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41449 Publications

Flying Adversarial Patches: Manipulating the Behavior of Deep Learning-based Autonomous Multirotors

Hanfeld, P.; Höhne, M. M.-C.; Bussmann, M.; Hönig, W.

Autonomous flying robots, e.g. multirotors, often rely on a neural network that makes predictions based on a camera image. These deep learning (DL) models can compute surprising results if applied to input images outside the training domain. Adversarial attacks exploit this fault, for example, by computing small images, so-called adversarial patches, that can be placed in the environment to manipulate the neural network's prediction. We introduce flying adversarial patches, where an image is mounted on another flying robot and therefore can be placed anywhere in the field of view of a victim multirotor. For an effective attack, we compare three methods that simultaneously optimize the adversarial patch and its position in the input image. We perform an empirical validation on a publicly available DL model and dataset for autonomous multirotors. Ultimately, our attacking multirotor would be able to gain full control over the motions of the victim multirotor.

Keywords: Adversarial Attacks; Multi-Robot Systems; Security

  • Open Access Logo Contribution to proceedings
    Workshop on Multi-Robot Learning, 29.05.-02.06.2023, London, United Kingdom
    International Conference on Robotics and Automation
    DOI: 10.48550/arXiv.2305.12859

Permalink: https://www.hzdr.de/publications/Publ-37015


Dynamic modeling of the neutronic behavior of pressure wave propagation in the Phenix reactor core by using nodal diffusion code DYN3D

Nikitin, E.; Fridman, E.

This paper presents a methodology for time-dependent neutronic analysis of non-uniform deformations
in Sodium Fast Reactor (SFR) cores using the coordinate transformation method. The
methodology was developed for the 3D nodal diffusion code DYN3D, which uses a regular nodal
mesh for its neutronic solvers. To test the methodology, static and dynamic reactivity variations
induced by a postulated pressure spike in the Phenix reactor leading to dynamic core deformation
were calculated with DYN3D. The time-dependent mechanical core deformations were evaluated
beforehand and provided to this study as CAD geometry snapshots. The validity of the method
was demonstrated by comparing the DYN3D results against a Monte Carlo reference solution.
Static reference calculations were carried out beforehand using the Monte Carlo code Serpent,
with CAD snapshots directly used as geometry inputs. The study achieved a very good agreement
between diffusion calculations using coordinate transformation and the MC calculations using
deformed CAD geometries.

Keywords: SFR; thermal expansion; core deformation; nodal diffusion; DYN3D

Related publications

  • Contribution to proceedings
    The International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering (M&C 2023), 13.-17.08.2023, Niagara Falls, Ontario, Canada
  • Lecture (Conference)
    2023 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2023, 13.-17.08.2023, Niagara Falls, Canada

Permalink: https://www.hzdr.de/publications/Publ-37014


Influence of EDTA and EGTA on the Eu(III)/Cm(III) speciation in the human digestive system

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

In mining and industrial areas involved in lanthanide (Ln) production, both environment and population show increased Ln concentrations. To lower the health risks of these heavy metal ions on the affected persons by decreasing the Ln concentration in the human body, chelation therapy is used as decorporation strategy. Chelation therapy is also an important tool for radiation protection. The aminopolycarboxylic acid diethylenetriaminepentaacetic acid (DTPA) is the only clinical approved decorporation agent against actinides (An). However, DTPA is not equally efficient for all An and can be also toxic at higher concentrations.
Therefore, we comprehensively studied the complexation behaviour of DTPA related compounds such as ethylenediaminetetraacetic acid (EDTA) and ethylene glycol-bis(β-aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA) with trivalent europium and curium by combining spectroscopy and isothermal titration calorimetry. The influence of these ligands on the speciation of Eu(III) in the simulated human digestive system has been determined on a molecular level using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Furthermore, the ligands were successfully synthesised in their deuterated form to perform 2H-NMR spectroscopy to overcome the large 1H-NMR background occurring from organic molecules such as proteins and enzymes in the artificial digestive system. These investigations contribute to an advanced understanding of the molecular processes in chelation therapy and its further development in the future.
This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant number 02NUK057A and is part of the joint project RADEKOR.

Keywords: Speciation; Complexation; Decorporation; Europium; Curium

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

Permalink: https://www.hzdr.de/publications/Publ-37013


Flow field analysis towards improved predictability of diffusive flux in host rocks for radioactive waste

Fischer, C.; Kulenkampff, J.; Bollermann, T.

The predictive power of numerical approaches for the analysis of flow fields and, e.g., radionuclide migration, depends on the quality of the underlying pore network geometry. Validation of the obtained simulation results can only be performed with a limited number of methods. Positron emission tomography (PET) is a suitable technique that has been established in geomaterial sciences in recent years. The employment of appropriate radiotracers allows the analysis of advective transport and diffusive flux in a variety of complex porous materials.
In addition to the visualization of time-resolved transport patterns, the statistical analysis of transport controlling parameters is currently in the focus of investigations using PET techniques. First, local transport properties can be extracted from single voxels or voxel layers of the transport tomograms. Second, the analysis of spatially correlated data sets, e.g. density data from micro-computed tomography (µCT) analyses, is the focus of interest. The purpose is to statistically compare the range of material heterogeneity with the range of transport heterogeneity and to derive generalizable conclusions.
Using low-permeability potential host rock types for underground radioactive waste repositories as examples, we analyzed the heterogeneity of the flow field at the laboratory scale.1 Reliable predictions of diffusive transport heterogeneity are critical for assessing sealing capacity. We identified diagenetic and sedimentary subfacies components based on the concentration of diagenetic minerals and grain size variability, and quantified their pore size distributions and pore network geometries. The resulting generalized pore network geometries are used in digital rock models to calculate effective diffusivities, using a combined upscaling workflow for transport simulations from nanometer to micrometer scales.2 Diffusion experiments analyzed with PET confirmed the simulation results and provided new insights into the heterogeneity of diffusive flux. We introduced a statistical treatment of the PET and µCT tomographic datasets based on the spatial variability of both PET tracer concentrations and rock density. Targeting a generalized applicability, we present and discuss results on diffusive flux in different lithotypes. The focus of the comparison is on quantitative analysis of propagation heterogeneity and the correlation with data characterizing compositional homogeneity. Here we discuss possibilities of statistical evaluation of data from µCT analysis and their potential for correlation with PET analysis methods.
1. Bollermann, T.; Yuan, T.; Kulenkampff, J.; Stumpf, T.; Fischer, C., Pore network and solute flux pattern analysis towards improved predictability of diffusive transport in argillaceous host rocks. Chemical Geology 2022, 606, 120997.
2. Yuan, T.; Fischer, C., The influence of sedimentary and diagenetic heterogeneity on the radionuclide diffusion in the sandy facies of the Opalinus Clay at the core scale. Applied Geochemistry 2022, 146, 105478.

  • Lecture (Conference)
    Interpore 2023, 22.-25.05.2023, Edinburgh, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-37012


Composition-Dependent Optical Properties of Cu−Zn−In−Se Colloidal Nanocrystals Synthesized via Cation Exchange

Bora, A.; Lox, J.; Hübner, R.; Weiß, N.; Bahmani Jalali, H.; Di Stasio, F.; Steinbach, C.; Gaponik, N.; Lesnyak, V.

Copper chalcogenide-based nanocrystals (NCs) are a suitable replacement for toxic Cd/Pb chalcogenide-based NCs in a wide range of applications including photovoltaics, optoelectronics, and biological imaging. However, despite rigorous research, direct synthesis approaches of this class of compounds suffer from inhomogeneous size, shape, and composition of the NC ensembles, which is reflected in their broad photoluminescence (PL) bandwidths. A partial cation exchange (CE) strategy, wherein host cations in the initial binary copper chalcogenide are replaced by incoming cations to form ternary/quaternary multicomponent NCs, has been proven to be instrumental in achieving better size, shape, and composition control to this class of
nanomaterials. Additionally, adopting synthetic strategies which help to eliminate inhomogeneities in the NC ensembles can lead to narrower PL bandwidths, as was shown by single-particle studies on I−III−VI2-based semiconductor NCs. In this work, we formulate a two-step colloidal synthesis of Cu−Zn−In−Se (CZISe) NCs via a partial CE pathway. The first step is the synthesis of Cu2−xSe NCs, which serve as a template for the subsequent CE reaction. The second step is the incorporation of the In3+ and Zn2+ guest cations into the synthesized Cu2−xSe NCs via simultaneous injection of both metal precursors, which results in gradient-alloyed CZISe NCs with a Zn-rich surface. The as-synthesized NCs exhibit near-infrared (NIR) PL without an additional shell growth, which is typically required in most of the developed protocols. The photoluminescence quantum yield (PLQY) of these Cu chalcogenide-based NCs reaches 20%. These NCs also exhibit intriguingly narrow PL bands, which challenges the notion of broad PL bands being an inherent property of this class of NCs. Additionally, a variation in the feed ratios of the incoming cations, i.e., In/Zn, results in the variation of the composition of the synthesized NCs. Henceforth, the optical properties of these NCs could be tuned by a simple variation of the composition of the NCs achieved by varying the feed ratios of the incoming cations. Within a narrow size distribution, the PL maxima range from 980 to 1060 nm, depending on the composition of the NCs. Post-synthetic surface modification of the synthesized NCs enabled the replacement of the parent long-chain organic ligands with smaller species, which is essential for their prospective applications requiring efficient charge transport. With PL emission extended into the NIR, the synthesized NCs are suitable for an array of potential applications, most importantly in the area of solar energy harvesting and bioimaging. The large Stokes shift inherent to these materials, their absorption in the solar range, and their NIR PL within the biological window make them suitable candidates.

Involved research facilities

Related publications

Permalink: https://www.hzdr.de/publications/Publ-37009


Synthesis and In Vitro Biological Evaluation of p-Carborane-based Di-tert-butylphenol Analogs

Braun, S.; Jelača, S.; Laube, M.; George, S.; Hofmann, B.; Lönnecke, P.; Steinhilber, D.; Pietzsch, J.; Mijatović, S.; Maksimović-Ivanić, D.; Hey-Hawkins, E.

Targeting inflammatory mediators and related signaling pathways may offer a rational strategy for the treatment of cancer. The incorporation of metabolically stable, sterically demanding, and hydrophobic carboranes in dual cycloxygenase-2 (COX-2)/5-lipoxygenase (5-LO) inhibitors that are key enzymes in the biosynthesis of eicosanoids is a promising approach. The di-tert-butylphenol derivatives R-830, S-2474, KME-4, and E-5110 represent potent dual COX-2/5-LO inhibitors. The incorporation of p-carborane and further substitution of the p-position resulted in four carborane-based di-tert-butylphenol analogs that show no or weak COX inhibition but high 5-LO inhibitory activities in vitro. Cell viability studies on five human cancer cell lines revealed that the p-carborane analogs R-830-Cb, S-2474-Cb, KME-4-Cb, and E-5110-Cb exhibit lower anticancer activity compared to the related di-tert-butylphenols. Inter-estingly, R-830-Cb did not affect the viability of primary cells and suppressed HCT116 cell pro-liferation more potently than its carbon-based R-830 counterpart. Considering all the ad-vantages of boron cluster incorporation for enhancement of drug biostability, selectivity, and availability of drugs, R-830-Cb can be tested in further mechanistic and in vivo studies.

Keywords: carboranes; inflammation; cyclooxygenases; lipoxygenases; cancer

Permalink: https://www.hzdr.de/publications/Publ-37008


Temperature-driven flexomagnetic effects in thin Cr2O3 films

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

Antiferromagnetic ordering, being prevalent over ferromagnetic one in nature, is very sensitive to the lattice structure. For example, in the absence of magnetostatics, the stress fields can be responsible for the domain formation in easy-plane antiferromagnets, while the hydrostatic pressure provides a possibility to manipulate the phase transition temperature between magnetically ordered and disordered phases [1]. Phenomena related to the strain gradient being allowed in the majority of magnetic symmetry classes are much less explored [2].Here, we provide a theoretical and experimental evidence of flexomagnetism in the uniaxial room-temperature antiferromagnet Cr2O3 [3]. In the experiment, high-quality Cr2O3 thin films grown on sapphire substrate are considered. Their magnetic state is accessed by a combination of magnetotransport measurements and Nitrogen vacancy (NV) magnetometry, which allows one to address both the uncompensated magnetization at the film surface and the interior of the film. We found a gradual transition from antiferro- to paramagnetic state by thickness with heating, which is substantially enhanced in comparison with bulk Cr2O3. To explain this observation, we provide a systematic analysis of sources of magnetization and symmetry analysis regarding the presence of a sizeable strain gradient along the film thickness. The latter enables (i) the net uniform bulk magnetization along the film thickness, which cannot be directly detected by NV magnetometry, and (ii) distribution of the Neel temperature along the film thickness. The gradual change of the magnetic phase transition temperature along the sample breaks the compensation of antiferromagnetic sublattices. The respective magnetization is proportional to the Neel vector and changes its direction betwen antiferromagnetic domains contributing to the stray fields and being detectable by NV magnetometry. We provide a theoretical description of this strain-gradient-driven effects in thin Cr2O3 films and quantify the respective contribution to the flexomagnetic coefficient to be about 15 μB/nm2 [3]. Our findings provide a platform for further fundamental research of flexomagnetic effects in antiferromagnets and use of the Cr2O3 films for thermally reconfigurable devices.[1] S. Reimers et al., Nat. Comm. 13, 724 (2022); Y. Kota et al, Appl. Phys. Express, 6, 113007 (2013)
[2] E. Eliseev et al., Phys. Rev. B, 84, 174112 (2011)
[3] P. Makushko, T. Kosub, O. Pylypovskyi et al., Nat. Comm. 13, 6745 (2022)

Keywords: flexomagnetism; Cr2O3; strain effects

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

Permalink: https://www.hzdr.de/publications/Publ-37007


Chiral and anisotropic responses in curved anitferromagnetic spin chains

Pylypovskyi, O.; Borysenko, Y.; Tomilo, A.; Sheka, D.; Makarov, D.

Geometry-driven effects in magnetism arise due to (i) sample boundaries, (ii) non-zero curvature of low-dimensional magnets and (iii) non-trivial sample’s geometry. For ferromagnets, all these directions are under intensive studies for a long time, with the primary driver being shape anisotropy stemming from magnetostatics [1]. Antiferromagnets (AFMs) possess more complex magnetic ordering, with a much less fundamental understanding of the interplay between geometry and magnetic textures.The simplest systems uncovering the specific features of AFM exchange in curvilinear geometries are spin chains, which can be arranged along plane and space curves. The dipolar interaction provides the strong hard-axis shape anisotropy for AFM spin chains. Break of the spatial inversion symmetry by geometry leads to the appearance of the chiral response of Dzyaloshinsksii-Moriya interaction symmetry, which enables geometry-driven helimagnetic phase transition for chains along space curves [2]. The weak easy axis for the Neel vector comes from the exchange-driven anisotropy [2]. The presence of the easy axis and easy-plane anisotropies in total allows to observe the field-driven spin-reorientation transitions with the critical fields proportional to the curvature and a family of the topologically different states in spin-flop phase [3]. Furthermore, localized curvature behaves as the effective pinning potential for non-collinear antiferromagnetic textures [4]. [1] D. Sheka, Appl. Phys. Lett., 118, 230502 (2021); D. Makarov et al. Adv. Mater., 34, 2101758 (2022)
[2] O. Pylypovskyi, D. Kononenko et al, Nano Lett., 20, 8157–8162 (2020)
[3] O. Pylypovskyi et al, App. Phys. Lett., 118, 182405 (2021); Y. Borysenko et al., Phys. Rev. B, 106, 174426 (2022)
[4] K. Yershov, Phys. Rev. B, 105, 064407 (2022)

Keywords: spin chains; curvilinear antiferromagnets

  • Invited lecture (Conferences)
    CMD30 FisMat 2023, 04.-08.09.2023, Milan, Italy

Permalink: https://www.hzdr.de/publications/Publ-37006


Numerical investigation of Ultra-high temperature electrical thermal energy storage system integrated with sCO2 power cycle

Bangalore Mohankumar, M.; Unger, S.; Hampel, U.

An energy storage (ES) system is an economical and reliable technology that plays a predominant role in making the renewable energy sector sustainable. Integration of ES with wind and solar plants provides solution to problem of grid instability caused by to fluctuating power output. The Thermal Energy Storage (TES) system is simple and has low environmental and social impacts compared to other ES technologies like batteries, pumped hydro, compressed air and chemical storage. However, application of a TES at high temperatures is quite unexplored and has a limited deployment globally.
Solid sensible TES (STES) stores excess electricity in form of sensible heat, the solid medium is directly electrical heated or indirectly heated using heat transfer fluids (HTF). In STES systems, no phase change nor chemical reactions involved. Hence, it is simple, easy to maintain and the cost of construction materials is low. The aforesaid advantages make it suitable for high temperature applications provided the solid material selected exhibits higher temperature stability.
In the current study, indirect heating via Heat transfer fluid is considered and various solid mediums at different geometrical patterns are considered. The One-dimensional Model is developed in Matlab for the preliminary study and further optimization will be carried out using numerical analysis in ANSYS CFX.

This study will enable the thermal and economical assessment of SSTES systems and their application in Power to heat to Power systems. The study is focused on the integration of TEs systems into power cycles specifically with supercritical carbon dioxide power cycles.

Keywords: Solid sensible medium; Supercritical CO2; Thermal energy storage; Numerical analysis; 1D model

  • Lecture (Conference)
    Numerical investigation of Ultra-high temperature electrical thermal energy storage system integrated with sCO2 power cycle, 26.-27.09.2023, Siegburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-37004


Status report of the n_TOF facility after the 2nd CERN long shutdown period

Patronis, N.; Mengoni, A.; Goula, S.; Aberle, O.; Alcayne, V.; Altieri, S.; Amaducci, S.; Andrzejewski, J.; Babiano-Suarez, V.; Bacak, M.; Balibrea Correa, J.; Beltrami, C.; Bennett, S.; Bernardes, A. P.; Berthoumieux, E.; Beyer, R.; Boromiza, M.; Bosnar, D.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Cescutti, G.; Chasapoglou, S.; Chiaveri, E.; Colombetti, P.; Colonna, N.; Console Camprini, P.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Cristallo, S.; Dellmann, S.; Di Castro, M.; Di Maria, S.; Diakaki, M.; Dietz, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Eleme, Z.; Fargier, S.; Fernández, B.; Fernández-Domínguez, B.; Finocchiaro, P.; Fiore, S.; García-Infantes, F.; Gawlik-Ramiega, A.; Gervino, G.; Gilardoni, S.; González-Romero, E.; Guerrero, C.; Gunsing, F.; Gustavino, C.; Heyse, J.; Hillman, W.; Jenkins, D. G.; Jericha, E.; Junghans, A.; Kadi, Y.; Kaperoni, K.; Kaur, G.; Kimura, A.; Knapová, I.; Kokkoris, M.; Krticka, M.; Kyritsis, N.; Ladarescu, I.; Lederer-Woods, C.; Lerendegui-Marco, J.; Lerner, G.; Manna, A.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Michalopoulou, V.; Milazzo, P. M.; Mucciola, R.; Murtas, F.; Musacchio-Gonzalez, E.; Musumarra, A.; Negret, A.; Pérez De Rada, A.; Pérez-Maroto, P.; Pavón-Rodríguez, J. A.; Pellegriti, M. G.; Perkowski, J.; Petrone, C.; Pirovano, E.; Plaza Del Olmo, J.; Pomp, S.; Porras, I.; Praena, J.; Quesada, J. M.; Reifarth, R.; Rochman, D.; Romanets, Y.; Rubbia, C.; Sánchez-Caballero, A.; Sabaté-Gilarte, M.; Schillebeeckx, P.; Schumann, D.; Sekhar, A.; Smith, A. G.; Sosnin, N. V.; Stamati, M. E.; Sturniolo, A.; Tagliente, G.; Tarifeño-Saldivia, A.; Tarrío, D.; Torres-Sánchez, P.; Vagena, E.; Valenta, S.; Variale, V.; Vaz, P.; Vecchio, G.; Vescovi, D.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Woods, P. J.; Zarrella, R.; Zugec, P.

