Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

35836 Publications

The PSMA-11-derived hybrid molecule PSMA-914 specifically identifies prostate cancer by preoperative PET/CT and intraoperative fluorescence imaging

Eder, A.; Omrane, M.; Stadlbauer, S.; Roscher, M.; Khoder, W.; Gratzke, C.; Kopka, K.; Eder, M.; Meyer, P.; Jilg, C.; Ruf, J.

Resection of tumor tissue represents one of the standard curative treatment options for the clinical management of prostate cancer. However, intraoperative localization and precise delineation of malignant tissue from surrounding healthy structures still remain challenging. The development of PSMA-targeting hybrid molecules enabling the pre- and intraoperative detection of tumor tissue supported by both radioactivity (e.g., using DROP-IN technology) and fluorescence might help to overcome these limitations. Here, we report for the first time preoperative PET/CT imaging and subsequent fluorescence-guided surgery aided by a PSMA-11-derived peptidomimetic PSMA-targeting hybrid molecule.

  • Open Access Logo European Journal of Nuclear Medicine and Molecular Imaging 48(2021)6, 2057-2058
    Online First (2021) DOI: 10.1007/s00259-020-05184-0

Publ.-Id: 32159

Telemedicine pre and post COVID-19: Lessons for commercialization based on previous use cases

Ferenczi, G. L.; Mahmood, A.; Bergmann, R.

Telemedicine used to be slow, difficult, expensive and widely neglected by doctors and patients. COVID-19 changed everything; telemedicine is entering a period of rapid economic and business growth. This paper discusses the reasons for change in telemedicine over the last 20 years, through real-life medical technology projects, telemetry, ehealth and health IT. Our methods are based on the analysis of telemedicine projects we have implemented and characteristic historical data. The results of our investigation demonstrate a clear increase of significance in telemedicine in the present and near future. We envision the evolution of mobile phones to personal telehealth monitors. Prior to COVID-19, market penetration and economic factors of telemedicine evolved slowly and in an uneven manner on a global scale. Many of the projects remained active only as long as the grant or corporate or national support was provided. The age of novel globally spreading infectious diseases, exemplified by COVID-19, has created an unusual, different setting. Recent pandemics and epidemics have changed global economics significantly and generated a new motivation and a new market with a projected trillion- dollar market value. Post COVID-19, regular and periodic epidemics and pandemics are expected to continue to occur. This will generate an enormous global market for isolated high-tech services, including telemedicine and telemetry.

Keywords: COVID-19; telemedicine; health system; respiratory diagnostics; cardiology

  • Open Access Logo Journal of the International Society for Telemedicine and eHealth 8(2020), e8
    DOI: 10.29086/JISfTeH.8.e8

Publ.-Id: 32158

Particle Stiffness and Surface Topography Determine Macrophage‐Mediated Removal of Surface Adsorbed Particles

Lee, A.; Septiadi, D.; Taladriz-Blanco, P.; Almeida, M.; Haeni, L.; Spuch-Calvar, M.; Abdussalam, W.; Rothen-Rutishauser, B.; Petri-Fink, A.

Cellular surface recognition and behavior are driven by a host of physical and chemical features which have been exploited to influence particle–cell interactions. Mechanical and topographical cues define the physical milieu which plays an important role in defining a range of cellular activities such as material recognition, adhesion, and migration through cytoskeletal organization and signaling. In order to elucidate the effect of local mechanical and topographical features generated by the adsorption of particles to an underlying surface on primary human monocyte‐derived macrophages (MDM), a series of poly(N‐isopropylacrylamide) (pNIPAM) particles with differing rigidity are self‐assembled to form a defined particle‐decorated surface. Assembly of particle‐decorated surfaces is facilitated by modification of the underlying glass to possess a positive charge through functionalization using 3‐aminopropyltriethoxysilane (APTES) or coating with poly(L‐lysine) (PLL). MDMs are noted to preferentially remove particles with higher degrees of crosslinking (stiffer) than those with lower degrees of crosslinking (softer). Alterations to the surface density of particles enabled a greater area of the particle‐decorated surface to be cleared. Uniquely, the impact of particle adsorption is evinced to have a direct impact on topographical recognition of the surface, suggesting a novel approach for controllably affecting cell‐surface recognition and response.

Publ.-Id: 32157

Quantum disordered state in the J1-J2 square-lattice antiferromagnet Sr2Cu(Te0.95W0.05)O6

Yoon, S.; Lee, W.; Lee, S.; Park, J.; Lee, C. H.; Choi, Y. S.; Do, S.-H.; Choi, W.-J.; Chen, W.-T.; Chou, F.; Gorbunov, D.; Oshima, Y.; Ali, A.; Singh, Y.; Berlie, A.; Watanabe, I.; Choi, K.-W.

The B-site ordered double perovskites Sr2Cu(Te1−xWx)O6 provide an excellent arena for investigating exotic phases expected for the J1-J2 square-lattice Heisenberg antiferromagnet. Here, combining magnetic susceptibility and specific-heat measurements with electron spin resonance (ESR) and muon spin rotation/relaxation (μSR) techniques, we explore a spin-liquid-like state in the vicinity of the Néel critical end point (x = 0.05–0.1). The specific heat and the ESR and muon relaxation rates give evidence for an energy hierarchy of low-energy excitations, reminiscent of randomness-induced singlet states. In addition, the weak transverse μSR data show a fraction of frozen magnetic moments in the random-singlet background. The origin of a random-singlet-like state near the phase boundary is discussed in terms of concomitant exchange randomness and local strain generated by the W6+-for-Te6+ substitution.

Publ.-Id: 32156

Emergence of Frustrated Short-Range Order above Long-Range Order in the S = 1/2 Kagome Antiferromagnet CaCu3(OD)6Cl2·0.6D2O

Ihara, Y.; Matsui, K.; Kohama, Y.; Luther, S.; Opherden, D.; Wosnitza, J.; Kühne, H.; Yoshida, H. K.

We report on the low-energy dynamics in the kagome antiferromagnet CaCu3(OD)6Cl2·0.6D2O (Ca-kapellasite) as studied by use of 2D-NMR measurements. Previous 35Cl-NMR measurements revealed that the nuclear spin–lattice relaxation rate (1/T1) shows two peaks at temperatures, T* = 7.2 K and Ts ≃ 25 K. While the low-temperature peak at T* is ascribed to the critical fluctuations near the long-range magnetic ordering, the origin of the high-temperature peak has not been fully understood. From the 1/T1 measurements on the D sites at the OD groups (DOD), we find no peak at Ts, evidencing that the high-temperature peak is not related to the molecular dynamics of the OD groups. We discuss the possibility of a frustration-induced short-range ordered state below Ts before the long-range order is stabilized by the Dzyaloshinskii–Moriya interaction. We also observed static internal fields at the DOD site in the long-range ordered state below T*, and confirm the previously proposed negative-chirality q = 0 magnetic structure.

Publ.-Id: 32155

A new prognostic hypoxia biomarker consisting of imaging and gene-based data.

Thomas, E.; Krause, M.

In the research article of EBioMedicine [1], Fjeldbo and colleagues developed a combined biomarker based on hypoxic fraction from dynamic contrast enhanced (DCE)-MRI imaging and genetic data of cervical cancer. They were able to predict the response to radiochemotherapy of these patients. The patients were divided into groups less or more hypoxic, based on a previously defines cut-off for the gene-based biomarkers (6 hypoxia-related genes) [2]. In the same group of 41 patients, a cut-off for the imaging biomarker was newly assessed by analyzing DCE-MRI data and using ABrix-images as parameter for the hypoxic fraction. In the next step these cut-offs were validated in 77 patients and subsequently a combined hypoxic biomarker was generated. The combination of the biomarkers revealed the same hypoxic status in 75% of the 118 patients. Therefore, besides the more and less hypoxic group, a third group with different hypoxia status was constituted.

Publ.-Id: 32154

Achieving Sustainable Development Goals in rare earth magnets production: A review on state of the art and SWOT analysis

Canal Bonfante, M.; Prats Raspini, J.; Belo Fernandes, I.; Fernandes, S.; Campos, L. M. S.; Estevam Alarcon, O.

Rare Earth Magnets (REM), especially the NdFeB type, are essential components in high-performance electric motors and wind turbines, playing an important role in the shift towards a low-carbon energy matrix. However, little work has been done to understand how the production of REM can be in line with the global sustainable transition. To overcome this lack and help with future research, as well as decision-making, this paper provides a literature overview of which aspects of sustainability are being investigated in the REM supply chain, and how each of them contributes to achieving Sustainable Development Goals (SDG). This research is developed through a consistent analysis of 44 peer-reviewed publications, followed by an analysis of strengths, weaknesses, opportunities, and threats. Four main subjects of studies were identified: environmental impact; social impact; economic aspects and circular economy. Most of the studies focus on computing the environmental impact through life cycle assessment and discussing techniques towards exploring the circular economy concept. In addition to contributing to a greener economy, the majors identified strengths of REM are the great potential of its supply chain in reducing primary resource extraction, since REM recovery and recycling seem to be viable, and the promising techniques to minimize environmental impacts along the rare earth elements production chain.

Keywords: NdFeB; Energy resources; Energy transition; Rare earth; Sustainable development goals; Critical review

Publ.-Id: 32153

First application of a high-resolution silicon detector for proton beam Bragg peak detection in a 0.95 T magnetic field

Causer, T. J.; Schellhammer, S.; Gantz, S.; Lühr, A.; Hoffmann, A. L.; Metcalfe, P. E.; Rosenfeld, A. B.; Guatelli, S.; Petasecca, M.; Oborn, B. M.

Purpose: To report on experimental results of a high spatial resolution silicon-based detector exposed to therapeutic quality proton beams in a 0.95 T transverse magnetic field. These experimental results are important for the development of accurate and novel dosimetry methods in future potential real-time MRI-guided proton therapy systems.
Methods: A permanent magnet device was utilized to generate a 0.95 T magnetic field over a 4 9 20 9 15 cm3 volume. Within this volume, a high-resolution silicon diode array detector was positioned inside a PMMA phantom of 4 9 15 9 12 cm3. This detector contains two orthogonal strips containing 505 sensitive volumes spaced at 0.2 mm apart. Proton beams collimated to a circle of 10 mm diameter with nominal energies of 90 MeV, 110 MeV, and 125 MeV were incident on the detector from an edge-on orientation. This allows for a measurement of the Bragg peak at 0.2 mm spatial resolution in both the depth and lateral profile directions. The impact of the magnetic field on the proton beams, that is, a small deflection was also investigated. A Geant4 Monte Carlo simulation was performed of the experimental setup to aid in interpretation of the results.
Results: The nominal Bragg peak for each proton energy was successfully observed with a 0.2 mm spatial resolution in the 0.95 T transverse magnetic field in both a depth and lateral profiles. The proton beam deflection (at 0.95 T) was a consistent 2 +-0.5 mm at the center of the magnetic volume for each beam energy. However, a pristine Bragg peak was not observed for each energy. This was caused by the detector packaging having small air gaps between layers of the phantom material surrounding the diode array. These air gaps act to degrade the shape of the Bragg peak, and further to this, the nonwater equivalent silicon chip acts to separate the Bragg peak into multiple peaks depending on the proton path taken. Overall, a promising performance of the silicon detector array was observed, however, with a qualitative assessment rather than a robust quantitative dosimetric evaluation at this stage of development.
Conclusions: For the first time, a high-resolution silicon-based radiation detector has been used to measure proton beam Bragg peak deflections in a phantom due to a strong magnetic field. Future efforts are required to optimize the detector packaging to strengthen the robustness of the dosimetric quantities obtained from the detector. Such high-resolution silicon diode arrays may be useful in future efforts in MRI-guided proton therapy research.

Keywords: magnetic deflection; magnetic field; MRI-guided proton therapy; proton beam; silicon detectors

Publ.-Id: 32152

Radiotherapy and COVID-19-everything under control or just the start of a long story?

Nestle, U.; Krause, M.

This pandemic is an imposition! We all are exhausted by repeated discussions on the current situation. Would like to be “back to normal”—whatever that might be—very soon.
Unfortunately, this is still a dream and we are in the middle of the corona reality. Almost forgotten: the initial panic that radiooncology could no longer operate according to law under pandemic conditions was quickly and effectively countered by an unprecedented concerted response from the authorities.
Then we had all these practical questions: How to deal with potentially limited personnel resources? How to treat potentially infected patients in routine care? To this end, at a very early stage, the German Society for Radiooncology (DEGRO), together with the Working Group for Radiooncology (ARO) of the German Cancer Society and the National Association of German Radiotherapists (BVDST), compiled two helpful statements and recommendations [1–3].
At a previously unimagined speed, we then dealt with hygiene concepts, made friends with hypofractionation, optimized our workflow, discussed home office solutions, formed staff groups, and reorganized the aftercare outpatient clinics. In their interesting survey in this issue, Matuschek et al. report on how well all this has worked out [4]. Overall, in Germany, only a relatively small number of COVID-positive patients have had to be treated by radiotherapy so far. We will see how the situation will develop during the remainder of this year. At least we are very well prepared—both with concepts and organizational skills—for higher infection rates.

Publ.-Id: 32151

3D Cell Culture-Based Global miRNA Expression Analysis Reveals miR-142-5p as a Theranostic Biomarker of Rectal Cancer Following Neoadjuvant Long-Course Treatment.

Kunigenas, L.; Stankevicius, V.; Dulskas, A.; Budginaite, E.; Alzbutas, G.; Stratilatovas, E.; Cordes, N.; Suziedelis, K.

Altered expression of miRNAs in tumor tissue encourages the translation of this specific molecular pattern into clinical practice. However, the establishment of a selective biomarker signature for many tumor types remains an inextricable challenge. For this purpose, a preclinical experimental design, which could maintain a fast and sensitive discovery of potential biomarkers, is in demand.
The present study suggests that the approach of 3D cell cultures as a preclinical cancer model that is characterized to mimic a natural tumor environment maintained in solid tumors could successfully be employed for the biomarker discovery and validation. Subsequently, in this study, we investigated an environment-dependent miRNA expression changes in colorectal adenocarcinoma DLD1 and HT29 cell lines using next-generation sequencing (NGS) technology. We detected a subset of 16 miRNAs differentially expressed in both cell lines cultivated in multicellular spheroids compared to expression levels in cells grown in 2D. Furthermore, results of in silico miRNA target analysis showed that miRNAs, which were differentially expressed in both cell lines grown in MCS, are involved in the regulation of molecular mechanisms implicated in cell adhesion, cell-ECM interaction, and gap junction pathways. In addition, integrins and platelet-derived growth factor receptors were determined to be the most significant target genes of deregulated miRNAs, which was concordant with the environment-dependent gene expression changes validated by RT-qPCR. Our results revealed that 3D microenvironment-dependent deregulation of miRNA expression in CRC cells potentially triggers essential molecular mechanisms predominantly including the regulation of cell adhesion, cell–cell, and cell–ECM interactions important in CRC initiation and development. Finally, we demonstrated increased levels of selected miR-142-5p in rectum tumor tissue samples after neoadjuvant long course treatment compared to miR-142-5p expression levels in tumor biopsy samples collected before the therapy. Remarkably, the elevation of miR-142-5p expression remained in tumor samples compared to adjacent normal rectum tissue as well. Therefore, the current study provides valuable insights into the molecular miRNA machinery of CRC and proposes a potential miRNA signature for the assessment of CRC in further clinical research.

Keywords: colorectal carcinoma; rectal cancer; 3D cell culture; miRNA; tumor microenvironment; cell adhesion; cancer biomarkers; neoadjuvant therapy; miR-142

Publ.-Id: 32150

Comparison of GeneChip, nCounter, and Real-Time PCR-Based Gene Expressions Predicting Locoregional Tumor Control after Primary and Postoperative Radiochemotherapy in Head and Neck Squamous Cell Carcinoma

Schmidt, S.; Linge, A.; Grosser, M.; Lohaus, F.; Gudziol, V.; Nowak, A.; Tinhofer, I.; Budach, V.; Sak, A.; Stuschke, M.; Balermpas, P.; Rödel, C.; Schäfer, H.; Grosu, A. L.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Combs, S. E.; Mönnich, D.; Zips, D.; Baretton, G. B.; Buchholz, F.; Baumann, M.; Krause, M.; Löck, S.

This article compares the expression and applicability of biomarkers, from single genes and gene signatures, identified in patients with locally advanced head and neck squamous cell carcinoma using the GeneChip Human Transcriptome Array 2.0, nCounter, and real-time PCR analyses. Two multicenter, retrospective cohorts of patients with head and neck squamous cell carcinoma from the German Cancer Consortium Radiation Oncology Group who received postoperative radiochemotherapy or primary radiochemotherapy were considered. Real-time PCR was performed for a limited number of 38 genes of the cohort who received postoperative radiochemotherapy only. Correlations between the methods were evaluated by the Spearman rank correlation coefficient. Patients were stratified based on the expression of putative cancer stem cell markers, hypoxia-associated gene signatures, and a previously developed seven-gene signature. Locoregional tumor control was compared between these patient subgroups using log-rank tests. Gene expressions obtained from nCounter analyses were moderately correlated to GeneChip analyses (median r Z approximately 0.68). A higher correlation was obtained between nCounter analyses and real-time PCR (median r Z 0.84). Significant associations with locoregional tumor control were observed for most of the considered biomarkers evaluated by GeneChip and nCounter analyses. In general, all applied biomarkers (single genes and gene signatures) classified approximately 70% to 85% of the patients similarly. Overall, gene signatures seem to be more robust and had a better transferability among different measurement methods.

