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33407 Publications

Thermo-physical properties of coatings in the Ti(B,N) system grown by chemical vapor deposition

Kainz, C.; Schalk, N.; Tkadletz, M.; Saringer, C.; Winkler, M.; Stark, A.; Schell, N.; Julin, J.ORC; Czettl, C.
Hard protective coatings are commonly subjected to temperatures exceeding 1000 °C, which has significant influence on their thermo-physical properties and the associated performance in application. Within the present work, temperature dependent physical properties of coatings within the Ti(B,N) system grown by chemical vapor deposition were correlated with their chemical composition. High-energy X-ray diffraction experiments in inert atmosphere proved that TiN, TiB₂ and ternary TiBxNy coatings with varying B contents are thermally stable up to 1000 °C. First order lattice strains of TiN and TiBxNy coatings diminish during heating, whereas TiB₂ exhibits compressive strain enhancement up to the deposition temperature. Nanocrystalline TiB₂ exhibits more pronounced grain growth during annealing compared to coarse grained columnar TiN. Within the investigated coatings, the mean thermal expansion coefficient decreases as the B content increases. The same trend was observed for the thermal conductivity, which correlates with the grain size of the coatings.
Keywords: Chemical vapor deposition; X-ray diffraction; Ti(B,N); thermal conductivity; strain

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Permalink: https://www.hzdr.de/publications/Publ-29858
Publ.-Id: 29858


Produktion und Reinigung von n.c.a. 48V am Leipziger Zyklotron für Extraktionsstudien

Mansel, A.; Franke, K.
Vanadium ist ein Bestandteil in Eisen-Chromschlacken und gilt als strategisches Wertmetall. Um effiziente Abtrennungsverfahren von fünfwertigem Vanadium vom dreiwertigen Chrom bzw. sechswertigem Chromat mit Hilfe der Ionenchromatographie zu entwickeln, wurde die Radiotracertechnik eingesetzt [48V; T1/2 = 15,97 d; E = 984 keV; 99,97 %]. Die Produktion dieses Radionuklides wurde am Leipziger Zyklotron CYCLONE 18/9® durch die Kernreaktion natTi(p,n)48V realisiert. Eine Titanfolie (natürliche Isotopenzusammensetzung; 140 mg) wurde mit Protonen der Energie 12 MeV bei einem Strom von 22 µA für zwei Stunden bestrahlt. Das bestrahlte Target wurde für einen Tag zum Abklingen des kurzlebigen Radionuklides 47V (T1/2 = 32,6 min) aufbewahrt und anschließend in konzentrierter Schwefelsäure und wenigen Tropfen Flußsäure in einem Teflonbecher aufgelöst. Nach dem Eindampfen wurde der Rückstand mit 3 g Natriumcarbonat / 80 mg Natriumnitrat in einem Platintiegel für 30 Minuten bei 800 °C aufgeschlossen. Durch mehrmaliges Anlösen mit Wasser wurde das 48V in Form von Natriumvanadat vom Targetmaterial Titandioxid herausgelöst. Spuren von Titan wurden mit Hilfe eines Kationenaustauschers (DOWEX 50 W X-8) bei pH 3 abgetrennt und das Vanadylion in Form von Vanadat mit 20 %igem Ammoniak eluiert. Die radiochemische Ausbeute betrug (95 ± 8) %. Die Aktivität betrug fünf Stunden nach Bestrahlungsende ~ 245 MBq und die Nachweisgrenze wurde zu 8 fM (~0,4 pg/L) für n.c.a. 48V ermittelt.
  • Poster
    GDCh Jahrestagung der Fachgruppe Nuklearchemie, 24.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29857
Publ.-Id: 29857


Coupled processes across a claystone-concrete interface: results of a combined X-ray CT and PET transport experiment

Mäder, U.; Bernard, E.; Kulenkampff, J.; Jenni, A.
Interfaces between dense clay materials and cementitious materials are studied in the context of deep disposal of radioactive waste for one main reason: mineral reactions due to contrasting chemistries will modify the pore network and affect transport of water, solutes and gas. Substantial research efforts were directed towards mineralogical and physical characterisation of interface regions (e.g. Mäder et al. 2018) but little evidence exists on direct observations of transport behaviour across such skins. This study aims at providing evidence on how mineralogical-physical changes at such an interface affect transport of water and solutes, and linking mineralogical-physical characterisation, X-ray computed tomography and positron emission tomography (PET).

We developed an X-ray transparent core infiltration apparatus whereby a sample core subject to a hydraulic confining pressure can be tested with a hydraulic gradient (Mäder, 2018, for details of method and design in steel and titanium). This compact apparatus uses a carbon fibre tube as pressure vessel and various polymer plastics for other components. Several small pressure tanks integrated into the apparatus allow for self-contained operation for several days, and switching of the percolating fluid. A further extension in form of an integrated lead-shielded pressure container allows also for using radioactive tracers such that the equipment can be used for positron-emission tomography (PET). PET is a superb method to directly image the mobile phase in 3D, and its time evolution (Kuhlenkampff et al., 2017).

A 14 year-old sample core was recovered by stabilized drilling from a long term in situ experiment (CI) at the Mont Terri rock laboratory (Mäder et al., 2018), containing a physically preserved interface between Opalinus Clay and OPC concrete. This larger sample (101 mm DM) was sub-sampled and a 50x50 mm core was stabilised and cored from it. The clay part shows pre-existing bedding-parallel weak jointing that can also be seen in high resolution X-ray CT. The aged interface shows mineral transformations at the mm scale with complex mineral alteration patterns in both clay and cement matrix at a sub-mm scale, including porosity re-distribution and net reduction. The OPC concrete contains aggregate and gas pores. The compound sample may represent a repository situation of a claystone somewhat disturbed by excavation, in contact with a concrete liner, with pore water transport from clay across concrete.

A long-term transport experiment was set up by injecting a synthetic claystone pore water into the core sample on the clay-side, and force advection/diffusion across the interface and out of the cement-side. The fluid is traced with deuterium as water tracer, and periodically sampled for chemical and isotopic analysis. The sample was monitored frequently by high resolution X-ray CT during the first few days, and then regularly for the first 4 months. The running experiment was then transported to Leipzig and prepared for PET. 124I was used as PET tracer, and the chosen dose allowed for continuous PET scanning during two weeks, initially every 3 hrs.

A very large data set of 2D interface characterisation (SEM/EDX mapping, etc.) and time-resolved 3D CT and PET is presently being evaluated, enhanced, imaged and interpreted. Preliminary results document an initial self-sealing effect of the joint system in the Opalinus Clay, permeation into the diffusion-controlled pore network in claystone and cement matrix, and partial filling of gas pores. PET captures some preferential flow across claystone along some remaining joints, a spreading of the tracer plume at the clay/cement interface, and some moderate preferential flow across OPC.

This approach provides much more detailed information of coupled processes in complex porous media by imaging both the stationary and the mobile phase. Compared to summation parameters, such as tracer breakthrough, there is infinitely more information obtained about the localisation of flow and the nature of the pore network and its temporal evolution.

The research leading to these results has also received funding from the European Union's European Atomic Energy Community's (Euratom) Horizon 2020 Programme (NFRP-2014/2015) under grant agreement, 662147 – Cebama. Uni Bern acknowledges funding contributions by Nagra and the Mont Terri Consortium (CI Experiment).



Kulenkampff, J., Gründig, M., Zakhnini, A., Lippmann-Pipke, J. (2016). Geoscientific process monitoring with positron emission tomography (GeoPET). Solid Earth 7, 1207-2015.
U. Mäder (2018). Advective Displacement Method for the Characterisation of Pore Water Chemistry and Transport Properties in Claystone, Geofluids, 2018.
U. Mäder, A. Jenni, C. Lerouge, S. Gaboreau, S. Miyoshi, Y. Kimura, V. Cloet, M. Fukaya, F. Claret, T. Otake, M. Shibata, B. Lothenbach (2017). 5-year chemico-physical evolution of concrete-claystone interfaces, Swiss Journal of Geosciences, 110, 307-327.
Keywords: radioactive waste disposal clay-cement interface transport experiments positron emission tomography x-rax computed tomography
  • Open Access Logo Lecture (Conference)
    Decovalex 2019, 04.-05.11.2019, Brugg, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-29855
Publ.-Id: 29855


Lichtinduzierte Freisetzung von Kohlenstoffmonoxid aus Ruthenium(II)-Komplexen und deren biologische Bewertung

Geri, S.
Der Schwerpunkt der vorliegenden Masterarbeit liegt auf der Synthese neuer Ru(II)-basierter PhotoCORMs der Summenformel [RuL(CO)2Cl2] (L = Ligand). Als Liganden sollen 4,4‘-substituierte Derivate des 2,2‘-Bipyridins verwendet werden. 2,2‘-Bipyridine sind zweizähnige Lewis-Basen mit σ-Donor-Charakter, die mit Ruthenium in der Oxidationsstufe II stabile Chelatkomplexe bilden. Geeignete Funktionalisierung und strukturelle Erweiterung an den 4,4‘-Positionen des 2,2‘-Bipyridins soll den entstehenden PhotoCORMs neue Eigenschaften verleihen.
Der Schwerpunkt dieser Masterarbeit wird zunächst auf die Synthese eines Alkin-funktionalisierten PhotoCORMs gelegt. Alkin-Gruppen stellen eine Basis für die Bindung eines Azid-funktionalisierten Peptides mittels kupferkatalysierter Azid-Alkin 1,3-dipolarer Cycloaddition (CuAAC, „Click-Reaktion“) dar. Peptide geeigneten Designs können eine erhöhte Spezifität gegenüber bestimmtem Zelltyp induzieren, sodass das Peptid-funktionalisierte PhotoCORM bevorzugt in diesen Zellen angereichert wird.
Auch im zweiten Teil dieser Masterarbeit steht die Synthese eines Alkin-funktionalisierten PhotoCORMs im Vordergrund, allerdings soll hierbei der Fokus auf dessen Weiterfunktionalisierung mit einem Fluoreszenzfarbstoff gelegt werden. Durch direkte Substitution eines Fluoreszenzfarbstoffes am Grundgerüst des Bipyridins soll eine Erweiterung des bestehenden π-Systems erzielt werden. Als Folge werden eine bathochrome Verschiebung der MLCT-Bande, größere Quantenausbeuten sowie starke Fluoreszenz des neu synthetisierten PhotoCORMs erwartet. Letztere soll eine einfache visuelle Verfolgung der zellulären Aufnahme des in vitro verabreichten PhotoCORMs ermöglichen. Alternativ zu dieser Herangehensweise soll ein PhotoCORM synthetisiert werden, bei dem der Fluoreszenzfarbstoff mit dem Bipyridin-Grundgerüst über einen Amid-Linker verbunden ist.
Keywords: CO, Ru(II)-Komplexe, Therapie
  • Master thesis
    TU Dresden, 2019
    Mentor: Dr. Manja Kubeil / Dr. habil. Constantin Mamat
    108 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-29852
Publ.-Id: 29852


Neuartige Calix[4]benzokronen zur Komplexierung von schweren Erdalkalimetallionen

Blumberg, M.
Der Fokus dieser Arbeit liegt auf der Synthese neuer Chelatoren für die Komplexierung der schweren Erdalkalimetallionen Sr2+, Ba2+ und Ra2+. Ein besonderes Augenmerk liegt hierbei auf den für die Krebstherapie interessanten Radiumisotopen 223Ra und 224Ra und dem SPECT-Nuklid 131Ba als Matched Pair. Strontium besitzt mit 89Sr ebenfalls ein in der Nuklearmedizin nutzbares Nuklid. Außerdem kann auf Grundlage der Untersuchung der drei Erdalkalimetalle der Einfluss des Ionenradius auf die Komplexierungseigenschaften der Chelatoren bewertet werden. Zudem soll auch die Komplexierung mit dem ebenfalls zweiwertigen Pb2+ untersucht werden. Der β--Strahler 212Pb wird in der Radiopharmazie als in vivo-Generator des kurzlebigen α-Strahlers 212Bi in der Immuntherapie genutzt. 212Pb kommt wie 224Ra in der natürlichen Zerfallsreihe des 232Th vor.
Für die Komplexierung der genannten Metallionen sollen neuartige Calix[4]kronen synthetisiert werden, die nach dem Vorbild von Zhou et al. mit sauren Sulfonamidseitenketten funktionalisiert sind. Vorherige Extraktionsexperimente unserer Arbeitsgruppe haben gezeigt, dass Derivate mit perfluorierten Isopropylresten am Sulfonamid die effektivste Extraktion von Ba2+ und Ra2+ erlauben. Daher sollen Derivate mit diesen Seitenketten synthetisiert werden.
In dieser Arbeit soll die Modifizierung der Kronenetherüberbrückung der Calixarenderivate untersucht werden. Dafür soll ein aromatisches System in Form einer Benzokrone in den Chelator eingebaut werden. Eine solche Benzokrone bietet gegenüber der Krone-6 den Vorteil, dass sie mit zusätzlichen funktionellen Gruppen ausgestattet werden kann, um daran biologisch aktive Vektormoleküle zu binden. Die Einführung einer Amin-, Azid- oder Säurefunktion ermöglicht eine Kupplung an Peptide, Proteine oder Antikörper.
Keywords: Calixarene, Barium, Radium, Alpha-Therapie
  • Master thesis
    TU Dresden, 2019
    Mentor: Dr. habil. Constantin Mamat
    135 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-29851
Publ.-Id: 29851


Neuartige Käfigverbindungen zur Komplexierung von Barium und Radium

Eiselt, E.
Calixarene sind eine Gruppe von Verbindungen, welche eine vielseitige Nutzung zur Komplexierung von Ionen und kleinen Molekülen ermöglichen. Unter anderem können sie, durch die Einführung von Donorgruppen als Chelatoren für Gruppe-2-Metalle eingesetzt werden. Für eine zielgerichtete interne α-Therapie mit den therapeutisch zugänglichen Radiumisotopen 223Ra und 224Ra, ist es von Nöten, diese ausreichend stabil zu komplexieren. Damit soll eine unerwünschte Freisetzung und Anreicherung an anderen Orten im Körper weitgehend unterbunden werden.
Im Rahmen dieser Arbeit sollen Chelatoren entwickelt werden, welche Ba2+ als Surrogat für Ra2+ stabil und selektiv binden und eine weitere Funktionalisierung mit biologisch aktiven, zielsuchenden Molekülen zulassen. Auf Basis, der von Steinberg et al. veröffentlichten Ergebnisse sollen Verbindungen synthetisiert werden, welche statt einer Krone-6-Überbrückung offenkettige Etherfunktionen als Strukturmerkmal aufweisen. Dabei sollen sowohl Derivate mit zyklischen Amidfunktionen, als auch mit verschiedenen fluorierten Sulfonamiden funktionalisierte Verbindungen hergestellt werden. Weiterhin sollen Vorstufen für Liganden synthetisiert werden, welche über eine kurze Seitenkette mit zyklischen tertiären Aminen verfügen.
Alle Liganden sowie deren Vorstufen sollen mittels NMR-Spektroskopie und Massenspektrometrie eingehend charakterisiert werden. Die fertiggestellten Chelatoren werden mit der Methode der UV-Vis-Titration hinsichtlich ihrer Komplexbildungseigenschaften mit Ba2+, Sr2+ und Pb2+ untersucht. Die ermittelten Komplexstabilitäten sollen mit den analogen Krone-6-überbrückten Derivaten verglichen werden.
Keywords: Calixarene, Barium, Radium, Alpha-Therapie
  • Master thesis
    HTW Dresden, 2019
    Mentor: Dr. habil. Constantin Mamat (HZDR) / Prof. Dr. Marina Vogel (HTW)
    94 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-29850
Publ.-Id: 29850


Combining trace element measurements with analytical uncertainties for a better characterization of plant geochemistry

Pospiech, S.; van den Boogaart, K. G.ORC; Tolosana Delgado, R.; Wiebke, F.
Trace element analysis in plants is often subject to a high measurement uncertainty and accordingly the variability of the geochemical composition of trace elements in plants is – especially close to the detection limit - very high. In this contribution we propose a method to estimate models respecting the uncertainty and capable of treating values below and around the detection limit. We suggest to use all measurement signals, but report it alongside with the individual uncertainties for each value. The standard descriptive and statistical analysis mainly ignores these uncertainties by simply reporting if a signal value is below the detection limit (BDL) or above. BDL-values are either ignored or replaced by an arbitrary small value. In both cases this can substantially distort the analysis. Our methodology could substantially reduce this bias.
In order to take into account the constraints of concentration data we use methods of compositional data analysis, i.e. represent population by their compositional expectation, typically represented in an log-ratio transform. The uncertainties are incorporated in statistical methods by estimating the reported value not by a simple mean, but by an estimation procedure using the model assumption that a signal observed in the geochemical analysis has two components of variability: i) A population spread that could e.g. be modeled by a compositional distribution, and ii) a signal variability to be modeled according to the measurement instrument, typically assuming additive normal or Poisson errors and calibration errors. The parameters for the model of the signal variability are estimated from blind values, duplicate analysis as well as precision and accuracy of repeatedly measured reference samples.
We will present the change of results produced by the methodology over a standard approach with reporting BDL-values by demonstrating the applicability of the methodology with simulated data and a dataset of rye, ryegrass, faba bean, triticale and amaranth from two agricultural test sites in Germany. All samples had been treated by a four-acid digestion and analyzed by ICP-MS and ICP-OES.
Keywords: plant geochemistry, compositional data, uncertainty, analytics, ICP-MS, ICP-OES, Bayesian statistics
  • Open Access Logo Poster
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29847
Publ.-Id: 29847


