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39109 Publications

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

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

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

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

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


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

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

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

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


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

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

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

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

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

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


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

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

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

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

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

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


hmctFOAM - heat mass concentration transport FOAM

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

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

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

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

Keywords: liquid metal batteries; OpenFOAM

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


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

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

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

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

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


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

Kaever, C.; Windisch, D.

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

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


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

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

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

Keywords: antiferromagnetism; ring; spin-flop

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


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

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

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

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

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


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

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

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

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

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


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

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

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

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


Low thermal conductivity in bournonite PbCuSbS3: A comprehensive study

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

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

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


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

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

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

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


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

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

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

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


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

Kaden, C.; Bergner, F.

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

Keywords: nanoindentation; ion irradiation

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

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


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

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

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

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


Synchronization dynamics on power grids in Europe and the United States

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

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

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

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


First experiences with custom pipelines for compression

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

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

Keywords: Data compression; Tomography

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

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


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

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

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

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

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

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

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

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

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


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

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

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

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

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

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


Preface: State of the art in mineral exploration

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

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

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

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


Spin-wave channeling in magnetization-graded nanostrips

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

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

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

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


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

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

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

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

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

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

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


Real-time tracking of individual droplets in multiphase microfluidics

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

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

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

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

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


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

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

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

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

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


Sulfated glycosaminoglycans inhibit transglutaminase 2 by stabilizing its closed conformation

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

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

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


Flexible and printed electronics: from interactive on-skin devices to bio/medical applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive through consumer electronics to virtual and augmented reality applications [3]. These skin-conformal flexible and printable magnetosensitive elements enable touchless interactivity with our surroundings based on the interaction with magnetic fields, which is relevant for smart skins for human-machine interfaces [4-9] and soft robotics [10].
Highly flexible functional elements are demanded for bio/medical applications. We will introduce an implantable, multifunctional device on ultrathin polymeric foils for targeted thermal treatment of cancer [11] as well as a flexible light weight diagnostic platform based on highly sensitive Si nanowire field effect transistors revealing remarkable limit of detection at 40 pM for Avian Influenza Virus (AIV) subtype H1N1 DNA sequences [12].
For the emerging field of biosensing technologies, we developed droplet-based magnetofluidic platforms encompassing integrated novel functionalities [13] including analytics in a flow cytometry format [14], magnetic detection, barcoding and sorting of magnetically encoded emulsion droplets using rigid [15,16] and flexible [17] microfluidic devices. These features are crucial to address the needs of modern medical research, e.g. drug discovery.

[1] D. Makarov et al., Adv. Mater. (Review) 34, 2101758 (2022).
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] G. S. Cañón Bermúdez et al., Adv. Funct. Mater. (Review) 31, 2007788 (2021).
[4] G. S. Cañón Bermúdez et al., Science Advances 4, eaao2623 (2018).
[5] G. S. Cañón Bermúdez et al., Nature Electronics 1, 589 (2018).
[6] J. Ge et al., Nature Communications 10, 4405 (2019).
[7] M. Ha et al., Adv. Mater. 33, 2005521 (2021).
[8] P. Makushko et al., Adv. Funct. Mater. 31, 2101089 (2021).
[9] S. Li et al., Nano Energy 92, 106754 (2022).
[10] M. Ha et al., Adv. Mater. 33, 2008751 (2021).
[11] G. S. Cañón Bermúdez et al., Adv. Eng. Mater. 21, 1900407 (2019).
[12] D. Karnaushenko et al., Adv. Healthcare Mater. 4, 1517 (2015).
[13] G. Lin et al., Lab Chip (Review) 17, 1884 (2017).
[14] G. Lin et al., Small 12, 4553 (2016).
[15] J. Schütt et al., ACS Omega 5, 20609 (2020).
[16] W. Song et al., ACS Sensors 2, 1839 (2017).
[17] G. Lin et al., Lab Chip 14, 4050 (2014).

Keywords: curvature effects in magnetism; flexible magnetic field sensors; printed magnetic field sensors; lab-on-chip applications; skin-conformal electronics

Related publications

  • Invited lecture (Conferences)
    Joint European Magnetic Symposia (JEMS), 24.-29.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34972
Publ.-Id: 34972


Scaling IT Services for Germany's Largest Research Organisation - An Experience Report

Hüser, C.; Ziegner, N.; Huste, T.

Helmholtz Federated IT Services (HIFIS, see hifis.net) is a joint platform in which most of the research centres in the Helmholtz Association collaborate. HIFIS offers cloud and fundamental backbone services free of charge to scientists in Helmholtz and their partners. A special focus is put on Research Software Engineering with consulting, trainings and community building. One cloud service, which is of particular interesting in terms of DevOps, is a GitLab service called "the Helmholtz Codebase" - a self-hosted free tier of the popular software project management and DevOps platform. By applying DevOps best practices in combination with a high level of automation we observed three major gains: We were able to shrink the downtimes to almost zero and establish a release cycle that is quite close to the one that GitLab Inc. achieves themselves, whilst scaling the service up. With several thousand satisfied scientific users, Helmholtz Codebase has become quite successful. It is a great example for illustrating the transition from a local service bound to one centre to a distributed service accessible by everyone in the Helmholtz Association.

Keywords: HIFIS; Codebase; GitLab; Automation; DevOps; GitOps

  • Open Access Logo Invited lecture (Conferences)
    Scaling IT Services for Germany's Largest Research Organisation - An Experience Report, 21.-22.09.2022, Berlin, Deutschland
    DOI: 10.5281/zenodo.7248114

Permalink: https://www.hzdr.de/publications/Publ-34971
Publ.-Id: 34971


Dose formation using a pulsed high-field solenoid beamline for radiobiological in vivo studies at a laser-driven proton source

Brack, F.-E.

Proton sources driven by high-power lasers are a promising addition to the portfolio of conventional proton accelerators. Regarding particle cancer therapy, where tumours are irradiated with protons or ions, the novel accelerator technology can be particularly beneficial for translational research - the research branch in which results of basic research are transferred to new approaches for the prevention, diagnosis and treatment of cancer.
The overarching aim in the thesis at hand was a translational pilot study to irradiate tumours on mice’s ears with laser-accelerated protons while achieving the quality level of conventional proton accelerators. This is the only way to compare the radiobiological data of the novel accelerator technology with those of the established ones. To enable such experiments a predetermined dose distribution according to the radiobiological model’s requirements must be delivered to a sample volume. Ergo, the laser-driven protons have to be transported and shaped after their initial acceleration. Intense laser-driven proton pulses, inherently broadband and highly divergent, pose a challenge to established beamline concepts on the path to application-adapted irradiation field formation, particularly for 3D. This work demonstrates the successful implementation of a highly efficient and tuneable pulsed dual solenoid setup to generate a homogeneous (laterally and in depth) volumetric dose distribution using only a single dose pulse from the broad laser-driven proton spectrum. The experiments using the ALBUS-2S beamline were conducted at the titanium:sapphire high-power laser Draco PW at the Helmholtz-Zentrum Dresden–Rossendorf. The beamline and its model were characterised and verified via independent methods, leading to first experimental studies providing volumetrically homogeneous dose distributions to detector targets as well as tumour and normal tissue in proof-of-concept studies. To perform the mouse pilot study, a new solenoid with cooling capacities was designed, characterised and implemented in the course of this thesis. The combination of the new solenoid and an overall performance improvement of the laser-proton accelerator, enabled the successful conduction of the mouse model study. The results show that laser-accelerated protons induce a comparable tumour growth delay as protons from conventional accelerators. This outcome and the demonstration of the flawless interaction between laser-proton accelerator, beam transport, dosimetry and biology qualify the laser-based accelerator technology for complex studies in translational cancer research. Looking into the future, their unique extremely high intensity renders them of particular interest for the investigation into the ultra-high dose rate regime. There, the so-called FLASH effect shows fewer side effects in normal tissue while maintaining the same effect in the tumour when the target dose is administered in milliseconds rather than minutes, as currently common. The ALBUS-2S setup at Draco PW already provides all necessary conditions to realise irradiation times of around ten nanoseconds in preclinical studies. This significantly expands the parameter space for investigating the FLASH effect and is presented as a proof-of-concept in this thesis.

Keywords: LPA; TNSA; Laser-driven protons; Radiobiology

  • Doctoral thesis
    TU Dresden, 2022
    Mentor: Dr. Karl Zeil
    121 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-121 2022
    ISSN: 2191-8708, eISSN: 2191-8716
  • Lecture (others)
    Disputation, 19.07.2022, Dresden, Deutschland
  • Open Access Logo Lecture (Conference)
    BLIN5, 12.10.2022, München, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-34969
Publ.-Id: 34969


Calix[4]crowns with perfluoroalkylsulfonylcarboxamide functions: a complexation approach for heavy group 2 metal ions

Reissig, F.; Bauer, D.; Al-Ameed, K.; Luber, S.; Köckerling, M.; Steinbach, J.; Pietzsch, H.-J.; Mamat, C.

Heavy alkaline earth metals offer radionuclides which are promising candidates for radiopharmaceutical applications like barium-131 for diagnosis or radium-223/-224 – with similar properties to barium – for targeted alpha-particle therapy. However, there is a lack of suitable chelation agents especially for these metal ions. A series of calix[4]crown-6 derivatives with perfluoroalkylsulfonylcarboxamide functions (RF = CF3, C2F5, i-C3F7, n-C4F9) was synthesized to serve as cage-like chelators for a strong complexation of Ba2+ and Ra2+. These functional ligands are deprotonated even at slightly acidic pH due to the intense electron withdrawing effect of the sulfonamide group. The obtained ligands were easily converted the desired barium complexes as well as into calix-crown compounds containing two sodium ions. DFT calculation methods were used to discover either the binding behavior of the metal ions with the desired ligands as well as the influence of the different donor groups from the chelating moiety of the calixarenes with respect to different pH. Radiolabeling procedures with the radionuclides barium-133 and radium-224 as [133Ba]BaCl2 and [224Ra]Ra(NO3)2 were performed to determine association constant values between 4.1 and 8.2 for the appropriate M2+ complexes using a two-phase extraction procedure. A stability test using physiological Ca2+ solution showed a minor release of approx. 1-7% of the central ions (Ba2+ respectively Ra2+) from the complexes.

Keywords: Calix[4]arene; Radium-223; Barium-131; targeted Alpha therapy

  • Inorganic Chemistry Frontiers 10(2022), 370-382
    Online First (2022) DOI: 10.1039/d2qi01637k

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  • Secondary publication expected from 21.01.2024

Permalink: https://www.hzdr.de/publications/Publ-34968
Publ.-Id: 34968


Effect of magnetism and phonons on localized carriers in ferrimagnetic kagome metals GdMn₆Sn₆ and TbMn₆Sn₆

Wenzel, M.; Tsirlin, A.; Iakutkina, O.; Yin, Q.; Lei, H. C.; Dressel, M.; Uykur, E.

Kagome metals possess a peculiar optical spectrum consisting of contributions from free charge carriers, localized carriers seen as a strongly temperature-dependent localization peak, and, in some cases, phonons displaying strong anomalies. The magnetic rare-earth kagome metal series, ReMn₆Sn₆, provides a marvelous playground to study the electronic properties of kagome metals in the presence of magnetism. Here, we report temperature-dependent reflectivity studies on two members of the ReMn₆Sn₆ family, GdMn₆Sn₆ (in-plane ferrimagnet) and TbMn₆Sn₆ (out-of-plane ferrimagnet), in a broad energy range (50 -18000 cm$^{-1}$, equivalent to 6 meV - 2.25 meV) down to 10 K. At high temperatures, a phonon mode at 160 cm$^{-1}$ is observed, which becomes screened out in TbMn₆Sn₆ below 150 K as the localization peak linearly passes through the mode. In GdMn₆Sn₆, the disappearance of the phonon is accompanied by the onset of saturation of the peak position, suggesting an unusual interplay between the two features. Lastly, our calculations reveal the strongly correlated nature of ReMn₆Sn₆ compounds and hence, significant deviations from the simple band picture.

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Permalink: https://www.hzdr.de/publications/Publ-34967
Publ.-Id: 34967


Diffraction and Raman spectroscopy studies of zirconia solid phases containing cerium

Braga Ferreira Dos Santos, L.; Huittinen, N. M.; Svitlyk, V.; Hennig, C.; Stumpf, T.; Marquardt, J.

Zirconia (ZrO2) doped with lanthanides or actinides has been extensively studied for several tailored applications, such as for the immobilization of actinides present in High-Level Radioactive Waste streams (HLW) or as inert matrix fuel for the incineration of e.g. waste plutonium. Doped zirconia matrices have been reported to have a very high radiation tolerance, however, inconsistencies exist concerning the role of the different structural polymorphs in the high radiation resistance. In addition, the role of oxygen vacancies, which are formed for charge compensation when subvalent dopants are incorporated into the ZrO2 crystal structure, has not been clarified. The lanthanide cerium is often used as a surrogate for plutonium due to its similar ionic radius and comparable chemical properties in the oxidation states +III and +IV. In this study, different Ce concentrations were incorporated into zirconia via the co-precipitation route, to stabilize the cubic zirconia polymorph. Due to the extraordinary luminescent properties of Eu, a trace amount of this lanthanide was added together with Ce in the synthesis process. A series of zirconia samples doped with 14 to 70 mol % Ce was prepared. Seven selected compositions are presented here, namely, samples with 14, 22, 30, 42, 50, 62, and 70 mol% Ce, as they demonstrate a clear phase transformation. The phase composition was evaluated by Powder X-Ray Diffraction (PXRD), and Raman spectroscopy. In the PXRD diffractograms, the monoclinic phase, characterized by diffraction peaks at 28.2 o and 31.3o, is dominant only in the composition with 14 mol % Ce. Above this concentration, a peak around 29.9o, assigned to the tetragonal phase, increases in intensity as a function of increasing Ce concentration in the zirconia matrix up to a concentration of 42 mol%. Beyond this, the cubic phase starts to dominate the phase composition, with the intensive characteristic peak around 29.3o. Additionally, the presence of a tetragonal metastable phase in samples with 30, 42, and 50 mol % Ce, and a trace of the tetragonal phase in the composition with 70 mol % Ce were identified. Generally, the diffraction peaks are shifted to lower 2 angles as a result of the substitution of Zr4+ by the larger Ce4+ cation which increases the lattice parameters. The Raman results corroborate the assignment of the different phase compositions identified in the PXRD studies. However, a large band at 512 cm-1 becomes visible in the samples with 30 mol % Ce and grows in intensity with increasing Ce-doping. This band has been reported to arise from Frenkel-type defects, typically found in samples with oxygen vacancies or/and due to partial reduction of Ce4+ to Ce3+ occurring in the samples, and causing the formation of oxygen vacancies in the ZrO2 structure for charge compensation. This, however, has to be verified in future XANES experiments. No solid phase separation was detected in both characterization analyses, PXRD and Raman. Luminescence spectroscopic studies, probing the Eu ion which has been incorporated together with Ce in all ZrO2 solid phases, will be conducted in future studies. Preliminary results of these investigations will be shown at the RadChem conference.

Related publications

  • Open Access Logo Lecture (Conference)
    19th Radiochemical Conference, 15.-20.05.2022, Marianske Lazne, Czech Republic
    PURL: https://indico.fjfi.cvut.cz/event/195/contributions/3628/contribution.pdf

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Permalink: https://www.hzdr.de/publications/Publ-34966
Publ.-Id: 34966


Synthesis and characterization of cerium doped zirconia: a study of solid phase transformations

Braga Ferreira Dos Santos, L.; Huittinen, N. M.; Svitlyk, V.; Hennig, C.; Stumpf, T.

