Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Liquid drainage through foam is driven by gravity, capillary, and, to a lesser extent, viscous forces.
In the of stress on the foam, the liquid distributes uniformly, however, imposed stress changes the
alignment of the foam’s structural elements. Previous numerical simulations [1] predicted that a vertical
drainage flow will be deflected horizontally if the foam is sheared. We investigated such phenomena by
measuring the distribution of liquid fraction within a foam formed in a flat rectangular cell. The foam was
subjected to shear stress under a forced liquid supply at the top of the cell. Two dimensional neutron
radiography images of stress-free and sheared foam were analyzed to extract measurements of liquid
content. Deflections in the distribution of the drainage liquid were detected, and found to be positively
correlated with increasing foam shear. To the best of our knowledge, this is the first experimental
observation of anisotropic drainage in a liquid foam.

Neutron radiography is a useful tool for researching opaque multi phase flow such as foam and froth.

Der Einsatz moderner Meßtechnik kann einen wesentlichen Beitrag für den ressourceneffizienten Betrieb von Anlagen für die Schaumflotation leisten. Insbesondere die Kenntnis der
Stoffzusammensetzung des überströmenden Schaums kann hilfreich für die optimierte Echtzeit-Steuerung des Flotationsprozesses sein. Aufgrund der komplexen und lichtundurchlässigen Struktur der Schaumphase existieren zum heutigen Zeitpunkt allerdings nur wenige Möglichkeiten die Schaumzusammensetzung in Echtzeit und im Volumen zu bestimmen. Zusätzliche Anforderungen an die Robustheit des Maßsystems entstehen aus den rauhen Umgebungsbedingungen in industriellen Anwendungen.

Various physicochemical properties play a decisive role in the evaluation of foods, influencing
taste, odor, texture and mouthfeel when the food is distorted. Therefore, rheological investiga-
tions of foods are used in product development to specifically improve the texture or mouthfeel
of a product. Since mouthfeel describes the physical interaction between the food and various
haptic sensors in the mouth during the chewing and swallowing process, it is advantageous to
perform rheological measurements in geometries and under conditions that reflect the flow
conditions present in the mouth. Up to now, such investigations have been limited primarily to
viscous or lumpy foodstuffs. Here, foam, as a multiphase system consisting of a (highly) vis-
cous liquid and dispersed gas, exhibits complex rheological behavior due to its compressibility.
In addition, the foam undergoes partial destruction of its structure during the swallowing pro-
cess, which can change its rheological properties over time.
For the imaging of the swallowing process, an experimental setup was developed consisting
of a two-dimensional replica of the palate and a movable tongue based on dental impressions.
Foam with different properties such as the mean bubble size and the liquid content or the
degree of polydispersity can be generated. Furthermore, two tongue geometries with different
roughness are available. The flow as well as the deformation of the foam is evaluated by optical
methods such as PIV and particle tracking. The resulting velocity, shear rate and (wall) shear
stress distributions can provide information about the haptic perception in the mouth during the
swallowing process.

Flotation processes are essential processes for resource separation, the monitoring of which can save vast amounts of water and energy. To control them, it is necessary to measure the phase fractions present in the froth. Currently, no suitable measurement method exists that can be easily integrated into the existing process and has a penetration depth of more than 5 cm. Therefore, in this paper we present a measurement system for determining the liquid distribution in foam using ultrasound. To counteract the strong attenuating effect of the foam on the ultrasound, we use low-frequency probes with a center frequency of 135 kHz. Electrodes determine an integral liquid fraction by conductivity measurement. Within a liquid range of 0.17 x 10(exp −2) to 0.82 x 10(exp −2), the measurement system was first calibrated for a penetration depth of 9.2 cm and validated by simultaneous neutron imaging. An absolute and relative measurement uncertainty of 0.23 x 10(exp −2) and 42.5% was the respective result. A resolution of 7.5mm in the axial, 13mm in lateral direction and 1 Hz in time were obtained. In a dynamic inhomogeneous case, the measurement system was additionally validated for a use case. This investigation represents a first step towards process optimization in flotation processes.

Today, the availability of methods for the activity-preserving and cost-efficient downstream processing of enzymes forms a major bottleneck to the use of these valuable tools in technical processes. A promising technology appears to be foam fractionation, which utilizes the adsorption of proteins at a gas–liquid interface. However, the employment of surfactants and the dependency of the applicability on individual properties of the target molecules are considerable drawbacks. Here, we demonstrate that a reversible fusion of the large, surface-active protein Ranaspumin-2 (Rsn-2) to a β-lactamase (Bla) enabled both surfactant-free formation of a stable foam and directed enrichment of the enzyme by the foaming. At the same time, Bla maintained 70% of its catalytic activity, which was in stark contrast to the enzyme without fusion to Rsn-2. Rsn-2 predominantly mediated adsorption. Comparable results were obtained after fusion to the structurally more complex penicillin G acylase (PGA) as the target enzyme. The results indicate that using a surface-active protein as a fusion tag might be the clue to the establishment of foam fractionation as a general method for enzyme downstream processing.

Controlling the pore connectivity of polymer foams is key for most of their applications, ranging from liquid uptake, mechanics, and acoustic/thermal insulation to tissue engineering. Despite their importance, the scientific phenomena governing the pore-opening processes remain poorly understood, requiring tedious trial-and-error procedures for property optimization. This lack of understanding is partly explained by the high complexity of the different interrelated, multiscale processes which take place as the foam transforms from an initially fluid foam into a solid foam. To progress in this field, this work takes inspiration from long-standing research on liquid foams and thin films to develop model experiments in a microfluidic “Thin Film Pressure Balance.” These experiments allow the investigation of isolated thin films under well-controlled environmental conditions reproducing those arising within a foam undergoing cross-linking and drying. Using the example of alginate hydrogel films, the evolution of isolated thin films undergoing gelation and drying is correlated with the evolution of the rheological properties of the same alginate solution in bulk. The overall approach is introduced and a first set of results is presented to propose a starting point for the phenomenological description of the different types of pore-opening processes and the classification of the resulting pore-opening types.

In this study, the specific activities of selected RPV components’ segments (such as the RPV, core barrel, etc.) of a German PWR were calculated with a novel method based on the combined use of two Monte-Carlo codes, MCNP6.2 and FLUKA2021. In the first step, the MCNP6.2 code was used to calculate the neutron fluence rate characteristics (spectrum, distribution, and current entering the segment surfaces) in the studied segment using a 3D detailed reactor model. The neutron fluence rate prediction capability of the MCNP6.2 model has been validated via metal foil-activation measurements carried out in two German PWRs. The validation studies showed that the MCNP6.2 model is reliable and suitable for evaluating the neutron radiation field in the reactor for the ensuing activation calculations. In the second step, the FLUKA2021 code was used to calculate the specific activity distribution in the studied segment using a 3D exact model of the segment and complex source terms built based on the neutron fluence rate parameters calculated using the MCNP6.2 code. The results of the calculations were obtained with great accuracy and evidenced that the used method can serve as a powerful and non-destructive tool for the radiological characterization of the RPV and its internals.

In this study, a 3D detailed Monte-Carlo (MC) model of a German PWR was developed to calculate the neutron fluence characteristics within the ex-vessel components of the reactor. The neutron fluence prediction capability of the developed model was validated based on metal foil-activation measurements. Metal foil-activation measurement has been successfully used in reactor dosimetry for many years. It is an ideal method for collecting information on neutron fluence in an active reactor. This paper gives an overview of the MC model of the reactor and presents the foils activation measurement procedure. Then, the results of the MC simulations and the experimental measurements are presented and discussed.

Rotierende Stoffaustauschmaschinen (engl. „Rotating Packed Beds“, RPBs) sind ein vielversprechender Ansatz, um Trennprozesse effizienter und flexibler zu gestalten. Die durch die Rotation der RPB-Packung wirkenden Zentrifugalkräfte resultieren in hohen Scherraten und damit dünnen Flüssigkeitsfilmen nahezu auf der gesamten Packungsoberfläche, die zu großer effektiver Phasengrenzfläche und hohem volumetrischen Stofftransport führen. Dadurch benötigen RPBs ein drastisch kleineres Packungsvolumen als herkömmliche Trennkolonnen.
Allerdings sind beim Betrieb von RPBs – insbesondere in den äußeren Regionen von isotropen Drahtgestrick- oder Metallschaumpackungen – Phasenfehlverteilungen und lokal geringe Stofftransportraten zu beobachten, die das enorme Intensivierungspotential von RPBs noch limitieren. Daher sind spezielle RPB-Packungsdesigns erforderlich, die gleichmäßige fluiddynamische Bedingungen im gesamten Packungsvolumen ermöglichen.
In dieser Arbeit wird untersucht, ob und wie neu entwickelte Zickzack-Packungen zu einer Homogenisierung der Phasenverteilung in der Packung beitragen können. Dazu wird mithilfe der nicht-invasiven winkelaufgelösten Gammastrahlen-Computertomographie die Phasenverteilung während des rotierenden Betriebs untersucht und anschließend analysiert. Die rekonstruierten Schnittbilder geben einen detaillierten Einblick auf die Flüssigkeitsverteilung innerhalb der Packung bei verschiedenen Betriebsbedingungen. Komplementäre Stofftransportmessungen geben ein verbessertes Verständnis über das Zusammenspiel von Packungsstruktur, Fluiddynamik und Trennleistung.

Population Kinetics for PIC

Standard atomic physics models in PIC simulation either neglect excited states, predict
atomic state population in post processing only, or assume quasi-thermal plasma conditions.