Microresonator-integrated magnetic tunnel junctions allowing for thermal gradient sign reversal designed using COMSOL simulations

Cansever, H.; Lindner, J.; Huebner, T.; Niesen, A.; Reiss, G.; Fassbender, J.; Deac, A. M.
In magnetic tunnel junctions (MTJs), it was theoretically predicted that magnetization dynamics can be induced by thermal gradients via thermal-spin transfer torques (T-STTs), similar to STTs induced by applied voltages[1]. We recently proposed an approach based on microresonators (µR) in order to detect T-STT terms acting on the free layer of an MTJ device by means of investigating the ferromagnetic response of an MTJ exposed to a cw laser in open-circuit conditions. The linewidth of the ferromagnetic signal is modified by the damping-like torque induced by thermal gradient, while the frequency is subject to changes induced by the field-like torque[2]. Here, we used COMSOL simulations to determine the temperature profile of Co2FeAl/MgO/CoFeB MTJs, when the MR structure is considered, see Fig 1. In this design, the structure is defined with laterally larger Co2FeAl (CFA) layer below CoFeB (CFB) layer. This allows for the laser beam to be focused on the CFA layer surface, in order to heat the bottom electrode of the MTJ rather than the top, as commonly investigated[3-6]. The temperature of both layers and temperature differences (ΔT) as a function of lateral width are shown in Fig 2. The temperature on the CFA layer decreases laterally about 25K towards to center of the structure and yields a ΔT over the barrier of about 680mK, if a gold pad is placed on the CFA layer, in the position where the laser is shined on (Fig 2). Without the gold pad and leaving the MgO on the CFA unpatterned, the ΔT over the barrier is reduced almost by factor of 2, and is estimated to be around 320mK and 270mK respectively. When both layers have gold contacts, ΔT drops to 20mK (Fig 2). Consequently, the magnitude and the sign of ΔT over the barrier can be engineered by appropriately designing the design of the device, which would allow for T-STTs induced by thermal gradients of different sign to be investigated experimentally in a single MTJ.

*Figure 1 2D sketch of an MTJ structure considered for COMSOL modelling, where the loop of µR was taken into account and only the bottom layer is exposed to the laser.

*Figure 2 Temperature profile of the MTJ versus lateral size, ΔT dependence on designed structure.
References
[1] Jia X, Xia K and Bauer G E W 2011 Phys. Rev. Lett.107 176603
[2] H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac, 2018 J. Phys. D: Appl. Phys. 51 22400
[3] N. Liebing, S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker, H. W. Schumacher, 2011, Phys. Rev. Lett. 107, 177201.
[4] J. C. Leutenantsmeyer, M. Walter, V. Zbarsky, M. Münzenberg, R. Gareev, K. Rott, A. Thomas, G. Reiss, P. Peretzki, H. Schuhmann, M. Seibt, M. Czerner, C. Heiliger, 2013, Spin 3, 1350002.
[5] A. Boehnke, M. Milnikel, M. Ehe, C. Franz, V. Zbarsky, M. Czerner, K. Rott, A. Thomas, C. Heiliger, G. Reiss, M. Münzenberg, 2015, Sci. Rep. 5, 8945.
[6] H. Cansever, J. Lindner, T. Huebner, A. Niesen, G. Reiss, J. Fassbender, A. M. Deac, 2019, IEEE Trans.Magn. 51(17) Early Access
Keywords: COMSOL, thermal spin-transfer torque, magnetic tunnel junction, microresonator
  • Lecture (Conference)
    Annual Conference on Magnetism and Magnetic Materials, MMM Las Vegas 2019, 04.-08.11.2019, Las Vegas, USA

Permalink: https://www.hzdr.de/publications/Publ-29846
Publ.-Id: 29846


Spectral Random Masking für PIV in Mehrphasenströmung

Anders, S.ORC; Noto, D.ORC; Eckert, S.ORC
Im vorliegenden Beitrag wird eine neuartige Maskierungsmethode für die Particle Image Velocimetry (PIV) von Mehrphasenströmungen vorgestellt. Mit diesem neuen Ansatz können Geschwindigkeitsfelder einer unmaskierten Partikelfraktion (z. B. PIV-Tracer) unabhängig von der Bewegung einer zweiten, maskierten Partikel-Fraktion (z. B. Blasen oder Feststoffpartikel) bestimmt werden.
Ausgehend von einer segmentierten Bilderserie in welcher die verschiedenen Partikelfraktionen für alle Einzelbilder detektiert wurden, werden verschiedene Maskierungsverfahren diskutiert. Hierbei werden die Probleme, welche durch Standardverfahren für den Fall dynamischer Maskierung unter realen Belichtungsbedingungen entstehen besonders hervorgehoben. Als entsprechende Lösung stellen wir unseren Ansatz des Spectral Random Masking (vgl. Anders et al. 2019) vor, bei welchem maskierte Bildbereiche durch spektral angepasste, zufällige Intensitätsverteilungen ersetzt werden. Damit sollen die maskierten Bereiche für eine anschließende PIV-Analyse “unsichtbar” gemacht werden. Die Vorteile dieser Methode gegenüber konventionellen Maskierungsverfahren werden anhand eines Modellexperimentes dargestellt, bei welchem wässrige Ammonium-Chlorid Lösungen (NH₄Cl(aq)) durch Unterkühlung erstarrt werden. Dabei treten unter anderem verschiedene Konvektionsströmungen zeitgleich mit kolumnarer und äquiaxialer Kristallisation von NH₄Cl auf.
Keywords: Bild Segmentierung, dynamische Bildmaskierung, Mehrphasenströmung, Particle Image Velocimetry
  • Open Access Logo Contribution to proceedings
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland
    Spectral Random Masking für PIV in Mehrphasenströmung, 978-3-9816764-6-4, 20.1-20.7
  • Lecture (Conference)
    Experimentelle Strömungsmechanik, 27. Fachtagung, 03.-05.09.2019, Erlangen, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-29844
Publ.-Id: 29844


Comparative Study of Monosalen Complexes with Tetravalent Actinides

Radoske, T.ORC
Two series of tetravalent actinide complexes with the salen ligand were synthesized. The coordination sphere supports two labile positions for small neutral solvent molecules, which were filled with either methanol or acetonitrile molecules. Solid state characterization reveals additional interactions of U(IV) and Np(IV) with the organic ligands.
  • Poster
    Migration 2019, 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29842
Publ.-Id: 29842


Tetravalent Actinide N-Donor Affinity in Monosalen Complexes

Radoske, T.ORC
Complexes with a range of differently substituted pyridines were synthesized using tetravalent actinides. The affinity of actinides for N-donors is discussed.
  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29841
Publ.-Id: 29841


Tetravalent Actinide Complexes with Schiff bases: Comparison with Isostructural Transition Metal and 4f Element Compounds

Radoske, T.ORC
Isostructural complex series with tetravalent actinides were characterized and results are discussed for observable trends.
  • Lecture (others)
    FENABIUM Projekttreffen, 27.02.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29840
Publ.-Id: 29840


Amidinates as Versatile Ligands for Tetravalent Actinides

Schöne, S.ORC; März, J.ORC; Kaden, P.ORC
A summary of work based on the synthesis and characterization of tetravalent actinide amidinates is given. Structural features are compared in solid and in solution phase. Comprehensive quantum chemical calculations support the findings.
  • Lecture (others)
    FENABIUM Projekttreffen, 28.06.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29839
Publ.-Id: 29839


Relative Stability of Actinide(IV) Bissalen Complexes

Radoske, T.ORC; Schöne, S.ORC; Kloditz, R.; März, J.ORC; Stumpf, T.; Ikeda-Ohno, A.ORC
Schiff bases of salen-type have a wide range of applications and have proven to be a versatile ligand system for the investigation of complexation behavior. In particular, due to its hetero N/O-donor coordination properties, the salen ligands are often considered as a simplified analog of naturally-occuring organic ligands, which have potential implications for the migration behavior of radionuclides under geochemical conditions We have investigated the complexation behavior of salen ligands (L, H2salen = N,N’-bis(salicyliden)ethylenediamine) towards tetravalent metal cations and synthesized a series of complexes of tetravalent actinides (Th, U, Np, and Pu) as well as analogous tetravalent metals (Zr, Ce, and Hf). In all cases, the ligand forms bissalen ML2 complexes (M = metal). When the ML2 compound is treated with an equimolar amount of the metal tetrachloride, some metals also form M:L = 1:1 complexes with additional two Cl- in the primary coordination shell to form MLCl2. Based on this observation, we assume a trilateral equilibrium between the starting materials of metal tetrachlorides, the 1:1, and the 1:2 complex (Scheme 1), being similar to the study by Calderazzo et al.[1] This equilibrium holds even if ML2 is insoluble in the reaction medium and, therefore, we can apply the exchange reactions to determine the relative stability of the An(IV)-bissalen complexes when more than one types of metal are used. The relative stability of the complexes can then be directly compared to the results from quantum chemical calculations based on DFT. Hence, this study aims to understand the reaction mechanism and stability of salen complexes with a series of tetravalent metals, in particular tetravalent actinides (An(IV)).
  • Lecture (Conference)
    Fachtagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29838
Publ.-Id: 29838


Tetravalent Actinide and Transition Metal Amidinates – Trends and Perspectives

Schöne, S.ORC
A series of tetravalent actinide amidinates with chiral (S)-HPEBA ligands is presented. The complexes are structurally characterized in solid state and in solution. Further reactivity is proved by reduction to trivalent homoleptic complexes.
  • Lecture (others)
    Challenges in f-element chemistry - Bilaterales Meeting HZDR/KIT, 10.01.2019, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29837
Publ.-Id: 29837


Amidinates – Versatile Ligands for Tetravalent Actinides

Schöne, S.ORC; Kloditz, R.ORC; März, J.ORC; Kaden, P.ORC; Patzschke, M.ORC; Roesky, P. W.; Stumpf, T.
Amidinates, a group of heteroallylic nitrogen donor ligands of type [RC(NR‘)2]–, have been used in a widespread manner in coordination chemistry and organometallics. They usually coordinate in a N,N’-bidendate mode to almost all metals in the periodic table including lanthanides and early actinides. The steric and electronic properties can be easily tuned by varying the substituents R and R’ to make them a valuable class of spectator ligands.
We have expanded the rich chemistry of amidinates to the tetravalent transuranic elements Np and Pu and compared the results to the earlier actinides Th and U and other tetravalent analogues. The focus of our investigations lies in the comprehensive characterization of An(IV) complexes with amidinates, both in the solid state and in solution. A comparison within the series enables us to perform a detailed structural analysis, which is complemented by high-level quantum chemical calculations to gain deeper insight into the bonding properties of tetravalent actinides (An(IV)).
Several An(IV) amidinate complexes have been synthesized including a series of chiral complexes using the chiral benzamidine, (S,S)-N,N‘-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA) [1]. We obtained the first enantiopure amidinate complexes [AnIVCl((S)-PEBA)3] (An = Th, U, and Np) as well as the analogous Ce(IV) compound, a chemical analog of An(IV). The tris-amidinate complexes have been structurally characterized in solid state and in solution showing a comparable complex geometry.
The presence of one chloro ligand in addition to three stabilizing amidinate ligands in the An coordination sphere points to complex reactivity. This could indeed be demonstrated by reduction to homoleptic trivalent actinide amidinates [An((S)-PEBA)3] (An = U, Np) as well as halogen exchange with pseudo-halogenides (i.e. N3–).
  • Lecture (Conference)
    GdCh Fachgruppentagung Nuklearchemie, 25.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29836
Publ.-Id: 29836


La–Sr–Mn–Co–O Films for High Pulsed Magnetic Field Measurements at Cryogenic Temperatures

Rudokas, V.; Zurauskiene, N.; Lukose, R.; Kersulis, S.; Stankevic, V.; Pavilonis, D.; Balevicius, S.; Plausinaitiene, V.; Vagner, M.; Skapas, M.; Arsenijevic, S.
The magnetoresistance of nanostructured La1−xSrx(Mn1−yCoy)zO3±δ (La–Sr–Mn–Co–O) films with substitution of Co for Mn with amount of Co/(La + Sr) = 0.12 and different Mn excess Mn/(La + Sr) = 1.05, 1.07, nd 1.11 was investigated at temperatures of 4–230 K in pulsed magnetic fields up to 60 T. It was found that the manganite–cobaltite films exhibit larger magnetoresistance in comparison with manganite films without Co doping. The largest magnetoresistance values and sensitivity to the magnetic field are obtained for La–Sr–Mn–Co–O films having Mn Content close to the stoichiometric ratio for manganites: Mn/(La + Sr) = 1.05. It was found that magnetoresistance at high fields (20–60 T) has a minimum at (50–80 K) and increases with the decrease of temperature. The possibility to use these films for magnetic field measurements at cryogenic temperatures is demonstrated.

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Permalink: https://www.hzdr.de/publications/Publ-29835
Publ.-Id: 29835


Microorganisms for biological remediation of uranium contaminated sites – a microscopic and spectroscopic approach

Krawczyk-Bärsch, E.; Gerber, U.; Müller, K.; Rossberg, A.; Merroun, M. L.
Environmental pollution by metals and radionuclides is one of the biggest challenges. For remediation of contaminated environments after activities such as uranium mining and uranium processing, microorganisms could be important due to their ability to immobilize radionuclides and heavy metals. Bioremediation strategies can be improved by a better understanding of binding mechanisms on the molecular level. Therefore, we applied uranium interaction experiments with Acidovorax facilis, an aerobic, Gram-negative Betaproteobacteria, which is commonly found in soils but also in the mine water of uranium mines. For spectroscopic and microscopic studies, kinetic uranium(VI) sorption experiments were performed under aerobic conditions with an Acidovorax facilis strain by adjusting an initial uranium(VI) concentration to 0.1 mM to the batch culture at a neutral pH range. A high-resolution image of the cellular localization of uranium by A. facilis was achieved by using electron microscopy (STEM/HAADF). The elemental distribution analysis of phosphorus and uranium clearly indicates that uranium is entirely present in the cell membrane and only with minor amounts in the poly-phosphate granules (PPGs) during the first hour of incubation (s. Fig.1). By cryo-Time-resolved laser-induced fluorescence spectroscopy (cryo-TRLFS) studies it was shown that the local coordination of uranium species associated with the cells depends upon time contact. Uranium is bound mainly to phosphate groups of lipopolysaccharide [1] at the outer membrane within the first hour. And, that both, phosphoryl and carboxyl functionality groups of LPS and peptidoglycan of A. facilis cells may effectuate the removal of high uranium amounts from solution at 24–48 h of incubation. These results support those obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS), where a relative short average U-Oeq bond length of 2.35 Å was observed for the uranium(VI) interaction with lipopolysaccharide indicating a binding of the uranium(VI) via organic phosphate groups in a monodentate fashion. Our results clearly demonstrate that A. facilis may play an important role in predicting the transport behaviour of uranium in the environment and that the results will contribute to the improvement of bioremediation methods of uranium-contaminated sites.
Keywords: uranium, sorption, Acidovorax facilis, STEM, EXAFS
  • Lecture (Conference)
    3rd International Caparica Conference on Polutant Toxic Ions and Molecules, 04.-07.11.2019, Costa da Caparica, Portugal

Permalink: https://www.hzdr.de/publications/Publ-29833
Publ.-Id: 29833


Superconductivity of Organic Charge-Transfer Salts

Wosnitza, J.
Forty years after the discovery of the first organic superconductor, the nature of the superconducting state in these materials is still not fully understood. Here, I present an overview on the historical developments and current knowledge on this topic for the quasi-one- and quasi-two-dimensional (2D) organic charge-transfer salts. Thereby, I focus on the prototype materials based on the donor molecules tetramethyltetraselenafulvalene (TMTSF) and bisethylenedithio-tetrathiafulvalene (BEDT-TTF or ET for short). 2D organic superconductors based on the latter molecule are found to show Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states at high magnetic fields and low temperatures. Thermodynamic and nuclear magnetic resonance data give robust evidence for the existence of this FFLO state with modulated order parameter.

