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41396 Publications

Liquid Metal Alloy Ion Sources for magnetic nano-structures

Bischoff, L.; Pilz, W.; Klingner, N.; Hlawacek, G.; Mazarov, P.; Meyer, F.

Focused Ion Beam (FIB) is a modern tool for µm and sub-µm structure fabrication and analysis. Commercial systems work mostly with a Gallium - Liquid Metal Ion Source (LMIS) and can achieve a resolution lower than 10 nm and current densities more than 10 Acm-2. The use of alloy LMIS, mainly developed at HZDR, opens a broad field of new applications. In combination with modern FIB systems, like the VELION (Raith) the application field can be extended due to a broad spectrum of available ion species in high resolution ion beams and the stage properties. All these aspects will be concentrated to the ZIM project GRANT No.-ZF4330902 DF7 dealing with the prospective modern topic of nano-magnetic structures from basic research up to new applications. Main topics are: i) the local modification of magnetic single nano-structures using a FIB with Co, Ni, Fe, … ions and ii) the fabrication and investigation of magnonic crystals, made by writing FIB implantation with rare earth ions (Nd, Dy, Ho, Er, …).

Keywords: Focused Ion Beam; ion sources; magnetic nanostructures; magnonic crystals

Related publications

  • Lecture (others)
    Kick-off meeting, ZIM Project No.-ZF4494801 DF7, 14.-16.09.2020, Dortmund, Germany

Permalink: https://www.hzdr.de/publications/Publ-31442
Publ.-Id: 31442


X-ray and neutron radiographic experiments on particle-laden molten metal flows

Lappan, T.; Sarma, M.; Heitkam, S.; Mannes, D.; Trtik, P.; Shevchenko, N.; Eckert, K.; Eckert, S.

In metallurgical processing, non-metallic inclusions in metallic materials are one highly relevant challenge. Bubble injection into molten metals boosts the inclusion control and removal, thus enhancing metal homogenisation and purification. Although this principle of bubble flotation has been used for a long time, the effects of bubble-inclusion interactions in molten metals are not yet well researched. Imaging measurements of multiphase metal flows are challenging for two main reasons: the metals’ high melting temperatures, and their opaqueness for visible light. This work focuses on X-ray and neutron radiographic experiments employing low-melting gallium alloys laden with model particles smaller than 1 mm in diameter. Both, bubbles and particles, are visualised simultaneously with high spatial and temporal resolution to analyse their motions by tracking algorithms. We demonstrate the capability of time-resolved X-ray and neutron radiography to image multiphase flows in particle-laden optically opaque liquid metal, thus contributing to pave the way for systematic investigations on bubble-inclusion interactions in molten metals.

Keywords: X-ray radiography; neutron radiography; bubble flotation; non-metallic inclusions; liquid metal

  • Lecture (Conference) (Online presentation)
    TMS2021 Virtual, 15.-18.03.2021, Orlando, Florida, USA
  • Book chapter
    Lee J., Wagstaff S., Anderson A., Tesfaye F., Lambotte G., Allanore A.: Materials Processing Fundamentals 2021, Cham: Springer, 2021, 978-3-030-65253-1, 13-29
    DOI: 10.1007/978-3-030-65253-1_2
    Cited 3 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-31441
Publ.-Id: 31441


Simulation of hard x-rays source produced by a picosecond laser irradiated solid target for Compton radiography

Meng-Ting, L.; Guang-Yue, H.; Huang, L.; Jian, Z.

A bremsstrahlung radiation hard x-ray source, produced by a picosecond intense laser irradiated solid target, was used to diagnose an implosion capsule at stagnation phase via Compton radiography in experiments. By performing Monte Carlo and particle-in-cell simulation, we investigated the influence of target materials and laser intensity on the >70 keV bremsstrahlung hard x-ray emission. We found that the brightness of the hard x-rays is proportional to the atomic number multiplied by area density (ZρL), which indicates that the higher Z and higher density gold or uranium material will produce the brightest hard x-rays source at the same thickness. In relativistic laser solid interactions, hot electron recirculation plays an important role in hard x-ray emission. Without recirculation, hard x-ray conversion efficiency decays when increasing the laser intensity. While the hard x-ray emission comes to the maximal saturated conversion efficiency at relativistic laser intensity if considering the electron recirculation.
These results provide valuable insights into the experimental design of Compton radiography

Keywords: Inertial confined fusion; Compton radiography; Numerical modeling

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Permalink: https://www.hzdr.de/publications/Publ-31440
Publ.-Id: 31440


Three-dimensional cell culture systems in radiopharmaceutical cancer research

Doctor, A.; Seifert, V.; Ullrich, M.; Hauser, S.; Pietzsch, J.

In preclinical cancer research, three-dimensional (3D) cell culture systems such as multicellular spheroids and organoids are becoming increasingly important. They provide valuable information before studies on animal models begin and, in some cases, are even suitable for reducing or replacing animal experiments. Furthermore, they recapitulate microtumors, metastases and the tumor microenvironment much better than monolayer culture systems could. 3D models show higher structural complexity and diverse cell interactions, while reflecting (patho)physiological phenomena such as oxygen and nutrient gradients in the course of their growth or development. These interactions and properties are of great importance for understanding the pathophysiological importance of stromal cells and the extracellular matrix for tumor progression, treatment response or resistance mechanisms of solid tumors. Special emphasis is placed on co-cultivation with tumor-associated cells, which further increases the predictive value of 3D models, e.g. for drug development. The aim of this overview is to shed light on selected 3D models and their advantages and disadvantages, especially from the radiopharmacist´s point of view with focus on the suitability of 3D models for the radiopharmacological characterization of novel radiotracers and radiotherapeutics. Special attention is paid to pancreatic ductal adenocarcinoma (PDAC), as predestined target for the development of new radionuclide-based theranostics.

Keywords: Co-culture; organoids; pancreatic cancer; radiotherapeutics; radiotracer; spheroids; stromal cells; 3D model; tumor microenvironment

Permalink: https://www.hzdr.de/publications/Publ-31439
Publ.-Id: 31439


The dipole response of 87Rb and its impact on the 86Rb(n,γ)87Rb cross section

Wilhelmy, J.; Müscher, M.; Rusev, G.; Schwengner, R.; Beyer, R.; Bhike, M.; Erbacher, P.; Fiedler, F.; Friman-Gayer, U.; Glorius, J.; Greifenhagen, R.; Hammer, S.; Hensel, T.; Isaak, J.; Junghans, A. R.; Krishichayan, F.; Löher, B.; Müller, S. E.; Pietralla, N.; Reinicke, S.; Savran, D.; Scholz, P.; Sonnabend, K.; Szücs, T.; Tamkas, M.; Tornow, W.; Turkat, S.; Wagner, A.; Zilges, A.

Background: Detailed information on the low-lying dipole response in atomic nuclei along isotonic or isotopic chains is well suited to systematically investigate the structure and evolution of the Pygmy Dipole Resonance (PDR). Moreover, the dipole strength below and around the neutron separation energy Sn has impact on statistical model calculations for nucleosynthesis processes. Purpose: The photon strength function (PSF) of 87 Rb, which is directly connected to the photoabsorption cross section, is a crucial input for statistical model calculations constraining the Maxwellian-averaged cross section (MACS) of the neutron capture of the unstable s-process branching-point nucleus 86 Rb. Within this work, the photoabsorption cross section is investigated.
Methods: The photoabsorption cross section of the N = 50 nucleus 87 Rb was determined from photon-scattering experiments via the Nuclear Resonance Fluorescence (NRF) technique. Bremsstrahlung beams at the γELBE facility in conjunction with monoenergetic photon beams at the HIGS facility were used to determine the integrated cross sections Is of isolated states as well as the averaged cross section as function of the excitation energy. Decays to the ground state were disentangled from decays to first low-lying excited states. Statistical and experimental approaches for the γ-decay properties at various excitation energies were applied. The linearly polarized photon beams at HIGS provide information on the ratio of electric and magnetic type of radiation.
Results: Within this work, more than 200 ground-state decays and associated levels in 87Rb were identified. Moreover, transitions below the sensitivity limit of the state-by-state analysis were taken into account via a statistical approach from the bremsstrahlung data as well as model-independently from the HIGS data. The photoabsorption cross sections at various excitation energies were determined. The dipole response between 6 and 10 MeV of 87 Rb is in agreement with assuming contributions of electric multipolarity, only.
Conclusions: The photoabsorption cross section of 87Rb does not contradict with the trend of decreasing E1 strength with increasing proton number along the N = 50 isotonic chain but might also be associated with a constant trend. The experimental γ decay at various excitation energies of the HIGS data supports the statistical approach but does not provide a stringent proof due to the limited sensitivity in the decay channels. The additional E1 strength observed in the present experiments significantly enhances the MACSs compared to recent microscopic D1M HFB+QRPA calculations only. Moreover, theoretical estimations provided by the KADoN iS project could be significantly improved.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31438
Publ.-Id: 31438


Uranium(VI) bioassociation by different fungi – a comparative study into molecular processes

Wollenberg, A.; Drobot, B.; Hübner, R.; Kretzschmar, J.; Freitag, L.; Lehmann, F.; Günther, A.; Stumpf, T.; Raff, J.

After the Chernobyl and Fukushima incidents it has become clear that fungi can take up and accumulate large quantities of radionuclides and heavy metals, but the underlying processes are not well understood yet. For this study, the molecular interactions of uranium(VI) with the white-rot fungi, Schizophyllum commune and Pleurotus ostreatus, and the soil-living fungus, Leucoagaricus naucinus, were investigated. First, the uranium concentration in the biomass was determined by time-dependent bioassociation experiments. To characterize the molecular interactions, uranium was localized in the biomass by transmission electron microscopy analysis. Second, the formed uranyl complexes in both biomass and supernatant were determined by fluorescence spectroscopy. Additionally, possible bioligands in the supernatant were identified. The results show that the discernible interactions between metals and fungi are similar, namely biosorption, accumulation, and subsequent crystallization. But at the same time, the underlying biochemical mechanisms are different and specific to the fungal species. In addition, Schizophyllum commune was found to be the only fungus that, under the chosen experimental conditions, released tryptophan and other indole derivatives in the presence of uranium(VI) as determined by nuclear magnetic resonance spectroscopy. These released substances most likely act as messenger molecules rather than serving the direct detoxification of uranium(VI).

Keywords: radionuclides; mycelium; microscopy; spectroscopy; metabolite; quorum sensing

Related publications

Permalink: https://www.hzdr.de/publications/Publ-31437
Publ.-Id: 31437


Trapped-ion toolkit for studies of quantum harmonic oscillators under extreme conditions

Wittemer, M.; Schröder, J.-P.; Hakelberg, F.; Kiefer, P.; Fey, C.; Schützhold, R.; Warring, U.; Schaetz, T.

Many phenomena described in relativistic quantum field theory are inaccessible to direct observations, but analogue processes studied under well-defined laboratory conditions can present an alternative perspective. Recently, we demonstrated an analogy of particle creation using an intrinsically robust motional mode of two trapped atomic ions. Here, we substantially extend our classical control techniques by implementing machine-learning strategies in our platform and, consequently, increase the accessible parameter regime. As a proof of methodology, we present experimental results of multiple quenches and parametric modulation of an unprotected motional mode of a single ion, demonstrating the increased level of real-time control. In combination with previous results, we enable future experiments that may yield entanglement generation using a process in analogy to Hawking radiation. This article is part of a discussion meeting issue 'The next generation of analogue gravity experiments'.

Keywords: Trapped Ions; Qubits; Ion Traps (Instrumentation)

Permalink: https://www.hzdr.de/publications/Publ-31436
Publ.-Id: 31436


Prognostic value of baseline [18F]-fluorodeoxyglucose positron emission tomography parameters MTV, TLG and asphericity in an international multicenter cohort of nasopharyngeal carcinoma patients

Zschaeck, S.; Li, Y.; Lin, Q.; Beck, M.; Amthauer, H.; Bauersachs, L.; Hajiyianni, M.; Rogasch, J.; Ehrhardt, V. H.; Kalinauskaite, G.; Weingärtner, J.; Hartmann, V.; van den Hoff, J.; Budach, V.; Stromberger, C.; Hofheinz, F.

Purpose

[18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) parameters have shown prognostic value in nasopharyngeal carcinomas (NPC), mostly in monocenter studies. The aim of this study was to assess the prognostic impact of standard and novel PET parameters in a multicenter cohort of patients.
Methods

The established PET parameters metabolic tumor volume (MTV), total lesion glycolysis (TLG) and maximal standardized uptake value (SUVmax) as well as the novel parameter tumor asphericity (ASP) were evaluated in a retrospective multicenter cohort of 114 NPC patients with FDG-PET staging, treated with (chemo)radiation at 8 international institutions. Uni- and multivariable Cox regression and Kaplan-Meier analysis with respect to overall survival (OS), event-free survival (EFS), distant metastases-free survival (FFDM), and locoregional control (LRC) was performed for clinical and PET parameters.
Results

When analyzing metric PET parameters, ASP showed a significant association with EFS (p = 0.035) and a trend for OS (p = 0.058). MTV was significantly associated with EFS (p = 0.026), OS (p = 0.008) and LRC (p = 0.012) and TLG with LRC (p = 0.019). TLG and MTV showed a very high correlation (Spearman’s rho = 0.95), therefore TLG was subesequently not further analysed. Optimal cutoff values for defining high and low risk groups were determined by maximization of the p-value in univariate Cox regression considering all possible cutoff values. Generation of stable cutoff values was feasible for MTV (p<0.001), ASP (p = 0.023) and combination of both (MTV+ASP = occurrence of one or both risk factors, p<0.001) for OS and for MTV regarding the endpoints OS (p<0.001) and LRC (p<0.001). In multivariable Cox (age >55 years + one binarized PET parameter), MTV >11.1ml (hazard ratio (HR): 3.57, p<0.001) and ASP > 14.4% (HR: 3.2, p = 0.031) remained prognostic for OS. MTV additionally remained prognostic for LRC (HR: 4.86 p<0.001) and EFS (HR: 2.51 p = 0.004). Bootstrapping analyses showed that a combination of high MTV and ASP improved prognostic value for OS compared to each single variable significantly (p = 0.005 and p = 0.04, respectively). When using the cohort from China (n = 57 patients) for establishment of prognostic parameters and all other patients for validation (n = 57 patients), MTV could be successfully validated as prognostic parameter regarding OS, EFS and LRC (all p-values <0.05 for both cohorts).
Conclusions

In this analysis, PET parameters were associated with outcome of NPC patients. MTV showed a robust association with OS, EFS and LRC. Our data suggest that combination of MTV and ASP may potentially further improve the risk stratification of NPC patients.

Permalink: https://www.hzdr.de/publications/Publ-31435
Publ.-Id: 31435


Unusual scandium enrichments of the Tørdal pegmatites, south Norway. Part I: Garnet as Sc exploration pathfinder

Steffenssen, G.; Müller, A.; Munnik, F.; Friis, H.; Erambert, M.; Kristoffersen, M.; Rosing-Schow, N.

The granitic pegmatites of the Tørdal area in southern Norway have been known for their Sc enrichment for about 100 years. Scandium is a compatible element in garnet. In this study, 32 garnet samples from 16 pegmatite localities across the Tørdal pegmatite field were investigated to determine the Sc distribution within garnets (crystal scale), within pegmatite bodies (pegmatite scale) and across the Tørdal pegmatite field (regional scale). In the Tørdal pegmatites, Sc content in garnet is representative for the Sc bulk composition of pegmatites, defining garnet as a reliable pathfinder mineral for the exploration of Sc mineralization in pegmatite fields. Garnets with highest Sc concentrations of up to 2197 µg/g have a spessartine component ranging from 50 to 60 mol.%. Since most garnets crystallized during the early stage of pegmatite formation (wall zone stage) Sc decreases in the remaining pegmatite melt, as documented by generally decreasing Sc from core to rim of crystals and by the occurrence of late-stage garnets (albite zone stage) with low Sc. Thus, with progressing crystallization Sc decreases in the melt. The regional Sc distribution in the Tørdal pegmatite field revealed that the Skardsfjell-Heftetjern-Høydalen pegmatites have highest Sc enrichments to sub-economic levels, with an average bulk Sc content of 53 µg/g and an average Sc content in garnet of about 1900 µg/g in the Heftetjern 2 pegmatite.
The assumed resources of the Skardsfjell-Heftetjern-Høydalen area are about 125,000 t ore grading c. 50 µg/g Sc resulting in a total of 625 t Sc, which is too small to have economic potential. However, the strong Sc enrichment of the Tørdal pegmatites is unusual for granitic pegmatites, making them a specific Sc deposit type. The amphibolitic host rocks of the Tørdal pegmatites are identified as the source rocks of Sc. The host rocks, which are part of the Nissedal Outlier supracrustals, are enriched in Sc (mean 34 µg/g) compared to average crustal compositions (mean 14 µg/g). Scandium of amphiboles was preferentially released at the onset of partial melting of the amphibolites. Thus, the Sc content in the pegmatite is strongly dependent on the degree of partial melting.

Keywords: scandium; pegmatite; garnet; Sveconorwegian orogeny; Tørdal

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Permalink: https://www.hzdr.de/publications/Publ-31434
Publ.-Id: 31434


Coarse-Grain molecular model development and dynamics simulations study of dodecane droplet spreading at the coal-water interface

Liu, Z.; Liao, Y.; Xu, M.; Wu, H.; Rudolph, M.; Wang, Y.

