Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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36084 Publications

Development of ¹²³I-labelled acrylamides as radiotracer candidates for transglutaminase 2

Laube, M.; Brandt, F.; Kopka, K.; Pietzsch, H.-J.; Pietzsch, J.; Löser, R.; Wodtke, R.

Objectives: The development of radiotracers for transglutaminase 2 (TGase 2) based on irreversible inhibitors appears highly attractive to further uncover the role of this enzyme for the emergence and progression of various tumour entities. However, the present imaging probes labeled with carbon-11 or fluorine-18 suffer from unfavourable pharmacokinetic properties such as fast blood clearance and metabolism. [1] Furthermore, incorporation of radionuclides with a longer half-life is desirable as the irreversible reaction between the molecular target and the probe might lead to a better signal-to-noise ratio at later time points. To tackle these two aspects, we developed the potent inhibitors 1 and 2 (Scheme) containing pyridine-3-yl residues with electron withdrawing groups and a iodinated phenylacetyl moiety. Herein, we present the radiosynthesis of [¹²³I]1 and [¹²³I]2 using their respective boronic acid pinacol esters as precursors.
Methods: Compounds 1 and 2 and the precursors 1-P and 2-P were synthesised starting from Nα-Boc-L-lysine in a sequence consisting of Nε-acrylation, PyBOP-mediated amide bond formation, Boc deprotection and HATU-mediated Nα-acylation. [2] For optimisation of radioiodination, reactions were performed in HPLC vials as reaction vessels applying 0.5-2 MBq [¹²³I]iodide in 50-100 µL of solvent. In addition to varying additive/precursor/water concentrations, the storage life and premixing time of reagent solutions were investigated. Radiolabelling at higher activity levels (up to 600 MBq) was conducted using 15-50 µL [¹²³I]iodide in total reaction volumes of 200-300 µL. Radiotracers were separated by semi-preparative HPLC. Solid-phase extraction was performed to provide [¹²³I]1 and [¹²³I]2 in suitable formulations for preclinical studies.
Results: 80-100 mg of each reference and precursor compound were obtained in sufficient purities (>95%). While chloramine T did not lead to the formation of [¹²³I]1 and [¹²³I]2, both compounds were accessible by the use of copper(II) trifluoroacetate and 1,10-phenanthroline [3] or tetrakis(pyridine)copper(II) triflate (Cu(OTf)₂(py)₄) [4]. In this context, Cu(OTf)₂(py)₄ in a 4-fold excess to precursor appeared to be most favourable leading to radiochemical conversions of >90% already after 10 min at room temperature (Scheme). These conditions allow for efficient radioiodinations even at 0.1 mM of precursor as well as with a water portion of up to 26%. Furthermore, the reagent solutions can be stored up to 3 month (at -20°C) without significant loss of radiochemical conversion. [¹²³I]1 and [¹²³I]2 were obtained as solutions in ethanol (2 MBq/µL) with (radio)chemical purities of ≥98% and radiochemical yields of >80%.
Conclusion: ¹²³I-labelled irreversible inhibitors of TGase 2 were prepared for the first time. The use of boronic acid pinacol ester as precursor and Cu(OTf)₂(py)₄ as catalyst facilitated the efficient radiolabelling with [¹²³I]iodide. This enables the radiopharmacological characterisation of these potential radiotracers towards their target TGase 2 in vitro and in vivo.
Acknowledgments: The authors thank ROTOP Radiopharmacy for continuously providing [¹²³I]iodide. Financial support by “Europäischer Fonds für regionale Entwicklung (EFRE)” (ML, HJP, and RW) is gratefully acknowledged.
References: [1] van der Wildt et al. Amino Acids 2017, 49, 585; [2] Wodtke et al. J. Med. Chem. 2018, 61, 4528; [3] Wilson et al. Chem. Comm. 2016, 52, 13277; [4] Reilly et al. Org. Lett. 2018, 20, 1752.

  • Lecture (Conference) (Online presentation)
    eSRS 2021, 17.-19.05.2021, Fredericksburg, United States of America
    DOI: 10.1016/S0969-8051(21)00396-6

Permalink: https://www.hzdr.de/publications/Publ-33481
Publ.-Id: 33481


Transition-metal-free reductive coupling of an 18F-labeled nitro-arene with boronic acids as a potential access to 18F-labeled fenamates

Laube, Markus; Roscales Garcia, Silvia; Pietzsch, Jens; Csákÿ, Aurelio G.

Objectives

A recently developed synthetic route for the transition metal-free reductive coupling of aryl boronic acids with nitro1 or nitroso2 substituted arenes gives access to a variety of diaryl amines like fenamates.3 Radiotracers targeting COX-2 have been developed and tested as PET tracer but no clinically approved radiotracer emerged up to now. Aim of this project is to evaluate this novel synthetic route as a general access to 18F-labeled N,N-diaryl amines which are principally not activated for 18F-labeling by nucleophilic aromatic substitution, and by that access to fenamates like flufenamic acid as COX-targeting radiotracers in a wider sense. In this report, we present first results with focus on radiolabeling and reactivity of an asymmetric 18F-labeled nitro-arene.

Methods

The asymmetric sydnone-substituted nitroarene was radiolabeled under optimized conditions with fluorine-18 using K222/K2CO3 in DMF at 90°C and was purified by a C18-based solid phase extraction (SPE). Elution from the dried C18 SPE-cartridge with ortho-dichlorobenzene over a SEP-Pak Dry cartridge provided the intermediate [18F]A for further testing and optimization of the reductive coupling step. Subsequent radiochemical conversion of [18F]A with different boronic acids was monitored via radio-UHPLC. 3-Cyanophenyl boronic acid was used to optimize the coupling reaction with [18F]A with respect to the parameters base/reducing agent, temperature, reaction time. Furthermore, [18F]A was subjected to the reaction with other ortho-, meta-, and para-substituted boronic acids to get a first impression about the scope of this reaction.

Results

[18F]A was isolated after radiolabeling and purification by SPE in 16-54% isolated RCY (n=4). Optimizations using aliquots of 50 µL allowed for optimization of several reaction conditions with one batch of [18F]A. Triphenylphosphine but not triethylphosphite was found to mediate the reductive coupling of 3-cyanophenylboronic acid at reaction temperatures of 140°C and 170°C. Compared to 170°C, radiochemical conversion of [18F]A was found to be slightly higher at 180°C. A clear rationale for the amount of boronic acid and PPh3 was not found since both ratios of 5.4 to 2.5 as well as 2.4 to 4.2 gave highest RCC at 180°C. [18F]A was found to react with a variety of different boronic acids, although proof of identity for the reaction products to the respective diarylamines has still to be performed. In general, however, reaction kinetics were found to be slow leading to radiochemical conversions above 80% only after a reaction time of 80 min which represents a main limitation for radiochemical reactions using fluorine-18.

Conclusion

18F-labeling of N,N-diarylamines represents a challenge for classical nucleophilic aromatic substitution approaches. The use of an 18F-labeled nitroarene and a transition-metal free reductive coupling methodology gave access to this type of compounds but slow reaction kinetics likely hinders the general use in 18F-chemistry. Hence, the evaluation of a respective nitrosoarene is currently under the way representing a highly attractive alternative in this regard due to the much faster reaction kinetics.

References

1. a) Nykaza, J.Am.Chem.Soc. 2020, 142, 6786. b) Roscales, Adv.Synth.Catal. 2020, 362, 111.

2. Roscales, Org.Lett. 2018, 20, 1667; 3. Roscales, J.Chem.Educ. 2019, 96, 1738.

Figure 1. Radiosynthesis of flufenamic acid derivates by transition metal-free reductive coupling with [18F]A

  • Poster (Online presentation)
    eSRS 2021 Virtual Meeting, 17.-19.05.2021, Online, -

Permalink: https://www.hzdr.de/publications/Publ-33480
Publ.-Id: 33480


Data publication: Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes

Körber, L.; Zimmermann, M.; Wintz, S.; Finizio, S.; Kronseder, M.; Bougeard, D.; Dirnberger, F.; Weigand, M.; Raabe, J.; Otálora, J. A.; Schultheiß, H.; Josten, E.; Lindner, J.; Kézsmárki, I.; Back, C. H.; Kakay, A.

This dataset contains the experimental and numerical raw data for our publication "Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes" published in Physical Review B. The experimental data is described in detail in the PDF "MAXYMUS_Tube210nm_antje500nm_2017_10_14". 

The dynamic matrix data contains eparam.yaml and sparam.yaml files containing the simulation and sample parameters used for micromagnetic modeling.

Keywords: spin wave; dispersion; curvature; micromagnetic modeling; hexagonal; symmetry; STXM

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-26
    DOI: 10.14278/rodare.1277
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33475
Publ.-Id: 33475


Electrical and structural properties of NixGey thin films made by Magnetron sputtering and flash lamp annealing

Begeza, V.; Rebohle, L.; Mehner, E.; Zhou, S.

Due to its higher charge carrier mobility compared to silicon, germanium belongs to the promising materials to surpass the physical limitations of the silicon based CMOS technology. For the integration of germanium into the CMOS process, the ohmic contact material with sufficiently low resistivity plays a crucial role. One of the promising candidates is nickel-germanide (NiGe) with a specific resistivity of (13.5 – 22) cm. Those values are comparable with the nickel-silicides used in the CMOS process with electrical resistivities of around 17 cm
This work is focused on the formation process of NiGe films on different germanium layer morphologies, by the flash lamp annealing approach. Furthermore, the investigation on the NixGey phase formation at different annealing temperatures was performed by grazing incidence X-ray diffraction and cross section transmission electron microscopy. The electrical properties were investigated by the application of four-point-probe, Hall effect and circular transfer length measurement techniques.

Keywords: Germanium; Nickel-germanide; Thin films; Flash Lamp Annealing; Millisecond Thermal Treatment; Phase Formation

  • Open Access Logo Poster (Online presentation)
    From Matter to Materials and Life 2021, 22.-24.11.2021, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33471
Publ.-Id: 33471


Plasmonic terahertz nonlinearity in graphene disks

Han, J.; Chin, M. L.; Matschy, S.; Poojali, J.; Seidl, A.; Winnerl, S.; Hafez, H. A.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

"Analysis_code_Final" contains the theoretical calculations. "FELmeasurements" contains the raw data of the pump-probe measurements with the FEL. "LabBook" contains the corresponding lab book pages.

Keywords: graphene; terahertz; nonlinearity

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1275

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Permalink: https://www.hzdr.de/publications/Publ-33469
Publ.-Id: 33469


Helmholtz AI Consulting for matter research at HZDR

Steinbach, P.; Hoffmann, H.; Pape, D.; Schmerler, S.; Starke, S.

In this presentation, I'd like to present the current status of Helmholtz AI consultancy for matter research in Helmholtz. I'd provide sneak previews into past and ongoing vouchers we embarked upon for the accelerator physics community and other collaborators. I'll try my best to give some insights on what we use our cluster for and why. Last but not least, I'll discuss challenges we faced along the way and will highlight some future directions if time allows.

Keywords: machine learning; HPC; history; artificial intelligence

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Hardware & Numerics Seminar at HZDR, 23.11.2021, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-33467
Publ.-Id: 33467


Asymptotic properties of Dirichlet kernel density estimators

Ouimet, F.; Tolosana Delgado, R.

We study theoretically, for the first time, the Dirichlet kernel estimator introduced by Aitchison and Lauder (1985) for the estimation of multivariate densities supported on the d-dimensional simplex. The simplex is an important case as it is the natural domain of compositional data and has been neglected in the literature on asymmetric kernels. The Dirichlet kernel estimator, which generalizes the (non-modified) unidimensional Beta kernel estimator from Chen (1999), is free of boundary bias and non-negative everywhere on the simplex. We show that it achieves the optimal convergence rate O(n−4/(d+4)) for the mean squared error and the mean integrated squared error, we prove its asymptotic normality and uniform strong consistency, and we also find an asymptotic expression for the mean integrated absolute error. To illustrate the Dirichlet kernel method and its favorable boundary properties, we present a case study on minerals processing.

Keywords: Asymmetric kernel; Asymptotic normality; Beta kernel; Boundary bias; Density estimation; Dirichlet kernel; Mean integrated absolute error; Multivariate associated kernel; Simplex; Strong consistency

Permalink: https://www.hzdr.de/publications/Publ-33466
Publ.-Id: 33466


Data publication: MHT-X: Offline Multiple Hypothesis Tracking with Algorithm X

Akashi, M.; Eckert, S.

There are images of bubbles in the liquid metal obtained through X-ray radiography. Bubbles are injected by a top-submerged lance. Experiments were performed in ELBE in HZDR.

Keywords: Algorithm X; two-phase flow; bubble dynamics; liquid metal; X-ray radiography; neutron imaging; image processing

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1273
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33465
Publ.-Id: 33465


Data publication: Prograde and retrograde precession of a fluid-filled cylinder

Pizzi, F.; Giesecke, A.; Simkanin, J.; Stefani, F.

This dataset included the data and figures for the associated publication "Prograde and retrograde precession of a fluid-filled cylinder".

Keywords: precession; core flow; dynamo; instability; transition

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1271
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33464
Publ.-Id: 33464


Autocorrected off-axis holography of two-dimensional materials

Kern, F.; Linck, M.; Wolf, D.; Alem, N.; Arora, H.; Gemming, S.; Erbe, A.; Zettl, A.; Büchner, B.; Lubk, A.

The reduced dimensionality in two-dimensional materials leads to a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high-resolution microscopy techniques are indispensable. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the two-dimensional material. We demonstrate these features with the example of h-BN, for which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges.

