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41780 Publications

Wechselwirkung von Tc mit Eisen(II)phosphaten

Börner, C.

Abstract

Technetium (Tc, Ordnungszahl 43) ist das leichteste Element, welches keine stabilen Isotope besitzt. Das Hauptvorkommen von Tc stammt aus anthropogen Quellen, wie abgebrannten Brennstoffen aus Kernkraftwerken, Atomwaffentests, sowie nuklearen Unfällen. Das Radionuklid Tc-99 entsteht hierbei als ein Spaltprodukt mit rund 6% Ausbeute und ist somit im nuklearen Abfall vorhanden, welcher im geologischen Tiefenendlager für 1Mio Jahre gelagert werden soll. Zusätzlich wird Tc-99m als Kontrastmittel in der Medizindiagnostik angewendet, welches zu Tc-99 zerfällt und in das Abwasser gelangt. Aus diesen Gründen besteht die Notwendigkeit, die Interaktion von Tc mit Mineralen zu untersuchen, um Möglichkeiten zur immobilisierung zu finden. Das in Wasser mobile Pertechnetat (Tc(VII)O₄⁻) kann durch Sorption und Reduktion zu schwerlöslichem TcO₂ an Fe(II)-haltigen Mineralen zurückgehalten werden.
In dieser Arbeit wurde die Retention an Vivianit (Fe₃(PO₄)₂·8 H₂O) untersucht. Das türkisfarbene Mineral wurde erfolgreich über eine Präzipitation unter Inertgas synthetisch hergestellt. Mittels XRD und Raman konnte die Übereinstimmung mit Referenzspektren für Vivianit bei dem Gleichwichts-pH-Wert pH 6,7 festgestellt werden. Bei einer Verringerung des pH-Wertes auf pH 5 ist Vivianit weiterhin stabil, während bei einem pH-Wert von pH 12 eine Phasenänderung zu Amakinit (Fe(II)(OH)₂) stattfindet. TcO₄− kann durch suspendiertes Vivianit aus der Lösung bei pH 8 im Verlauf von 20 d entfernt werden, während bei pH 6,5 die Immobilisierung nicht stattfindet. Mit steigender Konzentration an Vivianit in der Lösung steigt auch die Entfernung von TcO₄− bei pH 6,5. Bei pH 8 hingegen sinkt die Entfernung mit größerer Mineralkonzentration bei 3 d Sorptionszeit, wobei nach 10 d Tc in der Lösung nicht mehr detektierbar ist. Vermutet wird die Bildung löslicher Tc-phosphate. Mit steigendem pH-Wert steigt die Immobilisierung von Tc aus der Lösung. Bei niedrigen pH-Werten ist die geringe Sorption auf die hohe Löslichkeit des Minerals und damit auf die kinetisch gehinderte Homoreduktion von Tc(VII) durch gelöstes Fe(II) zurückzuführen. Die Untersuchung der Oberfläche mit XPS deutet auf eine vollständige Reduktion von Tc(VII) zu Tc(IV) hin. Die weiterhin hohe Löslichkeit des Tc untermauert die Theorie der Tc-phosphatverbindungen.
Ein Anstieg an oxidischen Verbindungen, welche auf TcO₂ hindeuten, wurden einzig bei pH 12 detektiert. Die Reoxidationsexperimente in dieser Arbeit haben eine geringe Remobilisierung von Technetium unter oxidierenden Bedingungen nach 30 d gezeigt. Im Gegenteil konnte sogar eine Steigerung der Immobilisierung bei niedrigen pH-Werten festgestellt werden.

Keywords: Technetium; Vivianite; Immobilization; Re-oxidation; Reduction

  • Master thesis
    Technische Universität Dresden, 2023
    Mentor: Prof. Thorsten Stumpf and Dr. Natalia Mayordomo

Permalink: https://www.hzdr.de/publications/Publ-37815


Application of dissimilatory iron reduction by a novel Desulfitobacterium sp. isolate for Tc-99 immobilization

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

Abstract

Dissimilatory iron reduction is an anaerobic respiratory pathway, wherein ferric (Fe³) reducers couple the oxidation of organic acids, sugars and aromatic hydrocarbons to the reduction of Fe³-species [1]. This may lead to the formation of minerals such as magnetite (Fe²Fe³₂O₄) and siderite (Fe²CO₃) [2], which, in turn, can mediate the reduction of soluble pollutants as pertechnetate (Tc⁷O₄⁻) to insoluble oxides (Tc⁴O₂) [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 Fe³ 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 Fe³ 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 (Fe²₃(PO₄)₂). Moreover, Raman spectra revealed the possible presence of pyrite (Fe²S₂), siderite, magnetite and hematite (Fe³₂O₃). These results suggest the ability of the bacterium of forming different Fe²-minerals. Notwithstanding, both methods indicate the change of the chemistry of the precipitates according to environmental factors. The Fe²-minerals formation by this microorganism depending on Fe³-compounds and background electrolytes is currently ongoing. The biogenic ferrous minerals will be studied regarding the reduction of Tc⁷O₄⁻.
The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of NukSiFutur TecRad young investigator group (02NUK072).

Keywords: microorganisms; iron minerals; technetium; deep geological repositories

  • Lecture (Conference)
    ChemTUgether 2023 & Alumni Meeting 2023, 29.09.2023, TU Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37814


Tc(VII) reductive immobilization by S(-II) pre-sorbed on alumina

Garcia-Gomez, S.; Börner, C.; Gimenez, J.; Casas, I.; Llorca, J.; de Pablo, J.; Müller, K.; Mayordomo, N.

Abstract

Tc-99 is a fission product of U-235 and Pu-239 with a long half-live (2.14∙10⁵ years). Under oxidizing conditions, Tc main species (Tc(VII)O₄⁻) exhibits a high solubility and hardly interacts with minerals. In contrast, under reducing conditions, Tc(IV) presents a more limited mobility, either because Tc(IV) interacts with minerals or Tc(IV)O₂ is formed [1]. However, the formation of Tc(IV)O₂ is not sufficient to ensure the immobilization of Tc, since when it is in contact with O₂, the reoxidation of Tc(IV) to Tc(VII) would be thermodynamically favorable. In contrast, the formation of Tc(IV) polysulfide species (such as TcSx or Tc₂S7) could inhibit Tc oxidation under oxidizing conditions [2]. Therefore, S(-II) seems a promising candidate to immobilize Tc. Sulfide would be present in the nuclear waste repository due to the addition of fly ash in the concrete, as well as the presence of minerals such as pyrite (FeS₂). It has been proven for Fe(II) that Tc(VII) reduction is more favorable when Fe(II) takes part in the mineral structure or it is sorbed on a surface than when Tc(VII) reduction is carried by dissolved Fe(II) homoreduction) [3]. We have recently showed that Tc(VII) heteroreduction (reduction occurring at the mineral-water interface) by Fe(II) pre-sorbed on alumina nanoparticles is highly efficient [4].
Thus, in this work, we have studied kinetically as a function of pH: i) S(-II) sorption on alumina, and ii) subsequent Tc uptake promoted by S(-II) pre-sorbed on alumina. We have also focused on the effect of different sulfide sources on Tc(VII) reduction. All the experiments were performed in a N₂ glove box free of CO₂ and O₂ (< 2 ppm). The alumina
nanoparticles used in the experiments has been previously characterized with 127 m² /g N₂ BET and pH 9 as isoelectric point pH [5]. For the batch sorption experiments, suspensions of alumina (0.5 g/L) containing 50 μM of NaHS at pH 5.3, 6.7 and 7.7 were prepared and shaken for two days. Then, KTcO₄ was added to the suspensions to obtain 5 μM of KTcO₄. Subsequently, the suspensions were placed in a horizontal shaker. The suspension pH was monitored frequently and readjusted when needed. Samples were taken periodically and centrifuged at 14,000 rpm for 45 min. The Tc concentration in the supernatant solution was measured by liquid scintillation counter to determine the percentage of Tc removed.
Figure 1 shows the uptake of Tc in % as a function of time and pH. Tc removal increases with decreasing pH. This is in agreement with the highest anion sorption on alumina nanoparticles at lower pH, when alumina surface is positive charged [5]. The maximum Tc retention is 70% at pH 5.3, being complete after one day of contact. Whereas at higher pH values, Tc removal is significantly lower, i.e., 10% at pH 6.7 and 5% at pH 7.7. It is noteworthy to mention that the NaHS reactant used for the experiments in Figure 1. was partially oxidized. Despite of its oxidation, reduction of Tc(VII) yield at pH 5.3 was above 70% after one day of contact.

Further contact experiments have been performed to isolate the contribution of S(-II) in Tc(VII) heteroreduction, and the effect of the sulfide source on Tc removal. Raman microscopy and X-ray absorption spectroscopy have been used to determine the changes occurring at a molecular level when Tc(VII) is heteroreduced by S(-II).

Acknowledgements: The authors acknowledge the Spanish Ministry of Research and Universities for the abroad internship fellowship (PRE2018-085618) and the project (ENE2017-83048-R). Part of this work was financially supported by the German Federal Ministry of Education and Research (BMBF) NukSiFutur TecRad young investigator group (02NUK072).

Keywords: Technetium; Sulfide; Reduction; Removal; Scavenging

  • Poster
    18th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (Migration), 25.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-37813


Luminescence spectroscopy and diffraction studies of zirconia solid phases containing cerium

Braga Ferreira Dos Santos, L.; Svitlyk, V.; Richter, S.; Hennig, C.; Huittinen, N. M.

Abstract

Zirconia is largely studied because of its ability to incorporate lanthanides and actinides; this has been one of the strategies adopted to try to immobilize ions from High-Level Radioactive Waste (HLW). Furthermore, cerium is often used as a surrogate for plutonium due to its analogous chemical properties1. In this study, zirconia samples with different Ce concentrations were syntehsized via the co-precipitation route. A small amount of Eu as co-dopants was added during synthesis to enable luminescence spectroscopic analyses of the solids phases2. Six zirconia compositions doped with 15 to 80 mol%Ce were prepared. The phase composition was evaluated by site selective luminescence spectroscopy (ss-TRLFS) and Synchrotron Powder X-Ray Diffraction. The latter method showed, that more than one phase coexists in all samples with concentrations lower than 80 mol% Ce. The tetragonal phase is predominant until 30 mol% Ce-doping, and above this concentration, a metastable phase (t’’) starts becomes dominant. The phase transformation can also be deduced from the coordination environment of europium, showing a small band at 583 nm, characteristic for the monoclinic phase, and another one at around 581.1 nm for Eu incorporated in the tetragonal phase. The systematic shift of this signal to shorter wavelengths points toward a lengthening of the Eu-O bonds with increasing Ce concentration, as the unit cell becomes systematically larger. The excitation peaks are clearly broader for the samples with predominantly t’’-ZrO2, which points toward a less ordered environement. This is in agreement with the hypothesized displacement of oxygen atoms from ideal (cubic) crystallographic positions, in this metastable (transition) phase.

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Related publications

  • Lecture (Conference)
    Ace-Methods Workshop, 20.-22.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-37812


Spectroscopy and diffraction investigations of cerium/uranium doped zirconia solid solutions

Braga Ferreira Dos Santos, L.; Svityk, V.; Richter, S.; Hennig, C.; Gaona, X.; Szabo, P.; Huittinen, N. M.

Abstract

Recent studies have suggested that crystalline ceramic matrices, such as monazites and zirconia (ZrO₂) have a high potential to be used as immobilization matrices for radioactive waste. At room temperature, zirconia has a monoclinic (m) structure. At higher temperatures, tetragonal (t) and cubic (c) structures can be stabilized. The phase stabilization can also be achieved at ambient conditions by incorporating oversized cations. In addition, several metastable phases (t′, t′′, κ, and t*), can be formed for doped zirconia materials. Out of the several structural polymorphs, especially the cubic structure shows high radiation tolerance, which is important for host matrices containing radioactive elements. In the current study, cerium has been used as an analog for plutonium as these f-elements have identical cation radii and can be stabilized in the trivalent and tetravalent oxidation states. The zirconia samples were co-doped with a small amount of Eu(III) to allow for luminescence spectroscopic analyses of the solid phases. In a first step, the co-precipitation route was applied to synthesize Ce-doped zirconia samples over a wide Ce-concentration range. The phase composition of the samples was investigated with X-ray diffraction, and showed that the radiation tolerant cubic phase was stabilized only for samples with Ce concentrations above 75 mol% . At lower dopant concentrations, a mixture of different phases were present, including monoclinic in a low doping concentration range, tetragonal and tetragonal double prime phases appearing for intermediate Ce-concentrations. The latter phase was detected only by Raman spectroscopy, showing the presence of a defect band at 526.5 cm-1. In addition, luminescence spectroscopy revealed structural changes in terms of different Eu environments in the t´´ and c samples. To stabilize the cubic phase for low tetravalent doping concentrations, trivalent yttrium (Y) was incorporated as a co-dopant. XRD and Raman analyses show that the cubic phase was stabilized when the concentration of Y was higher than 15 mol%. Finally, using the same co-precipitation route, a series of uranium-doped zirconia samples was synthesized. XRD investigations show a phase transformation from monoclinic to tetragonal and orthorhombic with increasing uranium doping. Identical to the Ce-doped samples, the pure cubic phase was stabilized only in the presence of Y for concentrations higher than 15 mol%. Discerning the crystal structure is crucial to understanding the properties of these phases. Although the binary zirconia systems with only one dopant show different phase compositions for Ce and U, the scenario changes when adding a trivalent co-dopant such as yttrium, which stabilizes the cubic phase both in the presence of uranium and cerium.
Preliminary solubility results for the pure cubic phase of uranium/cerium-doped zirconia co-doped with yttrium will be shown in the poster session.

Keywords: zirconia; ceramic materials; crystal structures; solubility

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Related publications

  • Lecture (Conference)
    47th Scientific Basis for Nuclear Waste Management (SBNWM), 06.-10.11.2023, Cologne, Germany
  • Poster
    47th Scientific Basis for Nuclear Waste Management (SBNWM), 06.-10.11.2023, Cologne, Germany

Permalink: https://www.hzdr.de/publications/Publ-37811


Comparing Ce/U Doped Zirconia: Exploring Similarities and Differences in These Solid Solutions.

Braga Ferreira Dos Santos, L.; Svitlyk, V.; Richter, S.; Hennig, C.; Huittinen, N. M.

Abstract

Recent research indicates that crystalline ceramic materials, such as zirconia (ZrO2),
hold great potential as matrices for immobilizing radioactive waste [1]. Zirconia can exist
in various crystal structures, including monoclinic (m), tetragonal (t), and cubic (c), as
well as several metastable ones (t', t'', κ, and t*), which form in doped zirconia
materials[2]. In this study, we synthesized tetravalent Ce- and U-doped zirconia
samples, both in the presence and absence of trivalent Y3+ as co-dopant. The Cedoped
zirconia samples were prepared with a wide range of cerium concentrations (10-
95 mol%) using co-precipitation and calcination methods, while the U-doped samples
contained a maximum of 30 mol% U. The trivalent co-dopant concentration was varied
between 10 and 20 mol%. All samples underwent thorough characterization using Xray
diffraction and Raman spectroscopy. Despite the close similarity in cation radii
between Ce(IV) and U(IV) of only 3%, the resulting zirconia phase compositions were
remarkably different for these two tetravalent dopants. The monoclinic phase
dominated up to concentrations of 15 mol% in case of Ce and 1 mol% for U doped Zr.
Thereafter, t and t'' phases became prominent for Ce(IV) concentrations up to 75
mol%. The identification of the t'' phase relied on Raman data, revealing a defect band
at 526.5 cm-1 characteristic of metastable phases (Fig 1a). Notably, the t'' phase cannot
be distinguished from the cubic phase using only XRD[3]. In contrast, the results for Udoped
zirconia with a concentration higher than 1 mol%, compositions indicated the
formation of orthorhombic and cubic phases. When the trivalent co-dopant (Y3+) was
added to the samples, both U- and Ce-doped compositions demonstrated similar
behavior. XRD and Raman data revealed that the pure cubic phase was stabilized in
both cases when the concentration of Y exceeded 15 mol% (Fig 1b). These findings
shed light on the diverse phase behavior of Ce- and U-doped zirconia and the
significant influence of co-dopants on the host crystal structure.

Keywords: radioactive waste; ceramic materials; zirconia; crystal structures

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  • Poster
    23. Norddeutsches Doktorandenkolloquium, 05.-06.10.2023, Berlin, Germany
  • Poster
    ChemTUgether, 29.09.2023, Dresden, Germany
  • Poster
    Krimi Winter School, 10.-13.10.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-37810


Fundamental investigations of actinide immobilization by incorporation into solid phases relevant for final disposal

Huittinen, N. M.; Braga Ferreira Dos Santos, L.; Gilson, S.; Hennig, C.; Lender, T.; Marquardt, J.; Murphy, G.; Nießen, J.; Peters, L.; Richter, S.

Abstract

This contribution provides an overview of a current research network funded by the German Federal Ministry of Education and Research (BMBF), entitled “Fundamental investigations of actinide immobilization by incorporation into solid phases relevant for final disposal” – AcE. The AcE project aims at understanding the incorporation and immobilization of actinides (An) in crystalline, repository-relevant solid phases, such as zirconia (ZrO2) and UO2, but also in zircon (ZrSiO4), pyrochlores (Ln2Zr2O7) and orthophosphates of the monazite type (LnPO4), which may find use as host matrices for the immobilization and safe disposal of high-level waste streams.
Recent studies by the AcE-project consortium, addressing the structure, properties, and the radiation tolerance of monazites and Zr(IV)-based solid phases containing actinides or their surrogates from the lanthanide series will be presented. Material synthesis strategies in the AcE project have aimed at generating single-phase solid solutions in the form of polycrystalline powders, dense ceramics, and single crystals. Structural studies using powder X-ray diffraction at ambient conditions, but also at high temperatures and pressures have been complemented with a wide range of microscopic and spectroscopic techniques to address differences between the host- and dopant environments in the solid matrices at ambient and extreme conditions. The radiation tolerance of the synthetic solid phases have been investigated by combining external heavy-ion irradiation of inactive Ln-doped materials and in situ self-irradiation of 241Am-doped Zr(IV)-phases with monoclinic, cubic defect fluorite and pyrochlore structures. The latter experiments have been conducted in joint efforts with the Joint Research Center in Karlsruhe within the ActUsLab programme.

Involved research facilities

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  • Poster
    Actinides 2023, 04.-08.06.2023, Golden Colorado, United States

Permalink: https://www.hzdr.de/publications/Publ-37809


Evaluation of Ce/U doped zirconia: similarities and differences between these solid solutions

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

Abstract

Recent studies have suggested that crystalline ceramic materials, such as zirconia (ZrO2), have a high potential to be used as immobilization matrices for radioactive waste. Zirconia can have different crystal structures such as monoclinic (m), tetragonal (t), and cubic (c), but also several metastable ones (t′, t′′, κ, and t*), which are formed for doped zirconia materials. In this study, tetravalent Ce- and U-doped zirconia samples were synthesized in the absence and presence of trivalent Gd or Y as co-dopants. Ce-doped zirconia samples were synthesized for a wide range of cerium concentrations (10-95mol%) via coprecipitation and calcination, while U-doped samples contained a maximum of 30 mol% U. The trivalent co-dopant concentration was varied between 10 and 20 mol%. All samples were characterized with X-ray diffraction and Raman spectroscopy. Although the Ce(IV) and U(IV) cation radii show a difference of only 3%, the resulting zirconia phase compositions are very different for the two tetravalent dopants, Figure 1 (left and middle). Briefly, the monoclinic phase is dominating the Ce-doped samples up to Ce concentrations of 15mol%. Thereafter t and t´´ phases are prevailing in the samples for Ce(IV) concentrations up to 75mol%. The t´´ phase could be assigned only with the help of the Raman data, showing a defect band at 526.5cm-1 characteristic for metastable phases, as the t´´phase cannot be distinguished from the cubic phase using only XRD. On the other hand, for U(IV)-doped samples, phase transformation from the monoclinic phase starts already for U(IV)-concentrations above 1 mol%. In contrast to the Ce-doped samples, results for U-doped zirconia compositions indicate the formation of orthorhombic and cubic zirconia phases. For samples with the trivalent co-dopants, the U- and Ce-doped samples have the same behavior, the XRD and the Raman show that the pure cubic phase is stabilized in both cases when the concentration of Y or Gd is higher than 15mol%.

Keywords: Ce-doped zirconia; immobilization matrices; crystal structures

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  • Lecture (Conference)
    Actinides 2023, 04.-08.06.2023, Golden Colorado, United States

Permalink: https://www.hzdr.de/publications/Publ-37808


Interaction of Marangoni and buoyancy effects during mass transfer at liquid interfaces

Schwarzenberger, K.; Köllner, T.; Boeck, T.; Eckert, K.

Abstract

Complex flow patterns frequently emerge when a surface active substance undergoes mass transfer between an organic and an aqueous phase. At the same time, density effects can play a major role, e.g. during the partial dissolution of floating organic droplets \cite{cejkova2019dancing}. The resulting droplet ensemble dynamics can be understood by highly resolved measurements of the transient velocity field via particle image velocimetry (PIV). At bubbles in a shear flow, the interaction of the Marangoni effect with the surrounding bulk flow leads to the formation of a circulating flow at the bubble surface \cite{eftekhari2021interfacial}. Bubbles or droplets which are placed in a vertical concentration gradient of a surface-active solute show an intriguing interaction of solutal Rayleigh and Marangoni convection in the form of relaxation oscillations \cite{mokbel2018information}. Depending on the distance between multiple droplets, convective interaction can lead to collective relaxation oscillations over the whole ensemble.

A repeated coupling of Rayleigh and Marangoni effects likewise can occur during mass transfer of a solute at a planar interface between two liquid layers. Solutal Rayleigh instability is able to provoke intense Marangoni-driven spreading motions at the interface, even if the mass transfer system is primarily stable towards stationary Marangoni convection \cite{koellner2016eruptive}. A more detailed study \cite{koellner2023eruptive} unravels the underlying mechanisms by a defined variation of key parameters: the layer height and the initial concentration of the solute. The flow structures are analyzed in detail by experiments and elaborate three-dimensional simulations of the two liquid layers. The flow in the interfacial region decouples from the bulk volume flow since for deep layers, the interfacial velocity gets invariant under a change of the nondimensional layer height. Due to the additional convection, mass transfer is strongly enhanced in comparison to the purely diffusive process. This can significantly increase the efficiency of liquid-liquid extraction processes.

