Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41346 Publications

Impact of blood parameters and normal tissue dose on treatment outcome in esophageal cancer patients undergoing neoadjuvant radiochemotherapy

Bütof, R.; Häberlein, L.; Jentsch, C.; Kotzerke, J.; Lohaus, F.; Makocki, S.; Valentini, C.; Weitz, J.; Löck, S.; Troost, E. G. C.

Despite technological advances, normal tissue sparing in photon beam irradiation is still challenging. Since in esophageal cancer this may inflict damage on the lungs, heart and bone marrow, possibly impacting on outcome, the aim of this study was to investigate the association of normal tissue dose and blood parameters on the survival of patients having undergone neoadjuvant radiochemotherapy (RCTx) followed by surgery. This retrospective study included 125 patients irradiated to 40–41.4 Gy with photons or protons combined with concurrent chemotherapy. On initial and restaging 18F-FDG-PET/CT, the lungs and heart were contoured as organs at risk for which standardized uptake values (SUV) were evaluated. The mean radiation dose (Dmean) to the lungs and
heart, the volume of the lungs receiving at least 20 Gy (V20Gy_lung) and various pre- and per-treatment blood parameters were included in the Cox regression analyses. Results: The median follow-up time was 19.8 months and median overall survival 37 months (95% confidence interval: 16–58.9 months). In multivariate analysis, higher radiation doses to the lungs and heart were statistically significantly associated with decreased overall survival (Dmean_lung: p < 0.001; V20Gy_lung: p < 0.002; Dmean_heart: p = 0.005). Neither the 18F-FDG-PET nor blood parameters were predictive for overall survival. In patients with locally advanced esophageal cancer treated with RCTx, the radiation dose to the heart and lungs was significantly associated with overall survival.

Keywords: esophageal cancer; radiochemotherapy; normal tissue dose; neoadjuvant; outcome; PET; blood parameter

Permalink: https://www.hzdr.de/publications/Publ-35079
Publ.-Id: 35079


Deutschlands Ausstieg aus der Atomkraft - Was passiert mit dem Müll und welche Rolle spielen Mikroorganismen?

Matschiavelli, N.

Vortrag über mikrobiologische Themen in der Abteilung Biogeochemie am HZDR

  • Invited lecture (Conferences)
    Tag der Wissenschaften, 24.11.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35078
Publ.-Id: 35078


Fracture Mechanics Testing of Neutron Irradiated RPV Steels using Mini-C(T) Specimens

Das, A.; Chekhonin, P.; Houska, M.; Obermeier, F.; Altstadt, E.

Neutron irradiation induced embrittlement of the reactor pressure vessel (RPV) reduces the operating lifetime of nuclear reactors and leads to an increase in the transition temperature T0. Fracture mechanics testing of RPV steels before and after neutron irradiation, which reveals the shift in T0, is often limited by the shortage of irradiated material. To solve this, we tested sub-sized 0.16T C(T) specimens manufactured from already tested SE(B) standard Charpy sized specimens using the Master Curve concept. The transferability of fracture mechanics data from small to standard sized specimens forms a key part of this study. To investigate the effect of chemical composition on neutron irradiation, four western RPV steels are chosen in this study, three base and one weld metal. Fractography is performed on broken mini-C(T) specimens using scanning electron microscopy in order to determine the location of the fracture initiating particles as well as the mode of fracture. In order to make the testing procedure simpler, based on large statistical data, we studied the impact of the slow stable crack growth censoring criterion on the determination of T0. We found that the results from the small specimens are comparable to the standard specimens. RPV steels containing higher amounts of Cu, Ni and P exhibit a higher increase in T0 after irradiation. The fracture initiating particles were located at greater distances from the crack front in irradiated specimens of the weld material as compared to the unirradiated specimens. The fracture toughness of all materials remained constant for similar test temperatures irrespective of their irradiation state. Furthermore, we found that the stable crack growth censoring criterion did not influence the T0 significantly. Our results demonstrate the validity of small specimen testing and confirms the role of the impurity elements Cu and P in neutron embrittlement.

Keywords: Fracture mechanics testing; sub-sized specimen; transition temperature; reactor pressure vessel steels; Master Curve; neutron-irradiation

  • Lecture (Conference)
    The Nuclear Materials Conference 2022, 24.-28.10.2022, Ghent, Belgium

Permalink: https://www.hzdr.de/publications/Publ-35077
Publ.-Id: 35077


Development of Radiotracers for Imaging of the PD-1/PD-L1 Axis

Krutzek, F.; Kopka, K.; Stadlbauer, S.

Immune checkpoint inhibitor (ICI) therapy has emerged as a major treatment option for a variety of cancers. Among the immune checkpoints addressed, the programmed death receptor 1 (PD-1) and its ligand PD-L1 are the key targets for an ICI. PD-L1 has especially been proven to be a reproducible biomarker allowing for therapy decisions and monitoring therapy success. However, the expression of PD-L1 is not only heterogeneous among and within tumor lesions, but the expression is very dynamic and changes over time. Immunohistochemistry, which is the standard diagnostic tool, can only inadequately address these challenges. On the other hand, molecular imaging techniques such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) provide the advantage of a whole-body scan and therefore fully address the issue of the heterogeneous expression of checkpoints over time. Here, we provide an overview of existing PET, SPECT, and optical imaging (OI) (radio)tracers for the imaging of the upregulation levels of PD-1 and PD-L1. We summarize the preclinical and clinical data of the different molecule classes of radiotracers and discuss their respective advantages and disadvantages. At the end, we show possible future directions for developing new radiotracers for the imaging of PD-1/PD-L1 status in cancer patients.

Keywords: tumor microenvironment; PD-1/PD-L1 targeting radiotracer; immune checkpoint; molecular imaging

Permalink: https://www.hzdr.de/publications/Publ-35076
Publ.-Id: 35076


Coacervation-induced viscous fingering by surfactant-polymer interaction

Stergiou, Y.; Perrakis, A.; Keshavarzi, B.; Javadi, A.; Eckert, K.; Schwarzenberger, K.

The dynamics of a fluid’s displacement by another fluid are always dictated by the viscosity contrast between the two due to phenomena related to the Saffman-Taylor instability. In this study, a miscible displacement of a less viscous liquid by a more viscous shear-thinning liquid in a Hele-Shaw cell was investigated. Due to a coacervation process between the two fluids, a hydrodynamic instability, in the form of inward viscous fingering, appears, in an otherwise hydrodynamically stable system. The aqueous miscible system used consisted of an anionic xanthan gum dispersion, as the injection liquid, which displaced a cationic C14TAB solution. The two oppositely charged species form polymer-surfactant complexes due to electrostatic interactions, which in turn separate from the water phase forming a gel-like membrane. In the course of the displacement, a variety of patterns was observed, the mechanism behind of them is suspected to be governed by a synergy of background contributing factors related to the rheological properties of the system involving viscosity gradients, the non-Newtonian nature of the displacing solution and the complex rheology of the coacervate phase as well as the mechanisms related to the membrane growth. The displacement flow rate and the Hele-Shaw cell gap width were found to determine the distinct displacement regimes; one viscosity-dominated, the other buoyancy-dominated. The above aspects are relevant to applications of displacement-involving coacervation systems in engineering and technology.

  • Poster
    Oscillations and Dynamic Instabilities in Chemical Systems, 17.07.2022, Easton, MA, USA

Permalink: https://www.hzdr.de/publications/Publ-35075
Publ.-Id: 35075


Coupled thermo-fluid-mechanical FEM simulations for thermoelastic harvesting of low-grade waste heat

Neumann, B.; Eckert, K.; Fähler, S.

In a world that heats up, it is essential to use primary energy as efficient as possible. This includes the need to recover waste heat. However, in particular for low grade waste heat hardly any suitable technology is available. Here we simulate the conversion of waste heat into mechanical energy with a NiTi shape memory wire through the coupling of heat exchange, fluid mechanics and structural mechanics. We investigate the influence of preload on the wire and temperature of the fluid to optimize the thermodynamic efficiency, which could act as a base for more complex energy harvesting solutions using shape memory alloys (SMA).

Keywords: Energy; FEM; Thermoelastic Energy Harvesting; simulation

  • Contribution to proceedings
    European Simulation and Modelling Conference 2022, 26.-28.10.2022, Porto, Portugal, 978-9-492859-24-2

Permalink: https://www.hzdr.de/publications/Publ-35074
Publ.-Id: 35074


Impact of curvature-induced Dzyaloshinskii-Moriya interaction on magnetic vortex texture in spherical caps

Sloika, M.; Gaididei, Y.; Kravchuk, V.; Pylypovskyi, O.; Makarov, D.; Sheka, D.

Geometric curvature of nanoscale magnetic shells brings about curvature-induced anisotropy and Dzyaloshinskii-Moriya interaction (DMI). Here, we derive equations to describe the profile of the magnetic vortex state in a spherical cap. We demonstrate that the azimuthal component of magnetization acquires a finite tilt at the edge of the cap, which results in the increase of the magnetic surface energy. This is different compared to the case of a closed spherical shell, where symmetry of the texture does not allow any tilt of magnetization at the equator of the sphere. Furthermore, we analyze the size of the vortex core in a spherical cap and show that the presence of the curvature-induced DMI leads to the increase of the core size independent of the product of the circulation and polarity of the vortex. This is in contrast to the case of planar disks with intrinsic DMI, where the preferred direction of circulation as well as the decrease or increase of the size of vortex core is determined by the sign of the product of the circulation and polarity with respect to the sign of the constant of the intrinsic DMI.

Keywords: curvilinear magnetism; ferromagnet; cap; Dzyaloshinskii-Moriya interaction

Permalink: https://www.hzdr.de/publications/Publ-35073
Publ.-Id: 35073


Circular stripe domains and cone state vortices in disk-shaped exchange coupled magnetic heterostructures

Zaiets, O.; Kravchuk, V.; Pylypovskyi, O.; Makarov, D.; Sheka, D.

Vertically stacked exchange coupled magnetic heterostructures of cylindrical geometry can host complex noncolinear magnetization patterns. By tuning the interlayer exchange coupling between a layer accommodating magnetic vortex state and an out-of-plane magnetized layer, one can efficiently realize new topological chiral textures such as cone state vortices and circular stripe domains. We study how the number of circular stripes can be controlled by both the interlayer exchange coupling and the sample geometrical parameters. By varying geometrical parameters, a continuous phase transition between the homogeneous state, cone state vortex, circular stripe domains, and the imprinted vortex takes place, which is analysed by full scale micromagnetic simulations. The analytical description provides an intuitive pictures of the magnetization textures in each of these phases. The possibility to realize switching between different states allows for engineering magnetic textures with possible applications in spintronic devices.

Keywords: multilayer; vortex; heterostructure; stripe domain

Permalink: https://www.hzdr.de/publications/Publ-35072
Publ.-Id: 35072


Wafer-scale nanofabrication of telecom single-photon emitters in silicon

Hollenbach, M.; Klingner, N.; Jagtap, N.; Bischoff, L.; Fowley, C.; Kentsch, U.; Hlawacek, G.; Erbe, A.; Abrosimov, N. V.; Helm, M.; Berencen, Y.; Astakhov, G.

A highly promising route to scale millions of qubits is to use quantum photonic integrated circuits (PICs), where deterministic photon sources, reconfigurable optical elements, and single-photon detectors are monolithically integrated on the same silicon chip. The isolation of single-photon emitters, such as the G centers and W centers, in the optical telecommunication O-band, has recently been realized in silicon. In all previous cases, however, single-photon emitters were created uncontrollably in random locations, preventing their scalability. Here, we report the controllable fabrication of single G and W centers in silicon wafers using focused ion beams (FIB) with a probability exceeding 50%. We also implement a scalable, broad-beam implantation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabricate single telecom emitters at desired positions on the nanoscale. Our findings unlock a clear and easily exploitable pathway for industrial-scale photonic quantum processors with technology nodes below 100 nm.

Keywords: Quantum technology; Single photons; Ion implantation; Silicon photonics; Optical telecommunication; CMOS-compatible processing

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Permalink: https://www.hzdr.de/publications/Publ-35071
Publ.-Id: 35071


ARIEL & SANDA nuclear data activities

Franzen, C.; Junghans, A.; Gonzalez, E. M.; Plompen, A. J. M.

Nuclear data are fundamental quantities for developing nuclear energy concepts and research.
They are essential for the simulation of nuclear systems, safety and performance calculations, and reactor
instrumentation. Nuclear data improvement requires a combination of many different know-hows that are
distributed over many institutions along Europe. In the EURATOM call for Nuclear Fission and Radiation
Protection NFRP-2018, two nuclear data projects were started in September 2019: The Coordination and
Support Action ARIEL (Accelerator and Research reactor Infrastructures for Education and Learning)
and the Research and Innovation Action SANDA (Solving Challenges in Nuclear Data for the Safety of
European Nuclear facilities). The ARIEL project integrates education and training of young scientists and
technicians with access to neutron beam research infrastructures and supports scientific visits to conduct
short-term research projects relevant to thesis works. The SANDA project is focuses on research innovation
actions, including detector and nuclear target development, important nuclear data measurements, nuclear
data evaluation, and validation. A description of these ongoing projects, including the first results, is the
subject of this article.

Permalink: https://www.hzdr.de/publications/Publ-35070
Publ.-Id: 35070


Direct Sampling Strategy for Extensive Hard Data-based Training Image

Selia, S. R. R.; Tolosana Delgado, R.; van den Boogaart, K. G.

Extensive hard data could potentially replace the training image in doing MPS. However, direct use of the the standard MPS Direct Sampling algorithm will typically not produce proper results, owing to the absence (or at least, sufficient replication) of every necessary data pattern in the data set. As a result, during the step of training image scanning, there will be a reduction of the conditional data neighbourhood in the simulation grid data event, generating inconsistencies of neighbourhood size in simulating each point. Here, we propose to use a spatial tolerance in extracting the training image data events. This has long been used to obtain experimental variogram in two-point geostatistics, and is also common in high-order cumulant based methods.

A synthetic case study of a fluvial depositional environment will be presented, together with a comparison of the usage of various types of training images (e.g. hard data, complete training image, multiple training images). This framework can also be extended to MPS for the purpose of estimation rather than simulation.
This is achieved by obtaining marginal
conditional probabilities by storing potential simulated values during the training image scan-
ning step for each grid cell, conditioning only to hard data. This could be a time saver for
users interested only in the point-wise statistics of the realizations without having to generate
multiple realizations.

Keywords: Extensive hard data; Direct Sampling; Multi-point geostatistics

  • Lecture (Conference)
    IAMG 2022 - 21st Annual Conference, 29.08.-03.09.2022, Nancy, France

Permalink: https://www.hzdr.de/publications/Publ-35069
Publ.-Id: 35069


Observation of Collective Resonance Modes in a Chiral Spin Soliton Lattice with Tunable Magnon Dispersion

Shimamoto, Y.; Matsushima, Y.; Hasegawa, T.; Kousaka, Y.; Proskurin, I.; Kishine, J.; Ovchinnikov, A. S.; Trindade Goncalves, F. J.; Togawa, Y.

A chiral spin soliton lattice (CSL), one of the representative systems of a magnetic superstructure, exhibits reconfigurability in periodicity over a macroscopic length scale. Such coherent and tunable characteristics of the CSL lead to an emergence of elementary excitation of the CSL as phononlike modes due to translational symmetry breaking and bring a controllability of the dispersion relation of the CSL phonon. Using a broadband microwave spectroscopy technique, we directly found that higher-order magnetic resonance modes appear in the CSL phase of a chiral helimagnet CrNb3S6, which is ascribed to the CSL phonon response. The resonance frequency of the CSL phonon can be tuned between 16 and 40 GHz in the vicinity of the critical field, where the CSL period alters rapidly. The frequency range of the CSL phonon is expected to extend over 100 GHz as extrapolated on the basis of the theoretical model. The present results indicate that chiral helimagnets could work as materials useful for broadband signal processing in the millimeter-wave band.

Keywords: Chiral helimagnetism; Collective spin dynamics; Ferromagnetic resonance; Magnon dispersion; DMI materials; Bulk crystals

Permalink: https://www.hzdr.de/publications/Publ-35068
Publ.-Id: 35068


Data publication: Importance of valence-band anharmonicity and carrier distribution for third- and fifth-harmonic generation in Si:B pumped with intense terahertz pulses

Meng, F.; Walla, F.; Ul-Islam, Q.; Pashkin, O.; Schneider, H.; Jungemann, C.; Thomson, M. D.; Roskos, H. G.

High-hamonic spectra induced by FEL pumping; FTIR and THz transmission spectra of utilized spectral filters

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Permalink: https://www.hzdr.de/publications/Publ-35067
Publ.-Id: 35067


Time-resolved measurements in pulsed magnetic fields

Kohama, Y.; Nomura, T.; Zherlitsyn, S.; Ihara, Y.

Tracking the time-dependence of a state and its observable, i.e., time-resolved measurement, is one of the ways of understanding physical principles of the system. In this Perspective, we review some of the time-resolved measurements performed in pulsed high magnetic fields, where the duration of the pulsed field restricts the available measurement timescale from a few to several hundred milliseconds. We present some successful examples with a focus on the recent technical breakthroughs both in the measurement and magnetic-field generation techniques. These experimental techniques can be used in other experimental conditions in order to increase the signal-to-noise ratio and the repetition rate of time-resolved measurements. Taking the impacts of these applications on current condensed matter research into consideration, we also discuss the future direction of the time-resolved measurement in pulsed magnetic fields.

Permalink: https://www.hzdr.de/publications/Publ-35066
Publ.-Id: 35066


Fermi surface of the chiral topological semimetal PtGa

Schwarze, B. V.; Uhlarz, M.; Hornung, J.; Chattopadhyay, S.; Manna, K.; Shekhar, C.; Felser, C.; Wosnitza, J.

PtGa is a topological semimetal with giant spin-split Fermi arcs. Here, we report on angular-dependent de Haas–van Alphen (dHvA) measurements combined with band-structure calculations to elucidate the details of the bulk Fermi surface of PtGa. The strong spin–orbit coupling leads to eight bands crossing the Fermi energy that form a multitude of Fermi surfaces with closed extremal orbits and results in very rich dHvA spectra. The large number of experimentally observed dHvA frequencies make the assignment to the equally large number of calculated dHvA orbits challenging. Nevertheless, we find consistency between experiment and calculations verifying the topological character with maximal Chern number of the spin-split Fermi surface.

Permalink: https://www.hzdr.de/publications/Publ-35065
Publ.-Id: 35065


Ultrahigh transverse thermoelectric power factor in flexible Weyl semimetal WTe2

Pan, Y.; He, B.; Helm, T.; Chen, G.; Schnelle, W.; Felser, C.

Topological semimetals are well known for their interesting physical properties, while their mechanical properties have rarely received attention. With the increasing demand for flexible electronics, we explore the great potential of the van der Waals bonded Weyl semimetal WTe2 for flexible thermoelectric applications. We find that WTe2 single crystals have an ultrahigh Nernst power factor of ~3 Wm−1K−2, which outperforms the conventional Seebeck power factors of the state-of-the-art thermoelectric semiconductors by 2–3 orders of magnitude. A unique band structure that hosts compensated electrons and holes with extremely high mobilities is the primary mechanism for this huge Nernst power factor. Moreover, a large Ettingshausen signal of ~5 × 10−5 KA−1m is observed at 23.1 K and 9 T. In this work, the combination of the exceptional Nernst–Ettingshausen performance and excellent mechanical transformative ability of WTe2 would be instructive for flexible micro-/nano-thermoelectric devices.