The mesoscopic scale is usually used to realize the dynamics calculation on a larger spatial scale and time scale. However, there have been few dynamic simulation calculations attempted on the mesoscopic scale for coal flotation systems. In this study, based on the Martini force field, the Coarse-Grain (CG) models of coal, dodecane, and water were established, and the dynamics simulations were performed to study the collector droplet spreading at the coal-water interface. The CG dynamics simulations results showed that the interaction between dodecane and coal was a spontaneous process, and dodecane existed as a collector at the coal-water interface. The radial distribution function of dodecane around coal and water indicated that dodecane was more likely to be distributed around the coal, and as far away as possible from the water. The CG dynamics simulations also revealed the specific spreading stages of the dodecane droplet. The dodecane drop first moved in the form of droplets to the coal-water interface in the aqueous phase. Then at the coal-water interface, the circular droplet broke its shape and spread rapidly on the coal surface through the dodecane CG molecules. Finally, the dodecane CG molecules penetrated deeper into the coal surface layer and formed a dynamic and stable oil film. This provided a good attempt and reference for studying the spreading of collector droplets on the coal-water interface.

Keywords: coarse-grained model; molecular dynamics simulation; droplet spreading; interfacial adsorption; coal flotation

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Permalink: https://www.hzdr.de/publications/Publ-31433
Publ.-Id: 31433


Applying tissue slice culture in cancer research—insights from preclinical proton radiotherapy

Suckert, T.; Rassamegevanon, T.; Müller, J.; Dietrich, A.; Graja, A.; Reiche, M.; Löck, S.; Krause, M.; Beyreuther, E.; von Neubeck, C.

A challenge in cancer research is the definition of reproducible, reliable, and practical models, which reflect the effects of complex treatment modalities and the heterogeneous response of patients. Proton beam radiotherapy (PBRT), relative to conventional photon-based radiotherapy, offers the potential for iso-effective tumor control, while protecting the normal tissue surrounding the tumor. However, the effects of PBRT on the tumor microenvironment and the interplay with newly developed chemo-and immunotherapeutic approaches are still open for investigation. This work evaluated thin-cut tumor slice cultures (TSC) of head and neck cancer and organotypic brain slice cultures (OBSC) of adult mice brain, regarding their relevance for translational radiooncology research. TSC and OBSC were treated with PBRT and investigated for cell survival with a lactate dehydrogenase (LDH) assay, DNA repair via the DNA double strand break marker γH2AX, as well as histology with regards to morphology. Adult OBSC failed to be an appropriate model for radiobiological research questions. However, histological analysis of TSC showed DNA damage and tumor morphological results, comparable to known in vivo and in vitro data, making them a promising model to study novel treatment approaches in patient-derived xenografts or primary tumor material.

Keywords: tumor biology; DNA damage; organotypic brain slice culture; head and neck cancer; proton beam radiotherapy; thin-cut tissue slices

Permalink: https://www.hzdr.de/publications/Publ-31432
Publ.-Id: 31432


Coherent Optical Signatures of Electron Microbunching in Laser-Driven Plasma Accelerators

Lumpkin, A. H.; Laberge, M.; Rule, D. W.; Zgadzaj, R.; Hannasch, A.; Zarini, O.; Bowers, B.; Irman, A.; Couperus Cabadağ, J. P.; Debus, A.; Köhler, A.; Schramm, U.; Downer, M. C.

We report observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched∼200-MeV electrons as they emerge from a laser-driven plasma accelerator. The divergence of the microbunched portion of electrons, deduced by comparison to a COTRI model, is ∼9× smaller than the ∼3 mrad ensemble beam divergence, while the radius of the microbunched beam, obtained from COTR images on the same shot, is <3 μm. The combined results show that the microbunched distribution has estimated transverse normalized emittance∼0.4mm mrad.

Keywords: Beam diagnostics; LWFA; COTRI; CTR; transition radiation

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Permalink: https://www.hzdr.de/publications/Publ-31431
Publ.-Id: 31431


Freestanding and Supported MoS2 Monolayers under Cluster Irradiation: Insights from Molecular Dynamics Simulation

Ghaderzadeh, S.; Ladygin, V.; Ghorbani Asl, M.; Hlawacek, G.; Schleberger, M.; Krasheninnikov, A.

Two-dimensional (2D) materials with nanometer-size holes are promising systems for DNA sequencing, water purification, and molecule selection/separation. However, controllable creation of holes with uniform sizes and shapes is still a challenge, especially when the 2D material consists of several atomic layers as, e.g., MoS2, the archetypical transition metal dichalcogenide.We use analytical potential molecular dynamics simulations to study the response of 2D MoS2tocluster irradiation. We model both freestanding and supported sheets and assess the amount of damage created in MoS2by the impacts of noble gas clusters in a wide range of cluster energies and incident angles. We show that cluster irradiation can be used to produce uniform holes in 2DMoS2with the diameter being dependent on cluster size and energy. Energetic clusters can also beused to displace sulfur atoms preferentially from either top or bottom layers of S atoms in MoS2and also clean the surface of MoS2sheets from adsorbents. Our results for MoS2, which should be relevant to other 2D transition metal dichalcogenides, suggest new routes toward cluster beam engineering of devices based on 2Dinorganic materials.

Keywords: two-dimensional materials; MoS2; cluster irradiation; pore formation; sputtering yield; atomistic simulation

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Permalink: https://www.hzdr.de/publications/Publ-31430
Publ.-Id: 31430


A supervised technique for drillcore mineral mapping using Hyperspectral data

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Gloaguen, R.

D rilling is a key task in exploration campaigns to characterize mineral deposits at depth. Drillcores are first logged in the field by a geologist and with regards to, e.g., mineral assemblages, alteration patterns, and structural features. The core-logging information is then used to locate and target the important ore accumulations and select representative samples that are further analyzed by laboratory measurements (e.g., Scanning Electron Microscopy (SEM), Xray diffraction (XRD), X-ray Fluorescence (XRF)). However, core-logging is a laborious task and subject to the expertise of the geologist. Hyperspectral imaging is a non invasive and non-destructive technique that is increasingly being used to support the geologist in the analysis of drill-core samples. Nonetheless, the benefit and impact of using hyperspectral data depend on the applied methods. With this in mind, machine learning techniques, which have been applied in different research fields, provide useful tools for an advance and more automatic analysis of the data. Lately, machine learning frameworks are also being implemented for mapping minerals in drill-core hyperspectral data. In this context, this work follows an approach to map minerals on drill-core hyperspectral data using supervised machine learning techniques, in which SEM data, integrated with the mineral liberation analysis (MLA) software, are used in training a classifier. More specifically, the high-resolution mineralogical data obtained by SEM-MLA analysis is resampled and co-registered to the hyperspectral data to generate a training set. Due to the large difference in spatial resolution between the SEM-MLA and hyperspectral images, a pre-labeling strategy is required to link these two images at the hyperspectral data spatial resolution. In this study, we use the SEM-MLA image to compute the abundances of minerals for each hyperspectral pixel in the corresponding SEM-MLA region. We then use the abundances as features in a clustering procedure to generate the training labels. In the final step, the generated training set is fed into a supervised classification technique for the mineral mapping over a large area of a drill-core. The experiments are carried out on a visible to near-infrared (VNIR) and shortwave infrared (SWIR) hyperspectral data set and based on preliminary tests the mineral mapping task improves significantly.

  • Open Access Logo Poster (Online presentation)
    European Geosciences Union (EGU) General Assembly, 04.-08.05.2020, Vienna, Austria

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Permalink: https://www.hzdr.de/publications/Publ-31429
Publ.-Id: 31429


Fusion of VNIR-SWIR and LWIR for Mineral Mapping in a Machine Learning Framework

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Gloaguen, R.

Mineral mapping is an important task in exploration campaigns where it is required to obtain a preliminary idea about the composition of ore deposits. Hyperspectral imaging is becoming a trending technology within the mining community to map minerals during exploration campaigns. This is because minerals have unique spectral responses in specific parts of the electromagnetic spectrum. These responses depend on the bonds between the atoms and electron orbitals of the minerals. In other words, based on the molecular vibrations and composition of the minerals the light reflects differently from the minerals and therefore, the spectral responses vary. In general, alteration minerals (e.g., phyllosilicates) can be mapped using the visible to near-infrared (VNIR) and short-wave infrared (SWIR) parts of the electromagnetic spectrum, whereas rock-forming minerals, (e.g., feldspars and quartz) are better distinguishable using the long-wave infrared (LWIR). Therefore, fusing the VNIR-SWIR and LWIR parts of the electromagnetic spectrum provides a complete range of data for the mineral mapping task. The benefit of using hyperspectral data from both regions of the electromagnetic spectrum to map minerals is clear and it has been previously implemented in an independent manner. However, in this work, we focus on different machine learning strategies to fuse VNIR-SWIR and LWIR hyperspectral data for an accurate mineral mapping. We test two fusion scenarios: feature level fusion and decision-level fusion. For the feature-level fusion, we adopt a state-of-the-art multiple feature learning technique to adequately exploit the information containing in both data types. Hence, we take advantage of the complementary information using only one classifier. For the decision-level fusion, we integrate the independent classification results obtained using the VNIR-SWIR and LWIR data. In this way, higher robustness is expected from the combination of the classification results. The experiments are carried out on real hyperspectral datasets of drill core samples. With this contribution, we introduce a novel approach for the mining community to map minerals using a full range of hyperspectral data where not only alteration minerals but rock-forming minerals can be jointly mapped. Moreover, our proposed approach can accurately map minerals with weak spectral responses in both wavelength ranges. Based on preliminary attempts, the fusion of the VNIRSWIR and LWIR at both decision and feature levels performed better than considering both datasets independently.

  • Open Access Logo Lecture (Conference)
    European Geosciences Union (EGU) General Assembly, 07.-12.04.2019, Vienna, Austria

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Permalink: https://www.hzdr.de/publications/Publ-31428
Publ.-Id: 31428


Multi-label Classification for Drill-core Hyperspectral Mineral Mapping

Contreras Acosta, I. C.; Khodadadzadeh, M.; Gloaguen, R.

A multi-label classification concept is introduced for the mineral mapping task in drill-core hyperspectral data analysis. As opposed to traditional classification methods, this approach has the advantage of considering the different mineral mixtures present in each pixel. For the multi-label classification, the well-known Classifier Chain method (CC) is implemented using the Random Forest (RF) algorithm as the base classifier. High resolution mineralogical data obtained from Scanning Electron Microscopy (SEM) instrument equipped with the Mineral Liberation Analysis (MLA) software are used for generating the training data set. The drillcore hyperspectral data used in this paper cover the visible-near infrared (VNIR) and the short-wave infrared (SWIR) range of the electromagnetic spectrum. The quantitative and qualitative analysis of the obtained results shows that the multi-label classification approach provides meaningful and descriptive mineral maps and outperforms the single-label RF classification for the mineral
mapping task.

Keywords: Mineral mapping; drill-core hyperspectral data; mineral liberation analysis; classifier chains; random forest; multi-label classification; machine learning

Permalink: https://www.hzdr.de/publications/Publ-31427
Publ.-Id: 31427


Geochemical and Hyperspectral Data Fusion for Drill-core Mineral Mapping

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tusa, L.; Loidolt, C.; Tolosana Delgado, R.; Gloaguen, R.

Hyperspectral imaging is increasingly being used in the mining industry for the investigation of drill-core samples. It provides the means to analyze a large amount of cores considerably faster than traditional methods and in a non-invasive and non-destructive manner. Traditional approaches used to analyse drill-core hyperspectral data are mainly based on visual observations and need significant human interactions. Thus, they are time-consuming and subjective. In this paper, we explore the use of supervised machine learning techniques for mineral mapping in drill-core hyperspectral data. For this purpose, we suggest to use geochemical data for generating a training set. The main contribution of this work is to fuse geochemical and hyperspectral data within a machine learning framework. Moreover, for a more complete mineral mapping task, we integrate visible near-infrared (VNIR), short-wave infrared (SWIR) and long-wave infrared (LWIR) hyperspectral data. For the extraction of input features, the traditional Principal Component Analysis (PCA) is implemented. For classification, we propose to use Random Forest (RF) because of its significant performance in hyperspectral data classification when there are few training samples available. Experimental results show that the proposed method provides comprehensive mineral maps in which the distribution and patterns of different minerals are well characterised.

Keywords: Data fusion; mineral mapping; hyperspectral data; geochemical data; machine learning

  • Contribution to proceedings
    2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS), 24.-26.09.2019, Amsterdam, The Netherlands
    2019 10th Workshop on Hyperspectral Imaging and Signal Processing: Evolution in Remote Sensing (WHISPERS): IEEE
    DOI: 10.1109/WHISPERS.2019.8921163
    Cited 6 times in Scopus

Permalink: https://www.hzdr.de/publications/Publ-31426
Publ.-Id: 31426


Drill-Core Hyperspectral and Geochemical Data Integration in a Superpixel-Based Machine Learning Framework

Contreras Acosta, I. C.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gloaguen, R.

The analysis of drill-core samples is one of the most important steps in the mining industry for the exploration and discovery of mineral resources. Geochemical assays are a common approach to represent the abundance of different chemical elements and aid at quantifying the concentrations of the important ore accumulations. However, their acquisition is time-consuming and usually averages of long core portions. Hyperspectral data are increasingly being used in the mining industry to complement the analysis of drill-cores due to their efficiency and fast turn-around time. Moreover, hyperspectral imaging is a technique able to provide data with high spatial resolution. In this article, we propose to integrate the complementary information derived from hyperspectral and geochemical data via a superpixel-based machine learning framework. This framework considers the difference in spatial resolution through segmentation. We extract labels from the geochemical assays and select, from the hyperspectral data, representative samples for each measurement. A supervised machine learning classification (composite kernel support vector machine) is then used to extrapolate the elements relative abundance to the entire core length. We propose an innovative integration of hyperspectral data covering different regions of the electromagnetic spectrum in a kernel-based framework to facilitate the identification of a larger amount of elements. A qualitative and quantitative evaluation of the results demonstrates the capabilities of the proposed method, which provides approximately 20% more accurate results than the pixel-based approach. Results also imply that the method could be beneficial for the reduction of geochemical assays needed for the detailed analysis of the cores.

Keywords: Data integration; drill-cores; geochemical data; hyperspectral data; machine learning; superpixel segmentation

Permalink: https://www.hzdr.de/publications/Publ-31425
Publ.-Id: 31425


Mass Spectrum of Pseudo-Scalar Glueballs from a Bethe–Salpeter Approach with the Rainbow–Ladder Truncation

Kaptari, L. P.; Kämpfer, B.

We suggest a framework based on the rainbow approximation to the Dyson–Schwinger and Bethe–Salpeter equations with effective parameters adjusted to lattice QCD data to calculate the masses of the ground and excited states of pseudo-scalar glueballs. The structure of the truncated Bethe–Salpeter equation with the gluon and ghost propagators as solutions of the truncated Dyson–Schwinger equations is analyzed in Landau gauge. Both, the Bethe–Salpeter and Dyson–Schwinger equations, are solved numerically within the same rainbow–ladder truncation with the same effective parameters which ensure consistency of the approach. We found that with a set of parameters, which provides a good description of the lattice data within the Dyson–Schwinger approach, the solutions of the Bethe–Salpeter equation for the pseudo-scalar glueballs exhibit a rich mass spectrum which also includes the ground and excited states predicted by lattice calculations. The obtained mass spectrum contains also several intermediate excitations beyond the lattice approaches. The partial Bethe–Salpeter amplitudes of the pseudo-scalar glueballs are presented as well.

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Permalink: https://www.hzdr.de/publications/Publ-31424
Publ.-Id: 31424


Ab initio results for the plasmon dispersion and damping of the warm dense electron gas

Hamann, P.; Vorberger, J.; Dornheim, T.; Moldabekov, Z.; Bonitz, M.

Warm dense matter (WDM) is an exotic state on the border between condensed matter and dense plasmas. Important occurrences of WDM include dense astrophysical objects, matter in the core of our Earth, as well as matter produced in strong compression experiments. As of late, x-ray Thomson scattering has become an advanced tool to diagnose WDM. The interpretation of the data requires model input for the dynamic structure factor S(q,ω) and the plasmon dispersion ω(q). Recently the first \textit{ab initio} results for S(q,ω) of the homogeneous warm dense electron gas were obtained from path integral Monte Carlo simulations, [Dornheim et al., Phys. Rev. Lett. 121, 255001 (2018)]. Here, we analyse the effects of correlations and finite temperature on the dynamic dielectric function and the plasmon dispersion. Our results for the plasmon dispersion and damping differ significantly from the random phase approximation and from earlier models of the correlated electron gas. Moreover, we show when commonly used weak damping approximations break down and how the method of complex zeros of the dielectric function can solve this problem for WDM conditions.

Keywords: warm dense matter; electron gas; correlation; exchange; plasmon dispersion; plasmon width; collective effects; dynamic structure factor

Permalink: https://www.hzdr.de/publications/Publ-31423
Publ.-Id: 31423


Highly ordered silicide ripple patterns induced by medium-energy ion irradiation

Redondo-Cubero, A.; Palomares, F. J.; Hübner, R.; Gago, R.; Vázquez, L.

We study the nanopatterning of silicon surfaces under near-normal 40-keV Ar+ sputtering with simultaneous Fe oblique codeposition. The ion-beam incidence was kept at 15°, for which no pattern is produced in the absence of metal incorporation. Morphological and compositional analyses were performed by atomic force microscopy, in its morphological and electrical modes, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, scanning Auger, as well as transmission and scanning electron microscopy. Initially, nanodot structures randomly emerge, which, with increasing ion fluence, become progressively aligned along the perpendicular direction to the Fe flux. With increasing fluence, they coalesce, leading to a ripple pattern. The pattern dynamics and characteristics are faster and enhanced, respectively, as the distance to the metal source decreases (i.e., as the metal content increases). For the highest metal flux, the ripples can become rather large (up to 18 μm) and straighter, with few defects, and a pattern wavelength close to 500 nm, while keeping the surface roughness close to 15 nm. Furthermore, for a fixed ion fluence, the pattern order is improved for higher metal flux. In contrast, the pattern order enhancement rate with ion fluence does not depend on the metal flux. Our experimental observations agree with the predictions and assumptions of the model by Bradley [R. M. Bradley, Phys. Rev. B 87, 205408 (2013)] Several compositional and morphological studies reveal that the ripple pattern is also a compositional one, in which the ripple peaks have a higher iron silicide content, in agreement with the model. Likewise, the ripple structures develop along the perpendicular direction to the Fe flux, and the pattern wavelength increases as the metal flux decreases with a behavior qualitatively consistent with the model predictions.

