Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

INTRODUCTION

Safe disposal of spent nuclear fuel (SNF) requires matrix materials with strong resistance against corrosion and dissolution over a period of 106 years. Derivatives of zirconium-based ceramics, in particular zirconia, ZrO2, are promising materials for these applications since these phases are known to remain stable in geological cycles of up to 109 years. Here scientific and technological goals are to obtain zirconium-based ceramic materials containing maximum possible tetravalent actinides (An) without Zr/An phase separation. In addition, structural stability of these phases under various external parameters, e.g. temperature (T), pressure (P), irradiation and leaching resistance is essential in order to exclude possible discharge of the incorporated radioactive elements over a long time scale.
Five different structural modifications of zirconia are known to exist. At ambient pressure undoped ZrO2 phase exhibits three different polymorphs as a function of temperature - low-temperature (LT) monoclinic (7-fold coordination of Zr atoms, P21/c ) and parent HT tetragonal (T > 1440 K), and cubic (T > 2640 K) forms (8-fold coordination, P42/nmc and Fm-3m, respectively) [1]. Upon application of high pressure (HP) monoclinic modification of zirconia transforms into orthorhombic-I phase (Pbca, 7-fold coordination of Zr atoms similar to that observed for the parent monoclinic P21/c phase) at pressure of ~ 4 GPa [2]. Upon further compression at P > 25 GPa orthorhombic-I modification transforms into orthorhombic-II phase (Pnma, 9-fold coordination) [3] and this phase was found to be stable up to at least 100 GPa [4].
Various properties of ZrO2 can be efficiently controlled by doping. In particular, introduction of Y3+ ions is known to significantly influence phase stability range of zirconia and to stabilize desired HT modifications. Specifically, tetragonal Y-stabilized zirconia (YSZ) phases, denoted as t′, can be obtained at ambient temperature for Y content of ~ 3 - 15 at.% and the cubic YSZ phase can be stabilized for Y content > ~15 at.% [5]. The YSZ phases are, however, much more poorly studied as a function of temperature and pressure compared to the parent ZrO2 compound and the reported results are sometimes contradictory. In this work we present synchrotron radiation diffraction studies on incorporation of Th and Ce atoms in various YSZ phases as a function of composition, temperature and pressure.

DESCRIPTION OF THE WORK

Five series of samples have been synthesized for the current study: ZrxY0.11ThyO2-z (y = 1 – 7%, ~ 1% step), ZrxY0.14ThyO2-z (y = 4, 7, 10, 12%), ZrxY0.21ThyO2-z (y = 0 – 11%, ~ 3% step), ZrxY0.10CeyO2-z (y = 0 – 8%, ~ 1.5% step) and ZrxY0.16CeyO2-z (y = 0 – 8%, ~ 1.5% step). All samples have been obtained via precipitation of the corresponding metal salts by increasing the pH (pH equal 8 for Th- and 11 for Ce-containing samples, correspondingly). Obtained suspensions were subsequently centrifuged and the residues were dried at 350 K. Final oxide phases were formed by annealing at 1673 K for two hours with further quenching.
Ambient, T- and P-dependent in situ synchrotron radiation diffraction experiments were performed at the ROBL BM20 beamline [6] at ESRF, Grenoble. HT was obtained with hot gas blower and HP was generated using diamond anvil cells (DAC). Diffraction data were collected on high resolution XRD1 (Pilatus 100k) and multipurpose XRD2 (Pilatus3 X 2M, HT and HP experiments) diffractometers of ROBL [6].

RESULTS AND DISCUSSION

For the tetragonal ZrxY0.11ThyO2-z and ZrxY0.14ThyO2-z series maximum Th intake was found to be ~ 10 at.%, as concluded from the corresponding expansion of the unit cell volume as a function of % Th (Fig. 1, left). In addition, appearance of ThO2 in the sample with 12 at. % Th also confirms this solubility limit. Introduction of Th atoms into the YSZ system induces flattening of the ZrO8 polyhedra (Fig. 2). This behaviour is explained by the larger ionic radius of Th4+ compared to Ce4+ (1.19 vs. 0.98 Å, respectively, in 8-fold coordination [7]). Thus, insertion of Th atoms introduces additional volume in the unit cell allowing for the coordinating oxygen atoms to arrange in a more symmetrical way with more equilibrated Zr-O distances. Accordingly, the higher Th at. % content may be expected to be favoured by higher (cubic) symmetry. Indeed, cubic ZrxY0.21ThyO2-z system featured intake of Th up to at least 11 at.%, as concluded from the corresponding expansion of the unit cell volume (Fig. 1, right). Investigations in the cubic YSZ system for higher Th content are in progress.
Structural stability of An-containing compounds is one of key requirements for introduction of these materials in the underground nuclear waste repositories (NWR) for long-term storage. This includes resistance against corrosion and internal irradiation. While the underground T-P conditions at the NWR level (typically 500 m below the ground) are rather mild (T ~ 310 K, P ~ 100 bars (or 0.01 GPa)), partial subduction of NWR over a period of million years can not be excluded. This would expose An-containing phases to more extreme temperatures and pressures. In addition, elevated T can be produced in case of a fire outbreak. Therefore, studies of structural stabilities of the corresponding matrix materials under extreme T-P conditions allow to simulate and accelerate processes which can possibly occur during the storage period.
For the corresponding studies we have synthesized Ce-containing YSZ series. Ce is widely used as surrogate atom to simulate tetravalent radioactive elements like Th, U or Pu. In situ T-dependent diffraction studies on tetragonal ZrxY0.10CeyO2-z and cubic ZrxY0.16CeyO2-z series in a RT-1150 K range revealed excellent structural stability for all the studied compounds. In particular, occupancy of Ce4+ atoms as a function of temperature does not decrease in these systems (Fig. 3, Ce0.05Y0.10Zr0.85O1.95 phase is shown as an example) indicating that the mobility of these ions does not increase with temperature. Within the error range unit cell volume increases linearly for all the phases. The corresponding coefficients of thermal expansion, defined as α = 1/V0*((V-V0)/(T-T0)), with V0(V) and T0(T) being the initial (final) unit cell volume and the sample temperature, are listed in Table 1. Cubic Ce-YSZ samples are slightly stiffer than the corresponding tetragonal phases.
Application of external pressure on the Ce0.05Y0.10Zr0.85O1.95 phase induced a structural transformation to a higher cubic symmetry around the P ~ 8.5 GPa. Interesting, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of Ce atoms with the host YSZ matrices. The parent YSZ phases are, therefore, promising candidates as host matrices for radiotoxic tetravalent elements like U, Th or Pu.

ACKNOWLEDGEMENTS

We acknowledge the Federal Ministry of Education and Research (Germany) for the support of this project (BMBF grant 02NUK060).

REFERENCES

1. M. Bocanegra-Bernal et al., “Phase transitions in zirconium dioxide and related materials for high performance engineering ceramics,” J. Mater. Sci., 37, 4947, 2002. 2. O. Ohtaka et al., “Structural Analysis of Orthorhombic ZrO2 by High Resolution Neutron Powder Diffraction,” Proc. Jpn. Acad. Ser. B, 66, 193, 1990. 3. J. Haines et al., “Crystal Structure and Equation of State of Cotunnite-Type Zirconia,” J. Am. Ceram. Soc., 78, 2, 445, 1995. 4. O. Ohtaka et al., “Phase relations and equation of state of ZrO2 to 100GPa,” J. Appl. Crystallogr., 38, 5, 727–733, 2005. 5. H. G. Scott, “Phase relationships in the zirconia-yttria system,” J. Mater. Sci., 10, 9, 1527, 1975. 6. A. C. Scheinost et al., “ROBL-II at ESRF: a synchrotron toolbox for actinide research,” J. Synchr. Rad., 28, 1, 333, 2021. 7. R. D. Shannon, “Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides,” Acta Crystallogr. Sect. A, 32, 5, 751, 1976.

A key component of risk assessment for radioactive waste repositories in deep geological formations is the prediction of potential radionuclide (RN) transport through the geosphere. One big challenge for such large-scale heterogeneous transport simulations is the integration of realistic geochemical models and their parameters at affordable computational costs. Sorption on minerals is an important retardation process and typically applying constant distribution coefficients (Kd) that can be easily included in reactive transport codes. One of the advantage of this approach is the computational efficiency, but it cannot reflect changes in geochemical conditions. On the other hand, mechanistic surface complexation models used for process understanding can be directly coupled to transport codes with geochemical solvers, but usually only at high computational costs. An alternative is provided by the smart Kd concept (www.smartkd-concept.de) [1], specifically developed to describe variable RN sorption in transport models as consequence of changing geochemical conditions over space and time. The philosophy behind this concept is to compute multidimensional look-up tables storing distribution coefficients - but here referred to as smart Kd as they are based on mechanistic sorption models. These tables can cover wide ranges of important geochemical parameters, e.g. pH, ionic strength, and concentrations of dissolved ions. The information stored in such a look-up table can be accessed by reactive transport codes at each simulation step. This approach was already implemented in the code d3f++ [2]. Here, an additional implementation and validation of the smart Kd-approach in the code OpenGeoSys OGS6 [3, 4] is presented. The application case selected is sorption of repository-relevant RNs and possible migration scenarios through a typical sedimentary rock system covering potential host rock formations in Northern Germany. This serves as a comprehensive proof-of-concept and demonstrates the capability to describe the sorption behaviour in dependence of changing geochemical conditions quite well. As a side-effect, the large Kd-matrices that were computed can be further analysed by sensitivity and uncertainty analysis (SA/UA). Results of this case study showed that the smart Kd-approach goes considerably beyond the conventional concepts. We can illustrate that constant Kd values previously used in transport simulations are rough approximations (and not necessarily conservative ones), as in reality they rather range over several orders of magnitude. Moreover, with the results from the SA, those input parameters influencing strongest the radionuclide retardation can be identified. The results of the transport simulations with the newly implemented smart Kd-approach showed a good agreement to full reactive transport simulations using PHAST [5] or a direct coupling OGS6#PhreeqC and reflect a radionuclide-specific retardation effect. This real application case serves as a benchmark for field-scale transport simulations.

Kenntnisse über die Durchmischung und die Strömungsvorgänge in Biogasfermentern ermöglichen Optimierungspotenziale bezogen auf die Vermischung, aber auch auf die Biogasausbeute und Energieeinsparung. Aufgrund der Beschaffenheit der Fermenter (große Abmessungen, Stahlbeton) und des Biosubstrats (nicht opakes Fluid) gibt es derzeit kein Messsystem, um Strömungen und räumlich verteilte Prozessparameter zu vermessen. In dem Projekt „NeoBio“ wurde dazu eine Wireless Sensor Network (WSN) entwickelt.

Radiolabeled fluorescent dyes are decisive for bimodal imaging as well as highly in demand for nuclear- and optical imaging. Silicon-rhodamines (SiRs) show unique near-infrared (NIR) optical properties, large quantum yields and extinction coefficients as well as high photostability. Here, we describe the synthesis, characterization and radiolabeling of novel NIR absorbing and emitting fluorophores from the silicon-rhodamine family for use in optical imaging (OI) combined with positron emission tomography (PET) or single photon emission computed tomography (SPECT), respectively. The presented photostable SiRs were characterized using NMR-, UV-Vis-NIR-spectroscopy and mass spectrometry. Moreover, the radiolabeling conditions using fluorine-18 or iodine-123 were extensively explored. After optimization, the radiofluorinated NIR imaging agents were obtained with radiochemical conversions (RCC) up to 70% and isolated radiochemical yields (RCY) up to 54% at molar activities of g.t. 70 GBq/µmol. Radioiodination delivered RCCs over 92% and allowed to isolate the 123I-labeled product in RCY of 54% at a molar activity of g.t. 7.6 TBq/µmol. The radiofluorinated SiRs exhibit in vitro stabilities g.t. 70% after two hours in human serum. The first described radiolabeled SiRs are a promising step toward their further development as multimodal PET/SPECT-NIR imaging agents for planning and subsequent imaging-guided oncological surgery.

Purpose/Objective
Pencil beam scanning (PBS) proton therapy (PT) in patients with intra-fraction, breathing-induced tumour motion might result in unrecognized deviations from the planned dose distribution. Our work pursued the clinical roll-out of a 4D log file-based proton dose reconstruction (4DlogReco). By that, we monitor the interplay effect and study its relevancy in an ongoing clinical study at the University Proton Therapy Dresden (UPTD).

Material/Methods
We had developed and experimentally validated a 4DlogReco (in RayStation v.8) based on amplitude-sorted 4DCTs, PBS machine log files and synchronized motion log files. The workflow and data handling was verified in the clinical treatment planning system by a retrospective analysis of four complete PBS-PT treatment series (incl. lung, oesophageal and pancreatic carcinoma; mean motion ≤5mm; 20-33 fractions) of patients who received weekly in-room 4DCTs for monitoring interfraction changes. For the final 4DlogReco translation into clinical practice, we initiated the MOBIL study (Monitoring Of Breathing for Interplay study with Logfiles).
Available patient data were analysed fraction-wise (Fig1). We considered individual critical organs at risk (OAR; lung, heart, spinal cord, kidneys, oesophagus), the clinical target volume (CTV) coverage, mean dose, near-maximum dose and homogeneity index [D98, Dmean, D1, HI=(D1-D98)/Dprescribed] and the deviations from the plan in the fraction-wise worst case (Δwc) and in the accumulated dose (Δacc).

Results
The 4DlogReco was successfully translated into clinical application. So far, two patients (oesophageal and pancreatic carcinoma; mean motion ≤5mm; 19 and 30 fractions) had been treated within the MOBIL study. Daily 4DlogReco took about 15min incl. data processing and dose calculation, and should speed up by an automatic log file retrieval and GPU-based dose calculation after TPS upgrade.
For the six investigated patients (incl. the four workflow test patients), intra-fraction motion led to CTV parameter differences in the worst-case fractions of Δwc(D98)=( 15.5 – 3.4)pp, Δwc(D1)=( 0.1 – 3.5)pp and Δwc(HI)=0.04 – 0.17, while there were smaller changes in the accumulated dose of Δacc(D98)=( 2.6 – -0.6)pp, Δacc(D1)=(-1.3 – 0.4)pp and Δacc(HI)=0.00 – 0.03 (Fig2). The individually relevant OAR dose parameters remained uncritical in line with the so far investigated minor motion amplitudes.

Conclusion
The first 4DlogReco workflow capable to deal correctly with amplitude-sorted 4DCTs provides a fraction-wise verification of the interplay-affected delivered and accumulated dose to moving targets. The clinical implementation of this QA module at UPTD had a direct influence on our institutional treatment protocols, as PBS-PT of lung cancer patients is now admissible for motions up to 15mm. The monitoring of such patients will provide valuable insights on the necessity of further motion compensation and of considering the accumulated 4DlogReco doses during treatment adaptation.

We study the enhancement of tunneling through a potential barrier V(x) by a time-dependent electric field with special emphasis on pulse-shaped vector potentials such as A(t)=A0/cosh^2(ωt). In addition to the known effects of pre-acceleration and potential deformation already present in the adiabatic regime, as well as energy mixing in analogy to the Franz-Keldysh effect in the non-adiabatic (impulse) regime, the pulse A(t) can enhance tunneling by ``pushing'' part of the wave-function out of the rear end of the barrier. Besides the natural applications in condensed matter and atomic physics, these findings could be relevant for nuclear fusion, where pulses A(t) with ω=1 keV and peak field strengths of 10^16 V/m might enhance tunneling rates significantly.

We use energy discrimination of keV ions transmitted through a thin, single-crystalline silicon membrane to correlate specific angular distribution patterns formed in channelling geometry with trajectory-dependent electronic energy loss. The integral energy and intensity distribution of transmitted ions can thus be dissected into on one side axially channelled projectiles travelling along rather straight trajectories and on the other side dechannelled projectiles predominantly experiencing blocking. Angular distributions of transmitted ions are further simulated with two different Monte-Carlo codes.

