Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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40439 Publications

New Insights in Controlling Freckle Defect Formation using Magnetic Fields

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

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

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

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

Publ.-Id: 37986

Manipulation of Encapsulated Plasmons in Solids for Photonic Applications

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

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

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

Related publications

Publ.-Id: 37983

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

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

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

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

Related publications

Publ.-Id: 37980

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

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

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


Publ.-Id: 37978

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

Starke, S.; Smid, M.

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

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

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


Publ.-Id: 37977

Near-infrared photodetectors based on single germanium nanowires

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

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

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

Related publications

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

Publ.-Id: 37976

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

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

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

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

Related publications

Publ.-Id: 37974

Visualisation of flow effects in liquid and solidified metals

Shevchenko, N.; Lappan, T.; Eckert, S.

X-ray radiographic imaging is an efficient tool for investigating flow phenomena and solidification processes in optically opaque metallic alloys. This contribution is an overview of the latest advances in in-situ radiographic experiments made by the authors, as well as recent applications, including magnetohydrodynamic systems. We investigated a range of phenomena, such as bubble flow in liquid metal under an applied magnetic field, collective bubble dynamics, particle flow in liquid metal channels, and mesoscale solidification of alloys. Radiography measurements in liquid/solidified metal experiments are inevitably performed under adverse conditions of low signal-to-noise ratio, low image contrast, scattering, etc. To extract meaningful information from experimental data we combine both well-known methodology of data processing and our original codes. Examples of image analysis and results of in-situ experiments performed with low melting point alloys are presented and discussed in this contribution. A focus of these experiments is exploring scaled-down representative systems of industrial processes in metallic alloys.

Keywords: X-ray radiographic imaging; flow phenomena; solidification; Ga-In alloys

  • Lecture (Conference)
    Helmholtz Imaging Conference 2023, 14.-16.06.2023, Hamburg, Germany

Publ.-Id: 37969

Molybdenum Chloride Nanostructures with Giant Lattice Distortions Intercalated into Bilayer Graphene

Liu, Q.; Lin, Y.-C.; Kretschmer, S.; Ghorbani Asl, M.; Solís-Fernández, P.; Siao, M.-D.; Chiu, P.-W.; Ago, H.; Krasheninnikov, A.; Suenaga, K.

The nanospace of the van der Waals (vdW) gap between structural units of two-dimensional (2D) materials serves as a platform for growing unusual 2D systems through
intercalation and studying their properties. Various kinds ofmetal chlorides have previously been intercalated for tuning the properties of host layered materials, but the atomic structure of
the intercalants remains still unidentified. In this study, we investigate the atomic structural transformation of molybdenum(V) chloride (MoCl 5 ) after intercalation into
bilayer graphene (BLG). Using scanning transmission electron microscopy, we found that the intercalated material represents MoCl 3 networks, MoCl 2 chains, and Mo 5 Cl 10 rings. Giant lattice distortions and frequent structural transitions occur in the 2D MoCl x that have never been observed in metal chloride systems. The trend of symmetric to nonsymmetric structural
transformations can cause additional charge transfer from BLG to the intercalated MoCl x , as suggested by our density functional theory calculations. Our study deepens the understanding of the behavior of matter in the confined space of the vdW gap in BLG and provides hints at a more efficient tuning of material properties by intercalation for potential applications,
including transparent conductive films, optoelectronics, and energy storage.

Publ.-Id: 37966

Electron holographic mapping of structural reconstruction at mono- and bilayer steps of h-BN

Subakti, S.; Daqiqshirazi, M.; Wolf, D.; Linck, M.; Kern, F. L.; Jain, M.; Kretschmer, S.; Krasheninnikov, A.; Brumme, T.; Lubk, A.

Here, by making use of medium and high resolution autocorrected off-axis electron holography, we directly probe the electrostatic potential as well as in-plane structural reconstruction at edges and steps in multilayer hexagonal boron nitride. In combination with ab initio calculations, the data allows revealing the formation of folded zigzag edges at steps comprising two monolayers and their absence at monolayer steps.

Publ.-Id: 37962

Measurement and Simulation of Ultra-Low-Energy Ion–Solid Interaction Dynamics

Titze, M.; Poplawsky, J. D.; Kretschmer, S.; Krasheninnikov, A.; Doyle, B. L.; Bielejec, E. S.; Hobler, G.; Belianinov, A.

Ion implantation is a key capability for the semiconductor industry. As devices shrink, novel materials enter the manufacturing line, and quantum technologies transition to being more mainstream. Traditional implantation methods fall short in terms of energy, ion species, and positional precision. Here, we demonstrate 1 keV focused ion beam Au implantation into Si and validate the results via atom probe tomography. We show the Au implant depth at 1 keV is 0.8 nm and that identical results for low-energy ion implants can be achieved by either lowering the column voltage or decelerating ions using bias while maintaining a sub-micron beam focus. We compare
our experimental results to static calculations using SRIM and dynamic calculations using binary collision approximation codes TRIDYN and IMSIL. A large discrepancy between the static and dynamic simulation is found, which is due to lattice enrichment with high-stopping-power Au and surface sputtering. Additionally, we demonstrate how model details are particularly important to the simulation of these low-energy heavy-ion implantations. Finally, we discuss how our results pave a way towards much lower implantation energies while maintaining high spatial resolution.

Keywords: focused ion beam; ion implantation; ultra-low energy

Publ.-Id: 37961

Terahertz Néel spin-orbit torques drive nonlinear magnon dynamics in antiferromagnetic Mn2Au

Behovits, Y.; Chekhov, A. L.; Bodnar, S. Y.; Gueckstock, O.; Reimers, S.; Lytvynenko, Y.; Skourski, Y.; Wolf, M.; Seifert, T. S.; Gomonay, O.; Kläui, M.; Jourdan, M.; Kampfrath, T.

Antiferromagnets have large potential for ultrafast coherent switching of magnetic order with minimum heat dissipation. In materials such as Mn2Au and CuMnAs, electric rather than magnetic fields may control antiferromagnetic order by Néel spin-orbit torques (NSOTs). However, these torques have not yet been observed on ultrafast time scales. Here, we excite Mn2Au thin films with phase-locked single-cycle terahertz electromagnetic pulses and monitor the spin response with femtosecond magneto-optic probes.We observe signals whose symmetry, dynamics, terahertz-field scaling and dependence on sample structure are fully consistent with a uniform inplane antiferromagnetic magnon driven by field-like terahertz NSOTs with a torkance of (150 ± 50) cm2 A−1 s−1. At incident terahertz electric fields above 500 kV cm−1, we find pronounced nonlinear dynamics with massive Néelvector deflections by asmuch as 30°. Our data are in excellent agreement with a micromagnetic model. It indicates that fully coherent Néel-vector switching by 90° within 1 ps is within close reach.

Publ.-Id: 37957

Effect of carbon content on electronic structure of uranium carbides

Butorin, S. M.; Bauters, S.; Amidani, L.; Beck, A.; Rossberg, A.; Weiss, S.; Vitova, T.; Kvashnina, K.; Tougait, O.

The electronic structure of UC (x = 0.9, 1.0, 1.1, 2.0) was studied by means of x-ray absorption spectroscopy (XAS) at the C K edge and measurements in the high energy resolution fluorescence detection (HERFD) mode at the U and edges. The full-relativistic density functional theory calculations taking into account the Coulomb interaction U and spin-orbit coupling (DFT+U+SOC) were also performed for UC and UC. While the U HERFD-XAS spectra of the studied samples reveal little difference, the U HERFD-XAS spectra show certain sensitivity to the varying carbon content in uranium carbides. The observed gradual changes in the U HERFD spectra suggest an increase in the C 2p-U 5f charge transfer, which is supported by the orbital population analysis in the DFT+U+SOC calculations, indicating an increase in the U 5f occupancy in UC as compared to that in UC. On the other hand, the density of states at the Fermi level were found to be significantly lower in UC, thus affecting the thermodynamic properties. Both the x-ray spectroscopic data (in particular, the C K XAS measurements) and results of the DFT+U+SOC calculations indicate the importance of taking into account U and SOC for the description of the electronic structure of actinide carbides.

Related publications

Publ.-Id: 37950

Influence of the cement additive PBTC on aquatic uranium(VI) speciation and retention on cementitious material

Wollenberg, A.; Acker, M.; Kretzschmar, J.; Schmeide, K.; Tsushima, S.; Chiorescu, I.; Krüger, S.

The ingress of water into an underground nuclear repository, described as a worst-case scenario, can lead to the degradation of cement-based engineered barriers and thus to the release of organic cement additives that can affect radionuclide immobilisation. The additive 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) is one of the most commonly used long-term retarders in cement, and also used as a corrosion inhibitor in reinforced concrete and steel. PBTC
is an organophosphonate ligand with one phosphonate and three carboxyl groups [1]. These functional groups make PBTC an effective dispersant and strong complexing agent for various metal ions (e.g. Ca2+, Al3+, Fe3+). However, neither the complexation of radionuclides by PBTC nor the influence of PBTC on radionuclide retention in cement phases has been investigated.
Therefore, both the complexation of U(VI) with PBTC in solution (binary system) and the influence of PBTC on the U(VI) retention by cementitious materials (ternary system) were investigated for the first time. The U(VI) complexation studies were performed by different series varying the pH from 2 to 11 and/or the U(VI) to PBTC ratio. The structure-sensitive methods NMR, IR and Raman spectroscopy were used to characterize the complex structure. Complementary DFT calculations were carried out. The U(VI) speciation in presence of PBTC was determined by UV-Vis and TRLFS spectroscopy. In the case of PBTC excess, soluble complex species are formed up to pH >10, which is relevant for cementitious systems due to degradation processes. For the U(VI) retention studies both calcium (aluminate) silicate hydrate (C-(A-)S-H) phases of different compositions, representing different cement degradation stages, as well as hardened cement paste were applied. TRLFS was applied to characterize the U(VI) binding. The PBTC retention was quantified by 1H and 31P solution NMR.

Keywords: uranium; 2-phosphonobutane-1,2,4-tricarboxylic acid; complexation; stability constants; cement; retention; spectroscopy

  • Lecture (Conference)
    Joint 6th International Workshop on Mechanisms and Modelling of Waste / Cement Interactions, 20.-22.11.2023, Prague, Czech Republic

Publ.-Id: 37949

Structural identification of aquatic U(VI)-PBTC complexes by spectroscopic investigations

Wollenberg, A.; Kretzschmar, J.; Tsushima, S.; Krüger, S.; Acker, M.; Taut, S.; Stumpf, T.

