Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41396 Publications

Volume 141: European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases, 14 September 2020, Virtual Conference

Bischl, B.; Guhr, O.; Seibold, H.; Steinbach, P.

Proceedings of Machine Learning Research

Keywords: teaching; machine learning; ECML/PKDD 2020

  • Open Access Logo Book (Editorship)
    www: PMLR, 2021

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Permalink: https://www.hzdr.de/publications/Publ-33193
Publ.-Id: 33193


Machine Learning for Accelerator Physics and Engineering

Steinbach, P.; Hoffmann, H.; Schmerler, S.; Starke, S.

Helmholtz AI has been available for members of ARD since its inception 2019/20. In this presentation, I'd like to present the current status of Helmholtz AI consultancy for matter research in Helmholtz. I'd provide sneak previews into past and ongoing vouchers we embarked upon for the accelerator physics community. Last but not least, I'll discuss challenges we faced along the way and will highlight some future directions if time allows.

Keywords: machine learning; Helmholtz AI; accelerator physics; seminar

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    MT ARD ST3 Meeting 2021 in Hamburg, 29.09.-01.10.2021, virtuell, Germany
    DOI: 10.6084/m9.figshare.16709350.v2

Permalink: https://www.hzdr.de/publications/Publ-33192
Publ.-Id: 33192


Predicting the shoe size of workshop participants

Starke, S.; Schmerler, S.; Steinbach, P.

A jupyter notebook that can predict the shoe size of a person based on their gender, height and weight. This is a notebook meant for training purposes to show case how public data can be used to train a machine learning predictor.

This notebook uses a public crowd-sourced dataset from https://doi.org/10.5281/zenodo.5541145 to conduct the training.

Keywords: jupyter notebook; notebook; machine learning; scikit-learn; shoe size; csv

Permalink: https://www.hzdr.de/publications/Publ-33191
Publ.-Id: 33191


crowdsourced body parameters of workshop attendants at the Helmholtz MT ARD ST3 meeting

Steinbach, P.; Schmerler, S.

This data set was crowdsourced at the 2021 Helmholtz MT ARD ST3 meeting from attendants of the Machine Learning Tutorial on Sep 30, 2021. For more details on the event, see
https://indico.desy.de/event/28823/

Keywords: shoe size; body height; body mass; gender; crowdsource; csv

Permalink: https://www.hzdr.de/publications/Publ-33190
Publ.-Id: 33190


Publishing the (PaN) Experiment

Knodel, O.

The talk gives an overview on the publication of an (PaN) experiment in general, including data and software publication. An additional overall workflow describes the dependencies between all data objects with the aim to create a comprehensible experiment. The live demo introduces our training catalogue developed in WP5 with the special workflow feature.

Keywords: ExPaNDS; Data Management; PaN Training Catalogue

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    ExPaNDS Symposium for Librarians and Data Managers, 30.09.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33189
Publ.-Id: 33189


Demonstrator for using e-learning platforms for PaN

Knodel, O.; Konrad, U.

A definition of the most suitable training materials for PaN communities in accordance with the requirements and recommendations made by the targeted e-platform providers.

A demonstrator for using e-learning platforms was developed and provided by HZDR in the frame of the ExPaNDS project.

Keywords: ExPaNDS; E-learning; Photon and Neutron

Permalink: https://www.hzdr.de/publications/Publ-33188
Publ.-Id: 33188


Solid-phase synthesis of selectively mono-fluorobenz(o)ylated polyamines as a basis for for the Development of 18F-Labeled Radiotracers

Wodtke, R.; Pietzsch, J.; Löser, R.

Polyamines are highly attractive vectors for tumor targeting, particularly with regards to the development of radiolabeled probes for imaging by positron emission (PET) and single-photon emission computed tomography (SPECT). However, the synthesis of selectively functionalized derivatives remains challenging owing to the presence of multiple amino groups of similar re-activity. In this work, we established a synthetic methodology for the selective mono-fluorobenz(o)ylation of various biogenic diamines and polyamines as lead compounds for the perspective development of substrate-based radiotracers for targeting polyamine-specific membrane transporters and enzymes such as transglutaminases. To this end, the polyamine scaffold was constructed by solid-phase synthesis of the corresponding oxopolyamines and subsequent re-duction with BH₃/THF. Primary and secondary amino groups were selectively protected using Dde and Boc as protecting groups, respectively, in orientation to previously reported proce-dures, which enabled the selective introduction of the reporter groups. For example, N¹-FBz-spermidine, N⁴-FBz-spermidine, N⁸-FBz-spermidine, and N¹-FBz-spermine and N⁴-FBz-spermine (FBz=4-fluorobenzoyl) were obtained in good yields by this approach. The advantages and disadvantages of this synthetic approach are discussed in detail and its suitability for radiolabeling was demonstrated for the solid-phase synthesis of N¹-[¹⁸F]FBz-cadaverine.

Keywords: amide bond reduction; reductive alkylation; ¹⁸F-labeling; prosthetic groups; site-selective chemical modification; transglutaminases; polyamine transport system; substrate-based probes; PET tracers; tumor targeting

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33187
Publ.-Id: 33187


Limitations and gaps in global bat wing morphology trait data

Matt, C.; Simoes Silva, I. M.; Matthew, J. G.; George, A. G.

Species’ life-history traits have a wide variety of applications in ecological and conservation research, particularly when assessing threats. The development and growth of global species’ trait databases are critical for improving trait-based analyses; however, it is vital to understand the gaps and biases in the available data.
We reviewed bat wing morphology data, specifically mass, wingspan, wing area, wing loading, and aspect ratio, to identify issues with data reporting and ambiguity. Additionally, we aimed to assess taxonomic and geographic biases in trait data coverage. We found that most studies used similar field methodology, but that data reporting and quality were inconsistent/poor. Additionally, we noted several issues regarding semantic ambiguity in trait definitions, specifically around what constitutes wing area. Globally, we found that bat wing morphology trait coverage was low. Only six bat families had ≥40% trait coverage, and, of those, none consisted of more than 11 species in total. We found similar biases in trait coverage across International Union for Conservation of Nature Red List categories, with threatened species having lower coverage.
Geographically, North America, Europe, and the Indomalayan regions exhibited higher overall trait coverage, while both the Afrotropical and Neotropical ecoregions showed poor trait coverage.
The underlying biases and gaps in bat wing morphology data have implications for researchers conducting global trait-based assessments. Implementing imputation techniques may address missing data, but only for smaller regional subsets with substantial trait coverage. Due to generally low overall trait coverage, increasing species’ representation in the database should be prioritised. We suggest adopting an Ecological Trait Standard Vocabulary to reduce semantic ambiguity in bat wing morphology traits, to improve data compilation and clarity. Additionally, we advocate that researchers adopt an Open Science approach to facilitate the growth of a bat wing morphology trait database.

Keywords: open science; ecology; bats; aspect ratio; reproducibility; data availability; spatial biases; species traits

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Permalink: https://www.hzdr.de/publications/Publ-33186
Publ.-Id: 33186


Emerging opportunities for wildlife with sustainable autonomous transportation

Simoes Silva, I. M.; Calabrese, J.

Autonomous vehicles (AV) are expected to play a key role in the future of transportation, introducing a disruptive yet potentially beneficial change for vehicle-wildlife interactions. However, this assumption has not been critically examined. Here, we introduce a new conceptual framework covering the intersection between AV technological innovation and wildlife conservation to reduce wildlife-vehicle collisions. We suggest future research within this framework to focus on developing robust warning systems and animal detection methods for AV systems, and to incorporate wildlife-vehicle interactions into decision-making algorithms. With large-scale deployment a looming reality, it is vital to incorporate conservation and sustainability into the societal, ethical, and legal implications of AV technology. We appeal for further debate and interdisciplinary collaborations between scientists, developers, and policymakers.

Keywords: conservation; autonomous vehicles; ecology; sustainability; self-driving cars; automated vehicles; traffic accidents; animal-vehicle collisions; wildlife-vehicle collisions; conceptual framework

Permalink: https://www.hzdr.de/publications/Publ-33185
Publ.-Id: 33185


Defect characterization using positron annihilation spectroscopy on laser ablated surfaces

Hosemann, P.; Auguste, R.; Lam, S.; Butterling, M.; Liedke, M. O.; Elsherif, A. G. A.; Hirschmann, E.; Wagner, A.; Grigoropoulos, C. P.; Selim, F.; Uberuaga, B. P.

In recent years, short, pulsed laser ablation has been gaining popularity for machining small scale test geometries from bulk samples and for efficient serial sectioning. These laser-based techniques are being added to the toolbox in material science, which makes it necessary to understand the changes in the material that occur from the laser-material interaction. Positron annihilation spectroscopy is a unique, nondestructive technique to investigate small defects in materials difficult to investigate by other tools. In this work, Doppler broadening and positron lifetime annihilation spectroscopy are utilized to help quantify the damage in materials treated with short, pulsed lasers. Using a femtosecond laser on single crystal silicon, this manuscript shows that clusters of vacancy-like defects and small voids increase systematically with laser power. The damage induced by the laser can also reach to micrometer depths.

Keywords: Si; fs-laser; positron annihilation spectroscopy; Doppler broadening; pores

Related publications

  • Open Access Logo JOM: The Journal of the Minerals, Metals & Materials Society 73(2021), 4221-4230
    Online First (2021) DOI: 10.1007/s11837-021-04965-8

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Permalink: https://www.hzdr.de/publications/Publ-33184
Publ.-Id: 33184


Using of light and heavy ion beams in modern FIBs

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

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. Therefore, we have extended the FIB technology towards the stable delivery of multiple ion species by liquid metal alloy ion sources (LMAIS) [2].
These LMAIS provides single and multiple charged ion species of different masses. As an example we introduce the GaBiLi LMAIS [3]. Such “universal” source enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from the same ion source. Light ions are of
increasing interest due to the available high resolution in the nanometer range and their special chemical and physical behavior in the substrate. We compare helium and neon ion beams from a helium ion microscope with beams such as lithium, boron, and silicon, obtained from a mass-separated FIB using a LMAIS with respect
to the imaging and milling resolution, as well as the current stability [4]. The bombardment of solids by poly-atomic (cluster) ions leads to nonlinear collision cascades in near-surface regions. In comparison with linear cascades by monoatomic ions, much higher energy deposition occurs up to local surface melting [5]. Here, we also report the study on the sputter yield of Si under the bombardment by atomic Bi+ and cluster Bin+ (n = 2-4) ions with the same specific energy related to one incidence single atom [6].
[1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63
(2020) 1219.
[2] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative
for Focused Ion Beam Technology, Appl. Phys. Rev. 3 (2016) 021101.
[3] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal
alloy ion sources, JVSTB 37(2), Mar/Apr (2019) 021802.
[4] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, L. Bischoff, Imaging and Milling Resolution
of Light Ion Beams from HIM and Liquid Metal Alloy Ion Source driven FIBs, Beilstein J. Nanotechnol. 11
(2020) 1742.
[5] L. Bischoff, K.-H. Heinig, B. Schmidt, S. Facsko, and W. Pilz, Self-organization of Ge nanopattern under
erosion with heavy Bi monomer and cluster ions, Nucl. Instr. Meth. B 272 (2012) 198.
[6] A. Tolstogouzov, P. Mazarov, A. Ieshkin, S.Belykh, N. Korobeishchikov, V. Pelenovich, D.J. Fu,
Sputtering of silicon by atomic and cluster bismuth ions: An influence of projectile nuclearity and specific
kinetic energy on the sputter yield, Vacuum 188 (2021) 110188.

Keywords: liquid metal alloy ion source; FIB technology; nanostructures; poly-atomic ions

Related publications

  • Lecture (Conference)
    4th EuFN and FIT4NANO Joint Workshop / Meeting, 27.-30.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-33183
Publ.-Id: 33183


Investigation of Boron Liquid Metal Alloy Ion Sources for Focused Ion Beam Applications

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

Focused Ion Beam (FIB) processing is established as a well-suited and promising technique in R&D in nearly all fields of nanotechnology for patterning and prototyping on the μm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent an alternative to expand the FIB application fields beside all other source concepts [1]. Due to the interest on light elements, especially boron, various alloys were investigated and characterized. In this contribution we will describe Co31Nd64B5 as the most promising alloy in more detail. The mass spectrum of such a source was obtained in a VELION FIB-SEM system (Raith GmbH) [2]. The source operation life time was longer than 600 μAh and a first imaging characterization showed a lateral resolution of (30 ± 5) nm so far. This LMAIS is suited for several mass-filtered FIB applications like implantation, high rate sputtering, surface patterning or ion lithography [3]. The switching between the certain ion species. B – very light, suitable for ion lithography or writing p-type doping. Co – medium mass for applications in the field of nano-magnetics or CoSi2 for ion beam synthesis of conductive nano-structures on Si. Finally Nd as double charged heavy ion for ion sputtering. The change between ion species can be done in seconds and leads to remarkable expansion of the application spectrum of FIB technology.
[1] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources - An Alternative for Focused Ion Beam Technology; Appl. Phys. Rev. 3 (2016) 021101.
[2] L. Bischoff, N. Klingner, P. Mazarov, W. Pilz, and F. Meyer, Boron Liquid Metal Alloy Ion Sources for special FIB applications, JVST B 38 (2020) 042801.
[3] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of Technologies for Nano Device Prototyping with a Special Focus on Ion Beams – A Review,
Appl. Phys. Rev. 4 (2017), 011302.

Keywords: Focused Ion Beam; Liquid Metal Alloy Ion Source; boron; mass filter

Related publications

  • Lecture (Conference)
    4th EuFN and FIT4NANO Joint Workshop / Meeting, 27.-30.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-33182
Publ.-Id: 33182


Data driven high resolution modeling and spatial analyses of the COVID-19 pandemic in Germany

Schüler, L.; Calabrese, J.; Attinger, S.

The SARS-CoV-2 virus has spread around the world with over 100 million infections to date, and currently many countries are fighting the second wave of infections. With neither sufficient vaccination capacity nor effective medication, non-pharmaceutical interventions (NPIs) remain the measure of choice. However, NPIs place a great burden on society, the mental health of individuals, and economics. Therefore the cost/benefit ratio must be carefully balanced and a target-oriented small-scale implementation of these NPIs could help achieve this balance. To this end, we introduce a modified SEIRD-class compartment model and parametrize it locally for all 412 districts of Germany. The NPIs are modeled at district level by time varying contact rates. This high spatial resolution makes it possible to apply geostatistical methods to analyse the spatial patterns of the pandemic in Germany and to compare the results of different spatial resolutions. We find that the modified SEIRD model can successfully be fitted to the COVID-19 cases in German districts, states, and also nationwide. We propose the correlation length as a further measure, besides the weekly incidence rates, to describe the current situation of the epidemic.

Keywords: COVID-19; Germany; Epidemiology; Pandemics; SARS-CoV-2; Death rates; Spatial epidemiology

Permalink: https://www.hzdr.de/publications/Publ-33181
Publ.-Id: 33181


Far-infrared Near-field Optical Imaging and Kelvin Probe Force Microscopy of Laser-crystallized and amorphized Phase Change Material Ge₃Sb₂Te₆

Barnett, J.; Wehmeier, L.; Heßler, A.; Lewin, M.; Pries, J.; Wuttig, M.; Klopf, J. M.; Kehr, S. C.; Eng, L. M.; Taubner, T.

Chalcogenide phase change materials reversibly switch between non-volatile states with vastly different optical properties, enabling novel active nanophotonic devices. However, a fundamental understanding of their laser-switching behavior is lacking and the resulting local optical properties are unclear at the nanoscale. Here, we combine infrared scattering-type scanning near-field optical microscopy (SNOM) and Kelvin probe force microscopy (KPFM) to investigate four states of laser-switched Ge3Sb2Te6 (as-deposited amorphous, crystallized, reamorphized, and recrystallized) with nanometer lateral resolution. We find SNOM especially sensitive to differences between crystalline and amorphous states, while KPFM has higher sensitivity to changes introduced by melt-quenching. Using illumination from a free-electron laser, we employ that far-infrared (THz) SNOM is more sensitive to free charge carriers compared to mid-infrared SNOM and prove that the local conductivity of crystalline states depends on the switching process. This insight into the local switching of optical properties is essential for developing active nanophotonic devices.

Keywords: scattering-type scanning near-field optical microscopy; free-electron laser; phase change material; Kelvin probe force microscopy; GST; optical switching; metavalent bonding

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33180
Publ.-Id: 33180


Dosimetric benefit of 4D robustly optimized proton plans for NSCLC patients with intrafractional motion above 5 mm

Spautz, S.; Haase, L.; Tschiche, M.; Makocki, S.; Troost, E. G. C.; Richter, C.; Stützer, K.

Background: We analyse the benefit of 4D robust plan optimization (RO) for proton therapy treatments of NSCLC patients with pronounced breathing-induced anatomical variations.