Publ.-Id: 32149

The Role of lncRNAs TAPIR-1 and -2 as Diagnostic Markers and Potential Therapeutic Targets in Prostate Cancer

Friedrich, M.; Wiedemann, K.; Reiche, K.; Puppel, S. H.; Pfeifer, G.; Zipfel, I.; Binder, S.; Köhl, U.; Müller, G. A.; Engeland, K.; Aigner, A.; Füssel, S.; Fröhner, M.; Peitzsch, C.; Dubrovska, A.; Rade, M.; Christ, S.; Schreiber, S.; Hackermüller, J.; Lehmann, J.; Toma, M. I.; Muders, M. H.; Sommer, U.; Baretton, G. B.; Wirth, M.; Horn, F.

In search of new biomarkers suitable for the diagnosis and treatment of prostate cancer, genome-wide transcriptome sequencing was carried out with tissue specimens from 40 prostate cancer (PCa) and 8 benign prostate hyperplasia patients. We identified two intergenic long non-coding transcripts, located in close genomic proximity, which are highly expressed in PCa. Microarray studies on a larger cohort comprising 155 patients showed a profound diagnostic potential of these transcripts (AUC~0.94), which we designated as tumor associated prostate cancer increased lncRNA (TAPIR-1 and -2). To test their therapeutic potential, knockdown experiments with siRNA were carried out. The knockdown caused an increase in the p53/TP53 tumor suppressor protein level followed by downregulation of a large number of cell cycle- and DNA-damage repair key regulators. Furthermore, in radiation therapy resistant tumor cells, the knockdown leads to a renewed sensitization of these cells to radiation treatment. Accordingly, in a preclinical PCa xenograft model in mice, the systemic application of nanoparticles loaded with siRNA targeting TAPIR-1 significantly reduced tumor growth. These findings point to a crucial role of TAPIR-1 and -2 in PCa.

Keywords: lncRNA; prostate cancer; diagnostic marker; therapeutic target; p53; cell cycle arrest; radiation resistance

Publ.-Id: 32148

Men who stare at bone: multimodal monitoring of bone healing

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

Knowledge of the physiological and pathological processes taking place in bone during fracture healing or defect regeneration is essential in order to develop strategies to enhance bone healing under normal and critical conditions. Preclinical testing allows a wide range of imaging modalities that may be applied both simultaneously and longitudinally which will in turn lower the number of animals needed to allow a comprehensive assessment of the healing process. This work provides an up-to-date review on morphological, functional, optical, biochemical and biophysical imaging techniques including their advantages, disadvantages, and potential for combination of different modalities. The focus lies on preclinical testing of biomaterials modified with artificial extracellular matrices (aECM) in various animal models to enhance bone remodeling and regeneration.

Keywords: bone; soft tissue; remodeling; in vivo; ex vivo; matrix engineering


  • Secondary publication expected from 26.07.2022

Publ.-Id: 32147

Research data: THz-driven structural phase transition in a hybrid perovskite

Deinert, J.-C.; Kovalev, S.
Project Leader: Kim, Heejae; Project Member: Jäger, Sebastian

Research data for the May 2020 beamtime on "THz-driven structural phase transition in a hybrid perovskite".

PI: Heejae Kim, MPI for polymer research, Mainz.

Keywords: Terahertz; Phase transition; Perovskite; field-driven; 2D-spectroscopy; ultrafast

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-22
    DOI: 10.14278/rodare.756


Publ.-Id: 32146

Data for: "A metabolic switch regulates the transition between growth and diapause in C. elegans"

Penkov, S.; Raghuraman, B.; Erkut, C.; Oertel, J.; Galli, R.; Ackerman, E.; Vorkel, D.; Verbavatz, J.; Koch, E.; Fahmy, K.; Shevchenko, A.; Kurzchalia, T.

calorimetry data in excel format

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-23
    DOI: 10.14278/rodare.759
    License: CC-BY-4.0


Publ.-Id: 32145

Research data: Non-perturbative high-harmonic generation in the three-dimensional Dirac semimetal Cd₃As₂

Wang, Z.; Kovalev, S.; Deinert, J.-C.

Reserach data for Publication: Non-perturbative high-harmonic generation in the three-dimensional Dirac semimetal Cd₃As₂

DOI: 10.1038/s41467-020-16133-8

Keywords: Terahertz; high harmonics; Dirac material; carrier dynamics; ultrafast

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-31
    DOI: 10.14278/rodare.728


Publ.-Id: 32144

Freezing of molecular rotation in a paramagnetic crystal studied by 31P NMR

Opherden, D.; Bärtl, F.; Yamamoto, S.; Zhang, Z. T.; Luther, S.; Molatta, S.; Wosnitza, J.; Baenitz, M.; Heinmaa, I.; Stern, R.; Landee, C. P.; Kühne, H.

We present a detailed 31P nuclear magnetic resonance (NMR) study of the molecular rotation in the compound [Cu(pz)2(2-HOpy)](PF6)2, where pz = C4H4N2 and 2-HOpy = C5H4NHO. Here, a freezing of the PF6 rotation modes is revealed by several steplike increases of the temperature-dependent second spectral moment, with accompanying broad peaks of the longitudinal and transverse nuclear spin-relaxation rates. An analysis based on the Bloembergen-Purcell-Pound (BPP) theory quantifies the related activation energies as Ea/kB = 250 and 1400 K. Further, the anisotropy of the second spectral moment of the 31P absorption line was calculated for the rigid lattice, as well as in the presence of several sets of PF6 reorientation modes, and is in excellent agreement with the experimental data. Whereas the anisotropy of the frequency shift and enhancement of nuclear spinrelaxation rates is driven by the molecular rotation with respect to the dipole fields stemming from the Cu ions, the second spectral moment is determined by the intramolecular interaction of nuclear 19F and 31P moments in the presence of the distinct rotation modes.


Publ.-Id: 32143

Methane as a novel doping precursor for deposition of highly conductive ZnO thin films by magnetron sputtering

Vasin, A. V.; Rusavsky, A. V.; Bortchagovsky, E. G.; Gomeniuk, Y. V.; Nikolenko, A. S.; Strelchuk, V. V.; Yatskiv, R.; Tiagulskyi, S.; Prucnal, S.; Skorupa, W.; Nazarov, A. N.

ZnO thin films were deposited by RF-magnetron sputtering of ZnO powder target using pure argon and argon with methane as reactive gas. It is found that growth morphology and electronic properties of the films are strongly affected by adding of methane to argon during the deposition process. Adding of methane resulted in a high energy shift of near band edge ultraviolet photoluminescence band and quenching of deep level emission in the visible spectral range. The strongest effect of methane has been found for electrical resistivity that reduced by 3 orders of magnitude in comparison with films deposited in pure argon. Unexpectedly, the analysis of the chemical composition showed no carbon incorporated from methane. Therefore, modification effects were assigned to hydrogen incorporation. However, the direct comparison of resistivity of the films deposited using methane and molecular hydrogen as doping precursors has demonstrated that doping efficiency of the methane is about an order of magnitude larger than that of molecular hydrogen under similar deposition conditions. This advantage of the methane is discussed and assigned to specific surface chemistry of Zn–O–C–H system that enhances the formation of shallow donor defects during plasma assisted deposition process.

Keywords: ZnO; doping; photoluminescence

Publ.-Id: 32142

Current Transport Mechanisms in Zinc Oxide/Silicon Carbide Heterojunction Light‐Emitting Diodes

Przezdziecka, E.; Chusnutdinow, S.; Wierzbicka, A.; Guziewicz, M.; Prucnal, S.; Stachowicz, M.; Zaleszczyk, W.; Zhou, S.; Kozanecki, A.

Herein, the properties of ZnO:N/n‐SiC heterojunctions (HJs) and light‐emitting diodes based on them are studied. The HJs are grown by molecular beam epitaxy. Active nitrogen generated by a radio frequency plasma source is used for p‐type doping. The location of the space charge area on the ZnO:N/n‐SiC interface is revealed by electron‐beam‐induced current (EBIC) scans. The diffusion lengths of holes and electrons are calculated. This article presents the characterization of ZnO:N/n‐SiC HJs and reveals the presence of tunneling‐related current transport in them as well as the contribution of exponentially distributed traps at large voltage bias. Electroluminescence (EL) is measured at ambient pressure by a standard EL system and also at 77 K in vacuum by a system utilizing EBIC in a scanning electron microscope. Analysis of the light output power at higher current level indicates the limited effect of nonradiative defects in this structure. EL results are compared with cathodoluminescence spectra. Color temperature for HJs based on the EL spectra is also calculated.

Keywords: ZnO; doping; p-n diode; electroluminescence

Publ.-Id: 32141

Soft X-ray absorption study of tantalum incorporation in titanium oxide films: Impact of flash-lamp annealing

Gago, R.; Prucnal, S.; Esteban-Mendoza, D.

The impact of Ta incorporation (up to similar to 21 at.%) in titanium dioxide (TiO2) films subjected to post-deposition millisecond-range flash-lamp annealing (FLA) is addressed. Phase formation with short-range information was established by means of soft X-ray absorption near-edge structure (XANES) in combination with standard X-ray diffraction. As-grown films are X-ray amorphous, but display a significant structural improvement upon FLA. Up to relatively large Ta concentrations (similar to 12 at.%), FLA can be used to effectively incorporate Ta into a nano-crystalline anatase TiO2 phase, although its structural quality deteriorates progressively with the Ta content. For the intermediate Ta range between 12 and 17 at.%, the structure of the FLA films is highly disordered, being unable to overcome the initial distorted arrangement. In any case, rutile- or Ta2O5-like environments emerge for low and high contents, respectively. Finally, for the highest Ta content (similar to 21 at.%), the formation of good-quality nanocrystalline Ta2O5 phase occurs after FLA. As assessed by XANES, the structural evolution upon FLA seems to be determined by the initial (amorphous) structure. Lastly, all the samples are highly transparent from the visible to the near-infrared region, and the band-gap can be tailored from similar to 3.2 to similar to 3.8 eV with increasing the amount of incorporated Ta.

Keywords: Oxide materials; Doping; Sputter deposition; Flash-lamp-annealing; XANES; Band-gap engineering

Publ.-Id: 32140

Kinetics of Bulk Lifetime Degradation in Float-Zone Silicon: Fast Activation and Annihilation of Grown-In Defects and the Role of Hydrogen versus Light

Hiller, D.; Markevich, V. P.; de Guzman, J. A. T.; König, D.; Prucnal, Slawomir; Bock, W.; Julin, J.; Peaker, A. R.; Macdonald, D.; Grant, N. E.; Murphy, J. D.

Float‐zone (FZ) silicon often has grown‐in defects that are thermally activated in a broad temperature window (≈300–800 °C). These defects cause efficient electron‐hole pair recombination, which deteriorates the bulk minority carrier lifetime and thereby possible photovoltaic conversion efficiencies. Little is known so far about these defects which are possibly Si‐vacancy/nitrogen‐related (VxNy). Herein, it is shown that the defect activation takes place on sub‐second timescales, as does the destruction of the defects at higher temperatures. Complete defect annihilation, however, is not achieved until nitrogen impurities are effused from the wafer, as confirmed by secondary ion mass spectrometry. Hydrogenation experiments reveal the temporary and only partial passivation of recombination centers. In combination with deep‐level transient spectroscopy, at least two possible defect states are revealed, only one of which interacts with H. With the help of density functional theory V1N1‐centers, which induce Si dangling bonds (DBs), are proposed as one possible defect candidate. Such DBs can be passivated by H. The associated formation energy, as well as their sensitivity to light‐induced free carriers, is consistent with the experimental results. These results are anticipated to contribute to a deeper understanding of bulk‐Si defects, which are pivotal for the mitigation of solar cell degradation processes.

Keywords: Solar cells; Si; doping; defects

Publ.-Id: 32139

Correlations between the structural transformations and concentration quenching effect for RE-implanted ZnO systems

Ratajczak, R.; Mieszczynski, C.; Prucnal, S.; Krajewski, T. A.; Guziewicz, E.; Wozniak, W.; Kopalko, K.; Heller, R.; Akhmadaliev, S.

In this paper, we present optical, structural and electrical studies of the phenomenon called concentration quenching effect occurring in ZnO doped with Rare Earth (RE) ions. For this purpose, the epitaxial ZnO layers grown by the Atomic Layer Deposition (ALD) are doped by ion implantation with Yb and Er elements with fluencies ranging from 5 × 1013 to 1 × 1016/cm2. In order to activate optically the implanted RE and to remove defects, the post-implantation thermal annealing was performed at 800 °C for 10 min in the O2 atmosphere using a Rapid Thermal Annealing (RTA) system. Two-step processed samples, before and after annealing, were evaluated by Rutherford Backscattering Spectrometry (RBS/c) to investigate the damage build-up process in the ZnO lattice after RE ion bombardment and the lattice site location of RE. The annealed samples were examined using the photoluminescence (PL) spectroscopy and Hall effect measurements. Our studies show that the luminescence quenching effect, as well as the electrical resistivity response to the increased RE concentration, are strongly connected with the threshold of the structural transformation due to defects accumulation. It suggests that during structural transformations the RE-ion centers are sufficiently close together to be able to interact and transfer the excitation energy between each other, increasing ipso facto the probability to lose the excitation energy by non-radiative processes. Moreover, in contrast to the popular belief, that the concentration quenching effect in RE-doped ZnO depends strongly on the kind of RE-doped ion, the presented results do not provide any evidence to support such an assumption.

Keywords: Rare earth; Ytterbium; Ion Implantation; Rutherford Backscattering Spectrometry (RBS/c); Erbium

Publ.-Id: 32138

Effect of roughness and nanoporosity on optical properties of black and reflective Al films prepared by magnetron sputtering

Hruška, P.; More-Chevalier, J.; Novotný, M.; Čížek, J.; Melikhova, O.; Fekete, L.; Poupon, M.; Bulíř, J.; Volfová, L.; Butterling, M.; Liedke, M. O.; Wagner, A.; Fitl, P.

In this work, a comparison of the microstructure of black and classic reflective aluminum films is provided. The N2 concentration during the magnetron sputtering deposition has a key impact on the growth process and final moth-eye-like morphology of black Al films. The study of films with thickness ~1.5 μm and ~8 μm and fully developed microstructure enabled us to clarify the origin of different optical properties of black and reflective Al. Atomic force microscopy measurements showed high roughnesses for both types of films leading to light scattering from their surface. In the case of black Al, the incident light is absorbed in a fractallike nanoporous surface. Less than 3 % of the intensity in the wavelength range from 190 nm to 1200 nm is reflected. Positronium formation in columnar nanopores with a diameter of 4 – 5 Å was observed by positron annihilation lifetime spectroscopy. The nanoporosity rather than the roughness is the key feature of black films compared to reflective ones.

Keywords: black aluminum; magnetron sputtering; atomic force microscopy; spectrophotometric reflectance; positron annihilation spectroscopy


  • Secondary publication expected from 02.04.2022

Publ.-Id: 32137

Pushing the doping limit for future FETs

Zhou, S.

In recent years, small-sized transistors including FinFETs or Nanowire FETs (or Gate-all-around FETs) have been manufactured to reduce the voltage and power consumption of devices. When CMOS transistors are scaled down below the 10 nm technology node, the effect of contact resistance on power consumption increases because the contact area decreases for smaller transistors. For nodes of <7 nm, the metal–semiconductor contact resistance become a dominant contributor to the total parasitic resistances of the transistor [1, 2]. To solve the problem, n- or p-type impurities were introduced at the alloy concentration in Si and SiGe [1, 2]. However, due to the self-compensation via defect complexes at high impurity concentration, the free carrier concentration saturates. In this talk, I will discuss our approaches to tackle this challenge. One is the use of deep level impurities for doping Si, for instance, chalcogen Te [3]. Contrary to general expectations, we find that with increasing Te doping concentration its interstitial fraction decreases and substitutional Te dimers become the dominant configuration. As shown by first-principle calculations, these Te dimers have the lowest formation energy and donate two electrons each to the conduction band. Another approach is to play with different annealing time scale. We find that by millisecond flash lamp annealing the dead P-dopants can be deliberated [4, 5]. Positron lifetime measurements indicate the dissolving of single vacancies. Therefore, we trace the origin of the unprecedented electron concentrations in Si and in Ge to the atomistic scale. Our results have fundamental implications in semiconductor physics as well as to the source/drain applications for future FETs.
[1] Z. Ye, et al., Applied Materials, ECS Trans. 98, 239 (2020).
[2] G. Rengo, et al., IMEC, ECS Trans. 98, 27 (2020).
[3] M. Wang, et al., Phys. Rev. Appl. 11, 054039 (2019), arXiv:1809.06055
[4] S. Prucnal, et al., Phys. Rev. Appl. 10, 064055 (2018), arXiv:1901.01721
[5] S. Prucnal, et al., New J. Phys., in press (2020).