Zirconia (ZrO2) doped with lanthanides, such as cerium (Ce), has been extensively studied for a multitude of tailored applications. The ZrxCe1-xO2 solid solutions can occur in three stable structures: monoclinic (m), tetragonal (t), and cubic (c), but also in several metastable ones (t′, t′′, κ, and t*)1. The phase transformation depends on the dopant concentration and the synthesis conditions, such as sintering temperature or cooling rate. In this study, to understand the behavior of cerium in the zirconia structure, 5 solid solution compositions with Ce4⁺ concentrations of 14, 18, 22, 26, and 30 mol % were synthesized through co-precipitation route. As an additional structural probe, a figurative amount of europium was added to the samples to enable luminescence spectroscopic analyses (TRLFS). In addition to these TRLFS investigations, the phase compositions were evaluated by Raman spectroscopy and synchrotron powder X-ray diffraction (PXRD). The PXRD results show that the diffraction peak around 14.9o can be attributed to the tetragonal phase, and the amount of this phase increases with increasing Ce concentration. Due to the substitution of Zr4+ by the larger Ce4+cation, the diffraction peaks are shifted to lower 2, here from 14.92 to 14.87o2. The t’ and c phases are not easy to distinguish. Owing to the high-resolution PXRD data, however, the diffraction peak around 16.91o could be attributed to the t’ phase and the peak at 16.77o to the cubic one. Both peaks could be identified in the compounds with more than 22 mol % of Ce3. At this concentration, no more monoclinic phase could be detected. TRLFS measurements of the Eu environment, corroborated the presence of the above mentioned phases, going from the dominant monoclinic to tetragonal metastable and cubic phases with increasing Ce substitution4. Combining the PXRD, TRLFS, and Raman data, no solid phase separation (CeO2+ZrO2) was detected.

Keywords: zirconia doped cerium; solid phases; tetragonal prime phase; PXRD; RAMAN; TRLFS; syntheses

Related publications

  • Poster
    ChemTugether 2022: Graduate Exchange to Enhance Excellent Research, 13.-14.05.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-34964
Publ.-Id: 34964


Actinide physics and chemistry with synchrotron radiation

Kvashnina, K. O.; Butorin, S. M.; Wang, S.; Shi, W.

Actinide research is currently experiencing a renaissance in the fields of material science,
nanotechnology, medicine and environmental science. It is now possible to study the
chemistry and physics of the actinide elements (all radioactive) using state-of-the-art
non-destructive techniques at synchrotrons which have not been available before. The
beamlines and instruments dedicated to actinide research have made various spectro-
scopic and scattering methods accessible to scientists worldwide. The new synchrotron
sources at the large-scale facilities offer more advanced possibilities for the development
of new methodologies in actinide science in the future. Theoretical studies of actinides
are followed by unique experimental methods and novel experimental data.

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Permalink: https://www.hzdr.de/publications/Publ-34963
Publ.-Id: 34963


Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling

Stagg, O.; Morris, K.; Townsend, L. T.; Kvashnina, K.; Baker, M. L.; Dempsey, R.; Abrahamsen-Mills, L.; Shaw, S.

Over 60 years of nuclear activity have resulted in a global legacy of contaminated land and radioactive waste. Uranium (U) is a significant component of this legacy and is present in radioactive wastes and at many contaminated sites. U-incorporated iron (oxyhydr)oxides may provide a long-term barrier to U migration in the environment. However, reductive dissolution of iron (oxyhydr)oxides can occur on reaction with aqueous sulfide (sulfidation), a common environmental species, due to the microbial reduction of sulfate. In this work, U(VI)-goethite was initially reacted with aqueous sulfide, followed by a reoxidation reaction, to further understand the long-term fate of U species under fluctuating environmental conditions. Over the first day of sulfidation, a transient release of aqueous U was observed, likely due to intermediate uranyl(VI)-persulfide species. Despite this, overall U was retained in the solid phase, with the formation of nanocrystalline U(IV)O2 in the sulfidized system along with a persistent U(V) component. On reoxidation, U was associated with an iron (oxyhydr)oxide phase either as an adsorbed uranyl (approximately 65%) or an incorporated U (35%) species. These findings support the overarching concept of iron (oxyhydr)oxides acting as a barrier to U migration in the environment, even under fluctuating redox conditions.

Keywords: iron (oxyhydr)oxides; persulfide; sulfidation; uranium; XAS

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  • Secondary publication expected from 30.11.2023

Permalink: https://www.hzdr.de/publications/Publ-34962
Publ.-Id: 34962


Uranium reduction by magnetite – mechanism of UO2 formation monitored by STEM, SAED and EELS

Lagrange, T.; Pan, Z.; Bártová, B.; Butorin, S. M.; Hyatt, N. C.; Stennett, M. C.; Kvashnina, K. O.; Bernier-Latmani, R.

Uranium (U) is a ubiquitous element in the Earth’s crust, having a concentration of about 2 ppm.
Soluble hexavalent uranium (U(VI)) is reduced and immobilized in anoxic environments. The
underlying reduction mechanism is unknown but is likely of critical importance to explain variability in
U biogeochemical behaviors. In this study, we focused on the mechanism of reduction of U(VI) by the
mixed-valence iron oxide magnetite

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Permalink: https://www.hzdr.de/publications/Publ-34961
Publ.-Id: 34961


Nanochips assisted peptide screening for clinical development of CAR-T cell immunotherapy

Anh Nguyen-Le, T.; Bartsch, T.; Wodtke, R.; Brandt, F.; Arndt, C.; Feldmann, A.; Isabel Sandoval Bojorquez, D.; Perez Roig, A.; Ibarlucea, B.; Lee, S.; Baek, C.-K.; Cuniberti, G.; Bergmann, R.; Puentes-Cala, E.; Andrés Soto, J.; T. Kurien, B.; Bachmann, M.; Baraban, L.

Immunotherapy using CAR-T cells is a new paradigm technology for cancer treatment. To avoid severe side effects and tumor escape variants observed for conventional CAR-T cells approach, adaptor CAR technologies are under development, where intermediate target modules redirect immune cells against cancer cells. In this work, silicon nanowire field effect transistors are used to assist in the development of target modules for an optimized CAR-T cell operation. Focusing on a library of seven variants of E5B9 peptide that is used as CAR peptide epitope, we performed multiplexed binding tests in serum using nanosensor chips. Peptides have been immobilized onto the sensor to compare the signals of transistor upon titration with anti-E5B9 antibodies. Correlation analysis of binding affinities and sensitivities enabled a selection of best candidates for the interaction between CAR and target modules. Finally, cytotoxic functionality of CAR-T cells in combination with the selected target modules were successfully proven. Our results open the perspective for the nanobiosensorics to go beyond the early diagnostics in the field of clinical cancer research, and paves the way towards personalization and efficient monitoring of the immunotherapeutic treatment, where the quantitative analysis with the standard techniques is not an option.

Keywords: CAR-T cells; Nanobiosensors

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  • Secondary publication expected from 15.06.2023

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Publ.-Id: 34960


CO2 Electroreduction on Unsupported PdPt Aerogels: Effects of Alloying and Surface Composition on Product Selectivity

Diercks, J. S.; Georgi, M.; Herranz, J.; Diklić, N.; Chauhan, P.; Clark, A. H.; Hübner, R.; Faisnel, A.; Chen, Q.; Nachtegaal, M.; Eychmüller, A.; Schmidt, T. J.

Due to its unique ability to reduce carbon dioxide (CO2) into CO or formate at high versus low overpotentials, respectively, palladium is a promising catalyst for the electrochemical CO2-reduction reaction (CO2RR). Further improvements aim at increasing its activity and selectivity toward either of these value-added species, while reducing the amount of hydrogen produced as a side product. With this motivation, in this work, we synthesized a range of unsupported, bimetallic PdPt aerogels and pure Pt or Pd aerogels and extensively characterized them using various microscopic and spectroscopic techniques. These revealed that the aerogels’ porous web consists of homogenous alloys of Pt and Pd, with palladium and platinum being present on their surface for all compositions. The subsequent determination of these aeorgels’ CO2RR performance unveiled that the high activity of these Pt surface atoms toward hydrogen evolution causes all PdPt alloys to favor this reaction over CO2 reduction. In the case of the pure Pd aerogel, although, its unsupported nature leads to a suppression of H2 evolution and a concomitant increase in the selectivity toward CO when compared to a commercial, carbon-supported Pd-nanoparticle catalyst.

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Permalink: https://www.hzdr.de/publications/Publ-34959
Publ.-Id: 34959


Synchronizing the helicity of Rayleigh-Bénard convection by a tide-like electromagnetic forcing

Jüstel, P.; Röhrborn, S.; Eckert, S.; Galindo, V.; Gundrum, T.; Stepanov, R.; Stefani, F.

We present results on the synchronization of the helicity in a liquid-metal Rayleigh-Bénard (RB) experiment under the influence of a tide-like electromagnetic forcing with azimuthal wavenumber m = 2. We show that for a critical forcing strength the typical Large Scale Circulation (LSC) in the cylindrical vessel of aspect ratio unity is entrained by the period of the tide-like forcing, leading to synchronized helicity oscillations with opposite signs in two half-spaces. The obtained experimental results are consistent with and supported by numerical simulations. A similar entrainment mechanism for the helicity in the solar tachocline may be responsible for the astonishing synchronization of the solar dynamo by the 11.07-year triple synodic alignment cycle of the tidally dominant planets Venus, Earth and Jupiter.

Keywords: Electromagnetic forcing; Magnetohydrodynamics; Helicity synchronization

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Publ.-Id: 34958


The influence of the bentonite type on the corrosion of cast iron

Sushko, V.; Dressler, M.; Kluge, S.; Matschiavelli, N.; Schierz, A.; Stumpf, T.; Cherkouk, A.

1 Introduction
Bentonite is considered as buffer and sealing material in a multi-barrier system for a deep geologic repositories (DGR) of nuclear waste and spent fuel [1]. Another part of the engineered barrier system is the containment of the radioactive waste. Cast iron is often taking into account for the construction of the containers as a candidate material [2]. But the cast iron components are fairly unstable, can corrode to insoluble corrosion products and react with the bentonite buffer matrix. Anaerobic corrosion together with microbially influenced corrosion are dominant forms of corrosion in the a DGR and the interactions at the metal/bentonite interface determines the performance of bentonite-based radioactive waste barriers [3]. The aim of the current study was to characterize the surface damage associated with corrosion of the cast iron and to compare the potential of the indigenous microorganisms present in different bentonites to influence the corrosion of cast iron.

2 Results
Three types of bentonite (B25, Calcigel, MX-80) were chosen for mesocosm-experiment setup as described in [4]. All three bentonites have different smectite content and an indigenous microbial community. The mesocosms with cast iron coupons, artificial Opalinus clay porewater and bentonite were incubated in N2/CO2 atmosphere for 271 days at 30 °C. Some of the mesocosms were supplemented with 5 mM sodium lactate and hydrogen (to a 0.5 bar of total pressure) to stimulate microbial activity. After the incubation period the content of the mesocosms was divided and subjected to different analysis, including geochemical analysis (as e.g. ICP-MS, ion and high-performance liquid chromatography), DNA isolation and amplification of the intergenic spacer to determine the microbial community structure, SEM-EDX and RAMAN spectroscopy to characterize the surface damage of the cast iron coupons.
The black precipitates were visible in the mesocosms containing Calcigel with lactate as substrate and for all the substrate-containing samples with MX-80. The obtained geochemical data confirmed the differences in the different microcosms by demonstrating unequal levels of sulphate and lactate consumption. Moreover, surface analysis of the cast iron coupons showed that corrosion rate and metabolite accumulation are also dependent on the bentonite type. In addition different microbial community structure was observered by intergenic spacer analysis (RISA) depending on the conditions applied and used bentonite. Therefore, the used bentonites varied in respect to reactivity and microbial activity.
Overall, the results show the importance of selection of suitable bentonite for DGR to adjust microbial implications and possibly faster corrosion rate of the metal containers.
We acknowledge funding by the BMBF (Grant 02NUK053B) and HGF (Grant SO-093).
References
[1] P. Sellin and etc., The Use of Clay as an Engineered Barrier in Radioactive-Waste Management – A Review, Clays and Clay Minerals 61(6), pp. 477-498 (2014).
[2] F. King. Container Materials for the Storage and Disposal of Nuclear Waste, Corrosion 69(10), pp. 986-1011 (2013).
[3] S. Kaufhold and etc. About the Corrosion Mechanism of Metal Iron in Contact with Bentonite, ACS Earth Space Chem. 4, 5, pp. 711–721 (2020).
[4] N. Matschiavelli and etc., The Year-Long Development of Microorganisms in Uncompacted Bavarian Bentonite Slurries at 30 and 60 °C, Environ. Sci. Technol., 53, 17, 10514–10524 (2019)

Keywords: Corrosion; Bentonite

  • Open Access Logo Poster (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34957
Publ.-Id: 34957


Simulation of potential and species distribution in a Li||Bi liquid metal battery using coupled meshes

Duczek, C.; Weber, N.; Godinez-Brizuela, O. E.; Weier, T.

In this work a 1D finite volume based model using coupled meshes is introduced to capture potential and species distribution throughout the discharge process in a lithium–bismuth liquid metal battery while neglecting hydrodynamic effects, focusing on the electrochemical properties of the cell and the mass transport
in electrolyte and cathode. Interface reactions in the electrical double layer are considered through the introduction of a discrete jump of the potential modelled as periodic boundary condition to resolve interfacial discontinuities in the cell potential. A balanced-force like approach is implemented to ensure consistent calculation at the interface level. It is found that mass transport and concentration gradients have a significant effect on the cell overpotentials and thus on cell performance and cell voltage. By quantifying overvoltages in the Li||Bi cell with a mixed cation electrolyte, it is possible to show that diffusion and migration current density could have counteractive effects on the cell voltage. Furthermore, the simulated limiting current density is observed to be much lower than experimentally measured, which can be attributed to convective effects in the electrolyte that need to be addressed in future simulations.
The solver is based on the open source library OpenFOAM and thoroughly verified against the equivalent system COMSOL multiphysics and further validated with experimental results.

Keywords: OpenFOAM; liquid metal battery; molten salt battery; species transfer

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Publ.-Id: 34956


Long-term excessive dietary phosphate increases arterial blood pressure, activates the renin-angiotensin-aldosterone system, and stimulates sympathetic tone in mice

Latic, N.; Peitzsch, M.; Zupcic, A.; Pietzsch, J.; Erben, R. G.

Increased dietary phosphate intake has been associated with severity of coronary artery disease, increased carotid intima–media thickness, left ventricular hypertrophy (LVH), and increased cardiovascular mortality and morbidity in individuals with nor-mal renal function as well as in patients suffering from chronic kidney disease. How-ever, the underlying mechanisms are still unclear. To elucidate further the cardiovas-cular sequelae of long-term elevated phosphate intake we maintained male C57BL/6 mice on a calcium, phosphate, and lactose‐enriched diet (CPD, 2% Ca, 1.25% P, 20% lactose) after weaning for 14 months and compared them with age-matched male mice fed a normal mouse diet (ND, 1.0% Ca, 0.7% P). Notably, the CPD has a balanced cal-cium/phosphate ratio, allowing to investigate the effects of elevated dietary phosphate intake largely independent of changes in parathyroid hormone (PTH). In agreement with the rationale of this experiment, mice maintained on CPD for 14 months were characterized by unchanged serum PTH but showed elevated concentrations of circu-lating intact fibroblast growth factor-23 (FGF23) compared with mice on ND. Cardio-vascular phenotyping did not provide evidence for LVH, as evidenced by unchanged LV chamber size, normal cardiomyocyte area, lack of fibrosis, and unchanged molecu-lar markers of hypertrophy (Bnp) between the two groups. However, intra-arterial catheterization revealed increases in systolic pressure, mean arterial pressure, and pulse pressure in mice fed the CPD. Interestingly, chronically elevated dietary phos-phate intake stimulated the renin-angiotensin-aldosterone system (RAAS) as evi-denced by increased urinary aldosterone in animals fed the CPD, relative to ND con-trols. Furthermore, the catecholamines epinephrine, norepinephrine, and dopamine as well as the catecholamine metabolites metanephrine. normetanephrine and methoxy-tyramine as measured by mass spectrometry were elevated in the urine of mice on CPD, relative to mice on ND. These changes were partially reversed by switching 14-month-old mice on CPD back to ND for 2 weeks. In conclusion, our data suggest that excess dietary phosphate induces a rise in blood pressure independent of second-ary hyperparathyroidism, and that this effect may be mediated through activation of the RAAS and stimulation of the sympathetic tone.