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Permalink: https://www.hzdr.de/publications/Publ-31422
Publ.-Id: 31422


Towards Bacteria Counting in DI Water of Several Microliters or Growing Suspension Using Impedance Biochips

Kiani, M.; Tannert, A.; Du, N.; Hübner, U.; Skorupa, I.; Bürger, D.; Zhao, X.; Blaschke, D.; Rebohle, L.; Cherkouk, C.; Neugebauer, U.; Schmidt, O. G.; Schmidt, H.

We counted bacterial cells of E. coli strain K12 in several-microliter DI water or in several-microliter PBS in the low optical density (OD) range (OD = 0.05-1.08) in contact with the surface of Si-based impedance biochips with ring electrodes by impedance measurements. The multiparameter fit of the impedance data allowed calibration of the impedance data with the concentration cb of the E. coli cells in the range of cb = 0.06 to 1.26 × 109 cells/mL. The results showed that for E. coli in DI water and in PBS, the modelled impedance parameters depend linearly on the concentration of cells in the range of cb = 0.06 to 1.26 × 109 cells/mL, whereas the OD, which was independently measured with a spectrophotometer, was only linearly dependent on the concentration of the E. coli cells in the range of cb = 0.06 to 0.50 × 109 cells/mL.

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Permalink: https://www.hzdr.de/publications/Publ-31421
Publ.-Id: 31421


Sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase: Batch experiments, Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) and Surface Complexation Modeling (SCM)

Brinkmann, H.; Neumann, J.; Britz, S.; Brendler, V.; Stumpf, T.; Schmidt, M.

Sorption is one of the main processes, which determine the retention of radionuclides (RN) in a repository for nuclear waste. In a multi-barrier system, the host rock poses the ultimate barrier retarding the release of RN into the environment. Feldspars (e.g. orthoclase) are one of the main constituents of crystalline rock (e.g. granite), which is considered one potential host rock type in many countries (e.g. Finland, Sweden, Germany). In this study, the sorption of trivalent actinides (Cm, Am) and their rare earth analogues (Lu, Y, Eu, Nd, La) onto orthoclase (K feldspar) is investigated. For reliable predictions concerning the migration of RN, a process understanding on the molecular level of such processes is necessary. To achieve this, batch sorption experiments are combined with TRLFS and SCM.
Batch experiments were performed covering a broad range of experimental conditions (pH 4-11, oxic and anoxic conditions, [M3+] = 10-6-10-4 M, 3-50 g/L orthoclase (grain size: < 21 and 63-200 µm; SSA: 4.2 and 0.2 m2g-1)). Weak retardation below pH 5, followed by a strong increase between pH 5 and 7 and complete removal from solution at pH ≥ 8 was observed for all investigated metals. Cm- and Eu-TRLFS-measurements suggested the formation of an outer-sphere surface complex at lower (pH<5) and two different inner-sphere surface complexes at higher pH values (pH > 5 and pH > 7.5, respectively). Surface precipitation was observed for higher metal concentrations (10-4 M). As the investigated metals revealed a similar behavior over a broad range of conditions, a generic approach was used for the SCM to describe the system as a whole. Experimental data of different series with different metals were simultaneously fitted by coupling PHREEQC with UCODE using the same underlying speciation model. Resulting generic stability constants for the involved surface complexes will be presented.
The identification of comparable processes and their unified description with one suitable model is important to map the complexity of natural systems onto simplified geochemical models. This step is crucial for large-scale reactive transport calculations needed for a reliable safety assessment of potential repository sites, as they require enormous computing efforts.

Keywords: Actinides; Sorption; Orthoclase; Spectroscopy; Modeling

Permalink: https://www.hzdr.de/publications/Publ-31420
Publ.-Id: 31420


Analysis of technetium immobilization and its molecular retention mechanisms by Fe(II)-Al(III)-Cl layered double hydroxide.

Mayordomo, N.; Rodriguez Hernandez, D. M.; Roßberg, A.; Foerstendorf, H.; Heim, K.; Brendler, V.; Müller, K.

Layered double hydroxides (LDH) play a decisive role in regulating the mobility of contaminants in natural and engineered environments. In this work, the retention of an Fe(II)-Al(III)-Cl LDH towards pertechnetate (TcO₄⁻ ), which is the most stable and highly mobile form of Tc under aerobic conditions, is investigated comprehensively as a function of pH, Tc concentration and ionic strength. For a technetium initial concentration of 5 µM, its retention yield is higher than 80% from pH 3.5 to pH 10.5, especially at NaCl concentration below 0.1 M. A combination of vibrational and X-ray absorption spectroscopy provides structural information on the retention mechanism on a molecular scale. X-ray absorption near edge spectroscopy (XANES) confirms that most of the Tc uptake is due to Tc(VII) reduction to Tc(IV). The analysis of the extended X-ray absorption fine structure (EXAFS) reveals two different mechanisms of Tc(IV) interaction with hematite (sub-product of the LDH oxidation and confirmed by Raman microscopy). At low pH, sorption of Tc(IV) dimers via inner-sphere monodentate complexation on hematite dominates. In contrast, under alkaline conditions, Tc(IV) is incorporated into the structure of hematite. Additionally, in situ attenuated total reflection Fourier-transform infrared spectroscopy (ATR FT-IR) evidences a small contribution of the total uptake corresponding to Tc(VII) anion exchange.
The derived molecular structures increase confidence in predictive modelling of Tc migration patterns in subsurface environments, e.g. in the vicinity of a radioactive waste repository and treatment sites or in polluted areas due to other anthropogenic Tc sources.

Keywords: LDH; hematite; reduction; retardation; XAS; ATR FT-IR

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Permalink: https://www.hzdr.de/publications/Publ-31419
Publ.-Id: 31419


Mapping the stray fields of a micromagnet using spin centers in SiC

Bejarano, M.; Trindade Goncalves, F. J.; Hollenbach, M.; Hache, T.; Hula, T.; Berencen, Y.; Faßbender, J.; Helm, M.; Astakhov, G.; Schultheiß, H.

We report the use of optically addressable spin qubits in SiC to probe the static magnetic stray fields generated by a ferromagnetic microstructure lithographically patterned on the surface of a SiC crystal. The stray fields cause shifts in the resonance frequency of the spin centers. The spin resonance is driven by a micrometer-sized microwave antenna patterned adjacent to the magnetic element. The patterning of the antenna is done to ensure that the driving microwave fields are delivered locally and more efficiently compared to conventional, millimeter-sized circuits. A clear difference in the resonance frequency of the spin centers in SiC is observed at various distances to the magnetic element, for two different magnetic states. Our results offer a wafer-scale platform to develop hybrid magnon-quantum applications by deploying local microwave fields and the stray field landscape at the micrometer lengthscale.

Keywords: Quantum sensing; Magnonics; Spin qubits in SiC; Microwave circuits; electron beam lithography

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  • Open Access Logo IEEE Magnetics Letters 12(2021), 9380379
    DOI: 10.1109/LMAG.2021.3066341
    Cited 1 times in Scopus
  • Poster (Online presentation)
    Magnetism and Magnetic Materials Conference 2020 (MMM2020), 02.-06.11.2020, Online, United States
  • Open Access Logo Poster (Online presentation)
    Around-the-Clock Around-the-Globe Magnetics Conference, 24.08.2021, Online, Online
  • Open Access Logo Poster (Online presentation)
    SKM DPG 2021, 27.09.-01.10.2021, Online, Online
  • Open Access Logo Poster (Online presentation)
    Summer School Dresden Microelectronics Academy 2021, 20.-24.09.2021, Online, Online

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Permalink: https://www.hzdr.de/publications/Publ-31418
Publ.-Id: 31418


Studies of Big Data Processing at Linear Accelerator Sources Using Machine Learning

Bawatna, M.; Green, B. W.

In linear accelerator sources such as the electron beam of the super-conducting linear accelerator at the radiation source Electron Linear accelerator for beams with high Brilliance and low Emittance (ELBE), different kinds of secondary radiation can be produced for various research purposes from materials science up to medicine. A variety of different beam detectors generate a huge amount of data, which take a great deal of computing power to capture and analyse. In this contribution, we will discuss the possibilities of using Machine Learning method to solve the big data challenges. Moreover, we will present a technique that employ the machine learning strategy for the diagnostics of high-field terahertz pulses generated at the ELBE accelerator with extremely flexible parameters such as repetition rate, pulse form and polarization.

Keywords: Cloud computing; Machine learning; Big data; Deep neural networks

  • Contribution to proceedings
    Computer Science On-line Conference, CSOC 2020: Artificial Intelligence and Bioinspired Computational Methods, 20.-24.05.2020, Berlin, Germany
    Advances in Intelligent Systems and Computing, Volume 1225 AISC, 2020, Pages 450-460: Springer, 978-3-030-51970-4
    DOI: 10.1007/978-3-030-51971-1_37

Permalink: https://www.hzdr.de/publications/Publ-31417
Publ.-Id: 31417


Real-Time Data Compression System for Data-Intensive Scientific Applications Using FPGA Architecture

Bawatna, M.; Knodel, O.; Spallek, R.

Particle accelerators are continually advancing and offer insights into the world of molecules, atoms, and particles on the ever shorter length and timescales. A variety of detectors, which are connected to different front-end electronics are installed in various kinds of Data Acquisition (DAQ) systems, to collect a huge amount of raw data. This goes along with a rapid and highly accurate transformation of analog quantities into discrete values for electronic storage and processing with exponentially increasing amounts of data. Therefore, data reduction or compression is an important feature for the DAQ systems to reduce the size of the data transmission path between the detectors and the computing units or storage devices. The flexibility of the Field Programmable Gate Arrays (FPGAs) allows the implementation of real-time data compression algorithms inside these DAQ systems. In this contribution, we will present our developed real-time data compression technique for continuous data recorded by high-speed imaging detectors at the terahertz source facility at ELBE particle accelerator. The hardware implementation of the algorithm proved its real-time suitability by compressing one hundred thousand consecutive input signals without introducing dead time.

Keywords: Lossless data compression; FPGA; Real-time; Data-intensive

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  • Contribution to proceedings
    Computer Science On-line Conference, Applied Informatics and Cybernetics in Intelligent Systems, 20.-24.05.2020, Berlin, Germany
    CSOC 2020: Applied Informatics and Cybernetics in Intelligent Systems: Springer, 978-3-030-51974-2, 304-313
    DOI: 10.1007/978-3-030-51974-2_29

Permalink: https://www.hzdr.de/publications/Publ-31416
Publ.-Id: 31416


Possibilities and Challenges for Reconfigurable Hardware and Cloud Architectures in Data-Intensive Scientific Applications

Bawatna, M.; Knodel, O.; Spallek, R.

Advances in process technology and new design tools have expanded the scope of embedded systems. This ranges from the implementation in several chips on board to module groups in integrated circuits. Reconfigurable hardware and, in particular, FPGAs are used more frequently in scientific applications, where they enable the development of complex and intelligent field devices. Furthermore, this increased the use of a platform-based design approach that facilitates the development and verification of complex FPGAs through the full reuse of hardware and software modules. Especially in the area of heterogeneous accelerators, which can improve the exploitation of modern data centers. Another critical aspect in the evolution of embedded systems is the trend towards networking embedded nodes using specialized computational and networking technologies called cloud computing. In this paper, we will present our data-intensive experiments at the terahertz source at ELBE accelerator-based light source, and its integration into a reproducible data management workflow at the heterogeneous cluster in our data centre

Keywords: Reconfigurable computing; cloud; data-intensive scientific applications

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  • Contribution to proceedings
    Seventh International Conference on Software Defined Systems (SDS), 20.-23.04.2020, Paris, France
    Proceedings of Seventh International Conference on Software Defined Systems: IEEE, 978-1-7281-7218-7
    DOI: 10.1109/SDS49854.2020.9143904

Permalink: https://www.hzdr.de/publications/Publ-31415
Publ.-Id: 31415


In silico finding of key interaction mediated α3β4 and α7 nicotinic acetylcholine receptor ligand selectivity of quinuclidine-triazole chemotype

Arunrungvichian, K.; Chongruchiroj, S.; Sarasamkan, J.; Schüürmann, G.; Brust, P.; Vajragupta, O.

The selective binding of six (S)-quinuclidine-triazole and their (R)-enantiomers to nicotinic acetylcholine receptor (nAChR) subtypes α3β4 and α7, respectively, was analyzed by in silico docking to provide the insight into the molecular basis for the observed stereospecific subtype discrimination. Homology modeling follwed by molecular docking and molecular dynamics (MD) simulations revealed that unique amino acid residues in the complementary subunits of the nAChR subtypes are involved in subtype-specific selectivity profiles. In the complementary β4-subunit of the α3β4 nAChR binding pocket, non-conserved AspB173 through a salt bridge was found to be the key determinant for the α3β4 selectivity of the quinuclidine-triazole chemotype, explaining the 47-327-fold affinity of the (S)-enantiomers as compared to their (R)-enantiomer counterparts. Regarding the α7 nAChR subtype, the aminio acids promoting a however significantly lower preference for the (R)-enantiomers were the conserved TyrA93, TrpA149 and TrpB55 residues. The non-conserved amino acid residue in the complementary subunit of nAChR subtypes appeard to play a significant role for the nAChR subtype-selective binding, particularly at the heteropentameric subtype, wheras the conserved amino acid residues in both principal and complementary subunits are essential for ligand potency and efficacy.

Keywords: stereoselectivity; anti-1,2,3-triazole; α7 nAChR; α3β4 nAChR; quinuclidine

Permalink: https://www.hzdr.de/publications/Publ-31414
Publ.-Id: 31414


Effects of Acquisition Parameter Modifications and Field Strength on the Reproducibility of Brain Perfusion Measurements Using Arterial Spin-Labeling

Baas, K.; Petr, J.; Kuijer, J.; Nederveen, A.; Mutsaerts, H.-J.; van de Ven, K.

Background and Purpose: To encourage clinical adoption of ASL-based perfusion MRI, we investigated the reproducibility of CBF measurements and the effects of protocol variations at clinical field strengths in adult participants with a broad age range. This study increases the knowledge on the tolerance to variations in scan parameters compared to the recommended ASL implementation.
Materials and Methods: Thirty-four volunteers (mean age 57.8±17.0y, range 22-80y) underwent two separate scan sessions on clinical field strengths (1.5T and 3T, single vendor), using a fifteen channel head coil. Both sessions contained repeated 3D and 2D pseudo-continuous ASL (pCASL) vendor-recommended protocols, followed by three 3D pCASL scans; two with post-labeling delays (PLD) of 1600ms and 2000ms and one with increased spatial resolution. All pCASL scans were acquired with a single PLD. The effect of scan parameter variations on CBF and spatial coefficient of variation (CoV) was examined, as well as the reproducibility of the recommended protocols, both intrasession (two identical protocols scanned 5 min apart) and intersession (first 2D and 3D protocol of the first and second session).
Results: Intrasession CBF reproducibility was similar across image readouts and field strengths ( coefficient of variation (CV) ranging from 4.0% to 6.9%) and did not show a statistically significant correlation with age. Intersession wsCV ranged from 6.8% to 14.8%, scanning twice at 3T versus mixed 3T-1.5T respectively. At 3T, there is sufficient SNR to increase the spatial resolution of the 3D protocol, causing less mixing of gray matter (GM) and white matter signal, therewith decreasing the bias in GM CBF between 2D and 3D protocols (ΔCBF = 2.49 (p<0.001) ml/100g/min. Changes in PLD resulted in a modest bias (ΔCBF ranging from -3.78 (p<0.001) to 2.83 (p<0.001) ml/100g/min).
Conclusion: Our data shows that ASL imaging is reproducible at both field strengths and does not show a statistically significant correlation with age. Furthermore, 3T offers more tolerance for scan parameter variations and allows for protocol optimizations such that 3D and 2D protocols can be compared.

Permalink: https://www.hzdr.de/publications/Publ-31413
Publ.-Id: 31413


GliMR: Cross-border collaborations to promote advanced MRI biomarkers in glioma

Clement, P.; Borovecki, F.; Emblem, K. E.; Figueiredo, P.; Hirschler, L.; Jancalek, R.; Keil, V. C.; Maumet, C.; Ozsunar, Y.; Pernet, C.; Petr, J.; Pinto, J.; Smits, M.; Warnert, E. A. H.

Every year, 50.000 new glioma cases occur in Europe. The optimal treatment strategy is highly personalised, depending on tumour type, grade, spatial localization, and tissue infiltration level. In research settings, advanced magnetic resonance imaging (MRI) has shown great promise to inform personalised treatment decisions. However, the use of advanced MRI in clinical practice is still scarce, due to a scattered imaging research landscape, a limited representation of MRI in established consortia for glioma, and the lack of tools and expertise for advanced MRI, available in standard clinical settings. These shortcomings delay the translation of scientific breakthroughs into novel treatment strategy developments, and limit the progression of personalised medicine.
Therefore, in this work, the network Glioma MR Imaging 2.0 (GliMR) is presented. GliMR aims to build a pan-European and multidisciplinary network of experts and progress beyond the state-of-the-art in glioma imaging, by accelerating the use of advanced MRI in glioma. The Action ‘Glioma MR Imaging 2.0 (GliMR)’ was granted funding by the European Cooperation in Science and Technology (COST) in June 2019.
GliMR’s first grant period ran from September 2019 to April 2020, during which several networking meetings were held and projects were initiated by the different working groups, such as reviewing of the current knowledge on advanced MRI, developing a GDPR-compliant consent form, initiating relationships with European scientific organisations, and setting up several dissemination channels, including the website www.glimr.eu. The action is funded until September 2023 and is accepting new members during its entire duration.