During the second long shutdown period of the CERN accelerator complex (LS2, 2019-2021), several upgrade activities took place at the n_TOF facility. The most important have been the replacement of the spallation target with a next generation nitrogen-cooled lead target. Additionally, a new experimental area, at a very short distance from the target assembly (the NEAR Station) was established. In this paper, the core commissioning actions of the new installations are described. The improvement in the n_TOF infrastructure was accompanied by several detector development projects. All these upgrade actions are discussed, focusing mostly on the future perspectives of the n_TOF facility. Furthermore, some indicative current and future measurements are briefly reported.

Keywords: CERN n ToF

Permalink: https://www.hzdr.de/publications/Publ-37003


Combining x-ray real and reciprocal space mapping techniques to explore the epitaxial growth of semiconductors

Magalhaes, S.; Salgado Cabaco, J.; Concepcion, O.; Buca, D.; Stachowicz, M.; Oliveira, F.; Cerqueira, M. F.; Lorenz, K.; Alves, E.

In the present work, the importance of determining the strain states of semiconductor compounds with high accuracy is
demonstrated. For the matter in question, new software titled LAPAs, the acronym for LAttice PArameters is presented. The
lattice parameters as well as the chemical composition of Al1−xIn x N and Ge1−xSn x compounds grown on top of GaN- and
Ge- buffered c-Al2O3 and (001) oriented Si substrates, respectively, are calculated via the real space Bond’s method. The
uncertainties in the lattice parameters and composition are derived, compared and discussed with the ones found via x-ray
diffraction reciprocal space mapping. Broad peaks lead to increased centroid uncertainty and are found to constitute up to
99% of the total uncertainty in the lattice parameters. Refraction correction is included in the calculations and found to have
an impact of 0.001 Å in the lattice parameters of both hexagonal and cubic crystallographic systems and below 0.01% in the
quantification of the InN and Sn contents. Although the relaxation degrees of the nitride and tin compounds agree perfectly
between the real and reciprocal-spaces methods, the uncertainty in the latter is found to be ten times higher. The impact of
the findings may be substantial for the development of applications and devices as the intervals found for the lattice match
the condition of Al1−xIn x N grown on GaN templates vary between ∼1.8% (0.1675-0.1859) and 0.04% (0.1708-0.1712) if
derived via the real- and reciprocal spaces methods. © 2023 The Author(s). Published by IOP Publishing Ltd.

Keywords: Bond's method; Chemical composition; Lattice parameters; Uncertainties; Gallium Nitride; III-V Semiconductors

Permalink: https://www.hzdr.de/publications/Publ-37002


Investigation of Autonomous Multi-UAV Systems for Target Detection in Distributed Environment: Current Developments and Open Challenges

Adoni, W. Y. H.; Lorenz, S.; Shaik Fareedh, J.; Gloaguen, R.; Bachmann, M.

Uncrewed aerial vehicles (UAVs), also known as drones, are ubiquitous and their use cases extend today from governmental applications to civil applications such as the agricultural, medical, and transport sectors, etc. In accordance with the requirements in terms of demand, it is possible to carry out various missions involving several types of UAVs as well as various onboard sensors. According to the complexity of the mission, some configurations are required both in terms of hardware and software. This task becomes even more complex when the system is composed of autonomous UAVs that collaborate with each other without the assistance of an operator. Several factors must be considered, such as the complexity of the mission, the types of UAVs, the communication architecture, the routing protocol, the coordination of tasks, and many other factors related to the environment. Unfortunately, although there are many research works that address the use cases of multi-UAV systems, there is a gap in the literature regarding the difficulties involved with the implementation of these systems from scratch. This review article seeks to examine and understand the communication issues related to the implementation from scratch of autonomous multi-UAV systems for collaborative decisions. The manuscript will also provide
a formal definition of the ecosystem of a multi-UAV system, as well as a comparative study of UAV types and related works
that highlight the use cases of multi-UAV systems. In addition to the mathematical modeling of the collaborative target
detection problem in distributed environments, this article establishes a comparative study of communication architectures
and routing protocols in a UAV network. After reading this review paper, readers will benefit from the multicriteria decisionmaking
roadmaps to choose the right architectures and routing protocols adapted for specific missions. The open challenges
and future directions described in this manuscript can be used to understand the current limitations and how to overcome
them to effectively exploit autonomous swarms in future trends.

Keywords: autonomous aerial vehicles; autonomous swarm; collaborative missions; communication architectures; distributed environment; distributed path planning; drones; FANET; multi-UAV systems; RPAS; UAS; UAV; uncrewed aerial vehicles

Permalink: https://www.hzdr.de/publications/Publ-37001


Hydrogen Bubble Size Distribution on Nanostructured Ni Surfaces: Electrochemically Active Surface Area Versus Wettability

Krause, L.; Skibińska, K.; Rox, H.; Baumann, R.; Marzec, M. M.; Yang, X.; Mutschke, G.; Żabiński, P.; Lasagni, A. F.; Eckert, K.

Emerging manufacturing technologies make it possible to design the morphology of electrocatalysts on the nanoscale in order to improve their efficiency in electrolysis processes. The current work investigates the effects of electrode-attached hydrogen bubbles on the performance of electrodes depending on their surface morphology and wettability. Ni-based electrocatalysts with hydrophilic and hydrophobic nanostructures are manufactured by electrodeposition and their surface properties are characterized. Despite a considerably larger electrochemically active surface area, electrochemical analysis reveals that the samples with more pronounced hydrophobic properties perform worse at industrially relevant current densities. High-speed imaging shows significantly larger bubble detachment radii with higher hydrophobicity, meaning that the electrode surface area that is blocked by gas is larger than the area gained by nanostructuring. Furthermore, a slight tendency towards bubble size reduction of 7.5% with an increase in the current density is observed in 1 M KOH.

Keywords: hydrogen evolution; water electrolysis; bubble dynamics; structured electrocatalyst; image analysis

Permalink: https://www.hzdr.de/publications/Publ-37000


FLT3-directed UniCAR T-cell therapy of Acute Myeloid Leukaemia

Peschke, J.; Bergmann, R.; Mehnert, M.; González Soto, K. E.; Rodrigues Loureiro, L. R.; Mitwasi, N.; Kegler, A.; Altmann, H.; Wobus, M.; Máthé, D.; Szigeti, K.; Feldmann, A.; Bornhäuser, M.; Bachmann, M.; Fasslrinner, F.; Arndt, C.

Adaptor chimeric antigen receptor (CAR) T-cell therapy offers solutions for improved safety and antigen escape which represent main obstacles for the clinical translation of CAR T-cell therapy in myeloid malignancies. The adaptor CAR T-cell platform “UniCAR” is currently under early clinical investigation. Recently, first proof-of-concept of a well-tolerated, rapidly switchable, CD123-directed UniCAR T-cell product treating patients with acute myeloid leukaemia (AML) was reported. Relapsed and refractory AML is prone to a high plasticity under therapy pressure targeting one single tumour antigen. Thus, targeting of multiple tumour antigens seems to be required to achieve durable anti-tumour responses, underlining the need to further design alternative AML-specific target modules (TM) for the UniCAR platform. We here present the preclinical development of a novel FMS-like tyrosine kinase 3 (FLT3)-directed UniCAR T-cell therapy, which is highly effective for in vitro killing of both AML cell lines and primary AML samples. Furthermore, we show in vivo functionality in a murine xenograft model. PET analyses further demonstrate a short serum half-life of FLT3 TMs, which will enable a rapid on/off-switch of UniCAR T-cells. Overall, the presented preclinical data encourage the further development and clinical translation of FLT3-specific UniCAR T-cells for the therapy of AML.

Keywords: FLT3; CD135; UniCAR; CAR T-cells; Acute Myeloid Leukaemia

Permalink: https://www.hzdr.de/publications/Publ-36999


Background Studies and Normalization of Signal Events in the Mu2e Experiment

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

The Mu2e experiment is currently being constructed at Fermilab to search for the neutrino-less conversion of negative muons into electrons in the field of an aluminum nucleus. The experiment aims at a sensitivity of four orders of magnitude higher than previous related experiments, which implies highly demanding accuracy requirements both in the design and during the operation. To achieve such a goal, two important tasks should be accomplished. First, it is essential to estimate precisely the particle yields and all the backgrounds that could mimic the monoenergetic conversion electron signal. Second, it is necessary to normalize the signal events accurately. The normalization of the signal events is planned to be done using a detector system made of an HPGe detector and a Lanthanum Bromide detector, which will measure the rate of muons stopped on the aluminum target by looking at the emitted characteristic X-and γ-rays of energies up to 1809 keV. Therefore, it is essential to evaluate the detector system's performance before the start of the actual experiment. In this study, the first task was addressed by an extensive campaign of Monte Carlo simulations to investigate the relevant parameters and their impact on the experiment's sensitivity. The second task was handled by taking advantage of the Helmholtz-Zentrum Dresden-Rossendorf pulsed Bremsstrahlung photon beam at the ELBE facility. The detector system was tested at the ELBE facility under timing and background conditions similar to the ones expected at the Mu2e experiment. The study presents and discusses the simulation results and the detector system testing campaign.

Keywords: Mu2e experiment; Charged Lepton Flavor Violation; Muon to Electron conversion; ELBE facility; Monte Carlo

Involved research facilities

Related publications

  • Lecture (Conference)
    New Frontiers in Lepton Flavor, 15.-17.05.2023, Pisa, Italy
  • Contribution to proceedings
    New Frontiers in Lepton Flavor, 15.-17.05.2023, Pisa, Italy
  • Open Access Logo Journal of Instrumentation 18(2023), C11024
    DOI: 10.1088/1748-0221/18/11/C11024

Permalink: https://www.hzdr.de/publications/Publ-36998


Activation calculations of selected German PWR components using the MCNP-FLUKA codes

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

On April 15, the last German nuclear power plants (NPPs) were shut down. The final shutdown is followed by a post-operational phase in which measures can be carried out to prepare for the NPPs dismantling and decommissioning. One of the essential tasks in planning and preparing an NPP for decommissioning is to obtain precise knowledge of the activation levels in its reactor pressure vessel (RPV), the biological shielding, and other internal components. In that regard, a method based on the combined use of two Monte Carlo codes, MCNP6 and FLUKA2021, was developed to serve as a non-destructive tool for evaluating the activation in an NPP. The presentation will give an overview of the methodology and demonstrate its application through the activation calculations of selected components of a German pressurized water reactor (PWR), which is the most common NPP type in Germany.

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

  • Lecture (Conference)
    AAA Workshop, 10.05.2023, Garching, Germany

Permalink: https://www.hzdr.de/publications/Publ-36997


Specific Immunotherapeutic Targeting of Glioblastoma using the switchable RevCAR NK-92 Cell System

Abdelfatah Saleh Hassan, H. A.; Mitwasi, N.; Rodrigues Loureiro, L. R.; Arndt, C.; Bachmann, M.; Feldmann, A.

Chimeric antigen receptor (CAR)-expressing immune cells, such as CAR Natural Killer (NK) cells and CAR NK-92 cell lines have shown promising therapeutic potential over the past years against solid tumors. Targeting Glioblastoma (GBM) with conventional CAR therapies is still challenging due to the sophisticated tumor microenvironment, antigen escape, and on-target/off-tumor toxicity. Therefore, our project aims to develop a safer and more flexible adapter CAR NK-92 platform, called the Reverse CAR (RevCAR) NK-92 system, which consists of two components, the RevCAR NK-92 cell expressing an extracellular short peptide epitope and a bispecific Rev Target Module (RevTM) that redirect the RevCAR NK-92 cells to tumor cells. Only upon this cross-linkage, redirected RevCAR NK-92 cells are activated to lyse tumor cells. The fibroblast growth factor-inducible 14 (Fn14) surface receptor is a promising target antigen overexpressed on GBM. Therefore, we have developed Fn14-specific RevTM to specifically redirect RevCAR NK-92 cells against Fn14-expressing GBM cells. Through in vitro and in vivo analyses, we assessed the cytotoxic effect of our system on GBM and showed for the first time that GBM cells were efficiently killed by redirected RevCAR NK-92 cells using the novel Fn14-specific RevTM in picomolar concentration, and that the tumor cell killing was associated with increased IFNγ secretion. Hence, these findings give an insight into the clinical potential of the RevCAR NK-92 system as a safe and specific immunotherapy against glioblastoma.

  • Poster
    International Conference on Lymphocyte Engineering, 12.-14.09.2023, Munich, Germany

Permalink: https://www.hzdr.de/publications/Publ-36996


Specific Targeting of Fn14-expressing glioblastoma using RevCAR NK-92 cell system

Abdelfatah Saleh Hassan, H. A.; Mitwasi, N.; Bachmann, M.; Feldmann, A.

Novel immunotherapeutic approaches such as chimeric antigen receptor (CAR)-expressing immune cells are showing promising results against cancer. Among these are the CAR Natural Killer (NK) cells that can be produced from either established cell lines such as NK-92 or allogenic NK cells, which can attack cancer cells. However, some challenges are encountered, when targeting solid tumors, in general and in particular glioblastoma, including the immunosuppressive tumor microenvironment, the antigen escape, the on-target/off-tumor toxicity and neurotoxicities. In addition to the inability to control the activity of conventional CAR NK cells once they are transferred into the patient in case of toxicities occur. Therefore, we aimed to develop a safer and more tumor-specific CAR NK cell platform called the Reverse CAR (RevCAR) NK-92 system. This system consists of two components, the NK-92 cells expressing RevCARs having an extracellular short peptide epitope incapable of recognizing surface antigens by itself, unless redirected by the other component of the system, which is a bispecific molecule called Rev Target Module (RevTM). The RevTM contains two scFvs, one is targeting the respective E5B9 or E7B6 epitope of the RevCAR NK-92 cells and the other one binds to the tumor associated antigen (TAA) of interest. Only in the presence of the respective RevTM, RevCAR NK cells can be directed towards tumor cells, resulting in tumor lysis. By dosing of the short-living RevTMs, we enabled the control of the RevCAR NK cell activity. Furthermore, the modular character of the RevCAR system provides the flexibility for targeting of different TAAs of interest simply by exchanging RevTMs with different specificities. Out of these TAAs, the fibroblast growth factor-inducible 14 (Fn14) surface receptor and its ligand (tumor necrosis factor-related weak inducer of apoptosis (TWEAK)) have been shown to be upregulated in many solid tumors, like glioblastoma. The activation of TWEAK/Fn14 pathway enhances the proliferation, invasion, and migration of tumor cells, and thus a specific targeting of Fn14 is considered a promising approach in glioblastoma therapy. Therefore, we employed here our RevCAR NK-92 system to specifically target Fn14-expressing glioblastoma cells. Through in vitro and in vivo analyses, we showed for the first time that glioblastoma cells were efficiently killed by redirected RevCAR NK-92 cells using picomolar concentrations of the novel Fn14-specific RevTM which was associated with increased IFNγ secretion. Hence, these findings give an insight into the clinical potential of the RevCAR NK-92 system for a safer, specific and more tailored immunotherapy against glioblastoma.

  • Poster
    Tumor Immunology meets Oncology (TIMO) XVII 2023 Halle, 20.-22.04.2023, Halle, Germany

Permalink: https://www.hzdr.de/publications/Publ-36995


Development of an immune therapeutic approach against SARS-CoV-2

Drewitz, L.; Kegler, A.; Laube, M.; Ziehr, H.; Heine, M.; Moreira-Soto, A.; Kühne, A.; Felix Drexler, J.; Seliger, B.; Arndt, C.; Bergmann, R.; Feldmann, A.; Bachmann, M.

Immunotherapies are already successfully used for cancer treatment. In our lab two modular platform technologies were developed which demonstrated high success against various types of malignant cells: the universal chimeric antigen receptor (UniCAR) system, and the bispecific antibody (bsAb) based UniMAB system. Both approaches have the aim to recruit T cells to kill the malignant cells carrying a tumor associated antigen (TAA) on their surface. In the first case, UniCAR modified T cells are linked via a TAA specific target module (TM) to cancer cells. In the case of the UniMAB system, natural T cells are recruited to cancer cells via a TAA specific TM and a bsAb based effector module (EM) which binds to CD3 of T cells and to an epitope tag of the TM. In both cases, an immune complex is formed leading to T cell activation and tumor cell elimination. Most importantly, the T cell activation is dependent on the cross-linkage of T cells and tumor cells via the TM or TM/EM complex. Thus, T cell activation is steerable which increases the safety of these approaches. With the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) leading
to millions of deaths worldwide, we aimed to apply the UniCAR and UniMAB technology against SARS-CoV-2 and virus infected cells as novel immunotherapeutic treatment approach.
For this purpose, we designed two TMs binding to the receptor binding domain (RBD) of SARS-CoV-2. The first TM is based on a single chain fragment variable (scFv) with specificity for RBD, whereas the second one contains the extracellular domain of the human ACE2 receptor which is the entry receptor of SARS-CoV-2. Both TMs were able to efficiently recruit either UniCAR T cells or, in combination with the EM of the UniMAB system, natural T cells to efficiently kill human cells having the RBD of SARS-CoV-2 on their surface. Remarkably, the ACE2-Mb-TM is additionally able to block RBD/ACE2 interaction and potently neutralizes pseudo- as well as live SARS-CoV-2 which is even more pronounced when variants of concern are tested in these assays instead of the respective wild type. Thus, the ACE2-Mb TM represents a potent therapeutic drug against SARS-CoV-2, as it not only recruits UniCAR T cells and, in combination with the EM, natural T cells, but also neutralizes virus particles.

Involved research facilities

  • ZRT
  • Poster
    Tumor Immunology meets Oncology Halle, 20.-22.04.2023, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36994


The La-protein as an inducible target for CAR T cell therapy

Bartsch, T.; Arndt, C.; Neuber, C.; Feldmann, A.; Bachmann, M.

