Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

In this talk I will review our recent activities on curvilinear and magnetoelectric antiferromagnets.

Conventional magnetic field sensors are fabricated on flat substrates and are rigid. Extending 2D structures into 3D space relying on the flexible electronics approaches allows to enrich conventional or to launch novel functionalities of spintronic-based devices. The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and Dzyaloshinskii-Moriya interaction (DMI) are characteristic of curved surfaces, leading to curvature-driven magnetochiral responses and topologically induced magnetization patterning. The possibility to tailor magnetic responses by geometry of the object is a new approach to material science, which allows to obtain a desired functionality of spintronic and spin-orbitronic devices yet without the need to rely on the optimization of the intrinsic material properties. Here, we will review fundamentals of 3D curved magnetic thin films and focus on their applications in eMobility, virtual and augmented reality, soft robotics, and human-machine interfaces.

Magnetic fields are not visible. As humans we know cannot feel them. In contrast to birds, we humans do not use them for navigation. There might be even an impression that magnetic fields are of very limited relevance for our everyday life. This is in strong contrast to the fact that the magnetic field of the Earth protects life from dangerous cosmic radiation, that there are numerous magnetic field sensors, which are implemented in devices around us including electronic compasses in our cellphones, crucial component of motors in electrical cars, even level of water in our coffee machines is measured using magnetic field sensors. Our society with all known industrial and technology revolutions is not thinkable without the use of magnetic fields and magnetic field sensors. Still, this is an established fact that for thousands of years humans believed that they are not susceptible to magnetic fields. Therefore, in contrast to vision, audio or haptic perception, magnetic field as an information channel was not considered seriously for humans.
The situation changed very recently. New studies show that similar to birds, mammals including humans also feel geomagnetic fields, the property which is called magnetoception. Although this sense for humans is still to be understood, we are working on the realisation of artificial magnetoception. We design and fabricate electronic skins - magnetosensitive devices prepared on mechanically soft and compliant support, which does not disturb our everyday activity when applied to skin or integrated in a textile. Mit unserer hochempfindlichen, aber tragbaren und sogar implantierbaren Sensorplattform möchten wir die Magnetorezeption quasi in einen „Sechsten-Sinn“ verwandeln. Die Anwendungsmöglichkeiten dieser Technologie sind kaum zu überschätzen und tangieren viele wichtige gesellschaftliche Bereiche; von der Informationstechnologie, über die Halbleitertechnologie, die E-Mobilität bis zur Realisierung neuartiger Mensch-Maschine-Schnittstellen zur Hilfe bei schweren Erkrankungen.

The Helmholtz Innovation Lab “FlexiSens” focuses on the development and application of a flexible and printable magnetic field sensors (Hall effect and magneto-resistive effects). We have developed novel high-performance magnetic field sensors on ultra-thin flexible substrates that have a high mechanical adaptability. Due to their extremely thin and unconventional mechanical properties, flexible and printed sensors can be used not only on various flat, but also curved objects. Our technology enables new fields of application, for example as wearable electronics on the skin, as smart implants in medicine or for monitoring movements in large glass or roof structures.

The lift coeffcient C_L of a bubble in a shear flow is known to change its sign depending on the bubble shape, i.e. C_L of spherical bubbles are positive for any the bubble Reynolds numbers while those of ellipsoidal bubbles can be negative due to the deformation-induced negative lift. The critical bubble diameter, d_C, for the lift reversal was discussed in this study by making use of available CL correlations for clean bubbles in linear shear flows. As a result, the following conclusions were obtained: (1) the C_L correlations well describe the complex characteristics of d_C and the lift reversal criterion in terms of Re_C is well reproduced with the correlations, (2) in the surface tension and inertial force dominant regime, the critical Eötvös and Weber numbers can be used to develop a simple criterion of lift reversal, i.e.they are almost constant, and the Capillary number for d_C can be expressed in terms of the Morton number only, M; these dimensionless groups in the viscous force dominant regime, however, show more complex dependence on M, and (3) the critical Ohnesolge number, Oh_C, monotonically increases with increasing M even in the viscous force dominant regime.

Terahertz (THz) generation via optical rectification (OR) of near-infrared femtosecond pulses in DSTMS is systematically studied using a quasi-3D theoretical model, which takes into account cascaded OR, three-photon absorption (3PA) of the near-infrared radiation, and material dispersion/absorption properties. The simulation results and the comparison with experimental data for pump pulses with the center wavelength of 1.4 μm indicate that the 3PA process is one of the main limiting factors for THz generation in DSTMS at high pump fluences. The THz conversion efficiency is reduced further by the enhanced group velocity dispersion effect caused by the spectral broadening due to the cascaded OR. We predict that for broadband pump pulses with a duration of 30 fs, the THz conversion efficiency can be enhanced by a factor of 1.5 by using a positive pre-chirping that partially suppresses the cascaded OR and the 3PA effects.

Polymer electrolyte electrochemical cells (PECs) offer exciting possibilities as energy converters in the form of both fuel cells and electrolyzers. Computational fluid dynamics can be used to analyse the performance of virtual prototypes at the micro-scale, as well as the cell and stack levels. This presentation details a comprehensive program of development of open source tools to describe and predict PEC operation. The software employed is OpenFOAM, which mimics the governing partial differential equations that describe the physics of PEC behaviour. Models range from detailed two-phase flow in porous transport layers based on digital reconstructions and the volume of fluid method, through single and multi-fluid cell models employing Eulerian-Eulerian solvers, to stack-level models whereby volume averaging also known as local homogenization is employed for both single-phase and two-phase formulations. The development of a multi-phase stack model represents an original and novel scheme not previously published.
The results of mathematical calculations are compared with analytical solutions for one-dimensional idealizations, previous three-dimensional (3-D) numerical work by other researchers, and detailed experimental data gathered in-house. Comparisons are made in terms of local current density and species mass/molar fractions, as well as current density vs. voltage, i.e., polarization characteristics. Different levels of model complexity are also considered, for instance comparisons of a 2-D electrochemical formulation based on a Kirchhoff-Ohm equation (ideal potential less losses/over-potentials) vs. a fully 3-D simulation of both ionic and protonic potential fields. The presentation concludes with an assessment of the needs/requirements of the next generation of PEC analysis tools.

Further development of proton therapy takes place largely through in-vivo experiments, which are subject to increasingly strict ethical and technical requirements. Proton irradiation of small animal organs demand for highly suitable experimental setups and intelligent protocols to mimic clinical workflows as closely as possible. This includes the possibility of on-beam imaging for precise positioning and treatment. To meet these requirements, proton radiography was integrated into an existing beam setup for mouse brain proton irradiation at the University Proton Therapy Dresden (UPTD).
For the realization of the radiography a flat panel detector was installed on proton beam axis behind mouse position. Transmission imaging was achieved by increasing the proton energy significantly above that required for brain irradiation, i.e. the protons pass through the mouse and reach the detector with minimal dose deposition.
The final workflow includes the acquisition of cone-beam computed tomography scans and planar X-ray images before the irradiation to receive anatomical information and perform a treatment planning. The hippocampus as target region for current mouse brain irradiation experiments can be determined by registration with mouse brain atlas data. Proton radiography is acquired with a scattered proton beam right before the irradiation, resulting in a radiograph, which can be registered to the X-ray image. Finally, the target volume can be aligned to the collimated proton beam for accurate brain irradiation, which was validated by immunohistochemical staining of DNA damage region.
The setup for proton radiography and mouse brain irradiation, parameters influencing the radiography quality and experimental data will be presented.

Presentation at "PrecisionSM" Working Group Meeting, 26.5.2021 (virtual)

Drug-resistant epilepsy is a diagnostic and therapeutic challenge, mainly in patients with negative MRI findings. State-of-the-art imaging methods complement standard epilepsy protocols with new information and help epileptologists to increase the reliability of their decisions. In this study, we investigate whether arterial spin labeling (ASL) perfusion MRI can help localize the epileptogenic zone (EZ). To that end, we developed an image processing method to detect the EZ as an area with hypoperfusion relative to the contralateral unaffected side, using subject-specific thresholding of the asymmetry index in ASL images. We demonstrated three thresholding criteria (termed minimal product criterion, minimal distance criterion, and elbow criterion) on 29 patients with MRI-negative epilepsy (age 32.98 ± 10.4 years). The minimal product criterion showed optimal results in terms of positive predictive value (mean 0.12 in postoperative group and 0.22 in preoperative group) and true positive rate (mean 0.71 in postoperative group and 1.82 in preoperative group). Additionally, we found high accuracy in determining the EZ side (mean 0.86 in postoperative group and 0.73 in preoperative group out of 1.00). ASL can be easily incorporated into the standard presurgical MR protocol, and it provides an additional benefit in EZ localization.

Antiferromagnets (AFMs) emerged as a versatile material science platform, which enabled numerous fundamental discoveries including the observation of monopole quasiparticles in frustrated systems and collective quantum effects, such as spin superfluidity and Bose–Einstein condensation of magnetic excitations [1]. Primary advantages of antiferromagnets are their terahertz operating frequencies, the absence of stray fields, magnetic field robustness, all of which result in numerous advantages including those in spintronics and spinorbitronics [2]. The key enabler of those applications is the presence of the Dzyaloshinskii-Moriya interaction (DMI). This, in turn, put stringent requirements on the magnetic symmetry of AFM, which should support weak ferromagnetism and chiral helimagnetism. This makes the portfolio of material systems available for these studies very limited that renders the progress in AFM-related fundamental and technological research to depend on time-consuming material screening and optimization of intrinsic chiral properties of AFMs. The field of curvilinear magnetism is well explored for ferromagnets, where magnetic responses are tailored by local curvatures [3]. By contrast, the topic of curvilinear AFMs is at its infancy [4-9]. The energy landscape of ring AFM and geometrically frustrated chains at non-zero temperature is characterized by a large number of metastable states including long-living noncollinear textures if anisotropy is strong enough [6]. In experiment, curvilinear AFMs are mainly represented by the molecular magnets [7] and metalized DNA molecules [8]. The shape anisotropy stemming from magnetostriction plays the major role in the ordering of the Neel vector in perovskite zig-zag stripes and nanodots determining the easy direction as the parallel or perpendicular to the boundary [9]. In this presentation, we will demonstrate that chiral responses of AFMs can be tailored by a geometrical curvature without the need to adjust material parameters. In a general case, an intrinsically achiral one-dimensional curvilinear AFM spin chain behaves as a chiral helimagnet with geometrically tunable DMI, orientation of the Neel vector and the helimagnetic phase transition, see Fig. 1 [4]. The helix-shaped spin chain possesses two ground states: the so-called homogeneous and periodic ones with respect to the motion along the chain. The energetically favorable state is determined by the direction of the geometry-driven DMI vector. In contrast to ferromagnets, there is no easy axis anisotropy competing with the geometry-driven one. Furthermore, the curvature-induced DMI results in the hybridization of spin wave modes. The low-frequency branch is gapless for straight chains and possesses the gap for any finite curvature. In addition, the DMI enables a geometrically-driven local minimum of the low frequency branch which increases for larger curvature and torsion, see Fig. 2. This opens exciting perspectives to study long-lived collective magnon states in AFMs. These findings position curvilinear 1D antiferromagnets as a novel platform for the realization of geometrically tunable chiral antiferromagnets for antiferromagnetic spinorbitronics and fundamental discoveries in the formation of coherent magnon condensates in the momentum space. The proposed description of vector fields living at curvilinear geometries can be applied for other systems with complex order parameters, such as ferroelectrics [10] or liquid crystals [11].

[1] C. Castelnovo, R. Moessner, S. L. Sondhi, Nature, Vol. 451, p. 42 (2008); N. Nagaosa, Y. Tokura, Phys. Scr. Vol. T146, p. 014020 (2012);
A. A. Zvyagin, Low Temp. Phys. Vol. 39, p. 901 (2013) [2] T. Jungwirth, J. Sinova, A. Manchon et al, Nat. Phys. Vol. 14, p. 200 (2018); V. Baltz,
A. Manchon, M. Tsoi et al, Rev. Mod. Phys. Vol. 90, p. 015005 (2018) [3] R. Streubel, P. Fischer, F. Kronast et al, J. Phys. D: Appl. Phys. Vol. 49,
p. 363001 (2016); A. Fernandez-Pacheko, R. Streubel, O. Fruchart et al, Nat. Comm. Vol. 8, p. 15756 (2016); D. D. Sheka, O. V. Pylypovskyi, P.
Landeros et al., Comm. Phys. 3, 128 (2020) [4] O. V. Pylypovskyi, D. Y. Kononenko, K. V. Yershov et al, Nano Lett. Vol. 20, p. 8157 (2020) [5]
K. K. Nanda, A. W. Addison, E. Sinn et al, Inorg. Chem. Vol 35, p. 5966 (1996); O. Cador, D. Gatteschi, R. Sessoli et al, Ang. Chem. Int. Ed. vol 43,
p. 5196 (2004); M. Grzelczak, M. Correa-Duarte, V. Salgueirino-Maceira et al, Ang. Chem. Int. Ed. Vol. 46, p. 7026 (2007); T. Guidi, B. Gillon, S. A.
Mason et al, Nat. Comm. Vol. 6, p. 7061 (2015) [6] S. Castillo-Sepulveda, R. A. Escobar, D. Altbir et al, Phys. Rev. B, Vol. 96, p. 024426 (2017) [7] S.
J. Blundell, F. L. Pratt, J. Phys.: Cond. Matt. Vol. 16, p. R71 (2004) [8] K. Mizoguchi, S. Tanaka, M. Ojima et al, J. Phys. Soc. Jap. Vol. 76, p. 043801
(2007) [9] A. D. Bang, I. Hallsteinsen, R. V. Chopdekar et al, Appl. Phys. Lett. Vol. 115, p. 112403 (2019); M. S. Lee, P. Lyu, R. V. Chopdekar et al,
J. Appl. Phys. Vol. 127, p. 203901 (2020) [10] M. Owczarek, K. A. Hujsak, D. P. Ferris et al, Nat. Comm. Vol. 7, p. 13108 (2016) [11] G. Napoli, L.
Vergori, Phys. Rev. Lett. Vol. 108, p. 207803 (2012)