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  • Secondary publication expected from 05.09.2020

Permalink: https://www.hzdr.de/publications/Publ-29831
Publ.-Id: 29831


A numerical simulator for modeling the coupling processes of subsurface fluid flow and reactive transport processes in fractured carbonate rocks

Yuan, T.ORC; Wei, C.; Zhang, C.-S.; Qin, G.
Water–rock interactions can alter rock properties through chemical reactions during subsurface transport processes like geological CO2 sequestration (GCS), matrix acidizing, and waterflooding in carbonate formations. Dynamic changes in rock properties cause a failure of waterflooding and GCS and could also dramatically affect the efficiency of the acidizing. Efficient numerical simulations are thus essential to the optimized design of those subsurface processes. In this paper, we develop a three-dimensional (3D) numerical model for simulating the coupled processes of fluid flow and chemical reactions in fractured carbonate formations. In the proposed model, we employ the Stokes–Brinkman equation for momentum balance, which is a single-domain formulation for modeling fluid flow in fractured porous media. We then couple the Stokes–Brinkman equation with reactive-transport equations. The model can be formulated to describe linear as well as radial flow. We employ a decoupling procedure that sequentially solves the Stokes–Brinkman equation and the reactive transport equations. Numerical experiments show that the proposed method can model the coupled processes of fluid flow, solute transport, chemical reactions, and alterations of rock properties in both linear and radial flow scenarios. The rock heterogeneity and the mineral volume fractions are two important factors that significantly affect the structure of conductive channels.
Keywords: reactive-transport; fracture evolution; mineral dissolution; fractured carbonate formations

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Permalink: https://www.hzdr.de/publications/Publ-29830
Publ.-Id: 29830


Population balance modelling of isothermal and non-isothermal bubbly flows

Liao, Y.
In bubbly flows, bubble size may vary with time and space as the result of coalescence and breakage, shrinkage and growth due to mass and/or heat transfer as well as other dynamic and transport processes occurring at the interface. One major task and challenge in modelling of bubbly flows is to reconstruct these processes and trace the change of local bubble size, since it is crucial in affecting the rate of all interfacial transfers. The population balance equation provides the basis for the description of the dynamics of particulate systems. It has become of great interest in a number of scientific disciplines or application fields. Different forms of the population balance models have been presented, and they all allow one to take into account above bubble size change mechanisms through so-called kernels. Nevertheless, continuous efforts are needed in developing, calibrating and validating the kernels. In addition, reliable and efficient solution of the population balance equation is not trivial. The presentation will focus on the class method of population balance modelling, its coupling with the two-fluid-model and application to adiabatic air-water, condensing and evaporating steam-water bubbly flows as well as recent progresses in developing coalescence and breakup kernels.
Keywords: Bubbly flow, Coalescence and breakup, CFD-PBM coupled method, Phase change, Population balance model
  • Invited lecture (Conferences)
    NSFC-DEG International Workshop on Three-Phase Flow Modelling and Simulation, 23.-25.10.2019, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-29825
Publ.-Id: 29825


The intensive DT neutron generator of TU Dresden

Klix, A.; Döring, T.; Domula, A.; Zuber, K.
TU Dresden operates an accelerator-based intensive DT neutron generator. Experimental activities comprise investigation into material activation and decay, neutron and photon transport in matter and R&D work on radiation detectors for harsh environments. The intense DT neutron generator is capable to produce a maximum of 1012 n/s. The neutron source is a solid-type water-cooled tritium target based on a titanium matrix on a copper carrier. The neutron yield at a typical deuteron beam current of 1 mA is of the order of 1011 n/s in 4Π. A pneumatic sample transport system is available for short-time irradiations and connected to wo high-purity germanium detector spectrometers for the measurement of induced activities. The overall design of the experimental hall with the neutron generator allows a flexible setup of experiments including the possibility of investigating larger structures and cooled samples or samples at high temperatures.

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Permalink: https://www.hzdr.de/publications/Publ-29823
Publ.-Id: 29823


ATM controls DNA repair and mitochondria transfer between neighboring cells

Jin, S.; Cordes, N.
Intercellular communication is essential for multicellular tissue vitality and homeostasis. We show that healthy cells message protective signals through direct cell–cell connections to adjacent DNA–damaged cells in a microtubule–dependent manner. In DNA–damaged cells, mitochondria restoration is facilitated by fusion with undamaged mitochondria from healthy cells and their DNA damage repair is optimized in presence of healthy cells. Both, mitochondria transfer and intercellular signaling for an enhanced DNA damage response are critically regulated by the activity of the DNA repair protein ataxia telangiectasia mutated (ATM). These healthy–to–damaged prosurvival processes sustain normal tissue integrity and may be exploitable for overcoming resistance to therapy in diseases such as cancer.
Keywords: Cell–cell communication, genotoxic stress, mitochondria exchange, DNA damage repair, ataxia telangiectasia mutated (ATM)

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Permalink: https://www.hzdr.de/publications/Publ-29822
Publ.-Id: 29822


Studies on Flat Sandwich-type Self-Powered Detectors for Flux Measurements in ITER Test Blanket Modules

Raj, P.; Angelone, M.; Döring, T.; Eberhardt, K.; Fischer, U.; Klix, A.; Schwengner, R.ORC
Neutron and gamma flux measurements in designated positions in the test blanket modules (TBM) of ITER will be important tasks during ITER's campaigns. As part of the ongoing task on development of nuclear instrumentation for application in European ITER TBMs, experimental investigations on self-powered detectors (SPD) are undertaken. This paper reports the findings of neutron and photon irradiation tests performed with a test SPD in flat sandwich-like geometry. Whereas both neutrons and gammas can be detected with appropriate optimization of geometries, materials and sizes of the components, the present sandwich-like design is more sensitive to gammas than 14 MeV neutrons. Range of SPD current signals achievable under TBM conditions are predicted based on the SPD sensitivities measured in this work.

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Permalink: https://www.hzdr.de/publications/Publ-29821
Publ.-Id: 29821


Comparison between Silicon-Carbide and diamond for fast neutron detection at room temperature

Obraztsova, O.; Ottaviani, L.; Klix, A.; Döring, T.; Palais, O.; Lyoussi, A.
Neutron radiation detector for nuclear reactor applications plays an important role in getting information about the actual neutron yield and reactor environment. Such detector must be able to operate at high temperature (up to 600° C) and high neutron flux levels. It is worth nothing that a detector for industrial environment applications must have fast and stable response over considerable long period of use as well as high energy resolution. Silicon Carbide is one of the most attractive materials for neutron detection. Thanks to its outstanding properties, such as high displacement threshold energy (20-35 eV), wide band gap energy (3.27 eV) and high thermal conductivity (4.9 W/cm·K), SiC can operate in harsh environment (high temperature, high pressure and high radiation level) without additional cooling system. Our previous analyses reveal that SiC detectors, under irradiation and at elevated temperature, respond to neutrons showing consistent counting rates as function of external reverse bias voltages and radiation intensity. The counting-rate of the thermal neutron-induced peak increases with the area of the detector, and appears to be linear with respect to the reactor power. Diamond is another semi-conductor considered as one of most promising materials for radiation detection. Diamond possesses several advantages in comparison to other semiconductors such as a wider band gap (5.5 eV), higher threshold displacement energy (40-50 eV) and thermal conductivity (22 W/cm·K), which leads to low leakage current values and make it more radiation resistant that its competitors. A comparison is proposed between these two semiconductors for the ability and efficiency to detect fast neutrons. For this purpose the deuterium-tritium neutron generator of Technical University of Dresden with 14 MeV neutron output of 1010 n·s-1 is used. In the present work, we interpret the first measurements and results with both 4H-SiC and chemical vapor deposition (CVD) diamond detectors irradiated with 14 MeV neutrons at room temperature.

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Permalink: https://www.hzdr.de/publications/Publ-29820
Publ.-Id: 29820


Comparing the Response of a SiC and a sCVD Diamond Detectors to 14-MeV Neutron Radiation

Obraztsova, O.; Ottaviani, L.; Klix, A.; Döring, T.; Palais, O.; Lyoussi, A.
Radiation detectors based on wide-bandgap semiconductors have received considerable attention in many applications such as the experiments in material testing reactors, high energy particle physics experiments, or fusion facilities for plasma diagnostics. In this paper, we compared a 4H-silicon-carbide (SiC)-based detector with a single crystal chemical vapor deposited (sCVD) diamond-based detector for 14-MeV neutron detection. For this purpose, the deuterium- tritium neutron generator of Technical University of Dresden with 14-MeV neutron output up to 10 11 n/sin 4π has been used. In this paper, we interpret the results of our first measurements with both 4H-SiC and sCVD diamond detectors at low neutron flux of 9.4 × 10 6 n/(cm 2 · s) and at room temperature.

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Permalink: https://www.hzdr.de/publications/Publ-29819
Publ.-Id: 29819


Neutron flux measurements on a mock-up of a storage cask for high-level nuclear waste using 2.5 MeV neutrons

Saurí Suárez, H.; Becker, F.; Klix, A.; Pang, B.; Döring, T.
To store and dispose spent nuclear fuel, shielding casks are employed to reduce the emitted radiation. To evaluate the exposure of employees handling such casks, Monte Carlo radiation transport codes can be employed. Nevertheless, to assess the reliability of these codes and nuclear data, experimental checks are required. In this study, a neutron generator (NG) producing neutrons of 2.5 MeV was employed to simulate neutrons produced in spent nuclear fuel. Different configurations of shielding layers of steel and polyethylene were positioned between the target of the NG and a NE-213 detector. The results of the measurements of neutron and γ radiation and the corresponding simulations with the code MCNP6 are presented. Details of the experimental set-up as well as neutron and photon flux spectra are provided as reference points for such NG investigations with shielding structures.

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Permalink: https://www.hzdr.de/publications/Publ-29818
Publ.-Id: 29818


Radiosynthesis and Biological Investigation of a Novel Fluorine-18 Labeled Benzoimidazotriazine- based Radioligand for Imaging of Phosphodiesterase 2A with Positron Emission Tomography

Ritawidya, R.; Wenzel, B.; Teodoro, R.; Toussaint, M.; Kranz, M.; Deuther-Conrad, W.; Dukic-Stefanovic, S.; Ludwig, F.-A.; Scheunemann, M.; Brust, P.ORC
A specific radioligand for imaging of cyclic nucleotide phosphodiesterase 2A (PDE2A) via positron emission tomography (PET) would be helpful for research on the physiology and disease-related changes in the expression of this enzyme in the brain. In this report, the radiosynthesis of a novel PDE2A radioligand and the subsequent biological evaluation is described. Our prospective compound 1-(2-chloro-5-methoxy phenyl)-8-(2-fluoropyridin-4-yl)-3- methylbenzo[e]imidazo[5,1-c][1,2,4]triazine, BIT1 (IC50 PDE2A = 3.33 nM; 16-fold selectivity over PDE10A) was fluorine-18 labeled via aromatic nucleophilic substitution of the corresponding nitro precursor using the K[18F]F‐K2.2.2‐carbonate complex system. The new radioligand [18F]BIT1 was obtained with a high radiochemical yield (54 ± 2%, n = 3), a high radiochemical purity (≥99%) and high molar activities (155‐175 GBq/μmol, n = 3). In vitro autoradiography on pig brain cryosections exhibited an heterogenous spatial distribution of [18F]BIT1 corresponding to the known pattern of expression of PDE2A. The investigation of in vivo metabolism of [18F]BIT1 in mouse revealed a sufficient metabolic stability. PET studies in mouse exhibited a moderate brain uptake of [18F]BIT1 with a maximum standardized uptake value of ~0.7 at 5 minutes p.i. However, in vivo blocking studies revealed a non-target specific binding of [18F]BIT1. Therefore, further structural modifications are needed to improve target selectivity.
Keywords: cyclic nucleotide phosphodiesterase; PDE2A radioligand; nitro-precursor; fluorine-18; in vitro autoradiography; PET imaging

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Permalink: https://www.hzdr.de/publications/Publ-29817
Publ.-Id: 29817


Ferromagnetic resonance detection in magnetic single objects via a novel microresonator and microantenna approach

Cansever, H.ORC; Lenz, K.ORC; Narkowicz, R.; Kowalska, E.ORC; Faßbender, J.ORC; Deac, A. M.; Lindner, J.
Ferromagnetic resonance has been commonly used as a spectroscopic technique investigating the fundamental properties of ferromagnetic materials, such as magnetization, g-factor, magnetic anisotropy and damping (relaxation) parameters [1-4].Conventionally, an FMR spectrometer is operating at a fixed microwave frequency to detect the microwave absorption of the magnetic object by sweeping an external magnetic field through the resonance. The sensitivity of this weak absorption process is typically enhanced by using a microwave bridge setup. However, for a reliable quantification of key magnetic parameters like the g-factor or spin relaxation times, the measurements should be performed within a broad range of frequencies. This is achieved by broadband FMR spectrometers which employ vector network analyzers (VNA) that detect the microwave transmission or reflection parameters of the sample [5-6]. However, neither conventional cavities nor broadband FMR spectrometers are able to detect signals of micro/nano size samples due to the tiny sample volume. To achieve optimal sensitivity for small objects, planar microresonators were introduced for electron paramagnetic resonance (EPR) experiments [7]. Microresonators have been used to investigate magnetization dynamics of magnetic object to understand uniform and spin wave modes [8], as well as the spin-Seebeck effect in magnetic tunnel junctions [9.] The microresonator approach allows producing rf magnetic fields homogeneously concentrated inside a metallic loop, thereby increasing the filling factor of the resonator. Here, we explain the novel microesonator approach in detail and introduce moreover a microantenna approach which allows to perform experiments in the range of 8-18 GHz employing a co-planar layout. We investigate magnetization dynamics within Permalloy (Ni80Fe20) wires by using both, microresonator and microantenna approach.

[1] P. E. Wigen, C.F. Kooi, M. R Shanaberger, T. R. Rosing, Phys. Rev. Lett. 9, 206, 1962.
[2] P. E. Wigen, Z. Zhang, Braz. J. Phys. 22, 267, 1992.
[3] M. Farle, “Rep. Prog. Phys. 61, 755, 1998.
[4] J. R. Fermin, A. Azevedo, F. M. Aguiar, B. Li, S. M. J. Rezende, Appl. Phys. 85, 7316, 1999.
[5] M. Vroubel, Y. Zhuang, B. Rejaei, J. N. Burghartz, J. Appl. Phys. 99, 08P506, 2006.
[6] C. Nistor, K. Sun, Z. Wang, M. Wu, C. Mathieu, M. Hadley Appl. Phys. Lett. 95, 012504, 2009.
[7] R. Narkowicz, D. Suter, I. Niemeyer, Rev. Sci. Instrum. 79, 084702, 2008.
[8] A Banholzer, R Narkowicz, C Hassel, R Meckenstock, S Stienen, O Posth, D Suter, M Farle, J Lindner, Nanotechnology, 22, 295713, 2011.
[9] H. Cansever, R. Narkowicz, K. Lenz, C. Fowley, L. Ramasubramanian, O. Yildirim, A. Niesen, T. Huebner, G. Reiss, J. Lindner, J. Fassbender, A. M. Deac, J. Phys. D: Appl. Phys. 51, 22400, 2018.
Keywords: ferromagnetic resonance, microresonator, microantenna
  • Invited lecture (Conferences)
    9th APMAS 2019 - International Advances in Applied Physics & Materials Science Congress & Exhibition, 20.-28.10.2019, Fethiye- Mugla, Turkey

Permalink: https://www.hzdr.de/publications/Publ-29814
Publ.-Id: 29814


Enhanced Fiberoptical Dosimetry through Time-resolved Single Photon Detection in Proton Fields

Kormoll, T.; van der Graaf, E. R.; van Goethem, M. J.; Gonzalez Torres, M. J.; Lachmann, P.; Pausch, G.ORC; Majchrowski, A.; Makarevich, K.; Weinberger, D.; Zuber, K.; Teichmann, T.
Fiberoptical dosimetry uses compact solid state radioluminescence probes coupled to long to flexible light guides. Such probes are convenient, robust small. Especially in the presence of magnetic fields, such optical probes can be advantageous over the transmission of a current signal, e.g. from a photodiode directly attached to a scintillator. These characteristics make such probes attractive for emerging medical applications like particle therapy in combination with MRI. Challenging remains the discrimination of so called “stem” effect light which is generated in the fiber from the actual signal light from the probe. In this work, fiber probes attached to a single photon sensor have been exposed to a proton beam from a proton cyclotron in order to study the feasibility of fiber dosimetry in therapeutic proton fields. Probes with different luminophores have been placed in the beam within a PMMA holder of 1 cm thickness. The light guide was coupled to a Hamamatsu H12386-210 single photon detector. For timing information, the pulse was sampled and analyzed with a Serious Dynamics DAQ125 board. This is a 16 bit sampling ADC board which was running synchronous to the cyclotron. An interpolated time stamp with a resolution of 30 ps was calculated in realtime. It could be shown that a time resolved measurement of the single luminescence photons exhibits the time structure of the luminophore, e.g. the long decay which appears uncorrelated of beryllium oxide or lithium tetraborate or the decay in the ns range of plastic scintillators. Blank fiber measurements exhibit the microbunch width of the accelerator. Thereby, stem identification in therapeutic hadron fields is possible without further reference measurements. Additionally, the issue of quenching of many luminophores in hadron fields can be addressed. A further beamtime at the AGOR cyclotron in Groningen will be conducted in May 2019 and recent results will be presented at the conference.
Keywords: Fiberoptical dosimetry, radioluminescence, magnetic fields, scintillator, MRI, proton beam, therapeutic proton fields, timing, ADC, beryllium oxide, lithium tetraborate, therapeutic hadron fields
  • Contribution to proceedings
    2019 IEEE Nuclear Science Symposium & Medical Imaging Conference, 26.10.-02.11.2019, Manchester, UK
    Proceedings of the 2019 IEEE Nuclear Science Symposium & Medical Imaging Conference