Permalink: https://www.hzdr.de/publications/Publ-35064
Publ.-Id: 35064


Coupled frustrated ferromagnetic and antiferromagnetic quantum spin chains in the quasi-one-dimensional mineral antlerite Cu3SO4(OH)4

Kulbakov, A. A.; Kononenko, D. Y.; Nishimoto, S.; Stahl, Q.; Chakkingal, A. M.; Feig, M.; Gumeniuk, R.; Scurschii, I.; Bhaskaran, L.; Zvyagin, S.; Embs, J. P.; Puente-Orench, I.; Wildes, A.; Geck, J.; Janson, O.; Inosov, D. S.; Peets, D. C.

Magnetic frustration, the competition among exchange interactions, often leads to novel magnetic ground states with unique physical properties which can hinge on details of interactions that are otherwise difficult to observe. Such states are particularly interesting when it is possible to tune the balance among the interactions to access multiple types of magnetic order. We present antlerite Cu3SO4(OH)4 as a potential platform for tuning frustration. Contrary to previous reports, the low-temperature magnetic state of its three-leg zigzag ladders is a quasi-one-dimensional analog of the magnetic state recently proposed to exhibit spinon-magnon mixing in botallackite. Density functional theory calculations indicate that antlerite’s magnetic ground state is exquisitely sensitive to fine details of the atomic positions, with each chain independently on the cusp of a phase transition, indicating an excellent potential for tunability.

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Permalink: https://www.hzdr.de/publications/Publ-35063
Publ.-Id: 35063


Theory of ultrasound propagation in LuCo3 near the low-spin–high-spin crossover

Tereshchenko, A. A.; Ovchinnikov, A. S.; Gorbunov, D.; Neznakhin, D. S.

The possibility of experimental observation of the ultrasonic attenuation in the ferromagnet LuCo3 near the low-spin-high-spin crossover is discussed. We show that ultrasound propagation gives rise to transitions between states of the magnon band due to absorption of phonons, and this process is highly sensitive to the value of magnetization. The high magnetic field, which governs the crossover, alters the ultrasound propagation regime from off-resonant to resonant and we formulate a criterion of the change. Calculated temperature and field dependences of the ultrasonic wave number and attenuation clearly demonstrate anomalies in these characteristics in the vicinity of the crossover at intermediate temperatures far below the Curie temperature.

Permalink: https://www.hzdr.de/publications/Publ-35062
Publ.-Id: 35062


Orbital-induced crossover of the Fulde-Ferrell-Larkin-Ovchinnikov phase into Abrikosov-like states

Kotte, T.; Kühne, H.; Schlueter, J. A.; Zwicknagl, G.; Wosnitza, J.

The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state can emerge in superconductors for which the orbital critical field exceeds the Pauli limit. Here, we present angular-resolved specific-heat data of the quasi-twodimensional organic superconductor κ-(ET)2Cu(NCS)2, with a focus on high fields in the regime of the FFLO transition. For an increasing out-of-plane tilt of the applied magnetic field, which leads to an increase of orbital contributions, we found that the nature of the superconducting transition changes from second to first order and that a further transition appears within the high-field superconducting phase. However, the superconducting state above the Pauli limit is stable for field tilt of several degrees. Since any finite perpendicular component of the magnetic field necessarily leads to quantization of the orbital motion, the resulting vortex lattice states compete with the modulated order parameter of the FFLO state leading to complex high-field superconducting phases. By solving the linearized self-consistency equation within weak-coupling BCS theory, we show that our results are clear experimental evidence of an orbital-induced transformation of the FFLO order parameter into Abrikosov-like states of higher Landau levels.

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Permalink: https://www.hzdr.de/publications/Publ-35061
Publ.-Id: 35061


Magnetic and magnetoelastic properties of Er3Al2

Gorbunov, D.; Palazzese Di Basilio, S.; Ishii, I.; Andreev, A. V.; Sebek, J.; Buturlim, V.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.

We report on comprehensive investigations of Er3Al2 exhibiting a number of magnetic states. We observe three spontaneous antiferromagnetic transitions at 10, 14, and 24 K. Furthermore, our high-field magnetization and sound-velocity measurements reveal a number of crystal-electric-field (CEF) transitions. Additionally, the velocity of transverse acoustic waves shows a pronounced softening with decreasing temperature in the paramagnetic state. A CEF model that includes quadrupolar interactions explains the observed magnetic and elastic properties and provides a CEF scheme of Er3Al2. However, to explain some of the observations, a refined, more sophisticated model needs to be developed.

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Permalink: https://www.hzdr.de/publications/Publ-35060
Publ.-Id: 35060


Effect of nonhydrostatic pressure on the superconducting kagome metal CsV₃Sb₅

Tsirlin, A. A.; Ortiz, B. R.; Dressel, M.; Wilson, S. D.; Winnerl, S.; Uykur, E.

High-pressure single-crystal x-ray diffraction experiments reveal that the superconducting kagome metal CsV₃Sb₅ transforms from hexagonal (P6/mmm) to monoclinic (C2/m) symmetry above
10 GPa if nonhydrostatic pressure conditions are created in a diamond anvil cell with silicon oil as pressure-transmitting medium. This is contrary to the behavior of CsV₃Sb₅ under quasi-hydrostatic conditions in neon, with the hexagonal symmetry retained up to at least 20 GPa. Monoclinic distortion leaves the kagome planes almost unchanged but deforms honeycomb nets of the Sb atoms. Using ab initio density-functional calculations, we show that this distortion facilitates the pressure-induced shift of van Hove singularities away from the Fermi level and preserves the overall scenario of the Fermi surface reconstruction caused by the formation of interlayer Sb-Sb bonds.

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Permalink: https://www.hzdr.de/publications/Publ-35059
Publ.-Id: 35059


Importance of valence-band anharmonicity and carrier distribution for third- and fifth-harmonic generation in Si:B pumped with intense terahertz pulses

Meng, F.; Walla, F.; Ul-Islam, Q.; Pashkin, O.; Schneider, H.; Jungemann, C.; Thomson, M. D.; Roskos, H. G.

We observe third-harmonic generation (THG) and fifth-harmonic generation (FHG) of free holes in the valence band of bulk Si:B at cryogenic temperature upon irradiation with intense terahertz pulses from a free-electron laser, polarized along the Γ−X direction. The intensities of both signals increase as a function of pulse energy following power laws with respective exponents of 4.2 and 6.2, larger than the exponents of 3 and 5 expected for xi(3) and xi(5) processes with constant susceptibilities and a fixed number of holes. The larger values are attributed to the increase in the density of mobile holes, which results from impact ionization of boron dopants by thermally activated holes in the electric field of the terahertz pulses as already observed in our studies of THG in Si:B reported in Phys. Rev. B 102, 075205 (2020). We apply Monte Carlo simulations of the nonlinear heavy- and light-hole field response, coupled with a finite-difference time-domain treatment of the pump-pulse propagation in the sample, which reproduce the experimental THG:FHG intensity ratio reasonably well. An analysis of the local response demonstrates that, in our pump regime, the harmonic generation is dominated by the band anharmonicity as opposed to the energy-dependent momentum scattering rates or interband scattering. Comparison with the results of a simple one-dimensional model and scrutiny of the three-dimensional band structure shows that one must account for the extent of the carrier distribution transverse to the Γ−X axis as the anharmonicity grows rapidly away from this axis.

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Permalink: https://www.hzdr.de/publications/Publ-35058
Publ.-Id: 35058


Characterization of microbial communities in sedimentary clays used for deep geological repository

Wei, T.-S.; Matschiavelli, N.; Sushko, V.; Schleicher, A. M. S.; Cherkouk, A.

A deep geological repository (DGR) is a multi-barrier concept that has been a solution to store high-level nuclear waste (HLW). The natural Opalinus clay rocks are one of the candidates for entire DGR due to their unique geochemical features. However, the first direct barrier is bentonites which are the processed clay materials that embed metal containers for HLW. The microbial impact, especially when porewater is introduced into DGR and H2 gas is generated via anoxic corrosion of containers, on these clay barriers remains elusive.
Here, we showed that mineral composition between sandy and shaley Opalinus clays from underground laboratory Mt. Terri were discernible. The microbial diversity of Opalinus clay, together with Calcigel bentonite (CaB) and previously published data from Opalinus porewater and Bavarian bentonite (B25) were significantly distinct principal coordinates analysis. The CaB supported diverse phyla, whereas other communities were dominated by Proteobacteria. Moreover, genus Desulfobacterium (phylum Desulfobacterota) was largely enriched by injecting H2 gas into the porewater communities; however, in the B25 incubated with synthetic Opalinus porewater, genera Desulfosporosinus and Pelotomaculum (phylum Firmicutes) were enriched by H2 gas. Interestingly, the signature of these bacteria was also identified in the sandy clay and CaB communities, indicating that these two communities have the capacity in alleviating H2 pressure accumulated in DGR.
In the future, microcosm setup with porewater and H2 gas will be applied to Opalinus clay and CaB samples with different compacted dry density. The understanding of impact on these clay materials will be achieved via metagenome and geochemical analyses.

Keywords: Bentonite; Opalinus clay; Deep geological repository (DRG); Nuclear waste management; 16S amplicon sequencing

  • Poster
    18th International Symposium on Microbial Ecology, 14.-19.08.2022, Lausanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35057
Publ.-Id: 35057


Vibrio salinus sp. nov., a marine nitrogen-fixing bacterium isolated from the lagoon sediment of an islet inside an atoll in the western Pacific Ocean

Huang, W.; Wang, L.; Chen, J.; Chen, Y. C.; Wei, T.-S.; Chiang, Y. C.; Wang, P.; Lee, T.; Lin, S.; Huang, L.; Shieh, W. Y. S.

A marine, facultatively anaerobic, nitrogen-fixing bacterium, designated strain DNF-1T, was isolated from the lagoon
sediment of Dongsha Island, Taiwan. Cells grown in broth cultures were Gram-negative rods that were motile by means of
monotrichous flagella. Cells grown on plate medium produced prosthecae and vesicle-like structures. NaCl was required and
optimal growth occurred at about 2–3% NaCl, 25–30 °C and pH 7–8. The strain grew aerobically and was capable of
anaerobic growth by fermenting D-glucose or other carbohydrates as substrate. Both the aerobic and anaerobic growth
could be achieved with NH4Cl as a sole nitrogen source. When N2 served as the sole nitrogen source only anaerobic
growth was observed. Major cellular fatty acids were C14:0, C16:0 and C16:1ω7c, while major polar lipids were
phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content was 42.2 mol% based on the genomic DNA
data. Phylogenetic analyses based on 16S rRNA genes and the housekeeping genes, gapA, pyrH, recA and gyrB, revealed
that the strain formed a distinct lineage at species level in the genus Vibrio of the family Vibrionaceae. These results and
those from genomic, chemotaxonomic and physiological studies strongly support the assignment of a novel Vibrio species.
The name Vibrio salinus sp. nov. is proposed for the novel species, with DNF-1T (= BCRC 81209T = JCM 33626T) as the
type strain. This newly proposed species represents the second example of the genus Vibrio that has been demonstrated to
be capable of anaerobic growth by fixing N2 as the sole nitrogen source

Keywords: Marine bacteria; Multilocus sequence analysis (MLSA); Nitrogen-fixing bacteria; Vibrio; Vibrio salinus; Vibrionaceae

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Publ.-Id: 35056


Development of a neurotensin-derived 68Ga-labeled PET ligand with high in vivo stability for imaging of NTS1 receptor-expressing tumors

Schindler, L.; Moosbauer, J.; Schmidt, D.; Spruss, T.; Grätz, L.; Lüdeke, S.; Hofheinz, F.; Meister, S.; Echtenacher, B.; Bernhardt, G.; Pietzsch, J.; Hellwig, D.; Keller, M.

Overexpression of the neurotensin receptor type 1 (NTS1R), a peptide receptor located at the plasma membrane, was reported for a variety of malignant tumors. Thus, targeting the NTS1R with 18F- or 68Ga- labeled ligands is considered a straight-forward approach towards in vivo im-aging of NTS1R-expressing tumors via positron emission tomography (PET). The development of suitable peptidic NTS1R PET ligands derived from neurotensin is challenging due to proteolytic degradation. In this study, we prepared a series of NTS1R PET ligands based on the C-terminal fragment of neurotensin (NT(8-13), Arg8-Arg9-Pro10-Tyr11-Ile12-Leu13) by attachment of the che-lator 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) via an Nω-carbamoylated arginine side chain. Insertion of Ga3+ in the DOTA cage gave potential PET ligands that were evaluated concerning NTS1R affinity (range of Ki values: 1.2-21 nM) and plasma stability. Four candidates were labeled with 68Ga3+ and used for biodistribution studies in HT-29 tumor bearing mice. [68Ga]UR-LS130 ([68Ga]56), containing an N-terminal methyl group and a β,β-dimethylated tyrosine instead of Tyr11, showed the highest in vivo stability and afforded a tumor-to-muscle ratio of 16 at 45 min p.i. Likewise, dynamic PET scans enabled a clear tumor visualization. The accumulation of [68Ga]56 in the tumor was NTS1R mediated as proven by blocking studies.

Permalink: https://www.hzdr.de/publications/Publ-35055
Publ.-Id: 35055


Structural and Chemical Modifications of Few-layer Transition Metal Phosphorous Trisulfides by Electron Irradiation

Köster, J.; Storm, A.; Ghorbani Asl, M.; Kretschmer, S.; Gorelik, T. E.; Krasheninnikov, A.; Kaiser, U.

Transition metal phosphorous trisulfides (TMPTs) are inorganic materials with inherent magnetic properties. Due to their layered structure, they can be exfoliated into ultra-thin sheets, which show properties different from their bulk counterparts. Herein, we present a detailed analysis of the interaction of the electron beam (30 – 80 kV) in a transmission electron microscope (TEM) with freestanding few-layer TMPTs, with the aim to tailor their properties. The irradiation-induced structure modifications were systematically investigated by various TEM methods on FePS3, MnPS3, and NiPS3, and the results are rationalized with the help of ab-initio calculations, which predict that the knock-on threshold for removing sulfur is significantly lower than that for phosphorus. Therefore, a targeted removal of sulfur is feasible. Eventually, our experiments confirm the dose-dependent, predominantly removal of sulfur by the impinging electrons, thus showing the possibility to tune the sulfur concentration. Using ab-initio calculations, we analyze the electronic structure of the TMPTs with single vacancies and oxygen impurities, and predict distinct electronic properties depending on the type of defect. Therefore, our study shows the possibility of tuning the properties of ultrathin freestanding TMPTs by controlling their stoichiometry.

Keywords: Two-dimensional materials; Transition metal phosphorous trisulfides; Defects; Electron irradiation; Transmission electron microscope; ab-initio calculations

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Permalink: https://www.hzdr.de/publications/Publ-35054
Publ.-Id: 35054


Controlling stoichiometry in ultrathin van der Waals films: PtTe₂, Pt₂Te₃, Pt₃Te₄, and Pt₂Te₂

Lasek, K.; Ghorbani Asl, M.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

The platinum-tellurium phase diagram exhibits various (meta)stable van der Waals (vdW) materials, that can be constructed by stacking PtTe2 and Pt2Te2 layers. Mono phase PtTe2, being the thermodynamically most stable compound, can readily be grown as thin films. Obtaining the other phases (Pt2Te3, Pt3Te4, Pt2Te2), especially in their ultimate thin form, is significantly more challenging. We show that PtTe2 thin films can be transformed by vacuum annealing-induced Te-loss into Pt3Te4- and Pt2Te2- bilayers. These transformations are characterized by scanning tunneling microscopy, x-ray and angle resolved photoemission spectroscopy. Once Pt3Te4 is formed, it is thermally stable up to 350˚C. To transform Pt3Te4 into Pt2Te2, a higher annealing temperature of 400˚C is required. The experiments combined with density functional theory calculations provide insights into these transformation mechanisms and show that a combination of the thermodynamic preference of Pt3Te4 over a phase segregation into PtTe2 and Pt2Te2 and an increase in the Te-vacancy formation energy for Pt3Te4 compared to the starting PtTe2 material is critical to stabilize the Pt3Te4 bilayer. To desorb more tellurium from Pt3Te4 and transform the material into Pt2Te2, a higher Te-vacancy formation energy has to be overcome by raising the temperature. Interestingly, bilayer Pt2Te2 can be re-tellurized by exposure to Te-vapor. This causes the selective transformation of the topmost Pt2Te2 layer into two layers of PtTe2, and consequently the synthesis of e Pt2Te3. Thus, all known Pt-telluride vdW compounds can be obtained in their ultrathin form by carefully controlling the stoichiometry of the material.

Keywords: van der Waals materials; 2D materials; interlayer interaction; charge transfer; phase stability; platinum telluride; composition control

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Fluorination of silyl prosthetic groups by fluorine mediated silyl ether linker cleavage: a concept study with conditions applicable in radiofluorination

Kramer, C. S.; Greiner, L.; Kopka, K.; Schäfer, M.

Background: Positron emission tomography (PET) is a powerful tool in medical imaging, especially in combination with the PET radionuclide fluorine-18 that possesses optimal characteristics. For labelling of biomolecules and low-molecular weight tracers, fluorine-18 can be covalently bound to silicon by either nucleophilic replacements of leaving groups (like ethers) or by isotope exchange of fluorine-19. While nucleophilic substitutions require additional purification steps for the removal of contaminants, isotope exchange with fluorine-18 results in low molar activity. Both challenges can be addressed with a detagging-fluorination of an immobilized silyl ether motif.
Results: By overcoming the susceptibility towards hydrolysis, optimized detagging conditions (improved reaction time, fluorination reagent, linker, and resin) could afford the highly sterically hindered silyl fluoride motifs, that are commonly applied in radiochemistry in small and semipreparative scales. The described reaction conditions with fluorine-19 are transferrable to conditions with [18F]fluoride and silyl fluorides were obtained after approx. 10 min reaction time and in high-purity after mechanical filtration.
Conclusions: We present a proof-of-concept study for a detagging-fluorination of two silyl ethers that are bound to an optimized amino alcohol resin. We show with our model substrate that our solid-phase linker combination is capable of yielding the desired silicon fluoride in amounts sufficient for biological studies in animals or humans under standard fluorination conditions that may also be transferred to a radiolabelling setting. In conclusion, our presented approach could optimize the molar activity and simplify the preparation of radiofluorinated silyl fluorides.

Keywords: Detagging; Fluorine-18; PET; Radiofluorination; SiFA; Silyl fluorides; Solid phase synthesis; Solid support

Permalink: https://www.hzdr.de/publications/Publ-35052
Publ.-Id: 35052


Covalent Triazine Frameworks and Porous Carbons: Perspective from an Azulene-Based Case

Jiang, K.; Peng, P.; Tranca, D.; Tong, G.; Ke, C.; Lu, C.; Hu, J.; Liang, H.; Li, J.; Zhou, S.; Kymakis, E.; Zhuang, X.