In a nuclear waste repository, cement-based materials are to be used for waste conditioning and as an engineered barrier. The ingress of water into the nuclear waste repository, described as a worst-case scenario, leads to increased aging and degradation of the concrete. These processes are associated with a leaching of diverse organic substances usually added to the cement to realize the desired physicochemical and mechanical properties of the cement-based materials. The impact of the additives is based on their excellent ability to complex metal ions. Consequently, the complexation behavior of such additives towards radionuclides (RN) and thus their impact on RN mobilization and migration into the environment is essential for a comprehensive risk assessment. One of the additives commonly used for long-term retardation of cement hardening is 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC).
PBTC is a polyfunctional ligand possessing three carboxyl groups and one phosphonate group, which have been shown to make PBTC a strong complexing agent for various metal ions (e.g. Ca2+, Zn2+, Al3+, Fe3+) [1,2]. However, to date, there are no studies on PBTC interaction with radionuclides. Therefore,
the complexation of PBTC with U(VI) was investigated for the first time, using different spectroscopic methods over a wide pH range (2 through 11) to identify and characterize possible complex species.
U(VI)-PBTC species with solubility as high as 100 mM were observed throughout the entire pH range studied, especially when PBTC is in excess. This allowed the convenient application of structuresensitive methods such as NMR, IR, and Raman spectroscopies. Furthermore, time-resolved laserinduced
fluorescence spectroscopy (TRLFS) and UV-Vis titration studies provided insight into U(VI)–PBTC system’s speciation.

Keywords: uranium(VI); 2-phosphonobutane-1,2,4-tricarboxylic acid; complexation; stability constants; spectroscopy

  • Lecture (Conference)
    18th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere - Migration 2023, 24.-29.09.2023, Nantes, France

Publ.-Id: 37948

Characterisation of highly soluble U(VI)-PBTC complexes

Wollenberg, A.; Kretzschmar, J.; Schmeide, K.; Acker, M.; Taut, S.; Stumpf, T.

Organophosphonates are used multipurpose in the chemical industry. One of the most commonly used organophosphonates is 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC).[1] The functional groups of PBTC consist of one phosphonate and three carboxylate groups, which make PBTC not only an effective dispersant, but also a very good complexing agent for various metal ions (e.g. Ca2+, Al3+, Fe3+).[2,3] Due to these properties, PBTC is used, for example, as an efficient long-term retarder in cement, as a corrosion inhibitor in reinforced concrete and steel, or as a scale inhibitor in water treatment plants or cooling water circulation systems.[4,5] However, this ubiquitous use can also lead to anthropogenic discharge into the environment, where PBTC can complex heavy metals or even radionuclides. Complexation can increase the solubility of metal ions and thus their bioavailability. As a result, there is an increased risk of toxic metal ions being distributed in the environment and thus also being absorbed into the human food chain.
However, to date there have been no studies on the complexation of PBTC with radionuclides. For this reason, the complexation of PBTC with U(VI) in the pH range from 1 to 11 was investigated for the first time using various spectroscopic methods. The studies were performed by different series varying the pH or the U(VI) to PBTC ratio. For the methods used, U(VI) concentrations in the mM range were employed, which was possible due to the very good water solubility of the U(VI)-PBTC complexes. The structure-sensitive methods NMR, IR and Raman spectroscopy were used to characterise the complex structure. Supporting DFT calculations were carried out. The stability constants of the complex species were determined by UV-Vis spectroscopy. By applying the different spectroscopic methods, it was possible to determine chelation of U(VI) by the phosphonate group and one of the carboxyl groups. Furthermore, by means of factor analysis, the distribution of complex species as well as the complexation constants could be determined for the first time. Therefore, the results of this study make it possible to evaluate the risk of PBTC entering the environment in relation to the radionuclide uranium.

Keywords: uranium(VI); 2-phosphonobutane-1,2,4-tricarboxylic acid; complexation; stability constants; spectroscopy

  • Lecture (Conference)
    5th International Caparica Conference on Pollutant Toxic Ions and Molecules (PTIM) 2023, 06.-09.11.2023, Caparica, Portugal

Publ.-Id: 37947

Magnetic structure and phase diagram of the Heisenberg-Ising spin chain antiferromagnetic PbCo2V2O8

Puniak, K.; Aguilar-Maldonado, C.; Feyerherm, R.; Prokes, K.; Islam, A. T. M. N.; Skourski, Y.; Keller, L.; Lake, B.

The effective spin-1/2 antiferromagnetic Heisenberg-Ising chain materials, ACo2V2O8, A = Sr, Ba, are a rich source of exotic fundamental phenomena and have been investigated for their model magnetic properties both in zero and nonzero magnetic fields. Here we investigate a new member of the family, namely, PbCo2V2O8. We synthesize powder and single-crystal samples of PbCo2V2O8 and determine its magnetic structure using neutron diffraction. Furthermore, the magnetic field/temperature phase diagrams for a magnetic field applied along the c, a, and [110] crystallographic directions in the tetragonal unit cell are determined via magnetization and heat capacity measurements. A complex series of phases and quantum phase transitions are discovered that strongly depend on both the magnitude and direction of the field. Our results show that PbCo2V2O is an effective spin-1/2 antiferromagnetic Heisenberg-Ising chain with properties that are, in general, comparable to those of SrCo2V2O8 and BaCo2V2O8. One interesting departure from the results of these related compounds is, however, the discovery of a new field-induced phase for the field direction H ӏӏ [110].

Publ.-Id: 37943

300 mm CMOS-compatible superconducting HfN and ZrN thin films for quantum applications

Potjan, R.; Wislicenus, M.; Ostien, O.; Hoffmann, R.; Lederer, M.; Reck, A.; Emara, J.; Roy, L.; Lilienthal-Uhlig, B.; Wosnitza, J.

The rising interest in increased manufacturing maturity of quantum processing units is pushing the development of alternative superconducting materials for semiconductor fab process technology. However, these are often facing CMOS process incompatibility. In contrast to common CMOS materials, such as Al, TiN, and TaN, reports on the superconductivity of other suitable transition-metal nitrides are scarce, despite potential superiority. Here, we demonstrate fully CMOS-compatible fabrication of HfN and ZrN thin films on state-of-the-art 300mm semiconductor process equipment, utilizing reactive DC magnetron sputtering on silicon wafers. Measurement of mechanical stress and surface roughness of the thin films demonstrates process compatibility. We investigated the materials phase and stoichiometry by structural analysis. The HfN and ZrN samples exhibit superconducting phase transitions with critical temperatures up to 5.84 and 7.32 K, critical fields of 1.73 and 6.40 T, and coherence lengths of 14 and 7 nm, respectively. A decrease in the critical temperature with decreasing film thickness indicates mesoscopic behavior due to geometric and grain-size limitations. The results promise a scalable application of HfN and ZrN in quantum computing and related fields.

  • Open Access Logo Applied Physics Letters 123(2023), 172602
    Online First (2023) DOI: 10.1063/5.0176060

Publ.-Id: 37942

Local-symmetry-sensitive elastic softening in the Kramers doublet system Y1−xNdxCo2Zn20

Ishii, I.; Umeno, T.; Yamamoto, R.; Onimaru, T.; Suzuki, T.; Araki, K.; Miyata, A.; Zherlitsyn, S.; Wosnitza, J.

We investigated the elastic properties of Y1−xNdxCo2Zn20 with localized Nd f electrons and ground-state Kramers doublet. All longitudinal and transverse moduli of NdCo2Zn20 (x = 1) show an elastic softening below 50 K accompanied by a minimum around 2.5 K. The softening, which is robust to magnetic fields up to 8 T, is not observed for samples with Nd concentrations of x = 0.19, 0.05, and 0. In localized f electron systems, elastic softening from high temperatures is often understood by crystal electric field effects; however, this cannot explain the behavior in NdCo2Zn20. Our experimental and calculated results reveal that the softening neither is caused by a phonon contribution, a Nd3+ single-site effect, nor a magnetic interaction. We conclude that the softening is due to a local-symmetry-sensitive electronic state in NdCo2Zn20.

Publ.-Id: 37941

Giant irreversibility of the inverse magnetocaloric effect in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy

Kamantsev, A. P.; Koshkidko, Y. S.; Bykov, E.; Gottschall, T.; Gamzatov, A. G.; Aliev, A. M.; Varzaneh, A. G.; Kameli, P.

Direct studies of the adiabatic temperature change (ΔTad) in the Ni47Mn40Sn12.5Cu0.5 Heusler alloy in steady magnetic fields up to 8 T by the extraction method and in pulsed magnetic fields up to 50 T were carried out in this paper. The alloy Ni47Mn40Sn12.5Cu0.5 demonstrates a magnetostructural phase transition (MSPT) of the first order in the 254–283 K temperature range as well as a second order phase transition near the Curie temperature TC = 313 K. An inverse magnetocaloric effect (MCE) was found in the region of the MSPT, and it reaches the maximum value ΔTad = -12 K in 20 T at the initial temperature T0 = 275 K. The irreversible part of the MCE reached ΔTir = -10 K when the field is completely removed. We consider the dynamics of the MCE in the vicinity of the MSPT and discuss the mechanisms that cause the giant irreversibility of the MCE as well as the possibilities of its application in hybrid cooling systems.

Publ.-Id: 37940

Foundational Competencies and Responsibilities of a Research Software Engineer

Goth, F.; Alves, R.; Braun, M.; Jael Castro, L.; Chourdakis, G.; Christ, S.; Cohen, J.; Erxleben, F.; Grad, J.-N.; Hagdorn, M.; Hodges, T.; Juckeland, G.; Kempf, D.; Lamprecht, A.-L.; Linxweiler, J.; Schwarzmeier, M.; Seibold, H.; Philipp Thiele, J.; von Waldow, H.; Wittke, S.

The term Research Software Engineer, or RSE, emerged a little over 10 years ago as a way to represent
individuals working in the research community but focusing on software development. The term has been widely
adopted and there are a number of high-level definitions of what an RSE is. However, the roles of RSEs vary
depending on the institutional context they work in. At one end of the spectrum, RSE roles may look similar to
a traditional research role. At the other extreme, they resemble that of a software engineer in industry. Most
RSE roles inhabit the space between these two extremes. Therefore, providing a straightforward, comprehensive
definition of what an RSE does and what experience, skills and competencies are required to become one is
challenging. In this community paper we define the broad notion of what an RSE is, explore the different types
of work they undertake, and define a list of fundamental competencies as well as values that define the general
profile of an RSE. On this basis, we elaborate on the progression of these skills along different dimensions, looking
at specific types of RSE roles, proposing recommendations for organisations, and giving examples of future
specialisations. An appendix details how existing curricula fit into this framework.

Keywords: research software engineering; curriculum design; training; learning; competencies; certification

Publ.-Id: 37938

Helmholtz Metadata Collaboration - Facilitating FAIR metadata in Helmholtz

Schaller, T.; Günter, G.; Kubin, M.; Özkan, Ö.; Rau, F.; Steinmeier, L.

Data are an essential part of every scientific endeavour. An efficient and future oriented research data management is therefore essential in order to ensure long-term availability of the generated data. This in turn ensures the reproducibility of scientific results. In order to facilitate FAIR data management within the Helmholtz community the incubator platform “Helmholtz Metadata Collaboration (HMC)” was established.

HMC develops and provides services, tools and trainings to support and improve FAIR (meta)data management in the Helmholtz Association and aligns these approaches with national and international approaches and initiatives (e.g. RDA, EOSC, NFDI) to ensure compatibility with international research communities.