  • Invited lecture (Conferences)
    International Virtual School on Ion Beams in Materials Science, 01.-05.12.2020, New Delhi, India

Publ.-Id: 32136

Tuned AFM-FM coupling by the formation of vacancy complex in Gd0.6Ca0.4MnO3 thin film lattice

Beiranvand, A.; Liedke, M. O.; Haalisto, C.; Lähteenlahti, V.; Schulman, A.; Granroth, S.; Palonen, H.; Butterling, M.; Wagner, A.; Huhtinen, H.; Paturi, P.

The effect of in situ oxygen and vacuum annealings on the low bandwidth manganite Gd1-xCaxMnO3 (GCMO) thin film with x = 0:4 was investigated. Based on the magnetic measurements, the AFM-FM coupling is suppressed by the vacuum annealing treatment via destroying the double exchange interaction and increasing the unit cell volume by converting the Mn4+ to the Mn3+. Consequently, resistance increases significantly compared to pristine film. The results are explained by a model obtained from the positron annihilation studies, where the vacuum annealing increased the annihilation lifetime in A and B sites due to the formation of vacancy complexes VA;B - VO, which was not the case in the pristine sample. The positron annihilation analysis indicated that most of the open volume defects have been detected in the interface region rather than on the subsurface layer and this result is confirmed by detailed x-ray reflection analysis. On the other hand, the effect of oxygen annealing on the unit cell volume and magnetization was insignificant. This is in agreement with positron annihilation results which demonstrated that the introduction of oxygen does not change the number of cation vacancies significantly. This work demonstrates that the modification of oxygen vacancies and vacancy complexes can tune magnetic and electronic structure of the epitaxial thin films to provide new functionalities in future applications.

Keywords: positron annihilation spectroscopy; positron annihilation lifetime spectroscopy; Doppler broadening; defetcs; Gd; annealing; Ca; MnO3


  • Secondary publication expected from 24.05.2022

Publ.-Id: 32135

Ansible GitLab Base Role

Hüser, C.; Ziegner, N.; Huste, T.

This Ansible Role provides a basic setup for services based on GitLab Omnibus.

Keywords: gitlab; ansible

  • Software in external data repository
    Publication year 2020
    Programming language: Ansible
    System requirements: Centos, Ubuntu
    License: Apache-2.0 (Link to license text)
    Hosted on Link to location

Publ.-Id: 32133

Ansible Role Redis

Hüser, C.; Ziegner, N.; Huste, T.

An Ansible role to set up multiple Redis instances to be used as caching servers in a High Availability and Scalability context.

Keywords: redis; ansible; cache; high availability

  • Software in external data repository
    Publication year 2020
    Programming language: Ansible
    System requirements: Ubuntu
    License: Apache-2.0 (Link to license text)
    Hosted on Link to location

Publ.-Id: 32132

Ansible Role HAProxy

Hüser, C.; Ziegner, N.; Huste, T.

An Ansible role to set up HAProxy to be used as a load balancer in a high availability and scalability context.

Keywords: haproxy; loadbalancer; networking; web; ansible

  • Software in external data repository
    Publication year 2020
    Programming language: Ansible
    System requirements: Ubuntu
    License: Apache-2.0 (Link to license text)
    Hosted on Link to location

Publ.-Id: 32131

Ansible Role GitLab

Hüser, C.; Huste, T.; Ziegner, N.

Ansible role to configure GitLab Omnibus installation.

Keywords: gitlab; ansible

  • Software in external data repository
    Publication year 2020
    Programming language: Ansible
    System requirements: Ubuntu
    License: Apache-2.0 (Link to license text)
    Hosted on Link to location

Publ.-Id: 32130

Sub-20 nm multilayer nanopillar patterning for hybrid SET/CMOS integration

Pourteau, M.-L.; Gharbi, A.; Brianceau, P.; Dallery, J.-A.; Laulagnet, F.; Rademaker, G.; Tiron, R.; Engelmann, H.-J.; Borany, J.; Heinig, K.-H.; Rommel, M.; Baier, L.

SETs (Single-Electron-Transistors) arouse growing interest for their very low energy consumption. For future industrialization, it is crucial to show a CMOS-compatible fabrication of SETs, and a key prerequisite is the patterning of sub-20 nm Si Nano-Pillars (NP) with an embedded thin SiO2 layer. In this work, we report the patterning of such multi-layer isolated NP with e-beam lithography combined with a Reactive Ion Etching (RIE) process. The Critical Dimension (CD) uniformity and the robustness of the Process of Reference are evaluated.
Characterization methods, either by CD-SEM for the CD, or by TEM cross-section for the NP profile, are compared and discussed.

Keywords: Single-electron transistor; Multilayer nanopillars; Silicon nanodots; E-beam lithography; Reactive ion etching; Energy-filtered transmission electron microscopy

Related publications

Publ.-Id: 32129

ESUO - The European Synchrotron and FEL User Organisation: Aims and activities

Aksoy, A.; Arčon, I.; Arikan, P.; Bittencourt, C.; Boscherini, F.; Braz Fernandes, F. M.; Brooks, N.; Casu, B.; Cianci, M.; Feiters, M.; Froideval, A.; Granroth, S.; Gross, S.; Gutt, C.; Hase, T.; Jablonska, K.; Jergel, M.; Karsli, Ö.; Khan, A.; Kirm, M.; Kokkinidis, M.; Kövér, L.; Kuzmin, A.; Landau, M.; Larsen, H. B.; Lechner, R. T.; Le-Hir, R.; Logan, D. T.; López, O.; Lorentz, K.; Mariani, C.; Marinkovic, B.; McGuinness, C.; Meedom Nielsen, M.; Mičetić, M.; Mikulík, P.; Padežnik Gomilšek, J.; Petukhov, A.; Pietsch, U.; Renault, L.; Russell, A.; Shivachev, B.; Sobierajski, R.; Stangl, J.; Thissen, R.; Tromp, M.; Vankó, G.; Witkowska, A.; Blasetti, C.; Freire Anselmo, A. S.; Grobosch, M.; Helm, M.; Schramm, B.; Schultheiss, K.; Vollmer, A.

The European Synchrotron and free-electron laser User Organisation (ESUO) represents about 22.000 users from 30 European member states and associated countries. Each country is represented within ESUO by one up to four national delegate(s), depending on the size of the user community in the respective country. The ESUO aims and activities are shown in this poster.

  • Poster (Online presentation)
    12th BESSY@HZB USER MEETING, 10.12.2020, Berlin-Adlershof, Deutschland

Publ.-Id: 32128

Proposal for the delineation of neoadjuvant target volumes in oesophageal cancer

Thomas, M.; Mortensen, H.; Hoffmann, L.; Møller, D.; Troost, E. G. C.; Muijs, C.; Berbee, M.; Bütof, R.; Nicholas, O.; Radhakrishna, G.; Defraene, G.; Nafteux, P.; Nordsmark, M.; Haustermans, K.

To define instructions for delineation of target volumes in the neoadjuvant setting in oesophageal cancer.
Materials and methods
Radiation oncologists of five European centres participated in the following consensus process: [1] revision of published (MEDLINE) and national/institutional delineation guidelines; [2] first delineation round of five cases (patient 1–5) according to national/institutional guidelines; [3] consensus meeting to discuss the results of step 1 and 2, followed by a target volume delineation proposal; [4] circulation of proposed instructions for target volume delineation and atlas for feedback; [5] second delineation round of five new cases (patient 6–10) to peer review and validate (two additional centres) the agreed delineation guidelines and atlas; [6] final consensus on the delineation guidelines depicted in an atlas.
Target volumes of the delineation rounds were compared between centres by Dice similarity coefficient (DSC) and maximum/mean undirected Hausdorff distances (Hmax/Hmean).
In the first delineation round, the consistency between centres was moderate (CTVtotal: DSC = 0.59–0.88; Hmean = 0.2–0.4 cm). Delineations in the second round were much more consistent. Lowest variability was obtained between centres participating in the consensus meeting (CTVtotal: DSC: p < 0.050 between rounds for patients 6/7/8/10; Hmean: p < 0.050 for patients 7/8/10), compared to validation centres (CTVtotal: DSC: p < 0.050 between validation and consensus meeting centres for patients 6/7/8; Hmean: p < 0.050 for patients 7/10).
A proposal for delineation of target volumes and an atlas were generated.
We proposed instructions for target volume delineation and an atlas for the neoadjuvant radiation treatment in oesophageal cancer. These will enable a more uniform delineation of patients in clinical practice and clinical trials.

Keywords: Oesophageal cancer; Neoadjuvant chemoradiation; Proposal for delineation; Delineation atlas; Consensus

Publ.-Id: 32127

Solvent extraction of boric acid: comparison of five different monohydric alcohols and equilibrium modeling with numerical methods

Balinski, A.; Recksiek, V.; Kelly, N.

Solvent extraction is one of the common methods for the recovery of boric acid (or boron) from aqueous solutions. A wide variety of different compounds including monohydric alcohols has been tested and there is a wide recognition that they are rather ineffective compared to other extractants such as diols. Nevertheless, monohydric alcohols find application in industrial processes demonstrating their efficiency. The intention of this study is to clarify this discrepancy and to provide an overall picture of monohydric alcohols as an extractant for boric acid. Five different monohydric alcohols are the object of this study: n-octanol, 2-ethyl-1-hexanol, 2-butyl-1-octanol, 2-octanol and 3,7-dimethyl-3-octanol. A special focus is to examine the effect of the structure of carbon chain and the effect of the composition of aqueous phase on the extraction efficiency. Despite the extraction efficiency for boric acid other important properties are examined such as the viscosity of organic phase, the solubility of alcohols in aqueous phase and the co-extraction of salts used as a salting-out agent (NaCl, Na₂SO₄, MgCl₂, LiCl, LiNO₃). Finally, the relationship between the number of theoretical stages and the phase ratio at equilibrium for selected extraction systems is evaluated with MATLAB.

Keywords: boron; boric acid; solvent extraction; separation; monohydric alcohols; n-octanol; 2-ethyl-1-hexanol; 2-butyl-1-octanol; 2-octanol; 3,7-dimethyl-3-octanol

Publ.-Id: 32126

Integrated Environmental Monitoring of AMD Affected Waters using Hyperspectral Imaging and In-situ Analytics

Flores Rojas, H. M.; Lorenz, S.; Jackisch, R.; Tusa, L.; Contreras Acosta, I. C.; Gloaguen, R.

One of the potential major consequences of mining activities is the degradation of the surrounding ecosystems by Acid Mine Drainage (AMD). A high-resolution hyperspectral drone-borne survey provides a useful, fast, and non-invasive tool to monitor the acid mine drainage mineralogy in mining sites. In this study, we propose to integrate drone-borne visible-to-near infrared (VNIR) hyperspectral data and physicochemical field data from water and sediments together with laboratory analysis for precise mineralogical and surface water mapping. The Tintillo River is an extraordinary case of the collection of acidic leachates in southwest Spain. This river is highly contaminated, with large quantities of dissolved metals (Fe, Al, Cu, Zn, etc.) and acidity, which later discharged into the Odiel River. At the confluence of the Tintillo and Odiel rivers, different geochemical and mineralogical processes typical of the interaction of very acidic water (pH 2.5 - 3.0) with circum-neutral water (pH 7.0 - 8.0) occur. The high contrast among waters makes this area propitious for the use of hyperspectral data to characterize both rivers and better evaluate mine water bodies with remote sensing imagery. We present an approach that makes use of a supervised random forest regression for the extended mapping of water properties, using the data from collected field samples, as training set for the algorithm. Experimental results show water surface maps that quantify the concentration of dissolved metals and physical-chemical properties along the covered region and mineral classification maps distribution (jarosite, goethite, schwertmannite, etc.). These results highlight the capabilities of drone-borne hyperspectral data for monitoring mining sites by extrapolating the hydrochemical properties from certain and specific areas, covered during field campaigns, to larger regions where accessibility is limited. By following this method, it is possible to rapidly discriminate and map the degree of AMD contamination in water for its future treatment or remediation.

Keywords: hyperspectral; remote sensing; machine learning; unmanned aerial system; acid mine drainage

Publ.-Id: 32125

Slice2Volume: Fusion of multimodal medical imaging and light microscopy data of irradiation-injured brain tissue in 3D.

Müller, J.; Suckert, T.; Beyreuther, E.; Schneider, M.; Boucsein, M.; Bodenstein, E.; Stolz-Kieslich, L.; Krause, M.; von Neubeck, C.; Haase, R.; Lühr, A.; Dietrich, A.

The dataset contains comprehensive image data for a total of nine mice, which underwent normal tissue brain irradiation with 90 MeV protons.             
In particular, the image data comprise cone-bem computed tomographies (CBCT), Monte Carlo beam transport simulations based on those CTs, regular magnetic resonance imaging (MRI) follow-up (≥ 26 weeks), a co-aligned DSURQE mouse brain atlas and scanned whole-brain tissue sections with histochemical and immunofluorescent markers for morphology (H&E), cell nuclei (DAPI), astrocytes (GFAP), microglia (Iba1), the intermediate filament protein Nestin, proliferation (Ki67), neurons (NeuN) and oligodendrocytes (OSP).          
The volumetric image data (i.e. CBCT, MRI and brain atlas) were co-aligned using the ImageJ plugin Big Warp. The CBCT data was used as spatial reference to allow for mask-based, slice-wise alignment of CBCT and light microscopy image data in 3D with the scriptable registration tool Elastix.  

We provide the data in raw format and as aligned data sets, as well as their spatial transformations.

Keywords: Preclinical; Image fusion; Proton radiation; Medical imaging; Histology

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-20
    DOI: 10.14278/rodare.557
    License: CC-BY-4.0


Publ.-Id: 32124

B20-type FeGe on Ge(100) prepared by pulsed laser melting

Li, Z.; Xie, Y.; Yuan, Y.; Wang, M.; Xu, C.; Hübner, R.; Prucnal, S.; Zhou, S.

B20-type FeGe is one of the noncentrosymmetric materials hosting magnetic skymions. In this work, we have prepared B20-type FeGe films by pulsed laser melting of metal Fe deposited on Ge(100). The formation of the B20 phase is confirmed by X-ray diffraction. The FeGe samples show a superparamagnetic behaviour and their blocking temperatures increase with increasing the pulsed laser energy density. We conclude that this phenomenon is due to the increased grain size of the B20-type FeGe with increasing laser energy density. The presented method can be used to obtain different B20-type transition metal germanides and silicides, which can be magnetic skyrmion-hosting materials for spintronics.

Keywords: B20 phase; FeGe; Pulsed laser melting; Superparamagnetism


  • Secondary publication expected from 31.03.2022

Publ.-Id: 32122

Teaching ML in Compact Courses

Fouilloux, A.; Steinbach, P.

This talk summarizes the experiences made with teaching Machine Learning within compact events that stretch over several days to a week maximum. Both speakers explain pitfalls they were caught in as well as solutions they found.

This talk was given at the Teaching Machine Learning workshop at ECML-PKDD 2020. For more details and information see

Keywords: teaching; compact courses; machine learning; artificial intelligence

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-09-08
    DOI: 10.14278/rodare.752
    License: CC-BY-4.0


Publ.-Id: 32121

Teaching ML in Compact Courses

Fouilloux, A.; Steinbach, P.

This talk summarizes the experiences made with teaching Machine Learning within compact events that stretch over several days to a week maximum. Both speakers explain pitfalls they were caught in as well as solutions they found.

Keywords: Machine Learning; Teaching; Artificial Intelligence; Bootcamp; courses

  • Open Access Logo Lecture (Conference) (Online presentation)
    European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, 14.-18.09.2020, virtual, virtual
    DOI: 10.14278/rodare.753

Publ.-Id: 32120

Study of effective parameters on generating submicron (nano)-bubbles using the hydrodynamic cavitation

Hassanzadeh, A. C.; Nazari, S. A.; Shafaei, S. Z. A.; Azizi, A. D.; Gharabaghi, M. A.; Ahmadi, R. E.; Shahbazi, B. F.

Although submicron (nano)-bubbles (NBs) have been broadly used in the laboratory flotation processes, the role of critical factors in their generation is not adequately explored in the literature. The present study investigates the effect of six key factors on generating submicron-sized bubbles and its application to coarse-sized quartz flotation. Interaction of influential factors is highlighted, which was generally overlooked in previous studies. These parameters i.e. frother type (MIBC and A65), frother dosage (50-130 mg/L), air flow rate (0.1-0.4 L/min), pressure in Venturi tube (250-400 kPa), liquid temperature (22-42 °C) and pH (6-10) were evaluated through software based statistical fractional factorial design. The size distribution of NBs produced by the principle of hydrodynamic cavitation was measured using a laser particle size analyzer (LPSA), and Sauter mean bubble diameter (d32) was considered as the experimental design response. Batch flotation experiments were performed with and without the A65 and MIBC-NBs. The results of experimental design showed that relative intensity of the main factors followed the order of air flow rate>temperature>frother type as the most effective parameters on the bubble size. It was revealed that the lowest air flow rate (0.1 L/min) produced the smallest bubbles. Meanwhile, the d32 decreased as the liquid temperature increased, and the bubble size strongly was related to the frother type and its concentration. Indeed, with changing frother from MIBC to A65, the reduction in mean bubble size was two-fold. Interaction of frother type with its dosage, air flow rate and pressure were statistically recognized significant on the mean bubble size, which was confirmed by p-values. Finally, flotation recovery of quartz particles improved ca. 22% in the presence of NBs compared to the conventional flotation. © Wroclaw University of Science and Technology.

