Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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38247 Publications

Translating widefield microscopy images into the 3D using neural networks

Li, R.; Kudryashev, M.; Yakimovich, A.

Understanding the 3D structure of biological entities is crucial for gaining mechanistic biomedical knowledge. A confocal light microscope is a well-established tool used to obtain 3D data from biological specimens. Yet, it comes with the drawbacks of high equipment prices and heavy human labor. In this project, we introduce a 3D focal stacking solution using deep neural networks (DNN). Instead of restoring 3D models from confocal microscopes, our model produces in-focus images by inputting widefield microscope images, which may be obtained with significantly simpler equipment. This enables the translation from widefield microscope images into the 3D model by segmenting the in-focus pixels, allowing the image of 3D biological specimens in vivo.

Keywords: 3D microscopy; machine learning

  • Poster
    6th International Symposium "Image-based Systems Biology, 08.-09.09.2022, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-35782
Publ.-Id: 35782


BHP Tailings Challenge

Büttner, P.; Engelhardt, J.

BHP with the support of Fundacion Chile, through its open innovation program EXPANDE, has launched “BHP Tailings Challenge”, an initiative that seeks to promote the development of innovative solutions for repurposing copper tailings. The BHP Tailings Challenge is a global competition aimed at identifying the most innovative companies, startups, consortia, research centers and universities to help transform fresh tailings and create innovative business models. The recomine-proposal, which was one of the 10 selected proposals out of 153, suggests a variable flowsheet that comprises three major modules: (I) processing of tailings, (II) processing of solid residues and (III) water recovery. The following paragraphs describe the modules individually but outline the material flow from one module to the next. The first module deals with the output of BHP’s processing route. The recomine-proposal starts with a bulk sulfide flotation that produces a sulfide concentrate and a silicate residue as an output. Two potential processes represent the concentrate’s subsequent treatment: (a) leaching and (b) roasting of the concentrate. The major aim of treating the concentrate by leaching is to produce schwertmannite as a product after precipitation. Alternatively, roasting the sulfide concentrate may result in other economic products: sulfuric acid, ferric sulfate and residual calcine. The exothermal roasting may furthermore provide heat emissions as an energy source for usage in BHP’s processing routine. The silicate residue from module one will appear in a sequence of processing steps in module two. This module has a twofold aim: (1) separating ferro- and paramagnetic fractions and (2) dewatering the residues. Several steps will accomplish a separation of concentrated, iron-rich garnet. Novel membrane technologies will treat wastewater streams from modules one and two and represent the key-technology in module three. The major purpose of water treatment is to maximize the amount of clean water for nearby and downstream communities.

Keywords: recomine; BHP; HIF; remining; Tailings; Challenge; re-mining

  • Open Access Logo Lecture (others) (Online presentation)
    BHP Tailings Challenge Demo Day, 19.01.2021, Online, Online
  • Invited lecture (Conferences) (Online presentation)
    BHP Tailings Challenge - Proof-of-Concept Final Pitch, 15.12.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-35770
Publ.-Id: 35770


Data publication: Accurate temperature diagnostics for matter under extreme conditions

Dornheim, T.

Data for the temperature analysis of X-ray Thomson scattering (XRTS) measurements based on imaginary-time correlation functions. The files correspond to various figures in the main text; the same units are used.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35755
Publ.-Id: 35755


Can flow phenomena be observed in-operando in realistic liquid metal battery systems?

Sarma, M.; Weber, N.; Weier, T.

There is a wide range of flow phenomena to be expected in liquid metal battery systems. However, most of them have only been investigated numerically or in low-temperature model systems. To understand what actually takes place during operation and which flow phenomena prevail in a realistic liquid metal battery, an investigative study of a relatively new type of molten salt battery, Na||ZnCl2, is planned. This poster will present the objectives, challenges, and current status of a recently started x-ray and neutron imaging campaign of flow phenomena in high-temperature batteries at 600 oC.

  • Poster
    Liquid metal battery workshop, 15.11.2022, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-35751
Publ.-Id: 35751


Modeling of Reactivity Effects and Transient Behavior of Large Sodium Fast Reactor

Ponomarev, A.; Mikityuk, K.

In the paper, the reactivity characteristics of the core of the large sodium fast reactor Superphenix (SPX) were evaluated and compared with available experimental data. The analysis was performed using the TRACE system code modified for the fast reactor applications. The simplified core model was developed aiming to overcome the lack of detailed information on design and realistic core conditions. Point kinetics neutronic model with all relevant reactivity feedbacks was used to calculate transient power. The paper focuses on challenging issue of modeling of the transient thermal responses of primary system structural elements resulting in reactivity feedback specific to such large fast reactor, which cannot be neglected. For these effects, the model was equipped with dedicated heat structures to reproduce important feedback due to vessel wall, diagrid, strongback, control rod drive lines thermal expansion. Peculiarly, application of the model was considered for a whole range of core conditions from zero power to 100% nominal. The developed core model allowed reproducing satisfactorily the core reactivity balance between zero power at 180C and full power conditions. Additionally, the reactivity coefficients k, g, and h at three power levels (about 20, 50, and 80% of the nominal power) were calculated and satisfactory agreement with experimental measurements was also observed. The study demonstrated feasibility of application of relatively simple model with adjusted parameters for analysis of different conditions of very complex system. Reducing some differences with experimentally observed behavior of feedback coefficients,
would require more sophisticated approaches on fuel pin model, more detailed information on management of control rods during power rise, more complicated models of primary system, its structural elements, and flow paths.

Keywords: Sodium Fast Reactor; SPX; reactivity balance; reactivity feedback coefficients; Point Kinetics

  • Journal of Nuclear Engineering and Radiation Science 8(2021), 11
    DOI: 10.1115/1.4051514

Permalink: https://www.hzdr.de/publications/Publ-35742
Publ.-Id: 35742


Saxonian Wastewater dashboard – a geospatial visual analysis of the wastewater indicators in Saxony

Mertel, A.

In recent years, wastewater-based epidemiology has proven its potential in predicting the pandemic outbreak and helping to understand the spread of the virus. This talk introduces the Saxonian Wastewater dashboard that explores the spatio-temporal relations between indicator values derived from sewage systems and COVID-19 incidence, as measured by conventional testing, in the neighborhood of the wastewater plants. The presented dashboard infrastructure is a collaboration between the projects Wastewater-CoV-2-Tracking (UFZ Leipzig) and Where2test (CASUS/HZDR).

Keywords: Wastewater epidemiology; Application development; Geovisualization

  • Open Access Logo Lecture (others)
    Saxonian Wastewater dashboard – a geospatial visual analysis of the wastewater indicators in Saxony, 22.11.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35741
Publ.-Id: 35741


Analysis of sodium boiling initiated by unprotected loss of flow in European sodium fast reactor core with different subassembly designs

Bodi, J.; Ponomarev, A.; Mikityuk, K.

In this paper, an Unprotected Loss of Flow (ULOF) assessment has been performed on the European Sodium Fast Reactor
developed in the ESFR-SMART EU project. To conduct the analysis, a simplified 42 channel thermal–hydraulic model has
been established in the TRACE system code, using a point kinetics model accounting for various reactivity feedback effects. The
assessment reveals the core behavior of a commercial size, 3600 MWth, sodium fast reactor using a state-of-the-art low
void effect reactor core design. The study focuses on the sodium boiling phenomenon and sodium reactivity feedback effect
evolution during the accident with the reference subassembly (SA) design. Following this analysis, a study has been
performed with a modified SA design. The boiling progression and phenomenology within the reference and the modified
core have been compared, and the impact of the SA modification was described.

Keywords: ESFR; Sodium boiling; Sodium-cooled Fast Reactor; ULOF

Permalink: https://www.hzdr.de/publications/Publ-35740
Publ.-Id: 35740


Emergent many-body composite excitations of interacting spin-1/2 trimers

Kumar Bera, A.; Yusuf, S. M.; Kumar Saha, S.; Kumar, M.; Voneshen, D.; Skourski, Y.; Zvyagin, S.

Understanding exotic forms of magnetism in quantum spin systems is an emergent topic of modern condensed matter physics. Quantum dynamics can be described by particle-like carriers of information, known-as quasiparticles that appear from the collective behaviour of the underlying system. Spinon excitations, governing the excitations of quantum spin-systems, have been accurately calculated and precisely verified experimentally for the antiferromagnetic chain model. However, identification and characterization of novel quasiparticles emerging from the topological excitations of the spin system having periodic exchange interactions are yet to be obtained. Here, we report the identification of emergent composite excitations of the novel quasiparticles doublons and quartons in spin-1/2 trimer-chain antiferromagnet Na2Cu3Ge4O12 (having periodic intrachain exchange interactions J1-J1-J2) and its topologically protected quantum 1/3 magnetization-plateau state. The characteristic energies, dispersion relations, and dynamical structure factor of neutron scattering as well as macroscopic quantum 1/3 magnetization-plateau state are in good agreement with the state-of-the-art dynamical density matrix renormalization group calculations.

Permalink: https://www.hzdr.de/publications/Publ-35739
Publ.-Id: 35739


Accelerating Multiscale Materials Modeling with Machine Learning

Modine, N. A.; Stephens, J.; Swiler, L. P.; Thompson, A.; Vogel, D.; Fiedler, L.; Cangi, A.; Rajamanickam, S.

The focus of this project is to accelerate and transform the workflow of multiscale materials modeling by developing an integrated toolchain seamlessly combining DFT, SNAP, LAMMPS, (shown in Figure 1-1) and a machine-learning (ML) model that will more efficiently extract information from a smaller set of first-principles calculations. Our ML model enables us to accelerate first-principles data generation by interpolating existing high fidelity data, and extend the simulation scale by extrapolating high fidelity data ( 10 2 atoms) to the mesoscale ( 10 4 atoms). It encodes the underlying physics of atomic interactions on the microscopic scale by adapting a variety of ML techniques such as deep neural networks (DNNs), and graph neural networks (GNNs). We developed a new surrogate model for density functional theory using deep neural networks. The developed ML surrogate is demonstrated in a workflow to generate accurate band energies, total energies, and density of the 298K and 933K Aluminum systems. Furthermore, the models can be used to predict the quantities of interest for systems with more number of atoms than the training data set. We have demonstrated that the ML model can be used to compute the quantities of interest for systems with 100,000 Al atoms. When compared with 2000 Al system the new surrogate model is as accurate as DFT, but three orders of magnitude faster. We also explored optimal experimental design techniques to choose the training data and novel Graph Neural Networks to train on smaller data sets. These are promising methods that need to be explored in the future.

Keywords: Machine learning; Neural networks; Materials science; Density functional theory

  • Open Access Logo Contribution to external collection
    in: U.S. Department of Energy Office of Scientific and Technical Information, Technical Reports, United States: U.S. Department of Energy Office, 2022
    DOI: 10.2172/1889336

Permalink: https://www.hzdr.de/publications/Publ-35738
Publ.-Id: 35738


Data publication: Y(III) sorption at the orthoclase (001) surface measured by X-ray reflectivity

Neumann, J.; Lessing, J.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Demnitz, M.; Fenter, P.; Schmidt, M.

CTR/RAXR raw and reduced data

Keywords: solid liquid interface; rare earth elements; trivalent actinides; crystal truncation rod; resonant anomalous X-ray reflectivity; feldspars

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35735
Publ.-Id: 35735


Improving Predictive Capability in REHEDS Simulations with Fast, Accurate, and Consistent Non-Equilibrium Material Properties

Hansen, S. B.; Baczewski, A. D.; Gomez, T.; Hentschel, T. W.; Jennings, C. A.; Kononov, A.; Nagayama, T.; Adler, K.; Cangi, A.; Cochrane, K.; Robinson, B.; Schleife, A.

Predictive design of REHEDS experiments with radiation-hydrodynamic simulations requires knowledge of material properties (e.g. equations of state (EOS), transport coefficients, and radiation physics). Interpreting experimental results requires accurate models of diagnostic observables (e.g. detailed emission, absorption, and scattering spectra). In conditions of Local Thermodynamic Equilibrium (LTE), these material properties and observables can be pre-computed with relatively high accuracy and subsequently tabulated on simple temperature-density grids for fast look-up by simulations. When radiation and electron temperatures fall out of equilibrium, however, non-LTE effects can profoundly change material properties and diagnostic signatures. Accurately and efficiently incorporating these non-LTE effects has been a longstanding challenge for simulations. At present, most simulations include non-LTE effects by invoking highly simplified inline models. These inline non-LTE models are both much slower than table look-up and significantly less accurate than the detailed models used to populate LTE tables and diagnose experimental data through post-processing or inversion. Because inline non-LTE models are slow, designers avoid them whenever possible, which leads to known inaccuracies from using tabular LTE. Because inline models are simple, they are inconsistent with tabular data from detailed models, leading to ill-known inaccuracies, and they cannot generate detailed synthetic diagnostics suitable for direct comparisons with experimental data. This project addresses the challenge of generating and utilizing efficient, accurate, and consistent non-equilibrium material data along three complementary but relatively independent research lines. First, we have developed a relatively fast and accurate non-LTE average-atom model based on density functional theory (DFT) that provides a complete set of EOS, transport, and radiative data, and have rigorously tested it against more sophisticated first-principles multi-atom DFT models, including time-dependent DFT. Next, we have developed a tabular scheme and interpolation methods that compactly capture non-LTE effects for use in simulations and have implemented these tables in the GORGON magneto-hydrodynamic (MHD) code. Finally, we have developed post-processing tools that use detailed tabulated non-LTE data to directly predict experimental observables from simulation output.

Keywords: High-energy-density physics; Equation of state; Magneto-hydrodynamics; Radiation physics; Plasma properties

  • Open Access Logo Contribution to external collection
    in: U.S. Department of Energy Office of Scientific and Technical Information, Technical Reports, United States: U.S. Department of Energy Office, 2022
    DOI: 10.2172/1890268

Permalink: https://www.hzdr.de/publications/Publ-35734
Publ.-Id: 35734


Large magnetic saturation field in the antiferromagnet EuIrSi3

Maurya, A.; Uhlarz, M.; Isobe, M.; Thamizhavel, A.; Kumar Dhar, S.

We report a saturation magnetic field of 41 T at 4.2 K in the antiferromagnet EuIrSi3 (TN = 51.8 K), much larger than the values in typical S-state (net orbital state, L = 0) magnetic systems but consistent with the mean-field theory. We interpret this anomalous behaviour in conjunction with a higher density of states of conduction electrons in EuIrSi3 compared to other isostructural members in the EuTX3 (T = Ni, Pt, Rh, Ir; X = Si, Ge) homologous series. Moreover, low-temperature isothermal magnetization indicates spin orientation occurring at fields 13 T and 33 T, respectively. A magnetic phase diagram by aid of pulsed-field magnetization and magnetoresistivity measurements of EuIrSi3 is constructed.

Permalink: https://www.hzdr.de/publications/Publ-35725
Publ.-Id: 35725


ASL-BIDS and OSIPI Pipeline Inventory

Petr, J.

ASL-BIDS and OSIPI Pipeline Inventory

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    MRI Together, 5.12.2022, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-35724
Publ.-Id: 35724


Tailoring oxide quantum materials by ion beams

Wang, C.; Chang, C.-H.; Herklotz, A.; Kentsch, U.; Chen, D.; Chu, Y.-H.; Helm, M.; Zhou, S.

Complex oxides host a multitude of novel phenomena in condensed matter physics, such as various forms of multiferroicity, colossal magnetoresistance, quantum magnetism and superconductivity. Defect engineering via ion irradiation can be a useful knob to control these physical properties for future practical applications. Two prominent effects are disorder and uniaxial strain. Particularly, the uniaxial strain, manifesting as the elongation of the out-of-plane lattice spacing, is not limited to available substrates. In this contribution, we will take SrRuO3 thin films as an example to show the emerging properties upon defect engineering by ion irradiation. The irradiated SRO films exhibit a pronounced topological Hall effect in a wide temperature range from 5 to 80 K. It can be attributed to the emergence of Dzyaloshinskii–Moriya interaction as a result of artificial inversion symmetry breaking associated with the lattice defect engineering. Ion irradiation has been well developed for semiconductor-chip technology and is readily applicable for all kinds of oxide quantum materials.

Related publications

  • Poster
    LEAPS meets Quantum Technology, 15.-20.05.2022, La Biodola, Italy

Permalink: https://www.hzdr.de/publications/Publ-35700
Publ.-Id: 35700


Ultra-doped semiconductors and their photonic applications

Zhou, S.

Doping allows us to modify semiconductor materials for desired electrical and optical properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Ultra-doping or hyper-doping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. In this talk, we show that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can realize ultra-doping in widely used semiconductors, including Si [1-5], Ge [6-8] and GaAs [9]. Various dopants, from conventional shallow-level impurities to deep-level ones, can be substitutionally incorporated up to a few atomic percent. This leads to the insulator-to-metal transition and the large modification to the semiconductor bandgap. The ultra-doped semiconductors can be used as photodetectors and plasmonic elements [10]. Ion implantation followed by annealing is a well-established method to dope Si, being maturely integrated with the IC industry production line. Therefore, ultra-doped semiconductors can be a wafer-scale platform for photonics.

[1] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018)
[2] M. Wang, et al., Phys. Rev. Applied. 11, 054039 (2019)
[3] M. Wang, et al., Phys. Rev. B 102, 085204 (2020)
[4] M. Wang, et al., Adv. Optical Mater. 9, 2001546 (2021)
[5] M. Wang, et al., Nanoscale, 14, 2826-2836 (2022)
[6] S. Prucnal, et al., Scientific Reports 6, 27643 (2016)
[7] S. Prucnal, et al., Phys. Rev. Materials 3, 054802 (2019)
[8] S. Prucnal, et al., New J. Phys. 22, 123036 (2020)
[9] J. Duan, et al., New J. Phys. 23, 083034 (2021)
[10] G. V. Naik, V.M. Shalaev, A. Boltasseva, Alternative Plasmonic Materials: Beyond Gold and Silver, Adv. Mater. 25, 3264 (2013).

Related publications

  • Lecture (others)
    Seminar at Department of Electrical and Photonics Engineering, Technical University of Denmark, 27.06.2022, Lyngby, Denmark

Permalink: https://www.hzdr.de/publications/Publ-35699
Publ.-Id: 35699


Tellurium hyperdoped Silicon

Zhou, S.

