Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Membrane-scaffolding proteins (MSPs) derived from apolipoprotein A-1 have become a versatile tool in generating nano-sized discoidal membrane mimetics (nanodiscs) for membrane protein research. Recent efforts have aimed at exploiting their controlled lipid protein ratio and size distribution to arrange membrane proteins in regular supramolecular structures for diffraction studies. Thereby, direct membrane protein crystallization, which has remained the limiting factor in structure determination of membrane proteins, would be circumvented. We describe here the formation of multimers of membrane-scaffolding protein MSP1D1-bounded nanodiscs using the thiol reactivity of engineered cysteines. The mutated positions N42 and K163 in MSP1D1 were chosen to support chemical modification as evidenced by fluorescent labeling with pyrene. Minimal interference with the nanodisc formation and structure was demonstrated by circular dichroism spectroscopy, differential light scattering and size exclusion chromatography. The direct disulphide bond formation of nanodiscs formed by the MSP1D1_N42C variant led to dimers and trimers with low yield. In contrast, transmission electron microscopy revealed that the attachment of oligonucleotides to the engineered cysteines of MSP1D1 allowed the growth of submicron-sized tracts of stacked nanodiscs through the hybridization of nanodisc populations carrying complementary strands and a flexible spacer.

The effects of substitutional and interstitial atoms on the magnetic and magnetocaloric properties are investigated for RNi (R is rare earth) compounds attractive for magnetic solid-state cooling at cryogenic temperatures. We focused on combining weakly and highly anisotropic rare earth compounds and obtained GdxDy1-xNi (x = 0.1 and 0.9) compounds and their Gd_xDy_1-xNiH₃ hydrides. We observed a considerable decrease in Curie temperatures (TC) in the hydrides Gd_xDy_1-xNiH₃ compared to their parent alloys. The magnetocaloric effect (MCE) values of Gd_xDy_1-xNiH_y (y = 0 and 3) in the vicinity of TC were obtained and compared with literature data for the final GdNi and DyNi compounds. The maximum specific isothermal entropy changes –Δs_T at μ₀ΔH = 5 T were 14.5, 17, and 17.5 J kg⁻¹K⁻¹ for GdNi, Gd_0.9Dy_0.1Ni, and Gd_0.9Dy_0.1NiH₃, respectively. For DyNi, Gd_0.1Dy_0.9Ni, and Gd_0.1Dy_0.9NiH₃, they were –Δs_T = 18, 15.5, and 12.5 J kg⁻¹K⁻¹ at μ₀ΔH = 5 T, respectively. –Δs_T(H) in Gd_0.9Dy_0.1NiH₃ at T = T_C linearly increased in fields up to 7 T, while Gd_0.1Dy_0.9NiH₃ at T ≥ T_C showed a plateau-like magnetocaloric effect at μ₀ΔH = 5 and 7 T. The observed effects were explained based on altered exchange and magnetocrystalline interactions in the modified compounds.

Nanotechnology and modern materials science demand reliable local probing techniques on the nanoscopic length scale. Most commonly, scanning probe microscopy methods are applied in numerous variants and shades, for probing the different sample properties. Scattering scanning near-field optical microscopy (s-SNOM), in particular, is sensitive to the local optical response of a sample, by scattering light off an atomic force microscopy (AFM) tip, yielding a wavelength-independent lateral resolution in the order of ∼10 nm. However, local electric potential variations on the sample surface may severely affect the probe-sample interaction, thereby introducing artifacts into both the optical near-field signal and the AFM topography. On the other hand, Kelvin-probe force microscopy (KPFM) is capable of both probing and compensating such local electric potentials by applying a combination of ac and dc-voltages to the AFM tip. Here, we propose to combine s-SNOM with KPFM in order to compensate for undesirable electrostatic interaction, enabling the in situ probing of local electric potentials along with pristine optical responses and topography of sample surfaces. We demonstrate the suitability of this method for different types of materials, namely, metals (Au), semiconductors (Si), dielectrics (SiO2), and ferroelectrics (BaTiO3), by exploring the influence of charges in the systems as well as the capability of KPFM to compensate for the resulting electric force interactions.

Purpose: Experimental assessment of inter-centre variation and absolute accuracy of stopping-power ratio (SPR) prediction within 17 particle therapy centres of the European Particle Therapy Network.
Material and Methods: A head and body phantom with seventeen tissue-equivalent materials were scanned consecutively at the participating centres using their individual clinical CT scan protocol and translated into SPR with their in-house CT-number-to-SPR conversion. Inter-centre variation and absolute accuracy in SPR prediction were quantified for three tissue groups: lung, soft tissues and bones. The integral effect on range prediction for typical clinical beams traversing different tissues was determined for representative beam paths for the treatment of primary brain tumours as well as lung and prostate cancer.
Results: An inter-centre variation in SPR prediction (2σ) of 8.7%, 6.3% and 1.5% relative to water was determined for bone, lung and soft-tissue surrogates in the head setup, respectively. Slightly smaller variations were observed in the body phantom (6.2%, 3.1%, 1.3%). This translated into inter-centre variation of integral range prediction (2σ) of 2.9%, 2.6% and 1.3% for typical beam paths of prostate-, lung- and primary brain-tumour treatments, respectively. The absolute error in range exceeded 2% in every fourth participating centre. The consideration of beam hardening and the execution of an independent HLUT validation had a positive effect, on average.
Conclusion: The large inter-centre variations in SPR and range prediction justify the currently clinically used margins accounting for range uncertainty, which are of the same magnitude as the inter-centre variation. This study underlines the necessity of higher standardisation in CT-number-to-SPR conversion.

Two-terminal electronic transport systems with a rectangular transmission can violate standard thermodynamic uncertainty relations. This is possible beyond the linear response regime and for parameters that are not accessible with rate equations obeying detailed-balance. Looser bounds originating from fluctuation theorem symmetries alone remain respected. We demonstrate that optimal finite-sized quantum dot chains can implement rectangular transmission functions with high accuracy and discuss the resulting violations of standard thermodynamic uncertainty relations as well as heat engine performance.

Light ions are of increasing interest by application of focused ion beam (FIB) techniques due to the available high beam resolution in the nanometer range and their special chemical and physical behavior in the substrate [1, 2]. We compare helium and neon ion beams from a helium ion microscope with ion beams such as lithium, boron, and silicon, obtained from a mass-separated FIB using a liquid metal alloy ion source (LMAIS) with respect to the imaging and milling resolution, as well as the current stability [3]. While He+ offers, experimentally and in simulations, the smallest minimum trench width, light ion species such as Li+ from a LMAIS [4] offer higher milling rates and ion currents while outperforming the milling resolution of Ne+ from a gas field ion source. The comparison allows one to select the best possible ion species for the specific demands in terms of resolution, beam current, and volume and time for milling.

References
[1] L. Bischoff et al., Appl. Phys. Rev. 3 021101 (2016).
[2] P. Mazarov et al., Phys. Usp. 63 1219–1255 (2020).
[3] N. Klingner et al., Beilstein J. Nanotechnol. 11 1742–1749 (2020).
[4] W. Pilz et al., JVSTB 37 021802 (2019).

Presentation in parallel session "Detector Systems (T19.1)" at 2021 spring meeting of German Physical Society (DPG), section "Particle Physics"

X-ray Thomson scattering (XRTS) is a powerful diagnostic technique that involves an x-ray source interacting with a dense plasma sample,
resulting in a spectrum of elastically and inelastically scattered x-rays. Depending on the plasma conditions, one can measure a range of
parameters from the resulting spectrum, including plasma temperature, electron density, and ionization state. To achieve sensitivity to collective
electron oscillations, XRTS measurements require limited momentum transfer where the spectral separation of elastic and inelastic scattering
is small. Such measurements require an x-ray probe source with a narrow bandwidth in order to reduce the spectral overlap between
scattering contributions, allowing for the different features to be more precisely deconvolved. In this investigation, we discuss the theory
behind how the bandwidth for a common XRTS probe, Zn He-a emission at 9 keV, can be reduced using a Cu K-edge filter. Proof-of-principle
experiments conducted at the OMEGA laser facility confirm that this is an effective method for attenuating the higher energy He-a peak in
the Zn emission spectrum. Calibration measurements at the National Ignition Facility show a reduction in spectral bandwidth from 87 eV to
48 eV when using the Cu filter, which will be important to improve the spectral resolution of future XRTS measurements that will probe plasmon
oscillations in strongly compressed plasmas of low-Z materials at densities of tens of g/cm3.

etailed description of the transport processes in plasma is crucial for many disciplines. When the mean-free-path of the electrons is comparable or exceeds a characteristic length scale of the plasma profile, non-local behavior can be observed. Predictions of the diffusion theory are not valid and non-local electric and magnetic fields are generated. Kinetic modeling of these phenomena on time scales several orders of magnitude longer than the electron–electron collision time has proven to be cumbersome due to prohibitive requirements on the time step and violation of the conservation laws in the classical explicit Vlasov–Fokker–Planck methods. Therefore, a multi-dimensional conservative implicit Vlasov–Fokker–Planck–Maxwell method is proposed, where the distribution function is approximated by a truncated Cartesian tensor expansion. The electric and magnetic fields are modeled self-consistently, describing the generation process and emergence of non-locality in detail. Mixed finite elements are employed in space and the velocity dimension is discretized by staggered finite differences. Conservation properties are proved theoretically and the overall features are benchmarked on a series of physically representative problems. The second order convergence in velocity and the spatial order proportional to the polynomial order of the finite elements is shown. Further possible extensions of the method are discussed.