Introduction: Dysregulated activity of matrix metalloproteinases (MMPs) drives a variety of pathophysiological conditions. Non-invasive imaging of MMP activity in vivo promises diagnostic and prognostic value. However, current targeting strategies by small molecules are typically limited with respect to the bioavailability of the labeled MMP binders in vivo. To this end, we here introduce and compare three chemical modifications of a recently developed barbiturate-based radiotracer with respect to bioavailability and potential to image MMP activity in vivo.
Methods: Barbiturate-based MMP inhibitors with an identical targeting unit but varying hydrophilicity were synthesized, labeled with technetium-99m, and evaluated in vitro and in vivo. Biodistribution and radiotracer elimination were determined in C57/BL6 mice by serial SPECT imaging. MMP activity was imaged in a MMP-positive subcutaneous xenograft model of human K1 papillary thyroid tumors. In vivo data were validated by scintillation counting, autoradiography, and MMP immunohistochemistry.
Results: We prepared three new 99mTc-labeled MMP inhibitors, bearing either a glycine ([99mTc]MEA39), lysine ([99mTc]MEA61), or the ligand HYNIC with the ionic co-ligand TPPTS ([99mTc]MEA223) yielding gradually increasing hydrophilicity. [99mTc]MEA39 and [99mTc]MEA61 were rapidly eliminated via hepatobiliary pathways. In contrast, [99mTc]MEA223 showed delayed in vivo clearance and primary renal elimination. In a thyroid tumor xenograft model, only [99mTc]MEA223 exhibited a high tumor-to-blood ratio that could easily be delineated in SPECT images.
Conclusion: Introduction of HYNIC/TPPTS into the barbiturate lead structure ([99mTc]MEA223) results in delayed renal elimination and allows non-invasive MMP imaging with high signal-to-noise ratios in a papillary thyroid tumor xenograft model.

The environmental fate of metal ions is influenced by their interactions with natural organic and inorganic ligands, which modify the ions’ structure and charge and thus influence their interactions with mineral phases. We investigate the impact of ubiquitous sulfate on the retention of trivalent f-element cations (M(III) = Am, Eu, Y) by muscovite. We combine ex situ alpha spectrometry and in situ surface X-ray diffraction (i.e., crystal truncation rod and resonant anomalous X-ray reflectivity) to determine M(III) coverages and interfacial structures at the molecular level. M(III) cations adsorb as two distinct outer-sphere (OS) complexes (i.e., adsorbed and extended OS complexes) whose coverages vary with increasing sulfate concentration, [SO42-]. When [SO42-] ≤ 0.4 mM, coverages increase and exceed the amounts needed for surface charge compensation of muscovite by a factor of ~3. This overcompensation is likely controlled by ion-ion correlations at the mineral/water interface rather than adsorption of MSO4+, which has a lower thermodynamic stability in the solutions and weaker electrostatic attraction to the mica surface than M3+. For higher [SO42-], MSO4+ and M(SO4)2- dominate solution speciation, leading to a strong decrease of the M(III) coverage due to their lower sorption affinity and weaker ion-ion correlations compared to M3+.

A mechanistic understanding of the formation of actinide nanoparticles (NPs) and its impact on the mobility of radionuclides in the environment is important for a reliable risk assessment of repositories for radioactive waste. Previous studies using surface x-ray diffraction (SXD) reported an unexpected impact of electrolyte composition on the sorption of Th(IV) on the muscovite (001) basal plane. Th uptake decreased following an unexpected trend: LiClO4 > KClO4 > NaClO4. A significantly higher coverage than needed for surface charge compensation (0.25 Th/AUC, AUC = 46.72 Ų, area of mica (001) unit cell) was observed for LiClO4 (4.9 Th/AUC), suggesting the formation of Th-NPs [1]. It remained unclear, if the electrolyte affects a reaction at the mineral surface or in solution.
We combined SXD and in situ AFM to address this question. At low [Th] (0.1 mM), the investigated electrolytes include LiCl and KCl, in comparison with the reported Th uptakes for the respective perchlorate electrolytes, and the series is extended to NH4Cl and CsCl. The results are compared to reported value for NaCl [2]. The interfacial structures show an extremely broad distribution of Th electron density up to 50 Å from the surface for LiCl and KCl. A decrease of Th uptake within the alkali series is found (Figure 1). A strong linear correlation (R2 = 0.9962) between Th uptake and ionic radius of the alkali metal ion is found, indicating that sorption competition between Th4+ and the electrolyte cation is the origin of the observed effect. The value for NaCl is a clear outlier in this series, showing a much lower uptake of Th than expected according to the trend.
Perfect agreement between the number of formed particles per area, obtained by in situ AFM, and Th uptake, observed by SXD, is found. Particles show a vertical size of ~1 – 2 nm and lateral dimensions of ~10 – 20 nm, indicating that retention occurs by the formation of NPs at the mineral-solution interface (heterogeneous nucleation), which is strongly influenced by the electrolyte.
Additionally, SXD was performed at higher [Th] = 3 mM, where the formation of Th oligomers in solution is expected. Under these conditions, LiCl (2.0 Th/AUC), NaCl (1.4 Th/AUC), and KCl (1.7 Th/AUC) show similar Th uptake, indicating a much smaller impact of electrolyte composition. The obtained interfacial structures are dominated by a high Th loading at a distinct distance (~ 6.5 Å) from the muscovite surface. Therefore, the main retention mechanism at high [Th] is suggested to be the (electrolyte-independent) formation of Th oligomers in solution and their subsequent sorption on the mineral surface.

References
[1] - M. Schmidt et al., Geochim. Cosmochim. Acta. 165, 280–293 (2015).
[2] - M. Schmidt et al., Geochim. Cosmochim. Acta. 88, 66–76 (2012).

INTRODUCTION

Transport of radionuclides (RNs), from deep geological repositories for radioactive waste, such as the highly toxic trivalent minor actinides (An(III)) Am and Cm, will be controlled by their interactions with charged mineral phases. Many countries such as Finland, Sweden, and Germany consider a repository in crystalline rock, which contains large amounts of feldspars, e.g. orthoclase (K-feldspar). Hence, reliable risk assessments of potential repository sites depend on a fundamental understanding of sorption quantity and structure of An(III) on feldspars. Typically, those interactions are investigated using mineral powder samples [1], which depict an idealization of the natural system due to the small grain size of the mineral. In those studies, information about macroscopic effects on sorption processes, like crystal orientation or surface roughness, are not accessible. Therefore, in this work we study the adsorption of Y(III), as an inactive rare earth analogue for An(III), on natural single crystal orthoclase samples of the (001) crystal orientation using the modern synchrotron-based, surface X-ray diffraction technique.

DESCRIPTION OF THE WORK

Natural single crystal orthoclase samples were freshly cleaved along their (001) orientation and reacted overnight in a solution of [Y3+] = 0.01 M at pH = 5.0 or 6.9. After the reaction was finished, surface X-ray diffraction (SXRD) was measured in situ at beamline 13 ID-C (GeoSoilEnviroCARS) of the Advanced Photon Source at Argonne National Laboratory. SXRD yields the total electron density profile of the mineral/water interface by measuring crystal truncation rods (CTR). For the first time, resonant anomalous X-ray reflectivity (RAXR) is applied on orthoclase for identification and quantification of sorption species, in our case Y3+. Coverage of adsorbed Y3+ is given in units of Y/AUC (area of the orthoclase (001) unit cell = 55.57 Å2).

RESULTS AND DISCUSSION

The study investigates the adsorption of Y3+ on orthoclase (001) at two different pH values. RAXR spectra of both samples show strong modulations at the Y X-ray absorption edge (17.038 keV), indicating that Y3+ has been adsorbed to the orthoclase surface. Analysis of amplitudes and phases of the RAXR spectra yield information about coverage and distance of the adsorbed species from the surface.
At pH 5.0, two sorption species at a distance of 2.47 (Species A) and 8.35 Å (Species B1) from the uppermost oxygen-atoms (Osurf) of the mineral surface are identified. At higher pH (6.9), the adsorbed Y is located at a distance of 1.50 (Species C) and 4.38 Å (B2) from Osurf. The Y3+ aquo ion has hydration shells in a distance of 2.36 and 4.40 Å. Therefore, Species A can be attributed to an outer-sphere (OS) and species B1 and B2 to extended outer-sphere (EOS) sorption complexes. In contrast, Species C is closer to the surface than any other sorption species observed in this study. At the investigated pH of 6.9, more sites of the orthoclase surface are deprotonated, obviously leading to the release of parts of the hydration shell of Y. Therefore, Species C is interpreted as an inner-sphere (IS) sorption complex. A plausible, bidentate binding motif for Species C is suggested based on the obtained results, where Y3+ is bound to two nearest Osurf resulting in a Y-O bond length of 2.46 Å in an angle of 39.0°.
While the interfacial speciation between the two samples is different, the total Y coverage is found to be similar for both samples (~0.6 Y/AUC). At pH 6.9 more than 70 % of the adsorbed Y3+ is bound as IS complex (Species C, 0.43 Y/AUC). The obtained coverage of the IS complex corresponds to ~2/3 of an adsorbed Y3+ monolayer, assuming bidentate coordination to two Osurf. Overall, the obtained sorption quantity and interfacial speciation are in good agreement with the powder studies, supporting the applicability of the previously developed SCMs to simulate retention of An(III) by K-feldspar for macroscopic systems.
However, we also identify reasonable amounts of adsorbed EOS complexes that are typically not found in studies using mineral powders and therefore not considered thermodynamic models. This result points out the need of studies working on macroscopic mineral samples to assess the impact of those species, and more general the controlling parameters relevant for natural systems, such as crystal orientation, surface roughness, and a realistic solid-liquid ratio. In conclusion, the results of this study contribute to a more realistic and reliable prediction of the mobility of trivalent actinides in the environment, and will enable a better risk assessment for deep geological repositories for radioactive waste.

The mobility of radionuclides in the environment, in particular in the context of a deep geological repository for radioactive waste, is heavily influenced by their interactions with charged mineral surfaces. This study investigates the retention potential of feldspars, a main component of granite as one potential host rock for a repository. The focus is on the sorption of trivalent actinides (Am, Cm) and their rare earth analogues (Eu, La, Lu, Nd, Y) as a main source of radiotoxicity in spent nuclear fuel.
A multi-method approach was used, consisting of traditional batch sorption experiments over a broad range of experimental conditions to determine uptake. Generally, retention increases with increasing pH and reaches quantitative retention at near neutral conditions. Furthermore, a spectroscopic study of the sorption structure on the molecular level was conducted. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) using the actinide Cm as a luminescent probe, shows that four surface complexes are formed, an inner sphere sorption complex and its two hydrolysis forms, as well as a ternary feldspar/Cm/silicate complex at alkaline conditions (pH > 10).
Based on the observed comprehensive batch sorption dataset a generic surface complexation model (SCM-A) was developed that describes sorption of trivalent actinides and their rare earth analogues as a function of a variety of geochemical parameters (pH, ionic strength, metal concentration, solid-liquid ratio,…). In a second step, the dataset for the model was further increased by taking the quantitative spectroscopic results into consideration (SCM-B).
The developed SCMs deliver surface complexation parameters of the formed sorption species, which are included in thermodynamic databases. This data is essential for the subsequent calculation of distribution coefficients in modern approaches like the Smart KD-concept[1] as well as reactive transport modeling. Therefore, this study provides a contribution to a more reliable safety assessment of repositories for radioactive waste.[2]
[1] Stockmann, M. et al., "Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems", Chemosphere., 187, 277–285 (2017).
[2] Neumann, J. et al., "A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar", J. Colloid Interface Sci. (2020). https://doi.org/10.1016/j.jcis.2020.11.041.

1 Introduction
Transport of contaminants, e.g. radionuclides, in the environment depends strongly on their interactions with mineral phases. In a repository for radioactive waste, crystalline rock (e.g. granite) as one potential host rock in Germany and many other countries, may affect the mobility of radionuclides. Main constituents of granite are feldspars. In spent nuclear fuel, trivalent actinides (Am, Cm, but also Pu) contribute strongly to the radiotoxicity. Therefore, this work studies the retention of Am and Cm, as well as their rare earths element analogues (Eu, La, Lu, Nd, Y) on K-feldspar. By combining batch sorption experiments and time-resolved laser-induced fluorescence spectroscopy (TRLFS), a generic surface complexation model (SCM) was obtained that is valid for all investigated M3+. Thermodynamic sorption data were obtained and an understanding of sorption mechanisms on the molecular level was achieved.
2 Results
Batch sorption experiments were performed over a broad range of environmental conditions (pH 4 – 10, [M3+] = 52 nM – 10 µM, 3 – 50 g/L K-feldspar (dp < 21 µm; 63 – 200 µm))[1]. Sorption is weak for pH < 5, strongly increases between pH 5 – 7 and reaches complete uptake at higher pH. By deconvolution of Cm emission spectra, an inner-sphere complex and its first two hydrolysis forms were found to be responsible for retention in this pH range.
For determination of the deprotonation constant pKa of K-feldspar, as one important input parameter of the model, column titration experiments were conducted. Batch sorption results of all studied M3+ were used to develop two alternative SCMs. The experimental sorption data were used to determine surface complexation parameters by coupling the parameter estimation code UCODE with PHREEQC (SCM-A). In a second approach, spectroscopic data were also considered (SCM-B). A generic approach was used to develop the geochemical models that satisfactorily describe all of the derived M3+/K feldspar sorption edges as well as TRLFS-derived speciation. The model delivered respective stability constants of the sorption complexes, which were added to the data base of the Smart Kd-concept[2]. Therefore, this work improves the risk assessment of repositories for radioactive waste.

Figure 1: Experimental batch sorption data (symbols) and calculation results using the two developed SCMs for different experimental conditions.[1]
References
[1] Neumann, J. et al., "A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar", J. Colloid Interface Sci. (2020). https://doi.org/10.1016/j.jcis.2020.11.041.
[2] Stockmann, M. et al., "Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems", Chemosphere., 187, 277–285 (2017).

Electrochemical N₂ reduction reaction (NRR) under ambient conditions is attractive for the great potential in replacing the current Haber-Bosch process towards sustainable ammonia production. Metal-heteroatom-doped carbon-rich materials have emerged as the most promising electrocatalysts for NRR. However, simultaneously boosting their activity and selectivity toward NRR remains a grand challenge, while the principle for precisely tailoring the active sites has been elusive. Herein, we report the first case of crystalline two-dimensional conjugated covalent organic frameworks (2D c-COFs) incorporated with M-N₄-C centers as novel, defined and effective catalysts, and achieve a simultaneous enhancement in the activity and selectivity towards electrochemical NRR to yield ammonia. Such 2D c-COFs are synthesized based on metal-phthalocyanine (M = Fe, Co, Ni, Mn, Zn and Cu) and pyrene building blocks bonded by pyrazine linkages. Significantly, the 2D c-COF catalysts with Fe-N₄-C center exhibit higher ammonia yield rate (33.6 μg h⁻¹mg⁻¹cat) and Faradaic efficiency (FE, 31.9 %) at -0.1 V vs. reversible hydrogen electrode than those with other M-N₄-C centers, making them among the best NRR electrocatalysts (yield rate >30 μg h⁻¹mg⁻¹cat and FE >30 %). In-situ X-ray absorption spectroscopy, Raman spectroelectrochemistry and theoretical calculations unveil that the Fe-N₄-C center acts as a catalytic site. It shows a unique electronic structure with localized electronic states at the Fermi level, allowing for higher N₂ affinity and stronger binding energy of N₂, enabling faster N₂ activation and NRR kinetics than other M-N₄-C centers. Our work opens the possibility of developing metal-nitrogen-doped carbon-rich 2D c-COFs as superior NRR electrocatalysts and provides an atomic understanding of the NRR process on M-Nx-C based electrocatalysts for the design of high-performance NRR catalysts

AMS measurements typically are lasting minutes to hours, but are usually preceded by time-consuming (typically days to weeks of) chemical preparation. Both, physicists and chemists are dreaming of an AMS-world without any chemistry.

Some of our earlier studies have already proven AMS being reasonable, fast and easily accessible for ⁷Be [1] and ⁴¹Ca [2] analysis if largely reducing radiochemical separation. However, to our knowledge there are only a few cases completely omitting wet chemical separation, e.g., ¹⁰Be/⁹Be in a Be mineral (phenakite) [3] and ¹⁴C/¹²C by laser-ablation AMS of stalagmites and corals [4]. Here, we focus on two new examples for “Instrumental” AMS (IAMS) at the DREsden AMS (DREAMS) facility and the Vienna Environmental Research Accelerator (VERA):

First, a pilot study to quantify ⁵⁵Fe (t₁/₂=2.76 a) in steel from a reactor vessel of a nuclear power plant by IAMS was validated (after radiochemical separation) by liquid scintillation counting (LSC) and AMS [5]. DREAMS reaches an uncertainty <10% at the 1 kBq g(Fe)⁻¹ level within 10 min measuring unprocessed steel chips. The background (<3 Bq g(Fe)⁻¹) is limited by the short measurement time. IAMS for analysing ⁵⁵Fe from neutron-capture production is reasonable and fast compared to other analytical methods.