Keywords: Hypertension; left ventricular hypertrophy; renin-angiotensin-aldosterone system; cardiovascular disease; catecholamines; liquid chromatography-tandem mass spectrometry

Permalink: https://www.hzdr.de/publications/Publ-34955
Publ.-Id: 34955


Experimental simulation of phase evolution in conditions of underground storage: from million years to one day

Svitlyk, V.; Weiss, S.; Hennig, C.

Long-living radiotoxic isotopes present in spent nuclear fuel (SNF) requires procedures of complete immobilization of these species. Incorporation of the corresponding elements on atomic level into robust host crystalline matrices is one way to secure SNF during long-term underground storage. Derivatives of zirconia, ZrO2, are promising materials for these applications since these phases are known to remain structurally stable in geological cycles of up to 109 years [1]. The candidate host matrix must provide a sufficient solubility limit for radiotoxic elements, which is studied initially. Afterwards, structural stability of these phases against irradiation and leaching are established in order to asses possible discharge of the incorporated radioactive elements over a long-time scale. In this work we studied systematically structural behaviour of ZrO2-based materials incorporated with Th4+ and Ce4+ under extreme conditions of temperature (T) and pressure (P) in order to simulate experimentally possible phase evolution in conditions of underground storage.
In situ synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the HZDR ROBL BM20 beamline at ESRF, Grenoble, France [2]. It was found that cubic YSZ phases could dissolve 20% more of Th atoms compared to their tetragonal analogues. In situ T-dependent diffraction studies on radionuclide surrogate tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent phase stabilities. No discharge of guest Ce4+ ions was observed. Nevertheless, application of external pressure on tetragonal Ce-YSZ phase induced transition towards a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. Thus, we suggest in situ studies under extreme conditions as a part of standard protocol to validate phases of interest as host matrixes for long-term underground storage of SNF.

References
[1] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993). [2] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

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  • Lecture (Conference)
    Goldschmidt 2022, 10.-15.07.2022, Honolulu, HI, USA

Permalink: https://www.hzdr.de/publications/Publ-34954
Publ.-Id: 34954


Extreme conditions: towards secure and long-term storage of nuclear waste

Svitlyk, V.; Weiss, S.; Hennig, C.

Majority of man-made radiotoxic elements originate from spent nuclear fuel (SNF). It is composed essentially of uranium and plutonium and some minor actinides (An) like 237Np, 241Am/243Am, and 244Cm. Half-life of these elements can range from few decades up to millions of years (ca. 2.1 million years for 237Np [1]). Therefore, safe disposal of SNF requires matrix materials with strong resistance against corrosion and dissolution over a period of 106 years. Derivatives of zirconium-based ceramics, in particular zirconia, ZrO2, are promising materials for these applications since these phases are known to remain stable in geological cycles of up to 109 years [2]. Here scientific and technological goals are to obtain zirconium-based ceramic materials containing maximum possible tetravalent actinides (An) without Zr/An phase separation. In addition, structural stability of these phases under various external parameters, e.g. temperature (T), pressure (P), irradiation and leaching resistance is essential in order to exclude possible discharge of the incorporated radioactive elements over a long-time scale.
Two series of samples have been synthesized for current study: (I) Th-doped Y-stabilized ZrO2 (YSZ) and (II) Ce-doped YSZ phases, both of tetragonal and cubic symmetries. The series (I) was studied in order to determine maximum possible intake of Th4+ ions into the tetragonal and cubic YSZ matrices. The series II used Ce4+ species as surrogate ions for An4+ for studies under extreme conditions of T and P. Synchrotron radiation powder diffraction experiments under ambient and extreme conditions were performed at the ROBL BM20 beamline at ESRF [3]. Relevant technical details will be presented.
For the tetragonal YSZ phases maximum possible Th intake on the Zr/Y metal site reached ca. 10.3 at.%. Cubic phases could dissolve up to ca. 12.3 at.% Th under non-equilibrium conditions. Larger Th-Zr/Y solubility range for cubic phases was found to be symmetry related. Specifically, introduction of Th into tetragonal YSZ induces flattening of the Zr/YO8 polyhedra with concomitant decrease in tetragonality. This results in better accommodation of larger Th atoms via structural stabilization of longer bonding distances.
To simulate phase stability under conditions of underground nuclear repositories, Ce-based analogues were subjected to in situ studies under elevated temperatures and pressures. T-dependent diffraction studies on tetragonal and cubic Ce-YSZ series in a RT-1150 K range revealed excellent structural stability for all the studied compounds. In particular, occupancy of guest Ce4+ atoms as a function of temperature does not decrease in these systems. However, application of external pressure on tetragonal Ce-YSZ phase induced a structural transformation to a higher cubic symmetry around the P ~ 8.5 GPa. Remarkably, occupancy of Ce4+ remains stable throughout the transition. This together with T-dependent data indicates excellent affinity of guest Ce atoms with the YSZ structures. The parent YSZ phases are, therefore, promising candidates as host matrices for radiotoxic tetravalent elements like U, Th or Pu for a long-term underground storage.

References
[1] R. C. Ewing, W. J. Weber, J. Lian, J. Appl. Phys. 95, 5949 (2004).
[2] L. M. Heaman, A. N. LeCheminant, Chem. Geol. 110, 95 (1993).
[3] A. C. Scheinost et al., J. Synchr. Rad. 28, 333 (2021).

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  • Lecture (Conference) (Online presentation)
    New opportunities for High Pressure Science at the ESRF-EBS, 07.-09.02.2022, ESRF, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-34953
Publ.-Id: 34953


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

Kaever, C.

Ultrafast electron beam X-ray computed tomography [4] (UFXCT) is a non-invasive imaging technique based on scanning an electron beam on a tungsten target. This way, a moving X-ray source is generated without mechanically moving parts allowing for very high imaging rates up to 8000 fps.
This technique is used, e.g., for the investigation of multiphase flows, such as bubbly flow in industrial bubble column reactors. The goal of the ROOF experiment is to investigate the hydrodynamics of such a bubbly flow by apply UFXCT for scanning and tracking of objects alongside a vertical axis in real time based on the acquired cross-sectional images. To accomplish the tracking, software is needed to recognize objects in the reconstructed images, as a human would not fulfill realtime constraints. The current CPU-based implementation is the slowest step in the current workflow, thus, the goal of this work is to design a faster algorithm. In this work, the approach used by the RISA [5] (Realtime Image Stream Algorithms) software to realize the tracking of objects is presented and improved by using the GPU to recognize the objects.

  • Study thesis
    TU Dresden, 2022
    Mentor: Dominic Windisch
    14 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34952
Publ.-Id: 34952


Microcosm study of indigenous microorganisms in bentonite and its effect on the corrosion of cast iron

Sushko, V.; Kluge, S.; Matschiavelli, N.; Schierz, A.; Stumpf, T.; Cherkouk, A.

INTRODUCTION

Bentonite is a potential barrier material in deep geological repositories (DGR) for nuclear waste and spent fuel [1] and it is critical to maintain its functionality for long periods of time. Bacteria, that can originate from the bentonite itself, can affect important properties of the engineered barrier system, including bentonite’s swelling capability and integrity of the container material [2]. Cast iron is often considered as a suitable material for constructing the containers for the radioactive waste storage [3]. But the container material could be unstable and can corrode to insoluble corrosion products, which react with the bentonite barrier. In a DGR, anaerobic corrosion and microbially influenced corrosion are dominant forms of corrosion and the interactions at the metal/bentonite interface determine the long-term performance of bentonite-based radioactive waste barriers [4].

DESCRIPTION OF THE WORK

Microcosm-type setup described in [5] was used for the current study. Three types of bentonite with different indigenous microorganisms were chosen for the setup: B25, Calcigel, MX-80. Incubation of the microcosms, containing GGG40 cast iron coupons, synthetic Opalinus Clay porewater (OPA) and bentonite, was performed in N2/CO2 atmosphere at 30 °C. Some of the microcosms were supplemented with 5 mM sodium lactate or 0.5 bar of hydrogen to stimulate microbial activity. After a 271-day incubation period, the microcosms were investigated by various geochemical analyses (as e.g. ICP-MS, ion and high-performance liquid chromatography), DNA isolation and amplification of the ribosomal RNA (rRNA) intergenic spacer (RISA) for microbial community analysis, SEM-EDX and RAMAN spectroscopy to characterize the surface structure of the cast iron coupons.
In addition, a similar 3-component experiment was set up with Calcigel including 4 time points to study in more detail the microbial-induced process of cast iron corrosion in Calcigel-microcosms.

RESULTS AND DISCUSSION

After 271 days of incubation under anaerobic conditions at 30 °C, the presence of black precipitants in microcosms containing Calcigel and sodium lactate, and all substrate-containing MX-80 samples became apparent. Geochemical investigation of the respective samples showed a decrease in sulphate concentration which was dominant in microcosms containing MX-80.
Surface analysis with SEM-EDX showed severe damage for all the samples, except B25 without substrates. Two types of crystalline structures were found: iron and/or calcium carbonates and iron sulphide. The presence of the latter could be an indication of the activity of sulphate-reducing bacteria.
Different microbial community structures were observed by RISA analysis depending on the used bentonite and the applied conditions.
Overall, the results show that the reactivity at the bentonite/metal interface and the microbial activity are bentonite-type dependent and the selection of the bentonite for the DGR is highly important for preventing possible microbial implications that could lead to a faster deterioration of the metal container.

ACKNOWLEDGEMENT

Funding was provided by the German Federal Ministry of Education and Research (BMBF, Grant 02NUK053) and the Helmholtz Association (Grant SO-093).

REFERENCES

1. P. Sellin et al., “The Use of Clay as an Engineered Barrier in Radioactive-Waste Management – A Review” Clays and Clay Minerals, 61(6), pp. 477-498 (2014).
2. F. King, “Container Materials for the Storage and Disposal of Nuclear Waste” Corrosion, 69(10), pp. 986-1011 (2013).
3. F. King et al., “Nature of the near-field environment in a deep geological repository and the implications for the
corrosion behaviour of the container” Corrosion Engineering, Science and Technology, 52, 1, pp. 25-30 (2017).
4. S. Kaufhold et al., “About the Corrosion Mechanism of Metal Iron in Contact with Bentonite” ACS Earth Space Chem., 4, 5, pp. 711–721 (2020).
5. N. Matschiavelli et al., “The Year-Long Development of Microorganisms in Uncompacted Bavarian Bentonite Slurries at 30 and 60 °C” Environ. Sci. Technol., 53, 17, 10514–10524 (2019)

Keywords: Microbially influenced corrosion; Microcosm experiment; SEM; Microbial diversity

  • Poster (Online presentation)
    TransRet2020 - Workshop on Processes Influencing Radionuclide Transport and Retention, 12.-13.10.2021, Karlsruhe, Germany

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Publ.-Id: 34951


Investigation of the Cannabinoid Receptor 2 (CB2R) Expression and Preliminary In Vitro Evaluation of the CB2R Specific PET Radioligand [18F]JHU94620-d8 in Different Breast Cancer Models

Heerklotz, A.; Moldovan, R.-P.; Deuther-Conrad, W.; Bormans, G.; Pietzsch, J.; Belter, B.; Kopka, K.; Gündel, D.

Introduction
The cannabinoid receptor 2 (CB2R) is involved in inflammatory processes [1], whereby an increased expression correlates with malignancy in various cancer types like human epidermal growth receptor 2 positive (HER2+) or triple negative breast cancer (TNBC) [2]. Hence, the CB2R is suggested as a pharmacological target and prognostic marker for stratification and staging of patients [3].
In the present in vitro studies, we investigated the expression of the CB2R in HER2+ and TNBC models, as well as the potential of our novel radioligand [18F]JHU94620-d8 to assess the CB2R availability in TNBC models.

Methods
The colocalisation of CB2R with Iba1 (macrophages) and CD31 (blood vessels) in cryosections of mouse TNBC 4T1 tumours heterotopically implanted in both NMRI-nude and Balb/c mice was investigated by immunofluorescence staining (IF). The CB2R expression in 4T1, the human HER2+ cell lines HCC1954 (HCC and LCC2) and human TNBC cell lines MDA-MB-231 (MDA and BrM2) was determined by IF.
Competitive radioligand binding assays with the CB2R-specific ligands [3H]WIN55,212-2 and [3H]A-836339 were performed vs. 10 µM JHU94620-d8, GW405833 and WIN55,212-2, and A 836339 as competitor (n=1). Autoradiography with the CB2R-specific [18F]JHU94620-d8 vs. 10 µM competitor was performed with cryosections obtained from 4T1 tumours (n=3) as well as rat brains harbouring a local overexpression of the human CB2R (AAV-hCB2R, n=1) [4].

Results
A high correlation between the heterogeneously distributed CB2R and Iba1, and a weak correlation between CB2R and CD31 was found in 4T1 tumours. Colocalisation of CB2R and Iba1 (Balb/c: Pearson’s coefficient r=0.69±0.03, Manders’ coefficient M1: 0.7±0.12; NMRI-nude: r=0.7±0.12, M1=0.71±0.15) or CD31 (Balb/c: r=0.35±0.09, M1=0.15±0.02; NMRI-nude: r=0.35±0.11; M1=0.19±0.09) was independent of the mouse breed (CB2R/Iba1: pr=0.9, pM1=0.972; CB2R/CD31: pr=0.41, pM1=0.52).
By IF the expression of CB2R and HER2 was confirmed in HCC and LCC2, but absent in all TNBC cell lines.
The total binding of [3H]WIN55,212-2 in HCC (329.04±37.65 fmol/mg protein) and LCC (160.87±9.53 fmol/mg) homogenates could be reduced by homologues competition with WIN55,212 2 (HCC: 229.66±56.56 fmol/mg, -30.2%; LCC2: 117.73±18.49 fmol/mg, -26.82%) and GW405833 (LCC2: 99.41±2.81 fmol/mg, -38.20%) in contrast to JHU94620-d8. Moreover, a specific binding of [3H]A 836339 was not detectable.
In cryosections of AAV-hCB2R binding of [18F]JHU94620-d8 could be displaced by >80% in the target region with all competitors, however in 4T1 tumours a non-displaceable binding was found.

Conclusions
CB2R expression was detectable in Iba1 positive tumour-associated cells of 4T1 tumours cryosections. In HER2+ cells CB2R expression was cross-validated by IF and competitive binding studies. [18F]JHU94620-d8 binds target specific in the artificial AAV-hCB2R model, whereas heterogenous binding was non-displaceable in cryo-sections of mammary tumours.

Keywords: Patient stratification; Cannabinoid Receptor 2; Breast Cancer; PET

  • Lecture (Conference)
    5th GyMICMolecular Imaging Symposium, 15.-16.09.2022, Leipzig, Deutschland
  • Lecture (Conference)
    MOBI 2022, 15.-16.09.2022, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34950
Publ.-Id: 34950


Platform for Probing Radiation Transport Properties of Hydrogen at Conditions Found in the Deep Interiors of Red Dwarfs

Lütgert, B. J.; Bethkenhagen, M.; Bachmann, B.; Divol, L.; Gericke, D. O.; Glenzer, S. H.; Hall, G. N.; Izumi, N.; Khan, S. F.; Landen, O. L.; Maclaren, S. A.; Masse, L.; Redmer, R.; Schörner, M.; Schölmerich, M. O.; Schumacher, S.; Shaffer, N. R.; Starrett, C. E.; Sterne, P. A.; Döppner, T.; Kraus, D.

