Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

36783 Publications

Dynamics and length scales in vertical convection of liquid metals

Zwirner, L.; S. Emran, M.; Schindler, F.; Singh, S.; Eckert, S.; Vogt, T.; Shishkina, O.

Using complementary experiments and direct numerical simulations, we study turbulent thermal convection of a liquid metal (Prandtl number Pr≈0.03) in a box-shaped container, where two opposite square sidewalls are heated/cooled. The global response characteristics like the Nusselt number Nu and the Reynolds number Re collapse if the side height 𝐿 is used as the length scale rather than the distance 𝐻 between heated and cooled vertical plates. These results are obtained for various Rayleigh numbers 5×103≤Ra𝐻≤108 (based on 𝐻) and the aspect ratios 𝐿/𝐻=1,2,3 and 5. Furthermore, we present a novel method to extract the wind-based Reynolds number, which works particularly well with the experimental Doppler-velocimetry measurements along vertical lines, regardless of their horizontal positions. The extraction method is based on the two-dimensional autocorrelation of the time–space data of the vertical velocity.

Keywords: Convection in cavities

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34106
Publ.-Id: 34106


Nonlinear response of semiconductor systems under intense THz excitation

Pashkin, O.

Intense narrowband terahertz pulses from the FELBE free-electron laser facility are utilized to study nonlinear excitation regimes of various degrees of freedom in semiconductors. In this talk we present several recent examples including plasmons in InGaAs nanowires, intersubband transitions in Ge/SiGe quantum wells, and impurity transitions in boron doped Si.

  • Invited lecture (Conferences) (Online presentation)
    The 10th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2021), 16.-19.06.2021, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-34105
Publ.-Id: 34105


Experimental and Numerical Investigations for an Advanced Modeling of Two-Phase Flow and Mass Transfer on Column Trays

Vishwakarma, V.

Distillation is the leading thermal separation technology that is carried out in many industrial tray columns worldwide. Although distillation columns are expensive in terms of cost and energy, they will remain in service due to unavailability of any equivalent industrially-viable alternative. However, rising energy costs and urgent needs to reduce greenhouse gas emissions demand improvements in the energy efficiency of separation processes, globally. This can be achieved by tuning the dynamics of the evolving two-phase dispersion on column trays via design modification and revamping. Thus, it becomes necessary to understand how the two phases evolve over the tray and how they link to tray efficiency for given tray designs, systems and operating conditions. Only then, the cost and energy reduction can be achieved by strategically iterating the tray design and revamps with respect to the resulting tray efficiency. To pursue this strategy, accurate prediction of the separation efficiency based on flow and mixing patterns on the trays is an important prerequisite.

In this thesis, the mathematical models relying on flow and mixing patterns for predicting the tray efficiencies were reviewed. These models were developed based on the analyses of two-phase flow, crossflow hydraulics and mass transfer over the trays. Several limitations in the existing models were identified that could lead to inaccurate tray efficiency predictions. First, the conventional models do not account for any variation in the local two-phase flow in their formulation. These models rather consider a homogeneous flow scenario based on flow monitoring at the tray boundaries only, which indicates a black box efficiency estimation. Second, the existing models do not consider any vapor flow maldistribution, which can be detrimental to the tray efficiency. In response to these limitations, a new model based on refinement of the conventional residence time distribution (RTD) model (referred to as the ‘Refined RRTD model’) was proposed. The new model involves geometric partitioning of the tray into compartments along the flow path length, which permits computing the tray efficiency through quantification of the efficiency of the individual compartments. The proposed model ensures that the fluid dynamics of each compartment contribute towards the overall tray efficiency, which specifically targets the black box prediction of the tray efficiency by the conventional models. The tray discretization further aids in analyzing the impact of vapor flow maldistribution on the tray efficiency. In the initial assessment, the new model capabilities were demonstrated in appropriate case studies after theoretical validation of the model for the limiting cases of the two-phase flows. For the experimental validation of the new model, a full hydrodynamic and mass transfer description of the two-phase dispersion specific to the tray operation is indispensable. Because of the inherently complex dispersion characteristics, significant advancements in the imaging and efficiency modeling methods were required.

In this thesis, a DN800 column simulator equipped with two sieve trays (each with 13.55% fractional free area) was used with air and tap water as the working fluids. Deionized water was used as a tracer. The gas loadings in the column in terms of 𝐹-factor were 1.77 Pa0.5 and 2.05 Pa0.5, whereas the weir loadings were 2.15 m3m-1h-1, 4.30 m3m-1h-1 and 6.45 m3m-1h-1. An advanced multiplex flow profiler comprising 776 dual-tip conductivity probes for simultaneous conductivity measurements was introduced for hydrodynamic characterization. The spatial resolution of the profiler based on the inter-probe distance was 21 mm × 24 mm, whereas the temporal resolution was 5000 Hz. The design characteristics of the new profiler, electronic scheme, measurement principle, reference framework, and data processing schemes are explained in detail. By analyzing the two-phase dispersion data gathered by the profiler at multiple elevations above the tray, the effective froth height distributions were obtained for the first time based on a newly proposed approach. Uniform froth heights were seen over the majority of the tray deck, whereas both minimum and maximum froth heights were detected immediately after the tray inlet. Based on threshold-based calculation (accompanied by γ-ray CT scans), 3D time-averaged liquid holdup distributions were visualized for the first time, too. Homogeneous liquid holdup distributions were observed at multiple elevations above the deck with the highest holdups occurring near the average effective froth heights. The detailed flow and mixing patterns of the liquid in the two-phase dispersion were retrieved via tracer monitoring. With respect to tray centerline, axisymmetric liquid flow and mixing patterns were detected with parabolic velocity distributions near the tray inlet. The liquid velocities over the remaining tray deck were nearly uniform for the prescribed loadings. Eventually, the RRTD model was applied by discretizing the tray geometrically, and accordingly employing the available hydrodynamic data. The conventional models often applied in the literature were also evaluated with the new model.

For evaluating the model predictions, a new system add-on for the existing air-water column facility was proposed for direct efficiency measurements. The air-led stripping of isobutyl acetate from the aqueous solution is a safe and viable approach that overcomes numerous limitations posed by the existing chemical systems. Based on liquid sampling at different tray locations, the liquid concentration distributions were obtained at each operating condition via UV spectroscopy. The tray and point efficiencies as well as stripping factors were calculated from those distributions. Because of the low liquid diffusivity and high liquid backmixing, low efficiencies were observed at the given loadings. The model predictions were consistent with the experimental counterparts (even for the extrapolated values of the involved parameters), because of the uniform liquid flow and mixing in the compartments. For the given predictions, those corresponding to the new RRTD model were the most accurate. Additional hydrodynamic and efficiency data are needed for more conclusive evidence regarding the promise of the RRTD model.

Keywords: column tray; two-phase crossflow; efficiency prediction model; 3D liquid holdup; tracer-response analysis; tray efficiency calculation

Related publications

  • Doctoral thesis
    TU Dresden, 2021

Permalink: https://www.hzdr.de/publications/Publ-34102
Publ.-Id: 34102


Voltage‐driven motion of oxygen and nitrogen ions: role of defects in magneto‐ionics

Liedke, M. O.; Butterling, M.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Menéndez, E.; de Rojas, J.; Sort, J.

Nowadays magnetoelectronic devices are still controlled by electric currents, a scheme which suffers from energy losses due to heat dissipation. Employing electrical fields as a substitution of
currents can strongly reduce ohmic losses and is expected to be crucial for energy-efficient applications. Here, a voltage-induced ionic motion (magneto-ionics) is proposed to control the magnetic properties. In traditional magneto-ionic systems oxygen or lithium are exploited as transport
ions and, only recently, nitrogen. We will demonstrate magneto-ionic effects in single-layer iron
and cobalt nitride films. Their microstructural and magnetic properties are evaluated and compared with previously studied oxides using positron annihilation spectroscopy and magnetometry
techniques. The electrolyte-gated ionic migration enables switching between paramagnetic and
ferromagnetic states. The role of vacancies and their agglomerations at grain boundaries are emphasized as diffusion channels, which allow for a fast migration and large incorporation of the
ionic species.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; magneto-ionics; oxide; nitride

Related publications

  • Poster (Online presentation)
    MML-Workshop 2021 - "From Matter to Materials and Life", 22.-24.11.2021, Darmstadt, Germany

Permalink: https://www.hzdr.de/publications/Publ-34100
Publ.-Id: 34100


Vacancy kinetics during magnetic phase transitions

Liedke, M. O.; Butterling, M.; Ehrler, J.; Eggert, B.; Griggs, W.; Anwar, M. S.; Bali, R.; Thomson, T.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.

Two model magnetic systems, FeAl and FeRh, will be discussed in terms of defect kinetics during magnetic phase transitions. Open volume defects have been investigated with Doppler broadening and positron annihilation lifetime spectroscopy techniques using continuous [1] and pulsed [2] slow positron beams, respectively.
The first system, FeAl, exhibits the so-called disorder induced ferromagnetism, where anti-site disorder promotes ferromagnetic A2 phase over paramagnetic ordered B2 phase. The overall control of the phase transition is given by ion irradiation and annealing [1,3]. The main physical origin correlates strongly with the anti-site disorder [4], however the concentration and size of open volume defects is crucial for kinetics of the reordering processes. It will be shown that Fe and Al mono-vacancies introduced by Ne+ irradiation increase the A2 → B2 ordering rate, whereas triple defects and vacancy clusters are stable during annealing. The ordering is achieved through the diffusion of Al and Fe atoms which is mediated by vacancies, and the splitting of vacancy clusters and triple defects into single vacancies during irradiation allows control of the A2 → B2 re-ordering rates, strongly accelerating thermal diffusion [3]. These results provide insights into thermal reordering processes in binary alloys, and the consequent effect on magnetic behavior.
The second system investigated, FeRh, shows a first-order metamagnetic transition from a low temperature antiferromagnetic to a high temperature ferromagnetic phase at about 370 K. During this transition the local Fe magnetic moments align ferromagnetically while the Rh atoms acquire a moment of approximately 1 μB. Moreover, the lattice volume expands by about 1%. The phase transition can also be induced by ion or laser irradiation which drives a disorder-induced mechanism where so-called static disorder plays a key role. It can occur in the form of mono-vacancies, vacancy clusters, grain boundaries or as anti-site disorder, which lead to the formation of ferromagnetism. It will be demonstrated that ion irradiation damages the film structure introducing open volume defects, where concentration scales with ion fluence. Moreover, defect kinetics during thermal annealing across the antiferromagnetic-ferromagnetic phase transition critical temperature will be discussed in detail.

[1] M.O. Liedke, W. Anwand, R. Bali et al., J. Appl. Phys. 117 (2015) 163908.
[2] A. Wagner, M. Butterling, M.O. Liedke et al., AIP Conf. Proc. 1970 (2018), 040003.
[3] J. Ehrler, M.O. Liedke, J. Čížek et al., Acta Mater. 176 (2019) 167.
[4] R. Bali, S. Wintz, F. Meutzner et al., Nano Lett. 14 (2014) 435.

* The Impulse- and Networking Fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox), and the Helmholtz Energy Materials Characterization Platform (03ET7015) are acknowledged.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; FeRh; FeAl

Related publications

  • Lecture (Conference) (Online presentation)
    Int. Workshop on Positron Studies of Defects-2021, 01.-05.03.2021, Mumbai, India

Permalink: https://www.hzdr.de/publications/Publ-34098
Publ.-Id: 34098


Oxygen vs. Nitogen Magneto-ionics

de Rojas, J.; Quintana, A.; Lopeandía, A.; Salguero, J.; Muñiz, B.; Ibrahim, F.; Chshiev, M.; Nicolenco, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Henderick, L.; Dendooven, J.; Detavernier, C.; Sireus, V.; Abad, L.; Jensen, C. J.; Liu, K.; Nogues, J.; Costa-Krämer, J.; Menéndez, E.; Sort, J.

Voltage-controlled magnetism, where magnetic properties are controlled via an applied electricfield instead of current, could represent a significant increase in energy savings in future magnetically actuateddevices. Practically, however, this approach faces several important obstacles, such as thickness limitations inelectrically charged metallic films, mechanical failure in strain-mediated piezoelectric/magnetostrictive devices,and a lack of room-temperature multiferroics. Voltage-driven ionic motion (magneto-ionics) may provide a pathforward by avoiding many of these drawbacks, in addition to its own interesting magnetoelectric phenomena.Nevertheless, translating magneto-ionics into real world devices requires significant improvements in magneto-ionic rates, cyclability, and magnetization. Here, we report on the development of magneto-ionics in single-layer, semiconducting transition metal oxides and nitrides, and the subsequent enhancements in theirperformance. We first present electrolyte-gated and defect-mediated O transport in single-layer, paramagneticCo
O
at room temperature (i.e. without thermal assistance), which allows voltage-controlled magneticswitching (referred to here as ON-OFF ferromagnetism: Fig. 1) via internal reduction/oxidation processes
.Negative bias partially reduces Co
O
to Co, resulting in films with Co- and O-rich areas (ferromagnetism: ON).Positive bias re-oxidizes Co back to Co
O
(paramagnetism: OFF). We show that the bias-induced motion of Ois caused by mixed vacancy clusters, with O motion promoted at grain boundaries and assisted by thedevelopment of O-rich diffusion channels. The generated ferromagnetism is shown to be stable, and easilyerased by sufficient positive bias. This voltage-induced process is demonstrated to be compositionally,structurally, and magnetically reversible and self-contained, as no oxygen reservoir besides Co
O
is needed.We then show that room-temperature magneto-ionic effects in electrolyte-gated paramagnetic Co
O
films canbe significantly increased, both in terms of generated magnetization (6 times larger) and speed (35 timesfaster), if the electric field is applied using an electrochemical capacitor configuration (utilizing an underlyingconducting buffer layer: Fig. 2) instead of electric-double-layer transistor-like configuration (placing the electriccontacts at the side of the semiconductor)
. In addition to gains in speed, magnetization measurements showa marked increase in the squareness ratio and a decrease in the switching field distribution of the hysteresisloops in Co
O
biased in the capacitor configuration, the result of the formation of more uniform ferromagneticregions. These results are attributed to the uniform electric field applied throughout the film, as confirmed byCOMSOL simulations. As the measured films are quite thick, further miniaturization promises even greatermagneto-ionic rates. We then demonstrate room-temperature voltage-driven nitrogen magneto-ionics (i.e., Ntransport) by electrolyte-gating of a CoN film
. Nitrogen magneto-ionics in CoN is compared to oxygenmagneto-ionics in Co
O
, in films using an electrochemical capacitor configuration. Both materials are shownto be nanocrystalline (face-centered cubic structure), and show reversible voltage-driven ON-OFFferromagnetism (Fig. 1). Nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front, without assistance of diffusion channels. Nitrogen magneto-ionics also requires lowerthreshold voltages and exhibits enhanced rates and cyclability, due to the combination of a lower criticalelectric field required to overcome the energy barrier for ion diffusion and the lower electronegativity of nitrogenwith respect to oxygen, consistent with
ab initio
calculations contrasting N vs. O motion in cobalt stacks. Theseresults place nitrogen magneto-ionics as a robust alternative for efficient voltage-driven effects and, along withoxygen magneto-ionics, may enable the use of magneto-ionics in devices that require endurance and moderate speeds of operation, such as brain-inspired/stochastic computing or magnetic micro-electro-mechanical systems.
References:
[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, Vol. 12, p. 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Advanced Functional Materials, Vol. 30, p. 2003704 (2020)
[3] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, Vol. 11, p. 5871 (2020)
KEYWORDS:
magneto-ionics, voltage-controlled magnetism, oxygen, nitrogen.
IMAGE CAPTION:
Fig. 1. Hysteresis loops (M vs. H) of as-prepared, negatively-biased, and positively-biased CoN films atmagneto-ionic activation voltages.
Fig. 2. A schematic of the electrochemical capacitor configuration used to bias cobalt-oxide (Co
O
) andcobalt-nitride (CoN) films.

Related publications

  • Lecture (Conference)
    INTERMAG 2021, 26.-30.04.2021, Lyon, France

Permalink: https://www.hzdr.de/publications/Publ-34097
Publ.-Id: 34097


Precipitation stripping of nanometrical particles for the recovery of vanadium

Kelly, N.; Helbig, T.; Ebert, D.; Möckel, R.; Chekhonin, P.; O'Toole, N.; Sanchez Loredo, M. G.

The demand for strategic metals such as chromium and vanadium is predicted to rise in the future. These metals can currently be found in the slag by-products of certain steel production processes. To help meet the rising demand, the CHROMIC project seeks to develop a hydrometallurgical process for the recovery and purification of these valuable resources. Various methods are being investigated for separation of the metal value from the resulting alkaline leach feeds, including solvent extraction.
In case of the recovery of vanadium an interesting modification of the conventional solvent extraction process is the addition of a crystallization operation (precipitation stripping). The extraction was carried out using an Aliquat 336 solution in n-octanol/kerosene as extractant. Precipitation stripping was carried out using metal salt dissolved in a concentrated chloride solution. For some experiments, polyvinylpyrrolidone was used as stabilizer in order to avoid agglomeration and control growth. The metal vanadate particles are nanometrical in size, with morphologies varying from nanowires to spherical particles.

  • Poster (Online presentation)
    International Conference on Resource Chemistry, 08.-09.03.2021, online (ursprünglich Darmstadt), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34096
Publ.-Id: 34096


The radiolabeling of silicon rhodamines for multimodal PET/ SPECT- and NIR optical imaging

Kanagasundaram, T.; Laube, M.; Carsten, S. K.; Stadlbauer, S.; Pietzsch, J.; Kopka, K.

Objectives: The combination of non-invasive molecular imaging (PET/SPECT)- and optical imaging (OI) techniques for tumor identification and resection are emerging. This powerful strategy promises to precisely differentiate between healthy and affected tumor tissues which is of most relevance for preoperative planning (prestaging) followed by R0-tumor resection via image-guided intraoperative surgery. The goal of this work is the development of radiolabeled near-infrared (NIR) fluorophores for PET/SPECT and optical imaging. The fluorophores were prepared for radiolabeling with the positron emitter fluorine-18 and with the gamma emitter iodine-123 for SPECT imaging with the aim to elucidate their potential as imaging agents for the detection of tumor tissues. Moreover, the radiolabeled dyes are intended to be bioconjugated to the PSMA-1007 binding motif, as a generic prominent tumor targeting vector for enrichment in prostate tumors (1).
Methods: We have developed fluorophores belonging to the silicon rhodamine (SiR) family with optical properties in the NIR spectral range (2). The photostable fluorophores have been characterized using NMR-, UV/VIS/NIR-spectroscopy and mass spectrometry. Furthermore the SiRs were radiolabeled by using the approach for copper-mediated radiolabeling of arylboronic acids, functioning as precursors both for fluorine-18 and iodine-123 labeling (3). The radiolabeling conditions were optimized based on radiochemical conversions (RCC) as analyzed by using radio-HPLC and radio-TLC. The model and lead compound [18F]F-SiR was isolated by radio-HPLC followed by SPE for further in vitro experiments, e.g. in vitro stability was determined in human serum.
Results: Novel boronic acid functionalized SiRs with chemical yields up to 68% were received via multistep organic syntheses. The blue dyes show high extinction coefficients up to 95.000 M-1cm-1, quantum yields of 0.33 and high photo stability making them useful for NIR optical imaging. After careful optimization of the radiolabeling conditions, [18F]F-SiR was obtained in isolated radiochemical yields of up to 31% and a molar activity of 70 GBq/µmol. Moreover, radioiodination experiments led to [123I]I-SiRs with radiochemical conversions higher than 90% (figure 1).
Demonstrated by human serum stability, the lead fluorophore [18F]F-SiR showed promising performance for in vitro and in vivo experiments.
The current work is focused on the synthesis of 18F/123I-radiolabeled SiRs and their reference analogs containing an active ester for bioconjugation with prominent biological vectors (e.g. PSMA-1007 motif) to perform first proof-of-concept studies.
Conclusions: The very first radiolabeled NIR fluorophores based on the SiR lead structure were synthesized and their labeling efficiencies for radiofluorination and radioiodination were evaluated. Ideal optical- and radiolabeling properties show promising features for further bioconjugation with prominent target vectors (e.g. PSMA-1007 binding motif) and biological evaluation of the novel SiR-PSMA-1007 conjugates in vitro and in vivo.
Acknowledgements:
This project is supported by the Wilhelm Sander-Stiftung for a grant on dual-labeled tumor tracers, grant number 2018.024.1.
References:
(1) K. Kopka et al., J. Nucl. Med. 2015, 56, 914–920.
(2) T. Nagano et al., J. Am. Chem. Soc. 2012, 134, 5029–5031.
(3) B. Neumaier et al., Chem. Eur. J. 2017, 23, 3251–3556.

Keywords: PET/SPECT Imaging; Optical Imaging; Organic Chemistry; Si-Rhodamines; Radiochemistry

Permalink: https://www.hzdr.de/publications/Publ-34095
Publ.-Id: 34095


Potential of industrial hemp (Cannabis sativa L.) for bioenergy production in Canada: Status, challenges and outloo

Mahmud Parvez, A.; David Lewis, J.; Afzal, M. T.

