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41396 Publications

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

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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


Die Suche nach Terahertz-Materialien

Deinert, J.-C.; Kovalev, S.; Gensch, M.

Der Terahertz-Frequenzbereich umfasst ein technisch wenig erschlossenes Grenzgebiet im elektromagnetischen Spektrum. Es ist aber besonders interessant, weil es viele Eigenfrequenzen verschiedener, komplexer Quantenphänomene enthält. Teil 2 widmet sich den Dirac-Materialien wie Graphen und topologischen Isolatoren, die extrem stark mit Terahertz-Feldern wechselwirken.

Keywords: Terahertz; Dirac Material; Graphene; Topological Insulator; Nonlinear Optics; Carrier Dynamics; High Harmonic Generation; Metamaterials

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Permalink: https://www.hzdr.de/publications/Publ-35593
Publ.-Id: 35593


Biggs Theorem for Directed Cycles and Topological Invariants of Digraphs

Hecht, M.; Sbalzarini, I. F.

We generalize Biggs Theorem to the case of directed cycles of multi-digraphs allowing to compute the dimension of the directed cycle space independently of the graph representation with linear runtime complexity. By considering two-dimensional CW complex of elementary cycles and deriving formulas for the Betti numbers of the associated cellular homology groups, we extend the list of representation independent topological inavariants measuring the graph structure. We prove the computation of the 2nd Betti number to be sharp #P hard in general and present specific representation invariant sub-fillings yielding efficiently computable homology groups. Finally, we suggest how to use the provided structural measures to shed new light on graph theoretical problems as graph embeddings, discrete Morse theory and graph clustering.

Keywords: Biggs Theorem; Elementary and Simple Cycles; CW Complexes of Graphs; Cellular and Singular Homology

Permalink: https://www.hzdr.de/publications/Publ-35592
Publ.-Id: 35592


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.

  • Open Access Logo Lecture (Conference)
    The 12th pamir International Conference on Fundamental and Applied MHD, 04.07.2022, Krakow, Poland
  • Open Access Logo Lecture (Conference)
    9th International Symposium on Bifurcations and Instabilities in Fluid Dynamics, 16.-19.08.2022, Groningen, Netherlands
  • Open Access Logo Contribution to WWW
    arXiv:2211.10811 [physics.flu-dyn]: https://arxiv.org/abs/2211.10811
  • Open Access Logo Physical Review Fluids 8(2023)8, 083902
    Online First (2023) DOI: 10.1103/PhysRevFluids.8.083902
    Cited 1 times in Scopus

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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

Related publications

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


Snow chemistry for exploration in Finland – a workflow for reliable results

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

Snow as an environmental memory is mostly known only in relation to substances from the air, such as dust or pollen in the ice sheets or glaciers. But earlier studies, among them from Russia and Canada, suggest that snow could also act as an environmental memory for gases from the ground (Taivalkoski et al. 2019). Hence, could snow even possibly be used as catchment media for signals from bedrock? This would require that elements as well as hydrocarbons are released from the bedrock, and migrated through the overlying transported cover, often glacial sediments, as ions or gases and are eventually captured by the snow. Of course, the expected element concentrations in snow are very low, especially for snow that exists for only one winter season. But snow as a sampling material would have the great advantage that the sampling and analytical methods have almost no impact on the environment.
In order to investigate whether snow could be used as an environmental memory in relation to the geological subsurface, and thus also for the detection of mineralization, snow was sampled within the framework of the EU project NEXT (New Exploration Technologies, Grant Agreement...) with regard to two questions: 1) Are the measured concentrations evaluable with regard to environmental properties, i.e., can they be measured reliably enough at all? and 2) does the element composition in the snow change significantly with changes in the bedrock lithologies, independent of soil properties?

Keywords: snow; exploration; compositional data analysis; geochemistry; environmental geochemistry; low impact sampling media; analytics

  • Open Access Logo Contribution to proceedings
    MinProXT, 01.-03.11.2022, Freiberg, Germany
    MinProXT 2022 Mineral Prospectivity and Exploration Targeting, Espoo: Geological Survey of Finland, Open File Research R

Permalink: https://www.hzdr.de/publications/Publ-35586
Publ.-Id: 35586


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

  • 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

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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


Impact of the Coulomb field on charged-pion spectra in few-GeV heavy-ion collisions

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Ciepał, I.; Deveaux, C.; Dreyer, J.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Nabroth, M.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Parschau, M.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Rathod, N.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schild, N.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Singh, U.; Smyrski, J.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Sturm, C.; Sumara, K.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

In nuclear collisions the incident protons generate a Coulomb field which acts on produced charged particles. The impact of these interactions on charged-pion transverse-mass and rapidity spectra, as well as on pion–pion momentum correlations is investigated in Au + Au collisions at sNN = 2.4 GeV. We show that the low-mt region (mt< 0.2 GeV/c2) can be well described with a Coulomb-modified Boltzmann distribution that also takes changes of the Coulomb field during the expansion of the fireball into account. The observed centrality dependence of the fitted mean Coulomb potential energy deviates strongly from a Apart2/3 scaling, indicating that, next to the fireball, the non-interacting charged spectators have to be taken into account. For the most central collisions, the Coulomb modifications of the HBT source radii are found to be consistent with the potential extracted from the single-pion transverse-mass distributions. This finding suggests that the region of homogeneity obtained from two-pion correlations coincides with the region in which the pions freeze-out. Using the inferred mean-square radius of the charge distribution at freeze-out, we have deduced a baryon density, in fair agreement with values obtained from statistical hadronization model fits to the particle yields. © 2022, The Author(s).

Permalink: https://www.hzdr.de/publications/Publ-35577
Publ.-Id: 35577


Formation of vertical SnSe/SnSe2 p-n heterojunction by NH3 plasma-induced phase transformation

Li, Y.; Duan, J.; Berencen, Y.; Hübner, R.; Tsai, H.-S.; Kuo, C.-N.; Chin-Shan, L.; Helm, M.; Zhou, S.; Prucnal, S.

Layered van der Waals crystals host unique properties making them attractive for applications in nanoelectronics, optoelectronics, and sensing. The integration of two-dimensional materials with complementary metal-oxide-semiconductor (CMOS) technology requires controllable n- and p-type doping. In this work, we demonstrate the fabrication of vertical p-n heterojunctions made of p-type tin monoselenide (SnSe) and n-type tin diselenide (SnSe2). The p-n heterojunction is created in a single flake by the NH3-plasma-assisted phase transformation from SnSe2 to SnSe. We show that the transformation rate and crystal quality strongly depend on the plasma parameters like plasma power, temperature, partial pressure, NH3 flow, and duration of plasma treatment. With optimal plasma parameters, the full transformation of SnSe2 flakes to SnSe is achieved within a few seconds. The crystal quality and the topography of the fabricated SnSe-SnSe2 heterostructures are investigated using micro-Raman spectroscopy and cross-sectional transmission electron microscopy. The formation of a p-n junction is verified by current-voltage measurements.

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Permalink: https://www.hzdr.de/publications/Publ-35576
Publ.-Id: 35576


Effect of driver charge on wakefield characteristics in a plasma accelerator probed by femtosecond shadowgraphy

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

We report on experimental investigations of plasma wave structures in a plasma wakefield acceleration (PWFA) stage which is driven by electron beams from a preceding laser plasma accelerator. Femtosecond optical probing is utilized to allow for direct visualization of the plasma dynamics inside the target. We compare two regimes in which the driver propagates either through an initially neutral gas, or a preformed plasma. In the first case, plasma waves are observed that quickly damp after a few oscillations and are located within a narrow plasma channel ionized by the driver, having about the same transverse size as the plasma wakefield cavities. In contrast, for the latter robust cavities are recorded sustained over many periods. Furthermore, here an elongation of the first cavity is measured, which becomes stronger with increasing driver beam charge. Since the cavity length is linked to the maximum accelerating field strength, this elongation implies an increased field strength. This observation is supported by 3D particle-in-cell simulations performed with PIConGPU. This work can be extended for the investigation of driver depletion by probing at different propagation distances inside the plasma, which is essential for the development of high energy efficiency PWFAs.

Keywords: wakefield acceleration; ultrafast optical probing; hybrid wakefield acceleration; plasma shadowgram; beam driven wakefield acceleration

Permalink: https://www.hzdr.de/publications/Publ-35575
Publ.-Id: 35575


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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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


Evaluation of nanoparticle resistance development of microorganisms

Schuba, S.; Schütt, J.; Faßbender, J.; Makarov, D.

Over the last century, antibiotics against bacterial infections have led to increased life expectancy and quality of people worldwide. Yet the WHO has brought attention to the increasing resistance development of bacterial pathogens against antibiotics - many bacteria are already multi-resistant. In the search of alternatives to classical antibiotics, nanotechnology and nanoparticles (NP) are moving into the focus of scientific research. Particular attention is paid to the Nano-silver (Ag-NP), which has experienced an immense upswing in recent years and is used in many medical products such as wound dressings or consumer products. However, are Ag-NPs safe for health and environment? To tackle this challenge, conventional methods have been used to explore nanoparticle resistance. Conversely, these methods have proven to be limited in terms of labor, cost, and statistical power. In our work, we intend to overcome these barriers by developing a droplet-based microfluidic analytical platform as a tool to elucidate the impact and biological influence of nanoparticles on living microorganisms with high statistical evaluation and detection efficiency. This method allows the separation of bacteria into single droplets, the generation of individual bioreactors, and the screening of the bacterial metabolism in the presence of Ag-NP.

Keywords: Nanoparticle; Silver; droplet-based microfluidics

  • Open Access Logo Contribution to proceedings
    DPG Spring meeting SKM, 26.-31.03.2023, Dresden, Deutschland
  • Open Access Logo Poster
    SKM DPG Spring Meeting, 26.-31.03.2023, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35572
Publ.-Id: 35572


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

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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

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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


Modification of three-magnon splitting in a flexed magnetic vortex

Körber, L.; Heins, C.; Soldatov, I.; Schäfer, R.; Kakay, A.; Schultheiß, H.; Schultheiß, K.