To achieve this goal, HMC builds its work along three strategic areas: (1) Assessing and monitoring the state of FAIR data across Helmholtz, (2) Facilitating the connectivity of Helmholtz research data, and (3) Transforming (meta)data recommendations into implementations. At the centres, HMC supports research communities and data professionals with six research-field specific hubs: At HZDR HMC is represented locally by a unit dedicated to research field Energy and remotely by a unit for research field Matter. In our poster we will illustrate how research and data professional communities at HZDR can benefit from HMC's services, tools and trainings.

Keywords: Helmholtz-Zentrum Dresden-Rossendorf; HZDR data management day; metadata management; Helmholtz Metadata Collaboration

  • Poster
    HZDR Data Management Day, 21.11.2023, Dresden, Dresden

Publ.-Id: 37937

Influence of selected organics on the retention of uranium(VI) by calcium-(aluminate-)silicate-hydrate phases

Schmeide, K.; Kretzschmar, J.; Huittinen, N. M.

Most underground nuclear waste disposal concepts envisage the extensive use of cementitious materials in the geo-engineered barrier as a buffer and borehole sealing material and to ensure the mechanical stability of disposal systems. In order to assess the radionuclide (RN) retention potential of these barrier materials, it is necessary to study the impact of various repository relevant conditions that will evolve over time, such as changed pH values, increased ionic strength, elevated temperatures, or the release of organic components. The U(VI) retention by calcium (aluminate) silicate hydrate (C-(A-)S-H) phases, forming owing to Al-rich additives in cement formulations, was studied for samples with C/S molar ratios of 0.8, 1.2, and 1.6, representing different alteration stages of concrete, and with increasing A/S molar ratios of 0, 0.06, and 0.18 in each series, with special focus on the presence of organics. The latter thereby comprise gluconate (GLU), 2-phosphonobutane-1,2,4,-tricarboxylate (PBTC), and a mixture of cellulose degradation products (CDP) obtained from dry radiolysis (dose rate 0.6 kGy/h, absorbed dose ~ 1.37 MGy) followed by hydrolysis in artificial cement water (pH > 13, anoxic conditions) provided by project partners within the CORI framework. Complementary analytical techniques were applied to address the different specific aspects of the cement / organics / RN ternary systems. 27Al and 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy and powder X-ray diffraction (XRD) were applied to determine the bulk structure and composition of the synthesized C-(A-)S-H phases. 13C-, and in case of PBTC also 31P-, MAS NMR measurements aimed at localization and speciation of the organic components involved [1]. 1H and 31P solution NMR of the aqueous phase allowed for quantification of the organics’ fraction removed from solution and hence associated with the solid phase. Retained U(VI) species were identified by time-resolved laser-induced luminescence spectroscopy (TRLFS). Zeta-potential measurements were conducted to study the organics’ influence on the surface charge and, upon changing the order of mixing the individual components of the ternary systems (e.g., C-(A-)S-H phases synthesized in absence or presence of U(VI) and/or organics), along with results from spectroscopies, to derive mechanistic understanding of retention processes as well as surface complex models.

Keywords: uranium; C-S-H; C-A-S-H; hydrothermal synthesis; luminescence; spectroscopy

  • Lecture (Conference)
    Joint 6th International Workshop on Mechanisms and Modelling of Waste / Cement Interactions, 20.-22.11.2023, Prague, Czech Republic

Publ.-Id: 37936

NiGe formation on thin Ge films by flash lamp annealing: electrical properties

Begeza, V.; Rebohle, L.; Stöcker, H.; Mehner, E.; Hübner, R.; Zhou, S.

Flash lamp annealing (FLA) is an ultra-short annealing method which excellently meets the requirements of thin film processing and has already been used in microelectronics. Due to the relatively high hole mobility, thin Ge layers are highly interesting as a transistor channel material or generally as a functional layer both in CMOS technology and in the field of low-cost electronics. One possibility to realize ohmic contacts with low contact resistance is the use of metal germanides, especially the stoichiometric NiGe phase.
In this work, NiGe contacts on thin Ge films were fabricated by magnetron sputtering followed by FLA. The evolution of microstructure with increasing thermal budget was traced by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The electrical measurements focus on the determination of contact resistance by the circular transfer length method (cTLM). The contacts were fabricated by two different approaches, and the influence of different process steps on layer morphology and the uncertainty of the measurement was studied.

Keywords: germanium; nickel germanide; thin films; sputtering; flash lamp annealing; circular transfer length

Related publications

  • Lecture (Conference)
    E-MRS SPRING MEETING 2023, 29.05.-02.06.2023, Strasbourg, Frankreich

Publ.-Id: 37931

NiGe formation on thin Ge films by flash lamp annealing

Begeza, V.; Rebohle, L.; Stöcker, H.; Mehner, E.; Hübner, R.; Zhou, S.

In this work, NiGe contacts on thin Ge films were fabricated by magnetron sputtering followed by flash lamp annealing (FLA). The evolution of microstructure with increasing thermal budget was traced by transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The film sheet resistance, the free charge carrier mobility and concentration, and the contact resistance were measured by the four-point-probe method, by Hall effect measurements, and by the circular transfer length method, respectively. Based on this data, the formation process of NiGe contacts during FLA is described, which passes through a stage of Ni-rich phases with high electrical resistivity, before the final stoichiometric NiGe phase is formed.

Keywords: germanium; nickel germanide; thin films; sputtering; flash lamp annealing; circular transfer length

Related publications

  • Lecture (Conference)
    Nutzertreffen Heissprozesse und Ionenimplantation, 10.-11.05.2023, Erlangen, Deutschland

Publ.-Id: 37930

Data publication: Cadmium sorption on alumina nanoparticles, and mixtures of alumina and smectite: An experimental and modelling study

Mayordomo, N.; Missana, T.; Alonso, U.

Data is shown in origin, the thermodynamic database of Cd is adapted for Chess V2 software

Keywords: Cd; sorption model; retention; immobilization; heavy metals; Al2O3


Publ.-Id: 37929

Learning Crop-Type Mapping From Regional Label Proportions in Large-Scale SAR and Optical Imagery

La Rosa, L.; Oliveira, D.; Ghamisi, P.

The application of deep learning (DL) algorithms to Earth observation (EO) in recent years has enabled substantial progress in fields that rely on remotely sensed data. However, given the data scale in EO, creating large datasets with pixel-level annotations by experts is expensive and highly time-consuming. In this context, priors are seen as an attractive way to alleviate the burden of manual labeling when training DL methods for EO. For some applications, those priors are readily available. Motivated by the great success of contrastive-learning methods for self-supervised feature representation learning in many computer-vision tasks, this study proposes an online deep clustering method using crop label proportions as priors to learn a sample-level classifier based on government crop-proportion data for a whole agricultural region. We evaluate the method using two large datasets from two different agricultural regions in Brazil. Extensive experiments demonstrate that the method is robust to different data types [synthetic-aperture radar (SAR) and optical images], reporting higher accuracy values considering the major crop types in the target regions. Thus, it can alleviate the burden of large-scale image annotation in EO applications.


Publ.-Id: 37928

Leveraging involution and convolution in an explainable building damage detection framework

Teymoor Seydi, S.; Hasanlou, M.; Chanussot, J.; Ghamisi, P.

Timely and accurate building damage mapping is essential for supporting disaster response activities. While RS satellite imagery can provide the basis for building damage map generation, detection of building damages by traditional methods is generally challenging. The traditional building damage mapping approaches focus on damage mapping based on bi-temporal pre/post-earthquake dataset extraction information from bi-temporal images, which is difficult. Furthermore, these methods require manual feature engineering for supervised learning models. To tackle the abovementioned limitation of the traditional damage detection frameworks, this research proposes a novel building damage map generation approach based only on post-event RS satellite imagery and advanced deep feature extractor layers. The proposed DL based framework is applied in an end-to-end manner without additional processing. This method can be conducted in five main steps: (1) pre-processing, (2) model training and optimization of model parameters, (3) damage mapping generation, (4) accuracy assessment, and (5) visual explanations of the proposed method’s predictions. The performance of the proposed method is evaluated by two real-world RS datasets that include Haiti-earthquake and Bata-explosion. Results of damage mapping show that the proposed method is highly efficient, yielding an OA of more than 84%, which is superior to other advanced DL-based damage detection methods.

Publ.-Id: 37927

Development Of A Novel ACE2 Decoy For Both SARS-CoV-2 Variant Neutralization And Infected Cell Elimination Via Unmodified Or CAR Modified Immune Cells

Drewitz, L.; Kegler, A.; Arndt, C.; Daglar, C.; Rodrigues Loureiro, L. R.; Mitwasi, N.; Neuber, C.; González Soto, K. E.; Bartsch, T.; Baraban, L.; Ziehr, H.; Heine, M.; Nieter, A.; Moreira-Soto, A.; Kühne, A.; Drexler, J. F.; Seliger, B.; Laube, M.; Máthé, D.; Pályi, B.; Hajdrik, P.; Forgách, L.; Kis, Z.; Sziget, K.; Bergmann, R.; Feldmann, A.; Bachmann, M.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic with millions of infections and deaths worldwide and devastating impact on global economy. Up to now, vaccines and monoclonal antibody (mAb) therapies lack to provide a long-lasting protection against rapidly evolving new emerging SARS-CoV-2 variants. Thus, novel therapeutic options are pressingly needed especially for immunocompromised patients and/or patients with high risk for developing a severe coronavirus disease 2019 (COVID-19).
In that regard, we developed a novel immunotherapeutic drug based on the SARS-CoV-2 entry receptor angiotensin-converting enzyme 2 (ACE2). This ACE2 decoy potently binds to the SARS-CoV-2 receptor binding domain (RBD), neutralizes SARS-CoV-2 as well as the Delta and Omicron variant and protects hamsters from a SARS-CoV-2 infection. To additionally use this ACE2 decoy for elimination of virus infected cells, we equipped it with an epitope tag. Thus, it can be applied as adapter molecule in the modular platform technologies UniMAB and UniCAR, which already demonstrated great success in the setting of malignant diseases. As adapter molecule the ACE2 decoy is able to efficiently recruit either universal chimeric antigen receptor (UniCAR) modified T cells or, in combination with an anti-peptide epitope-anti-CD3 bispecific Ab of the UniMAB system, unmodified T cells to efficiently kill SARS-CoV-2 RBD expressing human cells.
Taken together, the ACE2 decoy represents a very promising immunotherapeutic drug for both SARS-CoV-2 variant neutralization and infected cell killing via the UniMAB and UniCAR system and might, therefore, clearly improve the treatment of COVID-19 patients.

  • Open Access Logo Abstract in refereed journal
    Human Gene Therapy 34(2023), 92
    Online First (2023) DOI: 10.1089

Publ.-Id: 37905

openPMD – the Open Standard for Particle-Mesh Data

Huebl, A.; Wan, L.; Lehe, R.; Podhorszki, N.; Gu, J.; Thévenet, M.; Schnetter, E.; Pöschel, F.; Bussmann, M.

The Open Standard for Particle-Mesh Data (openPMD) is a F.A.I.R. metadata standard for tabular (particle/dataframe) and structured mesh data in science and engineering.
We show the basic components of openPMD, its extensions to specific domains, applications from laser-plasma physics, particle accelerators, material physics to imaging and the ability to bridge multiple heterogeneous scientific models with a commonly-understood markup.

