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41421 Publications

Time- and dose-dependent volume decreases in subcortical grey matter structures of glioma patients after radio(chemo)therapy

Raschke, F.; Witzmann, K.; Seidlitz, A.; Wesemann, T.; Jentsch, C.; Platzek, I.; van den Hoff, J.; Kotzerke, J.; Beuthien-Baumann, B.; Baumann, M.; Linn, J.; Krause, M.; Troost, E. G. C.

Background and purpose: Radiotherapy (RT) is an adjuvant treatment option for glioma patients. Side effects include tissue atrophy, which might be a contributing factor to neurocognitive decline after treatment. The goal of this study was to determine potential atrophy of the hippocampus, amygdala, thalamus, putamen, pallidum and caudate nucleus in glioma patients having undergone magnetic resonance imaging (MRI) before and after RT. Materials and methods: Subcortical volumes were measured using T1-weighted MRI from patients before RT (N = 91) and from longitudinal follow-ups acquired in three-monthly intervals (N = 349). The volumes were normalized to the baseline values, while excluding structures touching the clinical target volume (CTV) or abnormal tissue seen on FLAIR imaging. A multivariate linear effects model was used to determine if time after RT and mean RT dose delivered to the corresponding structures were significant predictors of tissue atrophy. Results: The hippocampus, amygdala, thalamus, putamen, and pallidum showed significant atrophy after RT as function of both time after RT and mean RT dose delivered to the corresponding structure. Only the caudate showed no dose or time dependant atrophy. Conversely, the hippocampus was the structure with the highest atrophy rate of 5.2 % after one year and assuming a mean dose of 30 Gy. Conclusion: The hippocampus showed the highest atrophy rates followed by the thalamus and the amygdala. The subcortical structures here found to decrease in volume indicative of radiosensitivity should be the focus of future studies investigating the relationship between neurocognitive decline and RT. © 2022 The Authors

Keywords: Amygdala; Atrophy; Caudate; Hippocampus; Proton therapy; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-35044
Publ.-Id: 35044


Data publication: Electrokinetic Janus micromotors moving on topographically flat chemical patterns

Huang, T.; Misko, V.; Caspari, A.; Synytska, A.; Ibarlucea, B.; Nori, F.; Faßbender, J.; Cuniberti, G.; Makarov, D.; Baraban, L.

Uploaded data show the research discussions of the electroosmotic flows at the boundary between positive and negative surfaces .

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Permalink: https://www.hzdr.de/publications/Publ-35042
Publ.-Id: 35042


Comparison of manual and automated ventricle segmentation in the maternal immune stimulation rat model of schizophrenia

Winter, R.; Akinola, B.; Barroeta-Hlusicka, E.; Meister, S.; Pietzsch, J.; Winter, C.; Bernhardt, N.

Maternal immune stimulation (MIS) is strongly implicated in the etiology of neuropsychiatric disorders. Magnetic resonance imaging (MRI) studies provide evidence for brain structural abnormalities in rodents following prenatal exposure to MIS. Reported volumetric changes in adult MIS offspring comprise among others larger ventricular volumes, consistent with alterations found in patients with schizophrenia. Linking rodent models of MIS with non-invasive small animal neuroimaging modalities thus represents a powerful tool for the investigation of structural endophenotypes. Traditionally manual segmentation of regions-of-interest, which is laborious and prone to low intra- and inter-rater reliability, was employed for data analysis. Recently automated analysis platforms in rodent disease models are emerging. However, none of these has been found to reliably detect ventricular volume changes in MIS nor directly compared manual and automated data analysis strategies. The present study was thus conducted to establish an automated, structural analysis method focused on lateral ventricle segmentation. It was applied to ex-vivo rat brain MRI scans. Performance was validated for phenotype induction following MIS and preventive treatment data and compared to manual segmentation. In conclusion, we present an automated analysis platform to investigate ventricular volume alterations in rodent models thereby encouraging their preclinical use in the search for new urgently needed treatments.

Permalink: https://www.hzdr.de/publications/Publ-35041
Publ.-Id: 35041


Helical dislocations and dislocation line decoration in ion-irradiated Fe-9Cr studied by scanning transmission electron microscopy

Vogel, K.; Engelmann, H.-J.; Chekhonin, P.; Bergner, F.; Kaden, C.

Fe-9Cr is a model alloy for studying irradiation effects that are relevant for potential applications of high-chromium ferritic/martensitic steels in nuclear energy devices. Here we report on scanning transmission electron microscopy (STEM) studies of the microstructure of Fe-9Cr irradiated with 8 MeV Fe3+ ions. Two samples were irradiated with different ion fluences resulting in peak values of displacement damage of 2 and 10 dpa, respectively. The spatial distribution of irradiation-induced dislocation loops was studied with special emphasis on the effects of pre-existing network dislocations.
The most striking feature of the irradiated microstructure is the presence of helical dislocations. From comparison of the irradiated layer with the dislocation arrangement in the non-irradiated substrate it is concluded that the helices were formed from straight pre-existing line dislocations that originally had a dominating screw component. Other types of dislocations observed in the material did not adopt a helical shape during irradiation. Decreasing the dose has a significant effect on the helical dislocations, the helices are less developed and have a smaller diameter. For both irradiation conditions, an inhomogeneous distribution of irradiation-induced dislocation loops is observed. A high number of loops is present close to the helical dislocations and also close to dislocations that have not adopted a helical shape. In areas away from the dislocations, the number of visible loops is very low.
The loop clustering close to helical dislocations resembles observations reported for neutron irradiated Fe-9Cr. Hence we conclude that ion irradiations can produce similar defect configurations like neutron irradiations when the arrangement of pre-existing dislocations is comparable.

Keywords: irradiation-induced defects; helical dislocations; dislocation loops; ion-irradiated Fe-Cr; scanning TEM

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  • Poster
    Nuclear Materials Conference 2022, 24.-28.10.2022, Ghent, Belgium

Permalink: https://www.hzdr.de/publications/Publ-35040
Publ.-Id: 35040


Electrokinetic Janus micromotors moving on topographically flat chemical patterns

Huang, T.; Misko, V.; Caspari, A.; Synytska, A.; Ibarlucea, B.; Nori, F.; Faßbender, J.; Cuniberti, G.; Makarov, D.; Baraban, L.

Ionic and molecular selectivity are considered unique for the nanoscale and not realizable in microfluidics. This is due to the scale-matching problem – a difficulty to match the dimensions of ions and electrostatic potential screening lengths with micron-sized confinements. Here, we demonstrate a microscale realization of ionic transport processes closely resembling those specific to ionic channels or in nanofluidic junctions, including selectivity, guidance and flow focusing. As a model system, we explore electrokinetic spherical Janus micromotors moving over charged surfaces with complex charge distribution and without any topographical wall. We discuss peculiarities of the long-range electrostatic interaction on the behavior of the system including interface crossing and reflection of positively charged particles from negatively charged interfaces. These results are crucial for understanding the electrokinetic transport of biochemical species under confinement, have the potential to increase the precision of lab-on-chip-based assays, as well as broadening use cases and control strategies of nano-/micromachinery.

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Permalink: https://www.hzdr.de/publications/Publ-35039
Publ.-Id: 35039


Resummation for quantum propagators in bounded spaces

Edwards, J. P.; González-Domínguez, V. A.; Huet, I.; Trejo Espinosa, M. A.

We outline an approach to calculating the quantum mechanical propagator in the presence of geometrically nontrivial Dirichlet boundary conditions. The method is based on a generalization of an integral transform of the propagator studied in previous work (the so-called “hit function”) and a convergent sequence of Padé approximants that exposes the limit of perfectly reflecting boundaries. In this paper the generalized hit function is defined as a many-point propagator, and we describe its relation to the sum over trajectories in the Feynman path integral. We then show how it can be used to calculate the Feynman propagator. We calculate analytically all such hit functions in D = 1 and D = 3 dimensions, giving recursion relations between them in the same or different dimensions and apply the results to the simple cases of propagation in the presence of perfectly conducting planar and spherical plates. We use these results to conjecture a general analytical formula for the propagator when Dirichlet boundary conditions are present in a given geometry, also explaining how it can be extended for application for more general, nonlocalized potentials. Our work has resonance with previous results obtained by Grosche in the study of path integrals in the presence of delta potentials. We indicate the eventual application in a relativistic context to determining Casimir energies using this technique.

Keywords: Integral equations; Quantum theory; Bounded spaces; Convergent sequences; Dirichlet boundary conditions; Feynman path integrals; Generalisation; Integral transform; Pade approximants; Quantum mechanical; Reflecting boundary; Resummation

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Permalink: https://www.hzdr.de/publications/Publ-35038
Publ.-Id: 35038


Enhanced Longitudinal Relaxation of Magnetic Solitons in Ultrathin Films

Yastremsky, I. A.; Faßbender, J.; Ivanov, B. A.; Makarov, D.

Relaxation fundamentally determines the operation speed and energy efficiency of spintronic and
spinorbitronic devices. We develop a theory of the longitudinal contribution to the relaxation of domain
walls in ferromagnetic films of any thickness with the Dzyaloshinskii-Moriya interaction, which allows
quantitative comparison with experiments. We show that the longitudinal contribution increases with a
decrease of the transversal relaxation (e.g., the Gilbert constant). We predict a substantial enhancement
of the contribution of the longitudinal relaxation to the damping of magnetic solitons with a decrease of
the film thickness. We demonstrate that for ultrathin ferromagnetic films, the contribution of the longitudinal
relaxation to the damping of domain walls is comparable to or stronger than any other traditional
transversal mechanisms, including spin pumping. Although in this work we focus on the analysis of longitudinal
relaxation for domain walls, in ultrathin samples it should be taken into account also for other
magnetic solitons including skyrmions. This work adds to the fundamental understanding of the design
and optimization of spintronic and spinorbitronic devices based on moving solitons in ultrathin films.

Keywords: Longitudinal Relaxation; magnetic thin films; magnetic solitons

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Permalink: https://www.hzdr.de/publications/Publ-35037
Publ.-Id: 35037


Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Rezvanov, A. A.; Attallah, A. G.; Liedke, M. O.; Butterling, M.; Bogdanova, M. A.; Vishnevskiy, A. S.; Seregin, D. S.; Vorotyntsev, D. A. V.; Palov, A. P.; Hirschmann, E.; Wagner, A.; Naumov, S.; Vorotilov, K. A.; Rakhimova, T. V.; Rakhimov, A. T. R.; Baklanov, M.

Modification of spin-on-deposited porous PMO
(periodic mesoporous organosilica) ultralow-k (ULK) SiCOH
films (k = 2.33) containing both methyl terminal and methylene
bridging groups by vacuum ultraviolet (VUV) emission from Xe
plasma is studied. The temporal evolution of chemical composition,
internal defects, and morphological properties (pore structure
transformation) is studied by using Fourier transform infrared
spectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry,
ellipsometric porosimetry (EP), positron-annihilation lifetime
spectroscopy (PALS), and Doppler broadening positron-annihilation spectroscopy. Application of the different advanced diagnostics
allows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure in
the current investigation can be divided into two phases. During the first short phase, film loses almost all of its surface methyl and
matrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage is
found by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when the
treated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUV
exposure time according to PAS and EP data. The last is the result of the additional film shrinkage caused by atmosphere exposure.
During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all the
time as it is expected from in situ ellipsometry, but it is masked by the air exposure

Keywords: ultralow-k materials; vacuum ultraviolet emission; porosimetry; positron-annihilation spectroscopy; in situ ellipsometry

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Permalink: https://www.hzdr.de/publications/Publ-35036
Publ.-Id: 35036


Laser-generated supersonic plasma jets and shocks in a transverse magnetic field

Bohlin, H.; Brack, F.-E.; Cervenak, M.; Chodukowski, T.; Cikhardt, J.; Dostál, J.; Dudžák, R.; Hubner, J.; Huo, W.; Jelinek, S.; Klír, D.; Kroll, F.; Krupka, M.; Krůs, M.; Pisarczyk, T.; Rusiniak, Z.; Schramm, U.; T.-H, N.-B.; Weber, S.; Zaraś-Szydłowska, A.; Zeil, K.; Kumar, D.; Schlegel, T.; Tikhonchuk, V.

The influence of a transverse magnetic field on the formation and evolution of supersonic plasma jets and shocks was studied experimentally, and compared with 3D numerical simulations. An improved jet collimation was seen due to the change in the magnetic field topology restricting the radial expansion of the ablated plasma. The magnetic field was also shown to strongly affect the shock structures, both indirectly through the modified jet geometry, as well as due to a compression of the field lines in the shock region. The interaction characteristics were found to depend on the relative contribution of the magnetic and plasma pressure in balancing the ram pressure of the jet.

Keywords: Laser; Plasma; Astrophysics; Pulsed Magnet

Permalink: https://www.hzdr.de/publications/Publ-35035
Publ.-Id: 35035


Flue Dust Reactions and Sticking Mechanisms in a Copper Flash Smelting Furnace Waste Heat Boiler - A Sampling Study

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

Formation of accretion layers within the copper Flash Smelting Furnace Waste Heat Boiler is a serious operational concern, as it can potentially increase boiler downtime and hence limit continuous production. In previous Computational Fluid Dynamics studies, the accretion formation was predicted for an industrial-scaleWaste Heat Boiler, using a dust stickiness sub-routine of the model. In this study, a dust sampling campaign was used to validate this stickiness sub-routine. Furthermore, sticking and reaction mechanisms of flue dust were investigated and compared to thermodynamic predictions. While the sub-routine was validated, the comparison of thermodynamics and species in the samples showed that the thermodynamic conversion limit was not reached for the investigated species.

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

Permalink: https://www.hzdr.de/publications/Publ-35034
Publ.-Id: 35034


Transient CFD Calculation of Accretion Formation in a Copper Waste Heat Boiler

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

The operation of a copper Flash Smelting Furnace (FSF) is often limited by the availability of the downstream Waste Heat Boiler (WHB). Carry-over of concentrate into the boiler leads to accretion formation, which can cause boiler downtime. Hence, the minimization of flue dust and its accretions is an important operational goal. In this study, a Computational Fluid Dynamics (CFD) model is used to investigate how three different baffle plate designs influence accretion formation over a period of 24h. The predicted dust accretion patterns were compared for all baffle plate modifications, with differences found both in the resulting sedimentation and accretion of dust particles. While the dispersive design led to large, but evenly coated accretion risk zones, a streamlined design minimized their size, but led to locally thick accretion layers. Based on these findings, design recommendations for the baffle plate were derived.

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

Permalink: https://www.hzdr.de/publications/Publ-35032
Publ.-Id: 35032


Numerical modeling of horizontal stratified two-phase flows using the AIAD model

Yan, H.; Zhang, H.; Höhne, T.; Liao, Y.; Lucas, D.; Liu, L.

In nuclear reactor safety research, the countercurrent gas-liquid two-phase flow in the hot leg of a pressurized water reactor (PWR) has attracted considerable attention. Previous work has proven that the algebraic interfacial area density (AIAD) model implemented in ANSYS CFX can effectively capture the gas-liquid interface and avoid the loss of information regarding the interfacial structure, which occurs after phase averaging in the Euler–Euler two-fluid approach. To verify the accuracy of the AIAD module implementation in ANSYS Fluent, the model based on the experimental data from the WENKA facility is validated in this work. The effects of the subgrid wave turbulence model, turbulence damping model, and droplet entrainment model are simultaneously investigated, which have been shown to be important in the previous work with CFX. The results show that the simulations are considerably and significantly deviate from the experiments when the turbulence damping is not considered. The free surface modeling of two-phase flow can be optimized by using the droplet entrainment model. The consistency between the simulation and experimental results is not enhanced after the subgrid wave turbulence model is adopted. Further investigations regarding the implementation of the subgrid wave turbulence model are necessary.

Keywords: AIAD; CFD; droplet entrainment; subgrid wave turbulence; thermal hydraulics; turbulence damping

Permalink: https://www.hzdr.de/publications/Publ-35031
Publ.-Id: 35031


Understanding structure–properties relationships of porphyrin linked to graphene oxide through π–π-stacking or covalent amide bonds

Lewandowska-Andralojc, A.; Gacka, E.; Pedzinski, T.; Burdzinski, G.; Lindner, A. A.; O’Brien, J. M.; Senge, M. O.; Siklitskaya, A.; Kubas, A. G.; Marciniak, B.; Walkowiak-Kulikowska, J.

Two graphene oxide nanoassemblies using 5-(4-(aminophenyl)-10,15,20-triphenylporphyrin
(TPPNH2) were fabricated by two synthetic methods: covalent (GO-CONHTPP) and noncovalent
bonding. GO-CONHTPP was achieved through amide formation at the periphery of GO sheets and the
hybrid material was fully characterized by FTIR, XPS, Raman spectroscopy, and SEM. Spectroscopic
measurements together with theoretical calculations demonstrated that assembling TPPNH2
on the GO surface in DMF-H2O (1:2, v/v) via non-covalent interactions causes changes in the absorption
spectra of porphyrin, as well as efficient quenching of its emission. Interestingly, covalent binding
to GO does not affect notably neither the porphyrin absorption nor its fluorescence. Theoretical
calculations indicates that close proximity and π–π-stacking of the porphyrin molecule with the GO
sheet is possible only for the non-covalent functionalization. Femtosecond pump–probe experiments
revealed that only the non-covalent assembly of TPPNH2 and GO enhances the efficiency of the
photoinduced electron transfer from porphyrin to GO. In contrast to the non-covalent hybrid,
the covalent GO-CONHTPP material can generate singlet oxygen with quantum yields efficiency
(ΦΔ = 0.20) comparable to that of free TPPNH2 (ΦΔ = 0.26), indicating the possible use of covalent
hybrid materials in photodynamic/photothermal therapy. The spectroscopic studies combined with
detailed quantum-chemical analysis provide invaluable information that can guide the fabrication of
hybrid materials with desired properties for specific applications.

Keywords: porphyrin; graphene oxide; photochemistry

Permalink: https://www.hzdr.de/publications/Publ-35030
Publ.-Id: 35030


Ressourceneffizienzsteigerung in der Metallindustrie - Substitution von Primärrohstoffen durch optimiertes legierungsspezifisches Recycling

Raatz, S.; Seidel, P.; Tuma, A.; Thorenz, A.; Helbig, C.; Reller, A.; Faulstich, M.; Joachimsthaler, C.; Steger, S.; Hagedorn, W.; Bickel, M.; Liedtke, C.

Das durch das Umweltbundesamt geförderte Projekt befasst sich mit der Ressourceneffizienz-
steigerung in der Metallindustrie in Hinblick auf die Substitution von Primärrohstoffen, die im
Recyclingprozess zur Verdünnung unerwünschter Begleitelemente beim Recycling eine wesent-
liche Rolle spielen. Das damit einhergehend Downcycling soll mittels innovativer Sortiertechni-
ken (Kamera-/Sensorsysteme) vermindert und der Recyclingprozess von metallischen Legie-
rungen durch eine höhere Trennschärfe deutlich verbessert werden.
Der Fokus der Untersuchungen liegt in diesem Projekt auf der Untersuchung eines legierungs-
spezifischen Recyclings von Stahl-, Aluminium-, Kupfer- und Zinkschrotten. Hier soll der Ver-
gleich verschiedener Schrottfraktionen vor bzw. nach innovativen Analyse- bzw. Sortier- und Se-
parier-Prozessen neue Erkenntnisse liefern. Darüber hinaus werden definitorische Grundlagen
sowie Steuerungsgrößen für Up- und Downcycling und Regeln für sortenarmes Design erarbei-
tet.
Auf Grundlage der Analyseergebnisse werden politische Empfehlungen zur besseren Erschlie-
ßung bisher nicht genutzter, hochwertiger Metallpotenziale erarbeitet. Zu den Bewertungsmaß-
stäben gehören die Einsparpotenziale von primären Rohstoffen und damit Treibhausgasemissio-
nen sowie die Kostenstruktur für die Herstellung von möglichst hochwertigen Legierungen aus
Rezyklaten.
Eine erfolgreiche, das heißt mit minimalen Downcycling-Prozessen „belastete“ Bereitstellung
von sekundären Rohstoffen erfordert eine umfassende Wissensbasis über die wissenschaftli-
chen Hintergründe von Downcycling, bestehende Recyclingstrukturen und verwendete Sortier-
techniken, technologische Potenziale, metallurgische Prozesssimulationen und Bewertungsan-
sätzen von Recyclingprozessen, die im Rahmen dieses Projektes entwickelt und genutzt werden.