Antiferromagnets (AFMs) have regained strong attention from the magnetism community especially with the advent of antiferromagnetic spintronics [1]. The key operational element of spintronic devices is represented by information carriers, such as domain walls (DWs) and skyrmions. The simplest AFM DW separates two regions with the opposite orientation of the Neel order parameter. Although highly relevant, the experimental studies of AFM DWs (visualization, dynamics, mechanics) are challenging because of strict requirements on measurement techniques to access their properties. Here, we overcome these limitations and conduct detailed, quantitative studies of the mechanics and the nanoscale properties of individual, antiferromagnetic DWs in a single crystal Cr2O3 – a room-temperature, magnetoelectric, insulating AFM [2]. Our results reveal a remarkably pristine DW behaviour, which is governed by DW energy minimization and boundary conditions, but largely unaffected by pinning or disorder – a “textbook example” of antiferromagnetic DW physics. In our experiment, the crystal’s (0001) surface is patterned by a grid of mesas with mean thickness and width t=166 nm and w=2400 nm, respectively. The DW is nucleated by means of magnetoelectric field cooling by inverting the electric bias field over opposite halves of the sample. The DW may also be dragged through the mesa pattern by a focused laser spot. The magnetic texture is imaged using Nitrogen Vacancy (NV) magnetometry [3]. We find that the DW mimics an elastic surface with specific mechanical properties, determined by the interaction with the topographic features of the sample where the DW is (i) deflected from the straight plane crossing the mesa; (ii) bent around mesa corners. To address the DW behaviour theoretically, we perform large-scale spin-lattice simulations with GPU speed-up [4]. The analytical Ansatz is developed based on the numerically-obtained, three-dimensional DW profile. All main features of the DW behaviour can be determined taking into account the nearest-neighbour exchange and uniaxial anisotropy for a general model of a bipartite AFM. Crossing the mesa, the DW experiences an S-shaped distortion observed at the mesa surface, which is the result of exchange-driven boundary conditions at the side faces of the mesa, see Fig. 1. Below the top surface, the DW possesses a twist to match this distortion with the straight plane far below the sample’s surface. We find that the DW surface is deflected from the plane over a characteristic depth of 0.34w. Comparison of the equilibrium DW direction in bulk and at the mesa’s top surface allows us to derive an effective Snell’s law for the DW behaviour at the sample’s surface with the given incidence and refraction angles θ1 and θ2. The effective refraction coefficient is determined by the analytical energy minimization and reads neff = 1 + 3.1t/w + O(θ1). Controlled manipulation via laser not only enables DW dragging through the mesa, but also pinning at mesa corners. The shape of the DW surface is governed by its intrinsic elasticity. In terms of mechanics of an elastic ribbon, the corresponding tension coefficient is determined by the temperature-dependent exchange stiffness and anisotropy coefficient. This allows for curved DW states in which it is pinned at the opposite mesa sides. Using mesas as bistable pinning sites, we propose a potential DW-based AFM memory concept. Here, the memory state “0” or “1” is associated with the direction of the Neel order parameter at the mesa surface. We have realized such pinning sites experimentally and have shown manipulation of the state via laser dragging. In summary, we realize engineered DW potentials and control over DW trajectories by topographic structuring and manipulation of the DW position by means. The physics of AFM DWs in a single crystal with non-trivial surface topography is described theoretically by means of spin-lattice simulations and analytical model. A novel nanoscale AFM memory architecture is suggested.

[1] T. Jungwirth, J. Sinova, A. Manchon et al, Nat. Phys. Vol. 14, p. 200 (2018); T. Jungwirth, X. Marti, P. Wadley et al, Nat. Nano. Vol. 11, p. 231 (2016); V. Baltz, A. Manchon, M. Tsoi et al, Rev. Mod. Phys. Vol. 90, p. 015005 (2018); O. V. Pylypovskyi, D. Y. Kononenko, K. V. Yershov et al, Nano Lett. Vol. 20, p. 8157 (2020) [2] N. Hedrich, K. Wagner, O. V. Pylypovskyi et al, arXiv:2009.08086 [3] L. Rondin, J.-P. Tetienne, T. Hingant et al, Rep. Prog. Phys. Vol. 77, p. 056503 (2014); N. Hedrich, D. Rohner, M. Batzer et al, Phys. Rev. Applied, Vol. 14, p. 064007 (2020) [4] SLaSi simulation package, http://slasi.knu.ua; O. V. Pylypovskyi, D. D. Sheka, Book of Abstracts, EUROPT Workshop, p. 11 (2013)

The behaviour of any physical system is governed by the order parameter, determined by the geometry of the physical space of the object, namely their dimensionality and curvature. Usually, the effects of curvature are described using local interactions only, e.g. local spin-orbit- or curvature-induced Rashba and Dzyaloshinskii-Moriya interactions (DMI). In the specific case of ferromagnetism, until recently, there was no analytical framework, which was treating curvature effects stemming from local [1] and non-local [2] interactions on the same footing. The lack of a proper theoretical foundation impedes the description of essential micromagnetic textures like magnetic domains, skyrmion-bubbles and vortices. Here, we present a micromagnetic theory of curvilinear ferromagnetic shells, which allows to describe the geometry-driven effects stemming from exchange and magnetostatics within the same framework [3]. A general description of magnetic curvilinear shells can be done using tangential derivatives of the unit magnetization vector. Tangential derivatives are represented by the covariant derivatives of in-surface components and the regular derivative of the normal magnetization component, normalized by the square root of the corresponding metric tensor coefficient. This allows to separate the explicit effects of curvature and spurious effects of the reference frame. The shape of a given thin shell can be determined by two principal curvatures k1 and k2, which are functions of coordinate. The respective classification of curvilinear surfaces operates with (i) developable surfaces, where one of the principal curvatures equals to zero; (ii) minimal ones, where the mean curvature k1 + k2 = 0; and (iii) the general case. The local geometry-driven energy contributions are represented by the DMI and anisotropy, whose coefficients are determined by powers of the principal curvatures. This allows to cancel the influence of one of the DMI terms for the developable surfaces for any magnetic texture. The magnetostatic interaction is a source of new chiral effects, which are essentially non-local in contrast to the conventional DMI. The physical origin is the non-zero mean curvature of a shell and the non-equivalence between the top and bottom surfaces of the shell. We demonstrate that the analysis of non-local effects in curvilinear thin shells can become more straightforward when introducing three magnetostatic charges. In this respect, in contrast to the classical approach by Brown [4], we split a conventional volume magnetostatic charge into two terms: (i) magnetostatic charge, governed by the tangent to the sample’s surface, and (ii) geometrical charge, given by the normal component of magnetization and the mean curvature. In addition to the shape anisotropy (local effect), there appear four additional non-local terms, determined by the surface curvature. Three of them are zero for any magnetic texture in shells with the geometry of minimal surfaces. The fourth term is determined by the non-equivalence of the top and bottom surfaces of the shell and becomes zero only for the special symmetries of magnetic textures. The discovered non-local magnetochiral effects introduce handedness in an intrinsically achiral material and enables the design of magneto-electric and ferro-toroidic responses. This will stimulate to rethink the origin of chiral effects in different systems, e.g. in fundamentally appealing and technologically relevant skyrmionic systems, and further theoretical investigations in the field of curvilinear magnetism as well as experimental validation of these theoretical predictions. These developments will pave the way towards new device ideas relying on curvature effects in magnetic nanostructures. The impact of effects predicted in this work goes well beyond the magnetism community. Our description of the vector field behaviour can be applied to different emergent field of studies of curvature effects. The prospective applications include curved superconductors [5], twisted graphene bilayers [6], flexible ferroelectrics [7], curved liquid crystals [8].

[1] Yu. Gaididei, V. P. Kravchuk, D. D. Sheka, Phys. Rev. Lett., 112, 257203 (2014); D. D. Sheka, V. P. Kravchuk, Yu. Gaididei, J. Phys. A: Math. Theor., 48, 125202 (2015); O. V. Pylypovskyi, V. P. Kravchuk, D. D. Sheka et al, Phys. Rev. Lett., 114, 197204 (2015); V. P. Kravchuk, D. D. Sheka, A. Kakay et al, Phys. Rev. Lett., 120, 067201 (2018) [2] P. Landeros, A. S. Nunez, J. Appl. Phys. Vol. 108, p. 033917 (2010); J. A. Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. Lett., 117, 227203 (2016); J. A. Otalora, M. Yan, H. Schultheiss et al, Phys. Rev. B, 95, 184415 (2017) [3] D. D. Sheka, O. V. Pylypovskyi, P. Landeros et al., Comm. Phys. 3, 128 (2020) [4] W. F. Brown Jr. Micromagnetics (Wiley, New York, 1963) [5] V. Vitelly, A. M. Turner, Phys. Rev. Lett., 93, 215301 (2004) [6] W. Yan, W.-Y. He, Z.-D. Chu et al, Nat. Comm., 4, 2159 (2013) [7] M. Owczarek, K. A. Hujsak, D. P. Ferris et al, Nat. Comm., 7, 13108 (2016) [8] G. Napoli, L. Vergori, Phys. Rev. Lett., 108, 207803 (2012)

Targeted alpha therapy is currently one of the most intensively investigated topics in radiopharmaceutical sciences and cancer management in nuclear medicine. Especially, the alpha emitter ²²⁵Ac provides excellent physical and chemical properties (t_1/2 = 10 d, 4 α and 2 β decays). Thus, it is consistently gaining an increasing interest for the radioligand therapy (RLT) of various tumor entities. The aim of this study was to synthesize macropa-based chelators that allow room temperature labeling and offer the modular functionalization properties for a straightforward coupling of temperature-sensitive biomolecules by e.g. click chemistry approaches. As a proof of concept study, the chelators were coupled to known PSMA-targeting vector molecules and then evaluated in vitro as well as in vivo.

We recognize ¹³¹Ba as a SPECT radionuclide, which provides a diagnostic match for the therapeutic alpha-emitting radionuclides ²²³Ra and ²²⁴Ra. The gamma-emitter barium-131 (t_½ = 11.5 d) decays with an energy of 123.8 keV (30% intensity) of the first decay via cesium-131 (t_½ = 9.7 d) to stable xenon-131, each by electron capture. Our aim was to develop of a straightforward resin-based radiochemical separation to yield ¹³¹Ba with high radionuclide purity. Furthermore, the radiolabeling of the complexing agent macropa with [¹³¹Ba]Ba²⁺ using mild labeling conditions was intended. For this purpose, different TLC systems as reaction control were utilized. The radiopharma-cological characterization of ¹³¹Ba-labeled macropa in comparison to uncomplexed [¹³¹Ba]Ba²⁺ was carried out in healthy mice, including biodistribution and small animal SPECT/CT experiments.

The dynamic behavior of glacial retreat following the Last Glacial Maximum (LGM), which is globally diachronous, is poorly understood. Along strike of the northern Alpine margin, multiple lobes of large foreland glaciers left 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 part. We use these local geologic variations to explore how regional climatic conditions relate to global climate during this period of rapid late Pleistocene climate change. The chronology for this interval has been well-constrained in Switzerland, but radiometric ages have only been reported for a few locations along the Alpine Foreland in Germany. 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 along a transect perpendicular to three moraine ridges previously interpreted to represent the LGM along with two post-LGM retreat stands. Our preliminary raw data show that the sampled lithology provides internally consistent, reproducible, and geologically meaningful dates. We discuss our results taking into account limestone weathering, erosion and local postglacial landscape stabilization, and apply appropriate correction factors to obtain more accurate ages. This exposure age data gives first insights into the spatio-temporal patterns of glacial retreat in the northern Alpine Foreland, which can be used to reconstruct Central European paleoclimate in the late Pleistocene.

Over the last decades, nanoparticles have become a key element in a number of scientific and technological fields, spanning from materials science to life sciences. The characterisation of nanoparticles or samples containing nanoparticles in terms of morphology, chemical composition and other parameters typically involves investigations with various analytical tools, requiring complex workflows and extending the duration of such studies to several days or even weeks. Here, we report about the development of a new unique in-situ correlative instrument, allowing to answer questions about the nanoparticles’ shape, size, size-distribution and chemical composition using a single probe. Combining various microscopic and analytical capabilities in one single instrument allows a considerable increase in flexibility and a reduction of the duration of such complex investigations. The new instrument is based on focused ion beam microscopy technology, using a gas field ion source as a key enabler and combining it with specifically developed secondary ion mass spectrometry and scanning transmission ion microscopy technology. We will present the underlying concept, the instrument and its main components, and proof of concept studies performed on this novel instrument. For this purpose, different titanium dioxide nanoparticular samples, as well as their distribution and localisation in biological model systems, have been investigated. Our results demonstrate the performance and usefulness of the instrument for nanoparticle investigations, laying the ground for a number of future applications, including in particular nanotoxicological research.

The laser intensity dependence of nonlinear Compton scattering is discussed in some detail. For sufficiently hard photons with energy ω', the spectrally resolved differential cross section dσ/dω'|ω'=const, rises from small toward larger laser intensity parameter ξ, reaches a maximum, and falls toward the asymptotic strong-field region. Such a rise and fall of a differential observable is to be contrasted with the monotonously increasing laser intensity dependence of the total probability, which is governed by the soft spectral part. We combine that hard-photon yield from Compton scattering with the seeded Breit–Wheeler pair production in a folding model and obtain a rapidly increasing e+e− pair number at ξ ≲ 4. Laser bandwidth effects are quantified in the weak-field limit of the related trident pair production.

