Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41709 Publications

MgO-S3 - MgO-Spritzbeton für Streckenverschlüsse für HAW-Endlager im Steinsalz - Röntgen-CT und Positronen-Emissions-Tomographie

Kulenkampff, J.

Abstract

Die Herstellung und Zusammensetzung des MgO-Spritzbetons sind im Bericht des Projektkoordinators, dem Institut für Bergbau und Spezialtiefbau der TU Bergakademie Freiberg (FKZ 02E11769A), beschrieben.
Im Teilprojekt des HZDR wurden bildgebende Methoden angewendet, um die innere Struktur des Materials zu charakterisieren und die Art des Transports von Lösungen anhand prozesstomographischer Bildgebung aufzuklären. Hierfür wurde einerseits Mikrofokus-Röntgen-Computertomographie (µCT), andererseits Positronen-Emissions-Tomographie (PET) eingesetzt. Bei dem Material handelt es sich um Proben aus dem GV2-Bauwerk (Projekt CARLA II, FKZ 02C1204, Dammbauwerk im Carnallitit aus MgO-Spritzbeton mit Kieszuschlag), die nach einer Alterung über etwa 10 Jahre gewonnen wurden, sowie um frisch hergestellte Proben mit veränderter Rezeptur aus den Versuchen GSBV3 und GSBV4 (in-situ Großspritzbetonversuche mit Salzzuschlag). Eine Probe aus der GSBV4 konnte vor und nach der Durchströmung mit Salzlösung untersucht werden.
Die Proben in Bohrkerngröße wurden mit µCT strukturell charakterisiert. Die Tomogramme haben eine Auflösung von 50 µm. Dies erlaubt die Charakterisierung größerer Porenklassen und der Körnung.
Es zeigte sich, dass die Verteilung der Körnung und die Porenradienverteilung mit dem Abstand zur Betonierabschnittsgrenze (BAG) in charakteristischer Weise variieren: Mit Annäherung zur BAG nimmt der Anteil feiner Poren an der Gesamtverteilung zu, große Poren zeigen ein uneinheitliches Muster. Gleichzeitig nimmt der Anteil grober Körnung ab. Dieses Verhalten ist plausibel, weil große Körner nicht die BAG durchdringen können.
Die Zunahme des Anteils feiner Poren bedeutet eine homogenere, feinere Struktur des Materials in der Nähe der BAGs, aber nicht notwendig eine Abnahme der Permeabilität. Wegen der begrenzten Ausdehnung der Zone würde sich eine Veränderung der Permeabilität mittels üblicher Verfahren kaum nachweisen lassen, deshalb wurde das Fortschreiten einer mit ²²Na markierten Lösung mit Hilfe von Langzeit-PET-Aufnahmen dargestellt. Dies lieferte verlässlichere Information über den Prozessverlauf, insbesondere über dessen Homogenität oder präferentielle Wegsamkeiten.
Hierfür wurden spezielle Druckkammern und Injektionsverfahren entwickelt. Einerseits wurde ein Schutzring-Oberflächenpacker angewendet, wobei die Probe sich nicht unter einem Einspanndruck befand, andererseits wurde ein strahlungstransparentes Druckgefäß entwickelt, in dem sich die Probe unter hydrostatischem Einspanndruck befindet, wie dies für Permeabilitätsuntersuchungen gebräuchlich ist.
Es hat sich anhand der µCT-Untersuchungen gezeigt, dass die frischen Proben großräumig verbundene Poren besitzen können, deren maximale Ausdehnung von einigen Zentimetern nicht die Größe der Probe erreicht. Zwischen solchen porösen Bereichen befinden sich kurze Abschnitte, oft unterhalb einer Länge von 1 mm, die als Engstellen die bereits anfänglich geringe Permeabilität bewirken.
PET-Untersuchungen an solchen Proben zeigten den merklichen Einfluss solcher lokalen Wegsamkeiten. Sie konnten aber insofern nicht erfolgreich durchgeführt werden, weil die einsetzende – gemäß µCT-Untersuchungen isotrope – Expansion der Proben im Kontakt mit der Lösung Risse bewirkte.
Dagegen bleiben Proben nach Lösungsinjektion unter Einspanndruck intakt. Nach der Durchströmung mit Salzlösung zeigte es sich anhand der µCT-Bilder, dass auch eine eingespannte Probe merklich expandiert war, aber verbundene poröse Zonen weitgehend verschwunden waren. Vor allem hatte der Anteil von Poren mit Größen unter 1 mm signifikant abgenommen, größere Poren blieben als isolierte Objekte erhalten. PET-Untersuchungen im Anschluss daran zeigten keine präferentiellen Wegsamkeiten, sondern homogene Ausbreitung des Tracers.
Eine gealterte Probe aus dem GV2-Bauwerk wies ebenfalls isolierte Luftporen größer als 1 mm auf. In der PET-Untersuchung bewirkte eine solche angeschnittene und tiefer reichende Pore im Bereich der BAG ein anfängliches lokales Eindringen des Tracers bis in Zentimeter-Tiefe, darüber hinaus geschah die Ausbreitung der Lösung ebenfalls homogen, bei einer Permeabilität von 1e‑20 m².
Dieses Ergebnis weist darauf hin, dass durch den Kontakt mit Salzlösung und generell durch den Alterungsprozess ursprünglich vorhandene flächige Wegsamkeiten verschlossen werden und der anfänglich ablaufende räumlich heterogen verteilte Prozess danach unter signifikanter Reduktion des Porenanteils unterhalb des Millimeterbereichs durch langsamen homogenen Transport ersetzt wird.
Daraus folgt, dass als Untersuchungsmethodik für die strukturelle Analyse eine Kombination von Quecksilber-Kapillardruckmessungen (mercury injection porosimetry MIP), für die Charakterisierung der transportwirksamen Porosität, und µCT, zum Ausschluss verbundener makroskopisch poröser Bereiche, geeignet ist. Sofern solche verbundenen Bereiche ausgeschlossen werden können, lassen sich einfache homogene Rechenmodelle für Transportsimulationen einsetzen. Für die Verifikation, sowohl der Transportmodelle, als auch der räumlichen Homogenität des Prozesses, eignet sich die PET-Methodik.

Keywords: Positron Emission Tomography; Permeability; Porosity; µCT; MgO-shotcrete; Final repository; Salinar rock

Permalink: https://www.hzdr.de/publications/Publ-36810


The Asymmetry Quantification of Spin-Wave Dynamics in Single and Double Confined Rectangular Ni80Fe20 Microstrips

Pile, S.; Ney, A.; Lenz, K.; Narkovic, R.; Lindner, J.; Wintz, S.; Förster, J.; Mayr, S.; Weigand, M.

Abstract

Research of the spin-wave (SW) dynamics in confined rectangular microstructures is important for the their
potential use for information transport and processing [1]. The design of a microstructure can affect the SW be-
havior, which can be used as a manipulating mechanism [2, 3]. The development of planar microresonators/mi-
croantennas with a micro-coil (loop) allows for measuring FMR of a single ferromagnetic microstrip including
resonance lines corresponding to the SW excitations [4, 5]. TR-STXM [6] with the use of the planar microres-
onators enables direct, time-dependent imaging of the spatial distribution of the precessing magnetization across
the nm-thin microstrips during FMR excitation at the GHz frequency range with elemental selectivity [7, 8]
[...]

  • Lecture (Conference)
    IEEE Intermag 2023, 15.-19.05.2023, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-36809


Quantifying the spin-wave asymmetry in single and double rectangular Ni80Fe20 microstrips by TR-STXM, FMR and micromagnetic simulations

Pile, S.; Ney, A.; Lenz, K.; Narkovic, R.; Lindner, J.; Wintz, S.; Förster, J.; Mayr, S.; Weigand, M.

Abstract

The asymmetry of spin-wave patterns in confined rectangular Ni80Fe20 microstrips, both in single and double-strip geometries, is quantified. The results of time-resolved scanning transmission x-ray microscopy (TR-STXM) and micromagnetic simulations are compared. The micromagnetic simulations were set up based on the parameters determined from ferromagnetic resonance measurements at 14.015 GHz. For the TR-STXM measurements and the corresponding simulations the excitation was a uniform microwave field with a fixed frequency of 9.43 GHz, while the external static magnetic field was swept. In the easy axis orientation of the analyzed microstrip, the results show a higher asymmetry for the double microstrip design, indicating an influence of the additional microstrip placed in close proximity to the analyzed one.

Keywords: ferromagnetic resonance; magnonics; micromagnetic simulations; mumax3; spin-wave dynamics; spin-wave imaging; scanning transmission x-ray microscopy

Permalink: https://www.hzdr.de/publications/Publ-36808


Electronic Density Response of Warm Dense Matter: From Simulations to Experiments

Dornheim, T.

Abstract

Matter at extreme densities and pressures is ubiquitous throughout our universe and naturally
occurs in astrophysical objects such as giant planet interiors. In addition, such warm dense
matter (WDM) is important for technological applications such as inertial confinement fusion
and the discovery of novel materials. Consequently, WDM is routinely studied in experiments
at large research facilities around the globe, including NIF, LCLS, Omega, and the Sandia Z-
machine in the USA, SACLA in Japan, and the European XFEL in Germany.
In practice, the extreme conditions render the accurate diagnostics of WDM a formidable
challenge as even basic parameters such as the temperature cannot be directly measured, and
have to be inferred indirectly from other observations. In this context, a particularly important
property is given by the electronic density response to an external perturbation, which is
probed for example in X-ray Thomson scattering (XRTS) experiments.
In this talk, I give an overview of a number of recent developments in this field [1].
Specifically, I show how we can use state-of-the-art computational methods such as quantum
Monte Carlo (QMC) [2,3] and density functional theory (DFT) simulations [4] to model a
gamut of electronic density response properties of WDM with unprecedented accuracy. In
addition, I present a new approach that allows one to diagnose the temperature of arbitrary
materials from XRTS experiments in the imaginary-time domain without any simulations or
approximations [5]. Finally, I outline a strategy for future developments based on the close
interplay between simulations and experiments.
Keywords: Warm-dense matter, Inelastic X-ray scattering, Path-integral Monte Carlo,
Density functional theory
References:
[1] T. Dornheim et al., Phys. Plasmas 30, 032705 (2023)
[2] T. Dornheim, J. Vorberger, and M. Bonitz, PRL 125, 085001 (2020)
[3] M. Böhme, Zh. Moldabekov, J. Vorberger, and T. Dornheim, PRL 129, 066402 (2022)
[4] Zh. Moldabekov et al., J. Chem. Theory. Comput. 19, 1286-1299 (2023)
[5] T. Dornheim et al., Nature Comm. 13, 7911 (2022)

  • Lecture (others)
    Tel Aviv Universtiy invited seminar talk, 27.04.2023, Tel Aviv, Israel

Permalink: https://www.hzdr.de/publications/Publ-36807


Data publication: Energy response and spatial alignment of the perturbed electron gas

Dornheim, T.

Abstract

This repository contains the PIMC results presented in the publication "Energy response and spatial alignment of the perturbed electron gas"

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Permalink: https://www.hzdr.de/publications/Publ-36806


Data: Particle dispersions 3D characterization of chromite ore particles with different sizes

Da Assuncao Godinho, J. R.; Gupta, S.; Guimaraes Da Silva Tochtrop, C.

Abstract

Particle dispersions for 3D analysis using computed tomography prepared according to a standardized sample preparation procedure. 

Particles are from a Chromite ore (Kemi mine). Each sample has a specific size class.

Analysis of the data a published open source

Keywords: computed tomography; minerals engineering; raw materials; X-ray imaging; processing; MSPaCMAn; data; particles 3D

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Permalink: https://www.hzdr.de/publications/Publ-36805


Quantitative 3D characterization of chromite ore particles

Da Assuncao Godinho, J. R.; Gupta, S.; Guimaraes Da Silva Tochtrop, C.; Demanou Tekeng, R.; Hicks, M.; Ebert, D.; Ihanus, J.; Roine, A.; Liipo, J.; Renno, A.

Abstract

The main techniques used to characterize raw materials are currently bulk or 2D. This is a consequence of the current lack of standardized and automated methods to characterize particulate materials in 3D. Here, we apply a workflow to characterize a crushed chromite ore with nine particle size classes below 1 mm using X-ray computed tomography. All data processing of all samples follows the same sequence of steps, which means that the analysis can be automated with limited user input as opposed to traditional 3D image processing methods. Results of chromite composition, particle size distribution and chromite liberation are obtained for individual particles and compared with the results from x-ray diffraction and 2D-based automated mineralogy. The results shows a consistent accuracy across all size classes down to 75 μm. For the larger particle sizes (>600 μm) the chromite liberation curves are more consistent than those obtained from 2D-based automated mineralogy, possibly due to the stereological bias of 2D sections. The particle size distributions is the property for which the 2D bias is more contrasting with 3D. In conclusion, the workflow is more automatable (thus, faster and cheaper) and less bias (thus, more accurate and standardisable) than other 3D image analysis methods. Additionally, it stands as complementary to established techniques for particle-based characterization, especially to measure particle properties that 2D-based methods may not measure representatively. Further testing of the workflow in progressively more complex materials is necessary, but its potential to transform the way mineral particulate materials are characterized is demonstrated.

Keywords: computed tomography; minerals engineering; raw materials; X-ray imaging; processing; MSPaCMAn; chromite

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Permalink: https://www.hzdr.de/publications/Publ-36804


Spin pumping into a partially compensated antiferromagnetic/paramagnetic insulator

Buchner, M.; Lenz, K.; Ney, V.; Lindner, J.; Ney, A.

Abstract

Spin pumping from a metallic ferromagnet (FM) into an insulating antiferromagnet has been studied across the magnetic phase transition by means of temperature-dependent, broad-band ferromagnetic resonance (FMR) experiments. A set of spin pumping heterostructures consisting of Permalloy (Ni80Fe20) as FM and Zn1−xCoxO with x = 0.3, 0.5 and 0.6 (Co:ZnO) as antiferromagnetic insulator has been used where previous experiments have already pointed out the possibility of the existence of spin-pumping. The present experiment allow to reliably separate the various contributions of the temperature-dependent Gilbert damping parameter to the FMR line-width. A careful analysis of the obtained data demonstrates a significant increase of the temperature-dependence of the Gilbert damping parameter alpha(T ) around the magnetic phase transition of Co:ZnO which extends up to room temperature, confirming spin pumping into the fluctuating spin sink of an antiferromagnetic/paramagnetic insulator.

Keywords: spin pumping; ferromagnetic resonance; magnetic oxides

Permalink: https://www.hzdr.de/publications/Publ-36803


Non-destructive evaluation of ductile-porous versus brittle 3D printed vascular networks in self-healing concrete

Shields, Y.; Tsangouri, E.; Riordan, C.; de Nardi, C.; Da Assuncao Godinho, J. R.; Antonaci, P.; Palmer, D.; Al-Tabbaa, A.; Jefferson, T.; de Belie, N.; van Tittelboom, K.

Abstract

Additive manufacturing (AM) can produce complex vascular network configurations, yet limited testing has been done to characterize the damage and healing behavior of concrete with embedded networks for self-healing. In this study, different AM methods and network wall materials were used to produce vascular networks for self-healing concrete prisms, where their load-response behavior, healing efficiency and microstructure were evaluated using non-destructive techniques: acoustic emission (AE), ultrasonic pulse velocity (UPV), digital image correlation (DIC), and X -ray computed tomography (CT). The types of healing agent release mechanisms that were studied include a ductile-porous network that supplies fluid from its pores and a brittle network that fractures under load to release fluid. DIC coupled with AE verified debonding of ductile-porous networks from the cementitious matrix, and was able to track damage progression as well as healing for all networks with load regains up to 56% and stiffness regains up to 91% using polyurethane.

Keywords: vascular networks; self-healing concrete; 3D printing; non-destructive testing

Permalink: https://www.hzdr.de/publications/Publ-36802


Accurate temperature diagnostics for matter under extreme conditions

Dornheim, T.

Abstract

The experimental investigation of matter under extreme densities and temperatures, as in
astrophysical objects and nuclear fusion applications, constitutes one of the most active frontiers at
the interface of material science, plasma physics, and engineering. The central obstacle is given by
the rigorous interpretation of the experimental results, as even the diagnosis of basic parameters like
the temperature T is rendered difficult at these extreme conditions. Here, we present a simple,
approximation-free method [1,2] to extract the temperature of arbitrarily complex materials in
thermal equilibrium from X-ray Thomson scattering experiments, without the need for any
simulations or an explicit deconvolution. Our paradigm can be readily implemented at modern
facilities and corresponding experiments will have a profound impact on our understanding of warm
dense matter and beyond, and open up a variety of appealing possibilities in the context of
thermonuclear fusion, laboratory astrophysics, and related disciplines.
[1] T. Dornheim, M. Böhme, D. Kraus, T. Döppner, Th. Preston, Zh. Moldabekov, and J. Vorberger,
Accurate temperature diagnostics for matter under extreme conditions, Nature Comm. 13, 7911
(2022)
[2] T. Dornheim, M. Böhme, D. Chapman, D. Kraus, T. Döppner, Th. Preston, Zh. Moldabekov, and
J. Vorberger, Temperature analysis of X-ray Thomson scattering data, arXiv:2212.10510

  • Lecture (Conference)
    Optics & Photonics International Congress, 17.-21.04.2023, Tokio, Japan

Permalink: https://www.hzdr.de/publications/Publ-36801


Polymorph Conversion in Gallium Oxide via Focused Ion Beam Irradiation

Bektas, U.; Chekhonin, P.; Klingner, N.; Hlawacek, G.

Abstract

Monoclinic gallium oxide (β-Ga2O3) is the chemically and thermally most stable compound, compared to its other four polymorphs, with an ultra-wide bandgap of 4.9 eV. It is a promising semiconductor material for power electronics, optoelectronics, and batteries. However, controlling the metastable polymorph phases is quite hard, and the fabrication technology at the nanoscale is immature. Our goal is to understand polymorph conversion. Controlling the crystalline structure will allow us to establish new fabrication methods of single-phase polymorph coatings, buried layers, multilayers, and different nanostructures in Ga2O3 using focused ion beams (FIBs). The research aims to better understand and control the polymorph conversion with special emphasis on laterally resolved modifications by utilizing focused ion beams.
In a previous study, our project partners Kuznetsov et.al. [1] demonstrated the ion-beam-induced β-to-κ phase transformation in Ga2O3 as shown in Fig.1. However, later, Garcia Fernandez et.al. [2] showed that the monoclinic β-phase actually transforms into the cubic γ-phase.
Here, we used Helium Ion Microscopy (HIM) and other focused ion beams (FIBs) to locally irradiate the (-201) oriented β-Ga2O3 sample with different ions (Ne, Co, Nd, Si, Au, In) to induce the polymorph transition. The successful conversion into γ- Ga2O3 under Ne+ irradiation (Fig.2(a)) has been confirmed using Electron Backscattered Diffraction (EBSD) and indexing the Kikuchi patterns (Fig.2(b)). Furthermore, Positron Annihilation Lifetime Spectroscopy (PALS) was performed for broad beam irradiated implants to better understand the fluence-dependent creation and distribution of defects. Transmission Electron Microscopy (TEM) images also provide information about the distinct and sharp interfaces between different polymorphs of Ga2O3. The first results indicate that the damage/strain created by the FIB irradiation leads to a local transformation of β- Ga2O3 to γ- Ga2O3.