Methods: Eight NSCLC patients with relevant maximal intrafractional motion of the primary (CTVp; 5.6-24.5mm) and/or nodal CTV (CTVn; 5.8-17.3mm) on the planning 4DCT (pCT) were included. We optimized three robust normo-fractionated plans with a criterion of 5mm setup and 3.5%+2mm range uncertainty: RO on the AverageCT with iGTVp density override (3DRO); RO on the AverageCT and three 4DCT phases (4DRO3); and RO on the AverageCT and all eight 4DCT phases (4DRO8). Setup and range error scenarios were analysed on the pCT. To assess robustness against intra- and inter-fractional changes, 4D doses were calculated on the pCT and up to two control 4DCTs (cCTs) assuming equal weights between breathing phases. Interplay effects were simulated on the pCT from patient breathing signals and machine logfiles of plan deliveries with and without 5 layered rescans. Fractionation effects were emulated by accumulating four interplay scenarios with different starting times.

Results: All nominal plans fulfilled target coverage (D98%>95%) and OAR sparing; CTVp/CTVn coverage failed setup and range robustness in 12%/35% (3DRO), 14%/18% (4DRO3) and 13%/20% (4DRO8) of the scenarios (Fig1a), respectively. 4D dose target coverage on the pCT was >94% for all plans; interfractional changes in the cCTs reduced the CTVp coverage by about 2pp (Fig1b). Interplay analyses (Fig1c) revealed a mean CTVp/CTVn coverage loss by 3.4pp/2.4pp, 3.0pp/2.3pp, and 2.9pp/3.2pp in single scenarios of 3DRO, 4DRO3 and 4DRO8 plans, respectively. D98% values were improved on average by 1.0pp with rescanning, but were even worsened in some scenarios. Irrespective of rescanning, the simulated fractionation fullfilled the target coverage in all cases.

Conclusion: 3DRO and 4DRO showed similar robustness against different motion effects. 4DRO provides benefits for some patients, but 3DRO demands less workload.

  • Poster
    4D treatment workshop on particle therapy, 12.-13.11.2021, Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-33179
Publ.-Id: 33179


Solar selective coatings and materials for high-temperature solar thermal applications

Escobar Galindo, R.; Krause, M.; Niranjan, K.; Barshilia, H.

In this chapter, we will present and summarize the latest innovative materials science approaches devoted to increase the CSP plant efficiency by implementing higher operation temperatures and reducing the levelized costs of electricity (LCOE). The chapter is organized as follows: The first section provides statistical data (Section 13.3.1) and the basic knowledge (Section 13.3.2) necessary to understand the state-of-the-art and the recent R&D directions of the field “high-temperature solar thermal applications”. In the second section 13.2 we introduce the concept of solar selectivity. Based on realistic operational parameters of CSP plants, their potentials and limitations are discussed and graphically illustrated. State-of-the-art results from the last decade are briefly reviewed in the third section for: absorber paints (Section 13.3.1), solar selective coatings (SSCs) (Section 13.3.2), and volumetric receivers (Section 13.3.3). The fourth Section 13.4 focuses on the need of comparable stability studies of newly developed SSCs and materials along with the demand and the criteria for standardized characterization protocols.

Keywords: Solar thermal; Concentrated solar power; High-temperature energy conversion; High-temperature materials

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33178
Publ.-Id: 33178


A Hybrid Radiomics Approach to Modeling Progression-free Survival in Head and Neck Cancers

Starke, S.; Thalmeier, D.; Steinbach, P.; Piraud, M.

We present our contribution to the HECKTOR 2021 challenge.
We created a Survival Random Forest model based on clinical features, and a few radiomics features that have been extracted with and without using the given tumor masks, for Task 3 and Task 2 of the challenge, respectively.
To decide on which radiomics features to include into the model, we proceeded both to automatic feature selection, using several established methods, and to literature review of radiomics approaches for similar tasks.
Our best performing model includes one feature selected from the literature (Metabolic Tumor Volume derived from the FDG-PET image), one via stability selection (Inverse Variance of the Gray Level Co-occurrence Matrix of the CT image), and one selected via permutation-based feature importance (Tumor Sphericity).
This hybrid approach turns-out to be more robust to overfitting than models based on automatic feature selection.
We also show that simple ROI definition for the radiomics features, derived by thresholding the Standard Uptake Value in the FDG-PET images, outperforms the given expert tumor delineation in our case. Team name on the AIcrowd platform: ia-h-ai.

Keywords: Head and Neck Cancer; Radiomics; Survival analysis; CT; PET

  • Contribution to proceedings
    HECKTOR Challenge 2021 - Head and Neck tumor segmentation and outcome prediction in PET/CT images, 27.09.2021, Strasbourg, France
    Lecture Notes in Computer Science: Springer, 978-3-030-98252-2
    DOI: 10.1007/978-3-030-98253-9_25
    Cited 6 times in Scopus
  • Open Access Logo Lecture (Conference) (Online presentation)
    24th International Conference on Medical Image Computing & Computer Assisted Intervention (MICCAI 2021), 27.09.-01.10.2021, Strasbourg, France
    DOI: 10.5281/zenodo.5606514

Permalink: https://www.hzdr.de/publications/Publ-33177
Publ.-Id: 33177


Laser-Ion Acceleration in the Optimized TNSA-Regime via Temporal Pulse Shaping

Garten, M.; Göthel, I.; Wetzel, J.; Miethlinger, T.; Ziegler, T.; Püschel, T.; Bock, S.; Zeil, K.; Marre, B. E.; Bussmann, M.; Cowan, T.; Schramm, U.; Kluge, T.

Establishing precise control over the beam parameters of laser-accelerated ions from the interaction of ultrashort ultra-high intensity (UHI) laser pulses with ultrathin foils has been the major goal of the last 20 years since the first description of the TNSA process. Especially the quest for repeatable, highest maximum energies continues to be challenging as the spatiotemporal coupling of laser-pulse- and target parameters down to the femtosecond-nanometer level was found to be decisive for the overall acceleration performance. In particular, precise control and metrology of the driving UHI laser pulses are paramount to achieving this goal. We present a multi-parameter-space study, bridging the scales from picosecond preplasma formation over transient, non-equilibrium dynamics of the tens of femtosecond laser duration down to attosecond plasma oscillations performed through 1D– up to 3D particle-in-cell simulations. By taking into account realistic temporal intensity contrast features of the last picosecond prior and up to the first picosecond after the main pulse peak, we show how temporal pulse shaping optimizes the TNSA process.

Keywords: laser ion acceleration; TNSA; particle-in-cell; PIConGPU; Smilei; temporal laser contrast

  • Poster (Online presentation)
    47th EPS Conference on Plasma Physics, 21.-25.06.2021, online, online
  • Poster
    17th International Conference on the Physics of Non-Ideal Plasmas, 19.-24.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33176
Publ.-Id: 33176


Hydrothermal wall rock alteration related to Late Variscan Pb-Zn-Ag-(Au) mineralisation and its implication for exploration in the Freiberg District, Germany

Birtel, S.; Gutzmer, J.

Although epithermal Pb-Zn-Ag-(Au) vein-hosted mineralisation in the Freiberg District, Germany, has been widely studied, closely associated wall rock alteration remains hardly understood. In order to deduce alteration stages in the proximity to mineralised veins, suites of wall rock samples ranging from least altered to intensely altered were studied from two localities in the central part of the district in order to describe and quantify the effects of hydrothermal wall rock alteration.

Least altered host rocks at both localities are medium to coarse- grained biotite –plagioclase orthoclase augengneisses. In weakly altered samples the foliation, and the primary assemblage are well preserved with typical alteration assemblages comprising of fine-grained carbonate, kaolinite, epidote, sericite and chlorite. This alteration assemblage dominates also in moderately altered samples, with metamorphic quartz and the original foliation partly preserved. Intensively altered samples, in contrast, comprise a massive fabric with globular quartz and fine-grained sericite that are very finely intergrown arsenopyrite and/or pyrite occur finely disseminated in this alteration assemblage. Fe-Mn-rich carbonates also occur in the matrix or as thin veinlets in the altered wall rock. In hand specimen, this strongly sericitized rock is of light green to yellow colour.

Hydrothermal alteration related to vein-hosted magmatic-hydrothermal mineralization in the Freiberg District is best described as fabric destructive with distinct discoloration, an effect that can be simply detected visually in core. Sericitization and silicification are dominant – and appear limited to the immediate vicinity around and within relevant structural zones and veins. Visual core inspection, possibly complemented by hyperspectral drill core scanning and whole rock geochemistry (by pXRF) are simple tools that can be used to trace this alteration during ongoing exploration efforts in the district.

Keywords: host rock alteration; exploration; mineralisation in Freiberg District

  • Contribution to proceedings
    16th Biennial meeting SGA 2022, 28.-31.03.2022, Rotorua, New Zealand
    Christie AB (ed.), Proceedings of the 16th SGA Biennial Meeting

Permalink: https://www.hzdr.de/publications/Publ-33174
Publ.-Id: 33174


Effect of the deposition method and ageing in atmosphere on the optical properties of tetraphenylporphyrins (TPPs) films

Lungwitz, F.; Fronk, M.; Richter, P.; Mende, C.; Rüffer, T.; Gordan, O. D.; Himcinschi, C.; Zahn, D. R. T.; Lang, H.; Salvan, G.

In this work thin films of 5,10,15,20-tetraphenylporphyrin (H2TPP) and 5,10,15,20-tetrakis(4-methoxyphenyl)porpyhrin (H2TMPP)) were prepared by organic molecular beam deposition (OMBD). In addition, spin coating was applied as an alternative preparation technique for thin films of H2TPP to investigate the influence of the deposition method on the optical properties. The preservation of the molecular structure was proven by comparative Raman spectroscopy studies between films and powder. Modelling of the spectroscopic ellipsometry data yields a uniaxial anisotropy of the optical constants for the films of both molecules deposited by OMBD, which was used to determine the relative orientation of the molecules with respect to the substrate. The effect of the storage in air on the optical properties of the OMBD films was investigated using the example of H2TMPP. The molecular order in the films was found to decrease while the film roughness increased compared to samples stored in nitrogen.

Keywords: Tetraphenylporphyrin; Tetramethoxyphenylporpyhrin; Organic molecular beam deposition; Spin coating; Optical constants; Atmosphere exposure

Permalink: https://www.hzdr.de/publications/Publ-33173
Publ.-Id: 33173


Neural Solvers

Stiller, P.; Zhdanov, M.; Rustamov, J.; Bethke, F.; Hoffmann, N.

Neural Solvers are neural network-based solvers for partial differential equations and inverse problems. The framework implements scalable physics-informed neural networks Physics-informed neural networks allow strong scaling by design. Therefore, we have developed a framework that uses data parallelism to accelerate the training of physics-informed neural networks significantly. To implement data parallelism, we use the Horovod framework, which provides near-ideal speedup on multi-GPU regimes.

Keywords: PINNs; PDEs; Neural Solver; Scalable AI

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Permalink: https://www.hzdr.de/publications/Publ-33172
Publ.-Id: 33172


In-situ GISAXS observation of ion-induced nanoscale pattern formation on crystalline Ge(001) in the reverse epitaxy regime

Erb, D.; Myint, P.; Evans-Lutterodt, K.; Ludwig, K.; Facsko, S.

The ion-induced nanoscale pattern formation on a crystalline Ge(001) surface is observed in-situ by means of Grazing Incidence Small Angle X-ray Scattering (GISAXS). Analysis of the GISAXS intensity maps yields the temporal develoment of geometric parameters characterizing the changing pattern morphology. In comparison with theoretical predictions and with simulations of the patterning process based on a continuum equation we find good agreement for the temporal evolution of the polar facet angle, characteristic length, and surface roughness in the non-linear regime. To achieve this agreement, we included an additional term in the continuum equation which adjusts the pattern anisotropy.

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Permalink: https://www.hzdr.de/publications/Publ-33171
Publ.-Id: 33171


Real-Time Observation of Temperature-Induced Surface Nanofaceting in M-Plane α-Al2O3

Erb, D.; Perlich, J.; Roth, S.; Röhlsberger, R.; Schlage, K.

The spontaneous crystal surface reconstruction of M-plane Al₂O₃ is employed for nanopatterning and nanofabrication in various fields of research including, among others, magnetism, superconductivity, and optoelectronics. However, investigating this reconstruction process from a planar surface to one with a nanoscale ripple topography is challenging, since it occurs at high temperatures above approximately 1000 °C. This contribution presents an approach combining ex-situ Atomic Force Microscopy with in-situ and simulated Grazing Incidence Small Angle X-ray Scattering to further elucidate this morphological transition. It provides time-resolved information on all relevant morphological characteristics required to trace the surface topography during recon-
struction and thereby offers a comprehensive picture of this process on a nanometer scale.

Keywords: crystal surface reconstruction; nanofaceted Al₂O₃; pattern formation; in-situ GISAXS; AFM

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Permalink: https://www.hzdr.de/publications/Publ-33170
Publ.-Id: 33170


The role of data science and machine learning to achieve sustainable mineral exploration

Lorenz, S.

Europes’ journey towards a sustainable and digitized future relies fundamentally on the secured supply with critical raw materials. Lithium, Rare Earths, Indium and Tungsten, to name a few, are fundamental requisites for green and smart technologies, e-mobility and the energy transition. Securing the access to such materials is one of the fundamental questions for Europes ambition to deliver the Green Deal. Fast, versatile and accurate but at the same time socially acceptable and less invasive mineral exploration technologies are required to meet this goal. Innovative sensors and acquisition platforms for spectral imaging allow to gain insights on the composition of materials without destroying or even touching them. The complexity, diversity and sheer amount of respective data produced in a typical exploration scenario require a joint understanding of geoscience, image processing and machine learning to retrieve geologically meaningful results in a reasonable time. The presentation will give an overview on our current research highlighting important challenges in modern mineral exploration in regards to image processing, multi-sensor data fusion, data classification and real-time processing.

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Women in Machine Learning & Data Science (WiMLDS) Meetup, 17.03.2021, online, online

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Permalink: https://www.hzdr.de/publications/Publ-33169
Publ.-Id: 33169


Targeted mapping using self-organizing drone swarms

Lorenz, S.

Drohnen unterstützen heutzutage viele Anwendungsfelder als preiswerte und flexible Flugplattformen. Durch die fortschreitende Entwicklung miniaturisierter Sensorik können Drohnen inzwischen auch für komplexe Observierungsaufgaben eingesetzt werden. Sie unterstützen auf diese Weise Wissenschaft und Industrie bei der Analyse schwer erreichbarer Ziele, zum Beispiel in Bergbau, Landwirtschaft oder Bauindustrie. Der notwendige Kompromiss zwischen Zuladung und Flugzeit ist dabei für die zivile Drohnenanwendung nach wie vor eine große Herausforderung. Mit seiner neuesten Projektidee zu autonomen, selbstorganisierten Drohnenverbänden will die Abteilung Erkundung des Helmholtz-Institutes Freiberg für Ressourcentechnologie Abhilfe schaffen: Scouting-Drohnen mit langer Flugzeit und leichten multispektralen Sensoren übernehmen eine Vorab-Analyse des Zielgebietes in Echtzeit. Anhand der Ergebnisse koordinieren sie selbsttätig weitere Drohnen ihres Verbandes für eine detaillierte Analyse ausgewählter kleinerer Zielpolygone. Jene mit schwereren, aber genaueren Sensoren ausgerüsteten Drohnen sparen so nicht nur Flugzeit ein, sondern nehmen auch nur dort detaillierte Daten auf wo sie wirklich benötigt werden. Neben der Entwicklung der Drohnen- und Multisensortechnologie sind Echtzeitverarbeitung und künstliche Intelligenz die Kernherausforderungen des Projektes.

  • Lecture (Conference) (Online presentation)
    Silicon Saxony Day, 27.05.2021, virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33168
Publ.-Id: 33168


Hyper 3D-AI: Artificial Intelligence for 3D multimodal point cloud classification

Lorenz, S.

Independent of the application field, spatially detailed information is commonly provided in the form of image data. Accordingly, major developments in image processing and artificial intelligence (AI) for image data interpretation are based on an image-like data structure, i.e. a spatially two-dimensional data grid with a custom number of informative layers. While sufficient for large-scale geographical data, this approach has major flaws when applied in any oblique-angle scenario, in particular as it inherently distorts the spatial characteristics of the observed target (virtual vs. real-world neighborhood relationships, occlusions). Todays’ most crucial image data applications (e.g., resources, energy, mobility, medicine), however, heavily rely on the accurate interpretation of the spatial relationship of objects in all three dimensions. It has been shown that the upscaling of 2D-images to multi-feature attributed 3D point clouds boosts the interpretational value of the dataset. This approach is not only beneficial for the fusion of image data with 3D-information (such as orientation, shape, and surface roughness), but also offers a straightforward solution for the fusion of higher dimensional multi-sensor data. Although point clouds or meshes are routinely used as 3D analogues of real-world targets, the processing of multi-feature point clouds in terms of clustering, classification or material characterization is still in its infancy. Innovative AI approaches such as PointNets or 3D-CNN have shown great potential for point cloud clustering using the spatial relationships of the individual points. However, classifications based on both spatial and auxiliary, high-dimensional point information such as spectral signatures or compositional characteristics is yet to be developed. The proposed project aims at the development of advanced machine (deep) learning approaches to fill this exact gap. These approaches comprise both the challenging fusion of multiple sensors as well as the subsequent classification and segmentation. Besides the algorithm design, the testing on representative scenarios from different application fields is a main work package, including the creation of reusable benchmark datasets for the validation and future development of algorithms. If successful, the project will improve the characterization of objects and surfaces for a wide range of potential applications such as exploration and mining, recycling, autonomous systems, quality assessment, sorting systems or detection of falsified objects. From a resource perspective, an enhanced material characterization will directly contribute to making processes more material and energy efficient. Regarding autonomous systems, the project will advance the research and implementation of methods for robust sensor fusion of multimodal sensors. Due to the versatility in application, the project outcome could support any process that requires a multi-sensor-based discrimination of objects and materials.