This is no longer sufficient for high-intensity short-pulse laser generated plasmas, due
to their non-equilibrium, transient and non-thermal plasma conditions, which are now becoming
accessible in XFEL experiments at HIBEF (EuropeanXFEL), SACLA (Japan) or at MEC (LCLS/SLAC).
To remedy this, we have developed a new extension for our ParticleInCell simulation
framework PIConGPU to allow us to model atomic population kinetics in situ in PIC-Simulations,
in transient plasmas and without assuming temperatures.
This extension is based on a reduced atomic state model, which is directly coupled to the
existing PIC-simulation and for which the atomic rate equation is solved explicitly in
time, depending on local interaction spectra and with feedback to the host simulation.
This allows us to model de-/excitation and ionization and of ions in transient plasma
conditions, as typically encountered in laser generated plasmas.
This new approach to atomic physics modeling will be very useful in plasma
emission prediction, plasma condition probing with XFELs and better understanding
of isochoric heating processes, since all of these rely on an accurate prediction of
atomic state populations inside transient plasmas.

The shear stress of an axisymmetric flow field triggers a nonuniform distribution of adsorbed surfactants at the surface of a rising bubble. This creates a surface tension gradient that counteracts the viscous shear stress of the flow and thus reduces the mobility of the interface. However, in technological processes the flow field often is asymmetric, e.g. due to the vorticity in the flow. Under such conditions, the interface experiences an unbalanced shear stress that is not free of curl, i.e. it cannot be compensated by the redistribution of the surfactants at the interface (Vlahovska et al., 2009).
Here, we conduct model experiments with a bubble at the tip of a capillary placed in a defined asymmetric flow field, in the presence of surfactants and nanoparticles. Unlike classical surfactants, nanoparticles adsorb irreversibly at the bubble surface. Thus, a different interaction between the bulk flow and the interface is expected.
In this study, we show a direct experimental observation of the circulating flow at the interface under asymmetric shear stress (Eftekhari et al., 2021a,b). The results indicate that the interface remains mobile regardless of the surfactant concentration. Additionally, we show that the nanoparticle-laden interface adopts a solid-like state and resists the interfacial flow upon surface compression. Our results imply that the immobilization of the interface can be described by the ratio of the interfacial elasticity to the bulk viscous forces.

Well-known - and often to see in the daily weather forecast - are the chaotic macroscopic flow-systems of air and sea-water in one`s own land and occasional also about the whole world.

The non-classical human leukocyte antigen (HLA)-G exerts immune-suppressive properties modulating both NK and T cell responses. While it is physiologically expressed at the maternal–fetal interface and in immune-privileged organs, HLA-G expression is found in tumors and in virus-infected cells. So far, there exists little information about the role of HLA-G and its interplay with immune cells in biopsies, surgical specimen or autopsy tissues of lung, kidney and/or heart muscle from SARS-CoV-2-infected patients compared to control tissues. Heterogeneous, but higher HLA-G protein expression levels were detected in lung alveolar epithelial cells of SARS-CoV-2-infected patients compared to lung epithelial cells from influenza-infected patients, but not in other organs or lung epithelia from non-viral-infected patients, which was not accompanied by high levels of SARS-CoV-2 nucleocapsid antigen and spike protein, but inversely correlated to the HLA-G-specific miRNA expression. High HLA-G expression levels not only in SARS-CoV-2-, but also in influenza-infected lung tissues were associated with a high frequency of tissue-infiltrating immune cells, but low numbers of CD8+ cells and an altered expression of hyperactivation and exhaustion markers in the lung epithelia combined with changes in the spatial distribution of macrophages and T cells. Thus, our data provide evidence for an involvement of HLA-G and HLA-G-specific miRNAs in immune escape and as suitable therapeutic targets for the treatment of SARS-CoV-2 infections.

Hydrogen (H 2 ) produced from renewables will have a
growing impact on the global energy dynamics towards sustainable
and carbon-neutral standards. The share of green H 2 is still too low to
meet the net-zero target, while the demand for high-quality hydrogen
continues to rise. These factors amplify the need for economically
viable H 2 generation technologies. The present article aims at
evaluating the existing technologies for high-quality H 2 production
based on solar energy. Technologies such as water electrolysis,
photoelectrochemical and solar thermochemical water splitting, liquid
metal reactors and plasma conversion utilize solar power directly or
indirectly (as carbon-neutral electrons) and are reviewed from the
prospective of their current development level, technical limitations
and future potential.

Heavy-liquid metals (HLMs), such as lead and lead–bismuth eutectic (LBE), are proposed as primary coolants in accelerator driven systems and next-generation fast reactors. In Europe, the reference systems using HLMs are MYRRHA (LBE) and ALFRED (lead). Extensive R&D programs have been established for supporting their detailed design and safety assessment, including thermal–hydraulic experiments at representative operating conditions in an HLM environment. These experiments aim both at a design verification and at the validation of numerical models, which allow an extrapolation of the results. Advanced instrumentation, capable of sustaining high temperatures and corrosion, is necessary for accurate measurements, often in compact geometries. This article presents an overview of recent experiences and ongoing activities on pool-type and loop-type HLM experiments. Pool tests include the measurement of forced- and natural-circulation flow patterns in several scenarios representative of nominal and decay heat removal conditions. Loop tests are focused on the evaluation of specific components, like mockups of the fuel assembly, control rod and heat exchangers. They involve the measurement of global variables, such as flow rate and pressure difference, and local quantities like temperature, velocity and vibrations. In addition to traditional techniques, other instrumentation based on optical fibers, ultrasonic and electromagnetic methods are discussed.

The upcoming DRESDYN (DREsden Sodium facility for DYNnamo and thermohydraulic
studies) precession experiment will test the possibility to achieve magnetohydrodynamic
dynamo action solely driven by precession. Here, after the description of the experi-
mental facility, we present the results from direct numerical simulations with the aim to
understand the flow behavior and its dynamo capability. The main conclusion is that
in the nonlinear regime the nutation angle is an essential governing parameter which
determines the flow structures and the possibility of dynamo action. We obtain clear
indications about the optimum configuration for the future experimental runs.

In this presentation, we will review our recent activities on thin films and bulk of Cr2O3 for energy efficient memory devices and antiferromagnetic spintronic applications. The newly discovered flexomagnetic effect in thin films of Cr2O3 will be presented as well.
[1] Nature Physics 17, 574 (2021).
[2] Nature Comm. 13, 6745 (2022).
[3] Small 18, 2201228 (2022).
[4] ACS Appl. Electron. Mater. 4, 2943 (2022).

In this overview talk, we will discuss on our recent activities on the realization of flexible, printed and self-healable magnetic field sensors and their potential application scenarios.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films [3] and nanowires [4]. In this talk, we will address fundamentals of curvature-induced effects and discuss experimental realisations of geometrically curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of the exchange-driven chiral effects [5]. Geometrically curved magnetic thin films are interesting not only fundamentally. They are the key component of mechanically flexible magnetic field sensors. We will briefly outline activities on shapeable magnetoelectronics [6,7], which includes flexible, stretchable and printable magnetic field sensors for the realisation of human-machine interfaces [8,9], interactive electronics for virtual [10] and augmented [11] reality applications and soft robotics [12] to mention just a few. Very recently, self-healable magnetic field sensors for interactive printed electronics were reported [13]. The presence of the geometrical curvature in a magnetic thin film influences pinning of magnetic domain walls and in this respect it affects the sensitivity of mechanically flexible magnetic field sensors. This is an intimate link between the fundamental topic of curvilinear magnetism and application-oriented activities on shapeable magnetoelectronics. This link will be discussed in the presentation as well.

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications. Springer Nature Switzerland (2022). https://link.springer.com/book/10.1007/978-3-031-09086-8
[3] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[4] D. Sheka et al., Fundamentals of Curvilinear Ferromagnetism: Statics and Dynamics of Geometrically Curved Wires and Narrow Ribbons. Small (Review) 18, 2105219 (2022).
[5] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[6] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[7] G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Advanced Functional Materials (Review) 31, 2007788 (2021).
[8] P. Makushko et al., Flexible Magnetoreceptor with Tunable Intrinsic Logic for On-Skin Skin Touchless Human-Machine Interfaces. Advanced Functional Materials 31, 2101089 (2021).
[9] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[10] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] G. S. Canon Bermudez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[12] M. Ha et al., Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly. Advanced Materials 33, 2008751 (2021).
[13] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Knowledge of the chemical speciation of platinum and the solubility of Pt-bearing minerals in hydrothermal fluids is required to assess Pt transport, remobilization and concentration in the Earth’s crust. In this study, we combined PtS(s) solubility measurements in a hydrothermal reactor allowing fluid sampling, in situ X-ray absorption spectroscopy, and first-principles molecular dynamics simulations to systematically investigate the structure, composition and stability of Pt sulfide complexes in model aqueous H2S-bearing solutions up to 300 °C and 600 bar. The results demonstrate that tetrahydrosulfide, PtII(HS)42–, is the major Pt-bearing complex in aqueous solutions saturated with PtS(s) over a wide range of dissolved hydrogen sulfide concentrations, from < 0.2 to ∼ 2 molal. The equilibrium constants of the dissolution reaction of PtS(s) generated in this study, PtS(s) + 3 H2S(aq) = Pt(HS)42– + 2 H+ (β4), are described by the equation log10β4 = 0.9 × 1000/T(K) – 19.7 (± 0.5) over the temperature range 25–300 °C and pressure range Psat–600 bar. Furthermore, the stepwise formation constants of four PtII-HS complexes, Pt(HS)+, Pt(HS)20, Pt(HS)3–, and Pt(HS)42–, were estimated, for the first time, from molecular dynamics simulations. The generated constants indicate that the maximum solubility of platinum in the form of Pt(HS)42– in reduced H2S-dominated hydrothermal fluids at moderate temperatures (≤ 350 °C) is close to 1 ppb Pt at near-neutral pH of 6–8 and hydrogen sulfide concentrations of 0.1 molal. Although this solubility is much greater than that of Pt-Cl, Pt-OH and Pt-SO4 complexes at such conditions, it is yet too low to account for significant Pt transport in most shallow-crust hydrothermal settings, characterized by the presence of both sulfide and sulfate. Complexes with S-bearing ligands, very likely other than H2S/HS–, such as S3–, would be required to account for Pt hydrothermal mobility. Our results provide a basis for more systematic future studies, using combined approaches, of the role of hydrothermal fluids in the behavior of platinum group elements in nature.