Tellurium is one of the deep-level impurities in Si, leading to states of 200-400 meV below the conduction band. Non-equilibrium methods allow for doping deep-level impurities in Si well above the solubility limit, referred as hyperdoping, that can result in exotic properties, such as extrinsic photo-absorption well below the Si bandgap [1]. In this contribution, we will present an overview about Te hyperdoped Si. The hyperdoping is realized by ion implantation and pulsed laser melting. We will present the resulting optical, electrical properties and the perspective applications as infrared photodetectors. With increasing the Te concentration, the samples undergo an insulator to metal transition [2,3]. The metallic phase is governed by a power law dependence of the conductivity at temperatures below 25 K, whereas the conductivity in the insulating phase is well described by a variable-range hopping mechanism with a Coulomb gap. Surprisingly, the electron concentration obtained in Te-hyperdoped Si is approaching 10 21 cm-3 and does not show saturation [4]. It is even high than that of P or As doped Si and potentially meets the criteria of source/drain applications in future nanoelectronics. The infrared optical absorptance is found to increase with increasing dopant concentration [2]. We demonstrate the room-temperature operation of a mid-infrared photodetector based on Te-hyperdoped Si. The key parameters, such as the detectivity, the bandwidth and the rise/fall time, show competitiveness with the commercial products [5]. To
understand the microscopic picture, we have performed Rutherford backscattering/channeling angular scans and first-princiles calcluations [4]. The Te-dimer complex sitting on adjacent Si lattice sites has the smallest formation energy and is thus the preferred configuration at high doping concentration. Those substitutional Te-dimers are effective donors, leading to the insulator-to-metal transition, the non-saturating carrier concentration as well as the sub-band photoresponse. Moreover, the Te-hyperdoped Si layers exhibit thermal stability up to 400 °C with a duration of at least 10 minutes [6]. Therefore, Te-hyperdoped Si presents a test-bed for electrical and optical applications utilizing deep-level impurities.
[1] J. M. Warrender, Laser hyperdoping silicon for enhanced infrared optoelectronic properties, Appl. Phys.Rev. 3, 031104 (2016).
[2] M. Wang, ..., S. Zhou, Extended Infrared Photoresponse in Te-Hyperdoped Si at Room Temperature, Phys.Rev. Appl. 10, 024054 (2018).
[3] M. Wang, ..., S. Zhou, Critical behavior of the insulator-to-metal transition in Te-hyperdoped Si, Phys. Rev.B 102, 085204 (2020).
[4] M. Wang, ... Breaking the doping limit in silicon by deep impurities, Phys. Rev. Appl. 11, 054039 (2019).
[5] M. Wang, ..., S. Zhou, Silicon-Based Intermediate-Band Infrared Photodetector Realized by Te Hyperdoping, Adv. Opt. Mater. 9, 2001546, (2020).
[6] M. Wang, ..., S. Zhou, Thermal stability of Te-hyperdoped Si: Atomic-scale correlation of the structural, electrical, and optical properties, Phys. Rev. Mater. 3, 044606 (2019).

Related publications

  • Lecture (Conference)
    19th Conference on Gettering and Defect Engineering in Semiconductor Technology, 10.-16.09.2022, Mondsee, Austria

Permalink: https://www.hzdr.de/publications/Publ-35697
Publ.-Id: 35697


Ferromagnetism and superconductivity in hyperdoped semiconductors

Zhou, S.

Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. In this talk, we show that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. Mn hyperdoped III-V compound semiconductors become ferromagnetic, where Mn impurities are in 2+ valence and providing local moments of 5 μB and free holes [1-5]. Their Curie temperatures can be varied either by the Mn or free hole concentration, and also depend on the host semiconductors, which reveal different pd exchange strength. On the other hand, Ga and Al hyperdoped Ge exhibits superconductivity with controllable critical temperature [6, 7]. In combination with first-principles calculation, phonon-mediated superconductivity is counted for the mechanism. The critical-field reveals significant difference when the field is in-plane or out-of-plane. This remarkable anisotropy may be considered as proof that Ga is incorporated in the Ge matrix homogeneously in a thin layer. Ion implantation followed by annealing is a well-established method to dope Si and Ge, being maturely integrated with the IC industry production line. We propose ferromagnetic and superconducting semiconductors prepared by ion implantation can be a scalable platform for quantum technology.

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).
[6] T. Herrmannsdörfer, et al., Phys. Rev. Lett. 102, 217003 (2009).
[7] S. Prucnal, et al., Phys. Rev. Materials 3 054802 (2019).

Related publications

  • Lecture (others)
    Condensed Matter Seminar Series at Niels Bohr Institute, University of Copenhagen, 24.06.2022, University of Copenhagen, Denmark

Permalink: https://www.hzdr.de/publications/Publ-35694
Publ.-Id: 35694


Doping semiconductors by ion implantation and subsecond annealing

Zhou, S.

Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortenedto millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-5], superconducting Ge [6] and chalcogen doped Si [10-12].
[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).
[6] S. Prucnal, et al., Phys. Rev. Materials 3, 054802 (2019).
[7] S. Prucnal, et al., New J. Phys., 22 123036 (2020).
[8] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018).
[9] M. Wang, et al., Phys. Rev. Applied. 11, 054039 (2019).
[10] M. Wang, et al., Nanoscale 14, 2826 (2022).

Related publications

  • Lecture (others)
    Seminar at CNRS / Université Paris-Sud, 02.12.2022, CNRS / Université Paris-Sud, France

Permalink: https://www.hzdr.de/publications/Publ-35692
Publ.-Id: 35692


Consistency-Regularized Region-Growing Network for Semantic Segmentation of Urban Scenes With Point-Level Annotations

Xu, Y.; Ghamisi, P.

Deep learning algorithms have obtained great success in semantic segmentation of very high-resolution (VHR) remote sensing images. Nevertheless, training these models generally requires a large amount of accurate pixel-wise annotations, which is very laborious and time-consuming to collect. To reduce the annotation burden, this paper proposes a consistency-regularized region-growing network (CRGNet) to achieve semantic segmentation of VHR remote sensing images with point-level annotations. The key idea of CRGNet is to iteratively select unlabeled pixels with high confidence to expand the annotated area from the original sparse points. However, since there may exist some errors and noises in the expanded annotations, directly learning from them may mislead the training of the network. To this end, we further propose the consistency regularization strategy, where a base classifier and an expanded classifier are employed. Specifically, the base classifier is supervised by the original sparse annotations, while the expanded classifier aims to learn from the expanded annotations generated by the base classifier with the region-growing mechanism. The consistency regularization is thereby achieved by minimizing the discrepancy between the predictions from both the base and the expanded classifiers. We find such a simple regularization strategy is yet very useful to control the quality of the region-growing mechanism. Extensive experiments on two benchmark datasets demonstrate that the proposed CRGNet significantly outperforms the existing state-of-the-art methods. Codes and pre-trained models are available online ( https://github.com/YonghaoXu/CRGNet ).

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Permalink: https://www.hzdr.de/publications/Publ-35682
Publ.-Id: 35682


(Data set) Effect of magnetism and phonons on localized carriers in ferrimagnetic kagome metals GdMn6Sn6 and TbMn6Sn6

Wenzel, M.; Tsirlin, A. A.; Iakutkina, O.; Yin, Q.; Lei, H. C.; Dressel, M.; Uykur, E.

  1. Data from the publication are given in Origin format with Figure codes.
  2. More data are available upon request.

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Permalink: https://www.hzdr.de/publications/Publ-35681
Publ.-Id: 35681


(Data set) Effect of nonhydrostatic pressure on the superconducting kagome metal CsV₃Sb₅

Tsirlin, A. A.; Ortiz, B. R.; Dressel, M.; Wilson, S. D.; Winnerl, S.; Uykur, E.

  1. Data from the publication are given in Origin format with Figure codes.
  2. More data are available upon request.

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35680
Publ.-Id: 35680


Geospatial flow data extraction and visualization using Earth mover's distance

Mertel, A.; Calabrese, J.

A flow map is a common visualization technique displaying the significant trends and changes in data over a given spatial and temporal domain. While most flow maps are constructed using trajectory datasets as input, only a few research initiatives focus on producing flow maps from other data forms. This paper uses the Earth Mover's Distance to extract flows from geospatial data in two consecutive temporal snapshots. We further perform a generalization of the flows to avoid visual cluttering. To demonstrate the proposed approach, we provide an interactive web application where the user can see the pre-calculated flows extracted from the 2021 COVID incidence data in the regions of Germany, Poland, and Czechia.

Keywords: flow extraction; geospatial visualization; Earth mover's distance

  • Poster
    VIS22, 15.-21.10.2022, Oklahoma City, USA

Permalink: https://www.hzdr.de/publications/Publ-35679
Publ.-Id: 35679


Topological Hall effect arising from the mesoscopic and microscopic non-coplanar magnetic structure in MnBi

He, Y.; Schneider, S.; Helm, T.; Gayles, J.; Wolf, D.; Soldatov, I.; Borrmann, H.; Schnelle, W.; Schaefer, R.; Fecher, G. H.; Rellinghaus, B.; Felser, C.

The topological Hall effect (THE), induced by the Berry curvature that originates from non-zero scalar spin chirality, is an important feature for mesoscopic topological structures, such as skyrmions. However, the THE might also arise from other microscopic non-coplanar spin structures in the lattice. Thus, the origin of the THE inevitably needs to be determined to fully understand skyrmions and find new host materials. Here, we examine the Hall effect in both, bulk- and micron-sized lamellar samples of MnBi. The sample size affects the temperature and field range in which the THE is detectable. Although a bulk sample ex- hibits the THE only upon exposure to weak fields in the easy-cone state, in micron-sized lamella the THE exists across a wide temperature range and occurs at fields near saturation. Our results show that both the non-coplanar spin structure in the lattice and topologically non-trivial skyrmion bubbles are respon- sible for the THE, and that the dominant mechanism depends on the sample size. Hence, the magnetic phase diagram for MnBi is size-dependent. Our study provides an example in which the THE is simulta- neously induced by two mechanisms, and builds a bridge between mesoscopic and microscopic magnetic structures.

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Publ.-Id: 35677


Observation of a 1/3 magnetization plateau in Pb2Cu10O4(SeO3)4Cl7 arising from (Cu2+)7 clusters of corner-sharing (Cu2+)4 tetrahedra

Vasiliev, A. N.; Berdonosov, P. S.; Kozlyakova, E. S.; Maximova, O. V.; Murtazoev, A. F.; Dolgikh, V. A.; Lyssenko, K. A.; Pchelkina, Z. V.; Gorbunov, D.; Chung, S. H.; Koo, H.-J.; Whangbo, M.-H.

A mixed-valence compound Pb2Cu10O4(SeO3)4Cl has a complex structure consisting of one nonmagnetic Cu+ (S = 0) ion and four nonequivalent magnetic Cu2+ (S = 1/2) ions. It exhibits antiferromagnetic ordering at TN = 10.2 K. At a temperature below TN, a sequence of spin-flop transition at Bspin-flop = 1.3 T and 1/3 plateau formation at Bspin-flip = 4.4 K is observed in the magnetization curve M(B). The 1/3 magnetization plateau persists at least up to 53.5 T. The spin exchanges of Pb2Cu10O4(SeO3)4Cl7 evaluated by performing energy-mapping analysis based on DFT+U calculations show that the magnetic properties of Pb2Cu10O4(SeO3)4Cl7 are described by the (Cu2+)7 cluster of corner-sharing (Cu2+)4 tetrahedra, and that each (Cu2+)7 cluster has a S = 3/2 spin arrangement in the ground state. The 1/3 magnetization plateau observed for Pb2Cu10O4(SeO3)4Cl7 is explained by the field-induced flip of every second (Cu2+)7 cluster within a unit cell.

Permalink: https://www.hzdr.de/publications/Publ-35676
Publ.-Id: 35676


Magnetocaloric effect and magnetic phase diagram of Ni-Mn-Ga Heusler alloy in steady and pulsed magnetic fields

Koshkid'Ko, Y. S.; Dilmieva, E. T.; Kamantsev, A. P.; Cwik, J.; Rogacki, K.; Mashirov, A. V.; Khovaylo, V. V.; Salazar Mejia, C.; Zagrebin, M. A.; Sokolovskiy, V. V.; Buchelnikov, V. D.; Ari-Gur, P.; Bhale, P.; Shavrov, V. G.; Koledov, V. V.

The work is devoted to the study of the phenomenon of irreversibility of the magnetocaloric effect (MCE) in the vicinity of the magnetostructural phase transition (PT) in Ni-Mn-Ga Heusler alloys. For this purpose, the MCE was studied by the direct method in stationary (up to 14 T) and pulsed magnetic fields (up to 50 T), and a magnetic phase diagram was constructed. Using a specially designed microscope, in-situ studies of the magnetostructural phase transition were carried out in magnetic fields of up to 14 T. Comparing the results of the MCE with those of the phase diagram, as well as in-situ studies, made it possible to determine the width of the irreversible MCE region. In-situ studies have shown, that the main reason of the occurrence of the irreversible MCE is the presence of the residual martensite formed as a result of the first magnetization of the sample. The results are discussed within the framework of Landau's phenomenological PT theory, which predicts the disappearance of thermal hysteresis under a field of 30 T. Within the framework of the same theory, a recommendation is made to reduce the value of the critical field and, as a result, the width of the hysteresis.

Permalink: https://www.hzdr.de/publications/Publ-35674
Publ.-Id: 35674


Signatures of a magnetic-field-induced Lifshitz transition in the ultra-quantum limit of the topological semimetal ZrTe5

Galeski, S.; Legg, H. F.; Wawrzynczak, R.; Förster, T.; Zherlitsyn, S.; Gorbunov, D.; Uhlarz, M.; Lozano, P. M.; Li, Q.; Gu, G. D.; Felser, C.; Wosnitza, J.; Meng, T.; Gooth, J.

The quantum limit (QL) of an electron liquid, realised at strong magnetic fields, has long been proposed to host a wealth of strongly correlated states of matter. Electronic states in the QL are, for example, quasi-one dimensional (1D), which implies perfectly nested Fermi surfaces prone to instabilities. Whereas the QL typically requires unreachably strong magnetic fields, the topological semimetal ZrTe5 has been shown to reach the QL at fields of only a few Tesla. Here, we characterize the QL of ZrTe5 at fields up to 64 T by a combination of electrical-transport and ultrasound measurements. We find that the Zeeman effect in ZrTe5 enables an efficient tuning of the 1D Landau band structure with magnetic field. This results in a Lifshitz transition to a 1D Weyl regime in which perfect charge neutrality can be achieved. Since no instability-driven phase transitions destabilise the 1D electron liquid for the investigated field strengths and temperatures, our analysis establishes ZrTe5 as a thoroughly understood platform for potentially inducing more exotic interaction-driven phases at lower temperatures.

Permalink: https://www.hzdr.de/publications/Publ-35673
Publ.-Id: 35673


Anisotropic magnetization and electronic structure of the first-order ferrimagnet ErCo2 studied by polarization dependent hard X-ray photoemission spectroscopy

Abozeed, A. A.; Gorbunov, D.; Kadono, T.; Kanai-Nakata, Y.; Yamagami, K.; Fujiwara, H.; Sekiyama, A.; Higashiya, A.; Yamasaki, A.; Tamasaku, K.; Yabashi, M.; Ishikawa, T.; Wada, H.; Andreev, A. V.; Imada, S.

The first-order ferrimagnet ErCo2 attracts interest not only because of metamagnetism and magnetocaloric effect just above TC ≈ 32–34 K but also because it is closely related with the itinerant metamagnetism of YCo2 and LuCo2. We study the electronic structure of single crystals with hard X-ray photoemission spectroscopy (HAXPES). Magnetization measurements reconfirm the first-order magnetic transition, metamagnetism, and strong magnetic anisotropy. Calculated ErCo2 band structures of the ferrimagnetic and paramagnetic phases are presented in detail. In the ferrimagnetic state, the density of states just below EF is smaller than in the paramagnetic phase. Valence band spectra in the paramagnetic state show strong polarization dependence. Furthermore, the change across the first-order ferrimagnetic transition in the valence band electronic structures is observed. These experimental data are well described by the band structure calculation incorporated with the polarization dependent cross-sections of orbitals. We further discuss possible effects of electron correlation and spin fluctuation

Permalink: https://www.hzdr.de/publications/Publ-35671
Publ.-Id: 35671


Ab initio path integral Monte Carlo simulation of electrons at extreme conditions

Dornheim, T.

I present an overview of ab initio path integral Monte Carlo simulations of electrons at extreme conditions.

  • Invited lecture (Conferences) (Online presentation)
    NHR-Atomistic Simulation Symposium 2022, 28.-29.11.2022, Paderborn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35669
Publ.-Id: 35669


Pickering foams and parameters influencing their characteristics

Amani, P.; Miller, R.; Javadi, A.; Firouzi, M.

Pickering foams are available in many applications and have been continually gaining interest in the last two decades. Pickering foams are multifaceted, and their characteristics are highly dependent on many factors, such as particle size, charge, hydrophobicity and concentration as well as the charge and concentration of surfactants and salts available in the system. A literature review of these individual studies at first might seem confusing and somewhat contradictory, particularly in multi-component systems with particles and surfactants with different charges in the presence of salts. This paper provides a comprehensive overview of particle-stabilized foams, also known as Pickering foams and froths. Underlying mechanisms of foam stabilization by particles with different morphology, surface chemistry, size and type are reviewed and clarified. This paper also outlines the role of salts and different factors such as pH, temperature and gas type on Pickering foams.

Further, we highlight recent developments in Pickering foams in different applications such as food, mining, oil and gas, and wastewater treatment industries, where Pickering foams are abundant. We conclude this overview by presenting important research avenues based on the gaps identified here. The focus of this review is limited to Pickering foams of surfactants with added salts and does not include studies on polymers, proteins, or other macromolecules.