Secondly, the ILIAMS set-up at VERA (Martschini et al., this meeting) allows to determine ratios of ²⁶Al (t₁/₂=0.7 Ma) to ²⁷Al and ⁴¹Ca (t₁/₂=0.104 Ma) to ⁴⁰Ca in stony meteorites by IAMS. The nearly complete suppression of isobars, i.e., ²⁶MgO⁻, when extracting AlO⁻, and ⁴¹KF₃⁻ when extracting CaF₃⁻, make pressure digestion (HF/HNO₃), ion exchange and precipitations unnecessary. Most stony meteorites contain ~1% Al, mainly in the form of Na-rich-Ca-poor plagioclase ((Na,Ca)(Si,Al)₄O₈)). Additional sources for >1% Ca are pyroxene (CaMgSi₂O₆) and phosphates (mainly apatite: Ca₅(PO₄)₃Cl)) [6]. IAMS has been performed using 1-2 mg representative powder of the previously-investigated chondrite Dhurmsala [7], either pure, mixed with Fe or PbF₂ powder.

For IAMS of ²⁶Al, AlO⁻ currents from Dhurmsala were - independent of mixing with Fe or pure - about 2% of Al₂O₃(Fe) ones. At ²⁶Al/²⁷Al of ~1.3x10⁻¹⁰ statistical uncertainties of 3% are reached within 15 min sputtering while cathodes last several hours. IAMS data at VERA - in the presence of about 15% Mg - are comparable to earlier (chemical processing) AMS results at DREAMS and ETH Zurich.

For IAMS of ⁴¹Ca, very stable CaF₃⁻ currents from Dhurmsala are ~5% of chemically-processed CaF₂ ones (each mixed with PbF₂). At ~1x10⁻¹¹ ⁴¹Ca/Ca, count rates of 1 min⁻¹ sputtering time are reached. IAMS data measured in the presence of about 1‰ K at VERA are comparable to earlier (chemical processing) AMS results at ANU, DREAMS and ETH Zurich.

The major uncertainty for both nuclides, originating from the current differences of standards and samples, will be addressed soon.

References: [1] Tiessen et al., JRNCh 319 (2017) 965. [2] Hampe et al., JRNCh 296 (2013) 617. [3] Merchel et al., JRNCh 298 (2013) 1871. [4] Welte et al., Anal.Chem. 88 (2016) 8570. [5] Merchel et al., JRNCh, submitted. [6] A. Bischoff, pers.comm. (2021.) [7] Merchel, PhD thesis, (1998).

In the DREsden Acclerator Mass Spectrometry (DREAMS) chemistry laboratory, we see elevated but constant ¹⁰Be/⁹Be levels (1.2-2.0x10⁻¹⁵) when using a customised ⁹Be carrier [1]. In satellite and DREAMS laboratories unexperienced researchers and students are performing their own chemical separation, but the “human influence” is unlikely the sole explanation. Different levels of processing blanks as a function of the preparation laboratory are well-known also at other AMS facilities [2]. In our constant approach lowering processing blank levels for ¹⁰Be/⁹Be we have investigated two potential ¹⁰Be sources: ⁹Be and ²⁷Al carrier solutions.

Beryllium-9 carrier solutions are obvious ¹⁰Be sources and commercial and customised ones from minerals were already investigated earlier [3]. Inspired by numerous users asking for ⁹Be carrier analysis, we have compiled all (new) results from different AMS facilities. Remarkably, ¹⁰Be/⁹Be varies in the range of 1-10x10⁻¹⁵ from batch to batch (LOT) of the same company, very likely related to production date [4]. Currently, Australian Chemical Reagents and LGC provide carriers with the lowest intrinsic ¹⁰Be/⁹Be. For AMS users not affording a customised ⁹Be carrier, we advise buying larger quantities of commercial carriers to guarantee long-time low ¹⁰Be/⁹Be and saving precious AMS time from analysing new batches.

Another potential source for elevated and varying ¹⁰Be/⁹Be in processing blanks are Al carrier solutions (added to processing blanks) when performing ¹⁰Be/²⁶Al projects. According to [5] commercial aluminium contained ¹⁰Be in the range of 4-10x10⁷ ¹⁰Be atoms/g(Al). Nowadays, laboratories use 0.5-3.0 mg Al for processing blanks, which would yield into 4-10x10⁵ ¹⁰Be atoms/blank increasing the ¹⁰Be/⁹Be ratio to 6-10x10⁻¹⁵.

We asked in-situ dating researchers to provide their Al solutions. To differentiate between ¹⁰Be from Al and other sources (contamination in the chemistry laboratory or the ion source) we used a “basic standard-addition approach”: For each Al solution, two AMS targets containing ~300 µg ⁹Be and either 1 mg ²⁷Al or 3 mg ²⁷Al were prepared. After minimal chemistry (hydroxide precipitation, cation exchange, Be(OH)₂ precipitation, washing, drying, ignition, mixing with Nb) samples were measured at DREAMS.

Todays’ Al solutions are lower in ¹⁰Be compared to the Al investigated by [5]. None of our results is higher than 3.55x10⁻¹⁵, however, the two processing blanks without any Al have ¹⁰Be/⁹Be ratios of 1.2-1.7x10⁻¹⁵, which is in the same range as 12 out of 14 samples from ACROS, MERCK, ROTH and Traceselect, but 2-3 times higher than the machine blank. This means ~5x10⁴ ¹⁰Be atoms/sample are added from chemicals-consumables-materials or laboratory air-dust.
For more quantitative results about the ¹⁰Be concentration of Al carriers and to identify the main sources of the ¹⁰Be contribution for the processing blanks, additional experiments with larger amounts of Al (10-50 mg) and chemicals are needed.

Acknowledgments: Thanks to ASTER, DREAMS, Trondheim, VERA colleagues for ¹⁰Be data, and ANU, AWI, BOKU, CENIEH, CSFK, U Bratislava, U Jerusalem, U Potsdam colleagues for carrier solutions.

References: [1] Merchel et al., JRNCh (2013). [2] Wilcken et al., NIMB (2019). [3] Merchel et al., NIMB (2008). [4] Merchel et al., MethodsX (2021). [5] Middleton et al., NIMB (1994).

The dynamic behavior of glacial retreat following the globally diachronous Last Glacial Maximum (LGM) is poorly understood. In the Northern Alpine Foreland, multiple lobes of foreland glaciers produced a complex morpho-sedimentary record. While the reconstructed LGM ice extent is laterally constant in the west, it shows significant variations in the central and eastern parts. We explore how these geological differences relate to local climatic variability and global paleoclimate during a period of rapid climate change in the late Pleistocene.

In this study, we employ cosmogenic ³⁶Cl in limestone to constrain the in-situ exposure age of glacial erratics situated on moraine walls of the Iller Piedmont Glacier. We sampled erratic boulders from three moraine crests previously interpreted to represent the LGM and two post-LGM retreat stands. We measured ³⁶Cl/Cl and Cl-nat of seven samples from all three locations by applying routine chemistry protocols (Merchel et al., 2013) and isotope-dilution AMS measurements using a dedicated ion source for halogenides (Pavetich et al., 2014) at the DREsden AMS facility.

Preliminary results show that the sampled boulder surfaces provide internally consistent, reproducible, and geologically meaningful dates. Field investigations indicate that some of the erratic boulders were affected by chemical weathering, slope processes or human activities after their glacial deposition, thereby influencing the measured in-situ ³⁶Cl concentrations. In order to account for these complexities, we apply appropriate correction factors to obtain more accurate ages and discuss the related uncertainties.

Sample preparation of 14 additional samples was performed at the Laboratory for cosmogenic nuclide extraction at the University of Natural Resources and Life Sciences (BOKU) in Vienna. We will likely present ³⁶Cl/Cl and Cl-nat data of these additional samples measured at the Vienna Environmental Research Accelerator (VERA) at the time of the meeting. The exposure age data elucidate the spatio-temporal patterns of receding glaciers in the Northern Alpine Foreland, and place constraints on climate reconstructions for Central Europe during the late Pleistocene.

Acknowledgements:

We are grateful to Stephanie Neuhuber (BOKU Vienna) for providing access to her CN laboratory. Kathrin Strößner, Hagen Hoemann, Paul Herwegh, Kaja Schulz and Sami Akber (all LMU Munich) are thanked for assistance with sample preparation. This work was funded by DFG (German Science Foundation) grant FR 1673/15-1. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden–Rossendorf (HZDR) e. V., a member of the Helmholtz Association, supported by the HZDR Beamtime Proposal 20002195-ST. AMS measurements and sample preparation in Vienna are supported by the RADIATE project under the Grant Agreement 824096319 from the EU Research and Innovation programme HORIZON 2020 trough the Transnational Access grant 21002431-ST.

References:

Merchel et al., Quat. Geochron. 18 (2013) 54.
Pavetich et al., NIMB 329 (2014) 22.

Introduction:

Adjuvant radio(chemo)therapy (RT) is part of the treatment of patients with primary brain tumors. A major challenge following radiotherapy is to distinguish between tumor recurrence and radiation-induced effects. Hyperintensities in T2-weighted (T2w) MRI are commonly observed after radiotherapy but are not specific to the underlying tissue changes. The value of advanced methods, such as perfusion MRI, has already been shown for differentiating between tumor and treatment effect [1,2]. The aim of this study was to evaluate changes of relative cerebral blood volume (rCBV) in areas of T2w-hyperintensities in order to establish an imaging biomarker differentiating between tumor and treatment effect.

Methods:

In a longitudinal study, anatomical and functional MRI data of glioma patients undergoing gross tumor resection followed by RT were collected. We analyzed a subset of this cohort, which consisted of 14 glioma patients (3 grade II, 8 grade III, 3 grade IV, average age 48.1y ± 13.5y) with tissue hyperintensities on T2w FLAIR images after proton beam irradiation. All MRI data were collected on a 3T Philips Ingenuity PET/MR scanner (Philips, Eindhoven, The Netherlands) using an 8 channel head coil and included anatomical T1w images [3D-GRE, TR/TE=10/3.7ms, FA=20°, voxel size 1×1×1mm3], contrast enhanced T1w images (CET1w) [3D Turbo Field Echo (TFE), TR/TE=8.2/3.7ms, FA=8°, voxel size 1×1×1mm3], 3D FLAIR images [TR/TE = 4800/293ms, TI = 1650ms, 2 averages, voxel size 0.49×0.49×0.5mm3, 360 slices], and dynamic susceptibility contrast (DSC) images using a PRESTO sequence [TR/TE=15/21ms, FA=7°, 60 dynamics, dynamic scan time=1.7s, voxel size 1.8×1.8×3.5mm3] with intravenous gadolinium contrast agent (0.1mol/kg, 4ml/s, 7s delay) followed by a saline flush (20ml, 4ml/s). The same dose of contrast agent was given as a pre-bolus for leakage correction of the DSC perfusion images. MRI scans were acquired prior to RT and post RT in three monthly intervals. In this analysis only the baseline data and the measurement of the latest follow-up time point (18.9 ± 8.2 months after RT) were considered.
To determine cerebral blood volume (CBV) with DSC, the signal time curves of the dynamic PRESTO measurements were converted to concentration time curves. CBV was calculated by the division of the area under the time curve determined by a gamma variate fit function with the arterial input function. CBV-maps were normalized to a normal appearing WM ROI receiving a radiation dose less than 1Gy resulting in the rCBV. The hyperintensity mask indicated on T2w images was determined by the ratio of follow-up and baseline FLAIR images which were registered non-linearly to each other with ANTs [3]. The area showing contrast enhancements in the follow-up measurement was identified by comparing CET1w and T1w images. Hyperintensity mask (HI), contrast enhancement mask (CE), planning computed tomography images (CTs), radiation dose, clinical target volume (CTV) and gross tumor volume (GTV) resp. tumor bed volume (TBV) contour were rigidly registered first to the T1w image and then to the CBV image using ANTs [3] . The region of interest (ROI) was defined based on the hyperintensity mask in the follow-up measurement excluding the GTV resp. TBV and the CE. Four patients did not show any contrast enhancement. The ROI was transferred to the baseline images to evaluate the same region in baseline and follow-up measurement. The rCBV distributions were evaluated comparing the histograms of follow-up and baseline measurement and the Kolmogorow-Smirnow (KS)-test was used to examine the similarity of the histograms. Additionally, the rCBV alterations were analyzed visually.

Results:

The KS-test revealed a significant inequality between follow-up and baseline histograms for all patients, which was expressed by a shift to lower rCBV values in the follow-up measurement (figure 2). Visual examination confirmed the impression of decreasing perfusion in the hyperintense areas, as shown for one patient in figure 1.

Discussion:

We found decreasing perfusion in the hyperintense areas which can be interpreted as treatment effect appearing after RT according to previous studies [4-6]. The baseline evaluation is more distorted by the vascular influence due to inaccuracies in registration and tissue deformation to the transmitted ROI. This can potentially lead to higher baseline perfusion values in some areas caused by grey matter (GM) or vessels. The baseline maps (figure 1B-D) show this effect of blood vessels to the rCBV in the ROI. Due to these factors, comparing mean rCBV values within the ROIs or voxel-based evaluation of the perfusion changes is compromised. Further work is now needed to correlate the observed perfusion changes with histological data.

Conclusion:

The combination of visual impression and histogram analysis showed a decreasing perfusion in the hyperintense areas. Quantitative evaluation requires the exclusion of the influence of the vessels as well as the consideration of tissue displacements. For further studies, the appearance of rCBV changes in areas depending on proximity to CE would be of high interest [7,8] as well as a dose-dependent evaluation.

Structural inversion symmetry breaking in low-dimensional magnetic systems determines their electronic and magnetic properties at interfaces [1,2]. Asymmetrically sandwiched magnetic films can provide strong perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interactions (DMI), which is necessary for prospective memory and logic devices based on chiral non-collinear magnetic textures, e.g. skyrmions [3,4], skyrmion bubbles and chiral domain walls (DWs) [5]. The device performance is determined by the static and dynamic micromagnetic parameters [6,7]. In particular, the speed of a DW-based racetrack memory is defined by both the strength of the external driving, e.g. magnetic field or spin-polarized current, and internal magnetic parameters, e.g. the DMI constant and damping parameter [6,7]. The necessity of having a strong DMI in asymmetrically sandwiched magnetic structures requires the utilization of ultrathin (in the range of 1 nm) magnetic films, which implies the polycrystalinity and compromized structural quality of the layer stack. Structural imperfections in addition to the spin-pumping mechanism [8,9], that arises due to the proximity of a ferromagnetic material with a heavy-metal, lead to a substantial enhancement of the magnetic damping parameter of ultrathin films compared to bulk. Accessing this parameter typically requires dynamic experiments on the motion of DWs in confined geometries, which are usually done in the creep regime due to the pronounced pinning.

Here, we demonstrate both experimentally and theoretically the presence of tilted DWs in statics in perpendicularly magnetized asymmetric //CrOx/Co/Pt layer stacks with surface-induced DMI, Fig. 1. We show that in such systems there are two possible theoretical mechanism for the appearance of titled DWs: (I) A unidirectional tilt could appear in equilibrium as a result of the competition between the DMI and additional in-plane easy-axis anisotropy, which breaks the symmetry of the magnetic texture and introduce tilts [10]. (II) A static DW tilt could appear due to the spatial variation of magnetic parameters, which introduce pinning centers for DWs. A moving DW can be trapped in a tilted state after the external driving field is off. Based on these theoretical approaches, we perform a statistical analysis of the DW tilt angles obtained in staticts after the external magnetic field used for the sample demagnetization was off. We found that the second approach corresponds better to the experimental observations and allows to determine self-consistently the range of DW damping parameters and DMI constants for the particular layer stack. Using two reference fields, which provide two characteristic tilt angles, allow us to retrieve the range of DMI strength mJ/m2 and DW damping parameters . The upper limit for the DMI constant agrees with an independent transport-based measurement giving mJ/m2, which further refines our estimate of the damping parameter . This value lies in a typical DW damping range for the Co-based asymmetrical layer stacks, that are obtained from dynamic experiments [11,12]. Thus, the combination of the proposed method with standard metrological techniques opens up opportunities for the quantification of both static and dynamic micromagnetic parameters based on static measurements of the DW morphology.
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[4] S. Woo, K. Litzius, B. Krüger, et al., Nature Materials 15, 501 (2016).
[5] S. Emori, U. Bauer, S.-M. Ahn, et al., Nature Materials 12, 611 (2013).
[6] C. Garg, S.-H. Yang, T. Phung, et al., Science Advances 3, e1602804 (2017).
[7] S. Parkin and S.-H. Yang, Nature Nanotechnology 10, 195 (2015).
[8] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, et al., Reviews of Modern Physics 77, 1375 (2005).
[9] A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, Physical Review Letters 101, 037207 (2008).
[10] O. V. Pylypovskyi, V. P. Kravchuk, O. M. Volkov, et al., Journal of Physics D: Applied Physics 53, 395003 (2020).
[11] J.-M. L. Beaujour, J. H. Lee, A. D. Kent, et al., Physical Review B 74 (2006).
[12] A. J. Schellekens, L. Deen, D. Wang, et al., Applied Physics Letters 102, 082405 (2013).

