Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Research software is a central pillar in the scientific work in general, in the Helmholtz Association and in particular at the Helmholtz-Zentrum Dresden - Rossendorf e.V. (HZDR). The software policy at the HZDR supports researchers in their independence and ability to act and is a framework that provides orientation. It gives advice and makes recommendations for the whole software lifecycle from development and documentation to publication and distribution as well as maintenance of the research software.

The HZDR software policy is derived from a model policy provided by the Task Group Research Software of the Helmholtz Open Science Office. Adaptations were made, for example, regarding the recommended software quality ensurance measures based on the software application classes suggested by the German Aerospace Center (DLR) as well as the choice of Open-Source Software (OSS) licenses. A selection process and decision tree were defined to recommend the preferred use a specific set of OSS licenses at the HZDR.

The introduction of a policy at HZDR and for each of the research centres in the Helmholtz Association involves not only behavioural but also cultural change in the whole research association and all related research groups. The overall objectives are to achieve better sustainability and higher quality in research software engineering leading to better verifiability, traceability and reproducibility of scientific results.

The electron-phonon interaction is in many ways a solid state equivalent of quantum electrodynamics. Being always present, the e-p coupling is responsible for the intrinsic resistance of metals at finite temperatures, making it one of the most fundamental interactions present in solids. In typical metals, different regimes of e-p scattering are separated by a characteristic phonon energy scale—the Debye temperature. However, in metals harboring very small Fermi surfaces a new scale emerges—the Bloch-Grüneisen temperature. This is a temperature at which the average phonon momentum becomes comparable to the Fermi momentum of the electrons. Here we report sub-Kelvin transport and sound propagation experiments on the Dirac semimetal ZrTe₅. The combination of the simple band structure with only a single small Fermi surface sheet allowed us to directly observe the Bloch-Grüneisen temperature and its consequences on electronic transport of a 3D metal in the limit where the small size of the Fermi surface leads to effective restoration of translational invariance of free space. Our results indicate that on entering this hydrodynamic transport regime, the viscosity of the Dirac electronic liquid undergoes an anomalous increase beyond the theoretically predicted T⁵ temperature dependence. Extension of our measurements to strong magnetic fields reveal that, despite the dimensional reduction of the electronic band structure, the electronic liquid retains characteristics of the zero-field hydrodynamic regime up to the quantum limit. This is vividly reflected by an anomalous suppression of the amplitude of quantum oscillations seen in the Shubnikov-de Haas effect.

We investigated the magnetic and magnetoelastic properties of MnSc₂Se₄ single crystals at low temperature under a magnetic field directed along the crystallographic [111] axis. The magnetization data at low temperature show a linear increase with magnetic field, until saturation is reached above 15 T. In ultrasound, a longitudinal acoustic mode shows a softening in field, which is absent for a transverse acoustic mode.We discuss these results using a microscopic model based on the framework of linear spin-wave theory. The magnetic and magnetoelastic data are qualitatively reproduced by considering magnon-phonon interactions arising from exchange-striction coupling between the crystal lattice and spin-wave fluctuations in the zero-temperature limit.

Spinon-magnon mixing was recently reported in botallackite Cu₂(OH)₃Br with a uniaxially compressed triangular lattice of Cu²⁺ quantum spins [H. Zhang et al., Phys. Rev. Lett. 125, 037204 (2020)]. Its nitrate counterpart rouaite, Cu₂(OH)₃NO₃, has a highly analogous structure and might be expected to exhibit similar physics. To lay a foundation for research on this material, we clarify rouaite’s magnetic phase diagram and identify both low-field phases. The low-temperature magnetic state consists of alternating ferromagnetic and antiferromagnetic chains, as in botallackite, but with additional canting, leading to net moments on all chains which rotate from one chain to another to form a 90° cycloidal pattern. The higher-temperature phase is a helical modulation of this order, wherein the spins rotate from one Cu plane to the next. This extends to zero temperature for fields perpendicular to the chains, leading to a set of low-temperature field-induced phase transitions. Rouaite may offer another platform for spinon-magnon mixing, while our results suggest a delicate balance of interactions and high tunability of the magnetism.

We present a thorough experimental investigation on single crystals of the rare-earth based frustrated quantum antiferromagnet Pr₃BWO₉, a purported spin-liquid candidate on the breathing kagome lattice. This material possesses a disordered ground state with an unusual excitation spectrum involving a coexistence of sharp spin waves and broad continuum excitations. Nevertheless, we show through a combination of thermodynamic, magnetometric, and spectroscopic probes with detailed theoretical modeling that it should be understood in a completely different framework. The crystal field splits the lowest quasidoublet states into two singlets moderately coupled through frustrated superexchange, resulting in a simple effective Hamiltonian of an Ising model in a transverse magnetic field. While our neutron spectroscopy data do point to significant correlations within the kagome planes, the dominant interactions are out-of-plane, forming frustrated triangular spin-tubes through two competing ferro-antiferromagnetic bonds. The resulting ground state is a simple quantum paramagnet, where the presence of strongly hyperfine-coupled nuclear moments and weak structural disorder causes significant modifications to both thermodynamic and dynamic properties.

Universal Chimeric Antigen Receptor (UniCAR) T-cell therapy, has proven to be a successful and safer cancer treatment strategy especially in targeting non-solid tumors. Unlike conventional CAR T-cell, UniCAR T-cells recognize the Tumor Associated Antigen (TAA) indirectly through an adaptor molecule called the Target Module (TM). The administration of the TMs should be carefully monitored, in order to avert undesired effects such as cytokine release syndrome (CRS) or tumor lysis syndrome (TLS), and the dose administration needs to be adjusted according to the patient´s response. Established monitoring techniques such as Enzyme-Linked Immunosorbent Assay (ELISA), Positron Emission Tomography (PET) or Magnetic Resonance Imaging (MRI) face their own limitations such as low-sensitivity, high cost and radiolabeling requirements. Therefore, in this pilot study we introduce an Extended Gate Field Effect Transistor (EG-FET) based biosensor for label-free, high sensitivity and low-cost monitoring of the TM concentration. Additionally, our sensor is an effective tool for tracking the pharmacokinetics of TMs in mice models, demonstrating results comparable to those achieved by conventional radiolabeling.

The kinetic energy (KE) kernel, which is defined as the second order functional derivative of the KE functional with respect to density, is the key ingredient to the construction of KE models for orbital free density functional theory (OFDFT) applications. For solids, the KE kernel is usually approximated using the uniform electron gas (UEG) model or the UEG-with-gap model. These kernels do not have information about the effects from the core electrons since there are no orbitals for the projection on nonlocal pseudopotentials. To illuminate this aspect, we provide a methodology for computing the KE kernel from Kohn-Sham DFT and apply it to the valence electrons in bulk aluminum (Al) with a face-centered cubic lattice and in bulk silicon (Si) in a semiconducting crystal diamond state. We find that bulk-derived local pseudopotentials provide accurate results for the KE kernel in the interstitial region. The effect of using nonlocal pseudopotentials manifests at short wavelengths, defined by the diameter of an ion surrounded by its core electrons. Specifically, we find that the utilization of nonlocal pseudopotentials leads to significant deviations in the KE kernel from the von Weizsacker result in this region, which is, as a rule, explicitly enforced in most widely used KE functional approximations for OFDFT simulations.

Recent promising results from inertial fusion energy (IFE) facilities, such as the National Ignition Facility in the USA, have sparked a strong interest in IFE technologies. Because it is a multiscaled problem from a simulation standpoint, significant effort is required to accurately model the dense plasmas on various length and time scales, which is crucial for developing IFE technology. One of the main challenges in modeling is creating reliable simulation tools to study the dynamic dielectric and transport properties of dense plasmas across different temperature and density ranges. Quantum many-body theory is crucial in developing a dependable method for computing these properties, provided the density response function of plasmas is known. This presentation discusses the advanced simulation methods being used and developed at the Center of Advanced Systems Understanding [1-4] for this property and the associated computational and work expenses.

[1] Tobias Dornheim, Zhandos A. Moldabekov, Kushal Ramakrishna, Panagiotis Tolias, Andrew D. Baczewski, Dominik Kraus, Thomas R. Preston, David A. Chapman, Maximilian P. Böhme, Tilo Döppner, Frank Graziani, Michael Bonitz, Attila Cangi, Jan Vorberger, Electronic density response of warm dense matter, Phys. Plasmas 30, 032705 (2023).
[2] Zhandos Moldabekov, Jan Vorberger, Tobias Dornheim, Density Functional Theory Perspective on the Nonlinear Response of Correlated Electrons across Temperature Regimes, J. Chem. Theory Comput. 2022, 18, 5, 2900–2912
[3] Zhandos A. Moldabekov, Michele Pavanello, Maximilian P. Böhme, Jan Vorberger, and Tobias Dornheim, Linear-response time-dependent density functional theory approach to warm dense matter with adiabatic exchange-correlation kernels, Phys. Rev. Research 5, 023089 (2023)
[4] Maximilian Böhme, Zhandos A. Moldabekov, Jan Vorberger, and Tobias Dornheim, Static Electronic Density Response of Warm Dense Hydrogen: Ab Initio Path Integral Monte Carlo Simulations, Phys. Rev. Lett. 129, 066402 (2022)

In this experimental study, we explore the dynamics of the thermal boundary layer in liquid metal Rayleigh–Bénard convection, covering the parameter ranges of 0.026 ≤ Prandtl numbers (Pr) ≤0.033 and Rayleigh numbers (Ra) up to 2.9×10^9. Our research focuses on characterising the thermal boundary layer near the top plate of a cylindrical convection cell with an aspect ratio of 0.5, distinguishing between two distinct regions: the shear-dominated region around the centre of the top plate and a location near the side wall where the boundary layer is expected to be affected by the impact or ejection of thermal plumes. The dependencies of the boundary layer thickness on Ra at these positions reveal deviating scaling exponents with the difference diminishing as Ra increases. We find stronger fluctuations in the boundary layer and increasing deviation from the Prandtl–Blasius–Pohlhausen profile with increasing Ra, as well as in the measurements outside the centre region. Our data illustrate the complex interplay between flow dynamics and thermal transport in low-Pr convection.

The potential impact and capabilities of utilizing the flexibility of metal-organic frameworks (MOFs) in catalysis are widely unexplored. Here, one of the prominent and representative examples of breathing MOFs, MIL-53(Cr), able to structurally adapt with pore size adjustment when exposed to specific chemical species in solution, was employed as a novel catalyst for photocatalytic dehalogenation reaction. The powder X-ray diffraction and pair distribution function analysis, applied to visualize the framework configuration of the host and host-guest interaction between adsorptive molecules and MOF skeleton, reveals stabilization effects induced by specific organic solvents resulting in a characteristic pore opening degree, whereas introduced substrate and generated product molecules further adaptively affect the pore aperture. The framework dynamics cause an adaptive catalytic efficiency of the MOF, as evidenced by the dehalogenation model reaction. The photocatalytic efficiency could thus be finely tuned by the controlled breathing of the host pore system, regulated by guest solvent molecules. This work emphasized the controllable catalytic activity of flexible MOFs and advances the control of catalytic selectivity by deliberate tailoring of flexibility.

Magnetic refrigeration based on the principle of the magnetocaloric effect (MCE) in magnetic solids has been considered as a prospective cooling technology. Exploring suitable magnetocaloric materials (MCMs) is a vital prerequisite for practical applications. Herein, an excellent cryogenic MCM—the B-site-ordered Gd₂CuTiO₆ double perovskite (DP) oxide—which exhibits the largest MCE among known Gd-based DP oxides, is identified. Such enhanced cryogenic MCE in the Gd₂CuTiO₆ DP oxide likely stems from the exchange interaction effect between Gd-4f and Cu-3d magnetic sublattices. Under a magnetic field change of 0–7 T, the maximum magnetic entropy change (−ΔS_T ^max) of the Gd₂CuTiO₆ DP oxide reaches 51.4 J kg⁻¹ K⁻¹ (378.2 mJ cm⁻³ K⁻¹), which is much larger than that of the commercialized magnetic refrigerant Gd₃Ga₅O₁₂, which is 38.3 J kg⁻¹ K⁻¹ (271.2 mJ cm⁻³ K⁻¹), and it is also superior to most of the recently reported benchmarked cryogenic MCMs, indicating the possibility for practical applications. This work also provides a productive route for future cryogenic MCM design by harnessing 4f–3d exchange interactions.