We present an experimental and numerical study of three-magnon splitting in a micrometer-sized magnetic disk with the vortex state strongly deformed by static in-plane magnetic fields. Excited with a large enough power at frequency fRF, the primary radial magnon modes of a cylindrical magnetic vortex can decay into secondary azimuthal modes via spontaneous three-magnon splitting. This nonlinear process exhibits selection rules leading to well-defined and distinct frequencies fRF/2±Δf of the secondary modes. Here, we demonstrate that three-magnon splitting in vortices can be significantly modified by deforming the magnetic vortex with in-plane magnetic fields, leading to a much richer three-magnon response. We find that, with increasing field, an additional class of secondary modes is excited which are localized to the highly-flexed regions adjacent to the displaced vortex core. While these modes satisfy the same selection rules of three-magnon splitting, they exhibit a much lower three-magnon threshold power compared to regular secondary modes of a centered vortex. The applied static magnetic fields are small (≃ 10 mT), providing an effective parameter to control the nonlinear spectral response of confined vortices. Our work expands the understanding of nonlinear magnon dynamics in vortices and advertises these for potential neuromorphic applications based on magnons.

Keywords: spin wave; magnon; vortex; BLS; micromagnetic modeling; Kerr microscopy; three-magnon splitting; reservoir computing

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Permalink: https://www.hzdr.de/publications/Publ-35559
Publ.-Id: 35559


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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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.

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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


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


Neutronenradiographie des anisotropen Drainageflusses in Schaum

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

Liquid drainage through foam is driven by gravity, capillary, and, to a lesser extent, viscous forces.
In the of stress on the foam, the liquid distributes uniformly, however, imposed stress changes the
alignment of the foam’s structural elements. Previous numerical simulations [1] predicted that a vertical
drainage flow will be deflected horizontally if the foam is sheared. We investigated such phenomena by
measuring the distribution of liquid fraction within a foam formed in a flat rectangular cell. The foam was
subjected to shear stress under a forced liquid supply at the top of the cell. Two dimensional neutron
radiography images of stress-free and sheared foam were analyzed to extract measurements of liquid
content. Deflections in the distribution of the drainage liquid were detected, and found to be positively
correlated with increasing foam shear. To the best of our knowledge, this is the first experimental
observation of anisotropic drainage in a liquid foam.

  • Lecture (Conference)
    Fachtagung "Experimentelle Strömungsmechanik", 06.-08.09.2022, Ilmenau, Germany

Permalink: https://www.hzdr.de/publications/Publ-35549
Publ.-Id: 35549


Neutron radiography of foam and froth.

Heitkam, S.; Skrypnik, A.; Lappan, T.; Trtik, P.; Eckert, K.

Neutron radiography is a useful tool for researching opaque multi phase flow such as foam and froth.

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

Permalink: https://www.hzdr.de/publications/Publ-35548
Publ.-Id: 35548


Characterizing foam and froth with ultrasound reflectometry.

Knüpfer, L.; Emmerich, H.; Büttner, L.; Czarske, J.; Heitkam, S.

Der Einsatz moderner Meßtechnik kann einen wesentlichen Beitrag für den ressourceneffizienten Betrieb von Anlagen für die Schaumflotation leisten. Insbesondere die Kenntnis der
Stoffzusammensetzung des überströmenden Schaums kann hilfreich für die optimierte Echtzeit-Steuerung des Flotationsprozesses sein. Aufgrund der komplexen und lichtundurchlässigen Struktur der Schaumphase existieren zum heutigen Zeitpunkt allerdings nur wenige Möglichkeiten die Schaumzusammensetzung in Echtzeit und im Volumen zu bestimmen. Zusätzliche Anforderungen an die Robustheit des Maßsystems entstehen aus den rauhen Umgebungsbedingungen in industriellen Anwendungen.

  • Lecture (Conference)
    Tagung Aufbereitung und Recycling, 10.-11.11.2022, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35547
Publ.-Id: 35547


Optical Measurement of the stress and flow profile of foams in an idealized deglutition

Heitkam, S.; Gerstenberg, C.; Skrypnik, A.; Morelle, E.; McHardy, C.; Rauh, C.

Various physicochemical properties play a decisive role in the evaluation of foods, influencing
taste, odor, texture and mouthfeel when the food is distorted. Therefore, rheological investiga-
tions of foods are used in product development to specifically improve the texture or mouthfeel
of a product. Since mouthfeel describes the physical interaction between the food and various
haptic sensors in the mouth during the chewing and swallowing process, it is advantageous to
perform rheological measurements in geometries and under conditions that reflect the flow
conditions present in the mouth. Up to now, such investigations have been limited primarily to
viscous or lumpy foodstuffs. Here, foam, as a multiphase system consisting of a (highly) vis-
cous liquid and dispersed gas, exhibits complex rheological behavior due to its compressibility.
In addition, the foam undergoes partial destruction of its structure during the swallowing pro-
cess, which can change its rheological properties over time.
For the imaging of the swallowing process, an experimental setup was developed consisting
of a two-dimensional replica of the palate and a movable tongue based on dental impressions.
Foam with different properties such as the mean bubble size and the liquid content or the
degree of polydispersity can be generated. Furthermore, two tongue geometries with different
roughness are available. The flow as well as the deformation of the foam is evaluated by optical
methods such as PIV and particle tracking. The resulting velocity, shear rate and (wall) shear
stress distributions can provide information about the haptic perception in the mouth during the
swallowing process.

  • Contribution to proceedings
    Fachtagung “Experimentelle Strömungsmechanik", 06.-08.09.2022, Ilmenau, Germany
    ISSN: 978-3-9816764-8-8
  • Lecture (Conference)
    Fachtagung "Experimentelle Strömungsmechanik", 06.-08.09.2022, Ilmenau, Germany

Permalink: https://www.hzdr.de/publications/Publ-35546
Publ.-Id: 35546


Planar mapping of the liquid fraction of froth using ultrasound

Emmerich, H.; Knüpfer, L.; Trtik, P.; Eckert, K.; Heitkam, S.; Starke, E.; Weik, D.; Buettner, L.; Czarske, J.

Flotation processes are essential processes for resource separation, the monitoring of which can save vast amounts of water and energy. To control them, it is necessary to measure the phase fractions present in the froth. Currently, no suitable measurement method exists that can be easily integrated into the existing process and has a penetration depth of more than 5 cm. Therefore, in this paper we present a measurement system for determining the liquid distribution in foam using ultrasound. To counteract the strong attenuating effect of the foam on the ultrasound, we use low-frequency probes with a center frequency of 135 kHz. Electrodes determine an integral liquid fraction by conductivity measurement. Within a liquid range of 0.17 x 10(exp −2) to 0.82 x 10(exp −2), the measurement system was first calibrated for a penetration depth of 9.2 cm and validated by simultaneous neutron imaging. An absolute and relative measurement uncertainty of 0.23 x 10(exp −2) and 42.5% was the respective result. A resolution of 7.5mm in the axial, 13mm in lateral direction and 1 Hz in time were obtained. In a dynamic inhomogeneous case, the measurement system was additionally validated for a use case. This investigation represents a first step towards process optimization in flotation processes.

  • Contribution to proceedings
    Sensors and Measuring Systems; 21th ITG/GMA-Symposium, 10.-11.05.2022, Nürnberg, Germany, 277-280
    PISSN: 978-3-8007-5835-7

Permalink: https://www.hzdr.de/publications/Publ-35545
Publ.-Id: 35545


Rsn‐2‐mediated directed foam enrichment of β‐lactamase

Krause, T.; Keshavarzi, B.; Dressel, J.; Heitkam, S.; Mb, A.

Today, the availability of methods for the activity-preserving and cost-efficient downstream processing of enzymes forms a major bottleneck to the use of these valuable tools in technical processes. A promising technology appears to be foam fractionation, which utilizes the adsorption of proteins at a gas–liquid interface. However, the employment of surfactants and the dependency of the applicability on individual properties of the target molecules are considerable drawbacks. Here, we demonstrate that a reversible fusion of the large, surface-active protein Ranaspumin-2 (Rsn-2) to a β-lactamase (Bla) enabled both surfactant-free formation of a stable foam and directed enrichment of the enzyme by the foaming. At the same time, Bla maintained 70% of its catalytic activity, which was in stark contrast to the enzyme without fusion to Rsn-2. Rsn-2 predominantly mediated adsorption. Comparable results were obtained after fusion to the structurally more complex penicillin G acylase (PGA) as the target enzyme. The results indicate that using a surface-active protein as a fusion tag might be the clue to the establishment of foam fractionation as a general method for enzyme downstream processing.

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Permalink: https://www.hzdr.de/publications/Publ-35544
Publ.-Id: 35544


Investigating Pore‐Opening of Hydrogel Foams at the Scale of Freestanding Thin Films

Sébastien, A.; Mayur, P.; Leandro, J.; Aurélie, H.-F.; Heitkam, S.; Wiebke, D.

Controlling the pore connectivity of polymer foams is key for most of their applications, ranging from liquid uptake, mechanics, and acoustic/thermal insulation to tissue engineering. Despite their importance, the scientific phenomena governing the pore-opening processes remain poorly understood, requiring tedious trial-and-error procedures for property optimization. This lack of understanding is partly explained by the high complexity of the different interrelated, multiscale processes which take place as the foam transforms from an initially fluid foam into a solid foam. To progress in this field, this work takes inspiration from long-standing research on liquid foams and thin films to develop model experiments in a microfluidic “Thin Film Pressure Balance.” These experiments allow the investigation of isolated thin films under well-controlled environmental conditions reproducing those arising within a foam undergoing cross-linking and drying. Using the example of alginate hydrogel films, the evolution of isolated thin films undergoing gelation and drying is correlated with the evolution of the rheological properties of the same alginate solution in bulk. The overall approach is introduced and a first set of results is presented to propose a starting point for the phenomenological description of the different types of pore-opening processes and the classification of the resulting pore-opening types.

Permalink: https://www.hzdr.de/publications/Publ-35543
Publ.-Id: 35543


Activation calculations of selected RPV internal components for optimal decommissioning of nuclear power plants

Rachamin, R.; Konheiser, J.; Seidl, M.