Permalink: https://www.hzdr.de/publications/Publ-33457
Publ.-Id: 33457


Data publication: Controlled Silicidation of SiNW using FLA

Khan, M. B.; Prucnal, S.; Ghosh, S.; Deb, D.; Hübner, R.; Pohl, D.; Rebohle, L.; Mikolajick, T.; Erbe, A.; Georgiev, Y.

The folder contains the following: 1. all the SEM and TEM images. 2. The schematics of fabrication 3. comparison of silicidation with FLA and RTA and 4. temperature simulations to estimate temperature during FLA process.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-23
    DOI: 10.14278/rodare.1269
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33452
Publ.-Id: 33452


Effect of Interfacial Defects on the Electronic Properties of MoS₂ Based Lateral T-H Heterophase Junctions

Bahmani, M.; Ghorbani Asl, M.; Frauenheim, T.

The coexistence of semiconducting (2H) and metallic (1T) phases of MoS₂ monolayers have further pushed their strong potential for applications in the next generation of electronic devices based on two-dimensional lateral heterojunctions. Structural defects have considerable effects on the properties of these 2D devices. In particular, the interfaces of two phases are often imperfect and may contain numerous vacancies created by phase engineering techniques, e.g. under the electron beam. Here, the transport behaviors of the heterojunctions in the existence of point defects are explored by means of first-principles calculations and non-equilibrium Green's function approach. While vacancies in semiconducting MoS₂ act as scattering centers, their presence at the interface improves the flow of the charge carriers. In the case of Vmo, the current has been increased by two orders of magnitude in comparison to the perfect device. The enhancement of transmission was explained by changes in the electronic densities at the T-H interface, which open new transport channels for electron conduction.

Keywords: two-dimensional materials; defects; lateral heterostructure; conductivity; quantum transport; DFT

Permalink: https://www.hzdr.de/publications/Publ-33451
Publ.-Id: 33451


Direct visualization of highly resistive areas in GaN by means of low-voltage scanning electron microscopy

Jóźwik, I.; Jagielski, J.; Caban, P.; Kamiński, M.; Kentsch, U.

The damage-induced voltage alteration (DIVA) contrast mechanism in scanning
electron microscope (SEM) at low electron energy has been presented as a fast and
convenient method of direct visualization of increased resistivity induced by energetic
ions irradiation in gallium nitride (GaN). Epitaxially grown GaN layers on sapphire
covered with a metallic masks with etched windows were subjected to He 2+
irradiations at 600 keV energy. The resulting two-dimensional damage profiles at the
samples cross-sections were imaged at SEM at different e-beam energies and scan
speeds. The gradual development of image contrast was observed with the increase of
cumulative charge deposited by electron beam irradiation, to finally reach the
saturation level of the contrast related to the local resistivity of the ion-irradiated part of
GaN.
The presented method allows one to directly visualize the ion-irradiated zone even for
the lowest resistivity changes resulting from ion damage, i.e. all levels of insulation
build-up in GaN upon irradiation with ions. Taking into account that it is not possible to
apply the etch-stop technique by wet chemistry to GaN, it makes the presented
technique the only available method of visualization of highly resistant and insulating
regions in GaN-based electronic devices.
Main aim of the presented work is to get a deeper insight into a DIVA contrast in GaN
with the special emphasize to discuss the role of rastering speed and electron beam
current, i.e. details of charge build-up ion the sample surface.

Keywords: GaN; Ion damage; Ion implantation; Low-kV SEM

Permalink: https://www.hzdr.de/publications/Publ-33450
Publ.-Id: 33450


Process simulation for comprehensive sustainability assessment of the silicon photovoltaic life cycle

Bartie, N.; Cobos-Becerra, L.; Froehling, M.; Schlatmann, R.; Reuter, M.

The photovoltaic industry has shown vigorous growth over the last decade and will continue on its trajectory to reach terawatt-level deployment by 2022–2023 and an estimated 4.5 TW by 2050. Presently, its elaboration is driven primarily by cost reduction. Growth will, however, be fuelled by the consumption of various resources, bringing with it unavoidable losses and environmental, economic, and societal impacts. Additionally, strong deployment growth will be trailed by waste growth, which needs to be managed, to support Sustainable Development and Circular Economy (CE). A rigorous approach to quantifying the resource efficiency, circularity and sustainability of complex PV life cycles, and exploring opportunities for partially sustaining industry growth through the recovery of high-quality secondary resources is needed. We create a high-detail digital twin of a Silicon PV life cycle using process simulation. The scalable, predictive simulation model accounts for the system's non-linearities by incorporating the physical and thermochemical principles that govern processes down to the unit operation level. Neural network-based surrogate functions are subsequently used to analyse the system's response to variations in end-of-life and kerf recycling in terms of primary resource and power consumption, PV power generation capacity, and CO2 emission. Applying the second law of thermodynamics, opportunities for improving the sustainability of unit operations, the larger processes they are the building blocks of, and the system as a whole are pinpointed, and the technical limits of circularity highlighted. We show the significant effects changes in technology can have on the conclusions drawn from such analyses.

Keywords: Silicon photovoltaics; Circular Economy; Digital twin simulation; Neural networks Exergy

Permalink: https://www.hzdr.de/publications/Publ-33448
Publ.-Id: 33448


Coordination and Electrochemical Switching on Paddle-Wheel Complexes Containing an As−Ru or a Sb−Ru Axis

Gericke, R.; Wagler, J.

Inspired by the known complex [PhP(μ-PyO)₄Ru(CO)] (PyO = 2-pyridyloxy), the family of group 15 paddle-wheel complexes has been expanded to [PhPn(μ-PyO)₄Ru(L)] (Pn = P, As, Sb; L = NCMe, CO). Solvent-dependent reversible switching between [PhAs(μ-PyO)₄Ru(NCMe)] and [PhAs(μ-PyO)₃Ru(κ²-PyO)] was detected. Electrochemical investigations of the [PhPn(μ-PyO)₄Ru(L)] complexes showed reversible oxidation of the complexes with L = NCMe and back-formation of the complexes with L = NCMe upon oxidation of the complexes with L = CO in NCMe. In the series of [PhPn(μ-PyO)₄RuL)] complexes, the Pn→Ru bonding mode is shifted from L-type Pn to X-type upon going from Pn = P and As to Pn = Sb, resulting in a pronounced electron-rich Ru site in the latter case. The easily accessible complex [PhSb(μ-PyO)₄RuCl] exhibits reversible electrochemical and coordinative exchange with its reduced analogue [PhSb(μ-PyO)₄Ru(NCMe)] under retention of the paddle-wheel motif and Sb−Ru bond properties.

Keywords: ambidentate ligands; ruthenium; pnictogen; hetero bimetallic; electrochemical switching

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  • Secondary publication expected from 23.11.2022

Permalink: https://www.hzdr.de/publications/Publ-33447
Publ.-Id: 33447


The precession dynamo experiment at HZDR

Giesecke, A.; Pizzi, F.; Kumar, V.; Anders, S.; Ratajczak, M.; Gundrum, T.; Stefani, F.

Cosmic magnetic fields exist on all scales, from planets and stars to
galaxies and beyond. The generation of these fields via the
hydromagnetic dynamo effect involves the formation of electrical
currents by means of complex flows of conducting fluids or plasmas. At
HZDR a related experiment is under construction within the project
DRESDYN. In that experiment a precessing flow of liquid sodium will
provide the required energy for magnetic field generation.

Here we address preliminary numerical and experimental studies aimed
at the identification of parameter ranges where a dynamo can be
expected. Our kinematic dynamo models show that dynamo action is
possible just before the transition from a laminar flow state to
vigorous turbulence where the flow structure is determined by a
combination of axisymmetric and nonaxisymmetric large scale modes. By
applying the derived scaling laws, the results can be directly applied
to the parameters of the planned large device.

Keywords: Dynamo

  • Poster (Online presentation)
    MML-Workshop 2021, 22.-24.11.2021, virtuell, virtuell

Permalink: https://www.hzdr.de/publications/Publ-33446
Publ.-Id: 33446


Polyoxoplatinates as Covalently Dynamic Electron Sponges and Molecular Electronics Materials

Kondinski, A.; Ghorbani Asl, M.

Dynamic covalent chemistry is an adaptive approach that utilizes thermodynamic equilibriums towards tailoring the structural and the electronic properties of molecular assemblies. The primary application of the latter approach lies in the design of organic self-healing materials, sensors, and actuators. Herein we apply density functional theory (DFT) to explore the structural, electronic and transport properties of the [Pt₁₂O8(SO₄)₁₂]⁴⁻ cluster and its derivatives. The cluster is a polyoxometalate (POM) that exhibits six {O−Pt−Pt−O} moieties. The latter moieties are redox responsive and covalently dynamic, allowing the POM to store up to twelve electrons. In our proposed Au/POM/Au junction, the simulations show that the electron conduction strongly depends on the redox of POM but more weakly on its rotations with respect to the Au surface. Moreover, the POM shows promising spin-polarized current behaviour, which can be modulated using bias and gate voltages.

Keywords: polyoxometalates (POMs); platinum; computational modelling; DFT; charge storage; molecular electronics

Permalink: https://www.hzdr.de/publications/Publ-33445
Publ.-Id: 33445


Probing ultrafast laser plasma processes inside solids with resonant small angle X-ray scattering

Gaus, L.; Bischoff, L.; Bussmann, M.; Cunningham, E.; Curry, C. B.; E, Juncheng; Galtier, E.; Gauthier, M.; Laso García, A.; Garten, M.; Glenzer, S.; Grenzer, J.; Gutt, C.; Hartley, N.; Huang, L.; Hübner, U.; Kraus, D.; Lee, H. J.; McBride, E. E.; Metzkes-Ng, J.; Nagler, B.; Nakatsutsumi, M.; Nikl, J.; Ota, M.; Pelka, A.; Prencipe, I.; Randolph, L.; Rödel, M.; Sakawa, Y.; Schlenvoigt, H.-P.; Smid, M.; Treffert, F.; Voigt, K.; Zeil, K.; Cowan, T.; Schramm, U.; Kluge, T.

Data Description

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-22
    DOI: 10.14278/rodare.596
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33444
Publ.-Id: 33444


Dynamo action of the large scale flow in a precessing cylinder

Giesecke, A.; Pizzi, F.; Stefani, F.

Precession is a well known phenomenon that (in a very general sense) paraphrases the
temporal change of the orientation of the spin axis of rotating objects. In rotating celestial bodies
with liquid interior precession causes a volume force that directly drives a non-axisymmetric fluid
flow [1]. Paradigmatic example is the liquid core of the Earth [2], for which the forcing is
considerably strong due to the rather large angle between rotation axis and precession axis. An even
stronger forcing is assumed for the ancient moon three to four billion years ago [3]. Precessional
forcing of the fluid interior of planets or moons is of interest because the resulting internal flows in
terms of inertial modes or turbulence back-react on the rotation of the whole body, which may
become evident for example in length of day variations or periodic changes of the nutation angle.
Furthermore a precession-driven flow of an electrically conductive fluid is capable of generating a
large scale magnetic field [4]. From an energetic point of view, the directly driven non-
axissymmetric flow is not sufficient to generate a magnetic field [5], however, multifaceted
instabilities of the primary flow provide the possibility to extract a large a amount of kinetic energy
from the rotational fluid motions into a fluid flow, which may be more suitable of generating a
magnetic field via electromagnetic induction [6].
In order to investigate to what extent a precession-driven flow can power a dynamo, and what
properties the related magnetic field would have, an experiment is currently being constructed at
HZDR, in which 6 tons of liquid sodium will precess in a cylinder with 2 meters height and 2
meters in diameter [7]. The design of the experiment is attended by comprehensive numerical
simulations, which showed that at the edge of the transition between a complex but still laminar
flow to a fully developed turbulent state, onset of dynamo action can be expected [8]. This state of
flow is characterized by an almost complete transformation of the original rotation into large-scale
inertial waves and small-scale turbulent flow. The dynamo effect found in the simulations is mainly
due to an evolving axially symmetric flow component and the strong shear layer near the outer
walls due to the massive extraction of rotational energy [9]. Free inertial waves in the form of
triadic resonances as the first instability, which describe the transition from the stationary to the
time-dependent state, do not seem to play any special role for the dynamo-effect. Open questions
concern the role of this triadic instability as a trigger for the transition to turbulence, the character of
the turbulence itself (is it three-dimensional or quasi-geostrophic) and the very mechanism that
causes the redistribution of the internal angular momentum and/or torque that goes along with the
significant modification of the large scale pattern of the velocity field.

1.
2.
3.
4.
5.
6.
7.
8.
9.
Stewartson & Roberts 1963, J. Fluid Mech. 17 (1), 1-20.
Malkus 1968, Science, 160, 259
Cebron et al. 2019, Geophys. J. Int., 219 (1), 34-57
Tilgner 2005, Phys. Fluids, 17, 034104
Loper 1975, Phys. Earth Planet. Inter. 11 (1), 43-60
Kerswell 1999, J. Fluid Mech. 382, 283-306
Stefani et al. 2015, Magnetohydrodynamics, 51 (2), 275-284
Giesecke et al. 2018, Phys. Rev. Lett. 120, 024502
Giesecke et al. 2018, Geophys. Astrophys. Fluid Mech., 113 (1-2), 235-255

Keywords: Dynamo

  • Invited lecture (Conferences)
    IV Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-33443
Publ.-Id: 33443


Rational Linker Design to Accelerate Excretion and Reduce Background Uptake of Peptidomimetic PSMA-Targeting Hybrid Molecules.