Permalink: https://www.hzdr.de/publications/Publ-31412
Publ.-Id: 31412


Integrated Geological and Geophysical Mapping of a Carbonatite-Hosting Outcrop in Siilinjärvi, Finland, Using Unmanned Aerial Systems

Jackisch, R.; Lorenz, S.; Kirsch, M.; Zimmermann, R.; Tusa, L.; Pirttijärvi, M.; Saartenoja, A.; Ugalde, H.; Madriz Diaz, Y. C.; Savolainen, M.; Gloaguen, R.

Mapping geological outcrops is a crucial part of mineral exploration, mine planning and ore extraction. With the advent of unmanned aerial systems (UAS) for rapid spatial and spectral mapping, opportunities arise in fields where traditional ground-based approaches are established and trusted, but fail to cover sufficient area or compromise personal safety. Multi-sensor UAS are a technology that change geoscientific research, but they are still not routinely used for geological mapping in exploration and mining due to lack of trust in their added value, missing expertise and guidance in the selection and combination of drones and sensors. To address these limitations and highlight the potential of using UAS in exploration settings, we present a UAS multi-sensor mapping approach based on the integration of drone-borne photography, multi- and hyperspectral imaging, and magnetics. Data are processed with conventional methods as well as innovative machine-learning algorithms and validated by geological field mapping, yielding a comprehensive and geologically interpretable product. As a case study, we chose the northern extension of the Siilinjärvi apatite mine in Finland, in a brownfield exploration setting with plenty of ground truth data available and a survey area that is only partly covered by vegetation. We conducted rapid UAS surveys from which we created a multi-layered dataset to investigate properties of the ore-bearing carbonatite-glimmerite body. Our resulting geologic map discriminates between the principal lithologic units and distinguishes ore-bearing from waste rocks. Structural orientations and lithological units are deduced based on high-resolution, hyperspectral image-enhanced point clouds. UAS-based magnetic data allow an insight into their subsurface geometry through modelling based on magnetic interpretation. We validate our results via ground survey including rock specimen sampling, geochemical and mineralogical analysis and spectroscopic point measurements. We are convinced that the presented non-invasive, data-driven mapping approach can complement traditional workflows in mineral exploration as a flexible tool. Mapping products based on UAS data increase efficiency and maximize safety of the resource extraction process, reduce expenses and incidental wastes.

Keywords: unmanned aerial vehicles; hyperspectral; multispectral; magnetic; geologic mapping; drones; UAV

Permalink: https://www.hzdr.de/publications/Publ-31411
Publ.-Id: 31411


Live-cell Imaging with Aspergillus Fumigatus-specific fluorescent Siderophore Conjugates

Pfister, J.; Lichius, A.; Summer, D.; Haas, H.; Kanagasundaram, T.; Kopka, K.; Decristoforo, C.

Live-cell imaging allows to analyse the subcellular localisation dynamics of physiological processes with high spatial-temporal resolution in vivo. So far, only few fluorescent dyes have been custom-designed to facilitate species-specific live-cell imaging approaches in filamentous fungi. Therefore, we developed fluorescent dye conjugates based on the sophisticated iron acquisition system of Aspergillus fumigatus by chemical modification of the siderophore Triacetylfusarinine C (TAFC).
Various fluorophores (FITC, NBD, Ocean Blue, BODIPY 630/650, SiR, TAMRA and Cy5) were conjugated to Diacetylfusarinine C (DAFC). Gallium-68 labelling enabled in-vitro and in-vivo characterisations. LogD, uptake assays and growth assays were performed and complemented by live-cell imaging in different Aspergillus species.
Siderophore conjugates were specifically recognised by the TAFC transporter MirB and utilized in growth assays as an iron source. Fluorescence microscopy revealed uptake dynamics and differential subcellular accumulation patterns of all compounds inside fungal hyphae. [Fe]DAFC-NBD and -Ocean Blue accumulated in vacuoles, whereas [Fe]DAFC-BODIPY, -SiR and -Cy5 localised to mitochondria. [Fe]DAFC -FITC showed a uniform cytoplasmic distribution, whereas [Fe]DAFC-TAMRA was not internalised at all. Co-staining experiments with commercially available fluorescent dyes confirmed these findings.
Overall we developed a new class of fluorescent dyes varying in intracellular fungal targeting providing novel tools for live-cell imaging applications for Aspergillus fumigatus.

Keywords: Live-cell Imaging; Aspergillus Fumigatus; Fluorescence Microscopy; Siderophores; Fluorescent Dyes

Permalink: https://www.hzdr.de/publications/Publ-31410
Publ.-Id: 31410


Data for: An analysis for detecting potential relocation of the inventory of dry storage containers during prolonged interim storage via changes in the wall temperature fields

Wagner, M.; Reinicke, S.

Geometry files of the performed simulations (ANSYS Fluent).

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Permalink: https://www.hzdr.de/publications/Publ-31409
Publ.-Id: 31409


Radiomics-based prediction of tumor phenotype from tumor microenvironment and medical imaging

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

Magnetic resonance imaging (MRI) and immunohistochemical tissue stainings are pivotal for radiotherapeutic workflows. Yet, recent efforts herald a paradigm shift: Radiomic methods are used to extract a large number of quantitative features from image data to detect high-dimensional patterns, which are correlated with relevant clinical endpoints. Preclinical experiments help to understand underlying mechanisms, yet require the backtranslation of clinically used methods and their application to a heterogeneous patient cohort. In the present preclinical experiment, we determine the tumor phenotype from MRI and tumor microenvironment (TME) features in a patient cohort of xenograft tumor models of the head and neck.
An artificial heterogeneous patient population was created by mixing two tumor models of different radiosensitivity (SAS & UT-SCC-14) in pooled cohort (N = 108) and exposure to one week of fractionated irradiation with photons and protons. After irradiation, contrast agent-enhanced T1-weighted 3D gradient-echo MRI scans were acquired, tumors were excised and characterized immunohistochemically regarding vascularity (CD31), hypoxia (Pimonidazole) and morphology (H&E). Approximately 200 quantitative features were extracted from MRI and light-microscopy image data with an automated medical image radiomics processor and trainable image segmentation, respectively. TME parameters were analyzed regarding effects of radiation with two-sided t-tests. A fully automated radiomic framework was used for feature selection, model generation using leave-one-out cross validation with the individual tumor model’s identity (i.e. its phenotype) as endpoint. Model performance was assessed through area under the curve (AUC).
The used image quantification methods allowed for robust feature extraction. No effects of radiation on the TME were detected except for changes in vessel-adjacent hypoxia. Radiomic analysis was able to predict the tumor model based on TME features (AUC = 0.86), MRI features (AUC = 0.90) or combined features (AUC = 0.86).
We demonstrated backtranslation of radiomic methods in a preclinical setting with multi-modal image data. Further analysis of automatically extracted MRI and TME features may allow for a more biologically informed interpretation of MRI data.

Keywords: Radiomics; Medical Imaging; Preclinical; Microenvironment; Hypoxia; Radiation

  • Lecture (Conference) (Online presentation)
    Virtual Meeting 2020, 18.-21.10.2020, (Virtual), (Virtual)

Permalink: https://www.hzdr.de/publications/Publ-31408
Publ.-Id: 31408


A convolutional neural network for fully automated blood SUV determination in oncological FDG-PET

Nikulin, P.; Hofheinz, F.; Maus, J.; Pietsch, J.; Li, Y.; Bütof, R.; Lange, C.; Furth, C.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.

Aim: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor's glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.

Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), namely U-Net. 632 FDG PET/CT scans from 4 different sites were used for network training (N=208) and testing (N=424). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.

Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Notably, using both CT and PET data as input for network training allows the trained network to derive unbiased BSUVs by detecting and excluding aorta segments affected by attenuation artifacts or spill-over. Comparison of manually (M) and automatically (A) derived BSUVs shows excellent concordance: the mean paired M-A difference in the 424 test cases is (mean +/- SD)=(0.2 +/- 3.1)% with a 95% confidence interval of [-6.6, 5.7]%. For a single test case the M-A difference exceeded 10%.

Conclusion: CNNs offer a viable approach for automatic BSUV determination. Our trained network exhibits a performance comparable to an experienced human observer and might already be considered suitable for supervised clinical use.

Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network

  • Poster (Online presentation)
    Nuklearmedizin 2020, 07.-09.07.2020, Online, Online
  • Lecture (Conference) (Online presentation)
    EANM’20 Congress, 22.-30.10.2020, Online, Online

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Permalink: https://www.hzdr.de/publications/Publ-31407
Publ.-Id: 31407


A convolutional neural network for fully automated blood SUV determination to facilitate SUR computation in oncological FDG-PET

Nikulin, P.; Hofheinz, F.; Maus, J.; Li, Y.; Bütof, R.; Lange, C.; Furth, C.; Zschaeck, S.; Kreissl, M. C.; Kotzerke, J.; van den Hoff, J.

Purpose: The standardized uptake value (SUV) is widely used for quantitative evaluation in oncological FDG-PET but has well-known shortcomings as a measure of the tumor’s glucose consumption. The standard uptake ratio (SUR) of tumor SUV and arterial blood SUV (BSUV) possesses an increased prognostic value but requires image-based BSUV determination, typically in the aortic lumen. However, accurate manual ROI delineation requires care and imposes an additional workload which makes the SUR approach less attractive for clinical routine. The goal of the present work was the development of a fully automated method for BSUV determination in whole-body PET/CT.
Methods: Automatic delineation of the aortic lumen was performed with a convolutional neural network (CNN), using the U-Net architecture. 946 FDG PET/CT scans from several sites were used for network training (N = 366) and testing (N = 580). For all scans, the aortic lumen was manually delineated, avoiding areas affected by motion-induced attenuation artifacts or potential spill-over from adjacent FDG-avid regions. Performance of the network was assessed using the fractional deviations of automatically and manually derived BSUVs in the test data.
Results: The trained U-Net yields BSUVs in close agreement with those obtained from manual delineation. Comparison of manually and automatically derived BSUVs shows excellent concordance: the mean relative BSUV difference was (mean ± SD) = (-0.5± 2.2)% with a 95% confidence interval of [−5.1, 3.8]% and a total range of [-10.0, 12.0]%. For four test cases the derived ROIs were unusable (<1 ml).
Conclusion: CNNs are capable of performing robust automatic image-based BSUV determination. Integrating automatic BSUV derivation into PET data processing workflows will significantly facilitate SUR computation without increasing the workload in the clinical setting.

Keywords: FDG-PET; standardized uptake value; SUV; standardized uptake ratio; SUR; convolutional neural network

Permalink: https://www.hzdr.de/publications/Publ-31406
Publ.-Id: 31406


Hierarchical Sparse Subspace Clustering (HESSC): An Automatic Approach for Hyperspectral Image Analysis

Rafiezadeh Shahi, K.; Khodadadzadeh, M.; Tusa, L.; Ghamisi, P.; Tolosana Delgado, R.; Gloaguen, R.

Hyperspectral imaging techniques are becoming one of the most important tools to remotely acquire fine spectral information on different objects. However, hyperspectral images (HSIs) require dedicated processing for most applications. Therefore, several machine learning techniques were proposed in the last decades. Among the proposed machine learning techniques, unsupervised learning techniques have become popular as they do not need any prior knowledge.
Specifically, sparse subspace-based clustering algorithms have drawn special attention to cluster the HSI into meaningful groups since such algorithms are able to handle high dimensional and highly mixed data, as is the case in real-world applications. Nonetheless, sparse subspace-based clustering algorithms usually tend to demand high computational power and can be time-consuming.
In addition, the number of clusters is usually predefined. In this paper, we propose a new hierarchical sparse subspace-based clustering algorithm (HESSC), which handles the aforementioned problems in a robust and fast manner and estimates the number of clusters automatically. In the experiment, HESSC is applied to three real drill-core samples and one well-known rural benchmark (i.e., Trento) HSI datasets. In order to evaluate the performance of HESSC, the performance of the new proposed algorithm is quantitatively and qualitatively compared to the state-of-the-art sparse subspace-based algorithms. In addition, in order to have a comparison with conventional clustering algorithms, HESSC’s performance is compared with K-means and FCM. The obtained clustering results demonstrate that HESSC performs well when clustering HSIs compared to the other applied clustering algorithms.

Keywords: hyperspectral images; subspace-based clustering; hierarchical structure; unsupervised learning; sparse representation; ensemble learning

Permalink: https://www.hzdr.de/publications/Publ-31405
Publ.-Id: 31405


Magnetic properties of biogenic selenium nanomaterials

Dixit, R.; Gupta, A.; Jordan, N.; Zhou, S.; Schild, D.; Weiß, S.; Guillon, E.; Jain, R.; Lens, P.

The properties of biogenic elemental selenium (BioSe) need to be studied in order to understand its environmental fate. In this paper, the magnetic properties of biogenic elemental selenium nanospheres (BioSe-Nanospheres) and nanorods (BioSe-Nanorods) obtained via the reduction of selenium(IV) using anaerobic granular sludge were investigated. The study indicated that the BioSe nanomaterials have a strong paramagnetic contribution with some ferromagnetic component due to the incorporation of Fe(III) (high spin and low spin species) as indicated by Electron Paramagnetic Resonance (EPR). X-Ray Photoelectron Spectroscopy (XPS) also confirmed the weak presence of Fe(III) and combined with EPR data, the Fe(III) availability through the nanomaterial was established. It is likely that Fe(III) being abundantly present in sludge got entrapped in the extracellular polymeric substances (EPS) coating the biogenic nanomaterials. The presence of Fe(III) in BioSe nanomaterials increases the mobility of Fe(III) and can have an effect on phytoplankton growth in the environment. Further, there is a potential to exploit the magnetic properties of BioSe nanomaterials in drug delivery system as well as in space refrigeration.

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Permalink: https://www.hzdr.de/publications/Publ-31404
Publ.-Id: 31404


Thermal kinetics of free volume in porous spin-on dielectrics: exploring the network- and pore-properties

Elsherif, A. G. A.; Koehler, N.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Ecke, R.; Schulz, S. E.; Wagner, A.

Comprehensive ex-situ and in-situ investigations of thermal curing processes in spin-on ultra-low-k thin films conducted by positron annihilation spectroscopy and Fourier transform infrared spectroscopies are presented. Positron annihilation lifetime spectroscopy of ex-situ cured samples reveals an onset of the curing process at about 200 °C, which advances with increasing curing temperature. Porogen agglomeration followed by diffusive migration to the surface during the curing process leads to the generation of narrow channels across the film thickness. The size of those channels is determined by a pore size distribution analysis of positron lifetime data. Defect kinetics during in-situ thermal curing has been investigated by means of Doppler broadening spectroscopy of the annihilation radiation, showing several distinct partially superposed and subsequent curing stages, i.e., moisture and residual organic solvents removal, SiOx network cross-linking, porogen decomposition, and finally creation of a stable porous structure containing micropore channels interconnecting larger mesopores formed likely due to micelle like interaction between porogen molecules, for curing temperatures not larger than 500 °C. Static (sequencing curing) states captured at specific temperature steps confirm the conclusions drawn during the dynamic (continuous curing) measurements. Moreover, the onset of pore inter-connectivity is precisely estimated as pore interconnectivity sets in at 380–400 °C.

Keywords: In-situ curing; Positron annihilation spectroscopy; Porogen removal; Porosimetry; FTIR; Dielectrics; Pore size distribution; Positronium

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Permalink: https://www.hzdr.de/publications/Publ-31402
Publ.-Id: 31402


Geostatistics for compositional data with R

Tolosana Delgado, R.; Müller, U.

Many real world data sets feature positively valued variables that represent parts of a whole and contain only relative information, in addition to this these variables are often location dependent, so that the data set as a whole is spatial and compositional . Variables of this type are common in geosciences, but also in ecology and geography-based sciences. Traditional statistical techniques are not applicable because of constraints on the data arising from their nature. This book provides practitioner with a consistent treatment, with code and workflows to assist in producing internally consistent results, maps and 3D volume models.

This book is a contribution to the UseR series and provides a guide to the use of R for the geostatistical modelling of compositional data. It provides code based on the R-packages "gstat" and "compositions" together with a customized package "gmGeostats", providing an integrated approach to the modelling of compositional data. This consists of the following aspects: decision criteria to determine whether a compositional treatment is required, statistical and spatial analysis of the input data, modelling of the spatial continuity and more general structure analysis, spatial prediction via estimation or simulation, change of support and validation tools. The methods are illustrated via three geochemical data sets, two from environmental geochemical surveys at two different campaigns (Northern Ireland and Australia) and the other from a mining context.

Keywords: Logratio; simplex; variography; crossvalidation; estimation; cokriging and simulations; change of support; spatial decorrelation; spatial factor analysis,; multivariate normal score transform

Permalink: https://www.hzdr.de/publications/Publ-31401
Publ.-Id: 31401


Transition from steady to oscillating convection rolls in Rayleigh-Bénard convection under the influence of a horizontal magnetic field

Yang, J.; Vogt, T.; Eckert, S.