Keywords: Particles; Foam stability; Stabilizing mechanism; Pickering foam; Salts

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Permalink: https://www.hzdr.de/publications/Publ-35665
Publ.-Id: 35665


Unfolded Lipase at Interfaces Studied via Interfacial Dilational Rheology: The Impact of Urea

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

Unfolding can interrupt the activity of enzymes. Lipase, the enzyme responsible for triglyceride catalysis, can be deactivated by unfolding, which can significantly affect the yield of enzymatic processes in biochemical engineering. Different agents can induce lipase unfolding, among which we study the impact of urea as a strong denaturant. Unfolding weakens the rigidity and stability of globular proteins, thereby changing the viscoelastic properties of the protein adsorbed layers. These changes can be detected and quantified using interfacial dilational rheology. The urea-induced unfolding of lipase destructs its globular structure, making it more flexible. The interfacial tension and viscoelastic moduli of lipase adsorbed layers reduce upon the addition of urea in the range of studied concentrations. The results agree with the theory that, upon unfolding, a distal region of the loop and tail domain forms adjacent to the proximal region of the interface. The exchange of matter between these regions reduces the viscoelasticity of the unfolded lipase adsorbed layers. Additionally, unfolding reduces the rigidity and brittleness of the lipase adsorbed layers: the aged adsorbed layer of native lipase can break upon high-amplitude perturbations of the interfacial area, unlike the case for urea-induced unfolded lipase.

Keywords: Lipase; protein unfolding; interfacial dilational rheology; interfacial viscoelasticity; profile analysis tensiometer; urea-induced unfolding

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Publ.-Id: 35663


Reply: Discussion Cerebral Blood Flow of the Frontal Lobe in Untreated Children with Trigonocephaly versus Healthy Controls: An Arterial Spin Labeling Study

de Planque, C. A.; Petr, J.; Gaillard, L.; Mutsaerts, H. J. M. M.; van Veelen, M.-L. C.; Versnel, S. L.; Dremmen, M. H. G.; Mathijssen, I. M. J.

Dear Editor,
We have read the letter to the editor from Long et al. with great interest. 1 The authors of this
letter stated two methodological concerns on which we will respond.
The first concern is that objective criteria are missing for true trigonocephaly or benign metopic
ridge. We only included moderate to severe trigonocephaly patients according to the definitions
of Birgfeld et al2. Birgfeld et al. provide both a phenotypical distinction between benign metopic
ridge and metopic synostosis in their article, as well as illustrative photographs with
corresponding CT-imaging in Figure 1.2 Cho et al. and Anolik et al. described CT measures to
assess severity of metopic synostosis. In both articles the cut-off point to determine surgical
indication remains subjective and poor consensus for the intermediate presentation of metopic
craniosynostosis is found.3, 4 In addition, Sisti et al. recently reviewed all literature in Pubmed
on trigonocephaly, relating to 15 anthropometric cranial measurements for surgical
indications.5 This study illustrates that most papers have a lack of diagnostic criteria for
trigonocephaly.5 At our center, the decision for surgery is made through shared decision
making with parents. In 2021 this resulted in surgery for 14 patients (moderate or severe
presentation) and a conservative treatment for 40 patients (18 mild, and 22 moderate or severe
presentation).
The second raised concern is the potential blunting effect of sevoflurane on CBF. If it does, a
similar effect on both the patients and controls is expected. In our previous ASL study in
patients with syndromic craniosynostosis using the same sedation protocol, we found a
difference between the groups.6 This suggests that the normal findings in patients with
trigonocephaly reflect normal CBF.
Very few studies have investigated the influence of anesthesia on ASL CBF in the pediatric
population. Carsin-Vu et al. included 84 subjects from 6 months to 15 years and showed no
significant CBF changes with sevoflurane in comparison with general anesthesia.7 Kaisti et al.
Without sedation, scanning of one sequence is possible, because of the limited timeframe.
However, more sequences, as in our protocol, requires a longer time period. Without sedation,
motion artifacts would make it impossible to analyze.
Finally, Long et al. mention that cerebral perfusion is a limited measure of neurodevelopment
and that fMRI studies in scaphocephaly patients have shown a difference in functional brain
connectivity compared to controls. However, there is still a lot unknown about the optimal way
of scanning, reproducibility, and interpretation of the fMRI results. Finding a difference in
connectivity in fMRI studies would be at the same level of evidence as the ASL brain MRI
study.
To conclude, our study further supports our hypothesis that surgery for trigonocephaly is rarely
indicated functionally. Parents should be informed about the unknown added value of surgery
regarding raised intracranial pressure and brain perfusion. Comparative research on outcome of
conservative versus surgical treatment of moderate to severe trigonocephaly is needed to establish clinical guidelines.

Permalink: https://www.hzdr.de/publications/Publ-35662
Publ.-Id: 35662


Role of assortativity in predicting burst synchronization using echo state network

Roy, M.; Senapati, A.; Poria, S.; Mishra, A.; Hens, C.

In this study, we use a reservoir computing based echo state network (ESN) to predict the collective burst synchronization of neurons. Specifically, we investigate the ability of ESN in predicting the burst synchronization
of an ensemble of Rulkov neurons placed on a scale-free network. We have shown that a limited number of nodal
dynamics used as input in the machine can capture the real trend of burst synchronization in this network. Further,
we investigate the proper selection of nodal inputs of degree-degree (positive and negative) correlated networks.
We show that for a disassortative network, selection of different input nodes based on degree has no significant
role in the machine’s prediction. However, in the case of assortative network, training the machine with the
information (i.e., time series) of low degree nodes gives better results in predicting the burst synchronization.
The results are found to be consistent with the investigation carried out with a continuous time Hindmarsh-Rose
neuron model. Furthermore, the role of hyperparameters like spectral radius and leaking parameter of ESN on the
prediction process has been examined. Finally, we explain the underlying mechanism responsible for observing
these differences in the prediction in a degree correlated network.

Keywords: Echo State Network; Assortativity; Complex network; Synchronization

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Permalink: https://www.hzdr.de/publications/Publ-35659
Publ.-Id: 35659


Data publication: Quantifying how post-transcriptional noise and gene copy number variation bias transcriptional parameter inference from mRNA distributions

Fu, X.; Patel, H. P.; Coppola, S.; Xu, L.; Cao, Z.; Lenstra, T. L.; Grima, R.

The url https://github.com/palmtree2013/RNAInferenceTool.jl is a Julia GitHub code repository for the paper https://doi.org/10.7554/eLife.82493:

Related publications

  • Software in external data repository
    Publication year 2022
    Programming language: Julia
    System requirements: Linux
    License: MIT license
    Hosted on https://github.com/palmtree2013/RNAInferenceTool.jl: Link to location
    DOI: 10.7554/eLife.82493

Permalink: https://www.hzdr.de/publications/Publ-35658
Publ.-Id: 35658


Biotechnology meets Resource Technology - Metal recovery with biological means

Pollmann, K.

Biotechnological approaches for metal recovery

Keywords: biohydrometallurgy; microbiology; metals

  • Invited lecture (Conferences)
    Mini-Workshop with Wroclaw University, 22.-23.06.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35656
Publ.-Id: 35656


Biohydrometallurgical Concepts for Metal Recovery from Primary and Secondary Resources

Pollmann, K.

Presentation of different approaches for bio-based metal recovery

Keywords: biohydrometallurgy; microbiology; biotechnology; metals

  • Invited lecture (Conferences)
    CASUSCON, 12.-14.06.2022, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-35655
Publ.-Id: 35655


Bubble dynamics on laser structured porous nickel electrodes

Rox, H.; Baumann, R.; Bashkatov, A.; Yang, X.; Ränke, F.; Lasagni, A. F.; Mutschke, G.; Eckert, K.

Hydrogen produced by water electrolysis using renewable energy sources is a promising approach towards a net-zero-emission-industry that is replacing fossil fuels [1]. One cost effective and mature technology for hydrogen production is alkaline water electrolysis. The advantage is the usage of non-critical electrode materials like nickel instead of noble metals such as platinum needed for acidic water electrolysis [2]. However, compared to other technologies alkaline water electrolysis shows larger partial load limits, lower current densities and lower operating pressures [3]. Nevertheless, by enhancing the bubble growth and detachment from the electrode, the overall efficiency of alkaline electrolysis can be improved [4] to make it even more competitive for future large scale installations.

By influencing the detachment behavior of the bubbles, the efficiency can be increased. Laser technology depicts a promising approach to create a supportive micro- and nano-texturing of the electrodes. Specifically, the Direct Laser Interference Pattering (DLIP) technique is applied for structuring the electrode surfaces to increase their wettability [5]. By two overlapping laser beams, a periodic line-like pattern with a spatial period of 6.0 μm is generated.

The present study uses a 3D printed electrolysis cell developed for the analysis of the bubble dynamics and the electrochemical performance of structured and non-structured electrodes. Therefore, a removable working electrode holder is applied to a cell with optical access from the side and the top of the working electrode. Two different observation perspectives allow to study the bubble growth, the detachment size and the electrode coverage at the same time. By characterizing the electrodes beforehand using cyclic voltammetry (CV) to determine the double-layer capacitance and thus the electrochemical active surface area, a profound characterization of different laser structured electrodes is given.

References:

[1] L. Lüke, Chem. Ing. Tech. 2020, 92, No. 1–2, 70–73.
[2] S. Wang, Nano Converg. 2021, 8, 4.
[3] M. Carmo, Int. J. Hydrog. Energy. 2003, 38, 4901-4934.
[4] R. Iwata, Joule. 2021, 5, 1-14.
[5] R. Baumann, J. Laser Micro Nanoeng. 2020, 15, 2.

Keywords: Electrolysis; Hydrogen bubble; Laser structured; Porous electrode

  • Lecture (Conference)
    Electrochemistry 2022, 27.-30.09.2022, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35650
Publ.-Id: 35650


Actinide Chemistry - From Small Molecules To Real Rock

Schmidt, M.

Actinide chemistry is of utmost importance for chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories. Yet, their chemistry remains underexplored relative to other elements in the periodic table. This is equally true for fundamental studies regarding complexation chemistry or redox properties and applied investigations of geochemical behavior and environmental transport.
In this presentation, I will give an overview of recent (and not so recent) studies attempting to link the actinides’ fundamental properties with their environmental transport. Systematic studies of their coordination chemistry offer a promising route to obtain fundamental knowledge about chemical bonding in actinide compounds. Here, a suitable approach is to study series of isostructural actinide compounds, in which the metal is present in the same oxidation state. Changes in structures, bond distances, or spectroscopic properties can then be related to changes in f-orbital occupation. One important issue in this context is the degree of covalency in these compounds and how it depends on the donor atoms of a ligand, or the electronic structure and oxidation state of the actinide.
It is this chemical behavior, which then affects how mobile actinides can be if they are released into the environment as a consequence of nuclear accidents, other accidental releases or in the context of nuclear waste disposal. In these scenarios, special attention must be paid to processes occurring at the water/mineral interface. Here, we will discuss how a combination of spectroscopy, microscopy, and surface X-ray diffraction can be used to both, obtain molecular level information from the interfacial region and also relate this molecular processes to retention behavior in macroscopic, close-to-realistic systems, such as natural crystalline rock.

Keywords: Actinides; Coordination Chemistry; Sorption; Geochemistry; TRLFS; Spectroscopy; XRD

  • Invited lecture (Conferences)
    GDCh Fachtagung Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35648
Publ.-Id: 35648


Local Neumann semitransparent layers: Resummation, pair production, and duality

Ahmadiniaz, N.; Franchino-Vinas, S.; Manzo, L.; Mazzitelli, F. D.

We consider local semitransparent Neumann boundary conditions for a quantum scalar field as imposed by a quadratic coupling to a source localized on a flat codimension-one surface. Upon a proper regularization to give meaning to the interaction, we interpret the effective action as a theory in a first-quantized phase space. We compute the relevant heat-kernel to all order in a homogeneous background and quadratic order in perturbations, giving a closed expression for the corresponding effective action in $D=4$. In the dynamical case, we analyze the pair production caused by a harmonic perturbation and a Sauter pulse. Notably, we prove the existence of a strong/weak duality that links this Neumann field theory to the analogue Dirichlet one.

Keywords: Neumann boundary conditions; Dynamical Casimir effect; Quantum field theory in background fields; Effective action; Pair creation; Duality; Dirichlet semitransparent boundary conditions

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Permalink: https://www.hzdr.de/publications/Publ-35643
Publ.-Id: 35643


In Search of Covalency in Tetravalent Actinide (Th - Pu) Monosalen Complex Series

Blei, M. K.; Patzschke, M.; Kvashnina, K.; Waurick, L.; Schmidt, M.; Stumpf, T.; März, J.

Actinides play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories.[1] One of the major tools to obtain a profound basic knowledge about actinide (An) binding is the coordination chemistry of An using model ligands. However, fundamental An chemistry is still relatively little explored. Characteristic of the actinides is their huge variety of possible oxidation states, typically ranging from +II to +VII for early An, making their chemistry complex but interesting. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state.[2] Observed changes in e.g. the binding situation or magnetic effects among the An series may deliver insight into their unique electronic properties mainly originating from the f-electrons. A question still remaining in the field of An chemistry is the degree of “covalency” in compounds across the An series,[3] which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
In this study we investigate the coordination chemistry of tetravalent actinides (An(IV)), which are dominant particularly under anoxic environmental conditions, using the organic salen ligand (salen = N,N’-bis(salicylidene)ethylenediamine) as a small N,O donor.[4] In addition, we change halogen (F, Cl, Br, I) and solvent (MeOH, THF, MeCN, pyridine) donors (see Figure 1) in order to analyse the ligand’s effect on covalency trends as well as their mutual influence, mainly using single crystal X-ray diffraction (SC-XRD), high-energy-resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES), and quantum chemical calculations (QCC).

Keywords: actinides; complexes; SC-XRD; quantum chemical calculations; thorium; uranium; neptunium; plutonium; N-donor ligands

Related publications

  • Invited lecture (Conferences)
    Plutonium Futures, 27.09.2022, Avignon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-35642
Publ.-Id: 35642


Early An(IV) complexes with N-donor ligands

März, J.; Fichter, S.; Patzschke, M.; Kaden, P.; Köhler, L.; Schmidt, M.; Stumpf, T.

The 5f electrons of particularly the early actinides are found to participate in bonding, e.g. to organic ligands, in contrast to the strongly shielded 4f electrons of the lanthanides. Reactivity and complexation strength of such bonds are affected by donor properties of the ligand and the electronic situation of the actinide metal center. Furthermore, coinciding properties of ligand and actinide ion regarding Pearson’s principle of hard and soft acids and bases (HSAB) can even drive the development of selective ligands, e.g. for extraction processes. Here, soft N-donor ligands were found to interact stronger with trivalent actinides in comparison to their harder lanthanide analogues.1
To evaluate how these electronic properties can be extended to a series of tetravalent actinides and their interactions with N-donor ligands, we have studied the complexation of tetravalent Th, Pa, U, Np, and Pu with the amidinate (S,S)-N,N’-bis-(1-phenylethyl)-benzamidine (PEBA), and the Schiff base N,N’-ethylene-bis((pyrrole-2-yl)methan¬imine (pyren).2-4
Complex syntheses using one equivalent of AnCl4(dme)x (An = Th, U, Np, Pu; x = 0 for U, x = 2 for Th, Np, Pu) and three equivalents of PEBA, or two equivalents of pyren led to isostructural heteroleptic 3:1 complexes [AnCl(PEBA)3] or homoleptic 2:1 complexes [An(pyren)2]. Both series were analyzed in the solid state by SC-XRD and IR, as well as in solution by NMR spectroscopy. SC-XRD results and quantum chemical calculations (QCC) revealed differences in AnIV–ligand bond length and strength between the different nitrogen donors (Namidinate, Nimine, Npyrrolide). In addition, with the help of QCC, trends regarding the covalency of the metal-ligand bonds could be derived and assigned to the involved orbitals. Delocalization indices for N–PaIV showed a strong preference of the highly polarizable 5f 1 configuration of PaIV to pyren in its homoleptic complex. This effect disappears in the heteroleptic amidinate complex. Calculated quadrupole moments give a first explanation, showing an isotropically distributed charge arround PaIV in [Pa(pyren)2] but a polarization in [PaCl(PEBA)3].
Halogen exchange reactions of Cl in [AnCl(PEBA)3] was successful for F, Br, and N3 (see Fig. 1). NMR spectra revealed a strong effect of the halogen on the paramagnetic shift, potentially again indicating the impact of the halogen on the polarizabiliy of charge arround the tetravalent actinide.

Keywords: actinides; complex; SC-XRD; quantum chemical calculations; thorium; uranium; neptunium; plutonium; N-donor ligands

  • Lecture (Conference)
    Actinides Revisited, 21.09.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35641
Publ.-Id: 35641


Bonding trends in full early actinide (Th-Pu) pyren complex series

Köhler, L.; Patzschke, M.; Kaden, P.; Kvashnina, K.; Schmidt, M.; Stumpf, T.; März, J.

In contrast to the strongly shielded 4f electrons of the lanthanides, 5f electrons of particularly the early actinides are found to participate in bonding, e.g. to organic ligands. Reactivity and complexation strength of such bonds are the most influenced by donor properties of the ligand and the electronic situation of the actinide metal center. Furthermore, coinciding properties of ligand and actinide ion regarding Pearson’s principle of hard and soft acids and bases (HSAB) can even drive the development of selective ligands, e.g. for extraction processes. Here, soft N-donor ligands were found to interact stronger with trivalent actinides in comparison to their harder lanthanide analogues.1
To evaluate how these HSAB properties can be extended to a series of tetravalent actinides and their interactions with N-donor ligands, we have studied the complexation of tetravalent Th, Pa, U, Np, and Pu with N,N’-ethylene-bis((pyrrole-2-yl)methanimine (pyren) in comparison to its structural N,O-analogue, the salen ligand.2
Complex syntheses using one equivalent of AnCl4(dme)x (An = Th, U, Np, Pu; x = 0 for U, x = 2 for Th, Np, Pu) and two equivalents of pyren led to isostructural 2:1 complexes, which were analyzed in the solid state by SC-XRD and IR, as well as in solution via NMR spectroscopy. SC-XRD results and quantum chemical calculations revealed differences in AnIV–ligand bond length and strength within pyren (Nimine vs. Npyrrolide donors) or salen (Nimine vs. Ophenolate). Interestingly, the overall bond strength of the N-donor vs. N,O-donor to An(IV), however, is almost equal for both, [An(pyren)2] and [An(salen)2] (An = Th-Pu). Delocalization indices even confirmed slightly more covalent interactions between the N,O-donor salen and Th, U, Np, and Pu in comparison with pyren. For Pa, on the other hand, this trend is reversed. QTAIM analysis could prove particularly strong interactions with the pure N-donor ligand pyren. This extraordinarily good electron sharing between pyren and Pa can be explained by the 5f1 configuration of Pa(IV), being particularly well polarizable and thus well suited for an effective backbonding to the soft N-donors of the pyren ligand.

