Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Approved and published publications
Only approved publications

41396 Publications

Three-dimensional distribution of platinum group minerals in natural MSS-ISS ores from the Norilsk 1 Deposit, Russia

Sittner, J.; Brovchenko, V.; Siddique, A.; Buyse, F.; Boone, M.; Renno, A.; Cnudde, V.; Merkulova, M.; Sluzhenikin, S.

The Mt. Rudnaya Mss-Iss fine-grained ores from a NE termination of Norilsk 1 deposit were analyzed using a combination of X-ray computed micro tomography, spectral X-ray computed micro tomography and scanning electron microscopy to achieve both, 2D and 3D data. The ores consist of a copper-rich Iss composed of tiny lamellar intergrowths of cubanite and chalcopyrite solid solutions, which form up to 4-mm distinct globules surrounded by an Iss-Mss matrix. Our X-ray computed micro tomography results provide 3D textural evidence of a possible natural sulfide-sulfide liquid immiscibility between Cu-rich and Cu-poor sulfide liquids. The platinum-group minerals (PGM) distribution shows that 20.6 Vol.-% of all PGMs occur in the Iss-Mss matrix and 79.4 Vol.-% in the Iss globules. We believe that this distributional behavior is due to the fact that the platinum group elements (PGE) cannot be dissolved in Iss, which led to the formation of the large PGM grains, which are up to 120 μm on their longest axis. The initial enrichment of Iss with PGEs was controlled by differences in the partition coefficients of platinum and palladium Cu-poor and Cu-rich liquids.

Keywords: Norilsk; Platinum Group Minerals; X-ray computed tomography; Spectral X-ray computed tomography; 3D imaging; SEM-EDS

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34099
Publ.-Id: 34099


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


Physics and Theory of Defects in 2D Materials: The Role of Reduced Dimensionality

Komsa, H.-P.; Krasheninnikov, A.

Similar to their bulk counterparts, most crystalline two-dimensional materials (2DMs) have defects and impurities. Even when the formation energy of defects in a 2D system is high, so that the equilibrium defect concentration is negligible (as, e.g., in graphene in a wide range of temperatures), the defects can appear due to the interaction with the environment, as 2DMs have a very high surface-to-volume ratio. Moreover, any species on the surface of 2DMs can have strong effect on the material properties, while most species found on the surfaces of bulk systems are normally completely ignored in the context of point and line defects. Defects can have both detrimental and beneficial effects on the properties of 2DMs, as in the case of the bulk systems. Specifically, defects can deteriorate the electronic, optical and mechanical characteristics of 2DMs, and at the same time, add new functionalities, e.g., magnetism, or improve their catalytic performance. The reduced dimensionality of 2DMs, however, modifies the influence of defects on the materials properties. The geometry of 2DMs also makes it possible to deliberately introduce defects with nearly atomic spatial resolution using focused ion and electron beams and also helps in imaging the defects using scanning probe and transmission electron microscopy. At the same time, the reduced dimensionality of 2DMs also requires to modify the theoretical approaches aimed at assessing the formation energy of defects to account for the environment and much weaker screening of electrical point charges when defects are not neutral. In this chapter, we give a brief overview of the types of defects in 2DMs and bulk systems with the main focus on the differences originating from the reduced dimensionality of the former. We also discuss the changes which should be made in the theoretical description of point and line defects and give examples of the calculations for 2DMs with defects.

Keywords: 2D materials; Defects

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34094
Publ.-Id: 34094


In situ study of solidification patterns of a ternary Ga-In-Bi alloy in presence of melt convection

Shevchenko, N.; Budenkova, O.; Birjukovs, M.; Chichignoud, G.; Eckert, S.

In situ real-time observations, which are important in studies of binary alloy systems for verification of theoretical hypotheses, are scarce for ternary and multi-component alloys. This work is devoted to in situ visualization of solidification patterns observed during bottom-up solidification of a Ga-In-Bi alloy in a Hele-Shaw cell under buoyancy-driven convection. The investigations are based on a combination of micro-focus X-ray radiography and advanced image processing techniques. A model ternary system is selected from the family of low-temperature metallic alloys with working temperatures below 100 °C. The phase diagram of the ternary Ga-In-Bi system indicates the appearance of an indium-based primary solid phase and only a minor amount of intermetallic phase for concentrations chosen within this study.
Our observations show complex and strongly disoriented solidification patterns with curved primary and secondary branches. By studying the solidification dynamics we establish that some grains exhibit a morphology that is rather similar to the "seaweed" pattern. The appearance of seaweed grains is usually related to the low anisotropy of the surface energy of metal crystals that can be relatively easy modified by the presence of another element. We focus on the role of melt flow in transition from dendritic arrays to seaweed structures in this ternary system. Morphological analysis and comparison of dendritic and seaweed patterns are performed using a new X-ray image processing approach.

Keywords: Ternary alloy; in situ X-ray imaging; solidification; seaweed pattern; melt convection

  • Lecture (Conference)
    6th International Conference on Advances in Solidification Processes, 20.-24.06.2022, Le Bischenberg, France

Permalink: https://www.hzdr.de/publications/Publ-34093
Publ.-Id: 34093


An image processing pipeline for in-situ dynamic X-ray imaging of directional solidification of metal alloys in thin cells

Birjukovs, M.; Shevchenko, N.; Eckert, S.

The interplay between solidification and convection, which are usually strongly coupled, occurs via many different mechanisms resulting in very complex dynamics. Melt convection changes the solutal field near the solidification front leading to different microstructures or formation of freckle defects. Quantitative of dendritic structure evolution and melt flow during in situ solidification experiments is rather challenging and requires new/improved approaches to image processing. We present an image processing algorithm designed for quantitative analysis of meso-scale solidification of metal alloys in thin cells via X-ray imaging. Our methodology enables one to identify the bulk liquid volume, liquid channels and cavities, and separate them from the solidified structures. It also enables morphological analysis within the solid domain, including automatic decomposition into dominant grains by orientation and connectivity. Furthermore, convective plumes within the bulk liquid can also be studied. The applied image filters enable the developed code (will be made open-source) to reliably operate even for single images with low signal- and contrast-to-noise ratio at low image resolution. This is demonstrated by applying the code to several in situ dynamic X-ray imaging experiments involving a solidifying gallium-indium alloy in a thin cell. We show that primary spacings, grain (and global) dendrite orientation statistics, convective plume parametrization, etc. can be obtained. The limitations of the presented approach are also explained.

Keywords: Dynamic X-ray imaging; In situ analysis; Image processing; Directional solidification; Liquid metal alloys

Downloads

  • Secondary publication expected from 16.07.2024

Permalink: https://www.hzdr.de/publications/Publ-34092
Publ.-Id: 34092


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

Parvez, A. M.; 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


Predicting Concurrent Structural Mechanical Mechanisms During Microstructure Evolution

Soar, P.; Kao, A.; Shevchenko, N.; Eckert, S.; Djambazov, G.; Pericleous, K.

The interdependence between structural mechanics and microstructure solidification has been widely observed experimentally as a factor leading to undesirable macroscopic properties and casting defects. Despite this, numerical modelling of microstructure solidification often neglects this interaction and is therefore unable to predict key mechanisms such as the development of misoriented grains. This paper presents a numerical method coupling a Finite Volume Structural Mechanics Solver to a Cellular Automata Solidification Solver, where gravity or pressure-driven displacements alter the local orientation and thereby growth behaviour of the solidifying dendrites. Solutions obtained using this model are presented which show fundamental behaviours observed in experiments. The results show that small, localised deformations can lead to significant changes in crystallographic orientation of a dendrite and ultimately affect the overall microstructure development.