Covalent triazine frameworks (CTFs) are among the most valuable
frameworks owing to many fantastic properties. However, molten
salt-involved preparation of CTFs at 400–600 °C causes debate on whether
CTFs represent organic frameworks or carbon. Herein, new CTFs based on the
1,3-dicyanoazulene monomer (CTF-Azs) are synthesized using molten ZnCl2
at 400–600 °C. Chemical structure analysis reveals that the CTF-Az prepared at
low temperature (400 °C) exhibits polymeric features, whereas those prepared
at high temperatures (600 °C) exhibit typical carbon features. Even after being
treated at even higher temperatures, the CTF-Azs retain their rich porosity, but
the polymeric features vanish. Although structural de-conformation is a widely
accepted outcome in polymer-to-carbon rearrangement processes, the study
evaluates such processes in the context of CTF systems. A proof-of-concept
study is performed, observing that the as-synthesized CTF-Azs exhibit
promising performance as cathodes for Li- and K-ion batteries. Moreover, the
as-prepared NPCs exhibit excellent catalytic oxygen reduction reaction (ORR)
performance; hence, they can be used as air cathodes in Zn-air batteries. This
study not only provides new building blocks for novel CTFs with controllable
polymer/carbon features but also offers insights into the formation and
structure transformation history of CTFs during thermal treatment.

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Publ.-Id: 35051


Towards Tomography-Based Real-Time Control of Multiphase Flows: A Proof of Concept in Inline Fluid Separation

Garcia, M. M.; Sattar, M. A.; Atmani, H.; Legendre, D.; Babout, L.; Schleicher, E.; Hampel, U.; Portela, L. M.

The performance of multiphase flow processes is often determined by the distribution of phases inside the equipment. However, controllers in the field are typically implemented based on flow variables, which are simpler to measure, but indirectly connected to performance (e.g., pressure). Tomography has been used in the study of the distribution of phases of multiphase flows for decades, but only recently, the temporal resolution of the technique was sufficient for real-time reconstructions of the flow. Due to the strong connection between the performance and distribution of phases, it is expected that the introduction of tomography to the real-time control of multiphase flows will lead to substantial improvements in the system performance in relation to the current controllers in the field. This paper uses a gas–liquid inline swirl separator to analyze the possibilities and limitations of tomography-based real-time control of multiphase flow processes. Experiments were performed in the separator using a wire-mesh sensor (WMS) and a high-speed camera to show that multiphase flows have two components in their dynamics: one intrinsic to its nonlinear physics, occurring independent of external process disturbances, and one due to process disturbances (e.g., changes in the flow rates of the installation). Moreover, it is shown that the intrinsic dynamics propagate from upstream to inside the separator and can be used in predictive and feedforward control strategies. In addition to the WMS experiments, a proportional–integral feedback controller based on electrical resistance tomography (ERT) was implemented in the separator, with successful results in relation to the control of the distribution of phases and impact on the performance of the process: the capture of gas was increased from 76% to 93% of the total gas with the tomography-based controller. The results obtained with the inline swirl separator are extended in the perspective of the tomography-based control of quasi-1D multiphase flows.

Keywords: tomography-based control; inline fluid separator; swirl separator; hydrocyclone; gas– liquid swirl flow; electrical resistance tomography; real-time control; multiphase flows

Permalink: https://www.hzdr.de/publications/Publ-35050
Publ.-Id: 35050


Super-SIMS; Combining a SIMS with AMS – Status of this challenging initiative

Ziegenrücker, R.

Super-SIMS is a project, where a commercial SIMS (Secondary Ion Mass Spectrometer) is used as an ion source for the 6 MV Tandem accelerator at the HZDR's Ion Beam Center. This combination allows the complete suppression of molecular isobaric ions, which are a major challenge for standard SIMS. The presentation gives an overview about the advantages such a device would have and its possible applications.

Keywords: Super-SIMS; Mass spectrometry; Accalerator mass spectrometry; AMS; SIMS; molecular interference

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  • Invited lecture (Conferences)
    GEOANALYSIS 2022 - Workshop SIMS ANALYSIS, 06.-15.08.2022, Freiberg/Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35049
Publ.-Id: 35049


Quality assurance for chemical databases using the example of the thermodynamic reference database THEREDA

Bok, F.; Moog, H. C.; Gaona, X.; Freyer, D.; Wissmeier, L.

Quality assurance for thermodynamic databases is essential to increase confidence in predictive models based on such data. Demands are numerous and range from the review and selection of data, their correct input into a digital database, internal calculations and conversions, to the output of the data to the users - as formatted- parameter files specific for geochemical modeling programs as well as a display on a website with open access to the public. Both technical procedures and reciprocal audits by the editors are used in this process.
An essential part of data quality checks are comparative calculations against experimental measurements. This is accompanied by internal, automated test calculations before each new data release. Moreover, the uncertainty information is given for all data, which are also evaluated and accordingly labelled in terms of quality using a simple scheme. All this information helps users to evaluate the sensitivity of individual parameters and their influence on the result of geochemical calculations in their work.
Maximum transparency is also intended to demonstrate the trustworthiness of the data: For each datum included, the primary source is given in detail, and the results of all comparative calculations are openly presented on the project website (https://www.thereda.de/).
The reliability of the database also includes its long-term availability. THEREDA's system is completely based on free and open source software and extended by self-developed, fully documented components. This guarantees independence from software manufacturers and at the same time ensures the future availability of the data.

Keywords: thermodynamic database; THEREDA; quality assurance

  • Invited lecture (Conferences)
    BASE-Workshop „Trust in Models“ (TiM 2022), 17.-18.11.2022, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35047
Publ.-Id: 35047


Dipeptide-derived alkynes as potent and selective irreversible inhibitors of cysteine cathepsins

Behring, L.; Ruiz-Gomez, G.; Trapp, C.; Morales, M.; Wodtke, R.; Köckerling, M.; Kopka, K.; Pisabarro, M. T.; Pietzsch, J.; Löser, R.

The potential of designing irreversible alkyne-based inhibitors of cysteine cathepsins by isoelectronic replacement in reversibly acting potent peptide nitriles was explored. The synthesis of the dipeptide alkynes was developed with special emphasis on stereochemically homogenous products obtained in the Gilbert-Seyferth homologation for C-C triple bond formation. 23 dipeptide alkynes and 12 analogous nitriles were synthesized and investigated for their inhibition of cathepsins B, L, S and K. Numerous combinations of residues in the P1 and P2 positions as well as terminal acyl groups, allowed for the derivation of extensive structure-activity relationships, which were rationalized by computational covalent docking for selected examples. The determined inactivation constants of the alkynes at the target enzymes span a range of more than three orders of magnitude (3-10,133 M-1<\sup>s-1<\sup>). Notably, the selectivity profiles of alkynes do not necessarily reflect those of the nitriles. Inhibitory activity at the cellular level was demonstrated for selected compounds.

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Permalink: https://www.hzdr.de/publications/Publ-35046
Publ.-Id: 35046


Stable Multi-Day Performance of a Laser Wakefield Accelerator for FEL Applications

Couperus Cabadağ, J. P.; Bock, S.; Chang, Y.-Y.; Debus, A.; Gebhardt, R.; Ghaith, A.; Helbig, U.; Irman, A.; Köhler, A.; Laberge, M.; Pausch, R.; Püschel, T.; Schramm, U.; Schöbel, S.; Steiniger, K.; Ufer, P.; Zarini, O.; Roussel, E.; Couprie, M.- . E.; Labat, M.; Downer, M. C.

We report on the operation of the DRACO Laser Driven electron source for stable multi-day operation for Free Electron Laser (FEL) applications. The nC-class accelerator can deliver charge densities around 10 pC/MeV , <1 mrad rms divergence at energies up to 0.5 GeV and peak currents of over 10 kA*.
Precise characterisation is paramount for controlled operation, including: spectrally resolved charge diagnostic, coherent optical transition radiation (TR) to resolve microbunch beam structures** and TR-based multioctave high-dynamic range spectrometry for sub-fs resolved characterisation of the 10 fs rms electron bunches***. Achieved stability allows for systematic exploration of demanding applications, resulting in the recent demonstration of the first LWFA based Beam-driven Plasma Wakefield Accelerator (LPWFA)****.
Fulfilling the high demands required for FEL operation, the COXINEL manipulation line***** developed at Synchotron SOLEIL has recently been installed at our facility. Based on successful beam transport of over 13000 shots within 9 experimental days during commissioning, we were able to demonstrate the very first operation of a seeded FEL driven by a laser plasma accelerator******.

* J.P. Couperus et al., Nat. Comm. 8 (2017)
** O. Zarini et al., PRAB (2022)
*** A. Lumpkin et al., Phys. Rev. Lett., 125, 014801 (2020)
**** T. Kurz, T. Heinemann et al., Nature Commun., 12, 2895 (2021)
***** M.-E. Couprie et al., J. Phys B, 47, 234001 (2014) & M.-E. Couprie et al., PPCF, 58, 034020 (2016)
****** M. Labat et al., in review, (2022), doi:10.21203/rs.3.rs-1692828/v1

Keywords: FEL; LWFA

  • Poster
    FEL conference Trieste (FEL2022), 22.-26.08.2022, Trieste, Italy

Permalink: https://www.hzdr.de/publications/Publ-35045
Publ.-Id: 35045


Time- and dose-dependent volume decreases in subcortical grey matter structures of glioma patients after radio(chemo)therapy

Raschke, F.; Witzmann, K.; Seidlitz, A.; Wesemann, T.; Jentsch, C.; Platzek, I.; van den Hoff, J.; Kotzerke, J.; Beuthien-Baumann, B.; Baumann, M.; Linn, J.; Krause, M.; Troost, E. G. C.

Background and purpose: Radiotherapy (RT) is an adjuvant treatment option for glioma patients. Side effects include tissue atrophy, which might be a contributing factor to neurocognitive decline after treatment. The goal of this study was to determine potential atrophy of the hippocampus, amygdala, thalamus, putamen, pallidum and caudate nucleus in glioma patients having undergone magnetic resonance imaging (MRI) before and after RT. Materials and methods: Subcortical volumes were measured using T1-weighted MRI from patients before RT (N = 91) and from longitudinal follow-ups acquired in three-monthly intervals (N = 349). The volumes were normalized to the baseline values, while excluding structures touching the clinical target volume (CTV) or abnormal tissue seen on FLAIR imaging. A multivariate linear effects model was used to determine if time after RT and mean RT dose delivered to the corresponding structures were significant predictors of tissue atrophy. Results: The hippocampus, amygdala, thalamus, putamen, and pallidum showed significant atrophy after RT as function of both time after RT and mean RT dose delivered to the corresponding structure. Only the caudate showed no dose or time dependant atrophy. Conversely, the hippocampus was the structure with the highest atrophy rate of 5.2 % after one year and assuming a mean dose of 30 Gy. Conclusion: The hippocampus showed the highest atrophy rates followed by the thalamus and the amygdala. The subcortical structures here found to decrease in volume indicative of radiosensitivity should be the focus of future studies investigating the relationship between neurocognitive decline and RT. © 2022 The Authors

Keywords: Amygdala; Atrophy; Caudate; Hippocampus; Proton therapy; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-35044
Publ.-Id: 35044


Data publication: Electrokinetic Janus micromotors moving on topographically flat chemical patterns

Huang, T.; Misko, V.; Caspari, A.; Synytska, A.; Ibarlucea, B.; Nori, F.; Faßbender, J.; Cuniberti, G.; Makarov, D.; Baraban, L.

Uploaded data show the research discussions of the electroosmotic flows at the boundary between positive and negative surfaces .

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Permalink: https://www.hzdr.de/publications/Publ-35042
Publ.-Id: 35042


Comparison of manual and automated ventricle segmentation in the maternal immune stimulation rat model of schizophrenia

Winter, R.; Akinola, B.; Barroeta-Hlusicka, E.; Meister, S.; Pietzsch, J.; Winter, C.; Bernhardt, N.

Maternal immune stimulation (MIS) is strongly implicated in the etiology of neuropsychiatric disorders. Magnetic resonance imaging (MRI) studies provide evidence for brain structural abnormalities in rodents following prenatal exposure to MIS. Reported volumetric changes in adult MIS offspring comprise among others larger ventricular volumes, consistent with alterations found in patients with schizophrenia. Linking rodent models of MIS with non-invasive small animal neuroimaging modalities thus represents a powerful tool for the investigation of structural endophenotypes. Traditionally manual segmentation of regions-of-interest, which is laborious and prone to low intra- and inter-rater reliability, was employed for data analysis. Recently automated analysis platforms in rodent disease models are emerging. However, none of these has been found to reliably detect ventricular volume changes in MIS nor directly compared manual and automated data analysis strategies. The present study was thus conducted to establish an automated, structural analysis method focused on lateral ventricle segmentation. It was applied to ex-vivo rat brain MRI scans. Performance was validated for phenotype induction following MIS and preventive treatment data and compared to manual segmentation. In conclusion, we present an automated analysis platform to investigate ventricular volume alterations in rodent models thereby encouraging their preclinical use in the search for new urgently needed treatments.

Permalink: https://www.hzdr.de/publications/Publ-35041
Publ.-Id: 35041


Helical dislocations and dislocation line decoration in ion-irradiated Fe-9Cr studied by scanning transmission electron microscopy

Vogel, K.; Engelmann, H.-J.; Chekhonin, P.; Bergner, F.; Kaden, C.

Fe-9Cr is a model alloy for studying irradiation effects that are relevant for potential applications of high-chromium ferritic/martensitic steels in nuclear energy devices. Here we report on scanning transmission electron microscopy (STEM) studies of the microstructure of Fe-9Cr irradiated with 8 MeV Fe3+ ions. Two samples were irradiated with different ion fluences resulting in peak values of displacement damage of 2 and 10 dpa, respectively. The spatial distribution of irradiation-induced dislocation loops was studied with special emphasis on the effects of pre-existing network dislocations.
The most striking feature of the irradiated microstructure is the presence of helical dislocations. From comparison of the irradiated layer with the dislocation arrangement in the non-irradiated substrate it is concluded that the helices were formed from straight pre-existing line dislocations that originally had a dominating screw component. Other types of dislocations observed in the material did not adopt a helical shape during irradiation. Decreasing the dose has a significant effect on the helical dislocations, the helices are less developed and have a smaller diameter. For both irradiation conditions, an inhomogeneous distribution of irradiation-induced dislocation loops is observed. A high number of loops is present close to the helical dislocations and also close to dislocations that have not adopted a helical shape. In areas away from the dislocations, the number of visible loops is very low.
The loop clustering close to helical dislocations resembles observations reported for neutron irradiated Fe-9Cr. Hence we conclude that ion irradiations can produce similar defect configurations like neutron irradiations when the arrangement of pre-existing dislocations is comparable.

Keywords: irradiation-induced defects; helical dislocations; dislocation loops; ion-irradiated Fe-Cr; scanning TEM

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  • Poster
    Nuclear Materials Conference 2022, 24.-28.10.2022, Ghent, Belgium

Permalink: https://www.hzdr.de/publications/Publ-35040
Publ.-Id: 35040


Electrokinetic Janus micromotors moving on topographically flat chemical patterns

Huang, T.; Misko, V.; Caspari, A.; Synytska, A.; Ibarlucea, B.; Nori, F.; Faßbender, J.; Cuniberti, G.; Makarov, D.; Baraban, L.

Ionic and molecular selectivity are considered unique for the nanoscale and not realizable in microfluidics. This is due to the scale-matching problem – a difficulty to match the dimensions of ions and electrostatic potential screening lengths with micron-sized confinements. Here, we demonstrate a microscale realization of ionic transport processes closely resembling those specific to ionic channels or in nanofluidic junctions, including selectivity, guidance and flow focusing. As a model system, we explore electrokinetic spherical Janus micromotors moving over charged surfaces with complex charge distribution and without any topographical wall. We discuss peculiarities of the long-range electrostatic interaction on the behavior of the system including interface crossing and reflection of positively charged particles from negatively charged interfaces. These results are crucial for understanding the electrokinetic transport of biochemical species under confinement, have the potential to increase the precision of lab-on-chip-based assays, as well as broadening use cases and control strategies of nano-/micromachinery.

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Permalink: https://www.hzdr.de/publications/Publ-35039
Publ.-Id: 35039


Resummation for quantum propagators in bounded spaces

Edwards, J. P.; González-Domínguez, V. A.; Huet, I.; Trejo Espinosa, M. A.

We outline an approach to calculating the quantum mechanical propagator in the presence of geometrically nontrivial Dirichlet boundary conditions. The method is based on a generalization of an integral transform of the propagator studied in previous work (the so-called “hit function”) and a convergent sequence of Padé approximants that exposes the limit of perfectly reflecting boundaries. In this paper the generalized hit function is defined as a many-point propagator, and we describe its relation to the sum over trajectories in the Feynman path integral. We then show how it can be used to calculate the Feynman propagator. We calculate analytically all such hit functions in D = 1 and D = 3 dimensions, giving recursion relations between them in the same or different dimensions and apply the results to the simple cases of propagation in the presence of perfectly conducting planar and spherical plates. We use these results to conjecture a general analytical formula for the propagator when Dirichlet boundary conditions are present in a given geometry, also explaining how it can be extended for application for more general, nonlocalized potentials. Our work has resonance with previous results obtained by Grosche in the study of path integrals in the presence of delta potentials. We indicate the eventual application in a relativistic context to determining Casimir energies using this technique.

Keywords: Integral equations; Quantum theory; Bounded spaces; Convergent sequences; Dirichlet boundary conditions; Feynman path integrals; Generalisation; Integral transform; Pade approximants; Quantum mechanical; Reflecting boundary; Resummation

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Permalink: https://www.hzdr.de/publications/Publ-35038
Publ.-Id: 35038


Enhanced Longitudinal Relaxation of Magnetic Solitons in Ultrathin Films

Yastremsky, I. A.; Faßbender, J.; Ivanov, B. A.; Makarov, D.

Relaxation fundamentally determines the operation speed and energy efficiency of spintronic and
spinorbitronic devices. We develop a theory of the longitudinal contribution to the relaxation of domain
walls in ferromagnetic films of any thickness with the Dzyaloshinskii-Moriya interaction, which allows
quantitative comparison with experiments. We show that the longitudinal contribution increases with a
decrease of the transversal relaxation (e.g., the Gilbert constant). We predict a substantial enhancement
of the contribution of the longitudinal relaxation to the damping of magnetic solitons with a decrease of
the film thickness. We demonstrate that for ultrathin ferromagnetic films, the contribution of the longitudinal
relaxation to the damping of domain walls is comparable to or stronger than any other traditional
transversal mechanisms, including spin pumping. Although in this work we focus on the analysis of longitudinal
relaxation for domain walls, in ultrathin samples it should be taken into account also for other
magnetic solitons including skyrmions. This work adds to the fundamental understanding of the design
and optimization of spintronic and spinorbitronic devices based on moving solitons in ultrathin films.