Keywords: actinides; complex; SC-XRD; quantum chemical calculations; thorium; uranium; neptunium; plutonium; N-donor ligands

Related publications

  • Invited lecture (Conferences)
    19th Radiochemical Conference, 16.-20.05.2022, Mariánské Lázně, Tschechien

Permalink: https://www.hzdr.de/publications/Publ-35640
Publ.-Id: 35640


Recycling battery casing materials

Lyon, T.; Staudacher, M. T. L.; Mütze, T.; Peuker, U. A.

Lithium-ion batteries (LIBs) have become an indispensable part of modern life. Whether in tools, mobile phones, scooters, or electric cars, the demand for LIBs is increasing in many areas of everyday life. Various scenarios predict an almost exponential growth in the demand for electrochemically stored energy and thus also in the demand for key elements for LIBs such as lithium, cobalt, and nickel. Many of the current recycling processes are limited to recovering valuable metals such as cobalt and nickel due to economic viability. Base metals such as aluminum are usually not recovered and are thus lost to the raw material cycle.

Keywords: Mechanical processing; Selective crushing; Air classifier; Eddy-current separation; Housing fraction; Liberation comminution; Lithium-ion battery; Cell housing

  • Book chapter
    Siamak Farhad, Ram K. Gupta, Ghulam Yasin, Tuan Anh Nguyen: Nano Technology for Battery Recycling, Remanufacturing, and Reusing, Amsterdam, Oxford, Cambridge: Elsevier, 2022, 9780323911344, 349-370
    DOI: 10.1016/b978-0-323-91134-4.00004-2

Permalink: https://www.hzdr.de/publications/Publ-35638
Publ.-Id: 35638


Mechanical and physical processes of battery recycling

Werner, D. M. M.; Mütze, T.; Kaas, A.; Peuker, U. A.

The rising production of lithium-ion batteries (LIBs) due to the introduction of stationary and portable energy-storage devices as well as electric mobility in particular demands an efficient and sustainable waste management scheme. In principle, the material transformation from end-of-life (EOL) LIBs to secondary (raw) materials follows the recycling chain for wastes. Therein, processing aims to break up the bonds between the individual components and materials of the battery to enrich them into defined concentrates for subsequent metallurgical refining. In general, mechanical processes are more energyefficient and economically affordable than thermal, chemical, and metallurgical ones. Consequently, a combination of several crushing, size classifying, and sorting steps are commonly used to prepare concentrates for further treatment. This chapter presents the principles of mechanical liberation and physical separation processes for EOL LIB processing. Combinations of specific processes categorized by their feed materials are proposed and discussed, outlining possible material fractions and further potential for research and development. LIB recycling with a mechanical processing unit is shown to achieve high recycling efficiencies that enable the fulfill the upcoming and updated European legal framework regarding LIB disposal.

Keywords: waste processing; physical separation; mechanical liberation; Lithium-ion battery; fractions; coarse fractions

  • Book chapter
    Siamak Farhad, Ram K. Gupta, Ghulam Yasin, Tuan Anh Nguyen: Nano Technology for Battery Recycling, Remanufacturing, and Reusing, Amsterdam, Oxford, Cambridge: Elsevier, 2022, 9780323911344, 455-486
    DOI: 10.1016/b978-0-323-91134-4.00004-2

Permalink: https://www.hzdr.de/publications/Publ-35637
Publ.-Id: 35637


Insights into Uranium binding properties by magnetotactic bacteria

Krawczyk-Bärsch, E.; Ramtke, J.; Drobot, B.; Müller, K.; Steudtner, R.; Hübner, R.; Raff, J.

Magnetotactic bacteria are characterized by intracellular magnetic mineral crystals of magnetite (Fe3O4) or greigite (Fe3S4), which helps them to orientate themselves along the Earth's magnetic field for reaching regions of optimal oxygen concentrations. They are facultative anaerobe and usually found in a large abundance in oxic-anoxic transition zones of aquatic environments, in sediments of freshwater, brackish, marine, and hypersaline habitats [1]. Assuming that magnetotactic bacteria can also be found in the far-field of a nuclear waste repository, studies on the interaction of a natural bacterial strain of Magnetospirillum magneticum AMB-1 cells with U were carried out for the first time using a multidisciplinary approach combining microscopy and different spectroscopic techniques to achieve a better molecular understanding. Results of batch sorption experiments show that Magnetospirillum magneticum AMB-1 can survive both in a wide pH range and with relatively high U concentrations of up to 0.1 mM, while effectively and almost completely immobilizing U in the first hours of incubation. (S)TEM/EDXS studies on ultrathin sections of cells loaded with 0.1 mM U clearly indicate that U is predominantly located in the cell wall. Since it is known from previous studies [2] that U often binds to the cell wall of bacteria by interacting with cell wall compounds, important ligands were used, such as peptidoglycan, lipopolysaccharide, L-rhamnose, D-(+) galactose and D-(+) mannose as possible complexants for U and measured by cryo-TRLFS combined with PARAFAC. The results show five U species and highlight the dominant role of peptidoglycan as main sorbent of U on the cell wall of Magnetospirillum magneticum AMB-1 cells, showing three characteristic peptidoglycan species. In-situ ATR FT-IR studies confirm the predominant binding to carboxylic functionalities and reveal that polynuclear species seem to play an important role at higher pH.

Keywords: magnetotactic bacteria; uranium; sorption; peptidoglycan

  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2022, 04.-06.10.2022, Bergisch-Gladbach, Germany

Permalink: https://www.hzdr.de/publications/Publ-35636
Publ.-Id: 35636


A local model to study precessing turbulence

Pizzi, F.; Mamatsashvili, G.; Giesecke, A.; Stefani, F.

Precession driven flows are ubiquitous natural phenomena. Similarly to other
forcing mechanism, precession motion causes complex behavior in the fluid flow
consisting of interplay between rotating and inertial wave turbulence. Turbulent
precessing flows can drive dynamo action

Keywords: Rotating turbulence; Precession

  • Poster
    17TH SEDI (Study Earth's Deep Interior) symposium, 11.07.2022, Zurich, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35635
Publ.-Id: 35635


Data publication: Numerical and theoretical framework for the DRESDYN precession dynamo experiment

Pizzi, F.; Giesecke, A.; Simkanin, J.; Kumar, V.; Gundrum, T.; Stefani, F.

This dataset is the base of the publication. It has been computed through a fully nonlinear DNS code (SEMTEX) and a code for the computation of magnetic field written by Dr. Andre' Giesecke.

Keywords: Direct Numerical Simulations (DNS); Dynamo; MHD

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35633
Publ.-Id: 35633


Microbially induced reduction of Uranium in contaminated mine water for bioremediation purposes: A multidisciplinary approach study

Newman Portela, A.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Kassahun, A.; Roßberg, A.; Kvashnina, K.; Bazarkina, E.; Raff, J.; Merroun, M. L.

The legacy of the former uranium (U) mining in Saxony and Thuringia (Germany) still shows uranium concentrations, e.g., in the mine water of some mines. The present study describes the biostimulation of the native U reducing microbial community in a U contaminated mine water as an efficient and eco-friendly strategy for in situ bioremediation to prospectively support or outperform chemical water treatments.

The microbial community was characterized by 16S and ITS1 rRNA gene analyses, showing a relative abundance of native microbial groups with the ability to alter the speciation and redox state of soluble U (e.g., Desulfovibrio, Gallionella, Penicillium and Aspergillus). Additionally, Inductively Coupled Plasma-Mass spectrometry (ICP-MS) and Ionic Chromatography (IC) were used to determine geochemical profile of the mine water, exhibiting a notable concentration of U (1.01mg/L), SO4 2- (335mg/L), Fe (0.99mg/L) and Mn (1.44mg/L). Cryo-Time-Resolved Laser Fluorescence spectroscopy (cryo-TRLFS) and Parallel Factor Analysis (PARAFAC) determined the aqueous species Ca2UO2(CO3)3 4- as the main U species in mine water. A set of anerobic microcosms, supplemented with glycerol (10mM) as electron donor to stimulate U reducing bacteria, were designed as basis of an in situ bioremediation strategy for uranium contaminated waters. A thermodynamic Eh-pH dominance diagram calculated using Geochemist's Workbench predicted the reduction of U(VI) and the formation of the solid U-ore (uraninite). At the end of the experiment, ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of U (≈98%), Fe (≈91%) and SO4 2- (≈88%). Furthermore, the black precipitate formed at the bottom of the microcosm was analyzed by High Energy Resolution Fluorescence Detected Near-edge X-ray absorption fine structure (HERFD-XANES) and Extended X-ray absorption fine structure (EXAFS) identifying mainly U(IV) (≈80%) and U(V) (≈20%).

The results obtained revealed that microbial cycling processes have a significant impact on the complete enzymatic reduction of soluble U(VI) to U(IV) and U(V) by the addition of an electron donor in low U concentration contaminated mine water. Therefore, this methodology could be an efficient bioremediation approach for the management of U contaminated mine water, as well as low U contaminated mine water scenarios, through the biostimulation of its indigenous microbial community.

Keywords: microorganisms; uranium; mine water; reduction

Related publications

  • Lecture (Conference)
    Symposium on Remediation, 29.-30.09.2022, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-35632
Publ.-Id: 35632


Suppression of Interband Heating for Random Driving

Zhao, H.; Knolle, J.; Moessner, R.; Mintert, F.

Heating to high-lying states strongly limits the experimental observation of driving induced nonequilibrium phenomena, particularly when the drive has a broad spectrum. Here we show that, for entire
families of structured random drives known as random multipolar drives, particle excitation to higher bands
can be well controlled even away from a high-frequency driving regime. This opens a window for
observing drive-induced phenomena in a long-lived prethermal regime in the lowest band.

Permalink: https://www.hzdr.de/publications/Publ-35631
Publ.-Id: 35631


Biostimulation of uranium reducing bacteria in contaminated mine water for bioremediation purposes: multidisciplinary approach study

Newman Portela, A.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Merroun, M. L.; Raff, J.

Uranium (U) and its mining have historically been strongly related to East Germany. From the second half of the 20th century onwards, the Federal States of Saxony and Thuringia have been the scene of intense mining activity. The cessation of mining activities in 1990, has led to the generation of U contaminated areas. Nowadays, conventional remediation methodologies are not able to remove soluble U entirely. Microorganisms offer an environmental friendly water remediation strategy for U through bioreduction or biomineralization. The present study describes a strategy for in situ bioremediation of U(VI) from a U mine water by biostimulation of the native U reducing microbial community.
The geochemical profile of the mine water was characterized by Inductively Coupled Plasma-Mass spectrometry (ICP-MS) and Ionic Chromatography (IC), showing a substantial concentration of U (1.01mg/L), SO4 2- (335mg/L), Fe (0.99mg/L) and Mn (1.44mg/L). Cryo-Time-Resolved Laser Fluorescence spectroscopy (cryo-TRLFS) and Parallel Factor Analysis (PARAFAC) determined the aqueous species Ca2UO2(CO3)3 4- as the main U species in mine water. In addition, 16S and ITS1 rRNA gene analyses were used to characterize the microbial community, indicating a relative abundance of natural microbial groups with U(VI)-reduction ability (e.g., Desulfovibrio, GallionellaSideroxydans). For the design of an in situ bioremediation technology for U contaminated waters, a set of anoxic microcosms supplemented with glycerol (10mM) as electron donor was previously designed. A thermodynamic Eh-pH dominance diagram calculated using Geochemist's Workbench predicted the reduction of U(VI) and the formation of the solid U-mineral (uraninite). After 3 months, ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of U (≈98%), SO42- (≈88%) and Fe (≈91%). Furthermore, the black precipitate formed at the bottom of the microcosm was analyzed by UV-Vis spectroscopy, identifying mainly U(IV).
The results obtained revealed the U enzymatic reduction of U(VI) to U(IV) by the addition of an electron donor in low concentrated U contaminated mine waters. Thus, this strategy might be an efficient bioremediation approach for U contaminated mine waters, by biostimulating their indigenous microbial community.

Keywords: microorganismens; uranium; mine water; reduction

  • Lecture (Conference)
    Goldschnmidt Conference 2022, 10.-15.07.2022, Honolulu, Hawaii, US

Permalink: https://www.hzdr.de/publications/Publ-35630
Publ.-Id: 35630


A glimpse into pion gravitational form factor

Xing, Z.; Ding, M.; Chang, L.

We provide a novel approach to calculate the gravitational form factor of pion under the ladder approximation of the Bethe-Salpeter equation, with contact interactions. Central to this approach is a symmetry-preserving treatment of the dressed ππ amplitude, which shows explicitly the contributions from intrinsic quarks and bound states, the latter being necessary to produce the D-term of pion in the soft-pion limit. The approach we provide in this work can be applied to many processes of physical significance.

Permalink: https://www.hzdr.de/publications/Publ-35627
Publ.-Id: 35627


High dimensional tori and chaotic and intermittent transients in magnetohydrodynamic Couette flows

Garcia Gonzalez, F.; Ogbonna, J. E.; Giesecke, A.; Stefani, F.

The magnetised spherical Couette (MSC) problem, a three dimensional magnetohydrodynamic paradigmatic model in geo- and astrophysics, is considered to investigate bifurcations to high-dimensional invariant tori and chaotic flows in large scale dissipative dynamical systems with symmetry. The main goal of the present study is to elucidate the origin of chaotic transients and intermittent behaviour from two different sequences of Hopf bifurcations involving invariant tori with four fundamental frequencies, which may be resonant. Numerical evidence of the existence of a crisis event destroying chaotic attractors and giving rise to the chaotic transients is provided. It is also shown that unstable invariant tori take part in the time evolution of these chaotic transients. For one sequence of bifurcations, the study demonstrates that chaotic transients display on-off intermittent behaviour. A possible explanatory mechanism is discussed.

Permalink: https://www.hzdr.de/publications/Publ-35626
Publ.-Id: 35626


Experimental investigation of the nutation angle's effect on the flow inside a precessing cylinder

Kumar, V.; Giesecke, A.; Gundrum, T.; Pizzi, F.; Ratajczak, M.; Anders, S.; Stefani, F.

Precession-driven flows are considered as potential sources of dynamo action on Earth, ancient moon, and some asteroids. At the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), a precession-driven dynamo experiment is now being constructed as part of the DRESDYN project. It is a cylinder filled with liquid sodium with a radius of 1 m and a height of 2 m. The cylinder rotates at a frequency of up to 10 Hz and precesses around the second axis at a rate of up to 1 Hz.
To gain a better understanding of the hydrodynamics of a precessing cylinder, a downscaled 1:6 water mockup with the same aspect ratio, rotation, and precession frequency was built. The typical non-axisymmetric Kelvin mode, which initially increases as the precession ratio increases, is alone not suitable for dynamo action in the experiment. However, a secondary axisymmetric mode that appears in a narrow region of the precession ratio was demonstrated to be particularly promising for dynamo action in the sodium experiment.
To predict dynamo behavior for different precession ratios and precession angles, a thorough understanding of the flow structure in the precessing cylindrical vessel is required. For that purpose, we performed a series of precession measurements on the downscaled water experiment with Ultrasonic Doppler velocimetry (UDV) at various precession angles of 60o, 75o, and 90o. We present the effect of precession angle and rotation direction (i.e. prograde or retrograde) on the dominant flow modes, and quantify this behaviour in dependence on the rotation rate, which is parameterized by the Reynolds number Re = ΩcR2/ν, and the precession ratio Po = Ωp/Ωc, where ν is the viscosity and Ωp = 2πfp is the angular frequency of the precession. The experimental results are compared with numerical simulations.

  • Poster
    9th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 16.-19.08.2022, Groningen, the Netherlands

Permalink: https://www.hzdr.de/publications/Publ-35619
Publ.-Id: 35619


The Effect of the Nutation Angle on the Flow in a Precessing Cylinder: Experimental Results

Kumar, V.; Giesecke, A.; Gundrum, T.; Pizzi, F.; Ratajczak, M.; Stefani, F.

Precession-driven flows are discussed as possible sources for dynamo action in the Earth [1], the ancient moon, and in some asteroids. A precession-driven dynamo experiment is currently under construction at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) as part of the DRESDYN project. It consists of a liquid sodium filled cylinder with a radius of 1 m and a height of 2 m. The cylinder rotates at a frequency of up to 10 Hz and precesses at a frequency of up to 1 Hz around the second axis [2].
A downscaled 1:6 water mockup with the same aspect ratio and rotation and precession frequencies was developed to better understand the hydrodynamics in a precessing cylinder. The typical non-axisymmetric Kelvin mode, which initially increases as the precession ratio increases, is alone not suitable for dynamo action in the experiment. However, a secondary axisymmetric mode that appears in a narrow region of the precession ratio was demonstrated to be particularly promising for dynamo action in the sodium experiment [3].
To be able to anticipate dynamo behaviour for various precession ratios and precession angles, a complete understanding of the flow structure in the precessing cylindrical vessel is required. For that purpose, we conducted a series of precession measurements using Ultrasonic Doppler velocimetry (UDV) on the downscaled water experiment at various precession angles of 60o, 75o, and 90o. We present the effect of precession angle and rotation direction (i.e. prograde or retrograde) on the dominant flow modes, and quantify this behaviour in dependence on the rotation rate, which is parameterized by the Reynolds number Re = ΩcR2/ν, and the precession ratio Po = Ωp/Ωc, where ν is the viscosity and Ωp = 2πfp is the angular frequency of the precession. The experimental results are compared with numerical simulations [4].

  • Contribution to proceedings
    12th International PAMIR Conference - Fundamental and Applied MHD, 04.-08.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35618
Publ.-Id: 35618


NMR spectroscopy of selected aqueous systems investigated at HZDR–IRE

Kretzschmar, J.; Stumpf, T.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful method for both structure elucidation of molecules and their metal complexes, and also for studying their behavior in terms of thermodynamics and kinetics, as well as reactions occurring in situ in dependence on a variety of physico-chemical parameters. In this context, NMR spectroscopy of aqueous (D₂O) solutions features some peculiarities. That is, first and foremost, the pH (pD) of the solution affects the speciation of both the molecule (ligand) and the metal ion (actinide or lanthanide) under study. Furthermore, the ligand can be subject to deuteration, and either component can undergo redox reactions.