Keywords: Structural mechanics; Microstructure solidification; Cellular Automata Solidification; Numerical method; Dendrites

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34090
Publ.-Id: 34090


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

Parvez, A. M.; 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


Microbial consortium: A promising strategy for bioleaching of metals from industrial wastes

Chakankar, M. V.; Hocheng, H.

Advances in biohydrometallurgical technology have made it possible to utilize the microorganisms and their metabolites in the recovery and resource recycling of metals from secondary sources like industrial wastes. Various strategies have been developed to apply these microorganisms to improve the efficiency of the method. Use of microbial consortia is one of the promising strategies. Microbial consortia can be applied in various approaches and this chapter discusses the current applications and some promising emerging technologies that can assist in enhancing the bioleaching performance. Furthermore, interesting applications of microbial consortia for metal recovery from different industrial wastes are described along with the role of consortia and mechanisms involved.

Keywords: Microbial consortia; bioleaching; industrial waste; metal

  • Book chapter
    Christon J Jurst: Microbial Metabolism of Metals and Metalloids, Germany: Springer, 2022, 978-3-030-97184-7, 109-134

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34088
Publ.-Id: 34088


Radiomics-based tumor phenotype determination based on medical imaging and tumor microenvironment in a preclinical setting

Müller, J.; Leger, S.; Zwanenburg, A.; Suckert, T.; Lühr, A.; Beyreuther, E.; von Neubeck, C.; Krause, M.; Löck, S.; Dietrich, A.; Bütof, R.

Background and purpose: Radiomics analyses have been shown to allow for the prediction of clinical outcomes of radiotherapy based on medical imaging-derived biomarkers. However, the biological meaning attached to such image features often remains unclear, thus hindering the clinical translation of radiomics analysis. In this manuscript, we describe a preclinical radiomics trial, which attempts to establish correlations between the expression of histological tumor microenvironment (TME)- and magnetic resonance imaging (MRI)-derived image features.
Materials & Methods: 114 mice were transplanted with the radioresistant and radiosensitive head and neck squamous cell carcinoma cell lines SAS and UT-SCC-14, respectively. The models were irradiated with five fractions of protons or photons using different doses. Post-treatment T1-weighted MRI and histopathological evaluation of the TME was conducted to extract quantitative features. We performed radiomics analysis with leave-one-out cross validation to identify the features most strongly associated with the tumor’s phenotype. Performance was assessed using the area under the curve (AUCValid) and F1-score. Furthermore, we analyzed correlations between TME- and MRI features using the Spearman correlation coefficient ρ.
Results: TME and MRI-derived features showed good performance (AUCValid, TME = 0.72, AUCValid, MRI = 0.85, AUCValid, Combined = 0.85) individual tumor phenotype prediction. We found correlation coefficients of ρ = - 0.46 between hypoxia-related TME features and texture-related MRI features. Tumor volume was a strong confounder for MRI feature expression.
Conclusion: We demonstrated a preclinical radiomics implementation and notable correlations between MRI- and TME hypoxia-related features. Developing additional TME features may help to further unravel the underlying biology.

Permalink: https://www.hzdr.de/publications/Publ-34087
Publ.-Id: 34087


Development of the bioionflotation process using rhamnolipid for metal recovery from industrial wastewaters

Chakankar, M. V.; Oestreich, A.; Pollmann, K.; Rudolph, M.

Recovery of critical metals like Gallium (Ga) from industrial wastewaters helps in resource recycling and reducing environmental burden. Low concentration of target metals and high concentration of unwanted metals makes such a recovery challenging. Ion flotation is a promising separation and recovery process in this regards. However, low selectivity and secondary pollution by used chemicals limits its practical application. Rhamnolipid is microbial biosurfactant having both hydrophilic and hydrophobic moieties. High surface activity and metal complexing ability makes rhamnolipid a molecule of interest for their application in bioionflotation for selective recovery of metals from wastewaters. When applied as a flotation reagent, rhamnolipid plays a dual role of frother and ion collector. Our objective is to provide an insight into the role of rhamnolipid in the process and its efficiency for removal of Ga by bioionflotation. The results of these investigations provide an insight into the process fundamentals and form the basis for development of the bioionflotation process for resource recovery from wastewaters.

Keywords: Rhamnolipid; Bioionflotation; Metal; Wastewater; Gallium

  • Lecture (Conference)
    ACS Spring 2022, 20.-24.03.2022, San Diego, CA, United States of America

Permalink: https://www.hzdr.de/publications/Publ-34086
Publ.-Id: 34086


Significance of pulmonary endothelial injury and the role of cyclooxygenase-2 and prostanoid signaling

Nickl, R.; Hauser, S.; Pietzsch, J.; Richter, T.

The endothelium plays a key role in the dynamic balance of hemodynamic, humoral and inflam-matory processes in the human body. Its central importance and the resulting therapeutic concepts are the subject of ongoing research efforts and form the basis for the treatment of numerous dis-eases. The pulmonary endothelium is an essential component for the gas exchange in humans. Pulmonary endothelial dysfunction has serious consequences for the oxygenation with the poten-tial of consecutive multiple organ failure. Therefore, we provide an overview of pulmonary endo-thelial dysfunction due to viral, bacterial and fungal infections, ventilator induced injury or aspi-ration in a medical context. The elucidation of the underlying causes and mechanisms of damage and repair results in new therapeutic approaches. Specific emphasis is placed on the processes leading to the induction of cyclooxygenase-2 and downstream prostanoid-based signaling path-ways associated with this enzyme.

Keywords: acute respiratory distress; cyclooxygenases; eicosanoids; endothelial permeability; endothelial barrier dysfunction; lung endothelium; lung infection; lung inflammation; prostanoid receptors; traditional non-steroidal anti-inflammatory drugs (tNSAIDs)

Permalink: https://www.hzdr.de/publications/Publ-34085
Publ.-Id: 34085


Improvement of wire-mesh sensor accuracy via adapted circuit design and integrated energy loss measurement

de Assis Dias, F.; Wiedemann, P.; Schleicher, E.; Da Silva, M. J.; Hampel, U.

We reviewed the electronic principles and design of the wire-mesh sensor with respect to inherent energy losses. From the analysis we derived a new circuit design with an optimized amplifier circuit and extended the sensor by an extra transmitter electrode embedded into the dielectric construction material. The latter allows an inherent determination of the energy losses that cannot be suppressed by circuit optimization only. Experimental analysis showed that we achieve an improvement in measurement accuracy with respect to the local and average phase fractions. Deviations in a single crossing point are reduced from more than 30% down to less than 5% and deviations in the average phase fraction are reduced from more than 15% down to less than 2%.

Keywords: wire-mesh sensor; multiphase flow; impedance measurement; energy loss

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34084
Publ.-Id: 34084


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

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


Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection

Schindler, F.; Eckert, S.; Zürner, T.; Schumacher, J.; Vogt, T.