Keywords: Metallwirtschaft; OptiMet; Ressourceneffizienz; Downcycling; Sortierung; Recycling; Legierung; Sortiertechnologien; LIBS; XRT; XRF; NAA

  • Open Access Logo Other report
    06844 Dessau-Roßlau: Umweltbundesamt, 2022
    354 Seiten

Permalink: https://www.hzdr.de/publications/Publ-35029
Publ.-Id: 35029


A terminology for downcycling

Raatz, S.; Huether, J.; Joachimsthaler, C.; Lehmann, C.; Helbig, C.; Thorenz, A.; Faulstich, M.; Tuma, A.

The term downcycling is often used anecdotally to describe imperfections in recycling. However, it is rarely defined. Here, we identify six meanings of the term downcycling as used in scientific articles and reports. These encompass the material quality of reprocessed materials, target applications, product value, alloying element losses, material systems, and additional primary production. In a proposal for harmonized and more specific terminology, we define downcycling as the phenomenon of quality reduction of materials reprocessed from waste relative to their original quality. We further identify that the reduced quality can express itself thermodynamically, functionally, and economically, covering all perspectives on downcycling. Dilution, contamination, reduced demand for recycled materials, and design-related issues can cause those downcycling effects. We anticipate that this more precise terminology can help quantify downcycling, keep materials in the loop longer, use materials more often and at higher quality, and therefore assist in reducing material-related environmental impacts.

Keywords: circular economy; downcycling; downgrading; industrial ecology; recycling; waste

Permalink: https://www.hzdr.de/publications/Publ-35028
Publ.-Id: 35028


Electrical Conductivity of Iron in Earth’s Core from Microscopic Ohm’s Law (SCCS 22)

Lokamani, M.; Vorberger, J.; Cangi, A.; Baczewski, A.; Ramakrishna, K.

Understanding the electronic transport properties of iron under high temperatures and pressures is essential for constraining geophysical processes. The difficulty of reliably measuring these properties under for sophisticated theoretical methods that can support diagnostics. We present results of the electrical conductivity from simulating microscopic Ohm’s law using time-dependent density functional theory.

Keywords: TDDFT; Matter under Extreme Conditions; Computational Physics; Ab-initio methods

  • Lecture (Conference)
    Strongly Coupled Coulomb Systems (SCCS) 2022, 25.07.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35027
Publ.-Id: 35027


Steps towards Reliable Data - Basic Tools and Concepts

Pospiech, S.

Uncertainties in geochemical data can have many different sources. The previous workshop sections focused on the definitions of data reliability, uncertainties and errors, and how these can be calculated. In this part of the workshop, we will discuss how (hidden) uncertainties in data and errors in geochemical analyses can be detected during data handling, what measures help to minimize uncertainties and errors, and how to deal with the errors that arise to obtain data with high reliability. Simple but effective tools will be presented using a sample snow data set.

Keywords: workshop; geoanalsysis 2022; uncertainty; data reliability; snow

  • Lecture (Conference)
    Geoanalysis 2022, 06.-12.08.2022, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35026
Publ.-Id: 35026


Cosmic nucleosynthesis: A multi-messenger challenge

Diehl, R.; Korn, A. J.; Leibundgut, B.; Lugaro, M.; Wallner, A.

The origins of the elements and isotopes of cosmic material is a critical aspect of understanding the evolution of the universe. Nucleosynthesis typically requires physical conditions of high temperatures and densities. These are found in the Big Bang, in the interiors of stars, and in explosions with their compressional shocks and high neutrino and neutron fluxes. Many different tools are available to disentangle the composition of cosmic matter, in material of extraterrestrial origins such as cosmic rays, meteorites, stardust grains, lunar and terrestrial sediments, and through astronomical observations across the electromagnetic spectrum. Understanding cosmic abundances and their evolution requires combining such measurements with approaches of astrophysical, nuclear theories and laboratory experiments, and exploiting additional cosmic messengers, such as neutrinos and gravitational waves. Recent years have seen significant progress in almost all these fields; they are presented in this review.

The Sun and the solar system are our reference system for abundances of elements and isotopes. Many direct and indirect methods are employed to establish a refined abundance record from the time when the Sun and the Earth were formed. Indications for nucleosynthesis in the local environment when the Sun was formed are derived from meteoritic material and inclusion of radioactive atoms in deep-sea sediments. Spectroscopy at many wavelengths and the neutrino flux from the hydrogen fusion processes in the Sun have established a refined model of how the nuclear energy production shapes stars. Models are required to explore nuclear fusion of heavier elements. These stellar evolution calculations have been confirmed by observations of nucleosynthesis products in the ejecta of stars and supernovae, as captured by stardust grains and by characteristic lines in spectra seen from these objects. One of the successes has been to directly observe
rays from radioactive material synthesised in stellar explosions, which fully support the astrophysical models. Another has been the observation of radioactive afterglow and characteristic heavy-element spectrum from a neutron-star merger, confirming the neutron rich environments encountered in such rare explosions. The ejecta material captured by Earth over millions of years in sediments and identified through characteristic radio-isotopes suggests that nearby nucleosynthesis occurred in recent history, with further indications for sites of specific nucleosynthesis. Together with stardust and diffuse gamma-rays from radioactive ejecta, these help to piece together how cosmic materials are transported in interstellar space and re-cycled into and between generations of stars. Our description of cosmic compositional evolution needs such observational support, as it rests on several assumptions that appear challenged by recent recognition of violent events being common during evolution of a galaxy. This overview presents the flow of cosmic matter and the various sites of nucleosynthesis, as understood from combining many techniques and observations, towards the current knowledge of how the universe is enriched with elements.

Keywords: Nuclear Astrophysics; Nucleosynthesis; Stars; Supernovae; Interstellar medium; Stardust; accelerator mass spectrometry

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Permalink: https://www.hzdr.de/publications/Publ-35025
Publ.-Id: 35025


The recovery effects of electron-beam pulse treatment in Sn implanted Ge

Werner, Z.; Barlak, M.; Ratajaczak, R.; Kentsch, U.; Heller, R.; Munnik, F.; Konarski, P.; Dłużewski, P.; Pisarek, M.; Kozłowski, M.; Ażgin, J.; Zagórski, J.; Staszkiewicz, B.

The paper describes the recovery effects of pulsed electron beam treatment in Ge single crystals implanted with various doses of Sn ions at room and low temperatures. A protective coat of 100 nm Sn was applied as a sacrificial layer. The implanted layers were studied by RBS/cRBS (Rutherford BackScattering/channeled Rutherford BackScattering) method, SIMS (Secondary Ion Mass Spectrometry) and TEM (Transmission Electron Microscopy). Defects revealed in channelled RBS spectra were analysed by McChasy code. The results show that the Sn concentration attains 1% and more with very good substitutionality. They also reveal excellent lattice recovery after e-beam melting. Suggestions are derived as regards further improvement of pulsed e-beam technique.

Keywords: Germanium; Sn implantation; pulsed e-beam treatments; RBS/cRBS study; TEM and DLTS measurements

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Permalink: https://www.hzdr.de/publications/Publ-35024
Publ.-Id: 35024


Non-van der Waals quasi-2D materials; recent advances in synthesis, emergent properties and applications

Balan, A. P.; Puthirath, A. B.; Roy, S.; Costin, G.; Oliveira, E. F.; Saadi, M. A. S. R.; Sreepal, V.; Friedrich, R.; Serles, P.; Biswas, A.; Iyengar, S. A.; Chakingal, N.; Bhattacharyya, S.; Saju, S. K.; Pardo, S. C.; Sassi, L. M.; Filleter, T.; Krasheninnikov, A.; Galvao, D. S.; Vajtai, R.; Nair, R. R.; Ajayan, P. M.

The discovery of novel materials that are stable at ambient conditions with emergent functionalities is a pressing need of the
21st century to keep the pace of social and technological advancement in a sustainable manner. Nanotechnology and
nanomaterials are one of this kind and the current era has already witnessed several groundbreaking discoveries of
materials and disruptive technological advancements. Starting from 0D fullerene, the invention of 1D carbon nanotubes, and
most recently 2D graphene, all are allotropes of carbon, have brought a lot of research opportunities to understand different
physical and chemical phenomena at atomic and molecular scales and to convert such properties into useful applications.
Among them, 2D materials find special attention due to unique properties such as ballistic carrier transport, immunity from
substrate effects and commendable in plane mechanical robustness. However, the library of such materials is limited, and
one can see that most of the technically viable materials that are already industrialized in a large scale belong to the class of
non-van der Waals materials. The effect of confinement in one dimension on non-van der Waals materials remains
unexplored owing to the difficulty in fabricating these materials to the ultra-thin limit with large lateral size or area. Recent
advancement of cleaving non-van der Waals bulk materials to their ultra-thin counter parts through the state-of-the-art liquid
phase exfoliation approach leads to renewed research interest among scientific community. The existence of
cleaving/parting planes in certain directions of non-van der Waals materials, where the bonding strength is relatively weak
compared to other crystallographic directions of the bulk crystal, facilitate smooth exfoliation when subjected to shear force
through suitable methods. Herein, we attempt to discuss the rationale of such methods in the synthesis of non-van der
Waals 2D materials that possess cleavage/parting planes with a special attention to natural ores, and to review the recent
progress made in non-van der Waals two-dimensional materials with a special emphasis on emergent magnetism, catalysis,
energy storage, and optoelectronics and related applications.

Keywords: 2D magnetism; 2D materials; Catalysis; Non-van der Waals materials; Photodetectors; Tribology

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Permalink: https://www.hzdr.de/publications/Publ-35023
Publ.-Id: 35023


Experimental Study on Inter-Bubble Distances in Dense Bubbly Flows

Kipping, R.; Hampel, U.

The design of bubble column reactors require a comprehensive understanding of the fluid dynamics. The type of gas distributor has a main impact on bubble size distribution and flow regime. With increasing gas flow rate, the interaction of the bubble increases and the dispersion of the bubbles changes. Although these effects play an important role also on the mass transfer in bubble columns, the distance parameters of bubbles in dense swarms has been poorly investigated so far.

This contribution presents an experimental study carried out with ultrafast X-ray CT (UFXCT) on a dense bubbly flow. Experiments were conducted in a bubble column of 10 cm inner diameter and for gas superficial velocities up to 3.5 cms-1. UFXCT allows for non-invasive plane measurement of the phase distribution at different scanning heights of the column. Based on the extracted coordinates of the bubble centers the distances of nearest neighbors of all bubbles were computed. In addition, pair correlation function has been applied to reveal information on the near order of bubbles. The Sauter Mean Diameter was found to have a remarkable influence on the clustering characteristics and the near order of the bubbles.

  • Lecture (Conference) (Online presentation)
    15th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-15), 07.-10.08.2022, Ottawa, Canada

Permalink: https://www.hzdr.de/publications/Publ-35022
Publ.-Id: 35022


Tailored engineering of crystalline surface enabled by ion-irradiation-assisted femtosecond laser ablation

Ren, Y.; Wang, C.; Cui, Z.; Liu, H.; Han, X.; Liu, P.; Akhmadaliev, S.; Zhou, S.; Cai, Y.

Ion irradiation and femtosecond laser ablation (FLA) are powerful technologies for micro-/nano-machining of transparent materials. In this work, we demonstrate selective surface engineering of optical crystal surface via ion irradiation and subsequent FLA, namely ion-irradiation-assisted FLA. Based on the material modification effects in the ion-irradiated layers, different types of surface structuring characterized by grooves, nanogratings or sub-micron tracks are selectively induced by FLA. It is revealed that the ion-electron interaction induced localized lattice defects and related property modulation in target crystal play important roles in the formation and evolution of laser ablation regimes. Furthermore, the formation process of high-spatial-frequency nanograting is illustrated with the periodical enhancement of local field through the excitation of surface plasmon polaritons, which is experimentally supported through the measurements of transmission electron microscope and energy-dispersive spectroscopy. Our findings further clarify the ion- and laser-matter interactions and the correlation between these processes and surface modifications. The approach proposed in this work shows potential applications in the rapid fabrication of hybrid and versatile surface structures on crystalline materials.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35021
Publ.-Id: 35021


Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning

Pang, C.; Li, R.; Dong, H.; Saggau, C. N.; Kern, F. L.; Potapov, P.; Schultz, J.; Lubk, A.; Hübner, R.; Kentsch, U.; Zhou, S.; Helm, M.; Chen, F.; Ma, L.; Schmidt, O. G.

The combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane-formed whispering-gallery-mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.

Keywords: ion implantation; microtube cavity; nanomembrane; plasmonic nanoparticles; resonant mode tuning

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Permalink: https://www.hzdr.de/publications/Publ-35020
Publ.-Id: 35020


Magnetic patterning using Ne, Co, and Dy FIB

Lenz, K.; Pablo-Navarro, J.; Klingner, N.; Hlawacek, G.; Samad, F.; Narkovic, R.; Hübner, R.; Kakay, A.; Canzever, H.; Pilz, W.; Meyer, F.; Mazarov, P.; Bischoff, L.; Bali, R.; Lindner, J.

Magnetic nanostructures needed for magnonics and spintronics are usually processed by conventional lithography techniques in combination with lift-off or broad-beam ion etching. However, it has been shown [1] that the quality and shape of the structures’ edges play an important role for the magnetization dynamics as structures become smaller and smaller. Furthermore, regarding optical measurement techniques, hard-to-remove resist masks that become hardened by ion etching are problematic. Direct-writing focused ion beams (FIB) do not have these issues. In addition, using non-standard ion species opens various paths for local magnetic patterning, i.e., influencing the magnetic properties locally.
I will present results for maskless magnetic patterning of ferromagnetic nanostructures using He and Ne ions as well as a few liquid metal alloy ion sources (LMAIS) for FIB systems. He/Ne FIBs are well established and commercially available. Irradiation of (paramagnetic) FeAl films by Ne ions creates local ferromagnetic nanostructures caused by disorder that are embedded in a paramagnetic matrix [2]. The precise Ne FIB also enables us to trim the edges of magnetic nanostructures enhancing their magnetic fidelity and creating certain localized magnon states at the edges of the samples. Using specifically developed LMAIS, like e.g., Co36Nd64, CoDy, or CuDy [3,4] in combination with a Wien mass filter offers further new paths for magnetic patterning. I will present results on the modification of Ni80Fe20 (permalloy) strip samples. Using the CoNd LMAIS a narrow track of Co ions was implanted. The induced magnetic changes were measured with microresonator ferromagnetic resonance (FMR) before and after the implantation. Structures as small as 30 nm can be implanted up to a concentration of 10 % near the surface. Such lateral resolution is hard to reach for other lithographic methods. Using Dy ions one can locally increase the Gilbert damping parameter of the magnetization dynamics by more than a factor of four with a lateral resolution of about 100 nm.

Keywords: FIB; ferromagnetic resonance; nanostructuring; ferromagnetism

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  • Invited lecture (Conferences)
    5. European FIB Network Workshop 2022, 31.08.-02.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35019
Publ.-Id: 35019


Application of a Microfabricated Microwave Resonator in a Co-Pd–Based Magnetic Hydrogen-Gas Sensor

Schefer, T. A.; Narkovic, R.; Lenz, K.; Ganss, F.; Roberts, M. P.; Hellwig, O.; Martyniuk, M.; Lindner, J.; Kostylev, M.

We investigate the ferromagnetic resonance (FMR) response of microfabricated microwave resonators loaded with small Co16Pd84 alloy rectangles. A major increase in the FMR signal-to-noise ratio is achieved by employing the microwave-resonator structure. A FMR peak shift similar to that of Co16Pd84 continuous films is measured in the presence of hydrogen gas in the sample environment. We show that the very high sensitivity of the FMR signal of the Co16Pd84 alloy rectangle to hydrogen exposure can be used to measure relatively small hydrogen-concentration steps near 100% H2. Additionally, we also demonstrate that this structure can measure hydrogen over a concentration range from 3% to 100% H2 in N2. In time-dependent FMR measurements, we discover a temperature dependence of the FMR signal, which we relate to intrinsic temperature-dependent changes in saturation magnetization and the magnetic anisotropy of the Co-Pd alloy.

Keywords: hydrogen sensors; ferromagnetic resonance; CoPd alloys; Nanostructures; gas sensors

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35018
Publ.-Id: 35018


Control and tunability of magnetic bubble states in multilayers with strong perpendicular magnetic anisotropy at ambient conditions

Salikhov, R.; Samad, F.; Arekapudi, S. S. P. K.; Ehrler, R.; Lindner, J.; Kiselev, N. S.; Hellwig, O.

The reversal of magnetic bubble helicity through topologically trivial transient states provides an additional
degree of freedom that promises the development of multidimensional magnetic memories. A key requirement
for this concept is the stabilization of bubble states at ambient conditions on application-compatible substrates.
In the present work, we demonstrate a stabilization routine for remanent bubble states in high perpendicular magnetic anisotropy [Co(0.44 nm)/Pt(0.7 nm)]X , X = 48, 100, and 150 multilayers on Si/SiO2 substrates by exploring the effect of external magnetic fields (Hm) of different strength and angles (θ) with respect to the film surface normal. By systematic variation of these two parameters, we demonstrate that remanent bubble density and mean bubble diameter can be carefully tuned and optimized for each sample. Our protocol based on magnetometry only reveals the densest remanent bubble states at Hm = 0.87Hs (Hs is the magnetic saturation field) and θ = 60◦–75◦ for all X with a maximum of 3700 domains/100 μm2 for the X = 48 sample. The experimental observations are supported by micromagnetic simulations, taking into account the nanoscale lateral grain structure of multilayers synthesized by magnetron sputter deposition, and thus helping to understand the different densities of the bubble states found in these systems.

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Permalink: https://www.hzdr.de/publications/Publ-35017
Publ.-Id: 35017


LDOS/SNAP data for MALA: Beryllium at 298K

Fiedler, L.; Cangi, A.

Beryllium data set for Machine Learning applications

This dataset contains DFT inputs, outputs, LDOS data and fingerprint vectors for a beryllium cell at ambient conditions and varying sizes. Different levels of k-grid convergence were employed:
-  Gamma point (gamma_point)
-  total energy convergence (k-grid converged to 1meV/atom to total energy difference, total_energy_convergence)
-  LDOS convergence (k-grid converged to LDOS without unphyiscal oscillations, ldos_convergence)

The data set contains a .zip file for each system size (see below), as well as one .zip file containing sample scripts for recalculation and preprocessing of data.
The cutoff energy was converged with respect to the energy convergence and held fixed 40Ry for all three levels of k-grids. Note that not for all sizes of unit cells data for all types of k-grid were generated.

Authors:

- Fiedler, Lenz (HZDR / CASUS)
- Cangi, Attila (HZDR / CASUS)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf

CASUS - Center for Advanced Systems Understanding

Dataset description

- Total size: 143G GB 
- System: Be128, Be256, Be512, Be1024, Be2048
- Temperature(s): 298K
- Mass density(ies): 1.896 gcc
- Crystal Structure: hpc (material mp-87 in the materials project)
- Number of atomic snapshots: 145
    - 40 (Be128)
    - 35 (Be256)
   - 30 (Be512)
   - 20 (Be1024)
   - 10 (Be2048)
- Contents:
   - ideal crystal structure: yes
    - MD trajectory: yes
    - Atomic positions: yes
   - DFT inputs: yes
    - DFT outputs (energies): yes
    - SNAP vectors: yes (partially, see below)
        - dimensions: XxYxZx94 (last dimension: first three entries are x,y,z coordinates, data size is 91), where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 447MB)
         - Be256: 144x72x120  (size per file: 893MB)
         - Be512: 144x144x120 (size per file: 1.8GB)
        - units: a.u./Bohr
    - LDOS vectors: yes (partially, see below)
        - dimensions: XxYxZx250, where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 1.2GB)
         - Be256: 144x72x120  (size per file: 2.4GB)
         - Be512: 144x144x120 (size per file: 4.7GB)
        - units: 1/eV
      - note: LDOS parameters are the same for all sizes of the unit cell
    - trained networks: no

Data generation

Ideal crystal structures were obtained using the Materials Project. (https://materialsproject.org/materials/mp-87/)
DFT-MD calculations were performed using either QuantumESPRESSO (https://www.quantum-espresso.org/, QE, for Be128, Be256 and Be512) or the Vienna Ab initio Simulation Package (https://www.vasp.at/, VASP, for Be1024, Be2048). DFT calculations were performed using QuantumESPRESSO. 
For the VASP calculations, the standard VASP pseudopotentials were used. For Quantum Espresso, pslibrary was used (https://dalcorso.github.io/pslibrary/).
SNAP vectors were calculated using MALA (https://github.com/mala-project/mala) and its LAMMPS (https://github.com/mala-project/mala) interface. The LDOS was preprocessed using MALA as well.