The dynamics of hydrogen bubbles produced by water electrolysis in an acidic electrolyte are studied using electrochemical and optical methods. A defined cyclic modulation of the electric potential is applied at a microelectrode to produce pairs of interacting H$_2$ bubbles in a controlled manner. Three scenarios of interactions are identified and systematically studied. The most prominent one consists in a sudden reversal in the motion of the first detached bubble, its return to the electrode and finally its coalescence with the second bubble. Attested by Toepler's schlieren technique, an explanation of contactless motion reversal is provided by the competition between buoyancy and thermocapillary effects.

Precipitation reactions are of constant interest to research because of their importance in nature and in industry. In this study, we
present a precipitation Reaction-Diffusion-Advection system using a CaCO3 forming reaction by injecting one reactant solution
into the initially stagnant second reactant solution. We studied the resulting precipitate reactive flow system both from a
microscopic and a macroscopic point of view. We identified three different flow regimes depending on the flow conditions and
chemical system: a particle-laden regime, a clogging regime and a gelation regime. The results are a basis for further investigation
and improvement of such displacements in technological applications.

This lecture is about neutron scattering methods and their applications in the field of nuclear material science.

This lecture is about X-ray and electron diffraction methods and their application in the field of nuclear material science

Terahertz (THz) electromagnetic radiation is key to access collective excitations such as magnons (spins), plasmons (electrons), or phonons (atomic vibrations), thus bridging topics between optics and solid-state physics. Confinement of THz light to the nanometer length scale is desirable for local probing of such excitations in low-dimensional systems, thereby circumventing the large footprint and
inherently low spectral power density of far−field THz radiation. For that purpose, phonon polaritons (PhPs) in anisotropic van der Waals (vdW) materials have recently emerged as a promising platform for THz nanooptics. Hence, there is a demand for the exploration of materials that feature not only THz PhPs at different spectral regimes, but also host anisotropic (directional) electrical, thermoelectric,
and vibronic properties. To that end, we introduce here the semiconducting vdW material alpha−germanium (II) sulfide (GeS) as an intriguing candidate. By employing THz nanospectroscopy supported by theoretical analysis, we provide a thorough characterization of the different in−plane hyperbolic and elliptical PhP modes in GeS. We find not only PhPs with long lifetimes (τ > 2 ps) and excellent THz light confinement (λ[₀]/λ) 45), but also an intrinsic, phonon-induced anomalous dispersion as well as signatures of naturally
occurring, substrate-mediated PhP canalization within a single GeS slab.

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale invariant. Thus, if the Standard Model is truly a part of the theory of Nature, then the proton mass is an emergent feature of QCD; and emergent hadron mass (EHM) must provide the basic link between theory and observation. Nonperturbative tools are necessary if such connections are to be made; and in this context, we sketch recent progress in the application of continuum Schwinger function methods to an array of related problems in hadron and particle physics. Special emphasis is given to the three pillars of EHM – namely, the running gluon mass, process-independent effective charge, and running quark mass; their role in stabilising QCD; and their measurable expressions in a diverse array of observables.

The thermodynamical conditions of plasma density, temperature, pressure and the neutron density produced in a laser-induced implosion of a deuterium-tritium (DT) filled capsule at the National Ignition Facility (NIF) are the closest laboratory analog of stellar conditions. We plan to investigate neutron-induced reactions on 40Ar, namely the 40Ar(n, 2n)39Ar(t1/2 =268 y), the 40Ar(n,gamma)41Ar(110 min) and the potential rapid two-neutron capture reaction 40Ar(2n,gamma)42Ar(33 y) in the same implosion on an Ar-loaded DT capsule. The chemical inertness of noble gas Ar enables reliable collection of the reaction products. We describe here the technique of Noble-Gas Accelerator Mass Spectrometry (NOGAMS) to be used for ultra-sensitive detection of the long-lived 39Ar and 42Ar at Argonne National Laboratory. A 42Ar(33 y) sample was produced via the slow two-neutron capture reaction 40Ar(2n, gamma)42Ar
in a high thermal-neutron flux irradiation. 39Ar and for the first time 42Ar atoms were directly detected in the abundance range 10^-12 -- 10^-13 .
The present sensitivity of 42Ar detection is of the order of 104 atoms.

Recently, experiments carried out with high-resolution measurement techniques showed the formation of a thin liquid microlayer (~µm) underneath a growing bubble in nucleate boiling. However, a deep understanding of the heat transfer enhancement induced by this microlayer is still lacking. In this work, we investigate the heat transfer characteristics of the microlayer in the early stage of nucleate boiling by using direct numerical simulations with the PHASTA solver. The microlayer formation and evaporation during the bubble growth driven by the local temperature gradient are simulated and fully resolved by very fine boundary layer meshes and the level-set method. We obtain the microlayer evolution comparable to recent experimental observations for the first time. The detailed microlayer dynamics indicates that the microlayer formation in the early stage of nucleate boiling can be considered a quasi-steady process without contact line motion. Furthermore, we find that the microlayer thickness is not determined by hydrodynamic effects, thus suggesting a rather constant microlayer heat transfer under different hydrodynamic conditions in nucleate boiling. Here, the local heat flux in the microlayer exceeds 20 MW/m2 near the contact line within 0.6 ms after the bubble inception, and the overall heat transfer from the microlayer evaporation contributes over 70% to the bubble growth. This value emphasizes the significance of microlayer evaporation in the modeling of nucleate boiling heat transfer.

Hypothesis: When a droplet starts sliding on a solid surface, the droplet-solid friction force develops in a manner comparable to the solid-solid friction force, showing a static regime and a kinetic regime. Today, the kinetic friction force that acts on a sliding droplet is well-characterized. But the mechanism underlying the static friction force is still less understood. Here we hypothesize that we can further draw an analogy between the detailed droplet-solid and solid-solid friction law, i.e., the static friction force is contact area dependent.
Methods: We deconstruct a complex surface defect into three primary surface defects (atomic structure, topographical defect, and chemical heterogeneity). Using large-scale Molecular Dynamics simulations, we study the mechanisms of droplet-solid static friction forces induced by primary surface defects.
Findings: Three element-wise static friction forces related to primary surface defects are revealed and the corresponding mechanisms for the static friction force are disclosed. We find that the static friction force induced by chemical heterogeneity is contact line length dependent, while the static friction force induced by atomic structure and topographical defect is contact area dependent. Moreover, the latter causes energy dissipation and leads to a wiggle movement of the droplet during the static-kinetic friction transition.

This paper presents the potential use of carbon sorbents in recovering rhenium(VII) from highly diluted electrolytes. Tests were performed using synthetic solutions containing selenium(VI) as an impurity. Adsorption of Re(VII) is selective with respect to selenium(VI). Activated carbon is a suitable sorbent for rhenium recovery because unlike ion-exchange resins, it has high chemical resistance and osmotic-shock resistance. The results show that the sorption mechanism is complex. Two follow-up processes occurred—physical adsorption and the reduction of Re(VII) to Re(VI). The processes were strongly influenced by the temperature. The lower the temperature, the higher the process efficiency. The observed sorption capacity was as high as 7.6 mg/g at 298 K and decreased as the temperature increased. The adsorption was a mixed-control process. Increasing the temperature altered the rate-limiting process. The activation parameters were determined using rate constant (k) and Arrhenius equation. In the first step, the activation energy was approximately 0 kJ mol-1. In the second step, the activation energy for k2,obs and k3,obs was determined as 57.3 kJ mol-1. The pre-exponential factors were calculated; their value was 2.98 × 107 min-1. For k1,obs, the activation energy was nearly 0 kJ mol-1.

Activities introduction of Molecular Dynamics simulation on bubble related issues in FWDF, HZDR.

Young contact angle is widely applied to evaluate liquid wetting phenomena on solid surfaces. For example, it gives a truncated-spherical shape prediction of a droplet/bubble profile through the Young-Laplace equation. However, recent measurements have shown the deviation of a microscopic droplet profile from the spherical shape, indicating that the conventional Young contact angle as the boundary condition is insufficient to describe the microscopic liquid wetting phenomena which play a critical role when nanobubbles on the wall. Here, we reveal a liquid-gas interface nano-bending, which is caused by the nonlinear coupling between the effects of the microscopic interface geometry and solid-liquid interactions and is responsible for this deviation. Based on molecular dynamics simulations and mathematical modeling, we describe the structure of the nano-bending and explain the mechanism of the nonlinear-coupled effect. We further apply our findings to illustrate the saddle-shaped profile in the vicinity near the contact region. The interface nano-bending, rather than the Young contact angle, acts as the boundary at the contact line and dictates the liquid wetting system. In this way, we succeed in accurately predicting the microlayer profile (µm thickness liquid film beneath a nucleation bubble) captured by different experiments. These findings not only provide insight into recent nano-scale droplet- and bubble-related wetting phenomena, but are also helpful for surface engineering concerning nano-scale wetting control.

Microlayer plays a critical role in the bubble dynamics and heat transfer in nucleate boiling. Yet, an accurate description of the microlayer has been a challenge for decades. In this work, we investigate the microlayer profile in the inertia-controlled bubble growth stage by using molecular simulations and mathematical modeling. A multiscale microlayer model was established through the disjoining pressure method and lubrication theory. Our model succeeds in accurately describing the microlayer profile captured by different experiments for the first time in decades. We reveal that the nonlinear coupling between microscopic liquid/vapor interface geometry and surface energy near the surface has a dominant effect on the overall microlayer profile. An interface nano-bending caused by the coupling acts as a three-dimensional boundary for the liquid wetting system and governs the wetting behavior. These findings provide insight into the understanding of heat transfer in nucleate boiling.

A formal introduction to density functional theory.

