Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

We investigate the effect of Ga substitution on the magnetic properties of nanometer-thin Ga:YIG (Y_3Fe_5-xGa_xO_12) films grown by liquid phase epitaxy (LPE) [1,2]. The Ga content was varied between 1.1–1.3 f.u. and film thicknesses were 30 to 230 nm. The substitution of Fe sites by Ga ions reduces the remanent magnetization. Together with the tensile strain it causes a stronger out-of-plane uniaxial anisotropy (PMA) making thin Ga:YIG films perpendicularly magnetized. We also demonstrate that, independent of the thickness and of the substrate orientation, i.e. GGG(111) vs. (001), the PMA gradually increases with the Ga-content, resulting in a 14 times larger perpendicular anisotropy for the highest Ga content used in this study compared to pure YIG. This allows for an easy tuning of the PMA by variation of the Ga concentration. One feature of YIG almost remains: the Gilbertdamping increases only slightly with the amount of Ga. The inhomogeneous broadening shows a stronger dependence.

Magnetization Dynamics in Nanostructures probed by Ferromagnetic Resonance

Matter at extreme densities and temperatures displays a complex quantum behavior that is characterized by
Coulomb interactions, thermal excitations, and partial ionization. Such warm dense matter (WDM) is
ubiquitous throughout the universe and occurs in a host of astrophysical objects such as giant planet
interiors and white dwarf atmospheres. A particularly intriguing application is given by inertial confinement
fusion, where both the fuel capsule and the ablator have to traverse the WDM regime in a controlled way to
reach ignition. In practice, rigorously understanding WDM is highly challenging both from experimental
measurements and numerical simulations [1]. On the one hand, interpreting and diagnosing experiments with
WDM requires a suitable theoretical description. One the other hand, there is no single method that is
capable of accurately describing the full range of relevant densities and temperatures, and the interpretation
of experiments is, therefore, usually based on a number of de-facto uncontrolled approximations. The result
is the vicious cycle of WDM diagnostics: making sense of experimental observations requires theoretical
modeling, whereas theoretical models must be benchmarked against experiments to verify their inherent
assumptions. In this work, we outline a strategy to break this vicious cycle by combining the X-ray Thomson
scattering (XRTS) technique [2] with new ab initio path integral Monte Carlo (PIMC) capabilities [3,4,5]. As
a first step, we have proposed to interpret XRTS experiments in the imaginary-time (Laplace) domain, which
allows for the model-free diagnostics of the temperature [6] and normalization [7]. Moreover, by switching
to the imaginary-time, we can directly compare our quasi-exact PIMC calculations with the experimental
measurement [5]. This opens up novel ways to diagnose the experimental conditions, as we have recently
demonstrated for the case of strongly compressed beryllium at the National Ignition Facility. Our results
open up new possibilities for improved XRTS set-ups that are specifically designed to be sensitive to
particular parameters of interest [8]. Moreover, the presented PIMC capabilities are important in their own
right and will allow for a gamut of applications, including equation-of-state calculations and the
estimation of structural properties and linear response functions.

Double-differential cross section (DDX) data on the neutron-induced emission of light charged particles are required for assessing the risk of secondary tumors in particle radiation therapy. There are only very few DDX data available for discrete neutron energies close to and above 100 MeV for carbon. A measurement of DDX on carbon is planned at continuous neutron energies from 20 MeV to 200 MeV with particle detector telescopes at n_TOF (CERN). Several detector development criteria and challenges are reported such as coincidence timing and electromagnetic oscillations for high neutron energy events with particle separation.

We propose a self-consistent explanation of Rieger-type periodicities, the Schwabe cycle, and the Suess-de Vries cycle of the solar dynamo in terms of resonances of various wave phenomena with gravitational forces exerted by the orbiting planets. Starting on the high-frequency side, we show that the two-planet spring tides of Venus, Earth, and Jupiter are able to excite magneto-Rossby waves, which can be linked with typical Rieger-type periods. We argue then that the 11.07-year beat period of those magneto-Rossby waves synchronizes an underlying conventional alpha-Omega dynamo by periodically changing either the field storage capacity in the tachocline or some portion of the alpha-effect therein. We also strengthen the argument that the Suess-de Vries cycle appears as an 193-year beat period between the 22.14-year Hale cycle and a spin-orbit coupling effect related with the 19.86-year rosette-like motion of the Sun around the barycenter.

The upcoming generation of repetition-rate petawatt class lasers drives the development of laser-plasma proton accelerators and enables new applications e.g. in cancer radiotherapy
research. To harness the full potential of these laser systems and their applications, it is crucial to characterize and control the density profile of the target at the arrival of the ultra-intense laser peak. Cryogenic solid-density hydrogen jets were successfully demonstrated as a promising target platform to investigate various aspects of the high intensity interaction. In combination with optical and X-ray probing techniques, the unique properties of these jets as self-replenishing, debris free, low-density, pure hydrogen targets provide an ideal test bed to study processes like ionization and pre-expansion that occur during irradiation of the leading edge of the laser pulse.
In this contribution, we present the results of laser-target interaction studies with intensities ranging from the relativistic regime down to the intensities of dielectric breakdown of hydrogen. They were conducted using the cryogenic hydrogen jet platform together with the high-resolution optical probing capabilities at the Draco laser facility at Helmholtz-Zentrum Dresden-Rossendorf and the X-ray free electron laser at the HiBEF facility at European XFEL. Changing the drive laser pulse parameters enabled extensive studies, e.g., of the transition from an initial solid state to a plasma state, i.e., the onset of laser-induced breakdown of the solid defining the starting point of the subsequent pre-expansion. As a further example, insights into pre-plasma formation are obtained by investigating the intensity-dependent evolution of the target density profile. These results, together with technical advancements of the target, will be valuable for optimizing laser-driven proton acceleration at high-intensity laser facilities.

In this contribution, we present the results of laser-target interaction studies with intensities ranging from the relativistic regime down to the intensities of dielectric breakdown of hydrogen. They were conducted using the cryogenic hydrogen jet platforms together with the high-resolution optical probing capabilities at the Draco laser facility at Helmholtz-Zentrum Dresden-Rossendorf and the HiBEF facility at European XFEL. Changing the laser parameters enables to utilize specific plasma processes for controlled plasma density tailoring. These results, together with technical advancements of the target, pave the way towards a stable platform for near-critical density targets that will enable stable, repetition-rated proton sources for a multitude of applications at superb energies.

After the interaction of ultra-short high intensity laser pulses with thin solid targets, strong electric fields within the resulting plasma can accelerate ions to energies of tens of MeV. The performance of such laser driven ion sources critically depends on the initial conditions of the target plasma at the arrival time of the driving laser pulse. Pre-pulses and pedestals in the intrinsic temporal laser contrast can cause dielectric breakdown of the target long before the arrival of the main laser pulse, causing the target to ionize and pre-expand uncontrolledly.

Here, we present a study of the laser-induced breakdown (LIB) threshold intensity of 300nm thin formvar foils as well as cryogenic solid hydrogen jets, which are both used as targets for ion accleration at the Draco laser facility at Helmholtz-Zentrum Dresden-Rossendorf. By stretching the pump laser pulse, the dependence of LIB threshold intensity on laser pulse duration is investigated. This helps to understand and model the pre-plasma formation during the rising flank of a high power laser pulse impinging on a thin dielectric target.

Laser-driven ion sources are a rapidly developing technology producing high energy, high peak current beams. Their suitability for applications, such as compact medical accelerators, motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers. These applications not only require high beam energy, but also place demanding requirements on the source stability and controllability. This can be seriously affected by the laser temporal contrast, precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters. Here, we present the experimental generation of >60 MeV protons and >30 MeV u^{−1} carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities >10^{21} W/cm^{2}. Ions are accelerated by an extreme localised space charge field ≳30 TVm^{−1}, over a million times higher than used in conventional accelerators. The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency, in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma. We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion. Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.

Target densities near the critical plasma density are of great interest for the laser-ion acceleration community, as new and interesting acceleration mechanisms can occur at these densities due to the effect of relativistically induced transparency.
Designing and builing near-critical densitiy targets with closely defined parameters has thus been the goal of much recent and ongoing target development.
Here, we present our approach for a density tailored near-critical target, that utilizes controlled preexpansion of a cryogenic hydrogen jet target used at the Draco laser facility at Helmholtz-Zentrum Dresden-Rossendorf (HZDR).
The cylindrical solid hydrogen jet target is irradiated with pump laser pulses in the range of 10¹² to10¹⁸ W/cm². The expansion of the emerging plasma cloud is studied over several tens of picoseconds by means of high resolution two-color off-harmonic optical probing.
At high pump laser intensities, a simple toy model of the radial density profile of the expanding jet target is applied to estimate the evolution of the plasma density during the expansion process.
We show, how the expansion process can be directly influenced by controlling intensity and temporal shape of the pump laser pulses.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators enable generation of short, high-intensity pulses of high energy ions with special beam properties. These accelerators promise to expand the portfolio of conventional machines in many application areas. The maturation of laser driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased scrutiny on reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is essential for many applications and a matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency regime.
In this talk we report on experimental proton acceleration studies at the onset of relativistic transparency using linearly polarized laser pulses with peak intensities of 6x21 W/cm2 focused on thin, pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell simulations helped to identify the most promising target parameter range matched to the carefully measured prevailing laser contrast conditions. In a nutshell, the ultra-intense femtosecond pulse interaction induces large accelerating gradients and energy gain dominantly arising from significant space charge fields due to electron expulsion from the relativistic transparent target core followed by weaker post-acceleration in diffuse sheath fields at later times. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.

References
[1] Ziegler, T. et al. Proton beam quality enhancement by spectral phase control of a PW-class laser system. Sci Rep 11, 7338 (2021)
[2] Kroll, F. et al. Tumour irradiation in mice with a laser-accelerated proton beam. Nat. Phys. 18, 316–322 (2022)

Laser-driven ion accelerators can deliver high-energy, high peak current beams and are thus attracting attention as a compact alternative to conventional accelerators. However, achieving sufficiently high energy levels suitable for applications such as radiation therapy remains a challenge for laser-driven ion accelerators. Here, we generate proton beams with a spectrally separated high-energy component of up to 150MeV by irradiating solid-density plastic foil targets with ultrashort laser pulses from a repetitive petawatt laser. The preceding laser light heats the target, leading to the onset of relativistically-induced transparency upon main pulse arrival. The laser peak then penetrates the initially opaque target and triggers proton acceleration through a cascade of different mechanisms, as revealed by three-dimensional particle-in-cell simulations. The transparency of the target can be used to identify the high-performance domain, making it a suitable feedback parameter for automated laser and target optimisation to enhance stability of plasma accelerators in the future.

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 unique magnetic properties owing to the magnetic
cations at the surface of the sheets. Despite of several ferromagnetic
candidates, 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. At the same time, chemical tuning by surface passivation
provides a valuable handle to further control the magnetic properties
of these novel 2D compounds [4] thus rendering them an attractive
platform for fundamental and applied nanoscience.
[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., submitted, arXiv:2310.07329 (2023).

High entropy materials have recently attracted significant interest due to their appealing mechanical, catalytic, and electronic properties.
High-entropy ceramics consist of an ordered anion sublattice of carbon, nitrogen or oxygen and a disordered cation sublattice maximizing configurational entropy by randomly occupying it by five or more cation species (transition metal elements).
The reliable computational modelling of such systems can be realized by the partial occupation algorithm [1] implemented within the AFLOW software for materials design [2,3] by expanding the disordered system into a large set of ordered structures. These cells can then be treated by high-throughput ab initio calculations. For the actual realization of high-entropy materials, predictive synthesizability descriptors such as the entropy-forming ability (EFA) [4] are needed. We present here results on several high-entropy ceramic candidates, apply different synthesizability descriptors, and study their electronic and mechanical properties.
[1] K. Yang et al., Chem. Mater. 28, 6484 (2016).
[2] C. Oses et al., Comput. Mater. Sci. 217, 111889 (2023).
[3] M. Esters et al., Comput. Mater. Sci. 216, 111808 (2023).
[4] P. Sarker et al., Nat. Commun. 9, 4980 (2018).

