Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Abstract Carbonyl aromatic compounds are promising cathode candidates for lithium-ion batteries (LIBs) because of their low weight and absence of cobalt and other metals, but they face constraints of limited redox-potential and low stability compared to traditional inorganic cathode materials. Herein, by means of first-principles calculations, a significant improvement of the electrochemical performance for carbonyl-bridged heterotriangulenes (CBHTs) is reported by introducing pyridinic N in their skeletons. Different center atoms (B, N, and P) and different types of functionalization with nitrogen effectively regulate the redox activity, conductivity, and solubility of CBHTs by influencing their electron affinity, energy levels of frontier orbitals and molecular polarity. By incorporating pyridinic N adjacent to the carbonyl groups, the electrochemical performance of N-functionalized CBHTs is significantly improved. Foremost, the estimated energy density reaches 1524 Wh kg−1 for carbonyl-bridged tri (3,5-pyrimidyl) borane, 50\% higher than in the inorganic reference material LiCoO2, rendering N-functionalized CBHTs promising organic cathode materials for LIBs. The investigation reveals the underlying structure-performance relationship of conjugated carbonyl compounds and sheds new lights for the rational design of redox-active organic molecules for high-performance lithium ion batteries (LIBs).

Characterization of diglycolamide resin using XRF, SEM, XPS, FTIR.

Abstract Partially occupied orbitals play a pivotal role in enhancing the performance of electrocatalyst by facilitating electron acceptance and donation, thus enabling the activation of molecular bonds. According to this principle, the basal plane of most 2D semiconductors is inert for electrocatalysis because of the fully occupied orbitals at the surface. Here, taking monolayer CrX (X = P, As, Sb) and Cr2PY (Y = As, Sb) as examples and through first-principles calculations, it is revealed that even with fully occupied surface orbitals, the basal planes exhibit remarkable catalytic activity for the nitrogen oxide reduction reaction (NORR). This leads to the concept of the pseudo-inert electrocatalyst. The underlying physics behind such pseudo-inert character can be attributed to the reversal-activation mechanism: contrary to conventional expectations, the adsorbed NO molecule reversely triggers the activity of the inert basal plane first, and then the basal plane activates NO molecules, forming the intriguing “Reversal Activation-Transfer-Donation-Backdonation” process. This study further predicts that such pseudo-inert character can demonstrate many distinctive properties, for example, it can introduce a novel type of surface catalysis, one that selectively targets radicals possessing an inherent dipole moment such as NO. The explored phenomena and insights greatly enrich the realms of electrocatalysis and 2D materials.

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The quality of results obtained by a scanning electron microscope-based automated mineralogy systems strongly depend on the project-specific library of spectra of the minerals considered to form the samples analysed, the mineral table. Mineral tables can be selected from existing universal libraries according to the expected or suspected minerals, and/or can be constructed based on spectra collected in the samples of a specific project. One can prefer extense mineral tables to enhance the chances of capturing variations in chemical composition of specific minerals; or else smaller, compact mineral tables to reduce misclassification. No general, perfect balance within generality-specificity or extension-compaction exists, so that users end up interactively and iteratively building the spectral library for each project in tedious steps of adding and removing mineral spectral candidates. This process is also project- and ore-specific. While some automated mineralogy devices provide operating modes for automatically constructing mineral lists throughout a measurement, these commonly offer only limited settings and are not clear about the data processing steps.

The goal of this contribution is to compare the performance of several components of a strategy to automatically construct automated mineralogy mineral lists - making use of several machine learning algorithms, for the specific case of dataset collected with the Mineral Liberation Analyser (MLA). The strategy has five steps: (1) preliminary data transformation, (2) dimension reduction, (3) endmember detection, (4) phase detection, and (5) unmixing.

For each of these steps, several options were tested. These included for data transformation peak extraction and Box-Cox transformations, which at the same time embraces logarithm/log-ratio transformations, square root transformations and the identity transformation. Regarding dimension reduction, principal component analysis and minimum-maximum autocorrelation factors were tested. In step three, we considered QHull convex hull detection, and N-FINDER, a conventional linear endmember detection method. In step four, the goal is to find the groups of spectra that can be identified with the members of the mineral table, not all of them being necessarily endmembers. Algorithms tested here correspond to model-free unsupervised classification algorithms, such as k-means, hyerarchical clustering methods and topological spectral clustering among other. Finally, in step five we tried several sparse and unconstrained linear unmixing algorithms. This unmixing was done within the sample of spectra forming the training data only in order to determine the number of necessary groups (or clusters) to extract from step four, as the actual final phase attribution will be done by the MLA software for the whole project after delivering the mineral table. The strategy presented here offers not only improvements to the workflow of scanning electron microscope-based automated mineralogy systems but also is a step stone for compiling mineral lists in analytical devices such as µX-Ray Fluorescence automated mineralogy, where spectra mixing is a bigger issue.

Electron-phonon interactions, crucial in condensed matter, are rarely seen in Metal-Organic Frameworks (MOFs). Detecting these interactions typically involves analyzing luminescence in lanthanide- or actinide-based compounds. Prior studies on Ln- and Ac-based MOFs at high temperatures revealed additional peaks, but these were too faint for thorough analysis. In our research, we fabricated a high-quality, crystalline uranium-based MOF (KIT-U-1) thin film using a layer-by-layer method. Under UV light, this film showed two distinct 'hot bands,' indicating a strong electron-phonon interaction. At 77 K, these bands were absent, but at 300 K, a new emission band appeared with half the intensity of the main luminescence. Surprisingly, a second hot band emerged above 320 K, deviating from previous findings in rare-earth compounds. We conducted a detailed ab-initio analysis employing time-dependent density function theory to understand this unusual behaviour and to identify the lattice vibration responsible for the strong electron-phonon coupling. The KIT-U-1 film's hot-band emission was then utilized to create a highly sensitive, single-compound optical thermometer. This underscores the potential of high-quality MOF thin films in exploiting the unique luminescence of lanthanides and actinides for advanced applications.

Freshwater shortages causes challenges in mineral processing in Chile, especially in arid regions. As a result, froth flotation; a mineral process, is shifting usage of freshwater to seawater. This has consequences in the consumption of flotation reagents and decreasing the flotation efficiency. Biotechnological developments allow conceptualising the use of bacterial cells and their metabolites as bioreagents in flotation; classified as bioflotation.
In this thesis, 5 halophilic bacteria, namely, Halomonas boliviensis, Marinobacter spp., Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 have been screened for the potential use as pyrite biodepressants at micro- and batch-scale flotation. The effect of bioconditioning minerals with these bacteria was studied using zeta potential, fluorescence microscopy and contact angle.
Experiments measuring zeta potential show the isoelectric point (IEP) of pyrite, chalcopyrite and molybdenite became more acidic post-bioconditioning. Fluorescence microscopy with Nile red; a hydrophobic stain, allowed for a method to visualize bacterial cells or collector potassium isopropyl xanthate (KIPX) on mineral particles of pyrite, chalcopyrite and molybdenite. Additionally contact angle experiments show that strains Halobacillus litoralis Hol-1, Marinococcus halophilus KOR-3 and Halomonas eurihalina P6-1 had an influence on the contact angle of pyrite and chalcopyrite, inducing changes in their hydrophobicity.
Microflotation experiments showed a decreased recovery of pyrite in presence of all strains, but notably, Halobacillus litoralis Hol-1 and Marinococcus halophilus KOR-3, also showed an increased recovery of chalcopyrite, making them ideal candidates as pyrite biodepressants. Halomonas eurihalina P6-1 showed low recoveries of both minerals, but a higher selectivity depressing more pyrite than chalcopyrite. Usage of autoclaved biomass from the three aforementioned strains in batch-flotation experiments resulted in the recovery of chalcopyrite improving, with a small decrease in the recovery of pyrite, overall showing a positive potential but not improving the system.
Halophilic bacteria such as the ones used in this study show an influence on the floatability of pyrite, which could be commercially exploited to substitute lime as a pyrite depressant. Furthermore, the work in this thesis focused on studying the effects of cells in artificial seawater, both at micro and batch-scales which brings the laboratory experiments a step closer to industrially relevant conditions.

Due to their special properties, lanthanides (Ln) are of utmost importance in the current technological era – both in the present and in the future. Besides their indispensable contribution to high-tech products, they are also increasingly used in environmental technology. In recent years, attention has turned to alternative solutions such as the recycling of Ln from end-of-life products or wastewater from industry and mining. However, these contain only low concentrations of rare earth elements (REE), which are additionally very similar in their chemical and physical properties, so that the separation is cost-intensive and an efficient recovery still far away. Research and development of new recycling processes should change this and enable a cost-effective and environmentally friendly separation from electronic scrap and wastewater in order to conserve primary resources and make us independent of them. We are researching a promising approach for such a novel recycling technology and try to solve the separation problem using selective peptides. Immobilized on a suitable carrier material, this kind of biohybrid separation platform can finally be used for REE recovery.
By combining phage surface display technique with next generation sequencing and running parallel biopannings on target ion and immobilization material, we were able to enrich and identify peptide sequences showing an affinity for the europium ion (Eu3+). Most enriched and repetitive peptide variants in several biopannings with different elution types were characterized by time-resolved laser fluorescence spectroscopy and isothermal titration calorimetry with respect to their Eu3+ affinity. Calmodulin’s EF-hand 4 peptide serves as a reference system.

Weight window, a variance reduction tool, is often used to improve the performance of radiation shielding calculations. One common issue with the weight window is determining the optimal set of weight window parameters for solving deep penetration shielding problems. To address this issue, the recursive Monte-Carlo methodology has been used with the in-house TRAWEI code. The program is responsible for generating the optimal weight parameters in a single run with minimum computational time. This paper presents the results of a numerical test conducted using a simple reactor model to evaluate the performance of the developed weight generator program. The findings reveal that MCNP simulations utilizing TRAWEI-generated weight values exhibit significantly higher calculation efficiency compared to both analog simulation and MCNP simulation using weights generated by the existing MCNP weight window generator. Overall, the utilization of the RMC methodology has shown its potential to significantly contribute to deep penetration shielding calculations.

Electronic structure theory calculations offer an understanding of matter at the quantum level, complementing experimental studies in materials science and chemistry. One of the most widely used methods, density functional theory (DFT), maps a set of real interacting electrons to a set of fictitious non-interacting electrons that share the same probability density. Ensuring that the density remains the same depends on the exchange-correlation (XC) energy and, by a derivative, the XC potential. Inversions provide a method to obtain exact XC potentials from target electronic densities, in hopes of gaining insights into accuracy-boosting approximations. Neural networks provide a new avenue to perform inversions by learning the mapping from density to potential. In this work, we learn this mapping using physics-informed machine learning (PIML) methods, namely physics informed neural networks (PINNs) and Fourier neural operators (FNOs). We demonstrate the capabilities of these two methods on a dataset of one-dimensional atomic and molecular models. The capabilities of each approach are discussed in conjunction with this proof-of-concept presentation. The primary finding of our investigation is that the combination of both approaches has the greatest potential for inverting the Kohn-Sham equations at scale.

Improving the sustainability of critical raw
materials extraction

This presentation provides insights into the development of the HZDR's in-house laboratory notebook for the documentation of scientific experiments. A special focus is placed on the integration of a variety of third-party systems in order to optimise the automated enrichment of data in the laboratory notebook and to facilitate documentation for scientists.

The talk addresses critical components of the FAIR data principles by examining the central role of data policies and infrastructure services. On the path to making data findable, accessible, interoperable and reusable (FAIR), the talk provides insights in the fundamental strategies for creating effective data policies and implementing infrastructure services that support these principles. Drawing on real-world experiences at HZDR, this talk will provide actionable insights for advancing FAIR data practices in research domains and highlight the essential cornerstones on this transformative journey.