\bibitem{cejkova2019dancing} J.~{\v{C}}ejkov{\'a}, K.~Schwarzenberger, K.~Eckert, S.~Tanaka, Colloids and Surfaces A, 566, 141 (2019)
\bibitem{mokbel2018information} M.~Mokbel, K.~Schwarzenberger, S.~Aland, K.~Eckert, Soft Matter, 14, 9250 (2018)
\bibitem{eftekhari2021interfacial} M.~Eftekhari, K.~Schwarzenberger, S.~Heitkam, K.~Eckert, Journal of Colloid and Interface Science, 599, 837 (2021)
\bibitem{koellner2016eruptive} T.~K{\"o}llner, K.~Schwarzenberger, K.~Eckert, T.~Boeck, Journal of Fluid Mechanics, 791, R4 (2016)
\bibitem{koellner2023eruptive} T.~K{\"o}llner, K.~Schwarzenberger, K.~Eckert, T.~Boeck, in progress (2023)

  • Lecture (Conference)
    Dynamic Days Europe 2023 Conference, 03.-08.09.2023, Neapel, Italien

Permalink: https://www.hzdr.de/publications/Publ-37807


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

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

Abstract

The shear stress of an axisymmetric flow field triggers a nonuniform distribution of adsorbed
surfactants at the surface of a rising bubble. This creates a surface tension gradient that
counteracts the viscous shear stress of the flow and thus reduces the mobility of the interface.
However, in technological processes the flow field often is asymmetric, e.g. due to the
vorticity in the flow. Under such conditions, the interface experiences an unbalanced shear
stress that is not free of curl, i.e. it cannot be compensated by the redistribution of the surfactants
at the interface (Vlahovska et al., 2009). Here, we conduct model experiments with
a bubble at the tip of a capillary placed in a defined asymmetric flow field, in the presence of
surfactants and nanoparticles. Unlike classical surfactants, nanoparticles adsorb irreversibly
at the bubble surface. Thus, a different interaction between the bulk flow and the interface
is expected. In this study, we show a direct experimental observation of the circulating flow
at the interface under asymmetric shear stress (Eftekhari et al., 2021a,b). The results indicate
that the interface remains mobile regardless of the surfactant concentration. Additionally, we
show that the nanoparticle-laden interface adopts a solid-like state and resists the interfacial
flow upon surface compression. Our results imply that the immobilization of the interface
can be described by the ratio of the interfacial elasticity to the bulk viscous forces.
Vlahovska, P. M., Bławzdziewicz, J., & Loewenberg, M. (2009). Small-deformation theory for a
surfactant-covered drop in linear flows. J.Fluid Mech., 624, 293.
Eftekhari, M., Schwarzenberger, K., Heitkam, S., & Eckert, K. (2021). Interfacial flow of a surfactant-
laden interface under asymmetric shear flow. J. Colloid Interface Sci., 599, 837.
Eftekhari, M., Schwarzenberger, K., Heitkam, S., Javadi, A., Bashkatov, A., Ata, S., & Eckert, K.
(2021). Interfacial behavior of particle-laden bubbles under asymmetric shear flow. Langmuir,
37, 13244.

  • 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-37805


Grenzflächenkonvektion an Tropfen und Blasen

Schwarzenberger, K.; Eftekhari, M.; Mokbel, M.; Weber, N.; Aland, S.; Eckert, K.

Abstract

Die Grenzflächenkonvektion (Marangoni-Effekt) ist eine kleinskalige Strömung, die
durch Gradienten der Grenzflächenspannung verursacht wird. Sie beeinflusst den
Stofftransport und die Strömungsbedingungen in einer Vielzahl von natürlichen und
technologischen Prozessen. Grenzflächenkonvektion kann an Tropfen oder Blasen
beobachtet werden, die in einem vertikalen Konzentrationsgradienten einer gelösten
grenzflächenaktiven Substanz platziert werden [1,2]. Die Frequenz der
Strömungswirbel wird direkt vom anliegenden Konzentrationsgradienten des
gelösten Stoffs bestimmt. Mehrere benachbarte Tropfen oder Blasen (Abb. 1, links)
synchronisieren sich durch konvektive Interaktion zu Oszillationen über das gesamte
Ensemble. Die genannten Erkenntnisse werden durch numerische Simulationen
bestätigt.
Abbildung 1: Wechselwirkung von Grenzflächenkonvektion an benachbarten Tropfen (links [2]),
Geschwindigkeitsfeld um zwei schwimmende Decanoltropfen (mittig [4]), asymmetrische
Bulkströmung um partikelbeladene Blasenoberfläche (rechts)
Grenzflächenkonvektion beeinflusst zudem die Dynamik von schwimmenden
Dichlormethan- und Decanoltropfen [3,4]. Durch zeitlich und örtlich hochaufgelöste
Particle Image Velocimetry (PIV)-Messungen kann der Einfluss der
Grenzflächenkonvektion auf die Deformation und Interaktion der schwimmenden
Tropfen verstanden werden (Abb. 1, mittig).
1 mm
Mit dieser Technik konnte auch zum ersten Mal eine kontinuierliche
Grenzflächenkonvektion auf der Blasenoberfläche aufgrund einer asymmetrischen
Scherkraft durch die anliegende Bulkströmung visualisiert werden [5]. In diesem
Prozess bleibt die Grenzfläche unabhängig von der Konzentration eines klassischen
Tensids mobil. Bei Adsorption von Partikeln auf der Blasenoberfläche nimmt die
Mobilität der Grenzfläche jedoch ab (Abb. 1, rechts). Durch eine Kompression der
Oberfläche bildet sich weiterhin ein zusammenhängendes Netzwerk aus Partikeln,
das die Grenzflächenkonvektion schließlich zum Erliegen bringt [6].
Dies zeigt, dass in Abhängigkeit von der Art des adsorbierten Stoffs deutlich
unterschiedliche Randbedingungen für die Strömung an der Grenzfläche von Tropfen
und Blasen vorherrschen können [7]. Die kleine Längenskala der
Grenzflächenkonvektion eröffnet zudem die Möglichkeit, diesen Effekt zur passiven
Durchmischung [8] oder zur Informationsübertragung in mikrofluidischen Prozessen
zu nutzen [2].
Publikationen:
[1] Schwarzenberger, K., Aland, S., Domnick, H., Odenbach, S., & Eckert, K. (2015). Relaxation
oscillations of solutal Marangoni convection at curved interfaces. Colloids and Surfaces A, 481, 633.
[2] Mokbel, M., Schwarzenberger, K., Aland, S., & Eckert, K. (2018). Information transmission by
Marangoni-driven relaxation oscillations at droplets. Soft Matter, 14(45), 9250.
[3] Antoine, C., Irvoas, J., Schwarzenberger, K., Eckert, K., Wodlei, F., & Pimienta, V. (2016). Selfpinning
on a liquid surface. The Journal of Physical Chemistry Letters, 7(3), 520.
[4] Čejková, J., Schwarzenberger, K., Eckert, K., & Tanaka, S. (2019). Dancing performance of
organic droplets in aqueous surfactant solutions. Colloids and Surfaces A, 566, 141.
[5] Eftekhari, M., Schwarzenberger, K., Heitkam, S., & Eckert, K. (2021). Interfacial flow of a
surfactant-laden interface under asymmetric shear flow. Journal of Colloid and Interface Science, 599,
837.
[6] Eftekhari, M., Schwarzenberger, K., Heitkam, S., Javadi, A., Bashkatov, A., Ata, S., & Eckert, K.
(2021). Interfacial Behavior of Particle-Laden Bubbles under Asymmetric Shear Flow. Langmuir,
37(45), 13244.
[7] Keshavarzi, B., Krause, T., Sikandar, S., Schwarzenberger, K., Eckert, K., Ansorge-Schumacher,
M. B., & Heitkam, S. (2022). Protein enrichment by foam Fractionation: Experiment and modeling.
Chemical Engineering Science, 256, 117715.
[8] Bratsun, D., Kostarev, K., Mizev, A., Aland, S., Mokbel, M., Schwarzenberger, K., & Eckert, K.
(2018). Adaptive micromixer based on the solutocapillary Marangoni effect in a continuous-flow
microreactor. Micromachines, 9(11), 600.

  • Lecture (Conference)
    Jahrestreffen der DECHEMA-Fachgruppen Kristallisation, Grenzflächenbestimmte Systeme und Prozesse sowie Mechanische Flüssigkeitsabtrennung, 09.-10.03.2023, Frankfurt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37804


Jupyter notebooks to calculate the electric field and properties of focusing (Gaussian) laser pulses

Steiniger, K.

Abstract

These are the Jupyter notebooks which are used to compute the figures in K. Steiniger et al., "Distortions in focusing laser pulses due to spatio-temporal couplings - An analytic description".

They can be used to:

(1) Numerically calculate the electric field of laser pulses in time-space domain which are defined in frequency-space domain,

(2) Analytically calculate the properties and dispersion parameters of Gaussian laser pulses in time-space domain in the course of propagation through their focus,

(3) Compute the values of laser dispersion parameters in the focus of an off-axis parabolic mirror from the dispersion parameters before focusing at the mirror.

Keywords: laser pulse propagation; pulse-front tilt; laser dispersion; high-power laser; ultrafast optics

Involved research facilities

  • Data Center

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Permalink: https://www.hzdr.de/publications/Publ-37803


Machine Learning-Driven Structure Prediction for Iron Hydrides

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

Abstract

We created a computational workflow to analyze the potential energy surface (PES) of materials using machine-learned interatomic potentials in conjunction with the minima hopping algorithm. We demonstrate this method by producing a versatile machine-learned interatomic potential for iron hydride via a neural network using an iterative training process to explore its energy landscape under different pressures. To evaluate the accuracy and comprehend the intricacies of the PES, we conducted comprehensive crystal structure predictions using our neural network-based potential paired with the minima hopping approach. The predictions spanned pressures ranging from ambient to 100 GPa. Our results reproduce the experimentally verified global minimum structures such as \textit{dhcp}, \textit{hcp}, and \textit{fcc}, corroborating previous findings. Furthermore, our in-depth exploration of the iron hydride PES at different pressures has revealed complex alterations and stacking faults in these phases, leading to the identification of several new low-enthalpy structures. This investigation has not only confirmed the presence of regions of established FeH configurations but has also highlighted the efficacy of using data-driven, extensive structure prediction methods to uncover the multifaceted PES of materials.

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Permalink: https://www.hzdr.de/publications/Publ-37800


Measurement of the flux-weighted cross-sections for the natYb(γ,xn)175,169,167Yb reactions in the Bremsstrahlung end-point energies of 12 - 16 MeV and 60 - 70 MeV

Naik, H.; Kim, G. N.; Schwengner, R.; Wooyoung, J.; Nguyen, T. H.; Shin, S. G.; Kye, Y.; Massarczyk, R.; John, R.; Junghans, A.; Wagner, A.; Cho, M. H.

Abstract

The flux-weighted cross-sections of the natYb(γ,xn)175,169,167Yb reactions were measured at the bremsstrahlung end-point energies of 12, 14, 16, 60, 65, and 70 MeV by the activation and off-line γ-ray spectrometric technique using the 20 MeV electron linac (ELBE) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany, and 100 MeV electron linac at the Pohang Accelerator Laboratory (PAL), Korea. The
natYb(γ,xn)175,169,167Yb reaction cross-sections as a function of photon energy were also calculated theoretically using the TALYS 1.9 code. The flux-weighted average values at different end-point energies were obtained from the literature as well as from the theoretical values reported in
the TALYS library based on mono-energetic photons. They were compared with the flux-weighted values based on the present experimental data and were found to be in general agreement. It was also found that the experimental and theoretical cross-section data increased from the threshold values to a certain energy, where other reaction channels opened, which highlights the role of excitation energy. After a certain value, the individual reaction cross-sections
decrease with an increase in bremsstrahlung energy owing to the opening of other reaction channels, which indicates the partitioning of energy in different reaction channels.

Keywords: Nuclear structure; nuclear reactions; photoactivation; bremsstrahlung; gamma-ray spectroscopy; statistical reaction model

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-37799


Role of Protein Solvation in Liquid-Liquid Phase Separation

Adams, E.

Abstract

Solvation water is integral in influencing in the structure, dynamics, and function of proteins. Coupling of water molecules to the protein surface results in an interfacial region in which water molecules within this region have distinctly different properties than bulk water. Using Terahertz (THz) spectroscopy, we are able to gain insight into protein hydration water by monitoring changes in the water hydrogen-bonding network.

Liquid-liquid phase separation (LLPS) of intrinsically disordered proteins results in the formation of biomolecular condensates, which are membrane-less liquid-like protein enriched droplets. Here we investigate how protein solvation water contributes to condensate formation. Characterization of the hydrogen bonding network reveals that water solvating hydrophobic groups is stripped away in the membrane-less biomolecular condensates. Additionally, water left inside of the biomolecular condensates is highly constrained, indicative of a population of bound hydration water. These results uncover the vital role of hydration water in LLPS: the entropically favorable release of unfavorable hydration water serves as a driving force for LLPS.

  • Invited lecture (Conferences) (Online presentation)
    CMWS Seminar, 02.11.2023, DESY, Germany

Permalink: https://www.hzdr.de/publications/Publ-37795


Selecting active matter according to motility in an acoustofluidic setup: Self-propelled particles and sperm cells

Misko, V. R.; Baraban, L.; Makarov, D.; Huang, T.; Gelin, P.; Mateizel, I.; Wouters, K.; de Munck, N.; Nori, F.; de Malsche, W.

Abstract

Active systems – including sperm cells, living organisms like bacteria, fish, birds, or active soft matter systems like synthetic “microswimmers” – are characterized by motility, i.e., the ability to propel using their own “engine”. Motility is the key feature that distinguishes active systems from passive or externally driven systems. In a large ensemble, motility of individual species can vary in a wide range. Selecting active species according to their motility represents an exciting and challenging problem. We propose a new method for selecting active species based on their motility using an acoustofluidic setup where highly motile species escape from the acoustic trap. This is demonstrated in simulations and in experiments with self-propelled Janus particles and human sperm. The immediate application of this method is selecting highly motile sperm for medically assisted reproduction (MAR). Due to the tunable acoustic trap, the proposed method is more flexible than the existing passive microfluidic methods. The proposed selection method based on motility can also be applied to other active systems that require selecting highly motile species or removing immotile species.

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  • Secondary publication expected from 30.10.2024

Permalink: https://www.hzdr.de/publications/Publ-37787


Spark Plasma Sintering for synthesis of transition metal oxides

Veremchuk, I.; Grin, Y.; Makarov, D.

Abstract

The solid-state synthesis of transition metal oxides (TMO’s) is a challenging task. Slow diffusion and mass transfer of reagents are characteristic of such solid-state reactions (SSR’s). In this context, spark plasma sintering (SPS) seems to emerge a promising and technologically applicable synthetic route to obtain TMO’s. We successfully conducted SSR of Ti2O3 synthesis using SPS with dc-current acting as an accelerator of the diffusion-controlled processes between TiO2 and Ti [1]. Further, this approach was applied to directly synthesize different TMO’s (titanium oxides [2], molybdenum oxides [3], tungsten oxides [4], and chromium oxides [5]). Among the advantages of such synthetic routes, we would like to stress: i) simple pre-experiment preparation (i.e., mixing of the initial powders); ii) simultaneous compaction and shaping of products; iii) short synthesis time (i.e., from minutes to about the few hours), iv) enormous accuracy (i.e., ≅ 0.1 at % of oxygen) as well as v) high degree of reproducibility.
New types of electrochemical using SPS SSR was recently performed in our laboratories using SPS. By sintering TiO2 (insulator) with WO2 (metal) mixed in different proportions, we obtained solid solution based on rutile (i.e., TiO2) structure. However, an appearance of elemental tungsten cannot be avoided while performing the synthesis with graphite foils as separators between the reacting mixture and the punches. To shed light on the mechanism of such an electrochemical process we performed two reactions, applying the opposite polarity of dc-current pulses, to the placed in graphite die layers of unmixed TiO2 and WO2. The further combined metallographic-EDX investigation of the polished cuts of the reacted specimens revealed that in the case when WO2 was under positive pole (i.e., being an anode) free W is forming at “+”-electrode, whereas the switch of the polarity results in the formation of tungsten inclusion on the phases border between reactants. Thus, elemental tungsten seems to be the product of electrochemical reduction of WO2. Avoiding this reaction, a single phase Ti1-xWxO2 is obtained replacing the graphite foils by tungsten ones.

[1] Veremchuk I., Antonyshyn I., Candolfi C., et al. Inorg. Chem. (2013) 52, 4458.
[2] Feng B., Martin H.‐P., Börner F.‐D., Veremchuk I., et al. Adv. Eng. Mat. (2014) 16, 1252.
[3] Kaiser F., Schmidt M., Grin Yu., Veremchuk I., Chem. of Mater. (2020) 32, 2025.
[4] Kaiser F., Simon P., Burkhardt U., Kieback B., Grin Yu., Veremchuk I. Crystals (2017)7, 271.
[5] Veremchuk I., et al. ACS Appl. Electron. Mater. (2022) 4, 2943.

  • Lecture (Conference)
    2nd Conference on FAST/SPS from Research to Industry, 16.-18.10.2023, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-37786


Magnetism and magnetoelectricity of textured thin films and polycrystalline bulk α-Cr2O3

Veremchuk, I.; Makushko, P.; Hedrich, N.; Zabila, Y.; Kosub, T.; Liedke, M. O.; Butterling, M.; Elsherif, A. G. A.; Wagner, A.; Ganss, F.; Burkhardt, U.; Pylypovskyi, O.; Hübner, R.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Abstract

Magnetoelectric antiferromagnets like α-Cr2O3 are attractive for the realization of energy-efficient and high-speed spin−orbitronic-based memory devices controlled by electric fields [1-3]. In contrast to single crystals, the quality of Cr2O3 thin films and bulk polycrystalline samples is usually compromised by the presence of point defects and their agglomerations at grain boundaries, putting into question their application potential. Here, we experimentally investigated the defect nanostructure of magneton-sputtered 250-nm-thick Cr2O3 thin films prepared under different conditions on single crystals of Al2O3 (0001) and correlate it with the integral and local magnetic properties of the samples [4]. Also, we fabricated of polycrystalline bulk α-Cr2O3 sample in conditions far out of equilibrium relying on spark plasma sintering (SPS) allows high quality material with a density close to that of a single crystal [5]. The sintered sample possesses a preferential [0001] texture at the surface, which can be attributed to uniaxial strain applied to the sample during the sintering process [5]. We evaluated the type and relative concentration of defects. For this purpose, positron annihilation spectroscopy (PAS) was used as a unique probe for open-volume defects in the samples. Our analysis reveals that the Cr2O3 samples are characterized by the presence of complex defects at grain boundaries, formed by groups of single monovacancies, coexisting with complex defects and dislocations. The concentration of complex defects for the thin films can be controlled by the sample fabrication conditions including the deposition temperature as well as the post-annealing in vacuum or in air [4]. The antiferromagnetic state of the sample and linear magnetoelectric effect are accessed all electrically relying on the spin Hall magnetoresistance effect in the Pt electrode interfaced with Cr2O3 [6]. In line with the integral magnetometry measurements, the magnetotransport characterization reveals that the samples possesses the magnetic phase transition temperature of about 308 K, which is hardly affected by the formed defects. The antiferromagnetic domain patterns consist of small domains with size equals the grain size, which is formed due to the granular structure of the samples. Furthermore, the presence of larger defects like grain boundaries has a strong influence on the pinning of magnetic domain walls in studied samples. The possibility to access the magnetoelectric properties of the samples relying on magnetotransport measurements indicates the potential of the thin films and polycrystalline bulk Cr2O3 samples for prospective research in antiferromagnetic spintronics.
[1] X. He, Y. Wang, N. Wu, A. N. Caruso, E. Vescovo, K. D. Belashchenko, P. A. Dowben, C. Binek, Nature Mater., 9, 579 (2010).
[2] T. Kosub, M. Kopte, R. Hühne, P. Appel, B. Shields, P. Maletinsky, R. Hübner, M. O. Liedke, J. Fassbender, O. G. Schmidt, D. Makarov, Nature Commun., 8, 13985 (2017).
[3] N. Hedrich, K. Wagner, O. V. Pylypovskyi, B. J. Shields, T. Kosub, D. D. Sheka, D. Makarov, P. Maletinsky, Nature Phys., 17, 574 (2021).
[4] I. Veremchuk, M. O. Liedke, P. Makushko, T. Kosub, N. Hedrich, O. V. Pylypovskyi, F. Ganss, M. Butterling, R. Hübner, E. Hirschmann, A. G. Attallah, A. Wagner, K. Wagner, B. Shields, P. Maletinsky, J. Fassbender, D. Makarov, Small, 18, 2201228 (2022).
[5] I. Veremchuk, P. Makushko, N. Hedrich, Y. Zabila, T. Kosub, M. O. Liedke, M. Butterling, A. G. Attallah, A. Wagner, U. Burkhardt, O. V. Pylypovskyi, R. Hübner, J. Fassbender, P. Maletinsky, and D. Makarov, ACS Appl. Electron. Mater., 4, 2943 (2022).
[6] R. Schlitz, T. Kosub, A. Thomas, S. Fabretti, K. Nielsch, D. Makarov, S. T. B. Goennenwein, Appl. Phys. Lett., 112, 132401 (2018).

Involved research facilities

  • P-ELBE
  • Lecture (Conference)
    CMD30 FisMat, 04.-08.09.2023, Milan, Italy

Permalink: https://www.hzdr.de/publications/Publ-37785


Defect nanostructure and its impact on magnetism of α-Cr2O3 thin films.

Veremchuk, I.; Liedke, M. O.; Makushko, P.; Kosub, T.; Hedrich, N.; Pylypovskyi, O.; Ganss, F.; Butterling, M.; Hübner, R.; Hirschmann, E.; Wagner, A.; Elsherif, A. G. A.; Wagner, K.; Shields, B.; Maletinsky, P.; Faßbender, J.; Makarov, D.