Flotation tailings from a former lead-zinc mine near Freiberg (Germany) consist of fine-grained quartz, feldspar, mica and the sulfide minerals pyrite, galena and sphalerite, which are not recovered by flotation. Sphalerite contains significant amounts of indium (up to 0.38 % (w/w)) in addition to iron, copper and cadmium, resulting in assumed average indium content of 30 mg/kg in the tailings. The presentation shows the development of biohydrometallurgical recovery of indium from laboratory to pilot scale. In a 2 m³ bioreactor, maximum zinc and indium leaching rates of 80 % were obtained at a pulp density of 25%. For the recovery of indium from the PLS (pregnant leaching solution), a stepwise precipitation process is being developed consisting of a combined iron/indium precipitation and a subsequent treatment of the indium precipitate product. A new project has been started in which a modular plant for the utilization of valuable materials from these sulfide tailings and their environmentally friendly remediation is being set up directly at the tailings site. Combining resource technology to utilize valuable elements (indium and zinc) from tailings and environmental technology to eliminate harmful substances (arsenic and cadmium) with the use of inert components (e.g. as building material) represents a win-win situation. After its completion, the modular plant consists of three parts: the leaching, the recyclables and the environmental modules. Results and findings of the project will be processed for environmental education in schools and used for the development of a web application (app) that can be used to content for integration into existing tourism concepts. Through the implementation of the aforementioned goals, the project provides a decisive contribution to the structural change in the region, as it a concept for linking rehabilitation and secondary raw material extraction and a possible economic and touristic reuse.

The researches on nuclear reactor thermal-hydraulics have achieved outstanding progresses in the past decades. In recent years, basic research on multiphase flow dynamics and corresponding measurement technology, as well as preliminary research on Gen IV reactors based on experiments and simulations are attracting more and more attention. However, the inside complicated physics and outside extreme conditions will also bring risks and challenges to the development of nuclear industry.

It is well known that a magnetohydrodynamic dynamo, i.e. the
generation of a magnetic field from a flow of an electrically
conductive fluid, takes or took place in the interior of the Sun or
stars as well as in planets and smaller celestial bodies like the
ancient moon or the asteroid Vesta. The ubiquity and diversity of
astrophysical dynamo action and its great importance for formation and
evolution of the objects generating them has motivated related studies
in the laboratory. Currently, a new dynamo experiment is under
construction at Helmholtz-Zentrum Dresden-Rossendorf within the
project DRESDYN (DREsden Sodium facility for DYNamo and
thermohydraulic studies). In that experiment a flow of liquid sodium
will be driven by precession of a cylindrical container. Previous
experiments by Gans (1971) and more recent numerical models
indicate that dynamo action can be expected in the vicinity of the
transition from a laminar flow state to vigorous turbulence if the
system is sufficiently large.

In our contribution we describe the progress in construction of the
experiment and present new results from simulations and accompanying
water experiments in which the precession-driven flow was recorded
with Ultrasonic Doppler Velocimetry (UDV) and Particle Image
Velocimetry (PIV). The analysis of the data by means of the
decomposition into different classes of inertial modes provides an
impression of flow features, which are supposed to be beneficial for
the dynamo, like axisymmetric large scale flow modes, shear layers due
to the modification of the rotational base flow, or the appearance of
intermittent mid-scale vortices. Our focus will be on the influence of
the precession angle on the fluid flow and the dynamo, as well as
on investigating the possibility of increasing the internal flow
amplitude by means of baffles mounted at the end caps of the
container. The main aim is to provide general global characteristics
that are also relevant for a more natural spherical/spheroidal
geometry.

Precession represents a possibility to power the early geodynamo or the ancient lunar dynamo.
Precession driven dynamo action was found in simulations in various geometries (sph/cyl/cube).
related experiments by R. Gans yield an amplification of an external field by a factor of three.

There is no abtract.

The planned liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) is a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. Most ambitious experiment will be a large-scale precession driven dynamo experiment. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo (Malkus, Science 1968, 160, 3825) or the ancient lunar dynamo (Noir and Cebron 2013, JFM, 737, 412; Dwyer et al. 2011, Nature, 479, 7372; Weiss et al. 2014, Science 346, 1246753). Precessional forcing is of great interest from the experimental point of view, because it represents a natural mechanism which allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Currently, we conduct preparative studies that involve numerical simulations and flow measurements at a downscaled model experiment filled with water. These studies aim at the design of the planned large scale experiment and provide parameter island where dynamo action is most likely.

The growth of single hydrogen bubbles at micro-electrodes is studied in an acidic electrolyte over a wide range of concentrations and cathodic potentials. New bubble growth regimes have been identified which differ in terms of whether the bubble evolution proceeds in the presence of a monotonic or oscillatory variation in the electric current and a carpet of microbubbles underneath the bubble. Key features such as the growth law of the bubble radius, the dynamics of the microbubble carpet, the onset time of the oscillations and the oscillation frequencies have been characterized as a function of the concentration and electric potential. Furthermore, the system's response to jumps in the cathodic potential has been studied. Based on the analysis of the forces involved and their scaling with the concentration, potential and electric current, a sound hypothesis is formulated regarding the mechanisms underlying the micro-bubble carpet and oscillations.

Ultrasound application presents a promising non-intrusive way to enhance and facilitate
mass transfer in aqueous systems. This enhanced mass transfer can influence
the sorption processes in multiphase flows. Previous studies investigating the
impact of ultrasound on sorption, have reported an increase in either desorption
due to the rise in liquid temperature or adsorption due to the additional convective
mass transfer resulting from acoustic streaming. In this study, low intensity
ultrasound with a frequency of 36 kHz was deployed to evaluate the sorption process
of Triton X-100 on the surface of a single bubble, placed along the standing
acoustic wave using profile analysis tensiometry. Furthermore, microscopic particle
image velocimetry was used to understand the role acoustic streaming might
play during different stages of the sorption process. Contrary to expectations, the
results showed no considerable change in surface tension and sorption dynamics
after sonicating both fresh and surfactant-loaded bubbles. The results of this study
suggest that the observations from previous studies may be attributed to the additional
energy input of the acoustic wave into the system rather than the presence
of an external acoustic field.

Monolayers of platinum tellurides are particularly interesting 2D materials because they exhibit phases with different stoichiometries and electronic properties. Specifically, PtTe₂ is a narrow gap semiconductor while Pt₂Te₂ is a metal. Here we show that the former can be transformed into the latter by reaction with vapor-deposited Pt atoms. Owing to low surface diffusion barriers of Pt ad-atoms, the transformation occurs by nucleating the Pt₂Te₂ phase within the PtTe₂ islands, so that a metal-semiconductor lateral junction is formed. Using scanning tunneling microscopy/spectroscopy, the electronic structure of this lateral junction is studied. A flat band structure is found with the Fermi-level of the metal aligning with the Fermi-level of the intrinsically p-doped PtTe₂ suggesting low contact resistance. This flat band is achieved by an interface dipole that accommodates the ~0.2 eV shift in the work functions of the two materials. First-principles calculations indicate that the origin of the interface dipole is the atomic scale charge redistributions at the heterojunction. The demonstrated compositional phase transformation of a 2D semiconductor into a 2D metal is a promising approach for making in-plane metal contacts that are required for efficient charge injection and is of particular interest for semiconductors with large spin-orbit coupling, like PtTe₂.

Charge transfer and mass transport are directly linked with operating batteries. In liquid metal batteries (LMBs) additional flow phenomena heavily influence the cell performance. Those have widely been investigate numerically as well as experimentally. But, concentration gradients due to mass transport were mostly neglected in previous research – especially in the electrolyte. Implementing the prevalent equations into the finite volume solver OpenFOAM and investigating mass transfer overpotentials in the electrolyte independently revealed that they can have a significant influence on the cell performance. So, the interplay between flow phenomena and electrochemical transport should be subject of future investigations.
Na||Zn batteries differ from the previously investigated “classical” LMBs, hence it is important to asses the possible flow phenomena and their area of occurrence.

We demonstrate the fluidics-based low-cost methodology to reproducibly generate the alginate and alginate-chitosan microcapsules and apply it to grow human hepatoma (HepG2) spheroids of different dimensions and geometries. Focusing specifically on the composition and thickness of the hydrogel shell, permeability of the microcapsules was selectively tuned. The diffusion of the selected benchmark molecules through the shell has been systematically investigated using both, experiments and simulations, which is essential to ensure efficient mass transfer and/or filtering of the biochemical species. Depending on available space, phenotypically different 3D cell assemblies have been observed inside the capsules, varying in the tightness of cell aggregations and their shapes. Metabolic activity of spheroids in microcapsules was confirmed by tracking the turnover of testosterone to androstenedione with chromatography studies in a metabolic assay. Because of the facile tuning of the shell thickness and permeability, we believe that our system is suitable for studying the formation of cancer spheroids and their functional interaction with the surrounding microenvironment.

Der zunehmende Anteil fluktuierender Stromerzeuger erfordert den Ausbau der Speicherkapazität, wenn die Elektrizitätsversorgung weitgehend nachfrageorientiert geschehen soll. Der Vortrag geht auf verschiedene Aspekte der Speicherproblematik ein und legt den Schwerpunkt dabei auf Flüssigmetall- und Salzschmelzenbatterien.

There is a close and multifaceted relation between fluid dynamics and
the charge/discharge behavior of liquid metal batteries. The talk will
give an overview of experimental and - to a minor extend - numerical
work on instabilities that might be relevant for the operational
safety of large cells and on flows that are able influence mass
transport overvoltages, like solutal and thermal convection.

In mineral processing, froth flotation is based on recovering valuable mineral particles by means of the overflowing froth. Industrial-scale froth flotations cells are typically equipped with optical measurement systems, which monitor bubble sizes and flow velocities at the froth surface. However, the velocity profile of the overflowing froth underneath its free surface is not accessible by optical observation. The present study combines X-ray radiography and particle tracking velocimetry in a laboratory-scale experiment, aiming to measure local flow velocities within an opticially opaque foam at a horizontal overflow. For this purpose, we prepared custom-tailored tracer particles: light- weight tetrahedra with an edge length of 4 mm were 3D-printed from a polymer material, and metal beads of 0.5 mm in diameter glued at each corner of a tetrahedron served as radiopaque features. In parallel to the velocity measurements by means of X-ray particle tracking, we determined the liquid fraction of the overflowing foam by electric conductivity measurements using electrode pairs. The experiment was performed with aqeuous foams of two different surfactant concentrations, but similar bubble size range and superficial gas velocity, yielding around 10 % liquid fraction near the overflow. Employing the particles as tools for flow tracing in X-ray image sequences, we identified an unexpected velocity maximum underneath the free surface of the overflowing foam. In a sequel, we will compare the X-ray radiographic measurements with optical measurements of the foam flow velocity through a transparent wall and at the free surface.