HELIPORT is a data management solution that aims at making the components and steps of the entire research experiment’s life cycle discoverable, accessible, interoperable and reusable according to the FAIR principles.
Among other information, HELIPORT integrates documentation, scientific workflows, and the final publication of the research results - all via already established solutions for proposal management, electronic lab notebooks, software development and devops tools, and other additional data sources. The integration is accomplished by presenting the researchers with a high-level overview to keep all aspects of the experiment in mind, and automatically exchanging relevant metadata between the experiment’s life cycle steps.
Computational agents can interact with HELIPORT via a REST API that allows access to all components, and landing pages that allow for export of digital objects in various standardized formats and schemas. An overall digital object graph combining the metadata harvested from all sources provides scientists with a visual representation of interactions and relations between their digital objects, as well as their existence in the first place. Through the integrated computational workflow systems, HELIPORT can automate calculations using the collected metadata.
By visualizing all aspects of large-scale research experiments, HELIPORT enables deeper insights into a comprehensible data provenance with the chance of raising awareness for data management.

Non-reciprocal wave propagation arises in systems with broken time-reversal symmetry and is key to the functionality of devices, such as isolators or circulators, in microwave, photonic and acoustic applications. In magnetic systems, collective wave excitations known as magnon quasiparticles so far yielded moderate non-reciprocities, mainly observed by means of incoherent thermal magnon spectra, while their occurrence as coherent spin waves (magnon ensembles with identical phase) is yet to be demonstrated. Here, we report the direct observation of strongly non-reciprocal propagating coherent spin waves in a patterned element of a ferromagnetic bilayer stack with antiparallel magnetic orientations. We use time-resolved scanning transmission x-ray microscopy (TR-STXM) to directly image the layer-collective dynamics of spin waves with wavelengths ranging from 5 µm down to 100 nm emergent at frequencies between 500 MHz and 5 GHz. The experimentally observed non-reciprocity factor of these counter-propagating waves is greater than 10 with respect to both group velocities and specific wavelengths. Our experimental findings are supported by the results from an analytic theory and their peculiarities are further discussed in terms of caustic spin-wave focusing.

The world is witnessing unprecedented advances in the field of renewable energy generation, storage,
electrical mobility, and digital technologies. These developments are necessary to achieve our
ambitions of becoming a green and sustainable society that retains economic prosperity. Behind the
scenes this transition is enabled by a multitude of increasingly complex materials marked by impressive
optoelectronic and/ magnetic properties. Not only does the complexity of materials increase, but also
similar is true for the compositional architecture of machines, gadgets and installations. This is
combined with an ever-increasing speed with which advanced technologies penetrate global markets
and the often very limited life span / planned obsolence of many advanced technologies. Together,
these factors yield a rapidly increasing volume of waste materials of complex composition. Such
complex waste materials do not only contain a vast variety of valuable resources but, if left untreated,
may cause great harm to humans and the environment. It is, therefore, obvious that we need no less
than a paradigm shift. EoL products should be regarded not as waste but as valuable secondary
resource. Technological solutions are urgently needed to drive the transition towards holistic recycling
concepts.
The simple, holistic and yet sustainable answer to all these questions is the adoption of circular
economy strategies. This talk will present the opportunities and challenges in management of
advanced materials with end-of-life perspective. How the fundamental understanding of materials
properties and quantities is necessary in viable circular economy process developments and
implementation. It will be complemented by select examples of technologies developed for the
recycling of relevant materials and its materials safety-related implications.

Efficient sequestration of arsenic from drinking water is a global need. Herein we report eco-friendly porous hybrid adsorbent beads for removal of arsenic, through in situ synthesis of MIL-100(Fe) in the chitosan solvogel. To understand the structural vs. performance correlation, series of hybrid adsorbents were synthesized by modulating synthesis conditions like temperature, crystallization time, and concentration. Adsorbents were investigated using PXRD, FT-IR, SEM, and ICP-OES. Intriguing correlation between crystallinity and adsorption performance was observed as low and high crystalline MIL-100(Fe)-chitosan (ChitFe5 and ChitFe7, respectively) exhibited exceptional adsorption towards As5+ by removing it from water with 99% efficiency, whereas for As3+ species removal of about 85% was afforded. Adsorption isotherms indicated that increase in crystallinity (ChitFe5 -> ChitFe7), adsorption capacities of As5+ and As3+ increased from 23.2 to 64.5, and from 28.1 to 35.3 mg/g, respectively. Selectivity tests of the adsorbents towards As5+ and As3+ over competitive anions in the equimolar competitive systems having nitrates, sulfates, and carbonates demonstrated that the performance of the absorbents was fully maintained, relative to the control system. Through this study a highly selective and efficient adsorbent for arsenic species is designed and a clear insight into the structural tuning and its effect on adsorption performance is provided.

Appropriate waste and resource management are essential for a sustainable circular economy with reduced environmental impact. With critical resources, e-waste may serve as indirect raw material. For example, with NdFeB permanent magnets, Neodymium (Nd) and the co-present Dysprosium (Dy) are critical rare earth elements (REEs). However, there exists no economically viable technology for recycling them from electronic waste (e-waste). Here, a method is presented based on cloud point extraction (CPE). The work involves basic complexation chemistry in a cloud medium with pure REE salts, as well as, with real NdFeB-magnets (nearly 28% REE content by weight) from an old hard disk drive (5.2 g magnet in a 375 g HDD). High extraction efficiency (>95%) was achieved for each REE targeted (Nd, Dy, Praseodymium (Pr)). With the magnet waste, the cloud phase did hardly contain any Nickel (Ni), Cobalt (Co), or Boron (B), but some Aluminium (Al) and Iron (Fe). Dynamic light scattering results indicated aggregation of ligand-surfactant micelles with the cloud phase. The preconcentrated products can be used for new Nd magnet manufacturing or further enriched using established transition metal removal techniques. Reuse of solvent, low chemical inventory demand, and using non-inflammable, non-volatile organic extractants promise safe large-scale operation, low process costs, and less environmental impact than using hydrometallurgical methods used with urban or primary mining.

At the electron accelerator for beams with high brilliance and low emittance (ELBE), the second version of a superconducting radio-frequency (SRF) photoinjector was brought into operation in 2014. After a period of commissioning, a gradual transfer to routine operation took place in 2017, so that now more than 1800h of user beam are generated every year. Since the commission, a total of 24 cathodes (2 Cu, 12 Mg, 10 Cs2Te) have been used, without observing serious cavity degradation. The contribution summarized commissioning and operational experience of the last years, with special emphasis on SRF properties but also on specialties such as dark current and multipacting that are directly linked to the integration of a normal conducting cathode into the SRF cavity.

original input and output files to create tables and figures as described in the corresponding paper.

This repository contains all input files and the thereby generated raw data used to generate figures and other results described in the corresponding paper.

dataset to calculate DEED; code of the algorithm to perform the DEED calculation

The need for improved functionalities in extreme environments is fuelling interest
in high-entropy ceramics. Except for the computational discovery of high-entropy
carbides, performed with the entropy-forming-ability descriptor, most innovation
has been slowly driven by experimental means. Hence, advancement in the field
needs more theoretical contributions. Here we introduce disordered enthalpy–
entropy descriptor (DEED), a descriptor that captures the balance between
entropy gains and enthalpy costs, allowing the correct classification of functional
synthesizability of multicomponent ceramics, regardless of chemistry and structure.
To make our calculations possible, we have developed a convolutional algorithm that
drastically reduces computational resources. Moreover, DEED guides the experimental
discovery of new single-phase high-entropy carbonitrides and borides. This work,
integrated into the AFLOW computational ecosystem, provides an array of potential
new candidates, ripe for experimental discoveries.

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The Random-Phase approximation (RPA) provides an appealing framework for semi-local density functional theory. In its Resolution-of-the-Identity (RI) approach it is a very accurate and more cost-effective method than most other wavefunction-based correlation methods. For widespread applications efficient implementations of nuclear gradients for structure optimizations and data sampling of machine learning approaches is required. We report a well scaling implementation of RI-RPA nuclear gradients on massively parallel computers. The approach is applied to two polymorphs of the benzene crystal obtaining very good cohesive and relative energies. Different correction and extrapolation schemes are investigated for further improvement of the results and estimations of error bars.

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Water adsorption and dissociation processes on pristine low-index TiO2 interfaces are important but poorly understood outside the well-studied anatase (101) and rutile (110). To understand these, we construct three sets of machine learning potentials that are simultaneously applicable to various TiO2 surfaces, based on three density-functional-theory approximations. Here we show the water dissociation free energies on seven pristine TiO2 surfaces, and predict that anatase (100), anatase (110), rutile (001), and rutile (011) favor water dissociation, anatase (101) and rutile (100) have mostly molecular adsorption, while the simulations of rutile (110) sensitively depend on the slab thickness and molecular adsorption is preferred with thick slabs. Moreover, using an automated algorithm, we reveal that these surfaces follow different types of atomistic mechanisms for proton transfer and water dissociation: one-step, two-step, or both. These mechanisms can be rationalized based on the arrangements of water molecules on the different surfaces. Our finding thus demonstrates that the different pristine TiO2 surfaces react with water in distinct ways, and cannot be represented using just the low-energy anatase (101) and rutile (110) surfaces.

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Particle-in-cell (PIC) simulations are a widely-used tool to model kinetics-dominated plasmas in ultrarelativistic laser-solid interactions (dimensionless vectorpotential a0 > 1). However, interactions approaching subrelativistic laser intensities (a0 ≲ 1) are governed by correlated and collisional plasma physics, calling for benchmarks of available modeling capabilities and the establishment of standardized testbeds. Here, we propose such a testbed to experimentally benchmark PIC simulations of laser-solid interactions using a laser-irradiated micron-sized cryogenic hydrogen-jet target. Time-resolved optical shadowgraphy of the expanding plasma density, complemented by hydrodynamics and ray-tracing simulations, is used to determine the bulk-electron-temperature evolution after laser irradiation. We showcase our testbed by studying isochoric heating of solid hydrogen induced by laser pulses with a dimensionless vectorpotential of a0 ≈ 1. Our testbed reveals that the initial surface-density gradient of the target is decisive to reach quantitative agreement at 1 ps after the interaction, demonstrating its suitability to benchmark controlled parameter scans at subrelativistic laser intensities.

We present results for direct maskless magnetic patterning of ferromagnetic nanostructures using a special liquid metal alloy ion source for focused ion beam (FIB) systems. We used a Co36Nd64 alloy as the FIB source [1]. A Wien mass filter allows for quick switching between the ion species in the alloy without changing the FIB source. A 5000×1000×50 nm3 permalloy strip served as the sample. Using the FIB we implanted a 300-nm-wide track with Co ions (see Fig.1). We observed the Co-induced changes by measuring the sample with microresonator ferromagnetic resonance before and after the implantation. Structures as small as 30 nm can be implanted up to a concentration of 10 % near the surface. Such lateral resolution is hard to reach for other lithographic methods. This allows for easy magnetic modification of edge-localized spin waves.
In another set of samples, we implanted Dy ions to locally increase the damping in a stripe pattern of ~120-nm-wide strips with 400 nm periodicity on a total area of 1×1 mm². Thus, the Gilbert damping parameter can be easily increased by one order of magnitude with a lateral resolution of about 100 nm.
In contrast to electron beam lithography in combination with broad-beam ion implantation, the maskless FIB process does not require the cumbersome and difficult removal of the ion-hardened resist if optical measurements like BLS or TR-MOKE are needed.