Keywords: Bulk nanobubbles (NBs); Frother typeTemperatur; Fractional factorial design; Coarse quartz particles

Publ.-Id: 32119

Phase selection in Mn-Si alloys by fast solid-state reaction with enhanced skyrmion stability

Li, Z.; Xie, Y.; Yuan, Y.; Ji, Y.; Begeza, V.; Cao, L.; Hübner, R.; Rebohle, L.; Helm, M.; Kornelius, N.; Prucnal, S.; Zhou, S.

B20-type transition-metal silicides or germanides are noncentrosymmetric materials hosting magnetic skyrmions, which are promising information carriers in spintronic devices. The prerequisite is the preparation of thin films on technology-relevant substrates with magnetic skyrmions stabilized at a broad temperature and magnetic-field working window. The canonical example is the B20-MnSi film grown on Si substrates. However, the as-yet unavoidable contamination with MnSi1.7 occurs due to the lower nucleation temperature of this phase. In this work, we report a simple and efficient method to overcome this problem and prepare single-phase MnSi films on Si substrates. It is based on the millisecond reaction between metallic Mn and Si using flash lamp annealing (FLA). By controlling the FLA energy density, we can grow single-phase MnSi or MnSi1.7 or their mixture at will. Compared with bulk MnSi the prepared MnSi films show an increased Curie temperature of up to 41 K. In particular, the magnetic skyrmions are stable over a much wider temperature and magnetic-field range than reported previously. Our results constitute a novel phase selection approach for alloys and can help enhance specific functional properties such as enhancing the stability of magnetic skyrmions.

Keywords: B20-MnSi; Flash lamp annealing; Phase separation; Skyrmions

Publ.-Id: 32117

Non-reciprocal spin wave propagation in magnetic bilayer structures

Gladii, O.; Salikhov, R.; Gallardo, R. A.; Hellwig, O.; Lindner, J.; Schultheiß, H.

One of the peculiar features of waves in general is their option of non-reciprocal dispersion relation, meaning the modification of the transport characteristics upon reversal of the waves’ propagation direction. Non-reciprocity in case of Magnetostatic Surface Spin Waves (MSSW) can be caused by various factors, such as surface anisotropy [1], interfacial Dzyaloshinskii-Moriya interaction [2] or inhomogeneous saturation magnetization across the film thickness [3]. Recently, it has been shown that a strong non-reciprocal propagation can be induced by the dynamic dipole-dipole interaction between two magnetic layers in spin-valve-like structures, for which the relative magnetization orientation in remanence is stabilized in antiparallel configuration [4]. In the present work we investigate the frequency non-reciprocity in ferromagnetic bilayer systems, where a nonmagnetic thin Ru interlayer is used to achieve antiferromagnetic alignment at zero field. Using conventional Brillouin light scattering, we perform systematic measurements of the frequency non-reciprocity as a function of an external magnetic field. As expected [4], for antiparallel alignment of the magnetic moments in the two layers we observe a large frequency non-reciprocity up to a few GHz, which vanishes when the relative magnetization orientation switches to the parallel configuration. Moreover, a non-monotonous dependence of the frequency non-reciprocity is found in the transition from the antiparallel to the parallel orientation, where the maximum of the frequency shift corresponds to the spin-flop phase. By varying the parameters of the bilayer structures, the non-reciprocal propagation at the spin-flop transition is studied. We demonstrate that by adjusting the strength of the exchange coupling between the two ferromagnetic layers via the appropriate choice of the stack parameters, one can precisely control the non-reciprocal propagation of spin waves via the field-driven magnetization reorientation.

Keywords: spin wave; Brillouin light scattering; non-reciprocity; magnetic bilayers

  • Poster (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual event, Virtual event

Publ.-Id: 32115

Impact of Surface Reactivity on the Simulation of Mineral Dissolution Rates

Schabernack, J.; Fischer, C.

The kinetics of mineral dissolution plays a key role in many environmental and technical fields, e.g., weathering, building materials, as well as host rock characterization for potential nuclear waste repositories. Mineral dissolution rates are controlled by two parameters: (1) transport of dissolved species over and from the interface determined by advective fluid flow and diffusion (transport control) and (2) availability and distribution of reactive sites on the crystal surface (surface reactivity control). Reactive transport models (RTM) simulating species transport commonly calculate mineral dissolution by using rate laws [1]. However, the applied rate laws solely depend on species concentration in the fluid. While the effect of transport-controlled processes is addressed in current RTM approaches, the intrinsic variability of surface reactivity is neglected. Experimental studies under surface-controlled dissolution conditions have shown that surface reactivity is heterogeneously distributed over the surface [e.g., 2]. This heterogeneity in reactivity is largely caused by nanotopographical structures on the crystal surface, such as steps and etch pits. These structures are generated through defects in the crystal lattice. At these structures, the high density of reactive kink sites is leading to a local increase in surface reactivity observable through high dissolution rates.
In this study, we test whether the current rate calculation approach applied in RTMs is sufficient to reproduce experimentally observed rate heterogeneities. We apply a standard RTM approach combined with the measured surface topography of a calcite single crystal [2]. Calcite is an important mineral component in the sandy facies of the Opalinus clay formation, that is under investigation for nuclear waste storage. The modeled surface dissolution rate maps are compared to experimentally derived rate maps. Results show that the current RTM is not able to reproduce the measured rate heterogeneities on the calcite surface. To improve the predictive capabilities of RTMs over the large time scales required for the safety assessment of nuclear waste repositories, the surface reactivity that is intrinsic to the mineral needs to be implemented into future rate calculations. Investigating calcite surface reactivity in the context of dissolution can also yield information about other kinetic surface processes such as the adsorption of radionuclides during transport. We show the integration of surface reactivity into rate calculation by using a proxy parameter. The slope of the crystal surface at the nm scale is applied. We show that by adding a factor based on the slope to the rate law the RTM is able to approximate experimental rate maps. Other proxy parameters such as surface roughness could yield similar results as well. The implementation of surface reactivity proxy parameters will allow for a more precise prediction of host rock-fluid interaction over large time scales in RTMs, relevant for safety assessment of nuclear waste repositories.

[1] Agrawal, P., Raoof, A., Iliev, O. and Wolthers, M. (2020): Evolution of pore-shape and its impact on pore conductivity during CO2 injection in calcite: Single pore simulations and microfluidic experiments. Advances in Water Resources, 136, 103480.
[2] Bibi, I., Arvidson, R.S., Fischer, C. and Lüttge, A. (2018): Temporal Evolution of Calcite Surface Dissolution Kinetics. Minerals, 8, 256.

Keywords: Reactive Transport Model; Mineral Dissolution; Crystal Surface Reactivity

  • Lecture (Conference) (Online presentation)
    EGU General Assembly 2021 vEGU21: Gather Online, 19.-30.04.2021, Online, Online
    DOI: 10.5194/egusphere-egu21-11079

Publ.-Id: 32113

Development of Machine Learning Framework for Interfacial Force Closures Based on Bubble Tracking Data

Tai, C.-K.; Lucas, D.; Bolotnov, I.

This work aims to develop data-driven modeling framework with the aid of machine learning methods and high-fidelity dataset. To gain confidence on the methodology, a bubble drag regression task using artificial dataset is conducted. Result shows FNN’s capability performing non-linear fitting. On the other hand, the sample size test would give sense on model underfitting with same amount of knowledge. Inspired by the previous task, the focus then moved on to utilize DNS bubble tracking dataset for modeling interfacial momentum exchange terms. A novel way to approach interfacial momentum exchange is proposed. Preliminary result reveals the concern of model accuracy on unseen data points. Improvement on model generalization is suggested. Also, further refinement on label formation and data processing should be taken care of. Nonetheless, the potential using high fidelity data and NN to directly model interaction between phases in bubbly flow has been shown.

Keywords: DNS; bubbly flow; drag; machine learning

  • Contribution to proceedings
    2020 ANS Virtual Winter Meeting, 16.-19.11.2020, Online, USA
  • Lecture (Conference) (Online presentation)
    2020 ANS Virtual Winter Meeting, 16.-19.11.2020, Online, USA

Publ.-Id: 32111

Stress-Induced Modification of Gyration Eigen-Frequencies in Stacked Double-Vortex Structures

Iurchuk, V.; Kakay, A.; Deac, A. M.

The ground state of nanoscale circular magnetic disks of certain geometric aspect ratios is a spontaneously forming stable vortex configuration with circulating in-plane magnetization and a vortex core pointing out-of-plane. Resonantly exciting the VC via either an rf magnetic field or an rf spin-polarized current yields a gyrotropic motion around its equilibrium position, characterised by a specific eigen-frequency, which depends on the material parameters and the disk geometry [1]. Such oscillations, which can be read out via periodic magnetoresistance changes, generate rf signals with high quality factors (>10000) in the sub-GHz bandwidth [2,3]. While all these features make vortex-based nano-oscillators interesting as nanoscale rf sources, the major drawback remains their low frequency tunability associated with the linear characteristics of the gyrotropic mode.
Here, we investigate the role of magnetostriction in improving the tunability of vortex nano-oscillators. Specifically, we consider a double-disk structure comprising magnetostrictive (CoFe) and non-magnetostrictive (Py) layers separated vertically by a non-magnetic spacer. We show that, when the two vortices have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the synchronized gyration of the two vortex cores (Fig. 1). The stress-induced transition from double-frequency to single-frequency dynamics is mostly controlled by the polarization of the vortices and the magnetostatic coupling strength (i.e. spacer thickness). These findings offer a frequency tunability of vortex-based oscillators via mechanical stress, which can be generated and controlled electrically, for example, using piezoelectric substrates [4].

Funding from the EU Horizon 2020 project No. 737038 (TRANSPIRE) is acknowledged.

[1] K. Yu. Guslienko, et al, J. Appl. Phys. 91, 8037 (2002).
[2] A. Dussaux, et al, Nat. Commun. 1, 1 (2010).
[3] N. Locatelli, et al, Appl. Phys. Lett. 98, 062501 (2011).
[4] M. Filianina, et al, Appl. Phys. Lett. 115, 062404 (2019).

Keywords: Magnetic vortex; Micromagnetic modelling; Magnetoelastic effect

  • Poster (Online presentation)
    MMM 2020 Virtual Conference, 02.-06.11.2020, Virtual event, Virtual event

Publ.-Id: 32110

Synthesis, structure and magnetic properties of Sm1.2Ho0.8Fe17Нx (x = 0; 4.4)

Veselova, S. V.; Paukov, M. A.; Tereshina, I. S.; Verbetsky, V. N.; Zakharov, K. V.; Gorbunov, D.; Vasil`Ev, A. N.

Intermetallic compounds based on rare-earth metals and iron are by far the most promising materials for permanent magnets. In this work, the multicomponent compound Sm1.2Ho0.8Fe17 was prepared by induction melting. The hydride Sm1.2Ho0.8Fe17H4.4 with a high hydrogen content was obtained by direct hydrogenation of the intermetallic compound. The rhombohedral Th2Zn17-type of structure (space group R3m) is inherent to parent compound and hydride as well. The effect of hydrogenation on the magnetic properties of Sm1.2Ho0.8Fe17 was investigated. Curie temperature of the hydride Sm1.2Ho0.8Fe17H4.4 is higher than that of parent compound by ΔTC = 138 K. The hydrogen embedded in Sm1.2Но0.8Fe17 crystal lattice increases the saturation magnetization (σS) at T = 300 K, but does not significantly affect σS at Т = 4.2 K. The ferrimagnetic structure is retained in magnetic fields up to 58 T in the parent compound, while, in the hydride, there is a spin-reorientation phase transition observed at 55 T. It is found that the parameter of the intersublattice exchange interaction decreases significantly in the hydride Sm1.2Ho0.8-Fe17H4.4 (and in the nitride Sm1.2Ho0.8Fe17N2.4) which is associated with boosting of the unit-cell volume and distances between magnetic ions.

Publ.-Id: 32109

He⁺ Ion Irradiation Induced Sn Extrusion out of SnO Covered Tin Spheres – a Combined Computer Simulation of Defect Generation and Defect Kinetics

Tucholski, D.; Heinig, K.-H.; Möller, W.; Klingner, N.; Hlawacek, G.; Facsko, S.; Hübner, R.

Here we report on a combined computer simulation of defect generation and defect kinetics for 30 keV He⁺ ion irradiation of sub-μm-scale tin spheres. In the process to be simulated, the irradiation was performed in a Helium Ion Microscope which allows the in-situ monitoring of morphological changes of the nanospheres during He⁺ ion irradiation. Above a He⁺ fluence of ∼10¹⁷ /cm², Sn extrusions appear on the surface of the spheres. Initially, small, pyramidally facetted extrusions evolve at the equator of the tin spheres (north pole pointing to the ion source), later on each sphere becomes completely covered with tin, then turning into facetted single crystals. No Sn extrusions were observed for tin spheres with diameters smaller than ∼100nm. Transmission electron microscopy and Auger electron spectroscopy investigations show that the tin spheres are covered with a few-nm-thick SnO skin and that the extrusions are single crystals.
For the computer simulations a model was developed which assumes that He⁺ ions generate interstitials ISn and vacancies VSn in the body-centered tetragonal lattice of tin. Due to the SnO skin, the ISn and VSn are confined to the tin sphere. A coherent Sn-SnO interface with a strong Sn-SnO interaction prevents ISn and VSn annihilation and void formation here. The projected range of 30 keV He⁺ ions is smaller than the diameter of the sub-μm spheres, the He accumulates and partly fills the VSn. Thus, the “pressure” of ISn increases steadily. Simultaneously, He⁺ ion erosion creates openings in the SnO skin. The sputter coefficient increases with the angle of incidence, thus openings in the SnO skin form at the equator regions first. Once the tin interstitials find such an opening in the SnO skin, they can escape from the interior of the Sn sphere and form an epitaxial, regular Sn lattice outside. Due to the high Sn-SnO bond strength the extruded tin wets the outer SnO surface.
The defect generation at He⁺ ion irradiation was simulated with TRI3DYN [1], a 3D program calculating atomic displacements in the binary collision approximation. The reaction-diffusion behavior of the ISn and VSn as well as their clustering into voids and growth to extrusions were simulated with a 3D kinetic lattice Monte Carlo program [2] using an RGL potential for tin. The simulated reaction pathway of the morphology agrees very well with the sequence of HIM images taken during He⁺ ion irradiation. A quantitative comparison of the extruded material with simulations provides conclusions on the defect kinetics under ion irradiation.

[1] Möller, Nucl. Instr. Meth. B 322 (2014) 23
[2] Strobel et al., Phys. Rev. B 64 (2001) 245422

  • Lecture (Conference) (Online presentation)
    2021 Spring Meeting of the European Materials Research Society (E-MRS) / Symposium L - New developments in the modeling and analysis of radiation damage in materials II, 31.05.-04.06.2021, ONLINE, ONLINE

Publ.-Id: 32108

Effect of power ultrasound on wettability and collector-less floatability of chalcopyrite, pyrite and quartz

Ahmad, H.; Hamed, G.; Safak, G. Ö.; Tomasz, N.; Agnieszka, S.

Numerous studies have addressed the role of ultrasonication on floatability of minerals macroscopically. However, the impact of acoustic waves on the mineral hydrophobicity and its physicochemical aspects were entirely overlooked in the literature. This paper mainly investigates the impact of ultrasonic power and its time on the wettability and floatability of chalcopyrite, pyrite and quartz. For this purpose, contact angle and collectorless microflotation tests were implemented on the ultrasonic-pretreated and non-treated chalcopyrite, pyrite and quartz minerals. The ultrasonic process was carried out by a probe-type ultrasound (Sonopuls, 20 kHz and 60 W) at various ultrasonication time (0.5–30 min) and power (0–180 W) while the dissolved oxygen (DO), liquid temperature, conductivity (CD) and pH were continuously monitored. Comparative assessment of wettabilities in the presence of a constant low-powered (60 W) acoustic pre-treatment uncovered that surface of all three minerals became relatively hydrophilic. Meanwhile, increasing sonication intensity enhanced their hydrophilicities to some extent except for quartz at the highest power-level. This was mainly related to generation of hydroxyl radicals, iron-deficient chalcopyrite and elemental sulfur (for chalcopyrite), formation of OH and H radicals together with H2O2 (for pyrite) and creation of SiOH (silanol) groups and hydrogen bond with water dipoles (for quartz). Finally, it was also found that increasing sonication time led to enhancement of liquid temperature and conductivity but diminished pH and degree of dissolved oxygen, which indirectly influenced the mineral wettabilities and floatabilities. Although quartz and pyrite ultrasound-treated micro-flotation recoveries were lower than that of conventional ones, an optimum power-level of 60–90 W was identified for maximizing chalcopyrite recovery.