Experimental diagnostics as well as theoretical modeling of warm
dense matter (WDM) heavily rely on linear response theory.
However, Dornheim et. al. [Phys. Rev. Lett.125, 085001 (2020)]
showed that assuming the linear regime may not always be
justified in experiments studying WDM. In addition, the
intentional driving of non-linear effects should make new insight
into many-particle effects possible. We use ab initio Path-Integral
Monte-Carlo (PIMC) to obtain exact results for a harmonically
perturbed homogeneous electron gas. A thorough analysis for
different perturbation amplitudes is carried out. The
corresponding density response reveals resonances at the higher
harmonics of the perturbation wave vector. Analyzing the induced
density response as a function of the perturbation amplitude
shows the importance of the cubic response at the first harmonic
and of the quadratic response at the second harmonic.

The Horizon 2020 ESFR-SMART project investigates the behaviour of the commercial-size European Sodium-cooled Fast Reactor (ESFR) throughout its lifetime. This paper reports work focused on the End of Equilibrium Cycle (EOEC) loading of the ESFR, including neutronic analysis, core- and zone-wise reactivity coefficients, and more detailed local mapping of important safety-relevant parameters. Sensitivity and uncertainty analysis on these parameters have also been performed and a detailed investigation into decay heat mapping carried out.
Due to the scope of this work the results have been split into three papers. The nominal operating conditions and both zone-wise and local mapping of reactivity coefficients are considered in this paper; the sensitivity and uncertainty analysis are detailed in Margulis et al. and the decay heat mapping calculations are reported in Jimenez-Carrascosa et al. The work was performed across four institutions using both continuous-energy Monte Carlo and deterministic reactor physics codes. A good agreement is observed between the methods, verifying
the suitability of these codes for simulation of large, complicated reactor configurations; and giving confidence in the results for the most limiting ESFR EOEC core state for safety analysis. The results from this work will inform the transient calculations planned for the next stage of work on the ESFR, allowing for more in-depth studies to be performed on the multiphysics behaviour of the reactor.

The paper presents a transient simulation phase of the new benchmark on a large sodium fast reactor core. This phase of the benchmark was devoted to the modelling of selected operational transients performed during start-up tests of French SFR Superphénix in order to evaluate its reactivity characteristics and core response to certain perturbations. Six operational transients were selected for the analysis. The specification of a simplified thermal hydraulic model equipped with point kinetics reactivity data and boundary conditions for the selected transients are given in the paper and the results of simulations with several system codes are reported. The study uses the results of the reference Serpent 2 Monte Carlo solution obtained during the first phase of the benchmark related to static neutronic characterization of the core. The developed model contains necessary thermal hydraulic description of primary system components and assumptions to account for thermal expansion reactivity feedbacks from in-reactor structures, neutron kinetics parameters, power distribution and reactivity coefficients. Thus the transient benchmark appears as an effective tool for validation and cross comparisons of system codes including approbation and comparison of different modelling features for thermal expansion of the in-reactor structures, giving a reference core behaviour with use of relatively simple models. The results of the modelling demonstrate a reasonable agreement between all solutions and with the experimentally measured evolution of the core parameters. Particular discrepancies with experimental data could not be resolved using the simplified benchmark model and available experimental data reconstructed from the published analysis of start-up tests. Because of that, the future steps for achieving the improved agreement between the simulated results and the experimental data were proposed.

In this work a detailed assessment of the decay heat power for the commercial-size European Sodium-cooled Fast Reactor (ESFR) at the end of its equilibrium cycle has been performed. The summation method has been used to compute very accurate spatial- and time-dependent decay heat by employing state-of-the-art coupled transport-depletion computational codes and nuclear data. This detailed map provides basic information for subsequent transient calculations of the ESFR. A comprehensive analysis of the decay heat has been carried out and interdependencies among decay heat and different parameters characterizing the core state prior to shutdown, such as discharge burnup or type of fuel material, have been identified. That analysis has served as a basis to develop analytic functions to reconstruct the spatial-dependent decay heat power for the ESFR for cooling times within the first day after shutdown.

n the paper, the specification of a new neutronics benchmark for a large Sodium cooled Fast Reactor
(SFR) core and results of modelling by different participants are presented. The neutronics benchmark describes
the core of the French sodium cooled reactor Superphénix at its startup configuration, which in particular was
used for experimental measurement of reactivity characteristics. The benchmark consists of the detailed
heterogeneous core specification for neutronic analysis and results of the reference solution. Different core
geometries and thermal conditions from cold “as fabricated” up to full power were considered. The reference
Monte Carlo solution of Serpent 2 includes data on multiplication factor, power distribution, axial and radial
reaction rates distribution, reactivity coefficients and safety characteristics, control rods worth, kinetic data.
The results of modelling with seven other solutions using deterministic and Monte Carlo methods are also
presented and compared to the reference solution. The comparisons results demonstrate appropriate
agreement of evaluated characteristics. The neutronics results will be used in the second phase of the
benchmark for evaluation of transient behaviour of the core.

Vortrag für Schüler des Heidelberger Life-Science Labs (HLSL) am Deutschen Krebsforschungszentrum (DKFZ) im Rahmen der Freitagsvorträge, einer öffentlichen Vortragsreihe

Manufactured nanoparticles, such as CeO2, give rise to novel risks when released into the environment. To assess these risks it is important to quantify the nanoparticle mass flows, as well as their speciation and the mechanisms of their transformation. We developed an innovative dual-radiolabelling strategy for CeO2 nanoparticles using neutron activation and in-diffusion labelling to radiolabel CeO2 nanoparticles with both Ce-141 and Ce-139. The different distribution of the radiolabels in the particles does not only allow easy dose determination in uptake studies but also enables us to track the uptake pathways of the anthropogenic cerium. By measuring the activity as well as the isotope ratio we tracked the uptake, transformation and excretion of CeO2 nanoparticles in freshwater shrimp. We found that 99.99 % of the uptaken particles are excreted, leaving the gut with excrement. The remaining 0.01 % was internalized via a dissolution based pathway and accumulated in the hepatopancreas of the shrimp at a dose range of pg CeO2 per shrimp. Most importantly, our results show that dissolution is not only coincidental but instrumental in the uptake of the cerium into the internal organs of the shrimp.

We present here new experimental and numerical results for the resuspension of microscopic glass particles from a monolayer bed into a turbulent gas flow. With an intermediate surface coverage, here about 10 % of the field of
view, we report two distinct detachment mechanisms: collision-induced resuspension at low flow velocities and individual particle resuspension at higher fluid velocities.

In this work we propose a deep neural network based surrogate model for a plasma shadowgraph - a technique for visualization of perturbations in a transparent medium. We are substituting the numerical code by a computationally cheaper projection based surrogate model that is able to approximate the electric fields at a given time without computing all preceding electric fields as required by numerical methods. This means that the projection based surrogate model allows to recover the solution of the governing 3D partial differential equation, 3D wave equation, at any point of a given compute domain and configuration without the need to run a full simulation. This model has shown a good quality of reconstruction in a problem of interpolation of data within a narrow range of simulation parameters and can be used for input data of large size.

The magnetoelectric effect is a fundamental physical phenomenon that synergizes electric and magnetic degrees of freedom to generate distinct material responses like electrically tuned magnetism, which serves as a key foundation of the emerging field of spintronics. Here, we show by first-principles studies that ferroelectric (FE) polarization of an In2Se3 monolayer can modulate the magnetism of an adjacent transition-metal (TM)-decorated graphene layer via a ferroelectrically induced electronic transition. The TM nonbonding d-orbital shifts downward and hybridizes with carbon-p states near the Fermi level, suppressing the magnetic moment, under one FE polarization, but on reversed FE polarization this TM d-orbital moves upward, restoring the original magnetic moment. This finding of robust magnetoelectric effect in the TM-decorated graphene/In2Se3 heterostructure offers powerful insights and a promising avenue for experimental exploration of ferroelectrically controlled magnetism in two-dimensional (2D) materials.

Doping of materials beyond the dopant solubility limit remains a challenge, especially when spatially nonuniform doping is required. In 2D materials with a high surface‐to‐volume ratio, such as transition metal dichalcogenides, various post‐synthesis approaches to doping have been demonstrated, but full control over spatial distribution of dopants remains a challenge. A post‐growth doping of single layers of WSe2 is performed by adding transition metal (TM) atoms in a two‐step process, which includes annealing followed by deposition of dopants together with Se or S. The Ti, V, Cr, and Fe impurities at W sites are identified by using transmission electron microscopy and electron energy loss spectroscopy. Remarkably, an extremely high density (6.4–15%) of various types of impurity atoms is achieved. The dopants are revealed to be largely confined within nanostripes embedded in the otherwise pristine WSe2. Density functional theory calculations show that the dislocations assist the incorporation of the dopant during their climb and give rise to stripes of TM dopant atoms. This work demonstrates a possible spatially controllable doping strategy to achieve the desired local electronic, magnetic, and optical properties in 2D materials.

Controlled production of defects in hexagonal boron nitride (h-BN) through ion irradiation has recently been demonstrated to be an effective tool for adding new functionalitites to this material such as single photon generation and for developing optical quantum applications. Using analytical potential molecular dynamics, we study the mechanisms of vacancy creation in single- and multi-layer h-BN under low- and high-fluence ion irradiation. Our results quantify the densities of defects produced by noble gas ions in a wide range of ion energies and elucidate the types and distribution of defects in the target. The simulation data can directly be used to guide the experiment aimed at the creation of defects of particular types in h-BN targets for single-photon emission, spin-selective optical transitions and other applications by using beams of energetic ions.