Non-metallic inclusions in metallic materials are a key challenge in metallurgical processing such as steelmaking. Aiming to control the population of inclusions and to remove them from the metal in its molten state, gas bubbles are commonly used for melt stirring, homogenisation and purification during ladle treatment. However, the effects of bubble–inclusion interactions in molten metals are not yet well researched, as experimental investigations at high processing temperatures are challenging. To circumvent these harsh conditions, model experiments are performed at room temperature, employing low-melting alloys based on gallium. In such laboratory-scale experiments, the interactions between gas and solid phases in the liquid metal are observable by means of transmission imaging with X-rays or neutron radiation.

Starting from the essentials of the measurement principle, this contribution presents two exam-ples of dynamic X-ray and neutron radiography studies in liquid metals, thus showcasing the unique capabilities as well as limitations of imaging measurements at high spatial and temporal resolution. X-ray radiography is able to image both, gas bubbles and solid particles in the liquid metal, at high contrast-to-noise ratio, but only if these particles are rather coarse and heavy [1]. Using neutron radiography, the focus is on a configuration motivated by a single bubble: the particle-laden liquid metal flow around a cylindrical obstacle, measured at 100 Hz imaging frame rate [2]. Combining particle image velocimetry and particle tracking algorithms, we detected particle trajectories in the cylinder wake flow [3], derived particle residence times and velocity statistics [4]. Such radiography studies provide valuable insights into multi-phase liquid metal flows, and the experimental findings may improve the understanding of the inclusion behaviour in bubble-stirred metallurgical reactors.

References
[1] Lappan T., Sarma M., Heitkam S. et al. Materials Processing Fundamentals 2021, 13-29, 2021.
[2] Lappan T., Sarma M., Heitkam S. et al. Magnetohydrodynamics, 56(2-3), 167-176, 2020.
[3] Birjukovs M., Zvejnieks P., Lappan T. et al. Experiments in Fluids, 63, 99, 2022.
[4] Birjukovs M. et al. Experiments in Fluids, 2024, accepted for publication.

The increasing energy demand in information technologies requires novel low-power procedures to store and process data. Magnetic materials, central to these technologies, are usually controlled through magnetic fields or spin-polarized currents that are prone to Joule heating effect. Magneto-ionics is a unique energy-efficient strategy to control magnetism that can induce large non-volatile modulation of magnetization, coercivity and other properties through voltage-driven ionic motion. Recent studies have shown promising magneto-ionic effects using nitrogen ions. However, either liquid electrolytes or prior annealing procedures have been necessary to induce the desired N3- ion motion. In this work, magneto-ionic effects are voltage-triggered in solid-state at room temperature in CoxMn1-xN films, without the need of thermal annealing. Upon gating, a rearrangement of nitrogen ions in the layers is observed, leading to changes in the co-existing ferromagnetic and antiferromagnetic phases, which result in substantial increase of magnetization at room temperature and modulation of the exchange bias effect at low temperatures. A detailed correlation between the structural and magnetic evolution of the system upon voltage application is provided. The obtained results offer promising new avenues for the utilization of nitride compounds in energy-efficient spintronic and other memory devices.

Data Science is playing an ever increasing role in physics. While some departments have offered courses, many of the examples are in the context of social science and other disciplines. In this tutorial, we will introduce data science in the physics context. We will start by introducing Jupyter notebooks and how to explore and visualize data. We will then introduce unsupervised learning techniques including clustering, random forests, etc. We will conclude with an introduction to neural networks and object tracking.
Graduate students, post-docs, and other scientists interested in learning how to apply data science to their research should attend this tutorial. The lectures will provide an introduction to data science and its applications in physics. We assume that participants will have some experience with Python, Numpy, and Matplotlib at the level of a software carpentry course and we will provide a link to learning materials before the tutorial.
Topics covered:
Data visualization and exploratory data analysis
Unsupervised learning
Convolutional neural networks

High energy resolution fluorescence detected X-ray absorption spectroscopy is a powerful method for probing the electronic structure of functional materials. The X-ray penetration depth and photon-in/photon-out nature of the method allow operando experiments to be performed, in particular in electrochemical cells. Here, operando high-resolution X-ray absorption measurements of a BiVO4 photoanode are reported, simultaneously probing the local electronic states of both cations. Small but significant variations of the spectral lineshapes induced by the applied potential were observed and an explanation in terms of the occupation of electronic states at or near the band edges is proposed.

In this presentation, I will provide an overview of our recent activities on the realization of mechanically flexible, printed and eco-sustainable magnetic field sensors for different applications including smart skins and smart wearables.

In the past years, there is an active research of materials displaying the non-linear Hall effect with time-reversal symmetry [1-5]. From a fundamental point of view, this quantum transport effect provides a direct way to detect in nonmagnetic materials the Berry curvature – a quantity in which the geometry of the electronic wavefunctions is encoded. The nonlinear Hall effect is also at the basis of terahertz optoelectronic applications of interest for instance for sixth generation (6G) communication networks.

An appropriate material platform for such applications should satisfy a number of criteria: i) the nonlinear Hall effect should survive up to room temperature; ii) the effect should be tunable; iii) the material fabrication should be technologically relevant (simple chemical composition of the material and low-cost microstructure); iv) ideally the material should not contain toxic heavy rare-earth elements. So far, candidate materials address only partially these requirements.

Here, we discover the first material addressing all the requirements at the same time: polycrystalline bismuth thin films [6]. We demonstrate that in this elemental green (semi)metal, the room-temperature nonlinear Hall effect is generated by surface states that are characterized by a Berry curvature triple: a quantity governing a skew scattering effect that generates non-linear transverse currents. Furthermore, we also show that the strength of nonlinear Hall effect can be controlled on demand using an extrinsic classical shape effect: the geometric nonlinear Hall effect. We demonstrate this by fabricating arc-shaped bismuth Hall bars. This endows the nonlinear Hall effect of Bismuth with the tunability encountered only in low-dimensional materials at low temperatures.

To show the potential of polycrystalline Bi thin films for optoelectronic applications in the terahertz (THz) spectral domain, we have performed high harmonic generation experiments. Polycrystalline Bi thin films reveal a high efficiency of THz third-harmonic generation (THG) that reaches levels >1% at room temperature. Moreover, our material possesses a non-saturating trend of the efficiency of the THz THG. This enables the use of Bi thin films for high- and wide- THz bandwidth electronics which works at high peak power and long pulses.

[1] Z. Z. Du et al., Nonlinear Hall effects. Nature Reviews Physics 3, 744 (2021).
[2] I. Sodemann et al., Quantum Nonlinear Hall Effect Induced by Berry Curvature Dipole in Time-Reversal Invariant Materials. Phys. Rev. Lett. 115, 216806 (2015).
[3] Q. Ma et al., Observation of the nonlinear Hall effect under time-reversal-symmetric conditions. Nature 565, 337 (2019).
[4] K. Kang et al., Nonlinear anomalous Hall effect in few-layer WTe2. Nature Mater. 18, 324 (2019).
[5] P. He et al., Quantum frequency doubling in the topological insulator Bi2Se3. Nature Communications 12, 698 (2021).
[6] P. Makushko et al., A tunable room-temperature nonlinear Hall effect in elemental bismuth thin films. Nature Electronics 7, 207 (2024).

A Fourier–Matsubara series expansion is derived for imaginary–time correlation functions that constitutes the imaginary–time generalization of the infinite Matsubara series for equal-time correlation
functions. The expansion is consistent with all known exact properties of imaginary–time correlation
functions and opens up new avenues for the utilization of quantum Monte Carlo simulation data.
Moreover, the expansion drastically simplifies the computation of imaginary–time density–density
correlation functions with the finite temperature version of the self-consistent dielectric formalism.
Its existence underscores the utility of imaginary–time as a complementary domain for many-body
physics.

Periodic magnetic stripe domain patterns are a prominent feature of perpendicular anisotropy thin film systems. Here, we focus on the behavior of [Co(3.0 nm)/Pt(0.6 nm)]\textsubscript{$X$} multilayers within the transitional regime from preferred in-plane (IP), $X=6$, to out-of-plane (OOP), $X=22$, magnetization orientation, particularly, we examine a sample with $X=11$ repetitions, which exhibits a remanent state characterized by a significant presence of both OOP and IP magnetization components, here referred to as the "tilted" stripe domain state*. We investigate this specific sample with vibrating sample magnetometry, magnetic force microscopy and micromagnetic simulations, and find an unusual OOP field reversal behavior via a remanent parallel stripe domain state and a single point of irreversibility. Finally, we show that this characteristic reversal behavior is a rather general feature of transitional IP to OOP systems by comparing the Co/Pt multilayers with c-axis single Co thin films and Fe/Gd multilayers. \newline *[L. Fallarino et al., Phys. Rev. B 99, 024431 (2019)]

Perpendicular anisotropy thin film systems are well known for their periodic magnetic stripe domain structures. In this study, we focus on investigating the behavior of [Co(3.0 nm)/Pt(0.6 nm)]\textsubscript{$X$} multilayers within the transitional regime from preferred in-plane (IP) to out-of-plane (OOP) magnetization orientation, particularly, we examine the sample with $X=11$ repetitions, which exhibits a remanent state characterized by a significant presence of both OOP and IP magnetization components, here referred to as the "tilted" stripe domain state*. Using vibrating sample magnetometry, magnetic force microscopy and micromagnetic simulations we investigate this specific sample and find an unusual OOP field reversal behavior via a remanent parallel stripe domain state and a single point of irreversibility. While the reversal via distinct points of irreversibility is qualitatively similar to that of a nano-sized Stoner Wohlfarth particle or a vortex reversal in a micron-sized IP magnetized disk, our system is macroscopic. Finally, we show that this characteristic behavior is a rather general feature of transitional IP to OOP systems. \newline *[L. Fallarino et al., Phys. Rev. B 99, 024431 (2019)]

Warm dense matter (WDM) is now routinely created and probed in laboratories
around the world, providing unprecedented insights into conditions achieved in
stellar atmospheres, planetary interiors, and inertial confinement fusion
experiments. However, the interpretation of these experiments is often filtered
through models with systematic errors that are difficult to quantify. Due to the
simultaneous presence of quantum degeneracy and thermal excitation, processes in
which free electrons are de-excited into thermally unoccupied bound states
transferring momentum and energy to a scattered x-ray photon become viable [1].
Here we show that such free-bound transitions are a particular feature of WDM and
vanish in the limits of cold and hot temperatures. The inclusion of these processes
into the analysis of recent X-ray Thomson Scattering (XRTS) experiments on
WDM at the National Ignition Facility [2] (see the figure below) and the Linac
Coherent Light Source [3] significantly improves model fits, indicating that free-
bound transitions have been observed without previously being identified. This
interpretation is corroborated by agreement with a recently developed model-free
thermometry technique [4,5] and presents an important step for precisely
characterizing and understanding the complex WDM state of matter.

Matter at extreme densities and temperatures displays a complex quantum behavior that is characterized by Coulomb interactions, thermal excitations, and partial ionization. Such warm dense matter (WDM) is ubiquitous throughout the universe and occurs in a host of astrophysical objects such as giant planet interiors and white dwarf atmospheres. A particularly intriguing application is given by inertial confinement fusion, where both the fuel capsule and the ablator have to traverse the WDM regime in a controlled way to reach ignition.

In practice, rigorously understanding WDM is highly challenging both from experimental measurements and numerical simulations [1]. On the one hand, interpreting and diagnosing experiments with WDM requires a suitable theoretical description. One the other hand, there is no single method that is capable of accurately describing the full range of relevant densities and temperatures, and the interpretation of experiments is, therefore, usually based on a number of de-facto uncontrolled approximations. The result is the vicious cycle of WDM diagnostics: making sense of experimental observations requires theoretical modeling, whereas theoretical models must be benchmarked against experiments to verify their inherent assumptions.