Laser-driven ion accelerators can produce pulsed multi-MeV beams with high-peak currents, which can be used for multidisciplinary applications, including radiotherapy, injectors for advanced accelerator concepts, neutron production and fast ignition in inertial confinement fusion. However, the evolution from complex physics experiments to turnkey particle sources for applications requires breakthroughs in the generated beam parameters, their robustness and scalability to higher repetition rates and efficiencies.
Previous research has shown enhanced acceleration performance when the laser main pulse arrival coincides with the onset of relativistically induced transparency (RIT) of the target. In a series of experiments, using the DRACO-PW and the J-KAREN-P laser system, we scanned laser and target parameters to identify optimal interaction conditions for ion acceleration in the RIT regime [1]. Our results demonstrate the immense potential of this regime by accelerating protons to a record energy of 150MeV using only 22J laser energy [2]. The proton beam featured a high-energy component with low divergence, which is spectrally and spatially separated. Target transparency was identified as a simple control parameter for determining the high-performance domain owing to its sensitivity to subtle changes in the initial laser–target conditions. Start-to-end simulations validate these results and elucidate the role of preceding laser light in pre-expanding the target along with the detailed acceleration dynamics during the main pulse interaction. The insights into the role of the ultrashort pulse duration and the temporal contrast of the laser represent a significant step forward in understanding and controlling ion acceleration in the RIT regime.

In case it is desirable to dispose of inventories of separated civil PuO2 that have no further use, a
suitable immobilisation matrix is required, prior to disposition in a geological disposal facility. Conversion
of Pu into a mixed oxide (MOX)-type material with characteristics suitable for disposal has previously
been suggested, but not yet demonstrated at laboratory or industrial scale. We here demonstrate the
feasibility of different synthesis routes for simulant ‘‘disposal-MOX’’, using Th 4+ as a Pu4+ surrogate and
containing Gd3+ in a suitable quantity to ensure criticality control. Compositions of (U(1(x+y))ThxGdy)O2d,
where x = 0.1, 0.2 and x : y = 10 : 1 or 100 : 1, were synthesised by a solid state route mimicking the industrial
MIMAS MOX fuel fabrication process, or through an oxalic wet co-precipitation
method. Both synthesis routes gave a single phase fluorite structure upon heat-treatment at 1700 1C, with a
grain size similar to (Pu,U)O2 MOX fuel. The relative density of the sintered pellets was 490% but was
highest in co-precipitated materials, with Th4+ and Gd3+ additions more homogenously distributed. Though
no unincorporated ThO2 or Gd2O3 was observed in any sample, Th and Gd-rich regions were more
prevalent in materials produced through solid state synthesis, in accordance with MIMAS MOX fuel
microstructures. The incorporation of Gd3+ within the fluorite lattice, which is favourable from a criticality
control perspective in a Pu wasteform, was found to be charge balanced via the generation of oxygen
vacancy defects, but not U5+. These results demonstrate feasible synthesis routes for a disposal-MOX
wasteform product via both solid state and wet co-precipitation fabrication routes.

Positron annihilation spectroscopy (PAS) is a precise probe of point defects in bulk and nanomaterials, such as semiconductors. Positrons localize in the neutral and negatively charged open volume defects, i.e. vacancies and their agglomerations, extended defects or pores. The time to the inevitable annihilation of the positron with the electron depends on the local electron density and scales with the open volume size. Positrons pre-accelerated to a given kinetic energy are implanted into solids, allowing depth profiling. In a defect, their lifetime increases and the energetics of the annihilation photons changes. These characteristics are measured using two main measurement techniques, namely positron annihilation lifetime spectroscopy (PALS) and coincidence Doppler broadening spectroscopy (cDBS or cDB-PAS), respectively. Both techniques are available at the large-scale user facility ELBE at HZDR, Germany. PALS allows the evaluation of defect size and concentration, while cDBS provides sensitivity to positron annihilation with valence and core electrons, the latter a fingerprint of the nearest neighbor atoms.
This contribution discusses the role of open volume defects and defect chemistry in the context of heavily doped semiconductors, such as sulfur- and telluride-doped GaAs [1] and Si [2], Al doped ZnO (AZO) [3], or pulsed laser and flash lamp annealed GeSn [4]. We will show that incomplete recrystallization processes resulting from intense pulsed laser melting (PLM) and flash lamp annealing (FLA) are related to defect distribution and electrical activation efficiency in chalcogenide-implanted GaAs. Similarly, in thermally treated chalcogenide-implanted Si, vacancy accumulation processes correlate with variations in carrier concentration and electron mobility. A combination of PAS measurements and DFT calculations allows to translate the experimental results into defect types/sizes and highlights the role of vacancy-dopant complexes for electrical deactivation. On the other hand, the relationship between the crystal quality of AZO films, i.e. single, polycrystalline or amorphous structures, and deposition parameters, such as growth pressure and thickness, can be related to the concomitant increase in vacancy agglomeration size and density. We will discuss the role of dislocations and Sn-decorated germanium vacancies, resulting from Sn diffusion and clustering due to PLM, on the electrical properties of GeSn. The change in defect microstructure depending on the Sn content will be highlighted, too. Finally, a new perspective for PAS is given, where the simultaneous light illumination together with positron measurements will allow new insights into sub-bandgap defect levels in semiconductors, e.g. in GaN.
[1] J. Duan et al., J. Appl. Phys., 134 (2023) 95102
[2] M.S. Shaikh et al., Appl. Surf. Sci., 567 (2021) 150755
[3] R.M. Maffei et al., Appl. Surf. Sci., 665 (2024) 160240
[4] O. Steuer et al., J. Phys. Condens. Matter, 36 (2024) 085701

In contrast to corresponding nitrosyl compounds, thionitrosyl complexes of rhenium and technetium are rare. Synthetic access to the thionitrosyl core is possible by two main approaches: (i) the treatment of corresponding nitrido complexes with S₂C₂ and (ii) by reaction of halide complexes with trithiazyl chloride. The first synthetic route was applied for the synthesis of novel rhenium and technetium thionitrosyls with the metals in their oxidation states “+1” and “+2”. [MᵛNCl₂(PPh₃)₂], [MᵛNCl(PPh₃)(LOMe)] and [MᵛᶦNCl₂(LOMe)] (M = Re, Tc; {LOMe}⁻ = (η⁵-cyclopentadienyl)tris(dimethyl phosphito-P)cobaltate(III)) complexes have been used as starting materials for the synthesis of [Reᴵᴵ(NS)Cl₃(PPh₃)₂] (1), [Reᴵᴵ(NS)Cl₃(PPh₃)(OPPh₃)] (2), [Reᴵᴵ(NS)Cl(PPh₃)(LOMe)]⁺ (4a), [Reᴵᴵ(NS)Cl₂(LOMe)] (5a), [Tcᴵᴵ(NS)Cl(PPh₃)(LOMe)]⁺ (4b) and [Tcᴵᴵ(NS)Cl₂(LOMe)] (5b). The triphenylphosphine complex 1 is partially suitable as a precursor for ongoing ligand exchange reactions and has been used for the synthesis of [Reᴵ(NS)(PPh₃)(Et₂btu)₂] (3a) (HEt₂btu = N,N-diethyl-N′-benzoyl thiourea) containing two chelating benzoyl thioureato ligands. The novel compounds have been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods including IR, NMR and EPR spectroscopy and (where possible) mass spectrometry. A comparison of structurally related rhenium and technetium complexes allows for conclusions about similarities and differences in stability, reaction kinetics and redox behavior between these 4d and 5d transition metals.

Die Protonentherapie zeichnet sich durch steile Dosisgradienten und damit einen gut lokalisierbaren Energieübertrag aus. Um dieses Potential voll ausschöpfen zu können, werden weltweit Möglichkeiten erforscht, die Dosisdeposition und insbesondere die Reichweite der Protonen im Patienten zu verifizieren. Eine vielversprechende, erst im letzten Jahrzehnt entdeckte Methode ist das Prompt Gamma-Ray Timing (PGT), das auf der Abhängigkeit der detektierten Flugzeitverteilung prompter Gammastrahlung von der Transitzeit der Protonen im Patienten beruht. In dieser Arbeit wird eine Geant4-Simulation zur Vorhersage der PGT-Spektren bei Bestrahlung eines PMMA-Phantoms entwickelt und durch den Vergleich mit experimentellen Daten validiert. Sowohl die Emissionsausbeute prompter Gammastrahlung im Phantom als auch die Detektionsrate werden abhängig von der Protonenenergie analysiert. Zur Vergleichbarkeit mit den gemessenen Spektren wird eine mehrschrittige Prozessierung der Simulationsergebnisse vorgestellt. Schließlich wird die Simulation genutzt, um die Sensitivität der PGT-Methode auf Reichweitenänderungen zu demonstrieren. Dafür können in das Phantom Cavitäten unterschiedlicher Dicke und verschiedenen Materials eingefügt werden. Für geeignet gewählte Verteilungsparameter der simulierten PGT-Spektren wird deren detektierte Änderung mit der bekannten induzierten Reichweitenänderung ins Verhältnis gesetzt. Die so bestimmte Sensitivität ist mit früheren Ergebnissen für gemessene Spektren im Rahmen der Unsicherheiten in Übereinstimmung.

The mixed state transport properties of type-II superconductors are strongly influenced by the dynamic behavior of quantized magnetic fluxoids around the critical temperature (Tc), where a combination of normal and superconducting properties is exhibited. To understand the mixed state transport properties of type-II superconducting NbN ultrathin films (2D) we measured sheet resistance (RxxM) and Hall resistance (RxyM) of a 5-nm-thick NbN film around Tc (10.75 K) at temperatures 10.40, 10.68, and 10.77 K. Hall resistance (HR) was measured in external out-of-plane and in-plane magnetic fields up to 6 T, using 100 μA and 1 mA driving current in Van der Pauw geometry. The electric field of applied bias and Lorentz force of applied external magnetic field causes a movement of the normal conducting electrons within each fluxoid. The moving fluxoids cause dissipation and generation of Hall voltage. We developed a macroscopic analysis of the Hall resistance arising from fluxoids, to advance the differentiation between dissipating current and superconducting currents in type-II superconductors at Tc. We have extracted the number of normal conducting carriers per fluxoid and areal density and mobility of the fluxoids in dependence on the external magnetic field. This differentiation provides valuable insights into the dissipation mechanisms observed during transport measurements, e.g., after localized heating due to single photon absorption in nanostructured type-II superconductors. Furthermore, the developed macroscopic analysis of Hall resistance of fluxoids shows promising potential for investigating the fundamental aspects of fluxoid-defect interactions in type-II superconductors. © 2024 authors. Published by the American Physical Society.

The mass transfer between gas bubbles and the liquid surrounding them during absorption or desorption of a chemical species is an important process in many technical applications as well as of fundamental interest. Multiphase CFD simulations of such processes up to the scale of industrial equipment become feasible by the Eulerian two-fluid framework of interpenetrating continua. While an ensuing change in bubble size is frequently considered by including a discretized population balance equation, this apparently has not been the case for an accompanying change in bubble composition. The present work provides the necessary equations to track the average bubble composition as a secondary property within a class method to discretize the population balance equation. Since suitable validation data providing measurements of the bubble composition are not readily available, an analytically solvable test case is developed and used to verify the implementation of the method in the OpenFOAM Foundation software.

Semiconductor spin qubits combine excellent quantum performance with the prospect of manufacturing quantum devices using industry-standard metal-oxide-semiconductor (MOS) processes. This applies also to ion-implanted donor spins, which further afford exceptional coherence times and large Hilbert space dimension in their nuclear spin. Here multiple strategies are demonstrated and integrated to manufacture scale-up donor-based quantum computers. 31PF_2 molecule implants are used to triple the placement certainty compared to 31P ions, while attaining 99.99% confidence in detecting the implant. Similar confidence is retained by implanting heavier atoms such as 123Sb and 209Bi, which represent high-dimensional qudits for quantum information processing, while Sb_2 molecules enable deterministic formation of closely-spaced qudits. The deterministic formation of regular arrays of donor atoms with 300 nm spacing is demonstrated, using step-and-repeat implantation through a nano aperture. These methods cover the full gamut of technological requirements for the construction of donor-based quantum computers in silicon.

Proton-exchange membrane (PEM) electrolysis is one of the mostly used principles for H2 generation. Different attempts are currently under investigation to increase its efficiency and attractiveness by reducing overvoltage and improving cooling. Hereby, we aim on the adjustment of the transition from dissolved O2 in the aqueous phase into its own gas phase by nucleation. Surface functionalization via plasma-enhanced chemical vapour deposition (PECVD) of the industrial materials polypropylene and stainless steel 316L is used to tune the affinity of the nonpolar gas to the substrates by varying their hydrophilicity/hydrophobicity. The water contact angle is used to characterize the wettability, showing that the aging of the coatings is highly dependent on the surrounding media (ambient air or DI water). While the hydrophilic coating based on hexamethyldisiloxane (HMDSO) features a slight hydrophobisation due to reorientation of polar groups on the surface, the hydrophobic coating based on 1H,1H,2H,2H-perfluorooctylacrylate (C6) shows a hydrophilisation due to defluorination. Our experimental findings are supported by XPS and confocal microscopy measurements. Via optical recordings and analysis based on the neural network Stardist we were able to show that despite the aging process the PECVD functionalization still has a major impact on the O2 bubble nucleation even after 150 days of storage.