Eder, A.; Schäfer, M.; Schmidt, J.; Bauder-Wüst, U.; Roscher, M.; Leotta, K.; Haberkorn, U.; Kopka, K.; Eder, M.

The evolution of peptidomimetic hybrid molecules for preoperative imaging and guided surgery targeting the prostate-specific membrane antigen (PSMA) significantly progressed over the past few years, and some approaches are currently being evaluated for further clinical translation. However, accumulation in nonmalignant tissue such as kidney, bladder, spleen, or liver might limit tumor-to-background contrast for precise lesion delineation, particularly in a surgical setting. To overcome these limitations, a rational linker design aims at the development of a second generation of PSMA-11-based hybrid molecules with an enhanced pharmacokinetic profile and improved imaging contrast. Methods: A selection of rationally designed linkers was introduced to the PSMA-targeting hybrid molecule Glu-urea-Lys-HBED-CC-IRDye800CW, resulting in a second-generation peptidomimetic hybrid molecule library. The biologic properties were investigated in cell-based assays. In a preclinical proof-of-concept study with the radionuclide 68Ga, the impact of the modifications was evaluated by determination of specific tumor uptake, pharmacokinetics, and fluorescence imaging in tumor-bearing mice. Results: The modified hybrid molecules carrying various selected linkers revealed high PSMA-specific binding affinity and effective internalization. The highest tumor-to-background contrast of all modifications investigated was identified for the introduction of a histidine- (H) and glutamic acid (E)-containing linker ((HE)3-linker) between the PSMA-binding motif and the chelator. In comparison to the parental core structure, uptake in nonmalignant tissue was significantly reduced to a minimum, as exemplified by an 11-fold reduced spleen uptake from 38.12 ± 14.62 percentage injected dose (%ID)/g to 3.47 ± 1.39 %ID/g (1 h after injection). The specific tumor uptake of this compound (7.59 ± 0.95 %ID/g, 1 h after injection) was detected to be significantly higher than that of the parental tracer PSMA-11. These findings confirmed by PET and fluorescence imaging are accompanied by an enhanced pharmacokinetic profile with accelerated background clearance at early time points after injection. Conclusion: The novel generation of PSMA-targeting hybrid molecules reveals fast elimination, reduced background organ enrichment, and high PSMA-specific tumor uptake meeting the key demands for potent tracers in nuclear medicine and fluorescence-guided surgery. The approach's efficacy in improving the pharmacokinetic profile highlights the strengths of rational linker design as a powerful tool in strategic hybrid-molecule development.

Keywords: PSMA; guided surgery; hybrid molecules; pharmacokinetic profile; prostate cancer

Permalink: https://www.hzdr.de/publications/Publ-33442
Publ.-Id: 33442


Spectroscopic and modeling study of the sorption of Ln³⁺ (Eu) and An³⁺ (Am, Cm) on Ca-feldspars

Lessing, J.; Neumann, J.; Bezzina, J. P.; Bok, F.; Lützenkirchen, J.; Brendler, V.; Stumpf, T.; Schmidt, M.

INTRODUCTION
Deep geological repositories are considered as a safe disposal strategy for radioactive waste due their ability to isolate toxic components from the biosphere over hundreds of thousands of years. Minor actinides and Pu dominate the radiotoxicity of spent nuclear fuel over these long time scales. Due to the expected reducing conditions in the underground repository, the trivalent oxidation state is dominant for Am and Cm, and will also be relevant for Pu. For investigations of the mobility of the trivalent actinides Am(III) and Cm(III), the less toxic trivalent rare earth elements, in particular Eu(III), are commonly used.
In Germany and many other countries, crystalline rock is being considered as a possible host rock. Therefore, there is a need for understanding the sorption behavior of radionuclides on this material. Crystalline rock (e.g. granite), consists mainly of quartz, feldspars, and mica. Recently, the retention of trivalent actinides by K-feldspar was investigated from a thermodynamic and structural point of view.[1] Here, we extend this study towards Ca-feldspars (plagioclases), which may show a different sorption behavior due to their different elemental composition, crystal structure, and surface charge behavior.
DESCRIPTION OF THE WORK
Synthetic Ca-feldspar and natural plagioclases of different Ca amounts were used for zeta potential measurements and batch sorption experiments under different geochemical conditions ([M³⁺] = 52 nM – 10 μM; solid-liquid ratio = 1 – 3 g/L, I = 0,1 M NaCl, pH = 3 – 9) to quantify the uptake of Am(III) and Eu(III). For analysis of the sorption structure of trivalent f-elements on the molecular level, time-resolved laser-induced spectroscopy (TRLFS) using Cm(III) as a luminescent probe was carried out on synthetic Ca-feldspar. The obtained data were used to develop a surface complexation model (SCM) and to derive surface complexation parameters for the spectroscopically identified surface complexes.
RESULTS AND DISCUSSION
Zeta potential investigations of all Ca-feldspars show a decrease of the potential for pH = 2 – 4 due to surface site deprotonation. In contrast to the previously reported trend for K-feldspar, the zeta potential increases for pH = 4 – 7, with a stronger increase with higher Ca²⁺ concentration in the crystal lattice of the investigated plagioclases, even reaching positive values in the case of the synthetic Ca-feldspar. This effect can be traced to dissolved Al³⁺: Due to differences in solubility, Al³⁺ concentration in solution increases with increasing Ca²⁺ in the crystal lattice. Experiments on K-feldspar with added Al³⁺ reveal a connection between its concentration and the increase of the zeta potential.
All observed Ca-feldspars show a strong sorption uptake of trivalent f-elements for pH > 6. K- and Ca-feldspars seem to have a similar sorption behavior for low [M³⁺].[1] In contrast, Ca-feldspar has a slightly stronger sorption affinity when the metal concentrations is increased. This leads to a steeper sorption edge with increasing Ca²⁺ concentration in the crystal lattice of the mineral.
Spectroscopic studies with Cm(III) on synthetic Ca-feldspar reveal three sorption complexes: one inner sphere complex (IS) and its two hydrolysis forms, which have the same band positions as previously determined for K-feldspar.[1] Therefore, it can be concluded that the structure of the formed IS complexes is independent on the feldspar type. Differences are only observed for the quantitative contributions of the surface complexes. In particular, hydrolysis of the IS complex is stronger in the case of the Ca-feldspar.
Batch sorption data and the information about spectroscopically identified surface complexes were then combined to develop a SCM for Ca-feldspar that describes the experimental data. The formation constants of the surface complexes were determined to be −8.37; −10.81, and −16.35, respectively and are very similar to those of the K-feldspar.[1]
From the applied multi-method approach, we conclude that the sorption of trivalent f-elements on K- and Ca-feldspar is most likely comparable for relevant, natural conditions. Therefore, it may be possible not to distinguish between the two minerals in reactive transport simulations, which will reduce calculation resources needed for a reliable risk assessment of repositories for radioactive waste.
REFERENCES
[1] J. Neumann et al., “A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar,” Journal of Colloid Interface Science, vol. 591, pp. 490–499 (2021)
[2] Neumann and Lessing et al., “Structural and modeling study of the retention of trivalent f-elements (Am, Cm, Eu) by natural and synthetic Ca-feldspars”, in preparation.

Keywords: Sorption; Trivalent metal ions; Actinides; Ca-feldspar; Surface complexation model; TRLFS; Zeta potential

  • Poster
    TransRet2020, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33441
Publ.-Id: 33441


The disappearance and return of nanoparticles upon low energy ion irradiation

Choupanian, S.; Nagel, A.; Möller, W.; Pacholski, C.; Ronning, C.

Ion irradiation of bulk and thin film materials is tightly connected to well described effects such as sputtering or/and ion beam mixing. However, when a nanoparticle is ion irradiated and the ion range is comparable to the nanoparticle size, these effects are to be reconsidered essentially. This study investigates the morphology changes of silver nanoparticles on top of silicon substrates, being irradiated with Ga+ ions in an energy range from 1 to 30 keV. The hemispherical shaped nanoparticles become conical due to an enhanced and curvature-dependent sputtering, before they finally disappear. The sputter yield and morphology changes can be well described by 3D Monte Carlo TRI3DYN simulations. However, the combination of sputtering, ion beam mixing, ion beam induced diffusion, and Ostwald ripening at ion energies lower than 8 keV results in the reappearance of new particles. These newly formed nanoparticles appear in various structures depending on the material and ion energy

Keywords: Ag nanoparticles; Ion beam mixing; Ion-nanoparticle interaction; Ostwald ripening; Phase sepereation

Permalink: https://www.hzdr.de/publications/Publ-33440
Publ.-Id: 33440


Deterministic Shallow Dopant Implantation in Silicon with Detection Confidence Upper-Bound to 99.85% by Ion–Solid Interactions

Jakob, A. M.; Robson, S. G.; Schmitt, V.; Mourik, V.; Posselt, M.; Spemann, D.; Johnson, B. C.; Firgau, H. R.; Mayes, E.; McCallum, J. C.; Morello, A.; Jamieson, D. N.

Silicon chips containing arrays of single dopant atoms can be the material of choice for classical and quantum devices that exploit single donor spins. For example, group-V donors implanted in isotopically purified 28Si crystals are attractive for large-scale quantum computers. Useful attributes include long nuclear and electron spin lifetimes of 31P, hyperfine clock transitions in 209Bi or electrically controllable 123Sb nuclear spins. Promising architectures require the ability to fabricate arrays of individual near-surface dopant atoms with high yield. Here, an on-chip detector electrode system with 70 eV root-mean-square noise (≈20 electrons) is employed to demonstrate near-room-temperature implantation of single 14 keV 31P+ ions. The physics model for the ion–solid interaction shows an unprecedented upper-bound single-ion-detection confidence of 99.85 ± 0.02% for near-surface implants. As a result, the practical controlled silicon doping yield is limited by materials engineering factors including surface gate oxides in which detected ions may stop. For a device with 6 nm gate oxide and 14 keV 31P+ implants, a yield limit of 98.1% is demonstrated. Thinner gate oxides allow this limit to converge to the upper-bound. Deterministic single-ion implantation can therefore be a viable materials engineering strategy for scalable dopant architectures in silicon devices.

Keywords: Deterministic single-ion implantation; Near-surface dopant location; Quantum computers; Ion Beam Induced Charge Collection

Permalink: https://www.hzdr.de/publications/Publ-33439
Publ.-Id: 33439


Stable acceleration of intense proton beams to energies beyond 80 MeV at rep-rated laser systems

Ziegler, T.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Kiriyama, H.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

We report on experimental investigations of proton acceleration from laser-irradiated solid foils with the Draco-PW laser, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantlyfrom those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape ofthe last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that short and asymmetric pulses generated by positive third order dispersion values are favourable for proton acceleration and can lead to maximum energies above 60 MeV at 18 J laser energy for thin plastic foils, effectively doubling the maximum energy compared to ideally compressed FTL pulses. This performance optimization was the key to perform worlds first dose-controlled in-vivo studies with laser accelerated protons.

The talk will further report on experiments we have carried out in the relativistically induced transparancy regime where the target turns transparent during the laser pulse interaction. We show recent data how the experimental signatures of the accelerated protons in this regime change compared to standard TNSA conditions and how we could reproduce those results at another similar laser laser system.

  • Invited lecture (Conferences)
    5th European Advanced Accelerator Concepts Workshop, 20.-23.09.2021, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-33435
Publ.-Id: 33435


Assessment of the validity of a log-law for wall-bounded turbulent bubbly flows

Bragg, A.; Liao, Y.; Fröhlich, J.; Ma, T.

There has been considerable discussion in recent years concerning whether a log-law exists for wall-bounded,
turbulent bubbly flows. Previous studies have argued for the existence of such a log-law, with a modified von
K´arm´an constant, and this is used in various modelling studies. We provide a critique of this idea, and present
several theoretical reasons why a log-law need not be expected in general for wall-bounded, turbulent bubbly
flows. We then demonstrate using recent data from interface-resolving Direct Numerical Simulations that when
the bubbles make a significant contribution to the channel flow dynamics, the mean flow profile of the fluid can
deviate significantly from the log-law behaviour that approximately holds for the single-phase case. The departures
are not surprising and the basic reason for them is simple, namely that for bubbly flows, the mean flow is
affected by a number of additional dynamical parameters, such as the void fraction, that do not play a role for the
single-phase case. As a result, the inner/outer asymptotic regimes that form the basis of the derivation of the loglaw
for single-phase flow do not exist in general for bubbly turbulent flows. Nevertheless, we do find that for
some cases, the bubbles do not cause significant departures from the unladen log-law behaviour. Moreover, we
show that if departures occur these cannot be understood simply in terms of the averaged void fraction, but that
more subtle effects such as the bubble Reynolds number and the competition between the wall-induced turbulence
and the bubble-induced turbulence must play a role.

Keywords: Bubbly flow; Log-law; Wall-bounded turbulent flows

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  • Secondary publication expected from 16.09.2022

Permalink: https://www.hzdr.de/publications/Publ-33434
Publ.-Id: 33434


A Machine-Learning Surrogate Model for ab initio Electronic Correlations at Extreme Conditions

Dornheim, T.; Moldabekov, Z.; Cangi, A.

The electronic structure in matter under extreme conditions is a challenging complex system prevalent in astrophysical objects and highly relevant for technological applications. We show how machine-learning surrogates in terms of neural networks have a profound impact on the efficient modeling of matter under extreme conditions. We demonstrate the utility of a surrogate model that is trained on \emph{ab initio} quantum Monte Carlo data for various applications in the emerging field of warm dense matter research.