Dataset structure

The folder called "sample_inputs" is provided to show how MALA preprocessing and LDOS calculation have been performed. 
For each temperature/mass density/number of atoms, the following subfolders exist:

- md_inputs: Input files for the MD simulations, either as QE or VASP file(s)
- md_outputs: The MD trajectory plus a numpy array containing the temperatures at the individual time steps
- gamma_point
- total_energy_convergence
- ldos_convergence

Each gamma_point/total_energy_convergence/ldos_convergence contains the following folders:

- ldos: holds the LDOS vectors
- fingerprints: holds the SNAP fingerprint vectors
- snapshots: holds the atomic positions of the atomic snapshots for which DFT and LDOS calculations were performed (as .xyz files)
- dft_outputs: holds the outputs from the DFT calculations, i.e. energies in the form of a QE output file
- dft_inputs: holds the inputs for the DFT calculations, in the form of a QE input file

Please note that the numbering of the snapshots is contiguous per temperature/mass density/number of atoms, NOT within the k-grids themselves. 
Also, LDOS and fingerprint files have only been calculated for snapshots in the ldos_convergence 
folders. Therefore, no LDOS and fingerprint files have been calculated for the 1024 anf 2048 atom systems.

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Permalink: https://www.hzdr.de/publications/Publ-35016
Publ.-Id: 35016


Immunohistochemical analyses of paraffin-embedded sections after primary surgery or trimodality treatment in esophageal carcinoma

Igbo, B. T.; Linge, A.; Frosch, S.; Suckert, T.; Stolz-Kieslich, L.; Löck, S.; Sankari Kumaravadivel, M.; Welsch, T.; Weitz, J.; Sommer, U.; Aust, D.; Troost, E. G. C.

Background: The microscopic tumor extension before, during or after radiochemotherapy (RCHT) and its correlation with the tumor microenvironment
(TME) are presently unknown. This information is, however, crucial in the era of image-guided, adaptive high-precision photon or particle therapy.
Materials and methods: In this pilot study, we analyzed formalin-fixed paraffin-embedded (FFPE) tumor resection specimen from patients with histologically
confirmed squamous cell carcinoma (SCC; n=10) or adenocarcinoma (A; n=10) of the esophagus, having undergone neoadjuvant radiochemotherapy followed by resection (NRCHT+R) or resection (R)]. FFPE tissue sections were analyzed by immunohistochemistry regarding tumor hypoxia (HIF-1α), proliferation (Ki67), immune status (PD1), cancer cell stemness (CXCR4), and p53 mutation status. Marker expression in HIF-1α subvolumes was part of a sub-analysis. Statistical analyses were performed using one-sided Mann-Whitney tests and Bland-Altman analysis.
Results: In both SCC and AC patients, the overall percentages of positive tumor cells among the five TME markers, namely HIF-1α, Ki67, p53, CXCR4 and PD1 after NRCHT+ R were lower than in the R cohort. However, only PD1 in SCC and Ki67 in AC showed significant association (Ki67: p=0.03, PD1: p=0.02). In the sub-analysis of hypoxic subvolumes among the AC patients, the percentage of positive tumor cells within hypoxic regions were statistically significantly lower in the NRCHT+R than in the R cohort across all the markers except for PD1.
Conclusion: In this pilot study, we showed changes in the TME induced by NRCHT in both SCC and AC. These findings will be correlated with microscopic tumor extension measurements in a subsequent cohort of patients.

Keywords: Tumor microenvironment; esophageal cancer; microscopic tumor extension; radiochemotherapy; whole slide image analysis

Permalink: https://www.hzdr.de/publications/Publ-35015
Publ.-Id: 35015


Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon

Jiang, H.; Wang, M.; Fu, J.; Li, Z.; Shaikh, M. S.; Li, Y.; Nie, C.; Sun, F.; Tang, L.; Yang, J.; Qin, T.; Zhou, D.; Shen, J.; Sun, J.; Feng, S.; Zhu, M.; Kentsch, U.; Zhou, S.; Shi, H.; Wei, X.

Highly sensitive short-wave infrared (SWIR) detectors, compatible with the silicon-based complementary metal oxide semiconductor (CMOS) process, are regarded as the key enabling components in the miniaturized system for weak signal detection. To date, the high photogain devices are greatly limited by a large bias voltage, low-temperature refrigeration, narrow response band, and complex fabrication processes. Here, we demonstrate high photogain detectors working in the SWIR region at room temperature, which use graphene for charge transport and Te-hyperdoped silicon (Te–Si) for infrared absorption. The prolonged lifetime of carriers, combined with the built-in potential generated at the interface between the graphene and the Te–Si, leads to an ultrahigh photogain of 109 at room temperature (300 K) for 1.55 μm light. The gain can be improved to 1012, accompanied by a noise equivalent power (NEP) of 0.08 pW Hz–1/2 at 80 K. Moreover, the proposed device exhibits a NEP of 4.36 pW Hz–1/2 at 300 K at the wavelength of 2.7 μm, which is exceeding the working region of InGaAs detectors. This research shows that graphene can be used as an efficient platform for silicon-based SWIR detection and provides a strategy for the low-power, uncooled, high-gain infrared detectors compatible with the CMOS process.

Keywords: short-wave infrared detector; lifetime; built-in potential; photogain; graphene; Te-hyperdoped Si

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Permalink: https://www.hzdr.de/publications/Publ-35014
Publ.-Id: 35014


HELIPORT and MLOps

Knodel, O.; Voigt, M.; Pape, D.; Lokamani, M.; Kelling, J.; Müller, S.; Gruber, T.; Juckeland, G.; Kessler, A.; Hein, J.; Schuller, B.

The talk introduces the use of HELIPORT for MLOps and introduces the general idea behind the HELIPORT project, which aims to make the entire life cycle of a scientific experiment or project discoverable, accessible, interoperable and reusable by providing an overview from a top-level perspective.

Keywords: Data Management; Metadata; FAIR; Data provenance; Digital Objects; MLOps; Machine Learning

  • Open Access Logo Lecture (others) (Online presentation)
    Optima WP7 Meeting, 10.08.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-35013
Publ.-Id: 35013


Epigenetic drugs in somatostatin type 2 receptor radionuclide theranostics and radiation transcriptomics in mouse pheochromocytoma models

Ullrich, M.; Richter, S.; Liers, J.; Drukewitz, S.; Friedemann, M.; Kotzerke, J.; Ziegler, C. G.; Nölting, S.; Kopka, K.; Pietzsch, J.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are catecholamine-producing tumors. In inoperable and metastatic cases, somatostatin type 2 receptor (SSTR2) expression allows for peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE. Insufficient receptor levels, however, limit treatment efficacy. This study evaluates whether the epigenetic drugs valproic acid (VPA) and 5-Aza-2'-deoxycytidine (DAC) modulate SSTR2 levels and sensitivity to [177Lu]Lu-DOTA-TATE in two mouse PCC models (MPC and MTT). Methods: Drug-effects on Sstr2/SSTR2 were investigated in terms of promoter methylation, mRNA and protein levels, and radiotracer binding. Radiotracer uptake was measured in subcutaneous allografts in mice using PET and SPECT imaging. Tumor growth and gene expression (RNAseq) were characterized after drug treatments. Results: DAC alone and in combination with VPA increased SSTR2 levels along with radiotracer uptake in vitro in MPC (high-SSTR2) and MTT cells (low-SSTR2). MTT but not MPC allografts responded to DAC and VPA combination with significantly elevated radiotracer uptake, although activity concentrations remained far below those in MPC tumors. In both models, combination of DAC, VPA and [177Lu]Lu-DOTA-TATE was associated with additive effects on tumor growth and specific transcriptional responses in gene sets involved in cancer and treatment resistance. Effects of epigenetic drugs were unrelated to CpG island methylation of the Sstr2 promoter. Conclusion: This study demonstrates that SSTR2 induction in mouse pheochromocytoma models has some therapeutic benefit that occurs via yet unknown mechanisms. Transcriptional changes in tumor allografts associated with epigenetic treatment and [177Lu]Lu-DOTA-TATE provide first insights into genetic responses of PCCs/PGLs, potentially useful for developing additional strategies to prevent tumor recurrence.

Keywords: decitabine; neuroendocrine tumors; radiation biology; small animal multimodal imaging; valproic acid

Permalink: https://www.hzdr.de/publications/Publ-35012
Publ.-Id: 35012


Data publication: Time-of-Flight spectroscopy for laser-driven proton beam monitoring

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Karsch, L.; Kraft, S.; Kroll, F.; Löser, M.; Nossula, A.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

This dataset contains the raw and evaluated data of the paper plus the script for plotting the results.

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Permalink: https://www.hzdr.de/publications/Publ-35011
Publ.-Id: 35011


The impact of Mn nonstoichiometry on the oxygen mass transport properties of La0.8Sr0.2MnyO3±δ thin films

Chiabrera, F.; Baiutti, F.; Börgers, J. M.; Harrington, G. F.; Yedra, L.; Liedke, M. O.; Kler, J.; Nandi, P.; de Dios Sirvent, J.; Santiso, J.; López-Haro, M.; Calvino, J. J.; Estradé, S.; Butterling, M.; Wagner, A.; Peiró, F.; de Souza, R. A.; Tarancón, A.

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry (IEDP-SIMS) to study oxygen mass transport and the defect compensation mechanism of Mn-deficient La0.8Sr0.2MnyO3±δ epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modelling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La_Mn^× antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties.

Keywords: LSM; perovskite oxides; cation nonstoichiometry; antisite defects

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Permalink: https://www.hzdr.de/publications/Publ-35008
Publ.-Id: 35008


Time-of-Flight spectroscopy for laser-driven proton beam monitoring

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Karsch, L.; Kraft, S.; Kroll, F.; Löser, M.; Nossula, A.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Application experiments with laser plasma-based accelerators (LPA) for protons have to cope with the inherent fluctuations of the proton source. This creates a demand for non-destructive and online spectral characterization of the proton pulses, which are for application experiments mostly spectrally filtered and transported by a beamline. Here, we present a scintillator-based time-of-flight (ToF) beam monitoring system (BMS) for the recording of single-pulse proton energy spectra. The setup’s capabilities are showcased by characterizing the spectral stability for the transport of LPA protons for two beamline application cases. For the two beamline settings monitored data of 122 and 144 proton pulses collected over multiple days were evaluated, respectively. A relative energy uncertainty of 5.5 % (1σ) is reached for the ToF BMS, allowing for a Monte-Carlo based prediction of depth dose distributions, also used for the calibration of the device. Finally, online spectral monitoring combined with the prediction of the corresponding depth dose distribution in the irradiated samples is demonstrated to enhance applicability of plasma sources in dose-critical scenarios.

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Permalink: https://www.hzdr.de/publications/Publ-35006
Publ.-Id: 35006


Synthesis, Structure–Activity Relationships, Radiofluorination, and Biological Evaluation of [18F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET

Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Bormans, G.; Kopka, K.; Brust, P.; Moldovan, R.-P.

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation in various pathological conditions, such as neuroinflammation and cancer. Herein we report on the enantioselective synthesis of a series of highly affine fluorinated indole-2-carboxamide ligands targeting the CB2R in the brain. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity (Ki = 2.1 nM) and pronounced selectivity over CB1R (factor >300). A fully automated copper-mediated radiofluorination of [18F]RM365 was established starting from the corresponding aryl boronic acid pinacol ester precursor. Preliminary in vitro evaluation of [18F]RM365 revealed an unprecedentedly high species differences affinity towards CB2R owing a dissociation constant (KD) of 2.32 nM for the human CB2R (hCB2R) and > 10000 nM for the rat CB2R (rCB2R). Metabolism studies in mice revealed high stability of [18F]RM365 with fractions of parent compound of > 90% in the brain and > 54% in the plasma at 30 min p.i.. PET imaging in a rat model of local hCB2R overexpression demonstrate the ability of [18F]RM365 to reach and selectively label the hCB2R in the brain with high signal-to-background ratio. Thus, [18F]RM365 is a very promising PET radioligand for the imaging of upregulated hCB2R expression under pathological conditions with high potential towards clinical application in humans.

Keywords: cannabinoid receptor type 2; indole-2-carboxamide; binding affinity; radiochemistry; fluorine-18 labeling; positron-emission tomography

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Permalink: https://www.hzdr.de/publications/Publ-35005
Publ.-Id: 35005


Towards the development of a PET radioligand for imaging gliomas bearing mIDH1

Kaur, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Wenzel, B.; Toussaint, M.; Kopka, K.; Moldovan, R.-P.

Introduction
Isocitrate dehydrogenase mutation 1 (mIDH1, IDH1R132H) is commonly reported in gliomas and is proposed as an interesting target for the diagnosis, prognosis and therapy for patients with gliomas. Some preclinical evaluations of 125I- or 18F-labeled mIDH1 ligands are reported for non-invasive imaging of mIDH1-bearing gliomas,1-3 however, to date, no radiotracers for PET imaging of mIDH1 are clinically available owing to hitherto low potency, selectivity and metabolic stability. Herein, the efforts to develop a novel mIDH1 selective PET radiotracer for imaging gliomas with mIDH1 are reported.
Methods
Compound GSK321 bearing the absolute configuration 3-R, 27-S (Fig.1) has been selected as the starting point to develop an 18F-labelled PET radioligand for imaging of mIDH1 due to the high potency (IC50 mIDH1 = 4.6 nM).4 A non-enantioselective synthesis of GSK321 was envisaged to get access to all stereoisomers for biological evaluation. The separation of the four stereoisomers of GSK321 was attempted via isocratic semi-preparative chiral HPLC using a CHIRALPAK IA column (10*250mm, 5µm) and an eluent mixture of ACN/H2O (1/1, v/v) at a flow rate of 3 mL/min. The IC50 values of separated stereoisomers of GSK321 were measured by enzymatic assays for wildtype IDH1 and IDH1R132H coupled to diaphorase. The introduction of the 18F-label into the most potent and selective stereoisomer of GSK321 will be performed via the copper-mediated radiofluorination of the corresponding boronic acid pinacol ester.
Results
The stereoisomeric mixture of GSK321 was synthesized from N-boc-protected piperidone with an overall yield of 22 % over seven steps. In a first attempt to separate the stereoisomers by semi-preparative chiral HPLC, only one enantiomeric pair [(3-R,27-S)- and (3-S,27-R)-GSK321)]was obtained in pure form which was further characterized by NMR spectroscopy. For the isolation of other enantiomeric pair [(3-R,27-S)- and (3-S,27-R)-GSK321], further chiral HPLC methods will be tested in the future. For (3-R,27-S)-GSK321, IC50 values of 6.5 and 477 nM were determined towards mIDH1 and wildtype IDH respectively. The opposite enantiomer, (3-S,27-R)-GSK321 inhibits mIDH1 with an IC50 of 242 nM.
Conclusions
Compound (3-R,27-S)-GSK321 proved as a suitable candidate for the development of an 18F-labeled radioligand for imaging of mIDH1 in glioma with PET. In the next steps, an enantioselective synthesis will be performed to give easy access to substantial amounts of (3-R,27-S)-GSK321 and the enantiomerically pure precursor for radiofluorination.

Keywords: mIDH1; radiofluorination; GSK321; PET (Positron Emission Tomography)

  • Lecture (Conference)
    MoBi 2022 - 5th GyMIC Molecular Imaging Symposium, 15.-16.09.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35004
Publ.-Id: 35004


Experimental investigation of fluid dynamics during gas-liquid swirl separation for a wide working range using a swirl element

Condriuc, I.; Kipping, R.; Schleicher, E.; Hampel, U.

The cost-effective production of large amounts of green hydrogen using a new generation of proton exchange membrane (PEM) electrolyzers generates very high gas fractions, resulting from the high current densities. Hence, the shift of operating membrane conditions in the anode circuit into new and hitherto incomprehensible areas occurs. The mass fraction of oxygen prevails over the mass fraction of hydrogen by a factor of 8. Thus, the space and material requirements for conventional separators are very high. The main goal for the separation process of oxygen from the two-phase flow mixture is a completely gas-free operation fluid before the water enters the heat exchanger. This requires the optimization of oxygen separation technologies. For this purpose, a vertically arranged separator on the pilot scale was built up at Helmholtz -Zentrum Dresden – Rossendorf, which is based on the principle of swirl separation. This contribution provides results on the experimental study of different types of swirl geometries, which have the main impact on the separation efficiency of the process. Different types of swirl geometries are investigated and the development of the gas core and its stability are analyzed for single and two-phase flow at various flow rates of the gas and the liquid.
Project
The authors acknowledge the financial support by the Federal Ministry of Education and Research of Germany in the programme ”H2GIGA. Project identification number: 03HY123E.

Keywords: gas-liquid separation; swirl separation

  • Lecture (Conference) (Online presentation)
    International Congress on Separation and Purification Technology (ISPT22), 10.-14.12.2022, Live and On-Demand, Live and On-Demand

Permalink: https://www.hzdr.de/publications/Publ-35003
Publ.-Id: 35003


Integration of energy transition and circularity in copper production: A techno-economic and environmental study

Parvez, A. M.; Abadias Llamas, A.

Over the years, energy transition (fossil to renewable) and sustainable economy (from linear to circular) are being regarded as the key approaches to comply and implement the regional and international environmental protocols. Meanwhile, copper demand has been increasing in the past decade and will continuously expand in future. Hence, the objective of this work was to systematically investigate the energy transition-circular economy approach in copper production through optimizing technological, economic, regulatory and societal variables. In particular, the potential of Power-to-X technology in the existing copper production chain was investigated, with a particular focus on copper recycling. The HSC Chemistry software was used to model and simulate copper production processes using secondary raw materials (e.g. waste printed circuit boards and copper-containing waste cable). A simulation-based techno-economic and environmental impact assessment was performed to evaluate the integration of the renewable energies into the secondary copper production. The results showed that enhanced sustainability can be achieved through adopting this integration. Finally, challenges associated from flexibility (e.g., fossil to renewable energy) in copper production have been identified and further discussed.

Keywords: Secondary Copper; Energy Transition; Circular Economy; Flexibility

  • Lecture (Conference)
    The COPPER 2022 conference, 13.-17.11.2022, Santiago, Chile

Permalink: https://www.hzdr.de/publications/Publ-35002
Publ.-Id: 35002


hmctFOAM - heat mass concentration transport FOAM

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

This software illustrates the applications of the programming
techniques detailed in the book chapter

Norbert Weber, Tom Weier (2022) Liquid Metal Batteries. In: Steven
Beale, Werner Lehnert (eds.) Electrochemical Cell Calculations with
OpenFOAM. Lecture Notes in Energy 42, pp. 193-212.

The included solver handles the heat and mass transport equations
under the assumption of pure diffusion and with solutal convection.
It is a single region solver that is based on laplacianFoam and
boussinesqPimpleFoam from OpenFOAM 6.

Keywords: liquid metal batteries; OpenFOAM

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Permalink: https://www.hzdr.de/publications/Publ-35001
Publ.-Id: 35001


Aliovalent Ta-Doping-Engineered Oxygen Vacancy Configurations for Ultralow-Voltage Resistive Memory Devices: A DFT-Supported Experimental Study

Barman, A.; Das, D.; Deshmukh, S.; Sarkar, P. K.; Banerjee, D.; Hübner, R.; Gupta, M.; Saini, C. P.; Kumar, S.; Johari, P.; Dhar, S.; Kanjilal, A.

Alteration of transport properties of any material, especially metal oxides, by doping suitable impurities is not straightforward as it may introduce multiple defects like oxygen vacancies (Vo) in the system. It plays a decisive role in controlling the resistive switching (RS) performance of metal oxide-based memory devices. Therefore, a judicious choice of dopants and their atomic concentrations is crucial for achieving an optimum Vo configuration. Here, we show that the rational designing of RS memory devices with cationic dopants (Ta), in particular, Au/Ti1−xTaxO2−δ/Pt devices, is promising for the upcoming non-volatile memory technology. Indeed, a current window of ∼104 is realized at an ultralow voltage as low as 0.25 V with significant retention (∼104 s) and endurance (∼105 cycles) of the device by considering 1.11 at % Ta doping. The obtained device parameters are compared with those in the available literature to establish its excellent performance. Furthermore, using detailed experimental analyses and density functional theory (DFT)-based first-principles calculations, we comprehend that the meticulous presence of Vo configurations and the columnar-like dendritic structures is crucial for achieving ultralow-voltage bipolar RS characteristics. In fact, the dopant-mediated Vo interactions are found to be responsible for the enhancement in local current conduction, as evidenced from the DFT-simulated electron localization function plots, and these, in turn, augment the device performance. Overall, the present study on cationic-dopant-controlled defect engineering could pave a neoteric direction for future energy-efficient oxide memristors.