In this work, we outline a strategy to break this vicious cycle by combining the X-ray Thomson scattering (XRTS) technique [2] with new ab initio path integral Monte Carlo (PIMC) capabilities [3,4,5]. As a first step, we have proposed to interpret XRTS experiments in the imaginary-time (Laplace) domain, which allows for the model-free diagnostics of the temperature [6] and normalization [7]. Moreover, by switching to the imaginary-time, we can directly compare our quasi-exact PIMC calculations with the experimental measurement [5]. This opens up novel ways to diagnose the experimental conditions, as we have recently demonstrated for the case of strongly compressed beryllium at the National Ignition Facility.

Our results open up new possibilities for improved XRTS set-ups that are specifically designed to be sensitive to particular parameters of interest [8]. Moreover, the presented PIMC capabilities are important in their own right and will allow for a gamut of applications, including equation-of-state calculations and the estimation of structural properties and linear response functions.

[1] T. Dornheim et al., Phys. Plasmas 30, 032705 (2023)
[2] S. Glenzer and R. Redmer, Rev. Mod. Phys. 81, 1625 (2009)
[3] T. Dornheim et al., J. Phys. Chem. Lett. 15, 1305-1313 (2024)
[4] T. Dornheim et al., arXiv:2403.01979
[5] T. Dornheim et al., arXiv:2402.19113
[6] T. Dornheim et al., Nature Commun. 13, 7911 (2022)
[7] T. Dornheim et al., arXiv:2305.15305
[8] Th. Gawne et al., arXiv:2403.02776

We present extensive new \emph{ab initio} path integral Monte Carlo (PIMC) results for a variety of structural properties of warm dense hydrogen and beryllium. To deal with the fermion sign problem -- an exponential computational bottleneck due to the antisymmetry of the electronic thermal density matrix -- we employ the recently proposed [\textit{J.~Chem.~Phys.}~\textbf{157}, 094112 (2022); \textbf{159}, 164113 (2023)] -extrapolation method and find excellent agreement with exact direct PIMC reference data where available. This opens up the intriguing possibility to study a gamut of properties of light elements and potentially material mixtures over a substantial part of the warm dense matter regime, with direct relevance for astrophysics, material science, and inertial confinement fusion research.

Reactive transport investigations of subsurface hydrogeochemical processes have shown that the heterogeneity in dissolution rate observed in numerous experiments cannot be explained by fluid transport effects alone. Instead, this heterogeneity is attributed to intrinsic variability in the surface reactivity of the dissolving material. Therefore, reactive transport models require a parameterization of the surface reactivity for reliable predictions. Here we discuss and propose how to parameterize such varying surface reactivity of pore-scale systems, from the crystal surface to the single crystal geometry, going beyond the previous reactivity parameterization. We compare the results between classically parameterized models, models with new parameterization, and experimental data. We show how this parameterization is able to accurately reproduce the experimental results on a crystal surface with a broad field of view, a large height variability of the topography, and over a long reaction period.
Recently, dissolution rate maps revealed the existence of rhythmic pulses of the material flux from the crystal surface. Until now, the dominant factor underlying this behavior has not been understood, and both surface- and transport-controlled conditions have been discussed to govern the pulsating reaction kinetics in the system. Numerical investigations with the new parameterization presented above now allow the conclusion that the self-organization of various reactive surface building blocks causes the pulsating resolution. This is a fundamental factor in crystal dissolution and deserves to be considered for an in-depth understanding and improved upscaling of dissolution kinetics.

Pressure evolution of the crystal structure and magnetism of the honeycomb α-RuBr₃ is studied using high-pressure x-ray diffraction, magnetometry, and density-functional band-structure calculations. Hydrostatic compression transforms antiferromagnetic α-RuBr₃ (R-3) into paramagnetic α′-RuBr₃ (P-1) where short Ru–Ru bonds cause magnetism collapse above 1.3GPa at 0K and 2.5GPa at 295 K. Below this critical pressure, the Neel temperature of α-RuBr₃ increases with the slope of 1.8K/GPa. Pressure tunes α-RuBr₃ away from the Kitaev limit, whereas increased thirdneighbor in-plane coupling and interlayer coupling lead to a further stabilization of the collinear zigzag state. Both α- and α′-RuBr₃ are metastable at ambient pressure, but their transformation into the thermodynamically stable β-polymorph is kinetically hindered at room temperature.

I. EINLEITUNG
Für eine umfassende Sicherheitsbewertung der geologi-schen Tiefenlagerung hochradioaktiver Abfälle müssen verschiedene Aspekte berücksichtigt werden. Neben den geologischen, geochemischen und geophysikalischen Eigen-schaften spielt der Einfluss von natürlich vorkommenden Mikroorganismen im umgebenden Wirtsgestein und im Verfüllmaterial eine entscheidende Rolle in der Umgebung eines solchen Endlagers. Tongesteine sind potenzielle Wirts-gesteine für die Endlagerung dieser Abfälle, während Ben-tonite als Verfüllmaterial nicht nur für ein Endlager in Ton-gesteinen, sondern auch in kristallinen Gesteinen vorgesehen sind. Wenn im ungünstigsten Fall Wasser in das Endlager eindringt, können Radionuklide aus den Abfallbehältern austreten und mit den Mikroorganismen interagieren. Dies kann z. B. zu Veränderungen der chemischen Speziation oder des Oxidationszustandes der Metallionen führen.
II. ERGEBNISSE UND DISKUSSION
Unter endlagerrelevanten Bedingungen stellen Desul-fosporosinus spp. wichtige Vertreter der sulfatreduzierenden anaeroben Bakterien dar, welche sowohl in Tonformatio-nen als auch im Verfüllmaterial Bentonit vorkommen (Bagnoud et al. 2016, Matschiavelli et al. 2019). Verschie-dene Studien zeigen, dass sie eine wichtige Rolle in den mik-robiellen Gemeinschaften dieser Umgebung spielen. Ein mit den isolierten Arten eng verwandter Mikroorganismus ist Desulfosporosinus hippei DSM 8344T (Vatsurina et al. 2008). Daher wurde dieses Bakterium ausgewählt, um des-sen Wechselwirkungen mit Uran(VI) zu untersuchen, insbe-sondere im Hinblick auf die Reduktion zum weniger mobi-len Uran(IV), welches günstige Eigenschaften wie eine gerin-gere Mobilität aufweist und damit eine verbesserte Rückhal-tung des Radionuklids im Wirtgestein ermöglicht wird.
Zeitabhängige Reduktionsexperimente in künstlichem Opalinuston-Porenwasser (Wersin et al. 2011) mit einer Uran(VI)-Konzentration von 100 µM bei einem pH von 5.5 zeigten eine Abnahme der Uran(VI)-Konzentrationen von ca. 80 % aus den Überständen innerhalb von 48 h. Zugehö-rige UV/Vis-Messungen der aufgelösten Zellpellets liefern einen eindeutigen Nachweis des gebildeten Uran(IV). Der Anteil dieser Oxidationsstufe am zellgebundenen Uran steigt nach einer Woche auf bis zu 40 % an. Daher ist ein kombi-nierter Sorptions-Reduktionsprozess ein möglicher Wech-selwirkungsmechanismus für dieses Bakterium.
Zeitaufgelöste laserinduzierte Lumineszenzspektrosko-pie zeigt die Anwesenheit von zwei Uran(VI)-Spezies im Überstand. Ein Vergleich mit Referenzspektren erlaubt die Zuordnung zu einem Uranyl(VI)-Laktat- und einem Uranyl(VI)-Carbonat-Komplex. Die Speziesverteilung zeigt eine Abnahme des Anteils der Laktat-Spezies mit der Zeit, während der Anteil der Carbonat-Spezies nahezu konstant bleibt.
Während der Versuche bilden sich Uranaggregate auf der Oberfläche der Zellen, welche mittels Rastertransmissi-onselektronenmikroskopie nachgewiesen werden konnten. Zusätzlich setzen die Zellen uranhaltige Vesikel als mögli-chen Abwehrmechanismus gegen die Verkrustung der Zellen frei.
Darüber hinaus bestätigten HERFD-XANES-Messungen die Reduktion von Uran(VI). Mit diesen Messungen konnte auch Uran(V) in den Zellpellets nachgewiesen werden. Dies ist der erste Nachweis für die Beteiligung von Uran(V) an der Uran(VI)-Reduktion durch sulfatreduzierende Mikroorga-nismen. Mit Hilfe von EXAFS-Messungen konnten zudem verschiedene zellgebundene Uranspezies nachgewiesen werden.
III. FAZIT
Die Ergebnisse dieser Studie tragen dazu bei, bestehende Lücken in einem umfassenden Sicherheitskonzept für ein Endlager für hochradioaktive Abfälle in Tongestein zu schließen. Darüber hinaus liefert diese Studie neue Erkennt-nisse über die Wechselwirkungen sulfatreduzierender Mik-roorganismen mit Uran(VI) und zeigen eine verbesserte Rückhaltung des Radionuklids durch eine Reduktion zum weniger mobilen Uran(IV), wodurch dessen Rückhaltung verbessert wird.
IV. LITERATURVERZEICHNIS
Bagnoud A., Chourey K., Hettich R., De Bruijn I., Andersson A. F., Leupin O. X., Schwyn B., Bernier-Latmani R.: Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock, Nature Communications, 2016, 7, 1-10.
Matschiavelli N., Kluge S., Podlech C., Standhaft D., Grathoff G., Ikeda-Ohno A., Warr L. N., Chukharkina A., Arnold T., Cherkouk A.: The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C, En-vironmental Science & Technology, 2019, 53, 10514-10524.
Vatsurina A., Badrutdinova D., Schumann, P., Spring S., Vainshtein M.: Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost, International Jour-nal of Systematic and Evolutionary Microbiology, 2008, 58, 5, 1228-1232.
Wersin P., Leupin O. X., Mettler S., Gaucher E. C., Mäder U., De Cannière P., Vinsot A., Gäbler H. E., Kunimaro T., Kiho K., Eichinger L.: Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and wa-ter data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland, Applied Geo-chemistry, 2011, 26, 6, 931-953.

In this work, we demonstrate the efficacy of a neural network model
implemented as the Materials Learning Algorithms (MALA) package
in predicting the electronic structure of a system of hydrogen molecules
under various pressure and temperature conditions across the molecular liquid-solid phase boundary, demonstrating the potential of our
methods for molecular systems. Additionally, we investigate the use
of SE(3)-Transformer Graph Neural Networks to improve the generalizability and extrapolation capabilities of our models. Our results
indicate that the MALA framework provides a powerful and efficient
tool for accelerating Kohn-Sham density functional theory calculations
in molecular systems. This work paves the way for future research in
developing advanced machine-learning algorithms for accelerating electronic structure calculations both accurately and efficiently.

B, Si, and Ge dopants are inserted into SMoSe Janus layers (JLs) at Mo, S, and Se as well as at interstitial sites. Spin-polarized density functional theory calculations are employed to investigate the modified structural and electronic properties of the layers, the energetics of dopant incorporation, and the effect of doping on the interaction of the two-dimensional material with hydrogen. The detailed structural analysis exposes the influence of dopant atomic sizes on lattice distortion. The formation energy Ef of dopant X (X = B, Si, and Ge) at substitutional and interstitial sites is studied for two different chemical environments: (i) bulk X – or X-rich conditions, and (ii) dimer X2 – or X-poor conditions. It is found that under X-poor conditions, the stability of the dopants is always higher. Doping at the S site is energetically most favored, with EBf < ESif < EGef . The electron redistribution in the JLs due to the presence of dopants is explored using Bader analysis. Atomic sites with a number of electrons different from that on atoms in pristine SMoSe JLs may be potential hydrogen traps and are therefore interesting for the hydrogen evolution reaction (HER). Consequently, the interaction of H atoms with these sites is studied and the H adsorption energy is calculated. While pristine SMoSe JLs repel H, several attractive sites are found in the vicinity of the dopant atoms. In order to quantify the feasibility of the doped SMoSe JLs for use as a catalyst for the HER, the free adsorption energy is determined. The data show that all dopants may improve SMoSe for HER applications. The most favorable sites are B at S and Se, Si at Mo and S, and Ge at Mo and S. In particular, adsorption and desorption of H on B-doped (at S and Se sites) and on Ge doped (at an Mo site) JLs may be rapid. The present results demonstrate the potential of metalloid doped , SMoSe JLs as efficient HER catalysts.