Keywords: Machine Learning; Surrogate model; warm dense matter

Permalink: https://www.hzdr.de/publications/Publ-33432
Publ.-Id: 33432


Robust formation of nanoscale magnetic skyrmions in easy-plane anisotropy thin film multilayers with low damping

Flacke, L.; Ahrens, V.; Mendisch, S.; Körber, L.; Böttcher, T.; Meidinger, E.; Yaqoob, M.; Müller, M.; Liensberger, L.; Kakay, A.; Becherer, M.; Pirro, P.; Althammer, M.; Geprägs, S.; Huebl, H.; Gross, R.; Weiler, M.

We experimentally demonstrate the formation of room-temperature skyrmions with radii of about 25 nm in easy-plane anisotropy multilayers with an interfacial Dzyaloshinskii-Moriya interaction (DMI). We detect the formation of individual magnetic skyrmions by magnetic force microscopy and find that the skyrmions are stable in out-of-plane fields up to about 200 mT. We determine the interlayer exchange coupling as well as the strength of the interfacial DMI. Additionally, we investigate the dynamic microwave spin excitations by broadband
magnetic resonance spectroscopy. From the uniform Kittel mode we determine the magnetic anisotropy and lowdamping α < 0.04. We also find clear magnetic resonance signatures in the nonuniform (skyrmion) state. Our findings demonstrate that skyrmions in easy-plane multilayers are promising for spin-dynamical applications.

Keywords: skyrmion; ferromagnetic resonance; DMI; low damping

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Permalink: https://www.hzdr.de/publications/Publ-33420
Publ.-Id: 33420


Leptin counteracts hypothermia in hypothyroidism through its pyrexic effects and by stabilizing serum thyroid hormone levels

Weiner, J.; Roth, L.; Kranz, M.; Brust, P.; Boelen, A.; Klöting, N.; Heiker, J. T.; Blüher, M.; Tönjes, A.; Pfluger, P. T.; Stumvoll, M.; Mittag, J.; Krause, K.

Objective: Thyroid hormones (TH) are essential for the homeostatic control of energy metabolism and the regulation of bodytemperature. The hypothalamic–pituitary–thyroid (HPT) axis is regulated by negative feedback mechanisms, ensuring that TH levels are maintained at a constant level. However, the feedback mechanisms underlying the resetting of the HPT axis regulation in the control of body temperature are still not fully understood. Here, we aimed to determine the thermoregulatory response in hypothyroid mice to different environmental temperatures and the underlying mechanisms. Methods: Distinct
thermogenic challenges were induced in hypothyroid female C57BL/6N and leptin-deficient ob/ob mice through housing at either room temperature or thermoneutrality. The thermogenic and metabolic effects were analyzed through metabolic chambers, 18F-FDG-PET/MRI, infrared thermography, metabolic profiling, histology, gene expression and Western blot analysis. Results: In hypothyroid mice maintained at room temperature, high leptin serum levels induce a pyrexic effect leading to the stabilization of body temperature through brown adipose tissue thermogenesis and white adipose tissue browning. Housing at thermoneutrality leads to the normalization of leptin levels and a reduction of the central temperature set point, resulting in decreased thermogenesis in brown and white adipose tissue and skeletal muscle and a significant decline in body temperature. Furthermore, anapyrexia in hypothyroid leptin-deficient ob/ob mice indicates that besides its pyrexic actions, leptin exerts a stimulatory effect on the HPT axis to stabilize the remaining TH serum levels in hypothyroid mice. Conclusion: This study led to the identification of a previously unknown endocrine loop in which leptin acts in concert with the HPT axis to stabilize body temperature in hypothyroid mice.

Keywords: Beige adipose tissue; Brown adipose tissue; Leptin; Thermogenesis; Thyroid hormone; White adipose tissue browning

Permalink: https://www.hzdr.de/publications/Publ-33417
Publ.-Id: 33417


Data publication: Uptake of niobium by cement systems relevant for nuclear waste disposal: impact of ISA and chloride

Franke, K.

Daten zur Bestrahlung und Gammaspektroskopiemessung des Targets

Keywords: niobium; cyclotron; gamma spectroscopy

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-19
    DOI: 10.14278/rodare.1265
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33416
Publ.-Id: 33416


High-gain quantum free-electron laser: Long-time dynamics and requirements

Kling, P.; Giese, E.; Carmesin, C. M.; Sauerbrey, R.; Schleich, W. P.

We solve the long-time dynamics of a high-gain free-electron laser in the quantum regime. In this regime each electron emits at most one photon on average, independently of the initial field. In contrast, the variance of the photon statistics shows a qualitatively different behavior for different initial states of the field. We find that the realization of a seeded quantum free-electron laser is more feasible than self-amplified spontaneous emission.

Permalink: https://www.hzdr.de/publications/Publ-33415
Publ.-Id: 33415


Zr-PAPER

Mansel, A.

Rohdaten Zr-PAPER

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-18
    DOI: 10.14278/rodare.1263
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33414
Publ.-Id: 33414


Therapy-naïve and radioresistant 3D pancreatic cancer cell cultures are effectively radiosensitized by β1 integrin targeting

Görte, J.; Danen, E.; Cordes, N.

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is one of the cancers with unmet need. The role of highly conformal radiotherapy is still under debate for PDAC. Owing to its desmoplastic nature, integrin-mediated interactions between PDAC cells and extracellular matrix (ECM) profoundly contribute to PDAC resistance. In this study, we investigated the radiochemosensitizing potential of β1 integrin targeting in therapy-naïve and radioresistant PDAC cell cultures grown in three-dimensional (3D) extracellular matrix (ECM).
Materials and Methods: In a panel of 3D, ECM based PDAC cell cultures, β1 integrin was inhibited by antibodies or siRNA-mediated knockdown. Together with X-ray irradiation and specific chemotherapies, we determined 3D colony formation capacity in therapy-naïve and radioresistant PDAC cultures. Kinome profiling, Western blotting and immunofluorescence stainings were employed to characterize these cell lines. Various siRNA screens were conducted to identify novel therapeutic targets.
Results: A significant radiosensitizing potential of β1 integrin inhibition was found both in therapy-naïve and radioresistant PDAC cell cultures. Kinome profiling upon β1 integrin targeting identified a generally declined tyrosine and serine/threonine kinase activity, which presented less prominent in radioresistant than in therapy-naïve PDAC cells. siRNA screens employing the top 34 deregulated kinases in combination with β1 integrin inhibition revealed less efficacy and less radiosensitization in radioresistant relative to therapy-naïve PDAC cell cultures. Triple inhibition of β1 integrin, protein kinase D1 (PDK1) and rearranged during transfection (RET) turned out to be most effective in reducing 3D colony formation of radioresistant PDAC cells.
Conclusion: Our study clearly shows that β1 integrins are robust targets for overcoming radioresistance in PDAC. This seems to apply equally to therapy-sensitive and radioresistant cells. Concerning tumor heterogeneity, this dual therapy-sensitizing potential might be exploitable for a significant improvement of patient survival.

Keywords: Radiotherapy; Integrins; Resistance; PDAC

Permalink: https://www.hzdr.de/publications/Publ-33412
Publ.-Id: 33412


Control of Stripe-Domain-Wall Magnetization in Multilayers Featuring Perpendicular Magnetic Anisotropy

Salikhov, R.; Samad, F.; Böhm, B.; Schneider, S.; Pohl, D.; Rellinghaus, B.; Ullrich, A.; Albrecht, M.; Lindner, J.; Kiselev, N. S.; Hellwig, O.

We report on the controlled switching of domain-wall (DW) magnetization in aligned stripe-domain
structures, stabilized in [Co(0.44 nm)/Pt(0.7 nm)]X (X = 48, 100, 150) multilayers with perpendicular
magnetic anisotropy. The switching process, induced by an external magnetic field, is monitored by measuring the evolution of the in-plane magnetization. We show that the remanent in-plane magnetization originates from the polarization of the Bloch-type DWs. With micromagnetic simulations, we reveal that
the reversal of the DW polarization is the result of the emergence and collapse of horizontal Bloch lines
within the DWs at particular strengths of the external magnetic field, applied opposite to the DW polarization. Our findings are relevant for DW-based magnonics and bubble-skyrmion applications in magnetic multilayers.

Keywords: Magnetic domains; Domain walls; Magnetization switching; Skyrmions; Spintronics; Micromagnetism

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Permalink: https://www.hzdr.de/publications/Publ-33411
Publ.-Id: 33411


Microscopic and spectroscopic investigations of uranium(VI) reduction by Desulfosporosinus hippei DSM 8344

Hilpmann, S.; Drobot, B.; Steudtner, R.; Hübner, R.; Bok, F.; Stumpf, T.; Cherkouk, A.

Clay formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository. Bentonites are supposed to serve as backfill material, not only for a final disposal site in clay formations but also in crystalline rock. For a long-term safety assessment, various aspects must be taken into account. Besides geological, geochemical, and geophysical considerations, also naturally occurring microorganisms play a crucial part in the environment of such a repository. In the event of a worst-case scenario, if water enters the disposal site, they can interact with the radionuclides and change for example the chemical speciation or the oxidation state (Lloyd et al., 2002).
Desulfosporosinus spp. are an important representative of anaerobic, sulfate-reducing microorganisms, which are present in clay formations as well as in bentonites. Various studies show that they are playing a major role in the microbial communities of these surroundings (Bagnoud et al., 2016; Matschiavelli et al., 2019). A closely related microorganism to the isolated species is Desulfosporosinus hippei DSM 8344, which was originally found in permafrost soil (Vatsurina et al., 2008). This bacterium was used to investigate its interactions with uranium(VI) especially regarding the reduction to the less mobile uranium(IV).
Time-dependent reduction experiments in artificial Opalinus Clay pore water (Wersin et al., 2011) (100 µM uranium(VI), pH 5.5) showed the removal of about 80% of the uranium(VI) from the supernatants within 48 h. Corresponding UV/Vis measurements of the dissolved cell pellets exhibit an increasing proportion of uranium(IV) in the cell-bound uranium. Calculations with the inclusion of extinction coefficients lead to a ratio of 39% uranium(IV) after one week. Therefore, a combined sorption-reduction process is a possible interaction mechanism.
Time-resolved laser-induced luminescence spectroscopy verifies the presence of two uranium(VI) species in the supernatant. A comparison with reference spectra leads to an assignment to a uranyl(VI) lactate and a uranyl(VI) carbonate complex. The species distribution shows a decrease of the proportion of the lactate species with time, whereas the proportion of the carbonate species remains almost constant.
Uranium aggregates are formed on the cell surface during the process, as determined by transmission electron microscopy (TEM). Furthermore, uranium occurs inside and outside the cells as well as uranium-containing vesicles.
These findings help to close existing gaps in a comprehensive safeguards concept for a repository for high-level radioactive waste in clay rock. Moreover, this study provides new insights into the interactions of sulfate-reducing microorganisms with uranium(VI).

References
Bagnoud, A., Chourey, K., Hettich, R. L., De Bruijn, I., Andersson, A. F., Leupin, O. X., Schwyn, B., and Bernier-Latmani, R.: Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock, Nat. Commun., 7, 1-10, 2016.
Lloyd, J. R. and Macaskie, L. E.: Biochemical basis of microbe-radionuclide interactions, in: Interactions of Microorganisms with Radionuclides, edited by: Keith-Roach, M. J. and Livens, F. R., Elsevier, 313-381, 2002.
Matschiavelli, N., Kluge, S., Podlech, C., Standhaft, D., Grathoff, G., Ikeda-Ohno, A., Warr, L. N., Chukharkina, A., Arnold, T., and Cherkouk, A.: The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C, Environ. Sci. Technol., 53, 10514-10524, 2019.
Vatsurina, A., Badrutdinova, D., Schumann, P., Spring, S., Vainshtein, M.: Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost, Int. J. Syst. Evol. Microbiol., 58, 1228-1232, 2008.
Wersin, P., Leupin, O. X., Mettler, S., Gaucher, E. C., Mäder, U., De Cannière, P., Vinsot, A., Gäbler, H. E., Kunimaro, T., Kiho, K., Eichinger, L.: Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland, Appl. Geochemistry, 26, 931-953, 2011.

Keywords: uranium(VI) reduction; sulfate-reducing microorganisms; Opalinus Clay

  • Poster
    Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33410
Publ.-Id: 33410


Microscopic and spectroscopic study of the uranium(VI) reduction by a sulfate-reducing microorganism

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

INTRODUCTION

Clay rock is a possible host rock for the long-term storage of high-level radioactive waste and bentonites are a suitable backfill material for a final repository in clay rock and crystalline rock. For a comprehensive safety assessment of such a repository over a long period, different aspects must be taken into account. Besides intensive research regarding geological, geochemical and geophysical properties, these surroundings represent a habitat for naturally occurring microorganisms. In the event of a worst-case scenario, water can enter the repository. It is possible that microorganisms can interact with the radionuclides and thereby change the chemical speciation or the oxidation state by various processes.
Desulfosporosinus spp. play an important role as a representative of anaerobic, sulfate-reducing and spore-forming microorganisms. These bacteria occur in different clay formations as well as in bentonites.1,2 A very closely related bacterium to an isolated species from bentonite is Desulfosporosinus hippei DSM 8344, which was originally found in permafrost soils.3 Therefore, this strain was selected to get a more profound insight into the uranium(VI) interactions with naturally occurring microorganisms from deep geological layers by different microscopic and spectroscopic techniques.

DESCRIPTION OF THE WORK

For the time-dependent experiments in artificial Opalinus Clay pore water4 (100/500 µM uranium(VI), pH 5.5) the cells were cultivated in specific media and harvested in the late exponential growing phase. After washing, suspensions containing cells, uranium(VI) and lactate, were incubated at room temperature and samples were taken between zero hours and one week.