Deutsch:

Die vorliegende Arbeit beschäftigt sich mit der Suche nach einem für die ultraschnelle Röntgencomputertomografie geeigneten Strahlbahn-Monitoring-Konzept. Mehrere Sekundäreffekte, die durch den Primärelektronenstrahl ausgelöst werden, wurden analysiert und aus ihnen die Rückstreuelektronenverteilung als Parameter für das Monitoring ausgewählt. Auf Grundlage von für verschiedene Strahlpositionen durchgeführten Simulationen des Elektronenflusses mit dem Monte-Carlo-Simulationspaket FLUKA wurden geeignet positionierte Kupferelektroden als Elektronendetektoren verwendet. Mit diesen Elektroden wurden Testmessungen durchgeführt. Die aufgenommenen Spannungskurven wurden mit den simulierten Elektronenflusskurven verglichen, wobei die Kurvenformen ähnlich waren. Das Spannungssignal wurde dagegen von den Simulationen unterschätzt. Da es während der ersten Messungen zu Spannungsüberschlägen kam, wurde ein zweites, verbessertes System entwickelt, das diese vermeiden soll.

English:

This thesis shows the search for a beam path monitoring concept suitable for ultrafast X-ray computed tomography. Several secondary effects triggered by the primary electron beam were analysed and from them the backscattered electron distribution was selected as a parameter to monitor the beam position. Based on simulations of the electron fluence, carried out for different beam positions with the Monte Carlo simulation package FLUKA, well positioned copper electrodes were used as electron detectors. Test measurements were done with these electrodes. The recorded voltage curves were compared with the simulated electron fluence curves which showed that the curve shapes are similar. However, the voltage signal was underestimated by the simulations. Because voltage flashovers occurred during the first measurements, a second improved system was developed to avoid them.

We present experimental results on the counting rate measurements for several single-gap ¹⁰B‑RPCs with anodes made from standard float glass, low-resistivity glass and ceramic. The measurements were performed at the V17 monochromatic neutron beamline (3.35 Å) at the Helmholtz-Zentrum Berlin. For the ¹⁰B-RPCs with 0.28 mm thick float glass a maximum counting rate density of about 8×10³ Hz/cm² was obtained. In the case of low resistivity glass and ceramic, the counting rate density did not deviate from linear dependence on the neutron flux up to the maximum flux available at this beamline and exceeded a value of 3×10⁴ Hz/cm².

The formation of nanopores by highly charged ion impacts on freestanding fluorine-functionalized graphene is demonstrated. The process is driven by potential sputtering, which becomes active by changing the semi-metallic properties of graphene into a strongly insulating state by fluorination. The interaction of fluorographene with highly charged ions is also studied in terms of charge exchange and kinetic energy loss. A higher number of captured electrons and a larger kinetic energy loss than in pristine graphene are observed, which can be well explained by an increase in the ion's neutralization length and in the atomic areal density of the target, respectively. Using a computer code based on a time-dependent scattering potential model, a connection between the efficiency of charge exchange and the fluorine coverage is revealed. Our results suggest a competition of two distinct nanostructure formation processes leading either to pore formation or fluorine desorption.

Artificial magnetoception is a new and yet to be explored path for humans to interact with our surroundings. This technology is enabled by thin film magnetic field sensors embedded in a soft and flexible format to constitute magnetosensitive electronic skins (e-skins). Being limited by the sensitivity to in-plane magnetic fields, magnetosensitive e-skins are restricted to basic proximity and angle sensing and are not used as switches or logic elements of interactive wearable electronics. Here, we demonstrate a novel magnetoreceptive platform for on-skin touchless interactive electronics based on flexible spin valve switches with the sensitivity to out-of-plane magnetic fields. The technology relies on all-metal Co/Pd-based spin valves with a synthetic antiferromagnet possessing perpendicular magnetic anisotropy. The flexible magnetoreceptors act as logic elements, namely momentary and permanent (latching) switches. The switches maintain their performance even upon severe bending to a radius of less than 5 mm and withstand repetitive bending for hundreds of cycles. We integrated flexible switches in on-skin interactive electronics and demonstrated their performance as touchless human-machine interfaces, which are intuitive to use, energy efficient, and insensitive to external magnetic disturbances. This technology offers qualitatively new functionalities for electronic skins and paves the way towards full-fledged on-skin touchless interactive electronics.

Comprehending cellular changes of radiation-induced brain injury is crucial to prevent and treat the pathology. We provide a unique open dataset of proton-irradiated mouse brains consisting of medical imaging, radiation dose simulations, and large-scale microscopy images, all registered into a common coordinate system. This allows dose-dependent analyses on single-cell level.

Control over the motion of micromotors is of high relevance for lab-on-a-chip and biomedical engineering, wherein such particles encounter complex microenvironments. Here, we introduce an efficient way to influence the direction of motion and speed of Janus micromotors by modifying their surface properties and those of their immediate surroundings. We fabricated light-responsive Janus micromotors with positive and negative surface charge, both driven by ionic self-diffusiophoresis. These were used to observe direction-of-motion reversal in proximity to glass substrates for which we varied the surface charge. Quantitative analysis allowed us to extract the dependence of the particle velocity on the surface charge density at the substrate. This constitutes the first quantitative demonstration of the substrate’s surface charge on the motility of the light-activited diffusiophoretic motors in water. We provide qualitative understanding of these observations in terms of osmotic flow along the substrate generated through the ions released by the propulsion mechanism. Our results constitute a crucial step in moving toward practical application of self-phoretic artificial micromotors.

Purpose/Objective:

The precise and reliable knowledge of radiological tissue properties is essential for a multitude of radiotherapeutic applications, such as input parameters for Monte Carlo simulation, stoichiometric CT calibration as well as for tissue-mimicking phantoms. However, so far only limited data based on ex-vivo experimental studies is available, summarized in ICRU46. Utilizing a clinically validated Dual-Energy-CT (DECT)-based tissue characterization approach (DirectSPR), we present a precise in-vivo assessment of relative electron density (RED), effective atomic number (EAN) and stopping-power ratio (SPR) for organs in the head and pelvis in a patient cohort analysis of clinical DECT scans.
Material/Methods:
Organ-specific tissue parameters were obtained from clinical DECT scans of 107 brain-tumour and 103 pelvic cancer patients applying the DirectSPR approach. DirectSPR is characterised by a voxel-wise, patient-specific parameter determination based on a specific superposition of low- and high-energy DECT scans. In total, six structures in the head (brain, brainstem, spinal cord, chiasm, optical nerve, lens) and four in the pelvic region (prostate, kidney, liver, bladder) were investigated. To minimise contamination from surrounding tissues, clinical contours were shrunk and smoothed in 2D. Image slices with artefacts (e.g. due to metal implants) were omitted from analysis. Organ tissue parameters were characterised regarding the cohort mean value as well as the variation within each patient (2σ_intra) and between the investigated patients (2σ_inter).
Results:
For 10 organs, including 4 organs not listed in ICRU46, the mean RED, EAN and SPR as well as their respective intra- and inter-patient variation were determined (Table 1). Results are exemplarily illustrated for SPR, crucial for proton therapy planning (Figure 1). SPR intra-patient variation was higher than 1.4% (1.4-5.3%) in all organs and always exceeded the inter-patient variation of the organ mean SPR (0.5-2.0%). The largest intra-patient variation was observed in the kidney, where renal parenchyma and calyx were included in the contours. The average inter-patient variation over all organs was 1.2%, highlighting the potential benefit of considering variation in tissue parameters instead of using tabulated mean values. For brain, lens, liver and urine the ICRU46 values are within the determined 2σ_inter interval around the respective mean value, while for prostate and kidney the ICRU46 values are outside this interval. For kidney, cohort mean SPR was 2.3% below ICRU46.
Conclusion:
Radiological tissue parameters in the head and pelvis were characterised in-vivo in a large patient cohort using dual-energy CT. This substantially expands and reassesses the current standard database defined in ICRU46 by smaller substructures in the brain as well as by the quantification of organ-specific inter- and intra-patient variation. Our results can be used as input to simulate intra- and inter-patient variability e.g. in Monte Carlo simulations.

Purpose/objectives: For particle therapy, the clinical implementation of Real-time Respiratory Motion Management (RRMM) is of vital importance to mitigate the detrimental effects of motion on dose delivery. We introduced a worldwide questionnaire on the Patterns of Practice for Adaptive and Real-time Particle Therapy (POP-ART PT), aiming to determine the current status and the potential barriers for motion management implementation in clinical practice at particle therapy centers. Here we summarize the result of RRMM implementation at European centers.
Material and methods: A questionnaire was distributed worldwide to evaluate the current clinical practice, wishes for expansion and barriers to new implementation. Two types of RRMM technique were considered: 1) passive, using volumetric/layered rescanning, 2) active, using free-breathing gating, breath-hold (BH), or tracking/synchronization where beam and target are continuously re-aligned. The tumor sites breast, lung, liver, pancreas, esophagus, and lymphoma were specifically surveyed.
Results: Answers from 44 centers from 16 countries worldwide have been received so far. Here we present the results for 23 European centers from 13 countries (92% response rate). RRMM was used in 16(69%) centers clinically, of which 5(22%) have both passive and active method implemented (figure 1). Of the 22 centers using pencil beam scanning, 13(56%) were applying rescanning, 7(31%) indicated the plan to implement it in the future, and 2(9%) reported rescanning incompatibility due to machine limitations. However, no clear agreement on an optimal rescanning method was found, as 6/7 centers used layered/volumetric rescanning with large variations in rescan numbers (2-6 times). Only 8(34%) centers have been using BH/gating as active RRMM in at least one tumour site (Lymphoma: 100%), but all centers wished to implement it in the future. Surface motion or breathing volume monitoring was the most common method to guide active RRMM. Four centers (…% of those using active RRMM) provided audio/visual feedback to the patient with 2 acquiring additional images to verify surrogate accuracy during dose delivery. No center conducted separate coaching for BH/gating. No center used or wished to use tracking/motion synchronization in the future. Furthermore, 12(54%) and 20(87%) centers wished to extend the use of active RRMM for current tumour sites and to implement it for new tumour sites, respectively. Priority was given to lung (58% and 83%). The main barriers (figure 2) to extend/implement RRMM for current/new tumour sites were technical limitations, limited equipment and human resources.
Conclusion: 69% of particle therapy centers in Europe have implemented RRMM to mitigate the effects of intrafractional respiratory motion in clinical practice. A significant interest was reported to implement more active RRMM in the future, in particular for lung cancer, requiring more support to address technical limitations.