Keywords: resistive memory; vacancy engineering; ultralow-voltage switching; conducting filaments; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-35000
Publ.-Id: 35000


Data publication: Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography

Kaever, C.; Windisch, D.

Benchmark data for the student work "Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography" by Christian Kaever.

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Permalink: https://www.hzdr.de/publications/Publ-34999
Publ.-Id: 34999


Field-induced spin reorientation transitions in antiferromagnetic ring-shaped spin chains

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

Easy axis antiferromagnets are robust against external magnetic fields of moderate strength. Spin reorientations in strong fields can provide an insight into more subtle properties of antiferromagnetic materials, which are often hidden by their high ground state symmetry. Here, we investigate theoretically effects of curvature in ring-shaped antiferromagnetic achiral anisotropic spin chains in strong magnetic fields. We identify the geometry-governed helimagnetic phase transition above the spin-flop field between vortex and onion states. The curvature-induced Dzyaloshinskii--Moriya interaction results in the spin-flop transition being of first- or second-order depending on the ring curvature. Spatial inhomogeneity of the Neel vector in the spin-flop phase generates weak ferromagnetic response in the plane perpendicular to the applied magnetic field. Our work contributes to the understanding of the physics of curvilinear antiferromagnets in magnetic fields and guides prospective experimental studies of geometrical effects relying on spin-chain-based nanomagnets.

Keywords: antiferromagnetism; ring; spin-flop

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Permalink: https://www.hzdr.de/publications/Publ-34998
Publ.-Id: 34998


Das „lernende“ Standortauswahlverfahren für ein Endlager radioaktiver Abfälle - Interdisziplinäre Beiträge

Smeddinck, U.; Röhlig, K.-J.; Mbah, M.; Brendler, V.

Das Standortauswahlverfahren für Endlager hochradioaktiver Abfälle soll ein "lernendes" sein. Doch was bedeutet das? Im Gesetzestext und in der Begründung finden sich kaum konkrete
Hinweise zur Ausgestaltung des lernenden Verfahrens. Wissenschaft und Zivilgesellschaft führen den Diskurs über das lernende Standortauswahlverfahren seit geraumer Zeit. Insbesondere die zentralen Akteure des Standortauswahlverfahrens sind dazu aufgefordert, aktiv darin einzutreten und gegebenenfalls auch den Gesetzgeber einzubeziehen.
Der Band versammelt Beiträge aus verschiedenen Disziplinen, konturiert die fachlichen Anforderungen an ein wirklich lernendes Verfahren und ordnet die aktuelle Diskussion im Verhältnis zur Umsetzung des Standortauswahlverfahrens für ein Endlager nach den formalrechtlichen Vorgaben ein.

Keywords: Standortauswahlverfahren; Endlager; hochradioaktiver Abfall; Wissenschaft; Zivilgesellschaft; lernendes Verfahren

Permalink: https://www.hzdr.de/publications/Publ-34997
Publ.-Id: 34997


Three-Dimensional, Km-Scale Hyperspectral Data of Well-Exposed Zn–Pb Mineralization at Black Angel Mountain, Greenland

Lorenz, S.; Thiele, S. T.; Kirsch, M.; Unger, G.; Zimmermann, R.; Guarnieri, P.; Baker, N.; Vest Sørensen, E.; Rosa, D.; Gloaguen, R.

Hyperspectral imaging is an innovative technology for non-invasive mapping, with increas- ing applications in many sectors. As with any novel technology, robust processing workflows are required to ensure a wide use. We present an open-source hypercloud dataset capturing the complex but spectacularly well exposed geology from the Black Angel Mountain in Maarmorilik, West Green- land, alongside a detailed and interactive tutorial documenting relevant processing workflows. This contribution relies on very recent progress made on the correction, interpretation and integration of hyperspectral data in earth sciences. The possibility to fuse hyperspectral scans with 3D point cloud representations (hyperclouds) has opened up new possibilities for the mapping of complex natural targets. Spectroscopic and machine learning tools allow or the rapid and accurate characterization of geological structures in a 3D environment. Potential users can use this exemplary dataset and the associated tools to train themselves or test new algorithms. As the data and the tools have a wide range of application, we expect this contribution to benefit the scientific community at large.

Keywords: open-source dataset; hyperspectral data; spectral imaging; 3D hyperclouds; photogrammetry; Black Angel Maarmorilik; minimum wavelength mapping; interactive workflow

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Permalink: https://www.hzdr.de/publications/Publ-34996
Publ.-Id: 34996


Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing

Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type-doped Ge with an electron concentration in the order of 10^19-10^20 cm^{-3}. Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on P-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.

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Permalink: https://www.hzdr.de/publications/Publ-34995
Publ.-Id: 34995


Low thermal conductivity in bournonite PbCuSbS3: A comprehensive study

Zuniga-Puelles, E.; Cardoso-Gil, R.; Ozden, A.; Bulut, N.; Himcinschi, C.; Kortus, J.; Svitlyk, V.; Gumeniuk, R.

Two natural bournonites have been characterized by structural, chemical, spectroscopical, magnetic and thermodynamic analyses. This study confirmed them to possess the PbCuSbS3 stoichiometric composition and to be of an outstanding quality allowing us to consider their properties as being intrinsic for this material. Electronic structure calculations, electrical and spectroscopical characterizations reveal PbCuSbS3 to be a direct n-type semiconductor with an energy gap Eopt g = 1.69 eV, huge Seebeck coefficient and electrical resistivity (e.g. ∼-1200 μV K−1 and ∼ 1000 Ω m at RT, respectively). The thermal conductivity in PbCuSbS3 is found to be very low [κ(T) ∼ 2-0.5 W m−1 K−1 in temperature range 100-600 K] and to be dominated by optical phonons (T > 100 K), which poorly transport heat, strongly scatter the acoustic ones and substantially intensify the phonon-phonon umklapp processes. Additionally, strong phonon-phonon scattering in bournonite is caused by many empty voids in its structural arrangement as well as by more than 60 Raman modes appearing in the frequency range of 150-250 cm−1 (∼5-8 THz) at RT. All these result in high Gruneisen parameter (Γ = 4.8-3.2) and very short phonon mean free path (lph = 11-3 ˚A for 100-300 K). Thus, the low thermal conductivity in bournonite is a reflection of combination of many different factors leading to a huge phonon anharmonicity.

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Permalink: https://www.hzdr.de/publications/Publ-34993
Publ.-Id: 34993


Anti-cancer prodrug cyclophosphamide exerts thrombogenic effects on human venous endothelial cells independent of CYP450 activation – relevance to thrombosis

Krüger-Genge, A.; Köhler, S.; Laube, M.; Haileka, V.; Lemm, S.; Majchrzak, K.; Kammerer, S.; Schulz, C.; Storsberg, J.; Pietzsch, J.; Küpper, J.-H.; Jung, F.

Cancer patients are at a very high risk of serious thrombotic events, often fatal. The causes discussed include the detachment of thrombogenic particles from tumor cells or the adverse effects of chemotherapeutic agents. Cytostatic agents can either act directly on their targets or, in the case of a prodrug approach, require metabolization for their action. Cyclophosphamide (CPA) is a widely used cytostatic drug that requires prodrug activation by cytochrome P450 enzymes (CYP) in the liver. We hypothesize that CPA could induce thrombosis in one of the following ways: (1) damage to endothelial cells (EC) after intra-endothelial metabolization; or (2) direct damage to EC without prior metabolization. In order to investigate this hypothesis, endothelial cells (HUVEC) were treated with CPA in clinically relevant concentrations for up to 8 days. HUVECs were chosen as a model representing the first place of action after intravenous CPA administration. No expression of CYP2B6, CYP3A4, CYP2C9 and CYP2C19 was found in HUVEC, but a weak expression of CYP2C18 was observed. CPA treatment of HUVEC induced DNA damage and a reduced formation of an EC monolayer and caused an increased release of prostacyclin (PGI2) and thromboxane (TXA) associated with a shift of the PGI2/TXA balance to a prothrombotic state. In an in vivo scenario, such processes would promote the risk of thrombus formation.

Keywords: cancer; cyclophosphamide; human umbilical vein endothelial cells; HUVEC; liver; cytochrome P450 enzymes (CYP); thrombosis

Permalink: https://www.hzdr.de/publications/Publ-34992
Publ.-Id: 34992


Role of Ni, Si and P on the formation of solute-rich clusters under irradiation in Fe-Cr alloys

Gueye, P.-M.; Gómez-Ferrer, B.; Kaden, C.; Pareige, C.

After irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), minor solute elements as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small dislocation loops. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, Fe-15at.%Cr-X (X=Si, Ni, P, NiSiP) alloys of different composition have been ion irradiated and characterized using atom probe tomography. Irradiation were performed at 300 °C up to 2.5 dpa in four alloys: Fe15CrNi, Fe15CrSi, Fe15CrP and Fe15CrNiSiP. Influence of C atoms implanted during irradiation on the nanostructure evolution is also discussed. The study of the evolution of the nanofeatures formed under irradiation with the dose as a function of the composition highlights the role of P and C on the formation of the nano-clusters and confirm the radiation-induced nature of solute-rich clusters.

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Permalink: https://www.hzdr.de/publications/Publ-34991
Publ.-Id: 34991


Solute rich cluster formation and Cr precipitation in irradiated Fe-Cr-(Ni,Si,P) alloys: Ion and neutron irradiation

Pareige, C.; Etienne, A.; Gueye, P.-M.; Medvedev, A.; Kaden, C.; Konstantinovic, M.; Malerba, L.

Ion irradiation is a powerful and affordable tool to rapidly test a wide range of irradiation conditions and make the link with the corresponding microstructural evolution. However, several issues of transferability of results from ion to neutron irradiation have been evidenced. This paper presents an atom probe investigation of the microstructural evolution of FeCr-NiSiP alloys with different contents of Cr and minor solutes under both ion and neutron irradiation at 300 °C. Impurities and Cr are known to form solute rich clusters (SRCs) and ' clusters in ferritic and martensitic FeCr alloys, which are one of the causes of hardening. The objective of this work is to highlight the differences and the commonalities between ion and neutron irradiations in these alloys. The use of two ion beam energies (8 MeV and 5 MeV) revealed that this parameter has an impact on the formation of SRCs. The SRCs present similar characteristics after 8 MeV Fe ion irradiation and neutron irradiation, despite the different dose rate, when Ni, Si and P are present. It is not the case for 5 MeV Fe ions, for which the SRCs were less developed. A nonlinear effect of the concentration of minor elements has been evidenced, as well. The presence of Ni, Si and P has been shown to impact both the number density and the size of SRCs in Fe9CrNiSiP alloys and the onset of ' formation.

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Permalink: https://www.hzdr.de/publications/Publ-34990
Publ.-Id: 34990


Nanoindentation as a tool to assess mechanical property changes under ion irradiation

Kaden, C.; Bergner, F.

Nanoindentation using sharp, geometrically self-similar indenters has attracted much interest as a tool to assess the mechanical response of ion-irradiated materials. This tool is of value in the framework of both fast materials screening of candidate nuclear materials and more fundamental studies of radiation effects on materials. The ambition is to obtain bulk-equivalent information that can be correlated with macroscopic mechanical properties and is ideally transferable to neutron irradiation. A major challenge arises from the unavoidable interplay of the steep damage gradient in the thin ion-irradiated layer with the indentation size effect (ISE).
The talk will revisit aspects related to the good practise of conducting nanoindentation experiments. The main factors relevant for obtaining reproducible quantitative bulk-equivalent hardness values will be addressed. Finally, approaches aimed at isolating the bulk-equivalent irradiation-induced hardening in (thin and graded) ion-irradiated layers will be reviewed.

Keywords: nanoindentation; ion irradiation

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  • Invited lecture (Conferences)
    NUMAT2022 - The Nuclear Materials Conference, 24.-28.10.2022, Gent, Belgien

Permalink: https://www.hzdr.de/publications/Publ-34989
Publ.-Id: 34989


Cyclam with a phosphinate-bis(phosphonate) pendant arm is a bone-targeting carrier of copper radionuclides

Pazderová, L.; Benešová, M.; Havlíčková, J.; Vojtíčková, M.; Kotek, J.; Lubal, P.; Ullrich, M.; Walther, M.; Schulze, S.; Neuber, C.; Rammelt, S.; Pietzsch, H.-J.; Pietzsch, J.; Kubíček, V.; Hermann, P.

Ligands combining a bis(phosphonate) group with a macrocycle function as metal isotope carriers for radionuclide-based imaging and for treating bone metastases associated with several cancers. However, bis(phosphonate) pendant arms often slow down complex formation and decrease radiochemical yields. Nevertheless, their negative effect on complexation rates may be mitigated by using a suitable spacer between bis(phosphonate) and the macrocycle. To demonstrate the potential of bis(phosphonate) bearing macrocyclic ligands as a copper radioisotope carrier, we report the synthesis of a new cyclam derivative bearing a phosphinate-bis(phosphonate) pendant (H5te1PBP). The ligand showed a high selectivity to CuII over ZnII and NiII ions, and the bis(phosphonate) group was not coordinated in the CuII complex, strongly interacting with other metal ions in solution. The CuII complex formed quickly, in 1 s, at pH 5 and at a millimolar scale. The complexation rates significantly differed under a ligand or metal ion excess due to the formation of reaction intermediates differing in their metal-to-ligand ratio and protonation state, respectively. The CuII-te1PBP complex also showed a high resistance to acid-assisted hydrolysis (t1/2 2.7 h; 1 M HClO4, 25 °C) and was effectively adsorbed on the hydroxyapatite surface. H5te1PBP radiolabeling with [64Cu]CuCl2 was fast and efficient, with specific activities of approximately 30 GBq 64Cu per 1 μmol of ligand (pH 5.5, room temperature, 30 min). In a pilot experiment, we further demonstrated the excellent suitability of [64Cu]CuII-te1PBP for imaging active bone compartments by dedicated small animal PET/CT in healthy mice and subsequently in a rat femoral defect model, in direct comparison with [18F]fluoride. Moreover, [64Cu]CuII-te1PBP showed a higher uptake in critical bone defect regions. Therefore, our study highlights the potential of [64Cu]CuII-te1PBP as a PET radiotracer for evaluating bone healing in preclinical and clinical settings with a diagnostic value similar to that of [18F]fluoride, albeit with a longer half-life (12.7 h) than 18F (1.8 h), thereby enabling extended observation times.

Permalink: https://www.hzdr.de/publications/Publ-34988
Publ.-Id: 34988


Synchronization dynamics on power grids in Europe and the United States

Ódor, G.; Deng, S.; Hartmann, B.; Kelling, J.

Dynamical simulation of the cascade failures on the EU and USA high-voltage power grids has been done via solving the second-order Kuramoto equation. We show that synchronization transition happens by increasing the global coupling parameter K with metasatble states depending on the initial conditions so that hysteresis loops occur. We provide analytic results for the time dependence of frequency spread in the large K approximation and by comparing it with numerics of d=2,3 lattices, we find agreement in the case of ordered initial conditions. However, different power-law (PL) tails occur, when the fluctuations are strong. After thermalizing the systems we allow a single line cut failure and follow the subsequent overloads with respect to threshold values T. The PDFs p(Nf) of the cascade failures exhibit PL tails near the synchronization transition point Kc. Near Kc the exponents of the PL-s for the US power grid vary with T as 1.4≤τ≤2.1, in agreement with the empirical blackout statistics, while on the EU power grid we find somewhat steeper PL-s characterized by 1.4≤τ≤2.4. Below Kc we find signatures of T-dependent PL-s, caused by frustrated synchronization, reminiscent of Griffiths effects. Here we also observe stability growth following the blackout cascades, similar to intentional islanding, but for K>Kc this does not happen. For Tc, bumps appear in the PDFs with large mean values, known as "dragon king" blackout events. We also analyze the delaying/stabilizing effects of instantaneous feedback or increased dissipation and show how local synchronization behaves on geographic maps.

Keywords: Kuramoto model; synchronization; synchronization transition; power grid

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Permalink: https://www.hzdr.de/publications/Publ-34987
Publ.-Id: 34987


First experiences with custom pipelines for compression

Gernhardt, F. P. D.; Steinbach, P.

This presentation gives an overview of our recent activities in the development of custom pipelines for data compression.

Keywords: Data compression; Tomography

  • Open Access Logo Lecture (Conference)
    LEAPS-Innov Annual Meeting 2022, 03.-05.05.2022, Barcelona, Spanien

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Permalink: https://www.hzdr.de/publications/Publ-34986
Publ.-Id: 34986


The Open Science Initiative for Perfusion Imaging (OSIPI): ASL Pipeline inventory

Fan, H.; Mutsaerts, H. J. M. M.; Anazodo, U.; Arteaga, D.; Baas, K. P. A.; Buchanan, C.; Camargo, A.; Keil, V. C.; Lin, Z.; Lindner, T.; Hirschler, L.; Hu, J.; Padrela, B. E.; Taghvaei, M.; Thomas, D. L.; Dolui, S.; Petr, J.

Purpose: To create an inventory of automated image processing pipelines of Arterial Spin Labeling (ASL) and summarize their features and accessibility for users to choose an optimal pipeline to fit their needs.

Methods: Pipeline developers were invited to self-assess their pipelines using a questionnaire developed by the Task Force 1.1 of the Open Science Initiative for Perfusion Imaging (OSIPI). Additionally, publicly available pipelines were evaluated by two independent testers using an objective unified scoring system. The testing focused on the capability, flexibility, and ease of use of the pipelines on various datasets.

Results: The developers of twenty-one pipelines filled in the questionnaire. Most pipelines support data from the three major vendors, i.e., GE (n=15), Philips (n=15), and Siemens (n=16), are free for research (n=18), work with the standard neuroimaging data format NIfTI (n=15), and can process standard 3D single PLD pseudo-continuous ASL images (n=21). Pipelines mainly differed in their support of advanced sequences and advanced features. Nine publicly available pipelines were included in the independent testing. Whereas certain pipelines were easy to use for users without programming skills, other pipelines offered more flexibility for configuring advanced processing options.

Conclusion: ASL data from the most commonly used ASL sequences saved in the standard neuroimaging data formats can be easily processed using publicly available pipelines. A specific choice of a pipeline should consider specific requirements on features and users’ skills, and the ASL inventory can serve as a valuable guide to facilitate this choice.

Permalink: https://www.hzdr.de/publications/Publ-34985
Publ.-Id: 34985


The value of arterial spin labelling perfusion MRI in brain age prediction

Dijsselhof, M.; Barboure, M.; Stritt, M.; Nordhøy, W.; Wink, A. M.; Beck, D.; Westlye, L. T.; Cole, J. H.; Barkhof, F.; Mutsaerts, H. J. M. M.; Petr, J.

Background: Biological brain age estimates from structural MRI data and their difference from chronological age — the brain age gap (BAG) — have been successfully applied in a range of diseases, but remain limited to capturing structural characteristics only. To incorporate physiological properties, we operationalized ‘Cerebrovascular brain age’ using a combination of structural, and arterial spin labelling (ASL) image data, investigate their optimal feature and algorithm combinations, and evaluate its repeatability.
Methods: Healthy participants (n = 341, 62 % female, age 59.7 ± 14.8 years, range: 21 - 95 years) were scanned at baseline and after 1.7 ± 0.5 years (n = 248, 62.9 % female, mean age 62.4 ± 13.3 years, range: 27 - 86). At 3 T MRI, 3D structural T1-weighted (T1w) and Fluid Attenuated Inversion Recovery (FLAIR), and 3D ASL image data were acquired to extract within grey matter (GM) and deep white matter (WM) ROIs: volumetrics, WM hyperintensity volume and count; and cerebral blood flow (CBF) and spatial coefficient of variation (CoV). Multiple combinations of features and machine learning algorithms were evaluated to train brain age algorithms on 70 % of the subjects and evaluated on the remainder, for 300 Monte-Carlo cross-validations, using the Mean Absolute Error (MAE). Feature importance of the best performing model was assessed by determining the feature weights. Model repeatability of the best model was assessed by comparing the BAGs between baseline and follow-up, also using T1w + FLAIR or ASL-only features.
Results: The lowest MAE was observed for the ElasticNetCV algorithm using T1w + FLAIR + ASL (MAE = 5.03 ± 0.34 years) and significantly better compared to using T1w + FLAIR (MAE = 6.01 ± 0.39, p < 0.01) and ASL-only features (MAE = 6.04 ± 0.39, R2 = 0.70 ± 0.04, p < 0.01). The three most important features were GM CBF (6.2 ± 1.18), GM/ICV (5.34 ± 0.6), and WM CBF (4.16 ± 0.36).
Average baseline and follow-up BAGs were not different (-1.51 ± 6.29 and -1.14 ± 6.40 years respetively, ICC = 0.85, 95% CI: 0.79 - 0.90, p = 0.16). The ElasticNetCV model with T1w+FLAIR+ASL performed similar to the same model with the T1w + FLAIR feature set (0.37 ± 3.48 years and 0.01 ± 2.95 years respectively, p = 0.14), and the ASL-only feature set (0.29 ± 4.03, p = 0.39).
Conclusion: The addition of ASL features to structural brain age improved brain age prediction, with the ElasticNetCV algorithm and a combination of all tested features (T1w+FLAIR+ASL) performing the best in a cross-sectional and repeatability comparison. These findings encourage future studies to explore the value of ASL in brain age in various pathologies.