RESULTS AND DISCUSSION

The experiments showed the removal of about 80% of the uranium(VI) from the supernatants within 48 h at a concentration of 100 µM. Corresponding UV/Vis measurements of the dissolved cell pellets revealed an increasing proportion of uranium(IV) in the samples with time. After one week round about 40% of the uranium in the cell pellets was reduced. Therefore, the interaction mechanisms can be assigned to a combined sorption-reduction process.
TEM images of the uranium-incubated cells reveal the formation of uranium aggregates on the cell surface. Uranium can be found not only outside the cell in vesicles, but also inside the cell.
HERFD-XANES measurements show the presence of three oxidation states in the cell pellets. Besides uranium(VI) and uranium(IV), also uranium(V) plays a major role in the cellular reduction process. With the help of EXAFS measurements, three cell-related uranium species were detected.
This study helps to close existing gaps in a comprehensive safeguard concept for a final repository for high-level radioactive waste in clay rock. Moreover, new insights into the interaction mechanisms of sulfate-reducing microorganisms with uranium are presented.

REFERENCES

1. A. BAGNOUD et al., “Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock” Nat. Commun., 7, 1-10 (2016).

2. N. MATSCHIVELLI et al., “The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C” Environ. Sci. Technol., 53, 10514-10524 (2019).

3. A. VATSURINA et al., “Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost” Int. J. Syst. Evol. Microbiol., 58, 1228-1232 (2008).

4. P. WERSIN et al., “Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland” Appl. Geochemistry, 26, 931-953 (2011).

Keywords: uranium(VI) reduction; sulfate-reducing microorganisms; Opalinus Clay

  • Poster (Online presentation)
    TransRet2020, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33409
Publ.-Id: 33409


Tungsten (VI) speciation in hydrothermal solutions up to 400°c as revealed by in-situ Raman spectroscopy

Carocci, E.; Truche, L.; Cathelineau, M.; Bazarkina, E.

Tungsten (VI) speciation in hydrothermal solutions is investigated through in-situ Raman spectroscopy coupled to the fused silica glass capillary technique at temperatures up to 400 °C. The effect of temperature, pH, chlorinity and carbonate speciation are evaluated in systems with highly soluble salts Na2WO4 and Na6W12O39. At all investigated temperatures, the tungstate ion WO42- (927 cm-1) is the only W species in solution at pH > 10. At a given pH, the presence of dissolved carbonates and chloride does not affect the tungsten speciation. Tungsten polymers reveal to be stable up to 400 °C under acidic to circum-neutral pH conditions and total tungsten concentration above 0.01 molkgH2O-1-. Among the three observed polymers, namely [W7O24]6- (paratungstate-A, ~ 960 cm-1), [W10O32]4- (tungstate-Y, ~ 970 cm-1), and α-[H2W12O40]6- (α-metatungstate, ~ 990 cm-1), only the hepta and dodeca-tungstate are stable at elevated temperature. Combined with revised literature data, these results allow the thermodynamic stability constants of these W polymers to be constrained, enabling quantitative predictions of their relative abundance at T up to 300 °C. These predictions suggest that W polymerization occurs under hydrothermal conditions even at low W concentration (down to 10-5 mol·kgH2O-1) under acidic conditions. These observations imply that the currently available geochemical models on W transport and deposition in deep and hot geological fluids need to be revised.

Keywords: Tungsten polymers; Polytungstates; Fused silica glass capillary technique; Ore deposits

Permalink: https://www.hzdr.de/publications/Publ-33405
Publ.-Id: 33405


Ein „Wireless Sensor Network“ zur Prozesscharakterisierung in Biogasfermentern

Buntkiel, L.; Budelmann, C.; Heller, A.; Annas, S.; Reinecke, S.; Hampel, U.

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

Keywords: Wireless Sensor Network; Sensorpartikel; Biogas; Abwasser

  • Open Access Logo Contribution to proceedings
    Biogas in der Landwirtschaft, 29.-30.09.2021, Online, Deutschland
    Biogas in der Landwirtschft - Stand und Perspektiven, Darmstadt: KTBL, 978-3-945088-83-8
  • Open Access Logo Poster (Online presentation)
    Biogas in der Landwirtschaft, 29.-30.09.2021, Online, Deutschland
  • Open Access Logo Lecture (Conference) (Online presentation)
    Biogas in der Landwirtschaft, 29.-30.09.2021, Online, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-33402
Publ.-Id: 33402


Radiolabeled Silicon-Rhodamines as Bimodal PET/SPECT-NIR Imaging Agents

Kanagasundaram, T.; Laube, M.; Wodtke, J.; Kramer, S. C.; Stadlbauer, S.; Pietzsch, J.; Kopka, K.

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

Keywords: multimodal imaging; PET imaging; SPECT imaging; optical imaging; organic chemistry; near-infrared fluorophores; silicon-rhodamines; radiochemistry; radiofluorination; radioiodination

Permalink: https://www.hzdr.de/publications/Publ-33401
Publ.-Id: 33401


Dynamically assisted tunneling in the impulse regime

Kohlfürst, C.; Queißer, F.; Schützhold, R.

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

Keywords: Tunneling & traversal time; Nuclear fusion; Schroedinger equation

Permalink: https://www.hzdr.de/publications/Publ-33399
Publ.-Id: 33399


Towards Optimized Bioavailability of 99mTc‑Labeled Barbiturates for Non‑invasive Imaging of Matrix Metalloproteinase Activity

Honold, L.; Austrup, M.; Faust, A.; Konken, C.; Schwegmann, K.; Zinnhardt, B.; Daniliuc, C.; Haufe, G.; Schäfers, M.; Kopka, K.; Hermann, S.

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

Keywords: Barbiturates; Matrix metalloproteinase inhibitors; Pyrimidine-2,4,6-triones Single photon emission; Single photon emission computed tomography; Tumor imaging

Permalink: https://www.hzdr.de/publications/Publ-33397
Publ.-Id: 33397


Impact of background electrolyte composition on the interfacial formation of Th(IV) NPs on mica (001)

Neumann, J.; Qiu, C.; Eng, P.; Stumpf, T.; Schmidt, M.

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

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

  • Poster (Online presentation)
    ESRF User Meeting 1-2021, 08.-10.02.2021, Grenoble, Frankreich
  • Poster (Online presentation)
    APS/CNM User Meeting 2021, 10.-14.05.2021, Lemont, USA

Permalink: https://www.hzdr.de/publications/Publ-33394
Publ.-Id: 33394


Structural Investigation of the Adsorption von Y(III) on Orthoclase (001) Single Crystals using Resonant Surface X ray Diffraction

Neumann, J.; Lessing, J.; Demnitz, M.; Eng, P.; Stubbs, J.; Stumpf, T.; Schmidt, M.

INTRODUCTION

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

DESCRIPTION OF THE WORK

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

RESULTS AND DISCUSSION

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

  • Lecture (Conference)
    TransRet Workshop: Processes Influencing Radionuclide Transport and Retention, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33393
Publ.-Id: 33393


f-element sorption onto K-feldspar – A comprehensive characterization of mechanism and thermodynamics

Neumann, J.; Brinkmann, H.; Britz, S.; Lützenkirchen, J.; Bok, F.; Stockmann, M.; Brendler, V.; Stumpf, T.; Schmidt, M.

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

  • Lecture (Conference) (Online presentation)
    Goldschmidt Konferenz, 04.-09.07.2021, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33392
Publ.-Id: 33392


Umfassende Untersuchung und Bestimmung thermodynamischer Daten der Sorption von dreiwertigen Metallionen an K-Feldspat

Neumann, J.; Brinkmann, H.; Britz, S.; Lützenkirchen, J.; Bok, F.; Stockmann, M.; Brendler, V.; Stumpf, T.; Schmidt, M.

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

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

Keywords: sorption; trivalent; lanthanides; actinides; K-feldspar; TRLFS; SCM

  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33391
Publ.-Id: 33391


Data Publication: Development of [18F]LU14 for PET Imaging of Cannabinoid Receptor Type 2 in the Brain

Moldovan, R.-P.

Cannabinoid receptors type 2 (CB2R) represent an attractive therapeutic target for neurodegenerative diseases and cancer. Aiming at a positron emission tomography (PET) radiotracer to monitor receptor density and/or occupancy during a CB2R-tailored therapy, we developed here cis-[18F]1-(4-fluorobutyl-N-((1s,4s)-4-methylcyclohexyl)-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamide ([18F]LU14) starting from the corresponding mesylate precursor. First biological evaluation revealed that [18F]LU14 is a highly affine CB2R radioligand with >80% intact tracer in brain at 30 min p.i. Its further evaluation in a well-established rat model of CB2R overexpression by PET demonstrated its ability to selectively image the CB2R in the brain and its potential as tracer to further investigate diseased related CB2R changes in expression.

Keywords: Cannabinoid receptor type 2; naphtyrid-2-one; binding affinity; radiochemistry; fluorine-18 labeling; brain; positron emission tomography

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-11
    DOI: 10.14278/rodare.1260
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33389
Publ.-Id: 33389


Domain wall damping in ultrathin nanostripes with Dzyaloshinskii-Moriya interaction

Volkov, O.; Pylypovskyi, O.; Kronast, F.; Abert, C.; Oliveros Mata, E. S.; Makushko, P.; Mawass, M.-A.; Kravchuk, V.; Sheka, D.; Faßbender, J.; Makarov, D.

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

Here, we demonstrate both experimentally and theoretically the presence of tilted DWs in statics in perpendicularly magnetized asymmetric //CrOx/Co/Pt layer stacks with surface-induced DMI, Fig. 1. We show that in such systems there are two possible theoretical mechanism for the appearance of titled DWs: (I) A unidirectional tilt could appear in equilibrium as a result of the competition between the DMI and additional in-plane easy-axis anisotropy, which breaks the symmetry of the magnetic texture and introduce tilts [10]. (II) A static DW tilt could appear due to the spatial variation of magnetic parameters, which introduce pinning centers for DWs. A moving DW can be trapped in a tilted state after the external driving field is off. Based on these theoretical approaches, we perform a statistical analysis of the DW tilt angles obtained in staticts after the external magnetic field used for the sample demagnetization was off. We found that the second approach corresponds better to the experimental observations and allows to determine self-consistently the range of DW damping parameters and DMI constants for the particular layer stack. Using two reference fields, which provide two characteristic tilt angles, allow us to retrieve the range of DMI strength mJ/m2 and DW damping parameters . The upper limit for the DMI constant agrees with an independent transport-based measurement giving mJ/m2, which further refines our estimate of the damping parameter . This value lies in a typical DW damping range for the Co-based asymmetrical layer stacks, that are obtained from dynamic experiments [11,12]. Thus, the combination of the proposed method with standard metrological techniques opens up opportunities for the quantification of both static and dynamic micromagnetic parameters based on static measurements of the DW morphology.
[1] A. Fert, N. Reyren, and V. Cros, Nature Reviews Materials 2, 17031 (2017).
[2] R. Wiesendanger, Nature Reviews Materials 1, 16044 (2016).
[3] A. N. Bogdanov and D. A. Yablonskiı̆, Zh. Eksp. Teor. Fiz. 95, 178 (1989).
[4] S. Woo, K. Litzius, B. Krüger, et al., Nature Materials 15, 501 (2016).
[5] S. Emori, U. Bauer, S.-M. Ahn, et al., Nature Materials 12, 611 (2013).
[6] C. Garg, S.-H. Yang, T. Phung, et al., Science Advances 3, e1602804 (2017).
[7] S. Parkin and S.-H. Yang, Nature Nanotechnology 10, 195 (2015).
[8] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, et al., Reviews of Modern Physics 77, 1375 (2005).
[9] A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, Physical Review Letters 101, 037207 (2008).
[10] O. V. Pylypovskyi, V. P. Kravchuk, O. M. Volkov, et al., Journal of Physics D: Applied Physics 53, 395003 (2020).
[11] J.-M. L. Beaujour, J. H. Lee, A. D. Kent, et al., Physical Review B 74 (2006).
[12] A. J. Schellekens, L. Deen, D. Wang, et al., Applied Physics Letters 102, 082405 (2013).

Keywords: Nanomagnetism; Dzyaloshinskii-Moriya interaction

  • Open Access Logo Lecture (Conference) (Online presentation)
    INTERMAG 2021, 26.-30.04.2021, Online, France

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Permalink: https://www.hzdr.de/publications/Publ-33381
Publ.-Id: 33381


Experimental confirmation of curvature-induced effects in magnetic nanosystems

Volkov, O.; Kakay, A.; Kronast, F.; Mawass, M.-A.; van den Brink, J.; Kravchuk, V.; Sheka, D.; Faßbender, J.; Makarov, D.

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

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

Keywords: Nanomagnetism; Curvilinear magnetism

  • Poster (Online presentation)
    717. WE-Heraeus-Seminar — Curvilinear Condensed Matter: Fundamentals and Applications, 24.-26.06.2021, Online, Germany

Permalink: https://www.hzdr.de/publications/Publ-33378
Publ.-Id: 33378


RevCAR platform as a combinatorial approach for targeting acute myeloid leukemia

Rodrigues Loureiro, L. R.; González Soto, K. E.; Kittel-Boselli, E.; Hoffmann, A.; Bergmann, R.; Arndt, C.; Mitwasi, N.; Kegler, A.; Bartsch, T.; Berndt, N.; Altmann, H.; Fasslrinner, F.; Bornhäuser, M.; Bachmann, M.; Feldmann, A.

