Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34121 Publications

Magnetic transition due to the inter-singlet spin-exchange interaction and elastic softening by the interplay of electric quadrupoles in the distorted kagome lattice antiferromagnet Tb3Ru4Al12

Ishii, I.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Kurata, Y.; Suzuki, T.; Gorbunov, D.; Henriques, M. S.; Andreev, A. V.

The distorted kagome lattice antiferromagnet Tb3Ru4Al12 with a hexagonal structure has the Néel temperature TN = 22 K. To clarify the 4 f -electronic state and an influence of electric quadrupoles in Tb3Ru4Al12, ultrasonic measurements on a single-crystalline sample at zero magnetic field and under fields were carried. A characteristic elastic softening of the transverse modulus C66 originating from a quadrupole interaction was found. The crystal electric field parameters were determined to reproduce C66, magnetic susceptibilities, and magnetization curves. The obtained level scheme is that the ground and first excited states are singlets, despite the existence of both the magnetic transition and the quadrupole interaction, indicating that Tb3Ru4Al12 is a curious compound. The positive sign of the quadrupole-quadrupole coupling constant for C66 indicates a ferroquadrupolar-type interaction of the electric quadrupole Oxy or O2. The anisotropic magnetic field dependencies of TN in the field along [100] and [001] were also clarified.

Permalink: https://www.hzdr.de/publications/Publ-30927
Publ.-Id: 30927


The role of microorganisms in the bentonite barrier of high-level radioactive waste repositories

Matschiavelli, N.; Dressler, M.; Neubert, T.; Kluge, S.; Schierz, A.; Cherkouk, A.

The global production of 12,000 metric tonnes of high-level radioactive waste (HLW) every year is a big challenge with respect to its safe long-term storage. In the favored multi-barrier system, bentonite is used as a geo-technical barrier in many disposal programs worldwide. The bentonite seals the space between the canister containing the HLW and the surrounding host rock, thereby fulfilling two major tasks: 1) slow down the process of corrosion when water enters the disposal site, and 2) hinder the discharge of radionuclides into the bio-geosphere in case of a leaking canister. Due to their metabolic activity, microorganisms could influence the properties of the bentonite barrier. In order to investigate the metabolic potential of naturally occurring microorganisms, we conducted anaerobic bentonite-slurry experiments containing uncompact bentonite and a synthetic Opalinus Clay pore water solution. Within one-year incubation at 30 and 60 °C, lactate- or H2-stimulated microcosms at 30 °C showed the dominance and activity of strictly anaerobic, sulfate-reducing and spore-forming microorganisms. Consequently, hydrogen sulfide gas was generated in the respective set ups, leading to the formation of fractures and iron-sulfur precipitations. Experiments that incubated at 60 °C, showed the dominance of thermophilic bacteria, independent of the presence of substrates. The respective set ups showed no significant changes in the analyzed bio-geochemical parameters. The obtained results clearly show that indigenous microorganisms evolve in a temperature- and substrate-dependent manner. The formed metabolites can potentially affect the dissolution behavior of minerals and ions within the bentonite as well as the corrosion process of the canister material and require further investigations.

  • Open Access Logo Lecture (Conference) (Online presentation)
    EGU General Assembly 2020, 04.-08.05.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30926
Publ.-Id: 30926


Solid-liquid Flow in Stirred Tanks: Euler-Euler / RANS Modeling

Shi, P.; Rzehak, R.

Stirred tanks are widely used equipment in process engineering. CFD simulations of such equipment on industrial scales are feasible within the Euler-Euler / RANS approach. In this approach, phenomena on particle scale are not resolved and, accordingly, suitable closure models are required. The present work applies a set of closure relations that originates from a comprehensive review of existing results. Focus is on the modeling of interfacial forces which include drag, lift, turbulent dispersion, and virtual mass. Specifically, new models for the drag and lift forces are considered based on the best currently available description. To validate the model a comprehensive set of experimental data including solid velocity and volume fraction as well as liquid velocity and turbulence has been assembled. The currently proposed model compares reasonably well with this dataset and shows generally better prediction compared with other model variants that originate from different combinations of force correlations.

Keywords: stirred tanks; solid-liquid flow; Euler-Euler two-fluid model; closure relations; Reynolds-stress turbulence model

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  • Secondary publication expected from 20.06.2021

Permalink: https://www.hzdr.de/publications/Publ-30925
Publ.-Id: 30925


Characterization of blood coagulation dynamics and oxygenation in ex‐vivo retinal vessels by fluorescence hyperspectral imaging

Podlipec, R.; Arsov, Z.; Koklic, T.; Strancar, J.

Blood coagulation mechanisms forming a blood clot and preventing hemorrhage have been extensively studied in the last decades. Knowing the mechanisms behind becomes very important particularly in the case of blood vessel diseases. Real‐time and accurate diagnostics accompanied by the therapy are particularly needed for example in diseases related to retinal vasculature. In our study, we employ for the first time fluorescence hyperspectral imaging (fHSI) combined with the spectral analysis algorithm concept to assess physical as well as functional information of blood coagulation in real‐time. By laser‐induced local disruption of retinal vessels to mimic blood leaking and subsequent coagulation and a proper fitting algorithm, we were able to reveal and quantify the extent of local blood coagulation through direct identification of the change of oxyhemoglobin concentration within few minutes. We confirmed and illuminated the spatio‐temporal evolution of the essential role of erythrocytes in the coagulation cascade as the suppliers of oxygenated hemoglobin. By additional optical tweezers force manipulation, we showed immediate aggregation of erythrocytes at the coagulation site. The presented fluorescence‐based imaging concept could become a valuable tool in various blood coagulation diagnostics as well as theranostic systems if coupled with the laser therapy.

Keywords: Blood coagulation; hemoglobin oxygenation; fluorescence hyperspectral imaging; optical tweezers; comparative animal models; biomedical optics and biophotonics; diagnostics

Related publications

Permalink: https://www.hzdr.de/publications/Publ-30922
Publ.-Id: 30922


How to integrate geochemistry at affordable costs into reactive transport for large-scale systems

Stockmann, M.; Brendler, V.

This international workshop entitled “How to integrate geochemistry at affordable costs into reac-tive transport for large-scale systems” was organized by the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden Rossendorf in Feb-ruary 2020. A mechanistic understanding and building on that an appropriate modelling of geochemical processes is essential for reliably predicting contaminant transport in groundwater systems, but also in many other cases where migration of hazardous substances is expected and consequently has to be assessed and limited. In case of already present contaminations, such modelling may help to quantify the threads and to support the development and application of suitable remediation measures. Typical application areas are nuclear waste disposal, environmental remediation, mining and milling, carbon capture & storage, or geothermal energy production. Experts from these fields were brought together to discuss large-scale reactive transport modelling (RTM) because the scales covered by such pre-dictions may reach up to one million year and dozens of kilometers. Full-fledged incorporation of geochemical processes, e.g. sorption, precipitation, or redox reactions (to name just a few important basic processes) will thus create inacceptable long computing times. As an effective way to integrate geochemistry at affordable costs into RTM different geochemical concepts (e.g. multidimensional look-up tables, surrogate functions, machine learning, utilization of uncertainty and sensitivity analysis etc.) exist and were extensively discussed throughout the workshop. During the 3-day program of the workshop keynote and regular lectures from experts in the field, a poster session, and a radio lab tour had been offered. In total, 40 scientists from 28 re-search institutes and 8 countries participated. The focus of the workshop was: (1) To provide and discuss existing geochemical concepts in reactive transport modelling to describe sorption and related retardation processes of contaminants on a variety of sedi-ments and rocks. (2) To explicitly set focus on large-scale natural systems as experienced, e.g., in nuclear waste disposal, carbon capture & storage, environmental remediation, or geothermal applications. (3) To explore how the discussed approaches can be integrated at affordable costs into cur-rent paradigms in THMC models and long-term safety assessments in general. (4) To promote the exchange of scientific knowledge and practical experience between the workshop participants in an efficient way. Based on the intensive discussions and very posi-tive feedback on the workshop, a continuation is intended to bundle and strengthen the respective research activities and stipulate the international network that started to form during the conference days.

Keywords: Geochemistry; Large-scale reactive transport modelling; Workshop

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-111 2020
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-30921
Publ.-Id: 30921


Data for: Photoluminescence dynamics in few-layer InSe

Venanzi, T.; Arora, H.; Winnerl, S.; Pashkin, O.; Chava, P.; Patane, A.; Kovalyuk, Z.; Kudrynskyi, Z.; Watanabe, K.; Taniguchi, T.; Erbe, A.; Helm, M.; Schneider, H.

We study the optical properties of thin flakes of InSe encapsulated in hexagonal boron nitride. Mores pecifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL line shape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguishable at low temperature: direct band-gap electron-hole and defect-assisted recombination. The two recombination processes have lifetimes ofτ1∼8ns andτ2∼100 ns, respectively. The relative weights of the direct band-gap and defect-assisted contributions show a strong layer dependence due to the direct-to-indirect band-gap crossover. Electron-hole PL lifetime is limited by population transfer to lower-energy states and no dependence on the number of layers was observed. The lifetime of the defect-assisted recombination gets longer for thinner samples. Finally, we show that the PL lifetime decreases at high temperatures as a consequence of more efficient nonradiative recombinations.

Keywords: 2D semiconductors; time-resolved photoluminescence

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-14
    DOI: 10.14278/rodare.412
    License: CC-BY-1.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30918
Publ.-Id: 30918


Photoluminescence dynamics in few-layer InSe

Venanzi, T.; Arora, H.; Winnerl, S.; Pashkin, O.; Chava, P.; Patanè, A.; Kovalyuk, Z. D.; Kudrynskyi, Z. R.; Watanabe, K.; Taniguchi, T.; Erbe, A.; Helm, M.; Schneider, H.

We study the optical properties of thin flakes of InSe encapsulated in hexagonal boron nitride. More specifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL line shape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguishable at low temperature: direct band-gap electron-hole and defect-assisted recombination. The two recombination processes have lifetimes ofτ1∼8ns andτ2∼100 ns, respectively. The relative weights of the direct band-gap and defect-assisted contributions show a strong layer dependence due to the direct-to-indirect band-gap crossover. Electron-hole PL lifetime is limited by population transfer to lower-energy states and no dependence on the number of layers was observed. The lifetime of the defect-assisted recombination gets longer for thinner samples. Finally, we show that the PL lifetime decreases at high temperatures as a consequence of more efficient nonradiative recombinations.

Keywords: 2D semiconductors; time-resolved photoluminescence

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-30917
Publ.-Id: 30917


Two-Pion production in the second resonance region in π−p collisions with HADES

Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Chernenko, S.; Chlad, L.; Chudoba, P.; Ciepał, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kuboś, J.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Ramstein, B.; Rathod, N.; Reshetin, A.; Rodriguez-Ramos, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sing, U.; Smyrski, J.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Ungethüm, C.; Vazquez-Doce, O.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wójcik, D.; Zanevsky, Y.; Zumbruch, P.

Pion induced reactions provide unique opportunities for an unambiguous description of baryonic resonances and their coupling channels by means of a partial wave analysis. Using the secondary pion beam at SIS18, the two pion production in the second resonance region has been investigated to unravel the role of the N(1520)32− resonance in the intermediate ρ production. Results on exclusive channels with one pion (π−p) and two pions (π+π−n, π0π−p) in the final state measured in the π−−p reaction at four different pion beam momenta (0.650, 0.685, 0.733, and 0.786 GeV/c) are presented. The excitation function of the different partial waves and Δπ, Nσ and Nρ isobar configurations is obtained, using the Bonn-Gatchina partial wave analysis. The N(1520)32− resonance is found to dominate the Nρ final state with the branching ratio BR=12.2±1.9%.

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Permalink: https://www.hzdr.de/publications/Publ-30916
Publ.-Id: 30916


Argon gas flow investigations in liquid Sodium using ultrafast electron beam X-ray computed tomography (NaFEX) - Data set

Bieberle, A.

For investigations on Argon gas bubbles in liquid Sodium ultrafast electron beam X-ray computed tomography is applied. The repository comprises imaging data obtained at

  • different heights of the test facility and
  • various gas volume rates.

The CT scanner is operated in dual-plane mode with a deflection frequency of 2 kHz for approximately 30s.

Keywords: ultrafast X-ray CT; gas-liquid two-phase flow

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-16
    DOI: 10.14278/rodare.291
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30915
Publ.-Id: 30915


Measurements to verify different concepts of multi-plane detectors for ultrafast electron beam X-ray computed tomography

Bieberle, A.

The measurements in this dataset repository contain raw signal data obtained from novel multi-plane detectors that are experimentally tested with the ultrafast electron beam X-ray CT (UFXCT) scanner at the HZDR. The CT scanner is operated with a constant deflection frequency of 2 kHz, an acceleration voltage of +150 keV and in dual-plane CT scanning mode. The voltage output signals of four multi-plane detector channels are sampled with 2 MHz and 24 bit (±5 V) using a commercial eight-channel data acquisition system (LTT24, Labortechnik Tasler GmbH). The applied reverse voltage to the avalanche photodiodes and the three deflection coil signals are recorded simultaneously. The detectors are collimated with lead and are analysed for

  • various electron beam currents,
  • various detector heights and
  • two different designs.

Keywords: ultrafast X-ray CT; scintillation detectors; multi-plane imaging

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-17
    DOI: 10.14278/rodare.288
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30914
Publ.-Id: 30914


Ferromagnetism in Undoped ZnO Grown by Pulsed Laser Deposition

Waqar, A.; Cai-Qin, L.; Xu, C.; Zhou, S.; Wagner, A.; Butterling, M.; Muhammad, Y.; Francis, C.-C. L.

Undoped ZnO films grown on sapphire by pulsed laser deposition are magnetic at room temperature. A comprehensive study involving x-ray diffraction, positron annihilation spectroscopy, and superconducting quantum Interference device-vibrating sample magnetometer is performed to study the origin of the observed magnetization. Correlations between the saturation magnetization, VZn-2VO concentration and surface to volume ratio of the grain found experimentally show that the magnetization is associated with the vacancy cluster and probably VZn-2VO residing on the grain surface.

Keywords: ZnO films pulsed laser deposition magnetic x-ray diffraction positron annihilation spectroscopy magnetization vacancy cluster grain surface

Permalink: https://www.hzdr.de/publications/Publ-30912
Publ.-Id: 30912


Passive Shutdown Systems for Fast Neutron Reactors

International Atomic Energy Agency; Batra, C.; Baudrand, O.; Bubelis, E.; Burgazzi, L.; Farmer, M.; Fomin, O.; Gugiu, D.; Hidemasa, Y.; Kriventsev, V.; Kuzina, J.; Kuznetsov, V.; Lamberts, D.; Lee, J.; Lüley, J.; Monti, S.; Nikitin, E.; Qvist, S.; Rineiski, A.; Schikorr, M.; Sorokin, A.; van Wert, C.; Vijayashree, R.; Vrban, B.; Yllera, J.

Designs for nuclear power plants increasingly include passive features. A major focus of the design of modern fast reactors is on inherent and passive safety. Inherent and passive safety features are especially important when active systems such as emergency shutdown systems for reactor shutdown are not functioning properly. This publication discusses the past experience in the development of such systems along with the research that is ongoing. It is a comprehensive publication which provides information on the basic design principles for passive shutdown systems and the related operational experience gathered so far, and also reviews the innovative concepts under development and the needs for research and development and qualification tests.

Keywords: Fast reactors; Passive safety measures; Nuclear reactors; Safety measures

  • Other report
    IAEA Nuclear Energy Series No. NR-T-1.16: International Atomic Energy Agency, 2020
    110 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-30909
Publ.-Id: 30909


Tuning Tailored Single-Walled Carbon Nanotubes by Highly Energetic Heavy Ions

El-Said, A. S.; Rao, S.; Akhmadaliev, S.; Facsko, S.