We provide an experimental investigation on the mechanism of the bubble formation from sub-millimeter orifices under variable gas flow conditions VGFC. The effect of influential parameters including the volumetric gas flow rate Q, the orifice diameter dor, and the volume of the gas reservoir Vc upstream of the orifice are investigated in detail. We found that, by enlarging Vc, q increases. This affects various aspects of bubble formation dynamics such as the bubble base expansion, the apparent contact angle at the three-phase contact point, and the bubble detachment criterion. The effect of Vc is best presented by its dimensionless group, the capacitance number Nc. The minimum Nc from which the influence of the gas reservoir becomes important depends on the orifice size. Moreover, a significant increase in Vc leads to a change in the bubbling regime towards multiple bubble formation.

The talk introduces the current status of the research and metadata management at HZDR.

The dipole strength of the nuclide 76Ge was studied in photon-scattering experiments using bremsstrahlung produced with electron beams of energies of 7.8 and 12.3 MeV at the γELBE facility. We identified 210 levels up to an excitation energy of 9.4 MeV and assigned spin J = 1 to most of them. The quasicontinuum of unresolved transitions was included in the analysis of the spectra and the intensities of branching transitions were estimated on the basis of simulations of statistical γ-ray cascades. The photoabsorption cross section up to the neutron-separation energy was determined and compared with predictions of the statistical reaction model as well as with results of experiments using other reactions.

Techntium-99 (99Tc) is one of the most concerning fission products due to its long half-life (2.14∙10⁵ years) and the mobility of the anion pertechnetate (TcO₄⁻). [1] However, Tc migration decreases when Tc(VII) is reduced to Tc(IV). This scavenging step is favored by reductive material, among which Fe(II) minerals have been widely studied due to their versatility, low cost and ubiquity. [2]
Green rust is a Fe(II)-Fe(III) mixed hydroxide that possesses adsorption, anion exchange and reduction capabilities. Its presence is expected in the near- and far-field of a nuclear waste repository because it is an iron corrosion product, and it is also formed in the environment when Fe²⁺ interacts with Fe(III) minerals. [3]
Batch contact studies have been performed under a wide range of conditions, i.e. pH (3-11), Tc concentration (nM-mM), and ionic strength (0-0.1 M). X-ray diffraction, Raman microscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) provided information on Tc oxidation state and speciation as well as on secondary redox products related to the Tc interaction with green rust. In addition, re-oxidation experiments have been performed during six months.
The results show that green rust removes Tc from solution with efficiencies between 80% (Kd = 8.0∙103 mL/g) and ≈100% (Kd = 9.9∙10⁵ mL/g) for pH > 6.0, regardless on the ionic strength and the Tc concentration. In contrast, Tc removal for pH < 6.0 drops with decreasing pH, and ranges from 80% to 50% (Kd = 2.0∙10³ mL/g), reaching a minimum at pH 3.5. XPS analysis reveals the predominance of Tc(IV) at all evaluated pH values (3.5 to 11.5), supporting that Tc reductive immobilization is the main retention mechanism. Re-oxidation experiments show that Tc is slowly solubilized when time increases.
We thank the German Federal Ministry of Economic Affairs and Energy (BMWi) for funding the VESPA II project (02E11607B).
[1] Meena, A.H.; Arai, Y. Env. Chem Lett (2017), 15, 241–263.
[2] Pearce, C.I. et al. Sci. Total Environ. (2020), 716, 132849.
[3] Usman, M. et al. Chem. Rev. (2018), 118, 3251–3304.

Hypothesis
The shear stress of the axisymmetric flow field triggers a nonuniform distribution of the surfactants at the surface of a rising bubble, known as stagnant cap. The formation of the stagnant cap gives rise to Marangoni stresses that reduce the mobility of the interface, which in return reduces the rising velocity. However, the conditions in technological processes usually deviate from the linear rise of a single bubble in a quiescent unbounded liquid. Asymmetric shear can act on the bubble surface e.g. due to the vorticity in the surrounding flow, bubble-bubble interactions, or influence of the reactor wall. A different surfactant distribution at the interface is expected under asymmetric shear, which can change the hydrodynamic behavior of the interface drastically.
Experiments
Here we conduct model experiments with a bubble or a drop at the tip of a capillary placed in a defined flow field. Thereby we investigate the influence of asymmetric shear forces on the interface in the presence of surfactants. Microscopic particle tracking velocimetry is employed to measure the velocity of the surfactant-laden interface for different degrees of asymmetry in the surrounding liquid flow.
Findings
We show a direct experimental observation of the circulating flow at the interface under asymmetric shear, which prevents the formation of the typical stagnant cap. Additionally, we reveal that the interface remains mobile regardless of the surfactant concentration. Our results confirm that increasing the degree of asymmetry increases the shear forces and thus the interfacial velocity.

In a safety assessment of a high-level radioactive waste repository, interactions of radionuclides (e.g. neptunium(V)) with corroded phases in the near field of the repository have to be taken into account. The corrosion product of the zircaloy cladding material of spent nuclear fuel rods, namely zirconia (ZrO₂), potentially represents a first migration barrier towards mobilized radionuclide ions.
The interactions of Np(V) with monoclinic zirconia were studied at room temperature on a macroscopic and molecular scale. To gain comprehensive characteristics on the macroscopic level, batch sorption experiments were conducted to investigate the influence of different parameters (time, pH, Np(V) concentration and ionic strength). Np(V) showed increasing sorption to ZrO₂, starting from pH 3 and with a maximum uptake reached at pH ≥ 7. The Np(V) sorption is independent of ionic strength in the studied range (0.01 ‒ 0.1 M), indicating the formation of Np(V) inner-sphere sorption complexes on the ZrO₂ surface. Electrophoretic measurements further support this result by shifting the isoelectric point of ZrO₂ towards higher pH values in the presence of Np(V) compared to neat zirconia material.
Spectroscopic studies enable a deeper understanding of Np(V) sorption on a molecular scale. In situ Attenuated Total Reflection Fourier-transform Infrared spectroscopy potentially provides information on the number of sorption species, their denticity and the reversibility of the sorption process. From Extended X-ray Absorption Fine Structure spectroscopy access is given to the interatomic Np-Zr distances and the coordination numbers. Information gained on the macroscopic and molecular level will subsequently be used for surface complexation modelling (SCM) to parametrize a comprehensive description of the Np(V)-ZrO₂ system. This will contribute to a more reliable prediction of the environmental fate of neptunium(V).

Scaling of the lift reversal for a deformed bubble in the surface tension-inertial force dominant regime was discussed. Lift data of bubbles in water recently reported in literature were used. The negative lift component was well correlated in terms of the drag coefficient, which, in turn, implies that the vorticity produced at the bubble surface plays a key role in both drag and lift forces as is the case with the viscous force dominant regime. The scaling was confirmed to give good evaluations of the lift coefficients.

The shear stress of an axisymmetric flow field triggers a nonuniform distribution of the surfactants at the surface of a rising bubble, known as stagnant cap. This nonuniform surfactant distribution creates a surface tension gradient that counteracts the viscous shear stress of the flow and thus reduces the mobility of the interface. However, in technological processes the flow field often is asymmetric e.g. due to the vorticity in the flow. Under such conditions, the interface experiences an unbalanced shear stress that is not curl-free. Thus, it cannot be compensated by the redistribution of the surfactants at the interface [1].
Here, we conduct model experiments with a bubble at the tip of a capillary placed in a defined asymmetric flow field. Thereby, we investigate the mobility of the interface in the presence of surfactants and nanoparticles using microscopic particle tracking velocimetry. Compared to surfactants, nanoparticles have substantially higher desorption energy, leading to irreversible adsorption. Thus, a different interaction between the bulk flow and the interface is expected for different types of adsorbed materials.
In this study, we show a direct experimental observation of the circulating flow at the interface under asymmetric shear stress. The results indicate that the interface remains mobile regardless of the surfactant concentration [2]. Additionally, we show that the nanoparticle-laden interface adopts a solid-like state and resists the interfacial flow upon surface compression. Our results imply that the immobilization of the interface can be described by the ratio of the interfacial elasticity to the bulk viscous forces.

This talk presents the current state of LLAMA, the library for Low Level Abstraction of Memory Access.

Thallium(Tl) is a highly toxic trace metal. Lead(Pb)-zinc(Zn) smelting, which is a pillar industry in various countries, is regarded as one of the dominant anthropogenic sources of Tl contamination in the environment. In this study, thallium isotope data have been evaluated for raw material and a set of industrial wastes produced at different stages of Pb-Zn smelting in a representative large facility located by the North River, South China, in order to capture Tl isotope signatures of such typical anthropogenic origin for laying the foundation of tracking Tl pollution. Large variations in Tl isotopic compositions of raw Pb-Zn ores and solid smelting wastes produced along the process chain were observed. The ε²⁰⁵Tl value of raw Pb-Zn ores and return fines are −0.87 ± 0.26 and −1.0 ± 0.17, respectively, contrasted by increasingly more negative values for electrostatic precipitator dust (ε²⁰⁵Tl = −2.03 ± 0.14), lime neutralizing slag (ε²⁰⁵Tl = −2.36 ± 0.18), and acid sludge (ε²⁰⁵Tl = −4.62 ± 0.76). The heaviest ε²⁰⁵Tl (1.12 ± 0.51) was found in clinker. These results show that isotopic fractionation occurs during the smelting processes. Obviously, the lighter Tl isotope is enriched in the vapor phase (−3.75 ε²⁰⁵Tl units). Further XPS and STEM-EDS analyses show that Tl isotope fractionation conforms to the Rayleigh fractionation model, and adsorption of ²⁰⁵Tl onto hematite (Fe₂O₃) may play an important role in the enrichment of the heavier Tl isotope. The findings demonstrate that Tl isotope analysis is a robust tool to aid our understanding of Tl behavior in smelting processes and to provide a basis for source apportionment of Tl contaminations.

Our planet is flooded with plastics and the need for sustainable recycling strategies of polymers has become increasingly urgent. Enzyme-based hydrolysis of post-consumer plastic is an emerging strategy for closed-loop recycling of polyethylene terephthalate (PET). The polyester hydrolase PHL7 isolated from a compost metagenome completely hydrolyzed amorphous PET films, releasing 91 mg of terephthalic acid per hour and mg of enzyme. Degradation rates of the PET film of 6.8 µm h^-1 were monitored by vertical scanning interferometry. Structural analysis indicated the importance of leucine at position 210 for the extraordinarily high PET-hydrolyzing activity of PHL7. Within 24 h, 0.6 mg_enzyme g_PET ^-1 completely degraded post-consumer thermoform PET packaging in an aqueous buffer at 70°C without any energy-intensive pretreatments. Terephthalic acid recovered from the enzymatic hydrolysate was used to synthesize virgin PET, demonstrating the potential of polyester hydrolases as catalysts in sustainable PET recycling processes with a low carbon footprint.

Part I of this study introduced a novel methodology for the optimization of energy group structures to be used in diffusion calculations of Sodium Fast Reactors (SFRs). Such a methodology is assisted by either direct or simulated annealing search techniques. The capabilities of the method were preliminarily demonstrated on a single core state of the Superphénix reactor by using the DYN3D nodal diffusion code.
The scope of Part II is the further demonstration of the methodology efficiency through its application to more challenging “real-life” cases. In this respect, a static Superphénix neutronic benchmark comprising 13 different core states and a transient test initiated by an increase of the core inlet temperature at the Phénix reactor are considered.
For both Superphénix and Phénix reactor cores, 2- to 12-group optimal condensed energy group structures are identified using the 24-group structure as a starting point. The obtained optimal structures are thus employed in DYN3D and compared to the reference 24-group DYN3D solutions.
The outcomes show that also for a broader range of core configurations and under transient conditions the optimal energy group structures allow for significant acceleration of the DYN3D performance with practically negligible degradation of the solution accuracy.

Gold and silicon ions emitted from high brightness liquid metal ion sources (LMIS) are used as ionic targets for strong field laser interaction with femtosecond laser beams. Field ionization processes in the field emission source at electrostatic fields of some 10 V/nm allow the generation of various metallic and metalloid ion beams with charge states such as Au2+ and Si2+. Studying the ionization in strong femtosecond laser fields with intensities of up to 1016 W/cm2, we observed for these elements charge states of up to Au11+ and Si4+.

The determination of the magnesium level in a titanium reduction retort by inductive methods
is often hampered by the formation of titanium sponge rings which disturb the propagation of
electromagnetic signals between excitation and receiver coils. We present a new method for the
reliable identification of the magnesium level which explicitly takes into account the presence of sponge rings with unknown geometry and conductivity. The resulting inverse problem is solved by a look-up-table method, based on the solution of the inductive forward problems for several tens thousands of parameter combinations. The feasibility of that method is demonstrated by performing numerical simulations and measurements on a model experiment. This method is not limited to the production of titanium but can also be applied to other applications in metal production and processing.

The Eddy Current Flow Meter is an inductive flow rate sensor which can be used in many liquid metal applications and is well suited for operation in liquid metal cooled fast reactors. There it can be used as part of the safety instrumentation in order to detect a loss of flow in the reactor core. To further qualify the Eddy Current Flow Meter for use in liquid metal cooled reactors, measurements with a high temperature prototype of the sensor have been performed at the sodium loop SUPERFENNEC for sodium temperatures between 200 °C and 300 °C and flow velocities of up to 2.5 m/s. By measuring the magnitude or phase shift of the output voltage of the sensor, the flow rate or velocity of the liquid sodium in a certain volume around the sensor can be determined. Depending on the frequency of the excitation current, the sensitivity of the sensor is changing. Therefore, measurement results for different frequencies and temperatures are presented as well as the results of a frequency sweep for determining the optimal excitation frequency of the sensor.

The Eddy Current Flow Meter is an inductive velocity sensor which can be used in liquid metal applications, such as liquid metal cooled fast reactors. There it can be used as part of the safety instrumentation in order to monitor the coolant flow through subassemblies under normal operating conditions or to detect and locate blockages in case of a local freezing of the coolant. Typically the Eddy Current Flow Meter is used in pipe flows where the flow is mostly parallel to the sensor axis, whereas the flow angle may change significantly above subassemblies in a liquid metal cooled reactor. In the first part, the paper therefore deals with investigating the influence of varying flow angles on the performance of the Eddy Current Flow Meter. By performing measurements in a model experiment, the effect of different flow angles on the measured velocities will be demonstrated. In the second part of the paper, multiple Eddy Current Flow Meters in an array are used to detect and locate blockages in an array of seven subassemblies in the same model experiment. All experiments are carried out at room temperature with a liquid alloy of gallium, indium and tin.