Flotation is a separation process in which hydrophobic particles inside a liquid bath
attach to uprising bubbles, which subsequently form a froth layer on the liquid
surface. This froth phase, which consist of foam with particles, has a large impact on
the transport of separated materials and therefore the overall process efficiency.
Despite the importance for process control, a notable lack of suitable techniques for
on-line characterization of the froth’s properties such as the liquid fraction or particle
content can be found. An potential approach to gain information on the different
phase fractions in froth is the application of low-frequency ultrasound measurement
techniques. In this contribution an overflowing froth containing varying mass fractions
of Quartz particles and liquid is analyzed using combined optical and ultrasonic
measurements. The measured intensity of the ultrasonic reflections sent from above
the froth’s surface correlate to the fraction of solids inside the froth (Figure 1).
Therefore it is shown, that current optical froth characterization techniques can be
improved by incorporating ultrasonic measurements, which can be seen as a first
step towards advanced process control in industrial flotation processes.

An inconsistency exists in bubble force models used in the standard Euler-Euler simulations. The bubble force models are typically developed by assuming that the forces act on the bubbles' centers of mass. However, in the standard Euler-Euler model, each bubble force is a function of the local gas volume fraction because the phase-averaging method is used. This inconsistency can lead to gas over-concentration in the center or near the wall of a channel when the bubble diameter is larger than the computational cell size. Besides, a mesh-independent solution may not exist in such cases. In addition, the bubble dimension is not fully considered in the standard Euler-Euler model.
In the present study, a particle-center-averaging method is used to represent the bubble forces as forces that act on the bubbles' centers of mass. A particle-center-averaged Euler-Euler approach for bubbly flow simulations is developed by combining the particle-center-averaged Euler-Euler framework with a Gaussian convolution method. The convolution method is used to convert the phase-averaged and the particle-center-averaged quantities. The test results illustrate that the particle-center-averaging method alleviates the over-prediction of the gas volume fraction peak in the channel center and provides a mesh-independent solution. In the particle-center-averaged Euler-Euler model, the bubble dimension is fully considered and bubble deformation can be considered by using anisotropic diffusion in quantities conversion.

Since 2011, fluid dynamics research in liquid metal batteries has been pursued at HZDR, with multiple flow instabilities identified as critical for safe and efficient operation. This is still an ongoing process from which new research topics are constantly emerging. In the poster presentation, I will introduce two future research projects closely connected to liquid metal batteries: firstly, a new model experiment to study the metal pad roll instability, which is currently under preparation in the framework of a recently approved DFG project. Secondly, we are planning another project on the investigation of different solutal- and electrocapillary flow phenomena, hitherto widely disregarded in the context of liquid metal batteries.

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

We present a new shallow-water formulation of forced magnetohydrodynamic Ross-
by waves originating in the tachocline of solar-like stars. As a novelty to former descriptions,
we add an external tidal potential to the equations and further include a linear damping law,
allowing us to study wave motions driven by arbitrary tidal forces. The model is applied to the
specific case of our sun, where we consider the action of the tidally dominant planet Jupiter.
We present an explicit analytic solution to this problem, which we finally use to estimate
characteristic responding wave amplitudes.

Electrochemical energy conversion technologies play a crucial role in space missions,
for example, in the Environmental Control and Life Support System (ECLSS) on the
International Space Station (ISS). They are also vitally important for future long-term
space travel for oxygen, fuel and chemical production, where a re-supply of resources
from Earth is not possible. Here, we provide an overview of currently existing
electrolytic energy conversion technologies for space applications such as proton
exchange membrane (PEM) and alkaline electrolyzer systems. We discuss the
governing interfacial processes in these devices influenced by reduced gravitation and
provide an outlook on future applications of (photo)-electrolysis systems in, e.g., in-
situ resource utilization (ISRU) technologies. A perspective of computational modelling
to predict the impact of the reduced gravitational environment on governing
electrochemical processes is also discussed and experimental suggestions to better
understand efficiency-impacting processes such as gas bubble formation and
detachment in reduced gravitational environments are outlined

The magnetization of crystalline red diamond bulk samples were investigated in the temperature range between 2 K and 125 K and with the applied maximal magnetic field of ±7 T. The investigated diamond samples are of Type Ib with a nitrogen content less than 200 ppm. Diamonds without any treatment display a yellow color and were transformed to red color after irradiation with 10 MeV electrons at T = 900 °C, in vacuum, owing to the formation of nitrogen-vacancy centers. Field dependent magnetization m(H) measurements for temperatures T ≲ 10 K show unusual hysteresis loops, which we interpret as consequence of the superposition of coexisting superconducting and paramagnetic regions present in the sample. Temperature dependence of the magnetization m(T) measured in the zero field and field cooled modus shows a paramagnetic behavior accompanied with an irreversibility for T ≲ 13 K, while at higher temperatures shows a diamagnetic behavior which is similar to undoped diamond. Coexistence of superconductivity and paramagnetism is established because both phenomena exist in the same temperature range and fits done to the m(H) using an equation based upon Bean model, support our conclusion. Room temperature confocal photoluminescence measurements were done on both yellow and red diamond, showing that in the red diamond the amount of neutral NV° and negative charged nitrogen-vacancy centers NV° have been significantly created. The transformation process from yellow to red diamond has mainly caused the alteration of the superparamagnetic regions into paramagnetic, while the superconducting contribution of the sample was less affected, according to the parameters obtained after we fitted the field dependent magnetization results.

The direct chemical reactivity between phosphorus and nitrogen was induced under high-pressure and high-temperature conditions (9.1 GPa and 2000−2500 K), generated by a laser heated diamond anvil cell and studied by synchrotron X-ray diffraction, Raman spectroscopy, and DFT calculations. α-P3N5 and γ-P3N5 were identified as reaction products. The structural parameters and vibrational frequencies of γ-P3N5 were characterized as a function of pressure during room-temperature compression and decompression to ambient conditions, determining the equation of state of the material up to 32.6 GPa and providing insight about the lattice dynamics of the unit cell during compression, which essentially proceeds through the rotation of the PN5 square pyramids and the distortion of the PN4 tetrahedra. Although the identification of α-P3N5 demonstrates for the first time the direct synthesis of this compound from the elements, its detection in the outer regions of the laser-heated area suggests α-P3N5 as an intermediate step in the progressive nitridation of phosphorus toward the formation of γ-P3N5 with increasing coordination number of P by N from 4 to 5. No evidence of a higher pressure phase transition was observed, excluding the existence of predicted structures containing octahedrally hexacoordinated P atoms in the investigated pressure range.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications.
On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH₁₀, encounters a serious complication because of the large upper critical magnetic field H_c2(0), exceeding 120–160 T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH₁₀: each at% of Nd causes a decrease in T_c by 10–11 K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68 T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H₁₀ demonstrates completely linear H_c2(T) ∝ |T – T_c|, which calls into question the applicability of the Werthamer–Helfand–Hohenberg model for polyhydrides. The suppression of superconductivity in LaH₁₀ by magnetic Nd atoms and the robustness of T_c with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson’s theorem gives new experimental evidence of the isotropic (s-wave) character of conventional electron–phonon pairing in lanthanum decahydride.

In the industry 4.0 eco-system, flexible electronic devices bear a huge potential for a broad range of applications due to their diverse properties, such as high stretchability, biocompatibility, portability, light weight, and low costs. In this work, Cobalt-samarium permanent magnetic thin films on flexible polyimide substrate are studied. The influence of the sputter deposition pressure on the structural, morphological, and magnetic properties is analyzed. A method for growing flexible magnetic films is proposed by achieving a maximum coercivity of 13.86 kOe and an energy product of 16.9 MGOe. These results lay the foundations for the design and fabrication of flexible magnetic devices.

We report a comprehensive study of the static susceptibility, high-field magnetization and highfrequency/high-magnetic field electron spin resonance (HF-ESR) spectroscopy of polycrystalline samples of the bismuth cobalt oxyphosphate BiCoPO₅. This compound features a peculiar spin system that can be considered as antiferromagnetic (AFM) chains built of pairs of ferromagnetically coupled Co spins and interconnected in all three spatial directions. It was previously shown that BiCoPO₅ orders antiferromagnetically at T_N ≈ 10 K and this order can be continuously suppressed by magnetic field towards the critical value μ₀H_c ≈ 15 T. In our experiments we find strongly enhanced magnetic moments and spectroscopic g factors as compared to the expected spin-only values, suggesting a strong contribution of orbital magnetism for the Co²⁺ ions. This is quantitatively confirmed by ab initio quantum chemical calculations.Within the AFM ordered phase, we observe a distinct field-induced magnetic phase transition. Its critical field rises to ∼6 T at T << T_N. The HF-ESR spectra recorded at T << T_N are very rich comprising up to six resonance modes possibly of the multimagnonic nature that soften towards the critical region around 6 T. Interestingly, we find that the Co moments are not yet fully polarized at H_c which supports a theoretical proposal identifying H_c as the quantum critical point for the transition of the spin system in BiCoPO₅ to the quantum disordered state at stronger fields.