Carbon-based nanomaterials have attracted a lot of interest lately due to their highly promising applications. Here, we report on the modifications of single-walled carbon nanotubes (SWCNTs) induced by swift (highly energetic) heavy ions. Using scanning force microscopy and Raman spec- troscopy, we observed a dramatic change in the structure of the irradiated SWCNTs, accompanied by an increase of the adhesion force as a function of ion fluence and electronic energy loss. With increasing ion fluence the SWCNTs exhibit a partial transformation from metallic to more semicon- ducting. Moreover, at high fluence they break into segments of 10–20 nm length.

Keywords: Swift Heavy Ion; Ion Irradiation; Carbon Nanotubes

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Permalink: https://www.hzdr.de/publications/Publ-30908
Publ.-Id: 30908


Chemical manipulation of hydrogen induced high p-type and n-type conductivity in Ga₂O₃

Islam, M. M.; Liedke, M. O.; Winarski, D.; Butterling, M.; Wagner, A.; Hosemann, P.; Wang, Y.; Uberuaga, B. P.; Selim, F. A.

Advancement of optoelectronic and high-power devices is tied to the development of wide band gap materials with excellent transport properties. However, bipolar doping (n-type and p-type doping) and realizing high carrier density while maintaining good mobility have been big challenges in wide band gap materials. Here P-type and n-type conductivity was introduced in β-Ga₂O₃, an ultra-wide band gap oxide, by controlling hydrogen incorporation in the lattice without further doping. Hydrogen induced a 9-order of magnitude increase of n-type conductivity with donor ionization energy of 20 meV and resistivity of 10⁻⁴ Ωcm. The conductivity was switched to p-type with acceptor ionization energy of 42 meV by altering hydrogen incorporation in the lattice. Density functional theory calculations were used to examine hydrogen location in the Ga₂O₃ lattice and identified a new donor type as the source of this remarkable n-type conductivity. Positron annihilation spectroscopy measurements confirm this finding and the interpretation of the experimental results. This work illustrates a new approach that allows a tunable and reversible way of modifying the conductivity of semiconductors and it is expected to have profound implications on semiconductor field. At the same time, it demonstrates for the first time p-type and remarkable n-type conductivity in Ga₂O₃ which should usher in the development of Ga₂O₃ devices and advance optoelectronics and high-power devices.

Keywords: optoelectronics high-power wide band gap transport bipolar doping β-Ga₂O₃ semiconductors

Permalink: https://www.hzdr.de/publications/Publ-30907
Publ.-Id: 30907


Phase-resolved Higgs response in superconducting cuprates

Chu, H.; Kim, M.-J.; Katsumi, K.; Kovalev, S.; Dawson, R. D.; Schwarz, L.; Yoshikawa, N.; Kim, G.; Putzky, D.; Li, Z. Z.; Raffy, H.; Germanskiy, S.; Deinert, J.-C.; Awari, N.; Ilyakov, I.; Green, B. W.; Chen, M.; Bawatna, M.; Christiani, G.; Logvenov, G.; Gallais, Y.; Boris, A. V.; Keimer, B.; Schnyder, A.; Manske, D.; Gensch, M.; Wang, Z.; Shimano, R.; Kaiser, S.

In high energy physics, the Higgs field couples to gauge bosons and fermions and gives mass to their elementary excitations. Experimentally, such couplings can be verified from the decay product of the Higgs boson, the scalar (amplitude) excitation of the Higgs field. In superconductors, Cooper pairs bear a certain analogy to the Higgs field. Coulomb interactions between the Cooper pairs give mass to the electromagnetic field, which leads to the Meissner effect. Additional coupling with other types of interactions or collective modes is foreseeable, and even highly probable for high-Tc superconductors, where multiple degrees of freedom are intertwined. The superconducting Higgs mode may reveal such couplings spectroscopically and uncover interactions directly relevant to Cooper pairing. To this end, we investigate the Higgs mode of several cuprate thin films using phase-resolved terahertz third harmonic generation (THG) to. In addition to the heavily damped Higgs mode itself, we observe a universal jump in the phase of the driven Higgs oscillation as well as a non-vanishing THG above Tc. These findings indicate coupling of the Higgs mode to other collective modes and a nonzero pairing amplitude above Tc. Our study demonstrates a new approach for investigating unconventional superconductivity. We foresee a fruitful future for phase-resolved spectroscopy in various superconducting systems.

Keywords: Superconductors; terahertz; Higgs; Nonlinear dynamics; ultrafast

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-15
    DOI: 10.14278/rodare.276
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30902
Publ.-Id: 30902


Role of Hydrogen-Related Defects in Photocatalytic Activity of ZnO Films Grown by Atomic Layer Deposition

Peter, R.; Salamon, K.; Omerzu, A.; Grenzer, J.; Badovinac, I. J.; Saric, I.; Petravic, M.

The photocatalytic activity of ZnO films, grown by atomic layer deposition on sapphire, was investigated for different amounts of residual hydrogen incorporated unintentionally into the matrix during the crystal growth. A close correlation was found between the level of incorporated hydrogen ; the rate of photocatalytic degradation of methylene blue on ZnO films. The rate of degradation is consistent with predominantly zero-order reaction kinetics. An enhanced photocatalytic activity, observed for films of predominantly (001)-oriented grains ; low concentration of residual hydrogen, is explained by the reduced number of hydrogen-related defects responsible for recombination of charge carriers in combination with the preferential adsorption of water on polar (001) surfaces of ZnO grains.

Keywords: atomic layer deposition; photocatalytic degradation

Permalink: https://www.hzdr.de/publications/Publ-30899
Publ.-Id: 30899


Formation of Defects in Two-Dimensional MoS2 in the Transmission Electron Microscope at Electron Energies below the Knock-on Threshold: The Role of Electronic Excitations

Kretschmer, S.; Lehnert, T.; Kaiser, U.; Krasheninnikov, A.

Production of defects under electron irradiation in a transmission electron microscope (TEM) due to inelastic effects has been reported for various materials, but the microscopic mechanism of damage development in periodic solids through this channel is not fully understood. We employ non-adiabatic Ehrenfest, along with constrained density functional theory molecular dynamics, and simulate defect production in two-dimensional MoS2 under electron beam. We show that when excitations are present in the electronic system, formation of vacancies through ballistic energy transfer is possible at electron energies which are much lower than the knock-on threshold for the ground state. We further carry out TEM experiments on single layers of MoS2 at electron voltages in the range of 20−80 kV and demonstrate that indeed there is an additional channel for defect production. The mechanism involving a combination of the knock-on damage and electronic excitations we propose is relevant to other bulk and nanostructured semiconducting materials.

Keywords: Two-dimensional materials; transition-metal dichalcogenides; high-resolution transmission electron microscopy; defects

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  • Secondary publication expected from 20.03.2021

Permalink: https://www.hzdr.de/publications/Publ-30894
Publ.-Id: 30894


Recent advances in experimental techniques for flow and mass transfer analyses in thermal separation systems

Hampel, U.; Schubert, M.; Döß, A.; Sohr, J.; Vishwakarma, V.; Repke, J.-U.; Gerke, S. J.; Leuner, H.; Rädle, M.; Kapoustina, V.; Schmitt, L.; Grünewald, M.; Brinkmann, J. H.; Plate, D.; Kenig, E. Y.; Lutters, N.; Bolenz, L.; Buckmann, F.; Toye, D.; Arlt, W.; Linder, T.; Hoffmann, R.; Klein, H.; Rehfeldt, S.; Winkler, T.; Bart, H.-J.; Wirz, D.; Schulz, J.; Scholl, S.; Augustin, W.; Jasch, K.; Schlüter, F.; Schwerdtfeger, N.; Jupke, A.; Kabatnik, C.; Braeuer, A. S.; D'Auria, M.; Runowski, T.; Casal, M. F.; Becker, K.; David, A.-L.; Górak, A.; Skiborowski, M.; Groß, K.; Qammar, H.

Modelling flow and mass transfer of thermal separation equipment constitutes one of the most challenging tasks in fluids process engineering. The difficulty of this task comes from the multiscale multiphase flow phenomena in rather complex geometries. Both analysis of flow and mass transfer on different scales as well as validation of models and simulation results require advanced experimental and measurement techniques. As a follow-up to intensive discussions during the 2019 Tutzing Symposium “Separation Units 4.0” we present in this article a wide set of available modern experimental technologies, which are used in different research and industry laboratories.

Keywords: Thermal separation systems; experimental techniques; measurement techniques

Permalink: https://www.hzdr.de/publications/Publ-30890
Publ.-Id: 30890


Anomalous Lattice Softening Near a Quantum Critical Point in a Transverse Ising Magnet

Matsuura, K.; Pham, T. C.; Zherlitsyn, S.; Wosnitza, J.; Abe, N.; Arima, T.

We have investigated the elastic response of a transverse Ising magnet CoNb2O6 by means of ultrasound velocity measurement. A huge elastic anomaly in the C66 mode is observed near a quantum critical Point when sweeping a magnetic field perpendicular to the Ising axis. This anomaly appears to become critical only for the Faraday configuration (field parallel to the sound propagation direction) but is much less pronounced for the Voigt geometry (field perpendicular to the sound propagation direction). We propose that the relativistic spin-orbit interaction plays a crucial role in the quantum critical regime resulting in the elastic anomaly, which is enhanced by quantum fluctuations.

Permalink: https://www.hzdr.de/publications/Publ-30889
Publ.-Id: 30889


Single Photon Emission Computed Tomography Tracer

Pietzsch, H.-J.; Mamat, C.; Müller, C.; Schibli, R.

Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years.
Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., 99mTc, 123I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases.
Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.

  • Book chapter
    Schober, Otmar, Kiessling, Fabian, Debus, Jürgen: Molecular Imaging in Oncology, Switzerland: SpringerNature, 2020, 978-3-030-42617-0
    DOI: 10.1007/978-3-030-42618-7

Permalink: https://www.hzdr.de/publications/Publ-30888
Publ.-Id: 30888


Wieviel 'normales' Risiko birgt COVID in sich?

Spiegelhalter, D.; Steinbach, P.

Eine Übersetzung des Artikels "How much ‘normal’ risk does Covid represent?" von David Spiegelhalter, der am 21. März 2020 auf https://medium.com/wintoncentre/how-much-normal-risk-does-covid-represent-4539118e1196 erschien. Sir David John Spiegelhalter ist britischer Statistiker und Winton Professor für das öffentliche Verständnis von Risiko an der the Universität Cambridge. Er ist Fellow am Churchill College, Cambridge.

Keywords: COVID19; Corona; Risk; Statistics; Mortality

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Permalink: https://www.hzdr.de/publications/Publ-30887
Publ.-Id: 30887


Nonlinear Charge Transport in InGaAs Nanowires at Terahertz Frequencies

Rana, R.; Balaghi, L.; Fotev, I.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.

We probe the electron transport properties in the shell of GaAs/In0.2Ga0.8As core/shell nanowires at high electric fields using optical pump/THz probe spectroscopy with broadband THz pulses and peak electric fields up to 0.6 MV/cm. The plasmon resonance of the photoexcited charge carriers exhibits a systematic redshift and a suppression of its spectral weight for THz driving fields exceeding 0.4 MV/cm. This behavior is attributed to the intervalley electron scattering that results in the doubling of the average electron effective mass. Correspondingly, the electron mobility at the highest fields drops to about half of the original value. We demonstrate that the increase of the effective mass is nonuniform along the nanowires and takes place mainly in their middle part, leading to a spatially inhomogeneous carrier response. Our results quantify the nonlinear transport regime in GaAs-based nanowires and show their high potential for development of nanodevices operating at THz frequencies.

Keywords: Terahertz (THz); Nanowire; Localized Plasmon; Intervalley Scattering

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Permalink: https://www.hzdr.de/publications/Publ-30886
Publ.-Id: 30886


Numerical framework for a morphology adaptive multi-field two-fluid model in OpenFOAM

Meller, R.; Schlegel, F.; Lucas, D.

A solver for multiphase flows based on the incompressible Eulerian multi-field two-fluid model for the OpenFOAM release of The OpenFOAM Foundation for numerical simulations of multiphase flows with morphology changes and resolved interfaces.

Features:

  • morphology adaptive modeling framework for modelling of dispersed and resolved interfaces based on Eulerian multi-field two-fluid model
  • compact interpolation method according to Cubero et al. (Comput Chem Eng, 2014, Vol. 62, 96-107), including virtual mass
  • numerical drag according to Strubelj and Tiselj (Int J Numer Methods Eng, 2011, Vol. 85, 575-590) to describe resolved interfaces in a volume-of-fluid like manner
  • strong phase coupling resolved by partial elimination algorithm
  • selected test cases:
    • a two-dimensional gas bubble, rising in a liquid, which is laden with micro gas bubbles, and
    • a two-dimensional stagnant stratification of water and oil, sharing a large-scale interface

Keywords: OpenFOAM, C++, CFD, Finite volume method, Multiphase flow, Multi-field two-fluid model, Eulerian-Eulerian model, Momentum interpolation, Partial elimination algorithm

  • Software in the HZDR data repository RODARE
    Publication date: 2020-04-06
    DOI: 10.14278/rodare.286
    License: GPL-3.0

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Permalink: https://www.hzdr.de/publications/Publ-30885
Publ.-Id: 30885


Rühr- und Mischvorgänge in Biogasanlagen: Potentiale und Erfolgschancen

Annas, S.; Elfering, M.; Jantzen, H.-A.; Scholz, J.; Janoske, U.; Heller, A.; Buntkiel, L.

Im Rahmen des Forschungsvorhabens NeoBio wird die Problematik des optimalen Mischprozesses in Biogasanlagen aufgegriffen, um praktikable Lösungsansätze für die optimale Auslegung der Mischprozesse zu finden.
In diesem Zusammenhang steht die Bestimmung instationärer Geschwindigkeitsfelder in Biogasanlagen über in der Fermentersuspension mitschwimmende Funksensoren im Fokus, welche ihre Position über Laufzeitmessungen detektieren. In Kombination mit Inertialsensoren können Bewegungen auch unterhalb des Flüssigkeitsspiegels be-stimmt werden. Die ermittelten Geschwindigkeitsdaten werden für die Auslegung von Rührwerksgeometrien, -korrespondenzen und die Validierung von Modellversuchen genutzt.
In modellmaßstäblichen Untersuchungen an einem Fermenter mit Paddelrührwerk (Maßstab 1:40) konnte bereits gezeigt werden, welchen Einfluss alternative Rührwerk-spositionen auf den Mischprozess haben. Eine Verringerung von Totzonen sowie die Reduzierung der Rühr- bzw. Mischzeit um bis zu 80 % sind erreichbar. Dabei sind die notwendigen Anpassungen überschaubar und somit in der Praxis leicht zu realisieren.
Diese Erkenntnisse werden bereits in aktuellen Anlagen umgesetzt und sind ein Bau-stein bei der Wirkungsgradsteigerung. Um das Optimierungspotential sicher bewerten zu können, müssen die Ergebnisse noch im Originalmaßstab validiert werden. In die-sem Zusammenhang soll die beschriebene Messtechnik eingesetzt werden

  • Open Access Logo Contribution to proceedings
    14. Rostocker Bioenergieforum, 16.-17.06.2020, Rostock, Deutschland
    Tagungsband zum 14. Rostocker Bioenergieforum / 19. DIALOG Abfallwirtschaft MV
    DOI: 10.18453/rosdok_id00002650

Permalink: https://www.hzdr.de/publications/Publ-30884
Publ.-Id: 30884


Synthesis and evaluation of new 1-oxa-8-azaspiro[4.5]decane derivatives as candidate radioligands for sigma-1 receptors

Tian, J.; He, Y.; Deuther-Conrad, W.; Fu, H.; Xie, F.; Zhang, Y.; Wang, T.; Zhang, X.; Zhang, J.; Brust, P.; Huang, Y.; Jia, H.

