Finally, a set of recommendations is proposed to support future research.

Permalink: https://www.hzdr.de/publications/Publ-33109
Publ.-Id: 33109


Low-level ¹⁶⁶mHo 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 νe by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T1/2=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 any contamination with the long-lived radionuclide 166mHo 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 mass separator. The separation from ¹⁶⁶mHo, however, cannot be quantified to such low levels as needed. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). This requires the formation of negative ions, we find the highest negative ion yield for the anion HoO₂. For first tests ¹⁶⁵Ho was implanted by RISIKO in various metal foils and we obtained results for the Ho detection efficieny. This allows for extrapolations for the expected measurement limit of the ¹⁶⁶mHo/¹⁶³Ho ratio.

Related publications

  • Lecture (Conference) (Online presentation)
    DPG-Tagung der Sektion Atome, Moleküle, Quantenoptik und Plasmen (SAMOP), 20.-24.09.2021, Kaiserslautern, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-33108
Publ.-Id: 33108


Temperature determination during Flash Lamp Annealing

Begeza, V.; Rebohle, L.; Schumann, T.

Flash lamp annealing (FLA) is a modern technology for the thermal treatment of materials which currently opens up new application areas. During FLA, an intense pulse of light with a pulse duration of milliseconds and below is applied to the surface of a material. In contrast to traditional methods like furnace annealing, temperature now strongly depends on the material properties and the thickness of the sample. In addition, the short time scale leads to a temperature distribution over depth and makes direct temperature measurements very challenging.
In this work we first review in brief the existing possibilities for a direct temperature measurement during FLA. The main part presents our own concept which is a combination of direct measurements, calibration and thermodynamic simulation. The latter point is of special interest as it allows to get information about the temperature distribution within the material, provided that the relevant material parameters are known. Finally, the impact of such temperature distributions on physical processes like diffusion, crystallization and phase formation is discussed.

Keywords: Flash Lamp Annealing; Short time annealing; Temperature determination

  • Invited lecture (Conferences) (Online presentation)
    CERC 2021, 09.-10.09.2021, Cork, Irland

Permalink: https://www.hzdr.de/publications/Publ-33106
Publ.-Id: 33106


Layer coupling between solutal and thermal convection in liquid metal batteries

Personnettaz, P.; Klopper, T. S.; Weber, N.; Weier, T.

For longer than one decade, liquid metal batteries (LMBs) are developed with the primary aim to provide economic stationary energy storage. Featuring two liquid metal electrodes separated by a molten salt electrolyte, LMBs operate at elevated temperature as simple concentration cells. Therefore, efficient mass transfer is a basic prerequisite for their economic operation. A thorough understanding of the relevant mechanisms cannot be achieved by studying single layers in isolation. With this motivation, the effects of solutal- and thermally-driven flow are studied, as well as the flow coupling between the three liquid layers of the cell. It is shown that solutal convection appears first and thermal convection much later. While the presence of solutal flow depends on the mode of operation (charge or discharge), the occurrence of thermal convection is dictated by the geometry (thickness of layers). The coupling of the flow phenomena between the layers is intriguing: while thermal convection is confined to its area of origin, i.e. the electrolyte, solutal convection is able to drive flow in the positive electrode and in the electrolyte.

Keywords: liquid metal battery; mixing; solutal convection; Rayleigh-Bénard convection; internally heated convection; layer coupling

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  • Secondary publication expected from 01.06.2023

Permalink: https://www.hzdr.de/publications/Publ-33105
Publ.-Id: 33105


Experimental Oxygen Mass Transfer Study of Micro-perforated Diffusers

Herrmann-Heber, R.; Ristau, F.; Mohseni, E.; Reinecke, S.; Hampel, U.

We studied new micro-perforated diffuser concepts for the aeration process in the wastewater treatment plant and evaluated their aeration efficiency. These are micro-perforated plate diffusers with orifice diameters of 30 µm, 50 µm and 70 µm and a micro-perforated tube diffuser with orifice diameter of 50 µm. The oxygen transfer of the diffuser concepts was tested in clean water and it is compared with commercial aerators from the literature. The micro-perforated tube diffuser and micro-perforated plate diffusers outperform the commercial membrane diffusers up to 44% and 20%, respectively, with regard to the oxygen transfer efficiency. The most relevant reason for the improved oxygen transfer is the fine bubble aeration with bubble sizes down to 1.8 mm. Furthermore, the more homogenous cross-sectional bubble distribution of the micro-perforated tube diffuser has a beneficial effect on the gas mass transfer due to less bubble coalescence. However, the pressure drop of micro-perforated diffusers seems to be the limiting factor for their standard aeration efficiencies due to the size and the number of orifices. Nevertheless, this study shows the potential for a better aeration efficiency through the studied conceptual micro-perforated diffuses.

Keywords: micro-perforated diffuser; oxygen transfer efficiency; oxygen mass transfer; aeration efficiency

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Permalink: https://www.hzdr.de/publications/Publ-33104
Publ.-Id: 33104


Restoring betatron phase coherence in a beam-loaded laser-wakefield accelerator

Köhler, A.; Pausch, R.; Bussmann, M.; Couperus Cabadağ, J. P.; Debus, A.; Krämer, J. M.; Schöbel, S.; Zarini, O.; Schramm, U.; Irman, A.

Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening the accelerating electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we experimentally demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of the micrometer-small beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the minimization of chromatic betatron decoherence. These findings are supported by rigorous three-dimensional particle-in-cell simulations tracking self-consistently particle trajectories from injection, acceleration until beam extraction to vacuum. We conclude that beam-loaded LWFA enables highest longitudinal and transverse phase space densities.

Keywords: laser-wakefield acceleration; beam loading; beam coherence restoration; beam decoherence; betatron radiation; ionization injection; particle-in-cell simulations

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Permalink: https://www.hzdr.de/publications/Publ-33103
Publ.-Id: 33103


THEREDA - Thermodynamic Reference Database

Moog, H. C.; Scharge, T.; Seher, H.; Bok, F.; Brendler, V.; Richter, A.; Wissmeier, L.; Altmaier, M.; Gaona, X.; Cevirim-Papaioannou, N.; Freyer, D.; Pannach, M.; Sohr, J.; Voigt, W.

Abstract.
Part of the process to ensure the safety of radioactive waste disposal is the predictive modeling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modeling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA 15 (Moog et al., 2015).
THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients which allow for the calculation of solubilities in high-saline solutions. Registered users may either download single thermodynamic data or ready-to-use parameter files for the geochemical speciation codes 20 PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. Data can also be downloaded in a generic JSON-format to allow for the import into other codes. The database can be accessed via the world wide web: www.thereda.de
Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side 25 effects on calculations are caused. Furthermore, our website offers an increasing number of examples for applications, including graphical representation, which can be filtered by components of the calculated system.

References
Moog, H. C., Bok, F., Marquardt, C. M., and Brendler, V.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84, doi: 30 10.1016/j.apgeochem.2014.12.016, 2015.

Keywords: THEREDA; Thermodynamic Reference Database; Pitzer; Solubility; Thermodynamic data

  • Poster (Online presentation)
    SafeND Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland
  • Open Access Logo Contribution to proceedings
    Safety of Nuclear Waste Disposal, 10.-12.11.2021, Berlin, Deutschland
    Safety of Nuclear Waste Disposal, Berlin: BASE, 157-158
    DOI: 10.5194/sand-1-157-2021

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Permalink: https://www.hzdr.de/publications/Publ-33102
Publ.-Id: 33102


Not just a background: pH buffers do interact with lanthanide ions – a Europium(III) case study

Mandal, P.; Kretzschmar, J.; Drobot, B.

The interaction between Eu(III) ion and different pH buffers, popular in biology and biochemistry viz. HEPES, PIPES, MES, MOPS, and TRIS have been studied by solution nuclear magnetic resonance spectroscopy (NMR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) techniques. The Good’s buffers reveal non-negligible interaction with Eu(III) as determined from their complex stability constants, where the sites of interaction are the morpholine and piperazine nitrogen atoms, respectively. In contrast, TRIS buffer shows practically no affinity towards Eu(III). Therefore, when investigating lanthanides, TRIS buffer should be preferred over Good’s buffers. 

Keywords: Europium; Buffer; TRLFS; NMR; Stability Constant

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Permalink: https://www.hzdr.de/publications/Publ-33100
Publ.-Id: 33100


Research data: Terahertz signatures of ultrafast Dirac fermion relaxation at the surface of topological insulators

Kovalev, S.; Tielrooij, K.-J.; Deinert, J.-C.; Ilyakov, I.; Chen, M.; Ponomaryov, O.; de Oliveira, T.; Eng, L. M.; Gensch, M.

This research data publication contains: - Experimental datasets which were evaluated and presented in the corresponding article. - Origin software file that contains the raw data as well as the different steps of the data analysis, the results of which are presented in the article.

Keywords: Terahertz; Ultrafast; Harmonic Generation; Topological Insulators; Surface Science; Dirac Material

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Publ.-Id: 33099


Raw data related to publication entitled "Turbulent resuspension of micron particles from a wall surface functionalized with cylindrical micropillars" by Banari, A. et al.

Lecrivain, G.
Project Leader: Lecrivain, Gregory

# 'Flowrate.JPG': Table associating a raw image (see 'org' folder below) with the flow rate (Q) in L/min

# 'Rough': raw data obtained with the rough substrate

# 'Smooth': raw data obtained with the smooth substrate

# "Smooth" and "Rough" folders contain a list of subfolders Mi, with i=0,1,2,... the measurement index. Ex: M1: is a first series of measurements and M2: a second series of measurements. Each Mi folder contains the following data:

## 'org': List of pictures (Acquisition_AAA_-BBBBBB.jpg) taken with the high-resolution camera. With AAA=000,001,002,... is the flow rate association. To associate AAA with the flow rate, see 'Flowrate.JPG'. Ex: '000' -> Q = 0 L/min, '001' -> Q = 20 L/min. BBB=000001,000002 or 000003 are pictures of the same particle bed taken at increasing time interval. These 3 pictures are used to check particle bed equilibrium.

## 'pic_CCC.jpg' with CCC=001, 002, 003: simply a copy of the raw picture in 'org' with bed at equilibrium. The association between the index (CCC) and the  flow rate (Q) is identical to that described in 'org' (AAA).

## 'Particles_CCC.csv' with CCC=001, 002, 003: List of particle positions (called tags in the manuscript) in each respective image.

Keywords: Particle resuspension; Particle adhesion; Turbulent gas flow; Surface functionalization; Surface roughness.

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Permalink: https://www.hzdr.de/publications/Publ-33098
Publ.-Id: 33098


Interaction of Th(IV), Pu(IV) and iron(III) with ferritin protein : how similar ?

Zurita, C.; Tsushima, S.; Lorenzo Solari, P.; Jeanson, A.; Creff, G.; Den Auwer, C.

Ferritin is the main actor of Fe storage in eukaryote and prokaryote cells. It is a large multifunctional, multi-subunit protein consisting of heavy H and light L subunits. In the field of nuclear toxicology, it has been suggested that some actinides elements, such as thorium and plutonium at oxidation state +IV, have a comparable "biochemistry" as iron at oxidation state +III due to their very high tendency for hydrolysis and somehow comparable ionic radii. Therefore the possible mechanisms of interaction of such actinide elements with Fe storage protein is a fundamental question of bio-actinidic chemistry. We have recently described the complexation of Pu(IV) and Th(IV) with horse spleen ferritin (composed mainly of L subunits). In this article we bring another view point to this question by further combining modeling with our previous EXAFS data for Pu(IV) and Th(IV). As a result, the interaction between the L subunits and both actinides appear to be not specific but only driven by the density of presence of Asp and Glu residues on the protein shell. The formation of an oxyhydroxide Th or Pu core has not been observed in our experimental condition, nor the interaction of Th or Pu with the ferric oxyhydroxide core.

Permalink: https://www.hzdr.de/publications/Publ-33096
Publ.-Id: 33096


Animal models for the evaluation of radiopharmaceuticals

Toussaint, M.

As the nuclear medicine community strives to make the promise of personalised medicine a reality, it is more essential than ever to have highly relevant translational models to recapitulate human disease. Indeed, personalized medicine aims to identify the predictive factors of a disease at the patient level and animal models can be an essential element if they meet certain key criteria.
In addition of choosing the right animal model, the evaluation of potential new radiopharmaceuticals requires consideration of animal model-specific differences (in terms of target expression and distribution, physiology, pharmacokinetics…) that may predict differences between preclinical and clinical observations, as well as the design of imaging or therapy protocols that are representative of clinical protocols.
This teaching session will therefore, be an opportunity to discuss the optimisation of preclinical approaches in experimentations, data interpretation and reporting with the aim of improving the translational power of new radiopharmaceutical candidates.