The large-scale flow structure and the turbulent transfer of heat and momentum are directly measured in highly turbulent liquid metal convection experiments for Rayleigh numbers varied between $4 \times 10^5$ and $\leq 5 \times 10^9$ and Prandtl numbers of $0.025~\leq~Pr~\leq ~0.033$. Our measurements are performed in two cylindrical samples of aspect ratios $\Gamma =$ diameter/height $= 0.5$ and 1 filled with the eutectic alloy GaInSn. The reconstruction of the three-dimensional flow pattern by 17 ultrasound Doppler velocimetry sensors detecting the velocity profiles along their beamlines in different planes reveals a clear breakdown \FIN{of coherence} of the large-scale circulation for $\Gamma = 0.5$. As a consequence, the scaling laws for heat and momentum transfer inherit a dependence on the aspect ratio. We show that this breakdown of coherence is accompanied with a reduction of the Reynolds number $Re$. The scaling exponent $\beta$ of the power law $Nu\propto Ra^{\beta}$ crosses \FIN{eventually} over from $\beta=0.221$ to 0.124 when the liquid metal flow at $\Gamma=0.5$ reaches $Ra\gtrsim 2\times 10^8$ \FIN{and the coherent large-scale flow is completely collapsed}.

Keywords: Rayleigh-Benard Convection; liquid metal; low Pr; cylinder; Ultrasound Doppler Velocimetry; large scale flow structure

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34082
Publ.-Id: 34082


Dynamics of hot refluxing electrons in ultra-short relativistic laser foil interactions

Huang, L.; Molodtsova, M.; Ferrari, A.; Laso García, A.; Toncian, T.; Cowan, T.

We investigate the dynamics of hot refluxing electrons in the interaction of an ultra-short relativistic laser pulse with a thin foil target via particle-in-cell (PIC) simulations, that is governed by the multidimensional spatio-temporal evolution of self-generated sheath field. The comparison of time-integrated energy spectra of refluxing and escaping electrons indicates the refluxing efficiency is higher than 95\% in average for each bounce. The characteristics of wide transverse spatial distribution and energy-resolved angular distribution caused by the refluxing electrons show a direct correlation with the angular-dependent photon yield of Bremsstrahlung emission, as verified by the hybrid simulations of coupling the PIC results with Monte-Carlo particle transport code. We further clarify the energy dissipation mechanisms of refluxing electrons through the recirculation in the thin target under the electron-refluxing dominated regime, and conclude that the self-generated sheath field plays a dominant role over the competing processes such as the radiation loss, collisional stopping and anomalous inhibition via the resistive field. The lifetime of recirculation is calculated to be few hundred femtoseconds, that is one order of magnitude shorter than the time scale of collisional dissipation, while one order of magnitude longer than the laser pulse duration. The results could provide useful insight to understand the hot electron transport and stopping, secondary radiation generation and ion acceleration in the high energy density plasmas.

Keywords: ultra-short relativistic laser pulse; particle-in-cell; refluxing electrons; high energy density plasmas; plasma physics

Permalink: https://www.hzdr.de/publications/Publ-34080
Publ.-Id: 34080


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


The QED four – photon amplitudes off-shell: part 1

Ahmadiniaz, N.; Lopez-Arcos, C.; Lopez-Lopez, M. A.; Schubert, C.

The QED four-photon amplitude has been well-studied by many authors, and on-shell is treated in many textbooks. However, a calculation with all four photons off-shell is presently still lacking, despite of the fact that this amplitude appears off-shell as a subprocess in many different contexts, in vacuum as well as with some photons connecting to external fields. The present paper is the first in a series of four where we use the worldline formalism to obtain this amplitude explicitly in terms of hypergeometric functions, and derivatives thereof, for both scalar and spinor QED. The formalism allows us to unify the scalar and spinor loop calculations, to avoid the usual breaking up of the amplitude into three inequivalent Feynman diagrams, and to achieve manifest transversality as well as UV finiteness at the integrand level by an optimized version of the integration-by-parts procedure originally introduced by Bern and Kosower for gluon amplitudes. The full permutation symmetry is maintained throughout, and the amplitudes get projected naturally into the basis of five tensors introduced by Costantini et al. in 1971. Since in many applications of the “four-photon box” some of the photons can be taken in the low-energy limit, and the formalism makes it easy to integrate out any such leg, apart from the case of general kinematics (part 4) we also treat the special cases of one (part 3) or two (part 2) photons taken at low energy. In this first part of the series, we summarize the application of the worldline formalism to the N-photon amplitudes and its relationto Feynman diagrams, derive the optimized tensor-decomposed integrands of the four-photon amplitudes in scalar and spinor QED, and outline the computational strategy tobe followed in parts 2 to 4. We also give an overview of the applications of the four-photon amplitudes, with an emphasis on processes that naturally involve some off-shell photons, either because external fields are involved or we use the amplitude as a building block for higher-order process. The case where all photons are taken at low energy (the “Euler-Heisenberg approximation”) is simple enough to be doable for arbitrary photon numbers,and we include it here for completeness

Keywords: Four-photon amplitude; Worldline formalism; Bern-Kosower formalism

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34076
Publ.-Id: 34076


Non-perturbative gauge transformations of arbitrary fermion correlation functions inquantum electrodynamics

Nicasio, J.; Edwards, J. P.; Schubert, C.; Ahmadiniaz, N.

We study the transformation of the dressed electron propagator and the general N-point functions under a change in the covariant gauge of internal photon propagators. We re-establish the well known Landau-Khalatnikov-Fradkin transformation for the propagator and generalise it to arbitrary correlation functions in configuration space, finding that it coincides with the analogous result for scalar fields. We comment on the consequences for perturbative application in momentum-space.

Keywords: LKF transformations; Worldline formalism; Dressed fermion propagator

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34075
Publ.-Id: 34075


Color-kinematics duality from the Bern-Kosower formalism

Ahmadiniaz, N.; Balli, F. M.; Lopez-Arcos, C.; Quintero Velez, A.; Schubert, C.

Berends-Giele currents are fundamental building blocks for on-shell amplitudes in non-abelian gauge theory. We present a novel procedure to construct them using the Bern-Kosower formalism forone-loop gluon amplitudes. Applying the pinch procedure of that formalism to a suitable special casethe currents are naturally obtained in terms of multi-particle fields and obeying color-kinematics duality. As a feedback to the Bern-Kosower formalism, we outline how the
multi-particle polarisations and field-strength tensors can be used to significantly streamline the pinch procedure

Keywords: Berends-Giele currents; on-shell amplitudes; Bern-Kosower formalism

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34074
Publ.-Id: 34074


Numerical simulation of tidal synchronization of the Large-Scale Circulation in Rayleigh-Bénard Convection with aspect ratio 1

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

A possible explanation for the apparent phase stability of the 11.07-year Schwabe cycle of the solar dynamo was the subject of a series of recent papers [1, 2, 3]. The synchronization of the helicity of an instability with azimuthal wavenumber m=1 by a tidal m=2 perturbation played a key role here. To analyze this type of interaction in a paradigmatic set-up, we study a thermally driven Rayleigh-Bénard Convection (RBC) of a liquid metal under the influence of a tide-like electromagnetic forcing. As shown previously, the time-modulation of this forcing emerges as a peak frequency in the m=2 mode of the radial flow velocity component. In this paper we present new numerical results on the interplay between the Large Scale Circulation (LSC) of a RBC flow and the time modulated electromagnetic forcing.

Keywords: Magnetohydrodynamics; Rayleigh-Bénard convection; liquid metal flow; electromagnetic forcing; CFD

Related publications

  • Open Access Logo Lecture (Conference)
    RMHD-2021, 20.-22.09.2021, Perm, Russia Federation
  • Open Access Logo Magnetohydrodynamics 58(2022)3, 285-292
    DOI: 10.22364/mhd.58.3.5
    arXiv: 2209.07173

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34073
Publ.-Id: 34073


Manifest colour-kinematics duality and double-copy in the string-based formalism

Ahmadiniaz, N.; Balli, F. M.; Corradini, O.; Lopez-Arcos, C.; Quintero Velez, A.; Schubert, C.