A new versatile chelating ligand for intermediate size and softness radiometals [64Cu]Cu2+ and [111In]In3+, H2pyhox, was synthesized by introducing
pyridine as a new donor moiety to complement 8-hydroxyquinoline on an ethylenediamine backbone. The combination of pyridine
and oxine as donor sets was explored through structural analysis, and crystals of the three metal complexes with Cu2+, La3+ and In3+ demonstrate how the ligand adapts to accommodate metal ions of different sizes and charge. Exhaustive in-batch UV solution studies characterized the protonation constants of the free ligand as well as the formation constants of the metal complexes with Cu2+, In3+ and La3+. Preliminary concentration dependent radiolabeling studies with [111In]In3+ and [64Cu]Cu2+ show the robustness of H2pyhox to successfully coordinate both radiometals under mild conditions (< 15 min, room temperature, pH 6). H2pyhox is the first oxinate ligand to successfully radiolabel [225Ac]Ac3+, albeit only at high concentrations (0.1 – 1 mM) with gentle heating to 37℃. Whole serum, protein and ligand challenge assays further demonstrate the kinetic inertness of the radiometal-ligand complexes, confirming H2pyhox to be a promising versatile radiopharmaceutical chelator.

We study the topology and the temporal dynamics of turbulent Rayleigh-B´enard convection in a liquid metal with a Prandtl number of 0.03 located inside a box with a square base area and an aspect ratio of Γ = 5. Experiments and numerical simulations are focused on the Rayleigh number range, 6.7 × 10⁴ < Ra 3.5 × 10⁵
, where a new cellular flow regime has been reported by a previous study (Akashi et al., Phys. Rev. Fluids, vol.4, 2019, 033501). This flow structure shows symmetries with respect to the vertical mid-planes of the fluid container. The dynamic behaviour is dominated by strong three-dimensional oscillations with a periodic time that corresponds to the turnover time. Our analysis reveals that the flow structure in the Γ = 5 box corresponds in key features to the jump rope vortex structure, which has recently been discovered in a Γ = 2 cylinder (Vogt et al., Proc. Natl Acad. Sci. USA, vol.115, 2018, 12674-12679). While in the Γ = 2 cylinder a single jump rope vortex occurs, the coexistence of four recirculating swirls is detected here. Their cycling movement is restrained by the limited height of the fluid layer in the Γ = 5 box. Their approach to the lid or the bottom causes a temporal deceleration of both the horizontal velocity at the respective plate and the vertical velocity, which in
turn is reflected in Nusselt number oscillations. The cellular flow regime shows remarkable similarities to properties commonly attributed to turbulent superstructures.

Head and neck squamous cell carcinoma (HNSCC) is often being diagnosed at an advanced stage, conferring a poor prognosis. The probability of local control after radiotherapy depends on the eradication of cancer stem cells (CSCs) with activated DNA repair. This study provides evidence that the CSC-related transcription factor Oct4 contributes to HNSCC radioresistance by regulating DNA damage response and the CSC phenotype. Knockdown of Oct4 A isoform reduced self-renewal capacity in HNSCC and led to partial tumor cell radiosensitization caused by transcriptional downregulation of the cell cycle checkpoint kinases CHK1 and WEE1 and homologous recombination (HR) repair genes PSMC3IP and RAD54L. Besides, PARP inhibition with Olaparib selectively radiosensitized Oct4 A knockout, but not wild type HNSCC cells. This finding links Oct4 A to the HR-mediated DNA repair mechanisms. In turn, knockdown of PSMC3IP and RAD54L reduced the HNSCC self-renewal capacity and clonogenic cell survival after irradiation, suggesting the interplay between DNA repair and the CSC phenotype. Similar to the effect of Oct4 knockdown, overexpression of Oct4 also resulted in significant HNSCC radiosensitization and increased DNA damage, suggesting that Oct4-dependent regulation of DNA repair depends on its fine-tuned expression. In line with this observation, HNSCC patients with high and low nuclear Oct4 expression at the invasive tumor front exhibited poor loco-regional tumor control after postoperative radio(chemo)therapy compared to the intermediate expression subgroup. Thus, we found that the Oct4-driven transcriptional program plays a critical role in regulating HNSCC radioresistance, and a combination of radiotherapy with PARP inhibitors may induce synthetic lethality in Oct4-deregulated tumors.

Nuclear resonant reflectivity (NRR) from an Fe60Al40 film was measured using synchrotron radiation at several grazing angles near the critical angle of the total external reflection. By laterally resolved measurements after 20 keV Ne+ ion irradiation with gradually varied fluences of 0 - 3.0 x 10^14 ions/cm2, the progressive creation of the ferromagnetic A2 phase with increasing ion fluence was confirmed. The observed depth-selectivity of the method has been explained by application of the standing wave approach. From the time spectra of the nuclear resonant scattering in forward or diffraction directions the depth-profiles for different hyperfine fields were extracted. The results evidence that the highest magnetic hyperfine fields (~ 18 % 23 T) are initially created at the center part of the film and partially at the bottom interface with SiO2 substrate. The evolution of the ferromagnetic onset, commencing at a fixed depth within the film and propagating towards the interfaces has been directly observed. At higher fluence (3.01014 ions/cm2) the depth distribution of the ferromagnetic fractions became more homogeneous across the film depth in accordance with previous results.

Modern scientific collaborations and projects (MSCPs) employ various processing stages, starting with the proposal submission, continuing with data acquisition and concluding with final publications. The realization of such MSCPs poses a huge challenge due to (1) the complexity and diversity of the tools, (2) the heterogeneity of various involved computing and experimental platforms, (3) flexibility of analysis targets towards data acquisition and (4) data throughput. Another challenge for MSCPs is to provide additional metadata according to the FAIR principles for all processing stages for internal and external use. Consequently, the demand for a system, that assists the scientist in all project stages and archives all processes on the basis of metadata standards like DataCite to make really everything transparent, understandable and citable, has risen considerably. The aim of this project is the development of the HELmholtz ScIentific Project WORkflow PlaTform (HELIPORT), which ensures data provenance by accommodating the complete life cycle of a scientific project and linking all employed programs and systems. The modular structure of HELIPORT enables the deployment of the core applications to different Helmholtz centers (HZs) and can be adapted to center-specific needs simply by adding or replacing individual components. HELIPORT is based on modern web technologies and can be used on different platforms.

Polydisperse bubbly flows appear in many industrial applications and are particularly relevant for nuclear and process engineering. A popular approach for their simulation is the two-fluid model, which requires information about the bubble size. An associated challenge is to incorporate the effects of coalescence and breakup on the size distribution, which can be tracked by a population balance equation. It can be solved by the method of classes, which splits the bubble population into a finite number of size groups. However, this technique is expensive because the source term assembly involves the computation of coalescence and breakup frequencies between all bubble size pairs. This work focuses on improving the performance of the class method implementation within the OpenFOAM Foundation release (www.openfoam.org), an open source computational fluid dynamics software that allows for domain decomposition and parallel execution on multiple central processing units. Here, the parallel computation of the coalescence and breakup frequencies is shifted to graphics processing units using the Nvidia CUDA framework. Calculations are done asynchronously with overlapping data transfers, treating size pairs as independent units of work that are computed in parallel. The coalescence and breakup frequency computation on graphics processing units leads to a significant speedup compared to the pre-existing implementation. The improvement is demonstrated for a co-current two-phase flow in a vertical pipe. Both the source code and the case setup are made publicly available.

Nuclear power plants (NPPs) have been considered an important energy source in Europe over a long time. However, in Germany the government decided that NPPs must terminate their operation end of 2022 at the latest, due to their possible threats on humans and the environment. The question arises, how much the long term irradiation of an NPP poses safety risks, in particular, in the reactor pressure vessel (RPV), which is the main shielding barrier of the radioactive fuel. For this purpose, the microstructural features, the composition, and the radioactive inventory of the steel shielding material in the RPV are investigated.

Understanding competition and cooperation within microbiota is of high fundamental and clinical importance, helping to comprehend species' evolution and biodiversity. We co-encapsulated and cultured two isogenic Escherichia coli strains expressing blue (BFP) and yellow (YFP) fluorescent proteins into numerous emulsion droplets and quantified their growth by employing fluorescence measurements. To characterize and compare the bacterial growth kinetics and behavior in mono and co-culture, we compared the experimental observations with predictions from a simple growth model. Varying the initial ratio (R0) of both cell types injected, we observed a broad landscape from competition to cooperation between both strains in their confined microenvironments depending on start frequency: from a nearly symmetric situation at R0 = 1, up to the domination of one subpopulation when R0 ≫ 1 (or R0 ≪ 1). Due to competition between the strains, their doubling times and final biomass ratios (R1) continuously deviate from the monoculture behavior. The correlation map of the two strains' doubling times reveals that the R0 is one of the critical parameters affecting the competitive interaction between isogenic bacterial strains. Thanks to this strategy, different species of bacteria can be monitored simultaneously in real-time. Further advantages include high statistical output, unaffected bacteria growth, and long-time measurements in a well-mixed environment. We expect that the millifluidic droplet-based reactor can be utilized for practical clinical applications, such as bacterial antibiotic resistance and enzyme reaction kinetics studies.

Microlayers, the thin layers of liquid forming at the underside of a steam bubble growing at a heated wall, have shown to contribute significantly to the bubble growth under certain wall boiling conditions.
The measurement of their shape and thickness remains an experimental and the simulation of their formation via CFD a computational challenge.
Thus, it is difficult to develop microlayer evaporation models covering a wide enough parameter space, which would allow their inclusion into advanced Euler-Euler wall boiling models.
In this work we present a feed-forward neural network (NN), which was trained by a small set of direct numerical simulation (DNS) data with the aim to predict microlayer profiles and volumes under different wall boiling conditions. Various configurations of such machine learning (ML) models were studied and introduced into the OpenFOAM open source CFD solver.
The training data consists of interface-tracking simulation results of the early bubble growth stages. Using the level-set and phase-change capabilities of PHASTA the transient evolution of evaporating microlayer profiles was computed for three different superheats for water at atmospheric pressure.
Data mining was then applied to pre-process and feed these results to a neural network in order for it to learn how to predict the microlayer volume depending on different wall superheats and bubble departure sizes.
The computed microlayer-to-bubble volume ratio allowed the trained NN model to be embedded into the RPI wall boiling model of OpenFOAM, which was extended in order to account for an additional microlayer evaporation term. Whilst the overall evaporation component remains unchanged in magnitude, the proposed model does distinguish between the evaporation contributions from the upper curved bubble surface and from the microlayer region.
The NN extended RPI wall boiling model is applied to two demonstration cases: the DEBORA wall boiling case [1], for which no microlayer contribution is expected, and the experimental case of Lee et al. [2] for water under atmospheric pressure, for which the microlayer evaporation is expected to be significant. The NN extended RPI wall boiling model is shown to predict reasonable contributions of the different evaporation mechanisms.
The application of ML techniques, where experimental and computational limits hinder sufficient data collection, seems a promising alternative to the conventional development of Euler-Euler models. In the future the NN model presented here can be fed with additional DNS data as well as experimental data for more refined results under various boiling conditions and for different working fluids. The particular implementation of the ML models in the RPI wall boiling model needs to be further researched and discussed with the broad scientific community.

[1] J. Garnier, E. Manon, G. Cubizolles, Local measurments on flow boiling of refrigerant r12 in a vertical tube, Multiphase Science and Technology 13 (2001) 1–111.
[2] T. Lee, G. Park, D. Lee, Local flow characteristics of subcooled flow boil-ing flow of water in a vertical concentric annulus, International Journal of Multiphase Flow 28 (2002) 1351–1368.

The dual nature of Janus particles confers fascinating properties such as a response to multiple stimuli. In this communication, we systematically study the sensitivity to a uniform external magnetic field of isolated Janus rod-shaped and spherical particles in water confined to two dimensions. The Janus asymmetry of the particles is given by magnetic [Co(0.28 nm)/Pd(0.90 nm)]8 multilayer films deposited onto monodisperse polystyrene (PS) nanorods and microspheres, respectively. It is shown that the particles dispersed in water respond to weak magnetic field applied in in-plane direction. Here we demonstrate that a precise control of the in-plane particle orientation can be obtained for magnetic field strengths higher than 0.1 mT for microspheres and 0.4 mT for nanorods.

On the nanoscale, iron oxides can be used for multiple applications ranging from medical treatment to biotechnology. We aimed to utilize the specific properties of these nanoparticles for new process concepts in flotation. Magnetic nanoparticles were synthesized by alkaline coprecipitation, leading to a primary particle size of 9 nm, and coated with oleate. The nanomaterial was characterized for its superparamagnetism and its colloidal stability at different ionic strengths, with and without an external magnetic field. The nanomaterial was used for model experiments on magnetic carrier flotation of microplastic particles, based on magnetically induced heteroagglomeration. We were able to demonstrate the magnetically induced aggregation of the nanoparticles which allows for new flotation strategies. Since the nanomaterial has zero remanent magnetization, the agglomeration is reversible which facilitates the process control. Magnetic carrier flotation based on iron oxide nanoparticles can pave the way to promising new recycling processes for microplastic wastes.

Schiff bases like the mixed N, O donor ligands of the salen (Bis(salicyliden)ethylendiamin) family are frequently chosen systems for complexation studies. Advantageous is their ability to stabilize a large number of metals including actinides, as well as their tuneable electronical and sterical properties.1–4 Pyrrol-based ligands are salen’s structural relatives, but only exhibit N-donor functionalities. This provides the possibility to investigate and compare the binding situation between early actinides and N atoms in different environments.
In this study a complex series from Th to Pu with the pyrrol-based ligands 1,2-ethylenediamine-N,N’-bis(1H-pyrrol-2-yl)methylene (pyrenH2) L¹ H₂ and 1,2-benzenediamine-N,N’-bis(1H-pyrrol-2-yl)methylene (pyrophenH2) L² H₂ was synthesized. Characterization in solution (NMR) and solid state (SC-XRD) in combination with quantum chemical calculations reveal the different binding situations to the different N donors at the electronic level, which leads to unique paramagnetic behavior in solution.