In this study, the specific activities of selected RPV components’ segments (such as the RPV, core barrel, etc.) of a German PWR were calculated with a novel method based on the combined use of two Monte-Carlo codes, MCNP6.2 and FLUKA2021. In the first step, the MCNP6.2 code was used to calculate the neutron fluence rate characteristics (spectrum, distribution, and current entering the segment surfaces) in the studied segment using a 3D detailed reactor model. The neutron fluence rate prediction capability of the MCNP6.2 model has been validated via metal foil-activation measurements carried out in two German PWRs. The validation studies showed that the MCNP6.2 model is reliable and suitable for evaluating the neutron radiation field in the reactor for the ensuing activation calculations. In the second step, the FLUKA2021 code was used to calculate the specific activity distribution in the studied segment using a 3D exact model of the segment and complex source terms built based on the neutron fluence rate parameters calculated using the MCNP6.2 code. The results of the calculations were obtained with great accuracy and evidenced that the used method can serve as a powerful and non-destructive tool for the radiological characterization of the RPV and its internals.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; FLUKA

  • Open Access Logo Lecture (Conference)
    15th workshop on Shielding aspects of Accelerators, Targets, and Irradiation Facilities (SATIF-15), 20.-23.09.2022, East Lansing, USA
  • Open Access Logo Contribution to proceedings
    15th workshop on Shielding aspects of Accelerators, Targets, and Irradiation Facilities (SATIF-15), 20.-23.09.2022, East Lansing, USA

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Permalink: https://www.hzdr.de/publications/Publ-35542
Publ.-Id: 35542


Dosimetry for Decommissioning of Nuclear Power Plants

Rachamin, R.; Konheiser, J.; Barkleit, A.; Seidl, M.

In this study, a 3D detailed Monte-Carlo (MC) model of a German PWR was developed to calculate the neutron fluence characteristics within the ex-vessel components of the reactor. The neutron fluence prediction capability of the developed model was validated based on metal foil-activation measurements. Metal foil-activation measurement has been successfully used in reactor dosimetry for many years. It is an ideal method for collecting information on neutron fluence in an active reactor. This paper gives an overview of the MC model of the reactor and presents the foils activation measurement procedure. Then, the results of the MC simulations and the experimental measurements are presented and discussed.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; Validation

  • Contribution to proceedings
    14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD 2022), 25.-29.09.2022, Seattle, USA
  • Lecture (Conference)
    14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD 2022), 25.-29.09.2022, Seattle, USA
  • Invited lecture (Conferences)
    ANS Annual Meeting, 11.-14.06.2023, Indianapolis, IN, USA

Permalink: https://www.hzdr.de/publications/Publ-35541
Publ.-Id: 35541


Phasenverteilung in Zickzack-Packungen für Rotating Packed Beds

Loll, R.; Bieberle, A.; Schubert, M.; Koop, J.; Held, C.; Schembecker, G.

Rotierende Stoffaustauschmaschinen (engl. „Rotating Packed Beds“, RPBs) sind ein vielversprechender Ansatz, um Trennprozesse effizienter und flexibler zu gestalten. Die durch die Rotation der RPB-Packung wirkenden Zentrifugalkräfte resultieren in hohen Scherraten und damit dünnen Flüssigkeitsfilmen nahezu auf der gesamten Packungsoberfläche, die zu großer effektiver Phasengrenzfläche und hohem volumetrischen Stofftransport führen. Dadurch benötigen RPBs ein drastisch kleineres Packungsvolumen als herkömmliche Trennkolonnen.
Allerdings sind beim Betrieb von RPBs – insbesondere in den äußeren Regionen von isotropen Drahtgestrick- oder Metallschaumpackungen – Phasenfehlverteilungen und lokal geringe Stofftransportraten zu beobachten, die das enorme Intensivierungspotential von RPBs noch limitieren. Daher sind spezielle RPB-Packungsdesigns erforderlich, die gleichmäßige fluiddynamische Bedingungen im gesamten Packungsvolumen ermöglichen.
In dieser Arbeit wird untersucht, ob und wie neu entwickelte Zickzack-Packungen zu einer Homogenisierung der Phasenverteilung in der Packung beitragen können. Dazu wird mithilfe der nicht-invasiven winkelaufgelösten Gammastrahlen-Computertomographie die Phasenverteilung während des rotierenden Betriebs untersucht und anschließend analysiert. Die rekonstruierten Schnittbilder geben einen detaillierten Einblick auf die Flüssigkeitsverteilung innerhalb der Packung bei verschiedenen Betriebsbedingungen. Komplementäre Stofftransportmessungen geben ein verbessertes Verständnis über das Zusammenspiel von Packungsstruktur, Fluiddynamik und Trennleistung.

Keywords: Stoffaustauschmaschinen; Trennprozesse; Gammastrahlen-Computertomographie

  • Contribution to proceedings
    Jahrestreffen der "Prozess-, Apparate- und Anlagentechnik", 21.-22.11.2022, Frankfurt am Main, Deutschland
  • Poster
    Jahrestreffen der "Prozess-, Apparate- und Anlagentechnik", 21.-22.11.2022, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35540
Publ.-Id: 35540


Population Kinetics for Particle in Cell Simulations

Marre, B. E.; Hübl, A.; Bastrakov, S.; Bussmann, M.; Widera, R.; Schramm, U.; Cowan, T.; Kluge, T.

Population Kinetics for PIC

Standard atomic physics models in PIC simulation either neglect excited states, predict
atomic state population in post processing only, or assume quasi-thermal plasma conditions.

This is no longer sufficient for high-intensity short-pulse laser generated plasmas, due
to their non-equilibrium, transient and non-thermal plasma conditions, which are now becoming
accessible in XFEL experiments at HIBEF (EuropeanXFEL), SACLA (Japan) or at MEC (LCLS/SLAC).
To remedy this, we have developed a new extension for our ParticleInCell simulation
framework PIConGPU to allow us to model atomic population kinetics in situ in PIC-Simulations,
in transient plasmas and without assuming temperatures.
This extension is based on a reduced atomic state model, which is directly coupled to the
existing PIC-simulation and for which the atomic rate equation is solved explicitly in
time, depending on local interaction spectra and with feedback to the host simulation.
This allows us to model de-/excitation and ionization and of ions in transient plasma
conditions, as typically encountered in laser generated plasmas.
This new approach to atomic physics modeling will be very useful in plasma
emission prediction, plasma condition probing with XFELs and better understanding
of isochoric heating processes, since all of these rely on an accurate prediction of
atomic state populations inside transient plasmas.

Keywords: Atomic Population Kinetics; FLYonPIC; PIConGPU; PIC; Particle in Cell; Simulation; Atomic Physics

  • Lecture (Conference)
    Radiation Properties of Hot Dense Matter, 14.-18.11.2022, Santa Fe, New Mexico, United States of America

Permalink: https://www.hzdr.de/publications/Publ-35539
Publ.-Id: 35539


Response of a surfactant- and particle-laden bubble surface to asymmetric shear flow

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

The shear stress of an axisymmetric flow field triggers a nonuniform distribution of adsorbed surfactants at the surface of a rising bubble. This creates a surface tension gradient that counteracts the viscous shear stress of the flow and thus reduces the mobility of the interface. However, in technological processes the flow field often is asymmetric, e.g. due to the vorticity in the flow. Under such conditions, the interface experiences an unbalanced shear stress that is not free of curl, i.e. it cannot be compensated by the redistribution of the surfactants at the interface (Vlahovska et al., 2009).
Here, we conduct model experiments with a bubble at the tip of a capillary placed in a defined asymmetric flow field, in the presence of surfactants and nanoparticles. Unlike classical surfactants, nanoparticles adsorb irreversibly at the bubble surface. Thus, a different interaction between the bulk flow and the interface is expected.
In this study, we show a direct experimental observation of the circulating flow at the interface under asymmetric shear stress (Eftekhari et al., 2021a,b). The results indicate that the interface remains mobile regardless of the surfactant concentration. Additionally, we show that the nanoparticle-laden interface adopts a solid-like state and resists the interfacial flow upon surface compression. Our results imply that the immobilization of the interface can be described by the ratio of the interfacial elasticity to the bulk viscous forces.

  • Lecture (Conference)
    Annual European Rheology Conference (AERC 2022), 26.-28.04.2022, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-35538
Publ.-Id: 35538


Complex Dissipative Structures Mainly at Liquid/Liquid and Liquid/Gas Interfaces

Linde, H.; Schwarzenberger, K.; Eckert, K.

Well-known - and often to see in the daily weather forecast - are the chaotic macroscopic flow-systems of air and sea-water in one`s own land and occasional also about the whole world.

Permalink: https://www.hzdr.de/publications/Publ-35537
Publ.-Id: 35537


Induction of pulmonary HLA-G expression by SARS-CoV-2 infection

Seliger, B.; Jasinski-Bergner, S.; Masssa, C.; Müller, A.; Biehl, K.; Yang, B.; Bachmann, M.; Jonigk, D.; Eichhorn, P.; Hartmann, A.; Wickenhauser, C.; Bauer, M.

The non-classical human leukocyte antigen (HLA)-G exerts immune-suppressive properties modulating both NK and T cell responses. While it is physiologically expressed at the maternal–fetal interface and in immune-privileged organs, HLA-G expression is found in tumors and in virus-infected cells. So far, there exists little information about the role of HLA-G and its interplay with immune cells in biopsies, surgical specimen or autopsy tissues of lung, kidney and/or heart muscle from SARS-CoV-2-infected patients compared to control tissues. Heterogeneous, but higher HLA-G protein expression levels were detected in lung alveolar epithelial cells of SARS-CoV-2-infected patients compared to lung epithelial cells from influenza-infected patients, but not in other organs or lung epithelia from non-viral-infected patients, which was not accompanied by high levels of SARS-CoV-2 nucleocapsid antigen and spike protein, but inversely correlated to the HLA-G-specific miRNA expression. High HLA-G expression levels not only in SARS-CoV-2-, but also in influenza-infected lung tissues were associated with a high frequency of tissue-infiltrating immune cells, but low numbers of CD8+ cells and an altered expression of hyperactivation and exhaustion markers in the lung epithelia combined with changes in the spatial distribution of macrophages and T cells. Thus, our data provide evidence for an involvement of HLA-G and HLA-G-specific miRNAs in immune escape and as suitable therapeutic targets for the treatment of SARS-CoV-2 infections.

Keywords: HLA-G; Immune cell infiltration; Immune response; microRNA; SARS-CoV-2

Permalink: https://www.hzdr.de/publications/Publ-35535
Publ.-Id: 35535


Technological Pathways to Produce Compressed and Highly Pure Hydrogen from Solar Power

Ivanova, M. E.; Peters, R.; Müller, M.; Haas, S.; Seidler, F.; Mutschke, G.; Eckert, K.; Röse, P.; Calnan, S.; Bagacki, R.; Grosslindemann, C.; Schäfer, L.-A.; Weber, A.; van de Krol, R.; Liang, F.; Abdi, F. F.; Brendelberger, S.; Neumann, N.; Grobbel, I.; Roeb, M.; Sattler, C.; Duran, I.; Dietrich, B.; Hofberger, C.; Stoppel, L.; Uhlenbruck, N.; Wetzel, T.; Rauner, D.; Hecimovic, A.; Frantz, U.; Kulyk, N.; Harting, J.; Guillon, O.