We report the design, synthesis, and evaluation of a series of 1-oxa-8-azaspiro[4.5]decane and 1,5-dioxa-9-azaspiro[5.5]undecane derivatives as selective σ1 receptor ligands. All seven ligands exhibited nanomolar affinity for σ1 receptors (Ki(σ1) = 0.61 – 12.0 nM) and moderate selectivity toward σ2 receptors (Ki(σ2)/ Ki(σ1) = 2 – 44). Compound 8 with the best selectivity among these ligands was selected for radiolabeling and further evaluation. Radioligand [18F]8 was prepared via nucleophilic 18F-substitution of the corresponding tosylate precursor, with an overall isolated radiochemical yield of 12-35%, a radiochemical purity of >99%, and molar activity of 94 – 121 GBq/μmol. Biodistribution studies of [18F]8 in mice demonstrated high initial brain uptake at 2 min. Pretreatment with SA4503 resulted in significantly reduced brain-to-blood ratio (70% - 75% at 30 min). Ex vivo autoradiography in ICR mice demonstrated high accumulation of the radiotracer in σ1 receptor-rich brain areas. These findings suggest that [18F]8 could be a lead compound for further structural modification to develop potential brain imaging agent for σ1 receptors.

Keywords: 1-oxa-8-azaspiro[4.5]decane derivatives; 1,5-dioxa-9-azaspiro[5.5]undecane derivatives; σ1 receptor; fluorine-18; positron emission tomography

Permalink: https://www.hzdr.de/publications/Publ-30882
Publ.-Id: 30882


Establishment and Characterisation of Heterotopic Patient-Derived Xenografts for Glioblastoma

Meneceur, S.; Annett, L.; Matthias, M.; Sandra, H.; Steffen, L.; Rebecca, B.; Dietmar, K.; Gabriele, S.; Achim, T.; Baumann, M.; Krause, M.; Cläre, V. N.

Glioblastoma is an aggressive brain tumour with a patient median survival of approximately 14 months. The development of innovative treatment strategies to increase the life span and quality of life of patients is hence essential. This requires the use of appropriate glioblastoma models for preclinical testing, which faithfully reflect human cancers. The aim of this study was to establish glioblastoma patient-derived xenografts (PDXs) by heterotopic transplantation of tumour pieces in the axillae of NMRI nude mice. Ten out of 22 patients’ samples gave rise to tumours in mice. Their human origin was confirmed by microsatellite analyses, though minor changes were observed. The glioblastoma nature of the PDXs was corroborated by pathological evaluation. Latency times spanned from 48.5 to 370.5 days in the first generation. Growth curve analyses revealed an increase in the growth rate with increasing passages. The methylation status of the MGMT promoter in the primary material was maintained in the PDXs. However, a trend towards a more methylated pattern could be found. A correlation was observed between the take in mice and the proportion of Sox2+ cells (r = 0.49, p = 0.016) and nestin+ cells (r = 0.55, p = 0.007). Our results show that many PDXs maintain key features of the patients’ samples they derive from. They could thus be used as preclinical models to test new therapies and biomarkers.

Keywords: patient-derived xenografts; preclinical models; cancer stem cell markers; glioblastoma; growth data

Permalink: https://www.hzdr.de/publications/Publ-30881
Publ.-Id: 30881


Photocatalytic biocidal effect of copper doped TiO2 nanotube coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila

Podlipec, R.

Raw datasets and images performed on the Helium Ion Microscope for the published study with the title Photocatalytic biocidal effect of copper doped TiO2 nanotube coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-17
    DOI: 10.14278/rodare.284
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30880
Publ.-Id: 30880


Disturbance-Promoted Unconventional and Rapid Fabrication of Self-Healable Noble Metal Gels for (Photo-)Electrocatalysis

Du, R.; Joswig, J.-O.; Fan, X.; Hübner, R.; Spittel, D.; Hu, Y.; Eychmüller, A.

As an emerging class of porous materials, noble metal aerogels (NMAs) have drawn tremendous attention and displayed unprecedented potential in diverse fields. However, the development of NMAs is impeded by the fabrication methods because of their time- and cost-consuming procedures, limited generality, and elusive understanding of the formation mechanisms. Here, by revealing the self-healing behavior of noble metal gels and applying it in the gelation process at a disturbing environment, an unconventional and conceptually new strategy, i.e., a disturbance-promoted gelation method, is developed by introducing an external force field. It overcomes the diffusion limitation in the gelation process, thus producing monolithic gels within 1–10 min at room temperature, 2–4 orders of magnitude faster than for most reported methods. Moreover, versatile NMAs are acquired by using this method, and their superior (photo-)electrocatalytic properties are demonstrated for the first time in light of combined catalytic and optic properties.

Permalink: https://www.hzdr.de/publications/Publ-30879
Publ.-Id: 30879


A smart multi-plane detector design for ultrafast electron beam X-ray computed tomography

Bieberle, A.; Windisch, D.; Iskander, K.; Bieberle, M.; Hampel, U.

In this paper, a novel concept for multi-plane ultrafast electron beam X-ray computed tomography (UFXCT) is presented. The concept is based on multi-plane electron beam scanning on a semi-transparent X-ray target and cuboid-shape scintillation detectors for radiation detection over an extended axial range. The optical part of the scintillation detector acts as both a scintillator and a light guide. With that, we achieve a low detector complexity and number of detector elements, overall power consumption and detector costs. We investigated the performance of this new concept with a prototypical detector module made of cerium doped lutetium yttrium orthosilicate (LYSO:Ce) as scintillator and an avalanche photodiode (APD) array. Thereby, we assessed two design variants: a monolithic LYSO bar detector and a sandwich detector made of multiple LYSO crystals and glass light-guides.

Keywords: Ultrafast computed tomography; 3D tomography; scintillation detectors

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Permalink: https://www.hzdr.de/publications/Publ-30878
Publ.-Id: 30878


data of " A detailed EP and PAS study of porous structure of OSG films with various ratios of methyl terminal and ethylene bridging groups"

Rasadujjaman, M.; Wang, Y.; Zhang, L.; Naumov, S.; Elsherif, A. G. A.; Liedke, M. O.; Koehler, N.; Redzheb, M.; Vishnevskiy, A. S.; Seregin, D. S.; Wu, Y.; Zhang, J. L.; Wagner, A.; Vorotilov, K. A.; Schulz, S. E.; Baklanov, M. R.

Raw data of "A detailed EP and PAS study of porous structure of OSG films with various ratios of methyl terminal and ethylene bridging groups"- The positron part only.

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-02
    DOI: 10.14278/rodare.280

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Permalink: https://www.hzdr.de/publications/Publ-30876
Publ.-Id: 30876


Lithium Diffusion in Ion-Beam Sputter-Deposited Lithium-Silicon Layers

Strauss, F.; Hüger, E.; Julin, J. A.; Munnik, F.; Schmidt, H.

Lithium-silicon compounds are used as active material in negative electrodes of Li-ion batteries. The knowledge of Li diffusion in these materials is of importance for an optimization of charging/discharging rates and achievable maximum specific capacity as well as for an understanding of the basic lithiation mechanism. We carried out Li tracer self-diffusion experiments on ion-beam sputter-deposited LixSi(O) thin films for x ~ 0.25 and x ~ 4.5 using LixSi/6LixSi hetero-structures in combination with secondary ion mass spectrometry in line scan like mode. Measurements with elastic recoil detection analysis revealed the presence of a considerable amount of oxygen in the films. The diffusivities follow the Arrhenius law in the temperature range between 300 and 500 °C with an activation energy of 0.8 – 0.9 eV. The film containing a higher amount of Li shows faster diffusion by one order of magnitude. The Li diffusivities in the investigated Li-rich materials are several orders of magnitude higher than in Li-poor LixSi films (x = 0.02 to 0.06) as given in literature because of a lower activation energy. This indicates the presence of a direct interstitial-like mechanism. Oxygen present in samples with the same Li concentration of x = 0.06 also enhances diffusion but does not lead to a reduction in the activation energy.

Permalink: https://www.hzdr.de/publications/Publ-30875
Publ.-Id: 30875


A detailed ellipsometric porosimetry and positron annihilation spectroscopy study of porous organosilicate-glass films with various ratios of methyl terminal and ethylene bridging groups

Rasadujjaman, M.; Wang, Y.; Zhang, L.; Naumov, S.; Elsherif, A. G. A.; Liedke, M. O.; Koehler, N.; Redzheb, M.; Vishnevskiy, A. S.; Seregin, D. S.; Wu, Y.; Zhang, J. L.; Wagner, A.; Vorotilov, K. A.; Schulz, S. E.; Baklanov, M. R.

Organosilicate-glass films with a varying ratio of terminal methyl and bridging ethylene groups are synthesized using BTMSE/MTMS mixtures and sol-gel technology. The films have been characterized by Fourier Transform Infrared spectroscopy, Ellipsometric Porosimetry and Positron Annihilation Spectroscopy. The hard bake at 400 ºC generates the final pore structure, which depends on the curing environment. It is shown that ethylene bridge is destructed during the hard bake in air via formation of peroxide radicals that form ΞSiOH during the further transformation. Continuous hard bake leads to condensation of silanol groups and form a structure similar to the ordinary silica.
The pore size of highly porous materials (>30%) is larger in air cured films. Destruction of the ethylene bridge makes the films matrix soft and micropores collapse during the template evaporation due to the capillary forces. It leads to the film shrinkage, increases the size of internal voids. The air cured samples showed better mechanical properties than N 2 cured ones although in the last case ethylene bridging groups were preserved. The reason is that the collapse of micropores increases internal density and creates more favorable condition for condensation of silanol groups.

Keywords: Low-k films; Pore structure; Ellipsometric Porosimetry; Positron annihilation spectroscopy; Young's Modulus

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Permalink: https://www.hzdr.de/publications/Publ-30874
Publ.-Id: 30874


Adjuvant drug-assisted bone healing: advances and challenges in drug delivery approaches

Rothe, R.; Hauser, S.; Neuber, C.; Laube, M.; Schulze, S.; Rammelt, S.; Pietzsch, J.

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Keywords: Angiogenesis; bioactive scaffolds; bone grafting; critical-size bone defects; drugs; inflammation; tissue regeneration; osteoconduction; osteoinduction; osseointegration

Permalink: https://www.hzdr.de/publications/Publ-30872
Publ.-Id: 30872


Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites

Lumetzberger, J.; Buchner, M.; Pile, S.; Ney, V.; Gaderbauer, W.; Daffé, N.; Moro, M. V.; Primetzhofer, D.; Lenz, K.; Ney, A.

An in-depth analysis of Zn/Al doped nickel ferrite thin films grown by reactive magnetron sputtering was conducted to gain insight into the magnetic properties interesting for applications in spintronics. The material is insulating, ferromagnetic at room temperature and has a low magnetic damping with additional strong magnetoelastic coupling. The sample system is analyzed with regard to crystal structure, chemical composition and static as well as dynamic magnetic properties. Thus a correlation between composition, strain, cation distribution, magnetocrystalline anisotropy and damping is evidenced. X-ray magnetic circular dichroism spectra and field dependent curves at the L3;2 edges of Ni and Fe are performed to complement integral magnetometry measurements and identify their magnetic contributions to the hysteresis. In particular, a strong in uence of the lattice site occupation of Ni2+ Td and cation coordination of Fe2+ Oh on the intrinsic damping is found. Furthermore, the vital role of the incorporation of Zn2+ and Al3+ is evidenced by comparison with a sample of altered composition. A strain-independent reduction of the magnetic anisotropy and damping by adapting the cation distribution is demonstrated.

Keywords: ferrites; ferromagnetic resonance; x-rays; XMCD; cation distribution; damping; hysteresis; magnetic properties; thin films

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Permalink: https://www.hzdr.de/publications/Publ-30870
Publ.-Id: 30870


Formation of PuSiO4 under hydrothermal conditions

Estevenon, P.; Welcomme, E.; Tamain, C.; Jouan, G.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Moisy, P.; Dacheux, N.

Attempts to synthesize plutonium (IV) silicate, PuSiO4, have been performed on the basis of the results recently reported in the literature for CeSiO4, ThSiO4 and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4 by applying the conditions reported for thorium and uranium, an efficient way of PuSiO4 synthesis was established following those optimized for CeSiO4 system. This method was based on the slow oxidation of plutonium (III) silicate reactants under hydrothermal conditions at 150°C in hydrochloric acid (pH = 3 – 4). This result shed a new light on the potential behavior of plutonium in reductive environment, highlighted the representativeness of cerium surrogates to study plutonium in such conditions and brought some important pieces of information on plutonium chemistry in silicate solutions.

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Permalink: https://www.hzdr.de/publications/Publ-30869
Publ.-Id: 30869


High-sensitivity investigation of low-lying dipole strengths in 120Sn

Müscher, M.; Wilhelmy, J.; Savran, D.; Schwengner, R.; Massarczyk, R.; Grieger, M.; Isaak, J.; Junghans, A. R.; Kögler, T.; Ludwig, F.; Symochko, D.; Takacs, M. P.; Tamkas, M.; Wagner, A.; Zilges, A.

Background: The term Pygmy Dipole Resonance (PDR) denotes electric dipole excitations below and around the neutron separation threshold. It may be important, e.g., for the nucleosynthesis of heavy nuclei or the symmetry energy in the Equation of State (EoS). For a deeper understanding of the PDR systematic studies are essential.
Purpose: The tin isotopic chain is a well-suited candidate to investigate the systematics of the PDR and the (g,g') reactions on 112,116,120,124Sn have already been measured in experiments using bremsstrahlung. It was claimed that the extracted electric dipole transition strengths of these isotopes increase with increasing neutron-to-proton ratio with the exception of 120 Sn. Furthermore, previous results from elastic photon scattering experiments on 120Sn are in disagreement with corresponding (p,p') Coulomb excitation data. To examine this discrepancy an additional high-sensitivity bremsstrahlung experiment on 120Sn was performed.
Method: The Nuclear Resonance Fluorescence (NRF) method is used which bases on real photon scattering. The bremsstrahlung experiment presented in this work was performed with a maximum energy of E = 9.5 MeV at the gELBE facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Besides a state-to-state analysis, the quasi-continuum was investigated as well.
Results: Above Ex = 4 MeV 236 dipole transitions were clearly identified and 168 of those were observed for the first time. Assuming that all analyzed transitions have electric dipole character the summed electric dipole strength equals B(E1) = 374(35) e2 fm2 (0.54(5) % of the TRK sum rule) for transitions from 4 MeV to Sn = 9.1 MeV. This is an enhancement of a factor 2.3 compared to the previously published 120Sn(g,g') results.
Especially, the observation of many weaker transitions in the state-to-state analysis lead to this increase. The photo-absorption cross sections deduced from the quasi-continuum analysis are about two times higher than the results of the (p,p') experiment.
Conclusion: The newly extracted summed B(E1) value of the state-to-state analysis is larger than those of 112,116Sn and smaller than that of 124 Sn. The difference between the present (g,g') data and the results of the inelastic proton scattering experiment above 6.3 MeV is still striking. The deviation may be explained by unobserved decay branchings and unresolved strength. Up to now, there is no explanation for the discrepancy between the extracted photo-absorption cross sections of the analysis of the quasi-continuum and the (p,p')
measurement. Additional experiments may shed light on this deviation.

Keywords: Photon scattering; Photoabsorption cross section; Electromagnetic transition strengths

Permalink: https://www.hzdr.de/publications/Publ-30867
Publ.-Id: 30867


Unveiling reductant chemistry in fabricating noble metal aerogels for superior oxygen evolution and ethanol oxidation

Du, R.; Wang, J.; Wang, Y.; Hübner, R.; Fan, X.; Senkovska, I.; Hu, Y.; Kaskel, S.; Eychmüller, A.

Amongst various porous materials, noble metal aerogels attract wide attention due to their concurrently featured catalytic properties and large surface areas. However, insufficient understanding and investigation of key factors (e.g. reductants and ligands) in the fabrication process limits on-target design, impeding material diversity and available applications. Herein, unveiling multiple roles of reductants, we develop an efficient method, i.e. the excessive-reductant-directed gelation strategy. It enables to integrate ligand chemistry for creating gold aerogels with a record-high specific surface area (59.8 m2 g−1), and to expand the composition to all common noble metals. Moreover, we demonstrate impressive electrocatalytic performance of these aerogels for the ethanol oxidation and oxygen evolution reaction, and discover an unconventional organic-ligand-enhancing effect. The present work not only enriches the composition and structural diversity of noble metal aerogels, but also opens up new dimensions for devising efficient electrocatalysts for broad material systems.