Permalink: https://www.hzdr.de/publications/Publ-34984
Publ.-Id: 34984


Current- and Oersted-field- dynamics of a Bloch Point in cylindrical Ni nanowires

Fernandez Roldan, J. A.; Oksana, C.-F.

As three-dimensional nanomagnetism evolves, novel non-trivial magnetic textures emerge as appealing information carriers for spintronics based on curved nanosystems and particularly Cylindrical Nanowires (NWs) [1,2]. One of the most fascinating candidates that is likely to reach the high velocities required for fast recording technologies is the Bloch Point (BP) domain wall (DW). Recently, theoretical evidence indicated that BPs in NWs could reach high velocities close to 2 km/s in the magnonic regime [2]. While the observation of the BP DW in cylindrical NWs is no longer recent [2], scarce numerical studies that combine both spin-polarized current and Oersted field have been published in NWs [4,5], despite first attempts to measure DW velocities are in progress [6].
In this work we evaluate the dynamics of the BP DW under both current directions in a Ni NW with 100 nm in diameter. We investigate two cases: i) pre-nucleated BP DW, and ii) the BP DW formed from the transformation of a Vortex-Antivortex DW. Here the effects of both spin-polarized current and Oersted field are considered. We discuss in detail the role of the chirality of the BP in relation to the Oersted field, also reported previously in precursors of BPs [4].

Here we show that while the pre-nucleated DW with the same chirality as that of the Oersted field propagates always against the current direction, the BP originated either from the transformation of the BP with the opposite chirality or from the vortex-antivortex DW can either stop the propagation or propagate parallel to the current. Finally, we provide values of the velocities achieved by the BP in the NW as a function of applied current in Fig. 1.

We conclude that BPs with vanishing momentum propagate opposite to the current with velocities that may be suppressed by the Oersted field. Importantly for spintronic applications, momentum plays a major role in the dynamics of BPs that has not been envisaged up to know.

[1] A. Fernandez-Pacheco et al., Three-dimensional nanomagnetism. Nat Commun 8, 15756 (2017)
[2] S. Da Col et al., Observation of Bloch-point domain walls in cylindrical magnetic nanowires, Phys. Rev. B, 89, 180405 (2014).
[3] X.-P. Ma et al., Cherenkov-type three-dimensional breakdown behavior of the Bloch-point domain wall motion in the cylindrical nanowire, Appl. Phys. Lett. 117, 062402 (2020).
[4] J.A. Fernandez-Roldan et al., Electric current and field control of vortex structures in cylindrical magnetic nanowires, Phys. Rev. B 102, 024421 (2020).
[5] C. Bran et al, Magnetic Configurations in Modulated Cylindrical Nanowires, Nanomaterials 11, 600 (2021). DOI: 10.3390/nano11030600
[6] M. Schöbitz et al., Fast Domain Wall Motion Governed by Topology and Oersted Fields in Cylindrical Magnetic Nanowires. Phys. Rev. Lett. 123, 217201 (2019).

Keywords: Bloch Point; magnetic domain wall; cylindrical nanowire; current; Oersted field

  • Poster
    XXXVIII Biennial of Physics of the Spanish Royal Physics Society (R.S.E.F.), 11.-15.07.2022, Murcia, Spain
  • Lecture (Conference)
    2022 Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34983
Publ.-Id: 34983


Tidally Forced Planetary Waves in the Tachocline of Solar-like Stars

Horstmann, G. M.; Mamatsashvili, G.; Giesecke, A.; Zaqarashvili, T.; Stefani, F.

Can atmospheric waves in planet-hosting solar-like stars substantially resonate to tidal forcing, perhaps at a level of impacting the space weather or even being dynamo-relevant? In particular, low-frequency Rossby waves, which have been detected in the solar near-surface layers, are predestined to respond to sunspot cycle-scale perturbations. In this paper, we seek to address these questions as we formulate a forced wave model for the tachocline layer, which is widely considered as the birthplace of several magnetohydrodynamic planetary waves, i.e., Rossby, inertia-gravity (Poincaré), Kelvin, Alfvén, and gravity waves. The tachocline is modeled as a shallow plasma atmosphere with an effective free surface on top that we describe within the Cartesian β-plane approximation. As a novelty to former studies, we equip the governing equations with a conservative tidal potential and a linear friction law to account for viscous dissipation. We combine the linearized governing equations into one decoupled wave equation, which facilitates an easily approachable analysis. Analytical results are presented and discussed within several interesting free, damped, and forced wave limits for both midlatitude and equatorially trapped waves. For the idealized case of a single tide-generating body following a circular orbit, we derive an explicit analytic solution that we apply to our Sun for estimating leading-order responses to Jupiter. Our analysis reveals that Rossby waves resonating to low-frequency perturbations can potentially reach considerable velocity amplitudes on the order of 101–102 cm s−1, which, however, strongly rely on the yet unknown frictional damping parameter.

Keywords: Sun: interior; Sun: magnetic fields; Sun: oscillations

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Permalink: https://www.hzdr.de/publications/Publ-34982
Publ.-Id: 34982


Data: Study of a possible silicon photomultiplier based readout of the large plastic scintillator neutron detector NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; Boretzky, K.; Gasparic, I.; Stach, D.; Wagner, A.; Zuber, K.

The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV
neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany.
In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each
end by fast timing photomultipliers.
Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM)
are reported.  For this purpose, a typical NeuLAND bar was instrumented on each end with a prototype of the same
geometry as a 1” photomultiplier tube, including four 6×6 mm2 SiPMs, amplifiers, high voltage supply, and micro-
controller.
Tests were carried out using the 35 MeV electron beam from the ELBE superconducting linac with its ps-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-usermode with 1-60 electrons per bunch, using Acqiris fast digitizers. In addition, offline tests using cosmic rays and the NeuLAND data acquisition scheme were carried out.
Typical time resolutions of σ≤120 ps were found for ≥ 95% efficiency, improving on previous work at ELBE and exceeding the NeuLAND timing goal of σ <150 ps. Over a range of 10-300 MeV deposited energy in the NeuLAND bar,  the  gain  was  found  to  deviate  by ≤ 10%  (≤20%)  from  linearity  for  35μm  (75μm)  SiPM  pitch,  respectively, satisfactory for calorimetric use of the full NeuLAND detector.  The dark rate of the prototype studied was found to
be 70-200 s-1, comparable with the unavoidable cosmic-ray induced background.

The dataset contains the with the Acqiris Digitzier recorded waveforms and analysis scripts for interpretation of the data. Also GEANT4 simulations of the light propagation in a NeuLAND bar and the electron beam propagation are included.

Keywords: SiPM; saturation; NeuLAND; dark rate; electron beam; timeresolution

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Permalink: https://www.hzdr.de/publications/Publ-34981
Publ.-Id: 34981


Preface: State of the art in mineral exploration

Alcalde, J.; Carbonell, R.; Pospiech, S.; Gil, A.; Bullock, L. A.; Tornos, F.

Minerals that comprise raw materials for energy, metal, construction and other industrial applications are considered strategic commodities, fundamental in stock markets worldwide, and key ingredients to sustain our ever more technology-based society (Wellmer et al., 2019). The utilization of such economically important minerals has shown a continued steady increase since the early twentieth century, with a greater focus in recent years on resources required for the development of renewable technologies, such as wind and solar operations, and for electrification of domestic and transportation systems (e.g. concrete, aluminium, chromium, copper, iron, manganese, molybdenum, nickel, zinc or rare earths) (Meinert et al., 2016). As our society ramps up the global transition to low-carbon energies and a reduced reliance on fossil fuels, the inevitable rise in consumption and demand for a more diverse range of resources can only be facilitated through increasingly novel methods of mineral exploration (Ali et al., 2017).

Keywords: mineral exploration; state of the art; geophysics; geochemistry; geology; remote sensing; critical raw materials

Permalink: https://www.hzdr.de/publications/Publ-34980
Publ.-Id: 34980


Creating reproducible, scalable, portable and adaptable CFD validation workflows with Snakemake

Lehnigk, R.; Lucas, D.; Rehm, M.; Schlegel, F.

The modelling and simulation of nuclear reactors is increasingly carried out with open-source tools. To researchers, the most appealing benefits are the possibility to study and verify existing implementations and the freedom to add code for prototyping new concepts and models. Further, there is no direct dependency on a software manufacturer, which generally makes open-source codes a solid basis for collaboration. An important downside however is that the responsibility of controlling quality and reliability lies with the users. For actively developed code this is a continuous task and demands considerable resources which should be bundled.
In the area of Computational Fluid Dynamics, a well-established open-source solution is OpenFOAM. Its development follows agile principles with a strong focus on maintainability and usability. This increases the demands on users to keep their setups functional. Since 2020, HZDR is creating an IT environment that supports the centralized and continuous maintenance of OpenFOAM code and simulation setups developed by members of the German nuclear safety research community. The project focuses on work relevant for the reactor cooling system and is referred to as OpenFOAM_RCS. Both, an addon to the OpenFOAM release from The OpenFOAM Foundation and a dedicated repository for simulation setups are supplied. The basis for the project is the web-based software development environment GitLab provided by the Helmholtz Federated IT Services (HIFIS), which allows for a high degree of automation with the help of continuous integration and deployment pipelines. Part of the project is the creation of a validation workflow
Validation workflows should, among other things: (1) allow for continuous and automated checks of the setup input syntax; (2) frequently validate the simulation results by comparison against reference solutions; (3) be able to evaluate the impact of model substitutions on the overall “goodness” of results; (4) automatically create self-contained reports; (5) be executable on different environments, i.e. be portable and scalable; (5) allow for easy integration of new setups, i.e. be adaptable; (6) enable design point studies; (7) be comprehensible, ideally be self-documenting; (8) follow well-defined standards.
All aforementioned requirements can be fulfilled with the popular and actively developed Python-based workflow management system Snakemake (Mölder et al., 2021), which was originally written for Bioinformatics workflows, but is far more versatile. In this work Snakemake is configured to embed all setups archived in OpenFOAM_RCS in a single workflow. Execution of simulation setups is controlled via so-called Snakefiles, which list inputs and outputs of a simulation, the required resources as well as the commands to run them. Within a top-level configuration file utilizing the easy to read markup language YAML, all setups to be incorporated in a workflow are listed. Once properly configured, users can run the workflow in four steps: (1) configuration, i.e. assembly of selected setups; (2) running the simulations; (3) post-processing the simulations; (4) creating HTML reports gathering all generated plots together with runtime statistics and provenance information. The third step can be executed on a workstation or a cluster. For the latter case, a top-level job organizes the workflow and automatically submits sub-jobs to the cluster.
The proposed framework provides the opportunity to reduce cost and effort for CFD validation and verification. It also is of great help for complex model development such as multi-phase CFD where a large range of test cases and test conditions is mandatory to judge the performance of a given model choice.

This work is carried out in the frame of a current research project funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection, project number 1501604.

  • Lecture (Conference)
    Computational Fluid Dynamics for Nuclear Reactor Safety (CFD4NRS-9), 20.-21.02.2023, College Station, Texas, United States of Americs
  • Lecture (Conference) (Online presentation)
    34th German CFD Network of Competence Meeting, 14.-15.03.2023, München, Deutschland
  • Lecture (others) (Online presentation)
    Framatome CFD-Community Meeting, 30.03.2023, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34979
Publ.-Id: 34979


Spin-wave channeling in magnetization-graded nanostrips

Gallardo, R. A.; Alvarado-Seguel, P.; Brevis, F.; Roldán-Molina, A.; Lenz, K.; Lindner, J.; Landeros, P.

Magnetization-graded ferromagnetic nanostrips are proposed as potential prospects to channel spin waves. Here, a controlled reduction of the saturation magnetization enables the localization of the propagating magnetic excitations in the same way that light is controlled in an optical fiber with a varying refraction index. The approach is based on the dynamic matrix method, where the magnetic nanostrip is divided into small sub-strips. The dipolar and exchange interaction between sub-strips is accounted to reproduce the spin-wave dynamics of the magnonic fiber. The transition from one strip to an infinite thin film is presented for the Damon-Eshbach geometry, where the nature of the spin-wave modes is discussed. An in-depth analysis of the spin-wave transport as a function of the saturation magnetization profile is provided. It is predicted that it is feasible to induce a remarkable channeling of the spin waves along the zones with a reduced saturation magnetization, even when such a reduction is tiny. The results are compared with micromagnetic simulations, where a good agreement is observed between both methods. The findings have relevance for envisioned future spin-wave-based magnonic devices operating at the nanometer scale.

Keywords: spin waves; ferromagnetic resonance; magnetization dynamics; magnonics; magnetic gradients; theory

Permalink: https://www.hzdr.de/publications/Publ-34978
Publ.-Id: 34978


Helical dislocations in ion-irradiated Fe-9Cr studied by scanning transmission electron microscopy

Vogel, K.; Engelmann, H.-J.; Chekhonin, P.; Bergner, F.; Kaden, C.

Fe-9Cr is a model alloy for studying irradiation effects relevant for potential applications of high-chromium ferritic/martensitic steels in nuclear energy devices. Ion irradiation is a tool extensively employed with the aim to emulate the neutron damage characteristic for irradiation environments in fission or fusion reactors. Here we report on STEM studies of the microstructure of ion-irradiated Fe-9Cr with special emphasis on the effects of pre-existing dislocations.
Irradiations with 8 MeV Fe3+ ions were carried out at the 3 MV tandetron accelerator at the Ion Beam Center at HZDR. Profiles of displacement damage and implanted ions were calculated using the binary collision code SRIM. Cross-sectional TEM specimens were prepared by focused ion beam lift-out technique using a Thermo Fisher Helios 5CX. The microstructure was studied in a Talos F200X scanning transmission electron microscope.
The most striking feature of the irradiated microstructure in the range of high displacement damage, but low concentration of implanted ions, is the presence of helical dislocations. From the results of the Burgers vector analysis we conclude, that the helices were formed from pre-existing straight line dislocations with a dominating screw component. After transformation into the helical shape, the dislocations contain screw, mixed and edge segments. The STEM images also reveal large numbers of small dislocation loops mainly located close to the helices.
The presence of helical dislocations and the accumulation of loops close to them resembles observations reported for neutron-irradiated Fe-9Cr. Hence we conclude that - in the depth range of low implanted ion concentration - ion irradiation can produce similar defect configurations like neutron irradiation if the arrangement of pre-existing dislocations is comparable.

Keywords: irradiation-induced defects; helical dislocations; dislocation loops; ion-irradiated Fe-Cr

Related publications

  • Contribution to proceedings
    Microscopy Conference 2023, 26.02.-02.03.2023, Darmstadt, Deutschland
    MC2023 Darmstadt Microscopy Conference Proceedings, 978-3-948023-29-4, 122-123
  • Poster
    Microscopy Conference 2023, 26.02.-02.03.2023, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34977
Publ.-Id: 34977


Spatial distribution of Eu(III) in environmental samples by chemical microscopy

Klotzsche, M.; Vogel, M.; Steudtner, R.; Drobot, B.

Lanthanides (Ln) have become critical components in science and industry. Their anthropogenic release into the environment and entry into the food chain poses a risk for the health of living beings. Therefore, a comprehensive understanding of the transfer and migration behaviour, the resulting localization and molecular characterization of Ln in geological and biological systems is crucial for a reasonable risk assessment and remediation strategies.
Trivalent europium (Eu(III)) exhibits chemical similarities to Ca(II) and excellent luminescent properties, hence it is well suited to study the interaction of Ln(III) with plants on a cellular level. Herein, we utilized chemical microscopy[1] – a combination of light microscopy and high resolution luminescence spectroscopy – in order to spatially resolve the Eu(III) species distribution in both, an imitation of a natural sample and an Eu(III)-incubated agricultural crop.

[1] M. Vogel, R. Steudtner, T. Fankhänel, J. Raff, B. Drobot, Analyst 2021, 146, 6741.

Keywords: Chemical microscopy; Europium; Laser spectroscopy; Bioassociation; Environmental samples; Plant; Spatial imaging

  • Poster
    Chemistry Summer School on f-Elements, 12.-16.06.2022, Aussois, France

Permalink: https://www.hzdr.de/publications/Publ-34976
Publ.-Id: 34976


Real-time tracking of individual droplets in multiphase microfluidics

Ibarlucea, B.; Schütt, J.; Baraban, L.; Makarov, D.; Medina Sánchez, M.; Cuniberti, G.

Multiphase microfluidics enables the high-throughput operation of droplets for multitude of applications, from the confined fabrication of nano- and micro-objects to the parallelization of chemical reactions of biomedical or biological interest. While the standard methods to follow droplets on a chip are represented by a visual observation through optical or fluorescence microscopy, the conjunction of microfluidic platforms with miniaturized transduction mechanisms opens new ways toward the real-time and individual tracking of each independent reactor. Here we provide an overview of the most recent droplet sensing techniques, with a special focus on those based on electrical signals for optics-less analysis.

Keywords: droplet microfluidics; lab-on-a-chip; nanosensors; biosensors; field-effect transistors

  • Open Access Logo Book chapter
    Prof. Mingzhou Yu: Microfluidics and Nanofluidics - Fundamentals and Applications, London, England: IntechOpen, 2022, 978-1-80356-336-7
    DOI: 10.5772/intechopen.106796

Permalink: https://www.hzdr.de/publications/Publ-34975
Publ.-Id: 34975


Data publication: Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T

Hilpmann, S.; Roßberg, A.; Steudtner, R.; Drobot, B.; Hübner, R.; Bok, F.; Prieur, D.; Bauters, S.; Kvashnina, K.; Stumpf, T.; Cherkouk, A.

The stored data sets represent both the raw data and the evaluated data that were used for the publication about uranium(VI) reduction by a sulfate-reducing bacterium.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Opalinus Clay pore water; Pentavalent uranium; Membrane vesicles

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Permalink: https://www.hzdr.de/publications/Publ-34974
Publ.-Id: 34974


Sulfated glycosaminoglycans inhibit transglutaminase 2 by stabilizing its closed conformation

Müller, C. D.; Ruiz-Gómez, G.; Cazzonelli, S.; Möller, S.; Wodtke, R.; Löser, R.; Freyse, J.; Dürig, J.-N.; Rademann, J.; Hempel, U.; Pisabarro, M. T.; Vogel, S.

Transglutaminases (TGs) catalyze the covalent crosslinking of proteins via isopeptide bonds. The most prominent isoform, TG2, is associated with physiological processes such as extracellular matrix (ECM) stabilization and plays a crucial role in the pathogenesis of e.g. fibrotic diseases, cancer and celiac disease. Therefore, TG2 represents a pharmacological target of increasing relevance. The glycosaminoglycans (GAG) heparin (HE) and heparan sulfate (HS) constitute high-affinity interaction partners of TG2 in the ECM. Chemically modified GAG are promising molecules for pharmacological applications as their composition and chemical functionalization may be used to tackle the function of ECM molecular systems, which has been recently described for hyaluronan (HA) and chondroitin sulfate (CS). Herein, we investigate the recognition of GAG derivatives by TG2 using an enzyme-crosslinking activity assay in combination with in silico molecular modeling and docking techniques. The study reveals that GAG represent potent inhibitors of TG2 crosslinking activity and offers atom-detailed mechanistic insights.

Permalink: https://www.hzdr.de/publications/Publ-34973
Publ.-Id: 34973


Flexible and printed electronics: from interactive on-skin devices to bio/medical applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive through consumer electronics to virtual and augmented reality applications [3]. These skin-conformal flexible and printable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins for human-machine interfaces [4-9] and soft robotics [10].
Highly flexible functional elements are demanded for bio/medical applications. We will introduce an implantable, multifunctional device on ultrathin polymeric foils for targeted thermal treatment of cancer [11] as well as a flexible light weight diagnostic platform based on highly sensitive Si nanowire field effect transistors revealing remarkable limit of detection at 40 pM for Avian Influenza Virus (AIV) subtype H1N1 DNA sequences [12].
For the emerging field of biosensing technologies, we developed droplet-based magnetofluidic platforms encompassing integrated novel functionalities [13] including analytics in a flow cytometry format [14], magnetic detection, barcoding and sorting of magnetically encoded emulsion droplets using rigid [15,16] and flexible [17] microfluidic devices. These features are crucial to address the needs of modern medical research, e.g. drug discovery.

