Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Developing efficient and stable Pt-based oxygen reduction reaction (ORR) electrocatalysts via both economical and controllable routes is critical for the
practical application of electrochemical energy devices. Herein, a scalable, controllable, and general ambient-O₂-involved aqueous-solution cultivating strategy to prepare Pt_xM_y (M = Ni, Fe, Co) bunched-nanocages aerogels (BNCs AG) is demonstrated, based on a newly established high-M-to-Pt-precursor-ratio-and-B-incorporation-facilitated M-rich core and Pt-rich shell hydrogel formation process. The Pt₈₃Ni₁₇ BNCs AG shows prominent ORR performance with a mass activity (MA) of 1.95 A mg_Pt ⁻¹ and specific activity of 3.55 mA cm⁻², which are 8.9-times and 9.6-times that of Pt supported on carbon (Pt/C), respectively. Particularly,
the Pt₈₃Ni₁₇ BNCs AG displays greatly enhanced durability (MA 82.6% retention) compared to Pt/C (MA 31.8% retention) after a 20 000-cycles accelerated durability test. Systematic studies including density functional theory calculations uncover that the excellent activity is closely related to the optimized ligand and strain effects with the optimized Ni content in this aerogel; the outstanding durability is endowed by the lowered-down Ni leaching with the optimized Pt/Ni ratio and the inhibited sintering due to its appropriate porosity. This work provides new perspectives on the development of electrocatalysts with both high performance and low cost.

For a magnetic material, the easy and hard magnetic axes describe the directions of favourable respectively unfavourable alignment of the magnetisation. In this article, we describe how to determine these axes for cubic magnetic crystals. Usually it is assumed without further reasoning that they coincide with some principal symmetry directions of the crystal [Bozorth, Phys. Rev. 50, 1076–1081 (1936)], which is however invalid in general. In contrast, we present a full and elementary analysis using symmetric polynomial inequalities, which are well suited to the symmetry of the problem.

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.

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 Cu_2−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 Cu_2−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.

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.

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.

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.

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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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.

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,

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

In magnetischen Materialien „frieren“ die magnetischen Momente üblicherweise in wohlgeordneten oder glasartigen Strukturen ein. Quanteneffekte können dazu führen, dass diese Strukturen „schmelzen“ und die Spinflüssigkeit selbst am absoluten Nullpunkt nicht ordnet.

Several technologies, including photodetection, imaging and data communication, could greatly benefit from the availability of fast and controllable conversion of terahertz (THz) light to visible light. Here, we demonstrate that the exceptional properties and dynamics of electronic heat in graphene allow for THz-to-visible conversion, which is switchable at a sub-nanosecond timescale. We show a tunable on/off ratio of more than 30 for the emitted visible light, achieved through electrical gating using a gate voltage on the order of one Volt. We also demonstrate that a grating-graphene metamaterial leads to an increase in THz-induced emitted power in the visible range by two orders of magnitude. The experimental results are in agreement with a thermodynamic model that describes black-body radiation from the electron system heated through intraband Drude absorption of THz light. These results provide a promising route towards novel functionalities of optoelectronic technologies in the THz regime.

Strain and temperature are important physiological parameters for health monitoring, providing access to the respiration state, movement of joints and inflammation processes. The challenge for smart wearables is to unambiguously discriminate strain and temperature using a single sensor element assuring a high degree of sensor integration. Here, we report a dual-modal sensor with two electrodes and tubular mechanically heterogeneous structure enabling simultaneous sensing of strain and temperature without cross-talk. The sensor structure consists of a thermocouple coiled around an elastic strain-to-magnetic induction conversion unit, revealing a giant magnetoelastic effect, and accommodating a magnetic amorphous wire. The thermocouple provides access to temperature and its coil structure allows to measure impedance changes caused by the applied strain. The dual-modal sensor also exhibits interference-free temperature sensing performance with high coefficient of 54.49 μV/°C, low strain and temperature detection limits of 0.1% and 0.1 °C, respectively. We demonstrate the use of these sensors in smart textiles to monitor continuously breathing, body movement, body temperature and ambient temperature. The developed multifunctional wearable sensor is needed for applications in early disease prevention, health monitoring and interactive electronics as well as for smart prosthetics and intelligent soft robotics.