Quelloffene Software ist aus der heutigen Wissenschaft nicht mehr wegzudenken und insbesondere im Hinblick auf die Sicherstellung der FAIR Prinzipien stellt sie eine hinreichende Bedingung dar. Die Verwendung von quelloffener Software ist jedoch durch eine Vielzahl von Besonderheiten geprägt, beispielsweise gibt es kein eindeutiges Finanzierungsmodel, wie es für kommerzielle Software in Form von Lizenzgebühren normalerweise der Fall ist. Die freie Verfügbarkeit der Software ermöglicht zudem völlig neue Konzepte in der Ausgestaltung der Beziehung zwischen den Anbietern und den Nutzern, sowie für die Organisation der Community. Hierdurch eröffnet sich ein Gestaltungsspielraum, welcher bisher nur bedingt durch die Forschungseinrichtungen genutzt wird, aber in sich ein enormes Potential für die Zukunft birgt.

Eine im Ingenieurwesen sehr erfolgreiche quelleoffene Software ist die C++-Bibliothek OpenFOAM1 zur Lösung partieller, nichtlinearer Differenzialgleichungen. OpenFOAM wird für eine Vielzahl von unterschiedlichen Anwendungen, wie beispielsweise in der Aerodynamik, in der Hydrodynamik oder in der Chemie- und Verfahrenstechnik eingesetzt. Die Anwender finden sich dabei nicht nur im akademischen Umfeld, sondern auch in der Industrie bei unterschiedlicher Firmen. In den letzten Jahrzehnten hat sich um OpenFOAM eine sehr aktive Community gebildet, mit zum Teil sehr unterschiedlichen Interessen und einem großen Konfliktpotential. Eine der wichtigsten Fragen beim Einsatz von OpenFOAM ist die langfristige und nachhaltige Softwareentwicklung, einerseits bei den Hauptentwicklern, aber vor allem auch bei den Wissenschaftlern. In einem typischen Arbeitsablauf wird zu Beginn einer Promotion ein Fork von OpenFOAM erstellt, in welchem der Doktorand seine Entwicklungen umsetzt. Häufig wird dieser Fork nach Abschluss der Promotion weder langfristig gepflegt, noch ins Release überführt und die Forschungsergebnisse gehen teilweise verloren. Die Ursachen hierfür sind vielfältig, u. a. mangelnde Finanzierung des notwendigen Re-Factorings und des langwierigen Diskussionsprozesses mit den Hauptentwicklern durch den Fördermittelgeber oder eine unzureichende Abbildung solcher Arbeiten in den Kennzahlen der wissenschaftlichen Arbeit und den Beschäftigungsmodellen des öffentlichen Dienstes.

Das Helmholtz-Zentrum Dresden-Rossendorf hat es sich zum Ziel gesetzt eine nachhaltige Softwareentwicklung für OpenFOAM gemeinsam mit der OpenFOAM Foundation anzustreben. Der geplante Beitrag soll die bisher gesammelten Erfahrungen des Helmholtz-Zentrum Dresden-Rossendorf im Umgang mit quelloffener Software am Beispiel von OpenFOAM präsentieren, welche aus dem intensiven Engagement als OpenFOAM Community Mitglied resultieren. Hierbei profitieren die Entwickler u. a. von den Möglichkeiten der Helmholtz-Gemeinschaft, insbesondere von den Helmholtz Federated IT Services (HIFIS)2. Der Vortrag zeigt einen möglichen Weg für eine wissenschaftliche Einrichtung mit einem guten Beispiel vorangehen und vernünftige Konzepte zu entwickeln quelloffene Software adäquat einzusetzen, nachhaltig weiterzuentwickeln, langfristig zu unterstützen und zu fördern. Ziel des Beitrages ist es Erfahrungen zu teilen, Probleme anzusprechen und eine Diskussion zur Beschreibung weiterer Wege anzuregen.

Curvilinear magnetism is the emerging field in micromagnetism which studies influences of external geometry and its topology on magnetic vector fields [1]. Much attention was paid to fundamental theoretical investigations of curvature-induced effects for local [2,3] and non-local magnetic interactions [4], which results in the prediction of various magnetochiral effects [2,5], topologically-induced magnetic patterns [5,6], stabilization of individual skyrmions [7,8] and skyrmion lattices [9] on curvilinear defects. Recently, we provided the very first experimental confirmation and quantitative assessment of the existence of the curvature-induced chiral interaction of exchange origin in a conventional soft ferromagnetic material [10]. In its turn, the interplay between the intrinsic and exchange-induced Dzyaloshinskii-Moriya interaction (DMI) paves the way to a mesoscale DMI [3], whose symmetry and strength depends both on the geometrical and material parameters of the magnetic system. Extending this concept we proposed a novel approach towards artificial magnetoelectric materials with helimagnetic nanohelices embedded in a piezoelectric matrix [11], where electric field could control magnetic states through the utilization of curvature-induced effects.

[1] R. Streubel et. al., J. Phys. D: Appl. Phys. 49,363001 (2016).
[2] Y. Gaididei et al., Phys. Rev. Lett. 112, 257203 (2014).
[3] O. Volkov et al., Sci. Rep. 8, 866 (2018).
[4] D. D. Sheka et al., Commun. Phys. 3, 128 (2020).
[5] V. P. Kravchuk et al., Phys. Rev. B 85, 144433 (2012).
[6] O. V. Pylypovskyi et al., Phys. Rev. Lett. 114, 197204 (2015).
[7] V. P. Kravchuk et al., Phys. Rev. B 94, 144402 (2016).
[8] O. V. Pylypovskyi et al., Physical Review Applied 10, 064057 (2018).
[9] V. P. Kravchuk et al., Phys. Rev. Lett. 120, 067201 (2018).
[10] O. M. Volkov et al., Phys. Rev. Lett. 123, 077201 (2019).
[11] O. M. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).

Background:

In the past years, the treatment of acute myeloid leukemia (AML) has been significantly shifted towards the development of targeted approaches. Nonetheless, clinical translation of novel immunotherapeutic strategies such as chimeric antigen receptor (CAR) T-cells in AML is still at an early stage. Given the heterogeneity of such disease, major challenges include immune escape and disease relapse, which demand for further improvements in the CAR design. To overcome such hurdles, we have invented the switchable, flexible and programmable adaptor RevCAR platform. This consists of T-cells engineered with RevCARs that are primarily inactive as they express an extracellular short peptide epitope incapable of recognizing surface antigens. RevCAR T-cells can be redirected to tumor antigens and controlled by bispecific antibodies cross-linking RevCAR T- and tumor cells resulting in tumor lysis. Remarkably, the RevCAR platform enables combinatorial tumor targeting following Boolean logic gates in which two separate RevCARs with different specificities can be simultaneously expressed and used to accomplish dual gated targeting of prominent AML antigens such as CD33 and CD123. We herein show for the first time the applicability of the RevCAR platform to target myeloid malignancies such as AML.

Methods:

Binding, functionality and proof-of-concept for combinatorial tumor targeting using the RevCAR system was assessed using both in vitro and in vivo models in different settings. For that, flow cytometry-based, cytokine release and cytotoxicity assays were performed using established AML cell lines or patient-derived material.

Results:

We have proven that AML cell lines as well as patient-derived AML blasts could be efficiently killed by redirected RevCAR T-cells targeting CD33 and CD123 in a flexible manner. Furthermore, by targeting both antigens, an AND gate logic targeting could be achieved using the RevCAR platform. This is a particular important approach to overcome existing or treatment related tumor escape variants and to tackle AML cancer heterogeneity.

Conclusions:

These accomplishments validate the preclinical versatility and controllability of the RevCAR platform embedded in one single system thereby paving the way for an improved and personalized immunotherapy of AML patients.

The microporosity, structure and permeability of SiOx thin films deposited by microwave plasma enhanced chemical vapour deposition and by plasma-enhanced atomic layer deposition on PDMS substrates were investigated by positron annihilation spectroscopy and complementary techniques. The chemical composition and morphology were analysed by X-ray photoelectron spectroscopy, polarization modulated-infrared reflection-absorption spectroscopy, time of flight spectroscopy and atomic force microscopy. The SiOx films were deposited onto spin-coated PDMS substrates, which were exposed to an oxygen plasma prior to thin film deposition. A correlation between the oxygen fluence during the oxygen plasma treatment and the microporosity of bth PE-CVD and PE-ALD SiOx films could be established. It was observed that a longer exposure to the oxygen plasma treatment resulted in formation of a SiOx-like surface near region of the PDMS film. In comparison to the as spin-coated PDMS surface, the oxidised surface near region led to an overall decrease in micropore density and to a shift towards smaller pore sizes within the deposited SiOx films.

Curvilinear magnetic objects are in focus of intensive research due to the possibility to obtain new
fundamental effects and stabilize topologically non-trivial magnetic textures at the nanoscale [1]. In
geometrically-broken magnetic objects all energy functionals, that contains spatial derivatives, e.g.
exchange, magnetostatic and intrinsic Dzyaloshinskii-Moriya (DMI) interactions, are reshaping in a
way of appearance additional curvature-induced chiral and anisotropy terms. These novel chiral
magnetic responses arise in the physical space, by introducing bends and twists to magnetic
architectures even of conventional materials. We address both experimentally and theoretically the
appearance of curvature-induced exchange effects in parabolic nanostripes with different
geometrical parameters [2]. We show that a pinning of transversal domain wall at the parabolic apex
is originated due to the presence of local curvature-induced DMI that creates a subsequent pinning
potential. Measuring the depinning field enables to quantify the effective exchange-driven DMI
interaction constant. In its turn, the interplay between the intrinsic and exchange-induced DMI
paves the way to a mesoscale DMI, whose symmetry and strength depend both on the geometrical
and material parameters [3]. Developing this concept we propose a novel approach towards
artificial ME materials with helimagnetic nanohelices embedded in a piezoelectric matrix [4]. By
applying an electric field, small geometrical changes of pitch and radius could lead to the phase
transition from a homogeneously magnetized state (full average magnetic moment) to a periodical
one (zero average magnetic moment).

[1] R. Streubel et. al., J. Phys. D: Appl. Phys. 49,363001 (2016).
[2] O. Volkov et al.. Phys. Rev. Lett. 123, 077201 (2019).
[3] O. Volkov et al., Sci. Rep. 8, 866 (2018).
[4] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).

Mit der Initiative MaterialDigital fördert das BMBF die Digitalisierung der Materialwissen-
schaft und Werkstoff technik in Deutschland. In diesem Rahmen fungiert die Plattform
MaterialDigital als Anlaufstelle für alle Interessenten und koordiniert die Aktivitäten zu
Digitalisierung in der Werkstoff welt. Mit dem im März 2021 gestarteten Projekt KupferDigital
ist nun auch der Werkstoff Kupfer ist bei der Initiative Plattform MaterialDigital vertreten. Das
Ziel des Projektes ist es, den Kupferlebenszyklus von der Erzgewinnung über die Material-
entwicklung und Herstellung sowie des Produktlebens bis hin zum Recycling digital zu
repräsentieren. Als Basis der Digitalisierung dienen hierzu Ontologien, die die digitale Material-
und Prozessbeschreibung einheitlich ermöglichen sollen und auch im größeren Zusammenhang
der Plattform MaterialDigital als gemeinsamer Standard entwickelt werden sollen.
Entstehen soll ein Datenökosystem, in dem der Datenaustausch über die verschiedenen
Instanzen des Lebenszyklus hinweg ermöglicht werden soll. Damit kann die Material- und
Produktentwicklung im eigenen Unternehmen Aspekte aus den anderen Stationen des
Lebenszyklus berücksichtigen und zum Beispiel Aspekte der Nachhaltigkeit berücksichtigen.

Low-dimensional magnetic architectures including wires and thin films are key enablers of prospective ultrafast and energy efficient memory, logic and sensor devices relying on spin-orbitronic and magnonic concepts. Curvilinear magnetism emerged as a novel approach in material science, which allows tailoring of the fundamental anisotropic and chiral responses relying on the geometrical curvature of magnetic architectures. Much attention is dedicated to magnetic wires of Möbius, helical or DNA-like double helical shapes, which act as prototypical objects for the exploration of the fundamentals of curvilinear magnetism. Although there is a bulk number of original publications covering fabrication, characterization and theory of magnetic wires, there is no comprehensive review of the theoretical framework of how to describe these architectures. Here, we summarize theoretical activities on the topic of curvilinear magnetic wires and narrow nanoribbons, providing a systematic review of the emergent interactions and novel physical effects caused by the curvature. We discuss prospective research directions of curvilinear spintronics and spin-orbitronics, outline the fundamental framework for curvilinear magnonics and introduce mechanically flexible curvilinear architectures for soft robotics.

Oxide minerals (include oxides, hydroxides, oxyhydroxides and hydrated oxides) are primary and secondary minerals of Si, Fe, Mn, Al and Ti. Secondary oxides, particularly of Fe, Al and Mn, are perhaps the most reactive and important components in many soils due to their high specific surface area and strong sorption capacity for many essential and potentially toxic elements. Iron and Mn oxides also play key roles in many redox reactions and have major influence on the transformation and availability of organic and inorganic contaminants in soils. This chapter provides an overview of the oxide minerals in soils, with an emphasis on their structure and composition, environmental conditions for their formation and their properties.

INTRODUCTION:

Proton therapy (PT) produces highly conformal dose distributions with steep gradients at the target boundaries due to the finite range of protons. This reduces normal-tissue doses, particularly at the distal side of the tumor where the Bragg peak is located. However, the targeting precision of PT is compromised by a lack of image guidance: imaging modalities in treatment rooms of PT facilities are often limited to X-ray based on-board 2D kV or 3D cone-beam CT imaging. The integration of fast real-time MR imaging could significantly improve on-board imaging and therefore increase the targeting accuracy of PT, especially for moving tumors [1].
However, a full integration of MRI and PT at the treatment isocenter is technically challenging due to the electromagnetic interaction between both systems. Although a first proof-of-concept for in-beam MRI has proven successful in combination with a static proton research beamline [2], the combination of a research prototype in-beam MRI system with a beamline featuring an actively scanned proton beam (figure 1) has proven problematic. MR images acquired during proton pencil beam scanning (PBS) dose delivery were blurred by coherent ghosting artefacts due to dynamic magnetic fringe fields produced by nearby beam steering magnets overlapping with the B0 field of the MR scanner (figure 2) [3]. One way to eliminate these artifacts could be passive magnetic shielding of the beam steering magnets. This would lead to decoupling the magnetic fields of the MR scanner and the PBS nozzle. To be able to design an optimal shielding solution, a detailed understanding of the magnitude of the magnetic fringe fields produced by the PBS nozzle is mandatory. The aim of this study was to measure the magnetic fringe fields produced by the PBS nozzle. The experimental data will be used to help optimize and validate a finite element model (FEM) of the PBS nozzle that is under development.
METHODS:
A proton beam of therapeutic quality was generated by an isochronous cyclotron (C230, IBA SA, Louvain-la-Neuve, Belgium). The proton PBS nozzle of a horizontal research beamline included two sets of dipole magnets to scan the beam in horizontal (X) and vertical (Y) direction across a target volume during dose delivery. A fluxgate magnetometer (Mag649-200, Metrolab Technology SA, Geneva, Switzerland) was used to measure the magnitude of the magnetic fringe fields produced by the beam scanning magnets. It was positioned on a mobile tripod in front of the PBS nozzle at 13 locations as demonstrated in figure 3 at the height of the central beam axis (i.e. 126 cm above floor level). The delivery of two dose spot maps was emulated by energizing the magnets of the PBS beamline for a proton beam of 220 MeV, but no beam was released from the cyclotron in order to prevent radiation damage to the magnetometer. A beam energy of 220 MeV was chosen to achieve the maximum magnitude of magnetic fringe fields produced by the beamline magnets, and thus represent the worst-case scenario. Each dose spot map included a single dose point of 4500 monitor units (MUs) irradiated at a dose rate of approximately 155.2 MU/s. The X scanning magnets were energized to emulate the delivery of two dose spots to extreme positions at (X = -20 cm, Y = 0 cm) and (X = 20 cm, Y = 0 cm) relative to the beam isocenter. This experiment was repeated three times. The Y scanning magnets were not energized, as their fringe fields were previously shown not to affect the MR image quality [3].
RESULTS:
The maximum magnitude of the magnetic fringe field of scanning magnets was measured on the central beam axis at PBS isocenter (Figure 4). The fringe field magnitude varied from 2 µT to 6 µT over the volume where the in-beam MR scanner will be placed. A slight asymmetry in the measured values along the lateral direction (i.e. perpendicular to the central beam axis) was observed (see figure 4a).