The relation for the gravity polarisation tensor as the tensor product of two gluon polarisation vectors has been well-known for a long time, but a version of this relation for multi-particle fields is presently still not known. Here we show that in order for this to happen we first have to ensure that the multi-particle polarisations satisfy color-kinematics duality. In previous work, it has been show that this arises naturally from the Bern-Kosower formalism for one-loop gluon amplitudes, and here we show that the tensor product for multi-particle fields arise naturally in the Bern-Dunbar-Shimada formalism for one-loop gravity amplitudes. This allows us to formulate a new prescription for double-copy gravity Berends-Giele currents,and to obtain both the colour-dressed Yang-Mills Berends-Giele currents in the Bern-Carrasco-Johanssongauge and the gravitational Berends-Giele currents explicitly. An attractive feature of our formalism is that it never becomes necessary to determine gauge transformation terms. Our double-copy prescription can also be applied to other cases, and to make this point we derive the double-copy perturbers for α′-deformed gravity and the bi-adjoint scalar model

Keywords: Bern-Dunbar-Shimada formalism; Berends-Giele currents; color-kinematics duality; gravity amplitudes

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34072
Publ.-Id: 34072


Analyzing a modulated electromagnetic m=2 forcing and its capability to synchronize the Large Scale Circulation in a Rayleigh-Bénard cell of aspect ratio Г = 1

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

The synchronization of the helicity of an instability with azimuthal wavenumber m = 1 by a weak tidal m = 2 perturbation might play a key role in explaining the phase-stable Schwabe cycle of the solar dynamo [1]. In order to elucidate this type of interaction, we study a thermally driven Rayleigh-Bénard Convection (RBC) under a tide-like influence. We focus first on the generation of the m = 2 mode flow by an electromagnetic forcing, and second on its low-frequency modulation. In the last part, we present preliminary results on the interaction of this perturbation with the sloshing/torsional motion of the Large Scale Circulation (LSC) of an RBC flow. While the main focus of the paper is on the numerical side, some comparisons with experimental results are also made.

Keywords: Magnetohydrodynamics; Rayleigh-Bénard convection; liquid metal flow; electromagnetic forcing; CFD

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34071
Publ.-Id: 34071


Worldline master formulas for the dressed electron propagato, part 2: on-shell amplitudes

Ahmadiniaz, N.; Banda Guzman, V. M.; Bastianelli, F.; Corradini, O.; Edwards, J. P.; Schubert, C.

In the first part of this series, we employed the second-order formalism and the“symbol” map to construct a particle path-integral representation of the electron propagator in a background electromagnetic field, suitable for open fermion-line calculations. Its main advantages are the avoidance of long products of Dirac matrices, and its ability to unify whole sets of Feynman diagrams related by permutation of photon legs along the fermion lines. We obtained a Bern-Kosower type master formula for the fermion propagator, dressedwithNphotons, in terms of the “N-photon kernel,” where this kernel appears also in“subleading” terms involving only N−1 of the N-photons.In this sequel, we focus on the application of the formalism to the calculation of on-shell amplitudes and cross-sections. Universal formulas are obtained for the fully polarised matrix elements of the fermion propagator dressed with an arbitrary number of photons, as well as for the corresponding spin-averaged cross-sections. A major simplification of the on-shell case is that the subleading terms drop out, but we also pinpoint other, less obvious simplifications. We use integration by parts to achieve manifest transversality of these amplitudes at the integrand level and exploit this property using the spinor helicity technique. We give a simple proof of the vanishing of the matrix element for all “+” photon helicities in the massless case and find a novel relation between the scalar and spinor spin-averaged cross-sections in the massive case. Testing the formalism on the standard linear Comptonscattering process, we find that it reproduces the known results with remarkable efficiency. Further applications and generalisations are pointed out.

Keywords: On-shell amplitudes; Dressed fermion propagator; Worldline formalism

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34069
Publ.-Id: 34069


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


Tadpole contribution to magnetic photon-graviton conversion

Ahmadiniaz, N.; Bastianelli, F.; Karbstein, F.; Schubert, C.

Photon-graviton conversion in a magnetic field is a process that is usually studied at tree-level, but the one-loop corrections due to scalars and spinors have also been calculated. Differently from the tree-level process, at one-loop one finds the amplitude to depend on the photon polarization, leading to dichroism. However, previous calculations overlooked tadpole contribution of the type that was considered to be vanishing in QED for decades but erroneously so, as shown by H. Gies and one of the authors in 2016. Here we compute this missing diagram in closed form and show that it does not contribute to dichroism.

Keywords: Photon-Graviton amplitude; Worldline formalism; Tadpole contribution

  • Open Access Logo Contribution to proceedings
    Sixteenth Marcel Grossmann Meeting, 05.-10.07.2021, Virtual Meeting, Virtual Meeting
    Proceedings of the Sixteenth Marcel Grossmann Meeting: WORLD SCIENTIFIC, 978-981-126-976-9, 4393-4400
    DOI: 10.1142/13149
    arXiv: https://arxiv.org/pdf/2111.01980.pdf

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34065
Publ.-Id: 34065


Data publication: Bubble Formation from Sub-millimetre Orifices

Mohseni, E.

This is the data used in the thesis "Bubble Formation from Sub-millimetre Orifices".

Keywords: Bubble formation; Sub-millimetre orifice; Bubble dynamics; Modelling; Bubble in-rush; Controlled bubble formation

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34063
Publ.-Id: 34063


Bubble Formation from Sub-millimetre Orifices

Mohseni, E.

Efficient contacting of gas and liquid is an important problem in many industrial processes. Examples can be found (bio-) chemical engineering, medicine, water and wastewater treatment among others. To operate these processes in a more efficient manner, usually the gas phase is dispersed into the continuous phase in the form of bubbles. In this case, it is often required to reduce the bubble size to enhance the mass transfer. This is often done by scaling down the opening from which bubbles are generated. Hence, gas bubble generation from sub-millimetre orifices has been an interesting topic in research and technology. The present thesis is an endeavour to bring more physical insights on the mechanism of bubble formation and detachment from sub-millimetre orifices as this phenomenon is not yet well-understood.

Formation of bubbles from a submerged orifice depends on various parameters such as orifice diameter dor, gas flow rate Q, volume of the gas reservoir upstream of the orifice Vc and others. On the basis of these parameters, the bubble growth dynamics, bubbling regime, and bubble volume strongly vary. To further advance the fundamental understanding of the bubble formation at sub-millimetre orifices, two series of experiments were conducted, and the nfluence of the design parameters namely dor, Q, and Vc were investigated in detail. In the experiments, pressurized air is used to generate bubbles in eionized water using stainless-steel orifices in the range of 0.03 mm< dor <1 mm. Based on the findings of these experiments, a mechanism is designed to control the formation process and therefore the bubble volume. Accordingly, in a separate series of experiments, periodic modulations in the gas reservoir is utilised to control the formation and detachment of bubbles from the orifice.