Proton-exchange membrane (PEM) electrolysis is one of the mostly used principles for H2 generation. Different attempts are currently under investigation to increase its efficiency and attractiveness by reducing overvoltage and improving cooling. Hereby, we aim on the adjustment of the transition from dissolved O2 in the aqueous phase into its own gas phase by nucleation. Surface functionalization via plasma-enhanced chemical vapour deposition (PECVD) of the industrial materials polypropylene and stainless steel 316L is used to tune the affinity of the nonpolar gas to the substrates by varying their hydrophilicity/hydrophobicity. The water contact angle is used to characterize the wettability, showing that the aging of the coatings is highly dependent on the surrounding media (ambient air or DI water). While the hydrophilic coating based on hexamethyldisiloxane (HMDSO) features a slight hydrophobisation due to reorientation of polar groups on the surface, the hydrophobic coating based on 1H,1H,2H,2H-perfluorooctylacrylate (C6) shows a hydrophilisation due to defluorination. Our experimental findings are supported by XPS and confocal microscopy measurements. Via optical recordings we were able to show that despite the aging process the PECVD functionalization still has a major impact on the O2 bubble nucleation even after 150 days of storage.

A data-driven framework is presented for building spin-aware machine-learning interatomic potentials (ML-IAPs) for large-scale spin-lattice dynamics simulations. The ML-IAPs are constructed by coupling a collective atomic spin model with an ML-IAP. Together, they represent a potential energy surface from which the mechanical forces on the atoms and the precession dynamics of the atomic spins are computed. Both the atomic spin model and the ML-IAP are parametrized on data from first-principles methods - Density Functional Theory (DFT) using Spectral Neighbor Analysis Potential (SNAP) descriptors. The generated spin-aware ML-IAP can be directly used in the LAMMPS package to perform coupled spin-molecular dynamics simulations. Leveraging the framework enables performing simulations to study magnetic materials at large lengthscales and longer timescales with first-principles accuracy.

Despite its broad potential applications, substitution of carbon by transition metal atoms in graphene has so far been explored only to a limited extent. We report the realization of substitutional Mn doping of graphene to a record high atomic concentration of 0.5%, which was achieved using ultralow-energy ion implantation. By correlating the experimental data with the results of ab initio Born−Oppenheimer molecular dynamics calculations, we infer that direct substitution is the dominant mechanism of impurity incorporation. Thermal annealing in ultrahigh vacuum provides efficient removal of surface contaminants and additional implantation-induced disorder, resulting in Mn-doped graphene that, aside from the substitutional Mn impurities, is essentially as clean and defect-free as the as-grown layer. We further show that the Dirac character of graphene is preserved upon substitutional Mn doping, even in this high concentration regime, making this system ideal for studying the interaction between Dirac conduction electrons and localized magnetic moments. More generally, these results show that ultralow energy ion implantation can be used for controlled functionalization of graphene with substitutional transition-metal atoms, of relevance for a wide range of applications, from magnetism and spintronics to single-atom catalysis.

Online adaptation can improve the dose distributions during the proton therapy course, but requires a fast plan optimization within a few minutes, while the patient remains on the treatment couch. For the 3D robust optimization of ten non-small cell lung-cancer treatment plans we systematically varied different optimization parameters in RayStation (Figure 1). The selected parameters represent a compromise between optimization time (median 3:59 min) and dosimetric plan quality. The suitability of these parameters during retrospective online-adaptation was validated on repeated CTs for the same patients and proved efficient (dosimetrically and time) wise, especially compared to offline and no adaptation.

Figure 1: The influence of different optimization parameters on the median optimization time for the 10 plans (indicated below the x-axis) and their dosimetric scores, which summarize the values of multiple dosimetric parameters for clinical target volume (CTV) and organs at risk (OAR). While one parameter was systematically varied, the other parameters were kept constant to 100 iterations, with constraints, 3 range uncertainty scenarios and relative energy layer- and spot spacing of 1.0. The selected parameters are marked with red boxes.

This study assesses the impact of Treated Distillate Aromatic Extract (TDAE) oil, at concentrations of 0–20 parts
per hundred rubber (phr), on the glass transition temperature (Tg) of High Vinyl/Low Styrene Styrene-Butadiene
Rubber (HVLSS-SBR), polybutadiene rubber (BR), and their blends with weight ratios of 70/30 and 50/50. Using
Dynamic Mechanical Analysis, Broadband Dielectric Spectroscopy, and Positron Annihilation Lifetime Spectroscopy,
we found that TDAE modifies Tg and fractional free volume (Fv) differently across materials. In HVLSSSBR,
TDAE reduced Tg by approximately 10 ◦C and increased Fv by 0.8 %. In BR, TDAE raised Tg by 5–7 ◦C
without altering Fv. The 70/30 blend showed no Tg change but a 0.6 % Fv increase. For the 50/50 blend, one
Havriliak-Negami equation indicated a Tg rise of 2–3 ◦C and a 0.4 % Fv increase. A two-equation analysis
revealed a 6 ◦C Tg increase and 0.9 % Fv boost in the BR-rich phase, versus a 2 ◦C rise and 0.3 % Fv uptick in the
HVLSS-SBR-rich phase. The sequence of compatibility, influenced by TDAE, is crystalline BR > amorphous BR >
HVLSS-SBR >70/30 blend >50/50 blend. This study provides valuable insights into the behavior of TDAE oil in
rubber blends and can serve as a basis for further research in this field.

The design of novel materials for various scientific and technological purposes such
as in electronics and the energy sector has in recent years benefitted from the
introduction of data-driven design strategies. Here, the power of this approach is
leveraged for two exemplary materials classes.
The recent surprising experimental realization of non-van der Waals 2D compounds
obtained from non-layered crystals [1] foreshadows a new direction in 2D systems
research. We present several dozens of candidates of this novel materials class
derived from applying data-driven research methodologies in conjunction with
autonomous ab initio calculations [2,3,4]. The candidates exhibit a wide range of
appealing electronic, optical, and magnetic properties making them an attractive
platform for fundamental and applied nanoscience.
Also high-entropy materials have recently attracted significant interest due to their
favorable properties within mechanically and thermally demanding environments.
For their actual design, predictive synthesizability descriptors such as the disordered
enthalpy-entropy descriptor (DEED) [5] are crucial prerequisites. We present an
extensive validation of the predictive power of this approach and its prospective
combination with enthalpy corrections for ionic materials [6] for the efficient
computational design of high-entropy compounds for extreme conditions.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[3] T. Barnowsky et al., Adv. Electron. Mater. 9, 2201112 (2023).
[4] T. Barnowsky et al., Nano Lett. 24, 3874 (2024).
[5] S. Divilov et al., Nature 625, 66 (2024).
[6] R. Friedrich et al., npj Comput. Mater. 5, 59 (2019).

The computational design of ionic materials such as ceramics relies on accurate
enthalpies. While standard electronic structure approaches based on density functional
theory can provide quantitatively accurate results for intermetallic compounds, they fail
to yield a proper description of the thermodynamics of ionic materials such as oxides as
the mean absolute errors for formation enthalpies are on the order of several hundred
meV/atom [1]. This hinders the materials design of for instance high-entropy ceramics
or lower dimensional systems such as 2D oxides.
To address this pressing issue, we have recently developed the coordination corrected
enthalpies (CCE) method based on the number of cation-anion bonds and the cation
oxidation states. This correction scheme founded on the bonding topology decreases
the prediction errors by almost an order of magnitude down to the room temperature
thermal energy scale of ~25 meV/atom for oxides, halides, and nitrides [1,2]. It is also
capable of correcting the relative stability of crystal polymorphs. The efficient
implementation of this scheme into the AFLOW framework for materials design in the
form of the AFLOW-CCE module [3] enables now the correction of enthalpies in large
materials databases as well as for the construction of convex hull phase diagrams.
These computational advances are an important enabler for the design of novel highentropy
materials. The reliable computational modelling of such systems can be
realized by the partial occupation algorithm [4] by expanding the disordered system into
a large set of ordered structures. For the actual design of these compositionally
complex disordered high-entropy systems, predictive synthesizability descriptors such
as the disordered enthalpy-entropy descriptor (DEED) [5] are crucial prerequisites. It
critically relies on the accuracy of the enthalpies of all competing phases within the
chemical space of interest as provided by the CCE method.
Literature:
[1] R. Friedrich et al., npj Comput. Mater. 2019, 5, 59. [2] R. Friedrich & S. Curtarolo, J.
Chem. Phys. 2024, 160, 042501. [3] R. Friedrich et al., Phys. Rev. Mater. 2021, 5,
043803. [4] K. Yang et al., Chem. Mater. 2016, 28, 6484. [5] S. Divilov et al., Nature
2024, 625, 66 (2024).

While 2D materials are traditionally derived from bulk layered crystals bonded by weak van
der Waals (vdW) forces, the recent surprising experimental realization of non-vdW 2D compounds
obtained from non-layered transition metal oxides [1] foreshadows a new direction in
2D systems research.
As outlined by our recent data-driven investigations [2, 3], these materials exhibit in particular
unique magnetic properties owing to the magnetic cations at the surface of the sheets. Based on
screening the AFLOW materials database first by a structural criterion for representatives similar
to the experimentally realized systems and focusing then on magnetic compounds, we obtain
12 magnetic candidates (Fig. 1a). Despite of a few ferromagnetic systems, even for the
antiferromagnetic representatives, the surface spin polarizations are diverse ranging from moderate
to large values modulated in addition by ferromagnetic and antiferromagnetic in-plane
coupling (Fig. 1b). At the same time, chemical tuning by surface passivation provides a valuable
handle to further control the magnetic properties of these novel 2D compounds and eventually
to even induce ferromagnetism as demonstrated by hydrogenation of 2D CdTiO3 [4] (Fig. 1c).
These features thus make these compounds an attractive platform for fundamental as well as
applied nanoscience and in particular spintronics.
[1] A. Puthirath Balan et al., Nat. Nanotechnol. 13, 602 (2018).
[2] R. Friedrich et al., Nano Lett. 22, 989 (2022).
[3] T. Barnowsky et al., Adv. Electron. Mater. 9, 2201112 (2023).
[4] T. Barnowsky et al., Nano Lett. 24, 3974 (2024).

Raw data and metadata related to the publication

Emitters based on photoconductive materials excited by ultrafast lasers are well-
established and popular devices for THz generation. However, so far, these emitters – both
photoconductive antennas and large area emitters - were mostly explored using driving lasers
with moderate average powers (either fiber lasers with up to hundreds of milliwatts or Ti:Sapphire
systems up to few watts). In this paper, we explore the use of high-power, MHz repetition
rate Ytterbium (Yb) based oscillator for THz emission using a microstructured large-area
photoconductive emitter, consist of semi-insulating GaAs with a 10 × 10 mm2 active area. As a
driving source, we use a frequency-doubled home-built high average power ultrafast Yb-oscillator,
delivering 22 W of average power, 115 fs pulses with 91 MHz repetition rate at a central
wavelength of 516 nm. When applying 9 W of average power (after an optical chopper with
a duty cycle of 50%) on the structure without optimized heatsinking, we obtain 65 μW THz
average power, 4 THz bandwidth; furthermore, we safely apply up to 18 W of power on the
structure without observing damage. We investigate the impact of excitation power, bias voltage,
optical fluence, and their interplay on the emitter performance and explore in detail the sources
of thermal load originating from electrical and optical power. Optical power is found to have
a more critical impact on large area photoconductive emitter saturation than electrical power,
thus optimized heatsinking will allow us to improve the conversion efficiency in the near future
towards much higher emitter power. This work paves the way towards achieving hundreds of
MHz or even GHz repetition rates, high-power THz sources based on photoconductive emitters,
that are of great interest for example for future THz imaging applications.