Hydrogen (H 2 ) produced from renewables will have a
growing impact on the global energy dynamics towards sustainable
and carbon-neutral standards. The share of green H 2 is still too low to
meet the net-zero target, while the demand for high-quality hydrogen
continues to rise. These factors amplify the need for economically
viable H 2 generation technologies. The present article aims at
evaluating the existing technologies for high-quality H 2 production
based on solar energy. Technologies such as water electrolysis,
photoelectrochemical and solar thermochemical water splitting, liquid
metal reactors and plasma conversion utilize solar power directly or
indirectly (as carbon-neutral electrons) and are reviewed from the
prospective of their current development level, technical limitations
and future potential.

Keywords: electrolysis; hydrogen; green hydrogen; pure hydrogen; energy conversion; renewable energy; technology

Permalink: https://www.hzdr.de/publications/Publ-35534
Publ.-Id: 35534


Advanced thermal-hydraulic experiments and instrumentation for heavy liquid metal reactors

Pacio, J.; van Tichelen, K.; Eckert, S.; Wondrak, T.; Di Piazza, I.; Lorusso, P.; Tarantino, M.; Daubner, M.; Litfin, K.; Ariyoshi, G.; Obayashi, H.; Sasa, T.

Heavy-liquid metals (HLMs), such as lead and lead–bismuth eutectic (LBE), are proposed as primary coolants in accelerator driven systems and next-generation fast reactors. In Europe, the reference systems using HLMs are MYRRHA (LBE) and ALFRED (lead). Extensive R&D programs have been established for supporting their detailed design and safety assessment, including thermal–hydraulic experiments at representative operating conditions in an HLM environment. These experiments aim both at a design verification and at the validation of numerical models, which allow an extrapolation of the results. Advanced instrumentation, capable of sustaining high temperatures and corrosion, is necessary for accurate measurements, often in compact geometries. This article presents an overview of recent experiences and ongoing activities on pool-type and loop-type HLM experiments. Pool tests include the measurement of forced- and natural-circulation flow patterns in several scenarios representative of nominal and decay heat removal conditions. Loop tests are focused on the evaluation of specific components, like mockups of the fuel assembly, control rod and heat exchangers. They involve the measurement of global variables, such as flow rate and pressure difference, and local quantities like temperature, velocity and vibrations. In addition to traditional techniques, other instrumentation based on optical fibers, ultrasonic and electromagnetic methods are discussed.

Keywords: liquid metal; experiment; instrumentation

Permalink: https://www.hzdr.de/publications/Publ-35532
Publ.-Id: 35532


Numerical and theoretical framework for the DRESDYN precession dynamo experiment

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

The upcoming DRESDYN (DREsden Sodium facility for DYNnamo and thermohydraulic
studies) precession experiment will test the possibility to achieve magnetohydrodynamic
dynamo action solely driven by precession. Here, after the description of the experi-
mental facility, we present the results from direct numerical simulations with the aim to
understand the flow behavior and its dynamo capability. The main conclusion is that
in the nonlinear regime the nutation angle is an essential governing parameter which
determines the flow structures and the possibility of dynamo action. We obtain clear
indications about the optimum configuration for the future experimental runs.

Related publications

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  • Secondary publication expected from 30.03.2024

Permalink: https://www.hzdr.de/publications/Publ-35531
Publ.-Id: 35531


Nano- and Flexomagnetism in Magnetoelectric Cr2O3 Thin-Film Antiferromagnets

Makarov, D.

In this presentation, we will review our recent activities on thin films and bulk of Cr2O3 for energy efficient memory devices and antiferromagnetic spintronic applications. The newly discovered flexomagnetic effect in thin films of Cr2O3 will be presented as well.
[1] Nature Physics 17, 574 (2021).
[2] Nature Comm. 13, 6745 (2022).
[3] Small 18, 2201228 (2022).
[4] ACS Appl. Electron. Mater. 4, 2943 (2022).

Keywords: antiferromagnetic spintronics; magnetic thin films; Cr2O3

Related publications

  • Lecture (others) (Online presentation)
    Lu Jiaxi International Team Annual Meeting, 02.12.2022, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-35530
Publ.-Id: 35530


Flexible, printed and self-healable high-performance magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

In this overview talk, we will discuss on our recent activities on the realization of flexible, printed and self-healable magnetic field sensors and their potential application scenarios.

Keywords: flexible magnetic field sensors; printable magnetic field sensors; magnetic soft robots

Related publications

  • Lecture (others)
    Seminar of the Graduiertenkolleg 2430 „Interaktive Faser-Elastomer-Verbunde“, 06.12.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-35529
Publ.-Id: 35529


Curvilinear micromagnetism: from fundamentals to applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films [3] and nanowires [4]. In this talk, we will address fundamentals of curvature-induced effects and discuss experimental realisations of geometrically curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of the exchange-driven chiral effects [5]. Geometrically curved magnetic thin films are interesting not only fundamentally. They are the key component of mechanically flexible magnetic field sensors. We will briefly outline activities on shapeable magnetoelectronics [6,7], which includes flexible, stretchable and printable magnetic field sensors for the realisation of human-machine interfaces [8,9], interactive electronics for virtual [10] and augmented [11] reality applications and soft robotics [12] to mention just a few. Very recently, self-healable magnetic field sensors for interactive printed electronics were reported [13]. The presence of the geometrical curvature in a magnetic thin film influences pinning of magnetic domain walls and in this respect it affects the sensitivity of mechanically flexible magnetic field sensors. This is an intimate link between the fundamental topic of curvilinear magnetism and application-oriented activities on shapeable magnetoelectronics. This link will be discussed in the presentation as well.

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications. Springer Nature Switzerland (2022). https://link.springer.com/book/10.1007/978-3-031-09086-8
[3] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[4] D. Sheka et al., Fundamentals of Curvilinear Ferromagnetism: Statics and Dynamics of Geometrically Curved Wires and Narrow Ribbons. Small (Review) 18, 2105219 (2022).
[5] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[6] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[7] G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Advanced Functional Materials (Review) 31, 2007788 (2021).
[8] P. Makushko et al., Flexible Magnetoreceptor with Tunable Intrinsic Logic for On-Skin Skin Touchless Human-Machine Interfaces. Advanced Functional Materials 31, 2101089 (2021).
[9] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[10] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] G. S. Canon Bermudez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[12] M. Ha et al., Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly. Advanced Materials 33, 2008751 (2021).
[13] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: flexible magnetic field sensors; printable magnetic field sensors; curved magnetic thin films

Related publications

  • Lecture (others)
    Seminar at the Northeastern University, Electrical and Computer Engineering, 28.11.2022, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-35528
Publ.-Id: 35528


Stability and structure of platinum sulfide complexes in hydrothermal fluids

Laskar, C.; Bazarkina, E.; Kokh, M.; Hazemann, J.-L.; Vuilleumier, R.; Desmale, E.; Pokrovski, G. S.

Knowledge of the chemical speciation of platinum and the solubility of Pt-bearing minerals in hydrothermal fluids is required to assess Pt transport, remobilization and concentration in the Earth’s crust. In this study, we combined PtS(s) solubility measurements in a hydrothermal reactor allowing fluid sampling, in situ X-ray absorption spectroscopy, and first-principles molecular dynamics simulations to systematically investigate the structure, composition and stability of Pt sulfide complexes in model aqueous H2S-bearing solutions up to 300 °C and 600 bar. The results demonstrate that tetrahydrosulfide, PtII(HS)42–, is the major Pt-bearing complex in aqueous solutions saturated with PtS(s) over a wide range of dissolved hydrogen sulfide concentrations, from < 0.2 to ∼ 2 molal. The equilibrium constants of the dissolution reaction of PtS(s) generated in this study, PtS(s) + 3 H2S(aq) = Pt(HS)42– + 2 H+ (β4), are described by the equation log10β4 = 0.9 × 1000/T(K) – 19.7 (± 0.5) over the temperature range 25–300 °C and pressure range Psat–600 bar. Furthermore, the stepwise formation constants of four PtII-HS complexes, Pt(HS)+, Pt(HS)20, Pt(HS)3–, and Pt(HS)42–, were estimated, for the first time, from molecular dynamics simulations. The generated constants indicate that the maximum solubility of platinum in the form of Pt(HS)42– in reduced H2S-dominated hydrothermal fluids at moderate temperatures (≤ 350 °C) is close to 1 ppb Pt at near-neutral pH of 6–8 and hydrogen sulfide concentrations of 0.1 molal. Although this solubility is much greater than that of Pt-Cl, Pt-OH and Pt-SO4 complexes at such conditions, it is yet too low to account for significant Pt transport in most shallow-crust hydrothermal settings, characterized by the presence of both sulfide and sulfate. Complexes with S-bearing ligands, very likely other than H2S/HS–, such as S3–, would be required to account for Pt hydrothermal mobility. Our results provide a basis for more systematic future studies, using combined approaches, of the role of hydrothermal fluids in the behavior of platinum group elements in nature.

Keywords: Platinum sulfide complexes; Hydrothermal fluid; Solubility; X-ray absorption spectroscopy; Molecular dynamics; Stability constant

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Permalink: https://www.hzdr.de/publications/Publ-35527
Publ.-Id: 35527


H2 bubble motion reversals during water electrolysis

Bashkatov, A.; Babich, A.; Hossain, S. S.; Yang, X.; Mutschke, G.; Eckert, K.

The dynamics of hydrogen bubbles produced by water electrolysis in an acidic electrolyte are studied using electrochemical and optical methods. A defined cyclic modulation of the electric potential is applied at a microelectrode to produce pairs of interacting H$_2$ bubbles in a controlled manner. Three scenarios of interactions are identified and systematically studied. The most prominent one consists in a sudden reversal in the motion of the first detached bubble, its return to the electrode and finally its coalescence with the second bubble. Attested by Toepler's schlieren technique, an explanation of contactless motion reversal is provided by the competition between buoyancy and thermocapillary effects.

Keywords: water electrolysis; bubble dynamics; hydrogen; H2 bubbles; thermocapillary effect; Marangoni force; motion reversals

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Permalink: https://www.hzdr.de/publications/Publ-35526
Publ.-Id: 35526


Precipitation reaction flows in microscale geometries

Stergiou, Y.; Eckert, K.; Schwarzenberger, K.