The La-protein is a multifunctional abundantly expressed protein in the nucleus of all human cells, where it for example functions as a chaperone for newly synthesized RNA-polymerase III transcripts. Recently, it has been shown that La is overexpressed in malignant cells and can be translocated to the cell surface under certain conditions, e. g. radio- or chemotherapy-induced necrosis, where it becomes a promising, inducible target for so-called “Death Targeting” approaches.
The aim of this study was to investigate whether the La-protein could also be used as an inducible target for CAR T cell therapy. Therefore, three different CAR T cells directed against the La-protein (La-CARs) were developed and tested regarding their potential for “Death Targeting” of tumor cells. For construction of the La-CARs, we selected three different anti-La mAbs (5B9, 7B6 and 312B), which recognize distinct epitopes within the La-protein in a redox-dependent manner. This allowed us to determine, if the redox-state influences the ability of the La-CARs to target cell surface-bound La-protein.
We first examined if La-CARs could eliminate tumor cells that were artificially labeled with wildtype La-protein or its oxidation-resistant triple-cysteine-mutant (TCM). By performing luciferase-based killing assays, we showed, that all La-CARs were specifically activated for lysis of La- or TCM-decorated tumor cells, which also resulted in significant secretion of pro-inflammatory cytokines. Redox-dependent differences of the La-CARs could be observed, whereby the non-redox-dependent 5B9-CAR was activated by La-wt- and TCM-labeled cells, the 7B6-CAR preferably by La-wt-labeled and the 312B-CAR preferably by TCM-labeled tumor cells.
We could further prove that La-release from tumor cells could be induced by treatment with the cytotoxic drug cisplatin and La-CARs could be redirected against remaining tumor-cells after cisplatin treatment. Thereby, the 5B9-CAR, which recognizes La-protein independent of its redox-state, induced highest tumor cell killing after cisplatin treatment.
In summary, we could show that the La-protein is a promising target for CAR T cell therapy. Release of La-protein can be induced by the cytotoxic drug cisplatin, making a combinatorial strategy of chemotherapy and CAR T cell therapy a promising approach for tumor immuno-therapy.

  • Lecture (Conference)
    Tumor Immunology meets Oncology (TIMO) XVII 2023, 20.-22.04.2023, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36993


Targeting immune checkpoint molecules with RevCAR platform for immunotherapy and modulation of the tumor microenvironment

Crespo, E.; Rodrigues Loureiro, L. R.; Arndt, C.; Schmitz, M.; Bachmann, M.; Feldmann, A.

Chimeric antigen receptors (CARs) are used for redirection of T cells against tumor cells and have demonstrated remarkable therapeutic effects against some hematological cancers. The modular system termed RevCAR can overcome the dangerous side effects associated with conventional CAR T cell therapy, such as cytokine release syndrome. It is composed of RevCAR T cells and a bispecific molecule target module, termed RevTM. This system is highly safe since RevCAR T cell activity can be controlled by RevTM and immediately switched off if side effects are detected. It is also versatile, since the same RevCAR T cell can be directed to different tumor-associated antigens (TAA) simply by adding RevTMs with different specificities. However, to improve the effectiveness in the treatment of solid tumors, the immunosuppressive tumor microenvironment (TME) still needs to be addressed. For this purpose, we have developed novel RevTMs targeting immune checkpoint molecules such as PD-L1, which are often upregulated by cancer cells to escape the immune cells. We have demonstrated that our novel RevTMs can redirect RevCAR T cells to specifically kill cell lines expressing immune checkpoint molecules. In addition to this strategy, the combinatorial targeting of a TAA and an immune checkpoint is very promising strategy to overcome the immunosuppressive microenvironment of solid tumors and thus to improve the treatment outcome.

  • Lecture (Conference)
    Tumor Immunology meets Oncology (TIMO) XVII 2023, 20.-22.04.2023, Halle, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36989


Tomographic analysis of advective flow and diffusive flux toward improved migration predictability in host rocks for radioactive waste

Fischer, C.; Kulenkampff, J.; Cardenas Rivera, M. A.; Zhou, W.; Schöngart, J.

The predictive power of numerical approaches for the analysis of flow fields, e.g. for radionuclide
migration, depends on the quality of the underlying pore network geometry. Validation of the
obtained simulation results can only be performed with a limited number of methods. Positron
emission tomography (PET) is a suitable technique that has been established in geomaterial
sciences in recent years. The use of suitable radiotracers allows the analysis of advective transport
and diffusive flux in a variety of complex porous materials. In addition to the visualization of timeresolved
transport patterns, the statistical analysis of transport controlling parameters is currently
in the focus of investigations using PET techniques.
Using potential host rock types with low permeability for underground radioactive waste
repositories as examples, we have analyzed the heterogeneity of the flow field at laboratory scale.1
Diagenetic and sedimentary components and their pore size distributions and pore network
geometries are responsible for the flow field properties. The resulting generalized pore network
geometries are used in digital rock models to calculate effective diffusivities, using a combined
upscaling workflow for transport simulations from the nanometer to the micrometer scale.2 For
advective transport in fractured crystalline rocks, PET provides evidence for the influence of
fracture wall geometries over a wide range of the length scale. Surface building blocks from nm to
mm size are responsible for the observed changes in breakthrough curve behavior. Finally,
another hot topic is the testing of reactive PET tracers for materials analysis. In addition to the use
of conservative tracers described above, reactive tracers provide insight into the density of
reactive surface sites in complex porous materials.
1Bollermann, T.; Yuan, T.; Kulenkampff, J.; Stumpf, T.; Fischer, C., Pore network and solute flux
pattern analysis towards improved predictability of diffusive transport in argillaceous host rocks.
Chemical Geology 2022, 606, 120997.
2Yuan, T.; Fischer, C., The influence of sedimentary and diagenetic heterogeneity on the
radionuclide diffusion in the sandy facies of the Opalinus Clay at the core scale. Applied
Geochemistry 2022, 146, 105478.
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Permalink: https://www.hzdr.de/publications/Publ-36983


Interaction of domain walls with grain boundaries in uniaxial insulating antiferromagnets

Pylypovskyi, O.; Hedrich, N.; Tomilo, A.; Kosub, T.; Wagner, K.; Hübner, R.; Shields, B.; Sheka, D.; Faßbender, J.; Maletinsky, P.; Makarov, D.

A search for high-speed and low-energy memory devices puts antiferromagnetic thin films at the forefront of spintronic research. Here, we develop a material model of a granular antiferromagnetic thin film with uniaxial anisotropy and provide fundamental insight into the interaction of antiferromagnetic domain walls with grain boundaries. This model is validated on thin films of the antiferromagnetic insulator \ch{Cr2O3}, revealing complex maze-like domain patterns hosting localized nanoscale domains down to 50 nm. We show that the inter-grain magnetic parameters can be estimated based on an analysis of high-resolution images of antiferromagnetic domain patterns examining the domain patterns' self-similarity and the statistical distribution of domain sizes. Having a predictive material model and understanding of the pinning of domain walls on grain boundaries, we put forth design rules to realize granular antiferromagnetic recording media.

Keywords: antiferromagnetism; granular media; spin-lattice simulations; Nitrogen vacancy magnetometry

Permalink: https://www.hzdr.de/publications/Publ-36982


Bioethanol sustainable supply chain design: A multi-attribute bi-objective structure

Kheybari, S.; Davoodi Monfared, M.; Salimirad, A.; Rezaei, J.

To design a bioethanol supply chain, along with the transportation and operational costs, it is vital to consider more factors categorized into three sustainability pillars (i.e. economy, social and environment). In this paper, to develop a mathematical model for bioethanol supply chain (BSC), we propose a two-phase methodology; in the first phase, using a sustainable framework of attributes contributing to the facility location selection in the BSC network, we calculate the sustainability score of alternatives through employing the best-worst method (BWM). Then, considering the results of the multi-attribute step as the parameters of an objective function called the sustainability value function, we develop a bi-objective multi-level bioethanol supply chain model. To solve the proposed model, a Nested bi-objective Optimization Genetic Algorithm (NbOGA) is introduced in this research. Finally, we evaluate the performance of the presented BSC model and the algorithm for a real-world problem. The results show that using the proposed structure, both sustainability attributes and transportation costs are appropriately satisfied in the BSC network.

Keywords: Bioethanol Supply Chain; Bi-objective optimization; Genetic Algorithm; Sustainability index; best-worst method

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36980


The Main Results of Structural Materials Research for Safe Long-Term Operation of LWR NPPs from the Viewpoint of Dissemination Activities

Shugailo, O.; Kolluri, M.; Gillemot, F.; Ulbricht, A.; Brumovsky, M.

One of the main points of any project implementation is the dissemination of the obtained results among the nuclear
community, young researchers, public, stakeholders, etc. Communication and dissemination activities are considered as high-priority elements in European collaborative research projects. The article briefly presents EUROATOM project “STRUctructural MATerials Research for Safe Long-Term Operation of LWR NPPs” (STRUMAT-LTO), that was started in September 2020, describes its goals, main steps, expected outputs, approaches used for dissemination and communication activities and brief status update on interim results after 2 years’ implementation. In general, the deployment of the STRUMAT-LTO project was dedicated to studying synergetic effects of Ni-Mn-Si on RPV embrittlement at high fluences by exploiting unique RPV model steels irradiated in LYRA-10 irradiation experiment and assessing the Embrittlement Trend Curves for LTO and Master curve approach for LTO. All these activities are aimed at finding a solution to justify safe LTO until 80 years of operation.

Keywords: ageing management; dissemination activity; embrittlement; fluence; long-term operation; LYRA-10; reactor pressure vessel; STRUMAT-LTO; synergetic effects

Permalink: https://www.hzdr.de/publications/Publ-36979


Data publication: Design and Biological Evaluation of Small-Molecule PET-Tracers for Imaging of Programmed Death Ligand 1

Krutzek, F.; Donat, C.; Ullrich, M.; Zarschler, K.; Ludik, M.-C.; Feldmann, A.; Rodrigues Loureiro, L. R.; Kopka, K.; Stadlbauer, S.

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

Involved research facilities

  • PET-Center

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Permalink: https://www.hzdr.de/publications/Publ-36978


Design and Biological Evaluation of Small-Molecule PET-Tracers for Imaging of Programmed Death Ligand 1

Krutzek, F.; Donat, C.; Ullrich, M.; Zarschler, K.; Ludik, M.-C.; Feldmann, A.; Rodrigues Loureiro, L. R.; Kopka, K.; Stadlbauer, S.

Noninvasive molecular imaging of the PD-1/PD-L1 immune checkpoint is of high clinical relevance for patient stratification and therapy monitoring in cancer patients. Here we report nine small-molecule PD-L1 radiotracers with solubilizing sulfonic acids and a linker–chelator system, designed by molecular docking experiments and synthesized according to a new, convergent synthetic strategy. Binding affinities were determined both in cellular saturation and real-time binding assay (LigandTracer), revealing dissociation constants in the single digit nanomolar range. Incubation in human serum and liver microsomes proved in vitro stability of these compounds. Small animal PET/CT imaging, in mice bearing PD-L1 overexpressing and PD-L1 negative tumors, showed moderate to low uptake. All compounds were cleared primarily through the hepatobiliary excretion route and showed a long circulation time. The latter was attributed to strong blood albumin binding effects, discovered during our binding experiments. Taken together, these compounds are a promising starting point for further development of a new class of PD-L1 targeting radiotracers.

Involved research facilities

  • PET-Center

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Permalink: https://www.hzdr.de/publications/Publ-36977


Resolution-Adaptive Modelling in Nuclear Safety: Free Surfaces and Bubbles

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

Process engineering and energy production systems often feature gas-liquid flows with coexisting two-phase flow regimes and a broad range of interfacial and turbulent scales. Suitable simulation methods can be found for each particular morphology, such as Volume-of-Fluid for larger, resolvable and continuous features of stratified flows, and the two-fluid model for unresolved dispersed bubbles or droplets. A morphology-adaptive multifield two-fluid model (MultiMorph) presented here is developed based on the OpenFOAM Foundation Release, with the aim to handle different coexisting dispersed and continuous flow structures for a wide range of spatial resolutions within a common computational tool.

The present work highlights specifically the following aspects of the model: a resolution-adaptive momentum transfer for under-resolved flow structures on coarse meshes, interface turbulence damping in strong shear flow near a gas-liquid surface with high density ratios between the phases, and morphology transfer models. This enables both transitions, disintegration and accumulation, between dispersed and continuous phase morphologies of the same fluid. Application of the MultiMorph model is presented on the following selected set of safety related test cases: a stratified counter-current flow case with partial flow reversal and liquid waves, and a plunging jet case, with entrainment of gas bubbles. Results are evaluated with measurements from the corresponding experiments.

  • Poster
    International Conference Nuclear Energy for New Europe (NENE), 11.-14.09.2023, Portorož, Slovenia

Permalink: https://www.hzdr.de/publications/Publ-36976


Development of the High-Affinity Carborane-Based Cannabinoid Receptor Type 2 PET Ligand [18F]LUZ5-d8

Ueberham, L.; Gündel, D.; Kellert, M.; Deuther-Conrad, W.; Ludwig, F.-A.; Lönnecke, P.; Kazimir, A.; Kopka, K.; Brust, P.; Moldovan, R.-P.; Hey-Hawkins, E.

The development of cannabinoid receptor type 2 (CB2R) radioligands for positron emission tomography (PET) imaging was intensively explored. To overcome the low metabolic stability and simultaneously increase the binding affinity of known CB2R radioligands, a carborane moiety was used as a bioisostere. Here we report the synthesis and characterization of carboranebased 1,8-naphthyridinones and thiazoles as novel CB2R ligands. All tested compounds showed low nanomolar CB2R affinity, with (Z)-N-[3-(4-fluorobutyl)-4,5-dimethylthiazole-2(3H)-ylidene]-(1,7-dicarba-closo-dodecaboranyl)-carboxamide (LUZ5) exhibiting the highest affinity (0.8 nM). Compound [18F]LUZ5-d8 was obtained with an automated radiosynthesizer in high radiochemical yield and purity. In vivo evaluation revealed the improved metabolic stability of [18F]LUZ5-d8 compared to that of [18F]JHU94620. PET experiments in rats revealed high uptake in spleen and low uptake in brain. Thus, the introduction of a carborane moiety is an appropriate tool for modifying literature-known CB2R ligands and gaining access to a new class of high-affinity CB2R ligands, while the in vivo pharmacology still needs to be addressed.

Keywords: cannabinoid receptor; ligand; protein binding; animal; brain; diagnostic imaging; metabolism; positron emission tomography; procedures; rat; Animals; Brain; Ligands; Positron-Emission Tomography; Protein Binding; Rats; Receptors; Cannabinoid

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Permalink: https://www.hzdr.de/publications/Publ-36975


Experimental investigations and Simulations of Dark Current in ELBE SRF gun-II

Xiang, R.; Arnold, A.; Gatzmaga, S.; Ma, S.; Michel, P.; Murcek, P.; Niemczyk, R.; Ryzhov, A.; Schaber, J.; Teichert, J.

In the high gradient rf photoinjectors, dark current is the “unwanted beam” not produced by the cathode drive laser. It is a part of field emission from the cavity and photocathode, which is accelerated through the gun. Dark current can cause beam loss, increase the risk of damage to accelerator components, and create additional background for beam users. Furthermore, during operation of the ELBE srf gun, the dark current has been found to correlate with the photocathode QE and life time. Therefore, understanding the sources as well as the dynamics of dark current is crucial to machine safety and gun quality.
In this paper we present our experimental investigations of the dark current at the ELBE SRF gun-II. The beam dynamics of the dark current is studied with the ASTRA code, which helps us to track the field electrons starting from the cathode area and from other sources, so that we can understand their different contributions to the dark current.

Keywords: photocathode; SRF gun; Dark current; field emission

Involved research facilities

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  • Open Access Logo Poster
    14th International Particle Accelerator Conference (IPAC2023), 07.-12.05.2023, Venezia, Italy

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Permalink: https://www.hzdr.de/publications/Publ-36974


Low-emittance SRF photo-Injector phototype cryomodule for the LCLS-II High-Energy upgrade: design and fabrication

Xu, T.; Choi, Y.; Compton, C.; Chang, W.; Du, X.; Greene, D.; Hartung, W.; Kim, S.-H.; Konomi, T.; Miller, S. J.; Morris, D.; Patil, M. S.; Popielarski, L.; Saito, K.; Wei, J.; Yin, Z.; Smedley, J.; Adolphsen, C.; Coy, R.; Ji, F.; Murphy, M.; L, X.; Kelly, M.; Petersen, T.; Piot, P.; Arnold, A.; Gatzmaga, S.; Murcek, P.; Xiang, R.; Teichert, J.; Lewellen, J. W.

The high-energy upgrade of the Linac Coherent Light Source II (LCLS-II-HE) will extend the X-ray energy range up to 20 keV. The goal is to produce low emittance (0.1 mm∙mrad) electron bunches (100 pC/bunch) and accelerate 30 μA beams through the superconducting linac to 8 GeV. A low-frequency superconducting radio-frequency photo-injector (SRF-PI) will be a key aspect of the upgrade. An SRF-PI cryomodule with a 185.7 MHz QuarterWave Resonator (QWR) for operation at a cathode field of 30 MV/m and a cathode system compatible with high quantum efficiency photo-cathodes operating at 55-80 K or 300 K are currently being developed. We report on the design and fabrication status of the SRF-PI cryomodule and cathode system for LCLS-II-HE.

  • Open Access Logo Poster
    14th International Particle Accelerator Conference (IPAC2023), 07.-12.05.2023, Venice, Italy
    DOI: 10.18429/JACoW-IPAC-23-TUPA028
  • Open Access Logo Contribution to proceedings
    14th Int. Particle Acc. Conf. (IPAC2023), 07.-12.05.2023, Venezia, Italy
    Proceedings of the 14th International Particle Accelerator Conference
    DOI: 10.18429/JACoW-IPAC-23-TUPA028

Permalink: https://www.hzdr.de/publications/Publ-36973


Adhesion force measurement and resuspension of glass particles from a wall surface functionalized with well-defined microasperities

Lecrivain, G.; Graebe, K.; Rudolph, M.; Lorenz, P.; Zimmer, K.; Henry, C.; Hampel, U.

The resuspension of microparticles by a turbulent gas flow occurs in many industrial
systems. Industrial surfaces, onto which particles initially adhere, are rarely smooth and
this surface roughness affects their resuspension. Available experimental data on particle
resuspension have been obtained with substrates, whose surfaces are either unaltered or
manually abraded with, for instance, sand blasting. In these experiments, the roughness
elements span a wide size range and are in-homogeneously distributed in space. Surface
functionalization is a modern technique allowing the precise fabrication of a wall surface
with well-characterized microstructures, hence reducing the asperity randomness associated
with conventional abrasion techniques. Taking advantage of surface functionalization, we
present here a new set of reference data, where the wall asperities are represented by a
structured arrangement of micropillars and microcubes. Adhesion force measurements and
particle remaining fraction against gas velocity, at Reynolds number up to 8000, are reported
for one reference and two artificially roughened substrates. Laboratory measurements show
that the microasperities have little to moderate effect on the mean adhesion force and the
threshold velocity, at which half of the 100 μm particles resuspend. The standard deviations
are, however, significantly affected. The presented results will primary contribute to the
improvement of resuspension models, which until now rely on a simplified representation of
the surface roughness elements.

Keywords: Particle resuspension; Turbulent flows; Experiment

  • Lecture (Conference)
    Euromech Colloquium 628 “Complex Particles in Turbulent Flows”, 03.-05.05.2023, Nice, France
  • Poster
    International Congress on Particle Technology, 26.-28.09.2023, Nürnberg, Gremany

Permalink: https://www.hzdr.de/publications/Publ-36972


Designing chiral magnetic responses by tailoring geometry of thin films: curvilinear ferro- and antiferromagnets

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films and nanowires [2,3]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and discuss realizations of curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of exchange-driven chiral effects [4]. Geometrically curved architectures can support a new chiral symmetry breaking effect: it is essentially non-local and manifests itself even in static spin textures living in curvilinear magnetic nanoshells [5]. The field of curvilinear magnetism was extended towards curvilinear antiferromagnets [6,7], offering a novel material science platform for antiferromagnetic spinorbitronics. It was demonstrated that intrinsically achiral 1D curvilinear antiferromagnets behave as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition [6]. Application potential of geometrically curved magnetic thin films is being explored as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices as well as on-skin interactive flexible [8,9] and printed self-healable electronics [10].