Copper impregnated SiO₂ and MgO catalysts were prepared, characterised, and tested for the synthesis of methyl formate (MF) from methanol by dehydrogenation. Compared to the Cu-impregnated pure oxides, MF formation was improved when SiO₂/MgO mixtures were used as support. For further comparison, a silver impregnated mixed oxide catalyst, known for its dehydrogenation ability, and a typical methanol catalyst (Cu/ZnO/Al₂O₃) were tested. Both catalysts displayed non or poorer performance under tested reaction conditions. High catalytic activity was assigned, besides the Cu content, to the presence of both medium acidic and basic sites. At 240 °C and 1 bar, the highest MF yield of 34 % has been obtained with the mixture of oxides containing the highest MgO ratio of 35 mol%. By exposing the prepared catalyst to a methanol/water mixture (36 wt% water), methanol conversion drops to 5 %, but compared to the reference Cu/ZnO/Al₂O₃ catalyst, two times the selectivity towards MF was obtained. With respect to sustainable technology development, direct coupling of green methanol synthesis from CO₂/H₂ gas feed and MF production without water removal is not recommended, since the yield to MF is below 2 % in this case.

The present work deals with the investigation of ion-beam assisted annealing/mixing effects on compositional and structural changes in Al-Cu-Co multilayers. 800 nm thick Al₆₄Cu₂₀Co₁₆ multilayers prepared by magnetron sputtering deposition, consisting of 28 successive single-metal Al-, Cu-, and Co-nanolayers were treated by thermal annealing at 300°C, 400°C, or 500°C as well as ion irradiation by 30 MeV Cu⁵⁺ ions at fluences of 1x10¹³ to 5x10¹⁴ with an average flux of 2.38×10¹⁰ at.cm⁻²s⁻¹. The samples were characterized with SEM, EDX, XRD, and TEM including HAADF. In contrast to the original multilayer, the treated samples were found to consist of two types of alternating nanolayers. A wider coarse-grained structurally and chemically homogeneous single-phase nanolayer formed by Al₂Cu, and a narrow fine-grained two-phase nanolayer, which has a heterogeneous composite structure in which the central Co sublayer (being a residue of the original single-metal Co nanolayer) is surrounded from both sides with Al-Co sublayers, consisting of Al₉Co₂. This Co sublayer is considered to be a diffusion blocker for Al and Cu as well as hindering the movement of borders between particular nanolayers. The formation of a ternary phase in the investigated samples was not confirmed in any of the samples.

Alkaline water electrolysis holds promise for large-scale hydrogen production, yet it encounters challenges like high voltage and limited stability at higher current densities, primarily due to inefficient electron transport kinetics. Herein, a novel cobalt-based metallic heterostructure (Co₃Mo₃N/Co₄N/Co) is designed for excellent water electrolysis. In operando Raman experiments reveal that the formation of the Co₃Mo₃N/Co₄N heterointerface boosts the free water adsorption and dissociation, increasing the available protons for subsequent hydrogen production. Furthermore, the altered electronic structure of the Co₃Mo₃N/Co₄N heterointerface optimizes ΔG_H of the nitrogen atoms at the interface. This synergistic effect between interfacial nitrogen atoms and metal phase cobalt creates highly efficient active sites for the hydrogen evolution reaction (HER), thereby enhancing the overall HER performance. Additionally, the heterostructure exhibits a rapid OH^- adsorption rate, coupled with great adsorption strength, leading to improved oxygen evolution reaction (OER) performance. Crucially, the metallic heterojunction accelerates electron transport, expediting the afore-mentioned reaction steps and enhancing water splitting efficiency. The Co₃Mo₃N/Co₄N/Co electrocatalyst in the water electrolyzer delivers excellent performance, with a low 1.58 V cell voltage at 10 mAcm^-2, and maintains 100% retention over 100 hours at 200 mAcm^-2, surpassing the Pt/C // RuO₂ electrolyzer.

Density functional theory (DFT) is well-known as the workhorse of electronic structure calculations in materials science and quantum chemistry. However, its applications stretch beyond these traditionally-studied fields, such as to the warm-dense matter (WDM) regime. Under WDM conditions, there are different challenges to consider (compared to ambient conditions) when using DFT. Namely, the electronic structure problem must be solved (i) for large particle numbers, (ii) for a range of temperatures, and (iii) for a range of pressures. Promising solutions were demonstrated for problems (i) and (ii) [1,2] using a recently-developed workflow to machine-learn the local density of states (LDOS) [3]. In this talk, we discuss our progress in developing a solution for problem (iii). This problem presents additional challenges because the LDOS varies quite significantly with changes in the pressure, making it a difficult problem for neural network models.

[1] L Fiedler et al., npj Comput Mater 9, 115 (2023) [2] L Fiedler et al., Phys. Rev. B 108, 125146 (2023) [3] J. A. Ellis et al., Phys. Rev. B 104, 035120 (2021)

Objectives
Membraneless alkaline electrolyzer (MAEL) allow higher current densities compared to conventional designs [1] and provide very good access to the electrodes, making them ideal for research to better understand bubble formation and detachment.

Methods
In the present study both elements of a MAEL, porous electrodes and cell geometry, are optimized individually. For the geometrical optimization, CFD and current simulations were performed to obtain an optimized cell geometry that ensures constant conditions for the water splitting reaction over the entire electrode area. A three-electrode cell was used to perform parametric studies of HER on porous electrodes [2] and functionalized surfaces [3]. Therefore, Particle Image Velocimetry and Shadowgraphy were used to systematically study the influence of the electrode surface and the electrolyte flow as driving force for an effective H2 and O2 separation in a MAEL.

Results & Conclusions
It is shown that below a critical Recrit the evolving bubbles are stuck on the porous electrodes and lead to a blockage of the electrochemical active sites and to an increase of the cell potential. At the optimal flow rate to current density ratio high gas purity and overall efficiency were observed. Importantly, this study presented an experimental framework that guides the electrode and cell design of MAELs and analyzes their performance limits.

Literature
[1] D.V. Esposito, Joule. 2017, 1, 651-658.
[2] H. Rox et al., Int. J. Hydrog. Energy. 2023, 48, 2892-2905.
[3] L. Krause et al., ACS Applied Materials & Interfaces. 2023, 15, 14, 18290-18299.

Bovine serum albumin (BSA) has a uranyl(VI) binding hotspot where uranium is tightly bound by three carboxylates. Uranyl oxygen is “soaked” into the hydrophobic core of BSA. Isopropyl hydrogen of Val is trapped near UO22+ and upon photoexcitation, C–H bond cleavage is initiated. A unique hydrophobic contact with “yl”-oxygen, as observed here, can be used to induce C-H activation.

Energy barriers inhibit the transition of a system from one state to another. This is evident in phenomena such as bubble nucleation during boiling, droplet expansion and contraction when it impacts a heated surface, and also cavitation. In this presentation, we will elucidate our insights and understanding of the exploitation of energy barriers post-state transition to augment heat and mass transfer in various processes. Specifically, in processes like bubble nucleation in boiling, the high energy required for nucleation (attributable to the energy barrier) triggers rapid bubble expansion and results in a semi-2D microlayer, just a few micrometers thin, on the surface. This can be viewed as a typical semi-dimensional reduction effect, transitioning a part of system from 3D to 2D. As a result, this thin liquid layer brings high efficiency on heat transfer. A similar phenomenon occurs when a droplet impacts a heated surface. Following impact, the droplet’s expansion and contraction on the surface incite capillary waves that propagate along the droplet interface, inducing a semi-1D, prickle-like jet along the droplet’s axis on the top side. This jet disrupts the vapor film beneath the droplet, expelling the vapor and delaying the Leidenfrost point. As a one more thing, cavitation, one of the most typical cases of ‘dimensional reduction’, utilizes a reduction from 3D to 0D and also the large energy barrier for bubble nucleation. Following bubble collapse, the local temperature and pressure reach 5000 K and ~ Mpa, respectively. Combined with O3, this effect facilitates a highly efficient oxidation process.

Using the methodology of Kozlowski et al. [arXiv 2308.03319 (2023)] to extend the temperature dependence of the Perdew–Burke–Ernzerhof (PBE) generalized gradient approximation, we implement the thermal equivalent of the PBE functional (tPBE) in a plane wave code to study the equilibrium properties such as energies, pressures, and forces of warm dense matter using density functional theory and linear-response properties such as the electrical conductivity, dynamic structure factor using time-dependent density functional theory. In addition, we compare the effects with the thermal equivalent of LDA and the ground-state LDA and PBE functionals.

Recently, machine-learned interatomic potentials (ML-IAPs) have emerged as a solution to the computational limitations of density functional theory (DFT)-based approaches, enabling the modeling of large systems with hundreds or even thousands of atoms. Here, we demonstrate the efficacy of automated and systematic methods for training and validating transferable ML-IAPs through global optimization techniques.

We utilize the PyFLAME code [1] to construct a highly transferable neural network potential. With this accurate and fast potential, we systematically investigate the potential energy surfaces (PESs) of FeH through global sampling using the minima hopping method [2] over a wide range of pressures. This comprehensive exploration enables us to predict stable and metastable iron hydrides from 0 to 100 GPa.

Our analysis reveals the experimentally observed global minimum structures -the dhcp, hcp, and fcc phases- in agreement with previous studies. Furthermore, our exploration of the PESs of FeH at various pressures uncovers numerous interesting modifications and stacking faults of the aforementioned phases, including several remarkably low-enthalpy structures.

This investigation led to the discovery of a rich array of novel stoichiometric crystal phases of FeH across a wide pressure range, confirming the presence of coexisting regions containing known FeH structures. This finding demonstrates one of the benefits of using large-scale structure prediction techniques to uncover the PESs of materials.

[1] H. Mirhosseini, H. Tahmasbi, S. R. Kuchana, S. A. Ghasemi, and T. D. Kühne, Comput. Mater. Sci. 197, 110567 (2021).

[2] M. Amsler and S. Goedecker, J. Chem. Phys. 133, 224104 (2010).

We demonstrate live-updating ptychographic reconstruction with ePIE, an iterative ptychography method, during ongoing data acquisition. The reconstruction starts with a small subset of the total data, and as the acquisition proceeds the data used for reconstruction is extended. This creates a live-updating view of object and illumination that allows monitoring the ongoing experiment and adjusting parameters with quick turn-around. This is particularly advantageous for long-running acquisitions. We show that such a gradual reconstruction yields interpretable results already with a small subset of the data. We show simulated live processing with various scan patterns, parallelized reconstruction, and real-world live processing at the hard X-ray ptychographic nanoanalytical microscope PtyNAMi at the PETRA III beamline.

Heavy metals pose a potential health risk to humans when they enter the organism. Renal excretion is one of the elimination pathways and, therefore, investigations with kidney cells are of particular interest. In the present study, the effects of Ba(II), Eu(III), and U(VI) on rat and human renal cells were investigated in vitro. A combination of microscopic, biochemical, analytical, and spectroscopic methods was used to assess cell viability, cell death mechanisms, and intracellular metal uptake of exposed cells as well as metal speciation in cell culture medium and inside cells.

For Eu(III) and U(VI), cytotoxicity and intracellular uptake are positively correlated and depend on concentration and exposure time. An enhanced apoptosis occurs upon Eu(III) exposure whereas U(VI) exposure leads to enhanced apoptosis and (secondary) necrosis. In contrast to that, Ba(II) exhibits no cytotoxic effect at all and its intracellular uptake is time-independently very low. In general, both cell lines give similar results with rat cells being more sensitive than human cells.