Keywords: Longitudinal Relaxation; magnetic thin films; magnetic solitons

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Publ.-Id: 35037


Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Rezvanov, A. A.; Attallah, A. G.; Liedke, M. O.; Butterling, M.; Bogdanova, M. A.; Vishnevskiy, A. S.; Seregin, D. S.; Vorotyntsev, D. A. V.; Palov, A. P.; Hirschmann, E.; Wagner, A.; Naumov, S.; Vorotilov, K. A.; Rakhimova, T. V.; Rakhimov, A. T. R.; Baklanov, M.

Modification of spin-on-deposited porous PMO
(periodic mesoporous organosilica) ultralow-k (ULK) SiCOH
films (k = 2.33) containing both methyl terminal and methylene
bridging groups by vacuum ultraviolet (VUV) emission from Xe
plasma is studied. The temporal evolution of chemical composition,
internal defects, and morphological properties (pore structure
transformation) is studied by using Fourier transform infrared
spectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry,
ellipsometric porosimetry (EP), positron-annihilation lifetime
spectroscopy (PALS), and Doppler broadening positron-annihilation spectroscopy. Application of the different advanced diagnostics
allows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure in
the current investigation can be divided into two phases. During the first short phase, film loses almost all of its surface methyl and
matrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage is
found by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when the
treated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUV
exposure time according to PAS and EP data. The last is the result of the additional film shrinkage caused by atmosphere exposure.
During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all the
time as it is expected from in situ ellipsometry, but it is masked by the air exposure

Keywords: ultralow-k materials; vacuum ultraviolet emission; porosimetry; positron-annihilation spectroscopy; in situ ellipsometry

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Permalink: https://www.hzdr.de/publications/Publ-35036
Publ.-Id: 35036


Laser-generated supersonic plasma jets and shocks in a transverse magnetic field

Bohlin, H.; Brack, F.-E.; Cervenak, M.; Chodukowski, T.; Cikhardt, J.; Dostál, J.; Dudžák, R.; Hubner, J.; Huo, W.; Jelinek, S.; Klír, D.; Kroll, F.; Krupka, M.; Krůs, M.; Pisarczyk, T.; Rusiniak, Z.; Schramm, U.; T.-H, N.-B.; Weber, S.; Zaraś-Szydłowska, A.; Zeil, K.; Kumar, D.; Schlegel, T.; Tikhonchuk, V.

The influence of a transverse magnetic field on the formation and evolution of supersonic plasma jets and shocks was studied experimentally, and compared with 3D numerical simulations. An improved jet collimation was seen due to the change in the magnetic field topology restricting the radial expansion of the ablated plasma. The magnetic field was also shown to strongly affect the shock structures, both indirectly through the modified jet geometry, as well as due to a compression of the field lines in the shock region. The interaction characteristics were found to depend on the relative contribution of the magnetic and plasma pressure in balancing the ram pressure of the jet.

Keywords: Laser; Plasma; Astrophysics; Pulsed Magnet

Permalink: https://www.hzdr.de/publications/Publ-35035
Publ.-Id: 35035


Flue Dust Reactions and Sticking Mechanisms in a Copper Flash Smelting Furnace Waste Heat Boiler - A Sampling Study

Schmidt, A.; Guy, B. M.; Montenegro, V.; Reuter, M.; Charitos, A.; Stelter, M.; Richter, A.

Formation of accretion layers within the copper Flash Smelting Furnace Waste Heat Boiler is a serious operational concern, as it can potentially increase boiler downtime and hence limit continuous production. In previous Computational Fluid Dynamics studies, the accretion formation was predicted for an industrial-scaleWaste Heat Boiler, using a dust stickiness sub-routine of the model. In this study, a dust sampling campaign was used to validate this stickiness sub-routine. Furthermore, sticking and reaction mechanisms of flue dust were investigated and compared to thermodynamic predictions. While the sub-routine was validated, the comparison of thermodynamics and species in the samples showed that the thermodynamic conversion limit was not reached for the investigated species.

Keywords: Flash Smelting Furnace; Waste Heat Boiler; Flue Dust; Sampling Study; CFD

Permalink: https://www.hzdr.de/publications/Publ-35034
Publ.-Id: 35034


Transient CFD Calculation of Accretion Formation in a Copper Waste Heat Boiler

Schmidt, A.; Montenegro, V.; Reuter, M.; Charitos, A.; Stelter, M.; Richter, A.

The operation of a copper Flash Smelting Furnace (FSF) is often limited by the availability of the downstream Waste Heat Boiler (WHB). Carry-over of concentrate into the boiler leads to accretion formation, which can cause boiler downtime. Hence, the minimization of flue dust and its accretions is an important operational goal. In this study, a Computational Fluid Dynamics (CFD) model is used to investigate how three different baffle plate designs influence accretion formation over a period of 24h. The predicted dust accretion patterns were compared for all baffle plate modifications, with differences found both in the resulting sedimentation and accretion of dust particles. While the dispersive design led to large, but evenly coated accretion risk zones, a streamlined design minimized their size, but led to locally thick accretion layers. Based on these findings, design recommendations for the baffle plate were derived.

Keywords: Flash Smelting Furnace; Waste Heat Boiler; Flue Dust; Dust Accretions; CFD

Permalink: https://www.hzdr.de/publications/Publ-35032
Publ.-Id: 35032


Numerical modeling of horizontal stratified two-phase flows using the AIAD model

Yan, H.; Zhang, H.; Höhne, T.; Liao, Y.; Lucas, D.; Liu, L.

In nuclear reactor safety research, the countercurrent gas-liquid two-phase flow in the hot leg of a pressurized water reactor (PWR) has attracted considerable attention. Previous work has proven that the algebraic interfacial area density (AIAD) model implemented in ANSYS CFX can effectively capture the gas-liquid interface and avoid the loss of information regarding the interfacial structure, which occurs after phase averaging in the Euler–Euler two-fluid approach. To verify the accuracy of the AIAD module implementation in ANSYS Fluent, the model based on the experimental data from the WENKA facility is validated in this work. The effects of the subgrid wave turbulence model, turbulence damping model, and droplet entrainment model are simultaneously investigated, which have been shown to be important in the previous work with CFX. The results show that the simulations are considerably and significantly deviate from the experiments when the turbulence damping is not considered. The free surface modeling of two-phase flow can be optimized by using the droplet entrainment model. The consistency between the simulation and experimental results is not enhanced after the subgrid wave turbulence model is adopted. Further investigations regarding the implementation of the subgrid wave turbulence model are necessary.

Keywords: AIAD; CFD; droplet entrainment; subgrid wave turbulence; thermal hydraulics; turbulence damping

Permalink: https://www.hzdr.de/publications/Publ-35031
Publ.-Id: 35031


Understanding structure–properties relationships of porphyrin linked to graphene oxide through π–π-stacking or covalent amide bonds

Lewandowska-Andralojc, A.; Gacka, E.; Pedzinski, T.; Burdzinski, G.; Lindner, A. A.; O’Brien, J. M.; Senge, M. O.; Siklitskaya, A.; Kubas, A. G.; Marciniak, B.; Walkowiak-Kulikowska, J.

Two graphene oxide nanoassemblies using 5-(4-(aminophenyl)-10,15,20-triphenylporphyrin
(TPPNH2) were fabricated by two synthetic methods: covalent (GO-CONHTPP) and noncovalent
bonding. GO-CONHTPP was achieved through amide formation at the periphery of GO sheets and the
hybrid material was fully characterized by FTIR, XPS, Raman spectroscopy, and SEM. Spectroscopic
measurements together with theoretical calculations demonstrated that assembling TPPNH2
on the GO surface in DMF-H2O (1:2, v/v) via non-covalent interactions causes changes in the absorption
spectra of porphyrin, as well as efficient quenching of its emission. Interestingly, covalent binding
to GO does not affect notably neither the porphyrin absorption nor its fluorescence. Theoretical
calculations indicates that close proximity and π–π-stacking of the porphyrin molecule with the GO
sheet is possible only for the non-covalent functionalization. Femtosecond pump–probe experiments
revealed that only the non-covalent assembly of TPPNH2 and GO enhances the efficiency of the
photoinduced electron transfer from porphyrin to GO. In contrast to the non-covalent hybrid,
the covalent GO-CONHTPP material can generate singlet oxygen with quantum yields efficiency
(ΦΔ = 0.20) comparable to that of free TPPNH2 (ΦΔ = 0.26), indicating the possible use of covalent
hybrid materials in photodynamic/photothermal therapy. The spectroscopic studies combined with
detailed quantum-chemical analysis provide invaluable information that can guide the fabrication of
hybrid materials with desired properties for specific applications.

Keywords: porphyrin; graphene oxide; photochemistry

Permalink: https://www.hzdr.de/publications/Publ-35030
Publ.-Id: 35030


Ressourceneffizienzsteigerung in der Metallindustrie - Substitution von Primärrohstoffen durch optimiertes legierungsspezifisches Recycling

Raatz, S.; Seidel, P.; Tuma, A.; Thorenz, A.; Helbig, C.; Reller, A.; Faulstich, M.; Joachimsthaler, C.; Steger, S.; Hagedorn, W.; Bickel, M.; Liedtke, C.

Das durch das Umweltbundesamt geförderte Projekt befasst sich mit der Ressourceneffizienz-
steigerung in der Metallindustrie in Hinblick auf die Substitution von Primärrohstoffen, die im
Recyclingprozess zur Verdünnung unerwünschter Begleitelemente beim Recycling eine wesent-
liche Rolle spielen. Das damit einhergehend Downcycling soll mittels innovativer Sortiertechni-
ken (Kamera-/Sensorsysteme) vermindert und der Recyclingprozess von metallischen Legie-
rungen durch eine höhere Trennschärfe deutlich verbessert werden.
Der Fokus der Untersuchungen liegt in diesem Projekt auf der Untersuchung eines legierungs-
spezifischen Recyclings von Stahl-, Aluminium-, Kupfer- und Zinkschrotten. Hier soll der Ver-
gleich verschiedener Schrottfraktionen vor bzw. nach innovativen Analyse- bzw. Sortier- und Se-
parier-Prozessen neue Erkenntnisse liefern. Darüber hinaus werden definitorische Grundlagen
sowie Steuerungsgrößen für Up- und Downcycling und Regeln für sortenarmes Design erarbei-
tet.
Auf Grundlage der Analyseergebnisse werden politische Empfehlungen zur besseren Erschlie-
ßung bisher nicht genutzter, hochwertiger Metallpotenziale erarbeitet. Zu den Bewertungsmaß-
stäben gehören die Einsparpotenziale von primären Rohstoffen und damit Treibhausgasemissio-
nen sowie die Kostenstruktur für die Herstellung von möglichst hochwertigen Legierungen aus
Rezyklaten.
Eine erfolgreiche, das heißt mit minimalen Downcycling-Prozessen „belastete“ Bereitstellung
von sekundären Rohstoffen erfordert eine umfassende Wissensbasis über die wissenschaftli-
chen Hintergründe von Downcycling, bestehende Recyclingstrukturen und verwendete Sortier-
techniken, technologische Potenziale, metallurgische Prozesssimulationen und Bewertungsan-
sätzen von Recyclingprozessen, die im Rahmen dieses Projektes entwickelt und genutzt werden.

Keywords: Metallwirtschaft; OptiMet; Ressourceneffizienz; Downcycling; Sortierung; Recycling; Legierung; Sortiertechnologien; LIBS; XRT; XRF; NAA

  • Open Access Logo Other report
    06844 Dessau-Roßlau: Umweltbundesamt, 2022
    354 Seiten

Permalink: https://www.hzdr.de/publications/Publ-35029
Publ.-Id: 35029


A terminology for downcycling

Raatz, S.; Huether, J.; Joachimsthaler, C.; Lehmann, C.; Helbig, C.; Thorenz, A.; Faulstich, M.; Tuma, A.

The term downcycling is often used anecdotally to describe imperfections in recycling. However, it is rarely defined. Here, we identify six meanings of the term downcycling as used in scientific articles and reports. These encompass the material quality of reprocessed materials, target applications, product value, alloying element losses, material systems, and additional primary production. In a proposal for harmonized and more specific terminology, we define downcycling as the phenomenon of quality reduction of materials reprocessed from waste relative to their original quality. We further identify that the reduced quality can express itself thermodynamically, functionally, and economically, covering all perspectives on downcycling. Dilution, contamination, reduced demand for recycled materials, and design-related issues can cause those downcycling effects. We anticipate that this more precise terminology can help quantify downcycling, keep materials in the loop longer, use materials more often and at higher quality, and therefore assist in reducing material-related environmental impacts.

Keywords: circular economy; downcycling; downgrading; industrial ecology; recycling; waste

Permalink: https://www.hzdr.de/publications/Publ-35028
Publ.-Id: 35028


Electrical Conductivity of Iron in Earth’s Core from Microscopic Ohm’s Law (SCCS 22)

Lokamani, M.; Vorberger, J.; Cangi, A.; Baczewski, A.; Ramakrishna, K.

Understanding the electronic transport properties of iron under high temperatures and pressures is essential for constraining geophysical processes. The difficulty of reliably measuring these properties under for sophisticated theoretical methods that can support diagnostics. We present results of the electrical conductivity from simulating microscopic Ohm’s law using time-dependent density functional theory.

Keywords: TDDFT; Matter under Extreme Conditions; Computational Physics; Ab-initio methods

  • Lecture (Conference)
    Strongly Coupled Coulomb Systems (SCCS) 2022, 25.07.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35027
Publ.-Id: 35027


Steps towards Reliable Data - Basic Tools and Concepts

Pospiech, S.

Uncertainties in geochemical data can have many different sources. The previous workshop sections focused on the definitions of data reliability, uncertainties and errors, and how these can be calculated. In this part of the workshop, we will discuss how (hidden) uncertainties in data and errors in geochemical analyses can be detected during data handling, what measures help to minimize uncertainties and errors, and how to deal with the errors that arise to obtain data with high reliability. Simple but effective tools will be presented using a sample snow data set.

Keywords: workshop; geoanalsysis 2022; uncertainty; data reliability; snow

  • Lecture (Conference)
    Geoanalysis 2022, 06.-12.08.2022, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35026
Publ.-Id: 35026


Cosmic nucleosynthesis: A multi-messenger challenge

Diehl, R.; Korn, A. J.; Leibundgut, B.; Lugaro, M.; Wallner, A.

The origins of the elements and isotopes of cosmic material is a critical aspect of understanding the evolution of the universe. Nucleosynthesis typically requires physical conditions of high temperatures and densities. These are found in the Big Bang, in the interiors of stars, and in explosions with their compressional shocks and high neutrino and neutron fluxes. Many different tools are available to disentangle the composition of cosmic matter, in material of extraterrestrial origins such as cosmic rays, meteorites, stardust grains, lunar and terrestrial sediments, and through astronomical observations across the electromagnetic spectrum. Understanding cosmic abundances and their evolution requires combining such measurements with approaches of astrophysical, nuclear theories and laboratory experiments, and exploiting additional cosmic messengers, such as neutrinos and gravitational waves. Recent years have seen significant progress in almost all these fields; they are presented in this review.

The Sun and the solar system are our reference system for abundances of elements and isotopes. Many direct and indirect methods are employed to establish a refined abundance record from the time when the Sun and the Earth were formed. Indications for nucleosynthesis in the local environment when the Sun was formed are derived from meteoritic material and inclusion of radioactive atoms in deep-sea sediments. Spectroscopy at many wavelengths and the neutrino flux from the hydrogen fusion processes in the Sun have established a refined model of how the nuclear energy production shapes stars. Models are required to explore nuclear fusion of heavier elements. These stellar evolution calculations have been confirmed by observations of nucleosynthesis products in the ejecta of stars and supernovae, as captured by stardust grains and by characteristic lines in spectra seen from these objects. One of the successes has been to directly observe
rays from radioactive material synthesised in stellar explosions, which fully support the astrophysical models. Another has been the observation of radioactive afterglow and characteristic heavy-element spectrum from a neutron-star merger, confirming the neutron rich environments encountered in such rare explosions. The ejecta material captured by Earth over millions of years in sediments and identified through characteristic radio-isotopes suggests that nearby nucleosynthesis occurred in recent history, with further indications for sites of specific nucleosynthesis. Together with stardust and diffuse gamma-rays from radioactive ejecta, these help to piece together how cosmic materials are transported in interstellar space and re-cycled into and between generations of stars. Our description of cosmic compositional evolution needs such observational support, as it rests on several assumptions that appear challenged by recent recognition of violent events being common during evolution of a galaxy. This overview presents the flow of cosmic matter and the various sites of nucleosynthesis, as understood from combining many techniques and observations, towards the current knowledge of how the universe is enriched with elements.

Keywords: Nuclear Astrophysics; Nucleosynthesis; Stars; Supernovae; Interstellar medium; Stardust; accelerator mass spectrometry

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Permalink: https://www.hzdr.de/publications/Publ-35025
Publ.-Id: 35025


The recovery effects of electron-beam pulse treatment in Sn implanted Ge

Werner, Z.; Barlak, M.; Ratajaczak, R.; Kentsch, U.; Heller, R.; Munnik, F.; Konarski, P.; Dłużewski, P.; Pisarek, M.; Kozłowski, M.; Ażgin, J.; Zagórski, J.; Staszkiewicz, B.

The paper describes the recovery effects of pulsed electron beam treatment in Ge single crystals implanted with various doses of Sn ions at room and low temperatures. A protective coat of 100 nm Sn was applied as a sacrificial layer. The implanted layers were studied by RBS/cRBS (Rutherford BackScattering/channeled Rutherford BackScattering) method, SIMS (Secondary Ion Mass Spectrometry) and TEM (Transmission Electron Microscopy). Defects revealed in channelled RBS spectra were analysed by McChasy code. The results show that the Sn concentration attains 1% and more with very good substitutionality. They also reveal excellent lattice recovery after e-beam melting. Suggestions are derived as regards further improvement of pulsed e-beam technique.

Keywords: Germanium; Sn implantation; pulsed e-beam treatments; RBS/cRBS study; TEM and DLTS measurements

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Permalink: https://www.hzdr.de/publications/Publ-35024
Publ.-Id: 35024


Non-van der Waals quasi-2D materials; recent advances in synthesis, emergent properties and applications

Balan, A. P.; Puthirath, A. B.; Roy, S.; Costin, G.; Oliveira, E. F.; Saadi, M. A. S. R.; Sreepal, V.; Friedrich, R.; Serles, P.; Biswas, A.; Iyengar, S. A.; Chakingal, N.; Bhattacharyya, S.; Saju, S. K.; Pardo, S. C.; Sassi, L. M.; Filleter, T.; Krasheninnikov, A.; Galvao, D. S.; Vajtai, R.; Nair, R. R.; Ajayan, P. M.