Permalink: https://www.hzdr.de/publications/Publ-29812
Publ.-Id: 29812


Crystal size versus paddle wheel deformability: selective gated adsorption transitions of the switchable metal–organic frameworks DUT-8(Co) and DUT-8(Ni)

Ehrling, S.ORC; Senkovska, I.ORC; Bon, V.ORC; Evans, J. D.ORC; Petkov, P.ORC; Krupskaya, Y.; Kataev, V.ORC; Wulf, T.ORC; Krylov, A.ORC; Vtyurin, A.ORC; Krylova, S.ORC; Adichtchev, S.; Slyusareva, E.ORC; Weiss, M. S.ORC; Büchner, B.ORC; Heine, T.ORC; Kaskel, S.ORC
Switchable pillared layer metal–organic frameworks M₂(2,6-ndc)₂(dabco) (DUT-8(M), M = Ni, Co, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]octane, DUT – Dresden University of Technology) were synthesised in two different crystallite size regimes to produce particles up to 300 μm and smaller particles around 0.1 μm, respectively. The textural properties and adsorption-induced switchability of the materials, obtained from both syntheses, were studied by physisorption of N2 at 77 K, CO2 at 195 K and n-butane at 273 K, revealing pronounced differences in adsorption behavior for Ni and Co analogues. While the smaller nano-sized particles (50–200 nm) are rigid and show no gating transitions confirming the importance of crystallite size, the large particles show pronounced switchability with characteristic differences for the two metals resulting in distinct recognition effects for various gases and vapours. Adsorption of various vapours demonstrates consistently a higher energetic barrier for the “gate opening” of DUT-8(Co) in contrast to DUT-8(Ni), as the “gate opening” pressure for Co based material is shifted to a higher value for adsorption of dichloromethane at 298 K. Evaluation of crystallographic data, obtained from single crystal and powder X-ray diffraction analysis, showed distinct geometric differences in the paddle wheel units of the respective MOFs. These differences are further disclosed by solid-state UV-vis, FT-IR and Raman spectroscopy. Magnetic properties of DUT-8(Co) and DUT-8(Ni) were investigated, indicating a high-spin state for both materials at room temperature. Density functional theory (DFT) simulations confirmed distinct energetic differences for Ni and Co analogues with a higher energetic penalty for the structural “gate opening” transformation for DUT-8(Co) compared to DUT-8(Ni) explaining the different flexibility behaviour of these isomorphous MOFs.

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Permalink: https://www.hzdr.de/publications/Publ-29811
Publ.-Id: 29811


Testing RPC Performance with Discharges Ignited by UV Laser Pulses: Precise measurement of gas parameters in approximately realistic RPC configurations

Fan, X.
This thesis is devoted in two associated topics: a unique laser facility for researches of gaseous detectors; the investigations of Resistive Plate Chamber (RPC) detectors and the measurement of gas parameters in a realistic condition of timing RPC.
A pulsed UV laser test facility has been assembled in HZDR. The focus of pico-second laser pulses is placed in a specific position in a gaseous detector sample to produce laser plasma, where free electrons are generated in ionizations with well defined number, micro-meter spatial accuracy in a volume of micro-meter scale. It provides a method, independent from accelerators, to make investigations with gaseous detectors in a laboratory.
Samples of RPC detectors are designed and assembled for experiments with the laser test facility. Methods are developed to acquire the waveforms of electron avalanches for different drift lengths and to obtain the key gas parameters: the effective Townsend coefficient and the electron drift velocity. We have succeeded in the direct measurement of gas parameters at the field strength of timing RPC under atmospheric pressure for the first time in experimental conditions.
The research has obtained different achievements. The laser test facility is proven to be qualified for the measurement of gas parameters, and has a potential to contribute to the eco-gas research for future RPC. The possible measurement range of electric field of gas parameter at atmospheric pressure is extended by a factor of two, from the range of trigger RPC to timing RPC. The results of experiments have revealed some fundamental mechanisms, which will extend the understanding of RPC performance and electron avalanche process.
Keywords: Laser, Resistive Plate Chamber, Electron Avalanche
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-106 2019

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Permalink: https://www.hzdr.de/publications/Publ-29810
Publ.-Id: 29810


Modular Digital Low Level Radio Frequency Control (LLRF) for CW Operation at ELBE

Zenker, K.
A digital LLRF control has been implemented at the CW linac ELBE at Helmholtz-Zentrum Dresden-Rossendorf. The system is based on the MicroTCA.4 standard and drives four superconducting TESLA cavities and two normal conducting buncher cavities. The system enables a higher flexibility of the field control, improved diagnostics and field stability compared to the analogue system which was used before. The presentation will give an overview on the design specification, detailed system structure, software architecture and latest performance test results.
  • Invited lecture (Conferences)
    19th International Conference on RF Superconductivity, 30.06.-05.07.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29805
Publ.-Id: 29805


ELBE and DALI at HZDR

Zenker, K.; Evtushenko, P.ORC; Schwarz, A.; Kuntzsch, M.; Schneider, C.; Kovalev, S.ORC
Facility status report for ELBE and TELBE
  • Invited lecture (Conferences)
    MT ARD ST3 Annual Meeting, 16.-18.10.2019, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29803
Publ.-Id: 29803


Proximity effect in crystalline framework materials: stacking-induced functionality in MOFs and COFs

Kuc, A. B.ORC; Springer, M.; Batra, K.; Juarez-Mosqueda, R.; Wöll, C.; Heine, T.
Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid-state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by the van-der-Waals interactions between stacked aromatic building blocks. This Progress Report shows how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary electronic and optoelectronic properties emerge in MOFs and COFs. After discussing the proximity effect in graphene-related materials, its importance for layered COFs and MOFs is shown. For MOFs with well-defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer- by-layer growth technique for well-ordered surface-mounted MOFs is summarized.

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Permalink: https://www.hzdr.de/publications/Publ-29800
Publ.-Id: 29800


Morphology modification of Si nanopillars under ion irradiation at elevated temperatures: plastic deformation and controlled thinning to 10 nm

Xu, X.ORC; Heinig, K.-H.; Möller, W.; Engelmann, H.-J.; Klingner, N.ORC; Gharbi, A.; Tiron, R.; Borany, J.; Hlawacek, G.ORC
Si nanopillars of less than 50 nm diameter have been irradiated in a helium ion microscope with a focused Ne+ beam. The morphological changes due to ion beam irradiation at room temperature and elevated temperatures have been studied with the transmission electron microscope. We found that the shape changes of the nanopillars depend on irradiation-induced amorphization and thermally driven dynamic annealing. While at room temperature, the nanopillars evolve to a conical shape due to ion-induced plastic deformation and viscous flow of amorphized Si, simultaneous dynamic annealing during the irradiation at elevated temperatures prevents amorphization which is necessary for the viscous flow. Above the critical temperature of ion-induced amorphization, a steady decrease of the diameter was observed as a result of the dominating forward sputtering process through the nanopillar sidewalls. Under these conditions the nanopillars can be thinned down to a diameter of ∼10 nm in a well-controlled manner. A deeper understanding of the pillar thinning process has been achieved by a comparison of experimental results with 3D computer simulations based on the binary collision approximation.
Keywords: helium ion microscopy, Monte Carlo simulation, sub-10 nm fabrication, ion beam damage, amorphization

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Permalink: https://www.hzdr.de/publications/Publ-29799
Publ.-Id: 29799


Automated SEM Mineral Liberation Analysis (MLA) with Generically Labelled EDX Spectra in the Mineral Processing of Rare Earth Element Ores

Schulz, B.; Merker, G.; Gutzmer, J.ORC
Many rare earth element (REE) deposits have experienced multistage geological enrichment processes resulting in REE bearing mineral assemblages of considerable complexity and variability. Automated scanning electron microscopy (SEM) mineral liberation analysis of such REE ores is confronted by the difficult assignment of energy-dispersive X-ray (EDX) spectra to REE mineral names. To overcome and bypass this problem, a generic and reliable labelling of EDX reference spectra obtained from REE-bearing minerals based on their contents of Si, Ca, F and P in a bulk normalised analysis is proposed. The labelled spectra are then combined into groups of REE-P (similar to monazite), REE-Ca-Si-P (similar to britholite), REE-Ca-F (similar to synchysite) and REE-F (similar to bastnaesite, parisite, fluocerite). Mixed spectra with low counts for REE from minute REE mineral grains are combined into a separate group. This classification scheme is applied to automated SEM mineral liberation analysis (MLA) data from beneficiation products by comminution and multistage flotation of REE carbonatite ores. Mineral modes, mineral grain size distribution, mineral liberation, mineral locking and mineral grade versus recovery curves based on the analysis of >200,000 particles in a sample can be recognised and interpreted in virtual grain size fractions. The approach as proposed here will allow future process mineralogical studies of REE deposits to be robust and comparable.

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Permalink: https://www.hzdr.de/publications/Publ-29796
Publ.-Id: 29796


Independent Geometrical Control of Spin and Charge Resistances in Curved Spintronics

Das, K. S.; Makarov, D.ORC; Gentile, P.; Cuoco, M.; van Wees, B. J.; Ortix, C.; Vera-Marun, I. J.
Spintronic devices operating with pure spin currents represent a new paradigm in nanoelectronics, with a higher energy efficiency and lower dissipation as compared to charge currents. This technology, however, will be viable only if the amount of spin current diffusing in a nanochannel can be tuned on demand while guaranteeing electrical compatibility with other device elements, to which it should be integrated in high-density three-dimensional architectures. Here, we address these two crucial milestones and demonstrate that pure spin currents can effectively propagate in metallic nanochannels with a three-dimensional curved geometry. Remarkably, the geometric design of the nanochannels can be used to reach an independent tuning of spin transport and charge transport characteristics. These results laid the foundation for the design of efficient pure spin current-based electronics, which can be integrated in complex three-dimensional architectures.
Keywords: curved nanoarchitectures, electrical and spin resistance, geometrical control, nonlocal spin valves, Spintronics

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Publ.-Id: 29794


Effects of Magnetic Field on Hydrogen Bubble Detachment during Water Electrolysis

Yang, X.ORC; Mutschke, G.ORC; Margitta, U.; Eckert, K.ORC
Water electrolysis is a promising option for hydrogen production from renewable resources. One main challenge in making water electrolysis economically competitive is to raise its efficiency by decreasing the cell voltage. In this respect, electrode coverage by gas bubbles is one of the key sources which creates undesired overpotential.

Better understanding of the fundamentals of bubble nucleation, growth, and detachment in detail might bring new ideas in such effective manipulating of bubbles and substantially accelerate a way toward advanced electrolysis. Despite extensive efforts in the past, important aspects of bubble dynamics, such as the interaction/coalescence of bubbles significantly affecting their evolution or different growth modes of the bubbles themselves, are not yet fully understood. To provide that necessary information on the bubble shape profile, including the contact angle, the contact line the bubble forms with the electrode [1], the Marangoni convection[2], we use a micro electrode to produce single hydrogen bubbles. Water electrolysis was carried out under potentiostatic conditions in a 1 M H2SO4 solution in a small electrochemical cell ([2], [3], [4]). The behavior of a single hydrogen bubble evolving on a microelectrode (100 µm in diameter) was analyzed by measurements of the current transient as well as by microscopic high speed imaging. Tracer particles were additionally added to the solution to measure the flow in the vicinity of the bubble.

The contribution will present experimental results of the hydrogen bubble release size and the bubble growing mechanism at two different magnetic field orientations and at different field intensities. As shown in Fig.1, the bubble departure size decreased with increase of the magnetic field intensity when the magnetic field was applied parallel to the electrode surface. However, an increase of the departure size was observed when the field was applied perpendicular to the electrode surface. The effects were further explained by the MHD convection around the bubble. A comparison of the flow field by measurements and numerical simulation will be presented.
  • Lecture (Conference)
    The 8th International Conference on Magneto-Science, 10.-14.10.2019, Hefei, China

Permalink: https://www.hzdr.de/publications/Publ-29792
Publ.-Id: 29792


Engineering Self-Supported Noble Metal Foams Toward Electrocatalysis and Beyond

Du, R.; Jin, X.; Hübner, R.; Fan, X.; Hu, Y.; Eychmüller, A.
Noble metals, despite their expensiveness, display irreplaceable roles in widespread fields. To acquire novel physicochemical properties and boost the performance-to-price ratio for practical applications, one core direction is to engineer noble metals into nanostructured porous networks. Noble metal foams (NMFs), featuring self-supported, 3D interconnected networks structured from noble-metal-based building blocks, have drawn tremendous attention in the last two decades. Inheriting structural traits of foams and physicochemical properties of noble metals, NMFs showcase a variety of interesting properties and impressive prospect in diverse fields, including electrocatalysis, heterogeneous catalysis, surface-enhanced Raman scattering, sensing and actuation, etc. A number of NMFs have been created and versatile synthetic approaches have been developed. However, because of the innate limitation of specific methods and the insufficient understanding of formation mechanisms, flexible manipulation of compositions, structures, and corresponding properties of NMFs are still challenging. Thus, the correlations between composition/structure and properties are seldom established, retarding material design/optimization for specific applications. This review is devoted to a comprehensive introduction of NMFs ranging from synthesis to applications, with an emphasis on electrocatalysis. Challenges and opportunities are also included to guide possible research directions in this field and promote the interest of interdisciplinary scientists.

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Publ.-Id: 29789


Identical pion intensity interferometry at sqrt(s_NN)=2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wójcik, D.; Zanevsky, Y.; Zumbruch, P.
High-statistics π−π− and π+π+ femtoscopy data are presented for Au+Au collisions at sqrt(s_NN)=2.4 GeV, measured with HADES at SIS18/GSI. The experimental correlation functions allow the determination of the space-time extent of the corresponding emission sources via a comparison to models. The emission source, parametrized as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, azimuthal emission angle with respect to the reaction plane, collision centrality and beam energy. For all centralities and transverse momenta, a geometrical distribution of ellipsoidal shape is found in the plane perpendicular to the beam direction with the larger extension perpendicular to the reaction plane. For large transverse momenta, the corresponding eccentricity approaches the initial eccentricity. The eccentricity is smallest for most central collisions, where the shape is almost circular. The magnitude of the tilt angle of the emission ellipsoid in the reaction plane decreases with increasing centrality and increasing transverse momentum. All source radii increase with centrality, largely exhibiting a linear rise with the number of participants, irrespective of transverse momentum. A substantial charge-sign difference of the source radii is found, appearing most pronounced at low transverse momentum. The extracted source parameters are consistent with the extrapolation of their energy dependence down from higher energies.