Climate change from carbon emissions and rising energy demands poses a serious threat to global sustainability. This issue is particularly noticeable in Canada where per capita energy demands are high and fossil fuels are used. Industrial hemp can be used for bioenergy production as an alternative to fossil fuels to capture and utilize carbon, with applications in various markets at high values. Despite this, industrial hemp has faced legal barriers that have hampered its viability. This review describes industrial hemp, its status in global markets, its performance as bioenergy feedstock, and potential in Canada, so research can target gaps in available knowledge. Numerous bioenergy applications for industrial hemp exist; the production of bioethanol and biodiesel from industrial hemp has strong potential to reduce greenhouse gas emissions and improve the Canadian economy. The current study found that industrial hemp can compete with many energy crops in global markets as a feedstock for many bioenergy products with solid hemp yielding 100 GJ/ha/y, allowing for economical emissions reductions for example in coal/biochar blends that can reduce emissions by 10%, and in co-production of bioethanol and grain, generating $2632/ha/y. This work also suggests industrial hemp has unique potential for growth in Canada, though processing facilities are severely lacking, and hemp growing has some negative environmental impacts related to fertilizer use. Responsible growth could be realized through incentivizing or subsidizing processing facility investment, implementing co-production where possible, and funding research to improve conversion, harvesting and polygeneration processes.

Keywords: Canada; Industrial hemp; Second-generation biofuel

Permalink: https://www.hzdr.de/publications/Publ-34091
Publ.-Id: 34091


Sorption enhanced gasification (SEG) of biomass for tailored syngas production with in-situ CO2 capture: Current status, process scale-up experiences and outlook

Mahmud Parvez, A.; Hafner, S.; Hornberger, M.; Schmid, M.; Scheffknecht, G.

Sorption Enhanced Gasification (SEG) is being considered as a promising solid fuel conversion and carbon capture and sequestration technology since it can produce tailored syngas coupled with in-situ CO2 capture. Over the years, considerable research has been conducted with high grade biomass in laboratory and pilot scale facilities targeting technical and process scale-up viabilities of the SEG process. SEG has successfully been tested at semi industrial scale which demonstrates further scale-up potential (e.g. commercial demonstration plant) of this innovative technology. The results showed that the operation window of SEG laid at a gasification temperature ranging from 600 °C to 750 °C. By optimizing the process parameters, H2-rich syngas (>70 vol %db) and desired H2/CO ratios can be attained. Also, the total tar content of the optimized process is reported to be low compared to those obtained from classical fluidized bed gasification processes. So far, wood is mostly used as the feedstocks while tests with wastes including solid recovered fuels (SRFs) have also been conducted. Cheap and readily available natural sorbents (such as limestone) enable a satisfactory operation, however, issues associated with attrition and deactivation still need to be addressed. Accordingly, natural sorbents with improved properties, synthetic CaO-based sorbents as well as pre-treated natural sorbents are considered to overcome these limitations. This paper therefore discusses the current status of the SEG technology with an emphasis on its industrial applications for flexible syngas production with in-situ CO2 reduction. Moreover, challenges, process scale-up experiences and research gaps for the commercialization of this novel technology are identified in this review.

Keywords: Sorption enhanced gasification; Biomass; In-situ CO2 capture; Limestone/CaO sorbent; Carbon capture and sequestration

Permalink: https://www.hzdr.de/publications/Publ-34089
Publ.-Id: 34089


Experimental investigations of hard x-ray source produced by picosecond laser-irradiated solid target

Li, M.-T.; An, H.-H.; Hu, G.-Y.; Xiong, J.; Lei, A.-L.; Xie, Z.-Y.; Wang, C.; Wang, W.; Zhang, Z.-C.; Huang, L.

Measurements of Kα line and bremsstrahlung continuous x-ray emission from high-intensity laser-irradiated thin targets are presented. The experiments were performed at the SG-II UP Petawatt laser. Self-standing Sn foils varying thicknesses and Sn foils backed by the thick substrate were irradiated by the laser pulses up to 300 J of energy with peak intensity higher than 10^18 W/cm^2. A transmission curved crystal spectrometer and a filter-stack spectrometer were used to measure the Kα line and bremsstrahlung x-ray spectral distribution, respectively. Both Kα and 70–200 keV x-ray yields decrease 3- to 5-fold for target backed by the substrate. 2- to 4-fold reduction of Kα and 70–200 keV x-ray yields for the 8.5 μm targets relative to 50 μm targets was observed. Moreover, a significant background x-ray emission generated from the target holder reduces the ratio of signal to noise. Adopting a low-Z material holder can mitigate the x-ray background noises. This study is instructive to optimize target design for the high-intensity laser-driven Kα or continuous x-ray sources.

Downloads:

  • Secondary publication expected from 20.01.2023

Permalink: https://www.hzdr.de/publications/Publ-34083
Publ.-Id: 34083


Evolution of Molecular Binding in Mechanically controlled Break-Junctions

Lokamani, M.; Günther, F.; Kelling, J.; Gemming, S.

Mechanically controllable break junctions (MCBJs) are devices, in which the electrical properties of single molecules can be investigated with extreme precision using atomically structured metallic electrodes. The current-voltage (IV) characteristics in such junctions are considerably affected by the binding positions of the anchoring groups on the tip-facets and the configuration of the molecule. Hence, characterizing the electronic transport properties during a single tip-tip opening provides interesting insights in to the tip-molecule interaction.
In this contribution/talk, we present a novel, high-throughput approach to reproduce the time evolution of the electronic transport characteristics. For this, we performed transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB)[1] approach and the Green’s function formalism. In particular, we evaluated the energy level E0 and the coupling Γ of the dominating transport channel using the single level model[2]. In contrast to standard approaches, we consider not just one molecule orientation but many thermodynamically relevant configurations. The obtained parameters were averaged using statistical weights obtained from Metropolis simulation considering up to 80.000 different configurations for selected tip-tip distances. The dependence of the averaged quantities with respect to the tip-tip separation reveals characteristic features also observed in experiments for similar molecular systems.
Our approach allows us to relate these features to binding-site and molecule-curvature effects and therefore provides a better interpretation of the experimental results.

1. M. Elstner, D. Porezag, G. Jungnickel, J. Elsner, M. Haugk, T. Frauenheim, S. Suhai, and G. Seifert, Self-consistent-charge density-functional tight-binding method for simulations of complex materials properties, Phys. Rev. B 58, 7260 (1998)
2. Cuevas, J. C.; Scheer, E. In Molecular Electronics: An Introduction to Theory and Experiment; Reed, M., Ed.; World Scientific Series in Nanoscience and Nanotechnology, Vol. 1; World Scientific: Singapore,Hackensack, NJ, 201

Keywords: mechanically controlled break junctions; high-throughput simulations

  • Open Access Logo Lecture (others)
    Seminar Theorie, Modellierung, Simulation https://www.tu-chemnitz.de/physik/TQPS/TheorieSeminar.html, 15.09.2021, Chemnitz, Germany

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34079
Publ.-Id: 34079


Forming Federal Communities

Lokamani, M.; Erxleben, F.; Knodel, O.; Juckeland, G.

Forming Federal Communities
Building Research Collaboration Networks

Keywords: Federal Communities; Research Collaboration Networks

  • Open Access Logo Lecture (Conference) (Online presentation)
    TEACH - Talk about Education Across Communities in Helmholtz, 07.-10.12.2021, Dresden, Germany

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34078
Publ.-Id: 34078


Dynamics of H2 Bubbles Growing at Microelectrodes

Bashkatov, A.; Hossain, S. S.; Yang, X.; Mutschke, G.; Eckert, K.

Recently a new phenomenon of long-lasting position oscillations of hydrogen gas bubbles produced via electrolysis at horizontally installed microelectrodes has been found. The bubbles grow until their detachment when buoyancy exceeds the retarding forces. The phenomenon itself consists in multiple bubble returns to the electrode. It was found that the mother bubble sits on and is fed by a carpet of small bubbles. The dynamics of the growing bubble was systematically studied and found to be strongly dependent on the cathodic potential and electrolyte concentration.

Keywords: electrolysis; hydrogen bubble; oscillations; electric force

  • Lecture (Conference) (Online presentation)
    ISE Annual 72nd meeting, 29.08.-03.09.2021, Jeju Island, Korea
  • Lecture (Conference) (Online presentation)
    The 25th International Congress of Theoretical and Applied Mechanics (25th ICTAM), 22.-27.08.2021, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-34077
Publ.-Id: 34077


Sauter-Schwinger effect for colliding laser pulses

Kohlfürst, C.; Ahmadiniaz, N.; Oertel, J.; Schützhold, R.

We study electron-positron pair creation by the electromagnetic field of two colliding laser pulses as described by the vector potential
A(t,r) = [f(ct−x) +f(ct+x)]ey. Employing the world-line instanton technique as well as a generalized WKB approach, we find that the pair creation rate along the symmetry axisx= 0(where one would expect the maximum contribution) displays the same exponential dependence as for a purely time-dependent electric field A(t) = 2f(ct)ey. The pre-factor in front of this exponential does also contain corrections due to focusing or de-focusing effects induced by the spatially inhomogeneous magnetic field. We compare our analytical results to numerical simulations using the Dirac-Heisenberg-Wigner method and find good agreement.

Keywords: Sauter-Schwinger effect; WKB; Worldline instanton; Numerical analysis

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34066
Publ.-Id: 34066


Motion reversals of rising electrogenerated hydrogen bubbles

Bashkatov, A.; Babich, A.; Yang, X.; Boenke, J.; Hossain, S. S.; Mutschke, G.; Eckert, K.

The growth of hydrogen bubbles in water electrolysis is of high practical relevance due to the prominent role of hydrogen in the future energy system. The dynamics even of a single bubble is already multifaceted and is associated with several interdisciplinary phenomena such as Marangoni convection [1, 2], bubble-microlayer interaction [3, 4] and electric forces on the bubbles [4,5].

In this contribution, the dynamics of a single hydrogen bubble was studied during water electrolysis at a horizontal Pt microelectrode in an acidic environment. A new phenomenon was observed. It consists of the ability of already detached hydrogen bubbles, expected to continue buoyant rise, to reverse the direction of motion and to return to the electrode from relatively large distances (350 μm). The phenomenon was systematically studied at different cathodic potentials and electrolyte concentrations by using high-speed microscopic shadowgraphy and electric current measurements.

Acknowledgment
This project is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry of Economics and Technology (BMWi) due to the enactment of the German Bundestag under Grant No. DLR 50WM2058 (project MADAGAS II).

Keywords: Hydrogen evolution; Electrolysis; Microelectrode; Microbubbles

  • Poster (Online presentation)
    18th Multiphase Flow Conference and Short Course, 08.-11.11.2021, Helmholtz-Zentrum Dresden-Rossendorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-34061
Publ.-Id: 34061


MADAGAS II - Untersuchungen zum Einfluss von Marangoni-Konvektion und Doppelschicht-Effekten auf die Ablösung von Gasblasen an Mikroelektroden

Eckert, K.; Mutschke, G.

Für die Energiewende spielen Technologien zur Erzeugung von Wasserstoff aus regenerativen Energiequellen eine wichtige Rolle. Bei der Elektrolyse zur Spaltung von Wasser beeinflusst das Verhalten der entstehenden Wasserstoff- und Sauerstoffblasen ganz wesentlich die Prozesseffizienz. Jedoch ist die Dynamik der Gasblasen noch nicht vollständig verstanden. Erst unlängst wurde in der Literatur auf den möglichen Einfluss kapillarer und elektrischer Kräfte hingewiesen.
In unserem Projekt beschäftigen wir uns im Detail mit der Dynamik von bei der Elektrolyse an Mikroelektroden entstehenden Wasserstoffblasen. Wir untersuchen die auf die Blasen wirkenden elektrischen Kräfte, um diese genauer zu quantifizieren, sowie ebenfalls den Einfluss von Marangonieffekten und Koaleszenzphänomenen. Wir verwenden optische Hochgeschwindigkeits- und elektrochemische Methoden, um die schnelle Dynamik der Blasen in unseren Testzellen zu erfassen, und komplementieren die Untersuchungen mit numerischen Simulationen.
Zur Durchführung der Elektrolyse-Experimente in unseren Testzellen nutzen wir ebenfalls Parabelflüge, bei denen periodisch Phasen der Schwerelosigkeit und der Hypergravitation auftreten. Hierdurch können die genannten Effekte genauer und selektiv untersucht werden, da die Schwerebeschleunigung die Dynamik der Gasblasen wesentlich beeinflusst. Ebenfalls können hierbei Erkenntnisse zur Verbesserung der Ablösung von Gasblasen in Raumfahrt-Anwendungen gewonnen werden.

Keywords: Elektrolyse; Wasserstoff

  • Poster
    1. Mitteldeutscher Wasserstoffkongress und 7. HYPOS-Forum, 02.-04.11.2021, Leuna, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34060
Publ.-Id: 34060


Reduced Hall carrier density in the overdoped strange metal regime of cuprate superconductors

Putzke, C.; Benhabib, S.; Tabis, W.; Ayres, J.; Wang, Z.; Malone, L.; Licciardello, S.; Lu, J.; Kondo, T.; Takeuchi, T.; Hussey, N. E.; Cooper, J. R.; Carrington, A.

Efforts to understand the microscopic origin of superconductivity in the cuprates are dependent on knowledge of the normal state. The Hall number in the low-temperature, high-field limit nH(0) has a particular importance because, within conventional transport theory, it is simply related to the number of charge carriers, so its evolution with doping gives crucial information about the nature of the charge transport. Here we report a study of the high-field Hall coefficient of the single-layer cuprates Tl2Ba2CuO6+δ (Tl2201) and (Pb/La)-doped Bi2Sr2CuO6+δ (Bi2201), which shows how nH(0) evolves in the overdoped—so-called strange metal—regime of cuprates. We find that nH(0) increases smoothly from p to 1 + p, where p is the number of holes doped into the parent insulating state, over a wide range of doping. The evolution of nH correlates with the emergence of the anomalous linear-in-temperature term in the low-temperature in-plane resistivity. The results could suggest that quasiparticle decoherence extends to dopings well beyond the pseudogap regime.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34058
Publ.-Id: 34058


Stretchable Printed Magnetic Sensors Based on Giant Magnetoresistive Microflakes for On-Skin Electronic Interfaces

Oliveros Mata, E. S.; Ha, M.; Canon Bermudez, G. S.; Zabila, Y.; Faßbender, J.; Makarov, D.

On-demand fabrication of electronic devices is expected to be enabled by high throughput printing technologies1. Due to the simplified processing, printing is particularly attractive for flexible and stretchable electronics that are typically fabricated over polymeric soft substrates2. Wide research efforts are directed towards the development of conductive pastes with reliable electrical and mechanical properties.

Sensing pastes able to detect external stimuli are central for the operation of on-skin electronic interfaces. Among others, magnetic sensors are less prone to mechanical failure due to their touchless nature3. Solution processable pastes for magnetic sensing typically consist of composites of magnetoresistive micro- or nanoparticles embedded in polymeric binders4-7. Despite the research progress on printable magnetic sensors, until now there were no reports of printed magnetic sensors showing stable response after typical skin deformations: bending and stretching.

Here, we will show the fabrication and implementation of skin-compliant printed magnetic field sensors. These rely on microflakes obtained from a giant magnetoresistive (GMR) multilayer [Py/Cu]30 stacks. The microflakes were embedded on a poly(styrene-butadiene-styrene) copolymer (SBS) matrix that enables stretchability and high adherence properties. The stretchable printed magnetic sensors were obtained after dispensing the GMR paste over an ultrathin (3-µm-thick) Mylar substrate. We demonstrated stable sensing and mechanical performance even at 100% strain and 16 µm bending deformations, representing two orders of magnitude of performance enhancement with respect to previous works. The obtained sensors showed maximum sensitivity at 0.88 mT, which is compatible with the 40 mT safety threshold established by the World Health Organization7. These characteristics enabled a safe and conformal integration of the sensor for on-skin interactive electronics applications. We showed the use of the printed sensor platform for navigating through documents and digital maps. We foresee that the future development of this technology for user-specific fabrication of human-machine touchless interfaces with task-specific capabilities and integration8.
1 J.S. Chang, A.F. Facchetti and R. Reuss., IEEE Trans. Emerg. Sel. Topics Circuits Syst., Vol. 7, p.7 (2017)
2 Q. Huang and Yong Zhu., Adv Mater. Technol., Vol. 4, p.1800546 (2019)
3 S. Zuo, H. Heidari and D. Farina. Adv Mater. Technol., Vol. 5, p.2000185 (2020)
4 D. Karnaushenko, D. Makarov and M. Stöber, Adv. Mater., Vol.27, p.880 (2015)
5 J. Meyer, T. Rempel and M. Schäfers, Smart Mater. Struct., Vol. 22, p.025032 (2013)
6 B. Cox, D. Davis, N. Crews, Sens. Actuators, A, Vol. 203, p.335 (2013)
7 E.S. Oliveros Mata, G.S. Cañón Bermúdez and M. Ha,. Appl. Phys. A, Vol. 127, p.280 (2021)
8 Static Fields. World Health Organization. (2006)
9 M. Ha, E.S. Oliveros Mata and G. S. Cañón Bermúdez, Adv. Mater. Vol. 33, p.2005521 (2021)

  • Lecture (Conference)
    2022 Joint MMM-Intermag Conference, 10.-14.01.2022, New Orleans, United States

Permalink: https://www.hzdr.de/publications/Publ-34054
Publ.-Id: 34054


Printable Magnetoresistive Sensors for On-Skin Interactive Electronics

Oliveros Mata, E. S.; Canon Bermudez, G. S.; Ha, M.; Zabila, Y.; Faßbender, J.; Makarov, D.

Ultra-portable, imperceptible[1], and shapeable[2] devices are expected to be widespread due to the emergence of flexible electronics as an industrial technology. Printing is an affordable and high throughput method to process electronics in soft substrates that is still to be optimized to deliver electrically and mechanically reliable electronic devices[3].

In particular, printable magnetoresistive pastes have been developed as an alternative single-step fabrication method to obtain magnetic field sensors [4]. These pastes usually consist of composites of magnetic particles embedded in a non-magnetic matrix[5,6]. Particle-based pastes can achieve large magnetoresistance ratios at the expense of high resistivity and noise levels[5-7]. We previously reported magnetoresistive pastes based on microflakes as an alternative to overcome the problems presented in particle-based pastes[8,9]. Magnetoresistive flakes were produced after the delamination of thin-film stacks from a deposited sacrificial layer. With this technology, it was showed that flakes-based Co/Cu printed sensors exhibit low resistance and 37% GMR response at moderate magnetic fields (500 mT)[9].

Despite the advances in printable magnetic sensors, there are no reports of systems that show good sensitivity at low magnetic fields relevant for safe integration into consumer and wearable electronics. Electronics with magnetic components have to perform below the WHO limit of continuous exposure to magnetic fields (<40mT) to comply with this health standard[10]. Especially for on-skin electronics that experience considerable strain, there are not examples of magnetic printed sensors that deliver steady sensing behaviour after stretching.

Here, we will present low-noise printable magnetic field sensors sensitive down to sub-mT, which are mechanically stretchable after printing. We demonstrate the fabrication of printable sensors in ultrathin foils (3-μm-thick Mylar) based on magnetoresistive pastes that can undergo 100 % strain and 16 μm bending radius maintaining stable sensing and mechanical performance. The pastes are composites of poly(styrene-butadiene-styrene) copolymer (SBS) with embedded magnetoresistive microflakes. Using [Py/Cu]30 and [Ta/Py] flakes, we obtained printed giant (GMR)[11] and anisotropic (AMR)[12] magnetoresistive-based sensors, respectively. We address the key role of SBS to enable an enhancement of two orders of magnitude improvement in bendability and sensitivity at low magnetic fields.

Due to the good performance at low fields, reduced noise levels and high compliance, we will show the direct lamination of the printed sensors as an on-skin interactive device for scrolling through documents or digital maps. We envision that the proposed magnetic sensors will enable printing on-demand utilities for physical activity tracking systems or human-machine interfaces that can improve and even expand our sensing capabilities.

[1] M. Melzer et al., Nat. Commun. 6, 6080 (2015)
[2] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[3] Q. Huang et al., Adv. Mater. Technol. 4, 1800546 (2019)
[4] D. Makarov et al., ChemPhysChem 14, 1771 (2013)
[5] J. Meyer et al., Smart Mater. Struct. 22, 025032 (2013)
[6] J. L. Mietta et al., Langmuir 28, 6985 (2012)
[7] L. Ding et al., ACS Appl. Mater. Interfaces 12, 20955 (2020)
[8] D. Karnaushenko et al., Adv. Mater. 24, 4518 (2012)
[9] D. Karnaushenko et al., Adv. Mater. 27, 880 (2015)
[10] World Health Organization, Static fields (2006)
[11] M. Ha et al., (2020) [Submitted]
[12] E. S. Oliveros Mata et al., (2020) [Submitted]

  • Lecture (Conference) (Online presentation)
    2021 MRS Spring Meeting and Exhibit, 17.-23.04.2021, Seatle, United States

Permalink: https://www.hzdr.de/publications/Publ-34053
Publ.-Id: 34053


Supervised folding of origami soft actuators enabled by magnetic e-skins

Oliveros Mata, E. S.; Ha, M.; Canon Bermudez, G. S.; Liu, J. A.-C.; Evans, B. A.; Tracy, J. B.; Makarov, D.