The openPMD-api builds upon established portable I/O formats such as HDF5 and ADIOS2, enabling workflows that scale from single-user computers up to Exascale simulations, in-transit data processing, 3D visualization, GPU-accelerated data analytics and AI/ML. openPMD links into the existing ecosystems of its scalable I/O backends and extends them with tooling that understands the openPMD data markup.
An overview over the openPMD ecosystem and community is shown.

Attention is given to recent developments in openPMD that interplay with HDF5, including mesh refinement and the Helmholtz Metadata Collaboration's HELPMI project which aims for an easier integration of openPMD with other HDF5-based standards, this way bringing openPMD closer to experiment workflows.


[1] Axel Huebl, Remi Lehe, Jean-Luc Vay, David P. Grote, Ivo F. Sbalzarini, Stephan Kuschel, David Sagan, Christopher Mayes, Frederic Perez, Fabian Koller, and Michael Bussmann. “openPMD: A meta data standard for particle and mesh based data,” DOI:10.5281/zenodo.591699 (2015)
[2] Homepage:
[3] GitHub Organization:
[4] Projects using openPMD:
[4] Reference API implementation: Axel Huebl, Franz Poeschel, Fabian Koller, and Junmin Gu. “openPMD-api 0.14.3: C++ & Python API for Scientific I/O with openPMD,” DOI:10.14278/rodare.1234 (2021)
[5] Selected earlier presentations on openPMD:
[6] Axel Huebl, Rene Widera, Felix Schmitt, Alexander Matthes, Norbert Podhorszki, Jong Youl Choi, Scott Klasky, and Michael Bussmann. “On the Scalability of Data Reduction Techniques in Current and Upcoming HPC Systems from an Application Perspective,” ISC High Performance 2017: High Performance Computing, pp. 15-29, 2017. arXiv:1706.00522, DOI:10.1007/978-3-319-67630-2_2
[7] Franz Poeschel, Juncheng E, William F. Godoy, Norbert Podhorszki, Scott Klasky, Greg Eisenhauer, Philip E. Davis, Lipeng Wan, Ana Gainaru, Junmin Gu, Fabian Koller, Rene Widera, Michael Bussmann, and Axel Huebl. Transitioning from file-based HPC workflows to streaming data pipelines with openPMD and ADIOS2, Part of Driving Scientific and Engineering Discoveries Through the Integration of Experiment, Big Data, and Modeling and Simulation, SMC 2021, Communications in Computer and Information Science (CCIS), vol 1512, 2022. arXiv:2107.06108, DOI:10.1007/978-3-030-96498-6_6
[8] The Helmholtz Metadata Collaboration's ongoing HELPMI project:

Keywords: F.A.I.R.; openPMD; HDF5; ADIOS2; HPC

  • Open Access Logo Lecture (Conference)
    2023 European HDF User Group (HUG) plugins and data compression summit, 19.-21.09.2023, Hamburg, Deutschland
  • Open Access Logo Invited lecture (Conferences)
    9. Annual MT Meeting, 09.-11.10.2023, Karlsruhe, Deutschland
  • Open Access Logo Poster
    9. Annual MT Meeting, 09.-11.10.2023, Karlsruhe, Deutschland
  • Open Access Logo Poster
    DMA ST1 synergy workshop, 08.-10.11.2023, Hamburg, Deutschland

Publ.-Id: 37902

On the anatomy and structural control of a dyke swarm that fed caldera-forming ignimbrite eruptions

Tomek, F.; Olšanská, I.; Trubač, J.; Cerny, J.; Rejšek, J.; Ackerman, L.

The evolution of eruptive vents related to calderas is not fully understood. We focus on a structural, rock-magnetic, and geochemical investigation of a ∼314 Ma rhyolite dyke swarm associated with the late-orogenic Altenberg–Teplice Caldera, Bohemian Massif, eastern Variscan belt. The whole-rock major element, trace element, and Nd–Pb isotope geochemistry along with the published U-Pb zircon geochronology link the extra-caldera dyke swarm with intra-caldera ignimbrites. The magnetic fabrics determined using the anisotropy of magnetic susceptibility are interpreted to record a continuum from magma ascent, emplacement, and eruption during sinistral shearing. The latter evidences an interplay with regional tectonics associated with the activity of crustal-scale shear zones. The sinistral kinematics and strike of the dyke swarm, the elongation of caldera intrusive units, and the kinematics of major caldera faults are consistent with the dextral Riedel shear system, where the dykes correspond to antithetic Ŕ/X-shears. Such a kinematic configuration implies that the maximum and minimum principal stresses were oriented roughly north-south and east-west, respectively. The relation between the stress field with respect to the caldera elongation and orientation is not typical. We suggest that a pre-existing mutually perpendicular set of cross-cutting structural lineaments largely controlled the magma chamber and caldera formation.

  • Journal of the Geological Society 180(2023), jgs2022-119
    Online First (2023) DOI: 10.1144/jgs2022-119

Publ.-Id: 37899

Datengestützte Intralogistik zur Optimierung von Aufbereitungs- & Recyclingprozessen

Nagel, M.; Rau, F.; Pereira, L.

Intralogistik gewinnt bei der Produktionssteuerung für die Organisation und Optimierung von Zulieferung und Warenumschlag stetig an Bedeutung. Darüber hinaus werden durch Intralogistik innerbetriebliche Materialflüsse und Informationsströme gesteuert und – wenn möglich – die Produktionslogistik intelligent gesteuert.

Die Intralogistik von Aufbereitungs- und Recyclingprozesse unterscheidet sich erheblich von der Intralogistik bei Produktionsprozessen. Bei Herstellung von Produkten und Halbzeugen sind Eigenschaften von Ausgangsmaterialien meist chargengenau bekannt. Während bei der Aufbereitung von Bergbauhalden oder dem Recycling die relevanten Stoffe in den Ausgangsmaterialien in ihrer Zusammensetzung, Qualität und Quantität höchst inhomogen verteilt und weitgehend unbekannt sind. Die Intralogistik bei solchen Prozessen ist hochkomplex und muss daher bei der dynamischen Analyse des Ausgangsmaterials beginnen und mit Ergebnissen des Aufbereitungsprozesses enden. Die Steuerung des Aufbereitungsprozesses muss dynamisch und datengesteuert angepasst werden.

Am Beispiel der Aufbereitung von Haldenmaterial mit Hilfe der Flotation soll die Verknüpfung der Datenerfassung des Aufgabegutes mit der Prozesssteuerung, der Intralogisitk und weiteren Verarbeitungs- und Optimierungsschritten gezeigt werden.

Keywords: DigiFloat

  • Lecture (Conference)
    Finden statt Suchen – agieren statt reagieren, 24.11.2023, Chemnitz, Deutschland

Publ.-Id: 37897

Changes to Captions: An Attentive Network for Remote Sensing Change Captioning

Shizhen, C.; Ghamisi, P.

In recent years, advanced research has focused on the direct learning and analysis of remote-sensing images using natural language processing (NLP) techniques. The ability to accurately describe changes occurring in multi-temporal remote sensing images is becoming increasingly important for geospatial understanding and land planning. Unlike natural image change captioning tasks, remote sensing change captioning aims to capture the most significant changes, irrespective of various influential factors such as illumination, seasonal effects, and complex land covers. In this study, we highlight the significance of accurately describing changes in remote sensing images and present a comparison of the change captioning task for natural and synthetic images and remote sensing images. To address the challenge of generating accurate captions, we propose an attentive changes-to-captions network, called Chg2Cap for short, for bi-temporal remote sensing images. The network comprises three main components: 1) a Siamese CNN-based feature extractor to collect high-level representations for each image pair; 2) an attentive encoder that includes a hierarchical self-attention block to locate change-related features and a residual block to generate the image embedding; and 3) a transformer-based caption generator to decode the relationship between the image embedding and the word embedding into a description. The proposed Chg2Cap network is evaluated on two representative remote sensing datasets, and a comprehensive experimental analysis is provided. The code and pre-trained models will be available online at .


Publ.-Id: 37894

BDD-Net+: A Building Damage Detection Framework Based on Modified Coat-Net

Seydi, S. T.; Hasanlou, M.; Chanussot, J.; Ghamisi, P.

The accurate and fast assessment of damaged buildings following a disaster is critical for planning rescue and reconstruction efforts. The damage assessment by the traditional methods is time-consuming and with limited performance. In this article, we propose an end-to-end deep-learning network named building damage detection network-plus (BDD-Net+). The BDD-Net+ is based on a combination of convolution layers and transformer blocks. The proposed framework takes the advantage of the multiscale residual convolution blocks and self-attention layers. The proposed framework consists of four main steps: data preparation, model training, damage map generation and evaluation, and the use of an explainable artificial intelligence (XAI) framework for understanding and interpretation of the operation model. The experimental results include two representative real-world benchmark datasets (i.e., the Haiti earthquake and the Bata explosion). The obtained results illustrate that BDD-Net+ achieves excellent efficacy in comparison with other state-of-the-art methods. Furthermore, the visualization of the results by XAI shows that BDD-Net+ provides more interpretable and explainable results for damage detection than the other studied methods.

  • Open Access Logo IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 16(2023), 4232-4247
    DOI: 10.1109/JSTARS.2023.3267847

Publ.-Id: 37893

X-ray Thomson Scattering as a high-precision tool for Warm Dense Matter diagnostics

Dornheim, T.

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 talk, I will explain how we can use X-ray Thomson scattering (XRTS) measurements [2] to infer important system parameters such as the temperature, density, and degree of ionization. Interestingly, standard forward modeling methods based on the widespread Chihara decomposition have neglected transitions between free and bound electrons (the inverse process of the usual bound-free transitions), which are negligible at ambient conditions, but become important in the WDM regime [3]. In addition, I will show how switching to the imaginary-time representation opens up new avenues towards the model-free interpretation of XRTS signals, and gives one direct access to the temperature [4,5] and electronic correlations [6] of the system. Finally, I will outline new PIMC capabilities [7,8] that allow for quasi-exact simulations of experiments conducted at the Gbar platform at the National Ignition Facility (NIF) in Livermore.

[1] M. Bonitz et al, Physics of Plasmas 27, 042710 (2020)
[2] S. Glenzer and R. Redmer, Reviews of Modern Physics 81, 1625 (2009)
[3] M. Böhme et al, arXiv:2306.17653 (submitted)
[4] T. Dornheim et al, Nature Communications 13, 7911 (2022)
[5] T. Dornheim et al, Physics of Plasmas 30, 042707 (2023)
[6] T. Dornheim et al, arXiv:2305.15305 (submitted)
[7] M. Böhme et al, Physical Review Letters 129, 066402 (2022)
[8] T. Dornheim et al, Journal of Chemical Physics 159, 164113 (2023)

  • Lecture (others)
    GSI Plasmaphysik-Seminar, 28.11.2023, Darmstadt, Deutschland

Publ.-Id: 37891

Hyperspectral Remote Sensing Benchmark Database for Oil Spill Detection With an Isolation Forest-Guided Unsupervised Detector

Duan, P.; Kang, X.; Ghamisi, P.; Li, S.

