Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41444 Publications

First Principles Investigation on Structural and Optoelectronic Properties of newly designed Janus Lead Halides PbXY (X, Y = F, Cl, Br, I )

Sudheer, A. E.; Tejaswini, G.; Devaraj, M.; Posselt, M.

Inspired by the beauty in the asymmetry, we design a novel class of Janus structures PbXY (X,Y = F, Cl, Br, I) and propose it for the solar mediated photocatalytic water splitting hydrogen production as well as for the photovoltaic solarcell applications.These novel Janus structures show large modulation in layer thickness, bond lengths and bond angles due to asymmetry of two sides. Charge analysis shows that covalent bonding for less electronegative atoms (I and Br) and ionic bonding for more electronegative (Cl and F) atoms. Strong dual bonding like ionic one side and covalent other side is observed when heavy and lighter atoms are part of the same Janus structures. The as designed Janus structures show good dynamical stability through phonon calculations. Basic electronic structure using Generalised Gradient Approximation (GGA) reveal both direct and indirect nature of band gap with large tunability
varying from 2.5 to 3.5 eV. Such a large tunability of band gap can be exploitedfor multifunctional applications. Heyd-Scuseria-Ernzerhof (HSE) electronic structure calculations are performed for more accuracy and wider band gaps are predicted for these Janus structures. The calculated electron and hole effective masses show robust charge carrier dynamics. The orbital resolved electronic density of states (DOS) shows that the conduction band edge is composed of pz orbital of Pb atom. The partial charge density calculated at conduction band minimum (CBM) also support the result obtained from PDOS analysis. Breaking of centrosymmetry, covalent bonding along z-direction, polarization in the out of plane direction, the z-oriented orbitals of CBM all points that these materials are suitable for shift current generation. The calculated optical absorption spectra show that the Janus structures are suitable for visible light absorption. The calculated potential difference between the top and bottom layer show significant variation and maximum (1.02 eV) is observed for PbClF. Further, we show that combining both potential difference and HSE bandgap, valence band maximum (VBM) and CBM straddle the water redox potentials, thus making the Janus structures suitable for hydrogen evolution reaction (HER) and oxygen evolution reactions (OER) on the opposite sides of the Janus structures.

Keywords: 2D materials; Janus Lead Halides; First-principle study

Permalink: https://www.hzdr.de/publications/Publ-38099


Random Quantum Neural Networks for Noisy Image Recognition

Konar, D.; Gelenbe, E.; Bhandary, S.; Das Sarma, A.; Cangi, A.

The application of classical Random Neural Networks (RNN) has been restricted to deterministic digital systems that generate probability distributions instead of the stochastic characteristics of random spiking signals. To optimize the utilization of the stochastic properties inherent in RNN, we propose a new category of supervised Random Quantum Neural Networks (RQNN) that incorporate a resilient training methodology. The RQNN under consideration utilizes a combination of classical and quantum algorithms, incorporating superposition state and angle encoding characteristics that draw inspiration from quantum information theory. Additionally, the model incorporates the stochastic random spiking property of neuron information encoding, which is known to exhibit spatial-temporal features similar to those observed in the brain. The proposed RQNN model has undergone thorough validation, relying on hybrid classical-quantum algorithms through a real IBM quantum processor. The proposed RQNN model is tested on the MNIST, Fashion-MNIST, and KMNIST datasets. The results indicate that it achieved an average classification accuracy of 59.6% when presented with unseen noisy test images. The experimental results demonstrate the efficacy and robustness of the proposed RQNN in classifying noisy images that have not been previously encountered.

Keywords: Recurrent neural networks; Computational modeling; Stochastic processes; Encoding; Robustness

  • Contribution to proceedings
    2023 IEEE International Conference on Quantum Computing and Engineering (QCE), 17.-22.09.2023, Bellevue, USA
    2023 IEEE International Conference on Quantum Computing and Engineering (QCE), 276
    DOI: 10.1109/QCE57702.2023.10240

Permalink: https://www.hzdr.de/publications/Publ-38098


Characterization of Magnetic and Mineralogical Properties of Slag Particles from WEEE Processing

Siddique, A.; Boelens, P.; Long, F.; Zhou, S.; Cnudde, V.; Leißner, T.

Magnetic separation has wide-ranging applications in both mineral processing and recycling
industries. Nevertheless, its conventional utilization often overlooks the interplay between
mineral and particle characteristics and their impact on operational conditions, ultimately influencing
the efficacy of the separation process. This work describes a methodology able to achieve
the comprehensive characterization and classification of Waste Electrical and Electronic Equipment
(WEEE) slag. The primary objective is to establish a meaningful connection between the distinct
properties of slag phases and their influence on the separation process. Our methodology consists
of several stages. Firstly, the WEEE slag is sieved into distinct size classes, followed by classification
into magnetic susceptibility classes by using the Frantz Isodynamic separator. To quantify the
magnetic susceptibility of each class, we used a magnetic susceptibility balance, and to identify
paramagnetic and ferromagnetic fractions and phases within these magnetic susceptibility classes,
we conducted vibrating-sample magnetometer measurements. Finally, to establish a meaningful link
between the magnetic characterization, mineralogical, and particle-level details, Mineral Liberation
Analysis was conducted for each magnetic susceptibility class. This in-depth analysis, encompassing
both particle properties and magnetic susceptibility classes, provides a better understanding of
the separation behavior of different phases and can help to enrich phases with a specific range of
magnetic susceptibility values. This knowledge advances progress towards the development of
predictive separation models that are capable of bridging the gap between theoretical understanding
and practical application in the field of magnetic separation.

Keywords: magnetic characterization; magnetic susceptibility classes; WEEE slag; vibrating-sample magnetometer (VSM)

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Permalink: https://www.hzdr.de/publications/Publ-38097


Compressing simulation output with cINNs and continual learning

Willmann, A.; Schmerler, S.; Ebert, J.; Kesselheim, S.; Bussmann, M.; Chandrasekaran, S.; Debus, A.; Hoffmann, N.; Holsapple, K.; Juckeland, G.; Pausch, R.; Pöschel, F.; Schramm, U.; Steiniger, K.

The output of simulations can be extremely challenging to work with. For example, in large-scale particle-in-cell simulations in plasma physics, trillions of particles are simulated over millions of time steps, creating Petabytes of data. In this project, we develop methods to compress particle data by training conditional invertible neural networks (cINNs) on the particle data. The particles then can be reconstructed by running the trained model in generative mode. This allows us to reach up to millionfold compression, and a controlled loss of a accuracy. The models can be conditioned not only on the temporal axis but also on other types of simulation outputs of smaller data volume, leading potentially to even higher compression factors.

In order to enable the neural network model to represent simulation data over long time spans, we apply methods from Continual Learning, where each new learning task is represented by a dataset produced by a simulation time step. This approach enables us to efficiently solve the inverse problem of particle data reconstruction from radiation data in a time-resolved manner by side-stepping demanding simulations.

  • Poster
    Helmholtz AI Conference 2023, 12.-14.06.2023, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-38096


Rohstoffe aus der Lampe

Boelens, P.; Lederer, F.

Rohstoffe aus der Lampe - ein biotechnologischer Ansatz für ein umweltfreundliches Recycling von Hochtechnologiemetallen

  • Invited lecture (Conferences)
    Lange Nacht der Wissenschaften Dresden, 30.06.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38095


Peptide-based biomagnetic separation for the recycling of critical raw materials from ultrafine particles in complex waste streams

Boelens, P.; Lederer, F.

In the global transition towards a low-carbon economy, the current dependence of fossil fuels is rapidly replaced by an increased demand in critical raw materials (CRMs). For example, rare-earth elements (REEs) play an essential role in the large-scale electrification, due to their requirement for the production of permanent magnets, lamp phosphors and rechargeable batteries [1]. However, the REEs’ supply chain is under a high pressure due to a combination of the rising demand, a monopolistic market structure and very low overall recycling rates [2]. The Helmholtz Institute Freiberg for Resource Technology (HIF) aims to promote the energy transition by developing innovative methods and technologies along entire material cycles, ranging from the exploration, to the recycling of CRMs. In this context, the application of biotechnological methods (such as biosorption, bioleaching and biocomplexation) could offer feasible and green solutions for the recycling of complex waste streams, resulting in increased recycling rates of CRMs [3].

At the HIF, the junior research group BioKollekt aims to develop a feasible and upscalable biomagnetic separation method for a novel recycling process of CRMs in the form of ultrafine particles. As a proof of concept, we are currently focussing on the recycling of REEs from fluorescent lamp phosphors. We have identified surface binding peptides, i.e. a type of biomolecules, that selectively bind to the green phosphor LaPO4:Ce,Tb [4]. Subsequently, we have functionalized various magnetic carriers, such as composite beads, core-shell magnetic nanoparticles and bacterial magnetosomes, with the identified peptides. The obtained bifunctional materials (due to their 1) highly selective binding to target particles and 2) high response to an external magnetic field) are ideal carriers to facilitate a separation in challenging waste streams. Finally, using the target materials, we have conducted lab-scale binding experiments, as well as, upscalable separation experiments in a high-gradient magnetic separator (HGMS) [5,6]. In the coming period, we will work to develop an integrated multistep separation process for REE phosphors and explore the possibilities to expand our method to other waste streams.

Keywords: Establish and assess a secure and sustainable energy and raw materials supply

  • Lecture (Conference)
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Germany

Permalink: https://www.hzdr.de/publications/Publ-38094


Impact of Quaternary Glaciations on Denudation Rates in North Pamir—Tian Shan Inferred From Cosmogenic 10Be and Low-Temperature Thermochronology

Kudriavtseva, A.; Codilean, A. T.; Sobel, E. R.; Landgraf, A.; Fülöp, R.-H.; Dzhumabaeva, A.; Abdrakhmatov, K.; Wilcken, K. M.; Schildgen, T.; Fink, D.; Fujioka, T.; Gong, L.; Rosenwinkel, S.; Merchel, S.; Rugel, G.

We explore the spatial and temporal variations in denudation rates in the northern Pamir—Tian Shan region using 10Be-derived denudation rates from modern (n = 110) and buried sediment (2.0–2.7 Ma; n = 3), and long-term exhumation rates from published apatite fission track (AFT; n = 705) and apatite (U-Th-Sm)/He (AHe; n = 211) thermochronology. We found moderate correlations between denudation rates and topographic metrics and weak correlations between denudation rates and annual rainfall, highlighting complex linkages among tectonics, climate, and surface processes that vary locally. The 10Be data show a spatial trend of decreasing modern denudation rates from west to east, suggesting that deformation and precipitation control denudation in the northern Pamir and western Tian Shan. Farther east, the denudational response of the landscape to Quaternary glaciations is more pronounced and reflected in our data. Modern 10Be denudation rates are generally higher than the long-term AFT and AHe exhumation rates across the studied area. In the Kyrgyz Tian Shan, on average, the highest 10Be denudation rates are recorded in the Terskey range, south of Lake Issyk-Kul. Here, modern denudation rates are higher than 10Be-derived paleo-denudation rates, which are comparable in magnitude with the long-term exhumation rates inferred from AFT and AHe. We propose that denudation in the region, particularly in the Terskey range, remained relatively steady during the Neogene and early Pleistocene. Denudation increased due to glacial-interglacial cycles in the Quaternary, but this occurred after the onset and intensification of the Northern Hemisphere glaciations at 2.7 Ma.

Involved research facilities

Related publications

  • Open Access Logo Journal of Geophysical Research - Earth Surface 128(2023)12, e2023JF007193
    DOI: 10.1029/2023JF007193

Permalink: https://www.hzdr.de/publications/Publ-38093


Machine Learning-based Data Analysis and Surrogate Modeling For COXINEL Experiment

Willmann, A.; Ghaith, A.; Chang, Y.-Y.; Debus, A.; La Berge, M.; Labat, M.; Ufer, P.; Schöbel, S.; Hoffmann, N.; Bussmann, M.; Couprie, M.-E.; Schramm, U.; Irman, A.

Recently, free electron lasing at UV wavelength has been demonstrated by deploying the COXINEL beamline driven by HZDR plasma accelerator in a seeded configuration[1]. Further control and optimization of such an FEL radiation require full knowledge of strongly-coupled multivariate parameters involved in laser plasma acceleration, electron beam transport and radiation generation. For this purpose, one has to solve an inverse problem, i.e. finding matching parameters of the simulation to reproduce the experiment. Such inverse problems are ill-posed and cannot be easily resolved due to high computational complexity. Here, machine learning-based methods have a high potential to accelerate theoretical comprehension of the system, novel means for design space exploration and promise reliable in-situ analysis of experimental diagnostics and parameters. We apply simulation-based inference technique for this purpose. This method is a combination of deep learning and statistical approaches to resolve an inverse problem up to a posterior distribution of the simulation parameters given an experimental sample. In addition, we have developed machine learning-based surrogate models that can significantly accelerate forward computations for even faster results of the inverse solver.

[1] M. Labat, et al. "Seeded free-electron laser in driven by a compact laser plasma accelerator", Nat. Photonics, 17, 150(2023)

  • Open Access Logo Lecture (Conference)
    The 6th European Advanced Accelerator Concepts Workshop, 2023, 17.-23.09.2023, Isola d'Elba, Italy
  • Open Access Logo Poster
    The 6th European Advanced Accelerator Concepts Workshop, 2023, 17.-23.09.2023, Isola d'Elba, Italy
  • Open Access Logo Poster
    The 9th annual meeting of the programme "Matter and Technologies", 09.-11.10.2023, Karlsruhe Institute of Technology, Germany
  • Open Access Logo Poster
    Doctoral Seminar 2023, 17.-19.10.2023, Schillbach, Germany

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Permalink: https://www.hzdr.de/publications/Publ-38092


Implicit Convolutional Kernels for Steerable CNNs

Zhdanov, M.; Hoffmann, N.; Cesa, G.

Steerable convolutional neural networks (CNNs) provide a general framework for building neural networks equivariant to translations and transformations of an origin-preserving group G, such as reflections and rotations. They rely on standard convolutions with G-steerable kernels obtained by analytically solving the group-specific equivariance constraint imposed onto the kernel space. As the solution is tailored to a particular group G, implementing a kernel basis does not generalize to other symmetry transformations, complicating the development of general group equivariant models. We propose using implicit neural representation via multi-layer perceptrons (MLPs) to parameterize G-steerable kernels. The resulting framework offers a simple and flexible way to implement Steerable CNNs and generalizes to any group G for which a G-equivariant MLP can be built. We prove the effectiveness of our method on multiple tasks, including N-body simulations, point cloud classification and molecular property prediction.

Keywords: machine learning; equivariant networks; convolutional neural networks

Involved research facilities

  • Data Center

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Permalink: https://www.hzdr.de/publications/Publ-38090


Prompt-Gamma-Imaging: Clinical application demonstrates potential for online-adaptive proton therapy

Berthold, J.

Treatment verification in proton therapy is important for 1) detecting anatomical changes during treatment 2) independent quality assurance during online-adaptive proton therapy (OAPT) and, hence, 3) potentially reducing safety margins. In this context, clinical Prompt-Gamma-Imaging (PGI) data were evaluated which demonstrated the potential of PGI for treatment verification.

Involved research facilities

  • OncoRay
  • Lecture (others)
    NCRO Retreat 2023, 04.-06.05.2023, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38089


Data publication: Ab initio path integral Monte Carlo simulations of the uniform electron gas on large length scales

Dornheim, T.; Schwalbe, S.; Moldabekov, Z.; Vorberger, J.; Tolias, P.

This repository contains the PIMC simulation results shown in the publication "Ab Initio Path Integral Monte Carlo Simulations of the Uniform Electron Gas on Large Length Scales"

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Permalink: https://www.hzdr.de/publications/Publ-38085


Data publication: The origin of native metal-arsenide mineralization in the world-class Schlema-Alberoda uranium deposit (Germany): Insights from arsenide compositions and fluid inclusion systematics

Guilcher, M.; Gutzmer, J.; Hiller, A.; Krause, J.; Blamey, N.; Härtel, B.; Burisch-Hassel, M.

This dataset contains the mineral descriptions, mineral chemical compositions and fluid inclusion data from the samples investigated in the study as well as the analytical parameters for the analytical methods used.

Keywords: Cobalt; Uranium; Arsenide; Fluid inclusion; Microthermometry; Crush-fast scan gas mass spectrometry; Erzgebirge; Five-element mineralization

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Permalink: https://www.hzdr.de/publications/Publ-38084


Comparative analysis of next-generation sequencing data generated from phage display trails with inorganic materials

Bloß, C.

The aim of this work is to find meaningful and statistical proven ways to identify metal binding peptides in multiple trail phage display experiments with inorganic materials.

Keywords: Biotechnology; Bioinformatics; Phage Surface Display; Next-Generation Sequencing; Statistical Analysis; Illumina; Data Science; Ressource Technology; Recycling

  • Open Access Logo Poster
    15th annual PEGS - Protein & Antibody Engineering Summit 2023, 13.-16.11.2023, Lissabon, portugal

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Permalink: https://www.hzdr.de/publications/Publ-38083


Recyclable pickering emulsions for enzymatic phenol degradation of oily wastewater

Gong, Z.; Gao, S.; Lu, K.; Hübner, R.; Wu, C.

Enzymatic degradation offers a sustainable solution for waterborne phenolic pollutants. However, its application within industrial, non-aqueous contexts — particularly in mitigating phenolic contaminants in oily wastewater — remains significantly challenging. To address this challenge, the present study exploits the potential of Fe3O4@PDA nanoparticles to form oil-in-water Pickering emulsions for the enzymatic degradation process. The uniform stability of the prepared emulsion, with droplet sizes under 5 μm, protects enzyme activity and expands the water-oil interfacial area, leading to an enhancement in the efficiency of horseradish peroxidase (HRP) catalytic degradation. The application of this emulsion resulted in a substantial increase in the degradation rate of phenol, achieving 100% within 30 min as opposed to an only 13.6% without it. The study also highlights the excellent stability, reusability, and versatility of the Fe3O4@PDA nanoparticles, enabled by magnetic separation and their ability to form emulsions with diverse oil phases. Consequently, our research offers valuable insights into the development of environmentally sustainable strategies for the degradation of phenolic contaminants in various industrial oily wastewater.