Permalink: https://www.hzdr.de/publications/Publ-30866
Publ.-Id: 30866


Development of a radiofluorinated adenosine A2B receptor antagonist as potential ligand for PET imaging

Lindemann, M.; Moldovan, R.-P.; Hinz, S.; Deuther-Conrad, W.; Gündel, D.; Dukic-Stefanovic, S.; Toussaint, M.; Teodoro, R.; Juhl, C.; Steinbach, J.; Brust, P.; Müller, C. E.; Wenzel, B.

The adenosine A2B receptor has been proposed as a novel therapeutic target in cancer, as for example, its expression is drastically elevated in several tumors and cancer cells. Noninvasive molecular imaging by using positron emission tomography (PET) would allow the in vivo quantification of this receptor in pathological processes and most likely enable the identification and clinical monitoring of respective cancer therapies. On the basis of a bicyclic pyridopyrimidine-2,4-dione core structure, the new adenosine A2B receptor ligand 9 was synthesized containing a 2-fluoropyridine moiety suitable for labeling with the short-lived PET radionuclide fluorine-18. Compound 9 showed a high binding affinity for the human A2B receptor (Ki(A2B) = 2.51 nM) along with high selectivities versus the A1, A2A, and A3 receptor subtypes. Therefore, it was radiofluorinated via nucleophilic aromatic substitution of the corresponding nitro precursor using [18F]F-/K2.2.2./K2CO3 in DMSO at 120 °C. Metabolism studies of [18F]9 in mice revealed about 60 % of intact radiotracer in plasma at 30 minutes p.i. A preliminary PET study in healthy mice showed an overall biodistribution of [18F]9 corresponding to the known ubiquitous but low expression of the A2B receptor. Consequently, [18F]9 represents a novel PET radiotracer with high affinity and selectivity toward the adenosine A2B receptor and a suitable in vivo profile. Subsequent studies are envisaged to investigate the applicability of [18F]9 to detect alterations in the receptor density in certain cancer-related disease models.

Keywords: A2B receptor; adenosine, PET; fluorine-18; metabolism; radiofluorination

Permalink: https://www.hzdr.de/publications/Publ-30865
Publ.-Id: 30865


Microstructure and Nanoscopic Porosity in Black Pd Films

Melikhova, O.; Čížek, J.; Hruška, P.; Lukáč, F.; Novotný, M.; More-Chevalier, J.; Fitl, P.; Liedke, M. O.; Butterling, M.; Wagner, A.

In the present work the microstructure of a black Pd film prepared by thermal evaporation and a glossy Pd film deposited by magnetron sputtering was compared. While the glossy Pd film exhibits typical polycrystalline structure with column-like grains, the black Pd film has fractal-like porous structure. Positron annihilation spectroscopy revealed that positronium is formed in nanoscopic cavities of the black Pd film. In conventional metals positronium does not form due to screening by conduction electrons. However, in porous metals containing nanoscopic porosity a thermalized positron may pick an electron on inner surface of a pore and escape into a cavity forming positronium. The average size of nanoscopic pores in the black Pd film was determined from the lifetime of long-lived ortho-positronium component.

Keywords: thin film; positron annihilation; porosity; black metal; black gold; magnetron sputtering

Permalink: https://www.hzdr.de/publications/Publ-30864
Publ.-Id: 30864


Defects in Thin Layers of High Entropy Alloy HfNbTaTiZr

Lukáč, F.; Hruška, P.; Cichoň, S.; Vlasák, T.; Cížek, J.; Kmječ, T.; Melikhova, O.; Butterling, M.; Liedke, M. O.; Wagner, A.

High entropy alloys represent a new type of materials with unique combination of physical properties originating due to occurrence of single phase solid solution of numerous elements. Preparation of high entropy alloys films with nanosized grains promises increased effective surface and high intergranular diffusion of elements. In the present work HfNbTaTiZr films were deposited by magnetron sputtering from single phase HfNbTaTiZr target prepared by spark plasma sintering. Chemical composition of high entropy alloys thin films prepared this way was enriched in Ti and depleted in Zr and Nb. Very fine microstructure of the film was documented and defect distribution was found to be non-uniform with depth.

Keywords: high entropy alloy; thin film; positron annihilation; nano grain

Permalink: https://www.hzdr.de/publications/Publ-30863
Publ.-Id: 30863


Positron Structural Analysis of ScN Films Deposited on MgO Substrate

More-Chevalier, J.; Horák, L.; Cichoň, S.; Hruška, P.; Čížek, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Bulíř, J.; Hubík, P.; Gedeonová, Z.; Lančok, J.

Scandium nitride (ScN) is a semiconductor with a rocksalt-structure that has attracted attention for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices. Two ScN films of 118 nm and 950 nm thicknesses were deposited at the same conditions on MgO (001) substrate by reactive magnetron sputtering. Poly-orientation of films was observed with first an epitaxial growth on MgO and then a change in the orientation growth due to the decrease of the adatom mobility during the film growth. Positron lifetime measurements showed a high concentration of nitrogen vacancies in both films with a slightly higher concentration for the thicker ScN film. Presence of nitrogen vacancies explains the values of direct band gaps of 2:53+-0:01 eV, and 2:56+-0:01 eV which has been measured on ScN films of 118 nm and 950 nm thicknesses, respectively.

Keywords: positron annihilation; semiconductor; ScN; band gap; defects; vacancies

Permalink: https://www.hzdr.de/publications/Publ-30862
Publ.-Id: 30862


Cation exchange protocols to radiolabel aqueous stabilized ZnS, ZnSe and CuFeS2 nanocrystals with 64Cu for dual radio- and photo-thermal therapy

Avellini, T.; Soni, N.; Silvestri, N.; Fiorito, S.; de Donato, F.; de Mei, C.; Cassani, M.; Ghosh, S.; Walther, M.; Manna, L.; Stephan, H.; Pellegrino, T.

In metal chalcogenide nanocrystals (NCs), the cations can be partially or fully replaced with other cations through the so-called cation exchange (CE) reactions. Here, we took advantage of these CE reactions to replace the cations on different chalcogenides NCs with 64Cu ions in order to radiolabel them. With respect to other approaches reported in the literature, our CE protocol is easily transferable to the clinic. It requires indeed one single step, in which the water-soluble NCs are mixed with a 64Cu copper(II) chloride solution of high specific activity, in the presence of vitamin C used as a reducing agent for Cu(II) to Cu(I)). Given the quantitative replacement of the cations of the NCs with 64Cu(I), a high radiochemical yield up to 90-95% can be reached. Provided that there is no free 64Cu, no purification step is needed, making the protocol straightforward. At the same time, the amount of NCs required for the exchange is so low (in the range of μg) that the dose of NCs shows no intrinsic cytotoxicity. This protocol works on different types of metal chalcogenide NCs. In ZnSe and ZnS NCs, the Zn(II) ions are exchanged with 64Cu (I) ions, and in CuFeS2 NCs the Fe(III) ions are exchanged with 64Cu(I). To ensure the stability of the NCs during and after the CE reaction, a multi-anchoring coating procedure based on PEG, cysteamine and poly-maleic anhydride was proven to be more efficient than the use of monothiol PEG ligands. With our approach we managed to achieve an unprecedented high specific activity, i.e. the amount of 64Cu radionuclide loaded per NC dose, to dispatch remarkable ionizing effects. Indeed, by exploiting a volumetric cations exchange, our strategy enables to concentrate a large dose of 64Cu (18.5 MBq) in a small NC dose (0.4 μg), reaching a specific activity of about 50 TBq/g. Remarkably, for CuFeS2 NCs even after the CE, the radiolabeled 64Cu:CuFeS2 NCs still show the characteristic dielectric resonance that enables the generation of heat under laser exposure for clinical use (1 W/cm2). The synergic toxicity of photo-ablation and 64Cu radiation exposure is here demonstrated in an in vitro study on glioblastoma and epidermoid carcinoma tumor cells.

Permalink: https://www.hzdr.de/publications/Publ-30861
Publ.-Id: 30861


Interplay between MycN and c-Myc regulates radioresistance and cancer stem cell phenotype in neuroblastoma upon glutamine deprivation

Le, G. M.; Mukha, A.; Püschel, J.; Valli, E.; Kamili, A.; Vittorio, O.; Dubrovska, A.; Kavallaris, M.

Targeting glutamine metabolism has emerged as a potential therapeutic strategy for Myc overexpressing cancer cells. Myc proteins contribute to an aggressive neuroblastoma phenotype. Radiotherapy is one of the treatment modalities for high-risk neuroblastoma patients. Herein, we investigated the effect of glutamine deprivation in combination with irradiation in neuroblastoma cells representative of high-risk disease and studied the role of Myc member interplay in regulating neuroblastoma cell radioresistance. Methods: Cell proliferation and viability assays were used to establish the effect of glutamine deprivation in neuroblastoma cells expressing c-Myc or MycN. Gene silencing and overexpression were used to modulate the expression of Myc genes to determine their role in neuroblastoma radioresistance. qPCR and western blot investigated interplay between expression of Myc members. The impact of glutamine deprivation on cell response following irradiation was explored using a radiobiological 3D colony assay. DNA repair gene pathways as well as CSC-related genes were studied by qPCR array. Reactive Oxygen Species (ROS) and glutathione (GSH) levels were detected by fluorescence and luminescence probes respectively. Cancer-stem cell (CSC) properties were investigated by sphere-forming assay and flow cytometry to quantify CSC markers. Expression of DNA repair genes and CSC-related genes was analysed by mining publicly available patient datasets. Results: Our results showed that glutamine deprivation decreased neuroblastoma cell proliferation and viability and modulated Myc member expression. We then demonstrated for the first time that combined glutamine deprivation with irradiation led to a selective radioresistance of MYCN-amplified neuroblastoma cells. By exploring the underlying mechanism of neuroblastoma radioresistance properties, our results highlight interplay between c-Myc and MycN expression suggesting compensatory mechanisms in Myc proteins leading to radioresistance in MYCN-amplified cells. This result was associated with the ability of MYCN-amplified cells to dysregulate the DNA repair gene pathway, maintain GSH and ROS levels and to increase the CSC-like population and properties. Conversely, glutamine deprivation led to radiosensitization in non-MYCN amplified cell lines through a disruption of the cell redox balance and a trend to decrease in the CSC-like populations. Mining publicly available gene expression dataset obtained from pediatric neuroblastoma patients, we identified a correlation pattern between Myc members and CSC-related genes as well as a specific group of DNA repair gene pathways. Conclusions: This study demonstrated that MycN and c-Myc tightly cooperate in regulation of the neuroblastoma CSC phenotypes and radioresistance upon glutamine deprivation. Pharmacologically, strategies targeting glutamine metabolism may prove beneficial in Myc-driven tumors. Consideration of MycN/c-Myc status in selecting neuroblastoma patients for glutamine metabolism treatment will be important to avoid potential radioresistance.

Keywords: Myc members; glutamine metabolism; neuroblastoma; radioresistance; Cancer-Stem Cells

Permalink: https://www.hzdr.de/publications/Publ-30860
Publ.-Id: 30860


Enhanced room temperature ferromagnetism in MoS2 by N plasma treatment

Wang, B.; Zhang, D.; Wang, H.; Zhao, H.; Liu, R.; Li, Q.; Zhou, S.; Du, J.; Xu, Q.

The introduction of ferromagnetism in MoS2 is important for its applications in semiconductor spintronics. MoS2 powders were synthesized by hydrothermal method, followed by the N plasma treatment at room temperature. Weak ferromagnetism with saturated ferromagnetic magnetization of 0.64 memu/g has been observed in the as-synthesized MoS2 at room temperature, which is significant enhanced to 3.67 memu/g after the N plasma treatment for the proper duration. X-ray photoelectron spectroscopy demonstrates the adsorption of N, and higher valence state of Mo than +4 due to the bonding with N after the N plasma treatment. First principle calculation has been performed to disclose the possible origin of ferromagnetism. One chemical adsorbed N ion on S ion may form conjugated π bonds with adjacent two Mo ions to have a total magnetic moment of 0.75 μB, contributing to the enhanced ferromagnetism.

Permalink: https://www.hzdr.de/publications/Publ-30859
Publ.-Id: 30859


3D-Ising critical behavior in antiperovskite-type ferromagneticlike Mn3GaN

Yuan, Y.; Liu, Y.; Xu, C.; Kang, J.; Wang, W.; Wang, Q.; Song, B.; Zhou, S.; Wang, X.

In this work, a systematic investigation on magnetic critical behavior is performed for the first time on an antiperovskite-type Mn3GaN, which is prepared by intentionally modifying stoichiometry. According to the XRD results, the antiperovskite structure is well preserved, even though all lattice parameters shrink upon reducing Ga and N content down to 60%. The sample exhibits a ferromagneticlike feature with a Curie temperature (T_C) of 394 K rather than frustrated behavior in stoichiometric Mn3GaN. Most importantly, the modified Arrott plots, Kouvel–Fisher plots, as well as critical isotherm method self-consistently co-confirm the critical exponents of β = 0.33, γ = 1.23, and δ = 4.7, unambiguously indicating that the critical behavior follows the 3D-Ising model around T_C.

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Permalink: https://www.hzdr.de/publications/Publ-30858
Publ.-Id: 30858


An Infrared Transmission Study of Ge:Mn Thick Films Prepared by Ion Implantation and Post-Annealing

Obied, L. H.; Roorda, S.; Prucnal, S.; Zhou, S.; Crandles, D. A.

Ge:Mn thick films (t$\approx 3\mu$m) with low average Mn concentration (< 0.3 %) were prepared by ion implantation at 77K followed by either conventional or flash lamp annealing. The films were characterized by Xray diffraction, Secondary Ion Mass Spectrometry, magnetometry and infrared transmission (100-6500 cm^{-1}). Post-annealing at high enough temperature recrystallizes the amorphous Ge:Mn films without significant migration of Mn to the surface while solid phase epitaxy does not occur, resulting in polycrystalline films. Annealing causes an estimated 50-80\% of the implanted Mn to migrate to Mn-rich clusters or form Mn_5Ge_3 while the remainder enters the Ge lattice substitutionally creating free holes. Evidence for free holes comes from structure in the mid-infrared absorption coefficient that is similar to previous observations in p-type Ge. The data suggest that the maximum solubility of Mn in the Ge crystalline lattice has an upper limit of <0.08%.

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Permalink: https://www.hzdr.de/publications/Publ-30857
Publ.-Id: 30857


Size Dependence of Lattice Parameter and Electronic Structure in CeO2 Nanoparticles

Prieur, D.; Bonani, W.; Popa, K.; Walter, O.; Kriegsman, K.; Engelhard, M.; Guo, X.; Eloirdi, R.; Gouder, T.; Beck, A.; Vitova, T.; Scheinost, A.; Kvashnina, K.; Martin, P.

Intrinsic properties of a compound (e.g. electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio.
Here, we explore the size-dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. XRD, XPS and HERFD-XANES demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to FTIR and TGA measurements. In addition, the size-dependence of the t2g states in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.

Keywords: Lanthanide; CeO2; HEFRD-XANES; Electronic Structure

Permalink: https://www.hzdr.de/publications/Publ-30856
Publ.-Id: 30856


Quadrupolar response from the crystal electric field level scheme consisting of only Kramers doublets in DyNiAl

Suzuki, D.; Ishii, I.; Kumano, S.; Umeno, T.; Andreev, A. V.; Gorbunov, D.; Suzuki, T.

The rare earth compound DyNiAl shows ferromagnetic and antiferromagnetic phase transitions at TC = 30 K and T1 = 15 K, respectively. Elastic properties of DyNiAl have been investigated by means of ultrasonic spectroscopy. The transverse elastic modulus C44 shows an elastic softening below 60 K and exhibits a bend at TC. The softening continues down to T1 and an elastic hardening is observed below T1. The softening above TC is well reproduced by Curie-Weiss-type equation including a quadrupole interaction. A quadrupole-quadrupole coupling constant obtained from C44 is negative, suggesting an antiferroquadrupolar-type interaction between quadrupoles Oyz or Ozx.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011165
    DOI: 10.7566/JPSCP.30.011165

Permalink: https://www.hzdr.de/publications/Publ-30855
Publ.-Id: 30855


Magnetocaloric Effect in Alloy Fe49Rh51in Pulsed Magnetic Fields up to 50 T

Kamantsev, A. P.; Amirov, A. A.; Koshkid'Ko, Y. S.; Salazar Mejia, C.; Mashirov, A. V.; Aliev, A. M.; Koledov, V. V.; Shavrov, V. G.