  • Invited lecture (Conferences) (Online presentation)
    Helmholtz Imaging Virtual Conference, 23.09.2021, virtual, Germany

Permalink: https://www.hzdr.de/publications/Publ-33167
Publ.-Id: 33167


Quasi‑1D XY antiferromagnet Sr2Ni(SeO3)2Cl2 at Sakai‑Takahashi phase diagram

Kozlyakova, E. S.; Moskin, A. V.; Berdonosov, P. S.; Gapontsev, V. V.; Streltsov, S. V.; Uhlarz, M.; Spachmann, S.; Elghandour, A.; Klingeler, R.; Vasiliev, A. N.

Uniform quasi-one-dimensional integer spin compounds are of interest as a potential realization of the Haldane conjecture of a gapped spin liquid. This phase, however, has to compete with magnetic anisotropy and long-range ordered phases, the implementation of which depends on the ratio of interchain J′ and intrachain J exchange interactions and both uniaxial D and rhombic E single-ion anisotropies. Strontium nickel selenite chloride, Sr2Ni(SeO3)2Cl2, is a spin-1 chain system which passes through a correlations regime at Tmax ~ 12 K to long-range order at TN = 6 K. Under external magnetic field it experiences the sequence of spin-flop at Bc1 = 9.0 T and spin-flip transitions Bc2 = 23.7 T prior to full saturation at Bsat = 31.0 T. Density functional theory provides values of the main exchange interactions and uniaxial anisotropy which corroborate the experimental findings. The values of J′/J = 0.083 and D/J = 0.357 place this compound into a hitherto unoccupied sector of the Sakai-Takahashi phase diagram.

Permalink: https://www.hzdr.de/publications/Publ-33164
Publ.-Id: 33164


THEREDA - Thermodynamic Reference Database

Gaona, X.; Bok, F.; Freyer, D.; Moog, H. C.; Wissmeier, L.

Part of the process to ensure the safety of radioactive waste disposal is the predictive modelling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modelling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA [1].

THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients, which allow for the calculation of solubilities in high-saline solutions. Registered users may either view single thermodynamic data and Pitzer interaction parameters or download ready-to-use parameter files for the geochemical speciation codes PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. The dataset can also be downloaded in a generic JSON-format to allow the import into other codes. The database can be accessed via the World Wide Web: www.thereda.de

Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side effects on calculations are caused. Furthermore, our website offers an in-creasing number of examples for applications, including graphical representation, which can be filtered by com-ponents of the calculated system.

REFERENCES
[1] Moog, H. C., Bok, F., Marquardt, C. M., and Brendler, V.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84, 2015

Keywords: THEREDA; Thermodynamic Reference Database; Solubility; Modelling; Pitzer

  • Poster (Online presentation)
    Processes Influencing Radionuclide Transport and Retention - Investigations Across Scales (TransRet2020), 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33162
Publ.-Id: 33162


Effects of hydrogen absorption on magnetism in Ni80Fe20/Y/Pd trilayers

Weiss, C.; Hübner, R.; Saunders, M.; Semisalova, A.; Ehrler, J.; Schmidt, N.; Seyd, J.; Albrecht, M.; Anwar, S.; Lindner, J.; Potzger, K.; Kostylev, M.

The effects of hydrogen absorption on the effective magnetization (4πMeff), gyromagnetic ratio (γ), Gilbert damping constant (αG), and the inhomogeneous linewidth broadening in Py(x)/Y(16 nm)/Pd(15 nm) trilayer films (x = 2, 3, 5, 8, 10, 20, 40 nm) were investigated with ferromagnetic resonance (FMR), transmission electron microscopy, and vibrating sample magnetometry. In the presence of a hydrogen atmosphere, the samples show a reduction of their FMR linewidth which is found to stem purely from a reduction of the inhomogeneous linewidth broadening. This is attributed to a rearrangement of atoms at the Py/Y interface in the presence of hydrogen, making the Py/Y interface more homogeneous. In addition, a reduction of 4πMeff was seen for all samples in the hydrogen atmosphere which is typical for an increase of the interfacial perpendicular magnetic anisotropy at the Py/Y interface.

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Permalink: https://www.hzdr.de/publications/Publ-33161
Publ.-Id: 33161


Trident process in laser pulses

Dinu, V.; Torgrimsson, G.

We study the trident process in laser pulses. We provide exact numerical results for all contributions, including the difficult exchange term. We show that all terms are in general important for a short pulse. For a long pulse, we identify a term that gives the dominant contribution even if the intensity is only moderately high, a0≳1, which is an experimentally important regime where the standard locally constant field (LCF) approximation cannot be used. We show that the spectrum has a richer structure at a0∼1, compared to the LCF regime a0≫1. We study the convergence to LCF as a0 increases and how this convergence depends on the momentum of the initial electron. We also identify the terms that dominate at high energy.

Permalink: https://www.hzdr.de/publications/Publ-33160
Publ.-Id: 33160


Large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi

He, Y.; Gayles, J.; Yao, M.; Helm, T.; Reimann, T.; Strocov, V. N.; Schnelle, W.; Nicklas, M.; Sun, Y.; Fecher, G. H.; Felser, C.

A large non-saturating magnetoresistance has been observed in several nonmagnetic topological Weyl semi-metals with high mobility of charge carriers at the Fermi energy. However, ferromagnetic systems rarely display a large magnetoresistance because of localized electrons in heavy d bands with a low Fermi velocity. Here, we report a large linear non-saturating magnetoresistance and high mobility in ferromagnetic MnBi. MnBi, unlike conventional ferromagnets, exhibits a large linear non-saturating magnetoresistance of 5000% under a pulsed field of 70 T. The electrons and holes’ mobilities are both 5000 cm2V−1s−1 at 2 K, which are one of the highest for ferromagnetic materials. These phenomena are due to the spin-polarised Bi 6p band’s sharp dispersion with a small effective mass. Our study provides an approach to achieve high mobility in ferromagnetic systems with a high Curie temperature, which is advantageous for topological spintronics.

Permalink: https://www.hzdr.de/publications/Publ-33159
Publ.-Id: 33159


Approximating higher-order nonlinear QED processes with first-order building blocks

Dinu, V.; Torgrimsson, G.

Higher-order tree-level processes in strong laser fields, i.e., cascades, are in general extremely difficult to calculate, but in some regimes the dominant contribution comes from a sequence of first-order processes, i.e., nonlinear Compton scattering and nonlinear Breit-Wheeler pair production. At high intensity the field can be treated as locally constant, which is the basis for standard particle-in-cell codes. However, the locally-constant-field (LCF) approximation and these particle-in-cell codes cannot be used when the intensity is only moderately high, which is a regime that is experimentally relevant. We have shown that one can still use a sequence of first-order processes to estimate higher orders at moderate intensities provided the field is sufficiently long. An important aspect of our new “gluing” approach is the role of the spin and polarization of intermediate particles, which is more nontrivial compared to the LCF regime.

Permalink: https://www.hzdr.de/publications/Publ-33158
Publ.-Id: 33158


The High Energy Density Scientific Instrument at the European XFEL

Zastrau, U.; Appel, K.; Bähtz, C.; Bähr, O.; Batchelor, L.; Berghäuser, A.; Banjafar, M.; Brambrink, E.; Cerantola, V.; Cowan, T.; Damker, H.; Dittrich, S.; Di Dio Cafiso, S. D.; Dreyer, J.; Engel, H.-O.; Feldmann, T.; Findeisen, S.; Foese, M.; Fulla-Marsa, D.; Göde, S.; Hassan, M. K. Y.; Hauser, J.; Herrmannsdörfer, T.; Höppner, H.; Kaa, J.; Kaever, P.; Knöfel, K.; Konopkova, Z.; Laso García, A.; Liermann, H.-P.; Mainberger, J.; Makita, M.; Martens, E.-C.; McBride, E. E.; Möller, D.; Nakatsutsumi, M.; Pelka, A.; Plueckthun, C.; Prescher, C.; Preston, T. R.; Röper, M.; Schmidt, A.; Seidel, W.; Schwinkendorf, J.-P.; Schoelmerich, M. O.; Schramm, U.; Schropp, A.; Strohm, C.; Sukharnikov, K.; Talkovski, P.; Thorpe, I.; Toncian, M.; Toncian, T.; Wollenweber, L.; Yamamoto, S.; Tschentscher, T.

The European XFEL delivers up to 27000 intense (>1012 photons) pulses per second, of ultrashort (≤50 fs) and transversely coherent X-ray radiation, at a maximum repetition rate of 4.5 MHz. Its unique X-ray beam parameters enable groundbreaking experiments in matter at extreme conditions at the High Energy Density (HED) scientific instrument. The performance of the HED instrument during its first two years of operation, its scientific remit, as well as ongoing installations towards full operation are presented. Scientific goals of HED include the investigation of extreme states of matter created by intense laser pulses, diamond anvil cells, or pulsed magnets, and ultrafast X-ray methods that allow their diagnosis using self-amplified spontaneous emission between 5 and 25 keV, coupled with X-ray monochromators and optional seeded beam operation. The HED instrument provides two target chambers, X-ray spectrometers for emission and scattering, X-ray detectors, and a timing tool to correct for residual timing jitter between laser and X-ray pulses.

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Permalink: https://www.hzdr.de/publications/Publ-33157
Publ.-Id: 33157


Nonlinear trident in the high-energy limit: Nonlocality, Coulomb field and resummations

Torgrimsson, G.

We study nonlinear trident in laser pulses in the high-energy limit, where the initial electron experiences, in its rest frame, an electromagnetic field strength above Schwinger’s critical field. At lower energies the dominant contribution comes from the “two-step” part, but in the high-energy limit the dominant contribution comes instead from the one-step term. We obtain new approximations that explain the relation between the high-energy limit of trident and pair production by a Coulomb field, as well as the role of the Weizsäcker-Williams approximation and why it does not agree with the high-χ limit of the locally-constant-field approximation. We also show that the next-to-leading order in the large-a0 expansion is, in the high-energy limit, nonlocal and is numerically very important even for quite large a0. We show that the small-a0 perturbation series has a finite radius of convergence, but using Padé-conformal methods we obtain resummations that go beyond the radius of convergence and have a large numerical overlap with the large-a0 approximation. We use Borel-Padé-conformal methods to resum the small-χ expansion and obtain a high precision up to very large χ. We also use newer resummation methods based on hypergeometric/Meijer-G and confluent hypergeometric functions.

Permalink: https://www.hzdr.de/publications/Publ-33156
Publ.-Id: 33156


Nonlinear photon trident versus double Compton scattering and resummation of one-step terms

Torgrimsson, G.

We study the photon trident process, where an initial photon turns into an electron-positron pair and a final photon under a nonlinear interaction with a strong plane-wave background field. We show that this process is very similar to double Compton scattering, where an electron interacts with the background field and emits two photons. We also show how the one-step terms can be obtained by resumming the small- and large-\chiχ expansions. We consider a couple of different resummation methods, and also propose new resummations (involving Meijer-G functions) which have the correct type of expansions at both small and large \chiχ. These new resummations require relatively few terms to give good precision.

Permalink: https://www.hzdr.de/publications/Publ-33155
Publ.-Id: 33155


Loops and polarization in strong-field QED

Torgrimsson, G.

In a previous paper we showed how higher-order strong-field-QED processes in long laser pulses can be approximated by multiplying sequences of ‘strong-field Mueller matrices’. We obtained expressions that are valid for arbitrary field shape and polarization. In this paper we derive practical approximations of these Mueller matrices in the locally-constant- and the locally-monochromatic-field regimes. The spin and polarization can also change due to loop contributions (the mass operator for electrons and the polarization operator for photons). We derive Mueller matrices for these as well, for arbitrary laser polarization and arbitrarily polarized initial and final particles.

Permalink: https://www.hzdr.de/publications/Publ-33154
Publ.-Id: 33154


Resummation of Quantum Radiation Reaction in Plane Waves

Torgrimsson, G.

We propose a new approach to obtain the momentum expectation value of an electron in a high-intensity laser, including multiple photon emissions and loops. We find a recursive formula that allows us to obtain the O(αn) term from O(αn-1), which can also be expressed as an integro-differential equation. In the classical limit we obtain the solution to the Landau-Lifshitz equation to all orders. We show how spin-dependent quantum radiation reaction can be obtained by resumming both the energy expansion as well as the α expansion.

Permalink: https://www.hzdr.de/publications/Publ-33153
Publ.-Id: 33153


Resummation of quantum radiation reaction and induced polarization

Torgrimsson, G.

In a previous paper we proposed a new method based on resummations for studying radiation reaction of an electron in a plane-wave electromagnetic field. In this paper we use this method to study the electron momentum expectation value for a circularly polarized monochromatic field with a0=1, for which standard locally constant-field methods cannot be used. We also find that radiation reaction has a significant effect on the induced polarization, as compared to the results without radiation reaction, i.e., the Sokolov-Ternov formula for a constant field, or the zero result for a circularly monochromatic field. We also study the Abraham-Lorentz-Dirac equation using Borel-Padé resummations.

Permalink: https://www.hzdr.de/publications/Publ-33152
Publ.-Id: 33152


High-field soft-x-ray dichroism of a hard ferrimagnet with easy-plane anisotropy

Yamamoto, S.; Gorbunov, D.; Diaz-Ortega, I. F.; Miyata, A.; Kihara, T.; Kotani, Y.; Nakamura, T.; Mushnikov, N. V.; Andreev, A. V.; Nojiri, H.; Wosnitza, J.

We performed soft x-ray spectroscopic studies of the ferrimagnet TbFe5Al7 with strong easy-plane anisotropy in pulsed magnetic fields up to 29 T along with bulk magnetization and magnetostriction measurements. We observed pronounced amplitude changes of x-ray magnetic circular dichroism and x-ray absorption spectra at the field-induced magnetic transition. This microscopically evidences the simultaneous rotation of the Tb 4 f and Fe 3d magnetic moments from a collinear ferrimagnetic order along the [100] axis to a state with the moments close to [010], the other easy-axis direction of the tetragonal lattice in magnetic fields applied along the [100] axis. We determined the magnetic-anisotropy constant of TbFe5Al7 by simulating the high-field macro- and microscopic magnetization process using a two-sublattice model.

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Permalink: https://www.hzdr.de/publications/Publ-33151
Publ.-Id: 33151


Neutron diffraction of field-induced magnon condensation in the spin-dimerized antiferromagnet Sr3Cr2O8

Gazizulina, A.; Quintero-Castro, D. L.; Wang, Z.; Duc, F.; Bourdarot, F.; Prokes, K.; Schmidt, W.; Daou, R.; Zherlitsyn, S.; Islam, N.; Kolnes, N. H.; Kademane, A. B.; Schilling, A.; Lake, B.

In this work, we investigate the evolution and settling of magnon condensation in the spin-1/2 dimer system Sr3Cr2O8 using a combination of magnetostriction in pulsed fields and inelastic neutron scattering in a continuous magnetic field. The magnetic structure in the Bose-Einstein condensation phase was probed by neutron diffraction in pulsed magnetic fields up to 39 T. The magnetic structure in this phase was confirmed to be an XY-antiferromagnetic structure validated by irreducible representational analysis. The magnetic phase diagram as a function of an applied magnetic field for this system is presented. Furthermore, zero-field neutron diffraction results indicate that dimerization plays an important role in stabilizing the low-temperature crystal structure.

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Permalink: https://www.hzdr.de/publications/Publ-33150
Publ.-Id: 33150


Drastic reduction of the R-Fe exchange in interstitially modified (Nd, Ho)2Fe14B compounds probed by megagauss magnetic fields

Kostyuchenko, N. V.; Tereshina, I. S.; Tereshina-Chitrova, E. A.; Ivanov, L. A.; Paukov, M.; Gorbunov, D.; Andreev, A. V.; Doerr, M.; Politova, G. A.; Zvezdin, A. K.; Veselova, S. V.; Pyatakov, A. P.; Miyata, A.; Drachenko, O.; Portugall, O.

In this paper, the full magnetization process demonstrated by the series of ferrimagnetic intermetallic compounds (Nd, Ho)2Fe14B and Ho2FeB and their hydrides with the maximum possible hydrogen content (for the given crystal structure type) is studied theoretically and experimentally using megagauss magnetic fields. We observe field-induced phase transitions from the initial ferrimagnetic to the forced-ferromagnetic state in magnetic fields up to 130 T and describe the magnetization process analytically.We find a drastic decrease of the critical transition fields in the hydrogenated compounds. This is due to extremely strong, nearly twofold reduction of the R-Fe intersublattice exchange interaction because of the combined substitution and hydrogenation effects. A comparative analysis of the magnetization behavior for the system Ho2Fe17-H is also performed.