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Publ.-Id: 29788


Versatile Bispidine-based Bifunctional Chelators for 64CuII-Labelling of Biomolecules

Singh, G.ORC; Zarschler, K.ORC; Hunoldt, S.; Santana Martinez, I. I.; Rühl, C.; Matterna, M.; Bergmann, R.ORC; Mathe, D.; Hegedüs, N.; Bachmann, M.ORC; Comba, P.; Stephan, H.ORC
Bifunctional chelators as parts of modular metal-based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable CuII chelator 3,7-diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine-isothiocyanate) and the Cu-free strain promoted alkyne-azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody-based biomolecule and validate the obtained conjugate in vitro and in vivo.
Keywords: bispidines; bifunctional chelator; site-specific labelling; imaging; EGFR

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  • Secondary publication expected from 22.11.2020

Permalink: https://www.hzdr.de/publications/Publ-29787
Publ.-Id: 29787


Updates on the FLUKA geometry for the MU2E experiment

Müller, S.ORC; Ferrari, A.ORC; Rachamin, R.ORC
Presentation at Mu2e Collaboration Meeting 16.10.2019
Keywords: Mu2e, FLUKA, Monte Carlo, CLFV
  • Lecture (Conference)
    Mu2e Collaboration Meeting, 16.-19.10.2019, Fermilab, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29784
Publ.-Id: 29784


Synthesis and cyclooxygenase inhibition of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their potential prodrugs

Laube, M.ORC; Gassner, C.; Knieß, T.ORC; Pietzsch, J.ORC
Non-invasive imaging of cyclooxygenase-2 (COX-2) by radiolabeled ligands is attractive for the diagnosis of cancer and novel highly affine leads with optimized pharmacokinetic profile are of high interest for future developments. Recent findings have shown that methylsulfonyl-substituted (dihydro)pyrrolo[3,2,1-hi]indoles represent highly potent and selective COX-2 inhibitors but possess unsuitable pharmacokinetic properties for radiotracer applications. Based on these results, we herein present the development and evaluation of a second series of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their conversion into the respective more hydrophilic N-propionamide-substituted analogs. In comparison to the methylsulfonyl-substituted leads, COX inhibition potency and selectivity was retained in the sulfonamide-substituted compounds; however, the high lipophilicity might hinder their future use. The N-propionamide-substituted analogs showed a significantly decreased lipophilicity and, as expected, lower or no COX-inhibition potency. Hence, the N-(sulfonyl)propionamides can be regarded as potential prodrugs, which represents a potential approach for more sophisticated radiotracer developments.
Keywords: Cancer; Imaging; Inflammation; Lipophilicity; McMurry cyclization; Structure-Activity-Relationship

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Publ.-Id: 29783


Characterization of Tissue Transglutaminase as a Potential Biomarker for Tissue Response toward Biomaterials

Hauser, S.ORC; Wodtke, R.ORC; Tondera, C.; Wodtke, J.; Neffe, A. T.; Hampe, J.; Lendlein, A.; Löser, R.ORC; Pietzsch, J.ORC
Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial−tissue interactions due to its
presence and versatile functions in the extracellular environment. TGase 2 catalyzes the cross-linking of proteins through its Ca2+-dependent acyltransferase activity. Moreover, it enhances the interactions between fibronectin and integrins, which in turn mediates the adhesion, migration, and motility of the cells. TGase 2 is also a key player in the pathogenesis of fibrosis. In this study, we investigated whether TGase 2 is present at the biomaterial−tissue interface and might serve as an informative biomarker for the visualization of tissue response toward gelatin-based biomaterials. Two differently cross-linked hydrogels were used, which were obtained by the reaction of gelatin with lysine diisocyanate ethyl ester. The overall expression of TGase 2 by endothelial cells, macrophages, and granulocytes was partly influenced by contact to the hydrogels or their degradation products, although no clear correlation was evidenced. In contrast, the secretion of TGase 2 differed remarkably between the different cells, indicating that it might be involved in the cellular reaction toward gelatin-based hydrogels. The hydrogels were implanted subcutaneously in immunocompetent, hairless SKH1-Elite mice. Ex vivo immunohistochemical analysis of tissue sections over 112 days revealed enhanced expression of TGase 2 around the hydrogels, in particular at days 14 and 21 post-implantation. The incorporation of fluorescently labeled cadaverine derivatives for the detection of active TGase 2 was in accordance with the results of the expression analysis. The presence of an irreversible inhibitor of TGase 2 led to attenuated incorporation of the cadaverines, which verified the catalytic action of TGase 2. Our in vitro and ex vivo results verified TGase 2 as a potential biomarker for tissue response toward gelatin-based hydrogels. In vivo, no TGase 2 activity was detectable, which is mainly attributed to the unfavorable physicochemical properties of the cadaverine probe used.
Keywords: extracellular matrix modifying enzymes, gelatin-based hydrogels, biomaterial−tissue interface, polyamines, optical imaging

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Permalink: https://www.hzdr.de/publications/Publ-29782
Publ.-Id: 29782


Accuracy and robustness of 4D logfile-based dose reconstruction

Spautz, S.; Peters, N.; Meijers, A.; Jakobi, A.; Knopf, A.; Troost, E. G. C.ORC; Richter, C.ORC; Stützer, K.ORC
Introduction: We plan to use 4D logfile-based dose reconstruction for daily monitoring and potential intervention in PBS treatments of non-small cell lung cancer patients, restricted to limited motion (≤5mm). Here, we assessed the validity of reconstructed doses and their sensitivity to selected disturbed input parameters by dedicated phantom experiments.
Material/Methods: Quasi-monoenergetic proton fields were delivered to a dynamic thorax phantom (G.C. Technology, Germany) equipped with a 3cm soft-tissue target intersected by a radiochromic film. The surrogate signal (AZ733-V, ANZAI Medical Co.,Ltd, Japan) of the motion patterns (cos/cos4, period: 5s, peak-to-peak amplitude: 5mm and 30mm) was recorded in synchronization with the machine logfiles. 4D reconstructions with 1mm/3mm dose grid resolution were performed using 4DCTs of 12 amplitude-sorted phases and either ground truth or automatically generated deformation vector fields. Characteristic 1D profiles of the reconstructed and measured doses were compared by gamma index analyses (2mm, 2%). Maximum dose deviations due to simulated offsets between motion and machine logfiles (±1/±5/±25/±250ms) were assessed for quasi-monoenergetic and 4D optimized plans.
Results: Characteristic dose patterns were well reproduced (Fig.1). Gamma pass rates were >98% under static conditions. For 5mm motion, the pass rate of 94.2% for an ideal reconstruction with 1mm³ dose voxels dropped to 93.0% with clinically used voxel sizes (3×3×3mm³), 83.6% when using automated DIR and 78.2% for the combination of both, respectively. For the 30mm motion, the CT artifacts and residual motion were predominant and lead for 3mm dose grids to gamma pass rates of approximately 84%, irrespective of chosen DIR. Fig.2 depicts the effect of simulated logfile asynchrony.
Conclusions: The implemented method is robust against disturbed input parameters for the small, clinically aimed motion amplitudes. Reconstruction accuracy decreases with deformation-related inaccuracies and increasing 4DCT artifacts for large motion. Consistent breathing and regular control CTs are compulsory for meaningful 4D logfile-based dose reconstructions.
  • Poster
    4D Treatment Workshop for Particle Therapy 2019, 22.-23.11.2019, Kraków, Polska

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Publ.-Id: 29781


A Simulation-Based Study on Reprocessing of Phosphate Tailings for Recovering Pyrochlore and Monazite

Vicino Pacheco De Aquino, T.; Pereira, L.ORC; Hassanzadehmahaleh, A.; Belo Fernandes, I.ORC; Rudolph, M.ORC; Mischo, H.; Barakos, G.
The present study aims to investigate possibilities for improving the recovery of pyrochlore ((Na, Ca)₂Nb₂O₆) and monazite ((Ce, La, Th, Sm)PO4) as by-products from a phosphate mine with current niobium (Nb) production from geometallurgical perspectives. With this purpose, process mineralogy of Nb- and REE-bearing minerals together with operating properties of the concentration plant are examined using respectively mineral liberation analyzer (MLA) and the HSC® Chemistry 9 simulation module. A plant-site sampling campaign was performed and key operating parameters such as throughputs and pulp densities for individual streams were measured. The results obtained by MLA analyses as the base of mineral mass balances were compared and validated by commonly used chemical characterization techniques i.e. X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–optical emission spectroscopy (ICP-OES). Simulation results showed that the combination of Nb flotation rougher and scavenger cells into one single rougher bank plus the addition of a new scavenger bank (4x1.4 m³ cells) can increase pyrochlore recovery in the silica/niobium flotation circuit from approximately 31% to 44%. This cell configuration improves the ultimate pyrochlore’s plant recovery from 27% to 38% leading to a substantial enhancement in final concentrate throughput from 540 to 740 kg/h. Future studies on this topic include the use of wet high intensity magnetic separation (WHIMS) and froth flotation respectively for the pre-concentration and concentration of monazite.
Keywords: Pyrochlore, phosphate deposit, rare earth elements (REE), HSC Sim®, process simulation
  • Contribution to proceedings
    International Mineral Processing Conference Eurasia (IMPC 2019), 31.10.-02.11.2019, Antalya, Turkey
    Proceedings of IMPC 2019

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Publ.-Id: 29779


⁹⁹Tc immobilization by aluminum solids containing Fe(II) moieties

Mayordomo Herranz, N.ORC; Rodriguez Hernandez, D. M.; Molodtsov, K.; Johnstone, Erik V.; Roßberg, A.; Heim, K.; Foerstendorf, H.ORC; Schild, Dieter; Brendler, V.ORC; Müller, K.ORC
The immobilization of ⁹⁹Tc is predominantly mediated by the reduction of Tc(VII) to Tc(IV), primarily due to the fact that [Tc(VII)O₄] ⁻ interactions with solid interfaces are limited, whereas Tc(IV)O₂ is a hardly soluble solid [1]. Tc reduction is facilitated by Fe²⁺, particularly when it is present as a sorbed species or a constituent mineral phase [2].
The present work analyzes the ⁹⁹Tc aqueous removal by two aluminum solids containing Fe(II) moieties: γ-Al₂O₃ with sorbed Fe²⁺ and Fe(II)-Al(III) layered double hydroxide (LDH). Batch contact experiments demonstrate that both solids are effective Tc scavengers, yielding a complete removal for pH > 6.5 and from pH 3.5 to 10.5, respectively. Characterization via XPS, XAS, and in situ ATR FT-IR spectroscopy provided information of the Tc speciation and uptake mechanism. Secondary Fe-minerals (hematite, magnetite, ferrihydrite) formed in the reduction were also identified by Raman microscopy.

Bibliography
[1] Meena, A. H.; Arai, Y. Env. Chem Lett 2017, 15, 241–263.
[2] Cui, D.; Eriksen, T. E. Environ. Sci. Technol. 1996, 30 (7), 2259–2262.
  • Lecture (Conference)
    The 43th symposium on scientific basis for nuclear waste management, 21.-24.10.2019, Viena, Austria

Permalink: https://www.hzdr.de/publications/Publ-29778
Publ.-Id: 29778


Some microbial issues regarding the storage of high-level radioactive waste

Matschiavelli, N.ORC; Kluge, S.; Dressler, M.; Cherkouk, A.ORC
The talk summerizes bio-geochemical results regarding the potential geo-technical barrier bentonite in a repositors of high-level radioactive waste.
  • Lecture (others)
    18th bilateral meeting HZDR/IRE - PSI/LES, 28.-29.10.2019, HZDR, IRE, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29777
Publ.-Id: 29777


Nonstoichiometric Phases of Two-Dimensional Transition-Metal Dichalcogenides: From Chalcogen Vacancies to Pure Metal Membranes

Joseph, T.ORC; Ghorbani Asl, M.ORC; Kvashnin, A. G.ORC; Larionov, K. V.ORC; Popov, Z. I.; Sorokin, P. B.ORC; Krasheninnikov, A.ORC
Two-dimensional (2D) membranes consisting of a single layer of Mo atoms were recently manufactured [ Adv. Mater. 2018, 30, 1707281] from MoSe2 sheets by sputtering Se atoms using an electron beam in a transmission electron microscope. This is an unexpected result as formation of Mo clusters should energetically be more favorable. To get microscopic insights into the energetics of realistic Mo membranes and nonstoichiometric phases of transition-metal dichalcogenides (TMDs) MaXb, where M = Mo and W and X = S, Se, and Te, we carry out first-principles calculations and demonstrate that the membranes, which can be referred to as metallic quantum dots embedded into a semiconducting matrix, can be stabilized by charge transfer. We also show that an ideal neutral 2D Mo or W sheet is not flat but a corrugated structure, with a square lattice being the lowest-energy configuration. We further demonstrate that several intermediate nonstoichiometric phases of TMDs are possible as they have lower formation energies than pure metal membranes. Among them, the orthorhombic metallic 2D M4X4 phase is particularly stable. Finally, we study the properties of this phase in detail and discuss how it can be manufactured by the top-down approaches.
Keywords: 2D, non-stoichiometric phases, Transition-Metal Dichalcogenides, DFT, metal membrane

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Permalink: https://www.hzdr.de/publications/Publ-29776
Publ.-Id: 29776


Thickness of polyelectrolyte layers of separately confined bacteria alters key physiological parameters on a single cell level

Rybkin, I.; Gorin, D.; Sukhorukov, G.; Lapanje, A.
Confinement of bacterial cells in matrix or capsules is an integral part of many biotechnological applications. Here, it is adopted the well-known layer-by-layer method of deposition of a few nanometer thick polyelectrolyte layers to confine separated bacterial cells in permeable and physically durable shells. Due to the physical properties of such a confinement, here it is found that this method enables investigation of effects of physical barrier against the mass gain and cell division. Using the method of time-lapse confocal microscopy, it is observed a prolonged lag phase, dependent on the number of polyelectrolyte layers. In the confinement, both the GFP fluorescent signal from the leaking T7 promoter and cell size, were increased by more than five and two times, respectively. This creates paradigm shift that enables using mechanical entrapment for control of bacterial cell physiology which opens possibilities of controlling the division rate as well as gene expression. These effects can be attributed to the perturbation of the sensing of the cell size, which results in disproportional synthesis of cell envelope against the intracellular material and compels cells to grow rapidly. In addition, the charged surface of cells enabled longer intercellular physical interaction resulting in spherically shaped microcolonies.
Keywords: time-lapse confocal microscopy, polyelectrolytes, layer-by-layer encapsulation, electrostatic interactions, cell surface modification

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Publ.-Id: 29775


M4F - Materials Modelling For Fusion and Fission Materials - Domain 1

Heintze, C.; Olsson, P.; Konstantinovic, M.; Caturla, M.-J.
The talk provides on overview on the objectives, activities and first results of Domain 1 of the H2020/EU project M4F. It aims at providing a broader scientific motivation and background for the benefit of the PhD students and post-docs participating in the project.
  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29774
Publ.-Id: 29774


Behaviour of C, Ni, Si, P under ion irradiation at different doses in model FeCr(Ni, Si, P) alloys

Gueye, P.-M.; Gomez-Ferrer, B.; Heintze, C.; Pareige, C.
Ferritic-martensitic steels with high chromium content are considered as promising candidates as structural materials in Gen-IV reactors because of their low swelling value for operating conditions and low ductile-brittle transition temperature (DBTT) shift under irradiation. Nevertheless, they tend to harden and embrittle under irradiation at low temperatures (350°C). Impurities as Ni, Si and P are known to increase hardening in these steels by creating solute-rich clusters (SRCs) [1-4].
In order to understand the role of each impurity on the formation of SRCs under irradiation, FeCr (NiSiP) alloys with different concentrations in Ni, Si and P have been ion irradiated with 5 MeV Fe2+ ions up to 0.1, 0.5 and 2.5 dpa at 300°C. The evolution of the solute distribution has been investigated by atom probe tomography (APT).
The results reveal the tendency to cluster of Ni, Si and P under irradiation from 0.1 dpa. Moreover, differences on the solutes distributions between materials containing one low-alloying element (Ni, Si or P) and the alloy containing Ni, Si and P, suggest a synergetic effect between these species. Results show the major role of P on the formation of the SRCs. The influence of C on the formation of SRCs will also be discussed.