Magnetocaloric effect (MCE) in pulsed magnetic fields up to 50 T was directly studied in alloyFe49Rh51. An inverse MCE ΔT ≈ –8 K is observed at different initial temperatures around the metamagneticphase transition upon field rising to 20 T; further growth of the field to 50 T leads to a decrease in the absoluteadiabatic temperature change by nearly 1 K, which is due to the direct MCE and proves that the whole sampleundergoes a transition into the ferromagnetic phase. Upon the field decrease, the maximal absolute value ofthe adiabatic temperature change of |ΔT| = 9.8 K was revealed at 6 T when the initial temperature is 310 K.

Permalink: https://www.hzdr.de/publications/Publ-30854
Publ.-Id: 30854


Development of novel analogs of the monocarboxylate transporter ligand FACH and biological validation of one potential radiotracer for PET imaging

Sadeghzadeh, M.; Wenzel, B.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Fischer, S.; Teodoro, R.; Jonnalagadda, S.; Jonnalagadda, S. K.; Mereddy, V. R.; Drewes, L. R.; Brust, P.

Monocarboxylate transporters 1-4 (MCT1-4) are involved in several metabolism-related diseases, especially cancer, providing the chance to be considered as relevant targets for diagnosis and therapy. [18F]FACH was recently developed and showed very promising preclinical results as a potential PET radiotracer for imaging of MCTs, which encouraged us to develop the novel analogs 1 and 2 of FACH. They were synthesized via Buchwald-Hartwig amination starting from m-anisidine followed by Vilsmeier-Haack formylation and Knoevenagel condensation in moderate overall yields. MCT1 inhibition was estimated by [14C]lactate uptake assay on rat brain endothelial (RBE4) cells. Although 2 showed 25-times lower MCT1 inhibitory potency than FACH (IC50 = 11 nM), compound 1 could be a suitable PET candidate with an IC50 value of 118 nM. Therefore, 1 was selected for radiosynthesis of [18F]1 and subsequent biological evaluation as a potential PET radiotracer for imaging of the MCT expression in mouse brain. By in vitro autoradiography in cryosections of the mouse kidney, 50% displacement of [18F]1 by 10 µM of the specific MCT1 inhibitor α-cyano-4-hydroxycinnamic acid (α-CHC) was observed. Despite a higher lipophilicity of [18F]1 compared to [18F]FACH, in vivo brain uptake of [18F]1 was in a similar range, likely to be related to similar transport rates by MCTs on RBE4 cells. The high uptake of the new radiotracer in kidney and other peripheral MCT-expressing organs together with significant reduction by α-CHC, suggests the suitability of [18F]1 for imaging of the MCTs expression in vivo.

Keywords: monocarboxylate transporters (MCTs); FACH; 18F-labeled analog of FACH; α-CHC; blood-brain barrier (BBB); positron emission tomography (PET) imaging

Permalink: https://www.hzdr.de/publications/Publ-30853
Publ.-Id: 30853


Local Structure in U(IV) and U(V) Environments: The Case of U3O7

Leinders, G.; Bes, R.; Kvashnina, K.; Verwerft, M.

A comprehensive analysis of X-ray absorption data obtained at theUL3-edge for a systematic series of single-valence (UO2, KUO3,UO3) and mixed-valence uranium compounds (U4O9,U3O7,U3O8) is reported. High-energyresolutionfluorescence detection (HERFD) X-ray absorption near-edge spectros-copy (XANES) and extended X-ray absorptionfine structure (EXAFS) methodswere applied to evaluate U(IV) and U(V) environments, and in particular, toinvestigate the U3O7local structure. Wefind that the valence state distribution inmixed-valence uranium compounds cannot be confidently quantified from aprincipal component analysis of the UL3-edge XANES data. The spectral linebroadening, even when applying the HERFD-XANES method, is sensibly higher(∼3.9 eV) than the observed chemical shifts (∼2.4 eV). Additionally, the white line shape and position are affected not only by thechemical state, but also by crystalfield effects, which appear well-resolved in KUO3. The EXAFS of a phase-pure U3O7sample wasassessed based on an average representation of the expanded U60O140structure. Interatomic U−O distances are found mainly tooccur at 2.18 (2), 2.33 (1), and 3.33 (5) Å, and can be seen to correspond to the spatial arrangement of cuboctahedral oxygenclusters. The interatomic distances derived from the EXAFS investigation support a mixed U(IV)−U(V) valence character in U3O7

Permalink: https://www.hzdr.de/publications/Publ-30852
Publ.-Id: 30852


Topological Hall effect in single thick SrRuO3 layers induced by defect engineering

Wang, C.; Chang, C.-H.; Herklotz, A.; Chen, C.; Ganss, F.; Kentsch, U.; Chen, D.; Gao, X.; Zeng, Y.-J.; Hellwig, O.; Helm, M.; Gemming, S.; Chu, Y.-H.; Zhou, S.

The topological Hall effect (THE) has been discovered in ultrathin SrRuO3 (SRO) films, where the interface between the SRO layer and another oxide layer breaks the inversion symmetry resulting in the appearance of THE. Thus, THE only occurs in ultra-thin SRO films of several unit cells. In addition to employing a heterostructure, the inversion symmetry can be broken intrinsically in bulk by introducing defects. In this study THE is observed in 60 nm thick SRO films, in which defects and lattice distortions are introduced by helium ion irradiation. The irradiated SRO films exhibit a pronounced THE in a wide temperature range from 5 K to 80 K. These observations can be attributed to the emergence of Dzyaloshinskii-Moriya interaction as a result of artificial inversion symmetry breaking associated with the lattice defect engineering. The creation and control of the THE in oxide single layers can be realized by ex situ film processing. Therefore, this work provides new insights into the THE and illustrates a promising strategy to design novel spintronic devices.

Keywords: defect engineering; Dzyaloshinskii-Moriya interaction; lattice distortion; oxide thin film; topological Hall effect

Permalink: https://www.hzdr.de/publications/Publ-30851
Publ.-Id: 30851


CFD simulation of aeration and mixing processes in a full-scale oxidation ditch

Höhne, T.; Mamedov, T.

This study aims to build a computational fluid dynamics (CFD) model that can be used to predict fluid flow pattern and to analyse the mixing process in a full-scale OD. CFD is a widely used numerical tool for analysing, modelling and simulating fluid flow patterns in wastewater treatment processes. In this study, a three-dimensional (3D) computational geometry was used, and the Eulerian-Eulerian multiphase flow model was built. Pure water was considered as the continuous phase, whereas air was modelled as the dispersed phase. The Shear Stress Transport (SST) turbulence model was specified which predicts turbulence eddies in free stream and wall-bounded region with high accuracy. The momentum source term approach and the transient rotor-stator approach were implemented for the modelling of the submersible agitators. The hydrodynamic analysis was successfully performed for four different scenarios. In order to prevent the incorrect positioning of the submerged agitators, thrust analysis was also done. The results show that the minimum required water velocity was reached to maintain the solid particles suspended in the liquid media and adequate mixing was determined.

Keywords: CFD; Multiphase flow; Hydrodynamics; Oxidation ditch

Permalink: https://www.hzdr.de/publications/Publ-30850
Publ.-Id: 30850


The Crystal Electric Field Effect in the Distorted Kagome Lattice Ferromagnet Nd3Ru4Al12

Ishii, I.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Suzuki, T.

The distorted kagome lattice compound Nd3Ru4Al12 shows a ferromagnetic phase transition at TC =39 K. Reduced Nd magnetic moments with two different values of 2.66 and 0.95 µB are aligned along the c-axis below TC. It was previously reported that a crystal electric field (CEF) effect may affect the reduced magnetic moments. To clarify the 4f -electronic state in Nd3Ru4Al12, we performed CEF analyses for the inverse magnetic susceptibility and magnetization. We proposed the CEF level scheme of which the inverse magnetic susceptibilities along both a- and c-axes are reproduced. The ferromagnetic phase transition at TC along the c-axis can be explained by a simple CEF model. In contrast, reduced magnetic moments cannot be understood by the simple CEF model, because calculated magnetization curves are quite larger than the experimental data.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011161
    DOI: 10.7566/JPSCP.30.011161

Permalink: https://www.hzdr.de/publications/Publ-30849
Publ.-Id: 30849


Phonon-induced near-field resonances in multiferroic BiFeO₃ thin films at infrared and THz wavelengths

Wehmeier, L.; Nörenberg, T.; de Oliveira, T. V. A. G.; Klopf, J. M.; Yang, S.-Y.; Martin, L. W.; Ramesh, R.; Eng, L. M.; Kehr, S. C.

Multiferroic BiFeO3 (BFO) shows several phonon modes at infrared (IR) to THz energies, which are expected to carry information on any sample property coupled to crystal lattice vibrations. While macroscopic IR studies of BFO are often limited by single-crystal size, scattering-type scanning near-field optical microscopy (s-SNOM) allows for IR thin film spectroscopy of nanoscopic probing volumes with negligible direct substrate contribution to the optical signal. In fact, polaritons such as phonon polaritons of BFO introduce a resonant tip–sample coupling in s-SNOM, leading to both stronger signals and enhanced sensitivity to local material properties. Here, we explore the near-field response of BFO thin films at three consecutive resonances (centered around 5 THz, 13 THz, and 16 THz), by combining s-SNOM with a free-electron laser. We study the dependence of these near-field resonances on both the wavelength and tip–sample distance. Enabled by the broad spectral range of the measurement, we probe phonon modes connected to the predominant motion of either the bismuth or oxygen ions. Therefore, we propose s-SNOM at multiple near-field resonances as a versatile and very sensitive tool for the simultaneous investigation of various sample properties.

Permalink: https://www.hzdr.de/publications/Publ-30848
Publ.-Id: 30848


Low frequency dependent elastic modulus in UCo1-xOsxAl

Kumano, S.; Ishii, I.; Horio, R.; Mizuno, T.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Yamamura, T.; Suzuki, T.

UCoAl with the hexagonal ZrNiAl-type structure shows an itinerant metamagnetic phase transition at 0.7 T in the magnetic field along the c-axis. Whereas, this compound becomes to undergo a ferromagnetic phase transition in zero field by substituting Os for Co. UCo0.995Os0.005Al exhibits the ferromagnetic phase transition at TC = 8 K. At high temperatures, the temperature dependence of the transverse elastic modulus C44 in UCo0.995Os0.005 Al shows a slight softening below 50 K. The softening turns to an abrupt hardening below 30 K. With further decreasing temperature, a bending is observed at TC. Although TC changes sensitively by applying the magnetic fields, the temperature of the elastic hardening is robust in the magnetic fields. This elastic hardening is not caused by a magnetic origin. We measured ultrasonic frequency dependences of C44 and found that the temperature of the elastic hardening increases with increasing ultrasonic frequency. We propose that this ultrasonic frequency dependence is due to a large amplitude atomic motion of constituent atoms.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011173
    DOI: 10.7566/JPSCP.30.011173

Permalink: https://www.hzdr.de/publications/Publ-30847
Publ.-Id: 30847


Preclinical incorporation dosimetry of [18F]FACH - a novel 18F-labeled MCT1/MCT4 lactate transporter inhibitor for imaging cancer metabolism with PET

Sattler, B.; Kranz, M.; Wenzel, B.; Thachaantara Jain, N.; Moldovan, R.-P.; Toussaint, M.; Deuther-Conrad, W.; Ludwig, F.-A.; Teodoro, R.; Sattler, T.; Sadeghzadeh, M.; Sabri, O.; Brust, P.

Overexpression of monocarboxylate transporters (MCTs) has been shown for a variety of human cancers (e.g. colon, brain, breast, and kidney) and inhibition resulted in intracellular lactate accumulation, acidosis and cell death. Thus, MCTs are promising targets to investigate tumor cancer metabolism with positron emission tomography (PET). Here, the organ doses (OD) and the effective dose (ED) of the first 18F-labeled MCT1/MCT4 inhibitor were estimated in juvenile pigs. Whole-body dosimetry was performed in three piglets (age: ~6 weeks, weight: ~13-15 kg). The animals were anaesthetized and subjected to sequential PET/CT up to 5h after i.v. injection of 156 ± 54 MBq [18F]FACH. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity data. Time and mass scales were adapted to the human order of magnitude and the ODs calculated using the ICRP 89 adult male phantom with OLINDA 2.1. The ED was calculated using tissue weighting factors as published in the ICRP103. The highest organ dose was received by the urinary bladder (62.6 ± 28.9 µSv/MBq), followed by the gall bladder(50.4 ± 37.5 µSv/MBq) and the pancreas (30.5 ± 27.3 µSv/MBq). The highest contribution to the ED was by the urinary bladder (2.5 ± 1.1 µSv/MBq) followed by the red marrow (1.7 ± 0.3 µSv/MBq) and the stomach (1.3 ± 0.4 µSv/MBq). According to this preclinical analysis,the ED to humans is 12.4 µSv/MBq when applying the ICRP103 tissue weighing factors. Taking into account that preclinical dosimetry underestimates the dose to humans by up to 40%, the conversion factor applied for estimation of the ED to humans would raise to 20.6 µSv/MBq. Resultantly, the ED to humans upon an i.v. application of ~300 MBq [18F]FACH would be about 6.2mSv. This risk assessment encourages to translate [18F]FACH to clinical study phases and to further investigate its potential as a clinical tool for cancer imaging with PET.

Keywords: preclinical radiopharmaceutical dosimetry, image based internal dosimetry, OLINDA, MCT1/MCT4 lactate transporter inhibitor; [18F]FACH; radiation safety

Permalink: https://www.hzdr.de/publications/Publ-30846
Publ.-Id: 30846


Crystal-field effects in Er3RuAl12with a distorted kagome lattice

Gorbunov, D.; Ishii, I.; Kurata, Y.; Andreev, A. V.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.

We report on the magnetic and elastic properties of Er3Ru4Al12 in static and pulsed magnetic fields up to 58 T. From the ultrasound results, we obtain evidence for a phase transition at 2 K related to magnetic ordering. Furthermore, in the paramagnetic state, Er3Ru4Al12 shows pronounced anomalies in the magnetization and elastic moduli as a function of temperature and magnetic field. We explain our findings using a crystal-electricfield (CEF) model that includes quadrupolar interactions and propose a CEF level scheme for this material. However, the CEF effects cannot explain all field-induced anomalies, which indicates that refined models are needed for explaining these.

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Permalink: https://www.hzdr.de/publications/Publ-30845
Publ.-Id: 30845


Ultrasonic Dispersion in the Hexagonal Ferromagnet Nd3Ru4Al12

Suzuki, T.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Ishii, I.

The rare-earth ferromagnet Nd3Ru4Al12 has Curie temperature TC= 39 K and crystallizes in the hexagonal Gd3Ru4Al12-type structure (space group P63/mmc), which is a non-caged structure. A previous measurement of the elastic moduli has shown an upturn around 10 K in the temperature dependence of the longitudinal modulus C33. The upturn is not caused by any phase transition. To investigate the origin of the upturn in Nd3Ru4Al12, we have measured the temperature dependence of C33 at various ultrasonic frequencies. The temperature of the upturn increases with increasing ultrasonic frequency indicating the ultrasonic dispersion, and it does not change under applied magnetic fields. These results suggest that the upturn originates from the rattling effect at one of the aluminium sites in the crystal structure. Assuming a Debye-type relaxation for the elastic modulus and an Arrhenius-type relaxation time for the rattling, the activation energy was estimated as E = 115 K and the relaxation time as Ƭ0 = 1.5 x 10-13s.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011091
    DOI: 10.7566/JPSCP.30.011091

Permalink: https://www.hzdr.de/publications/Publ-30843
Publ.-Id: 30843


Thermal and flow performance of tilted oval tubes with novel fin designs

Unger, S.; Beyer, M.; Szalinski, L.; Hampel, U.