Reconfigurable[1], soft[2], and lightweight[3] actuators are expected to be implemented in robotic systems biomimicking the multifunctional and adaptive capabilities of living organisms. The integration of sensing elements in soft actuators enables smart motion events increasing reliability, efficiency, and safe integration in diverse environments[4]. Specifically, for origami-based systems[5], the tracking of the orientation and the readiness of the folding is important to achieve reliable assembly of the structures.
Integration of sensing elements with soft actuators is typically addressed with stimuli-responsive materials[6] and commercial sensors[7] that lack feedback capabilities and high compliancy, respectively. Recent approaches measuring strain[8], curvature[9], and optical[10] signals have been demonstrated for localized single folding in soft actuators. Until recently, there were no reports of an onboard sensing platform that enables the folding of multiple flaps as needed for origami.
Here, we will show the integration of flexible e-skins on magnetic actuators for supervision of the sequence and folding assembly of hinges defined on the fly. Highly compliant magnetic sensors (GMR and Hall effect) were laminated into ultrathin magnetic origami actuators enabling the detection of the readiness for actuation, the orientation, and the hinge folding process. The actuator, a magnetic composite based on a shape memory polymer with embedded NdFeB microparticles, actuates during a light softening and magnetic stimuli sequence[11]. We optimized the thickness (60 µm) and composition (NdFeB - 40 wt%) of the composite to achieve the 180 deg basic fold for origami structures. The capabilities of the system with laminated sensing e-skin were demonstrated after self-guided assembly of the origami platform with multiple hinges into box- and boat-like layouts[12]. We envision that further development of alike self-supervised systems will bring closer the realization of adaptive mechatronic soft systems for different environments and even remote applications.

[1] H. Song et al., Nano Lett. 20, 5185 (2020)
[2] Y.F. Zhang et al., Adv. Func. Mater. 29, 1806698 (2019)
[3] C. Lu et al., Materials 13, 656 (2020)
[4] S. Cheng et al., Adv. Mater. Interfaces 6, 1900985 (2019)
[5] M. Taghavi et al., Sci. Robot. 3, (2018)
[6] L. Hines et al., Adv. Mater. 29, 1603483 (2017)
[7] M. Salerno et al., Sens. Actuators, A 265, 70 (2017)
[8] S. Mousavi et al., ACS App. Mater. Interfaces 12, 15631 (2020)
[9] A. Koivikko et al., IEEE Sens. J. 18, 223 (2018)
[10] C. Wang et al., Adv. Mater. 30, 1706695 (2018)
[11] J. A.-C. Liu et al., Sci. Adv. 5, eaaw2897 (2019)
[12] M. Ha, E.S. Oliveros Mata et al., Adv. Mater. 2008751 (2021)

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting and Exhibition, 06.-08.12.2021, Boston, United States

Permalink: https://www.hzdr.de/publications/Publ-34052
Publ.-Id: 34052


Stretchable Printed Giant Magnetoresistive Sensors for On-Skin Interactive Electronics

Oliveros Mata, E. S.; Ha, M.; Canon Bermudez, G. S.; Kosub, T.; Mönch, J. I.; Zabila, Y.; Illing, R.; Wang, Y.; Faßbender, J.; Makarov, D.

Printed electronics are expected to be implemented as a set of industrial technologies that will facilitate the on-demand fabrication of imperceptible[1] and shapeable[2] devices. Conductive pastes are typically composed of polymeric matrices with embedded conductive fillers. The properties of the fillers can be exploited to deliver functional devices as printed transistors[3], displays[4] and sensors[5]. The smart integration of such elements will allow task-specific integration in consumer electronics and even personalized wearable devices.
Aiming to develop on-skin printed interfaces, it is necessary to ponder mechanical, performance, and health safety considerations. Integrating magnetic sensors on interactive platforms is attractive due to their touchless, action-at-distance nature, which increases the reliability of the devices[6]. In the past, solution processable magnetic field sensors have been fabricated from composite pastes embedding magnetic particles. Among the previous reports on printable magnetic sensors, there are not examples of devices able to maintain high performance sensing during usual skin deformations[7]. Concomitantly, there is a lack of research on skin-compliant printed magnetic sensors able to perform below the 40 mT safety continuous exposure threshold established by the World Health Organization[8].
Here, we will present the fabrication and implementation of stretchable printed magnetic field sensors. They are based on composite pastes with embedded flakes of [Py/Cu]30 Giant Magnetoresistance (GMR) thin-film stacks. We demonstrated printed GMR sensors on ultrathin (3-µm-thick Mylar) foils which are skin compliant, and with maximum sensitivity at 0.88 mT. The stretchable sensors maintained stable sensing performance at 16 µm bending radius and 100 % strain which corresponds to two orders of magnitude increase with respect to previous reports. We demonstrate the implementation of the technology on interactive applications after laminating the printed sensors on the user's skin to navigate through digital maps and scroll through text documents. The ability of the sensor to comply with the skin creases and deformations, and to detect field changes in the safe threshold limit, place this technology as a prospective method for fabricating on-demand printed human-machine interfaces[9].

[1] M. Melzer et al., Nat. Commun. 6, 6080 (2015)
[2] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)
[3] J.A. Lim et al., Adv. Func. Mater. 20, 3292 (2010)
[4] S. Cho et al. ACS Appl. Mater. Interfaces 9, 44096 (2017)
[5] X. Wang et al. ACS Appl. Mater. Interfaces 10, 7371 (2018)
[6] P. Makushsko et al., Adv. Func. Mater, 2101089 (2021)
[7] E.S. Oliveros Mata, et al. Appl. Pys. A 127, 280 (2021)
[8] Static Fields. World Health Organization. (2006)
[9] M. Ha, E.S. Oliveros Mata, et al. Adv. Mater. 33, 2005521 (2021)

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting and Exhibit, 06.-08.12.2021, Boston, United States

Permalink: https://www.hzdr.de/publications/Publ-34051
Publ.-Id: 34051


Photon polarization effects in polarized electron-positron pair production in a strong laser field

Dai, Y.-N.; Shen, B.-F.; Li, J.-X.; Shaisultanov, R.; Hatsagortsyan, K. Z.; Keitel, C. H.; Chen, Y.-Y.

Deep understanding of the impact of photon polarization on pair production is essential for the efficient generation of laser-driven polarized positron beams and demands a complete description of polarization effects in strong-field QED processes. Employing fully polarization-resolved Monte Carlo simulations, we investigate correlated photon and electron (positron) polarization effects in the multiphoton Breit–Wheeler pair production process during the interaction of an ultrarelativistic electron beam with a counterpropagating elliptically polarized laser pulse. We show that the polarization of e−e+ pairs is degraded by 35% when the polarization of the intermediate photon is resolved, accompanied by an ∼13% decrease in the pair yield. Moreover, in this case, the polarization direction of energetic positrons at small deflection angles can even be reversed when high-energy photons with polarization parallel to the laser electric field are involved.

  • Open Access Logo Matter and Radiation at Extremes 7(2022), 014401
    Online First (2021) DOI: 10.1063/5.0063633

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34048
Publ.-Id: 34048


Comment on "Enhanced deuterium-tritium fusion cross sections in the presence of strong electromagnetic fields"

Queißer, F.; Schützhold, R.

In their article [Phys.\ Rev.\ C {\bf 100}, 064610 (2019)], Lv, Duan, and Liu study the enhancement of deuterium-tritium fusion reactions by the electromagnetic field of an x-ray free-electron laser (XFEL). While we support the general idea (which was put forward earlier in our rapid communication [Phys.\ Rev.\ C {\bf 100}, 041601(R) (2019)]), we find that the time-averaged potential approximation used by Lv, Duan, and Liu is not justified in this regime and does not take into account important effects. Due to those effects, the enhancement mechanism may actually be more efficient than predicted by Lv, Duan, and Liu.

Keywords: Fusion; Dynamical assistance

Permalink: https://www.hzdr.de/publications/Publ-34047
Publ.-Id: 34047


The magnetized spherical couette system: From numerics to experiments

Garcia Gonzalez, F.; Ogbonna, J. E.; Gundrum, T.; Seilmayer, M.; Giesecke, A.; Stefani, F.

The study of magnetohydrodynamic (MHD) instabilities occurring in liquid metals, with
imposed differential rotation and magnetic field, is of fundamental importance in the astrophysical
context. MHD instabilities are especially relevant in planets or stars, where electrically conducting
flows are confined within their interiors. Such environments could be modeled by solving the
Navier-Stokes and induction equations with appropriate conditions in a spherical shell composed of
two concentric spheres. In particular, we consider the case where the liquid metal (GaInSn in our
case), bounded by a stationary outer sphere and a uniformly rotating inner sphere, is subjected to an
axial magnetic field. When the aspect ratio of the radii of the two spheres is fixed, only two
parameters, namely, the Reynolds number (associated with the differential rotation) and the
Hartmann number (associated with the applied magnetic field strength), govern the dynamics of the
system (see [1,2] for full details).
For the magnetized spherical Couette system, three different types of instabilities have so far
been identified and characterized by means of numerical simulations (e.g. [1,3]), and also in
experiments (e.g. [2,4]). These instabilities can each be described as a hydrodynamic radial jet
instability, a return flow instability, and a Kelvin-Helmholtz-like Shercliff layer instability. We
provide an overview of these instabilities with a focus on the description and analysis of the
different spatio-temporal symmetries of the MHD flow. In particular, numerical and experimental
bifurcation diagrams of nonlinear waves in the quasi-laminar regime (with moderate differential
rotation) are presented and some numerical tools, related to nonlinear dynamics and chaos theory
[5], are outlined. These tools include the numerical continuation of periodic solutions and their
stability assessment, time series analysis such as the computation of the fundamental frequencies in
one or several spatial dimensions, time dependent frequency spectra, and Poincaré sections.
Our results show how periodic and quasiperiodic MHD flows with two, three and even four
incommensurable frequencies, as well as MHD chaotic flows, are developed following a sequence
of bifurcations from the base state. The knowledge of the different routes to chaos is of fundamental
importance in turbulence theory. In addition, by taking into account the symmetries of the solutions
several regions of multistability (and also hysteretic behavior) are identified in the parameter space
with a good agreement between simulations and experiments, both in their temporal and spatial
structures. Although unstable MHD flows are not experimentally realized, their numerical
computation as in [1,6] provides a more complete picture of the dynamics and aids the
understanding of transient and hysteretic behaviors in experiments.
This work is funded by the European Research Council (ERC), Horizon 2020 research and
innovation programme (grant agreement No. 787544). The authors wish to thank Kevin Bauch for
technical support.

1. Garcia, F. and Stefani, F., Continuation and stability of rotating waves in the magnetized spherical Couette
system: Secondary transitions and multistability. – Proc. R. Soc. A (474), 2018. – p. 20180281.
2. Ogbonna, J., Garcia, F., Gundrum, T., Seilmayer, M. and Stefani, F., Experimental investigation of the return
flow instability in magnetized spherical Couette flows. – Phys. Fluids (32), 2020. – p. 124119.
3. Travnikov, V., Eckert, K. and Odenbach, S., Influence of an axial magnetic field on the stability of spherical
Couette flows with different gap widths. – Acta Mech. (219), 2011. – p. 255.
4. Kasprzyk, C., Kaplan, E., Seilmayer, M. and Stefani, F., Transitions in a magnetized quasi-laminar spherical
Couette flow. – Magnetohydrodynamics (53), 2017. – p. 393.
5. Kuznetsov, Y. A., Elements of Applied Bifurcation Theory, 2nd Edition – Springer, New York, 1998.
6. Garcia, F., Seilmayer, M., Giesecke, A. and Stefani, F., Four-frequency solution in a magnetohydrodynamic
Couette flow as a consequence of azimuthal symmetry breaking. – Phys. Rev. Lett. (125), 2020. – p. 264501.

  • Open Access Logo Lecture (Conference) (Online presentation)
    The Fourth Russian Conference on Magnetohydrodynamics, RMHD-2021, 20.-22.09.2021, Perm, Russia

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34046
Publ.-Id: 34046


Numerics and experiments of nonlinear MHD waves in differentially rotating spherical geometry

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

An overview of the nonlinear dynamics of the magnetised spherical Couette flow is presented. This problem is fundamental for understanding magnetohydrodynamic MHD instabilities occurring when a liquid metal flow, driven by the rotation of the inner boundary in a spherical shell, is subjected to an axial magnetic field. The analysis, at a moderate rotation rate and applied magnetic fields, is based on direct numerical simulations and numerical tools from dynamical systems and chaos theory, as well as laboratory experiments. Several type of MHD waves are classified and a reasonable agreement between simulations and experiments is obtained.

  • Lecture (Conference) (Online presentation)
    25th International Congress of Theoretical and Applied Mechanics, ICTAM2020+1, 22.-27.08.2021, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-34045
Publ.-Id: 34045


Intermittent chaotic flows in the weakly magnetised spherical Couette system

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

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

  • Lecture (Conference) (Online presentation)
    91th Annual Meeting of the International Association of Applied Mathematics and Mechanics, GAMM2020., 15.-19.03.2021, Kassel, Germany

Permalink: https://www.hzdr.de/publications/Publ-34044
Publ.-Id: 34044


Methods and models to investigate the physicochemical functionality of pulmonary surfactant

Ravera, F.; Miller, R.; Zuo, Y. Y.; Noskov A., B.; Bykov G., A.; Volodymyr I., K.; Loglio, G.; Javadi, A.; Liggieri, L.

The pulmonary surfactant (PS) is a complex mixture of lipids and proteins dispersed in the aqueous lining layer of the alveolar surface. Such a layer plays a key role in maintaining the proper lung functionality. It acts as a barrier against inhaled particles and pathogens, including viruses, and may represent an important entry point for drugs delivered via aerosols. Understanding the physicochemical properties of PS is therefore of importance for the comprehension of pathophysiological mechanisms affecting the respiratory system. That can be of particular relevance for supporting the development of novel therapeutic interventions against COVID-19–induced acute respiratory distress syndrome. Owing to the complexity of the in vivo alveolar lining layer, several in vitro methodologies have been developed to investigate the functional and structural properties of PS films or interfacial films made by major constituents of the natural PS. As breathing is a highly dynamic interfacial process, most applied methodologies for studying PSs need to be capable of dynamic measurements, including the study of interfacial dilational rheology. We provide here a review of the most frequently and successfully applied methodologies that have proven to be excellent tools for understanding the biophysics of the PS and of its role in the respiratory mechanics. This overview also discusses recent findings on the dynamics of PS layers and the impact of inhalable particles or pathogens, such as the novel coronavirus, on its functionality.

Keywords: Pulmonary surfactants; Surface tension; Mechanical behaviour of DPPC; Bubble tensiometry; Dilational rheology and elasticity; Dynamic surface phenomena; Respiratory system; Corona Virus

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34043
Publ.-Id: 34043


Contactless inductive flow tomography for Rayleigh-Bénard convection

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

In this talk we give an overview of the current state of the developments of the contactless inductive flow tomography (CIFT) for two different cylindrical cells with aspect ratio 1 and 0.5 for Rayleigh-Bénard convection. Both cylindrical vessels are filled with the eutectic alloy GaInSn. We address the challenges in the flow induced magnetic field measurement and show first reconstructions of the complex three-dimensional flow structure in the cell with aspect ratio 0.5.

Keywords: contactless inductive flow tomography; flow measurement; liquid metal; Rayleigh-Bénard convection

  • Invited lecture (Conferences)
    Institutskolloquium des Fachgebiets technische Thermodynamik, 11.11.2021, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34040
Publ.-Id: 34040


Stabilization of proton beam performance enabling a pilot in vivo tumor irradiation study

Kroll, F.

Highlight talk on the stabilization of proton beam performance enabling a pilot in vivo tumor irradiation study

Keywords: Laser acceleration; TNSA; radiobiology

  • Lecture (others) (Online presentation)
    7th Annual Helmholtz MT Meeting Online, 03.02.2021, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34038
Publ.-Id: 34038


Stable delivery of well-characterized proton bunches for application experiments at Draco PW

Kroll, F.

Explanation on the stable delivery of well-characterized proton bunches for application experiments at Draco PW

Keywords: TNSA; Laser acceleration; LIGHT

  • Lecture (others) (Online presentation)
    Annual Meeting of the LIGHT collaboration, 28.10.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34037
Publ.-Id: 34037


Laser-driven ion accelerators for applications in radiobiology

Kroll, F.

Overview on Llaser-driven ion accelerators for applications in radiobiology

Keywords: TNSA; Laser acceleration; Radiobiology

  • Lecture (others) (Online presentation)
    4th Laser-Plasma Summer School (LaPlaSS 4), 27.09.-01.10.2021, Salamanca, Spanien

Permalink: https://www.hzdr.de/publications/Publ-34036
Publ.-Id: 34036


First systematic in vivo tumor irradiation in mice with laser accelerated and dose homogenized proton beams from the Draco PW laser

Kroll, F.; Brack, F.-E.; Elisabeth, B.; Brüchner, K.; Karsch, L.; Kraft, S.; Leßmann, E.; Meister, S.; Metzkes-Ng, J.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Reimold, M.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Beyreuther, E.

After the rediscovery of the normal tissue sparing effect of high dose rate radiation, i.e. the so-called FLASH effect, by Favaudon et al. in 2014, research activities on this topic have been revived and are flourishing ever since. Yet, the exact biological mechanism as well as the required boundary conditions and radiation qualities to reach said sparing remain mostly unclear. We present a laser-based irradiation platform at the Draco PW facility that enables systematic studies into the FLASH regime using proton peak dose rates of up to 10^9 Gy/s. Besides the PW class laser acceleration source, a key component is a pulsed high-field beamline to transport and shape the laser driven proton bunches spectrally and spatially in order to generate homogeneous dose distributions tailored to match the irradiation sample. Making use of the diverse capabilities of the laser driven irradiation platform a pilot experiment of highest complexity has been conducted – a systematic in-vivo tumor irradiation in a specifically developed mouse model. A plethora of online particle diagnostics, including Time-of-Flight, bulk scintillators and screens as well as ionization chambers, in conjunction with diagnostics for retrospective absolute dosimetry (radiochromic films) allowed for an unprecedented level of precision in mean dose delivery (±10 %) and dose homogeneity (±5 %) for the challenging beam qualities of a laser accelerator. The tailored detector suite is complemented by predictive simulations. The talk addresses how our interdisciplinary team overcame all hurdles from animal model development, over enhancing the laser and laser acceleration stability, to dose delivery and online dose monitoring. Results on radiation induced tumor growth delay by laser driven as well as conventionally accelerated proton beams are critically discussed.

Keywords: Laser acceleration; radiobiology; FLASH; TNSA

  • Invited lecture (Conferences) (Online presentation)
    SPIE Optics + Optoelectronics Digital Forum 2021, 19.-23.04.2021, Prag (Online Only), Tschechische Republik
    DOI: 10.1117/12.2589523
  • Contribution to proceedings
    SPIE Optics + Optoelectronics, 19.-23.04.2021, online, online
    Proceedings Volume 11779, Laser Acceleration of Electrons, Protons, and Ions VI, 117790I
    DOI: 10.1117/12.2589523

Permalink: https://www.hzdr.de/publications/Publ-34035
Publ.-Id: 34035


Model experiments in a liquid metal mockup focusing on the bubble dynamics in a steel ladle

Wondrak, T.; Bruch, C.; Eckert, S.; Gardin, P.; Hackl, G.; Lachmund, H.; Bodo Lüngen, H.; Odenthal, H.-J.; Timmel, K.; Willers, B.

In metallurgy, gas is often injected into melts for mixing, degassing or refining. The knowledge of the two-phase flow behaviour is of utmost relevance for optimisation and process control. However, the measurement of the flow structure, the gas distribution and the characteristics of the bubbles is very challenging, because of the opaqueness and the high temperature of industrial relevant melts. Although numerical models have significantly improved recently, it is indispensable to validate the simulation results with experimental data. A new experimental facility has be designed and recently commissioned at Helmholtz-Zentrum Dresden - Rossendorf for systematic investigation of bubble plumes in liquid SnBn at 200 °C. The thermophysical properties of this alloy are very similar to those of steel. The experiment is a 1:5.25 model of an industrial 185 t ladle and consists of a cylindrical vessel with inner diameter of 600 mm, which is filled with 1.7 tons of SnBi. Gas can be injected at the bottom of the vessel at four different locations, which can be equipped with different plug types. Furthermore, low-pressure conditions for modelling VOD (Vacuum Oxygen Decarburization) application can be achieved by the use of a vacuum pump.
The gas distribution was measured by an array of 64 resistive probes with a spacing of 10 mm and a time resolution of 1 kHz. This technique allows also the determination of bubble properties like bubble speed and diameter. The velocity of the liquid was measured by Ultrasound Doppler Velocimetry. The paper provides a description of the new setup in detail and presents measurement results characterizing the bubbly flow for varying gas flow rates and different configurations for gas injection.