The discovery of novel materials that are stable at ambient conditions with emergent functionalities is a pressing need of the
21st century to keep the pace of social and technological advancement in a sustainable manner. Nanotechnology and
nanomaterials are one of this kind and the current era has already witnessed several groundbreaking discoveries of
materials and disruptive technological advancements. Starting from 0D fullerene, the invention of 1D carbon nanotubes, and
most recently 2D graphene, all are allotropes of carbon, have brought a lot of research opportunities to understand different
physical and chemical phenomena at atomic and molecular scales and to convert such properties into useful applications.
Among them, 2D materials find special attention due to unique properties such as ballistic carrier transport, immunity from
substrate effects and commendable in plane mechanical robustness. However, the library of such materials is limited, and
one can see that most of the technically viable materials that are already industrialized in a large scale belong to the class of
non-van der Waals materials. The effect of confinement in one dimension on non-van der Waals materials remains
unexplored owing to the difficulty in fabricating these materials to the ultra-thin limit with large lateral size or area. Recent
advancement of cleaving non-van der Waals bulk materials to their ultra-thin counter parts through the state-of-the-art liquid
phase exfoliation approach leads to renewed research interest among scientific community. The existence of
cleaving/parting planes in certain directions of non-van der Waals materials, where the bonding strength is relatively weak
compared to other crystallographic directions of the bulk crystal, facilitate smooth exfoliation when subjected to shear force
through suitable methods. Herein, we attempt to discuss the rationale of such methods in the synthesis of non-van der
Waals 2D materials that possess cleavage/parting planes with a special attention to natural ores, and to review the recent
progress made in non-van der Waals two-dimensional materials with a special emphasis on emergent magnetism, catalysis,
energy storage, and optoelectronics and related applications.

Keywords: 2D magnetism; 2D materials; Catalysis; Non-van der Waals materials; Photodetectors; Tribology

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Permalink: https://www.hzdr.de/publications/Publ-35023
Publ.-Id: 35023


Experimental Study on Inter-Bubble Distances in Dense Bubbly Flows

Kipping, R.; Hampel, U.

The design of bubble column reactors require a comprehensive understanding of the fluid dynamics. The type of gas distributor has a main impact on bubble size distribution and flow regime. With increasing gas flow rate, the interaction of the bubble increases and the dispersion of the bubbles changes. Although these effects play an important role also on the mass transfer in bubble columns, the distance parameters of bubbles in dense swarms has been poorly investigated so far.

This contribution presents an experimental study carried out with ultrafast X-ray CT (UFXCT) on a dense bubbly flow. Experiments were conducted in a bubble column of 10 cm inner diameter and for gas superficial velocities up to 3.5 cms-1. UFXCT allows for non-invasive plane measurement of the phase distribution at different scanning heights of the column. Based on the extracted coordinates of the bubble centers the distances of nearest neighbors of all bubbles were computed. In addition, pair correlation function has been applied to reveal information on the near order of bubbles. The Sauter Mean Diameter was found to have a remarkable influence on the clustering characteristics and the near order of the bubbles.

  • Lecture (Conference) (Online presentation)
    15th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-15), 07.-10.08.2022, Ottawa, Canada

Permalink: https://www.hzdr.de/publications/Publ-35022
Publ.-Id: 35022


Tailored engineering of crystalline surface enabled by ion-irradiation-assisted femtosecond laser ablation

Ren, Y.; Wang, C.; Cui, Z.; Liu, H.; Han, X.; Liu, P.; Akhmadaliev, S.; Zhou, S.; Cai, Y.

Ion irradiation and femtosecond laser ablation (FLA) are powerful technologies for micro-/nano-machining of transparent materials. In this work, we demonstrate selective surface engineering of optical crystal surface via ion irradiation and subsequent FLA, namely ion-irradiation-assisted FLA. Based on the material modification effects in the ion-irradiated layers, different types of surface structuring characterized by grooves, nanogratings or sub-micron tracks are selectively induced by FLA. It is revealed that the ion-electron interaction induced localized lattice defects and related property modulation in target crystal play important roles in the formation and evolution of laser ablation regimes. Furthermore, the formation process of high-spatial-frequency nanograting is illustrated with the periodical enhancement of local field through the excitation of surface plasmon polaritons, which is experimentally supported through the measurements of transmission electron microscope and energy-dispersive spectroscopy. Our findings further clarify the ion- and laser-matter interactions and the correlation between these processes and surface modifications. The approach proposed in this work shows potential applications in the rapid fabrication of hybrid and versatile surface structures on crystalline materials.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35021
Publ.-Id: 35021


Plasmonic Nanoparticles Embedded in Nanomembrane Microcavity for Flexible Optical Tuning

Pang, C.; Li, R.; Dong, H.; Saggau, C. N.; Kern, F. L.; Potapov, P.; Schultz, J.; Lubk, A.; Hübner, R.; Kentsch, U.; Zhou, S.; Helm, M.; Chen, F.; Ma, L.; Schmidt, O. G.

The combination of plasmonic nanoparticles and optical microcavities has attracted broad interest for both fundamental and applied studies. However, the conventional scheme of plasmonic nanoparticles being located at microcavity outer surfaces suffers from serious problems such as significant radiative/scattering losses and chemical/mechanical instabilities. Here, silver nanoparticles (NPs) and dispersed ions embedded in nanomembrane-formed whispering-gallery-mode (WGM) microtube cavities are prepared by ion implantations as compact and stable optoplasmonic microcavities. Upon low ion fluence implantation, dispersed silver ions are generated in the tube cavity wall, leading to a redshift of the WGM resonant cavity modes due to the increased refractive index. The silver ions start to aggregate into plasmonic NPs in the cavity wall when increasing implantation ion fluences. The competition and transition between redshift induced by the refractive index increase and blueshift induced by the formation of plasmonic NPs are investigated. Moreover, quality factor enhancement of the WGM modes is observed owing to the improved light confinement caused by the presence of NPs. This work demonstrates a convenient approach for the fabrication of stable optoplasmonic microcavities and fine tuning of resonant modes, indicating wide applications such as wavelength selective tuning and enhanced light–matter interactions.

Keywords: ion implantation; microtube cavity; nanomembrane; plasmonic nanoparticles; resonant mode tuning

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Permalink: https://www.hzdr.de/publications/Publ-35020
Publ.-Id: 35020


Magnetic patterning using Ne, Co, and Dy FIB

Lenz, K.; Pablo-Navarro, J.; Klingner, N.; Hlawacek, G.; Samad, F.; Narkovic, R.; Hübner, R.; Kakay, A.; Canzever, H.; Pilz, W.; Meyer, F.; Mazarov, P.; Bischoff, L.; Bali, R.; Lindner, J.

Magnetic nanostructures needed for magnonics and spintronics are usually processed by conventional lithography techniques in combination with lift-off or broad-beam ion etching. However, it has been shown [1] that the quality and shape of the structures’ edges play an important role for the magnetization dynamics as structures become smaller and smaller. Furthermore, regarding optical measurement techniques, hard-to-remove resist masks that become hardened by ion etching are problematic. Direct-writing focused ion beams (FIB) do not have these issues. In addition, using non-standard ion species opens various paths for local magnetic patterning, i.e., influencing the magnetic properties locally.
I will present results for maskless magnetic patterning of ferromagnetic nanostructures using He and Ne ions as well as a few liquid metal alloy ion sources (LMAIS) for FIB systems. He/Ne FIBs are well established and commercially available. Irradiation of (paramagnetic) FeAl films by Ne ions creates local ferromagnetic nanostructures caused by disorder that are embedded in a paramagnetic matrix [2]. The precise Ne FIB also enables us to trim the edges of magnetic nanostructures enhancing their magnetic fidelity and creating certain localized magnon states at the edges of the samples. Using specifically developed LMAIS, like e.g., Co36Nd64, CoDy, or CuDy [3,4] in combination with a Wien mass filter offers further new paths for magnetic patterning. I will present results on the modification of Ni80Fe20 (permalloy) strip samples. Using the CoNd LMAIS a narrow track of Co ions was implanted. The induced magnetic changes were measured with microresonator ferromagnetic resonance (FMR) before and after the implantation. Structures as small as 30 nm can be implanted up to a concentration of 10 % near the surface. Such lateral resolution is hard to reach for other lithographic methods. Using Dy ions one can locally increase the Gilbert damping parameter of the magnetization dynamics by more than a factor of four with a lateral resolution of about 100 nm.

Keywords: FIB; ferromagnetic resonance; nanostructuring; ferromagnetism

Related publications

  • Invited lecture (Conferences)
    5. European FIB Network Workshop 2022, 31.08.-02.09.2022, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35019
Publ.-Id: 35019


Application of a Microfabricated Microwave Resonator in a Co-Pd–Based Magnetic Hydrogen-Gas Sensor

Schefer, T. A.; Narkovic, R.; Lenz, K.; Ganss, F.; Roberts, M. P.; Hellwig, O.; Martyniuk, M.; Lindner, J.; Kostylev, M.

We investigate the ferromagnetic resonance (FMR) response of microfabricated microwave resonators loaded with small Co16Pd84 alloy rectangles. A major increase in the FMR signal-to-noise ratio is achieved by employing the microwave-resonator structure. A FMR peak shift similar to that of Co16Pd84 continuous films is measured in the presence of hydrogen gas in the sample environment. We show that the very high sensitivity of the FMR signal of the Co16Pd84 alloy rectangle to hydrogen exposure can be used to measure relatively small hydrogen-concentration steps near 100% H2. Additionally, we also demonstrate that this structure can measure hydrogen over a concentration range from 3% to 100% H2 in N2. In time-dependent FMR measurements, we discover a temperature dependence of the FMR signal, which we relate to intrinsic temperature-dependent changes in saturation magnetization and the magnetic anisotropy of the Co-Pd alloy.

Keywords: hydrogen sensors; ferromagnetic resonance; CoPd alloys; Nanostructures; gas sensors

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-35018
Publ.-Id: 35018


Control and tunability of magnetic bubble states in multilayers with strong perpendicular magnetic anisotropy at ambient conditions

Salikhov, R.; Samad, F.; Arekapudi, S. S. P. K.; Ehrler, R.; Lindner, J.; Kiselev, N. S.; Hellwig, O.

The reversal of magnetic bubble helicity through topologically trivial transient states provides an additional
degree of freedom that promises the development of multidimensional magnetic memories. A key requirement
for this concept is the stabilization of bubble states at ambient conditions on application-compatible substrates.
In the present work, we demonstrate a stabilization routine for remanent bubble states in high perpendicular magnetic anisotropy [Co(0.44 nm)/Pt(0.7 nm)]X , X = 48, 100, and 150 multilayers on Si/SiO2 substrates by exploring the effect of external magnetic fields (Hm) of different strength and angles (θ) with respect to the film surface normal. By systematic variation of these two parameters, we demonstrate that remanent bubble density and mean bubble diameter can be carefully tuned and optimized for each sample. Our protocol based on magnetometry only reveals the densest remanent bubble states at Hm = 0.87Hs (Hs is the magnetic saturation field) and θ = 60◦–75◦ for all X with a maximum of 3700 domains/100 μm2 for the X = 48 sample. The experimental observations are supported by micromagnetic simulations, taking into account the nanoscale lateral grain structure of multilayers synthesized by magnetron sputter deposition, and thus helping to understand the different densities of the bubble states found in these systems.

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Permalink: https://www.hzdr.de/publications/Publ-35017
Publ.-Id: 35017


LDOS/SNAP data for MALA: Beryllium at 298K

Fiedler, L.; Cangi, A.

Beryllium data set for Machine Learning applications

This dataset contains DFT inputs, outputs, LDOS data and fingerprint vectors for a beryllium cell at ambient conditions and varying sizes. Different levels of k-grid convergence were employed:
-  Gamma point (gamma_point)
-  total energy convergence (k-grid converged to 1meV/atom to total energy difference, total_energy_convergence)
-  LDOS convergence (k-grid converged to LDOS without unphyiscal oscillations, ldos_convergence)

The data set contains a .zip file for each system size (see below), as well as one .zip file containing sample scripts for recalculation and preprocessing of data.
The cutoff energy was converged with respect to the energy convergence and held fixed 40Ry for all three levels of k-grids. Note that not for all sizes of unit cells data for all types of k-grid were generated.

Authors:

- Fiedler, Lenz (HZDR / CASUS)
- Cangi, Attila (HZDR / CASUS)

Affiliations:

HZDR - Helmholtz-Zentrum Dresden-Rossendorf

CASUS - Center for Advanced Systems Understanding

Dataset description

- Total size: 143G GB 
- System: Be128, Be256, Be512, Be1024, Be2048
- Temperature(s): 298K
- Mass density(ies): 1.896 gcc
- Crystal Structure: hpc (material mp-87 in the materials project)
- Number of atomic snapshots: 145
    - 40 (Be128)
    - 35 (Be256)
   - 30 (Be512)
   - 20 (Be1024)
   - 10 (Be2048)
- Contents:
   - ideal crystal structure: yes
    - MD trajectory: yes
    - Atomic positions: yes
   - DFT inputs: yes
    - DFT outputs (energies): yes
    - SNAP vectors: yes (partially, see below)
        - dimensions: XxYxZx94 (last dimension: first three entries are x,y,z coordinates, data size is 91), where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 447MB)
         - Be256: 144x72x120  (size per file: 893MB)
         - Be512: 144x144x120 (size per file: 1.8GB)
        - units: a.u./Bohr
    - LDOS vectors: yes (partially, see below)
        - dimensions: XxYxZx250, where X, Y, Z are:
         - Be128: 72x72x120 (size per file: 1.2GB)
         - Be256: 144x72x120  (size per file: 2.4GB)
         - Be512: 144x144x120 (size per file: 4.7GB)
        - units: 1/eV
      - note: LDOS parameters are the same for all sizes of the unit cell
    - trained networks: no

Data generation

Ideal crystal structures were obtained using the Materials Project. (https://materialsproject.org/materials/mp-87/)
DFT-MD calculations were performed using either QuantumESPRESSO (https://www.quantum-espresso.org/, QE, for Be128, Be256 and Be512) or the Vienna Ab initio Simulation Package (https://www.vasp.at/, VASP, for Be1024, Be2048). DFT calculations were performed using QuantumESPRESSO. 
For the VASP calculations, the standard VASP pseudopotentials were used. For Quantum Espresso, pslibrary was used (https://dalcorso.github.io/pslibrary/).
SNAP vectors were calculated using MALA (https://github.com/mala-project/mala) and its LAMMPS (https://github.com/mala-project/mala) interface. The LDOS was preprocessed using MALA as well.

Dataset structure

The folder called "sample_inputs" is provided to show how MALA preprocessing and LDOS calculation have been performed. 
For each temperature/mass density/number of atoms, the following subfolders exist:

- md_inputs: Input files for the MD simulations, either as QE or VASP file(s)
- md_outputs: The MD trajectory plus a numpy array containing the temperatures at the individual time steps
- gamma_point
- total_energy_convergence
- ldos_convergence

Each gamma_point/total_energy_convergence/ldos_convergence contains the following folders:

- ldos: holds the LDOS vectors
- fingerprints: holds the SNAP fingerprint vectors
- snapshots: holds the atomic positions of the atomic snapshots for which DFT and LDOS calculations were performed (as .xyz files)
- dft_outputs: holds the outputs from the DFT calculations, i.e. energies in the form of a QE output file
- dft_inputs: holds the inputs for the DFT calculations, in the form of a QE input file

Please note that the numbering of the snapshots is contiguous per temperature/mass density/number of atoms, NOT within the k-grids themselves. 
Also, LDOS and fingerprint files have only been calculated for snapshots in the ldos_convergence 
folders. Therefore, no LDOS and fingerprint files have been calculated for the 1024 anf 2048 atom systems.

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Permalink: https://www.hzdr.de/publications/Publ-35016
Publ.-Id: 35016


Immunohistochemical analyses of paraffin-embedded sections after primary surgery or trimodality treatment in esophageal carcinoma

Igbo, B. T.; Linge, A.; Frosch, S.; Suckert, T.; Stolz-Kieslich, L.; Löck, S.; Sankari Kumaravadivel, M.; Welsch, T.; Weitz, J.; Sommer, U.; Aust, D.; Troost, E. G. C.

Background: The microscopic tumor extension before, during or after radiochemotherapy (RCHT) and its correlation with the tumor microenvironment
(TME) are presently unknown. This information is, however, crucial in the era of image-guided, adaptive high-precision photon or particle therapy.
Materials and methods: In this pilot study, we analyzed formalin-fixed paraffin-embedded (FFPE) tumor resection specimen from patients with histologically
confirmed squamous cell carcinoma (SCC; n=10) or adenocarcinoma (A; n=10) of the esophagus, having undergone neoadjuvant radiochemotherapy followed by resection (NRCHT+R) or resection (R)]. FFPE tissue sections were analyzed by immunohistochemistry regarding tumor hypoxia (HIF-1α), proliferation (Ki67), immune status (PD1), cancer cell stemness (CXCR4), and p53 mutation status. Marker expression in HIF-1α subvolumes was part of a sub-analysis. Statistical analyses were performed using one-sided Mann-Whitney tests and Bland-Altman analysis.
Results: In both SCC and AC patients, the overall percentages of positive tumor cells among the five TME markers, namely HIF-1α, Ki67, p53, CXCR4 and PD1 after NRCHT+ R were lower than in the R cohort. However, only PD1 in SCC and Ki67 in AC showed significant association (Ki67: p=0.03, PD1: p=0.02). In the sub-analysis of hypoxic subvolumes among the AC patients, the percentage of positive tumor cells within hypoxic regions were statistically significantly lower in the NRCHT+R than in the R cohort across all the markers except for PD1.
Conclusion: In this pilot study, we showed changes in the TME induced by NRCHT in both SCC and AC. These findings will be correlated with microscopic tumor extension measurements in a subsequent cohort of patients.

Keywords: Tumor microenvironment; esophageal cancer; microscopic tumor extension; radiochemotherapy; whole slide image analysis

Permalink: https://www.hzdr.de/publications/Publ-35015
Publ.-Id: 35015


Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon

Jiang, H.; Wang, M.; Fu, J.; Li, Z.; Shaikh, M. S.; Li, Y.; Nie, C.; Sun, F.; Tang, L.; Yang, J.; Qin, T.; Zhou, D.; Shen, J.; Sun, J.; Feng, S.; Zhu, M.; Kentsch, U.; Zhou, S.; Shi, H.; Wei, X.

Highly sensitive short-wave infrared (SWIR) detectors, compatible with the silicon-based complementary metal oxide semiconductor (CMOS) process, are regarded as the key enabling components in the miniaturized system for weak signal detection. To date, the high photogain devices are greatly limited by a large bias voltage, low-temperature refrigeration, narrow response band, and complex fabrication processes. Here, we demonstrate high photogain detectors working in the SWIR region at room temperature, which use graphene for charge transport and Te-hyperdoped silicon (Te–Si) for infrared absorption. The prolonged lifetime of carriers, combined with the built-in potential generated at the interface between the graphene and the Te–Si, leads to an ultrahigh photogain of 109 at room temperature (300 K) for 1.55 μm light. The gain can be improved to 1012, accompanied by a noise equivalent power (NEP) of 0.08 pW Hz–1/2 at 80 K. Moreover, the proposed device exhibits a NEP of 4.36 pW Hz–1/2 at 300 K at the wavelength of 2.7 μm, which is exceeding the working region of InGaAs detectors. This research shows that graphene can be used as an efficient platform for silicon-based SWIR detection and provides a strategy for the low-power, uncooled, high-gain infrared detectors compatible with the CMOS process.