The dominant binding motifs of Eu(III) in cell culture medium as well as cell suspensions are (organo-) phosphate groups. Additionally, a protein complex is formed in medium at low Eu(III) concentration. In contrast, U(VI) forms a carbonate complex in cell culture medium as well as each one phosphate and carbonate complex in cell suspensions. Using chemical microscopy, Eu(III) was localized in granular, vesicular compartments near the nucleus and the intracellular Eu(III) species equals the one in cell suspensions.

Overall, this study contributes to a better understanding of the interactions of Ba(II), Eu(III), and U(VI) on a cellular and molecular level. Since Ba(II) and Eu(III) serve as inactive analogs of the radioactive Ra(II) and Am(III)/Cm(III), the results of this study are also of importance for the health risk assessment of these radionuclides.

Vertical stacking of different two-dimensional (2D) materials into van der Waals heterostructures exploits the properties of individual materials as well as their interlayer coupling, thereby exhibiting unique electrical and optical properties. Here, we study and investigate a system consisting entirely of different 2D materials for the implementation of electronic devices that are based on quantum mechanical band-to-band tunneling transport such as tunnel diodes and tunnel field-effect transistors. We fabricated and characterized van der Waals heterojunctions based on semiconducting layers of WSe2 and MoS2 by employing different gate configurations to analyze the transport properties of the junction. We found that the device dielectric environment is crucial for achieving tunneling transport across the heterojunction by replacing thick oxide dielectrics with thin layers of hexagonal boronnitride. With the help of additional top gates implemented in different regions of our heterojunction device, it was seen that the tunneling properties as well as the Schottky barriers at the contact interfaces could be tuned efficiently by using layers of graphene as an intermediate contact material.

Floatability evaluation is critical to predicting flotation results and designing a flotation flowsheet. Laboratory-scale flotation cells are commonly used to study particle floatability, but differences in cell design and governing hydrodynamics make extrapolation to industrial scale operations difficult.
In this work, a new experimental approach based on particle attachment dynamics is proposed to evaluate particle floatability. This method allows precise control of hydrodynamic conditions, visualization of attachment processes, and direct observation of the bubble surfaces. It is therefore ideal for studying attachment dynamics as a function of collector concentration, particle size and concentration, and propeller speed. In addition, it opens the possibility for future studies of the packing density of the particles at the interface and their selective attachment. By evaluating the time-dependent surface coverage as a function of bubble residence time, we illustrate its ability to predict flotation kinetics within a flotation cell. This innovative technique provides a faster, more versatile means of studying particle floatability and attachment dynamics with practical implications for flotation cell optimization.

Due to the growing importance of Computational Fluid Dynamics (CFD) for reactor safety research, there have been activities aimed at qualifying the associated methods for many years. This entails the development and validation of models on the basis of detailed experimental data, generated in comprehensive projects. There was and is a need for development, among other things, for multiphase flows, in particular for accident scenarios in the reactor coolant system. In order to be able to use the model developments and validation data generated throughout various publicly funded projects in the long term, these are carried out using the software provided by the OpenFOAM Foundation, which is thereby qualified for application. The project presented here is funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection (project number 1501658) and has the objective of gathering and maintaining addon software and simulation setups from partner institutions in a common repository, referred to as "Nuclear Safety Repository for OpenFOAM Foundation Software for Reactor Cooling System (NUSAR-RCS)". To this end, a GitLab-based IT environment has been developed that fosters collaborative developments and facilitates the maintenance of results from completed projects. The talk will highlight some recent additions to the environment. The first part is dedicated to a Python package, which, among other things, supplies functionality for bulk processing of simulation results, e.g. to extract global information on the agreement between simulation and experiment using statistical key figures. The second part will present efforts of making the NUSAR-RCS software more portable by means of containerization using Apptainer images.

We probe the magnetic field-induced Tomonaga-Luttinger liquid (TLL) state in the bond-alternating spin-1/2 antiferromagnetic (AFM) chain compound NaVOPO₄ using thermodynamic as well as local μSR and ³¹P NMR probes down to mK temperatures in magnetic fields up to 14 T. The μSR and NMR relaxation rates in the gapless TLL regime decay slowly following characteristic power-law behavior, enabling us to directly determine the interaction parameter K as a function of the magnetic field. These estimates are crosschecked using magnetization and specific heat data. The field-dependent K lies in the range of 0.4 < K < 1 and indicates the repulsive nature of interactions between the spinless fermions, in line with the theoretical predictions. This renders NaVOPO₄ the first experimental realization of TLL with repulsive fermionic interactions in hitherto studied S = 1/2 bond-alternating AFM-AFM chain compounds.

We present a comprehensive study of the magnetic properties of the strongly anisotropic ferrimagnet ErFe₅Al₇ in pulsed magnetic fields up to 30 T applied along the hard magnetization axis within the basal plane of the tetragonal lattice around the compensation temperature (T_comp). Macroscopic measurements showed two anomalies at about 8 T and 25 T in a small temperature range around T_comp. High-field x-ray magnetic circular dichroism (XMCD) data at the Er M₅- and the Fe L₃-edge resonances provide insight into the element-selective magnetization processes, revealing a coherent rotation of Er 4f and Fe 3d moments, with stepwise jumps including an unexpected one from an easy to a hard magnetization axis. XMCD at the Er L₃-edge resonance elucidates the role of Er 5d electrons in coupling the Er 4f and the Fe 3d moments. Finally, an in-plane anisotropy constant was evaluated from a simulation of the magnetization process at temperatures well below T_comp using a two-sublattice model.

Strongly correlated spin systems can be driven to quantum critical points via various routes. In particular, gapped quantum antiferromagnets can undergo phase transitions into a magnetically ordered state with applied pressure or magnetic field, acting as tuning parameters. These transitions are characterized by z = 1 or z = 2 dynamical critical exponents, determined by the linear and quadratic low-energy dispersion of spin excitations, respectively. Employing high-frequency susceptibility and ultrasound techniques,we demonstrate that the tetragonal easy-plane quantum antiferromagnet NiCl₂ ⋅ 4SC(NH₂)₂ (aka DTN) undergoes a spin-gap closure transition at about 4.2 kbar, resulting in a pressure-induced magnetic ordering. The studies are complemented by high-pressure electron-spin-resonance measurements confirming the proposed scenario. Powder neutron diffraction measurements revealed that no lattice distortion occurs at this pressure and the high spin symmetry is preserved, establishing DTN as a perfect platform to investigate z = 1 quantum critical phenomena. The experimental observations are supported by DMRG calculations, allowing us to quantitatively describe the pressure-driven evolution of critical fields and spin-Hamiltonian parameters in DTN.

Todate,multipleadvancedmagneticresonanceimaging(MRI)methodsbeyondconventionalqualitativestructuralimagingforthediagnosis,prognosis,andtreatmentfollow-upofgliomahavedemonstratedtheirutilityforclinicalstudies.However,thesemethodsoftenrelyoncomplexoff-scannerprocessingtoyieldthemostinformationandtoextractquantitativebiomarkers,limitingtheirpracticaluseforstudies,aswellastheirclinicaltranslation.Whilecommunity-drivensoftwaresolutionsexistfortheseadvancedMRImethods,manyaspiringclinicalresearchersfacechallengesinacquiringthenecessaryknowledgetoeffectivelyapplythesetools.Thisguide,aninitiativeoftheGliomaMRimaging2.0network(GliMR),aimstoprovideanoverviewofexistingsolutions,communities,andrepositorieswiththeultimategoalofenablingstandardization,openscience,andreproduciblequantitativeimagingstudiesofgliomas.Yet,mostofthereviewedtoolsandapproachestoimagedataanalysesmayalsobeusedinthecontextofstudiesondiseasesotherthanglioma.

The small modular reactor (SMR) NuScale has been modelled in the framework of the EURATOM McSAFER project. The main objective was to demonstrate the feasibility of a coupled approach using a thermal-hydraulic system code (ATHLET), a 3-D reactor dynamics code (DYN3D) and a CFD software (TrioCFD) to model the whole primary coolant loop and large parts of the secondary side of the plant, including the downcomer-integrated, helical-coiled steam generators (SG) and the decay heat removal system (DHRS). The 3-D neutronic calculation of the reactor core was performed with a cross-section library developed with Serpent, and the coolant flow in the downcomer and lower plenum of the pressure vessel was analyzed by CFD. A double-ended, non-isolatable steam line break sequence served as a test case for the code coupling. Simulation results at steady-state show agreement with the reference values from the Design certification Application (DCA) report. The transient simulation shows that the rapid depressurization and boil-off with high steam rates towards the break lead to enhanced primary-to-secondary heat removal. However, the symmetrical arrangement of SGs in the NuScale reactor limits the coolant temperature reduction at the core inlet to prevent a possible power excursion which highlights the inherent safety of this reactor design.

Strain- and defect-engineering are two powerful approaches to tailor the opto-electronic properties of two-dimensional (2D) materials, but the relationship between applied mechanical strain and behavior of defects in these systems remains elusive. Using first-principles calculations, we study the response to external strain of $h$-BN, graphene, MoSe$_2$, and phosphorene, four archetypal 2D materials, which contain substitutional impurities. We find that the formation energy of the defect structures can either increase or decrease with bi-axial strain, depending on the atomic radius of the impurity atom, which can be larger or smaller than that of the host atom. Analysis of the strain maps indicates that this behaviour is associated with the compressive or tensile local strains produced by the impurities that interfere with the external strain. We further show that the change in the defect formation energy is related to the change in elastic moduli of the 2D materials upon introduction of impurity, which can correspondingly increase or decrease. The discovered trends are consistent across all studied 2D materials and are likely to be general. Our findings open up opportunities for combined strain- and defect-engineering to tailor the opto-electronic properties of 2D materials, and specifically, the location and properties of single-photon emitters.

Introduction Loss of blood-brain barrier (BBB) integrity is
hypothesised to be one of the earliest microvascular signs
of Alzheimer’s disease (AD). Existing BBB integrity imaging
methods involve contrast agents or ionising radiation, and
pose limitations in terms of cost and logistics. Arterial
spin labelling (ASL) perfusion MRI has been recently
adapted to map the BBB permeability non-invasively. The
DEveloping BBB-ASL as a non-Invasive Early biomarker
(DEBBIE) consortium aims to develop this modified
ASL-MRI technique for patient-specific and robust BBB
permeability assessments. This article outlines the study
design of the DEBBIE cohorts focused on investigating
the potential of BBB-ASL as an early biomarker for AD
(DEBBIE-AD).
Methods and analysis DEBBIE-AD consists of a
multicohort study enrolling participants with subjective
cognitive decline, mild cognitive impairment and AD, as
well as age-matched healthy controls, from 13 cohorts.
The precision and accuracy of BBB-ASL will be evaluated
in healthy participants. The clinical value of BBB-ASL will
be evaluated by comparing results with both established
and novel AD biomarkers. The DEBBIE-AD study aims to
provide evidence of the ability of BBB-ASL to measure BBB
permeability and demonstrate its utility in AD and ADrelated pathologies.
Ethics and dissemination Ethics approval was obtained
for 10 cohorts, and is pending for 3 cohorts. The results of
the main trial and each of the secondary endpoints will be
submitted for publication in a peer-reviewed journal.