Permalink: https://www.hzdr.de/publications/Publ-33149
Publ.-Id: 33149


Highly sensitive band structure of the Stoner-enhanced Pauli paramagnet SrCo2P2

Götze, K.; Kraft, I.; Klotz, J.; Förster, T.; Uhlarz, M.; Lorenz, V.; Bergmann, C.; Prots, Y.; Bruin, J. A. N.; McCollam, A.; Sheikin, I.; Wosnitza, J.; Geibel, C.; Rosner, H.

The compound SrCo2P2 is a Pauli paramagnet very close to ferromagnetic order. To study its electronic structure in close vicinity to the Fermi level, we report measurements of the de Haas–van Alphen effect in magnetic fields up to 35 T in combination with density-functional-theory band-structure calculations in different approximations. The resulting electronic band structure not only depends significantly on the choice of the functional, but also crucially on the exact values of the structural parameters that have been determined at low temperatures by synchrotron x-ray diffraction. We find the best correspondence between the measured and the calculated de Haas–van Alphen frequencies for the general gradient approximation functional and the structural parameters that were determined at 10 K. Although SrCo2P2 crystallizes in the uncollapsed tetragonal structure with a large P-P distance between the CoP2 layers, we observe a rather three-dimensional Fermi-surface topology. We obtain a mass-enhancement factor of about 2 deduced from the ratio between experimental and calculated quasiparticle masses. The temperature dependence of the structural parameters leads to a significant reduction of the electronic density of states at the Fermi level and in comparison with the measured Sommerfeld coefficient to an overall mass renormalization in line with our experiment.

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Permalink: https://www.hzdr.de/publications/Publ-33148
Publ.-Id: 33148


Multiple field-induced phases in the frustrated triangular magnet Cs3Fe2Br9

Brüning, D.; Fröhlich, T.; Gorkov, D.; Cisarova, I.; Scurschii, I.; Rossi, L.; Bryant, B.; Wiedmann, S.; Meven, M.; Ushakov, A.; Streltsov, S. V.; Khomskii, D.; Becker, P.; Bohatý, L.; Braden, M.; Lorenz, T.

The recently discovered material Cs3Fe2Br9 contains Fe2Br9 bi-octahedra forming triangular layers with hexagonal stacking along the c axis. In contrast to isostructural Cr-based compounds, the zero-field ground state is not a nonmagnetic S = 0 singlet-dimer state. Instead, the Fe2Br9 bi-octahedra host semiclassical S = 5/2 Fe3+ spins with a pronounced easy-axis anisotropy along c, and interestingly, the intradimer spins are ordered ferromagnetically. The high degree of magnetic frustration due to (various) competing intradimer and interdimer couplings leads to a surprisingly rich magnetic phase diagram. The zero-field ground state is already reached via an intermediate phase, and the high-field magnetization and thermal expansion data for H ǀǀ c identify 10 different ordered phases. Among them are phases with constant magnetization of 1/3 , respectively 1/2, of the saturation value, and several transitions are strongly hysteretic with pronounced length changes, reflecting strong magnetoelastic coupling.

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Permalink: https://www.hzdr.de/publications/Publ-33147
Publ.-Id: 33147


Folding of laser-cut templates with plasmonic functionalized surfaces into micro cubes

Lorenz, P.; Yu, Y.; Franz, R.; Petersen, C.; Zajadacz, J.; Ehrhardt, M.; Lecrivain, G.; Kirchner, R.; Zimmer, K.

Functional 3D microstructures offer enhanced functionalities but need specific fabrication schemas. One approach is (self) folding of planar structures that enable to apply traditional microelectronic-based fabrication schemas and allows the cost-effective fabrication of such 3D microstructures. Following this approach we combined templating lithographic techniques for plasmonic gold patterns with laser patterning and subsequent folding of the planar structures. Hence, the nanopattern design and the cut out shape can be separated and optimized independently. The micro cubes were realized in polyimide foil which was attached to a wafer for patterning the plasmonic structures. Thereafter the laser patterning and the folding procedure follows. Two different folding concepts was studied: suction and water droplet supported folding.

  • Poster
    Micro and Nano Engineering Conference, 20.-23.09.2021, Turin, Italy

Permalink: https://www.hzdr.de/publications/Publ-33146
Publ.-Id: 33146


Übertragung von SARS Coronaviren über die Luft – Von der Grundlagenforschung zu effizienten Luftreinigungssystemen

Lecrivain, G.; Hampel, U.

Neben Tröpfchen- und Schmierinfektion ist der nach derzeitiger Kenntnis effektivste Übertragungsweg des Corona-Virus der Aerosoltransport. Diese Formen der Übertragung führen leicht zu sogenannten Superspreading-Ereignissen. Solange keine wirksamen Impfstoffe verfügbar sind, sind strenge Hygieneregeln, wie das Tragen von Masken, Abstandhalten, häufiges Reinigen und Desinfizieren von Händen und Oberflächen sowie ausreichendes Lüften von Räumen, einzig wirksame Maßnahmen gegen eine Virenausbreitung. Da der Erfolg solcher Maßnahmen stark vom Faktor Mensch abhängt, ist eine der wesentlichen Erkenntnisse aus dem bisherigen Pandemieverlauf die, dass es dringend notwendig ist, wirksame, sichere und bezahlbare Technologien zur Verhinderung der Virenausbreitung zu entwickeln. Damit können drastische Maßnahmen, wie öffentliche Schließungen und Quarantäne, verhindert werden. Dies gilt nicht nur für die aktuelle, sondern auch für zukünftige Pandemien dieser Art. Das Vorhaben CORAERO der Helmholtz-Gemeinschaft zielt darauf ab, mittels interdisziplinärer wissenschaftlich-technologischer Zusammenarbeit signifikante Beiträge zum Erkenntnisgewinn bezüglich des aerosolgetriebenen Virustransports sowie zur Entwicklung von Technologien für eine effiziente physikalische Virenbekämpfung zu leisten. Es verbindet Wissenschaftler/innen aus der Virologie, der Medizin, der angewandten Physik, der Chemie, der Materialforschung und des Ingenieurwesens, schafft neues Wissen und entwickelt Technologien entlang der Infektionskette von der Aerosolentstehung im Atemweg bis zur effektiven Zerstörung des Virus durch Luftbehandlung in öffentlichen Räumen wie Schulen, Betrieben, Passagierfahrzeugen oder Konzerthallen

Keywords: Corona-Virus; Tröpfchen; Pandemieverlauf; Aerosolentstehung

  • Poster
    13. Dresdner Kolloquium zur Luftreinhaltung, 14.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33145
Publ.-Id: 33145


Magnetic phase diagram, magnetoelastic coupling, and Grüneisen scaling in CoTiO3

Hoffmann, M.; Dey, K.; Werner, J.; Bag, R.; Kaiser, J.; Wadepohl, H.; Scurschii, I.; Abdel-Hafiez, M.; Singh, S.; Klingeler, R.

High-quality single crystals of CoTiO3 are grown and used to elucidate in detail structural and magnetostructural effects by means of high-resolution capacitance dilatometry studies in fields up to 15 T which are complemented by specific heat and magnetization measurements. In addition, we refine the single-crystal structure of the ilmenite (R¯3) phase. At the antiferromagnetic ordering temperature TN pronounced λ-shaped anomaly in the thermal expansion coefficients signals shrinking of both the c and b axes, indicating strong magnetoelastic coupling with uniaxial pressure along c yielding six times larger effect on TN than pressure applied in-plane. The hydrostatic pressure dependency derived by means of Grüneisen analysis amounts to ∂TN/∂ p ≈ 2.7(4) K/GPa. The high-field magnetization studies in static and pulsed magnetic fields up to 60 T along with high-field thermal expansion measurements facilitate in constructing the complete anisotropic magnetic phase diagram of CoTiO3. While the results confirm the presence of significant magnetodielectric coupling, our data show that magnetism drives the observed structural, dielectric, and magnetic changes both in the short-range ordered regime well above TN as well as in the long-range magnetically ordered phase.

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Permalink: https://www.hzdr.de/publications/Publ-33144
Publ.-Id: 33144


Evidence of collision-induced effects in particle resuspension

Banari, A.; Henry, C.; Lecrivain, G.

This study addresses the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here set to about 10 % of the field of view, we report two distinct detachment mechanisms. At relatively low flow velocities, few loosely adhering particles move on the wall to eventually collide with neighboring particles resulting in a clustered resuspension. At higher fluid velocities, mostly individual particles resuspend due to their interaction with the turbulent flow. The resuspension curve, showing the remaining particle fraction as a function of the flow velocity, exhibits a strong bimodal character, that has not been reported so far.

Keywords: Multiphase flow; Particle resuspension; Collision-propagation

  • Lecture (Conference)
    35th French Aerosol Congress, 26.-27.01.2022, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-33143
Publ.-Id: 33143


Sputter yields of rough surfaces: Importance of the mean surface inclination angle from nano- to microscopic rough regimes

Cupak, C.; Szabo, P. S.; Biber, H.; Stadlmayr, R.; Grave, C.; Fellinger, M.; Brötzner, J.; Wilhelm, R. A.; Möller, W.; Mutzke, A.; Moro, M. V.; Aumayr, F.

The roughness of a surface is known to have a strong influence on the sputtering process. Commonly used 1D Monte Carlo codes for calculating sputter yields show good agreement with experimental data only for comparably flat surfaces, whereas local ion incidence angles, shadowing and redeposition influence the sputter yields in both magnitude and angular dependence on rough surfaces. In the present work, we therefore investigated tungsten samples of largely different roughness, characterised by atomic force and confocal microscopy. A highly sensitive quartz crystal microbalance was used to determine sputter yields during ion irradiation. Low ion fluences were applied to ensure that the surface morphology did not change during irradiation. The results were used to benchmark our new ray-tracing simulation code SPRAY, which can take microscopy images without limitations in size as input. SPRAY was furthermore applied to perform systematic simulations for artificially roughened and computer-generated surfaces. A clear result was that the governing parameter for description of the sputtering behaviour is the mean value of the surface inclination angle distribution, rather than the commonly used root mean square roughness. Our simulations show that this parameter is universally applicable for a wide range of different surface structures.

Keywords: Quartz crystal microbalance; Sputtering; Sputtering simulation; Surface roughness; Tungsten

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Permalink: https://www.hzdr.de/publications/Publ-33142
Publ.-Id: 33142


Gas-dynamic density downramp injection in a beam-driven plasma wakefield accelerator

Couperus Cabadağ, J. P.; Pausch, R.; Schöbel, S.; Bussmann, M.; Chang, Y.-Y.; Corde, S.; Debus, A.; Ding, H.; Dopp, A.; Foerster, F. M.; Gilljohann, M.; Haberstroh, F.; Heinemann, T.; Hidding, B.; Karsch, S.; Köhler, A.; Kononenko, O.; Knetsch, A.; Kurz, T.; Martinez De La Ossa, A.; Nutter, A.; Raj, G.; Steiniger, K.; Schramm, U.; Ufer, P.; Irman, A.

We present the experimental demonstration of density downramp injection at a gas-dynamic shock in a beam-driven plasma accelerator.
The ultrashort driver electron beam with a peak-current exceeding 10 kA allows operation in the blowout regime and enables injection of electron witness bunches at gentle density ramps, i.e. longer than the plasma wavelength, which nurtures prospects for ultralow bunch emittance.
By precision control over the position of injection we show that these bunches can be energy-tuned in acceleration gradients of near 120 GV/m.

Keywords: PWFA; LWFA; Downramp injection; Particle-in-cell; Particle acceleration in plasmas; Plasma-beam interactions; Novel acceleration methods; Beam-driven plasma acceleration

Permalink: https://www.hzdr.de/publications/Publ-33140
Publ.-Id: 33140


Recent Advances Towards a Flow Pattern Adaptive Hybrid Multifield Two-Fluid Model

Schlegel, F.; Krull, B.; Lehnigk, R.; Meller, R.; Petelin, G.; Tekavcic, M.

Physical phenomena in industrial gas-liquid flows typically span a wide range of length and time scales. Individual flow regimes are usually described using a tailored approach, prohibiting simulation of transitions and interactions. In order to address these challenges, a hybrid multiphase model is established by combining the Euler-Euler model with the Volume-of-Fluid (VOF) model. Interactions and transitions between different morphologies and scales require special attention, which is accounted for with dedicated models. This work gives an overview over recent advances towards a fully scalable hybrid multiphase model.
In particular, large interfaces might be represented on coarse numerical grids. With a usual VOF model this typically leads to over-prediction of interfacial shear stress, resulting in a deteriorated prediction of interface dynamics. By accounting for the resolved part of the flow in the vicinity of an interface, the interfacial drag between both phases is controlled. In that way the phases may slip along each other in the direction parallel to the interface surface, improving the prediction, i.e., of interface shape or of bubble rising velocity.
Furthermore, each disperse structure needs to be resolved as soon as it becomes large enough in relation to the local cell sizes. Unresolved bubbles may coalesce, grow, or enter highly-refined mesh regions, so that they should no longer be treated as disperse. Therefore, a transition to a continuous representation is realised, to make optimal use of the available numerical degrees of freedom. A necessary condition for such a transition is a stable behaviour of the disperse model on unusual fine meshes.
Another important aspect of the model is to track the number and size of dispersed phase particles. A class-method based solution approach was implemented, providing complete information about the size distribution, a necessity for modelling the number-conservative transition between dispersed and resolved structures. However, the associated computational cost is significant. Fortunately, the adopted solution procedure could be parallelised by outsourcing it to graphics processing units, which leads to a significant improvement in performance.
The hybrid model is implemented in OpenFOAM with strong focus on sustainable research, including a state-of-the-art IT approach. Both the source code and a comprehensive suite of simulation cases are publicly available.

Keywords: Hybrid Multiphase Model; CFD; Morphology Transitions; Euler-Euler; Volume-of-Fluid

  • Poster (Online presentation)
    18th Multiphase Flow Conference and Short Course, 08.-12.11.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33139
Publ.-Id: 33139


Berechnungsverfahren für Zweiphasenströmungen

Höhne, T.

Two-phase flows occur in many industrial relevant processes in
power plants,
chemical engineering,
oil and gas industries and others.

Reliable predictions of the flow characteristics are important for the design of the facilities, the optimization of processes and safety analyses.

Experimental results are often hardly transferable to modified geometries, flow condition or scales.

need for reliable numerical simulations
In general fluid flow is 3D Computation Fluid Dynamics - CFD

Keywords: CFD; Multiphase flow; AIAD; GENTOP

  • Invited lecture (Conferences) (Online presentation)
    Numerische Methoden in der Lebensmitteltechnologie, Biotechnologie und chemischen Verfahrenstechnik, 27.-29.09.2021, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33138
Publ.-Id: 33138


Data publication: Effects of surface roughness and mineralogy on the sorption of Cm(III) on crystalline rock

Demnitz, M.; Molodtsov, K.; Schymura, S.; Schierz, A.; Müller, K.; Jankovsky, F.; Havlova, V.; Stumpf, T.; Schmidt, M.

In the following we have compiled the data used in publication (mappings, taken pictures and measurements) as well as the used python scripts.

Keywords: curium; luminescence; crystalline rock; granite; sorption; correlative spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-33137
Publ.-Id: 33137


Holographic bottomonium formation in a cooling strong-interaction medium at finite baryon density

Zöllner, R.; Kämpfer, B.

The shrinking of the bottomonium spectral function towards narrow quasi-particle states in a cooling strong-interaction medium at finite baryon density is followed within a holographic bottom- up model. The 5-dimensional Einstein-dilaton-Maxwell background is adjusted to lattice-QCD results of sound velocity and susceptibilities. The zero-temperature bottomonium spectral function is adjusted to experimental $\Upsilon$ ground-state mass and first radial excitations. At baryo-chemical potential $\mu_B = 0$, these two pillars let emerge the narrow quasi-particle state of the $\Upsilon$ ground state at a temperature of about 150 MeV. Excited states are consecutively formed at lower temperatures by about 10 (20) MeV for the 2S (3S) vector states. The baryon density, i.e. $\mu_B$ > 0, pulls that formation pattern to lower temperatures. At $\mu_B = 200$ MeV, we find a shift by about 15 MeV.

Keywords: Bottomonium; AdS/CFT; lattice-QCD thermodynamics

Permalink: https://www.hzdr.de/publications/Publ-33136
Publ.-Id: 33136


Targeting acute myeloid leukemia using the RevCAR platform: a programmable, switchable and combinatorial strategy

Kittel-Boselli, E.; González Soto, K. E.; Loureiro, L. R.; Hoffmann, A.; Bergmann, R.; Arndt, C.; Koristka, S.; Mitwasi, N.; Kegler, A.; Bartsch, T.; Berndt, N.; Altmann, H.; Fasslrinner, F.; Bornhäuser, M.; Bachmann, M.; Feldmann, A.