In this study we consider the effect of a horizontal magnetic field on the Rayleigh-Bénard convection in a finite liquid metal layer contained in a cuboid vessel (200x200x40 mm^3) of aspect ratio Gamma = 5. Laboratory experiments are performed for measuring temperature and flow field in the low melting point alloy GaInSn at Prandtl number Pr = 0.03 and in a Rayleigh number range 2.3x10^4 < Ra < 2.6x10^5. The field direction is aligned parallel to one pair of the two side walls. The field strength is varied up to a maximum value of 320 mT (Ha = 2470, Q = 6.11x10^6, definitions of all non-dimensional numbers are given in the text). The magnetic field forces the flow to form two-dimensional rolls whose axes are parallel to the direction of the field lines. The experiments confirm the predictions made by Busse and Clever (J. Mécanique Théorique et Appliquée, 1983 [1]) who showed that the application of the horizontal magnetic field extends the range in which steady two-dimensional roll structures exist (‘Busse balloon’) towards higher Ra numbers. A transition from the steady to a time-dependent oscillatory flow occurs when Ra exceeds a critical value for a given Chandrasekhar number Q, which is also equivalent to a reduction of the ratio Q/Ra. Our measurements reveal that the first developing oscillations are clearly of two-dimensional nature, in particular a mutual increase and decrease in the size of adjacent convection rolls is observed without the formation of any detectable gradients in the velocity field along the magnetic field direction. At a ratio of Q/Ra = 1, the first 3D structures appear, which initially manifest themselves in a slight inclination of the rolls with respect to the magnetic field direction. Immediately in the course of this, there arise also disturbances in the spaces between adjacent convection rolls, which are advected along the rolls due to the secondary flow driven by Ekman pumping. The transition to fully-developed three-dimensional structures and then to a turbulent regime takes place with further lowering Q/Ra.

Keywords: Rayleigh-Benard convection; liquid metal; horizontal magnetic field; convection rolls; oscillatory instability

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Permalink: https://www.hzdr.de/publications/Publ-31399
Publ.-Id: 31399


Strengthening of ods silver wires

Wasserbäch, W.; Skrotzki, W.; Chekhonin, P.

The present work is part of an experimental program in which the mechanical behavior and the evolution of microstructure and texture of different industrially manufactured oxide-dispersion strengthened silver alloys upon different processing steps like hot-extrusion, cold-working and further annealing have been investigated. The investigations reveal that the incoherent oxide particles strongly influence the evolution of microstructure and texture during processing and consequently the deformation behavior at room temperature. Small oxide particles cause a high strengthening of the material but only a small change of the microstructure and texture. Increasing the oxide particle size subsequently reduces the strength and changes the original microstructure and texture in a more pronounced way. The yield strength at room temperature can be explained with a linear superposition of the Orowan stress for bypassing of oxide particles by dislocations and grain boundary strengthening according to Hall-Petch. The impact of texture of the materials on the yield strength is accounted for.

Keywords: Silver; Metal matrix composites; Cold-working; Strain hardening; Texture

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Permalink: https://www.hzdr.de/publications/Publ-31397
Publ.-Id: 31397


Keap1 inhibition sensitizes head and neck squamous cell carcinoma cells to ionizing radiation via impaired non-homologous end joining and induced autophagy

Deville, S.; Luft, S.; Kaufmann, M.; Cordes, N.

The function of Keap1 (Kelch-like ECH-associated protein 1), a sensor of oxidative and electrophilic stress, in the radiosensitivity of cancer cells remains elusive. Here, we investigated the effects of pharmacological inhibition of Keap1 with ML344 on radiosensitivity, DNA double strand break (DSB) repair and autophagy in head and neck squamous cell carcinoma (HNSCC) cell lines. Our data demonstrate that Keap1 inhibition enhances HNSCC cell radiosensitivity. Despite elevated, Nrf2-dependent activity of non-homologous end joining (NHEJ)-related DNA repair, Keap1 inhibition seems to impair DSB repair through delayed phosphorylation of DNA-PKcs. Moreover, Keap1 inhibition elicited autophagy and increased p62 levels when combined with X-ray irradiation. Our findings suggest HNSCC cell radiosensitivity, NHEJ-mediated DSB repair and autophagy to be co-regulated by Keap1.

Keywords: HNSCC; radiosensitivity; Keap1; autophagy

Permalink: https://www.hzdr.de/publications/Publ-31395
Publ.-Id: 31395


c-Abl tyrosine kinase is regulated downstream of the cytoskeletal protein synemin in head and neck squamous cell carcinoma radioresistance and DNA repair

Deville, S.; Delgadillo, L.; Vehlow, A.; Cordes, N.

The intermediate filament synemin has been previously identified as novel regulator of cancer cell therapy resistance and DNA double strand break (DSB) repair. c-Abl tyrosine kinase is involved in both of these processes. Using PamGene technology, we performed a broad-spectrum kinase activity profiling in three-dimensionally, matrix grown head and neck cancer cell cultures. Upon synemin silencing, we identified 86 deactivated tyrosine kinases, including c-Abl, in irradiated HNSCC cells. c-Abl hyperphosphorylations on tyrosine (Y) 412 and threonine (T) 735 upon irradiation were significantly reduced after synemin inhibition prompting us to hypothesize that c-Abl tyrosine kinase is an important signaling component of the synemin-mediated radioresistance pathway. Simultaneous targeting of synemin and c-Abl resulted in similar radiosensitization and DSB repair compared with single synemin depletion suggesting synemin as an upstream regulator of c-Abl. Immunoprecipitation assays revealed a protein complex formation between synemin and c-Abl pre- and post-irradiation. Upon pharmacological inhibition of ATM, synemin/c-Abl protein-protein interactions were disrupted implying synemin function to depend on ATM kinase activity. Moreover, deletion of the ∆SH2 domain in c-Abl demonstrated a decrease in interaction indicating the dependency of the protein-protein interaction on this domain. Mechanistically, impairment of DNA repair seems to be related with radiosensitization upon synemin knockdown via regulation of non-homologous end joining, independent of c-Abl function. Our data generated in more physiological 3D cancer cell culture models suggest c-Abl as further key determinant of radioresistance downstream of synemin.

Keywords: Ionizing radiation; HNSCC; Synemin; DNA repair

Permalink: https://www.hzdr.de/publications/Publ-31394
Publ.-Id: 31394


Comparative proton and photon irradiation combined with pharmacological inhibitors in 3D pancreatic cancer cultures

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

Pancreatic ductal adenocarcinoma (PDAC) is a highly therapy resistant tumor entity of unmet need. Over the last decades, radiotherapy has been considered as additional treatment modality to surgery and chemotherapy. Owing to radiosensitive abdominal organs, high precision proton beam radiotherapy has been regarded superior to photon radiotherapy. To further elucidate the potential of combination therapies, we employed a more physiological 3D, matrix-based cell culture model to assess tumoroid formation capacity after photon and proton irradiation. Additionally, we investigated proton and photon irradiation-induced phosphoproteomic changes for identifying clinically exploitable targets. Here, we show that proton irradiation elicits a higher efficacy to reduce 3D PDAC tumoroid formation and a greater extent of phosphoproteome alterations compared with photon irradiation. Targeting of proteins identified in the phosphoproteome that were uniquely altered by protons or photons failed to cause radiation type-specific radiosensitization. Targeting DNA repair proteins associated with non-homologous endjoing, however, revealed a strong radiosensitizing potential independent from the radiation type. In conclusion, our findings suggest proton irradiation to be potentially more effective in PDAC than photons without additional efficacy when combined with DNA repair inhibitors.

Keywords: PDAC; radiotherapy; proton beam irradiation; 3D cell culture; molecular targeting

Permalink: https://www.hzdr.de/publications/Publ-31393
Publ.-Id: 31393


Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions

Schwestka, J.; Inani, H.; Tripathi, M.; Niggas, A.; Mcevoy, N.; Libisch, F.; Aumayr, F.; Kotakoski, J.; Wilhelm, R. A.

The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van-der-Waals heterostructures. Tailoring of heterostructure properties post-growth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van-der-Waals MoS2/graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nm-sized pores that appear only in the MoS2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS2 underneath. Our main focus is here on monolayer MoS2, but we also analyzed areas with few-layer structures, and observed that the perforation is limited to the two topmost MoS2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono(or bi-)layer manipulation of van-der-Waals heterostructures when also the localized potential energy deposition of highly charged ions is added to the toolbox.

Keywords: 2d material modification; ion beam surface modification; monolayer precision; van der Waals heterostructure

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Permalink: https://www.hzdr.de/publications/Publ-31392
Publ.-Id: 31392


The role of contaminations in ion beam spectroscopy with freestanding 2D materials: A study on thermal treatment

Niggas, A.; Schwestka, J.; Creutzburg, S.; Gupta, T.; Eder, D.; Bayer, B. C.; Aumayr, F.; Wilhelm, R. A.

As surface-only materials, freestanding 2D materials are known to have a high level of contamination—mostly in the form of hydrocarbons, water, and residuals from production and exfoliation. For well-designed experiments, it is of particular importance to develop effective clean- ing procedures, especially since standard surface science techniques are typically not applicable. We perform ion spectroscopy with highly charged ions transmitted through freestanding atomically thin materials and present two techniques to achieve clean samples, both based on thermal treatment. Ion charge exchange and energy loss are used to analyze the degree of sample contamination. We find that even after cleaning, heavily contaminated spots remain on single layer graphene. The contamination coverage, however, clusters in strand-like structures leaving large clean areas. We present a way to discriminate clean from contaminated areas with our ion beam spectroscopy if the heterogeneity of the surface is increased sufficiently enough. We expect a similar discrimination to be necessary in most other experimental techniques.

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Permalink: https://www.hzdr.de/publications/Publ-31391
Publ.-Id: 31391


PIMC data for the nonlinear electronic density response in warm-dense matter (WDM)

Dornheim, T.

This repository contains the PIMC raw data for the actual density response of the harmonically perturbed electron gas.

The data can be freely re-used. Please cite:

T. Dornheim, J. Vorberger, and M. Bonitz, Nonlinear Electronic Density Response in Warm Dense Matter, Phys. Rev. Lett. (in press), arXiv:2004.03229

Keywords: PIMC; density response; warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-31390
Publ.-Id: 31390


Trimeric uranyl(VI)–citrate forms Na+, Ca2+, and La3+ sandwich complexes in aqueous solution

Kretzschmar, J.; Tsushima, S.; Drobot, B.; Steudtner, R.; Schmeide, K.; Stumpf, T.

Basile et al. (Chem. Commun., 2015, 51, 5306–5309) showed that a sodium ion is sandwiched by the uranyl(VI) oxygen atoms of two 3:3 uranyl(VI)–citrate complex molecules in single-crystals. By means of NMR spectroscopy supported by DFT calculation we provide unambiguous evidence for this complex to persist in aqueous solution above a critical concentration of 3 mM uranyl citrate. Unprecedented Ca2+ and La3+ coordination by a bis-(η3-uranyl(VI)-oxo) motif advances the understanding of uranium’s aqueous chemistry. As determined from 17O NMR, Ca2+ and especially La3+ cause strong O=U=O polarization which opens up new ways for uranyl(VI)-oxygen activation and functionalization.

Keywords: uranium; uranyl; U(VI); citric acid; NMR; DFT; spectroscopy; molecular structure

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Permalink: https://www.hzdr.de/publications/Publ-31389
Publ.-Id: 31389


Tumor markers as an entry for SARS-CoV-2 infection?

Pu, X.; Dubrovska, A.

Coronavirus disease 2019 (COVID-19), the highly contagious illness caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread across the globe, becoming one of the most challenging public health crisis of our times. SARS-CoV-2 can cause severe disease associated with multiple organ damage. Cancer patients have a higher risk of SARS-CoV-2 infection and death. While the virus uses angiotensin-converting enzyme 2 (ACE2) as the primary entry receptor, the recent experimental and clinical findings suggest that some tumor markers, including CD147 (Basigin), can provide a new entry for SARS-CoV-2 infection through binding to the viral spike (S) protein. In the absence of specific viral drugs, blocking of CD147 might be a way to prevent virus invasion. Identifying other target proteins is of high importance as targeting the alternative receptors for SARS-CoV-2 might open up a promising avenue for the treatment of COVID-19 patients, including those who have cancer.

Keywords: SARS-CoV-2; COVID-19; CD147; Basigin; Emmprin; spike protein

Permalink: https://www.hzdr.de/publications/Publ-31388
Publ.-Id: 31388


Metal dissociation from humic colloids: Kinetics with time-dependent rate constants

Lippold, H.; Zedek, L.

The mobility of contaminant metals in aqueous subsurface environments is largely controlled by their interaction with humic substances as colloidal constituents of Dissolved Organic Matter. Transport models for predicting carrier-bound migration are based on a competitive partitioning process between solid surface and colloids. However, it has been observed that dissociation of multivalent metals from humic complexes is a slow kinetic process, which is even more impeded with increasing time of contact. Based on findings obtained in isotope exchange experiments, the convoluted time dependence of dissociation was fully described by a complex two-site approach, integrating rate “constants” that are in turn time-dependent. Thus, this study presents the treatment of a particular phenomenon: kinetics within kinetics. The analysis showed that the inertization process does not lead to irreversible binding. Consequently, thermodynamic concepts using equilibrium constants remain applicable in speciation and transport modeling if long time frames are appropriate.

Keywords: Colloids; Desorption; Humic complexes; Kinetic model; Metal binding; Natural organic matter

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Permalink: https://www.hzdr.de/publications/Publ-31387
Publ.-Id: 31387


Quantitative isotopic fingerprinting of thallium associated with potentially toxic elements (PTEs) in fluvial sediment cores with multiple anthropogenic sources

Liu, J.; Zhou, Y.; She, J.; Tsang, D. C. W.; Lippold, H.; Wang, J.; Jiang, Y.; Wei, X.; Yuan, W.; Luo, X.; Zhai, S.; Song, L.

Thallium (Tl) is a dispersed trace metal showing remarkable toxicity. Various anthropogenic activities may generate Tl contamination in river sediments, posing tremendous risks to aquatic life and human health. This paper aimed to provide insight into the vertical distribution, risk assessment and source tracing of Tl and other potentially toxic elements (PTEs) (lead, cadmium, zinc and copper) in three representative sediment cores from a riverine catchment impacted by multiple anthropogenic activities (such as steel-making and Pb-Zn smelting). The results showed high accumulations of Tl combined with associated PTEs in the depth profiles. Calculations according to three risk assessment methods by enrichment factor (EF), geoaccumulation index (Igeo) and the potential ecological risk index (PERI) all indicated a significant contamination by Tl in all the sediments. Furthermore, lead isotopes were analyzed to fingerprint the contamination sources and to calculate their quantitative contributions to the sediments using the IsoSource software. The results indicated that a steel-making plant was the most important contamination source (~56%), followed by a Pb-Zn smelter (~20%). The natural parental bedrock was found to contribute ~24%. The findings highlight the importance of including multiple anthropogenic sources for quantitative fingerprinting of Tl and related metals by the lead isotopic approach in complicated environmental systems.

Keywords: Thallium contamination; Spatial distribution; Pollution risk assessment; Multiple end-members; Isotopic tracing

Permalink: https://www.hzdr.de/publications/Publ-31386
Publ.-Id: 31386


Lattice dynamics and ultrafast energy flow between electrons, spins, and phonons in a 3d ferromagnet

Zahn, D.; Jakobs, F.; William Windsor, Y.; Seiler, H.; Vasileiadis, T.; Butcher, T. A.; Qi, Y.; Engel, D.; Atxitia, U.; Vorberger, J.; Ernstorfer, R.

The ultrafast dynamics of magnetic order in a ferromagnet are governed by the interplay between electronic, magnetic and lattice degrees of freedom. In order to obtain a microscopic understanding of ultrafast demagnetization, information on the response of all three subsystems is required. A consistent description of demagnetization and microscopic energy flow, however, is still missing. Here, we combine a femtosecond electron diffraction study of the ultrafast lattice response of nickel to laser excitation with ab initio calculations of the electron-phonon interaction and energy conserving atomistic spin dynamics simulations. Our model is in agreement with the observed lattice dynamics and previously reported electron and magnetization dynamics. Our approach reveals that the spin system is the dominating heat sink in the initial few hundreds of femtoseconds and implies a transient non-thermal state of the spins. Our results provide a clear picture of the microscopic energy flow between electronic, magnetic and lattice degrees of freedom on ultrafast timescales and constitute a foundation for theoretical descriptions of demagnetization that are consistent with the dynamics of all three subsystems.

Keywords: magnetization; relaxation; laser; phonon; spin; DFT; electron beam; femtosecond

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Permalink: https://www.hzdr.de/publications/Publ-31385
Publ.-Id: 31385


gmGeostats: an R package for Geostatistics for Compositional Analysis with R

Tolosana Delgado, R.; van den Boogaart, K. G.; Mueller, U.; Talebi, H.

The package provides support for geostatistical analysis of multivariate data, in particular data with restrictions, e.g. positive amounts data, compositional data, distributional data, microstructural data, as occur in Geometallurgy. It includes descriptive analysis and modelling for such data, both from a two-point Gaussian perspective and multipoint perspective, in an unified integrated approach.

Keywords: R programming; Geostatistics; Compositional data analysis; 3D modelling; Uncertainty

  • Software in external data repository
    Publication year 2020
    Programming language: R
    System requirements: multiplatform
    License: CC BY-SA 4.0 | GPL (≥ 2)
    Hosted on CRAN: Link to location

Permalink: https://www.hzdr.de/publications/Publ-31384
Publ.-Id: 31384


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

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

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

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Permalink: https://www.hzdr.de/publications/Publ-31383
Publ.-Id: 31383


All-THz pump-probe spectroscopy of the intersubband AC-Stark effect in a wide GaAs quantum well

Schmidt, J.; Winnerl, S.; Dimakis, E.; Hübner, R.; Schneider, H.; Helm, M.

We report the observation of the intersubband AC-Stark effect in a single wide GaAs/AlGaAs quantum well. In a three-level configuration, the n = 2 to n = 3 intersubband transition is resonantly pumped at 3:5 THz using a free-electron laser. The induced spectral changes are probed using THz time-domain spectroscopy with a broadband pulse extending up to 4 THz. We observe an Autler Townes splitting at the 1 -> 2 intersubband transition as well as an indication of a Mollow triplet at the 2 -> 3 transition, both evidencing the dressed states. For longer delay times, a relaxation of the hot-electron system with a time constant of around 420 ps is measured.