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Permalink: https://www.hzdr.de/publications/Publ-38080


Die Morphologie der Schuppen der aus der Paläarktis bekannten Arten der Unterfamilie Procridinae Boisduval, 1828 (Lepidoptera, Zygaenidae) und deren Bedeutung für die Systematik und Phylogenie

Keil, T.; Hübner, R.; Worbs, A.

In dieser Arbeit werden erstmals die Form und Gestaltung der Schuppen der meisten (>90 %) der aus der Paläarktis bekannten Arten der Unterfamilie Procridinae Boisduval, 1828 abgebildet und Möglichkeiten der Determinationsunterstützung sowie deren Bedeutung für phylogenetische Interpretationen in Verbindung mit anderen morphologischen Merkmalen diskutiert.

The morphology of the scales of the Palaearctic species of the subfamily Procridinae Boisduval, 1828 (Lepidoptera, Zygaenidae) and their importance for systematics and phylogeny. – The present publication illustrates morphology and design of the scales of most (>90 %) of the Palaearctic species of the subfamily Procridinae Boisduval, 1828 for the first time. Possible support of identifications and the importance for phylogenetic interpretations in combination with other morphological features are discussed.

Involved research facilities

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  • Entomologische Nachrichten und Berichte 67(2023)3, 181-201

Permalink: https://www.hzdr.de/publications/Publ-38079


Synthesis and characterization of titanium and aluminum complexes of 2-methoxybenzyl alcoholate and their use in base-catalyzed twin polymerization

Scharf, S.; Rüffer, T.; Formánek, P.; Hübner, R.; Weber, M.; Mehring, M.; Lang, H.

The synthesis and characterization of twin monomers [Ti(OCH2-2-MeO-C6H4)4(HOCH2-2-MeO-C6H4)]2 (3) and [Al(OCH2-2-MeO-C6H4)3]4 (5) by reacting HOCH2-2-MeO-C6H4 (1) with Ti(OiPr)4 (2), or 1 with AlMe3 (4) is discussed. Single crystal X-ray structure analysis of 3 shows a dimeric structure with two alkoxide ligands bridging the titanium ions, while the others are terminal bonded. The respective phenolic resin / metal oxide hybrid materials HM_Ti and HM_Al were obtained in moderate (HM_Ti) to excellent (HM_Al) yields using typical base-catalyzed twin polymerization conditions (230 °C, 2 h). Nuclear magnetic resonance and infrared spectroscopy as well as scanning electron microscopy and scanning transmission electron microscopy combined with energ-dispersive X-ray spectroscopy proved the formation of inorganic–organic hybrid materials consisting of resin and MxOy materials (HM_Ti, TiO2; HM_Al, Al2O3) containing interpenetrating phase nano-domains with sizes of < 5 nm, as is charcteristic for twin polymerization processes. Oxidation of HM_Ti and HM_Al yielded the respective oxide materials Ox_Ti (TiO2) and Ox_Al (Al2O3), which possess low surface areas of ABET = 53 m2/g and 76 m2/g, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-38078


Complete Glucose Electrooxidation Enabled by Coordinatively Unsaturated Copper Sites in Metal-Organic Frameworks

Shi, X.; Ling, Y.; Li, Y.; Li, G.; Li, J.; Wang, L.; Min, F.; Hübner, R.; Yuan, S.; Zhan, J.; Cai, B.

The electrocatalytic oxidation of glucose plays a vital role in biomass conversion, renewable energy, and biosensors, but significant challenges remain to achieve high selectivity and high activity simultaneously. In this study, we present a novel approach for achieving complete glucose electrooxidation utilizing Cu-based metal-hydroxide-organic framework (Cu-MHOF) featuring coordinatively unsaturated Cu active sites. In contrast to traditional Cu(OH)2 catalysts, the Cu-MHOF exhibits a remarkable 40-fold increase in electrocatalytic activity for glucose oxidation, enabling exclusive oxidation of glucose into formate and carbonate as the final products. The critical role of open metal sites in enhancing the adsorption affinity of glucose and key intermediates was confirmed by control experiments and density functional theory simulations. Subsequently, a miniaturized nonenzymatic glucose sensor was developed showing superior performance with a high sensitivity of 214.7 μAmM-1cm-2, a wide detection range from 0.1 μM to 22 mM, and a low detection limit of 0.086 μM. Our work provides a novel molecule-level strategy for designing catalytically active sites and could inspire the development of novel metal-organic framework for next-generation electrochemical devices.

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-38077


PyPlaque: An Open-source Python Library for Phenotypic Analysis of Virus Plaque Assays

De, T.; Andriasyan, V.; Yakimovich, A.

Virological plaque assay is the primary way for the quantification of infectious virus particles in a virus suspension. It is performed by incubating a serial dilution of the virus inoculum with a monolayer of indicator cells. While some tools for automated quantification have been proposed in the past, they lack modularity and are often closed-source. PyPlaque is open-source software written in Python programming language for the analysis and quantification of plaque phenotypes that are observed in plaque assays by virologists. It is based on an abstract software architecture allowing to take into account glassware and specimen carriers and focus on phenotype-specific information. This, in turn, allows biologist to construct modular and simple program code that follows the logical flow of the experimental design and desired quantification outcomes. Furthermore, we demonstrate the comparability of PyPlaque to existing software and show how phenotype-based abstraction allows for seamless coding using Pythonic conventions.

Keywords: plaque assays; viral quantification; automated masking; image and object quantification

  • Poster
    ScaDS.AI 9th International Summer School on AI and Big Data, 03.07.2023, Dresden, Germany
  • Poster
    PoL BioImage Analysis Symposium 2023, 30.08.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38076


Silicon anode processing using flash lamp annealing for lithium ion batteries

Cherkouk, C.; Folgner, C.; Worbs, A.; Hübner, R.; Prucnal, S.; Schumann, T.; Krüger, S.; Zhou, S.; Rebohle, L.

In the near future, silicon will play a key role as anode material for rechargeable lithium ion batteries (LIBs). It shows a low discharge potential and an extremely high specific theoretical capacity of about 4200 mAhg-1 in comparison to that of graphite with a theoretical capacity of 370 mAhg-1. However, the intrinsic volume change of Si particles of more than 400 % during the lithiation and delithiation processes hinders the Si to fully replace the conventional graphite in commercial LIBs. Using planar flash-lamp annealing (FLA) with annealing times in the sub-second range directly after the deposition of a Si thin film on a copper foil, we fabricated a copper silicide anode (CuSi-anode) with outstanding electrical and electrochemical properties. Herein, structural investigations using scanning electron microscopy and X-ray diffraction show a Cu-mediated silicidation at generating mixed phases of copper silicides, SiOx, Cu, and Si nanoparticles. The performance of battery cells with CuSi-anode having a Si thickness of 5 µm versus LiFePO4 shows a surface capacity of 2mAh/cm2 over 100 cycles with capacity loss in the course of cycling but with good electrical conductivity between the anode and current collector. Finally, we compare the electrochemical performance of the CuSi-anode with a conventional graphite anode at the same cell configuration and chemical conditions.

Keywords: Silicon anode; lithium ion batteries; copper silicide anode; flash-lamp annealing; FLA

  • Poster
    AABC Europe: Advanced Automotive Battery Conference, 19.-22.06.2023, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-38074


recomine: Technologies and concepts for a holistic mine waste treatment made in Saxony

Büttner, P.; Engelhardt, J.

recomine is an alliance of predominantly regional partners from industry, science and society in the Erzgebirge (Saxony/Germany). The alliance is funded by the German Federal Ministry of Education and Research (BMBF) since 2018 with a total of €12.7 million and is coordinated by the Helmholtz Institute Freiberg for Resource Technology. With the vision of developing innovative and holistic solutions for mining waste, recomine supports R&D projects that address the intersection of environmental technology, resource technology, Industry 4.0 and social issues. The aim is to bring regional know-how at real development sites together. The Davidschacht tailing in Freiberg is such a site that allows testing new solutions under real conditions. The necessity of innovative technologies is illustrated the new Global Industry Standard on Tailings Management published in 2020 by the International Council on Mining & Metals (ICMM). It was developed in response to recent devastating tailings accidents (e.g. Brumadinho/Brazil in 2019) and is based on the "Zero Harm" principle. Numerous activities of large mining companies (e.g. BPH, Vale, Rio Tinto) started to promote the development of new approaches as a consequence of the new standard. In 2021, for example, the BHP Tailings Challenge called the global raw material community to submit concepts for the recycling and reduction of mining waste from a large copper mine. recomine succeeded in being among the ten selected from over 150 teams. These teams had to proof their submitted recycling concept in a first phase of the challenge. This success is now being continued, e.g. in a project for Amira, a global not-for-profit organization representing members from the resources industry, which is currently being prepared. Direct R&D agreements with mining companies are also under negotiation. recomine's long-term goal is to act as a bridge between regional know-how providers and the global mining industry. The developed technologies can be divided into four groups: analysis, avoidance, remining and transformation. While new technologies for the characterization of tailings or mine water play a role in the area of analysis, the area of avoidance deals with technologies to minimize fine-grained tailings in primary ore processing (e.g. machine-learning optimized sensor-based sorting). In remining, processing technologies are developed to recover the remaining metals, even from the previously undevelopable grain size ranges, e.g. by further development of pneumatic flotation. The Transformation then deals with the use of mining waste, e.g. in the building materials sector, and also provides new approaches to renaturation.

Keywords: recomine; remining; mine waste; tailings; Circular economy; HIF

  • Lecture (Conference)
    WISSYM 2023 - 5. Internationales Bergbausymposium, 25.-28.09.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38072


recomine: Environmental technologies for the development of disperse raw material sources

Büttner, P.

Under the umbrella of recomine 18 R&D projects are running today. The presentation shows the results and the goal of recomine to develop holistic solutions for mining waste.

Keywords: recomine; remining; HIF; Recycling; Circular economy

  • Invited lecture (Conferences)
    PDAC German Day “Shaping the Future of Resources – German Canadian Partnerships in Times of Transformation”, 07.03.2023, Toronto, Kanada

Permalink: https://www.hzdr.de/publications/Publ-38071


Data publication: Effect of ISA and chloride on the uptake of niobium(V) by hardened cement paste and C-S-H phases: quantitative description and mechanistic understanding

Jo, Y.; Çevirim-Papaioannou, N.; Franke, K.; Fuss, M.; Pedersen, M.; Lothenbach, B.; de Blochouse, B.; Altmaier, M.; Gaona, X.

This dataset is a report about gamma spectroscopy measurement of the irradiated cyclotron target generated by GammaVision software (ORTEC/AMETEK, Version 8.00.03).

Keywords: niobium; cyclotron; gamma spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-38070


Nonlinear response of semiconductor under intense THz excitation

Pashkin, O.

Intense narrowband terahertz pulses from the FELBE free-electron laser facility and a complementary table-top high-field THz source are utilized to study nonlinear excitation regimes in semiconductors. In this talk we present several recent examples including impurities transitions in boron doped Si, HgTe topological quantum wells and plasmons in individual InGaAs nanowires.

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  • Invited lecture (Conferences)
    Joint ELI Workshop on Advanced Technologies, 04.-06.12.2023, Szeged, Hungary

Permalink: https://www.hzdr.de/publications/Publ-38069


AutoTarget : Autonomous Multi-UAV (Unmanned Aerial Vehicle) for the Characterization of Remote and Isolated Targets

Adoni, W. Y. H.; Shaik Fareedh, J.; Lorenz, S.; Gloaguen, R.; Kühne, T. D.-S.

This research focus on the development of an autonomous multi-UAV (Unmanned Aerial Vehicles) system, capable of performing target detection and characterization via a domaining approach. The core concept lies in the distribution of tasks to at least two communicating UAVs with specified capabilities (UAV1 and UAV n), flying at the same time. The obtained results are processed in (near- )real time to property maps and passed to the operator by UAV 1 for further interpretation and decision-making. With this concept, the multi-UAV approach allows the fast detection and characterization of isolated, remote targets in a time and resource efficient manner. As high- dimensional / high-detail data is only acquired where it matters, large volumes of superfluous data can be avoided from the start, and such, processing time and computational requirements are reduced. In parallel, the knowledge on the targets’ properties can be tremendously increased for more accurate and detailed characterization as well as the avoidance of false positives. The targeted multi-drone approach further decreases the impact of the survey on environment, wildlife, and population by reducing the necessary impact to a minimum as well as the flight time.

Keywords: Unmanned Aerial Vehicle (UAV); Uncrewed Aerial Vehicle; Autonomous Swarm; Collaborative Mission; Autonomous Aerial Vehicle; Autonomous Aerial Swarm; Drones

  • Open Access Logo Lecture (Conference)
    2023 HZDR Science Conference, 15.-16.11.2023, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-38067


Concept and Design of Intelligent Swarm for Distributed Mission

Adoni, W. Y. H.; Shaik Fareedh, J.; Lorenz, S.; Gloaguen, R.; Kühne, T. D.-S.

Single drones have been already used for basic missions. Drone swarms have further extended advantages as they can cover much larger areas in shorter times. In accordance with the requirements in terms of demand, it is possible to carry out various missions involving several types of UAVs as well as various onboard sensors. This task becomes even more complex when the system is composed of autonomous UAVs that collaborate with each other without the assistance of an operator. Several factors must be considered, such as the complexity of the mission, the types of UAVs, the communication architecture, the routing protocol, the coordination of tasks, and many other factors related to the environment. In this proposal, we will discuss the conceptual model and implementation of a multi-UAV system based on a decentralized master-slave architecture. We will then discuss the development environment using tools such as the ROS, MAVLINK, Gazebo, MavProxy/APM/QGround. We will address the communication concerns between UAVs that underlie the messages, services and actions enabling efficient swarm interation. Finally, we'll discuss the technical challenges and constraints involved in setting up such a project.

Keywords: Unmanned Aerial Vehicle (UAV); Uncrewed Aerial Vehicle; Autonomous Swarm; Collaborative Mission; Autonomous Aerial Vehicle; Autonomous Aerial Swarm; Drones

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  • Open Access Logo Lecture (Conference)
    PX4 autopilot Developer Summit 2023, 21.-22.10.2023, New Orleans, LA, USA

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Permalink: https://www.hzdr.de/publications/Publ-38066


Removal of antibiotic resistance genes from wastewater using diethylaminoethyl cellulose as a promising adsorbent

Pant, A.; Jain, R.; Ahammad, S. Z.; Ali, S. W.

The implications associated with the emergence of antibiotic resistance genes (ARGs) are dangerous, and there is an urgent need for their effective removal from the environment. The current study is a comprehensive evaluation of the potential of diethylaminoethyl cellulose (DEAE-C) to target the adsorptive removal of ARGs using a template DNA under different working conditions like varying adsorbate concentrations, time, working pH, coexisting anions and real waste water matrix. The obtained results exhibited excellent adsorption efficiency of DEAE-C with high Langmuir maximum adsorption capacity of 65.40 μg/mg at pH 7 ± 0.5. The adsorption process was majorly governed by the electrostatic force of attraction. Desorption study was performed for the adsorbent reusability. Maximum desorption was attained at pH 8 ± 0.5 using 2 ml 0.5 M NaCl. The adsorbent exhibited great recyclability up to 10 regeneration

Keywords: AMR; Wastewater; adsorption; antibiotics

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Permalink: https://www.hzdr.de/publications/Publ-38065


Siderophores assisted recovery of critical metals from mining residues

Jain, R.; Pollmann, K.; Ghosh, A.; Dhiman, S.; Mondol, P.; Jain, P.

Critical raw materials (CRM) such as gallium (Ga), germanium (Ge), indium (In) are necessary for the development of high-tech and low carbon emission technologies such as photovoltaics, fiber optics cable, liquid crystal display and light emitting diodes. The supply of these CRM is not assured in future due to several reasons. One of the ways to overcome this shortage is through CRM recovery from low concentrated mining/urban wastes. However, such a recovery is impeded because of high concentration of contaminants and very low concentration of the CRM. Thus, a sensitive and specific process is needed.
Siderophores are highly selective molecules towads Fe(III) and their this selectivitiy is also extended towards other CRM. Thus, the siderphores, desferrioxamine B (DFOB), has been exploited for the recovery of these CRMs from different wastes. The complexation of free DFOB with Ga and Ge was investigated. pH and ionic strength has no effect on the DFOB complexation with Ga while Ge showed much better complexity at low pH values and higher ionic stregth. There was again little to no effect of anions on the DFOB complexation with Ga while DFOB complexation with Ge increased with the increase in presence of anions. The EDTA was able to completely decomplex both Ga-DFOB and Ge-DFOB complexes.

For the technology development, DFOB was immobilized onto the solid-matrix with the free NH3 tail. The optimized length of the linker was needed for the successful immobilization of DFOB. Maximum of 3 - 6 mg of Ga/Ge/In per g of the DFOB immobilized solid matrix was achieved during batch adsorption studies. In the next steps, DFOB immobilized solid-matrix was packed in the column and the technology was demonstrated at 10 L/day and 100 L/day capacity with the real wastewater from the wafer manufacturing company. Maximization of the flow rate and identification of the upscaling parameters was carried out. Further, flowsheet were developed with pretreatment for the recovery of Ga and Ge from the mining residues. The GaLIophore techology is already patented and has potential to economically recover CRM from low concentrated wastes/wastewater with much lower environmental impact compared to traditional processes.