Keywords: froth flotation; power ultrasound; ultrasonic treatment; chalcopyrite-pyrite-quartz flotation system; hydrophobicity

Publ.-Id: 32107

Transformation of tin spheres into hollow cubes by He+ irradiation

Klingner, N.; Heinig, K.-H.; Tucholski, D.; Möller, W.; Hübner, R.; Hlawacek, G.; Facsko, S.

Broad ion irradiation of nanoobjects can considerably change their shape. Examples are ion-beam hammering [1], ion-induced shaping of buried particles [2], and ion-induced viscous flow of nanopillars [3]. Such shape changes are mainly driven by the kinetics of defects generated by binary collisions of ions and recoils. Here we report a new kind of ion-induced structure evolution.
Sub-micrometer Sn spheres were irradiated with 30 keV He+ ions in a Helium Ion Microscope (HIM). Above a He+ fluence of ~ 10E17 /cm², Sn extrusions appear on the surface of the spheres and were imaged with the HIM. Initially, small, pyramid-like facetted extrusions form at the equator of the tin spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered with tin and appears like a facetted single crystal cube. No Sn extrusions were observed for tin spheres with diameters smaller than ~100 nm. Transmission Electron Microscopy and Auger electron spectroscopy studies show that the tin spheres are covered with a few nm thick SnOx skin and that the extrusions are single crystals.

A model was developed which assumes that the He+ ions generate Frenkel pairs in the body-centered tetragonal lattice of tin. The point defects are confined to the tin sphere by the SnO skin, and there is no preferred nucleation or annihilation of the point defects at the Sn-SnO interface. The recombination of interstitials with vacancies is partly inhibited by occupation with He atoms. This results in an increasing pressure of the “interstitial gas”. Simultaneously, He+ ion erosion creates openings in the SnO skin. The sputter coefficient increases with the angle of incidence, so that openings in the SnO skin form in the equator regions first. Once the tin interstitials find an opening in the SnO skin, they can escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the outside. Due to the high Sn-SnO bond strength, the extruded tin wets the outer SnO surface.

Computer simulations were performed based on this model. The Frenkel pair generation and the SnO skin sputtering are simulated with dynamical programs based on the Binary Collision Approximation TRI3DYN [4]. Reaction-diffusion dynamics as well as nucleation and extended defect growth were simulated with a 3D kinetic lattice Monte Carlo program [5] using an RGL-potential for tin. The formation of cavities and their filling with He reproduces the experimentally observed tendency for hollow cube formation.

[1] Snoeks et al., Nucl. Instr. Meth B 178 (2001) 62
[2] Schmidt et al., Nucl. Instr. Meth. B 267 (2009) 1345
[3] Xu et al., Semicond. Sci. Technol. 35 (2020) 15021
[4] Möller, Nucl. Instr. Meth. B 322 (2014) 23
[5] Strobel et al., Phys. Rev. B 64 (2001) 245422

  • Lecture (Conference) (Online presentation)
    European Materials Research Society 2021 Spring Meeting, 31.05.-04.06.2021, ONLINE, ONLINE

Publ.-Id: 32106

Magnetic structure of the quantum magnet SrCuTe2O6

Chillal, S.; Isman, A. T. M. N.; Luetkens, H.; Canévet, E.; Scurschii, I.; Khalyavin, D.; Lake, B.

SrCuTe2O6 consists of a three-dimensional arrangement of spin-1/2 Cu2+ ions. The first-, second-, and third-neighbor interactions, respectively, couple Cu2+ moments into a network of isolated triangles, a highly frustrated hyperkagome lattice consisting of corner-sharing triangles and antiferromagnetic chains. Of these, the chain interaction dominates in SrCuTe2O62O6 using muon relaxation spectroscopy and neutron diffraction and present the low-temperature magnetic structure as well as the directional-dependent magnetic phase diagram as a function of field.

Publ.-Id: 32105

Momentum distribution function and short-range correlations of the warm dense electron gas -- ab initio quantum Monte Carlo results

Hunger, K.; Schoof, T.; Dornheim, T.; Bonitz, M.; Filinov, A.

In a classical plasma the momentum distribution, n(k), decays exponentially, for large k, and the same is observed for an ideal Fermi gas. However, when quantum and correlation effects are relevant simultaneously, an algebraic decay, n∞(k)∼k−8 has been predicted. This is of relevance for cross sections and threshold processes in dense plasmas that depend on the number of energetic particles. Here we present the first \textit{ab initio} results for the momentum distribution of the nonideal uniform electron gas at warm dense matter conditions. Our results are based on first principle fermionic path integral Monte Carlo (CPIMC) simulations and clearly confirm the k−8 asymptotic. This asymptotic behavior is directly linked to short-range correlations which are analyzed via the on-top pair distribution function (on-top PDF), i.e. the PDF of electrons with opposite spin. We present extensive results for the density and temperature dependence of the on-top PDF and for the momentum distribution in the entire momentum range.

Publ.-Id: 32103

Preclinical evaluation of [18F]FACH in healthy mice and piglets: An 18F-labeled ligand for imaging of monocarboxylate transporters with PET

Gündel, D.; Sadeghzadeh, M.; Deuther-Conrad, W.; Wenzel, B.; Cumming, P.; Toussaint, M.; Ludwig, F.-A.; Moldovan, R.-P.; Kranz, M.; Teodoro, R.; Sattler, B.; Sabri, O.; Brust, P.

: The expression of monocarboxylate transporters (MCTs) is linked to pathophysiological changes in diseases including cancer, such that MCTs could potentially serve as diagnostic markers or therapeutic targets. We recently developed [18F]FACH as a radiotracer for non-invasive molecular imaging of MCTs by positron emission tomography (PET). The aim of this study was to evaluate further the specificity, metabolic stability, and pharmacokinetics of [18F]FACH in healthy mice and piglets. We measured the [18F]FACH plasma protein binding fractions in mice and piglets and the specific binding in cryosections of murine kidney and lung. The biodistribution of [18F]FACH was evaluated by tissue sampling ex vivo and by dynamic PET/MRI in vivo, with and without pre-treatment by the MCT inhibitor α-CCA-Na or the reference compound, FACH-Na. Addition-ally, we performed compartmental modelling of the PET signal in kidney cortex and liver. Satu-ration binding studies in kidney cortex cryosections indicated a KD of 118±12 nM and Bmax of 6.0 pmol/mg wet weight. The specificity of [18F]FACH uptake in the kidney cortex was confirmed in vivo by reductions in AUC0-60min after pre-treatment with α-CCA-Na in mice (-47%) and in piglets (-66%). [18F]FACH was metabolically stable in mouse, but polar radio-metabolites were present in plasma and tissues of piglets. The [18F]FACH binding potential (BPND) in the kidney cortex was approximately 1.3 in mice. [18F]FACH has suitable properties for the detection of the MCTs in kidney, and thus has potential as a molecular imaging tool for MCT-related pathologies, which should next be assessed in relevant disease models.

Keywords: monocarboxylate transporters (MCTs); [18F]FACH; PET imaging; metabolism; kidney; cancer

  • Open Access Logo International Journal of Molecular Sciences 22(2021)4, 1645
    Online First (2021) DOI: 10.3390/ijms22041645

Publ.-Id: 32102

Small scale short circuits due to metal-droplet transfer in liquid metal batteries

Benard, S.; Landgraf, S.; Weber, N.; Weier, T.

Liquid metal batteries (LMBs) have been discussed as stationary energy storage for integrating highly volatile renewable energy sources into the electric grid. The cheap and abundant electrode materials, extreme current densities and potentially very long life time make LMBs excellent candidates for storage applications. As a typical cell, Li-Bi LMBs consist of a molten Bi-electrode on the bottom, an ion-conducting liquid electrolyte in the middle and a molten Li-electrode on the top – as illustrated schematically in Fig. 1. In order to avoid contact of the anode with the cell housing, the molten Li is typically contained in a solid Ni-Fe foam. During discharge, the anode metal Li is oxidized, and the ion crosses the electrolyte layer before alloying with the molten Bi. At charge, this process is reversed and Li de-alloyed and transferred back into the metal-foam anode.
When cycling such batteries for several days, sometimes short voltage drop-offs can be observed. As illustrated in Fig. 1, such quick changes of the cell potential can most probably be explained by a sudden non-faradaic Li-transfer from the anode to the cathode. After operating Li-Bi cells and removing the current collector with the Ni-Fe-foam, sometimes solid spots, formed of an intermetallic phase, can be observed below of the foam – as shown in the inset in Fig. 1. These intermetallic phases can appear only if Bi from the cathode touches the anode, e.g. during a localized short circuit. Considering that the metal foam reacts slightly with the molten salt, it might happen that the wetting behavior between molten Li and foam changes with time. A missing wetting could – finally – lead to the formation of small Li-droplets below of the foam when charging the cell. If such droplets grow too much, they might lead to a local short circuit and may thus explain the phenomena illustrated in Fig. 1. Bases on this motivation, the formation, detachment and transport of such droplets as well as a possible short circuit is studied.

  • Lecture (Conference)
    Electromagnetic processing of materials, 13.-17.06.2021, Riga, Lettland

Publ.-Id: 32100

Suppression of Metastatic Melanoma Growth in Lung by Modulated Electro-Hyperthermia Monitored by a Minimally Invasive Heat Stress Testing Approach in Mice

Thomas, M. J.; Major, E.; Benedek, A.; Horvath, I.; Mathe, D.; Bergmann, R.; Szasz, A. M.; Krenacs, T.; Benyo, Z.

Modulated electro-hyperthermia (mEHT) is a novel complementary therapy in oncology which is based on the higher conductivity and permittivity of cancerous tissues due to their enhanced glycolytic activity and ionic content compared to healthy normal tissues. We aimed to evaluate the potential of mEHT, inducing local hyperthermia, in the treatment of pulmonary metastatic melanoma. Our primary objective was the optimization of mEHT for targeted lung treatment as well as to identify the mechanism of its potential anti-tumor effect in the B16F10 mouse melanoma pulmonary metastases model while investigating the potential treatment-related side effects of mEHT on normal lung tissue. Repeated treatment of tumor-bearing lungs with mEHT induced significant anti-tumor effects as demonstrated by the lower number of tumor nodules and the downregulation of Ki67 expression in treated tumor cells. mEHT treatment provoked significant DNA double-strand breaks indicated by the increased expression of phosphorylated H2AX protein in treated tumors, although treatment-induced elevation of cleaved/activated caspase-3 expression was insignificant, suggesting the minimal role of apoptosis in this process. The mEHT-related significant increase in p21waf1 positive tumor cells suggested that p21waf1-mediated cell cycle arrest plays an important role in the anti-tumor effect of mEHT on melanoma metastases. Significantly increased CD3+, CD8+ T-lymphocytes, and F4/80+CD11b+ macrophage density in the whole lung and tumor of treated animals emphasizes the mobilizing capability of mEHT on immune cells. In conclusion, mEHT can reduce the growth potential of melanoma, thus offering itself as a complementary therapeutic option to chemo- and/or radiotherapy.

Keywords: B16F10 melanoma; DNA double-strand breaks; cell cycle arrest; immune cell mobilization; modulated electro-hyperthermia; pulmonary metastases

Publ.-Id: 32099

Metal ion size profoundly affects H3glyox chelate chemistry

Choudhary, N.; Barett, K.; Kubeil, M.; Radchenko, V.; Engle, J.; Stephan, H.; de Guadalupe Jaraquemada-Pelaez, M.; Orvig, C.

The bisoxine hexadentate chelating ligand H3glyox was investigated for its affinity for Mn2+, Cu2+ and Lu3+ ions; all three metal ions are medicinally relevant with applications in nuclear medicine and medicinal inorganic chemistry. The aqueous coordination chemistry and thermodynamic stability of all three metal complexes was thoroughly investigated by detailed DFT structure calculations and stability constant determination, by employing UV in-batch spectrophotometric titrations, giving pM values – pCu (25.2) > pLu (18.1) > pMn (12.0). DFT calculated structures revealed different geometries and coordination preferences of the three metal ions; notable was an inner sphere water molecule in the Mn2+ complex. H3glyox labels [52Mn]Mn2+, [64Cu]Cu2+ and [177Lu]Lu3+ at ambient conditions with apparent molar activities of 40 MBq/mol, 500 MBq/mol and 25 GBq/mol, respectively. Collectively, these initial investigations provide significant insight into the effects of metal ion size and charge on the chelation with the hexadentate H3glyox and the potential use of the Mn2+-H3glyox complex in 52/55Mn-based bimodal imaging.

Publ.-Id: 32097

Radial pressure forces in Euler-Euler simulations of turbulent bubbly pipe flows

Rzehak, R.; Liao, Y.; Meller, R.; Schlegel, F.; Lehnigk, R.; Lucas, D.

Two-equation turbulence models based on the Boussinesq eddy viscosity hypothesis that have been used in the vast majority of previous simulation studies on bubbly pipe flows contain a term which renders the radial pressure distribution non-constant. In single phase simulations this effect is invariably absorbed in the definition of a modified pressure, from which the real pressure may be recovered if necessary. For bubbly multiphase flows however, this is not possible since the bubbles experience a force which depends, of course, on the real pressure rather than the modified one. As it turns out, most software codes by default rely on the approximation of neglecting the difference between modified and real pressure for bubbly flows. The purpose of the present study is to assess the influence of this approximation on the final simulations results. Fortunately it turns out that at least for the conditions considered in this study, the error is small.

Keywords: turbulent dispersed gas liquid multiphase flow; Euler-Euler two fluid model; closure relations; CFD


  • Secondary publication expected from 01.04.2022

Publ.-Id: 32095

Magnetische Kühlung

Gottschall, T.

  • Lecture (others)
    Seniorenakademie der TU Dresden, 15.09.2020, Dresden, Deutschland

Publ.-Id: 32093

Advanced characterization of multicaloric materials in pulsed magnetic fields

Gottschall, T.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    JEMS 2020, 07.12.2020, Lissabon, Portugal

Publ.-Id: 32092

Dynamics of Rising Bubbles in a Quiescent Slag Bath with Varying Thermo-Physical Properties

Reuter, M. A.; Obiso, D.; Schwittala, D. H.; Korobeinikov, I.; Meyer, B.; Richter, A.

The motion of bubbles in a liquid slag bath with temperature gradients is investigated by means of 3D fluid dynamic computations. The goal of the work is to describe the dynamics of the rising bubbles, taking into account the temperature dependency of the thermo-physical properties of the slag. Attention is paid to the modeling approach used for the slag properties and how this affects the simulation of the bubble motion. In particular, the usage of constant values is compared to the usage of temperature-dependent data, taken from models available in the literature and from in-house experimental measurements. Although the present study focuses on temperature gradients, the consideration of varying thermo-physical properties is greatly relevant for the fluid dynamic modeling of reactive slag baths, since the same effect is given by heterogeneous species and solid fraction distributions. CFD is applied to evaluate the bubble dynamics in terms of the rising path, terminal bubble shape, and velocity, the gas–liquid interface area, and the appearance of break-up phenomena. It is shown that the presence of a thermal gradient strongly acts on the gas–liquid interaction when the temperature-dependent properties are considered. Furthermore, the use of literature models and experimental data produces different results, demonstrating the importance of correctly modeling the slag’s thermo-physical properties.

Keywords: rising bubbles; liquid slag

Publ.-Id: 32091

Local short-circuits in liquid metal batteries - influence of the contact angle on the droplet movement in VOF-simulations

Benard, S.; Landgraf, S.; Weber, N.; Weier, T.

The presentation will give an overview about Li-droplet formation, as well as their detachment and transport, which finally might lead to a localised short-circuit in liquid metal batteries.

  • Lecture (Conference)
    16th OpenFOAM Workshop 2021, 08.-11.06.2021, Dublin, Ireland

Publ.-Id: 32090

Ultrathin Co films with Pt and Au covers - magnetic and structural properties driven by Ga+ ion irradiation

Mazalski, P.; Ohnoutek, L.; Sveklo, I.; Beran, L.; Kurant, Z.; Powroźnik, W.; Wawro, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Faßbender, J.; Hamrle, J.; Antoš, R.; Kletecka, V.; Veis, M.; Maziewski, A.

The X/Co 3nm/Y (where X, Y=Au, Pt) trilayers with as deposited in-plane magnetization alignment were irradiated with 30 keV Ga+ ions in the wide range of ion fluence. The samples were investigated by means of complementary techniques: magneto-optical magnetometry and spectroscopy (in the photon energy range from 1.2 eV to 4.5 eV), magnetic force microscopy, positron annihilation spectroscopy, X-ray diffraction and reflectivity. Difference in miscibility of interface atoms is clearly manifested in various intermixing extent at Co/Pt and Co/Au interfaces and consequently in magnetic properties of the irradiated trilayers. Low irradiation fluence (~1014 ions/cm2) leads to ~1nm interfaces broadening without visible surface etching for all samples, which is related with a distinct drop of magnetic anisotropy. However, the high irradiation fluence (~5·1015 ions/cm2) results in enhanced interface broadening and significant surface etching (~5 nm) partially removing also Co atoms. Tensile strains (up to 0.5%) were developed in the cover layers. The tensile strain, layers intermixing and the creation of Co-Pt(Au) alloys with different composition formed by irradiation are correlated with the increase of magnetic anisotropy. Moreover it was observed that substitution of Au instead of Pt (as a cap or buffer layer) results in substantial increase of perpendicular magnetic anisotropy. Maximal increase of magnetooptical parameters was observed for Pt/Co/Pt layer. Irradiation induced changes of concentration profiles are revealed using magnetooptical spectra, X-ray reflectivity spectra and simulations with use of binary collision approximation.