We studied the thermal and flow performance of tube heat exchangers with novel fin designs for tube tilt angles of "0°,20°,30°" and "40°" to the horizontal. The novel fin designs target to enhance the conduction heat transfer within the fin and the convective heat transfer along the fin surface simultaneously. Tubes with three different fin designs, the circular plain fin (CPF), the circular integrated pin fin (CIPF) and the serrated integrated pin fin (SIPF), were additively manufactured by selective laser melting and experimentally investigated in an air flow channel for Reynolds number between "1800" and "7800" . We analysed the performance evaluation criterion, the volumetric heat flux density and the global performance criterion. It was found, that the SIPF achieves highest performance evaluation criterion and the CPF performs worst. Thus, the SIPF is recommended, when the required surface area, the material cost and the weight of the finned tube heat exchanger are relevant. Highest heat transfer per volume heat exchanger and temperature difference was achieved for the CIPF at highest tube tilt angle. The value of the global performance criterion strongly depends on the fin design and the tube tilt angle. For the horizontal orientation the CPF reaches highest global performance and for the 40° tube tilt angle the CIPF gives best performance. From the experimental data we derived appropriate heat transfer correlations for Reynolds number, Prandtl number, tube tilt angle and fin designs.

Keywords: Finned tube heat exchanger; Novel fin designs; Heat transfer; Friction factor; Tube tilt angle; Thermal-flow performance; Additive Manufacturing

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Permalink: https://www.hzdr.de/publications/Publ-30841
Publ.-Id: 30841


Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs

Unger, S.; Beyer, M.; Pietruske, H.; Szalinski, L.; Hampel, U.

These are the raw data and the processed data of the journal paper "Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs".

The raw data contains the measured values on the experimental setup and the processed data contains the data of the data used in the corresponding journal publication.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-23
    DOI: 10.14278/rodare.271
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30840
Publ.-Id: 30840


Rhenium and technetium-complexed silicon rhodamines as near-infrared imaging probes for bimodal SPECT- and optical imaging

Kanagasundaram, T.; Kramer, C. S.; Boros, E.; Kopka, K.

Radiolabelled fluorescent dyes are decisive for bimodal imaging and currently in demand for scintigraphic and optical imaging. This powerful method allows the combination of nuclear imaging (e.g. SPECT-imaging) and optical imaging which leads to synergistic effects, resulting in high spatial resolution and high tissue penetration from the whole body to the subcellular level. The new approaches in tumor imaging and its resection enables the accurate differentiation of healthy and diseased (e.g. tumor) tissues. Organic dyes belonging to the rhodamine family show unique optical properties such as high quantum yields, large extinction coefficients, absorption and emission properties in the optical window. The goal of this work was the development of small molecule near-infrared (NIR) light-emitting silicon-rhodamines (SiR) for scintigraphic and optical imaging. We utilized the dyes for copper(I)-catalyzed alkyne-azide [3+2]-cycloaddition to receive respective 1,2,3-triazoles for complexing the prominent SPECT-radiometal 99mTc(I)- and rheniumtricarbonyl core using the click-to-chelate concept from Mindt et al. The dyes were fully characterized using NMR-, UV/VIS/NIR-spectroscopy, IR and mass spectrometry. The presented silicon rhodamines with optical properties in the near-infrared region with emission wavelengths of ca. 650 nm and quantum yields in aqueous solution of up to 0.10 were received in seven reaction steps. The determined extinction coefficients of ca. 150.000 M-1cm-1 show promising results, making them potentially useful for bimodal imaging. Furthermore the dyes were prepared as precursors for radiolabelling with the SPECT-compatible radiometal technetium-99m. Corresponding rhenium-Si-rhodamines [used as a non-radioactive technetium-surrogate] were chemically characterized as well. Subsequently perfomed radiolabelling experiments have shown radiochemical yields of up to 59% and a radiochemical purity greater than 98%. The complexes show high stability both in aqueous solution and even in challenging experiments with histidine under physiological conditions. The first-in-class dyes have been synthesized to elucidate their potential for fluorescence- and radio-guided surgery. The non-targeted radiolabelled rhodamine dyes are subject of ongoing biological evaluations and the incorporation of biovectors into the dye for selective (tumor) targeting are topics of current research.

Keywords: Radiochemistry; Organic Synthesis; Click Chemistry; Technetium-99m Chemistry; Fluorescent Dyes; Silicon Rhodamines; Bimodal Imaging; Multimodal Imaging; SPECT Imaging; Optical Imaging

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Permalink: https://www.hzdr.de/publications/Publ-30839
Publ.-Id: 30839


The application of HEXS and HERFD XANES for accurate structural characterization of actinide nanomaterials: application to ThO₂.

Amidani, L.; Vaughan, G. B. M.; Plakhova, T. V.; Romanchuk, A. Y.; Gerber, E.; Svetogorov, R.; Weiß, S.; Joly, Y.; Kalmykov, S. N.; Kvashnina, K.

Structural characterization of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non‐homogeneous samples with NPs below 3 nm. By combining High Energy X‐ray Scattering (HEXS) and High‐Energy‐Resolution Fluorescence Detected X‐ray Near‐Edge Structure (HERFD XANES), we characterized for the first time both short‐ and medium‐range order of ThO₂ NPs obtained by chemical precipitation. With this methodology, a novel insight into the structure of NPs at different steps of their formation process is achieved. The Pair Distribution Function (PDF) reveals a high concentration of ThO₂ small units similar to Th hexamer clusters mixed with 1 nm ThO₂ NPs in the initial steps of formation. Drying the precipitates at ⁓150 °C promotes recrystallization of the smallest units into more thermodynamically stable ThO₂ NPs. HERFD XANES at Th M₄ edge, a direct probe of the f states, shows variations that we correlate to the break of the local symmetry around Th atoms, which most likely concerns surface atoms. Together, HEXS and HERFD are a powerful methodology to investigate actinide NPs and their formation mechanism.

Keywords: actinides; HERFD; HEXS; nanoparticles; ThO₂

Permalink: https://www.hzdr.de/publications/Publ-30838
Publ.-Id: 30838


Drone-based surveys of mineral deposits

Jackisch, R.

Drones are becoming important tools for mineral exploration by contributing to the safe, efficient and sustainable provision of the high-tech metals that are required by modern society.

Keywords: economic geology; mineralogy; UAV; hyperspectral; magnetics

Permalink: https://www.hzdr.de/publications/Publ-30836
Publ.-Id: 30836


UniCAR T cell immunotherapy enables efficient elimination of radioresistant cancer cells

Arndt, C.; Loureiro, L. R.; Feldmann, A.; Jureczek, J.; Bergmann, R.; Máthé, D.; Hegedüs, N.; Berndt, N.; Koristka, S.; Metwasi, N.; Fasslrinner, F.; Lamprecht, C.; Kegler, A.; Hoffmann, A.; Bartsch, T.; Köseer, A. S.; Egan, G.; Schmitz, M.; Hořejší, V.; Krause, M.; Dubrovska, A.; Bachmann, M.

Induction or selection of radioresistant cancer (stem) cells following standard radiotherapy is presumably one of the major causes for recurrence of metastatic disease. One possibility to prevent tumor relapse is application of targeted immunotherapies including e.g. chimeric antigen receptor (CAR) T cells. In light of long-term remissions it is highly relevant to clarify whether radioresistant cancer cells are susceptible to CAR T cell-mediated killing. To answer this question, we evaluated the anti-tumor activity of the switchable universal chimeric antigen receptor (UniCAR) system against highly radioresistant head and neck squamous cell carcinoma cells both in vitro and in vivo. Following specific UniCAR T cell engagement via EGFR or CD98 target modules, T cell effector mechanisms were induced including secretion of pro-inflammatory cytokines, up-regulation of granzyme B and perforin as well as T cell proliferation. CD98- or EGFR-redirected UniCAR T cells further possess the capability to efficiently lyse radioresistant tumor cells. Observed anti-tumor effects were comparable to those against the radiosensitive parental cell lines. Finally, redirected UniCAR T cells significantly inhibited growth of radioresistant cancer cells in immunodeficient mice. Taken together, our obtained data underline that the UniCAR system is able to overcome radio-resistance. Thus, it represents an attractive technology for the development of combined radioimmunotherapeutic approaches that might improve the outcome of patients with metastatic radioresistant tumor diseases.

Keywords: radio-resistance; CD98; EGFR; adaptor CAR; T cell immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-30835
Publ.-Id: 30835


General Colloidal Synthesis of Transition-Metal Disulfide Nanomaterials as Electrocatalysts for Hydrogen Evolution Reaction

Meerbach, C.; Klemmed, B.; Spittel, D.; Bauer, C.; Park, Y. J.; Hübner, R.; Jeong, H. Y.; Erb, D.; Shin, H. S.; Lesnyak, V.; Eychmüller, A.

The material-efficient monolayers of transition-metal dichalcogenides (TMDs) are a promising class of ultrathin nanomaterials with properties ranging from insulating through semiconducting to metallic, opening a wide variety of their potential applications from catalysis and energy storage to optoelectronics, spintronics, and valleytronics. In particular, TMDs have a great potential as emerging inexpensive alternatives to noble metal-based catalysts in electrochemical hydrogen evolution. Herein, we report a straightforward, low-cost, and general colloidal synthesis of various 2D transition-metal disulfide nanomaterials, such as MoS2, WS2, NiSx, FeSx, and VS2, in the absence of organic ligands. This new preparation route provides many benefits including relatively mild reaction conditions, high reproducibility, high yields, easy upscaling, no post-thermal annealing/treatment steps to enhance the catalytic activity, and, finally, especially for molybdenum disulfide nanosheets, high activity in the hydrogen evolution reaction. To underline the universal application of the synthesis, we prepared mixed CoxMo1-xS2 nanosheets in one step to optimize the catalytic activity of pure undoped MoS2, which resulted in an enhanced hydrogen evolution reaction performance characterized by onset potentials as low as 134 mV and small Tafel slopes of 55 mV/dec.

Permalink: https://www.hzdr.de/publications/Publ-30833
Publ.-Id: 30833


Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand-Directed Modulation

Fan, X.; Zerebecki, S.; Du, R.; Hübner, R.; Marzum, G.; Jiang, G.; Hu, Y.; Barcikowki, S.; Reichenberger, S.; Eychmüller, A.

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano-sized highly-active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser-generated inorganic-salt-stabilized metal nanoparticles, various impurity-free NMAs (Au, Pd, and Au-Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.

Keywords: aerogels; electrocatalysis; laser; ligand; noble metals

Permalink: https://www.hzdr.de/publications/Publ-30832
Publ.-Id: 30832


Engineering Multimetallic Aerogels for pH-Universal HER and ORR Electrocatalysis

Du, R.; Jin, W.; Hübner, R.; Zhou, L.; Hu, Y.; Eychmüller, A.

The advent of noble metal aerogels (NMAs), that feature the high catalytic activity of noble metals and unique structural attributes of aerogels, has stimulated research on a new class of outstanding electrocatalysts. However, limited by the available compositions, the explored electrocatalytic reactions on NMAs are highly restricted and certain important electrochemical processes have not been investigated. Here, an effective gelation approach is demonstrated by using a strong salting-out agent (i.e., NH4F), thereby expanding the composition of NMAs to various multimetallic systems and providing a platform to investigate composition-dependent electrocatalytic performance of NMAs. Combining structural features of aerogels and optimized chemical compositions, the Au-Pt and Au-Rh aerogel catalysts manifest remarkable pH-universal (pH = 0-14) performance surpassing commercial Pt/C and many other nanoparticle (NP)-based catalysts in the electrocatalytic oxygen reduction reaction, hydrogen evolution reaction, and water splitting, displaying enormous potential for the electrochemical hydrogen production, fuel cells, etc.

Keywords: electrocatalysis; hydrogen evolution reaction; metal aerogels; oxygen reduction reaction; pH

Permalink: https://www.hzdr.de/publications/Publ-30831
Publ.-Id: 30831


Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic elds. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with sufficiently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-18
    DOI: 10.14278/rodare.269
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30829
Publ.-Id: 30829


Round robin into best practices for the determination of indentation size effects

Ruiz-Moreno, A.; Hähner, P.; Kurpaska, L.; Jagielski, J.; Spätig, P.; Trebala, M.; Hannula, S.-P.; Merino, S.; de Diego, G. . .; Namburi, H.; Libera, O.; Terentyev, D.; Khvan, T.; Heintze, C.; Jennett, C.

The paper presents a statistical study of nanoindentation results obtained in seven European laboratories which have joined a round robin exercise to assess methods for the evaluation of indentation size effects. The study focuses on the characterization of ferritic/martensitic steels T91 and Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively. Depth-controlled single cycle measurements at various final indentation depths, force-controlled single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters at room temperature have been combined to calculate the indentation hardness and the elastic modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The correction modifies the statistical hardness profiles and allows determining more reliable indentation size effects.

Permalink: https://www.hzdr.de/publications/Publ-30828
Publ.-Id: 30828


Rethinking ore sorting - The search for the optimal sensor

Kern, M.; Tusa, L.; Khodadadzadeh, M.; Leißner, T.; Gloaguen, R.; van den Boogaart, K. G.; Gutzmer, J.

Zusammenfassung: Sensorgestützte Sortierung ist eine Technologie, die in zunehmendem Maße zur Aufbereitung von Primärrohstoffen verwendet wird. Mit dem hier vorgestellten simulations-basierten Ansatz ist es möglich, den optimalen Sensor durch quantitative Analysen der Mineralogie und Datenverwertung in Kombination mit Maschinellem Lernen (ML) gezielt zu bestimmen. Dieses Vorgehen ist generisch und kann auf viele Rohstofftypen angepasst werden. Darüber hinaus birgt das Vorgehen das Potenzial, eine Schlüsseltechnologie zur Optimierung von Aufbereitungsprozessen zu werden.

Summary: Sensor-based sorting is a technology which is increasingly used for processing primary raw materials. With the simulation-based approach presented in this paper, it is possible to specifically determine the optimal sensor based on quantitative analyses of the mineralogy and data utilization in combination with machine learning (ML). This approach is generic and can be adapted to many types of raw material. Moreover, the approach has the potential to become a key technology for the optimization of processing operations.

  • AT Minerals Processing 61(2020)3, 54-64

Permalink: https://www.hzdr.de/publications/Publ-30826
Publ.-Id: 30826


Pilot-scale investigation of two Electric Pulse Fragmentation (EPF) approaches for the mineral processing of a low-grade cassiterite schist ore

Bru, K.; Sousa, R.; Machado Leite, M.; Broadbent, C.; Stuart, G.; Pashkevich, D.; Kern, M.; Parvaz, D. B.

Two approaches for the use of the Electric Pulse Fragmentation (EPF) in the beneficiation of a low-grade cassiterite schist ore were investigated through pilot-scale tests performed on samples of about 270 kg. The first approach used EPF treatment for pre-concentration while in the second approach the EPF technology was mostly used for crushing. Comparison with the use of conventional crushers was performed.
Results showed that the EPF pre-treatment led to a decrease of the Bond rod mill work index while the Bond ball mill work index remained unchanged. This means that the decrease in the energy consumption requested to grind the material down to 1.18 mm (closing screen of the Bond rod mill work index) is no longer noticeable with additional grinding stage to reach a size down to 106 μm (closing screen of the Bond ball mill work index).
This may be due to the fracture network generated during EPF being consumed immediately in the subsequent comminution step. Alternatively, it may be that the Bond ball mill work index is not appropriate for exhibiting the weakening effect of the EPF technology when the mineral liberation size is coarser than the closing screen size used for the test. Concentration tests performed on the sample treated with the first approach for EPF showed no marked change in separation performance. However, a higher concentrate grade was obtained when using this EPF pre-treatment, indicating a probable potential for improvement.

Keywords: Cassiterite; Electric Pulse Fragmentation; Selective comminution; Pre-concentration

Permalink: https://www.hzdr.de/publications/Publ-30825
Publ.-Id: 30825


The effect of noise on the synchronization dynamics of the Kuramoto model on a large human connectome graph

Ódor, G.; Kelling, J.; Deco, G.