Keywords: Critical metals; Siderophores; GaLIophore; scale-up; Mining residues

  • Lecture (Conference)
    Goldschmidt 2023, 09.-14.07.2023, English, France

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Permalink: https://www.hzdr.de/publications/Publ-38064


Numerical Investigation of Liquid-Solid Flow Dynamics in an Oscillatory Baffled Reactor

Mondol, P.; Ambekar, A. S.; Jain, R.; Ahammad, S. Z.

The oscillatory baffled reactor (OBR) is widely used in the chemical and biochemical industry to perform solid-catalyzed reactions such as fermentation, leaching, polymerization, etc., and is a good reactor intensification strategy. The overall performance of these reactors depends on the dynamics of the spatial distribution of micron-scale catalyst particles. The spatial distribution of the particles is not only a function of the physical properties of the solid and liquid phase but also a function of baffle geometry and oscillatory conditions [i.e., frequency and amplitude], which substantially influences the hydrodynamics of OBR. To the best of the author's knowledge, the hydrodynamics of OBR, in the presence of particles is not investigated. In view of the above, we investigate the hydrodynamics of OBR, in the presence of particles, with the aid of a 3D two-fluid Eulerian-Eulerian approach combined with the kinetic theory of granular flow (EE-KTGF). Before using the simulations to investigate the hydrodynamics for a wide range of conditions, the predictions of EE-KTGF were validated with aid of measurements in terms of mixing/settling time as a function of solid properties. The validated model is further used to understand the role of particle size (10 to 100 µm), density (1100 to 2200 kg/m3), and (0.833 to 1.583 Hz) on the local liquid-solid hydrodynamics. The predictions demonstrate that, at a high, small particle size and density, recirculatory vortices are formed, aiding uniform radial mixing. However, at low, large particle sizes, and densities, local dead zones start appearing leading to the sedimentation of particles. The presented hydrodynamics predictions provide a useful basis for further intensification of liquid-solid OBRs.

Keywords: Oscillatory baffled reactor; hydrodynamics; solid-liquid separation; CFD

  • Lecture (Conference)
    Fluidization 2023, 21.-25.05.2023, English, Unites States

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Permalink: https://www.hzdr.de/publications/Publ-38063


Mineralogy and critical metal deportment of Fe-Ni-Co laterite ores from Sebuku Island, SE Kalimantan, Indonesia

Giorno, M. A.; Kontonikas-Charos, A.; Ebert, D.; Krause, J.; Möckel, R.; Sandmann, D.; Burisch, M.; Ernowo, E.; Idrus, A.; Swamidharma, Y.; Krisnanto, Y.; Frenzel, M.

Laterite deposits in Indonesia are a major source of Ni and Co. Here, we present new geological data on the Sebuku laterite deposit (Island of Sebuku, SE Kalimantan, Indonesia), with a JORC-compliant resource of ~390 Mt at 42.5 wt.% Fe, 0.9 wt.% Ni, and 0.15 wt.% Co. The laterites are mostly limonitic, oxide-dominated Fe-Ni-Co (±Sc)-rich horizons, which formed by weathering of Jurassic-Cretaceous ophiolitic units. Although the deposit is under production since 2006 (primarily for Fe), there is little mineralogical and geochemical data available, which would allow optimizing beneficiation and recovery of Ni, Co, and Sc.
Typical laterite profiles at Sebuku consist of: 1) weathered bedrock composed of serpentinized dunites and harzburgites overlain by 2) a 0.2-7 m-thick saprolite zone, 3) a 2-8.5 m-thick yellow limonite zone, and 4) a 1-3.5 m-thick red-limonite zone.
Preliminary X-ray fluorescence (XRF), X-ray diffraction (XRD), and mineral liberation analysis (MLA) data show a decrease in Mg and Si and an increase in Fe moving upwards through the laterite profile, corresponding to a transition from silicate- to oxide-rich mineralogy. Oxides and (oxy)-hydroxides comprise goethite, maghemite, hematite, magnetite, chromium spinel, gibbsite/bayerite, and various Mn-minerals, whereas silicates consist of serpentine, chlorite, talc, quartz, pyroxene, olivine, clay minerals, and “garnierite”-like minerals. Ni is hosted by various minerals, which include goethite, Mn-oxides, serpentine, and garnierite, whereas Co is mainly hosted by Mn-oxides and garnierite. It is still unclear in which minerals Sc is primarily hosted.
Mineral chemical analyses (EPMA) are planned to further understand critical metal variability and distribution within the host minerals and throughout the deposits. The first results will be presented here. Our ultimate goal is to characterize and quantify the distribution of Ni, Co and Sc in order to develop more efficient beneficiation processes.

  • Poster
    SEG 2023 Conference: Resourcing the Green Transition, 26.-29.08.2023, London, UK

Permalink: https://www.hzdr.de/publications/Publ-38062


The MALA package - Transferable and Scalable Electronic Structure Simulations Powered by Machine Learning

Fiedler, L.; Cangi, A.

Interactions between electrons and nuclei, the principal building blocks of matter, determine all materials properties. Understanding and modeling these interactions therefore is of paramount importance to pressing scientific questions, e.g., in the context of renewable energy solutions or sustainable materials. However, electronic structure simulations often face a trade-off between accuracy and system size . One may simulate materials at quantum-accuracy, but can only do so for a few thousand atoms, even with the most advanced electronic structure tools, such as density functional theory (DFT). Conversely, large-scale simulations suffer from drastically reduced predictive power due to necessary approximations.

The Materials Learning Algorithms (MALA) package tackles this challenge by combining neural networks, physically constrained optimization algorithms, and efficient post-processing routines to construct machine-learning models of DFT (ML-DFT). Unlike existing ML approaches, MALA creates ML-DFT models that completely replace DFT, providing access to both scalar quantities like energies and volumetric information about the electronic structure, such as the electronic density. We have demonstrated that MALA can be used with any number of atoms (successfully tested with 100’000 atoms), covering a wide range of temperatures and pressures. MALA enables a promising approach for materials modeling at unattained scale and accuracy.

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Invited lecture (Conferences)
    2023 HZDR Science Conference, 16.11.2023, Dresden, Görlitz
  • Lecture (Conference)
    DPG-Frühjahrstagung, 18.-22.03.2024, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38061


Multi-sensor data fusion using deep learning for bulky waste image classification

Bihler, M.; Roming, L.; Jiang, Y.; Afifi, A. J.; Aderhold, J.; Čibiraitė-Lukenskienė, D.; Lorenz, S.; Gloaguen, R.; Gruna, R.; Heizmann, M.

Deep learning techniques are commonly utilized to tackle various computer vision problems, including recognition, segmentation, and classification from RGB images. With the availability of a diverse range of sensors, industry-specific datasets are acquired to address specific challenges. These collected datasets have varied modalities, indicating that the images possess distinct channel numbers and pixel values that have different interpretations. Implementing deep learning methods to attain optimal outcomes on such multimodal data is a complicated procedure. To enhance the performance of classification tasks in this scenario, one feasible approach is to employ a data fusion technique. Data fusion aims to use all the available information from all sensors and integrate them to obtain an optimal outcome. This paper investigates early fusion, intermediate fusion, and late fusion in deep learning models for bulky waste image classification. For training and evaluation of the models, a multimodal dataset is used. The dataset consists of RGB, hyperspectral Near Infrared (NIR), Thermography, and Terahertz images of bulky waste. The results of this work show that multimodal sensor fusion can enhance classification accuracy compared to a single-sensor approach for the used dataset. Hereby, late fusion performed the best with an accuracy of 0.921 compared to intermediate and early fusion, on our test data.

Keywords: multispectral data; data fusion; image classification; CNN; multi-stream model; intermediate fusion; late fusion; multi-sensor data; multimodal data

Permalink: https://www.hzdr.de/publications/Publ-38060


Multi-Sensor Characterization for an Improved Identification of Polymers in WEEE Recycling

de Lima Ribeiro, A.; Fuchs, M.; Lorenz, S.; Röder, C.; Heitmann, J.; Gloaguen, R.

Polymers represent around 25% of total waste from electronic and electric equipment. Any successful recycling process must ensure that polymer-specific functionalities are preserved, to avoid downcycling. This requires a precise characterization of particle compounds moving at high speeds on conveyor belts in processing plants. We present an investigation using imaging and point measurement spectral sensors on 23 polymers including ABS, PS, PC, PE-types, PP, PVC, PET-types, PMMA, and PTFE to assess their potential to perform under the operational conditions found in recycling facilities. The techniques applied include hyperspectral imaging sensors (HSI) to map reflectance in the visible to near infrared (VNIR), short-wave (SWIR) and mid-wave infrared (MWIR) as well as point Raman, FTIR and spectroradiometer instruments. We show that none of the sensors alone can identify all the compounds while meeting the industry operational requirements. HSI sensors successfully acquired simultaneous spatial and spectral information for certain polymer types. HSI, particularly the range between (1600–1900) nm, is suitable for specific identification of transparent and light-coloured (non-black) PC, PE-types, PP, PVC and PET-types plastics; HSI in the MWIR is able to resolve specific spectral features for certain PE-types, including black HDPE, and light-coloured ABS. Fast-acquisition Raman spectroscopy (down to 500 ms) enabled the identification of all polymers regardless their composition and presence of black pigments, however, it exhibited limited capacities in mapping applications. We therefore suggest a combination of both imaging and point measurements in a sequential design for enhanced robustness on industrial polymer identification.

Keywords: e-waste; electronic waste; plastics; sensor network; hyperspectral imaging sensors; raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-38059


Structural and magnetic properties of thin cobalt films with mixed hcp and fcc phases

Patel, G. I.; Ganss, F.; Salikhov, R.; Stienen, S.; Fallarino, L.; Ehrler, R.; Gallardo, R. A.; Hellwig, O.; Lenz, K.; Lindner, J.

Cobalt is a magnetic material that finds extensive use in various applications, ranging from
magnetic storage to ultrafast spintronics. Usually, it exists in two phases with different crystal lattices, namely in
hexagonal close-packed (hcp) or face-centered cubic (fcc) structure. The crystal structure of Co films
significantly influences their magnetic and spintronic properties. We report on the thickness dependence of the
structural and magnetic properties of sputter-deposited Co on a Pt seed layer. It grows in an hcp lattice at low
thicknesses, while for thicker films, it becomes a mixed hcp-fcc phase due to a stacking fault progression along
the growth direction. The X-ray based reciprocal space map technique has been employed to distinguish and
confirm the presence of both phases. Moreover, the precise determination of Landé’s g-factor by ferromagnetic
resonance provides valuable insights into the structural properties. In our detailed experiments, we observe
that a structural variation results in a nonmonotonic variation of the magnetic anisotropy along the thickness.
The work offers information of great significance and insight for both fundamental physics and potential
applications of thin films with perpendicular magnetic anisotropy.

Keywords: Magnetic Anisotropy; Reciprocal Space Mapping; Ferromagnetic Resonance

  • Lecture (Conference)
    Magnetism and Magnetic Materials, 30.10.-03.11.2023, Hyatt Regency Dallas, Texas, USA

Permalink: https://www.hzdr.de/publications/Publ-38057


Influences of the wall distance and initial shape on the dynamic behaviors of near-wall bubbles

Yan, H.; Zhang, H.; Zhang, H.; Liao, Y.; Wu, D.; Liu, L.

The phenomenon of buoyancy-driven bubbles near a fluid‒solid interface is common in both natural settings and industrial processes, such as oil and gas exploration and production. The intricate dynamics of bubbles are profoundly shaped by their interactions with adjacent solid walls. In this study, a direct numerical simulation of bubbles rising near a wall is conducted using the volume of fluid method. The motion behavior and wake vortex structure of bubbles with three types of migration trajectories (linear, zigzag, and spiral) are analyzed. The influences of the initial shape and wall distance of the bubbles on their motion trajectory, rising velocity, and wake structure is investigated. The results show that the presence of a nearby wall obstructs the diffusion of eddies across a bubble surface, and the repulsive force induced by the wall increases as the distance between the bubble and the wall decreases. Remarkably, at a dimensionless wall distance of 0.6, a change in the lateral lift direction triggers a collision between a zigzagging bubble and the wall, consequently setting the bubble into a bouncing motion mode. In the case of spiral-moving bubbles, proximity to the wall enhances the likelihood of oscillations within the bubble's migration trajectory along the x-y plane while maintaining stability along the z-y plane. While variations in the initial aspect ratio of bubbles have marginal impacts on the migration paths of linear and zigzagging bubbles, the initial shape affects the migration trajectory of spiral bubbles to some extent. The bubble migration trajectory first experiences oscillations when the initial deformation reaches its maximum.

Keywords: Bubble; Wall effect; wall distance; initial shape; wake vortex structure

Permalink: https://www.hzdr.de/publications/Publ-38055


Surface Functionalization of Industrial Materials and its Influence on Oxygen Nucleation

Heinrich, J.; Schwarzenberger, K.; Yang, X.; Eckert, K.

Proton-exchange membrane (PEM) electrolysis is one of the mostly used principles for H2 generation. To increase its efficiency, an enhanced O2 separation in the anodic cycle is necessary to reduce overvoltage and improve cooling. In this work, we investigate the surface functionalization with direct laser interference pattering (DLIP) and plasma coating (PECVD) of Ti64 and polypropylene to tune the affinity of the nonpolar gas to the materials by varying the hydrophilicity/hydrophobicity. The water contact angle is used to characterize the wettability. It gradually increases after the DLIP due to the adsorption of carbon compounds from the environment [1]. We observed that the effect is highly dependent on the surrounding media and also is reversible. Our experimental findings are supported by XPS and confocal microscopy measurements. Since DLIP requires heat resistant materials, we further investigated low-pressure plasma coating. Via optical recording we analyse the influence of the wettability on the O2 nucleation and provide first insights on how the oxygen separation of the anodic cycle of PEM electrolysers can be tuned by surface functionalization.

Keywords: surface functionalization; wettability; oxygen; bubble nucleation

  • Lecture (Conference)
    9th Bubble and Drop Conference, 11.-16.06.2023, Lublin, Poland

Permalink: https://www.hzdr.de/publications/Publ-38054


EMFL - a Distributed User Facility

Wosnitza, J.

Abstract nicht vorgelegen

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Invited lecture (Conferences)
    Regional Meeting on Research in High Magnetic Fields, 06.-08.09.2023, Prag, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-38053


Materials Research in High Magnetic Fields at the HLD

Wosnitza, J.

Abstract nicht vorgelegen

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Invited lecture (Conferences)
    Magnetic Fields in Materials Research, 22.-24.05.2023, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-38052


Linking Sn-Li-(W-Cu) mineralization to post-collapse caldera evolution through cassiterite LA-ICP-MS U-Pb geochronology

Leopardi, D.; Gerdes, A.; Albert, R.; Gutzmer, J.; Lehmann, B.; Burisch-Hassel, M.

The Sadisdorf Sn-Li-(W-Cu) prospect, eastern Erzgebirge/ Krušné hory, is one of several Sn-W vein- and greisen-style deposits that are associated to the Altenberg-Teplice Caldera (ATC) system. Cassiterite mineralization is hosted by greisen alteration and stockworks intimately related to the composite Sadisdorf leucogranitic porphyry as well as a NE-SW striking vein system. The latter appears spatially – and possibly also genetically - unrelated to the Sadisdorf leucogranitic porphyry. Here, we applied LA-ICP-MS U-Pb geochronology to 16 cassiterite samples from the Sadisdorf prospect in order to constrain the timing of ore formation in the regional context of the evolution of the ATC.

All cassiterite ages range between 315.1± 3.3 Ma and 311± 4.0 Ma site and overlap within uncertainty across the Sadisdorf prospect – irrespective of the style of mineralization. Their calculated weighted mean average ages for greisen / stockwork and vein-hosted mineralization are 313.07±0.56 Ma and 313.2±1.6 Ma, respectively. This suggests that cassiterite mineralization at Sadisdorf is related to one single magmatic-hydrothermal event, albeit possibly associated to two spatially separated magmatic centers.

The cassiterite ages also coincide with the intrusion age of several microgranitic and rhyolitic dikes (314-313 Ma) that were emplaced late during the collapse of the ATC. This relates Sn mineralization to the late stages of the caldera evolution and suggests that Sn mineralization in the eastern Erzgebirge occurred 5-12 Ma later than previously assumed. The occurrence of fertile intrusion during the late stages of a caldera evolution is documented elsewhere (e.g. Mt. Aetna, USA and Mt. Pleasant, Canada) and provides useful criteria for regional exploration targeting.

Keywords: Caldera; Lithium; Tin; U-Pb cassiterite; geochronology

  • Lecture (Conference)
    SEG Conference 2023, 26.-29.08.2023, London, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-38051


LA-ICP-MS U-Pb cassiterite age data of the Sadisdorf deposit link Sn-Li-(W-Cu) mineralization in the eastern Erzgebirge to the collapse of the Altenberg-Teplice Caldera

Leopardi, D.; Gerdes, A.; Albert, R.; Gutzmer, J.; Lehmann, B.; Burisch-Hassel, M.