[1] P. Gentile et al., Nature Electronics (Review) 5 (2022) 551.
[2] D. Makarov et al., Advanced Materials (Review) 34 (2022) 2101758.
[3] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022). https://link.springer.com/book/10.1007/978-3-031-09086-8
[4] O. Volkov et al., Physical Review Letters 123 (2019) 077201.
[5] D. Sheka et al., Communications Physics 3 (2020) 128.
[6] O. Pylypovskyi et al., Nano Letters 20 (2020) 8157.
[7] O. Pylypovskyi et al., Appl. Phys. Lett. 118 (2021) 182405.
[8] J. Ge et al., Nature Communications 10 (2019) 4405.
[9] G. S. Canon Bermudez et al, Nature Electronics 1 (2018) 589.
[10] R. Xu et al., Nature Communications 13 (2022) 6587.

Keywords: curvilinear magnetism; magnetic solitons

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  • Invited lecture (Conferences)
    4th Solid-State Science & Research meeting (SCIRES), 28.-30.06.2023, Zagreb, Croatia

Permalink: https://www.hzdr.de/publications/Publ-36971


Magnetic textures: from fundamentals to applications

Makarov, D.

This will be a lecture for students in the frame of the IEEE Summer School in Bari, Italy from 11-16 June 2023.

Keywords: magnetic domain walls; magnetic solitons

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  • Invited lecture (Conferences)
    IEEE Magnetics Society Summer School 2023, 11.-16.06.2023, Bari, Italy

Permalink: https://www.hzdr.de/publications/Publ-36970


Curvilinear magnetism: from fundamentals to applications

Makarov, D.

The behaviour of any physical system is determined by the order parameter whose distribution is governed by the geometry of the physical space of the object, in particular its dimensionality and curvature. In magnetism, the coupling between geometry (topology) of a ferromagnet and magnetic order parameter brings about novel responses of curved thin films and nanowires [1]. In thin film limit, local curvatures can force a geometry-driven local interactions like Dzyaloshinskii–Moriya interaction (DMI) and anisotropy as well as novel non-local chiral effects. In addition to activities on geometrically curved ferromagnets, there are recent appealing developments for curvilinear antiferromagnets where curvature effects results in the appearance of chiral responses, helimagnetic phase transitions, weak ferromagnetism and hybridisation of spin wave modes. Contrary to planar non-collinear structures, curvilinear design enables 3D architectures, which can revolutionize magnetic devices with respect to size, functionality and speed. At present, 3D-shaped magnetic architectures are explored as spin-wave filters, racetrack memory, artificial magnetoelectric materials, and shapeable magnetoelectronics for human-machine interfaces and soft robotics [2]. These fundamental and application-oriented topics will be covered in the presentation [3].
[1] D. Makarov et al., Adv. Mater. (Review), 34, (2022), 2101758.
[2] G. S. Canon Bermudez et al., Adv. Funct. Mater. (Review), 31, (2021), 2007788.
[3] D. Makarov and D. Sheka (Editors), Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022). https://link.springer.com/book/10.1007/978-3-031-09086-8

Keywords: curvilinear magnetism; shapeable magnetoelectronics; printed magnetoelectronics; soft magnetic composites

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  • Invited lecture (Conferences)
    Zakopane School of Physics Breaking Frontiers: Submicron Structures in Physics and Biology, 23.-27.05.2023, Zakopane, Poland

Permalink: https://www.hzdr.de/publications/Publ-36969


What is going on in a laser plasma wakefield accelerator (LPWFA)? - a theoretical perspective on the hybrid concept

Pausch, R.; Bussmann, M.; Assmann, R. W.; Corde, S.; Couperus Cabadağ, J.; Chang, Y.-Y.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Götzfried, J.; Heinemann, T.; Hidding, B.; Karsch, S.; Köhler, A.; Kononenko, O.; Kurz, T.; Martinez De La Ossa, A.; Raj, G.; Schöbel, S.; Steiniger, K.; Schindler, S.; Zarini, O.; Irman, A.; Schramm, U.; Debus, A.

The combination of laser wakefield acceleration (LWFA) with plasma wakefield acceleration (PWFA) provides a miniaturized testbed for the study of PWFA. Since the first experimental implementation of this hybrid concept, various driver generation methods and witness injection have been investigated. Extensive simulation studies accompanied these experiments and provided insights into the complex interplay between the individual stages and the processes occurring within them. This real-world implementation allowed us to revisit and refine the original concepts. Here we present this revised implementation guide for LPWFA.

Derived from these simulation campaigns, we present a theoretical analysis of the processes relevant to LPWFA hybrid accelerators. Requirements and possible methods for generating a driver package in the LWFA stage are discussed, and different laser extraction techniques are compared. The driver evolution in the PWFA stage is studied and the implications for performance limits relevant to current experiments are discussed. Different witness generation methods are also compared in terms of reproducibility and beam quality.

The analysis is based on 3D3V particle-in-cell simulations performed with PIConGPU. Its 3D capability and efficiency allows studying non-rotational effects such as oblique density profiles of shocks and higher laser modes originating from experimental measurements. Their influences are briefly discussed, as well as general requirements on start-to-end simulations.

Keywords: laser plasma accelerator; LWFA; PWFA; LPWFA; PIConGPU; hybrid

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

Permalink: https://www.hzdr.de/publications/Publ-36968


Hardware-agnostic Interactive Exascale In situ Visualization of Particle-In-Cell Simulations

Meyer, F.; Hernandez, B.; Pausch, R.; Widera, R.; Groß, D.; Bastrakov, S.; Hübl, A.; Juckeland, G.; Kelling, J.; Leinhauser, M.; Rogers, D.; Schramm, U.; Steiniger, K.; Gumhold, S.; Young, J.; Bussmann, M.; Chandrasekaran, S.; Debus, A.

The volume of data generated by exascale simulations requires scalable tools for analysis and visualization. Due to the relatively low I/O bandwidth of modern HPC systems, it is crucial to work as close as possible with simulated data via in situ approaches. In situ visualization provides insights into simulation data and, with the help of additional interactive analysis tools, can support the scientific discovery process at an early stage. Such in situ visualization tools need to be hardware-independent given the ever-increasing hardware diversity of modern supercomputers. We present a new in situ 3D vector field visualization algorithm for particle-in-cell (PIC) simulations and performance evaluation of the solution developed at large-scale. We create a solution in a hardware-agnostic approach to support high throughput and interactive in situ processing on leadership class computing systems. To that end, we demonstrate performance portability on Summit’s and the Frontier’s pre-exascale testbed at the Oak Ridge Leadership Computing Facility.

Keywords: PIConGPU; ISAAC; HPC; particle-in-cell; in-situ; rendering; live visualization; exascale

  • Contribution to proceedings
    The Platform for Advanced Scientific Computing (PASC) Conference, 26.-28.06.2023, Davos, Schweiz
    Platform for Advanced Scientific Computing Conference (PASC '23): ACM, 979-8-4007-0190-0/23/06
    DOI: 10.1145/3592979.3593408
  • Lecture (Conference)
    The Platform for Advanced Scientific Computing (PASC) Conference, 26.-28.06.2023, Davos, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-36967


Radiofluorination of an anionic, azide-functionalized teroligomer by copper-catalyzed azide-alkyne cycloaddition

Wenzel, B.; Schmid, M.; Teodoro, R.; Moldovan, R.-P.; Lai, T. H.; Mitrach, F.; Kopka, K.; Fischer, B.; Schulz-Siegmund, M.; Brust, P.; Hacker, M. C.

This study describes the synthesis, radiofluorination and purification of an anionic amphiphilic teroligomer developed as stabilizer for siRNA-loaded calcium phosphate nanoparticles (CaP-NP). As the stabilizing amphiphile accumulates on nanoparticle surfaces, the fluorine-18 labeled polymer should enable to track the distribution of the CaP-NP in brain tumors after ap-plication by convection-enhanced delivery. At first, an unmodified teroligomer was synthesized with a number average molecular weight of 4550 ± 20 Da by free radical polymerization of a de-fined composition of methoxy-PEG-monomethacrylate, tetradecyl acrylate and maleic anhy-dride. Subsequent derivatization of anhydrides with azido-TEG-amine provided an azido func-tionalized polymer precursor (o14PEGMA-1) for radiofluorination. The 18F-labeling was accom-plished by copper-catalyzed cycloaddition of o14PEGMA-1 with the diethylene glycol - alkyne substituted heteroaromatic prosthetic group [18F]2 which was synthesized with a radiochemical yield (RCY) of about 38% within 60 min using a radiosynthesis module. The 18F-labeled polymer [18F]fluoro-o14PEGMA-2 was obtained after a short reaction time of 2-3 min by using CuSO4/sodium ascorbate at 90 °C. Purification was performed by solid-phase extraction on an anion-exchange cartridge followed by size-exclusion chromatography to obtain [18F]fluoro-o14PEGMA-2 with a high radiochemical purity and an RCY of about 15%.

Keywords: teroligomer; fluorine-18; 18F-polymer; click reaction; CuAAC; PEG-[18F]FPyKYNE

Permalink: https://www.hzdr.de/publications/Publ-36965


XUV Fluorescence Detection of Laser-Cooled Stored Relativistic Ions

Ueberholz, K.; Bozyk, L.; Bussmann, M.; Eizenhöfer, N.; Hannen, V.; Horst, M.; Kiefer, D.; Kiefer, N.; Klammes, S.; Kühl, T.; Langfeld, B.; Löser, M.; Ma, X.; Nörtershäuser, W.; Sánchez, R.; Schramm, U.; Siebold, M.; Spiller, P.; Steck, M.; Stöhlker, T.; Walther, T.; Wang, H.; Weinheimer, C.; Wen, W.; Winters, D.

An improved moveable in vacuo XUV fluorescence detection system was employed for the laser cooling of bunched relativistic (β = 0.47) carbon ions at the Experimental Storage Ring (ESR) of GSI Helmholtzzentrum Darmstadt, Germany. Strongly Doppler boosted XUV fluorescence (∼90 nm) was emitted from the ions in a forward light cone after laser excitation of the 2s–2p transition (∼155 nm) by a new tunable pulsed UV laser system (257 nm). It was shown that the detected fluorescence strongly depends on the position of the detector around the bunched ion beam and on the delay (∼ns) between the ion bunches and the laser pulses. In addition, the fluorescence information could be directly combined with the revolution frequencies of the ions (and their longitudinal momentum spread), which were recorded using the Schottky resonator at the ESR. These fluorescence detection features are required for future laser cooling experiments at highly relativistic energies (up to γ∼ 13) and high intensities (up to 1011 particles) of ion beams in the new heavy ion synchrotron SIS100 at FAIR.

Permalink: https://www.hzdr.de/publications/Publ-36964


Control Systems and Data Management for High-Power Laser Facilities

Feister, S.; Cassou, K.; Dann, S.; Döpp, A.; Gauron, P.; Gonsalves, A. J.; Joglekar, A.; Marshall, V.; Neveu, O.; Schlenvoigt, H.-P.; Streeter, M. J. V.; Palmer, C. A. J.

The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than was possible using the prior generation. Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology. A distributed networked control system can enable laboratory-wide automation and feedback control loops. These higher-repetition-rate experiments will create enormous quantities of data. A consistent approach to managing data can increase data accessibility, reduce repetitive data-software development, and mitigate poorly organized metadata. An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken. We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities, and we illustrate these topics with case studies from our community.

Keywords: control systems; data management; high-power lasers; high-repetation-rate; big data; community organization; metadata; standards; stabilization; feedback loops

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  • Draco

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Permalink: https://www.hzdr.de/publications/Publ-36963


X-ray polarimetry and its application to strong-field quantum electrodynamics

Yu, Q.; Xu, D.; Shen, B.; Cowan, T.; Schlenvoigt, H.-P.

Polarimetry is a highly sensitive method to quantify changes of the polarization state of light when passing through matter and is therefore widely applied in material science. The progress of synchrotron and X-Ray Free Electron Laser (XFEL) sources has led to significant developments of X-ray polarizers, opening perspectives for new applications of polarimetry to study source and beamline parameters as well as sample characteristics. X-ray polarimetry has shown to date a polarization purity of \num{<1.4e-11}, enabling detection of very small signals from ultrafast phenomena. A prominent application is the detection of vacuum birefringence. Vacuum birefringence is predicted in Quantum Electrodynamics (QED) and expected to be probed by combining an XFEL with a petawatt-class optical laser. We review how source and optical elements affect X-ray polarimeters in general and what qualities are required for detection of vacuum birefringence.

Keywords: X-rays; polarizer; polarimetry; birefringence; QED

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  • HIBEF

Permalink: https://www.hzdr.de/publications/Publ-36962


Quantification of surface changes and volume losses of selected rock types due to different cleaning processes

Koch, T.; Fischer, C.; Schad, F.; Siegesmund, S.

The restorative cleaning of natural stones has a special significance for the preservation of important cultural assets or the slowing of their deterioration. Organisms such as fungi, lichens or mosses, but also emission dirt such as soot soften and otherwise damage both the surface and the internal structure of the building stone. In order to quantify the effects and in particular the abrasiveness of selected cleaning methods, cleaning experiments were carried out on six different naturally and artificially weathered rocks using cold water under high pressure, hot water under high pressure as well as hot-water steam. The types of rocks studied include marble, limestone, granite, sandstone and tuff. Surface changes in roughness and topography were quantified using two surface-sensitive methods: confocal microscopy as well as 3D shadow triangulation. The two high-pressure cleaning methods were found to have a significantly stronger abrasive effect than steam cleaning when the distances were too small. The cleaning performance, which was compared using biologically weathered samples, was lowest for steam cleaning. However, the high temperatures of the steam also permanently eliminate much of the biological matter on and under the surface, as observed in the field test. The results presented should make it possible for the conservator to assess, which cleaning procedures to use for the different rock varieties depending on the degree of weathering.

Permalink: https://www.hzdr.de/publications/Publ-36961


Donor-Acceptor Conjugated Acetylenic Polymers for Co- Catalysts-Free Overall Photoelectrochemical Water Splitting

Borrelli, M.; An, Y.; Joy Querebillo, C.; Morag, A.; Neumann, C.; Turchanin, A.; Sun, H.; Kuc, A. B.; Weidinger, I. M.; Feng, X.

Due to the drastic required thermodynamical requirements, a photoelectrode material that can function as both a photocathode and a photoanode remains elusive. In this work, we demonstrate for the first time that, under simulated solar light and without co-catalysts, donor- acceptor conjugated acetylenic polymers (CAPs) exhibit both impressive oxygen evolution (OER) and hydrogen evolution (HER) photocurrents in alkaline and neutral medium, respectively. In particular, poly(2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine) (pTET) provides a benchmark OER photocurrent density of ~200 μA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) at pH 13 and a remarkable HER photocurrent density of ~190 μA cm-2 at 0.3 V vs. RHE at pH 6.8. By combining theoretical investigations and electrochemical-operando Resonance Raman spectroscopy, we show that the OER proceeds with two different mechanisms, with the electron-depleted triple bonds acting as single-site OER in combination with the C4-C5 atoms of the phenyl rings as dual sites. The HER, instead, occurs via an electron transfer from the tri-acetylenic linkages to the triazine rings, which act as the HER active sites. This work represents a novel application of organic-based materials and contributes to the development of high-performance photoelectrochemical catalysts for the solar fuels’ generation.

Permalink: https://www.hzdr.de/publications/Publ-36960


Understanding hydrogen diffusion in between layers of 2D materials

Eren, I.; Yun, A.; Kuc, A. B.

In 2018, the group of Geim from Manchester performed very interesting experiments, in which hydrogen atoms were diffused and transported inside the interstitial space of layered materials, such as hexagonal boron nitride or MoS2, showing a good sieving of deuterium from protium. We later showed theoretically that indeed hydrogen atoms rather than ions are transported between the layers and reported their diffusion coefficients. We also showed that the transport is assisted by the layer shearing mode. In this work, we investigated the hydrogen diffusion between layers of different transition-metal dichalcogenides (TMDCs), where we studied the influence of possible stackings, stoichiometry, and exemplary twist angles between layers on the self-diffusion coefficient. The calculations were performed using well-tempered metadynamics simulations as implemented in CP2K package, which gives us access to the free energy surface. We found that TMDCs with Se or Mo atoms have lower free energy barriers than these with S or W. Furthermore, structural stackings of MoS2 (𝐻ℎℎ(2H), 𝑅ℎ𝑋 (3R), 𝑅ℎℎ, 𝐻ℎ𝑀, 𝐻ℎ𝑋) also result in different free energy barriers. These energy barriers affect strongly the self-diffusion coefficients, because they enter the diffusion equation as exponent.

  • Poster
    Symposium on Theoretical Chemistry 2022, 15.-18.09.2022, Heidelberg, Germany
  • Poster
    Chem2dmat, 15.-18.05.2023, Bologna, Italy
  • Poster (Online presentation)
    20 years of metadynamics, 05.-08.09.2022, Lausanne, Switzerland
  • Poster
    PISACMS 2022: Paris International School on Advanced Computational Materials Science, 28.08.-01.09.2022, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-36959


Preclinical trial comparing radiotherapy alone versus standard radiochemotherapy in three human papilloma virus (HPV) negative and three HPV-positive head and neck squamous cell carcinoma (HNSCC) xenograft tumour models.

Valentini, C.; Ebert, N.; Koi, L.; Pfeifer, M.; Löck, S.; Erdmann, C.; Krause, M.; Baumann, M.

Purpose: To perform a preclinical trial comparing the efficacy of fractionated radiotherapy versus
radiochemotherapy with cisplatinum in HPV-positive and negative human head and neck
squamous cell carcinoma (HNSCC) xenografts.
Material and methods: Three HPV-negative and three HPV-positive HNSCC xenografts in nude
mice were randomized to radiotherapy (RT) alone or to radiochemotherapy (RCT) with weekly
cisplatinum. To evaluate tumour growth time, 20 Gy radiotherapy (± Cisplatin) were administered
in 10 fractions over 2 weeks. Dose-response curves for local tumor control were generated for RT
with 30 fractions over 6 weeks to different dose levels given alone or combined with cisplatinum
(RCT).
Results: One of three investigated HPV-negative and two out of three HPV-positive tumour
models showed a significant increase in local tumour control after RCT compared to RT alone.
Pooled analysis of HPV-positive tumour models showed a statistically significant and substantial
benefit of RCT versus RT alone, with an enhancement ratio of 1.34. Although heterogeneity in
response to both RT and RCT was also observed between the different HPV-positive HNSCC,
these overall were more RT and RCT sensitive than HPV-negative models.
Conclusion: The impact of adding chemotherapy to fractionated radiotherapy on local control was
heterogenous, both in HPV-negative and in HPV-positive tumours, calling for predictive
biomarkers. RCT substantially increased local tumour control in the pooled group of all HPVpositive
tumours whereas this was not found in HPV-negative tumours. Omission of chemotherapy
in HPV-positive HNSCC as part of a treatment de-escalation strategy is not supported by this
preclinical trial.