[1] D. Makarov et al., Adv. Mater. (Review) 34, 2101758 (2022).
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] G. S. Cañón Bermúdez et al., Adv. Funct. Mater. (Review) 31, 2007788 (2021).
[4] G. S. Cañón Bermúdez et al., Science Advances 4, eaao2623 (2018).
[5] G. S. Cañón Bermúdez et al., Nature Electronics 1, 589 (2018).
[6] J. Ge et al., Nature Communications 10, 4405 (2019).
[7] M. Ha et al., Adv. Mater. 33, 2005521 (2021).
[8] P. Makushko et al., Adv. Funct. Mater. 31, 2101089 (2021).
[9] S. Li et al., Nano Energy 92, 106754 (2022).
[10] M. Ha et al., Adv. Mater. 33, 2008751 (2021).
[11] G. S. Cañón Bermúdez et al., Adv. Eng. Mater. 21, 1900407 (2019).
[12] D. Karnaushenko et al., Adv. Healthcare Mater. 4, 1517 (2015).
[13] G. Lin et al., Lab Chip (Review) 17, 1884 (2017).
[14] G. Lin et al., Small 12, 4553 (2016).
[15] J. Schütt et al., ACS Omega 5, 20609 (2020).
[16] W. Song et al., ACS Sensors 2, 1839 (2017).
[17] G. Lin et al., Lab Chip 14, 4050 (2014).

Keywords: curvature effects in magnetism; flexible magnetic field sensors; printed magnetic field sensors; lab-on-chip applications; skin-conformal electronics

Related publications

  • Invited lecture (Conferences)
    Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34972
Publ.-Id: 34972


Scaling IT Services for Germany's Largest Research Organisation - An Experience Report

Hüser, C.; Ziegner, N.; Huste, T.

Helmholtz Federated IT Services (HIFIS, see hifis.net) is a joint platform in which most of the research centres in the Helmholtz Association collaborate. HIFIS offers cloud and fundamental backbone services free of charge to scientists in Helmholtz and their partners. A special focus is put on Research Software Engineering with consulting, trainings and community building. One cloud service, which is of particular interesting in terms of DevOps, is a GitLab service called "the Helmholtz Codebase" - a self-hosted free tier of the popular software project management and DevOps platform. By applying DevOps best practices in combination with a high level of automation we observed three major gains: We were able to shrink the downtimes to almost zero and establish a release cycle that is quite close to the one that GitLab Inc. achieves themselves, whilst scaling the service up. With several thousand satisfied scientific users, Helmholtz Codebase has become quite successful. It is a great example for illustrating the transition from a local service bound to one centre to a distributed service accessible by everyone in the Helmholtz Association.

Keywords: HIFIS; Codebase; GitLab; Automation; DevOps; GitOps

  • Open Access Logo Invited lecture (Conferences)
    Scaling IT Services for Germany's Largest Research Organisation - An Experience Report, 21.-22.09.2022, Berlin, Deutschland
    DOI: 10.5281/zenodo.7248114

Permalink: https://www.hzdr.de/publications/Publ-34971
Publ.-Id: 34971


Dose formation using a pulsed high-field solenoid beamline for radiobiological in vivo studies at a laser-driven proton source

Brack, F.-E.

Proton sources driven by high-power lasers are a promising addition to the portfolio of conventional proton accelerators. Regarding particle cancer therapy, where tumours are irradiated with protons or ions, the novel accelerator technology can be particularly beneficial for translational research - the research branch in which results of basic research are transferred to new approaches for the prevention, diagnosis and treatment of cancer.
The overarching aim in the thesis at hand was a translational pilot study to irradiate tumours on mice’s ears with laser-accelerated protons while achieving the quality level of conventional proton accelerators. This is the only way to compare the radiobiological data of the novel accelerator technology with those of the established ones. To enable such experiments a predetermined dose distribution according to the radiobiological model’s requirements must be delivered to a sample volume. Ergo, the laser-driven protons have to be transported and shaped after their initial acceleration. Intense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. This work demonstrates the successful implementation of a highly efficient and tuneable pulsed dual solenoid setup to generate a homogeneous (laterally and in depth) volumetric dose distribution using only a single dose pulse from the broad laser-driven proton spectrum. The experiments using the ALBUS-2S beamline were conducted at the titanium:sapphire high-power laser Draco PW at the Helmholtz-Zentrum Dresden–Rossendorf. The beamline and its model were characterised and verified via independent methods, leading to first experimental studies providing volumetrically homogeneous dose distributions to detector targets as well as tumour and normal tissue in proof-of-concept studies. To perform the mouse pilot study, a new solenoid with cooling capacities was designed, characterised and implemented in the course of this thesis. The combination of the new solenoid and an overall performance improvement of the laser-proton accelerator, enabled the successful conduction of the mouse model study. The results show that laser-accelerated protons induce a comparable tumour growth delay as protons from conventional accelerators. This outcome and the demonstration of the flawless interaction between laser-proton accelerator, beam transport, dosimetry and biology qualify the laser-based accelerator technology for complex studies in translational cancer research. Looking into the future, their unique extremely high intensity renders them of particular interest for the investigation into the ultra-high dose rate regime. There, the so-called FLASH effect shows fewer side effects in normal tissue while maintaining the same effect in the tumour when the target dose is administered in milliseconds rather than minutes, as currently common. The ALBUS-2S setup at Draco PW already provides all necessary conditions to realise irradiation times of around ten nanoseconds in preclinical studies. This significantly expands the parameter space for investigating the FLASH effect and is presented as a proof-of-concept in this thesis.

Keywords: LPA; TNSA; Laser-driven protons; Radiobiology

  • Doctoral thesis
    TU Dresden, 2022
    Mentor: Dr. Karl Zeil
    121 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-121 2022
    ISSN: 2191-8708, eISSN: 2191-8716
  • Lecture (others)
    Disputation, 19.07.2022, Dresden, Deutschland
  • Open Access Logo Lecture (Conference)
    BLIN5, 12.10.2022, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-34969
Publ.-Id: 34969


Calix[4]crowns with perfluoroalkylsulfonylcarboxamide functions: a complexation approach for heavy group 2 metal ions

Reissig, F.; Bauer, D.; Al-Ameed, K.; Luber, S.; Köckerling, M.; Steinbach, J.; Pietzsch, H.-J.; Mamat, C.

Heavy alkaline earth metals offer radionuclides which are promising candidates for radiopharmaceutical applications like barium-131 for diagnosis or radium-223/-224 – with similar properties to barium – for targeted alpha-particle therapy. However, there is a lack of suitable chelation agents especially for these metal ions. A series of calix[4]crown-6 derivatives with perfluoroalkylsulfonylcarboxamide functions (RF = CF3, C2F5, i-C3F7, n-C4F9) was synthesized to serve as cage-like chelators for a strong complexation of Ba2+ and Ra2+. These functional ligands are deprotonated even at slightly acidic pH due to the intense electron withdrawing effect of the sulfonamide group. The obtained ligands were easily converted the desired barium complexes as well as into calix-crown compounds containing two sodium ions. DFT calculation methods were used to discover either the binding behavior of the metal ions with the desired ligands as well as the influence of the different donor groups from the chelating moiety of the calixarenes with respect to different pH. Radiolabeling procedures with the radionuclides barium-133 and radium-224 as [133Ba]BaCl2 and [224Ra]Ra(NO3)2 were performed to determine association constant values between 4.1 and 8.2 for the appropriate M2+ complexes using a two-phase extraction procedure. A stability test using physiological Ca2+ solution showed a minor release of approx. 1-7% of the central ions (Ba2+ respectively Ra2+) from the complexes.

Keywords: Calix[4]arene; Radium-223; Barium-131; targeted Alpha therapy

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Permalink: https://www.hzdr.de/publications/Publ-34968
Publ.-Id: 34968


Effect of magnetism and phonons on localized carriers in ferrimagnetic kagome metals GdMn₆Sn₆ and TbMn₆Sn₆

Wenzel, M.; Tsirlin, A.; Iakutkina, O.; Yin, Q.; Lei, H. C.; Dressel, M.; Uykur, E.

Kagome metals possess a peculiar optical spectrum consisting of contributions from free charge carriers, localized carriers seen as a strongly temperature-dependent localization peak, and, in some cases, phonons displaying strong anomalies. The magnetic rare-earth kagome metal series, ReMn₆Sn₆, provides a marvelous playground to study the electronic properties of kagome metals in the presence of magnetism. Here, we report temperature-dependent reflectivity studies on two members of the ReMn₆Sn₆ family, GdMn₆Sn₆ (in-plane ferrimagnet) and TbMn₆Sn₆ (out-of-plane ferrimagnet), in a broad energy range (50 -18000 cm$^{-1}$, equivalent to 6 meV - 2.25 meV) down to 10 K. At high temperatures, a phonon mode at 160 cm$^{-1}$ is observed, which becomes screened out in TbMn₆Sn₆ below 150 K as the localization peak linearly passes through the mode. In GdMn₆Sn₆, the disappearance of the phonon is accompanied by the onset of saturation of the peak position, suggesting an unusual interplay between the two features. Lastly, our calculations reveal the strongly correlated nature of ReMn₆Sn₆ compounds and hence, significant deviations from the simple band picture.

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Diffraction and Raman spectroscopy studies of zirconia solid phases containing cerium

Braga Ferreira Dos Santos, L.; Huittinen, N. M.; Svitlyk, V.; Hennig, C.; Stumpf, T.; Marquardt, J.

Zirconia (ZrO2) doped with lanthanides or actinides has been extensively studied for several tailored applications, such as for the immobilization of actinides present in High-Level Radioactive Waste streams (HLW) or as inert matrix fuel for the incineration of e.g. waste plutonium. Doped zirconia matrices have been reported to have a very high radiation tolerance, however, inconsistencies exist concerning the role of the different structural polymorphs in the high radiation resistance. In addition, the role of oxygen vacancies, which are formed for charge compensation when subvalent dopants are incorporated into the ZrO2 crystal structure, has not been clarified. The lanthanide cerium is often used as a surrogate for plutonium due to its similar ionic radius and comparable chemical properties in the oxidation states +III and +IV. In this study, different Ce concentrations were incorporated into zirconia via the co-precipitation route, to stabilize the cubic zirconia polymorph. Due to the extraordinary luminescent properties of Eu, a trace amount of this lanthanide was added together with Ce in the synthesis process. A series of zirconia samples doped with 14 to 70 mol % Ce was prepared. Seven selected compositions are presented here, namely, samples with 14, 22, 30, 42, 50, 62, and 70 mol% Ce, as they demonstrate a clear phase transformation. The phase composition was evaluated by Powder X-Ray Diffraction (PXRD), and Raman spectroscopy. In the PXRD diffractograms, the monoclinic phase, characterized by diffraction peaks at 28.2 o and 31.3o, is dominant only in the composition with 14 mol % Ce. Above this concentration, a peak around 29.9o, assigned to the tetragonal phase, increases in intensity as a function of increasing Ce concentration in the zirconia matrix up to a concentration of 42 mol%. Beyond this, the cubic phase starts to dominate the phase composition, with the intensive characteristic peak around 29.3o. Additionally, the presence of a tetragonal metastable phase in samples with 30, 42, and 50 mol % Ce, and a trace of the tetragonal phase in the composition with 70 mol % Ce were identified. Generally, the diffraction peaks are shifted to lower 2 angles as a result of the substitution of Zr4+ by the larger Ce4+ cation which increases the lattice parameters. The Raman results corroborate the assignment of the different phase compositions identified in the PXRD studies. However, a large band at 512 cm-1 becomes visible in the samples with 30 mol % Ce and grows in intensity with increasing Ce-doping. This band has been reported to arise from Frenkel-type defects, typically found in samples with oxygen vacancies or/and due to partial reduction of Ce4+ to Ce3+ occurring in the samples, and causing the formation of oxygen vacancies in the ZrO2 structure for charge compensation. This, however, has to be verified in future XANES experiments. No solid phase separation was detected in both characterization analyses, PXRD and Raman. Luminescence spectroscopic studies, probing the Eu ion which has been incorporated together with Ce in all ZrO2 solid phases, will be conducted in future studies. Preliminary results of these investigations will be shown at the RadChem conference.

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    19th Radiochemical Conference, 15.-20.05.2022, Marianske Lazne, Czech Republic
    PURL: https://indico.fjfi.cvut.cz/event/195/contributions/3628/contribution.pdf

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Synthesis and characterization of cerium doped zirconia: a study of solid phase transformations

Braga Ferreira Dos Santos, L.; Huittinen, N. M.; Svitlyk, V.; Hennig, C.; Stumpf, T.

Zirconia (ZrO2) doped with lanthanides, such as cerium (Ce), has been extensively studied for a multitude of tailored applications. The ZrxCe1-xO2 solid solutions can occur in three stable structures: monoclinic (m), tetragonal (t), and cubic (c), but also in several metastable ones (t′, t′′, κ, and t*)1. The phase transformation depends on the dopant concentration and the synthesis conditions, such as sintering temperature or cooling rate. In this study, to understand the behavior of cerium in the zirconia structure, 5 solid solution compositions with Ce4⁺ concentrations of 14, 18, 22, 26, and 30 mol % were synthesized through co-precipitation route. As an additional structural probe, a figurative amount of europium was added to the samples to enable luminescence spectroscopic analyses (TRLFS). In addition to these TRLFS investigations, the phase compositions were evaluated by Raman spectroscopy and synchrotron powder X-ray diffraction (PXRD). The PXRD results show that the diffraction peak around 14.9o can be attributed to the tetragonal phase, and the amount of this phase increases with increasing Ce concentration. Due to the substitution of Zr4+ by the larger Ce4+cation, the diffraction peaks are shifted to lower 2, here from 14.92 to 14.87o2. The t’ and c phases are not easy to distinguish. Owing to the high-resolution PXRD data, however, the diffraction peak around 16.91o could be attributed to the t’ phase and the peak at 16.77o to the cubic one. Both peaks could be identified in the compounds with more than 22 mol % of Ce3. At this concentration, no more monoclinic phase could be detected. TRLFS measurements of the Eu environment, corroborated the presence of the above mentioned phases, going from the dominant monoclinic to tetragonal metastable and cubic phases with increasing Ce substitution4. Combining the PXRD, TRLFS, and Raman data, no solid phase separation (CeO2+ZrO2) was detected.

Keywords: zirconia doped cerium; solid phases; tetragonal prime phase; PXRD; RAMAN; TRLFS; syntheses

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  • Poster
    ChemTugether 2022: Graduate Exchange to Enhance Excellent Research, 13.-14.05.2022, Dresden, Germany

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Publ.-Id: 34964


Actinide physics and chemistry with synchrotron radiation

Kvashnina, K. O.; Butorin, S. M.; Wang, S.; Shi, W.

Actinide research is currently experiencing a renaissance in the fields of material science,
nanotechnology, medicine and environmental science. It is now possible to study the
chemistry and physics of the actinide elements (all radioactive) using state-of-the-art
non-destructive techniques at synchrotrons which have not been available before. The
beamlines and instruments dedicated to actinide research have made various spectro-
scopic and scattering methods accessible to scientists worldwide. The new synchrotron
sources at the large-scale facilities offer more advanced possibilities for the development
of new methodologies in actinide science in the future. Theoretical studies of actinides
are followed by unique experimental methods and novel experimental data.

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Permalink: https://www.hzdr.de/publications/Publ-34963
Publ.-Id: 34963


Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling

Stagg, O.; Morris, K.; Townsend, L. T.; Kvashnina, K.; Baker, M. L.; Dempsey, R.; Abrahamsen-Mills, L.; Shaw, S.

Over 60 years of nuclear activity have resulted in a global legacy of contaminated land and radioactive waste. Uranium (U) is a significant component of this legacy and is present in radioactive wastes and at many contaminated sites. U-incorporated iron (oxyhydr)oxides may provide a long-term barrier to U migration in the environment. However, reductive dissolution of iron (oxyhydr)oxides can occur on reaction with aqueous sulfide (sulfidation), a common environmental species, due to the microbial reduction of sulfate. In this work, U(VI)-goethite was initially reacted with aqueous sulfide, followed by a reoxidation reaction, to further understand the long-term fate of U species under fluctuating environmental conditions. Over the first day of sulfidation, a transient release of aqueous U was observed, likely due to intermediate uranyl(VI)-persulfide species. Despite this, overall U was retained in the solid phase, with the formation of nanocrystalline U(IV)O2 in the sulfidized system along with a persistent U(V) component. On reoxidation, U was associated with an iron (oxyhydr)oxide phase either as an adsorbed uranyl (approximately 65%) or an incorporated U (35%) species. These findings support the overarching concept of iron (oxyhydr)oxides acting as a barrier to U migration in the environment, even under fluctuating redox conditions.

Keywords: iron (oxyhydr)oxides; persulfide; sulfidation; uranium; XAS

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Uranium reduction by magnetite – mechanism of UO2 formation monitored by STEM, SAED and EELS

Lagrange, T.; Pan, Z.; Bártová, B.; Butorin, S. M.; Hyatt, N. C.; Stennett, M. C.; Kvashnina, K. O.; Bernier-Latmani, R.

Uranium (U) is a ubiquitous element in the Earth’s crust, having a concentration of about 2 ppm.
Soluble hexavalent uranium (U(VI)) is reduced and immobilized in anoxic environments. The
underlying reduction mechanism is unknown but is likely of critical importance to explain variability in
U biogeochemical behaviors. In this study, we focused on the mechanism of reduction of U(VI) by the
mixed-valence iron oxide magnetite

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Permalink: https://www.hzdr.de/publications/Publ-34961
Publ.-Id: 34961


Nanochips assisted peptide screening for clinical development of CAR-T cell immunotherapy

Anh Nguyen-Le, T.; Bartsch, T.; Wodtke, R.; Brandt, F.; Arndt, C.; Feldmann, A.; Isabel Sandoval Bojorquez, D.; Perez Roig, A.; Ibarlucea, B.; Lee, S.; Baek, C.-K.; Cuniberti, G.; Bergmann, R.; Puentes-Cala, E.; Andrés Soto, J.; T. Kurien, B.; Bachmann, M.; Baraban, L.

Immunotherapy using CAR-T cells is a new paradigm technology for cancer treatment. To avoid severe side effects and tumor escape variants observed for conventional CAR-T cells approach, adaptor CAR technologies are under development, where intermediate target modules redirect immune cells against cancer cells. In this work, silicon nanowire field effect transistors are used to assist in the development of target modules for an optimized CAR-T cell operation. Focusing on a library of seven variants of E5B9 peptide that is used as CAR peptide epitope, we performed multiplexed binding tests in serum using nanosensor chips. Peptides have been immobilized onto the sensor to compare the signals of transistor upon titration with anti-E5B9 antibodies. Correlation analysis of binding affinities and sensitivities enabled a selection of best candidates for the interaction between CAR and target modules. Finally, cytotoxic functionality of CAR-T cells in combination with the selected target modules were successfully proven. Our results open the perspective for the nanobiosensorics to go beyond the early diagnostics in the field of clinical cancer research, and paves the way towards personalization and efficient monitoring of the immunotherapeutic treatment, where the quantitative analysis with the standard techniques is not an option.

Keywords: CAR-T cells; Nanobiosensors

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CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity

Diercks, J. S.; Georgi, M.; Herranz, J.; Diklić, N.; Chauhan, P.; Clark, A. H.; Hübner, R.; Faisnel, A.; Chen, Q.; Nachtegaal, M.; Eychmüller, A.; Schmidt, T. J.

Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels’ porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels’ CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.

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Publ.-Id: 34959


Synchronizing the helicity of Rayleigh-Bénard convection by a tide-like electromagnetic forcing

Jüstel, P.; Röhrborn, S.; Eckert, S.; Galindo, V.; Gundrum, T.; Stepanov, R.; Stefani, F.

We present results on the synchronization of the helicity in a liquid-metal Rayleigh-Bénard (RB) experiment under the influence of a tide-like electromagnetic forcing with azimuthal wavenumber m = 2. We show that for a critical forcing strength the typical Large Scale Circulation (LSC) in the cylindrical vessel of aspect ratio unity is entrained by the period of the tide-like forcing, leading to synchronized helicity oscillations with opposite signs in two half-spaces. The obtained experimental results are consistent with and supported by numerical simulations. A similar entrainment mechanism for the helicity in the solar tachocline may be responsible for the astonishing synchronization of the solar dynamo by the 11.07-year triple synodic alignment cycle of the tidally dominant planets Venus, Earth and Jupiter.