The Sadisdorf Sn-Li-(W-Cu) prospect in the eastern Erzgebirge (Germany) comprises two distinct styles of magmatic-hydrothermal mineralization, namely greisen-type mineralization at the Kupfergrube site, and stockwork-type mineralization at both the Kupfergrube and the Zinnklüfte sites. Previously, these two sites were regarded as expressions of two temporally distinct mineralization events. In this study, this temporal relation was tested by LA-ICP-MS U-Pb data obtained for 16 cassiterite samples, including samples from both sites and styles of mineralization. All 16 samples define a narrow range of ages between 315.1 ± 1.7 / 3.3 Ma and 311 ± 3.1 / 4.0 Ma. All ages overlap within uncertainty, suggesting that mineralization across the Sadisdorf prospect is likely related to the same magmatic-hydrothermal event.
On the regional scale, the cassiterite ages suggest that Sn-Li mineralization is associated with late-stage felsic magmatism directly following the collapse (~314-313 Ma) of the Altenberg-Teplice Caldera. The cassiterite ages also overlap with garnet U-Pb LA-ICP-MS ages of Sn-rich skarn occurrences in the western Erzgebirge (e.g., Breitenbrunn, Antonsthal and Hämmerlein). This observation provides direct evidence that greisen and skarn-hosted Sn mineralization are related to the same period of magmatism. The data indicate that the majority of Sn-mineralization in the Erzgebirge formed after 318 Ma (likely between 318-310 Ma), challenging previous models which invoked an older suite of granites (326-318 Ma) as causative source intrusions.

Keywords: LA-ICP-MS; geochronology; U-Pb cassiterite; Tin; Lithium; Caldera

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Permalink: https://www.hzdr.de/publications/Publ-38049


Data publication: A continuous multiphase model for liquid metal batteries

Godinez-Brizuela, O. E.; Duczek, C.; Weber, N.; Nash, W.; Sarma, M.; Einarsrud, K. E.

Cycling data for experiment 3: Raw data, processed data and figures.

Keywords: liquid metal battery; energy storage; multiphase flow; Na-Zn

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-38048


Selected case studies on the bioremediation of uranium-contaminated (mine) waters

Raff, J.; Krawczyk-Bärsch, E.; Hilpmann, S.; Wollenberg, A.; Günther, A.; Klotzsche, M.; Steudtner, R.; Drobot, B.

The aim of the lecture is to give an overview of the equipment at the Institute of Resource Ecology and what analytical options this includes. Furthermore, current research work is presented in the context of the remediation of contaminated water and soil. Building on this, the potential and limits of biological processes and possibilities for collaboration will be shown.

Keywords: Bacteria; Fungi; Plants; Uranium accumulation; Uranium reduction

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    Interregional Training Course on Environmental Remediation Design and Implementation, 27.11.-01.12.2023, Nanchang, China

Permalink: https://www.hzdr.de/publications/Publ-38046


Magnetic Properties of Actinide 2-Pyridone Complexes

Grödler, D.; Kaden, P.; Stumpf, T.; Gericke, R.

The anionic form of 2-pyridone (2-pyridyloxy; PyO) has proven to be a useful ligand for the synthesis of heterobimetallic complexes and thus supporting bonds between transitions metals (TM) and/or main-group elements. However, this chemistry has so far been limited to these groups, although interesting coordination motifs can be expected especially with actinides. Together with the high coordination numbers and various oxidation states, actinide 2-pyridyloxy complexes would have the necessary flexibility to bind a variety of transition metals.
Initially, we were interested in binding modes of 2-pyridone towards Th(IV) and U(IV). We have synthesized and characterized a series of heteroleptic actinide 2-pyridone complexes [AnCl₄(HPyO)₂], [ThCl₄(HPyO)₄], [AnX₂(HPyO)₆]X₂ and [AnCl(HPyO)₇]Cl₃ starting from [AnX₄(THF)₃] (An = Th, U; X = Cl, Br) and various equivalents of HPyO (2-7 equiv.). In addition, recent results show that Cu(I) is a suitable transition metal to realize heterobimetallic An-TM complexes.

Keywords: heterobimetallic; nuclear magnetic resonance spectroscopy; SQUID; single crystal X-ray diffraction

  • Poster
    2023 HZDR Science Conference, 15.-16.11.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38045


Fundamentals and concepts for the bioremediation of contaminated sites and water

Raff, J.

The presentation gives an overview of the different microbial diets and how plants, fungi and bacteria can be used for the bioremediation of uranium contaminated sites and waters. In particular, the advantages and disadvantages of the various approaches are named and a recommendation is given.

Keywords: Bioremediation; Uranium mining; Microbial metabolism

  • Invited lecture (Conferences)
    Interregional Training Course on Environmental Remediation Design and Implementation., 27.11.-01.12.2023, Nanchang, China

Permalink: https://www.hzdr.de/publications/Publ-38044


Heteroleptic Actinide 2-Pyridone Complexes

Grödler, D.; Kaden, P.; Stumpf, T.; Gericke, R.

The anionic form of 2-pyridone (2-pyridyloxy; PyO) has proven to be a useful ligand for the synthesis of heterobimetallic complexes and thus supporting bonds between transitions metals (TM) and/or main-group elements. However, this chemistry has so far been limited to these groups, although interesting coordination motifs can be expected especially with actinides. Together with the high coordination numbers and various oxidation states, actinide 2-pyridyloxy complexes would have the necessary flexibility to bind a variety of transition metals.

Keywords: heterobimetallic; nuclear magnetic resonance spectroscopy; single crystal X-ray diffraction

  • Poster
    Projektstatusgespräch 2023 zu BMUV-geförderten FuE-Projekten zur Entsorgung radioaktiver Abfälle, 06.-07.11.2023, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-38043


The Hexacoordinate Si Complex SiCl₄(4-Azidopyridine)₂—Crystallographic Characterization of Two Conformers and Probing the Influence of SiCl₄-Complexation on a Click Reaction with Phenylacetylen

Riedel, S.; Gerwig, M.; Gerlach, D.; Brendler, E.; Gericke, R.; Kroke, E.; Wagler, J.

4-Azidopyridine (1) and SiCl₄ react with the formation of the hexacoordinate silicon complex SiCl₄(4-azidopyridine)₂ (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl₄ and forms back upon cooling. Depending on the cooling, two different crystalline modifications of 2 were obtained, which feature two different trans-conformers. Slow cooling to room temperature afforded conformer 2′, which features coplanar pyridine rings. Rapid cooling to −39 °C afforded crystals of conformer 2′′, in which the planes of the pyridine ligands are nearly orthogonal to one another. Whereas 2′ resembles the molecular arrangement of various other known SiX₄(pyridine)₂ (X = halide) complexes, 2′′ represents the first crystallographically confirmed example of a SiX₄(pyridine)₂ complex in this conformation. Conformers 2′ and 2′′ were studied with ¹³C and ²⁹Si solid state NMR spectroscopy. Their differences in ²⁹Si chemical shift anisotropy, as well as energetic differences, were further investigated with computational analyses. In spite of the similar stabilities of the two conformers as isolated molecules, the crystal packing of 2′′ is less stable, and its crystallization is interpreted as a kinetically controlled effect of seed formation. (3+2)-cycloaddition of 1 and phenylacetylene in toluene at 110 °C yields a mixture of 1-(4-pyridyl)-4-phenyl-1,2,3-triazole (1,4-3) and 1-(4-pyridyl)-5-phenyl-1,2,3-triazole (1,5-3) in approximate 1:2 molar ratio. The crystal structures of the two isomers were determined via X-ray diffraction. In chloroform (at 60 °C), this reaction is slow (less than 2% conversion within 4 h), but the presence of SiCl₄ enhanced the rate of the reaction slightly, and it shifted the triazole isomer ratio to ca. 1:6 in favor of 1,5-3.

Keywords: chemical shift anisotropy; (3+2)-cycloaddition; Hirshfeld surface analysis; hypercoordination; packing efficiency; polymorphism; silicon; triazole

Permalink: https://www.hzdr.de/publications/Publ-38042


Bridging scales to understand species spatial organization

Colombo, E. H.; Saraiva De Menezes, J. F.; Calabrese, J.

From data we first construct a Langevin equation to describe the movement of the individuals. The ctmm1 package can be used to extract the parameters behind intrinsic dynamics of each individual (potential, diffusion coefficient, etc.). However, individuals’ home-range (i.e. the area they occupy) are also shaped by its interaction with individual nearby. For that we need to resolve the forces felt by individuals during encounters2 and then scale-up their effects. This coarse-graining process generates a PDE for the temporal evolution of the occupancy probability of a given individual. This final equation, extracted from data, provides a data-driven description of the formation and maintenance of home-ranges.

Keywords: Animal movement; Home-range; Interactions

  • Poster
    Big data analytical methods for complex systems, 18.10.2023, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-38041


Optimizing animal movement studies: developing an application to evaluate study design

Simoes Silva, I. M.; Fleming, C. H.; Noonan, M. J.; Fagan, W. F.; Calabrese, J.

The study of movement behavior and home range in animals is fundamental to understanding ecological dynamics, yet designing efficient tracking studies remains a challenge due to the lack of clear guidelines. To address this knowledge gap we created 'movedesign,' a user-friendly application that enables researchers to evaluate the precision of three commonly reported movement and spatial ecology estimates: home range area, speed, and distance traveled. Leveraging the 'ctmm' R package, our application employs autocorrelated kernel density estimators (AKDEs) and continuous-time speed and distance (CTSD) estimators, effectively addressing biases inherent in animal movement datasets. By evaluating the interplay between data resolution and battery life, 'movedesign' guides researchers in making informed decisions to achieve reliable estimates of home range and velocity while considering trade-offs. With broad applications for researchers and decision-makers, this tool empowers efficient deployment strategies, optimizing sampling design for insightful and robust outcomes in movement ecology studies.

Keywords: ecology; conservation; software development; experimental design; biologgers; GPS sampling; GPS tracking; simulations; home range; space use

  • Open Access Logo Lecture (Conference)
    HZDR Science Conference 2023, 15.-16.11.2023, Helmholtz-Zentrum Dresden-Rossendorf e. V., Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-38040


A material study on magnetocaloric liquefaction of hydrogen

Gottschall, T.

Es hat ein Abstrakt vorgelegen.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • Lecture (Conference)
    MML Workshop, 27.-29.09.2023, Jena, Deutschland
  • Lecture (Conference)
    2023 MRS Spring Meeting & Exhibit, 10.-14.04.2023, San Francisco, USA

Permalink: https://www.hzdr.de/publications/Publ-38039


Structures and ore deposits in the Eastern Erzgebirge: Linking the mineral system with post-Variscan transtension

Cerny, J.; Thiele, S. T.; Guilcher, M.; Burisch-Hassel, M.; Gutzmer, J.

The Eastern Erzgebirge region is exceptionally well endowed in magmatic-hydrothermal ore deposits related to granitic magmatism following the Paleozoic Variscan Orogeny. The Elbe Shear Zone (ESZ) is a major geological structure that forms the prominent eastern border of the Erzgebirge. The ESZ separates the Erzgebirge from the Lausitz Block – the latter being poor in known magmatic-hydrothermal mineralizations. This raises the question about the possible role of the ESZ in the evolution of the Eastern Erzgebirge mineral systems.
The ESZ is well known to be a zone of long-lived (and still ongoing) tectonic activity with mostly dextral kinematics and a total of ~40–50 km offset. It has been subject to a complex interplay of late to post-Variscan tectonic, magmatic, and sedimentary processes, which have left a distinct signature in the magmatic and sedimentary rock record. At least two distinct trans-tensional events can be distinguished and attributed to the dextral activity on the ESZ. These are recorded by (1) the Meissen Massif, a complex intrusion that was emplaced at 330–320 Ma in a dilatational jog, and (2) the Döhlen Basin near Freital, the volcano-sedimentary infill of a small pull-apart basin with abundant ignimbrite/tuff units ranging in age from ~294–286 Ma. The latter evidences for tectonic reactivation along the ESZ and synchronous magmatic events.
These ages bracket a potentially extensive period of activity of the ESZ, supporting a potential for a spatio-temporal link between the ESZ and formation of the Tharandt and Altenberg-Teplice Calderas at ~315–310 Ma. The latter is well known to host a number of small granitic stocks with related Sn-Li-(W-Cu) mineralization. This contribution is a part of the “New Potential” project initiated by the State Geological Survey of Saxony, which deals with the exploration of new perspective areas in the Eastern Erzgebirge mountains. Here, we explore the link between this trans-tensional tectonics and granitic magma emplacement in the Eastern Erzgebirge to better understand the tectonic control on the associated magmatic mineral systems. Significantly, we find that zones of strain-transfer between NW–SE striking dextral strike-slip faults localize felsic magmatism, by accommodating intrusions and establishing favorable pathways to the lower crust through which melts can ascend.

Keywords: Transtension; Erzgebirge; Elbe shear zone; Post-Variscan intrusions; Dilatational jog

  • Lecture (others)
    Pre-Conference Field Trip FT02: Erzgebirge - The Ore Mountains of Saxony and Bohemia: Old District–New Opportunities - Sn, W, Li, Ag, Base Metals, 18.-24.08.2023, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-38036


DATIV-Dynamic Aerosol Transport for Indoor Ventilation with Smart Array of Particulate MAtter Sensors (SAPMAS)

Schunk, C.

DATIV is an open source, low cost, distributed, portable sensor system which incorporates cameras and particulate matter sensors (PMS). This system can employ multiple sensors simultaneously and can be remotely operated using a web based GUI.

Keywords: Raspberry Pi; Camera; Particulate Matter; SBC; Aerosol; Sensor; COVID-19; Wi-Fi; Ventilation

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-38035


Needs for a Comprehensive European Plan to Acquire and Curate Nuclear Data

Körner, G.-E.; Dimitriou, P.; Boeltzig, A.; Garbil, R.; Leray, S.; Lewitowicz, M.; Widmann, E.

A Consultant’s Meeting was held at the IAEA to discuss the needs for a comprehensive European plan to acquire and curate nuclear data. Participants representing nuclear data groups, the nuclear physics community (NuPECC), and the existing funding agency (EURATOM), reviewed the status of nuclear data curation in Europe, including coordination, funding, and capacity building. A summary of the discussions as well as the list of recommendations and actions are included in this report.

Keywords: Nuclear Data; IAEA Nuclear Data Section; INDC International Nuclear Data Committee

  • Open Access Logo Other report
    Vienna, Austria: IAEA International Atomic Energy Agency, 2023

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Permalink: https://www.hzdr.de/publications/Publ-38032


The world-class Schlema-Alberoda U-(Ag-Co-Ni) deposit (Germany): mineralogy and fluid characteristics

Guilcher, M.; Gutzmer, J.; Hiller, A.; Krause, J.; Blamey, N.; Härtel, B.; Burisch-Hassel, M.

The Schlema-Alberoda deposit represents one of the largest uranium deposits in Europe with uranium ores closely associated with native metal-arsenide mineralization. All mineralization styles occur in veins and stockwork zones that crosscut carbon-rich Devonian to Silurian metasediments and metabasites. This study investigates the native metal-arsenide veins in the district and provides an update on mineral paragenesis and novel fluid inclusion data. Native metal-arsenide mineralization occurs as vein-hosted ore shoots with native metals (Ag, Bi, As) and Co-Ni-Fe arsenides. Within the native metal-arsenide stage, five mineral associations are identified: (i) bismuth-skutterudite-safflorite, (ii) silver-rammelsbergite-skutterudite, (iii) arsenic-silver-loellingite, (iv) loellingite and (v) arsenic-sulfosalt-sulphide. Fluid inclusions measured in dolomite-ankerite that occur as gangue minerals have homogenization temperatures of ~115-150°C with fluid salinities of ~24.4-27.3 wt% (NaCl+CaCl2) eq. The spatial relationship between native metal-arsenide across the deposit and carbon-rich lithologies suggest reduction of the ore fluid as a decisive precipitation process. Microthermometric data indicate mixing of a sedimentary and a basement brine, which is also documented for other occurrences of native metal-arsenide mineralization across Europe that are all related to Mesozoic continental rifting.

Keywords: Cobalt; Uranium; Arsenide; Fluid inclusion; Microthermometry; Crush-fast scan gas mass spectrometry; Erzgebirge; Five-element mineralization

  • Lecture (Conference)
    17th SGA Biennial Meeting, 28.08.-01.09.2023, ETH Zürich, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-38028


Neues Potenzial project, first interim report

Cerny, J.; Guilcher, M.; Thiele, S. T.; Burisch-Hassel, M.; Gutzmer, J.

This document is the first internal report for the “Neues Potenzial” project in collaboration with the Sächsisches Landesamt für Umwelt, Landwirtschaft und Geologie (LfULG). This two-year project will develop a novel mineral systems model for the Eastern Erzgebirge (Germany) with a focus on magmatic-hydrothermal Li-Sn-W greisen, skarn and Ag-Pb-Zn vein-style mineralization related to late Variscan or post-orogenic granitoid intrusions. The results obtained will be used to constrain search space and to define exploration vectors for future mineral exploration in the Eastern Erzgebirge region.

  • Other report
    Freiberg: HZDR and LfULG, 2023
    49 Seiten

Permalink: https://www.hzdr.de/publications/Publ-38027


Magnetochiral effects in geometrically curved magnetic architectures

Volkov, O.

Symmetry effects are fundamental in condensed matter physics as they define not only interactions but also resulting responses for the intrinsic order parameter depending on its transformation properties with respect to the operations of space and time reversal. Magnetic materials or layer stacks with structural space inversion symmetry breaking obtained much research attention due to the appearance of chiral Dzyaloshinskii-Moriya interaction (DMI) [1,2]. The latter manifests itself in the formation of non-trivial chiral and topological spin textures (e.g. skyrmions, bubbles, homochiral spirals and domain walls), that are envisioned to be utilized for prospective spintronic devices. At present, tailoring magnetochirality is done by the selection of materials and adjustment of their composition. Alternatively, space inversion symmetry breaking of the magnetic order parameter appears in geometrically curved systems [3]. In curvilinear ferromagnets, curvature governs the appearance of geometry-induced chiral and anisotropic responses, which introduce a new toolbox to create artificial chiral nanostructures from achiral magnetic materials suitable for the stabilization of non-trivial chiral textures [4,5].
Recently, much attention was dedicated to the exchange interaction, which enables curvature-induced extrinsic DMI as was proposed theoretically and validated experimentally for the case of conventional achiral magnetic materials [6]. Here, we demonstrate the existence of non-local chiral effects in geometrically curved asymmetric permalloy cap with the vortex texture. Using the full-scale simulation of the asymmetric nanodots we study how the vortex texture is changing with respect to the introduced sample asymmetry.