Keywords: liquid metal; two-phase flow; bubble measurement

  • Lecture (Conference) (Online presentation)
    9th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM 2021), 04.-7.10.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-34034
Publ.-Id: 34034


Investigating the flow structure in two model slab casting moulds using contactless inductive flow tomography

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

The contactless inductive flow tomography (CIFT) allows for reconstructing the mean flow structure of liquid metals by measuring the flow induced perturbations of one or more applied magnetic fields, and subsequently inferring the flow field by solving a linear inverse problem. We will give an overview of the application of CIFT to two models of continuous casting available at Helmholtz-Zentrum Dresden – Rossendorf. These include a 1:8 cold model of a slab casting mould under the influence of an electromagnetic brake, and a 1:2 model of a slab mould operating at 250 °C.

Keywords: slab casting; flow measurement; contactless inductive flow tomography; electromagnetic brake

  • Contribution to proceedings
    10th European Conference on Continuous Casting (ECCC), 20.-22.10.2021, Bari, Italy
  • Lecture (Conference)
    10th European Conference on Continuous Casting (ECCC), 20.-22.10.2021, Bari, Italy

Permalink: https://www.hzdr.de/publications/Publ-34033
Publ.-Id: 34033


11C-Methionine Uptake in the Lactating Human Breast

Michler, E.; Hilliger, S.; Kopka, K.; Kotzerke, J.

A 33-year-old nursing mother who underwent resection of a glioblastoma of the right hemisphere was referred for a 11C-methionine PET/MR scan to exclude cancer recurrence. In whole-body PETimaging, a slight radiotracer uptake could be observed in themammary glands, reflecting lactation status. In this case report, we initially describe 11C-methionine uptake in the human breast and discuss any consequences arising from this special situation.

Keywords: 11C-methionine; lactating breast; PET

Downloads:

  • Secondary publication expected from 01.01.2023

Permalink: https://www.hzdr.de/publications/Publ-34032
Publ.-Id: 34032


Local and Non-local Curvature-induced Chiral Effects in Nanomagnetism

Volkov, O.

The structural inversion symmetry plays an important role in low-dimensional nanomagnets, due to its strong influence on magnetic and electrical properties. It can lead to the appearance of chiral effects, such as the topological Hall effect [1], or to the formation of chiral noncollinear magnetic textures, as skyrmions [2] and chiral domain walls (DWs) [3]. These chiral structures are envisioned to be the key components for realizing novel concepts for magnonics [4], antiferromagnetic spintronics [5], spin-orbitronics [6], and oxitronics [7]. The main magnetic interaction being responsible for the stabilization of chiral magnetic textures is the intrinsic Dzyaloshinskii-Moriya interaction (DMI) [8,9]. It originate in certain magnetic crystals in which the unit cell lacks inversion symmetry, such as the gyrotropic magnetic crystals, or appear typically in ultrathin films or bilayers due to the inversion symmetry breaking on the film interface [3]. At present, tailoring of DMI is done by optimizing materials, either doping a bulk single crystal or adjusting interface properties of thin films and multilayers.

A viable alternative to the conventional material screening approach can be the exploration of the interplay between geometry and topology. This interplay is of fundamental interest throughout many disciplines in condensed matter physics, including thin layers of superconductors [10] and superfluids [11], nematic liquid crystals [12], cell membranes [13], semiconductors [14]. In the emergent field of curvilinear magnetism chiral effects are associated to the geometrically broken inversion symmetries [15]. Those appear in curvilinear architectures of even conventional materials. There are numerous exciting theoretical predictions of exchange- and magnetostatically-driven curvature effects, which do not rely on any specific modification of the intrinsic magnetic properties, but allow to create non-collinear magnetic textures in a controlled manner by tailoring local curvatures and shapes [16,17]. Until now the predicted chiral effects due to curvatures remained a neat theoretical abstraction.

Recently, we provided the very first experimental confirmation of the existence of the curvature-induced chiral interaction with exchange origin in a conventional soft ferromagnetic material. It is experimentally explored the theoretical predictions, that the magnetisation reversal of flat parabolic stripes shows a two step process [18,19]. At the first switching event, a domain wall pinned by the curvature induced exchange-driven DMI is expelled leading to a magnetisation state homogeneous along the parabola's long axis. Measuring the depinning field enables to quantify the effective exchange-driven DMI interaction constant. The magnitude of the effect can be tuned by the parabola's curvature. It is found that the strength of the exchange-induced DMI interaction for the experimentally realised geometries is remarkably strong, namely ~0.4 mJ/m2, compared the surface induced DMI. The presented study legitimates the predictive power of full-scale micromagnetic simulations to design the properties of ferromagnets through their geometry, thus stabilising chiral textures. We explore these curvilinear magnetic thin films for the realization of novel artificial magnetoelectric materials based on curvilinear helimagnets embedded in piezoelectric matrix [20], to enable the geometrical tuning of the magnetochirality in curvilinear 1D architectures [21], tailoring of magnetic states in flat nanospirals [22] and as components of shapeable magnetoelectronics for interactive wearables [23].

[1] N. Nagaosa, et al., Nature Nanotech. 8, 899 (2013)
[2] U. K. Rößler, et al., Nature 442, 797 (2006)
[3] A. Fert, et al., Nature Rev. Mat. 2, 17031 (2017)
[4] A. V. Chumak, et al., Nature Physics 11, 453 (2015)
[5] T. Jungwirth, et al., Nature Nanotech. 11, 231 (2016)
[6] I. M. Miron, et al., Nature 476, 189 (2011)
[7] V. Garcia, et al., Nature 460, 81 (2009)
[8] I. Dzyaloshinsky, J. Phys. Chem. Solids 4, 241 (1958).
[9] T. Moriya, Phys. Rev. Lett. 4, 228 (1960).
[10] J. Tempere, et al., Phys. Rev. B 79, 134516 (2009)
[11] H. Kuratsuji, Phys. Rev. E 85, 031150 (2012)
[12] T. Lopez-Leon, et al., Nature Physics 7, 391 (2011)
[13] H. T. McMahon, et al., Nature 438, 590 (2005)
[14] C. Ortix, Phys. Rev. B 91, 245412 (2015)
[15] Y. Gaididei, et al., Phys. Rev. Lett. 112, 257203 (2014)
[16] J. A. Otálora, et al., Phys. Rev. Lett. 117, 227203 (2016)
[17] V. P. Kravchuk, et al., Phys. Rev. Lett. 120, 067201 (2018)
[18] O. Volkov et al., PRL 123, 077201 (2019).
[19] O. Volkov et al., PSS-RRL 13, 1800309 (2019).
[20] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).
[21] O. Volkov et al., Scientific Reports 8, 866 (2018).
[22] M. Nord, et al., Small 1904738 (2019).
[23] J. Ge, et al., Nature Comm. 10, 4405 (2019).

Keywords: Curvilinear magnetism; Micromagnetism; Chiral effects

  • Invited lecture (Conferences) (Online presentation)
    2022 Joint MMM-INTERMAG, 10.-14.01.2022, New Orleans, LA / Online, USA

Permalink: https://www.hzdr.de/publications/Publ-34031
Publ.-Id: 34031


Extraordinary anisotropic magnetoresistance in CaMnO3/CaIrO3 heterostructures

Vagadia, M.; Sardar, S.; Tank, T.; Das, S.; Gunn, B.; Pandey, P.; Hübner, R.; Rodolakis, F.; Fabbris, G.; Choi, Y.; Haskel, D.; Frano, A.; Rana, D. S.

The realization of fourfold anisotropic magnetoresistance (AMR) in 3d-5d heterostructures has boosted major efforts in antiferromagnetic (AFM) spintronics. However, despite the potential of incorporating strong spinorbit coupling, only small AMR signals have been detected thus far, prompting a search for mechanisms to enhance the signal. In this paper, we demonstrate an extraordinarily elevated fourfold AMR of 70% realized in CaMnO3/CaIrO3 thin film superlattices.We find that the biaxial magnetic anisotropy and the spin-flop transition in a nearly Mott insulating phase form a potent combination, each contributing one order of magnitude to the total signal. Dynamics between these phenomena capture a subtle interaction of pseudospin coupling with the lattice and external magnetic field, an emergent phenomenon creating opportunities to harness its potential in AFM spintronics.

Permalink: https://www.hzdr.de/publications/Publ-34027
Publ.-Id: 34027


Initial observations of the femtosecond timing jitter at the European XFEL

Kirkwood, H. J.; Letrun, R.; Tanikawa, T.; Liu, J.; Nakatsutsumi, M.; Emons, M.; Jezynski, T.; Palmer, G.; Lederer, M.; Bean, R.; Buck, J.; Di Dio Cafiso, S. D.; Graceffa, R.; Grünert, J.; Göde, S.; Höppner, H.; Kim, Y.; Konopkova, Z.; Mills, G.; Makita, M.; Pelka, A.; Preston, T. R.; Sikorski, M.; Takem, C. M. S.; Giewekemeyer, K.; Chollet, M.; Vagovic, P.; Chapman, H. N.; Mancuso, A. P.; Sato, T.

Intense, ultrashort, and high-repetition-rate X-ray pulses, combined with a femtosecond optical laser, allow pump-probe experiments with fast data acquisition and femtosecond time resolution. However, the relative timing of the X-ray pulses and the optical laser pulses can be controlled only to a level of the intrinsic error of the instrument which, without characterization, limits the time resolution of experiments. This limitation inevitably calls for a precise determination of the relative arrival time, which can be used after measurement for sorting and tagging the experimental data to a much finer resolution than it can be controlled to. The observed root-mean-square timing jitter between the X-ray and the optical laser at the SPB/SFX instrument at European XFEL was 308\&\#x00A0;fs. This first measurement of timing jitter at the European XFEL provides an important step in realizing ultrafast experiments at this novel X-ray source. A method for determining the change in the complex refractive index of samples is also presented.

Keywords: Electric fields; Femtosecond lasers; Free electron lasers; Refractive index; X ray lasers

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34026
Publ.-Id: 34026


A Truly Spatial Random Forests Algorithm for Geoscience Data Analysis and Modelling

Talebi, H.; Peeters, L. J. M.; Otto, A.; Tolosana Delgado, R.

Spatial data mining helps to find hidden but potentially informative patterns from large and high-dimensional geoscience data. Non-spatial learners generally look at the observations based on their relationships in the feature space, which means that they cannot consider spatial relationships between regionalised variables. This study introduces a novel spatial random forests technique based on higher-order spatial statistics for analysis and modelling of spatial data. Unlike the classical random forests algorithm that uses pixelwise spectral information as predictors, the proposed spatial random forests algorithm uses the local spatial-spectral information (i.e., vectorised spatial patterns) to learn intrinsic heterogeneity, spatial dependencies, and complex spatial patterns. Algorithms for supervised (i.e., regression and classification) and unsupervised (i.e., dimension reduction and clustering) learning are presented. Approaches to deal with big data, multi-resolution data, and missing values are discussed. The superior performance and usefulness of the proposed algorithm over the classical random forests method are illustrated via synthetic and real cases, where the remotely sensed geophysical covariates in North West Minerals Province of Queensland, Australia, are used as input spatial data for geology mapping, geochemical prediction, and process discovery analysis

Keywords: Geostatistical learning; Higher-order spatial statistics; Random forests; Spatial correlation; Spatial data

Permalink: https://www.hzdr.de/publications/Publ-34024
Publ.-Id: 34024


Incommensurate two-dimensional checkerboard charge density wave in the low-dimensional superconductor Ta4Pd3Te16

Zhenzhong, S.; Kuhn, S. J.; Flicker, F.; Helm, T.; Lee, J.; Steinhardt, W.; Dissanayake, S.; Graf, D.; Ruff, J.; Fabbris, G.; Haskel, D.; Haravifard, S.

We report the observation of a two-dimensional (2D) checkerboard charge density wave (CDW) in the low-dimensional superconductor Ta4Pd3Te16. By determining its CDW properties across the temperature-pressure (T−P) phase diagram and comparing with prototypical CDW materials, we conclude that Ta4Pd3Te16 features (a) an incommensurate CDW with a mixed character of dimensions [quasi-1D (Q1D) considering its needlelike shape along the b axis, Q2D as the CDW has checkerboard wave vectors, and 3D because of CDW projections along all three axes], and (b) one of the weakest CDWs compared to its superconductivity (SC), i.e., enhanced SC with respect to CDW, suggesting an interesting interplay of the two orders.

Permalink: https://www.hzdr.de/publications/Publ-34021
Publ.-Id: 34021


Relativistically transparent magnetic filaments: scaling laws, initial results and prospects for strong-field QED studies

Rinderknecht, H. G.; Wang, T.; Laso García, A.; Bruhaug, G.; Wei, M. S.; Quevedo, H. J.; Ditmire, T.; Williams, J.; Haid, A.; Doria, D.; Spohr, K. M.; Toncian, T.; Arefiev, A.

Relativistic transparency enables volumetric laser interaction with overdense plasmas and direct laser acceleration of electrons to relativistic velocities. The dense electron current generates a magnetic filament with field strength of the order of the laser amplitude (>10⁵ T). The magnetic filament traps the electrons radially, enabling efficient acceleration and conversion of laser energy into MeV photons by electron oscillations in the filament. The use of microstructured targets stabilizes the hosing instabilities associated with relativistically transparent interactions, resulting in robust and repeatable production of this phenomenon. Analytical scaling laws are derived to describe the radiated photon spectrum and energy from the magnetic filament phenomenon in terms of the laser intensity, focal radius, pulse duration, and the plasma density. These scaling laws are compared to 3D particle-in-cell (PIC) simulations, demonstrating agreement over two regimes of focal radius. Preliminary experiments to study this phenomenon at moderate intensity (a₀ ∼ 30) were performed on the Texas Petawatt Laser. Experimental signatures of the magnetic filament phenomenon are observed in the electron and photon spectra recorded in a subset of these experiments that is consistent with the experimental design, analytical scaling and 3D PIC simulations. Implications for future experimental campaigns are discussed.

Keywords: relativistic transparency; laser-plasma interactions; strong-field physics

Permalink: https://www.hzdr.de/publications/Publ-34020
Publ.-Id: 34020


Trajectory-dependent electronic excitations at keV ion energies

Lohmann, S.; Holeňák, R.; Primetzhofer, D.

We present experiments directly demonstrating the significance of charge-state dynamics in close collisions at ion velocities below the Bohr velocity resulting in a drastic trajectory dependence of the specific energy loss.
Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. In our 3D-transmission approach [2], pulsed beams of singly charged ions are transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. We record ion energy together with the angular distributions of deflected particles and can additionally insert a deflector to measure exit charge states [3].
We specifically studied the difference in energy loss between channelled (ΔEch) and random trajectories (ΔEr) for ions with masses ranging from 1 (protons) to 40 u (Ar+) as shown in Fig. 1 [4,5]. For protons, the observed effect can be explained with increasing contributions of core-electron excitations in close collisions only attainable in random geometry. For He and heavier ions we observe a reverse trend – a decrease of the ratio ΔEch/ ΔEr with decreasing ion velocity. Due to the inefficiency of core-electron excitations at these velocities, we explain this behaviour by contributions of collision-induced charge-exchange events along random trajectories. The resulting higher mean charge state leads to higher electronic stopping along random trajectories. For heavier ions, local losses due to electron promotion, also including several electrons, are expected to contribute strongly to the energy deposition in random geometry. By studying the trajectory dependence of the statistical distribution of electronic excitations (electronic energy straggling), we present evidence that for heavier ions, individual events with large energy transfer indeed significantly contribute to the energy loss. Finally, we show that our experimental approach leads to results that can serve to benchmark dynamic theories such as time-dependent density functional theory [5].

References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B 463 (2020) 16-20.
[2] R. Holeňák, S. Lohmann and D. Primetzhofer, Ultramicroscopy 217 (2020) 113051.
[3] R. Holeňák et al., Vacuum 185 (2021) 109988.
[4] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett. 124 (2020) 096601.
[5] S. Lohmann, R. Holeňák and D. Primetzhofer, Phys. Rev. A 102 (2020) 062803.

  • Invited lecture (Conferences) (Online presentation)
    25th International Conference on Ion Beam Analysis & 17th International Conference on Particle Induce X-ray Emission & International Conference on Secondary Ion Mass Spectrometry, 11.-15.10.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34019
Publ.-Id: 34019


Bioleaching of metals from mine waste by acidophilic consortium

Opara, C.

An acidophilic consortium leached over 70% of the total Zn, As, Co and Cd contents of a tailing and waste rock samples obtained from Neves Corvo mine, Portugal. Also, about 20 and 50 % of the total Cu and Mn contents of the sulfidic mine wastes were also leached by the consortium.

Keywords: bioleaching; tailing; waste rock; acidophilic consortium

  • Lecture (others) (Online presentation)
    SULTAN Network Wide Event 5, 17.-19.02.2021, Clausthal, Germany

Permalink: https://www.hzdr.de/publications/Publ-34018
Publ.-Id: 34018


Microwave-assisted bioleaching of metals from mine waste

Opara, C. B.

The bioleaching of metals (Pb, Ag and In) by marine sulfur-oxidising bacteria was improved after microwave roasting of a waste rock sample at 400 and/or 500°C. The bioleaching of Pb, Ag and In was increased from 20, 6 and 0 % (before microwave roasting) to 63, 37 and 27 % after microwave roasting.

Keywords: bioleaching; microwave roasting; marine sulfur-oxidising bacteria

  • Lecture (others)
    SULTAN Network Wide Event 6, 30.08.-03.09.2021, University of OULU, Finland

Permalink: https://www.hzdr.de/publications/Publ-34017
Publ.-Id: 34017


An Innovative Bioleaching Approach for the Extraction of Valuable and Hazardous Metals from Mining Waste

Opara, C. B.

The global demand for various metals has greatly increased over the past few years and this demand is envisaged to double over the next coming decades. The extractive waste residue (tailings) by the EU mining industries is a large waste stream and could constitute various environmental hazards such as acid mine drainage, especially when poorly managed. Reprocessing of these tailings could be a significant source of valuable metals and could alleviate environmental risks. This calls for a cost-effective metal mining technology with minimal damaging effect to the environment. We hereby propose the use of (halo)alkaliphilic and/or marine sulfur-oxidizing bacteria that live at neutral to alkaline conditions for the bioleaching of elements from these tailings. This will prevent the acidification of the environment, which is the case when bioleaching with acidophilic bacteria. In addition, this bioleaching approach which could be applicable in seawater is beneficial as fresh water could be saved.

Keywords: biomining; extractive waste residue; sulfur-oxidizing bacteria

  • Lecture (Conference) (Online presentation)
    10th International Symposium on Biomining (Biomining '21), 07.-10.06.2021, Falmouth, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-34015
Publ.-Id: 34015


An Innovative bioleaching Approach for the Extraction of Valuable and Hazardous Elements from Mining Waste

Opara, C.

The use of microorganisms and their products for the extraction of metals from low grade ores has proven overtime to be more economically viable than other extractive metallurgical processes such as pyrometallurgy. However, the most extensively studied microorganisms for bioleaching are the acidophilic Sulfur and/or Iron-oxidizing chemolithotrophs that are able to catalyze mineral dissolution at low pH. The use of acidophilic bacteria for bioleaching leads to the acidification of the environment as these activities are usually performed at pH ≤ 2. This could have a negative impact on the environment. We hereby propose the use of (halo)alkaliphilic and/or marine sulphur-oxidising microorganisms that live at less acidic, neutral or alkaline conditions for the bioleaching of metals from mining waste. This will prevent the acidification of the environment and save fresh water, as this bioleaching approach could be applicable in seawater. Bioleaching results with Thioclava electrotropha and Thioclava pacifica autotrophs seem promising, as up to 30% Co and 10% Cu, Pb, Zn, Cd, As, K and Mn were solubilised from a fresh waste rock sample. To optimize the bioleaching process, the interaction of these microorganisms with minerals will be studied. The tailing residues cleaned via this approach will be analyzed for subsequent valorization into various circular-economy applications such as inorganic polymers, green cements and ceramics.

Keywords: bioleaching; mine waste; sulfur-oxidizing bacteria

  • Open Access Logo Lecture (Conference) (Online presentation)
    8th International Conference on Microbial Communication for Young Scientists, 29.-31.03.2021, Jena, Germany

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34014
Publ.-Id: 34014


Exploiting Isospin Symmetry to Study the Role of Isomers in Stellar Environments

Hallam, S.; Lotay, G.; Gade, A.; Doherty, D. T.; Belarge, J.; Bender, P. C.; Brown, B. A.; Browne, J.; Catford, W. N.; Elman, B.; Estradé, A.; Hall, M. R.; Longfellow, B.; Lunderberg, E.; Montes, F.; Moukaddam, M.; O’Malley, P.; Ong, W.-J.; Schatz, H.; Seweryniak, D.; Schmidt, K.; Timofeyuk, N. K.; Weisshaar, D.; Zegers, R. G. T.