We have extended the study of the Kuramoto model with additive Gaussian noise running on the KKI-18 large human connectome graph. We determined the dynamical behavior of this model by solving it numerically in an assumed homeostatic state, below the synchronization crossover point we determined previously. The desynchronization duration distributions exhibit power-law tails, characterized by the exponent in the range 1.1 < τt < 2, overlapping the in vivo human brain activity experiments by Palva et al. We show that these scaling results remain valid, by a transformation of the ultra-slow eigen-frequencies to Gaussian with unit variance.
We also compare the connectome results with those, obtained on a regular cube with N = 106 nodes, related to the embedding space, and show that the quenched internal frequencies themselves can cause frustrated synchronization scaling in an extended coupling space.

Keywords: Frustrated Synchronization; Human Connectome; Chimera states; Noisy Kuramoto; Criticality in resting state

Permalink: https://www.hzdr.de/publications/Publ-30824
Publ.-Id: 30824


Contemporary Synthesis of Ultrasmall (sub-10 nm) Upconverting Nanomaterials

Joshi, T.; Mamat, C.; Stephan, H.

Due to their unique photophysical properties, upconverting nanoparticles (UCNPs), i.e. particles capable of converting near-infrared (NIR) photons into tunable emissions in the range of ultraviolet (UV) to NIR, have great potential for use in various biomedical fields such as bioimaging, photodynamic therapy and bioanalytical applications. As far as biomedical applications concerned, these materials have a number of advantageous properties such as brilliant luminescence and exceptional photo-stability. Very small “stealth” particles (sub-10 nm), which can circulate in the body largely undetected by the immune system, are particularly important for in vivo use. The fabrication of such particles, which simultaneously have a defined (ultrasmall) size and the required optical properties, is a great challenge and an area that is in its infancy. This minireview provides a concise overview of recent developments on appropriate synthetic methodologies to produce such UCNPs. Particular attention was given to the influence of both surfactants and dopants used to precisely adjust size, crystalline phase and optical properties of UCNPs.

Keywords: Lanthanides; Nanomaterials; Synthesis; Ultrasmall; Upconversion

Permalink: https://www.hzdr.de/publications/Publ-30823
Publ.-Id: 30823


Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic fields. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with suffciently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Keywords: magnetism; spin Hall; nano-oscillator; auto-oscillations; bipolar; oscillator; nanofabrication; microwave; high-frequency

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Permalink: https://www.hzdr.de/publications/Publ-30822
Publ.-Id: 30822


Structure variations within RSi2 and R2TSi3 silicides. Part I. Structure overview

Nentwich, M.; Zschornak, M.; Sonntag, M.; Gumeniuk, R.; Gemming, S.; Leisegang, T.; Meyer, D. C.

Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group–subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.

Keywords: silicide; lanthanide; ordering phenomena; structure prediction; DFT

Permalink: https://www.hzdr.de/publications/Publ-30821
Publ.-Id: 30821


Grundlegende F&E-Arbeiten zu Methoden der Zustandsüberwachung von Transport- und Lagerbehältern für abgebrannte Brennelemente und wärmeentwickelnde hochradioaktive Abfälle bei verlängerter Zwischenlagerung

Wagner, M.; Rachamin, R.; Fiß, D.; Schmidt, S.; Reinicke, S.; Kratzsch, A.; Hampel, U.

Mit der verlängerten Zwischenlagerung von abgebrannten Brennelementen ergeben sich verschie-dene regulatorische und sicherheitstechnische Fragestellungen. Eine davon ist die nach der Lang-zeitintegrität der Brennelemente in den Trockenlagerbehältern. Ihre Beantwortung hat direkte Relevanz für den späteren Transport zum Endlager und die Umladung des abgebrannten Kernbrennstoffs in andere Behälter. In dem Verbundvorhaben untersuchten die TU Dresden und die Hochschule Zittau/Görlitz Potenziale und Grenzen von nichtinvasiven Verfahren zur Überwachung des Zustands des radioaktiven Inventars von Trockenlagerbehältern. Als solche wurden Thermographie, strahlungsbasierte Messverfahren sowie akustische Messverfahren betrachtet. Für diese erfolgte eine Bewertung der Empfindlichkeit und Nachweisgrenzen mittels numerischer Simulationen und Durchführung von Experimenten an skalierten Behältermodellen. Es stellte sich heraus, dass insbesondere die Myonenbildgebung und die Analyse der Gamma- und Neutronenstrahlungsfelder am Behälter für ein Überwachungskonzept geeignet sind. Mit diesen Verfahren können Brennstoffverlagerungen ortsaufgelöst detektiert werden.

Keywords: Zwischenlagerung; nicht-invasive Überwachung

  • Other report
    -: -, 2020

Permalink: https://www.hzdr.de/publications/Publ-30818
Publ.-Id: 30818


The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?

Eftekhari, M.; Schwarzenberger, K.; Javadi, A.; Eckert, K.

The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.

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  • Secondary publication expected from 09.01.2021

Permalink: https://www.hzdr.de/publications/Publ-30817
Publ.-Id: 30817


Influence of finite temperature Exchange-Correlation effects in Hydrogen

Ramakrishna, K.; Dornheim, T.; Vorberger, J.

We use density functional molecular dynamics (DFT-MD) to study the effect of finite temperature exchange-correlation (xc) in Hydrogen. Using the Kohn-Sham approach, the xc energy of the system, $E_{xc}(r_{s})$ is replaced by the xc free energy $f_{xc}(r_{s},\theta)$ within the local density approximation (LDA) based on parametrized path integral Monte Carlo (PIMC) data for the uniform electron gas (UEG) at warm dense matter (WDM) conditions. We observe insignificant changes in the equation of state (EOS) at the region of metal-insulator transition compared to the regular LDA form, whereas significant changes are observed for T>10000 K, i.e., in the important WDM regime. Thus, our results further corroborate the need for temperature-dependent xc functionals for DFT simulations of WDM systems. Moreover, we present the first finite-temperature DFT results for the EOS of Hydrogen in the electron liquid regime up to $r_{s}=14$ and find a drastic impact (the EOS changes by more than 20%) of thermal xc effects, which manifests at lower temperatures compared to WDM. We expect our results to be important for many applications beyond DFT, like quantum hydrodynamics and astrophysical models.

Keywords: Computational Physics; Plasma Physics; Warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-30815
Publ.-Id: 30815


Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe

Kasahara, S.; Sato, Y.; Licciardello, S.; Culo, M.; Arsenijevic, S.; Ottenbros, T.; Tominaga, T.; Böker, J.; Eremin, I.; Shibauchi, T.; Wosnitza, J.; Hussey, N. E.; Matsuda, Y.

We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 Tapplied parallel to the ab plane. At low temperatures, the upper critical field μ0Habc2 shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ0H* ≈ 24 T well below μ0Habc2, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties.We attribute the high-field phase to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.

Permalink: https://www.hzdr.de/publications/Publ-30814
Publ.-Id: 30814


Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4O6

Knaflic, T.; Jeglic, P.; Komelj, M.; Zorko, A.; Biswas, P. K.; Ponomaryov, O.; Zvyagin, S.; Reehuis, M.; Hoser, A.; Geiß, M.; Janek, J.; Adler, P.; Felser, C.; Jansen, M.; Arcon, D.

Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide Cs4O6 was deduced from the charge ordering of molecular peroxide O2−2 and superoxide O2 anions accompanied by the structural transformation and a dramatic change in electronic conductivity [Adler et al., Sci. Adv. 4, eaap7581 (2018)]. Here, we report that in the sister compound Rb4O6, a similar Verwey-type charge ordering transition is strongly linked to O2 orbital and spin dynamics. On cooling, a powder neutron diffraction experiment reveals a charge ordering and a cubic-to-tetragonal transition at TCO = 290 K, which is followed by a further structural instability at Ts = 92 K that involves an additional reorientation of magnetic O2 anions. Magnetic resonance techniques supported by density functional theory computations suggest the emergence of a peculiar type of π*-orbital ordering of the magnetically active O2 units, which promotes the formation of a quantum spin state composed of weakly coupled spin dimers. These results reveal that as in 3d transition-metal compounds, also in the π* open-shell alkali sesquioxides the interplay between Jahn-Teller-like electron-lattice coupling and Kugel-Khomskii-type superexchange determines the nature of orbital ordering and the magnetic ground state.

Permalink: https://www.hzdr.de/publications/Publ-30813
Publ.-Id: 30813


Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Dornheim, T.; Sjostrom, T.; Tanaka, S.; Vorberger, J.

The strongly coupled electron liquid provides a unique opportunity to study the complex interplay of strong coupling with quantum degeneracy effects and thermal excitations. To this end, we carry out extensive ab initio path integral Monte Carlo (PIMC) simulations to compute the static structure factor, interaction energy, density response function, and the corresponding static local field correction in the range of 20≤rs≤100 and 0.5≤θ≤4. We subsequently compare these data to several dielectric approximations and find that different schemes are capable to reproduce different features of the PIMC results at certain parameters. Moreover, we provide a comprehensive data table of interaction energies and compare those to two recent parametrizations of the exchange-correlation free energy, where they are available. Finally, we briefly touch upon the possibility of a charge-density wave. The present study is complementary to previous investigations of the uniform electron gas in the warm dense matter regime and, thus, further completes our current picture of this fundamental model system at finite temperature. All PIMC data are available online.

Keywords: warm dense matter; electron liquid; dielectric theory; quantum monte carlo; local field correction; ab initio

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Permalink: https://www.hzdr.de/publications/Publ-30812
Publ.-Id: 30812


Radiopharmaceutical Sciences

Ermert, J.; Benešová, M.; Hugenberg, V.; Gupta, V.; Spahn, I.; Pietzsch, H.-J.; Liolios, C.; Kopka, K.

Clinical Nuclear Medicine, 2nd ed., Chapter 2 Radiopharmaceutical Sciences
Abstract: Chapter 2 Radiopharmaceutical Sciences
Chapter 2 elucidates the field Radiopharmaceutical Sciences from the perspective of its clinical relevance. Radiopharmaceutical Sciences summarize all scientific aspects comprising chemistry, physics and biology/pharmacology that deal with incorporating a suitable radionuclide into a pharmaceutical or other biologically active molecule or molecular entity. The resulting radiopharmaceuticals are used in Nuclear Medicine applications both for diagnosis [meaning non-invasive scintigraphic imaging] and for internal radiotherapy. Internal radiotherapy is nowadays called radioligand therapy (RLT) or endoradiotherapy and altogether is summarized under the term radiothera(g)nostics.
To transfer Radiopharmaceutical Sciences into Clinical Nuclear Medicine first of all radionuclides with corresponding decay characteristics are demanded making these suitable for diagnostic or therapeutic applications. Depending on the short physical half-lives of the radionuclides fast and efficient radiolabeling strategies are required that can be also transferred into the GMP-compliant production of radiopharmaceuticals.
The major challenges in the development of a new radiopharmaceuticals include i.a. the identification of an adequate ligand that specifically binds to the biological target of interest, the chemical modification of the ligand to enable radiolabeling while preserving the binding affinity to the biological target, and the translation of the preclinical evaluations into first in-human studies.
In summary this chapter summarises in a concise manner the current status of clinically relevant radionuclides, SPECT and PET tracers as well as the introduced thera(g)nostic classes of radiopharmaceuticals through the eyes of eight representative radiopharmaceutical scientists.

  • Book chapter
    Ahmadzadehfar H, Biersack HJ, Freeman LM, Zuckier LS: Clinical Nuclear Medicine – 2nd edition, Springer Nature Switzerland AG: Springer International Publishing, 2020, 978-3-030-39455-4, 49-191
    DOI: 10.1007/978-3-030-39457-8

Permalink: https://www.hzdr.de/publications/Publ-30811
Publ.-Id: 30811


Why should we care about microorganisms in the bentonite back fill material for the storage of high-level radioactive waste in deep geological repositories?

Matschiavelli, N.; Dressler, M.; Neubert, T.; Kluge, S.; Schierz, A.; Cherkouk, A.

Every year 12,000 metric tonnes of high-level radioactive waste (HLW) are produced worldwide. For the long-term storage of this highly radiotoxic waste, a deep geological disposal by using multiple barriers is favored. Bentonite is proposed as a potential material for sealing the space between the canister containing the HLW and the surrounding host rock. In order to investigate the microbial diversity and metabolic activity of naturally occurring microorganisms as well as their time-dependent evolution, we conducted anaerobic microcosm experiments containing bentonite and a synthetic Opalinus Clay pore water solution. During the one-year incubation at 30 and 60 °C, lactate- or H2-stimulated microcosms at 30 °C showed the dominance and activity of strictly anaerobic, sulfate-reducing and spore-forming microorganisms. The subsequent generation of hydrogen sulfide gas in the respective set ups, led to the formation of fractures and iron-sulfur precipitations. In microcosms that incubated at 60 °C, thermophilic bacteria dominated, independent from the availability of substrates. In the respective microcosms, no significant metabolic activity was detected and there was no change in the analyzed bio-geochemical parameters. Our results show that indigenous microorganisms evolve in a temperature- and substrate-dependent manner. Potentially formed metabolites could affect the dissolution behavior of minerals and ions within the bentonite as well as the corrosion process of the canister material and require further investigations.

  • Lecture (Conference)
    6th Joint Conference of DGHM & VAAM, 08.-11.03.2020, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30807
Publ.-Id: 30807


The Potential Role of Colloidal Silica as a Depressant in Scheelite Flotation

Kupka, N.; Babel, B. M.; Rudolph, M.

The main challenge in scheelite flotation lies in the contamination of the concentrate by other calcium-bearing minerals, mainly calcite. To remedy this problem, sodium silicate is frequently used as a depressant. According to the literature, one hypothesis for the mechanism of water glass consists in its absorption onto calcite through colloidal silica formation, preventing hydrophobization by the collector. This short communication presents research conducted on the direct use of colloidal silica as a depressant in scheelite flotation. Colloidal silica is shown to have an impact on scheelite flotation, especially by depressing silicates.

Keywords: scheelite flotation; colloidal silica; depressant

Permalink: https://www.hzdr.de/publications/Publ-30806
Publ.-Id: 30806


Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type

Kupka, N.; Möckel, R.; Rudolph, M.

To improve the performance of sodium silicate in scheelite flotation and allow the selective separation of scheelite from other semi-soluble salt-type minerals such as calcite, three acids, sulfuric, oxalic and for the first time hydrochloric are used to acidify sodium silicate (also called water glass). A literature review of previous usage of acidified water glass shows that no comparison between acids was made before, that comparisons with alkaline water glass were limited and that the idea that acidified water glass is more efficient at lower dosages has not been proven in scheelite flotation. As a consequence, the impact of the acid type, the ratio between acid and sodium silicate and acid dosage is tested in single mineral flotation and batch flotation experiments. All three acids allow a higher performance of acidified water glass compared to alkaline water glass at lower dosages and with little addition of acid: the tungsten recovery and grade are improved while silicates and to a lesser extent calcium-bearing minerals float less. The dosage of acid is less determining than the mass ratio of the acid to sodium silicate, except in the case of hydrochloric acid. Overall, the acid type does not matter as all three acids perform well in flotation, whereby oxalic and hydrochloric acid are better.

Keywords: acidified water glass; scheelite calcite separation; froth flotation

  • Open Access Logo Physicochemical Problems of Mineral Processing 56(2020)2, 238-251
    DOI: 10.37190/ppmp19101

Permalink: https://www.hzdr.de/publications/Publ-30805
Publ.-Id: 30805


Rapid Thermodynamically Stable Complex Formation of [nat/111In]In3+, [nat/90Y]Y3+, and [nat/177Lu]Lu3+ with H6dappa

Kostelnik, T.; Xiaozhu, W.; Southcott, L. D.; Wagner, H.; Kubeil, M.; Stephan, H.; Jaraquemada-Pelaez, M. D. G.; Orvig, C.