Keywords: HPV; HNSCC; Radiotherapy; Radiochemotherapy; Tumour models

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  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-36957


Polymorph Conversion in Gallium Oxide via Focused Ion Beam

Bektas, U.; Klingner, N.; Chekhonin, P.; Liedke, M. O.; Hübner, R.; Heller, R.; Ganss, F.; Hlawacek, G.

Monoclinic gallium oxide (β-Ga2O3) is the chemically and thermally most stable compound, compared to its other four polymorphs, with an ultra-wide bandgap of 4.9 eV. It is a promising semiconductor material for power electronics, optoelectronics, and batteries. However, controlling the metastable polymorph phases is quite hard, and the fabrication technology at the nanoscale is immature. Our goal is to understand and utilize ion beam-induced polymorph conversion. Controlling the crystalline structure will allow us to establish new fabrication methods of single-phase polymorph layers, buried layers, multilayers, and different nanostructures in Ga2O3 using focused ion beams (FIBs). The research aims to better understand and control the polymorph conversion, emphasizing spatially resolved modifications by utilizing focused ion beams.
Most of the semiconductor materials transform into an amorphous phase under a high dose of ion irradiation, however, gallium oxide is an exceptionally radiation-tolerant material even at high fluences. In a previous study, Kuznetsov et.al. [1] demonstrated the ion-beam-induced β-to-κ phase trans-formation in Ga2O3 as shown in Fig.1. However, later, Garcia Fernandez et.al. [2] showed that the monoclinic β-phase actually transforms into the cubic γ-phase. Additional experimental and simulation results suggest that the formed gamma layer is not only stable up to several hundred degrees but also can tolerate high fluencies of additional ion irradiation. The conversion from the stable to the meta-stable phase seems to be enabled by the formation of a defective spinel structure in which the oxygen lattice remains unchanged [3].
Here, we used Helium Ion Microscopy (HIM) and liquid metal alloy ion source (LMAIS) FIBs to locally irradiate the (-201) oriented β-Ga2O3 sample with different ions (Ne, Ga, Co, Nd, Si, Au, In) to induce the polymorph transition. The successful conversion into γ- Ga2O3 under Ne+ irradiation (Fig.2(a)) has been confirmed by using Electron Backscattered Diffraction (EBSD) and indexing the Kikuchi patterns (Fig.2(b)). Furthermore, Doppler broadening variable energy positron annihilation spectroscopy (DB-VEPAS) and Rutherford Backscatter Spectrometry (RBS) were performed for neon broad beam irradiated implants to better understand the fluence-dependent creation and distribution of defects. Transmission Electron Microscopy (TEM) images also provide information about the distinct and sharp interfaces between different polymorphs of Ga2O3. The first results indicate that the damage/strain created by the Ne+, Co+, and Si+ FIB irradiation leads to a local transformation of β- Ga2O3 to γ- Ga2O3 and the structure maintains its crystallinity even under the high fluence of ion irradiation instead of being amorphized.

Keywords: Gallium Oxide; Helium Ion Microscopy; Focused Ion Beam; Positron Annihilation Lifetime Spectroscopy; Polymorph Transition; Transmission Electron Microscopy; Electron Backscatter Diffraction; Rutherford backscatter spectroscopy

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  • Open Access Logo Lecture (Conference)
    3rd FIT4NANO, 15.-19.07.2023, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36956


How to grow single-crystalline and epitaxial NiTi films in (100)- and (111)-orientation

Lünser, K.; Undisz, A.; Nielsch, K.; Fähler, S.

Understanding the martensitic microstructure in NiTi thin films helps to optimize their properties for applications in microsystems. Epitaxial and single-crystalline films can serve as model systems to understand the microstructure, as well as to exploit the anisotropic mechanical properties of NiTi. Here, we analyze the growth of NiTi on single-crystalline MgO(100) and Al2O3(0001) substrates and optimize film and buffer deposition conditions to achieve epitaxial films in (100)- and (111)-orientation. On MgO(100), we compare the transformation behavior and crystal quality of (100)-oriented NiTi films on different buffer layers. We demonstrate that a vanadium buffer layer helps to decrease the low-angle grain boundary density in the NiTi film, which inhibits undesired growth twins and leads to higher transformation temperatures. On Al2O3(0001), we analyze the orientation of a chromium buffer layer and find that it grows (111)-oriented only in a narrow temperature range around 500 °C. By depositing the Cr buffer below the NiTi film, we can prepare (111)-oriented, epitaxial films with transformation temperatures above room temperature. Transmission electron microscopy (TEM) confirms a martensitic microstructure with Guinier Preston (GP)-zone precipitates at room temperature. We identify the deposition conditions to approach the ideal single crystalline state, which is beneficial for the analysis of the martensitic microstructure and anisotropic mechanical properties in different film orientations.

Keywords: NiTi films; shape memory alloys; epitaxial film growth; Nitinol

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Permalink: https://www.hzdr.de/publications/Publ-36955


Europium(III) Meets Etidronic Acid (HEDP): a Coordination Study Combining Spectroscopic, Spectrometric, and Quantum Chemical Methods

Heller, A.; Senwitz, C.; Foerstendorf, H.; Tsushima, S.; Holtmann, L.; Drobot, B.; Kretzschmar, J.

Etidronic acid (HEDP, H4L) is a proposed decorporation agent for U(VI). In this paper, we studied its complex formation with Eu(III), an inactive analog of trivalent actinides, over a wide pH range, at varying metal to ligand ratios (M:L) and total concentrations. Combining spectroscopic, spectrometric, and quantum chemical methods, five distinct Eu(III)−HEDP complexes were found, four of which were characterized. At acidic pH, the readily soluble EuH2L+ and Eu(H2L)2− species with log β values of 23.7 ± 0.1 and 45.1 ± 0.9 are formed. At near-neutral pH, EuHL0s forms with a log β of ~23.6 and, additionally, a most probably polynuclear complex. At alkaline pH, the readily dissolved EuL− species with a log ß of ~11.2 is formed. A six-membered chelate ring is the key motif in all solution structures. The equilibrium between the Eu(III)–HEDP species is influenced by several parameters, i.e. pH, M:L, total Eu(III) and HEDP concentrations, and time. Overall, the present work sheds light on the very complex speciation in the HEDP–Eu(III) system and indicates that, for risk assessment of potential decorporation scenarios, side reactions of HEDP with trivalent actinides and lanthanides should also to be taken into account.

Permalink: https://www.hzdr.de/publications/Publ-36954


Efficient calculations of electronic structures with machine-learning models

Fiedler, L.

Quantum mechanical calculations of the electronic structure of matter enable accessing interesting thermodynamical properties without the need for prior experimental measurements.
Therefore, electronic structure calculations are of great interest in fields such as materials discovery or drug design. At the forefront of such simulations lies density functional theory (DFT), due to its excellent balance between computational accuracy and efficiency. Yet, as pressing environmental and social issues shift the research focus to increasingly complicated systems and conditions, even the most efficient of DFT implementations are approaching their limitations in terms of computational feasibility. A possible route to enable more complex calculations lies with machine learning (ML), i.e., algorithms that are capable of capturing complicated relationships based on large amounts of data.

Keywords: Density Functional Theory; Machine Learning

  • Open Access Logo Lecture (others)
    CASUS institute seminar, 02.05.2023, Görlitz, Deutschland
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    SciML Webinar Series, 09.11.2023, University of Michigan, USA

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Permalink: https://www.hzdr.de/publications/Publ-36953


Eulerian simulation of co-current solid-liquid flow in a vertical pipe

Draw, M.; Rzehak, R.

The prediction of solid-liquid flow in a pipe is of significance for a variety of industrial processes. Since the physical phenomena in such processes appear on widely differing length- and time-scales, many CFD methods are not quite cost-effective. The Euler-Euler multiphase approach makes it feasible to simulate such flows with reasonable computation time. The main challenge of this approach lies in the modeling of the interfacial momentum exchange between the phases, since the interface is not resolved. In this paper, a baseline model is validated that describes the interfacial forces (drag, virtual mass, (shear-) lift, wall (-lift), and turbulent dispersion) between solid particles and a liquid. This model is validated against experimental data of positively and negatively buoyant particles in a vertical pipe flow from the literature. The results show a reasonable agreement with the experimental data, except for the solid volume fraction distribution in the negatively buoyant particle cases. Possible reasons for this are discussed.

Keywords: solid-liquid two-phase flow; Euler-Euler two-fluid model; closure models; vertical pipe flow

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

Permalink: https://www.hzdr.de/publications/Publ-36952


Federated Deep Learning With Prototype Matching for Object Extraction From Very-High-Resolution Remote Sensing Images

Zhang, X.; Zhang, B.; Yu, W.; Kang, X.

Deep convolutional neural networks (DCNNs) have become the leading tools for object extraction from very-high-resolution (VHR) remote sensing images. However, the label scarcity problem of local datasets hinders the prediction performances of DCNNs, and privacy concerns regarding remote sensing data often arise in the traditional deep learning schemes. To cope with these problems, we propose a novel federated learning scheme with prototype matching (FedPM) to collaboratively learn a richer DCNN model by leveraging remote sensing data distributed among multiple clients. This scheme conducts the federated optimization of DCNNs by aggregating clients’ knowledge in the gradient space without compromising data privacy. Specifically, the prototype matching method is developed to regularize the local training using prototypical representations while reducing the distribution divergence across heterogeneous image data. Furthermore, the derived deviations across local and global prototypes are applied to quantify the effects of local models on the decision boundary and optimize the global model updating via the attention-weighted aggregation scheme. Finally, the sparse ternary compression (STC) method is used to alleviate communication costs. Extensive experimental results derived from VHR aerial and satellite image datasets verify that the FedPM can dramatically improve the prediction performance of DCNNs on object extraction with lower communication costs. To the best of our knowledge, this is the first time that federated learning has been applied for remote sensing visual tasks.

Keywords: Deep Learning; Federated Learning; Object Extraction; Remote Sensing Images; Semantic Segmentation

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Permalink: https://www.hzdr.de/publications/Publ-36951


Data publication: Gallium bioionflotation using rhamnolipid: Influence of frother addition and foam properties

Chakankar, M. V.; Oestreich, A.; Pollmann, K.; Rudolph, M.

The current study investigated the application of rhamnolipid biosurfactant as an ion collector in bioionflotation. In a top-down approach, the influence of rhamnolipid on gallium (Ga) ion flotation and recovery were investigated followed by detailed studies on the influencing parameters and foam characterization. Rhamnolipid exhibits extensive foaming properties and foam produced by rhamnolipid alone has higher stability making it difficult to collect the flotation concentrates. An addition of 1,2-decanediol introduces instability to this foam and also aids in concentrate collection. Observations during the flotation studies resulted in a series of investigations on rhamnolipid properties such as aggregate size, surface tension, and foam characterization. These results indicated that the addition of Ga and/or 1,2-decanediol affected the molecular aggregation of rhamnolipid. Moreover, the surface activity, foamability, foam drainage, and foam coarsening/coalescence of the rhamnolipid changed in the presence of Ga and/or 1,2-decanediol. In a batch bioionflotation process, rhamnolipid was able to remove nearly 80% Ga at pH 7 in presence of 1,2-decanediol. However, upgrading was higher at pH 6 without 1,2-decanediol, which is important when considering the flotation recovery in presence of other metals. Such biosurfactants have a high potential for wide applications in ion flotation and further optimization of flotation parameters is essential.

Keywords: Rhamnolipid; biosurfactant; ion flotation; Foam characterization; Gallium; surface tension

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Permalink: https://www.hzdr.de/publications/Publ-36950


Microbial Influence on Cast Iron Corrosion-Approach of the UMB-II project

Matschiavelli, N.

Talk about the recent results within the UMB-II Project. Main focus here is the influence of intrinsic microbial bentonite communities on the corrosion of cast iron.

  • Lecture (others)
    FWOB-Seminar, 25.05.2023, Helmholtz-Zentrum Dresden-Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36948


Further development, validation and verification of the Monte-Carlo code TRAMO on ex-vessel experiments of the Greifswald NPP

Baier, S.; Konheiser, J.; Pönitz, E.

TRAMO is a Monte Carlo code which is specially designed for geometries of nuclear power plants. In recent years, TRAMO has undergone a number of technical developments. In addition to the conversion to modern Fortran, standardized models for VVER-440 and VVER-1000 for the evaluation of monitor experiments on the surface of the reactor pressure vessel were developed, and the corresponding pre- and post-processing was automated. The new TRAMO version is continuously validated and verified. Here we present comparisons with experimental data from unit 1 of the Greifswald nuclear power plant and with MCNP calculations. Earlier calculations with TRAMO showed good agreements in the middle region of the fission zone, but significant deviations outside. A possible explanation is the wrong documentation of the experimental data – especially the heights of the monitors. Assuming a downward shift of the monitor positions by about 24cm, experimental and calculated data show very good agreement.

Keywords: reactor dosimetry; neutron fluence calculation; activity measurements; Monte Carlo code; Monte Carlo calculation

  • Poster
    17th International Symposium on Reactor Dosimetry, 21.-26.05.2023, Lausanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-36947


Data for "How to grow single-crystalline and epitaxial NiTi films in (100)- and (111)-orientation"

Lünser, K.; Undisz, A.; Nielsch, K.; Fähler, S.

This dataset belongs to the paper "How to grow single-crystalline and epitaxial NiTi films in (100)- and (111)-orientation" and contains all raw data used for the paper. It includes AFM, SEM, R(T), TEM, Texture measurements and rocking curves.  Information about samples, measurement techniques and file naming conventions can be found in README.txt. 

Keywords: NiTi films; shape memory alloys; epitaxial film growth; Nitinol

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Permalink: https://www.hzdr.de/publications/Publ-36945


surface pressure isotherms for punicine derivatives and oleic acid/sodium oleate

Pfeufer, R. A.

Data sets of surface pressure isotherms for punicine derivatives (octyl-, nonyl-, decyl-, undecyl- and heptadecyl-punicine) and oleic acid/sodium oleate.

Measurements were carried out at the Langmuir-Blodgett Minitrough of KSV Instruments Ltd. For each measurement the surfactant was solubilized in 1:1 EtOH and chloroform. This solution was placed on top of water (conductivity < 0.8 µS) and after an evaporation time of 10 min measurements were started.

Keywords: Langmuir-Blodgett trough; punicine; surface pressure isotherm

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Permalink: https://www.hzdr.de/publications/Publ-36944


dynamic contact angles of water of uncoated and coated (heptadecyl punicine) on quartz, hiddenite and kunzite

Pfeufer, R. A.

data sets of dynamic contact angle measurements of water onuncoated and coated (heptadecyl punicine) hiddenite, kunzite and quartz.

Measurements were carried out at the OCA25 from DataPhysics Instruments GmbH with the ARCA method.

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Permalink: https://www.hzdr.de/publications/Publ-36943


Pendant drop mesurements for water and decyl punicine in water

Pfeufer, R. A.

data sets of pendant drop measurements of aqueous decyl punicine solution.

Measurements were carried out at the OCA25 from DataPhysics Instruments GmbH .

Keywords: punicine; pendant drop; interfacial tension

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Permalink: https://www.hzdr.de/publications/Publ-36942


bubble pressure tensiometry for punicine derivatives and oleic acid/sodium oleate

Pfeufer, R. A.

Data sets of surface tension of puncine derivatives (octyl-, nonyl-, decyl-, undecyl- and heptadecyl-punicine) and oleic acid/sodium oleate in water measured with bubble pressure tensiometry at different pH and different concentrations.

Measurements were done at BP100 of KRÜSS GmbH. For each mesurement the adequate amount of a 25mM surfactant solution (40 vol-% EtOH and 60vol-% distilled water) werde diluted in 70 mL of distilled water.

Keywords: bubble pressure; punicine; surface tension

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Permalink: https://www.hzdr.de/publications/Publ-36941


zetapotential of spodumene with decyl punicine

Pfeufer, R. A.

Data set of zetapotential measurements of a spodumene dispersion and spodumene dispersion with decyl punicine.

Measurements were carried out in 10 mM KCl background at 2.5 wt-% spodumene (x < 10 µm). For the measurement with decyl punicine a concentration of 10 µM surfactant was used.

Keywords: Zetapotential; punicine; spodumene

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Permalink: https://www.hzdr.de/publications/Publ-36940


Effect of physical exercise on brain perfusion in chemotherapy-treated breast cancer patients: a randomized controlled trial (PAM study)

Koevoets, E. W.; Petr, J.; Monninkhof, E. M.; Geerlings, M. I.; Witlox, L.; van der Wall, E.; Stuiver, M. M.; Sonke, G. S.; Velthuis, M. J.; Jobsen, J. J.; van der Palen, J.; Jmm Mutsaerts, H.; de Ruiter, M. B.; May, A. M.; Schagen, S. B.

BACKGROUND Breast cancer patients may experience cognitive difficulties after chemotherapy.
PURPOSE To investigate whether an exercise intervention can affect cerebral blood flow (CBF) in breast cancer patients and if CBF changes relate to memory function.
STUDY TYPE Prospective.
POPULATION Chemotherapy-treated breast cancer patients with cognitive problems, and with relatively low physical activity levels were randomized to an exercise intervention (n=91) or control group (n=90).
FIELDSTRENGTH/SEQUENCE A 3-T arterial spin labeling CBF scan was performed.
ASSESSMENT The 6-month intervention consisted of (supervised) aerobic and strength training, 4x1 hour/week. Measurements at baseline (2-4 years post-diagnosis) and after six months included the arterial spin labeling CBF scan, from which we calculated gray matter CBF in the whole brain, hippocampus, anterior cingulate cortex, and posterior cingulate cortex. Furthermore, we measured physical fitness and memory functioning.
STATISTICAL TESTS Multiple regression analyses with a two-sided alpha of 0.05 for all analyses.
RESULTS We observed significant improvement in physical fitness (VO2peak) in the intervention group (n=53) compared to controls (n=51, B1.47, 95%CI:0.44; 2.50), nevertheless no intervention effects on CBF were found (e.g. whole brain: B0.98, 95%CI:-2.38; 4.34). Highly fatigued patients showed larger, but not significant, treatment effects. Additionally, change in physical fitness, from baseline to post-intervention, was positively associated with changes in CBF (e.g., whole brain: B0.75, 95%CI:0.07; 1.43). However, we observed no relation between CBF changes and change in memory performance.
DATA CONCLUSION The exercise intervention did not affect CBF of cognitively affected breast cancer patients. However, a change in physical fitness was related to a change in CBF, but a change in CBF was not associated with memory functioning.

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  • PET-Center
  • Open Access Logo Journal of Magnetic Resonance Imaging 59(2024)5, 1667-1680
    Online First (2023) DOI: 10.1002/jmri.28967

Permalink: https://www.hzdr.de/publications/Publ-36939


Brain tumor imaging without gadolinium-based contrast agents: Feasible or Fantasy?

Wamelink, I. J. H. G.; Azizova, A.; Booth, T. C.; Mutsaerts, H. J. M. M.; Ogunleye, A.; Mankad, K.; Petr, J.; Barkhof, F.; Keil, V. C.