Precipitation reactions are of constant interest to research because of their importance in nature and in industry. In this study, we
present a precipitation Reaction-Diffusion-Advection system using a CaCO3 forming reaction by injecting one reactant solution
into the initially stagnant second reactant solution. We studied the resulting precipitate reactive flow system both from a
microscopic and a macroscopic point of view. We identified three different flow regimes depending on the flow conditions and
chemical system: a particle-laden regime, a clogging regime and a gelation regime. The results are a basis for further investigation
and improvement of such displacements in technological applications.

  • Lecture (Conference)
    11th International Conference on Multiphase Flow, 02.-07.04.2023, Kobe, Japan

Permalink: https://www.hzdr.de/publications/Publ-35525
Publ.-Id: 35525


Neutron scattering methods

Bergner, F.

This lecture is about neutron scattering methods and their applications in the field of nuclear material science.

Keywords: Small-angle neutron scattering; Diffuse neutron scattering; Nuclear materials

  • Lecture (others)
    European School on Nuclear Materials Science, 07.-11.11.2022, Cargèse, France

Permalink: https://www.hzdr.de/publications/Publ-35523
Publ.-Id: 35523


X-ray and electron diffraction methods

Bergner, F.

This lecture is about X-ray and electron diffraction methods and their application in the field of nuclear material science

Keywords: X-ray diffraction; Electron diffraction; Nuclear materials

  • Lecture (others)
    European School on Nuclear Materials Science, 07.-11.11.2022, Institut d'Etudes Scientifiques (IESC) Cargèse, France

Permalink: https://www.hzdr.de/publications/Publ-35522
Publ.-Id: 35522


Germanium Monosulfide as a Natural Platform for Highly Anisotropic THz Polaritons

Nörenberg, T.; Álvarez-Pérez, G.; Obst, M.; Wehmeier, L.; Hempel, F.; Klopf, J. M.; Nikitin, A. Y.; Kehr, S. C.; Eng, L. M.; Alonso-Gonzaléz, P.; de Oliveira, T.

Terahertz (THz) electromagnetic radiation is key to access collective excitations such as magnons (spins), plasmons (electrons), or phonons (atomic vibrations), thus bridging topics between optics and solid-state physics. Confinement of THz light to the nanometer length scale is desirable for local probing of such excitations in low-dimensional systems, thereby circumventing the large footprint and
inherently low spectral power density of far−field THz radiation. For that purpose, phonon polaritons (PhPs) in anisotropic van der Waals (vdW) materials have recently emerged as a promising platform for THz nanooptics. Hence, there is a demand for the exploration of materials that feature not only THz PhPs at different spectral regimes, but also host anisotropic (directional) electrical, thermoelectric,
and vibronic properties. To that end, we introduce here the semiconducting vdW material alpha−germanium (II) sulfide (GeS) as an intriguing candidate. By employing THz nanospectroscopy supported by theoretical analysis, we provide a thorough characterization of the different in−plane hyperbolic and elliptical PhP modes in GeS. We find not only PhPs with long lifetimes (τ > 2 ps) and excellent THz light confinement (λ[₀]/λ) 45), but also an intrinsic, phonon-induced anomalous dispersion as well as signatures of naturally
occurring, substrate-mediated PhP canalization within a single GeS slab.

Keywords: van der Waals materials; optical anisotropy; terahertz; phonon polaritons; polariton interferometry

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Permalink: https://www.hzdr.de/publications/Publ-35521
Publ.-Id: 35521


Emergence of Hadron Mass and Structure

Ding, M.; Roberts, C. D.; Schmidt, S. M.

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale invariant. Thus, if the Standard Model is truly a part of the theory of Nature, then the proton mass is an emergent feature of QCD; and emergent hadron mass (EHM) must provide the basic link between theory and observation. Nonperturbative tools are necessary if such connections are to be made; and in this context, we sketch recent progress in the application of continuum Schwinger function methods to an array of related problems in hadron and particle physics. Special emphasis is given to the three pillars of EHM – namely, the running gluon mass, process-independent effective charge, and running quark mass; their role in stabilising QCD; and their measurable expressions in a diverse array of observables.

Keywords: confinement of gluons and quarks; continuum Schwinger function methods; Dyson- Schwinger equations

Permalink: https://www.hzdr.de/publications/Publ-35519
Publ.-Id: 35519


40Ar proposed as probe of neutron-induced reactions in a high-density stellar-like plasma at the National Ignition Facility

Paul, M.; Sahoo, S. N.; Tessler, M.; Jeet, J.; Velsko, C.; Zylstra, A.; Avila, M.; Dickerson, C.; Fougeres, C.; Jayatissa, H.; Pardo, R. C.; Rehm, K. E.; Scott, R.; Toltsukhin, I.; Vondrasek, R.; Bailey, T.; Callahan, L.; Clark, A. M.; Collon, P.; Kashiv, Y.; Nelson, A.; Köster, U.; Hoffmann, H. F. R.; Pichotta, M.; Zuber, K.; Döring, T.; Schwengner, R.

The thermodynamical conditions of plasma density, temperature, pressure and the neutron density produced in a laser-induced implosion of a deuterium-tritium (DT) filled capsule at the National Ignition Facility (NIF) are the closest laboratory analog of stellar conditions. We plan to investigate neutron-induced reactions on 40Ar, namely the 40Ar(n, 2n)39Ar(t1/2 =268 y), the 40Ar(n,gamma)41Ar(110 min) and the potential rapid two-neutron capture reaction 40Ar(2n,gamma)42Ar(33 y) in the same implosion on an Ar-loaded DT capsule. The chemical inertness of noble gas Ar enables reliable collection of the reaction products. We describe here the technique of Noble-Gas Accelerator Mass Spectrometry (NOGAMS) to be used for ultra-sensitive detection of the long-lived 39Ar and 42Ar at Argonne National Laboratory. A 42Ar(33 y) sample was produced via the slow two-neutron capture reaction 40Ar(2n, gamma)42Ar
in a high thermal-neutron flux irradiation. 39Ar and for the first time 42Ar atoms were directly detected in the abundance range 10^-12 -- 10^-13 .
The present sensitivity of 42Ar detection is of the order of 104 atoms.

Keywords: Neutron-indiced reactions; DT generator; 40Ar target; noble-gas accelerator mass scpectroscopy (NOGAMS)

Related publications

  • Open Access Logo Contribution to proceedings
    Nuclear Physics in Astrophysics - X, 04.-09.09.2022, Genf, Schweiz
    EPJ Web of Conferences, 40123 Bologna: EPJ Web of Conferences, 13004-1-13004-5
    DOI: 10.1051/epjconf/202327913004

Permalink: https://www.hzdr.de/publications/Publ-35518
Publ.-Id: 35518


Direct numerical simulation of microlayer formation and evaporation underneath a growing bubble driven by the local temperature gradient in nucleate boiling

Zhang, J.; Rafique, M.; Ding, W.; Bolotnov, I.; Hampel, U.

Recently, experiments carried out with high-resolution measurement techniques showed the formation of a thin liquid microlayer (~µm) underneath a growing bubble in nucleate boiling. However, a deep understanding of the heat transfer enhancement induced by this microlayer is still lacking. In this work, we investigate the heat transfer characteristics of the microlayer in the early stage of nucleate boiling by using direct numerical simulations with the PHASTA solver. The microlayer formation and evaporation during the bubble growth driven by the local temperature gradient are simulated and fully resolved by very fine boundary layer meshes and the level-set method. We obtain the microlayer evolution comparable to recent experimental observations for the first time. The detailed microlayer dynamics indicates that the microlayer formation in the early stage of nucleate boiling can be considered a quasi-steady process without contact line motion. Furthermore, we find that the microlayer thickness is not determined by hydrodynamic effects, thus suggesting a rather constant microlayer heat transfer under different hydrodynamic conditions in nucleate boiling. Here, the local heat flux in the microlayer exceeds 20 MW/m2 near the contact line within 0.6 ms after the bubble inception, and the overall heat transfer from the microlayer evaporation contributes over 70% to the bubble growth. This value emphasizes the significance of microlayer evaporation in the modeling of nucleate boiling heat transfer.

Keywords: nucleate boiling; microlayer; heat transfer; direct numerical simulation

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  • Secondary publication expected from 14.07.2024

Permalink: https://www.hzdr.de/publications/Publ-35516
Publ.-Id: 35516


How droplets pin on solid surfaces

Zhang, J.; Ding, W.; Hampel, U.

Hypothesis: When a droplet starts sliding on a solid surface, the droplet-solid friction force develops in a manner comparable to the solid-solid friction force, showing a static regime and a kinetic regime. Today, the kinetic friction force that acts on a sliding droplet is well-characterized. But the mechanism underlying the static friction force is still less understood. Here we hypothesize that we can further draw an analogy between the detailed droplet-solid and solid-solid friction law, i.e., the static friction force is contact area dependent.
Methods: We deconstruct a complex surface defect into three primary surface defects (atomic structure, topographical defect, and chemical heterogeneity). Using large-scale Molecular Dynamics simulations, we study the mechanisms of droplet-solid static friction forces induced by primary surface defects.
Findings: Three element-wise static friction forces related to primary surface defects are revealed and the corresponding mechanisms for the static friction force are disclosed. We find that the static friction force induced by chemical heterogeneity is contact line length dependent, while the static friction force induced by atomic structure and topographical defect is contact area dependent. Moreover, the latter causes energy dissipation and leads to a wiggle movement of the droplet during the static-kinetic friction transition.

Keywords: droplet-solid friction; static friction force; surface defects; contact line pinning; energy dissipation; wetting dynamics

Permalink: https://www.hzdr.de/publications/Publ-35515
Publ.-Id: 35515


Study on kinetics and mechanism of Re(VII) ion adsorption and desorption using commercially available activated carbon and solutions containing Se(VI) as an impurity

Kołczyk-Siedlecka, K.; Socha, R. P.; Yang, X.; Eckert, K.; Wojnicki, M.

This paper presents the potential use of carbon sorbents in recovering rhenium(VII) from highly diluted electrolytes. Tests were performed using synthetic solutions containing selenium(VI) as an impurity. Adsorption of Re(VII) is selective with respect to selenium(VI). Activated carbon is a suitable sorbent for rhenium recovery because unlike ion-exchange resins, it has high chemical resistance and osmotic-shock resistance. The results show that the sorption mechanism is complex. Two follow-up processes occurred—physical adsorption and the reduction of Re(VII) to Re(VI). The processes were strongly influenced by the temperature. The lower the temperature, the higher the process efficiency. The observed sorption capacity was as high as 7.6 mg/g at 298 K and decreased as the temperature increased. The adsorption was a mixed-control process. Increasing the temperature altered the rate-limiting process. The activation parameters were determined using rate constant (k) and Arrhenius equation. In the first step, the activation energy was approximately 0 kJ mol-1. In the second step, the activation energy for k2,obs and k3,obs was determined as 57.3 kJ mol-1. The pre-exponential factors were calculated; their value was 2.98 × 107 min-1. For k1,obs, the activation energy was nearly 0 kJ mol-1.