Reference list
1. I. Dzyaloshinsky, J. Phys. Chem. Solids 4 (1958), 241.
2. T. Moriya, Phys. Rev. Lett. 4 (1960), 228.
3. R. Hertel, SPIN 3 (2013), 1340009.
4. D. Makarov, et al., Adv. Mater. 34 (2021), 2101758.
5. D. D. Sheka, et al., Commun. Phys. 3 (2020), 128.
6. O. M. Volkov, et al., Phys. Rev. Lett. 123 (2019), 077201.

Keywords: Dzyaloshinskii-Moriya interaction; Non-local chirality breaking; Magnetic vortex; Micromagnetics

Involved research facilities

  • Data Center
  • Invited lecture (Conferences) (Online presentation)
    NATO Advanced Research Workshop 2023, 25.-28.09.2023, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-38025


Local and non-local effects in curvilinear micromagnetism

Volkov, O.

Dzyaloshinskii-Moriya interaction, also known as an antisymmetric exchange interaction, is the main source of chiral symmetry breaking effects in micromagnetic systems [1]. The later manifests itself in magnetic materials and layer stacks with structural space inversion symmetry breaking, where it leads to the formation of non-trivial chiral and topological spin textures (e.g. skyrmions, bubbles, homochiral spirals and domain walls). Such textures potentially could be utilized for prospective spintronic devices as a bit carrier. Still, tailoring of magnetochirality is only done by the selection of materials and adjustment of their composition in layer stacks.
Alternatively, we demonstrate that space inversion symmetry breaking of the magnetic order parameter appears in geometrically curved systems [2]. In curvilinear ferromagnets, curvature governs the appearance of geometry-induced chiral and anisotropic responses, which introduce a new toolbox to create artificial chiral nanostructures from achiral magnetic materials suitable for the stabilization of non-trivial chiral textures [2,3]. Moreover, curvilinear geometry also leads to the appearance of non-local chiral effects, that arise from the asymmetry of the top and bottom surfaces and existence of both in- and out-of-plane magnetization components of different parity with respect to the reflection procedure [4]. Recently, we demonstrate the existence of non-local chiral effects in geometrically curved asymmetric permalloy cap with the vortex texture [5]. We find that the equilibrium vortex core obtain both bend and curling deformation, that are dependent on the geometric symmetries and magnetic parameters.

References
[1] A. Fert, N. Reyren and V. Cros, Nature Reviews Materials 2, 17031 (2017).
[2] D. Makarov, O. M. Volkov, A. Kákay, O. V. Pylypovskyi, B. Budinská and O. V. Dobrovolskiy, Adv. Mater. 34, 2101758 (2021).
[3] O. M. Volkov, A. Kákay, F. Kronast, I. Mönch, M.-A. Mawass, J. Fassbender and D. Makarov, Phys. Rev. Lett. 123, 077201 (2019).
[4] D. D. Sheka, O. V. Pylypovskyi, P. Landeros, Y. Gaididei, A. Kákay and D. Makarov, Commun. Phys. 3, 128 (2020).
[5] O. M. Volkov, D. Wolf, O. V. Pylypovskyi, A. Kákay, D. D. Sheka, B. Büchner, J. Fassbender, A. Lubk and D. Makarov, Nat. Commun. 14, 1491 (2023).

Keywords: Dzyaloshinskii-Moriya interaction; Non-local chirality breaking; Curvilinear Magnetism; Micromagnetics; Magnetic vortex

Involved research facilities

  • Data Center
  • Invited lecture (Conferences)
    ”Nanomaterials: Applications & Properties” (IEEE NAP) 2023, 11.-15.09.2023, Bratislava, Slovakia

Permalink: https://www.hzdr.de/publications/Publ-38024


Local and non-local chiral effects in curvilinear nanomagnets

Volkov, O.; Wolf, D.; Pylypovskyi, O.; Kakay, A.; Sheka, D.; Büchner, B.; Faßbender, J.; Lubk, A.; Makarov, D.

Dzyaloshinskii-Moriya interaction, also known as an antisymmetric exchange interaction, is the main source of chiral symmetry breaking effects in micromagnetic systems [1]. The later manifests itself in magnetic materials and layer stacks with structural space inversion symmetry breaking, where it leads to the formation of non-trivial chiral and topological spin textures (e.g. skyrmions, bubbles, homochiral spirals and domain walls). Such textures potentially could be utilized for prospective spintronic devices as a bit carrier. Still, tailoring of magnetochirality is only done by the selection of materials and adjustment of their composition in layer stacks.
Alternatively, we demonstrate that space inversion symmetry breaking of the magnetic order parameter appears in geometrically curved systems [2]. In curvilinear ferromagnets, curvature governs the appearance of geometry-induced chiral and anisotropic responses, which introduce a new toolbox to create artificial chiral nanostructures from achiral magnetic materials suitable for the stabilization of non-trivial chiral textures [2,3]. Moreover, curvilinear geometry also leads to the appearance of non-local chiral effects, that arise from the asymmetry of the top and bottom surfaces and existence of both in- and out-of-plane magnetization components of different parity with respect to the reflection procedure [4]. Recently, we demonstrate the existence of non-local chiral effects in geometrically curved asymmetric permalloy cap with the vortex texture [5]. We find that the equilibrium vortex core obtain both bend and curling deformation, that are dependent on the geometric symmetries and magnetic parameters.

References
[1] A. Fert, N. Reyren and V. Cros, Nature Reviews Materials 2, 17031 (2017).
[2] D. Makarov, O. M. Volkov, A. Kákay, O. V. Pylypovskyi, B. Budinská and O. V. Dobrovolskiy, Adv. Mater. 34, 2101758 (2021).
[3] O. M. Volkov, A. Kákay, F. Kronast, I. Mönch, M.-A. Mawass, J. Fassbender and D. Makarov, Phys. Rev. Lett. 123, 077201 (2019).
[4] D. D. Sheka, O. V. Pylypovskyi, P. Landeros, Y. Gaididei, A. Kákay and D. Makarov, Commun. Phys. 3, 128 (2020).
[5] O. M. Volkov, D. Wolf, O. V. Pylypovskyi, A. Kákay, D. D. Sheka, B. Büchner, J. Fassbender, A. Lubk and D. Makarov, Nat. Commun. 14, 1491 (2023).

Keywords: Dzyaloshinskii-Moriya interaction; Topological spin textures; Magnetic vortex; Curvilinear magnetism

Involved research facilities

  • Data Center
  • Lecture (Conference)
    Joint Conference of the Italian and European Community of Condensed Matter Physics 2023, 04.-08.09.2023, Milan, Italy

Permalink: https://www.hzdr.de/publications/Publ-38023


Local and non-local chirality breaking effects in curvilinear nanoarchitectures

Volkov, O.

The main origin of the chiral symmetry breaking and, thus, for the magnetochiral effects in magnetic materials is associated with an antisymmetric exchange interaction, the intrinsic Dzyaloshinskii-Moriya interaction (DMI) [1,2]. The later manifests itself in magnetic materials or layer stacks with structural space inversion symmetry breaking. The DMI is responsible for the formation of non-trivial chiral and topological spin textures (e.g. skyrmions, bubbles, homochiral spirals and domain walls), that are envisioned to be utilized for prospective spintronic devices. At present, tailoring of magnetochirality is done by the selection of materials and adjustment of their composition.
Alternatively, we demonstrate that space inversion symmetry breaking of the magnetic order parameter appears in geometrically curved systems [3]. In curvilinear ferromagnets, curvature governs the appearance of geometry-induced chiral and anisotropic responses, which introduce a new toolbox to create artificial chiral nanostructures from achiral magnetic materials suitable for the stabilization of non-trivial chiral textures [4,5,6]. Moreover, curvilinear geometry also leads to the appearance of non-local chiral effects, that arise from the asymmetry of the top and bottom surfaces and existence of both in- and out-of-plane magnetization components of different parity with respect to the reflection procedure [5]. Recently, we demonstrate the existence of non-local chiral effects in geometrically curved asymmetric permalloy cap with the vortex texture. We find that the equilibrium vortex core obtain both bend and curling deformation, that are dependent on the geometric symmetries and magnetic parameters.

References
[1] I. Dzyaloshinsky, J. Phys. Chem. Solids 4 (1958), 241.
[2] T. Moriya, Phys. Rev. Lett. 4 (1960), 228.
[3] R. Hertel, SPIN 3 (2013), 1340009.
[4] D. Makarov, et al., Adv. Mater. 34 (2021), 2101758.
[5] D. D. Sheka, et al., Commun. Phys. 3 (2020), 128.
[6] O. M. Volkov, et al., Phys. Rev. Lett. 123 (2019), 077201.

Keywords: Dzyaloshinskii-Moriya interaction; Cuvilinear magnetism; 3D magnetic architectures; Micromagnetics; Magnetic vortex

Involved research facilities

  • Data Center
  • Invited lecture (Conferences)
    The Joint European Magnetic Symposia 2023, 28.08.-01.09.2023, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-38022


Micromagnetic parameters and longitudinal relaxation in ultrathin asymmetrically sandwiched magnetic films

Volkov, O.; Yastremsky, I. A.; Pylypovskyi, O.; Kronast, F.; Abert, C.; Oliveros Mata, E. S.; Makushko, P.; Mawass, M.-A.; Kravchuk, V. P.; Sheka, D.; Ivanov, B. A.; Faßbender, J.; Makarov, D.

Ultrathin asymmetric magnetic films are a prominent material science platform, which combines unique magnetic and electronic properties enabling prospective memory and logic spin-orbitronic devices. Here, we present the quantification mechanism to distinguish all static and dynamic micromagnetic parameters of the layer stack based on magnetometry [1] and quasi-static morphology experiments on domain wall equilibrium tilts [2]. The DW damping is found to be about 0.1 [2] and it is demonstrated to arise from a longitudinal relaxation being dominant among transversal mechanisms for ultrathin films [3].

[1] I. A. Yastremsky et al., Phys. Rev. Appl. 12, 064038 (2019).
[2] O. M. Volkov et al., Phys. Rev. Appl. 15, 034038 (2021).
[3] I. A. Yastremsky et al., Phys. Rev. Appl. 17, L061002 (2022).

Keywords: Ultrathin asymmetric magnetic film; Domain wall; Spin-otbit torque; Micromagnetics

Involved research facilities

  • Data Center
  • Lecture (Conference)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38021


Chirality coupling in curvilinear nanoarchitectures

Volkov, O.; Wolf, D.; Pylypovskyi, O.; Kakay, A.; Sheka, D.; Büchner, B.; Faßbender, J.; Lubk, A.; Makarov, D.

Symmetry effects are key building blocks of condensed matter physics as they define not only interactions but also resulting re- sponses for the intrinsic order parameter. Namely, in magnetism geometric curvature governs the appearance of chiral and anisotropic responses [1], that introduce a new toolbox to create artificial chi- ral nanostructures from achiral magnetic materials [2,3]. Here, we demonstrate both theoretically and experimentally the existence of non-local chiral effects in geometrically curved asymmetric permalloy caps with the vortex texture. We find that the equilibrium vortex core obtain bend and curling deformation, that are dependent on the geometric symmetries and magnetic texture parameters.
[1] D. D. Sheka et al., Comm. Phys. 3, 128 (2020).
[2] O. M. Volkov et al., Phys. Rev. Lett, 123, 077201 (2019).
[3] D. Makarov et al., Adv. Mater. 34, 2101758 (2022).

Keywords: Symmetry effects; Cuvilinear magnetism; Magnetic vortex; Micromagnetics

Involved research facilities

  • Data Center
  • Lecture (Conference)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-38020


Data publication: Ab initio insights on the ultrafast strong-field dynamics of anatase TiO2

Suma Balakrishnan, S. L.; Lokamani, M.; Ramakrishna, K.; Cangi, A.; Murali, D.; Posselt, M.; Assa Aravindh, S.

Data and input scripts of the project "Ab initio insights on the ultrafast strong-field dynamics of anatase TiO2".

Keywords: Density functional theory; Electron dynamics; Quantum systems; Thin films

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Permalink: https://www.hzdr.de/publications/Publ-38018


Evolution of point defects in pulsed-laser-melted Ge1-xSnx probed by positron annihilation lifetime spectroscopy

Steuer, O.; Liedke, M. O.; Butterling, M.; Schwarz, D.; Schulze, J.; Li, Z.; Wagner, A.; Fischer, I. A.; Hübner, R.; Zhou, S.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.

Direct-band-gap Germanium-Tin alloys (Ge1-xSnx) with high carrier mobilities are promising materials for nano- and optoelectronics. The concentration of open volume defects in the alloy, such as Sn and Ge vacancies, influences the final device performance. In this article, we present an evaluation of the point defects in molecular-beam-epitaxy grown Ge1-xSnx films treated by post-growth nanosecond-range pulsed laser melting (PLM). Doppler broadening – variable energy positron annihilation spectroscopy and variable energy positron annihilation lifetime spectroscopy are used to investigate the defect nanostructure in the Ge1-xSnx films exposed to increasing laser energy density. The experimental results, supported with ATomic SUPerposition calculations, evidence that after PLM, the average size of the open volume defects increases, which represents a raise in concentration of vacancy agglomerations, but the overall defect density is reduced as a function of the PLM fluence. At the same time, the positron annihilation spectroscopy analysis provides information about dislocations and Ge vacancies decorated by Sn atoms. Moreover, it is shown that the PLM reduces the strain in the layer, while dislocations are responsible for trapping of Sn and formation of small Sn-rich-clusters.

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-38017


Non-local chirality breaking in curvilinear nanoarchitectures

Volkov, O.; Wolf, D.; Pylypovskyi, O.; Kakay, A.; Sheka, D.; Büchner, B.; Faßbender, J.; Lubk, A.; Makarov, D.

Symmetry effects are fundamental in condensed matter physics as they define not only interactions but also resulting responses for the intrinsic order parameter depending on its transformation properties with respect to the operations of space and time reversal. Magnetic materials or layer stacks with structural space inversion symmetry breaking obtained much research attention due to the appearance of chiral Dzyaloshinskii-Moriya interaction (DMI) [1,2]. The latter manifests itself in the formation of non-trivial chiral and topological spin textures (e.g. skyrmions, bubbles, homochiral spirals and domain walls), that are envisioned to be utilized for prospective spintronic devices. At present, tailoring magnetochirality is done by the selection of materials and adjustment of their composition. Alternatively, space inversion symmetry breaking of the magnetic order parameter appears in geometrically curved systems [3]. In curvilinear ferromagnets, curvature governs the appearance of geometry-induced chiral and anisotropic responses, which introduce a new toolbox to create artificial chiral nanostructures from achiral magnetic materials suitable for the stabilization of non-trivial chiral textures [4,5].
Recently, much attention was dedicated to the exchange interaction, which enables curvature-induced extrinsic DMI as was proposed theoretically and validated experimentally for the case of conventional achiral magnetic materials [6]. Here, we demonstrate the existence of non-local chiral effects in geometrically curved asymmetric permalloy cap with the vortex texture. Using the full-scale simulation of the asymmetric nanodots we study how the vortex texture is changing with respect to the introduced sample asymmetry. We find that the equilibrium vortex core obtain both bend and curling deformation, that are dependent on the geometric symmetries and magnetic parameters. We relate the observed changes in the vortex string to the non-local chiral effects, that arise from the asymmetry of the top and bottom surfaces and existence of both in- and out-of-plane magnetization components of different parity with respect to the reflection procedure [5]. The obtained micromagnetic results were confirmed by magnetic imaging using transmission electron microscopy based electron holography for the asymmetric permalloy cap. These results will be discussed in the talk.
[1] I. Dzyaloshinsky, J. Phys. Chem. Solids 4 (1958), 241.
[2] T. Moriya, Phys. Rev. Lett. 4 (1960), 228.
[3] R. Hertel, SPIN 3 (2013), 1340009.
[4] D. Makarov, et al., Adv. Mater. 34 (2021), 2101758.
[5] D. D. Sheka, et al., Commun. Phys. 3 (2020), 128.
[6] O. M. Volkov, et al., Phys. Rev. Lett. 123 (2019), 077201.

Keywords: Symmetry effects; Non-local chirality breaking; Magnetic vortex; Micromagnetics

Involved research facilities

  • Data Center
  • Lecture (Conference)
    4th IEEE International Conference on Advances in Magnetics, IEEE AIM 2023, 16.-21.01.2023, Moena, Italy

Permalink: https://www.hzdr.de/publications/Publ-38016


IAEA’s Coordinated Research Projects on Thermal Hydraulics of Fast Reactors

Morelová, N.; Kriventsev, V.; Sumner, T.; Moisseytsev, A.; Heidet, F.; Wootan, D. W.; Casella, A. M.; Nelson, J. V.; Piazza, I. D.; Hassan, H.; Lorusso, P.; Martelli, D.; Yang, X.; Wang, J.; Lu, D.; Zhang, D.; Gerschenfeld, A.; Kliem, S.; Fridman, E.; Rineiski, A.; Kumaresan, N.; Giannetti, F.; Petruzzi, A.; Tanaka, M.; Jeong, J.-H.; Hong, J.; Stempniewicz, M.; Tsaun, S.; Volkov, A.; Wallenius, J.; Fiorina, C.; Mikityuk, K.; Vaghetto, R.; Omotowa, O.; Kelly, J.; Lane, J.