Clinical translation of novel immunotherapeutic strategies such as chimeric antigen receptor (CAR) T-cells in acute myeloid leukemia (AML) is still at an early stage. Major challenges in-clude immune escape and disease relapse demanding for further improvements in CAR design. To overcome such hurdles, we have invented the switchable, flexible and programmable adap-tor Reverse (Rev) CAR platform. This consists of T-cells engineered with RevCARs that are pri-marily inactive as they express an extracellular short peptide epitope incapable of recognizing surface antigens. RevCAR T-cells can be redirected to tumor antigens and controlled by bispecif-ic antibodies cross-linking RevCAR T- and tumor cells resulting in tumor lysis. Remarkably, the RevCAR platform enables combinatorial tumor targeting following Boolean logic gates. We herein show for the first time the applicability of the RevCAR platform to target myeloid ma-lignancies like AML. Applying in vitro and in vivo models, we have proven that AML cell lines as well as patient-derived AML blasts were efficiently killed by redirected RevCAR T-cells target-ing CD33 and CD123 in a flexible manner. Furthermore, by targeting both antigens, a Boolean AND gate logic targeting could be achieved using the RevCAR platform. These accomplish-ments pave the way towards an improved and personalized immunotherapy for AML patients.

Keywords: chimeric antigen receptor (CAR); tumor immunotherapy; combinatorial gated targeting; acute myeloid leukemia (AML)

Permalink: https://www.hzdr.de/publications/Publ-33135
Publ.-Id: 33135


Positron energy distribution in factorized trident process

Titov, A.; Hernandez Acosta, U.; Kämpfer, B.

We estimate the energy distribution of positrons produced in the interaction of ultra-relativistic electrons with a high-intensity laser beam. The underlying trident process is factorized on the probabilistic level. That is, we deploy a two-step mechanism for the formation of electron-positron pairs. In the first step, a high-energy photon is produced as a result of nonlinear Compton scattering. In the second step, an electron-positron pair is created by the nonlinear (multi-photon) Breit-Wheeler process.

Keywords: trident; nonlinear Compton scattering; nonlinear Breit-Wheeler pair production; strong-field QED

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Publ.-Id: 33134


Tungsten Oxide/Reduced Graphene Oxide Aerogel with Low-Content Platinum as High-Performance Electrocatalyst for Hydrogen Evolution Reaction

Li, Y.; Jiang, K.; Yang, J.; Zheng, Y.; Hübner, R.; Ou, Z.; Dong, X.; He, L.; Wang, H.; Li, J.; Sun, Y.; Lu, X.; Zhuang, X.; Zheng, Z.; Liu, W.

Designing cost-effective, highly active, and durable platinum (Pt)-based electrocatalysts is a crucial endeavor in electrochemical hydrogen evolution
reaction (HER). Herein, the low-content Pt (0.8 wt%)/tungsten oxide/reduced graphene oxide aerogel (LPWGA) electrocatalyst with excellent HER activity and durability is developed by employing a tungsten oxide/reduced graphene oxide aerogel (WGA) obtained from a facile solvothermal process as a support, followed by electrochemical deposition of Pt nanoparticles. The WGA support with abundant oxygen vacancies and hierarchical pores plays the roles of anchoring the Pt nanoparticles, supplying continuous mass transport and electron transfer channels, and modulating the surface electronic state of Pt, which endow the LPWGA with both high HER activity and durability. Even under a low loading of 0.81 μgPt cm-2, the LPWGA exhibits a high HER activity with an overpotential of 42 mV at 10 mA cm-2, an excellent stability under 10000-cycle cyclic voltammetry and 40 h chronopotentiometry at 10 mA cm-2, a low Tafel slope (30 mV dec-1), and a high turnover frequency of 29.05 s-1 at η = 50 mV, which is much superior to the commercial Pt/C and the low-content Pt/reduced graphene oxide aerogel. This work provides a new strategy to design high-performance Pt-based electrocatalysts with greatly reduced use of Pt.

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Permalink: https://www.hzdr.de/publications/Publ-33133
Publ.-Id: 33133


Development and preliminary evaluation of [18F]JHU94620-d8 for PET imaging of cannabinoid receptors type 2

Moldovan, R. P.

The development PET radioligands for imaging of the cannabinoid type 2 receptors (CB2R) has been intensively explored due to their upregulation in various pathological conditions [1]. Recently, we reported the development of [18F]JHU94620 [2], however, this radioligand suffered from low metabolic stability in vivo. Here, we describe the development of the deuterated analogues [18F]JHU94620-d4 and -d8 as well as their biological evaluation (Figure 1). The precursors for radiofluorination were obtained by coupling 4,5-dimethylthiazol-ylidene-2,2,3,3-tetramethylcyclopropane-1-carboxamide with either d4 or d8 1,4-butanediol-bistosylate and radiofluorinated in the presence of Kryptand K2.2.2. and K2CO3. [18F]JHU94620-d4 and -d8 were obtained in 10% radiochemical yield and >99% radiochemical purity. The fraction of radiometabolites was quantified in mice plasma, brain and spleen of CD1 mice at 30 min p.i. Both [18F]JHU94620-d4 and -d8 demonstrated an improved metabolic stability with 80% intact radioligand detected in the brain vs. 36% for [18F]JHU94620. The CB2 affinity and specificity of [18F]JHU94620-d8 was determined by in vitro binding experiments and a KD(rCB2) of 0.36 nM was determined. Additionally, we evaluated the [18F]JHU94620-d8 uptake by PET-studies into the spleen of healthy rats and in a rat model carrying an adeno-associated viral (AAV2/7) vector expressing hCB2R(D80N) at high densities in the right striatum (hCB2-rs) [3, 4]. Our PET study with [18F]JHU94620-d8 revealed a rCB2 specific uptake into the spleen (AUC0-30min = 33 vs. 17 SUV min after blocking with GW405833). In the hCB2-rs model we could show a target specific uptake of [18F]JHU94620-d8 with a constant SUV of 6.7±0.3 from 6 to 60 min p.i. and an SUVr (right striatum-to-cerebellum) of 43±7at 60 min p.i., as well as a reversible binding in displacement studies. Thus, [18F]JHU94620-d8 is a new PET tracer with improved metabolic stability and excellent ability to image the CB2 receptors in-vivo. Its further evaluation is underway.

  • Invited lecture (Conferences) (Online presentation)
    DPhG Annual Meeting 2021 Trends and Perspectives in Pharmaceutical Sciences, 30.09.2021, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-33132
Publ.-Id: 33132


X-ray Spectroscopies with increased resolution: principles and perspectives

Amidani, L.

In was only in the early 90s that the use of hard X-ray emission spectrometers to collect X-ray Absorption spectra was first suggested [1]. X-ray emission spectrometers based on Bragg’s law achieve resolutions below 2 eV, a huge improvement compared to solid-state detectors whose resolution is only 150 – 200 eV. With this technical improvement, the characteristic fluorescence of the excited atoms is collected with a resolution below the core-hole lifetime broadening, resulting in better-resolved XAS spectra [2]. Since then, the use of X-ray Spectroscopies with improved resolution exploded and dedicated synchrotron beamlines multiplied. Nowadays, these techniques are largely exploited in many diverse fields of science.
Lanthanides and actinides are among the elements that profit the most of the improved resolution because of their large core-hole lifetime broadenings. Indeed, the demonstration of principle was done on Dy L3 edge XANES [1]. For actinides, the resolution at L3 edge is largely improved, but the biggest boost was given to M4,5 edges, whose conventional XANES are almost featureless. These edges probe directly the 5f states. With better-resolved spectra, the oxidation state can be easily determined and the spectral features that were invisible before bring information about the local coordination and the charge exchange with ligands [3,4].
The information encrypted in these spectra is enormous. Improved resolution makes it more readily available by disclosing details and allowing smaller differences to be appreciated. However, the interpretation often represent the bottleneck to the extraction of relevant information. In this respect, theoretical simulations are fundamental. Nowadays, we have several user-friendly codes that interprets the spectra starting from different approaches, focusing on the intra-atomic interactions or favouring the multi-atomic picture of the system studied.
In this talk, I will briefly introduce some of the techniques exploiting the improved resolution and then focus on their application to actinide science. I will present few examples illustrating the high potential of these techniques and the approach we use in our group to interpret the data [5–7].

References:

[1] K. Hämäläinen et al., Phys. Rev. Lett. 67, 2850 (1991).
[2] P. Glatzel et al., J. Electron Spectrosc. Relat. Phenom. 188, 17 (2013).
[3] K. O. Kvashnina et al., Phys. Rev. Lett. 111, 253002 (2013).
[4] K. O. Kvashnina et al., J. Electron Spectrosc. Relat. Phenom. 194, 27 (2014).
[5] L. Amidani et al., Phys. Chem. Chem. Phys. 21, 10635 (2019).
[6] K. O. Kvashnina et al., Angew. Chem. Int. Ed. 58, 17558 (2019).
[7] A. S. Kuzenkova et al., Carbon 291 (2020).

  • Invited lecture (Conferences) (Online presentation)
    AVS 67, 24.-29.10.2021, Charlotte, USA

Permalink: https://www.hzdr.de/publications/Publ-33131
Publ.-Id: 33131


Instantaneous Frequency representation used for CPA laser simulation

Oksenhendler, T.; Bock, S.; Schramm, U.

We present a novel intuitive graphical method for the simulation of non-linear effects on stretched pulses characterized by a large time-bandwidth product. By way of example, it allows precise determination of effects occurring in CPA (chirped pulse amplification) laser chains, such as the pre-pulse generation by the non-linear Kerr effect. This method is not limited to first order dispersion and can handle all resulting distortions of the generated pre-pulse.

Keywords: ultra-short laser pulses; laser pulse contrast; high-power laser

Permalink: https://www.hzdr.de/publications/Publ-33130
Publ.-Id: 33130


Tests of the detector system for the Stopping Target Monitor of the MU2E experiment in a high flux pulsed gamma beam

Alvarez, C.; Chen, J.; Edmonds, A.; Ferrari, A.; Huang, S.; Keshavarzi, A.; Knodel, O.; Koltick, D.; Lancaster, M.; Miller, J. P.; Müller, S.; Popp, J. L.; Rachamin, R.; Simic, M.; Tickle, S.; Ufer, R.; Voigt, M.

This dataset contains data generated with LaBr and Nal detector (DSPEC and oszilloscope data) at the gELBE beam. The gELBE pulsed gamma beam to test the detector system for the Stopping Target Monitor of the MU2E experiment. The gELBE pulsed gamma beam with narrow pulses set to about 600 kHz repetition rate - the choice of the ELBE CW mode with micropulses at 406 kHz or 812.5 kHz is ideal in our case- is the unique facility in the world suited to study the performance of the Stopping Target Monitor detector of the Mu2e Experiment. The STM monitor has the crucial role to normalize the charged lepton flavor muon conversion rate in the Mu2e experiment. The ability to operate at high rate in presence of background is crucial. We have at ELBE the unique possibility to validate the final methodology that will be employed by the STM detector.

Keywords: dataset; detector; Stopping Target Monitor (STM); MU2E; gELBE; Data Management; DAQ; muon conversion

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Permalink: https://www.hzdr.de/publications/Publ-33129
Publ.-Id: 33129


Synthesis and Pharmacological Evaluation of 1,8-Naphythyridin-2(1H)-one-3-carboxamides Derivatives as Cannabinoid Receptor Type 2 (CB2R) Ligands

Kaur, S.

The primary aim of the present work was to develop fluorinated containing CB2R
ligands based on the lead compound 26 (Figure 10), reported by Lucchesi et al. with
a binding affinity of Ki(CB2R)< 0.67 nM and Ki(CB1R)>5140 nM [91]. Although the
lead compound 26 had a remarkable binding activity it has rather unfavorable
pharmacological properties (cLogP = 4.99 and MW = 459.52 g/mol). Most of the
compounds with cLogP>5 and MW >500 g/mol have poor absorption due to low
solubility and are also unable to cross BBB resulting in poor pharmacokinetics.
Therefore, this master thesis was aimed to synthesize new derivatives based on the
lead compound 26 with modifications to retain or further increase the CB2R binding
affinity and selectivity and improve the pharmacological properties by introducing
substituents containing electronegative atom (fluoro pyridine, fluoro alkoxy, etc) to
make them more polar and thereby also reducing their molecular weight. In general,
the research work was primarily aimed to variously functionalize at N-1 position. In
addition, the newly derivatized compounds should contain a fluorine atom at a
position that allows a facile incorporation of the 18F-label. The cLogP of the planned
derivatives was calculated (ChemDraw 19.0 software) to analyze the effect of
various substituents on the lipophilicity. The substitution of furyl group with a Br at
C-6 position was aimed to increase the hydrophilicity of the lead compound 26
leading to the bromo substituted derivatives with cLogP < 4.5. In order to further
decrease the lipophilicity of the lead compound (26), the replacement of the pfluorobenzyl
at N-1 position with pyridine (cLogP= 3.57) and alkoxy derivatives
(cLogP= 3.72) was planned to synthesize new derivatives (X= R1: furyl, R2:
fluoropyridine, fluoroalkoxy).

  • Master thesis
    Universität Leipzig, 2021
    Mentor: Prof. Bachmann
    78 Seiten

Permalink: https://www.hzdr.de/publications/Publ-33128
Publ.-Id: 33128


Stress-induced modification of gyration dynamics in stacked double-vortex structures studied by micromagnetic simulations

Iurchuk, V.; Körber, L.; Deac, A. M.; Faßbender, J.; Lindner, J.; Kakay, A.

In this paper, using micromagnetic simulations, we investigate the stress-induced frequency tunability of double-vortex nano-oscillators comprising magnetostrictive and non-magnetostrictive ferromagnetic layers separated vertically by a non-magnetic spacer. We show that the relative orientations of the vortex core polarities p1 and p2 have a strong impact on the eigen-frequencies of the dynamic modes. When the two vortices with antiparallel polarities have different eigen-frequencies and the magnetostatic coupling between them is sufficiently strong, the stress-induced magnetoelastic anisotropy can lead to the single-frequency resonant gyration mode of the two vortex cores. Additionally, for the case of parallel polarities, we demonstrate that for sufficiently strong magnetostatic coupling, the magnetoelastic anisotropy leads to the coupled vortex gyration in the chaotic regime and to the lateral separation of the vortex core trajectories. These findings offer a path for achieving a fine control over gyration frequencies and trajectories in vortex-based oscillators via adjustable elastic stress, which can be easily generated and tuned electrically, mechanically or optically.

Keywords: Magnetic vortex; Magnetization dynamics; Magnetoelastic anisotropy; Micromagnetic modelling

Permalink: https://www.hzdr.de/publications/Publ-33127
Publ.-Id: 33127


The Relevance of Electronic Perturbations in the Warm Dense Electron Gas

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

Warm dense matter (WDM) has emerged as one of the frontiers of both experimental and theoretical physics and is challenging traditional concepts of plasma, atomic, and condensed-matter physics. While it has become common practice to model correlated electrons in WDM within the framework of Kohn-Sham density functional theory, quantitative benchmarks of exchange-correlation (XC) functionals under WDM conditions are yet incomplete. Here, we present the first assessment of common XC functionals against exact path-integral Monte Carlo calculations of the harmonically perturbed thermal electron gas. This system is directly related to the numerical modeling of X-Ray scattering experiments on warm dense samples. Our assessment yields the parameter space where common XC functionals are applicable. More importantly, we pinpoint where the tested XC functionals fail when perturbations on the electronic structure are imposed. We indicate the lack of XC functionals that take into account the needs of WDM physics in terms of perturbed electronic structures.

Keywords: density functional theory; quantum monte-carlo; electronic structures; exchange-correlation; warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-33126
Publ.-Id: 33126


Terahertz pump-probe of liquid water at 12.3 THz

Novelli, F.; Hoberg, C.; Adams, E. M.; Klopf, J. M.; Havenith, M.

The dynamical complexity of the hydrogen-bonded water network can be investigated with intense Terahertz (THz) spectroscopy, which can drive the liquid into the nonlinear response regime and probe anharmonicity effects. Here we report single-color and polarization-dependent pump-probe experiments at 12.3 THz on liquid water, exciting the librational mode. By comparing results obtained on a static sample and a free-flowing water jet, we are able to disentangle the distinct contributions by thermal, acoustic, and nonlinear optical effects. We show that the transient transmission by the static water layer on a time scale of hundreds of microseconds can be described by thermal (slow) and acoustic (temperature-dependent) effects. In addition, during pump probe overlap we observe an anisotropic nonlinear optical response. This nonlinear signal is more prominent in the liquid jet than in the static cell, where temperature and density perturbations are more pronounced. Our measurements confirm that the THz excitation resonates with the rotationally-damped motion of water molecules, resulting in enhanced transient anisotropy. This model can be used to explain the non-linear response of water in the frequency range between about 1 and 20 THz.

Keywords: Ultrafast Spectroscopy; THz; FEL

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Permalink: https://www.hzdr.de/publications/Publ-33125
Publ.-Id: 33125


Ginzburg effect in a dielectric medium with dispersion and dissipation

Lang, S.; Sauerbrey, R.; Schützhold, R.; Unruh, W.

As a quantum analog of Cherenkov radiation, an inertial photon detector moving through a medium with constant refractive index n may perceive the electromagnetic quantum fluctuations as real photons if its velocity v exceeds the medium speed of light c/n. For dispersive Hopfield type media, we find this Ginzburg effect to extend to much lower v because the phase velocity of light is very small near the medium resonance. In this regime, however, dissipation effects become important. Via an extended Hopfield model, we present a consistent treatment of quantum fluctuations in dispersive and dissipative media and derive the Ginzburg effect in such systems. Finally, we propose an experimental test.