Keywords: AC Stark effect; Autler Townes splitting; high-field physics; intersubband transitions

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Publ.-Id: 31382


Modelling of late side effects following cranial proton beam therapy

Dutz, A.; Lühr, A.; Agolli, L.; Bütof, R.; Valentini, C.; Troost, E. G. C.; Baumann, M.; Vermeren, X.; Geismar, D.; Lamba, N.; Lebow, E.; Bussière, M.; Daly, J.; Bussière, M.; Krause, M.; Timmermann, B.; Shih, H.; Löck, S.

Background
The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies that can be based on normal tissue complication probability (NTCP) models. We developed and externally validated NTCP models for common late side-effects following PBT in brain tumour patients to optimise patients’ quality of life.
Methods
Cohorts from three PBT centres (216 patients) were investigated for several physician-rated endpoints at 12 and 24 months after PBT: alopecia, dry eye syndrome, fatigue, headache, hearing and memory impairment, and optic neuropathy. Dose-volume parameters of associated normal tissues and clinical factors were used for logistic regression modelling in a development cohort. Statistically significant parameters showing high area under the receiver operating characteristic curve (AUC) values in internal cross-validation were externally validated. In addition, analyses of the pooled cohorts and of time-dependent generalised estimating equations including all patient data were performed.
Results
In the validation study, mild alopecia was related to high dose parameters to the skin [e.g. the dose to 2% of the volume (D2%)] at 12 and 24 months after PBT. Mild hearing impairment at 24 months after PBT was associated with the mean dose to the ipsilateral cochlea. Additionally, the pooled analyses revealed dose-response relations between memory impairment and intermediate to high doses to the remaining brain as well as D2% of the hippocampi. Mild fatigue at 24 months after PBT was associated with D2% to the brainstem as well as with concurrent chemotherapy. Moreover, in generalised estimating equations analysis, dry eye syndrome was associated with the mean dose to the ipsilateral lacrimal gland.
Conclusion
We developed and in part validated NTCP models for several common late side-effects following PBT in brain tumour patients. Validation studies are required for further confirmation.

Keywords: NTCP models; brain tumours; late side-effects; proton beam therapy

Permalink: https://www.hzdr.de/publications/Publ-31380
Publ.-Id: 31380


Practice recommendations for lung cancer radiotherapy during the COVID-19 pandemic: An ESTRO-ASTRO consensus statement

Troost, E. G. C.; Nestle, U.; Putora, P.; Bussink, J.

COVID-19 Rapid Letter

Permalink: https://www.hzdr.de/publications/Publ-31378
Publ.-Id: 31378


Nonlinear Electronic Density Response in Warm Dense Matter

Dornheim, T.; Vorberger, J.; Bonitz, M.

Warm dense matter (WDM)—an extreme state with high temperatures and densities that occurse.g. in astrophysical objects—constitutes one of the most active fields in plasma physics and materials science. These conditions can be realized in the lab by shock compression or laser excitation, and the most accurate experimental diagnostics is achieved with lasers and free electron lasers which is theoretically modeled using linear response theory. Here, we present first ab initio path integral Monte Carlo results for the nonlinear density response of correlated electrons in WDM and show that for many situations of experimental relevance nonlinear effects cannot be neglected.

Keywords: Warm dense matter; Nonlinear effects; path integral Monte Carlo

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Publ.-Id: 31377


Imaging and Milling Resolution of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs

Klingner, N.; Hlawacek, G.; Mazarov, P.; Pilz, W.; Meyer, F.; Bischoff, L.

The application of Focused Ion Beams (FIB) has become a well-established and promising technique for patterning and prototyping on the nm-scale in research and development. Light ions in the range of m = 1 … 28 u (hydrogen to silicon) are of increasing interest due to the available high beam resolution in the nm range and their special chemical and physical behavior in the substrate. In this work helium and neon ion beams from a Helium Ion Microscope (HIM) are compared with ion beams like beryllium, lithium, boron, carbon and silicon obtained from a mass separated FIB using Liquid Metal Alloy Ion Sources (LMAIS) with respect to their imaging and milling resolution.

Keywords: Focused Ion Beam; Helium Ion Microscope; Gas Field Ion Source; Liquid Metal Alloy Ion Sources; resolution

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Permalink: https://www.hzdr.de/publications/Publ-31376
Publ.-Id: 31376


Mapping the Future of Particle Radiobiology in Europe: The INSPIRE Project

Henthorn, N.; Sokol, O.; Durante, M.; de Marzi, L.; Pouzoulet, F.; Miszczyk, J.; Olko, P.; Brandenburg, S.; van Goethem, M.-J.; Barazzuol, L.; Tambas, M.; Langendijk, J. A.; Davídková, M.; Vondráček, V.; Bodenstein, E.; Pawelke, J.; Lomax, A. J.; Weber, D. C.; Dasu, A.; Stenerlöw, B.; Poulsen, P. R.; Sørensen, B. S.; Grau, C.; Sitarz, M. K.; Heuskin, A.-C.; Lucas, S.; Warmenhoven, J. W.; Merchant, M. J.; Mackay, R. I.; Kirkby, K. J.

Particle therapy is a growing cancer treatment modality worldwide. However, there still remains a number of unanswered
questions considering differences in the biological response between particles and photons. These questions, and probing of biological mechanisms in general, necessitate experimental investigation. The “Infrastructure in Proton International Research” (INSPIRE) project was created to provide an infrastructure for European research, unify research efforts on the topic of proton and ion therapy across Europe, and to facilitate the sharing of information and resources. This work highlights the radiobiological capabilities of the INSPIRE partners, providing details of physics (available particle types and energies), biology (sample preparation and post-irradiation analysis), and researcher access (the process of applying for beam time). The collection of information reported here is designed to provide researchers both in Europe and worldwide with the tools required to select the optimal center for their research needs. We also highlight areas of redundancy in capabilities and suggest areas for future investment.

Keywords: Proton theraphy; Radiotherapy; Radiobiology; Beamline; Irradiation

Permalink: https://www.hzdr.de/publications/Publ-31375
Publ.-Id: 31375


A computational method to simulate mono- and poly-disperse two-dimensional foams flowing in obstructed channel

Carl Lavoratti, T.; Heitkam, S.; Hampel, U.; Lecrivain, G.

A modified phase-field model is presented to numerically study the dynamics of flowing foam in an obstructed channel. The bubbles are described as smooth deformable fields interacting with one another through a repulsive potential. A strength of the model lies in its ability to simulate foams with wide range of gas fraction. The foam motion, composed of about hundred two-dimensional gas elements, was analyzed for gas fractions ranging from 0.4 to 0.99, that is below and beyond the jamming transition. Simulations are preformed near the quasi-static limit, indicating that the bubble rearrangement in the obstructed channel is primarily driven by the soft collisions and not by the hydrodynamics. Foam compression and relaxation upstream and downstream of the obstacle are reproduced and qualitatively match previous experimental and numerical observations. Striking dynamics, such as bubbles being squeezed by their neighbors in negative flow direction, are also revealed at intermediate gas fractions.

Keywords: Flowing foam; Computational method; Phase-field method; Obstructed channel

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Permalink: https://www.hzdr.de/publications/Publ-31374
Publ.-Id: 31374


Benchmark hyperspectral field and laboratory data against X-ray diffraction (XRD), Portable X-ray fluorescence (pXRF) and Scanning Electron Microscopy with Mineral Liberation Analysis (SEM-MLA) data.

de La Rosa Ferna; Tolosana Delgado, R.; Gloaguen, R.

A benchmarking databank based on different spectral, multiscale, multisensor exploration technologies was created. The benchmarking is composed of 63 rock samples from drill cores from a polymetallic (Cu-Zn-Pb) massive sulphide deposit in the Iberian Pyrite Belt. The samples had been analyzed by portable XRF, point hyperspectral spectrometer, portable FTIR, VNIR-SWIR imaging hyperspectral sensor and a LWIR imaging thermal hyperspectral sensor.

The mineralogical information from the boreholes will be complemented with mineral chemistry extracted from the spectral features of the alteration minerals that display chemical variations. The chemical variations in minerals generate shifts on the position of the metal-OH vibrational absorptions. This systematic variation can be recorded using the SWIR wavelength region of hyperspectral data. The shifts sometimes occur systematically with respect to ore deposits and hence mineral chemical information extracted from hyperspectral surveys can be used for mineral exploration. The mineral chemistry of the samples will be validated using scanning electron microscopy data integrated with the mineral liberation analysis (SEM-MLA).

In order to apply this type of research techniques aiming at a 3D model of the alteration areas of the entire deposit based on the hyperspectral data, it is essential to have the availability of drill cores along the whole extension of the mineral deposit. Consequently, the research was focused in a study area in the Southern Spain, the Elvira deposit of the MATSA–VALORIZA mining company, where 7 km of drill core were scanned with the hyperspectral sensors.

New exploration technologies (NEXT) is a project that has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement nº 776804.

Keywords: Benchmarking; Hyperspectral; Drill core scanner; pFTIR; PXRF; VNIR - SWIR - LWIR

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Publ.-Id: 31373


Advanced Sandwich Composite Cores for Patient Support in Advanced Clinical Imaging and Oncology Treatment

Morris, R. H.; Geraldi, N. R.; Pike, L. C.; Pawelke, J.; Hoffmann, A. L.; Doy, N.; Stafford, J. L.; Spicer, A.; Newton, M. I.

Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as PET-CT and PET-MRI when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper we present a range of materials which are suitable for such purposes and evaluate the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We find that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins.

Keywords: Composite; Core; Clinical imaging; PET; CT; MRI; Proton

Permalink: https://www.hzdr.de/publications/Publ-31372
Publ.-Id: 31372


Brain geometry matters in Alzheimer disease progression: a simulation study

Hoore, M.; Kelling, J.; Sayadmanesh, M.; Mitra, T.; Schips, M.; Meyer-Hermann, M.

The Amyloid cascade hypothesis (ACH) for Alzheimer's disease (AD) is modeled over the whole brain tissue with a set of partial differential equations. Our results show that the amyloid plaque formation is critically dependent on the secretion rate of amyloid β(Aβ), which is proportional to the product of neural density and neural activity. Neural atrophy is similarly related to the secretion rate of Aβ. Due to a heterogeneous distribution of neural density and brain activity throughout the brain, amyloid plaque formation and neural death occurs heterogeneously in the brain. The geometry of the brain and microglia migration in the parenchyma bring more complexity into the system and result in a diverse amyloidosis and dementia pattern of different brain regions. Although the pattern of amyloidosis in the brain cortex from in-silico results is similar to experimental autopsy findings, they mismatch at the central regions of the brain, suggesting that ACH is not able to explain the whole course of AD without considering other factors, such as tau-protein aggregation or neuroinflammation.

Keywords: Neurdegenerative disease; Alzheimer's disease; Amyloid cascade hypothesis; mult-phase model

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Publ.-Id: 31371


Multiscale Tomographic Analysis for Micron-Sized Particulate Samples

Ditscherlein, R.; Furat, O.; de Langlard, M.; Martins De Souza E. Silva, J.; Sygusch, J.; Rudolph, M.; Leißner, T.; Schmidt, V.; Peuker, U. A.

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4–5.8 μm diameter) with glass fibers (diameter 10 μm, length 18–660 μm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

Keywords: multidimensional particle characterization; multiscale X-ray tomography; parametric copula; statistical image analysis

Permalink: https://www.hzdr.de/publications/Publ-31370
Publ.-Id: 31370


Yu-Shiba-Rusinov bands in ferromagnetic superconducting diamond

Zhang, G.; Samuely, T.; Iwahara, N.; Kačmarčík, J.; Wang, C.; May, P. W.; Jochum, J. K.; Onufriienko, O.; Szabó, P.; Zhou, S.; Samuely, P.; Moshchalkov, V. V.; Chibotaru, L. F.; Rubahn, H.-G.

The combination of different exotic properties in materials paves the way for the emergence of their new potential applications. An example is the recently found coexistence of the mutually antagonistic ferromagnetism and superconductivity in hydrogenated boron-doped diamond, which promises to be an attractive system with which to explore unconventional physics. Here, we show the emergence of Yu-Shiba-Rusinov (YSR) bands with a spatial extent of tens of nanometers in ferromagnetic superconducting diamond using scanning tunneling spectroscopy. We demonstrate theoretically how a two-dimensional (2D) spin lattice at the surface of a three-dimensional (3D) superconductor gives rise to the YSR bands and how their density-of-states profile correlates with the spin lattice structure. The established strategy to realize new forms of the coexistence of ferromagnetism and superconductivity opens a way to engineer the unusual electronic states and also to design better-performing superconducting devices.

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Permalink: https://www.hzdr.de/publications/Publ-31369
Publ.-Id: 31369


Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Ajayakumar, M.; Fu, Y.; Liu, F.; Komber, H.; Tkachova, V.; Xu, C.; Zhou, S.; Popov, A.; Liu, J.; Feng, X.

Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

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Publ.-Id: 31366


Revisiting the complexation of Cm(III) with aqueous phosphates: what can we learn from the complex structures using luminescence spectroscopy and ab initio simulations?

Huittinen, N. M.; Jessat, I.; Réal, F.; Vallet, V.; Starke, S.; Eibl, M.; Jordan, N.

The coordination chemistry of Cm(III) with aqueous phosphates was investigated by means of laser–induced luminescence spectroscopy and ab initio simulations.
For the first time, in addition to the presence of Cm(H2PO4)2+, the formation of Cm(H2PO4)2+ was unambiguously established from the luminescence spectroscopic data collected at various H+ concentrations (–log10[H+] = 2.52, 3.44, and 3.65), ionic strengths (0.5 – 3.0 mol∙L−1 NaClO4), and temperatures (25 – 90 °C). Complexation constants for both species were derived and extrapolated to standard conditions using the specific ion interaction theory.
The molal enthalpy ∆_R H_m^0 and molal entropy ∆_R S_m^0 of both complexation reactions were derived using the integrated van’t Hoff equation, and indicated an endothermic and entropy driven complexation. For the Cm(H2PO4)2+ complex, a more satisfactory description could be obtained when including the molal heat capacity term.
While monodentate binding of the H2PO4– ligand(s) to the central curium ion was found to be the most stable configuration for both complexes in our ab initio simulations and luminescence lifetime analyses, a different temperature–dependent coordination to hydration water molecules could be deduced from the electronic structure of the Cm(III)–phosphate complexes. More precisely, where the Cm(H2PO4)2+ complex could be shown to retain an overall coordination number of 9 over the entire investigated temperature range, a coordination change from 9 to 8 was established for the Cm(H2PO4)2+ species with increasing temperature.

Keywords: Cm(III); phosphate; complexation; luminescence; temperature; ab initio

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Publ.-Id: 31365


HIF2α supports pro-metastatic behavior in pheochromocytomas/paragangliomas

Bechmann, N.; Moskopp, M. L.; Ullrich, M.; Calsina, B.; Wallace, P. W.; Richter, S.; Friedemann, M.; Langton, K.; Fliedner, S. M. J.; Timmers, H. J. L. M.; Nölting, S.; Beuschlein, F.; Fassnacht, M.; Preijbisz, A.; Pacak, K.; Ghayee, H. K.; Bornstein, S. R.; Dieterich, P.; Pietzsch, J.; Wielockx, B.; Robledo, M.; Qin, N.; Eisenhofer, G.

Mutations that drive the stabilization of hypoxia inducible factor 2α (HIF2α) and downstream pseudohypoxic signaling are known to predispose to the development of pheochromocytomas and paragangliomas (PPGLs). However, any role of HIF2α in predisposition to metastatic disease remains unclear. To assess such a role we combined gene-manipulations in pheochromocytoma cell lines with retrospective analyses of patient data and gene expression profiling in tumor specimens. Among 425 patients with PPGLs identified with mutations in tumor-susceptibility genes, those with tumors due to activation of pseudohypoxic pathways had a higher frequency of metastatic disease than those with tumors due to activation of kinase- signaling pathways, even without inclusion of patients with mutations in SDHB (18.6% vs. 4.3% in, p<0.0001). Three out of nine (33%) of patients with gain-of-function mutations in HIF2α had metastatic disease. In cell line studies, elevated expression of HIF2α enhanced cell proliferation and led to increased migration and invasion capacity. Moreover, HIF2α expression in HIF2α-deficient cells resulted in increased cell motility, diffuse cluster formation and emergence of pseudopodia indicating changes in cell adhesion and cytoskeletal remodeling. In a mouse liver metastasis model, HIF2α enhanced the metastatic load. Transcriptomics data revealed alterations in focal adhesion and extracellular matrix-receptor interactions in HIF2α-mutated PPGLs. Our translational findings demonstrate that HIF2α supports pro-metastatic behavior in PPGLs, though other factors remain critical for subsequent transition to metastasis. We identified LAMB1 and COL4A2 as new potential therapeutic targets for HIF2α-driven PPGLs. Identified HIF2α downstream targets might open a new therapeutic window for aggressive HIF2α-expressing tumors.

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Publ.-Id: 31364


Dynamics of Bubble Formation at Micro-orifices under Constant Gas Flow Conditions

Mohseni, E.; Jose Kalayathine, J.; Reinecke, S.; Hampel, U.