The intracellularly occurring tripeptide glutathione (GSH) constitutes a redox equilibrium with its oxidized (dimeric) form glutathione disulfide (GSSG). Hexavalent uranium, U(VI), forms complexes with the latter over a wide pH range, while GSH reduces U(VI) to U(IV). However, the redox reaction occurs only between pH 6 and 10, i.e. close to the thiol group’s pKa, presumably due to homolytic cleavage of the S–H group in GSH’s cysteine residue. The redox reaction appears to take place intermolecularly without the need for U(VI) complexation by the reductant [1, 2].
Uranyl(VI) citrate dimeric and trimeric complexes exhibit interesting structural and (¹⁷O) NMR spectroscopic features such as superstructure formation upon varying pH or concentration, and polarization of uranyl units acting as Lewis base in metal ion coordination (O=U=O⟶Mn+) [3, 4]. Irradation of uranyl(VI) citrate by visible light yields complexes of lower valent uranium. The reaction again occurs intermolecularly, whereby in situ oxidation of excessive ligand through several intermediates can be comprehended by NMR spectroscopy.
In studies investigating the interaction of radionuclides (RNs) with a solid phase in equilibrium with an aqueous phase, the influence of organics on RN retention can be complemented by qualitative and quantitative solution NMR methods by determining their speciation (free, metal ion-bound, oxidized) and concentration in the supernatant.
NMR spectroscopy can also be utilized as a robust and elegant method for determining ligand’s pKa along with the originating site of the abstracted proton as shown for GSH/GSSG, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), as well as nitrilotriacetate (NTA) and ethylene glycol-bis(aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA) [5]. The latter two, being representatives of the so-called complexones, show Lewis acid-catalyzed in situ deuteration of the N acetyl methylene groups in NaOD media, which is applied for speciation analyses in artificial body fluids by means of ²H NMR spectroscopy as the only deuterated component.

Acknowledgement
This research received funding by the German Federal Ministry for Economic Affairs and Energy (BMWi) with-in the GRaZ II projects, nos. 02E11860B and 02E11860G, the German Federal Ministry of Education and Research (BMBF) within the RADEKOR project, no. 02NUK057A, as well as by the European Union’s Horizon 2020 research and innovation programme’s CORI project, no. 847593.

References
[1] Kretzschmar, J.; Haubitz, T.; et al. Chem. Commun., 2018, 54, 8697.
[2] Kretzschmar, J.; Strobel, A.; et al. Inorg. Chem., 2020, 59, 4244.
[3] Kretzschmar, J.; Tsushima, S.; et al. Chem. Commun., 2020, 56, 13133.
[4] Kretzschmar, J.; Tsushima, S.; et al. Inorg. Chem., 2021, 60, 7998.
[5] Kretzschmar, J.; Wollenberg, A.; et al. Molecules, 2022, 27, 4067.

Keywords: NMR spectroscopy; Uranium; Radioecology; Aqueous system; Thermodynamics; Kinetics; Redox reaction; Speciation

  • Lecture (Conference)
    Actinides revisited 2022, 21.-23.09.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35617
Publ.-Id: 35617


Influence of the precession angle on the flow inside a precessing cylinder

Kumar, V.; Giesecke, A.; Gundrum, T.; Pizzi, F.; Ratajczak, M.; Stefani, F.

Precession driven flows are potential drivers for dynamo action in the Earth [1], the ancient moon, and some asteroids. As part of the DRESDYN project at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a precession-driven dynamo experiment is presently under construction, which consists of a liquid sodium filled cylinder with a radius of 1 m and a height of 2 m respectively. The cylinder rotates with a frequency of up to 10 Hz and precess around the second axis with a frequency of up to 1 Hz [2].
To understand the hydrodynamics in a precessing cylinder a downscaled 1:6 water mockup was built with the same aspect ratio and rotation frequencies. The typical non-axisymmetric Kelvin mode that grows as the precession ratio rises is alone not suitable for dynamo action in the experiment. However, a secondary axisymmetric mode that emerges in a small region of the precession ratio was shown to be very promising for dynamo action in the sodium experiment [3].
The ability to predict dynamo behaviour for different precession ratios and precession angles requires a thorough understanding of the flow structure in the precessing cylindrical vessel. Consequently, we have performed series of precession measurements with Ultrasonic flow velocimetry (UDV) on the downscaled water experiment with various precession angles α at 60o, 75o, 90o [4]. In this paper, we present the effect of precession angle and rotation direction (i.e. prograde or retrograde) on the dominant flow modes, and quantify this behaviour in dependence of the rotation rate parameterized by the Reynolds number Re = ΩcR2/ν and the precession ratio Po = Ωp/Ωc, with ν the viscosity and Ωp = 2πfp the angular frequency of the precession. We have not taken into account the effect of the precession angle, which changes the definition of Reynolds number. The experimental results are supported by numerical simulations.

  • Lecture (Conference) (Online presentation)
    The Fourth Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russia

Permalink: https://www.hzdr.de/publications/Publ-35615
Publ.-Id: 35615


Element separation chemistry and cosmogenic 10Be dating of a ferromanganese crust

Koll, D.; Wallner, A.; Battisson, S.; Fichter, S.; Fifield, L. K.; Froehlich, M. B.; Lachner, J.; Merchel, S.; Pavetich, S.; Rugel, G.; Slavkovská, Z.; Tims, S. G.; Ziegenrücker, R.

Oceanic archives are contemporary witnesses of Earth's recent astrophysical history by incorporating extraterrestrial
radionuclides. VA13/2 - 237KD is one of the most studied ferromanganese crusts and it has been shown that the crust
contains live interstellar 60Fe. Here, we have characterized a large piece of this crust with a 3D optical scan, a micro-CT
scan and 3D modeling, followed by the chemical extraction of highly purified, element-specific fractions for accelerator mass
spectrometry. High-accuracy cosmogenic 10Be dating of two independent drill-holes showed a time-dependent variability in
growth rate across the surface of the crust. This well-characterized crust is used to search for interstellar radionuclides, such
as supernova-produced 60Fe and the r-process nuclide 244Pu. Other extraterrestrial radionuclides including 26Al, 53Mn,
129I, 182Hf or 247Cm could be investigated in the future.

Keywords: 10Be; 244Pu; 60Fe; AMS; Ferromanganese crust; Nuclear astrophysics; Separation chemistry

Related publications

Downloads

  • Secondary publication expected from 26.09.2023

Permalink: https://www.hzdr.de/publications/Publ-35614
Publ.-Id: 35614


Some news from the synchronization front

Stefani, F.

The lecture summarizes our recent activities to establish a self-consistent planetary synchronization model for short-, medium- and long-term cycles of the solar dynamo.

  • Lecture (Conference)
    5th Dynamo Thinkshop, 27.-28.06.2022, Freiburg im Breisgau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35612
Publ.-Id: 35612


Batteries, dynamos, and all that

Stefani, F.

The lecture gives an overview about the various flow phenomena which can occur in liquid metal batteries, including the Tayler instability, thermal and solutal convection, electrovortex flows, metal pad roll instabilities, and various surface waves. For some of those cases, surprising links to corresponding effects with relevance to the solar dynamo are also discussed.

  • Invited lecture (Conferences)
    Open for Business event: Liquid Metal Batteries, 15.-16.11.2022, Cambridge, UK

Permalink: https://www.hzdr.de/publications/Publ-35610
Publ.-Id: 35610


Shaken and stirred: precessionally driven and tidally synchronized dynamos

Stefani, F.

The first part of the lecture gives an overview about our recent efforts to set-up a self-consistent planetary synchronization model for short-, medium- and long-term cycles of the solar dynamo. In the second part, we discuss the scientific background and the present status of the preparations of the precession-driven dynamo experiment in frame of the DRESDYN project.

  • Invited lecture (Conferences)
    Leeds satellite workshop: Fluid flow and magnetic field generation in fluids and plasmas, 17.-21.10.2022, Leeds, UK

Permalink: https://www.hzdr.de/publications/Publ-35609
Publ.-Id: 35609


Dynamo experiments: A grateful tribute to Karl-Heinz Rädler

Stefani, F.

The talk commemorates the various contributions of Karl-Heinz Rädler to the preparation and interpretation of liquid-metal dynamo experiments.

  • Invited lecture (Conferences)
    Special colloquium in honour of Karl-Heinz Rädler's life achievements: “Tracing the origin of magnetic fields throughout the cosmos”, 23.06.2022, Potsdam, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35605
Publ.-Id: 35605


Laboratory experiments on the generation and action of cosmic magnetic fields

Stefani, F.

After an introduction about the various interactions between the flows of electrically conducting fluids with magnetic fields, including the homogeneous dynamo effect and the celebrated magnetorotational instability in accretion disks, the talk continuous with an overview about previous liquid metal experiments dedicated to the laboratory demonstration of both effects. The main part of the lecture is concerned with the large-sale liquid sodium experiments that are planned in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    Seminar in the Institute of Geophysics of the Czech Academy of Sciences, 19.05.2022, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-35604
Publ.-Id: 35604


Liquid metal experiments on the generation and action of cosmic magnetic fields

Stefani, F.

The lecture starts with an introduction about the various interactions between the flows of electrically conducting fluids with magnetic fields, including the homogeneous dynamo effect and the celebrated magnetorotational instability in accretion disks. It continuous with an overview about previous liquid metal experiments dedicated to the laboratory demonstration of both effects, and concludes with an outlook on the large-sale liquid sodium experiments that are planned in the framework of the DRESDYN project.

  • Invited lecture (Conferences)
    Institutsseminar am Lehrstuhl Aerodynamik und Strömungslehre an der Brandenburgischen Technischen Universität Cottbus-Senftenberg, 17.03.2022, Cottbus, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35603
Publ.-Id: 35603


Synthesis and preclinical evaluation of rhenium and technetium-99m “4 + 1” mixed-ligand complexes bearing quinazoline derivatives as potential EGFR imaging agents

Kiritsis, C.; Shegani, A.; Makrypidi, K.; Roupa, I.; Lazopoulos, A.; Panagiotopoulou, A.; Triantopoulou, S.; Paravatou-Petsotas, M.; Pietzsch, H.-J.; Pelecanou, M.; Papadopoulos, M.; Pirmettis, I.

Epidermal growth factor receptors (EGFR) of tyrosine kinase (TK) have shown high expression levels in most cancers and are considered a promising target for cancer diagnosis and therapy. Expanding the investigation for novel targeted radiopharmaceuticals, an EGFR inhibitor such as 4-aminoquinazoline derivatives along with a radionuclide such as technetium-99m (99mTc) could be ideal. Thus, we report herein the synthesis, characterization, and biological evaluation of new “4 + 1” mixed-ligand ReIII- and 99mTcIII-complexes of the general formula [99mTc][Tc(NS3)(CN-R)] bearing tris(2-mercaptoethyl)-amine (NS3) as the tetradentate tripodal ligand and a series of isocyanide derivatives (CN-R) of tyrosine kinase inhibitor (3-bromophenyl)quinazoline-4,6-diamine as the monodentate ligand. The quinazoline isocyanide derivatives 4a-d were prepared in two steps and reacted with the [Re(NS3)PMe2Ph] precursor leading to the final complexes 5a-d in high yield. All compounds were characterized by elemental analysis, IR, and NMR spectroscopies. In vitro studies, for their potency to inhibit the cell growth, using intact A431 cells indicate that the quinazoline derivatives 4a-d and the Re complexes 5a-d significantly inhibit the A431 cell growth. In addition, the EGFR autophosphorylation study of complex 5b shows an IC50 value in the nanomolar range. The corresponding “4 + 1” 99mTc-complexes 6a-d were prepared by employing the [99mTc]TcEDTA intermediate and the appropriate monodentate 4a-d in a two-step synthetic procedure with a radiochemical yield (RCY) from 63 to 77 % and a radiochemical purity (RCP) > 99 % after HPLC purification. Their structures have been established by HPLC comparative studies using the well-characterized Re-complexes 5a-d as reference. All 99mTc-complexes remain stable for at least 6 h, and their logD7.4 values confirmed their anticipated lipophilic character. Biodistribution studies in healthy Swiss albino mice of 99mTc-complexes showed hepatobiliary excretion and initial fast blood clearance. Complex 6b was also tested in Albino SCID mice bearing A431 tumors and showed rapid tumor uptake at 5 min (2.80 % ID/g) with a moderate tumor/muscle ratio (2.06) at 4 h p.i. The results encourage further investigation for this type of 99mTc-complexes as single-photon emission computed tomography (SPECT) radio agents for imaging tumors overexpressing EGFR. © 2022 Elsevier Ltd

Keywords: EGFR; Quinazolines; Rhenium; SPECT; Technetium-99m

Permalink: https://www.hzdr.de/publications/Publ-35602
Publ.-Id: 35602


DPA calculation with FLUKA2021, PHITS and MCNP6

Ferrari, A.; Müller, S.; Rachamin, R.

Input-files for Monte Carlo-Codes FLUKA2021, PHITS, MCNP62 to calculate the DPA results presented at SATIF15

Keywords: Monte Carlo; FLUKA; PHITS; MCNP; DPA

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Permalink: https://www.hzdr.de/publications/Publ-35601
Publ.-Id: 35601


Data publication: Synchronizing the helicity of Rayleigh-Bénard convection by a tide-like electromagnetic forcing

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

Package of raw and refined data underlying the figures of the connected paper. Included is also the software used to generate the figures.

Keywords: Electromagnetic forcing; Magnetohydrodynamics; Helicity synchronization

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35600
Publ.-Id: 35600


Future air quality predictions using a machine learning-based model over the contiguous United States

Fan, K.; Lee, Y. H.

Air quality regulations have reduced emissions of pollutants in the U.S., but many prognostic studies suggest that future air quality might be degraded by global climate change. The simulated climate by various climate models shows a large variation in the future decades, and it is important to account for such variations to study future air quality. We have developed a machine learning (ML) based air quality model to study, in an efficient way, how future air quality might be influenced by climate change. Our ML model uses two-phase random forest to predict the O3 and PM2.5 concentrations with training datasets of key meteorological information and air quality pollutant emissions. To evaluate the model performance, we used the input datasets for the U.S. Environmental Protection Agent (EPA) the Community Multiscale Air Quality Modeling System (CMAQ) simulations and compared our model predictions against the CMAQ output as a benchmark. The ML model is well performed for hourly O3 predictions over the whole domain in four selected months (January, February, July, and August), and the R2 values are in 0.5 – 0.7, the normalized mean bias (NMB) values are within ±3%, the overall normalized mean error (NME) values are below 20%. Predicting PM2.5 is more challenging than predicting O3, but our ML model performance is still acceptable. The overall R2 values of PM2.5 predictions are in 0.4 – 0.6, and the NMB values are within ±6%, but the NME can be up to 60%. Our ML model with GPU acceleration runs less than one hour using a single GPU processor to predict 11-year one-month (total 11 months) simulations. It uses significantly less computing resources compared to the 3D models, like CMAQ, while it results in comparable predictability to CMAQ. It shows that our ML model a reliable and efficient tool to assess the air quality under various climate change scenarios.

Keywords: Machine learning; Air quality prediction; GPU acceleration

  • Open Access Logo Lecture (Conference) (Online presentation)
    Sustainability Research & Innovation Congress 2022 (SRI2022) / Early-career pathways and resources: communication, cross-disciplinary collaboration, and FE's mission, 20.-24.06.2022, Pretoria, South Africa

Permalink: https://www.hzdr.de/publications/Publ-35599
Publ.-Id: 35599


research data: Rsn-2-mediated directed foam enrichment of β-lactamase

Krause, T.; Keshavarzi, B.; Dressel, J.; Heitkam, S.; B. Ansorge-Schumacher, M.

the excel data attached includes the flotation data, the surface tension data, and the activity of the enzyemes before and after the flotation.

Keywords: downstream processing; foaming; β-lactamase; penicillin G acylase; protein enrichment; Ranaspumin-2

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35595
Publ.-Id: 35595


Data-driven approach to early estimate the inflection points of infected cases in Saxony, Germany

Fan, K.

We develop a data-driven forecasting model of COVID-19 for Saxony using autoregressive integrated moving average (ARIMA) and Holt’s models in the presence and absence of seasonal parameters. Owing to a daily-updated data curation facility, we employ a version control of daily-updated data for Saxony which serve as training data of seasonal parameter to forecast up to 4 horizons. We find that this method is capable of immediately estimating inflection points after a turning point is present. The results are also compatible with the counties of Saxony. We also tried to use multiple datasets (including infection, death, recovery, vaccination data) to train a random forest machine learning model. The preliminary result looks promising and further exploration will be done.

Keywords: COVID-19; Database server; Forecast

  • Open Access Logo Lecture (Conference)
    1st Symposium for Machine Learning for Infection and Disease in Görlitz, 15.-16.09.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35594
Publ.-Id: 35594


Precise tuning of interlayer electronic coupling in layered conductive metal-organic frameworks

Lu, Y.; Zhang, Y.; Yang, C.-Y.; Revuelta, S.; Qi, H.; Huang, C.; Jin, W.; Li, Z.; Vega-Mayoral, V.; Liu, Y.; Huang, X.; Pohl, D.; Položij, M.; Zhou, S.; Cánovas, E.; Heine, T.; Fabiano, S.; Feng, X.; Dong, R.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have attracted increasing interests for (opto)-electronics and spintronics. They generally consist of van der Waals stacked layers and exhibit layer-depended electronic properties. While considerable efforts have been made to regulate the charge transport within a layer, precise control of electronic coupling between layers has not yet been achieved. Herein, we report a strategy to precisely tune interlayer charge transport in 2D c-MOFs via side-chain induced control of the layer spacing. We design hexaiminotriindole ligands allowing programmed functionalization with tailored alkyl chains (HATI_CX, X = 1,3,4; X refers to the carbon numbers of the alkyl chains) for the synthesis of semiconducting Ni3(HATI_CX)2. The layer spacing of these MOFs can be precisely varied from 3.40 to 3.70 Å, leading to widened band gap, suppressed carrier mobilities, and significant improvement of the Seebeck coefficient. With this demonstration, we further achieve a record-high thermoelectric power factor of 68 ± 3 nW m−1 K−2 in Ni3(HATI_C3)2, superior to the reported holes-dominated MOFs.