1 B. E. Klamm et al., Chem. Commun., 2018, 54, 8634–8636.
2 A. N. Dame et al., Eur. J. Inorg. Chem., 2015, 2015, 2996–3005.
3 B. E. Klamm et al., Inorg. Chem., 2018, 57, 15389–15398.
4 T. Radoske et al., Chem. – Eur. J., 2020, 26, 16853–16859.

Silicon carbide with optically and magnetically active point defects offers unique opportunities for quantum technology applications. Since interaction with these defects commonly happens through optical excitation and deexcitation, a complete understanding of their light-matter interaction in general and optical signatures in particular is crucial. Here, we employ quantum mechanical density functional theory calculations to investigate the photoluminescence line shapes of selected, experimentally observed color centers (including single vacan- cies, double vacancies, and vacancy-impurity pairs) in 4H-SiC. The analysis of zero-phonon lines as well as Huang-Rhys and Debye-Waller factors is accompanied by a detailed study of the underlying lattice vibrations. We show that the defect line shapes are governed by strong coupling to bulk phonons at lower energies and localized vibrational modes at higher energies. Generally, good agreement with the available experimental data is obtained, and thus we expect our theoretical work to be beneficial for the identification of defect signatures in the photoluminescence spectra and thereby advance the research in quantum photonics and quantum information processing.

The effect of deformation temperature and strain rate (collectively described by the Zener-Hollomon parameter Z) on the deformation mechanism and texture formation of the metastable β-titanium alloy Ti5321 across the β-transus temperature during hot-compression was investigated by electron backscatter diffraction. In the β-phase field, it is found that the deformation behavior and texture formation varies depending on Z. With decreasing Z dynamic recovery and dynamic recrystallization become more and more important. The activation energy for steady state deformation is 240 kJ/mol and 370 kJ/mol in the β- and (α + β)-phase field, respectively. The texture developed is a <100> <111> double-fiber with < 100 > dominating at all deformation conditions. The <111> fiber gets more prominent with increasing Z suggesting that it is mainly related to deformation. Flow softening behavior of Ti5321 is associated with dynamic globularization of the α-phase and promotion of β-grain formation by continuous dynamic recrystallization.

This presentation introduces the HELIPORT project, which aims at developing a platform which accommodates the complete life cycle of a scientific project and links all corresponding programs, systems and workflows to create a more FAIR and comprehensible project description. Heliport is linked with our local Handle-Server and generates uniform PIDs from and for various systems and services. With the integration of the Handle system Heliport can support digital twins.

Magnetization switching using in-plane charge current recently has been widely investigated in heavy metal/ferromagnet bilayers with the switching mechanism usually attributed to the action of the spin-orbit coupling. Here we study in-plane current induced magnetization switching in model epitaxial bilayers that consist of Au(001) and Fe(001) grown on MgO(001). We use the planar Hall effect combined with magnetooptical Kerr effect (MOKE) microscopy to investigate magnetic properties of the bilayers and current-induced switching. We show that a current density beyond 1.4×10^7 A/cm can be employed for reproducible electrical switching of the magnetization between multiple stable states that correspond to different arrangements of magnetic domains with magnetization direction along one of the in-plane easy magnetization axes of the Fe(001) film. Lower current densities result in stable intermediate transversal resistances which are interpreted based on MOKE-microscopy investigations as resulting from the current-induced magnetic domain structure that is formed in the area of the Hall cross. We find that the physical mechanism of the current-induced magnetization switching of the Au/Fe/MgO(001) system at room temperature can be fully explained by the Oersted field, which is generated by the charge current flowing mostly through the Au layer.

1 Introduction

The characterization of steel regarding its content of the short-lived 55Fe (T_1/2 = 2.756 years [1]) is considered important in processes of nuclear decommissioning. In steel, 55Fe is mainly produced in a neutron capture reaction on 54Fe. We present a pilot study using Accelerator Mass Spectrometry (AMS) at the DREAMS (DREsden AMS) facility showing that 55Fe determination in steel samples with a weight of some mg is possible without any radiochemical separation [2]. The minimalist requirements in sample preparation together with reduced measurement times allow for very short turnaround times and low costs.

2 Experimental Methods & Results

We used a few mg of fine to coarse grained steel chips from a nuclear reactor vessel without any chemical processing, which were directly pressed in the AMS sample holder. For validation the same material was chemically processed and prepared for liquid scintillation counting (LSC) and AMS, respectively. AMS uses negative ions of Fe created in a Cs sputter ion source. The use of negative ions is an advantage: There is no isobaric background from the stable 55Mn as this element does not form negative atomic ions. The counting of 55Fe events is performed relative to the measurement of ion currents of the stable isotopes 54Fe or 56Fe.
Three instances of quality control were carried out: (1) AMS measurements in three aliquots of the steel chips without further pretreatment, (2) an AMS-internal comparison of the steel chips and chemically treated AMS samples, and (3) a comparison of AMS data and LSC measurements. For these different comparisons results overlap within 3% to 20% on levels of 10² Bq/g Fe to 10⁴ Bq/g Fe. At those levels, the actual AMS measurement of a single sample can be carried out within a few minutes. In this pilot study, the sensitivity of the AMS determination reached 3 Bq/g Fe and was mainly limited by the short measurement time.

3 Outlook

Collaboration and further development of 55Fe and other radionuclide (e.g. 36Cl, 41Ca [4]) measurements within trans-national access are supported by the Horizon 2020 program RADIATE [3]. A dedicated AMS facility is planned at HZDR, for which allocation of beam times can be handled more flexibly than at the larger multi-user facility DREAMS, leading to further reduction of turnaround times. Additionally, an isobar suppression technique using the interaction of lasers with the ion beam is presently developed and may open options for AMS analysis of 59Ni, 93Zr and other isotopes also of interest for nuclear decommissioning.

References:

[1] Pommé, S., Stroh, H., Van Ammel, R.: The 55Fe half-life measured with a pressurised proportional counter. Appl Rad Isot (2019) 148:27-34.
[2] Merchel, S., Rugel, G., Lachner, J., Wallner, A., Walther, D., Ziegenrücker, R.: Evaluation of a sensitive, cheap, and fast detection method for 55Fe in steel. J Radioanal Nucl Chem (2021) submitted.
[3] https://www.ionbeamcenters.eu/radiate/radiate-transnational-access/
[4] Hampe, D. Gleisberg, B., Akhmadaliev, S., Rugel, G., Merchel, S.: Determination of 41Ca with LSC and AMS: method development, modifications and applications. J Radioanal Nucl Chem (2013) 296:617-624.

We report the emission of high-field terahertz pulses from a GaAs large-area photoconductive emitter pumped with a Ti:Sapphire amplifier laser system at 800 nm wavelength and 1 kHz repetition rate. The maximum estimated terahertz electric field at the focus is ≳ 230 kV/cm. We also demonstrate the capability of the terahertz field to cause a non-linear effect, which usually requires high-field terahertz pulses generated through optical rectification or an air plasma. A significant drop in the optical conductivity of optically pumped GaAs due to Γ-L inter-valley scattering of free electrons caused by the strong THz field is found.

A talk and demo session on various topics of advanced usage regarding the version control system Git.

This contribution provides an overview of a current research network funded by the German Federal Ministry of Education and Research (BMBF), entitled “Fundamental investigations of actinide immobilization by incorporation into solid phases relevant for final disposal” – AcE. The AcE project aims at understanding the incorporation and immobilization of actinides (An) in crystalline, repository-relevant solid phases, such as zirconia (ZrO2) and UO2, but also in zircon (ZrSiO4), pyrochlores (Ln2Zr2O7) and orthophosphates of the monazite type (LnPO4), which may find use as host matrices for the immobilization and safe disposal of high-level waste streams.
The main objectives of the AcE project are (i) the development of synthesis strategies for An(IV)-doped solid phases, (ii) understanding their associated structural and physical properties using combined modelling and experimental approaches and (iii) determining their performance after irradiation with particular regard to an assessment of their long-term stability, dissolution behavior, and suitability for An matrix incorporation.
Recent results obtained for ZrO2, the main corrosion product of the Zircaloy cladding material surrounding nuclear fuel rods, in terms or actinide immobilization and radiation tolerance, will also be discussed.
ZrO2 is monoclinic phase (P21/c) at ambient conditions, and transforms into tetragonal (P42/nmc) and cubic phases (Fm3 ̅m) at high temperatures of around 1200 °C and 2370 °C, respectively. However, particle size effects, the incorporation of foreign ions such as the actinides, as well as high radiation fields are known to also influence the stability fields of the polymorphs. A short overview of experimental studies conducted by the AcE partners, addressing both the ZrO2 bulk structure, irradiation-induced

The Bailadila Group of the Bastar Craton, India, is host to a 200-m-thick banded iron formation (BIF). We document the lithostratigraphic context for the BIF, informally referred to as the Bose iron formation, and provide radiometric constraints for its depositional age. Field evidence illustrates that the BIF was deposited on an inner-shelf succession with a quartz arenite that grades upward into the BIF through storm-dominated offshore shelf deposits. The quartz arenite to BIF transition records a relative sea level rise from transgressive to highstand systems tract when the BIFs were deposited in a starved outer continental shelf. U-Pb SHRIMP analyses of zircons from the basement of the Bailadila Group yielded mostly highly discordant U-Pb SHRIMP ages. However, the ages fall on well-defined discordia lines from which concordia intercept ages could be determined. These ages, in combination with the ages of a few zircons that are less than 6% discordant, indicate that the granitoid basement crystallized at 3500–3550 Ma. The maximum depositional age of the Bailadila Group is constrained from the weighted mean207 Pb/206 Pb SHRIMP age of 2725 5 57 Ma from detrital zircons from the basal arenites. A well-constrained weighted mean207 Pb/206 Pb SHRIMP age of 2733 5 53 Ma for zircons from a unit that unconformably overlies the Bailadila Group is within error of that age. Stratigraphic relationships suggest that the Bailadila succession is unconformably overlain by the ~2.5 Ga Kotri and Dongargarh Supergroups. The depositional age of the Bailadila Group is well constrained between ~2.7 and 2.5 Ga. In contrast to most other Archean Algoma-type iron formations of peninsular India, which are closely related to volcanic rocks in greenstone belts, the Bose iron formation is associated with siliciclastic shelf succession. It thus is considered a Superior-type iron formation that represents the oldest known one of its kind in India.

A concept for 3D-motion tracking of instrumented flow-following sensor particles, equipped with a gyroscope, accelerometer, magnetometer and pressure sensor, has been developed. Consisting of an error state Kalman filter (ESKF) the algorithm can track the attitude of the sensor particle in relation to a reference coordinate system. In this short paper we investigated if the estimated attitude returns to the reference trajectory after experiencing motion similar to a motion that is expected to be found in the multidisperse fluid flows of a biogas fermenter or a waste water treatment basin. Results show the feasibility of the proposed method. However, the strategy of the measurement update in the ESKF needs improvement.

The Davidschacht tailings storage facility (TSF), operated from 1944 to 1964, represents one of the largest tailings dams in the historic Freiberg mining district. It contains a volume of 760,000 m³ of sulfidic flotation tailings, residues of former base metal and silver ore beneficiation. The tailings material still contains elevated concentrations of valuable elements such as zinc (0.4 wt.% on average), lead (0.2 wt.%) and copper (0.05 wt.%) as well as indium (10 ppm). The material has thus become the focus of efforts to enable eventual re-mining and recovery of valuable metals. However, such efforts have to take into account a number of important interests of the public. The first of these is the fact that the unrehabilitated tailings pose a significant risk to the environment. Cd (44 ppm on average) and As (0.6 wt.%) concentrations are particularly high – and have a marked influence on the adjacent water bodies, such as the Freiberg Mulde river. Curbing this influence has been the subject of multiple remediation studies, but pressure to act has risen recently due to increasing regulatory demands on the quality of surface water (EU Water Framework Directive of 2000). This is, in principle, very much in favour of re-mining the tailings in an effort to remove also hazardous components. Counteracting this reclamation scenario is the fact that the TSF is part of the UNESCO World Heritage Site “Erzgebirge / Krusne Hory” that was awarded in 2019. Another restriction pertains to the highly protected status of individual species (esp. sand lizard) settling on the TSF surface. This constellation obviously provides ample space for discussion as to how to deal with the tailings material contained in the Davidschacht TSF in future. Different sustainable development goals (SDG) have to be weighed against each other in order to find a holistic and sustainable. Airlift reactor-based bioleaching has been considered as an opportunity to maximize the sustainability of re-mining activities on the Davidschacht TSF. This innovative approach – and its circumstantial limitations – are documented in this contribution.

Parkinson's disease (PD) is known to involve the peripheral nervous system (PNS) and the enteric nervous system (ENS). Functional changes in PNS and ENS appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients like constipation, that can precede the appearance of motor symptoms by years. Here we analyzed the effect of the pesticide rotenone, a mitochondrial Complex I inhibitor, on the function and neuronal composition of the ENS by measuring intestinal contractility in a tissue bath and by analyzing related protein expression. Our results show that rotenone changes the normal physiological response of the intestine to carbachol, dopamine and electric field stimulation (EFS). Changes in the reaction to EFS seem to be related to the reduction in the cholinergic input but also related to the noradrenergic input, as suggested by the non-adrenergic non-cholinergic (NANC) reaction to the EFS in rotenone-exposed mice. The magnitude and direction of these alterations varies between intestinal regions and exposure times and is associated with an early up-regulation of dopaminergic, cholinergic and adrenergic receptors and an irregular reduction in the amount of enteric neurons in rotenone-exposed mice. The early appearance of these alterations, that start occurring before the substantia nigra is affected in this mouse model, suggests that these alterations could be also observed in patients before the onset of motor symptoms and makes them ideal potential candidates to be used as radiological markers for the detection of Parkinson's disease in its early stages.