Gadolinium-based contrast agents (GBCA) form the cornerstone of current primary brain tumor MRI protocols at all stages of the patient journey. Though an imperfect of tumor grade, GBCA is repeatedly used for diagnosis and monitoring.
In practice, however, radiologists will encounter situations where GBCA injection is unwanted or of doubtful benefit. Reducing GBCA administration could improve the patient burden of (repeated) imaging, especially in vulnerable patient groups such as children, minimize risks of putative side effects, as well as benefit costs, logistics, and the environmental footprint.
This review presents standard imaging strategies to reduce GBCA exposure for pediatric and adult patients with primary brain tumors, including the effect of prolonging follow-up intervals and omitting contrast-enhanced sequences. The potential of novel pulse sequences, such as arterial spin labeling, and upcoming artificial intelligence methods, e.g., to generate synthetic post-contrast images, promise to replace GBCA-dependent approaches. To attain a concise summary of the knowledge in the field, gliomas and meningiomas as typical representatives of primary brain tumors are the review’s focus. Special attention is paid to study quality and real-life applicability.

Involved research facilities

  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-36938


Data publication: Integration of Multifunctional Epitaxial (Magnetic) Shape Memory Films in Silicon Microtechnology

Fink, L.; Kar, S.; Lünser, K.; Nielsch, K.; Reith, H.; Fähler, S.

Measured raw data (XRD, texture, SEM, PPMS and EDX)

Keywords: Magnetic shape memory alloys; Silicon microtechnology; Ni2MnGa; NiTi; Epitaxial film growth

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Permalink: https://www.hzdr.de/publications/Publ-36937


Millisecond Flash Lamp Curing for Porosity Generation in Thin Films

Attallah, A. G.; Prucnal, S.; Butterling, M.; Hirschmann, E.; Koehler, N.; Schulz, S. E.; Wagner, A.; Liedke, M. O.

Flash lamp annealing (FLA) with millisecond pulse duration is reported as a novel curing method for pore precursors degradation in thin films. A case study on the curing of dielectric thin films is presented. FLA-cured films are being investigated by means of positron annihilation spectroscopy and Fourier-transform infrared (FTIR) spectroscopy in order to quantify the nm-scale porosity and post-treatment chemistry, respectively. Results from positron annihilation reveal the onset of formation of porous voids inside the samples at 6 ms flash treatment time. Moreover, parameter adjustment (flash duration and energy density) allows for identifying the optimum conditions of effective curing. Within such a systematic investigation, positron results indicate that FLA is able to decompose the porogen (pore precursors) and to generate interconnected (open porosity) or isolated pore networks with self-sealed pores in a controllable way. Furthermore, FTIR results demonstrate the structural evolution after FLA, that help for setting the optimal annealing conditions whereby only a residual amount of porogen remains and at the same time a well-densified matrix, and a hydrophobic porous structures are created. Raman spectroscopy suggests that the curing-induced self-sealing layer developed at the film surface is a graphene oxide-like layer, which could serve as the outside sealing of the pore network from intrusions.

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  • P-ELBE

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Permalink: https://www.hzdr.de/publications/Publ-36933


Preclinical Characterization of the 177Lu-Labeled Prostate Stem Cell Antigen (PSCA)-Specific Monoclonal Antibody 7F5

Striese, F.; Neuber, C.; Gräßel, S.; Arndt, C.; Ullrich, M.; Steinbach, J.; Pietzsch, J.; Bergmann, R.; Pietzsch, H.-J.; Sihver, W.; Frenz, M.; Feldmann, A.; Bachmann, M.

: Prostate specific membrane antigen (PSMA) is an excellent target for imaging and treatment of prostate carcinoma (PCa). Unfortunately, not all PCa cells express PSMA. Therefore, alternative theranostic targets are required. The membrane protein prostate stem cell antigen (PSCA) is highly overexpressed in most primary prostate carcinoma (PCa) cells and in metastatic and hor-mone refractory tumor cells. Moreover, PSCA expression positively correlates with tumor pro-gression. Therefore, it represents a potential alternative theranostic target suitable for imaging and/or radioimmunotherapy. In order to support this working hypothesis, we conjugated our previously described anti-PSCA monoclonal antibody (mAb) 7F5 with the bifunctional chelator CHX-A″-DTPA and subsequently radiolabeled it with the theranostic radionuclide 177Lu. The re-sulting radiolabeled mAb ([177Lu]Lu-CHX-A″-DTPA-7F5) was characterized both in vitro and in vivo. It showed a high radiochemical purity (>95%) and stability. The labelling did not affect its binding capability. Biodistribution studies showed a high specific tumor uptake compared to most non-targeted tissues in mice bearing PSCA-positive tumors. Accordingly, SPECT/CT images re-vealed a high tumor-to-background ratios from 16 h to 7 days after administration of [177Lu]Lu-CHX-A″-DTPA-7F5. Consequently, [177Lu]Lu-CHX-A″-DTPA-7F5 represents a promising candidate for imaging and in the future also for radioimmunotherapy.

Keywords: 177Lu-labeled antibody; prostate stem cell antigen; CHX-A’’-DTPA; prostate cancer

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  • PET-Center

Permalink: https://www.hzdr.de/publications/Publ-36931


Multivalent adaptor proteins specifically target NK cells carrying a universal chimeric antigen receptor to ErbB2 (HER2)-expressing cancers

Pfeifer Serrahima, J.; Zhang, C.; Oberoi, P.; Bodden, M.; Röder, J.; Arndt, C.; Feldmann, A.; Kiefer, A.; Prüfer, M.; Kühnel, I.; Tonn, T.; Bachmann, M.; Wels, W. S.

Chimeric antigen receptor (CAR)-engineered immune effector cells constitute a promising approach for adoptive cancer immunotherapy. Nevertheless, on-target/off-tumor toxicity and immune escape due to antigen loss represent considerable challenges. These may be overcome by adaptor CARs that are selectively triggered by bispecific molecules that crosslink the CAR with a tumor-associated surface antigen. Here, we generated NK cells carrying a first- or second-generation universal CAR (UniCAR) and redirected them to tumor cells with so-called target modules (TMs) which harbor an ErbB2 (HER2)-specific antibody domain for target cell binding and the E5B9 peptide recognized by the UniCAR. To investigate differential effects of the protein design on activity, we developed homodimeric TMs with one, two or three E5B9 peptides per monomer, and binding domains either directly linked or separated by an IgG4 Fc domain. The adaptor molecules were expressed as secreted proteins in Expi293F cells, purified from culture supernatants and their bispecific binding to UniCAR and ErbB2 was confirmed by flow cytometry. In cell killing experiments, all tested TMs redirected NK cell cytotoxicity selectively to ErbB2-positive tumor cells. Nevertheless, we found considerable differences in the extent of specific cell killing depending on TM design and CAR composition, with adaptor proteins carrying two or three E5B9 epitopes being more effective when combined with NK cells expressing the first-generation UniCAR, while the second-generation UniCAR was more active in the presence of TMs with one E5B9 sequence. These results may have important implications for the further development of optimized UniCAR and target module combinations for cancer immunotherapy.

Keywords: Chimeric antigen receptor; ErbB2; HER2; NK-92; Natural killer cells; UniCAR

Permalink: https://www.hzdr.de/publications/Publ-36930


Generation of optimal weight values based on the Recursive Monte Carlo (RMC) method for using in MC deep penetrations calculations

Yadav, P.; Rachamin, R.; Konheiser, J.; Baier, S.

In nuclear engineering, Monte Carlo (MC) methods are commonly used for reactor analysis and radiation shielding problems. These methods are capable of dealing with both simple and complex system models with accuracy. The application of Monte Carlo methods experiences challenges when dealing with the deep penetration problem that is typically encountered in radiation shielding cases. It is difficult to produce statistically reliable results due to poor particle sampling in the region of interest. Therefore, such calculations are performed by the Monte Carlo N-Particle Transport (MCNP) code in association with the weight window (WW) variance reduction technique, which increases the particle statistics in the desired tally region. However, for large problems, the MCNP’s built-in weight window generator produces zero weight window parameters for the tally regions located far from the source. To address this issue, the recursive Monte Carlo (RMC) method was proposed. This paper focuses on the RMC methodology and its implementation in the HZDR’s in-house code (TRAWEI), which is responsible for producing optimal zone weight parameters used for optimizing the deep penetration MC calculations. In addition, this paper discusses the verification of the TRAWEI weight generator program to that of an existing MCNP weight window generator. The performance of TRAWEI-generated weight values is assessed using a handful of test cases involving two shield materials. Globally, the TRAWEI-generated weight values improved the statistical variance and computational efficiency of the Monte Carlo run compared to the analog MCNP simulation, and that of the simulation with weight window values generated by the standard MCNP weight window generator (WWG).

Keywords: deep penetration problem; weight window (WW); recursive Monte Carlo (RMC)

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Permalink: https://www.hzdr.de/publications/Publ-36928


Spin–orbit coupling corrections for the GFN-xTB method

Jha, G.; Heine, T.

Spin–orbit coupling (SOC) is crucial for correct electronic structure analysis in molecules and materials, for example, in large molecular systems such as superatoms, for understanding the role of transition metals in enzymes, and when investigating the energy transfer processes in metal–organic frameworks. We extend the GFN-xTB method, popular to treat extended systems, by including SOC into the hamiltonian operator. We followed the same approach as previously reported for the density–functional tight-binding method and provide and validate the necessary parameters for all elements throughout the Periodic Table. The parameters have been obtained consistently from atomic SOC calculations using the density–functional theory. We tested them for reference structures where SOC is decisive, as in the transition metal containing heme moiety, chromophores in metal–organic frameworks, and in superatoms. Our parameterization paves the path for incorporation of SOC in the GFN-xTB based electronic structure calculations of computationally expensive molecular systems.

Keywords: Spin-Orbit Coupling; GFN-xTB; Semi-empirical method

Permalink: https://www.hzdr.de/publications/Publ-36926


Activity measurement and calculation for gamma-emitting radionuclides in concrete drill cores of unit 2 of the Greifswald NPP

Pönitz, E.; Roode-Gutzmer, Q. I.; Barkleit, A.; Konheiser, J.

Due to Germany's nuclear phase-out, decommissioning and final disposal of construction materials of Nuclear Power Plants (NPP) become increasingly important. The reliable determination of radionuclides produced by neutron activation, the activity as a function of time since shutdown and investigation of subsequent radionuclide mobility are subject of a research project. Drill cores of the concrete shielding of unit 2 of the Greifswald NPP were retrieved. Specific activities of gamma emitters and the elemental composition were measured. The radiation transport code MCNP 6 was used for the calculation of spectral neutron fluences. A neutron radiation field calculation reveals that the maximum neutron fluence in the concrete component is located in the floor just below the RPV. The concrete structures closest to the reactor core are shielded efficiently against neutron radiation by the annular water tank. Measured and calculated specific activities of 152Eu, 154Eu and 60Co for the cement screed at the position of the maximum neutron fluence are surprisingly low. A specific exemption (i.e. release from radiation protection surveillance but mandatory for final disposal) of the screed sample according to Germany’s Radiation Protection Ordnance is expected to be possible approximately 4 decades after the shutdown of the NPP.

  • Lecture (Conference)
    17th International Symposium on Reactor Dosimetry, 21.-26.05.2023, Lausanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-36925


Modification of Three-Magnon Splitting by In-Plane Magnetic Fields

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

Over the past few decades, extensive research has been conducted on magnetic vortices due to their fundamental physical properties and potential applications as magnetic storage devices or resonators. Information can be encoded in the polarity or gyrotropic motion of the vortex core. Moreover, magnetic vortices offer a versatile spectrum of radial and azimuthal magnon modes, which exhibit interesting linear and nonlinear dynamics. One notable example is three-magnon splitting, where one mode can spontaneously split into two secondary magnon modes when excited above a threshold power. Three-magnon splitting follows specific selection rules, with the split modes having distinct frequencies and mode numbers to fulfill energy and angular momentum conservation [1]. Magnetic vortices offer the potential to stimulate these processes below their intrinsic threshold powers [2, 3], making them promising candidates for novel computing approaches such as reservoir computing.

In this study, we demonstrate that the application of in-plane magnetic fields in the order of a few mT can efficiently modify three-magnon splitting [4]. Using micromagntic simulations and Brillouin-light-scattering microscopy, we show that the deformation of the vortex results in additional secondary butterfly modes that follow the same selection rules as the regular modes but exhibit different localization and much lower three-magnon splitting threshold powers.

[1] K. Schultheiss et al. PRL 122, 097202 (2019)
[2] L. Körber et al. PRL 125, 207203 (2020)
[3] L. Körber et al. arXiv 2211.02328 (2022)
[4] L. Körber et al. APL 122, 092401 (2023)

Keywords: magnetic vortex; spin waves; magnons; nonlinearity

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  • Poster
    Magnonics Conference, 30.07.-3.8.2023, Le Touquet - Paris - Plague, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-36924


Special Issue “Advances in Monitoring Metabolic Activities of Microorganisms by Calorimetry”

Matulis, D.; Wadsö, L.; Fahmy, K.

Editorial Special Issue “Advances in Monitoring Metabolic Activities of Microorganisms by Calorimetry”

Keywords: heavy metals; toxicity; metabolic heat; bacterial growth; antibiotics; fungal metabolism

Permalink: https://www.hzdr.de/publications/Publ-36923


Strong-field QED in Furry-picture momentum-space formulation: Ward identities and Feynman diagrams

Hernandez Acosta, U.; Kämpfer, B.

The impact of a strong electromagnetic background field on otherwise perturbative QED processes is studied in the momentum-space formulation. The univariate background field is assumed to have finite support in time, thus being suitable to provide a model for a strong laser pulse in plane-wave approximation. The usually employed Furry picture in position space must be equipped with some non-obvious terms to ensure the Ward identity. In contrast, the momentum space formulation allows for an easy and systematic account of these terms, both globally and order-by-order in the weak-field expansion. In the limit of an infinitely long-acting (monochromatic) background field, these terms become gradually suppressed, and the standard perturbative QED Feynman diagrams are recovered in the leading-order weak-field limit. A few examples of three- and four-point amplitudes are considered to demonstrate the application of our Feynman rules which employ free Dirac spinors, the free photon propagator, and the free Fermion propagator, while the external field impact is solely encoded in the Fermion-Fermion-photon vertex function. The appearance of on-/off-shell contributions, singular structures, and Oleinik resonances is pointed out.

Keywords: strong-field QED; Ward identity; laser pulses in plane-wave approximation; Feynman diagrams

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Permalink: https://www.hzdr.de/publications/Publ-36922


Carborane-based Tebufelone Analogs and their Biological Evaluation In Vitro

Braun, S.; Paskas, S.; Laube, M.; George, S.; Hofmann, B.; Lönnecke, P.; Steinhilber, D.; Pietzsch, J.; Mijatović, S.; Maksimović-Ivanić, D.; Hey-Hawkins, E.

The presence of inflammatory mediators in the tumor microenvironment, such as cytokines, growth factors or eicosanoids, indicate cancer-related inflammatory processes. Targeting these inflammatory mediators and related signal pathways may offer a rational strategy for the treatment of cancer. This study focuses on the incorporation of metabolically stable, sterically demanding, and hydrophobic dicarba-closo-dodecaboranes (carboranes) into dual cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LO) inhibitors that are key enzymes in the biosynthesis of eicosanoids. The di-tert-butylphenol derivative tebufelone represents a selective dual COX-2/5-LO inhibitor. The incorporation of meta- or para-carborane into the tebufelone scaffold resulted in eight carborane-based tebufelone analogs that show no COX inhibition but 5-LO inhibitory activities in vitro. Cell viability studies on HT29 colon adenocarcinoma cells revealed that the para-carborane analog 8 exhibits higher anticancer activity compared to tebufelone through the inhibition of cell proliferation. Hence, this strategy proved to be a promising approach to design potent 5-LO inhibitors with potential application as cytostatic agents.

Permalink: https://www.hzdr.de/publications/Publ-36921


Basics of gas flow modulation applied to bubble columns

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

Bubble columns are industrial equipment used for promoting the contact between the gas and the liquid phase. In the column, the gas phase rises in form of bubbles in a pool of liquid. The fraction of the column’s volume occupied by the gas is called gas holdup. Bubble column applications include bioreactors, production of food and beverage as well as of crucial chemicals. The Axial Dispersion Model is the most accepted model for describing the gas flow in bubble columns. In this model, all phenomena deviating from plug-flow conditions are combined and indicated as dispersion. Knowledge of the axial dispersion coefficient is crucial for designing bubble column reactors. This study provides a new non-invasive approach for measuring axial gas dispersion coefficients in bubble column reactors and the application of the new approach at different operating conditions.

  • Poster
    Doctoral Seminar of HZDR, 19.-21.10.2022, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-36920


Flow and mass transfer in structured packings with modified surfaces

Giustacori, P.; Brunazzi, E.; Schubert, M.; Shabanilemraski, I.; Marchini, S.

Commonly, structured packings are operated in film flow. In this case, the entire surface of the packing is completely covered by the liquid to make maximum
use of the available surface area on the elements. However, perfect wetting of the packing is usually difficult to achieve. Moreover, when film flow is targeted, the interfacial area cannot exceed the geometric surface area provided by the packing. Thus, other flow configurations must be alternatively considered increasing the interfacial area potentially available for mass transfer. Droplet flow is one way to achieve this goal. Considering the extreme case of a spherical droplet in contact with the packing on a single infinitesimally small point. For equal volume of droplet and film, the interfacial area in this case is almost five times higher compared to film flow. The developed work is meant to characterize flow structures alternative to the classical film flow over structured packings to determine potential improvement in mass transfer performances. To achieve changes in the flow structure, the surface of the packings elements was modified. In particular, surface treatments were used to improve the hydrophobic properties of the surface. In this way, the formation of liquid droplets on the surface was promoted. A preliminary literature review allowed the selection of self-assembled monolayers (SAMs) as surface modification methods due to the simplicity of performing the treatment. A characterization campaign of the modified surfaces was carried out. Smooth metal sheets specimens of which the packings are made were used for the investigation of contact angles via optical techniques. Behavior of obtained droplets and rivulets as well as their tendency to coalesce were also analyzed. Subsequently, the mass transfer performance of the modified packings was compared with that of the standard packings by air-led stripping of isobutyl acetate from an aqueous solution. A model was developed in this work for droplet and rivulet flow in order to determine specific surface area from packings characteristic and liquid flow rate. Experimental liquid holdup values were used as reference parameter for model validation. This work showed that the considered packing coated with the selected SAMs has a worse performance compared to the non-coated packing in terms of liquid holdup and mass transfer performance, at least when tested with aqueous solutions. However, the value of the present work mainly consists of the developed mathematical model and procedure for packing characterization and performance comparison. In fact, this will allow characterization of possible other surface treatments applicable to the surfaces of structured packings.

Keywords: structured packing; Self-assembling monolayers; droplets; surface modification; mass transfer study

  • Master thesis
    University of Pisa, 2023
    Mentor: Schubert, Markus; Marchini, Sara; Brunazzi, Elisabetta; Shabanilemraski, Iman
    117 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36919


Experimental and Numerical Investigation of a Counter-Current Flow Bubble Column

Khan, H.; Kováts, P.; Zähringer, K.; Rzehak, R.