The environmental fate of radiotoxic actinides is controlled by their interactions with feldspars. Here, the sorption of trivalent minor actinides (Am, Cm) and their rare earth analogue Eu onto synthetic pure Ca-feldspar (anorthite) and natural plagioclases of different Ca contents is investigated, covering ranges of [M3+] (52 nM–10 μM), solid-liquid ratios (1–3 g/L), pH (3–9), and ionic strengths (0.01–0.1 M NaCl) under both ambient and CO2-free conditions. The zeta potential shows an unusual increase and charge reversal between pH 4 and 7 with increasing amount of Ca and Al in the feldspar crystal lattice, which is likely connected to adsorption and/or surface precipitation of dissolved Al3+. Streaming potential measurements yield (de)protonation constants for anorthite surface sites of log K- = -6.94 ± 0.38 and log K+ = +6.84 ± 0.38. Batch sorption data shows strong immobilization of M3+ by plagioclases at mildly acidic and basic pH. Time-resolved laser fluorescence spectroscopy using Cm indicates the formation of an inner-sphere complex and its two hydrolyzed forms. The complex reactivity of dissolved Al3+ at the plagioclase-water interface severely complicated the development of a surface complexation model, emphasizing the need for additional research in this area.

summary of metallurgical processes commonly used in the industry from sulfide concentrates to the metal products; based on this, the current technological approaches and emerging challenges in the metal recovery from marine sources will be discussed

Next-generation Radioimmunotherapy using CAR T Cells Combined with Photon vs. Proton vs. Carbon Irradiation

Bone marrow mesenchymal stromal cells (MSCs) have been described as potent regulators of T cell function, though whether they could impede the effectiveness of immunotherapy against acute myeloid leukemia (AML) is still under investigation. We examine whether they could interfere with the activity of leukemia-specific clonal cytotoxic T lymphocytes (CTLs) and chimeric antigen receptor (CAR) T cells, as well as whether the immunomodulatory properties of MSCs could be associated with the induction of T cell senescence. Co-cultures of leukemia-associated Wilm’s tumour protein 1 (WT1)- and Tyrosine-protein kinase transmembrane receptor 1 (ROR1)-reactive CTLs and of CD123-redirected switchable CAR T cells were prepared in the presence of MSCs and assessed for cytotoxic potential, cytokine secretion and proliferation. T cell senescence within functional memory sub-compartments was investigated for the senescence-associated phenotype CD28-CD57+ using unmodified peripheral blood mononuclear cells (PBMCs). We describe inhibition of expansion of AML-redirected switchable CAR T cells by MSCs via indoleamine 2,3-dioxygenase 1 (IDO-1) activity, as well as reduction of interferon gamma (IFNγ) and interleukin 2 (IL-2) release. In addition, MSCs interfered with the secretory potential of leukemia-associated WT1- and ROR1-targeting CTL clones, inhibiting the release of IFNγ, tumour necrosis factor alpha (TNFα), and IL-2. Abrogated T cells were shown to retain their cytolytic activity. Moreover, we demonstrate induction of a CD28loCD27loCD57+KLRG1+ senescent T cell phenotype by MSCs. In summary, we show that MSCs are potent modulators of anti-leukemic T cells, and targeting their modes of action would likely be beneficial in a combinatorial approach with AML-directed immunotherapy.

In recent years, several studies have been conducted to improve the process steps of rare earth elements (REEs) production. Beneficiation & separation stages varies according to type and concentration of impurities. One of the most complex process can be the selective separation of rare earth elements from each other due to their similar physical and chemical properties. At industrial scale,msolvent extraction is the most common separation and enrichment technology for REEs.
The efficiency of solvent extraction depends on several factors. The selection of extractant strongly depends on the composition of the leachate. In sulphate media, carboxylic acids are preferred because of their high extraction rates. Furthermore, primary amines can be used for extraction of rare earths in sulphate media. In amine system, extraction follows a reverse order comparing to cationic extractants.
In the presented study, primary amine Primene 81-R was selected as an alternative extractant in order to investigate its potential for a highly selective separation of REEs. The separation of HREEs from LREEs was determined in dependence on pH and concentration of the extractant using a model solution consisting mainly of LREES (97% of the total REE content). In the extraction experiment, approximately 40-50% of LREE were extracted into the organic phase, while the extraction of HREEs was obtained to be only between 5-30% under these conditions. However, for further development of the solvent extraction process, optimization studies are ongoing.

A brief summary of user operation experiences with SRF-Gun II at ELBE (since 2014) with an emphasis on most recent results and an oulook.

An update on activities of ELBE SRF-Gun group

Spin systems with honeycomb structures have recently attracted a great deal of attention in connection with the Kitaev quantum spin liquid state (QSL) predicted theoretically. One possible Kitaev QSL candidate is Na₂Co₂TeO₆ realizing a honeycomb lattice of pseudospin 1/2. Field-dependent single-crystal neutron diffraction technique allows us to determine the microscopic spin-spin correlations across the field-induced phase transitions for H II a and H II a∗ in plane field directions. Our results reveal phase transitions, initially to a canted zigzag antiferromagnetic state at approximately 60 kOe, followed by a possible transition to a partially polarized state over the range 90–120 kOe, and finally to a field-induced fully polarized state above 120 kOe. We observe distinct field dependencies of the magnetic peak intensities for H II a and H II a∗. In addition, low-temperature electron spin resonance in magnetic fields H _ c yields a complete softening for one of the antiferromagnetic resonances at ∼40 kOe, revealing a field-induced phase transition. The present work thus provides insights into the field evolution of the important Kitaev-Heisenberg spin system Na₂Co₂TeO₆.

The dwindling agricultural earnings and decrease in crop yield in recent years due to improper crop selection and fluctuation/ uncertainty in weather necessitate proper machine learning-based analysis. Machine learning methods can potentially alleviate the predicament caused by the lack of appropriate soil testing, consultation, and bias in manual suggestion. This work attempted to comprehend the agricultural sensor data and weather conditions and formulated the task in terms of supervised classification. The work obtained accurate suggestions in the presence of missing data, noise, etc. by using advanced machine learning methods. But recommendation alone is insufficient to convince farmers and other stakeholders to adopt this approach. Hence, this paper introduced explainable machine learning to completely comprehend the decision-making process. This work quantified the importance of features, explained individual prediction outcomes, and uncovered the rationale for decisions. The work employed state-of-the-art local interpretable model-agnostic, post-hoc explanation methods to provide in-depth insights. The insights obtained from the explanations can help the farmers develop a knowledge base and assist the farmers in choosing the appropriate sensors for the task. The human interpretable analysis enables the farmers to obtain satisfactory yields in these ever-changing and extreme weather conditions and environmental degradation.

We report the experimental observation of dielectric relaxation by quantum critical magnons. Complex capacitance measurements reveal a dissipative feature with a temperature-dependent amplitude due to lowenergy lattice excitations and an activation behavior of the relaxation time. The activation energy softens close to a field-tuned magnetic quantum critical point at H = H_c and follows single-magnon energy for H > H_c, showing its magnetic origin. Our study demonstrates the electrical activity of coupled low-energy spin and lattice excitations, an example of quantum multiferroic behavior.

Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, B hyperdoped diamond reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortened to millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-5] and chalcogen doped Si [6-10].

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).

[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).

[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).

[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).

[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).

[6] S. Zhou, et al., Sci. Reports 5, 8329(2015).

[7] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018).

[8] M. Wang, et al., Phys. Rev. Applied. 11, 054039 (2019).

[9] M. Wang, et al., Phys. Rev. B 102, 085204 (2020)

[10] M. Wang, et al., Adv. Optical Mater. 9, 2001546 (2021).

Ion implantation followed by thermal annealing is a well-established method to dope semiconductors, e.g. Si and Ge. This approach has been maturely integrated with the integrated circuit (IC) industry production line for area- and depth-selective n/p doping as well as for lifetime engineering [1]. As a national lab in Germany, our center is running an Ion Beam Center for materials research [2]. It is open free to the international community for fundamental research based on a proposal system. Within the research department “Semiconductor Materials”, we are running unique annealing methods, including millisecond flash lamp annealing and nanosecond pulsed laser melting, to repair the ion beam induced damage and to activate the dopants [3, 4]. I will show diverse research examples by using ion beam to modify semiconductor materials. They include pushing the doping limits in semiconductors well above the solubility limits [5-7], functionalizing 2D materials [8] and creating color centers for quantum technologies [9, 10].

[1] Ye Yuan, S. Zhou and X. Wang, Modulating properties by light ion irradiation: From novel functional materials to semiconductor power devices, J. Semicond. 43 063101 (2022).
[2] https://www.hzdr.de/db/Cms?pNid=1984
[3] S. Zhou, Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting, J. Phys. D: Appl. Phys. 48, 263001 (2015) (Topical Review)
[4] L. Rebohle, S. Prucnal, Y. Berencén, V. Begeza, S. Zhou, A snapshot review on flash lamp annealing of semiconductor materials, MRS Advances 7, 1301–1309 (2022)
[5] M. Wang et al, Breaking the doping limit in silicon by deep impurities, Phys. Rev. Appl. 11, 054039 (2019)
[6] S. Prucnal, et al., Dissolution of donor-vacancy clusters in heavily doped n-type germanium, New J. Phys. 22, 123036 (2020)
[7] M. Hoesch, Active sites of Te-hyperdoped silicon by hard x-ray photoelectron spectroscopy, Appl. Phys. Lett. 122, 252108 (2023)
[8] F. Long, Ferromagnetic interlayer coupling in CrSBr crystals irradiated by ions, arXiv:2305.18791 (2023)
[9] C. Kasper, et al, Influence of irradiation on defect spin coherence in silicon carbide, Phys. Rev. Appl. 13, 044054 (2020)
[10] Z. Shang, et al, Microwave-assisted spectroscopy of vacancy-related spin centers in hexagonal SiC, Phys. Rev. Appl. 15, 034059 (2021)

Ion implantation followed by thermal annealing is a well-established method to dope semiconductors, e.g. Si and Ge. This approach has been maturely integrated with the integrated circuit (IC) industry production line for area- and depth-selective n/p doping as well as for lifetime engineering [1]. As a national lab in Germany, our center is running an Ion Beam Center for materials research [2]. It is open free to the international community for fundamental research based on a proposal system. With my research department “Semiconductor Materials”, we are running unique annealing methods, including millisecond flash lamp annealing and nanosecond pulsed laser melting, to repair the ion beam induced damage and to activate the dopants [3, 4]. I will show diverse research examples by using ion beam. They include pushing the doping limits in semiconductors well above the solubility limits [5-7], functionalizing 2D materials [8] and creating color centers for quantum technologies [9, 10].

[1] Ye Yuan, S. Zhou and X. Wang, Modulating properties by light ion irradiation: From novel functional materials to semiconductor power devices, J. Semicond. 43 063101 (2022).
[2] https://www.hzdr.de/db/Cms?pNid=1984
[3] S. Zhou, Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting, J. Phys. D: Appl. Phys. 48, 263001 (2015) (Topical Review)
[4] L. Rebohle, S. Prucnal, Y. Berencén, V. Begeza, S. Zhou, A snapshot review on flash lamp annealing of semiconductor materials, MRS Advances 7, 1301–1309 (2022)
[5] M. Wang et al, Breaking the doping limit in silicon by deep impurities, Phys. Rev. Appl. 11, 054039 (2019)
[6] S. Prucnal, et al., Dissolution of donor-vacancy clusters in heavily doped n-type germanium, New J. Phys. 22, 123036 (2020)
[7] M. Hoesch, Active sites of Te-hyperdoped silicon by hard x-ray photoelectron spectroscopy, Appl. Phys. Lett. 122, 252108 (2023)
[8] F. Long, Ferromagnetic interlayer coupling in CrSBr crystals irradiated by ions, arXiv:2305.18791 (2023)
[9] C. Kasper, et al, Influence of irradiation on defect spin coherence in silicon carbide, Phys. Rev. Appl. 13, 044054 (2020)
[10] Z. Shang, et al, Microwave-assisted spectroscopy of vacancy-related spin centers in hexagonal SiC, Phys. Rev. Appl. 15, 034059 (2021)

Tellurium is one of the deep-level impurities in Si, leading to states of 200-400 meV below the conduction band. Non-equilibrium methods allow for doping deep-level impurities in Si well above the solubility limit, referred as hyperdoping, that can result in exotic properties, such as extrinsic photo-absorption well below the Si bandgap [1]. In this talk, we will present an overview about Te hyperdoped Si. The hyperdoping is realized by ion implantation and pulsed laser melting. We will present the resulting optical, electrical properties and the perspective applications as infrared photodetectors. With increasing the Te concentration, the samples undergo an insulator to metal transition [2, 3]. Surprisingly, the electron concentration obtained in Te-hyperdoped Si is approaching 1021 cm-3 and does not show saturation [4]. It is even high than that of P or As doped Si and potentially meets the criteria of source/drain applications in future nanoelectronics. The infrared optical absorptance is found to increase with increasing dopant concentration [2]. We demonstrate the room-temperature operation of a mid-infrared photodetector based on Te-hyperdoped Si. The key parameters, such as the detectivity, the bandwidth and the rise/fall time, show competitiveness with the commercial products [5]. To understand the microscopic picture, we have performed Rutherford backscattering angular scans and first-principles calculations [4]. The Te-dimer complex sitting on adjacent Si lattice sites has the smallest formation energy and is thus the preferred configuration at high doping concentration. Those substitutional Te-dimers are effective donors, leading to the insulator-to-metal transition, the non-saturating carrier concentration as well as the sub-band photoresponse. Moreover, the Te-hyperdoped Si layers exhibit thermal stability up to 400 °C with a duration of at least 10 minutes [6]. Therefore, Te-hyperdoped Si presents a test-bed for electrical and optical applications utilizing deep-level impurities.
[1] J. M. Warrender, Laser hyperdoping silicon for enhanced infrared optoelectronic properties, Appl. Phys. Rev. 3, 031104 (2016).
[2] M. Wang, et al., Extended Infrared Photoresponse in Te-Hyperdoped Si at Room Temperature, Phys. Rev. Appl. 10, 024054 (2018).
[3] M. Wang, et al., Critical behavior of the insulator-to-metal transition in Te-hyperdoped Si, Phys. Rev. B 102, 085204 (2020).
[4] M. Wang, et al., Breaking the doping limit in silicon by deep impurities, Phys. Rev. Appl. 11, 054039 (2019).
[5] M. Wang, et al., Silicon-Based Intermediate-Band Infrared Photodetector Realized by Te Hyperdoping, Adv. Opt. Mater. 9, 2001546, (2020).
[6] M. Wang, et al., Thermal stability of Te-hyperdoped Si: Atomic-scale correlation of the structural, electrical, and optical properties, Phys. Rev. Mater. 3, 044606 (2019).