Abstract

Thin films of the magnetoelectric insulator Cr$_{2}$O$_{3}$ are technologically relevant for energy-efficient magnetic memory devices controlled by electric fields. We experimentally investigated the defect nanostructure of 250-nm-thick Cr$_{2}$O$_{3}$ thin films prepared under different conditions on single crystals of Al$_{2}$O$_{3}$ (0001) and correlate it with the integral and local magnetic properties of the samples. Positron annihilation spectroscopy (PAS) was used as a unique probe for open-volume defects in thin films. Analysis reveals that the Cr$_{2}$O$_{3}$ thin films are characterized by the presence of complex defects at grain boundaries, formed by groups of monovacancies, coexisting with monovacancies and dislocations. The concentration of complex defects can be controlled by the sample fabrication conditions. The defect nanostructure strongly affects the magnitude of the electrical readout, which is measured of the Cr$_{2}$O$_{3}$ samples capped with a thin layer of Pt relying on spin Hall effect. Furthermore, the presence of larger defects like grain boundaries has a strong influence on the pinning of magnetic domain walls in thin films. Independent of these findings, we showed that the N\'{e}el temperature, which is one of the important technological metrics, is hardly affected by the formed defects in a broad range of deposition parameters.

Involved research facilities

  • P-ELBE
  • Lecture (Conference)
    DPG spring meeting 2023, 26.-31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-37784


Low temperature diffusion in thin film Pt-(Au-)-Co heterostructures: structural and magnetic characterization

Pedan, R.; Makushko, P.; Yavorskyi, Y.; Dubikovskyi, O.; Bodnaruk, A.; Burmak, A.; Golub, V.; Voloshko, S.; Hübner, R.; Makarov, D.; Igor, V.

Abstract

Formation of functional thin films for nanoelectronics and magnetic data storage via thermally induced diffusion-driven structural phase transformations in multilayer stacks is a promising technology-relevant approach. Ferromagnetic thin films based on Co Pt alloys are considered as a material science platform for the development of various applications such as spin valves, spin orbit torque devices, and high-density data storage media. Here, we study diffusion processes in Pt-Co-based stacks with the focus on the effect of layers inversion (Pt/Co/substrate vs. Co/Pt/substrate) and insertion of an intermediate Au layer on the structural transitions and magnetic properties. We demonstrate that layer stacking has a pronounced effect on the diffusion rate at temperatures, where the diffusion is dominated by grain boundaries. We quantify effective diffusion coefficients, which characterize the diffusion rate of Co and Pt through the interface and grain boundaries, providing the possibility to control the homogenization rate of Pt-Co-based heterostructures. The obtained values are in the range of 10-16 – 10-13 cm2/s for temperatures of 150 °C – 350 °C. Heat treatment of thin-film samples results in the coercivity enhancement, which is attributed to short-range chemical ordering effects. We show that introducing an additional Au intermediate layer leads to an increase of the coercive field of the annealed samples due to a modification of exchange coupling between the magnetic grains at the grain boundaries.

Keywords: diffusion coefficient; grain boundary diffusion; magnetic thin films; short-range chemical order; Co-Pt alloy

Permalink: https://www.hzdr.de/publications/Publ-37783


Tunable room temperature nonlinear Hall effect from the surfaces of elementary bismuth thin films

Makushko, P.; Kovalev, S.; Zabila, Y.; Ilyakov, I.; Ponomaryov, O.; Arshad, A.; Prajapati, G. L.; de Oliveira, T.; Deinert, J.-C.; Chekhonin, P.; Veremchuk, I.; Kosub, T.; Scurschii, I.; Ganss, F.; Makarov, D.; Carmine, O.

Abstract

The nonlinear Hall effect (NLHE) with time-reversal symmetry constitutes the appearance of a transverse voltage quadratic in the applied electric field. It is a secondorder electronic transport phenomenon that induces frequency doubling and occurs in non-centrosymmetric crystals with large Berry curvature – an emergent magnetic field encoding the geometric properties of electronic wavefunctions. The design of (opto)electronic devices based on the NLHE is however hindered by the fact that this nonlinear effect typically appears at low temperatures and in complex compounds characterized by Dirac or Weyl electrons Here, we show a strong room temperature NLHE in the centrosymmetric elemental material bismuth synthesized in the form of technologically relevant polycrystalline thin films. The (111) surface electrons of this material are equipped with a Berry curvature triple that activates side jumps and skew scatterings generating nonlinear transverse currents. We also report a boost of the zero field nonlinear transverse voltage in arc-shaped bismuth stripes due to a extrinsic geometric classical counterpart of the NLHE This electrical frequency doubling in curved geometries is then extended to optical second harmonic generation in the terahertz (THz) spectral range. The strong nonlinear electrodynamical responses of the surface states are further demonstrated by a concomitant highly efficient THz third harmonic generation which we achieve in a broad range of frequencies in Bi and Bi-based heterostructures. Combined with the possibility of growth on CMOS-compatible and mechanically flexible substrates, these results highlight the potential of Bi thin films for THz (opto)electronic applications.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)
  • T-ELBE

Permalink: https://www.hzdr.de/publications/Publ-37781


Flexomagnetic Effects in Antiferromagnetic Epitaxial Cr2O3 Thin Films

Makushko, P.; Kosub, T.; Pylypovskyi, O.; Hedrich, N.; Li, J.; Pashkin, O.; Avdoshenko, S.; Hübner, R.; Ganss, F.; Wolf, D.; Lubk, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Wagner, K.; Shields, B.; Lehmann, P.; Veremchuk, I.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Abstract

Thin films of antiferromagnetic insulators (Cr2O3, Fe2O3, NiO etc.) are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and non-volatile data storage. A standard micromagnetic approach for the description of thin film system commonly relies on the effective parameters, assumed to be homogeneously distributed within a material. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the strain-gradient-driven magnetomechanical coupling promises technological advantages: the cross-coupling between elastic, magnetic and electric subsystems opens additional degrees of freedom in the control of the respective order parameters [1]-[3].
In this work, we discover the presence of flexomagnetic effects in epitaxial antiferromagnetic Cr2O3 thin films [4]. We demonstrate that a gradient of mechanical strain affect the order-disorder magnetic phase transition resulting in the distribution of the Néel temperature along the thickness of Cr2O3 thin film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15 µB nm-2. The antiferromagnetic ordering in the strained films can persist up to 100 °C, rendering Cr2O3 as a prospective material for industrial spintronic applications. Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with continuously graded parameters.

Involved research facilities

  • P-ELBE
  • Lecture (Conference)
    8th International conference on superconductivity and magnetism, 04.-11.05.2023, Fethiye, Turkey

Permalink: https://www.hzdr.de/publications/Publ-37779


Flexomagnetism and vertically graded Néel temperature in the epitaxial Cr2O3 thin films

Makushko, P.; Kosub, T.; Pylypovskyi, O.; Hedrich, N.; Li, J.; Pashkin, O.; Avdoshenko, S.; Hübner, R.; Ganss, F.; Wolf, D.; Lubk, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Wagner, K.; Shields, B.; Lehmann, P.; Veremchuk, I.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Abstract

Thin films of magnetoelectric antiferromagnetic insulators (Cr2O3, BiFeO3 etc.) have emerged as a prospective material platform for magnonics, spin superfluidity, THz spintronics, and energy efficient spin-orbitronics. Understanding the magnetomechanical coupling in antiferromagnets offers vast advantages in the control of the primary order parameters. A standard micromagnetic approach for the description of a material relies on the effective parameters being homogeneously distributed throughout the system. Such an approach is commonly sufficient, but does not provide full characterization of the system. The family of magnetomechanical effects includes piezo- and flexomagnetic responses, which determine the modification of the magnetic order parameters due to homogeneous or inhomogeneous strain, respectively. Accounting for the flexomagnetic effects promises technological advantages for multiferroic and antiferromagnetic materials, where cross-coupling between elastic, magnetic and electric subsystems open additional degrees of freedom in the control of the respective order parameters [1, 2].
In this work, we discover the effect of strain gradient onto the magnetic behaviour of epitaxial Cr2O3 thin films [3, 4]. We demonstrate that by tuning the parameters of Cr2O3 epitaxial growth a fine control of the crystallographic and defect structure can be realized. A persistent strain gradient was obtained in Cr2O3 affecting its magnetic order parameters rendering a distribution of the Néel temperature along the thickness of the thin film. The antiferromagnetic ordering in the strained films can persist up to 100°C, rendering Cr2O3 as a prospective material for industrial electronics applications. The inhomogeneous enhancement of the antiferromagnetic order parameter induced by the strain gradient renders a flexomagnetic response of about 15 µB nm-2.
Strain gradient in Cr2O3 thin films enables fundamental research on magnetomechanics and thermodynamics of antiferromagnetic solitons, spin waves and artificial spin ice systems in magnetic materials with graded parameters. Distribution of the Neel temperature along the thin film thickness introduces temperature as a took for realization of reconfigurable spintronic and magnonic devices.

Involved research facilities

  • P-ELBE
  • Lecture (Conference)
    CMD30 FisMat 2023, 04.-08.09.2023, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-37778


Flexomagnetism and vertically graded Néel temperature of antiferromagnetic Cr2O3 thin films

Makushko, P.; Kosub, T.; Pylypovskyi, O.; Hedrich, N.; Li, J.; Pashkin, O.; Avdoshenko, S.; Hübner, R.; Ganss, F.; Wolf, D.; Lubk, A.; Liedke, M. O.; Butterling, M.; Wagner, A.; Wagner, K.; Shields, B.; Lehmann, P.; Veremchuk, I.; Faßbender, J.; Maletinsky, P.; Makarov, D.

Abstract

Thin films of antiferromagnetic insulators are a prospective material platform for magnonics, spin superfluidity, THz spintronics, and nonvolatile data storage. Here, we explore the presence of flexomagnetic effects in epitaxial Cr2O3 [1]. We demonstrate that a gradient of mechanical strain effect the order-disorder magnetic phase transition, resulting in the distribution of the Néel temperature along the thickness of a Cr2O3 film. The inhomogeneous reduction of the antiferromagnetic order parameter induces a flexomagnetic coefficient of about 15µB nm−2. The
antiferromagnetic ordering in the strained films can persist up to 100∘C, rendering Cr2O3 as a prospective material for industrial electronics applications.

Involved research facilities

  • P-ELBE
  • Lecture (Conference)
    DPG Spring Meeting 2023, 26.-31.03.2023, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-37777


Rollenscan Data Science und KI

Ernst, M.; Hartmann, M.; Marx, S.; Schindler, T.; Steinbach, P.; Wilde, A.

Abstract

Im Zeitalter der datengestützten Entscheidungsfindung hat sich der Bereich Datenwissenschaft (Data Science) zu einem wichtigen Katalysator für Innovation und Fortschritt sowohl in der Industrie als auch in der Wissenschaft entwickelt. Die Rollen und Aufgaben von Data Scientists haben sich jedoch erheblich weiterentwickelt und umfassen ein breites Spektrum an Fähigkeiten, Fachwissen und Anwendungen. Um die Vielschichtigkeit dieser Rollen zu erfassen und unser kollektives Verständnis zu vermitteln, traf sich eine Gruppe von sechs Fachleuten bei Silicon Saxony und nutzte "Personas" als Methode, um unsere derzeitigen Ansichten über die Rolle von Datenwissenschaftler:innen zu formulieren. Dieses Papier fasst die Erkenntnisse dieser Aktivität zusammen.

Keywords: Data Science; Skill Set; Beruf; Industrie

Permalink: https://www.hzdr.de/publications/Publ-37776


Laser-Induced Positional and Chemical Lattice Reordering Generating Ferromagnetism

Pflug, T.; Pablo-Navarro, J.; Anwar, M. S.; Olbrich, M.; Magén, C.; Ibarra, M. R.; Potzger, K.; Faßbender, J.; Lindner, J.; Horn, A.; Bali, R.

Abstract

Atomic scale reordering of lattices can induce local modulations of functional material properties, such as reflectance and ferromagnetism. Pulsed femtosecond laser irradiation enables lattice reordering in the picosecond range. However, the dependence of the phase transitions on the initial lattice order as well as the temporal dynamics of these transitions remain to be understood. This study investigates the laser-induced atomic reordering and the concomitant onset of ferromagnetism in thin Fe-based alloy films with vastly differing initial atomic orders. The optical response to single fs laser pulses on selected prototype systems, one that initially possesses positional disorder, Fe60V40, and a second system initially in a chemically ordered state, Fe60Al40, has been tracked with time. Despite the vastly different initial atomic orders the structure in both systems converges to a positionally ordered but chemically disordered state, accompanied by the onset of ferromagnetism. Time-resolved measurements of the transient reflectance combined with simulations of the electron and phonon temperature reveal that the reordering processes occur via the formation of a transient molten state with an approximate lifetime of 200 ps. These findings provide insights into fundamental processes involved in laser-induced atomic reordering, paving the way for controlling material properties in the picosecond range.

Keywords: positional order; chemical order; atomic reordering; ferrmagnetism; pump-probe reflectometry

Permalink: https://www.hzdr.de/publications/Publ-37775


Data publication: Fermionic physics from ab initio path integral Monte Carlo simulations of fictitious identical particles

Dornheim, T.

Abstract

This repository contains the PIMC/CPIMC results shown in J. Chem. Phys. 159, 164113 (2023).

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Permalink: https://www.hzdr.de/publications/Publ-37774


Virial coefficients of the Uniform Electron Gas from Path Integral Monte Carlo Simulations

Röpke, G.; Dornheim, T.; Vorberger, J.; Blaschke, D.; Mahato, B.

Abstract

The properties of plasmas in the low-density limit are described by virial expansions. Analytical expressions are known from Green's function approaches only for the first three virial coefficients. Accurate path integral Monte Carlo (PIMC) simulations have recently been performed for the uniform electron gas, allowing the virial expansions to be analyzed and interpolation formulas to be derived. The exact expression for the second virial coefficient is used to test the accuracy of the PIMC simulations and the range of validity of the interpolation formula of Groth {\it et al.}~[Phys.~Rev.~Lett.~\textbf{119}, 135001 (2017)]. We discuss the fourth virial coefficient, which is of interest, e.g., for properties of solar plasmas, but has not yet been precisely known. Combining PIMC simulations with benchmarks from exact results of the virial expansion would allow us to obtain precise results for the equation of state (EoS) in a wide range of parameters.

Permalink: https://www.hzdr.de/publications/Publ-37773


Calorimetry as a tool to improve the dosimetric accuracy in novel radiotherapy modalities

Horst, F. E.

Abstract

The main quantity of interest in radiotherapy dosimetry is absorbed dose to water, i.e. the energy that is deposited by the radiotherapy beam in water per unit mass. The most common method to measure dose in radiotherapy is by using air-filled ionization chambers via the charge released in their active volume by ionizations. These ionization chambers are typically absolute calibrated in 60Co beams in terms of absorbed dose to water. If a measurement is carried out in another radiation quality (e.g. proton beams), the different response of the chamber in that radiation quality compared to 60Co photons due to a different water-to-air stopping power ratio and chamber-specific geometry effects is taken into account by applying a beam quality correction factor kQ. Because kQ might be sensitive to several factors, it is recommended that absolute absorbed dose to water measurements should be performed within defined reference conditions (e.g. field size and water depth), and therefore such measurements are referred to as reference dosimetry [1]. In addition to kQ, also several other corrections may be necessary (e.g., recombination or air density correction).
Compared to ionization chamber dosimetry, a more direct way to measure dose is calorimetry where the deposited energy in the detector is measured via its temperature increase. Calorimetry is considered as the most accurate method of dose determination but requires a large logistic effort, stable thermal conditions in the room plus a good isolation and those devices are usually very sensitive and complicated to operate. Therefore calorimetry is at present mostly applied as primary standard for absorbed dose in permanently installed setups at national metrology institutes [2], to which the calibration of ionization chambers used in radiotherapy clinics can be traced back to.
The natural choice of the calorimeter medium is water because absorbed dose to water is the quantity of interest in radiotherapy dosimetry. Due to some practical limitations of water calorimeters, there are also calorimeter designs based on solid materials, typically graphite. Graphite calorimeters can be a lot more compact than water calorimeters and due to the smaller specific heat capacity of graphite, the temperature increase (i.e., the measurement signal) is about a factor 5 higher than for water at the same dose. However, the higher thermal conductivity of graphite requires additional insulation of the calorimeter core. Another characteristic of graphite calorimetry is that it requires a conversion from absorbed dose to graphite to absorbed dose to water and therefore the stopping power ratio in the radiation field of interest must be calculated.
Besides applications as primary standard for absorbed dose to water, calorimetric measurements can also be helpful to guarantee the dosimetric accuracy when novel radiotherapy modalities, for which standard dosimetry protocols are not suitable, are introduced. Recent examples are magnetic resonance guided radiotherapy [3], where the response of ionization chambers is modified by the magnetic field, or FLASH radiotherapy at ultra-high dose rate (UHDR) [4,5] where recombination effects in ionization chambers become more pronounced than in conventional radiotherapy. For calorimetric measurements, the UHDR delivery can even be considered an advantage because the quasi-instantaneous dose application makes the heat drift become less relevant. For instance at the Physikalisch-Technische Bundesanstalt (PTB) in Germany, efforts were made to establish a water calorimeter as primary standard in the UHDR beam of their 20 MeV electron accelerator [4]. Another example is the first proton FLASH patient trial at the Cincinnati Children’s Hospital Medical Center in the USA where a group from the National Physical Laboratory (NPL) of the United Kingdom supported the dosimetric characterization of UHDR beams with their graphite calorimeter [5]. Recently, water calorimeters have been used to determine ionization chamber specific beam quality correction factors in clinical proton (6) and carbon ion beams [7,8].
Generally, for protons and heavy ions no actual primary standards have been established up to now [9], because the national metrology institutes do not have suitable accelerators and beam qualities on-site but would have to travel to clinical facilities with their calorimetry equipment. For this purpose, since several years many metrology groups work on the development of portable calorimeters (see for example ref. [10] for an early work).
At NPL a portable graphite calorimeter was developed [11]. This device is now intended to be applied for secondary standard measurements in UHDR proton beams in order to improve the dosimetric accuracy for this novel radiotherapy modality. Like ionization chamber dosimetry, also calorimetry requires a number of correction factors to be applied to the measured signal. Cotterill and colleagues present in their paper [12], published in this ESTRO 2023 Physics Highlights special issue of phiRO, detailed Monte Carlo simulations on their so-called Small-body Portable Graphite Calorimeter. They derived correction factors for 250 MeV protons correcting for the graphite impurity and the air gap between the graphite core and its jacket. They show that the dominating perturbation (almost 0.5%) is due to missing scatter contributions from the styrofoam insulation around the device, for which they introduce a new correction factor. By applying the obtained correction factors, the dosimetric accuracy of the calorimeter can be improved considerably. The in- and out-scattering of protons from the different components of the device was studied in detail and the dose conversion factor from absorbed dose in the graphite core to absorbed dose to water at the reference point was calculated.
Even though portable calorimeters like the one presented by Cotterill et al. are still more complicated to operate than ionization chambers, they are much more convenient to transport and set up than classic calorimetry setups.
It will be very interesting to see if these developments will contribute to a wider spread of calorimetric measurements in radiotherapy, or even a routine use in radiotherapy clinics as envisioned by Cotterill et al., and if the establishment of a primary standard for absorbed dose to water in proton (and heavy ion) beams will finally succeed.

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  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-37772


Selective leaching of indium from spent LCD screens by siderophore desferrioxamine E

Zheng, K.; Benedetti, M. F.; Jain, R.; Guy, B. M.; Pollmann, K.; van Hullebusch, E. D.

Abstract

Given the criticality of indium (In), spent LCD screens can represent a viable secondary resource of In. In this work, an innovative and alternative technology to selectively leach In from spent LCD screens using a microbial chelating agent, desferrioxamine E (DFOE), was developed. Indium was concentrated from spent LCD screens by implementing an adapted pre-treatment procedure, allowing the isolation of an indium-rich glassy fraction. During leaching, the competition between Aluminum (Al) and In for complexation with DFOE leads to the precipitation of In(OH)3 at low DFOE concentration (12-240 µM). After adjusting the optimal conditions (fraction size: 0-36 μM, pH 5.5, S/L ratio: 1 g/L, room temperature), the In leaching yield reached 32%, ten times higher than Al over 90 days with 5 mM DFOE. Thus, selective leaching of In, while mitigating the influence of competing element Al, makes it possible to achieve a high In recovery by extending leaching time. This is the first attempt to selectively leach In by a selected siderophore from end-of-life (EoL) products with high concentrations of non-targeted elements (i.e. Al, Si, and Ca). This work shows good potential to generate indium-rich leachates that can be further processed by the GaLIophore technology for indium refinery.

Keywords: Waste liquid crystal displays; selective leaching; optimal conditions; competition; modeling

Permalink: https://www.hzdr.de/publications/Publ-37771


Magnetic membrane polymers with onboard electronic skins for supervised actuation

Oliveros Mata, E. S.; Ha, M.; Canon Bermudez, G. S.; Liu, J. A.-C.; Evans, B. A.; Tracy, J. B.; Makarov, D.

Abstract

Soft actuators have been developed to mimic the biomechanics of living organisms, enabling complex movements such as crawling, flapping, and twisting upon the application of physical and chemical stimuli [1]. Magnetic membrane soft polymers have been used for controlled, programmable, and fast actuation in uniform and gradient magnetic fields [2,3]. This allows for multipurpose biomimetic systems that can move untethered using permanent magnets and electromagnets for use in remote surgery, cargo transport, and artificial muscles [4]. To achieve the full potential of these types of soft actuators, it is needed a suitable system that mimics the sensory and proprioception capabilities of living beings.
Here, we show the integration of highly flexible electronic skins that are laminated to the body of magnetic flexible membranes to supervise their actuation mechanisms [5]. The electronic skins contain flexible magnetic field sensors based on thin films fabricated on ultrathin (2.5-µm-thick) polymeric foils. This highly compliant e-skin acts as an onboard sensory system of magnetic cues, such as the own magnetization state of the soft actuator and the magnetic fields employed for deforming the membranes. This allows the system to orient itself with respect to a reference magnetic source and be aware of its folding state. We demonstrate the signal readout and supervision of magnetic soft membrane actuators during their assembly into box and boat-like layouts [5].
[1] D. Rus, et al. Nature. 521, 467 (2015).
[2] X. Wang, et al. Commun. Mater. 67, 1 (2020)
[3] H. Chung, et al. Adv. Intell. Syst. 3, 2000186 (2021).
[4] S. Wu, et al. Multifunct. Mater. 3, 042003. (2020).
[5] M. Ha, E.S. Oliveros Mata, et al. Adv. Mater. 33, 2008751 (2021)

Keywords: magnetic; soft robot; actuator; polymer; composite

  • Lecture (Conference)
    European-MRS 2023 Spring Meeting, 29.05.-02.06.2023, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-37769


Printed human machine interfaces using touchless interaction via magnetic fields

Oliveros Mata, E. S.; Voigt, C.; Xu, R.; Ha, M.; Canon Bermudez, G. S.; Zabila, Y.; Fritsch, M.; Mosch, S.; Kusnezoff, M.; Vinnichenko, M.; Makarov, D.