Keywords: Gallium Oxide; Helium Ion Microscopy; Focused Ion Beam; Positron Annihilation Lifetime Spectroscopy; Polymorph Transition

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  • Lecture (Conference)
    6th EUFN Workshop 2023, 07.-09.06.2023, Zurich, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36800


Mapping the gas fraction distribution in bubble flows through open-porous foams by radiographic imaging

Lappan, T.; Jiao, G.; Michak, R. L.; Loos, S.; Shevchenko, N.; Trtik, P.; Eckert, K.; Eckert, S.

Abstract

The cost-efficient production of green hydrogen using renewable energies requires next-generation proton exchange membrane (PEM) electrolysers to be operated at higher current density. Under this new operating condition, the elevated temperature of the ultra-pure water and its supersaturation with oxygen on the anode side have strong effects on the formation and transport of gas bubbles. The resulting gas-liquid two-phase flow through the porous transport layer at the membrane electrode assembly is characterised by up to 50 % gas fraction, which is exceptionally high. Such a foam-like flow within the porous medium is not accessible by optical measurements. Instead, we performed imaging flow measurements by means of time-resolved radiography using polychromatic X-rays as well as thermal neutrons at 100 frames per second imaging frame rate. On a laboratory scale, we aimed to study the bubble transport by mapping the local gas fraction distribution over time. This conference contribution presents two model experiments with open-porous metal and polymer foams, namely made of nickel and polyurethane, showcasing the advantages but also limitations of X-ray and neutron radiography for investigating bubble transport phenomena within such foam structures. In both experiments, foam samples of approximately 70 mm x 70 mm in width and height were sandwiched between the X-ray- or neutron-transparent front and back windows of a vessel filled with deionised water. As neutrons are strongly attenuated in water, the thickness of the water-filled vessel and the foam sample were set to 5 mm along the beam direction in all measurements. Bubbles were generated continuously by injecting compressed air at different but constant volumetric flow rates through a single hollow needle releasing the bubbles directly into the water-soaked foam. Based on calibration radiographs acquired both in the absence and presence of water, quantitative image analysis yielded a pixelwise mapping of the gas fraction at approximately 0.06 mm image pixel size without binning. While X-ray radiography visualised the pulsating transport of bubble plumes through a nickel foam of 1.2 mm pore size, neutron radiography gave insights into the jumping motion of single bubbles through a polyurethane foam of approximately 3 mm pore size. In conclusion, we characterised the gas transport depending on the volumetric gas flow rate, the bubble size in relation to the foam pore size and the wettability of the inner foam surface. Further radiographic studies will consider bubble flows through open-porous materials with different pore geometry or functionalised surface wettability.

Keywords: gas-liquid two-phase flow; metal foam; neutron radiography; polymer foam; X-ray radiography

  • Lecture (Conference)
    93rd Annual Meeting of the International Association of Applied Mathematics and Mechanics, 30.05.-02.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36799


Combining optical and X-ray measurements of an overflowing foam

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

Abstract

The flow behaviour of liquid foam is of central importance in froth flotation for mineral processing. Flotation separates valuable mineral particles from gangue material based on the surface wettability. To this end, the solids are finely ground and suspended in an aqueous solution with flotation reagents. In aerated flotations cells, gas bubbles selectively attach to the hydrophobic mineral particles, rise to the surface, and form a froth. To recover the valuables, they are transported out of the flotation cell with the froth. In flotation plants, the recovery of solid and liquid is monitored by optical observation of the overflowing froth. However, this monitoring is limited to the free surface of the particle-laden froth. Aiming for detailed insights into the flow behaviour underneath the surface-near foam bubbles, the laboratory-scale experiment in this work investigates the velocity field of an overflowing foam in combined optical and X-ray measurements. For this purpose, foam was generated continuously, moved similar to a plug-flow in a vertical channel with rectangular cross-section, and flowed off over a one-sided horizontal weir into the open surrounding. The imaging measurements focused on the foam flow in the region of interest around the weir. Simultaneously, the liquid fraction of the foam was monitored by measuring its electric conductivity between electrode pairs mounted near the weir. We used aqueous foams of two different surfactant concentrations but similar bubble size range and superficial gas velocity, yielding around 10 % liquid fraction. The optical measurements carried out through the transparent side wall of the flow channel as well as at the free surface of the overflowing foam. They captured light reflections on the foam bubbles were analysed by an adapted particle image velocimetry algorithm. While the opacity of the foam limits optical measurements to the wall- or surface-near foam bubbles, our approach of X-ray particle tracking velocimetry with custom-tailored tracer particles sheds light on the velocity field in a truly three-dimensional measurement volume. We prepared tracers consisting of small 3D-printed polymer tetrahedra with tiny metal beads glued to the tetrahedral tips. Owing to their shape and the light-weight material composite, these tracers adhered to the bubble-scale foam structure and, therefore, were carried with the foam flow very well. X-ray radiography visualised the motion paths of each tracer’s metal beads, representing the local streamlines of the foam flow. Besides, the X-ray images mapped the liquid fraction distribution in the entire field of view, i.e. also directly at the weir, thus extending the local measurement of the liquid fraction by means of the electrode pairs. The tracer-based X-ray measurements revealed the velocity profile increasing in vertical direction above the weir, whereas the optical flow measurements were subjected to wall and surface effects, resulting in lower velocities. Combining all measurement results, we identified an unexpected velocity maximum underneath the free surface of the overflowing foam.

Keywords: froth flotation; particle image velocimetry; particle tracking velocimetry; tracer particles; X-ray radiography

  • Poster
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36798


Comparative saturation binding analysis of ⁶⁴Cu-labeled somatostatin analogs using cell homogenates and intact cells

Ullrich, M.; Brandt, F.; Löser, R.; Pietzsch, J.; Wodtke, R.

Abstract

The development of novel ligands for G-protein-coupled receptors (GPCRs) typically entails the characterization of their binding affinity, which is often performed with radioligands in a competition or saturation binding assay format. Since GPCRs are transmembrane proteins, receptor samples for binding assays are prepared from tissue sections, cell membranes, cell lysates, or intact cells. As part of our investigations on modulating the pharmacokinetics of radiolabeled peptides for improved theranostic targeting of neuroendocrine tumors with a high abundance of the somatostatin receptor sub-type 2 (SST₂), we characterized a series of ⁶⁴Cu-labeled [Tyr³]octreotate (TATE) derivatives in vitro in saturation binding assays. Herein, we report on the SST₂ binding parameters measured toward intact mouse pheochromocytoma cells (MPC) and corresponding cell lysates and discuss the observed differences taking the physiology of SST₂ and GPCRs in general into account. Furthermore, we point out method-specific advantages and limitations.

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  • ZRT

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Permalink: https://www.hzdr.de/publications/Publ-36797


The complex chemistry of light actinides

März, J.

Abstract

The actinides (An) are located at the bottom of the periodic table. These elements are exclusively radioactive, highly chemo-toxic, and play an important role in chemical engineering and environmental science related to the nuclear industry or nuclear waste repositories. In contrast to the strongly shielded 4f electrons of the lanthanides, 5f electrons of particularly the early An are found to participate in bonding, e.g. to organic ligands. Another characteristic of the An is their huge variety of possible oxidation states, typically ranging from +II to +VII for early actinides, making their chemistry complex but interesting. A suitable approach to explore fundamental physico-chemical properties of the actinides is to study series of isostructural An compounds in which the An is in the same oxidation state. Observed changes in e.g. the binding situation or magnetic effects among the An series may deliver insight into their unique electronic properties mainly originating from the f-electrons. A question still remaining in the field of An chemistry is the degree of “covalency” in compounds across the actinide series, which may be addressed by systematic studies on series of An compounds, including transuranium (TRU) elements.
We investigate the coordination chemistry of low-valent actinides using organic N-, O-, or S-donor ligands. Information on covalency trends as well as mutual ligand influences can be obtained by the analysis of solid-state structures derived by SC-XRD in combination with quantum chemical calculations (QCC) and high-energy-resolution fluorescence detection X-ray absorption near edge spectroscopy (HERFD-XANES). In solution, NMR spectroscopy permits to draw conclusions about the complex speciation in solution, the intrinsic magnetic properties of the actinides, or subtle changes in covalency in the ligand-actinide-bonding.

Keywords: actinides; transuranium; covalency; coordination chemistry

  • Invited lecture (Conferences)
    Öffentlicher Vortrag Department Chemie, 10.07.2023, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36796


Data publication: Halomonas gemina sp. nov. and Halomonas llamarensis sp. nov., two siderophore-producing organisms isolated from high-altitude salars of the Atacama Desert

Hintersatz, C.; Singh, S.; Antonio Rojas, L.; Kretzschmar, J.; Wei, T.-S.; Khambhati, K.; Kutschke, S.; Lehmann, F.; Singh, V.; Jain, R.; Pollmann, K.

Abstract

The effect of various media components on the production of desferrioxamine E by Halomonas gemina ATCH28 was investigated. Concentration of the compound was determined via HPLC using commercially available desferrioxamine E as standard for calibration.

Keywords: Halophilic bacteria; siderophores; polyphasic taxonomic; desferrioxamine E; Atacama Desert

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Permalink: https://www.hzdr.de/publications/Publ-36794


Bayes Spaces, An overview

van den Boogaart, K. G.

Abstract

Bayes Hilbert spaces \(B^2(P)\) describe a Hilbert space structure
on a set of mutally continues probability measures, improper priors
and likelihoods with origin \(P\).

The talk will give an overview of Bayes Spaces and their relation to
various concepts of mathematical statistics. Several deep results of
statistics and information theory become obvious and geometrically
intuitive corrolaries, when viewed in the light of this vector space
structure.

The name comes from the fact that vector addition in this space is
given by Bayes theorem. A distribution family is an exponential
family if and only if its a finite dimensional subspaces of a Bayes
Space. In case of regular exponential families its a Bayes Hilbert
Space. The geometry of the space is closely related to Fisher
information. There is a cannocial isometric mapping to \(L^2_0(P)\)
called centered log ratio transform, proving score functions. The
\(P\)-a.s. constant ratio of this centred log ratio transform to the
log density is Kulback Leibler Divergence. The Basis vectors of
conjugated priors can be directly interpreted in terms of
information and the basis of the original family. I.e. we explicitly
give the conjugated prior for every exponential family.

In a multivariate setting, we can identify conditional distributions
with qotient spaces, and provide a straight forward decomposition
into a sum of products of marginal spaces closely related to the
Hammersley Clifford Theorem, Graphical models and generalizing
log-linear models to continues distributions.

Keywords: Information Theory; Mathematical Statistics; Inference; Exponential Families

  • Invited lecture (Conferences)
    Olomoucian Days of Applied Mathematics 2023, 12.-14.06.2023, Olomouc, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-36792


Bioaerosols Spreading in Confined Spaces

Cavagnola, M. A.; Hampel, U.; Lecrivain, G.

Abstract

Ultraviolet germicidal irradiation has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne virus/bacteria inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between the microorganism particles and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to the physical reality of the inactivation process, i.e. that the ultraviolet inactivation effect is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against published data of inactivation of aerolized Escherichia coli bacteria in a UV-reactor.

  • Poster
    CORAERO PhD School, 07.11.2022, Technische Universität München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36791


Photonic Model for Airborne Viruses/Bacteria Inactivation by UV-Radiation

Cavagnola, M. A.; Eßlinger, F.; Hampel, U.; Ebert, G.; Lecrivain, G.

Abstract

Since the coming of the COVID-19 pandemic in 2019, virus spreading in confined spaces has been in the spotlight. Ultraviolet germicidal irradiation has proven to be an efficient method of rendering airborne microorganisms inactive. In the present study, a novel model for airborne virus/bacteria inactivation using UV-light is presented. A particle-to-particle photonic approach that takes into account each of the interactions between the microorganism particles and UV-light photons is obtained. The main advantage of the presented model is its faithfulness to the physical reality of the inactivation process, i.e. that the ultraviolet inactivation effect is a stochastic process not a deterministic one. This characteristic allows the model to track and calculate the inactivation success for each of the single particles conforming a particle cloud. The model is validated against published data of inactivation of aerolized Escherichia coli bacteria in a UV-reactor and will be validated experimentally using a seasonal coronavirus in a Potential Aerosol Mass Oxidation Flow Reactor at the Helmholtz-Zentrum in Munich.

  • Lecture (Conference)
    DECHEMA 2023/Aerosoltechnik, 29.03.2023, Paderborn Universität, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36790


PICMI: Simulation input meta-data standardisation for Particle-in-Cell(PIC) codes

Marre, B. E.; Tröpgen, H.; Tippey, K. E.; Kluge, T.; Schlenvoigt, H.-P.; Debus, A.

Abstract

Publishing raw PIC-simulation results according to the FAIR principle is difficult,
primarily size with a single large simulation's raw data reaching 100s TeraByte up to
1-2 PetaByte.
Fulfilling the FAIR principles therefore requires a different approach, with only
compressed results and simulation setup/initial state made directly available in direct
access public data bases.
This assures findability of simulations if initial conditions are automatically searchable, makes raw data on slow, high capacity archive storage accessible for specific simulations of interest, or allows rerunning the same simulation if additional data is required.

This is currently hindered by the different historically grown input description standards of different PIC-codes.

Simulation setups can neither be parsed, searched or understood without implementing a dedicated parser for each code and with more than 4 PIC-simulation codes, (PIConGPU, WARPX, Smilei, PICLS, ...) in use at HZDR alone this is unfeasible.
To realise the above a common standardized description for PIC-codes is needed. PICMI is being implemented and developed by HZDR and Berkley Labs for this purpose.
Besides fulfilling the above requirements, PICMI will also allow reuse of user interfaces between codes, make the simulations more accessible to users and allow using a common setup for different codes thereby al Bytelowing easy direct comparisons between codes for better reproducibility as well as lay the ground work for automated machine learning on simulations.

Keywords: PICMI; PIConGPU; meta data standarisation; simualtions; Particle in Cell; PIC; Daphne NFDI; Daphne

  • Poster
    DAPHNE4NFDI Annual meeting 2023, 03.-05.04.2023, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36789


Atomic Population Kinetics for Particle in Cell

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

Abstract

Atomic Population Kinetics for ParticleInCell

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 PIC simulation framework PIConGPU
to allow us to model atomic population kinetics in-situ in PIC-Simulations, in transient
plasmas and without assuming any 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 of ions in transient plasma conditions,
as typically encountered in laser accelerator 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 physics; FLYonPIC; Particle in Cell; PIC; PIConGPU; excited atomic states

  • Lecture (Conference)
    43rd Workshop on High-Energy-Density Physics with laser and Ion beams, 30.01.-03.02.2023, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36788


Improved Planar Hall Effect sensors for fluid measurement techniques

Schmidtpeter, J.; Wondrak, T.; Makarov, D.; Zabila, Y.

Abstract

Inductive flow measurement techniques such as the Contactless Inductive Flow Tomography require sensors that provide a magnetic field resolution of 1 nT while operating in magnetic fields of several mT. With advancements in state-of-the-art magnetoresistive thin-film sensors the required behavior regarding sensitivity, precision and hysteresis can be achieved [1]. Planar Hall Effect sensor have been shown to be one of the leading sensor types in this area. Therefore we present a detailed study on the effect of different sensor layouts, geometries, magnetic flux concentrators and other parameters on the characteristics of single layer Permalloy Planar Hall Effect sensors. [1] Granell, Pablo Nicolás, et al. npj Flexible Electronics 3.1 (2019): 1-6.

Keywords: Planar Hall Effect; Sensors; DPG

  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (SKM), 31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36787


Growth twins and premartensite microstructure in epitaxial Ni-Mn-Ga films

Kar, S.; Ikeda, Y.; Lünser, K.; George Woodcock, T.; Nielsch, K.; Reith, H.; Maaß, R.; Fähler, S.

Abstract

Magnetic shape memory alloys have been examined intensively due to their multifunctionality and multitude of
physical phenomena. For both areas, epitaxial films are promising since the absence of grain boundaries is beneficial for applications in microsystems and they also allow to understand the influence of a reduced dimension on the physical effects. Despite many efforts on epitaxial films, two particular aspects remain open. First, it is not
clear how to keep epitaxial growth up to high film thickness, which is required for most microsystems. Second, it
is unknown how the microstructure of premartensite, a precursor state during the martensitic transformation,
manifests in films and differs from that in bulk.
Here, we focus on micrometer-thick austenitic Ni-Mn-Ga films and explain two distinct microstructural features
by combining high-resolution electron microscopy and X-ray diffraction methods. First, we identify pyramid-
shaped defects, which originate from {1 1 1} growth twinning and cause the breakdown of epitaxial growth.
We show that a sufficiently thick Cr buffer layer prevents this breakdown and allows epitaxial growth up to a
thickness of at least 4 μm. Second, premartensite exhibits a hierarchical microstructure in epitaxial films. The reduced dimension of films results in variant selection and regions with distinct premartensite variants, unlike its
microstructure in bulk.

Keywords: Epitaxial films; Magnetic shape memory alloy; Twinning; Premartensite; Hierarchical microstructure

Permalink: https://www.hzdr.de/publications/Publ-36786


THEREDA: Polythermal extension of the Pitzer database for strontium

Bok, F.; Moog, H. C.; Voigt, W.

Abstract

INTRODUCTION
Radioactive strontium isotopes are products of the fission of uranium in the context of nuclear energy production. Furthermore, strontium is often used in geochemical calculations as an analog for radium, both being alkaline earth metals.
In the THEREDA database [1,2], a thermodynamic Pitzer dataset for Sr in the system of oceanic salts (Na⁺, K⁺, Mg²⁺, Ca²⁺ | Cl⁻, SO₄²⁻ – H₂O) is available [3]. Yet, this dataset is valid for the temperature T = 25 °C only. However, several strontium solid phases show a large variation in solubility with temperature, e.g. strontium chloride hydrates (SrCl₂∙xH₂O with x = 6, 2 and 1) [4] or strontium hydroxide (Sr(OH)₂∙8H₂O) [5].
In this work, a polythermal extension of the existing Sr dataset for the chloride system is presented, which is valid in the range T = 0–100 °C.

DESCRIPTION OF THE WORK
Experimental data (osmotic coefficients) from literature were used to generate a temperature function for the binary Pitzer interaction coefficients (β⁰, β¹, and CΦ). Solubility data of SrCl₂ in water [4] were then used to parameterize temperature functions for the solubility products of the different strontium chloride hydrates. Consistency with the existing 25 °C data set was ensured.
Solubility data of SrCl₂ in water [4] were then used to parameterize temperature functions for the solubility products of the different strontium chloride hydrates. Polythermal expansions of the ternary Pitzer coefficients also were required for a few subsystems only.
Furthermore, the data set was extended to quaternary acidic systems (Sr²⁺, H⁺ | Cl⁻ – H₂O).

RESULTS
With the obtained dataset, it is possible to model the ternary system (Sr²⁺, Na⁺ | Cl⁻ – H₂O) in the temperature range T = 0–100 °C. The solubility of all known solid phases is correctly reproduced, see Fig. 1. The dataset now also allows polythermal calculation of higher systems such as the quaternary system (Sr²⁺, Na⁺, K⁺ | Cl⁻ – H2O) in the temperature range for which experimental solubility data are available (T = 15–50 °C), see Fig. 2. For those two systems, no adjustment of the existing ternary Pitzer interaction coefficients was necessary.
The presented polythermal extension of the strontium Pitzer model allows robust calculation of the geochemical behavior of strontium in the chloride system over a wide temperature range. This extension of the THEREDA data set will become part of the next official data release and will be complemented by polythermal data for strontium sulfate (SrSO₄) and hydroxide (Sr(OH)₂∙8H₂O) in future work.