Complex oxides host a multitude of novel phenomena in condensed matter physics, such as various forms of multiferroicity, colossal magnetoresistance, quantum magnetism, and superconductivity. This is largely due to the strong correlation between charge, spin, orbital, and lattice parameters. Specifically, tilting the delicate energy balance in lattice interactions and kinetics, achieved by temperature, strain, or chemical doping, can result in significant modifications in these materials. In this context, defect engineering by ion irradiation, which can introduce strain and electronic disorder, has emerged as a powerful technique to fine-tune complex phases of oxide thin films. The induced uniaxial strain, manifested as the elongation of the out-of-plane lattice spacing, is not limited to available substrates, the conventional and well-known strain engineering approach. In this contribution, we will introduce the tailoring of oxide thin films by ion irradiation, with examples including the modification of magnetic and magneto-transport properties of NiCo2O4 [1] and SrRuO3 [2,3], and ferroelectric properties of BiFeO3, KTN (KTaNbO3), and PbZrO3 [4-6]. The irradiated SrRuO3 films exhibit a pronounced topological Hall effect in a wide temperature range from 5 to 80 K, which can be attributed to the emergence of Dzyaloshinskii–Moriya interaction resulting from artificial inversion symmetry breaking associated with lattice defect engineering. In BiFeO3, we have obtained a super-tetragonal phase with the largest c/a ratio (~1.3) ever experimentally achieved [2]. For both KTN and PbZrO3, ion irradiation induces the formation of polar nanoregions [5, 7]. In PbZrO3, both the energy storage density and the breakdown strength are effectively increased. We show that ion irradiation is a very versatile pathway for tailoring oxide functionalities, analogous to ion-implantation doping for conventional semiconductors. It is worth noting that ion beam technology has been well-developed for microelectronics. Once the principle of concept is approved, the approach can be easily scaled up and integrated into the industry production line.
References:
[1] P. Pandey, et al., APL Materials 6 (2018) 066109.
[2] C. Wang, et al., ACS Appl. Mater. Interfaces 10 (2018) 27472.
[3] C. Wang, et al., Adv. Electron. Mater. 6 (2020) 2000184.
[4] C. Chen, et al., Nanoscale 11 (2019) 8110.
[5] Q. Yang, et al., Acta Mater. 221 (2021) 117376.
[6] Y. Luo, et al, Appl. Phys. Rev. 10 (2023) 011403.

Attrition of employees is vital for any organization as it significantly influences productivity and hampers the long-term growth strategies of the organization. Since employee attrition leads to loss of skills and experiences any organization always try to find a way to retain their employees to reduce training and recruiting cost as well as to achieve their business goal smoothly. Machine learning approaches, which predict the possibility of attrition based on the employee attributes avoid the tedious, and biased manual prediction, and help the organization take preventive measures. This paper presents a framework for attrition prediction that emphasizes imbalance classification and the adoption of genetic algorithms to optimize the model. First, we have adopted different oversampling methods like Synthetic Minority Over-sampling Technique (SMOTE), Adaptive Synthetic (ADASYN), and Borderline Synthetic Minority Over-sampling Technique to balance our data set. We have used XGBoost classifiers for classification with the data that are obtained from different over-sampling techniques. As the XGBoost classifier has many hyperparameter a genetic algorithm is used to optimize our model where the accuracy is chosen as the fitness function. The comparative performance analysis of different over-sampling methods as well as hyper-parameter tuning (Amongst Genetic algorithm, GridSearchCV, and with the default value of different hyper-parameter) on the real dataset suggests that SMOTE for oversampling techniques and genetic algorithm for optimization attains improved performance.

The hyperspectral unmixing process is central to identifying the objects in a ground scene and quantifying their fractional abundance in each pixel. However, the high spatial resolution and the intrinsic interactions pose a challenge in object identification from hyperspectral images by non-linear unmixing. Typically the data points are generated due to non-linear, intimate mixing from non-linear subspaces. In this work, we propose a deep subspace clustering framework to identify the underlying non-linear subspaces in the initial stage and perform non-linear unmixing on the local clusters. To this aim, we proposed a deep auto-encoder network with additional total variation and spatial consistency regularization to determine the underlying non-linear mixing process from each cluster separately. Next, we identify the pixels which contain a dominant source from the latent representation obtained after the encoding stage. Subsequently, we carried out unmixing on local clusters using a linear algebraic based on the low-rank structure of the data. A detailed comparative analysis of the unmixing algorithms on three real hyperspectral images exhibits that our proposed algorithm achieves improved performance.

FET PET is a valuable tool for managing brain tumors. Quantitative image analysis is of obvious relevance in this context. One clinically useful image derived measure is the maximal tumor-to-background SUV ratio which can be used for therapy response assessment as well
as for discrimination between tumor recurrence and treatment-related changes. Computation of this ratio requires determination of the background SUV (bSUV) from a suitable ROI defined within healthy brain tissue. Currently, the standard procedure requires manual definition of the background ROI by an experienced human observer while adhering to a set of somewhat loosely defined rules. This process is time consuming and prone to inter- and intra-observer variability. The goal of this study, therefore, was development of a reliable automated method for bSUV derivation in FET PET of brain tumor patients.

Automated delineation of the healthy brain regions was performed with a residual 3D U-Net convolutional neural network (CNN). 561 FET PET scans were used for network training (N=448) and testing (N=113). In these data, reference brain regions were manually delineated by an experienced observer. The network was trained to reproduce the corresponding manual bSUVs by identifying a suitable brain ROI (rather than aiming at reproducing the manual ROI delineation). Performance of the trained network model was assessed in the test data using the fractional difference between automatically and manually derived bSUVs.

The trained U-Net was able to accurately reproduce the manually derived bSUVs in the test data: the fractional bSUV difference was (mean +/- SD)=(-0.9 +/- 5.3)% with a 95% confidence interval of [-10.9, 8.4]%.

The achieved concordance of the network's results with the given ground truth bSUV is in line with typical achievable levels of inter- and intra-observer concordance for this task. It thus might be considered for supervised routine use to reduce user workload and improve reproducibility.

Eine für die numerische Simulation von Strömungen sehr beliebte und erfolgreiche Software ist die quelloffene Software der OpenFOAM Foundation, welche sowohl in der Industrie als auch im akademischen Umfeld Anwendung findet. Forschungsgruppen, die keine reine Inhouse-Entwicklung leisten können oder anstreben, gewährt sie eine optimale Basis um eigene Ideen und Konzepte in einer transparenten Umgebung effizient testen zu können. Obwohl der Wartungsaufwand im Vergleich zu einer Eigenentwicklung insgesamt erheblich geringer ist, müssen Erweiterungen dennoch gepflegt werden um diese mit dem jeweils aktuellen Stand des Hauptrelease kompatibel zu halten. Die damit verbundene Arbeit erlangt umso größere Bedeutung, wenn Erweiterungen im Sinne der FAIR-Prinzipien zusammen mit wissenschaftlichen Publikationen bereitgestellt werden. Als agil entwickelte und intensiv gewartete Software stellt die Software der OpenFOAM Foundation in dieser Hinsicht besondere Anforderungen an die nachgelagerten Entwickler.
Das Helmholtz-Zentrum Dresden – Rossendorf e.V. (HZDR) verfolgt hierbei einen möglichst nachhaltigen Ansatz. Abgeschlossene und zitierfähige Entwicklungen werden entweder in einer eigenen Softwarepublikation veröffentlicht, oder, in enger Abstimmung mit den Kernentwicklern der OpenFOAM Foundation, in das Hauptrelease integriert. Die für die Arbeit an der Erweiterung (Multiphase Code Repository by HZDR for OpenFOAM Foundation Software) geschaffene IT-Infrastruktur zeichnet sich durch einen hohen Automatisierungsgrad aus und bietet Anwendern innerhalb und außerhalb des HZDR eine nützliche Plattform für die Erforschung von numerischen Methoden und Modellen.
Rückgrat der Arbeiten ist die über die Helmholtz Cloud bereitgestellte GitLab-Instanz (Helmholtz Codebase). Darin werden zwei Repositorien gepflegt: Eines für die Codeerweiterung und eines für Setups zur Simulation konkreter Anwendungen (Multiphase Cases Repository by HZDR for OpenFOAM Foundation Software). Zur Sicherung der Qualität und Funktionalität wird die Arbeit in der GitLab-Umgebung von Continuous-Integration-Pipelines (CI) begleitet, in deren Rahmen unter anderem statische Code-Checks, Build-Tests und Testläufe automatisiert vorgenommen werden. Für die Verwendung in CI-Pipelines sowie die lokale Entwicklung der Erweiterung wird die Installation als Container (Docker) bereitgestellt. Reine Anwender können auf die Installation per Debian-Paket zurückgreifen. Die zitierfähige Veröffentlichung des Quellcodes erfolgt mit jeder wissenschaftlichen Publikation im Rossendorf Data Repository (RODARE). Die Verwendung des Workflowmanagementsystems Snakemake ermöglicht skalierbare Validierungsläufe. Um die Portierbarkeit der Entwicklungen zu verbessern konzentrieren sich jüngere Arbeiten auf die Bereitstellung der Software als HPC-Container (Apptainer) für die Anwendung auf Hochleistungsrechnern. Dieser Beitrag gibt einen Überblick über die genannten Elemente der Umgebung und deren Zusammenspiel.

Because of its high interfacial area density and mixing efficiency bubbly flow are utilized in diverse technical applications to enhance the interfacial mass and heat transfer rate. However, due to the superposition of complex shape variation as well as bubble-bubble interaction, many aspects concerning the effect of bubbles on the bulk flow remain unclear, and bubble-induced turbulence (BIT) is one of them. In the past great effort has been made towards the BIT modelling in the framework of two-equation turbulence models, but the understanding of physics is still far from satisfactory. This work revisits the model proposed by Ma et al. [Phys. Rev. Fluids 2, 034301 (2017)], which considers the BIT with an additional source term in the k- and epsilon" (or omega)- equation, respectively, and has been widely adopted in the simulations of bubbly flows.
Recent experiments show that contamination of the carrier phase plays a considerable role in BIT: although the bubbles rise slower with adding surfactants, the BIT increases. This trend cannot be reproduced by any current BIT models, including Ma et al. (2017). We have further investigated the reason for this and discuss the new possibility for the prefactor in the source term of the "epsilon-equation that may improve the results.