Abstract

Printed and flexible electronics have gained significant attention in recent years for their potential in various applications including medical, wearable, and Internet of Things (IoT) devices [1]. In this work, we focus on the development and characterization of printed magnetic field sensors for use in human-machine interfaces enabling the control and monitoring of various systems and devices. We developed a set of printable magnetically sensitive pastes based on microflakes and microparticles showing anisotropic [2,3], giant [4], and large magnetoresistance [5] effects. Our sensors are fabricated using cost-effective, scalable, and large-area automatized printing techniques, making them prospectively suitable for large-scale
production.
The design and production of the printed sensors are based on the properties of the paste fillers, binder, substrate, and techniques used in the fabrication process. By adjusting the mechanical properties of the binder, we were able to give the printed sensors the capability to conform to various shapes and surfaces. The use of polymeric binders in the printing process on flexible foils allowed us to laminate the sensors onto objects with complex geometries, including human skin. For example, we were able to create stretchable magnetic field sensors that can undergo 100% strain by using a styrene-butadiene-styrene block copolymer as a binder. We have also demonstrated that these sensors remain functional even when folded to a
radius of 16 µm. [4]
We have also shown that it is possible to produce large quantities of magnetic field sensors using automatized dispenser printing and laser sintering Bi pastes [5]. This method allows large-area, cost-effective, and customizable fabrication of flexible, fully printed magnetic field sensors using minimal materials. This manufacturing capability has the potential to pave the way for more extensive interactive smart surfaces and touchless control boards. Our research represents a significant advancement in the integration of printed and flexible electronics into human machine interfaces, and it opens the door for further research for creating customized solutions to user-specific needs.
[1] Y. Khan, et al. Adv. Mater. 32, 1905279 (2020)
[2] E.S. Oliveros Mata, et al. Appl. Phys. A 127, 280 (2021)
[3] R. Xu, et al. Nat. Commun. 13, 6587 (2022)
[4] M. Ha, et al. Adv. Mater. 33, 2005521 (2021)
[5] E.S. Oliveros‐Mata, E. S., C. Voigt, et al. Adv. Mater. Technol. 2200227 (2022)

Keywords: printed electronics; magnetic; human machine interfaces; flexible electronics

  • Lecture (Conference)
    European-MRS 2023 Spring Meeting, 29.05.-02.06.2023, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-37768


Yamdb - Yet Another Materials DataBase

Weier, T.; Nash, W.; Personnettaz, P.; Weber, N.

Abstract

Yamdb (Yet Another Materials Database/YAMl materials DataBase) is a
Python library providing thermophysical properties of liquid metals
and molten salts in an easily accessible manner. Mathematical
relations describing material properties - usually determined by
experiment - are taken from the literature and implemented in
Python. The coefficients of these equations are stored separately in
YAML files.

Keywords: material properties; liquid metals; molten salts; YAML; Python

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Permalink: https://www.hzdr.de/publications/Publ-37766


Goma - using Yamdb material databases from the commandline

Weier, T.; Nash, W.; Personnettaz, P.; Weber, N.

Abstract

Goma (GO MAterials database) is a program enabling command line access to the  YAML files distributed with Yamdb. It implements the equations necessary to calculate the thermophysical properties from the coefficients stored in the YAML database. Yamdb (Yet another materials data base) and Goma address the need to provide thermophysical properties of liquid metals and molten salts in an easily accessible manner. Mathematical relations describing material properties - usually determined by experiment - are taken from the literature. Equations and their coefficients are stored separately. The former can be implemented in any programming language (Go in this case) and the latter are kept in YAML files together with additional information (source, temperature range, composition, accuracy if available, etc).

Keywords: material properties; liquid metal; molten salts; YAML; Go

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Permalink: https://www.hzdr.de/publications/Publ-37765


First measurement of the low-energy direct capture in ²⁰Ne(p,γ)²¹Na and improved energy and strength of the E(c.m.) = 368 keV resonance

Masha, E.; Barbieri, L.; Skowronski, J.; Aliotta, M.; Ananna, C.; Barile, F.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Campostrini, M.; Casaburo, F.; Cavanna, F.; Ciani, G. F.; Ciapponi, A.; Colombetti, P.; Compagnucci, A.; Corvisiero, P.; Csedreki, L.; Davinson, T.; Depalo, R.; Di Leva, A.; Elekes, Z.; Ferraro, F.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; José, J.; Junker, M.; Lugaro, M.; Manoj, P.; Marigo, P.; Menegazzo, R.; Paticchio, V.; Piatti, D.; Prati, P.; Rapagnani, D.; Rigato, V.; Robb, D.; Schiavulli, L.; Sidhu, R. S.; Straniero, O.; Szücs, T.; Zavatarelli, S.

Abstract

The ²⁰Ne(p,γ)²¹Na reaction is the slowest in the NeNa cycle and directly affects the abundances of the Ne and Na isotopes in a variety of astrophysical sites. Here we report the measurement of its direct capture contribution, for the first time below E(c.m.) = 352 keV, and of the contribution from the E(c.m.) = 368 keV resonance, which dominates the reaction rate at T = 0.03–1.00 GK. The experiment was performed deep underground at the Laboratory for Underground Nuclear Astrophysics, using a high-intensity proton beam and a windowless neon gas target. Prompt γ rays from the reaction were detected with two high-purity germanium detectors. We obtain a resonance strength ωγ = (0.112 ± 0.002(stat) ± 0.005(sys)) meV, with an uncertainty a factor of 3 smaller than previous values. Our revised reaction rate is 20% lower than previously adopted at T < 0.1 GK and agrees with previous estimates at temperatures T ≤ 0.1 GK. Initial astrophysical implications are presented.

Keywords: Nuclear Astrophysics; Underground Laboratory; Cross Section Measurement; Neon-Sodium-Cycle; LUNA

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Observing the onset of pressure-driven K-shell delocalization

Döppner, T.; Bethkenhagen, M.; Gericke, D.; Kraus, D.; Bachmann, B.; Chapman, D.; Böhme, M.; Divol, L.; Dornheim, T.; Falcone, R.; Fletcher, L.; Kruse, M.; Landen, O.; Macdonald, M.; Glenzer, S.; Redmer, R.; Schörner, M.; Sterne, P.; Vorberger, J.

Abstract

We have developed an experimental platform for x-ray Thomson scattering (XRTS) at NIF to characterize plasma conditions in ICF indirectly-driven capsule implosions near stagnation [1,2]. This enabled us to investigate up to 30 times compressed ablator materials reaching pressures above 3 Gigabars, at conditions where the distance between the nuclei becomes comparable to the extent of the core shell bound states, which will eventually lead to their pressure ionization. In this talk we will present results from experiments with beryllium shells. We observe reduced elastic scattering for the most extreme conditions [2]. We interpret this reduction as the precursor of pressure ionization of the remaining K-shell electrons, that is, a strongly modified bound state. The beryllium charge state inferred from the data is considerable higher than standard models predict but agrees well with results from DFT simulations [2,3]. Accurate modelling of the K-shell occupation of light elements is imperative for creating predictive capabilities for ICF implosions. Our experiments yield valuable benchmarks for this process and demonstrating a complex pathway of pressure ionization.

  • Lecture (Conference)
    APS DPP, 30.10.-03.11.2023, Denver, USA

Permalink: https://www.hzdr.de/publications/Publ-37763


Towards a model-free interpretation of X-ray Thomson scattering signals

Dornheim, T.

Abstract

Matter under extreme densities and temperatures is ubiquitous throughout our universe and naturally occurs in a plethora of astrophysical objects such as giant planet interiors and brown dwarfs. In addition, such warm dense matter (WDM) is of key importance for a number of technological applications, most notably inertial confinement fusion. Yet, the accurate diagnostics of experiments with WDM is rendered challenging by the extreme conditions. Indeed, even basic parameters such as the temperature often cannot be measured directly and have to be inferred from other observations. In this context, X-ray Thomson scattering (XRTS) [1] has emerged as a key diagnostic, but the interpretation of an XRTS signal is often based on de-facto uncontrolled approximations such as the decomposition into bound and free electrons within the popular Chihara model.

In this contribution, I outline how one can get direct access to the physical properties of interest by analyzing the measured signal in the imaginary-time domain [2]. No simulations/models and, therefore, no approximations are required. First and foremost, this allows us to infer the temperature of a given system with high accuracy [3]. Moreover, we can use XRTS to probe electron—electron correlations by utilizing the f-sum rule in the imaginary-time domain [4]. Finally, we show how the idea of imaginary-time correlation functions can be generalized to characterize the degree of nonequilibrium in the probed system [5], with important implications for equation-of-state measurements and the understanding of relaxation times.

[1] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)

[2] T. Dornheim et al, arXiv:2209.02254 (submitted)

[3] T. Dornheim et al, Nature Communications 13, 7911 (2022)

[4] T. Dornheim et al, arXiv:2305.15305 (submitted)

[5] J. Vorberger et al, arXiv:2302.11309 (submitted)

  • Lecture (Conference)
    APS DPP, 30.10.-03.11.2023, Denver, USA

Permalink: https://www.hzdr.de/publications/Publ-37762


Dose and dose rate dependence of the tissue sparing effect at ultra-high dose rate studied for proton and electron beams using the zebrafish embryo model.

Horst, F. E.; Bodenstein, E.; Brand, M.; Hans, S.; Karsch, L.; Leßmann, E.; Löck, S.; Schürer, M.; Pawelke, J.; Beyreuther, E.

Abstract

Purpose: A better knowledge of the dependence of the tissue sparing effect at ultra-high dose rate (UHDR) on physical beam parameters (dose, dose rate, radiation quality) would be helpful towards a mechanistic understanding of the FLASH effect and for its broader clinical translation.
To address this, a comprehensive study on the normal tissue sparing at UHDR using the zebrafish embryo (ZFE) model irradiated with protons and electrons was conducted.

Methods: 1 day old ZFE were irradiated over a wide dose range (15-95 Gy) in three different beams (proton entrance channel, proton spread out Bragg peak and 30 MeV electrons) at UHDR and reference dose rate. After irradiation the ZFE were incubated for 4 days and then analyzed
for their development and morphological characteristics.

Results: Dose-effect curves for four different biological endpoints of ZFE (pericardial edema, curved spine, embryo length and eye diameter) were obtained and a sparing effect was observed for all three beams. It was demonstrated that proton relative biological effectiveness and UHDR sparing are both relevant to consider in order to predict the resulting dose response. Dose dependent FLASH modifying factors (FMF) for ZFE, calculated based on the obtained dose-effect curves, were found to be compatible with rodent data from the literature. It was found that the UHDR sparing effect saturates at doses above ~50 Gy with an FMF of ~0.7-0.8. Only a moderate dependence of the tissue sparing effect in ZFE on the biological endpoint, but a strong dose rate
dependence were observed.

Conclusion: The ZFE model was shown to be a suitable high-throughput pre-clinical model for radiobiological studies on FLASH radiotherapy, providing results comparable to rodent models. The obtained results emphasize to further clarify the nature of the observed dose rate dependence.

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Permalink: https://www.hzdr.de/publications/Publ-37761


Fate of Oxidation States at Actinide Centers in Redox-Active Ligand Systems Governed by Energy Levels of 5f Orbitals

Takeyama, T.; Tsushima, S.; Gericke, R.; Kaden, P.; März, J.; Takao, K.

Abstract

We report the formation of a Np(IV) complex from the complexation of Np(VI)O22+ with the redox-active ligand tBu-pdiop2-=2,6-bis[N-(3,5-di-tert-butyl-2-hydroxyphenyl)iminomethyl]pyridine. To the best of our knowledge, this is the first example of the direct complexation-induced chemical reduction of Np(VI)O22+ to Np(IV). In contrast, the complexation of U(VI)O22+ with tBu-pdiop2- did not induce the reduction of U(VI)O22+, not even after the two-electron electrochemical reduction of [U(VI)O2(tBu-pdiop)]. This contrast between the Np and U systems may be ascribed to the decrease of the energy of the 5f orbitals in Np compared to those in U. The present findings indicate that the redox chemistry between U(VI)O22+ and Np(VI)O22+ should be clearly differentiated in redox-active ligand systems.

Permalink: https://www.hzdr.de/publications/Publ-37759


Extended-gate field-effect transistor chemo- and biosensors: State of the art and perspectives

Janićijević, Ž.; Nguyen Le, T. A.; Baraban, L.

Abstract

Extended-gate field-effect transistor (EG-FET) chemo- and biosensors are emerging tools for a wide range of biomedical applications. Significant efforts have been made to make them ultrasensitive to biomolecules via the development of miniaturized sensing transistors, design and optimization of extended gate sensing layer, exploration of the multiplexing ability of EG-FET configuration, and advanced data analysis. Here, we specifically focus on several important aspects related to the construction and current applications of EG-FET sensors. Namely, we review the materials, fabrication, properties of the transducer, specificities of the conditioning electronics, and signal analysis. At the same time, we discuss the current drawbacks of these sensors preventing their straightforward commercialization, such as output signal variation and non-linearities of the response. We also review the recent key applications of EG-FET sensors in the areas of early medical diagnostics, ecology, food and chemical industries, and others. Finally, we briefly discuss the future perspectives in the development of this class of sensors.

Keywords: Extended gate; Field-effect transistors; Bioelectronics; Biosensors; Potentiometric measurement; Nanosensors

Permalink: https://www.hzdr.de/publications/Publ-37758


Possible Eliashberg-Type Superconductivity Enhancement Effects in a Two-Band Superconductor MgB2 Driven by Narrow-Band THz Pulses

Sobolev, S.; Lanz, A. P.; Dong, T.; Pokharel, A.; Kabanov, V.; Xu, T.-Q.; Wang, Y.; Gan, Z.-Z.; Shi, L.-Y.; Wang, N.-L.; Pashkin, O.; Uykur, E.; Winnerl, S.; Helm, M.; Demsar, J.

Abstract

We study THz-driven condensate dynamics in epitaxial thin films of MgB2, a prototype two-band superconductor (SC) with weak interband coupling. The temperature and excitation density dependent dynamics follow the behavior predicted by the phenomenological bottleneck model for the single-gap SC, implying adiabatic coupling between the two condensates on the ps timescale. The amplitude of the THz-driven suppression of condensate density reveals an unexpected decrease in pair-breaking efficiency with increasing temperature—unlike in the case of optical excitation. The reduced pair-breaking efficiency of narrow-band THz pulses, displaying minimum near ≈0.7  Tc, is attributed to THz-driven, long-lived, nonthermal quasiparticle distribution, resulting in Eliashberg-type enhancement of superconductivity, competing with pair breaking.

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Investigation of microalgae and bubble interaction in electroflotation via image processing

Marquardt, T.; Schwarzenberger, K.; Krujatz, F.; Eckert, K.

Abstract

Microalgae are becoming increasingly important for numerous applications such as food or pharmaceutical products. Flotation is an effective and comparatively inexpensive process for dewatering of the algal biomass after cultivation. In electroflotation, the hydrophobic algal cells attach to the surface of rising gas bubbles generated by water electrolysis and can be removed as a concentrated froth. For enhanced floatability, the size of microalgae can be increased by flocculation, e.g., with chitosan. Chitosan is a non-toxic, non-contaminating biopolymer that has proven to be a practical flocculant for microalgae. The effectiveness of the flotation process is influenced by numerous variables. At the same time, the mechanisms of the attachment of the algae to the bubbles are not fully understood. Hence, the aim of the presented work is to gain a deeper insight into the processes involved in the electroflotation of microalgae, like the algae-bubble-interaction, using optical measurement methods and machine learning (ML) based image processing.
A main focus is on the number and size of bubbles generated by electrolysis, as well as the size of Chlorella vulgaris agglomerates created by flocculation with chitosan. The properties of the bubbles were influenced by changing the electrolysis voltage and evaluated by image processing methods on microscopic images. Using laser diffraction spectroscopy, the influence of different chitosan dosages and flocculation times on the agglomerate size were analyzed. The size distribution is found to depend strongly on the varying biological properties of the microalgal suspension. Nevertheless, some general recommendations for an optimal chitosan concentration range could be deduced. In order to identify conditions promoting a successful attachment of algae to bubbles, an ML based method using series of microscopic images for visualization of the rising bubble and agglomerate paths during bubble-algal interaction was developed. The results show that a similar size of bubble and microalgal agglomerate is beneficial for enhanced bubble-algae interaction. For the analyzed voltage range, the mean bubble size was approximately 20 μm. The flocculation experiments showed that agglomerate sizes of 20 μm or higher are also achievable and thus, the microalgae flocs can be tuned to a well-floatable size range. Summing up, it was possible to derive first conclusions on how to promote effective electroflotation of microalgae. The developed visualization method contributes to a better understanding of flotation mechanisms and can be used as a basis for further research.

Keywords: Electroflotation; Microalgae; Image Processing; Flocculation; Rising Bubbles

  • 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-37756


Evaluating Iron Ore Characteristics through Machine Learning and 2D LiDAR Technology

Matos, S.; Pinto, T.; Domingues, J.; Ranieri, C.; Albuquerque, K.; Moreira, V.; Souza, E.; Ueyama, J.; Melo Euzebio, T. A.; Pessin, G.

Abstract

Conveyor belts are the most effective way to transport ore in a mining complex. The ore that comes from the mining areas can be heterogeneous in size and type. As the ore needs to pass through several processing steps, online information about the ore’s type and degree of fragmentation can help improve mineral processing for both safety and efficiency. Current instrumentation systems are expensive and require frequent calibration and maintenance. This paper presents a novel intelligent instrument for online recognition of type and degree of fragmentation. A 2D LiDAR sensor and machine learning techniques were used to estimate the characteristics of iron ore particles on conveyor belts. An experiment was conducted using several types of ore and granulometry. Five machine learning models were compared using statistical methods, including analysis of average accuracy and normality and hypotheses tests. Among them, the Random Forest models achieved the highest average accuracy, 93.81% for ore type and 85.52% for the degree of fragmentation. These models were improved by a voting mechanism, resulting in a reduction of classification errors of 93.3% for ore type and 99.2% for the degree of fragmentation. These findings demonstrate potential for improving mineral processing controls and elevating operational safety within the mining sector.

Keywords: Light Detection and Ranging; Conveyor Belt; Machine Learning; Mining Industry

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  • Secondary publication expected from 13.12.2024

Permalink: https://www.hzdr.de/publications/Publ-37754


Data publication: Unraveling dispersion and buoyancy dynamics around radial A + B → C reaction fronts: microgravity experiments and numerical simulations.

Stergiou, Y.; Escala Vodopivec, D.; Papp, P.; Horváth, D.; Hauser, M.; Brau, F.; de Wit, A.; Tóth, Á.; Eckert, K.; Schwarzenberger, K.

Abstract

This dataset includes the image data obtained from the Sounding Rocket experiment (TEXUS 57) and numerical simulation data.

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Permalink: https://www.hzdr.de/publications/Publ-37753


Understanding the effect of phosphorous on the ion-irradiation behaviour of RPV model steels using atom probe tomography and nanoindentation

Sharma, D.; Etienne, A.; Henry, R.; Kaden, C.; Picor, M.; Radiguet, B.

Abstract

Understanding the formation of the embrittling Mn-Ni-Si (MNS)-rich clusters in reactor pressure vessel (RPV) steels is of economic, environmental, and safety importance. Hence we investigated the influence of phosphorous (P) on the formation of MNS-rich clusters in RPV model steels employing atom probe tomography and nanoindentation tests. The atom probe tomography results show that the average number density and volume fraction of clusters decrease slightly with an increase in the bulk P content; however, higher bulk P led to a slight increase in the average diameter of the clusters. A higher amount of bulk P led to higher Cu in the clusters; suggesting synergy between Cu and P. An increase in the irradiation hardening values was observed due to higher bulk P content. This is attributed to the stabilisation of the self-interstitial atoms (SIA) clusters by P. A higher recovery for the sample containing higher bulk P indicated that the SIA clusters dissolved after post-irradiation annealing.

Keywords: Reactor pressure vessel steels; Irradiation effects; Atom probe tomography; Solute clustering; Hardening

Involved research facilities

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Permalink: https://www.hzdr.de/publications/Publ-37752


µCT data of two drill cores of fractured crystalline rock (Grimsel)

Kulenkampff, J.
DataCollector: Loesel, Dagmar; DataCollector: Schoessler, Claudia; Researcher: Jankovsky, Filip; Researcher: Zuna, Milan

Abstract

Two crystalline rock drill cores from the Grimsel site were scanned with a Nikon XT H 225 - scanner. The samples were prepared (formatted and cast in epoxy) by UJV Rez, Czech Republic. The CT-data were acquired and processed at HZDR-FWOT.

Sample 1 (GAM_UJV_1C_1) contains a complex system of interconnected fractures.
Sample 2 (GAM_UJV_1C_2) contains one single end-to-end fracture with larger aperture.

Size of both samples: Diameter 80 mm, length 165 mm.

Two tomograms were acquired for both samples:
1) Complete drill core as one scan, voxel size ca. 75 µm.
2) HR-tomogram merged from three sections with maximum resolution, voxel size ca. 40 µm.

The tomograms were stored as 3D-raw files. Data format, acquisition parameters, and processing workflow, are documented in the tomogram header files (nrrd-format (text):  see https://teem.sourceforge.net/nrrd/format.html).
This data format is importable into open-source visualization programs as 3D slicer (https://www.slicer.org) or Paraview (https://www.paraview.org). The data processing has been conducted with Avizo (https://www.thermofisher.com/de/de/home/electron-microscopy/products/software-em-3d-vis/avizo-software.html).