A Coordinated Research Project on “Benchmark Analysis of FFTF Loss of Flow Without Scram Test” was launched by the International Atomic Energy Agency (IAEA) in 2018. A series of passive safety tests were conducted from 1980-1992 at the Fast Flux Test Facility (FFTF), 400 MW(th) liquid sodium cooled nuclear test reactor owned by U.S. Department of Energy (DOE) to demonstrate the potential of FFTF to survive severe accident initiators with no core damage. Amongst these tests was a series of Loss of Flow Without Scram (LOFWOS) tests from power levels up to 50%, also commonly referred to as Unprotected Loss of Flow (ULOF) tests, which were studied in the IAEA CRP. The data were provided by the Argonne National Laboratory (ANL) and Pacific Northwest National Laboratory (PNNL).

Another Research Coordinated Project on “Benchmark of Transition from Forced to Natural Circulation Experiment with Heavy Liquid Metal Loop” was launched by the IAEA in 2022. Three tests were conducted in 2017 to study the thermal-hydraulic behavior of a test fuel assembly cooled by lead-bismuth eutectic alloy during transition from forced to natural convection at the NACIE-UP facility at Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Italy. This project is the first IAEA CRP that is dedicated to the thermal hydraulics of lead and lead bismuth eutectic (LBE) technology.

The paper provides a general overview of the two CRPs within the framework of the IAEA activities on thermal hydraulics of fast reactors.

  • Contribution to proceedings
    30th International Conference on Nuclear Engineering (ICONE30), 21.-26.05.2023, Kyoto, Japan
    DOI: 10.1299/jsmeicone.2023.30.1632

Permalink: https://www.hzdr.de/publications/Publ-38015


Junctionless Nanowire Transistor: From Devices to Sensing Applications

Ghosh, S.; Khan, M. B.; Echresh, A.; Kentsch, U.; Prucnal, S.; Vardhan, V.; Biswas, S.; Hellebust, S.; Holmes, J.; Erbe, A.; Georgiev, Y.

Downscaling of complementary metal-oxide-semiconductor (CMOS) technology is fraught with difficulties. As a result, novel devices and circuits, sophisticated nanomaterials, and enhanced fabrication processes have become increasingly important in recent decades. Particularly, silicon nanowires have been employed effectively in innovative electronic devices, including sensors, solar cells and in logic circuitry. Due to their high surface to volume ratio, silicon nanowires have been demonstrated as energy efficient devices, which is the key for the next generation of information processing. Field-effect-transistors based on silicon nanowires have been extensively used for sensing applications since the compact nanoscale structures allow excellent regulation of electrostatic potential across the nanowire channel. One such nanowire concept is junctionless nanowire transistor (JNT). A JNT is a highly doped nanowire channel without p-n junctions, where the gate electrode regulates the flow of charge carriers. Silicon JNTs have shown excellent sensi tivity to record-low concentrations of the protein streptavidin in liquid phase. However, they have not yet been operated as gas sensors.
In this work, we report the fabrication and characterization of silicon-based JNT devices and their initial tests as gas sensors. Intrinsic silicon-on-insulator (SOI) substrates are ion-implanted with phosphorus (n-type) dopant. Millisecond range flash lamp annealing (FLA) is used for dopant activation and implantation defect healing. Top-down approach is carried out for nanowire fabrication using electron beam lithography patterning of the negative resist HSQ followed by reactive ion etching. Successive processes of rapid thermal oxidation, nitrogen purge step and forming gas annealing are performed to create SiO2 shell around the silicon nanowires. SiO2 thickness is controlled by optimizating the time and temperature in these steps. UV lithography and metal evaporation are employed to create 50 nm thick Nickel contacts to the nanowires. Electrical characterization of these JNTs is performed by back-gating the nanowires. Unipolar device behavior is observed . However, these characteristics are changed after contact annealing leading to the ambipolarity in the devices. Two such transfer characteristics of JNTs based on unpassivated nanowires and nanowires with 3 nm SiO2 shell. These devices exhibit an on/off ratio of ~10^6. To further investigate the ambipolar nature of the silicon JNTs, output characteristics are measured, which shows Schottky barrier-based behavior of the devices. Furthermore, van der Pauw and Hall Effect measurements are performed to determine their carrier concentration and hall mobility. Successive measurements of electrical characteristics of these devices are also performed in vacuum to compare them with the usual ambient measurements. Unfunctionalized JNTs are tested as sensors in purified air and NO2 atmosphere. These sensor tests exhibited characteristic shifts in the transfer curve and a systematic increase and decrease of p- and ntype current, respectively, under the influence of NO2. These tests confirmed the potential suitability of the ambipolar JNT as sensors in gaseous environment. Additionally, these devices will be functionalized and tested for electrical detection of atmospheric free radicals.

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Related publications

  • Lecture (Conference)
    49th Micro and Nano Engineering Conference (MNE), 25.-28.09.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-38014


Ultrafast Optical Pump-probe of Magnetic Kagome Metals

Goncalves Faria, M. V.; Winnerl, S.; Pashkin, O.; Helm, M.; Uykur, E.

The Kagome lattice is a two-dimensional network of corner-sharing triangles that is known to combine linear bands hosting massless Dirac fermions and dispersionless flat bands featuring massive localized electrons, both arising due to its geometry. FeSn binary compounds and the RM$_6$Sn$_6$(R=Tb,Gd and Y) series are commonly studied magnetic Kagome metals, which possess different magnetic ground states and interlayer Kagome coupling. Several steady-state experimental techniques have been used to study the magnetic and electronic structure of these materials and the effects of magnetism on the band structure. However, the ultrafast dynamics and the interplay of these unusual features have not yet been widely explored in the scope of time-domain spectroscopy. Here we present temperature- and fluence-dependent carrier dynamics of various magnetic Kagome metals studied using the optical pump-probe technique. Distinct carrier relaxations have been observed, and they can be partially attributed to the simple two-temperature model, as these are highly metallic compounds.

Keywords: Kagome metals; Optical pump-probe spectroscopy

  • Contribution to proceedings
    International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 17.09.2023, Montreal, Canada
    DOI: 10.1109/IRMMW-THz57677.2023.10299354
  • Lecture (Conference)
    International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 17.09.2023, Montreal, Canada

Permalink: https://www.hzdr.de/publications/Publ-38012


Intrusion tip velocity controls the emplacement mechanism of sheet intrusions

Köpping, J.; Cruden, A. R.; Thiele, S. T.; Magee, C.; Bunger, A.

Space for intruding magma is created by elastic, viscous, and/or plastic deformation of
host rocks. Such deformation impacts the geometries of igneous intrusions, particularly
sills and dikes. For example, tapered intrusion tips indicate linear-elastic fracturing during
emplacement, whereas fluidization of host rocks has been linked to development of elongate
magma fingers with rounded tips. Although host rock fluidization has only been observed at
the lateral tips of magma fingers, it is assumed to occur at their leading edges (frontal tips)
and thereby control their propagation and geometry. Here, we present macro- and micro-
structural evidence of fluidized sedimentary host rock at the lateral tips of magma fingers
emanating from the Shonkin Sag laccolith (Montana, western United States), and we explore
whether fluidization could have occurred at their frontal tips. Specifically, we combine heat
diffusion modeling and fracture tip velocity estimates to show that: (1) low intrusion tip ve-
locities (≤10−5 m s−1) allow pore fluids ahead of the intrusion to reach temperatures sufficient
to cause fluidization, but (2) when tip velocities are high (∼0.01–1 m s−1), which is typical for
many sheet intrusions, fluidization ahead of propagating tips is inhibited. Our results suggest
that intrusion tip velocity (i.e., strain rate) is a first-order control on how rocks accommodate
magma. Spatially and temporally varying velocities of lateral and frontal tips suggest that
deformation mechanisms at these sites may be decoupled, meaning magma finger formation
may not require host rock fluidization. It is thus critical to consider strain rate and three-
dimensional intrusion geometry when inferring dominant magma emplacement mechanisms.

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Permalink: https://www.hzdr.de/publications/Publ-38011


Geometallurgy workshop @ UFMG

Pereira, L.

The field of automated mineralogy has largely contributed to our understanding of mineral processing. Lately, by evaluating the particle information collected with automated mineralogy using statistical learning methods, it became possible to quantify the process behaviour of individual particles with consideration to their size, shape, liberation, and mineral association. In this workshop, we explore the latest methods used to quantify the recoverability of individual particles and how their results can be used to better understand mineral processing.

Keywords: Froth flotation; Particle based modelling; Geometallurgy; Raw materials

  • Invited lecture (Conferences)
    Geometallurgy workshop @ UFMG, 24.11.2023, Belo Horizonte, Brazil

Permalink: https://www.hzdr.de/publications/Publ-38010


Froth flotation study of SEDEX and VMS Pb-Zn ores under different pulp temperature constraints

Pashkevich, D.; Duggal, A.; Pereira, L.; Waters, K. E.

Sphalerite flotation represents one of a few sulfide recovery systems that experience significant variations in seasonal performance. The correlation between temperature and plant performance is observable in several zinc mines across the world, where both too high and too low temperatures impact recovery and grade. Here, we study the rougher flotation performance of two lead-zinc ores, of distinct geological settings, under controlled temperature conditions. A central composite design of the experiment approach is used to also investigate the effect of different flotation modifiers, namely lime, copper sulfate pentahydrate, and zinc sulfate heptahydrate. Process performance is evaluated by means of flotation kinetics, bubble size distribution (top), concentrate grade, yield, and water recovery. Results indicate that temperature variations lead to changes in froth stability, where a more stable froth is observed at colder temperatures and leads to higher yield and water recovery – presumably explaining the lower concentrate grades observed industrially.

Keywords: Froth flotation; Temperature; SEDEX; VMS

  • Contribution to proceedings
    Flotation '23, 06.-09.11.2023, Cape Town, South Africa
    Proceedings of Flotation '23
  • Lecture (Conference)
    Flotation '23, 06.-09.11.2023, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-38009


An open-source laboratory assistant tailored for flotation test work

Pereira, L.; Ben Said, B.; Hassan, A.; Rau, F.; Hoang, D. H.; Rudolph, M.

The role of laboratory-scale flotation test work for improving process understanding is unquestionable. Yet, to a large extent, laboratory routines are not standardized and may lead to considerable human errors. Operators have to simultaneously perform multiple tasks, and most data generated is often not saved, or saved without a proper structure. Laboratory assistants can potentially be used to overcome these issues. Yet, most options available are either dedicated to other scientific fields or cannot be easily tailored for flotation test work. Besides, sensors compatible with these solutions are often costly. Here, we introduce an open-source laboratory assistant tailored for flotation test work, which provides not only guidance for users, but also collects and orderly saves information from a series of affordable sensors (e.g., froth camera, pH, temperature, Eh, etc.). Benefits of using the laboratory assistant are demonstrated on two case studies: a reagent- and a flotation cell hydrodynamics-specific investigation.

  • Poster
    Flotation '23, 06.-09.11.2023, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-38008


Structural transformations in few-layer MnPSe₃ stimulated by thermal annealing and electron irradiation

Storm, A.; Köster, J.; Ghorbani Asl, M.; Kretschmer, S.; Gorelik, T. E.; Krasheninnikov, A.; Kaiser, U.

Transition metal phosphorous trichalcogenides (TMPTs) are inorganic materials with exciting properties, such as inherent magnetism combined with the electronic band gap. Due to their layered structure, these materials can be exfoliated into ultra-thin sheets, which show properties different from their bulk counterparts. In this work, we present an experimental study supported by first-principles calculations focused on tuning the properties of freestanding few-layer MnPSe₃ by local structural transformations stimulated by electron beam irradiation and thermal annealing under high vacuum conditions in a transmission electron microscope (TEM). In both cases, we observe the emergence of α- or γ-MnSe crystal structures. Using different TEM methods, we systematically investigate the irradiation-induced structural modifications. The results are rationalized with the help of ab-initio calculations, which predict that the elastic knock-on threshold for removing selenium is significantly higher than that for phosphorus. Nevertheless, an increased sputtering rate of Se as compared to P was detected by complementary spectroscopic experiments in this ternary compound, which indicates that inelastic damage mechanisms and etching play the dominant role within the low-voltage region. Moreover, the locally formed MnSe phases arise after the complete degradation of the host MnPSe₃ structure. First-principles calculations predict that the electronic and magnetic properties of 2D MnSe structures depend on the crystal types, facets, that is orientation of the crystallographic planes of the parent bulk material, and crystallite thickness.

Keywords: two-dimensional materials; Transition metal phosphorous trichalcogenides; transmission electron microscope; first-principles calculations; magnetism

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  • Secondary publication expected from 18.12.2024

Permalink: https://www.hzdr.de/publications/Publ-38007


Data publication: Portable Droplet-Based Real-Time Monitoring of Pancreatic α-Amylase in Postoperative Patients

Zhao, X.; Kolbinger, F. R.; Distler, M.; Weitz, J.; Makarov, D.; Bachmann, M.; Baraban, L.

research data on amylase concentration detection (Pancreatic α-Amylase in Postoperative Patients) with millifluidic device and plate reader and their statistical analysis

Keywords: pancreatic surgery; postoperative pancreatic fistula; pancreatic α-amylase; droplet-based millifluidics; point-of-care diagnostics

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Permalink: https://www.hzdr.de/publications/Publ-38005


Where I am – Chemical microscopy of Eu(III)

Steudtner, R.; Klotzsche, M.; Vogel, M.; Stadler, J.; Drobot, B.

Linking microscopy and spectroscopy based on the correlative application of state of the art spectroscopic, microscopic and biochemical methods and equipment is inevitable in the modern time of f-element biochemistry. The aim of this work was the direct visualization and localization in combination with the chemical identification and characterization of f-elements, here Eu(III), interacting with biostructures.
Herein, we utilized chemical microscopy – a combination of light microscopy and high resolution luminescence spectroscopy [1] – in order to spatially resolve the Eu(III) species distribution in an artificial natural sample. In this proof-of-concept study, a ternary system consisting of Eu(III), calcite and the metal reducing bacterium Shewanella oneidensis MR-1 was employed to confirm the applicability of chemical microscopy for environmental samples. Subsequent luminescence spectroscopic mapping and data deconvolution by the means of non-negative iterative factor analysis (NIFA) [2] resulted in three distinct signal sets: one Raman (pure calcite) and two Eu(III) emission spectra. Luminescence species assigned to Eu(III), on the one hand, that has been complexed with biofilm extracellular DNA (magenta-colored - Figure 1) and, on the other hand, protein bonded Eu(III), depicted in green. These findings emphasize the strength of the described analytical technique and open the field for further studies applying Eu(III) as molecular probe in order to understand complex interaction pathways of lanthanides in the environment. The utilization of Eu(III) as a luminescent probe for chemical microscopy additionally revealed the microscopic distribution of the Eu(III) in roots, root cross sections and individual cells presented by several examples.

  • Poster
    11th International Conference on f-Elements, 22.-26.08.2023, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-38004


Radioökologische Forschung am HZDR – Spannend bis in die Haarspitzen!

Steudtner, R.; Drobot, B.; Cherkouk, A.; Sachs, S.; Raff, J.

In der Umwelt beeinflussen physikalische, chemische und biologische Prozesse das Wanderungsverhalten von langlebigen Radionukliden (RN). Ziel der Forschung der Abteilung Biogeochemie ist es, dominierende Prozesse der Wechselwirkung von Radionukliden in der Biosphäre einschließlich der Nahrungskette zu identifizieren, die Biochemie dieser Prozesse auf molekularer Ebene zu verstehen und ihre Relevanz für Radionuklidmigration und -transfer nicht nur in der Natur, sondern auch im Umfeld eines Endlagers für hochradioaktive Abfälle zuverlässiger abschätzen zu können.
Für den sensitiven Nachweis, die Identifikation des Chemismus sowie der Lokalisation von Radionukliden in verschiedenen biologischen Matrices und aquatischen Systemen nutzen wir eine Vielzahl von spektroskopischen und mikroskopischen Verfahren. Eine zentrale Rolle spielt dabei die Laser-induzierte Anregung der Lumineszenz von Actiniden und Lanthaniden, welche in Verbindung mit hochauflösender Mikroskopie die Beschreibung radioökologischer Prozesse in einer neuen Detailtiefe erlaubt. Mit dieser einzigartigen Kombination konnte zum Beispiel eine Actinid-induzierte Stressantwort bei Pflanzenzellen nachgewiesen, und die chemische Bindungsform von Uran in komplexen Umweltproben analysiert werden. Ein wichtiger Teilaspekt ist dabei außerdem die qualitative und quantitative Erfassung der chemo- und radiotoxischen Wirkung endlagerrelevanter als auch natürlich vorkommender Radionuklide (naturally occuring radioactive materials - NORM) in Organismen und ihre Zellen.
Weitere Arbeiten befassen sich aktuell mit der Fragestellung, wie sich eine Uranbelastung in der Umgebung von Goldminen auf die im Umland lebende Bevölkerung auswirkt. Dazu wird gegenwärtig in einem gemeinsamen Projekt mit dem VKTA und der Wismut GmbH der Schwermetallgehalt in Haarproben von Personen mittels massenspektrometrischer Methoden bestimmt und bewertet, die im Umland von Johannisburg und nahe des weltweit größten Goldvorkommens, der Witwatersrand-Lagerstätte, leben. Beim Abbau des begehrten Edelmetalls gelangt auch gesundheitsschädlicher, giftiger und radioaktiver Bergbauabfall als Nebenprodukt an die Oberfläche.
Die aufgeführten Beispiele belegen eindrücklich, wie wichtig es ist, das Verhalten von Radionukliden in der Umwelt zu erforschen, zu verstehen und vorhersagbar zu machen, um die Bevölkerung und Natur effektiv zu schützen.

  • Poster
    10. RCA Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38003


Portable Droplet-Based Real-Time Monitoring of Pancreatic α-Amylase in Postoperative Patients

Zhao, X.; Kolbinger, F. R.; Distler, M.; Weitz, J.; Makarov, D.; Bachmann, M.; Baraban, L.