We describe an experimental concept at the National Ignition Facility for specifically tailored spherical im- plosions to compress hydrogen to extreme densities (up to ∼ 800× solid density, electron number density ne ∼ 4 × 10^25 cm−3) at moderate temperatures (T ∼ 200 eV), i.e. to conditions, which are relevant to the interiors of red dwarf stars. The dense plasma will be probed by laser-generated X-ray radiation of differ- ent photon energy to determine the plasma opacity due to collisional (free-free) absorption and Thomson scattering. The obtained results will benchmark radiation transport models, which in the case for free-free absorption show strong deviations at conditions relevant to red dwarfs. This very first experimental test of free-free opacity models at these extreme states will help to constrain where inside those celestial objects energy transport is dominated by radiation or convection. Moreover, our study will inform models for other important processes in dense plasmas, which are based on electron-ion collisions, e.g. stopping of swift ions or electron-ion temperature relaxation.

Permalink: https://www.hzdr.de/publications/Publ-34948
Publ.-Id: 34948


Real-Time Regulation of Beam-Based Feedback: Implementing an FPGA Solution for a Continuous Wave Linear Accelerator

Maalberg, A.; Kuntzsch, M.; Petlenkov, E.

Control applications targeting fast industrial processes rely on real-time feasible implementations. One of such applications is the stabilization of an electron bunch arrival time in the context of a linear accelerator. In the past, only the electric field accelerating the electron bunches was actively controlled in order to implicitly stabilize the accelerated electron beam. Nowadays, beam properties are specifically measured at a target position and then stabilized by a dedicated feedback loop acting on the accelerating structures. This dedicated loop is usually referred to as a beam-based feedback. Following this, the control system at the linear accelerator ELBE is planned to be upgraded by the beam-based feedback, and the problem of implementing a designed control algorithm becomes highly relevant. In this work, we propose an FPGA-based real-time feasible implementation of a high-order H2 regulator. By presenting the results of the corresponding VHDL simulation and hardware synthesis, we show that the proposed digital solution is fast enough to cover the bunch repetition rates frequently used at ELBE, such as 100 kHz. Finally, we verify the implementation by using a dedicated FPGA testbench.

Keywords: Regulation; Beam-based feedback; FPGA; Linear accelerator; Continuous Wave

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Permalink: https://www.hzdr.de/publications/Publ-34947
Publ.-Id: 34947


Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction

He, Z.; Rödel, M.; Lütgert, J.; Bergermann, A.; Bethkenhagen, M.; Chekrygina, D.; Cowan, T.; Descamps, A.; French, M.; Galtier, E.; Gleason, A. E.; Glenn, G. D.; Glenzer, S. H.; Inubushi, Y.; Hartley, N.; Hernandez, J.-A.; Heuser, B.; Humphries, O. S.; Kamimura, N.; Katagiri, K.; Khaghani, D.; Ja Lee, H.; McBride, E. E.; Miyanishi, K.; Nagler, B.; Ofori-Okai, B.; Ozaki, N.; Pandolfi, S.; Qu, C.; Ranjan, D.; Redmer, R.; Schoenwaelder, C.; Schuster, A.; Stevenson, M. G.; Sueda, K.; Togashi, T.; Vinci, T.; Voigt, K.; Vorberger, J.; Yabashi, M.; Yabuuchi, T.; Zinta, L. M. V.; Ravasio, A.; Kraus, D.

Extreme conditions inside ice giants like Uranus and Neptune can result in peculiar chemistry and structural transitions, e.g., the precipitation of diamonds or superionic water, as so far experimentally observed only for pure C-H and H2O systems, respectively. Here we investigate a stoichiometric mixture of C and H2O by shock-compressing PET plastics and performing in situ X-ray probing. We observe diamond formation at pressures between 72±7 GPa and 125±13 GPa at temperatures ranging from ~3500 K to ~6000 K. Combining X-ray diffraction and small angle X-ray scattering, we access the kinetics of this exotic reaction. The observed demixing of C and H2O suggests that diamond precipitation inside the ice giants is enhanced by oxygen, which can lead to isolated water and thus the formation of superionic structures relevant to the planets’ magnetic fields. Moreover, our measurements indicate a way of producing nanodiamonds by simple laser-driven shock-compression of cheap PET plastics.

Permalink: https://www.hzdr.de/publications/Publ-34946
Publ.-Id: 34946


Impact of sulfated hyaluronan on bone metabolism in diabetic Charcot neuroarthropathy and degenerative arthritis

Schulze, S.; Neuber, C.; Möller, S.; Hempel, U.; Hofbauer, L. C.; Schaser, K.-D.; Pietzsch, J.; Rammelt, S.

Bone in diabetes mellitus is characterized by an altered microarchitecture caused by abnormal metabolism of bone cells. Together with diabetic neuropathy, this is associated with serious complications including impaired bone healing culminating in complicated fractures and dislocations, especially in the lower extremities, so-called Charcot neuroarthropathy (CN). The underlying mechanisms are not yet fully understood, and treatment of CN is challenging. Several in vitro and in vivo investigations have suggested positive effects on bone regeneration by modifying biomaterials with sulfated glycosaminoglycans (sGAG). Recent findings described a beneficial effect of sGAG for bone healing in diabetic animal models compared to healthy animals. We therefore aimed at studying the effects of low- and high-sulfated hyaluronan derivatives on osteoclast markers as well as gene expression patterns of osteoclasts and osteoblasts from patients with diabetic CN compared to non-diabetic patients with arthritis at the foot and ankle. Exposure to sulfated hyaluronan (sHA) derivatives reduced the exaggerated calcium phosphate resorption as well as the expression of genes associated with bone resorption in both groups, but more pronounced in patients with CN. Moreover, sHA derivatives reduced the release of pro-inflammatory cytokines in osteoclasts of patients with CN. The effects of sHA on osteoblasts differed only marginally between patients with CN and non-diabetic patients with arthritis. These results suggest balancing effects of sHA on osteoclastic bone resorption parameters in diabetes.

Keywords: Charcot neuroarthropathy; diabetes mellitus; ankle arthritis; osteoblasts; osteoclasts; sulfated hyaluronan

Permalink: https://www.hzdr.de/publications/Publ-34944
Publ.-Id: 34944


Saccoite, Ca2Mn+32F(OH)8·0.5(SO4), a new, microporous mineral from the Kalahari Manganese Fields, South Africa

Giester, G.; Lengauer, C. L.; Chanmuang N., C.; Topa, D.; Gutzmer, J.; von Bezing, K.-L.

2
transparent, with white streak and vitreous luster. No luminescence is observed. Saccoite is uniaxial (–) with refractive indices at 589(1) nm  = 1.705(5) and  = 1.684(2). Pleochroism is distinct, i.e. bluish green (ω) and yellowish green (ε). The chemical composition was studied by means of an electron probe micro-analyser (EPMA) using wavelength-dispersive X-ray spectrometry (WDS). The empirical mineral formula is Ca2.06Mn3+1.78Cu0.10Mg0.07F0.97(OH)8.02(SO4)0.39. The unit-cell dimensions of saccoite (space group P4/ncc) are a = 12.834(3) Å, c = 5.622(2) Å, V = 926.0(4) Å3), and the calculated mass density is 2.73 g·cm-3. Saccoite exhibits a heteropolyhedral framework structure that is composed of edge- and cornersharing CaF2(OH)6 and M(OH)6 polyhedra (M = Mn3+, Cu2+) with large channels along [001], which host disordered and only partially occupied groups, especially SO42-. The hydrogen atoms of the OH groups point into the channel to form hydrogen bonds with the channel anions. Ca–F distances are about 2.3 Å, the Ca–OH distances in the range of 2.44 -2.58 Ǻ, and the M(OH)6 octahedron is strongly 4+2 Jahn-Teller distorted (4 × ~ 1.92 Å, 2 × 2.27 Å). The F atom is tetrahedrally coordinated to calcium atoms. The strongest lines in the X-ray powder pattern [d in Å (relative intensity) (hkl)] are: 9.0735 (35) (110), 4.5370 (95) (220), 4.0644 (20) (310), 3.0105 (100) (321), 2.8117 (20) (002), 2.7242 (75) (411), 1.9755 (35) (611), and 1.8142 (20) (550).

Keywords: saccoite; Ca2Mn+32F(OH)8·0.5(SO4); new mineral; microporous structure; Kalahari Manganese Field; South Africa

Permalink: https://www.hzdr.de/publications/Publ-34943
Publ.-Id: 34943


Unravelling the Origin of Ultra-Low Conductivity in SrTiO3 Thin Films: Sr Vacancies and Ti on A-Sites Cause Fermi Level Pinning

Morgenbesser, M.; Viernstein, A.; Schmid, A.; Herzig, C.; Kubicek, M.; Taibl, S.; Bimashofer, G.; Stahn, J.; Antonio Fernandes Vaz, C.; Döbeli, M.; Biautti, F.; de Dios Sirvent, J.; Liedke, M. O.; Butterling, M.; Kamiński, M.; Tolkiehn, M.; Vonk, V.; Stierle, A.; Wagner, A.; Tarancon, A.; Limbeck, A.; Fleig, J.

Different SrTiO3 thin films are investigated to unravel the nature of ultra-low conductivities recently found in SrTiO3 films prepared by pulsed laser deposition. Impedance spectroscopy reveals electronically pseudo-intrinsic conductivities for a broad range of different dopants (Fe, Al, Ni) and partly high dopant concentrations up to several percent. Using inductively-coupled plasma optical emission spectroscopy and reciprocal space mapping, a severe Sr deficiency is found and positron annihilation lifetime spectroscopy revealed Sr vacancies as predominant point defects. From synchrotron-based X-ray standing wave and X-ray absorption spectroscopy measurements, a change in site occupation is deduced for Fe-doped SrTiO3 films, accompanied by a change in the dopant type. Based on these experiments, a model is deduced, which explains the almost ubiquitous pseudo-intrinsic conductivity of these films. Sr deficiency is suggested as key driver by introducing Sr vacancies and causing site changes (FeSr and TiSr) to accommodate nonstoichiometry. Sr vacancies act as mid-gap acceptor states, pinning the Fermi level, provided that additional donor states (most probably Ti_Sr) are present. Defect chemical modeling revealed that such a Fermi level pinning also causes a self-limitation of the Ti site change and leads to a very robust pseudo-intrinsic situation, irrespective of Sr/Ti ratios and doping.

Keywords: STO; Sr vacancies; conductivity; PALS

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Permalink: https://www.hzdr.de/publications/Publ-34942
Publ.-Id: 34942


Three-dimensional quasiquantized Hall insulator phase in SrSi2

Manna, K.; Kumar, N.; Chattopadhyay, S.; Noky, J.; Yao, M.; Park, J.; Förster, T.; Uhlarz, M.; Chakraborty, T.; Schwarze, B. V.; Hornung, J.; Strocov, V. N.; Borrmann, H.; Shekhar, C.; Sun, Y.; Wosnitza, J.; Felser, C.; Gooth, J.

In insulators, the longitudinal resistivity becomes infinitely large at zero temperature. For classical insulators, the Hall conductivity becomes zero at the same time. However, there are special systems, such as two-dimensional quantum Hall insulators, in which a more complex scenario is observed at high magnetic fields. Here, we report experimental evidence for a quasiquantized Hall insulator in the quantum limit of the three-dimensional compound SrSi2. Our measurements reveal a magnetic-field range, in which the longitudinal resistivity diverges with decreasing temperature, while the Hall conductivity approaches a quasiquantized value that is given only by the conductance quantum and the Fermi wave vector in the field direction. The quasiquantized Hall insulator appears in a magnetic field induced insulating ground state of three-dimensional materials and is deeply rooted in quantum Hall physics.

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Permalink: https://www.hzdr.de/publications/Publ-34941
Publ.-Id: 34941


Comprehensive study of silicon photomultiplier based readout of the large plastic scintillator based neutron detector NeuLAND

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

The NeuLAND (New Large-Area Neutron Detector) plastic scintillator based time of flight detector for 0.2-1.6 GeV neutrons is currently under construction at the Facility for Antiproton and Ion Research (FAIR), Darmstadt, Germany. In its final configuration, NeuLAND will consist of 3,000 2.7 m long plastic scintillator bars that are read out on each end by fast timing photomultipliers.

Here, data from a comprehensive study of an alternative light readout scheme using silicon photomultipliers (SiPM) are reported. For this purpose, a typical NeuLAND bar was instrumented on each end with a prototype of the same geometry as a 1'' photomultiplier tube, including four 6x6 mm^2 SiPMs, amplifiers, high voltage supply, and microcontroller.

Tests were carried out using the 35 MeV electron beam from the ELBE superconducting linac with its ps-level time jitter in two different modes of operation, namely parasitic mode with one electron per bunch and single-user mode with 1-60 electrons per bunch, using Acqiris fast digitizers. In addition, offline tests using cosmic rays and the NeuLAND data acquisition scheme were carried out.

Typical time resolutions of sigma <= 100 ps were found for $\geq$99\% efficiency, improving on previous work at ELBE and exceeding the NeuLAND timing goal of sigma < 150 ps. Over a range of 10-300 MeV deposited energy in the NeuLAND bar, the gain was found to deviate by <=10% <=20% from linearity for 35 um (50 um) SiPM pitch, respectively, satisfactory for calorimetric use of the full NeuLAND detector. The dark rate of the prototype studied was found to be 70-200 s^-1, comparable with the unavoidable cosmic-ray induced background.

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Permalink: https://www.hzdr.de/publications/Publ-34940
Publ.-Id: 34940


Metal-assisted chemically etched silicon nanopillars hosting telecom photon emitters

Hollenbach, M.; Jagtap, N. S.; Fowley, C.; Baratech, J.; Guardia-Arce, V.; Kentsch, U.; Eichler-Volf, A.; Abrosimov, N. V.; Erbe, A.; Shin, C.; Kim, H.; Helm, M.; Lee, W.; Astakhov, G.; Berencen, Y.

Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of an ensemble of telecom photon emitters in a two-dimensional array of silicon nanopillars. We developed a top-down nanofabrication method, enabling the production of thousands of nanopillars per square millimeter with state-of-the-art photonic-circuit pitch, all the while being free of fabrication-related radiation damage defects. We found a waveguiding effect of the 1278 nm-G center emission along individual pillars accompanied by improved brightness compared to that of bulk silicon. These results unlock clear pathways to monolithically integrating single-photon emitters into a photonic platform at a scale that matches the required pitch of quantum photonic circuits.

Keywords: G centers; Silicon nanopillars; Photonic integration; Metal-assisted chemical etching; Ion implantation

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  • Secondary publication expected from 15.07.2023

Permalink: https://www.hzdr.de/publications/Publ-34938
Publ.-Id: 34938


DNS and Highly-Resolved LES of Heat and Mass Transfer in Two-Phase Counter-Current Condensing Flow

Apanasevich, P.; Lucas, D.; Sato, Y.; Niceno, B.