References
[1] F. Garner, M. Toloczko, B. Sencer, J. Nucl. Mater. 276 (2000) 123.
[2] R. L. Klueh, A. T. Nelson, J. Nucl. Mater. 371 (2007) 37-52.
[3] A. Kohyama, A. Hishinuma, D. S. Gelles, R. L. Klueh, W. Dietz, K. Ehrlich, J. Nucl. Mater. 233-237 (1996) 138-147.
[4] B. Gomez-Ferrer, C. Heintze, C. Pareige, J. Nucl. Mater. 515 (2019) 35-44.
  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29773
Publ.-Id: 29773


On the role of Ni, Si and P on the nanostructural evolution of FeCr alloys under irradiation – link with hardening

Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Oñorbe, E.; Hernandez-Mayoral, M.; Desgardin, P.; Malerba, L.
High-chromium ferritic-martensitic (F-M) steels are promising candidates for structural components in Gen-IV reactors because of their excellent swelling resistance and good thermal properties. However, the operating window of these steels is constrained by irradiation hardening at low temperature (<350°C). This issues has been addressed within the FP7/MatISSE project.
After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small invisible dislocation loops1. 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, FeCr(SiNiP) alloys of different composition has been ion irradiated and characterized using transmission electron microscopy, atom probe tomography, positron annihilation and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the concentration of vacancy defects, formation of solute clusters and dislocation loops and to make the link with irradiation hardening.
  • Lecture (Conference)
    SMINS 5 - NEA International Workshop on Structural Materials for Innovative Nuclear Systems, 08.-11.07.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29772
Publ.-Id: 29772


Influence of impurities in microstructural evolution of FeCr alloys under ion irradiation – link with hardening

Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Onorbe, E.; Hernándet Mayoral, M.; Gueye, P.-M.; Malerba, L.
After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities 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, FeCr(SiNiP) alloys of different composition have been ion irradiated and characterized using transmission electron microscopy, atom probe tomography and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the formation of solute clusters and dislocation loops and to make the link with irradiation hardening. Influence of C atoms on the nanostructure evolution will also be discussed.
  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29771
Publ.-Id: 29771


Neutron irradiated microstructure of FeCr alloys investigated by TEM

Hernández Mayoral, M.; Onorbe, E.; Gómez-Ferrer, B.; Heintze, C.; Malerba, L.; Gueye, P.-M.; Pareige, C.
Different parameters have been observed to influence the nature and evolution of the neutron radiation induced features, which are responsible of the mechanical behavior of FeCr-based alloys. In this work, the experimental conditions were selected so as to focus on the effect of both, composition and irradiation temperature. The study has been performed in the framework of collaborative European funded projects, where a combination of advanced characterization techniques was applied to a set of alloys of varying composition and initial microstructure, which were irradiated together under different conditions of temperature, dose and also dose-rate. The characterization of dislocation loops has been performed on the basis of Transmission Electron Microscopy (TEM), while the solute redistribution has been studied by Atom Probe Tomography (APT). The results, that show how the involved variables affect the neutron irradiated microstructure, will be presented and discussed.
  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29770
Publ.-Id: 29770


Hyperspectral outcrop models for palaeoseismic studies

Kirsch, M.ORC; Lorenz, S.; Zimmermann, R.ORC; Andreani, L.ORC; Tusa, L.; Pospiech, S.; Jackisch, R.ORC; Unger, G.; Khodadadzadeh, M.; Ghamisi, P.; Middleton, M.; Ojala, A.; Mattila, J.; Nordbäck, N.; Palmu, J.-P.; Ruskeeniemi, T.; Sutinen, R.; Tiljander, M.; Heikkilä, P.; Gloaguen, R.ORC
The traditional study of palaeoseismic trenches, involving logging, stratigraphic and structural interpretation, can be time consuming and affected by biases and inaccuracies. To overcome these limitations, a new workflow is presented that integrates infrared hyperspectral and photogrammetric data to support field-based palaeoseismic observations. As a case study, this method is applied on two palaeoseismic trenches excavated across a post-glacial fault scarp in northern Finnish Lapland. The hyperspectral imagery (HSI) is geometrically and radiometrically corrected, processed using established image processing algorithms and machine learning approaches, and co-registered to a structure-from-motion point cloud. HSI-enhanced virtual outcrop models are a useful complement to palaeoseismic field studies as they not only provide an intuitive visualisation of the outcrop and a versatile data archive, but also enable an unbiased assessment of the mineralogical composition of lithologic units and a semi-automatic delineation of contacts and deformational structures in a 3D virtual environment.
Keywords: palaeoseismology, SfM photogrammetry, hyperspectral imaging, geology, remote sensing, outcrop models

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Permalink: https://www.hzdr.de/publications/Publ-29768
Publ.-Id: 29768


Direct Synthesis of Large-Scale Multilayer TaSe2 on SiO2/Si Using Ion Beam Technology

Tsai, H.-S.; Liu, F.-W.; Liou, J.-W.; Chi, C.-C.; Tang, S.-Y.; Wang, C.ORC; Ouyang, H.; Chueh, Y.-L.; Liu, C.; Zhou, S.ORC; Woon, W.-Y.
The multilayer 1T-TaSe2 is successfully synthesized by annealing a Se-implanted Ta thin film on the SiO2/Si substrate. Material analyses confirm the 1T (octahedral) structure and the quasi-2D nature of the prepared TaSe2. Temperaturedependent resistivity reveals that the multilayer 1T-TaSe2 obtained by our method undergoes a commensurate charge-density wave (CCDW) transition at around 500 K. This synthesis process has been applied to synthesize MoSe2 and HfSe2 and expanded for synthesis of one more transition-metal dichalcogenide (TMD) material. In addition, the main issue of the process, that is, the excess metal capping on the TMD layers, is solved by the reduction of thickness of the as-deposited metal thin film in this work.
Keywords: TaSe2, charge-density wave, ion beam, synthesis

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Permalink: https://www.hzdr.de/publications/Publ-29766
Publ.-Id: 29766


Production of the amphiphilic siderophore Marinobactin for the application as froth flotation reagent. 

Schrader, S.; Kutschke, S.; Rudolph, M.ORC; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Lecture (Conference)
    23. International Biohydrometallurgy Symposium, 20.10.2019, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-29765
Publ.-Id: 29765


Amphiphilic Siderophores – A group of complexing surfactant bioreagents for the application in froth flotation separation

Schrader, S.; Kutschke, S.; Hartmann, S.; Pollmann, K.; Rudolph, M.ORC
The consumption of metallic raw materials is constantly increasing. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, new approaches will have to be developed, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in conventional froth flotation processes. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to selectively form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate functional groups, is responsible for the selective binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same and even more selective functional groups are highly potential as ecofriendly collector molecules for flotation and should generally be interesting for the surfactant industry. The molecule’s tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work includes also interaction studies and flotation experiments of different scales, including bubble pick-up tests, Halimond tube microflotation and batch lab flotation experiments of iron and copper bearing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Zerkleinern und Klassieren, Kristallisation und Grenzflächenbestimmte Systeme und Prozesse, 12.-13.03.2019, Bamberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29764
Publ.-Id: 29764


Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

Reschke, E.ORC; Konrad, U.ORC
Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien (https://www.go-fair.org/fair-principles/) zu unterstützen, wurde am HZDR ein integriertes Publikationsmanagement aufgebaut. Insbesondere Daten- und Softwarepublikationen erfordern die Entwicklung bedarfsgerechter organisatorischer und technischer Strukturen ergänzend zu bereits sehr gut funktionierenden Services im Publikationsmanagement. In der Zusammenarbeit mit Wissenschaftlern des HZDR und internationalen Partnern in ausgewählten Projekten wurde der Bedarf an Unterstützung im Forschungsdatenmanagement analysiert. Darauf aufbauend wurde schrittweise ein integriertes System von Infrastrukturen und Services entwickelt und bereitgestellt. In einer seit Mai 2018 gültigen Data Policy wurden die Rahmenbedingungen und Regelungen sowohl für wissenschaftliche Mitarbeiter als auch für externe Messgäste definiert. Im Vortrag wird auf die Erfahrungen im integrierten Publikationsmanagement für Artikel, Forschungsdaten und Forschungssoftware eingegangen und daraus resultierend werden die nächsten Aufgaben und Ziele entwickelt.
Keywords: Open Access, Research Data, Rodare, Robis, Research Infrastructure
  • Open Access Logo Invited lecture (Conferences)
    „Forschungsdaten in Sachsen: Planen – Organisieren – Nachnutzen“ – 1. sächsische FDM-Tagung, 19.09.2019, Dresden, Deutschland
    Published in the HZDR-Repository RODARE (Test)
    DOI 10.14278/rodare.353

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Permalink: https://www.hzdr.de/publications/Publ-29763
Publ.-Id: 29763


Production of the amphiphilic siderophore marinobactin and the application as froth flotation reagent

Schrader, S.; Kutschke, S.; Rudolph, M.ORC; Pollmann, K.
The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.
Keywords: Marinobactin, Marinobacter, amphiphilic, Siderophores froth flotation
  • Poster
    4th Green & Sustainable Chemistry Conference, 05.-08.05.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29762
Publ.-Id: 29762


Design and Evaluation of a STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment

Knodel, O.ORC
Overview and status of the STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment located Fermilab.
Keywords: Data Management; DAQ; FPGA; Mu2e
  • Invited lecture (Conferences)
    STM-Working Group Meeting, 09.10.2019, Batavia, United States

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Permalink: https://www.hzdr.de/publications/Publ-29759
Publ.-Id: 29759


HZDR Data Management Strategy — An Overview

Knodel, O.ORC; Müller, S.ORC
Overview of the HZDR data management strategy, hosted services for collaborative work and a (planned) technical realization.
Keywords: Data Management
  • Invited lecture (Conferences)
    Meeting with the Scientific Computing Division at Fermilab, 08.10.2019, Batavia, United States

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Permalink: https://www.hzdr.de/publications/Publ-29758
Publ.-Id: 29758


Recent progress in application of computational chemistry to actinide interaction with biomolecules

Tsushima, S.ORC
Thanks to rapid advancement in computing technology, computer chemistry is becoming increasingly important in the field of biology. This approach is nowadays a common tool for drug discovery or for studying diseases such as HIV. In this talk, I will present several examples in which computer chemistry was applied for studying potential health risk of accidental ingestion of actinides and lanthanides. The new approach called “fragment molecular orbital method” has been implemented to drastically reduce computing time, which made it possible to calculate interactions of actinide/lanthanide with large biological molecules such as DNA and protein using full quantum mechanical description. In one example, how uranium ingestion could damage DNA in a molecular scale will be presented.
  • Invited lecture (Conferences)
    Engineering Physics Seminar Series at the Department of Engineering Physics of the McMaster University, 04.10.2019, Hamilton, Canada

Permalink: https://www.hzdr.de/publications/Publ-29757
Publ.-Id: 29757


Crystallization of Anhydrous Proton from Acidic Aqueous Solution with Diamide Building Block

Kazama, H.; Tsushima, S.; Takao, K.
Although H+ has the largest hydration enthalpy amongst all the monovalent cations, we have demonstrated that anhydrous H+ can be crystallized together with selected diamide building block (L) and NO3− even in acidic aqueous solutions, which were confirmed in 3 different structures. One of these anhydrous H+ adducts constitutes of H+-involved hydrogen bond polymers [L···H+]n, which are coupled with another H+ adduct [O2NO−···H+···O−NO2]− as a counteranion unit. The anhydrous H+ can also be trapped between L and NO3− to form heteroleptic O···H+···O hydrogen bonds observed in two different crystal structures. DFT calculations revealed that there is no energetic barrier in these O···H+···O hydrogen bonds, having so-called a single-well hydrogen bond.

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Permalink: https://www.hzdr.de/publications/Publ-29756
Publ.-Id: 29756


Re-mining of mine wastes in Germany: Challenges and opportunities

Büttner, P.; Nühlen, J.; Meima, J.; Gutzmer, J.ORC
The Fraunhofer Institute for Environmental, Safety, and Energy Technology and the Helmholtz Institute Freiberg for Resource Technology (HIF) have together compiled a mine waste cadaster for Germany on behalf of the Federal Institute for Geosciences and Natural Resources (BGR). For this purpose, a wide variety of data sources was evaluated with the aim to create a national database able to provide an overview about the content of critical raw materials (CRM) in mine waste repositories in Germany. Yet, even though mine wastes containing economically significant amounts of CRM, re-mining these anthropogenic “ore bodies” faces considerable technical and non-technical challenges.

Mine wastes often create environmental problems, such as acid rock drainage with associated high sulfate and heavy metal concentrations. This creates societal pressure for remediation. Remediation, however, is usually achieved by covering the surface with a water impermeable layer, an approach that is not sustainable, because of the required follow-up care and the inaccessibility of the resources that remain contained in the mine wastes. Besides that, legislative barriers are in conflict with recovering CRM and other metals and minerals from historic mine wastes. Many sites have essentially been abandoned since mining ceased in the 20th century. High metal contents and acidity released during sulfide oxidation has facilitated the establishment of a very specific flora and fauna. Species on these sites are often rare and strictly protected by environmental legislation. Metal recovery is all but impossible from such sites, despite the fact that acid rock drainage from these sites leads to environmental degradation downstream from the mine waste site.

Another important aspect is the general lack of suitable beneficiation and metallurgical infrastructure in Germany. Large capital investment would thus be necessary to enable the recovery of strategic metals from historic mine waste. Even if high metal concentrations are present in some mine wastes, small volumes will render the set-up of large, stationary plants unfeasible. Instead, flexible and semi-mobile small-scale technologies need to be developed. Such technologies are, at present, not available on the market.

To work at the intersection of society, legislation, remediation and re-mining is the aim of the new rECOmine partnership. This partnership is funded by the Federal Ministry of Education and Research (BMBF) for the next five years within the WIR! Program. It will be coordinated by HIF and build up three test sites in Saxony to develop combined remediation and re-mining technologies under real conditions with local partners.
Keywords: Re-Mining, Mine Waste, Resource, Tailing, Feasilbility, MLA
  • Lecture (Conference)
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-29755
Publ.-Id: 29755


Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease

Palhaugen, L.; Selnes, P.; Tecelao, S.; Lysvik, E. K.; Ingala, S.; Petr, J.ORC; Bjornerud, A.; Mutsaerts, H. J.; Fladby, T.
Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease
  • Open Access Logo Contribution to proceedings
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway
  • Poster
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway

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Permalink: https://www.hzdr.de/publications/Publ-29751
Publ.-Id: 29751


Scalable particle-in-cell simulations on many-core hardware with the free and open source code PIConGPU

Steiniger, K.ORC; Bastrakov, S.ORC; Cowan, T.ORC; Debus, A.ORC; Garten, M.ORC; Göthel, I.; Hübl, A.ORC; Juckeland, G.ORC; Kelling, J.; Kluge, T.ORC; Koßagk, S.; Matthes, A.ORC; Pausch, R.ORC; Schramm, U.ORC; Starke, S.; Widera, R.ORC; Worpitz, B.; Bussmann, M.ORC
Exploring new regimes, optimizing experimental setups, or quantifying sensitivity of final beam parameters on experimental parameters, represent current challenges for simulations of laser plasma accelerators. Time-to-solution and scalability are key parameters for codes to minimize turnaround times in order to scan e.g. tens of parameters such as the laser leading edge, resolve solid density target physics and run full-scale start-to-end simulations. PIConGPU reaches unprecedented performance by accelerating 100% of its computations on many-core architectures and leveraging next-generation scalable I/O. High-resolution, full-geometry studies on top-ten listed supercomputers decisively enhance predictive capabilities. PIConGPU's design allows for utilizing various compute architectures, including modern X86 and ARM CPUs and GPUs with a single, adaptable code base. Users can now run PIConGPU on almost any machine, either by easy recompiling or using predefined Docker images, and everybody can download, use and contribute to the code without extensive knowledge in compute architectures. We highlight latest additions to PIConGPU such as scalable file I/O via a new openPMD-API including ADIOS2 support for on the fly loosely coupled data analysis, live visualization with particle and field rendering, non-standard Gaussian laser pulses via Laguerre modes, in-situ X-ray scattering image generation, and an pythonic simulation setup interface.
Keywords: PIConGPU, Manycore, Scalable I/O, Alpaka, openPMD
  • Open Access Logo Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop (EAAC2019), 15.-20.09.2019, La Biodola Bay - 57037 Portoferraio Isola d’Elba, Repubblica Italiana

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Permalink: https://www.hzdr.de/publications/Publ-29750
Publ.-Id: 29750


Origin of the butterfly magnetoresistance in a Dirac nodal-line system

Chiu, Y.-C.; Chen, K.-W.; Schönemann, R.; Quito, V. L.; Sur, S.; Zhou, Q.; Graf, D.; Kampert, W. A. G.; Förster, T.; Yang, K.; Mccandless, G. T.; Chan, J. Y.; Baumbach, R. E.; Johannes, M. D.; Balicas, L.
We report a study on the magnetotransport properties and on the Fermi surfaces (FS) of ZrSi(Se,Te) semimetals. Density-functional theory (DFT) calculations, in absence of spin orbit coupling (SOC), reveal that both the Se and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level εF at symmorphic and nonsymmorphic positions, respectively. We find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe displays low residual resistivities, pronounced magnetoresistivity, high carrier mobilities, and a butterflylike angle-dependent magnetoresistivity (AMR), although its DNL is not protected against gap opening. As in Cd3As2, its transport lifetime is found to be 102 to 103 times larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays conventional transport properties. Our evaluation indicates that both compounds most likely are topologically trivial. Nearly angle-independent effective masses with strong angle-dependent quantum lifetimes lead to the butterfly AMR in ZrSiSe.

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Permalink: https://www.hzdr.de/publications/Publ-29749
Publ.-Id: 29749


The tremendous influence of hydrogenation on magnetism of NdMnGe

Ovchenkova, I. A.; Tereshina, I. S.; Bogdanov, A. E.; Tereshina-Chitrova, E. A.; Paukov, M. A.; Gorbunov, D.; Nikitin, S. A.
The hydride NdMnGeH with the tetragonal ZrSiCuAs-type of structure (P4/nmm, N129, tP8) was obtained by hydrogen absorption at 523 K and 1 MPa from the NdMnGe intermetallic compound with a the tetragonal CeFeSi crystal structure (P4/nmm, N129, tP6). Measurements of magnetization in high magnetic fields up to 60 T and heat capacity measurements reveal pronounced changes in the magnetic properties of NdMnGe after hydrogenation. The Nd sublattice changes its ordering type from ferromagnetic to the antiferromagnetic one with a more than twofold decrease of and its magnetic ordering temperature (from 199 to 84 K). We explain the observed effects by the altered exchange interactions within the Nd sublattice resulting from the changed Nd–Nd interplane distances by interstitial atoms. The results are compared with data obtained previously for the NdMn1- xTixGe compounds, where the Ti substitution also changes significantly the magnetic properties.