Electrically conductive coordination polymers and metal–organic frameworks are attractive emerging electroactive materials for (opto-)electronics. However, developing semiconducting coordination polymers with high charge carrier mobility for devices remains a major challenge, urgently requiring the rational design of ligands and topological networks with desired electronic structures. Herein, we demonstrate a strategy for synthesizing high-mobility semiconducting conjugated coordination polymers (c-CPs) utilizing novel conjugated ligands with D2h symmetry, namely, “4 + 2” phenyl ligands. Compared with the conventional phenyl ligands with C6h symmetry, the reduced symmetry of the “4 + 2” ligands leads to anisotropic coordination in the formation of c-CPs. Consequently, we successfully achieve a single-crystalline three-dimensional (3D) c-CP Cu4DHTTB (DHTTB = 2,5-dihydroxy-1,3,4,6-tetrathiolbenzene), containing orthogonal ribbon-like π–d conjugated chains rather than 2D conjugated layers. DFT calculation suggests that the resulting Cu4DHTTB exhibits a small band gap (∼0.2 eV), strongly dispersive energy bands near the Fermi level with a low electron-hole reduced effective mass (∼0.2m0*). Furthermore, the four-probe method reveals a semiconducting behavior with a decent conductivity of 0.2 S/cm. Thermopower measurement suggests that it is a p-type semiconductor. Ultrafast terahertz photoconductivity measurements confirm Cu4DHTTB’s semiconducting nature and demonstrate the Drude-type transport with high charge carrier mobilities up to 88 ± 15 cm2 V–1 s–1, outperforming the conductive 3D coordination polymers reported till date. This molecular design strategy for constructing high-mobility semiconducting c-CPs lays the foundation for achieving high-performance c-CP-based (opto-)electronics.

In this Letter, we report a tailored 532/1064-nm demultiplexer based on a multimode interference (MMI) coupler with an efficiency of 100%. The device structure is designed according to the self-imaging principle, and the propagation and the wavelength division performance are simulated by the beam propagation method. The demultiplexer is fabricated in a y-cut LiNbO3 crystal by femtosecond laser direct writing (FLDW) combined with the ion implantation technique. The end-face coupling system is used to measure the near field intensity distribution, and the spectra collected from the output ports are obtained by spectrometers. The simulated and the experimental results indicate that the customized demultiplexer in the LiNbO3 crystal presents excellent wavelength division performance operating at 532 nm and 1064 nm. This work demonstrates the application potential of FLDW technology for developing miniaturized photonic components and provides a new strategy for fabricating high-efficiency integrated wavelength division devices on an optical monocrystalline platform.

Uptake of uranium (U) by secondary minerals, such as carbonates and iron (Fe)-sulfides, that
occur ubiquitously on Earth, may be substantial in deep anoxic environments compared to
surficial settings due to different environment-specific conditions. Yet, knowledge of U
reductive removal pathways and related fractionation between 238 U and 235 U isotopes in
deep anoxic groundwater systems remain elusive. Here we show bacteria-driven degradation
of organic constituents that influences formation of sulfidic species facilitating reduction of
geochemically mobile U(VI) with subsequent trapping of U(IV) by calcite and Fe-sulfides.
The isotopic signatures recorded for U and Ca in fracture water and calcite samples provide
additional insights on U(VI) reduction behaviour and calcite growth rate. The removal effi-
ciency of U from groundwater reaching 75% in borehole sections in fractured granite, and
selective U accumulation in secondary minerals in exceedingly U-deficient groundwater
shows the potential of these widespread mineralogical sinks for U in deep anoxic
environments.

Interplay between the geometry and behavior of magnetic textures in statics and dynamics has been traditionally considered regarding planar confined samples and their boundaries (vortices in nanodisks, interaction of skyrmions and domain walls with notches etc.). Recent developments of experimental techniques on fabrication of freestanding 3D nanostructures gave a possibility to access and validate theoretical predictions of behavior of magnetic textures, related to the intrinsic geometric properties of extended films and complex sample topologies [1].

Properties of energy functionals in both, ferro- and antiferromagnetic samples reflect geometric symmetries in curvature-driven Dzyaloshinskii-Moriya interaction and anisotropies, which are proportional to the first and second powers of the curvatures, respectively [1]. Magnetostatics is also sensitive to the breaks of the geometric symmetries. In thin films, it is possible to tease out an interplay between the out-of-surface magnetization component and mean curvature of the film [2]. Furthermore, for such non-local textures as vortices hosted by asymmetric Py caps, it enables complex magnetochiral effects pronounced in twisting of the vortex string in a helix and coupling of this helix chirality with the vorticity of the whole texture [3].