Keywords: perpendicular magnetic anisotropy; ion irradiation; positron annihilation spectroscopy; magneto-optical Kerr spectroscopy; molecular beam epitaxy

Publ.-Id: 32089

Thermoelectric Performance of the Half-Heusler Phases RNiSb (R = Sc, Dy, Er, Tm, Lu): High Mobility Ratio between Majority and Minority Charge Carriers

Ciesielski, K.; Synoradzki, K.; Veremchuk, I.; Skokowski, P.; Szymanski, D.; Grin, Y.; Kaczorowski, D.

Deeper understanding of electrical and thermal transport is critical for further development of thermoelectric materials. Here we describe the thermoelectric performance of a group of rare-earth-bearing half-Heusler phases determined in a wide temperature range. Polycrystalline samples of ScNiSb, DyNiSb, ErNiSb, TmNiSb, and LuNiSb are synthesized by arc melting and densified by spark plasma sintering. They are characterized by powder x-ray diffraction and scanning electron microscopy. The physical properties are studied by means of heat-capacity and Hall-effect measurements performed in the temperature range from 2 to 300 K, as well as electrical-resistivity, Seebeck-coefficient, and thermal-conductivity measurements performed in the temperature range from 2 to 950 K. All the materials except TmNiSb are found to be narrow-gap intrinsic p-type semiconductors with rather light charge carriers. In TmNiSb, the presence of heavy holes with large weighted mobility is evidenced by the highest power factor among the series (17 mu W K-²cm(-¹) at 700 K). The experimental electronic relaxation time calculated with the parabolic band formalism is found to range from 0.8 x 10(-¹⁴) to 2.8 x 10(-¹⁴) s. In all the materials studied, the thermal conductivity is between 3 and 6 W m(-¹) K-¹ near room temperature (i.e., smaller than in other pristine d-electron half-Heusler phases reported in the literature). The experimental observation of the reduced thermal conductivity appears fully consistent with the estimated low sound velocity as well as strong point-defect scattering revealed by Debye-Callaway modeling. Furthermore, analysis of the bipolar contribution to the measured thermal conductivity yields abnormally large differences between the mobilities of n-type and p-type carriers. The latter feature makes the compounds examined excellent candidates for further optimization of their thermoelectric performance via electron doping.


Publ.-Id: 32088

Discovery of high-performance thermoelectric copper chalcogenide using modified diffusion-couple high-throughput synthesis and automated histogram analysis technique

Deng, T.; Xing, T.; Brod, M. K.; Sheng, Y.; Qiu, P.; Veremchuk, I.; Song, Q.; Wei, T.-R.; Yang, J.; Snyder, G. J.; Grin, Y.; Chen, L.; Shi, X.

Discovery of novel high-performance materials with earth-abundant and environmentally friendly elements is a key task for civil applications based on advanced thermoelectric technology. Advancements in this area are greatly limited by the traditional trial-and-error method, which is both time-consuming and expensive. The materials genome initiative can provide a powerful strategy to screen for potential novel materials using high-throughput calculations, materials characterization, and synthesis. In this study, we developed a modified diffusion-couple high-throughput synthesis method and an automated histogram analysis technique to quickly screen high-performance copper chalcogenide thermoelectric materials, which has been well demonstrated in the ternary Cu-Sn-S compounds. A new copper chalcogenide with the composition of Cu₇Sn₃S₁₀ was discovered. Studies on crystal structure, band gap, and electrical and thermal transport properties were performed to show that it is a promising thermoelectric material with ultralow lattice thermal conductivity, moderate band gap, and decent electrical conductivity. Via Cl doping, the thermoelectric dimensionless figure of merit zT reaches 0.8 at 750 K, being among the highest values reported in Cu-Sn-S ternary materials. The modified diffusion-couple high-throughput synthesis method and automated histogram analysis technique developed in this study also shed light on the development of other advanced thermoelectric and functional materials.

Keywords: ultralow thermal conductivity; ternary; scattering; sulfides; Cu₂SnS₃; model


  • Secondary publication expected

Publ.-Id: 32087

Robust Fermi-Surface Morphology of CeRhIn5 across the Putative Field-Induced Quantum Critical Point

Mishra, S.; Hornung, J.; Raba, M.; Klotz, J.; Förster, T.; Harima, H.; Aoki, D.; Wosnitza, J.; McCollam, A.; Sheikin, I.

We report a comprehensive de Haas–van Alphen (dHvA) study of the heavy-fermion material CeRhIn5 in magnetic fields up to 70 T. Several dHvA frequencies gradually emerge at high fields as a result of magnetic breakdown. Among them is the thermodynamically important β1 branch, which has not been observed so far. Comparison of our angle-dependent dHvA spectra with those of the non-4f compound LaRhIn5 and with band-structure calculations evidences that the Ce 4f electrons in CeRhIn5 remain localized over the whole field range. This rules out any significant Fermi-surface reconstruction, either at the suggested nematic phase transition at B* ≈ 30 T or at the putative quantum critical point at Bc ≃ 50 T. Our results rather demonstrate the robustness of the Fermi surface and the localized nature of the 4f electrons inside and outside of the antiferromagnetic phase.

Publ.-Id: 32086

Can microorganisms significantly influence cast iron corrosion in a DGR?

Matschiavelli, N.; Sushko, V.; Dressler, M.; Neubert, T.; Kühn, L.; Schierz, A.; Cherkouk, A.

For the safe storage of high-level radioactive waste (HLW) in deep geological repositories (DGR), several metals could potentially act as canister material and are under investigation with respect to their properties under disposal-relevant conditions. An essential requirement for the selected metal(s) is the long-term stability which is mainly realized by the resistance to corrosion. The process of corrosion depends on the overall environment in the surrounding of the metal canister and which will change over time. Here, parameters like redox potential, pH, the presence of (pore-) water, the salinity and also the presence of metabolically active microorganisms are of relevance, among others. In order to analyze the influence of different pore waters and the natural microbial community of a Bavarian bentonite, which acts as geotechnical barrier and will be in direct contact to the canister, microcosm experiments were set up. These slurry experiments contained B25 bentonite, synthetic Opalinus Clay pore water or saline cap rock solution as well as copper- or cast iron plates in various combinations. During an incubation time of 400 days under anaerobic conditions at 37 °C, several bio-geochemical parameters (e.g. pH, redox potential and the concentration of minerals, sulfate, iron(II/III) and organic acids) were analyzed as well as the corrosion process and a potential microbial influence. The obtained results provide insights into the complex interplay between bentonite, pore water, metals and microorganisms. Different precipitates like carbonates, iron oxides and sulfides were identified on the cast iron surface, potentially accelerating or slowing down the corrosion process and, thus, affecting the long-term stability of the metal canister in a DGR.

  • Lecture (Conference) (Online presentation)
    EGU 2021 General Assembly, 19.-30.04.2021, Wien, Österreich

Publ.-Id: 32085

Magnetoelastic study on the frustrated quasi-one-dimensional spin-1/2 magnet LiCuVO4

Miyata, A.; Hikihara, T.; Furukawa, S.; Kremer, R. K.; Zherlitsyn, S.; Wosnitza, J.

We investigated the magnetoelastic properties of the quasi-one-dimensional spin-1/2 frustrated magnet LiCuVO4. Longitudinal-magnetostriction experiments were performed at 1.5 K in high magnetic fields of up to 60 T applied along the b axis, i.e., the spin-chain direction. The magnetostriction data qualitatively resemble the magnetization results, and saturate at Hsat ≈ 54 T, with a relative change in sample length of ΔL/L ≈ 1.8 × 10−4. Remarkably, both the magnetostriction and the magnetization evolve gradually between Hc3 ≈ 48 T and Hsat, indicating that the two quantities consistently detect the spin-nematic phase just below the saturation. Numerical analyses for a weakly coupled spin-chain model reveal that the observed magnetostriction can overall be understood within an exchange-striction mechanism. Small deviations found may indicate nontrivial changes in local correlations associated with the field-induced phase transitions.


Publ.-Id: 32083

Advanced mineral exploration in the glaciated terrain using topsoil geochemistry and the compositional statistical data analysis

Sarala, P.; Pospiech, S.; Middleton, M.; Taivalkoski, A.; Hulkki, H.

Mineral exploration in northern, vulnerable nature areas demands on the development of new, environmentally friendly sampling and analyses techniques. Those areas are typically covered by the transported cover of which the glacigenic sediments such as a till are the most dominant as a result of several glaciation stages. To avoid conventional basal till and bedrock sampling using heavy machines, the use of different surface geochemical sampling media and techniques have increased recently. Particularly, the development of selective and weak leach techniques for the topsoil (Ah and B horizons) geochemistry has been intensive, and the use of those techniques has led to the observation of new mineralization.
In this research, carried out under the project New Exploration Technologies (NEXT), funded by the European Union’s Horizon 2020 research and innovation programme, we used stratified random sampling strategy for creating a sampling grid and developed novel compositional statistical data analysis for the interpretation of geochemical data obtained by the multi-source surface geochemical techniques. The test area located in northern Finland where there is an active exploration campaign going on for Au-U-Co mineralizations in the Rajapalot area, Ylitornio by the Mawson Oy. Glacial morphology in the study area is dominated by the ribbed moraine ridges with peatlands in between. The thickness of till cover varied from some metres to 15 m. A sampling network for both the Ah and B horizon samples comprised 98 proper and 10 field duplicate sampling stations from the mineral soil dominated by the Podsol-type soil horizon. The chemical analyses methods used were Ultratrace 1:1:1 Aqua Regia leach and 0.1 M sodium pyrophosphate leach for the Ah horizon samples, and Ionic leach and Super Trace Aqua Regia leach methods for the B horizon samples. The laboratory analyses were supported by the portable X-Ray Fluorescence (pXRF) analyses done directly in the field. The statistical analysis methods of the results were based on conventional supervised and unsupervised classification techniques using as explanatory variables: a) log-ratio transformations of the geochemical compositions, b) enrichment factors between sampled media, and c) the summaries of the two preceding systems of variables provided by the parallel principal component analysis.
The preliminary results of the topsoil geochemistry show a significant response to many elements to known geochemical features and elevated contents in the base-of-till and underlying bedrock geochemical data. Anomaly patterns are also reflecting the lithological variations of the rock units in the bedrock. Based on the results, it is obvious that a) there is good correlation between the surface geochemistry and underlying bedrock, b) stratified randomization in the planning phase and statistical methods in data interpretation stage increases the quality of the data and the reliability of geochemical exploration, and c) topsoil sampling with selective analysis methods is effective and environmentally friendly geochemical exploration technique in the glaciated terrains.

Keywords: soil; mineral exploration

  • Lecture (Conference) (Online presentation)
    EGU General Assembly 2021, 19.-30.04.2021, online, Austria

Publ.-Id: 32082

Snow as proxy for mineral exploration – a case study from Northern Finland

Pospiech, S.; Taivalkoski, A.; Lahaye, Y.; Sarala, P.; Kinnunen, J.; Middleton, M.

Modern mineral exploration techniques for Europe are required to be sustainable, environmental friendly and social acceptable. Especially for the geochemical exploration of the ecologically sensitive areas of northern Europe this poses a challenge, because any heavy machinery or invasive methods might cause long-lasting damage to the natural systems. One way of reducing the impact of mineral exploration on the environment during early stages of the exploration is to use surface media, such as upper soil horizons, water, plants and snow. Of these options, snow has several advantages: Sampling and analysing snow is fast and low in costs, it has no impact on the environment, and it is (in winter time) ubiquitous, i.e. available independent of land cover and environment.
In the “New Exploration Technologies (NEXT)” project, funded by the European Union’s Horizon 2020 research and innovation programme, 171 snow samples and 13 field duplicate snow samples for quality control, were collected in March-April 2019 to strengthen the idea of using snow as a sampling material for mineral exploration. The Rajapalot Au-Co prospect in northern Finland, 60 km west from Rovaniemi and operated by Mawson Oy, was selected as a test site. Stratified random sampling was used to create the uneven sampling net over the test area. The samples were analysed at GTK using a Nu AttoM single collector inductively coupled plasma mass spectrometry (SC-ICPMS) which returned analytical results for 52 elements at the ppt level. Due to strict quality control, only Ba, Ca, Cr, Cs, Ga, Li, Mg, Rb, Sb, Sr, Tk, V and Zn passed and were used in the final data analysis.
The preliminary results based on PCA show a strong dependency of snow composition on the soil type. That is, there is a difference if the snow sample was taken above mineral soil or organic soil. Thus, the soil type should be included in the models or the data analysis should be looked separately for different soil types. The linear model predictions were used to test if the snow geochemistry can predict the bedrock geochemistry. For Al, Ca, Li, Sr and Na the prediction works well. Instead of using snow directly for detecting the mineralization for pinpointing drill targets for exploration purposes, snow geochemistry could be used as a lithogeochemical mapping tool to delineate the areas where to continue exploration with more sensitive methods.

Keywords: snow; mineral exploration; compositional data; environmental friendly; sustainable; NEXT

  • Lecture (Conference) (Online presentation)
    EGU General Assembly 2021, 19.-30.04.2021, online, Austria

Publ.-Id: 32081

Tuning of ferromagnetic behavior of GaN films by N ion implantation: an experimental and first principle-based study

Singh, P.; Ghosh, S.; Mishra, V.; Barman, S.; Barman, S. R.; Singh, A.; Kumar, S.; Li, Z.; Kentsch, U.; Srivastava, P.

Magnetic properties of N-ion implanted GaN films (150 nm) have been reported. It is found that GaN films grown by the MOCVD technique show strong room temperature ferromagnetic behavior, which can be tuned by implanting N-ions at different fluences (1×10¹⁵ to 5×10¹⁶ ions- cm⁻²). Presence of implanted N at interstitial sites of the GaN host matrix is indicated from the strain observed in GaN by analysis of XRD data. PL spectra show presence of different types of defects in the as deposited film and engineering of defects after N-ion implantation. XPS spectra of Ga 3d-core level and valence band reveal the bonding of implanted N with the host Ga and/or N. The origin of ferromagnetic behavior is ascribed to unpaired electrons created at N sites due to Ga vacancies. First principle-based calculations also confirm ferromagnetism due to Ga vacancies and the reduction of magnetic behavior in Ga deficient GaN with N-ion implantation at interstitial site. The systematic reduction in the saturation magnetic moment value after N-ion implantation is explained on the basis of pairing of the unpaired electrons due to the bond formation of interstitial N with Ga and N present in the host matrix.

Keywords: ion implantation; defects; ferromagnetism; nitrogen interstitials; tuning

Publ.-Id: 32080

Magnetic Refrigeration: From material to application

Gottschall, T.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences)
    31. Edgar Lüscher Seminar, 09.02.2020, Klosters, Schweiz

Publ.-Id: 32079

Recent progress and future projects at HLD and LNCMI - Toulouse

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    The 16th Japanese High Magnetic Field Forum, 03.12.2020, Tuhoku, Japan

Publ.-Id: 32078

Magnetoelastic coupling in frustrated magnets: The cases of LiCuVO4 and MnCr2S4

Miyata, A.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 02.12.2020, Tohoku, Japan

Publ.-Id: 32076

Pressure-tuned magnetic interactions in the triangular-lattice Quantum antiferromagnet Cs2CuCl4

Zvyagin, S.

es hat kein aussagefähiges Abstract vorgelegen

  • Invited lecture (Conferences) (Online presentation)
    ARHMF 2020 and KINKEN Materials Science School 2020 for Young Scientists, 01.-03.12.2020, Tohoku, Japan

Publ.-Id: 32075

Contactless generation of cavitation in high temperature liquid metals and its impact on particle dispersion in solidified iron and steel samples

Sarma, M.; Grants, I.; Herrmannsdörfer, T.; Gerbeth, G.

A recently developed method for the contactless magnetic generation of cavitation is demonstrated for high-melting-point metals. The approach is based on the floating-zone technique, which is truly contactless and crucible-free as it uses electromagnetic forces. Using this method, ultra-high-temperature ceramic particles, such as TiN, TiB₂ and TiC, are admixed in liquid iron and 316L steel. The dispersion and particle refinement caused by cavitation treatment during melting and solidification are investigated. Magnetic fields up to 8 T that correspond to pressure oscillation amplitude of 0.83 MPa are used. The signal emitted by the collapsing bubbles is captured and visualized for iron melts. Samples with a higher number of cavitation nuclei exhibit a more stable cavitation response. Improved reinforcement refinement is demonstrated for increasing cavitation intensity – the size of precipitates is evidently reduced due to the cavitation


  • Secondary publication expected from 01.05.2022

Publ.-Id: 32074

Spin dynamics in low-D spin systems: high-field ESR

Zvyagin, S.

es lag kein aussagefähiges Abstract vor

  • Invited lecture (Conferences) (Online presentation)
    Workshop on Neutrons and Complementary Techniques for Quantum Materials, 18.-21.08.2020, Oak Ridge, USA

Publ.-Id: 32073

Shaken and stirred: When Bond meets Suess-de Vries and Gnevyshev-Ohl

Stefani, F.; Stepanov, R.; Weier, T.