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Permalink: https://www.hzdr.de/publications/Publ-29748
Publ.-Id: 29748


Noble gases and radionuclides in Washington County iron meteorite

Ott, U.; Vogt, M.; Merchel, S.ORC; Hopp, J.; Koll, D.; Lachner, J.ORC; Trieloff, M.; Wallner, A.ORC
The Washington County iron meteorite is unique in that it contains solar-type noble gases (He and Ne). We report additional noble gas analyses, supplemented by radionuclide data obtained at ANU (Canberra) and VERA (Univ. Vienna). Activities in dpm/kg measured on two specimens taken close to those analyzed for noble gases are: 5.15/5.40 (¹⁰Be); 3.46/2.66 (²⁶Al); 23.7/22.2 (³⁶Cl); 425/448 (⁵³Mn). ⁶⁰Fe is 1.09/1.29 dpm/kg Ni. Both cosmogenic noble gases and radionuclides indicate a preatmospheric radius of at most 15 cm. The ³⁶Cl-³⁶Ar cosmic ray exposure age of ~120 Ma agrees well with that of [1] based on noble gases only and is in disagreement with the much longer age (575 Ma) obtained by [2] using the ⁴¹K/⁴⁰K method. The new noble gas data further confirm that the solar noble gases are volume-correlated, an inference being that the Earth’s iron core may constitute a potential source reservoir for the solar-type Ne observed in terrestrial mantle materials.
We thank S. Beutner for ICP-MS analyses.
[1] Vogt, M. (2018), PhD Diss., Univ. Heidelberg. [2] Voshage, H. (1967) Z. Naturforsch 22a, 477–506.
Keywords: meteorite, AMS
  • Lecture (Conference)
    Paneth Kolloquium, 29.-31.10.2019, Nördlingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29747
Publ.-Id: 29747


The effect of long-range order on intermolecular interactions in organic semiconductors: zinc octaethyl porphyrin molecular thin film model systems.

Kumar, A.; Naumenko, D.; Rossi, G.; Magnano, E.; Nappini, S.; Bondino, F.; Segoloni, E.; Amidani, L.ORC; D’Acapito, F.; Boscherini, F.; Barba, L.; Pace, E.; Benfatto, M.; Casassa, S.; Pedio, M.
In order to optimize the performance of devices based on porphyrin thin films it is of great importance to gain a physical understanding of the various factors which affect their charge transport and lightharvesting properties. In this work, we have employed a multi-technique approach to study vacuum deposited zinc octaethyl porphyrin (ZnOEP) thin films with different degrees of long-range order as model systems. An asymmetrical stretching of the skeletal carbon atoms of the porphyrin conformer has been observed and attributed to ordered molecular stacking and intermolecular interactions. For ordered films, a detailed fitting analysis of the X-ray absorption near edge structure (XANES) using the MXAN code establishes a symmetry reduction in the molecular conformer involving the skeletal carbon atoms of the porphyrin ring; this highlights the consequences of increased p–p stacking of ZnOEP molecules adopting the triclinic structure. The observed asymmetrical stretching of the p conjugation network of the porphyrin structure can have significant implications for charge transport and light harvesting, significantly influencing the performance of porphyrin based devices.

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  • Secondary publication expected from 07.11.2020

Permalink: https://www.hzdr.de/publications/Publ-29746
Publ.-Id: 29746


THz relaxation dynamics and nonlinear optics in graphene

Helm, M.
Graphene, because of its peculiar linear band structure, shows some fascinating effects in the relaxation processes of excited electrons. Due to the zero band gap, many of those processes are best investigated at low energies, in the THz region. By linearly polarized pump-probe measurements we show that fast thermalization occurs only with respect to energy, but not to momentum, i.e. the electron distribution remains anisotropic for more than 5 ps (Phys. Rev. Lett. 117, 087401 (2016)). Applying a magnetic field splits the bands into non-equidistant Landau levels. This gives rise to a situation, where strong pumping of a Landau level actually leads to its depletion, due to strong Auger type electron-electron scattering (Nat. Phys. 11, 75 (2015)). In the same system, a large, resonant third-order optical nonlinearity is demonstrated via degenerate four-wave mixing (Nano Lett. 17, 2184 (2017)). All experiments were performed with a THz free-electron laser at frequencies around 20 THz, in collaboration with M. Mittendorff, J. König-Otto, S. Winnerl, A. Pashkin H. Schneider, with theory support by F. Wendler, T. Winzer, F. Kadi, E. Malic, A. Knorr, Y. Wang, A. Belyanin, and samples from W. de Heer and C. Berger.
Keywords: free electron laser, graphene, terahertz, relaxation, nonlinear optics
  • Invited lecture (Conferences)
    2D Materials 2019, 30.09.-04.10.2019, Sochi, Russia

Permalink: https://www.hzdr.de/publications/Publ-29745
Publ.-Id: 29745


Challenges for MR integrated Particle Therapy (MRiPT)

Lühr, A.ORC
The increasing interest for particle therapy (PT) builds on its unique depth-dose characteristics, which are exploited to achieve a significant reduction in normal-tissue dose deposition proximal and distal to the tumor volume. At the same time, this feature makes PT more susceptible to morphological variations (i.e. anatomical changes and organ motion) and patient set-up uncertainties than conventional high-energy X-ray therapy (XT).
The integration of magnetic resonance (MR) imaging and PT (MRiPT) at treatment isocenter would offer an opportunity to fully exploit the dosimetric benefit of PT and realize its true clinical potential, especially for moving tumors in the thorax and abdomen. The unparalleled soft-tissue contrast and real-time imaging capabilities provided by MR imaging allow for online tumor tracking and plan adaptation. Given the steep dose gradients of PT, its targeting accuracy is expected to benefit even more from MR-guidance than XT performed with hybrid MR-linear accelerator systems. Therefore, as a next step in the technological development of image-guided radiation therapy, the concept of integrating real-time MR image guidance with PT has gained significant interest in the scientific community over the past few years.
In this presentation, a number of technological challenges will be discussed that need to be overcome before patient treatment with MRiPT can safely be realized. These challenges include the following aspects: (a) distortion of the proton dose distribution by the magnetic fields of the MR scanner, (b) impact on the MR image quality by the static and dynamic electromagnetic fields of a PT facility, and (c) integration of the MR and PT systems for online adaptive treatment. Furthermore, the current status of a first functional proof-of-concept system for in-beam MR imaging at a PT research beam line installed at OncoRay in Dresden, Germany will be presented.
  • Invited lecture (Conferences)
    ESTRO meets Asia 2019, 06.-08.12.2019, Singapore, Singapore

Permalink: https://www.hzdr.de/publications/Publ-29744
Publ.-Id: 29744


Infrared nanospectroscopy at cryogenic temperatures and on semiconductor nanowires

Lang, D.ORC
This PhD thesis concentrates on scattering scanning near-field infrared microscopy (s-SNIM) which utilizes the radiation from the free-electron laser (FEL) at the Helmholtz-Zentrum Dresden-Rossendorf. The FEL is an intense, narrow-band radiation source, tunable from the mid- to far-infrared spectral range (5 meV to 250 meV). The s-SNIM technique enables infrared microscopy and spectroscopy with a wavelength-independent spatial resolution of about 10nm. The first part demonstrates the extension of s-SNIM at the FEL towards cryogenic temperatures as low as 5K. To this end, we show the functionality of our low-temperature s-SNIM apparatus on different samples such as Au, structured Si/SiO2, as well as the multiferroic material gallium vanadium sulfide (GaV4S8). The latter material recently attracted a lot of interest since it hosts a Néel-type skyrmion lattice – a periodic array of spin vortices. Below T = 42K, GaV4S8 undergoes a structural phase transition and then forms ferroelectric domains, which we can map out by low-tempererature s-SNIM. Notably, we found a strong impact on the ferroelectric domains upon infrared irradiation, which we further utilize to calibrate the local heat contribution of the focused infrared beam beneath the s-SNIM probe.
The second part of this thesis contains comprehensive s-SNIM investigations of high-quality semiconductor nanowires (NWs) rown by molecular beam epitaxy. Such NWs are promising building blocks for fast (opto-)electronic nanodevices, amongst thers due to their high carrier mobility. We have examined highly doped GaAs/InGaAs core/shell NWs and observed a strong and spectrally sharp plasmonic resonance at about hw = 125 meV, using a continuous wave CO2 laser for probing. If we probe the same NWs utilizing the intense, pulsed FEL radiation, we observe a pronounced redshift to hw < 100 meV and a broading of the plasmonic response. This nonlinear response is most likely induced by heating of the electron gas upon irradiation by the strong FEL pulses. Our observations open up the possibility to actively induce and observe non-equilibrium states in s-SNIM directly by the mid-infrared beam. Beside the nonlinear effect, we prepared and measured cross sections of both homogeneously-doped and modulation-doped core/shell NWs.
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-105 2019

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Permalink: https://www.hzdr.de/publications/Publ-29741
Publ.-Id: 29741


Reducible contributions to quantum electrodynamics in external fields

Ahmadiniaz, N.ORC; Edwards, J. P.; Ilderton, A.
We consider one-particle reducible (1PR) contributions to QED and scalar QED processes in external fields, at one-loop and two-loop order. We investigate three cases in detail: constant crossed fields, constant magnetic fields, and plane waves. We find that 1PR tadpole contributions in plane waves and constant crossed fields are non-zero, but contribute only divergences to be renormalised away. In constant magnetic fields, on the other hand, tadpole contributions give physical corrections to processes at one-loop and beyond. Our calculations are exact in the external fields and we give strong and weak field expansions in the magnetic case.

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Permalink: https://www.hzdr.de/publications/Publ-29739
Publ.-Id: 29739


Compton-like scattering of a scalar particle with N photons and one graviton

Ahmadiniaz, N.; Balli, F. M.; Corradini, O.; Dávila, J. M.; Schubert, C.
Tree-level scattering amplitudes for a scalar particle coupled to an arbitrary number N of photons and a single graviton are computed. We employ the worldline formalism as the main tool to compute the irreducible part of the amplitude, where all the photons and the graviton are directly attached to the scalar line, then derive a tree replacement rule to construct the reducible parts of the amplitude which involve irreducible pure N-photon two-scalar amplitudes where one photon line emits the graviton. We test our construction by verifying the on-shell gauge and diffeomorphism Ward identities, at arbitrary N.
Keywords: Scattering amplitudes, gravitons, Ward identities

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Permalink: https://www.hzdr.de/publications/Publ-29738
Publ.-Id: 29738


Compliant magnetic field sensors for flexible electronics

Makarov, D.
I will review our recent activities on compliant magnetic field sensors.
Keywords: flexible electronics, shapeable magnetoelectronis
  • Invited lecture (Conferences)
    FFlexCom Meeting 2019; DFG Priority Programme “High Frequency Flexible Bendable Electronics for Wireless Communication Systems”, SPP 1796, 07.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29737
Publ.-Id: 29737


Helium interactions with (Y, Ti, O) nanoclusters in bcc Fe

Vallinayagam, M.; Posselt, M.ORC; Faßbender, J.ORC
Nanometer size (Y, Ti, O) clusters in nanostructured ferritic/martensitic Fe-Cr alloys can act as sinks for the transmutation product helium. In this manner irradiation swelling can be retarded significantly. Many details of He storage in or near the clusters are still not understood. In this work interactions of He with (Y, Ti, O) clusters in bcc Fe are investigated by density functional theory (DFT) calculations. Four different cluster structures studied in our previous work [1] are considered: Cage-type clusters with (i) 6 O atoms, 9 vacancies (v) and 6 Y atoms, and (ii) with 7 O, 9 v, 3 Y, and 3 Ti, as well as clusters with O in the center containing (iii) 6 O, 9 v, 6 Y, and (iv) 7 O, 9 v, 3 Y, 3 Ti. It is found that the most stable position of He is in the center of the cluster, followed by the interfacial substitutional site and other interstitial positions between metal or oxygen atoms, and sites away from the cluster. This shows the He trapping may be nearly irrespective of cluster morphology and mainly depend on cluster composition. Adding a second He atom to the cluster structure is investigated for selected cases. Furthermore, barriers for possible jumps between different sites at the rim of the cluster and the center are determined. First results show that these barriers are higher if the cluster contains Ti and that there is a strong dependence on the particular position at the rim. For the discussion of the results also the DFT data obtained from studies on the interaction of He with single O, Y, and Ti atoms as well as with a single vacancy are used.

[1] Vallinayagam et.al. Investigation of structural models for O-Y and O-Y-Ti clusters in bcc Fe: A DFT study J. Phys.: Condens. Matter (2018) https://doi.org/10.1088/1361-648X/aaf9cd
Keywords: DFT ODS He storage
  • Lecture (Conference)
    EUROMAT-2019 Conference, 01.-05.09.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-29736
Publ.-Id: 29736


Validating the Predictive Power of Statistical Models in Retrieving Leaf Dry Matter Content of a Coastal Wetland from a Sentinel-2 Image

Ali, A. M.; Darvishzadeh, R.; Rafiezadeh Shahi, K.; Skidmore, A.
Leaf dry matter content (LDMC), the ratio of leaf dry mass to its fresh mass, is a key plant trait, which is an indicator for many critical aspects of plant growth and survival. Accurate and fast detection of the spatiotemporal dynamics of LDMC would help understanding plants' carbon assimilation and relative growth rate, and may then be used as an input for vegetation process models to monitor ecosystems. Satellite remote sensing is an effective tool for predicting such plant traits non-destructively. However, studies on the applicability of remote sensing for LDMC retrieval are scarce. Only a few studies have looked into the practicality of using remotely sensed data for the prediction of LDMC in a forest ecosystem. In this study, we assessed the performance of partial least squares regression (PLSR) plus 11 widely used vegetation indices (VIs), calculated based on different combinations of Sentinel-2 bands, in predicting LDMC in a coastal wetland. The accuracy of the selected methods was validated using LDMC, destructively measured in 50 randomly distributed sample plots at the study site in Schiermonnikoog, the Netherlands. The PLSR applied to canopy reflectance of Sentinel-2 bands resulted in accurate prediction of LDMC (coefficient of determination (R-2) = 0.71, RMSE = 0.033). PLSR applied to the studied VIs provided an R-2 of 0.70 and RMSE of 0.033. Four vegetation indices (enhanced vegetation index(EVI), specific leaf area vegetation index (SLAVI), simple ratio vegetation index (SRVI), and visible atmospherically resistant index (VARI)) computed using band 3 (green) and band 11 of the Sentinel-2 performed equally well and achieved a good measure of accuracy (R-2 = 0.67, RMSE = 0.034). Our findings demonstrate the feasibility of using Sentinel-2 surface reflectance data to map LDMC in a coastal wetland.
Keywords: LDMC; PLSR; vegetation indices; Sentinel-2; wetland

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Permalink: https://www.hzdr.de/publications/Publ-29735
Publ.-Id: 29735


First principles calculations of the thermodynamic stability of Ba, Zr, and O vacancies in BaZrO3

Nadarajan, R.; Devaraj, M.; Satyanarayana, S. V. M.; Posselt, M.ORC
The temperature dependence of the stability of bulk BaZrO3 (BZO) and of the vacancies in this material is investigated by considering phonon contributions to the free energy. The stability diagram of BZO is determined for different chemical environments. With increasing temperature the stability region becomes smaller which is particularly caused by the strong temperature dependence of the chemical potential of gaseous oxygen. The free formation energy of Ba, Zr, and O vacancies in BZO is calculated for all possible charge states and for different atomic reservoirs. While the free formation energy of Zr vacancies is strongly influenced by temperature a weaker dependence is found for Ba and O vacancies. This has also an effect on the charge transition levels at different temperatures. Present results demonstrate that O poor reservoir conditions and a Fermi level close to the valence band maximum favour a high concentration of doubly positively charged O vacancies which is a prerequisite to get a large number of protonic defects and a good proton conductivity. In such a chemical environment the amount of Ba and Zr vacancies is low so that Ba and Zr deficiencies are not an important issue and BZO stays sufficiently stable.
Keywords: DFT, Barium Zirconate, thermodynamic stability, vacancies

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Permalink: https://www.hzdr.de/publications/Publ-29734
Publ.-Id: 29734


Comparison of Eulerian QBMM and classical Eulerian – Eulerian method for the simulation of polydisperse bubbly flows

Li, D.; Marchisio, D.; Hasse, C.; Lucas, D.
The spatial gas distribution of poly-disperse bubbly flows depends greatly on the bubble size. To reflect the resulting polycelerity, more than two momentum balance equations (typically for the gas and liquid phases) have to be considered, as done in the multifluid approach. The inhomogeneous multiple-size group model follows this approach, also combined with a population balance model. As an alternative, in a previous work, an Eulerian quadrature-based moments method (E-QBMM) was implemented in OpenFOAM; however, only the drag force was included. In this work, different nondrag forces (lift, wall lubrication, and turbulent dispersion) are added to enable more complex test cases to be simulated. Simulation results obtained using E-QBMM are compared with the classical E – E method and validated against experimental data for different test cases. The results show that there is good agreement between E-QBMM and E – E methods for mono-disperse cases, but E-QBMM can better simulate the separation and segregation of small and large bubbles.
Keywords: bubbly flow, E – E method, E-QBMM, non-drag forces, wall peak

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Permalink: https://www.hzdr.de/publications/Publ-29733
Publ.-Id: 29733