Analysis, optimization and uncertainty quantification of the aerodynamic behaviour of turbomachinery components is a fundamental part of the current industrial design process and requires the extensive use of compute-intensive CFD simulations. In this paper we investigate whether graph neural networks can be useful as surrogate models to accelerate the design process, for example in a multi-fidelity framework. Graph neural networks promise to provide good estimates of flow quantities while maintaining the geometric accuracy at a fraction of the computational effort of classical CFD. An application to industrially relevant turbomachinery flows is performed to gain a good understanding of the capabilities and limitations of such methods. We therefore apply a state-of-the-art graph neural network to a turbomachinery setup of industry-relevant mesh size. In particular, a multiscale graph neural network is used to overcome the problems of large information distances when applying message-passing based graph-net blocks to large meshes. The database used to train the network consists of a space-filling DoE of 100 CFD solutions with different geometries. The first use case encompasses the prediction of the flow quantities of the complete fluid domain with 2.5e6 mesh points. The second use case focuses on predicting a single scalar (e.g. pressure or temperature) on surface meshes with up to 30e3 mesh points. In both cases, the networks are employed to predict time-averaged and unsteady flow fields on unstructured meshes of variable point sizes for new geometries not present in the training set. The results demonstrate the proficiency of the approach in predicting time-averaged and unsteady flow quantities on surfaces as well as for full fluid domains for new geometries.

Microfluidic technology, especially the droplet-based format, redefined biochemical methods, enhancing detection efficiency, reducing material consumption, and enabling real-time tracking of reactors, with applications spanning biology, biotechnology, and clinical diagnosis. Gaining insight into the dynamic fluctuations of biomarker levels in patients over time holds significant value for health tracking and postoperative diagnostics, as biomarkers serve as measurable indicators providing information within an organism. For instance, α-amylase levels in drainage fluid diagnose complications, but current methods delay adjustments due to only testing on the first and third day after the operation. Our strategy employs a portable device merging droplet-based microfluidic reactors and an optical biosensor for continuous α-amylase monitoring. This enables real-time detection, notably enhances sensitivity, minimizes fluid and reagent usage, and conserves resources.
The device's adjustability allows the detection of other enzymes and metabolism products, such as lipase, lactate, etc. For example, we used our portable device to monitor the lactate concentration in animal trials, with promising results correlating well with clinical blood measurements. In our lab, we also gelation the droplet reactors as 3D cancer cell models for T cell therapy. We expect to use our innovative droplet-based reactors in broader applications in clinical diagnosis for enabling personalized clinical treatment.

Biomarkers play an important role in early detection and prognosis; evaluating and monitoring their levels can indicate various clinical conditions of diseases (e.g., cancer and metabolic disorders).1 However, the traditional diagnostic methods often involve time-consuming laboratory assays, delaying clinical decisions. In recent years, there has been a growing interest in developing portable point-of-care diagnostic tools for rapid and accurate detecting of biomarkers.2 However, these biomolecular tests mainly focus on detecting biomolecules intermittently, lacking real-time and continuous monitoring. In our group, we present a novel portable droplet-based microfluidic system, combined with optical sensors, for the real-time continuous and long-term monitoring of biomarker (amylase or lactate) levels. Based on encapsulating samples within discrete droplets, our platform integrates sample acquisition, enzymatic assays, and optical detection, enabling real-time monitoring of biomarker concentrations with minimal sample volumes, reagent dose, and processing time. Moreover, our approach can analyze diverse clinical samples, including blood, interstitial fluids, and drain liquid with high sensitivity, selectivity, and accuracy. In previous work, we have achieved real-time sensing of drain α-amylase activity of patients undergoing pancreatic surgery with a bedside portable droplet-based millifluidic device.3 This strategy significantly improves the determination time (3 min), the detection limit of 7 nmol/s·L, and minimal material requirement (ca. 10 μL) and wastes. In the latest work, the portable droplet-based strategy performed well in accurately tracking lactate levels in the blood and interstitial liquid during animal trials, which aims to locally monitor lactate levels to indicate tissue blood perfusions during skin graft surgery. In summary, the droplet-based platform used in biomarkers monitoring brings a big potential in medical diagnosis, disease monitoring, peri-, and postoperative monitoring, and metabolism tracking during exercise.
1 S. Qiuet al, Signal Transduction and Targeted Therapy 8.1 (2023): 132.
2. A. Natalia et al., Nature Reviews Bioengineering 1.7 (2023): 481-498.
3. X. Zhao et al., Biosensors and Bioelectronics 251 (2024): 116034.

Copper nanowires (Cu NWs) are popular potential building blocks of various interconnecting components, microscale circuits, and nanoelectronics. Making interconnects at the nanoscale is still an open problem, and various methods have been explored during the past decades. While ion beam joining has been known for quite some time, the beam parameter-dependent processes leading to joining is yet to be understood in detail. A low-energy (5 keV) and broad argon ion beam is unable to induce joining among the Cu NW mesh, at the low ion currents (<400 nA). However, when the ion current was elevated to 1 µA at the same energy, a large-scale joining was observed. We developed a 3D finite volume model for heat transfer and Joule heating-based melting, which successfully explains the ion current-induced joining. When the current is increased to a significantly high level, the network fragments into smaller copper nanoparticles due to the heat produced. On the other hand, at higher argon ion energy (200 keV) a large-scale joining is observed even at small (<400 nA) beam current. A state-of-the-art, Monte Carlo-based TRI3DYN simulation predicted the role of recoils, redeposition, and ion beam mixing in such joining process at high ion energy, which is mostly due to elastic collisional consequences. Such ion current-induced nanowelded copper mesh-coated PET substrate shows good transmission in the optical range of wavelengths and a notable decrease in the sheet resistance is observed.

Online monitoring of the froth phase in flotation processes has considerable potential for optimization because its properties, such as froth height, are closely related to product quality. Since the insertion of a probe is often not feasible, measuring the froth height from above could be a simple, contactless possibility to capture the height over a large area of the froth surface. To evaluate the applicability of laser-based techniques for height measurements in foam and froth experiments, we tested a lidar sensor and laser triangulation using an industrial laser line scanner. Both techniques proved to be generally suitable for foam and froth height measurement. Investigating the measurement uncertainties, we found that the height of rising and overflowing foam is systematically underestimated. Additionally, the experiments revealed that the sensors can be used to detect changes in foam properties such as the liquid fraction or foam stability.

Foam height is an important parameter in many industrial processes, for example froth flotation, as well as in laboratory experiments. Existing height measurement techniques, such as conductivity-based sensors, often require the insertion of a probe which can affect the flow behavior of the foam or does not allow for continuous measurement. Non-invasive optical measurements through a transparent sidewall are possible in many laboratory experiments, but usually not applicable in industrial contexts. Further, the measured foam or froth height is biased by wall effects on the foam flow and possible wall contamination by particles in froth [1]. Measuring the foam height from above could be a simple, contactless possibility to capture the height over a larger area of the foam surface.
In order to assess the applicability of optical and laser-based techniques to height measurements in foam and froth experiments, we tested lidar, laser triangulation and stereo photogrammetry. Lidar sensors have already been used for froth height monitoring in laboratory-scale flotation tests [2]. Based on a time-of-flight principle, they allow for measuring foam height in a small area and with high temporal resolution. Additionally, we found that the signal intensity is a suitable measure to detect changes in foam properties, such as stability or liquid fraction. Besides lidar, we used an industrial laser scanner that projects a line on the surface of an overflowing foam. The height profile along the line can be calculated by triangulation. Its change over time reveals the foam velocity and points towards bursting bubbles. Lidar or laser triangulation yields quasi-1D or -2D height measurements, respectively. To reconstruct the 3D height profile of a foam surface at high spatial resolution, we demonstrate a photogrammetric method for processing foam images acquired with two synchronised stereo cameras. In future experiments, we will quantify the measurement uncertainties of the proposed methods and test their applicability to foam and froth experiments as well as to industrial flotation processes.

The new generation of satellite hyperspectral (HS) sensors provides remarkable potential  for  regional-scale  mineralogical  mapping.  However,  as  with  any  satellite  sensor,  mapping  results  are  dependent  on  a  typically  complex  correction  procedure  needed  to  remove  atmospheric,  topographic  and  geometric  distortions  before  accurate  reflectance  spectra  can  be  retrieved.  These  are  typically applied by the satellite operators but use different approaches that can yield different results. In this study, we conduct a comparative analysis of PRISMA, EnMAP, and EMIT hyperspectral  satellite  data,  alongside  airborne  data  acquired  by  the  HyMap  sensor,  to  investigate  the  consistency between these datasets and their suitability for geological mapping. Two sites in Namibia  were selected for this comparison, the Marinkas-Quellen and Epembe carbonatite complexes, based  on their geological significance, relatively good exposure, arid climate and data availability. We conducted qualitative and three different quantitative comparisons of the hyperspectral data from these  sites.  These  included  correlative  comparisons  of  (1)  the  reflectance  values  across  the  visible-near  infrared (VNIR) to shortwave infrared (SWIR) spectral ranges, (2) established spectral indices sensitive to minerals we expect in each of the scenes, and (3) spectral abundances estimated using linear  unmixing. The results highlighted a notable shift in inter-sensor consistency between the VNIR and  SWIR spectral ranges, with the VNIR range being more similar between the compared sensors than  the SWIR. Our qualitative comparisons suggest that the SWIR spectra from the EnMAP and EMIT  sensors are the most interpretable (show the most distinct absorption features) but that latent features (i.e., endmember abundances) from the HyMap and PRISMA sensors are consistent with geological  variations.  We conclude  that  our  results  reinforce  the  need  for  accurate  radiometric  and  topographic  corrections,  especially  for  the  SWIR  range  most  commonly  used  for  geological  mapping.

Plant growth on mine wastes is restricted by the lack of water, nutrients, phytotoxic responses and
the absence of a seedbank. In a mesocosm study, we addressed the establishment of vegetation
on metalliferous mine wastes from two seed mixtures. Besides the composition of the vegetation
and the increase in plant cover and biomass over time, we studied concentrations of heavy metals
in the shoot and analyzed the quantity of throughflow, its pH and EC to follow pollutant discharge.
We hypothesized that the types of mine wastes and sown grasslands will affect species composition
and the formation of a protective plant cover. Our platform was well-suited to study build-up and
succession of a vegetation layer and its potential to stabilize mine wastes. However, the establishing
community was less diverse than expected. The dilution of wastes increased species number and
biomass, and we found a reduction of material discharge with increasing vegetation cover. Over
time, drainage was reduced, while pH of the throughflow did not change. However, it was higher
under the addition of greywater. Interestingly, the use of greywater led to a higher biomass in one
mixture and slight changes in the chemistry of the throughflow and the plant matter.

3D in vitro illustration of the impact of Viscosity on Human Hepatoma

Three-dimensional (3D) in vitro cancer models are gaining increasing popularity as pre-clinical platforms for evaluating the efficacy of existing anti-cancer drugs and discovering innovative therapeutic approaches. However, it is worth noting that only a minority of 3D cancer models are built on biomaterial-based matrices, and many of these systems do not fully replicate the complex tumor microenvironment, which can significantly impact the overall therapeutic performance. In our research, we have successfully established 3D prostate cancer and fibrosarcoma co-culture models and utilize them to investigate the dual-targeting of malignant tumor cells and fibroblast activation protein-α (FAP), a marker of tumor microenvironment.

Two series of Th1-xZrxSiO4 phases were synthesized hydrothermally under weakly basic (pH = 8) and strongly acidic (pH = 1) conditions. Changes in pH were found to have a significant effect on experimental phase diagrams. Synthesis at pH = 8 favors the formation of Th-rich phases with resulting Th1-xZrxSiO4 solid solution for x = 0 – 0.5. Contrary, synthesis at pH = 1 results in the formation of pure end-members of the ThSiO4-ZrSiO4 pseudo-binary system separated by multiple miscibility gaps. Phases formed both under basic and acidic conditions were found to retain water, which can be discharged from the structure upon heating. A different high-pressure (HP) behaviour was found for Th-rich and Zr-rich solid solutions. While Th-rich Th0.9Zr0.1SiO4 and Th0.6Zr0.4SiO4 phases retain their stoichiometry and crystal structure upon compression at HP, a significant reduction of the Th occupancy related to a decrease of the Th-O distances is observed for the Th-poor Th0.26Zr0.74SiO4 phase at P > 8 GPa, with the subsequent formation of a Th-rich amorphous phase. The Th diffusion between the crystalline and amorphous phases was found to be fully reversible. This unique self-healing property makes these phases promising candidates for nuclear applications under extreme pressure and temperature conditions, in particular those found in underground repositories.

Research Data Management according to the F.A.I.R. principles using git, git-annex and datalad software tools as well as gitlab and Nocodb web services.

The dataset consists of Infrared photodissociation (IRPD) spectra of Cu+(H2O)(H2)n (with n ≤ 3) and its isotopologue measured on the Leipzig 5 K ring-electrode ion-trap triple mass spectrometer. Besides, it contains the Energy Decomposition Analysis (EDA), the benchmark results, the harmonic and the anharmonic VPT2 frequencies results as well as the script used to get the predicted separation factor for the adsorbed dihydrogen isotopologue.