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

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

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

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

  • Open Access Logo Lecture (Conference) (Online presentation)
    World Immunotherapy Council´s 4th Young Investigator Symposium (WIC), 10.11.2021, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-33377
Publ.-Id: 33377


Curvature-induced effects in magnetic nanosystems

Volkov, O.; Sheka, D.; Kravchuk, V.; Rößler, U.; Faßbender, J.; Makarov, D.

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

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

Keywords: Nanomagnetism; Curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    APS March Meeting 2021, 15.-19.03.2021, Online, USA

Permalink: https://www.hzdr.de/publications/Publ-33375
Publ.-Id: 33375


Numerical reverse engineering of general spin-wave dispersions: Bridge between numerics and analytics using a dynamic-matrix approach

Körber, L.; Kakay, A.

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

Keywords: spin wave; Micromagnetic simulations; theory; dispersion; dynamic-matrix approach; normal modes; hybridization; numerics

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Permalink: https://www.hzdr.de/publications/Publ-33366
Publ.-Id: 33366


Data for: Heterogeneous sorption of radionuclides predicted by crystal surface nanoroughness

Yuan, T.; Schymura, S.; Bollermann, T.; Molodtsov, K.; Chekhonin, P.; Schmidt, M.; Stumpf, T.; Fischer, C.

Reactive transport modeling (RTM) is an essential tool for the prediction of contaminants’ behavior in the bio- and geosphere. However, RTM of sorption reactions is constrained by the reactive surface site assessment. The reactive site density variability of the crystal surface nanotopography provides an “energetic landscape”, responsible for heterogeneous sorption efficiency, not covered in current RTM approaches.  Here, we study the spatially heterogeneous sorption behavior of Eu(III), as an analogue to trivalent actinides, on a polycrystalline nanotopographic calcite surface and quantify the sorption efficiency as a function of surface nanoroughness. Based on experimental data from micro-focus time-resolved laser-induced luminescence spectroscopy (µTRLFS), vertical scanning interferometry, and electron back-scattering diffraction (EBSD), we parameterize a surface complexation model (SCM) using surface nanotopography data. The validation of the quantitatively predicted spatial sorption heterogeneity suggests that retention reactions can be considerably influenced by nanotopographic surface features. Our study presents a way to implement heterogeneous surface reactivity into a predictive SCM for enhanced prediction of radionuclide retention.

Keywords: Sorption reactions; Crystal surface reactivity; µTRLFS; Surface complexation modeling; Radionuclide migration

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-08
    DOI: 10.14278/rodare.1254

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33364
Publ.-Id: 33364


Data publication: Nanoindentation response of ion-irradiated Fe, Fe-Cr alloys and ferritic-martensitic steel Eurofer 97: The effect of ion energy

Das, A.; Altstadt, E.; Kaden, C.; Kapoor, G.; Akhmadaliev, S.; Bergner, F.

The dataset consists of inputs from ion irradiation experiments, nanoindentation and empirical modeling results for Fe (G379), ferrritic Fe-9Cr (G385), martensitic Fe-9Cr (L252) and Eurofer 97 steel. The dataset also includes the basic characterization of microstructure.

Keywords: iron; Fe-Cr alloy; ferritic-martensitic steel; ion irradiation; displacement damage; nanoindentation; irradiation hardeníng; indentation size effect

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-08
    DOI: 10.14278/rodare.1250
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33362
Publ.-Id: 33362


A Small Step, a Giant Leap: Somatic Hypermutation of a Single Amino Acid Leads to Anti-La Autoreactivity

Bartsch, T.; Arndt, C.; Rodrigues Loureiro, L. R.; Kegler, A.; Puentes-Cala, E.; Soto, J. A.; Kurien, B. T.; Feldmann, A.; Berndt, N.; Bachmann, M.

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

  • Open Access Logo International Journal of Molecular Sciences 22(2021)21, 12046
    Online First (2021) DOI: 10.3390/ijms222112046

Permalink: https://www.hzdr.de/publications/Publ-33361
Publ.-Id: 33361


Characterizing material liberation of multi-material lightweight structures from shredding experiments and finite element simulations

Heibeck, M.; Rudolph, M.; Modler, N.; Reuter, M.; Filippatos, A.

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

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

Keywords: Recycling; Shredding; Multi-material design; Material liberation; Joint characterization; Composites; Finite Element Method

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Permalink: https://www.hzdr.de/publications/Publ-33360
Publ.-Id: 33360


SOLSTICE - Na-Zn molten salt batteries

Weber, N.; Heinz, M.; Lee, J.; Weier, T.

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

  • Invited lecture (Conferences) (Online presentation)
    Horizon 2020 Batteries Projects clustering event, 17.-18.11.2021, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-33356
Publ.-Id: 33356


Germanium as an ultrabroadband THz material

Helm, M.; Singh, A.; Pashkin, O.; Winnerl, S.; Beckh, C.; Sulzer, P.; Leitenstorfer, A.; Schneider, H.

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

Keywords: germanium; THz; photoconductive antenna; braodband

  • Invited lecture (Conferences) (Online presentation)
    RJUSE TeraTech 2021, 01.-04.11.2021, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-33354
Publ.-Id: 33354


Data publication: How 5f electron polarizability drives covalency and selectivity in actinide N-donor complexes

Köhler, L.; Patzschke, M.; Schmidt, M.; Stumpf, T.; März, J.

Diese Daten beinhalten die Synthese und Charakterisierung neuartiger Actinid (Th, U, Np, Pu) Komplexe mit pyrrolbasierten Liganden, sowie ebenfalls die Ligandsynthese. Darunter fallen SC-XRD, NMR, IR, UV-VIS und EA Daten. Des weiteren quantenchemische Berechnungen zu den Systemen, sowie der Vergleich zum bereits bekannten Salen System.

Keywords: actinides; N donor ligands; bonding analysis; f electrons; pyrrole

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-05
    DOI: 10.14278/rodare.1245
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33353
Publ.-Id: 33353


Computational Science at HZDR: Tools, Services, and Consulting to Empower Your Research

Pape, D.; Lokamani, M.; Knodel, O.; Müller, S.; Huste, T.; Steinbach, P.; Juckeland, G.; Fiedler, M.

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

Keywords: Computational Science; Research Software Engineering; High Performance Computing; Data Management; Machine Learning; Artificial Intelligence; Data Science

  • Lecture (others)
    PhD Seminar 2021, 18.10.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33351
Publ.-Id: 33351


Data publication: Strong Binding of Noble Gases to [B₁₂X₁₁]⁻: a theoretical study

Wöhner, K.; Wulf, T.; Vankova, N.; Heine, T.

This dataset contains output files of DFT and DLPNO calculations of the investigated species. At the DFT level of theory full geometry optimizations and frequency analysis where done. At DLPNO level of theory single point calculations were done.

Keywords: Boron; Anions; Complexation; Cluster chemistry; Group 17 compounds

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-04
    DOI: 10.14278/rodare.1241
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33348
Publ.-Id: 33348


Data publication: Development of fluorinated and methoxylated benzothiazole derivatives as highly potent and selective cannabinoid CB2 receptor ligands

Aly, M. W.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.; Abadi, A. H.; Moldovan, R.-P.; Osman, N. A.

Numerous studies have indicated the upregulation of the cannabinoid type 2 receptors (CB2 receptors) in neuroinflammation and cancer, and that their visualization with PET (Positron emission tomography) could provide a valuable diagnostic and/or therapy-monitoring tool in such disorders. However, the availability of reliable CB2-selective imaging probes is still lacking in clinical practice. Encouraged by promising CB2 affinity results obtained for a benzothiazole lead compound, 6a, further structural optimizations led to the development of a series of fluorinated and methoxylated benzothiazole derivatives, endowed with extremely high CB2 binding affinity and an exclusive selectivity to the CB2 receptor, along with structural sites suitable for radiolabeling. Compounds 20, 21, 24, 25, 29, 32 and 33 displayed subnanomolar CB2 Ki values (ranging from 0.16 nM to 0.68 nM) while lacked affinity to the CB1 receptor subtype. The fluorinated analogs, 21 and 29, were evaluated for their in vitro metabolic stability in mouse and human liver microsomes (MLM and HLM). Both 21 and 29 displayed an exceptionally high stability (98% and 91% intact compounds, respectively) after 60 min incubation with MLM. Contrastingly, compound 29 revealed an almost 2-fold greater metabolic stability after incubation with HLM for 60 min. Taken together, our data represent remarkably potent and selective CB2 ligands as credible leads that can be further exploited for 18F- or 11C-radiolabeling and utilization as PET tracers.

Keywords: Benzothiazole; Cannabinoid receptor type 2; CB2 ligands; Fluorine; Metabolic studies; PET

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-19
    DOI: 10.14278/rodare.1267
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33347
Publ.-Id: 33347


Data publication: Design, radiosynthesis and preliminary biological evaluation in mice of a brain-penetrant 18F-labelled σ2 receptor ligand

Moldovan, R.-P.; Gündel, D.; Teodoro, R.; Ludwig, F.-A.; Fischer, S.; Toussaint, M.; Schepmann, D.; Wünsch, B.; Brust, P.; Deuther-Conrad, W.

The σ2 receptor (transmembrane protein 97), which is involved in cholesterol homeostasis, is of high relevance for neoplastic processes. The upregulated expression of σ2 receptors in cancer cells and tissue in combination with the antiproliferative potency of σ2 receptor ligands motivates the research in the field of 2 receptors for the diagnosis and therapy of different types of cancer. Starting from the well described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds, we synthesized a novel series of fluorinated derivatives, bearing the F-atom at the aromatic indole/azaindole subunit. RM273 (2-[4-(6-fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) was selected for labelling with 18F and evaluation regarding detection of σ2 receptors in the brain by positron emission tomography. Initial metabolism and biodistribution studies of [18F]RM273 in healthy mice revealed promising penetration of the radioligand into the brain. Preliminary in vitro autoradiography on brain cryosections of an orthotopic rat glioblastoma model proved the potential of the radioligand to detect the upregulation of σ2 receptor in glioblastoma cells compared to healthy brain. The results indicate that the herein developed σ2 receptor ligand [18F]RM273 has potential to assess by non-invasive molecular imaging the correlation between the availability of σ2 receptors with properties of brain tumors such as tumor proliferation or resistance towards particular therapies

Keywords: σ2 receptor; transmembrane protein 97; azaindoles; binding affinity; radiochemistry; fluorine-18 labeling; positron emission tomography (PET); brain-penetration; glioblastoma; orthotopic

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-09
    DOI: 10.14278/rodare.1256
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33346
Publ.-Id: 33346


Continuous-time movement modeling

Alston, J.; Simoes Silva, I. M.; Fleming, C. F.; Noonan, M. J.

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

  • Lecture (Conference) (Online presentation)
    2021 The Wildlife Society Annual Meeting, 01.11.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33341
Publ.-Id: 33341


Movement ecology research at CASUS

Alston, J.; Calabrese, J.

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

  • Open Access Logo Lecture (Conference) (Online presentation)
    2021 EuroBoar Annual Meeting, 25.10.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33340
Publ.-Id: 33340


State with spontaneously broken time-reversal symmetry above the superconducting phase transition

Grinenko, V.; Weston, D.; Caglieris, F.; Wuttke, C.; Hess, C.; Gottschall, T.; Maccari, I.; Gorbunov, D.; Zherlitsyn, S.; Wosnitza, J.; Rydh, A.; Kihou, K.; Lee, C.-H.; Sarkar, R.; Dengre, S.; Garaud, J.; Charnukha, A.; Hühne, R.; Nielsch, K.; Büchner, B.; Klauss, H.-H.; Babaev, E.

The most well-known example of an ordered quantum state—superconductivity—is caused by the formation and condensation of pairs of electrons. Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of pairs of electrons, leading to zero resistivity and diamagnetism. Here we report a set of experimental observations in hole-doped Ba1−xKxFe2As2. Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. This combined evidence indicates the existence of a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs.

Permalink: https://www.hzdr.de/publications/Publ-33339
Publ.-Id: 33339


A two-sublattice model for extracting rare-earth anisotropy constants from measurements on (Nd,Ce)2(Fe,Co)14B single crystals

Gomez Eslava, G.; Fayyazi, B.; Skokov, K.; Scurschii, I.; Gorbunov, D.; Gutfleisch, O.; Dempsey, N. M.; Givord, D.

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

Permalink: https://www.hzdr.de/publications/Publ-33338
Publ.-Id: 33338


Data publication: Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

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

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

Related publications

  • Software in external data repository
    Publication year 2021
    Programming language: Python
    System requirements: python, numpy, scipy, sklearn, torch, matplotlib, seaborn, pandas
    License: MIT
    Hosted on GitHub: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33337
Publ.-Id: 33337


Antiferromagnetic resonance in the cubic iridium hexahalides (NH4)2IrCl6 and K2IrCl6

Bhaskaran, L.; Ponomaryov, O.; Wosnitza, J.; Khan, N.; Tsirlin, A. A.; Zhitomirsky, M. E.; Zvyagin, S.

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

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33336
Publ.-Id: 33336


Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

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

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33335
Publ.-Id: 33335


Electric-field manipulation of the magnetocaloric effect in a Fe49Rh51/PZT composite

Amirov, A. A.; Gottschall, T.; Chirkova, A. M.; Aliev, A. M.; Baranov, N. V.; Skokov, K. P.; Gutfleisch, O.

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

Permalink: https://www.hzdr.de/publications/Publ-33334
Publ.-Id: 33334


Data - CST Studio files used for "Modeling of the effective permittivity of open-cell ceramic foams inspired by Platonic solids"

Camacho Hernandez, J. N.