A phosphinate-bearing picolinic acid-based chelating ligand (H6dappa) was synthesized and characterized to assess its potential in a bifunctional chelator (BFC) for inorganic radiopharmaceuticals. Nuclear magnetic resonance (NMR) spectroscopy was employed to investigate the chelator coordination chemistry with a variety of nonradioactive trivalent metal ions (In3+, Lu3+, Y3+, Sc3+, La3+, Bi3+). Density functional theory (DFT) calculations explored the coordination environments of aforementioned metal complexes. The thermodynamic stability of H6dappa with four metal ions (In3+, Lu3+, Y3+, Sc3+) was deeply investigated via potentiometric and spectrophotometric (UV-vis) titrations, employing a combination of acidic in-batch, joint potentiometric/spectrophotometric, and ligand-ligand competition titrations; high stability constants and pM values were calculated for all four metal complexes. Radiolabeling conditions for three clinically relevant radiometal ions were optimized ([111In]In3+, [177Lu]Lu3+, [90Y]Y3+), and the serum stability of [111In][In(dappa)]3- was studied. Through concentration-, time-, temperature-, and pH-dependent labeling experiments, it was determined that H6dappa radiolabels most effectively at near-physiological pH for all radiometal ions. Furthermore, very rapid radiolabeling at ambient temperature was observed, as maximal radiolabeling was achieved in less than one minute. Molar activities of 29.8 GBq/mol and 28.2 GBq/mol were achieved for [111In]In3+ and [177Lu]Lu3+, respectively.

Permalink: https://www.hzdr.de/publications/Publ-30804
Publ.-Id: 30804


Special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

This is the second part of a special issue of the American Journal of Science examining a problem that defines, perhaps more than any other, the state-of-the-art in the geochemistry of fluid-solid interaction: how to integrate data from both observations and modeling of events of brief duration at essentially atomic scales (for example, attachment, diffusion, detachment, hydrolysis), to that of mesoscale, ensemble processes (crystal dissolution, growth, alteration). The ultimate goal is an understanding of the long-term, phenomenological consequences of these interactions, often termed “upscaling”. Success in predicting and constraining these latter outcomes determines the larger value of this field, both to neighbors in environmental sciences and engineering, as well as to the public in terms of policy, education, and support. Nanoscale observation of mineral surfaces via instruments such as AFM and VSI is now widespread; increases in resolution and analytical capability of these instruments have also evolved in tandem with advances in the power and resolution of simulation and modeling approaches. Closely tied to an emerging theoretical framework, this “soft” progress in simulation and modeling was the focus of the first part of this issue.

  • Book (Editorship)
    New Haven CT 06220-8109: American Journal of Science, Yale University, 2020
    101 Seiten

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30803
Publ.-Id: 30803


Late complications following neo-/adjuvant radiotherapy and surgery for sarcomas of the extremities or pelvis/retroperitoneum Preventative measures

Jentsch, C.; Hofbauer, C.; Makocki, S.; Troost, E. G. C.

Radiotherapy is one of the pillars in the multimodal therapy of sarcomas of the extremities or pelvis/retroperitoneum. It can be delivered prior to or following surgery. Novel radiation techniques, such as intensity-modulated radiotherapy using high-energy photons or protons, contribute to the reduction of acute and late toxicities. This review article summarizes these concepts.

Keywords: Limb; Photon beam therapy; Proton beamtherapy; Radiotherapy, intensity-modulated; Soft tissue neoplasms

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  • Secondary publication expected from 12.02.2021

Permalink: https://www.hzdr.de/publications/Publ-30801
Publ.-Id: 30801


L1 cell adhesion molecule confers radioresistance to ovarian cancer and defines a new cancer stem cell population

Terraneo, N.; Jacob, F.; Peitzsch, C.; Dubrovska, A.; Krudewig, C.; Huang, Y.-L.; Heinzelmann-Schwarz, V.; Schibli, R.; Béhé, M.; Grünberg, J.

Many solid tumors, including ovarian cancer, contain small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and play a role in disease recurrence. We demonstrated that the L1 cell adhesion molecule (L1CAM) is a new CSC target in ovarian cancer, triggering radioresistance. Using fluorescence-activated cell sorting, specific cell populations expressing L1CAM alone or in combination with the established CSC marker CD133 were isolated from three ovarian cancer cell lines. Double-positive L1CAM+/CD133+ cells displayed higher spherogenic and clonogenic properties in comparison to L1CAM−/CD133− cells. Furthermore, L1CAM+/CD133+ cells retained highest clonogenic capacity after irradiation and exhibited up-regulation of some CSC-specific genes, enhanced tumor-initiating capacity, selfrenewal and higher tumor take rate in nude mice when compared with other cell populations. Superior radioresistance by L1CAM expression was confirmed by deletion of L1CAM using CRISPR-Cas9 technology. Moreover, we found expression signatures associated with epithelial-tomesenchymal transition phenotype in L1CAM deleted cells. These results indicate that L1CAM in combination with CD133 defines a new cancer cell population of ovarian tumor-initiating cells with the implication of targeting L1CAM as a novel therapeutic approach for ovarian CSCs.

Keywords: L1 cell adhesion molecule; ovarian cancer; stem cells; radioresistance; CRISPR-Cas9; epithelial-to-mesenchymal transition

Permalink: https://www.hzdr.de/publications/Publ-30800
Publ.-Id: 30800


Identification of the regime boundaries in bubble columns based on the degree of randomness in the signals

Nedeltchev, S.; Top, Y.; Hlawitschka, M. W.; Schubert, M.; Bart, H.-J.

A new parameter (degree of randomness (DR)) was defined for the identification of the main transition velocities, Utrans. The new method reconstructs the time series into multiple state vectors, thus generating non-overlapping vector pairs and then compares the distance between them with a pre-selected cut-off length. The DR values were extracted from gauge and differential pressure fluctuations as well as x-ray tomographic scans. At every Utrans value, the DR index exhibited a well-pronounced local minimum. Three cylindrical bubble columns (BCs) with various diameters (0.1, 0.14, and 0.45 m in ID) and one rectangular BC (width = 0.2 m, depth = 0.04 m) were used. They were aerated by means of different perforated plate gas distributors. It was found that in the cylindrical BCs the disintegration of the bubbly flow regime took place always at Utrans = 0.04 m/s. In the case of the rectangular BC the first critical velocity appeared at Utrans = 0.012 m/s. The lower boundary of the churn-turbulent regime was identified at Utrans = 0.11 m/s in the smallest cylindrical BC and at about Utrans = 0.095 m/s in the other two cylindrical BCs. In the case of the rectangular BC, the second critical velocity was identified at Utrans = 0.039 m/s. The low Utrans in the rectangular BC imply that the hydrodynamic regimes are less stable in this particular column due to higher degree of liquid turbulence. The calculated DR values from the gauge pressure fluctuations successfully distinguished the upper boundary of the gas maldistribution and the first transition sub-regime.

Keywords: bubble columns; pressure fluctuations; regime transitions; signal randomness; tomographic scans

  • Canadian Journal of Chemical Engeneering (2020)
    Online First (2020) DOI: 10.1002/cjce.23719

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Permalink: https://www.hzdr.de/publications/Publ-30799
Publ.-Id: 30799


Random singlet state in Ba5CuIr3O12 single crystals

Volkov, P. A.; Won, C.-J.; Gorbunov, D.; Kim, J.; Ye, M.; Kim, H.-S.; Pixley, J. H.; Cheong, S.-W.; Blumberg, G.

We study the thermodynamic and high-magnetic-field properties of the magnetic insulator Ba5CuIr3O12, which shows no magnetic order down to 2 K, consistent with a spin-liquid ground state. While the temperature dependence of the magnetic susceptibility and the specific heat shows only weak antiferromagnetic correlations, we find that the magnetization does not saturate up to a field of 59 T, leading to an apparent contradiction. We demonstrate that the paradox can be resolved, and all of the experimental data can be consistently described within the framework of random singlet states. We demonstrate a generic procedure to derive the exchange coupling distribution P(J ) from the magnetization measurements and use it to show that the experimental data are consistent with the power-law form P(J ) ∼ J−α with α ≈ 0.6. Thus, we reveal that high-magnetic-field measurements can be essential to discern quantum spin-liquid candidates from disorder dominated states that do not exhibit long-range order.

Permalink: https://www.hzdr.de/publications/Publ-30798
Publ.-Id: 30798


Spin-lattice coupling in a ferrimagnetic spinel: Exotic H-T phase diagram of MnCr2S4 up to 110 T

Miyata, A.; Suwa, H.; Nomura, T.; Prodan, L.; Felea, V.; Scurschii, I.; Deisenhofer, J.; Krug Von Nidda, H.-A.; Portugall, O.; Zherlitsyn, S.; Tsurkan, V.; Wosnitza, J.; Loidl, A.

In antiferromagnets, the interplay of spin frustration and spin-lattice coupling has been extensively studied as the source of complex spin patterns and exotic magnetism. Here, we demonstrate that, although neglected in the past, the spin-lattice coupling is essential to ferrimagnetic spinels as well. We performed ultrahigh-field magnetization measurements up to 110 T on a Yafet-Kittel ferrimagnetic spinel, MnCr2S4, which was complemented by measurements of magnetostriction and sound velocities up to 60 T. Classical Monte Carlo calculations were performed to identify the complex high-field spin structures. Our minimal model incorporating spin-lattice coupling accounts for the experimental results and corroborates the complete phase diagram, including two new high-field phase transitions at 75 and 85 T.Magnetoelastic coupling induces striking effects: An extremely robust magnetization plateau is embedded between two unconventional spin-asymmetric phases. Ferrimagnetic spinels provide a new platform to study asymmetric and multiferroic phases stabilized by spin-lattice coupling.

Permalink: https://www.hzdr.de/publications/Publ-30796
Publ.-Id: 30796


High-field phase transitions in the orbitally ordered multiferroic GeV4S8

Felea, V.; Pham, T. C.; Prodan, L.; Gorbunov, D.; Nomura, T.; Scurschii, I.; Zherlitsyn, S.; Wosnitza, J.; Wang, Z.; Miyata, A.; Portugall, O.; Widmann, S.; Krug Von Niddy, H.-A.; Deisenhofer, J.; Tsurkan, V.; Loidl, A.

The high-field (H,T) phase diagram of the multiferroic lacunar spinel GeV4S8 has been studied by ultrasound, magnetization, and pyrocurrent experiments in magnetic fields up to 60 T. The title compound consists of molecular building blocks, with vanadium V4 clusters characterized by a unique electron density. These vanadium tetrahedra constitute a Jahn-Teller active entity, which drive an orbital-ordering transition at 30K with the concomitant appearance of ferroelectricity. Ultrasound and magnetization experiments reveal sharp anomalies in magnetic fields of 46 T, which are associated with a first-order phase transition into an orbitally disordered state characterized by significant field and temperature hystereses. We report a sequence of complex magnetic, polar, and orbitally ordered states, i.e., the appearance of two orbitally ordered phases OO1 and OO2 for μ0H < 45 T and T < 30K. Beyond the paraelectric phase we further evidenced three ferroelectric phases, FE1, FE2, and FE3. Finally, antiferromagnetic (AFM) order (T < 15 K) and fully polarized ferromagnetic order (μ0H > 60 T) have been observed in GeV4S8. At low temperatures and for fields below 40 T, AFM order coexists with the polar phase FE3 identifying a multiferroic state. Our results demonstrate a fascinating competition of the different orders, which the material manifests in high magnetic fields and at low temperatures.

Permalink: https://www.hzdr.de/publications/Publ-30795
Publ.-Id: 30795


Structure and magnetic properties of (Sm,Ho)2Fe17Nx (x = 0; 2.4)

Veselova, S. V.; Tereshina, I. S.; Verbetsky, V. N.; Neznakhin, D. S.; Tereshina-Chitrova, E. A.; Kaminskaya, T. P.; Karpenkov, A. Y.; Akimova, O. V.; Gorbunov, D.; Savchenko, A. G.

The structural and magnetic properties of the compound Sm1.2Ho0.8Fe17 and the nitride powders Sm1.2Ho0.8Fe17N2.4 prepared by high energy ball milling under various milling regimes are reported. Magnetic properties of the samples are investigated at 2–300 K in steady magnetic field up to 70 kOe and in pulsed magnetic field up to 600 kOe. The application of high magnetic field reveals the presence of the second-order transition in Sm1.2Ho0.8Fe17N2.4 at 500 kOe. Magnetic hysteresis properties study shows that ball milling enhances magnetic performance of Sm1.2Ho0.8Fe17N2.4 making it perspective for the magnets fabrication.

Permalink: https://www.hzdr.de/publications/Publ-30794
Publ.-Id: 30794


Noncollinear magnetic structure in U2Pd2In at high magnetic fields

Prokes, K.; Bartkowiak, M.; Gorbunov, D.; Prokhnenko, O.; Rivin, O.; Smeidbidl, P.

We report an unexpected magnetic-field-driven magnetic structure in the 5 f -electron Shastry-Sutherland system U2Pd2In. This phase develops at low temperatures from a noncollinear antiferromagnetic ground state above the critical field of 25.8 T applied along the a axis. All U moments have a net magnetic Moment in the direction of the applied field, described by a ferromagnetic propagation vector qF = (0 0 0) and an antiferromagnetic component described by a propagation vector qAF = (0 0.30 1/2 ) due to a modulation in the direction perpendicular to the applied field. We conclude that this surprising noncollinear magnetic structure is due to a competition between the single-ion anisotropy trying to keep moments, similar to the ground state, along the [110]-type directions, Dzyaloshinskii-Moryia interaction forcing them to be perpendicular to each other and application of the external magnetic field attempting to align them along the field direction.

Permalink: https://www.hzdr.de/publications/Publ-30793
Publ.-Id: 30793


Slurm in Docker

Pape, D.

A Docker image with a Slurm setup to enable testing of HPC software in a container.

Keywords: Docker; Slurm; batch system; high performance computing; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Dockerfile, Shell
    System requirements: Docker Engine
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/slurm-in-docker:

Permalink: https://www.hzdr.de/publications/Publ-30792
Publ.-Id: 30792


GitLab HPC Driver Protoype

Pape, D.

GitLab HPC Driver prototype implementation.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Bash
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver-prototype:

Permalink: https://www.hzdr.de/publications/Publ-30791
Publ.-Id: 30791


GitLab HPC Driver

Pape, D.

Um gute Performance und Skalierbarkeit von hochparalleler wissenschaftlicher Software sicherzustellen, ist es wichtig, diese in einer möglichst realitätsnahen Umgebung zu testen. Wünschenswert ist dabei ein möglichst einfacher Zugriff auf die HPC-Ressourcen über ein bereits etabliertes System wie GitLab CI. Dafür wurde ein Driver für den GitLab-Runner entwickelt, der es erlaubt Continuous-Integration-Jobs auf Hochleistungsrechnern auszuführen. Der Driver wird vom GitLab-Runner-Service aufgerufen und kann vom Nutzer auf die gleiche Art und Weise verwendet werden, wie andere im GitLab-Ökosystem bekannte CI-Systeme. Es werden HPC-Ressourcen unterstützt, die vom Batchsystem Slurm verwaltet werden.

To ensure high performance and scalability in scientific software, a realistic testing environment plays an important role. Preferably, easy access to HPC resources is enabled via an established tool like GitLab CI. For that, a driver for GitLab runner has been developed that allows the execution of CI jobs on a supercomputer. The driver is called by GitLab runner service and can be used in the same way as other tools in the GitLab ecosystem. It supports HPC resources managed by the Slurm batch system.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver:

Permalink: https://www.hzdr.de/publications/Publ-30790
Publ.-Id: 30790


Two-Pion Intensity Interferometry in Au + Au @ 1.23A GeV

Greifenhagen, R.; (for the HADES collaboration)

High-statistics π−π− HBT data for non-central Au + Au collisions at 1.23A GeV, measured with HADES at SIS18/GSI, are presented. The three-dimensional emission source is studied in dependence on pair transverse momentum and centrality. A tilt of the source relative to the beam axis is observed. The spatial extension and the tilt magnitude of the source decrease with transverse momentum. The spatial extension decreases and the tilt magnitude increases going from central to peripheral collisions. The derived eccentricity perpendicular to the beam axis fits well to the initial nucleonic overlap region at high transverse momentum.

Permalink: https://www.hzdr.de/publications/Publ-30789
Publ.-Id: 30789


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