Little is known about the strong mediating effect of the ligand sphere and the coordination geometry on the strength and isotopologue selectivity of hydrogen adsorption on the undercoordinated copper(I) site. Here, we explore this effect using gas-phase complexes Cu+(H2O)(H2)n (with n ≤ 3) as model systems. Cu+(H2O) attracts dihydrogen (82 kJ mol−1) more strongly than bare Cu+ (64 kJ mol−1) does. Combining experimental and computational methods, we demonstrate a high isotopologue selectivity in dihydrogen binding to Cu+(H2O), which results from a large difference in the adsorption zero-point energies (2.8 kJ mol−1 between D2 and H2, including an anharmonic contribution of 0.4 kJ mol−1). We investigate its origins and the bond strengthening between Cu+ and H2 upon addition of a single H2O ligand. We discuss the role of the environment and the coordination geometry of the adsorption site in achieving a high selectivity and the ramifications for identifying and designing future materials for adsorptive dihydrogen isotopologue separation.

We present a novel approach to estimate gas hold-up in bubble columns using wall pressure fluctuations – without requiring knowledge of operating flow regime or physical properties. The approach uses machine learning and pressure fluctuations acquired from a wall mounted pressure sensor. The approach is validated by carrying out experiments with different physical properties of liquid (deionised water, deionised water – alcohol [ethanol, propanol and butanol] mixture up to 2% alcohol, deionised water – glycerine (30%), tap water). The majority of the data was obtained with 0.1 m diameter bubble column. Data with tap water was obtained for 0.15 m and 0.33 m diameter bubble columns. Gas velocity was varied up to 0.1 m/s. The covered physical properties, column diameter and gas velocities span different flow regimes. An artificial neural network (ANN) based model was developed to relate characteristics of wall pressure fluctuations and superficial gas velocity to the gas hold-up. The approach was validated by comparing predicted results with the experimental data unseen by the ANN model. The approach demonstrates the feasibility of using solely wall pressure fluctuations with machine learning to estimate key characteristics without prior knowledge of flow regimes or physical properties.

The alpaka library is a header-only C++17 abstraction library for accelerator development. Its aim is to provide performance portability across accelerators through the abstraction (not hiding!) of the underlying levels of parallelism.

This work aims to explore whether and how magnetic fields could support the manufacture of micro- and nano-cone arrays by electrodeposition on plain electrodes that are not externally templated. If a uniform external magnetic field is oriented perpendicular to the substrate, the magnetic gradient force enabled by the magnetization of ferromagnetic cones provides strong support for conical growth. Especially for cones of small size, it dominates over the Lorentz force and also the buoyancy force arising from electrode reactions. However, effective magnetic structuring for growing nano-cones is found to require proper design of the electrochemical cell, the electrochemical and magnetic field conditions.

Langevin dynamics simulations are used to analyze the static and dynamic properties of an XY model adapted to dimers forming on Si(001) surfaces. The numerics utilise high-performance parallel computation methods on GPUs. The static exponent ν of the symmetry-broken XY model is determined to ν=1.04. The dynamic critical exponent z is determined to z=2.13 and, together with ν, shows the behavior of the Ising universality class. For time-dependent temperatures, we observe frozen domains and compare their size distribution with predictions from Kibble-Zurek theory. We determine a significantly larger quench exponent that shows little dependence on the damping or the symmetry-breaking field.

The Helmholtz project FINEST addresses challenges in the fields of circular economy, recycling and sustainable resources. Part of this work involves the mixing of fine particles to recycle those materials, which cannot be separated further. The work includes Modelling of Powder Mixing and Segregation. Additionally, the process is studied using Microfocus X-Ray CT (μCT).
Industrial processes are inevitably associated with generating fine-grained particulate matter. Such fine-grained residues rarely find re-entry into industrial value chains; typically, they are disposed and become an environmental burden. Prominent examples are dusts from mineral processing, degraded end-
of-life fibers, or micro plastic entering the natural environment. FINEST will process different residues in an optimized manner to generate value and to minimize hazards. Economic and ecological assessment of waste management concepts provides opportunities to create value by decreased disposal costs. Associated institutions provide the capability to transfer FINEST results to the relevant industrial sectors and potential consumers. The appendant Research School educates a next generation of experts for leadership positions in industry and academia.
In powder mixing, segregation is caused by differences in particle properties. In the context of FINEST, it is by their different density, because the particles range from plastics to metals. We choose a noninvasive technique to investigate the process. Particles from 150 – 250 μm with densities between 0.5 – 5 g/cm³ are mixed in a cylindrical bladed mixer. The μCT scans of powder mixtures are acquired with voxel size of 100 μm. Using a 3D analysis method, the quality of mixture is described by a variance measure. We present the method on a few sample measurements. It describes the evolution of mixing quality over time.
Continuum modelling is chosen to simulate the mixing studied experimentally before. Discrete methods would reach their computational limits. Continuum models of powder mixing in a bladed mixer were given e.g. by Yang et al. (2022). They include size-segregation. Density driven segregation was covered in a continuum model of an annular shear cell (Tirapelle et al, 2021). We combine those approaches. First step was to implement our Finite Volume Model in OpenFOAM. It is an Eulerian model, featuring a transport equation with advection, diffusion and segregation term. Flow behavior of powders is described by μ(I)-rheology.

The recycling of fine-grained residues from various industrial sources poses challenges in terms of their processing. One processing step is the mixing of fine particles. When mixing powders, segregation can occur due to differences in particle properties. As part of a national consortium project, we are investigating the behaviour of powders with different densities, which is relevant when e.g. plastics and metals from shredding are processed together. For our study we used a non-invasive technique to investigate the mixing process: Microfocus X-ray Computed Tomography (μCT).
Particles from 150 - 250 μm with densities between 0.5 - 5 g/cm³ are mixed in a cylindrical bladed mixer. The μCT scans of the powder mixtures are taken with a voxel size of 100 μm. Using a 3D analysis method, the quality of the mixture is described by a variance measure. We discuss the method for selected experiments. It can be used to describe the evolution of mixture quality over time. When applied to a variety of mixtures, the method can be used to investigate the effects of different parameters such as mixing speed, density ratio and mixing time. This will reveal their contribution to segregation and the dependence of the variance measure (representing mixing quality).

Stratified flows are found in nature as well as in many industrial applications, and they can transition to wavy flows due to flow instabilities that are the onset of waves. When the instabilities grow in amplitude, it results in waves and local morphology transitions with huge intermittency involving regular waves, roll waves, or even breaking waves, which promote entrainment of droplets and, therefore, phase morphology transitions. Two-fluid models were historically developed with a focus on dispersed flows, such as bubbly or particulate flows. Consequently, many correlations for interfacial transfer in unresolved morphologies are found in the literature. Conversely, resolved morphologies are typically modeled through separate phase approaches such as VOF or level-set. However, in situations where both resolved and underesolved morphologies are present in the same fluid domain (e.g., dispersed and continuous phase morphologies), a multi-fluid approach is necessary, and in those cases, the closure relations for momentum transfer in resolved morpholo- gies are not well established. The main objective of this paper is to provide a systematic study of the momentum transfer models for resolved morphologies that lead to an enhanced model for stratified flows. In particular, standard models available in commercial or open-source codes are incapable of capturing experimentally observed wave formation. The proposed model includes an enhanced drag closure and turbulence damping for wavy flow. An annular inlet creates a perturbation in the flow that leads to wave formation, and both drag model and turbulence damping are required for wave growth and propagation. The numerical results are presented for distinct pattern conditions, including smooth stratified flow and wavy flow, using distinct approaches for drag and compared to experimental and analytical data. The average properties of the flow, such as water level and pressure, are evaluated from the simulation and compared to experimental results. The proposed model performs reasonably well, while the currently available drag models used for resolved mor- phologies are dependent on mesh refinement, which indicates a lack of consistency. In addition, the typical use of residual values for phase volume fraction in two-fluid models is also discussed. The limits of the two-fluid model for studying wave growth and propagation in stratified flows are discussed, and best practices for wave simulations are provided.

Technetium-99 (⁹⁹Tc) is a radioactive isotope with a long half-live (211,000 a). It is produced in nuclear power plants and nuclear weapon detonation since it is a fission product of U-235 and Pu-239. In addition, ⁹⁹Tc forms after the decay of metastable technetium-99 (⁹⁹ᵐTc), the most used isotope for cancer diagnosis [1]. The emission of ⁹⁹Tc in the environment is hazardous for living organisms, being especially decisive the oxidation state on Tc mobility in water. Thus, several works focused on Tc speciation (e.g., [2–4]) based on redox changes.
In this work, electrochemical reduction of pertechnetate (KTcO₄) was studied in carbonate medium using a three-electrode system, with a glassy carbon (GC) rod as working electrode, a platinum coil as counter electrode, and a Ag/AgCl as reference electrode. The impact of TcO₄⁻ (0.5– 3 mM) and carbonate (5–1000 mM) concentrations, pH (9.3 and10.0) and applied potential on Tc speciation was explored. Formation of reduced species was monitored in situ by UV/vis spectroscopy. TcO₄⁻ reduction at -0.60 V/SHE results in a change of solution color (λₘₐₓ 514 nm), corresponding to the formation of Tc(IV) carbonate species, whereas reduction at -0.74 V yields a bluish green solution (λₘₐₓ 630 nm), associated with the presence of Tc(III) carbonate complex [2]. These solutions were investigated ex situ by ⁹⁹Tc NMR spectroscopy. ⁹⁹Tc-NMR signals detected at ~1600 ppm and ~152 ppm (only for solutions isolated at -0.74 V) are assigned to TcV- and TcIII-carbonate species, respectively [5]. Additional electrochemical analysis by means of cyclic voltammetry and hydrodynamic voltammetry using a rotating disc electrode revealed that TcO₄⁻ reduction results firstly in deposition of solid TcO₂ at GC electrode and secondly the formation of Tc soluble species promoted by interaction of TcO₂ with carbonate.

Currently, we are working on the development of NMR-spectroelectrochemisty coupling for in situ monitoring of TcO₄⁻ electrochemical reduction and Tc structural changes.

References:

[1] A.H. Meena et al., Env. Chem Lett. 2017, 15, 241. [2] J. Paquette et al., Can. J. Chem. 1985, 63, 2369. [3] M. Chotkowski et al., J. Electroanal. Chem. 2018, 814, 83. [4] D.M. Rodríguez et al, Inorg. Chem. 2022, 61, 10159. [5] V.A. Mikhalev, Radiochemistry 2005, 47, 319.

Acknowledgements:

The authors acknowledge the German Federal Ministry of Education and Research (BMBF) for the financial support of NukSiFutur TecRad young investigator group (02NUK072)).

The connection between metadata, data, and software and the integration in an overall lifecycle is crucial for effective data management in research. The generic data management lifecycle, developed at HZDR, bridges these critical components, ensuring seamless data discovery, accessibility, and reproducibility. The approach emphasises the planning of experiments, the role of metadata, data storage, as well as software versioning, and the final publication of digital research artefacts, which enables comprehensive traceability from data creation to long-term archiving. By aligning these elements in a unified procedure, we recommend a uniform lifecycle that can be adapted to different research areas, with a particular focus on photon science and community services such as SciCat that improve data integrity and promote collaborative research.

Tailings generated during ore processing may host significant residual contents of valuable commodities, including critical metals. The particle properties of the tailings, such as mineralogy, particle size, and the surface liberation of ore minerals, strongly control processing behaviour. This study explores a novel combination of methods for incorporating particle data, derived from automated mineralogy, into geometallurgical models of tailings deposits to better understand their reprocessing potential and the economic feasibility of re-mining. This was achieved through binning of different particle types, geostatistical modelling of particle bin frequencies, and bootstrap resampling to reconstruct particle populations. The spatial distributions of processing-relevant particle properties throughout the tailings deposit were predicted with corresponding uncertainties. There are clear systematic trends in the spatial distributions of different particle types, resulting from the sedimentary-style deposition of the tailings. For instance, the tailings nearer the dam walls comprise coarser, silicate-rich particles, while fine-grained and well-liberated sulphide mineral particles are more abundant in the centre of the TSF. As a result, robust models could be developed for the spatial distributions of particle size and mineralogy, which strongly control the sorting of particles during deposition, and other related properties, such as sulphide mineral grain sizes. Finally, a bulk sulphide flotation process was simulated and acid mine drainage potential estimated using the interpolated particle data. Around 58 % of the sulphide minerals present could be recoverable by flotation, with the recoverable sulphide portion decreasing towards the centre of the TSF due to the fine-grained nature of the sulphide minerals. The acid mine drainage potential of the tailings is estimated to be moderate to high, indicating that the carbonate minerals present are not sufficient to neutralise the high acid-generating potential of the sulphide minerals. Overall, this study demonstrates how particle-based geometallurgical models can be developed and utilised for practical applications, with the aim of improving the accuracy of resource and reserve estimations of tailings deposits and the sustainable and responsible management of anthropogenic resources. The methodology proposed here can be easily transferred to other tailings deposits.