Postoperative complications after pancreatic surgery are frequent and can be life-threatening. Current clinical diagnostic strategies involve time-consuming quantification of α-amylase activity in abdominal drain fluid, which is performed on the first and third postoperative day. The lack of real-time monitoring may delay adjustment of medical treatment upon complications and worsen prognosis for patients. We report a bedside portable droplet-based millifluidic device enabling real-time sensing of drain α-amylase activity for postoperative monitoring of patients undergoing pancreatic surgery. Here, a tiny amount of drain liquid of patient samples is continuously collected and co-encapsulated with a starch reagent in nanoliter-sized droplets to track the fluorescence intensity released upon reaction with α-amylase. Comparing the α-amylase levels of 32 patients, 97% of the results of the droplet-based millifluidic system matched the clinical data. Our method reduces the α-amylase assay duration to approximately three minutes with the limit of detection 7 nmol/s·L, enabling amylase activity monitoring at the bedside in clinical real-time. The presented droplet-based platform can be extended for analysis of different body fluids, diseases, and towards a broader range of biomarkers, including lipase, bilirubin, lactate, inflammation, or liquid biopsy markers, paving the way towards new standards in postoperative patient monitoring.

Keywords: pancreatic surgery; postoperative pancreatic fistula; pancreatic α-amylase; droplet-based millifluidics; point-of-care diagnostics

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Permalink: https://www.hzdr.de/publications/Publ-38002


Actinide-MOF chemistry and applications

Schmidt, M.; Lyu, K.; März, J.; Fichter, S.; Patzschke, M.; Kaden, P.

Actinide metal-organic frameworks (An-MOFs) have garnered considerable attention in recent years.1 Yet, this class of compounds remains understudied compared with their transition metal or lanthanide homologues and this, despite a wide range of interesting properties, which may be turned into promising applications, from radiation detection to tailor-made nuclear waste forms. Moreover, this novel group of metal-organic compounds allows for straightforward comparison with molecular complexes, which have been the target of fundamental studies in actinide science for some time.
We will discuss a series of isoreticular MOFs based on mononuclear An(IV) (Th, U, Np, Pu) primary building units in which each actinide is coordinated by six molecules of 9,10-anthracenedicarboxylic acid (ADC).2 This arrangement leads to an unusually large coordination number of 12 in icosahedral symmetry. Quantum chemical calculations indicate that this large coordination number is only feasible in the high-symmetry environment provided by the An-MOFs. Moreover, these MOFs not only demonstrate autoluminescence but also wide-bandgap (2.89 eV) semiconducting properties. In addition, we will present recent findings, illustrating how selective crystallization from mixed-metal solutions may present a viable pathway for the production of actinide waste forms from specialized waste streams. As an example we will present the formation of Th-MOFs containing isonicotinic acid linkers in the presence of a wide range of metals representative of fission products.3

REFERENCES
[1] K. Lv et al., Coord. Chem. Rev. 446, 214011 (2021) and references therein.
[2] K. Lv et al., J. Am. Chem. Soc. 144, 2879 (2022).
[3] K. Lv et al., ACS Mater. Lett. 5, 536 (2023).

Involved research facilities

Related publications

  • Lecture (Conference)
    Actinides, 04.-08.06.2023, Golden, CO, USA
  • Lecture (Conference)
    Journées des Actinides, 17.-21.04.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-38001


Lisbon Summer School - Mid-term check - Innovative Target Modules for FAP-Targeting UniCAR T therapy

Boutier, H.; Feldmann, A.; Rodrigues Loureiro, L. R.; Arndt, C.; Hoffmann, L.; Bachmann, M.

This presentation was given in Lisbon for the first OncoProTools Summer School.

Keywords: Summer School; OncoProTools

  • Lecture (others)
    Mid-Term Check - Lisbon - OncoProTools Summer School, 14.-15.09.2023, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-38000


Thermoelectric Magnetohydrodynamic Control in Alloy Solidification

Kao, A.; Fan, X.; Shevchenko, N.; Tonry, C.; Soar, P.; Krastins, I.; Eckert, S.; Pericleous, K.; Lee, P. D.

Magnetic fields have been shown to have a significant effect during solidification in a wide range of conditions from the slow growth of traditional casting to the more rapid growth of Additive Manufacturing. An underlying phenomenon is Thermoelectric Magnetohydrodynamics (TEMHD), which, due to inherent thermal gradients, generate thermoelectric currents and ultimately a Lorentz force through interaction with the magnetic field. In casting this leads to inter-dendritic convective solute transport. This can be used to control freckle defect formation in the GaIn system, where the magnetic field can be used to reposition channel formation, introduce preferential growth of secondary arms, plume migration and complex grain boundary interactions. These mechanisms have been observed by X-ray synchrotron experiments and predicted by TESA (ThermoElectric Solidification Algorithm), a parallel Cellular Automata Lattice Boltzmann based numerical model.
In laser AM, melt pools are subject to large thermal gradients and consequently form relatively large thermoelectric currents. The system is highly dependent on the orientation and strength of the magnetic field with competition between Marangoni flow and TEMHD resulting in control of the depth, width and potential deflections of the melt pool. This leads to significant changes in the microstructure including modification to the melt pool boundary layer and epitaxial growth. The numerical predictions also compare favourably to X-ray synchrotron experiments.

Keywords: Magnetic fields; Alloy solidification; Additive Manufacturing; Thermoelectric Magnetohydrodynamics

  • Lecture (Conference)
    International scientific colloquium “Modelling for Materials Processing”, 18.-19.09.2023, Riga, Latvia

Permalink: https://www.hzdr.de/publications/Publ-37999


In-situ Measurements of Dendrite Tip Shape Selection in a Metallic Alloy

Neumann-Heyme, H.; Shevchenko, N.; Grenzer, J.; Eckert, K.; Beckermann, C.; Eckert, S.

The size and shape of the primary dendrite tips determine the principal length scale of the microstructure evolving during solidification of alloys. In-situ X-ray measurements of the tip shape in metals have been unsuccessful so far due to insufficient spatial resolution or high image noise. To overcome these limitations, high-resolution synchrotron radiography and advanced image processing techniques are applied to a thin sample of a solidifying Ga-35wt.%In alloy, as shown in Figure 1. Quantitative in-situ measurements are performed of the growth of dendrite tips during the fast initial transient and the subsequent steady growth period, with tip velocities ranging over almost two orders of magnitude. As shown in Figure 2, the value of the dendrite tip shape selection parameter is found to be σ^*=0.0768. According to microscopic solvability theory, this value suggests an interface energy anisotropy of ε_4=0.015 for the present Ga-In alloy. The non-axisymmetric dendrite tip shape amplitude coefficient is measured to be A_4≈0.004, which is in excellent agreement with the universal value previously established for dendrites.

Keywords: dendrite tip; In-situ Measurements; Ga - In alloys; Interface energy anisotropy

  • Invited lecture (Conferences)
    TMS 2023 Frontiers in Solidification: An MPMD Symposium Honoring Jonathan A. Dantzig, 19.-23.03.2023, San Diego, California, USA

Permalink: https://www.hzdr.de/publications/Publ-37998


The impact of melt flow on solidification patterns in a ternary Ga-In-Bi alloy

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

In situ X-ray observations are scarce for ternary and multi-component alloys. A Ga-In-Bi alloy is solidified in a Hele-Shaw cell under buoyancy-driven convection. A complex and strongly disoriented dendrite-type solid phase is formed that differs from a regular dendrite network. It is shown that primary arms of dendrites in a ternary system adapt their velocity to the local concentration ahead of their tips and change continuously or abruptly the growth direction. Some grains exhibit a morphology that is rather similar to the "seaweed" pattern. The appearance of seaweed grains is usually related to a solid/liquid interfacial energy. Further, we focus on the role of melt flow in transition from dendritic arrays to seaweed structures. In particular, it is shown that the splitting of a dendrite tip is preceded by the oscillation of the local intensity of the X-ray pattern which is related to the local concentration of the components.

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

  • Lecture (Conference)
    TMS 2023 Frontiers in Solidification: An MPMD Symposium Honoring Jonathan A. Dantzig, 19.-23.03.2023, San Diego, California, USA

Permalink: https://www.hzdr.de/publications/Publ-37997


Convolutional neural networks applied to quantify the process behaviour of complex individual particles in froth flotation

Pereira, L.; Avalos, S.; Li, T.; Ortiz, J.; Ballani, F.; Afifi, A. J. M.; Hassan, A.; Frenzel, M.; van den Boogaart, K. G.; Tolosana Delgado, R.

The field of automated mineralogy has largely contributed to our understanding of mineral processing. Lately, by evaluating the particle information collected with automated mineralogy using statistical learning methods, it became possible to quantify the process behaviour of individual particles with consideration to their size, shape, liberation, and mineral association. Yet, automated mineralogy still requires a large intervention from operators for constructing an ore-specific mineral list and performing a series of image processing tasks. Here, we propose a method to quantify the process behaviour of individual particles using convolutional neural networks on the raw data collected with automated mineralogy: backscattered electrons and characteristic X-Ray signals. The flotation of a complex copper porphyry ore is used as a case study. The accuracy of the method is compared to the current standard procedure: manually processing the automated mineralogy data followed by particle-based modelling with a logistic regression.

Keywords: raw materials; mineral processing; froth flotation; resource efficiency; convolutional neural networks

  • Contribution to proceedings
    Flotation '23, 06.-09.11.2023, Cape Town, South Africa
    Proceedings of Flotation '23
  • Lecture (Conference)
    Flotation '23, 06.-09.11.2023, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-37995


Multidimensional modelling of particle separation processes: an approach to highly increase the number of particle properties considered

Pereira, L.; Frenzel, M.; Tolosana Delgado, R.; Rudolph, M.

Two main approaches have been leading the latest contributions to the field of modelling particle separation processes: fundamental models that focus on the individual interactions taking place in a separation unit and empirical models that focus on the properties of individual particles (size, shape, and composition) and how they influence the separation process. Both these approaches have clear advantages and disadvantages. In this study we focus on the empirical approaches given their relevance to the raw materials field, where it is likely to encounter a large variation in particle properties, especially particle composition. Most importantly, the uniqueness of each particle in this field is expected to lead to a distinct process behaviour in a separation unit.
Tromp devised the partition curves, the first method to quantify particle behaviour in a separation process as a function of their properties. The latest developments in the field profited from the wealth of particle information provided by modern scanning electron microscope-based imaging techniques, which systematically quantifies, within a short time, a series of relevant particle properties – named here as particle data. These latest developments, however, require particles to be grouped into bins, and can only make use of up to ten particle properties. In this contribution, we present a strategy to fully benefit from the wealth of particle data, allowing to quantify the process behaviour of individual particles and to consider hundreds of particle properties. This strategy employs a regularized multinomial logistic regression, which is able to independently estimate the importance of different particle properties for the behaviour of a particle in a process and is sufficiently robust to deal with millions of particles. The relevance of the new strategy to the particle separation field is demonstrated here with a froth flotation experiment, where we highlight the effect of a particle size, shape, modal and surface composition to its overall behaviour in a flotation cell.

Keywords: raw materials; mineral processing; particle technology; resource efficiency

  • Lecture (Conference)
    PARTEC - International Congress on Particle Technology, 26.-28.09.2023, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37994


All About Particles: Modelling Ore Behaviour in Mineral Processing

Pereira, L.; Schach, E.; Tolosana Delgado, R.; Frenzel, M.

Mineral processing encompasses the series of operations used to first liberate the valuable minerals in an ore by comminution, and then separate the resulting particles by means of their geometric, compositional, and physical properties. From a geometallurgical perspective, it is fundamental to understand how ore textures influence the generation of ore particles and their properties. This contribution outlines the processes used to generate and concentrate ore particles, and how these are commonly modelled. A case study illustrates the main ideas. Finally, a brief outlook on the most important research challenges remaining in this branch of geometallurgy is presented.

Keywords: raw materials; mineral processing; particle technology; resource efficiency

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Permalink: https://www.hzdr.de/publications/Publ-37993


Momentum spectrum of Schwinger pair production in four-dimensional e-dipole fields

Degli Esposti, G.; Torgrimsson, G.

We calculate the momentum spectrum of electron-positron pairs created via the Schwinger mechanism by a class of four-dimensional electromagnetic fields called e-dipole fields. To the best of our knowledge, this is the first time the momentum spectrum has been calculated for 4D, exact solutions to Maxwell’s equations. Moreover, these solutions give fields that are optimally focused, and are hence particularly relevant for future experiments. To achieve this we have developed a worldline instanton formalism where we separate the process into a formation and an acceleration region.

Permalink: https://www.hzdr.de/publications/Publ-37992


Efficient Near-Infrared Light-Emitting Diodes Based on CdHgSe Nanoplatelets

Prudnikau, A.; Roshan, H.; Paulus, F.; Martín-García, B.; Hübner, R.; Bahmani Jalali, H.; de Franco, M.; Prato, M.; Di Stasio, F.; Lesnyak, V.

Cadmium mercury selenide (CdHgSe) nanocrystals exhibit a unique combination of low-energy optical absorption and emission, which can be tuned from the visible to the infrared range through both quantum confinement and adjustment of their composition. Owing to this advantage, such nanocrystals have been studied as a promising narrow-band infrared light emitter. However, the electroluminescence of CdHgSe-based nanocrystals has remained largely unexplored, despite their potential for emitting light in the telecom wavelength range. Further benefits to their optical properties are expected from their shape control, in particular the formation of 2D nanocrystals, as well as from a proper design of their heterostructures. In this work, a colloidal synthesis of CdHgSe/ZnCdS core/shell nanoplatelets (NPLs) starting from CdSe template NPLs employing a cation exchange strategy is developed. The heterostructures synthesized exhibit photoluminescence that can be tuned from ≈1300 to 1500 nm. These near-infrared-active NPLs are employed in light-emitting diodes, demonstrating low turn-on voltage and high external quantum efficiency.

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Permalink: https://www.hzdr.de/publications/Publ-37991


Lewis Acid-Base Adducts of α-Amino Acid-Derived Silaheterocycles and N-Methylimidazole

Seidel, A.; Gericke, R.; Kutzner, B.; Wagler, J.

In chloroform solution, the reaction of bis(tert-butylamino)dimethylsilane ((tBuNH)₂SiMe₂) and an α-amino acid (α-amino isobutyric acid, H₂Aib; D-phenylglycine, H₂Phg; L-valine, H₂Val) in the presence of N-methylimidazole (NMI) gave rise to the formation of the pentacoordinate silicon complexes (Aib)SiMe₂-NMI, (Phg)SiMe₂-NMI and (Val)SiMe₂-NMI, respectively. Therein, the amino acid building block was a di-anionic bidentate chelator at the silicon atom. In solution, the complexes were involved in rapid coordination–dissociation equilibria between the pentacoordinate Si complex (e.g., (Aib)SiMe₂-NMI) and its constituents NMI and a five-membered silaheterocycle (e.g., (Aib)SiMe₂), as shown by ²⁹Si NMR spectroscopy. The energetics of the Lewis acid-base adduct formation and the competing solvation of the NMI molecule by chloroform were assessed with the aid of computational methods. In CDCl₃ solution, deuteration of the silaheterocycle NH group proceeded rapidly, with more than 50% conversion within two days. Upon cooling to -44 °C, the chloroform solvates of the adducts (Aib)SiMe₂-NMI and (Phg)SiMe₂-NMI crystallized from their parent solutions and allowed for their single-crystal X-ray diffraction analyses. In both cases, the Si atom was situated in a distorted trigonal bipyramidal coordination sphere with equatorial Si–C bonds and an equatorial Si–N bond (the one of the silaheterocycle). The axial positions were occupied by a carboxylate O atom of the silaheterocycle and the NMI ligand’s donor-N-atom.

Keywords: bidentate ligands; deuterium transfer; hypercoordination; quantum chemical calculations; silicon; X-ray diffraction

Permalink: https://www.hzdr.de/publications/Publ-37990


Effects of a horizontal magnetic field on the cross-sectional distribution of gas bubbles chain rising in a gallium alloy

Murakawa, H.; Maeda, S.; Eckert, S.

Understanding the behavior of rising bubbles in a liquid metal under the influence of a magnetic field (MF) is
crucial for optimizing continuous casting processes. The study experimentally investigated the effects of a hor-
izontal MF on the behavior of bubble chains in a gallium alloy. High-speed ultrasonic computed tomography was
used to measure the instantaneous bubble crossing positions in a cylindrical column with an inner diameter of 50
mm. With an increase in the MF strength, the oscillations of the bubbles were suppressed, resulting in the
crossing position being concentrated in a certain area of the cross-section. The fluctuations in the time intervals
of the chain bubbles decreased. These effects were more pronounced when the magnetic interaction parameter
(or Stuart number) was greater than 1. The distribution of bubbles in the direction perpendicular to the MF was
widespread slightly compared to that in the direction parallel to the MF; this was noticeable at higher flow rates.
The suppression of the wake turbulence induced by the Lorentz force was larger in the direction parallel to the
MF than that in the direction perpendicular to the MF. Our results have the potential to be used for the direct
verification of numerical models.

Keywords: liquid metal; bubbly flow; magnetic field; high-speed ultrasonic computed tomography

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  • Secondary publication expected from 31.10.2024

Permalink: https://www.hzdr.de/publications/Publ-37988


Vibrations Analysis of Bubble Evolution in Liquids of Varying Physical Properties

Rigas, K.; Willers, B.; Eckert, S.; Glaser, B.