Oil spill detection has attracted increasing attention in recent years, since marine oil spill accidents severely affect environments, natural resources, and the lives of coastal inhabitants. Hyperspectral remote sensing images provide rich spectral information which is beneficial for the monitoring of oil spills in complex ocean scenarios. However, most of the existing approaches are based on supervised and semi-supervised frameworks to detect oil spills from hyperspectral images (HSIs), which require a massive amount of effort to annotate a certain number of high-quality training sets. In this study, we make the first attempt to develop an unsupervised oil spill detection method based on isolation forest (iForest) for HSIs. First, a Gaussian statistical model is designed to remove the bands corrupted by severe noise. Then, kernel principal component analysis (KPCA) is employed to reduce the high dimensionality of the HSIs. Next, the probability of each pixel belonging to one of the classes of seawater and oil spills is estimated with the iForest, and a set of pseudolabeled training samples is automatically produced using the clustering algorithm on the detected probability. Finally, an initial detection map can be obtained by performing the support vector machine (SVM) on the dimension-reduced data, and the initial detection result is further optimized with the extended random walker (ERW) model so as to improve the detection accuracy of oil spills. Experiments on hyperspectral oil spill database (HOSD) created by ourselves demonstrate that the proposed method obtains superior detection performance with respect to other state-of-the-art detection approaches. We will make HOSD and our developed library for oil spill detection publicly available at to further promote this research topic.


Publ.-Id: 37889

Report on research data management interviews conducted for HMC Hub Energy in 2022

Ballani, F.; Schaller, T.; Steinmeier, L.; Koubaa, M. A.; Schweikert, J.; Stucky, K.-U.; Süß, W.

The Energy Hub of the Helmholtz Metadata Collaboration (HMC) conducted interviews with various stakeholders from the Helmholtz Research Field Energy on the topic of research data management (RDM) in 2022. The intentions were to build and serve a metadata community in the energy research field and to extend the Helmholtz-wide survey conducted by HMC in 2021 Arndt et al., 2022). Besides the deeper insight into the current state of RDM and metadata handling at the Helmholtz sites relevant to the Energy Hub the interviews focused on the related needs and difficulties of researchers and their satisfaction with the current state. Furthermore, we tried to discover already existing workflows and software solutions, to establish contacts and to make HMC better known.

Keywords: Helmholtz Metadata Collaboration; Research data management

Publ.-Id: 37881

Data publication: Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser

Krása, J.; Burian, T.; Hájková, V.; Chalupský, J.; Jelínek, Š.; Frantálová, K.; Krupka, M.; Kuglerová, Z.; Kumar Singh, S.; Vozda, V.; Vyšín, L.; Smid, M.; Perez-Martin, P.; Kühlman, M.; Pintor, J.; Cikhardt, J.; Dreimann, M.; Eckermann, D.; Rosenthal, F.; Vinko, S. M.; Forte, A.; Gawne, T. D.; Campbell, T.; Ren, S.; Shi, Y.; Hutchinson, T.; Humphries, O. S.; Preston, T.; Makita, M.; Nakatsutsumi, M.; Pan, X.; Köhler, A.; Harmand, M.; Toleikis, S.; Falk, K.; Juha, L.

Data set on the ion emission of different materials. Each dataset is separate and titled with the chemical symbol or abbreviation of the specific material.

Related publications


Publ.-Id: 37880

Effect of Chain Length on Swelling Transitions of Brodie Graphite Oxide in Liquid 1-Alcohols

Iakunkov, A.; Nordenström, A.; Boulanger, N.; Li, G.; Hennig, C.; Jørgensen, M. R. V.; Kantor, I.; Talyzin, . A. V.

Swelling is the most fundamental property of graphite oxides (GO). Here, a structural study of Brodie graphite oxide (BGO) swelling in a set of long chain 1-alcohols (named C11 to C22 according to the number of carbons) performed using synchrotron radiation X-ray diffraction at elevated temperatures is reported. Even the longest of tested alcohols (C22) is found to intercalate BGO with enormous expansion of the interlayer distance from ≈6Å up to ≈63Å, the highest expansion of GO lattice ever reported. Swelling transitions from low temperature alpha-phase to high temperature beta-phase are found for BGO in all alcohols in the C11–C22 set. The transitions correspond to decrease of inter-layer distance correlating with the length of alcohol molecules, and change in their orientation from perpendicular to GO planes to layered parallel to GO (Type II transitions). These transitions are very different compared to BGO swelling transitions (Type I) found in smaller alcohols and related to insertion/de-insertion of additional layer of alcohol parallel to GO. Analysis of general trends in the whole set of 1-alcohols (C1 to C22) shows that the 1-alcohol chain length defines the type of swelling transition with Type I found for alcohols with C<10 and Type II for C>10.

Related publications

Publ.-Id: 37879

Ion Irradiation-Induced Sinking of Ag Nanocubes into Substrates

Choupanian, S.; Möller, W.; Seyring, M.; Pacholski, C.; Wendler, E.; Undisz, A.; Ronning, C.

Ion irradiation can cause burrowing of nanoparticles in substrates, strongly depending on the material properties and irradiation parameters. In this study, it is demonstrated that the sinking process can be accomplished with ion irradiation of cube-shaped Ag nanoparticles on top of silicon; how ion channeling affects the sinking rate; and underline the importance of the amorphous state of the substrate upon ion irradiation. Based on these experimental findings, the sinking process is described as being driven by capillary forces enabled by ion-induced plastic flow of the substrate.

Publ.-Id: 37872

Experimentelle und rechnerische Bestimmung der Aktivierung für die Rückbauplanung von Kernkraftwerken

Barkleit, A.; Rachamin, R.; Pönitz, E.; Konheiser, J.

Vorstellung der FORKA-Projekte EMPRADO und WERREBA

  • Lecture (Conference)
    55. Kraftwerkstechni­sches Kolloquium, 10.-11.10.2023, Dresden, Deutschland

Publ.-Id: 37871

Comparative structural and (radio-)chemical investigations of activated cement and concrete samples

Zilbermann, M. E.

To help with the decommissioning of the unit 2 of the Greifswald NPP, this study aims at determining the activities of 3H, 14C, 60Co, 152Eu and 154Eu in the concrete to estimate the maximal activity in the entire bioshield.
The study will focus on the activity as a function of depth in the concrete layer, as well as composition of the mineral phases. As the flux of neutrons generated during fission reaction encounters the mineral phases of concrete, the natural elements present in these phases absorb neutrons, which leads to the formation of their radioactive isotopes. Therefore, the elemental composition of each mineral phase in the concrete is important in the activation process, and the concrete being a heterogeneous material, different phases will present different activities.
A precise knowledge of the activities and of the elemental composition of the concrete and its mineral phases helps refining the models to calculate and predict the activities in a long-term scale. The calculations and the experimental results support the sorting of the materials for disposal.
This study will analyze the concrete with three main objectives:

  • Activation;
  • Chemical composition;
  • Structure of the concrete and mineral phases.
  • Master thesis
    TU Dresden, 2023
    Mentor: Prof. Dr. Thorsten Stumpf, Dr. Astrid Barkleit

Publ.-Id: 37870

On the missing single collision peak in low energy heavy ion scattering

Wilhelm, R. A.; Deuzeman, M. J.; Rai, S.; Husinsky, W.; Szabo, P. S.; Biber, H.; Stadlmayr, R.; Cupak, C.; Hundsbichler, J.; Lemell, C.; Möller, W.; Mutzke, A.; Hobler, G.; Versolato, O. O.; Aumayr, F.; Hoekstra, R.

We present experimental and simulation data on the oblique angle scattering of heavy Sn ions at 14 keV energy from a Mo surface. The simulations are performed with the binary collision approximation codes TRIM, TRIDYN, TRI3DYN, SDTrimSP, and IMSIL. Additional simulations were performed in the molecular dynamics framework with LAMMPS. Our key finding is the absence of an expected peak in the experimental energy spectrum of backscattered Sn ions associated with the pure single collision regime. In sharp contrast to this, however, all simulation codes we applied do show a prominent single collision signature both in the energy spectrum and in the angular scatter pattern. We discuss the possible origin of this important discrepancy and show in the process, that widely used binary collision approximation codes may contain hidden parameters important to know and to understand.

Keywords: Binary collision approximation; Heavy ions; Ion scattering; Molecular dynamics

Publ.-Id: 37866

Post growth thermal treatments of Si1-x-yGexSny alloys

Steuer, O.; Schwarz, D.; Oehme, M.; Ganss, F.; Khan, M. M.; Cheng, Y.; Rebohle, L.; Zhou, S.; Helm, M.; Cuniberti, G.; Georgiev, Y.; Prucnal, S.

Si1-x-yGexSny alloys are promising materials for future applications in opto- and
nanoelectronics. These alloys enable effective band gap engineering, a broad
adjustability of the lattice parameter, exhibit much higher carrier mobility than pure Si
and are compatible with CMOS technology. Unfortunately, the equilibrium solid
solubility of Sn in Si1-xGex is less than 1% and pseudomorphic growth of Si1-xyGexSny
on Ge or Si causes in-plane compressive strain in the grown layer, which
degrades the superior properties of the alloys. Therefore, the post-growth strain
engineering using ultrafast non-equilibrium thermal treatments like flash lamp
annealing (FLA) or pulsed laser annealing (PLA) to improve the layer quality is
needed. In this contribution, we discuss the influence of millisecond FLA and
nanosecond PLA on Si1-x-yGexSny alloys and present an efficient way to improve
the layer quality of thin film Si1-x-yGexSny on insulator by PLA. Different Si1-xyGexSny
alloys are directly grown on commercial silicon-on-insulator (SOI) wafers
and treated by FLA or PLA. The material is analysed by micro-Raman spectroscopy,
Rutherford backscattering spectrometry (RBS) and X-ray diffraction (XRD) before
and after the thermal treatments. It is shown that after annealing, the material is
single-crystalline with much better crystallinity than the as-grown layer.

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  • Poster
    E-MRS 2023 Spring Meeting, 29.05.-02.06.2023, Strasbourg, Frankreich

Publ.-Id: 37864

Comparando las estimaciones de selección de hábitat mediante modelos de distribución de especies y step selection functions

Saraiva De Menezes, J. F.

Recently, two methods of habitat selection have gained more relevance in the scientific literature: step selection functions (SSF) and MaxEnt. Despite their similarity these models are hardly ever used in the same context. The former is usually associated with studies based in movement ecology, and the latter is connected to species distribution modeling. Motivated by the difficulty in estimating habitat preferences using SSF, I compared the accuracy of predictions from both models based on movement data. As a case study, I utilized jaguar movement data from 5 countries in Latin American and created SSF and MaxEnt models based on climatic data and land use available from WorldClim and satellite imagery. I compared the accuracy of both types of models using the “Area Under Curve” (AUC) metric, on a separate subset of data. SSF models presented an average AUC of 0.5510 ± 0.0147 in comparison with 0.7544 ± 0.0185 of their MaxEnt equivalents. I believe those differences are partially caused by the convergence difficulties of SSF and conditional logistic regression. Consequently, I recommend the use of MaxEnt in predictive modelling, such as the ones needed in reserve and corridor design.