Keywords: Animal models; translation; radiopharmaceuticals

  • Invited lecture (Conferences) (Online presentation)
    34th annual congress of the European Association of Nuclear Medicine, 20.-23.10.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33094
Publ.-Id: 33094


Data Publication: Pump-induced terahertz anisotropy in bilayer graphene

Seidl, A.; Anvari, R.; Dignam, M. M.; Richter, P.; Seyller, T.; Schneider, H.; Helm, M.; Winnerl, S.

The raw data and lab book pages are given in the .zip folders. The results of the theoretical calculations in comparison to the experiment are given in Roozbeh_plot.opju. In the other two Origin files, the differential transmission signals and other relevant values are calculated from the raw data.The 2 THz measurement was performed in 2019, the 3.4 THz measurement in 2020.

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Permalink: https://www.hzdr.de/publications/Publ-33093
Publ.-Id: 33093


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

Wulf, T.; Warneke, J.; Heine, T.

We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of undeca-X-closo-dodecaborates B₁₂X₁₁⁻ (X = H, F, Cl, Br, I, CN) using ab initio quantum chemistry. With a Gibbs free energy of H₂ attachment reaching up to 80 kJ∙mol⁻¹ (ΔG at 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H₂ adsorption sites. Differences of the zero-point energy of attachment average 5.0 kJ∙mol⁻¹ between D₂ and H₂ and 2.7 kJ mol⁻¹ between HD and H₂, resulting in hypothetical isotopologue selectivities as high as 2.0 and 1.5, respectively, even at 300 K. Interestingly, even though attachment energies vary substantially according to the chemical nature of X, isotopologue selectivities remain very similar. We find that the H–H activation is so strong that it likely results in the instantaneous heterolytic dissociation of H₂ in all cases (except, possibly, for X = H), highlighting the extremely electrophilic nature of B₁₂X₁₁⁻ despite its negative charge. Unfortunately, this high reactivity also makes B₁₂X₁₁⁻ unsuitable for practical application in the field of dihydrogen isotopologue separation. Thus, this example stresses the two-edged nature of strong H₂ affinity, yielding a higher isotopologue selectivity on the one hand but risking dissociation on the other, and helps define a window of adsorption energies into which a material for selective adsorption near room temperature should ideally fall.

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

Permalink: https://www.hzdr.de/publications/Publ-33092
Publ.-Id: 33092


Data publication: Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

This data contains results from magnetometry and magnetic force microscopy from the irradiated synthetic antiferromagnets.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

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Permalink: https://www.hzdr.de/publications/Publ-33091
Publ.-Id: 33091


Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

We study layered synthetic antiferromagnets (SAFs) with out-of-plane interface anisotropy, where the layer-wise antiferromagnetic (AF)
alignment is induced by interlayer exchange coupling (IEC). By applying low energy He+ focused ion beam irradiation to the SAF, a depth-dependent
reduction of the IEC and anisotropy can be achieved due to layer intermixing. As a consequence, after irradiation, a specific field
reversal sequence of the SAF is energetically preferred. When tuning the pristine SAF to exhibit an inverted field reversal, we are thus able to
create AF domains in the irradiated regions. When irradiated with a fluence gradient, these AF domains can be further deterministically
manipulated by an external magnetic field. Among other applications, this could be utilized for engineering a controllable and local magnetic
stray field landscape, for example, at AF domain walls, within the otherwise stray field free environment provided by the SAF.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

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Permalink: https://www.hzdr.de/publications/Publ-33090
Publ.-Id: 33090


DYN3D and CTF Coupling within a Multiscale and Multiphysics Software Development (Part I)

Davies, S.; Litskevich, D.; Rohde, U.; Detkina, A.; Merk, B.; Bryce, P.; Levers, A.; Ravindra, V.

Understanding and optimizing the relation between nuclear reactor components or physical phenomena allows us to improve the economics and safety of nuclear reactors, deliver new nuclear reactor designs, and educate nuclear staff. Such relation in the case of the reactor core is described by coupled reactor physics as heat transfer depends on energy production while energy production depends on heat transfer with almost none of the available codes providing full coupled reactor physics at the fuel pin level. A Multiscale and Multiphysics nuclear software development between NURESIM and CASL for LWRs has been proposed for the UK. Improved coupled reactor physics at the fuel pin level can be simulated through coupling nodal codes such as DYN3D as well as subchannel codes such as CTF. In this journal article, the first part of the DYN3D and CTF coupling within the Multiscale and Multiphysics software development is presented to evaluate all inner iterations within one outer iteration to provide partially verified improved coupled reactor physics at
the fuel pin level. Such verification has proven that the DYN3D and CTF coupling provides improved feedback distributions over the DYN3D coupling as crossflow and turbulent mixing are present in the former.

Keywords: Nuclear Reactor; Coupled reactor physics; Nodal code; Subchannel code; DYN3D; CTF; KAIST

Permalink: https://www.hzdr.de/publications/Publ-33089
Publ.-Id: 33089


Intermittent chaotic flows in the weakly magnetised spherical Couette system

Garcia Gonzalez, F.; Seilmayer, M.; Giesecke, A.; Stefani, F.

Experiments on the magnetised spherical Couette system are presently being carried out at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). A liquid metal (GaInSn) is confined within two differentially rotating spheres and exposed to a magnetic field parallel to the axis of rotation. Intermittent chaotic flows, corresponding to the radial jet instability, are described. The relation of these chaotic flows with unstable regular (periodic and quasiperiodic) solutions obtained at the same range of parameters is investigated.

Keywords: Spherical Couette Flow

Permalink: https://www.hzdr.de/publications/Publ-33088
Publ.-Id: 33088


Modulated rotating waves and triadic resonances in spherical fluid systems: The case of magnetized spherical Couette flow

Garcia Gonzalez, F.; Giesecke, A.; Stefani, F.

The existence of triadic resonances in the magnetized spherical Couette system is related to the development of modulated rotating waves, which are quasiperiodic flows understood in terms of bifurcation theory in systems with symmetry. In contrast to previous studies in spherical geometry, the resonant modes are not inertial waves but related to the radial jet instability, which is strongly equatorially antisymmetric. We propose a general framework in which triadic resonances are generated through successive Hopf bifurcations from the base state. The study relies on an accurate frequency analysis of different modes of the flow, for solutions belonging to two different bifurcation scenarios. The azimuthal and latitudinal nonlinear coupling among the resonant modes is analyzed and interpreted using spherical harmonics, and the results are compared with previous studies in spherical geometry.

Keywords: Spherical Couette Flow

Permalink: https://www.hzdr.de/publications/Publ-33087
Publ.-Id: 33087


Size-Tunable Gold Aerogels: A Durable and Misfocus-Tolerant 3D Substrate for Multiplex SERS Detection

Zhou, L.; Peng, Y.; Zhang, N.; Du, R.; Hübner, R.; Wen, X.; Li, D.; Hu, Y.; Eychmüller, A.

The research on surface-enhanced Raman scattering (SERS) continuously draws wide attention because of its high detection sensitivity. However, the commonly investigated 2D SERS substrates cannot fully utilize the 3D active focal volume and require a tight focus on the correct plane, retarding signal enhancement and flexible use. Here, self-supported gold aerogels of centimeter-dimension with tunable ligament sizes are designed as 3D SERS substrates, featuring hot spots throughout the entire network. Unveiling a universal ligament-size-effect, the optimized gold aerogel showcases much larger enhancement factors compared to a 8 nm Au film toward dyes, pesticides, and carcinogens (up to 109). Aside from an excellent reusability and an exceptional stability (> 1 month), an outstanding misfocus tolerance (>300 μm along the z-axis) is also demonstrated for such aerogel-based SERS substrates for multiplex detection. This work may expand the application scope of metal aerogels and lay the foundation for designing next-generation 3D SERS substrates.

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Permalink: https://www.hzdr.de/publications/Publ-33086
Publ.-Id: 33086


The Multifaceted Role of Aldehyde Dehydrogenases in Prostate Cancer Stem Cells

Püschel, J.; Dubrovska, A.; Gorodetska, I.

: Cancer stem cells (CSCs) are the only tumor cells possessing self-renewal and differentiation properties, making them an engine of tumor progression and a source of tumor regrowth after treatment. Conventional therapies eliminate most non-CSCs, while CSCs often remain radiation- and drug-resistant, leading to tumor relapse and metastasis. Thus, targeting CSCs might be a powerful tool to overcome tumor resistance and increase the efficiency of current cancer treatment strategies. The identification and isolation of the CSC population based on its high aldehyde de-hydrogenase activity (ALDH) is widely accepted for PCa and many other solid tumors. In PCa, several ALDH genes contribute to the ALDH activity, which can be measured in the enzymatic assay by converting BODIPY aminoacetaldehyde (BAAA) into the fluorescent product BOD-IPY-aminoacetate (BAA). Although each ALDH isoform plays an individual role in PCa biology, a mutual functional interplay between them also contributes to PCa progression. Thus, ALDH proteins are markers and functional regulators of CSC properties representing an attractive target for cancer treatment. In this review, we discuss the current state of research regarding the role of individual ALDH isoforms in PCa development and progression, their possible therapeutic targeting, and provide an outlook for the future advances in this field.

Keywords: Prostate cancer; cancer stem cells; aldehyde dehydrogenase; cancer stem cell - targeted therapy; cancer stem cell vaccines

Permalink: https://www.hzdr.de/publications/Publ-33085
Publ.-Id: 33085


Beyond the double-strand breaks: the role of DNA repair proteins in cancer stem cell regulation

Nathansen, J.; Meyer, F.; Müller, L.; Schmitz, M.; Borgmann, K.; Dubrovska, A.

Cancer stem cells (CSCs) are pluripotent and highly tumorigenic cells that can re-populate a tumor and cause relapses even after initially successful therapy. Like tissue stem cells, CSCs possess enhanced DNA repair mechanisms. An active DNA damage response alleviates the increased oxidative and replicative stress and leads to therapy resistance. On the other hand, mutations in DNA repair genes cause genomic instability, thereby driving tumor evolution and developing highly aggressive CSC phenotypes. However, the role of DNA repair proteins in CSCs extends beyond the level of DNA damage. In recent years, more and more studies reported the unexpected role of DNA repair proteins in the regulation of transcription, CSC signaling pathways, intracellular levels of reactive oxygen species (ROS), and epithelial-mesenchymal transition (EMT). Moreover, DNA damage signaling plays an essential role in the immune response towards tumor cells. Due to its high importance for the CSC phenotype and treatment resistance, the DNA damage response is a promising target for individualized therapies. Furthermore, understanding the dependence of CSC on DNA repair pathways can be therapeutically exploited to induce synthetic lethality and sensitize CSCs to anti-cancer therapies. This review discusses the different roles of DNA repair proteins in CSC maintenance and their potential as therapeutic targets.

Keywords: Cancer stem cells; DNA repair; Replicative stress; Oxidative stress; Genomic instability; Immune response; Reprogramming; Cancer therapy

Permalink: https://www.hzdr.de/publications/Publ-33084
Publ.-Id: 33084


The Al Doping Effect on Epitaxial (In,Mn)As Dilute Magnetic Semiconductors Prepared by Ion Implantation and Pulsed Laser Melting

Yuan, Y.; Xie, Y.; Yuan, N.; Wang, M.; Heller, R.; Kentsch, U.; Zhai, T.; Wang, X.

One of the most attractive characteristics of diluted ferromagnetic semiconductors is the possibility to modulate their electronic and ferromagnetic properties, coupled by itinerant holes through various means. A prominent example is the modification of Curie temperature and magnetic anisotropy by ion implantation and pulsed laser melting in III–V diluted magnetic semiconductors. In this study, to the best of our knowledge, we performed, for the first time, the co-doping of (In,Mn)As diluted magnetic semiconductors by Al by co-implantation subsequently combined with a pulsed laser annealing technique. Additionally, the structural and magnetic properties were systematically investigated by gradually raising the Al implantation fluence. Unexpectedly, under a well-preserved epitaxial structure, all samples presented weaken Curie temperature, magnetization, as well as uniaxial magnetic anisotropies when more aluminum was involved. Such a phenomenon is probably due to enhanced carrier localization introduced by Al or the suppression of substitutional Mn atoms.

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Permalink: https://www.hzdr.de/publications/Publ-33083
Publ.-Id: 33083


Phase evolution of Te-hyperdoped Si upon furnace annealing

Shaikh, M. S.; Wang, M.; Hübner, R.; Liedke, M. O.; Butterling, M.; Solonenko, D.; Madeira, T. I.; Li, Z.; Xie, Y.; Hirschmann, E.; Wagner, A.; Zahn, D. R. T.; Helm, M.; Zhou, S.