The textures of the β- and α-phases of the metastable β-titanium alloy Ti5321 after hot
deformation were investigated by neutron diffraction. A hot-rolled bar was solutionized in the
β-phase field and then hot compressed above and below the β-transus temperature. The initial texture
after full recrystallization and grain growth in the β-phase field exhibits a weak cube component
{001}<100> and minor {112}<110> and {111}<110> components. After hot compression, a <100> fiber
texture is observed, increasing in intensity with compression temperature. Below the β-transus
temperature, dynamic recrystallization of the β-phase and dynamic spheroidization of the α-phase
interact strongly. The texture of the α-phase is a <11–20> fiber texture, increasing in intensity with
decreasing compression temperature. The mechanisms of texture formation during hot compression
are discussed.

Ziel dieser Masterarbeit ist es, neue Chelatliganden für radiometallische Alphastrahler und deren diagnostischen Pendants zu synthetisieren und zu charakterisieren. Diese sollen anschließend auf ihre Fähigkeit zur Radiomarkierung mit unterschiedlichen Radionukliden untersucht und erste Aussagen zur Komplexstabilität getroffen werden. Von besonderem Interesse für die therapeutische Anwendung sind dabei die Radionuklide 223/224Ra, 225Ac (Alphastrahler) und 212Pb (Betastrahler mit Alphaanteil in der Zerfallsreihe). Aufgrund des theranostischen Konzepts sind die diagnostischen Radiometallnuklide 131Ba, 133La, und 203Pb ebenfalls von Interesse.
Als Ausgangsverbindung dient der literaturbekannte Makrozyklus Tetraaza-18-krone-6. Dieser soll mit Polyethylenglycolen überbrückt und mit Picolinaten als Seitenarmen funktionalisiert werden. Es soll eine eigene Syntheseroute, ausgehend von der Startverbindung 2,2'-Oxybis(ethylamin) entwickelt werden, um eine regioselektive Synthese und unterschiedliche Funktionalisierung der Zielverbindungen zu ermöglichen. Die Funktionalisierung sollte mit
unterschiedlich langen Überbrückungen realisiert werden und auch in den alternierenden Positionen der Funktionalisierungen. Die Synthesen der in Abbildung 6 gezeigten Zielverbindungen werden angestrebt.

Macropa-PSMA-ligand conjugates used for targeted alpha-therapy (TAT) with actinium-225 were furnished with an albumin binder to improve their pharmacological behaviour in vivo. [1,2] Additionally, the introduction of an iodine-containing albumin binder provides the basis for the development of a novel theranostic radioconjugate pair using the radiohybrid approach. This involves the complexation of the alpha emitter actinium-225 (half-life: 9.9 d) and the introduction of the easily accessible SPECT-compatible radiohalogen iodine-123 into the same molecule. Advantageously, its ideal physical half-life of 13.2 h and mild radioiodination conditions allows the imaging of longer circulating radioconjugates. The PSMA-binding motif based on the PSMA-617 structure was prepared by a multi-step peptide synthesis followed by subsequent conjugation with the macropa chelator by Cu-catalysed azide-alkyne (CuAAC) click chemistry. The labelling precursor for the introduction of iodine-123 was synthesized by replacing the 4-(p-iodophenyl)butyrate by a trimethylstannyl group to enable labelling by electrophilic aromatic substitution reaction. To determine the binding affinity, LNCaP cells were incubated with the nonradioactive conjugates (with and without nonradioactive lanthanum (La) as congener for actinium-225) in a competition assay and spiked with the radioconjugate [133La]La-PSMA-617. The influence of the complexing agent and the metal ion loading on the binding affinity was evaluated. Two radioconjugates were developed: [123I]I-mcp-M-alb-PSMA with one PSMA-binding motif was prepared from the stannyl precursor (DMSO, Iodogen, 20 min, rt, RCY: 49%) and [123I]I-mcp-D-alb-PSMA with two PSMA-binding motifs was labelled under the same conditions with the exception of adding nonradioactive iodine after completion of radiolabelling to iodinate the second stannyl group (RCY: 20%). Both radioconjugates were purified by HPLC. Beneficially, no influence of chelator loading on cell binding was observed in vitro. The cell binding is comparable across the analogues (mcp-M-alb-PSMA: Ki = 8.46 nM (7.05 - 10.14), La-mcp-M-alb-PSMA: Ki = 8.46 nM (6.72 - 10.66) / mcp-D-alb-PSMA: Ki = 2.35 nM (2.03 - 2.71), La-mcp-D-alb-PSMA: Ki = 2.21 nM (1.64 - 2.96)). Preliminary small animal SPECT imaging with tumor-bearing mice was executed pointing out a biodistribution of [123I]I-mcp-M-alb-PSMA which is comparable to [225Ac]Ac-mcp-M-alb-PSMA. The synthesis of the tin precursors and subsequent radiolabelling with iodine-123 provided two new radioconjugates which act as diagnostic counterparts to the corresponding actinium-225 radioconjugates. The introduction of iodine-123, with or without metal ion loading of the macropa chelator, did not alter the PSMA binding affinity in vitro. The addition of the albumin binding domain opens up a new approach to use iodine-123 in combination with actinium-225 as new radiohybrid pair for the development of hybrid radiopharmaceuticals within the theranostic concept.

Gas evolution at surfaces occurs in a multitude of industrial processes and is a complex phenomenon. A wide range of length scales is involved from nucleation to bubble departure. The evolution of gas bubbles depends on the specific wetting dynamics at the surface and the local conditions like species distribution, temperature, pressure or outer flow. Advancing the bubble growth and gas transport in electrochemical electrolyzers for producing hydrogen can be expected to be beneficial with respect to the overall efficiency of the device.
The presentation will show detailed results of the gas evolution at surfaces of different morphology and surface in order to improve our knowledge how the gas transport can be improved. The results are based on numerical simulations by a VOF method and a mass transfer model that correctly accounts for the flux of dissolved gas into the bubble. Hereby, different wetting dynamics are considered to elaborate the surface influence. The results will further be compared with experimental results available in our group and from literature.

Dinuclear metal complexes present a well-known substance class in the chemistry of the transition metals with a wide variety of applications. However, for the 5f elements, the actinides, such complexes are still rare, with a focus on uranium complexes for the activation of small molecules. Due to their interesting electronic properties, however, the actinides differ greatly from other metals in the periodic table, and the possibility of having two of these metal ions in close proximity in a well-defined molecular framework might provide fascinating insights into the fundamental properties of these elements. The rigid, ambidentate phthalimidinyl anion is a promising ligand for the synthesis of bimetallic complexes
The synthesis of such bimetallic actinide complexes can be achieved by reacting the respective actinide tetrachlorides, UCl₄, [ThCl₄(DME)₂], [NpCl₄(DME)₂], and [PuCl₄(DME)₂] (DME = 1,2-dimethoxyethane), with the antimony compound phenyldi(phthalimidinyl)antimony. The antimony reagent bears two advantages over common salt metatheses reactions. 1) The Sb–N bond is quite weak resulting in an easy transfer of the phthalimidinyl ligand to the actinide, and 2) antimony is a highly chlorophilic element that can abstract the chloride ions from the actinide salts to form soluble antimony chloride compounds such as PhSbCl₂. The synthesis was carried out in the coordinating solvent pyridine which leads to the formation of well-defined dinuclear species by saturating the coordination sphere of the metals and prevents the formation of polymeric species. The compounds crystallize readily from the reaction solution in pyridine after standing for a few days in a nitrogen-filled glovebox.
This easy synthetic route proved to be effective for a series of tetravalent actinides, enabling the preparation of an isostructural series ranging from thorium to plutonium. The comparably close proximity (i.e. ~4.65 Å) of the two paramagnetic metal ions (in case of U, Np and Pu) lends itself to investigations of their magnetic coupling behavior with interesting effects detectable by paramagnetic NMR as well as SQUID magnetometry. Additionally, the determined crystal structures allow for the computational characterization of the compounds including calculated pseudocontact shift (PCS) fields that support the interpretation of paramagnetic shifts in NMR spectroscopy. Due to the close proximity of the metal atoms, the individual PCS cones merge, potentially leading to interesting effects on the NMR spectra of the complexes.
We will discuss structures in solid and solution as well as magnetic and bond properties of these novel bimetallic actinide compounds.

The process of electrolysis at microelectrodes in acidic solutions allows the detailed study of the dynamics of single hydrogen bubbles from nucleation to growth until detachment from the electrode. In earlier work, we have identified three different growth regimes of single hydrogen bubbles that occur depending on the potential applied and the electrolyte concentration [1]. At the bubble interface, a thermal Marangoni flow exists, and the hydrogen bubble may exhibit periodic oscillations or steady growth due to the varying influence of buoyancy, electric and surface tension force [2,3].
Although the thermocapillary effect during bubble growth at microelectrodes is well recognized, the interfacial flow velocity measured decays faster than found in the first simulation results of Massing et al. [4]. This might be caused by the presence of tracer particles in the electrolyte used for the flow measurements, which has been overlooked so far [5]. Our recent experimental findings underscore that variations in the concentration of tracer particles exert notable changes on both the shape and dynamics of bubbles, as well as the flow patterns of the nearby electrolyte. In the steady growth regime, the current and departure time are slightly increased when the particle volume concentration is increased, but the contact radius is reduced. In the oscillatory regime, the oscillating frequency, departure time and current all decrease with the increase in particle volume concentration.
Consequently, we propose a theoretical model elaborating the attraction of charged particles to the bubble interface and the resulting modification of the dynamics of the particle laden interface and the bubble [6]. This model enables quantitative corrections for the measurement and simulation deviations. The numerical simulations are conducted using COMSOL, revealing a good agreement in the tangential velocity profile at the bubble interface arising from both thermo- and soluto-capillary effects (see Figure 1). The oscillatory motion of a hydrogen bubble on the electrode is also simulated. Furthermore, the force balance on the bubble is studied in detail, which provides a deeper insight into the complex phenomena of electrolytic gas evolution.

Electrochemical gas evolution at electrodes beside mass transfer across the interface involves a variety of phenomena at different scales that are coupled with each other. Today, our understanding still seems to be limited, e.g. with respect of accurately predicting the bubble departure size. As the details of growth and transport of gas bubbles have a strong impact on the performance of electrolyzer devices, a better understanding is needed for improving their efficiency. The talk will elaborate on recent progress in understanding how capillary, thermal, electric and wetting effects influence the gas bubble evolution, thereby combining experimental and numerical efforts.

Background and Purpose: The cannabinoid receptors type 2 (CB2R) represent a target of increasing importance in neuroimaging due to its upregulation under various pathological conditions. Previous evaluation of [18F]JHU94620 for the non-invasive assessment of the CB2R availability by positron emission tomography (PET) revealed favourable binding properties and brain uptake. To reduce the bias of CB2R quantification by blood-brain barrier (BBB)-penetrating radiometabolites, we aimed to improve the metabolic stability by developing -d4 and -d8 deuterated isotopologues of [18F]JHU94620. Experimental Approach: [18F]JHU94620-d8 was further evaluated to characterize its metabolic stability, binding properties, BBB penetration of radiometabolites, in vitro autoradiography and biodistribution in mice and rats .
Key Results: The deuterated [18F]JHU94620 isotopologues showed an improved metabolic stability with a substantially reduced fraction of BBB-penetrating radiometabolites which did not accumulate in the brain over time. CB2R-specific binding in the CB2R rich spleen and KD values in the low nanomolar range for [18F]JHU94620-d8¬ towards the CB2R were determined across species. Dynamic PET studies revealed a CB2R-specific and reversible uptake of [18F]JHU94620-d8¬ in the spleen of rats, as well as to a local overexpression in the striatal region containing a hCB2R(D80N) in rats with high VT and BPND values in the target region.
Conclusion and Implications: These results support further investigations of [18F]JHU94620-d8¬ in pathological models and tissues with a CB2R overexpression as a prerequisite for clinical translation.