Discussed are two picolinate appended bispidine ligands (3,7-diazabicyclo[3.3.1]nonane derivatives) in comparison with an earlier described bis-pyridine derivative, which are all known to strongly bind CuII. The radiopharmacological characterization of the two isomeric bispidine complexes includes quantitative labeling with 64CuII at ambient conditions with high radiochemical purities and yields (molar activities > 200 MBq/nmol). Challenge experiments in presence of EDTA, cyclam, human serum and SOD demonstrate high stability and inertness of the 64Cu-bispidine complexes. Biodistribution studies performed in Wistar rats indicate a rapid renal elimination for both 64Cu-labeled chelates. The bispidine ligand with the picolinate group in N7 position was selected for further biological experiments, and its backbone was therefore substituted with a benzyl-NCS group at C9. Two tumor target modules (TMs), targeting prostate stem cell antigen (PSCA), overexpressed in prostate cancer, and the fibroblast activation protein (FAP) in fibrosarcoma, were selected for thiourea coupling with the NCS-functionalized ligand and lysine residues of TMs. Small animal PET experiments on tumor-bearing mice showed very good and specific accumulation of the 64Cu-labeled TMs in tumors.

For the first time, Introduction to Research Software Engineering was offered as a class in the Computer Science faculty of TU Dresden during this winter semester (2023/24) (https://tu-dresden.de/ing/informatik/smt/cgv/studium/lehrveranstaltungen/ws2324/RSE/index). This talk will briefly cover the content, feedback from students and own observations as well as ideas how to continue and extend the class in the future.

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf rely on a variety of systems and tools when it comes to administer their research data. Processes involving research data management include the project planning phase (proposal submission to the beamtime proposal management system, the creation of data management plans and data policies), the documentation during the experiment or simulation campaign (electronic laboratory notebooks, wiki pages), backup- and archival systems and the final journal and data publications (collaborative authoring tools, meta-data catalogs, software and data repositories, publication systems). In addition, modern research projects are often required to interact with a variety of software stacks and workflow management systems to allow reproducibility on the underlying IT infrastructure. The "HELmholtz ScIentific Project WORkflow PlaTform" (HELIPORT), which is currently developed by researchers at HZDR and their collaborators, tries to facilitate the management of research data and metadata by providing an overarching guidance system which combines all the information by interfacing the underlying processes and even includes a workflow engine which can be used to automate processes like data analysis or data retrieval.

Electric fields offer an easy means to manipulate liquid metal droplets. Now, directed droplet transfer between immersed electrodes is
achieved in an alkaline electrolyte without electrical short-circuit.

Modeling geochemical scenarios for the safety analyses of disposal of hazardous radioactive and (chemo)toxic waste requires comprehensive and consistent thermodynamic data as well as sorption data for the surrounding host rocks. Whereas there are several projects running worldwide to develop at the comprehensive and consistent thermodynamic database for the aqueous phase and forming solids, the situation is much more complicated concerning the reactions on the mineral-water interface. For sorption data, there is currently no database providing quality assured thermodynamic surface complexation modeling (SCM) data. Even though spectroscopic methods to determine the actual surface species have made great progress in recent years, the SCM data still contain questionable to assuredly non-existent species. This leads to hardly comparable results in geochemical modeling.
To address this problem, publicly available SCM (protolysis and sorption) data are currently being reevaluated and new reaction data are generated building on spectroscopically evidenced surface complexes. Critical data gaps shall be closed by the use of analogies (for both radionuclides’ chemistry as well as the mineral phases) or established estimation methods (e.g. linear free energy relationship). The RES³T sorption database¹, the PSI Chemical Thermodynamic Database² as well as the LLNL’s sorption raw data compilation³ provide the solid basis for this work. In combination with surface site density data from crystallographic calculations, this approach yields realistic and robust models that significantly improve sorption in geochemical calculations e.g. through so-called smart Kd values⁴. The results of this work will be published within the THEREDA framework⁵ including ready-to-use parameter files for common geochemical codes (e.g. GEMS, Geochemist’s Workbench, PHREEQC).
This work is funded by BGE – the federal company for radioactive waste disposal in Germany, with the contract number TEKFuE-21-03-js.
References:
1) RES³T – Rossendorf Expert System for Surface and Sorption Thermodynamics, Helmholtz-Zentrum Dresden-Rossendorf, (https://www.hzdr.de/res3t)
2) PSI Chemical Thermodynamic Database (https://www.psi.ch/de/les/thermodynamic-databases).
3) Smart-Kd concept (https://www.smartkd-concept.de/)
4) Zavarin M. et al. (2022): Community Based Data of Uranium Adsorption onto Quartz, ESS-DIVE repository, DOI: 10.15485/1880687.
5) THEREDA – Thermodynamic Reference Database (https://www.thereda.de)

HELIPORT is a data management guidance system that aims at making the components and steps of the entire research experiment’s life cycle findable, accessible, interoperable and reusable according to the FAIR principles. It integrates documentation, computational workflows, data sets, the final publication of the research results, and many more resources. This is achieved by gathering metadata from established tools and platforms and passing along relevant information to the next step in the experiment's life cycle. HELIPORT's high-level overview of the project allows researchers to keep all aspects of their experiment in mind.

A particularly interesting use case are machine learning projects. They are often prototypical in nature and driven by iterative development, so reproducibility and tranparency are a great concern. It is essential to keep track of the relationship between input data, choices in model parameters, the code version in use, and performance measures and generated outputs at all times. This requires a data management platform that automatically records the changes made and their effects. Existing MLOps tools (such as Weights and Biases, MLFlow) live entirely in the ML domain and start their workflow with the assumption that data is available. HELIPORT, on the other hand, takes care of the data lifecycle as well. Our envisioned platform interoperates with the domain specific tools already used by the scientists, and is able to extract relevant metadata (e.g. provenance). It can also make persistent any additional information such as papers the work was based on, documentation of software components, workflows, or failure cases. Moreover, it should be possible to publish these metadata in machine-readable formats.

The challenge arising from these aspects consists in integrating ML workflows into HELIPORT in such a way that they work on the provided data and metadata. The goal is also to enable the comprehensible development of ML models alongside the experiment documented in HELIPORT. This allows different teams (e.g. experimentalists and AI specialists) to work together on the same project in a seamless manner, and help generate FAIRer outcomes. In the long term we hope to aide in establishing digital twins of facilities, and making their maintenance a part of the data management proces.

We present a modular and cost-effective gamma ray computed tomography system for multiphase flow investigations in industrial apparatuses. It mainly comprises a Cs-137 isotopic source and an in-house-assembled detector arc, with a total of 16 scintillation detectors, offering a quantum efficiency of approximately 75% and an active area of 10 × 10 mm² each. The detectors are operated in pulse mode to exclude scattered gamma photons from counting by using a dual-energy discrimination stage. Flexible application of the computed tomography system, i.e., for various object sizes and densities, is provided by an elaborated detector arc design, in combination with a scanning procedure that allows for simultaneous parallel beam projection acquisition. This allows the scan time to be scaled down with the number of individual detectors. Eventually, the developed scanner successfully upgrades the existing tomography setup in the industry. Here, single pencil beam gamma ray computed tomography is already used to study hydraulics in gas–liquid contactors, with inner diameters of up to 440 mm. We demonstrate the functionality of the new system for radiographic and computed tomographic scans of DN110 and DN440 columns that are operated at varying iso-hexane/nitrogen liquid–gas flow rates.

This study introduces an adaptive model for estimating decay heat in nuclear reactors, particularly
during transient scenarios with steadily reducing reactor power. Traditional approaches to decay
heat calculation often rely on extensive nuclide tracking or standardized procedures. The former
approach can be resource-intensive, requiring detailed tracking of a multitude of nuclides, while the
latter often has limited applicability. The adaptive model proposed in this paper offers an alternative
solution that circumvents these challenges by utilizing precalculated decay heat curves from scram
scenarios. This methodology allows for on-the-fly decay heat calculation during simulation, adapting
to varying power levels without the need for detailed nuclide tracking.
The paper provides a description of the adaptive model, including its mathematical framework
and operational procedure. The model’s test case is developed using the IAEA benchmark exercise
related to the loss of flow without scram test conducted at the Fast Flux Test Facility, a sodium-cooled
fast reactor. The model is verified through single assembly calculations, where it demonstrates high
accuracy in comparison to the depletion solver of the Monte Carlo code Serpent. This demonstrates
the model’s potential as a promising alternative for decay heat estimation in the analysis of accident
scenarios.

Wildlife-vehicle collisions are an ongoing and widespread source of biodiversity loss. Understanding how, when and why these collisions happen is a key challenge in any conservation and management efforts. Data collection with biologgers can reveal information on how animals use their environment, interact with each other, and their adaptive responses to rapid environmental changes and anthropogenic features in the landscape —including their behavioral responses to linear infrastructures. The movement ecology field is rapidly shifting as we open new avenues of research, with increased access to modern tracking technologies, collecting high-volume high-resolution movement datasets for a growing number of animal species worldwide. Using these datasets to reveal road impacts on animal behavior is fundamental, since wildlife-vehicle collisions are the second-largest source of anthropogenic mortality for many vertebrate species. We will explore empirical examples with animal tracking data, as well as information collected through road surveys, and how these can serve as crucial tools to achieve a deeper understanding of animal movement and behavior towards roads and vehicles.

The presentation explores the intricate relationship between data management, computational processes and metadata descriptions. It delves into how metadata serves as a crucial bridge, facilitating the seamless connection between various data processes, RAW and derived data. The importance of the research institute's infrastructure facilities in preparing data and metadata and supporting systems such as Heliport to improve the understanding, accessibility and interoperability of data in different systems was highlighted. This research highlights the central role of metadata in optimising data-driven workflows and promoting efficient data use strategies.

Discriminating the absorption coefficients of aerosol mineral dust and black carbon (BC) in different aerosol size fractions is a challenge because of BC's large mass absorption cross-section compared to dust. Ambient aerosol wavelength dependent absorption coefficients in supermicron and submicron size fractions were determined with a high time resolution. The measurements were performed simultaneously using identical systems at an urban and a regional background site in Qatar. At each site, measurements were taken by co-located Aethalometers, one with a virtual impactor (VI) and the other with a PM1 cyclone to respectively collect super-micron-enhanced and submicron fractions. The combined measurement of aerosol absorption and scattering coefficients enabled the particles to be classified based on their optical properties' wavelength dependence. The classification reveals the presence of BC internally/externally mixed with different aerosols. Helium ion microscopy images provided information concerning the extent of mineral dust in the submicron fraction. The determination of absorption coefficients during dust storms and non-dust periods was used to establish the absorption Ångström exponent for dust and BC. Non-parametric wind regression, potential source contribution function and back-trajectory analysis reveal major regional sources of desert dust associated with north-westerly winds and a minor local dust contribution. In contrast, major BC sources found locally were associated with south-westerly winds with a smaller contribution made by offshore emissions transported by north-easterly and easterly winds. The use of a pair of Aethalometers with VI and PM1 inlets separates contributions of BC and dust to the aerosol absorption coefficient.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biannual highlight commentary to update the readership on trends in the field of radiopharmaceutical development.

Main Body: This selection of highlights provides commentary on 24 different topics selected by each coauthoring Editorial Board member addressing a variety of aspects ranging from novel radiochemistry to first-in-human application of novel radiopharmaceuticals.

Conclusion: Trends in radiochemistry and radiopharmacy are highlighted. Hot topics cover the entire scope of EJNMMI Radiopharmacy and Chemistry, demonstrating the progress in the research field in many aspects.

We theoretically propose a quantum simulation scheme for the toric-code Hamiltonian, the paradigmatic model of a quantum spin liquid, based on time-periodic driving. We develop a hybrid continuous-digital strategy that exploits the commutativity of different terms in the target Hamiltonian. It allows one to realize the required four-body interactions in a nonperturbative way, attaining strong coupling and the suppression of undesired processes. In addition, we design an optimal protocol for preparing the topologically ordered ground states with high fidelity. A proof-of-principle implementation of a topological device and its use to simulate the topological phase transition are also discussed. The proposed scheme finds natural implementation in architectures of superconducting qubits with tunable couplings.

In water electrolysis, the porous transport layer (PTL) is an essential component of both proton (PEM) as well as anion exchange membrane (AEM) electrolysers. Besides establishing an electrical contact, the PTL enables the electrolyte to be transported to the anode. In the opposite direction, the oxygen (O2) formed at the anode must be transported away, resulting in a complex counterflow of liquid and gas through the PTL, thus limiting the mass transport and, consequently, the conversion of electrical energy. The further development of electrolysers faces so far unexplored operating conditions, in particular by increasing the electric current density. This, in turn, affects the formation and transport of gas bubbles in the PTL, which is not yet sufficiently understood.