Si hyperdoped with chalcogens via ion implantation and pulsed laser melting is known to exhibit strong room-temperature sub-bandgap photoresponse. As a thermodynamically metastable system, an impairment of the optoelectronic properties in hyperdoped Si materials occurs upon subsequent high-temperature thermal treatment (>500 °C). The substitutional Te atoms that cause the sub-bandgap absorption are removed from the Si matrix to form Te-related complexes, which are electrically and optically inactive. In this work, we explore the formation of defects in Te-hyperdoped Si layers which leads to the electrical deactivation upon furnace annealing through the analysis of optical and microstructural properties as well as positron annihilation lifetime spectroscopy. Particularly, Te-rich clusters are observed in samples thermally annealed at temperatures reaching 950 °C and above. Combined with polarized Raman analysis and transmission electron microscopy, the observed crystalline clusters are suggested to be Si2Te3.

Keywords: Defect analysis; Furnace annealing; Ion-implantation; Positron annihilation spectroscopy; Raman spectroscopy; Silicon telluride; Te-hyperdoped Si; Transmission electron microscopy

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Permalink: https://www.hzdr.de/publications/Publ-33082
Publ.-Id: 33082


Strain-induced switching between noncollinear and collinear spin configuration in magnetic Mn5Ge3 films

Xie, Y.; Yuan, Y.; Birowska, M.; Zhang, C.; Cao, L.; Wang, M.; Grenzer, J.; Kriegner, D.; Doležal, P.; Zeng, Y.-J.; Zhang, X.; Helm, M.; Zhou, S.; Prucnal, S.

We report the temperature-dependent magnetic and structural properties of epitaxial Mn5Ge3 thin films grown
on Ge substrates. Utilizing density-functional theory (DFT) calculations and various experimental methods, we
reveal mechanisms governing the switching between collinear and noncollinear spin configuration in Mn5Ge3.
The Mn atoms in Mn5Ge3 occupy two distinct Wyckoff positions with fourfold (Mn1) and sixfold (Mn2)
multiplicity. The DFT calculations reveal that below a critical distance of approximately 3.002 Å the coupling
between Mn2 atoms is antiferromagnetic (AFM) while ferromagnetic (FM) above that critical distance. The FM
coupling between Mn1 atoms is weakly affected by the strain. The observed noncollinear spin configuration is
due to the coexistence of AFM and FM coupling at low temperatures. The findings give insight in developing
strain-controlled spintronic devices.

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Permalink: https://www.hzdr.de/publications/Publ-33081
Publ.-Id: 33081


Interfacial Synthesis of Layer-Oriented 2D Conjugated Metal-Organic Framework Films toward Directional Charge Transport

Wang, Z.; Walter, L. S.; Wang, M.; Petkov, P. S.; Liang, B.; Qi, H.; Ngan Nguyen, N.; Hambsch, M.; Zhong, H.; Wang, M.; Park, S.; Renn, L.; Watanabe, K.; Taniguchi, T.; Mannsfeld, S. C. B.; Heine, T.; Kaiser, U.; Zhou, S.; Weitz, T. R.; Feng, X.; Dong, R.

The development of layer-oriented two-dimensional conjugated metal-organic frameworks (2D c-MOFs) enables access to direct charge transport, dial-in lateral/vertical electronic devices, and the unveiling of transport mechanisms but remains a significant synthetic challenge. Here we report the novel synthesis of metal-phthalocyanine-based p-type semiconducting 2D c-MOF films (Cu2[PcM-O8], M = Cu or Fe) with an unprecedented edge-on layer orientation at the air/water interface. The edge-on structure formation is guided by the preorganization of metal-phthalocyanine ligands, whose basal plane is perpendicular to the water surface due to their π-πinteraction and hydrophobicity. Benefiting from the unique layer orientation, we are able to investigate the lateral and vertical conductivities by DC methods and thus demonstrate an anisotropic charge transport in the resulting Cu2[PcCu-O8] film. The directional conductivity studies combined with theoretical calculation identify that the intrinsic conductivity is dominated by charge transfer along the interlayer pathway. Moreover, a macroscopic (cm2 size) Hall-effect measurement reveals a Hall mobility of ∼4.4 cm2 V-1 s-1 for the obtained Cu2[PcCu-O8] film. The orientation control in semiconducting 2D c-MOFs will enable the development of various optoelectronic applications and the exploration of unique transport properties.

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Permalink: https://www.hzdr.de/publications/Publ-33080
Publ.-Id: 33080


Physicochemical constraints on indium-, tin-, germanium-, gallium-, gold-, and tellurium-bearing mineralizations in the Pefka and St Philippos polymetallic vein- and breccia-type deposits, Greece

Voudouris, P.; Repstock, A.; Spry, P. G.; Frenzel, M.; Mavrogonatos, C.; Keith, M.; Tarantola, A.; Melfos, V.; Tombros, S.; Zhai, D.; Cook, N. J.; Ciobanu, C. L.; Schaarschmidt, A.; Rieck, B.; Kolitsch, U.; Falkenberg, J. J.

The Pefka Cu-Au-Te-In-Se and nearby St Philippos Pb-Zn-Bi-Sn-Ge-Ga-In vein- and breccia-type deposits in western Thrace, Greece, display strong similarities, but also differences in terms of mineralization style, ore mineralogy, and chemistry, and host rock compositions. The Pefka mineralization consists of two crosscutting vein systems with high sulfidation (HS)- and intermediate-sulfidation (IS) assemblages hosted by andesitic lavas and is unusually enriched in In (up to 700 ppm), Te (>1000 ppm), Se (>100 ppm), and Cu (>1 wt%). The main In-carriers are roquesite (CuInS2) and In-bearing “tennantite-(Cu)” and Cu-rich “tennantite-(In)” which contains up to 6.5 wt% In, substituting into the C site. Roquesite is associated with enargite and arsenosulvanite/colusite, as part of the HS assemblage at Pefka. Selenium-bearing galena and a large suite of tellurides including calaverite, sylvanite, petzite, hessite, kostovite, empressite, tellurantimony, and coloradoite, in addition to native tellurium, account for the marked tellurium and selenium enrichment in the ores from Pefka. Tellurides and native gold at Pefka accompany the precipitation of Te-bearing minerals of the tetrahedrite group, such as “stibiogoldfieldite” and “arsenogoldfieldite”, and Cu-excess varieties of tetrahedrite and tennantite. However, the bulk of telluride deposition is associated with normal, fully substituted tetrahedrite-tennantite varieties.

The St Philippos deposit is associated with a brecciated fault zone hosted by Eocene sandstones and Oligocene quartz-feldspar porphyry dikes. It is enriched in a large suite of incompatible elements, including Bi (>2000 ppm), Sn (>100 ppm), U (up to 200 ppm), Pb (>1 wt%), Zn (>1 wt%), Mo (up to 62 ppm), Ge (>100 ppm), Ga (up to 466 ppm) and In (up to 222 ppm), contrasting with the element suite defining the nearby Pefka deposit. The main carrier of In, Ga, and Ge is sphalerite (and wurtzite) with In-rich zones in sphalerite containing up to 6.1. wt% In. Germanium and Ga in sphalerite reach concentrations of up to 0.27 and 0.32 wt%, respectively. Sphalerite from the St Philippos deposit is extremely Fe-poor (<0.04 wt%), and is associated with an unusual suite of Sn-bearing sulfosalts (kësterite-stannite, Mn-bearing kësterite, unnamed Cu2MnSnS4), and enargite, marking an early HS event. Kësterite also hosts indium (up to 0.6 wt% In). Mn-bearing varieties of tennantite host inclusions of minor tellurides (e.g., hessite, altaite, and tsumoite) and formed later in the paragenetic sequence under transitional HS-IS and IS conditions.

Both deposits are characterized by early high-temperature (>300 °C) and HS fluid conditions, followed by IS assemblages as temperatures waned. Rhyolitic oxidized magmas are considered to be the sources of metals in the St Philippos deposit; however, their anomalous W, Sn, U, and Bi contents suggest a contamination by crustal rocks. The Cu-Au-Te signature of the Pefka deposit is compatible with a genetic relationship to less fractionated andesitic magmas, although a possible contribution of In from rhyolitic magmas could explain the high In contents of the ore. However, other factors, as for example different metal-deposition mechanisms resulting in metal zonation around causative porphyry centers at depth, may also account for the observed metal endowment in these two deposits. The Sn-Te-In-(Ge-Ga) element association at Pefka and St Philippos is unusual in that it has been previously reported from only a few other places in the world (e.g., Capillitas deposit, Argentina, and the Kawazu deposit, Japan). We conclude based on this exotic mineralization-style that the northeastern part of Greece represents an area of great potential for the exploitation of critical metals and metalloids.

Keywords: Critical metals; Greece; High-intermediate sulfidation; Magmatic-hydrothermal

Permalink: https://www.hzdr.de/publications/Publ-33079
Publ.-Id: 33079


Charge distribution in U1-xCexO2+y nanoparticles

Prieur, D.; Vigier, J.-F.; Popa, K.; Walter, O.; Dieste, O.; Varga, Z.; Beck, A.; Vitova, T.; Scheinost, A.; Martin, P.

In view of a safe management of the nuclear wastes, a sound knowledge of the atomic-scale properties of U1-xMxO2+y nanoparticles is essential. In particular, their cation valences and oxygen stoichiometries are of great interest as these properties drive their diffusion and migration behaviour into the environment. Here, we present an in-depth study of U1-xCexO2+y, over the full compositional domain, by combining XRD and HERFD-XANES. We show on one hand the co-existence of UIV, UV and UVI and on the other hand that the fluorite structure is maintained despite this charge distribution.

Keywords: Uranium; UO2; CeO2; HERD-XANES

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Permalink: https://www.hzdr.de/publications/Publ-33078
Publ.-Id: 33078


Probing charged lepton flavor violation with the Mu2e experiment

Müller, S.; Ferrari, A.; Knodel, O.; Rachamin, R.

Presentation a 2021 DPG meeting (section "Matter & Cosmos"), September1, 2021

Keywords: MU2E; Charged Lepton Flavor Violation; DPG

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  • Lecture (Conference) (Online presentation)
    DPG Meeting SMUK, 30.08.-03.09.2021, virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33077
Publ.-Id: 33077


Checkliste zur Unterstützung der Helmholtz-Zentren bei der Implementierung von Richtlinien für nachhaltige Forschungssoftware

Messerschmidt, R.; Pampel, H.; Bach, F.; Zu Castell, W.; Denker, M.; Finke, A.; Fritzsch, B.; Hammitzsch, M.; Konrad, U.; Leifels, J.; Möhl, C.; Nolden, M.; Scheinert, M.; Schlauch, T.; Schnicke, T.; Steglich, D.

Mit der voranschreitenden Digitalisierung von Forschung und Lehre steigt die Zahl an Software-Lösungen, die an wissenschaftlichen Einrichtungen entstehen und zur Erkenntnisgewinnung genutzt werden. Die – unter dem Stichwort Open Science geforderte – Zugänglichkeit und Nachnutzung von wissenschaftlichen Ergebnissen kann in vielen Fachgebieten nur sichergestellt werden, wenn neben Forschungsdaten auch Programmcode offen zugänglich gemacht wird. Die vorliegende Handreichung richtet sich an Entscheider*innen in den Helmholtz-Zentren, die sich mit der Implementierung von Richtlinien für nachhaltige Forschungssoftware befassen. Sie ergänzt eine Muster-Richtlinie, die den Zentren bereits eine richtungsweisende und nachnutzbare Vorlage zur Erstellung von Regelungen für einen nachhaltigen Umgang mit Forschungssoftware gibt.

Keywords: Research Software; Open Access; Checkliste; Regelung; Software Policy

Permalink: https://www.hzdr.de/publications/Publ-33076
Publ.-Id: 33076


Models for translational proton radiobiology-from bench to bedside and back

Suckert, T.; Nexhipi, S.; Dietrich, A.; Koch, R.; Kunz-Schughart, L. A.; Bahn, E.; Beyreuther, E.

The number of proton therapy centers worldwide are increasing steadily, with more than two million cancer patients treated so far. Despite this development, pending questions on proton radiobiology still call for basic and translational preclinical research. Open issues are the on-going discussion on an energy-dependent varying proton RBE (relative biological effectiveness), a better characterization of normal tissue side effects and combination treatments with drugs originally de- veloped for photon therapy. At the same time, novel possibilities arise, such as radioimmunotherapy, and new proton therapy schemata, such as FLASH irradiation and proton mini-beams. The study of those aspects demands for radiobiological models at different stages along the translational chain, allowing the investigation of mechanisms from the molecular level to whole organisms. Focusing on the challenges and specifics of proton research, this review summarizes the different available models, ranging from in vitro systems to animal studies of increasing complexity as well as complementing in silico approaches.

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Permalink: https://www.hzdr.de/publications/Publ-33075
Publ.-Id: 33075


Not just a background: pH buffers do interact with lanthanide ions – a Europium(III) case study

Mandal, P.; Kretzschmar, J.; Drobot, B.