Keywords: Latin America; Jaguars; niche modelling; resource selection function; trajectory

Publ.-Id: 37859

Example data Publication Data Management Day

Fiedler, M.; Müller, S.; Knodel, O.

"This dataset is a multiyear mean Southern Ocean freshwater flux field that uses recently compiled measurements of ice sheet melting, iceberg calving, icerberg tracking, and river runoff"

Keywords: Test; Data; Publication; Data Management Day


Publ.-Id: 37854

Using Julia to Accelerate Monte Carlo Event Generation with Neural Importance Sampling

Jungnickel, T.; Steiniger, K.; Bussmann, M.; Hernandez Acosta, U.

Monte Carlo event generation is essential for analysis in high energy physics and fast implementations are required to keep up with the large amounts of data measured by experiments. Therefore, these methods need to reflect the theoretical predictions accurately to enable efficient data generation, e.g. by rejection sampling. However, traditional importance sampling algorithms, such as the commonly used VEGAS algorithm, often struggle with adapting targets with multiple or non-coordinate aligned features, as is common in high energy physics. Especially in strong-field QED, processes dynamically depend on field parameters, which means the use of established codes for these problems needs to be questioned. An importance sampling approach using neural networks applied to strong-field processes is presented within the framework QED.jl. The quality of the generated proposals, e.g. the unweighting efficiency, is compared to VEGAS, providing insights beneficial to applications beyond strong-field QED.

Keywords: strong field QED; machine learning; Julia; QED.jl; neural importance sampling

  • Lecture (Conference)
    JuliaHEP 2023, 06.-09.11.2023, Erlangen, Deutschland

Publ.-Id: 37848

Investigation of Mixing using Microfocus X-ray Computed Tomography (µCT)

Baecke, A. M.

Fine-grained solid particles from various industrial sources, which would otherwise be discarded, should ideally be processed to valuable products or inert residues. Among others, a) shredder fines from electronics and end-of-life vehicles, and b) flue dusts from non-ferrous metallurgical processes are of timely interest. They contain valuable residuals, such as metals, that can be returned to the industrial cycle instead of being landfilled. This is one aim of the Helmholtz project FINEST in which this work is embedded. In this work, mixing and agglomeration of such particles with a size below 1 mm are investigated for further use in the metallurgical industry. Different particle sizes and densities are considered. The process is observed experimentally using camera imaging technique and µCT. From the µCT images a mixing index is acquired. We present an experimental setup and methods for the aforementioned investigations.

Keywords: Microfocus X-Ray Computed Tomography; Particle Flow; Mixing and Segregation

  • Lecture (Conference)
    Bałdyga Technical Seminars - Mixing meets reality, 14.-15.09.2023, Berlin, Deutschland

Publ.-Id: 37846

Accelerating Event Generation in Strong-Field QED with Neural Importance Sampling

Jungnickel, T.; Steiniger, K.; Hernandez Acosta, U.; Bussmann, M.

Efficient Monte Carlo integreation is crucial for modeling processes at the European XFEL. However, traditional approaches to importance sampling like VEGAS do not perform well when integrands display multiple features or non-coordinate aligned features. In this work, we present an implementation of neural importance sampling (NIS) in the Julia programming language to address this challenge. We demonstrate the effectiveness of NIS by applying it to processes in strong-field QED at high energies, showing superior adaption of the integrand and thus enabling efficient event generation.

Keywords: strong field QED; machine learning; Julia; QED.jl; neural importance sampling

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

Publ.-Id: 37845

Probing Iron in Earth's Core With Molecular-Spin Dynamics

Nikolov, S.; Ramakrishna, K.; Rohskopf, A.; Lokamani, M.; Tranchida, J.; Carpenter, J.; Cangi, A.; Wood, M. A.

Dynamic compression of iron to Earth-core conditions is one of the few ways to gather important elastic and transport properties needed to uncover key mechanisms surrounding the geodynamo effect. Herein a new machine-learned ab-initio derived molecular-spin dynamics (MSD) methodology with explicit treatment for longitudinal spin-fluctuations is utilized to probe the dynamic phase-diagram of iron. This framework uniquely enables an accurate resolution of the phase-transition kinetics and Earth-core elastic properties, as highlighted by compressional wave velocity and adiabatic bulk moduli measurements. In addition, a unique coupling of MSD with time-dependent density functional theory enables gauging electronic transport properties, critically important for resolving geodynamo dynamics.

Keywords: Molecular dynamics; Density functional theory; Machine Learning; Phase transitions; Geodynamo

Publ.-Id: 37844

Critical review on production, characterization and applications of microalgal hydrochar: Insights on circular bioeconomy through hydrothermal carbonization

Supraja, K. V.; Doddapaneni, T. R. K. C.; Ramasamy, P. K.; Kaushal, P.; Ahammad, S. Z.; Pollmann, K.; Jain, R.

Exploitation of microalgal biomass as a valuable resource is hindered by the challenges associated with high downstream
processing costs, including biomass harvesting, drying, and product extraction. Direct utilization of microalgae as a solid fuel
source, soil conditioner, capacitor or adsorbent material raises environmental concerns. Hydrothermal carbonization (HTC)
is a highly efficient and promising technology for microalgal biomass conversion. This comprehensive review provides an indepth
understanding of the HTC reaction mechanisms involved in microalgal hydrochar production, shedding light on the
underlying processes and factors affecting the quality of hydrochar. HTC has the potential to improve fixed carbon content,
thermal stability and nutrient availability in the resulting hydrochar. Furthermore, this review explores the integration of HTC
with anaerobic digestion (AD) to establish a circular bioeconomy, thereby promoting sustainability in energy generation. The
synergistic combination offers a promising approach for the efficient utilization of microalgal biomass, where hydrochar can
serve as a renewable energy source while the aqueous fraction can be utilized as a nutrient-rich feedstock for biogas
production. By highlighting the potential benefits and futuristic directives associated with microalgal biomass valorisation
through HTC, this review aims to contribute to the development of sustainable waste management strategies for recovery of
value-added compounds from microalgae. Ultimately, this review strives to foster the transition towards a more
environmentally friendly and resource-efficient bioeconomy.

Keywords: Algae; Anaerobic digestion; Bioconversion; Biomass; Carbonization; Microorganisms; Nutrients; Soils


  • Secondary publication expected from 01.10.2024

Publ.-Id: 37842

Rohstoffe und Ressourcen

Möckel, R.

Im Vortrag geht es um Resourcen und Rohstoffe, Einteilung, Kritikalität, circular economy, Recycling und Alternativen, sowie als Beispiel um Seltene Erden

  • Lecture (others)
    Schulische Veranstaltung, 27.10.2023, Chemnitz, Montessori-Gymnasium, Deutschland

Publ.-Id: 37839

Mineralogy, Geochemistry, and Genesis of Agates from Chihuahua, Northern Mexico

Mrozik, M.; Götze, J.; Pan, Y.; Möckel, R.

The present study aimed to investigate the genesis and characteristics of some of the world-famous agate deposits in the state of Chihuahua, Mexico (Rancho Coyamito, Ojo Laguna, Moctezuma, Huevos del Diablo, Agua Nueva). Geochemical and textural studies of host rocks showed that all the studied deposits are related to the same rock type within the geological unit of Rancho el Agate andesite, a quartz-free latite that shows clear indications of magma mixing. As a result of their large-scale distribution and various differentiation processes, as well as transport separation, different textures and local chemical differences between rocks of different localities can be observed. These differences have also influenced the properties of SiO2 mineralization in the rocks. The mixing of near-surface fluids from rock alterations with magmatic hydrothermal solutions led to the accumulation of various elements in the SiO2 matrix of the agates, which were, on the one hand, mobilized during secondary rock alteration (Fe, U, Ca, K, Al, Si) and, on the other hand, transported with magmatic fluids (Zn, Sb, Si, Zr, Cr). Different generations of chalcedony indicate a multi-stage formation as well as multiple cycles of filling the cavities with fluids. The hydrothermal fluids are presumably related to the residual solutions of a rhyolitic volcanism, which followed the latitic extrusions in the area and probably caused the formation of polymetallic ore deposits in the Chihuahua area. The enrichment of highly immobile elements indicates the involvement of volatile fluids in the agate formation. The vivid colors of the agates are almost exclusively due to various mineral inclusions, which consist mainly of iron compounds.

Keywords: agate; chalcedony; trace elements; EPR spectroscopy; silica minerals; agate colors; cathodoluminescence; geology; Rancho Coyamito; Ojo laguna; Moctezuma; Agua Nueva

Publ.-Id: 37838

A new approach to model the fluid dynamics in sandwich packings

Franke, P.; Shabanilemraski, I.; Schubert, M.; Hampel, U.; Kenig, E. Y.

Sandwich packings represent new separation column internals, with a potential to intensify mass
transfer. They comprise two conventional structured packings with different specific geometrical surface areas.
In this work, the complex fluid dynamics in sandwich packings is modeled using a novel approach based on a onedimensional,
steady momentum balance of the liquid and gas phases. The interactions between the three present
phases (gas, liquid, and solid) are considered by closures incorporated into the momentum balance. The
formulation of these closures is derived from two fluid-dynamic analogies for the film and froth flow patterns.
The adjustable parameters in the closures are regressed for the film flow using dry pressure drop measurements
and liquid hold-up data in trickle flow conditions. For the froth flow, the tuning parameters are fitted to overall
pressure drop measurements and local liquid hold-up data acquired from ultra-fast X-ray tomography (UFXCT).
The model predicts liquid hold-up and pressure drop data with an average relative deviation of 16.4 % and 19 %,
respectively. Compared to previous fluid dynamic models for sandwich packings, the number of adjustable
parameters could be reduced while maintaining comparable accuracy.

Keywords: sandwich packings; modeling; tomography; fluid dynamics


Publ.-Id: 37836

Data publication: Fluid Transport in Ordinary Portland Cement and Slag Cement from in-situ Positron Emission Tomography

Reiss, A.; Kulenkampff, J.; Fischer, C.
RelatedPerson: Gruhne, Stefan; RelatedPerson: Lösel, Dagmar; RelatedPerson: Schößler, Claudia

Supplemental Primary PET Data to Fluid Transport in Ordinary Portland Cement and Slag Cement from in-situ Positron Emission Tomography Reiss, A.; Kulenkampff, J.; Bar-Nes, G.; Fischer, C.; Emmanuel, S. Submitted to Cement and Concrete Research 02.11.24 Material and procedure are characterized in the paper. PET data are supplied in Interfile format (Original: Cradduck T.D., Bailey D.L., Hutton BF, Deconinck F., Busemann Sokole E., Bergmann H., Noelpp U.: “A standard protocol for the exchange of nuclear medicine image files. Nucl Med Commun; 10:703-713 (1989), used version: The interfile format includes an ASCII header file (.hv) and a binary file containing the volume data (.v). Import filters exist for many visualization frameworks (e.g. Matlab, Avizo); otherwise the binary data files can be imported as raw data, taking into account the format given in the header file. The header tags were extended for relevant experimental parameters of non-medical PET experiments and in this way serve as experimental protocol. List of data files: cem1_F-18.7z: 17 PET frames from the 18F intrusion experiment cem1_Cu-64.7z: 31 PET frames from the 64Cu intrusion experiment cem1_I-124.7z: 34 PET frames from the 124I intrusion experiment The PET data sets (LMFs) were acquired with a tilted ClearPET-scanner (Elysia-Raytest) with a vertical axis of the cylindrical FOV at HZDR. The “trues”-projections were corrected for attenuation and scatter with a procedure based on the STIR-library (, version 3.0, Kris Thielemans, Charalampos Tsoumpas, Sanida Mustafovic, Tobias Beisel, Pablo Aguiar, Nikolaos Dikaios, and Matthew W Jacobson, STIR: Software for Tomographic Image Reconstruction Release 2, Physics in Medicine and Biology, 57 (4), 2012 pp.867-883).