Driving condensed matter systems with periodic electromagnetic fields can result in exotic states not found in equilibrium. Termed Floquet engineering, such periodic driving applied to electronic systems can tailor quantum effects to induce topological band structures and control spin interactions. However, Floquet engineering of magnon band structures in magnetic systems has proven challenging so far. Here, we present a class of Floquet states in a magnetic vortex that arise from nonlinear interactions between the vortex core and microwave magnons. Floquet bands emerge through the periodic oscillation of the core, which can be initiated by either driving the core directly or pumping azimuthal magnon modes. For the latter, the azimuthal modes induce core gyration through nonlinear interactions, which in turn renormalizes the magnon band structure. This represents a self-induced mechanism for Floquet band engineering and offers new avenues to study and control nonlinear magnon dynamics.

Engineers, geomorphologists, and ecologists acknowledge the need for time and spatially resolved measurements of sediment clogging (also known as colmation) in permeable gravel bed rivers due to its adverse impacts on water and habitat quality. In this paper, we present a novel method for non-destructive, real-time measurements of pore-scale sediment deposition and monitoring of clogging by using wire-mesh sensors (WMS) embedded in spheres, forming a smart gravel bed (GravelSens). The measuring principle is based on one-by-one voltage excitation of transmitter electrodes, followed by simultaneous measurements of the resulting current by receiver electrodes at each crossing measuring pores. The currents are then linked to the conductive component of fluid impedance. The measurement performance of the developed sensor is validated by applying the Maxwell Garnett and parallel models to sensor data and comparing the results to data obtained by gamma ray computed tomography (CT). GravelSens is tested and validated under varying filling conditions of different particle sizes ranging from sand to fine gravel. The close agreement between GravelSens and CT measurements indicates the technology’s applicability in sediment-water research, while also suggesting its potential for other solid-liquid two-phase flows. This pore-scale measurement and visualization system offers the capability to monitor clogging and de-clogging dynamics within pore spaces up to 10,000 Hz, making it the first laboratory equipment capable of performing such in-situ measurements without radiation. Thus, GravelSens is a major improvement over existing methods and holds promise for advancing the understanding of flow sediment ecology interactions.

In this work, we developed a direct strategy to fabricate Palladene (i. e. Palladium metallene) aerogels and propose a temperature-dependent growth mechanism. Besides the typical three-dimensional networks and wrinkled surface morphologies, the as-prepared Palladene₅₀ aerogel is endowed with abundant Pd²⁺. The as-prepared Palladene₅₀ aerogel exhibits an excellent mass activity in the formic acid oxidation reaction and a good half-wave potential in the oxygen reduction reaction in comparison with Pd/C and a Pd aerogel. This work expands the range of metal aerogels from the perspective of the building block units and demonstrates a direct approach to fabricate highly promising bifunctional electrocatalysts for fuel cells.

Nitrilotris(methylenephenylphosphinic) acid (NTPAH₃) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe₃)₃. From the latter, upon alcoholysis in chloroform, NTPAH₃ could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH₃ synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H···O H-bonded networks (NTPAH₃P), in chloroform crystals in the space group R3c formed (NTPAH₃M), the constituents of which are individual molecules with exclusively intramolecular O-H···O hydrogen bonds. Both solids, NTPAH₃P and NTPAH₃M, were characterized by single-crystal X-ray diffraction, multi-nuclear (¹H, ¹³C, ³¹P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH₃P and NTPAH₃M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)₃ H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and ¹H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)₃ H-bond trimers of NTPAH₃M over those in NTPAH₃P.

The exploration of the coordination chemistry of actinides significantly lags behind that of transition metals as well as their lanthanide homologues. As such, a fundamental understanding of the binding properties in actinide compounds is still leaving many open questions. Therefore, systematic investigation of various coordination motives around an actinide centre can be used as benchmark to evaluate what analytic techniques can reveal about novel actinide-ligand bonding.
In this study, we focus on a square antiprism coordination of only oxygen donor atoms in an actinide series ranging from thorium to plutonium. Installing either one or two transition metals in close proximity to the actinide, leads to an 8+2 coordination at the actinide centre. These heterobi- and trimetallic complexes have been investigated using single-crystal X-ray diffraction, NMR, HERFD-XANES, and SQUID magnetometry. The experimental findings were further analysed with quantum chemical calculations. A comparison with their monometallic counterparts gives new insight into actinide-transition metal bonding.

The 2-pyridyloxy ligand (PyO−) has proven to be a useful ligand to isolate heterobimetallic complexes and thus supporting bonds between transition metals (TM) and/or main-group elements. Although interesting coordination motifs can be expected especially with actinides, metal-metal interactions remain a scarce phenomenon in actinide chemistry. Together with the high coordination numbers and various oxidation states, actinide 2-hydroxypyridinolate complexes would have the necessary flexibility to form a variety of actinide complexes also containing a transition metal.
Initially, treatment of tetravalent [AnCl₄(THF)₃] (An = Th, U, Np, Pu) with excess 2-hydroxypyridine gave a series of heteroleptic 2(1H)-pyridinone actinide complexes [AnCl(HPyO)₇]Cl₃. These complexes were good candidates to synthesise heterobimetallic complexes by the addition of [TMCl₂(THT)₂] (TM = Pd, Pt; THT = tetrahydrothiophene) and Et₃N as a supporting base. Using this synthesis method, a series of eight complexes of the type [TM(µ-PyO)₄An(µ-PyO)₄TM] (An = Th, U, Np, Pu; TM = Pd, Pt) could be isolated. These complexes have been investigated using single-crystal X-ray diffraction, NMR, HERFD-XANES spectroscopy, and SQUID magnetometry. The experimental findings were supported by quantum chemical calculations. The obtained data allows us to draw comparisons along the tetravalent actinide series and between palladium and platinum, whereby an unexpected trend in An-TM bonding has been observed.

Ultra-intense lasers that ionize atoms and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration. These instabilities can be difficult to characterize, but X-ray scattering at keV photon energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale. Here, we perform such experiment on laser-driven flat silicon membranes that shows the development of structure with a dominant scale of 60 nm in the plane of the laser axis and laser polarization, and 95 nm in the vertical direction with a growth rate faster than 0.1 fs−1 . Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced plasma density development, indicating the excitation of plasmons and a filamentation instability. Particle-in-cell simulations confirm that these signals are due to an oblique two-stream filamentation instability. These findings provide new insight into ultra-fast instability and heating processes in solids under extreme conditions at the nanometer level with possible implications laser particle acceleration, inertial confinement fusion, and laboratory astrophysics.

Imaging for Adaptive Radio Therapy

ART with particle therapy

10 years of proton therapy in Dresden: Achievements and outlook of translational physics research

Basic CT physics

Ein präzises Verständnis über die Entstehung der Elemente im Universum stellt ein hoch- relevantes Kernthema der nuklearen Astrophysik dar. Vor diesem Hintergrund wurde die 12C(p,γ)13N-Reaktion untersucht, die als Startreaktion des CNO-Zyklus Einfluss auf das Verhältnis von 12C zu 13C im Universum nimmt. Die analysierten Messdaten wurden in in- verser Kinematik am Tandetron-Beschleuniger des Helmholtz-Zentrum Dresden-Rossendorf aufgenommen. Der resultierende S-Faktor, vermessen im Bereich der 421keV-Resonanz, liegt im Mittel 23% unterhalb etablierter Literaturdaten, deckt sich aber mit den Ergeb- nissen anderer kürzlich veröffentlichter Messdaten.
Die in dieser Analyse ebenfalls erschwerte präzise Untersuchung niedriger, aber astrophy- sikalisch relevanter Energien kann durch Untertagelabore und der damit einhergehenden Abschirmung vor kosmischer Strahlung erreicht werden. In der vorliegenden Arbeit werden in diesem Bestreben erste mit dem 5 MV-Tandem-Beschleuniger untersuchte Kernreaktio- nen am Felsenkeller-Untertagelabor in Dresden vorgestellt.
Aus Untersuchungen der 14N(α,γ)18F-, der 13C(p,γ)14N- und der 27Al(p,γ)28Si-Reaktion wurden dabei präzise Werte für die Energiekalibration des Ionenbeschleunigers ermittelt. Es wird ein Vergleich mit weiteren Möglichkeiten zur Bestimmung dieses Kalibrationsfaktors präsentiert und aus diesem Vergleich ein Wert von k = 0,9572 ± 0,0004 zur Kalibration der Hochspannung des Beschleunigers abgeleitet.
Die vorgestellte Herangehensweise zur Bestimmung dieses Faktors und die dokumentier- ten Erkenntnisse und Analysen zu optimalen Betriebsparametern von Beschleuniger und der zugehörigen Radiofrequenz-Ionenquelle werden auch für zukünftige protonen- und he- liumstrahlinduzierte Untersuchungen im Felsenkeller-Untertagelabor von Relevanz sein.

Nanostructured silicon can reduce reflectance loss in optoelectronic applications, but intrinsic silicon cannot absorb photons with energy below its 1.1 eV bandgap. However, incorporating a high concentration of dopants, i.e., hyperdoping, to nanostructured silicon is expected to bring broadband absorption ranging from UV to short-wavelength IR (SWIR, <2500 nm). In this work, we prepare nanostructured silicon using cryogenic plasma etching, which is then hyperdoped with selenium (Se) through ion implantation. Besides sub-bandgap absorption, ion implantation forms crystal damage, which can be recovered through flash lamp annealing. We study crystal damage and broadband (250–2500 nm) absorption from planar and nanostructured surfaces. We first show that nanostructures survive ion implantation hyperdoping and flash lamp annealing under optimized conditions. Secondly, we demonstrate that nanostructured silicon has a 15% higher sub-bandgap absorption (1100–2500 nm) compared to its non-hyperdoped nanostructure counterpart while maintaining 97% above-bandgap absorption (250–1100 nm). Lastly, we simulate the sub-bandgap absorption of hyperdoped Si nanostructures in a 2D model using the finite element method. Simulation results show that the sub-bandgap absorption is mainly limited by the thickness of the hyperdoped layer rather than the height of nanostructures.

Two-dimensional (2D) van der Waals heterostructures that embody the electronic characteristics of each constituent material have found extensive applications. Alloy engineering further enables the modulation of the electronic properties in these structures. Consequently, we envisage the construction and modulation of composition-dependent antiambipolar transistors (AATs) using van der Waals heterostructures and alloy engineering to advance multivalued inverters. In this work, we calculate the electron structures of SnSe2(1–x)S2x alloys and determine the energy band alignment between SnSe2(1–x)S2x and 2H-MoTe2. We present a series of vertical AATs based on the SnSe2(1–x)S2x/MoTe2 type-III van der Waals heterostructure. These transistors exhibit composition-dependent antiambipolar characteristics through the van der Waals heterostructure, except for the SnSe2/MoTe2 transistor. The peak current (Ipeak) decreases from 43 nA (x = 0.25) to 0.8 nA (x = 1) at Vds = −2 V, while the peak-to-valley current ratio (PVR) increases from 4.5 (x = 0.25) to 6.7 × 103 (x = 1) with a work window ranging from 30 to 47 V. Ultimately, we successfully apply several specific SnSe2(1–x)S2x/MoTe2 devices in binary and ternary logic inverters. Our results underscore the efficacy of alloy engineering in modulating the characteristics of AATs, offering a promising strategy for the development of multivalued logic devices.

Fe-Cr alloys serve as model alloys for the investigation of radiation induced effects in ferritic-martensitic steels which are candidate structural materials for future fusion reactors. In this work the effect of Cr segregation and/ or agglomeration in 490 keV Fe+ ion irradiated Fe-10at%Cr alloys in the form of thin films is investigated. The irradiations took place at 300 ◦C at doses ranging from 0.5 to 20 displacements per atom (dpa). Polarized Neutron Reflectivity (PNR) measurements were used for the determination of the solute Cr concentration in the Fe-Cr matrix. Cr depletion from the Fe-Cr matrix up to 2.4 at% was found. This is related to solute Cr decrement as the accumulated dose increases. After the damage of 4 dpa, solute Cr reaches the asymptotic value of 8.4 at%, close to that of the thermodynamic equilibrium in Fe-Cr. Atom Probe Tomography (APT) measurements showed that after irradiation Cr accumulates into clusters the majority of which is co-located with oxygen.

The factors that influence the formation of helium blisters in copper were studied, including crystallographic grain orientation and thermomechanical conditions. Helium implantation experiments were conducted at 40 KeV with a dose of 5 × 10¹⁷ ions/cm², and the samples were then subjected to post-implantation heat treatments at 450 °C for different holding times. A scanning electron microscope (SEM) equipped with an electron backscatter diffraction (EBSD) detector was used to analyze the samples, revealing that the degree of blistering erosion and its evolution with time varied with the crystallographic plane of the free surface in different ways in annealed and cold rolled copper. Out of the investigated states, rolled copper with a (111) free surface had superior helium blistering durability. This is explained by the consideration of the multivariable situation, including the role of dislocations and vacancies. For future plasma-facing component (PFC) candidate material, similar research should be conducted in order to find the optimal combination of material properties for helium blistering durability. In the case of Cu selection as a PFC, the two practical approaches to obtain the preferred (111) orientation are cold rolling and thin layer technologies.