Proton capture on the excited isomeric state of 26Al strongly influences the abundance of 26Mg ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic 26Al in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical 26mAl(p,γ)27Si reaction. These constraints demonstrate that the rate is at least a factor ∼8 lower than previously expected, indicating an increase in the stellar production of 26Mg and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of 26Al.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34013
Publ.-Id: 34013


SiPM readout for NeuLAND - status report 2021

Hensel, T.; Weinberger, D.; Bemmerer, D.; R3B, Collaboration

Statusreport SiPM readout for NeuLAND (saturation effects, dark rate and time resolution measurements)

Keywords: SiPM; NeuLAND; saturation

  • Lecture (Conference) (Online presentation)
    R3B Collaboration Meeting, 13.12.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34012
Publ.-Id: 34012


Patentschrift DE 10 2020 120 788 B3 2021.12.09: MULTIPIXEL-PHOTODETEKTOR MIT AVALANCHE-PHOTODIODEN, STRAHLUNGSDETEKTOR UND POSITRONEN-EMISSIONS-TOMOGRAPH

Weinberger, D.

Ein Multipixel-Photodetektor weist elektrisch parallel geschaltete erste Avalanche-Photodioden mit jeweils einer Lichteintrittsfläche und elektrisch parallel geschaltete zweite Avalanche-Photodioden mit jeweils einer Lichteintrittsfläche auf. Die Lichteintrittsfläche jeder ersten Avalanche-Photodiode ist gleich oder größer einer Referenzfläche. Die Lichteintrittsfläche jeder zweiten Avalanche-Photodiode ist kleiner als die Referenzfläche. Die Lichteintrittsflächen der ersten und zweiten Avalanche-Photodioden bilden Teilflächen eines Belichtungsfeldes des Multipixel-Photodetektors.

Keywords: Multipixel-Photodetektor; Avalanche-Photodioden

  • Test
    (2021)09.12.2021

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-34011
Publ.-Id: 34011


Magnetochiral effect of phonons

Zherlitsyn, S.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    II International Advanced Study Conference Condensed Matter & Low Temperature Physics 2021, 06.-12.06.2021, Kharkiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34010
Publ.-Id: 34010


Quantum Magnets from the perspective of Electron Spin Resonance Spectroscopy

Bhaskaran, L.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    Grete-Herrmann Network (GHN), 07.12.2021, Würzburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34009
Publ.-Id: 34009


Status of the Pulsed-Magnet Program at the Dresden High Field Magnetic Laboratory

Zherlitsyn, S.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    MT27, 27th International Conference on Magnet Technology, 15.-19.11.2021, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-34005
Publ.-Id: 34005


Dominance of gamma-gamma electron-positron pair creation in a plasma driven by high-intensity lasers

He, Y.; Blackburn, T.; Toncian, Toma; Arefiev, A.

Creation of electrons and positrons from light alone is a basic prediction of quantum electrodynamics, but yet to be observed. Our simulations show that the required conditions are achievable using a high-intensity two-beam laser facility and an advanced target design. Dual laser irradiation of a structured target produces high-density gamma rays that then create > 10(8) positrons at intensities of 2 x 10(22) Wcm(-2). The unique feature of this setup is that the pair creation is primarily driven by the linear Breit-Wheeler process (gamma gamma -> e(+)e(-)), which dominates over the nonlinear Breit-Wheeler and Bethe-Heitler processes. The favorable scaling with laser intensity of the linear process prompts reconsideration of its neglect in simulation studies and also permits positron jet formation at experimentally feasible intensities. Simulations show that the positrons, confined by a quasistatic plasma magnetic field, may be accelerated by the lasers to energies >200 MeV.

Keywords: PHOTON-EMISSION;PHYSICS;LIGHT;PARTICLE;SCOLLISION;CASCADES;FIELD

Permalink: https://www.hzdr.de/publications/Publ-34004
Publ.-Id: 34004


Magnetostriction measurements in Dresden high magnetic field lab

Miyata, A.

es hat keine aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    FBG meeting, 22.02.2021, Tokyo, Japan

Permalink: https://www.hzdr.de/publications/Publ-34003
Publ.-Id: 34003


Pressure-tuned magnetic interactions in a triangular-lattice quantum antiferromagnet

Zvyagin, S.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    II International Advanced Study Conference "Condensed Matter and Low Temperature Physics 2021" (CM and LTP 2021), 06.-12.06.2021, Kharkov, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34001
Publ.-Id: 34001


EANM Position on the In-House Preparation of Radiopharmaceuticals

Hendrikse, H.; Kiß, O.; Kunikowska, J.; Wadsak, W.; Decristoforo, C.; Patt, M.

The daily clinical practice in Nuclear Medicine makes use of radiopharmaceuticals that either are obtained from
external commercial suppliers or prepared in-house for immediate use. The latter are usually non-commercial
preparations that represent the major source of radiopharmaceuticals for essential routine Nuclear Medicine
practices for both diagnostic and therapeutic applications. According to European legislation, namely directive
2001/83/EC, radiopharmaceuticals that are commercially distributed must have a marketing authorization (MA)
to be placed on the market. The availability of this type of finished radiopharmaceutical products with MA ready
to use is limited due to different reasons: one is the very short half-life or shelf life, which limits the shipment of
these radiopharmaceuticals from external sources. In addition, the market potential for radiopharmaceuticals that
are used in rare clinical indications is limited to be financially attractive for pharmaceutical industry, and therefore
the number of MA applications for radiopharmaceuticals is concise.
However, the development of innovative radiopharmaceuticals usually takes place in radiopharmacies, research
centres or nuclear medicine laboratories. Practically all recent major clinical breakthroughs in Nuclear Medicine
over the last decade, exemplified by the success of theranostics with Somatostatin analogs and prostate cancer
applications, were based on the use of in-house preparations of these innovative products. In case a new
radiopharmaceutical has both the technical (half-life) and clinical potential to be produced and distributed
commercially, these new radiopharmaceuticals more frequently make their way to pharmaceutical companies that
take over from academia and provide funding for further clinical trials besides phase 0 / phase I.
European legislation treats radiopharmaceuticals used in the preparation process of a radiopharmaceutical different
than other, i.e., non-radioactive pharmaceuticals, by requiring a marketing authorization not only for ready to use
radiopharmaceuticals that are to be placed on the market but as well for starting materials such as radionuclide
generators, radionuclide precursors and kits. To avoid misunderstanding, we shall refer throughout the remainder
of this document to the term “licensed” for starting materials with a MA.
This document describes the EANM commitment and support to the non-commercial in-house preparation of
radiopharmaceuticals for direct use in compliance with European and national regulations, including the
“compounding” using licensed starting materials (with MA) such as kits, radionuclide generators or radionuclide
precursors, as well as the preparation of diagnostic (PET and SPECT) and therapeutic radiopharmaceuticals using
more complex methods and usually unlicensed starting materials (without MA). Starting point for
recommendations have been laid down in the guidelines as described in the current Good Radiopharmaceutical
Practice (cGRPP).

Keywords: Radiopharmaceuticals; in-house preparation; regulation; EANM

Downloads:

  • Secondary publication expected from 20.01.2023

Permalink: https://www.hzdr.de/publications/Publ-33999
Publ.-Id: 33999


Thermodynamics of ionic materials (AFLOW-CCE)

Friedrich, R.

Autonomous computational frameworks such as AFLOW are generating large databases that
power materials discovery workflows. The AFLOW.org repository is the largest of its kind,
containing more than 3 million compounds each characterized by 180+ different properties. The
data has been employed for the discovery of two magnets – the first discovered by computational
approaches – and six new high-entropy, high-hardness metal carbides. Join us for an online weeklong
hands-on workshop on AFLOW. Topics covered include database structure and generation,
structure prototypes and crystal symmetry, thermal and elastic properties analysis, thermodynamic
stability analysis, and integration of machine learning models for property prediction and
descriptor development.

  • Invited lecture (Conferences) (Online presentation)
    AFLOW School for Materials Discovery 2021, 06.-10.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33998
Publ.-Id: 33998


Enabling materials design of ionic systems with automated corrections: AFLOW-CCE

Friedrich, R.; Esters, M.; Oses, C.; Ki, S.; Brenner, M. J.; Hicks, D.; Mehl, M. J.; Ghorbani-Asl, M.; Krasheninnikov, A.; Toher, C.; Curtarolo, S.

Materials databases such as AFLOW [1] leverage ab initio calculations
for autonomous materials design. The predictive power critically relies
on accurate formation enthalpies - quantifying the thermodynamic
stability of a system. For ionic materials such as oxides and nitrides,
standard DFT leads to errors of several hundred meV/atom [2,3].
We have recently developed the "coordination corrected enthalpies"
(CCE) method yielding highly accurate room temperature formation
enthalpies with mean absolute errors down to 27 meV/atom [3]. Here,
we introduce AFLOW-CCE [4]: a tool where users can input a structure
file and receive the CCE corrections, or even the CCE formation
enthalpies if pre-calculated LDA, PBE or SCAN values are provided.
The results can be used for the design of e.g. 2D materials.
[1] S. Curtarolo et al., Comput. Mater. Sci. 58, 218 (2012).
[2] V. Stevanović et al., Phys. Rev. B 85, 115104 (2012).
[3] R. Friedrich et al., npj Comput. Mater. 5, 59 (2019).
[4] R. Friedrich et al., Phys. Rev. Mater. 5, 043803 (2021).

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung SKM 2021, 27.09.-01.10.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33997
Publ.-Id: 33997


Enabling materials design of ionic systems

Friedrich, R.; Esters, M.; Oses, C.; Ki, S.; Brenner, M. J.; Hicks, D.; Mehl, M. J.; Ghorbani-Asl, M.; Krasheninnikov, A.; Toher, C.; Curtarolo, S.

Materials discovery and design critically relies on accurate enthalpies. The formation
enthalpy – quantifying the thermodynamic stability of a compound – is a key quantity
in ab initio materials databases such as AFLOW [1] to enable autonomous materials
design. For ionic systems such as chalcogenides (e.g. oxides), pnictides (e.g.
nitrides), and halides, standard semi-local DFT leads, however, to errors of several
hundred meV/atom [2,3] for this quantity inhibiting materials design.
To address this critical issue, we have developed the "coordination corrected
enthalpies" (CCE) method yielding highly accurate room temperature formation
enthalpies with mean absolute errors down to 27 meV/atom [3]. Recently, we have
also introduced AFLOW-CCE [4]: an implementation of the method into the freely
available AFLOW software for automated correction of DFT results. The tool returns
the CCE corrections, or even the CCE formation enthalpies if pre-calculated LDA, PBE
or SCAN values are provided. The autonomous implementation enables the enthalpy
correction of an extensive library of materials as well as the accurate and quick
generation of convex hull phase diagrams. The results can also be used for the
computational design of e.g. nanoscale materials [5].
[1] S. Curtarolo et al., Comput. Mater. Sci. 58, 218 (2012).
[2] V. Stevanović et al., Phys. Rev. B 85, 115104 (2012).
[3] R. Friedrich et al., npj Comput. Mater. 5, 59 (2019).
[4] R. Friedrich et al., Phys. Rev. Mater. 5, 043803 (2021).
[5] R. Friedrich et al., in preparation (2021).

  • Invited lecture (Conferences) (Online presentation)
    Cecam workshop Virtual Materials Design 2021, 20.-21.07.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33996
Publ.-Id: 33996


Software engineering in scientific computing: spin-lattice simulations as an example

Pylypovskyi, O.; Tomilo, A.

Nanomagnets of complex geometrical shape and nanosized characteristic scales are hardly accessible via conventional solutions for numerical modelling. In the meantime, they are of high fundamental and applied interest, showing a novel interplay between geometry and magnetic sublattice. Recent advances in fabrication and characterization of curvilinear magnets hold an additional interest to them and force the further development of analytical and numerical tools to address such systems at the large scale. The latter include a flexible user interface to describe the concrete problem, and parallel computing to handle billions of degrees of freedom. Here, we will overview the present approaches to design spin-lattice and micromagnetic solvers based on the Landau-Lifshitz equation and discuss our experience in the software engineering of these tools.

Keywords: spin-lattice simulations; antiferromagnetism

  • Lecture (others) (Online presentation)
    Hardware & Numerics, 07.12.2021, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-33995
Publ.-Id: 33995


Noncollinear antiferromagnetic textures in confined geometries

Pylypovskyi, O.; Hedrich, N.; Wagner, K.; Tomilo, A.; Shields, B.; Kosub, T.; Sheka, D.; Faßbender, J.; Makarov, D.

In comparison with ferromagnetic domain walls and skyrmions, their coun-
terparts in antiferromagnets (AFMs) demonstrate appealing properties in
their control and dynamics, e.g., absence of Walker limit and Magnus force
[1]. The complex intrinsic magnetic structure of AFMs leads to special prop-
erties such as negligibly small stray fields, exchange-enhanced resonance
frequencies up to THz range, and the presence of staggered spin-orbit torques.
Together they render AFMs as prospective materials for spintronic and
spin-orbitronic applications [2]. Here, we consider bipartite, easy-axis AFM
samples of finite size. We derive the boundary conditions for the Neel order
parameter in the presence of Dzyaloshinskii-Moriya interactions (DMI) of
Bloch type in addition to exchange (see Fig. 1), and apply them to describe
domain walls and skyrmions. DMI leads to the deformation of the uniform
ground state at the side faces, with the twist angle proportional to the DMI
coefficient. Both domain walls and skyrmions become wider and change
their type to the mixed Bloch-Neel one when approaching the top (bottom)
surface of the sample. The characteristic depth where the influence of the
boundary on magnetic texture is significant is about 5 magnetic lengths [3].
In the absence of the intrinsic DMI, the exchange-driven boundary conditions
determine the behavior of domain walls in AFMs with a patterned surface.
Imaging the domain wall in a single crystal Cr 2O3 using nitrogen vacancy
(NV) magnetometry, we show that it mimics the behavior of an elastic
ribbon deformed by the effective pinning sites created by mesas. Crossing
the mesa at an angle, the domain wall shape experiences an additional bend, determined by the aspect ratio of the mesa A=t/w with t and w being
its thickness and width, see Fig. 2. This deformation can be described by the
effective Snell’s law as sin θi/sin θr ≈ 1 + 3.1 A with θi and θr being incidence
and refraction angles at the top surface [4].
[1] O. Gomonay, V. Baltz, A. Brataas et al. Nat. Phys. Vol. 14, P. 213
(2018). [2] V. Baltz, A. Manchon, M. Tsoi etal. Rev. Mod. Phys. Vol. 90, P.
015005 (2018), H. Yan, Z. Feng, P. Qin etal. Avd. Mat. Vol. 32, P. 1905603
(2020). [3] O. V. Pylypovskyi, A. V. Tomilo, D. D. Sheka et al. Phys. Rev.
B, Vol. 103, P. 134413 (2021) [4] N. Hedrich, K. Wagner, O. V. Pyly-
povskyi et al. Nat. Phys. Vol. 17, P. 574 (2021)

Keywords: antiferromagnetism

  • Lecture (Conference) (Online presentation)
    MMM Intermag 2022, 10.01.2022, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-33994
Publ.-Id: 33994


Influence of Boundaries and Geometrical Curvatures on Antiferromagnetic Textures

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

A complex structure of magnetic subsystem in antiferromagnets (AFMs) determines challenges and technological perspectives for both, fundamental
research and their applications for spintronic and spin-orbitronic devices [1]. In this respect, properties of the confined samples are of key interest because
of the possibility to tune magnetic responses via effects of boundary and geometrical curvature [2]. Here, we consider textures in (i) AFM slabs with the
Dzyaloshniskii-Morya interaction (DMI) of bulk symmetry [3] and (ii) the intrinsically achiral curvilinear spin chains arranged along space curves [4].
We derive a transition from spin lattice of G-type AFM to the sigma-model with the respective boundary conditions for the AFM order parameter [3]. The
DMI influences a texture via boundary conditions modifying the ground state, domain wall shape and skyrmion profiles. Approaching the boundary in the
slab with easy-axis anisotropy, the domain wall becomes broader and of mixed Bloch-Neel type near the top surface. Near the edges of the sample, the
domain wall plane possesses and additional twist. Note, that the edge twists appear in achiral AFMs as well if the domain wall plane lies at an angle to the
side faces [5]. Similarly, skyrmions of any radius become of the Bloch-Neel type approaching the top/bottom surfaces of the sample. The radius of narrow
skyrmions changes up to 10% due to the boundary effects.
AFM spin chains arranged along space curves can model the simplest curvilinear nanoarchitectures. Their geometry is described by the curvature and
torsion, determining local bends and twists of the curve. The geometry-driven anisotropy and inhomogeneous DMI render them as chiral helimagnets [6].
In addition, the exchange interaction generates the weakly ferromagnetic response, scaling linearly with curvature and torsion. The inter- and single-ion
anisotropies in curvilinear AFM chains lead to the additional anisotropic contributions, scaling with curvature. The single-ion anisotropy leads to the
homogeneous DMI mixing normal and tangential components of ferro- and antiferromagnetic vector order parameters. Both anisotropy models contribute
to the additional easy axes, which determine the direction of the order parameters in spin-flop phase [4].
[1] V. Baltz et al, Rev. Mod. Phys. 90, 015005 (2018); A. Manchon et al, Rev. Mod. Phys. 91, 035004 (2019)
[2] P. Fischer et al, APL Mat. 8, 010701 (2020); R. Streubel et al, J. Appl. Phys. 129, 210902 (2021); D. D. Sheka, Appl. Phys. Lett. 118, 230502 (2021)
[3] O. V. Pylypovskyi et al, Phys. Rev. B 103, 134413 (2021)
[4] O. V. Pylypovskyi et al, Appl. Phys. Lett. 118, 182405 (2021)
[5] N. Hedrich et al, Nat. Phys. 17, 574 (2021)
[6] O. V. Pylypovskyi, D. Y. Kononenko et al, Nano Lett. 20, 8157 (2020)

Keywords: antiferromagnetism

  • Lecture (Conference) (Online presentation)
    2021 MRS Fall Meeting November 29--December 8, 2021, 07.12.2021, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-33993
Publ.-Id: 33993


Nematic versus ferromagnetic shells: new insights in curvature-induced effects

Napoli, G.; Pylypovskyi, O.; Sheka, D.; Vergori, L.

We draw a parallel between ferromagnetic materials and nematic liquid crystals
confined on curved surfaces, which are both characterized by local interaction and
anchoring potentials. We show that the extrinsic curvature of the shell combined with
the out-of-plane component of the director field gives rise to chirality effects. This
interplay produces an effective energy term reminiscent of the chiral term in
cholesteric liquid crystals, with the curvature tensor acting as a sort of anisotropic
helicity. We discuss also how the different nature of the order parameter, a vector in
ferromagnets and a tensor in nematics, yields different textures on surfaces with
the same topology as the sphere.

Keywords: nematics; curvilinear shells

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications. 717. WE-Heraeus-Seminar, 24.06.2021, On-line, Germany

Permalink: https://www.hzdr.de/publications/Publ-33992
Publ.-Id: 33992


Micromagnetic Description of Symmetry-Breaking Effects in Curvilinear Ferromagnetic Shells

Sheka, D.; Pylypovskyi, O.; Landeros, P.; Kakay, A.; Makarov, D.

The behaviour of any physical system is governed by the order parameter,
determined by the geometry of the physical space of the object, namely their
dimensionality and curvature. Usually, the effects of curvature are described
using local interactions only, e.g. local spin-orbit- or curvature-induced
Rashba and Dzyaloshinskii-Moriya interactions (DMI). In the specific case
of ferromagnetism, until recently, there was no analytical framework, which
was treating curvature effects stemming from local [1] and non-local [2]
interactions on the same footing. The lack of a proper theoretical foundation
impedes the description of essential micromagnetic textures like magnetic
domains, skyrmion-bubbles and vortices. Here, we present a micromag-
netic theory of curvilinear ferromagnetic shells, which allows to describe the
geometry-driven effects stemming from exchange and magnetostatics within
the same framework [3]. A general description of magnetic curvilinear shells
can be done using tangential derivatives of the unit magnetization vector.
Tangential derivatives are represented by the covariant derivatives of in-
surface components and the regular derivative of the normal magnetiza-
tion component, normalized by the square root of the corresponding metric
tensor coefficient. This allows to separate the explicit effects of curvature
and spurious effects of the reference frame. The shape of a given thin shell
can be determined by two principal curvatures k1 and k2, which are functions
of coordinate. The respective classification of curvilinear surfaces operates
with (i) developable surfaces, where one of the principal curvatures equals
to zero; (ii) minimal ones, where the mean curvature k1 + k2 = 0; and (iii)
the general case. The local geometry-driven energy contributions are repre-
sented by the DMI and anisotropy, whose coefficients are determined by
powers of the principal curvatures. This allows to cancel the influence of one
of the DMI terms for the developable surfaces for any magnetic texture. The
magnetostatic interaction is a source of new chiral effects, which are essen-
tially non-local in contrast to the conventional DMI. The physical origin is
the non-zero mean curvature of a shell and the non-equivalence between the
top and bottom surfaces of the shell. We demonstrate that the analysis of
non-local effects in curvilinear thin shells can become more straightforward
when introducing three magnetostatic charges. In this respect, in contrast
to the classical approach by Brown [4], we split a conventional volume
magnetostatic charge into two terms: (i) magnetostatic charge, governed by
the tangent to the sample’s surface, and (ii) geometrical charge, given by the
normal component of magnetization and the mean curvature. In addition to
the shape anisotropy (local effect), there appear four additional non-local
terms, determined by the surface curvature. Three of them are zero for any
magnetic texture in shells with the geometry of minimal surfaces. The fourth
term is determined by the non-equivalence of the top and bottom surfaces
of the shell and becomes zero only for the special symmetries of magnetic
textures. The discovered non-local magnetochiral effects introduce hand-
edness in an intrinsically achiral material and enables the design of magne-
to-electric and ferro-toroidic responses. This will stimulate to rethink the
origin of chiral effects in different systems, e.g. in fundamentally appealing
and technologically relevant skyrmionic systems, and further theoretical
investigations in the field of curvilinear magnetism as well as experimental
validation of these theoretical predictions. These developments will pave the
way towards new device ideas relying on curvature effects in magnetic nano-
structures. The impact of effects predicted in this work goes well beyond
the magnetism community. Our description of the vector field behaviour
can be applied to different emergent field of studies of curvature effects.
The prospective applications include curved superconductors [5], twisted
graphene bilayers [6], flexible ferroelectrics [7], curved liquid crystals [8].