ACKNOWLEDGMENTS
THEREDA is funded by the German “Bundesgesellschaft für Endlagerung (BGE)”, contract number 45181017.

REFERENCES
1. THEREDA – Thermodynamic Reference Database. Release 2021, https://www.thereda.de/, (2022).
2. H. C. Moog et al., “Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA)” Appl. Geochem., 55, 72–84 (2015), DOI: 10.1016/j.apgeochem.2014.12.016.
3. T. Scharge “Thermodynamic model for the systems Sr – Na, K, Mg, Ca – Cl, SO₄ – H2O at 298.15 K”, THEREDA Report (2016).
4. B. S. Krumgalz “Temperature Dependence of Mineral Solubility in Water. Part I. Alkaline and Alkaline Earth Chlorides” J. Phys. Chem. Ref. Data, 46, 043101, DOI: 10.1063/1.5006028.
5. I. Lambert et al. “Alkaline Earth Hydroxides in Water and Aqueous Solutions” IUPAC Solubility Data Series Vol. 52, Pergamon Press, Oxford, 388 p.

Keywords: THEREDA; Strontium chloride; Thermodynamic data; Solubility; Pitzer activity model

  • Lecture (Conference)
    Actinide and Brine Chemistry in a Salt Repository Workshop VII (ABC Salt VII), 15.-16.06.2023, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-36785


Experimental prompt gamma-ray timing data for proton treatment verification in a clinical facility using a fixed beam

Werner, T.; Hueso-González, F.; Kögler, T.; Petzoldt, J.; Schellhammer, S.; Pausch, G.
Project Leader: Pausch, Guntram; ContactPerson: Schellhammer, Sonja; ContactPerson: Kögler, Toni; ResearchGroup: Berthold, Jonathan; ResearchGroup: Römer, Katja; ResearchGroup: Rinscheid, Andreas

Abstract

This dataset comprises the data reported on by Werner et al. (2019) in Phys. Med. Biol. 64 105023, 20pp (https://doi.org/10.1088/1361-6560/ab176d). Please refer to this publication for details on the experimental setup, data acquisition and preprocessing. The process is summarised in the following.

A static, pulsed pencil beam was delivered to a target without and with cylindrical air cavities of 5 to 20 mm thickness and prompt gamma-ray timing distributions were acquired.

Experimental setup:

A homogeneous cylindrical phantom comprised of poly(methylmethacrylate) was used. Air cavities of varying thickness ∆R ∈ {0 mm, 5 mm, 10 mm, 20 mm} were successively introduced into the phantom to mimic anatomical variations leading to range deviations. For each air cavity thickness, the phantom was irradiated with proton pencil beams of two different kinetic energies (E_1 = 162 MeV and E_2 = 227 MeV) and a micropulse repetition rate of 106.3 MHz. Prompt-gamma ray timing distributions were measured with a detection unit consisting of a single ∅2 ” × 2 ” CeBr_3 crystal by Scionix, a Hamamatsu R13089-100 photomultiplier and a U100 digital spectrometer by Target Systemelektronik, which was placed at a backward angle of 130° . A static pencil beam was directed centrally at the phantom. The beam was pulsed in spots with a spot duration of 69 ms, a period of 72 ms and 1e9 (!) protons per spot (corresponding approximately to the combined signal of 8 prompt-gamma ray detection units for one strongly weighted clinical pencil beam scanning spot). One measurement consisted of 100 spots. Overall, the experiment comprised eight measurements covering the set of four cavity thicknesses ∆R and two beam energies E_1 and E_2. Experiments were carried out in the patient treatment room of OncoRay, Dresden.

Data preprocessing:

The raw data of each measurement was preprocessed as follows: The binary data was converted to ROOT. The photomultiplier gain drift was corrected for and the integral signal charge was converted into deposited energy. Time digitalisation nonlinearities were corrected for. The calibrated data was then saved in list-mode format. The data was assigned to the spot number and the detection time relative to the accelerator radiofrequency (fine time) was used to populate a prompt gamma-ray timing histogram for each spot. No background or phase shift correction were applied.

Data structure:

The dataset contains one root file for each measurement, named by the detector number in the format u100-p00XX and the measurement time. The spreadsheet MeasurementIndex_20160716_SingleSpot.xlsx contains the details of each measurement. The corrected and calibrated PGT spectra can be found in the root file at analysis/05_PGT_for_Layers_and_Spots.

Each root file contains the following directories:

  • analysis

    • 01_Layers_and_Spots_Detection: association between spot number and measurement time

    • 02_Gain_Correction: energy gain drift correction curve

    • 03_Energy_Calibration: energy calibration curve

    • 04_Fine_Time_Linearization: timing non-linearity calibration curve

    • 05_PGT_for_Layers_and_Spots: final PGT spectra - for each spot of each layer:

      • PGT_*_all: timing spectrum of the whole energy range

      • PGT_*_2,5to7MeV:  timing spectrum for events between 2.5 and 7 MeV only

      • PGT_*_3to5MeV: timing spectrum for events between 3 and 5 MeV only

      • ESpec: energy spectrum

      • EoT: two-dimensional energy-timing spectrum

  • data: list-mode data (not histogrammed)

    • uncorrected: before the correction and calibration steps

    • corrected: after the correction and calibration steps

  • meta: measurement meta data (log file containing applied detector HV etc.)

  • histograms: selected example histograms

For further questions, please refer to the contact persons stated in the Contributors section.

Keywords: proton therapy; treatment verification; prompt gamma-ray timing; experimental data

Involved research facilities

  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-36784


Evidence for a High-Valent Iron-Fluoride That Mediates Oxidative C(sp3)‐H Fluorination

Panda, C.; Anny-Nzekwue, O.; Doyle, L. M.; Gericke, R.; McDonald, A. R.

Abstract

(Fe(II)(NCCH₃)(NTB))(OTf)₂ (NTB = tris(2- benzimidazoylmethyl)amine, OTf = trifluoromethanesulfonate) was reacted with difluoro(phenyl)-λ³-iodane (PhIF₂) in the presence of a variety of saturated hydrocarbons, resulting in the oxidative fluorination of the hydrocarbons in moderate-to-good yields. Kinetic and product analysis point towards a hydrogen atom transfer oxidation prior to fluorine radical rebound to form the fluorinated product. The combined evidence supports the formation of a formally Fe(IV)(F)₂ oxidant that performs hydrogen atom transfer followed by the formation of a dimeric μ-F−(Fe(III))₂ product that is a plausible fluorine atom transfer rebound reagent. This approach mimics the heme paradigm for hydrocarbon hydroxylation, opening up avenues for oxidative hydrocarbon halogenation.

Keywords: high-valent iron; fluorination; hydrogen atom transfer; proton coupled electron transfer; fluorine atom transfer

Permalink: https://www.hzdr.de/publications/Publ-36782


Laser cutting of polymer templates for water-droplet induced self-folding of micron cubes: hinge geometry optimization

Lorenz, P.; Franz, R.; Ehrhardt, M.; Lecrivain, G.; Kirchner, R.; Zimmer, K.

Abstract

Droplet-induced self-folding processes enable the easy and cost-effective fabrication of submillimeter 3D structures from planar templates. These templates were fabricated by laser cutting of polymer foils that offers a high flexibility in design. The interaction of water droplets with template surfaces induces a surface tension force that causes deformation of the laser-cut templates needed to form the 3D structures. In this study, laser patterning of 25 µm thick polyimide (PI) foils by UV ultrashort pulse laser ablation was used to systematically investigate the effect of hinge thickness on the bending and self-folding process of cubes. The deposition of water droplets on the laser-structured samples leads to forces that move the side faces of the cube template causing a defined deformation of the hinges of the PI template and resulting in a bending angle between hinged template regions. The bending angle was determined as a function of hinge geometry and water droplet volume. The bending angle is increased with increasing droplet volume below a certain maximum, but decreased with increasing hinge thickness and width. The results provide guidelines for experimental optimization and reference data for computer-aided optimization of water droplet-induced self-folding of 3D structures.

Keywords: ps-laser; laser cutting; self-folding; water droplet

Permalink: https://www.hzdr.de/publications/Publ-36781


Data publication: Enantioselective Synthesis, Structure Activity Relationship, Radiofluorination and Biological Evaluation of [18F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET

Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Bormans, G.; Kopka, K.; Brust, P.; Moldovan, R.-P.

Abstract

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation in various pathological conditions, such as neuroinflammation and cancer. Herein we report on the enantioselective synthesis of a series of highly affine fluorinated indole-2-carboxamide ligands targeting the CB2R in the brain. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity (Ki = 2.1 nM) and pronounced selectivity over CB1R (factor > 300). A fully automated copper-mediated radiofluorination of [18F]RM365 was established starting from the corresponding aryl boronic acid pinacol ester precursor. Preliminary in vitro evaluation of [18F]RM365 indicated species differences in the binding to CB2R (KD of 2.32 nM for the human CB2R vs. KD > 10000 nM for the rat CB2R). Metabolism studies in mice revealed high stability of [18F]RM365 with fractions of parent compound of > 90% in the brain and > 54% in the plasma at 30 min p.i. PET imaging in a rat model of local hCB2R(D80N) overexpression in the brain demonstrate the ability of [18F]RM365 to reach and selectively label the intracranial expressed hCB2R(D80N) with high signal-to-background ratio. Thus, [18F]RM365 is a very promising PET radioligand for the imaging of upregulated hCB2R expression under pathological conditions with high potential towards clinical application in humans.

Keywords: cannabinoid receptor type 2; indole-2-carboxamide; binding affinity; radiochemistry; fluorine-18 labeling; positron-emission tomography

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Permalink: https://www.hzdr.de/publications/Publ-36778


Unraveling the multifaceted challenges and advances in validating tray efficiency prediction models

Vishwakarma, V.; Schubert, M.; Hampel, U.

Abstract

Industrial tray columns are widely used for distillation and absorption processes globally. They are known for high energy consumption, which is often overlooked due to unavailability of an equivalent industrially viable alternative. Rising energy costs and urgent need to control greenhouse gas emissions call for improvement in the performances of tray columns globally. This can be achieved by tuning the dynamics of the two-phase dispersion on individual trays for higher efficiencies via design modifications and revamping. To do so, it becomes necessary to understand how the two-phase flow evolves over a tray and relates to the tray efficiency. Such relation can be evaluated based on mathematical models called as tray efficiency prediction models. Hitherto, the existing models only provided black box estimations and ignored maldistributions in the vapor flow. These limitations were recently targeted by a new model referred to as ‘Refined Residence Time Distribution (RRTD) model’ [1].

The proof of concept of the RRTD model demands complete information pertaining to two-phase dispersion and mass transfer on a large-scale column tray. They are not available at desired resolution in the existing literature due to several limitations in the applied measurement techniques and systems. Thus, a recently-proposed multiplex flow profiler [2] was deployed inside an air-water column mockup (DN800) for characterizing the distributions of liquid holdup, residence time and mixing over a sieve tray for several loadings at high resolution. For the same operating conditions, the efficiency data over that tray was obtained based on air-led stripping of isobutyl acetate from the aqueous solution. Both hydrodynamic and efficiency data were applied together for assessing the validity of the new RRTD and other models. This works also sets new benchmarking standards for improved validation of CFD and efficiency prediction models in the future.

[1] Vishwakarma, V., Schubert, M. and Hampel, U., 2019. Development of a refined RTD-based efficiency prediction model for cross-flow trays. Industrial & Engineering Chemistry Research, 58(8), pp.3258-3268.
[2] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., 2020. Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten. Deutsches Patent und Markenamt, DE 10 2018 124 501.

Involved research facilities

  • TOPFLOW Facility
  • Open Access Logo Invited lecture (Conferences)
    2023 AIChE Spring Meeting and 19th Global Congress on Process Safety, 13.-16.03.2023, Houston, Texas, USA

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Permalink: https://www.hzdr.de/publications/Publ-36777


Where I am – Chemical microscopy of Eu(III) in plants

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

Abstract

The strongly luminescent Eu(III) was applied as molecular probe to retrace the distribution of trivalent lanthanides in plant cells and entire plants upon metal exposure.

Keywords: Europium; Luminescence; Chemical microscopy; Raman microscopy; Spectroscopy; Plants; Lanthanide

  • Lecture (Conference)
    ICOBTE & ICHMET 2023, 06.-10.09.2023, Wuppertal, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36775


Exploring the Eu(III) translocation in hydroponically grown plants

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

Abstract

Various biochemical, microscopic and spectroscopic techniques were applied to unravel the macroscopic and microscopic distribution and translocation of Eu(III) in hydroponically grown plants.

Keywords: Europium; Hydroponics; Plants; Spectroscopy; Chemical microscopy; Lanthanides

  • Lecture (Conference)
    Goldschmidt Conference 2023, 08.-13.07.2023, Lyon, Frankreich
  • Poster
    10. RCA Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36774


Eignung von Bestrahlungs-Logfiles für eine phantomlose patientenspezifische Qualitätssicherung in der Protonentherapie: Untersuchung der Reproduzierbarkeit von Logfile-Auswertungen

Wolter, L. C.; Hennings, F.; Bokor, J.; Richter, C.; Stützer, K.

Abstract

Einleitung
Da Bestrahlungs-Logfiles in der Protonentherapie Informationen über Energie, Position und Monitoreinheiten (MU) aller abgestrahlten Spots enthalten, ermöglichen sie eine Rekonstruktion der applizierten Dosis und bilden damit eine wichtige Komponente für eine phantomlose, patientenspezifische Qualitätssicherung (PSQA). Für eine zuverlässige Einschätzung der Dosisapplikation innerhalb einer solchen PSQA vor oder zum Therapiebeginn muss die Reproduzierbarkeit der Logfile-Parameter gewährleistet sein, d.h. tägliche Schwankungen der Logfile-Parameter dürfen keinen relevanten Einfluss auf die Fraktionsdosis haben. Wir haben Bestrahlungslogfiles diesbezüglich retrospektiv ausgewertet und deren Dosisverteilungen verglichen.

Material und Methoden
Die Logfile-Variabilität wurde sowohl auf Spotparameter- als auch auf Dosisebene untersucht. Für 14 Bestrahlungspläne (Tab.1; unterschiedliche Tumorlokalisationen und Gantrywinkel; 100 ≤ Energie/MeV ≤ 226,7; 0,02 ≤ MU/Spot ≤ 4,75) wurden die Logfiles aller Fraktionen analysiert. Aus den Parametern x/y-Position und MU wurden für 108.610 Spots die jeweilige mittlere Abweichung vom geplanten Wert (Genauigkeit) und die Standardabweichung vom Mittelwert (Reproduzierbarkeit) über alle Fraktionen berechnet. Die aus den Logfiles der insgesamt 339 Fraktionen rekonstruierten Dosisverteilungen wurden mittels 3D Gamma-Index-Analyse ausgewertet. Die dosisbasierte Γ-Durchlassrate wurde mit einer spotbasierten Logfile-Durchlassrate Λ(d) verglichen. Diese wurde definiert als die MU-Summe aller Spots, deren Distanz zur geplanten Position ≤ d ist, relativ zur Fraktions-MU.

Ergebnisse
Die mittlere spotweise Genauigkeit bezüglich der Planposition betrug (0,6 ± 0,3) mm und bezüglich der Plan-MU (0,0001 ± 0,0023) MU. Die mittlere Reproduzierbarkeit der Einzelspots lag bei (0,2 ± 0,1) mm und (0,0004 ± 0,0004) MU (Mittelwert ± Standardabweichung der Einzelwerte). Diese Abweichungen führen in allen untersuchten Fraktionen zu minimalen Änderungen in den Dosisverteilungen mit Gamma-Durchlassraten von Γ(2mm/2%) > 99%. Die Ergebnisse für sensitivere Kriterien Γ(1mm/1%) sind planspezifisch (Abb.1), jedoch pro Plan im Mittel > 92,6% und korrelieren mit der Λ(1mm)-Durchlassrate (Tab.1; 0,51 ≤ rPearson ≤ 0,99).

Zusammenfassung
Die untersuchten Einzelspotparameter sind über alle Fraktionen durchgängig stabil. Auch größere Positionsabweichungen sind im Submillimeterbereich reproduzierbar, was eher auf systematische Abhängigkeiten zwischen den Planparametern als auf Messfehler in den Strahlmonitoren hinweist. Geringe, klinisch nicht relevante Schwankungen in den Fraktionsdosisverteilungen konnten mittels sensitiver Gamma-Index-Analyse detektiert werden. Dies qualifiziert die Logfiles des Bestrahlungssystems für eine zuverlässige phantomlose PSQA und verspricht aufgrund der hohen Sensitivität einen außerordentlichen Nutzen für eine retrospektive Kontrolle der Bestrahlungsqualität im Rahmen einer zukünftigen online-adaptiven Protonentherapie.

Keywords: Proton therapy; Pencil beam scanning; Adaptive radiotherapy; Log-file analysis; Quality assurance

Involved research facilities

  • OncoRay
  • Lecture (Conference)
    54. Jahrestagung der DGMP, 26.-29.09.2023, Magdeburg, Sachsen-Anhalt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36773


Locally addressable energy efficient actuation of magnetic soft actuator array systems

Richter, M.; Sikorski, J.; Makushko, P.; Zabila, Y.; Kalpathy Venkiteswaran, V.; Makarov, D.; Misra, S.

Abstract

Advances in magnetoresponsive composites and (electro-)magnetic actuators have led to development of magnetic soft machines (MSMs) as building blocks for small-scale robotic devices. Near-field MSMs offer energy efficiency and compactness by bringing the field source and effectors in close proximity. Current challenges of near-field MSM are limited programmability of effector motion, dimensionality, ability to perform collaborative tasks, and structural flexibility. Herein, a new class of near-field MSMs is demonstrated that combines microscale thickness flexible planar coils with magnetoresponsive polymer effectors. We apply ultrathin manufacturing and magnetic programming of effectors to tailor their response to the nonhomogeneous near-field distribution on the coil surface. The MSMs are demonstrated to lift, tilt, pull, or grasp in close proximity to each other. These ultrathin (90 um) and lightweight (100 g/m2) MSMs can operate at high frequency (25 Hz) and low energy consumption (0.5 W), required for the use of MSMs in portable electronics.

Keywords: Magnetic soft machines; Planar coils; Magnetic near-field; Independent actuation

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-36772


ASL lexicon and reporting recommendations: A consensus report from the ISMRM Open Science Initiative for Perfusion Imaging (OSIPI)

Suzuki, Y.; Clement, P.; Dai, W.; Dolui, S.; Fernández-Seara, M.; Lindner, T.; Mutsaerts, H. J.; Petr, J.; Shao, X.; Taso, M.; Thomas, D. L.