Upon strain, most materials shrink normal to the direction of applied strain. Similarly, if a material is compressed, it will expand in the direction orthogonal to the pressure. Few materials, those of negative Poisson ratio, show the opposite behavior. Here, we show an unprecedented feature, a material that expands normal to the direction of stress, regardless if it is strained or compressed. Such behavior, namely, half-auxeticity, is demonstrated for a borophene sheet stabilized by decorating Pd atoms. We explore Pd-decorated borophene, identify three stable phases of which one has this peculiar property of half auxeticity. After carefully analyzing stability and mechanical and electronic properties we explore the origin of this very uncommon behavior and identify it as a structural feature that may also be employed to design further 2D nanomaterials.

Chiral antiferromagnets are currently considered for a broad range of applications in spintronics, spin-orbitronics, and magnonics. In contrast to the established approach relying on materials screening, the anisotropic and chiral responses of low-dimensional antiferromagnets can be tailored relying on the geometrical curvature. Here, we consider an achiral, anisotropic antiferromagnetic spin chain and demonstrate that these systems possess geometry-driven effects stemming not only from the exchange interaction but also from the anisotropy. Peculiarly, the anisotropy-driven effects are complementary to the curvature effects stemming from the exchange interaction and rather strong as they are linear in curvature. These effects are responsible for the tilt of the equilibrium direction of vector order parameters and the appearance of the homogeneous Dzyaloshinskii–Moriya interaction. The latter is a source of the geometry-driven weak ferromagnetism emerging in curvilinear antiferromagnetic spin chains. Our findings provide a deeper fundamental insight into the physics of curvilinear antiferromagnets beyond the σ-model and offer an additional degree of freedom in the design of spintronic and magnonic devices.

The diffusion of indium atoms in silicon-dioxide films previously implanted with arsenic ions with different energies is studied in relation to the temperature of postimplantation annealing. It is established that the diffusion properties of indium depend on the presence of arsenic atoms in the film and their energy. An increase in the As content in the region of the average projective range of In+ ions prevents the diffusion of In towards the SiO2 film surface at high annealing temperatures and stimulates the diffusion of In deep into the film in the form of a monovalent interstitial site. The experimentally observed effects are interpreted on the assumption of the formation of In–As pairs in neighboring substitutional positions in the SiO2 matrix.

We investigate the evolution of spin polarization, spontaneous Hall angle (SHA), saturation magnetization and Curie temperature of B2-ordered Fe60Al40 thin films under varying antisite disorder, induced by Ne+-ion irradiation. The spin polarization increases monotonically as a function of ion fluence. A relatively high polarization of 46 % and the SHA of 3.1 % are achieved on 40 nm thick films irradiated with 2 ⋅ 1016 ions/cm2 at 30 keV. An interesting divergence in the trends of the magnetization and SHA is observed for low disorder concentrations. The high spin polarization and its broad tunability range make ion-irradiated Fe60Al40 a promising material for application in spin electronic devices.

Multilayer position-sensitive 10B-RPC thermal neutron detectors offer an attractive combination of
sub-millimeter spatial resolution and high (>50%) detection efficiency. Here we describe a new
position reconstruction method based on statistical approach. Using experimental data, we compare
performance of this method with that of the centroid reconstruction. Both methods results in a
similar image quality and spatial resolution. However, the statistical method allows to improve the
image quality at the detector periphery, offers more flexible (and more easily configurable) event
filtering and allows to develop automatic quality monitoring procedures for early detection of
situations when a change in the detector operation conditions starts to affect reconstruction quality.

This document presents the progress of the ExPaNDS (European Open Science Cloud Photon and Neutron Services) project after i ts first 18 months of activities, spanning from September 2019 to February 2021. It reproduces the explanation of the work carried out by the ExPaNDS partners as provided to the European Commission in the first periodic report of the project.

Tissue diseases and related disorders need to be first recognized using diagnostic methods and then later treated by therapeutic methods–a joint procedure called theranostics. One of the main challenges in the field of retinal therapies remains in the success of the treatment, typically improving the local metabolism, by sparing the surrounding tissue and with the immediate information of the laser effect. In our study, we present a concept for real-time controlled tissue theranostics on a proof-of-concept study capable of using a single tunable ps
laser source (in terms of irradiance, fluence, and repetition rate), done on ex-vivo human retinal pigment epithelium. We have found autofluorescence intensity and lifetime imaging diagnostics very promising for the recognition and quantification of laser effects ranging from selective non-destructive molecular tissue modification to complete tissue ablation. The main novelty of our work presents the developed algorithm for optimized theranostics based on the model function used to quantify laser-induced tissue changes through the diagnostics
descriptors, fluorescence lifetime and fluorescence intensity parameters. This approach, together with the operation of the single adaptable laser source, can serve as a new theranostics method in personalized medicine in the future not only limited to treat retinal diseases.

Tailings are the fine-grained residues of ore processing operations, typically stored in dedicated tailings storage facilities (TSFs). Despite being viewed as ‘waste’ materials, tailings can contain significant amounts of valuable metals which were not recovered by original processing techniques or were previously not of economic interest. Re-processing of tailings deposits for the recovery of remaining metals has the additional benefits of mitigation of environmental hazards posed by the TSFs, such as Acid Mine Drainage (AMD). The estimation of mineral resources requires the construction of accurate and reproducible geospatial models. However, the sedimentary-style deposition and subsequent weathering of tailings results in a complex internal structure which is challenging to model, with a laterally and vertically heterogeneous distribution of the minerals comprising the residues. The present study investigates a novel approach for the geospatial modelling of a TSF case study. The surface of the tailings deposit was densely sampled in order to assess the intrinsic horizontal variability. Drill core samples were taken from a depth of 1-3 m, on a 30 m grid and nested grids of 15 m and 7.5 m, with additional random and twin holes. The entire depth of the TSF was sampled in 2 m intervals with a total of 10 drill holes to assess vertical variability. All drill core samples were analysed with x-ray fluorescence spectrometry and inductively coupled plasma mass spectrometry. The compositional data was log-ratio-transformed and variography and subsequent ordinary kriging and co-kriging were performed on the surface samples. The variogram models obtained for the surface samples were then applied for kriging of the deeper layers. Historical photographs of the surface of the TSF were used to improve estimates with co-kriging for the corresponding layers. The entire data set will be used to determine the most efficient sampling approach for the resource estimation of TSFs.

Introduction
An upregulation of cannabinoid receptors type 2 (₂) has been reported in association with inflammation processes, traumatic brain injury, neurodegeneration and cancer.[1] The activation of ₂ leads to an anti-inflammatory action. Therefore, the non-invasive assessment of the ₂ availability with PET can support decisions for ₂-directed therapies. Recently, we have reported on the development of the PET radiotracer [¹⁸F]JHU94620. This radioligand suffers from low metabolic stability in vivo.[2] Here, we describe the deuterated analogue [¹⁸F]JHU94620-d₈ and its biological evaluation.
Methods
The precursor for radiofluorination was obtained by coupling 4,5-dimethylthiazol-ylidene-2,2,3,3-tetramethylcyclopropane-1-carboxamide with 1,4-butandiol-1,1,2,2,3,3,4,4-d₈ bis(4-methylbenzenesulfonate) and radiofluorinated in the presence of the Kryptand K2.2.2. and K2CO3. The fraction of radiometabolites after injection of 27 to 50 MBq i.v. (AM ≈ 150 GBq/µmol) was quantified in mice plasma and brain 30 min p.i. The ₂ binding affinity (KD) and specificity (Ki) of [¹⁸F]JHU94620-d₈ was determined in vitro. Additionally, PET studies (injection of 23 ± 5 MBq i.v.) were performed to evaluate the [¹⁸F]JHU94620-d₈ uptake into the spleen of adult healthy Wistar rats and in rats overexpressing the functional inactive h₂(D𔕐N) in the right striatum[3] (h₂-rs).
Results/Discussion
[¹⁸F]JHU94620-d₈ was obtained in 10% radiochemical yield and >99% radiochemical purity, showing an improved metabolic stability of the deuterated analogue (80% vs. 36% for [¹⁸F]JHU94620, determined in the brain 30 min p.i.). It revealed a KD on rat ₂ of 0.36 nM and on human ₂ of 2.72 nM, as well as a Ki(hCB1) > 1 µM and Ki(h₂) of 0.9 nM. PET studies revealed a ₂-specific uptake of [¹⁸F]JHU94620-d₈ into the rat spleen (AUC0-30min = 33 vs. 17 SUV × min after blocking with GW405833). In the h₂-rs rats we could show a reversible and target-specific uptake of [¹⁸F]JHU94620-d₈ with an SUVmean of 6.7 ± 0.3 from 6 to 60 min p.i. and an SUVr (right striatum-to-cerebellum) of 43 ± 7 at 60 min p.i.
Conclusions
[¹⁸F]JHU94620-d₈ is a new PET tracer with improved metabolic stability as compared with the non-deuterated version, thus indicating an excellent ability to image the ₂ receptors in vivo.
Acknowledgement
This research was funded by Deutsche Forschungsgemeinschaft (DFG), grant number MO2677/4-1
Disclosure
A German patent application was filed Nr. 10 2020118 255.4
References
[1] Stasiulewicz, A., Znajdek, K., et al. 2020, ‘A Guide to Targeting the Endocannabinoid System in Drug Design’, IJMS, 2020, 21, 2778; doi:10.3390/ijms21082778
[2] Moldovan, R.-P., Deuther-Conrad, W., et al., 2015, ‘¹⁸F-JHU94620, a high affinity PET radioligand for imaging of cannabinoid subtype 2 receptors (₂R)’, J. Nucl. Med., 56, 1048
[3] Attili, B., Celen, S., et al., 2019, ‘Preclinical evaluation of [¹⁸F]MA3: a ₂ receptor agonist radiotracer for PET’, Br. J. Pharmacol., 176, 1481-1491

One of the most important activities after the decommissioning process of the nuclear power plant NPP is the determination of the neutron activated radionuclides RNs in the construction material of the reactor. Our work is mainly focused on the dismantled units of reactor pressure vessel RPV of Greifswald NPP. For this aim, both nondestructive and destructive methods were employed. Firstly, surface analysis methods based on scanning electron microscopy / energy dispersive X-ray spectroscopy SEM / EDX were performed, in order to understand the impact of the neutron fluencies on the RPV steel shielding material during the long-term operation. Furthermore, gamma spectrometry measurements were done for the analysis of the activity of the gamma emitting RN of Co-60 in the decommissioned RPV units. On the other hand, the determination of the long lived beta emitting RNs such as C-14 was determined by employing a commercial sample oxidizer, followed by liquid scintillation counting LSC measurements. Radiochemical procedure including precipitation, anion exchange chromatography and extraction steps was developed for the separation and purification of Ni-63 and Fe-55 prior to their activity determination.

Kurzfassung

In einer Vielzahl industrieller Prozesse spielen Strömungen mit verschiedenen gasförmigen und flüssigen Phasen eine wichtige Rolle. Die Phasengrenzflächen bilden sehr große Strukturen aus, wie z. B. eine freie Wasseroberfläche. Gleichzeitig können kleine, s. g. disperse Strukturen wie Gasbläschen auftreten. Um auch komplexe Prozesse zu simulieren ohne die Art der Strömung im Vorhinein zu kennen, werden unterschiedliche Methoden zur numerischen Beschreibung der verschiedenen Strömungstypen miteinander kombiniert. In der vorliegenden Arbeit wird die Euler-Euler-Methode für disperse Strukturen mit der algebraischen Volume-Of-Fluid-Methode für großskalige Phasengrenzflächen kombiniert. Das auf diese Weise formulierte hybride Mehrphasenmodell wird im Mehr-Fluid-Modell für eine beliebige Anzahl von Phasen formuliert, d. h. für jede vorhandene Phase gelten individuelle Erhaltungsgleichungen für Masse und Impuls. Für disperse Strömungen werden Formulierungen aus der Literatur für den Strömungswiderstand und die virtuelle Masse von Gasblasen genutzt, um den Impulsaustausch zwischen den verschiedenen Phasen zu beschreiben. Für großskalige Phasengrenzflächen wird das Widerstandsmodell von Štrubelj und Tiselj (2011) verwendet, mit dessen Hilfe die Impulserhaltungsgleichungen der individuellen Phasen stark aneinander gekoppelt werden. Zur Beschreibung des Platzens von Gasbläschen an einer freien Oberfläche wird eine neue Formulierung des Phasentransfers eingeführt, womit disperses in kontinuierliches Gas überführt wird.
Für die numerische Lösung des resultierenden Gleichungssystems wird die kompakte Impulsinterpolation von Cubero et al. (2014) genutzt. Die starke Kopplung der phasen-spezifischen Gleichungen für den Impulserhalt erfordert besondere numerische Maßnahmen, um das gesamte Gleichungssystem effizient zu lösen. Dazu wird die Methode der partiellen Eliminierung von Spalding (1981) durch eine Summenformulierung zur näherungsweise Auflösung dieser Kopplung auf das Mehr-Fluid-Modell erweitert. Anhand von zwei- und dreidimensionalen Fällen von aufsteigenden einzelnen Gasblasen wird nachgewiesen, dass das hybride Modell das Verhalten des Ein-Fluid-Modells zur Beschreibung großskaliger Phasengrenzflächen beschreiben kann. Darüber hinaus wird die Funktionsweise der Methode demonstriert, die Interaktion zwischen kleinen Gasbläschen und großskaliger Phasengrenzflächen zu beschreiben. Dies schließt den Phasentransfer von dispersem zu kontinuierlichem Gas ein.
In der Realität sind viele Strömungen turbulent und analog zu den Phasengrenzflächen sind die turbulenten Wirbel typischerweise von sehr verschiedenen Längenskalen. Ein möglicher Weg, solche Probleme numerisch zu beschreiben, ist die Grobstruktursimulation (engl. large-eddy simulation). Dazu werden die Erhaltungsgleichungen räumlich tiefpass-gefiltert. Dadurch entstehen im hiesigen Mehr-Fluid-Modell fünf ungeschlossene Feinstrukturterme, zu denen die Terme der konvektiven Feinstrukturspannungen und der Feinstruktur-Oberflächenspannung gehören. Für die Abschätzung dieser beiden Terme werden unterschiedliche Modelle genutzt. Bei manchen dieser Modelle wird die Struktur der Phasengrenzfläche direkt berücksichtigt. Der Einfluss dieser Modelle auf die Interaktion zwischen der Turbulenz und der Phasengrenzfläche wird anhand von Testfällen einzelner aufsteigender Gasblasen a posteriori untersucht.