Keywords: dielectric media; dispersion and dissipation; quantum vacuum phenomena; Ginzburg effect; inertial atom; spontaneous excitation

Permalink: https://www.hzdr.de/publications/Publ-33124
Publ.-Id: 33124


Quality Assessment of CFD Software Using Workflows and Decision Trees

Evdokimov, I.; Hänsch, S.

The present research focuses on the new efforts for leveraging so-called workflows for the management of dozens of CFD validation cases. Proposed workflows are meta-algorithms built on top of the free open-source Snakemake library. They allow manipulation of a growing database that currently contains 66 OpenFOAM cases representing various pipe and bubble column multiphase flows with supplied experimental data. The curated case set also provides documentation files. The proposed approach relies on the utilization of human-provided "keywords" for designing a featured dataset. We also use the method developed earlier for quantification of the fitness of simulated to experimental results. It leverages Fuzzy Logic for combining fitness metrics across various physical fields and produces single performance metric called "Goodness". By transforming metrics into a single crisp output value, the algorithm can assign then and additional categorized property to the simulation result of each individual case such that "degraded", "neutral" or "improved" with regard to available experimental data. At the top level, we demonstrate how successes and failures of case sets may be highlighted and analyzed with Decision Trees. The resulting tree is useful in the quality assessment of the CFD software in the final stages of solver development. Decision Trees provide a transparent way for analyzing diverse CFD validation case sets when investigating top-level CFD model changes (for example, applying a new turbulence model).

Keywords: CFD; OpenFOAM; Decision Trees; workflow

  • Contribution to proceedings
    Ivannikov ISPRAS Open Conference, 02.-03.12.2021, Москва, Россия
    Proceedings of Ivannikov ISPRAS Open Conference: IEEE, 978-1-6654-2330-4
    DOI: 10.1109/ISPRAS53967.2021.00027

Permalink: https://www.hzdr.de/publications/Publ-33123
Publ.-Id: 33123


LDOS/SNAP data for MALA: Aluminium at 298K and 933K

Fiedler, L.; Modine, N. A.; Thompson, A. P.; Cangi, A.; Rajamanickam, S.

# Aluminium data set for Machine Learning applications

This dataset contains DFT inputs, outputs, LDOS data and bispectrum descriptor vectors for an aluminium cell of 256 atoms at varying temperatures and ambient mass density. All simulations that include the LDOS have been performed at an LDOS converged k-grid of 8x8x8 k-points. Calculations which do not inlcude the LDOS have been performed at a total free energy converged k-grid of 4x4x4 k-points (i.e., the total free energy has been converged to 1 meV/atom accuracy).

For each temperature, a .zip file is included in this data set. All .zip files are structured in the same way. For the two largest temperatures, the zip files have been split into smaller portions for easier download; please note that you still have to download all parts of the zip file locally and re-assemble it via the zip command line utility.

Temperature here primarily refers to electronic temperature. However, in almost all cases, the ionic temperature is the same as the electronic temperature. The few cases where this does not hold true are detailed in the individual .zip files by a "different_ionic_temperatures.md" file. If no such file is present in .zip file, then all calculations have been performed at matching electronic and ionic temperatures.

## Authors:

- Fiedler, Lenz (HZDR / CASUS)
- Cangi, Attila (HZDR / CASUS)
- Modine, Normand A. (SNL)
- Thompson, Aidan P. (SNL)
- Rajamanickam, Siva (SNL)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf

CASUS - Center for Advanced Systems Understanding

SNL - Sandial National Laboratories

## Dataset description

- Total size: 1.1 TB
- System: Al256
- Temperature(s): 100K, 200K, 298K, 400K, 500K, 600K, 700K, 800K, 933K
- Mass density(ies): 2.699 gcc
- Crystal Structure: fcc (material mp-134 in the materials project)
- Number of atomic snapshots: 105
    - 30 (100K): 138 GB
    - 3  (200K): 42 GB
    - 10 (298K): 137 GB
    - 3  (400K): 41 GB
    - 20 (500K): 237 GB (zip file split in three portions)
    - 3  (600K): 42 GB
    - 3  (700K): 42 GB
    - 3  (800K): 42 GB
    - 30 (933K): 360 GB (zip file split in four portions)
- Contents:
    - ideal crystal structure: no
    - MD trajectory: no
    - Atomic positions: yno
    - DFT inputs: yes
    - DFT outputs (energies): yes
    - SNAP vectors: yes (partially, see below)
        - dimensions: 200x200x200x94 (last dimension: first three entries are x,y,z coordinates, data size is 91)
        - units: a.u.
    - LDOS vectors: yes (partially, see below)
        - dimensions: 200x200x200x250
        - units: 1/(Ry*Bohr^3)
        - note: LDOS parameters are the same for all sizes of the unit cell
    - trained networks: no


## Dataset structure

For each temperature, a .zip file is included which contains one folder per combination of mass density and number of atoms (only one folder in case of this dataset). Therein, one finds the following folders:

- ldos: holds the LDOS vectors
- bispectrum: holds the SNAP fingerprint vectors
- dft_outputs: holds the outputs from the DFT calculations, i.e. energies in the form of a QE output file
- dft_inputs: holds the inputs for the DFT calculations, in the form of a QE input file
- different_ionic_temperatures.md: If necessary, details which snapshots have an ionic temperature different from the given electronic temperature

Downloads

Permalink: https://www.hzdr.de/publications/Publ-33121
Publ.-Id: 33121


The H2020 McSAFER project: Main goals, technical work program, and status

Sanchez-Espinoza, V. H.; Gabriel, S.; Suikkanen, H.; Telkkä, J.; Valtavirta, V.; Bencik, M.; Kliem, S.; Queral, C.; Farda, A.; Abéeguilée, F.; Smith, P.; van Uffelen, P.; Ammirabile, L.; Seidl, M.; Schneidesch, C.; Grishchenko, D.; Lestani, H.

This paper describes the main objectives, the technical content and the status of the H2020 project entitled “High-performance advanced methods and experimental investigations for the safety evaluation of generic Small Modular Reactors (McSAFER)”. The main pillars of this project is are the combination of safety-relevant thermal hydraulic experiments and numerical simulations of different approaches for safety evaluations of Small Modular Reactors (SMR). It describes the goals and the consortium first. Then, the involved thermal hydraulic test facilities, e.g. COSMOS-H (KIT), HWAT (KTH), and MOTEL (LUT) including the experimental programs. It also outlines the different safety assessment methodologies applied to four different SMR-designs such as the CAREM (CNEA), SMART (KAERI), F-SMR (CEA) and NuScale e.g. the multiscale thermal hydraulic, conventional, low order and high fidelity neutron physical methods applied to demon-strate the inherent safety features of the SMR-core designs under postulated design-basis-accident conditions. Finally, the status of the investigations is shortly discussed followed by the dissemination activities and an outlook.

Keywords: SMR; Multi-physics; Multi-scale; High fidelity; safety evaluation; experiments

Permalink: https://www.hzdr.de/publications/Publ-33120
Publ.-Id: 33120


Implementing HZDR Interactive Baseline Closure Concept Using Fuzzy Logic and Snakemake Workflows

Evdokimov, I.; Hänsch, S.

Euler-Euler multiphase simulations imply numerical challenges and require taking into account many nuances. As pointed out by the authors of the Baseline concept [1], the successful framework for multiphase CFD should reflect a contemporary view on underlying physical phenomena and predict well arbitrary flow configurations. The Baseline methodology [1] specifies a particular meta-algorithm for proposing new sub-models and validating them on a large number of cases (re-interpretation of the original Baseline strategy [1] is shown on the Figure). Although original work presents a clear specification of methodology in general aspects, it lacks the most important definition of “overall improvement”.
The definition of overall improvements is not a single challenge. In addition, simultaneous evaluation of the whole case set becomes important when the number of cases approaches several dozen setups with at least 3 different plots per setup. Meanwhile, human evaluation of all generated plots may be viewed as a serious burden for the research of new better EE models at scale. To address both challenges we propose implementation of the Fuzzy Logic Controller (FLC) and the workflow architecture for scalable simulations and results evaluation of hundreds of cases (potentially).
FLC is applied universally for each case and it ensures that all requirements are fixed. It relies on two metrics calculated for each plot (i.e. void fraction or gas velocity). These are average relative error and Pearson coefficient serving as input crisp values. As an output value, FLC provides the Goodness value which is a crisp output and indicates badly fitting simulation data (with G=0) or perfectly fitting results (with G=1). It uses fuzzy sets “low”, “medium”, and “high” (similar to example in [2]) for each error and Pearson coefficient intervals and helps to achieve better flexibility and clarity than some artificially constructed function.
FLC is an important component of the post-processing Snakemake workflow(more details available in [3]). The combination allows improvements on many levels. Those are 1) explicit specification of the “improvement”, 2) productivity gain in a sense of aggregation of results in a single report, 3) extensible post-processing system which may help to analyze hundreds of cases simultaneously. The demonstrated approach may be also applied to other fields of study where multiparametric models must be tested against multiple simulation setups.

Keywords: fuzzy logic; workflow; CFD; multiphase

  • Open Access Logo Poster (Online presentation)
    Multiphase Flow Workshop 2021, 08.-10.11.2021, Online, Germany

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Permalink: https://www.hzdr.de/publications/Publ-33119
Publ.-Id: 33119


[nat/89Zr][Zr(pypa)]: Thermodynamically Stable and Kinetically Inert Binary Nonadentate Complex for Radiopharmaceutical Applications

Southcott, L.; Li, L.; Brian, P.; Stephan, H.; de Guadalupe Jaraquemeda-Pelaez, M.; Orvig, C.

Abstract
H4pypa is a nonadentate nonmacrocyclic chelator which previously demonstrated high affinity for scandium-44, lutetium-177 and indium-111. Herein, we report the highly stable binary [Zr(pypa)] complex; the non-radioactive complex was synthesized and characterized in detail using high resolution
electrospray-ionization mass spectroscopy (HR-ESI-MS) and various nuclear magnetic resonance spectroscopies (NMR), which revealed a C2v-symmetry of the complex. The geometry of [Zr(pypa)] was further detailed via X-ray crystallography and compared to the structure of [Fe(Hpypa)]. Despite a slow complexation rate with an association half-life of 31.4 h at pH 2 and room temperature, the [Zr(pypa)] complex is thermodynamically stable (log KML = 38.92, pZr =39.4). Radiochemical studies demonstrated quantitative radiolabeling achieved at 10 µM chelatorconcentration within 2 h at 40°C and pH = 7, antibody-compatible conditions. Of utmost importance, [89Zr][Zr(pypa)] is highly kinetically inert upon challenge with excess EDTA and DFO ligands, superior to [89Zr][Zr(DFO)], and maintains inertness towards human serum.

Permalink: https://www.hzdr.de/publications/Publ-33118
Publ.-Id: 33118


Radionuclide transport modelling: The Smart Kd-concept in reactive transport codes

Stockmann, M.; Lu, R.; Gehrke, A.; Montoya, V.; Noseck, U.; Brendler, V.

A key component of performance assessment for radioactive waste repositories in deep geological formations is the long-term prediction of potential radionuclide transport to the geosphere over periods longer than 100,000 years. Radionuclide sorption on minerals (host rocks and geotechnical barriers) is one of the most important retardation process. One big challenge for radionuclide transport calculations with large-scale heterogeneous geochemical compartments is the integration of realistic physico-chemical models and their parameters at affordable computational costs.
In performance assessment, sorption is an important retardation process and typically considered by constant distribution coefficients (Kd) that can be easily included in transport codes. One of the advantage of this approximation is their computational efficiency, but it cannot reflect changes in geochemical conditions. On the other hand, mechanistic surface complexation models used for process understanding can be directly coupled to transport codes with geochemical solvers, but usually only at high computational costs. An effective alternative to the above mentioned approaches is provided by the smart Kd concept (www.smartkd-concept.de) [1, 2], specifically developed to describe variable radionuclide sorption in transport models as consequence of changing geochemical conditions in time.
The fundamental strategy of the smart Kd-concept is to firstly compute multidimensional matrices (namely look-up tables) of distribution coefficients based on surface complexation and cation exchange models. The smart Kd-values are computed for different radionuclides as a function of a wide range of geochemical parameters. Such parameters are typically pH, ionic strength, and dissolved ions, e. g. calcium, carbonate. The look-up table is generated using the geochemical code PhreeqC [3].
The information stored in the look-up table can then be accessed by reactive transport codes at each point in time and space. This approach was already implemented in the d3f++ code [4]. Here, an additional implementation and validation of the smart Kd-approach in OGS6 [5, 6] is demonstrated. For this purpose, three benchmark test were defined with increasing complexity. Complexity is mainly related to the number of components (radionuclides) included in the simulation. Results obtained with the OGS6 were compared with OGS6#PhreeqC3.5.0, PHAST [7] and d³f++.

  • Poster (Online presentation)
    TransRet2020 Workshop, 12.-13.10.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-33117
Publ.-Id: 33117


Data associated with the publication "The relevance of electronic perturbations in the warm dense electron gas"

Moldabekov, Z.; Dornheim, T.; Böhme, M.; Vorberger, J.; Cangi, A.

This repository contains the Kohn-Sham density functional theory (KS-DFT) and path-integral Monte-Carlo (PIMC) data used in the journal publication "The relevance of electronic perturbations in the warm dense electron gas".

Keywords: Density Functional Theory; Path-Integral Monte-Carlo; Electronic Structure Theory

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-33115
Publ.-Id: 33115


Verification of the code DYN3D for calculations of neutron flux fluctuations

Viebach, M.; Lange, C.; Kliem, S.; Demaziere, C.; Rohde, U.; Hennig, D.; Hurtado, A.

Insufficiently explained magnitudes and patterns of flux fluctuation observed mainly in KWU PWRs are recently investigated
by various European institutions. Among the numerical tools used to investigate the neutron flux fluctuations is the time-domain
reactor dynamics code DYN3D. As DYN3D and comparable codes have not been developed with the primary intention to simulate
low-amplitude neutron flux fluctuations, their applicability in this field has to be verified.
In order to contribute to the verification of DYN3D for the simulation of neutron flux fluctuations, two special cases of perturbations
of the neutron flux (a localized absorber of variable/oscillatory strength and a travelling oscillatory perturbation) are considered
with DYN3D on the one hand and with the frequency-domain neutron noise tool CORE SIM as well as analytical frequency-domain
approaches, respectively, on the other hand. The obtained results are compared with respect to the distributions of the amplitude and
the phase of the induced neutron flux fluctuations. The comparisons are repeated with varied amplitudes and frequencies of the
perturbation.
The results agree well both qualitatively and quantitatively for each of the conducted calculations. The remaining deviations
between the DYN3D results and the reference results exhibit a dependence on the perturbation magnitude, which is attributed to the
neglect of higher-order terms (linear theory) of the perturbed quantities in the calculation of the reference solutions.

Keywords: neutron noise; deterministic reactor modeling; DYN3D; CORE SIM

Permalink: https://www.hzdr.de/publications/Publ-33114
Publ.-Id: 33114


Formation and time dynamics of hydrogen-induced vacancies in nickel

Chiari, L.; Kojima, K.; Endo, Y.; Teshigahara, H.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Fujinami, M.

The formation and time dynamics of hydrogen-induced defects in nickel by room temperature aging was investigated by positron annihilation spectroscopy. Low temperature conventional positron annihilation lifetime spectroscopy and positron lifetime measurements using a high-flux positron beam evidenced the formation of a large number of monovacancy-level defects simply by hydrogen addition at room temperature. Low-temperature coincidence Doppler broadening measurements proved that hydrogen was trapped and bound to these vacancies during the hydrogen charge. Room temperature aging, i.e. below the stage III temperature in Ni, and the concomitant hydrogen desorption induced the agglomeration of those monovacancies into large vacancy clusters which remained even after all the hydrogen had desorbed and hydrides had disappeared. These results demonstrated that vacancy-hydrogen complexes were induced in Ni only by hydrogen charging and that hydrogen has a primary role in the formation and stabilization of vacancies even at room temperature.

Keywords: hydrogen; nickel; vacancies; positron annihilation spectroscopy

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33113
Publ.-Id: 33113


Quantification of cerebral nicotinic α7 acetylcholine receptors (α7 nAChRs) under gastric stimulation of the vagus nerve in piglets

Rullmann, M.; Alexander Becker, G.; Antonov, A.; Sattler, B.; Sattler, T.; Deuther-Conrad, W.; Schimpf, S.; Patt, M.; Meyer, P. M.; Teodoro, R.; Wenzel, B.; Scheunemann, M.; Hesse, S.; Brust, P.; Leitzke, M.; Sabri, O.

Introduction
Electrical gastric vagus nerve stimulation (VNS) shifts the sympathetic-vagal balance toward a parasympathetic predominance (1). We aim to assess central changes in α7 nAChR-mediated transmission and hypothesize that VNS changes the parasympathetic tone by changing the α7 nAChR availability in the nucleus tractus solitarii (NTS) and distinct cortical and subcortical regions (2).