Files:
Sample 1
GAM_UJV_1C_1_complet-2_01_NLM: Graylevel image of complete sample, ring artifact removal, non-local-means filter
GAM_UJV_1C_1_complet-2_01_thresholded: Tentative label image of complete sample, threshold segmentation with manual edit
Merged-GAM_UJV_1C_1_HR.Frac_section: Graylevel image of merged fracture section, unfiltered
Merged-GAM_UJV_1C_1_HR.Frac_section.Threshold: Tentative label image of merged fracture section, adaptive threshold segmentation with manual edit
GAM_UJV_1C_1_complet_2.png: Figure of complete sample 
GAM_UJV_1C_1_HR_Frac_Y2.png: Figure of merged high-resolution tomogram

Sample 2
GAM_UJV_1C_2_complet_01.filtered: Graylevel image of complete sample, ring artifact removal, non-local-means filter
GAM_UJV_1C_2_complet_01.filtered.thresholded: Tentative label image of complete sample,  threshold segmentation with manual edit
Merged-GAM_UJV_1C_2_A_01.Frac_section.filtered: Graylevel image of merged fracture section, ring artifact removal, non-local-means filter
Merged-GAM_UJV_1C_2_A_01.Frac_section.filtered.segm: Tentative label image of merged fracture section, threshold segmentation with manual edit
GAM_UJV_1C_2_complett_2.png: Figure of complete sample
GAM_UJV_1C_2_HR_Frac_Y2.png: Figure of merged high-resolution tomogram

Original acquistion data are stored on the HZDR bulk data storage system and available for reprocessing on request.


Financial support was granted from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 847593 (EURAD, WP FUTURE, task 2.2).
 

Keywords: X-ray computed tomography; crystalline rock; granite; drill core; fracture

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Permalink: https://www.hzdr.de/publications/Publ-37750


A Monte Carlo photonic model to simulate the UV inactivation of airborne microorganisms

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

Abstract

The goal is to develop a model based on a photonic approach that allows us to track each of the flowing airborne microorganisms and predict, by using a kinetic Monte Carlo algorithm, whether it is active or not

  • Poster
    DLR GANDALF - Graduate School, 26.10.2023, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37748


Magneto-structural phase transitions for direct magnetic patterning

Bali, R.; Potzger, K.; Lindner, J.; Faßbender, J.

Abstract

The use of focused ion beams for sensitively controlling the intrinsic magnetic as well as transport properties at the nanoscale requires materials, wherein small atomic displacements results in large property changes. Typical examples are binary alloys consisting of a 3d metal such as Fe and elements such as Al [1], Rh [2] and most recently, V [3]. These materials act as non-ferromagnetic templates onto which atomic reordering within confined regions can be used to realize the direct writing of ferromagnetism. These alloys are deployed as prototypes for exploring nanoscale ion-induced property modulation.

The type of phase transition may vary, for instance, a transition in the chemical order of Fe60Al40 in contrast with the emergence of a crystalline lattice from a short-range ordered structure in Fe60V40. Due to chemical disordering, the localized ferromagnetic in the former alloy imparts spin scattering that can be observed in the anomalous Hall effect, whereas in the latter, the lattice reordering propagates in a layer like fashion providing homogenous ferromagnetic layers. The phase transition characteristics influence their potential applications, such as in ferromagnetic resonance and transport.

Observations of the evolving nearest-neighbour environment of atoms as a function of the atomic displacements helps unravel some of the microscopic processes leading to the large intrinsic property changes. This current research is being performed with the help of large-scale facilities, such as the Ion-Beam-Centre as well as the ELBE at HZDR.

References:

1. S. Sorokin et al., New J. Phys. (2023).
2. W. Griggs et al., APL Materials (2020) 8, 121103.
3. Md. S. Anwar et al., ACS Appl. Elec. Mater. (2022) 4, 8, 3860.

Keywords: ion irradiation; magnetism; magnetic patterning; structural phase transition

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    7th International Conference on Nanostructuring by Ion Beams (ICNIB 2023), 02.-04.11.2023, Dehradun, Indien

Permalink: https://www.hzdr.de/publications/Publ-37747


The sCO2 facility CARBOSOLA: Design, purpose and use for investigating geological energy storage cycles

Unger, S.; Fogel, S.; Schütz, P.; Ramirez, R. C.; Carro, A.; Carneiro, J.; Hampel, U.

Abstract

Renewable energy sources are the major pathway to reduce the carbon dioxide emission in the energy sector. However, the fluctuating electricity generation of solar or wind power plants encounter mismatches between energy generation and demand as well as possible grid instability issues. For that reason, large-scale thermal energy storage (TES) systems are one of the promising solutions to overcome these issues and to allow the operation of a sustainable and reliable energy system based on renewable energy sources. A TES system converts electrical energy into thermal energy during power surplus. The thermal energy is stored and reconverted to electricity during power demand by a supercritical carbon dioxide (sCO2) power cycle. TES has many advantages, such as simplicity, low cost and reliability over alternative storage technologies. The sCO2 power cycles on the other hand offer a variety of advantages, such as a high conversion efficiency, a compact turbomachinery and a temperature glide that fits well with sensible thermal energy storages.
To further develop and assess this approach, the EU-project CEEGS (CO2 based electrothermal energy and geological storage system) deals with the development of a high-efficient, cost-effective and scalable energy storage technology. Here, transcritical CO2 cycles are integrated with underground energy storage to achieve, simultaneously, long-term CO2 sequestration and, potentially, geothermal heat extraction. During periods of excess electricity generation, the charging cycle is in operation. Here, CO2 is received from a stationary source and an electric motor drives a compressor of a heat pump system to increase the CO2 pressure from approximately 35 bar to 200 bar, while increasing the temperature from approximately 15 °C to 150 °C. The sCO2 heats up a hot-water storage while reducing its temperature to approximately 45 °C before entering an expansion turbine During the expansion the temperature and pressure are reduced to 0°C and 35 bar, and is injected in supercritical state into a geological reservoir, at more than 1 km depth. Within the reservoir, the CO2 will equilibrate with the reservoir temperature, extracting some heat. Afterwards, the CO2 cools a cold-water storage, while increasing the temperature to approximately 15 °C. The resulting Carnot Battery closes the loop with CO2 underground injection. During periods of net electricity demand from the grid, the discharging cycle is in operation. Thereby, CO2 is back-produced from the geological reservoir through the same well and is pumped through a heat exchanger, while increasing the pressure of approximately 55 bar to 190 bar. In the heat exchanger the stored thermal energy from the hot-water storage is used to evaporate and heat the CO2 up to 140 °C. The high-pressure CO2 drives a turbine to generate electricity and the pressure reduces to 55 bar. The low-pressure CO2 flows through a condenser, to be cooled and liquified down to 10 °C by the cold-water storage, before entering the pump and is reinjected in liquid state in geological reservoir through a second injection well.
The development of a proof of concept, TRL4, based on the integration of models for system, components and energy system integration, a lab demonstration on a 200 kW power scale was set up at the Helmholtz-Centre Dresden-Rossendorf. Thus, the authors will present the design of the components and the facility as well as first results from operating the cycle. Special attention is paid to the challenges during design and commissioning as well as dynamic behavior of the facility.

Involved research facilities

  • TOPFLOW Facility
  • Lecture (Conference)
    The SCO2 Facility Carbosola: Design, Purpose and Use for Investigating Geological Energy Storage Cycles, 24.-28.06.2024, London, England

Permalink: https://www.hzdr.de/publications/Publ-37746


Systematic investigation of the Pygmy Dipole Resonance near the magic N = 82 shell closure

Kluwig, F.; Müscher, M.; Savran, D.; Schwengner, R.; Schüttler, T.; Zilges, A.

Abstract

The Pygmy Dipole Resonance is part of the electric dipole response of an atomic nucleus. There are still several open questions concerning, e.g., its structure. Systematic studies are crucial to improve the knowledge of this excitation mode. Such systematic studies have already been performed along the magic N = 82
isotonic chain using the Nuclear Resonance Fluorescence (NRF) technique, hinting to a trend of increasing strength with increasing N/Z ratio. Comparing these results to those from further NRF experiments on neighbouring non-magic isotopes and on 142Ce, a more fragmented strength distribution seems to occur.

Keywords: Nuclear structure; Dipole excitations; Nuclear resonance fluorescence; Photon scattering; Gamma-ray spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-37745


Dipole excitations in open shell nuclides near the neutron threshold energy from (g,g') experiments: The case of Ge isotopes

Benouaret, N.; Schwengner, R.; Massarczyk, R.; Shizuma, T.; Bemmerer, D.; Beyer, R.; Junghans, A.; Wagner, A.

Abstract

The dipole response of the open-shell nuclide 70Ge has been investigated in high-resolution (g,g') experiments using bremsstrahlung produced with electron beams of energies of 8.5 and 14.7 MeV at the linear accelerator ELBE. A resonance-like structure of levels mostly with spin J = 1 has been identified, distributed between 5 MeV up to neutron separation energy Sn as in the case of 76Ge and in contast to 74Ge where the level density is lower and ceases abruptly at about 1 MeV below Sn . The distibution strength was complemented by the unresolved levels using simulations of statistical gamma-ray cascades, corrected by estimations of branching transitions. The summed strength in 70 Ge, completed by the data from 74,76Ge do not fit with a linear trend as function
of the neutron excess. Such unexpected behaviour might be related to the nuclear deformation which seems to play the major role in the moderately deformed germanium isotopic chain.

Keywords: Nuclear structure; Dipole excitations; Photon scattering; Nuclear resonance fluorescence; Gamma-ray cascades

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Permalink: https://www.hzdr.de/publications/Publ-37744


Low-lying dipole response of 64Ni

Müscher, M.; Litvinova, E.; Schwengner, R.; Beck, T.; Bemmerer, D.; Fiedler, F.; Finch, S. W.; Hammer, S.; Isaak, J.; Janssens, R. V. F.; Junghans, A. R.; Kelly, N.; Kluwig, F.; Krishi, C.; Müller, S. E.; Römer, K.; Savran, D.; Scheck, M.; Schüttler, T.; Sinclair, J.; Szücs, T.; Tornow, W.; Wagner, A.; Wilhelmy, J.; Zilges, A.

Abstract

Two complementary real-photon scattering experiments were conducted on the proton-magic nucleus 64Ni to study the dipole response up to its neutron-separation threshold of Sn = 9.7 MeV. By combining both measurements, 87 E1 and 23 M1 transitions were identified above 4.3 MeV. The results of the observed M1 transitions were compared to shell-model calculations using two different model spaces. It was found that the inclusion of excitations across the Z = 28 shell gap in the calculations has a large impact. Furthermore, average cross sections for decays to the ground state (elastic transitions) as well as to lower-lying excited states (inelastic decays) were determined. The corresponding E1 channel was compared to calculations within the relativistic equation of
motion (REOM) framework. Whereas the calculation of highest possible complexity reproduces the fragmentation and overall behavior of the E1 average elastic cross section well, the predicted absolute cross sections are approximately twice as high as the experimental upper limits for the E1 cross section. The latter also include an estimation of the inelastic-decay channel.

Keywords: Nuclear structure; Dipole excitations; Photon scattering; Nuclear resonance fluorescence; Gamma-ray spectroscopy; Random-phase approximation; Shell model

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  • Secondary publication expected from 15.04.2025

Permalink: https://www.hzdr.de/publications/Publ-37741


Surface-symmetry-driven Dzyaloshinskii--Moriya interaction and canted ferrimagnetism in collinear magnetoelectric antiferromagnet Cr2O3

Pylypovskyi, O.; Weber, S. F.; Makushko, P.; Veremchuk, I.; Spaldin, N. A.; Makarov, D.

Abstract

Antiferromagnets are normally thought of as materials with compensated magnetic sublattices. This adds to their technological advantages but complicates readout of the antiferromagnetic state. We demonstrate theoretically the existence of a Dzyaloshinskii--Moriya interaction (DMI) which is determined by the magnetic symmetry classes of \ch{Cr2O3} surfaces with an in-plane magnetic easy axis. The DMI explains a previously predicted out-of-plane magnetization at the nominally compensated surfaces of chromia, leading to a surface-localized canted ferrimagnetism. This is in agreement with magnetotransport measurements and with density functional theory predictions which further allow us to quantify the strength of DMI. The temperature dependence of the transversal resistance for these planes shows distinct behavior in comparison with that of the \ch{Cr2O3} $c$~plane, which we attribute to the influence of DMI. Our work provides a framework to analyze surface-driven phenomena in antiferromagnets, and motivates the use of nominally compensated chromia surfaces for antiferomagnetic spintronics and magnonics.

Keywords: antiferromagnetism; DMI; surface; Cr2O3

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Permalink: https://www.hzdr.de/publications/Publ-37739


UQTestFuns: A Python3 Library of Uncertainty Quantification (UQ) Test Functions

Wicaksono, D. C.; Hecht, M.

Abstract

UQTestFuns is an open-source Python3 library of test functions commonly used within the applied uncertainty quantification (UQ) community. Specifically, the package provides:

  • an implementation with minimal dependencies (i.e., NumPy and SciPy) and a common interface of many test functions
  • single entry point collecting test functions and their probabilistic input specifications in a single Python package
  • an opportunity for an open-source contribution, supporting the implementation of new test functions or posting reference results.

In short, UQTestFuns is an homage to the Virtual Library of Simulation Experiments (VLSE).

v0.4.1 includes one additional test function used in the context of metamodeling. The package documentation has been updated following the review process during the submission to the Journal of Open Source Software (JOSS). This release is part of the acceptance of the package to JOSS.

This archive is part of the archival process to ROBIS.

Keywords: python; uncertainty-quantification; benchmark; sensitivity-analysis; metamodeling; reliability-analysis

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Permalink: https://www.hzdr.de/publications/Publ-37736


UQTestFuns: A Python3 library of uncertainty quantification (UQ) test functions

Wicaksono, D. C.; Hecht, M.

Abstract

Researchers are continuously developing novel methods and algorithms in the field of applied uncertainty quantification (UQ).
During the development phase of a novel method or algorithm, researchers and developers often rely on test functions taken from the literature for validation purposes.
Afterward, they employ these test functions as a fair means to compare the performance of the novel method against that of the state-of-the-art methods in terms of accuracy and efficiency measures.

UQTestFuns is an open-source Python3 library of test functions commonly used within the applied UQ community.
Specifically, the package provides:

  • an implementation with minimal dependencies (i.e., NumPy and SciPy) and a common interface of many test functions available in the UQ literature
  • a single entry point collecting test functions and their probabilistic input specifications in a single Python package
  • an opportunity for an open-source contribution, supporting the implementation of new test functions and posting reference results.

UQTestFuns aims to save the researchers' and developers' time from having to reimplement many of the commonly used test functions themselves.

Keywords: test functions; benchmark; uncertainty quantification; metamodeling; surrogate modeling; sensitivity analysis; reliability analysis; rare event estimation

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Permalink: https://www.hzdr.de/publications/Publ-37735


DAG Optimizations for Feynman Diagrams of High-Multiplicity Scattering Processes in Julia

Reinhard, A.; Ehrig, S.; Hernandez Acosta, U.; Widera, R.

Abstract

The description of scattering processes in high-energy physics is usually done with Feynman Diagrams. The number of Feynman Diagrams that can be generated for a given process explodes factorially with the number of particles. We discuss a possible approach enabling the calculation of higher-multiplicity scattering processes. We propose representing the calculation for a process as a directed acyclic graph (DAG) of small computation tasks. Using Julia, we can optimize this graph using subgraph replacement strategies together with an optimization algorithm. Finally, efficient code targeting arbitrary heterogeneous HPC systems can be generated from the optimized DAG.

Keywords: Julia; Scattering Processes; Compton; High-Energy Physics; DAG; Optimization; HPC

  • Open Access Logo Lecture (Conference)
    JuliaHEP 2023 Workshop, 06.-09.11.2023, Erlangen Centre for Astroparticle Physics, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-37734


Tunable room-temperature non-linear Hall effect from the surfaces of elementary bismuth thin films

Makarov, D.

Abstract

In this presentation I will describe our recent experiments with polycrystalline Bi thin films, where we observed non-linear Hall effect.

Keywords: Bi thin films; non-linear Hall effect; geometric non-linear Hall effect

Involved research facilities

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Annual meeting of the Lu Jiaxi international team, 25.-26.11.2023, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-37733


Magnetic composites: from printed, self-healable and eco-sustainable magnetoelectronics to smart magnetic soft robots

Makarov, D.

Abstract

In this lecture for magnetism students, I will cover the following topics: magnetic composites (i.e., mixtures of polymers and magnetic particles); flexible magnetoelectronics; printed magnetoelectronics; eco-sustainable magnetics; magnetic actuation (including locomotion). The aim is to provide an overview of new application scenarios of magnetic materials prepared in the form of composites for hingeless ultrafast actuators and printed magnetic field sensors. The lecture should stimulate activities on the realization of eco-sustainable magnetics including biodegradable and biocompatible magnetic field sensors.

Keywords: flexible magnetic field sensors; shapeable magnetoelectronics; printed magnetoelectronics; magnetic composites

Involved research facilities

Related publications

  • Invited lecture (Conferences)
    PETASPIN 2023 School on “Spintronics: fundamentals and applications” – II edition, 12.-15.12.2023, Messina, Italy

Permalink: https://www.hzdr.de/publications/Publ-37732


Floquet analysis of a superradiant many-qutrit refrigerator

Kolisnyk, D.; Queißer, F.; Schaller, G.; Schützhold, R.

Abstract

We investigate superradiant enhancements in the refrigeration performance in a set of N three-level systems that are collectively coupled to a hot and a cold thermal reservoir and are additionally subject to collective periodic (circular) driving. Assuming the system-reservoir coupling to be weak, we explore the regime of stronger periodic driving strengths by comparing collective weak-driving, Floquet-Lindblad, and Floquet-Redfield master equations. We identify regimes where the power injected by the periodic driving is used to pump heat from the cold to the hot reservoir and derive analytic sufficient conditions for them based on a cycle analysis of the Floquet-Lindblad master equation. In those regimes, we also argue for which parameters collective enhancements like a quadratic scaling of the cooling current with N can be expected and support our arguments by numerical simulations.

Keywords: Floquet theory; periodic driving; refrigeration; superradiance; cooling condition; collective effects

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Permalink: https://www.hzdr.de/publications/Publ-37731


Sequential Kibble-Zurek dynamics in the anisotropic Ising model of the Si(001) surface

Schaller, G.; Queißer, F.; Parya Katoorani, S.; Brand, C.; Kohlfürst, C.; Freeman, M. R.; Hucht, A.; Kratzer, P.; Sothmann, B.; Horn-Von Hoegen, M.; Schützhold, R.

Abstract

As a simplified description of the non-equilibrium dynamics of buckled dimers on the Si(001) surface, we consider the anisotropic 2D Ising model and study the freezing of spatial correlations during a cooling quench across the critical point. The dependence of the frozen correlation lengths ξ‖ and ξ⊥ on the cooling rate obtained numerically matches the Kibble-Zurek scaling quite well. However, we also find that the ratio ξ‖/ξ⊥ of their frozen values deviates significantly from the ratio in equilibrium. Supported by analytical arguments, we explain this difference by the fact that the deviation from equilibrium in the weakly coupled direction occurs earlier than in the strongly coupled direction.

Keywords: Kibble-Zurek mechanism; defect formation; temperature quench; silicon surface; Ising model; anisotropy effects

Permalink: https://www.hzdr.de/publications/Publ-37730


How small can Maxwell's demon be? -- Lessons from autonomous electronic feedback models

Schaller, G.

Abstract

External piecewise-constant feedback control can modify energetic and entropic balances, allowing in extreme scenarios for Maxwell demon operational modes. Without specifying the actual implementation of external feedback loops, one can only partially quantify the additional contributions to entropy production. This is different in autonomously operating systems with internal feedback. Traditional (bipartite) autonomous systems can be divided into controller and a controlled subsystem, but also non-bipartite systems can accomplish the same task. We consider examples of autonomous three-terminal models that transfer heat mainly from a cold to a hot reservoir by dumping a small fraction of it to an ultra-cold (demon) reservoir, such that their coarse-grained dynamics resembles an external feedback loop. We find that the minimal three-level implementation is most efficient in utilizing heat dissipation to change the entropy balance of the effective controlled system.

Keywords: Maxwell demon; autonomous operation; refrigerator; coarse-graining

Permalink: https://www.hzdr.de/publications/Publ-37729


Supporting microscope images: The Impact of Al2O3 Particles from Grit-Blasted Ti6Al7Nb (Alloy) Implant Surfaces on Biocompatibility, Aseptic Loosening, and Infection

Kocjančič, B.; Avsec, K.; Šetina Batič, B.; Feizpour, D.; Godec, M.; Kralj Iglič, V.; Podlipec, R.; Cor, A.; Debeljak, M.; Grant T., J.; Jenko, M.; Dolinar, D.

Abstract

Supporting confocal fluorescence microscope images of live cells grown on different implant surfaces

Keywords: Ti6Al7Nb implant alloy cementless hip endoprostheses; roughness; Al2O3 grit blasting; surface and subsurface implant contamination; cytotoxicity; aseptic loosening; infection; osteointegration

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Permalink: https://www.hzdr.de/publications/Publ-37728


The Impact of Al2O3 Particles from Grit-Blasted Ti6Al7Nb (Alloy) Implant Surfaces on Biocompatibility, Aseptic Loosening, and Infection

Kocjančič, B.; Avsec, K.; Šetina Batič, B.; Feizpour, D.; Godec, M.; Kralj Iglič, V.; Podlipec, R.; Cor, A.; Debeljak, M.; Grant T., J.; Jenko, M.; Dolinar, D.

Abstract

For the improvement of surface roughness, titanium joint arthroplasty (TJA) components are grit-blasted with Al2O3 (corundum) particles during manufacturing. There is an acute concern, particularly with uncemented implants, about polymeric, metallic, and corundum debris generation and accumulation in TJA, and its association with osteolysis and implant loosening. The surface morphology, chemistry, phase analysis, and surface chemistry of retrieved and new Al2O3 grit-blasted titanium alloy were determined with scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and confocal laser fluorescence microscopy, respectively. Peri-prosthetic soft tissue was studied with histopathology. Blasted retrieved and new stems were exposed to human mesenchymal stromal stem cells (BMSCs) for 7 days to test biocompatibility and cytotoxicity. We found metallic particles in the peri-prosthetic soft tissue. Ti6Al7Nb with the residual Al2O3 particles exhibited a low cytotoxic effect while polished titanium and ceramic disks exhibited no cytotoxic effect. None of the tested materials caused cell death or even a zone of inhibition. Our results indicate a possible biological effect of the blasting debris; however, we found no significant toxicity with these materials. Further studies on the optimal size and properties of the blasting particles are indicated for minimizing their adverse biological effects.