DISCUSSION:

The resolution and the measuring range of the magnetometer are well suited to perform the measurements in the volume of high interest, i.e. the volume where the in-beam MR scanner is positioned. Even the 1 µT changes in the magnetic field, e.g., the asymmetry along the lateral direction, were detected. The asymmetric measurement results from the asymmetric design of the PBS nozzle. However, the resolution of 0.5 µT did not allow measurements in lower magnetic fields and the magnetometer became oversaturated in the regions of higher magnetic field strengths. Further measurements outside the volume in which the MR scanner is positioned, e.g., in the immediate proximity of the PBS nozzle where the magnetic field strength is largest, require a magnetometer with an extended measuring range and resolution.

CONCLUSION:

The magnitude of the magnetic fringe field produced by the PBS nozzle was successfully measured experimentally for two dose spot maps at extreme spot scanning positions. The valuable measurement data will be used to optimize and validate the FEM model of the PBS nozzle. More measurements using different beam energies, dose spot positions and measurement positions of the magnetometer are needed to complete the validation of the FEM.

The uranium valence electronic structure in the prototypical undistorted perovskite
KUO3 is reported on the basis of a comprehensive experimental study using multi-
edge HERFD-XAS and relativistic quantum chemistry calculations based on DFT.
Very good agreement is obtained between theory and experiments, including the con-
firmation of previously reported Laporte forbidden f-f transitions and X-ray photo-
electron spectroscopic measurements. Many spectral features are clearly identified in
the probed U-f, U-p and U-d states and the contribution of the O-p states in those fea-
tures could be assessed. The octahedral crystal field strength, 10Dq, was found to be 6.6(1.5) eV and 6.9(4) eV from experiment and calculations respectively. Calculated
electron binding energies down to U-4f states are also reported.

EXAFS is one of the comprehensive usable method to characterize structures of various
materials including radioactive and nuclear materials. Unceasing discussions about the interpretation of
EXAFS results for actinides nanoparticles (NPs) or colloids remain during the last decates. In this paper,
the new experimental data for PuO2 and CeO2 NPs with different average sizes are compared with
published data on AnO2 NPs that shed the light on the best fit and interpretation of the structural data.
Structurally PuO2, CeO2, ThO2, and UO2 NPs demonstrate similar behavior. Only ThO2 NPs have a
more disordered and even partly amorphous structure that results in EXAFS characteristics. The
proposed new core-shell model for NPs with calculated effective coordination number perfectly fits the
results on variations in Me-Me shell with the decrease of NPs size.

Část interdisciplinárních studií v sociálních vědách se v posledních letech zastřešuje termíny jako "Cultural Analytics", "Cliodynamics" nebo "Digital (Geo) Humanities". Soustřeďují pozornost na otázky digitalizace, sdílení a popisu (metadata) zdrojů, datové analýzy a vizualizace ve vědeckých oblastech, kterým jsou tradičně vlastní spíše kvalitativní metody, což platí v neposlední řadě i pro historický výzkum. Úkolem (geografické) datové analýzy je obecně snaha transformovat data do podoby, ze které je možné získat novou vědomost. Přestože je dnes proces datové analýzy relativně standardizovaný, prostředí historického výzkumu má několik specifik, k nimž je třeba přihlížet. Prezentace se soustředí na tyto specifika v kontextu geografické datové analýzy, jež jsou přítomna v procesu sběru a zpracování dat, volby a implementace metodologie a také interpretace a validace výstupů.

Analytic and numerical studies on curved magnetic nano-objects predict numerous exciting effects that can be referred to as magneto-chiral effects, which do not originate from intrinsic Dzyaloshinskii–Moriya interaction or interface-induced anisotropies. In constrast, these chiral effects stem from isotropic exchange or dipole-dipole interaction, present in all magnetic materials, which acquire asymmetric contributions in case of curved geometry of the specimen. As a result, for example, the spin-wave dispersion in round magnetic nanotubes becomes asymmetric, namely spin waves of the same frequency propagating in opposite directions along the nanotube exhibit different wavelenghts. Here, using time-resolved scanning transmission X-ray microscopy experiments, standard micromagntic simulations and a dynamic-matrix approach, we show that the spin-wave spectrum undergoes additional drastic changes when transitioning from a continuous to a discrete rotational symmetry, i.e. from round to hexagonal nanotubes, which are much easier to fabricate. The polygonal shape introduces localization of the modes both to the sharp, highly curved corners and flat edges. Moreover, due to the discrete rotational symmetry, the degenerate nature of the modes with azimuthal wave vectors known from round tubes is partly lifted, resulting in singlet and duplet modes. For comparison with our experiments, we calculate the microwave absorption from the numerically obtained mode profiles which shows that a dedicated antenna design is paramount for magnonic applications in 3D nano-structures. To our knowledge these are the first experiments directly showing real space spin-wave propagation in 3D nano objects.

Modern problems in magnetization dynamics require more and more the numerical determination of the spin-wave spectra and -dispersion in magnetic systems where analytic theories are not yet available. Micromagnetic simulations can be used to compute the spatial mode profiles and oscillation frequencies of spin-waves in magnetic system with almost arbitrary geometry and different magnetic interactions. Although numerical approaches are very versatile, they often do not give the same insight and physical understanding as analytical theories. For example, it is not always possible to decide whether a certain feature (such as dispersion asymmetry, for example) is governed by one magnetic interaction or the other. Moreover, since numerical approaches typically yield the normal modes of the system, it is not always feasible to disentangle hybridized modes. In this manuscript, we build a bridge between numerics and analytics by presenting a methodology to calculate the individual contributions to general spin-wave dispersions in a fully numerical manner. We discuss the general form of any spin-wave dispersion in terms of the effective (stiffness) fields produced by the modes. Based on a special type of micromagnetic simulation, the numerical dynamic-matrix approach, we show how to calculate each stiffness field in the respective dispersion law, separately for each magnetic interaction. In particular, it becomes possible to disentangle contributions of different magnetic interactions to the dispersion asymmetry in systems where non-reciprocity is present. At the same time, dipolar-hybridized modes can be easily disentangled. Since this methodology is independent of the geometry or the involved magnetic interactions at hand, we believe it is attractive for experimental and theoretical studies of magnetic systems where there are no analytics available yet, but also to aid the development of new analytical theories.

The anti-La mab 312B, which was established by hybridoma technology from human-La transgenic mice after adoptive transfer of anti-human La T cells, immunoprecipitates both native eukaryotic human and murine La protein. Therefore, it represents a true anti-La autoantibody. During maturation, the anti-La mab 312B acquired somatic hypermutations (SHMs) which resulted in the replacement of four aa in the complementarity determining regions (CDR) and seven aa in the framework regions. The recombinant derivative of the anti-La mab 312B in which all the SHMs were corrected to the germline sequence failed to recognize the La antigen. We therefore wanted to learn which SHM(s) is (are) responsible for anti-La autoreactivity. Humanization of the 312B ab by grafting its CDR regions to a human Ig backbone confirms that the CDR sequences are mainly responsible for anti-La autoreactivity. Finally, we identified that a single amino acid replacement (D > Y) in the germline sequence of the CDR3 region of the heavy chain of the anti-La mab 312B is sufficient for anti-La autoreactivity.

Most products in automotive, aerospace, and household appliance industry are multi-material structures. Materials are connected through a variety of joining techniques with the aim of optimizing performance during production and operation phase. However, during recycling in the end-of-life phase, different materials combined in multi-material structures need to be liberated, e.g. disconnected, and separated again to enable high material recoveries. Typical recycling approaches use shredding technologies to liberate materials. Efficient material liberation contributes to achieving high recycling rates for end-of-life products set by the European Union, thereby reducing the need for primary resource extraction and leading to a more sustainable development.

To characterize material liberation, we conducted an experimental shredding study with multi-material lightweight structures typical for automotive A-frames consisting of steel and composite materials, which were shredded in two sequences in a pilot rotary shear. We characterized feed and resulting progeny particles through a set of quantitative and qualitative metrics, thereby tracking changes in joint characteristics, material composition and particle sizes over the course of two processing steps. We found that material liberation is dependent on many design and shredding parameters. Our characterization approach for feed and progeny particles allows for linking design parameters to liberation behaviour. Due to high variability of design and shredding parameters experimental data acquisition is effortful. Therefore, we present an outlook on first results of our physics-based, numerical simulation model using Finite Element Method. Once validated, shredding simulations of many design configurations shall inform the designer about the liberation behaviour of a multi-material structure, such as the A-frame specimens.

Similar to their bulk 3D counterparts, the properties of two-dimensional
(2D) materials can be tuned by controllable introduction of impurities
and defects using beams of energetic ions, which requires
complete microscopic understanding of their response to ion irradiation.
The behavior of 2D materials under ion beam is also interesting in the context of their applications in radiation-hostile environments such as cosmic space. While irradiation effects in 3D systems are well understood, a growing body of experimental facts indicate that many concepts of energetic particle-solid interaction developed for 3D materials are not applicable to 2D systems due to their very geometry, or require substantial modifications. In this Chapter, we discuss at length the response of 2D materials to ion irradiation in different regimes with the main focus on the role of reduced dimensionality. We illustrate the differences between the impact of ions on 3D and 2D materials by examples taken from the recent theoretical and experimental studies on the response of 2D materials to ion irradiation and outline general trends in their behavior under irradiation. Finally, we discuss how ion beams can be used to engineer the structure and properties of 2D materials.

Iron and copper are essential micronutrients needed for the proper function of every cell. However, in excessive amounts these elements are toxic as they may cause oxidative stress resulting in damage of liver and other organs. This may happen due to poisoning, as side effect of thalassemia infusion thera-py or due to hereditary diseases hemochromatosis or Wilson´s disease. The current golden standard of therapy of iron and copper overload is the use of low-molecular-weight chelators of these elements. However, these agents suffer from severe side effects, are often expensive and possess unfavourable pharmacokinetics, which is all limiting useability of such therapy. The emerging concept are poly-mer-supported iron- and copper-chelating therapeutics, either for parenteral or oral use, which show vivid potential to keep therapeutic efficacy of low-molecular-weight agents while avoiding their draw-backs and especially side effects. Critical evaluation of this new perspective polymer approach is the purpose of this review article.

The first results of the EU project SOLSTICE will be presented.

The talk gives a very short overview on the EU project SOLSTICE.

The rapid development of light-emitting-diode (LED) technology is attributed to its superiority over light sources of earlier generations. Although LED lamps, compared to compact fluorescent lamps, are considered less harmful to the environment, there is still no efficient solution to deal with them at the end of their lifecycle. The first part of the study provides a detailed characterisation of LED lamps, focusing on their most interesting component: the LED module. LED packages attached to the module are highly enriched with Ga, In, Pd, Ag, Au, Sr, Y, Ce, Eu, Gd, and Lu, with the content of each element varying greatly depending on the LED technology. In the second part of this research, two new approaches for liberation and concentration of valuable components from LED modules are presented and compared: a chemical route and a thermal route. The chemical treatment leads to a highly selective separation of LED chips and encapsulation. Enrichment factors up to about 125 are achieved, and a concentrate is obtained containing approximately 14 wt% of the aforementioned valuable components. However, the process requires aromatic solvents, which are viewed as toxic. The thermal treatment results in separation of the aluminium heat sink from all other components of the LED module. Enrichment is approximately ten times lower, but the approach is technically feasible.

Germanium, as an elemental semiconductor, has no Reststrahlen band and is thus suited as a broadband THz material, even for THz generation. The drawback of its long carrier lifetime due to the indirect band gap can be remedied through ion implantation, and the relatively small size of the gap allows excitation with fiber lasers in the telecom range. We demonstrate THz emission from Ge photoconductive antennas reaching as far as 70 THz.

The Computational Science Department FWCC and its sister departments offer various tools and services to empower scientists at HZDR in their research. This presentation held at the 2021 PhD seminar aims at introducing the working groups DMS and MT-DMA as well as the Helmholtz Incubator Platforms HIFIS and Helmholtz AI, all hosted by FWCC, and the library FWCB. It presents a selection of said services and shows options of contact for receiving help in the topics presented.

The presented poster was prepared for the doctoral seminar 2021 at HZDR. It gives a short overview about numerical modelling of sodium-zinc liquid metal batteries, which are investigated in the European Union's Horizon 2020 project "SOLSTICE".

Remediation of heavy-metal-contaminated sites represents a serious environmental problem worldwide. Currently, cost- and time-intensive chemical treatments are mainly performed. Bioremediation by heavy-metal-tolerant microorganisms is considered a more eco-friendly and comparatively cheap alternative. The fungus KS1 (Penicillium simplicissimum), isolated from the flooding water of a former uranium (U) mine in Germany, shows promising U bioremediation potential mainly through biomineralization. The adaption of KS1 to heavy-metal-contaminated sites is indicated by an increased U removal capacity of up to 550 mg U per g dry biomass compared to the non-heavy-metal-exposed P. simplicissimum reference strain DSM 62867 (200 mg U per g dry biomass). In addition, the effect of temperature and cell viability of KS1 on U biomineralization was investigated. While viable KS1 cells at 30 °C removed U mainly extracellularly via metabolism-dependent biomineralization, a decrease in temperature to 4 °C or implementation of dead-autoclaved KS1 cells at 30 °C revealed increased occurrence of passive biosorption and bioaccumulation, as observed by scanning transmission electron microscopy. The precipitated U species were assigned to uranyl phosphates with a structure similar to that of autunite via cryo-time-resolved laser fluorescence spectroscopy. The major involvement of phosphorus in U precipitation by the fungus KS1 was additionally supported by the observation of increased phosphatase activity for viable cells at 30 °C. Furthermore, viable KS1 cells actively secreted small molecules, most likely phosphorylated amino acids, which interacted with U in the supernatant and were not detected in experiments with dead-autoclaved cells. Our studies provide new insights into the influence of temperature and cell viability on U phosphate biomineralization by fungi and highlight the potential use of KS1 particularly for U bioremediation purposes.

In this workshop, we presented an introduction to continuous-time movement models for modeling animal movement

In this presentation, we provided an introduction to the animal movement research we conduct at CASUS.

The most well-known example of an ordered quantum state—superconductivity—is caused by the formation and condensation of pairs of electrons. Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of pairs of electrons, leading to zero resistivity and diamagnetism. Here we report a set of experimental observations in hole-doped Ba_1−xK_xFe₂As₂. Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. This combined evidence indicates the existence of a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs.

Anisotropy constants are obtained from an analysis of single crystal magnetization curves measured up to high fields. The anisotropy of the 3d transition metal sublattice is considered, as well as molecular exchange field coupling between the rare-earth (R) and transition metal sublattices (M). This procedure allows for non colinear R and M magnetic moments, meaning that their angles with respect to the easy axis are independent variables. With this approach we obtain anisotropy constants that are larger than those reported in the literature, which reflects the anisotropy of the isolated R sublattice. Results for Co and/or Ce doped Nd₂Fe₁₄B single crystals are presented, showing the influence of such substitutions on the magnetocrystalline anisotropy. These results indicate that the enhanced performance of NdFeB-based magnets co-doped with Ce and Co can be ascribed to an improvement in intrinsic properties.

Scripts and notebooks to reproduce the results presented in the paper "Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural
Networks", Maddu et al., 2021

We report on high-field electron spin resonance studies of two iridium hexahalide compounds (NH₄)₂IrCl₆ and K₂IrCl₆. In the paramagnetic state, our measurements reveal isotropic g factors g = 1.79(1) for the Ir⁴⁺ ions, in agreement with their cubic symmetries. Most importantly, in the magnetically ordered state, we observe two magnon modes with zero-field gaps of 11.3 and 14.2 K for (NH₄)₂IrCl₆ and K₂IrCl₆, respectively. Based on that and using linear spin-wave theory, we estimate the nearest-neighbor exchange couplings and anisotropic Kitaev interactions J₁/k_B = 10.3 K, K/k_B = 0.7 K for (NH₄)₂IrCl₆, and J₁/k_B = 13.8 K, K/k = 0.9 K for K₂IrCl₆, revealing the nearest-neighbor Heisenberg coupling as the leading interaction term, with only a weak Kitaev anisotropy.

We characterize and remedy a failure mode that may arise from multi-scale dynamics with scale imbalances during training of deep neural networks, such as Physics Informed Neural Networks (PINNs). PINNs are popular machine-learning templates that allow for seamless integration of physical equation models with data. Their training amounts to solving an optimization problem over a weighted sum of data-fidelity and equation-fidelity objectives. Conflicts between objectives can arise from scale imbalances, heteroscedasticity in the data, stiffness of the physical equation, or from catastrophic interference during sequential training. We explain the training pathology arising from this and propose a simple yet effective inverse-Dirichlet weighting strategy to alleviate the issue. We compare with Sobolev training of neural networks, providing the baseline of analytically epsilon-optimal training. We demonstrate the effectiveness of inverse-Dirichlet weighting in various applications, including a multi-scale model of active turbulence, where we show orders of magnitude improvement in accuracy and convergence over conventional PINN training. For inverse modeling using sequential training, we find that inverse-Dirichlet weighting protects a PINN against catastrophic forgetting.