In the first series of experiments, the influence of dor and Q on bubble formation dynamics are investigated. It is observed that the mechanism of bubble formation is not uniform throughout the sub-millimetre range. For orifices with dor > 0.4 mm, the bubble volume Vb progressively increases with both dor and Q. For smaller orifices, however, Vb is determined by the number of subsequent bubbles that merge with the leading bubble after its departure. This is eferred to as in-rush bubbling and it even occurs in the lowest range of Q, at which larger orifices generate bubbles with a single detachment. The bubble formation from orifices with dor < 0.4 mm is highly affected by the gas kinetic energy. Hence, in the balance of forces acting on the bubble, the gas momentum force and the liquid inertia force substantially contribute to the bubble growth rate and therefore Vb.

In the second series of experiments the influence of Vc on bubble formation is investigated. Experimental results showed that, by increasing Vc, the magnitude of the pressure variations in the gas reservoir reduces. Moreover, enlarging the gas reservoir, not only results in a variable gas flux q into the bubble, but also the average gas flux elevates with Vc. Consequently, larger bubbles at lower bubbling frequencies are generated. The impact of Vc on bubble formation for dor < 0.4 mm is, however, limited as the gas kinetic energy readily affects the bubble formation. According to the findings of the first two series of experiments, new models are developed to calculate Vb. The models agree well with experimental results. Moreover, new correlations for bubble detachment are delivered which correlate the non-spherical bubble shape from the observations in the experiments to the spherical bubble volumes calculated from the models.

Last but not least, a control mechanism by means of continuous pressure modulation of the gas phase in the reservoir upstream of the orifice is experimentally investigated. The modulation comes from a loudspeaker, which is mounted in the gas reservoir. The modulation propagates through the pipe to an orifice with a 0.5 mm diameter. Consequently, the onset and termination of the formation process is forced by each successive compression and rarefaction of the acoustic waves. Using the control mechanism, the bubble diameter can be reduced by a factor of four of that generated by uncontrolled formation process. Studying the force balance on the bubble revealed that the detachment of the bubble in the controlled method is determined by the hydrodynamic forces. Moreover, applicability of the Rayleigh-Plesset equation for calculation of the bubble size is examined for the presented bubble generator.

Keywords: Bubble formation; Sub-millimetre orifice; Bubble dynamics; Modelling; Bubble in-rush; Controlled bubble formation

Related publications

  • Doctoral thesis
    TU Dresden, 2021
    Mentor: Prof. Dr.–Ing. habil. Dr. h.c. Uwe Hampel
    202 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34062
Publ.-Id: 34062


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

Related publications

  • 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


Cellular plasticity upon proton irradiation determines tumor cell radiosensitivity

Schniewind, I.; Hadiwikarta, W. W.; Grajek, J.; Poleszczuk, J.; Richter, S.; Peitzsch, M.; Müller, J.; Klusa, D.; Beyreuther, E.; Löck, S.; Lühr, A.; Frosch, S.; Groeben, C.; Sommer, U.; Krause, M.; Dubrovska, A.; von Neubeck, C.; Kurth, I.; Peitzsch, C.

Novel particle therapy was implemented into standard-of-care for cancer patients during the
last years. However, experimental studies investigating cellular and molecular mechanisms
are lacking and prognostic biomarker are urgently needed. Cancer stem cell
(CSC)-related biomarkers such as aldehyde dehydrogenase (ALDH) are known to cellular radiosensitivity by affecting defense against reactive
oxygen species, DNA damage repair and cell survival. Within a previous study, we found that ionizing radiation itself enriches for
ALDH-positive CSCs.
Within the present study, we investigated CSC marker dynamics in prostate cancer, head and neck cancer and glioblastoma cells upon proton beam irradiation. We found that proton irradiation has an increased CSC targeting potential, reduced methylation of activating histone marks and
a lower induction of cellular senescence compared to conventional photon irradiation. Interestingly, mathematical modeling
indicated to differences in plasticity rates among ALDH-positive CSCs and ALDH-negative cancer cells between the two irradiation types.

Permalink: https://www.hzdr.de/publications/Publ-34059
Publ.-Id: 34059


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


Effect of neutron flux on irradiation-induced microstructure and hardening of reactor pressure vessel steel

Ulbricht, A.; Hernández-Mayoral, M.; Oñorbe, E.; Etienne, A.; Radiguet, B.; Hirschmann, E.; Wagner, A.; Hein, H.; Bergner, F.

Existing knowledge about the effect of neutron irradiation on the mechanical properties of reac-tor pressure vessel steels under reactor service conditions relies to a large extent on accelerated irradiations realized by exposing steel samples to a higher neutron flux. A deep understanding of flux effects is, therefore, vital for gaining service-relevant insight on the mechanical property degradation. Existing studies on flux effects often suffer from incomplete descriptions of the ir-radiation-induced microstructure. Our study aims at giving a detailed picture of irradia-tion-induced nanofeatures by applying complementary methods using atom probe tomography, positron annihilation, small-angle neutron scattering and transmission electron microscopy. The characteristics of the irradiation-induced nanofeatures and the dominant factors responsible for the observed increase of Vickers hardness are identified. The results rationalize why pronounced flux effects on the nanofeatures, in particular on solute atom clusters, only give rise to small or moderate flux effects on hardening.

Keywords: reactor pressure vessel steel; neutron irradiation; flux effect; microstructure; atom probe tomography; positron annihilation spectroscopy; small-angle neutron scattering; TEM

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34055
Publ.-Id: 34055


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


Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen mit biologisch basierten Aufbereitungstechnologien Identifizierung und Verwendung von Material spezifischen Biomaterialien in der Ressourcenrückgewinnung

Lederer, F.

Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen mit biologisch basierten Aufbereitungstechnologien
Identifizierung und Verwendung von Material spezifischen Biomaterialien in der
Ressourcenrückgewinnung

Keywords: Biotechnologie; Biolaugung; Bioflotation; Biokollekt

  • Invited lecture (Conferences) (Online presentation)
    Vorlesung Gezieltes Herauslösen von Substanzen aus Roh-und Reststoffen, 17.01.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-34050
Publ.-Id: 34050


Generation of arbitrarily polarized GeV lepton beams via nonlinear Breit-Wheeler process

Xue, K.; Guo, R.-T.; Wan, F.; Shaisultanov, R.; Chen, Y.-Y.; Xu, Z.-F.; Ren, X.-G.; Hatsagortsyan, K. Z.; Keitel, C. H.; Li, J.-X.

Generation of arbitrarily spin-polarized lepton (here refer in particular to electron and positron) beams has been investigated in the single-shot interaction of high-energy polarized γ photons with an ultraintense asymmetric laser pulse via nonlinear Breit-Wheeler (BW) pair production. We develop a fully spin-resolved semi-classical Monte Carlo method to describe the pair creation and polarization in the local constant field approximation. In nonlinear BW process the polarization of created pairs is simultaneously determined by the polarization of parent γ photons, the polarization and asymmetry of scattering laser field, due to the spin angular momentum transfer and the asymmetric spin-dependent pair production probabilities, respectively. In considered all-optical method, dense GeV lepton beams with average polarization degree up to about 80% (adjustable between the transverse and longitudinal components) can be obtained with currently achievable laser facilities, which could be used as injectors of the polarized e+e− collider to search for new physics beyond the Standard Model.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34049
Publ.-Id: 34049


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.

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


Data Publication: Enzymatic Hydrolysis of Triglycerides at the Water–Oil Interface Studied via Interfacial Rheology Analysis of Lipase Adsorption Layers

Javadi, A.; Dowlati, S.; Shourni, S.; Rusli, S.; Eckert, K.; Miller, R.; Kraume, M.