As the gas-liquid two-phase flow in the PTL is inaccessible for flow measurement by optical methods, we employed time-resolved X-ray and neutron radiography. Using the model experiment sketched in Fig. 1, we aimed for imaging measurements of the gas transport through open-porous foam by mapping the gas fraction distribution over time. In previous experimental studies, we have used X-ray and neutron radiography for flow visualisation in optically opaque fluids such as liquid metal [1] and aqueous foam [2]. Similar to the approach of radiographic measurements of the liquid fraction in aqueous foam [3], this conference contribution showcases the detection and tracking of bubbles based on their gas fraction in X-ray or neutron images. As exemplarily illustrated in Fig. 2, we observed preferred paths of the bubbles moving upwards through the open-porous foam samples. Moreover, we found that bubbles smaller than the pore size are significantly slowed down, even in the case of a hydrophilic surface character of the foam. In summary, the measurement results and conclusions from our experimental parameter study are available for comparison with computational fluid dynamics.

The synthesis and twin polymerization (TP) of Si(OCH₂py)₄ (3a, py=2-^cC₅H₄N; 3b, py=3-^cC₅H₄N; 3c, py=4-^cC₅H₄N) is discussed. The solid state structures of 3b, c were confirmed by single-crystal X-ray crystallography showing non-conventional H-bonding, forming 2D chains (3b) or 3D networks (3c). Thermally induced TP of 3a–c and their simultaneous polymerization with 2,2‘-spiro-bi[4H-1,3,2-benzodioxasiline] (4) is described. The resulting hybrid materials were characterized by ¹H, ¹³C{¹H}, and ²⁹Si{¹H} CP MAS NMR spectroscopy confirming the transformation of the SiOCH₂ moieties into CH₂ groups enabling the formation of the respective polymers. These results were supported by HAADF-STEM studies, displaying micro-structuring. Nitrogen-containing porous carbon materials C_1–C_3 show surface areas of 1300 and 1700 m²g^-1, large pore volumes between 0.6–1.2 cm³g^-1, and nitrogen contents of up to 3.1 at-%. X-ray photoemission spectroscopy reveal that pyrrolic, pyridine, and pyridone nitrogen atoms are present. If equimolar amounts of 3a–c and 4 are simultaneously polymerized in the presence of [Pd(OAc)₂] (5), then the Pd nanoparticle-decorated material Pd@C_3 (900 m²g^-1) was obtained, which showed k values of -0.083 and -0.066 min^-1 in the reduction of methylene blue and methyl orange, proving the accessibility of the Pd NPs.

Purpose: Arterial Spin Labeling (ASL) is widely used in clinical research as a contrast-free MRI method for
assessment of cerebral blood flow (CBF). While the recommended guideline for ASL acquisition is
generally adopted to standardize quantification of CBF, ASL analysis still produces wide variability in CBF
estimates, limiting research and clinical interpretation of ASL results. This study explored the extent of
variability in ASL CBF quantification through the ISMRM OSIPI ASL MRI Challenge. The goal of the challenge
was to minimize sources of variability in ASL analysis by establishing best practice in ASL data processing
to make ASL analysis more reproducible and clinically meaningful.
Methods: Eight international teams analyzed the challenge data consisting of a high-resolution T1-
weighted anatomical image and ten pseudo-continuous ASL (PCASL) datasets. The datasets were
simulated using an ASL digital reference object to produce ground-truth CBF values in normal and
pathological states. The accuracy of CBF quantification from each team’s analysis was compared to
ground-truth values across all voxels and within pre-defined brain regions. Reproducibility of CBF
estimates across analysis pipelines was assessed using intra-class correlation coefficient (ICC), the limits
of agreement (LOA) and the replicability of generating similar CBF estimates from the image processing
approaches as documented.
Results: The absolute errors in CBF estimates compared to the ground-truth synthetic data ranged from
18.36 to 48.12 ml/100g/min. Realistic motion incorporated in three of the ten synthetic data produced
the largest absolute CBF error, largest variability between teams, and the least agreement (ICC and LOA)
with ground truth results. Fifty percent (4/8) of the teams’ methods were replicated, and one method
produced three times larger CBF errors (46.59 ml/100g/min) compared to submitted results.
Conclusions: The apparent variability in CBF measurements, influenced by differences in image processing
strategies, particularly in compensating for motion, demonstrates the significance for standardization of
ASL image analysis workflow. Therefore, we provide a recommendation for ASL image processing based
on top performing approaches as a step towards standardization of ASL imaging for clinical use.

Field-effect transistors are capable of detecting electromagnetic radiation from less than 100 GHz up to very high frequencies reaching well into the infrared spectral range. Here, we report on frequency coverage of up to 30THz, thus reaching the technologically important frequency regime of CO2 lasers, using GaAs/AlGaAs high-electron-mobility transistors. A detailed study of the speed and polarization dependence of the responsivity allows us to identify a cross over of the dominant detection mechanism from ultrafast non-quasistatic rectification at low Terahertz frequencies to slow rectification based on a combination of the Seebeck and bolometric effects at high frequencies, occurring at about the boundary between the Terahertz frequency range and the infrared at 10THz.

The IRE is one of the ten institutes of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Our research ac-tivities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and fo-cus on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. The program NUSAFE, and therefore all work which is done at IRE, belong to the research field “Energy” of the HGF.

The historic mining activities have produced a vast amount of mine tailings covering a huge landscape and containing hazardous substances that are harmful to the environment. In addition, the mine tailings also contain valuable materials that become economical after a certain period depending on the criticality of the commodity. Likewise, the old silver mine tailings “Davidschachthalde” near Freiberg, Germany, bears hazardous substances such as As, Cd and valuable elements such as Zn, In, and Cu. Thus, an innovative flowsheet is developed to recover Zn from mine tailings. Firstly, the Fe and Al are removed using the precipitation method which also removes As. Then, the solution is passed through the cementation steps for Cu and Cd removal. In order to purify and enrich Zn(II) in the aqueous solution before electrowinning the conceptional flowsheet consists of a solvent extraction process.
The filtrate from precipitation steps with the composition of 1120 mg/L Zn(II), 4 mg/L Cu(II), 10 mg/L Al(III), 243 mg/L Ca(II), 21 mg/L Cd(II) and pHini 4.7 is subjected to solvent extraction unit with 3 extraction and 2 stripping stages in MEAB lab scale Mixer Settler. Figure 1 depicts the results for the extraction step which is carried out with 0.5 M Cyanex® 272 in kerosene as the organic phase, A/O ratio of 1:1, a contact time of 10 min with a 1-hour sampling interval. Under the chosen conditions Zn(II) extraction is 89% after reaching equilibrium and shows a high selectivity related to low concentrated impurities Cu(II), Cd(II) and Al(III). However, a Ca(II) co-extraction of up to 22% is observed during the process which would affect the following stripping and electrowinning processes in a negative way. Therefore, a high selectivity between Zn(II) and Ca(II) needs to be achieved in the extraction step.
Here, we report the development of the highly selective solvent extraction process for the Zn(II) containing solutions generated during the previous precipitation and cementation steps. Effects of crucial parameters such as pH control and A/O ratio as well as the composition of the stripping agent on extraction yields, up-concentration and selectivity are discussed in detail.

Mission: Impossible - Understanding Regulations For Radiopharmaceuticals

Outcome from an ITF EMA meeting of PRISMAP (quality requirements for new radionuclides in clinical trials)

Background: The aim of this retrospective study was to assess the value of 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ([18F]FDG PET/CT parameters in cN1-cN3 non-small cell lung cancer (NSCLC) patients.

Materials and methods: 59 consecutive patients (35 M, 24 F) with NSCLC who underwent pretreatment [18F]FDG PET/CT were enrolled to this study. Several primary tumor PET parameters, including the maximum and mean standardized uptake value (SUVmax and SUVmean), the metabolic active tumor volume (MTV) and the total lesion glycolysis (TLG = MTVxSUVmean), were extracted and analysed. Overall survival was defined as time from primary diagnosis to death or the last info.

Results: In the whole analysed group 44 patients underwent curative treatment, while 15, because of the severity of the disease, were classified for palliative treatment. Univariate Cox analysis of clinical and metric PET parameters revealed that MTV was a significant prognostic factor for OS (p = 0.024), while TLG and curative treatment showed a trend for significance (p < 0.1). In multivariate Cox regression (MTV and curative treatment) MTV remained a significant factor (p = 0.047).

Conclusions: Metabolic tumor volume of the primary tumor was the only independent prognostic factor for cN1–cN3 NSCLC patients.

Digital infrastructures have become indispensable in the field of modern research and science. These technological frameworks play a crucial role for the entire research cycle, supporting literature searches, aiding in data collection and analysis, facilitating the creation and publication of scholarly works, and ensuring the thorough documentation and long-term storage of research findings. Additionally, these infrastructures serve as a vital means for networking and communication among peers, creating the essential foundation of an open and transparent science and research ecosystem.
In this lecture, the entire digital research landscape at the HZDR will be presented and illustrated using a representative experiment.

In more recent studies we have established the unique adaptor chimeric antigen receptor (CAR) platform RevCAR which uses as extracellular CAR domain a peptide epitope instead of an antibody domain. RevCAR adaptors (termed RevCAR target modules, RevTMs) are bispecific antibodies. The reversible ON/OFF switch of the RevCAR system improves the safety compared to conventional CARs. Here we describe for the first time its use for retargeting of both T- and NK-92 cells. In addition, we describe the development and preclinical validation of a novel RevTM for targeting of the fibroblast growth factor-inducible 14 (Fn14) surface receptor which is overexpressed on Glioblastoma (GBM) cells and therefore a promising target for the treatment of GBM. The novel RevTM efficiently redirects RevCAR modified T- and NK92 cells and leads to the killing of GBM cells both in vitro and in vivo. Tumor cell killing is associated with increased IL-2, TNF-α and/or IFN-γ secretion. Hence, these findings give an insight into the complementary potential of both RevCAR T and NK-92 systems as a safe and specific immunotherapeutic approach against GBM.

A selection of Late Bronze Age glass objects from the site of Amarna (Egypt) was analysed for their overall chemical composition, colourants and transition metals associated with the sources of cobalt ore. The objects were analysed by means of Particle Induced X-Ray and Gamma-ray Emission and Rutherford Backscattering Spectrometry at the IBC, HZDR, Dresden and the New AGLAE facility, C2RMF, Paris. The data was subsequently compared with further measurements obtained by portable X-Ray Fluorescence (and by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry) in order to sound the potential of these non-destructive methods to obtain new insights into the production process of glass from Amarna and its provenancing.

The new multi-purpose 1-MV AMS facility HAMSTER (Helmholtz Accelerator Mass Spectrometer for Tracing Environmental Radionuclides) in Dresden-Rossendorf will get in operation in 2024. The new machine is dedicated to the analysis of ultra-trace levels of actinides in environmental samples. Thus, the aim of this study is to assess the actinide background on HZDR’s research campus to rule out any potential contamination caused by the former research reactor onsite. Hence, several soil samples close to the construction site of the new accelerator building and former radioisotope production facilities
have been analyzed. The samples have been processed in the existing chemistry labs of HZDR’s 6-MV DREAMS facility and the newly established
HAMSTER labs showing comparable low background levels. The measured Pu concentrations and isotopic ratios are in agreement with global fallout signature. However, in some samples increased 236U concentrations and relatively low 233U/236U atomic ratios have been detected pointing to an additional source of 236U. Additional sample analysis will be performed with HAMSTER in 2024.