Keywords: Ti6Al7Nb implant alloy cementless hip endoprostheses; roughness; Al2O3 grit blasting; surface and subsurface implant contamination; cytotoxicity; aseptic loosening; infection; osteointegration

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Permalink: https://www.hzdr.de/publications/Publ-37725


Challenges of the copper-mediated radiofluorination

Kaur, S.; Wenzel, B.; Deuther-Conrad, W.; Dukic-Stefanovic, S.; Toussaint, M.; Kopka, K.; Moldovan, R.-P.

Abstract

Ziel: Copper-mediated radiofluorination (CMRF) was a breakthrough of the last decade in the development of non-activated 18F-aryl-bearing radiopharmaceuticals.1 Despite extensive studies and improvements of the radiolabelling conditions, the formation of H-side product 3 and OH-side product 4 still possess a challenge in these Suzuki/Stille type reactions. In our work, we faced similar problems and additionally, the continuous hydrolysis of the boronic ester precursor 1 during the semi-preparative HPLC purification resulted in another impurity 5. In this study, we tried to address and overcome these challenges.

Methoden: The CMRF of 1 bearing a non-activating aromatic substituent at para position was optimized by varying the following parameters: solvent (DMA and DMI), reaction time (5 - 20 min), temperature (110 - 130 °C) and molar ratio of precursor 1 to Cu-complex (1:3, 1:4. 2:3, 1:8). Compounds 3 and 4 were synthesized as references for identification of the side-products in the final radiotracer formulation. Various stationary phases (pentafluorophenyl, cyano, phenyl, C18) and mobile phases were tested to separate unwanted side products 3 and 4 by HPLC. Solid phase extraction (SPE) was performed with the C18 plus cartridge before the semi-preparative HPLC purification of [18F]2.

Ergebnisse: [18F]2 was achieved with a high radiochemical conversion of 85 % using 2 mg of 1, 10 mg of [Cu(OTf)2(py)4] (molar ratio of 1:4) in n-BuOH/DMI (1:2, v/v) at 110 °C for 5 min. SPE under acidic conditions (pH 2) resulted in around 90 % recovery of [18F]2 compared to only 20 % under neutral conditions. Due to hydrolysis of residual precursor 1 with TFA prior to semi-preparative HPLC purification, the content of 5 in the formulated final product could be reduced from 25 % (without TFA hydrolysis) to 0.5-1 %. The side-products 3 and 4 were successfully separated using a ReproSil C18AQ column (250 x 20 mm) and 48 % THF/ACN (1:1, v/v) buffered with 20 mM ammonium acetate. Compound [18F]2 was isolated with a radiochemical purity of >95 % and molar activities in the range of 60 GBq/µmol were achieved.

Schlussfolgerungen: Despite a number of hurdles, the CMRF reactions are currently being widely employed for the production of radiopharmaceuticals embodying non-activated 18F-aryl scaffolds. To overcome the occasional purification difficulties of the resulting radioligands, further improvements and mechanistic studies need to be undertaken.

Referenzen:

[1] Preshlock, S., et al. Chemical Reviews 2016, 116(2), 719-766.

  • Lecture (Conference)
    29. Jahrestagung der Arbeitsgemeinschaft Radiochemie / Radiopharmazie, 28.-30.09.2023, Bad Salzuflen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37724


New high-resolution microscopy approaches for understanding biocompatibility of hip implants

Podlipec, R.; Štrancar, J.; Barlič, A.; Dolinar, D.; Jenko, M.

Abstract

Ensuring the biocompatibility of hip implants is essential for the safety, effectiveness, and longevity of these medical devices [1]. The material-induced tissue inflammation and immune reaction must be negligible while promoting tissue integration. However, the major unresolved issue in joint replacement is the occurrence of adverse biological reactions to wear debris, leading to severe inflammation [2] which has been observed at the subcellular level [3]. To gain a deeper understanding of the biocompatibility related to material chemistry and surface topography and to better predict the material functionality and clinical use, it is crucial to investigate the properties of cell adhesion, proliferation, and migration on the implant's surface. In this study, we demonstrate how Al2O3-coated titanium alloys with varying surface topographies and roughness affect the growth and morphology of human bone marrow mesenchymal stromal cells (BM-MSCs). This subcellular-level investigation was conducted on live cells using novel high-resolution 3D confocal fluorescence and backscatter microscopy.

1. Hu CY, Yoon TR. Biomaterials Research, 2018, 22, 33.
2. Cobelli N, Scharf B, Crisi GM, Hardin J, Santambrogio L. Nat Rev Rheumatol. 2011, 7, 600–608.
3. Podlipec R, Punzón-Quijorna E, Pirker L, Kelemen M, Vavpetič P, Kavalar R, Hlawacek G, Štrancar J, Pelicon P, Fokter SK, Materials, 2021, 14, 3048.

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  • Invited lecture (Conferences)
    5th International Symposium on Biomaterials (5ISB), 13.10.2023, Portorož, Slovenia

Permalink: https://www.hzdr.de/publications/Publ-37723


Supporting Data: Particulate matter triggers the formation of extracellular amyloid β and tau -containing plaques and neurite shortening in vitro

Sebastijanovič, A.; Podlipec, R.; Gianoncelli, A.; Hlawacek, G.; Bonanni, V.; Camassa, L. M. A.; Malmborg, V.; Kralj, S.; Pagels, J.; Vogel, U.; Zienolddiny-Narui, S.; Urbančič, I.; Koklič, T.; Štrancar, J.

Abstract

Supplementary material including sample preparation, microscope setup, correlative microscopy analysis and supporting images.

Keywords: neurite shortening; neuronal degeneration; amyloid beta (Aβ); microtubule-associated protein (tau); air pollution; particulate matter; TiO2 nanotubes; diesel exhaust; CeO2 nanoparticles; iron oxide

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Permalink: https://www.hzdr.de/publications/Publ-37722


Understanding electronic correlations in warm dense quantum plasmas

Dornheim, T.

Abstract

Warm dense matter (WDM)---an extreme state that is characterized by extreme densities and
temperatures---has emerged as one of the most active frontiers in plasma physics and material
science. In nature, WDM occurs in astrophysical objects such as giant planet interiors and brown
dwarfs. In addition, WDM is highly important for cutting-edge technological applications such as
inertial confinement fusion and the discovery of novel materials. In the laboratory, WDM is studied
experimentally in large facilities around the globe, and new techniques have facilitated
unprecedented insights. Yet, the interpretation of these experiments requires a reliable diagnostics
based on accurate theoretical modeling, which is a notoriously difficult task [1].
In this work, I will give an overview of how we can use exact ab-initio path integral Monte Carlo
(PIMC) simulations [2] together with thermal density functional theory (DFT) calculations to get
new insights into the behavior of WDM. Moreover, I will show how switching to the imaginary-
time representation allows us to significantly improve the interpretation of X-ray Thomson
scattering (XRTS) experiments, which are a key diagnostic for WDM [3]. Specifically, I will
present a model-free temperature diagnostic [4] based on the well-known principle of detailed
balance, but available for all wave numbers, and a new idea to directly extract the electron—
electron static structure factor from an XRTS measurement [5]. As an outlook, I will show how new
PIMC capabilities will allow to give us novel insights into electronic correlations in warm dense
quantum plasmas, leading to unprecedented agreement between experiments [6] and theory.
[1] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[2] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[3] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)
[4] T. Dornheim et al., Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al., arXiv:2305.15305 (submitted)
[6] T. Döppner et al., Nature 618, 270-275 (2023)

  • Lecture (others)
    CFEL Theorie Seminar, 25.10.2023, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37721


Design of a primary heat exchanger in a sCO2 power cycle for energy storage systems

Guille-Bourdas, A. F.; Unger, S.; Hampel, U.

Abstract

Renewable energy sources are the key for long-term decarbonisation of the energy system. However, the intermittent nature of renewables, such as solar energy or wind energy, does not always meet the energy demand in the electrical grid. Considering the fact that both electricity production and consumption vary independently, balancing the grid is a major challenge for the development of an energy system based on renewable energies. Within this framework, Thermal Energy Storage systems (TES) coupled with a power cycle have gained popularity since they can store energy from renewable sources during the periods of high production and release it when necessary.
To convert thermal energy into electricity, a power cycle is required. Given the relative high temperature range (600 - 1000 °C), supercritical CO2 (sCO2) is the most promising material as working fluid for the power cycle, from efficiency and safety considerations. Thus, the Primary Heat Exchanger (PHX) must be carefully designed as the fluid pressures in the TES and the power cycle are namely 1 - 10 bar and 200 - 250 bar.
The present work consists of two parts, one elaborates a 1D model in order to design the PCHE regarding a certain set of boundary conditions. The model requires heat transfer and pressure loss correlations from the literature to estimate the Nusselt number and friction factor, which strongly depends on the geometry. It was found that the zigzag channel design intensifies both heat transfer and pressure drop phenomena, which is not suitable for the hot fluid from an economic prospective. Furthermore, 3D simulations by Computational Fluid Dynamics (CFD) were done and compared to the results from the 1D model to ensure the validity of the correlations. It was also found that the results match those from the literature, thus validating the 1D model.

Keywords: Heat exchanger; Printed circuit heat exchanger; Supercritical CO2; Computational fluid dynamics; 1D model; Brayton power cycle

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  • TOPFLOW Facility
  • Poster
    Doctoral seminar, 17.-19.10.2023, Schöneck, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37720


Data from a case study of the application of Gas Flow Modulation technique for measuring the axial gas dispersion coefficient in bubble columns

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

Abstract

The data were used to exemplify the application of Gas Flow Modulation (GFM) for measuring the axial gas dispersion coefficient in bubble column reactors operated at ambient conditions. For more details, please refer to the atteched PDF.

Keywords: Gas flow modulation; Bubble column; Axial gas dispersion coefficient; case-study

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Permalink: https://www.hzdr.de/publications/Publ-37719


Grazing incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf Beamline

Svitlyk, V.; Braga Ferreira Dos Santos, L.; Niessen, J.; Gilson, S.; Marquardt, J.; Findeisen, S.; Richter, S.; Akhmadaliev, S.; Huittinen, N. M.; Hennig, C.

Abstract

Ce-doped yttria-stabilized zirconia (YSZ) and pure YSZ phases were subjected to irradiation with 14 MeV Au ions. The irradiation studies were performed to simulate long-term structural and microstructural damage due to self-irradiation in YSZ phases hosting alpha-active radioactive species. It was found that both the Ce-doped YSZ and YSZ phases were rather tolerant to irradiation at high ion fluences and the bulk crystallinity was well preserved. Nevertheless, local microstrain increased in all the studied compounds after the irradiation, with the Ce-doped phases being less affected than pure YSZ. Doping with cerium ions increased the microstructural stability of YSZ phases through a possible reduction in the mobility of oxygen atoms, which limits the formation of structural defects. Doping of YSZ with tetravalent actinide elements is expected to have a similar effect. Thus, YSZ phases are promising for the safe long-term storage of radioactive elements. Using synchrotron radiation diffraction, measurements of the thin irradiated layers of the Ce-YSZ and YSZ samples were performed in grazing incidence (GI) mode. A corresponding module for measurements in GI mode was developed at ROBL and relevant technical details of sample alignment and data collection are also presented.

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Permalink: https://www.hzdr.de/publications/Publ-37717


Unraveling dispersion and buoyancy dynamics around radial A + B → C reaction fronts: microgravity experiments and numerical simulations.

Stergiou, Y.; Escala Vodopivec, D.; Papp, P.; Horváth, D.; Hauser, M.; Brau, F.; de Wit, A.; Tóth, Á.; Eckert, K.; Schwarzenberger, K.

Abstract

Radial Reaction–Diffusion–Advection (RDA) fronts for A + B → C reactions find wide applications in many natural and technological processes. In liquid solutions, their dynamics can be perturbed by buoyancy-driven convection due to concentration gradients across the front. In this context, we conducted microgravity experiments aboard a sounding rocket, in order to disentangle dispersion and buoyancy effects in such fronts. We studied experimentally the dynamics due to the radial injection of A in B at a constant flow rate, in absence of gravity. We compared the obtained results with numerical simulations using either radial one– (1D) or two–dimensional (2D) models. We showed that gravitational acceleration significantly distorts the RDA dynamics on ground, even if the vertical dimension of the reactor and density gradients are small. We further quantified the importance of such buoyant phenomena. Finally, we showed that 1D numerical models with radial symmetry fail to predict the dynamics of RDA fronts in thicker geometries, while 2D radial models are necessary to accurately describe RDA dynamics where Taylor–Aris dispersion is significant.

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Permalink: https://www.hzdr.de/publications/Publ-37716


High-temperature solid thermal energy storage for Power-Heat-Power systems

Bangalore Mohankumar, M.

Abstract

Presentation for PhD seminar

  • Contribution to proceedings
    Annunal PhD. Seminar, 17.-19.10.2023, Schöneck/Vogtland, Germany
    High-temperature solid thermal energy storage for Power-Heat-Power systems

Permalink: https://www.hzdr.de/publications/Publ-37714


Thermal performance assessment of high-temperature sensible solid thermal energy storage (SSTES): Various designs, storage materials and heat transfer fluids

Bangalore Mohankumar, M.; Unger, S.; Hampel, U.; Chacartegui Ramirez, R.; Carro Paulete, A.

Abstract

Energy storage (ES) is a pivotal and cost-effective part of future energy systems. Its integration into an energy system with wind and solar power plants provides a solution to the problem of power balancing resulting from fluctuating power output. One promising approach is the use of Thermal Energy Storage (TES) systems, particularly Power-Heat-Power (PHP) systems, which offer low environmental and social impacts. Solid sensible TES (SSTES) stores excess electricity in the form of sensible heat, the solid medium being heated either directly or indirectly using heat transfer fluids (HTF). The benefit of SSTES systems is their simplicity due to no phase change or chemical reactions involved, making them cost-effective and easy to maintain. However, applications of SSTES at high temperatures remain relatively unexplored and have limited deployment globally. Nonetheless, the foresaid advantages make it suitable for high-temperature applications, provided the solid material selected exhibits higher temperature stability.
In the proposed work a SSTES is indirectly charged using an electrically heated working fluid. The stored thermal energy is discharged via a supercritical carbon dioxide (sCO2) power cycle, creating a power-to-heat-power system. Here CO2 is proposed for the downstream reconversion cycle due to its low viscosity, high density and excellent heat capacity at its supercritical phase (above 31 °C and 74 bar). This power cycle comes with highly compact components, in particular the turbomachinery, which, in turn, reduces investment costs and minimizes thermal losses. Furthermore, sCO2 power cycles can be operated at high system temperatures up to 600 °C and above to generate electricity at high thermal efficiency.
Thus, a SSTES coupled with a sCO2 power cycle is currently researched at the HZDR. The investigated candidates for the storage medium are most commonly used solid materials, like high-temperature ceramic, high-temperature concrete, and firebricks as well as waste material like AlferrockTM and vitrified fly ash. Another aspect is the heat transfer fluids (HTF), which are air, He, CO2 and N2 in the present study. The thermal performance of a SSTES was investigated for 10 MWth power output over 5 hours, resulting in a storage capacity of 50 MWhth at a high temperature of 800 °C. A one-dimensional model was developed in MATLAB for this investigation and validated with data available in the literature. The influence of geometry, flow rate, solid material configuration in the storage tank and heat transfer surface area on the heat transfer characteristics and efficiency of TES system cannot be ignored. Therefore, different STES designs were also included for an assessment in this research work. Based on the results, the performance parameters like temperature of the storage material during the charging/discharging cycle as well as overall thermal efficiency are presented.
Overall, a comprehensive thermal performance assessment based on various factors that influence the STES system was done. The comparative analysis of various materials, heat transfer fluids and geometries allows us to determine the impact on the TES design. These broad findings lead to further investigations applying 3D numerical methods.

Keywords: Power-Heat-Power (PHP) systems; Supercritical CO2; Thermal energy storage; sensible solid TES; 1D model

Involved research facilities

  • TOPFLOW Facility
  • Contribution to proceedings
    ASME Turbo Expo 2024, 24.-28.06.2024, London, United Kingdom
    Proceedings of ASME Turbo Expo 2024
  • Lecture (Conference)
    Thermal performance assessment of high-temperature sensible solid thermal energy storage (SSTES): various designs, storage materials and heat transfer fluids, 24.-28.06.2024, London, England

Permalink: https://www.hzdr.de/publications/Publ-37713


Synthese und Charakterisierung von Bispidinen als bifunktionelle Liganden für die spezifische Bindung von PSMA und der Radiomarkierung mit Quecksilber-197(m)

Ullrich, N.

Abstract

Für die Untersuchung des Radionuklidpaares 197(m)Hg in der Theranostik, ist die Entwicklung eines Radiopharmakons erforderlich, bei dem unter In-vivo-Bedingungen keine Dissoziation und somit keine Freisetzung von zytotoxischem Quecksilber stattfindet. Das potenzielle metallorganische Radiopharmakon soll dabei auf einem in vivo stabilen Bispidin-Grundgerüst basieren. Dieses bietet die Möglichkeit das Radionuklid durch einfache Substitution über eine benzylische Struktureinheit kovalent an das Grundgerüst zu binden. Durch die dreidimensionale Struktur erfährt das Radionuklid dabei eine sterische Abschirmung. Zusätzlich fungiert das Grundgerüst als bifunktioneller Ligand, der durch eine weitere Substitution in der C9-Position das PSMA-Bindungsmotiv binden kann.
Auf Grundlage der bisherigen Forschungsergebnisse soll das potenzielle Radiopharmakon auf einem Bispidin-Grundgerüst basieren. Hierfür müssen die pharmakologischen Eigenschaften wie die Lipophilie angepasst werden, was durch die Verwendung von Methylgruppen in den Positionen C1 und C5 erreicht werden soll. Weiterhin soll durch die gezielte Funktionalisierung der C9-Position des Bispidin-Grundgerüsts eine Bindung des PSMA-Bindungsmotivs an das Grundgerüst ermöglicht werden, wofür verschiedene Ansätze untersucht werden sollen. Das vorrangige Ziel besteht dabei in der Einführung und Funktionalisierung eines primären Amins und deren Substitution, um die Bindung des Vektormoleküls zu erreichen.
Nach Entfernung des C1-Bausteines aus dem Aminal soll durch nukleophile Substitution jeweils eine Trialkylstannyl-funktionalisierte Struktureinheit an den sekundären Aminen gebunden werden, um eine Fluchtgruppe für die folgende, kovalente Bindung des Quecksilbers zu ermöglichen. Hierfür soll einem vorangehenden Schritt das Trialkylstannyl-funktionalisierte Molekül synthetisiert werden. Basierend auf der Arbeit von I. M. GIPLIN und Kollegen soll statt der Trimethylstannyl- eine Triethylstannyl-Verbindung genutzt werden, um die beobachtete Instabilität zu umgehen.
Nachfolgend soll das PSMA-Bindungsmotiv über eine Peptidbindung an die funktionalisierte C9-Position des Grundgerüsts gebunden werden, wodurch sich das Radiopharmakon später selektiv an maligne Zellen anlagern kann. Darüber hinaus soll die anschließende Radiomarkierung mit dem Nuklidpaar 197(m)Hg ermöglicht werden.

Keywords: Quecksilber-197(m); Bispidine; theranostisches Konzept

  • Master thesis
    TU Dresden - Fakultät Chemie und Lebensmittelchemie, 2023
    Mentor: PD Dr. Constantin Mamat
    114 Seiten

Permalink: https://www.hzdr.de/publications/Publ-37712


Exchange gap in GdPtBi probed by magneto-optics

Polatkan, S.; Uykur, E.; Mohelsky, I.; Wyzula, J.; Orlita, M.; Shekhar, C.; Felser, C.; Dressel, M.; Pronin, A. V.

Abstract

We measured the magneto-reflectivity spectra (4 – 90 meV, 0 – 16 T) of the triple-point semimetal GdPtBi and found them to demonstrate two unusual broad features emerging in field. The electronic bands of GdPtBi are expected to experience large exchange-mediated shifts, which lends itself to a description via effective Zeeman splittings with a large g-factor. Based on this approach, along with an ab-initio band structure analysis, we propose a model Hamiltonian that describes our observations well and allows us to estimate the effective g-factor, g∗ = 95. We conclude that we directly observe the exchange-induced Γ8 band inversion in GdPtBi by the means of infrared spectroscopy.

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Permalink: https://www.hzdr.de/publications/Publ-37711


Viscosity influence on human hepatoma tumor spheroids formation in core-shell alginate-carboxymethylcellulose microcapsules

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

Abstract

Biomolecular and physical stimuli, such as stiffness and stress, of the extracellular environment, regulate collective cell dynamics and tissue patterning. The viscosity in the tumor microenvironment can increase due to the accumulation of macromolecules over time. Islands of rigid tumors are surrounded by soft cells that are more deformable than their healthy counterparts. Nonetheless, how the viscosities of the tumor microenvironment regulate collective cell spatial and temporal organization is not fully understood. Here, we used the human hepatoma (HepG2) cancer cells, the basic structural component of the liver, as an example to study the influence of viscosity (range from 0.8 cP to 15 cP) on cancer cell collective behavior in 3D microcapsules reactors. Alginate/Alginate-carboxymethylcellulose microcapsules (AL/AL-CMC MCs) with HepG2 cells were generated using a home-made high-throughput droplet-based microfluidic platform. Cell distribution, cell proliferation, spheroids growth, morphology change, and cytoskeleton difference were observed and quantified, showing a significant effect on viscosity change. Importantly, F-actin and keratin 8 intensity and distribution results can be a cue that viscosity increases enhancing the ability of cancer cells to squeeze through dense tissue. The results thus demonstrate that extracellular viscosity as an important physical cue regulates tumor development relevance to cancer biology.

Keywords: physical stimuli; viscosity; HepG2; gel matrix

  • Lecture (Conference)
    International Conference on Nanotechnologies & Bionanoscience, 14.09.2023, Heraklion, Greece

Permalink: https://www.hzdr.de/publications/Publ-37708


Online-adaptive proton therapy: Feasibility of prompt-gamma verification for CBCT-based adapted plan

Bertschi, S.; Stützer, K.; Berthold, J.; Pietsch, J.; Elstrøm, U.; Vestergaard, A.; Janssens, G.; Korreman, S.; Richter, C.