Keywords: Rhenium(VII) adsorption; selenium(VI) adsorption; chemical reduction; activated carbon; kinetic studies; selenium ions

Permalink: https://www.hzdr.de/publications/Publ-35514
Publ.-Id: 35514


Molecular Dynamics Simulation on Bubble Related Issues

Ding, W.

Activities introduction of Molecular Dynamics simulation on bubble related issues in FWDF, HZDR.

Keywords: Molecular Dynamics; Bubble

  • Lecture (others)
    ECCM Kick off meeting, 27.-28.10.2022, TU Twent, Niederland
  • Lecture (Conference)
    ICMF - The 11th International Conference on Multiphase Flow, 03.-07.04.2023, Kobe, Japan

Permalink: https://www.hzdr.de/publications/Publ-35512
Publ.-Id: 35512


Nanobending of the microscopic liquid-gas interface on the solid surface and its potential impact on nanobubbles

Zhang, J.; Ding, W.; Hampel, U.

Young contact angle is widely applied to evaluate liquid wetting phenomena on solid surfaces. For example, it gives a truncated-spherical shape prediction of a droplet/bubble profile through the Young-Laplace equation. However, recent measurements have shown the deviation of a microscopic droplet profile from the spherical shape, indicating that the conventional Young contact angle as the boundary condition is insufficient to describe the microscopic liquid wetting phenomena which play a critical role when nanobubbles on the wall. Here, we reveal a liquid-gas interface nano-bending, which is caused by the nonlinear coupling between the effects of the microscopic interface geometry and solid-liquid interactions and is responsible for this deviation. Based on molecular dynamics simulations and mathematical modeling, we describe the structure of the nano-bending and explain the mechanism of the nonlinear-coupled effect. We further apply our findings to illustrate the saddle-shaped profile in the vicinity near the contact region. The interface nano-bending, rather than the Young contact angle, acts as the boundary at the contact line and dictates the liquid wetting system. In this way, we succeed in accurately predicting the microlayer profile (µm thickness liquid film beneath a nucleation bubble) captured by different experiments. These findings not only provide insight into recent nano-scale droplet- and bubble-related wetting phenomena, but are also helpful for surface engineering concerning nano-scale wetting control.

Keywords: Nano Bending; Nano Bubble; nonlinear coupled effect

  • Poster
    Nanobubble, 19.-21.09.2022, Magdeburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35511
Publ.-Id: 35511


The effect of the microscopic liquid film interface on the heat transfer in multiphase dynamics

Zhang, J.; Ding, W.; Hampel, U.

Microlayer plays a critical role in the bubble dynamics and heat transfer in nucleate boiling. Yet, an accurate description of the microlayer has been a challenge for decades. In this work, we investigate the microlayer profile in the inertia-controlled bubble growth stage by using molecular simulations and mathematical modeling. A multiscale microlayer model was established through the disjoining pressure method and lubrication theory. Our model succeeds in accurately describing the microlayer profile captured by different experiments for the first time in decades. We reveal that the nonlinear coupling between microscopic liquid/vapor interface geometry and surface energy near the surface has a dominant effect on the overall microlayer profile. An interface nano-bending caused by the coupling acts as a three-dimensional boundary for the liquid wetting system and governs the wetting behavior. These findings provide insight into the understanding of heat transfer in nucleate boiling.

Keywords: Microlayer; Bubble; Molecular force; mutual effect; nano bending

  • Poster
    Annual Meeting on Reaction Engineering and ProcessNet Subject Division Heat and Mass Transfer 2022, 18.-20.07.2022, Würzburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35510
Publ.-Id: 35510


Introduction to Density Functional Theory

Cangi, A.

A formal introduction to density functional theory.

Keywords: Density Functional Theory

  • Invited lecture (Conferences) (Online presentation)
    Forschungsseminar "Vielteilchentheorie", Christian-Albrechts-Universität zu Kiel, 25.10.2022-14.02.2023, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35509
Publ.-Id: 35509


Recovery of valuable elements from tailings dumps accompanied by environmental remediation – the pilot plant project “ReMiningPlus”

Pinka, J.; Haubrich, F.; Werner, A.; Büttner, P.; Meißner, S.; Puschmann, R.; Pretzsch, E.

Flotation tailings from a former lead-zinc mine near Freiberg (Germany) consist of fine-grained quartz, feldspar, mica and the sulfide minerals pyrite, galena and sphalerite, which are not recovered by flotation. Sphalerite contains significant amounts of indium (up to 0.38 % (w/w)) in addition to iron, copper and cadmium, resulting in assumed average indium content of 30 mg/kg in the tailings. The presentation shows the development of biohydrometallurgical recovery of indium from laboratory to pilot scale. In a 2 m³ bioreactor, maximum zinc and indium leaching rates of 80 % were obtained at a pulp density of 25%. For the recovery of indium from the PLS (pregnant leaching solution), a stepwise precipitation process is being developed consisting of a combined iron/indium precipitation and a subsequent treatment of the indium precipitate product. A new project has been started in which a modular plant for the utilization of valuable materials from these sulfide tailings and their environmentally friendly remediation is being set up directly at the tailings site. Combining resource technology to utilize valuable elements (indium and zinc) from tailings and environmental technology to eliminate harmful substances (arsenic and cadmium) with the use of inert components (e.g. as building material) represents a win-win situation. After its completion, the modular plant consists of three parts: the leaching, the recyclables and the environmental modules. Results and findings of the project will be processed for environmental education in schools and used for the development of a web application (app) that can be used to content for integration into existing tourism concepts. Through the implementation of the aforementioned goals, the project provides a decisive contribution to the structural change in the region, as it a concept for linking rehabilitation and secondary raw material extraction and a possible economic and touristic reuse.

Keywords: Bioleaching; Circular Economy; Indium; Tailings; Zinc

  • Contribution to proceedings
    The 24th International Biohydrometallurgy Symposium, 20.-23.11.2022, Perth, Australia
    Biotechnology for resource sustainability and circular economy. Book of Abstracts., Australia: CSIRO, 101-101

Permalink: https://www.hzdr.de/publications/Publ-35508
Publ.-Id: 35508


Editorial: Experimental and simulation research on nuclear reactor thermal-hydraulics

Zhang, L.; Pan, L.-M.; Wang, J.; Ding, W.

The researches on nuclear reactor thermal-hydraulics have achieved outstanding progresses in the past decades. In recent years, basic research on multiphase flow dynamics and corresponding measurement technology, as well as preliminary research on Gen IV reactors based on experiments and simulations are attracting more and more attention. However, the inside complicated physics and outside extreme conditions will also bring risks and challenges to the development of nuclear industry.

Keywords: nuclear reactor; thermal; hydraulics; experiments; simulation

Permalink: https://www.hzdr.de/publications/Publ-35507
Publ.-Id: 35507


Precession-driven fluid flows and their ability to drive a dynamo

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

It is well known that a magnetohydrodynamic dynamo, i.e. the
generation of a magnetic field from a flow of an electrically
conductive fluid, takes or took place in the interior of the Sun or
stars as well as in planets and smaller celestial bodies like the
ancient moon or the asteroid Vesta. The ubiquity and diversity of
astrophysical dynamo action and its great importance for formation and
evolution of the objects generating them has motivated related studies
in the laboratory. Currently, a new dynamo experiment is under
construction at Helmholtz-Zentrum Dresden-Rossendorf within the
project DRESDYN (DREsden Sodium facility for DYNamo and
thermohydraulic studies). In that experiment a flow of liquid sodium
will be driven by precession of a cylindrical container. Previous
experiments by Gans (1971) and more recent numerical models
indicate that dynamo action can be expected in the vicinity of the
transition from a laminar flow state to vigorous turbulence if the
system is sufficiently large.

In our contribution we describe the progress in construction of the
experiment and present new results from simulations and accompanying
water experiments in which the precession-driven flow was recorded
with Ultrasonic Doppler Velocimetry (UDV) and Particle Image
Velocimetry (PIV). The analysis of the data by means of the
decomposition into different classes of inertial modes provides an
impression of flow features, which are supposed to be beneficial for
the dynamo, like axisymmetric large scale flow modes, shear layers due
to the modification of the rotational base flow, or the appearance of
intermittent mid-scale vortices. Our focus will be on the influence of
the precession angle on the fluid flow and the dynamo, as well as
on investigating the possibility of increasing the internal flow
amplitude by means of baffles mounted at the end caps of the
container. The main aim is to provide general global characteristics
that are also relevant for a more natural spherical/spheroidal
geometry.

Keywords: Dynamo; DRESDYN

  • Lecture (Conference)
    AGU Fall Meeting, 12.-16.12.2022, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-35506
Publ.-Id: 35506


Preparatory simulations and experiments for the DRESDYN precession dynamo

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

Precession represents a possibility to power the early geodynamo or the ancient lunar dynamo.
Precession driven dynamo action was found in simulations in various geometries (sph/cyl/cube).
related experiments by R. Gans yield an amplification of an external field by a factor of three.

Keywords: Dynamo; DRESDYN

  • Poster
    Fluid flow and magnetic field generation in fluids and plasmas - theory and laboratory experiments, 16.-21.10.2022, Leeds, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35505
Publ.-Id: 35505


Boundary conditions in MRI and Dynamo Experiments

Ji, H.; Giesecke, A.

There is no abtract.

Keywords: Dynamo; DRESDYN; MRI; Boundary Conditions

  • Invited lecture (Conferences)
    Frontiers in dynamo theory: from the Earth to the stars, 27.10.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35504
Publ.-Id: 35504


The Fluid Flow in a Precessing Cylinder

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

The planned liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) is a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. Most ambitious experiment will be a large-scale precession driven dynamo experiment. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo (Malkus, Science 1968, 160, 3825) or the ancient lunar dynamo (Noir and Cebron 2013, JFM, 737, 412; Dwyer et al. 2011, Nature, 479, 7372; Weiss et al. 2014, Science 346, 1246753). Precessional forcing is of great interest from the experimental point of view, because it represents a natural mechanism which allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Currently, we conduct preparative studies that involve numerical simulations and flow measurements at a downscaled model experiment filled with water. These studies aim at the design of the planned large scale experiment and provide parameter island where dynamo action is most likely.