Keywords: Electromagnetic forcing; Magnetohydrodynamics; Helicity synchronization

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Publ.-Id: 34958


The influence of the bentonite type on the corrosion of cast iron

Sushko, V.; Dressler, M.; Kluge, S.; Matschiavelli, N.; Schierz, A.; Stumpf, T.; Cherkouk, A.

1 Introduction
Bentonite is considered as buffer and sealing material in a multi-barrier system for a deep geologic repositories (DGR) of nuclear waste and spent fuel [1]. Another part of the engineered barrier system is the containment of the radioactive waste. Cast iron is often taking into account for the construction of the containers as a candidate material [2]. But the cast iron components are fairly unstable, can corrode to insoluble corrosion products and react with the bentonite buffer matrix. Anaerobic corrosion together with microbially influenced corrosion are dominant forms of corrosion in the a DGR and the interactions at the metal/bentonite interface determines the performance of bentonite-based radioactive waste barriers [3]. The aim of the current study was to characterize the surface damage associated with corrosion of the cast iron and to compare the potential of the indigenous microorganisms present in different bentonites to influence the corrosion of cast iron.

2 Results
Three types of bentonite (B25, Calcigel, MX-80) were chosen for mesocosm-experiment setup as described in [4]. All three bentonites have different smectite content and an indigenous microbial community. The mesocosms with cast iron coupons, artificial Opalinus clay porewater and bentonite were incubated in N2/CO2 atmosphere for 271 days at 30 °C. Some of the mesocosms were supplemented with 5 mM sodium lactate and hydrogen (to a 0.5 bar of total pressure) to stimulate microbial activity. After the incubation period the content of the mesocosms was divided and subjected to different analysis, including geochemical analysis (as e.g. ICP-MS, ion and high-performance liquid chromatography), DNA isolation and amplification of the intergenic spacer to determine the microbial community structure, SEM-EDX and RAMAN spectroscopy to characterize the surface damage of the cast iron coupons.
The black precipitates were visible in the mesocosms containing Calcigel with lactate as substrate and for all the substrate-containing samples with MX-80. The obtained geochemical data confirmed the differences in the different microcosms by demonstrating unequal levels of sulphate and lactate consumption. Moreover, surface analysis of the cast iron coupons showed that corrosion rate and metabolite accumulation are also dependent on the bentonite type. In addition different microbial community structure was observered by intergenic spacer analysis (RISA) depending on the conditions applied and used bentonite. Therefore, the used bentonites varied in respect to reactivity and microbial activity.
Overall, the results show the importance of selection of suitable bentonite for DGR to adjust microbial implications and possibly faster corrosion rate of the metal containers.
We acknowledge funding by the BMBF (Grant 02NUK053B) and HGF (Grant SO-093).
References
[1] P. Sellin and etc., The Use of Clay as an Engineered Barrier in Radioactive-Waste Management – A Review, Clays and Clay Minerals 61(6), pp. 477-498 (2014).
[2] F. King. Container Materials for the Storage and Disposal of Nuclear Waste, Corrosion 69(10), pp. 986-1011 (2013).
[3] S. Kaufhold and etc. About the Corrosion Mechanism of Metal Iron in Contact with Bentonite, ACS Earth Space Chem. 4, 5, pp. 711–721 (2020).
[4] N. Matschiavelli and etc., The Year-Long Development of Microorganisms in Uncompacted Bavarian Bentonite Slurries at 30 and 60 °C, Environ. Sci. Technol., 53, 17, 10514–10524 (2019)

Keywords: Corrosion; Bentonite

  • Open Access Logo Poster (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

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Publ.-Id: 34957


Simulation of potential and species distribution in a Li||Bi liquid metal battery using coupled meshes

Duczek, C.; Weber, N.; Godinez-Brizuela, O. E.; Weier, T.

In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport
in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li||Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations.
The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results.

Keywords: OpenFOAM; liquid metal battery; molten salt battery; species transfer

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Publ.-Id: 34956


Long-term excessive dietary phosphate increases arterial blood pressure, activates the renin-angiotensin-aldosterone system, and stimulates sympathetic tone in mice

Latic, N.; Peitzsch, M.; Zupcic, A.; Pietzsch, J.; Erben, R. G.

Increased dietary phosphate intake has been associated with severity of coronary artery disease, increased carotid intima–media thickness, left ventricular hypertrophy (LVH), and increased cardiovascular mortality and morbidity in individuals with nor-mal renal function as well as in patients suffering from chronic kidney disease. How-ever, the underlying mechanisms are still unclear. To elucidate further the cardiovas-cular sequelae of long-term elevated phosphate intake we maintained male C57BL/6 mice on a calcium, phosphate, and lactose‐enriched diet (CPD, 2% Ca, 1.25% P, 20% lactose) after weaning for 14 months and compared them with age-matched male mice fed a normal mouse diet (ND, 1.0% Ca, 0.7% P). Notably, the CPD has a balanced cal-cium/phosphate ratio, allowing to investigate the effects of elevated dietary phosphate intake largely independent of changes in parathyroid hormone (PTH). In agreement with the rationale of this experiment, mice maintained on CPD for 14 months were characterized by unchanged serum PTH but showed elevated concentrations of circu-lating intact fibroblast growth factor-23 (FGF23) compared with mice on ND. Cardio-vascular phenotyping did not provide evidence for LVH, as evidenced by unchanged LV chamber size, normal cardiomyocyte area, lack of fibrosis, and unchanged molecu-lar markers of hypertrophy (Bnp) between the two groups. However, intra-arterial catheterization revealed increases in systolic pressure, mean arterial pressure, and pulse pressure in mice fed the CPD. Interestingly, chronically elevated dietary phos-phate intake stimulated the renin-angiotensin-aldosterone system (RAAS) as evi-denced by increased urinary aldosterone in animals fed the CPD, relative to ND con-trols. Furthermore, the catecholamines epinephrine, norepinephrine, and dopamine as well as the catecholamine metabolites metanephrine. normetanephrine and methoxy-tyramine as measured by mass spectrometry were elevated in the urine of mice on CPD, relative to mice on ND. These changes were partially reversed by switching 14-month-old mice on CPD back to ND for 2 weeks. In conclusion, our data suggest that excess dietary phosphate induces a rise in blood pressure independent of second-ary hyperparathyroidism, and that this effect may be mediated through activation of the RAAS and stimulation of the sympathetic tone.

Keywords: Hypertension; left ventricular hypertrophy; renin-angiotensin-aldosterone system; cardiovascular disease; catecholamines; liquid chromatography-tandem mass spectrometry

Permalink: https://www.hzdr.de/publications/Publ-34955
Publ.-Id: 34955


Experimental simulation of phase evolution in conditions of underground storage: from million years to one day

Svitlyk, V.; Weiss, S.; Hennig, C.

Long-living radiotoxic isotopes present in spent nuclear fuel (SNF) requires procedures of complete immobilization of these species. Incorporation of the corresponding elements on atomic level into robust host crystalline matrices is one way to secure SNF during long-term underground storage. Derivatives of zirconia, ZrO2, are promising materials for these applications since these phases are known to remain structurally stable in geological cycles of up to 109 years [1]. The candidate host matrix must provide a sufficient solubility limit for radiotoxic elements, which is studied initially. Afterwards, structural stability of these phases against irradiation and leaching are established in order to asses possible discharge of the incorporated radioactive elements over a long-time scale. In this work we studied systematically structural behaviour of ZrO2-based materials incorporated with Th4+ and Ce4+ under extreme conditions of temperature (T) and pressure (P) in order to simulate experimentally possible phase evolution in conditions of underground storage.
In situ synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the HZDR ROBL BM20 beamline at ESRF, Grenoble, France [2]. It was found that cubic YSZ phases could dissolve 20% more of Th atoms compared to their tetragonal analogues. In situ T-dependent diffraction studies on radionuclide surrogate tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent phase stabilities. No discharge of guest Ce4+ ions was observed. Nevertheless, application of external pressure on tetragonal Ce-YSZ phase induced transition towards a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. Thus, we suggest in situ studies under extreme conditions as a part of standard protocol to validate phases of interest as host matrixes for long-term underground storage of SNF.

References
[1] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993). [2] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

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  • Lecture (Conference)
    Goldschmidt 2022, 10.-15.07.2022, Honolulu, HI, USA

Permalink: https://www.hzdr.de/publications/Publ-34954
Publ.-Id: 34954


Extreme conditions: towards secure and long-term storage of nuclear waste

Svitlyk, V.; Weiss, S.; Hennig, C.

Majority of man-made radiotoxic elements originate from spent nuclear fuel (SNF). It is composed essentially of uranium and plutonium and some minor actinides (An) like 237Np, 241Am/243Am, and 244Cm. Half-life of these elements can range from few decades up to millions of years (ca. 2.1 million years for 237Np [1]). Therefore, safe disposal of SNF requires matrix materials with strong resistance against corrosion and dissolution over a period of 106 years. Derivatives of zirconium-based ceramics, in particular zirconia, ZrO2, are promising materials for these applications since these phases are known to remain stable in geological cycles of up to 109 years [2]. Here scientific and technological goals are to obtain zirconium-based ceramic materials containing maximum possible tetravalent actinides (An) without Zr/An phase separation. In addition, structural stability of these phases under various external parameters, e.g. temperature (T), pressure (P), irradiation and leaching resistance is essential in order to exclude possible discharge of the incorporated radioactive elements over a long-time scale.
Two series of samples have been synthesized for current study: (I) Th-doped Y-stabilized ZrO2 (YSZ) and (II) Ce-doped YSZ phases, both of tetragonal and cubic symmetries. The series (I) was studied in order to determine maximum possible intake of Th4+ ions into the tetragonal and cubic YSZ matrices. The series II used Ce4+ species as surrogate ions for An4+ for studies under extreme conditions of T and P. Synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the ROBL BM20 beamline at ESRF [3]. Relevant technical details will be presented.
For the tetragonal YSZ phases maximum possible Th intake on the Zr/Y metal site reached ca. 10.3 at.%. Cubic phases could dissolve up to ca. 12.3 at.% Th under non-equilibrium conditions. Larger Th-Zr/Y solubility range for cubic phases was found to be symmetry related. Specifically, introduction of Th into tetragonal YSZ induces flattening of the Zr/YO8 polyhedra with concomitant decrease in tetragonality. This results in better accommodation of larger Th atoms via structural stabilization of longer bonding distances.
To simulate phase stability under conditions of underground nuclear repositories, Ce-based analogues were subjected to in situ studies under elevated temperatures and pressures. T-dependent diffraction studies on tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent structural stability for all the studied compounds. In particular, occupancy of guest Ce4+ atoms as a function of temperature does not decrease in these systems. However, application of external pressure on tetragonal Ce-YSZ phase induced a structural transformation to a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. The parent YSZ phases are, therefore, promising candidates as host matrices for radiotoxic tetravalent elements like U, Th or Pu for a long-term underground storage.

References
[1] R. C. Ewing, W. J. Weber, J. Lian, J. Appl. Phys. 95, 5949 (2004).
[2] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993).
[3] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

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  • Lecture (Conference) (Online presentation)
    New opportunities for High Pressure Science at the ESRF-EBS, 07.-09.02.2022, ESRF, Grenoble, France

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Publ.-Id: 34953


Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography

Kaever, C.

Ultrafast electron beam X-ray computed tomography [4] (UFXCT) is a non-invasive imaging technique based on scanning an electron beam on a tungsten target. This way, a moving X-ray source is generated without mechanically moving parts allowing for very high imaging rates up to 8000 fps.
This technique is used, e.g., for the investigation of multiphase flows, such as bubbly flow in industrial bubble column reactors. The goal of the ROOF experiment is to investigate the hydrodynamics of such a bubbly flow by apply UFXCT for scanning and tracking of objects alongside a vertical axis in real time based on the acquired cross-sectional images. To accomplish the tracking, software is needed to recognize objects in the reconstructed images, as a human would not fulfill realtime constraints. The current CPU-based implementation is the slowest step in the current workflow, thus, the goal of this work is to design a faster algorithm. In this work, the approach used by the RISA [5] (Realtime Image Stream Algorithms) software to realize the tracking of objects is presented and improved by using the GPU to recognize the objects.

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  • Study thesis
    TU Dresden, 2022
    Mentor: Dominic Windisch
    14 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34952
Publ.-Id: 34952


Microcosm study of indigenous microorganisms in bentonite and its effect on the corrosion of cast iron

Sushko, V.; Kluge, S.; Matschiavelli, N.; Schierz, A.; Stumpf, T.; Cherkouk, A.

INTRODUCTION

Bentonite is a potential barrier material in deep geological repositories (DGR) for nuclear waste and spent fuel [1] and it is critical to maintain its functionality for long periods of time. Bacteria, that can originate from the bentonite itself, can affect important properties of the engineered barrier system, including bentonite’s swelling capability and integrity of the container material [2]. Cast iron is often considered as a suitable material for constructing the containers for the radioactive waste storage [3]. But the container material could be unstable and can corrode to insoluble corrosion products, which react with the bentonite barrier. In a DGR, anaerobic corrosion and microbially influenced corrosion are dominant forms of corrosion and the interactions at the metal/bentonite interface determine the long-term performance of bentonite-based radioactive waste barriers [4].

DESCRIPTION OF THE WORK

Microcosm-type setup described in [5] was used for the current study. Three types of bentonite with different indigenous microorganisms were chosen for the setup: B25, Calcigel, MX-80. Incubation of the microcosms, containing GGG40 cast iron coupons, synthetic Opalinus Clay porewater (OPA) and bentonite, was performed in N2/CO2 atmosphere at 30 °C. Some of the microcosms were supplemented with 5 mM sodium lactate or 0.5 bar of hydrogen to stimulate microbial activity. After a 271-day incubation period, the microcosms were investigated by various geochemical analyses (as e.g. ICP-MS, ion and high-performance liquid chromatography), DNA isolation and amplification of the ribosomal RNA (rRNA) intergenic spacer (RISA) for microbial community analysis, SEM-EDX and RAMAN spectroscopy to characterize the surface structure of the cast iron coupons.
In addition, a similar 3-component experiment was set up with Calcigel including 4 time points to study in more detail the microbial-induced process of cast iron corrosion in Calcigel-microcosms.

RESULTS AND DISCUSSION

After 271 days of incubation under anaerobic conditions at 30 °C, the presence of black precipitants in microcosms containing Calcigel and sodium lactate, and all substrate-containing MX-80 samples became apparent. Geochemical investigation of the respective samples showed a decrease in sulphate concentration which was dominant in microcosms containing MX-80.
Surface analysis with SEM-EDX showed severe damage for all the samples, except B25 without substrates. Two types of crystalline structures were found: iron and/or calcium carbonates and iron sulphide. The presence of the latter could be an indication of the activity of sulphate-reducing bacteria.
Different microbial community structures were observed by RISA analysis depending on the used bentonite and the applied conditions.
Overall, the results show that the reactivity at the bentonite/metal interface and the microbial activity are bentonite-type dependent and the selection of the bentonite for the DGR is highly important for preventing possible microbial implications that could lead to a faster deterioration of the metal container.

ACKNOWLEDGEMENT

Funding was provided by the German Federal Ministry of Education and Research (BMBF, Grant 02NUK053) and the Helmholtz Association (Grant SO-093).

REFERENCES

1. P. Sellin et al., “The Use of Clay as an Engineered Barrier in Radioactive-Waste Management – A Review” Clays and Clay Minerals, 61(6), pp. 477-498 (2014).
2. F. King, “Container Materials for the Storage and Disposal of Nuclear Waste” Corrosion, 69(10), pp. 986-1011 (2013).
3. F. King et al., “Nature of the near-field environment in a deep geological repository and the implications for the
corrosion behaviour of the container” Corrosion Engineering, Science and Technology, 52, 1, pp. 25-30 (2017).
4. S. Kaufhold et al., “About the Corrosion Mechanism of Metal Iron in Contact with Bentonite” ACS Earth Space Chem., 4, 5, pp. 711–721 (2020).
5. N. Matschiavelli et al., “The Year-Long Development of Microorganisms in Uncompacted Bavarian Bentonite Slurries at 30 and 60 °C” Environ. Sci. Technol., 53, 17, 10514–10524 (2019)

Keywords: Microbially influenced corrosion; Microcosm experiment; SEM; Microbial diversity

  • Poster (Online presentation)
    TransRet2020 - Workshop on Processes Influencing Radionuclide Transport and Retention, 12.-13.10.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-34951
Publ.-Id: 34951


Investigation of the Cannabinoid Receptor 2 (CB2R) Expression and Preliminary In Vitro Evaluation of the CB2R Specific PET Radioligand [18F]JHU94620-d8 in Different Breast Cancer Models

Heerklotz, A.; Moldovan, R.-P.; Deuther-Conrad, W.; Bormans, G.; Pietzsch, J.; Belter, B.; Kopka, K.; Gündel, D.

Introduction
The cannabinoid receptor 2 (CB2R) is involved in inflammatory processes [1], whereby an increased expression correlates with malignancy in various cancer types like human epidermal growth receptor 2 positive (HER2+) or triple negative breast cancer (TNBC) [2]. Hence, the CB2R is suggested as a pharmacological target and prognostic marker for stratification and staging of patients [3].
In the present in vitro studies, we investigated the expression of the CB2R in HER2+ and TNBC models, as well as the potential of our novel radioligand [18F]JHU94620-d8 to assess the CB2R availability in TNBC models.

Methods
The colocalisation of CB2R with Iba1 (macrophages) and CD31 (blood vessels) in cryosections of mouse TNBC 4T1 tumours heterotopically implanted in both NMRI-nude and Balb/c mice was investigated by immunofluorescence staining (IF). The CB2R expression in 4T1, the human HER2+ cell lines HCC1954 (HCC and LCC2) and human TNBC cell lines MDA-MB-231 (MDA and BrM2) was determined by IF.
Competitive radioligand binding assays with the CB2R-specific ligands [3H]WIN55,212-2 and [3H]A-836339 were performed vs. 10 µM JHU94620-d8, GW405833 and WIN55,212-2, and A 836339 as competitor (n=1). Autoradiography with the CB2R-specific [18F]JHU94620-d8 vs. 10 µM competitor was performed with cryosections obtained from 4T1 tumours (n=3) as well as rat brains harbouring a local overexpression of the human CB2R (AAV-hCB2R, n=1) [4].

Results
A high correlation between the heterogeneously distributed CB2R and Iba1, and a weak correlation between CB2R and CD31 was found in 4T1 tumours. Colocalisation of CB2R and Iba1 (Balb/c: Pearson’s coefficient r=0.69±0.03, Manders’ coefficient M1: 0.7±0.12; NMRI-nude: r=0.7±0.12, M1=0.71±0.15) or CD31 (Balb/c: r=0.35±0.09, M1=0.15±0.02; NMRI-nude: r=0.35±0.11; M1=0.19±0.09) was independent of the mouse breed (CB2R/Iba1: pr=0.9, pM1=0.972; CB2R/CD31: pr=0.41, pM1=0.52).
By IF the expression of CB2R and HER2 was confirmed in HCC and LCC2, but absent in all TNBC cell lines.
The total binding of [3H]WIN55,212-2 in HCC (329.04±37.65 fmol/mg protein) and LCC (160.87±9.53 fmol/mg) homogenates could be reduced by homologues competition with WIN55,212 2 (HCC: 229.66±56.56 fmol/mg, -30.2%; LCC2: 117.73±18.49 fmol/mg, -26.82%) and GW405833 (LCC2: 99.41±2.81 fmol/mg, -38.20%) in contrast to JHU94620-d8. Moreover, a specific binding of [3H]A 836339 was not detectable.
In cryosections of AAV-hCB2R binding of [18F]JHU94620-d8 could be displaced by >80% in the target region with all competitors, however in 4T1 tumours a non-displaceable binding was found.

Conclusions
CB2R expression was detectable in Iba1 positive tumour-associated cells of 4T1 tumours cryosections. In HER2+ cells CB2R expression was cross-validated by IF and competitive binding studies. [18F]JHU94620-d8 binds target specific in the artificial AAV-hCB2R model, whereas heterogenous binding was non-displaceable in cryo-sections of mammary tumours.