The interaction between Eu(III) ion and different pH buffers, popular in biology and biochemistry viz. HEPES, PIPES, MES, MOPS, and TRIS have been studied by solution nuclear magnetic resonance spectroscopy (NMR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) techniques. The Good’s buffers reveal non-negligible interaction with Eu(III) as determined from their complex stability constants, where the sites of interaction are the morpholine and piperazine nitrogen atoms, respectively. In contrast, TRIS buffer shows practically no affinity towards Eu(III). Therefore, when investigating lanthanides, TRIS buffer should be preferred over Good’s buffers.

Keywords: Europium; Buffer; TRLFS; NMR; Stability Constant

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Permalink: https://www.hzdr.de/publications/Publ-33074
Publ.-Id: 33074


ARIEL - Accelerator and Research reactor Infrastructures for Education and Learning

Beyer, R.; Junghans, A.

Status and news from ARIEL

Keywords: ARIEL; nELBE

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  • Invited lecture (Conferences) (Online presentation)
    ENEN Special Event 2021 - Outlook of nuclear ETKM activities, 03.03.2021, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-33073
Publ.-Id: 33073


The nELBE neutron time-of-flight facility

Beyer, R.; Junghans, A.; Kögler, T.; Schwengner, R.; Urlaß, S.; Wagner, A.

The neutron time-of-flight facility nELBE at Helmholtz-Zentrum Dresden-Rossendorf features the first photo-neutron source at a superconducting electron accelerator. The electrons are focused onto a liquid lead target to produce bremsstrahlung which in turn produces neutrons via photo-nuclear reactions. The emitted neutron spectrum ranges from about 10 keV up to 15 MeV with a source strength of above 10¹¹ neutrons per second. The very precise time structure of the accelerator with a bunch width of a few ps enables time-of-flight measurements at very short flight path and experiments to investigate the time response of novel detector concepts.
The high repetition rate of 100 to 400 kHz in combination with the low instantaneous flux and the absence of any moderating materials provide favorable background conditions.
The very flexible beam properties at nELBE enable a broad range of nuclear physics experiments. Examples for the versatility of nELBE will be presented: From transmission measurements and inelastic neutron scattering and fission experiments to determine nuclear reaction cross sections with relevance for fundamental nuclear physics, reactor safety calculations, nuclear transmutation or particle therapy to experiments to investigate the response of novel particle detectors e.g. for dark matter search experiments, nuclear instrumentation or the range verification in cancer treatment.

Related publications

  • Poster (Online presentation)
    The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications ANIMMA 2021, 21.-25.06.2021, Prague, Czech Republic
  • Lecture (Conference) (Online presentation)
    The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications ANIMMA 2021, 21.-25.06.2021, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-33072
Publ.-Id: 33072


Total neutron cross section for ¹⁸¹Ta

Matic, A.; Beyer, R.; Birgersson, E.; Ferrari, A.; Grosse, E.; Junghans, A.; Schilling, K.-D.; Schwengner, R.; Wagner, A.; Hannaske, R.; Kögler, T.; Massarczyk, R.; Mosconi, M.; Nolte, R.

The neutron time of flight facility nELBE, produces fast neutrons in the energy range from 0.1 MeV to 10 MeV by impinging a pulsed relativistic electron beam on a liquid lead circuit. The short beam pulses (∼10 ps) and a small radiator volume give an energy resolution better than 1% at 1 MeV using a short flight path of about 6 m, for neutron TOF measurements. The present neutron source provides 2 ⋅ 10⁴  n/cm²s at the target position using an electron charge of 77 pC and 100 kHz pulse repetition rate. This neutron intensity enables to measure neutron total cross section with a 2%–5% statistical uncertainty within a few days. In February 2008, neutron radiator, plastic detector and data acquisition system were tested by measurements of the neutron total cross section for ¹⁸¹Ta and ²⁷Al. Measurement of ¹⁸¹Ta was chosen because lack of high quality data in an energy region below 700 keV. The total neutron cross – section for ²⁷Al was measured as a control target, since there exists data for ²⁷Al with high resolution and low statistical error.

Keywords: nELBE; neutron transmission

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Permalink: https://www.hzdr.de/publications/Publ-33071
Publ.-Id: 33071


Single Particle Detection System for Strong-Field QED Experiments

Salgado, F. C.; Cavanagh, N.; Tamburini, M.; Storey, D. W.; Beyer, R.; Bucksbaum, P. H.; Chen, Z.; Piazza, A. D.; Gerstmayr, E.; Harsh; Junghans, A.; Keitel, C. H.; Kuschel, S.; Nielsen, C. F.; Reis, D. A.; Roedel, C.; Sarri, G.; Seidel, A.; Schneider, C.; Uggerhøj, U. I.; Wulff, J.; Yakimenko, V.; Zepter, C.; Meuren, S.; Zepf, M.; Isele, E.

Measuring signatures of strong-field quantum electrodynamics (SF-QED) processes in an intense laser field is an experimental challenge: it requires detectors to be highly sensitive to single electrons and positrons in the presence of the typically very strong x-ray and γ-photon background levels. In this paper, we describe a particle detector capable of diagnosing single leptons from SF-QED interactions and discuss the background level simulations for the upcoming Experiment-320 at FACET-II (SLAC National Accelerator Laboratory). The single particle detection system described here combines pixelated scintillation LYSO screens and a Cherenkov calorimeter. We detail the performance of the system using simulations and a calibration of the Cherenkov
detector at the ELBE accelerator. Single 3 GeV leptons are expected to produce approximately 537 detectable photons in a single calorimeter channel. This signal is compared to Monte-Carlo simulations of the experiment. A signal-to-noise ratio of 15 in a single Cherenkov calorimeter detector is expected and a spectral resolution of 2 % is achieved using the pixelated LYSO screens.

Keywords: strong-field QED; pair-creation; single-particle detection; Cherenkov calorimeter; Breit-Wheeler process; ELBE

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Permalink: https://www.hzdr.de/publications/Publ-33070
Publ.-Id: 33070


Synthesis, characterisation, and crystal structure of a novel U(V) brannerite UTi1.23Al0.77O6 and the UTi2-xAlxO6 system

Dixon Wilkins, M. C.; Mottram, L. M.; Maddrell, E. R.; Stennett, M. C.; Corkhill, C. L.; Kvashnina, K. O.; Hyatt, N. C.

The synthesis, characterisation and crystal structure of a novel U5+ (dominant) brannerite of composition U1.09(6)Ti1.29(3)Al0.71(3)O6 is reported, as determined from Rietveld analysis of high resolution powder neutron diffraction data. Examination of the UTi2-xAlxO6 system demonstrated the formation of brannerite structured compounds with varying Al3+ and U5+ content, from U0.93(6)Ti1.64(3)Al0.36(3)O6 to U0.89(6)Ti1.00(3)Al1.00(3)O6. Substitution of Al3+for Ti4+, with U5+ charge compensation, resulted in near-linear changes in the b and c unit cell parameters and the overall unit cell volume, as expected from ionic radii considerations. The presence of U5+ as the dominant oxidation state in near single phase brannerite compositions was evidenced by complementary laboratory U L3 edge and high energy resolution fluorescence detected (HERFD) U M4 edge X-ray Absorption Near Edge Spectroscopy. No brannerite phase was found for compositions with Al3+ / Ti4+ > 1, which would require U6+ contribution for charge compensation. These data expand the crystal chemistry of uranium brannerites to the stabilisation of dominant U5+ brannerites by substitution of trivalent cations, such as Al3+, on the Ti4+ site

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Permalink: https://www.hzdr.de/publications/Publ-33069
Publ.-Id: 33069


High energy resolution X-ray spectroscopy at actinide M4,5 and ligand K edges: what we know, what we want to know, what we can know

Kvashnina, K. O.; Butorin, S. M.

In recent years, scientists have progressively recognized the role of electronic structure in the characterization of chemical properties for actinide containing materials. High energy resolution X-ray spectroscopy at the actinide M4,5 edges emerged as a promising direction because this method can probe actinide properties at the atomic level through the possibility of reducing the experimental spectral width below the natural core-hole life time broadening. Parallel to the technical developments of the X-ray method and experimental discoveries, theoretical models, describing the observed electronic structure phenomena, have also advanced. In this feature article, we describe the latest progress in the field of high energy resolution X-ray spectroscopy at the actinide M4,5 and ligand K edges and we show that the methods are able to a) provide fingerprint information on the actinide oxidation state and ground state character b) probe 5f occupancy, non-stoichiometry, defects, ligand/metal ratio c) investigate the local symmetry and effects of the crystal field. We discuss the chemical aspects of the electronic structure in terms familiar to chemists and materials scientists and conclude with a brief description of new opportunities and approaches to improve the experimental methodology and theoretical analysis for the f-electron systems

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Permalink: https://www.hzdr.de/publications/Publ-33068
Publ.-Id: 33068


The Contribution of Manure Utilisation in Biogas Plants in Terms of Climate Change

Eggemann, L.; Rau, F.; Stolten, D.

The main source of global CO2 is heat and electricity production, which requires an increase in renewables that cover fluctuating sources. Biogas plants are one possibility, which are already commonly used in the European energy system. This study focuses on the utilisation of raw manure to reduce direct emissions of methane within an advanced and expensive, and a simplified and less expensive plant. Therefore, the environmental impact in terms of CO2 eq emissions of a biogas plant with either subsequent combustion in an internal combustion engine or the direct use of the biogas in a simplified burner are investigated. The analysis shows that the more advanced system yields 493 t CO2 eq, while the simplified one causes 42 t CO2 eq per year. Nevertheless, increasing average annual temperatures generate higher manure credits and thus reduce emissions of both plant options to 726 and -178 t CO2 eq per year, respectively, making the direct biogas usage become more interesting. Thus, both systems hold the potential for savings in terms of improved manure management against the background of climate change.

Keywords: renewable/green energy resources; advanced energy technologies; energy conservation in buildings; energy systems for power generation; environment and climate change

  • Lecture (Conference) (Online presentation)
    International Conference on Applied Energy 2021, 29.11.-02.12.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33067
Publ.-Id: 33067


18F-Fluorodeoxyglucose Positron Emission Tomography of Head and Neck Cancer: Location and HPV Specific Parameters for Potential Treatment Individualization

Zschaeck, S.; Weingärtner, J.; Lombardo, E.; Marschner, S.; Hajiyianni, M.; Beck, M.; Zips, D.; Li, Y.; Lin, Q.; Amthauer, H.; Troost, E. G. C.; van den Hoff, J.; Budach, V.; Kotzerke, J.; Ferentinos, K.; Karagiannis, E.; Kaul, D.; Gregoire, V.; Holzgreve, A.; Albert, N. L.; Nikulin, P.; Bachmann, M.; Kopka, K.; Krause, M.; Baumann, M.; Kazmierska, J.; Cegla, P.; Cholewinski, W.; Strouthos, I.; Zöphel, K.; Majchrzak, E.; Landry, G.; Belka, C.; Stromberger, C.; Hofheinz, F.

Purpose
18F-fluorodeoxyglucose positron emission tomography (FDG-PET) is utilized for staging and treatment planning of head and neck squamous cell carcinomas (HNSCC). Some older publications on the prognostic relevance showed inconclusive results, most probably due to small study sizes. This study evaluates the prognostic and potentially predictive value of FDG-PET in a large multi-center analysis.
Methods
Original analysis of individual FDG-PET and patient data from 16 international centers (8 institutional datasets, 8 public repositories) with 1104 patients. All patients received curative intent radiotherapy/chemoradiation (CRT) and pre-treatment FDG-PET imaging. Primary tumors were semi-automatically delineated for calculation of SUVmax, SUVmean, metabolic tumor volume (MTV) and total lesion glycolysis (TLG). Cox regression analyses were performed for event-free survival (EFS), overall survival (OS), loco-regional control (LRC) and freedom from distant metastases (FFDM).
Results
FDG-PET parameters were associated with patient outcome in the whole cohort regarding clinical endpoints (EFS, OS, LRC, FFDM), in uni- and multivariate Cox regression analyses. Several previously published cut-off values were successfully validated. Subgroup analyses identified tumor- and human papillomavirus (HPV) specific parameters. In HPV positive oropharynx cancer (OPC) SUVmax was well suited to identify patients with excellent LRC for organ preservation. Patients with SUVmax of 14 or less were unlikely to develop loco-regional recurrence after definitive CRT. In contrast FDG PET parameters deliver only limited prognostic information in laryngeal cancer.
Conclusion
FDG-PET parameters bear considerable prognostic value in HNSCC and potential predictive value in subgroups of patients, especially regarding treatment de-intensification and organ-preservation. The potential predictive value needs further validation in appropriate control groups. Further research on advanced imaging approaches including radiomics or artificial intelligence methods should implement the identified cut-off values as benchmark routine imaging parameters.