[1] Yu. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett., 112,
257203 (2014); D. D. Sheka, V. P. Kravchuk, Yu. Gaididei, J. Phys. A:
Math. Theor., 48, 125202 (2015); O. V. Pylypovskyi, V. P. Kravchuk,
D. D. Sheka et al, Phys. Rev. Lett., 114, 197204 (2015); V. P. Kravchuk,
D. D. Sheka, A. Kakay et al, Phys. Rev. Lett., 120, 067201 (2018) [2] P.
Landeros, A. S. Nunez, J. Appl. Phys. Vol. 108, p. 033917 (2010); J. A.
Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. Lett., 117, 227203 (2016);
J. A. Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. B, 95, 184415 (2017)
[3] D. D. Sheka, O. V. Pylypovskyi, P. Landeros et al., Comm. Phys. 3, 128
(2020) [4] W. F. Brown Jr. Micromagnetics (Wiley, New York, 1963) [5]
V. Vitelly, A. M. Turner, Phys. Rev. Lett., 93, 215301 (2004) [6] W. Yan,
W.-Y. He, Z.-D. Chu et al, Nat. Comm., 4, 2159 (2013) [7] M. Owczarek, K.
A. Hujsak, D. P. Ferris et al, Nat. Comm., 7, 13108 (2016) [8] G. Napoli, L.
Vergori, Phys. Rev. Lett., 108, 207803 (2012)

Keywords: curvilinear magnetism; micromagnetism

  • Lecture (Conference) (Online presentation)
    IEEE International Magnetics Virtual Conference INTERMAG21, 30.04.2021, On-line, On-line

Permalink: https://www.hzdr.de/publications/Publ-33991
Publ.-Id: 33991


Genesis of sulphide vein mineralization at the Sakkatti Ni-Cu-PGE deposit, Finland

Fröhlich, F.; Siikaluoma, J.; Osbahr, I.; Gutzmer, J.

The Sakatti Ni-Cu-platinum-group element deposit is situated in northern Finland and comprises massive, disseminated, and
vein sulfide mineralization. A stockwork is formed by chalcopyrite-rich sulfide veins, which contain exceptionally high
platinum-group elements and Au grades. The mineralogy and geochemistry of this stockwork zone ore is documented in this
investigation. The results are used to develop the first robust genetic concept and its relationship to massive and
disseminated mineralization of the Sakatti deposit. This model is similar to that proposed for many Cu-rich magmatic sulfide
ores, most importantly the Cu-rich footwall veins described from the Sudbury Complex in Canada and the Cu-rich ore at
Noril’sk-Talnakh in Russia. Detailed petrographic studies using a sample suite from exploration drill core intersecting veinstyle
mineralization revealed a classic magmatic sulfide assemblage of chalcopyrite 6 pyrrhotite, pentlandite, and pyrite.
More than 1000 platinum-group mineral grains belonging almost exclusively to the moncheite (PtTe2) – merenskyite (PdTe2)
– melonite (NiTe2) solid solution series were identified in the studied samples. Notably, almost two thirds of the platinumgroup
element-bearing minerals consist of melonite. Some of the platinum-group minerals contain inclusions of Ag-rich gold
(AgAu2) and muthmannite (AuAgTe2). Most of the platinum-group minerals occur as inclusions in chalcopyrite, although a
few grains are located at base-metal sulfide grain boundaries and in fractures in base-metal sulfides. The whole-rock
compositions of the stockwork veins are Cu-rich and are interpreted to represent a fractionated Cu-rich sulfide liquid
enriched in Pt, Pd, Au, Ag, As, Bi, Pb, Se, Te, Zn, which separated from a monosulfide solid solution (mss). An intermediate
solid solution (iss) solidified from the Cu-rich sulfide liquid, recrystallizing chalcopyrite at,550 8C. Simultaneously, small
volumes of intercumulus residual melt contained mainly the precious metals, Bi, and Te due to their incompatibility in iss.
Solitary and composite platinum-group minerals as well as Au-minerals crystallized first from the residual melt (,600 8C),
followed by a succession of various Bi-, Ag-, and Pb-tellurides (~540 8C), and finally sphalerite and galena. Melonite
crystallized as mostly large, solitary grains exsolved directly from Ni-bearing intermediate solid solution (~600 C), shortly
after the formation of moncheite and merenskyite from the residual melt. Finally, remobilization of the platinum-group
minerals occurred at temperatures of,300 C, as suggested by the presence of minor amounts of Cl-bearing minerals and
ragged grain shapes. © 2021 Mineralogical Association of Canada. All rights reserved.

Keywords: Geochemistry; Mineral Liberation Analysis; Ni-Cu-PGE deposits; PGM; Sakatti

Permalink: https://www.hzdr.de/publications/Publ-33986
Publ.-Id: 33986


Second harmonic generation exploiting ultra-stable resistive switching devices for secure hardware systems

Chen, Z.; Du, N.; Kiani, M.; Zhao, X.; Skorupa, I.; Schulz, S.; Bürger, D.; Di Ventra, M.; Polian, I.; Schmidt, H.

In the era of big data and internet of things (IoT), information security has emerged as an essential system and application metric. The information exchange among the ubiquitously connected smart electronic devices requires functioning reliably in harsh environments, which highlights the need for securing the hardware root of trust. In this work, by leveraging the uniform nonlinear resistive switching of emerging electroforming-free analog memristive device based on BiFeO3 (BFO) thin film, the security-oriented hardware primitive (SoHP) system is developed and optimized with high-security level. The SoHP system utilizes the distinguishable power conversion efficiency generated at second and higher harmonics in low resistance state (memristor with diodelike behavior) and high resistance state (memristor with high resistive behavior) of memristive devices. By exploring the significant influence of writing bias and operational frequency in sourcing input voltage on the dynamic switching behavior of memristive device, the novel 2-memristor encoding scheme and 1-memristor decoding scheme are developed for SoHP system, which realizes a frequency enhancement of 4000 times in comparison to 1-memristor encoding scheme and 2-memristor decoding scheme. The encoded data bits that generated from physically implemented SoHP system pass diverse statistical test suites (i.e. ENT, BSI, and NIST SP-800.22 statistical test suites), which indicates the high randomness distribution of the encoded data and the high-security level of the proposed memristive encoding system.

Keywords: Electrodes; Hardware; hardware security; Harmonic analysis; Memristors; power conversion efficiency; second harmonic generation; Switches; ultra-stable resistive switching; Voltage; Writing

Permalink: https://www.hzdr.de/publications/Publ-33983
Publ.-Id: 33983


20 kW Pilot scale steam‑oxygen gasification of solid recovered fuel with a focus on newly developed off-line and on-line tar measurement methods

Chen, Y.-H.; Parvez, A. M.; Schmid, M.; Scheffknecht, G.; Chen, T.-L.

The steam‑oxygen gasification process of solid recovered fuel (SRF) was proved as a promising approach for energy and resource sustainability through a comprehensive product analysis. A high content of syngas was produced and suitable for the downstream chemical synthesis and hydrogen energy source. However, tar is a significant hazardous mixture from waste gasification, resulting in low gasification performance and releasing toxic containments. Tar monitoring is thus important. To improve existing tar measurement methods, a flexible tar sampling system (FTSS) and a novel gas chromatography (GC) were developed for off-line and on-line tar monitoring in the pilot-scale gasification process. FTSS is an improvement compared to the standard tar sampling system (STSS) regarding robustness, operation time, and handling. It showed a consistent tar capture performance with STSS. On the other hand, the on-line GC realized real-time tar qualification and quantification. For the gasification at 850 °C, loads of benzene, toluene, and xylene examined by the on-line GC (18.7 g/m3) were highly correspondent to the result from the off-line GC (17.8 g/m3). The carbon fractions of total hydrocarbon tar were also evaluated by the on-line GC with 68 and 25 gC/m3 at the gasification temperatures of 650 and 850 °C, respectively.

Keywords: New tar measurement methods; Solid recovered fuels; Steam‑oxygen gasification; Hydrogen-rich syngas

Permalink: https://www.hzdr.de/publications/Publ-33982
Publ.-Id: 33982


Targeting PARP for Chemoradiosensitization: Opportunities, Challenges, and the Road Ahead

Willers, H. A.; Krause, M.; Faivre-Finn, C. C.; Chalmers, A. J.

In many patients with cancer, the dose of radiation therapy (RT) that can be safely administered is insufficient to achieve high rates of local tumor control and cure. In others, damage to normal tissues is a concern even at moderate doses. In these settings, RT, or chemoradiation therapy (CRT), ideally would be combined with novel targeted drugs that can enhance the tumoricidal effects of standard therapy but without significantly increased normal tissue toxicity.
Over the past decade, major advances in precision medicine have supplied the field of radiation oncology with countless opportunities to enhance the antitumor effects of CRT. However, a large body of preclinical research and clinical investigations on molecular targeted drugs has not yet translated into any meaningful number of combinations of RT or CRT with targeted radiosensitizers that are approved by the US Food and Drug Administration.3 In fact, to date the epidermal growth factors receptor-directed monoclonal antibody cetuximab remains the only targeted agent approved by the Food and Drug Administration for concurrent administration with RT in head and neck (H&N) cancers. There are considerable challenges to clinical translation of combining targeted drugs with CRT or RT that the field has only recently begun to fully appreciate.

Permalink: https://www.hzdr.de/publications/Publ-33981
Publ.-Id: 33981


Screening and Validation of Molecular Targeted Radiosensitizers

Willers, H.; Pan, X.; Borgeaud, N.; Korovina, I.; Koi, L.; Egan, R.; Greninger, P.; Rosenkranz, A.; Kung, J.; Liss, A. S.; Parsels, L. A.; Morgan, M. A.; Lawrence, T. S.; Lin, S. H.; Hong, T. S.; Yeap, B. Y.; Wirth, L. J.; Hata, A. N.; Ott, C. J.; Benes, C. H.; Baumann, M.; Krause, M.

The development of molecular targeted drugs with radiation and chemotherapy is critically important for improving the outcomes of patients with hard-to-treat, potentially curable cancers. However, too many preclinical studies have not translated into successful radiation oncology trials. Major contributing factors to this insufficiency include poor reproducibility of preclinical data, inadequate preclinical modeling of intertumoral genomic heterogeneity that influences treatment sensitivity in the clinic, and a reliance on tumor growth delay instead of local control (TCD50) endpoints. There exists an urgent need to overcome these barriers to facilitate successful clinical translation of targeted radiosensitizers. To this end, we have used 3-dimensional (3D) cell culture assays to better model tumor behavior in vivo. Examples of successful prediction of in vivo effects with these 3D assays include radiosensitization of head and neck cancers by inhibiting epidermal growth factor receptor or focal adhesion kinase signaling, and radioresistance associated with oncogenic mutation of KRAS. To address the issue of tumor heterogeneity, we leveraged institutional resources that allow high-throughput 3D screening of radiation combinations with small-molecule inhibitors across genomically characterized cell lines from lung, head and neck, and pancreatic cancers. This high-throughput screen is expected to uncover genomic biomarkers that will inform the successful clinical translation of targeted agents from the National Cancer Institute Cancer Therapy Evaluation Program portfolio and other sources. Screening "hits" need to be subjected to refinement studies that include clonogenic assays, addition of disease-specific chemotherapeutics, target/biomarker validation, and integration of patient-derived tumor models. The chemoradiosensitizing activities of the most promising drugs should be confirmed in TCD50 assays in xenograft models with or without relevant biomarker and using clinically relevant radiation fractionation. We predict that appropriately validated and biomarker-directed targeted therapies will have a higher likelihood than past efforts of being successfully incorporated into the standard management of hard-to-treat tumors.

Permalink: https://www.hzdr.de/publications/Publ-33980
Publ.-Id: 33980


Recurrent HNSCC Harbor an Immunosuppressive Tumor Immune Microenvironment Suggesting Successful Tumor Immune Evasion

Watermann, C.; Pasternack, H.; Idel, C.; Ribbat-Idel, J.; Brägelmann, J.; Kuppler, P.; Offermann, A.; Jonigk, D.; Philipp Kühnel, M.; Schröck, A.; Dreyer, E.; Rosero, C.; Nathansen, J.; Dubrovska, A.; Tharun, L.; Kirfel, J.; Wollenberg, B.; Perner, S.; Krupar, R.

Purpose: Recurrent tumors (RT) of head and neck squamous cell carcinoma (HNSCC) occur in up to 60%, with poor therapeutic response and detrimental prognosis. We hypothesized that HNSCC RTs successfully evade antitumor immune response and aimed to reveal tumor immune microenvironment (TIME) changes of primary tumors (PT) and corresponding RTs.

Experimental Design: Tumor-infiltrating leukocytes (TIL) of 300 PTs and 108 RTs from two large independent and clinically well-characterized HNSCC cohorts [discovery cohort (DC), validation cohort (VD)] were compared by IHC. mRNA expression analysis of 730 immune-related genes was performed for 18 PTs and RTs after adjuvant chemoradiotherapy (CRT). The effect of chemotherapy and radiation resistance was assessed with an in vitro spheroid/immunocyte coculture model.

Results: TIME analysis revealed overall decrease of TILs with significant loss of CD8+ T cells (DC P = 0.045/VC P < 0.0001) and B lymphocytes (DC P = 0.036/VC P < 0.0001) in RTs compared with PTs in both cohorts. Decrease predominantly occurred in RTs after CRT. Gene expression analysis confirmed loss of TILs (P = 0.0004) and B lymphocytes (P < 0.0001) and showed relative increase of neutrophils (P = 0.018), macrophages (P < 0.0001), dendritic cells (P = 0.0002), and mast cells (P = 0.0057) as well as lower overall expression of immune-related genes (P = 0.018) in RTs after CRT. Genes involved in B-lymphocyte functions and number of tertiary lymphoid structures showed the strongest decrease. SPP1 and MAPK1 were upregulated in vivo and in vitro, indicating their potential suitability as therapeutic targets in CRT resistance.

Conclusions: HNSCC RTs have an immunosuppressive TIME, which is particularly apparent after adjuvant CRT and might substantially contribute to poor therapeutic response and prognosis.

Permalink: https://www.hzdr.de/publications/Publ-33979
Publ.-Id: 33979


Tumor DNA-methylome derived epigenetic fingerprint identifies HPV-negative head and neck patients at risk for locoregional recurrence after postoperative radiochemotherapy

Tawk, B.; Wirkner, U.; Schwager, C.; Rein, K.; Zaoui, K.; Federspil, P. A.; Adeberg, S.; Linge, A.; Ganswindt, U.; Hess, J.; Unger, K.; Tinhofer, I.; Budach, V.; Lohaus, F.; Krause, M.; Guberina, M.; Stuschke, M.; Balermpas, P.; Rödel, C.; Grosu, A. L.; Schäfer, H.; Zips, D.; Combs, S. E.; Pigorsch, S.; Zitzelsberger, H.; Baumeister, P.; Kirchner, T.; Bewerunge-Hudler, M.; Weichert, W.; Hess, J.; Herpel, E.; Belka, C.; Baumann, M.; Debus, J.; Abdollahi, A.; DKTK-ROG

Biomarkers with relevance for loco-regional therapy are needed in human papillomavirus negative aka HPV(-) head and neck squamous cell carcinoma (HNSCC). Based on the premise that DNA methylation pattern is highly conserved, we sought to develop a reliable and robust methylome-based classifier identifying HPV(-) HNSCC patients at risk for loco-regional recurrence (LR) and all-event progression after postoperative radiochemotherapy (PORT-C). The training cohort consisted of HPV-DNA negative HNSCC patients (n = 128) homogeneously treated with PORT-C in frame of the German Cancer Consortium-Radiation Oncology Group (DKTK-ROG) multicenter biomarker trial. DNA Methylation analysis was performed using Illumina 450 K and 850 K-EPIC microarray technology. The performance of the classifier was integrated with a series of biomarkers studied in the training set namely hypoxia-, 5-microRNA (5-miR), stem-cell gene-expression signatures and immunohistochemistry (IHC)-based immunological characterization of tumors (CD3/CD8/PD-L1/PD1). Validation occurred in an independent cohort of HPV(-) HNSCC patients, pooled from two German centers (n = 125). We identified a 38-methylation probe-based HPV(-) Independent Classifier of disease Recurrence (HICR) with high prognostic value for LR, distant metastasis and overall survival (P < 10-9 ). HICR remained significant after multivariate analysis adjusting for anatomical site, lymph node extracapsular extension (ECE) and size (T-stage). HICR high-risk tumors were enriched for younger patients with hypoxic tumors (15-gene signature) and elevated 5-miR score. After adjustment for hypoxia and 5-miR covariates, HICR maintained predicting all endpoints. HICR provides a novel mean for assessing the risk of LR in HPV(-) HNSCC patients treated with PORT-C and opens a new opportunity for biomarker-assisted stratification and therapy adaptation in these patients.

Keywords: DNA methylation; disease recurrence; head and neck cancers; radiotherapy; stratification

  • Open Access Logo International Journal of Cancer 150(2022), 603-616
    Online First (2021) DOI: 10.1002/ijc.33842

Permalink: https://www.hzdr.de/publications/Publ-33978
Publ.-Id: 33978


Comparison of the composition of lymphocyte subpopulations in non-relapse and relapse patients with squamous cell carcinoma of the head and neck before, during radiochemotherapy and in the follow-up period: a multicenter prospective study of the German Cancer Consortium Radiation Oncology Group (DKTK-ROG)

Niu, M.; E. Combs, S.; Linge, A.; Krause, M.; Baumann, M.; Lohaus, F.; Ebert, N.; Tinhofer, I.; Budach, V.; von der Grün, J.; Rödel, F.; Grosu, A.-L.; Multhoff, G.

Background
Radiochemotherapy (RCT) has been shown to induce changes in immune cell homeostasis which might affect antitumor immune responses. In the present study, we aimed to compare the composition and kinetics of major lymphocyte subsets in the periphery of patients with non-locoregional recurrent (n = 23) and locoregional recurrent (n = 9) squamous cell carcinoma of the head and neck (SCCHN) upon primary RCT.
Methods
EDTA-blood of non-locoregional recurrent SCCHN patients was collected before (t0), after application of 20–30 Gy (t1), in the follow-up period 3 (t2) and 6 months (t3) after RCT. In patients with locoregional recurrence blood samples were taken at t0, t1, t2 and at the time of recurrence (t5). EDTA-blood of age-related, healthy volunteers (n = 22) served as a control (Ctrl). Major lymphocyte subpopulations were phenotyped by multiparameter flow cytometry.
Results
Patients with non-recurrent SCCHN had significantly lower proportions of CD19+ B cells compared to healthy individuals before start of any therapy (t0) that dropped further until 3 months after RCT (t2), but reached initial levels 6 months after RCT (t3). The proportion of CD3+ T and CD3+/CD4+ T helper cells continuously decreased between t0 and t3, whereas that of CD8+ cytotoxic T cells and CD3+/CD56+ NK-like T cells (NKT) gradually increased in the same period of time in non-recurrent patients. The percentage of CD4+/CD25+/FoxP3+ regulatory T cells (Tregs) decreased directly after RCT, but increased above initial levels in the follow-up period 3 (t2) and 6 (t3) months after RCT. Patients with locoregional recurrence showed similar trends with respect to B, T cells and Tregs between t0 and t5. CD4+ T helper cells remained stably low between t0 and t5 in patients with locoregional recurrence compared to Ctrl. NKT/NK cell subsets (CD56+/CD69+, CD3−/CD56+, CD3−/CD94+, CD3−/NKG2D+, CD3−/NKp30+, CD3−/NKp46+) increased continuously up to 6 months after RCT (t0-t3) in patients without locoregional recurrence, whereas in patients with locoregional recurrence, these subsets remained stably low until time of recurrence (t5).
Conclusion
Monitoring the kinetics of lymphocyte subpopulations especially activatory NK cells before and after RCT might provide a clue with respect to the development of an early locoregional recurrence in patients with SCCHN. However, studies with larger patient cohorts are needed.