Keywords: Patient stratification; Cannabinoid Receptor 2; Breast Cancer; PET

  • Lecture (Conference)
    5th GyMICMolecular Imaging Symposium, 15.-16.09.2022, Leipzig, Deutschland
  • Lecture (Conference)
    MOBI 2022, 15.-16.09.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34950
Publ.-Id: 34950


Observing the onset of pressure-driven K-shell delocalization

Döppner, T.; Bethkenhagen, M.; Kraus, D.; Neumayer, P.; Chapman, D. A.; Bachmann, B.; Baggott, R. A.; Böhme, M.; Divol, L.; Falcone, R. W.; Fletcher, L. B.; Landen, O. L.; Macdonald, M. J.; Saunders, A. M.; Schörner, M.; Sterne, P. A.; Vorberger, J.; Witte, B. B. L.; Yi, A.; Redmer, R.; Glenzer, S. H.; Gericke, D. O.

The gravitational pressure in many astrophysical objects exceeds one Gigabar (1 billion atmospheres) for a large part of their interior. At theses extreme conditions, matter is compressed to a state where the distance between nuclei becomes as small as the K-shell, containing the most tightly bound electrons, of light elements. These strong interactions of neighbouring particles modify existing bound states and, above a certain pressure, drive the electrons into a delocalised, conducting state. Both modified bound states and increased ionisation significantly affect the equation of state and radiation transport which, in turn, determine the evolution and structure of these objects. Still, our understanding of this transition is far from satisfying and, up to now, experimental data are sparse due to the extreme conditions required. Here, we report on an experiment that creates and diagnoses matter at pressures above 3 Gigabar by utilising the full capabilities of the National Ignition Facility where 184 laser beams were used to implode a beryllium shell, generating highly compressed states. Bright X-ray flashes enable precision radiography and X-ray Thomson scattering measurements revealing both the macroscopic and the microscopic state of the highly compressed beryllium. The inelastic scattering component shows clear signs of quantum degenerate electrons with the density reaching up to 30 times compression, and a temperature of around 2 million Kelvin. At the most extreme conditions, we also observe strongly reduced elastic scattering, which mainly originates from bound K-shell electrons. We attribute this reduction to the onset of delocalisation of the remaining K-shell electron. With this interpretation, the ion charge inferred from the scattering data agrees well with ab initio simulations, but it is significantly higher than widely used models predict. Our results yield a profound understanding of matter in the interior of brown and white dwarfs and will enhance their evolutionary models required to accurately determine the age of stellar populations. They are also imperative for improving the predictive capabilities supporting inertial confinement fusion experiments, ultimately paving the way to an abundant, carbon-free source of energy.

Permalink: https://www.hzdr.de/publications/Publ-34949
Publ.-Id: 34949


Platform for Probing Radiation Transport Properties of Hydrogen at Conditions Found in the Deep Interiors of Red Dwarfs

Lütgert, B. J.; Bethkenhagen, M.; Bachmann, B.; Divol, L.; Gericke, D. O.; Glenzer, S. H.; Hall, G. N.; Izumi, N.; Khan, S. F.; Landen, O. L.; Maclaren, S. A.; Masse, L.; Redmer, R.; Schörner, M.; Schölmerich, M. O.; Schumacher, S.; Shaffer, N. R.; Starrett, C. E.; Sterne, P. A.; Döppner, T.; Kraus, D.

We describe an experimental concept at the National Ignition Facility for specifically tailored spherical im- plosions to compress hydrogen to extreme densities (up to ∼ 800× solid density, electron number density ne ∼ 4 × 10^25 cm−3) at moderate temperatures (T ∼ 200 eV), i.e. to conditions, which are relevant to the interiors of red dwarf stars. The dense plasma will be probed by laser-generated X-ray radiation of differ- ent photon energy to determine the plasma opacity due to collisional (free-free) absorption and Thomson scattering. The obtained results will benchmark radiation transport models, which in the case for free-free absorption show strong deviations at conditions relevant to red dwarfs. This very first experimental test of free-free opacity models at these extreme states will help to constrain where inside those celestial objects energy transport is dominated by radiation or convection. Moreover, our study will inform models for other important processes in dense plasmas, which are based on electron-ion collisions, e.g. stopping of swift ions or electron-ion temperature relaxation.

Permalink: https://www.hzdr.de/publications/Publ-34948
Publ.-Id: 34948


Real-Time Regulation of Beam-Based Feedback: Implementing an FPGA Solution for a Continuous Wave Linear Accelerator

Maalberg, A.; Kuntzsch, M.; Petlenkov, E.

Control applications targeting fast industrial processes rely on real-time feasible implementations. One of such applications is the stabilization of an electron bunch arrival time in the context of a linear accelerator. In the past, only the electric field accelerating the electron bunches was actively controlled in order to implicitly stabilize the accelerated electron beam. Nowadays, beam properties are specifically measured at a target position and then stabilized by a dedicated feedback loop acting on the accelerating structures. This dedicated loop is usually referred to as a beam-based feedback. Following this, the control system at the linear accelerator ELBE is planned to be upgraded by the beam-based feedback, and the problem of implementing a designed control algorithm becomes highly relevant. In this work, we propose an FPGA-based real-time feasible implementation of a high-order H2 regulator. By presenting the results of the corresponding VHDL simulation and hardware synthesis, we show that the proposed digital solution is fast enough to cover the bunch repetition rates frequently used at ELBE, such as 100 kHz. Finally, we verify the implementation by using a dedicated FPGA testbench.

Keywords: Regulation; Beam-based feedback; FPGA; Linear accelerator; Continuous Wave

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Permalink: https://www.hzdr.de/publications/Publ-34947
Publ.-Id: 34947


Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction

He, Z.; Rödel, M.; Lütgert, J.; Bergermann, A.; Bethkenhagen, M.; Chekrygina, D.; Cowan, T.; Descamps, A.; French, M.; Galtier, E.; Gleason, A. E.; Glenn, G. D.; Glenzer, S. H.; Inubushi, Y.; Hartley, N.; Hernandez, J.-A.; Heuser, B.; Humphries, O. S.; Kamimura, N.; Katagiri, K.; Khaghani, D.; Ja Lee, H.; McBride, E. E.; Miyanishi, K.; Nagler, B.; Ofori-Okai, B.; Ozaki, N.; Pandolfi, S.; Qu, C.; Ranjan, D.; Redmer, R.; Schoenwaelder, C.; Schuster, A.; Stevenson, M. G.; Sueda, K.; Togashi, T.; Vinci, T.; Voigt, K.; Vorberger, J.; Yabashi, M.; Yabuuchi, T.; Zinta, L. M. V.; Ravasio, A.; Kraus, D.

Extreme conditions inside ice giants like Uranus and Neptune can result in peculiar chemistry and structural transitions, e.g., the precipitation of diamonds or superionic water, as so far experimentally observed only for pure C-H and H2O systems, respectively. Here we investigate a stoichiometric mixture of C and H2O by shock-compressing PET plastics and performing in situ X-ray probing. We observe diamond formation at pressures between 72±7 GPa and 125±13 GPa at temperatures ranging from ~3500 K to ~6000 K. Combining X-ray diffraction and small angle X-ray scattering, we access the kinetics of this exotic reaction. The observed demixing of C and H2O suggests that diamond precipitation inside the ice giants is enhanced by oxygen, which can lead to isolated water and thus the formation of superionic structures relevant to the planets’ magnetic fields. Moreover, our measurements indicate a way of producing nanodiamonds by simple laser-driven shock-compression of cheap PET plastics.

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Permalink: https://www.hzdr.de/publications/Publ-34946
Publ.-Id: 34946


Pattern recognition in reciprocal space with a magnon-scattering reservoir

Körber, L.; Heins, C.; Hula, T.; Kim, J.-V.; Thlang, S.; Schultheiß, H.; Faßbender, J.; Schultheiß, K.

Magnons are elementary excitations in magnetic materials and undergo nonlinear multimode scattering processes at large input powers. In experiments and simulations, we show that the interaction between magnon modes of a confined magnetic vortex can be harnessed for pattern recognition. We study the magnetic response to signals comprising sine wave pulses with frequencies corresponding to radial mode excitations. Three-magnon scattering results in the excitation of different azimuthal modes, whose amplitudes depend strongly on the input sequences. We show that recognition rates above 95\% can be attained for four-symbol sequences using the scattered modes, with strong performance maintained with the presence of amplitude noise in the inputs.

Keywords: spin wave; magnon; vortex; Brillouin-light scattering; BLS; reservoir computing; neuromorphic computing; nonlinear; three-magnon scattering; micromagnetic simulations

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Permalink: https://www.hzdr.de/publications/Publ-34945
Publ.-Id: 34945


Impact of sulfated hyaluronan on bone metabolism in diabetic Charcot neuroarthropathy and degenerative arthritis

Schulze, S.; Neuber, C.; Möller, S.; Hempel, U.; Hofbauer, L. C.; Schaser, K.-D.; Pietzsch, J.; Rammelt, S.

Bone in diabetes mellitus is characterized by an altered microarchitecture caused by abnormal metabolism of bone cells. Together with diabetic neuropathy, this is associated with serious complications including impaired bone healing culminating in complicated fractures and dislocations, especially in the lower extremities, so-called Charcot neuroarthropathy (CN). The underlying mechanisms are not yet fully understood, and treatment of CN is challenging. Several in vitro and in vivo investigations have suggested positive effects on bone regeneration by modifying biomaterials with sulfated glycosaminoglycans (sGAG). Recent findings described a beneficial effect of sGAG for bone healing in diabetic animal models compared to healthy animals. We therefore aimed at studying the effects of low- and high-sulfated hyaluronan derivatives on osteoclast markers as well as gene expression patterns of osteoclasts and osteoblasts from patients with diabetic CN compared to non-diabetic patients with arthritis at the foot and ankle. Exposure to sulfated hyaluronan (sHA) derivatives reduced the exaggerated calcium phosphate resorption as well as the expression of genes associated with bone resorption in both groups, but more pronounced in patients with CN. Moreover, sHA derivatives reduced the release of pro-inflammatory cytokines in osteoclasts of patients with CN. The effects of sHA on osteoblasts differed only marginally between patients with CN and non-diabetic patients with arthritis. These results suggest balancing effects of sHA on osteoclastic bone resorption parameters in diabetes.

Keywords: Charcot neuroarthropathy; diabetes mellitus; ankle arthritis; osteoblasts; osteoclasts; sulfated hyaluronan

Permalink: https://www.hzdr.de/publications/Publ-34944
Publ.-Id: 34944


Saccoite, Ca2Mn+32F(OH)8·0.5(SO4), a new, microporous mineral from the Kalahari Manganese Fields, South Africa

Giester, G.; Lengauer, C. L.; Chanmuang N., C.; Topa, D.; Gutzmer, J.; von Bezing, K.-L.

2
transparent, with white streak and vitreous luster. No luminescence is observed. Saccoite is uniaxial (–) with refractive indices at 589(1) nm  = 1.705(5) and  = 1.684(2). Pleochroism is distinct, i.e. bluish green (ω) and yellowish green (ε). The chemical composition was studied by means of an electron probe micro-analyser (EPMA) using wavelength-dispersive X-ray spectrometry (WDS). The empirical mineral formula is Ca2.06Mn3+1.78Cu0.10Mg0.07F0.97(OH)8.02(SO4)0.39. The unit-cell dimensions of saccoite (space group P4/ncc) are a = 12.834(3) Å, c = 5.622(2) Å, V = 926.0(4) Å3), and the calculated mass density is 2.73 g·cm-3. Saccoite exhibits a heteropolyhedral framework structure that is composed of edge- and cornersharing CaF2(OH)6 and M(OH)6 polyhedra (M = Mn3+, Cu2+) with large channels along [001], which host disordered and only partially occupied groups, especially SO42-. The hydrogen atoms of the OH groups point into the channel to form hydrogen bonds with the channel anions. Ca–F distances are about 2.3 Å, the Ca–OH distances in the range of 2.44 -2.58 Ǻ, and the M(OH)6 octahedron is strongly 4+2 Jahn-Teller distorted (4 × ~ 1.92 Å, 2 × 2.27 Å). The F atom is tetrahedrally coordinated to calcium atoms. The strongest lines in the X-ray powder pattern [d in Å (relative intensity) (hkl)] are: 9.0735 (35) (110), 4.5370 (95) (220), 4.0644 (20) (310), 3.0105 (100) (321), 2.8117 (20) (002), 2.7242 (75) (411), 1.9755 (35) (611), and 1.8142 (20) (550).

Keywords: saccoite; Ca2Mn+32F(OH)8·0.5(SO4); new mineral; microporous structure; Kalahari Manganese Field; South Africa

Permalink: https://www.hzdr.de/publications/Publ-34943
Publ.-Id: 34943


Unravelling the Origin of Ultra-Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A-Sites Cause Fermi Level Pinning

Morgenbesser, M.; Viernstein, A.; Schmid, A.; Herzig, C.; Kubicek, M.; Taibl, S.; Bimashofer, G.; Stahn, J.; Antonio Fernandes Vaz, C.; Döbeli, M.; Biautti, F.; de Dios Sirvent, J.; Liedke, M. O.; Butterling, M.; Kamiński, M.; Tolkiehn, M.; Vonk, V.; Stierle, A.; Wagner, A.; Tarancon, A.; Limbeck, A.; Fleig, J.

Different SrTiO3 thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO3 films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo-intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively-coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron-based X-ray standing wave and X-ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe-doped SrTiO3 films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo-intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (FeSr and TiSr) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti_Sr) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self-limitation of the Ti site change and leads to a very robust pseudo-intrinsic situation, irrespective of Sr/Ti ratios and doping.

Keywords: STO; Sr vacancies; conductivity; PALS

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Permalink: https://www.hzdr.de/publications/Publ-34942
Publ.-Id: 34942


Three-dimensional quasiquantized Hall insulator phase in SrSi2

Manna, K.; Kumar, N.; Chattopadhyay, S.; Noky, J.; Yao, M.; Park, J.; Förster, T.; Uhlarz, M.; Chakraborty, T.; Schwarze, B. V.; Hornung, J.; Strocov, V. N.; Borrmann, H.; Shekhar, C.; Sun, Y.; Wosnitza, J.; Felser, C.; Gooth, J.

In insulators, the longitudinal resistivity becomes infinitely large at zero temperature. For classical insulators, the Hall conductivity becomes zero at the same time. However, there are special systems, such as two-dimensional quantum Hall insulators, in which a more complex scenario is observed at high magnetic fields. Here, we report experimental evidence for a quasiquantized Hall insulator in the quantum limit of the three-dimensional compound SrSi2. Our measurements reveal a magnetic-field range, in which the longitudinal resistivity diverges with decreasing temperature, while the Hall conductivity approaches a quasiquantized value that is given only by the conductance quantum and the Fermi wave vector in the field direction. The quasiquantized Hall insulator appears in a magnetic field induced insulating ground state of three-dimensional materials and is deeply rooted in quantum Hall physics.

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Permalink: https://www.hzdr.de/publications/Publ-34941
Publ.-Id: 34941


Study of a possible silicon photomultiplier based readout of the large plastic scintillator neutron detector NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; Boretzky, K.; Gasparic, I.; Stach, D.; Wagner, A.; Zuber, K.

The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany. In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each end by fast timing photomultipliers.

Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM) are reported. For this purpose, a typical NeuLAND bar was instrumented on each end with a prototype of the same geometry as a 1'' photomultiplier tube, including four 6x6 mm^2 SiPMs, amplifiers, high voltage supply, and microcontroller.

Tests were carried out using the 35 MeV electron beam from the ELBE superconducting linac with its ps-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-user mode with 1-60 electrons per bunch, using Acqiris fast digitizers. In addition, offline tests using cosmic rays and the NeuLAND data acquisition scheme were carried out.

Typical time resolutions of sigma <= 100 ps were found for $\geq$99\% efficiency, improving on previous work at ELBE and exceeding the NeuLAND timing goal of sigma < 150 ps. Over a range of 10-300 MeV deposited energy in the NeuLAND bar, the gain was found to deviate by <=10% <=20% from linearity for 35 um (50 um) SiPM pitch, respectively, satisfactory for calorimetric use of the full NeuLAND detector. The dark rate of the prototype studied was found to be 70-200 s^-1, comparable with the unavoidable cosmic-ray induced background.

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Permalink: https://www.hzdr.de/publications/Publ-34940
Publ.-Id: 34940


Metal-assisted chemically etched silicon nanopillars hosting telecom photon emitters

Hollenbach, M.; Jagtap, N. S.; Fowley, C.; Baratech, J.; Guardia-Arce, V.; Kentsch, U.; Eichler-Volf, A.; Abrosimov, N. V.; Erbe, A.; Shin, C.; Kim, H.; Helm, M.; Lee, W.; Astakhov, G.; Berencen, Y.

Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of an ensemble of telecom photon emitters in a two-dimensional array of silicon nanopillars. We developed a top-down nanofabrication method, enabling the production of thousands of nanopillars per square millimeter with state-of-the-art photonic-circuit pitch, all the while being free of fabrication-related radiation damage defects. We found a waveguiding effect of the 1278 nm-G center emission along individual pillars accompanied by improved brightness compared to that of bulk silicon. These results unlock clear pathways to monolithically integrating single-photon emitters into a photonic platform at a scale that matches the required pitch of quantum photonic circuits.

Keywords: G centers; Silicon nanopillars; Photonic integration; Metal-assisted chemical etching; Ion implantation

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Permalink: https://www.hzdr.de/publications/Publ-34938
Publ.-Id: 34938


DNS and Highly-Resolved LES of Heat and Mass Transfer in Two-Phase Counter-Current Condensing Flow

Apanasevich, P.; Lucas, D.; Sato, Y.; Niceno, B.

A comprehensive study of direct-contact condensation heat transfer for turbulent, counter-current, liquid/vapour flow in a nearly horizontal channel at high pressure (i.e. 5MPa) has been carried out based on Direct Numerical Simulation (DNS) and highly-resolved Large Eddy Simulation (LES) approaches. To simulate the two-phase flow situation, driven in this case by a constant pressure gradient, a single set of Navier-Stokes equations, coupled with an enthalpy conservation equation, have been employed. The interfacial mass transfer, seen in this case to be dominated by condensation, has been calculated directly from the heat flux at the liquid/vapour interface. To investigate the effect of condensation on the turbulence phenomena, and vice versa, cases have been considered involving two friction Reynolds numbers: namely Re∗ = u∗h/ν = 178 and Re∗ = u∗h/ν = 590 (u∗ = (hΔP/ρ)^1/2). At the lower Reynolds number, three levels of water subcooling – 0K, 10K and 40K – have been investigated. The use of water subcooling of 0K has enabled the validation and verification procedures associated with the numerical approach to be compared against experimental and numerical data reported in the literature. The choice of the maximum degree of water subcooling is dictated by the need to justify the periodic boundary conditions applied in this numerical study. In the simulation for the higher Reynolds number, only the case of 10K subcooling has been included, as a consequence of the very high computation effort involved.

A detailed statistical analysis of the DNS and LES data obtained from the application of the well-known wall laws has also been assessed. In the vicinity of the liquid/vapour interface, the characteristics of the turbulent motions appear somewhat diverse, depending on whether the interface is basically flat or wavy in character. For a flat interface, some damping effect of the presence of the interface on the turbulence intensity has been observed, a feature which becomes enhanced as the level of liquid subcooling is increased. In the case of a wavy interface, the damping effect is predicted as considerably less pronounced.

Keywords: DNS; Highly-resolved LES; Multiphase flows; Phase change; Direct contact condensation; Interfacial heat transfer

Permalink: https://www.hzdr.de/publications/Publ-34937
Publ.-Id: 34937


Role of network topology in between-community beta diversity on river networks

Tripathi, R.; Reza, A.; Calabrese, J.

The between-community beta diversity of fish species - characterized using the similarity of species between river basins shows a non-linear drop with topological distance on river networks. In this work, we investigate the pattern of this drop with network distances and the role of underlying topology. Using the framework of optimal channel networks, the species abundances are evolved under the neutral biodiversity model. We observe that the steady-state species-similarity shows a phase transition-like behaviour at a critical network distance. At this critical distance, the average degree over the nodes crosses the global average degree of the network. This study sheds light on the role of branching in dendritic networks in ecological community assembly rules.

Keywords: Beta Diversity; Optimal Channel networks; The neutral model of Biodiversity

  • Contribution to proceedings
    COMPLEX NETWORKS 2022, 08.-10.11.2022, Palermo, Italy
    The 11th International Conference on Complex Networks and their Applications, Switzerland: Springer Nature Switzerland, 637-647
    DOI: 10.1007/978-3-031-21131-7_49

Permalink: https://www.hzdr.de/publications/Publ-34935
Publ.-Id: 34935


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.]