Material and Methods
Following a standard 35-frames, 120-min protocol for dynamic brain PET imaging, data from eight piglets (15.6 ± 3.2 kg, ~6 weeks) were acquired post injection of 194.8 ± 9.4 MBq of [18F]DBT-10 (3) followed by T1-MPRAGE MRI: three baseline, two with infusion of the acetylcholine esterase inhibitor physostigmine (0.04 mg/kg, 1 ml/min, at 10 min prior to tracer injection; 0.24 mg/kg, 1 ml/min, at tracer injection/scan start over 120 min) and three with VNS in repeated sequences of 0.5 Hz over 5 min, 5 min pause started at scan start. TACs were analyzed using a 2-tissue compartment model involving a metabolite-corrected arterial input function to generate individual total distribution volumes (VT) as receptor parameter.

Results
Compared to baseline, we observed an increase of the mean VT after physostigmine infusion (61 %) as well as after VNS (28 %) without major alterations of K1 in the NTS (Figure 1 and 2).

Conclusion
These initial data indicate blood-flow-independent changes under VNS as compared with baseline suggesting an increase in α7 nAChR availability although the changes appear more heterogeneous in VNS as compared with physostigmine. The finding is in contrast to our hypothesis expecting lower α7 nAChR-availability as a result of increased acetylcholine release following VNS. We speculate that higher VT under VNS may reflect an increase in affinity of the α7 nAChR or result in an upregulation of the α7 nAChR. Increase of VT following physostigmine administration could be related to a positive allosteric effect on the α7 nAChR. Furthermore, the results of this study allow sample size estimations for further preclinical and clinical studies.

  • Lecture (Conference) (Online presentation)
    NRM2021 - XIII International Symposium of Functional Neuroreceptor Mapping of the Living Brain, 14.-16.12.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33112
Publ.-Id: 33112


Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems (Raw Data)

Michaux, B.

Files are containing the raw data of the dissertation:

Title: Advancement of Mineral Processing Simulation Platforms for the Integration of Water Quality – Process Performance Interactions in Water Management Systems

Author: M.Sc. Bruno Benjamin Xavier Michaux

Faculty: Faculty of Mechanical, Process and Energy Engineering of the Technische Universität Bergakademie Freiberg

Year: 2021

It contains 3 Excel sheets:

  • One for the flotation kinetics data
  • One for the water composition data in flotation
  • One for the water composition data in the mill.

Furthermore it contains a student report from 2017 which is describing the preparation of the synthetic water by

Miaad Farhan Fadami
Research Intern
miaad.farhanfadami@mail.mcgill.ca

Keywords: Flotation; Mineral Processing; Mining; Water

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Permalink: https://www.hzdr.de/publications/Publ-33111
Publ.-Id: 33111


SIMS analytics of quartz

Renno, A.

Secondary ion mass spectrometry (SIMS), as a high-precision, spatially resolved analytical method, is an alternative to the standard LA-ICP-MS and EPMA methods of quartz analysis. Quartz, with its "notoriously low" trace element contents, presented a welcome challenge from the beginning of the routine application of SIMS methods in mineralogy. In the course of instrument development, there has been an increasingly intensive instrumental differentiation of SIMS instruments. Today, it is possible to analyze almost all naturally occurring elements (H-U), isotope ratios as well as molecular ions and molecular fragments with resolutions from the millimeter to the nanometer range using SIMS. In principle, this allows its use in solving a variety of scientific problems closely related to quartz. Examples are the clarification of crystallochemical questions of the incorporation of different ions into the quartz lattice, questions of element diffusion (e.g. Li, Ti or H) in quartz, the determination of causes for certain spectroscopic features (e.g. CL or EPR), the reconstruction of formation conditions via isotope ratios (O, Si, Li or H), the application of geothermometers (e.g. TitaniQ), the mechanical behavior of quartz as a function of hydrogen content, provenance analyses for natural rocks but also archaeological artifacts, exploration-related questions for quartz deposits and in particular for deposits in which quartz occurs as a genetic-critical accompanying mineral, up to problems of quality testing and quality assurance of high-purity quartz and the engineering evaluation of processing technologies in particular flotation for quartz extraction.
The main limitation of SIMS is the extreme matrix dependence of secondary ion yield. This requires the use of meticulously characterized reference materials (Audétat et al., 2015). New promising developments in this field will be presented (Nachlas, 2016; Wu et al., 2019).
New instrumental developments such as the positive ion SIMS-SSAMS (Grabowski et al., 2019), the Super-SIMS (Rugel et al., 2016) or SIMS analysis in specially modified helium microscopes (Wirtz et al., 2019) and associated enhanced analytical capabilities of quartz will be presented.

References:

Audétat, A., Garbe-Schönberg, D., Kronz, A., Pettke, T., Rusk, B., Donovan, J.J. and Lowers, H.A. (2015) Characterisation of a Natural Quartz Crystal as a Reference Material for Microanalytical Determination of Ti, Al, Li, Fe, Mn, Ga and Ge. Geostandards and Geoanalytical Research 39, 171-184.
Grabowski, K.S., Groopman, E.E., Rock, B.Y. and Imam, M.A. (2019) Positive ion SIMS-SSAMS for trace analysis of materials. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 455, 158-164.
Nachlas, W.O. (2016) Precise and Accurate Doping of Nanoporous Silica Gel for the Synthesis of Trace Element Microanalytical Reference Materials. Geostandards and Geoanalytical Research 40, 505-516.
Rugel, G., Pavetich, S., Akhmadaliev, S., Baez, S.M.E., Scharf, A., Ziegenrucker, R. and Merchel, S. (2016) The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data. Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 370, 94-100.
Wirtz, T., Castro, O.D., Audinot, J.-N. and Philipp, P. (2019) Imaging and Analytics on the Helium Ion Microscope. Annual Review of Analytical Chemistry 12, 523-543.
Wu, H., Böttger, R., Couffignal, F., Gutzmer, J., Krause, J., Munnik, F., Renno, A.D., Hübner, R., Wiedenbeck, M. and Ziegenrücker, R. (2019) ‘Box-Profile’ Ion Implants as Geochemical Reference Materials for Electron Probe Microanalysis and Secondary Ion Mass Spectrometry. Geostandards and Geoanalytical Research 43, 531-541.

Keywords: SIMS; Mineralogy; Geochemistry; Quartz

Related publications

  • Lecture (Conference)
    QUARTZ2021 - International Symposium on Quartz, 05.-07.09.2021, Tønsberg, Norge

Permalink: https://www.hzdr.de/publications/Publ-33110
Publ.-Id: 33110


A systematic review on the use of quantitative imaging to detect cancer therapy adverse effects in normal-appearing brain tissue

Petr, J.; Hogeboom, L.; Nikulin, P.; Wiegers, E.; Schroyen, G.; Kallehauge, J.; Chmelik, M.; Clement, P.; Nechifor, R. E.; Fodor, L.-A.; de Witt Hamer, P.; Barkhof, F.; Pernet, C.; Lequin, M.; Deprez, S.; Jancalek, R.; Mutsaerts, H. J.; Pizzini, F. B.; Emblem, K. E.; Keil, V. C.

Cancer therapy for both central nervous system (CNS) and non-CNS tumors has been previously associated with transient and long-term cognitive deterioration, commonly referred to as ‘chemo fog’. This therapy-related damage to otherwise normal-appearing brain tissue is reported using post-mortem neuropathological analysis. Although the literature on monitoring therapy effects on structural magnetic resonance imaging (MRI) is well-established, such macroscopic structural changes appear relatively late and irreversible. Early quantitative MRI biomarkers of therapy-induced damage would potentially allow to take these treatment side-effects into account and pave the way towards a more personalized treatment planning.
This systematic review (PROSPERO number 224196) provides an overview of quantitative tomographic imaging methods, potentially identifying the adverse side-effects of cancer therapy
in normal-appearing brain tissue. Sixty-six studies were obtained from the MEDLINE and Web of Science databases. Studies reporting changes in normal-appearing brain tissue using MRI, PET, or SPECT quantitative biomarkers, related to radio-, chemo-, immuno-, or hormone therapy for any kind of solid, cystic, or liquid tumor were included. The reviewed studies were assessed for risk of bias using a modified QUADAS-2 tool, of which findings were summarized. For each imaging method, this review provides the methodological background, and the benefits and shortcomings of each method from the imaging perspective. Finally, a set of recommendations is proposed to support future research.

Permalink: https://www.hzdr.de/publications/Publ-33109
Publ.-Id: 33109


Low-level ¹⁶⁶mHo measurements with AMS for the ECHo-project

Rugel, G.; Berndt, S.; Düllmann, C. E.; Dorrer, H.; Forstner, O.; Kieck, T.; Kneip, N.; Lachner, J.; Merchel, S.; Vivo Vilches, C.; Wallner, A.; Wendt, K.

The Electron Capture in ¹⁶³Ho experiment (ECHo) aims at measuring the mass of νe by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T1/2=4570 a) with a metallic magnetic calorimeter (MMC). For the determination of a reasonable upper limit for the neutrino mass it is mandatory to keep any contamination with the long-lived radionuclide 166mHo nine orders of magnitude below the ¹⁶³Ho content. The ion-implantation of ultra-pure ¹⁶³Ho into a MMC for the experiment is carried out by the RISIKO mass separator. The separation from ¹⁶⁶mHo, however, cannot be quantified to such low levels as needed. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). This requires the formation of negative ions, we find the highest negative ion yield for the anion HoO₂. For first tests ¹⁶⁵Ho was implanted by RISIKO in various metal foils and we obtained results for the Ho detection efficieny. This allows for extrapolations for the expected measurement limit of the ¹⁶⁶mHo/¹⁶³Ho ratio.

Related publications

  • Lecture (Conference) (Online presentation)
    DPG-Tagung der Sektion Atome, Moleküle, Quantenoptik und Plasmen (SAMOP), 20.-24.09.2021, Kaiserslautern, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-33108
Publ.-Id: 33108


Temperature determination during Flash Lamp Annealing

Begeza, V.; Rebohle, L.; Schumann, T.

Flash lamp annealing (FLA) is a modern technology for the thermal treatment of materials which currently opens up new application areas. During FLA, an intense pulse of light with a pulse duration of milliseconds and below is applied to the surface of a material. In contrast to traditional methods like furnace annealing, temperature now strongly depends on the material properties and the thickness of the sample. In addition, the short time scale leads to a temperature distribution over depth and makes direct temperature measurements very challenging.
In this work we first review in brief the existing possibilities for a direct temperature measurement during FLA. The main part presents our own concept which is a combination of direct measurements, calibration and thermodynamic simulation. The latter point is of special interest as it allows to get information about the temperature distribution within the material, provided that the relevant material parameters are known. Finally, the impact of such temperature distributions on physical processes like diffusion, crystallization and phase formation is discussed.

Keywords: Flash Lamp Annealing; Short time annealing; Temperature determination

  • Invited lecture (Conferences) (Online presentation)
    CERC 2021, 09.-10.09.2021, Cork, Irland

Permalink: https://www.hzdr.de/publications/Publ-33106
Publ.-Id: 33106


Layer coupling between solutal and thermal convection in liquid metal batteries

Personnettaz, P.; Klopper, T. S.; Weber, N.; Weier, T.

For longer than one decade, liquid metal batteries (LMBs) are developed with the primary aim to provide economic stationary energy storage. Featuring two liquid metal electrodes separated by a molten salt electrolyte, LMBs operate at elevated temperature as simple concentration cells. Therefore, efficient mass transfer is a basic prerequisite for their economic operation. A thorough understanding of the relevant mechanisms cannot be achieved by studying single layers in isolation. With this motivation, the effects of solutal- and thermally-driven flow are studied, as well as the flow coupling between the three liquid layers of the cell. It is shown that solutal convection appears first and thermal convection much later. While the presence of solutal flow depends on the mode of operation (charge or discharge), the occurrence of thermal convection is dictated by the geometry (thickness of layers). The coupling of the flow phenomena between the layers is intriguing: while thermal convection is confined to its area of origin, i.e. the electrolyte, solutal convection is able to drive flow in the positive electrode and in the electrolyte.

Keywords: liquid metal battery; mixing; solutal convection; Rayleigh-Bénard convection; internally heated convection; layer coupling

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Publ.-Id: 33105


Experimental Oxygen Mass Transfer Study of Micro-perforated Diffusers

Herrmann-Heber, R.; Ristau, F.; Mohseni, E.; Reinecke, S.; Hampel, U.

We studied new micro-perforated diffuser concepts for the aeration process in the wastewater treatment plant and evaluated their aeration efficiency. These are micro-perforated plate diffusers with orifice diameters of 30 µm, 50 µm and 70 µm and a micro-perforated tube diffuser with orifice diameter of 50 µm. The oxygen transfer of the diffuser concepts was tested in clean water and it is compared with commercial aerators from the literature. The micro-perforated tube diffuser and micro-perforated plate diffusers outperform the commercial membrane diffusers up to 44% and 20%, respectively, with regard to the oxygen transfer efficiency. The most relevant reason for the improved oxygen transfer is the fine bubble aeration with bubble sizes down to 1.8 mm. Furthermore, the more homogenous cross-sectional bubble distribution of the micro-perforated tube diffuser has a beneficial effect on the gas mass transfer due to less bubble coalescence. However, the pressure drop of micro-perforated diffusers seems to be the limiting factor for their standard aeration efficiencies due to the size and the number of orifices. Nevertheless, this study shows the potential for a better aeration efficiency through the studied conceptual micro-perforated diffuses.

Keywords: micro-perforated diffuser; oxygen transfer efficiency; oxygen mass transfer; aeration efficiency

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Publ.-Id: 33104


Restoring betatron phase coherence in a beam-loaded laser-wakefield accelerator

Köhler, A.; Pausch, R.; Bussmann, M.; Couperus Cabadağ, J. P.; Debus, A.; Krämer, J. M.; Schöbel, S.; Zarini, O.; Schramm, U.; Irman, A.

Matched beam loading in laser wakefield acceleration (LWFA), characterizing the state of flattening the accelerating electric field along the bunch, leads to the minimization of energy spread at high bunch charges. Here, we experimentally demonstrate by independently controlling injected charge and accelerating gradients, using the self-truncated ionization injection scheme, that minimal energy spread coincides with a reduction of the normalized beam divergence. With the simultaneous confirmation of the micrometer-small beam radius at the plasma exit, deduced from betatron radiation spectroscopy, we attribute this effect to the minimization of chromatic betatron decoherence. These findings are supported by rigorous three-dimensional particle-in-cell simulations tracking self-consistently particle trajectories from injection, acceleration until beam extraction to vacuum. We conclude that beam-loaded LWFA enables highest longitudinal and transverse phase space densities.

Keywords: laser-wakefield acceleration; beam loading; beam coherence restoration; beam decoherence; betatron radiation; ionization injection; particle-in-cell simulations

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Permalink: https://www.hzdr.de/publications/Publ-33103
Publ.-Id: 33103


THEREDA - Thermodynamic Reference Database

Moog, H. C.; Scharge, T.; Seher, H.; Bok, F.; Brendler, V.; Richter, A.; Wissmeier, L.; Altmaier, M.; Gaona, X.; Cevirim-Papaioannou, N.; Freyer, D.; Pannach, M.; Sohr, J.; Voigt, W.

Abstract.
Part of the process to ensure the safety of radioactive waste disposal is the predictive modeling of the solubility of all relevant toxic components in a complex aqueous solution. To ensure the reliability of thermodynamic equilibrium modeling as well as to facilitate the comparison of such calculations done by different institutions it is necessary to create a mutually accepted thermodynamic reference database. To meet this demand several institutions in Germany joined efforts and created THEREDA 15 (Moog et al., 2015).
THEREDA is a suite of programs at the base of which resides a relational databank. Special emphasis is put on thermodynamic data along with suitable Pitzer coefficients which allow for the calculation of solubilities in high-saline solutions. Registered users may either download single thermodynamic data or ready-to-use parameter files for the geochemical speciation codes 20 PHREEQC, Geochemist’s Workbench, CHEMAPP, or TOUGHREACT. Data can also be downloaded in a generic JSON-format to allow for the import into other codes. The database can be accessed via the world wide web: www.thereda.de
Prior to release, the released part of the database is subjected to many tests. Results are compared to results from earlier releases and among the different codes. This is to ensure that by additions of new and modification of existing data no adverse side 25 effects on calculations are caused. Furthermore, our website offers an increasing number of examples for applications, including graphical representation, which can be filtered by components of the calculated system.

References
Moog, H. C., Bok, F., Marquardt, C. M., and Brendler, V.: Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem., 55, 72-84, doi: 30 10.1016/j.apgeochem.2014.12.016, 2015.

Keywords: THEREDA; Thermodynamic Reference Database; Pitzer; Solubility; Thermodynamic data

  • Poster (Online presentation)
    SafeND Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland
  • Open Access Logo Contribution to proceedings
    Safety of Nuclear Waste Disposal, 10.-12.11.2021, Berlin, Deutschland
    Safety of Nuclear Waste Disposal, Berlin: BASE, 157-158
    DOI: 10.5194/sand-1-157-2021

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Not just a background: pH buffers do interact with lanthanide ions – a Europium(III) case study

Mandal, P.; Kretzschmar, J.; Drobot, B.