Antiferromagnetic curvilinear nanoarchitectures provide more intrinsic material symmetries. In spin chains, the dipolar interaction provides the hard-axis shape anisotropy, with the anisotropy axis along the tangential direction to the chain. This makes the geometry-driven helimagnetic phase transition to be possible for any finite curvature and torsion of the chain [4]. The locally broken spatial translation symmetry of antiferromagnetic dimers in bipartite chains leads to the micromagnetic energy term of the non-chiral longitudinal Dzyaloshinskii energy symmetry and enables local weak ferromagnetic response related to the spatial inhomogeneity of the Neel vector [5]. The geometry-driven easy axis of anisotropy is present even if the material anisotropy is of the hard-axis type, which enables spin-flop transition governed by the chain shape. In a particular case of the ring with the hard-tangential anisotropy and uniform ground state, the helimagnetic phase transition appears in spin-flop phase and the intermediate canted phase for the case of strong Dzyaloshinskii-Moriya interaction [6].

References
1. D. Makarov, O. Volkov, A. Kakay et al., Adv. Mat. 34, 2101758 (2022)
2. D. Sheka, O. Pylypovskyi, P. Landeros et al., Commun. Phys. 3, 128 (2020)
3. O. Volkov, D. Wolf, O. Pylypovskyi, et al., Nat. Commun. In press (2023)
2. O. Pylypovskyi, D. Kononenko, K. Yershov et al., Nano Lett. 20, 8157 (2020)
5. O. Pylypovskyi, Y. Borysenko, J. Fassbender et al., Appl. Phys. Lett. 118, 182405 (2021)
6. Y. Borysenko, D. Sheka, J. Fassbender, et al., Phys. Rev. B 106, 174426 (2022)

Curvilinear spin chains are simplest antiferromagnetic systems revealing direct influence of their shape onto magnetic states via geometry-tracking anisotropies stemming from the dipolar interaction [1] or local surrounding [2]. Here, we show that in addition to the strongest effect onto magnetic state from exchange (biaxial anisotropy and chiral energy term) [1], the local break of the translational symmetry in curvilinear anisotropic antiferromagnets leads to (i) the longitudinal Dzyaloshinskii-Moriya energy term stemming from the single-ion anisotropy and (ii) the local weakly ferromagnetic response [2]. Furthermore, non-zero curvature κ can drive the helimagnetic phase transition in the spin-flop phase and enables the intermediate canted state for rings with large enough κ. [1] O. Pylypovskyi, D. Kononenko et al., Nano Lett. 20, 8157 (2020); [2] O. Pylypovskyi et al., Appl. Phys. Lett. 118, 182405 (2021); [3] Y. Borysenko et al., Phys. Rev. B, 106, 174426 (2022).

Understanding behavior of magnetic texture in antiferromagnetic nanostructures and thin films is crucial for the design of novel magnetic data storage and logic devices. Here, we derive the boundary conditions for the Néel vector in a two-sublattice antiferromagnet (AFM) and apply them to describe the shape of the domain walls [1,2] and skyrmions [2] in confined samples. In general, the surface of a 3D domain wall behaves as an elastic ribbon which bends in response on the topographic features of the single crystal Cr2 O3 [1]. In presence of the Dzyaloshinskii-Moriya interaction, topologically non-trivial AFM textures possess broadening near the surface. In thin films, the sample’s granularity becomes crucial. We present a model of a granular AFM and, by comparison with Nitrogen Vacancy magnetometry of 200-nm-thick Cr2O3 films, estimate the inter-grain exchange strength. The grain boundaries act as strong pinning sites for the AFM texture. [1] N. Hedrich et al., Nat. Phys. 17, 574 (2021); [2] O. Pylypovskyi et al., Phys. Rev. B 103, 134413 (2021).

Various continuous-wave (CW) electron gun technologies are reviewed, including DC, superconducting radio frequency RF (SRF), hybrid DC-SRF and normalconducting RF. Also, the SLAC Linac Coherent Light Source II (LCLS-II) normal-conducting RF gun and injector are described, and the performance to date, including the bunch emittance achieved and the dark current observed, is presented.

The Felsenkeller underground laboratory for nuclear astrophysics includes a 5 MV Pelletron ion accelerator and Germany’s lowest background high-purity germanium detector setup for radioactivity measurements. The lab is jointly operated by HZDR and TU Dresden. Protected by its 45 m thick rock overburden, the Felsenkeller cosmic-ray muon flux is 40 times lower than at surface. The natural neutron background is 180 times lower, and the background in a gamma-ray detector with muon veto more than 1000 times lower than at surface. These characteristics place the laboratory in a league with deep underground accelerator labs worldwide and enable highly sensitive nuclear reaction experiments.