Abstract

The 2015 consensus statement published by the ISMRM Perfusion Study Group and the EU COST Action ‘ASL in Dementia’ aimed to encourage the implementation of robust Arterial Spin Labeling (ASL) perfusion MRI for clinical applications and promote consistency across scanner types, sites, and studies. Subsequently, the recommended 3D pseudo-continuous ASL sequence has been implemented by most major MRI manufacturers. However, ASL remains a rapidly and widely developing field, leading inevitably to further divergence of the technique and its associated terminology, which could cause confusion and hamper research reproducibility.
On behalf of the ISMRM Perfusion Study Group, and as part of the ISMRM Open Science Initiative for Perfusion Imaging (OSIPI), the ASL Lexicon Task-Force has been working on the development of an ‘ASL Lexicon and Reporting Recommendations’ for perfusion imaging and analysis, aiming to 1) develop standardized, consensus nomenclature and terminology for the broad range of ASL imaging techniques and parameters, as well as the physiological constants required for quantitative analysis, and 2) provide a community-endorsed recommendation on the imaging parameters that we encourage authors to include when describing ASL methods in scientific reports/articles.
In this manuscript, the sequences and parameters in (pseudo-)continuous ASL, pulsed ASL, velocity-selective ASL and multi-timepoint ASL for brain perfusion imaging are included. However, the content of the lexicon is not intended to be limited to these techniques, and this paper provides the foundation for a growing online inventory that will be extended by the community as further methods and improvements are developed and established.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-36771


miniSCIDOM: a scintillator-based tomograph for volumetric dose reconstruction of single laser-driven proton bunches

Corvino, A.; Reimold, M.; Beyreuther, E.; Brack, F.-E.; Kroll, F.; Pawelke, J.; Schilz, J.; Schneider, M.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Abstract

Laser plasma accelerators enable the generation of intense and short proton bunches on a micrometer scale, thus offering new experimental capabilities to research fields like ultra-high dose rate radiobiology or material analysis. Being spectrally broadband, laser-accelerated proton bunches allow for tailored volumetric dose deposition in a sample via single bunches to excite or probe specific sample properties. The rising number of such experiments indicates a need for diagnostics providing spatially-resolved characterization of dose distributions with volumes of ∼1 cm³ for single proton bunches to allow for fast online feedback.
Here we present the scintillator-based miniSCIDOM detector for online single-bunch tomographic reconstruction of dose distributions in volumes of up to ∼1 cm³. The detector achieves a spatial resolution below 500 μm and a sensitivity of 100 mGy. The detector performance is tested at a proton therapy cyclotron and an LPA proton source. The experiments’ primary focus is the characterization of the scintillator’s ionization quenching behavior.

Keywords: laser-driven proton beams; ultra-high dose rate; beam monitoring detectors; scintillator-based diagnostics

Involved research facilities

  • OncoRay
  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36770


Development of Analysis and Visualization Methods for Next-Generation Sequencing Phage Surface Display Data, Master thesis 2022

Bloß, C.

Abstract

Efforts in the field of biomolecular probes and materials science have been accelerated by the application of phage surface display technology. A practical complement to this technology is next-generation sequencing. This combination provides deeper insight into biopanning rounds with impurity identification, display of sequence read content, visualization of phage library evolution, and methods for displaying binding motifs. To implement these approaches, a pipeline was developed to preprocess the next-generation sequencing data using Sequana and fastqjoin. The raw sequences are then extracted and the inserts of the pIII coat protein genes of the M13 phage are isolated. The inserts are translated and written into a frequency list. From this, a series of matrices are formed to detect enrichments of amino acid abundances per position in the library. Protein sequences are also clustered and written to additional matrices to create sequence logos for sequence motif discovery. The pipeline was used to analyze two data sets. In the first dataset, a customized, unamplified mini-library was created and tested for bias. No preservation of sequence motifs was detected. The second data set was used to test whether the sequence motifs QxQ and SxHS could be confirmed as conserved sequence motifs. However, this data set had serious qualitative problems and no meaningful results could be obtained. Overall, it can be concluded that the created pipeline provides good results for large data sets if
the quality is sufficient.

Keywords: Bioinformatics; Biotechnology; Next-Generation Sequencing; Phage Surface Display; Biopanning; Statistics; Stochastic; Master thesis; Vizualisation; Analysis

  • Master thesis
    Hochschule Mittweida, 2022
    Mentor: Röbbe Wünschiers, Katrin Pollmann, Franziska Lederer
    92 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36769


Challenges and advantages of an e-LINAC based positron beam facility

Wagner, A.

Abstract

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions (σt ≈100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments.
In the presentation advantages and caveats of employing a high-power electron LINAC for secondary positron beam production will be discussed.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and by the Helmholtz Energy Materials Characterization Platform.
[1] A. Wagner, et al., AIP Conference Proceedings, 1970, 040003 (2018).

Keywords: positron annihilation; electron accelerator; linac; bremsstrahlung

Involved research facilities

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Theme Meeting on Scientific Opportunities of ANURIB, 25.-27.04.2023, Kolkata, India

Permalink: https://www.hzdr.de/publications/Publ-36768


Investigating binary granular mixing in a rotating drum using ultrafast X-ray computed tomography

Papapetrou, T. N.; Bieberle, M.; Barthel, F.; Hampel, U.; Lecrivain, G.

Abstract

The transient mixing dynamics of an initially segregated binary granular system in a half-filled rotating drum are investigated. The granular system consists of spherical beads having identical size. The density ratio between the two granular phases is 2.8. With its ability to scan three-dimensional opaque systems with a high frequency, the ultrafast X-ray computed tomography is used to capture the transient and steady-state segregation dynamics in the bulk. The segregation dynamics are also compared to those at the circular end-wall caps, which have been captured with a high-speed camera. The results show an axial migration of the denser particles towards the bulk and, more importantly, second-order overshooting dynamics in the radial mixing index, which tend to increase with the Froude number. The results will find application in industrial systems, where rapid mixing occurs. We also believe the presented data can serve as validation for future three-dimensional simulations focusing on the transient formation of segregation patterns in the bulk.

Keywords: granular mixing; rotating drum; ultrafast X-ray computed tomography; segregation dynamics

Involved research facilities

  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-36766


Data and code: Investigating binary granular mixing in a rotating drum using ultrafast X-ray computed tomography

Papapetrou, T. N.; Bieberle, M.; Barthel, F.; Hampel, U.; Lecrivain, G.

Abstract

Original video camera data, and time-averaged, beam-hardening-corrected, drift-corrected dynamic and static UFXCT image data used in the associated publication; code used for the final processing; and the final processed data. More details are found in the publication and in the info in the respective folders.

Keywords: granular mixing; rotating drum; ultrafast X-ray computed tomography; image processing

Involved research facilities

  • ROFEX

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Permalink: https://www.hzdr.de/publications/Publ-36765


Uranium(VI) reduction by a Desulfitobacterium species in pure culture and in artificial multispecies bio-aggregates

Hilpmann, S.; Jeschke, I.; Deev, D.; Zugan, M.; Lapanje, A.; Rijavec, T.; Hübner, R.; Bok, F.; Schymura, S.; Cherkouk, A.

Abstract

The reduction of highly mobile and water soluble U(VI) to less mobile U(IV) represents a key process influencing the migration of this radionuclide in the environment. Microorganisms such as for example iron and sulfate-reducers are capable of reducing U(VI) under various conditions. This interaction mechanism between microbes and U could play an important role in a final disposal site for high-level radioactive waste deposited in deep geological layers. Different host rocks are suitable for the long-term storage of nuclear waste, e.g. clay formations, crystalline rock and rock salt. Besides the geochemical, geophysical and geological properties of such a repository, little is known about the influence of naturally occurring microorganism on the safety of such a site. In a worst-case scenario, if water enters the repository, radionuclides can get distributed in the surrounding host rock and thus interact with the native microorganisms, potentially leading to an immobilization of radionuclides via bioreduction. Furthermore, a reduction of U(VI) could also play an important role in the development of different bioremediation approaches for radionuclide-contaminated environments. As a potential component of new remediation strategies, we introduce the use of artificial bio-aggregates of different bacterial genera. By the use of these artificial biofilms insights into the complex interactions in a multi-species environment can be obtained. In this study, we used derivatized polyelectrolytes to form aggregates of two different microorganisms to connect advantageous properties of the microorganisms in a complementary way and to investigate the reduction of U(VI) under different conditions.
Desulfitobacterium sp. G1-2 was chosen as an important representative of iron-reducing bacteria in anaerobic environments. This bacterial strain was isolated from bentonite samples of the Full-scale Engineered Barrier Experiment – Dismantling Project (FEBEX-DP) at the Helmholtz Center Dresden-Rossendorf. Bentonites are supposed to serve as a possible backfill material, not only for a final disposal site in clay formations but also in crystalline rock. Furthermore, Desulfitobacterium species were detected in other clay formations as well, for example in Opalinus Clay.[1] These were used to form artificial bio-aggregates with different bacterial strains (among others Desulfitobacterium sp. G1-2 and aerobic marine inhabitant Cobetia marina DSM 50416) using electrostatic modifications of surface charge of bacterial cells.
Time-dependent experiments of Desulfitobacterium sp. G1-2 alone in 30 mM bicarbonate buffer (100 µM U(VI), 10 mM lactate) showed a decrease in U concentrations in the supernatants. Moreover, artificial Opalinus Clay pore water[2] (100 µM U(VI), 10 mM lactate, pH 5.5) was used as background electrolyte, as well, to create more environment-related conditions. In both cases, approximately 80% of the uranium was removed from the supernatants after one week. In order to be able to exclude abiotic influences on the uranium(VI) reduction, experiments using heat-killed cells were carried out, as well. Thermodynamic calculations of the U(VI) speciation in both solutions revealed the predominance of different U(VI) complexes in the used media. UV/Vis studies of the dissolved cell pellets verified the formation of U(IV) by an almost complete reduction of U(VI) in bicarbonate buffer and artificial Opalinus Clay pore water. In contrast, experiments with heat-killed cells did not show any reduction of U(VI) in the samples. STEM investigations coupled with EDX analysis of U-incubated cells showed the presence of two different U-containing aggregates inside the cells of Desulfitobacterium sp. G1-2. On the one hand, spherical nanoparticles are present, which are probably containing organic uranium phosphate compounds, as shown by EDX mapping of the samples. On the other hand, rod-shaped particles consisting of inorganic uranium phosphate compounds occur inside the cells as well.
First experiments with artificial bio-aggregates that were formed from different bacterial strains (e.g. Desulfitobacterium sp. G1-2 and Cobetia marina DSM 50416) using electrostatic modification of surface charge of bacterial cells by different polyelectrolytes showed a promising U reduction capacity in bicarbonate buffer (30 mM, 100 µM U(VI), 10 mM lactate). Future investigation will focus on the elucidation of the complex interaction mechanisms in multi-species environments.
This study helps to close existing gaps in a comprehensive safeguard concept for a repository for high-level radioactive waste in clay rock. Moreover, the results of these investigations provide new insights into the U(VI) reduction by iron-reducing microorganisms and thus, contribute to new knowledge on the migration of uranium in the environment. In addition, it may help to establish new bioremediation approaches of contaminated environments, because beneficial microbes can be used for the artificial bio-aggregates, even if they do not form biofilms themselves.

References
[1] A. Bagnoud et al. (2016). Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock. Nat. Commun. 2016, 7, 1–10
[2] P. Wersin et al. (2011). Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland. Appl. Geochemistry 2011, 26, 931–953

Keywords: Uranium(VI) reduction; Iron-reducing bacteria; Multispecies bio-aggregates

  • Lecture (Conference)
    Migration 2023, 24.-29.09.2023, Nantes, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36762


Redox transformation of uranium by iron-reducing bacteria as single culture and in artificial multispecies bio-aggregates

Hilpmann, S.; Jeschke, I.; Deev, D.; Zugan, M.; Lapanje, A.; Rijavec, T.; Hübner, R.; Schymura, S.; Cherkouk, A.

Abstract

Redox transformations have a strong influence on the mobility of different metal ions in the environment. A key process in influencing the migration of uranium is the reduction of highly mobile and water-soluble uranium(VI) to less mobile uranium(IV). Especially in the surroundings of former uranium mines, this radionuclide represents an important contaminant whose entry into the environment must be prevented. Different microorganisms, e.g. sulfate- and iron-reducing bacteria, are capable of reducing uranium under various conditions. Thus, microbes can offer an environmentally friendly remediation strategy for radionuclide-contaminated environments. Moreover, in this study, we introduce the use of artificial bio-aggregates of different bacterial genera as a potential bioremediation approach combining advantageous properties of the microorganisms in a complementary way.
Desulfitobacterium sp. G1-2, which was isolated from bentonite samples, was chosen as an important representative of iron-reducing bacteria in anaerobic environments. Furthermore, different Desulfitobacterium species were found in other natural environments, like clay formations as well. These bacteria were used to form artificial bio-aggregates with different other bacterial strains (e.g. aerobic marine inhabitant Cobetia marina DSM 50416) based on electrostatic modifications of the surface charge of the bacterial cells.
Time-dependent experiments of a pure Desulfitobacterium sp. G1-2 culture in 30 mM bicarbonate buffer as background electrolyte showed a decrease in uranium concentration in the supernatants (100 µM uranium(VI), 10 mM lactate, pH 6.8/5.5). Approximately 80% of the uranium were removed from the supernatants within one week. UV/Vis studies of the dissolved cell pellets verified the reduction of uranium(VI) in the samples. STEM imaging of ultra-thin sectioned samples of uranium-incubated cells coupled with EDX spectroscopy showed the presence of two different uranium-containing aggregates inside the microbes.
First experiments with artificial bio-aggregates that were formed from different bacterial genera (e.g. Desulfitobacterium sp. G1-2 and Cobetia marina DSM 50416) revealed a promising reduction capacity of uranium. Such artificial bio-aggregates have a potential in utilizing beneficial microbes in remediation strategies, even if they do not form biofilms themselves. Moreover, these investigations offer new insights in the complex interaction processes in multi-species environments.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Iron-reducing bacteria; Multispecies bio-aggregates

  • Poster
    Goldschmidt 2023, 09.-14.07.2023, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36760


Influence of microbial uranium reduction processes on the final disposal of radioactive waste

Hilpmann, S.; Jeschke, I.; Steudtner, R.; Hübner, R.; Schymura, S.; Stumpf, T.; Cherkouk, A.

Abstract

The safe disposal of high-level radioactive waste represents a major scientific and societal challenge. In addition to geological, geochemical and geophysical properties of such a repository, the influence of naturally occurring microorganisms from deep geological layers has to be taken into account for a comprehensive safeguard concept. Various sulfate- and iron-reducing bacteria are present in different clay formations, which can serve as a potential host rock for the long-term storage of the waste, as well as in the backfill material bentonite. In the event of a worst-case scenario, if water enters the repository, those microorganisms can interact with the waste and change for example the oxidation state or the chemical speciation, which can influence the mobility of the radionuclides.
In this study, the reduction of highly-mobile, water-soluble U(VI) to less mobile U(IV) by the iron-reducing microorganism Desulfitobacterium sp. G1-2 and the sulfate-reducer Desulfosporosinus hippei DSM 8344T were investigated. Desulfitobacterium sp. G1-2 has been isolated from a bentonite sample and Desulfosporosinus hippei DSM 8344T represents a genus of sulfate-reducing bacteria present in clay rock and bentonite.
During time-dependent experiments in bicarbonate buffer (30 mM, 100/550 µM U(VI)), Desulfitobacterium sp. G1-2 showed a removal of up to 80% of U within 5 days, whereas samples of Desulfosporosinus hippei DSM 8344T showed no decrease in U concentrations over time. Therefore, experiments were carried out in artificial Opalinus Clay pore water with this bacterium (100 µM U(VI), pH 5.5). In this case, the U concentration showed a decrease of up to 80% of the radionuclide from the supernatants within 48 h. UV/Vis studies of dissolved cell pellets of both bacteria after U incubation showed an almost complete reduction to U(IV) for Desulfitobacterium sp. G1-2. On the other hand, samples of Desulfosporosinus hippei DSM 8344T exhibited only a partial reduction. TEM imaging combined with EDX analysis revealed the release of membrane vesicles from cells of Desulfosporosinus hippei DSM 8344T as a possible defense reaction against cell incrustation. Furthermore, TEM images of Desulfitobacterium sp. G1-2 cells showed the presence of two different U-containing aggregates inside the cells.
These investigations showed clear differences in the reduction behavior of sulfate- and iron-reducing bacteria relevant to nuclear waste storage. This highlights the importance of studies on the U(VI) interactions of different microorganisms present in deep geological layers. Moreover, new aspects for a safety concept for a nuclear repository in clay formations and for final disposal sites using bentonite as backfill material could be revealed.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Iron-reducing bacteria; Nuclear waste disposal

  • Poster
    Interdisziplinäres Forschungssymposium SafeND, 13.-15.09.2023, Berlin, Deutschland
  • Open Access Logo Contribution to proceedings
    Interdisziplinäres Forschungssymposium Safe ND, 13.-15.09.2023, Berlin, Deutschland
    DOI: 10.5194/sand-2-151-2023

Permalink: https://www.hzdr.de/publications/Publ-36759


A Morphology-Adaptive Multifield Two-Fluid Model

Meller, R.; Schlegel, F.; Krull, B.

Abstract

Industrial multiphase flows are typically characterized by coexisting morphologies. Modern simulation methods are well established for dispersed (e.g., Euler-Euler) or resolved (e.g., Volume-of-Fluid) interfacial structures. A simulation method that requires less knowledge about the flow in advance would be desirable and should allow describing both interfacial structures – resolved and dispersed – in a single computational domain. Such methods that combine interface-resolving and non-resolving approaches are called hybrid models. A morphology adaptive multifield two-fluid model, named OpenFOAM-Hybrid, is proposed, which is able to handle dispersed and resolved interfacial structures coexisting in the computational domain with the same set of equations. An interfacial drag formulation for large interfacial structures is used to describe them in a volume-of-fluid-like manner. For the dispersed structures, the baseline model developed at Helmholtz-Zentrum Dresden - Rossendorf is applied. The functionality of the framework is demonstrated by several test cases, including a single rising gas bubble in a stagnant water column. Recent developments focus on the transition region, where bubbles are over- or under-resolved either for Euler-Euler or for Volume-of-Fluid.

  • Poster
    Helmholtz Energy Conference 2023, 12.-13.06.2023, Koblenz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36758


A Morphology-Adaptive Multifield Two-Fluid Model: Recent developments and applications

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

Abstract

Physical phenomena in industrial gas-liquid flows typically span a wide range of length
and time scales. Individual flow regimes are usually modelled using specific approaches,
which are mainly characterised by the level of detail the existing interfaces are handled
with. The cross-scale nature of multiphase flows requires the simultaneous application and
flexible switching between these methods in a single common framework.
For this reason, a morphology-adaptive model is established by combining the Euler-
Euler model with the Volume-of-Fluid (VOF) model. Interactions and transitions between
different morphologies and scales are taken into account by dedicated models. This work
gives an overview over recent advances towards a fully scalable morphology-adaptive
multiphase model (MultiMorph).
In order to be applicable to realistic, large-scale problems, special care is required to
ensure a robust model behaviour, even if the spatial resolution is not optimal in terms of
the respective flow phenomena. Large interfaces might be represented on coarse numerical
grids. The usual VOF model typically over-predicts the interfacial shear stress in such
a situation, resulting in unrealistic interface dynamics. Instead, a resolution-adaptive
interfacial coupling is proposed. In that way the phases may slip along each other in the
direction parallel to the interface, improving the prediction, i.e., of interface shape or of
bubble rising velocity.
A central building block of morphology-adaptive methods is the ability of structures to
evolve from one morphology to another. For example, unresolved bubbles may coalesce,
grow, or enter highly-refined mesh regions, such that a resolved representation becomes
possible. Therefore, a transition to a continuous representation is realised, to make optimal
use of the available numerical degrees of freedom. The opposite case, the transition from a
continuous to a dispersed representation, is handled as well. This becomes relevant in case
of mesh coarsening or if large continuous structures disintegrate into to smaller particles
which cannot longer be resolved by the given spatial resolution.
Another important feature of the model is the ability to track large numbers of dispersed
particles. A class-method based solution approach is included, providing complete
information about the size distribution, a necessity for modelling the number-conservative
transition between dispersed and resolved structures. However, the associated computational
cost is significant. Fortunately, the solution of the population balance equation could
be parallelised by outsourcing it to graphics processing units, which leads to a significant
improvement in performance.
The MultiMorph model is implemented in the software released by the OpenFOAM
Foundation with strong focus on sustainable research, including a state-of-the-art IT
approach. Both the source code and a comprehensive suite of simulation cases are publicly
available. Several multi-scale applications are presented, featuring for example a distillation
column, a swirl separator, and a impinging jet. Further details can be found at
www.hzdr.de/multimorph.