The enzymatic hydrolysis of sunflower oil occurs at the water–oil interface. Therefore, the characterization of dynamic interfacial phenomena is essential for understanding the related mechanisms for process optimizations. Most of the available studies for this purpose deal with averaged interfacial properties determined via reaction kinetics and dynamic surface tension measurements. In addition to the classical approach for dynamic surface tension measurements, here, the evolution of the dilational viscoelasticity of the lipase adsorbed layer at the water–oil interface is characterized using profile analysis tensiometry. It is observed that lipase exhibits nonlinear dilational rheology depending on the concentration and age of the adsorbed layer. For reactive water–oil interfaces, the response of the interfacial tension to the sinusoidal area perturbations becomes more asymmetric with time. Surface-active products of the enzymatic hydrolysis of triglycerides render the interface less elastic during compression compared to the expansion path. The lipolysis products can facilitate desorption upon compression while inhibiting adsorption upon expansion of the interface. Lissajous plots provide an insight into how the hysteresis effect leads to different interfacial tensions along the expansion and compression routes. Also, the droplet shape increasingly deviates from a Laplacian shape, demonstrating an irreversible film formation during aging and ongoing hydrolysis reaction, which supports our findings via interfacial elasticity analysis.

Keywords: Enzymatic reaction at the water oil interface; Hydrolysis of triglycerides in sunflower oil; Biodiesel; Dynamic surface phenomena; Interfacial elasticity; Protein adsorption at interface

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34042
Publ.-Id: 34042


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


Proof of concept for controlling an electromagnetic brake using contactless inductive flow tomography

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

The development of closed control loops for electromagnetic actuators in continuous casting based on the current flow conditions of the liquid steel in the mold is challenging due to the opaqueness and the high temperature of the melt. In this work we will investigate the applicability of Contactless Inductive Flow Tomography (CIFT) as a real-time measurement technique for controlling the strength of a ruler type Electromagnetic Brake (EMBr) in a model of a continuous caster. Because CIFT relies on the measurement of the small flow induced perturbation of an applied magnetic field, the measurement system is very sensitive to changes of the strength the EMBr. We will shortly delineate the developed compensation method that is able to cope with the non-linearity of the ferromagnetic yoke of the brake. In combination with the real-time reconstruction algorithm for solving the linear
inverse problem, CIFT is able to visualize the flow structure in the mold in real-time with a time resolution of 1 Hz.

As a proof of concept of a closed control loop, we implemented a simple controller which switches the EMBr off, when the impingement positions of the jets at the narrow faces are below a critical threshold. The implemented controller and the experiment will be described in detail.

Keywords: continuous casting; electromagnetic brake; contactless inductive flow tomography; control loop

  • Lecture (Conference)
    12th PAMIR international conference on fundamental and applied MHD, 04.-8.7.2022, Krakow, Poland
  • Contribution to proceedings
    12 th PAMIR international conference on fundamental and applied MHD, 04.-08.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-34039
Publ.-Id: 34039


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

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


Data Publication: Structure-Based Design, Optimization and Development of [18F]LU13, a novel radioligand for CB2R Imaging in the Brain with PET

Moldovan, R.-P.; Gündel, D.; Deuther-Conrad, W.; Ueberham, L.; Kaur, S.; Otikova, E.; Teodoro, R.; Lai, T. H.; Clauß, O.; Scheunemann, M.; Bormans, G.; Kopka, K.; Bachmann, M.; Brust, P.

The cannabinoid receptor type 2 (CB2R) is an attractive target for diagnosis and therapy of neurodegenerative diseases and cancer. Recently, we reported a novel naphthyrid-2-one based positron-emission tomography (PET) radioligand for imaging of the CB2R in the brain ([18F]5). In this study we aimed at the development of a novel 18F-labeled CB2R radioligand with improved binding properties and metabolic stability. Starting from the structure of 5, we developed a novel series of fluorinated derivatives by modifying the substituents at the naphthyrid-2-one subunit. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RKi = 0.6 nM; CB1RKi/CB2RKi > 1000) and was selected for radiolabeling with 18F and biological characterization. The radiofluorination was performed starting from the corresponding bromo-precursor (31) bearing a fully deuterated N-alkyl chain to protect against defluorination. The in vitro evaluation of [18F]LU13 proved the high binding affinity of the radioligand towards rat (rCB2RKD = 0.2 nM) and human (hCB2RKD = 1.1 nM) CB2R. Metabolism studies in mice revealed a metabolic stability at 30 min p.i. with fractions of parent compound of >80% in the brain and 90% in the spleen with only trace of defluorination products detected in plasma. PET imaging in a rat model of vector-based/related overexpression in the striatum revealed a high signal to background ratio, demonstrating the ability of [18F]LU13 to reach and selectively label the hCB2R in the brain. Thus, [18F]LU13 is a novel and highly promising PET radioligand for the imaging of up regulated CB2R expression under pathological conditions in the brain.

Keywords: cannabinoid receptor type 2; naphthyrid-2-one; binding affinity

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34030
Publ.-Id: 34030


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.

Related publications

Downloads

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

Related publications

  • 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

Related publications

  • Patent
    DE: 10 2020 120 788.3

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


Annual Report 2021 - Institute of Ion Beam Physics and Materials Research

Faßbender, J.; Helm, M.; Zahn, M.; Zahn, P.

The year 2021 was still overshadowed by waves of the COVID-19 pandemic, although the arrival of efficient vaccinations together with the experience of the preceding year gave us a certain routine in handling the situation. By now the execution of meetings in an online mode using zoom and similar video conference systems has been recognized as actually being useful in certain situations, e.g. instead of flying across Europe to attend a three-hours meeting, but also to be able to attend seminars of distinguished scientists which otherwise would not be easily accessible.
The scientific productivity of the institute has remained on a very high level, counting 190 publications with an unprecedented average impact factor of 8.0. Six outstanding and representative publications are reprinted in this Annual Report. 16 new third-party projects were granted, among them 7 DFG projects, but very remarkably also an EU funded project on nonlinear magnons for reservoir computing with industrial participation of Infineon Technologies Dresden and GlobalFoundries Dresden coordinated by Kathrin Schultheiß of our Institute.
The scientific success was also reflected in two HZDR prizes awarded to the members of the Institute: Dr. Katrin Schultheiß received the HZDR Forschungspreis for her work on “Nonlinear magnonics as basis for a spin based neuromorphic computing architecture”, and Dr. Toni Hache was awarded the Doktorandenpreis for his thesis entitled “Frequency control of auto-oscillations of the magnetization in spin Hall nano-oscillators”. Our highly successful theoretician Dr. Arkady Krasheninnikov was quoted as Highly Cited Researcher 2021 by Clarivate.
The new 1-MV facility for accelerator mass spectrometry (AMS) has been ordered from NEC (National Electrostatics Corporation). Design of a dedicated building to house the accelerator, the SIMS and including additional chemistry laboratories for enhanced sample preparation capabilities has started and construction is planned to be finished by mid 2023, when the majority of the AMS components are scheduled for delivery.
In the course of developing a strategy for the HZDR - HZDR 2030+ Moving Research to the NEXT Level for the NEXT Gens - six research focus areas for our institute were identified.
Concerning personalia, it should be mentioned that the long-time head of the spectroscopy department PD Dr. Harald Schneider went into retirement. His successor is Dr. Stephan Winnerl, who has been a key scientist in this department already for two decades. In addition, PD Dr. Sebastian Fähler was hired in the magnetism department who transferred several third-party projects with the associated PhD students to the Institute and strengthens our ties to the High Magnetic Field Laboratory, but also to the Institute of Fluid Dynamics.
Finally, we would like to cordially thank all partners, friends, and organizations who supported our progress in 2021. First and foremost we thank the Executive Board of the Helmholtz-Zentrum Dresden-Rossendorf, the Minister of Science and Arts of the Free State of Saxony, and the Ministers of Education and Research, and of Economic Affairs and Climate Action of the Federal Government of Germany. Many partners from universities, industry and research institutes all around the world contributed essentially, and play a crucial role for the further development of the institute. Last but not least, the directors would like to thank all members of our institute for their efforts in these very special times and excellent contributions in 2021.