Purpose/objectives: Adaptive particle therapy (APT) allows to account for anatomical changes throughout the treatment course resulting in more conformal target coverage and better sparing of organ at risk (OAR). Different types of APT ranging from weekly to daily to real-time adaptation have been proposed. Based on the POP-ART RT questionnaire [1], the Patterns Of Practice for Adaptive and Real-time Particle Therapy (POP-ART PT) questionnaire aims to determine the status of APT implementation worldwide. Here we focus on APT for interfractional anatomical changes in European centers.
Material/Methods: An institutional questionnaire was sent to particle therapy centers worldwide to determine the current extent of APT implementation in clinical practice. Respondents were asked if and which type of APT was used for selected treatment sites as well as details about the implemented workflow. Additionally, questions regarding the barriers to implementation and wishes for the future were addressed.
Results: Answers from 44 particle therapy centers worldwide have been received so far. Here we present the results for 23 European particle therapy centers from 13 countries, representing a 92% response rate for Europe. All responding centers except one use APT for at least one treatment site. The number of centers using APT for selected sites are shown in Table 1. None of the centers uses online APT (plan libraries or daily adaptation). The plan adaptation was in all cases motivated by both, target and OAR dose considerations. Reasons for adaptation are presented in Figure 1.
Three institutes are satisfied with their implemented adaptive workflows but would like to increase the number of treatment sites treated with APT. All other institutes would like to improve the plan adaptation workflow for a treatment site already treated with APT and 13 of those institutes would like to introduce APT to a new treatment site. One center explicitly stated that they would like to introduce an online adaptive workflow, first applied to skull base patients. Another center explicitly stated the aim to improve adaptive workflow efficiency. Other centers did not specify the type of improvement they wish for. The main barriers in the implementation of APT are presented in Figure 2. The biggest issues were the lack of integrated and efficient workflows and the lack of human resources.
Conclusion: Comprehensive data about APT implementation in clinical practice at particle centers were collected. Currently, no center uses online APT and more research and development for integrated and efficient workflow is needed to bring it to clinical practice. Until the end of the year, we will conclude data collection worldwide and summarize the results in a comprehensive report.

Atomic layer deposition (ALD) of lithium-containing films is of interest for the development of next-generation energy storage devices. Lithium hexamethyl disilazide (LiHMDS) is an established precursor to grow these types of films. The LiHMDS molecule can either be used as a single-source precursor molecule for lithium or as a dual-source precursor molecule for lithium and silicon. Single-source behavior of LiHMDS is observed in the deposition process with trimethylphosphate (TMP) resulting in the deposition of crystalline lithium phosphate (Li3PO4). In contrast, LiHMDS exhibits dual-source behavior when combined with O-2 plasma, resulting in a lithium silicate. Both processes were characterized with in situ ellipsometry, in situ time-resolved full-range mass spectrometry, X-ray photoelectron spectroscopy (XPS), and elastic recoil detection analysis (ERDA). When we combined both reactants into a three-step LiHMDS-TMP-O-2* or LiHMDS-O-2*-TMP process, the dual-source nature of LiHMDS emerged again. By carefully combining our measurements, it is shown that film growth with LiHMDS (in combination with TMP and O-2 plasma) is driven by dipole-driven self-saturated surface interactions combined with dissociative chemisorption. We show that when hydroxyl groups are present on the surface, silicon will be incorporated in the films. These insights benefit the general understanding of the behavior of the LiHMDS and TMP precursors and may facilitate their effective use in ternary or quaternary processes.

Fragestellung:

Die intrafraktionelle Bewegung von abdominellen Tumoren erfordert entsprechend große Sicherheitssäume in der Radioonkologie und führt zu einer erhöhten Strahlenbelastung des umliegenden gesunden Gewebes. Für die geplante Magnetresonanztomographie (MRT)-geführte Partikeltherapie (PT) von Pankreaskarzinomen wurde ein innovatives, patientenspezifisches abdominelles Korsett zur Reduktion der atmungsbedingten Pankreasbewegung entwickelt, welches die hohen Materialansprüche der MRT sowie der PT erfüllt. Das Maß an Bewegungsreduktion durch das Korsetts und dessen Verträglichkeit wurde in einer Patientenstudie untersucht.

Methodik:

Vorbereitend wurden drei abdominelle Korsetts unterschiedlicher Beschaffenheit und Patientenindividualität in ihrer Anwendbarkeit für die MRT-geführte PT bei abdominellen Tumoren untersucht. Das Modell, das die höchste Reproduzierbarkeit in der PT bei Oberbauchtumoren ermöglichte und so eine konformale Strahlentherapie ermöglichte, wurde in einer durch die lokale Ethikkommissioin gebilligte Patientenstudie getestet. Für 12 Patienten (neun weiblich, Alter 71.6±8.6 Jahre) mit Tumoren des Oberbauchs wurde ein Polyethylene-Korsett individuell hergestellt. An einem 3T MRT Scanner wurden von den Patienten sowohl mit Korsett als direkt darauffolgend auch ohne Korsett unter freier Atmung zeitauflösende Bildsequenzen (orthogonale 2D-cine MRT und retrospektiv rekonstruierte 4D-MRT) akquiriert. Das Pankreas wurde in allen Bildern manuell konturiert und die Bewegung des Massenschwerpunktes zwischen maximaler Inspiration und Exspiration in 3D analysiert. Basierend auf einem detaillierten Erhebungsbogen wurde die Verträglichkeit des Korsetts in klinischer Anwendung untersucht.

Ergebnis:

Durch Applikation des Korsetts wurde bei hoher Patientenverträglichkeit eine Reduktion der Pankreasbewegung vorwiegend in der Hauptrichtung der Atmung (inferior-superior) um 49% (p<0.05) erreicht, während kein signifikanter Effekt auf die Bewegung anterior-posterior und links-rechts gefunden wurde. Des Weiteren konnte eine Reduzierung der Bewegungsvariabilität von 36% (p<0.01) festgestellt werden.

Schlussfolgerung
Ein patienten-spezifisches Korsett konnte entwickelt werden, das den Materialansprüchen und dem klinischen Workflow der MRT-geführten PT genügt und die respirationsbedingte Pankreasbewegung in IS Richtung signifikant reduzieren konnte. Dies stimmt mit den Ergebnissen überein, die mit einem Korsett für die Photonentherapie gefunden wurden [1], dessen Beschaffenheit jedoch für die Protonentherapie ungeeignet ist. Bei hoher Patientenverträglichkeit konnte das Korsett so als innovatives Hilfsmittel in den klinischen Workflow überführt werden.

For the PET imaging of prostate cancer, radiotracers targeting the prostate-specific membrane antigen (PSMA) are nowadays used in clinical practice. [18F]PSMA-1007, a radiopharmaceutical labeled with fluorine-18, has excellent properties for the detection of prostate cancer. Essential for the human use of a radiotracer is its production and quality control under GMP-compliance. For this purpose, all analytical methods have to be validated. [18F]PSMA-1007 is easily radiosynthesized in a one-step procedure and isolated using solid phase extraction (SPE) cartridges followed by formulation of a buffered injection solution and for the determination of its chemical and radiochemical purity a robust, fast and reliable quality control method using radio-HPLC is necessary. After development and optimizations overcoming problems in reproducibility, the here described radio-HPLC method fulfills all acceptance criteria-for e.g., specificity, linearity, and accuracy-and is therefore well suited for the routine quality control of [18F]PSMA-1007 before release of the radiopharmaceutical. Recently a European Pharmacopeia monograph for [18F]PSMA-1007 was published suggesting a different radio-HPLC method for the determination of its chemical and radiochemical purity. Since the here described method has certain advantages, not least of all easier technical implementation, it can be an attractive alternative to the monograph method. The here described method was successfully validated on several radio-HPLC systems in our lab and used for the analysis of more than 60 batches of [18F]PSMA-1007. Using this method, the chemical and radiochemical purity of [18F]PSMA-1007 can routinely be evaluated assuring patient safety.

In radiopharmaceutical syntheses, maleimide is commonly used for linking thiol-bearing bioactive molecules to metal-complexing ligands (chelators). However, due to instability of the resulting linkage, phenyloxadiazolyl methylsulfone (PODS) was developed as an alternative to maleimide. This coupling strategy has never been attempted with HBED which is a powerful chelator for gallium-radiolabeling especially at ambient temperature. Here we present HBED-CC-PODS as a bifunctional chelator scaffold for the site-selective conjugation of thiol-bearing vectors and [68Ga]Ga-radiolabeling.

Purpose/Objective
The inclusion of breathing-induced variation using 4D robust plan optimization (RO) may yield more robust proton plans for non-small cell lung cancer (NSCLC) patients. Here, we analysed the benefit of 4DRO in terms of robustness against different motion effects.