Permalink: https://www.hzdr.de/publications/Publ-35591
Publ.-Id: 35591


Nonlinear Evolution of Magnetorotational Instability in a Magnetized Taylor-Couette Flow: Scaling Properties and Relation to Upcoming DRESDYN-MRI Experimen

Mishra, A.; Mamatsashvili, G.; Stefani, F.

Magnetorotational instability (MRI) is considered as the most likely mechanism driving angular
momentum transport in astrophysical disks. However, despite many efforts, a direct and conclusive
experimental evidence of MRI in laboratory is still missing. Recently, performing 1D linear analysis
of the standard version of MRI (SMRI) between two rotating coaxial cylinders with an imposed axial
magnetic field, we showed that SMRI can be detected in the upcoming DRESDYN-MRI experiment
based on cylindrical magnetized Taylor-Couette (TC) flow with liquid sodium. In this follow-up
study, being also related to the DRESDYN-MRI experiments, we focus on the nonlinear evolution
and saturation properties of SMRI and analyze its scaling behavior with respect to various param-
eters of the basic TC flow using a pseudo-spectral code. We conduct a detailed analysis over the
extensive ranges of magnetic Reynolds number Rm ∈ [8.5, 37.1], Lundquist number Lu ∈ [1.5, 15.5]
and Reynolds number, Re ∈ [103, 105]. For fixed Rm, we investigate the nonlinear dynamics of
SMRI for small magnetic Prandtl numbers down to P m ∼ O(10−4), aiming ultimately for those
values typical of liquid sodium used in the experiments. In the saturated state, the magnetic en-
ergy of SMRI and associated torque exerted on the cylinders, characterising angular momentum
transport, both increase with Rm for fixed (Lu, Re), while for fixed (Lu, Rm), the magnetic energy
decreases and torque increases with increasing Re. We also study the scaling of the magnetic en-
ergy and torque in the saturated state as a function of Re and find a power law dependence of the
form Re−0.6...−0.5 for the magnetic energy and Re0.4...0.5 for the torque at all sets of (Lu, Rm) and
sufficiently high Re ≥ 4000. We also explore the dependence on Lundquist number and angular
velocity. The scaling laws derived here will be instrumental in the subsequent analysis and com-
parison of numerical results with those obtained from the DRESDYN-MRI experiments in order to
conclusively and unambiguously identify SMRI in laboratory.Magnetorotational instability (MRI) is considered as the most likely mechanism driving angular
momentum transport in astrophysical disks. However, despite many efforts, a direct and conclusive
experimental evidence of MRI in laboratory is still missing. Recently, performing 1D linear analysis
of the standard version of MRI (SMRI) between two rotating coaxial cylinders with an imposed axial
magnetic field, we showed that SMRI can be detected in the upcoming DRESDYN-MRI experiment
based on cylindrical magnetized Taylor-Couette (TC) flow with liquid sodium. In this follow-up
study, being also related to the DRESDYN-MRI experiments, we focus on the nonlinear evolution
and saturation properties of SMRI and analyze its scaling behavior with respect to various param-
eters of the basic TC flow using a pseudo-spectral code. We conduct a detailed analysis over the
extensive ranges of magnetic Reynolds number Rm ∈ [8.5, 37.1], Lundquist number Lu ∈ [1.5, 15.5]
and Reynolds number, Re ∈ [103, 105]. For fixed Rm, we investigate the nonlinear dynamics of
SMRI for small magnetic Prandtl numbers down to P m ∼ O(10−4), aiming ultimately for those
values typical of liquid sodium used in the experiments. In the saturated state, the magnetic en-
ergy of SMRI and associated torque exerted on the cylinders, characterising angular momentum
transport, both increase with Rm for fixed (Lu, Re), while for fixed (Lu, Rm), the magnetic energy
decreases and torque increases with increasing Re. We also study the scaling of the magnetic en-
ergy and torque in the saturated state as a function of Re and find a power law dependence of the
form Re^(−0.6...−0.5) for the magnetic energy and Re^(0.4...0.5) for the torque at all sets of (Lu, Rm) and
sufficiently high Re ≥ 4000. We also explore the dependence on Lundquist number and angular
velocity. The scaling laws derived here will be instrumental in the subsequent analysis and com-
parison of numerical results with those obtained from the DRESDYN-MRI experiments in order to
conclusively and unambiguously identify SMRI in laboratory.

  • Lecture (Conference)
    The 12th pamir International Conference on Fundamental and Applied MHD, 04.07.2022, Krakow, Poland
  • Lecture (Conference)
    9th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 16.-19.08.2022, Groningen, Netherlands
  • Contribution to WWW
    arXiv:2211.10811 [physics.flu-dyn]: https://arxiv.org/abs/2211.10811

Permalink: https://www.hzdr.de/publications/Publ-35588
Publ.-Id: 35588


Dynamic transitions of the magnetized spherical Couette flow between its base state and the return flow instability

Ogbonna, J. E.; Garcia Gonzalez, F.; Gundrum, T.; Seilmayer, M.; Stefani, F.

The transition between the stable base state of the magnetized spherical Couette (MSC) flow and the return flow instability is experimentally investigated. The experiments are conducted using an MSC setup consisting of insulating spheres with the ratio of the inner to the outer radii ri/ro = 0.5, Reynolds number Re = 1000 and Hartmann number Ha ∈ [25, 29]. The transition is characterized by changes in the power spectra of the azimuthal modes in the flow as Ha is dynamically changed. The transition occurs in the interval Ha ∈ [26.5, 27.5]. The evolution of the power spectra of the azimuthal modes exhibits hysteretic effect depending on whether Ha is increased or decreased within the experimental interval. The power spectra in the azimuthal modes m ∈ {3, 4} increases and remains dominant as Ha is increased, while the power spectra in m ∈ {2, 4} are dominant while the flow is time dependent due to return flow instability as Ha is decreased.

Keywords: Magnetohydrodynamics; Experimental fluid mechanics; Fluid instability

Permalink: https://www.hzdr.de/publications/Publ-35587
Publ.-Id: 35587


Sorption and Modeling of Actinides on Ca-Feldspars

Lessing, J.; Neumann, J.; Bezzina, J. P.; Bok, F.; Lützenkirchen, J.; Brendler, V.; Stumpf, T.; Schmidt, M.

This poster gives a small overview of the investigations on sorption on plagioclases (Ca-feldspars). The topic is of main importance to find an suitable final radioactive waste repository.
The surface of the minerals was characterzied with zeta potenzial. Batch sorption experiments were conducted to gain information about the sorption of the lanthanide Eu3+ and actinide Am3+. Time resolved laser induced spectroscopy was applied to understand the sorption on a molecular level. All these data were then used for a surface complexation model, that will be used for simulation of the sorption of actinides at different geochemical conditions.

Keywords: Sorption; actinides; Ca-feldspar; plagioclase; TRLFS; batch sorption; SCM

  • Poster
    ChemTUgether, 13.-14.05.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35585
Publ.-Id: 35585


Natural and synthetic plagioclases: Surface charge characterization and sorption of trivalent Ln and An

Lessing, J.; Neumann, J.; Bezzina, J. P.; Bok, F.; Lützenkirchen, J.; Brendler, V.; Stumpf, T.; Schmidt, M.

Das Wissen über den Transport von Radionukliden in der Umwelt ist essenziell zur Beur-teilung der Sicherheit eines radioaktiven Endlagers. Einen globalen Konsens bildet zurzeit die tiefengeologische Lagerung, da diese verspricht den Abfall über geologische Zeiträume von der Biosphäre zu isolieren. In einigen Ländern, u. a. Deutschland wird Kristallingestein, welches sich neben Quarz und Glimmern vorwiegend aus Feldspäten zusammensetzt, als mögliches Wirtsgestein für ein tiefengeologisches Endlager betrachtet. Deshalb ist es von enormer Bedeutung, die Rückhaltung der dreiwertigen minoren Actinide (Cm, Am), welche über Jahrtausende die Radiotoxizität im Endlager dominieren an Feldspäte zu verstehen. In dieser Studie wurden speziell Ca-Feldspäte betrachtet, da deren Retentionsverhalten noch nicht ausreichend untersucht wurde, aber Unterschiede in Kristallstruktur und Gitterladung im Vergleich zum besser untersuchten K-Feldspat auftreten.
Zunächst wurden Zetapotenzial-Messungen von Ca-Feldspäten mit verschiedenen Ca-Anteilen durchgeführt. Sie zeigen einen ungewöhnlichen Anstieg der Oberflächenladung bei pH 4 – 7, wobei der Anstieg des Zetapotenzials mit steigender Ca-Konzentration im Kris-tallgitter des Feldspats zunimmt. Dies wird durch die Sorption von Ca2+ und AlDas Wissen über den Transport von Radionukliden in der Umwelt ist essenziell zur Beur-teilung der Sicherheit eines radioaktiven Endlagers. Einen globalen Konsens bildet zurzeit die tiefengeologische Lagerung, da diese verspricht den Abfall über geologische Zeiträume von der Biosphäre zu isolieren. In einigen Ländern, u. a. Deutschland wird Kristallingestein, welches sich neben Quarz und Glimmern vorwiegend aus Feldspäten zusammensetzt, als mögliches Wirtsgestein für ein tiefengeologisches Endlager betrachtet. Deshalb ist es von enormer Bedeutung, die Rückhaltung der dreiwertigen minoren Actinide (Cm, Am), welche über Jahrtausende die Radiotoxizität im Endlager dominieren an Feldspäte zu verstehen. In dieser Studie wurden speziell Ca-Feldspäte betrachtet, da deren Retentionsverhalten noch nicht ausreichend untersucht wurde, aber Unterschiede in Kristallstruktur und Gitterladung im Vergleich zum besser untersuchten K-Feldspat auftreten.
Zunächst wurden Zetapotenzial-Messungen von Ca-Feldspäten mit verschiedenen Ca-Anteilen durchgeführt. Sie zeigen einen ungewöhnlichen Anstieg der Oberflächenladung bei pH 4 – 7, wobei der Anstieg des Zetapotenzials mit steigender Ca-Konzentration im Kris-tallgitter des Feldspats zunimmt. Dies wird durch die Sorption von Ca2+ und Al3+ und/oder Ausfällung einer Al-Phase verursacht.[1]
Im Vergleich zum K-Feldspat treten nur geringe Unterschiede im Rückhaltevermögen und in der Oberflächenspeziation auf. Ca-Feldspäte zeigen ein leicht höheres Rückhaltevermö-gen gegenüber dreiwertigen Metallionen. Ein innersphärischer (IS) Oberflächenkomplex so-wie dessen zwei Hydrolyseformen wurden an beiden Mineralen identifiziert, allerdings tritt die Hydrolyse des IS-Komplexes an Ca-Feldspäten bereits bei niedrigeren pH-Werten auf.[1,2]
Batchsorptionsdaten und spektroskopische Informationen wurden schließlich kombiniert, um ein Oberflächenkomplexierungsmodell zu entwickeln und die Bildungskonstanten der drei Oberflächenkomplexe zu bestimmen (log K0 = -8,37; -10,81 bzw. -16,35). Diese Werte un-terscheiden sich nur unwesentlich von den Werten für K-Feldspat. [1,2]
Die gewonnenen Daten stehen für Transportsimulationen für die Sicherheitsbeurteilung eines potenziellen Endlagers für radioaktiven Abfall zur Verfügung.
und/oder Ausfällung einer Al-Phase verursacht.[1]
Im Vergleich zum K-Feldspat treten nur geringe Unterschiede im Rückhaltevermögen und in der Oberflächenspeziation auf. Ca-Feldspäte zeigen ein leicht höheres Rückhaltevermö-gen gegenüber dreiwertigen Metallionen. Ein innersphärischer (IS) Oberflächenkomplex so-wie dessen zwei Hydrolyseformen wurden an beiden Mineralen identifiziert, allerdings tritt die Hydrolyse des IS-Komplexes an Ca-Feldspäten bereits bei niedrigeren pH-Werten auf.[1,2]
Batchsorptionsdaten und spektroskopische Informationen wurden schließlich kombiniert, um ein Oberflächenkomplexierungsmodell zu entwickeln und die Bildungskonstanten der drei Oberflächenkomplexe zu bestimmen (log K0 = -8,37; -10,81 bzw. -16,35). Diese Werte un-terscheiden sich nur unwesentlich von den Werten für K-Feldspat. [1,2]
Die gewonnenen Daten stehen für Transportsimulationen für die Sicherheitsbeurteilung eines potenziellen Endlagers für radioaktiven Abfall zur Verfügung.
Referenzen:
[1] Neumann and Lessing et al., in preparation. [2] J. Neumann et al., J. Colloid Interface Sci., 2021, 591, 490–499.

Keywords: Plagioclases; surface chemistry; actinides; lanthanides

  • Open Access Logo Poster
    Jahrestagung der FG Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35584
Publ.-Id: 35584


Mineral revolution for the Wellbeing Economy

Gloaguen, R.; Ajjabou, L.; Ali, S.; Herrington, R.; Downey, E.; Stewart, I. S.

Non-technical summary. As we consider a transition to a low-carbon future, there is a need to examine the mineral needs for
this transformation at a scale reminiscent of the Green Revolution. The efficiency gains of the agrarian transition came at
ecological and social costs that should provide important lessons about future metal sourcing. We present three options for a
Mineral Revolution: status quo, incremental adaption and revolutionary change. We argue that a sustainable Mineral
Revolution requires a paradigm shift that considers wellbeing as a purpose and focuses on preserving natural capital.
Technical summary. As we consider a transition to a low-carbon future, there is a need to examine the mineral needs for this
transformation at a scale reminiscent of the Green Revolution. The efficiency gains of the agrarian transition came at
ecological and social costs that can also provide important lessons about the Mineral Revolution. We lay out some of the key
ways in which such a mineral revolution can be delineated over temporal scales in a paradigm shift that considers wellbeing
as a purpose and focuses on preserving natural capital. These prospects are conceptually presented as three pathways that
consider the status quo, incremental adaption and revolutionary change as a means of planning more effectively for a lowcarbon
transition. Social media summary. Sourcing metals sustainably will require to consider wellbeing as a purpose and to
preserve natural capital.

Keywords: industrial activities; social value; planning and design; natural resources (biological and non-biological)

Permalink: https://www.hzdr.de/publications/Publ-35583
Publ.-Id: 35583


Spectroscopic and modeling study of Ln³⁺ (Eu³⁺, Y³⁺) and An³⁺ (Cm³⁺, Am³⁺) on feldspars

Lessing, J.; Neumann, J.; Bezzina, J. P.; Brendler, V.; Lützenkirchen, J.; Stumpf, T.; Schmidt, M.

Influence of the competition of Al on the retention of trivalent actinides and their homologues in orthoclase
J. Lessing,1 M. Schmidt,1 T. Stumpf1
1 Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Resource Ecology, Bautzner Landstraße 400,
01328 Dresden, Germany, email: j.lessing@hzdr.de

Most countries worldwide consider disposal in a deep geological formation as the safest concept for nuclear waste disposal. For a realistic safety assessment of such a repository, understanding the mechanisms of the prevalent retention processes is of utmost importance. Sorption of radio-active elements on many minerals is well described in literature, but there is a lack of data re-garding the influence of other natural cations especially Al3+ [1]. These cations will be present in all scenarios as Al3+ is the third most common element (following O and Si) in the earth crust, and will occur locally e.g. due to the dissolution of minerals (especially alumino-silicates). Its concentration can be expected to exceed that of the actinides manifold. In addition to competi-tion for sorption site, Al3+ can then also re-precipitate on a primary mineral’s surface and form a secondary phase, which will impact the interaction of the radionuclides with these minerals.
Alumino-silicates, such as feldspars (orthoclase) and mica, together with quartz are the main components of crystalline rock, which is considered as possible host rock for radioactive waste repositories. The other common option are clay formations, which also consist of alumino-silicate minerals. The retention of trivalent actinides by feldspars was already investigated thor-oughly [2,3]. The minor actinides (Np, Am, and Cm) as well as plutonium dominate the radio-toxicity of spent nuclear fuel over geological time scales. Am and Cm are predominantly triva-lent in aqueous solution and Pu is also expected to occur at least partly in its trivalent state, due to the expected reducing conditions in deep geological formations. The less radiotoxic lantha-nide Eu3+ is often used as homologue for the trivalent actinides with excellent luminescence properties.
Here, we study the effect of dissolved Al3+ on the retention of trivalent actinides (Cm3+) and lan-thanides (Eu3+) on orthoclase. The quantitative effect of different [Al3+] on actinide retention was first evaluated in batch sorption experiments using Eu3+ as an analogue. For further analysis on a molecular level, time resolved laser spectroscopy (TRLFS) was applied, from which infor-mation about the formed surfaces complexes can be gained. We will discuss the results with re-spect to the impact of Al3+ on quantity and speciation of An3+ sorption on feldspars.
The derived speciation and quantitative retention data is foreseen to be implemented into a sur-face complexation model, with parameters available in thermodynamic databases. Ultimately this will provide a better understanding of the fundamental mechanisms of sorption process of the minor actinides Am and Cm on naturally occurring mineral phases under close to natural conditions.

Keywords: sorption; actinides; Cm3+; Eu3+; spectroscopy

  • Open Access Logo Poster
    ATAS/AnXAS joint workshop, 17.-21.10.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-35582
Publ.-Id: 35582


Flotation Process and Computational Modeling

Buchmann, M.; Draw, M.; Rzehak, R.; van den Boogaart, K. G.; Rudolph, M.

Results on modeling and simulation of flotation processes obtained by groups of Helmholtz-Zentrum Dresden-Rossendorf and Helmholtz Institute Freiberg for Resource Technologygroups are shown. These comprise a flotation kinetic model based on the multilayer structure and van der Waals interactions, and a hydrodynamic model using the Eularian multiphase framework. Unfortunately, a full validation of the combined model for data from a real flotation system was not possible yet due to numerical stability issues.

Keywords: Froth Flotation; hydrodynamic model; flotation kinetic model; Eulerian multiphase framework; van der Waals interactions

  • Poster
    FineFuture Final Conference, 14.-15.11.2022, Brussels, Belgium

Permalink: https://www.hzdr.de/publications/Publ-35581
Publ.-Id: 35581


openPMD – F.A.I.R Scientific I/O at the Exascale

Pöschel, F.; Hübl, A.