The increasing demand for computer data storage with a higher recording density can be addressed by using smaller magnetic objects, such as bubble domains. Small bubbles predominantly require a strong saturation magnetization combined with a large magnetocrystalline anisotropy to resist self-demagnetization. These conditions are well satisfied for highly anisotropic materials. Here, we study the domain structure of thin Nd₂Fe₁₄B lamellae. Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions. The stripe domain width and the bubble size are both thickness dependent. Furthermore, a kind of bubble was observed below the spin-reorientation transition temperature that combine bubbles with opposite helicity. In this paper, we reveal Nd₂Fe₁₄B to be a good candidate for a high-density magnetic bubble-based memory.

We report the structural and magnetic properties of a new spin-1/2 antiferromagnet NaZnVOPO₄(HPO₄) studied via x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, and ³¹P nuclear magnetic resonance (NMR) measurements, as well as density-functional band-structure calculations. While thermodynamic properties of this compound are well described by the J₁-J₂ square-lattice model, ab initio calculations suggest a significant deformation of the spin lattice. From fits to the magnetic susceptibility we determine the averaged nearest-neighbor and second-neighbor exchange couplings of J₁ ≃ −1.3 K and J₂ ≃ 5.6 K, respectively, resulting in the effective frustration ratio α = J₂/J₁ ≃ −4.3 that implies columnar antiferromagnetic order as the ground state. Experimental saturation field of 15.3 T is consistent with these estimates if 20 % spatial anisotropy in J₁ is taken into account. Specific heat data signal the onset of a magnetic long-range order at T_N ≃ 2.1 K, which is further supported by a sharp peak in the NMR spin-lattice relaxation rate. The NMR spectra mark the superposition of two P lines due to two nonequivalent P sites where the broad line with the strong hyperfine coupling and short T₁ is identified as the P(1) site located within the magnetic planes, while the narrow line with the weak hyperfine coupling and long T₁ is designated as the P(2) site located between the planes.

A first-principles approach combining density-functional and dynamical mean-field theories in conjunction with a quasiatomic approximation for the strongly localized 4 f shell is applied to Nd₂Fe₁₄B-based hard magnets to evaluate crystal-field and exchange-field parameters at rare-earth sites and their corresponding single-ion contribution to the magnetic anisotropy. In pure Nd₂Fe₁₄B, our calculations reproduce the easy-cone to easy-axis transition; theoretical magnetization curves agree quantitatively with experiment. Our study reveals that the rare-earth single-ion anisotropy in the 2-14-1 structure is strongly site dependent, with the g rare-earth site exhibiting a larger value. In particular, we predict that increased f- and g-site occupancy of R = Ce and Dy, respectively, leads to an increase of the magnetic anisotropy of the corresponding (Nd, R)₂Fe₁₄B-substituted
compounds.

The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure-induced face-centered cubic (fcc) to hexagonal close-packed (hcp) martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed transformation progress at the atomic level by employing in situ x-ray diffraction and absorption spectroscopy.We evidenced a four-stage pathway and suggest that the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain.We also determined precisely the effect of the transformation on the compression behavior of these materials.

Cr-doped UO2 is a leading accident tolerant nuclear fuel where the complexity of Cr chemical states in the bulk material has prevented acquisition of an unequivocal understanding of the redox chemistry and mechanism for incorporation of Cr in the UO2 matrix. To resolve this, we have used electron paramagnetic resonance, high energy resolution fluorescence detection X-ray absorption near energy structure and extended X-ray absorption fine structure spectroscopic measurements to examine Cr-doped UO2 single crystal grains and bulk material. Ambient condition measurements of the single crystal grains, which have been mechanically extracted from bulk material, indicated Cr is incorporated substitutionally for U+4 in the fluorite lattice as Cr+3 with formation of additional oxygen vacancies. Bulk material measurements reveal the complexity of Cr states, where metallic Cr (Cr0) and oxide related Cr+2 and Cr+32O3 were identified and attributed to grain boundary species and precipitates, with concurrent (Cr+3xU+41-x)O2-0.5x lattice matrix incorporation. The deconvolution of chemical states via crystal vs. powder measurements enables the understanding of discrepancies in literature whilst providing valuable direction for safe continued use of Cr-doped UO2 fuels for nuclear energy generation.

Aufgrund des hohen Energiebedarfs thermischer Trennverfahren werden trennwirksame Einbauten in Kolonnen stetig weiterentwickelt und optimiert. In Bodenkolonnen kommen hierbei verstärkt Ventilböden mit Fixed Valves und Float Valves zum Einsatz, bei denen im Gegensatz zu den in der Literatur bereits ausführlich untersuchten Siebböden noch großes Forschungspotential besteht.

Eine essenzielle fluiddynamische Größe ist dabei die Zweiphasenschichthöhe, die einen großen Einfluss auf den Stoffaustausch auf dem Boden hat. Trotz ihrer großen Bedeutung wird diese Messgröße im Rahmen von fluiddynamischen Untersuchungen bisher hauptsächlich visuell abgeschätzt, was keine objektive Wiederholbarkeit gewährleistet und somit zu großen Unsicherheiten führt. Um verlässliche Aussagen zur Zweiphasenschichthöhe treffen zu können, ist daher die Aufzeichnung objektiver Messgrößen und Anwendung automatisierter Auswerteverfahren erforderlich.

Im Rahmen des AiF-Forschungsvorhabens Werkzeuge und Methoden zur verbesserten fluiddynamischen Auslegung von Querstromböden mit Hochleistungsventilen wurden zwei unabhängige Messmethoden eingesetzt, die im Rahmen dieses Beitrags vergleichend bewertet werden. Als erste Methode wurden Messungen mit dem Lichtvorhang Rapidoscan® durchgeführt, der mittels Infrarot-Strahlung die Zweiphasenschicht nicht-invasiv auf dem Boden detektieren kann. Als zweite Methode kam ein vom Helmholtz-Zentrum Dresden-Rossendorf (HZDR) entwickelter Feldsensor zum Einsatz, der mit 360 Elektrodenpaaren die Phasenverteilung in mehreren Ebenen über dem Boden vermisst. Hieraus lässt sich ein dreidimensionales Feld der Phasenverteilung rekonstruieren, das ebenfalls Rückschlüsse auf die Zweiphasenschichthöhe zulässt.

Die Messungen wurden an einem Gas/Flüssig-Kolonnenversuchsstand am Lehrstuhl für Anlagen- und Prozesstechnik der TU München durchgeführt, der einen Durchmesser von 1,2 m aufweist und mit dem Stoffsystem Luft/Wasser betrieben wurde. Vermessen wurden fünf verschiedene Bodenkonfigurationen von Sieb- und Fixed-Valve-Böden, die unter Berücksichtigung von relevanten in der Industrie eingesetzten Ventiltypen ausgewählt wurden.

Die Untersuchungen mit dem Feldsensor geben detaillierte Informationen zur Phasenverteilung der Zweiphasenschicht auf dem Boden bei verschiedenen
Belastungszuständen. Auf Grundlage der gewonnenen topographischen Daten können zudem Aussagen über die Höhe der Zweiphasenschicht getroffen und ein Vergleich der beiden Messmethoden vorgenommen werden. Abschließend werden daraus abgeleitete Erkenntnisse zur Gültigkeit und Anwendbarkeit von bekannten Zweiphasenschichtmodellen aus der Literatur vorgestellt.

Real-time monitoring of gas-liquid pipe flow is highly demanded in industrial processes in the chemical and power engineering sector. Therefore, the present contribution describes the novel design of a robust wire-mesh sensor with integrated data processing unit. The developed device features a sensor body for industrial conditions of up to 400°C and 135 bar as well as real-time processing of measured data including phase fraction calculation, temperature compensation and flow pattern identification. Furthermore, user interfaces are included via a display and 4...20 mA connectivity for the integration into industrial process control systems. In the second part of the contribution we describe the experimental verification of the main functionalities of the developed system. Firstly, the calculation of cross-sectionally averaged phase fractions along with temperature compensation was tested. Considering temperature drifts of up to 55 K, an av-erage deviation of 3.9% across the full range of phase fraction was found by comparison against image references from camera recordings. Secondly, the automatic flow pattern identification was tested in an air-water two-phase flow loop. The results reveal reasonable agreement with well-established flow pattern maps for both horizontal and vertical pipe orientation. The present results indicate that all prerequisites for an application in industrial environments in near future are fulfilled.

In deep geological repositories for nuclear waste, the surrounding rock formation serves as an important barrier against radionuclide migration. Multiple potential host rocks contain phyllosilicates, which have shown high efficiency in radionuclide sorption. Recent experimental studies reported a heterogeneous distribution of adsorbed radionuclides on nanotopographic mineral surfaces. In this study, we investigated the energetic differences of surface sorption sites available at nanotopographic structures such as steps, pits, and terraces. Eleven important surface sites were selected and the energies of ad- and desorption reactions were obtained from density functional theory calculations. The adsorption energies were then used for the parameterization of a kinetic Monte Carlo model simulating the distribution of adsorbed europium on a typical nanotopographic muscovite surface. On muscovite, silicon step sites are favorable for europium sorption and lead to an increased adsorption in regions with high step concentrations. Under identical chemical conditions, sorption on typical nanotopographic surfaces is increased by a factor of three compared to atomically flat surfaces. Desorption occurs preferentially at terrace sites, leading to an overall 2.5 times increased retention at nanotopographic structures. This study provides a mechanistic explanation for heterogeneous sorption on nanotopographic mineral surfaces due to the availability of energetically favorable sorption sites.

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.

Recently, it was shown that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. In this article, we demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.
In our experiments, p-GaN on sapphire samples were cleaned with 99 % ethanol in an ultrasonic bath, followed by a thermal cleaning in a vacuum with the intention to remove carbon and oxygen contaminations on the p-GaN surface. Although still some carbon remained on the surface, the p-GaN was successfully activated by the deposition of a thin layer of cesium. Quantum efficiencies (QE) of
3 - 9 % were achieved. XPS photoemission spectra show a shift towards higher binding energies for the photoemission peaks, which is caused by a new component, so-called organic – cesium.
During the storage under ultra – high vacuum, the GaN:Cs photocathodes were measured from time to time in the photocurrent and by XPS. We found a shift of 0.35 eV towards lower binding energies, which is related to the formation of the organic – cesium islands. This island growth is assumed to be in close correlation to the photocathode degradation.
The p-GaN:Cs photocathodes showed a big QE loss after XPS analysis and therefore we investigated the potential damage from x-ray irradiation. The long-time irradiation experiments show that the x-ray damage has a high influence on the cesium component and the degradation of the p-GaN:Cs photocathode.