Material/Methods
Five NSCLC patients with relevant intrafractional motion in the primary (CTVp; on average 3.2-11.1mm) and nodal clinical target volumes (CTVn; 0.9-7.4mm) were included. CTVs and organs at risk (OARs) were contoured on the planning (pCT) and up to two control 4DCTs (cCT). In RayStation 7.99 (RaySearch, Sweden), we optimized three robust normo-fractionated plans [dose: 66Gy(RBE)]with our clinical criteria of 5mm setup and 3.5%+2mm range uncertainty: RO on the average CT with density override of the primary integral gross tumour volume (3DRO); RO on the average, minimum, maximum and mid inspiration CT image (4DRO3); and RO on the average CT and all eight 4DCT phases (4DRO8).
On each of the average, minimum and maximum inspiration pCT, 16 setup and range error scenarios were analysed. To assess the influence of intrafractional changes, a 4D dose was calculated for the pCT and compared to those for the cCTs assuming equal weights of all breathing phases. Interplay effects were simulated by 4D dynamic dose (4DDD) scenarios on the pCT using a logfile-based dose reconstruction with machine logfiles from mock treatments with and without 5 layered rescans and the breathing signals from 4DCT acquisition. To account for a possible fractionation effect within the first fractions, we accumulated 4DDD scenarios with 4 different starting times.

Results
All nominal plans fulfilled target coverage (D98%>95%) and OAR sparing; 3DRO achieved lower mean lung dose [up to 0.3 Gy(RBE)] in 4 patients and lower V5Gy of contralateral lung (up to 4pp). CTVp/CTVn coverage failed setup and range robustness on average in 7%/17% (3DRO), 9%/10% (4DRO3) and 9%/12% (4DRO8) of the scenarios, respectively. 4D dose target coverage on the pCT remained >97% and within 0.5pp difference to the nominal results for both CTVp and CTVn for all planning strategies; however, interfractional changes in the cCTs reduced mainly the CTVp coverage by about 2.5pp, 2.7pp and 2.5pp in the case of 3DRO, 4DRO3 and 4DRO8 plans, respectively. Compared to the nominal plans, single 4DDD scenarios showed a larger mean loss of CTVp/CTVn coverage in 3DRO plans (2.9pp/2.0pp) than in 4DRO plans (4DRO3: 2.2pp/1.6pp, 4DRO8: 2.2pp/1.9pp). Rescanning improved the D98% values by less than 1pp on average, but was even worse for single scenarios. Irrespective of rescanning, target coverage was restored to clinical acceptance (>95%) in all cases when considering potential fractionation on the pCT.

Conclusion
4DRO provided superior robustness for target coverage in some patients. However, 3DRO demands less workload, offers better healthy lung sparing and yields similar interplay effect reduction when combined with rescanning.

The transamidase activity of transglutaminase 2 (TGase 2) is considered to be important for several pathophysiological processes including fibrotic and neoplastic tissue growth, whereas in healthy cells this enzymatic function is predominantly latent. Methods that enable the highly sensitive detection of TGase 2, such as application of radiolabelled activity-based probes, will support the exploration of the enzyme’s function in various diseases. In this context, the radiosynthesis and detailed in vitro radiopharmacological evaluation of an ¹⁸F-labelled Nε-acryloyllysine piperazide is reported. Robust and facile detection of the radiotracer-TGase 2 complex by autoradiography of thin layer plates and polyacrylamide gels after chromatographic and electrophoretic separation owing to irreversible covalent bond formation was demonstrated for the isolated protein, cell lysates and living cells. Using this radiotracer, quantitative data on the expression profile of activatable TGase 2 in mouse organs and selected tumours were obtained for the first time by autoradiography of tissue sections.

The shear-induced lift force is known to influence the lateral distribution of gas bubbles in bubbly flows. Although the hydrodynamic behavior of a bubble can be greatly affected by surfactants that are present in the liquid bulk, their influence on the lift force has only been investigated to a limited extent. In our previous work we investigated the influence of impurities on the lift force in air-water flows and could reveal non-negligible changes even without a modification of the bubble drag or shape. To bring further insight on changes caused by higher surfactant concentrations, the lift coefficient of single ellipsoidal bubbles of different sizes, which rise in water with varying degree of contamination are experimentally determined in this work. For this purpose, different amounts of 1-Pentanol as well as Triton X-100 were added to the flow. The results reveal a strong dependency of the lift coefficient on the bubble shape, where different findings in the literature for bubbles with lower Reynolds numbers could also be observed for ellipsoidal bubbles in water.

Introduction
Dynamic magnetic fringe fields produced by the scanning magnets (SMs) of a proton pencil beam scanning (PBS) research beamline have shown to cause severe image artefacts during in-beam MR imaging [1]. In this study we investigate the effect of different design parameters of a passive magnetic shield positioned around the SMs on the reduction in magnitude of the magnetic fringe fields the SMs produce.

Methods
A finite element model of the PBS beamline was used to calculate the magnetic fringe fields produced by the SMs. Parameters investigated for a carbon steel magnetic shield included: geometry, material thickness, number of material layers, size of the air gap between layers. The shielding factor (SF) at the projected position of the MR isocenter was calculated. Previous measurements at our facility showed that a SF of at least 20 is required for artefact-free MR imaging during PBS dose delivery.

Results
A cost-efficient way to achieve the required SF was to use a multilayer cylindrical shield. A SF of 21 was achieved for two concentric layers of 10 mm thickness with a 10 mm air gap. The SF can be further increased to 25 by an additional layer. Setting the air gap equal to the layer thickness gave the highest shielding performance.

Conclusion
Computer simulations showed that a passive magnetic shield around the SM can provide the required SF using a multilayer cylindrical geometry with an interlayer air gap equal to the layer thickness.

References
[1] S. Gantz et al. 2020 Phys. Med. Biol.

The neutron flux fluctuation magnitude of KWU-built PWRs shows a hitherto unexplained correlation with the types of loaded fuel assemblies. Also, certain measured long-range neutron flux fluctuation patterns in neighboring core quadrants still lack a closed understanding of their origin. The explanation of these phenomena has recently revived a new interest in neutron noise research.

The contribution at hand investigates the idea that a synchronized coolant-driven vibration of major parts of the fuel-assembly ensemble leads to these phenomena. Starting with an assumed mode of such collective vibration, the resulting effects on the time-dependent neutron-flux distribution are analyzed via a DYN3D simulation. A three-dimensional representation of the time-dependent bow of all fuel assemblies is taken into account as a nodal DYN3D feedback parameter by time-dependent variations of the fuel-assembly pitch. The impact of its variation on the cross sections is quantified using a cross-section library that is generated from the output of corresponding CASMO5 calculations.
The DYN3D simulation qualitatively reproduces the measured neutron-flux fluctuation patterns. The magnitude of the fluctuations and its radial dependence are comparable to the measured details. The results imply that collective fuel-assembly vibrations are a promising candidate for being the key to understand long-known fluctuation patterns in KWU built PWRs. Further research should elaborate on possible excitation mechanisms of the assumed vibration modes.

One of challenges of the Monte Carlo full core simulations is to obtain acceptable statistical variance of local parameters throughout the whole reactor core at a reasonable computation cost. The statistical variance tends to be larger in low-power regions. To tackle this problem, the Uniform-Fission-Site method was implemented in Monte Carlo code MC21 and its effectiveness was demonstrated on NEA Monte Carlo performance benchmark. The very similar method is also implemented in Monte Carlo code Serpent under the name Uniform Fission Source (UFS) method.

In this work the effect of UFS method implemented in Serpent is studied on the BEAVRS benchmark which is based on a real PWR core with relatively flat radial power distribution and also on 3x3 PWR mini-core simulated with thermo-hydraulic and thermo-mechanic feedbacks. It is shown that the application of the Uniform Fission Source method has no significant effect on radial power variance but equalizes axial distribution of variance of local power.

An increasing interest on the development of highly accurate methodologies in reactor physics is nowadays observed, mainly stimulated by the availability of vast computational resources. As a result, an on-going development of a wide range of coupled calculation tools is observed within diverse projects worldwide. Under this framework, the McSAFE European Union project is a coordinated effort aimed to develop multiphysics tools based on Monte Carlo neutron transport and subchannel thermal-hydraulics codes. These tools are aimed to be suitable for high-fidelity calculations both for PWR and VVER reactors, with the final goal of performing pin-by-pin coupled calculations at full core scope including burnup. Several intermediate steps are to be analyzed in-depth before jumping into this final goal in order to provide insights and to identify resources requirements. As part of this process, this work presents the results for a pin-by-pin coupling calculation using the Serpent 2 code (developed by VTT, Finland) and the subchannel code SUBCHANFLOW (SCF, developed by KIT, Germany) for a full-core VVER model. For such purpose, a recently refurbished master-slave coupling scheme is used within a High Performance Computing architecture. A full-core benchmark for a VVER-1000 that provides experimental data is considered, where the first burnup step (i.e. fresh core at hot-full rated power state) is calculated. For such purpose a detailed (i.e. pin-by-pin) coupled Serpent-SCF model is developed, including a simplified equilibrium xenon distribution (i.e. by fuel assembly). Comparisons with main global reported results are presented and briefly discussed, together with a raw estimation of resources requirements and a brief demonstration of the inherent capabilities of the proposed approach. The results presented here provide valuable insights and pave the way to tackle the final goals of the on-going high-fidelity project.