Efficient compression is pertinent for the convenient storage, transmission, and processing of modern high-resolution hyperspectral images (HSI). This paper proposes a new high-performance HSI compression method using library-based spectral unmixing and tensor decomposition. Unlike the existing approaches, our proposed work incorporates unmixing in the compression framework and achieves significantly higher compression performance with negligible loss. The proposed library-based unmixing method includes a new index for accurate endmember number estimation, followed by exact library pruning and a novel sparsity regularized formulation with norm-smoothing to compute the abundance maps. As the spectral library is available at the reconstruction (decoder) side also; compressing the abundance maps is as good as compressing the original HSI data. Since the abundance constraints used for the unmixing indicate the correlation of the abundance maps, compressing all abundance maps seems to cause redundant computation. A metric using the image smoothness and information measures is used here to identify the abundance map hardest to compress and the remaining part is left uncompressed. Subsequently, the work compresses the abundance map tensor using orthogonal Parallel Factorisation (PARAFAC) decomposition with optimal rank determination. The orthogonalization process ensures that the factors span independent subspaces and reduces redundancy, while the rank selection prevents noisy or insignificant components. Extensive experiments are carried out to demonstrate that the unmixing workflow leads to negligible loss due to accurate endmember number estimation, exact library pruning, and accurate physically meaningful sparse inversion. Comparative assessments of compression efficacy suggest that the proposed work corresponds to better compression performance and higher classification accuracy.

In the past, many geochemical reference materials have been characterised either by the compilation of data published in the research literature, or by relatively informal ‘round-robin’ type of collaborative analysis programme. Neither approach complies with the most recent recommendations in ISO-REMCO Guide 35:2017. In order to develop a more rigorous approach that would lead to the full certification of such materials, Potts et al. (2019) published a certification protocol based on the well established GeoPT proficiency testing programme designed for laboratories that routinely analyse silicate rocks and related materials. In developing this certification protocol, a full assessment of compliance with the most recent version of ISO-REMCO Guide 35 was undertaken.
This protocol has now been applied to the certification of a leucomonzogranite (GMN-1), based on round 51 of the GeoPT programme that included participation by 112 laboratories from 43 countries. This exercise has led to the certification of 9 major and 39 trace elements.
In the development of this protocol, a number of issues remain that are not fully resolved in Guide 35. One is the potential clash between the requirements of proficiency testing in relation to procedures recommended for certification, perhaps the most important being the way in which well characterized consensus values derived from an assessment of data contributed to the proficiency testing programme effectively demonstrate the property of traceability.

Potts P J, Webb P C and Thompson M (2019). The GeoPT proficiency testing programme as a scheme for the certification of geological reference materials. Geostandards and Geoanalytical Research, 43, 409-418, doi: 10.1111/ggr.12261.

Nuclear energy is a crucial source of energy supply worldwide and is essential for achieving carbon neutrality. This is particularly true for advanced nuclear energy systems. In these systems, the complexity of flow and the efficiency and stability of heat transfer present ongoing challenges that necessitate further research efforts. In this specialized issue entitled "Complex Flow and Heat Transfer in Advanced Nuclear Energy Systems", a collection of related research works, including experimental research and numerical simulation works were gathered.Li Yong and colleagues conducted research focusing on condensation and acoustic characteristics of steam condensation. They experimentally studied the complex twophase flow regimes and acoustic characteristics of direct contact condensation when steam is injected into water.Mengmeng Liu, et al. carried out numerical simulations on heat transfer of supercritical pressure water in a helical tube. This process occurs in a supercritical steam generator, which may potentially be used for future high-temperature gas-cooled reactors.In the research carried out by Ji Wang, et al., an intriguing method was intruded to study

Curvilinear magnetism is a framework, which helps understanding the impact of geometrical curvature on complex magnetic responses of curved 1D wires and 2D shells [1,2]. In this talk, we will address fundamentals of curvature-induced effects in magnetism and review current application scenarios. In particular, we will demonstrate that curvature allows tailoring fundamental anisotropic and chiral magnetic interactions and enables fundamentally new nonlocal chiral symmetry breaking effect [3], which is responsible for the coexistence and coupling of multiple magnetochiral properties within the same magnetic object [4]. We will discuss the application potential of geometrically curved magnetic thin films as mechanically reshapeable magnetic field sensors for automotive applications, memory, spin-wave filters, high-speed racetrack memory devices, magnetic soft robotics as well as on-skin interactive electronics.
[1] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications (Springer, Zurich, 2022).
[2] D. Makarov et al., New dimension in magnetism and superconductivity: 3D and curvilinear nanoarchitectures. Adv. Mat. 34, 2101758 (2022).
[3] D. D. Sheka et al., Nonlocal chiral symmetry breaking in curvilinear magnetic shells. Comm. Phys. 3, 128 (2020).
[4] O. M. Volkov et al., Chirality coupling in topological magnetic textures with multiple magnetochiral parameters. Nat. Comm. 14, 1491 (2023).

The Dresden Advanced Light Infrastructure is a future infrastructure under consideration at the Helmholtz-Zentrum Dresden-Rossendorf. In the current conceptional design phase, we are surveying different control system options. To benefit as much as possible from community experiences with different control systems, in 2023 a survey was conducted and participants from accelerator and light source facilities world-wide were invited. The results of that survey are presented and conclusions for our center are drawn.

In this manuscript, we will discuss the notion of curved momentum space, as it arises in the discussion of noncommutative or doubly special relativity theories.We will illustrate it with two simple examples, the Casimir effect in anti-Snyder space and the introduction of fermions in doubly special relativity.We will point out the existence of intriguing results, which suggest nontrivial connections with spectral geometry and Hopf algebras.

We review recent discussions regarding the parity-odd contribution to the trace anomaly of a chiral fermion. We pay special attention to the perturbative approach in terms of Feynman diagrams, comparing in detail the results obtained using dimensional regularization and the Breitenlohner–Maison prescription with other approaches.

We show that there exists a generalized, universal notion of the trace anomaly for theories which are not conformally invariant at the classical level. The definition is suitable for any regularization scheme and clearly states to what extent the classical equations of motion should be used, thus resolving existing controversies surrounding previous proposals. Additionally, we exhibit the link between our definition of the anomaly and the functional Jacobian arising from a Weyl transformation.

The Ruwai Pb-Zn-Ag skarn deposit is located within the Schwaner Mountain Complex in Central Kalimantan, Indonesia. It is the largest polymetallic skarn deposit in Kalimantan with the resources is estimated up to 14.43 Mt. at 4.94 wt.% Zn, 3.28 wt.% Pb, 108.11 g/t Ag which hosted by Jurassic limestones of the Ketapang Complex and Cretaceous granitoids of Sukadana Complex. In order to study the complex mineralogy and deportment of critical-elements (Ag, Bi, Sb, In, Te, Cd) pulp samples from the main stages of the processing plant (Ball mill/feed, Pb concentrate, Zn concentrate, Pb scavenger, Zn scavenger, Fe screw, and tailings) as well as 66 core samples of Pb-Zn-Ag mineralization were obtained.
Preliminary results on the pulp samples from X-ray diffraction (XRD), X-ray fluorescence (XRF) and mineral liberation analysis (MLA) agree within analytical uncertainties. The data allows a preliminary assessment of the deportment and distribution of Ag and Bi in the skarn ores and processing products. Particularly, acanthite (Ag2S) and freibergite ((Ag,Cu,Fe)12(Sb,As)4S13) are likely to be important hosts of Ag, while Bi occurs within bismuthinite (Bi2S3) and native bismuth (Bi). For the core samples, µ-XRF measurements of slabs have so far provided a broad overview of elemental distribution within the samples, while XRD results indicate more complex mineralogical compositions than the pulp samples.
Further analytical work including electron probe microanalysis (EPMA) and laser ablation ICP-MS are planned for all samples to be also able to evaluate the resource potential of other critical elements of interest such as Sb, In, Te, Cd.

The flow past a clean spherical bubble translating steadily parallel to a no-slip wall in a stagnant fluid is studied numerically over a wide range of moderate to high Reynolds numbers. We focus on situations where the distance separating the bubble from the wall is smaller than the size of the bubble in order to explore the competition between viscous and inertial effects in the gap. More precisely, the range of the wall distance considered is $1.1\leq \LR \leq 2$ ($\LR$ being the distance from the bubble center to the wall normalized by the bubble radius), and that of the Reynolds number is $50\leq \Rey \leq 1000$ ($\Rey$ being based on the bubble diameter and the slip velocity). In contrast to predictions based on potential flow theory, the numerical results reveal that, when the gap is smaller than a critical value that depends on the Reynolds number, the transverse force starts to decrease with decreasing separation and may finally reverse, changing from attractive to repulsive. This effect is found to be due to the strong shear generated in the gap, which, combined with the local transverse gradient of the streamwise velocity, results in a system of two counter-rotating streamwise vortices and, consequently, a shear-induced lift pointing away from the wall. Computational results together with available high-Reynolds-number theory provide empirical expressions for the drag and transverse forces in the steady-state limit. Then the competition between the various transverse forces on a bubble bouncing close to the wall is examined, based on previously measured data for bubble trajectory. The central role of the history effects due to the misalignment between the wake and the instantaneous angle of the bubble path is confirmed. Computational results also reveal that, depending on the initial separation, a freely moving bubble may either reach a stable equilibrium position close to the wall or depart from the wall up to infinity.

The Spremberg-Graustein-Schleife Kupferschiefer deposit is a sediment-hosted stratabound copper (SSC) deposit located in eastern Germany. The Cu mineralization occurs at depths of 980 to 1,580 m below surface, predominantly in a Permian carbon-rich black shale unit, commonly known as the Kupferschiefer. Mineralization is not only restricted to this unit and can extend into the overlying Zechstein carbonates, as well as the underlying Redbed sandstones. Recent studies have confirmed 91.7 Mt of inferred mineral resource at an average grade of 1.5% Cu and 24.0 g/t Ag.

In addition to Cu and Ag, elevated levels of Co, Ni, and Re are also found in Kupferschiefer ores. This contribution provides the first detailed evaluation of the mineralogy of the complete mineralization interval of the Spremberg-Graustein-Schleife deposit, including the mineralogical deportment of Cu. Mineral chemistry work constraining the deportments of Ag and Re is planned.

Fifty-three individual samples were collected from three drill cores. The samples were crushed, milled, and composited into 19 composite samples. These were then subjected to multi-element analytical methods (XRF, ICP-OES, ICP-MS) for bulk-ore geochemistry, X-ray diffractometry (XRD), and mineral liberation analysis (MLA) for mineralogy. Electron probe micro-analysis (EPMA) and laser ablation ICP-MS (LA-ICP-MS) for trace element geochemistry are currently planned. Mineralogical results reveal that major Cu-bearing minerals vary both spatially between the three different drill cores and vertically between lithological units. For example, chalcocite and covellite (and to a lesser extent bornite) are the dominant carriers of Cu in the most mineralized core (80% of contained Cu), whereas chalcopyrite is the most prominent carrier of Cu in the Pb-Zn Kupferschiefer facies (75% of contained Cu). By combining different analytical results, we aim to develop a quantitative predictive model to describe the mineralogical distribution of the copper and potential by-products that will be usable for mineral processing and mine-planning purposes

The sediment-hosted Spremberg-Graustein-Schleife deposit is located in Lusatia, eastern Germany. Mineralization occurs in the lower Zechstein units, extending from the Grauliegend conglomerates and sandstones into the overlying organic-rich Kupferschiefer black shales and Zechstein carbonates. Around 100 Mt of Cu-Ag ore is present within the deposit. The ore is also enriched in Pb, Zn, Co, Ni, Au, Bi, Se, Re, and Ge (in addition to Cu and Ag). Despite the metal endowment, detailed quantitative metal deportment studies have not been carried out for this deposit, or indeed any other Kupferschiefer deposit. This study aims to bridge the gap. Core samples representing the complete mineralization interval (31 m in total) at three different sites within the deposit were mineralogically and geochemically analyzed. To ensure a comprehensive, high-quality and internally consistent dataset, various analytical methods including X-ray fluorescence (XRF), ICP-OES, ICP-MS, X-ray diffraction (XRD), Mineral Liberation Analysis (MLA), electron probe micro-analysis (EPMA) and laser ablation ICP-MS (LA-ICP-MS) were performed. The results reveal that the concentration and main hosts of copper and potential by-products vary vertically between the stratigraphical units, and spatially at different locations of the deposit. Such information will eventually help to predict deportments across the deposit, track each element within the minerals processing plants and also to get an idea of expected recoveries and thus optimizing the procedure.