Abstract

Purpose/Objective
Cone-beam CT (CBCT) is a promising solution for 3D in situ imaging in an online-adaptive proton therapy workflow. However, CBCT scans have an increased uncertainty in determined CT numbers, making online treatment verification essential. Our aim is to verify adapted treatment plans based on CBCTs with prompt-gamma imaging (PGI) to detect unexpected treatment deviations as well as to offer independent quality assurance of adaptation and treatment. A reliable reference simulation is a prerequisite for PGI-based online treatment verification where measured PGI data are compared with reference simulations based on the CBCT (Figure 1a). In this study, we investigated whether CBCTs are suitable for PGI reference simulations.

Material/Methods
For a homogeneous PMMA cylinder (∅: 18 cm) and an anthropomorphic head phantom (CIRS 731 HN), two CT scans were acquired – a conventional fan-beam CT for reference and a CBCT. For each phantom, a corrected CBCT (cCBCT) and a virtual CT (vCT) were generated using RayStation (v13.0, RaySearch Laboratories AB), yielding 3 CBCT datasets and one fan-beam CT dataset. For both phantoms, a treatment plan with one field on a cuboid target structure (30.6 cm3) was generated (Figure 1b). PGI simulations were performed on all 3 CBCT datasets as well as on the fan-beam CT, serving as reference. Spot-wise range shifts between PGI simulations on the fan-beam CT and each CBCT dataset were extracted to examine the change in reference range due to the CT number differences. According to [1], the potential deviation in CT number (CBCT vs fan-beam CT) influences both, the depth dose distribution depending on the SPR value and the material assignment as well as the spectral prompt gamma (PG) emission depending on the material assignment. Both quantities (depth dose distribution and spectral PG emission) impact the simulated PGI profile. To distinguish both effects, we additionally calculated the depth dose distribution independently by determining spot-wise integrated depth-dose (IDD) profiles. This allows for a direct spot-wise comparison between PGI range shifts and IDD range shifts.

Results
For the homogeneous PMMA phantom, the spot-wise PGI range shifts comparing the fan-beam CT (reference) to the CBCT, corrected CBCT and virtual CT were close to zero with mean range shifts of 0.37, 0.25, -0.08 mm and standard deviations (2σ) of 0.29, 0.18 and 0.21 mm, respectively. Compared to the reference fan-beam CT data, the observed deviations in PGI simulations on the CBCT data followed very closely the deviations of the corresponding IDD calculations (correlation "ρ=0.90" ).
For the anthropomorphic head phantom, the spot-wise PGI range shifts were larger with mean range shifts of -0.89, -0.53 and -0.24 mm and standard deviations (2σ) of 1.01, 0.54 and 0.20 mm for the CBCT, cCBCT and vCT, respectively. For the post-processed datasets with improved image quality (cCBCT, vCT), the PGI simulation was closer to the simulation on the fan-beam CT. The observed spot-wise deviations of PGI simulations on CBCT data compared to simulations on the fan-beam CT followed again closely the deviations of the corresponding IDD calculations (correlation "ρ=0.74" ) (Figure 2).
Hence, the changes in material composition (additionally influencing spectral PG emission) had a marginal effect on the PGI-retrieved ranges. For the corrected CBCT and the virtual CT, 98.5% of the PGI-retrieved ranges differed less than 1 mm from the IDD retrieved ranges.

Conclusion
In this phantom study, we have shown that CBCT data are suitable for PGI reference simulation where CBCT-based range prediction was correct. PGI range shifts and IDD range shifts showed a good correlation, revealing negligible additional impact of uncertainties in material assignment on PGI simulations.
As correct range prediction is a crucial requirement for plan adaptation, PGI can serve as an online treatment verification tool which is highly desirable in an online-adaptive proton therapy workflow. Furthermore, the results indicate that PGI could also be used to detect range prediction errors resulting from uncertainties in CT numbers of CBCT data. We are currently extending the study to patient data.

[1] E. Sterpin et al., “Physics in Medicine & Biology Analytical computation of prompt gamma ray emission and detection for proton range verification,” Phys. Med. Biol, vol. 60, pp. 4915–4946, 2015, doi: 10.1088/0031-9155/60/12/4915.

Keywords: Prompt-gamma imaging; Online-adaptive PT; CBCT

Involved research facilities

  • OncoRay
  • Open Access Logo Lecture (Conference)
    ESTRO 2024, 03.-07.05.2024, Glasgow, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-37707


Coherent phonon and unconventional carriers in the magnetic kagome metal Fe3Sn2

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

Abstract

Temperature- and fluence-dependent carrier dynamics of the magnetic Kagome metal Fe₃Sn₂ were
studied using the ultrafast optical pump-probe technique. Two carrier relaxation processes (τ₁ and
τ₂) and a laser induced coherent optical phonon were observed. By using the two-temperature model
for metals, we ascribe the shorter relaxation τ₁ (∼1 ps) to hot electrons transferring their energy
to the crystal lattice via electron-phonon scattering. τ₂ (∼25 ps), on the other hand, cannot be
explained as a conventional process and is attributed to the unconventional (localized) carriers in
the material. The observed coherent oscillation is assigned to be a totally symmetric A1g optical
phonon dominated by Sn displacements out of the Kagome planes, and possesses a prominently large
amplitude, on the order of 10^-3, comparable to the maximum of the reflectivity change (ΔR/R).
This amplitude is equivalent to charge-density-wave (CDW) systems, although no signs of such an
instability were hitherto reported in Fe₃Sn₂. Our results set an unexpected connection between
Fe₃Sn₂ and kagome metals with CDW instabilities, and suggest a unique interplay between phonon
and electron dynamics in this compound.

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Permalink: https://www.hzdr.de/publications/Publ-37706


Application of focused ion beams for quantum and information technologies

Astakhov, G.

Abstract

In the first part, we present our recent result on mask-free nanofabrication involving a quasi-deterministic creation of single G- and W-centers in silicon wafers using focused-ion beam (FIB) writing. Using these centers, we implement a scalable, broad-beam implantation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabricate telecom single photon emitters at desired positions on the nanoscale In the second part, we present a concept of ultralong, high-density data archiving based on optically active atomic-size defects in silicon carbide (SiC). The information is written in these defects by FIB and read using photoluminescence (PL) or cathodoluminescence (CL). With near-infrared laser excitation, grayscale encoding and multi-layer data storage, the areal density corresponds to that of Blu-ray discs.

Keywords: Quantum technology; Defects; Focused ion beam

Involved research facilities

Related publications

  • Invited lecture (Conferences) (Online presentation)
    Sino-German Symposium Defect Engineering in SiC and Other Wide Bandgap Semiconductor, 23.-24.10.2023, Conference Center, SUSTech, Shenzhen, Guangdong, China

Permalink: https://www.hzdr.de/publications/Publ-37705


Operating windows and techno-economics of a power-to-methanol process utilizing proton-conducting high temperature electrolyzers

Fogel, S.; Unger, S.; Hampel, U.

Abstract

Methanol is a crucial commodity in the chemical industry and is employed as precursor for many products. It can be used to store fluctuating renewable energy, specifically benefiting from its liquid state at ambient temperatures. As the demand for green, renewable methanol is projected to soar in the next decades, environmentally friendly and sustainable pathways for its production have to be provided. Through the combination of proton-conducting high temperature electrolysis for the provision of dry H2 with a heterogeneously catalyzed hydrogenation of CO2, efficient and simple power-to-methanol production processes can be established. Here, a novel power-to-methanol system model capable of real-time transient simulation is presented and viable operating windows are determined for different key operating parameters of the respective main process stages. A techno-economic assessment is carried out to determine the specific production costs of renewable methanol. Specific methanol production costs of 2419 €∙t-1MeOH for small-scale applications (1.12 MW) were retrieved, which corresponds to a more than fourfold increase over the current market price of conventionally produced methanol. Increases in system scale are found to decrease the methanol production costs due to economy-of-scale effects. The sensitivity of the process economics is assessed with regards to crucial operational and capital characteristics.

Keywords: System Model; Power-to-Methanol; SOEC; Techno-Economic Assessment; Proton-Conductors

Involved research facilities

  • TOPFLOW Facility

Permalink: https://www.hzdr.de/publications/Publ-37703


Learning to reconstruct the bubble distribution with conductivity maps using Invertible Neural Networks and Error Diffusion

Kumar, N.; Krause, L.; Wondrak, T.; Eckert, S.; Eckert, K.; Gumhold, S.

Abstract

Electrolysis is crucial for eco-friendly hydrogen production, but gas bubbles generated during the process hinder reactions, reduce cell efficiency, and increase energy consumption. Additionally, these gas bubbles cause changes in the conductivity inside the cell, resulting in corresponding variations in the induced magnetic field around the cell. Therefore, measuring these gas bubble-induced magnetic field fluctuations using external magnetic sensors and solving the inverse problem of Biot-Savart’s Law allows for estimating the conductivity in the cell and, thus, bubble size and location. However, determining high-resolution conductivity maps from only a few induced magnetic field measurements is an ill-posed inverse problem. To overcome this, we exploit Invertible Neural Networks (INNs) to reconstruct the conductivity field. Our qualitative results and quantitative evaluation using random error diffusion show that INN achieves far superior performance compared to Tikhonov regularization.

Keywords: Machine Learning; Invertible Neural Networks; Water Electrolysis; Biot-Savart Law

  • Open Access Logo Lecture (Conference)
    11th World Congress on Industrial Process Tomography, 06.-08.09.2023, Mexiko-Stadt, Mexiko
  • Open Access Logo Contribution to proceedings
    11th World Congress on Industrial Process Tomography, 06.-08.09.2023, Mexiko-Stadt, Mexiko

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Permalink: https://www.hzdr.de/publications/Publ-37702


Current Tomography - Localization of void fractions in conducting liquids by measuring the induced magnetic flux density

Krause, L.; Kumar, N.; Wondrak, T.; Gumhold, S.; Eckert, S.; Eckert, K.

Abstract

A novel concept of a measurement technology for the localization and determination of the size of gas bubbles is presented, which is intended to contribute to a further understanding of the dynamics of efficiency-reducing gas bubbles in electrolyzers. A simplified proof-of-concept (POC) model is used to numerically simulate the electric current flow through materials with significant differences in electrical conductivity. Through an automated approach, an extensive data set of electric current density and conductivity distributions is generated, complemented with determined magnetic flux densities in the surroundings of the POC cell at virtual sensor positions. The generated data set serves as testing data for various reconstruction approaches. Based on the measurable magnetic flux density, solving Biot-Savart’s law inversely is demonstrated and discussed with a model-based solution of an optimization problem, of which the gas bubble locations are derived.

Keywords: current tomography; magnetic field measurement; current density distribution; inverse problem

  • Open Access Logo Lecture (Conference)
    11th World Congress on Industrial Process Tomography, 06.-08.09.2023, Mexiko-Stadt, Mexiko
  • Open Access Logo Contribution to proceedings
    11th World Congress on Industrial Process Tomography, 06.-08.09.2023, Mexiko-Stadt, Mexiko

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Permalink: https://www.hzdr.de/publications/Publ-37701


Pre-treatment QA for online-adaptive PT: Status-quo workflow assessment and sanity check development

Wolter, L. C.; Poels, K.; Hennings, F.; Souris, K.; Lenk, T.; Stützer, K.; Richter, C.

Abstract

Purpose/Objective
Within a dedicated consortium, two clinical proton therapy (PT) centers collaborate with two industrial partners (PT system and treatment planning provider, respectively) to jointly develop, implement and evaluate an industrial solution for online-adaptive proton therapy (OAPT). This also requires a dedicated approach for patient-specific QA (pre- and post-treatment PSQA). As first step, we conducted a comprehensive assessment of the current clinical pre-treatment PSQA protocols in the two clinical PT facilities. Furthermore, so-called “sanity checks” have been defined, which play a crucial role in the OAPT QA concept: First, they speed up and automate checks that are currently performed manually and second, in combination with secondary dose calculation, they provide additional trust/evidence that the treatment is safe and as expected, before the delivery is started.

Materials/Methods
The current PSQA workflows (from plan approval until delivery of first fraction, Fig. 1A) were systematically analyzed for both PT facilities. Center 1 employs the MOSAIQ (Elekta AB, SE) oncology information system (OIS) in combination with RayStation (RaySearch Laboratories, Stockholm, SE) as treatment planning system (TPS). Center 2 utilizes the RayCare OIS (RaySearch Laboratories, SE) in combination with RayStation. The two workflows are hereinafter referred to as “Separate-OIS” and “Integrated-OIS”, respectively. Time required for all human operations in these systems, including data preparation for phantom measurements and double checks was assessed via the number of required mouse clicks and manual entries.
Sanity checks (SCs) are automated QA routines, aiming to replace manual checks carried out by the medical physics expert (MPE). They serve as an additional safety mechanism, which guarantees the plausibility of plan parameter adjustments induced by the adaptation process and verifies the integrity of transferred DICOM data. To achieve an OAPT-ready PSQA workflow while providing at least the same level of risk mitigation as the current protocol, we defined SCs for adapted treatment plans, based on existent QA procedures. We incorporated these features in a conceptual PSQA-workflow for OAPT (Fig. 1B), in which SCs are complemented by secondary dose calculation and log file-based QA to enable phantom-less PSQA. Furthermore, manual sub-processes in the current PSQA protocol, which are directly covered by SCs in the OAPT workflow were identified.

Results
The status-quo pre-treatment PSQA workload for the Separate-OIS workflow was estimated to 402 clicks, distributed over four chronological sub-processes: 40% plan approval and -documentation, 11% phantom-QA preparation, 19% 1st MPE check and 30% 2nd MPE check (Fig. 2A). For the Integrated-OIS workflow, a total of 269 clicks were recorded with 18%, 5%, 34% and 43% for the same sub-processes, respectively (Fig. 2B). The Separate-OIS and Integrated-OIS workflows demand 18 vs. 10 manual entries of treatment parameters, respectively. The lower number of clicks required for the Integrated-OIS workflow are associated with the seamless integration of OIS and TPS, combined with less time spent on the manual creation and review of report documents exchanged by separate systems.
Twenty-six SCs were defined, divided in 13 exact (“hard”) checks and 13 tolerance threshold-based (“soft”) checks. They are situated at two subsequent, designated workflow points: (1) After plan approval in the TPS and (2) after DICOM data transfer from the OIS to the treatment control system (TCS). SCs operate on patient data, prescription, gantry- and couch parameters as well as image-/structure sets, beam parameters and dose calculation settings (Fig. 2C/D). From the total 402 clicks recorded for PSQA operations in the Separate-OIS workflow, 47 (12%) clicks related to plan release and MPE checks would be directly covered by SCs in the envisioned OAPT workflow. For the Integrated-OIS workflow, 45 clicks (17%) would be covered by SCs. Notably, this portion only reflects the direct impact of SCs on the status-quo PSQA workload. The full OAPT-PSQA workflow will lead to a substantial additional decrease of manual operations (e.g. due to phantom-less QA and automated documentation), which was out of the scope of this work.

Conclusion
Time- and labor-intensive operations in the current PSQA workflow have been systematically assessed for two clinical PT centers. SCs were defined to automate key processes with high manual workload, enabling phantom-less PSQA in a future OAPT workflow and beyond. In addition, they would also speed-up today’s pre-treatment PSQA workflow, providing an even broader benefit. This work therefore represents a relevant step towards the implementation of OAPT for industrial PT solutions, ensuring a high level of safety while speeding up the PSQA process. In the next step, tolerance thresholds for soft SCs will be determined in a retrospective study, followed by a sensitivity analysis.

Keywords: Online-adaptive proton therapy; Patient-specific quality assurance

Involved research facilities

  • OncoRay
  • Lecture (Conference) (Online presentation)
    ESTRO 2024, 03.-07.05.2024, Glasgow, Scotland

Permalink: https://www.hzdr.de/publications/Publ-37700


Example Dataset from a Laser Ion Beam Accelearation Experiment for the Lecture on Research Software Engineering

Metzkes-Ng, J.; Zeil, K.; Bernert, C.; Reimold, M.; Gaus, L.; Assenbaum, S.; Schlenvoigt, H.-P.
DataCurator: Knodel, Oliver; ContactPerson: Juckeland, Guido

Abstract

The dataset is an example experiment with images and metadata from the Laser-driven Ion Acceleration at HZDR from 2019-08-29. The dataset is used for the lecture on research Software Engineering (RSE) at Technische Universität Dresden.

Keywords: Laser Ion Beam Accelearation; Data Management; Metadata; Research Software Engineering

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Permalink: https://www.hzdr.de/publications/Publ-37699


Structure prediction of iron hydrides at high pressures with machine-learned interatomic potentials

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

Abstract

Understanding the composition of Earth's core and mantle is a major challenge in geoscience
and materials science. The core is primarily made of iron, but its density is known to be
slightly lower than pure iron. Hydrogen contributes to this density deficit, leading to
significant interest in the properties and structure of iron hydrides under high pressure.

Previous studies have shown that the dhcp phase of FeH remains stable at lower pressures (10-40 GPa)
but undergoes phase transitions to hcp and fcc phases at higher pressures.
This study focuses on a theoretical exploration of the potential energy surfaces (PESs) of FeH under
varying pressure conditions. The objective is to demonstrate the effectiveness of automated and systematic
methods for training and validating transferable machine-learned interatomic potential (ML-IAP) using global
optimization techniques. By utilizing this potential, which significantly reduce computational costs,
the phase diagram of the stoichiometric Fe-H system is analyzed across a range of pressures.

To achieve this, we utilize the PyFLAME code to construct a highly transferable ML-IAP.
With this accurate potential, the PESs of bulk FeH structures are systematically investigated
through global sampling using the minima hopping method. This comprehensive exploration enables the prediction
of stable and metastable iron hydrides from 0 to 100 GPa. Density functional theory calculations are conducted
to refine the predicted structures and evaluate their dynamical stability.
The findings of this study reveal a wide range of novel low-energy polymorphs of FeH at each
pressure level, alongside the recovery of well-known structures in the literature.

  • Open Access Logo Poster
    NHR Conference 2023, 18.-19.09.2023, Berlin, Germany

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Permalink: https://www.hzdr.de/publications/Publ-37698


Orientational mercury removal from aqueous solution using three-dimensionally structured CuxS nanocluster anchored attapulgite

Dai, G.; Huang, J.; Ding, W.; Qiu, L.; Zhang, W.; Gu, Q.; Wang, Z.; Hu, Z.; Quan, C.; Li, P.

Abstract

Toxic mercury-containing wastewater emitted from mining and nonferrous metallurgy seriously threatens human health and aquatic ecosystem. Effective mercury removal interfered with other coexisting metal ions in wastewater poses major challenges, requiring simple and sustainable methods. In this work, a novel three-dimensional (3D) CuxS nanocluster-anchored attapulgite (ATP@CuxS) is tailored for orientational mercury adsorption from diluted mercury-containing wastewater. The prepared ATP@CuxS adsorbent exhibited an unparalleled Hg2+ adsorption capacity of 746.48 mg g-1 among ever-reported clay-based adsorbents. Mercury-containing wastewater with an initial concentration of 5 mg L-1, and solution pH of 6.5 was ~100% removed within 20 min, and no interference by coexisting anionic and cation ions was observed. In the determination of the adsorption mechanism, in-situ intercalation and vulcanization of Cu2+ on ATP base constructs nanoclusters shaped CuxS that provide abundant active sites for Hg2+ adsorption. The negatively charged ATP facilitates positive Cu2+ immobilization on its surface followed by inorganic sulfide generation. This interfacial electrical compatibility makes a compact and stable composite.
33 Hydrophilic ATP modulated the uniform dispersion performance of ATP@CuxS, and
34 the dense CuxS package contributed to easier sedimentation and recovery after Hg2+
35 adsorption in water. Furthermore, Hg2+ removal efficiency was maintained at 70% after
36 8 times repetitions, indicating a gentle feasibility as a mass-generated adsorbent. The
37 proposed interface engineering from the perspective of micro-interface electrical
38 compatibility creates an attractive and easily accessible system that combines efficiency,
39 capacity, selectivity, and reusability for orientational removing Hg2+ from wastewater.

Keywords: CuxS nanocluster; Attapulgite; Interface engineering; Mercury removal; Orientational removal; Feasibility evaluation

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  • Secondary publication expected from 26.01.2025

Permalink: https://www.hzdr.de/publications/Publ-37697


Nucleation of surface nanobubbles in electrochemistry: Analysis with nucleation theorem

Ma, Y.; Huang, M.; Mutschke, G.; Zhang, X.

Abstract

The formation of single bubbles at nanoelectrodes during electrochemical reactions allows to accurately identify the critical nucleus for bubble formation. As demonstrated before, combining nanoelectrode experiments and an analysis approach based on classical nucleation theory (CNT) delivers useful insight into bubble nucleation. In this work we propose an alternative approach to analyze the critical nuclei by applying the nucleation theorem (NT), which is able to overcome the inherent shortcomings of CNT. The size of the critical nucleus can be calculated more accurately by fitting experimental data in a simple form of the NT. Simulating the local gas concentration using a finite element approach, and considering the effect of gas oversaturation on the interfacial tension and the real gas compressibility, we obtain a more realistic estimation of the critical nuclei morphology. With the NT-based analysis presented, we re-analyze the nucleation data reported before. The properties of the critical nuclei obtained here are roughly consistent with those obtained from the CNT-based approach. In addition, we confirm that the critical nucleus for bubble formation in high gas oversaturation is featured with a contact angle much larger than Young’s contact angle.

Keywords: nanobubble; critical nucleous; nucleation theorem; finite element simulation; contact angle

Permalink: https://www.hzdr.de/publications/Publ-37696


Defect evolution in GaN thin film heterogeneously integrated with CMOS-compatible Si(100) substrate by ion-cutting technology

Shi, H.; Yi, A.; Ding, J.; Liu, X.; Qin, Q.; Yi, J.; Hu, J.; Wang, M.; Cai, D.; Wang, J.; Xu, K.; Mu, F.; Suga, T.; Heller, R.; Wang, M.; Zhou, S.; Xu, W.; Huang, K.; You, T.; Ou, X.