Hyperdoped germanium (Ge) has demonstrated increased sub-bandgap absorption, offering potential applications in the short-wavelength-infrared spectrum (1.0–3.0 μm). This study employs ion implantation to introduce a high concentration of selenium (Se) into Ge and investigates the effects of post-implantation annealing techniques on the recovery of implantation damage and alterations in optical properties. We identify optimal conditions for two distinct annealing techniques: rapid thermal annealing (RTA) at a temperature of 650 °C and ultrafast laser heating (ULH) at a fluence of 6 mJ/cm2. The optimized ULH process outperforms the RTA method in preserving high doping profiles and achieving a fourfold increase in sub-bandgap absorption. However, RTA leads to regrowth of single crystalline Ge, while ULH most likely leads to polycrystalline Ge. The study offers valuable insights into the hyperdoping processes in Ge for the development of advanced optoelectronic devices.

Recently, both large language models and large vision models (LVMs) have gained significant attention. Trained on large-scale datasets, these large models have showcased remarkable capabilities across various research domains. To enhance the accuracy of remote sensing (RS) scene classification, LVM-based methods are explored in this letter. Due to the differences between RS images and natural images, simply transferring LVMs to RS tasks is impractical. Therefore, we conducted research on relevant techniques and appended learnable prompt tokens to the input tokens while freezing the backbone weights, reducing the parameter scale and making the LVM weights easier to harness and to transfer. In consideration of latent catastrophic forgetting issues induced by ordinary finetuning techniques and the inherent complexity and redundancy of RS images, we introduced soft adaption mechanisms between backbone layers based on prompt tuning technique and implemented the first LVM tuning method, namely, the Large Vision Model Soft Adaption for RS scene classification (LVM-StARS)-Deep and the LVM-StARS-Shallow to make LVMs more suitable for RS scene classification tasks. The proposed methods are evaluated on two popular RS scene classification datasets, and the experimental results indicate that the proposed method outperforms other state-of-the-art methods. The experimental results demonstrate that our proposed method enhances overall accuracy (OA) by 1.71%–3.94%, while updating only 0.1%–0.5% of the parameters compared to full finetuning. Furthermore, our method outperforms the existing methods.

We present an atomically precise technique to create sulfur vacancies and control their atomic configurations in single-layer MoS2. It involves adsorbed Fe atoms and the tip of a scanning tunneling microscope, which enables single sulfur removal from the top sulfur layer at the initial position of Fe. Using scanning tunneling spectroscopy, we show that the STM tip can also induce two Jahn-Teller distorted states with reduced orbital symmetry in the sulfur vacancies. Density functional theory calculations rationalize our experimental results. Additionally, we provide evidence for molecule-like hybrid orbitals in artificially created sulfur vacancy dimers, which illustrates the potential of our technique for the development of extended defect lattices and tailored electronic band structures.

In recent years, the amount of non-compatible accelerating hardware has increased significantly, with
non-compatibility among vendors and hardware types such as Graphics Processing Units (GPUs) and
Central Processing Units (CPUs). As a consequence, multiple portability layers have emerged as attempts
to offer a common programming interface for the many different hardware types. This is usually done by
offering a machine model that unifies the properties of the supported hardware types. One of the features
of modern CPUs specifically is Single Instruction, Multiple Data (SIMD), which is usually implemented
in the form of instruction set extensions, as a way to add Instruction Level Parallelism (ILP), with the
goal of accelerating compute-bound programs. Ironically, the aforementioned portability layers largely
ignore SIMD, and the ones that do acknowledge it rely on the autovectorizer, with some of them help-
ing it by providing annotations or compile-time-unrollable loops that are easier to vectorize. This is in
spite of these portability layers being designed for High-Performance Computing (HPC), for which SIMD
is a necessity in the case of CPUs. Of course, the autovectorizers of modern compilers are very capa-
ble, meaning that significant effort must be invested to outperform them with explicit SIMD instrctions.
Nonetheless, there are cases where explicit ILP is desired but not inserted due inter-loop dependencies,
pointer aliasing, or other reasons. In this work, the possibility to extend existing portability layers with
a means to force the generation of SIMD instructions in assembly for CPU machines, while retaining its
portability to e.g. GPUs will be evaluated.

Subcooled nucleate flow boiling encompasses intricate simultaneous condensation and evaporation processes. It involves thin liquid microlayers trapped beneath growing bubbles, enabling high heat and mass transfer with fluxes exceeding 1MW/m². Understanding microlayer contribution to bubble growth is pivotal for developing reliable boiling models. Unlike previous studies, we account for condensation effects, important in the context of subcooled boiling
regime, in estimating microlayer contribution by simultaneously obtaining microlayer dynamics from thin-film interferometry and whole-field temperature from rainbow schlieren deflectometry. We establish that the microlayer evaporation significantly influences bubble growth in flow boiling, contributing up to 60% in the present study.

Advancements in Earth observation technologies have greatly enhanced the potential of integrating hyperspectral (HS) images with Light Detection and Ranging (LiDAR) data for land use and land cover classification. Despite this, most existing methods primarily focus on employing deep network layers to extract features from two heterogeneous data modalities, often overlooking a gradual modeling data representation approach from shallow to deep layers. Furthermore, excessive network layers can result in the deterioration of modality-specific features, therefore lowering the classification performance. The paper proposed a novel cross-modal feature aggregation and enhancement network for the joint classification of HSI and LiDAR data. Initially, a cross-modal feature fusion module is developed to exploit spatial scale consistency to complete the interchange and fusion of feature embedding at the pixel level, preserving the original information from the two heterogeneous modalities to a certain degree. Then two straightforward strategies (i.e., addition and concatenation) are employed in the shallow network layers before being sent to the transformer encoder. The former facilitates the model’s ability to discern more subtle distinctions and refine spatial location details. The latter ensures the preservation of information integrity, effectively mitigating the risk of feature loss. Moreover, invertible neural networks and a feature enhancement module are introduced, leveraging the complementary information of HSI and LiDAR data to enhance the detail and texture information extracted in deeper layers. Extensive experiments on Houston2013, Trento, and MUUFL datasets demonstrate that the proposed method outperforms several state-of-the-art models in three evaluation metrics, achieving an accuracy improvement of up to 2%. The proposed model brings new inspirations for HSI and LiDAR classification, which is critical for accurate environmental monitoring, urban planning, and precision agriculture. The source code is publicly accessible at
https://github.com/zhangyiyan001/CMFAEN
.

Electric fields operating at THz frequencies hold significant promise for inducing ultrafast coherent excitations in magnetic heterostructures. Through the utilization of ferromagnetic/heavy metal (FM/HM) heterostructures, we have demonstrated that THz radiation (0.1 – 30 THz) exhibits combined functionality of microwaves and visible light. 1) Similar to microwaves, THz fields can effectively generate spin currents through the spin-Hall effect (SHE), resulting in an excitation of THz-frequency magnon modes. 2) Akin to visible light excitation, THz fields deposit heat, leading to the demagnetization of FM layers. Harnessing the THz-induced demagnetization as a spin current source within FM/HM heterostructures, we exploit the half-cycle THz electric field to incite spin currents, which subsequently transformed into picosecond charge currents through the inverse SHE within the HM layer. This conversion process results in the emission of a THz second harmonic signal, offering the THz spintronic frequency conversion.

We will present our ongoing efforts to support physics research with
machine learning at HZDR. We will summarize our academic efforts in our
Young Investigator Group as well as the projects handled by our
consultant team. In this manner, we will highlight our approach to ML
based research and support at HZDR as well as the Helmholtz association
in Germany. In detail, our YIG is working on surrogate models for laser
and plasma physics problems, like laser wakefield acceleration,
providing fast estimates experimental or computational results to guide
parameter optimization or accelerate inverse parameter estimation and
ML-based approaches to solve inverse phase problems. In addition to this
aspects of trustworthiness and uncertainty play a key role in our work,
which are a specialty of our consultants team, also in connection with
further topics like segmentation and natural language processing.

Overview of needs and status of near real-time adaptive particle therapy

In this overview talk the following questions will be addressed:

-What is the status concerning fast adaptions in particle therapy also in relation to photon therapy?
-Why we need online-adaptive particle therapy (OAPT)?
-What are different approaches also in relation to different adaption speed?
-What are the different imaging approaches for OAPT?
-How can we verify the treatment delivery when no pre-treatment phantom QA is performed?
-What is the role of I-based decision support?
-What initiatives exist on national and international level? Where do we stand?

The fundamental understanding of the proton transport mechanism through graphene-based proton exchange membranes (PEMs) is crucial to develop novel and advanced two-dimensional (2D) separation materials for energy conversion devices. [1] We computationally investigate ways to enhance the balance between proton permeability and selectivity using a combination of ReaxFF molecular dynamics (ReaxFF-MD), Density Functional Theory (DFT), and metadynamics. In both the cases of graphene nanopore and pristine graphene, covalent benzenesulfonic functionalization introduces significant improvements in proton permeability and selectivity compared to other moieties. [2,3] For the graphene nanopore scenario, the benzenesulfonic functionality dynamically acts as a proton trap and proton shuttle by establishing a favourable hydrogen-bond network, resulting in an effective proton channel through the nanopore (Figure 1a). [2] In the pristine graphene case, the benzenesulfonic functionality guides the proton hopping toward the distorted basal plane, enabling successive proton tunnelling to the other side of the graphene monolayer (Figure 1b). [3,4] Notably, in these systems we achieve estimated proton diffusion coefficients that are comparable to or higher than the current state-of-the-art PEM, Nafion. [2,3] The mechanisms exhibited by these benzenesulfonic functionalized graphene-based systems set the ground for designing new 2D-PEMs with efficient unidirectional proton transport features.

References

[1] Liu, X. et al. Nat. Nanotechnol. 15, 307–312 (2020).
[2] Calvani, D. et al. J. Phys. Chem. C. 128, 8, 3514–3524 (2024).
[3] Zhang, W. et al. arXiv:2308.16112.
[4] An, Y. et al. Adv. Mater. 32 (37), 2002442 (2020).

Dual energy/spectral CT

CT for RTP*: technical requirements and QA guidlines

To the Editor, we thank the authors of the letter [1] for highlighting the importance of tissue-equivalent phantoms for CT-based stopping-power ratio (SPR) prediction, which is a key aspect of the consensus guide and described in its first step [2]. Their observation that applying the consensus guide with phantoms not tissue-equivalent for protons may lead to an inferior SPR prediction accuracy supports the conclusions drawn in the consensus guide.
Many proton centres use the stoichiometric CT number estimation for tabulated human tissues to define a Hounsfield look-up table (HLUT)[3]. While, theoretically, any phantom with known composition should suffice for the stoichiometric calibration [4], better performance has been demonstrated for phantoms with tissue-equivalent material properties regarding electron density, effective atomic number, mean excitation energy and thus SPR [5]. This was experimentally …

Objective
3D printing has seen use in many fields of imaging and radiation oncology, but applications in (anthropomorphic) phantoms, especially for particle therapy, are still lacking. The aim of this work was to characterize various available 3D printing methods and epoxy-based materials with the specific goal of identifying suitable tissue surrogates for dosimetry applications in particle therapy.
Methods
3D-printed and epoxy-based mixtures of varying ratios combining epoxy resin, bone meal, and polyethylene powder were scanned in a single-energy computed tomography (CT), a dual-energy CT, and a µCT scanner. Their CT-predicted attenuation was compared to measurements in a 148.2 MeV proton and 284.7 MeV/u carbon ion beam. The sample homogeneity was evaluated in the respective CT images and in the carbon beam, additionally via widening of the Bragg peak. To assess long-term stability attenuation, size and weight measurements were repeated after 6–12 months.
Results
Four 3D-printed materials, acrylonitrile butadiene styrene polylactic acid, fused deposition modeling printed nylon, and selective laser sintering printed nylon, and various ratios of epoxy-based mixtures were found to be suitable tissue surrogates. The materials’ predicted stopping power ratio matched the measured stopping power ratio within 3% for all investigated CT machines and protocols, except for µCT scans employing cone beam CT technology. The heterogeneity of the suitable surrogate samples was adequate, with a maximum Bragg peak width increase of 11.5 ± 2.5%. The repeat measurements showed no signs of degradation after 6–12 …