CST Studio files with the geometry of sintered and Platinic foams used for calculating their effective permittivity. The permittivity of the continuous medium and the skeleton can be changed in materials. To change the porosity of platinum foams, the diameter of the struts in the parameter list must be changed. These files were used for preparing the article "Modeling of the effective permittivity of open-cell ceramic foams inspired by Platonic solids"

  • Software in the HZDR data repository RODARE
    Publication date: 2021-11-03
    DOI: 10.14278/rodare.1232
    License: CC-BY-4.0
    Embargo: 01.06.2022

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Permalink: https://www.hzdr.de/publications/Publ-33329
Publ.-Id: 33329


The performance of ²¹⁰Pb AMS for the radioassay of materials considered for the construction of ultra-low background experiments in Astroparticle Physics

Vivo Vilches, C.; Gornea, R.; Weiser, B.; Zhao, X.; Francisco, B. B. A.; Kieser, W. E.

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

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

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

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

Keywords: ²¹⁰Pb contamination; Accelerator mass spectrometry; Rare event searches; Astroparticle physics; Radiopurity

  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 19.11.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33325
Publ.-Id: 33325


HELIPORT (HELmholtz ScIentific Project WORkflow PlaTform)

Knodel, O.; Voigt, M.; Ufer, R.; Pape, D.; Lokamani, M.; Müller, S.; Gruber, T.; Juckeland, G.

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

  • Invited lecture (Conferences) (Online presentation)
    Better Data for Better Science - Research Data Management Workshop, 28.-29.10.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-33323
Publ.-Id: 33323


Water dissociation and association on mirror twin boundaries in two-dimensional MoSe 2 : insights from density functional theory calculations

Joseph, T.; Ghorbani Asl, M.; Batzill, M.; Krasheninnikov, A.

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

Keywords: ORR; MTB; TMD; Water dissociation and association

Permalink: https://www.hzdr.de/publications/Publ-33321
Publ.-Id: 33321


Data for "Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1"

Skouteris, G.; Parra Ramirez, M. A.; Reinecke, S.; Hampel, U.

Input files and simulation results for the related publication.

Keywords: Energy flexibility; Wastewater treatment plant; Benchmark simulation model 1

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-02
    DOI: 10.14278/rodare.1229
    License: CC-BY-1.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33317
Publ.-Id: 33317


Substitutional synthesis of sub-nanometer InGaN/GaN quantum wells with high indium content

Vasileiadis, I. G.; Lymperakis, L.; Adikimenakis, A.; Gkotinakos, A.; Devulapalli, V.; Liebscher, C. H.; Androulidaki, M.; Hübner, R.; Karakostas, T.; Georgakilas, A.; Komninou, P.; Dimakis, E.; Dimitrakopulos, G. P.

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

Permalink: https://www.hzdr.de/publications/Publ-33316
Publ.-Id: 33316


Obvious phase transition status induced by He+-ions implantation in KTN crystal

Yang, Q.; Li, X.; Liu, H.; Zheng, D.; Akhmadaliev, S.; Zhou, S.; Wu, P.

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

Keywords: Implantation/irradiation; Ferroelectric; Relaxor; Phase stability; Polarized nanometric regions

Permalink: https://www.hzdr.de/publications/Publ-33315
Publ.-Id: 33315


Q-switched mode-locked laser generation by Au nanoparticles embedded in LiTaO3 crystals

Pang, C.; Li, R.; Li, Z.; Sun, X.; Dong, N.; Wang, J.; Zhou, S.; Chen, F.

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

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Permalink: https://www.hzdr.de/publications/Publ-33314
Publ.-Id: 33314


An E/E approach to model subcooled boiling for a stable/semi-stable system

Ding, W.; Setoodeh, H.; Lucas, D.; Hampel, U.

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

Keywords: WALL BOILING; HEAT PARTITIONING; FLOW PATTERN

  • Lecture (others) (Online presentation)
    DEBORA BENCHMARK MEETING, 05.-06.10.2021, Paris (Virtual), France

Permalink: https://www.hzdr.de/publications/Publ-33313
Publ.-Id: 33313


Data: Electrical Characterization of Germanium Nanowires Using a Symmetric Hall Bar Configuration: Size and Shape Dependence

Echresh, A.; Arora, H.; Fuchs, F.; Li, Z.; Hübner, R.; Prucnal, S.; Schuster, J.; Zahn, P.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

The uploaded data are related to electrical measurements including two- and four-probe, Hall effect, and temperature-dependent measurements. The simulation data is included as well.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-30
    DOI: 10.14278/rodare.1227

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33311
Publ.-Id: 33311


Electrical Characterization of Germanium Nanowires Using a Symmetric Hall Bar Configuration: Size and Shape Dependence

Echresh, A.; Arora, H.; Fuchs, F.; Li, Z.; Hübner, R.; Prucnal, S.; Schuster, J.; Zahn, P.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

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

Keywords: germanium nanowires; Hall bar configuration; Hall effect; electrical characterization

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-33310
Publ.-Id: 33310


How Can Drones Contribute to Mineral Exploration?

Booysen, R.; Lorenz, S.; Jackisch, R.; Gloaguen, R.; Madriz Diaz, Y. C.

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

Keywords: Drones; UAS; UAV; Hyperspectral; Magnetics; Machine learning; Exploration

  • Invited lecture (Conferences) (Online presentation)
    IGARSS 2021 - 2021 IEEE International Geoscience and Remote Sensing Symposium, 16.07.2021, Brussels, Belgium
    DOI: 10.1109/IGARSS47720.2021.9554041

Permalink: https://www.hzdr.de/publications/Publ-33308
Publ.-Id: 33308


HELIPORT use case POLARIS: Integration of a High Intensity Laser in a complete data life cycle workflow

Knodel, O.; Hein, J.; Kessler, A.

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

Keywords: HELIPORT; Data Management; Workflows; POLARIS; Laser; Data life cycle

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Better Data for Better Science - Research Data Management Workshop, 28.-29.10.2021, online, online

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33307
Publ.-Id: 33307


Data publication: Flow morphology of high-pressure steam condensation in an inclined tube at low inlet steam qualities

Boden, S.; Moonesi Shabestary, A.; Bieberle, A.; Pietruske, H.; Hampel, U.

This archive contains the processed X-ray data of the measurement campaign "Investigation of flow morphology and heat transfer in an inclined tube", which was conducted between June 2020 and June 2021 at the thermal hydraulic test facility COSMEA (COndenSation test rig for flow Morphology and hEAt transfer studies) at Helmholtz-Zentrum Dresden - Rossendorf (HZDR). The flow morphology of high-pressure (up to 65 bar) steam condensation in a slightly inclined tube at low inlet steam qualities (down to 2.8%) were are studied. Both X-ray computed tomography as well as X-ray radioscopy have been applied. The results include images of the local condensate distribution in selected cross-sections of the condenser tube as well as time resolved projections of the condensate distribution.

Keywords: steam condensation; two-phase flow; X-ray tomography; X-ray radioscopy

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-27
    DOI: 10.14278/rodare.1223

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33300
Publ.-Id: 33300


Universal Liquid Metal Alloy Ion Sources for FIB nanofabrication

Richter, T.; Mazarov, P.; Meyer, F.; Pilz, W.; Bischoff, L.; Klingner, N.

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

Keywords: Liquid Metal Alloy Ion Sources; FIB; nanofabrication

  • Lecture (Conference) (Online presentation)
    34th International Microprocesses and Nanotechnology Conference (MNC 2021), 26.-29.10.2021, Osaka, Japan

Permalink: https://www.hzdr.de/publications/Publ-33299
Publ.-Id: 33299


Towards multiscale ab-initio simulations: size transferability of density functional theory surrogates

Fiedler, L.

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

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    8th International Symposium on Optics & its applications, 19.-22.10.2021, Rostock, Dresden

Permalink: https://www.hzdr.de/publications/Publ-33296
Publ.-Id: 33296


Investigation of transferability in LDOS based DFT surrogate models for multiscale simulations

Fiedler, L.; Cangi, A.

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

Keywords: Machine Learning; Density Functional Theory; Surrogate Model

  • Lecture (Conference) (Online presentation)
    84. Jahrestagung der DPG und DPG-Tagung der Sektion Kondensierte Materie (SKM), 27.09.-01.10.2021, online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33295
Publ.-Id: 33295


Materials Learning Algorithms (MALA): An Efficient Surrogate for Ab-initio Simulations

Fiedler, L.

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

Keywords: Density Functional Theory; Machine Learning; Surrogate Model

  • Lecture (Conference)
    17th International Conference on the Physics of Non-Ideal Plasmas, 20.-24.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33294
Publ.-Id: 33294


Rapid Iron(III)-Fluoride Mediated Hydrogen Atom Transfer

Panda, C.; Doyle, L. M.; Gericke, R.; McDonald, A. R.

We anticipate high-valent metal fluoride species will be highly effective hydrogen atom transfer (HAT) oxidants because of the magnitude of the H–F bond (in the product) that drives HAT oxidation. We prepared a dimeric Fe(III)(F)–F–Fe(III)(F) complex (1) by reacting [Fe(II)(NCCH₃)₂(TPA)](ClO₄)₂ (TPA = tris-(2-pyridylmethyl)amine) with difluoro(phenyl)-λ3-iodane (difluoroiodobenzene). 1 was a sluggish oxidant, however, it was readily activated by reaction with Lewis or Brønsted acids to yield a monomeric [Fe(III)(TPA)(F)(X)] + complex (2) where X = F/OTf. 1 and 2 were characterised using NMR, EPR, UV-vis, and FT-IR spectroscopies and mass spectrometry. 2 was a remarkably reactive Fe III reagent for oxidative C–H activation, demonstrating reaction rates for hydrocarbon HAT comparable to the most reactive Fe III and Fe IV oxidants.

Keywords: high-valent oxidants; biomimetic; proton coupled electron transfer; fluoride oxidant

Permalink: https://www.hzdr.de/publications/Publ-33292
Publ.-Id: 33292


Comparing Metal–Halide and −Oxygen Adducts in Oxidative C/O–H Activation: Au(III)–Cl versus Au(III)–OH

Lovisari, M.; Gericke, R.; Twamley, B.; McDonald, A. R.

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

Keywords: Bond dissociation free energy; Hydrocarbons; Ligands; Gold; Oxidation

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Permalink: https://www.hzdr.de/publications/Publ-33291
Publ.-Id: 33291


Effects of torsion and curvature in antiferromagnetic spin chains

Pylypovskyi, O.; Kononenko, D. Y.; Yershov, K.; Roessler, U.; Tomilo, A.; Faßbender, J.; van den Brink, J.; Makarov, D.; Sheka, D.

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

Keywords: antiferromagnetism; curvilinear magnetism; spin chains

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33289
Publ.-Id: 33289


Parallel computation of 3D magnetic structures

Tomilo, A.; Pylypovskyi, O.; Yershov, K.; Sheka, D.

Intensive experimental and theoretical research for novel materials introduces new architectures for magnetic devices, where shape and topology plays a crucial role [1]. A powerful way to study them as well as confirm analytical predictions is to compute the corresponding equations of motion numerically. Here, we present a spin-lattice simulation suite SLaSi, which can address flexible magnetic one- and two- dimensional spin lattices. They can represent soft wires and ribbons, where the coupling between magnetic and mechanical subsystem results into spontaneous deformations and symmetry breaks [2]. The SLaSi is a C-written program, where exchange, single-ion anisotropy, Zeeman energy, dipolar interaction, and Dzyaloshinskii-Moriya interaction are taken into account for the description cubic, square, and triangular lattices. Dynamics of the mechanical sub-system is modelled by the overdamped Newton equations, while magnetic sub-system is modelled by LLG. Speedup of the computations is achieved by parallelization using MPI and CUDA frameworks.

Keywords: curvilinear magnetism; computations; CUDA; MPI

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33288
Publ.-Id: 33288


Nanoscale mechanics of antiferromagnetic domain walls in Cr2O3

Hedrich, N.; Wagner, K.; Lehmann, P.; Pylypovskyi, O.; Shields, B. J.; Kosub, T.; Sheka, D.; Makarov, D.; Maletinsky, P.

Magneto-electric antiferromagnets hold promise for future spintronic devices, as they offer magnetic field hardness, high switching speeds combined with electric and magnetic control of their order parameters, owing to the magneto-electric coupling [1]. As information and functionality is encoded in the antiferromagnetic order parameter, its manipulation, read-out and nanoscale texture are paramount for device operation, as well as interesting from a fundamental point of view. E.g. spin-textures in such materials are theorized to carry an intrinsic magnetization [2]. Here we study a single crystal ‘textbook’ magneto-electric antiferromagnet, Cr2O3, by nanoscale imaging of its surface magnetization via magnetic stray field imaging by scanning nitrogen vacancy magnetometry [3]. This surface magnetization is directly linked to the bulk Neel vector of Cr2O3 and thereby allows for nanoscale imaging of antiferromagnet spin textures. After confirming magneto-electric poling [4], local electrodes are utilized to nucleate single domain walls, which we then study on the nanometer scale. Manipulation of the domain wall is demonstrated both by local laser heating [5], as well as the creation of an energy landscape for the domain wall via topographic structuring [3]. We analyze the interaction of the domain wall with topographic islands both experimentally and in simulations. This analysis yields information about the domain wall boundary conditions at topographic edges and an estimate of the full 3D-profile of the texture based on minimizing the domain walls surface energy. A Snell like refraction of the domain wall path is found, that can be represented in an analytical approximation as a ‘refractive index’ for a given island dimension as demonstrated for a range of incidence angles.