A comprehensive study of direct-contact condensation heat transfer for turbulent, counter-current, liquid/vapour flow in a nearly horizontal channel at high pressure (i.e. 5MPa) has been carried out based on Direct Numerical Simulation (DNS) and highly-resolved Large Eddy Simulation (LES) approaches. To simulate the two-phase flow situation, driven in this case by a constant pressure gradient, a single set of Navier-Stokes equations, coupled with an enthalpy conservation equation, have been employed. The interfacial mass transfer, seen in this case to be dominated by condensation, has been calculated directly from the heat flux at the liquid/vapour interface. To investigate the effect of condensation on the turbulence phenomena, and vice versa, cases have been considered involving two friction Reynolds numbers: namely Re∗ = u∗h/ν = 178 and Re∗ = u∗h/ν = 590 (u∗ = (hΔP/ρ)^1/2). At the lower Reynolds number, three levels of water subcooling – 0K, 10K and 40K – have been investigated. The use of water subcooling of 0K has enabled the validation and verification procedures associated with the numerical approach to be compared against experimental and numerical data reported in the literature. The choice of the maximum degree of water subcooling is dictated by the need to justify the periodic boundary conditions applied in this numerical study. In the simulation for the higher Reynolds number, only the case of 10K subcooling has been included, as a consequence of the very high computation effort involved.

A detailed statistical analysis of the DNS and LES data obtained from the application of the well-known wall laws has also been assessed. In the vicinity of the liquid/vapour interface, the characteristics of the turbulent motions appear somewhat diverse, depending on whether the interface is basically flat or wavy in character. For a flat interface, some damping effect of the presence of the interface on the turbulence intensity has been observed, a feature which becomes enhanced as the level of liquid subcooling is increased. In the case of a wavy interface, the damping effect is predicted as considerably less pronounced.

Keywords: DNS; Highly-resolved LES; Multiphase flows; Phase change; Direct contact condensation; Interfacial heat transfer

Permalink: https://www.hzdr.de/publications/Publ-34937
Publ.-Id: 34937


Scalable fabrication of single quantum emitters in silicon

Astakhov, G.

Single-photon sources are one of the elementary building blocks for photonic quantum information and optical quantum computing. One of the upcoming challenges is the monolithic photonic integration and coupling of single-photon emission, reconfigurable photonic elements and single-photon detection on a silicon chip by a controllable manner. To this end, deterministic single-photon sources monolithically integrated with silicon quantum photonic integrated circuits (QPIC) represent a new tool in quantum photonics, complementing heralded probabilistic sources and offering very-large-scale integration (VLSI).
The isolation of single-photon emitters in the optical telecommunication O-band, such as the G centers and W centers, has recently been realized in silicon. In all previous cases, however, single-photon emitters were created randomly and uncontrollably, preventing their scalability. We realize the controllable fabrication of single G and W centers in silicon wafers using focused ion beams with high probability. We also implement a scalable, broad-beam implantation protocol compatible with the complementary-metal-oxide-semiconductor (CMOS) technology to fabricate single telecom emitters in desired positions on the nanoscale.
Our results enable the direct realization of QPIC with monolithically integrated single-photon sources with electrical control. Our findings also provide a route for the quasi-deterministic creation of single G and W centers at desired locations of photonic structures, including SOI waveguides and tunable cavities. This altogether unlocks clear pathways toward the implementation of industrial-scale photonic quantum processors.

Keywords: Single photons; Telecommunication band; Silicon; Quantum technologies

Related publications

  • Invited lecture (Conferences)
    Flagship Workshop: Defects in solids for quantum technologies, 12.-17.06.2022, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-34934
Publ.-Id: 34934


Design and qualification of the Mu2e electromagnetic calorimeter electronic system

Ceravolo, S.; Colao, F.; Diociaiuti, E.; Corradi, G.; Di Falco, S.; Donati, S.; Fiore, S.; Ferrari, A.; Gioiosa, A.; Giovannella, S.; Happacher, F.; Martini, M.; Miscetti, S.; Morescalchi, L.; Müller, S.; Paesani, D.; Pasciuto, D.; Pedreschi, E.; Raffaelli, F.; Saputi, A.; Sarra, I.; Sanzani, E.; Spinella, F.; Taffara, A.

The Mu2e experiment [1] at Fermilab will search for the neutrino-less coherent
conversion of a muon into an electron in the field of a nucleus. Mu2e detectors
comprise a strawtracker, an electromagnetic calorimeter and a veto for cosmic
rays. The calorimeter employs 1348 Cesium Iodide crystals readout by silicon
photomultipliers and fast front-end and digitization electronics. The front-end
electronics consists of two discrete chips for each crystal. These provide the
amplification and shaping stage,linear regulation of the SiPM bias voltage and
monitoring. The SiPM and front-end control electronics is implemented in a bat-
tery of mezzanine boards each equipped with an ARM processor that controls
a group of 20 Amp-HV chips, distributes the low voltage and the high-voltage
reference values, sets and reads back the locally regulated voltages. The elec-
tronic is hosted in crates located on the external surface of calorimeter disks.
The crates also host the waveform digitizer board (DIRAC) that performs dig-
itization of the front end signals and transmit the digitized data to the Mu2e
DAQ. Calorimeter electronic is hosted inside the cryostat and it must substain
very high radiation and magnetic field so it was necessary to fully qualify it.
The constraints on the calorimeter front-end and readout electronics, the design
technological choices and the qualification tests will be reviewed.

Keywords: Front-end electronics; Radiation hardness; Calorimetry

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  • Secondary publication expected from 26.11.2023

Permalink: https://www.hzdr.de/publications/Publ-34933
Publ.-Id: 34933


Combining Radiation- with Immunotherapy in Prostate Cancer: Influence of Radiation on T cells

Lindner, D.; Arndt, C.; Rodrigues Loureiro, L. R.; Feldmann, A.; Kegler, A.; Koristka, S.; Berndt, N.; Mitwasi, N.; Bergmann, R.; Frenz, M.; Bachmann, M.

Radiation of tumor cells can lead to the selection and outgrowth of tumor escape variants. As radioresistant tumor cells are still sensitive to retargeting of T cells, it appears promising to combine radio- with immunotherapy keeping in mind that the radiation of tumors favors the local conditions for immunotherapy. However, radiation of solid tumors will not only hit the tumor cells but also the infiltrated immune cells. Therefore, we wanted to learn how radiation influences the functionality of T cells with respect to retargeting to tumor cells via a conventional bispecific T cell engager (BiTE) and our previously described modular BiTE format UNImAb. T cells were irradiated between 2 and 50 Gy. Low dose radiation of T cells up to about 20 Gy caused an increased release of the cytokines IL2, TNF and interferon-g and an improved capability to kill target cells. Although radiation with 50 Gy strongly reduced the function of the T cells, it did not completely abrogate the functionality of the T cells.

Keywords: prostate stem cell antigen; prostate cancer; radiation; immunotherapy; bispecific T cell engager

Permalink: https://www.hzdr.de/publications/Publ-34932
Publ.-Id: 34932


Investigation of energy and orientation dependent effects of thimble type ionization detectors in an MRgPT prototype

Fuchs, H.; Gebauer, B.; Hoffmann, A. L.; Pawelke, J.; Lühr, A.; Georg, D.

Introduction
Combining MR imaging and beam delivery for image guided precision radiotherapy was already introduced clinically with hybrid MR-linac systems. For proton therapy, given the conformal treatment method as well as the sensitivity to changes in patient anatomy, a hybrid MR and proton therapy device might be even more beneficial. In Dresden, a clinical demonstrator prototype, consisting of an 0.32 T open MR scanner and a horizontal pencil beam scanning beamline was installed. From a medical phyics perspective, the establishment of reliable dosimetry methods is a prerequisite for further pre-clinical and clinical studies.
In MR guided proton therapy (MRgPT), the primary treatment beam itself is influenced by the magnetic field of the scanner. We investigated whether the response of the dosimetry detector depends on the detector orientation with respect to the magnetic field lines.
In this work we focused on potential effects of the 0.32 T magnetic field on commercially available ionization detectors. For photons, considerable orientation effects have been reported. Given the influence of the magnetic field on the particle trajectories, potential orientation effects could have a considerable influence on dosimetric measurements.
Material & Methods
Experiments were performed at the experimental room of the University Proton Therapy Dresden with and without the prototype MRgPT system positioned 58.2 cm downstream of the beam iso-center of the beam line. Four thimble type ionization detectors, a Farmer, a Semiflex, a PinPoint and a PinPoint 3D detector were positioned at 2 cm water-equivalent depth and irradiated using 10 x 15 cm² homogeneous proton fields. Lateral field shifts due to the vertical magnetic field were compensated for. Irradiations were performed for 3 nominal proton energies (100, 150 and 220 MeV) and repeated with the same set-up at 0.32 T (with MR scanner) and 0 T (MR scanner removed). Chambers were positioned in horizontal, vertical and 15° tilted orientation. Magnetic field correction factors were evaluated.

Results
Preliminary results show a small orientation dependence within 0.3 and 1% depending on the chamber, with larger effects for smaller chamber volumes.
A small, but consistent energy dependence of the magnetic field correction factor ranging from 0.5 to 1.6% was determined. The change in correction factors was found to be higher for lower energies as well as smaller sensitive detector volumes.

Discussion
Chamber readings inside an applied magnetic field of 0.32 T were found to depend on detector orientation as well as incident proton energy. For 0 T no noticeable influence was determined. In addition, the effect seems to be more pronounced for small volume chambers. Especially for small volume chambers, such as the PinPoint 3D, it is recommended to introduce a respective correction factor.

Keywords: chamber dosimetry; thimble chamber; proton; MRI; MRgPT; MRiPT; chamber correction factor; energy; orientation

  • Lecture (Conference)
    3 Verbände – Strahlenschutztagung, 29.09.-01.10.2022, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-34931
Publ.-Id: 34931


Dataset for Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction

Kraus, D.

Dataset for publication "Diamond formation kinetics in shock-compressed C-H-O samples recorded by small-angle X-ray scattering and X-ray diffraction"

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Permalink: https://www.hzdr.de/publications/Publ-34930
Publ.-Id: 34930


A FAIRly Integrated Scientific Project Lifecycle

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

The talk introduces the general idea behind the HELIPORT project, which aims to make the entire life cycle of a scientific experiment or project discoverable, accessible, interoperable and reusable by providing an overview from a top-level perspective. Specifically, our data management solution addresses the areas from data generation to publication of primary research data, computing workflows performed and the actual research results.

Keywords: Data Management; Metadata; FAIR; Data provenance; Digital Objects; Digital Twins

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    HMC Dialogue, 15.07.2022, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-34929
Publ.-Id: 34929


Broken axial symmetry as essential feature for a consistent modelling of various observables in heavy nuclei

Grosse, E.; Junghans, A.

Although most nuclear spectroscopy as well as atomic hyperfine structure data do not deliver accurate information on nuclear
axiality the ad-hoc assumption of symmetry about one axis found widespread use in nuclear model calculations. In the theoretical
interpretation of nuclear properties as well as in the analysis of experimental data triaxiality was considered – if at all – only
for some, often exotic, nuclides. A breaking of axial symmetry combined to a spin-independent moment of inertia results in a
surprisingly simple heuristic triaxial parametrization of the yrast sequence in all heavy nuclei, including well deformed ones. No
additional fit parameters are needed in detailed studies of the mass and charge dependence of the electric dipole strength in the range
of and outside of giant dipole resonances. Allowing triaxiality also avoids the introduction of an arbitrary level density parameter
˜a to fit the accurate values observed in n-capture experiments and ˜a can be taken from nuclear matter studies. A combination of
this value to the yrast energies no longer based on axiality and the related I(I+1) rule results in agreement to data independent of
spin. And predictions for radiative neutron capture as derived on the basis of non-axiality are improved as well. The experimentally
favoured broken axial symmetry is in accord to HFB and MC-shell model calculations already for nuclei in the valley of stability.

Permalink: https://www.hzdr.de/publications/Publ-34928
Publ.-Id: 34928


Modulating the pharmacokinetic profile of Actinium-225-labeled macropa-derived radioconjugates by dual targeting of PSMA and albumin

Reissig, F.; Zarschler, K.; Novy, Z.; Petrik, M.; Bendova, K.; Kurfurstova, D.; Bouchal, J.; Ludik, M.-C.; Brandt, F.; Kopka, K.; Khoylou, M.; Pietzsch, H.-J.; Hajduch, M.; Mamat, C.

Rationale: Small 225Ac-labeled prostate-specific membrane antigen (PSMA)-targeted radioconjugates have been described for targeted alpha therapy of metastatic castration-resistant prostate cancer. Transient binding to serum albumin as a highly abundant, inherent transport protein represents a commonly applied strategy to modulate the tissue distribution profile of such low-molecular-weight radiotherapeutics and to enhance radioactivity uptake into tumor lesions with the ultimate objective of improved therapeutic outcome.
Methods: Two ligands mcp-M-alb-PSMA and mcp-D-alb-PSMA were synthesized by combining a macropa-derived chelator with either one or two lysine-ureido-glutamate–based PSMA- and 4-(p-iodophenyl)butyrate albumin-binding entities using multistep peptide-coupling chemistry. Both compounds were labeled with [225Ac]Ac3+ under mild conditions and their reversible binding to serum albumin was analyzed by an ultrafiltration assay as well as microscale thermophoresis measurements. Saturation binding studies and clonogenic survival assays using PSMA-expressing LNCaP cells were performed to evaluate PSMA-mediated cell binding and to assess the cytotoxic potency of the novel radioconjugates [225Ac]Ac-mcp-M-alb-PSMA and [225Ac]Ac-mcp-D-alb-PSMA, respectively. The biodistribution of both 225Ac-radioconjugates was investigated in LNCaP tumor-bearing SCID mice. Histological examinations of selected organs were performed to analyze the occurrence of necrosis using H&E staining, DNA damage via γH2AX staining and proliferation via Ki67 expression in the tissue samples.
Results: Enhanced binding to serum components in general and to human serum albumin in particular was revealed for [225Ac]Ac-mcp-M-alb-PSMA and [225Ac]Ac-mcp-D-alb-PSMA, respectively. Moreover, the novel derivatives are highly potent PSMA ligands as their KD values in the nanomolar range (23.38 and 11.56 nM) are comparable to the reference radioconjugates [225Ac]Ac-mcp-M-PSMA (30.83 nM) and [225Ac]Ac-mcp-D-PSMA (10.20 nM) without albumin binders. The clonogenic activity of LNCaP cells after treatment with the 225Ac-labeled ligands was affected in a dose- and time-dependent manner, whereas the dimeric radioconjugate [225Ac]Ac-mcp-D-alb-PSMA has a stronger impact on the clonogenic cell survival than its monomeric counterpart [225Ac]Ac-mcp-M-alb-PSMA. Biodistribution studies performed in LNCaP tumor xenografts showed prolonged blood circulation times for both albumin-binding radioconjugates and a substantially increased tumor uptake (46.04 ± 7.77 %ID/g for [225Ac]Ac-mcp-M-alb-PSMA at 128 h p.i. and 153.48 ± 37.76 %ID/g at 168 h p.i. for [225Ac]Ac-mcp-D-alb-PSMA) with favorable tumor-to-background ratios. Consequently, a clear histological indication of DNA damage was discovered in the tumor tissues, whereas DNA double-strand break formation in kidney and liver sections was less pronounced.
Conclusion: The modification of the PSMA-based 225Ac-radioconjugates with one or two albumin-binding entities resulted in an improved radiopharmacological behavior including a greatly enhanced tumor accumulation combined with a low to neglectable uptake in non-targeted organs.

Keywords: Macropa; Actinium; Targeted Alpha Therapy; Albumin Binder; PSMA

Permalink: https://www.hzdr.de/publications/Publ-34927
Publ.-Id: 34927


Curvilinear magnetism: fundamentals and applications

Makarov, D.

In this talk I provide an overview of the activities of the FWID department with the focus on curvature effects in magnetic thin films and realization of flexible magnetic field sensors.