PSMA-PET/CT for imaging prostate cancer (PC) has spread worldwide since its clinical introduction in 2011. The majority of experiences have been collected for PSMA-PET-imaging of recurrent PC. Data for primary staging of high-risk PC are highly promising. Meanwhile, a plethora of PSMA-ligands are available for clinical use (e.g. 68Ga-PSMA-11, 68GaPSMA-I&T, 68Ga-PSMA-617, 18F-DCFBC, 18F-DCFPyL, 18F-PSMA-1007, 18F-rhPSMA-7 and 18F-JK-PSMA-7). However, an official approval is available only for 68Ga-PSMA-11 (approved by the US FDA in 2020) and 18F-DCFPyL (approved by the US FDA in 2021).
Recommendations for acquisition times vary from 1-2h p.i. It has been shown that for the majority of tumour lesions, the contrast in PSMAPET/CT increases with time. Therefore, additional late imaging can help to clarify unclear findings. PSMA-PET/CT should be performed prior to commencing an androgen deprivation therapy (ADT) since (long term) ADT reduces the visibility of PC lesions.
Following injection of PSMA-ligands, hydration and forced diuresis are recommended for PSMA-ligands with primarily excretion via the kidneys in order to increase the visibility of tumour lesions adjacent to the urinary bladder.
PSMA-ligands are physiologically taken up in multiple normal organs. For some 18F-labelled PSMA-ligands, presence of unspecific focal bone uptake has been reported. When using these tracers, focal bone uptake
without CT-correlate should be interpreted with great caution. Besides prostate cancer, practically all solid tumors express PSMA in their neovasculature thereby taking up PSMA-ligands, although usually at a lower extent compared to PC. Also multiple benign lesions and inflammatory processes (e.g. lymph nodes) take up PSMA-ligands, also
usually at lower extent compared to PC.

Achieving an atomically clean surface is an important step to improving the quality of semiconductor photocathodes, but it is a challenging requirement for surface treatment [1]. In order to understand the surface during the cleaning, the cesium deposition, and the storage of the photocathode, the use of an x-ray photoelectron spectrometer (XPS) is needed. The XPS probes the electronic structure of the p-doped gallium nitride (GaN) photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels of Ga, N, O, C and Cs are monitored.

Warm dense matter (WDM) an extreme state that is characterized by extreme densities and temperatures has emerged as
one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects
such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for cutting-edge technological
applications such as inertial confinement fusion and the discovery of novel materials.
In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated
unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1].
Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is
a notoriously difficult task [2].
In this talk, I give an overview of recent developments in this field [3,4,5], which will allow for a rigorous treatment of the
intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects based on approximation-
free quantum Monte Carlo (QMC) simulations. Finally, I will present a new idea to extract the exact temperature [6] and
other material properties [7] from an X-ray Thomson scattering experiment without any models or simulations.
[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
[2] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[3] T. Dornheim et al., Physics Reports 744, 1-86 (2018)
[4] T. Dornheim et al., Physical Review Letters 121, 255001 (2018)
[5] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[6] T. Dornheim et al., arXiv:2206.12805
[7] T. Dornheim et al., arXiv:2209.02254

Previously, we found that tetravalent actinides (An4+, An = Th, U, Np) in HNO3(aq) commonly afford sparingly soluble salts of [An(NO3)6]- with anhydrous H+ countercations stabilized by hydrogenbonding with bis(2-pyrrolidone) linker molecules selected appropriately. In contrast, this is not the case for Zr4+ in Group IV probably due to difference in the ionic radius. This fact motivated us to know how Ce(IV) behaves under the same condition. As a result, we have found that, after loading bis(2-pyrrolidone) linker molecule having trans-1,4-cyclohexyl bridging moiety (L), Ce(IV) in HNO3(aq) exclusively provides one of different crystalline phases, (HL)2[Ce(NO3)6] or [Ce2(mu-O)(NO3)6(L)2]n 2D MOF, depending on [HNO3]. The former has been obtained at [HNO3] = 4.70-9.00 M, and is isomorphous with the analogous (HL)2[An(NO3)6] we reported previously. In contrast, deposition of the latter phase at the lower [HNO3] conditions (1.00-4.30 M) demonstrates that hydrolysis and oxolation of Ce4+ proceeds even below pH 0 to provide a [Ce-O-Ce]6+ unit included in this compound. These different Ce(IV) phases are exchangeable each other under soaking in HNO3(aq), implying those chemical equilibria of dissolution/deposition of these crystalline phases, hydrolysis and oxolation of Ce4+, and its complexation with NO3- occur in parallel. Indeed, such coordination chemistry of Ce(IV) in HNO3(aq) was well corroborated by 17O NMR, Raman, and IR spectroscopy.

While antiferromagnets with the easy axis of anisotropy are considered to be robust against external magnetic fields of a moderate strength, strong-field-driven spin reorientations provide an insight into subtle properties of the material usually hidden by the high symmetry of the ground state. Here, we address theoretically the effects of curvature in the curvilinear antiferromagnetic achiral anisotropic ring-shaped spin chains in strong magnetic fields. We identify the geometry-driven helimagnetic phase transition above the spin-flop field between the vortex and onion states. The spin-flop transition is of the first- or second-order depending on the ring curvature, which is influenced by the geometry-induced Dzyaloshinskii–Moriya interaction. Inhomogeneity of the Néel vector distribution in spin-flop phase generates weakly ferromagnetic response, which lies in the plane perpendicular to the applied magnetic field. Our findings provide an understanding of complex responses of curvilinear antiferromagnets on magnetic fields and allow further experimental study of geometrical effects relying on spin-chain-based nanomagnets.

Uncertainty quantification for neural network models

We strive to popularize the usage of uncertainty quantification methods in machine learning through publications and application in various projects covering diverse fields from regression and classification to instance segmentation. In addition, we employ domain shift detection techniques to tackle population-level out-of-distribution scenarios. In all cases, the goal is to assess model prediction validity given unseen test data.

The zirconia (ZrO2) crystal structure can incorporate a variety of metal cations with differing oxidation states up to high dopant loadings, which is why the material has been considered as a potential host phase for the immobilization of especially actinide elements present in specific high-level waste streams. Furthermore, zirconia is the main corrosion product of the Zircaloy cladding material surrounding nuclear fuel rods. The corrosion of Zircaloy and subsequent formation of zirconia already occurs during reactor operation and is expected to proceed during long-term disposal of the spent nuclear fuel (SNF) assemblies. Thus, during final storage, zirconia may play an important role as the first retention barrier for released radionuclides. ZrO2 is monoclinic phase at ambient conditions, and transforms into tetragonal and cubic phases at high temperatures of around 1200 °C and 2370 °C, respectively. However, particle size effects, the incorporation of foreign ions such as the actinides, as well as high radiation fields are known to also influence the stability fields of the polymorphs.
In the present work, the incorporation of the trivalent actinide curium in the pristine, monoclinic ZrO2 structure has been investigated following synthesis (i) in aqueous solution at 80°C for several weeks [1], and (ii) at high temperatures (1000°C, 5h) [2]. The evolution of the ZrO2 crystal structure during synthesis was analyzed with powder x-ray diffraction, while the Cm-environment was studied via luminescence spectroscopy. For the syntheses, a hydrous zirconia phase was precipitated in the presence of Cm from alkaline NaCl solutions at pH 12. The precipitate was thereafter either re-suspended in 0.5 M NaCl at pH 5 or pH 12 and hydrothermally treated at 80°C for up to 117 days, or calcined at 1000°C for 5 hours. The hydrothermal samples at pH 12, show crystallization of the amorphous ZrO(OH)2 phase to a mixture of monoclinic and tetragonal ZrO2 after 16 d at 80°C. In contrast, the samples at pH 5 show no crystallinity even after 32 days. Luminescence emission spectra indicate the presence of two Cm-environments in the amorphous precipitate. With increasing crystallinity, a bathochromic shift and a narrowing of the emission spectra can be seen. The shift is untypically large, resulting in emission peak maxima at around 650 nm for crystalline ZrO2. A similar, equally pronounced shift is obtained for Cm incorporated into the monoclinic ZrO2 structure following calcination. Therefore, the actinide speciation seems to be identical in the solid phases obtained with the two different synthesis methods, at least for the fully crystalline solids. These combined results imply that actinides are incorporated into the crystal structure of ZrO2, even at low concentrations where no structural transformations take place, which in turn speaks for zirconia as a good retention barrier for released trivalent actinides from the SNF matrix.

Neurological manifestations are well-recognized in patients with COVID-19, with inflammation and damage to the brain vasculature being the common neuroimaging findings (1). A considerable number of individuals continue to experience – or even develop secondarily – neurological symptoms such as cognitive impairment (2.2% of individuals after SARS-CoV-2 infection) and fatigue or mood swings (3.2%) lasting up to several months after the recovery from COVID-19 (2). This condition is commonly referred to as “long COVID” or “post-COVID condition,” and it creates a substantial burden for social networks, health care, and economics beyond the personal suffering of the patient (3). Understanding the pathophysiological mechanisms of the condition plays a pivotal role in the quest for treatment approaches. Neuroimaging is a key diagnostic technique in this process.

An interesting neuroimaging method potentially sensitive to the long-term effects of COVID-19 is MRI perfusion measurement with arterial spin labeling (ASL). Previously, ASL was employed in applications assessing cognitive decline related to microvascular damage and neuroinflammation in the context of cancer therapy or dementia. In these cases, ASL was able to document longitudinal perfusion decrease following radiochemotherapy (4) or to help to detect changes in severe Alzheimer’s disease and even in the prodromal stage (5).