Keywords: short-wave infrared detector; lifetime; built-in potential; photogain; graphene; Te-hyperdoped Si

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Permalink: https://www.hzdr.de/publications/Publ-35014
Publ.-Id: 35014


HELIPORT and MLOps

Knodel, O.; Voigt, M.; Pape, D.; Lokamani, M.; Kelling, J.; Müller, S.; Gruber, T.; Juckeland, G.; Kessler, A.; Hein, J.; Schuller, B.

The talk introduces the use of HELIPORT for MLOps and introduces the general idea behind the HELIPORT project, which aims to make the entire life cycle of a scientific experiment or project discoverable, accessible, interoperable and reusable by providing an overview from a top-level perspective.

Keywords: Data Management; Metadata; FAIR; Data provenance; Digital Objects; MLOps; Machine Learning

  • Open Access Logo Lecture (others) (Online presentation)
    Optima WP7 Meeting, 10.08.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-35013
Publ.-Id: 35013


Epigenetic drugs in somatostatin type 2 receptor radionuclide theranostics and radiation transcriptomics in mouse pheochromocytoma models

Ullrich, M.; Richter, S.; Liers, J.; Drukewitz, S.; Friedemann, M.; Kotzerke, J.; Ziegler, C. G.; Nölting, S.; Kopka, K.; Pietzsch, J.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are catecholamine-producing tumors. In inoperable and metastatic cases, somatostatin type 2 receptor (SSTR2) expression allows for peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE. Insufficient receptor levels, however, limit treatment efficacy. This study evaluates whether the epigenetic drugs valproic acid (VPA) and 5-Aza-2'-deoxycytidine (DAC) modulate SSTR2 levels and sensitivity to [177Lu]Lu-DOTA-TATE in two mouse PCC models (MPC and MTT). Methods: Drug-effects on Sstr2/SSTR2 were investigated in terms of promoter methylation, mRNA and protein levels, and radiotracer binding. Radiotracer uptake was measured in subcutaneous allografts in mice using PET and SPECT imaging. Tumor growth and gene expression (RNAseq) were characterized after drug treatments. Results: DAC alone and in combination with VPA increased SSTR2 levels along with radiotracer uptake in vitro in MPC (high-SSTR2) and MTT cells (low-SSTR2). MTT but not MPC allografts responded to DAC and VPA combination with significantly elevated radiotracer uptake, although activity concentrations remained far below those in MPC tumors. In both models, combination of DAC, VPA and [177Lu]Lu-DOTA-TATE was associated with additive effects on tumor growth and specific transcriptional responses in gene sets involved in cancer and treatment resistance. Effects of epigenetic drugs were unrelated to CpG island methylation of the Sstr2 promoter. Conclusion: This study demonstrates that SSTR2 induction in mouse pheochromocytoma models has some therapeutic benefit that occurs via yet unknown mechanisms. Transcriptional changes in tumor allografts associated with epigenetic treatment and [177Lu]Lu-DOTA-TATE provide first insights into genetic responses of PCCs/PGLs, potentially useful for developing additional strategies to prevent tumor recurrence.

Keywords: decitabine; neuroendocrine tumors; radiation biology; small animal multimodal imaging; valproic acid

Permalink: https://www.hzdr.de/publications/Publ-35012
Publ.-Id: 35012


Data publication: Time-of-Flight spectroscopy for laser-driven proton beam monitoring

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Karsch, L.; Kraft, S.; Kroll, F.; Löser, M.; Nossula, A.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

This dataset contains the raw and evaluated data of the paper plus the script for plotting the results.

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Permalink: https://www.hzdr.de/publications/Publ-35011
Publ.-Id: 35011


The impact of Mn nonstoichiometry on the oxygen mass transport properties of La0.8Sr0.2MnyO3±δ thin films

Chiabrera, F.; Baiutti, F.; Börgers, J. M.; Harrington, G. F.; Yedra, L.; Liedke, M. O.; Kler, J.; Nandi, P.; de Dios Sirvent, J.; Santiso, J.; López-Haro, M.; Calvino, J. J.; Estradé, S.; Butterling, M.; Wagner, A.; Peiró, F.; de Souza, R. A.; Tarancón, A.

Oxygen mass transport in perovskite oxides is relevant for a variety of energy and information technologies. In oxide thin films, cation nonstoichiometry is often found but its impact on the oxygen transport properties is not well understood. Here, we used oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry (IEDP-SIMS) to study oxygen mass transport and the defect compensation mechanism of Mn-deficient La0.8Sr0.2MnyO3±δ epitaxial thin films. Oxygen diffusivity and surface exchange coefficients were observed to be consistent with literature measurements and to be independent on the degree of Mn deficiency in the layers. Defect chemistry modelling, together with a collection of different experimental techniques, suggests that the Mn-deficiency is mainly compensated by the formation of La_Mn^× antisite defects. The results highlight the importance of antisite defects in perovskite thin films for mitigating cationic nonstoichiometry effects on oxygen mass transport properties.

Keywords: LSM; perovskite oxides; cation nonstoichiometry; antisite defects

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Permalink: https://www.hzdr.de/publications/Publ-35008
Publ.-Id: 35008


Time-of-Flight spectroscopy for laser-driven proton beam monitoring

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Karsch, L.; Kraft, S.; Kroll, F.; Löser, M.; Nossula, A.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Application experiments with laser plasma-based accelerators (LPA) for protons have to cope with the inherent fluctuations of the proton source. This creates a demand for non-destructive and online spectral characterization of the proton pulses, which are for application experiments mostly spectrally filtered and transported by a beamline. Here, we present a scintillator-based time-of-flight (ToF) beam monitoring system (BMS) for the recording of single-pulse proton energy spectra. The setup’s capabilities are showcased by characterizing the spectral stability for the transport of LPA protons for two beamline application cases. For the two beamline settings monitored data of 122 and 144 proton pulses collected over multiple days were evaluated, respectively. A relative energy uncertainty of 5.5 % (1σ) is reached for the ToF BMS, allowing for a Monte-Carlo based prediction of depth dose distributions, also used for the calibration of the device. Finally, online spectral monitoring combined with the prediction of the corresponding depth dose distribution in the irradiated samples is demonstrated to enhance applicability of plasma sources in dose-critical scenarios.

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Permalink: https://www.hzdr.de/publications/Publ-35006
Publ.-Id: 35006


Synthesis, Structure–Activity Relationships, Radiofluorination, and Biological Evaluation of [18F]RM365, a Novel Radioligand for Imaging the Human Cannabinoid Receptor Type 2 (CB2R) in the Brain with PET

Teodoro, R.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Wenzel, B.; Bormans, G.; Kopka, K.; Brust, P.; Moldovan, R.-P.

The development of cannabinoid receptor type 2 (CB2R) PET radioligands has been intensively explored due to the pronounced CB2R upregulation in various pathological conditions, such as neuroinflammation and cancer. Herein we report on the enantioselective synthesis of a series of highly affine fluorinated indole-2-carboxamide ligands targeting the CB2R in the brain. Compound RM365 was selected for PET radiotracer development due to its high CB2R affinity (Ki = 2.1 nM) and pronounced selectivity over CB1R (factor >300). A fully automated copper-mediated radiofluorination of [18F]RM365 was established starting from the corresponding aryl boronic acid pinacol ester precursor. Preliminary in vitro evaluation of [18F]RM365 revealed an unprecedentedly high species differences affinity towards CB2R owing a dissociation constant (KD) of 2.32 nM for the human CB2R (hCB2R) and > 10000 nM for the rat CB2R (rCB2R). Metabolism studies in mice revealed high stability of [18F]RM365 with fractions of parent compound of > 90% in the brain and > 54% in the plasma at 30 min p.i.. PET imaging in a rat model of local hCB2R overexpression demonstrate the ability of [18F]RM365 to reach and selectively label the hCB2R in the brain with high signal-to-background ratio. Thus, [18F]RM365 is a very promising PET radioligand for the imaging of upregulated hCB2R expression under pathological conditions with high potential towards clinical application in humans.

Keywords: cannabinoid receptor type 2; indole-2-carboxamide; binding affinity; radiochemistry; fluorine-18 labeling; positron-emission tomography

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Permalink: https://www.hzdr.de/publications/Publ-35005
Publ.-Id: 35005


Towards the development of a PET radioligand for imaging gliomas bearing mIDH1

Kaur, S.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Wenzel, B.; Toussaint, M.; Kopka, K.; Moldovan, R.-P.

Introduction
Isocitrate dehydrogenase mutation 1 (mIDH1, IDH1R132H) is commonly reported in gliomas and is proposed as an interesting target for the diagnosis, prognosis and therapy for patients with gliomas. Some preclinical evaluations of 125I- or 18F-labeled mIDH1 ligands are reported for non-invasive imaging of mIDH1-bearing gliomas,1-3 however, to date, no radiotracers for PET imaging of mIDH1 are clinically available owing to hitherto low potency, selectivity and metabolic stability. Herein, the efforts to develop a novel mIDH1 selective PET radiotracer for imaging gliomas with mIDH1 are reported.
Methods
Compound GSK321 bearing the absolute configuration 3-R, 27-S (Fig.1) has been selected as the starting point to develop an 18F-labelled PET radioligand for imaging of mIDH1 due to the high potency (IC50 mIDH1 = 4.6 nM).4 A non-enantioselective synthesis of GSK321 was envisaged to get access to all stereoisomers for biological evaluation. The separation of the four stereoisomers of GSK321 was attempted via isocratic semi-preparative chiral HPLC using a CHIRALPAK IA column (10*250mm, 5µm) and an eluent mixture of ACN/H2O (1/1, v/v) at a flow rate of 3 mL/min. The IC50 values of separated stereoisomers of GSK321 were measured by enzymatic assays for wildtype IDH1 and IDH1R132H coupled to diaphorase. The introduction of the 18F-label into the most potent and selective stereoisomer of GSK321 will be performed via the copper-mediated radiofluorination of the corresponding boronic acid pinacol ester.
Results
The stereoisomeric mixture of GSK321 was synthesized from N-boc-protected piperidone with an overall yield of 22 % over seven steps. In a first attempt to separate the stereoisomers by semi-preparative chiral HPLC, only one enantiomeric pair [(3-R,27-S)- and (3-S,27-R)-GSK321)]was obtained in pure form which was further characterized by NMR spectroscopy. For the isolation of other enantiomeric pair [(3-R,27-S)- and (3-S,27-R)-GSK321], further chiral HPLC methods will be tested in the future. For (3-R,27-S)-GSK321, IC50 values of 6.5 and 477 nM were determined towards mIDH1 and wildtype IDH respectively. The opposite enantiomer, (3-S,27-R)-GSK321 inhibits mIDH1 with an IC50 of 242 nM.
Conclusions
Compound (3-R,27-S)-GSK321 proved as a suitable candidate for the development of an 18F-labeled radioligand for imaging of mIDH1 in glioma with PET. In the next steps, an enantioselective synthesis will be performed to give easy access to substantial amounts of (3-R,27-S)-GSK321 and the enantiomerically pure precursor for radiofluorination.

Keywords: mIDH1; radiofluorination; GSK321; PET (Positron Emission Tomography)

  • Lecture (Conference)
    MoBi 2022 - 5th GyMIC Molecular Imaging Symposium, 15.-16.09.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35004
Publ.-Id: 35004


Experimental investigation of fluid dynamics during gas-liquid swirl separation for a wide working range using a swirl element

Condriuc, I.; Kipping, R.; Schleicher, E.; Hampel, U.

The cost-effective production of large amounts of green hydrogen using a new generation of proton exchange membrane (PEM) electrolyzers generates very high gas fractions, resulting from the high current densities. Hence, the shift of operating membrane conditions in the anode circuit into new and hitherto incomprehensible areas occurs. The mass fraction of oxygen prevails over the mass fraction of hydrogen by a factor of 8. Thus, the space and material requirements for conventional separators are very high. The main goal for the separation process of oxygen from the two-phase flow mixture is a completely gas-free operation fluid before the water enters the heat exchanger. This requires the optimization of oxygen separation technologies. For this purpose, a vertically arranged separator on the pilot scale was built up at Helmholtz -Zentrum Dresden – Rossendorf, which is based on the principle of swirl separation. This contribution provides results on the experimental study of different types of swirl geometries, which have the main impact on the separation efficiency of the process. Different types of swirl geometries are investigated and the development of the gas core and its stability are analyzed for single and two-phase flow at various flow rates of the gas and the liquid.
Project
The authors acknowledge the financial support by the Federal Ministry of Education and Research of Germany in the programme ”H2GIGA. Project identification number: 03HY123E.

Keywords: gas-liquid separation; swirl separation

  • Lecture (Conference) (Online presentation)
    International Congress on Separation and Purification Technology (ISPT22), 10.-14.12.2022, Live and On-Demand, Live and On-Demand

Permalink: https://www.hzdr.de/publications/Publ-35003
Publ.-Id: 35003


Integration of energy transition and circularity in copper production: A techno-economic and environmental study

Parvez, A. M.; Abadias Llamas, A.

Over the years, energy transition (fossil to renewable) and sustainable economy (from linear to circular) are being regarded as the key approaches to comply and implement the regional and international environmental protocols. Meanwhile, copper demand has been increasing in the past decade and will continuously expand in future. Hence, the objective of this work was to systematically investigate the energy transition-circular economy approach in copper production through optimizing technological, economic, regulatory and societal variables. In particular, the potential of Power-to-X technology in the existing copper production chain was investigated, with a particular focus on copper recycling. The HSC Chemistry software was used to model and simulate copper production processes using secondary raw materials (e.g. waste printed circuit boards and copper-containing waste cable). A simulation-based techno-economic and environmental impact assessment was performed to evaluate the integration of the renewable energies into the secondary copper production. The results showed that enhanced sustainability can be achieved through adopting this integration. Finally, challenges associated from flexibility (e.g., fossil to renewable energy) in copper production have been identified and further discussed.

Keywords: Secondary Copper; Energy Transition; Circular Economy; Flexibility

  • Lecture (Conference)
    The COPPER 2022 conference, 13.-17.11.2022, Santiago, Chile

Permalink: https://www.hzdr.de/publications/Publ-35002
Publ.-Id: 35002


hmctFOAM - heat mass concentration transport FOAM

Personnettaz, P.; Weber, N.; Weier, T.

This software illustrates the applications of the programming
techniques detailed in the book chapter

Norbert Weber, Tom Weier (2022) Liquid Metal Batteries. In: Steven
Beale, Werner Lehnert (eds.) Electrochemical Cell Calculations with
OpenFOAM. Lecture Notes in Energy 42, pp. 193-212.

The included solver handles the heat and mass transport equations
under the assumption of pure diffusion and with solutal convection.
It is a single region solver that is based on laplacianFoam and
boussinesqPimpleFoam from OpenFOAM 6.

Keywords: liquid metal batteries; OpenFOAM

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Permalink: https://www.hzdr.de/publications/Publ-35001
Publ.-Id: 35001


Aliovalent Ta-Doping-Engineered Oxygen Vacancy Configurations for Ultralow-Voltage Resistive Memory Devices: A DFT-Supported Experimental Study

Barman, A.; Das, D.; Deshmukh, S.; Sarkar, P. K.; Banerjee, D.; Hübner, R.; Gupta, M.; Saini, C. P.; Kumar, S.; Johari, P.; Dhar, S.; Kanjilal, A.

Alteration of transport properties of any material, especially metal oxides, by doping suitable impurities is not straightforward as it may introduce multiple defects like oxygen vacancies (Vo) in the system. It plays a decisive role in controlling the resistive switching (RS) performance of metal oxide-based memory devices. Therefore, a judicious choice of dopants and their atomic concentrations is crucial for achieving an optimum Vo configuration. Here, we show that the rational designing of RS memory devices with cationic dopants (Ta), in particular, Au/Ti1−xTaxO2−δ/Pt devices, is promising for the upcoming non-volatile memory technology. Indeed, a current window of ∼104 is realized at an ultralow voltage as low as 0.25 V with significant retention (∼104 s) and endurance (∼105 cycles) of the device by considering 1.11 at % Ta doping. The obtained device parameters are compared with those in the available literature to establish its excellent performance. Furthermore, using detailed experimental analyses and density functional theory (DFT)-based first-principles calculations, we comprehend that the meticulous presence of Vo configurations and the columnar-like dendritic structures is crucial for achieving ultralow-voltage bipolar RS characteristics. In fact, the dopant-mediated Vo interactions are found to be responsible for the enhancement in local current conduction, as evidenced from the DFT-simulated electron localization function plots, and these, in turn, augment the device performance. Overall, the present study on cationic-dopant-controlled defect engineering could pave a neoteric direction for future energy-efficient oxide memristors.

Keywords: resistive memory; vacancy engineering; ultralow-voltage switching; conducting filaments; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-35000
Publ.-Id: 35000


Data publication: Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography

Kaever, C.; Windisch, D.

Benchmark data for the student work "Real-time Object Recognition for Ultrafast Electron Beam X-ray Computed Tomography" by Christian Kaever.

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Permalink: https://www.hzdr.de/publications/Publ-34999
Publ.-Id: 34999


Field-induced spin reorientation transitions in antiferromagnetic ring-shaped spin chains

Borysenko, Y.; Sheka, D.; Faßbender, J.; van den Brink, J.; Makarov, D.; Pylypovskyi, O.

Easy axis antiferromagnets are robust against external magnetic fields of moderate strength. Spin reorientations in strong fields can provide an insight into more subtle properties of antiferromagnetic materials, which are often hidden by their high ground state symmetry. Here, we investigate theoretically effects of curvature in ring-shaped antiferromagnetic achiral anisotropic spin chains in strong magnetic fields. We identify the geometry-governed helimagnetic phase transition above the spin-flop field between vortex and onion states. The curvature-induced Dzyaloshinskii--Moriya interaction results in the spin-flop transition being of first- or second-order depending on the ring curvature. Spatial inhomogeneity of the Neel vector in the spin-flop phase generates weak ferromagnetic response in the plane perpendicular to the applied magnetic field. Our work contributes to the understanding of the physics of curvilinear antiferromagnets in magnetic fields and guides prospective experimental studies of geometrical effects relying on spin-chain-based nanomagnets.

Keywords: antiferromagnetism; ring; spin-flop

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Permalink: https://www.hzdr.de/publications/Publ-34998
Publ.-Id: 34998


Das „lernende“ Standortauswahlverfahren für ein Endlager radioaktiver Abfälle - Interdisziplinäre Beiträge

Smeddinck, U.; Röhlig, K.-J.; Mbah, M.; Brendler, V.

Das Standortauswahlverfahren für Endlager hochradioaktiver Abfälle soll ein "lernendes" sein. Doch was bedeutet das? Im Gesetzestext und in der Begründung finden sich kaum konkrete
Hinweise zur Ausgestaltung des lernenden Verfahrens. Wissenschaft und Zivilgesellschaft führen den Diskurs über das lernende Standortauswahlverfahren seit geraumer Zeit. Insbesondere die zentralen Akteure des Standortauswahlverfahrens sind dazu aufgefordert, aktiv darin einzutreten und gegebenenfalls auch den Gesetzgeber einzubeziehen.
Der Band versammelt Beiträge aus verschiedenen Disziplinen, konturiert die fachlichen Anforderungen an ein wirklich lernendes Verfahren und ordnet die aktuelle Diskussion im Verhältnis zur Umsetzung des Standortauswahlverfahrens für ein Endlager nach den formalrechtlichen Vorgaben ein.