Keywords: curvature effects in magnetism; curvilinear magnetism; magnetic field sensing; human-machine interfaces; soft robotics

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  • Lecture (others)
    Invited talk at the Leibniz IFW (Institute for Metalic Materials), 12.07.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-34926
Publ.-Id: 34926


Neuromorphic computing with magnons

Schultheiß, K.

Within the last decade, spintronics and magnonics have demonstrated an impressive development in the experimental realization of Boolean logic gates. However, the exponential growth of data and the rise of the internet of things are pushing the deterministic Boolean computing of von-Neumann architectures to their limits or are simply to energy consuming. Moreover, it is accepted commonly that conventional Boolean computer architectures are likely to remain inefficient for certain cognitive tasks in which the human brain excels, such as pattern recognition, particularly when incomplete or noisy data are involved.
One of the most generic and abstract implementations of brain-inspired computing schemes is reservoir computing, where the nonlinear response of a physical system is used to separate patterns hidden in a temporal data stream into distinct manifolds of a higher dimensional output space. In this presentation, I will demonstrate the experimental realization of pattern recognition based on reservoir computing using magnons.
Recently, we reported on the nonlinear scattering of magnons in vortices in micron-sized Permalloy discs [1] which we also learned to control and stimulate by means of other magnons [2]. Now, we utilize these phenomena to employ magnons for pattern recognition without actually relying on magnon transport in real space. I will present a comprehensive overview of experimental results and numerical simulations demonstrating the capabilities and advantages of magnon reservoir computing in reciprocal space.

[1] K. Schultheiss, et al., Physical Review Letters 125, 207203 (2020)
[2] K. Schultheiss, et al., Physical Review Letters 122, 097202 (2019)

Keywords: spin waves; magnonics; reservoir computing; Brillouin light scattering

Related publications

  • Invited lecture (Conferences)
    CMD29 Conference, 22.8.2022, Manchester, United Kingdom
  • Invited lecture (Conferences)
    7th Workshop on Magnonics, 1.8.2022, Oxnard, Kalifornien, USA

Permalink: https://www.hzdr.de/publications/Publ-34924
Publ.-Id: 34924


Simple Growth–Metabolism Relations Are Revealed by Conserved Patterns of Heat Flow from Cultured Microorganisms

Fahmy, K.

Quantitative analyses of cell replication address the connection between metabolism and growth. Various growth models approximate time-dependent cell numbers in culture media, but physio-logical implications of the parametrizations are vague. In contrast, isothermal microcalorimetry (IMC) measures with unprecedented sensitivity to heat (enthalpy) release via chemical turnover in metabolizing cells. Hence, the metabolic activity can be studied independently of modeling the time-dependence of cell numbers. Unexpectedly, IMC traces of various origins exhibit conserved patterns when expressed in the enthalpy domain rather than the time domain, as exemplified by cultures of Lactococcus lactis (prokaryote), Trypanosoma congolese (protozoan) and non-growing Brassica napus (plant) cells. The data comply extraordinarily well with a dynamic Langmuir ad-sorption reaction model of nutrient uptake and catalytic turnover generalized here to the non-constancy of catalytic capacity. Formal relations to Michaelis–Menten kinetics and common analytical growth models are briefly discussed. The proposed formalism reproduces the “life span” of cultured microorganisms from exponential growth to metabolic decline by a succession of distinct metabolic phases following remarkably simple nutrient–metabolism relations. The analysis enables the development of advanced enzyme network models of unbalanced growth and has fundamental consequences for the derivation of toxicity measures and the transferability of metabolic activity data between laboratories.

Keywords: bacteria; enzyme kinetics; heavy metals; isothermal microcalorimetry; Michaelis–Menten; toxicity

Permalink: https://www.hzdr.de/publications/Publ-34922
Publ.-Id: 34922


The Open-Access European Prevention of Alzheimer’s Dementia (EPAD) MRI dataset and processing workflow

Lorenzini, L.; Ingala, S.; Wink, A. M.; Kuijer, J. P. A.; Wottschel, V.; Dijsselhof, M.; Sudre, C. H.; Haller, S.; Molinuevo, J. L.; Gispert, J. D.; Cash, D. M.; Thomas, D. L.; Vos, S. B.; Prados, F.; Petr, J.; Wolz, R.; Palombit, A.; Schwarz, A. J.; Chételat, G.; Payoux, P.; Di Perri, C.; Wardlaw, J. M.; Frisoni, G. B.; Foley, C.; Fox, N. C.; Ritchie, C.; Pernet, C.; Waldman, A.; Barkhof, F.; Mutsaerts, H. J. M. M.

The European Prevention of Alzheimer Dementia (EPAD) is a multi-center study that aims to characterize the
preclinical and prodromal stages of Alzheimer’s Disease. The EPAD imaging dataset includes core (3D T1w, 3D
FLAIR) and advanced (ASL, diffusion MRI, and resting-state fMRI) MRI sequences.
Here, we give an overview of the semi-automatic multimodal and multisite pipeline that we developed to
curate, preprocess, quality control (QC), and compute image-derived phenotypes (IDPs) from the EPAD MRI
dataset. This pipeline harmonizes DICOM data structure across sites and performs standardized MRI pre-
processing steps. A semi-automated MRI QC procedure was implemented to visualize and flag MRI images next to
site-specific distributions of QC features — i.e. metrics that represent image quality. The value of each of these
QC features was evaluated through comparison with visual assessment and step-wise parameter selection based
on logistic regression. IDPs were computed from 5 different MRI modalities and their sanity and potential clinical
relevance were ascertained by assessing their relationship with biological markers of aging and dementia.
The EPAD v1500.0 data release encompassed core structural scans from 1356 participants 842 fMRI, 831
dMRI, and 858 ASL scans. From 1356 3D T1w images, we identified 17 images with poor quality and 61 with
moderate quality. Five QC features — Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), Coefficient of
Joint Variation (CJV), Foreground-Background energy Ratio (FBER), and Image Quality Rate (IQR) — were
selected as the most informative on image quality by comparison with visual assessment. The multimodal IDPs
showed greater impairment in associations with age and dementia biomarkers, demonstrating the potential of
the dataset for future clinical analyses.

Permalink: https://www.hzdr.de/publications/Publ-34920
Publ.-Id: 34920


Data publication: Electronic Density Response of Warm Dense Hydrogen: Ab initio Path Integral Monte Carlo Simulations

Dornheim, T.; Böhme, M.; Moldabekov, Z.

This repository contains the PIMC raw data for the static electronic density response of warm dense hydrogen. Units etc are the same as in the figures in the main text / supplemental material.

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-34919
Publ.-Id: 34919


Atomic mechanisms of self-diffusion in amorphous silicon

Posselt, M.; Bracht, H.; Ghorbani Asl, M.; Radić, D.

Based on recent calculations of the self-diffusion (SD) coefficient in amorphous silicon (a-Si) by classical Molecular Dynamics simulation [M. Posselt, H. Bracht, and D. Radić, J. Appl. Phys. 131, 035102 (2022)] detailed investigations on atomic mechanisms are performed. For this purpose two Stillinger-Weber-type potentials are employed, one strongly overestimates the SD coefficient, while the other leads to values much closer to the experimental data. By taking into account the individual squared displacements (or diffusion lengths) of atoms the diffusional and vibrational contributions to the total mean squared displacement can be determined separately. It is shown that the diffusional part is not directly correlated with the concentration of coordination defects. The time-dependent distribution of squared displacements of atoms indicates that in a-Si a well-defined elemental diffusion length does not exist, in contrast to SD in the crystalline Si. The analysis of atoms with large squared displacements reveals that the mechanisms of SD in a-Si are characterized by complex rearrangement of bonds or exchange of neighbors. These are mono- and bi-directional exchanges of neighbors and neighbor replacements. Exchange or replacement may concern up to three neighbors and may occur in relatively short periods of some ps. Bi- or mono-directional exchange or replacement of one neighbor atom happen more frequently than processes including more neighbors. A comparison of results for the two interatomic potentials shows that an increased three-body parameter only slows down the migration, but does not change the migration mechanisms fundamentally.

Keywords: Amorphous silicon; Self-diffusion; Atomistic simulation; Atomic mechanisms

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Permalink: https://www.hzdr.de/publications/Publ-34918
Publ.-Id: 34918


Equivariant neural networks for image segmentation

Venkatesh, D. K.; Lokamani, M.; Juckeland, G.; Weigert, M.; Steinbach, P.

Deep neural networks have by today been established as the goto candidate for semantic or instance segmentation at many scales and image modalities. The pressing challenge in supervised segmentation approaches remains to be the requirement of large annotated image datasets for good performance.
In recent years the expressive capabilities of neural networks have been demonstrated to improve through group convolutional operations which exploit existing symmetries present in the data.
The increased capacity for weight-sharing alongside gains in sample efficiency for training a neural network have led to the empirical success of equivariant neural networks. In our study, we propose and experiment on an equivariant U-net-based model for the task of image segmentation. In this talk, we will discuss our preliminary results on a synthetic datasets consisting of polygonal objects. The results indicate that the performance of our implementation of an equivariant network improves well beyond a vanilla Unet when exposed to symmetrical objects in data different scenarios.

References:

1. Taco S. Cohen, Max Welling, “Group Equivariant convolution networks”, arXiv preprint arXiv: 1602.07576, 2016.
2. Maurice Weiler and Gabriele Cesa, ”General E(2)-Equivariant Steerable CNNs”, NeurIPS 2019.

Keywords: equivariant neural networks; image segmentation; data augmentation; group theory; symmetry

  • Open Access Logo Lecture (Conference)
    Swiss Equivariant Learning Workshop, 11.-14.07.2022, Lausanne, Schweiz

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Permalink: https://www.hzdr.de/publications/Publ-34917
Publ.-Id: 34917


Evolution of elctronic coupling in the mechanically controllable break junctions

Lokamani, M.; Kilibarda, F.; Günther, F.; Kelling, J.; Strobel, A.; Zahn, P.; Juckeland, G.; Gothelf, K.; Scheer, E.; Gemming, S.; Erbe, A.

The electrical properties of single molecules can be investigated using atomically sharp metallic electrodes in mechanically controllable break junctions (MCBJs). The current-voltage (IV) characteristics of single molecules in such junctions are influenced by the binding positions of the end groups on the tip-facets and tip-tip separation. In this talk, we present MCBJ experiments on N,N’-Bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine (Salen). We discuss the evolution of the single level model (SLM) parameters namely, a) the energetic level є of the dominant conducting channel and b) the coupling Γ of the dominant conducting channel to the metallic electrodes. The SLM-parameters were evaluated for IV-curves recorded during opening measurements and fitted to the single level model. We propose a novel, high-throughput approach to model the evolution of the SLM-parameters and explain the recurring peak-like features in the experimentally measured evolution of Γ with increasing tip-tip separation, which we relate to the deformation of the molecule and the sliding of the anchor group above the electrode surface.

Keywords: MCBJ; Single Level Model; high-throughput approach; evolution of the SLM-parameters

  • Open Access Logo Lecture (Conference)
    DPG Regensburg 2022, 04.-09.09.2022, Regensburg, Germany

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Permalink: https://www.hzdr.de/publications/Publ-34916
Publ.-Id: 34916


The effect of composition and microstructure on the creep behaviour of 14 Cr ODS steels consolidated by SPS

Meza, A.; Macía, E.; Chekhonin, P.; Altstadt, E.; Rabanal, M. E.; Torralba, J. M.; Campos, M.

There is a general need for alternative structural materials to improve power plants' efficiency and reduce CO2 emissions. Within this framework, two new compositions of temperature-resistant sintered ODS ferritic steels (14Cr-5Al-3W), strengthened by a fine dispersion of precipitates (5·1022 ox. /m3), have been developed. This work focuses on creep properties and microstructure evolution. The creep resistance (at 650°C) could be improved by prior microstructural optimisation, thanks to the consolidation by spark plasma sintering and the tailoring of precipitates' nature when a single compound introduces the oxide-forming elements (Y-Ti-Zr-O) synthesised for this purpose. To this end, the initial pre-alloyed ferritic powder was mechanically alloyed with the synthesised compound and sintered by spark plasma sintering (SPS). Afterwards, EBSD and TEM characterisation were employed to study the microstructures. Small punch creep tests (SPCT) were performed on the steels to analyse their creep performance. These showed an exceptional enhancement of the creep resistance in the steels containing the Y-Ti-Zr-O additions.

Keywords: 14Cr-ODS steel; fine grain; creep behaviour; SPCT

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  • Secondary publication expected from 27.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34915
Publ.-Id: 34915


Investigation of particle effects on bubble coalescence in slurry with a chimera MP-PIC and VOF coupled method

Liao, Y.; Wang, Q.; Caliskan, U.; Miskovic, S.

Bubble coalescence and breakup is still a complex challenging topic. How far it is understood affects directly the analysis and design optimization of multiphase reactors. Despite years of active research, bubble coalescence in three-phase systems is far from being understood. Contradictory
results on the effect of particles are often reported. Although it still lacks a unique explanation, a general conjecture is that the presence of solid particles affects the film drainage process, and hence the bubble coalescence time and behaviour. This paper presents insights into bubble-pair coalescence in slurry by coupling the multiphase particle in cell (MP-PIC) method with the volume of fluid (VOF) method. The mesh resolution for VOF fields is down to micrometers, which allows for analysis of the film drainage and rupture mechanism in detail. The accuracy of MP-PIC fields during the refinement of CFD grids is guaranteed by a chimera approach (Caliskan and Miskovic, Chemical Engineering Journal Advances 5 (2021) 100054), which allows two overlapping meshes in the Lagrangian-Eulerian framework, namely, a fine mesh for the CFD fields and a coarser mesh for the MP-PIC ones.

Keywords: Bubble coalescence; Chimera grid; MP-PIC and VOF coupled; Particle effects; Slurry

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  • Secondary publication expected from 29.10.2023

Permalink: https://www.hzdr.de/publications/Publ-34914
Publ.-Id: 34914


Electrode design of an electrical impedance spectroscopy system for fouling detection in a heat exchanger

de Assis Dias, F.; Schubert, M.; Schleicher, E.; Scholz, F.; Hampel, U.

We present a preliminary study of the electrode design of an electrical impedance spectroscopy (EIS) system for fouling detection in heat exchangers. In this study, a basic model of a heat exchanger is created based on finite element method (FEM). Here, an invasive and non-invasive electrode configuration was investigated. Numerical results show that both invasive and non-invasive electrode configurations are suitable for detecting fouling using impedance spectroscopy. The invasive one showed a better contrast between the fouling and non-fouling scenarios. However, from a practical point of view, the latter is preferable in our application since it does not disturb the surface where fouling is formed.

Keywords: electrical impedance spectroscopy; fouling; crystallization scale; heat exchanger

  • Contribution to proceedings
    8th International Conference on Sensors and Electronic Instrumentation Advances (SEIA 2022), 21.-23.09.2022, Corfu, Greece
    ISSN: 978-84-09-43854-9
  • Poster
    8th International Conference on Sensors and Electronic Instrumentation Advances, 21.-23.09.2022, Corfu, Greece
    ISSN: 978-84-09-43854-9

Permalink: https://www.hzdr.de/publications/Publ-34909
Publ.-Id: 34909


Electrical impedance spectroscopy for fouling detection in heat exchangers with earth connected working electrodes

de Assis Dias, F.; Schubert, M.; Schleicher, E.; Pelzs, P.-L.; Meyer, C.; Bulst, M.; Hampel, U.

We created a test cell to design a measurement system based on electrical impedance spectroscopy for heat exchangers. In the experimental heat exchanger, the working electrode is connected to the earth potential for safety reasons. To avoid short-circuiting, an isolation transformer to decouple the impedance analyzer from earth potential was used, thus allowing the detection and characterization of thin fouling layers even if the working electrode is still connected to earth.