The use of ASL perfusion MRI to measure acute and chronic effects of COVID-19 remains limited. ASL was used to demonstrate that a post-COVID olfactory dysfunction was associated with lower tissue perfusion in the orbital and medial frontal regions (6). ASL also showed decreased perfusion in hospitalized subjects with the severe disease three months after discharge (7). However, perfusion still needs to be systematically studied in the largest group of individuals that underwent COVID-19 but did not require hospitalization.

In this issue of JMRI, an article by [AuthorName] et al. provides new results in a cross-sectional ASL study of 39 subjects who self-isolated at home due to COVID-19 and were scanned on average four months after the positive test (10). Typically, CBF measured with ASL have a relatively large intra-subject variability due to instrumental issues and physiological confounders. In theory, CBF could be influenced by various physiological and psychological factors related to contracting an infectious disease other than COVID-19. To address this, the authors have included a control group of eleven subjects who experienced flu-like symptoms but tested negative for COVID-19. Decreased perfusion in the COVID-19 group relative to the control group was found in several brain regions, including the basal ganglia, thalami, and orbitofrontal gyri. Further differences were discovered between COVID-19 subgroups with and without fatigue.

Despite the smaller size of this study, it backs findings from the UK Biobank study, which have demonstrated gray matter tissue loss in the orbitofrontal cortex and whole brain and higher cognitive decline longitudinally in participants infected with SARS-CoV-2 (8). Further population studies are currently being conducted (9), and the presented study by [AuthorName] et al. indicated the value ASL could have to provide quantifiable perfusion information.

Limitations of the study are a lack of pre-COVID baseline measurements and long-term outcomes of the post-COVID symptoms. In addition, the limited sample size did not allow more detailed subgroup analyses. However, showing a correlation between severity and worsened perfusion compared with patients recovering from a non-COVID flu-like respiratory illness is a step in the right direction in shedding light on the long-term effects of COVID-19 on brain perfusion.

Understanding the properties of matter under extreme conditions is essential for advancing our fundamental understanding of astrophysical objects and guides the search for exoplanets, it propels the discovery of materials exhibiting novel properties that emerge under high temperatures and pressure, it enables novel technologies such as nuclear fusion, and supports diagnostics of experiments at large-scale brilliant photon sources. While modeling in this challenging research domain has so far relied on first-principles methods [1,2], these turn out to be computationally too expensive for simulations at the required time and length scales. Reduced models, such as average-atom models [3], come at a reduced computational and are useful by connecting atomistic details with hydrodynamics simulations, but they provide less accuracy. Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [4]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations with deep neural networks in terms of our Materials Learning Algorithms framework [5,6] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [7].

[1] T. Dornheim, A. Cangi, K. Ramakrishna, M. Böhme, S. Tanaka, J. Vorberger, Phys. Rev. Lett. 125, 235001 (2020).
[2] K. Ramakrishna, A. Cangi, T. Dornheim, J. Vorberger, Phys. Rev. B 103, 125118 (2021).
[3] T. J. Callow, E. Kraisler, S. B. Hansen, A. Cangi, Phys. Rev. Research 4, 023055 (2022).
[4] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301 (2022).
[5] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[6] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperatures with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview of our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperature with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview on our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, and A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, and S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022). (2022).

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

Invited Presentation at "Workshop on Muon Precision Physics" in Liverpool

We show that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. This reflects the nonlinear nature of the gravitational interaction. This effect is illustrated by the example of different types of background matter, which confirms its universality. We also demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

Today it is well known that our universe is expanding. However, even 100 years ago, the notion of a static universe was considered correct. In my talk, I will tell a fascinating story about how a few great men have changed our mind.

We investigate the effect of peculiar velocities of inhomogeneities and the spatial curvature of the universe on the shape of the gravitating potential. To this end, we consider scalar perturbations of the FLRW metric. The gravitational potential satisfies a Helmholtz-type equation which follows from the system of linearized Einstein equations. We obtain analytical solutions of this equation in the cases of open and closed universes, filled with cold dark matter in presence of the cosmological constant. We demonstrate that, first, peculiar velocities significantly affect the screening length of the gravitational interaction and, second, the form of the gravitational potential depends on the sign of the spatial curvature.

Due to the modern telescopes, we found that the Universe is filled with a cosmic web which is composed of interconnected filaments of galaxies separated by giant voids. The emergence of this large-scale structure is one of the major challenges of modern cosmology. We study this phenomenon with the help of relativistic N-body cosmological simulation based on General Relativity. It is well known that gravity is the main force responsible for the structure formation in the Universe. In the first part of my talk, I demonstrate that in the cosmological setting gravitational interaction undergoes an exponential cutoff at large cosmological scales.
This effect is called cosmic screening. It arises due to the interaction of the gravitational field with the background matter. Then, I compare two competing relativistic approaches to the N-body simulation of the Universe large-scale structure: “gevolution” vs. “screening”.
To this end, employing the corresponding alternative computer codes, I demonstrate that
the corresponding power spectra are in very good agreement between the compared schemes.
However, since the perturbed Einstein equations have much simpler form in the “screening” approach, the simulation with this code consumes less computational time, saving almost 40% of CPU (central processing unit) hours.

The cannabinoid receptor 2 (CB2R) is involved in inflammatory processes [1], whereby an increased expression correlates with malignancy in various cancer types like human epidermal growth receptor 2 positive (HER2+) or triple negative breast cancer (TNBC) [2]. Hence, the CB2R is suggested as a pharmacological target, as well as a prognostic biomarker for the stratification and staging of patients [3]. In this study, we evaluated the potential of our novel CB2R-specific radioligand [¹ ⁸F]JHU94620-d8 for the assessment of the CB2R expression in HER2+ breast cancer and TNBC models in vitro.
The KD value of [¹ ⁸F]JHU94620-d8 was determined by autoradiography on cryosections of rat and mouse spleen, as well as on rat brains harbouring a local overexpression of the hCB2R (AAV-hCB2R) [4]. The CB2R status was investigated by competitive radioligand binding assays (CRBA) in cell membranes of CHO cells overexpressing the human CB2R (CHOhCB2R), human breast cancer cell lines HCC1954 (HER2+) and MDA-MB-231 (TNBC) with 3.1±0.4 nM [³H]WIN55,212-2 using 10 µM of WIN55,212-2, GW405833 and JHU94620-d8 (each n=3) as agonistic competitors. CB2R expression was validated by immunofluorescence microscopy (IFM). On cryosections of 4T1 tumors the CB2R specific binding of [¹ ⁸F]JHU94620-d8 was investigated by CRBA and the colocalisation of CB2R with Iba1 (macrophages) and CD31 (blood vessels) by IFM.
We determined KD values for [¹ ⁸F]JHU94620-d8 of 30 nM in mouse spleen, of 1.0 nM in rat spleen, and of 42 nM in AAV-hCB2R. The cell membrane binding of [³H]WIN55,212-2 was comparable in all used cell lines between 20 ± 1 and 30 ± 11 fmol/106 cells. Competition by JHU94620-d8 decreased the total binding by 57 % (p<0.01) only in CHOhCB2R cells, WIN55,212-2 by 37 % (p=0.01) and 77 % (p<0.01) and GW405833 by 42 % (p<0.01) and 75 % (p<0.01) in HCC1954 and CHOhCB2R cells, respectively, however in MDA MB 231 cells binding was not affected by these compounds (Fig. 1A). The expression of CB2R was confirmed by IFM (Fig. 1B). IFM analysis of murine 4T1 tumours revealed a high correlation between the heterogeneously distributed CB2R and Iba1 (Pearson´s coefficient r=0.69±0.03), and a weak correlation between CB2R and CD31 (r=0.35±0.09), however autoradiography studies revealed a non-displaceable binding of [¹ ⁸F]JHU94620-d8 (Fig. 2).
The potential of [¹ ⁸F]JHU94620-d8 as radioindicator to assess the CB2R status of tumours as a prognostic imaging biomarker should be investigated in vivo in PET studies. As shown in this study, the apparently species depended CB2R binding affinity and cell type specific (tumour cells and tumour associated macrophages) CB2R expression should be considered.

References
1. Turcotte, C.; Blanchet, M.-R.; Laviolette, M.; Flamand, N. The CB2 Receptor and its Role as a Regulator of Inflammation. Cell. Mol. Life Sci. 2016, 73, 4449–4470, doi:10.1007/s00018-016-2300-4.
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Acknowledgement
The human mammary cell lines were provided by Dr. Joan Massagué (MSKCC, NY, USA).
This research was funded by the Deutsche Forschungsgemeinschaft (DFG), grant number MO2677/4-1.

We conducted boiling flow experiments and measured the void fraction in a 3 x 3 rod bundle with a spacer grid using high resolution X-ray computed tomography. We focused on the effects of mass and heat flux on the void fraction downstream of the spacer. We found that the void fraction increases as the
flow passes through the vanes and then decreases downstream until 𝑍 ≈ 4𝐷ℎ , and then increases again. In addition, we found that the mixing vanes cause a local increase in void fraction even at low heat flux or high mass flux, and that the arrangement of the vanes influences the size and location of the high and low void content regions. We also found that the effect of heat flux on the relative void fraction is more noticeable at high mass flux than at low mass flux. Furthermore, the experimental database obtained in this study can be used to validate CFD simulations.

Test whether two sets of points are samples from the same D-dimensional probability distribution without
having access to the PDF.

We share the status of long term operation of Cs2Te in SRF-gun for CW mode facility, which is intested for the ERL society.

we share the experience of Cs2Te operation in SRF gun for ELBE user facility.

The quality of the photocathodes is critical for the stable operation of the photoinjector. Thanks to the robust Cs2Te photocathodes, SRF gun at HZDR has been proven to be a type of successful CW e- source. In this contribution, we will present the operation experience of Cs2Te photocathodes in SRF gun, especially the QE evolution of Cs2Te photocathode during user operation. The possible reason for QE degradation will be discussed.

A Quarter Wave Resonator based SRF Gun for the LCLS II High Energy project