Abstract

Flows of gaseous and liquid phases play an important role in numerous industrial processes. The interface, which is the contact surface between different immiscible phases, may form large structures, e.g., a free water surface. At the same time small, so-called disperse structures such as micro gas bubbles may appear.In order to numerically describe such complex processes without knowing the type of flow in advance, different methods for the numerical description of different kinds of flows are combined with each other. In the present work the Euler-Euler method is applied for disperse structures and the algebraic volume-of-fluid method is used to describe large scale interfaces. The resulting hybrid multiphase model is formulated in the context of the multi-fluid model for an arbitrary number of phases, i.e., for each phase present individual conservation equations are considered for mass and momentum. This requires the definition of model forces to express the momentum transfer between different phases. For disperse flows appropriate formulations for drag and virtual mass of gas bubbles from the literature are employed. For large scale interfaces the drag model of Štrubelj and Tiselj (2011) is used, which strongly couples the momentum equations of the individual phases together. In order to describe the process of gas bubbles bursting at a free surface a new phase transfer formulation is introduced, such that disperse gas can be turned into continuous one.
The compact momentum interpolation according to Cubero et al. (2014) is utilized for the numerical solution of the resulting system of equations. The strong coupling of phase specific momentum conservation equations requires special treatment to allow the system of equations to be numerically solved in an efficient way. Therefore, the partial elimination algorithm of Spalding (1981) is expanded to the multi-field model via a sum formulation with the goal of an approximate resolution of phase coupling. The functionality of the hybrid method to reproduce the behaviour of the one-fluid model for the description of large scale interfaces is proven with several two- and three-dimensional test cases considering individual rising gas bubbles. Furthermore, the method's ability to predict interactions of small gas bubbles and large scale interfaces is demonstrated, which includes the phase transfer from disperse to continuous gas.
In reality many flows are turbulent and the according eddies are typically of widely varying length scales, just as it is the case for interfacial structures. Large-eddy simulation is a common approach to describe such problems numerically. Therefore, the conservation equations are spatially low-pass filtered, which leads to five unclosed sub-grid scale terms in the case of the presented multi-fluid model. Two of them are the convective sub-grid stress and the sub-grid surface tension term, which are modelled via several individual formulations taking the interface into account. The model influence on the interaction between turbulence and interface is assessed a posteriori considering single rising gas bubbles.

Reliable techniques for the numerical simulation of gas-liquid flows at industrial scales are of great interest for safety analysis and efficiency optimisation, e.g. in nuclear power or metal processing industries. This type of simulation is hard to carry out due to the immense range of scales, which is spanned by interfacial and turbulent structures. For this purpose, hybrid morphology-adaptive numerical frameworks are being developed in the recent years, combining different well established numerical methods for individual flow regimes. The present work follows the approach of Meller et al. (Int J Numer Meth Fluids. 2021; 93: 748-773), who utilise the Euler-Euler approach to statistically describe multiphase structures in dispersed flow regimes, such as bubbly flows, as a basis. At the same time, regimes with resolved gas-liquid interfaces, such as large rising gas bubbles or horizontal interfaces in stratified flows, are captured by means of a Volume-of-Fluid-like method (Tekavčič et al., Nucl Eng Des. 2021; 379: 111223). A fully morphology-adaptive numerical framework needs to comprise transitions between the aforementioned regimes. Hence, the limits of both underlying basic numerical approaches need to be pushed towards and beyond an overlapping region of grid resolution with adequate predictive power, such that the whole spectrum of length scales is covered, forming the basis of morphology transitions.
For this purpose, the present work focuses on the extension of the Volume-of-Fluid methodology towards reliable resolved simulations of gas-liquid interfaces with very coarse grid resolutions. By means of the underlying two-fluid model, an interfacial slip velocity in the interface region becomes generally possible and can be chosen physically motivated. The flow in the vicinity of the interface needs to be classified. For this purpose, the latter is categorised to be of shear type, stagnant type or in between the two. Furthermore, a dimensionless grid spacing is evaluated based on the shear stress across the interface, similarly to the y+ value for the cell thickness of wall-bounded flows. Besides that, interface curvature is considered in relation to grid spacing. From these information, a degree of under-resolution of the interface is determined, which subsequently serves as a criterion for the drag modelling framework. On this basis, interfacial drag coupling is manipulated, such that interfacial slip can take place in the direction tangential to the interface, whenever required. While the interfacial drag formulation of Štrubelj and Tiselj (Int J Numer Methods Engng. 2011; 85: 575-590) is used in case of proper resolution, the closure formulations of Porombka and Höhne (Chem Eng Sci. 2015; 134: 348-459) or Marschall (Technical University of Munich, PhD Thesis, 2011) are considered for portions of the computational domain, where interfaces are classified to be under-resolved. The functionality of the described procedure is validated in cases of 2D and 3D rising gas bubbles, considering their shape and rising velocity. Moreover, gas and liquid velocity profiles of a stratified flow serve as a validation in an additional flow regime.
In this way, the numerical prediction of the gas-liquid interface is improved, pushing the limit of spatial resolutions with adequately reliable predictions towards extremely coarse computational grids, which is the prerequisite for efficient numerical simulations in large-scale applications.

The metallic-associated adverse local tissue reactions (ALTR) and events accompanying worn-broken implant materials are still poorly understood on the subcellular and molecular lev-el. Current immunohistochemical techniques lack spatial resolution and chemical sensitivity to investigate causal relations between material and biological response on submicron or even na-noscale. In our study, new insights of titanium alloy debris-tissue interaction were revealed by the implementation of label-free high-resolution correlative microscopy approaches. Wear debris chemical and biological impact on the surrounding periprosthetic tissue obtained at revision surgery of a fractured titanium-alloy modular neck of a patient with hip osteoarthritis was suc-cessfully characterized by applying a combination of photon, electron and ion beam mi-cro-spectroscopy techniques, that includes hybrid optical fluorescence and reflectance mi-cro-spectroscopy, scanning electron microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), helium ion microscopy (HIM) and micro-particle-induced X-ray emission (micro-PIXE). Micron-sized wear debris was found as the main cause of the tissue oxidative stress exhibited through lipopigments accumulation in the nearby lysosomes. Furthermore, insights on extensive fretting and corrosion of the debris on nm scale and a quantitative measure of significant Al and V release into the tissue together with hydroxyapatite-like layer formation particularly bound to the regions with the highest Al content were revealed. The functional and structural information obtained at the molecular and subcellular level contributes to a better understanding of the mac-roscopic inflammatory processes observed on the tissue level. The established label-free correla-tive microscopy approach can efficiently be adopted to study any other clinical cases related to ALTR.

Introduction:

The use of radiolabelled amino acids (AAs) can provide high contrast SPECT/PET imaging of solid tumours. Among them, radiohalogenated tyrosine analogues ([123I]IMT, [18F]FDOPA, [123I]8-iodo-L-TIC(OH), etc) were developed mainly for imaging of neuroendocrine, prostatic and brain tumours. While radioiodinated derivatives are easily available via electrophilic aromatic substitutions with radioactive I+, radiofluorinated tyrosine analogues are difficult to obtain. Indeed, direct radiofluorination of electron-rich aromatic structures from [18F]F- remains a challenge as evidenced by the number of emerging methods recently published. The progresses reported for the radiosynthesis of the [18F]FDOPA illustrate the new opportunities to produce radiofluorinated arenes that could not be routinely accessed even a few years ago. Surprisingly, the [123I]8-iodo-L-TIC(OH), a promising radiotracer for SPECT imaging of prostatic tumours, did not benefit from these methodological advances and no corresponding radiofluorinated derivatives, which could allow the use of the TIC(OH) scaffold to PET imaging, were reported so far.

Materials and Methods:

A convergent synthetic route was developed to produce radioiodinated [125I]iodo-L-TIC(OH), and radiofluorinated [18F]fluoro-L-TIC(OH) tracers from common organotin intermediates, synthesized from iodinated analogues via palladium catalyzed I/SnMe3 exchange. The [125I]iodo-L-TIC(OH) radiotracers were obtained by electrophilic radioiododestannylation with [125I]I+, while the radiofluorinated analogues [18F]fluoro-L-TIC(OH) were produced from the organotin precursors by a copper-mediated aromatic radiofluorination using nucleophilic [18F]F-. For control of the purity, molar activity and enantiomeric excess, corresponding non-radiolabelled iodinated and fluorinated derivatives from the L and D series were synthesized.

Results:

Organotin compounds were radiolabelled using no-carrier-added [125I]NaI in the presence of Chloramine-T as mild oxidative agent at room temperature for 5 minutes with excellent labelling efficiencies (> 95%). After a two-step deprotection sequence and semipreparative RP-HPLC purification, [125I]iodo-L-TIC(OH) compounds were isolated with good radiochemical yields (RCY, 51-78%), high radiochemical purities (RCP, > 98%), molar activities (> 1.5-2.9 GBq/µmol) and enantiomeric excess (e.e., > 99%). [18F]fluoro-L-TIC(OH) derivatives were obtained by radiofluorination of organotin compounds in presence of tetrakis(pyridine)copper(II) triflate catalyst and nucleophilic [18F]F- at 110 °C for 10 minutes with high labelling efficiencies (54-92%). After purification by C18 solid phase extraction, deprotection under acidic conditions and semipreparative RP-HPLC purification, [18F]fluoro-L-TIC(OH) radiotracers were produced with good RCY (23-37% d.c.), high RCP (> 99%), molar activities (20-107 GBq/µmol) and e.e. (> 99%).

Conclusion:

A short and efficient synthetic pathway was developed to easily produce [125I]iodo-L-TIC(OH) and [18F]fluoro-L-TIC(OH) compounds from common organotin intermediates. In vitro studies on human cancer cell lines are ongoing to evaluate the potential of these radioligands to target AAs transporters.

The dynamics of single hydrogen bubbles electrogenerated in acidic electrolytes at a Pt microelectrode under potentiostatic conditions is investigated in microgravity during parabolic flights. Three bubble evolution scenarios have been identified depending on the electric potential applied and the acid concentration. The dominant scenario, characterized by lateral detachment of the grown bubble, is studied in detail. For that purpose, the evolution of the bubble radius, electric current and bubble trajectories, as well as the bubble lifetime are comprehensively addressed for different potentials and electrolyte concentrations. We focus particularly on analyzing bubble-bubble coalescence events which are responsible for reversals of the direction of bubble motion. Finally, as parabolic flights also permit hypergravity conditions, a detailed comparison of the characteristic bubble phenomena at various levels of gravity is drawn.

As part of the International Virtual Covid Challenge this talk gives an introduction on sustainable software development. Basing on the HIFIS course "Let's Make Your Script Ready for Publication" it details the steps necessary to build a sustainable software application that can easily be cited in a scientific publication.

Presentation at "Mu2e-II Snowmass22 Workshop", 28.04.2021

Plasma wakefield accelerators are capable of sustaining gigavolt-per-centimeter accelerating
fields, surpassing the electric breakdown threshold in state-of-the-art accelerator modules by
3-4 orders of magnitude. Beam-driven wakefields offer particularly attractive conditions for
the generation and acceleration of high-quality beams. However, this scheme relies on
kilometer-scale accelerators. Here, we report on the demonstration of a millimeter-scale
plasma accelerator powered by laser-accelerated electron beams. We showcase the acceleration
of electron beams to 128 MeV, consistent with simulations exhibiting accelerating
gradients exceeding 100 GVm⁻¹. This miniaturized accelerator is further explored by
employing a controlled pair of drive and witness electron bunches, where a fraction of the
driver energy is transferred to the accelerated witness through the plasma. Such a hybrid
approach allows fundamental studies of beam-driven plasma accelerator concepts at widely
accessible high-power laser facilities. It is anticipated to provide compact sources of energetic
high-brightness electron beams for quality-demanding applications such as free-electron
lasers.

Six indole-based derivatives with a methoxy group at the indole ring were synthesized and evaluated as σ2 receptor ligands with nanomolar affinity (Ki (σ2) = 4.40-9.46 nM) and moderate subtype selectivity (Ki(σ2)/Ki(σ1) = 7-102). Radioligands 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-4-(2-[18F]fluoroethoxy)-1H-indole ([18F]3) and 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-5-(2-[18F]fluoroethoxy)-1H-indole ([18F]4) with high σ2 receptor affinity and subtype selectivity were synthesized through a direct SN2 displacement reaction, with radiochemical yields of 36-50% and 20-29%, radiochemical purity of >99%, and molar activities of 29-151 GBq/μmol and 55-72 GBq/μmol, respectively. Radioligand [18F]3 displayed high brain uptake, high brain-to-blood ratio and slow washout from the brain in male ICR mice. Administration of compound CM398 5 min prior to the radiotracer injection led to a significantly dose-dependent reduction of the brain accumulation (29-54%) and the brain-to-blood ratio (60-88%) at 30 min, indicating high specific binding of [18F]3 to the σ2 receptors in the brain. Ex vivo autoradiography in male ICR mice showed widely and heterogeneous distribution of [18F]3 in the brain. Small animal positron emission tomography imaging in rats confirmed different distribution and high specific binding of [18F]3 to σ2 receptors in rat brain. These findings warrant [18F]3 as a potential probe used for neuroimaging of the σ2 receptors in the brain.