  • Poster
    19th Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 19.-23.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36757


Data publication: Electrical Conductivity of Iron in Earth's Core from Microscopic Ohm's Law

Ramakrishna, K.; Lokamani, M.; Baczweski, A. D.; Vorberger, J.; Cangi, A.

Abstract

Simulation and literature data on the electrical and thermal conductivity of iron. The raw simulation data was generated from time-dependent density functional theory calculations. Post-processing was applied to obtain the transport properties (conductivities) as described in the associated journal publication. The literature data was compiled from available publication data as referenced in the associated journal publication.

Keywords: transport properties; time-dependent density functional theory; Kubo-Greenwood; electrical conductivity; thermal conductivity; electronic structure theory; materials science

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Permalink: https://www.hzdr.de/publications/Publ-36755


Current state of Na-Zn battery research

Weber, N.

Abstract

Within the Horizon 2020 project SOLSTICE, two molten salt battery concepts, based on sodium and zinc, are developed. The first cell relies on a solid Na-beta’’-alumina membrane, and is very similar to the commercially available ZEBRA batteries. Operating at 300°C, this design benefits from a wide range of knowledge available from these existing batteries. The second cell concept, a fully liquid battery, operates around 600°C. Due to its novelty, this design presents a larger number of challenges, such as corrosion, sealing and self-discharge. Once these are solved, the sodium-zinc battery can be employed as a very competitive and sustainable stationary energy storage device due to the lower costs, abundance and recyclability of the active materials. The talk will give an overview on the current state of research in the SOLSTICE consortium, the achievements and the remaining challenges in Na-Zn battery development.

  • Lecture (Conference)
    SUPHER23 (SUstainable PolyEnergy generation and HaRvesting), 06.-08.09.2023, Savona, Italy

Permalink: https://www.hzdr.de/publications/Publ-36754


Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch den Einsatz von 3D-gedruckten Zickzack-Packungen

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

Abstract

Poster zum Thema: Vermeidung von Flüssigkeitsfehlverteilungen in RPBs durch Einsatz 3D-gedruckter Zickzack-Packungen

Keywords: Zickzack-Packungen; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

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  • Poster
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36753


Neues Konzept zur Flüssigkeitsverteilung für Rotating Packed Beds

Pyka, T.; Koop, J.; Bieberle, A.; Schubert, M.; Held, C.; Schembecker, G.

Abstract

Vorstellung eines neuen Konzepts zur Flüssigkeitsverteilung für Rotating Packed Beds

Keywords: Rotating Packed Beds; Trennprozesse; Gammastrahlen-Computertomographie

Involved research facilities

  • TOPFLOW Facility

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  • Lecture (Conference)
    Jahrestreffen Fachgruppe Fluidverfahrenstechnik, 21.-23.03.2023, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36752


OCTOPOD: single bunch tomography for angular-spectral characterization of laser-driven protons

Reimold, M.; Assenbaum, S.; Beyreuther, E.; Bodenstein, E.; Brack, F.-E.; Eisenmann, C.; Englbrecht, F.; Kroll, F.; Lindner, F.; Masood, U.; Pawelke, J.; Schramm, U.; Schneider, M.; Sobiella, M.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Abstract

Laser-plasma accelerated (LPA) proton bunches are now prepared and provided for research fields ranging from ultra-high dose rate radiobiology to material science and probing of extreme states of matter. Yet, the capabilities to fully characterize the spectrally and angularly broad LPA bunches lag behind the rapidly evolving applications. The Optical Cone beam TOmograph for Proton Online Dosimetry - short OCTOPOD - translates the angularly resolved spectral characterization of LPA proton bunches into the spatially resolved detection of the volumetric dose distribution deposited in a liquid scintillator. Up to 24 multi-pinhole arrays record projections of the volumetric scintillation light distribution and allow for tomographic reconstruction of the volumetric dose deposition pattern, from which proton spectra may be retrieved in arbitrary directions by spectral deconvolution.
Applying the OCTOPOD at a cyclotron, we show the reliable retrieval of various spatial dose deposition patterns and detector sensitivity over a broad dose range from less than 1 Gy to more than 100 Gy, as required for LPA proton bunch characterization. With a dedicated vacuum housing, the OCTOPOD was installed at a LPA proton source, providing real-time data on proton acceleration performance for various laser-target interaction parameters and attesting the system optimal performance in the harsh laser plasma environment.

Keywords: laser-plasma acceleration of protons; proton detector; tomographic reconstruction

Involved research facilities

  • OncoRay
  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36751


Direct numerical simulation of a flexible fiber interacting with a fluidic interface

Lecrivain, G.

Abstract

The dynamics of fibers at a fluidic interface is of significant importance in various processes, among which stand out textile flotation, stabilization of emulsions, micro-folding of elastic structures, and clogging of feather fibers by oil droplets. A consistent formulation for the direct numerical simulation of a flexible fiber interacting with a fluidic interface is presently suggested. The fiber is geometrically decomposed into a chain of spherical beads, which undergo stretching, bending, and twisting interactions. The capillary force, acting at the three-phase contact line, is calculated using a ternary diffuse-interface model. Each ingredient of the model was validated against theoretical solutions. Partial and complete wrapping of an immersed three-dimensional drop is successfully simulated. The results show that the fiber curvature increases linearly with the square of the elasto-capillary length, for both low and large structural deformation, in-line with previously experimental observations

Keywords: Simulation; Particle at interface

  • Invited lecture (Conferences)
    Final Conference - MSCA-ITN-EID COMETE, 28.-29.03.2023, Udine, Italy

Permalink: https://www.hzdr.de/publications/Publ-36750


Effect of helium ion implantation on nanomechanical resonators in 3C-SiC

Jagtap, N.; Klaß, Y.; David, F.; Bredol, P.; Weig, E.; Helm, M.; Astakhov, G.; Erbe, A.

Abstract

Silicon carbide (SiC) is a suitable candidate for nanoelectromechanical systems due to its superior mechanical properties. It is also an interesting material platform to study the coupling of mechanical modes with localized spins associated with irradiation-induced defects. Such a spin-mechanical system can be used for quantum sensing applications [1].
The nanomechanical resonators in 3C-SiC are fabricated by standard semiconductor processing techniques such as electron beam lithography and reactive ion etching. They are characterized using Fabry-Pérot interferometer. In the preliminary experiments, we focus on the material modification by helium ion broad beam implantation on strained 3C-SiC resonators. The effect of varying fluence on resonance frequencies and quality factors is studied. With the fluence of 1 X 10^14 /cm^2 we observe decrease in resonant frequencies (~ 15%) and quality factors.

[1] A. V. Poshakinskiy and G. V. Astakhov, "Optically detected spin-mechanical resonance in silicon carbide membranes”, PhysRevB.100.094104 (2019)

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  • Poster
    Frontiers of Nanomechanical Systems (FNS) workshop, 06.-09.06.2023, Art Center Delft, The Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36749


New Cross Section Data for Radiative Proton Capture on Carbon for Nuclear Astrophysics at LUNA

Boeltzig, A.; Skowronski, J.

Abstract

The observable ratio of 12C/13C can be used as a probe for stellar nucleosynthesis as well as for mixing processes during hydrogen burning, provided that the reaction rates of 12C(p,γ)13N and 13C(p,γ)14N are known. To obtain direct cross section measurements at low energies, which are required to better constrain these rates in astrophysical scenarios, both reactions were studied in a series of experiments at the LUNA-400 accelerator. Different targets and complementary detector setups were employed for a systematic study, and the sensitivity afforded by the low-background underground environment allowed for precise measurements at lower energies than previously available. We will present these experiments and their results for both reactions.

  • Lecture (Conference)
    DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36748


MetroPOEM – Metrology for the harmonisation of measurements of environmental pollutants in Europe

Arnold, D.; Eberhardt, J.; Flierl, L.; Rienitz, O.; Pramann, A.; Zapata, D.; Vogl, J.; Prem, P. S.; Lourenço, V.; Chambon, L.; Isnard, H.; Mazánová, M.; Sochorová, J.; Zuliani, T.; Goltnik, T.; Rovan, L.; Štrok, M.; Noireaux, J.; Kamarainen, M.; Engin, B. A.; Can, S. Z.; Cankur, O.; İşleyen, A.; Hansen, V.; Ulrich, T.; Andreasen, R.; Hou, X.; Qiao, J.; Pröfrock, D.; Wippermann, D.; Zimmermann, T.; Winkler, S.; Fichter, S.; Wallner, A.; Schöpke, C.; Johansen, I.; Yasin, V.; Ioan, M.-R.; Virgolici, M.; Olaru, C.; Badea, R.; Walther, C.; Irrgeher, J.; Lancaster, S.; Epov, A.; Chernonozhkin, S.; Wagner, S.; Jerome, S.; Skipperud, L.; Jensen, K.-A.; Salminen-Paatero, S.; Vukanac, I.; Čeliković, I.; Rajačić, I.; Djurašević, M.; Nikolić, J. K.; Christl, M.; Tribouillier, H. P.; Malinovskiy, D.; Hil, S.; Goenaga-Infante, H.; Strekopytov, S.; Russell, B.; Mohamud, H.; Thompkins, H.

Abstract

Summary

The European Green Deal’s ambition for zero pollution requires the development of highly sensitive techniques to detect ultra-low amounts of pollutants. This requirement will be delivered via strategies described by the two European Metrology Network (EMN) on Pollution Monitoring (PolMo) and the EMN on Radiation Protection, supporting the Basic Safety Standards directive. Implicit in these strategies is a strong need to improve data quality for monitoring and reporting pollution in the air, water, and soil. To detect radioactive isotopes and stable polluting elements in the environment, fast, sensitive, and inexpensive analytical procedures are needed. Mass spectrometry is a key method for determination of non-radioactive polluting elements and of increasing importance for long-lived radionuclides, however, application of single collector ICP-MS, this potential cannot be fully realised unless techniques are validated with traceable multi-element reference materials. However, multi-element certified reference materials are usually not available and single-element certified reference materials are limited to very few elements. Nevertheless, these reference materials are urgently needed to calibrate mass spectrometric measurements, to overcome mass bias effects occurring during the measurements in mass spectrometers. The MetroPOEM project (21GRD09) is designed to address these problems. MetroPOEM, coordinated by the Physikalisch-Technische Bundesanstalt of Germany, will be delivered by a consortium of 22 partners from 13 countries throughout Europe.

Objectives

The overall aim of MetroPOEM is to bridge the gap between radiometric techniques and mass spectrometry for the characterisation and detection of polluting long-lived radionuclides and stable elements and element tracers by comparing and linking both techniques, thus significantly improving measurement uncertainties and detection limits. These aims and objectives will be delivered through four technical work packages, supported by project and impact management activities:

  • Establish and compare (inter-laboratory) the selectivity and detection limits of diverse types of mass spectrometers for selected radioactive pollutants (e.g., U, Np, Pu, Am) using isotope reference materials and/or activity standards. This includes assessing relative instrument performance with respect to current measurement challenges and establishing detection limits in relation to environmental regulations.
  • Develop measurement methods for isotope ratios that are traceable to the SI by using multi-collector ICP-MS and apply these methods on more commonly available techniques (ICP-MS/MS, ICP-QMS) by providing suitable operating procedures focussing on stable polluting elements (e.g., Li, B, Cr, Cd, Ni, Sb, Pb, U). To produce recommendations for sample processing, treatment, uncertainty budgets, and if feasible, the quantification of the so-called mass bias.
  • Develop two radioactive reference materials with the sample matrix containing radioactive pollutants (e.g., U, Np, Pu, Am) for use in an inter-laboratory comparison employing techniques used WP1, which will demonstrate the variations in parameters including detection limits, sample preparation, sample introduction methods, total procedural time, and uncertainty budgets.
  • Implement and validate the methods for isotope ratio measurements established in objective 2 by the development of one aqueous certified reference material that is certified for the same stable polluting elements with lowest possible uncertainties using multi-collector instruments, to facilitate the calibration of single collector ICP-MS, instrument validation, as well as quality control.
  • Facilitate the acceptance of the technology and measurement infrastructure developed in the project by the measurement supply chain (e.g., accredited laboratories), standards developing organisations and international organisations and end users (e.g., environmental monitoring agencies).

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Related publications

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

Permalink: https://www.hzdr.de/publications/Publ-36747


Comparison of different CFD approaches for the simulation of developing free surface two-phase flow in straight and bent pipes

Döß, A.; Höhne, T.; Schubert, M.; Hampel, U.

Abstract

Two-phase flows in feed pipes of thermal separation columns have complex flow patterns and are difficult to predict during sizing and design for geometries with non-straight pipes. Numerical simulation codes have only been validated for very few pipe geometries. This work benchmarks the state-of-the-art Volume-of-Fluid model (VoF) and the Algebraic Interfacial Area Density model (AIAD) for the simulation of two-phase flows with the Eulerian/Eulerian CFD approach for straight pipes and horizontal bends as well as for different pipe diameters and flow rates. Both models are compared and shortcomings of the predicted velocity fields from AIAD in the vicinity of horizontal bends are highlighted. Predicted average phase fractions agree reasonably with experimental data. From the numerical results, recommendations for the selection of feed inlet devices are derived.

Keywords: Horizontal two-phase feeds; Flow morphology; Numerical simulation; VoF; AIAD; CFD; Wire-mesh sensors

Involved research facilities

  • TOPFLOW Facility

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  • Secondary publication expected from 18.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36746


Exploring the lowest levels of environmental 90Sr in carbonates and seawater using a new, highly sensitive Accelerator Mass Spectrometry technique

Winkler, S.; Martschini, M.; Merchel, S.; Steier, P.; Golser, R.

Abstract

1 Introduction

Strontium-90 (90Sr) is an anthropogenic radionuclide, which, due to its radiological relevance, has been most intensively monitored in the past. In terms of initial activity, over 630 PBb of this radioisotope have been distributed globally from stratospheric fallout of bomb-testing, and there are more localized contributions from test, accidents, and releases from reprocessing plants.[1] Despite of the massive spike of 90Sr from global fall-out has been very difficult to measure in the ocean, due to the massive dilution in the oceans and the low atom detection efficiency of decay counting measurements. Massive sample sizes (up to 100 l of seawater or 100 g of coral aragonite) were required even right after the peak period of global fall-out from bomb testing. On the other hand, the high amount of strontium dissolved in seawater complicates the use of mass spectrometric methods, as an isotopic abundance sensitivity of at least 1·10-15 is required to detect the estimated main signal. Here we report on the results of successful measurements of such samples using a new Accelerator Mass Spectrometry (AMS) technique [2].

2 Samples and Methods

Our interest in this study lies in the determination of 90Sr as geochemical and ocean current tracer in conjunction with another anthropogenic tracer isotope, 236U. Both the respective elements both get build into marine carbonates such a coral samples, and both are present in significant amounts in seawater. While 236U is a well-established isotope and can be measured at very low levels (<10-13 236U/U) with AMS, only recent advances in isobar separation technique in AMS at the University of Vienna have opened possibility to measure 90Sr at the required level. The new technique uses an ion-cooler and laser-photo-detachment to suppress the stable isobar 90Zr. Besides the isobar suppression in the mass spectrometer system, we also gain a boost in suppression using ion-exchange columns. Since we are interested in measuring 90Sr against 236U we developed a sample preparation technique to extract both efficiently from a calcium carbonate matrix, while suppressing 90Zr, and avoiding pre-concentration steps. In principle, this could also be applied to seawater samples, although the efficiency of uranium co-precipitation in with carbonates still needs investigation. In this study we relied on separate procedures in the case of sea water samples.

3 Results

With initial test samples we could confirm a detection limit for the method corresponding to 0.03 mBq (or better) and a 90Sr/Sr isotopic abundance sensitivity of <8·10-16. We will present results from contemporary coral skeleton material, the methods, requirements, and impact of sample preparation. Further, we explain our sample preparation scheme to extract 236U, another important anthropogenic radionuclide, simultaneously with 90Sr for multi-isotope applications of both. Finally, the sample preparation and blank levels for ocean water samples and the results will be shown.

  • Lecture (Conference)
    RCA-Workshop, 12.-14.06.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36745


Porous Magnesium Oxide by Twin Polymerization: From Hybrid Materials to Catalysis

Scharf, S.; Notz, S.; Thomas, R.; Mehring, M.; Tegenkamp, C.; Formánek, P.; Hübner, R.; Lang, H.

Abstract

Twin monomers [Mg(2-OCH2-cC6H4O)][L]0.8 (2, L=diglyme) and [Mg(2-OCH2-cC6H4O)][L]0.66 (3, L=tmeda) form by their thermal polymerization interpenetrating organic-inorganic hybrid materials in a straightforward manner. Carbonization (Ar) followed by calcination gave porous MgO (2: surface area 200 m2g-1, 3: 400 m2g-1), which showed in catalytic studies towards Meerwein-Ponndorf-Verley reductions excellent yields and complete conversions for cyclohexanone and benzaldehyde. However, with crotonaldehyde a mixture of C4–C8 compounds was obtained. When MgO was exposed to air then primarily crotyl alcohol was formed. The range of applications could be easily extended by twin polymerization of 3 in presence of [Cu-(O2CCH2O(CH2CH2O)2Me)2] (4) or [Ag(O2CCH2-cC4H3S)(PPh3)] (5), resulting in the formation of nanoparticle-decorated porous CuO@MgO or Ag@MgO materials, which showed high catalytic reactivity towards the reduction of methylene blue.

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Permalink: https://www.hzdr.de/publications/Publ-36744


How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) – A microspectroscopic study.

Klotzsche, M.; Vogel, M.; Sachs, S.; Raff, J.; Stumpf, T.; Drobot, B.; Steudtner, R.

Abstract

Herein, Eu(III) was representatively used as luminescent probe to study the chemical environment and to elucidate the molecular interactions of lanthanides with a suspension cell culture of Nicotiana tabacum BY-2. Biochemical methods were combined with luminescence spectroscopy, two-dimensional microspectroscopic mappings, and data deconvolution methods to resolve bioassociation behavior and spatial distribution of Eu(III) in plant cells.