We argue that the most prominent temporal features of the solar dynamo, in particular the Hale cycle, the Suess de Vries cycle (associated with variations of the Gnevyshev-Ohl rule), Gleissberg-type cycles, and grand minima can be self-consistently explained by double synchronization with the 11.07-years periodic tidal forcing of the Venus-Earth-Jupiter system and the (mainly) 19.86-years periodic motion of the Sun around the barycenter of the solar system. In our numerical simulation, grand minima, and clusters thereof, emerge as intermittent and non periodic events on millennial time scales, very similar to the series of Bond events which were observed throughout the Holocene and the last glacial period. If confirmed, such an intermittent transition to chaos would prevent any long-term prediction of solar activity, notwithstanding the fact that the shorter-term Hale and Suess-de Vries cycles are clocked by planetary motion.

Keywords: solar cycle

  • Invited lecture (Conferences) (Online presentation)
    Virtual Nordic Dynamo Seminar, 15.09.2020, Stockholm, Sweden
  • Open Access Logo Solar Physics 296(2021)6, 88
    DOI: 10.1007/s11207-021-01822-4

Publ.-Id: 32072

Schwabe, Gleissberg, Suess-de Vries: Towards a consistent model of planetary synchronization of solar cycles

Stefani, F.; Giesecke, A.; Seilmayer, M.; Stepanov, R.; Weier, T.

Aiming at a consistent planetary synchronization model of both short-term and long-term solar cycles, we start with an analysis of Schove’s historical data of cycle maxima. Their deviations (residuals) from the average cycle duration of 11.07 years show a high degree of regularity, comprising a dominant 200 year period (Suess-de Vries cycle), and a few periods around 100 years (Gleissberg cycle). Encouraged by their robustness, we support previous forecasts of an upcoming grand minimum in the 21st century. To explain the long-term cycles, we enhance our tidally synchronized solar dynamo model by a modulation of the field storage capacity of the tachocline with the orbital angular momentum of the Sun, which is dominated by the 19.86-year periodicity of the Jupiter–Saturn synodes. This modulation of the 22.14-year Hale cycle leads to a 193-year beat period of dynamo activity which is indeed close to the Suess-de Vries cycle. For stronger dynamo modulation, the model produces additional peaks at typical Gleissberg frequencies, which seem to be explainable by the non-linearities of the basic beat process, leading to a bi-modality of the Schwabe cycle. However, a complementary role of beat periods between the Schwabe cycle and the Jupiter–Uranus/Neptune synodic cycles cannot be completely excluded.

Keywords: solar cycle


  • Secondary publication expected

Publ.-Id: 32071

Evolution of a strong electrovortex flow in a cylindrical cell

Kolesnichenko, I.; Frick, P.; Eltishchev, V.; Mandrykin, S.; Stefani, F.

The mechanism of poloidal flow suppression in an electrovortex flow (EVF) is verified in a liquid metal experiment and supported by numerical simulations. Beyond a certain threshold of azimuthal forcing, a strong poloidal EVF flow develops only transiently, before the centrifugal forces of the slowly generated swirl compensate the EVF-driving forces. This result shows that EVFs can become of particular importance in large-scale liquid metal batteries, especially during the switch-on regime when the transient poloidal flows can be up to two orders of magnitude stronger than those expected in the saturated regime.

Keywords: electrovortex flow


Publ.-Id: 32070

Overview of mico- and millifluidic prototyping and sensing approaches

Schütt, J.; Makarov, D.

Kick-Off Präsentation des HZDRs im Zuge des Projektstarts. Angesprochene Themengebiete umfassen die aktuellen und zukünftigen Arbeitsgebiete der Arbeitsgruppe "Fluid Sensorics".

Keywords: Fluidic Sensorics; SiNW FETs; Nano-capacitors; Planar Hall Effect Sensors

  • Lecture (others) (Online presentation)
    Initial Scientific Meeting, 12.11.2020, Dresden, Deutschland

Publ.-Id: 32069

Using Diffuse Scattering to Observe X-Ray-Driven Nonthermal Melting

Hartley, N.; Grenzer, J.; Huang, L.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Lu, W.; Makita, M.; Matsuoka, T.; Nakajima, S.; Ozaki, N.; Pikuz, T.; Rode, A. V.; Sagae, D.; Schuster, A.; Tono, K.; Voigt, K.; Vorberger, J.; Yabuuchi, T.; McBride, E. E.; Kraus, D.

We present results from the SPring-8 Angstrom Compact free electron LAser facility, where we used a high intensity (∼10^20 W/cm2) x-ray pump x-ray probe scheme to observe changes in the ionic structure of silicon induced by x-ray heating of the electrons. By avoiding Laue spots in the scattering signal from a single crystalline sample, we observe a rapid rise in diffuse scattering and a transition to a disordered, liquidlike state with a structure significantly different from liquid silicon. The disordering occurs within 100 fs of irradiation, a timescale that agrees well with first principles simulations, and is faster than that predicted by purely inertial behavior, suggesting that both the phase change and disordered state reached are dominated by Coulomb forces. This method is capable of observing liquid scattering without masking
signal from the ambient solid, allowing the liquid structure to be measured throughout and beyond the phase change.

Publ.-Id: 32068

Design and performance characterisation of the HAPG von Hámos Spectrometer at the High Energy Density Instrument of the European XFEL

Preston, T. R.; Göde, S.; Schwinkendorf, J.-P.; Appel, K.; Brambrink, E.; Cerantola, V.; Höppner, H.; Makita, M.; Pelka, A.; Prescher, C.; Sukharnikov, K.; Schmidt, A.; Thorpe, I.; Toncian, T.; Amouretti, A.; Chekrygina, D.; Falcone, R. W.; Falk, K.; Fletcher, L. B.; Galtier, E.; Harmand, M.; Hartley, N.; Hau-Riege, S. P.; Heimann, P.; Huang, L.; Humphries, O. S.; Karnbach, O.; Kraus, D.; Lee, H. J.; Nagler, B.; Ren, S.; Schuster, A.; Smid, M.; Voigt, K.; Zhang, M.; Zastrau, U.

The von Hámos spectrometer setup at the HED instrument of the European XFEL is described in detail. The spectrometer is designed to be operated primarily between 5 and 15 keV to complement the operating photon energy range of the HED instrument. Four Highly Annealed Pyrolitic Graphite (HAPG) crystals are characterised with thicknesses of 40 μm or 100 μm and radius-of-curvature 50 mm or 80 mm, in conjunction with either an ePix100 or Jungfrau detector. The achieved resolution with the 50 mm crystals, operated between 6.5 and 9 keV, matches that reported previously: ~8 eV for a thickness of 40 μm, whereas, with an 80 mm crystal of thickness 40 μm, the resolution exceeds that expected. Namely, a resolution of 2 eV is demonstrated between 5–6 keV implying a resolving power of 2800. Therefore, we posit that flatter HAPG crystals, with their high reflectivity and improved resolving power, are a powerful tool for hard x-ray scattering and emission experiments allowing unprecedented measurements of collective scattering in a single shot.

Publ.-Id: 32067

A spectral library for laser-induced fluorescence analysis as a tool for rare earth element identification

Fuchs, M.; Beyer, J.; Lorenz, S.; Sharma, S.; Renno, A.; Heitmann, J.; Gloaguen, R.

With the recurring interest on rare-earth elements (REE), laser-induced fluorescence (LiF) may provide a powerful tool for their rapid and accurate identification at different stages along their value chain. Applications to natural materials such as rocks could complement the spectroscopy-based toolkit for innovative, non-invasive exploration technologies. However, the diagnostic assignment of detected emission lines to individual REE remains challenging, because of the complex composition of natural rocks in which they can be found. The resulting mixed spectra and the large amount of data generated demand for automated approaches of data evaluation, especially in mapping applications such as drill core scanning. LiF reference data provide the solution for robust REE identification, yet they usually remain in the form of tables of published emission lines. We show that a complete reference spectra library could open manifold options for innovative automated analysis.

We present a library of high-resolution LiF reference spectra using the Smithsonian rare-earth phosphate standards for electron microprobe analysis.We employ three standard laser wavelengths (325 nm, 442 nm, 532 nm) to record representative spectra in the UV-visible to near-infrared spectral range (340–1080 nm). Excitation at all three laser wavelengths yielded characteristic spectra with distinct REE-related emission lines for EuPO4, TbPO4, DyPO4 and YbPO4. In the other samples, the high-energy excitation at 325 nm caused unspecific, broadband defect emissions. Here, lower energy laser excitation showed successful for suppressing non-REE-related emission. At 442 nm excitation, REE-reference spectra depict the diagnostic emission lines of PrPO4, SmPO4 and ErPO4. For NdPO4 and HoPO4 most efficient excitation was achieved with 532 nm. Our results emphasise on the possibility of selective REE excitation by changing the excitation wavelength according to the suitable conditions for individual REEs. Our reference spectra provide a database for transparent and reproducible evaluation of REE-bearing rocks. The LiF spectral library is available at and the registered DOI: (Fuchs et al., 2020). It gives access to traceable data for manifold further studies on comparison of emission line positions, emission line intensity ratios and splitting into emission line sub-levels or can be used as reference or training data for automated approaches of component assignment.

Keywords: Laser-induced fluorescence; rare earth elements; exploration; spectral library


Publ.-Id: 32066

Drill-core mineral abundance estimation using hyperspectral and high-resolution mineralogical data

Tusa, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Rafiezadeh Shahi, K.; Fuchs, M.; Gloaguen, R.; Gutzmer, J.

Due to the extensive drilling performed every year in exploration campaigns for the discovery and evaluation of ore deposits, drill-core mapping is becoming an essential step. While valuable mineralogical information is extracted during core logging by on-site geologists, the process is time consuming and dependent on the observer and individual background. Hyperspectral short-wave infrared (SWIR) data is used in the mining industry as a tool to complement traditional logging techniques and to provide a rapid and non-invasive analytical method for mineralogical characterization. Additionally, Scanning Electron Microscopy-based image analyses using a Mineral Liberation Analyser (SEM-MLA) provide exhaustive high-resolution mineralogical maps, but can only be performed on small areas of the drill-cores. We propose to use machine learning algorithms to combine the two data types and upscale the quantitative SEM-MLA mineralogical data to drill-core scale. This way, quasi-quantitative maps over entire drill-core samples are obtained. Our upscaling approach increases result transparency and reproducibility by employing physical-based data acquisition (hyperspectral imaging) combined with mathematical models (machine learning). The procedure is tested on 5 drill-core samples with varying training data using random forests, support vector machines and neural network regression models. The obtained mineral abundance maps are further used for the extraction of mineralogical parameters such as mineral association.

Keywords: hyperspectral imaging; drill-core; SWIR; mineral abundance mapping; mineral association; machine learning


Publ.-Id: 32065

Object Detection Routine for Material Streams Combining RGB and Hyperspectral Reflectance Data Based on Guided Object Localization

Sudharshan, V.; Seidel, P.; Ghamisi, P.; Lorenz, S.; Fuchs, M.; Shaik Fareedh, J.; Neubert, P.; Schubert, S.; Gloaguen, R.

Electronic waste is the fastest growing type of scrap globally and is an important challenge due to its heterogeneity, intrinsic toxicity and potential environmental impact. With an objective of obtaining information on the composition of printed circuit boards (PCBs) through non-invasive analysis to aid in recycling and recovery of precious waste, the goal of this paper is to propose a scheme towards the fusion of RGB and hyperspectral data in object detection. State-of-art detectors come with their own set of challenges which make them inapplicable to PCB recycling. We introduce a method which promises to achieve object detection based on multi-sensor data by utilizing the hyperspectral data to localize components and compare the results to a conventional single-sensor (RGB) based approach.

Keywords: Object detection; Hyperspectral imaging; Recycling; Sensors; Spatial resolution; Training


Publ.-Id: 32064

Sediment Transit Time and Floodplain Storage Dynamics in Alluvial Rivers Revealed by Meteoric 10Be

Repasch, M.; Wittmann, H.; Scheingross, J. S.; Sachse, D.; Szupiany, R.; Orfeo, O.; Fuchs, M.; Hovius, N.

Quantifying the time scales of sediment transport and storage through river systems is fundamental for understanding weathering processes, biogeochemical cycling, and improving watershed management, but measuring sediment transit time is challenging. Here we provide the first systematic test of measuring cosmogenic meteoric Beryllium‐10 (10Bem) in the sediment load of a large alluvial river to quantify sediment transit times. We take advantage of a natural experiment in the Rio Bermejo, a lowland alluvial river traversing the east Andean foreland basin in northern Argentina. This river has no tributaries along its trunk channel for nearly 1,300 km downstream from the mountain front. We sampled suspended sediment depth profiles along the channel and measured the concentrations of 10Bem in the chemically extracted grain coatings. We calculated depth‐integrated 10Bem concentrations using sediment flux data and found that 10Bem concentrations increase 230% from upstream to downstream, indicating a mean total sediment transit time of 8.4 ± 2.2 kyr. Bulk sediment budget‐based estimates of channel belt and fan storage times suggest that the 10Bem tracer records mixing of old and young sediment reservoirs. On a reach scale, 10Bem transit times are shorter where the channel is braided and superelevated above the floodplain, and longer where the channel is incised and meandering, suggesting that transit time is controlled by channel morphodynamics. This is the first systematic application of 10Bem as a sediment transit time tracer and highlights the method's potential for inferring sediment routing and storage dynamics in large river systems.

Keywords: meteoric 10Be; sediment transit time; river sediment; floodplains; sediment routing


Publ.-Id: 32063

alpaka-group/alpaka: alpaka 0.5.0: C++14

Worpitz, B.; Matthes, A.; Zenker, E.; Hübl, A.; Widera, R.; Bastrakov, S.; Ehrig, S.; Kelling, J.; Krude, J.; Stephan, J.; Werner, M.

The alpaka library is a header-only C++14 abstraction library for accelerator development.
The release 0.5.0 is providing support for AMD HIP and dropped support for C++11, CUDA 8, gcc 4.9 and boost < 1.65.1.

Keywords: CUDA; HPC; alpaka; OpenMP; HIP; C++; GPU; heterogeneous computing; performance portability

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: OS: Linux, Windows, or OSX requirements: C++14 compiler, boost 1.65.1+
    License: MPL-2.0
    Hosted on GitHub: Link to location
    DOI: 10.5281/zenodo.3909421

Publ.-Id: 32062

αvβ3-Specific Gold Nanoparticles for Fluorescence Imaging of Tumor Angiogenesis

Pretze, M.; von Kiedrowski, V.; Runge, R.; Freudenberg, R.; Hübner, R.; Davarci, G.; Schirrmacher, R.; Wängler, C.; Wängler, B.

This paper reports on the development of tumor-specific gold nanoparticles (AuNPs) as theranostic tools intended for target accumulation and the detection of tumor angiogenesis via optical imaging (OI) before therapy is performed, being initiated via an external X-ray irradiation source. The AuNPs were decorated with a near-infrared dye, and RGD peptides as the tumor targeting vector for αvβ3-integrin, which is overexpressed in tissue with high tumor angiogenesis. The AuNPs were evaluated in an optical imaging setting in vitro and in vivo exhibiting favorable diagnostic properties with regards to tumor cell accumulation, biodistribution, and clearance. Furthermore, the therapeutic properties of the AuNPs were evaluated in vitro on pUC19 DNA and on A431 cells concerning acute and long-term toxicity, indicating that these AuNPs could be useful as radiosensitizers in therapeutic concepts in the future.

Keywords: gold nanoparticle; optical imaging; radiosensitizer; tumor angiogenesis; RGD peptide

Publ.-Id: 32061

Data for "Gold implanted germanium photoswitch for cavity dumping of a free-electron laser"

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

Measurements were carried out in ELBE 113 c lab. Free electron laser (FEL) pulses with a wavelength ranging from 6 to 90 µm from the FELBE laser operating at its maximum power level were used. Photoswitching of Ge and Ge:Au samples were carried out using a 1 kHz Ti:Sapphire Amplifier system at 800 nm. The data used in the paper is arranged in subfolders 1, 2, and 3. The description is as follows
1. Scheme of the experiment (used in Figure 1 and shows the idea of the experiment)
2. FEL pulse picking traces from photoswitched Ge and Ge: Au samples were recorded using an oscilloscope with 1 GHz bandwidth (Keysight InfiniiVision DSOX4104A).
Relevance: This data is used in Figures 2 and 3. This measurement showed the photoswitching attributes in both reflection and transmission geometry for the Ge and Ge: Au samples and suitability of Ge:Au sample for efficient cavity dumping.
3. Photoinduced reflectivity measurements for the Ge: Au sample as a function of the time delay between FEL pulses and the pulses from a kHz amplifier system is recorded. The fluence required to couple out FEL wavelengths with an efficiency of at least 50 % reflectivity and Matlab scripts used for simulation of photoinduced reflectivity for the same FEL wavelengths.
Relevance: This data is used in Figure 4 and shows the fluence requirements of the Ge:Au photoswitch and also a faster recovery time of sub-ns, much shorter than the FEL pulsing period of 77ns.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-01-07
    DOI: 10.14278/rodare.726


Publ.-Id: 32060

A discussion of two-phase flow in the gas channel and porous transport layer regions of polymer electrolyte cells

Steven, S. B.; Andersson, M.; Weber, N.; Marschall, H.; Lehnert, W.