Age information from ancient permafrost is key for understanding permafrost formation, stability and decay, and allows for interpreting past climate and environmental conditions over Pleistocene timescales. However, reliable permafrost geochronology is challenging, especially for deposits beyond the radiocarbon dating limit at about 50,000 years before present.
The headwall of the world’s largest retrogressive thaw slump at Batagay in the Yana Upland, East Siberia (67.58 °N, 134.77 °E), exposes four generations of ice and sand–ice (composite) wedges that formed synchronously with permafrost aggradation (Opel et al., 2019). The exposed Batagay stratigraphy separates into a lower ice complex that is covered by a lower sand unit, an upper ice complex and an upper sand unit. Two woody beds below and above the lower sand are remarkable (Murton et al., 2017).
We apply four dating methods to disentangle the chronology of the Batagay permafrost archive: optically-stimulated luminescence (OSL) dating of quartz and post-infrared-stimulated luminescence (pIR-IRSL) dating of feldspar as well as accelerator mass spectrometry-based Cl-36/Cl dating of wedge ice and radiocarbon dating of organic material (Murton et al., under review). All four chronometers produce stratigraphically consistent and comparable ages. However, OSL appears to date Marine Isotope Stage (MIS) 3 to MIS 2 deposits more reliably than pIR-IRSL, whereas the latter is more consistent with Cl-36/Cl ages for older deposits.
The age information obtained so far indicates that the Batagay permafrost sequence is discontinuous. The lower ice complex developed at least 650,000 years ago, potentially during MIS 16 and represents the oldest dated permafrost in western Beringia and the second oldest known ice in the Northern Hemisphere. The age of the overlying lower sand is poorly constrained, indicating formation some time during MIS 16–4. The upper ice complex formed during MIS 4–2 and the upper sand during MIS 3–2, respectively. Thus, the ancient permafrost at Batagay potentially provides one of the longest terrestrial records of Pleistocene environments in western Beringia.
Additional sampling for all dating approaches presented here took place in spring 2019, and is part of ongoing research to enhance the geochronology of the exceptional palaeoenvironmental archive of the Batagay megaslump.

References
Murton, J.B., Edwards, M.E., Lozhkin, A.V., Anderson, P.M., Savvinov, G.N., Bakulina, N., Bondarenko, O.V., Cherepanova, M., Danilov, P.P., Boeskorov, V., Goslar, T., Grigoriev, S., Gubin, S.V., Korzun, J., Lupachev, A.V., Tikhonov, A., Tsygankova, V.I., Vasilieva, G.V., & Zanina, O.G. (2017) - Preliminary palaeoenvironmental analysis of permafrost deposits at Batagaika megaslump, Yana Uplands, northern Siberia. Quat. Res., 87, 314–330
Murton, J.B., Toms, P., Blinov, A., Opel, T., Fuchs, M., Wood, J., Gärtner, A., Merchel, S., Rugel, G., Savvinov, G., & Wetterich, S. (under review) - A multi-method pilot dating study of ancient permafrost, Batagay megaslump, East Siberia. Quat. Res.
Opel, T., Murton, J.B., Wetterich, S., Meyer, H., Ashastina, K., Günther, F., Grotheer, H., Mollenhauer, G., Danilov, P., Boeskorov, V., Savvinov, G.N., & Schirrmeister, L. (2019) - Past climate and continentality inferred from ice wedges at Batagay megaslump in the Northern Hemisphere’s most continental region, Yana Highlands, interior Yakutia. Clim. Past, 15, 1443–1461.

Presentation at "MU2E-II workshop" (virtuell)

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Results: This commentary of highlights has resulted in 23 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals.
Conclusion: Trends in radiochemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

We performed high-magnetic-field ultrasonic experiments on YbB₁₂ up to 59 T to investigate the valence fluctuations in Yb ions. In zero field, the longitudinal elastic constant C₁₁, the transverse elastic constants C₄₄ and (C₁₁ −C₁₂)/2, and the bulk modulus C_B show a hardening with a change of curvature at around 35 K indicating a small contribution of valence fluctuations to the elastic constants. When high magnetic fields are applied at low temperatures, C_B exhibits a softening above a field-induced insulator-metal transition signaling field-induced valence fluctuations. Furthermore, at elevated temperatures, the field-induced softening of C_B takes place at even lower fields and C_B decreases continuously with field. Our analysis using the multipole susceptibility based on a two-band model reveals that the softening of C_B originates from the enhancement of multipole-strain interaction in addition to the decrease of the insulator energy gap. This analysis indicates that field-induced valence fluctuations of Yb cause the instability of the bulk modulus C_B.

A bentonite engineered barrier will be used in deep geological repositories in granitic host rock to retard the transport of radionuclides possibly released from corroded canisters to the geo- and biosphere. Thus, it is relevant to investigate the diffusion of radionuclides through bentonite and their consequent migration through water-conductive features in granitic rock.
Such scenario in the case of glacial melt water intrusion has been simulated at the Grimsel Test Site with the Long-Term in-situ Test (LIT). A packer-system containing bentonite rings spiked with radionuclide tracers was emplaced in the crystalline rock in contact with a water-conducting shear zone [1]. The bentonite pore-water mixing with Grimsel groundwater was collected at sampling points 5.6 cm from the bentonite for ca. 4.5 years. In these samples, we have determined the concentration of the actinide tracers 233U, 237Np, 242Pu, 241Am and 99Tc. The expected ultra-trace radionuclide concentrations could only be addressed via the high analytical sensitivity of Accelerator Mass Spectrometry. Actinide tracers were analyzed at the 3 MV tandem accelerator of VERA, while 99Tc at the 14 MV tandem accelerator of TUM, enabling quantification at the level of 25 at/g and 0.5 fg/g, respectively [2, 3]. In order to identify radionuclides originating from the LIT, an extensive analysis of the background originating from previous in-situ radionuclide tracer tests [2] was undertaken. First results suggest, that 242Pu release from the bentonite could not be detected. Concentrations of 233U, 237Np and 241Am were found slightly above background for samples collected within 600 days. The levels of 99Tc were always above background indicating the possible release of ca. 8.5 × 10-3 % of the total 99Tc within the experimental time frame. Such early appearance of tracers is unexpected. Further analysis is ongoing in order to identify the possible transport mechanism.

References:

[1] NAB 14-48. GTS Phase VI – CFM Phase 3. February 2015
[2] Quinto et al., (2017) Anal. Chem. 2017, 89, 7182-7189
[3] Quinto et al., (2019) Anal. Chem. 2019, 91, 4585-4591
Acknowledgments: German Federal Ministry for Economic Affairs and Energy, BMWi, grant number 02E11759B & international consortium of the CFM project

The structure of a new type of poly-oxo cluster complex that contains thirteen uranium atoms, {U13}, is reported. The complex crystallises from methanol containing tetravalent uranium (U(IV)) with a basic organic ligand, and is characterised as [U13(μ4-Ooxo)8(μ4-OMeO)2(μ2-OMeO)24Clx(OMeO)12-x] (x = 2.3, MeO: methoxide) (I) by single crystal X-ray diffraction. The characterised {U13} poly-oxo cluster complex (I) possesses a single cubic uranium polyhedron at the centre of the cluster core. To be best of our knowledge, this is the very first example of a poly-oxo f-element complex that maintains a single unit of cubic polyhedron in the structure. The cubic polyhedron in (I) is well comparable with those in bulk UO2 in shape. The U-O bonds in the cubic polyhedron of (I) are, however, significantly shorter than those not only in bulk UO2 but also in another cluster analogue of the {U38} cluster. This shortening of UO bonds, together with BVS calculations and the overall negative charge (2-) of (I), suggests that the central uranium atom in (I), that forms the single cubic polyhedron, is presumably oxidised to the pentavalent state (U(V)) from the original tetravalent state (U(IV)). Hence, (I) is a rare example possessing a single cubic coordination polyhedron of U(V). The {U13} cluster (I) is also a new member of the poly-oxo polymer/cluster family of f-elements, contributing to further development of the polymer/cluster chemistry of f-elements.

Currently, targeted alpha therapy is one of the most investigated topics in radiopharmaceutical cancer management. Especially, the alpha emitter ²²⁵ Ac provides excellent nuclear properties and is gaining increasing popularity for the treatment of various tumor entities. We herein report on the synthesis of two universal ²²⁵Ac-chelators for mild condition radiolabeling and binding sites to conjugate biomolecules via the copper-mediated click chemistry. A convenient radiolabeling procedure was investigated as well as the complex stability proved for both chelators and two PSMA-targeting model radioconjugates. Studies regarding affinity and cell survival were per-formed on LNCaP cells followed by biodistribution studies, which were performed using LNCaP tumor-bearing mice. High efficiency radiolabeling for all conjugates was demonstrated. Cell binding studies revealed a fourfold lower cell affinity for the PSMA conjugate with one targeting vector compared to the conjugate owing two targeting vectors. Additionally, these differences were verified by in vitro cell survival evaluation and biodistribution studies, both showing a higher therapeutic efficiency for the same dose on a cellular leve, a higher tumor up-take (15%ID/g) and a rapid whole body clearance after 24 hours. The synthesized chelators will overcome obstacles of lacking stability and worse labeling needs regarding ²²⁵Ac complexation using the DOTA chelator. Moreover, the universal functionalization expands the coverage of these chelators in combination with any sensitive bio(macro)molecule, thus improving treat-ment of any addressable tumor target.

We introduce the LUNA neutron detector array developed for the investigation of the 13C(𝛼, 𝑛)16O reaction towards its astrophysical 𝑠-process Gamow peak in the low-background environment of the Laboratori Nazionali del Gran Sasso (LNGS). Eighteen 3He counters are arranged in two different configurations (in a vertical and a horizontal orientation) to optimize neutron detection efficiency, target handling and target cooling over the investigated energy range E𝛼,lab = 300 − 400 keV (En = 2.2 − 2.6 MeV in emitted neutron energy). As a result of the deep underground location, the passive shielding of the setup and active background suppression using pulse shape discrimination, we reached a total background rate of 1.23 ± 0.12 counts/hour. This resulted in an improvement of two orders of magnitude over the state of the art allowing a direct measurement of the 13C(𝛼, 𝑛)16O cross-section down to E𝛼,lab = 300 keV. The absolute neutron detection efficiency of the setup was determined using the 51V(p,n)51Cr reaction and an AmBe radioactive source, and completed with a Geant4 simulation. We determined a (34 ± 3)% and (38 ± 3)% detection efficiency for the vertical and horizontal configurations, respectively, for En = 2.4 MeV neutrons.