The scientific program specifically addresses solar fusion, cosmology, and nucleosynthesis in neutron star precursors. The talk will new reaction data addressing deuterium and lithium from the Big Bang, and solar hydrogen burning.These science cases are highly topical and closely linked to efforts at GSI and FAIR.

In addition to in-house research by HZDR and TU Dresden, the lab is open as a facility for scientific users worldwide, with beam time applications reviewed by an independent science advisory board based on the scientific merits. In addition, EU-supported transnational access is available via the ChETEC-INFRA network of small and medium-scale European research infrastructures for nuclear astrophysics.

Data, code, and metadata that can be used to reproduce the analyses underlying 'Environmental drivers of body size in North American bats' by Alston et al. 2023 Functional Ecology (Preprint: https://doi.org/10.1101/2021.07.28.454183).

Individual data owners are detailed in the data. Data may only be used to reproduce the analyses underlying Alston et al. (2023). Any other use requires the written permission of the individual data owners.

For more detailed information, please visit the metadata file.

1. Bergmann's rule—which posits that larger animals live in colder areas—is thought to influence variation in body size within species across space and time, but evidence for this claim is mixed.

2. We used Bayesian hierarchical models to test four competing hypotheses for spatiotemporal variation in body size within 20 bat species across North America: (1) the heat conservation hypothesis, which posits that increased body size facilitates body heat conservation (and which is the traditional explanation for the mechanism underlying Bergmann's rule); (2) the heat mortality hypothesis, which posits that increased body size increases susceptibility to acute heat stress; (3) the resource availability hypothesis, which posits that increased body size is enabled in areas with more abundant food; and (4) the starvation resistance hypothesis, which posits that increased body size reduces susceptibility to starvation during acute food shortages.

3. Spatial variation in body mass was most consistently (and negatively) correlated with mean annual temperature, supporting the heat conservation hypothesis. Across time, variation in body mass was most consistently (and positively) correlated with net primary productivity, supporting the resource availability hypothesis.

4. Climate change could influence body size in animals through both changes in mean annual temperature and resource availability. Rapid reductions in body size associated with increasing temperatures have occurred in short-lived, fecund species, but such reductions will be obscured by changes in resource availability in longer-lived, less fecund species.

The MCPA herbicide mobilizes trace metals in soil by outcompeting adsorption by soil minerals[1]. Trace metal tracers are too immobile for the relatively short observation times available with positron emission tomography (PET). For the first time, however, timelapse movies of Cu migration in columns filled with artificial soil (68 % sand, 26 % silt, 5 % illite clay, 1 % goethite) were recorded. Soil solution was supplied from bottom up at a flow rate of 100 µL/min, low enough to allow for equilibration while maintaining a residence time in the order of tracer half-life (12.7 h). Up to 5 mL or 250 MBq of Cu-64 tracer was applied in one pulse run. The figure show volume renderings at different times (voxel size = 1 mm³, column high = 10 cm). The radiolabeled Cu-MCPA complex breakthrough occurred just about 10-fold slower than the inert solute tracer [F-18]KF used in control columns shown in the lower row of the figure. Imaging movies are accessible at [2].
1. Kulenkampff J. et al. (2018). Sci. Rep., 8(7091). Open access CC BY 4.0.
2. URL https://zenodo.org/record/852968

The sample preparation and evaluation of the effects of impurities on the determination of ¹ ⁰Be and ² ⁶Al by accelerator mass spectrometry (AMS) was performed as an initial part of research project determining the timing of early hominin occupation at Korolevo, western Ukraine. The rock samples analysed exhibited various levels of weathering, lithology, and mass. The follow-up mass spectrometry scans revealed Ti impurity in BeO targets which stimulated quantification of Ti in quartz concentrate. The ² ⁶Al to ¹ ⁰Be ratios were independent on Ti and Al impurity for samples from the same depositional
level. AMS Be current reduction was a function of BeO dilution by TiO₂ molecules.