Keywords: Standortauswahlverfahren; Endlager; hochradioaktiver Abfall; Wissenschaft; Zivilgesellschaft; lernendes Verfahren

Permalink: https://www.hzdr.de/publications/Publ-34997
Publ.-Id: 34997


Three-Dimensional, Km-Scale Hyperspectral Data of Well-Exposed Zn–Pb Mineralization at Black Angel Mountain, Greenland

Lorenz, S.; Thiele, S. T.; Kirsch, M.; Unger, G.; Zimmermann, R.; Guarnieri, P.; Baker, N.; Vest Sørensen, E.; Rosa, D.; Gloaguen, R.

Hyperspectral imaging is an innovative technology for non-invasive mapping, with increas- ing applications in many sectors. As with any novel technology, robust processing workflows are required to ensure a wide use. We present an open-source hypercloud dataset capturing the complex but spectacularly well exposed geology from the Black Angel Mountain in Maarmorilik, West Green- land, alongside a detailed and interactive tutorial documenting relevant processing workflows. This contribution relies on very recent progress made on the correction, interpretation and integration of hyperspectral data in earth sciences. The possibility to fuse hyperspectral scans with 3D point cloud representations (hyperclouds) has opened up new possibilities for the mapping of complex natural targets. Spectroscopic and machine learning tools allow or the rapid and accurate characterization of geological structures in a 3D environment. Potential users can use this exemplary dataset and the associated tools to train themselves or test new algorithms. As the data and the tools have a wide range of application, we expect this contribution to benefit the scientific community at large.

Keywords: open-source dataset; hyperspectral data; spectral imaging; 3D hyperclouds; photogrammetry; Black Angel Maarmorilik; minimum wavelength mapping; interactive workflow

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Permalink: https://www.hzdr.de/publications/Publ-34996
Publ.-Id: 34996


Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing

Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type-doped Ge with an electron concentration in the order of 10^19-10^20 cm^{-3}. Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on P-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.

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Permalink: https://www.hzdr.de/publications/Publ-34995
Publ.-Id: 34995


Low thermal conductivity in bournonite PbCuSbS3: A comprehensive study

Zuniga-Puelles, E.; Cardoso-Gil, R.; Ozden, A.; Bulut, N.; Himcinschi, C.; Kortus, J.; Svitlyk, V.; Gumeniuk, R.

Two natural bournonites have been characterized by structural, chemical, spectroscopical, magnetic and thermodynamic analyses. This study confirmed them to possess the PbCuSbS3 stoichiometric composition and to be of an outstanding quality allowing us to consider their properties as being intrinsic for this material. Electronic structure calculations, electrical and spectroscopical characterizations reveal PbCuSbS3 to be a direct n-type semiconductor with an energy gap Eopt g = 1.69 eV, huge Seebeck coefficient and electrical resistivity (e.g. ∼-1200 μV K−1 and ∼ 1000 Ω m at RT, respectively). The thermal conductivity in PbCuSbS3 is found to be very low [κ(T) ∼ 2-0.5 W m−1 K−1 in temperature range 100-600 K] and to be dominated by optical phonons (T > 100 K), which poorly transport heat, strongly scatter the acoustic ones and substantially intensify the phonon-phonon umklapp processes. Additionally, strong phonon-phonon scattering in bournonite is caused by many empty voids in its structural arrangement as well as by more than 60 Raman modes appearing in the frequency range of 150-250 cm−1 (∼5-8 THz) at RT. All these result in high Gruneisen parameter (Γ = 4.8-3.2) and very short phonon mean free path (lph = 11-3 ˚A for 100-300 K). Thus, the low thermal conductivity in bournonite is a reflection of combination of many different factors leading to a huge phonon anharmonicity.

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Permalink: https://www.hzdr.de/publications/Publ-34993
Publ.-Id: 34993


Anti-cancer prodrug cyclophosphamide exerts thrombogenic effects on human venous endothelial cells independent of CYP450 activation – relevance to thrombosis

Krüger-Genge, A.; Köhler, S.; Laube, M.; Haileka, V.; Lemm, S.; Majchrzak, K.; Kammerer, S.; Schulz, C.; Storsberg, J.; Pietzsch, J.; Küpper, J.-H.; Jung, F.

Cancer patients are at a very high risk of serious thrombotic events, often fatal. The causes discussed include the detachment of thrombogenic particles from tumor cells or the adverse effects of chemotherapeutic agents. Cytostatic agents can either act directly on their targets or, in the case of a prodrug approach, require metabolization for their action. Cyclophosphamide (CPA) is a widely used cytostatic drug that requires prodrug activation by cytochrome P450 enzymes (CYP) in the liver. We hypothesize that CPA could induce thrombosis in one of the following ways: (1) damage to endothelial cells (EC) after intra-endothelial metabolization; or (2) direct damage to EC without prior metabolization. In order to investigate this hypothesis, endothelial cells (HUVEC) were treated with CPA in clinically relevant concentrations for up to 8 days. HUVECs were chosen as a model representing the first place of action after intravenous CPA administration. No expression of CYP2B6, CYP3A4, CYP2C9 and CYP2C19 was found in HUVEC, but a weak expression of CYP2C18 was observed. CPA treatment of HUVEC induced DNA damage and a reduced formation of an EC monolayer and caused an increased release of prostacyclin (PGI2) and thromboxane (TXA) associated with a shift of the PGI2/TXA balance to a prothrombotic state. In an in vivo scenario, such processes would promote the risk of thrombus formation.

Keywords: cancer; cyclophosphamide; human umbilical vein endothelial cells; HUVEC; liver; cytochrome P450 enzymes (CYP); thrombosis

Permalink: https://www.hzdr.de/publications/Publ-34992
Publ.-Id: 34992


Role of Ni, Si and P on the formation of solute-rich clusters under irradiation in Fe-Cr alloys

Gueye, P.-M.; Gómez-Ferrer, B.; Kaden, C.; Pareige, C.

After irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), minor solute elements as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small dislocation loops. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, Fe-15at.%Cr-X (X=Si, Ni, P, NiSiP) alloys of different composition have been ion irradiated and characterized using atom probe tomography. Irradiation were performed at 300 °C up to 2.5 dpa in four alloys: Fe15CrNi, Fe15CrSi, Fe15CrP and Fe15CrNiSiP. Influence of C atoms implanted during irradiation on the nanostructure evolution is also discussed. The study of the evolution of the nanofeatures formed under irradiation with the dose as a function of the composition highlights the role of P and C on the formation of the nano-clusters and confirm the radiation-induced nature of solute-rich clusters.

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Permalink: https://www.hzdr.de/publications/Publ-34991
Publ.-Id: 34991


Solute rich cluster formation and Cr precipitation in irradiated Fe-Cr-(Ni,Si,P) alloys: Ion and neutron irradiation

Pareige, C.; Etienne, A.; Gueye, P.-M.; Medvedev, A.; Kaden, C.; Konstantinovic, M.; Malerba, L.

Ion irradiation is a powerful and affordable tool to rapidly test a wide range of irradiation conditions and make the link with the corresponding microstructural evolution. However, several issues of transferability of results from ion to neutron irradiation have been evidenced. This paper presents an atom probe investigation of the microstructural evolution of FeCr-NiSiP alloys with different contents of Cr and minor solutes under both ion and neutron irradiation at 300 °C. Impurities and Cr are known to form solute rich clusters (SRCs) and ' clusters in ferritic and martensitic FeCr alloys, which are one of the causes of hardening. The objective of this work is to highlight the differences and the commonalities between ion and neutron irradiations in these alloys. The use of two ion beam energies (8 MeV and 5 MeV) revealed that this parameter has an impact on the formation of SRCs. The SRCs present similar characteristics after 8 MeV Fe ion irradiation and neutron irradiation, despite the different dose rate, when Ni, Si and P are present. It is not the case for 5 MeV Fe ions, for which the SRCs were less developed. A nonlinear effect of the concentration of minor elements has been evidenced, as well. The presence of Ni, Si and P has been shown to impact both the number density and the size of SRCs in Fe9CrNiSiP alloys and the onset of ' formation.

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Permalink: https://www.hzdr.de/publications/Publ-34990
Publ.-Id: 34990


Nanoindentation as a tool to assess mechanical property changes under ion irradiation

Kaden, C.; Bergner, F.

Nanoindentation using sharp, geometrically self-similar indenters has attracted much interest as a tool to assess the mechanical response of ion-irradiated materials. This tool is of value in the framework of both fast materials screening of candidate nuclear materials and more fundamental studies of radiation effects on materials. The ambition is to obtain bulk-equivalent information that can be correlated with macroscopic mechanical properties and is ideally transferable to neutron irradiation. A major challenge arises from the unavoidable interplay of the steep damage gradient in the thin ion-irradiated layer with the indentation size effect (ISE).
The talk will revisit aspects related to the good practise of conducting nanoindentation experiments. The main factors relevant for obtaining reproducible quantitative bulk-equivalent hardness values will be addressed. Finally, approaches aimed at isolating the bulk-equivalent irradiation-induced hardening in (thin and graded) ion-irradiated layers will be reviewed.

Keywords: nanoindentation; ion irradiation

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  • Invited lecture (Conferences)
    NUMAT2022 - The Nuclear Materials Conference, 24.-28.10.2022, Gent, Belgien

Permalink: https://www.hzdr.de/publications/Publ-34989
Publ.-Id: 34989


Cyclam with a phosphinate-bis(phosphonate) pendant arm is a bone-targeting carrier of copper radionuclides

Pazderová, L.; Benešová, M.; Havlíčková, J.; Vojtíčková, M.; Kotek, J.; Lubal, P.; Ullrich, M.; Walther, M.; Schulze, S.; Neuber, C.; Rammelt, S.; Pietzsch, H.-J.; Pietzsch, J.; Kubíček, V.; Hermann, P.

Ligands combining a bis(phosphonate) group with a macrocycle function as metal isotope carriers for radionuclide-based imaging and for treating bone metastases associated with several cancers. However, bis(phosphonate) pendant arms often slow down complex formation and decrease radiochemical yields. Nevertheless, their negative effect on complexation rates may be mitigated by using a suitable spacer between bis(phosphonate) and the macrocycle. To demonstrate the potential of bis(phosphonate) bearing macrocyclic ligands as a copper radioisotope carrier, we report the synthesis of a new cyclam derivative bearing a phosphinate-bis(phosphonate) pendant (H5te1PBP). The ligand showed a high selectivity to CuII over ZnII and NiII ions, and the bis(phosphonate) group was not coordinated in the CuII complex, strongly interacting with other metal ions in solution. The CuII complex formed quickly, in 1 s, at pH 5 and at a millimolar scale. The complexation rates significantly differed under a ligand or metal ion excess due to the formation of reaction intermediates differing in their metal-to-ligand ratio and protonation state, respectively. The CuII-te1PBP complex also showed a high resistance to acid-assisted hydrolysis (t1/2 2.7 h; 1 M HClO4, 25 °C) and was effectively adsorbed on the hydroxyapatite surface. H5te1PBP radiolabeling with [64Cu]CuCl2 was fast and efficient, with specific activities of approximately 30 GBq 64Cu per 1 μmol of ligand (pH 5.5, room temperature, 30 min). In a pilot experiment, we further demonstrated the excellent suitability of [64Cu]CuII-te1PBP for imaging active bone compartments by dedicated small animal PET/CT in healthy mice and subsequently in a rat femoral defect model, in direct comparison with [18F]fluoride. Moreover, [64Cu]CuII-te1PBP showed a higher uptake in critical bone defect regions. Therefore, our study highlights the potential of [64Cu]CuII-te1PBP as a PET radiotracer for evaluating bone healing in preclinical and clinical settings with a diagnostic value similar to that of [18F]fluoride, albeit with a longer half-life (12.7 h) than 18F (1.8 h), thereby enabling extended observation times.

Permalink: https://www.hzdr.de/publications/Publ-34988
Publ.-Id: 34988


Synchronization dynamics on power grids in Europe and the United States

Ódor, G.; Deng, S.; Hartmann, B.; Kelling, J.

Dynamical simulation of the cascade failures on the EU and USA high-voltage power grids has been done via solving the second-order Kuramoto equation. We show that synchronization transition happens by increasing the global coupling parameter K with metasatble states depending on the initial conditions so that hysteresis loops occur. We provide analytic results for the time dependence of frequency spread in the large K approximation and by comparing it with numerics of d=2,3 lattices, we find agreement in the case of ordered initial conditions. However, different power-law (PL) tails occur, when the fluctuations are strong. After thermalizing the systems we allow a single line cut failure and follow the subsequent overloads with respect to threshold values T. The PDFs p(Nf) of the cascade failures exhibit PL tails near the synchronization transition point Kc. Near Kc the exponents of the PL-s for the US power grid vary with T as 1.4≤τ≤2.1, in agreement with the empirical blackout statistics, while on the EU power grid we find somewhat steeper PL-s characterized by 1.4≤τ≤2.4. Below Kc we find signatures of T-dependent PL-s, caused by frustrated synchronization, reminiscent of Griffiths effects. Here we also observe stability growth following the blackout cascades, similar to intentional islanding, but for K>Kc this does not happen. For Tc, bumps appear in the PDFs with large mean values, known as "dragon king" blackout events. We also analyze the delaying/stabilizing effects of instantaneous feedback or increased dissipation and show how local synchronization behaves on geographic maps.

Keywords: Kuramoto model; synchronization; synchronization transition; power grid

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Permalink: https://www.hzdr.de/publications/Publ-34987
Publ.-Id: 34987


First experiences with custom pipelines for compression

Gernhardt, F. P. D.; Steinbach, P.

This presentation gives an overview of our recent activities in the development of custom pipelines for data compression.

Keywords: Data compression; Tomography

  • Open Access Logo Lecture (Conference)
    LEAPS-Innov Annual Meeting 2022, 03.-05.05.2022, Barcelona, Spanien

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Permalink: https://www.hzdr.de/publications/Publ-34986
Publ.-Id: 34986


The Open Science Initiative for Perfusion Imaging (OSIPI): ASL Pipeline inventory

Fan, H.; Mutsaerts, H. J. M. M.; Anazodo, U.; Arteaga, D.; Baas, K. P. A.; Buchanan, C.; Camargo, A.; Keil, V. C.; Lin, Z.; Lindner, T.; Hirschler, L.; Hu, J.; Padrela, B. E.; Taghvaei, M.; Thomas, D. L.; Dolui, S.; Petr, J.

Purpose: To create an inventory of automated image processing pipelines of Arterial Spin Labeling (ASL) and summarize their features and accessibility for users to choose an optimal pipeline to fit their needs.

Methods: Pipeline developers were invited to self-assess their pipelines using a questionnaire developed by the Task Force 1.1 of the Open Science Initiative for Perfusion Imaging (OSIPI). Additionally, publicly available pipelines were evaluated by two independent testers using an objective unified scoring system. The testing focused on the capability, flexibility, and ease of use of the pipelines on various datasets.

Results: The developers of twenty-one pipelines filled in the questionnaire. Most pipelines support data from the three major vendors, i.e., GE (n=15), Philips (n=15), and Siemens (n=16), are free for research (n=18), work with the standard neuroimaging data format NIfTI (n=15), and can process standard 3D single PLD pseudo-continuous ASL images (n=21). Pipelines mainly differed in their support of advanced sequences and advanced features. Nine publicly available pipelines were included in the independent testing. Whereas certain pipelines were easy to use for users without programming skills, other pipelines offered more flexibility for configuring advanced processing options.

Conclusion: ASL data from the most commonly used ASL sequences saved in the standard neuroimaging data formats can be easily processed using publicly available pipelines. A specific choice of a pipeline should consider specific requirements on features and users’ skills, and the ASL inventory can serve as a valuable guide to facilitate this choice.

Permalink: https://www.hzdr.de/publications/Publ-34985
Publ.-Id: 34985


The value of arterial spin labelling perfusion MRI in brain age prediction

Dijsselhof, M.; Barboure, M.; Stritt, M.; Nordhøy, W.; Wink, A. M.; Beck, D.; Westlye, L. T.; Cole, J. H.; Barkhof, F.; Mutsaerts, H. J. M. M.; Petr, J.

Background: Biological brain age estimates from structural MRI data and their difference from chronological age — the brain age gap (BAG) — have been successfully applied in a range of diseases, but remain limited to capturing structural characteristics only. To incorporate physiological properties, we operationalized ‘Cerebrovascular brain age’ using a combination of structural, and arterial spin labelling (ASL) image data, investigate their optimal feature and algorithm combinations, and evaluate its repeatability.
Methods: Healthy participants (n = 341, 62 % female, age 59.7 ± 14.8 years, range: 21 - 95 years) were scanned at baseline and after 1.7 ± 0.5 years (n = 248, 62.9 % female, mean age 62.4 ± 13.3 years, range: 27 - 86). At 3 T MRI, 3D structural T1-weighted (T1w) and Fluid Attenuated Inversion Recovery (FLAIR), and 3D ASL image data were acquired to extract within grey matter (GM) and deep white matter (WM) ROIs: volumetrics, WM hyperintensity volume and count; and cerebral blood flow (CBF) and spatial coefficient of variation (CoV). Multiple combinations of features and machine learning algorithms were evaluated to train brain age algorithms on 70 % of the subjects and evaluated on the remainder, for 300 Monte-Carlo cross-validations, using the Mean Absolute Error (MAE). Feature importance of the best performing model was assessed by determining the feature weights. Model repeatability of the best model was assessed by comparing the BAGs between baseline and follow-up, also using T1w + FLAIR or ASL-only features.
Results: The lowest MAE was observed for the ElasticNetCV algorithm using T1w + FLAIR + ASL (MAE = 5.03 ± 0.34 years) and significantly better compared to using T1w + FLAIR (MAE = 6.01 ± 0.39, p < 0.01) and ASL-only features (MAE = 6.04 ± 0.39, R2 = 0.70 ± 0.04, p < 0.01). The three most important features were GM CBF (6.2 ± 1.18), GM/ICV (5.34 ± 0.6), and WM CBF (4.16 ± 0.36).
Average baseline and follow-up BAGs were not different (-1.51 ± 6.29 and -1.14 ± 6.40 years respetively, ICC = 0.85, 95% CI: 0.79 - 0.90, p = 0.16). The ElasticNetCV model with T1w+FLAIR+ASL performed similar to the same model with the T1w + FLAIR feature set (0.37 ± 3.48 years and 0.01 ± 2.95 years respectively, p = 0.14), and the ASL-only feature set (0.29 ± 4.03, p = 0.39).
Conclusion: The addition of ASL features to structural brain age improved brain age prediction, with the ElasticNetCV algorithm and a combination of all tested features (T1w+FLAIR+ASL) performing the best in a cross-sectional and repeatability comparison. These findings encourage future studies to explore the value of ASL in brain age in various pathologies.

Permalink: https://www.hzdr.de/publications/Publ-34984
Publ.-Id: 34984


Current- and Oersted-field- dynamics of a Bloch Point in cylindrical Ni nanowires

Fernandez Roldan, J. A.; Oksana, C.-F.