Orbital-free density functional theory constitutes a computationally highly effective tool for modeling electronic structures of systems ranging from room-temperature materials to warm dense matter. Its accuracy critically depends on the employed kinetic energy (KE) density functional, which has to be supplied as an external input. In this work we consider several nonlocal and Laplacian-level KE functionals and use an external harmonic perturbation to compute the static density response at T=0 K in the linear and beyond-linear response regimes. We test for the satisfaction of exact conditions in the limit of uniform densities and for how approximate KE functionals reproduce the density response of realistic materials (e.g., Al and Si) against the Kohn-Sham DFT reference, which employs the exact KE. The results illustrate that several functionals violate exact conditions in the uniform electron gas (UEG) limit. We find a strong correlation between the accuracy of the KE functionals in the UEG limit and in the strongly inhomogeneous case. This empirically demonstrates the importance of imposing the limit of UEG response for uniform densities and validates the use of the Lindhard function in the formulation of kernels for nonlocal functionals. This conclusion is substantiated by additional calculations for bulk aluminum (Al) with a face-centered cubic (fcc) lattice and silicon (Si) with an fcc lattice, body-centered cubic (bcc) lattice, and semiconducting crystal diamond state. The analysis of fcc Al, and fcc as well as bcc Si data follows closely the conclusions drawn for the UEG, allowing us to extend our conclusions to realistic systems that are subject to density inhomogeneities induced by ions.

In this paper, we report recent advances in the improvement of the measurement accuracy of capacitance wire-mesh sensors. We review the principles of the wire-mesh sensor and discuss the problem of inherent energy losses. An advanced model that combines finite element analysis and an electronic circuit model capable of predicting such losses is also introduced. Then, we discuss different procedures and methods, which improve the measurement accuracy of capacitance wire-mesh sensors by suppressing or correcting loss effects. First, limitations of a threshold method are discussed, in particular, for water-oil-gas three-phase mixtures. Next, we discuss a procedure based on the optimization of the electronic circuit of the sensor to suppress losses and crosstalk. This improves the measurement accuracy, but only for fluids with narrow dynamic range in their electrical impedance. Finally, we discuss a method based on a modified wire-mesh sensor with extra transmitter electrode embedded in the dielectric construction material, which allows predicting nonlinear behaviors in sensor readings and compensating for them in later post-processing. In contrast to the threshold method and the optimization circuit procedure, the latter allows improved measurement accuracy, reducing local phase fraction deviations from more than 30% to less than 5% for a much wider impedance range.

We have developed an experimental platform at the National Ignition Facility that employs colliding planar shocks to produce warm dense matter with uniform conditions and enable high-precision equation of state measurements. The platform uses simultaneous x-ray Thomson scattering and x-ray radiography to measure the density, electron temperature, and ionization state in warm dense matter. The experimental platform is designed to create a large volume of uniform plasma (approximately 700 x 700 x 150 μm3) at pressures approaching 100 Mbar and minimize the distribution of plasma conditions in the x-ray scattering volume, significantly improving the precision of the measurements. Here, we present the experimental design of the platform and compare hydrodynamic simulations to x-ray radiography data from initial experiments studying hydrocarbons, producing uniform densities within ±25% of the average probed condition. We show that the platform creates a homogeneous plasma that can be characterized using x-ray Thomson scattering. Thus, the new platform enables accurate measurements of plasma conditions necessary to test models for the equation of state and ionization potential depression in the warm dense matter regime.

We study ab initio approaches for calculating x-ray Thomson scattering spectra from density functional theory molecular dynamics simulations based on a modified Chihara formula that expresses the inelastic contribution in terms of the dielectric function. We study the electronic dynamic structure factor computed from the Mermin dielectric function using an ab initio electron-ion collision frequency in comparison to computations using a linear-response time-dependent density functional theory (LR-TDDFT) framework for hydrogen and beryllium and investigate the dispersion of free-free and bound-free contributions to the scattering signal. A separate treatment of these contributions, where only the free-free part follows the Mermin dispersion, shows good agreement with LR-TDDFT results for ambient-density beryllium, but breaks down for highly compressed matter where the bound states become pressure ionized. LR-TDDFT is used to reanalyze x-ray Thomson scattering experiments on beryllium demonstrating strong deviations from the plasma conditions inferred with traditional analytic models at small scattering angles.

Elastic accommodation of the high lattice mismatch in GaAs/In(Al,Ga)As core-shell nanowires holds great potential for applications in high-frequency electronics and optoelectronics. The unique core-shell geometry offers several advantages over planar systems. The reduced dimensionality of the core enables strain relaxation along the lateral dimension and strain partitioning, ultimately reducing the overall strain energy and expanding the limits of coherency [1]. Consequently, the GaAs core can undergo extreme elastic stretching, particularly along the nanowire axis, without the onset of plastic relaxation.

Growing thick Inx(Al,Ga)1-xAs shells with high In-contents on narrow [111]-oriented GaAs cores leads to extreme elastic dilatation of the core that promotes a 40% bandgap reduction [2] as well as a 30-50% boost in electron mobility [3]. In order to elucidate the intricate 3D strain fields of such nanowires, we have employed transmission and scanning-transmission electron microscopy ((S)TEM) methods to study a series of nanowires featuring narrow cores (25 nm diameter) and thick shells (80 nm thickness) with composition x ranging from 0.20 up to 1. To enable the nanoscale investigation of all strain components, we developed elaborate sample preparation methods to facilitate observation along three zone axes, i.e. [111], <1-10> and <11-2>, as shown in Fig.1. For (S)TEM and high-resolution TEM (HRTEM) observations, a 200 kV JEOL JEM F200 CFEG microscope was used. High resolution STEM (HRSTEM) was performed in a 300 kV probe-corrected Thermo Fisher Scientific Titan Themis 60/300 microscope. In an integrated approach, experimental strain fields were compared with finite element (FE) calculations, performed using thermal expansivity to model the lattice mismatch, and with energetic calculations by molecular dynamics (MD) using the Tersoff interatomic potential [4].

(S)TEM observations revealed that for indium contents up to x≈50%, the shells were coherent and dislocation-free (Fig.1), exhibiting only occasional (111) ortho-twins and stacking faults. These are typically associated with similar faults originating in the core and are unrelated to strain relaxation. The experimental strain fields were in good agreement with the FE and MD simulations. In the core, all strain components were tensile. The axial (ezz) strain was uniform, whereas the radial (err) and azimuthal (eθθ) strains were position-dependent and saturated at the same value, in the region where the shell was completely relaxed. Upon reaching a critical composition, threading dislocations emerged in the shell, spreading radially from the core towards the {1-10} free surfaces of the shell. Their Burgers vectors were analysed using weak-beam dark-field TEM and were found to lie on the (111) plane. In the defected nanowires, Moiré fringes observed in the core region normal to [111], revealed axial relaxation, attributed to the introduction of misfit dislocations. By measuring the spacing of the Moiré fringes, the residual elastic strain in the cores was calculated.

Figure 1. (a) Bright field STEM image showing an unrelaxed, coherent GaAs/In0.56Al0.44As core-shell NW observed along <11-2>. (b) Z-contrast STEM image showing a NW cross-section, observed along [111] (top) and the corresponding strain map from the GaAs core (bottom). The nominal In-composition in b is again ≈50%.

Acknowledgements
This work was supported by the program for the promotion of the exchange and scientific cooperation between Greece and Germany (IKYDA 2020), project title: Strain tuning of iii-v semiconductor nanowires (TUNE).

References
1. Th. E. Trammell, X. Zhang, Y. Li, L-Q. Chen and E. C. Dickey, Journal of Crystal Growth 310 (2008), 3084-3092.
2. L. Balaghi, G. Bussone, R. Grifone, R. Hübner, J. Grenzer, M. Ghorbani-Asl, A. V. Krasheninnikov, H. Schneider, M. Helm and E. Dimakis, Nature Communications 10 (2019), 2793.
3. L. Balaghi1, S. Shan, I. Fotev, F. Moebus, R. Rana, T. Venanzi, R. Hübner, Th. Mikolajick, H. Schneider, M. Helm, A. Pashkin and E. Dimakis, Nature Communications 12 (2021), 6642.
4. H. Detz and G. Strasser, Semicond. Sci. Technol. 28 (2013), 085011.

With the advent of advanced laser systems producing high-frequency X-ray beams, e.g. the Euro- peanXFEL as a prominent example, a regime of laser-plasma interaction is reached, where all-optical methods, as used in particle-in-cell simulations, are no longer applicable. Instead, the interaction of hot electrons and the X-ray laser pulse must be modeled with a QED-driven approach. Furthermore, future experiments taking place at HED-HIBEF, LCLS, and other facilities targeting this regime, will encounter processes in x-ray scattering from (laser-driven) relativistic electrons, where the effects of the energy spectrum of the x-ray laser field as well as multi-photon interactions can not be neglected anymore. To explore this regime, where strong fields meet high frequencies, we present a novel approach for a numerical modeling tool, QED.jl, which inherently uses exact strong-field QED descriptions. This brings, for the first time, the technique of Monte-Carlo event generation to X-ray laser physics experiments.

Short period superlattices comprising ultra-thin InGaN/GaN quantum wells (QWs) with thickness of a few (0002) monolayers (MLs) have gained significant attention in the field of advanced optoelectronics. These nano-heterostructures offer the ability to tune the band gap by precisely controlling the thickness of both the QW and the GaN barrier [1]. Moreover, their potential applications in quantum computing and spintronics have sparked interest due to their possible topological insulator behaviour [2,3]. These properties are intricately linked to the indium content as well as the thicknesses of the QWs and GaN barriers. Growth efforts aim at high quality heterostructures with ML-thick QWs and high indium content. Previous theoretical and experimental studies have indicated that the highest indium content in such ultra-thin QWs is kinetically limited to a maximum of ~33% for growth under nitrogen-rich conditions. Meanwhile, strained substrates offer a solution to surpass the limits of indium incorporation in InGaN QWs [4]. The aim of this work was to determine the impact of growth temperature on the incorporation of indium atoms in GaN, to develop a growth model of such ultra-thin QWs and investigate the influence of strained GaN barriers on band-gap variation in this material system.

An integrated methodology combining quantitative high resolution scanning transmission electron microscopy (HRSTEM), empirical potential and density functional theory (DFT) calculations, image simulations, and strain analysis was developed and employed [5,6,7]. A series of multi-QW heterostructures were fabricated by plasma-assisted molecular beam epitaxy (PAMBE) under metal-rich conditions, varying the growth temperatures of the QWs and GaN barriers. Our STEM-based analysis verified the formation of ultra-thin QWs with self-limited thickness up to 2 MLs along with the formation of ML-thick QWs with the highest known composition (~45%) (see Fig. 1(a)) under specific growth conditions [6]. The interplay between growth temperatures and incorporation of indium atoms in GaN was determined and this led to the development of a substitutional synthesis mechanism, involving the exchange between indium and gallium atoms at surface sites during the growth process. The proposed model presents promising routes for achieving higher indium contents in such QWs. DFT calculations were also utilized to address the impact of strained GaN barriers on the band gap of such heterostructures by considering that the deployment of tensile-strained barriers is an alternative option to further increase the indium incorporation limits. The changes in the band-gap energy were explored considering pseudomorphic QWs with thickness of only one ML grown on equibiaxially strained GaN barriers. The introduction of elastic strain into these heterostructures leads to modifications in their optoelectronic behaviour. The results indicated a reduction in the band gap for lower indium contents. However, for indium compositions above the mid-range, the trend is reversed, and the band gap increases with the indium content instead of reducing it (see Fig. 1 (b)) [7]. In general, while tensile-strained GaN can assist in the incorporation of indium, our calculations indicate that this strategy for reducing the band gap is only effective for lower indium concentrations.

Figure 1: (a) Pseudocolor HRSTEM image of a 1 ML InGaN/GaN QW with indium content ~45%. Inset illustrates the structural model of an InN/GaN QW. (b) Diagram of band-gap energy of 1ML-thick InGaN/GaN heterostructure with respect to the indium content of its QW. 0%, 1.5% and 3% in-plane strain of the GaN barriers are indicated by different colors. The vertical gray line shows the highest indium content experimentally achieved so far.