In recent years there is an attempt to control the gas stirring intensity in metal-making ladles with the aid of vibration measurements. Understanding better the induced vibrations in two-phase flows can substantially improve the existing models for gas stirring control. In this work, highly sensitive accelerometers were used for the vibration measurements in a liquid metal alloy; Sn–40 wt pctBi alloy at 200 °C and water at 20 °C. The examination of the liquids was conducted in the ladle mockup integrated into the Liquid Metal Model for Steel Casting facility at Helmholtz-Zentrum Dresden Rossendorf. Single bubbles were generated in the respective
liquids by controlled argon injection at low flow rates in the range of 0.01 to 0.15 NL/min through a single nozzle installed at the bottom of the ladle. Obtained results demonstrate differences between the induced vibrations in the examined liquids in terms of the magnitude of the root mean square values of vibration amplitude and the shape of the resulting curves with increasing flow rate. Furthermore, continuous wavelet transform reveals variations in the duration and vibrational frequency of the evolved bubble phenomena. The findings suggest that
differences in the physical properties of the examined liquids result in variations in the vibrations induced during bubble evolution.

Keywords: steel ladle; gas stirring; bubbly flow; vibration measurements

Involved research facilities

  • LIMMCAST

Permalink: https://www.hzdr.de/publications/Publ-37987


New Insights in Controlling Freckle Defect Formation using Magnetic Fields

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

Static magnetic fields have been shown to have a significant effect on channel formation in the GaIn freckle defect forming alloy. Inter-dendritic convective solute transport driven by the Thermoelectric Magnetoydrodynamics (TEMHD) phenomena leads to repositioning of the channel, preferential growth of secondary arms, plume migration and complex grain boundary interactions. This paper focuses on a secondary TEMHD mechanism that is generated by larger scale thermoelectric currents that circulate between the liquid and the entire mushy zone. This secondary mechanism is strongly dependent on the thermal profile and this leads to further modification of the bulk flow and ultimately plume migration. This mechanism has been observed by Xray synchrotron experiments and predicted by TESA (ThermoElectric Solidification Algorithm), a parallel Cellular Automata Lattice Boltzmann based numerical model, providing new insights into the intimate coupling between thermal solidification conditions and the effect of the magnetic field.

Keywords: Static magnetic fields; Solidification; Thermoelectric Magnetoydrodynamics; Freckle defect; Ga-In alloys

  • Lecture (Conference)
    TMS 2023 Frontiers in Solidification: An MPMD Symposium Honoring Jonathan A. Dantzig, 19.-23.03.2023, San Diego, California, USA

Permalink: https://www.hzdr.de/publications/Publ-37986


Structure prediction of iron hybrides at high pressures with machine-learned interactomic potentials

Tahmasbi, H.; Ramakrishna, K.; Lokamani, M.; Cangi, A.

Understanding the composition of Earth’s core and mantle is a major challenge in geoscience and materials science. The core is primarily made of iron, but its density is known to be slightly lower than pure iron. Hydrogen contributes to this density deficit, leading to significant interest in the properties and structure of iron hydrides under high pressure.
Previous studies have shown that the dhcp phase of FeH remains stable at lower pressures (10-40 GPa) but undergoes phase transitions to hcp and fcc phases at higher pressures. This study focuses on a theoretical exploration of the potential energy surfaces (PESs) of FeH under varying pressure conditions. The objective is to demonstrate the effectiveness of automated
and systematic methods for training and validating transferable machine-learned interatomic potential (ML-IAP) using global optimization techniques. Utilizing this potential, which significantly reduces computational costs, the phase diagram of the stoichiometric Fe-H system is analyzed across a range of pressures.
To achieve this, we utilize the PyFLAME code to construct a highly transferable ML-IAP. With this accurate potential, the PESs of bulk FeH structures are systematically investigated through global sampling using the minima hopping method. This comprehensive exploration enables the prediction of stable and metastable iron hydrides from 0 to 100 GPa. Density functional theory calculations are conducted to refine the predicted structures and evaluate their dynamical stability. The findings of this study reveal a wide range of novel low-energy polymorphs of FeH at each pressure level, alongside the recovery of well-known structures in the literature.

  • Poster
    Polish-German WE-Heraeus Seminar & Max Born Symposium, 03.-06.12.2023, Goerlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-37985


Temperature-Dependent Pump-Probe Spectroscopy of the Magetic Kagome Metal Fe3Sn2

Goncalves Faria, M. V.; Wang, Q.; Lei, H. C.; Pashkin, O.; Winnerl, S.; Helm, M.; Uykur, E.

In this study, we present optical pump-probe measurements on a magnetic kagome metal, Fe3Sn2, under different temperatures down to 10 K. The obtained spectra can be fitted with a double exponential decay, indicating that the system has two distinct relaxation processes. Additionally, some unexpected and pronounced oscillations are dominating the spectra, giving evidence of a strong electron-phonon coupling in Fe3Sn2, at least in this ultra-fast regime. The frequency of this coupled phonon is determined to be around 2.5 THz. Finally, we will discuss the temperature and pump fluence dependence of the observed phonon coupling and the distinct relaxation dynamics in this material.

  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft, 28.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37984


Manipulation of Encapsulated Plasmons in Solids for Photonic Applications

Li, R.; Pang, C.; Sun, X.; Jamshidi, K.; Zhou, S.; Chen, F.

Plasmonics offers a promising framework for next-generation photonic applications, including optical tweezers, ultrafast lasing, and quantum communication. Integrating plasmonics into photonics enables efficient interface coupling between heterogeneous systems, resulting in enhanced performance and diverse functionality. This review presents various unique encapsulation methods for developing plasmonics-embedded hybrid nanocomposite systems. Recent progress in the manipulation mechanisms of encapsulated plasmons is systematically summarized, offering an active modulation platform for optimizing optical performance. Considering the opportunities and challenges, the advancement of tunable encapsulated plasmons exhibits promising prospects, as demonstrated by a section discussing recent significant progress in photonic applications.

Keywords: Plasmonics; Nanostructures; Ion implantation; Optical tailoring; Integrated photonic application

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Permalink: https://www.hzdr.de/publications/Publ-37983


Fine-tuning of plasmonics by Au@AuY/Au core-shell nanoparticle monolayer for enhancement of third-order nonlinearity

Yong, L.; Pang, C.; Amekura, H.; Schumann, T.; Peng, L.; Zhixian, W.; Haocheng, L.; Li, R.

The manipulation of plasmonics on noble metal nanoparticles (NPs) is of great interest in developing nonlinear photonic devices, such as all-optical switches and frequency combs. An Au@AuY-core/Au-shell nanoparticle (Au@AuY/Au NP) monolayer is proposed for the fine-tuning of plasmonics and enhanced third-order nonlinearity. Based on the different thermodynamic mechanisms of Au and Y ions, the compact Au@AuY/Au core–shell architectures are designed and surface-modified in fused silica (SiO2) with enhanced free electron density, mobility, and quantum size effect. The flexible modulation of plasmonics is realized, resulting in significant absorption enhancement (165% for interband absorption and 38% for free electron absorption, respectively) and fine-tuning of the localized surface plasma resonance (LSPR) band. In addition, the physical mechanism is investigated by density functional theory (DFT) and Mie theory, which reveals a transition from size-independence to size-dependence of LSPR owing to the synergistic effect of multiple physical factors such as free electron density and mobility. With the above advantages, the third-order nonlinearity is enhanced by 4.4 times compared with traditional Au NPs. It indicates the significant potential of Au@AuY/Au core–shell NP monolayer in the performance improvement of nonlinear photonic devices.

Keywords: Plasmonics; Core-shell alloy nanostructure; Localized surface plasmon resonance; Third-order nonlinearity; Sequential ion implantation

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Permalink: https://www.hzdr.de/publications/Publ-37980


Coacervation-induced hydrodynamic instabilities in radial displacements

Stergiou, Y.; Perrakis, A.; Keshavarzi, B.; Eckert, K.; Schwarzenberger, K.

We investigated a miscible displacement of a less viscous liquid by a more viscous shear-thinning liquid in a Hele-Shaw cell. Due to a coacervation interaction between both liquids, a hydrodynamic instability appears in the form of inward viscous fingering. The liquids consisted of a solution of the anionic biopolymer xanthan gum, as the injection liquid, which displaced a cationic C14T AB aqueous solution. In the contact zone between the two solutions, the oppositely charged species form polymer-surfactant complexes due to electrostatic interactions. These complexes are insoluble in water and separate from the aqueous solution in the form of a gel-like growing membrane. During the continuing radial displacement, a large variety of patterns can emerge which is attributed to the rheological properties of the system involving viscosity gradients, the non-Newtonian nature of the displacing solution and the complex rheology of the coacervate phase. Variation of the flow rate and gap width of the Hele-Shaw cell revealed distinct instability regimes and allowed to identify main contributing mechanisms. These insights open the door for further investigation of fluid mechanics (i.e. Saffman-Taylor instability), pattern formation and self-organization problems in multiphase systems of complex rheology and its applications in engineering and technology.

  • Lecture (Conference)
    Dynamics Days Europe 2023, 06.09.2023, Napoli, Italia

Permalink: https://www.hzdr.de/publications/Publ-37979


Data publication: Piezostrain as a Local Handle to Control Gyrotropic Dynamics of Magnetic Vortices

Iurchuk, V.; Sorokin, S.; Faßbender, J.; Lindner, J.; Kakay, A.

The archive contains the experimental (MR and EDFMR) and simulated (mumax3) data related to the publication "Piezostrain as a Local Handle to Control Gyrotropic Dynamics of Magnetic Vortices" (Physical Review Applied 20(2023), 024080).

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Permalink: https://www.hzdr.de/publications/Publ-37978


Software: removal of bremsstrahlung background from SAXS signals with deep neural networks

Starke, S.; Smid, M.

Software for training and inference of neural network models to remove bremsstrahlung background from SAXS imaging data obtained at the European XFEL laboratory.

We thank Peter Steinbach for providing the codebase for the equivariant UNet, which we integrated into our repository.

Keywords: SAXS; XFEL; equivariant neural networks; noise removal

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Permalink: https://www.hzdr.de/publications/Publ-37977


Near-infrared photodetectors based on single germanium nanowires

Echresh, A.; Shaikh, M. S.; Helm, M.; Erbe, A.; Berencen, Y.; Rebohle, L.; Georgiev, Y.

Germanium (Ge) is a promising candidate for designing near-infrared photodetectors because of its bandgap (0.66 eV), which induces a large absorption coefficient at near-infrared wavelengths. Also, Ge has excellent compatibility of parallel processing with silicon technology [1,2]. Photodetectors based on Ge material have been fabricated with different structures such as metal-semiconductor-metal (MSM) and p−n junctions. On the other hand, the observation of high responsivity in semiconductor nanowires with a high surface-to-volume ratio has attracted growing interest in using nanowires in photodetectors. So far, significant efforts have been made to fabricate single nanowire-based photodetectors with different materials such as Si, Ge, and GaN to achieve miniaturized devices with high responsivity and short response time [3-5]. Hence, Ge nanowires are an excellent candidate to fabricate single nanowire-based near-infrared photodetectors.

In this work, we report on the fabrication and characterization of an axial p−n junction along Ge nanowires. First, through a resist mask created by electron beam lithography (EBL), the top Ge layers of germanium-on-insulator (GeOI) substrates were locally doped with phosphorus ions using ion beam implantation followed by rear-side flash lamp annealing. Then, the single Ge nanowire-based photodetectors containing an axial p−n junction were fabricated using EBL and inductively coupled plasma reactive ion etching. The fabricated single Ge nanowire devices demonstrate the rectifying current−voltage characteristic of a p−n diode in dark conditions. Moreover, the photoresponse of the axial p−n junction-based photodetectors was investigated under light illumination with three different wavelengths: 637 nm, 785 nm, and 1550 nm. The measurements indicated that the fabricated photodetectors can be operated at zero bias and room temperature under ambient conditions. A high responsivity of 3.7×102 AW-1 and a detectivity of 1.9×1013 cmHz1/2W-1 were observed at zero bias under illumination of a 785 nm laser diode. The responsivity of the single Ge NW photodetectors was increased by applying a reverse bias of 1V.

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  • Lecture (Conference)
    Micro and Nano Engineering (MNE) conference, 25.-28.09.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-37976


Piezostrain as a Local Handle to Control Gyrotropic Dynamics of Magnetic Vortices

Iurchuk, V.; Sorokin, S.; Lindner, J.; Faßbender, J.; Kakay, A.

We present a study of the piezostrain-tunable gyrotropic dynamics in Co40Fe40B20 vortex microstructures fabricated on a 0.7Pb[Mg1/3Nb2/3]O3-0.3PbTiO3 single-crystal substrate. Using field-modulated-spin-rectification measurements, we demonstrate large frequency tunability (up to 45%) in individual microdisks accessed locally with low surface voltages, and magnetoresistive readout. With increased voltage applied to the substrate, we observe a gradual decrease of the vortex-core gyrotropic frequency associated with the contribution of the strain-induced magnetoelastic energy. The frequency tunability strongly depends on the disk size, with increased frequency downshift for disks with larger diameter. Micromagnetic simulations suggest that the observed size effects originate from the joint action of the strain-induced magnetoelastic and demagnetizing energies in large magnetic disks. These results enable a selective energy-efficient tuning of the vortex gyrotropic frequency in individual vortex-based oscillators with all-electrical operation.

Keywords: Magnetic vortices; Magnetoelastic effect; Magnetoresistance; Spin dynamics

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Permalink: https://www.hzdr.de/publications/Publ-37975


Probing shock dynamics inside micro-wire targets after high-intensity laser irradiation using small angle x-ray scattering of a free-electron laser

Kluge, T.; Bussmann, M.; Galtier, E.; Glenzer, S.; Grenzer, J.; Gutt, C.; Hartley, N. J.; Huang, L.; Laso García, A.; Ja Lee, H.; McBride, E. E.; Metzkes-Ng, J.; Nakatsutsumi, M.; Nam, I.; Pelka, A.; Prencipe, I.; Randolph, L.; Rehwald, M.; Rödel, C.; Rödel, M.; Toncian, T.; Yang, L.; Zeil, K.; Schramm, U.; Cowan, T.

In this paper, we present an experiment that explores the plasma dynamics of a 7 μm diameter carbon wire after being irradiated with a near-relativistic-intensity short pulse laser. Using an x-ray free electron laser pulse to measure the small angle x-ray scattering signal, we observe that the scattering surface is bent and prone to instability over tens of picoseconds. The dynamics of this process are consistent with the presence of a sharp, propagating shock front inside the wire, moving at a speed close to the hole boring velocity or that expected from a thermal shock at a few tens of Mbar.

Keywords: plasma; SAXS; XFEL; laser; proton acceleration

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Permalink: https://www.hzdr.de/publications/Publ-37974


QED.jl - A Strong-field particle physics ecosystem

Hernandez Acosta, U.

We present a novel approach for an event generator inherently using exact QED descriptions to predict the results of high-energy electron-photon scattering experiments that can be performed at modern X-ray laser facilities.
With the advent of advanced laser systems producing high-frequency x-ray beams, e.g. the EuropeanXFEL as a prominent example, a regime of laser-plasma interaction is reached, where all-optical methods are increasingly questionable (see Fig. 1). Instead, the interaction of hot electrons and the X-ray laser pulse must be modeled with a QED-driven approach. Future experiments taking place at HED-HIBEF, LCLS, and other facilities targeting this regime, will encounter processes in x-ray scattering from (laser-driven) relativistic electrons, where the effects of the energy spectrum of the laser field as well as multi-photon interactions can not be neglected anymore.
In contrast to the application window of existing QED-PIC codes, our event generator makes use of the fact that the classical nonlinearity parameter barely approaches unity in high-frequency regimes. Therefore, based on a momentum-space Furry-picture formulation of strong-field QED, this allows taking the finite bandwidth of the x-ray laser into account in the description of the QED-like multi-photon interaction.

Keywords: Strong-field QED; Monte-Carlo Event-Generation; Julia programming language

  • Open Access Logo Lecture (Conference)
    JuliaHEP 2023 Workshop, 06.-09.11.2023, Erlangen, Germany

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Permalink: https://www.hzdr.de/publications/Publ-37973


Molecular imaging of bacterial outer membrane vesicles based on bacterial surface display

Szöllősi, D.; Hajdrik, P.; Tordai, H.; Horváth, I.; Veres, D. S.; Gillich, B.; Das Shailaja, K.; Smeller, L.; Bergmann, R.; Bachmann, M.; Mihály, J.; Gaál, A.; Jezsó, B.; Barátki, B.; Kövesdi, D.; Bősze, S.; Szabó, I.; Felföldi, T.; Oszwald, E.; Padmanabhan, P.; Zoltán Gulyás, B.; Hamdani, N.; Máthé, D.; Varga, Z.; Szigeti, K.

The important roles of bacterial outer membrane vesicles (OMVs) in various diseases and their emergence as a promising platform for vaccine development and targeted drug delivery necessitates the development of imaging techniques suitable for quantifying their biodistribution with high precision. To address this requirement, we aimed to develop an OMV specific radiolabeling technique for positron emission tomography (PET). A novel bacterial strain (E. coli BL21(DE3) ΔnlpI, ΔlpxM) was created for efficient OMV production, and OMVs were characterized using various methods. SpyCatcher was anchored to the OMV outer membrane using autotransporter-based surface display systems. Synthetic SpyTag-NODAGA conjugates were tested for OMV surface binding and 64Cu labeling efficiency. The final labeling protocol shows a radiochemical purity of 100% with a ~ 29% radiolabeling efficiency and excellent serum stability. The in vivo biodistribution of OMVs labeled with 64Cu was determined in mice using PET/MRI imaging which revealed that the biodistribution of radiolabeled OMVs in mice is characteristic of previously reported data with the highest organ uptakes corresponding to the liver and spleen 3, 6, and 12 h following intravenous administration. This novel method can serve as a basis for a general OMV radiolabeling scheme and could be used in vaccine- and drug-carrier development based on bioengineered OMVs.

Permalink: https://www.hzdr.de/publications/Publ-37972


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