Raw data for the article 'Revisiting power-law distributions in empirical outage data of power systems' (see the manuscript preprint https://arxiv.org/abs/2303.12714 for more details)

Continuous advancements in science and technology in the field of flexible devices encourage researchers to dedicate themselves to seeking candidates for new flexible transparent conductive films (FTCFs). Our recently developed two-dimensional (2D) metal aerogels are considered as a new class of FTCFs. Here, we describe a new large-scale self-assembly synthesis of bimetallic Pt-Ni 2D metal aerogels with controllable morphology during the synthesis. The
obtained 2D aerogels require only a low quantity of precursors for the synthesis of percolating nanoscale networks with areas of up to 6 cm² without the need of an additional drying step. Stacks of the obtained monolayer structures display low sheet resistances (down to 270 Ω/sq), while decreasing the optical transparency. In perspective, the 2D bimetallic Pt-Ni aerogels not only enrich the structural diversity of metal aerogels but also bring forth new materials for further applications in flexible electronics and electrocatalysis with reduced costs of production.

We investigate coherent lattice dynamics in optimally doped YBa2Cu3O7−δ driven by ultrashort (∼ 12 fs) near infrared (NIR) and near ultraviolet (NUV) pulses. Transient reflectivity experiments, performed at room temperature and under moderate (<0.1 mJ/cm2) excitation fluence, reveal phonon modes related to the O(2,3) bending in the CuO2 planes and to the apical O(4) stretching at frequencies between 10 and 15 THz, in addition to the previously reported Ba and Cu(2) vibrations at 3.5 and 4.5 THz. The relative coherent phonon amplitudes are in stark contrast to the relative phonon intensities in the spontaneous Raman scattering spectrum excited at the same wavelength. This contrast indicates mode-dependent contributions of the Raman and non-Raman mechanisms to the generation of the coherent phonons. The particularly intense amplitude of the coherent Cu(2) phonon, together with its initial phase, supports its generation to be dominated by non-Raman mechanism involving charge transfer within the CuO2 plane. By contrast, the coherent out-of-phase O(2,3) bending mode is unproportionally weak compared with its Raman counterpart, suggesting that the charge transfer is ineffective in generating such an "asymmetric" atomic displacement. When the pump light has the polarization component normal to the CuO2 plane, the coherent O(4) mode is strongly enhanced compared to the in-plane excitation, probably by the charge transfer from the apical oxygen to the Cu-O chains. Our findings demonstrate that the charge transfer excitations in YBa2Cu3O7−δ strongly contribute to the electron-phonon coupling on a femtosecond timescale.

For direct cross section measurements in nuclear astrophysics, in addition to suitable ion beams and detectors, also highly pure and stable targets are needed. Here, using a gas jet as a target offers an attractive approach that combines high stability even under significant beam load with excellent purity and high localisation. Such a target is currently under construction at the Felsenkeller underground ion accelerator lab for nuclear astrophysics in Dresden, Germany. The target thickness will be measured by optical interferometry, allowing an in-situ thickness determination including also beam-induced effects. The contribution reports on the status of this new system and outlines possible applications in nuclear astrophysics.

Decentralized electrochemical production of hydrogen peroxide (H₂O₂) is an attractive alternative to the industrial anthraquinone process, the application of which is hindered by the lack of high-performance electrocatalysts in acidic media. Herein, a novel catalyst design strategy is reported to optimize the Pd sites in pure metallic aerogels by tuning their geometric environments and electronic structures. By increasing the Hg content in the Pd-Hg aerogels, the Pd-Pd coordination is gradually diminished, resulting in isolated, single-atom-like Pd motifs in the Pd₂Hg₅ aerogel. Further heterometal doping leads to a series of M-Pd₂Hg₅ aerogels with an unalterable geometric environment, allowing for sole investigation of the electronic effects. Combining theoretical and experimental analyses, a volcano relationship is obtained for the M-Pd₂Hg₅ aerogels, demonstrating an effective tunability of the electronic structure of the Pd active sites. The optimized Au-Pd₂Hg₅ aerogel exhibits an outstanding H₂O₂ selectivity of 92.8% as well as transferred electron numbers of ≈2.1 in the potential range of 0.0-0.4 V_RHE. This work opens a door for designing metallic aerogel electrocatalysts for H₂O₂ production and highlights the importance of electronic effects in tuning electrocatalytic performances.