Fine gas dispersion into a liquid is requested in a number of industrial applications. One way to achieve fine gas dispersion is to downsize the openings from which gas bubbles are generated. Accordingly, we have investigated the dynamics of bubble formation from submerged orifices ranging from 0.04 to 0.8 mm at a comprehensive range of gas flow rates for a system of air and deionized water. In this range of orifice size, we observe a different mechanism of bubble formation compared with millimeter-range orifices. We discuss the observations on the basis of temporal change of the bubble shape, bubble base expansion, and detachment criteria. At submillimeter orifices, the mechanism of bubble formation is highly influenced by the capillary pressure and the gas kinetic energy. The latter results in congregation of small bubbles in the vicinity of the orifice, even at very small gas flow rates. Moreover, we studied the evolution of individual forces applied to the surface of bubbles during their formation. We have found that the formation of bubbles at submillimeter orifices cannot be described with a quasi-static force balance. Finally, we present a bubbling regime map using relevant dimensionless numbers.

Keywords: Bubble Formation; Submillimeter Orifices; Bubbling Regime; Bubbling Dynamics; Stainless Steel Orifice

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Permalink: https://www.hzdr.de/publications/Publ-31363
Publ.-Id: 31363


Sorption of Europium on Diatom Biosilica as Model of a “Green” Sorbent for f-Elements

Kammerlander, K. K. K.; Köhler, L.; Huittinen, N. M.; Bok, F.; Steudtner, R.; Oschatz, C.; Vogel, M.; Stumpf, T.; Brunner, E.

Removing f-elements from anthropogenically contaminated sites is a challenging, but ecologically important task. Some of these elements are not only radioactive, but also chemically toxic and can spread through various pathways in the environment. The present work investigates f-element sorption on biogenic silica, which may be a promising “green” material for remediation. Commercially available diatomaceous earth (DE) and the cleaned cell walls of the diatom species Stephanopyxis turris (S.t.) and Thalassiosira pseudonana (T.p.) are compared with artificial mesocellular foam (MCF) as porous silica reference material. Trivalent europium was chosen as model sorptive for chemically similar trivalent actinides. Accordingly, Eu(III) in concentrations of 10-3 M and 10-5 M was sorbed on the four silica materials at varying pH values. The zeta potentials of the implemented sorbents under the same conditions were determined. In addition, the sorption reaction and the aqueous speciation of Eu(III) in the (bio)silica suspensions were modeled using the Diffuse Double Layer (DDL) model. With time-resolved laser-induced fluorescence spectroscopy (TRLFS), two different uptake mechanisms can be discerned, surface adsorption and incorporation/precipitation.

Keywords: biosilica; diatoms; europium; fluorescence; sorption

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Permalink: https://www.hzdr.de/publications/Publ-31362
Publ.-Id: 31362


Magnetocaloric effect in GdNi2 for cryogenic gas liquefaction studied in magnetic fields up to 50 T

Taskaev, S.; Khovaylo, V.; Skokov, K.; Liu, W.; Bykov, E.; Ulyanov, M.; Bataev, D.; Basharova, A.; Kononova, M.; Plakhotskiy, D.; Bogush, M.; Gottschall, T.; Gutfleisch, O.

Natural gases have played a significant role in different sectors of the global economy. Recent analyses have shown that the world’s gas consumption doubled over the last three decades; further growth of the gas consumption is predicted, rising to be 23%–28% of the total primary energy demand by 2030. Therefore, liquefaction of natural gases rapidly gains global importance. In this context, magnetic refrigeration emerges as a modern energy-saving technique, which is an alternative to the traditional gas-compression refrigeration. This paper is devoted to the study of the magnetocaloric effect in magnetic fields up to 10 T on a representative of the Laves phase alloys, GdNi2, which is considered as a perspective material for liquefaction of natural gases. For a magnetic field change of 10 T, the magnetic entropy change ΔSm≈−17 J/kg K and the adiabatic temperature change ΔTad ≈ 6.8 K was attained around Curie temperature TC = 70 K. The maximal value of the adiabatic temperature change measured directly in pulsed magnetic fields up to 50 T is ΔTad ≈ 15 K.

Permalink: https://www.hzdr.de/publications/Publ-31361
Publ.-Id: 31361


Effect of uniaxial stress on the electronic band structure of NbP

Schindler, C.; Noky, J.; Schmidt, M.; Felser, C.; Wosnitza, J.; Gooth, J.

The Weyl semimetal NbP exhibits a very small Fermi surface consisting of two electron and two hole pockets, whose fourfold degeneracy in k space is tied to the rotational symmetry of the underlying tetragonal crystal lattice. By applying uniaxial stress, the crystal symmetry can be reduced, which successively leads to a degeneracy lifting of the Fermi-surface pockets. This is reflected by a splitting of the Shubnikov–de Haas frequencies when the magnetic field is aligned along the c axis of the tetragonal lattice. In this study, we present the measurement of Shubnikov–de Haas oscillations of single-crystalline NbP samples under uniaxial tension, combined with state-of-the-art calculations of the electronic band structure. Our results show qualitative agreement between calculated and experimentally determined Shubnikov–de Haas frequencies, demonstrating the robustness of the band-structure calculations upon introducing strain. Furthermore, we predict a significant shift of the Weyl points with increasing uniaxial tension, allowing for an effective tuning to the Fermi level at only 0.8% of strain along the a axis.

Permalink: https://www.hzdr.de/publications/Publ-31360
Publ.-Id: 31360


Impact of the microbial origin and active microenvironment on the shape of biogenic elemental selenium nanomaterials

Fischer, S.; Jain, R.; Krause, T.; Jain, P.; Tsushima, S.; Shevchenko, A.; Hübner, R.; Jordan, N.

The role of the microbial origin and environment of the discharged nanomaterials in their shape change was investigated. Here, we show that the biogenic elemental selenium nanospheres (BioSe-Nanospheres) produced under mesophilic conditions (30 °C) by Escherichia coli K-12 remain spherically when exposed to heating (55 °C for 7 days), whereas those obtained by anaerobic granular sludge transform to biogenic elemental selenium nanorods (BioSe-Nanorods). The larger quantity of proteins present in the corona of the BioSe-Nanospheres produced by E. coli K-12 are responsible for their shape stability. However, the protein corona of BioSe-Nanospheres produced by E. coli K-12 was degraded by extracellular peptidases secreted upon co-incubation with Bacillus safensis JG-B5T bacteria, which led to their transformation to BioSe-Nanorods. This study consequently demonstrates that the shape of biogenic nanomaterials depends both on their microbial origin and microbial surrounding, which increases the complexity in determining their risk assessment.

Permalink: https://www.hzdr.de/publications/Publ-31359
Publ.-Id: 31359


Evolution of a hydrothermal ore-forming system recorded by sulphide mineral chemistry: A case study from the Plaka Pb-Zn-Ag Deposit, Lavrion, Greece

Frenzel, M.; Voudouris, P.; Cook, N. J.; Ciobanu, C. L.; Gilbert, S.; Wade, B. P.

Laser ablation inductively-coupled plasma mass spectrometry and electron probe microanalysis were used to investigate the trace-element contents of sphalerite, chalcopyrite and pyrite from the Plaka Pb-Zn-Ag deposit, Lavrion, Greece. Using petrographic observations, the analytical results could be linked to the temporal evolution of the Plaka ore-forming system.
Sphalerite chemistry (Ga, Ge, In, Mn and Fe content) reliably records the temperature evolution of the system, with formation temperatures estimated by sphalerite geothermometry reproducing microthermometric results from previous fluid inclusion studies. Chalcopyrite chemistry also shows systematic variations with formation temperature, particularly for Cd, Co, Ge, In, Sn and Zn concentrations. Pyrite was only found in association with early high-temperature mineralisation, and no clear temperature trends could therefore be identified. We note, however, that its Se content is consistent with formation at the temperatures estimated from sphalerite chemistry.
In addition to these observations, comparing the results for the three investigated minerals allowed us to identify different classes of trace elements according to their temporal and spatial distribution in the ore-forming system. For instance, In concentrations appear to be highest in early high-temperature sulphide assemblages from the southern part of the deposit, while Ge concentrations are highest in late low-temperature assemblages from any part of the deposit.
These results demonstrate that the detailed study of multiple minerals in a single ore-forming system, well documented in terms of geology, paragenesis and conditions of formation, still has considerable untapped potential to provide important new insights into ore-forming processes.

Keywords: Sphalerite; Chalcopyrite; Pyrite; Trace elements; LA-ICP-MS; Lavrion

Permalink: https://www.hzdr.de/publications/Publ-31358
Publ.-Id: 31358


Adding CUDA® Support to Cling: JIT Compile to GPUs

Ehrig, S.; Hübl, A.; Naumann, A.; Vassilev, V.

Jupyter Notebooks are omnipresent in the modern scientist's and engineer's toolbox just as CUDA C++ is in accelerated computing. We present the first implementation of a CUDA C++ enabled read-eval-print-loop (REPL) that allows to interactively "script" the popular CUDA C++ runtime syntax in Notebooks. With our novel implementation, based on LLVM, Clang and CERN's C++ interpreter Cling, the modern CUDA C++ developer can work as interactively and productively as (I)Python developers while keeping all the benefits of the vast C++ computing and library ecosystem coupled with first-class performance.

Keywords: Cling; CUDA; Jupyter Notebook; interactive C++; LLVM; interactive simulation; rapid prototyping

  • Open Access Logo Lecture (Conference) (Online presentation)
    2020 Virtual LLVM Developers' Meeting, 06.-08.10.2020, Virtuell, USA

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Permalink: https://www.hzdr.de/publications/Publ-31357
Publ.-Id: 31357


Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation

Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castin, N.; Malerba, L.

Origin-files, data for figure 3 and figure 4 of publication in J. Nucl. Mater.

Keywords: Neutron irradiation; FeCr alloys and steels

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Permalink: https://www.hzdr.de/publications/Publ-31356
Publ.-Id: 31356


Evaluation of Recyclability of a WEEE Slag by Means of Integrative X-Ray Computer Tomography and SEM-Based Image Analysis

Buchmann, M.; Borowski, N.; Leißner, T.; Heine, T.; Reuter, M.; Friedrich, B.; Peuker, U. A.

Waste of electrical and electronic equipment (WEEE) is one of the fastest growing waste streams globally. Therefore, recycling of the valuable metals of this stream plays a vital role in establishing a circular economy. The smelting process of WEEE leads to significant amounts of valuable metals and rare earth elements (REEs) trapped in the slag phase. The effective manipulation of this phase transfer process necessitates detailed understanding and effective treatment to minimize these contents. Furthermore, an adequate process control to bring these metal contents into structures that make recycling economically applicable is required. Within the present study, a typical slag from a WEEE melting process is analyzed in detail. Therefore, the material is investigated with the help of X-ray computed tomography (XCT) and scanning electron microscopy (SEM)-based mineralogical analysis (MLA) to understand the typical structures and its implications for recycling. The influencing factors are discussed, and further processing opportunities are illustrated.

Keywords: waste of electrical and electronic equipment; X-ray computed tomography; mineral liberation analysis

Permalink: https://www.hzdr.de/publications/Publ-31355
Publ.-Id: 31355


Spectral X-ray Computed Micro Tomography: 3-dimensional chemical imaging

Sittner, J.; Da Assuncao Godinho, J. R.; Renno, A.; Cnudde, V.; Boone, M.; de Schryver, T.; van Loo, D.; Merkulova, M.; Roine, A.; Liipo, J.

We present a new approach to 3-dimensional chemical imaging based on computed tomography (CT), which allows a reconstruction of the internal elemental chemistry. The method uses a conventional laboratory based CT scanner combined with a semiconductor detector (CdTe). Based on the X-ray absorption spectrum, elements in a sample can be distinguished by their K-edge energy, which is specific. Different experiments have been preformed to test the performance of the system i.e. single pure element particle measurements, element differentiation in mixtures, and mineral differentiation in a gold ore sample. The results show that the method is able to distinguish elements in the samples with K-edges in the range of 20 to 160 keV, which corresponds to an elemental range from Ag to U. Furthermore, the spectral information allows a distinction between materials, which show no variation in contrast in the reconstructed CT image.

Keywords: X-ray computed tomography; Spectral X-ray tomography; Photon counting detector; 3D imaging

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Permalink: https://www.hzdr.de/publications/Publ-31354
Publ.-Id: 31354


CFD Modeling and Experimental Validation of Top-Submerged-Lance Gas Injection in Liquid Metal

Reuter, M. A.; Akashi, M.; Kriebitzsch, S.; Meyer, B.; Obiso, D.; Eckert, S.; Richter, A.

In the present work, the dynamics of a downward gas injection into a liquid metal bath is studied using a numerical modeling approach, and validated with experimental data. As in a top-submerged-lance (TSL) smelter, gas is injected through the lance into the melt. By this means, the properties of the liquid are closer to the actual industrial process than the typically used water/glycerol–air/helium systems. The experimental activity was carried out in a quasi-2D vessel (144 x 144 x 12 mm3) filled with GaInSn, a metal alloy with eutectic at room temperature. Ar was used as the inert gas. The structure and behavior of the gas phase were visualized and quantitatively analyzed by X-ray radiography and high-speed imaging. Computational Fluid Dynamics (CFD) was applied to simulate the multiphase flow in the vessel and the Volume Of Fluid (VOF) model chosen to track the interface using a geometric reconstruction of the interface. Three different vertical lance positions were investigated, applying a gas flow rate of Qgas = 6850 cm³/min: The CFD model is able to predict the bubble detachment frequency, the average void fraction distributions, and the bubble size and hydrodynamic behavior, demonstrating its applicability to simulate such complex multiphase systems. The use of numerical models also provides a deep insight into fluid dynamics to study particular phenomena such as bubble break-up and free surface oscillations.

Keywords: top-submerged-lance (TSL),; X-ray,; Computational Fluid Dynamics (CFD),; Volume Of Fluid (VOF),

Permalink: https://www.hzdr.de/publications/Publ-31353
Publ.-Id: 31353


Engineering telecom single-photon emitters in silicon for scalable quantum photonics

Hollenbach, M.; Berencen, Y.; Kentsch, U.; Helm, M.; Astakhov, G.

We create and isolate single-photon emitters with a high brightness approaching 10⁵ counts per second in commercial silicon-on-insulator (SOI) wafers. The emission occurs in the infrared spectral range with a spectrally narrow zero phonon line in the telecom O-band and shows a high photostability even after days of continuous operation. The origin of the emitters is attributed to one of the carbon-related color centers in silicon, the so-called G center, allowing purification with the ¹²C and ²⁸Si isotopes. Furthermore, we envision a concept of a highly-coherent scalable quantum photonic platform, where single-photon sources, waveguides and detectors are integrated on the same SOI chip. Our results provide a route towards the implementation of quantum processors, repeaters and sensors compatible with the present-day silicon technology.

Keywords: Signe photon source; telecommunication window; silicon photonics; quantum communication; color centers

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Permalink: https://www.hzdr.de/publications/Publ-31352
Publ.-Id: 31352


Investigation of inter-fraction target motion variations in the context of pencil beam scanned proton therapy in non-small cell lung cancer patients

Den Otter, L. A.; Anakotta, R. M.; Weessies, M.; Roos, C. T. G.; Sijtsema, N. M.; Muijs, C. T.; Dieters, M.; Wijsman, R.; Troost, E. G. C.; Richter, C.; Meijers, A.; Langendijk, J. A.; Both, S.; Knopf, A.-C.

Purpose: For locally advanced-stage non-small cell lung cancer (NSCLC), inter-fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS-PT) treatments of NSCLC patients during free breathing. Methods: Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases. Results: The median observed centroid motion was 3.4 mm (range: 0.2–12.4 mm) with an average variation of 2.2 mm (range: 0.1–8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5-mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0–6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case. Conclusions: Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed. ©2020 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.

Keywords: free breathing; lung cancer; moving target; spencil beam scanning proton therapy; inter-fractional motion monitoring

Permalink: https://www.hzdr.de/publications/Publ-31350
Publ.-Id: 31350


Adenosine/A2B Receptor Signaling Ameliorates the Effects of Aging and Counteracts Obesity

Gnad, T.; Navarro, G.; Lahesmaa, M.; Reverte-Salisa, L.; Copperi, F.; Cordomi, A.; Naumann, J.; Hochh€Auser, A.; Haufs-Brusberg, S.; Wenzel, D.; Suhr, F.; Zenius Jespersen, N.; Scheele, C.; Tsvilovskyy, V.; Brinkmann, C.; Rittweger, J.; Dani, C.; Kranz, M.; Deuther-Conrad, W.; Eltzschig, H. K.; Niemi, T.; Taittonen, M.; Brust, P.; Nuutila, P.; Pardo, L.; Fleischmann, B. K.; Bleuher, M.; Franco, R.; Bloch, W.; Virtanen, K. A.; Pfeifer, A.

The combination of aging populations with the obesity pandemic results in an alarming rise in non-communicable diseases. Here, we show that the enigmatic adenosine A2B receptor (A2B) is abundantly expressed in skeletal muscle (SKM) as well as brown adipose tissue (BAT) and might be targeted to counteract age-related muscle atrophy (sarcopenia) as well as obesity. Mice with SKM-specific deletion of A2B exhibited sarcopenia, diminished muscle strength, and reduced energy expenditure (EE), whereas pharmacological A2B activation counteracted these processes. Adipose tissue-specific ablation of A2B exacerbated age-related processes and reduced BAT EE, whereas A2B stimulation ameliorated obesity. In humans, A2B expression correlated with EE in SKM, BAT activity, and abundance of thermogenic adipocytes in white fat. Moreover, A2B agonist treatment increased EE from human adipocytes, myocytes, and muscle explants. Mechanistically, A2B forms heterodimers required for adenosine signaling. Overall, adenosine/A2B signaling links muscle and BAT and has both anti-aging and anti–obesity potential.

Permalink: https://www.hzdr.de/publications/Publ-31349
Publ.-Id: 31349


Advanced flow profiler for two-phase flow imaging on distillation trays

Vishwakarma, V.; Schleicher, E.; Bieberle, A.; Schubert, M.; Hampel, U.