This work presents the results for a coupled neutronic-thermalhydraulic-thermomechanic pin-level depletion calculation of a PWR fuel assembly using Serpent2-SUBCHANFLOWTRANSURANUS. This tool is based on a semi-implicit depletion scheme with pin-by-pin feedback, mesh-based field exchange and an object-oriented software design. The impact of including fuel-performance capabilities is analyzed, with focus on high-burnup effects. The treatment of the Doppler feedback to the neutronics is examined as well, in particular the use of radial fuel-temperature profiles or radially averaged values.

Advances in DNA nanotechnology allow to design and fabricate highly complex DNA structures, which uses specific programmable interactions between smaller nucleic acid building blocks. To convey this concept to the fabrication of metallic nanoparticles, an assembly platform was developed based on a few basic DNA structures that can serve as molds. Programming specific interactions between these elements allowed the assembly of mold superstructures with a range of different geometries. Subsequent seeded growth of gold within the mold cavities enabled the synthesis of complex metal structures including tightly DNA-caged particles, rolling pin- and dumbbell-shaped particles as well as T-shaped and loop particles with high continuity. The method further supports the formation of higher-order assemblies of the obtained metal geometries. Based on electrical and optical characterizations, we expect that the developed platform is a valuable tool for a self-assembly-based fabrication of nanoelectronic and nanooptic devices.

Topologically-protected surface states present rich physics and promising
spintronic, optoelectronic and photonic applications that require a proper
understanding of their ultrafast carrier dynamics. Here, we investigate
these dynamics in topological insulators (TIs) of the bismuth and antimony
chalcogenide family, where we isolate the response of Dirac fermions at the
surface from the response of bulk carriers by combining photoexcitation
with below-bandgap terahertz (THz) photons with TI samples with vary-
ing Fermi level, including one sample with the Fermi level located within
the bandgap. We identify distinctly faster relaxation of charge carriers
in the topologically-protected Dirac surface states (few hundred femtosec-
onds), compared to bulk carriers (few picoseconds). In agreement with
such fast cooling dynamics, we observe THz harmonic generation without
any saturation effects for increasing incident fields, unlike graphene which
exhibits strong saturation. This opens up promising avenues for increased
THz nonlinear conversion effciencies, and high-bandwidth optoelectronic
and spintronic information and communication applications.

Two sets of calix[4]arenes either with a 1,3-crown ether bridge or with an open-chained oligo ether moiety in 1,3-position were prepared and further functionalized with additional deprotonizable sulfonamide groups to form chelating systems for selected cations Sr²⁺, Ba²⁺, and Pb²⁺. To improve the complexation behaviour towards these cations, calix[4]arenes with oligo ether groups and modified crowns in different size were synthesized. Association constants were determined by UV/Vis titration in acetonitrile using the respective perchlorate salts and logK values between 3.2 and 8.0 were obtained. These findings were supported by the calculation of the binding energy exemplarily for Ba2+.

Modelling element enrichment into upper soil and uptake from soil to the plant organs in natural systems is challenged by the complexity due to mutual interaction of numerous processes and parameters. These parameters include the elemental composition of the sources like different soil horizons or underlying bedrock, varying availabilities of ions, redox conditions in the rhizosphere, and the characteristics of the plant species and their reaction to environmental changes like weather and climate. In this study, we present statistical models based on the principles of compositional data analysis (CoDa-principle) to decipher in a multi-variate and multi-parameter data set the major factors for element cycling between soil and plants.

The test site is located in an natural boreal forest area in Northern Finland and covers an area of ca. 4 km2. A stratified random sampling approach had been used to determine 90 sampling locations. For each location, soil samples of B-horizon and Ah-horizon and plant samples of Common Juniper, Norway Spruce and Scots Pine had been collected. The B-horizon samples had been analysed with XRF methods, Aqua regia and Ionic Leach. The Ah-horizon samples had been analysed by modified Aqua regia and Sodium pyrophosphate leach. Additionally, for each sampling location the soil conductivity, soil dielectric permittivity and pH had been measured. For the plants, the subsamples of twigs, needles and barks had been separately analysed. The elemental composition of all data sets is given as concentration values.
Because the concentrations are by definition constraint data and the uptake of one element often depends on concentration of other elements, the data analysis is performed on log-ratios scores of the elements instead of concentration values to avoid spurious effects in the data analysis. Three different statistical models had been defined: Specific, plant controlled uptake, regulated uptake and unspecific, source controlled uptake. These uptake models can be represented by compositional (Aitchison-space) linear models. It is shown, how this approach can be used to model the influence of elemental composition of sources, the availability of elements in aqueous solutions and the influence of pH and conductivity on the uptake in the various plant organs.

The predictive simulation of gas-liquid multiphase flows at industrial scales reveals the challenging task to consider turbulence and interfacial structures, which span a large range of length scales. For simulation of relevant applications, a hybrid model can be utilised, which combines the Euler-Euler model for the description of small interfacial structures with a Volume-of-Fluid model as a scale-resolving multiphase approach. Such a hybrid model needs to be able to simulate interfaces, which are hardly resolved on a coarse numerical grid. The goal of this work is to improve the prediction of interfacial gas-liquid flows on a numerical grid with comparably large grid spacing. From the low-pass filtering of the two-fluid model five unclosed sub-grid scale terms arise. The convective and the surface tension part of the aforementioned contributions are individually modelled with multiple closure formulations. Those models are a-posteriori assessed in cases of two- and three-dimensional gas bubbles rising in stagnant liquid. It is demonstrated, that predictions on interfacial flows on coarse numerical grids can be improved.

Spatial normalization is an important step for image processing and quantification of regional brain perfusion values using arterial spin labeling (ASL) MRI and is typically performed via high-resolution structural brain scans. However, structural segmentation and/or registration to standard space is complicated when gray-white matter contrast in structural images is low due to on-going myelination in newborns and infants. This problem is particularly of clinical relevance for imaging infants with inborn or acquired disorders that impair normal brain development. We investigated if the ASL MRI perfusion contrast is a viable alternative for spatial normalization. Four registration approaches have been compared: 1) using the structural image contrast, or perfusion contrast with 2) rigid, 3) affine, and 4) non-linear transformations - in 16 healthy controls (median age 0.83 years, IQR ± 0.56) and 36 trigonocephaly patients (median age 0.50 years, IQR ± 0.30) - a non-syndromic type of craniosynostosis. Registration performance was compared quantitatively using the Tanimoto coefficient (TC), visually by three blinded readers, and eventually by the impact on regional CBF values. For both patients and controls, non-linear registration using perfusion contrast showed the highest TC, a 17.51 (CI 6.66-49.38) times more likely to have a higher rating, and 17.45-18.88 mL/100g/min higher CBF compared to the standard registration. Using perfusion based contrast improved spatial registration compared to the use of structural images, significantly affected the regional CBF, and may open up new possibilities for future large pediatric ASL brain studies.

The bubble shape affects the gas-liquid interface momentum, heat and mass transfer, as well as the flow field around the bubble. Correctly predicting the bubble shape is challenging but indispensable under bubble swarm conditions. In this work, the bubble aspect ratio, which is adopted for the characterization of the bubble shape, is obtained through high-speed photography combined with an image processing algorithm from several experiments with an oscillating bubble plume. The results show that the bubble aspect ratio tends to be a constant value with increasing the bubble diameter, rather than decreasing as predicted by various empirical correlations developed in single bubble experiments. None of the available empirical correlations can accurately correlate the bubble aspect ratio with Weber number or Tadaki number. Among the available correlations in literature, Eo based correlation proposed by Besagni and Inzoli (2016) and Eo-Re based correlation proposed by Besagni and Deen (2019) show a better performance. The predicted values of Eo-Re based correlation developed in this work are the closest to the experimental data compared with others.

The International Atomic Energy Agency (IAEA) in cooperation with the International Society for Tracer and Radiation Applications (ISTRA) promotes the international standardization of basic industrial radiotracer and radiation applications. On behalf of IAEA and ISTRA experts from many countries employed in leading research centers and renowned industrial companies analyze existing international standards regarding the necessity of their update or amendment as well as the need for new standards in this field.
In June 2020 a new international standard on “Non-destructive testing - Gamma ray scanning method on process columns” was published as ISO 23159. About three years ago, the experts detected the need to standardize this method meanwhile widely used in petrochemical and chemical process plants as a possibility to check the interior and to locate the cause of malfunction in tray and packed bed columns to avoid basic errors at the application of this method.
In the field of flow rate measurements of fluids in conduits using radioactive tracers several international standards are known:
 Measurement of water flow in closed conduits (ISO 2975)
 Measurement of gas flow in conduits (ISO 4053)
 Measurement of liquid flow in open channels (ISO 9555).
All three standards describe more or less the same measuring methods. Therefore, there is no reason to maintain three independent standards on similar subjects. To bundle the existing diversity experts proposed a new international standard on “Measurement of Fluid Flow Rate in Closed Conduits – Radioactive Tracer Methods” which is under development just now. As soon as finalized, this standard will be published as ISO 24460.
The experts are planning further international standards using radioactive tracer methods for the near future. One of them will deal with leak testing in pressured vessels and underground pipelines, another one will be on determination of concentration or density of suspended and deposited sediment in water bodies by radiometric methods. For the last one, the working draft is already prepared, submitted to the responsible ISO Technical Committee 113 and got the number 6640.
ISO standards are part of accreditation of radiotracer and radiation applications groups, facilitating the promotion and implementation of these competitive technologies in national, regional and international scale.