A significant deceleration effect on a stored coasting ion beam by a continuous-wave laser light was observed in the Schottky-noise spectrum during the laser experiments with lithium-like oxygen ion beams stored at a relativistic energy of 275.7 MeV/u at the heavy-ion storage ring CSRe in Lanzhou, China. The observed deceleration range of the laser (Δp/p≈5.7×10−6) is much broader than the expected capture range (Δp/p≈3.6×10−8), as calculated from the natural linewidth of the O5+ ion’s electronic transition (2S1/2 −2 P1/2). In order to explain this huge deviation, a phase space tracking code has been developed to investigate the interaction between the stored coasting ion beam and the laser light. Simulations reveal that the deceleration range of the typically narrow CW laser force is highly enlarged by taking into account the transverse betatron oscillation of the ions with larger emittance and the angular misalignment of the laser light direction. The experimental observation is well described by the systematic simulations. The present work is crucial for forthcoming laser cooling and precision laser spectroscopy experiments and simulations on heavy highly charged ions at the CSRe and the future facility HIAF.

Hybrid organic–inorganic lead halide perovskites have drawn much interest due to their optical and electronic properties. The ability to fine-tune the structure by the organic component allows for obtaining a wide range of materials with various dimensionalities. Here, we combine experimental and theoretical work to investigate the structures and properties of a series of low-dimensional hybrid organic–inorganic perovskites, based on naphthalene ammonium cations, 2,6-diaminonaphthalene (2,6-DAN), 1-aminonaphthalene (1-AN) and 2-aminonaphthalene (2-AN). All materials exhibit edge- or face-sharing 1D chain structures. Compared to the 2D counterpart containing isomeric 1,5-diaminonaphthalene (1,5-DAN), 1D hybrid materials exhibit broadband light emission arising from the self-trapped excitons (STEs) owing to their highly distorted structure. This work expands the library of low-dimensional hybrid perovskites and opens new possibilities for obtaining broadband-light-emitting materials.

Glioblastoma (GBM) is still an incurable tumor that is associated with high
recurrence rate and poor survival despite the current treatment regimes. With
the urgent need for novel therapeutic strategies, immunotherapies, especially
chimeric antigen receptor (CAR)-expressing T cells, represent a promising
approach for specific and effective targeting of GBM. However, CAR T cells
can be associated with serious side effects. To overcome such limitation, we
applied our switchable RevCAR system to target both the epidermal growth
factor receptor (EGFR) and the disialoganglioside GD2, which are expressed in
GBM. The RevCAR system is a modular platform that enables controllability,
improves safety, specificity and flexibility. Briefly, it consists of RevCAR T cells
having a peptide epitope as extracellular domain, and a bispecific target module
(RevTM). The RevTM acts as a switch key that recognizes the RevCAR epitope and
the tumor-associated antigen, and thereby activating the RevCAR T cells to kill
the tumor cells. However, in the absence of the RevTM, the RevCAR T cells are
switched off. In this study, we show that the novel EGFR/GD2-specific RevTMs
can selectively activate RevCAR T cells to kill GBM cells. Moreover, we show that
gated targeting of GBM is possible with our Dual-RevCAR T cells, which have
their internal activation and co-stimulatory domains separated into two
receptors. Therefore, a full activation of Dual-RevCAR T cells can only be
achieved when both receptors recognize EGFR and GD2 simultaneously via
RevTMs, leading to a significant killing of GBM cells both in vitro and in vivo.

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

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

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

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

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

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

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

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

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

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

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

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

Vorstellung eines neuen Konzepts zur Flüssigkeitsverteilung für Rotating Packed Beds

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

Twin monomers [Mg(2-OCH₂-^cC₆H₄O)][L]_0.8 (2, L=diglyme) and [Mg(2-OCH₂-^cC₆H₄O)][L]_0.66 (3, L=tmeda) form by their thermal polymerization interpenetrating organic-inorganic hybrid materials in a straightforward manner. Carbonization (Ar) followed by calcination gave porous MgO (2: surface area 200 m²g^-1, 3: 400 m²g^-1), which showed in catalytic studies towards Meerwein-Ponndorf-Verley reductions excellent yields and complete conversions for cyclohexanone and benzaldehyde. However, with crotonaldehyde a mixture of C₄–C₈ compounds was obtained. When MgO was exposed to air then primarily crotyl alcohol was formed. The range of applications could be easily extended by twin polymerization of 3 in presence of [Cu-(O₂CCH₂O(CH₂CH₂O)₂Me)₂] (4) or [Ag(O₂CCH₂-^cC₄H₃S)(PPh₃)] (5), resulting in the formation of nanoparticle-decorated porous CuO@MgO or Ag@MgO materials, which showed high catalytic reactivity towards the reduction of methylene blue.

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

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

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

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

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

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