Keywords: Positron Emission Tomography (PET); Imbibition; Cement paste; Fluid transport


Publ.-Id: 37835

Large-Scale Formation of DNA Origami Lattices on Silicon

Tapio, K.; Kielar, C.; Parikka, J. M.; Keller, A.; Järvinen, H.; Fahmy, K.; Jussi Toppari, J.

In recent years, hierarchical nanostructures have found applications in fields like diagnostics, medicine, nano-optics, and nanoelectronics, especially in challenging applications like the creation of metasurfaces with unique optical properties. One of the promising materials to fabricate such nanostructures has been DNA due to its robust self-assembly properties and plethora of different functionalization schemes. Here, we demonstrate the assembly of a two-dimensional fishnet-type lattice on a silicon substrate using cross-shaped DNA origami as the building block, i.e., tile. The effects of different environmental and structural factors are investigated under liquid atomic force microscopy (AFM) to optimize the lattice assembly. Furthermore, the arm-to-arm binding affinity of the tiles is analyzed, revealing preferential orientations. From the liquid AFM results, we develop a methodology to produce closely-spaced DNA origami lattices on silicon substrate, which allows further nanofabrication process steps, such as metallization. This formed polycrystalline lattice has high surface coverage and is extendable to the wafer scale with an average domain size of about a micrometer. Further studies are needed to increase the domain size toward a single-crystalline large-scale lattice.

Publ.-Id: 37834

Pulsed interactions unify reaction-diffusion and spatial nonlocal models for biological pattern formation

Colombo, E. H.; Martinez Garcia, R.; Calabrese, J.; López, C.; Hernández-García, E.

The emergence of a spatially-organized population distribution depends on the dynamics of the population and mediators of interaction (activators and inhibitors). Two broad classes of models have been used to investigate when and how self-organization is triggered, namely, reaction-diffusion and spatially nonlocal models. Nevertheless, these models implicitly assume smooth propagation scenarios, neglecting that individuals many times interact by exchanging short and abrupt pulses of the mediating substance. A recently proposed framework advances in the direction of properly accounting for these short-scale fluctuations by applying a coarse-graining procedure on the pulse dynamics. In this paper, we generalize the coarse-graining procedure and apply the extended formalism to new scenarios in which mediators influence individuals' reproductive success or their motility. We show that, in the slow- and fast-mediator limits, pulsed interactions recover, respectively, the reaction-diffusion and nonlocal models, providing a mechanistic connection between them. Furthermore, at each limit, the spatial stability condition is qualitatively different, leading to a timescale-induced transition where spatial patterns emerge as mediator dynamics becomes sufficiently fast.

Keywords: self-organization; population dynamics; pattern formation; animal communication

Publ.-Id: 37832

Preparation of Volborthite by a Facile Synthetic Chemical Solvent Extraction Method

Sánchez-Loredo, M. G.; Palomares-Sánchez, S. A.; Labrada-Delgado, G. J.; Helbig, T.; Chekhonin, P.; Ebert, D.; Möckel, R.; Owusu Afriyie, J.; Kelly, N.

In this work, the extraction of vanadium (V) ions from an alkaline solution using a commercial quaternary ammonium salt and the production of metal vanadates through precipitation stripping were carried out. The crystallization of copper vanadates from the extracts was performed using a solution containing a copper(II) source in concentrated chloride media as a stripping agent. In an attempt to control growth, a stabilizing polymer (polyvinylpyrrolidone, PVP) was added to the stripping solution. The structural characteristics of the crystallized products, mainly copper pyrovanadate (volborthite, Cu3V2O7(OH)2·(H2O)2) nanoflakes and nanoflowers and the experimental parameter influencing the efficiency of the stripping process were studied. From the results, the synthesis of nanostructured vanadates is a simple and versatile method for the fabrication of valuable three-dimensional structures providing abundant active zones for energy and catalytic applications.

Keywords: vanadium(V) extraction; anion exchange; quaternary ammonium salt; precipitation stripping; nanostructured vanadates; volborthite; polyvinylpyrrolidone

Publ.-Id: 37830

Geochemistry and formation of agate-bearing lithophysae in Lower Permian volcanics of the NW-Saxonian Basin (Germany)

Götze, J.; Möckel, R.; Pan, Y.; Müller, A.

Geochemical and mineralogical investigations of the Lower Permian Kemmlitz rhyolite within the NW-Saxonian Basin
(Germany) and associated lithophysae (high-temperature crystallization domains) as well as agates were carried out to
constrain the genesis and characteristics of these volcanic rocks and the origin of the agate-bearing lithophysae. The
volcanic rocks of rhyolitic composition are dominated by quartz, sanidine, and orthoclase and most likely derive from lava
flows. Agate-bearing lithophysae were exclusively formed in a glassy facies (pitchstone) of the rhyolites, which was
afterwards altered to illite-smectite mixed-layer clays. The results of this study show that agate formation can be related to
the alteration of the volcanic rocks accompanied by the infill of mobilized silica into cavities of lithophysae. Fluid inclusion
studies point to temperatures of agate formation above 150 °C, indicating that the mobilization and accumulation of silica
started already during a late phase of or soon after the volcanic activities. Remarkable high concentrations of B (29 ppm),
Ge (> 18 ppm), and U (> 19 ppm) as well as chondrite-normalized rare earth element (REE) distribution patterns of the
agates with pronounced negative Eu-anomalies, slightly positive Ce-anomalies and enriched heavy rare earth elements
(HREE) indicate interactions of the host rocks and transport of SiO2 with magmatic volatiles (F/Cl, CO2) and heated
meteoric water. Characteristic yellow cathodoluminescence (CL), heterogeneous internal textures as well as high defect
density of micro- and macrocrystalline quartz detected by electron paramagnetic resonance (EPR) spectroscopy point to
crystallization processes via an amorphous silica precursor under non-equilibrium conditions.

Keywords: Agate; Geochemistry; Lithophysae; Permian rhyolites; Quartz

Publ.-Id: 37829

Neutron radiography of liquid foam structure near a vertical wall

Skrypnik, A.; Knüpfer, L.; Trtik, P.; Tholan, V.; Parkes, S.; Heitkam, S.

At a solid boundary, the structural formation of bubbles is different from that in the bulk of a liquid foam. The presence of a solid boundary imposes additional constraints, resulting in a crystalline arrangement of the bubbles. For dry and monodisperse foam, the Kelvin and Fejes-T ́ oth structure is expected in the vicinity of the wall, while a random ordering should occur in the bulk. In this study, we investigate the transition from a crystalline to a random structure near a vertical wall located in the middle of a flat foam cell. The corresponding layering of the liquid was quantified by measuring the distribution of liquid fraction within the cell using neutron radiography. The amplitude of the liquid fraction distribution and its decay with distance from the solid boundary were correlated with the foam bubble size and polydispersity. Furthermore, by applying forced drainage, we measured the corresponding permeability and wetting front velocity near the vertical wall. We found that the crystalline sorting reduces the permeability and wetting front velocity compared to a randomly packed foam.

Keywords: Neutron Radiography; Foam

Publ.-Id: 37827

A comparative study on the measurement of surface bubble size distributions in dry aqueous foams using optical methods

Knüpfer, L.; Eckert, K.; Heitkam, S.

The measurement of bubble sizes in aqueous foams based on images of the surface is a typical method used in laboratory and industrial scales. In this article the relationship between the size distribution of the facet areas and the bubble size of wall-touching bubbles is investigated. To achieve this an invasive sampling approach is used for in-situ collection of wall-touching bubbles in dry foams, while the surface is imaged in parallel. Bubble and facet
size distributions are obtained using automated image processing. It is shown that sharp peaks in the bubble size distribution will appear smoother in the facet size distribution. This results in an overestimation of polydispersity by the surface measurements. Furthermore, it is observed that the mean equivalent diameter of the facets is on average 6% smaller than the bubble diameter obtained using the sampling method. An approach proposed by
Wang and Neethling (Colloids Surf. A: Physicochem. Eng. Asp. 33, 73-81 (2009)) gives a good approximation of the relation between facet and bubble size and can be used to reduce potential uncertainties in surface based bubble size measurements.

Keywords: Foam; Bubble Size; Optical Measurement

Publ.-Id: 37825

Investigating the effect of multiple particle properties on the separation of ultrafine particles via froth flotation by means of MLA and multivariate Tromp maps

Sygusch, J.; Rudolph, M.

Although, the wettability is the most prominent separation feature in froth flotation, other particle properties, such as size or morphology also affect the separation process since it includes a number of complex micro processes with specific particle-bubble interactions that occur in the pulp and in the froth phase. A novel separation apparatus is used that combines the advantages of a mechanical flotation cell (high particle-bubble collision rate) with those from a flotation column (fractionating effect of the deep froth). A well-characterised model system of ultrafine particles (< 10 µm), consisting of glass spheres and glass fragments as the floatable fraction and magnetite as the non-floatable fraction is used for the separation tests. Based on image analysis bivariate tromp maps are computed which reveal the combined effect of the particle properties of size and shape on the separation behaviour of ultrafine particles.

Keywords: Ultrafine particles; Multidimensional separation; Flotation; Multivariate Tromp maps

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

Publ.-Id: 37824

Unit and Integration testing in modularized Julia package eco-systems

Ehrig, S.

In high-energy physics, we want to simulate complex physical processes that require computational resources of the fastest HPC systems in the world. In order to fully use the computational resources, software that is maintainable, performant and extensible is required. To achieve these goals, automated testing is essential.
Modern Julia HEP software is modularized into sub-packages to improve maintainability and extensibility. This creates new challenges for automated testing. Unit tests and integration tests are required. If the code of one package is changed, unit tests ensure that the package is still working, whereas integration tests ensure that in dependent packages no functionality break is caused by the change.
Using the QED.jl [1] project as an example, I will demonstrate how we implemented unit and integration tests for the main QED.jl package and its sub-packages.