Keywords: electrical impedance spectroscopy; fouling; heat exchanger

  • Contribution to proceedings
    International Workshop on Impedance Spectroscopy (IWIS), 27.-30.09.2022, Chemnitz, Deutschland
    2022 International Workshop on Impedance Spectroscopy (IWIS)
    DOI: 10.1109/IWIS57888.2022.9975121
  • Lecture (Conference) (Online presentation)
    15th International Workshop on Impedance Spectroscopy, 27.-30.09.2022, Chemnitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-34908
Publ.-Id: 34908


Modelling and Performance Analysis of Hydrocyclones: The Case of Buzwagi Gold Mine

Wikedzi, A.; Mütze, T.

The performance of hydrocyclones at Buzwagi Gold Mine (BGM) was investigated in three full scale survey campaigns. Thereafter, several empirical and theoretical hydrocyclone models were used for prediction of hydrocyclone performance. The survey data revealed poor performance of the grinding circuit caused by a circulating load higher than the design. Further, the poor performance of the grinding circuit had consequences on hydrocyclones overflow particle size (i.e. a much coarser product, xP,80 > 200 µm) than target (125 µm). In addition, the operation indicates overloading of the hydrocyclones due to feed rates being 10–18% above the design capacity. Apart from their deficiencies, BGM hydrocyclones can be categorized as very good or excellent separators in terms of separation efficiency based on partition curves, T(x). The modelling of BGM hydrocyclones revealed that Nageswararao’s model can well describe and predict the operation and is recommended for future simulation and optimization of the operation. Based on the survey data, there are opportunities to improve current operation through adjustment of operating conditions like dilution of hydrocyclone feed for improved classification efficiency.

Keywords: Grinding circuit; Hydrocyclone performance; Partition curve; Hydrocyclone Modelling

Permalink: https://www.hzdr.de/publications/Publ-34907
Publ.-Id: 34907


Data publication: ExponatONE: a high-precision small animal irradiation setup using proton radiography

Schneider, M.; Elisabeth, B.; Suckert, T.; Beyreuther, E.; Bock, J.; Dietrich, A.; Gantz, S.; Heuchel, L.; Krause, M.; von Neubeck, C.; Nexhipi, S.; Tillner, F.; Schürer, M.; Lühr, A.; Müller, J.

Daten, die für die Veröffentlichung "ExponatONE: eine hochpräzise Kleintierbestrahlungsanlage mit Protonenradiographie" verwendet wurden.
Das Repository enthält alle Daten, die zur Erstellung der quantitativen Ergebnisse und Abbildungen im eingereichten Manuskript verwendet wurden.
Satz von Skripten zur Aufnahme und Verarbeitung von Radiografiebildern/CTs, wie im zugehörigen Paper beschrieben.
Bei dem Datensatz handelt es sich um alle verwendeten Bilder und Grafen (CT, Röntgenbilder, Radiografiebilder, Simulationen, Mikroskopiebilder) für die Auswertung der Ergebnisse und die Darstellung in den Figures.

Keywords: Proton therapy; Proton radiography; Mouse brain irradiation; Preclinical high-precision setup; DNA damage; Relative biological effectiveness (RBE)

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34904
Publ.-Id: 34904


Shedding light on the enigmatic TcO₂·xH₂O structure with density functional theory and EXAFS spectroscopy

Faria Oliveira, A.; Kuc, A. B.; Heine, T.; Abram, U.; Scheinost, A.

The β-emitting 99Tc isotope is a high-yield fission product in 235U and 239Pu nuclear reactors, raising special concern in nuclear waste management due to its long half-life and the high mobility of pertechnetate (TcO4−). In the conditions of deep nuclear waste repositories, retention of Tc is achieved via biotic and abiotic reduction of TcO4− to compounds like amorphous TcO2·xH2O precipitates. It is generally accepted that these precipitates have linear (Tc(μ O)2(H2O)2)n chains, with trans H2O. Although corresponding Tc Tc and Tc O distances have been obtained from Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, this structure is largely based on analogy with other compounds. Here, we combine Density-Functional Theory with EXAFS measurements of fresh and aged samples to show that, instead, TcO2·xH2O forms zigzag chains that undergo a slow aging process whereby they combine to form longer chains and, later, a tridimensional structure that might lead to a new TcO2 polymorph.

Keywords: Chain structures; Density functional calculations; EXAFS spectroscopy; Nuclear waste management; Technetium

Related publications

  • Open Access Logo Chemistry - A European Journal 28(2022)59, e202202235
    Online First (2022) DOI: 10.1002/chem.202202235
  • Open Access Logo Lecture (Conference)
    ATAS-AnXAS 2022, 17.-21.10.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-34903
Publ.-Id: 34903


Data publication: Application of the Coordinate Transformation in Nodal Diffusion Calculations of Radially Expanding SFR Cores

Nikitin, E.; Fridman, E.

DYN3D calculations (inputs + outputs).

Keywords: DYN3D; Nodal methods; Serpent; SFR; Thermal expansion

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Permalink: https://www.hzdr.de/publications/Publ-34900
Publ.-Id: 34900


Cyclotron production of ⁹⁵Nb using a natZr solid target

Franke, K.; Mansel, A.

⁹⁴Nb (half-life of 2.03x10⁴ a) is part of the radioactive inventory of the waste in the dismantling process of nuclear power plants. Half-life (34.991 d) and decay mode point out ⁹⁵Nb as appropriate isotopic radiotracer to investigate the fate of ⁹⁴Nb in future waste repositories.

Keywords: cyclotron; solid target; ⁹⁵Nb; niobium radionuclide

  • Poster
    Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34899
Publ.-Id: 34899


Application of the Coordinate Transformation in Nodal Diffusion Calculations of Radially Expanding SFR Cores

Nikitin, E.; Fridman, E.

In this study, the coordinate transformation technique was assessed for radial expansion of Sodium cooled Fast Reactor (SFR) cores with the focus on time-dependent calculations. This method was implemented into nodal diffusion code DYN3D and was tested against the already available direct mesh expansion model. The newly implemented method was tested for uniform radial core expansion cases. Within DYN3D, the coordinate transformation method was verified on steady-state cases and was validated on one of the transient scenarios from the Phenix reactor experiments. The obtained results demonstrate equivalence between the coordinate transformation and direct mesh expansion techniques and therefore presenting the viability of the former one in transient calculations of SFR cores.

Keywords: DYN3D; Nodal methods; Serpent; SFR; Thermal expansion

  • Contribution to proceedings
    2019 International Conference on Mathematics and Computational Methods Applied to Nuclear Science and Engineering, M&C 2019, 25.-29.08.2019, Portland, USA, 978-089448769-9, 1624-1631

Permalink: https://www.hzdr.de/publications/Publ-34898
Publ.-Id: 34898


Evolution of Single-Level-Model parameters in the Mechanically controllable Break Junctions

Kilibarda, F.; Günther, F.; Kelling, J.; Strobel, A.; Zahn, P.; Juckeland, G.; Kurt, G.; Elke, S.; Gemming, S.; Erbe, A.

The electrical properties of single molecules can be investigated using atomically sharp metallic electrodes in mechanically controllable break junctions (MCBJs). The current-voltage (IV) characteristics of single molecules in such junctions are affected by the binding positions of the end groups on the tip-facets and tip-tip separation. In this poster, we present MCBJ experiments on N,N’-Bis(5-ethynylbenzenethiol-salicylidene)ethylenediamine (Salen). We discuss the evolution of the single level model (SLM) parameters namely, a) the energetic level (epsilon) of the dominant conducting channel and b) the coupling (Gamma) of the dominant conducting channel to the metallic electrodes. The SLM-parameters were evaluated for IV-curves recorded during opening measurements and fitted to the single level model. We explain the recurring peak-like features/protusions in the experimentally measured evolution of Gamma with increasing tip-tip separation, which we relate not only to the deformation of the molecule but also to the sliding of the anchor group above the electrode surface. We propose a novel, high-throughput approach to model the evolution of the SLM-parameters and perform transport calculations using the self-consistent charge scheme of the density-functional-based tight binding (SCC-DFTB) approach and the Green’s function formalism. Thereby, we consider many thermodynamically relevant configurations and assess the evolution of SLM-parameters using the SLM-curve fitting of the zero-bias transmission. The SLM-parameters are averaged using statistical weights obtained from a Metropolis simulation considering up to 200 000 configurations for selected tip-tip separations. The behavior of the averaged quantities with respect to the tip-tip separation reflects the experimentally observed evolution of the SLM-parameters astonishingly well.

Keywords: high-throughput approach; Mechanically controllable break junctions; single level model; Metropolis simulation; Evolution of Single-Level-Model parameters

  • Open Access Logo Poster (Online presentation)
    YOUNG RESEARCHER’S WORKSHOP ON MACHINE LEARNING FOR MATERIALS, 09.-13.05.2022, Trieste, Italy

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Permalink: https://www.hzdr.de/publications/Publ-34896
Publ.-Id: 34896


Pbx(OH)y cluster formation in STI framework-type zeolites: anomalous thermal behaviour and increased thermal stability

Cametti, G.; Roos, D. P.; Churakov, S. V.; Prieur, D.; Scheinost, A. C.

The structural modifications occurring in zeolites upon heating are of interest because of technological and industrial applications. In this study, we report the anomalous behaviour of a Pb-exchanged zeolite (Pb13.4(OH)10Al17.4Si54.6O144 ∙38H2O) with STI framework type. For the first time, we observed a switch forom negative to positive thermal expansion during continuous heating. The dehydration was tracked in situ from 25 to 450 °C by single crystal X-ray diffraction, infrared, and X-ray absorption spectroscopy. Furthermore, toTo assist interpretation of the experimental results, molecular dynamics simulations were performed on a series of different theoretical models. Initially, Pb-STI unit-cell volume contracts (ΔV = -3.5%) from 25 to 100°C. This is in line with the trend observed in STI zeolites. Surprisingly, at 125°C, the framework expanded (ΔV = +2%), adopting a configuration, which resembles that of the room temperature structure. Upon heating, the structure loses H2O but no de-hydroxylation occurred. This behaviour is explained via the formation of Pbx(OH)x (x= 2,4) clusters, which prevent the shrinking of the channels, rupture of the tetrahedral bonds and occlusion of the pores. This zeolite has therefore an increased thermal stability with respect to other STI metal-exchanged zeolites, with important consequences foron its applications.

Keywords: Zeolite; ROBL; negative thermal expansion

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Permalink: https://www.hzdr.de/publications/Publ-34893
Publ.-Id: 34893


Curvilinear Micromagnetism: from fundamentals to applications

Sheka, D.; Makarov, D.

This book presents a timely and fundamental overview of magnetism in curved geometries, highlighting numerous peculiarities emerging from geometrically curved magnetic objects such as curves wires, shells, as well as complex three-dimensional structures. Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines across electronics, photonics, plasmonics and magnetics. This approach provides the means to modify conventional and even launch novel functionalities by tailoring the local curvature of an object. The book covers the theory of curvilinear micromagnetism as well as experimental studies of curved magnets including both fabrication and characterization. With its coverage of theoretical and fundamental aspects, together with exploration of numerous applications across magnonics, bio-engineering, soft robotics and shapeable magnetoelectronics, this edited collection is ideal for all scientists in academia and industry seeking an overview and wishing to keep abreast of advances in the novel field of curvilinear micromagnetism. It provides easy but comprehensive access to the field for newcomers, and can be used for graduate-level courses on this subject.

Keywords: curvature effects in magnetism; curvilinear magnetism; printed electronics; magnetic field sensors; flexible magnetoelectronics; soft magnetic robots

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34892
Publ.-Id: 34892


Curvilinear Magnetic Shells

Sheka, D.; Kravchuk, V.; Peddis, D.; Varvaro, G.; Krupinski, M.; Albrecht, M.; Erb, D.; Facsko, S.; Makarov, D.

In this chapter, we extend the discussion of curvature effects in magnetism towards the description of
geometrically curved magnetic thin shells. A self-consistent micromagnetic framework of curvilinear
magnetism describes the impact of curvature–induced effects, driven by both local and nonlocal
interactions, on the statics and dynamics of magnetic textures in extended curved thin shells. In particular,
we focus on the effects in magnetic thin films with in-plane and out-of-plane easy axis of magnetization on
spherical, cone-, bump-, and indentation-like objects. The special interest will be addressed to skyrmions in
curved magnetic films. Statics of skyrmions as well as their magnetization dynamics will be considered.
We provide an overview of relevant experimental methods, which allow fabricating these geometrically
curved extended thin films including nanosphere lithography, ion beam induced surface patterning and also
chemical synthesis approaches to realize metal and oxide hollow nanostructures with a tunable
morphology. We anticipate that the strong theoretical background on the fundamental understanding of the
curvature effects in geometrically curved magnetic shells and the availability of the fabrication methods to
produce these architectures will stimulate experimental activities targeting the validation of the exciting
theoretical predictions including curvature–induced skyrmions, pinning of chiral domain walls on local
bends and exploring novel nonlocal chiral symmetry breaking effects.

Keywords: curvature effects in magnetism; curvilinear magnetism; curved magnetic thin films; magnetochirality

Related publications

  • Book chapter
    Denys Makarov and Denis Sheka: Curvilinear Micromagnetism: from fundamentals to applications, Switzerland: Springer Nature, 2022, 978-3-031-09085-1
    DOI: 10.1007/978-3-031-09086-8_3

Permalink: https://www.hzdr.de/publications/Publ-34891
Publ.-Id: 34891


Geometrically Curved Magnetic Field Sensors for Interactive Electronics

Canon Bermudez, G. S.; Makarov, D.

The concept of curvilinear magnetism can be applied to a wide range of materials and targets the
applications where the interplay of geometry, shape, and magnetic texture arises. A clear advantage of
these deformable magnetic materials is that they can be used for applications that demand flexibility or
stretchability, something that conventionally rigid ferromagnets cannot provide. This advantage can be
readily exploited in the field of flexible electronics, which aims to create electronic circuits and devices
that can be folded or bent upon usage. The firm link between the fundamentals and applications of curved
magnetic thin films is given by the fact that magnetic domain walls can be pinned at bends.
This fundamental discovery has deep consequences for magnetic field sensors based on geometrically
curved magnetic thin films. Indeed, curvature of the structure results in an additional pinning mechanism
for domain walls, which can lead to the enhancement of the coercive field and hence lower the sensitivity
of magnetic field sensors. These considerations came up very recently and its consequences are still to be
explored and confirmed experimentally. Here, we will discuss primary the current advances in the
application of flexible magnetic field sensors based on geometrically curved magnetic thin films and
multilayers. Based on this technology, we present and foresee a wide range of applications in the fields of
eMobility, health, and interactive electronics. The latter is the main focus of this chapter, in particular due
to the added value of flexible magnetoelectronics to the fields of human-machine interfaces and virtual or
augmented reality.

Keywords: flexible magnetic field sensors; flexible electronics; interactive electronics; human-machine interfaces

Related publications

  • Book chapter
    Denys Makarov and Denis Sheka: Curvilinear Micromagnetism: from fundamentals to applications, Europe: , 2022, Switzerland: Springer Nature, 2022, 978-3-031-09085-1
    DOI: 10.1007/978-3-031-09086-8_9

Permalink: https://www.hzdr.de/publications/Publ-34890
Publ.-Id: 34890


Actions for increased yields and easier maintenance at the Tracerlab FXC-pro system in the synthesis of L-[11C]methionine

Mäding, P.; Zessin, J.; Kreller, M.; Kopka, K.; Knieß, T.