Keywords: head and neck squamous cell carcinoma (HNSCC); fluorodeoxyglucose positron emission tomography (FDG PET); radiotherapy; metabolic tumor volume (MTV); standardized uptake value (SUV)

Permalink: https://www.hzdr.de/publications/Publ-33065
Publ.-Id: 33065


Timing of native metal-arsenide (Ag-Bi-Co-Ni-As±U) veins in continental rift zones – In situ U-Pb geochronology of carbonates from the Erzgebirge/Krušné Hory province

Guilcher, M.; Albert, R.; Gerdes, A.; Gutzmer, J.; Burisch, M.

Hydrothermal native metal-arsenide (five-element or Ag-Bi-Co-Ni-As±U) veins are a globally occurring mineralization style, which is particularly prevalent across Central Europe. Due to the limited amount of geochronological data available, the timing and the detailed geodynamic setting in which this mineralization style formed remains insufficiently understood. To fill this gap in knowledge, we applied innovative LA-ICP-MS U-Pb geochronology on carbonates from six districts in the Erzgebirge/Krušné Hory province of Germany and Czech Republic in order to constrain the timing of ore formation in the context of the geodynamic framework of Central Europe. In situ U-Pb ages of twelve samples, including dolomite-ankerite, calcite, and siderite coeval with Ni-Co-Fe-arsenides, range from ~129 to ~86 Ma. The ages of native metal-arsenide and fluorite-barite-Pb-Zn veins from the same occurrence (Annaberg-Buchholz district) are found to be consistent with each other, providing new and direct geochronological evidence that these two styles of mineralization are genetically related and may form coevally within one hydrothermal system. Complemented with available geochronological data from other occurrences, the formation of native metal-arsenide assemblage in Central Europe can be related to continental rifting affiliated with the Mesozoic opening of the Atlantic and Alpine Tethys Oceans (~200–100 Ma). The youngest age of ~86 Ma coincide with basin inversion associated with the onset of Alpine compressional tectonics, which most likely terminates the conditions favorable for the formation of native metal-arsenide mineralization in Europe. The onset of native metal-arsenide formation in proximal positions to the main rift axis starts at ~230–200 Ma (Penninic Alps, Anti-Atlas). In contrast, it occurs systematically later with increasing distance to the rift axis – namely at ~200–130 Ma in intermediate (Schwarzwald, Odenwald, Spessart) and ~140–86 Ma in distal (Erzgebirge, Harz) positions to the main rift axis.

Keywords: Arsenide; Carbonate geochronology; Cobalt; Erzgebirge; Five-element mineralization; U-Pb LA-ICP

Permalink: https://www.hzdr.de/publications/Publ-33064
Publ.-Id: 33064


DFT Surrogate modeling with the Materials Learning Algorithms (MALA) – Theoretical Background

Fiedler, L.

MALA (Materials Learning Algorithms) is a data-driven framework to generate surrogate models of density functional theory calculations based on machine learning. Its purpose is to enable multiscale modeling by bypassing computationally expensive steps in state-of-the-art density functional simulations. In this talk, an overview over the theoretical background that enables estimation of physical quantities based on the local density of states (LDOS) is given.

Keywords: Density Functional Theory; Machine Learning

  • Open Access Logo Lecture (Conference) (Online presentation)
    (TD)DFT Student Seminar Series (#5), 03.08.2021, Newark, USA

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Permalink: https://www.hzdr.de/publications/Publ-33063
Publ.-Id: 33063


A spectroscopic hike in the U-O phase diagram

Prieur, D.; Desagulier, M.-M.; Neuville, D.; Guéneau, C.; Epifano, E.; Dardenne, K.; Rothe, J.; Martin, P.

The U-O phase diagram is of paramount interest for nuclear related applications and has therefore been extensively studied. Experimental data have been gathered to feed the thermodynamic calculations and achieve an optimization of the U-O system modelling. Although considered as well established, a critical assessment of this large body of experimental data is necessary, especially in light of the recent development of new techniques applicable to actinide materials. Here we show how in situ XANES is suitable and relevant for phase diagram determination. New experimental data points have been collected using this method and discussed in regard to the available data. Comparing our experimental data with thermodynamic calculations, we observe that the current version of the U-O phase diagram misses some experimental data in specific domains. This lack of experimental data generates inaccuracy in the model, which can be overcome using in situ XANES. Indeed, as shown in the paper, this method is suitable to collect experimental data in non-ambient conditions and for multiphasic system.

Keywords: UO2; in situ XANES; Thermodynamics; CALPHAD method

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Permalink: https://www.hzdr.de/publications/Publ-33062
Publ.-Id: 33062


Data publication: Efficient laser-driven proton and Bremsstrahlung generation from cluster-assembled foam targets

Prencipe, I.; Metzkes-Ng, J.; Pazzaglia, A.; Bernert, C.; Dellasega, D.; Fedeli, L.; Formenti, A.; Garten, M.; Kluge, T.; Kraft, S.; Laso García, A.; Maffini, A.; Obst-Hübl, L.; Rehwald, M.; Sobiella, M.; Zeil, K.; Schramm, U.; Cowan, T.; Passoni, M.

Archiving of raw and results data and scripts as describef in the associated paper

Keywords: laser-driven ion acceleration; laser-driven Bremsstrahlung generation; TNSA; near-critical density plasma; nanostructured targets; foam targets

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Permalink: https://www.hzdr.de/publications/Publ-33061
Publ.-Id: 33061


Cell voltage model for Li-Bi liquid metal batteries

Weber, N.; Duczek, C.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Weier, T.; Sadoway, D. R.

Lithium-bismuth bimetallic cells are amongst the best explored liquid metal batteries. A simple and fast one-dimensional cell voltage model for such devices is presented. The equilibrium cell potential is obtained from a complex two-dimensional fit of data drawn from multiple studies of equilibrium cell potential and rendered congruent with the phase diagram. Likewise, several analytical and fit functions for the ohmic potential drop across the electrolyte are provided for different battery geometries. Mass transport overpotentials originating from the alloying of Li into Bi are modelled by solving a diffusion equation, either analytically or numerically, and accounting for the volume change of the positive electrode. The applicability and limitations of the model are finally illustrated in three distinct experimental settings.

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Permalink: https://www.hzdr.de/publications/Publ-33058
Publ.-Id: 33058


Scale-dependent anisotropy, energy transfer and intermittency in bubble-laden turbulent flows

Ma, T.; Ott, B.; Fröhlich, J.; Bragg, A.

Data from Direct Numerical Simulations of disperse bubbly flows in a vertical channel are used
to study the effect of the bubbles on the carrier-phase turbulence. We developed a new method,
based on an extension of the barycentric map approach, that allows to quantify and visualize the
anisotropy and componentiality of the flow at any scale. Using this we found that the bubbles
significantly enhance anisotropy in the flow at all scales compared with the unladen case, and
that for some bubble cases, very strong anisotropy persists down to the smallest scales of the
flow. The strongest anisotropy observed was for the cases involving small bubbles. Concerning
the energy transfer among the scales of the flow, our results indicate that for the bubble-laden
cases, the energy transfer is from large to small scales, just as for the unladen case. However,
there is evidence of an upscale transfer when considering the transfer of energy associated with
particular components of the velocity field. Although the direction of the energy transfer is the
same with and without the bubbles, the behaviour of the energy transfer is significantly modified
by the bubbles, suggesting that the bubbles play a strong role in altering the activity of the
nonlinear term in the flow. The skewness of the velocity increments also reveal a strong effect of
the bubbles on the flow, changing both its sign and magnitude compared with the single-phase
case. We also consider the normalized forms of the fourth-order structure functions, and the
results reveal that the introduction of bubbles into the flow strongly enhances intermittency in the
dissipation range, but suppresses it at larger scales. This strong enhancement of the dissipation
scale intermittency has significant implications for understanding how the bubbles might modify
the mixing properties of turbulent flows.

Keywords: turbulence; bubbly flows

Permalink: https://www.hzdr.de/publications/Publ-33057
Publ.-Id: 33057


CFD Study on the Physical Behavior of Flue Dust within an Industrial-Scale Copper Waste Heat Boiler

Schmidt, A.; Montenegro, V.; Reuter, M.; Charitos, A.; Stelter, M.; Richter, A.

The Flash Smelting Furnace (FSF) is one of the most common aggregates for primary smelting of copper concentrates. Its smooth operation depends on the availability and performance of the downstream Waste Heat Boiler (WHB). The WHB is especially sensitive to problems with its flue dust handling, such as formation of accretions, which can lead to downtime and equipment failures. Due to the limited accessibility and the harsh conditions of the WHB, experimental studies are challenging. Therefore, CFD simulations can be a promising option to increase the knowledge and evaluate several options. The present study investigates the physical behavior of flue dust within an industrial-scale WHB via a three-dimensional CFD model. Size-dependent particle sedimentation and the risk areas for flue dust accretions are predicted, finding good agreement with industrial experience and literature data. For making the evaluation of accretion risk zones possible, a new sticking function for flue dust is developed. The results are validated against dust samples. Finally, operational recommendations for minimizing flue dust accretions are derived.

Keywords: Flash Smelting Furnace; Waste Heat Boiler; Flue Dust; Dust Accretions; CFD

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Permalink: https://www.hzdr.de/publications/Publ-33056
Publ.-Id: 33056


Development of a three-dimensional CFD Model for the Estimation of Accretion Formation in an Industrial-Scale Copper Waste Heat Boiler

Schmidt, A.; Montenegro, V.; Reuter, M.; Stelter, M.; Richter, A.

While striving for a circular economy of metals, the Flash Smelting Furnace (FSF) is the most common and “green” aggregate for primary smelting of copper concentrates, because of already today low CO2-emissions compared to other smelting technologies. High dust carry-over often leads to problems with flue dust accretions in its subsequent cooling aggregate, the Waste Heat Boiler (WHB). Removing these accretions causes mechanical stress for the boiler tubes and can lead to extended downtime and maintenance. The WHB has a limited accessibility towards experimental studies because of its harsh process conditions. Hence, Computational Fluid Dynamics (CFD) models appear as convenient option for WHB studies and design, but are not used for the evaluation of flue dust accretions yet. For the inclusion of this feature into a three-dimensional CFD model of the entire WHB, a new sticking function is developed. It is based on the industrial experience that flue dust is only sticky above a certain softening temperature. Since the WHB has a varying dust input due to the flexible operation of the FSF, a parameter study is conducted for standard flue dust, pure copper oxide dust and pure iron oxide dust, finding minor sensitivity towards the flue dust density and no sensitivity towards the dust heat capacity. From these findings, recommendations for the minimization of flue dust accretion formation in the WHB are derived.

Keywords: Copper Production; Flash Smelting Furnace; Waste Heat Boiler; Flue Dust; Accretion Formation; 3D CFD

  • World of Metallurgy - Erzmetall 74(2021)5, 270-276

Permalink: https://www.hzdr.de/publications/Publ-33055
Publ.-Id: 33055


²⁶Al and ¹⁰Be in urban and Antarctic micrometeorites

Feige, J.; Airo, A.; Berger, D.; Brückner, D.; Genge, M.; Laya, I.; Habibi Marekani, F.; Klingner, N.; Lachner, J.; Nissen, J.; Patzer, A. B. C.; Schley, N.; Schropp, A.; Peterson, S.; Sager, C.; Suttle, M.; Trappitsch, R.; Weinhold, J.

Roughly 100 tons of extraterrestrial material released from asteroid collision events or cometary sublimation enter the Earth’s atmosphere each day. Some of this material reaches the surface as micrometeorites (MMs) – mostly submillimetre spherical melting droplets. For more than a century MMs were collected only in remote environments such as deep-sea sediments or Antarctic firn and ice. However, since 2017 significant numbers of MMs were found in urban areas, particularly on rooftops of buildings. In contrast to MMs originating from slow-accumulating environments that can have been deposited millions of years ago, the particles from the rooftops are not older than the buildings and currently are the youngest extraterrestrial particles ever collected.
The study of the irradiation histories of MMs provides an important step towards identifying the nature and origin of their parent bodies. During their million-year long journey on spiral trajectories to Earth, these small interplanetary particles are exposed to cosmic radiation producing long-lived radionuclides such as 26Al and 10Be.
Since the number of cosmogenic nuclides increases with the time the MMs travel through space it is possible to estimate from how far out in the Solar System they originated from. However, the very small amounts of a few million atoms of the radionuclides within a MM decrease after deposition on Earth, i.e., with increasing terrestrial age. Hence, urban MMs, with insignificant terrestrial ages, provide for the first time the opportunity to measure the highest possible concentrations of long-lived radionuclides within MMs.
We analyzed six urban MMs and, for comparison with MMs that have terrestrial ages up to 780 kyr, six MMs collected from Antarctic Moraine sediments for their 26Al and 10Be content. The MMs with sizes of 90-500 µm were dissolved and, after stable carrier addition, 10Be an 26Al were chemically extracted and measured with AMS at the Vienna Environmental Research Accelerator (VERA), Vienna, Austria. These experimental data were compared to results from numerical simulations yielding 26Al and 10Be concentrations in micrometeoroids having various orbital parameters, compositions, and irradiation profiles.
The 26Al/27Al and 10Be/9Be measurement results were significantly above the chemistry blank values, except for the smallest (90 µm) Antarctic MM. Conversion to 26Al and 10Be concentration yields values between 104 and 107 atoms per sample. Comparison with the theoretical data generally favours carbonaceous chondrite objects as the parent bodies of the MMs orbiting with several eccentricities within our Solar System.
Our results are influenced by the following assumptions: no pre-irradiation within the parent body, no mass loss during atmospheric entry, average carbonaceous or ordinary chondrite composition, no significant terrestrial ages, and the theoretical production rates for 26Al and 10Be are correct. Besides the use of additional methods such as mineralogical and isotope geochemical analysis better statistics of long-lived radionuclides within MMs may help to constrain some of these assumptions.