Bubble columns are gas-liquid contactors that are used in many process-engineering applications. A counter-current liquid flow is frequently imposed to adjust the bubbles’ residence-time and thus optimize mixing and mass-transfer. The present work describes measurements in such a device together with corresponding computational fluid dynamics simulations based on the Eulerian two-fluid framework. Bubble-size and -velocity are measured by shadow-imaging for a large range of gas and counter-current liquid flow rates, as well as different nozzle sizes. The corresponding liquid flow-fields are characterized by Particle Image Velocimetry. From the large experimental database, a few cases are selected to analyze the flow structure and effects of the bubble-size. In the simulations, different models for the drag- and lift-force acting on the bubbles are evaluated. While good agreement between experiments and simulations could be achieved for the gas-fraction and gas-velocity, differences are found for the liquid-velocity, which is generally overestimated in the calculations.

Keywords: countercurrent flow bubble column; shadowgraphy; PIV; Euler-Euler two-fluid model; CFD simulation

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  • Secondary publication expected from 09.12.2024

Permalink: https://www.hzdr.de/publications/Publ-36918


The application of encoder–decoder neural networks in high accuracy and efficiency slit-scan emittance measurements

Ma, S.; Arnold, A.; Michel, P.; Murcek, P.; Ryzhov, A.; Schaber, J.; Steinbrück, R.; Evtushenko, P.; Teichert, J.; Hillert, W.; Xiang, R.; Zhu, J.

A superconducting radio-frequency (SRF) photo injector is in operation at the electron linac for beams with high brilliance
and low emittance (ELBE) radiation center and generates continuous wave (CW) electron beams with high average current
and high brightness for user operation since 2018. The speed of emittance measurement at the SRF gun beamline can be
increased by improving the slit-scan system, thus the measurement time for one phase space mapping can be shortened
from about 15 min to 90 s. The convolution neural networks are applied to improve the efficiency and accuracy of beamlet
images processing. In order to estimate the uncertainty in the calculation of normalized emittance, we analyze the main error
contributions.

Keywords: Beam emittance; Machine learning; Slit-scan; SRF photo injectors

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Permalink: https://www.hzdr.de/publications/Publ-36917


Machine learning-based characterization of collected black carbon and desert dust using HIM microscopy supporting real-time Aethalometer measurements

Podlipec, R.; Lohman, S.; Ivančič, M.; Alföldy, B.; Gregorič, A.; Rigler, M.; Mahfouz, M. M. K.; Pandolfi, M.; Munnik, F.; Heller, R.

Accurate physical and chemical characterization of the aerosols from various sources, such as urban/industrial emissions, biomass burning to dust intrusion events, paramount to unveiling the impact on air quality, radiative forcing and public health, still presents a big challenge. The first step to assess the impact of aerosols is real-time light absorption measurements, typically characterizing spectral dependence with an absorption Angstrom exponent (AAE) approach (Liu et al 2018). Using new model of Aethalometer, AE36s (Aerosol Magee Scientific), with an enhanced spectral resolution, further helps with improved characterization and distinction between different collected aerosols revealing several specific events and sources of aerosol emission. Unfortunately, filter photometers cannot be equipped with analysers which would uncover the distribution and physicochemical properties of collected aerosols on single particle scale, important for an accurate interpretation of the real-time measurements. In the presented study we show for the first time capability of successfully implementing machine learning-based smart characterization of collected aerosols from dust intrusion events in Europe (Barcelona, Ljubljana) and the Middle East (Qatar), to support real-time Aethalometer measurements indicating significant black carbon (BC) and absorbing fraction of organic aerosols (brown carbon, BrC) presence. Briefly, quartz fiber filters with collected aerosols were transferred from the measuring sites to the imaging instrument, Helium Ion Microscope (HIM), which provides unique properties: sub-nm lateral resolution, nm surface sensitivity and high depth-of-field (Hlawacek et al 2014), enabling imaging of aerosols deep into the fibers (Figure 1), not capable with Scanning Electron Microscope (SEM). Imaging at different magnifications enabled accurate analysis of aerosol concentration, size distribution and detection of morphologies at a single particle scale. Imaging contrast sensitive to particle physiochemical properties enabled the distinction of BC from mineral dust, which provided quantification of both separately, using machine learning registration, segmentation and object classification done by Ilastik open-source software (Figure 2).
The results of this approach gave insights into diverse aerosol properties from mm down to nm scale and support real-time optical absorption measurements, key for accurate characterization and for predicting the environmental and health impact of sampled polluted air.

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  • Lecture (Conference)
    European Aerosol Conference 2023 (EAC 2023), 03.-08.09.2023, Malaga, Spain

Permalink: https://www.hzdr.de/publications/Publ-36915


Early mechanisms of ultrafine particulate matter toxicity on in vitro lung model by advanced correlative microscopies

Podlipec, R.; Krišelj, A.; Pirker, L.; Urbančič, I.; Štrancar, J.; Hlawacek, G.

A comprehensive understanding of molecular events leading to adverse outcomes in lungs after administration of ultrafine particulate matter (PM) is still lacking. These repeating exposures to the respiratory tract can eventually lead to persistent inflammation and further cardiovascular diseases (Li et al 2019, Underwood 2017). To better identify and characterize the initial sub-cellular to molecular events after nanomaterial contact, which triggers all following cascades leading to acute or even chronic inflammation, one urgently needs an appropriate high-resolution experimental approach to untangle these key processes.
In our first study focused on how metal oxide aerosols (TiO2) effect model lung epithelium we thus applied super-resolution STED microscopy together with fluorescence microspectroscopy (FMS), where we showed nanoparticle wrapping of cell membranes followed by their translocation across the cell layer (Figure 1) supporting the proposed causal link between the inhalation of nanoparticles and cardiovascular disease (Urbančič et al 2018). But to get more insight into complex and likely destructive nanoparticle interaction with biological matter our next aim was to identify and characterize individual paramount cellular responses by observing real-time structural changes implementing advanced correlative microscopy (CM) approach.
In one of our latest studies, we thus introduced a new CM pipeline, combining STED multimodal microscopy with helium ion microscopy (HIM), which revealed the morphology and the extent of biological wrapping of quarantined nanomaterial composites on the epithelium surface decisive for the onset of chronic inflammation on single molecule scale (Kokot et al 2020) (Figure 2).

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  • Lecture (Conference)
    European Aerosol Conference 2023 (EAC 2023), 03.-08.09.2023, Malaga, Spain

Permalink: https://www.hzdr.de/publications/Publ-36914


Different effect of anatase TiO2 nanotubes and nanocubes on microtubule fragmentation, mitotic arrest and aneuploidy indicating plausible carcinogenicity

Podlipec, R.; Hlawacek, G.

Ultra-high resolution Helium Ion Microscopy (HIM) images of lung epithelial cells exposed to titanium dioxide (TiO2) nanotubes. Images reveal cell nuclear envelope with nuclear pores and cytoskeleton structure showing local damage at the site with the presence of single TiO2 nanotubes. 

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Permalink: https://www.hzdr.de/publications/Publ-36913


Study of hydrodynamics in counter current bubble column

Khan, H.; Rzehak, R.; Kováts, P.; Zähringer, K.

Bubble column reactors are one of the simplest and most representative system for multiphase flows. Regardless of its simple geometry, complex hydrodynamics and its effect on transport properties requires better understanding in order to accomplish a reliable design and scale-up of bubble column reactors. Although with many other parameters, co- or counter-current liquid flow is often used to adjust the residence-time of the bubbles, which is especially important when mass transfer is present in the system. The present study comprises of the initial stage numerical effort to study the hydrodynamics and also the parametric effect in counter current bubble column. For this purpose, simulations are performed within the Eulerian two-fluid framework using OpenFOAM as a CFD software and later the results are being compared with the experimental data.

Keywords: bubble column; dispersed two-phase flow; closure relations; countercurrent flow; Euler-Euler simulation

  • Lecture (Conference)
    11th International Conference on Multiphase Flow, ICMF 2023, 02.-07.04.2023, Kobe, Japan

Permalink: https://www.hzdr.de/publications/Publ-36912


Different effect of anatase TiO2 nanotubes and nanocubes on microtubule fragmentation, mitotic arrest and aneuploidy indicating plausible carcinogenicity

Podlipec, R.

Time-lapse videos of cells and microtubule dynamics (in green) after exposure to different nanoparticles (in red) taken with confocal fluorescence microscopy. S1 - control experiment; S2-S3 - the exposure to titanium dioxide (TiO2) nanotubes measured at different image planes; S4-S5 - the exposure to TiO2 nanocubes measured at different image planes; S6-S7 - the exposure to multiwall carbon nanotubes (MWCNTs) measured at different image planes.

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Permalink: https://www.hzdr.de/publications/Publ-36911


Data publication: Selective removal of Gallium from mixed metal solutions with Arsenic by ion flotation using the biosurfactant rhamnolipid

Chakankar, M. V.; Pollmann, K.; Rudolph, M.

Rhamnolipids have received great attention in various environmental applications in terms of metal complexation and recovery. However, the influence of metal ions on the interfacial, foaming, and ion flotation properties of rhamnolipid are poorly investigated. In this study we investigated the effect of metal ions alone and in a mixed metal system on the interfacial and foaming properties of rhamnolipid. Further, the potential of rhamnolipid to recover and separate Gallium from a mixed metal system containing Gallium (Ga) and Arsenic (As) using bioionflotation has been investigated. The effect of operating parameters like pH, rhamnolipid concentration, and airflow rate were tested and found to have a significant influence on the separation performance. The maximum removal of Ga could reach 74 % when rhamnolipid concentration was 0.85 mM at pH 6 and an airflow rate of 80 ml/min. The selectivity index of Ga over As was highest (17.2) at 0.85 mM rhamnolipid concentration, pH 6, and an airflow rate of 40 ml/min. Also, the selective separation of Ga was dependent on the recovery of water from the foam. The results showed that rhamnolipid biosurfactant acted as a highly efficient ion collector for Ga and the optimized process parameters could be expected to provide very efficient separation and recovery of target metal via ion flotation.

Keywords: Rhamnolipid; gallium; arsenic; ion flotation; selectivity; metal recovery; water recovery

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Permalink: https://www.hzdr.de/publications/Publ-36908


Development of Carborane-Based Ligands for PET and SPECT Imaging

Ueberham, L.; Moldovan, R.-P.; Deuther-Conrad, W.; Gündel, D.; Brust, P.; Kopka, K.; Laube, M.; Pietzsch, J.; Hey-Hawkins, E.

The early detection of diseases like Alzheimer, Parkinson or cancer have gained importance over the last decade, since they are still the cause of death of millions of people worldwide.[1] To screen patients for disease markers, non-invasive imaging techniques like Positron Emission Tomography (PET) and Single-photon Emission Computed Tomography (SPECT) are suitable methods for diagnostics.[2]
Radiopharmaceuticals with ligands of high affinity and selectivity towards the targets involved in the maladies, like the cannabinoid receptor type 2 (CB2R) or cyclooxygenase 2 (COX-2) have to be developed. In addition to high affinity and selectivity, other requirements are also high metabolic stability or balanced hydrophobicity.[2,3]
The development of such radioligands is a challenge; for example, no CB2R radioligand is available for routine clinical applications so far. To overcome the lack in metabolic stability and increase the selectivity of suitable ligands, closo-dicarbadodecaboranes (carboranes) are employed. The hydrophobic carborane can be introduced as a replacement for phenyl, cyclohexyl or adamantyl groups, to name but a few.[4]
A new class of ligands based on (metalla)carboranes for application in PET and SPECT imaging for investigation of CB2R and COX-2 have been synthesized and in part biologically evaluated. These results will be presented and discussed in detail.

  • Poster
    Wissenschaftsforum GDCH, 04.-06.09.2023, Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-36906


Mirror twin boundaries in WSe2 induced by vanadium doping

Pathirage, V.; Lasek, K.; Krasheninnikov, A.; Komsa, H. P.; Batzill, M.

Mirror twin boundaries (MTBs) observed in MoSe2 are formed due to incorporation of excess Mo into the lattice. In contrast, MTBs in WSe2 have a high formation energy and consequently are not present in this system. Here we show that V-doping of WSe2, achieved by co-deposition of V and W during molecular beam epitaxy (MBE) growth of WSe2, can also induce MTB formation in WSe2, as revealed by scanning tunneling microscopy. Our experimental results are supported by density functional theory calculations that show that V-doped WSe2 is susceptible to the incorporation of more V-atoms at interstitial sites. This increases the transition metal atom concentration in the lattice, and these excess atoms rearrange into MTBs, which is associated with energy lowering of the excess metal atoms. While formation of MTBs gives rise to the pinning of the Fermi-level and thus prevents V-induced electronic doping, MTBs do not appear to affect the magnetic properties, and a diluted ferromagnetic material is observed for low V- doping levels, as reported previously for V-doped WSe2.

Keywords: 2D materials; doping

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Permalink: https://www.hzdr.de/publications/Publ-36905


Velocity distributions of particles sputtered from supported two-dimensional MoS2 during highly charged ion irradiation

Skopinski, L.; Kretschmer, S.; Ernst, P.; Herder, M.; Madauß, L.; Breuer, L.; Krasheninnikov, A.; Schleberger, M.

A key problem in ion-solid interaction is the lack of experimental access to the dynamics of the processes. While it is clear
that the mechanisms of interaction and sputtering depend on the kinetic and potential energy (sum of ionization energies) of
the projectile, the importance and interplay of the various interaction mechanisms are unknown. Here, we have irradiated
substrate-supported (Au, SiO2) monolayers of MoS2 with highly charged xenon ions (HCIs; charge state: 17+ to 40+),
extracted the emitted neutral postionized Mo particles in a time-of-flight mass spectrometer, and determined their velocity
distributions. We find two main contributions, one at high velocities and a second at lower velocities, and assign them to
kinetic and potential effects, respectively. We show that for slow HCIs (5 keV) the interaction mechanisms leading to particle
emission by electronic excitation and momentum transfer, respectively, are independent of each other, which is consistent
with our atomistic simulations. Our data suggest that the predominant mechanism for potential sputtering is related to
electron-phonon coupling, while nonthermal processes do not play a significant role. We anticipate that our work will be a
starting point for further experiments and simulations to better understand the interplay of processes arising from Epot and
Ekin.

Keywords: Ion bombardment; Ions; Xenon Ions; Velocity distribution; Charge state; Distribution of particles; Highly charged ions; Interaction mechanisms; Ion-solid interactions; Ions irradiation; Two-dimensional; Layered semiconductors; Gold; Molybdenum; Sulfur compounds; Au/SiO2; Silica; Mass spectrometers

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Permalink: https://www.hzdr.de/publications/Publ-36904


microscenery: stage explorer

Tiemann, J.; Michel, K.; McGinity, M.; Sbalzarini, I. F.; Günther, U.

In 3D microscopy, aligning the sample and region of interest can consume precious photon budget, time or other
resources which, as in the case of experiments with high throughput or short sample life span, are often limited.
To remedy this, additional overview cameras and 2D “stage explorer” software are often used, allowing rapid high-level
search and alignment of samples. However, such systems are not always available, or may not support 3D stage
exploration, which may be a critical requirement for certain experiments.
To alleviate this problem we present microscenery: stage explorer, an open-source 3D stage explorer system with
support for Virtual Reality (VR) and live microscope control.
Our software allows the experimenter to control the stage position along all three spatial axes and acquire images. In
addition to the traditional mouse and keyboard interface, our system natively supports VR display and interaction.
Virtual Reality can often provide improved spatial understanding and manipulation of 3D data, accelerating stage
exploration. In addition, manipulating a 3D stage can be easier and more intuitive with 3D hand tracking or 3D input
devices than with a traditional 2D mouse and keyboard interface.
In microscenery stage explorer, the user controls the microscope and views acquired images from within VR. Images are
displayed in a virtual 3D stage space with the correct real-world spatial relations to each other. If the pixel-to-
micrometer ratio is known and a precise stage is used, a seamlessly stitched image readily emerges, in realtime, as the
user explores the stage space, allowing the user to rapidly navigate large samples. For setups where the physical size
of the sample is small, large magnification is used, or multiple samples are mounted, our software helps navigate the
stage space and find the samples more easily.
In addition to manual sampling, we have also implemented two automated sampling functions. The first is full-stack
acquisition, in which an image stack is automatically obtained and rendered at the correct position by 3D volume
rendering. In the second, the stage space can be explored automatically. Here, the experimenter specifies a cubic
search area which our application then automatically samples at regular intervals. In both cases, the usable and safely
accessible stage space can be defined before use, both to reduce the search space and to observe limits of the
hardware.
Currently, microscenery: stage explorer targets light-sheet microscopes, but generally any system that is controllable
with MicroManager is supported. It connects to MicroManager via a plugin and can be run on the same machine or over
the network. It can therefore be used as an extension to existing MicroManager workflows. Our system currently
supports head-mounted VR displays, with support for CAVE systems in development

Keywords: Virtual Reality; Lightsheet microscopy; Instrument control; visualisation; microscopy

  • Poster
    Focus on Microscopy, 02.04.-05.05.2023, Porto, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36903


Investigation of RPV samples of the Greifswald NPP with focus on retrospective dosimetry

Pönitz, E.; Konheiser, J.

Reactor pressure vessel (RPV) samples of units 1 and 4 of the Greifswald NPP were investigated with focus on retrospective dosimetry. Specific activities of long-lived radionuclides 63Ni, 93mNb, 94Nb and 99Tc as well as the concentrations of the producing elements were measured. Investigated samples comprise base metal, welding metal and cladding of the RPV. Neutron fluences obtained with the Monte-Carlo codes TRAMO and MCNP were used to calculate specific activities. The gamma-emitter 94Nb appears as a promising candidate due to the large Nb concentration in the cladding of the VVER RPVs. For 93mNb, a very good agreement of measured und calculated activities was found for the RPV cladding samples where 93mNb is primarily produced by the threshold reaction 93Nb(n,n’)93mNb. A strong scatter of the ratios of calculated and experimental activities is observed for 63Ni which is primarily produced by slow neutrons. For 99Tc, a good agreement of calculated and measured activities was found for the majority of the base metal and welding metal samples but not for the cladding samples. Updated reaction cross section data for 62Ni(n,γ) and 92Mo(n,γ) lead to a better agreement of calculated and measured activities for 63Ni and 93mNb.

  • Poster
    17th International Symposium on Reactor Dosimetry, 21.-26.05.2023, Lausanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-36902


Progress in Hybrid Plasma Wakefield Acceleration

Hidding, B.; Assmann, R.; Bussmann, M.; Campbell, D.; Chang, Y.-Y.; Corde, S.; Couperus Cabadağ, J. P.; Debus, A.; Döpp, A.; Gilljohann, M.; Götzfried, J.; Moritz Foerster, F.; Haberstroh, F.; Habib, F.; Heinemann, T.; Hollatz, D.; Irman, A.; Kaluza, M.; Karsch, S.; Kononenko, O.; Knetsch, A.; Kurz, T.; Kuschel, S.; Köhler, A.; Martinez De La Ossa, A.; Nutter, A.; Pausch, R.; Raj, G.; Schramm, U.; Schöbel, S.; Seidel, A.; Steiniger, K.; Ufer, P.; Yeung, M.; Zarini, O.; Zepf, M.