This talk presents openPMD, an open and F.A.I.R. standard for particle-mesh data, and its impact in heterogeneous scientific workflows.
Particle accelerator codes need to span various time and length scales, leading to data processing pipelines consisting of multiple heterogeneous codes.
Standardization of physical data helps bridging the different models with a commonly-understood markup, creating interoperable and flexible workflows.

The openPMD standard is made accessible to scientific software via the openPMD-api, a library for the description of scientific data.
The backend implementations of the openPMD-api are based on established I/O framworks such as HDF5 and ADIOS2, and also include a scalable streaming backend for HPC workflows, provided by ADIOS2.
The talk gives an insight into the existing ecosystem of openPMD and describes the basic concepts of the data markup.

It shortly illuminates recent trends in large-scale I/O and their impact on scientific compute workflows. While traditional attempts at counteracting such trends, e.g. through compression, remain available in the openPMD-api, we propose loose coupling and online analysis via streaming workflows as a sustainable solution that avoids parallel filesystem bottlenecks.

Keywords: high performance computing; F.A.I.R; particle-mesh data; openPMD; streaming; big data

  • Open Access Logo Invited lecture (Conferences)
    EuroNNAc Special Topics Workshop, 18.-24.09.2022, La Biodola Bay, Isola d'Elba, Italien
  • Open Access Logo Poster
    EuroNNAc Special Topics Workshop, 18.-24.09.2022, La Biodola Bay, Isola d'Elba, Italien
  • Open Access Logo Poster
    8. Annual MT Meeting, 26.-27.09.2022, Hamburg, Deutschland

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35580
Publ.-Id: 35580


Hydrodynamic model validation of gas-solid-liquid flow in a slurry bubble column

Draw, M.; Rzehak, R.

The understanding of gas-solid-liquid three-phase flow is very importnant for the development of Reflux Flotation Cell. CFD simulations of such flows are feasible even on industrial scales within the Eulerian framework of interpenetrating continua. The performance of the framework, however, relies on the suitability of the closure models to account for phenomena on the scale of individual particles or bubbles, which are not resolved in this approach. To this end, the present work attempts to combine closure relations that were previously established for two-phase gas-liquid and solid-liquid flows. Due to the complexity of the RFC system, CFD-grade data to evaluate the overall closure model for three-phase gas-solid-liquid flows are not available yet. Therefore, comparison is made with a dataset from Rampure et al. [Can. J. Chem. Eng. 81 (2003), 692-706] for a slurry bubble column. Agreement of the combined model with the data is not entirely satisfactory yet. Possible reasons concerning both modeling and experiment are discussed and directions for further research identified.

Keywords: gas-solid-liquid three-phase flow; hydrodynamic validation; Reflux Flotation Cell; CFD simulation; closure model

  • Lecture (Conference)
    International RFC Upscaling Symposium, 04.-07.10.2022, Newcastle, Australia

Permalink: https://www.hzdr.de/publications/Publ-35579
Publ.-Id: 35579


openPMD – Open and F.A.I.R I/O for Particle-Mesh Data at the Exascale

Pöschel, F.; E, J.; Godoy, W. F.; Podhorszki, N.; Klasky, S.; Eisenhauer, G.; Davis, P. E.; Wan, L.; Gainaru, A.; Gu, J.; Koller, F.; Widera, R.; Bussmann, M.; Huebl, A.

This talk presents openPMD, an open and F.A.I.R. standard for particle-mesh data, and its impact in Exascale scientific workflows. The openPMD standard is made accessible to scientific software via the openPMD-api, a library for the description of scientific data. It approaches recent challenges posed by hardware heterogeneity by decoupling the data description in domain sciences, such as plasma physics simulations, from concrete implementations in hardware and IO. This concept helps us build a transition path from file-based IO to streaming-based workflows of scientific applications in an HPC environment. The streaming backend is provided by the ADIOS2 framework, developed at Oak Ridge National Laboratory.
This talk discusses two openPMD-based loosely coupled setups to demonstrate flexible applicability and to evaluate performance. In loose coupling, as opposed to tight coupling, two (or more) applications are executed separately, e.g. in individual MPI contexts, yet cooperate by exchanging data. This way, a streaming-based workflow allows for standalone codes instead of tightly-coupled plugins, using a unified streaming-aware API and leveraging high-speed communication infrastructure available in modern compute clusters for massive data exchange.
The presented setups show the potential for a more flexible use of compute resources brought by streaming IO as well as the ability to increase throughput by avoiding filesystem bottlenecks.

Keywords: high performance computing; big data; streaming; RDMA; openPMD; ADIOS

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    SIAM Conference on Parallel Processing for Scientific Computing (PP22), 23.-26.02.2022, Seattle, USA

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Permalink: https://www.hzdr.de/publications/Publ-35578
Publ.-Id: 35578


Euler-Euler Simulation of Absorption and Desorption in Co- and Counter-current Bubble Column Flows

Khan, H.; Lehnigk, R.; Rzehak, R.

Mass transfer in bubbly flows is important in many engineering applications. Simulation of such processes on technical scales is feasible by the Euler-Euler two-fluid model, which relies on suitable closure relations describing interfacial exchange processes. In comparison with the pure fluid dynamics of bubbly flows however, modeling and simulation of bubbly flows including mass transfer is significantly less developed. In particular, previous studies have focused entirely on absorption in upward vertical flows, whereas the present study considers a larger variety of conditions including desorption and counter-current (downward) flow. Suitable experimental data for comparison are available from the classic work of Deckwer et al. [Canadian Journal of Chemical Engineering 56 (1978) 43-55]. In line with previous studies on the co-current absorption cases from that work, a monodisperse approximation is made. In addition, a class method to treat bubble shrinkage and growth is implemented in the OpenFOAM code and tested by showing the crossover between two monodisperse cases.

Keywords: mass-transfer; dispersed gas-liquid multiphase flow; Euler-Euler two-fluid model; closure relations; CFD simulation; model validation

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  • Secondary publication expected from 17.11.2023

Permalink: https://www.hzdr.de/publications/Publ-35574
Publ.-Id: 35574


Complexation of Eu(III) and Cm(III) by EGTA related aminopolycarboxylic acids

Friedrich, S.; Kretzschmar, J.; Drobot, B.; Stumpf, T.; Barkleit, A.

For radiation protection and chelation therapy, aminopolycarboxylic acids like ethylenedia-minetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) are clinical approved decorporation agents. They show promising results in complexation of Ln(III)/An(III). For EDTA and DTPA related compound ethylene glycol-bis(β-aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA), complexes with trivalent europium (Eu) have been characterized by NMR spectroscopy and x-ray diffraction. In these complexes, EGTA acts as an octadentate lig-and.[1,2] In addition to this, the knowledge on the Eu-EGTA-system is extended by time-resolved laser-induced fluorescence spectroscopy (TRLFS), ²H-NMR spectroscopy and isother-mal titration calorimetry (ITC). These speciation studies on Eu(III) show promising results for EGTA as a complexing agent (Fig. 1).
To expand this group of ligands, EGTA related compounds were synthesized (Fig. 2). With these compounds, the complexation behavior with Eu(III) and curium(III) were determined and com-prehensively characterized with TRLFS from both sides: the ligands and metals perspective. The overall goal is a better understanding of the influence of the ligand design on the affinity to complex trivalent Ln and An. Hence, in the future these ligands may contribute to an advanced chelation therapy.
This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant number 02NUK057A and part of the joint project RADEKOR.

  • Open Access Logo Lecture (Conference)
    ATAS-AnXAS 2022 - Joint Workshop, 17.-21.10.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-35573
Publ.-Id: 35573


Incorporation of lanthanides into zirconia: a study of solid phase transformations

Braga Ferreira Dos Santos, L.; Marquardt, J.; Nießen, J.; Tonnesen, T.; Svitlyk, V.; Hennig, C.; Stumpf, T.; Huittinen, N. M.

Zirconia (ZrO2) is the primary corrosion product of the Zircaloy cladding material surrounding nuclear fuel rods [1]. It has also been envisioned as a ceramic host phase for specific high- level waste streams, immobilizing radionuclides and being able to become a protective barrier. In the case of doped ZrO2 matrices, a very high radiation tolerance has been reported, however, discrepancies exist regarding the role of the different structural polymorphs in the high radiation resistance. Ce has been used as a surrogate for Pu due to comparable chemical properties in the oxidation states +III and +IV, similar ionic radius, and its easier handling [2]. In the current study, phase transformations occurring in the ZrO2 material when doped with Ce(IV) and Gd(III), have been explored.

Related publications

  • Poster
    Plutonium Futures, 26.-29.09.2022, Avignon, France
    PURL: http://pufutures2022.org/img/PuFutures2022_Poster_Abstracts.pdf

Permalink: https://www.hzdr.de/publications/Publ-35571
Publ.-Id: 35571


Japan-Germany Research Network on Actinide Chemistry

Tsushima, S.

Ongoing Japan-Germany research network on actinide chemistry was introduced

  • Lecture (Conference) (Online presentation)
    Virtual Humboldt Colloquium "Top Global Research” and the Humboldt Network: New Frontiers of German-Japanese Scientific Cooperation, 17.-18.11.2022, Bonn, Germany

Permalink: https://www.hzdr.de/publications/Publ-35570
Publ.-Id: 35570


MRI-turbulence and large-scale dynamo in astrophysical disks: specific nonlinear anisotropy – transverse cascade – and sustenance scheme

Mamatsashvili, G.

We investigate the sustenance and dynamical balances of MRI-turbulence in accretion disks with a zero net magnetic flux. Zero net flux MRI has attracted a great interest in the last decade, because of its importance in MRI-dynamo in disks. It is unique, in the sense that there is no characteristic length-scale for MRI to grow purely exponentially and hence the instability is instead of a subcritical type, being energetically powered by linear nonmodal, or transient growth of perturbations. This transient growth of MRI is not, however, able to ensure a long-term sustenance of the turbulence and necessitates nonlinear feedback replenishing such transiently growing modes. To examine the existence of such a nonlinear feedback and ultimately understand the whole self-sustenance process of MRI-turbulence, we first performed simulations and then a detailed analysis of the turbulence dynamics in Fourier space. We showed that the disk flow shear gives rise to anisotropy of nonlinear processes in Fourier space. As a result, the key nonlinear process for the sustenance appears to be a topologically new type of angular (i.e., over wavevector orientations) redistribution of modes in Fourier space – the nonlinear transverse cascade – in contrast to the well-known direct/inverse cascades in the absence of shear in classical theories of isotropic turbulence. Moreover, the transverse cascade is a generic nonlinear process in different kinds of shear flows. The sustenance of zero net flux MRI-turbulence relies on the interplay between the two basic processes -- linear transient growth of MRI and the nonlinear transverse cascade. They mostly operate at length scales comparable to the box size (disk scale height), which we call the vital area of the turbulence in Fourier space. Base on this self-sustenance scheme we give a physical interpretation of the dependence (sensitivity) of the zero net flux MRI-turbulence with respect to magnetic Prandtl number in terms of competition between transverse and direct cascades.

Keywords: accretion; accretion discs; turbulence; MHD; instabilities

  • Open Access Logo Lecture (Conference)
    Leeds Dynamo Workshop: Fluid Flow and Magnetic Field Generation in Fluids and Plasmas, 16.-21.10.2022, Leeds, United Kingdom
  • Open Access Logo Lecture (others) (Online presentation)
    Seminar at the Georgian National Astrophysical Observtaory, 21.11.2022, Tbilisi, Georgia
  • Open Access Logo Lecture (others) (Online presentation)
    Nordic Dynamo Seminar (online), 06.12.2022, NORDITA, Stockholm, Sweden

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Permalink: https://www.hzdr.de/publications/Publ-35569
Publ.-Id: 35569


Specific anisotropy of nonlinear processes and self-sustenance of MRI-turbulence in accretion discs

Mamatsashvili, G.

We investigate the sustenance and dynamical balances of MRI-turbulence in accretion disks with a zero net magnetic flux. Zero net flux MRI has attracted a great interest in the last decade, because of its importance in MRI-dynamo in disks. It is unique, in the sense that there is no characteristic length-scale for MRI to grow purely exponentially and hence the instability is instead of a subcritical type, being energetically powered by linear nonmodal, or transient growth of perturbations. This transient growth of MRI is not, however, able to ensure a long-term sustenance of the turbulence and necessitates nonlinear feedback replenishing such transiently growing modes. To examine the existence of such a nonlinear feedback and ultimately understand the whole self-sustenance process of MRI-turbulence, we first performed simulations and then a detailed analysis of the turbulence dynamics in Fourier space. We showed that the disk flow shear gives rise to anisotropy of nonlinear processes in Fourier space. As a result, the key nonlinear process for the sustenance appears to be a topologically new type of angular (i.e., over wavevector orientations) redistribution of modes in Fourier space – the nonlinear transverse cascade – in contrast to the well-known direct/inverse cascades in the absence of shear in classical theories of isotropic turbulence. Moreover, the transverse cascade is a generic nonlinear process in different kinds of shear flows. The sustenance of zero net flux MRI-turbulence relies on the interplay between the two basic processes -- linear transient growth of MRI and the nonlinear transverse cascade. They mostly operate at length scales comparable to the box size (disk scale height), which we call the vital area of the turbulence in Fourier space. Base on this self-sustenance scheme we give a physical interpretation of the dependence (sensitivity) of the zero net flux MRI-turbulence with respect to magnetic Prandtl number in terms of competition between transverse and direct cascades.

Keywords: accretion; accretion discs; instabilities; MHD; turbulence

  • Lecture (others) (Online presentation)
    Seminar at Max Planck Institute for Gravitational Physics, 28.06.2022, Potsdam, Germany

Permalink: https://www.hzdr.de/publications/Publ-35568
Publ.-Id: 35568


From helical to standard magnetorotational instability: Predictions for upcoming sodium experiments

Mishra, A.; Mamatsashvili, G.; Stefani, F.

We conduct a linear analysis of axisymmetric magnetorotational instability (MRI) in a magnetized cylindrical Taylor-Couette (TC) flow for its standard version (SMRI) with a purely axial background magnetic field and two additional types—helically modified SMRI (H-SMRI) and helical MRI (HMRI)—in the presence of combined axial and azimuthal magnetic fields. This study is intended as preparatory for upcoming new cutting-edge large-scale liquid sodium MRI experiments planned within the DRESDYN project at Helmholtz-Zentrum Dresden-Rossendorf, so we explore these instability types for typical values of the main parameters: the magnetic Reynolds number, the Lundquist number, and the ratio of the angular velocities of the cylinders, which are attainable in these experiments. In contrast to previous attempts at detecting MRI in the laboratory, our results demonstrate that SMRI and its helically modified version can in principle be detected in the DRESDYN-TC device for the range of the above parameters, including the astrophysically most important Keplerian rotation, despite the extremely small magnetic Prandtl number of liquid sodium. Since in the experiments we plan to approach (H-)SMRI from the previously studied HMRI regime, we characterize the continuous and monotonous transition between these two regimes. We show that H-SMRI, like HMRI, represents an overstability (traveling wave) with nonzero frequency linearly increasing with azimuthal field. Because of its relevance to finite-size flow systems in experiments, we also analyze the absolute form of H-SMRI and compare its growth rate and onset criterion with the convective one.

Keywords: instabilities; MHD; Taylor-Couette flow

  • Lecture (Conference) (Online presentation)
    The 12th pamir International Conference on Fundamental and Applied MHD, 04.-08.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35567
Publ.-Id: 35567


MRI turbulence in accretion discs at large magnetic Prandtl numbers

Held, L.; Mamatsashvili, G.

The effect of large magnetic Prandtl number Pm (the ratio of viscosity to resistivity) on the turbulent transport and energetics of the magnetorotational instability (MRI) is poorly understood, despite the realization of this regime in astrophysical environments as disparate as discs from binary neutron star (BNS) mergers, the inner regions of low-mass X-ray binaries and active galactic nuclei, and the interiors of protoneutron stars. We investigate the MRI dynamo and associated turbulence in the regime Pm > 1 by carrying out fully compressible, 3D MHD-shearing box simulations using the finite-volume code PLUTO, focusing mostly on the case of Keplerian shear relevant to accretion discs. We find that when the magnetic Reynolds number is kept fixed, the turbulent transport (as parameterized by α, the ratio of stress to thermal pressure) scales with the magnetic Prandtl number as $α ~ Pm^δ$, with $δ ~ 0.5-0.7$ up to $Pm ~ 128$. However, this scaling weakens as the magnetic Reynolds number is increased. Importantly, compared to previous studies, we find a new effect at very large Pm - the turbulent energy and stress begin to plateau, no longer depending on Pm. To understand these results we have carried out a detailed analysis of the turbulent dynamics in Fourier space, focusing on the effect of increasing Pm on the transverse cascade - a key non-linear process induced by the disc shear flow that is responsible for the sustenance of MRI turbulence. Finally, we find that α-Pm scaling is sensitive to the box vertical-to-radial aspect ratio, as well as to the background shear.

Keywords: accretion; accretion discs; instabilities; MHD; turbulence

  • Open Access Logo Monthly Notices of the Royal Astronomical Society 517(2022)2, 2309-2330
    Online First (2022) DOI: 10.1093/mnras/stac2656
    arXiv: 2206.00497

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Permalink: https://www.hzdr.de/publications/Publ-35565
Publ.-Id: 35565


Status of the SLAC/MSU SRF Gun Development Project

Lewellen, J. W.; Adolphsen, C.; Coy, R.; Ge, L.; Ji, F.; Murphy, M.; Xiao, L.; Kelly, M.; Peterson, T.; Choi, Y.; Compton, C.; Du, X.; Greene, D.; Hartung, W.; Kim, S.-H.; Konomi, T.; Miller, S. J.; Morris, D.; Patil, M. S.; Popielarski, J. T.; Popielarski, L.; Saito, K.; Xu, T.; Arnold, A.; Gatzmaga, S.; Murcek, P.; Xiang, R.

The LCLS-II-HE Project at SLAC seeks to increase the photon energy reach of the LCLS-II FEL to at least 20 keV. In addition to upgrading the undulator system, and increasing the electron beam energy to 8 GeV, the project will also construct a low-emittance injector (LEI) in a new tunnel. To achieve the LEI emittance goals, a low-MTE photocathode will be required, as will on-cathode electric fields up to 50% higher than those achievable in the current LCLSII photoinjector.
The beam source for the LEI will be based around a superconducting quarter-wave cavity resonant at 185.7 MHz. A prototype gun is currently being designed and fabricated at the Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU). This paper presents performance goals for the new gun design, an overview of the prototype development effort, status, and future plans including fabrication of a “production” gun for the LEI.