By simultaneous measurements in a purpose-built setup, an electric-field manipulation of the magnetocaloric effect and strain in a Fe₄₉Rh₅₁/PZT composite with a sandwich-type connection was demonstrated. Using the strain measurements from two gauges attached to the opposite sides of the composite, as well as finite element modeling (FEM) simulations, it was shown that the deformation in the composite is of a bending type. Mechanical strain induced by the electric field does not exceed ∼500 ppm, which is four times smaller than the expansion of FeRh during the transition ∼2000 ppm. Applying an electric voltage to the PZT favors the transition, but the further expansion of FeRh is hindered and thus blocks the antiferromagnetic-ferromagnetic transition. Obtained experimental results and FEM simulations can be used in the design of new multicaloric composites with optimal ratio between PZT and multicaloric material.

MRI-based proton beam visualisation in water has proven feasible in exploratory irradiation experiments performed on a first research prototype in-beam MRI system. Beam-induced convection was hypothesised to be implicated into MR signal loss observed within the beam volume. In this study, this hypothesis was tested in liquid water-filled phantoms by suppression of convection-induced motion using mechanical barriers and temperature control of water expansivity. In absence of convection-induced motion, no beam-induced signal changes occurred, supporting the hypothesis that convection triggers local MR signal loss during proton beam irradiation. The elucidation of the exact mechanism of convection-induced signal loss requires further investigation.

The long-lived fission product ⁹⁰Sr is produced in the nuclear fuel cycle or in nuclear weapon tests with a high yield of 4%. It is very mobile in the environment and due to its chemical similarities to calcium is easily incorporated in the body, e.g. in bones or in teeth, following ingestion or inhalation. With a half-life of T1⁄2=28.90 years [1] its uptake and retention in the human body poses potential health risks. ⁹⁰Sr also has significant potential as an environmental tracer.

The established method to measure ⁹⁰Sr is decay counting. However, this is time consuming, as the ingrowth of ⁹⁰Y over a period of two weeks is needed due to ⁹⁰Sr being a pure and low-energy beta emitter. The main challenge in ⁹⁰Sr detection with mass spectrometric methods is the interference of isobars, i.e. ⁹⁰Zr and ⁹⁰Y. Limits of detection of mass spectrometric methods such as ICP-MS, RIMS and conventional AMS are all above or close to the radiometric detection limit of 3 mBq.

The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique [2,3] at the Vienna Environmental Research Accelerator (VERA) overcomes the isobaric problem. ILIAMS achieves near complete suppression of isobars via element selective laser photodetachment in a gas-filled radio frequency quadrupole ion guide. The technique exploits differences in the electron affinities (EA) between the isotope of interest and its isobars by neutralizing anions with EAs below the photon energy while leaving anions with EAs above the photon energy unaffected. Additionally, chemical reactions with the buffer gas may enhance separation.

The Sr samples are produced as SrF₂ and mixed with PbF₂, which allows the extraction of an intense SrF₃⁻ ion beam [4]. Using a 532 nm continuous wave laser at 10 W and a He+O₂ mixture, with an oxygen content of 3%, as buffer gas, ILIAMS achieves a suppression of ZrF₃⁻ and YF₃⁻ vs. SrF₃⁻ of >10⁷ at 35% ⁹⁰Sr transmission through ILIAMS. Extraction of SrF₃⁻ from the ion source and elemental separation in an ionization chamber leads to an additional ⁹⁰Zr suppression of 10⁵. The overall ⁹⁰Sr detection efficiency is 0.4‰; a blank level of ⁹⁰Sr/Sr = (4.5±3.2)×10⁻¹⁵ is reached. This corresponds to a more than tenfold improved detection limit of <0.1 mBq, i.e. 10⁵ atoms of ⁹⁰Sr in a 1 mg Sr sample. Measurements of samples from an in-house dilution series with ⁹⁰Sr/Sr ratios ranging from 10⁻¹¹ to 10⁻¹⁴ prove the linearity of this technique. First tests on different environmental samples – from bone to soils – were successful, showing no influence on the detection limit on “real” samples.

[1] R.R. Kinsey et.al., The NUDAT/PCNUDAT Program for Nuclear Data, Data extracted from the NUDAT database, version 2.8
[2] M. Martschini et.al., The ILIAMS project – An RFQ ion beam cooler for selective laser photodetachment at VERA, Nucl. Instrum. Methods. Phys. Res. B, 456 (2019) 213-217
[3] M.Martschini, this meeting
[4] X.-L. Zhao. et. al., Studies of anions from sputtering I: Survey of MFn⁻, Nucl. Instrum. Methods. Phys. Res. B, 268 (2010) 807-811

The isotopic ratio ¹³⁵Cs/¹³⁷Cs can be used to assign sources of anthropogenic cesium input, as a geochemical tracer, or for modifying anthropogenic radionuclide dispersion models. The long-lived ¹³⁵Cs is also of interest in stellar nucleosynthesis models, where ¹³⁴Cs is an important s-process branching point, defining the ¹³⁴Ba/¹³⁶Ba ratio as both those nuclides are shielded from the r-process. ¹³⁵Cs is a pure beta-emitter with a low end-point energy and a long but not very well known half-life around 2.3 Ma. Therefore, ¹³⁵Cs is hard to detect via radiometric methods. Mass spectrometry on the other side has to deal with the isobaric interferences ¹³⁵Ba and ¹³⁷Ba for Cs detection.
The new method of Ion Laser InterAction Mass Spectrometry (ILIAMS) at the Vienna Environmental Research Accelerator (VERA) overcomes this problem by exploiting differences in the electron affinities of CsF₂⁻ and BaF₂⁻. There, the ion beam is cooled and overlapped with a 532 nm laser beam of 10W power in a He buffer gas filled radiofrequency quadrupole. Ions like BaF₂⁻ with a detachment energy lower than the photon energy of 2.33 eV are efficiently suppressed by photodetachment, while CsF₂⁻ ions with a detachment energy higher than the photon energy remain unaffected. With this approach an isobar suppression of more than 10⁶ was achieved for BaF₂⁻, while reaching a CsF₂⁻ transmission of 40% through the RFQ ion cooler. A ¹³³CsF₂⁻ current on the order of 50 nA from a mixed Cs₂SO₄ and PbF₂ – matrix is extracted from the MC-SNICS ion source and measured in the 3+ charge state on the high-energy side with an accelerator transmission of 30%. In order to improve the yield for CsF₂⁻ and keep cross-contamination in the ion source between samples low, we investigated and present the results of two sputtering processes: Rubidium sputtering and negative ion production without external sputter agent.
We achieved reproducible detection of ¹³⁵Cs and ¹³⁷Cs in an in-house reference material with an isotopic ratio of ¹³⁵Cs/¹³⁷Cs ≈ 2.5. Further, first environmental samples showing the ¹³⁵Cs/¹³⁷Cs signature of the nuclear accidents in Chernobyl and Fukushima were measured at VERA and compared to values obtained by ICP-QQQ-MS by Zok et al. [1] at the Leibniz University of Hannover. The ILIAMS assisted AMS measurements at VERA reach blank levels of ¹³⁵Cs/¹³³Cs ≈ 6∙10⁻¹² and ¹³⁷Cs/¹³³Cs ≈ 3∙10⁻¹² .
Monitoring mass 136 throughout a measurement, where only stable barium and cerium are present, shows that at these levels there is no contribution to the background from insufficient isobar suppression so that the limitation for the AMS blank level is cross contamination in the ion source. We aim to reduce this blank value by at least two orders of magnitude to perform measurements of environmental samples also far from directly contaminated sites.

[1] Zok et al., Determination of Characteristic vs Anomalous ¹³⁵Cs/¹³⁷Cs Isotopic Ratios in Radioactively Contaminated Environmental Samples, Environ. Sci. Technol. 2021, 55, 8, 4984–4991

Recently, the atomic ²³³U/²³⁶U ratio was proposed as a superior oceanographic tracer as the ²³³U/²³⁶U signature allows to distinguish environmental emissions of civil nuclear industry from weapons fallout [1] and uranium (U) behaves conservatively in sea water. In this previous work, the ratios detected in representative compartments of the environment affected either by releases of nuclear power production or by weapons fallout differ by one order of magnitude and varied between 0.1·10-²and 3.7·10-². Significant amounts of ²³³U were only released in nuclear weapons fallout, either produced by fast neutron capture on ²³⁵U or directly by ²³³U fuelled devices. For tracer applications, a careful characterization of the principal sources of ²³³U including the contribution from natural production is required.

The ²³³U/²³⁶U ratios were analysed in samples from different locations, partly time-resolved or of well-known age to be able to narrow down the time span of the maximum ²³³U release. Samples comprised air filters from 1961-1965 collected in Austria, i.e. the period of maximum deposition of global fallout, two time-resolved sediment cores from the Baltic Sea and sediment from the urban layered archaeosphere in the underground of Vienna (Austria). In addition, a depth profile of ²³³U/²³⁶U in a water column located in the Northeast Pacific Ocean was also analysed. This sampling station is assumed to be less affected by tropospheric fallout from a suspected ²³³U fuelled device (Nevada Test Site, 1955). Whenever possible, the ²³³U/²³⁶U data were directly compared to other isotopic signatures and/or mono-isotopic makers, such as ²⁴⁰Pu/²³⁹Pu or ²⁴¹Am, respectively.

The Baltic Sea sediment core confirms a maximum deposition of ²³³U around 1954/1955 [2]. This finding is supported by the rather low ²³³U/²³⁶U ratios (below 0.5·10-²) on the air filters from Vienna indicating a comparatively low ²³³U deposition during global fallout maximum. Values of around 0.1 were measured for the maximum of the ²³³U/²³⁶U ratio in the Baltic Sea sediment. The isotope ratios including ²³³U/²³⁶U found in a layer of the Vienna underground material which was assigned to the 1960s, clearly point to atmospheric atomic bomb fallout. The ²³³U/²³⁶U ratios in the upper part of the Pacific water column showed very stable values of (1.33±0.13) ·10-² which are in good agreement with the published value for global fallout [1].

The new data confirms the previous result that the maximum releases of ²³³U happened before the global fallout maximum in 1963. The consistently high ratios found in the Pacific Ocean indicate at least a contribution from thermonuclear explosions to the global inventory of ²³³U. The unexpectedly high ²³³U/²³⁶U values in the Baltic Sea show the necessity to systematically identify the global and local ²³³U input sources. Nevertheless, our preliminary data indicate that the ²³³U/²³⁶U ratio serves as a potential marker for the on-set of the Anthropocene, even in the rather demanding urban environment.

References
[1] K. Hain, et al. Nat Commun 11(2020), 1275.
[2] M. Lin, et al. Environ. Sci. Technol. 55(2021), 13, 8918–8927

Laser photodetachment and molecular dissociation processes of anions provide unprecedented isobar suppression factors of >10¹⁰ for several established AMS isotopes like ³⁶Cl [1] or ²⁶Al [2] and give access to new AMS isotopes like ⁹⁰Sr [3], ¹³⁵Cs [4] or ¹⁸²Hf [5] at environmental levels. Five years ago, a setup for Ion-Laser InterAction Mass Spectrometry (ILIAMS) was coupled to the Vienna Environmental Research Accelerator (VERA) five years ago. Its potential and applicability as a new means of isobar suppression in AMS has since been explored at this state-of-the-art 3 MV tandem facility [6]. Over this time, ILIAMS has been proven to meet AMS requirements regarding efficiency, reliability and robustness with a typical reproducibility of results of 3%.

The benefits of the ILIAMS technique are in principle helpful for any AMS machine, irrespective of attainable ion beam energy. ILIAMS exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas, although the possibility of reverse reactions may cause some plateau effect not observed with laser photodetachment. In order to achieve the required ion-laser interaction times or ion-gas collision energies, the anion beam is decelerated to almost thermal energies within a gas-filled radiofrequency quadrupole.

Since isobar suppression via ILIAMS is so efficient, there is often no need for any further element separation in the detection setup. Hence, highly-populated charge states can be selected after the accelerator, which in combination with 100% efficient ion detection in an ionization chamber more than compensates for transmission losses in ILIAMS, which are on the order of 20-50%. Thus, counting statistics with ILIAMS are typically similar or better than with conventional AMS means, e.g. 500 cts of ²⁶Al in a 10 min run on a sample with 26Al/Al = 10−¹².

Recent test measurements also demonstrated that, owing to the virtually complete suppression of isobars, ²⁶Al (extraction of AlO−) and ⁴¹Ca (extraction of CaF₃−), can be measured directly from stony meteorite samples as little as 1-2 mg without doing any chemical sample preparation [7]. There is also potential for ILIAMS measurements of terrestrial cosmogenic ²⁶Al in in-situ-dating quartz originating from high altitudes. Last but not least, ³⁶Cl may even become accessible without the need for sulfur reduction by chemical treatment and, maybe, without accelerator at all.

[1] Lachner et al., NIMB 92 (2019) 146.
[2] Lachner et al., IJMS 465 (2021) 116576.
[3] Marchhart et al., this meeting
[4] Wieser et al., this meeting
[5] Martschini et al., EPJ Web of Conferences 232 (2020) 02003.
[6] Martschini et al., NIMB 456 (2019) 213.
[7] Merchel et al., this meeting

¹⁰Be measurements at DREAMS take up a large fraction of the AMS beam times at the 6MV accelerator at the ion beam center of HZDR. Currently, they are undertaken at a terminal voltage of 4.5 MV [Rugel et al., NIMB 2016]. Here, we investigated potential benefits from a change in accelerator terminal voltage in order to increase the efficiency of ¹⁰Be counting.
Presently, after the stripping in Ar gas in the accelerator, Be2+ ions are directed towards a 1 μm thin SiN foil placed after the analysing magnet on the high-energy side that helps to suppress the ¹⁰B interference by differential energy loss and separation in an electrostatic analyser. After passage through the absorber foil the mean charge state of Be ions is increased and the 4+ charge state is selected and transported to the detector. In this mode of operation, losses of ¹⁰Be ion beam intensity on the way from the low-energy side of the system to the detector are dominated by these two charge exchange processes [Arnold et al., NIMB 2010].
However, there is only limited data for the recharge behaviour of Be in a stripper gas at energies relevant for the measurements at DREAMS [Hofmann et al., NIMB 1987; Niklaus et al., NIMB 1994]. For an argon gas stripper, Niklaus et al. [NIMB 1994], suggest lower terminal voltages for optimal transmission of ¹⁰Be2+. On the other hand, an increase of the overall energy of the Be2+ beam after the accelerator will certainly allow for a higher Be4+ yield after the passage through the absorber foil.
In contrast to the original data by Niklaus et al. [NIMB 1994], we found that increasing the terminal voltage to ≥ 5MV does not reduce the yield of the Be2+ charge state after the accelerator.

As a further recharge to the 4+ charge state is conducted in a foil after the analysing magnet it is desirable to hit the foil with the highest available energy/velocity to have optimal stripping of Be2+ to the naked ion. Thus, the efficiency of ¹⁰Be measurements can indeed be improved by increasing the terminal voltage, both at DREAMS and at other AMS facilities of a similar size that are using the absorber method with a charge exchange from 2+ to 4+ for isobar suppression.
We present data on the performance of the system at higher beam energies documenting an increase in overall detection efficiency by 25%. Under these conditions the interfering isobar ¹⁰B is still well separated, and no additional interferences (e.g. from nuclear reactions) appear in our spectra.

One of the most important tasks in the design and construction of ultra-low background experiments is the radioassay of the materials used. This requires the selection of the materials and enables the calculation of expected detector background. The ASTREA project (Accelerator mass spectrometry Survey of Trace Radionuclides for Experiments in Astroparticle physics) addresses AMS radioassay challenges for a few rare event experiments. Some examples are nEXO, which is searching for neutrinoless double beta decay; and NEWS-G and DarkSide, which are attempting to directly detect dark matter. This project, led by the André E. Lalonde AMS Laboratory (AEL-AMS) at the University of Ottawa, is performed in collaboration with Carleton University, Queens University and University of Alberta.

The main focus of the project is screening Pb-210 in various detector construction materials, with emphasis on low background copper and high-performance polymers. We have studied the possibility of using 2 different materials for the AMS measurements: lead fluoride (PbF2) and lead oxide (PbO) targets, producing respectively (PbF3)- and (PbO2)- ions on the LE side. In both cases, the 210Pb/206Pb blank ratio is in the 1e-14–1e-13 range. Measurements on 1-2 g Kapton films have established upper limits in the range 850-2500 mBq/kg at 90% C.L.