Acknowledgements
Work supported by the project “INNOVATION-EL” (MIS 5002772). I.G.V. acknowledges support by the State Scholarships Foundation (IKY) project “Strengthening Human Resources Research Potential via Doctorate Research” (MIS-5000432). We would like to thank the Aristotle University of Thessaloniki HPC infrastructure for the provision of computing resources.

References
1. I. Gorczyca, T. Suski, N. E. Christensen et. al, J. Phys. Condens. Matter 30 (2018) 063001.
2. M. S. Miao, Q. Yan, C. G. Van de Walle et. al, Phys. Rev. Lett. 109 (2012) 186803.
3. W. Pan, E. Dimakis, G. T. Wang et. al, Appl. Phys. Lett. 105 (2014), 213503.
4. T. Schulz, L. Lymperakis, M. Anikeeva et. al, Phys. Rev. Materials 4 (2020) 073404.
5. G. P. Dimitrakopulos, I. G. Vasileiadis, C. Bazioti et. al, Appl. Phys. 123 (2018) 024304.
6. I. G. Vasileiadis, L. Lymperakis, A. Adikimenakis et. al, Scientific Reports 11 (2021) 20606
7. P. Chatzopoulou, I. G. Vasileiadis, Ph. Komninou et. al, Crystals 13 (2023) 700.

III-V semiconductor heterostructures have contributed to a wealth of studies in solid state physics, as well as to applied research and technology in electronics and photonics. More recently, the nanowire geometry introduced new possibilities, such as one-dimensional quantum transport, formation of Majorana modes, enhanced light-matter coupling, photon entanglement, as well as monolithic integration in Si-CMOS platforms for the realization of more-than-Moore hybrid systems. This talk will be focusing on the bottom-up fabrication and the structural and electronic properties of III-As nanowire heterostructures.

The first type of heterostructures will be radial ones, comprising a GaAs core and a lattice-mismatched InxAl1-xAs or InxGa1-xAs shell. Molecular beam epitaxy and a combination of vapor-liquid-solid and vapor-solid growth modes are employed to grow free-standing nanowires on Si substrates [1, 2]. Owing to its high surface-to-volume ratio and the peculiar geometry, the thin core can be hydrostatically tensile strained to extremely high levels, depending on the In content x and the thickness of the shell. As a welcome effect, the bandgap of GaAs can be tuned to be anywhere between the strain-free value of 1.4 and 0.8 eV, allowing for potential applications in telecom photonics [3]. Furthermore, the electron mobility in the GaAs core is increased with increasing the tensile strain, as a result of a corresponding decrease in electron effective mass [4]. This is of major importance for the realization of transistors with high speed and low-power consumption.

The second type of heterostructures will be axial ones, where the composition is modulated from GaAs to AlxGa1-x¬As and back to GaAs along the nanowire axis. Here, we develop a pulsed-growth technique [5], which grants precise control over the axial growth rate and droplet composition. Using advanced transmission electron microscopy methods and a thermodynamic equilibrium model, it becomes possible to quantitatively describe the compositional grading of Al across the heterostructure interfaces and to identify the control parameters. In the end, symmetric GaAs to AlxGa1-x¬As and AlxGa1-x-As to GaAs interfaces with widths of only 2 – 3 monolayers (comparable to, or better than, state-of-the-art thin film heterostructures) are achieved for the full range of x [6]. This is particularly important for quantum heterostructures and nano-devices, where the compositional grading at interfaces can critically affect the electronic properties and the device characteristics.

Acknowledgements
Part of this work was supported by the program for the promotion of the exchange and scientific cooperation between Greece and Germany (IKYDA 2020), project title: Strain tuning of III-V semiconductor nanowires (TUNE).

References
1. T. Tauchnitz et al., Cryst. Growth Des. 17 (2017) 5276.
2. T. Tauchnitz et al., Nanotechnology 29 (2018) 504004.
3. L. Balaghi et al., Nat. Commun. 10 (2019) 2793.
4. L. Balaghi et al., Nat. Commun. 12 (2021) 6642.
5. L. Balaghi et al., Nano Lett. 16 (2016) 4032.
6. D. Hilliard et al., in preparation (2023).

Usually, quantum electrodynamics acts as the prime example, when it comes to a well-understood and outstandingly precise description of elementary particle processes. However, modern laser facilities provide highly intense light with a non-trivial temporal structure, where an arbitrary number of ‘photons’ from the light source may interact with the colliding particles. In this case, the standard perturbative treatment known from quantum electrodynamics becomes cumbersome and impractical. Accordingly, there are, among others, wide theoretical investigations w.r.t. scattering processes of particles impinging these extreme light sources. This has been done by applying the strong-field quantum electrodynamics, a theory of electromagnetic interactions within coherent highly intense light treated as a classical background field. Here, the distinction between a classical background field and a quantized photon field revealed a vast amount of novel non-linear structures and non-perturbative phenomena. In this seminar, we introduce the basic concepts of strong-field QED and derive the Feynman rules for the theory in momentum space. Then, we explore their general structure and implications from fundamental principles, namely gauge invariance.

The elastic accommodation of lattice mismatch in core/shell nanowires presents unique features because both the shell and the core can be strained depending on their volume ratio. This allows the realization of heterostructure combinations with large lattice mismatch, as well as the extensive strain-mediated tailoring of their electronic properties [1]. Owing to the large stresses involved, any shell thickness asymmetry around the core may cause the bending of the nanowires, forming shapes like circular arcs, which can be a desired effect or not, depending on the targeted application.
Here, we monitor the asymmetric shell growth, the asymmetric strain, and the resulting bending during the growth of GaAs/In0.4Al0.6As core/shell nanowires [2]. We show how the profile of the elemental beams in a conventional MBE system accounts for the asymmetric growth rate of the shell around the core, in spite of the substrate rotation during growth. The resulting asymmetric stresses around the core cause the bending of the nanowires to the side of the thinner shell, which, in turn, enhances further the growth rate and stress asymmetry, and thus the bending itself, in a self-feeding circle. Nevertheless, after a critical minimum shell thickness on all core sides has been reached, the bending is reversed and the nanowires straighten up. Analyzing cross sections normal to the axis of such straightened up nanowires by STEM, we developed a method to reconstruct, for the first time, the evolution of the shell thickness on every core side and the corresponding bending angle during growth. Furthermore, geometric phase analysis revealed the spatial distribution of strain in the core and the shell with respect to the uneven shell thicknesses around the core. Our results shine a light on the growth of lattice-mismatched core/shell nanowires and could serve as a guide to design deliberate curved structures or, instead, strategies to suppress the bending.

Figure 1. (a) Side-view SEM image of as-grown core/shell nanowires on a Si substrate. Inset: HAADF-STEM image of a cross-sectional TEM lamella. (b) Evolution of the shell thickness on two opposite core sides (thinnest vs. thickest shell) during growth and the corresponding bending angle. (c) Schematic representation of the transient nanowire bending.

[1] L. Balaghi et al., Nature Commun 10, 2793 (2019); Nature Commun 12, 6642 (2021).
[2] D. Hilliard et al., in preparation.

When lowering the dimensions of semiconductor heterostructures, controlled compositional changes become paramount owing to the increasing role of the heterointerfaces in the electronic properties of the heterostructures. A common issue faced in fabricating axial heterostructures in vapor-liquid-solid (VLS)-grown nanowires is the compositional grading, which is caused by the involved growth mechanisms and broadens the interfaces.
Here, our previously developed nanowire growth technique called droplet-confined alternate pulsed-epitaxy (DCAPE) [1] (an adaptation of conventional molecular beam epitaxy), which grants precise control over the axial growth rate and droplet composition, is employed to grow AlxGa1-xAs axial insertions in self-catalyzed GaAs nanowires. Some examples showcasing the capability of DCAPE in growing systems of complex, abrupt heterostructures are shown in Fig. 1a, where AlxGa1-xAs is revealed as horizontal dark grey lines. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and a semi-empirical growth model [2] are utilized to gain an understanding of the compositional grading mechanism and its dependence on the growth temperature (TG), the nanowire radius (RNW), and the total Al content [2]. We show that pre-filling the Ga droplet with Al before the growth of an insertion is enough to sharpen the GaAs-to-AlxGa1-xAs interface at any TG. On the other hand, though, sharper AlxGa1-xAs-to-GaAs interfaces are obtained only at lower TG and/or smaller RNW, where the so-called reservoir effect is markedly reduced. In the best case, symmetric AlxGa1-xAs insertions with interface widths of only 2– 3 monolayers (comparable to, or better than, state-of-the-art thin film heterostructures) are achieved for the full range of x (Fig. 1b), proving the strength of VLS in the fabrication of sharp axial heterostructures.

Figure 1: (a) HAADF-STEM images with 5 examples of GaAs/AlxGa1-xAs heterostructures grown in self-catalyzed GaAs nanowires. Dark contrast denotes Al-containing regions. (b) Symmetric AlxGa1-xAs profiles obtained after optimization of all growth parameters.

[1] L. Balaghi et al., Nano Lett. 16, 4032 (2016).
[2] D. Hilliard et al., in preparation.

Axial heterostructures have diverse functionality in electronic and optoelectronic devices. Implementing such systems in freestanding semiconducting nanowires further broadens the scope of potential applications, for example: distributed Bragg reflectors, high-efficiency light-emitting diodes, and quantum dot heterostructures. Although, as the physical dimensions of such devices approach the atomic scale, managing the compositional grading effect of the constituent materials at the heterointerface becomes critical and can be particularly challenging in nanowires grown in vapor-liquid-solid mode.
We grow self-catalyzed GaAs nanowires with AlxGa1-xAs axial insertions on Si substrates using our previously developed nanowire growth technique called droplet-confined alternate pulsed-epitaxy (DCAPE) [1]. Here, nanowires are grown using alternating short beam pulses as opposed to the conventional molecular beam epitaxy analog where material is continuously supplied. With this approach, precise control over the axial growth rate, droplet composition and contact angle is granted along with the unique opportunity to grow nanowire heterostructures at CMOS compatible temperatures. To examine the compositional grading mechanism of Al in our AlxGa1-xAs axial insertions we employ high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Quantitative AlxGa1-xAs profiles are extracted from atomically resolved images to study in detail the profile’s interface sharpness and symmetry in relation to the profiles total Al content, heterostructure growth temperature and nanowire diameter. Additionally, building on a previously existing heterostructure growth model that describes the AlxGa1-xAs-to-GaAs interface while considering the solid-liquid thermodynamics and the so-called reservoir effect [2], we derive our own semi-empirical model that describes remarkably well the AlxGa1-xAs profile as a whole and allows for a rigorous analysis of both the profile’s leading and trailing interfaces.
We show the AlxGa1-xAs profile’s leading interface sharpness can be maximized in thin nanowires, largely due to the Al prefilling possibilities provided by DCAPE [3]. Furthermore, we demonstrate increases in trailing interface sharpness by decreasing the nanowire radius and, considerably more so, by decreasing the heterostructure growth temperature [3]. In the best case, practically symmetrical insertions with interface lengths of only 1 – 3 monolayers are achieved for a wide range of peak Al contents, accordingly approaching the absolute limit of atomically sharp interfaces [3].

References

[1] Balaghi et al., Nano Lett. 16, 4032 (2016)
[2] Priante et al., Nano Lett. 16, 1917 (2016)
[3] Hilliard et al., unpublished results

Antiferromagnets (AFMs) as materials with a high degree of magnetic compensation and complex dynamics attract attention for fundamental research and use in high-speed and low-energy-cosuming electronics. Technologically relevant AFM thin films usually possess a granular crystal structure, which alters the properties of domain walls and skyrmions [1,2]. Here, we provide a material model of a granular AFM and describe domain wall pinning at grain boundaries [3]. The model is applied to Cr2O3 films with a maze-like domain pattern visualized using nitrogen vacancy magnetometry. Using the statistical analysis of domain size and measuring the self-similarity parameters of the domain wall pattern, we estimate the material parameters characterizing the inter-grain coupling. Namely, for the films with a grain size of about 50 nm, the distribution of exchange bonds between grains is characterized by an average of 10% from the bulk value and a wide standard deviation, including a small amount of ferromagnetic bonds. The presented approach is compatible with machine learning techniques. Based on the material model, we provide design rules for the granular AFM recording media.