Abstract

Ion-cutting technology is an ingenious solution to the high-quality heterogeneous integration of GaN thin films with CMOS-compatible Si(100) substrate, which provides a platform to combine GaN-based optoelectronics, high-frequency and high-power electronics with digital signal processing, logic computation, and control of Si(100) CMOS. Previously, we reported the fabrication of 2-inch GaN film on SiO2/Si(100) substrate (GaNOI) by the ion-cutting technology. In this study, we further study the defect evolution in the transferred GaN films, which is needed to promote the practical applications of the GaNOI material platform.

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Permalink: https://www.hzdr.de/publications/Publ-37695


The Heterogeneity of the Sandy Facies of Opalinus Clay across Scales, from Seismic Surveys to Radionuclide Diffusion - an in-situ Test in the Swiss Rock Laboratory Mont Terri

Heberling, F.; Albers, H.; Beilecke, T.; Deissmann, G.; Fischer, C.; Furche, M.; Geckeis, H.; Hoyer, E.-M.; Joseph, C.; Liebscher, A.; van Loon, L.; Lüth, S.; Ma, B.; Metz, V.; Müller, K.; Nowak, U.; Quinto, F.; Rebscher, D.; Rühaak, W.; Schulte, F.; Steegborn, F.; Tietz, T.

Abstract

Many countries consider clay rock formations as potential host rocks for high-level nuclear waste disposal. Clay rocks may exhibit heterogeneity on various scales, from the micro- to the facies-scale. In the Mont Terri rock laboratory, Switzerland, various experiments study properties and characteristics of the Jurassic Opalinus Clay, which is the target host rock for the Swiss nuclear waste repository but may also provide proxies for other considered clay rock formations. At Mont Terri, the Opalinus Clay mainly appears in a shaly and two sandy facies. So far, diffusion experiments at Mont Terri focussed on the relatively homogeneous shaly facies. The upper sandy facies (SF-OPA) exhibits a more pronounced internal – mineralogical and textural – heterogeneity. Clay rocks with comparable heterogeneity to SF-OPA may be present among the lower Cretaceous clay rocks of northern Germany, which are among the potential host rock candidates for a future German nuclear waste repository. Since 2020, seven institutions develop an in-situ diffusion experiment in SF-OPA, the so-called DR-D experiment, to explore the impact of rock heterogeneity on radionuclide diffusion in low permeability clay rocks.
So far, the DR-D experiment combined high-resolution seismic tomography, borehole logging, and detailed drill core analyses to characterize the heterogeneity of the selected SF-OPA area. The targeted rock zone exhibits a layer starting ca. 10 m below the gallery surface, which is characterized by relatively high seismic velocities. This layer is as well evident in the natural gamma- and the neutron backscattering logs. In the drill cores it stands out as whitish rock characterized by large concretions and traces of bioturbation in contrast to the dark layered clay-rock above and below with smaller concretions. Detailed analysis of seismic signals and drill-cores is still ongoing. In future, an in-situ diffusion test using various radioactive and non-radioactive tracers (e.g., HTO, 129I, 22Na) will be conducted targeting the evidently heterogeneous rock section 10 m below the gallery surface. The evolution of tracer concentrations in a synthetic porewater circulating in the diffusion interval will be monitored. A second seismic tomography survey is planned after the termination of the diffusion experiment. Finally, overcoring and post-mortem analysis of the rock affected by tracer diffusion will be used to determine the local variability of diffusion parameters.
In this contribution, we present the general concept, technical layout, and expected scientific impact of the DR-D experiment, as well as first results from field and related laboratory studies.

  • Contribution to proceedings
    18th international conference on the chemistry and migration behaviour of actinides and fission products in the geosphere, 24.-29.09.2023, Nantes, France
  • Poster
    18th international conference on the chemistry and migration behaviour of actinides and fission products in the geosphere, 24.-29.09.2023, Nantes, France, 24.-29.09.2023, Nantes, France

Permalink: https://www.hzdr.de/publications/Publ-37694


Data publication: Chelator Impact: Investigating the Pharmacokinetic Behavior of Copper-64 Labeled PD-L1 Radioligands

Krutzek, F.; Donat, C.; Stadlbauer, S.

Abstract

Bei diesem Datensatz handelt es sich um die chemische Charakterisierung der Verbindungen, die in-vitro- und in-vivo-Daten.

Involved research facilities

  • PET-Center

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Permalink: https://www.hzdr.de/publications/Publ-37693


Poly(benzimidazobenzophenanthroline)-Ladder-Type Two-Dimensional Conjugated Covalent Organic Framework for Fast Proton Storage

Wang, M.; Wang, G.; Naisa, C.; Fu, Y.; Manoj Gali, S.; Paasch, S.; Wang, M.; Wittkaemper, H.; Papp, C.; Brunner, E.; Zhou, S.; Beljonne, D.; Steinrück, H.-P.; Dong, R.; Feng, X.

Abstract

Electrochemical proton storage plays an essential role in designing next-generation high-rate energy storage devices, e.g., aqueous batteries. Two-dimensional conjugated covalent organic frameworks (2D c-COFs) are promising electrode materials, but their competitive proton and metal-ion insertion mechanisms remain elusive, and proton storage in COFs is rarely explored. Here, we report a perinone-based poly(benzimidazobenzophenanthroline) (BBL)-ladder-type 2D c-COF for fast proton storage in both a mild aqueous Zn-ion electrolyte and strong acid. We unveil that the discharged C−O− groups exhibit largely reduced basicity due to the considerable π-delocalization in perinone, thus affording the 2D c-COF a unique affinity for protons with fast kinetics. As a consequence, the 2D c-COF electrode presents an outstanding rate capability of up to 200 A g−1 (over 2500 C), surpassing the state-of-the-art conjugated polymers, COFs, and metal–organic frameworks. Our work reports the first example of pure proton storage among COFs and highlights the great potential of BBL-ladder-type 2D conjugated polymers in future energy devices.

Permalink: https://www.hzdr.de/publications/Publ-37692


Preclinical evaluation of an ¹⁸F-labeled Nε-acryloyllysine piperazide for covalent targeting of transglutaminase 2

Wodtke, R.; Laube, M.; Hauser, S.; Meister, S.; Ludwig, F.-A.; Fischer, S.; Kopka, K.; Pietzsch, J.; Löser, R.

Abstract

Background: Transglutaminase 2 (TGase 2) is a multifunctional protein and has a prominent role in various physiological and pathophysiological processes. In particular, its transamidase activity, which is rather latent under physiological conditions, gains importance in malignant cells and supports tumor development and progression. Thus, there is a great need of theranostic probes for targeting tumor-associated TGase 2, and targeted covalent inhibitors appear particularly attractive as vector molecules in this regard. Such an inhibitor, equipped with a radionuclide suitable for noninvasive imaging, would be supportive for answering the general question on the possibility for functional characterization of tumor-associated TGase 2 in vivo. For this purpose, the recently developed ¹⁸F-labeled Nε-acryloyllysine piperazide [¹⁸F]7b, which is a potent and selective irreversible inhibitor of TGase 2, was subject to a detailed radiopharmacological characterization herein, including ex vivo biodistribution, metabolism and tumor uptake.
Results: An alternative radiosynthesis of [¹⁸F]7b under basic conditions is presented, which demands less than 300 µg of the respective trimethylammonio precursor per synthesis and provides [¹⁸F]7b in good radiochemical yields (17±7%) and high (radio)chemical purities (≥99%). Ex vivo biodistribution in healthy mice at 5 and 60 min p.i. revealed no permanent enrichment of ¹⁸F-activity in tissues with the exception of the bone tissue. In vivo pretreatment with ketoconazole and in vitro murine liver microsome (MLM) studies complemented by UPLC-MS/MS analysis demonstrated that bone uptake originates from metabolically released [¹⁸F]fluoride. Further metabolic transformations of [¹⁸F]7b include mono-hydroxylation and glucuronidation. Based on blood sampling data and MLM experiments, pharmacokinetic parameters such as plasma and intrinsic clearance were derived, which substantiated the apparently rapid distribution of [¹⁸F]7b in and elimination from the organisms. A TGase 2-mediated uptake of [¹⁸F]7b in different tumor cell lines could not be proven. Moreover, evaluation of [¹⁸F]7b in melanoma tumor xenograft models based on A375-hS100A4 (TGase 2 +) and MeWo (TGase 2 -) cells by ex vivo biodistribution and PET imaging were not indicative for a TGase 2-specific targeting.
Conclusion:
[¹⁸F]7b is a valuable radiometric tool to study TGase 2 in vitro under various conditions. However, its suitability for targeting tumor-associated TGase 2 is strongly limited due its unfavorable pharmacokinetic properties including a pronounced metabolization. Consequently, from a radiochemical perspective [18F]7b requires structural modifications to overcome these limitations.

Keywords: radiofluorination; liver microsomes; biodistribution; PET imaging; plasma clearance; pharmacokinetics; radiometabolites; defluorination

Involved research facilities

  • PET-Center

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Permalink: https://www.hzdr.de/publications/Publ-37691


Uranium(VI) interactions with Pseudomonas sp. PS-0-L, V4-5-SB and T5-6-I

Kasko, J.; Li, X.; Müller, K.; Ge, Y.; Vettese, G. F.; Law, G. T. W.; Siitari-Kauppi, M.; Huittinen, N. M.; Raff, J.; Bomberg, M.; Herzig, M.

Abstract

Pseudomonas sp. are indigenous inhabitants of ombrotrophic bogs which can survive in acidic, nutrient-poor environments with wide temperature fluctuations. Their interactions with contaminant radionuclides can influence radionuclide biogeochemistry in boreal environment. Here, uranium (U(VI)) bioassociation by Pseudomonas sp. PS-0-L, V4-5-SB and T5-6-I isolated from a boreal bog was studied by a combination of batch contact experiments, spectroscopy and microscopy. All strains removed U from the solution and the U bioassociation efficiency was affected by the nutrient source, incubation temperature, time and pH. Highest U bioassociation occurred in the strains PS-0-L (0.199 mg U/gBDW) and V4-5-SB (0.223 mg U/gBDW). Based on in-situ attenuated total reflection Fourier transformation infrared spectroscopy (ATR FT-IR) analyses, the most likely functional groups responsible for U binding were the cell surface carboxyl groups. In addition, transmission electron microscopy with energy dispersive X-ray spectroscopy (TEM/EDX) showed dense intra-cellular round- and needle-like U accumulations in the cytoplasm and near to the inner cell membrane. The presence of U with phosphorus was indicated in elemental mapping. Modelled data showed ≡SOOHx-1 and ≡SOCO2Hx-1 as the dominant surface sites, contributing to the negative cell surface charge. The U removal efficiency depended on the U(VI) speciation under different pH conditions. At pH 5, the main species reacting with bacterial cell surfaces was UO22+, while at pH 9 UO2(OH)2 and UO2(OH)3- dominated the reactions. Further, U bioassociation increased with increasing aqueous U(VI) concentrations. Our data suggests U bioassociation on 1) outer cell membrane/cell wall associated carboxyl groups (e.g., proteins), and 2) intracellular phosphate groups (e.g., phospholipids).

Keywords: bioassociation; biosorption; bioaccumulation; modelling; carboxyl group; phosphate group

Permalink: https://www.hzdr.de/publications/Publ-37690


Oppositely charged surfactants and nanoparticles at the air-water interface: Influence of surfactant to nanoparticle ratio

Eftekhari, M.; Schwarzenberger, K.; Karakashev, S. I.; Grozev, N. A.; Eckert, K.

Abstract

Hypothesis: The interactions between oppositely charged nanoparticles and surfactants can significantly influence the interfacial properties of the system. Traditionally, in the study of such systems, the nanoparticle concentration is varied while the surfactant concentration is kept constant, or vice versa. However, we believe that a defined variation of both components' concentration is necessary to accurately assess their effects on the interfacial properties of the system. We argue that the effect of nanoparticle-surfactant complexes can only be properly evaluated by keeping the surfactant to nanoparticle ratio constant.

Experiments: Zeta potential, dynamic light scattering, high amplitude surface pressure and surface tension measurements are employed synergistically to characterize the interfacial properties of the nanoparticle-surfactant system. Interferometric experiments are performed to highlight the effect of surface concentration on the stability of thin liquid films.

Findings: The interfacial properties of surfactant/nanoparticle mixtures are primarily determined by the surfactant/nanoparticle ratio. Below a certain ratio, free surfactant molecules are removed from the solution by the formation of surfactant-nanoparticle complexes. Surprisingly, even though the concentration and hydrophobicity of these complexes do not seem to have a noticeable impact on the surface tension, they do significantly affect the rheological properties of the interface. Above this ratio, free surfactant monomers and nanoparticle-surfactant complexes coexist and can co-adsorb at the interface, changing both the interfacial tension and the interfacial rheology, and thus, for example, the foamability and foam stability of the system.

Keywords: Nanoparticle surfactant complexes; Surfactant to nanoparticle ratio; Surface pressure isotherm; Zeta potential; Film stability

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  • Secondary publication expected from 04.10.2024

Permalink: https://www.hzdr.de/publications/Publ-37689


Opportunities and challenges for spintronics

Adelmann, C.; Jenkins, A.; Pirro, P.; Schultheiß, K.; van Dijken, S.; Kruglyak, V.; Bortolotti, P.

Abstract

Conventional electronics use the flow of electric charges and are based on standard semiconductors. Spintronic devices exploit the electrons’ spin to generate and control currents and to combine electric and magnetic signals. Today there is a strong effort worldwide to integrate spintronic devices with standard CMOS technology towards hybrid spin-CMOS chips, offering advantages in terms of power consumption, compactness, and speed. Recent results (from SAMSUNG [1], TSMC [2], etc.) confirm the merit of this approach.

Keywords: spintronics; magnonics

Permalink: https://www.hzdr.de/publications/Publ-37688


Research data management of laser-plasma science at HZDR

Schlenvoigt, H.-P.; Tippey, K. E.; Horn, W.; Bock, S.; Pape, D.; Knodel, O.; Kluge, T.; Irman, A.; Zeil, K.; Schramm, U.

Abstract

The Draco laboratory at HZDR is a versatile, multi-arm and multi-target-area facility, consisting of several, independent subsystems. The lack of an overarching DAQ is balanced by interfaces of the subsystems and custom inter-linking agents. We present recent progress of implementing such software agents, connecting to the center’s electronic lab documentation system. First, manual logging of shot parameters and observations is lifted from spreadsheet software to a flexible web-app, writing to a database (DB). The laser-internal logging is exported to a DB and internal software triggering is forwarded to experiments. That provides a connection between laser-internal indexing and experiment-based indexing (another DB) and enables near-online data processing. The latter comprises file path logging and validation according to the shot’s acquisition settings for further analysis as well as basic on-shot analysis scripts, both enabling near-online visualization to better guide the course of experiments.
Likewise, parameters and results from simulations are logged to databases, enabling machine learning techniques and better computing resource management.
For a long-term, FAIR storage, the HELPMI project starts exploring the possibilities of openPMD and NeXus to ingest experimental data. That project shall serve as initiative for the global LPA community to find a data and metadata standard.

Keywords: data standard; metadata

Involved research facilities

  • HIBEF
  • ATHENA
  • Draco
  • Penelope
  • Open Access Logo Poster
    6th European Advanced Accelerator Concepts workshop, 18.-22.09.2023, La Biodola Bay, Isola d'Elba, Italy

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Permalink: https://www.hzdr.de/publications/Publ-37687


Synthese und Radiomarkierung von macropa-PSMA-Derivaten für die Tumorbildgebung mit Iod-123

Krönke, T.

Abstract

Ziel: macropa-PSMA-Konjugate mit Albuminbinder zur zielgerichteten Alphatherapie mit 225Ac wurde innerhalb der Arbeitsgruppe bereits erfolgreich synthetisiert und in vitro und in vivo untersucht.[1,2] Die dabei eingeführte albuminbindende Einheit bietet die Grundlage zur Erarbeitung eines theranostischen Ansatzes indem, neben der Komplexierung des Alphaemitters 225Ac, die Bindung von Iod-123 als leicht zugängliches SPECT-Nuklid im gleichen Molekül ermöglicht wird. Vorteilhaft sind die milden Markierungsbedingungen sowie eine passende Halbwertszeit des Iodisotopes (t1/2 =13,2 h), welche die Bildgebung länger zirkulierender Substanzen ermöglicht.
Methoden: Die Synthese der peptidomimetischen Ausgangsverbindungen erfolgte angelehnt an die Vorarbeiten durch mehrstufige Peptidkupplungen und die Anbringung des Chelators mittels Cu-katalysierter Click-Reaktion. Anstelle der 4-(p-Iodphenyl)buttersäure wurde der entsprechende Zinnprecursor eingeführt, um die Verbindung durch eine elektrophile, aromatische Substitution mit 123I markieren zu können.

Keywords: macropa; Radiohybridkonjugate; Actinium-225; Iod-123; Alphatherapie

  • Master thesis
    TU Dresden - Fakultät Chemie und Lebensmittelchemie, 2023
    Mentor: PD Dr. Constantin Mamat
    72 Seiten

Permalink: https://www.hzdr.de/publications/Publ-37686


Synthese und Radiomarkierung von macropa-PSMA-Derivaten für die Tumorbildgebung mit Iod-123

Krönke, T.; Reissig, F.; Pietzsch, H.-J.; Kopka, K.; Mamat, C.

Abstract

Ziel: macropa-PSMA-Konjugate mit Albuminbinder zur zielgerichteten Alphatherapie mit Actinium-225 wurde innerhalb der Arbeitsgruppe bereits erfolgreich synthetisiert und in vitro und in vivo untersucht. Die dabei eingeführte albuminbindende Einheit bietet die Grundlage zur Erarbeitung eines theranostischen Ansatzes indem, neben der Komplexierung des Alphaemitters Actinium-225, die Bindung von Iod-123 als leicht zugängliches SPECT-Nuklid im gleichen Molekül ermöglicht wird. Vorteilhaft sind die milden Markierungsbedingungen sowie eine passende Halbwertszeit des Iodisotopes (t1/2 =13,2 h), welche die Bildgebung länger zirkulierender Substanzen ermöglicht.
Methoden: Die Synthese der peptidomimetischen Ausgangsverbindungen erfolgte angelehnt an die Vorarbeiten durch mehrstufige Peptidkupplungen und die Anbringung des Chelators mittels Cu-katalysierter Click-Reaktion. Anstelle der 4-(p-Iodphenyl)buttersäure wurde der entsprechende Zinnprecursor eingeführt, um die Verbindung durch eine elektrophile, aromatische Substitution mit Iod-123 markieren zu können.
Ergebnisse: Durch die erfolgreiche Entwicklung einer Methode zur Iodierung der synthetisierten Zinnprecursoren mit hohen radiochemischen Ausbeuten konnten schließlich die einfach bzw. doppelt PSMA-gebundenen Verbindungen [123I]I-mcp-M-alb-PSMA und [123I]I-mcp-D-alb-PSMA hergestellt werden. Nach der Iodierung der Verbindungen wurde in vitro der Einfluss des 139La-Komplexes als auch der des unkomplexierten Chelators an der PSMA-positiven Zelllinie LNCaP untersucht.
Schlussfolgerungen: Die Einführung von Iod-123 in die bereits untersuchten Derivate mit stabilem Iod-127 ergab keine Änderungen der biologischen Ergebnisse. Damit ergibt sich der neue Aspekt des theranostischen Nutzens als hybrides Radiopharmakon mit einer weiteren Markierungsstelle in der Peripherie des eigentlichen Liganden.

Keywords: Alphatherapie; Actinium-225; Iod-123; Macropa; Radiohybridkonjugate

  • Lecture (Conference)
    29. Jahrestagung der Arbeitsgemeinschaft Radiochemie/Radiopharmazie, 28.-30.09.2023, Bad Salzuflen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-37685


Detectors of SPM cantilever deflection based on field emission phenomenon

Gacka, E.; Kwoka, K.; Sierakowski, A.; Janus, P.; Hlawacek, G.; Gotszalk, T.

Abstract

The most common deflection detection methods for micro-electromechanical systems (MEMS), like microcantilevers used in scanning probe microscopy, include optical methods based on optical beam deflection systems, piezoresistive or capacitive methods. This issue is still being pursued in order to develop a method with the highest possible deflection sensitivity. For this reason, attention is focused on exploiting the field emission phenomenon – the tunnelling of electrons through a potential barrier that occurs when the applied threshold voltage between electrodes is exceeded.
This work presents a method for microcantilever deflection detection based on field emission phenomenon – fig. 1a. As a result of cantilever deflection, the distance between the emitter tips (electrodes) was changed, resulting in a variation of the threshold voltage and field emission current. Nanotip field emitters were integrated into the microcantilevers using a focused electron and ion beam induced deposition (FEBID/FIBID) (fig. 1b). This one-step process allowed for the simplification of their fabrication technology. The effect of distance between electrodes and emitter shape on the emission enhancement factor was analysed. Preliminary usability tests of the sensor have been performed.
Acknowledgements: This work was supported by the National Science Centre, Poland PRELUDIUM-21 grant [“Nanometrology of field emission phenomena from electron beam deposited nanowires operating as nano- and picodeflection sensors – FEmet”, grant number 2022/45/N/ST7/03049]; and a short term scientific mission funded by the COST Action CA19140 (http://www.fit4nano.eu/).

Keywords: HIM; FIB; SPM; FIBID

Involved research facilities

Related publications

  • Lecture (Conference)
    XII Workshop on Applications of Scanning Probe Microscopy – STM/AFM 2023, 29.11.-03.12.2023, Zakopane, Polen

Permalink: https://www.hzdr.de/publications/Publ-37683


The advent of biotechnology in resource technology

Braun, R.; Lederer, F.

Abstract

The usage of biotechnological molecules and processes is an indispensable part of the resource technology research. The development of novel biomolecules therefore needs to be adapted to the existing applicational conditions and biological processes are to be examined. Novel biosorbents may not only contribute to future applications but can be of further used, e.g. to better understand the interaction of known metal- and metalloid-interacting biological molecules and materials. This review highlights biotechnological approaches published so far for bioremediation as well as metal recovery with a special spotlight on cobalt, nickel and arsenic.

Keywords: biomining; bioleaching; biosorption; bioaccumulation; biomolecules; cobalt; nickel; arsenic

Permalink: https://www.hzdr.de/publications/Publ-37681


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