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

Permalink: https://www.hzdr.de/publications/Publ-33054
Publ.-Id: 33054


Implementing Heterogeneous Crystal Surface Reactivity in Reactive Transport Simulations: The Example of Calcite Dissolution

Karimzadeh, L.; Fischer, C.

Both surface reactivity and fluid dynamics control the dissolution kinetics of crystalline material. In this study, we performed a 3D reactive transport simulation to investigate the impact of surface topography heterogeneity superimposed to fluid transport heterogeneity on the dissolution rate of calcite. The
model simulates the chemical reaction of calcite dissolution, solute transport, and crystal surface geometry evolution. Importantly, we introduce heterogeneous surface reactivity into the reactive transport simulation. We test the surface slope factor as a proxy value for the intrinsic surface reactivity of dissolving crystal surface nanotopographies. Experimental data sets collected using vertical scanning interferometry validate this approach. The novel parametrization allows for the simulation of surface-controlled heterogeneous reactivity in reactive transport simulations of mineral surface dissolution.

Keywords: reactive transport modeling; crystal surface reactivity; rate map; dissolution rate variability; calcite dissolution

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Permalink: https://www.hzdr.de/publications/Publ-33053
Publ.-Id: 33053


Multiscale modelling for fusion and fission materials: the M4F project

Malerba, L.; Caturla, M. J.; Gaganidze, E.; Kaden, C.; Konstantinović, M. J.; Olsson, P.; Robertson, C.; Rodney, D.; Ruiz-Moreno, A. M.; Serrano, M.; Aktaa, J.; Anento, N.; Austin, S.; Bakaev, A.; Balbuena, J. P.; Bergner, F.; Boioli, F.; Boleininger, M.; Bonny, G.; Castin, N.; Chapman, J. B. J.; Chekhonin, P.; Clozel, M.; Devincre, B.; Dupuy, L.; Diego, G.; Dudarev, S. L.; Fu, C. C.; Gatti, R.; Gélébart, L.; Gómez-Ferrer, B.; Gonçalves, D.; Guerrero, C.; Gueye, P. M.; Hähner, P.; Hannula, S. P.; Hayat, Q.; Hernández-Mayoral, M.; Jagielski, J.; Jennett, N.; Jiménez, F.; Kapoor, G.; Kraych, A.; Khvan, T.; Kurpaska, L.; Kuronen, A.; Kvashin, N.; Libera, O.; Ma, P. W.; Manninen, T.; Marinica, M. C.; Merino, S.; Meslin, E.; Mompiou, F.; Mota, F.; Namburi, H.; Ortiz, C. J.; Pareige, C.; Prester, M.; Rajakrishnan, R. R.; Sauzay, M.; Serra, A.; Simonovski, I.; Soisson, F.; Spätig, P.; Tanguy, D.; Terentyev, D.; Trebala, M.; Trochet, M.; Ulbricht, A.; Vallet, M.; Vogel, K.; Yalcinkaya, T.; Zhao, J.

The M4F project brings together the fusion and fission materials communities working on the prediction of radiation damage production and evolution and its effects on the mechanical behaviour of irradiated ferritic/martensitic (F/M) steels. It is a multidisciplinary project in which several different experimental and computational materials science tools are integrated to understand and model the complex phenomena associated with the formation and evolution of irradiation induced defects and their effects on the macroscopic behaviour of the target materials. In particular the project focuses on two specific aspects: (1) To develop physical understanding and predictive models of the origin and consequences of localised deformation under irradiation in F/M steels; (2) To develop good practices and possibly advance towards the definition of protocols for the use of ion irradiation as a tool to evaluate radiation effects on materials. Nineteen modelling codes across different scales are being used and developed and an experimental validation programme based on the examination of materials irradiated with neutrons and ions is being carried out. The project enters now its 4th year and is close to delivering high-quality results. This paper overviews the work performed so far within the project, highlighting its impact for fission and fusion materials science.

Permalink: https://www.hzdr.de/publications/Publ-33052
Publ.-Id: 33052


Pump-induced terahertz anisotropy in bilayer graphene

Seidl, A.; Anvari, R.; Dignam, M. M.; Richter, P.; Seyller, T.; Schneider, H.; Helm, M.; Winnerl, S.

We investigate the intraband nonlinear dynamics in doped bilayer graphene in the
presence of strong, linearly-polarized, in-plane terahertz fields. We perform degenerate
pump-probe experiments with 3.4 THz fields on doped bilayer graphene at low temper-
ature (12 K) and find that when the pump is co-polarized with the probe beam, the
differential pump-probe signal is almost double that found in the cross-polarized case.
We show that the origin of this pump-induced anisotropy is the difference in the aver-
age electron effective mass in the probe direction when carriers are displaced in k-space
by the pump either parallel or perpendicular to the direction of the probe polarization.
We model the system using both a simple semiclassical model and a Boltzmann equa-
tion simulation of the electron dynamics with phenomenological scattering and find
good qualitative agreement with experimental results.

Keywords: bilayer graphene; nonlinear; terahertz; anisotropy

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Permalink: https://www.hzdr.de/publications/Publ-33051
Publ.-Id: 33051


Metal–Insulator Transition via Ion Irradiation in Epitaxial La0.7Sr0.3MnO3-δ Thin Films

Cao, L.; Herklotz, A.; Rata, D.; Yin, C.; Petracic, O.; Kentsch, U.; Helm, M.; Zhou, S.

Complex oxides provide rich physics related to ionic defects. For the proper tuning of functionalities in oxide heterostructures, it is highly desired to develop fast, effective and low temperature routes for the dynamic modification of defect concentration and distribution. In this work, we report on the use of helium-implantation to efficiently control the vacancy profiles in epitaxial La0.7Sr0.3MnO3-δ thin films. The viability of this approach is supported by lattice expansion in the out-of-plane lattice direction and dramatic change in physical properties, i.e., a transition from ferromagnetic metallic to antiferromagnetic insulating. In particular, a significant increase of resistivity up to four orders of magnitude is evidenced at room temperature, upon implantation of highly energetic He-ions. Our result offers an attractive means for tuning the emergent physical properties of oxide thin films, via strong coupling between strain, defects and valence.

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Permalink: https://www.hzdr.de/publications/Publ-33050
Publ.-Id: 33050


APR files

Nour, A.

APR  files for 4 different functions

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Permalink: https://www.hzdr.de/publications/Publ-33049
Publ.-Id: 33049


Internal Access: Full source data of publication: "Tumor irradiation in mice with a laser-accelerated proton beam"

Kroll, F.; Brack, F.-E.; Bernert, C.; Bock, S.; Bodenstein, E.; Brüchner, K.; Cowan, T.; Gaus, L.; Gebhardt, R.; Helbig, U.; Karsch, L.; Kluge, T.; Kraft, S.; Krause, M.; Leßmann, E.; Masood, U.; Meister, S.; Metzkes-Ng, J.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Püschel, T.; Reimold, M.; Rehwald, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Beyreuther, E.

All source data and scripts for publication: "Tumor irradiation in mice with a laser-accelerated proton beam"

Keywords: Laser acceleration; TNSA; Radiobiology; FLASH

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Permalink: https://www.hzdr.de/publications/Publ-33048
Publ.-Id: 33048


Source Data: Tumour irradiation in mice with a laser-accelerated proton beam (Open Access)

Kroll, F.; Brack, F.-E.; Bernert, C.; Bock, S.; Bodenstein, E.; Brüchner, K.; Cowan, T.; Gaus, L.; Gebhardt, R.; Helbig, U.; Karsch, L.; Kluge, T.; Kraft, S.; Krause, M.; Leßmann, E.; Masood, U.; Meister, S.; Metzkes-Ng, J.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Püschel, T.; Reimold, M.; Rehwald, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Beyreuther, E.

Source data for all figures of publication: "Tumor irradiation in mice with a laser-accelerated proton beam". The folder structure is adapted to match the figures in the publication.

Keywords: Laser acceleration; TNSA; Radiobiology; FLASH

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Permalink: https://www.hzdr.de/publications/Publ-33047
Publ.-Id: 33047


Layer-Dependent Band Gaps of Platinum-Dichalcogenides

Li, J.; Kolekar, S.; Ghorbani Asl, M.; Lehnert, T.; Biskupek, J.; Kaiser, U.; Krasheninnikov, A.; Batzill, M.

Owing to the relatively strong inter-layer interaction, the platinum-dichalcogenides exhibit tunability of their electronic properties by controlling the number of layers. Both PtSe2 and PtTe2 display a semi-metal to semi-conductor transition as they are reduced to bi- or single-layer. The value of the fundamental band gap, however, has been inferred only from density functional theory (DFT) calculations, which are notoriously challenging, as different methods give different results, and currently there is no experimental data. Here we determine the band gap as a function of the number of layers by local scanning tunneling spectroscopy on MBE-grown PtSe2 and PtTe2 islands. We find band gaps of 1.8 eV and 0.6 eV for mono- and bi-layer PtSe2, respectively, and 0.5 eV for monolayer PtTe2. Tri-layer PtSe2 and bilayer PtTe2 are semi-metallic. The experimental data are compared to DFT calculations carried out at different levels of theory. The calculated band gaps may differ significantly from the experimental values, emphasizing the importance of the experimental work. We further show that the variations in the calculated fundamental band gap in bilayer PtSe2 are related to the computed separation of the layers, which depends on the choice of the van der Waals functional. This sensitivity of the band gap to inter-layer separation also suggests that the gap can be tuned by uniaxial stress and our simulations indicate that only modest pressures are required for a significant reduction of the gap, making Pt-dichalcogenides suitable materials for pressure-sensing.

Keywords: 2D materials; layer dependence; PtSe2; PtTe2; scanning tunneling spectroscopy; van der Waals materials; transition metal dichalcogenides

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Permalink: https://www.hzdr.de/publications/Publ-33046
Publ.-Id: 33046


Efficient laser-driven proton and Bremsstrahlung generation from cluster-assembled foam targets

Prencipe, I.; Metzkes-Ng, J.; Pazzaglia, A.; Bernert, C.; Dellasega, D.; Fedeli, L.; Formenti, A.; Garten, M.; Kluge, T.; Kraft, S.; Laso García, A.; Maffini, A.; Obst-Hübl, L.; Rehwald, M.; Sobiella, M.; Zeil, K.; Schramm, U.; Cowan, T.; Passoni, M.

The interaction between intense 30 fs laser pulses and foam-coated 1.5 μm-thick Al foils in the relativistic regime (up to
5x10²⁰ W/cm2) is studied to optimize the laser energy conversion into laser-accelerated protons. A significant enhancement is
observed for foam targets in terms of proton cut-off energy (18.5 MeV) and number of protons above 4.7 MeV (4x10⁹
protons/shot) with respect to uncoated foils (9.5 MeV, 1x10⁹ protons/shot), together with a sixfold increase in the
Bremsstrahlung yield. This enhancement is attributed to increased laser absorption and electron generation in the foam meso-
and nanostructure.

Keywords: laser-driven ion acceleration; laser-driven Bremsstrahlung generation; TNSA; near-critical density plasma; nanostructured targets; foam targets

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Permalink: https://www.hzdr.de/publications/Publ-33045
Publ.-Id: 33045


Tumor irradiation in mice with a laser-accelerated proton beam

Kroll, F.; Brack, F.-E.; Bernert, C.; Bock, S.; Bodenstein, E.; Brüchner, K.; Cowan, T.; Gaus, L.; Gebhardt, R.; Helbig, U.; Karsch, L.; Kluge, T.; Kraft, S.; Krause, M.; Leßmann, E.; Masood, U.; Meister, S.; Metzkes-Ng, J.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Püschel, T.; Reimold, M.; Rehwald, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Beyreuther, E.