Keywords: Europium; Tobacco BY-2; Luminescence; Chemical microscopy; Raman microscopy; Plant cells; Species analysis; Lanthanides; Bioassociation

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  • Secondary publication expected from 30.08.2024

Permalink: https://www.hzdr.de/publications/Publ-36743


Data publication: Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

Data from flow visualization experiments, results of numerical simulations and Particle Image Velocimetry image data

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36742


Laser Transmission in the Relativistically Induced Transparency Regime for High Performance Proton Acceleration at PW Laser Systems

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by laser-plasma sources promises many applications, but reaching the required beam quality parameters demands a high level of understanding and control over the interaction process. Several advanced schemes, including the Relativistically Induced Transparency (RIT) regime, have been proposed and investigated in search of a stable acceleration for proton energies beyond 100 MeV. In the RIT scheme, the absorption of the electromagnetic laser field by the target and the generated plasma is critical. In joint experiments at the DRACO PW (HZDR) and J-KAREN (KPSI) lasers, we use transmission diagnostics to study the onset of transparency and learn about the sensitivity of the laser input to improve the process’s robustness. Using ultra-short pulses on thin solid density foil targets, we observe high performance proton beams in an expanded foil case. Our analysis of the effects on the transmission and its correlation with the acceleration performance indicates changes in the plasma interaction process.

Keywords: laser plasma; laser proton acceleration; high power laser

Involved research facilities

  • Draco
  • Lecture (Conference)
    DPG-Frühjahrstagung 2023; SMuK2023, 20.-24.03.2023, Dresden, Deutschland
  • Lecture (Conference)
    SPIE Optics + Optoelectronics, 24.-27.04.2023, Praha, Česká republika

Permalink: https://www.hzdr.de/publications/Publ-36740


Revisiting power-law distributions in empirical outage data of power systems

Hartmann, B.; Deng, S.; Ódor, G.; Kelling, J.

Abstract

The size distribution of planned and forced outages in power systems have been studied for
almost two decades and has drawn great interest as they display heavy tails. Understanding of this
phenomenon has been done by various threshold models, which are self-tuned at their critical points,
but as many papers pointed out, explanations are intuitive, and more empirical data is needed to
support hypotheses. In this paper, the authors analyze outage data collected from various public
sources to calculate the outage energy and outage duration exponents of possible power-law fits.
Temporal thresholds are applied to identify crossovers from initial short-time behavior to power-
law tails. We revisit and add to the possible explanations of the uniformness of these exponents.
By performing power spectral analyses on the outage event time series and the outage duration
time series, it is found that, on the one hand, while being overwhelmed by white noise, outage
events show traits of self-organized criticality (SOC), which may be modeled by a crossover from
random percolation to directed percolation branching process with dissipation. On the other hand,
in responses to outages, the heavy tails in outage duration distributions could be a consequence of
the highly optimized tolerance (HOT) mechanism, based on the optimized allocation of maintenance
resources.

Keywords: power grid; self-organized criticality; highly optimized tolerance

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Permalink: https://www.hzdr.de/publications/Publ-36739


Optimizing PW Laser-Driven Proton Acceleration by Characterizing Laser Transmission of Relativistically Transparent Targets

Umlandt, M. E. P.; Assenbaum, S.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Ditter, E. J.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Hicks, G. S.; Kiriyama, H.; Kluge, T.; Koga, J. K.; Kon, A.; Kondo, K.; Kraft, S.; Kroll, F.; Lowe, H. F.; Metzkes-Ng, J.; Miyatake, T.; Najmudin, Z.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Reimold, M.; Sakaki, H.; Schlenvoigt, H.-P.; Shiokawa, K.; Zeil, K.; Ziegler, T.; Schramm, U.

Abstract

Ion acceleration by compact laser-plasma sources has great potential for a range of applications, including those with medical relevance and fusion experiments. However, in order to achieve the necessary beam quality parameters for these applications, a thorough understanding and control over the laser-plasma interaction process is required.
Therefore, we are exploring laser plasma acceleration around the promising regime of Relativistically Induced Transparency (RIT) through joint studies at DRACO PW (HZDR) and the J-KAREN-P laser system at KPSI. We have performed thickness scans to investigate the relation between proton acceleration performance and target transparency, revealing high-performance proton beams (> 60 MeV) in an expanded foil case, with an optimum at the onset of target transparency. [1] Subsequent experiments showed even higher proton energies.
Clearly, the relationship between the transparency onset time and the acceleration performance is crucial for achieving optimal beam parameters, improving our understanding of the sensitivity of laser input parameters, and increasing the process’s robustness. Thus, we are using a combination of particle and laser diagnostics to investigate this correlation. In this contribution, we present a summary of our studies in which we use spectral interferometry with the unperturbed laser beam as a reference to evaluate the output of reflected and transmitted light diagnostics. Obtaining features like shown in Bagnoud et al. [2] and Williamson et al. [3], we additionally correlate these measures with the proton acceleration performance and show first results of spectral, spatial, and energy analysis of the effects on the laser transmission through the target.

References
[1] Dover, N. P. et al.: Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities. Light Sci. Appl. in press (2023).
[2] Bagnoud, V. et al.: Studying the Dynamics of Relativistic Laser-Plasma Interaction on Thin Foils by Means of Fourier-Transform Spectral Interferometry. Phys. Rev. Lett. 118, 255003 (2017).
[3] Williamson, S. D. R. et al.: Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions. Phys. Rev. Appl. 14, 034018 (2020).

Keywords: laser plasma; laser proton acceleration; high power laser

Involved research facilities

  • Draco
  • Poster
    Laser and Plasma Accelerators Workshop 2023, 06.-10.03.2023, Lagos, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36738


State-of-the-Art Room Temperature Operable Zero-Bias Schottky Diode-Based Terahertz Detector up to 5.56 THz

Yadav, R.; Ludwig, F.; Faridi, F. R.; Klopf, J. M.; Roskos, H. G.; Preu, S.; Penirschke, A.

Abstract

We present the characterization of a Zero-bias Schottky diode-based Terahertz (THz) detector up to 5.56 THz. The detector was operated with both a table-top system until 1.2 THz and at a Free-Electron Laser (FEL) facility at singular frequencies from 1.9 to 5.56 THz. We used two measurement techniques in order to discriminate the sub-ns-scale (via a 20 GHz oscilloscope) and the ms-scale (using the lock-in technique) responsivity. While the lock-in measurements basically contain all rectification effects, the sub-ns-scale detection with the oscilloscope is not sensitive to slow bolometric effects caused by changes of the IV characteristic due to temperature. The noise equivalent power (NEP) is 10 pW/√Hz in the frequency range from 0.2 to 0.6 THz and 17 pW/√Hz at 1.2 THz and increases to 0.9 μW/√Hz at 5.56 THz, which is at the state of the art for room temperature zero-bias Schottky diode-based THz detectors with non-resonant antennas. The voltage and current responsivity of ∼500 kV/W and ∼100 mA/W, respectively, is demonstrated over a frequency range of 0.2 to 1.2 THz with the table-top system.

Keywords: FELBE; THz detectors; FEL; Schottky; ultrafast

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Permalink: https://www.hzdr.de/publications/Publ-36737


Experimental and numerical investigation of a density-driven instability during a horizontal miscible displacement

Stergiou, Y.; Papp, P.; Horvath, D.; Toth, A.; Eckert, K.; Schwarzenberger, K.

Abstract

We performed an experimental and numerical investigation of a convective buoyancy-driven instability that arises during the injection of a denser miscible fluid into a less dense one in a rectilinear geometry. We visualized the instability using a shadowgraph technique and we obtained quantitative information using micro-Paricle Image Velocimetry. Numerical simulations provided further insights into the 3D velocity field. We suggest scalings of the critical time, TC and dimensionless wavelength, λ/h of the instability by using the Péclet and Rayleigh numbers. Finally, we investigated the interactions of the instability vortices with each other and the geometry boundaries.

Keywords: instabilities : buoyancy-driven; computational fluid dynamics; vortex flows; buoyancy; convection

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Permalink: https://www.hzdr.de/publications/Publ-36736


Positron beams for materials research

Wagner, A.; Butterling, M.; Hirschmann, E.; Liedke, M. O.; Krause-Rehberg, R.

Abstract

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions (σt ≈100 ps) at high average rates (105 s-1) and adjustable beam repetition rates allow performing high-throughput experiments.
The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). AIDA was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox) and by the Helmholtz Energy Materials Characterization Platform.
[1] A. Wagner, et al., AIP Conference Proceedings, 1970, 040003 (2018).

Keywords: positron annihilation; lifetime spectroscopy; superconducting linear accelerator; defect characterization; porosity; vacancies

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  • Lecture (Conference)
    Frühjahrstagung der Deutschen Physikalischen Gesellschaft, 26.-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36735


Quasi-2D FCC lithium crystals inside defective bi-layer graphene: insights from first-principles calculations

Zhang, X.; Ghorbani Asl, M.; Zhang, Y.; Krasheninnikov, A.

Abstract

Quasi-2D crystals inside bilayer graphene have been observed in in-situ TEM experiments [Nature 564 (2018) 234]. It was also revealed that Li crystals have the FCC structure, nucleate at point defects in graphene and contain impurity atoms. Using first-principles calculations, we systematically study the interaction of isolated Li atoms and those assembled in FCC crystals with vacancy-type defects in graphene and show that quasi-2D Li crystals encapsulated between graphene sheets must indeed nucleate at the defects and that the interaction of not only isolated Li atoms but also Li crystals with the defects in graphene is strong. We further demonstrate that a moiré pattern develops at the graphene/Li interface. Finally, we investigate the behavior of impurities most likely to be found in the encapsulated Li crystals, such as O, N, S, and F and show that all impurity atoms take octahedral interstitial positions and strongly interact with atoms in Li crystals, thus impeding the de-lithiation process. Our theoretical work focused on the fundamental aspects of the behavior of Li inside bilayer graphene should help rationalize the results of in-situ TEM experiments and shed light on the role of impurities in the degradation of anode materials during Li-ion battery operation.

Keywords: Li intercalation; graphene; defects; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-36733


Hydrodynamics in a bubble column – Part 1: Two-phase flow

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

Multiphase computational fluid dynamics (CFD) simulation is a useful tool to study the hydrodynamics in a bubble column, if appropriate closure models are known. Systematic assessment of different models is an ongoing venture that benefits from improved validation data. The present study accumulates a database on two-phase flow experiments in a bubble column. This is achieved by using a combination of Particle Image Velocimetry and Shadowgraphy to measure the liquid velocity field and gas dispersion properties simultaneously. This methodology is applied for different needle diameters and gas flow rates.

A detailed description of the experimental

The experimental data (Table 1) described in this repository is structured into different folders and files as follows:
Level 1: Folders classified by measurement configuration: TX_Jg_Y_Di_ZZZ as outlined in Table 1

  • TX = Identifier
  • Jg_Y = Superficial gas velocity in mm/s
  • Di_ZZZ = Inner diameter of the needle in µm

Level 2: Folders classified by measurement height: Z_XXX

  • Z_XXX = Measurement height in mm

Level 3: csv files classified by their analysis parameter:

  • Gas_Eg_ub_over_x.csv: Each csv file consists of five columns, namely the x-coordinate (in m), the gas holdup, the uncertainty of the gas holdup, the averaged bubble rising velocity (in m/s) and the corresponding uncertainty (in m/s).
  • Liquid_v_z_over_x.csv: Each csv file consists of three columns, namely the x-coordinate (in m), the averaged liquid velocity (in m/s) and the corresponding uncertainty (in m/s).

Table 1: Overview of the measurement cases in this repository.

| ID | Diameter of needle orifice in µm | Superficial gas velocity in mm/s |
|----|----------------------------------|----------------------------------|
| T1 | 200                              | 2                                |
| T2 | 200                              | 4                                |
| T3 | 200                              | 6                                |
| T4 | 600                              | 2                                |
| T5 | 600                              | 4                                |
| T6 | 600                              | 6                                |

Keywords: Particle Image Velocimetry (PIV); Shadowgraphy; Two-phase bubble column

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Permalink: https://www.hzdr.de/publications/Publ-36732


Data publication: Deconvoluting Cr States in Cr-Doped UO2 Nuclear Fuels via Bulk and Single Crystal Spectroscopic Studies

Murphy, G. L.; Gericke, R.; Gilson, S.; Bazarkina, E.; Roßberg, A.; Kaden, P.; Thümmler, R.; Klinkenberg, M.; Henkes, M.; Kegler, P.; Svitlyk, V.; Marquardt, J.; Lender, T.; Hennig, C.; Kvashnina, K.; Huittinen, N. M.

Abstract

Experimental and fitted EPR data of Cr-UO2 single crystal grains, EXAFS data Cr-UO2 single crystal grain and powder with Cr redox standards, XANES data Cr-UO2 single crystal grain and powder with Cr redox standards

Keywords: Cr-doped UO2; Nuclear Fuel; Uranium; EPR; HERFD-XANES; EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-36731


StarDist Models for "Hydrodynamics in a bubble column – Part 1: Two-phase flow"

Sommer, A.-E.; Draw, M.; Wang, L.; Schmidtpeter, J.; Hessenkemper, H.; Gatter, J.; Nam, H.; Eckert, K.; Rzehak, R.

Abstract

This package contains the software and the trained models described in the publication "Hydrodynamics in a bubble column – Part 1: Two-phase flow". Please refer to the readme.md for installation instructions and to the Prediction_demo.ipynb for usage demonstration.

Keywords: StarDist; Bubble detection; Shadowgraphy

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Permalink: https://www.hzdr.de/publications/Publ-36730


Klassifikation von Pulsdaten mit neuronalen Netzwerken auf einer FPGA Accelerator Card

Ufer, R.; Auer, B.; Hoffmann, H.; Knodel, O.; Lokamani, M.; Müller, S.

Abstract

Zur Analyse der entstehenden Detektordaten bei dem Mu2e Experiment am Fermilab soll die Datenauswertung mit Field Programmable Gate Array (FPGA) erfolgen. Diese übernehmen die notwendige Vorverarbeitung und Reduktion der Messdaten, noch während der Durchführung der Messung. Die dabei ausgeführten Anwendungen werden standardmäßig durch Algorithmen realisiert. Eine dieser Anwendungen führt die Klassifikation der ermittelten Pulsdaten durch. Mit den Testläufen an der gELBE Bremstrahlungs-Beamline am Helmholtz-Zentrum Dresden-Rossendorf (HZDR) konnte für das zukünftige Experiment eine große Menge dieser Datensätze erfasst werden. Diese dienen zur Charakterisierung des Detektorsystems und wurden mit einem Lanthanbromid (LaBr) Detektor gemessen. Für die Pulsdatenklassifikation wird auf der Basis des Algorithmus und der erfassten Datensätze, ein neuronales Netzwerk erstellt, trainiert und validiert. Um bei diesen Schritten etablierte Machine Learning Frameworks zu verwenden, wird für die Portierung des Netzwerks in eine High-Level Synthese (HLS) Sprache die Software hls4ml verwendet. Dabei werden verschiedene Konfigurationen genutzt, um unterschiedlich optimierte Implementierungen zu generieren. Zum Evaluieren erfolgt die Ausführung der Implementierungen auf einer Xilinx Alveo Accelerator Card.

Keywords: FPGA; ML; CI; Mu2e

  • Lecture (Conference)
    86. Jahrestagung der DPG und DPG-Frühjahrstagung, 20.-24.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36729


Investigation of contrast mechanisms for MRI phase signal-based proton beam visualization in water phantoms

Schieferecke, J.; Gantz, S.; Hoffmann, A. L.; Pawelke, J.

Abstract

Purpose: The low sensitivity and limitation to water phantoms of convection-dependent MRI
magnitude signal-based proton beam visualization hinder its in-vivo applicability in MR-integrated
proton beam therapy. The purpose of the present study was therefore to assess possible contrast
mechanisms for MRI phase signal-based proton beam visualization that can potentially be exploited
to enhance the sensitivity of the method and extend its applicability to tissue materials.
Methods: To assess whether proton beam-induced magnetic field perturbations, changes in material
susceptibility or convection result in detectable changes in the MRI phase signal, water phantom
characteristics, experiment timing and imaging parameters were varied in combined irradiation and
imaging experiments using a time-of-flight angiography pulse sequence on a prototype in-beam MRI
scanner. Velocity encoding was used to further probe and quantify beam-induced convection.
Results: MRI phase signal-based proton beam visualization proved feasible. The observed phase
difference contrast was evoked by beam-induced buoyant convection with flow velocities in the mm/s
range. Proton beam-induced magnetic field perturbations or changes in magnetic susceptibility did not
influence the MRI phase signal. Velocity encoding was identified as a means to further enhance the
detection sensitivity.
Conclusion: Because the MRI phase difference contrast observed during proton beam irradiation of water phantoms is caused by beam-induced convection, this method will unlikely be transferable to tightly compartmentalized tissue wherein flow effects are restricted. Strongly velocity encoded pulse
sequences, however, were identified as promising candidates for the future development of MRI-
based methods for water phantom-based geometric quality assurance in MR-integrated proton beam
therapy.

Keywords: in-beam MRI; proton therapy; proton beam visualization; phase difference imaging; velocity encoding; convection

Involved research facilities

  • OncoRay

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Permalink: https://www.hzdr.de/publications/Publ-36728


Characterization of defect microstructure in MgRE (RE=Ce, Nd) alloys after processing by High-Pressure Torsion using Positron Annihilation Spectroscopy and a High Resolution X-ray Diffraction

Bibimoune, I.; Bourezg, Y. I.; Abib, K.; Liedke, M. O.; Wagner, A.; Matej, Z.; Huang, Y.; Langdon, T. G.; Bradai, D.

Abstract

Two MgRE (RE=Ce, Nd) alloys with ultrafine-grain (UFG) microstructures were prepared by high-pressure torsion (HPT) at room temperature. The in-depth distribution of defects was
characterized by Doppler broadening –variable energy positron annihilation spectroscopy (DBVEPAS). The characteristic S parameter increases in bulk after HPT processing relative to an
as-received sample and shows a relative stability between ½ and 10 turns, which suggests a rise in the open volume defect density. However, a theoretical analysis of the S(E) depth profile reveals an increase in the positron diffusion length from ~115 nm for the as-received state to ~207 nm after 10 HPT turns. Almost all the open volume defect consisted of dislocations
(positron lifetime of τ = 260 ps). The dislocation density deduced from high-resolution X-ray diffraction in the HPT disc radial direction was reasonably homogeneous (around 4 - 6e14 m-2).

Keywords: Mg; rare earthhtp; dislocations; positron annihilation spectroscopy; VEPfit

Involved research facilities

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36727


Techno-economic assessment of PEM electrolysis for O2 supply in activated sludge systems – a simulation study based on the BSM2 wastewater treatment plant

Parra Ramirez, M. A.; Fogel, S.; Reinecke, S.; Hampel, U.