We then observe bistable domain wall paths configurations and switching between them is demonstrated and imaged experimentally. This pinning and control of the domain wall position constitutes the main ingredients for logic devices based on domain walls in magneto-electric antiferromagnets and their fundamental study.

Keywords: antiferromagnetism; Cr2O3; mesa; NV magnetometry

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33287
Publ.-Id: 33287


Ground states of the antiferromagnetic spin rings in strong magnetic fields

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

Antiferromagnetic (AFM) materials have distinct advances compared to ferromagnets, that allow to use them in variety of spintronic applications [1,2]. Antiferromagnetically coupled curvilinear spin chains are of fundamental interest as simplest systems possessing interplay between the geometry and magnetic subsystem [3].

In this work, we analyze the ground states of AFM ring-shaped spin chain with the nearest-neighbour Heisenberg exchange and single-ion anisotropy in presence of external magnetic field. The direction of magnetic field coincides with the symmetry axis of the ring. Collinear two-sublattice 1D curved AFM chain with even number of spins is considered, and the hard axis of anisotropy is oriented tangentially to the chain.

Within the classical continuum approach its magnetic state is described by two order parameters, the Néel and ferromagnetism vector fields. In the ground state, the Néel vector is oriented perpendicularly to the ring plane.

The magnetic field applied along the ring normal allows to observe spin-flop and spin-flip orientational phase transitions. We determine the dependency of spin-flop and spin-flip transition fields on the ring curvature and the critical curvature which separates two topologically different ground states above spin-flop transition. The first one with the Néel order parameter within the normal plane is mainly determined by the anisotropy at small curvatures. The second ground state at large curvatures is represented by onion ordering of the Néel vector. With the applied fields larger than critical spin-flip transition field Néel order parameter vanishes, which leads to ferromagnetic ground state. The phase diagram of AFM as a function of applied field intensity and the ring curvature is developed.

Keywords: antiferromagnetism; spin-flop; curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    Curvilinear Condensed Matter: Fundamentals and Applications 717. WE-Heraeus-Seminar, 24.-26.06.2021, Bad Honnef, Germany

Permalink: https://www.hzdr.de/publications/Publ-33286
Publ.-Id: 33286


Challenges Porting a C++ Template-Metaprogramming Abstraction Layer to Directive-based Offloading

Kelling, J.; Bastrakov, S.; Debus, A.; Kluge, T.; Leinhauser, M.; Pausch, R.; Steiniger, K.; Stephan, J.; Widera, R.; Young, J.; Bussmann, M.; Chandrasekaran, S.; Juckeland, G.

HPC systems employ a growing variety of compute accelerators with different architectures and from different vendors. Large scientific applications are required to run efficiently across these systems but need to retain a single code-base in order to not stifle development. Directive-based offloading programming models set out to provide the required portability, but, to existing codes, they themselves represent yet another API to port to. Here, we present our approach of porting the GPU-accelerated particle-in-cell code PIConGPU to OpenACC and OpenMP target by adding two new backends to its existing C++-template metaprogramming-based offloading abstraction layer alpaka and avoiding other modifications to the application code. We introduce our approach in the face of conflicts between requirements and available features in the standards as well as practical hurdles posed by immature compiler support.

Keywords: C++; OpenACC; OpenMP; Offloading

  • Contribution to WWW
    https://arxiv.org/abs/2110.08650
  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    SC21 - The International Conference for High Performance Computing, Networking, Storage, and Analysis: OpenMP Offloading and the 5.2 API Birds-of-a-Feather, 14.-19.11.2021, St. Louis, MO, USA

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Permalink: https://www.hzdr.de/publications/Publ-33285
Publ.-Id: 33285


Geometrical symmetry breaking in nanomagnets

Pylypovskyi, O.

Three-dimensional ferro- and antiferromagnetic nanoarchitectures possess a special interplay between their geometrical (topological) properties and the magnetic order parameter. The emergent chiral and anisotropic responses extend the intrinsic material properties and pave the way to novel functionalities of spintronic and spin-orbitronic devices.

Keywords: curvilinear magnetism; ferromagnets; antiferromagnets

  • Invited lecture (Conferences) (Online presentation)
    META 2021 The 11th International Conference on Metamaterials, Photonic Crystals and Plasmonics, 20.-23.07.2021, Warsaw (Online event), Poland

Permalink: https://www.hzdr.de/publications/Publ-33284
Publ.-Id: 33284


Skin-conformal flexible and printable magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

Motion sensing is the primary task in numerous disciplines including industrial robotics, prosthetics, virtual and augmented reality appliances. In rigid electronics, rotations, displacements and vibrations are typically monitored using magnetic field sensors prepared on flat and rigid substrates. Extending 2D structures into 3D space relying on the flexible and printed electronics approaches allows to enrich conventional or to launch novel functionalities of spintronic-based devices by tailoring geometrical curvature and 3D shape. We developed shapeable magnetoelectronics [1] – namely, flexible, stretchable [2] and even printable [3] skin-conformal magnetosensitive elements. The technology platform relies on high-performance magnetoresistive and Hall effect sensors fabricated on ultrathin polymeric foils based on thin film technologies or printing methods. These mechanically shapeable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins, soft robotics and human-machine interfaces. With these activities, we extended the use of high quality magnetic thin films to new research and technology fields. This topic is gaining visibility in the interdisciplinary community of physicists, chemists, mechanical and electrical engineers working on the fabrication of 3D shaped magnetic functional membranes, develops methods for their characterisation and theoretical frameworks for their description as well as puts forth concepts for the technological implementation of shapeable magnetoelectronics in different application fields. Here, we will review technological platforms allowing to realize mechanically imperceptible electronic skins for interactive electronics, which enable perception of the geomagnetic field, but also enable sensitivities down to ultra-small fields of sub-50 nT. These devices allow humans to orient with respect to earth’s magnetic field ubiquitously. Furthermore, biomagnetic orientation enables novel interactivity concepts for virtual and augmented reality applications. We showcase this by realizing touchless control of virtual units in a game using omnidirectional magnetosensitive skins [2]. This concept was further extended by demonstrating a flexible magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time [4]. This is crucial for smart home applications, interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly conformal integrated feedback system [5] as well as in medicine for physicians and surgeons. In 2019, we brought these research activities to the next level in the frame of the Helmholtz Innovation Lab FlexiSens. FlexiSens bridges fundamental and application-oriented activities with the focus on the transfer of the thin film fabricated sensor technologies for flexible and printable electronics to the market. For this purpose, together with Scia Systems GmbH, we establish a 300 mm grade production line (thin film deposition, lithography, chemical processing of 300 mm wafers) to bring the our sensor technologies to the industry-relevant scale. Flexible magnetic field sensors are offered to industry partners either directly via the HZDR or via the company HZDR Innovation GmbH and already bring financial benefit to the group. The fundamental and application-oriented aspects of this technology will be discussed in the presentation.

[1] D. Makarov, M. Melzer, D. Karnaushenko, O. G. Schmidt, Applied Physics Reviews, 2016, 3, 011101.
[2] G. S. Cañón Bermúdez, H. Fuchs, L. Bischoff, J. Fassbender, D. Makarov, Nature Electronics, 2018, 1, 589.
[3] M. Ha, G. S. Cañón Bermúdez, T. Kosub, I. Mönch, Y. Zabila, E. S. Oliveros Mata, R. Illing, Y. Wang, J. Fassbender, D. Makarov, Advanced Materials, 2021, 33, 2005521.
[4] J. Ge, X. Wang, M. Drack, O. Volkov, M. Liang, G. S. Cañón Bermúdez, R. Illing, C. Wang, S. Zhou, J. Fassbender, M. Kaltenbrunner, D. Makarov, Nature Communications, 2019, 10, 4405.
[5] M. Ha, G. S. Cañón Bermúdez, J. A.-C. Liu, E. S. Oliveros Mata, B. A. Evans, J. B. Tracy, D. Makarov, Advanced Materials, 2021, 33, 2008751.

Keywords: flexible electronics; printed electronics; magnetic field sensing; human-machine interfaces; soft robotics

  • Invited lecture (Conferences) (Online presentation)
    Advanced Nanomaterials Congress, 24.-27.10.2021, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-33281
Publ.-Id: 33281


Effect of Nozzle Geometry on Centerline Gas Holdup in Submerged Gas Injection

Xiao, J.; Yan, H.; Schubert, M.; Liu, L.; Döß, A.; Schleicher, E.; Hampel, U.

Non-circular nozzle geometries are widely used in many industrial processes with submerged gas injection for altering the centerline gas holdup to intensify the reaction process. However, the effect of the nozzle geometry on the centerline gas holdup is rarely investigated. In this work, hollow circular-shaped, gear-shaped, four-flower-shaped and multi-hole-shaped nozzle geometries are utilized to investigate the centerline gas holdup by wire-mesh sensors and
digital image processing. The results reveal that the centerline gas holdup is influenced by nozzle geometry, axial distance and gas flow rate. The centerline gas holdup for hollow circular-shaped,four-flower-shaped and multi-hole-shaped nozzles is larger than that of the gear-shaped nozzle.
The correlations for the centerline gas holdup are obtained based on modified Froude number Frm and dimensionless axial distance o via regression analysis. The correlations for hollow circular-shaped nozzle geometry obtained in this study are validated with experimental data
from this study and the literature.

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  • Secondary publication expected from 08.10.2022

Permalink: https://www.hzdr.de/publications/Publ-33280
Publ.-Id: 33280


Block model of passive seismic shear velocity and airborne electromagnetic resistivity in the Geyer area, Erzgebirge, Germany

Ryberg, T.; Kirsch, M.; Haberland, C.; Tolosana Delgado, R.; Viezzoli, A.; Gloaguen, R.

As a means of investigating the structure of the geological subsurface and delineating Sn-W-Li greisen-hosted mineral deposits in the Geyer-Ehrenfriedersdorf area, Central Erzgebirge, Germany, we collected an ambient noise dataset which was supplemented and analysed together with airborne time-domain electromagnetic data. The here presented dataset is a combined three-dimensional block model containing the following parameters:

(X), (Y), (Z) – Coordinates of the block model center nodes in ETRS89 UTM33N coordinates.

(PS_vel) – Shear wave velocity based on ambient noise data from a dense "LARGE-N" network comprising 400 low-power, short-period seismic stations tomographically inverted based on Bayesian statistics.

(logVTEM_res) – Logarithm of resistivity based on airborne time-domain electromagnetic data acquired using the Geotech Versatile Time Domain (VTEM™ ET) system and inverted using a layered earth approach.

(class_K-means) – Class labels of a spatially constrained clustering using K-means with 26 immediate neighbours performed on the bivariate velocity-resistivity 3D dataset.

Keywords: Ambient seismic noise; Airborne electromagnetics; Mineral exploration

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-21
    DOI: 10.14278/rodare.1221
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33279
Publ.-Id: 33279


Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier / supplementary data

Schoenig, J.; von Eynatten, H.; Tolosana Delgado, R.; Meinhold, G.

The database includes 13615 garnet compositions of eight oxides commonly analysed in lab routines: SiO2, TiO2, Al2O3, Cr2O3, FeOtotal, MnO, MgO, and CaO (in wt%). These are complemented by the following covariables:

setting and metamorphic facies class: code indicating the geologic/tectonic setting of the host rock

composition class: code indicating the compositional class of the host rock

author: authors of the original paper providing the data

journal: journal of the original paper

region: origin of the data, in the format "region, country"

sample name: sample ID in the original paper

Pavg(kbar): if available, indicated pressure

Tavg(°C): if available, indicated temperature

host-rock type and/or metamorphic facies: facies indication of host rock

lithology and/or protolith: composition indication of host rock

SiO2: wt%

TiO2: wt%

Al2O3: wt%

Cr2O3: wt%

FeOtotal: wt%

MnO: wt%

MgO: wt%

CaO: wt%

This research was funded by DFG grant EY 23/27-1.

Keywords: garnet major-element composition; host-rock discrimination

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-10-21
    DOI: 10.14278/rodare.1219
    License: CC-BY-4.0
    Embargo: 31.12.2022

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Permalink: https://www.hzdr.de/publications/Publ-33278
Publ.-Id: 33278


Energy Flexibility Chances for the Wastewater Treatment Plant of the Benchmark Simulation Model 1

Parra Ramirez, M. A.; Reinecke, S.; Skouteris, G.; Hampel, U.

Future energy systems must mainly generate electricity from renewable resources. To
deal with the fluctuating availability of wind and solar power, new versatile electricity markets and
sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated
the potential of energy flexibility achieved through demand-side response for the wastewater treat-
ment plant of the Benchmark Simulation Model 1. First, seven control strategies were simulated and
assessed. Next, the flexibility calls were identified, two energy flexibility scenarios were defined and
incorporated into the model, and the control strategies were evaluated anew. In this research, the
effluent ammonia concentration needed to be maintained within the limits for as long as possible.
Strategy 5, which controlled ammonia in Tank 5 at a low value and did not control any nitrate
in Tank 2, of Scenario 1, which was characterized by an undetermined on/off aeration cycle, was
then found to be the best. Although this control strategy led to high total energy consumption,
the percentage of time during which aeration was nearly suspended was one of the highest. This
work proposes a methodology that will be useful to plant operators who should soon reduce energy
consumption during spikes in electricity prices.

Keywords: Energy flexibility; Wastewater treatment plant; Benchmark Simulation Model 1; Control strategies; Aeration; Water quality

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Permalink: https://www.hzdr.de/publications/Publ-33277
Publ.-Id: 33277


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