As three-dimensional nanomagnetism evolves, novel non-trivial magnetic textures emerge as appealing information carriers for spintronics based on curved nanosystems and particularly Cylindrical Nanowires (NWs) [1,2]. One of the most fascinating candidates that is likely to reach the high velocities required for fast recording technologies is the Bloch Point (BP) domain wall (DW). Recently, theoretical evidence indicated that BPs in NWs could reach high velocities close to 2 km/s in the magnonic regime [2]. While the observation of the BP DW in cylindrical NWs is no longer recent [2], scarce numerical studies that combine both spin-polarized current and Oersted field have been published in NWs [4,5], despite first attempts to measure DW velocities are in progress [6].
In this work we evaluate the dynamics of the BP DW under both current directions in a Ni NW with 100 nm in diameter. We investigate two cases: i) pre-nucleated BP DW, and ii) the BP DW formed from the transformation of a Vortex-Antivortex DW. Here the effects of both spin-polarized current and Oersted field are considered. We discuss in detail the role of the chirality of the BP in relation to the Oersted field, also reported previously in precursors of BPs [4].

Here we show that while the pre-nucleated DW with the same chirality as that of the Oersted field propagates always against the current direction, the BP originated either from the transformation of the BP with the opposite chirality or from the vortex-antivortex DW can either stop the propagation or propagate parallel to the current. Finally, we provide values of the velocities achieved by the BP in the NW as a function of applied current in Fig. 1.

We conclude that BPs with vanishing momentum propagate opposite to the current with velocities that may be suppressed by the Oersted field. Importantly for spintronic applications, momentum plays a major role in the dynamics of BPs that has not been envisaged up to know.

[1] A. Fernandez-Pacheco et al., Three-dimensional nanomagnetism. Nat Commun 8, 15756 (2017)
[2] S. Da Col et al., Observation of Bloch-point domain walls in cylindrical magnetic nanowires, Phys. Rev. B, 89, 180405 (2014).
[3] X.-P. Ma et al., Cherenkov-type three-dimensional breakdown behavior of the Bloch-point domain wall motion in the cylindrical nanowire, Appl. Phys. Lett. 117, 062402 (2020).
[4] J.A. Fernandez-Roldan et al., Electric current and field control of vortex structures in cylindrical magnetic nanowires, Phys. Rev. B 102, 024421 (2020).
[5] C. Bran et al, Magnetic Configurations in Modulated Cylindrical Nanowires, Nanomaterials 11, 600 (2021). DOI: 10.3390/nano11030600
[6] M. Schöbitz et al., Fast Domain Wall Motion Governed by Topology and Oersted Fields in Cylindrical Magnetic Nanowires. Phys. Rev. Lett. 123, 217201 (2019).

Keywords: Bloch Point; magnetic domain wall; cylindrical nanowire; current; Oersted field

  • Poster
    XXXVIII Biennial of Physics of the Spanish Royal Physics Society (R.S.E.F.), 11.-15.07.2022, Murcia, Spain
  • Lecture (Conference)
    2022 Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34983
Publ.-Id: 34983


Tidally Forced Planetary Waves in the Tachocline of Solar-like Stars

Horstmann, G. M.; Mamatsashvili, G.; Giesecke, A.; Zaqarashvili, T.; Stefani, F.

Can atmospheric waves in planet-hosting solar-like stars substantially resonate to tidal forcing, perhaps at a level of impacting the space weather or even being dynamo-relevant? In particular, low-frequency Rossby waves, which have been detected in the solar near-surface layers, are predestined to respond to sunspot cycle-scale perturbations. In this paper, we seek to address these questions as we formulate a forced wave model for the tachocline layer, which is widely considered as the birthplace of several magnetohydrodynamic planetary waves, i.e., Rossby, inertia-gravity (Poincaré), Kelvin, Alfvén, and gravity waves. The tachocline is modeled as a shallow plasma atmosphere with an effective free surface on top that we describe within the Cartesian β-plane approximation. As a novelty to former studies, we equip the governing equations with a conservative tidal potential and a linear friction law to account for viscous dissipation. We combine the linearized governing equations into one decoupled wave equation, which facilitates an easily approachable analysis. Analytical results are presented and discussed within several interesting free, damped, and forced wave limits for both midlatitude and equatorially trapped waves. For the idealized case of a single tide-generating body following a circular orbit, we derive an explicit analytic solution that we apply to our Sun for estimating leading-order responses to Jupiter. Our analysis reveals that Rossby waves resonating to low-frequency perturbations can potentially reach considerable velocity amplitudes on the order of 101–102 cm s−1, which, however, strongly rely on the yet unknown frictional damping parameter.

Keywords: Sun: interior; Sun: magnetic fields; Sun: oscillations

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Permalink: https://www.hzdr.de/publications/Publ-34982
Publ.-Id: 34982


Data: Study of a possible silicon photomultiplier based readout of the large plastic scintillator neutron detector NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; Boretzky, K.; Gasparic, I.; Stach, D.; Wagner, A.; Zuber, K.

The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV
neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany.
In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each
end by fast timing photomultipliers.
Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM)
are reported.  For this purpose, a typical NeuLAND bar was instrumented on each end with a prototype of the same
geometry as a 1” photomultiplier tube, including four 6×6 mm2 SiPMs, amplifiers, high voltage supply, and micro-
controller.
Tests were carried out using the 35 MeV electron beam from the ELBE superconducting linac with its ps-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-usermode with 1-60 electrons per bunch, using Acqiris fast digitizers. In addition, offline tests using cosmic rays and the NeuLAND data acquisition scheme were carried out.
Typical time resolutions of σ≤120 ps were found for ≥ 95% efficiency, improving on previous work at ELBE and exceeding the NeuLAND timing goal of σ <150 ps. Over a range of 10-300 MeV deposited energy in the NeuLAND bar,  the  gain  was  found  to  deviate  by ≤ 10%  (≤20%)  from  linearity  for  35μm  (75μm)  SiPM  pitch,  respectively, satisfactory for calorimetric use of the full NeuLAND detector.  The dark rate of the prototype studied was found to
be 70-200 s-1, comparable with the unavoidable cosmic-ray induced background.

The dataset contains the with the Acqiris Digitzier recorded waveforms and analysis scripts for interpretation of the data. Also GEANT4 simulations of the light propagation in a NeuLAND bar and the electron beam propagation are included.

Keywords: SiPM; saturation; NeuLAND; dark rate; electron beam; timeresolution

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Permalink: https://www.hzdr.de/publications/Publ-34981
Publ.-Id: 34981


Preface: State of the art in mineral exploration

Alcalde, J.; Carbonell, R.; Pospiech, S.; Gil, A.; Bullock, L. A.; Tornos, F.

Minerals that comprise raw materials for energy, metal, construction and other industrial applications are considered strategic commodities, fundamental in stock markets worldwide, and key ingredients to sustain our ever more technology-based society (Wellmer et al., 2019). The utilization of such economically important minerals has shown a continued steady increase since the early twentieth century, with a greater focus in recent years on resources required for the development of renewable technologies, such as wind and solar operations, and for electrification of domestic and transportation systems (e.g. concrete, aluminium, chromium, copper, iron, manganese, molybdenum, nickel, zinc or rare earths) (Meinert et al., 2016). As our society ramps up the global transition to low-carbon energies and a reduced reliance on fossil fuels, the inevitable rise in consumption and demand for a more diverse range of resources can only be facilitated through increasingly novel methods of mineral exploration (Ali et al., 2017).

Keywords: mineral exploration; state of the art; geophysics; geochemistry; geology; remote sensing; critical raw materials

Permalink: https://www.hzdr.de/publications/Publ-34980
Publ.-Id: 34980


Creating reproducible, scalable, portable and adaptable CFD validation workflows with Snakemake

Lehnigk, R.; Lucas, D.; Rehm, M.; Schlegel, F.

The modelling and simulation of nuclear reactors is increasingly carried out with open-source tools. To researchers, the most appealing benefits are the possibility to study and verify existing implementations and the freedom to add code for prototyping new concepts and models. Further, there is no direct dependency on a software manufacturer, which generally makes open-source codes a solid basis for collaboration. An important downside however is that the responsibility of controlling quality and reliability lies with the users. For actively developed code this is a continuous task and demands considerable resources which should be bundled.
In the area of Computational Fluid Dynamics, a well-established open-source solution is OpenFOAM. Its development follows agile principles with a strong focus on maintainability and usability. This increases the demands on users to keep their setups functional. Since 2020, HZDR is creating an IT environment that supports the centralized and continuous maintenance of OpenFOAM code and simulation setups developed by members of the German nuclear safety research community. The project focuses on work relevant for the reactor cooling system and is referred to as OpenFOAM_RCS. Both, an addon to the OpenFOAM release from The OpenFOAM Foundation and a dedicated repository for simulation setups are supplied. The basis for the project is the web-based software development environment GitLab provided by the Helmholtz Federated IT Services (HIFIS), which allows for a high degree of automation with the help of continuous integration and deployment pipelines. Part of the project is the creation of a validation workflow
Validation workflows should, among other things: (1) allow for continuous and automated checks of the setup input syntax; (2) frequently validate the simulation results by comparison against reference solutions; (3) be able to evaluate the impact of model substitutions on the overall “goodness” of results; (4) automatically create self-contained reports; (5) be executable on different environments, i.e. be portable and scalable; (5) allow for easy integration of new setups, i.e. be adaptable; (6) enable design point studies; (7) be comprehensible, ideally be self-documenting; (8) follow well-defined standards.
All aforementioned requirements can be fulfilled with the popular and actively developed Python-based workflow management system Snakemake (Mölder et al., 2021), which was originally written for Bioinformatics workflows, but is far more versatile. In this work Snakemake is configured to embed all setups archived in OpenFOAM_RCS in a single workflow. Execution of simulation setups is controlled via so-called Snakefiles, which list inputs and outputs of a simulation, the required resources as well as the commands to run them. Within a top-level configuration file utilizing the easy to read markup language YAML, all setups to be incorporated in a workflow are listed. Once properly configured, users can run the workflow in four steps: (1) configuration, i.e. assembly of selected setups; (2) running the simulations; (3) post-processing the simulations; (4) creating HTML reports gathering all generated plots together with runtime statistics and provenance information. The third step can be executed on a workstation or a cluster. For the latter case, a top-level job organizes the workflow and automatically submits sub-jobs to the cluster.
The proposed framework provides the opportunity to reduce cost and effort for CFD validation and verification. It also is of great help for complex model development such as multi-phase CFD where a large range of test cases and test conditions is mandatory to judge the performance of a given model choice.

This work is carried out in the frame of a current research project funded by the German Federal Ministry for Environment, Nature Conservation, Nuclear Safety and Consumer Protection, project number 1501604.

  • Lecture (Conference)
    Computational Fluid Dynamics for Nuclear Reactor Safety (CFD4NRS-9), 20.-21.02.2023, College Station, Texas, United States of Americs
  • Lecture (Conference) (Online presentation)
    34th German CFD Network of Competence Meeting, 14.-15.03.2023, München, Deutschland
  • Lecture (others) (Online presentation)
    Framatome CFD-Community Meeting, 30.03.2023, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34979
Publ.-Id: 34979


Spin-wave channeling in magnetization-graded nanostrips

Gallardo, R. A.; Alvarado-Seguel, P.; Brevis, F.; Roldán-Molina, A.; Lenz, K.; Lindner, J.; Landeros, P.

Magnetization-graded ferromagnetic nanostrips are proposed as potential prospects to channel spin waves. Here, a controlled reduction of the saturation magnetization enables the localization of the propagating magnetic excitations in the same way that light is controlled in an optical fiber with a varying refraction index. The approach is based on the dynamic matrix method, where the magnetic nanostrip is divided into small sub-strips. The dipolar and exchange interaction between sub-strips is accounted to reproduce the spin-wave dynamics of the magnonic fiber. The transition from one strip to an infinite thin film is presented for the Damon-Eshbach geometry, where the nature of the spin-wave modes is discussed. An in-depth analysis of the spin-wave transport as a function of the saturation magnetization profile is provided. It is predicted that it is feasible to induce a remarkable channeling of the spin waves along the zones with a reduced saturation magnetization, even when such a reduction is tiny. The results are compared with micromagnetic simulations, where a good agreement is observed between both methods. The findings have relevance for envisioned future spin-wave-based magnonic devices operating at the nanometer scale.

Keywords: spin waves; ferromagnetic resonance; magnetization dynamics; magnonics; magnetic gradients; theory

Permalink: https://www.hzdr.de/publications/Publ-34978
Publ.-Id: 34978


Helical dislocations in ion-irradiated Fe-9Cr studied by scanning transmission electron microscopy

Vogel, K.; Engelmann, H.-J.; Chekhonin, P.; Bergner, F.; Kaden, C.

Fe-9Cr is a model alloy for studying irradiation effects relevant for potential applications of high-chromium ferritic/martensitic steels in nuclear energy devices. Ion irradiation is a tool extensively employed with the aim to emulate the neutron damage characteristic for irradiation environments in fission or fusion reactors. Here we report on STEM studies of the microstructure of ion-irradiated Fe-9Cr with special emphasis on the effects of pre-existing dislocations.
Irradiations with 8 MeV Fe3+ ions were carried out at the 3 MV tandetron accelerator at the Ion Beam Center at HZDR. Profiles of displacement damage and implanted ions were calculated using the binary collision code SRIM. Cross-sectional TEM specimens were prepared by focused ion beam lift-out technique using a Thermo Fisher Helios 5CX. The microstructure was studied in a Talos F200X scanning transmission electron microscope.
The most striking feature of the irradiated microstructure in the range of high displacement damage, but low concentration of implanted ions, is the presence of helical dislocations. From the results of the Burgers vector analysis we conclude, that the helices were formed from pre-existing straight line dislocations with a dominating screw component. After transformation into the helical shape, the dislocations contain screw, mixed and edge segments. The STEM images also reveal large numbers of small dislocation loops mainly located close to the helices.
The presence of helical dislocations and the accumulation of loops close to them resembles observations reported for neutron-irradiated Fe-9Cr. Hence we conclude that - in the depth range of low implanted ion concentration - ion irradiation can produce similar defect configurations like neutron irradiation if the arrangement of pre-existing dislocations is comparable.

Keywords: irradiation-induced defects; helical dislocations; dislocation loops; ion-irradiated Fe-Cr

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  • Contribution to proceedings
    Microscopy Conference 2023, 26.02.-02.03.2023, Darmstadt, Deutschland
    MC2023 Darmstadt Microscopy Conference Proceedings, 978-3-948023-29-4, 122-123
  • Poster
    Microscopy Conference 2023, 26.02.-02.03.2023, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34977
Publ.-Id: 34977


Spatial distribution of Eu(III) in environmental samples by chemical microscopy

Klotzsche, M.; Vogel, M.; Steudtner, R.; Drobot, B.

Lanthanides (Ln) have become critical components in science and industry. Their anthropogenic release into the environment and entry into the food chain poses a risk for the health of living beings. Therefore, a comprehensive understanding of the transfer and migration behaviour, the resulting localization and molecular characterization of Ln in geological and biological systems is crucial for a reasonable risk assessment and remediation strategies.
Trivalent europium (Eu(III)) exhibits chemical similarities to Ca(II) and excellent luminescent properties, hence it is well suited to study the interaction of Ln(III) with plants on a cellular level. Herein, we utilized chemical microscopy[1] – a combination of light microscopy and high resolution luminescence spectroscopy – in order to spatially resolve the Eu(III) species distribution in both, an imitation of a natural sample and an Eu(III)-incubated agricultural crop.

[1] M. Vogel, R. Steudtner, T. Fankhänel, J. Raff, B. Drobot, Analyst 2021, 146, 6741.

Keywords: Chemical microscopy; Europium; Laser spectroscopy; Bioassociation; Environmental samples; Plant; Spatial imaging

  • Poster
    Chemistry Summer School on f-Elements, 12.-16.06.2022, Aussois, France

Permalink: https://www.hzdr.de/publications/Publ-34976
Publ.-Id: 34976


Real-time tracking of individual droplets in multiphase microfluidics

Ibarlucea, B.; Schütt, J.; Baraban, L.; Makarov, D.; Medina Sánchez, M.; Cuniberti, G.

Multiphase microfluidics enables the high-throughput operation of droplets for multitude of applications, from the confined fabrication of nano- and micro-objects to the parallelization of chemical reactions of biomedical or biological interest. While the standard methods to follow droplets on a chip are represented by a visual observation through optical or fluorescence microscopy, the conjunction of microfluidic platforms with miniaturized transduction mechanisms opens new ways toward the real-time and individual tracking of each independent reactor. Here we provide an overview of the most recent droplet sensing techniques, with a special focus on those based on electrical signals for optics-less analysis.

Keywords: droplet microfluidics; lab-on-a-chip; nanosensors; biosensors; field-effect transistors

  • Open Access Logo Book chapter
    Prof. Mingzhou Yu: Microfluidics and Nanofluidics - Fundamentals and Applications, London, England: IntechOpen, 2022, 978-1-80356-336-7
    DOI: 10.5772/intechopen.106796

Permalink: https://www.hzdr.de/publications/Publ-34975
Publ.-Id: 34975


Data publication: Presence of uranium(V) during uranium(VI) reduction by Desulfosporosinus hippei DSM 8344T

Hilpmann, S.; Roßberg, A.; Steudtner, R.; Drobot, B.; Hübner, R.; Bok, F.; Prieur, D.; Bauters, S.; Kvashnina, K.; Stumpf, T.; Cherkouk, A.

The stored data sets represent both the raw data and the evaluated data that were used for the publication about uranium(VI) reduction by a sulfate-reducing bacterium.

Keywords: Uranium(VI) reduction; Sulfate-reducing bacteria; Opalinus Clay pore water; Pentavalent uranium; Membrane vesicles

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Permalink: https://www.hzdr.de/publications/Publ-34974
Publ.-Id: 34974


Sulfated glycosaminoglycans inhibit transglutaminase 2 by stabilizing its closed conformation

Müller, C. D.; Ruiz-Gómez, G.; Cazzonelli, S.; Möller, S.; Wodtke, R.; Löser, R.; Freyse, J.; Dürig, J.-N.; Rademann, J.; Hempel, U.; Pisabarro, M. T.; Vogel, S.

Transglutaminases (TGs) catalyze the covalent crosslinking of proteins via isopeptide bonds. The most prominent isoform, TG2, is associated with physiological processes such as extracellular matrix (ECM) stabilization and plays a crucial role in the pathogenesis of e.g. fibrotic diseases, cancer and celiac disease. Therefore, TG2 represents a pharmacological target of increasing relevance. The glycosaminoglycans (GAG) heparin (HE) and heparan sulfate (HS) constitute high-affinity interaction partners of TG2 in the ECM. Chemically modified GAG are promising molecules for pharmacological applications as their composition and chemical functionalization may be used to tackle the function of ECM molecular systems, which has been recently described for hyaluronan (HA) and chondroitin sulfate (CS). Herein, we investigate the recognition of GAG derivatives by TG2 using an enzyme-crosslinking activity assay in combination with in silico molecular modeling and docking techniques. The study reveals that GAG represent potent inhibitors of TG2 crosslinking activity and offers atom-detailed mechanistic insights.

Permalink: https://www.hzdr.de/publications/Publ-34973
Publ.-Id: 34973


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