Abstract

The conversion of renewable energy into hydrogen (H2) by power-to-gas technologies involving electrolysis is seen today as a key element in the transition to a renewable energy sector. Wastewater treatment plants (WWTP) could make use of oxygen (O2) produced alongside H2 in biological treatment steps, however, production costs of electrolysis O2 should be competitive with respect to those of conventional O2 production processes. In this study, mathematical models of a polymer electrolyte membrane electrolyser (PEME) plant and the WWTP of the Benchmark Simulation Model Nr. 2 (BSM2) were used to simulate electrolysis O2 supply to an activated sludge (AS) system and estimate net costs of production (NCP) via a techno-economic assessment (TEA). Assuming that produced H2 is sold to a nearby industry, NCPs for O2 were calculated for two scenarios regarding PEME plant dimensions, which correspond to average (scenario 1) and optimal (scenario 2) electricity availability, i.e. medium and high number of full load hours per year. For each scenario, estimations were made for four alternatives for electricity supply and costs, namely conventional sources, photovoltaic (PV), and on/off shore wind energy, and using sets of optimistic, neutral and pessimistic data regarding system performance and market conditions. The analyses were done for 2020 as reference year and again for 2030 based on forecasts of relevant data. The results of the dimensioning of the PEME plant in scenario 1 show that a 6.4 MW PEME operated for 4,073 full load hours per year is able to cover the O2 demand of the AS system during more than 99% of the simulated period. The same is true for a 4.8 MW PEME operated for 6,259 full load hours per year in scenario 2. The TEA shows that investment costs for the PEME stacks and the operational costs for electricity make up most of the NCP of electrolysis O2. Although NCP for electrolysis O2 are always higher than those of conventional O2 sources for the year 2020, in 2030 estimated NCPs for the smaller PEME plant of scenario 2 become competitive for PV and wind on shore electricity supply under optimistic market conditions. Potential minimum selling prices were also calculated for the produced O2, however, they were above those of conventional O2 sources both in 2020 and 2030. The approach described in this study can be applied to analyse O2 supply to biological wastewater treatment in WWTPs with different characteristics, in processes different to conventional AS, and under different assumptions regarding economic conditions.

Keywords: Wastewater treatment; Activated sludge; PEM electrolysis; Techno-economic assessment

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Permalink: https://www.hzdr.de/publications/Publ-36725


Influence of Eu(III) and U(VI) on rat and human kidney cells

Butscher, D.; Senwitz, C.; Heller, A.; Stumpf, T.; Barkleit, A.

Abstract

Radionuclides (RNs) that enter the human body, for example through ingestion or inhalation, pose a potential health risk due to their radio- and chemotoxicity. The kidneys are especially exposed to the incorporated RNs, as they are mainly responsible for the excretion of toxic substances from the blood stream. Therefore, the effect of uranium(VI) and europium(III), an analogue for trivalent actinides such as Am or Cm, on rat (NRK-52E) and human (HEK-293) kidney cells was studied in vitro at the cellular and molecular levels.
Exposure experiments were carried out in which cells were incubated with these metal ions (10−9 – 10−3 M) for 7, 24 and 48 hours. The cell viability after exposure to the metal ions was measured using the XTT-assay. The half-maximum effective concentration (EC50) was calculated on the basis of the dose-response curves. In addition, morphological changes due to metal ion exposure were investigated by staining selected cell compartments and intracellular uptake was determined by ICP-MS. The speciation of a metal determines its bioavailability, influencing both the effect on cells and its uptake into cells. Therefore, time resolved laser-induced fluorescence spectroscopy (TRLFS) was used to investigate the speciation of Eu(III) and U(VI) in the cell culture medium, in the cell-exposed medium and in cell suspension. The obtained results on the cellular and molecular level contribute to a better understanding of the toxic effects of RNs.
This work is funded in the frame of the RADEKOR project by the German Federal Ministry of Education and Research (BMBF, grant number: 02NUK057A and 02NUK057B).

Keywords: Cytotoxicity; Kidney cells; Uranium; Europium; EC50; Speciation

  • Lecture (Conference)
    7th International Conference on Environmental Radioactivity (ENVIRA), 17.-22.09.2023, Seville, España

Permalink: https://www.hzdr.de/publications/Publ-36723


Theorien und Experimente zur Entstehung und Wirkung kosmischer Magnetfelder

Stefani, F.

Abstract

Der Vortrag beschäftigt sich mit Theorien und Experimenten zur Entstehung und Wirkung kosmischer Magnetfelder. Ein besonderer Schwerpunkt liegt auf der Vorstellung des DRESDYN-Experiments am HZDR.

Involved research facilities

  • DRESDYN
  • Invited lecture (Conferences)
    Öffentlicher Vortrag im Palitzsch-Museum Dresden, 23.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36720


Finite Elemente Simulation der Aufschlusszerkleinerung von Verbundstrukturen im Recycling

Heibeck, M.; Richter, J.; Mütze, T.; Filippatos, A.

Abstract

Die Kombination von Materialien wie Metallen und Kunststoffen in Verbundstrukturen ermöglicht funktionsintegrative Designs. Im Recycling müssen die unterschiedlichen Materialien jedoch wieder aufgeschlossen werden, um materialspezifisch hohe Recyclingraten zu erzielen. Typischerweise erfolgt der Aufschluss durch mechanische Zerkleinerungsprozesse. Derzeit gibt es keine adäquate Beschreibung dieser Prozesse, die zu einer recyclingorientierten Produktgestaltung beitragen könnte. Im Beitrag wird ein Ansatz zu physikalisch basierten numerischen Simulationen mit der Finite-Elemente-Methode (FEM) vorgestellt.

Keywords: FEM; Aufschluss; Zerkleinerung; Rotorreißer; Verbundwerkstoff

  • Lecture (Conference)
    DECHEMA - Fachgruppentreffen Zerkleinern & Klassieren 2023, 21.-22.03.2023, Braunschweig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36719


Hands-on training on machine learning

Fiedler, L.

Abstract

Hands-on training on machine learning and the MALA library.

  • Lecture (others)
    Theoretical Chemistry Seminar, 21.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36718


Demonstrating temperature transferability of neural network models replacing modern density functional theory

Fiedler, L.; Cangi, A.

Abstract

Due to its balance between accuracy and computational cost, Density Functional Theory (DFT) is one of the most important computational methods within materials science and chemistry. However, current research efforts such as the modeling of matter under extreme conditions demand the application of DFT to larger length scales as well as higher temperatures. Such investigations are currently prohibited due to the computational scaling of DFT.

We have recently introduced a machine-learning workflow that replaces modern DFT calculations [1,2,3]. This workflow uses neural networks to predict the electronic structure locally. We show that by employing such an approach, models can be trained to predict the electronic structure of matter across temperature ranges. This paves the way for large-scale simulations of thermodynamically sampled observables relevant to modeling technologically important phenomena such as radiation damage in fusion reactor walls.

Keywords: Density Functional Theory; Surrogate Models; Machine Learning

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 27.03.2023, Dresden, Deutschland
  • Invited lecture (Conferences)
    Electronic Structure Workshop, 13.-16.06.2023, Merced, USA

Permalink: https://www.hzdr.de/publications/Publ-36717


Monte Carlo simulation studies of background contributions in the Mu2e experiment

Rachamin, R.; Di Falco, S.; Ferrari, A.; Giusti, V.; Müller, S. E.; Pronskikh, V. S.

Abstract

The Mu2e experiment is currently being constructed at Fermilab to search for the direct conversion of muons into electrons in the field of a nucleus without the emission of neutrinos. The experiment aims at a sensitivity of four orders of magnitude higher than previous related experiments, which implies highly demanding accuracy requirements both in the design and during the operation. Hence, it is essential to estimate precisely the backgrounds that could mimic the monoenergetic conversion electron signal and the particle yields relevant to the experiment sensitivity. In that regard, Monte Carlo simulations were performed to investigate key yields and beam-related and cosmic rays-related backgrounds. The investigation includes: (I) an evaluation of the antiproton and charged pion yields from an 8 GeV proton pencil beam impinging on a tungsten cylindrical target, (II) an evaluation of the transmission of cosmic neutrons and neutral kaons in a block of concrete. The simulations were performed using the FLUKA2021, MCNP6, GEANT4, PHITS, and MARS15 codes. The presentation will show the simulation results with a focus on the prediction obtained from each code and their impact on the experiment.

Keywords: Charged Lepton Flavor Violation; Muon to Electron conversion; Mu2e experiment; Monte Carlo; GEANT4; PHITS; MARS15; FLUKA; MCNP

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

Permalink: https://www.hzdr.de/publications/Publ-36716


The Stopping Target Monitor of the Mu2e experiment

Müller, S.; Ferrari, A.; Knodel, O.; Rachamin, R.

Abstract

The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless direct conversion of a muon to an electron in the field of an aluminum nucleus, aiming for a sensitivity four orders of magnitude better than previous experiments. The observation of a clear signal would imply Charged Lepton Flavor Violation, and hint at physics beyond the Standard Model.

The normalization of the signal events will be done by monitoring the rate of muons stopping on aluminum target discs. This will be accomplished with a detector system made of an HPGe detector and a Lanthanum Bromide detector, which detect the characteristic X- and γ-rays of energies up to 1809 keV produced when the muons are stopped or captured on the aluminum.

At the Helmholtz-Zentrum Dresden-Rossendorf, we have used a pulsed Bremsstrahlung photon beam at the ELBE radiation facility to study the performance of the detectors under conditions very similar to the ones expected at Mu2e.

In the presentation, a short overview of design and status of the Mu2e experiment and its detectors will be given, and results of the ELBE beamtime campaigns will be presented.

Keywords: Mu2e; STM; CLFV; FNAL

Involved research facilities

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  • Lecture (Conference)
    DPG Meeting SMuK, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36715


Activation calculations for decommissioning planning of NPPs

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

Abstract

By the middle of 2023, all German nuclear power plants (NPPs) will have been shut down. The final shutdown is followed by a post-operational phase in which measures can be carried out to prepare for the NPPs dismantling and decommissioning. One of the essential tasks in planning and preparing an NPP for decommissioning is to obtain precise knowledge of the activation levels in its reactor pressure vessel (RPV), the biological shielding, and other internal components. In that regard, a novel method based on the combined use of two Monte Carlo codes, MCNP6 and FLUKA2021, was developed to serve as a non-destructive tool for evaluating the activation in an NPP. The presentation will give an overview of the methodology and demonstrate its application through the activation calculations of selected components of a German pressurized water reactor (PWR), which is the most common NPP type in Germany.

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

  • Invited lecture (Conferences)
    86th Annual Conference of the DPG and DPG Spring Meeting, 20.-24.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36714


Sensing strategies for determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

The gas flow modulation technique (GFM) is a recently proposed approach for measuring the axial gas dispersion coefficient in bubble columns. It bases on a time-resolved measurement of the modulated gas holdup at different axial positions in the column and a subsequent calculation of the axial dispersion coefficient from amplitude damping and the phase lag of a gas holdup wave. In recent studies holdup has been measured with gamma-ray densitometry, which is advantageous in terms of measurement accuracy. However, the application of radiative measurement techniques in industrial settings poses several logistical and safety challenges. This study investigates the potential of non-radiative measurement techniques in the context of GFM. In particular, differential pressure sensors, conductivity needle probes and optical probes are considered. The results obtained using these alternative techniques are compared with gamma-ray measurements. The comparison qualifies differential pressure sensors as a particular viable alternative to gamma-ray densitometry.

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36713


Determining the axial gas dispersion coefficient in bubble columns via gas flow modulation technique and several sensing strategies

Marchini, S.; Bieberle, A.; Schleicher, E.; Schubert, M.; Hampel, U.

Abstract

Collected data refer to gas flow modulation measurements in a D=100 mm bubble column. The axial holdup wave is determined at three axial positions using different sensing stategies (gamma-ray densitometry, differential pressure sensors, transmittance optical probes and conductivity needle probes). Average gas holdup as well as amplitude damping and phase-shift have been determined at three different gas flow rates in the homogeneous regime. A description of the experimental setup is provided in the file "Experimental_setup.pdf". An overview of the performed experiments is provided in the Excel file "DataDescription.xlsx"

Keywords: gas flow modulation; axial dispersion coefficient; bubble columns; conductivity needle probes; transmittance optical probes

Involved research facilities

  • TOPFLOW Facility

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Permalink: https://www.hzdr.de/publications/Publ-36712


Halomonas gemina sp. nov. and Halomonas llamarensis sp. nov., two siderophore-producing organisms isolated from high-altitude salars of the Atacama Desert

Hintersatz, C.; Singh, S.; Antonio Rojas, L.; Kretzschmar, J.; Wei, T.-S.; Khambhati, K.; Kutschke, S.; Lehmann, F.; Singh, V.; Jain, R.; Pollmann, K.

Abstract

This study aimed to discover novel siderophore-producing organisms with the ability to produce high amounts of the iron-binding compounds. In the course of this, two not yet reported halophilic strains designated ATCHAT and ATCH28T were isolated from hypersaline, alkaline surface waters of Salar de Llamará and Laguna Lejía, respectively. As an alkaline milieu greatly reduces the bioavailability of iron, organisms native to those environments were suspected to produce greater amounts of siderophores to sequester the essential element. Both strains were characterized utilizing a polyphasic approach and further investigated to assess their ability to secrete siderophores. Comparative analysis of the 16S rRNA gene sequences revealed that the isolates belonged to the genus Halomonas. ATCHAT was closely related to Halomonas. salicampi and Halomonas vilamensis, while ATCH28T was related closest to Halomonas ventosae and Halomonas salina. Utilizing the chromeazurol S liquid assay, both strains were shown to produce iron-binding compounds. Via NMR and genomic analysis, the siderophore synthesized by strain ATCH28T has been determined to be desferrioxamine E (DFOE). Although this siderophore is common for various terrestrial microorganisms, it has not yet been reported to occur within Halomonas, making strain ATCH28T first member of the genus to produce a non-amphiphilic siderophore. Furthermore, the effect of various media components on the secretion of DFOE was investigated and obtained concentrations could be increased to more than 1000 µM of the compound. Genomic analysis of strain ATCHAT revealed the presence of a not yet reported NRPS-dependant gene cluster responsible for the secretion of siderophore. However, the strain only secreted small amounts of the iron-binding compound and therefore its siderophore was not investigated exhaustively within the scope of this study. Based on their phenotypic and genotypic characteristics, both strains unambiguously differed from other described members of the genus Halomonas. Average nucleotide identity (ANI) values and levels of DNA-DNA relatedness clearly indicated that the strains represented two novel species. Hence, both species should be added as new representatives of the genus Halomonas, for which the designations Halomonas llamarensis sp. nov. (type strain ATCHAT=DSM 114476=LMG 32709) and Halomonas gemina sp. nov. (type strain ATCH28T=DSM 114418=LMG 32708) are proposed.

Keywords: Halophilic bacteria; siderophores; polyphasic taxonomic; desferrioxamine E; Atacama Desert

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Permalink: https://www.hzdr.de/publications/Publ-36711


Concepts of statistical entropy for the evaluation of comminution and separation processes

Tolosana Delgado, R.; Schach, E.; Peuker, U.

Abstract

Statistical entropy, corresponding to Shannon entropy in information theory or Gibbs entropy in physical thermodynamics, can be used to evaluate the additional disorder in a system induced by its subdivision in components or subsystems. Several variations of this concept have been introduced in the last 20 years to quantify the efficiency of a separation process (or a chain of it) within the context of minerals processing both in mining and recycling. This contribution presents a coherent frame connecting these concepts, and extends them to evaluate comminution processes, in such a way that joint thermoeconomic zoptimization of whole beneficiation plants becomes possible.

The main idea is to split the system simultaneously into three dimensions: (1) mineral or chemical components, (2) particles or particle classes, and (3) output streams. In each of these dimensions, a different ratio can be defined to describe the way the mass (or volume or matter) of the system is split into the subsystems: (1) a composition; (2) a particle-wise distribution; a (3) set of partition coefficients. Entropy contributions can then be defined for each of these dimensions at different levels of integration, e.g. (1) component-wise or for a total, (2) particle-wise or bulk-wise, (3) per stream or per stage feed.

By systematically considering all possible entropy decompositions, the following results were found. Total stage entropy does not depend on the ordering of integration through the three dimensions. Comminution cannot decrease the stage entropy; a comminution that would generate perfectly liberated particles without overgrinding would keep the stage entropy constant. A separation process cannot decrease stage entropy, and perfect separation would keep it constant. However, once the masses of the output streams are measured, the output entropy does indeed decrease for any moderately good separation process. The difference between the stage entropy with and without controlling output masses can then be understood as the information value of the output mass flow measurements.

  • Open Access Logo Contribution to proceedings
    22nd Annual Conference of the International Association for Mathematical Geosciences, 05.-12.08.2023, Trondheim, Norway

Permalink: https://www.hzdr.de/publications/Publ-36710


In-situ flow visualization with Geo-Positron-Emission-Tomography in a granite fracture from Soultz-sous-Forêts, France

Pingel, J. L.; Kulenkampff, J.; Jara-Heredia, D.; Zhou, W.; Fischer, C.; Schäfer, T.

Abstract

We investigate the fluid flow field in a fractured granite core sample. Sequential imaging with Positron-Emission-Tomography (PET) allows direct reconstruction of flow streamlines, thus providing a unique insight into the fluid dynamics of complex fractured crystalline materials. Pulse migration experiments using the positron-emitting radionuclide 18F- as tracer were conducted on a fractured granitic drill core, originating from a depth of 1958 m of the Enhanced Geothermal System (EGS) reference site at Soultz-sous-Forêts, France. The flow field was analyzed as a function of in- and outlet positions across the fracture, as well as applied flow rates. Different flow path characteristics were identified. Both the fracture aperture variation and the topography of the fracture surface affect the flow field with consequences on flow channeling and preferential flow paths. Furthermore, pulse migration experiments were also numerically simulated with a 2.5D model using COMSOL Multiphysics®.
While the higher flow rate experiments show wider and higher dispersion of the flow path, lower velocity results in more localized flow and channeling behavior. This type of study thus yields enhanced experimental insights into the hydrodynamics of fracture flow and its relation to the rough structure of natural single fractures, compared to input‑output experiments. It can help to validate model simulations and experimentally determine hydrodynamic parameters needed for reactive transport modeling that are otherwise estimated with a high degree of uncertainty.

Keywords: Positron Emission Tomography; single fracture; fluid flow; flow channeling; fracture aperture; COMSOL

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Permalink: https://www.hzdr.de/publications/Publ-36709


Influence of soil microbiology on radionuclide transport and uptake into plants

Linares Jimenez, R. E.; Flemming, K.; Matschiavelli, N.; Cherkouk, A.; Raff, J.; Stumpf, T.; Sachs, S.

Abstract

Deep geological repositories (DGR) will be used for the final disposal of highly radioactive waste. For the safety assessment of the DGR, it is important to consider accident scenarios such as the ingress of water, which might lead to a release of radionuclides (RNs) from the repository into the groundwater. RNs in groundwater can migrate to the surface soil where they can interact with indigenous microorganisms and plants, entering the food chain and posing a health risk to humans. The reliable modelling of the RN uptake into plants requires more than just transfer factors. A more detailed process understanding of the RN uptake into plants, including the effects of soil microorganisms, is necessary. RNs may affect the soil microbial community altering the natural community composition and interactions. Root exudates from plants and microorganisms can alter the speciation of RNs, affecting their bioavailability and mobility.
We study the impact of soil microorganisms on the RN transport and uptake into plants at the molecular level. The experiments discussed focus on studying the modulation of soil microbial diversity in the presence of RNs and selected root exudates. In addition, radiation-resistant soil microorganisms will be isolated to study their interaction with RNs and their effect on the degradation of root exudates. This will include characterization of the degradation products and their interactions with RNs. These findings will be used to elaborate radioecological models for the assessment of the RN transport and uptake into the food chain.