The electronic properties of π -conjugated two-dimensional (2D) polymers near the Fermi level are determined by structural topology and chemical composition. Thus tight-binding (TB) calculations of the corresponding fundamental network can be used to explore the parameter space to find configurations with intriguing properties before designing the atomistic 2D polymer network. The vertex-transitive fes lattice, which is also called a square-octagon, 4-8, or 4.8_{2<\sup> lattice, is rich in interesting topological features including Dirac points and flat bands. Herein, we study its electronic and topological properties within the TB framework using representative parameters for chemical systems. Secondly, we demonstrate that the rational implementation of band structure features obtained from TB calculations in 2D polymers is feasible with a family of 2D polymers possessing fes structure. A one-to-one band structure correspondence between the fundamental network and 2D polymers is found. Moreover, changing the relative length of linkers connecting the triangulene units in the 2D polymers reflects tuning of hopping parameters in the TB model. These perturbations allow sizable local band gaps to open at various positions in the Brillouin zone. From analysis of the Berry curvature flux, none of the polymers exhibits a large topologically nontrivial band gap. However, we find a particular configuration of semimetallic characteristics with separate electron and hole pockets, which possess very low effective masses
both for electrons (as small as m^{∗<\sup> e<\sub> = 0.05) and for holes (as small as m∗<\sup> h<\sub> = 0.01).}}

Chemical microscopy combines high-resolution emission spectra with Abbe-limited spatial resolution and is used for studies of inhomogeneous samples at the nanoscale. The spatial distinction of multiple Eu(III) coordination sites allows for a comprehensive understanding of environmental samples and highlights the applicability of Eu(III) as molecular probe in medicine and biology

Targeted imaging and therapy approaches based on novel prostate-specific membrane antigen (PSMA) inhibitors have fundamentally changed the treatment regimen of prostate cancer. However, the exact mechanism of PSMA inhibitor internalization has not yet been studied, and the inhibitors' subcellular fate remains elusive. Here we investigated the intracellular distribution of peptidomimetic PSMA inhibitors and of PSMA itself by stimulated emission depletion (STED) nanoscopy, applying a novel non-standard live cell staining protocol. Imaging analysis confirmed PSMA cluster formation at the cell surface of prostate cancer cells and clathrin-dependent endocytosis of PSMA inhibitors. Following the endosomal pathway, PSMA inhibitors accumulated in prostate cancer cells at clinically relevant time points. In contrast to PSMA itself, PSMA inhibitors were found to eventually distribute homogeneously in the cytoplasm, a molecular condition that promises benefits for treatment as cytoplasmic and in particular perinuclear enrichment of the radionuclide carriers may better facilitate the radiation-mediated damage of cancerous cells. This study is the first to reveal the subcellular fate of PSMA/PSMA inhibitor complexes at the nanoscale and aims to inspire the development of new approaches in the field of prostate cancer research, diagnostics, and therapeutics.

Recent years have seen the establishment of several radionuclides as medicinal products in particular in the setting of theranostics and PET. [¹⁷⁷Lu]Lutetium Chloride or [⁶⁴Cu]Copper Chloride have received marketing authorization as radionuclide precursor [⁶⁸Ga]Gallium Chloride has received regulatory approval in the form of different ⁶⁸Ge/⁶⁸Ga generators. This is a formal requirement by the EU directive 2001/83, even though for some of these radionuclide precursors no licensed kit is available that can be combined to obtain a final radiopharmaceuticals, as it is the case for Technetium-99m. In view of several highly promising, especially metallic radionuclides for theranostic applications in a wider sense, the strict regulatory environment poses the risk of slowing down development, in particular for radionuclide producers that want to provide innovative radionuclide for clinical research purposes, which is the basis for their further establishment. In this position paper we address the regulatory framework for novel radionuclides within the EU, the current challenges in particular related to clinical translation and potential options to support translational development within Europe and worldwide.

Luminescent centres in the two-dimensional material hexagonal boron nitride have the potential to enable quantum applications at room temperature. In order to be utilized for applications it is crucial to generate these centres in a controlled manner and to identify their microscopic nature. Here we present a novel method inspired by irradiation engineering with oxygen atoms. We explore systematically the influence of the kinetic energy and the irradiation fluence on the generation of luminescent centres. We find modifications of their density for both parameters while a five-fold enhancement is observed with increasing fluence. Molecular dynamics simulations clarify the generation mechanism of these centres and their microscopic nature. We infer that V_N C_B and V_B are the most likely centres formed. Ab initio calculations of their optical properties show excellent agreement with our experiments. Our methodology generates quantum emitters in a controlled manner and provides new insights into their microscopic nature.

A simple route to generate magnetotransport data is reported that results in fractional quantum Hall plateaus in the conductance without invoking strongly correlated physics. Ingredients to the generating model are conducting tiles with integer quantum Hall effect and metallic linkers, further irchhoff rules. When connecting few identical tiles in a mosaic, fractional steps occur in the conductance values. Richer spectra representing several fractions occur when the tiles are parametrically varied. Parts of the simulation data are supported with purposefully designed graphene mosaics in high magnetic fields. The findings emphasize that the occurrence of fractional conductance values, in particular in two-terminal measurements, does not necessarily indicate interaction-driven physics. The importance of an independent determination of charge densities is underscored and similarities with and differences to the fractional quantum Hall effect are critically discussed.

Fe₄Si₂Sn₇O₁₆ hosts an undistorted kagome lattice of Fe²⁺ (3d⁶, S = 2) ions. We present results of bulk magnetization and Sn nuclear magnetic resonance (NMR) measurements on an oriented Fe₄Si₂Sn₇O₁₆ powder sample oriented in geometries parallel (II) and perpendicular (⊥) to the external applied magnetic field used for orienting the powder (B_ori). The bulk susceptibility χ shows a broad peak at T_N ∼ 3 K associated with antiferromagnetic ordering. NMR spectra indicate the presence of planar anisotropy in the kagome planes. From an analysis of the static NMR shift (K) and dynamic spin-lattice relaxation rate (1/T₁) we conclude the presence of dominant magnetic fluctuations in the kagome planes. For the II orientation, K scales linearly with the bulk susceptibility for temperatures down to ∼4 K, while in the ⊥ orientation K starts to deviate strongly below T ∼ 30 K. We associate this deviation with the onset of spin-tilting towards the kagome planes. These correlations are also reflected in the 1/T₁ data for the II orientation, which starts to decrease below T ∼ 30 K. In this correlated regime, T_N < T < ∼30 K, we discuss the formation of positive chiral spin correlations in the kagome planes.

Thin ferromagnetic [Co/Pt] multilayers with perpendicular magnetic anisotropy exhibit a variety of nanoscopic magnetic domain patternsat remanence, from long interlaced stripes to lattices of bubbles, depending on the multilayer structure but also on the magnetic historyof the sample. For optimized structural parameters, stripe-bubble transitions accompanied by drastic increases in domain density havebeen observed when the magnitude of the previously applied perpendicular fieldHmis finely tuned throughout the hysteresis loop. Here, we investigate the robustness of these morphological transitions against field sequencing and field cycling. We conducted this study on[Co(x)/Pt(7Å)]N=50where x varies from 4 to 60 Å. We mapped the morphological transition withHmvarying from 0 to 9 T, following bothan ascending sequence (0→9 T) and a descending sequence (9 T→0). We found that the optimal fieldHm=H∗at which the domain densityis maximized and its associated maximal density n∗ are not significantly affected by the field sequencing direction. We have also investigatedpossible pumping effects when cycling the applied field at the value H∗. We found that n∗ remains relatively stable through field cycling, andmuch more stable in the bubble state, compared to longer stripe states. The observed robustness of these morphological transitions againstfield sequencing and field cycling is of crucial importance for potential magnetic recording applications.

The magnetic and thermodynamic properties of layered single-crystal K₂Ni(MoO₄)₂ having both structural and magnetic dimers have been investigated. The crystal structure of K₂Ni(MoO₄)₂ is composed of edge-sharing NiO₆-octahedral pairs bridged by the MoO₄ ²⁻ polyatomic ion groups in a plane, and the K⁺ ions sit in the van der Waals gap between the layers. The temperature dependence of magnetic susceptibility shows a spin-singlet ground state with an activation gap of Δ/k_B ≈ 38 K. A high-field magnetization study at T = 1.5 K exhibits a half-magnetization plateau at μ₀H ∼ 25 T, corresponding to a level crossing of the singlet ground state with the lowest triplet state. Further, we have performed density functional theory calculations to determine magnetic exchange interactions. The nearest-neighbor coupling constant J₁ ∼ 10 K between the Ni spins turns out to be an order of magnitude larger than all interdimer couplings. Our experimental and theoretical results suggest that K₂Ni(MoO₄)₂ constitutes a nearly isolated two-dimensional S = 1 dimer model.

Most of solid-state spin physics arising from spin–orbit coupling, from fundamental phenomena to industrial applications, relies on symmetry-protected degeneracies. So does the Zeeman spin–orbit coupling, expected to manifest itself in a wide range of antiferromagnetic conductors. Yet, experimental proof of this phenomenon has been lacking. Here we demonstrate that the Néel state of the layered organic superconductor κ-(BETS)₂FeBr₄ shows no spin modulation of the Shubnikov–de Haas oscillations, contrary to its paramagnetic state. This is unambiguous evidence for the spin degeneracy of Landau levels, a direct manifestation of the Zeeman spin–orbit coupling. Likewise, we show that spin modulation is absent in electron-doped Nd_1.85Ce_0.15CuO₄, which evidences the presence of Néel order in this cuprate superconductor even at optimal doping. Obtained on two very different materials, our results demonstrate the generic character of the Zeeman spin–orbit coupling.