The determination of minute amounts of actinides in a huge variety of sample matrices is a challenging task. The current capabilities of state-of-the-art accelerator mass spectrometers enable detection limits close to a few hundred atoms per sample. However, proper sample preparation is inevitable to separate the element of interest from the overwhelming majority of the sample mass. Here, we present some of our current activities regarding the optimization of work-up procedures for different actinides (i.e. Pa, Np, Pu, Am, Cm) from environmental samples like water, soil, deep sea ferromanganese crusts and lunar
regolith.

Long-lived radionuclides in our environment provide important information on natural and anthropogenic processes. Their
presence and concentration reflect the balance of production and decay. Geological archives store such information and the nuclides
can be chemically extracted from the bulk sample. Accelerator mass spectrometry (AMS) represents a sensitive method to quantify
those nuclides at natural levels. Three different terrestrial archives are discussed here as examples for radionuclide extraction
using various chemical separation methods for subsequent AMS measurements. We focus on sample preparation for the cosmogenic
radionuclides Be-10 and Al-26, various anthropogenic actinide isotopes such as U, Pu and Am as well as the astrophysically
interesting nuclides Ca-41, Mn-53 and Fe-60. The processed materials cover samples with masses between a few mg and up to a
few hundred kg and protocols are presented for the quantitative extraction of some 10,000 atoms of cosmogenic or interstellar
origin per sample and even as low as a few hundred actinide atoms.

The K-Pg (Cretaceous–Paleogene) boundary at 66 Ma marks one of five major mass extinctions in Earth’s fossil history. Based on strong enrichments of the platinum-group elements in the boundary layer, Alvarez et al. [1], in 1980, suggested that the impact of a large asteroid was responsible for the K/Pg event.
Earlier, other possible causes for the mass extinction, e.g., a nearby supernova(SN)-explosion, were also discussed, and indeed also Alvarez et al. initially considered this option to explain the high Ir concentration. However, to explain the observed Ir content, the distance for a SN would have to be less than one light-year. To exclude the SN option for the K-Pg event, they searched for a specific long-lived radionuclide, 244Pu, which has a half-life of 81 Myr and does not exist naturally on Earth. Assuming that this radionuclide is predominantly produced and ejected in SNe, its presence could indicate a nearby SN. No 244Pu at required levels was detected, leaving an impact as the most plausible cause (which was later confirmed by the discovery of shocked minerals and also a source crater, Chicxulub). However, since 1980, strong evidence evolved that the heavy r-process elements, e.g., actinides such as 244Pu, are produced in rare explosive events (ca. 1000 times less frequent than common type II core-collapse SNe in the galaxy) [2]. Neutron star mergers are potential candidates or rare subsets of SNe. Thus, the common core-collapse SNe might not have contributed significantly to actinide nucleosynthesis for the past few 100 Myr. This assumption agrees also with recent observations following the gravitational-wave event GW170817 [3]. Furthermore, by searching deep-sea archives for interstellar signatures we confirmed recently that nucleosynthesis yields of 244Pu are much lower (possibly a factor of 100) than expected if SNe dominate heavy isotope r-process nucleosynthesis [4-6]. However, the detection of a significant 244Pu influx above background into these terrestrial archives suggests the possibility of a nearby explosive event within the past few hundred millions years, possibly from a rare event. Thus, a small r-process contribution to actinide production from SNe is still a possibility. In general, site and frequency of r-process events are still strongly debated [2]. Thus, in contrast to the assumption of Alvarez et al. [1], it is not clear that non-detection of 244Pu excludes a nearby supernova explosion at 66 Ma. Despite the overwhelming evidence for an asteroid impact, a new method for direct atom counting has emerged with superior detection efficiency for 244Pu: since the original work by Alvarez et al. in 1980, the 244Pu detection-sensitivity has improved by more than a factor of a million by applying the method of Accelerator Mass Spectrometry (AMS) [5,7,8]. This enormous gain in abundance sensitivity prompted us to reinvestigate the 244Pu concentration in the K-Pg boundary layers. Here we present first results for a set of samples covering this transition period from the Cretaceous to the Paleogene.

The present study presents the experimental measurements of the sodium flow rate in the KASOLA (KArlsruhe SOdium LAboratory) and SOLTEC-2 (SOdium Loop for TEst materials
and Corrosion) facilities available at KIT. KASOLA facility is a versatile sodium facility designed for thermal-hydraulic experiments and tests of components at prototypical and industrial scale [1]. The facility has a sodium inventory of 7 m3 and can be operated up to a temperature of 550°C at an overpressure of 2.5 bar. The maximal flow rate is specified at 150 m3/h, which can be achieved with a 75 kW annular linear induction pump. The sodium flow rate measurements have been performed using a Coriolis flowmeter, which has been used as reference for the calibration of a magnetic flow meter. The influence of the temperature field has been considered in the determination of the flow rate curve for the magnetic flow rate sensor. SOLTEC-2 facility is a 720 °C high temperature sodium loop currently used for experimental investigations of sodium corrosion on high temperature steels. The facility has a sodium inventory of ~14 L and it was operated up to 720 °C at an overpressure of 2.5 bar. The maximal mass flow rate specified is 300 kg/h. An innovative eddy current flowmeter (ECFM) sensor developed at HZDR, Dresden [2] has been installed in the high temperature side and operated in the SOLTEC loop. Successful measurements have been performed up to 700 °C, which to our knowledge represent so far a worldwide premiere. A comparison has been made between the results generated by the ECFM sensor with the experimental data delivered by the magnetic fly-wheel that is installed in the low temperature side of the loop. The study discusses the experience gained and the differences between these two flow rate sensors.

Measuring the flow velocity of liquid metals is a challenging task due to their high temperatures, their opacity and in many cases their chemical reactivity. There are several inductive methods to measure the flow velocity of liquid metals such as contactless inductive flow tomography (CIFT) [1], the magnetic distortion probe [2], Lorentz force velocimetry [3], the phase shift sensor [4] and eddy current flow meters (ECFM)[5]. ECFMs are often used in liquid metal fast breeder reactors due to their reliability and simple design. A disadvantage of the ECFM is that its output signal is influenced not only by changes in the flow velocity, but also by the electrical conductivity of the liquid metal, which depends on its temperature. Therefore, the ECFM must be calibrated according to the expected range of flow velocities and temperatures of a particular application, while simultaneously determining the temperature to distinguish between velocity and temperature changes. To solve this problem, we propose a new measurement method [6] that allows the simultaneous measurement of flow velocity and electrical conductivity by creating a so-called look-up table (LuT).

Hypoxia is a common feature of solid tumours affecting their biology and response
to therapy. One of the main transcription factors activated by hypoxia is hypoxia-
inducible factor (HIF), which regulates the expression of genes involved in various
aspects of tumourigenesis including proliferative capacity, angiogenesis, immune
evasion, metabolic reprogramming, extracellular matrix (ECM) remodelling, and
cell migration. This can negatively impact patient outcomes by inducing
therapeutic resistance. The importance of hypoxia is clearly demonstrated by
continued research into finding clinically relevant hypoxia biomarkers, and
hypoxia-targeting therapies. One of the problems is the lack of clinically
applicable methods of hypoxia detection, and lack of standardisation.
Additionally, a lot of the methods of detecting hypoxia do not take into
consideration the complexity of the hypoxic tumour microenvironment (TME).
Therefore, this needs further elucidation as approximately 50% of solid tumours are
hypoxic. The ECM is important component of the hypoxic TME, and is developed
by both cancer associated fibroblasts (CAFs) and tumour cells. However, it is
important to distinguish the different roles to develop both biomarkers and novel
compounds. Fibronectin (FN), collagen (COL) and hyaluronic acid (HA) are
important components of the ECM that create ECM fibres. These fibres are
crosslinked by specific enzymes including lysyl oxidase (LOX) which regulates
the stiffness of tumours and induces fibrosis. This is partially regulated by HIFs.
The review highlights the importance of understanding the role of matrix
stiffness in different solid tumours as current data shows contradictory results
on the impact on therapeutic resistance. The review also indicates that further
research is needed into identifying different CAF subtypes and their exact roles;
with some showing pro-tumorigenic capacity and others having anti-
tumorigenic roles. This has made it difficult to fully elucidate the role of
CAFs within the TME. However, it is clear that this is an important area of
research that requires unravelling as current strategies to target CAFs have
resulted in worsened prognosis. The role of immune cells within the tumour
microenvironment is also discussed as hypoxia has been associated with
modulating immune cells to create an anti-tumorigenic environment. Which
has led to the development of immunotherapies including PD-L1. These
hypoxia-induced changes can confer resistance to conventional therapies,
such as chemotherapy, radiotherapy, and immunotherapy. This review
summarizes the current knowledge on the impact of hypoxia on the TME
and its implications for therapy resistance. It also discusses the potential of
hypoxia biomarkers as prognostic and predictive indictors of treatment
response, as well as the challenges and opportunities of targeting hypoxia in
clinical trials.

C₃₁H₂₆NO₄P, monoclinic, P2₁/c (No. 14), a = 16.3835 (2) Å, b = 14.5755 (2) Å, c = 10.5388 (2) Å, β = 95.694 (1) °, V = 2504.22 (7) ų, Z = 4, R_gt(F) = 0.0435, wR_ref(F²) = 0.1170, T = 173 (2) K.

Fluid-rock interactions drive changes in porosity and permeability. This has important consequences for the flow field development in the complex porous material and thus controls the evolution of reactive transport processes. Important applications are in the vast field of reservoir rock alteration, e.g. by coupled dissolution and precipitation processes. While dissolution processes can cause local increases in pore space and permeability, they can also lead to pore throat blockage, which can cause formation damage due to precipitation reactions and particle retention in pore throats. Although these mechanisms are understood in principle, the direct changes in the flow field they cause are difficult to observe directly. Using positron emission tomography (PET), we show how flow field heterogeneities are quantitatively affected by the coupling of dissolution reactions and pore throat blockage by particles in a long-term experiment.
Specifically, we performed a dissolution experiment focusing on calcite cement in sandstones. While dissolution is responsible for a local increase in pore space, mobilized iron oxide and sheet silicate colloids are trapped and cause a local decrease in permeability. Direct comparison of sequences of PET-derived flow field data reveals a pattern of flow field modification during this experiment. PET thus becomes a key analytical tool to localize and quantify pore-scale flow field changes, in addition to recent advances focused on the identification of flow channeling effects of advective flow 1 and on the heterogeneity of diffusive flux in low permeability rocks 2.

1. Pingel, J. L.; Kulenkampff, J.; Jara-Heredia, D.; Stoll, M.; Zhou, W.; Fischer, C.; Schäfer, T., In-situ flow visualization with Geo-Positron-Emission-Tomography in a granite fracture from Soultz-sous-Forêts, France. Geothermics 2023, 111, 102705.
2. Bollermann, T.; Yuan, T.; Kulenkampff, J.; Stumpf, T.; Fischer, C., Pore network and solute flux pattern analysis towards improved predictability of diffusive transport in argillaceous host rocks. Chemical Geology 2022, 606, 120997.

ELBE is a compact, accelerator-driven photon and particle source. The variety of secondary radiation being offered extends from high-energy gamma rays to infrared and THz radiation as well as from neutrons to positrons and electrons. Since 2001 ELBE is operated as a user facility, providing more than 5500 hours of beamtime with an efficiency of more than 90% each year. The electron accelerator is based on four superconducting 9-cell TESLA cavities that are driven in CW operation to accelerate an average current of 1 mA up to beam energies of 40 MeV. In addition an upgraded version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017, so that now more than 1800h of user beam are generated by this unique CW electron source every year.

The talk will summarize our experiences of operating all our SRF cavities over two decades in CW. In detail, this includes the cavity performance and attempts to improve it, as well as investigations on their limitations. Additionally, we will discuss several issues that are related to the high average RF as well as beam power and we will present appropriate measures to protect the machine. In this regard we will also introduce a resonant ring for RF component tests at CW power levels up to 100 kW. Regarding the SRF gun, the main emphasis lies in seamlessly integrating a normal-conducting photocathode into the SRF cavity, alongside addressing associated intricacies like dark current, multipacting, and contamination of the resonator.