Keywords: Soil; Radionuclides; Microbial diversity; Root exudates; Plants

  • Poster
    ENVIRA 2023 - 7th International Conference on Environmental Radioactivity, 17.-22.09.2023, Sevilla, España

Permalink: https://www.hzdr.de/publications/Publ-36708


A continuous multiphase model for liquid metal batteries

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

Abstract

Liquid metal batteries (LMBs) are a promising candidate for large-scale stationary storage of renewably generated energy. Their Earth-abundant electrode materials and highly conductive molten salt electrolytes confer the low costs and high power densities required for grid-scale storage. LMB operation involves a complex interplay between mass transport mechanisms, and as a result their performance potential and operational limits are not fully understood. In this study, a multiphase numerical model is presented that simulates the charge and discharge processes of an LMB based on the Na-Zn couple. The model computes the changes in electrode and electrolyte volume, and resolves the spatial variations in the chemistry of the electrolyte that accompany the interfacial reactions. Volume change and species redistribution were found to be important in predicting the maximum theoretical capacity of the cell when neglecting other transport mechanisms.

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

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36707


Multiobjective tuning technique for MPC in grinding circuits

Yamashita, A. S.; Martins, W. T.; Pinto, T.; Raffo, G. V.; Melo Euzebio, T. A.

Abstract

We investigate the control challenges in grinding circuits---slow dynamics, long dead times, variable coupling--- and the controller tuning challenge, that is, the difficulty in translating operating goals into tuning goals and closed-loop performance. A tuning algorithm for DMC (dynamic matrix control), suitable for the mineral processing industry, is proposed. The tuning problem is posed as a multiobjective optimization problem, in which the tuning goals are directly related to the desired closed-loop performance of process variables. The problem is solved using a compromise optimization, which minimizes the Euclidian distance between a feasible solution and the Utopia solution. Three case studies are presented, which validate the tuning algorithm for DMC in linear and non-linear grinding circuit models. The closed-loop performance obtained with the proposed tuning algorithm is compared to the one obtained through a benchmark tuning technique from the literature. The proposed tuning method has the following features: i) it shapes the closed-loop response according to the goal definitions for linear systems; ii) it requires tailored initial guesses and search spaces to converge to a stabilizing solution in non-linear applications; and iii) it allows the user to specify the desired closed-loop performance behavior in the tuning procedure, allowing the implementation of an adequate controller for each situation.

Keywords: grinding circuit; model predictive control; dynamic matrix control; controller tuning; multiobjective optimization; compromise optimization

Permalink: https://www.hzdr.de/publications/Publ-36706


Superconducting radio frequency Photoinjectors for CW-XFEL

Xiang, R.; Arnold, A.; Lewellen, J. W.

Abstract

A dependable and consistent electron source is a crucial requirement for the achievement of high-power free electron lasers (FELs). Over the past two decades, it has been demonstrated that photoinjectors based on SRF technology (SRF guns) are suitable for continuous wave (CW) beam generation. SRF guns possess both the high accelerating field gradients of normal conducting RF photoinjectors and the low power dissipation thanks to mature SRF cavity technology, and therefore have the potential to provide the high-brightness, high-current beams required for CW-XFELs.
After the demonstration of the first SRF gun in Dresden-Rossendorf, several SRF gun programs based on different approaches have achieved promising progress and even succeeded in routine operation. SRF guns are expected to play an important role in XFEL facilities in the near future. In this paper, we give an overview of design concepts, important parameters and development status of the worldwide SRF gun projects.

Keywords: CW; FEL; SRF gun; low emittance

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Permalink: https://www.hzdr.de/publications/Publ-36705


Corrosion of Cast Iron for High-Level Nuclear Waste Containers in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Cast iron containers are currently used for the temporary storage of nuclear waste. At the current stage of research, it is not clear whether cast iron, together with coating materials, also is an option for long-time storage. In this study, we want to investigate its potential as a container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on cast iron. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupons showed surface corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron

  • Poster
    Goldschmidt, 09.-14.07.2023, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36704


Corrosion of Container Material for High-Level Nuclear Waste in the Presence of Bentonite or the SRB Desulfosporosinus burensis

Kirsch, K.; Matschiavelli, N.; Stumpf, T.; Koerdt, A.

Abstract

Ductile cast iron is investigated as a potential container material for the disposal of high-level nuclear waste in deep geological repositories (DGR) in claystone bedrock. The dynamic corrosion process depends on the conditions present in the DGR which are influenced and/or controlled by geochemical parameters (e.g., redox potential, pH, the ionic composition of the pore-water), physical parameters (e.g., pressure), and the influence of metabolically active microorganisms. Corrosion of cast iron will occur at the interface of the container surface and the bentonite backfill material, which contains natural microbial populations. In the investigated worst-case scenario, water would reach the container and introduce microorganisms inherent in the bedrock, such as sulfate-reducing bacteria (SRB).
The conditions in a DGR were simulated in microcosm experiments to investigate the impact of microbiologically influenced corrosion (MIC) on a potential container material. The anaerobic microcosms contained artificial Opalinus Clay pore water, N2 atmosphere, cast iron coupons, as well as a Wyoming bentonite or the SRB Desulfosporosinus burensis (DSM 24089) (isolated at the Andra Underground Research Laboratory in Buré, France).
After incubation at 25°C for 50 days, the microcosms were analysed for bio- and geochemical parameters, i.e., pH, Fe(II):Fe(III), changes in their microbial populations, as well as SEM-EDX and Raman spectroscopy to identify secondary iron phases and corrosion products. The coupon showed mild to severe pitting corrosion and various mineral phases on their surfaces. Additionally, the coupons from the D. burensis microcosms showed an increased concentration of carbon on their surface, i.e., an indication of a biofilm.
Furthermore, the interaction of technetium-99 with the corroded coupons was investigated to assess the immobilisation of Tc by exposed and corroded cast iron.

  • Poster
    EUROCORR, 27.-31.08.2023, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-36703


Fostering quality improvement for RSE projects through consulting offers

Förster, T.

Abstract

To promote FAIR principles and to improve the value and knowledge from data innovation, HIFIS – a Helmholtz IT platform, provides a wide variety of services. This talk focuses on the lessons learned and the impact of integrating a variety of RSE offers, including educational resources and consulting on the research community in Helmholtz. We discuss the structure of the HIFIS consulting service and the resources needed to provide a good and fruitful environment for improving our clients’ software projects.

Keywords: RSE; consulting; software development

Permalink: https://www.hzdr.de/publications/Publ-36702


Fracture mechanics investigation of reactor pressure vessel steels by means of sub-sized specimens (KLEINPROBEN)

Das, A.; Altstadt, E.; Chekhonin, P.; Houska, M.

Abstract

The embrittlement of reactor pressure vessel (RPV) steels due to neutron irradiation restricts the operating lifetime of nuclear reactors. The reference temperature 𝑇0, obtained from fracture mechanics testing using the Master Curve concept, is a good indicator of the irradiation resistance of a material. The measurement of the shift in 𝑇0 after neutron irradiation, which accompanies the embrittlement of the material, using the Master Curve concept, enables the
assessment of the reactor materials. In the context of worldwide life time extensions of nuclear power plants, the limited availability of neutron irradiated materials (surveillance materials) is a challenge. Testing of miniaturized 0.16T C(T) specimens manufactured from already tested standard Charpy-sized specimens helps to solve the material shortage problem. In this work, four different reactor pressure vessel steels with different compositions were
investigated in the unirradiated and in the neutron-irradiated condition. A total number of 189 mini-C(T) samples were fabricated and tested. An important component of this study is the transferability of fracture mechanics data from mini-C(T) to standard Charpy-sized specimen. Our results demonstrate good agreement of the reference temperatures from the mini-C(T) specimens with those from standard Charpy-sized specimens. RPV steels containing higher Cu and P contents exhibit a higher increase in 𝑇0 after irradiation. The fracture surfaces were investigated using SEM in order to record the location of the fracture initiators. The fracture modes were also determined. A large number of test results formed the basis for a censoring probability function, which was
used to optimally select the testing temperature in Master Curve testing. The effect of the slow stable crack growth censoring criteria from ASTM E1921 on the determination of 𝑇0 was analysed and found to have a minor effect. Our results demonstrate the validity of mini-C(T) specimen testing and confirm the role of the impurity elements Cu and P in neutron embrittlement. We anticipate further research linking microstructure to the fracture properties of materials before and after neutron irradiation and the optimization of Master Curve testing using the results from our statistical analysis.

Keywords: reactor pressure vessel steel; neutron embrittlement; Master Curve testing; mini-CT specimens; small specimen test technology

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-125 2023
    ISSN: 2191-8708, eISSN: 2191-8716
    ISSN: 2191-8708

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Permalink: https://www.hzdr.de/publications/Publ-36701


Visualizing Ultrafast Kinetic Instabilities in Laser-Driven Solids using X-ray Scattering

Ordyna, P.; Bussmann, M.; Gaus, L.; Grenzer, J.; Gutt, C.; Huang, L.; Laso García, A.; Garten, M.; Höppner, H.; Humpries, O.; Marre, B. E.; Metzkes-Ng, J.; Nakatsutsumi, M.; Öztürk, Ö.; Pan, X.; Paschke-Brühl, F.-L.; Pelka, A.; Prencipe, I.; Randolph, L.; Schlenvoigt, H.-P.; Smid, M.; Stefanikova, R.; Thiessenhusen, E.; Toncian, T.; Zeil, K.; Schramm, U.; Cowan, T.; Kluge, T.

Abstract

Ultra-intense lasers that ionize and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration.
These instabilities can be difficult to characterize, but a novel approach using X-ray scattering at keV energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale.
Our experiments on laser-driven flat silicon membranes show the development of structure with a dominant scale of $~60\unit{nm}$ in the plane of the laser axis and laser polarization, and $~95\unit{nm}$ in the vertical direction with a growth rate faster than $0.1/\mathrm{fs}$.
Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced instability development, indicating the excitation of surface plasmons and the growth of a new type of filamentation instability.
These findings provide new insight into the ultra-fast instability processes in solids under extreme conditions at the nanometer level with important implications for inertial confinement fusion and laboratory astrophysics.

Keywords: laser; proton; ion; acceleration; HIBEF; HED; European; XFEL; SAXS

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  • HIBEF

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Permalink: https://www.hzdr.de/publications/Publ-36700


Dataset: Basic verification of an industrial type of wire-mesh sensor

Wiedemann, P.; Trepte, M.

Abstract

The experimental data presented here was recorded with an industrial type of wire-mesh sensor and additional equipment. The experiments aim at verifying the main functionalities of the developed sensor and include tests of

  • Temperature compensation
  • Flow pattern identification in vertical gas-liquid flow
  • Flow pattern identification in horizontal gas-liquid flow

The experimental procedure and the results are described in detail in Wiedemann et al.: Towards Real-Time Analysis of Gas-Liquid Pipe Flow: A Wire-Mesh Sensor for Industrial Applications, Sensors 23 (2023) 4067, https://doi.org/10.3390/s23084067

Keywords: wire-mesh sensor; indWMS; two-phase flow

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Permalink: https://www.hzdr.de/publications/Publ-36699


International Standardization of Basic Industrial Radiotracer and Radiation Applications – Current State

Jentsch, T.; Thereska, J.; Jin, J.-H.; Brisset, P.

Abstract

The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. On behalf of IAEA and ISTRA experts from many countries employed in leading research centers and renowned industrial companies analyze existing international standards regarding the necessity of their update or amendment as well as the need for new standards in this field.
In June 2020, a new international standard on “Non-destructive testing - Gamma ray scanning method on process columns” was published as ISO 23159. About three years before, the experts detected the need to standardize this method, which is widely used in petrochemical and chemical plants to identify and locate the cause of malfunction inside various process columns.
In the field of flow rate measurements of fluids in conduits using radioactive tracers, a proposal for a new international standard was prepared in 2021. It united several old international standards in this technical field: measurement of water flow in closed conduits (ISO 2975), measurement of gas flow in conduits (ISO 4053) and measurement of liquid flow in open channels (ISO 9555). The new international standard with the title “Measurement of Fluid Flow Rate in Closed Conduits – Radioactive Tracer Methods” has now the state of a Draft International Standard (DIS) and will be published as ISO 24460 in this year.
Furthermore, two other international standards using radioactive tracer methods are under development. One of them is on leak testing in pressured vessels and underground pipelines, another one is on determination of concentration or density of suspended and deposited sediment in water bodies by radiometric methods. Both has already passed the New Work Item Proposal (NWIP) stage. The first one is being edited in ISO Technical Committee 135, Sub Committee 6, Working Group 1 (ISO TC 135/SC 6/WG 1), has the stage of a Committee Draft (CD) now and will be published as ISO 6640 in the middle of next year. The second one is being edited in ISO TC 113/SC 6/WG 5, has still the stage of a Working Draft (WD) and will be published as ISO 6366 also next year.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.

Keywords: International standards; ISO; radioactive tracers; radiometric methods

  • Lecture (Conference)
    NUTECH 2023 International Conference on Development and Applications of Nuclear Technologies, 20.-22.09.2023, Krakow, Polska

Permalink: https://www.hzdr.de/publications/Publ-36698


Trimorphic TaCrP – A diffraction and 31P solid state NMR spectroscopic study

Paulsen, C.; Maximilian Gerdes, J.; Svitlyk, V.; Kai Reimann, M.; Rabenbauer, A.; Nilges, T.; Ryan Hansen, M.; Pöttgen, R.

Abstract

The metal-rich phosphide TaCrP forms from the elements by step-wise solid state reaction in an alumina crucible (maximum annealing temperature 1180 K). TaCrP is trimorphic. The structural data of the hexagonal ZrNiAl high-temperature phase (space group P¯62m) was deduced from a Rietveld refinement. At room temperature TaCrP crystallizes with the TiNiSi type (Pnma, a = 623.86(5), b = 349.12(3), c = 736.78(6) pm, wR = 0.0419, 401 F2 values, 20 variables) and shows a Peierls type transition below ca. 280 K to the monoclinic low-temperature modification (P121/c1, a = 630.09(3), b = 740.3(4), c = 928.94(4) pm, β = 132.589(5)°, wR = 0.0580, 1378 F2 values, 57 variables). The latter phase transition is driven by pairwise Cr–Cr bond formation out of an equidistant chain in o-TaCrP. The phase transition was monitored via different analytical tools: differential scanning calorimetry, powder synchrotron X-ray diffraction, magnetic susceptibility measurements and 31P solid state NMR spectroscopy.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36697


A van der Waals Heterostructure with an Electronically Textured Moiré Pattern: PtSe₂/PtTe₂

Li, J.; Ghorbani Asl, M.; Lasek, K.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

Abstract

The interlayer interaction in Pt-dichalcogenides strongly affects their electronic structures. The modulations of the interlayer atom-coordination in vertical heterostructures based on these materials are expected to laterally modify these interlayer interactions and thus provide an opportunity to texture the electronic structure. To determine the effects of local variation of the interlayer atom coordination on the electronic structure of PtSe₂, van der Waals heterostructures of PtSe₂ and PtTe₂ have been synthesized by molecular beam epitaxy. The heterostructure forms a coincidence lattice with 13-unit cells of PtSe₂ matching 12-unit cells of PtTe₂, forming a moiré superstructure. The interaction with PtTe₂ reduces the band gap of PtSe₂ monolayers from 1.8 to 0.5 eV. While the band gap is uniform across the moiré unit cell, STS and dI/dV mapping identify gap states that are localized within certain regions of the moiré unit cell. Deep states associated with chalcogen pz-orbitals at binding energies of ~-2 eV also exhibit lateral variation within the moiré unit cell, indicative of varying interlayer chalcogen interactions. Density functional theory calculations indicate that local variations in atom coordination in the moiré unit cell causes variations in the charge transfer from PtTe2 to PtSe2 thus affecting the value of the interface dipole. Experimentally this is confirmed by measuring the local work function by field emission resonance spectroscopy, which reveals a large work function modulation of ~0.5 eV within the moiré structure. These results show that the local coordination variation of the chalcogen atoms in the PtSe2/PtTe2 van der Waals heterostructure induces a nanoscale electronic structure texture in PtSe₂.

Keywords: platinum dichalcogenides; van der Waals heterostructure; work function modulation; scanning tunneling microscopy; density functional theory

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Permalink: https://www.hzdr.de/publications/Publ-36696


Event generation in Julia and the path to GPUs

Hernandez Acosta, U.; Steiniger, K.; Reinhard, A.; Jungnickel, T.; Ehrig, S.; Bussmann, M.

Abstract

The inventors of the Julia programming language proclaim, that one can use high-level syntax to solve demanding numerical tasks. In order to evaluate this claim, we present possible applications of Julia by using it for the implementation of our Monte-Carlo event generator for laser-matter interaction. Especially the possible deployment of modern GPUs for demanding computing tasks during several stages of the event generation is discussed. In order to elaborate on these GPU capabilities, we show benchmarks of Julia's main programming interface for NVIDIA CUDA GPUs, namely `CUDA.jl`, and compare them with native CUDA-C++ implementations. Finally, Julia's capabilities for high-level abstraction for computations on heterogenous architectures are discussed and compared to low-level solutions like the `alpaka` library for C++.

Keywords: Julia programming language

  • Invited lecture (Conferences) (Online presentation)
    Compute Accelerator Forum, 08.03.2023, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36695


Biogenic minerals formation by an Fe(III)-reducing Desulfitobacterium sp. isolate

Cardaio, I.; Kluge, S.; Cherkouk, A.; Müller, K.; Stumpf, T.; Mayordomo, N.

Abstract

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe(III)) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe(III)-species [1]. This may lead to the formation of minerals such as magnetite (Fe(II)Fe(III)₂O₄) and siderite (Fe(II)CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc(VII)O₄⁻) to insoluble oxides (Tc(IV)O₂) [3].
The genus Desulfitobacterium contains obligate anaerobic bacteria that are capable of utilizing a wide range of electron acceptors, including nitrite, sulfite, metals, humic acids and halogenated organic compounds [4].
In this work, the Fe(III) reduction of a Desulfitobacterium species was examined. The microorganism has been isolated from bentonite, which is potentially used as geotechnical barrier in deep geological repositories for radioactive waste [5].
The cultivation conditions included DSMZ 579 medium with Na-acetate as electron donor to reduce Fe(III) citrate [6]. During cultivation, the formation of white precipitates was observed. The phases were collected both under aerobic and anaerobic conditions and repeatedly investigated by using Raman microscopy and powder X-ray diffraction (pXRD). It was noticed that the phases turned immediately to blue-greenish overnight under oxic conditions. Both Raman spectra and pXRD diffractograms can be attributed to vivianite (Fe(II)₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe(II)S₂), siderite, magnetite and hematite (FeIII₂O₃). These results suggest the ability of the bacterium of forming different Fe(II)-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe(II)-minerals formation by this microorganism depending on Fe(III)-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc(VII)O₄⁻.

The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of NukSiFutur TecRad young investigator group (02NUK072).

[1] Lovley, 1993, Annual Review of Microbiology, 47:263-290
[2] Lee, et al., 2007, Geomicrobiology Journal, 24:1, 31-41
[3] Lloyd, et al., 2000, Appl Environ Microbiol., 66(9):3743-9
[4] Villemur et al., 2006, FEMS Microbiol Rev. 2006, 30(5):706-33
[5] Drozdowski J., et al., 2018, HZDR Annual Report, pp. 40, ISSN 2191-870
[6] https://www.dsmz.de/microorganisms/medium/pdf/DSMZ_Medium579.pdf. Accessed on 27.02.23

Keywords: iron reducing bacteria; technetium; biogenic minerals; Raman microscopy; X-ray diffraction

  • Open Access Logo Poster
    Goldschmidt 2023, 09.-14.07.2023, Lyon, Frankreich

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Permalink: https://www.hzdr.de/publications/Publ-36694


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