Recent oncological studies identified beneficial properties of radiation applied at ultra-high dose rates several orders of magnitude higher than the clinical standard of the order of Gy/min. Sources capable of providing these ultra-high dose rates are under investigation. Here, we show that a stable, compact laser-driven proton source with energies greater than 60 MeV enables radiobiological in vivo studies. We performed a pilot irradiation study on human tumors in a mouse model, showing the concerted preparation of mice and laser accelerator, the dose-controlled, tumor-conform irradiation using a laser-driven as well as a clinical reference proton source, and the radiobiological evaluation of irradiated and unirradiated mice for radiation-induced tumor growth delay. The prescribed homogeneous dose of 4 Gy was precisely delivered at the laser-driven source. The results demonstrate a complete laser-driven proton research platform for diverse user-specific small animal models, able to deliver tunable single-shot doses up to around 20 Gy to millimeter-scale volumes on nanosecond time scales, equivalent to around 1E9 Gy/s, spatially homogenized and tailored to the sample. The platform provides a unique infrastructure for translational research with protons at ultra-high dose rate.

Keywords: Laser acceleration; TNSA; Radiobiology; FLASH

Permalink: https://www.hzdr.de/publications/Publ-33044
Publ.-Id: 33044


Elektrische Energiespeicherung mit Flüssigmetallen und Salzschmelzen

Weier, T.; Horstmann, G. M.; Landgraf, S.; Personnettaz, P.; Stefani, F.; Weber, N.

Stationäre Elektroenergiespeicher können helfen, momentane Differenzen von Elektrizitätsangebot und -nachfrage zu balancieren. Mit zunehmender Nutzung volatiler Stromquellen wird diese Aufgabe wichtiger. Dabei stehen verschiedene Speichertechnologien untereinander,
aber auch mit Alternativen im Wettbewerb.
Flüssigmetallbatterien sind Hochtemperaturspeicher. Sie basieren
auf der stabilen Dichteschichtung eines Alkalimetalls, einer Salzschmelze und eines Schwermetalls. Vermittelt durch die hohe Betriebstemperatur, die über den Schmelztemperaturen der einzelnen Phasen liegen
muss, verlaufen Grenzflächenreaktionen und Transportvorgänge sehr
rasch, was in hohen Strom- und Leistungsdichten resultiert. Der vollständig flüssige Zellinhalt ermöglicht einerseits eine konzeptionell einfache Skalierbarkeit auf Zellebene, die sehr günstige energiebezogene
Investitionskosten verspricht. Andererseits gewinnen durch den flüssige Aggregatzustand strömungsmechanische Vorgänge, die eng an den
Ladungstransport und -übergang gekoppelt sind, stark an Bedeutung.
Der Vortrag wird sowohl ausgewählte physikalische Phänomene in
Flüssigmetallbatterien vorstellen, als auch ihre mögliche Rolle in einem
zukünftigen Energiesystem diskutieren.

Keywords: liquid metal batteries; energy storage

  • Invited lecture (Conferences) (Online presentation)
    84. Jahrestagung der DPG und DPG-Tagung der Sektion Kondensierte Materie, 27.09.-01.10.2021, virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33043
Publ.-Id: 33043


Compositional convection in liquid metal electrodes

Personnettaz, P.; Klopper, T. S.; Benard, S.; Kubeil, C.; Landgraf, S.; Weber, N.; Weier, T.

Liquid metal electrodes are a crucial element of innovative electrochemical cells such as
liquid metal batteries (LMBs) and solutal - alkali metal thermal electric converters (S-AMTECs).
The liquid phase is a key to guarantee scalability, extended life time and high cyclability; at the same
time fluid mechanics plays a pivotal role in terms of cell capacity and efficiency. The geometry
of these electrodes is simple: a liquid metal alloy is confined by an electrochemically active interface
and inert walls. The active interface can be fluid (molten salt electrolyte) or solid (fast ionic
conductor). During operation of the cell a mass flux is established across the interface. The liquid
metal alloy experiences an enrichment or depletion of the electroactive species. This changes the
local density distribution and either induces or suppresses convective flows. Here, we focus
on the positive electrode of a liquid metal battery during the charging step. The electroactive species
(e.g. Li) is extracted from the alloy (e.g. Li(in Bi)), and the heavy alloy generated at the top interface
sinks down leading to strong compositional convection. The evolution of the concentration and
velocity fields are studied with numerical methods; the results of a finite volume code (OpenFOAM)
are compared with the ones of a spectral element code (SEMTEX). The effects of Schmidt number,
current density magnitude and distribution and electrode geometry are investigated. Furthermore,
the impact of a non-uniform temperature distribution and the mechanical coupling with a molten
salt layer are discussed.

Keywords: LMB; S-AMTEC; mass transport; solutal convection

  • Lecture (Conference) (Online presentation)
    IV Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russia

Permalink: https://www.hzdr.de/publications/Publ-33042
Publ.-Id: 33042


Deposition of silicon oxide films on silicon using HelixJet – an atmospheric-pressure plasma jet process below 100 °C

Rebohle, L.; Quade, A.; Schumann, T.; Blaschke, D.; Hübner, R.; Heller, R.; Foest, R.; Schäfer, J.; Skorupa, W.

Silicon oxide films are widely applied for their superior dielectric, chemical and mechanic properties as well as for their resistance against reactive chemicals. Simultaneously, there is an increasing number of applications which demand a low deposition temperature. In this work, we compare the material properties of SiOx layers deposited at ca. 70°C by atmospheric-pressure plasma jet deposition (PA) with those of SiO2 layers thermally grown or deposited by plasma-enhanced chemical vapour deposition. The films were deposited on silicon wafers and analysed using different analysis techniques. According to cross-sectional transmission electron microscopy and high-frequency capacitance-voltage measurements, the interface between the PA oxide and the Si substrate is smooth with no apparent defects and displays an electrically active interface defect density between 3.5-8.0×1012 cm-2 directly after deposition and below 2.0×1012 cm-2 after furnace annealing. Right after deposition, the PA oxide contains carbon and hydrogen in a concentration of several at%, and the SiO2 plasma polymer network comprises several active centres (residual charge, free radicals, non-saturated bonds). The most abundant configuration is the Si(-O)4 tetrahedron, followed by Si(-O)3 with similar intensity. This indicates that there are still dangling Si bonds or bonds terminated by hydroxyl or methyl groups. After furnace annealing, the formation of the SiO2 network is completed and the optical and electrical properties of the PA oxide converge to that of thermal oxide.

Keywords: dielectric coating; insulation; corrosion protection; silicon oxide; atmospheric plasma source; thin films

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  • Secondary publication expected from 21.04.2023

Permalink: https://www.hzdr.de/publications/Publ-33040
Publ.-Id: 33040


Data publication: Radiation damage evolution in pure W and W-Cr-Hf alloy caused by 5MeV Au ions in a broad range of dpa

Mackova, A.; Havranek, V.; Fernandes, S.; Matejicek, J.; Vilemova, M.; Holy, V.; Liedke, M. O.; Martan, J.; Vronka, M.; Potocek, M.; Babor, P.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.

Positron annihilation lifetime spectroscopy data taking for ELBE proposal POS19101496 by Sandrina Fernandes, Rez, CZ. Role of open volume defects in irradiated structural materials for fusion applications. Measurements performed 16.3.2019 at the MePS facility.

Keywords: positron annihilation lifetime spectroscopy; SIMS; alloys; W Tungsten

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Permalink: https://www.hzdr.de/publications/Publ-33039
Publ.-Id: 33039


Rapid synthesis of gold-palladium core-shell aerogels for selective and robust electrochemical CO2 reduction

Du, R.; Jin, W.; Wu, H.; Hübner, R.; Zhou, L.; Xue, G.; Hu, Y.; Eychmüller, A.

Noble metal aerogels (NMAs), one class of the youngest members in the aerogel family, have drawn increasing attention in the last decade. Featuring the high catalytic activity of noble metals and a 3D self-supported porous network of the aerogels, they have displayed profound potential for electrocatalysis. However, considerable challenges reside in the rapid fabrication of NMAs with a well-tailored architecture, constraining the manipulation of their electrochemical properties for optimized performance. Here, a disturbance-assisted dynamic shelling strategy is developed, generating self-supported Au–Pd core–shell gels within 10 min. Based on suitable activation and desorption energies of the involved species as suggested by theoretical calculations, the Au–Pd core–shell aerogel manifests outstanding CO selectivity and stability at low overpotential (faradaic efficiency > 98% at -0.5 V vs. RHE over 12 hours) for the electrochemical CO2 reduction reaction (CO2RR). The present strategy offers a new perspective to facilely design architecture-specified high-performance electrocatalysts for the CO2RR.

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Permalink: https://www.hzdr.de/publications/Publ-33038
Publ.-Id: 33038


Integrated complementary inverters and ring oscillators based on vertical-channel dual-base organic thin-film transistors

Guo, E.; Xing, S.; Dollinger, F.; Hübner, R.; Wang, S.-J.; Wu, Z.; Leo, K.; Kleemann, H.

Lateral-channel dual-gate organic thin-film transistors have been used in pseudo complementary metal-oxide-semiconductor (CMOS) inverters to control switching voltage. However, their relatively long channel lengths, combined with the low charge carrier mobility of organic semiconductors, typically leads to slow inverter operation. Vertical-channel dual-gate organic thin-film transistors are a promising alternative because of their short channel lengths, but the lack of appropriate p- and n-type devices has limited the development of complementary inverter circuits. Here, we show that organic vertical n-channel permeable single- and dual-base transistors, and vertical p-channel permeable base transistors can be used to create integrated complementary inverters and ring oscillators. The vertical dual-base transistors enable switching voltage shift and gain enhancement. The inverters exhibit small switching time constants at 10 MHz, and the seven-stage complementary ring oscillators exhibit short signal propagation delays of 11 ns per stage at a supply voltage of 4 V.

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Permalink: https://www.hzdr.de/publications/Publ-33037
Publ.-Id: 33037


Data for: On Inter-bubble Distances and Bubble Clustering in Bubbly Flows: An Experimental Study

Kipping, R.; Hampel, U.

This data set contains the processed data from ultrafast X-ray tomography measurements in a bubble column. Measurements were performed in a bubble column with 100 mm inner diameter and with deionized water and nitrogen as liquid and gas phase, respectively. This data set contains the measurement from the measurement height located 0.7m above the gas sparger. 

Hydrodynamic data, such as bubble size distribution and gas holdup distribution are provided. Furthermore, inter-bubble distances of gas bubbles (distance of the nearest neighbours) are given.

Further detailes on the experiments and the processed data is provided in the corresponding journal paper.

Keywords: bubbly flows; clustering; UFXCT

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Permalink: https://www.hzdr.de/publications/Publ-33036
Publ.-Id: 33036


Data publication: FPGA-based Real-Time Data Acquisition for Ultrafast X-Ray Computed Tomography

Windisch, D.; Knodel, O.; Juckeland, G.; Hampel, U.; Bieberle, A.

This data contains the firmwares used for all descirbed tests in the paper.

Keywords: Computed tomography; Data acquisition; Field programmable gate arrays

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Permalink: https://www.hzdr.de/publications/Publ-33035
Publ.-Id: 33035


Evidence of collision-induced resuspension of microscopic particles from a monolayer deposit

Banari, A.; Henry, C.; Fank Eidt, R. H.; Pierre, L.; Klaus, Z.; Hampel, U.; Lecrivain, G.

The present Letter addresses the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here set to about 10% of the field of view, we report two distinct detachment mechanisms. At relatively low flow velocities, few loosely adhering particles move on the wall to eventually collide with neighboring particles resulting in a clustered resuspension. At higher fluid velocities, mostly individual particles resuspend due to their interaction with the turbulent flow. The resuspension curve, showing the remaining particle fraction as a function of the flow velocity, exhibits a strong bimodal character.

Keywords: paticle resuspension; Inter-particle collisions; experimental test

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Permalink: https://www.hzdr.de/publications/Publ-33034
Publ.-Id: 33034


Fabrication and nanophotonic waveguide integration of silicon carbide colour centres with preserved spin-optical coherence

Babin, C.; Stöhr, R.; Morioka, N.; Linkewitz, T.; Steidl, T.; Wörnle, R.; Liu, D.; Hesselmeier, E.; Vorobyov, V.; Denisenko, A.; Hentschel, M.; Gobert, C.; Berwian, P.; Astakhov, G.; Knolle, W.; Majety, S.; Saha, P.; Radulaski, M.; Tien Son, N.; Ul-Hassan, J.; Kaiser, F.; Wrachtrup, J.