L-[11C]Methionine ([11C]Met) is frequently used for the diagnosis of tumours located in brain, head and neck or for tumours induced by the multiple myeloma. The radio synthesis of [11C]Met commonly starts with [11C]CO2 with subsequent transformation to [11C]CH4 followed by transfer into [11C]CH3I which is used for final labelling of the precursor L-homocystein thiolactone hydrochloride (HCTL). [1,2] By performing these steps with the TRACERLab FXC-pro System (GE HC), however, we observed inconstant radiochemical yields and high maintenance efforts especially of the absorber material used within the gas phase iodination. Accordingly, we have searched for optimization of this radio synthesis procedure.

  • Poster
    20th European Symposium on Radiopharmacy and Radiopharmaceuticals, 24.-27.11.2022, Verona, Italien

Permalink: https://www.hzdr.de/publications/Publ-34888
Publ.-Id: 34888


Free-electron lasers: past, present, and future challenges

Helm, M.

Free-electron lasers: past, present, and future challenges

Keywords: free electron laser

  • Invited lecture (Conferences) (Online presentation)
    International Conference on Free Electrons Laser Applications in Infrared and THz Studies of New States of Matter, 05.-08.07.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-34887
Publ.-Id: 34887


Review of recent progress on advanced photocathodes for SC RF guns

Xiang, R.; Schaber, J.

As well known, the quality of the photocathodes is essential for the stability and the reliability of photo injector operation. Especially for the superconducting ratio frequency photo injectors (SRF guns), the photocathode represents one of the most critical parts. Benefit from the fast de-veloping photocathode technology in last years, several SRF guns were successfully operated or tested for the beam generation at kHz - MHz repetition rate. In this paper, we will review the achievements as well as the open questions in the applications of the photocathodes for SRF gun operation. Furthermore, we will discuss the possible improvement from cathodes side for the future CW electron sources.

Keywords: photocathode; SRF gun; superconducting RF photo injector; quantum efficiency

Permalink: https://www.hzdr.de/publications/Publ-34886
Publ.-Id: 34886


Interface effect of Fe and Fe2O3 on the distributions of ion induced defects

Kim, H.; Chancey, M. R.; Chung, T.; Brackenbury, I.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Wagner, A.; Baldwin, J. K.; Derby, B. K.; Li, N.; Yano, K. H.; Edwards, D. J.; Wang, Y.; Selim, F. A.

The stability of structural materials in extreme nuclear reactor environments—with high temperature, high radiation and corrosive media—directly affects the lifespan of the reactor. In such extreme environments, an oxide layer on the metal surface acts as a passive layer protecting the metal underneath from corrosion. To predict the irradiation effect on the metal layer in these metal/oxide bilayers, nondestructive depth-resolved positron annihilation lifetime spectroscopy (PALS) and complementary transmission electron microscopy (TEM) were used to investigate small-scale defects created by ion irradiation in an epitaxially grown (100) Fe film capped with a 50 nm Fe2O3 oxide layer. In this study, the evolution of induced vacancies was monitored, from individual vacancy formation at low doses—10^-5 dpa—to larger vacancy cluster formation at increasing doses, showing the sensitivity of positron annihilation spectroscopy techniques. Furthermore, PALS measurements reveal how the presence of a metal-oxide interface modifies the distribution of point defects induced by irradiation. TEM measurements show that irradiation induced dislocations at the interface is the mechanism behind the redistribution of point defects causing their accumulation close to the interface. This work demonstrates that the passive oxide layers formed during corrosion impact the distribution and accumulation of radiation induced defects in the metal underneath, and emphasizes that the synergistic impact of radiation and corrosion will differ from their individual impacts.

Keywords: positron annihilation spectroscopy; Fe; Fe2O3; defects; ion irradiation; interface

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  • Secondary publication expected from 12.09.2023

Permalink: https://www.hzdr.de/publications/Publ-34885
Publ.-Id: 34885


Exploring the Reduction Mechanism of ⁹⁹Tc(VII) in NaClO₄: A Spectro-Electrochimical Approach

Rodriguez Hernandez, D. M.; Mayordomo, N.; Parra-Puerto, A.; Schild, D.; Brendler, V.; Stumpf, T.; Müller, K.

Technetium (Tc) is an environmentally relevant radioactive contaminant whose migration is limited when Tc(VII) is reduced to Tc(IV). However, its reaction mechanisms are not well understood yet. We have combined electrochemistry, spectroscopy, and microscopy (cyclic voltammetry, rotating disk electrode, X-ray photoelectron spectroscopy, and Raman and scanning electron microscopy) to study Tc(VII) reduction in non-complexing media: 0.5 mM KTcO₄ in 2 M NaClO₄ in the pH from 2.0 to 10.0. At pH 2.0, Tc(VII) first gains 2.3 ± 0.3 electrons, following Tc(V) rapidly receives 1.3 ± 0.3 electrons yielding Tc(IV). At pH 4.0−10.0, Tc(IV) is directly obtained by transfer of 3.2 ± 0.3 electrons. The reduction of Tc(VII) produced always a black solid identified as Tc(IV) by Raman and XPS. Our results
narrow a significant gap in the fundamental knowledge of Tc aqueous chemistry and are important to understand Tc speciation.
They provide basic steps on the way from non-complexing to complex media.

Keywords: Technetium; Raman spectroscopy; X-ray photoelectron spectroscopy; Non-complexing media

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  • Secondary publication expected from 24.06.2023

Permalink: https://www.hzdr.de/publications/Publ-34883
Publ.-Id: 34883


Complexation of Eu(III) and Cm(III) by EGTA related aminopolycarboxylic acids

Friedrich, S.; Holtmann, L.; Kretzschmar, J.; Drobot, B.; Stumpf, T.; Barkleit, A.

For purposes of chelation therapy and radiation protection, aminopolycarboxylic acids like ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA) are clinical approved decorporation agents against lanthanides (Ln) and actinides (An). This well known group of chelating agents shows promising results in complexation of Ln(III)/An(III). For EDTA and DTPA related compound ethylene glycol-bis(β-aminoethyl ether)-N,N,N’,N’-tetraacetic acid (EGTA), complexes with trivalent europium (Eu) have been characterized by NMR spectroscopy and x-ray diffraction. In these complexes, EGTA acts as an octadentate ligand.[1][2] In this work the knowledge on the Eu-EGTA-system is extended by time-resolved laser-induced fluorescence spectroscopy (TRLFS), electrospray ionization mass spectrometry (ESI-MS) and isothermal titration calorimetry (ITC). These speciation studies on Eu(III) show promising results for EGTA as complexing agent.
To expand this ligand group, EGTA related ligands are synthesized. With these compounds, the complexation behaviour towards Eu(III) and curium(III) are determined and comprehensively characterised from both the ligands and metals perspective with TRLFS, NMR spectroscopy, single crystal x-ray diffraction and fourier-transform infrared spectroscopy. The overall goal is a better understanding between ligand design and affinity to trivalent lanthanides and actinides. Hence, in the future these ligands may contribute to chelation therapy as decorporation agents.
This work is funded by the German Federal Ministry of Education and Research (BMBF) under grant number 02NUK057A and part of the joint project RADEKOR.

[1]. S. Aime, A. Barge, A. Borel, M. Botta, S. Chemerisov, A. E. Merbach, U. Müller, D. Pubanz, Inorg. Chem. 1997, 36, 5104.
[2]. R. Xu, D. Li, J. Wang, Y. X. Kong, B. X. Wang, Y. M. Kong, T. T. Fan, B. Liu, Russ. J. Coord. Chem. 2010, 36, 810.

  • Poster
    Actinides revisited 2022, 21.-23.09.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34882
Publ.-Id: 34882


Assessment of gene expressions from squamous cell carcinoma of the head and neck to predict radiochemotherapy-related xerostomia and dysphagia

Yahya, N.; Linge, A.; Leger, K.; Maile, T.; Kemper, M.; Haim, D.; Jöhrens, K.; Troost, E. G. C.; Krause, M.; Löck, S.

Purpose: We tested the hypothesis that gene expressions from biopsies of locally advanced head and neck squamous cell carcinoma (HNSCC) patients can supplement dose-volume parameters to predict dysphagia and xerostomia following primary radiochemotherapy (RCTx).
Material and methods: A panel of 178 genes previously related to radiochemosensitivity of HNSCC was considered for nanoString analysis based on tumour biopsies of 90 patients with locally advanced HNSCC treated by primary RCTx. Dose-volume parameters were extracted from the parotid, subman-
dibular glands, oral cavity, larynx, buccal mucosa, and lips. Normal tissue complication probability (NTCP) models were developed for acute, late, and for the improvement of xerostomia grade ≥2 and dysphagia grade ≥3 using a cross-validation-based least absolute shrinkage and selection operator (LASSO) approach combined with stepwise logistic regression for feature selection. The final signatures were included in a logistic regression model with optimism correction. Performance was assessed by the area under the receiver operating characteristic curve (AUC).
Results: NTCP models for acute and late xerostomia and the improvement of dysphagia resulted in optimism-corrected AUC values of 0.84, 0.76, and 0.70, respectively. The minimum dose to the contra-lateral parotid was selected for both acute and late xerostomia and the minimum dose to the larynx was selected for dysphagia improvement. For the xerostomia endpoints, the following gene expressions were selected: RPA2 (cellular response to DNA damage), TCF3 (salivary gland cells development), GBE1 (glycogen storage and regulation), and MAPK3 (regulation of cellular processes). No gene expression features were selected for the prediction of dysphagia.
Conclusion: This hypothesis-generating study showed the potential of improving NTCP models using gene expression data for HNSCC patients. The presented models require independent validation before potential application in clinical practice.

Keywords: gene expressions; head and neck cancer; xerostomia; dysphagia; radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-34881
Publ.-Id: 34881


Data publication: Tailoring pulsed laser deposition fabricated copper oxide film by controlling plasma parameters

Irimiciuc, S. A.; Chertopalov, S.; Volfová, L.; Hruska, P.; Cizek, J.; Vondracek, M.; Novotny, M.; Butterling, M.; Liedke, M. O.; Wagner, A.

Positron annihilation lifetime spectroscopy data from beamtime at ELBE

Keywords: pulsed laser deposition; copper oxide; defects; in situ plasma monitoring

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Permalink: https://www.hzdr.de/publications/Publ-34880
Publ.-Id: 34880


Tailoring pulsed laser deposition fabricated copper oxide film by controlling plasma parameters

Volfová, L.; Irimiciuc, S. A.; Chertopalov, S.; Hruska, P.; Cizek, J.; Vondracek, M.; Novotny, M.; Butterling, M.; Liedke, M. O.; Wagner, A.; Lancok, J.

Various copper oxide stoichiometries have been grown by Pulsed Laser Deposition (PLD) on MgO (100). The role of oxygen pressure on the structural and physical properties of the films was investigated in the 1·10 –5 Pa – 1 Pa range. Positron annihilation spectroscopy revealed positrons trapped at vacancies and large vacancy clusters with lifetimes ranging from 400 ps to 500 ps. Different stoichiometries were found to be dominated by characteristic vacancies. Single copper vacancies V Cu are found for CuO phase with good indication for p-type applications while for the Cu 2 O complexes of copper vacancies coupled with oxygen vacancies (V Cu + V O and V Cu + 2V O ) are seen. Particular O 2 atmosphere conditions induce a mixture of copper oxide phases with the CuO crystals growing on top of Cu 2 O films. The deposition process was monitored with in situ diagnostic techniques based on optical emission spectroscopy and Langmuir probe method. The kinetics of the plasma during the deposition process are well correlated with the properties of the deposited films.
The monitoring tools define clear energetic threshold for the formation of CuO or Cu 2 O phases.

Keywords: pulsed laser deposition; copper oxide; defects; in situ plasma monitoring

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Permalink: https://www.hzdr.de/publications/Publ-34879
Publ.-Id: 34879


Characterization of the binding behavior of specific cobalt- and nickel ion-binding peptides identified by phage surface display

Matys, S.; Morawietz, L.-M.; Lederer, F.; Pollmann, K.

In recent years, the application focus of phage surface display (PSD) technology has been extended to the identification of metal ion-selective peptides. In previous studies, two phage clones - a nickel-binding one with the peptide motif CNAKHHPRCGGG and a co-balt-binding one with the peptide motif CTQMLGQLCGGG - were isolated and their binding ability to metal-loaded NTA agarose beads was investigated. Here, the free cyclic peptides are characterized by UV/VIS spectroscopy and with respect to their binding capacity for the respective target ion as well as in crossover experiments for the other ion by isothermal titration calorimetry (ITC) in different buffer systems. This revealed differences in selectivity and affinity. While the cobalt-specific peptide is very sensitive to different buffers, but has a 20-fold higher affinity for cobalt and nickel under suitable conditions, the nickel-specific peptide binds more moderately and robustly in different buffers, but selectively only nickel.

Keywords: phage surface display; biopanning; metal binding peptides; nickel; cobalt; isothermal titration calorimetry

Permalink: https://www.hzdr.de/publications/Publ-34878
Publ.-Id: 34878


Visualisation of torsional modes with contactless inductive flow tomography

Molenaar, P.; Wondrak, T.; Jacobs, R. T.; Sonntag, S.; Krauthäuser, H. G.

The contactless inductive flow tomography is a procedure that enables the reconstruction of the global three-dimensional flow structure of an electrically conducting fluid by measuring the flow-induced perturbation of an applied static magnetic field and by subsequently solving the associated linear inverse problem. The method enables the visualisation of the dynamics of a large-scale circulation in the modified Rayleigh-Bénard experiment.

Keywords: flow measurement; ontactless inductive flow tomography

  • Lecture (Conference)
    20th International IGTE Symposium 2022 on Computational Methods in Electromagnetics and Multiphysics, 18.-21.09.2023, Graz, Österreich

Permalink: https://www.hzdr.de/publications/Publ-34877
Publ.-Id: 34877


Postoperative radiochemotherapy improves loco-regional control in a subset of patients with intermediate-risk head and neck squamous cell carcinoma (HNSCC): a matched pair analysis

Patil, S. G.; Linge, A.; Hiepe, H.; Grosser, M.; Lohaus, F.; Gudziol, V.; Kemper, M.; Nowak, A.; Haim, D.; Tinhofer, I.; Budach, V.; Guberina, M.; Stuschke, M.; Balermpas, P.; von der Grün, J.; Schäfer, H.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Combs, S. E.; Boeke, S.; Zips, D.; Jöhrens, K.; Baretton, G. B.; Baumann, M.; Krause, M.; Löck, S.

Abstract: (1) Background: Patients with locally advanced head and neck squamous cell carcinoma (HNSCC) who are at biologically high risk for the development of loco-regional recurrences af-ter postoperative radiotherapy (PORT) but at intermediate risk according to clinical risk factors may benefit from additional concurrent chemotherapy. In this matched-pair study, we aimed to identify a corresponding predictive gene signature. (2) Methods: Gene expression analysis was performed on a multicentre retrospective cohort of 221 patients that were treated with postoper-ative radiochemotherapy (PORT-C) and 283 patients that were treated with PORT alone. Propen-sity score analysis was used to identify matched patient pairs from both cohorts. From differen-tial gene expression analysis and Cox regression, a predictive gene signature was identified. (3) Results: 108 patient matched patient pairs were selected. We identified a 2-metagene signature that stratified patients into risk groups in both cohorts. The comparison of the high-risk patients between the two types of treatment showed higher LRC after treatment with PORT-C (p<0.001), which was confirmed by a significant interaction term in Cox regression (p=0.027), i.e. the 2-metagene signature was indicative for the type of treatment. (4) Conclusion: We have identi-fied a novel gene signature that may be helpful to identify patients with high-risk HNSCC amongst those at intermediate clinical risk treated with PORT, who may benefit from additional concurrent chemotherapy.

Keywords: head and neck squamous cell carcinoma; gene signature; postoperative radiotherapy; postoperative radiochemotherapy; propensity score matching

  • Open Access Logo Cancers (2022)

Permalink: https://www.hzdr.de/publications/Publ-34875
Publ.-Id: 34875


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