Keywords: Dynamo; DRESDYN

  • Invited lecture (Conferences)
    Frontiers in dynamo theory: from the Earth to the stars, 12.10.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35503
Publ.-Id: 35503


On the Growth Regimes of Hydrogen Bubbles at Microelectrodes

Bashkatov, A.; Hossain, S. S.; Mutschke, G.; Yang, X.; Rox, H.; Weidinger, I. M.; Eckert, K.

The growth of single hydrogen bubbles at micro-electrodes is studied in an acidic electrolyte over a wide range of concentrations and cathodic potentials. New bubble growth regimes have been identified which differ in terms of whether the bubble evolution proceeds in the presence of a monotonic or oscillatory variation in the electric current and a carpet of microbubbles underneath the bubble. Key features such as the growth law of the bubble radius, the dynamics of the microbubble carpet, the onset time of the oscillations and the oscillation frequencies have been characterized as a function of the concentration and electric potential. Furthermore, the system's response to jumps in the cathodic potential has been studied. Based on the analysis of the forces involved and their scaling with the concentration, potential and electric current, a sound hypothesis is formulated regarding the mechanisms underlying the micro-bubble carpet and oscillations.

Keywords: hydrogen; bubble dynamics; water electrolysis; force balance; electric force; marangoni convection; bubble oscillations

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Permalink: https://www.hzdr.de/publications/Publ-35502
Publ.-Id: 35502


Data publication: Shell engineering in soft alginate-based capsules for culturing liver spheroids

Peng, X.; Janićijević, Ž.; Lemm, S.; Laube, M.; Pietzsch, J.; Bachmann, M.; Baraban, L.

summary over: (a) raw data for the metabolic assays (b) raw data for the analysis of the permeability of the capsules (c) unpublished images: typical cross section analysis of the capsules and organoids

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35501
Publ.-Id: 35501


Surfactant Sorption on a Single Air Bubble in an Ultrasonic Standing Acoustic Wave Field

Keshmiri, A.; Heitkam, S.; Bashkatov, A.; Eftekhari, M.; Eckert, K.; Keshavarzi, B.

Ultrasound application presents a promising non-intrusive way to enhance and facilitate
mass transfer in aqueous systems. This enhanced mass transfer can influence
the sorption processes in multiphase flows. Previous studies investigating the
impact of ultrasound on sorption, have reported an increase in either desorption
due to the rise in liquid temperature or adsorption due to the additional convective
mass transfer resulting from acoustic streaming. In this study, low intensity
ultrasound with a frequency of 36 kHz was deployed to evaluate the sorption process
of Triton X-100 on the surface of a single bubble, placed along the standing
acoustic wave using profile analysis tensiometry. Furthermore, microscopic particle
image velocimetry was used to understand the role acoustic streaming might
play during different stages of the sorption process. Contrary to expectations, the
results showed no considerable change in surface tension and sorption dynamics
after sonicating both fresh and surfactant-loaded bubbles. The results of this study
suggest that the observations from previous studies may be attributed to the additional
energy input of the acoustic wave into the system rather than the presence
of an external acoustic field.

Keywords: Standing Acoustic Wave; Sorption on Bubble; Surface Tension; Ultrasound; Sonication; Tensiometry

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Permalink: https://www.hzdr.de/publications/Publ-35499
Publ.-Id: 35499


Formation of In-Plane Semiconductor-Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Lasek, K.; Li, J.; Ghorbani Asl, M.; Khatun, S.; Alanwoko, O.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

Monolayers of platinum tellurides are particularly interesting 2D materials because they exhibit phases with different stoichiometries and electronic properties. Specifically, PtTe₂ is a narrow gap semiconductor while Pt₂Te₂ is a metal. Here we show that the former can be transformed into the latter by reaction with vapor-deposited Pt atoms. Owing to low surface diffusion barriers of Pt ad-atoms, the transformation occurs by nucleating the Pt₂Te₂ phase within the PtTe₂ islands, so that a metal-semiconductor lateral junction is formed. Using scanning tunneling microscopy/spectroscopy, the electronic structure of this lateral junction is studied. A flat band structure is found with the Fermi-level of the metal aligning with the Fermi-level of the intrinsically p-doped PtTe₂ suggesting low contact resistance. This flat band is achieved by an interface dipole that accommodates the ~0.2 eV shift in the work functions of the two materials. First-principles calculations indicate that the origin of the interface dipole is the atomic scale charge redistributions at the heterojunction. The demonstrated compositional phase transformation of a 2D semiconductor into a 2D metal is a promising approach for making in-plane metal contacts that are required for efficient charge injection and is of particular interest for semiconductors with large spin-orbit coupling, like PtTe₂.

Keywords: lateral heterojunctions; two-dimensional materials; platinum Telluride; electronics

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Permalink: https://www.hzdr.de/publications/Publ-35498
Publ.-Id: 35498


Liquid Metal Batteries: Numerical Investigations on Fluid Flow and Mass Transfer

Duczek, C.; Weber, N.; Weier, T.

Charge transfer and mass transport are directly linked with operating batteries. In liquid metal batteries (LMBs) additional flow phenomena heavily influence the cell performance. Those have widely been investigate numerically as well as experimentally. But, concentration gradients due to mass transport were mostly neglected in previous research – especially in the electrolyte. Implementing the prevalent equations into the finite volume solver OpenFOAM and investigating mass transfer overpotentials in the electrolyte independently revealed that they can have a significant influence on the cell performance. So, the interplay between flow phenomena and electrochemical transport should be subject of future investigations.
Na||Zn batteries differ from the previously investigated “classical” LMBs, hence it is important to asses the possible flow phenomena and their area of occurrence.

  • Poster
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35495
Publ.-Id: 35495


Shell engineering in soft alginate-based capsules for culturing liver spheroids

Peng, X.; Janićijević, Ž.; Lemm, S.; Laube, M.; Pietzsch, J.; Bachmann, M.; Baraban, L.

We demonstrate the fluidics-based low-cost methodology to reproducibly generate the alginate and alginate-chitosan microcapsules and apply it to grow human hepatoma (HepG2) spheroids of different dimensions and geometries. Focusing specifically on the composition and thickness of the hydrogel shell, permeability of the microcapsules was selectively tuned. The diffusion of the selected benchmark molecules through the shell has been systematically investigated using both, experiments and simulations, which is essential to ensure efficient mass transfer and/or filtering of the biochemical species. Depending on available space, phenotypically different 3D cell assemblies have been observed inside the capsules, varying in the tightness of cell aggregations and their shapes. Metabolic activity of spheroids in microcapsules was confirmed by tracking the turnover of testosterone to androstenedione with chromatography studies in a metabolic assay. Because of the facile tuning of the shell thickness and permeability, we believe that our system is suitable for studying the formation of cancer spheroids and their functional interaction with the surrounding microenvironment.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35494
Publ.-Id: 35494


Energiespeicherung mit Flüssigmetallen und Salzschmelzen

Weier, T.; Horstmann, G. M.; Landgraf, S.; Personnettaz, P.; Stefani, F.; Weber, N.

Der zunehmende Anteil fluktuierender Stromerzeuger erfordert den Ausbau der Speicherkapazität, wenn die Elektrizitätsversorgung weitgehend nachfrageorientiert geschehen soll. Der Vortrag geht auf verschiedene Aspekte der Speicherproblematik ein und legt den Schwerpunkt dabei auf Flüssigmetall- und Salzschmelzenbatterien.

Keywords: Flüssigmetallbatterie; Salzschmelzenbatterie

  • Invited lecture (Conferences)
    Dresdner Seniorenakademie Wissenschaft und Kunst, 01.10.2022-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35493
Publ.-Id: 35493


Transport Phenomena in Liquid Metal Batteries

Weier, T.; Benard, S.; Horstmann, G. M.; Kim, C.; Klopper, T.; Kubeil, C.; Landgraf, S.; Personnettaz, P.; Stefani, F.; Weber, N.

There is a close and multifaceted relation between fluid dynamics and
the charge/discharge behavior of liquid metal batteries. The talk will
give an overview of experimental and - to a minor extend - numerical
work on instabilities that might be relevant for the operational
safety of large cells and on flows that are able influence mass
transport overvoltages, like solutal and thermal convection.

Keywords: liquid metal batteries; AMTEC; solutal convection; waves

  • Invited lecture (Conferences)
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-35492
Publ.-Id: 35492


X-ray particle tracking velocimetry in an overflowing foam

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

In mineral processing, froth flotation is based on recovering valuable mineral particles by means of the overflowing froth. Industrial-scale froth flotations cells are typically equipped with optical measurement systems, which monitor bubble sizes and flow velocities at the froth surface. However, the velocity profile of the overflowing froth underneath its free surface is not accessible by optical observation. The present study combines X-ray radiography and particle tracking velocimetry in a laboratory-scale experiment, aiming to measure local flow velocities within an opticially opaque foam at a horizontal overflow. For this purpose, we prepared custom-tailored tracer particles: light- weight tetrahedra with an edge length of 4 mm were 3D-printed from a polymer material, and metal beads of 0.5 mm in diameter glued at each corner of a tetrahedron served as radiopaque features. In parallel to the velocity measurements by means of X-ray particle tracking, we determined the liquid fraction of the overflowing foam by electric conductivity measurements using electrode pairs. The experiment was performed with aqeuous foams of two different surfactant concentrations, but similar bubble size range and superficial gas velocity, yielding around 10 % liquid fraction near the overflow. Employing the particles as tools for flow tracing in X-ray image sequences, we identified an unexpected velocity maximum underneath the free surface of the overflowing foam. In a sequel, we will compare the X-ray radiographic measurements with optical measurements of the foam flow velocity through a transparent wall and at the free surface.

Keywords: 3D printing; foam flow; froth flotation; tracer particles; X-ray radiography

Permalink: https://www.hzdr.de/publications/Publ-35490
Publ.-Id: 35490


Using ultrasound for characterizing overflowing froth

Knüpfer, L.; Emmerich, H.; Büttner, L.; Czarske, J.; Eckert, K.; Heitkam, S.

Flotation is a separation process in which hydrophobic particles inside a liquid bath
attach to uprising bubbles, which subsequently form a froth layer on the liquid
surface. This froth phase, which consist of foam with particles, has a large impact on
the transport of separated materials and therefore the overall process efficiency.
Despite the importance for process control, a notable lack of suitable techniques for
on-line characterization of the froth’s properties such as the liquid fraction or particle
content can be found. An potential approach to gain information on the different
phase fractions in froth is the application of low-frequency ultrasound measurement
techniques. In this contribution an overflowing froth containing varying mass fractions
of Quartz particles and liquid is analyzed using combined optical and ultrasonic
measurements. The measured intensity of the ultrasonic reflections sent from above
the froth’s surface correlate to the fraction of solids inside the froth (Figure 1).
Therefore it is shown, that current optical froth characterization techniques can be
improved by incorporating ultrasonic measurements, which can be seen as a first
step towards advanced process control in industrial flotation processes.