Optically addressable spin defects in silicon carbide (SiC) are an emerging platform for quantum information processing. Lending themselves to modern semiconductor nanofabrication, they promise scalable high-efficiency spin-photon interfaces. We demonstrate here nanoscale fabrication of silicon vacancy centres (VSi) in 4H-SiC without deterioration of their intrinsic spin-optical properties. In particular, we show nearly transform limited photon emission and record spin coherence times for single defects generated via ion implantation and in triangular cross section waveguides. For the latter, we show further controlled operations on nearby nuclear spin qubits, which is crucial for fault-tolerant quantum information distribution based on cavity quantum electrodynamics.

Keywords: Qubits; Silicon carbide; Quantum spintronics; Quantum photonics; Point defects

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Permalink: https://www.hzdr.de/publications/Publ-33033
Publ.-Id: 33033


Data and code for: A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise

Montano, Y.; Michael Marshall, B.; Ward, M.; Simoes Silva, I. M.; Artchawakom, T.; Waengsothorn, S.; Strine, C. T.

Supplemental materials for A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise on OSF Preprints, including data, code, figures and tables.

Keywords: ecology; testudine; autocorrelated kernel density estimator; spatial ecology; space use; Thailand; Indotestudo elongata

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  • Reseach data in external data repository
    Publication year 2021
    License: Creative Commons Attribution 4.0 International
    Hosted on OSF: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33032
Publ.-Id: 33032


A stable home: Autocorrelated Kernel Density Estimated home ranges of the critically endangered Elongated Tortoise

Montano, Y.; Michael Marshall, B.; Ward, M.; Simoes Silva, I. M.; Artchawakom, T.; Waengsothorn, S.; Strine, C. T.

Home range is a fundamental concept in ecology used to describe animal space use over their lifetimes. Numerous studies use a variety of metrics to quantify home range; however, most of these treat spatial data inappropriately. Here we re-analyse a publicly available data-set, collected by the authors of this study, using a relatively novel and appropriate home range metric Autocorrelated Kernel Density Estimators (AKDE). Our data includes the movements of 17 Elongated Tortoises (Indotestudo elongata; 12 females, 5 males) located on average once every three days for an average duration of 353.76 ±33.10 days. We found 14 of 17 individuals appear to be occupying a stable home range (using variograms to determine range residency). We made use of AKDEs bias-mitigating measures to counteract the low effective sample sizes stemming from low temporal resolution radio-tracking data. The average AKDE home range for all 14 individuals with range residency was 44.81 ±10.44 ha. Bayesian Regression Models suggest considerable overlap between male and female home range estimates despite males being physically larger than females in both mass and carapace length. These home range estimates have the added utility of being comparable with other studies, less susceptible to errors from a suboptimal tracking regime, and are optimised with code and data for inclusion in future meta-analyses.

Keywords: ecology; testudine; autocorrelated kernel density estimator; spatial ecology; space use; Thailand; Indotestudo elongata

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Permalink: https://www.hzdr.de/publications/Publ-33031
Publ.-Id: 33031


Data and code for: Lots of movement, little progress: A review of reptile home range literature

Crane​, M.; Simoes Silva, I. M.; Marshall, B. M.; Strine​, C. T.

Datasets, R code and figures pertaining to the manuscript: Crane, M., Silva, I., Marshall, B. M., & Strine, C. T. (2021). Lots of movement, little progress: A review of reptile home range literature. PeerJ, 9, e11742. DOI: 10.7717/peerj.11742

Keywords: ecology; reptiles; home range; open science; reproducibility; biotelemetry; space use; spatial ecology

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Permalink: https://www.hzdr.de/publications/Publ-33030
Publ.-Id: 33030


Lots of movement, little progress: A review of reptile home range literature

Crane​, M.; Simoes Silva, I. M.; Marshall, B. M.; Strine​, C. T.

Reptiles are the most species-rich terrestrial vertebrate group with a broad diversity of life history traits. Biotelemetry is an essential methodology for studying reptiles as it compensates for several limitations when studying their natural history. We evaluated trends in terrestrial reptile spatial ecology studies focusing upon quantifying home ranges for the past twenty years. We assessed 290 English-language reptile home range studies published from 2000–2019 via a structured literature review investigating publications’ study location, taxonomic group, methodology, reporting, and analytical techniques. Substantial biases remain in both location and taxonomic groups in the literature, with nearly half of all studies (45%) originating from the USA. Snakes were most often studied, and crocodiles were least often studied, while testudines tended to have the greatest within study sample sizes. More than half of all studies lacked critical methodological details, limiting the number of studies for inclusion in future meta-analyses (55% of studies lacked information on individual tracking durations, and 51% lacked sufficient information on the number of times researchers recorded positions). Studies continue to rely on outdated methods to quantify space-use (including Minimum Convex Polygons and Kernel Density Estimators), often failing to report subtleties regarding decisions that have substantial impact on home range area estimates. Moving forward researchers can select a suite of appropriate analytical techniques tailored to their research question (dynamic Brownian Bridge Movement Models for within sample interpolation, and autocorrelated Kernel Density Estimators for beyond sample extrapolation). Only 1.4% of all evaluated studies linked to available and usable telemetry data, further hindering scientific consensus. We ultimately implore herpetologists to adopt transparent reporting practices and make liberal use of open data platforms to maximize progress in the field of reptile spatial ecology.

Keywords: ecology; reptiles; home range; open science; reproducibility; biotelemetry; space use; spatial ecology

Permalink: https://www.hzdr.de/publications/Publ-33029
Publ.-Id: 33029


Indirect bandgap, optoelectronic properties, and photoelectrochemical characteristics of high-purity Ta₃N₅ photoelectrodes

Eichhorn, J.; Lechner, S. P.; Jiang, C.-M.; Folchi, G.; Munnik, F.; Sharp, I. D.

The (opto)electronic properties of Ta3N5 photoelectrodes are often dominated by defects, such as oxygen impurities, nitrogen vacancies, and reduced tantalum centers, impeding fundamental studies of its electronic structure, chemical stability, and photocarrier transport. Here, we synthesize high quality Ta3N5 thin films by reactive magnetron sputtering and subsequent NH3 annealing at varying temperatures. The resulting films are characterized by nearly-ideal N/Ta stoichiometry, low O content, and small Urbach energies. Both the crystallinity and material quality improve with increasing annealing temperatures up to 940 °C, while higher annealing temperatures introduce additional disorder within the Ta3N5 lattice, leading to reduced photoelectrochemical performance. These changes are also reflected in the surface and bulk composition, showing the elimination of oxygen impurities at moderate annealing temperatures and the loss of nitrogen at high annealing temperatures. As a consequence, defect-related sub-gap optical absorption initially decreases due to reduced oxygen impurity concentration, and subsequently increases due to increased formation of nitrogen vacancies. The high material quality enables us to unambiguously identify the nature of the Ta3N5 band gap as indirect, thereby resolving a long-standing controversy regarding the most fundamental characteristic of this material as a semiconductor. The assignment of Ta3N5 as indirect semiconductor is further supported by the suppression of disorder-induced band-edge photoluminescence with improved structural order within the Ta3N5 films.

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Permalink: https://www.hzdr.de/publications/Publ-33028
Publ.-Id: 33028


Simulating Multi Layer Targets for Grazing Incidence Small Angle X-ray Scattering

Paschke-Brühl, F.-L.

This bachelor thesis studies the feasibility of grazing-incidence small-angle x-ray scattering
(GISAXS) in the UHI laser-target interaction via computational simulations with SMILEI. In
this work we briefly analyze the front and back of the target. We find predominantly that the
compression of the target becomes apparent in the GISAXS pattern, while we can not observe
ablation. We will mainly focus on the density oscillation, a dynamic that has not been mentio-
ned in literature yet. The density oscillation dynamics depend on a simple pressure gradient
in between the layers. We observe the multi layers inversely oscillating in density and a global
density alteration moving through the target. The density alteration allows to recognize the
dynamic in a GISAXS pattern. We learn, that GISAXS is feasible in the high intensity regime,
but not for the same dynamics as in the lower intensity regime.

Keywords: GISAXS; SAXS; grazing-incidence small-angle x-ray scattering; SMILEI; Simulation; Density Oscialltion

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Permalink: https://www.hzdr.de/publications/Publ-33027
Publ.-Id: 33027


Simulating Multi Layer Targets for Grazing Incidence Small Angle X-ray Scattering

Paschke-Brühl, Franziska-Luise

This bachelor thesis studies the feasibility of grazing-incidence small-angle x-ray scattering
(GISAXS) in the UHI laser-target interaction via computational simulations with SMILEI. In
this work we briefly analyze the front and back of the target. We find predominantly that the
compression of the target becomes apparent in the GISAXS pattern, while we can not observe
ablation. We will mainly focus on the density oscillation, a dynamic that has not been mentio-
ned in literature yet. The density oscillation dynamics depend on a simple pressure gradient
in between the layers. We observe the multi layers inversely oscillating in density and a global
density alteration moving through the target. The density alteration allows to recognize the
dynamic in a GISAXS pattern. We learn, that GISAXS is feasible in the high intensity regime,
but not for the same dynamics as in the lower intensity regime.

Keywords: GISAXS; SAXS; grazing incidence small angle x-ray scattering; SMILEI; Simulation; Density Oscillation

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Permalink: https://www.hzdr.de/publications/Publ-33026
Publ.-Id: 33026


Radiation damage evolution in pure W and W-Cr-Hf alloy caused by 5MeV Au ions in a broad range of dpa

Mackova, A.; Havranek, V.; Fernandes, S.; Matejicek, J.; Vilemova, M.; Holy, V.; Liedke, M. O.; Martan, J.; Vronka, M.; Potocek, M.; Babor, P.; Butterling, M.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.

Pure W and W-Cr-Hf alloy which are prospective materials for nuclear fusion reactors, such as DEMO,
were irradiated at room temperature with 5 MeV Au2+ ions with fluences between 4 × 1014 and 1.3
× 1016 ions.cm-2 to generate various levels of lattice damage from about units up to tens of dpa. The distinct
character of radiation damage accumulation, microstructure and defect nature have been observed in
both pure W and W-Cr-Hf alloys, the latter exhibited interesting ability of damage reorganisation and
defect size decrease at the higher ion fluences as determined by positron annihilation spectroscopy (PAS),
X-ray diffraction analysis (XRD) identified vertical grain size modification as a function of the Au-ion
fluence. Originally more strained subsurface layer influenced by polishing procedure exhibited the defect
and strain release with the increased Au-ion irradiation fluence in both materials. Radiation damage
saturation has been observed in the deep buried layer at the lower Au-ion fluences in the W-samples
compared to W-Cr-Hf samples; contrary for the higher Au-ion fluence a slight damage decrease was
evidenced in W-Cr-Hf alloys. The distinct defect accumulation was accompanied with the different Au-ion, implanted distribution in the irradiated layer determined by Secondary Ion Mass Spectrometry (SIMS) as
well as the thermal properties have shown the consequent worsening in the depth in good agreement
with the Au-depth concentration profiles. TEM corroborated above mentioned findings, where the subsurface
layer exhibited defect release after the irradiation, the maximum of dislocation loop density has
been identified in the depth according the predicted dpa (displacement particles per atom) maximum for
the lower Au-ion fluences. Moreover, TEM shows the dislocation density band structure appeared in WCr-
Hf samples exhibiting the high density defect band according the projected range of the Au-ions
simultaneously with the additional layer with larger isolated dislocations pronounced in the higher depth
as a growing function of Au-ion ion fluence. Such phenomenon was not observed in W samples.

Keywords: positron annihilation lifetime spectroscopy; SIMS; alloys; W Tungsten

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Permalink: https://www.hzdr.de/publications/Publ-33025
Publ.-Id: 33025


On Inter-bubble Distances and Bubble Clustering in Bubbly Flows: An Experimental Study

Kipping, R.; Wagner, M.; Hampel, U.

Swarm effects in bubble columns result from the interaction of the bubbles at higher gas holdup. The flow around individual bubbles in a swarm influences the movement of the following bubbles and this has a feedback on the flow regime on a larger scale. That is, hydrodynamics that can no longer be described with models for single rising bubbles. The experimental investigation of the multiscale hydrodynamics in three-dimensional bubble columns was so far limited by the available measurement techniques. In this study, ultrafast X-ray tomography (UFXCT) was applied on bubbly flows in a lab scale bubble column to determine inter-bubble distances and clustering characteristics for different gas holdups and bubble diameters. Applying the pair correlation function reveals a pronounced vertical clustering for large bubbles with Eo ≥ 3.82, whereas no clustering has been observed for bubbles of lower Eo. It was found that clustering orientation mainly depends on deformability of the bubbles but not on gas holdup.

Keywords: bubbly flows; ultrafast X-ray tomography; inter-bubble distances; pair correlation function; bubble clustering

Permalink: https://www.hzdr.de/publications/Publ-33024
Publ.-Id: 33024


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