Keywords: SCCHN; Prediction of locoregional recurrence; Immunophenotyping; Radiochemotherapy; Lymphocyte subpopulations; NK cell subsets

Permalink: https://www.hzdr.de/publications/Publ-33977
Publ.-Id: 33977


Correction to: Value of PET imaging for radiation therapy

Lapa, C.; Nestle, U.; Albert, N. L.; Baues, C.; Beer, A.; Buck, A.; Budach, V.; Bütof, R.; Combs, S. E.; Derlin, T.; Eiber, M.; Fendler, W. P.; Furth, C.; Gani, C.; Gkika, E.; Grosu, A.-L.; Henkenberens, C.; Ilhan, H.; Löck, S.; Marnitz-Schulze, S.; Miederer, M.; Mix, M.; Nicolay, N. H.; Niyazi, M.; Pöttgen, C.; Todica, A. S.; Weber, W.; Wegen, S.; Wiegel, T.; Zamboglou, C.; Zips, D.; Zöphel, K.; Zschaeck, S.; Thorwarth, D.; Troost, E. G. C.

Correction to:
Strahlenther Onkol 2021
https://doi.org/10.1007/s00066-021-01812-2

Permalink: https://www.hzdr.de/publications/Publ-33975
Publ.-Id: 33975


Value of PET imaging for radiation therapy

Lapa, C.; Nestle, U.; Albert, N. L.; Baues, C.; Beer, A.; Buck, A.; Budach, V.; Bütof, R.; Combs, S. E.; Derlin, T.; Eiber, M.; Fendler, W. P.; Furth, C.; Gani, C.; Gkika, E.; Grosu, A.-L.; Henkenberens, C.; Ilhan, H.; Löck, S.; Marnitz-Schulze, S.; Miederer, M.; Mix, M.; Nicolay, N. H.; Niyazi, M.; Pöttgen, C.; Rödel, C. M.; Schatka, I.; Schwarzenboeck, S. M.; Todica, A. S.; Weber, W.; Wegen, S.; Wiegel, T.; Zamboglou, C.; Zips, D.; Zöphel, K.; Zschaeck, S.; Thorwarth, D.; Troost, E. G. C.

his comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Keywords: PET; Radiation oncology; Functional imaging; Radiomics

Permalink: https://www.hzdr.de/publications/Publ-33973
Publ.-Id: 33973


Metastatic Spread in Prostate Cancer Patients Influencing Radiotherapy Response

Klusa, D.; Lohaus, F.; Furesi, G.; Rauner, M.; Benešová, M.; Krause, M.; Kurth, I.; Peitzsch, C.

Radiotherapy and surgery are curative treatment options for localized prostate cancer (PCa) with a 5-year survival rate of nearly 100%. Once PCa cells spread into distant organs, such as bone, the overall survival rate of patients drops dramatically. The metastatic cascade and organotropism of PCa cells are regulated by different cellular subtypes, organ microenvironment, and their interactions. This cross-talk leads to pre-metastatic niche formation that releases chemo-attractive factors enforcing the formation of distant metastasis. Biological characteristics of PCa metastasis impacting on metastatic sites, burden, and latency is of clinical relevance. Therefore, the implementation of modern hybrid imaging technologies into clinical routine increased the sensitivity to detect metastases at earlier stages. This enlarged the number of PCa patients diagnosed with a limited number of metastases, summarized as oligometastatic disease. These patients can be treated with androgen deprivation in combination with local-ablative radiotherapy or radiopharmaceuticals directed to metastatic sites. Unfortunately, the number of patients with disease recurrence is high due to the enormous heterogeneity within the oligometastatic patient population and the lack of available biomarkers with predictive potential for metastasis-directed radiotherapy. Another, so far unmet clinical need is the diagnosis of minimal residual disease before onset of clinical manifestation and/or early relapse after initial therapy. Here, monitoring of circulating and disseminating tumor cells in PCa patients during the course of radiotherapy may give us novel insight into how metastatic spread is influenced by radiotherapy and vice versa. In summary, this review critically compares current clinical concepts for metastatic PCa patients and discuss the implementation of recent preclinical findings improving our understanding of metastatic dissemination and radiotherapy resistance into standard of care.

Keywords: prostate cancer; radiotherapy; metastasis; circulating tumor cells; radiopharmacy

Permalink: https://www.hzdr.de/publications/Publ-33972
Publ.-Id: 33972


Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

Klionsky, D. J.; Cordes, N.; Dubrovska, A.; Tong, C.-K.

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct auto-phagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Keywords: Autophagosome; cancer; flux; LC3; lysosome; macroautophagy; neurodegeneration; phagophore; stress; vacuole

Permalink: https://www.hzdr.de/publications/Publ-33971
Publ.-Id: 33971


ERCC2 gene single-nucleotide polymorphism as a prognostic factor for locally advanced head and neck carcinomas after definitive cisplatin-based radiochemotherapy

Guberina, M.; Sak, A.; Pöttgen, C.; Tinhofer-Keilholz, I.; Budach, V.; Balermpas, P.; von der Grün, J.; Michael Rödel, C.; Gkika, E.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Belka, C.; Pigorsch, S.; E. Combs, S.; Mönnich, D.; Zips, D.; De-Colle, C.; Welz, S.; Linge, A.; Lohaus, F.; Baretton, G.; Gauler, T.; Baumann, M.; Krause, M.; Schuler, M.; Bankfalvi, A.; Höing, B.; Lang, S.; Stuschke, M.

Identifying patients with locally advanced head and neck carcinoma on high risk of recurrence after definitive concurrent radiochemotherapy is of key importance for the selection for consolidation therapy and for individualized treatment intensification. In this multicenter study we analyzed recurrence-associated single-nucleotide polymorphisms (SNPs) in DNA repair genes in tumor DNA from 132 patients with locally advanced head and neck carcinoma (LadHnSCC). Patients were treated with definitive radiotherapy and simultaneous cisplatin-based chemotherapy at six partner sites of the German Cancer Consortium (DKTK) Radiation Oncology Group from 2005 to 2011. For validation, a group of 20 patients was available. Score selection method using proportional hazard analysis and leave-one-out cross-validation were performed to identify markers associated with outcome. The SNPs rs1799793 and rs13181 were associated with survival and the same SNPs and in addition rs17655 with freedom from loco-regional relapse (ffLRR) in the trainings datasets from all patients. The homozygote major rs1799793 genotype at the ERCC2 gene was associated with better (Hazard ratio (HR): 0.418 (0.234-0.744), p = 0.003) and the homozygote minor rs13181 genotype at ERCC2 with worse survival (HR: 2.074, 95% CI (1.177-3.658), p = 0.017) in comparison to the other genotypes. At the ffLRR endpoint, rs1799793 and rs13181 had comparable prognostic value. The rs1799793 and rs13181 genotypes passed the leave-one-out cross-validation procedure and associated with survival and ffLRR in patients with LadHnSCC treated with definitive radiochemotherapy. While findings were confirmed in a small validation dataset, further validation is underway within a prospective biomarker study of the DKTK.

Keywords: Cancer genetics; Prognostic markers

Permalink: https://www.hzdr.de/publications/Publ-33969
Publ.-Id: 33969


Correction: ERCC2 gene single-nucleotide polymorphism as a prognostic factor for locally advanced head and neck carcinomas after definitive cisplatin-based radiochemotherapy

Guberina, M.; Sak, A.; Pöttgen, C.; Tinhofer-Keilholz, I.; Budach, V.; Balermpas, P.; von der Grün, J.; Michael Rödel, C.; Gkika, E.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Belka, C.; Pigorsch, S.; E. Combs, S.; Mönnich, D.; Zips, D.; De-Colle, C.; Welz, S.; Linge, A.; Lohaus, F.; Baretton, G.; Gauler, T.; Baumann, M.; Krause, M.; Schuler, M.; Bankfalvi, A.; Höing, B.; Lang, S.; Stuschke, M.

The original version of this Article contained an error in the spelling of the author Eleni Gkika, which was incorrectly given as Eleni Gikka. As well as the author Stephanie E. Combs, this was incorrectly given as Stephanie Combs. Both have now been corrected in the PDF and HTML versions of the Article.

Permalink: https://www.hzdr.de/publications/Publ-33968
Publ.-Id: 33968


Joint EANM/SNMMI/ESTRO practice recommendations for the use of 2‑[18F]FDG PET/CT external beam radiation treatment planning in lung cancer V1.0

Vaz, S.; Adam, J.; Delgado Bolton, R.; Vera, P.; van Elmpt, W.; Herrmann, K.; Hicks, R.; Lievens, Y.; Santos, A.; Schöder, H.; Dubray, B.; Visvikis, D.; Troost, E. G. C.; de Geus-Oei, L.

Purpose 2-[18F]FDGPET/CT is of utmost importance for radiation treatment (RT) planning and response monitoring in lung cancer patients, in both non-small and small cell lung cancer (NSCLC and SCLC). This topic has been addressed in guidelines composed by experts within the feld of radiation oncology. However, up to present, there is no procedural guideline on this subject, with involvement of the nuclear medicine societies.
Methods A literature review was performed, followed by a discussion between a multidisciplinary team of experts in the different fields involved in the RT planning of lung cancer, in order to guide clinical management. The project was led by experts of the two nuclear medicine societies (EANM and SNMMI) and radiation oncology (ESTRO).
Results and conclusion This guideline results from a joint and dynamic collaboration between the relevant disciplines for this topic. It provides a worldwide, state of the art, and multidisciplinary guide to 2-[18F]FDG PET/CT RT planning in NSCLC and SCLC. These practical recommendations describe applicable updates for existing clinical practices, highlight potential faws, and provide solutions to overcome these as well. Finally, the recent developments considered for future application are also reviewed.

Keywords: Radiotherapy; EANM; SNMMI; ESTRO; 2-[18F]FDG PET; CT; Radiation therapy; Planning; Lung cancer

Permalink: https://www.hzdr.de/publications/Publ-33967
Publ.-Id: 33967


Correction: Görte et al. Comparative Proton and Photon Irradiation Combined with Pharmacological Inhibitors in 3D Pancreatic Cancer Cultures. Cancers 2020, 12, 3216

Görte, J.; Beyreuther, E.; Danen, E. H. J.; Cordes, N.

The authors wish to make the following corrections to this paper [...].

Permalink: https://www.hzdr.de/publications/Publ-33966
Publ.-Id: 33966


Toxicity and Efficacy of Local Ablative, Image-guided Radiotherapy in Gallium-68 Prostate-specific Membrane Antigen Targeted Positron Emission Tomography-staged, Castration-sensitive Oligometastatic Prostate Cancer: The OLI-P Phase 2 Clinical Trial

Hölscher, T.; Baumann, M.; Kotzerke, J.; Zöphel, K.; Paulsen, F.; Müller, A.-C.; Zips, D.; Koi, L.; Thomas, C.; Löck, S.; Krause, M.; Wirth, M.; Lohaus, F.

Background: Local ablative radiotherapy (aRT) of oligometastatic prostate cancer (PCa) is very promising and has become a focus of current clinical research.

Objective: We hypothesize that aRT is safe and effective in gallium-68 prostate-specific membrane antigen targeted positron emission tomography (PSMA-PET)-staged oligometastatic PCa patients.

Design, setting, and participants: A nonrandomized, prospective, investigator-initiated phase 2 trial recruited patients with oligometastatic PCa (five or fewer lymph node or osseous metastases) after local curative therapy, without significant comorbidity and androgen deprivation therapy (ADT), at two German centers from 2014 to 2018.

Intervention: All PSMA-PET-positive metastases were treated with aRT. No systemic therapy was initiated.

Outcome measurements and statistical analysis: The primary endpoint was treatment-related toxicity (grade ≥2) 24 mo after aRT. A one-sided single-sample test of proportions was planned to test whether the endpoint occurs in <15% of the patients. Key secondary endpoints were time to progression of prostate-specific antigen (PSA) and time to ADT, which were associated with potential prognostic factors by Cox regression.

Results and limitations: Of 72 patients, 63 received aRT (13% dropout rate). The median follow-up was 37.2 mo. No treatment-related grade ≥2 toxicity was observed 2 yr after treatment. The median time to PSA progression and time to ADT were 13.2 and 20.6 mo, respectively. Of the patients, 21.4% were free of PSA progression after 3 yr.

Conclusions: It was observed that aRT is safe, and midterm PSA progression and ADT-free time were achieved in one of five patients. Randomized clinical trials are indicated to further evaluate the option of delaying ADT in selected patients.

Patient summary: In this clinical trial, 63 patients with up to five metastases of prostate cancer without androgen deprivation therapy were included. We showed that local ablative radiotherapy is safe and that one in five patients had no recurrent prostate-specific antigen value after 3 yr. Local ablative radiotherapy might be an option to avoid systemic therapy in selected patients.

Keywords: Adult; Image guided Radiosurgery; Male; Neoplasm metastasis; Positron emission tomography; Prospective studies; Prostate-specific antigen; Prostatic neoplasms; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-33965
Publ.-Id: 33965


High Sulfur in Primitive Arc Magmas, Its Origin and Implications

Zelenski, M.; S. Kamenetsky, V.; Nekrylov, N.; Kontonikas-Charos, A.

Sulfur contents in 98.5% of melt inclusions (MI) from calc-alkaline subduction basalts do not exceed 4000 ppm, whereas experimentally established limits of sulfur solubility in basaltic melts with high fO2 (characteristic of subduction zones, e.g., QFM + 2) surpass 14,000 ppm. Here we show that primitive (Mg# 62-64) subduction melts may contain high sulfur, approaching the experimental limit of sulfur solubility. Up to 11,700 ppm S was measured in olivine-hosted MI from primitive arc basalt from the 1941 eruption of the Tolbachik volcano, Kamchatka. These MI often contain magmatic sulfide globules (occasionally enriched in Cu, Ni, and platinum-group elements) and anhydrite enclosed within a brown, oxidized glass. We conclude that the ubiquitous low sulfur contents in MI may originate either from insufficient availability of sulfur in the magma generation zone or early magma degassing prior to inclusion entrapment. Our findings extend the measured range of sulfur concentrations in primitive calc-alkaline basaltic melts and demonstrate that no fundamental limit of 4000 ppm S exists for relatively oxidized subduction basalts, where the maximum sulfur content may approach the solubility limit determined by crystallization of magmatic anhydrite.

Keywords: primitive basalts; olivine; melt inclusions; sulfur; igneous petrology

Permalink: https://www.hzdr.de/publications/Publ-33964
Publ.-Id: 33964


Noble metals in arc basaltic magmas worldwide: A case study of modern and pre-historic lavas of the Tolbachik volcano, Kamchatka

Kutyrev, A.; Zelenski, M.; Nekrylov, N.; Savelyev, D.; Kontonikas-Charos, A.; S. Kamenetsky, V.

Platinum-group elements (PGE) and gold are a promising tool to assess the processes of
mantle melting beneath the subduction zones. However, fractionation processes in
magmas inevitably overwrite the initial metal budgets of magmas, making constraints
on the melting processes inconclusive. Moreover, little is still known about the geochemical
behavior of a particular metal in a single arc magmatic system, from mantle melting
towards magma solidification. Here we compare noble metals in lavas from several
eruptions of the Tolbachik volcano (Kamchatka arc) to better understand the effects of
magma differentiation, estimate primary melt compositions and make constraints on the
mantle melting. We show that Ir, Ru, Rh and, to a lesser extent, Pt are compatible during
magmatic differentiation. The pronounced incompatible behavior of Cu and Pd, observed
in Tolbachik magmas, rules out the significant influence of sulfide melts on the early
magmatic evolution in this particular case. Gold is also incompatible during magmatic
differentiation; however, its systematics can be affected by the inferred gold recycling in the
plumbing system of Tolbachik. Although the Tolbachik lavas show only slightly higher PGE
fractionation than in MORB, a notable negative Ru anomaly (higher Pt/Ru and Ir/Ru) is
observed. We attribute this to be a result of greater oxidation in the subarc mantle (by 1–4
log units), which promotes crystallization of Ru-bearing phases such as Fe3+-rich Cr-spinel
and laurite. The estimated Pd contents for the parental melt of the Tolbachik lavas
approaches 6.5 ppb. This is several times higher than reported MORB values (1.5 ±
0.5 ppb), suggesting the enrichment of Pd in the mantle wedge. Our results highlight
the influence of the subduction-related processes and mantle wedge refertilization on the
noble metal budgets of arc magmas.

Keywords: basalt; island arc and continental margin arc environment; platinum; PGE; gold; sulfide; primitive basalts; igneous petrology

Permalink: https://www.hzdr.de/publications/Publ-33963
Publ.-Id: 33963


Origin of alkali-rich volcanic and alkali-poor intrusive carbonatites from a common parental magma

F. Chayka, I.; S. Kamenetsky, V.; V. Vladykin, N.; Kontonikas-Charos, A.; R. Prokopyev, I.; Yu Stepanov, S.; P. Krasheninnikov, S.

The discrepancy between Na-rich compositions of modern carbonatitic lavas (Oldoinyo Lengai volcano) and alkali-poor ancient carbonatites remains a topical problem in petrology. Although both are supposedly thought to originate via fractional crystallization of a “common parent” alkali-bearing Ca-carbonatitic magma, there is a significant compositional gap between the Oldoinyo Lengai carbonatites and all other natural compositions reported (including melt inclusions in carbonatitic minerals). In an attempt to resolve this, we investigate the petrogenesis of Ca-carbonatites from two occurrences (Guli, Northern Siberia and Tagna, Southern Siberia), focusing on mineral textures and alkali-rich multiphase primary inclusions hosted within apatite and magnetite. Apatite-hosted inclusions are interpreted as trapped melts at an early magmatic stage, whereas inclusions in magnetite represent proxies for the post-cumulus interstitial environment. Melts obtained by heating and quenching the inclusions, show a progressive increase in alkali concentrations transitioning from moderately-alkaline Ca-carbonatites through to the calcite-nyerereite/fairchildite peritectic, and finally towards Oldoinyo Lengai lava compositions. These results give novel empirical evidence supporting the view that Na-carbonatitic melts, similar to those of the Oldoinyo Lengai, may form via fractionation of a moderately alkaline Ca-carbonatitic melt, and therefore provide the “missing piece” in the puzzle of the Na-carbonatite’s origin. In addition, we conclude that the compositions of the Guli and Tagna carbonatites were in fact alkali-rich at the solidus, but were subsequently altered by replacement of alkaline assemblages by calcite and dolomite.

Keywords: Carbonatites; Melt inclusions; Igneous petrology

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33962
Publ.-Id: 33962


Trajectory-dependent electronic excitations of keV ions

Lohmann, S.; Holeňák, R.; Primetzhofer, D.

We present experiments directly demonstrating the significance of charge-exchange events for the energy deposition of ions with velocities below the Bohr velocity. The observed effects lead to a drastic trajectory-dependence of the specific energy loss.
Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. We employed pulsed beams of singly charged ions with masses ranging from 1 (H+) to 40 u (Ar+) and energies between 20 and 350 keV. Ions were transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. We assessed the energy and angular distributions of deflected particles for different alignments of the initial beam direction with the crystal axes and planes. A set-up for measuring the exit charge state was constructed to support the analysis [2].
For all ions we observe lower electronic stopping for channelled trajectories as compared to random ones as shown in Fig. 1 [3]. For protons, this difference is explained by increasing contributions of core-electron excitations more likely to happen at small impact parameters accessible only in random geometry. For heavier ions, core-electron excitations at employed ion velocities are inefficient and we, therefore, explain these results by reionisation events occurring in close collisions of ions with target atoms [4]. These events in turn result in trajectory-dependent mean charge states, which heavily affects the energy loss, and could be confirmed by first qualitative measurements of the trajectory dependence of exit charge states. The simplicity of our experimental geometry leads to results that can serve as excellent benchmark systems for calculations using time-dependent density functional theory.

References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B, 463 (2020) 16-20.
[2] R. Holeňák et al., Vacuum, 185 (2021) 109988.
[3] S. Lohmann et al., Phys. Rev. A, 102 (2020) 062803.
[4] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett., 124 (2020) 096601.

  • Lecture (Conference)
    Applied Nuclear Physics Conference, 12.-16.09.2021, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-33961
Publ.-Id: 33961


Ion-electron dynamics studied in a 3D-transmission approach

Lohmann, S.; Holeňák, R.; Grande, P. L.; Primetzhofer, D.