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-118 2022
    ISSN: 2191-8708, eISSN: 2191-8716

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34008
Publ.-Id: 34008


Isobar separation with cooled ions and laser light for compact AMS facilities

Lachner, J.; Findeisen, S.; Golser, R.; Kern, M.; Marchhart, O.; Martschini, M.; Wallner, A.; Wieser, A.

Ion-Laser InterAction Mass Spectrometry (ILIAMS) slows down anions to thermal kinetic energies in a radiofrequency quadrupole (RFQ) filled with He buffer gas. Laser light (e.g. 532 nm) is overlapped with the
decelerated anions to separate isobars via photodetachment.
Here, we present two applications of ILIAMS at the 3MV Vienna Environmental Research Accelerator (VERA): 26Al is an established AMS nuclide but its detection can be improved using AlO−, which is formed more likely than the customarily applied Al−. ILIAMS suppresses the isobar 26Mg by neutralization of MgO− and overcomes the disadvantage of AlO− compared to Al−, where Mg− is not extracted from the ion source. This enhances the sensitivity of 26Al detection and the prolific AlO− beam can be used at facilities with terminal voltages
<10 MV. 135,137Cs measurements are presented as an example of highly sensitive detection of novel AMS nuclides. In this case, we use 135,137CsF2− anions and ILIAMS suppresses the isobaric 135,137BaF− .
We furthermore present a new design of a modular ion cooler with multiple RFQ sections. With more control of the ion energy during their passage through the RFQ we want to improve the transport efficiency for molecular anions. This ion cooler will be integrated in a new 1MV AMS facility at Dresden in 2023.

Related publications

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    DPG Frühjahrstagung 2022 Erlangen, 14.-18.03.2022, Erlangen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34007
Publ.-Id: 34007


Late Pleistocene glacial advances, equilibrium-line altitude changes and paleoclimate in the Jakupica Mt. (North Macedonia)

Ruszkiczay-Rüdiger, Z.; Kern, Z.; Temovski, M.; Madarász, B.; Milevski, I.; Lachner, J.; Steier, P.

In the Jakupica Mt. (North Macedonia, Central Balkan Peninsula; ~41.7° N, ~21.4 E; maximum elevation: 2540 m asl) a large plateau glacier was reconstructed. The lowest mapped moraines in the northeastern valleys are at elevations of 1490-1720 m asl and suggest the former existence of glacier tongues of ~3 km length. The maximum ice extent and five deglaciation phases were reconstructed. The equilibrium line altitude (ELA) of the most extended glacial phase is 2073+37/-25 m asl. The 10Be Cosmic Ray Exposure (CRE) age (n=8) of this phase was estimated at 19.3+1.7/-1.3 ka, conformable with the LGM similarly to the nearby Jablanica Mt [1]. CRE ages from the next moraine generation placed the first phase of deglaciation to 18.2+1.0/-3.0 ka (n=8). The samples from the moraine of the penultimate deglaciation phase (n=5) provided CRE ages with large scatter and
biased towards old ages, which is probably the result of inherited cosmogenic nuclide concentrations within the rock [2, 3], as it was suggested in the cirques of the Retezat Mt. [4].
Glacio-climatological modelling was performed under constrains of geomorphological evidence in order to make paleoclimatological inferences. The degree-day model was used to calculate the amount of accumulation required to sustain the glaciological equilibrium assuming a certain temperature drop at the ELA for the most extended stage.
If the LGM mean annual temperature and the increased annual temperature range suggested by pollen-based paleoclimate reconstructions [5] are placed into the glaciological model the estimated annual total melt at the LGM ELA implies much wetter conditions compared to the current climate. This is in contrast with the regional LGM annual precipitation reconstructions of the same dataset, which suggests ~25% decrease in the Jakupica Mt. Alternatively, the model can be constrained with the current annual temperature range and the regional estimates of LGM temperature drop at 6-7 °C. This suggests 1.3 to 1.8 times more simulated precipitation than
today.
These results support paleoclimate models, which predict increased precipitation in this region and suggest that in the Central Balkan region either the precipitation or the annual temperature amplitude (or both) are inaccurate in the pollen-based paleoclimate reconstruction database.

Funding: NKFIH FK124807; GINOP-2.3.2-15-2016-00009; RADIATE 19001688-ST.
[1] Ruszkiczay-Rüdiger et al. 2020. Geomorphology 351: 106985
[2] Ruszkiczay-Rüdiger et al. 2021. GRA, EGU21-4573
[3] Ruszkiczay-Rüdiger et al. 2021. vDEUQUA2021, Book of Abstracts, DOI: 10.5281/zenodo.5526214
[4] Ruszkiczay-Rüdiger et al. 2021. Geomorphology, 107719.
[5] Bartlein, et al. 2011. Clim. Dyn. 37, 775–802.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-34006
Publ.-Id: 34006


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


Comparison of Contactless Inductive Flow Tomography with Ultrasound-Doppler Velocimetry in a large Rayleigh-Bénard Convection Cell

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

Contactless inductive flow tomography (CIFT) can reconstruct the global 3D flow field in liquid metals. The technique is based on measuring very small magnetic fields induced by currents in the conducting liquid arising from the fluid motion under the influence of two primary excitation fields and solving the according linear inverse problem [1]. We present experimental results of CIFT measurements on a large cylindrical vessel with a height of 640 mm and a diameter of 320 mm, i.e. aspect ratio 0.5, filled with the eutectic alloy GaInSn. The liquid metal is heated from the bottom and cooled from the top, i.e. a so-called Rayleigh-Bénard (RB) convection cell. The temperature gradient drives a complex flow, that varies spatially and temporally [2-5].
The experimental set-up includes a number of Fluxgate sensors for highly sensitive measurements of the induced magnetic field in the order of 10 nT [6] as well as Ultrasound-Doppler velocimetry probes, that directly measure the velocity of the flow along their line-of-sight. Our preliminary measurements used only the excitation field in vertical direction, yet show a very high agreement of the time-dependent velocity profiles measured by UDV and the according CIFT data, projected onto the line-of-sight of the UDV sensors.

Acknowledgement
This work was supported by the German Research Foundation (DFG) under project no. 374994652. T.V. and F.S. also thank the DFG for support under the grant VO 2331/1.

REFERENCES
[1] Stefani F., Gundrum T., Gerbeth G., Physical Review E 70: 056306. 2004.
[2] Akashi M. et al., J. Fluid Mech. 932 (2022).
[3] Zürner T. et al., J. Fluid Mech. 876 (2019).
[4] Vogt T. et al., PNAS 115 (2018).
[5] Mitra R. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].
[6] Sieger M. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].