Future ASTREA activities will focus on the Pb-210 assay in acrylic, which is considered for future low background dark matter detectors. Previous best results, obtained in 2014 by γ-counting 2 kg of acrylic, have established an upper limit for the Pb-210 concentration of 0.3 mBq/kg. Our proposed method, using AMS, should provide a limit of detection in the 0.01-0.1 mBq/kg range.

Other important study looks at the Pb-210 contamination in the electroformation process of the copper for the NEWS-G and nEXO detectors. For the Pb-210 concentration in the copper, we estimate a limit of detection in the 0.3-1.0 mBq/kg range.

Nanoindentation of ion-irradiated nuclear structural materials and model alloys has received considerable interest in the published literature. In the reported studies, the materials were typically exposed to irradiations using a single ion energy varying from study to study from below 1 MeV to above 10 MeV. However, systematic investigations into the effect of ion energy are still missing, meaning that the possibilities to gain insight from systematic energy variations are not yet exhausted. We have exposed pure Fe, ferritic Fe-9Cr, martensitic Fe-9Cr and the ferritic-martensitic reduced-activation steel Eurofer 97 to ion irradiations at 300 °C using 1 MeV, 2 MeV and 5 MeV Fe2+ ions as well as 8 MeV Fe3+ ions and applied nanoindentation, using a Berkovich diamond indenter, to characterize as-irradiated samples and unirradiated references. The effect of the ion energy on the measured nanoindentation response is discussed for each material. Two versions of a primary-damage-informed model are applied to fit the measured irradiation-induced hardening. The models are critically compared with the experimental results also taking into account reported microstructural evidence. Related ion-neutron transferability issues are addressed.

In this presentation we present how HELIPORT is targeted to bring together tools that help in handling data as part of experiments or simulations. As a result it can serve as the one platform for users to interact with the data generated as part of their measurement campaigns and also provide data provenance.

Open-cell solid foams are rigid skeletons permeable to fluids, which are used as direct heaters or thermal dissipaters in many industrial applications. Using dielectric materials for the skeleton and exposing them to microwaves is an efficient way to heat these excellent susceptors. The heating performance depends on the permittivity of the skeleton. However, a rigorous description of the effective permittivity is challenging and requires an appropriate consideration of the complex skeletal foam morphology. In this contribution, we propose Platonic solids as building elements of the open-cell skeletal structures to describe their effective permittivity. The derived new simplistic geometrical relation is used along with electromagnetic wave propagation calculations in representatives of the real foam. A geometrical parameter-free relation was then obtained, which is only based on foam porosity and the material´s permittivity. The derived relation enables efficient and reliable estimation of the effective permittivity of open-cell foams over a large range of porosity.

The adsorption and dissociation of water molecules on two-dimensional transition metal dichalcogenides(TMDs) is expected to be dominated by point defects, such as vacancies, and edges. At the same time, the role of grain boundaries, and particularly, mirror twinboundaries (MTBs), whose concentration in TMDs can be quite high, is not fully understood. Using density functional theory calculations, we investigate the interaction of water, hydroxyl groups, as well as oxygen and hydrogen molecules with MoSe2 monolayers when MTBs of various types are present. We show that the adsorption of all species on MTBs is energetically favorable as compared to that on the basal plane of pristine MoSe 2 , but the interaction with Se vacancies is stronger. We further assess the energetics of various surface chemical reactions involving oxygen and hydrogen atoms. Our results indicate that water dissociation on the basal plane should be dominated by vacancies even when MTBs are present, but they facilitate water clustering through hydroxyl groups at MTBs, which can anchor water molecules and give rise to the decoration of MTBs with water clusters. Also, the presence of MTBs affects oxygen reduction reaction(ORR) on the MoSe 2 monolayer. Unlike Se vacancies which inhibit ORR due to a high overpotential, it is found that the ORR process on MTBs is more efficient, indicating their important role in the catalytic activity of MoSe 2 monolayer and likely other TMDs.

Beryllium-10 is an important isotope for the AMS system at iThemba LABS in Johannesburg because of demand for cosmogenic radionuclide dating methods in the national, regional, and international earth science and paleosciences community. Rather than being designed as one system, the AMS system at iThemba LABS has been set up over several phases based on an existing tandem accelerator, which usually poses challenges implementing the best measurement approach for any given isotope. The injector-side features an in-house built multi-sample cesium sputter ion source, similar to systems employed at CAMS/Lawrence Livermore National Laboratory and Purdue Rare Isotope Measurement Laboratory. The ion source is followed by an in-house built electro-static analyzer and an (in-house built) analyzing magnet, with NEC’s multi-beam switching electronics system applied to our own insulated magnet chamber. The accelerator is a pelletron-refurbished HVEC Model EN tandem, and the high-energy beam line is modified by addition of a switching magnet beam-line from a typical setup delivered by NEC for 5 MV tandem accelerators. Unfortunately using the gas absorber cell employing Havar windows (as was delivered) requires higher energies, usually requiring the 3+ charge state and relatively high terminal voltage, which, for the purpose of AMS operations, are not currently delivered reliably enough by our tandem accelerator. Recently it has been shown that low-stress silicon nitride membranes can be used as absorber foils for full stopping of Boron-10 with a particle energy as low as 6 MeV for the measurement of Beryllium-10 [Steier, et al., 2019]. This allows for the use of the 2+ charge state, avoiding the charge state losses of the post-stripping method used with accelerators capable of similar or lower terminal voltage elsewhere, albeit at the expense of allowing some background from nuclear reactions. We implemented this method in lieu of the gas absorber cell, thus utilizing from the efficiency gain from using the 2+ charge state. In order to investigate the impact of Boron-10 interference and to devise a background correction formalism we conducted experiments using our own ultra-low-Beryllium-10 phenakite-based carrier, and a dilution series of deliberately added Boron-10. We present data which demonstrate good performance of the system on standards and the dilution series samples, and 14 comparison measurements with results obtained at CAMS/LLNL, with all the comparison samples having been prepared at University of Vermont for a landscape evolution study in South Africa. The independent AMS measurements results from the two laboratories are in excellent agreement. A correlation analysis for the two data sets yields a Pearson’s r of 0.9993, with slope (1.009+/-0.017) and offset fully consistent with cross-calibration between the laboratories. The mean difference between the laboratories’ results for individual samples is just 1.7%.

InGaN/GaN quantum wells (QWs) with sub-nanometer thickness can be employed in short-period superlattices for bandgap engineering of efficient optoelectronic devices, as well as for exploiting topological insulator behavior in III-nitride semiconductors. However, it had been argued that the highest indium content in such ultra-thin QWs is kinetically limited to a maximum of 33%, narrowing down the potential range of applications. Here, it is demonstrated that quasi two-dimensional (quasi-2D) QWs with thickness of one atomic monolayer can be deposited with indium contents far exceeding this limit, under certain growth conditions. Multi-QW heterostructures were grown by plasma-assisted molecular beam epitaxy, and their composition and strain were determined with monolayer-scale spatial resolution using quantitative scanning transmission electron microscopy in combination with atomistic calculations. Key findings such as the self-limited QW thickness and the non-monotonic dependence of the QW composition on the growth temperature under metal-rich growth conditions suggest the existence of a substitutional synthesis mechanism, involving the exchange between indium and gallium atoms at surface sites. The highest indium content in this work approached 50%, in agreement with photoluminescence measurements, surpassing by far the previously regarded compositional limit. The proposed synthesis mechanism can guide growth efforts towards binary InN/GaN quasi-2D QWs.

We report on the formation of a critical ferroelectric state induced by the He⁺ ion implantation in potassium tantalate niobate crystal. Obvious phase change has been observed in the ion irradiated region, which is mostly related to the stable polarized nanometric regions formed during the ion implantation process. Under the irradiation of 2 MeV He⁺ ions, two distinguishable layers corresponding to different energy transfer modes (elastic nuclear collision and inelastic electronic collision, respectively) between the incident He⁺ ions and the intrinsic lattices have been formed beneath the irradiated surface. Lattice dynamics before and after the ion implantation process are investigated by the confocal μ-Raman system. And the variations of typical Raman-active vibrational modes demonstrate the presence of lattice distortion in the irradiated region. X-ray diffraction experiments further suggest the mostly uniform lattice elongation in this region. Piezo-response force characteristic measurements reveal the existence of stable polarized nanometric regions with more intense polarization and verify that the crystal with such a phase status possesses extraordinary microscopic disorders, which is different from the traditional ferroelectric or paraelectric phase. Optical transmission experiments demonstrate that the irradiated region possesses relatively low propagation loss. The ion implantation method provides a new approach to form a temperature-stable critical ferroelectric state in relaxor ferroelectric materials. Analyses of the modification on the lattice dynamics of the irradiated region can help us build a clear awareness of the physical essence of this critical state and the relaxor ferroelectricity. Also, with good optical transmittance, the irradiated region is capable of promising optical functional devices.

Au nanoparticles (NPs) in lithium tantalate (LiTaO3) crystal were prepared by ion implantation technique. The microstructure of the formed Au NPs was observed by transmission electron microscope (TEM). The linear and non-linear optical response of the samples was investigated and Z-scan measured that the Au NPs embedded LiTaO3 has saturable absorption properties. Based on this, the sample was used as a saturable absorber (SA) embedded in a waveguide laser system to achieve a 1 μm Q-switched mode-locked laser with a pulse width of 90 ps and a repetition frequency of 6.54 GHz.

In this work, we report on the development of a time-averaged Eulerian multiphase approach
applied in the wall boiling process especially in the forced convective boiling process. Recently, in order to
obtain accurate bubble dynamics and reduce case dependency, a single bubble model for nucleate boiling
based on known published models was developed. The model considers geometry change and dynamic contact
and inclination angles during bubble growth. The model has good agreement with experiments. However, the
predicted bubble dynamics is dependent on the wall superheat (cavity activation temperature). This single
bubble model requires an update of the current nucleation site activation and heat flux partitioning models in
time-averaged Eulerian multiphase approaches. In this presentation, we will introduce this implementation in detail.
Further, with help of the MUSIG (MUltiple SIze Group) model, a breakup and coalescence model and GENTOP concept, this approach could simulate the bubble size distribution and further flow pattern and partten transitian in a heated pipe. With thenecessary calibration of the nucleation site density, the comparisons between the calculation results and DEBORA experiments demonstrate the success of the implementation and the accuracy of this approach.

Bubbly flow still represents a challenge for large-scale numerical simulation. Among many others the understanding and modelling of bubble-induced turbulence (BIT) are far from being satisfactory even though continuous efforts have been made. In particular, the buoyancy of the bubbles generally introduces turbulence anisotropy in the flow, which can not be captured by the standard eddy viscosity models with specific source terms representing BIT. Recently, on the basis of bubble-resolving Direct Numerical Simulations data, a new Reynolds-stress model considering BIT were developed by Ma et al. (J. Fluid Mech., vol. 883, 2020, A9) within the Euler–Euler framework. The objective of the present work is to assess this model and compare its performance with other standard Reynolds-stress models using a systematic test strategy. We select the experimental data in the BIT dominated range and find that the new model leads to major improvements in the prediction of full Reynolds-stress components.

The fabrication of individual nanowire-based devices and their comprehensive electrical characterization remains a major challenge. Here, we present a symmetric Hall bar configuration for highly p-type germanium nanowires (GeNWs), fabricated by a top-down approach using electron beam lithography and inductively coupled plasma reactive ion etching. The configuration allows two equivalent measurement sets to check the homogeneity of GeNWs in terms of resistivity and the Hall coefficient. The highest Hall mobility and carrier concentration of GeNWs at 5 K were in the order of 100 cm^2/(Vs) and 4×10^19 cm^-3, respectively. With a decreasing nanowire width, the resistivity increases and the carrier concentration decreases, which is attributed to carrier scattering
in the region near the surface. By comparing the measured data with simulations, one can conclude the existence of a depletion region, which decreases the effective cross-section of GeNWs. Moreover, the resistivity of thin GeNWs is strongly influenced by the cross-sectional shape.

Drones are getting more and more used to replace piloted platforms to reduce the costs and increase safety of activities such as monitoring, delivery or warfare. So far though, drones have barely been used as more than single-sensor platforms. In order to be used in mineral exploration we need to ensure that the data acquired by drones are versatile, accurate and adapted to the tasks but also that the platforms are robust and low-maintenance to ensure an operational use in remote locations. During the last years we developed and tested a series of workflows to rapidly provide relevant information to exploration teams. It starts with multi-source data acquisition, data integration and preprocessing. We then use machine learning to process the data and generate relevant geological information.

In this presentation we show how we deploy HELIPORT at Helmholtz Institute Jena. The integration of the High Intensity Laser POLARIS in a complete data life cycle workflow is an important aspect in the HMC funded HELIPORT project.

Efficient, socially acceptable and rapid methods of exploration are required to discover new deposits and enable the green energy transition. Sustainable exploration requires a combination of innovative thinking and new technologies. Hyperspectral imaging (HSI) is a rapidly developing technology and allows for fast and systematic mineral mapping, facilitating exploration of the Earth’s surface at various scales on a variety of platforms. Newly available sensors allow data capture over a wide spectral range, and provide information about the abundance and spatial location of ore and pathfinder minerals in drill-core, hand samples and outcrops with mm to cm precision. Conversely, the complex geometries of the imaged surfaces affect the spectral quality and signal-to-noise ratio (SnR) of HSI data at these very narrow spatial samplings. Additionally, the complex mineral assemblages found in hydrothermally altered ore deposits can make interpretation of spectral results a challenge. In this contribution, we propose an innovative approach that integrates multiple sensors and scales of data acquisition to help disentangle complex mineralogy associated with lithium and tin mineralisation in the Uis pegmatite complex, Namibia. We train this method using hand samples and finally produce a three-dimensional (3D) point cloud for mapping lithium mineralisation in the open pit. We were able to identify and map lithium-bearing cookeite and montebrasite at outcrop scale. The accuracy of the approach was validated by drill-core data, XRD analysis and LIBS measurements. This approach facilitates efficient mapping of complex terrains, as well as important monitoring and optimisation of ore extraction. Our method can easily be adapted to other minerals relevant to the mining industry.

Pool scrubbing with bubble swarm generated by gas jet is an effective technique for aerosol retention at severe accidents, owing to large interfacial area and long residence time. Correct understanding of the process and thus enhancing its efficiency relies on analysis of the hydrodynamic behaviour of the gas, since it affects particle removal mechanisms directly. The objective of the present work is to explore the gas jet structure in detail by means of VOF interface-capturing method and additional techniques for tracking bubble characteristics and trajectories. The main findings are: a) The breakup of globules in the injection zone becomes significant at high gas flow rates and has a great contribution in particle removal; b) The increase of bubble size
and velocity with the injection velocity will promote the inertial and centrifugal deposition of aerosol particles; c) However, the coalescence probability of
rising bubbles is found to increase with the gas flow rate, which may influence particle retention by re-enclosing particles from liquid film and reducing surface area; d) Furthermore, the reduction in bubble residence time as they rise through the pool is unfavourable for particle removal. Nevertheless, liquid recirculation originated from violent interaction between the gas jet and the pool surface as well as swarm effects helps to prolong the residence of bubbles. The effect of gas flow rates on the decontamination factor is found to be associated with a variety of gas-liquid hydrodynamic phenomena. The
proposed numerical approach is capable of acquiring detailed local information that is required for model development. Both the time-averaged spatial distribution of void fraction and the instantaneous size/rise velocity of individual bubbles obtained from the simulation conform to the experimental data. In the next step it will be extended to include aerosol particles.

The separation efficiency of a vane-type separator is greatly affected by swirl instability. The separator consists of a swirling vane, a recovery vane and a main pipe. Driven by centrifugal force, the bubbly flow tends to develop into stratified flow with a continuous gas core floating in the central axis of the separator and facilitating the separation. Yet, the straight gas core can turn into a double helix under some circumstances for example if the pressure difference across the orifices of recovery vane falls below the critical value, and swirl instability occurs. In order to reveal the underlying mechanism, a device with adjustable operating pres-sure was introduced to reproduce the dynamic process of gas core transform between stable and unstable. With the increase of pressure difference, the gas core morphology near the recovery vane will turn from double-helix to straight-line within several seconds. The whole process was investigated further by using the tomographic particle image velocimetry. Results show that the development of vorticity structures in the swirl flow gives rise to the evolution of gas core morphology and keeps it stable. Furthermore, the direction of axial velocity, which becomes negative by low pressure differences, is found to be crucial in controlling the formation of inner forced vortex and hence leading to the occurrence of swirl instability. In addition, the magnitude of positive axial velocity is identified to be of great significance in vorticity enhancement.