We present experiments demonstrating trajectory-dependent electronic excitations at low ion velocities attributed to charge-exchange events. Experiments were performed with the time-of-flight medium energy ion scattering set-up at Uppsala University [1]. We employed pulsed beams of singly charged ions with masses from 1 (H+) to 40 u (Ar+) and energies between 20 and 300 keV. Ions are transmitted through self-supporting Si(100) nanomembranes and detected behind the sample. Fig. 1 demonstrates our experimental approach, in which ion energy loss is measured together with angular distributions for different beam-crystal alignments. We have analysed both trajectory-dependent electronic stopping and electronic energy-loss straggling. Our results show higher electronic stopping for random than for channelled trajectories for all studied ions [2]. For ions heavier than protons, direct core-electron excitations at employed ion velocities are inefficient. We, therefore, explain our observation by reionisation events occurring in close collisions of ions with target atoms mainly accessible in random geometry [3]. These events result in trajectory-dependent mean charge states, which heavily affects the energy loss. The electronic energy-loss straggling likewise exhibits a strong dependence on ion type, velocity and trajectory. For all ions, straggling in random geometry is higher than in channelling orientation. While for He straggling increases with ion velocity, for B travelling along random trajectories a minimum is observed in the studied velocity range. We compare experimental results for these two ions with predictions by the Chu model and transport cross section calculations (Penn-TCS model). We provide strong evidence that electron-hole pair creation alone cannot explain electronic excitations by slow ions other than protons. Especially for heavy ions, additional energy-loss processes such as charge exchange and autoionisation including possible alterations of the scattering potential [4] have to be taken into account.
References
[1] M. A. Sortica et al., Nucl. Instrum. Methods Phys. Res. B, 463 (2020) 16-20.
[2] S. Lohmann et al., Phys. Rev. A, 102 (2020) 062803.
[3] S. Lohmann and D. Primetzhofer, Phys. Rev. Lett., 124, (2020) 096601.
[4] R. A. Wilhelm and P. L. Grande, Communications Physics, 2 (2019) 89.

  • Invited lecture (Conferences) (Online presentation)
    27th International Symposium on Ion-Atom Collisions (ISIAC), 14.-16.07.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33960
Publ.-Id: 33960


Treatment Planning and Dose Verification for Combined Internal and External Radiotherapy (CIERT)

Freudenberg, R.; Hartmann, H.; Andreeff, M.; Oehme, L.; Leichtner, T.; Fischer, A.; Paulus, T.; Krause, M.; Kotzerke, J.

Aim: The combined internal and external radiotherapy (CIERT) take advantage of the benefits from radionuclide therapy and external beam irradiation. These include steep dose gradients and a low toxicity to normal tissue due to the use of unsealed radioisotopes as well as homogeneous dose distribution within the tumor due to external beam irradiation. For a combined irradiation planning, an infrastructure has to be developed that takes into account the dose contributions from both modalities. A physical verification of the absorbed dose distribution should follow by measurements using OSL detectors.

Method: Internal irradiation was performed using Re-188 in a cylindrical phantom with three inserts. SPECT images were acquired to calculate the internal dose using the software STRATOS. The dose distribution was exported as DICOM-RT data and imported in the software Pinnacle. Based on the internal dose distribution the external irradiation using 6 MV photons was planned. The dose contributions of both modalities separately as well as for combined irradiation was measured using OSL detectors made out of Beryllium oxide.

Results: The planed doses of combined irradiation (1 Gy, 2 Gy, 4 Gy) could be verified within the uncertainty of the detectors. The mean energy response to Re-188 was (88.6 ± 2.4) % with respect to the calibration with 200 kV X-ray irradiation. The energy response to 6 MV photons was (146.0 ± 4.9) %.

Conclusion: A workflow for the treatment planning of combined internal and external radiotherapy has been developed and tested. Measurements verified the calculated doses. Therefore, the physical and technical basis for the dosimetry of combined irradiation were worked out.

Keywords: CIERT; kombinierte Bestrahlung; OSL; Dosimetrie

Permalink: https://www.hzdr.de/publications/Publ-33959
Publ.-Id: 33959


In reply to the Letter to the Editor by Chen and Lui regarding "Radiotherapy enhances uptake and efficacy of 90 Y-cetuximab: A preclinical trial" by A Dietrich et al

Dietrich, A.; Andreeff, M.; Koi, L.; Bergmann, R.; Schubert, M.; Schreiner, L.; Löck, S.; Sihver, W.; Freudenberg, R.; Hering, S.; Pietzsch, H.-J.; Steinbach, J.; Kotzerke, J.; Baumann, M.; Krause, M.

It is the reply to the Letter to the Editor by Chen and Lui regarding "Radiotherapy enhances uptake and efficacy of 90 Y-cetuximab: A preclinical trial" by A Dietrich et al.
Abstract: Background and purpose: Systemic molecular radiotherapy utilizes internal irradiation by radionuclide-labeled tumor-targeting agents with the potential to destroy (micro-)metastases. However, doses that are applicable in solid tumors do not reach the levels nessecary for tumor control. Thus, the combination of molecular and external radiotherapy is a promising treatment strategy, as enhanced tumor doses can be delivered with and without minor overlapping toxicities. Here, we combined a 90Y-labeled anti-EGFR antibody (Cetuximab) with clinically relevant fractionated radiotherapy in a preclinical trial using head and neck squamous cell carcinoma xenograft tumors.

Downloads:

  • Secondary publication expected from 11.06.2022

Permalink: https://www.hzdr.de/publications/Publ-33958
Publ.-Id: 33958


Efficient Heat Shock Response Affects Hyperthermia-Induced Radiosensitization in a Tumor Spheroid Control Probability Assay

Chen, O.; Michlíková, S.; Eckhardt, L.; Wondrak, M.; M. De Mendoza, A.; Krause, M.; D. McLeod, D.; A. Kunz-Schughart, L.

Hyperthermia (HT) combined with irradiation is a well-known concept to improve the curative potential of radiotherapy. Technological progress has opened new avenues for thermoradiotherapy, even for recurrent head and neck squamous cell carcinomas (HNSCC). Preclinical evaluation of the curative radiosensitizing potential of various HT regimens remains ethically, economically, and technically challenging. One key objective of our study was to refine an advanced 3-D assay setup for HT + RT research and treatment testing. For the first time, HT-induced radiosensitization was systematically examined in two differently radioresponsive HNSCC spheroid models using the unique in vitro "curative" analytical endpoint of spheroid control probability. We further investigated the cellular stress response mechanisms underlying the HT-related radiosensitization process with the aim to unravel the impact of HT-induced proteotoxic stress on the overall radioresponse. HT disrupted the proteome's thermal stability, causing severe proteotoxic stress. It strongly enhanced radiation efficacy and affected paramount survival and stress response signaling networks. Transcriptomics, q-PCR, and western blotting data revealed that HT + RT co-treatment critically triggers the heat shock response (HSR). Pre-treatment with chemical chaperones intensified the radiosensitizing effect, thereby suppressing HT-induced Hsp27 expression. Our data suggest that HT-induced radiosensitization is adversely affected by the proteotoxic stress response. Hence, we propose the inhibition of particular heat shock proteins as a targeting strategy to improve the outcome of combinatorial HT + RT.

Keywords: head and heck squamous cell carcinomas (HNSCC); heat shock proteins (Hsps); hyperthermia; proteotoxic stress; radiation therapy; spheroids

Permalink: https://www.hzdr.de/publications/Publ-33957
Publ.-Id: 33957


Dual role of ER stress in response to metabolic co-targeting and radiosensitivity in head and neck cancer cells

Chen, O.; Manig, F.; Lehmann, L.; Sorour, N.; Löck, S.; Yu, Z.; Dubrovska, A.; Baumann, M.; M. Kessler, B.; Stasyk, O.; A. Kunz-Schughart, L.

Arginine deprivation therapy (ADT) is a new metabolic targeting approach with high therapeutic potential for various solid cancers. Combination of ADT with low doses of the natural arginine analog canavanine effectively sensitizes malignant cells to irradiation. However, the molecular mechanisms determining the sensitivity of intrinsically non-auxotrophic cancers to arginine deficiency are still poorly understood. We here show for the first time that arginine deficiency is accompanied by global metabolic changes and protein/membrane breakdown, and results in the induction of specific, more or less pronounced (severe vs. mild) ER stress responses in head and neck squamous cell carcinoma (HNSCC) cells that differ in their intrinsic ADT sensitivity. Combination of ADT with canavanine triggered catastrophic ER stress via the eIF2α-ATF4(GADD34)-CHOP pathway, thereby inducing apoptosis; the same signaling arm was irrelevant in ADT-related radiosensitization. The particular strong supra-additive effect of ADT, canavanine and irradiation in both intrinsically more and less sensitive cancer cells supports the rational of ER stress pathways as novel target for improving multi-modal metabolic anti-cancer therapy.

Keywords: 3-D culture; Arginine-deprivation therapy; Canavanine; ER stress; Head and neck squamous carcinoma; Metabolic targeting; Radiosensitization

Permalink: https://www.hzdr.de/publications/Publ-33956
Publ.-Id: 33956


Data publication: Describing chain-like assembly of ethoxygroup-functionalized organic molecules on Au(111) using high-throughput simulations

Lokamani, M.; Kelling, J.; Ohmann, R.; Meyer, J.; Kühne, T.; Cuniberti, G.; Wolf, J.; Juckeland, G.; Huhn, T.; Zahn, P.; Moresco, F.; Gemming, S.

Bei diesem Datensatz handelt es sich um die Grundzustandsstruktur von PEEB auf Au(111) und die Inputdatei für DFTB+.

Keywords: DFTB; 1,4-bis(phenylethynyl)-2,5-bis(ethoxy)benzene (PEEB); STM; High-Throughput; Meta-Structures

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2022-01-12
    DOI: 10.14278/rodare.1374
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33955
Publ.-Id: 33955


Conceptual design report for the LUXE experiment

Abramowicz, H.; Hernandez Acosta, U.; Altarelli, M.; Assmann, R.; Bai, Z.; Behnke, T.; Benhammou, Y.; Blackburn, T.; Boogert, S.; Borysov, O.; Borysova, M.; Brinkmann, R.; Bruschi, M.; Burkart, F.; Büßer, K.; Cavanagh, N.; Davidi, O.; Decking, W.; Dosselli, U.; Elkina, N.; Fedotov, A.; Firlej, M.; Fiutowski, T.; Fleck, K.; Gostkin, M.; Grojean, C.; Andrew Hallford, J.; Harsh, H.; Hartin, A.; Heinemann, B.; Heinzl, T.; Helary, L.; Hoffmann, M.; Huang, S.; Huang, X.; Idzik, M.; Ilderton, A.; Magdalena Jacobs, R.; Kämpfer, B.; King, B.; Lakhno, H.; Levanon, A.; Levy, A.; Levy, I.; List, J.; Lohmann, W.; Ma, T.; John Macleod, A.; Malka, V.; Meloni, F.; Mironov, A.; Morandin, M.; Moron, J.; Negodin, E.; Perez, G.; Pomerantz, I.; Poeschl, R.; Prasad, R.; Quere, F.; Ringwald, A.; Roedel, C.; Rykovanov, S.; Salgado, F.; Santra, A.; Sarri, G.; Saevert, A.; Sbrizzi, A.; Schmitt, S.; Schramm, U.; Schuwalow, S.; Seipt, D.; Shaimerdenova, L.; Shchedrolosiev, M.; Skakunov, M.; Soreq, Y.; Streeter, M.; Swientek, K.; Tal Hod, N.; Tang, S.; Teter, T.; Thoden, D.; Titov, A.; Tolbanov, O.; Torgrimsson, G.; Tyazhev, A.; Wing, M.; Zanetti, M.; Zarubin, A.; Zeil, K.; Zepf, M.; Zhemchukov, A.

This Conceptual Design Report describes LUXE (Laser Und XFEL Experiment), an experimental campaign that aims to combine the high-quality and high-energy electron beam of the European XFEL with a powerful laser to explore the uncharted terrain of quantum electrodynamics characterised by both high energy and high intensity. We will reach this hitherto inaccessible regime of quantum physics by analysing high-energy electron-photon and photon-photon interactions in the extreme environment provided by an intense laser focus. The physics background and its relevance are presented in the science case which in turn leads to, and justifies, the ensuing plan for all aspects of the experiment: Our choice of experimental parameters allows (i) field strengths to be probed where the coupling to charges becomes non-perturbative and (ii) a precision to be achieved that permits a detailed comparison of the measured data with calculations. In addition, the high photon flux predicted will enable a sensitive search for new physics beyond the Standard Model. The initial phase of the experiment will employ an existing 40 TW laser, whereas the second phase will utilise an upgraded laser power of 350 TW. All expectations regarding the performance of the experimental set-up as well as the expected physics results are based on detailed numerical simulations throughout.

Keywords: energy: high; photon photon: interaction; new physics: search for; electron: beam; photon: flux; laser; quantum electrodynamics; numerical calculations: Monte Carlo; proposed experiment

Permalink: https://www.hzdr.de/publications/Publ-33954
Publ.-Id: 33954


From conventional to unconventional superconductivity

Wosnitza, J.

  • Invited lecture (Conferences)
    Quantum Matter Bordeaux School 2021, 15.-19.11.2021, Bordeaux, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33953
Publ.-Id: 33953


Verflüssigung von Wasserstoff durch magnetische Kühlung

Gottschall, T.

Magnetische Materialien ändern ihre Temperatur, wenn sie einem Magnetfeld ausgesetzt werden. Dieser sogenannte magnetokalorische Effekt lässt sich nutzen, um alternative Kühlkonzepte zu entwickeln. Während in den letzten Jahren der wissenschaftliche Fokus auf der Kühlung nahe Raumtemperatur lag, ist kürzlich die magnetische Verflüssigung von Wasserstoff als Anwendungsgebiet stärker ins Blickfeld gerückt. Die konventionelle Herstellung von Flüssigwasserstoff ist ein äußerst energieintensiver Prozess. Effizienzsteigerungen sind durch den Einsatz maßgeschneiderter magnetischer Materialien und hoher Magnetfelder möglich. In diesem Beitrag werden die physikalischen Grundlagen der magnetischen Kühlung diskutiert und ausgewählte magnetokalorische Materialklassen vorgestellt. Des Weiteren werden die technologischen Herausforderungen und Vorteile thematisiert.

  • Invited lecture (Conferences)
    Deutsche Kälte-und Klimatagung 2021 Dresden, 19.11.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33952
Publ.-Id: 33952


Magnetic cooling: from materials to application

Gottschall, T.

With the world's increasingly affluent population demanding more comfortable living and working conditions, it is vital that we address the development of much more efficient cooling technologies as an urgent priority. An alternative approach is based on solid-state refrigeration by one of the caloric effects – electrocaloric, magnetocaloric, barocaloric or elastocaloric - where the material's temperature is forced to change under the application of an electrical, magnetic, or mechanical field. However, there is also the possibility to combine these different effects in a beneficial way, in the so-called multicaloric cooling cycle. Magnetic Ni-Mn-based Heusler alloys are ideally suited for multicaloric applications due to their coupled magnetostructural transformation between martensite and austenite. In this work, we discuss the current progress in the characterization of these materials for novel cooling technologies.

  • Invited lecture (Conferences) (Online presentation)
    Phd-Retreat CRC 270, 02.12.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33950
Publ.-Id: 33950


Magnetic properties and microstructure of Sm5Fe17-based composite magnets

Dirba, I.; Sepehri-Amin, H.; Skokov, K.; Scurschii, I.; Hono, K.; Gutfleisch, O.

We have investigated synthesis, magnetic properties and microstructure of Sm5Fe17-based hard magnetic phase with a Sm20Fe70Ti10 composition. Ultrahigh coercivities, μ0Hc = 7.18 T at room temperature and μ0Hc = 8.86 T at 10 K, have been achieved. The room-temperature coercivity, determined from high-field pulse measurements, reaches 35 % of the anisotropy field μ0Ha = 20.7±0.8 T. Further, it is demonstrated that a coercivity of 2.18 T is maintained even at 500 K. The Curie temperature Tc of Sm20Fe70Ti10 is 577 K and the calculated exchange stiffness parameter A is 7.72 pJ/m. Detailed transmission electron microscopy investigations show a two-phase microstructure consisting of the Sm6Fe17-based hard magnetic matrix phase with grain size below 200 nm and finer, below 100 nm, Fe2Ti grains. Majority of the Fe2Ti phase is located at the grain boundaries with some finer inclusions found also inside the 5:17 grains. Despite the high fraction of the Fe2Ti grains, nearly single-phase demagnetization loops are observed. In order to enhance Ms, the effect of Ti content on phase constitution, magnetic properties and microstructure was studied in detail. Ms increases and Hc decreases for the Ti-lean compositions.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33949
Publ.-Id: 33949


Anisotropic magnetization, critical temperature, and paramagnetic Curie temperature in the highly anisotropic magnetic Heusler compound Rh2CoSb

He, Y.; Sibille, R.; Chen, D.; Kroder, J.; Helm, T.; Schnelle, W.; Felser, C.; Fecher, G. H.

The paramagnetic Curie temperature θp is a concept that describes the magnetic ordering temperature in the well-established Curie-Weiss law. Despite the successful explanations of the magnetic behavior, the anisotropy is not usually considered. Although anisotropic θp has been reported for several layered antiferromagnetic or ferrimagnetic materials owing to the orientation-dependent exchange, in ferromagnetic systems, θp was thought to be almost isotropic for decades, and the occasionally reported small difference has remained unexplained. In this paper, we experimentally report the anisotropic magnetization, critical temperature, and paramagnetic Curie temperature in highly anisotropic magnetic Rh2CoSb caused by a large magnetocrystalline anisotropy. The saturation magnetization along the c axis is 25% larger than that along the a axis. The critical temperature and paramagnetic Curie temperature along the c axis are 6 and 15 K higher than those along the a axis, respectively, as deduced from the Arrott plots and inverse susceptibility. A simple modification of the Curie-Weiss law was made to calculate the anisotropic θp, which well explains not only Rh2CoSb, but also many other previously reported ferromagnetic materials.

Permalink: https://www.hzdr.de/publications/Publ-33948
Publ.-Id: 33948


New limits on double-beta decay of 190Pt and 198Pt

Danevich, F. A.; Hult, M.; Junghans, A.; Kasperovych, D. V.; Kropivyansky, B. N.; Lutter, G.; Marissens, G.; Polischuk, O. G.; Romaniuk, M. V.; Stroh, H.; Tessalina, S.; Tretyak, V. I.; Ware, B.

A search for double-beta decay of 190Pt and 198Pt
with emission of γ -ray quanta was realized at the HADES
underground laboratory with a 148 g platinum sample measured
by two ultralow-background HPGe detectors over 8946
h. The isotopic composition of the platinum sample has
been measured with high precision using inductively coupled
plasma mass spectrometry. New lower limits for the
half-lives of 190Pt relative to different channels and modes
of the decays were set on the level of lim T1/2 ∼ 10^14–10^16
year. A possible exact resonant 0νKN transition to the 1,2
1326.9 keV level of 190Os is limited for the first time as
T1/2 ≥ 2.5 × 10^16 year. A new lower limit on the double beta
decay of 198Pt to the first excited level of 198Hg was set
as T1/2 ≥ 3.2 × 10^19 year, one order of magnitude higher
than the limit obtained in the previous experiment.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33943
Publ.-Id: 33943


The effect of magnetic fields on freckle evolution during solidification

Shevchenko, N.; Kao, A.; Fan, X.; Tonry, C.; Clark, S.; Atwood, R.; Lee, P.; Pericleous, K.; Eckert, S.

The formation of freckle defects in the presence of a static magnetic field is studied by combining in-situ synchrotron imaging with numerical simulations. The formation, growth and motion of freckle channels during directional solidification are investigated in a Hele-Shaw cell for a low melting point Ga-In alloy. The solidification setup is developed at HZDR and is described in detail elsewhere. The solidification cell is placed in a permanent magnet system providing a flux density of about 120 mT within the cell. The turn of the magnet system about a vertical cell axis allow to get both the Bx (perpendicular to a X-ray beam) and the Bz (parallel to a X-ray beam) component of the magnetic field.
Numerical simulations, using a microscopic parallelized Cellular Automata lattice Boltzmann method, are validated by these in situ experiments. An excellent match between the numerical model and experiments conducted on thin rectangle sample alloy is achieved. Evaluation of the in situ X-ray data and numerical analysis shows the role of thermoelectric magnetohydrodynamics (TEMHD) and electromagnetic damping (EMD) in the formation of channels and ultimately freckle defects. For instance, Figures 1c and 1d show clear evidence of the effect of the magnetic field on the microstructure. Figure 1d displays the formation of a solute channel at the left side of the sample in the presence of a magnetic field. This channel development can be attributed to the thermoelectric Lorentz force acting on the inter-dendritic liquid flow by causing the solute to accumulate at one side of the cell.
In situ synchrotron experiments allow us to resolve the complex channel dynamics and simultaneously show how large-scale flow fields may alter them. Both temperature gradient and grain orientation can affect the dynamics of the segregation channels formation in the presence of the magnetic field. The effect of electromagnetic damping force to convective transport needs future investigations. The in situ synchrotron data and numerical modelling will provide further understanding of the underlying mechanisms and identifying further interesting phenomena.

Keywords: solidification; magnetic fields; freckle defects; in-situ synchrotron imaging; numerical modelling

  • Lecture (Conference) (Online presentation)
    Electromagnetic Processing of Materials, EPM 2021, 14.-16.06.2021, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-33932
Publ.-Id: 33932


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