Plasma wakefield accelerators can be driven either by intense laser pulses (LWFA) or by intense particle beams (PWFA). A third approach that combines the complementary advantages of both types of plasma wakefield accelerator has been established with increasing success over the last decade and is called hybrid LWFA→PWFA. Essentially, a compact LWFA is exploited to produce an energetic, high-current electron beam as a driver for a subsequent PWFA stage, which, in turn, is exploited for phase-constant, inherently laser-synchronized, quasi-static acceleration over extended acceleration lengths. The sum is greater than its parts: the approach not only provides a compact, cost-effective alternative to linac-driven PWFA for exploitation of PWFA and its advantages for acceleration and high-brightness beam generation, but extends the parameter range accessible for PWFA and, through the added benefit of co-location of inherently synchronized laser pulses, enables high-precision pump/probing, injection, seeding and unique experimental constellations, e.g., for beam coordination and collision experiments. We report on the accelerating progress of the approach achieved in a series of collaborative experiments and discuss future prospects and potential impact.

Keywords: plasma wakefield acceleration; LWFA; PWFA; compact particle acceleration; radiation sources

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Permalink: https://www.hzdr.de/publications/Publ-36901


Universal radiation tolerant semiconductor

Azarov, A.; Fernández, J. G.; Zhao, J.; Djurabekova, F.; He, H.; He, R.; Prytz, Ø.; Vines, L.; Bektas, U.; Chekhonin, P.; Klingner, N.; Hlawacek, G.; Kuznetsov, A.

Radiation tolerance is determined as an ability of crystalline materials to withstand the accumulation of the radiation induced disorder. Based on the magnitudes of such disorder levels, semiconductors are commonly grouped into the low- or high-radiation tolerant. Nevertheless, upon exposing to sufficiently high fluences, in all cases known by far, it ends up with either extremely high disorder levels or amorphization. Here we show that gamma/beta double polymorph Ga2O3 structures exhibit unprecedently high radiation tolerance. Specifically, for room temperature experiments, they tolerate a disorder equivalent to hundreds of displacements per atom, without severe degradations of crystallinity; in comparison with, e.g., Si amorphizable already with the lattice atoms displaced just once. We explain this behavior by an interesting combination of the Ga- and O-sublattice properties in gamma-Ga2O3. In particular, O-sublattice exhibits a strong recrystallization trend to recover the face-centered-cubic stacking despite high mobility of O atoms in collision cascades compared to Ga. Concurrently, the characteristic structure of the Ga-sublattice is nearly insensitive to the accumulated disorder. Jointly it explains macroscopically negligible structural deformations in gamma-Ga2O3 observed in experiment. Notably, we also explained the origin of the beta-to-gamma Ga2O3 transformation, as a function of increased disorder in beta-Ga2O3 and studied the phenomena as a function of the chemical nature of the implanted atoms. As a result, we conclude that gamma-beta double polymorph Ga2O3 structures, in terms of their radiation tolerance properties, benchmark a new class of universal radiation tolerant semiconductors.

Keywords: FIB; Ga2O3; Nanostructure; Polymorph; HIM; EBSD

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Permalink: https://www.hzdr.de/publications/Publ-36900


Ultrathin positively charged electrode skin for durable anion-intercalation battery chemistries

Sabaghi, D.; Wang, Z.; Bhauriyal, P.; Lu, Q.; Morag, A.; Mikhailovia, D.; Hashemi, P.; Li, D.; Neumann, C.; Liao, Z.; Dominic, A. M.; Nia, A. S.; Dong, R.; Zschech, E.; Turchanin, A.; Heine, T.; Yu, M.; Feng, X.

The anion-intercalation chemistries of graphite have the potential to construct batteries with promising energy and power breakthroughs. Here, we report the use of an ultrathin, positively charged two-dimensional poly(pyridinium salt) membrane (C2DP) as the graphite electrode skin to overcome the critical durability problem. Large-area C2DP enables the conformal coating on the graphite electrode, remarkably alleviating the electrolyte. Meanwhile, the dense face-on oriented single crystals with ultrathin thickness and cationic backbones allow C2DP with high anion-transport capability and selectivity. Such desirable anion-transport properties of C2DP prevent the cation/solvent co-intercalation into the graphite electrode and suppress the consequent structure collapse. An impressive PF6−-intercalation durability is demonstrated for the C2DP-covered graphite electrode, with capacity retention of 92.8% after 1000 cycles at 1 C and Coulombic efficiencies of > 99%. The feasibility of constructing artificial ion-regulating electrode skins with precisely customized two-dimensional polymers offers viable means to promote problematic battery chemistries.

Keywords: batteries; dft; 2d polymers

Permalink: https://www.hzdr.de/publications/Publ-36899


Thermal and Radiation Stability of (Zr0.95241Am0.05)1-xNdxO2-x0.5 Phases: Updates from the RISE-241 ActUsLab JRC Project

Huittinen, N. M.; Gilson, S.; Popa, K.; Valu, O.; Colle, J.-Y.; Walter, O.; Murphy, G. L.

The thermal and radiation stability of Zircaloy cladding material that houses spent nuclear fuel (SNF) is an important factor when considering the safe storage and eventual disposal of SNF in a geological repository. It is known that on the surface of the cladding, oxidised zirconia (ZrO2) phases are inherently present. Following fuel swelling and rim contact, the zirconia layer on the interior surface can interact with SNF elements, leading to the formation of phases such as pyrochlore, A2Zr2O7, and other zirconates, A2ZrO3 , among others. These phases essentially act as the first intermediate barrier between the SNF and the metallic cladding and consequently are important to consider in safety design, particularly for transport/release of radionuclides (RNs). A pertinent RN that contributes significantly to the radiological hazard of SNF, is the minor actinide isotope Am-241. The chemistry of Am is largely unique, being able to readily dissociate between its tetravalent and trivalent states in oxides, making it difficult to investigate via surrogate studies using lanthanides. Furthermore, Am-241 has a relatively short t1/2 of 432 years and decays via alpha emission (5.486 MeV), resulting in significant ensuing radiation damage in host materials. Consequentially, understanding the thermal and radiation stability of host material phases incorporating Am-241 is a pertinent endeavor for safety and disposal of SNF. As a part of the national project “AcE” funded by the German Federal Ministry of Education and Research (BMBF) and through the European Commission ActUsLab program, we have investigated several zirconium oxide polymorphs, including but not limited to Nd-pyrochlore and zirconia, doped with 5 mol% Am-241. The particular focus of the investigation is to understand the thermal and radiation stability of the different oxide polymorphs when Am-241 is incorporated. This presentation will highlight a number of on-going results from this research program, including high-temperature phase transformations, radiation induced lattice swelling, phase separation, and associated apparent redox activity induced by the presence of Am-241.

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

Permalink: https://www.hzdr.de/publications/Publ-36898


High-Order Curvilinear Arbitrary Lagrangian-Eulerian MHD

Nikl, J.; Kuchařík, M.; Cangi, A.

Two-temperature resistive magnetohydrodynamics can model magnetized collisional plasmas present in inertial confinement fusion (ICF) experiments. In particular, Lagrangian methods excel in problems with strong compression or expansion, since the computational mesh follows the flow of the matter. However, simulations may loose precision, become unfeasible or even crash due to severely distorted or entangled meshes. A remedy is provided by the Arbitrary Lagrangian-Eulerian (ALE) method consisting of normal Lagrangian step(s), rezoning for regularization or untangling of the computational mesh, and remapping of the quantities from the old mesh to the new one. This procedure enables robust and precise simulations of ICF with the effects of magnetic field. We develop such a method for resistive two-temperature MHD. Unlike classical approaches, it conserves the magnetic flux and maintains the divergence-free structure of the magnetic field. Moreover, the numerical method is based on high-order curvilinear finite elements.

  • Poster
    Direct Drive and Fast Ignition Workshop 2023, 03.-05.05.2023, Oxford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-36897


Spectral characterisation of hydrothermal alteration associated with sediment-hosted Cu–Ag mineralisation in the central European Kupferschiefer

Géring, L.; Kirsch, M.; Thiele, S. T.; de Lima Ribeiro, A.; Gloaguen, R.; Gutzmer, J.

The analysis of hydrothermal alteration in exploration drill cores allows for fluid-rock interaction processes to be traced, for fluid flow paths to be identified, and thus for vectors in mineral systems to be determined. Hyperspectral imaging techniques are increasingly being employed to fill the scale gap between lab-based petrographic or geochemical analyses and the typical size of exploration targets. Hyperspectral imaging permits the rapid, cost-efficient, and continuous characterisation of alteration mineralogy and texture along entire drill cores, with a spatial sampling of a few millimetres. In this contribution, we present the results of an exploratory study on three mineralised drill cores from the Spremberg-Graustein Kupferschiefer-type Cu-Ag deposit in the Lusatia region of Germany. We demonstrate that hyperspectral imaging is well-suited to recognising and tracking the effects of hydrothermal alteration associated with strata-bound hydrothermal mineralisation. Micro X-ray fluorescence spectrometry was used to corroborate the alteration mineral assemblages identified in hyperspectral data acquired in the visible, near- (400 to 970 nm), shortwave (970 to 2500 nm), mid-wave (2700 to 5300 nm), and longwave infrared (7700 to 12300 nm). We identified two main shortcomings of the technique, namely the overlapping of some mineral features (e.g. carbonate and illite absorption in the shortwave infrared) and the darkness of the organic-matter-rich dolostones and shales that results in low reflectance. Nevertheless, spectral features associated with iron oxide, kaolinite, sulfate, and carbonates were successfully identified and mapped. We identified different markers of hydrothermal alteration spatially associated with or stratigraphically adjacent to Cu-Ag mineralisation. Importantly, we can clearly distinguish two mineralogically distinct styles of alteration (hematite and ferroan carbonate) that bracket high-grade Cu-Ag mineralisation. Intensive hydrothermal alteration is characterised by the occurrence of well-crystallised kaolinite in the sandstone units immediately below the Kupferschiefer horizon sensu stricto. Proximal Fe-carbonate and kaolinite alteration have not previously been documented for the high-grade Cu-Ag deposits of the central European Kupferschiefer, whereas hematite alteration is well-known in Kupferschiefer-type ore deposits. The latter marks the flow path of oxidising, metal-bearing hydrothermal fluids towards the site of hydrothermal sulfide mineralisation. In contrast, ferroan carbonate alteration in carbonate rocks located above the main mineralised zone is interpreted as a mark of hydrothermal fluid discharge from the mineralising system. Although this study is limited to a small number of drill cores, our results suggest that hyperspectral imaging techniques may be used to identify vectors towards high-grade Cu-Ag mineralisation in Kupferschiefer-type mineral systems.

Keywords: Hyperspectral; Mineral deposits; Drill core; Exploration; Alteration

Permalink: https://www.hzdr.de/publications/Publ-36896


Advancements of ELBE Timing System Upgrade

Kuntzsch, M.; Zenker, K.; Schwarz, A.; Justus, M.; Hrovatin, R.;  Peruško, L.;  Legat, U.;  Rojec, U.; Oven, Z.; Krmpotić, L.

Modern Big physics experiments call for optimizations of machines in various aspects. Integration of an advanced control system is one of them, and timing system as controls’ backbone is most often required to be upgraded significantly or even designed and implemented anew. The complexity of experiments at HZDR ELBE and the range of varieties of its instruments and subsystems is combined with top-notch performance requirements. These, coupled with hardware obsolescence, dictate an implementation of an advanced timing system, surpassing a system, that was designed initially. The new timing system must be compatible with all existing timing triggering patterns and must provide configuration option for new features. It is designed to generate trigger patterns for shot on demand to 26 MHz cw which requires a universal and complex implementation of the pattern composition and validity checks. The design of this timing solution further demands the adaptation and the modification of the event-based timing system built on MRF HW. As a result, we realized the new Control Software with an extended range of functionalities. While maintaining the common functionality we made it suitable for the most demanding experiments today.

Keywords: ELBE

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Related publications

  • Poster
    14th International Particle Accelerator Conference, 07.-12.05.2023, Venice, Italy
  • Contribution to proceedings
    14th International Particle Accelerator Conference, 07.-12.05.2023, Venice, Italy

Permalink: https://www.hzdr.de/publications/Publ-36895


MePS – the Mono-Energetic Positron Source for annihilation lifetime spectroscopy

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

The Helmholtz-Center Dresden - Rossendorf operates several user beamlines for materials research using positron-annihilation energy and lifetime spectroscopy. The superconducting electron linear accelerator ELBE drives several secondary beams including hard X-ray production from electron-bremsstrahlung, which serves as an intense source of positrons by means of pair production. The Mono-energetic Positron Source MePS [1] utilizes positrons with variable kinetic energies ranging from 0.5 to 18 keV for depth profiling of atomic defects and porosities on nm-scales in thin films. High timing resolutions (σt ≈100 ps) at high average event rates in excess of 105 s-1 and adjustable beam repetition rates allow performing high-throughput positron annihilation lifetime experiments. Acquiring an annihilation lifetime spectrum with 107 events takes about 80 s which paves the way to perform in-situ PALS experiments on dynamical defect evolution, migration and annealing [2,3,4].
We will present the actual status of the MePS facility and updates which are on the way. A recently constructed sample chamber will allow for fast and automated sample transfers, an increased sample temperature range (80 K to 800 K), and possibilities for sample illuminations with light sources (LED, Laser, and a broadband short arc Xe light source).
The facility is part of the ELBE Center for High-Power Radiation Sources which operates several secondary beam lines for international users.

The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). Trans-national access is available through the EU-Horizon project ReMADE for academic and industry.

[1] A. Wagner, et al., AIP Conf. Proc. 1970, 040003 (2018)
[2] L. Chiari, et al., Acta Mater. 219, 117264 (2021)
[3] M. Wenskat, et al., Sci. Rep. 10, 8300 (2020)
[4] M. Wenskat, et al., Phys. Rev. B 106, 094516 (2022)
[5] ReMADE, https://remade-project.eu/

Keywords: positron annihilation; materials science; lifetime spectroscopy

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  • Invited lecture (Conferences)
    16th International Workshop on Slow Positron Beam Techniques & Applications (SLOPOS-16), 16.-21.07.2023, Orléans, France

Permalink: https://www.hzdr.de/publications/Publ-36894


Recruiting Unicellular Algae for the Mass Production of Nanostructured Perovskites

Kuhrts, L.; Helmbrecht, L.; Noorduin, W. L.; Pohl, D.; Sun, X.; Palatnik, A.; Wetzker, C.; Jantschke, A.; Schlierf, M.; Zlotnikov, I.

Functional capacities of lead halide perovskites are strongly dependent on their morphology, crystallographic texture, and internal ultrastructure on the nano- and the meso-scale. In the last decade, significant efforts are directed towards the development of novel synthesis routes that would overcome the morphological constraints provided by the physical and crystallographic properties of these materials. In contrast, various living organisms, such as unicellular algae, have the ability to mold biogenic crystals into a vast variety of intricate nano-architectured shapes while keeping their single crystalline nature. Here, using the cell wall of the dinoflagellate L. granifera as a model, sustainably harvested biogenic calcite is successfully transformed into nano-structured perovskites. Three variants of lead halide perovskites CH3NH3PbX3 are generated with X = Cl−, Br− and I−; exhibiting emission peak-wavelength ranging from blue, to green, to near-infrared, respectively. The approach can be used for the mass production of nano-architectured perovskites with desired morphological, textural and, consequently, physical properties exploiting the numerous templates provided by calcite forming unicellular organisms.

Keywords: Perovskite; Algae; Crystallographic properties; Textures; Mass production

Permalink: https://www.hzdr.de/publications/Publ-36893


Passive SOBP generation from a static proton pencil beam using 3D-printed range modulators for FLASH experiments

Horst, F. E.; Beyreuther, E.; Bodenstein, E.; Gantz, S.; Misseroni, D.; Pugno, N.; Schuy, C.; Tommasino, F.; Weber, U.; Pawelke, J.

The University Proton Therapy facility in Dresden (UPTD), Germany, is equipped with an experimental room with a beamline providing a static pencil beam. High proton beam currents can be achieved at this beamline which makes it suitable for FLASH experiments. However, the established experimental setup uses only the entrance channel of the proton Bragg curve. In this work, a set of 3D-printed range modulators designed to generate spread out Bragg peaks (SOBPs) for radiobiological experiments at ultra-high dose rate at this beamline is described. A new method to optimize range modulators specifically for the case of a static pencil beam based on the central depth dose profile is introduced. Modulators for two different irradiation setups were produced and characterized experimentally by measurements of lateral and depth dose distributions using different detectors. In addition, Monte Carlo simulations were performed to assess profiles of the dose averaged linear energy transfer. These newly produced range modulators will allow future proton FLASH experiments in the SOBP at UPTD with two different experimental setups.

Keywords: proton therapy; range modulator; 3D-printing; spread out Bragg peak; FLASH effect; ultra-high dose rate

Involved research facilities

  • OncoRay

Permalink: https://www.hzdr.de/publications/Publ-36892


Transferable Interatomic Potentials for Aluminum from Ambient Conditions to Warm Dense Matter

Kumar, S.; Tahmasbi, H.; Ramakrishna, K.; Lokamani, M.; Nikolov, S.; Tranchida, J.; Wood, M. A.; Cangi, A.

We present a study on the transport and materials properties of aluminum spanning from ambient to warm dense matter conditions using a machine-learned interatomic potential (ML-IAP). Prior research has utilized ML-IAPs to simulate phenomena in warm dense matter, but these potentials have often been calibrated for a narrow range of temperature and pressures. In contrast, we train a single ML-IAP over a wide range of temperatures, using density functional theory molecular dynamics (DFT-MD) data. Our approach overcomes computational limitations of DFT-MD simulations, enabling us to study transport and materials properties of matter at higher temperatures and longer
time scales. We demonstrate the ML-IAP transferability across a wide range of temperatures using molecular-dynamics (MD) by examining the thermal conductivity, diffusion coefficient, viscosity, sound velocity, and ion-ion structure factor of aluminum up to about 60,000 K, where we find good agreement with previous theoretical data.

Keywords: Warm Dense Matter; Machine-Learned Interatomic Potential; Transport Coefficients; Molecular Dynamics; Materials Properties; Ion-Ion Structure Factor

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Permalink: https://www.hzdr.de/publications/Publ-36890


Nonreciprocal Phonon Propagation in a Metallic Chiral Magnet

Nomura, T.; Zhang, X.-X.; Takagi, R.; Karube, K.; Kikkawa, A.; Taguchi, Y.; Tokura, Y.; Zherlitsyn, S.; Kohama, Y.; Seki, S.

The phonon magnetochiral effect (MChE) is the nonreciprocal acoustic and thermal transports of phonons caused by the simultaneous breaking of the mirror and time-reversal symmetries. So far, the phonon MChE has been observed only in a ferrimagnetic insulator Cu2OSeO3, where the nonreciprocal response disappears above the Curie temperature of 58 K. Here, we study the nonreciprocal acoustic properties of a room-temperature ferromagnet Co9Zn9Mn2 for unveiling the phonon MChE close to room temperature. Surprisingly, the nonreciprocity in this metallic compound is enhanced at higher temperatures and observed up to 250 K. This clear contrast between insulating Cu2OSeO3 and metallic Co9Zn9Mn2 suggests that metallic magnets have a mechanism to enhance the nonreciprocity at higher temperatures. From the ultrasound and microwave-spectroscopy experiments, we conclude that the magnitude of the phonon MChE of Co9Zn9Mn2 mostly depends on the Gilbert damping, which increases at low temperatures and hinders the magnon-phonon hybridization. Our results suggest that the phonon nonreciprocity could be further enhanced by engineering the magnon band of materials.

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  • High Magnetic Field Laboratory (HLD)

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Permalink: https://www.hzdr.de/publications/Publ-36889


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