Keywords: contactless inductive flow tomography; liquid metal flow; Rayleigh-Bénard convection; Ultrasound-Doppler velocimetry

  • Lecture (Conference)
    12th pamir International Conference on Fundamental and Applied MHD, 04.-08.07.2022, Krakow, Poland
  • Contribution to proceedings
    12th pamir International Conference on Fundamental and Applied MHD, 04.-08.07.2022, Krakow, Poland
    Proceedings of the 12th pamir International Conference on Fundamental and Applied MHD

Permalink: https://www.hzdr.de/publications/Publ-34002
Publ.-Id: 34002


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


Fractionation of metal(loid)s in three European mine wastes by sequential extraction

Opara, C. B.; Kutschke, S.; Pollmann, K.

Mine waste can constitute environmental hazards, especially when poorly managed. Environmental assessment is essential for estimating potential threats and optimizing mine waste management. This study evaluated a potential environmental risk of sulfidic mine waste samples originating from the Neves Corvo Mine, Portugal and the closed Freiberg mining district, Germany. Metal(loid)s in the waste samples were partitioned into seven operationally defined fractions using the Zeien and Brummer sequential extraction scheme. Results showed similar partitioning patterns for the elements in the waste rock and tailing samples from Neves Corvo Mine; most metal(loid)s showed lower mobility as they were mainly residual-bound. On the contrary, the Freiberg tailing had considerably elevated (24-37%) mobile fractions of Zn, Co, Cd and Mn. The majority of Fe (83-96%) in all samples was retained in the residual fractions, while Ca was highly mobile. Overall, Pb was the most mobile toxic element in the three samples. A large portion of Pb (32-57%) was predominantly found in the most mobilizable fractions of the studied waste samples. This study revealed that the three mine wastes have a contamination potential for Pb, which can be easily released into the environment from these wastes.

Keywords: sulfidic mine waste; metal(loid) fractionation; metal(loid) mobility; sequential leaching/extraction; environmental risk; contamination

Permalink: https://www.hzdr.de/publications/Publ-34000
Publ.-Id: 34000


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

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.

Related publications

  • 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).

Related publications

  • 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).

Related publications

  • 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


Structure-Based Design, Optimization and Development of [18F]LU13, a novel radioligand for CB2R Imaging in the Brain with PET

Gündel, D.; Deuther-Conrad, W.; Ueberham, L.; Kaur, S.; Otikova, E.; Teodoro, R.; Lai, T. H.; Clauß, O.; Scheunemann, M.; Bormans, G.; Bachmann, M.; Kopka, K.; Brust, P.; Moldovan, R.-P.

The cannabinoid receptor type 2 (CB2R) is an attractive target for diagnosis and therapy of neurodegenerative diseases and cancer. Recently, we reported a novel naphthyrid-2-one based positron-emission tomography (PET) radioligand for imaging of the CB2R in the brain ([18F]5). In this study we aimed at the development of a novel 18F-labeled CB2R radioligand with improved binding properties and metabolic stability. Starting from the structure of 5, we developed a novel series of fluorinated derivatives by modifying the substituents at the naphthyrid-2-one subunit. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RKi = 0.6 nM; CB1RKi/CB2RKi > 1000) and was selected for radiolabeling with 18F and biological characterization. The radiofluorination was performed starting from the corresponding bromo-precursor (31) bearing a fully deuterated N-alkyl chain to protect against defluorination. The in vitro evaluation of [18F]LU13 proved the high binding affinity of the radioligand towards rat (rCB2RKD = 0.2 nM) and human (hCB2RKD = 1.1 nM) CB2R. Metabolism studies in mice revealed a metabolic stability at 30 min p.i. with fractions of parent compound of >80% in the brain and 90% in the spleen with only trace of defluorination products detected in plasma. PET imaging in a rat model of vector-based/related overexpression in the striatum revealed a high signal to background ratio, demonstrating the ability of [18F]LU13 to reach and selectively label the hCB2R in the brain. Thus, [18F]LU13 is a novel and highly promising PET radioligand for the imaging of up regulated CB2R expression under pathological conditions in the brain.

Keywords: cannabinoid receptor type 2; fluorine-18 labeling; radiochemistry; binding affinity; naphthyrid-2-one; brain; positron-emission tomography

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-33987
Publ.-Id: 33987


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


Ion Intercalation in Lanthanum Strontium Ferrite for Aqueous Electrochemical Energy Storage Devices

Tang, Y.; Chiabrera, F.; Morata, A.; Cavallaro, A.; Liedke, M. O.; Avireddy, H.; Maller, M.; Butterling, M.; Wagner, A.; Stchakovsky, M.; Baiutti, F.; Aguadero, A.; Tarancón, A.

Ion intercalation of perovskite oxides in liquid electrolytes is a very promising method for controlling their functional properties while storing charge, which opens the potential application in different energy and information technologies. Although the role of defect chemistry in the oxygen intercalation in a gaseous environment is well established, the mechanism of ion intercalation in liquid electrolytes at room temperature is poorly understood. In this study, the defect chemistry during ion intercalation of La0.5Sr0.5FeO3-δ thin films in alkaline electrolytes is studied. Oxygen and proton intercalation into the LSF perovskite structure is observed at moderate electrochemical potentials (0.5 V to -0.4 V), giving rise to a change in the oxidation state of Fe (as a charge compensation mechanism). The variation of the concentration of holes as a function of the intercalation potential was characterized by in-situ ellipsometry and the concentration of electron holes was indirectly quantified for different electrochemical potentials. Finally, a dilute defect chemistry model that describes the variation of defect species during ionic intercalation was developed.

Keywords: Lanthanum Ferrite; defects; perovskite; positron annihilation spectroscopy

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-33985
Publ.-Id: 33985


Multivariate Bayes Spaces and Compositions

van den Boogaart, K. G.; Tolosana Delgado, R.

The aim of this contribution is to present the necessary vector space structures and transforms
needed for the statistical analysis of multi-way compositions and multivariate distributions. Both
theoretical developments and examples will be provided.
Several contributions to past CoDaWorks and subsequent articles have dealt with two-way
compositions, covering the space structure, the interpretation of its subspaces and ilr coordinates
(e.g.: Egozcue et al., 2008; Fačevicová et al., 2014; de Sousa et al., 2021). This contribution
reviews these results from a common framework and extends towards multivariate distributions.
Multivariate compositions represent joint distributions of multiple categorical variables. They
form vector spaces and are a special case of multivariate Bayes-spaces, containing arbitrary mul-
tivariate distributions. In all these spaces conditional distributions, independent distributions,
and graphical models can be represented by certain subspaces. Appropriate isometric log ratio
representations are constructed from univariate representations. They explicitly separate rele-
vant subspaces related to their dependence structure as described by Markov graphs and the
Hammersley-Clifford theorem.
The contribution shows with three examples how this structural understanding can be used
to apply and interpret classical statistical methods applied to ilr-transformed multi-way compo-
sitions and multivariate distributions:
1. What are the mean and the variance of (observed) conditional distributions? As conditional
distributions are projections in these subspaces, their mean and variance are already well
defined in the projected space.
2. What are relevant hypotheses in linear models with multi-way compositional response? Clas-
sical multivariate linear models can test for the various kinds of dependence representable
by Markov graphs.
3. How to interpret the principal components from datasets of multivariate distributions? The
theory allows to attribute the influence of each PC to perturbations of the marginal distri-
butions and clique interactions.

Keywords: Multiway compositions; Multivarite Bayes Spaces; Graphical Models

  • Lecture (Conference)
    CoDaWork2022, 28.06.-01.07.2022, Toulouse, France
  • Contribution to proceedings
    CoDaWork2022, 28.06.-01.07.2022, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-33984
Publ.-Id: 33984


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


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