  • Open Access Logo Poster
    North American Particle Accelerator Conference 2022 (NAPAC'22), 07.-12.08.2022, Albuquerque, New Mexico, USA
  • Open Access Logo Contribution to proceedings
    North American Particle Accelerator Conference 2022 (NAPAC'22), 07.-12.08.2022, Albuquerque, New Mexico, USA
    Proceedings of North American Particle Accelerator Conference 2022: JACoW, 978-3-95450-232-5
    DOI: 10.18429/JACoW-NAPAC2022-WEPA03
    ISSN: 2226-0366

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Permalink: https://www.hzdr.de/publications/Publ-35564
Publ.-Id: 35564


Design of the Cathode Stalk for the LCLS-II-HE Low Emittance Injector

Konomi, T.; Hartung, W.; Kim, S.-H.; Miller, S.; Morris, D.; Popielarski, J.; Saito, K.; Taylor, A.; Xu, T.; Adolphsen, C.; Lewellen, J.; Gatzmaga, S.; Murcek, P.; Xiang, R.; Kelly, M.; Petersen, T.

Superconducting radio-frequency (SRF) electron guns are attractive for delivery of beams at a high bunch repetition rate with a high accelerating field. An SRF gun is the most suitable injector for the high-energy upgrade of the Linac Coherent Light Source (LCLS-II-HE), which will produce high-energy Xrays at high repetition rate. An SRF gun is being developed for LCLS-II-HE as a collaborative effort by FRIB, HZDR, ANL, and SLAC. The cavity operating frequency is 185.7 MHz, and the target accelerating field at the photocathode is 30 MV/m. The photocathode is replaceable. The cathode is held by a fixture ('cathode stalk') that is designed for thermal isolation and particle-free cathode exchange. The stalk must allow for precise alignment of the cathode position, cryogenic or room-temperature cathode operating temperature, and DC bias to inhibit multipacting. We are planning a test of the stalk to confirm that the design meets the requirements for RF power dissipation and biasing. In this presentation, we will describe the cathode stalk design and RF/DC stalk test plan.

  • Open Access Logo Poster
    North American Particle Accelerator Conference 2022 (NAPAC'22), 07.-12.08.2022, Albuquerque, New Mexico, USA
    DOI: 10.18429/JACoW-NAPAC2022-MOPA87
    ISSN: 2226-0366
  • Open Access Logo Contribution to proceedings
    North American Particle Accelerator Conference 2022 (NAPAC'22), 07.-12.08.2022, Albuquerque, New Mexico, USA
    Proceedings of North American Particle Accelerator Conference 2022: JACoW, 978-3-95450-232-5
    DOI: 10.18429/JACoW-NAPAC2022-MOPA87
    ISSN: 2226-0366

Permalink: https://www.hzdr.de/publications/Publ-35563
Publ.-Id: 35563


Robust spin injection via thermal magnon pumping in antiferromagnet/ferromagnet hybrid systems

Rodriguez, R.; Regmi, S.; Zhang, H.; Yuan, W.; Makushko, P.; Montoya, E. A.; Veremchuk, I.; Hübner, R.; Makarov, D.; Shi, J.; Cheng, R.; Barsukov, I.

Robust spin injection and detection in antiferromagnetic thin films is a prerequisite for the exploration
of antiferromagnetic spin dynamics and the development of nanoscale antiferromagnet-based spintronic applications.
Previous studies have shown spin injection and detection in antiferromagnet/nonmagnetic metal
bilayers; however, spin injection in these systems has been found effective at cryogenic temperatures only.
Here, we experimentally demonstrate sizable interfacial spin transport in a hybrid antiferromagnet/ferromagnet
system, consisting of Cr2O3 and permalloy, which remains robust up to the room temperature. We examine our
experimental data within a spin diffusion model and find evidence for the important role of interfacial magnon
pumping in the signal generation. The results bridge spin-orbitronic phenomena of ferromagnetic metals with
antiferromagnetic spintronics and demonstrate an advancement toward antiferromagnetic spin-torque devices.

Keywords: antiferromagnetic spintronics; Cr2O3 thin films; spin injection

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35561
Publ.-Id: 35561


Data publication: Longitudinal and multimodal radiomics models for head-and-neck cancer outcome prediction

Starke, S.; Zwanenburg, A.; Leger, K.; Zöphel, K.; Kotzerke, J.; Krause, M.; Baumann, M.; Troost, E. G. C.; Löck, S.

We include the input data, analysis scripts, analysis results and scripts to create the visualizations and plots used in the manuscript and supplement to our article "Longitudinal and multimodal radiomics models for head-and-neck cancer outcome prediction".

Keywords: radiomics; head-and-neck cancer; loco-regional control; survival analysis; computed tomography; positron emission tomography; cox proportional hazards; longitudinal imaging

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Permalink: https://www.hzdr.de/publications/Publ-35560
Publ.-Id: 35560


Data for: The influence of sedimentary heterogeneity on the diffusion of radionuclides in the sandy facies of Opalinus Clay at the field scale

Chen, C.; Yuan, T.; Lu, R.; Fischer, C.; Kolditz, O.; Shao, H.

Radionuclide migration in clay-rich formations is typically dominated by diffusion considering the low permeability of these formations. An accurate estimation of radionuclide migration in host rocks using numerical tools plays a key role in the safety assessment of disposal concepts for nuclear waste. In the sandy facies of the Opalinus Clay (SF-OPA), the spatial variability of the pore space network and compositional heterogeneity at the pore scale (nm to µm) cause heterogeneous diffusion at the core scale (cm to dm). Such heterogeneous diffusion patterns affect the migration of radionuclides in various sedimentary layers even above the core scale (m). In this work, we study the heterogeneous diffusion of cations based on a two-dimensional (2D) structural model at the m-scale. As key parameters for the diffusive transport calculation, the effective diffusion coefficients in different sedimentary layers are quantified based on our previous developed up-scaling workflow from pore- to core-scale simulation combined with the multi-scale digital rock models. The heterogeneous effective diffusivities are then implemented into the large-scale structural model for diffusive transport simulation using the FEM-based OpenGeoSys-6 simulator. The sensitivity analysis focuses on the effects of the SF-OPA bedding angle and the effect of different layer-succession layout with different canister emplacement on the spatio-temporal evolution of radionuclide diffusion front line. Results show that the moving distance of the diffusion front is farther away from the canister center, along the direction with the neighboring layer having lower diffusion coefficient within the total simulation time of 2000 years. When the bedding angle increases, the diffusion front moves farther in in vertical upward direction direction, which has less retardation effect for the radionuclide from the ground surface point. For different layer-succession layout with different canister emplacement, the smallest migration distance of the diffusion front line is 1.65 m. Within 2000 years, for the conceptual model 2B that the canister is emplaced in the layer with the highest diffusivity coefficient, the diffusion front can migrate 0.19 m farther along vertical downward direction due to the influence of the neighboring layer. The numerical results provide insight into the effects of rocks heterogeneity on diffusion of radionuclides, contributing to enhanced long-term predictability of radionuclide migration in SF-OPA as potential host rock for a deep geological repository.

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Permalink: https://www.hzdr.de/publications/Publ-35558
Publ.-Id: 35558


Investigation of Fluid-dynamics and Mass-transfer in a bubbly mixing layer by Euler-Euler simulation

Kappelt, C.; Rzehak, R.

Mass transfer in bubbly flows is a field of obvious technological importance. On industrially relevant scales it may be studied by simulations based on the Euler-Euler two-fluid model, which however requires closure models for the interfacial exchange processes. Despite recently increased efforts, modelling of the exchange of mass between the phases is still much less developed than the corresponding exchange of momentum. The present study compares several proposed models for the mass transfer coefficient using a previously established set of closure relations for the purely fluid dynamical part of the problem. A set of experimental data for the absorption of O2 into water in a bubbly mixing layer from the literature is used to assess their relative merits. A model for the pertinent material properties of this system has been assembled from available measurements. A rather sensitive dependence of the amount of absorbed O2 is found on the pressure, which varies with the hydrostatic head above the test section.

Keywords: Mass-transfer; Dispersed gas–liquid multiphase flow; Euler-Euler two-fluid model; Closure relations; CFD Simulation; Model validation

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  • Secondary publication expected from 29.09.2023

Permalink: https://www.hzdr.de/publications/Publ-35557
Publ.-Id: 35557


The influence of sedimentary heterogeneity on the diffusion of radionuclides in the sandy facies of Opalinus Clay at the field scale

Chen, C.; Yuan, T.; Lu, R.; Fischer, C.; Kolditz, O.; Shao, H.

Radionuclide migration in clay-rich formations is typically dominated by diffusion considering the low permeability of these formations. An accurate estimation of radionuclide migration in host rocks using numerical tools plays a key role in the safety assessment of disposal concepts for nuclear waste. In the sandy facies of the Opalinus Clay (SF-OPA), the spatial variability of the pore space network and compositional heterogeneity at the pore scale (nm to µm) cause heterogeneous diffusion at the core scale (cm to dm). Such heterogeneous diffusion patterns affect the migration of radionuclides in various sedimentary layers even above the core scale (m). In this work, we study the heterogeneous diffusion of cations based on a two-dimensional (2D) structural model at the m-scale. As key parameters for the diffusive transport calculation, the effective diffusion coefficients in different sedimentary layers are quantified based on our previous developed up-scaling workflow from pore- to core-scale simulation combined with the multi-scale digital rock models. The heterogeneous effective diffusivities are then implemented into the large-scale structural model for diffusive transport simulation using the FEM-based OpenGeoSys-6 simulator. The sensitivity analysis focuses on the effects of the SF-OPA bedding angle and the effect of different layer-succession layout with different canister emplacement on the spatio-temporal evolution of radionuclide diffusion front line. Results show that the moving distance of the diffusion front is farther away from the canister center, along the direction with the neighboring layer having lower diffusion coefficient within the total simulation time of 2000 years. When the bedding angle increases, the diffusion front moves farther in in vertical upward direction direction, which has less retardation effect for the radionuclide from the ground surface point. For different layer-succession layout with different canister emplacement, the smallest migration distance of the diffusion front line is 1.65 m. Within 2000 years, for the conceptual model 2B that the canister is emplaced in the layer with the highest diffusivity coefficient, the diffusion front can migrate 0.19 m farther along vertical downward direction due to the influence of the neighboring layer. The numerical results provide insight into the effects of rocks heterogeneity on diffusion of radionuclides, contributing to enhanced long-term predictability of radionuclide migration in SF-OPA as potential host rock for a deep geological repository.

Permalink: https://www.hzdr.de/publications/Publ-35556
Publ.-Id: 35556


Measurement of anisotropic drainage in liquid foam using neutron radiography.

Skrypnik, A.; Trtik, P.; Cole, K.; Lappan, T.; Brito-Parada, P. R.; Neethling, S. J.; Eckert, K.; Heitkam, S.

Transport of liquid through the foam is governed by the mutual effects of capillary, gravitational,
and inertia forces [Koehler, S. A. et. al. (2000)]. This process defines the distribution of liquid in
foam and is essential for industrial applications, e.g. production of polymeric and metal foams,
flotation etc. S. Neethling [Neethling, S. J. (2006)] have shown that sheared foam could not
anymore be considered as an isotropic media, and the direction of a drainage flow distinct from
the sense of a gravity vector. Thus, a non-uniform distribution of liquid in the foam is present.
This effect, for instance, has a major impact on a formation of convective rolls in foam [Heitkam,
S., & Eckert, K. (2021)].

  • Lecture (Conference)
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35555
Publ.-Id: 35555


Measurement of the liquid fraction of foam by conductive wire-mesh sensor.

Ziauddin, M.; Schleicher, E.; Trtik, P.; Knüpfer, L.; Skrypnik, A.; Lappan, T.; Eckert, K.; Heitkam, S.

The liquid fraction (Φ) of foam is an important quantity in engineering process control and essentially to interpret foam rheology. Currently available methods are either complex laboratory-based techniques or cannot provide spatial resolution. Therefore, in this work in-situ measurement of the liquid fraction from foam's electrical conductivity [Feitosa, 2005] was studied by employing conductive wire-mesh sensor (WMS) [Prasser, 1998]. Two arrays of wires are placed inside the foam (figure 1) and at each crossing point the local liquid fraction is determined. This approach offers 2D measurement of liquid fraction distribution (figure 1) with very high frame rate. The measurements were validated by simultaneous measurement of liquid fraction by neutron radiography (NR) [Heitkam, 2018].
An systematic dependency between WMS readings and the true liquid fraction from NR is found (figure 1). However, WMS overestimates the liquid fraction systematically, which could be an effect of the liquid bridge formation between the wires.

  • Lecture (Conference)
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35554
Publ.-Id: 35554


Removal of impurities from protein foam in foam fractionation process by wash water addition.

Keshavarzi, B.; Krause, T.; Schwarzenberger, K.; Eckert, K.; Ansorge-Schumacher, M. B.; Heitkam, S.

This work introduces a simple and efficient method to remove the impurities from a protein foam
through washing the foam in a foam fractionation process (figure 1). Since the protein molecules
adsorb irreversibly on the air interface, they do not desorb upon wash water addition and are
transferred to the foam outlet. However, the entrained substances are directed downward by
wash water to the drain outlet together with the liquid. Here, we performed experiments on
bovine serum albumin (BSA), as a model protein and NaCl salt, as a model of soluble impurities.
The experiments were conducted in a glass foam fractionation cell, where the liquid level was
kept constant. The wash water was added on the foam top with different flow rates and BSA and
NaCl concentrations were measured at the outlets for further analysis. The influence of initial
bubble size and the wash water rate on the purification efficiency were investigated. The results
revealed that the wash water displaces the entrained liquid in the foam and reduces the salt
content at the foam outlet. The process shows higher salt removal for higher wash water rates as
well as for foams with larger bubble sizes, where up to 93% of the salt was removed from the
main solution in a steady state process. The washing efficiency is also influenced by air flow
rate. Salt removal is enhanced in principle at lower air flow rates. However, the foam stability
becomes an important issue at smaller air flow rates, since the increased foam collapse
significantly reduces the foam flow to the outlet.

  • Lecture (Conference)
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35553
Publ.-Id: 35553


Measurement and simulation of foam drainage in two dimensions using neutron Radiography

Friedrich, W.; Ziauddin, M.; Knüpfer, L.; Lappan, T.; Trtik, P.; Eckert, K.; Heitkam, S.

After coarsening and coalescence, foam drainage is one of the processes that dynamically influence foams. It is therefore of general interest to understand it in its principle behaviour. Liquid drainage is typically described by the unsteady, three-dimensional drainage equation [Verbist, 1996]. However, apart from optical observation in a Hele-Shaw cell [Hutzler, 2005], unsteady and multi-dimensional measurement of liquid fraction distribution is scarcely approached. Here, two-dimensional foam drainage experiments and simulations were carried out to validate the horizontal terms of foam drainage equation and to show its limitations. The two-dimensional liquid fraction distribution in steady, dynamic and periodic drainage experiments was measured with neutron radiography [Heitkam, 2018]. In particular, the damping character of the foam drainage was quantified as a function of different frequencies and amplitudes. This yields guidelines for forced-drainage experiments with peristaltic pumps.

  • Lecture (Conference)
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35552
Publ.-Id: 35552


Combining optical and X-ray measurements of an overflowing foam.

Lappan, T.; Herting, D.; Stenzel, J.; Ziauddin, M.; Shevchenko, N.; Eckert, S.; Eckert, K.; Heitkam, S.

Froth flow is of central importance for mineral processing by froth flotation. In industrial-scale
flotation plants, the recovery of solid mineral particles [Neethling, 2002] and liquid from the overflowing froth [Stevenson, 2003] is monitored by optical observation and, therefore, limited to the
froth’s free surface. This lab-scale experimental work investigates the flow behaviour of an aqueous foam at a horizontal overflow in combined optical and X-ray radiographic measurements.
Simultaneously, the foam’s liquid fraction was determined by measuring the electrical conductivity between electrode pairs. The optical measurements, performed both through a transparent wall
and at the free surface of the overflowing foam, captured light reflexions on the foam bubbles,
which were analysed by adapting particle image velocimetry algorithms. While the opacity of the
foam limits optical measurements to the surface-near bubbles, our approach of X-ray particle
tracking velocimetry (X-PTV) [Lappan, 2020] sheds light on the three-dimensional foam flow.
The customised tracer particles used in this work consisted of a 3D-printed tetrahedral polymer
structure with a total of four small metal beads at its corners. Owing to their shape and the lightweight material composite, the tracers adhered to the bubble-scale foam structure and were carried
by the foam. X-ray radiography visualises the motion paths of each tracer’s metal beads, representing the local streamlines of the foam flow. Further, the X-ray radiographs map the foam’s
liquid fraction distribution, thus extending the local measurement of the liquid fraction by means
of the electrode pairs. X-PTV reveals comparatively high flow velocities of the three-dimensional
foam flow, in particular near the overflow, whereas the optical measurements are subjected to wall
or surface effects, yielding lower flow velocities. However, X-PTV with customised foam flow
tracers comes to its limit in unstable foams at high liquid fraction and high flow velocity.

  • Lecture (Conference)
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35551
Publ.-Id: 35551


A machine learning approach to segment images of foam at a transparent wall.

Knüpfer, L.; Heitkam, S.

This article describes the use of a machine learning based technique
to measure the bubble sizes of foam with small liquid fraction in contact with a
transparent wall. For two different experimental cases images are obtained of foam
in a cylindrical column and labeled with a classical image processing algorithm. An
available neural network based model, initially designed for cell image applications,
is trained and validated to segment the images. When comparing the bubble size
distribution in images found using the trained model with manually segmented images
a good agreement over a large range of diameters can be found. The error of the mean
diameter in both cases lies below 10%, mostly attributed to the failed recognition of
tiny round bubbles in dry foam. The trained model is provided for further usage.

  • Poster
    EUFOAM, 03.-06.07.2022, Krakow, Poland

Permalink: https://www.hzdr.de/publications/Publ-35550
Publ.-Id: 35550


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