The interaction between Eu(III) ion and different pH buffers, popular in biology and biochemistry viz. HEPES, PIPES, MES, MOPS, and TRIS have been studied by solution nuclear magnetic resonance spectroscopy (NMR) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) techniques. The Good’s buffers reveal non-negligible interaction with Eu(III) as determined from their complex stability constants, where the sites of interaction are the morpholine and piperazine nitrogen atoms, respectively. In contrast, TRIS buffer shows practically no affinity towards Eu(III). Therefore, when investigating lanthanides, TRIS buffer should be preferred over Good’s buffers. 

Keywords: Europium; Buffer; TRLFS; NMR; Stability Constant

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Publ.-Id: 33100


Research data: Terahertz signatures of ultrafast Dirac fermion relaxation at the surface of topological insulators

Kovalev, S.; Tielrooij, K.-J.; Deinert, J.-C.; Ilyakov, I.; Chen, M.; Ponomaryov, O.; de Oliveira, T.; Eng, L. M.; Gensch, M.

This research data publication contains: - Experimental datasets which were evaluated and presented in the corresponding article. - Origin software file that contains the raw data as well as the different steps of the data analysis, the results of which are presented in the article.

Keywords: Terahertz; Ultrafast; Harmonic Generation; Topological Insulators; Surface Science; Dirac Material

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Publ.-Id: 33099


Raw data related to publication entitled "Turbulent resuspension of micron particles from a wall surface functionalized with cylindrical micropillars" by Banari, A. et al.

Lecrivain, G.
Project Leader: Lecrivain, Gregory

# 'Flowrate.JPG': Table associating a raw image (see 'org' folder below) with the flow rate (Q) in L/min

# 'Rough': raw data obtained with the rough substrate

# 'Smooth': raw data obtained with the smooth substrate

# "Smooth" and "Rough" folders contain a list of subfolders Mi, with i=0,1,2,... the measurement index. Ex: M1: is a first series of measurements and M2: a second series of measurements. Each Mi folder contains the following data:

## 'org': List of pictures (Acquisition_AAA_-BBBBBB.jpg) taken with the high-resolution camera. With AAA=000,001,002,... is the flow rate association. To associate AAA with the flow rate, see 'Flowrate.JPG'. Ex: '000' -> Q = 0 L/min, '001' -> Q = 20 L/min. BBB=000001,000002 or 000003 are pictures of the same particle bed taken at increasing time interval. These 3 pictures are used to check particle bed equilibrium.

## 'pic_CCC.jpg' with CCC=001, 002, 003: simply a copy of the raw picture in 'org' with bed at equilibrium. The association between the index (CCC) and the  flow rate (Q) is identical to that described in 'org' (AAA).

## 'Particles_CCC.csv' with CCC=001, 002, 003: List of particle positions (called tags in the manuscript) in each respective image.

Keywords: Particle resuspension; Particle adhesion; Turbulent gas flow; Surface functionalization; Surface roughness.

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Publ.-Id: 33098


Interaction of Th(IV), Pu(IV) and iron(III) with ferritin protein : how similar ?

Zurita, C.; Tsushima, S.; Lorenzo Solari, P.; Jeanson, A.; Creff, G.; Den Auwer, C.

Ferritin is the main actor of Fe storage in eukaryote and prokaryote cells. It is a large multifunctional, multi-subunit protein consisting of heavy H and light L subunits. In the field of nuclear toxicology, it has been suggested that some actinides elements, such as thorium and plutonium at oxidation state +IV, have a comparable "biochemistry" as iron at oxidation state +III due to their very high tendency for hydrolysis and somehow comparable ionic radii. Therefore the possible mechanisms of interaction of such actinide elements with Fe storage protein is a fundamental question of bio-actinidic chemistry. We have recently described the complexation of Pu(IV) and Th(IV) with horse spleen ferritin (composed mainly of L subunits). In this article we bring another view point to this question by further combining modeling with our previous EXAFS data for Pu(IV) and Th(IV). As a result, the interaction between the L subunits and both actinides appear to be not specific but only driven by the density of presence of Asp and Glu residues on the protein shell. The formation of an oxyhydroxide Th or Pu core has not been observed in our experimental condition, nor the interaction of Th or Pu with the ferric oxyhydroxide core.

Permalink: https://www.hzdr.de/publications/Publ-33096
Publ.-Id: 33096


Animal models for the evaluation of radiopharmaceuticals

Toussaint, M.

As the nuclear medicine community strives to make the promise of personalised medicine a reality, it is more essential than ever to have highly relevant translational models to recapitulate human disease. Indeed, personalized medicine aims to identify the predictive factors of a disease at the patient level and animal models can be an essential element if they meet certain key criteria.
In addition of choosing the right animal model, the evaluation of potential new radiopharmaceuticals requires consideration of animal model-specific differences (in terms of target expression and distribution, physiology, pharmacokinetics…) that may predict differences between preclinical and clinical observations, as well as the design of imaging or therapy protocols that are representative of clinical protocols.
This teaching session will therefore, be an opportunity to discuss the optimisation of preclinical approaches in experimentations, data interpretation and reporting with the aim of improving the translational power of new radiopharmaceutical candidates.

Keywords: Animal models; translation; radiopharmaceuticals

  • Invited lecture (Conferences) (Online presentation)
    34th annual congress of the European Association of Nuclear Medicine, 20.-23.10.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33094
Publ.-Id: 33094


Data Publication: Pump-induced terahertz anisotropy in bilayer graphene

Seidl, A.; Anvari, R.; Dignam, M. M.; Richter, P.; Seyller, T.; Schneider, H.; Helm, M.; Winnerl, S.

The raw data and lab book pages are given in the .zip folders. The results of the theoretical calculations in comparison to the experiment are given in Roozbeh_plot.opju. In the other two Origin files, the differential transmission signals and other relevant values are calculated from the raw data.The 2 THz measurement was performed in 2019, the 3.4 THz measurement in 2020.

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Publ.-Id: 33093


B₁₂X₁₁(H₂)⁻: Exploring the limits of isotopologue selectivity of hydrogen adsorption

Wulf, T.; Warneke, J.; Heine, T.

We study the isotopologue-selective binding of dihydrogen at the undercoordinated boron site of undeca-X-closo-dodecaborates B₁₂X₁₁⁻ (X = H, F, Cl, Br, I, CN) using ab initio quantum chemistry. With a Gibbs free energy of H₂ attachment reaching up to 80 kJ∙mol⁻¹ (ΔG at 300 K for X = CN), these sites are even more attractive than most undercoordinated metal centers studied so far. We thus believe that they can serve as an edge case close to the upper limit of isotopologue-selective H₂ adsorption sites. Differences of the zero-point energy of attachment average 5.0 kJ∙mol⁻¹ between D₂ and H₂ and 2.7 kJ mol⁻¹ between HD and H₂, resulting in hypothetical isotopologue selectivities as high as 2.0 and 1.5, respectively, even at 300 K. Interestingly, even though attachment energies vary substantially according to the chemical nature of X, isotopologue selectivities remain very similar. We find that the H–H activation is so strong that it likely results in the instantaneous heterolytic dissociation of H₂ in all cases (except, possibly, for X = H), highlighting the extremely electrophilic nature of B₁₂X₁₁⁻ despite its negative charge. Unfortunately, this high reactivity also makes B₁₂X₁₁⁻ unsuitable for practical application in the field of dihydrogen isotopologue separation. Thus, this example stresses the two-edged nature of strong H₂ affinity, yielding a higher isotopologue selectivity on the one hand but risking dissociation on the other, and helps define a window of adsorption energies into which a material for selective adsorption near room temperature should ideally fall.

Keywords: hydrogen adsorption; closo-dodecaborates; hydrogen isotopes; boron clusters

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Permalink: https://www.hzdr.de/publications/Publ-33092
Publ.-Id: 33092


Data publication: Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

This data contains results from magnetometry and magnetic force microscopy from the irradiated synthetic antiferromagnets.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

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Publ.-Id: 33091


Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation

Samad, F.; Hlawacek, G.; Arekapudi, S. S. P. K.; Xu, X.; Koch, L.; Lenz, M.; Hellwig, O.

We study layered synthetic antiferromagnets (SAFs) with out-of-plane interface anisotropy, where the layer-wise antiferromagnetic (AF)
alignment is induced by interlayer exchange coupling (IEC). By applying low energy He+ focused ion beam irradiation to the SAF, a depth-dependent
reduction of the IEC and anisotropy can be achieved due to layer intermixing. As a consequence, after irradiation, a specific field
reversal sequence of the SAF is energetically preferred. When tuning the pristine SAF to exhibit an inverted field reversal, we are thus able to
create AF domains in the irradiated regions. When irradiated with a fluence gradient, these AF domains can be further deterministically
manipulated by an external magnetic field. Among other applications, this could be utilized for engineering a controllable and local magnetic
stray field landscape, for example, at AF domain walls, within the otherwise stray field free environment provided by the SAF.

Keywords: Bubble domains; Focused ion beam; Sputter deposition; Interlayer exchange coupling; Magnetic hysteresis

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Permalink: https://www.hzdr.de/publications/Publ-33090
Publ.-Id: 33090


DYN3D and CTF Coupling within a Multiscale and Multiphysics Software Development (Part I)

Davies, S.; Litskevich, D.; Rohde, U.; Detkina, A.; Merk, B.; Bryce, P.; Levers, A.; Ravindra, V.

Understanding and optimizing the relation between nuclear reactor components or physical phenomena allows us to improve the economics and safety of nuclear reactors, deliver new nuclear reactor designs, and educate nuclear staff. Such relation in the case of the reactor core is described by coupled reactor physics as heat transfer depends on energy production while energy production depends on heat transfer with almost none of the available codes providing full coupled reactor physics at the fuel pin level. A Multiscale and Multiphysics nuclear software development between NURESIM and CASL for LWRs has been proposed for the UK. Improved coupled reactor physics at the fuel pin level can be simulated through coupling nodal codes such as DYN3D as well as subchannel codes such as CTF. In this journal article, the first part of the DYN3D and CTF coupling within the Multiscale and Multiphysics software development is presented to evaluate all inner iterations within one outer iteration to provide partially verified improved coupled reactor physics at
the fuel pin level. Such verification has proven that the DYN3D and CTF coupling provides improved feedback distributions over the DYN3D coupling as crossflow and turbulent mixing are present in the former.

Keywords: Nuclear Reactor; Coupled reactor physics; Nodal code; Subchannel code; DYN3D; CTF; KAIST

Permalink: https://www.hzdr.de/publications/Publ-33089
Publ.-Id: 33089


Intermittent chaotic flows in the weakly magnetised spherical Couette system

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

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

Keywords: Spherical Couette Flow

Permalink: https://www.hzdr.de/publications/Publ-33088
Publ.-Id: 33088


Modulated rotating waves and triadic resonances in spherical fluid systems: The case of magnetized spherical Couette flow

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

The existence of triadic resonances in the magnetized spherical Couette system is related to the development of modulated rotating waves, which are quasiperiodic flows understood in terms of bifurcation theory in systems with symmetry. In contrast to previous studies in spherical geometry, the resonant modes are not inertial waves but related to the radial jet instability, which is strongly equatorially antisymmetric. We propose a general framework in which triadic resonances are generated through successive Hopf bifurcations from the base state. The study relies on an accurate frequency analysis of different modes of the flow, for solutions belonging to two different bifurcation scenarios. The azimuthal and latitudinal nonlinear coupling among the resonant modes is analyzed and interpreted using spherical harmonics, and the results are compared with previous studies in spherical geometry.

Keywords: Spherical Couette Flow

Permalink: https://www.hzdr.de/publications/Publ-33087
Publ.-Id: 33087


Size-Tunable Gold Aerogels: A Durable and Misfocus-Tolerant 3D Substrate for Multiplex SERS Detection

Zhou, L.; Peng, Y.; Zhang, N.; Du, R.; Hübner, R.; Wen, X.; Li, D.; Hu, Y.; Eychmüller, A.

The research on surface-enhanced Raman scattering (SERS) continuously draws wide attention because of its high detection sensitivity. However, the commonly investigated 2D SERS substrates cannot fully utilize the 3D active focal volume and require a tight focus on the correct plane, retarding signal enhancement and flexible use. Here, self-supported gold aerogels of centimeter-dimension with tunable ligament sizes are designed as 3D SERS substrates, featuring hot spots throughout the entire network. Unveiling a universal ligament-size-effect, the optimized gold aerogel showcases much larger enhancement factors compared to a 8 nm Au film toward dyes, pesticides, and carcinogens (up to 109). Aside from an excellent reusability and an exceptional stability (> 1 month), an outstanding misfocus tolerance (>300 μm along the z-axis) is also demonstrated for such aerogel-based SERS substrates for multiplex detection. This work may expand the application scope of metal aerogels and lay the foundation for designing next-generation 3D SERS substrates.

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Permalink: https://www.hzdr.de/publications/Publ-33086
Publ.-Id: 33086


The Multifaceted Role of Aldehyde Dehydrogenases in Prostate Cancer Stem Cells

Püschel, J.; Dubrovska, A.; Gorodetska, I.

: Cancer stem cells (CSCs) are the only tumor cells possessing self-renewal and differentiation properties, making them an engine of tumor progression and a source of tumor regrowth after treatment. Conventional therapies eliminate most non-CSCs, while CSCs often remain radiation- and drug-resistant, leading to tumor relapse and metastasis. Thus, targeting CSCs might be a powerful tool to overcome tumor resistance and increase the efficiency of current cancer treatment strategies. The identification and isolation of the CSC population based on its high aldehyde de-hydrogenase activity (ALDH) is widely accepted for PCa and many other solid tumors. In PCa, several ALDH genes contribute to the ALDH activity, which can be measured in the enzymatic assay by converting BODIPY aminoacetaldehyde (BAAA) into the fluorescent product BOD-IPY-aminoacetate (BAA). Although each ALDH isoform plays an individual role in PCa biology, a mutual functional interplay between them also contributes to PCa progression. Thus, ALDH proteins are markers and functional regulators of CSC properties representing an attractive target for cancer treatment. In this review, we discuss the current state of research regarding the role of individual ALDH isoforms in PCa development and progression, their possible therapeutic targeting, and provide an outlook for the future advances in this field.

Keywords: Prostate cancer; cancer stem cells; aldehyde dehydrogenase; cancer stem cell - targeted therapy; cancer stem cell vaccines

Permalink: https://www.hzdr.de/publications/Publ-33085
Publ.-Id: 33085


Beyond the double-strand breaks: the role of DNA repair proteins in cancer stem cell regulation

Nathansen, J.; Meyer, F.; Müller, L.; Schmitz, M.; Borgmann, K.; Dubrovska, A.

Cancer stem cells (CSCs) are pluripotent and highly tumorigenic cells that can re-populate a tumor and cause relapses even after initially successful therapy. Like tissue stem cells, CSCs possess enhanced DNA repair mechanisms. An active DNA damage response alleviates the increased oxidative and replicative stress and leads to therapy resistance. On the other hand, mutations in DNA repair genes cause genomic instability, thereby driving tumor evolution and developing highly aggressive CSC phenotypes. However, the role of DNA repair proteins in CSCs extends beyond the level of DNA damage. In recent years, more and more studies reported the unexpected role of DNA repair proteins in the regulation of transcription, CSC signaling pathways, intracellular levels of reactive oxygen species (ROS), and epithelial-mesenchymal transition (EMT). Moreover, DNA damage signaling plays an essential role in the immune response towards tumor cells. Due to its high importance for the CSC phenotype and treatment resistance, the DNA damage response is a promising target for individualized therapies. Furthermore, understanding the dependence of CSC on DNA repair pathways can be therapeutically exploited to induce synthetic lethality and sensitize CSCs to anti-cancer therapies. This review discusses the different roles of DNA repair proteins in CSC maintenance and their potential as therapeutic targets.

Keywords: Cancer stem cells; DNA repair; Replicative stress; Oxidative stress; Genomic instability; Immune response; Reprogramming; Cancer therapy

Permalink: https://www.hzdr.de/publications/Publ-33084
Publ.-Id: 33084


The Al Doping Effect on Epitaxial (In,Mn)As Dilute Magnetic Semiconductors Prepared by Ion Implantation and Pulsed Laser Melting

Yuan, Y.; Xie, Y.; Yuan, N.; Wang, M.; Heller, R.; Kentsch, U.; Zhai, T.; Wang, X.

One of the most attractive characteristics of diluted ferromagnetic semiconductors is the possibility to modulate their electronic and ferromagnetic properties, coupled by itinerant holes through various means. A prominent example is the modification of Curie temperature and magnetic anisotropy by ion implantation and pulsed laser melting in III–V diluted magnetic semiconductors. In this study, to the best of our knowledge, we performed, for the first time, the co-doping of (In,Mn)As diluted magnetic semiconductors by Al by co-implantation subsequently combined with a pulsed laser annealing technique. Additionally, the structural and magnetic properties were systematically investigated by gradually raising the Al implantation fluence. Unexpectedly, under a well-preserved epitaxial structure, all samples presented weaken Curie temperature, magnetization, as well as uniaxial magnetic anisotropies when more aluminum was involved. Such a phenomenon is probably due to enhanced carrier localization introduced by Al or the suppression of substitutional Mn atoms.

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Publ.-Id: 33083


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