This talk is about an ongoing programme of research on detailed performance calculations for two-phase liquid-gas flow in the gas channel and porous transport layer, as found, for example, on the cathode side of a polymer electrolyte fuel cell. The porous geometry is typically obtained by digital reconstruction from nano-computer tomography images. The domain may then tessellated with a computational mesh, whereupon the equations of mass and momentum are solved ,e.g., by means of a volume-of-fluid method. Liquid water is produced at the same time as gaseous oxygen is consumed by electrochemical reduction at the electrode surface, which is to be considered a boundary condition in the present problem. The problem was originally formulated in ref. [1]. Liquid-gas counter flow in the porous transport layer results in liquid drops being entrained in co-flow in the gas channels and convected downstream by the gas. The flow in the channels and adjacent parts of the porous transport layer is transient-periodic, but with some significant randomness, associated with the interactions between the different fluid streams percolating into the channel from the pores.

In this presentation, the complex micro-scale flow field is described in some detail. Consideration is also given as to the mechanisms for construction of macro-homogeneous properties such as absolute and relative permeability, capillary pressure vs. saturation for porous media, as well as macroscopic drag laws for two-phase channel flows based on calculations on a micro-scale. These are required for macro-scale homogeneous models, as typically employed at a cell-level. A discussion is also given of the impact of salient physical properties such as surface tension, and how these may be manipulated to improve future performance for electrochemical conversion devices such as fuel cells and electrolysers.

  • Open Access Logo Lecture (Conference)
    I Meeting on Energy Conversion and Storage Electrochemical Devices, 28.-29.01.2021, Madrid, Spanien

Publ.-Id: 32058

Theory of three-magnon interaction in a vortex-state magnetic nanodot

Verba, R.; Körber, L.; Schultheiß, K.; Schultheiß, H.; Tiberkevich, V.; Slavin, A.

This repository contains the data used to determine the numerical threshold fields for three-magnon scattering in a vortex-state disk used in our paper "Theory of three-magnon interaction in a vortex-state magnetic nanodot" published in Physical Review B. 

For different excitation frequencies, we provide:

  • mumax3 simulation file and table containing the time-dependent magnetic energy for simulations where the microwave-field power is decreased over time
  • mumax3 file and resulting power spectrum for a continuous-wave excitation at a given microwave-field power above threshold
  • spatial mode profiles (magnitude/amplitude) to identify the modes taking part in the three-magnon splitting channel

Keywords: spin wave; theory; nonlinear; vortex; micromagnetic simulation

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-05-01
    DOI: 10.14278/rodare.724
    License: CC-BY-4.0


Publ.-Id: 32057

Spin-transfer dynamics in MgO-based magnetic tunnel junctions with an out-of-plane magnetized free layer and an in-plane polarizer

Kowalska, E.; Sluka, V.; Kakay, A.; Fowley, C.; Lindner, J.; Fassbender, J.; Deac, A. M.

Here, we present an analytical and numerical model describing the magnetization dynamics in MgO-based spin-torque nano-oscillators with an in-plane magnetized polarizer and an out-of-plane free layer. We introduce the spin-transfer torque asymmetry by considering the cosine angular dependence of the magnetoresistance between the two magnetic layers in the stack. For the analytical solution, dynamics are determined by assuming a circular precession trajectory around the direction perpendicular to the plane, as set by the effective field, and calculating the energy integral over a single precession period. In a more realistic approach, we include the bias dependence of the tunnel magnetoresistance, which is assumed empirically to be a piecewise linear function of the applied voltage. The dynamical states are found by solving the stability condition for the Jacobian matrix for out-of-plane static states. We find that the bias dependence of the tunnel magnetoresistance, which is an inseparable effect in every tunnel junction, exhibits drastic impact on the spin-torque nano-oscillator phase diagram, mainly by increasing the critical current for dynamics and quenching the oscillations at high currents. The results are in good agreement with our experimental data published elsewhere.

Keywords: spin-torque nano-oscillator (STNO); MgO-based magnetic tunnel junctions; tunnel magnetoresistance


Publ.-Id: 32055

Multi-Feature Treatment Verification in Particle Therapy

Kögler, T.; Alagoz, E.; Beyer, R.; Hammer, S.; Hysing, L. B.; Lutz, B.; Meric, I.; Permatasari, F.; Pettersen, H. E. S.; Römer, K.; Schellhammer, S.; Skjerdal, K.; Turko, J. A. B.; Wagner, A.; Weinberger, D.; Werner, R.-D.; Ytre-Hauge, K.; Pausch, G.

Particle therapy constitutes a promising and rapidly developing method in modern cancer treatment. In order to exploit its full potential, however, it requires detailed dose verification.
Although the applicability of in-beam positron emission tomography and prompt gamma rays has already been demonstrated in patients, range verification is not yet part of the clinical routine in particle therapy. This is due to not only the methodological limitations of previous systems, but also to commercial, clinical and physical boundary conditions.
In pencil beam scanning, the state-of-the-art treatment method in particle therapy, the number of secondary particles (essentially positrons, prompt gamma rays and fast neutrons) available per spot (Δt = 10 ms to 100 ms) is limited. This leads to statistical accuracy limits for verification systems exploiting these secondary particles as range probes. The development of a clinically useable treatment verification system requires gathering as much information about the local dose, as possible.
The instantaneous fluence rate of prompt gamma rays reaching 5×10⁶ cm‾²s‾¹ to 10⁸ cm‾²s‾¹ challenges modern data acquisitions connected to monolithic inorganic scintillators with typical sizes used in present verification systems. In order to reduce the detector load, and also with regard to the ever higher intensities of next generation medical accelerators, future systems have to be more granular.
Multi-Feature Treatment Verification combines and extends established methods (prompt gamma-ray imaging, spectroscopy, timing, etc.) in order to achieve higher reliability and performance. This idea was taken up by the NOVO project and expanded by a multi-particle approach. The NOVO (i.e. N eutron and gamma ray imaging with quasi-monolithic organic detector arrays – a novel, holistic approach to real-time range assessment-based treatment verification in particle therapy) consortium is a large collaboration of medical, nuclear and detector physicists, nuclear engineers, and mathematicians, which aim to develop a holistic realtime treatment verification system in particle therapy.
Elements of a potential multi-feature/multi-particle treatment verification multi-channel system were characterized in a double time-of-flight experiment at the pulsed photo-neutron source nELBE (neutrons @ Electron Linac for beams with high Brilliance and low Emittance). The essential properties (time resolution, light yield, detection efficiency and pulse shape discrimination) of an EJ-276 plastic scintillator were determined. The very first experimental results show that the time resolution (ΔT < 400 ns) of a 20 × 20 × 200 mm³
EJ-276 plastic scintillator with double-sided readout will reach the high demands of such a proposed range verification system. However, the determined quality of the pulse-shape discrimination, the energy resolution and the quite high neutron detection threshold of above 200 keV show that the light yield of this type of scintillator is not high enough to be used in a multi-feature-based treatment verification system. Particle transport calculations with MCNP6 and GEANT4 were performed to confirm the experimental results of a single detector element. Furthermore, they also show a promising measurement accuracy of a multi-channel overall system.

Keywords: particle therapy; treatment verification; in-vivo range assessment; NOVO project

  • Lecture (Conference)
    The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, 21.-25.06.2021, Praha, Česká republika

Publ.-Id: 32054

A Roadmap for 3D Metal Aerogels: Materials Design and Application Attempts

Jiang, X.; Du, R.; Hübner, R.; Hu, Y.; Eychmüller, A.

Armed with merits of the metals (e.g., electrical conductivity, catalytic activity, and plasmonic properties) and aerogels (e.g., monolithic structure, porous network, and large specific surface area), metal aerogels (MAs) have stood out as a new class of porous materials in the last decade. With unparalleled potential in electrocatalysis, plasmonics, and sensing, they are envisaged to revolutionize the energy- and detection-related application fields. However, MA development is severely retarded by the lack of a sufficient material basis. Suffering from the ambiguous understanding of formation mechanisms, big challenges remain for tailoring MAs for task-specific applications. By surveying state-of-the-art developments, this review strives to summarize design principles and arouse interest in broad scientific communities. Moreover, critical challenges and opportunities are highlighted to provide a research roadmap for this young yet promising field.

Publ.-Id: 32053

Where2Test: Identifying optimal spatiotemporal testing policies for mitigating the shortage of SARS-CoV-2 testing capacity

Calabrese, J.

A poster giving an overview of the Where2Test project and its core goals and methods.

  • Poster
    Visit of the Polish Delegation to CASUS, 29.09.2020, CASUS, Germany

Publ.-Id: 32051

Where2Test: Spatiotemporal, multifactor optimization of COVID-19 testing strategies

Calabrese, J.; Bussmann, M.

We give an overview of the Where2Test project, focusing on the general approach and particular applications for machine learning.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Artificial Intelligence for a better living: medicine, science-business, 30.09.2020, Wroclaw, Poland

Publ.-Id: 32050

Magnetic Field Assisted Electrodeposition of Metal on Conically Structured Electrodes

Huang, M.; Eckert, K.; Mutschke, G.

Conical structures towards nanometer length scales are attractive for numerous applications including super-hydrophobic and electrocatalytic materials. Among the various methods of synthesizing arrays of micro- and nano-cones, electrochemical deposition techniques have been widely applied. We aim at enhancing the conical growth during deposition by applying an external magnetic field. Most of the magnetic field effects can be attributed to the Lorentz force and the magnetic gradient force [1]. If the magnetic field imposed on the electrochemical cell is well designed, the magnetic forces can generate an electrolyte flow which brings fresh electrolyte towards the tip of a cone, so that the local mass transfer would be enhanced and the conical growth would be supported.

We first performed analytical and numerical studies of electrodeposition on diamagnetic (Cu) and ferromagnetic (Fe) cones of mm size under the influence of a homogeneous vertical magnetic field. The beneficial structuring effects of the Lorentz force has already been shown for the Cu cone case [2]. The magnetization of the Fe cones causes additionally a strong magnetic gradient force near the cone tips and gives rise to a flow that can bring enriched electrolyte to the conical cathode. As the cathodes are placed at the bottom of the electrochemical cell, solutal buoyancy tends to bring upwards lighter electrolyte from the conical cathode and thus counteract the downward flow caused by the magnetic forces. Our results show that for the Cu cones, the Lorentz force becomes smaller than the buoyancy force after the first few seconds of the deposition, while the magnetic gradient force in case of the Fe cones keeps surpassing the buoyancy during the deposition.

Next, scaling studies on cones of sizes ranging from millimeter to micrometer allow to deliver insights into the magnetic field assisted electrodeposition towards micro- and nano-cones. As the cone size shrinks, the geometrical inhomogeneity decreases, and the current density gets more uniformly distributed on the cone, which is making the conical growth more difficult. Furthermore, the beneficial flow forced by the magnetic field near smaller cones suffers from higher wall friction. But this can be partially compensated by the larger magnetic gradients existing at smaller Fe cones, and the flow caused by the magnetic gradient force was found to decrease more slowly than the flow caused by other forces with the decreasing cone size. Such scaling behavior of the flow velocity corresponds well with a theoretical analysis of the Navier-Stokes equation. For a Fe cone with a radius of 10 micron under study here, the magnetic gradient force generates a beneficial downward flow with a velocity of about 5 micron per second. But in general the structuring effects during the deposition is much weaker than at larger length scales.

This work shows the potential of using the magnetic gradient force for growing ferromagnetic conical structures during electrodeposition. Optimization possibilities for conical growth at smaller scales by e.g. enhancing the cell current, applying stronger magnetic fields and pulsed electrodeposition will also be discussed.

Related publications

Publ.-Id: 32049

How range residency and long-range perception change encounter rates

Martinez-Garcia, R.; Fleming, C. H.; Seppelt, R.; Fagan, W. F.; Calabrese, J.

Encounter rates link movement strategies to intra- and inter-specific interactions, and therefore translate individual movement behavior into higher-level ecological processes. Indeed, a large body of interacting population theory rests on the law of mass action, which can be derived from assumptions of Brownian motion in an enclosed container with exclusively local perception. These assumptions imply completely uniform space use, individual home ranges equivalent to the population range, and encounter dependent on movement paths actually crossing. Mounting empirical evidence, however, suggests that animals use space non-uniformly, occupy home ranges substantially smaller than the population range, and are of- ten capable of nonlocal perception. Here, we explore how these empirically supported behaviors change pairwise encounter rates. Specifically, we derive novel analytical expressions for encounter rates under Ornstein-Uhlenbeck motion, which features non-uniform space use and allows individual home ranges to differ from the population range. We compare OU-based encounter predictions to those of Reflected Brownian Motion, from which the law of mass action can be derived. For both models, we further explore how the interplay between the scale of perception and home-range size affects encounter rates. We find that neglecting realistic movement and perceptual behaviors can lead to systematic, non-negligible biases in encounter-rate predictions.

Keywords: Ecological theory; Encounter rates; Movement ecology; Home ranges


Publ.-Id: 32048

How optimal allocation of limited testing capacity changes epidemic dynamics

Calabrese, J.; Demers, J.

Insufficient testing capacity continues to be a critical bottleneck in the worldwide fight against COVID-19. Optimizing the deployment of limited testing resources has therefore emerged as a keystone problem in pandemic response planning. Here, we use a modified SEIR model to optimize testing strategies under a constraint of limited testing capacity. We define pre-symptomatic, asymptomatic, and symptomatic infected classes, and assume that positively tested individuals are immediately moved into quarantine. We further define two types of testing. Clinical testing focuses only on the symptomatic class. Non-clinical testing detects pre- and asymptomatic individuals from the general population, and an information parameter governs the degree to which such testing can be focused on high infection risk individuals. We then solve for the optimal mix of clinical and non-clinical testing as a function of both testing capacity and the information parameter. We find that purely clinical testing is optimal at very low testing capacities, supporting early guidance to ration tests for the sickest patients.
Additionally, we find that a mix of clinical and non-clinical testing becomes optimal as testing capacity increases. At high but empirically observed testing capacities, a mix of clinical testing and unfocused (information=0) non-clinical testing becomes optimal. We further highlight the dvantages of early implementation of testing programs, and of combining optimized testing with contact reduction interventions such as lockdowns, social distancing, and masking.


Publ.-Id: 32047

Formation of spiral waves in cylindrical containers under orbital excitation

Horstmann, G. M.; Anders, S.; Kelley, D.; Weier, T.

The lowest swirling wave mode arising in upright circular cylinders as a response to orbital excitation has been widely studied in the last decade, largely owing to its high practical relevance for orbitally shaken bioreactors. Our recent theoretical study (Horstmann et al. 2020) revealed a damping-induced symmetry breaking mechanism that can cause spiral wave structures manifested in the so far widely disregarded higher rotating wave modes. Building on this work, we develop a spiralisation criterion and classify different spiral regimes as a function of the most relevant dimensionless groups. The analysis suggests that high Bond numbers and shallow liquid layers favour the formation of coherent spiral waves. This result paved the way to find the predicted wave structures in our interfacial sloshing experiment. We present two sets of experiments, with different characteristic damping rates, verifying the formation of both coherent and overdamped spiral waves in conformity with the theoretical predictions.

Publ.-Id: 32046

Autonomous implementation of thermodynamic cycles at the nanoscale

Strasberg, P.; Wächtler, C. W.; Schaller, G.

There are two paradigms to study nanoscale engines in stochastic and quantum thermodynamics.
Autonomous models, which do not rely on any external time-dependence, and models that make use of time-dependent control fields, often combined with dividing the control protocol into idealized strokes of a thermodynamic cycle. While the latter paradigm offers theoretical simplifications, its utility in practice has been questioned due to the involved approximations. Here, we bridge the two paradigms by constructing an autonomous model, which implements a thermodynamic cycle in a certain parameter regime. This effect is made possible by self-oscillations, realized in our model by the well studied electron shuttling mechanism. Based on experimentally realistic values, we find that a thermodynamic cycle analysis for a single-electron working fluid is unrealistic, but already a few-electron working fluid could suffice to justify it. We also briefly discuss additional open challenges to autonomously implement the more studied Carnot and Otto cycles.

Keywords: thermodynamic cycle; self-oscillation; autonomous control; electron shuttle


Publ.-Id: 32044

Spin stress contribution to the lattice dynamics of FePt

von Reppert, A.; Willig, L.; Pudell, J.-E.; Zeuschner, S.; Sellge, G.; Ganss, F.; Hellwig, O.; Ander Arregi, J.; Uhlíř, V.; Crut, A.; Bargheer, M.

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

Publ.-Id: 32043

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