Keywords: froth; flotation; ultrasound

  • Poster
    4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), 25.-28.09.2022, Berlin, Deutschland
  • Poster
    Tagung Aufbereitung und Recycling, 10.-11.11.2022, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35489
Publ.-Id: 35489


A particle-center-averaged Euler-Euler model for bubbly flow simulations

Lyu, H.; Lucas, D.; Rzehak, R.; Schlegel, F.

An inconsistency exists in bubble force models used in the standard Euler-Euler simulations. The bubble force models are typically developed by assuming that the forces act on the bubbles' centers of mass. However, in the standard Euler-Euler model, each bubble force is a function of the local gas volume fraction because the phase-averaging method is used. This inconsistency can lead to gas over-concentration in the center or near the wall of a channel when the bubble diameter is larger than the computational cell size. Besides, a mesh-independent solution may not exist in such cases. In addition, the bubble dimension is not fully considered in the standard Euler-Euler model.
In the present study, a particle-center-averaging method is used to represent the bubble forces as forces that act on the bubbles' centers of mass. A particle-center-averaged Euler-Euler approach for bubbly flow simulations is developed by combining the particle-center-averaged Euler-Euler framework with a Gaussian convolution method. The convolution method is used to convert the phase-averaged and the particle-center-averaged quantities. The test results illustrate that the particle-center-averaging method alleviates the over-prediction of the gas volume fraction peak in the channel center and provides a mesh-independent solution. In the particle-center-averaged Euler-Euler model, the bubble dimension is fully considered and bubble deformation can be considered by using anisotropic diffusion in quantities conversion.

Keywords: CFD; bubbly flow; Euler-Euler

  • Lecture (Conference)
    International Conference on Numerical Methods in Multiphase Flows 4, 28.-30.09.2022, Venice, Italy

Permalink: https://www.hzdr.de/publications/Publ-35488
Publ.-Id: 35488


Future Liquid Metal Battery Projects at HZDR

Horstmann, G. M.; Weber, N.; Duczek, C.; Sarma, M.; Weier, T.

Since 2011, fluid dynamics research in liquid metal batteries has been pursued at HZDR, with multiple flow instabilities identified as critical for safe and efficient operation. This is still an ongoing process from which new research topics are constantly emerging. In the poster presentation, I will introduce two future research projects closely connected to liquid metal batteries: firstly, a new model experiment to study the metal pad roll instability, which is currently under preparation in the framework of a recently approved DFG project. Secondly, we are planning another project on the investigation of different solutal- and electrocapillary flow phenomena, hitherto widely disregarded in the context of liquid metal batteries.

  • Poster
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-35487
Publ.-Id: 35487


Advancements in the fabrication and characterization of actinide targets for superheavy element production

Düllmann, C. E.; Artes, E.; Dragoun, A.; Haas, R.; Jäger, E.; Kindler, B.; Lommel, B.; Mangold, K. M.; Meyer, C. C.; Mokry, C.; Munnik, F.; Rapps, M.; Renisch, D.; Runke, J.; Seibert, A.; Stöckl, M.; Thörle‑Pospiech, P.; Trautmann, C.; Trautmann, N.; Yakushev, A.

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

Keywords: Superheavy elements; Actinide targets; Heavy-ion beam; Target backing; Molecular plating; Thin film analytics

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Permalink: https://www.hzdr.de/publications/Publ-35486
Publ.-Id: 35486


Theory on Tidally Forced Planetary Waves in the Tachocline of Solar-like Stars

Horstmann, G. M.; Mamatsashvili, G.; Giesecke, A.; Stefani, F.

We present a new shallow-water formulation of forced magnetohydrodynamic Ross-
by waves originating in the tachocline of solar-like stars. As a novelty to former descriptions,
we add an external tidal potential to the equations and further include a linear damping law,
allowing us to study wave motions driven by arbitrary tidal forces. The model is applied to the
specific case of our sun, where we consider the action of the tidally dominant planet Jupiter.
We present an explicit analytic solution to this problem, which we finally use to estimate
characteristic responding wave amplitudes.

  • Lecture (Conference)
    5th Dynamo Thinkshop, 26.-28.06.2022, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35485
Publ.-Id: 35485


Electrolysis in Reduced Gravitational Environments: Current Research Perspectives and Future Applications

Akay, Ö.; Bashkatov, A.; Coy, E.; Eckert, K.; Einarsrud, K. E.; Friedrich, A.; Loos, S.; Röntzsch, L.; Mutschke, G.; Symes, M. D.; Yang, X.; Brinkert, K.

Electrochemical energy conversion technologies play a crucial role in space missions,
for example, in the Environmental Control and Life Support System (ECLSS) on the
International Space Station (ISS). They are also vitally important for future long-term
space travel for oxygen, fuel and chemical production, where a re-supply of resources
from Earth is not possible. Here, we provide an overview of currently existing
electrolytic energy conversion technologies for space applications such as proton
exchange membrane (PEM) and alkaline electrolyzer systems. We discuss the
governing interfacial processes in these devices influenced by reduced gravitation and
provide an outlook on future applications of (photo)-electrolysis systems in, e.g., in-
situ resource utilization (ISRU) technologies. A perspective of computational modelling
to predict the impact of the reduced gravitational environment on governing
electrochemical processes is also discussed and experimental suggestions to better
understand efficiency-impacting processes such as gas bubble formation and
detachment in reduced gravitational environments are outlined

Keywords: Electrolysis; Micro-Gravity; hydrogen production; energy conversion; computational methods

Permalink: https://www.hzdr.de/publications/Publ-35484
Publ.-Id: 35484


Magnetic properties of red diamonds produced by high-temperature electron irradiation

Barzola-Quiquia, J.; Osmic, E.; Lühmann, T.; Böhlmann, W.; Meijer, J.; Knolle, W.; Abel, B.

The magnetization of crystalline red diamond bulk samples were investigated in the temperature range between 2 K and 125 K and with the applied maximal magnetic field of ±7 T. The investigated diamond samples are of Type Ib with a nitrogen content less than 200 ppm. Diamonds without any treatment display a yellow color and were transformed to red color after irradiation with 10 MeV electrons at T = 900 °C, in vacuum, owing to the formation of nitrogen-vacancy centers. Field dependent magnetization m(H) measurements for temperatures T ≲ 10 K show unusual hysteresis loops, which we interpret as consequence of the superposition of coexisting superconducting and paramagnetic regions present in the sample. Temperature dependence of the magnetization m(T) measured in the zero field and field cooled modus shows a paramagnetic behavior accompanied with an irreversibility for T ≲ 13 K, while at higher temperatures shows a diamagnetic behavior which is similar to undoped diamond. Coexistence of superconductivity and paramagnetism is established because both phenomena exist in the same temperature range and fits done to the m(H) using an equation based upon Bean model, support our conclusion. Room temperature confocal photoluminescence measurements were done on both yellow and red diamond, showing that in the red diamond the amount of neutral NV° and negative charged nitrogen-vacancy centers NV° have been significantly created. The transformation process from yellow to red diamond has mainly caused the alteration of the superparamagnetic regions into paramagnetic, while the superconducting contribution of the sample was less affected, according to the parameters obtained after we fitted the field dependent magnetization results.

Permalink: https://www.hzdr.de/publications/Publ-35482
Publ.-Id: 35482


High-Pressure and High-Temperature Chemistry of Phosphorus and Nitrogen: Synthesis and Characterization of α- and γ‑P3N5

Ceppatelli, M.; Scelta, D.; Serrano-Ruiz, M.; Dziubek, K.; Izquierdo-Ruiz, F.; Manuel Recio, J.; Garbarino, G.; Svitlyk, V.; Mezouar, M.; Peruzzini, M.; Bini, R.

The direct chemical reactivity between phosphorus and nitrogen was induced under high-pressure and high-temperature conditions (9.1 GPa and 2000−2500 K), generated by a laser heated diamond anvil cell and studied by synchrotron X-ray diffraction, Raman spectroscopy, and DFT calculations. α-P3N5 and γ-P3N5 were identified as reaction products. The structural parameters and vibrational frequencies of γ-P3N5 were characterized as a function of pressure during room-temperature compression and decompression to ambient conditions, determining the equation of state of the material up to 32.6 GPa and providing insight about the lattice dynamics of the unit cell during compression, which essentially proceeds through the rotation of the PN5 square pyramids and the distortion of the PN4 tetrahedra. Although the identification of α-P3N5 demonstrates for the first time the direct synthesis of this compound from the elements, its detection in the outer regions of the laser-heated area suggests α-P3N5 as an intermediate step in the progressive nitridation of phosphorus toward the formation of γ-P3N5 with increasing coordination number of P by N from 4 to 5. No evidence of a higher pressure phase transition was observed, excluding the existence of predicted structures containing octahedrally hexacoordinated P atoms in the investigated pressure range.

Permalink: https://www.hzdr.de/publications/Publ-35481
Publ.-Id: 35481


Effect of Magnetic Impurities on Superconductivity in LaH10

Semenok, D. V.; Troyan, I. A.; Sadakov, A. V.; Zhou, D.; Galasso, M.; Kvashnin, A. G.; Ivanova, A. G.; Kruglov, I. A.; Bykov, A. A.; Terent'Ev, K. Y.; Cherepakhin, A. V.; Sobolevskiy, O. A.; Pervakov, K. S.; Seregin, A. Y.; Helm, T.; Förster, T.; Grockowiak, A. D.; Tozer, S. W.; Nakamoto, Y.; Shimizu, K.; Pudalov, V. M.; Lyubutin, I. S.; Oganov, A. R.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications.
On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH10, encounters a serious complication because of the large upper critical magnetic field Hc2(0), exceeding 120–160 T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH10: each at% of Nd causes a decrease in Tc by 10–11 K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68 T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H10 demonstrates completely linear Hc2(T) ∝ |T – Tc|, which calls into question the applicability of the Werthamer–Helfand–Hohenberg model for polyhydrides. The suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of Tc with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson’s theorem gives new experimental evidence of the isotropic (s-wave) character of conventional electron–phonon pairing in lanthanum decahydride.

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