[1] Jing et al, Phys. Rev. B 103, 174430 (2021)
[2] Veremchuk et al, ACS Appl. El. Mat. 4, 2943 (2022); Erickson et al, RCS Adv. 13, 178 (2023)
[3] Pylypovskyi et al, Phys. Rev. Appl. 20, 014020 (2023)

Long-term care facilities have been widely affected by the COVID-19 pandemic. Empirical evidence demonstrated that older people are the most impacted and are at higher risk of mortality after being infected. Regularly testing care facility residents is a practical approach to detecting infections proactively. In many cases, the care staff must perform the tests on the residents while also providing essential care, which in turn causes imbalances in their working time. Once an outbreak occurs, suppressing the spread of the virus in retirement homes (RHs) is challenging because the residents are in contact with each other, and isolation measures cannot be widely enforced. Regular testing strategies, on the other hand, have been shown to effectively prevent outbreaks in RHs. However, high-frequency testing may consume substantial staff working time, which results in a trade-off between the time invested in testing and the time spent providing essential care to residents.

The increasing use of deep learning techniques has reduced interpretation time and, ideally, reduced interpreter bias by automatically deriving geological maps from digital outcrop models. However, accurate validation of these automated mapping approaches is a significant challenge due to the subjective nature of geological mapping and the difficulty in collecting quantitative validation data. Additionally, many state-of-the-art deep learning methods are limited to 2-D image data, which is insufficient for 3-D digital outcrops, such as hyperclouds. To address these challenges, we present Tinto, a multisensor benchmark digital outcrop dataset designed to facilitate the development and validation of deep learning approaches for geological mapping, especially for nonstructured 3-D data like point clouds. Tinto comprises two complementary sets: 1) a real digital outcrop model from Corta Atalaya (Spain), with spectral attributes and ground-truth data and 2) a synthetic twin that uses latent features in the original datasets to reconstruct realistic spectral data (including sensor noise and processing artifacts) from the ground truth. The point cloud is dense and contains 3242964 labeled points. We used these datasets to explore the abilities of different deep learning approaches for automated geological mapping. By making Tinto publicly available, we hope to foster the development and adaptation of new deep learning tools for 3-D applications in Earth sciences. The dataset can be accessed through this link: https://doi.org/10.14278/rodare.2256 .

The geochemistry of surficial Earth materials, e.g. (weathered) rocks, soils, plants, peatlands, waterbodies or snow, is influenced by many processes and environmental parameters. Often, however, it is unknown which of the observed environmental variables, like soil pH, precipitation, slope, underlying bedrock type, to name but a few, have a significant influence on the geochemical pattern of the respective material. For this purpose, one can test hypotheses about the influence of variables on the (ilr or alr transformed) composition, e.g. by means of linear regression. These tests can either be rejected or accepted. If the result of the statistical analysis shows that the variable(s) tested could have an influence on the overall composition of the surficial material, the question immediately arises for geochemists as to which of the elements or element groups change in relation to this variable. In the case of non-compositional and univariate data, there are the classical post-hoc tests, e.g. tests according to Scheffé or Bonferroni, that allow to check which of certain interpretable subhypothesis are responsible for significant result. However, as far as the authors are aware, there are no such tests developed for multivariate situations and geochemically or compositionally relevant sub-hypotheses, such as those that consider sub-compositions or balances of specific elements.
The contribution provides a systematic compilation of compositionally and geochemically potentially relevant subhypotheses and corresponding post-hoc tests. A particular challenge is that the number of compositional hypotheses is much larger than the number of subhypotheses (all subcompositions and balances) than in a contrast’s situation (all pairs). A Bonferroni approach is therefore impractical. We thus extend Scheffé’s principle of post-hoc testing to the situation where any number of additional subhypotheses can be tested simultaneously without the need for additional p-value corrections. Geochemists in this system of post-hoc tests can then either test geochemically interpretable relevant sub-hypotheses or test the model for the least explanatory sub-hypotheses and interpret these results based on a hierarchy of implied hypotheses.
The application of the method will be demonstrated on a snow data set, which was collected for exploration purposes on a Co-Au deposit.

COVID-19 lockdowns in early 2020 reduced human mobility, providing an opportunity to disentangle its effects on animals from those of landscape modifications. Using GPS data, we compared movements and road avoidance of 2300 terrestrial mammals (43 species) during the lockdowns to the same period in 2019. Individual responses were variable with no change in average movements or road avoidance behavior, likely due to variable lockdown conditions. However, under strict lockdowns 10-day 95th percentile displacements increased by 73%, suggesting increased landscape permeability. Animals’ 1-hour 95th percentile displacements declined by 12% and animals were 36% closer to roads in areas of high human footprint, indicating reduced avoidance during lockdowns. Overall, lockdowns rapidly altered some spatial behaviors, highlighting variable but substantial impacts of human mobility on wildlife worldwide.

In a deep geological repository for nuclear waste, the host rock forms the outermost shell of the multi-barrier system designed to prevent toxic radionuclides from reaching the biosphere and subsequently the food chain. As a natural material, this host rock is characterized by heterogeneities, anisotropies, and different types of fluid pathways. Accordingly, the prediction of radionuclide (RN) migration through the host rock is complex and subject to large uncertainties. Besides salt and clay rocks, crystalline or granitoid rocks can also be considered as host rocks. There, joints and fracture network are very important parameters for the estimation of RN migration. However, microcracks or spatial veriability in the mineral composition, especially with respect to exposed mineral surfaces along fluid migration paths, can also significantly increase the uncertainties of the sorption capacity of the host rock. Another important uncertainty component is the scarcity of RN sorption data, namely for mafic minerals like the Biotite group or Amphiboles. Often one has to resort to analogues. Thus, for the calculation of distribution coefficients (Kd values, see the Smart Kd concept [1]) for a given combination of RN and rock formation, the results depend both on the knowledge of which mineral phases are actually exposed to pore water (as opposed to average rock compositions) and on the sorption models used. In our contribution, we present a workflow to use geologic samples to capture the heterogeneity of mineral composition along pathways using an approach from graph theory. Data of these spatially variable mineral compositions obtained from real
samples are then used as input parameters for the calculation of Kd values of uranium. The geochemical modelling was based on background data from sorption and surface complexation models. Furthermore, we show the uncertainties that can arise from measurement artifacts or (incomplete or missing) sorption data for certain mineral phases, especially at different pH levels. This, in turn, paves the way for corresponding sensitivity analyses indicating which input parameters deserve highest priority in future research efforts.

Currently, most reported 2D conjugated metal-organic frameworks (2D c-MOFs) are based on planar polycyclic aromatic hydrocarbons (PAHs) with symmetrical functional groups, limiting the possibility of introducing additional substituents to fine-tune the crystallinity and electrical properties. Herein, a novel class of wavy 2D c-MOFs with highly substituted, core-twisted hexahydroxy-hexa-cata-benzocoronenes (HH-cHBCs) as ligands is reported. By tailoring the substitution of the c-HBC ligands with electron-withdrawing groups (EWGs), such as fluorine, chlorine, and bromine, it is demonstrated that the crystallinity and electrical conductivity at the molecular level can be tuned. The theoretical calculations demonstrate that F-substitution leads to a more reversible coordination bonding between HH-cHBCs and copper metal center, due to smaller atomic size and stronger electron-withdrawing effect. As a result, the achieved F-substituted 2D c-MOF exhibits superior crystallinity, comprising ribbon-like single crystals up to tens of micrometers in length. Moreover, the F-substituted 2D c-MOF displays higher electrical conductivity (two orders of magnitude) and higher charge carrier mobility (almost three times) than the Cl-substituted one. This work provides a new molecular design strategy for the development of wavy 2D c-MOFs and opens a new route for tailoring the coordination reversibility by ligand substitution toward increased crystallinity and superior electric conductivity.

Understanding how structural changes of the ligand scaffold influence the coordination chemistry of early actinides is indispensable for the development of selective ligands for e.g. decontamination purposes. To obtain a profound insight into the electronic und bonding properties of early actinides, Schiff base ligands based on the salen type, have been extensively used in our group and others.[1–4] Schiff bases have shown to be excellent model ligands due to their accessible synthesis and easy functionalization and their ability to coordinate to the 5f-elements. In this respect, we have been exploring the coordination chemistry of the early actinides (Th – Pu) with pyrophen, a pure nitrogen donor ligand formed by a condensation reaction of 2-formylpyrrole with o-phenylendiamine.[5,6] A series of homoleptic 2:1 complexes has been synthesized, allowing the comparison of the hard oxygen donor of the phenolate group in the salophen system versus the soft nitrogen donor of the pyrrolide group in pyrophen. Quantum chemical calculations along with spectroscopic studies by nuclear magnetic resonance (NMR) and single crystal x-ray diffraction (SC-XRD) have been performed to elucidate the influence of hard and soft donors on the bonding strength. In solution, as confirmed by NMR, we encountered just one set of signals corresponding to a 2:1 homoleptic complex in the pyrophen system compared to two sets of signals corresponding to 2:1 homoleptic isomers present in the salophen case. In the solid state, crystallographic analysis shows that the salophen ligand adopts a sandwich like structure whereas in the pyrophen system a pincer like arrangement is preferred (see figure below).

Figure 1 Uranium(IV) complexes of salophen (left) and pyrophen (right)
References
[1] T. Radoske et al., Dalton Transactions 2020, 49, 17559–17570.
[2] R. Kloditz et al., Inorg. Chem. 2021, 60, 2514–2525.
[3] L. Köhler et al., Chemistry – A European Journal 2021, 27, 18058–18065.
[4] B. E. Klamm et al., Inorg. Chem. 2018, 57, 15389–15398.
[5] C.D. Bérubé et al., Organometallics 2003, 22, 434–439.
[6] T. Duckworth et al. manuscript in preparation.

Acknowledgment
This work was supported by the German Federal Ministry of Education and Research (BMBF) under project number 02NUK059 (f-char).

Our laboratory has been actively engaged in exploring the fundamental behavior of the early 5f elements in solution and solid state, for instance with tetradentate coordinating Schiff base ligands.[1–4] Schiff base ligands are of special interest since they can easily be prepared by a condensation reaction and are known to coordinate to different metal centers in various oxidation states. To study the reactivity and complexation differences from the tetradentate to a hexadentate binding motif, with regards to bonding trends and electronic properties, we recently extended our palette of Schiff base chelators to the hexadentate pure N-donor (tris-((1H-pyrrol-2-ylmethyl-ene)ethane)-amine (trenpy) and began to explore its coordination chemistry with the early tetravalent actinides.
Applying a salt metathesis reaction of one equivalent of AnCl4(dme)2 (An = Th, U, Np, and Pu) and one equivalent of the trianionic trenpy ligand led to the formation of the respective complexes. SC-XRD measurements confirmed the coordination of three imine and three pyrrolide nitrogens of one trenpy ligand to the metal center in the predicted hexadentate fashion. In addition, a chloro ligand binds to the An(IV), forming a 7-coordinate distorted monocapped octahedron. Analysis of SC-XRD data and quantum chemical calculations revealed different bond lengths and strengths for the different nitrogen donors (Npyrrolide and Nimine) which are slightly longer for the first and slightly shorter for the later case compared to the reported homoleptic bispyren complexes.[3] Remarkably, quantum chemical calculations for Pa(IV)-N revealed no exceptional backbonding effects as seen in [Pa(pyren)2]. We can speculate that the chloride atom indicating an influence of the chlorine atom contributes to the suppression of this effect.

Acknowledgement: This work is supported by the German Federal Ministry of Education and Research (BMBF) under project number 02NUK059B (f-Char).

[1] T. Radoske et al., Chemistry – A European Journal 2020, 26, 16853–16859.
[2] T. Radoske et al., Dalton Transactions 2020, 49, 17559–17570.
[3] L. Köhler et al., Chemistry – A European Journal 2021, 27, 18058–18065.
[4] R. Kloditz et al., Inorganic Chemistry 2021, 60, 2514–2525.