Keywords: Julia; Integration Tests; QED.jl; Automatic Testing

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


Publ.-Id: 37823

Ion emission from warm dense matter produced by irradiation with a soft x-ray free-electron laser

Krása, J.; Burian, T.; Hájková, V.; Chalupský, J.; Jelínek, Š.; Frantálová, K.; Krupka, M.; Kuglerová, Z.; Kumar Singh, S.; Vozda, V.; Vyšín, L.; Smid, M.; Perez-Martin, P.; Kühlman, M.; Pintor, J.; Cikhardt, J.; Dreimann, M.; Eckermann, D.; Rosenthal, F.; Vinko, S. M.; Forte, A.; Gawne, T. D.; Campbell, T.; Ren, S.; Shi, Y.; Hutchinson, T.; Humphries, O. S.; Preston, T.; Makita, M.; Nakatsutsumi, M.; Pan, X.; Köhler, A.; Harmand, M.; Toleikis, S.; Falk, K.; Juha, L.

We report on an experiment performed at the FLASH2 free-electron laser (FEL) aimed at producing warm dense matter via soft x-ray isochoric heating. In the experiment, we focus on study of the ions emitted during the soft x-ray ablation process using time-of-flight electron multipliers and a shifted Maxwell–Boltzmann velocity distribution model. We find that most emitted ions are thermal, but that some impurities chemisorbed on the target surface, such as protons, are accelerated by the electrostatic field created in the plasma by escaped electrons. The morphology of the complex crater structure indicates the presence of several ion groups with varying temperatures. We find that the ion sound velocity is controlled by the ion temperature and show how the ion yield depends on the FEL radiation attenuation length in different materials.

Related publications

  • Open Access Logo Matter and Radiation at Extremes 9(2024)1, 016602
    Online First (2023) DOI: 10.1063/5.0157781

Publ.-Id: 37822

Synthesis and characterization of lanthanide and actinide doped zirconates

Richter, S.; Gilson, S.; Braga Ferreira Dos Santos, L.; Stumpf, T.; Huittinen, N. M.

Zirconium dioxide is a corrosion product of the Zircaloy cladding, which houses the nuclear fuel pellets. It can form solid solutions with uranium as well as fission and activation products. Moreover, ZrO2 and other zirconium bearing crystalline solid phases, such as pyrochlores, are being investigated as potential host matrices for the immobilization of radionuclides present in high-level waste streams. Zirconate pyrochlores are characterized by high chemical durability and radiation resistance. However, upon irradiation, some zirconate pyrochlores undergo a phase transition to the defect fluorite crystal structure, or become amorphous, which could hamper a continued immobilization of radionuclides in the solid matrix. In the current study, the influence of different synthesis methods on the phase purity of Ce/Nd-co-doped zirconates was investigated. Furthermore, phase transformations occurring in zirconate phases as a result of different U/Y-dopant concentrations were studied.
Ce/Nd-co-doped zirconates and U/Y-co-doped zirconates were obtained via coprecipitation. In addition, identical zirconate compositions were synthesized using three different solid-state methods involving manual mixing with a mortar and pestle, mechanical mixing with a ball mill or magnetic mixing in a slurry. PXRD measurements of all solids were done for crystal structure analysis.
For the Ce/Nd-co-doped zirconates synthesized via coprecipitation, rather phase-pure monoclinic, cubic defect fluorite and cubic pyrochlore structures could be obtained. The samples synthesized via solid-state methods were found to contain multiple phases due to insufficient mixing of the educts. Manual mixing led to the most phase-pure ceramics and was therefore chosen for further investigation. It was shown that re-sintering the ceramics as well as longer grinding time resulted in enhanced phase purity. Furthermore, an increase of the Nd-content also correlates with an improved phase purity.
PXRD data of the U-doped zirconates showed a peak-shift towards lower two theta values with increasing U-concentration. At the same dopant concentrations, U/Y-co-doped zirconates showed higher symmetry crystal structures than Ce/Nd-co-doped zirconates. This is caused by the larger ionic radius of U4+ compared to Ce4+ allowing for the stabilization of higher symmetry crystal structures at equal dopant concentrations.

Related publications

  • Poster
    NEA Global Forum Rising Stars Workshop in Nuclear Education, Science, Technology and Policy, 21.-22.09.2023, Boston, USA

Publ.-Id: 37820

Microbial immobilization of technetium-99

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

Iron-reducing bacteria perform anaerobic respiration by coupling the oxidation of organic molecules to the reduction of Fe(III)-species via dissimilatory iron reduction. This leads to the formation of ferrous minerals, such as vivianite [Fe(II)₃(PO₄)₂], pyrite (Fe(II)S₂), siderite (Fe(II)CO₃) and jahnsite [(CaMn(II))Fe(II)₂Fe(III)₂(PO₄)₄(OH)₂·(H₂O)₈], which, depending on oxygen exposure and the cultivation nutrients, may oxidize and generate magnetite (Fe(II)Fe(III)₂O₄) and/or hematite (Fe(III)₂O₃). The aforementioned secondary Fe(II)-minerals may promote the reduction of radionuclides such as the β-emitter technetium-99 (⁹⁹Tc).
⁹⁹Tc is a long lived fission product (t(1/2) = 2.13 × 10⁵ years) of ²³⁵U and ²³⁹Pu. It can also originate from the decay chain of ⁹⁹₄₂Mo, (Mo-99 → ₄₃Tc-99m + e⁻, 66 h; ₄₃Tc-99m → ₄₃Tc-99 + γ, 6.02 h). In the environment, Tc is prevalent as Tc(VII) or Tc(IV). Due to the common use of Tc-99m in radiodiagnostics, water contamination through the highly hydrosoluble pertechnetate Tc(VII)O₄⁻ must be considered. Nevertheless, Tc can be immobilized by reducing it to the low-soluble oxide Tc(IV)O₂.
This work aims at unravelling the interactions between pivotal anaerobic bacteria (e.g. the iron reducer Desulfitobacterium sp. G1-2) that can be found in bentonite (a clay potentially used as a barrier material for deep geological repositories) and Tc(VII), to achieve its reduction to Tc(IV) and preserve the environmental safeguard.
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; technetium; iron minerals; deep geological repositories

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

Publ.-Id: 37819

Molecular Adhesion of a Pilus-derived Peptide Involved in Pseudomonas aeruginosa Biofilm Formation on non-polar ZnO Surfaces

Prüßner, T.; Meinderink, D.; Zhu, S.; Orive, A. G.; Kielar, C.; Huck, M.; Steinrück, H.-G.; Keller, A.; Grundmeier, G.

Bacterial colonization and biofilm formation on abiotic surfaces are initiated by the adhesion of peptides and proteins. Understanding the adhesion of such peptides and proteins at a molecular level thus represents an important step toward controlling and suppressing biofilm formation on technological and medical materials. This study investigates the molecular adhesion of a pilus-derived peptide that facilitates biofilm formation of Pseudomonas aeruginosa, a multidrug-resistant opportunistic pathogen frequently encountered in healthcare settings. Single-molecule force spectroscopy (SMFS) was performed on chemically etched ZnO(112̅0)surfaces to gather insights about peptide adsorption force and its kinetics. Metal-free click chemistry for the fabrication of peptide-terminated SMFS cantilevers was performed on amine-terminated gold cantilevers and verified by X-ray photoelectron spectroscopy (XPS) and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). Atomic force microscopy (AFM) and XPS analyses reveal stable topographies and surface chemistries of the substrates that are not affected by SMFS. Rupture events described by the worm-like chain model (WLC) up to 600 pN were detected for the non-polar ZnOsurfaces. The dissociation barrier energy at zero force ΔG(0), the transition state distance xband bound-unbound dissociation rate at zero force koff(0) for the single crystalline substrate indicate that coordination and hydrogen bonds dominate thepeptide/surfaceinteraction.

Keywords: Adsorption; Bell-Evans theory; peptides; Single-molecule studies; ZnO

Publ.-Id: 37817

Wechselwirkung von Tc mit Eisen(II)phosphaten

Börner, C.

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

Publ.-Id: 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.

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

Publ.-Id: 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.

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

  • Open Access Logo 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

Publ.-Id: 37813

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.

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.

Related publications

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

Publ.-Id: 37809

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

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

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

Publ.-Id: 37807

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

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

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

Publ.-Id: 37805

Grenzflächenkonvektion an Tropfen und Blasen

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

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
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].
[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,
[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

Publ.-Id: 37804

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

Steiniger, K.

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


Publ.-Id: 37803

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.

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

Related publications

Publ.-Id: 37799

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.

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.


  • Secondary publication expected from 30.10.2024

Publ.-Id: 37787

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.

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.

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

Publ.-Id: 37784

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.

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.

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

Publ.-Id: 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.

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.

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

Publ.-Id: 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.

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.

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

Publ.-Id: 37777

Rollenscan Data Science und KI

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

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

Publ.-Id: 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.

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

Publ.-Id: 37775

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

Dornheim, T.

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

Related publications


Publ.-Id: 37774

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

Horst, F. E.

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.

Publ.-Id: 37772

Yamdb - Yet Another Materials DataBase

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

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


Publ.-Id: 37766

Goma - using Yamdb material databases from the commandline

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

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


Publ.-Id: 37765

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

Dornheim, T.

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

Publ.-Id: 37762

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.

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.

Publ.-Id: 37759

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

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

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

Publ.-Id: 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.

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.

Related publications


Publ.-Id: 37757

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.

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


Publ.-Id: 37753

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

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
This data format is importable into open-source visualization programs as 3D slicer ( or Paraview ( The data processing has been conducted with Avizo (

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


Publ.-Id: 37750

Magneto-structural phase transitions for direct magnetic patterning

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

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.


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

Related publications

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

Publ.-Id: 37747

High Field Suppression of Bremsstrahlung Emission in High-Intensity Laser-Plasma Interactions

Habibi, M.; Arefiev, A.; Toncian, T.

The interaction of high-intensity lasers with plasma is predicted to produce extreme quasi-static magnetic fields with magnitudes approach- ing Megatesla levels. In relativistically transparent plasmas, these fields can enhance direct laser acceleration and allow efficient gamma-ray emission by accelerated electrons. However, due to the so-called magnetic suppression effect, the magnetic field can also affect radiating elec- tron trajectories and, thus, reduce the emission probability of the bremsstrahlung. This is the first study to examine the bremsstrahlung sup- pression mechanism in the context of high-intensity laser–plasma interactions. Our paper describes a new module that integrates the suppression effect into the standard bremsstrahlung module of the EPOCH particle-in-cell code by considering the impact of magnetic fields and extending the analysis to electric fields. We also investigate this suppressing mechanism’s effect on the emitting electron’s dynamics. Our findings show that this mechanism not only suppresses low-energy emissions but also has an impact on the dynamics of the radiating electrons.

Keywords: Bremsstrahlung emission; High field suppression; Relativistic transparency; High-intensity laser-plasma interaction

Related publications


Publ.-Id: 37737

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

Wicaksono, D. C.; Hecht, M.

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

Related publications


Publ.-Id: 37736

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

Wicaksono, D. C.; Hecht, M.

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

Related publications

Publ.-Id: 37735

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

Makarov, D.

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

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    Annual meeting of the Lu Jiaxi international team, 25.-26.11.2023, Ningbo, China

Publ.-Id: 37733

Floquet analysis of a superradiant many-qutrit refrigerator

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

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

Publ.-Id: 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.

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

Publ.-Id: 37730

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