A profound knowledge of the two-phase cross-flow on large-scale distillation trays is pivotal to their efficient design and operation. For such trays, a novel flow profiler comprising of multiple dual-tip probes for simultaneous local conductivity measurements is proposed in this work. The profiler is applied for a DN800 air/water column simulator equipped with sieve trays. 3D distribution of liquid holdup and tracer-based liquid flow in the two-phase dispersion are assessed in high resolution. Non-uniform holdup is found along the dispersion height. Contrarily, the liquid flow is largely uniform and symmetric with respect to the tray centerline. Prior to measurements, the profiler design, electronic scheme, measurement principle and data processing schemes are described.

Keywords: column tray; two-phase cross-flow; 3D flow imaging; conductivity measurement; liquid holdup; tracer dispersion

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Permalink: https://www.hzdr.de/publications/Publ-31348
Publ.-Id: 31348


Numerical study of the appearance of short-circuits in liquid metal batteries

Benard, S.

The report gives an overview on small-scale interface instabilities in liquid metal batteries.

  • Other
    École normale supérieure Paris-Saclay, 2020

Permalink: https://www.hzdr.de/publications/Publ-31347
Publ.-Id: 31347


Magnetoelectric coupling in a frustrated spinel studied using high-field scanning probe microscopy

Rossi, L.; Brüning, D.; Ueda, H.; Scurschii, I.; Lorenz, T.; Bryant, B.

Below its Neél temperature, the frustrated magnet CdCr2O4 exhibits an antiferromagnetic spin-spiral ground state. Such states can give rise to a sizable magnetoelectric coupling. In this report, we measure the electric polarization induced in single-crystalline CdCr2O4 by large applied magnetic field. Because the detection of a macroscopic polarization is hindered by the structural domains in the tetragonal spin-spiral phase, we have pioneered an alternative method of measuring polarization induced by high magnetic fields, using electrostatic force microscopy. This method enables us to measure polarization from nanoscale areas of the sample surface, as well as imaging how charge inhomogeneities change with magnetic field.

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Publ.-Id: 31346


A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar

Neumann, J.; Brinkmann, H.; Britz, S.; Lützenkirchen, J.; Bok, F.; Stockmann, M.; Brendler, V.; Stumpf, T.; Schmidt, M.

The mobility of heavy metal contaminants and radionuclides in the environment is directly controlled by their interactions with charged mineral surfaces, hence an assessment of their potential toxicity, e.g. in the context of nuclear waste disposal sites, requires understanding of sorption processes on the molecular level. Here, we investigate the sorption of a variety of rare earth elements (REE) and trivalent actinides (Am, Cm) on K-feldspar using batch sorption and column transport experiments, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and a surface complexation model. Initially, a reliable pKa for K-feldspar’s surface deprotonation reaction was determined as 2.5 ± 0.02, in excellent agreement with a measured pHIEP of 2.8. Batch sorption experiments over a broad range of experimental conditions in terms of mineral grain size, pH, [M3+], ionic radius, solid/liquid ratio, ionic strength, and equilibration procedures were carried out to quantify macroscopic immobilization. Similar pH-dependent uptake behavior was found for all investigated trivalent REE and actinides. In parallel, spectroscopic investigations provided insight into surface speciation. Cm TRLFS spectra indicate the formation of three inner-sphere sorption complexes with increasing hydrolysis. Additionally, a ternary K-feldspar/Cm/silicate complex was found for pH > 10, and batch and spectroscopic data at low pH (< 4) point to small amounts of outer sphere sorption complexes. Based on TRLFS data, batch sorption, and titration data, a generic geochemical sorption model was developed, that describes sorption edges for all investigated M3+/K-feldspar systems satisfactorily. The derived stability constants for the binary sorption complexes (logK1-4 = −3.6, −7.7, −11.5, and −17.4, respectively) are in good agreement with previous studies on similar systems, and could successfully be used to reproduce literature data. The stability constants obtained for the surface complexes were included into the database for the Smart Kd-concept, which will further improve the safety assessment of potential repositories for radioactive waste.

Keywords: sorption; trivalent metal ions; actinides; K-feldspar; surface complexation model; TRLFS

Permalink: https://www.hzdr.de/publications/Publ-31345
Publ.-Id: 31345


Vacancy-solute clustering in Fe-Cr alloys after neutron irradiation

Konstantinovic, M. J.; Ulbricht, A.; Brodziansky, T.; Castina, N.; Malerba, L.

Vacancy-solute clustering in neutron irradiated Fe-Cr alloys with various concentrations of Cr and minor solutes (Ni, Si and P) were studied by using
coincidence Doppler broadening spectroscopy and small angle neutron scattering techniques. The results from both experiments, supported by an object kinetic Monte Carlo model, show in a very consistent way the existence and formation of vacancy-CrNiSiP clusters that play detrimental role in irradiation hardening. Similar solute cluster number density of about 30 to 50 x10^16cm-3 and an average diameter of about 1 nm were estimated for all alloys containing minor solutes, irrespectively of the chromium content. In Fe9Cr ferritic and Fe9Cr ferritic/martensitic alloys, with significantly reduced concentration of minor solute elements, the main defects are vacancy clusters, with an average cluster size size of about 10 and 2 vacancies, respectively. Large concentration of alpha'-precipitates was observed in Fe14Cr(NiSiP). However, both vacancy clusters and alpha'-precipitates provide significantly less impact to hardening in comparison to vacancy-CrNiSiP clusters. The fact that vacancy clustering in Fe9Cr ferritic alloy resembles that of pure iron suggests that Cr solutes may play lesser role in irradiation hardening of ferritic alloys and steels than previously believed.

Keywords: Neutron irradiation; FeCr alloys; Steels

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Permalink: https://www.hzdr.de/publications/Publ-31344
Publ.-Id: 31344


Uranium(VI) toxicity in tobacco BY-2 cell suspension culture - a physiological study

Rajabi, F.; Jessat, J.; Garimella, J. N.; Bok, F.; Steudtner, R.; Stumpf, T.; Sachs, S.

For the first time, the physiological and cellular responses of Nicotiana tabacum (BY-2) cells to uranium (U) as an abiotic stressor was studied in a multi analytic approach combining biochemical analysis, thermodynamic modeling and spectroscopic studies. It was focused on the determination of the U threshold toxicity in tobacco BY-2 cells, the influence of U on the homeostasis of micro-macro essential nutrients as well as the effect of Fe starvation on U bioassociation in cultured BY-2 cells. Our findings showed that U interferes with the homeostasis of essential elements. The interaction of U with BY-2 cells showed a time and concentration dependent kinetic. Under Fe deficiency, less U was detected in the cells compared to Fe sufficient conditions. Interestingly, blocking of Ca channels by gadolinium chloride caused a decrease in U concentration in BY-2 cells. Spectroscopic studies evidenced changes in the U speciation in the culture media with increasing exposure time under Fe sufficient and deficient conditions. Thusly, different stress response reactions related to the Fe metabolism are assumed. It is suggested that U toxicity in BY-2 cells is highly dependent on the existence of other micro-macro elements as showed by negative synergistic effects of U and Fe on the viability of cells.

Keywords: Nicotiana tabacum cells; uranium; toxicity; physiology; bioavailability; Fe starvation; speciation; plants; plant cells

Permalink: https://www.hzdr.de/publications/Publ-31343
Publ.-Id: 31343


Band Bending and Valence Band Quantization at Line Defects in MoS2

Murray, C.; van Efferen, C.; Jolie, W.; Fischer, J. A.; Hall, J.; Rosch, A.; Krasheninnikov, A.; Komsa, H.-P.; Michely, T.

The variation of the electronic structure normal to 1D defects in quasi-freestanding MoS2, grown by molecular beam epitaxy, is investigated through high resolution scanning tunneling spectroscopy at 5K. Strong upward bending of valence and conduction bands toward the line defects is found for the 4|4E mirror twin boundary and island edges but not for the 4|4P mirror twin boundary. Quantized energy levels in the valence band are observed wherever upward band bending takes place. Focusing on the common 4|4E mirror twin boundary, density functional theory calculations give an estimate of its charging, which agrees well with electrostatic modeling. We show that the line charge can also be assessed from the filling of the boundary-localized electronic band, whereby we provide a measurement of the theoretically predicted quantized polarization charge at MoS2 mirror twin boundaries. These calculations elucidate the origin of band bending and charging at these 1D defects in MoS2. The 4|4E mirror twin boundary not only impairs charge transport of electrons and holes due to band bending, but holes are additionally subject to a potential barrier, which is inferred from the independence of the quantized energy landscape on either side of the boundary.

Keywords: 2D materials; Line defects; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-31342
Publ.-Id: 31342


Strain robust spin gapless semiconductors/half-metals in transition metal embedded MoSe2 monolayer

Yang, Q.; Kou, L.; Hu, X.; Wang, Y.; Lu, C.; Krasheninnikov, A.; Sun, L.

The realization of spin gapless semiconductor (SGS) and half-metal (HM) behavior in two-dimensional (2D) transition metal (TM) dichalcogenides is highly desirable for their applications in spintronic devices. Here, using density functional theory calculations, we demonstrate that Fe, Co, Ni substitutional impurities can not only induce magnetism in MoSe2 monolayer, but also convert the semiconducting MoSe2 to SGS/HM system. We also study the effects of mechanical strain on the electronic and magnetic properties of the doped monolayer. We show that for all TM impurities we considered, the system exhibits the robust SGS/HM behavior regardless of biaxial strain values. Moreover, it is found that the magnetic properties of TM–MoSe2 can effectively be tuned under biaxial strain by controlling the spin polarization of the 3d orbitals of Fe, Co, Ni atoms. Our findings offer a new route to designing the SGS/HM properties and modulating magnetic characteristics of the TM–MoSe2 system and may also facilitate the implementation of SGS/HM behavior and realization of spintronic devices based on other 2D materials.

Keywords: 2D materials; first-principles simulations; magnetism

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Permalink: https://www.hzdr.de/publications/Publ-31341
Publ.-Id: 31341


Reversible crystalline-to-amorphous phase transformation in monolayer MoS2 under grazing ion irradiation

Valerius, P.; Kretschmer, S.; V. Senkovskiy, B.; Wu, S.; Hall, J.; Herman, A.; Ehlen, N.; Ghorbani Asl, M.; Grüneis, A.; Krasheninnikov, A.; Michely, T.

By combining scanning tunneling microscopy, low-energy electron diffraction, photoluminescence and Raman spectroscopy experiments with molecular dynamics simulations, a comprehensive picture of the structural and electronic response of a monolayer of MoS2 to 500 eV Xe+ irradiation is obtained. The MoS2 layer is epitaxially grown on graphene/Ir(1 1 1) and analyzed before and after irradiation in situ under ultra-high vacuum conditions. Through optimized irradiation conditions using low-energy ions with grazing trajectories, amorphization of the monolayer is induced already at low ion fluences of 1.5 × 1014 ions cm−2 and without inducing damage underneath the MoS2 layer. The crystalline-to-amorphous transformation is accompanied by changes in the electronic properties from semiconductor-to-metal and an extinction of photoluminescence. Upon thermal annealing, the re-crystallization occurs with restoration of the semiconducting properties, but residual defects prevent the recovery of photoluminescence.

Keywords: 2D materilas; irradiation; atomistic simulations; defects

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Publ.-Id: 31340


Increasing the Diversity and Understanding of Semiconductor Nanoplatelets by Colloidal Atomic Layer Deposition

Reichhelm, A.; Hübner, R.; Damm, C.; Nielsch, K.; Eychmüller, A.

Nanoplatelets (NPLs) are a remarkable class of quantum confined materials with size-dependent optical properties, which are determined by the defined thickness of the crystalline platelets. To increase the variety of species, the colloidal atomic layer deposition method is used for the preparation of increasingly thicker CdSe NPLs. By growing further crystalline layers onto the surfaces of 4 and 5 monolayers (MLs) thick NPLs, species from 6 to 13 MLs are achieved. While increasing the thickness, the heavy-hole absorption peak shifts from 513 to 652 nm, leading to a variety of NPLs for applications and further investigations. The thickness and number of MLs of the platelet species are determined by high-resolution transmission electron microscopy (HRTEM) measurements, allowing the interpretation of several contradictions present in the NPL literature. In recent years, different assumptions are published, leading to a lack of clarity in the fundamentals of this field. Regarding the ongoing scientific interest in NPLs, there is a certain need for clarification, which is provided in this study.

Keywords: CdSe; colloidal atomic layer deposition; nanoplatelets

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Permalink: https://www.hzdr.de/publications/Publ-31339
Publ.-Id: 31339


Unraveling Structure and Device Operation of Organic Permeable Base Transistors

Darbandy, G.; Dollinger, F.; Formánek, P.; Hübner, R.; Resch, S.; Roemer, C.; Fischer, A.; Leo, K.; Kloes, A.; Kleemann, H.

Organic permeable base transistors (OPBTs) are of great interest for flexible electronic circuits, as they offer very large on-current density and a record-high transition frequency. They rely on a vertical device architecture with current transport through native pinholes in a central base electrode. This study investigates the impact of pinhole density and pinhole diameter on the DC device performance in OPBTs based on experimental data and TCAD simulation results. A pinhole density of NPin = 54 μm−2 and pinhole diameters around LPin = 15 nm are found in the devices. Simulations show that a variation of pinhole diameter and density around these numbers has only a minor impact on the DC device characteristics. A variation of the pinhole diameter and density by up to 100% lead to a deviation of less than 4% in threshold voltage, on/off current ratio, and sub-threshold slope. Hence, the fabrication of OPBTs with reliable device characteristics is possible regardless of statistical deviations in thin film formation.

Keywords: organic permeable base transistors; organic electronics; technology computer-aided design simulation

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Permalink: https://www.hzdr.de/publications/Publ-31338
Publ.-Id: 31338


Elucidation of the electron transfer mechanism in Eu2+ and Sm3+ codoped CaF2: A step towards better understanding of trapping and detrapping in luminescent materials

Joos, J. J.; van der Heggen, D.; Amidani, L.; Seijo, L.; Barandiarán, Z.

Many-electron multiconfigurational ab initio calculations are combined with x-ray spectroscopy to scrutinize a popular model for electron transfer in lanthanide-doped crystals which hypothesizes that the electrons are conveyed by the conduction band of the host. Contrary to this accepted picture, our combined theoretical-experimental effort shows that the reversible electron phototransfer from Eu2+ to Sm3+ in CaF2 is direct, from metal to metal. It is theoretically predicted and experimentally verified that visible light induces the reverse electron transfer.

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Publ.-Id: 31337


Phase coherence and phase jumps in the Schwabe cycle

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

Guided by the working hypothesis that the Schwabe cycle of solar activity is synchronized by the 11.07 years alignment cycle of the tidally dominant planets Venus, Earth and Jupiter, we reconsider the phase diagrams of sediment accumulation rates in lake Holzmaar, and of methanesulfonate (MSA) data in the Greenland ice core GISP2, which are available for the period 10000-9000 cal. BP. Since some half-cycle phase jumps appearing in the output signals are, very likely, artifacts of applying a biologically substantiated transfer function, the underlying solar input signal with a dominant 11.04 years periodicity can be considered as mainly phase-coherent over the 1000 years period in the early Holocene. For more recent times, we show that the re-introduction of a hypothesized “lost cycle” at the beginning of the Dalton minimum would lead to a real phase jump. Similarly, by analyzing various series of 14C and 10Be data and comparing them with Schove’s historical cycle maxima, we support the existence of another “lost cycle” around 1565, also connected with a real phase jump. Viewed synoptically, our results lend greater plausibility to the starting hypothesis of a tidally synchronized solar cycle, which at times can undergo phase jumps, although the competing explanation in terms of a non-linear solar dynamo with increased coherence cannot be completely ruled out.

Keywords: Solar cycle; Synhcronization

Permalink: https://www.hzdr.de/publications/Publ-31336
Publ.-Id: 31336


Bioassociation of U(VI) and Eu(III) by plant (Brassica napus) suspension cell cultures – A spectroscopic investigation

Jessat, J.; Sachs, S.; Moll, H.; John, W.; Steudtner, R.; Hübner, R.; Bok, F.; Stumpf, T.

In this study, we investigated the interaction of U(VI) and Eu(III) with Brassica napus suspension plant cells as a model system. Concentration-dependent (0-200 µM) bioassociation experiments showed that more than 75% of U(VI) and Eu(III) were immobilized by the cells. In addition to this phenomenon, time-dependent studies for 1 to 72 h of exposure showed a multi-stage bioassociation process for cells that were exposed to 200 µM U(VI), where, after initial immobilization of U(VI) within 1 h of exposure, it was released back into culture medium starting within 24 h. A re-mobilization to this extent has not been previously observed. The MTT assay was used to correlate the bioassociation behavior of Eu and U with the cell vitality. Speciation studies by spectroscopy and in silico methods highlighted various U and Eu species over the course of exposure. We were able to observe a new U species, which emerged simultaneously with the re-mobilization of U back into solution, which we assume to be a U(VI) phosphate species. Thus, the interaction of U(VI) and Eu(III) with released plant metabolites could be concluded.

Keywords: plant cells; bioassociation; Brassica napus; time-resolved laser-induced fluorescence spectroscopy; radionuclides; uranium; europium; speciation

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Publ.-Id: 31335


Data set on DBTTs from SPT and CVN

Altstadt, E.; Bergner, F.; Houska, M.

The data set is related to a manuscript entitled "Use of the small punch test for the estimation of ductile-to-brittle transition temperature shift of irradiated steels". Contents raw data of small punch tests, evaluation data of small punch tests and Charpy impact tests, correlation and regression analysis.

Keywords: small punch test; Charpy impact test; ductile-to-brittle-transition temperature; reactor pressure vessel steel; neutron irradiation

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Permalink: https://www.hzdr.de/publications/Publ-31334
Publ.-Id: 31334


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