At the DREAMS (DREsden AMS) facility [1,2] we are implementing a so-called Super-SIMS (SIMS = Secondary Ion Mass Spectrometry) device [3] for specialized applications. The system combines the spatial resolution capability of a commercial SIMS (CAMECA IMS 7f-auto) with AMS capability, which should suppress molecular isobars in the ion beam allowing for the quantification of elemental abundances down to ~ E-9 – E-12. This would be more than an order of magnitude improvement over traditional dynamic SIMS (e.g. [4,5]). We aim to use this for the highly sensitive analysis of geological samples in the context of resource technology.

In the present setup, high efficiency transmission in the low-energy ion optics segment remains a challenge, as the beam needs to traverse two existing magnet chambers without deflection, where no steering or lens elements are available over a flight distance of 4 m. We have now improved the low-energy injection just after the ion beam exits the 7f-auto, upgrading the steerers directly after the SIMS and by adding a beam intensity attenuator. This provides both more stable conditions for instrument tuning and simplifies transition between measurements of the beam intensity in Faraday cups and the gas ionization chamber. Regarding the measurement of C, N and O in silicon, we found that a simple Wien-filter using permanent magnets for the primary Cs-sputter beam significantly reduces the background at the detector, as the 7f-auto uses a Cs₂CO₃ source – rather than metallic Cs – for the generation of the primary positive Cs beam.

Once the remaining issues associated with ion beam-path are fully addressed, we will still need to tackle the issue of establishing suitable, well characterized reference materials needed for our first suite of resource and geoscience applications (e.g., halides in naturally occurring sulphide minerals). We present ongoing developments and results, as well as plans for extending to other matrices and isotope systems.

[1] S. Akhmadaliev et al., NIMB 294 (2013) 5. [2] G. Rugel et al. NIMB 370 (2016) 94. [3] J. M. Anthony, D. J. Donahue, A. J. T. Jull, MRS Proceedings 69 (1986) 311-316. [4] C. Maden, PhD thesis, ETH Zurich 2003. [5] S. Matteson, Mass Spectrom. Rev., 27 (2008) 470.

The Electron Capture in ¹⁶³Ho experiment (ECHo) aims at measuring the mass of the electron neutrino by analysing the EC spectrum of the long-lived radionuclide ¹⁶³Ho (T_1/2 = 4570 a) with a metallic magnetic calorimeter (MMC). For the determination of a reasonable upper limit for the neutrino mass it is mandatory to keep the contamination with the long-lived radionuclide ¹⁶⁶mHo (T_1/2 = 1132.6 a) nine orders of magnitude below the ¹⁶³Ho content. The ion-implantation of ultra-pure ¹⁶³Ho into a MMC for the experiment is carried out by the RISIKO (Resonance Ionization Spectroscopy in KOllinear geometry) mass separator. The separation from ¹⁶⁶mHo, however, cannot be guaranteed to such low levels as needed in this project, it can only be estimated. Here we present our approach to determine the corresponding low isotopic ratio with accelerator mass spectrometry (AMS). Of course, this requires the formation of negative ions, where we find the highest negative ion yield for the anion HoO₂−. For first tests, stable ¹⁶⁵Ho was implanted by RISIKO into various different metal foils and we studied the overall Ho detection efficiency for our setup. We will present first results and estimates of the expected detection limit for the ¹⁶⁶mHo/¹⁶³Ho isotope ratio.

Novel transistor concepts based on semiconductor nanowires promise high performance, lower energy consumption and better integrability in various platforms in nanoscale dimensions. Concerning the intrinsic transport properties of electrons in nanowires, relatively high mobility values that approach those in bulk crystals have been obtained only in core/shell heterostructures, where electrons are spatially confined inside the core. Here, it is demonstrated that the strain in lattice-mismatched core/shell nanowires can affect the effective mass of electrons in a way that boosts their mobility to unprecedented levels. Specifically, electrons inside the hydrostatically tensile-strained gallium arsenide core of nanowires with a thick indium aluminium arsenide shell exhibit mobility values 30 – 50 % higher than in equivalent unstrained nanowires or bulk crystals, as measured at room temperature. With such an enhancement of electron mobility, strained gallium arsenide nanowires emerge as a unique means for the advancement of transistor technology.

The incident ion defines the interaction mechanism with the sample surface caused by the energy deposition and thus has significant consequences on resulting nanostructures [1]. In addition, nanofabrication requirements for FIB technologies are specifically demanding in terms of patterning resolution and stability [2].
Therefore, we have extended the technology towards a stable supply of multiple ion species selectable into a nanometer scale focused ion beam by employing a liquid metal alloy ion source (LMAIS) [3]. This LMAIS provides single and multiple charged ion species of different masses, resulting in significantly different interaction mechanisms. Nearly half of the elements of the periodic table are thus made available in the FIB technology because of continuous research in this area [4]. This range of ion species with different mass or charge can be beneficial for various nanofabrication applications. Recent developments could make these sources to an alternative technology feasible for nanopatterning challenges. In this contribution, the operation principle, first results and prospective domains for modern FIB applications will be presented. As examples, we will introduce the AuGeSi and GaBiLi LMAIS [5, 6]. Both sources provide light and heavy ions available from a single source to tailor chemical and physical properties of resulting nanostructures. GaBiLi enables high resolution imaging with light Li ions and sample modification with Ga or heavy polyatomic Bi clusters, all coming from one ion source. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB could benefit of providing additional ion species in a mass separated FIB without changing the ion source.
[1] P. Mazarov, V. Dudnikov, A. Tolstoguzov, Electrohydrodynamic emitters of ion beams, Phys. Usp. 63, 1219 (2020).
[2] L. Bruchhaus, P. Mazarov, L. Bischoff, J. Gierak, A. D. Wieck, and H. Hövel, Comparison of technologies for nano device prototyping with a special focus on ion beams: A review, Appl. Phys. Rev. 4, 011302 (2017).
[3] L. Bischoff, P. Mazarov, L. Bruchhaus, and J. Gierak, Liquid Metal Alloy Ion Sources – An Alternative for Focused Ion Beam Technology, Appl. Phys. Rev. 3, 021101 (2016).
[4] J. Gierak, P. Mazarov, L. Bruchhaus, R. Jede, L. Bischoff, Review of electrohydrodynamical ion sources and their applications to focused ion beam technology, JVSTB 36, 06J101 (2018).
[5] W. Pilz, N. Klingner, L. Bischoff, P. Mazarov, and S. Bauerdick, Lithium ion beams from liquid metal alloy ion sources, JVSTB 37, 021802 (2019).
[6] N. Klingner, G. Hlawacek, P. Mazarov, W. Pilz, F. Meyer, and L. Bischoff, Imaging and milling resolution of light ion beams from helium ion microscopy and FIBs driven by liquid metal alloy ion sources, Beilstein J. Nanotechnol. 11, 1742 (2020).

Clay minerals, as main components of the engineered barrier in deep geological repositories, are not only highly effective sorbents for a wide range of (cationic) contaminants, but due to their structural iron content, they can also modify the mobility and (bio)availability of redox-sensitive elements by changing their oxidation state. Here we will systematically address the retention of the redox-sensitive fission products Tc and Se by FeII/FeIII containing clays. The mobility of Tc and Se strongly depends on their oxidation states. The specific chemical form of Tc and Se is governed by many factors, such as pH, redox potential (Eh), solubility, mineralogical and chemical composition of the environment, biological (microbial) interactions and (redox) reaction kinetics. The most considerable influence, however, is exerted by redox potential, pH and solubility.
Tc(VII) in its anionic form (TcO4-) is highly mobile whereas under reducing conditions the mobility of Tc is decreased when it is reduced to Tc(IV). A few studies have shown that TcVII can be reduced to TcIV by Fe-bearing minerals, mainly forming TcO2.nH2O surface precipitates[1]. Most of these studies, however, were carried out at rather high Tc loadings. The focus of this study is on low to very low Tc loadings, which are more environmentally relevant.
Selenate (SeO42−, Se(VI)) and selenite (SeO32−, Se(IV)) are favoured under oxidizing conditions. Selenate reduction is kinetically hindered and very slow (high activation energy). Hence, the study focuses on selenite. There is little data on the retention of Se(IV) by Fe(II) bearing clay minerals. Reductive precipitation of Se(IV) to nanoparticulate Se(0) was observed when dissolved Fe(II) is sorbed onto synthetic montmorillonite[2].
By combining Tc and Se sorption experiments on native and reduced smectite clay samples with different FeII/FeIII ratios with Tc/Se K-edge extended X-ray absorption fine structure (EXAFS), mediated oxidation and reduction experiments (MEO/MER), Mössbauer spectrometry and microscopy, we aim at discriminating the contributions of the different available Fe sources to the overall adsorption and reduction of Tc and Se and to identify the surface products. The ultimate aim is to correlate mineral properties with respect to their redox reactive iron content, the degree of Tc and Se reduction and the molecular scale surface speciation, in order to improve the understanding of the coupled adsorption and electron transfer reactions contributing to the retention of Tc and Se on FeII/FeIII bearing clay minerals, and thus to contribute to a more reliable prediction of the Tc and Se retention in nuclear waste repositories.

1. Jaisi, D.P., et al., Reduction and long-term immobilization of technetium by Fe(II) associated with clay mineral nontronite. Chemical Geology, 2009. 264(1): p. 127-138.
2. Charlet, L., et al., Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay. Geochimica et Cosmochimica Acta, 2007. 71(23): p. 5731–5749.

Clay minerals are ubiquitous in the environment and are an important reactant to pollutants including radionuclides. Besides their adsorptive capacity, clay minerals can also participate in redox reactions due to the presence of iron (Fe) in their structure and can thereby influence the mobility of redox-active compounds such as technetium, selenium and uranium. However, not all Fe(II) or Fe(III) in the structure of clay minerals may be accessible for redox reactions. The redox activity of Fe can depend on the quantity and coordination of Fe in the clay mineral structure. Research on the redox activity of structural Fe in clay minerals has mainly focused on smectites whereas other types of clay minerals have received less attention. In this study we measured redox-activity of a variety of clay minerals, i.e. illites, chlorites, glauconites and mixed-layered illite-smectites. The redox-activity of the clay minerals was investigated by mediated electrochemistry. To examine the relation between electrochemically active structural Fe(II) in these clay minerals and their reactivity towards radionuclides, batch experiments were performed with selenite, a redox-active, mobile, long-lived radionuclide in radioactive waste. Both pristine (oxidized) clay minerals and chemically reduced clay minerals were tested. Results from mediated electrochemical oxidation and reduction show that all clay minerals have electrochemically active Fe to some extent, but there is a large variation in the fractions of electrochemically-active Fe between the different clay minerals, e.g. around 100% redox-active Fe in smectites, <20% redox-active Fe for the tested illites. K-edge XAFS spectroscopy of these batch experiment samples reveals that these different types of chemically reduced clay minerals reduce selenite to elemental selenium.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damage in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost due to using machine learning methods. In order to successfully model on multiple length and time scales, these models have to be transferable with respect to their size. Here, we present results of such an investigation, by showing how models trained on small numbers of atoms (e.g., 128) can be used to accurately calculate energies of much larger simulation cells (e.g., 1024 atoms). The models are based upon the Materials Learning Algorithms (MALA) package and the LDOS-based machine-learning workflow implemented therein.

Density Functional Theory (DFT) is one of the most important computational tools for materials science, as it combines high accuracy with general computational feasibility. However, applications important to scientific progress can pose problems to even the most advanced and efficient DFT codes due to size and/or complexity of the underlying simulations. Namely the modeling of materials across multiple length and time scales at ambient or extreme conditions, necessary for the understanding of important physical phenomena such as radiation damages in fusion reactor walls, evade traditional ab-initio treatment.
DFT surrogate models are a useful tool in achieving this goal by reproducing DFT results at drastically reduced computational cost by using machine learning methods. Yet, a lack of transferability of many approaches lead to repeated and costly training data generation procedures. Here, we present results of an investigation to transfer such machine learning DFT surrogate models between different simulation cell sizes, with the goal of reducing the overall amount of computational time for training data generation. The models are based upon the Materials Learning Algorithms (MALA) package [1] and the therein implemented LDOS based machine learning workflow [2].
[1]: https://github.com/mala-project
[2]: J. A. Ellis et al., Phys. Rev. B 104, 035120, 2021

Ab-initio simulations are crucial tools for many scientific applications, from materials science to drug discovery. This is due to powerful simulation techniques such as Density Functional Theory (DFT), that combine high accuracy with computational feasibility. Yet, there exist applications unattainable to even the most performant of DFT programs. A prominent example is the modeling of materials on multiple time and length scales, especially under ambient or extreme conditions. While these simulations hold the potential to both further our understanding of important physical phenomena such as planetary formation or radiation damages in fusion reactor wall, they evade traditional ab-initio approaches due to their size and complexity.
Surrogate models can mitigate these computational restrictions, by reproducing DFT-level results at a fraction of the cost. Here, were present the Materials Learning Algorithms (MALA) package, an open source python package for building neural network based surrogate models for materials science. MALA provides easy-to-use functions to process DFT data, build models and use these models to replace DFT calculations, as shown for simulations of Aluminium at both 298K and 933K, as well as Iron at 3000K. The source code for MALA is publicly available on Github and developed by the Center for Advanced Systems Understanding (CASUS), Sandia National Laboratories, and Oak Ridge National Laboratory.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

We anticipate high-valent metal fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H–F bond (in the product) that drives HAT oxidation. We prepared a dimeric Fe(III)(F)–F–Fe(III)(F) complex (1) by reacting Fe(II)(NCCH₃)₂(TPA) where X = F/OTf. 1 and 2 were characterised using NMR, EPR, UV-vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive Fe III reagent for oxidative C–H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive Fe III and Fe IV oxidants.

High-valent metal−halides have come to prominence as highly effective oxidants. A direct comparison of their efficacy against that of traditional metal−oxygen adducts is needed. AuIII(Cl)(terpy)](ClO₄)₂ (1; terpy = 2,2′:6′,2-terpyridine) readily oxidized substrates bearing O−H and C−H bonds via a hydrogen atom transfer mechanism. A direct comparison with [AuIII(OH)(terpy) showed that 1 was a kinetically superior oxidant with respect to 2 for all substrates tested. We ascribe this to the greater thermodynamic driving force imbued by the Cl ligand versus the OH ligand.

Oxygen diffusivity and surface exchange kinetics underpin the ionic, electronic, and catalytic functionalities of complex multivalent oxides. Towards understanding and controlling the kinetics of oxygen transport in emerging technologies, it is highly desirable to reveal the underlying lattice dynamics and ionic activities related to oxygen variation. In this study, the evolution of oxygen content is identified in real-time during the progress of a topotactic phase transition in La0.7Sr0.3MnO3-δ epitaxial thin films, both at the surface and throughout the bulk. Using polarized neutron reflectometry, a quantitative depth profile of the oxygen content gradient is achieved, which, alongside atomic-resolution scanning transmission electron microscopy, uniquely reveals the formation of a novel structural phase near the surface. Surface-sensitive x-ray spectroscopies further confirm a significant change of the electronic structure accompanying the transition. The anisotropic features of this novel phase enable a distinct oxygen diffusion pathway in contrast to conventional observation of oxygen motion at moderate temperatures. The results provide insights furthering the design of solid oxygen ion conductors within the framework of topotactic phase transitions.

Antiferromagnets represent a wide class of technologically promising materials for spintronic and spinorbirtonic devices with multiple magnetic sublattices [1]. An efficient manipulation of antiferromagnetic textures requires the presence of the Dzyaloshinskii-Moriya interaction (DMI), which is present in crystals of special symmetry, and thus limits the number of available materials. In contrast to antiferromagnets, it is already established that in ferromagnetic thin films and nanowires chiral responses can be tailored relying on curvilinear geometries [2]. Here, we explore curvature effects in curvilinear antiferromagnets which are stemming from exchange interaction [3]. It is shown that intrinsically achiral curvilinear antiferromagnetic spin chains behave as a biaxial chiral helimagnet with a curvature-tunable anisotropy and DMI. In contrast to ferromagnetic spin chains, the dipolar interaction leads to the hard-axis anisotropy. This allows to observe the effects of geometry even in chains with small curvature and torsion because of absence of other competing easy axis anisotropies except the geometry-induced one. The latter determines the homogeneous antiferromagnetic state at low curvatures and the gap for spin waves. The geometry-driven DMI determines the helimagnetic phase transition and leads to the appearance of the region with the negative group velocity at the dispersion curve. We note, that the anisotropy in curvilinear antiferromagnetic spin chains is an additional source of geometry-driven effects on magnetic textures [4].