The paper addresses the fluid–structure interaction of submerged aquatic canopies, with particular focus on the complex interplay between coherent flow structures and the motion of vegetation elements. New insights into the underlying mechanisms are gained from a large eddy simulation of a submerged model canopy flow. The model canopy is made up of 800 highly flexible blades, each individually resolved by an immersed boundary method. The obtained high-resolution flow data reveal well-known coherent turbulent structures, including velocity streaks, Kelvin–Helmholtz (KH) vortices in the mixing layer as well as hairpin (HP) vortices in the outer flow region. The present results show that the interaction of these prototypical structures plays a key role creating unique turbulent features such as composite KH/HP vortices located between a high-speed and low-speed streak. Under the influence of these pronounced eddies, groups of blades respond by a strong local reconfiguration. Due to the convection of the coherent structures by the mean flow this causes an apparent wave-like motion of the canopy in streamwise direction, known as monami. A frequency analysis of this phenomenon shows that the vegetation responds almost passively, merely reflecting local flow conditions.

The excess energy emitted during the positronium (Ps) formation in condensed matter may be released as light. Spectroscopic analysis of this light can be a new method of studying the electronic properties of materials. We report the first experimental attempt, according to our knowledge, to verify the existence of this emission process. As a result, the possibility of the emission of photons during Ps formation is within the experimental uncertainty in two different solids: an n-alkane and porous silica. However, it seems that the Ps formation on the alkane surface is not accompanied by the emission of photons with energy in the detection range of 1.6 – 3.8 eV. Various processes that can influence the energy of the photon emitted during the Ps formation are discussed to elucidate this issue. To aid future experiments, equations were developed to estimate the expected ratio of light emission events to annihilation events with the presence or absence of a photon during the Ps formation.

The diverse physical and chemical properties of aerosols can cause a diverse impact on air quality, cloud nucleation, planetary radiation balance, public health, etc. Besides carbon particles from incomplete combustion, mineral particles from Saharan dust also present a significant contribution to the changes. It is estimated that 400 to 700 million tons of dust is transported from Sahara every year and with the particular wind directions it is carried to the Mediterranean or even to the north of Europe (Prospero, 1996). It has recently been shown that these particles induce serious problems for asthmatics (Gutierrez et al., 2020).
To understand the origin of pollution, necessary input information presents knowing the source apportionment of aerosols. Techniques such as non-destructive particle induced X-ray emission (PIXE) (Lucarelli et al., 2018) and energy dispersive x-ray spectroscopy (SEM-EDS) (Longoria-Rodríguez et al., 2021) have been successfully applied for chemical microanalysis of individual particles. However, knowing both the physical and chemical properties of particles towards nm scales, which would cover all aerosol sizes, is still a challenging task.
In our study, we have thus implemented the correlative approach using advanced ion beam techniques to study both physical and chemical properties of mineral particles from Saharan dust collected on quartz fiber filters on Cyprus Atmospheric Observatory (35.04oN,33.06 Eo; 535 m a.s.l.) using a combination of the virtual impactor and Aethalometer AE33 (Aerosol d.o.o.). We have implemented Helium Ion Microscopy (HIM), capable of sub-nm resolution imaging with high depth-of-field contrast, followed by micro-PIXE elemental analysis done on the same filter region. Information from backscattered high-energy ions was found particularly suitable for the registration and overlap of complementary images (Figure 1).
The study has revealed the size, shape, architecture, and surface topography of individual mineral particles on nm scale, while micro-PIXE their chemical composition. Additionally, HIM resolution and surface sensitivity enabled the detection and identification of individual black carbon (BC) soot attached to the surface of mineral particles. This information can have a significant impact on our understanding of the optical properties of mineral dust and its relevance to climate changes and health effects. This finding urges for further investigations where additional focused ion beam techniques and instrumentation have been implemented and will be discussed.

1 Introduction

Concrete consists primarily of the mineral quartz as coarse and fine aggregates to a weight of 50-60 %. After quartz, feldspar is generally contained in a weight quantity of 15-20 %. Quartz in its pristine state is the least soluble of the silicates, thereby providing concrete the highest possible chemical durability. Biological shielding concrete that surrounds nuclear reactor pressure vessels are exposed to neutron radiation over decades during the course of nuclear power plant (NPP) operation. Minerals that are subjected to radiation, whether it be neutrons, electrons, or ions, of sufficient fluence and energy, accumulate defects in their crystal lattices. Once the threshold concentration of defects has been reached, structural relaxation occurs, which is a volume expansive amorphization process. Of all the minerals examined for neutron radiation-induced volume expansion, quartz exhibits the highest, followed by feldspar with volume expansion maxima respectively being 17.8 and 7.7 % [1]. Irradiated quartz accumulates E’-center defects [2], which are essentially unpaired sp³ dangling bonds and chemically reactive in aqueous solution, particularly at the higher pH values typically prevailing in pore water in concrete. It is the objective of this research to investigate the increased dissolution rates of irradiated silicate minerals, particularly in the context of the alkali-silica reaction (ASR), which is the most significant degradation reaction known to occur in concrete.

2 Experimental

Polished sections of concrete partially masked with aluminium foil were subjected to Si-ion irradiation with a fluence of 5·1014 ions/cm2 at 300 keV under vacuum without cooling. Changes in the vertical profiles of the irradiated samples were examined by Vertical Scanning Interferometry (VSI) and Confocal Microscopy.

3 Results

The minerals making up the aggregate were identified by µ Raman spectroscopy to be α-quartz and potassium feldspar (microcline: KAlSi₃O₈), the latter always intergrown with quartz. Quartz (grain A) exhibited an out-of-plane expansion of ~ 80 nm. No observable difference in average height between radiated and non-radiated areas on the aggregate containing feldspar (grain B) could be ascertained. This is mainly attributable to the surface roughness of feldspar (> 1 µm), which is essentially out of range for interferometric techniques. Furthermore, the penetration depths estimated in the Kinchin-Pease calculation by SRIM [3] for Si-ion irradiation at 300 keV are 429 and 604 nm, respectively for α-quartz and microcline. As the damage to the structure occurs initially at the point where the ion stops, structural relaxation in the feldspar begins much further away from the surface than it does for quartz. In our case, it is likely that the expansion in the feldspar has not detectably reached the surface.

Literature:

[1] Le Pape, Y., Alsaid, F., Alain, B. and Giorla, B.: J. Adv. Conc. Technol. (2018) 16, 191-209.
[2] Douillard, L. and Duraud, J. P.: Nucl. Instrum. Methods Phys. Res. (1996) B16, 191-209.
[3] Ziegler, J. F., Ziegler, M. D. and Biersack, J. P.: Nucl. Instrum. Methods Phys. Res. (2010) B268, 1818-1823. (http://www.SRIM.org)

Actinide metal-organic frameworks (An-MOFs) consisting of actinide nodes and organic linkers represent an underexplored category of coordination polymers due to challenges in their synthetic and characterization. The unparalleled coordination chemistry of actinide elements confers a huge opportunity to explore the rational design, chemical reactivity, and versatile properties of An-MOFs as one of the most intriguing class of metal-organic frameworks (MOFs). Significant advances in this “juvenile” MOF research field have been witnessed in recent years and progress in the An-MOFs area since 2003 has been reviewed from the aspects of the synthesis, structure, and applications. The preparative handling and synthetic strategies implemented in constructing An-MOFs are illustrated. Their structure motifs are then classified and expounded by actinide building blocks and organic linkers. The modularity, topology, and porosity of An-MOFs are specified to highlight a great potential to tune their electronic structures and ensuing properties. Ultimately, applications of An-MOFs as
selective adsorbents, heterogenous catalysts, luminescent sensors, conducting, and semiconducting materials, and nuclear targets are underlined. This updated review is envisaged to guide in-depth investigation of largely elusive transuranium MOFs and the development of thorium or uranium-based MOFs towards practical applications.

All over the world, societies are facing rapidly aging populations combined with a growing num-ber of patients suffering from Alzheimer’s disease (AD). One focus in pharmaceutical research to address this issue is on the reduction of the longer amyloid-β (Aβ) fragments in brain by modula-tion of γ-secretase, a membrane-bound protease. R-Flurbiprofen (tarenflurbil) was studied in this regard, but failed to show significant improvement in AD patients in a phase 3 clinical trial. This was mainly attributed to its low ability to cross the blood-brain barrier (BBB). We here present the synthesis and in vitro evaluation of a racemic meta-carborane analogue of flurbiprofen. By intro-ducing the carborane moiety, the hydrophobicity could be shifted into a more favourable range for the penetration of the blood-brain barrier, evident by a logD7.4 value of 2.0. Furthermore, our analogue retained γ-secretase modulator activity in comparison to racemic flurbiprofen in a cell-based assay. These findings demonstrate the potential of carboranes as phenyl mimetics also in AD research.

The recovery of rare earth elements through recycling of end-of-life electronics has become a goal of increasing importance as this helps create a more sustainable economy. Nevertheless, the recycling rates are still low. Rare earth elements could potentially be recovered from phosphors in end-of-life compact fluorescent lamps. In this thesis, LAP-specific peptides were immobilized on composite magnetic beads and these were brought in contact with LAP to see how much LAP interacts with the magnetic beads. LAP is an inorganic phosphor particle that emits green light when exposed to ultraviolet radiation. To be able to interpret the binding experiments, the fluorescent spectra of five different phosphors were measured and a simple quantification method was developed. In addition to this, the ratio of elements present in five different phosphors was investigated. This thesis has provided several insights into the fluorometric properties of suspended phosphors, single or in mixture, and into the effect of media on binding experiments. These insights can help in future work e.g. to be able to adapt the binding experiments for a mixture of phosphors. Furthermore, the proof-of-concept for binding experiments developed in this thesis could easily be applied for the investigation of other peptides phosphors as well.

We experimentally demonstrate the generation of spin-wave frequency combs based on the non-
linear interaction of propagating spin waves in a microstructured waveguide. By means of time- and space-resolved Brillouin light scattering spectroscopy, we show that the simultaneous excita- tion of spin waves with different frequencies leads to a cascade of four-magnon scattering events which ultimately results in well-defined frequency combs. Their spectral weight can be tuned by the choice of amplitude and frequency of the input signals. Furthermore, we introduce a model for stimulated four-magnon scattering which describes the formation of spin-wave frequency combs in the frequency and time domain.
Frequency

The widespread application of drones and associated miniaturization of imaging sensors has led to an explosion of remote sensing applications with very high spatial and spectral resolutions. Three dimensional (3-D) ultra-high resolution digital outcrop models created using drones and oblique imagery from ground-based sensors are now commonly used in the academic and industrial sectors. While the generation of spatially accurate models has been greatly facilitated by the development of com- puter vision tools such as Structure from Motion, correction of spectral attributes to achieve material reflectance measurements remains challenging. Following the development of a topograph- ical correction toolbox (mephysto), we now propose a series of new tools that can leverage the detailed geometry captured by digital outcrop models to correct for illumination effects caused by oblique viewing angles and the interaction of light with complex 3-D surfaces. This open source code is integrated into hylite, a python toolbox for the full 3-D processing and fusion of digital outcrop models with hyperspectral imaging data. We validate the performance of our novel method using a case study at an open pit mine in Tharsis, Spain, and demonstrate the importance of accurate illumination corrections for quantitative spectral analyses. Significantly, we show that commonly applied spectral analysis techniques can yield erroneous results for data corrected using current state of the art approaches. Our proposed method ameliorates many of the issues with these established approaches.

Field observations and unmanned aerial vehicle surveys from Caldera Taburiente (La Palma, Canary Islands, Spain) show that pre-existing dykes can capture and re-direct younger ones to form multiple dyke composites. Chill margins suggest that the older dykes were solidified and cooled when this occurred. In one multiple dyke example, an 40Ar/39Ar age difference of 200 kyr was determined between co-located dykes. Petrography and geomechanical measurements (ultrasonic pulse and Brazilian disc tests) show that a microscopic preferred alignment of plagioclase laths and sheet-like structures formed by non-randomly distributed vesicles give the solidified dykes anisotropic elastic moduli and fracture toughness. We hypothesise that this anisotropy led to the development of margin-parallel joints within the dykes, during subsequent volcanic loading. Finite element models also suggest that the elastic contrast between solidified dykes and their host rock elevated and re-oriented the stresses that governed subsequent dyke propagation. Thus, the margin-parallel joints, combined with local concentration and rotation of stresses, favoured the deflection of subsequent magma-filled fractures by up to 60° to form the multiple dykes. At the edifice scale, the capture and deflection of active intrusions by older ones could change the organisation of volcanic magma plumbing systems and cause unexpected propagation paths relative to the regional stress. We suggest that reactivation of older dykes by this mechanism gives the volcanic edifice a structural memory of past stress states, potentially encouraging the re-use of older vents and deflecting intrusions along volcanic rift zones or towards shallow magma reservoirs.

We present a numerical approach to efficiently calculate spin-wave dispersions and spatial mode profiles in magnetic waveguides of arbitrarily shaped cross section with any non-collinear equilibrium magnetization which is translationally invariant along the waveguide. Our method is based on the propagating-wave dynamic-matrix approach by Henry et al. and extends it to arbitrary cross sections using a finite-element method. We solve the linearized equation of motion of the magnetization only in a single waveguide cross section which drastically reduces computational effort compared to common three-dimensional micromagnetic simulations. In order to numerically obtain the dipolar potential of individual spin-wave modes, we present a plane-wave version of the hybrid finite-element/boundary-element method by Frekdin and Koehler which, for the first time, we extend to a modified version of the Poisson equation. Our method is applied to several important examples of magnonic waveguides including systems with surface curvature, such as magnetic nanotubes, where the curvature leads to an asymmetric spin-wave dispersion. In all cases, the validity of our approach is confirmed by other methods. Our method is of particular interest for the study of curvature-induced or magnetochiral effects on spin-wave transport but also serves as an efficient tool to investigate standard magnonic problems.