Radio- and photosensitization of plasmid DNA by DNA binding ligand propidium iodide: Investigation of Auger electron induction and detection of Cherenkov-emission

Kotzerke, J.; Runge, R.; Gotze, P.; Wunderlich, G.; Enghardt, W.; Freudenberg, R.
Purpose We investigated whether propidium iodide (PI) enhances DNA damaging effects of ionizing and non-ionizing radiation species (X-rays, alpha-, beta-, auger electron emission and light of various wavelengths, respectively). This biophysical experimental setting allowed us, furthermore, to investigate whether Cherenkov emission can be detected by photodynamic effects and increased DNA damage.
Material and methods Conformation changes of plasmid DNA were detected and quantified by gelelectrophoresis and fluorescence imaging. Hydrogen peroxide, stannous dichloride, and dimethylsulfoxide were used as chemical modulators, Tc-99m, Re-188, Ra-223, and x-ray (32 kV and 200 kV) reflected radiotoxicity and light (lambda = 254 nm, 366 nm and 530-575 nm) induced phototoxicity.
Results Radiotracers and x-rays induced dose dependent DNA damage. PI did not serve as radiosensitizer in radioisotopes, while a low effect was detected in X-rays. The phototoxicity was dependent on the wavelengths of light. Light with a wavelength range of 530-575 nm in combination with PI resulted in direct DNA damage. The yield of Cherenkov emission was far below the photon emission of light irradiation and not distinguishable from general radiotoxicity.
Conclusions PI binds to plasmid DNA, is not chemotoxic, and increases radiotoxicity only to minor extent. Phototoxicity and its stimulation by PI is dependent on the wavelength of the light. No kind of energy deposition was capable of inducing an Auger electron cascade.
Furthermore, no increase in DNA damage induced by photodynamic effects from Cherenkov emission was detectable.
Keywords: Probidium Iodide, Plasmid DNA, Auger Electrons, Cherenkov Emission

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Permalink: https://www.hzdr.de/publications/Publ-29732
Publ.-Id: 29732


Comparable radiation response of ex vivo and in vivo irradiated tumor samples determined by residual γH2AX

Rassamegevanon, T.; Löck, S.; Baumann, M.; Krause, M.ORC; von Neubeck, C.
Purpose: a) To investigate if an ex vivo cultured and irradiated tumor biopsy reflects and predicts the radiation response of the corresponding in vivo irradiated tumor measured with the DNA double strand break marker γH2AX foci. Materials and methods: Five human head and neck squamous cell carcinoma (hHNSCC) xenograft models were used. Fine needle biopsies were taken from anesthetized tumor-bearing NMRI nude mice prior to in vivo single dose irradiation (0, 2, 4, or 8 Gy) under ambient blood flow. Biopsies were ex vivo reoxygenated and irradiated with equivalent doses. Tumors and biopsies were fixed 24 h post irradiation, and γH2AX foci were assessed in oxygenated tumor regions. Results: Linear regression analysis showed comparable slopes of the residual γH2AX foci dose–response curves in four out of five hHNSCC models when in vivo and ex vivo cohorts were compared. The slopes from ex vivo biopsies and in vivo tumors could classify the respective tumor model as sensitive or resistant according to the intrinsic radiation sensitivity (TCD50). Conclusion: The ability of ex vivo irradiated tumor biopsies to reflect and predict the intrinsic radiation response of in vivo tumors increases the translational potential of the ex vivo γH2AX foci assay as a diagnostic tool for clinical practice. © 2019 Elsevier B.V.
Keywords: Intrinsic radiation sensitivity, Predictive biomarker, Radiation therapy, γH2AX foci

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  • Secondary publication expected from 21.08.2020

Permalink: https://www.hzdr.de/publications/Publ-29730
Publ.-Id: 29730


Lift Forces on Solid Spherical Particles in Wall-bounded Flows

Shi, P.ORC; Rzehak, R.
The present work is concerned with the lift forces acting on particles immersed in a wall-bounded fluid. Conditions where the particle translates in a fluid at rest and in a linear shear flow are considered. Likewise, non-rotating particles and particles in free rotation driven solely by the flow are considered. Furthermore, situations where the wall lies in the inner region and in the outer region of the flow disturbance produced by the particle are distinguished. The focus is on solid spherical particles at Reynolds numbers up to O(〖10〗^2 ) which are relevant for particulate flows in chemical and minerals engineering. A comprehensive review of existing results from analytical, experimental, and direct numerical simulation studies is given. The available correlations are critically assessed by comparison to data from these studies. Based on the comparison recommendations are given which correlations to use, including some new proposals, and gaps in the data are identified.
Keywords: lift force, particles, wall-bounded flow, particle rotation, inner / outer region, correlation

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Permalink: https://www.hzdr.de/publications/Publ-29729
Publ.-Id: 29729


Au incorporation into various ZnO crystallographic cuts realised by ion implantation – ZnO damage characterization

Mackova, A.; Malinsky, P.; Jagerova, A.; Miksova, R.; Nekvindova, P.; Cajzl, J.; Böttger, R.; Akhmadaliev, S.
Non-polar surfaces, such as a-plane (11–20) and m-plane (10-10), for ZnO have become more attractive as numerous efforts have recently been made to grow non-polar ZnO facets for applications in nanoscale photonic devices. Noble-metal incorporation into transparent semiconductors such as ZnO has been investigated because of the non-linear optical response of such structures. This paper presents a study of defect evolution in various ZnO crystallographic cuts caused by Au implantation. The investigation has focused on ZnO structure characterisation, Au distribution and the interior morphology of the a-, m- and c-planes ZnO single crystals implanted with 400 keV Au+ ions at the ion fluences of 5 × 1014 and 1 × 1015 cm−2 and subsequently annealed at 600 °C in O2. The structure modification was studied using Rutherford backscattering spectrometry (RBS) in the channelling mode (RBS/C) and Raman spectroscopy. After the ion-implantation process, low surface damage was observed in all ZnO orientations unlike deep structural damage. Deep structural damage grew with increased Au-ion fluence and Au did not exhibit strong out-diffusion from the depth to the surface during the post-implantation annealing. Small but noticeable differences were observed between different ZnO orientations. RBS measurements during ion implantation revealed more progressive deep-damage formation in the c- and m-planes than in the a-plane ZnO. Simultaneously, the smallest Zn sub-lattice disorder deduced from RBS/C measurements was observed in the a-plane ZnO. During post-implantation annealing, a slight structure recovery (about 4%) was observed in all orientations. Raman spectroscopy confirmed the increasing structure disorder with the enhanced ion fluence for all as-implanted ZnO orientations and a partial reconstruction of the ZnO structure during annealing, when the intensity of E2 phonons was increased and that of longitudinal optical (LO) phonons was suppressed because of the disorder recovery. E2 (high) and E1(LO) Raman phonon modes connected with oxygen sub-lattice ordering/disordering have been investigated in detail – they show a significant modification mainly in the m-plane. The cause of the different behaviour of ZnO planes as well as the differences in the incorporation and movement of Au and Er atoms in the ZnO structure are discussed in the work.

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Permalink: https://www.hzdr.de/publications/Publ-29728
Publ.-Id: 29728


Entwicklung des Gesamtsystems - Stand der Modellierungs- und Simulationsarbeiten

Fogel, S.ORC
Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)
  • Lecture (others)
    5. Projekttreffen DELTA, 25.04.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29727
Publ.-Id: 29727


3. Zwischenbericht DELTA

Fogel, S.ORC
Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)
  • Other report
    Dresden: HZDR, 2019
    27 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29726
Publ.-Id: 29726


Single Cell and System Modeling of Tubular Proton Conducting Solid Oxide Steam Electrolyzers for Intermittent Operation

Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Due to the constantly growing utilization of wind and solar energy, the demand for technologies for temporal and spatial decoupling of energy provision and consumption is steadily increasing. The application of proton-conducting solid oxide electrolysis cells (H-SOEC) has been a main concern in recent research activities since they offer an environmentally friendly and efficient technique for the conversion of excess energy into hydrogen. As renewables occur intermittently, SOEC designs and all employed materials have to be capable of withstanding large electrical transients and therefore harsh operating conditions. Tubular cell designs of SOEC received increased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat, thermal cycling, thermal stresses and high-pressure application capabilities. Since the knowledge of the dynamic behavior of SOECs is key to their future application, this work aims to study the transient behavior of a single, proton conducting SOEC during rapid load variations and of multi-tubular stacks on a system scale under high-pressure operation. The use of different load variation speeds is discussed with respect to cell control.
Keywords: SOEC, load variation, transient operation, tubular cell, proton conduction
  • Lecture (Conference)
    12th European Congress of Chemical Engineering ECCE, 15.-19.09.2019, Florence, Italy

Permalink: https://www.hzdr.de/publications/Publ-29725
Publ.-Id: 29725


Transient Operation of Tubular H-SOECs for Hydrogen Production in CCU Processes

Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Since the utilization of wind and solar energy is constantly growing, the demand for technologies for temporal and spatial decoupling of energy provision and consumption is steadily increasing. The application of proton-conducting solid oxide electrolysis cells (H-SOECs) has been a main concern of recent research activities since they offer an environmentally friendly and efficient technique for the conversion of excess energy and steam into hydrogen. An appropriate coupling of stationary carbon dioxide (CO2) emitters and consumers offers a promising option for chemical energy storage and the production of valuable chemicals (e.g. methanol). Using electrolytic hydrogen production together with suitable downstream syntheses units as combined power-to-liquid technologies, a promising method for the recycling of carbon dioxide (CCU) can be provided. Since renewables occur intermittently, SOECs have to be capable of withstanding harsh operating conditions and the knowledge of their dynamic behavior is crucial for their future system application. This work studies the transient behavior of a single tubular, proton conducting SOEC during rapid load variations through 2D-FEM single cell and quasi-2D system scale simulations and evaluates the usability of the cell in combination with fluctuating loads.
Keywords: SOEC, dynamic operation, CCU, hydrogen, proton conduction, renewable energy
  • Poster
    17th International Conference on Carbon Dioxide Utilization ICCDU 2019, 23.-27.06.2019, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29724
Publ.-Id: 29724


Transient behavior of tubular solid oxide electrolyzer cells under fast load variations

Fogel, S.ORC; Kryk, H.; Hampel, U.ORC
Solid oxide electrolyzer cells (SOEC) pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOEC under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conver-sion efficiency and application. As a consequence of the intermittent occurrence of renewables, SOEC designs and all employed materials have to be capable of with-standing harsh operating conditions, leading to strict demands regarding process control and the overall cell design. Tubular cell designs of SOECs received in-creased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat and thermal stresses. Further-more, tubular cells are characterized by significantly smaller sealing lengths in com-parison to planar cells, enabling a high-pressure application. Operating SOECs at elevated pressures poses beneficial opportunities for their future system application, since the produced hydrogen does not need to be compressed using a separate compressor stage or the electrolyzer can be combined with promising downstream synthesis units (e.g. methanol synthesis). Dynamic simulations can be used to de-termine the transient behavior of SOECs during operation with harsh load-transients. This simulation work aimed to study the transient behavior of a single, proton conducting SOEC during rapid load variations under high-pressure opera-tion. For this purpose, a two-dimensional model of a tubular SOEC was developed and different load steps and their influence on crucial operational parameters, such as temperature profiles, cell potential and species concentrations were investigated. The feasibility of the cell design regarding harsh transient load variations was stud-ied. Various load-pulse shapes and durations, different flow configurations and steam mass flow rates have been investigated and their influence on the short-term transient behavior of the cell were examined. With the aid of the aforementioned simulations, limiting operational states of the cell (e.g. steam starvation and tempera-ture hot-spots) as well as beneficial process parameter combinations for an im-proved cell operational behavior were ought to be identified with respect to advanc-es in cell control strategies.
Keywords: SOEC, dynamic operation, proton conduction
  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 06.-07.03.2019, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29723
Publ.-Id: 29723


Analog of cosmological particle creation in electromagnetic waveguides

Lang, S.ORC; Schützhold, R.
We consider an electromagnetic waveguide with a time-dependent propagation speed v(t) as an analog for cosmological particle creation. In contrast to most previous studies which focus on the number of particles produced, we calculate the corresponding two-point correlation function. For a small steplike variation delta v(t), this correlator displays characteristic signatures of particle pair creation. As another potential advantage, this observable is of first order in the perturbation delta v(t), whereas the particle number is second order in delta v(t) and thus more strongly suppressed for small delta v(t).

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Permalink: https://www.hzdr.de/publications/Publ-29722
Publ.-Id: 29722


Update the MUSIG model in ANSYS CFX for reliable modelling of bubble coalescence and breakup

Liao, Y.
The MUSIG (Multiple Size Group) model in the commercial CFD code ANSYS CFX is a population balance approach for describing binary bubble coalescence and breakup events. It is widely used in the simulation of poly-dispersed bubble flows. The purpose of this work is to identify some inconsistencies in the discrete method that applied for the solution of the population balance equation in MUSIG, and propose an improved one for discretising the source and sink terms that result from bubble coalescence and breakup. The new formulation is superior to the existing ones in preserving both mass and number density of bubbles, allowing arbitrary discretisation schemes and free of costly numerical integrations. The numerical results on the evolution of bubble size distributions in bubble flows reveal that the inconsistency in the original MUSIG regarding bubble breakup is non-negligible in both academic and practical cases. The updates presented in this work are necessary and important for calibration of bubble coalescence and breakup models using the MUSIG approach.
Keywords: MUSIG; ANSYS CFX; Coalescence and breakup; Method of classes; Discrete formulation; Population balance equation

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  • Secondary publication expected from 15.01.2021

Permalink: https://www.hzdr.de/publications/Publ-29721
Publ.-Id: 29721


Synthesis, Structural Characterisation, and Cytotoxicity Studies of Bi, W, and Mo containing Homo- and Hetero-bimetallic Polyoxometalates

Senevirathna, D.; Werrett, M.; Kubeil, M.ORC; Stephan, H.ORC; Andrews, P.
Three new and different homo- and hetero-bimetallic polyoxometalate (POM) species have been synthesised by simple one-pot synthetic methods utilising naturally occurring bismite (Bi2O3) (or Bi(NO3)3·5H2O) and aryl sulfonic acids. The POM species isolated are {(NH4)14[Bi2W22O76]·14H2O} (1·14H2O), {NH4[Bi(DMSO)7][Mo8O26]·H2O} (2·H2O) and {[(NH4)4(Mo36O108(OH)4·16H2O)]·45H2O} (3·45H2O). The compounds have been characterised by X-ray crystallography, energy dispersive X-ray spectroscopy (EDX), powdered X-ray diffraction (PXRD), mass spectrometry (ESI-MS), Raman spectroscopy, thermogravimetric (TGA) and ICP analyis. In vitro cytoxicity and proliferation studies conducted on 1 and 3, highlight the low toxicity of these species.

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  • Secondary publication expected from 01.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29719
Publ.-Id: 29719


Effect of nozzle geometry on pressure drop in submerged gas injection

Xiao, J.; Yan, H.-J.; Schubert, M.; Unger, S.; Liu, L.; Schleicher, E.; Hampel, U.ORC
Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths.
Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter AoL o −2 and on the modified Froude number gd o 5 Q−2 with the hydraulic diameter of the nozzle do as characteristic length.
Keywords: submerged gas injection; nozzle geometry; hydraulic diameter; pressure drop; modified Euler number

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Permalink: https://www.hzdr.de/publications/Publ-29718
Publ.-Id: 29718


Effect of Bath Depth and Nozzle Geometry on Spout Height in Submerged Gas Injection at Bottom

Xiao, J.; Yan, H.; Liu, L.; Möller, F.; Hu, Z.; Unger, S.
Spout height is a widely used parameter to quantitatively analyze the performance of the submerged gas injection in industrial applications. However, the effect of bath depth and nozzle geometry on spout height in submerged gas injection is still unclear. In this work, the effect of bath depth and nozzle geometry on spout height in submerged gas injection at bottom was experimentally investigated. Circular-shaped, three-leaf-shaped, four-leaf-shaped, and four-flower-shaped nozzles were used for this study. Spout height was extracted from the images captured by high-speed camera and analyzed by digital image processing. The results indicate that the effect of nozzle geometry on spout height is as important as gas flow rate and bath depth. Through dimensional analysis, predictive correlations of spout height from circular shape and four-leaf shape were developed with dimensionless bath depth and a modified Froude number using orifice perimeter and opening area as characteristic parameters. Experimental data were compared with the correlations from literature and good agreement was found.

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Permalink: https://www.hzdr.de/publications/Publ-29717
Publ.-Id: 29717


Control and stimulation of three-magnon scattering in a magnetic vortex

Körber, L.ORC; Schultheiß, K.ORC; Hula, T.; Verba, R.ORC; Hache, T.ORC; Schultheiß, H.ORC
When applying a large enough RF field amplitude, spin waves in a magnetic vortex disk can decay into two other spin waves via three-magnon scattering. In order to reach the threshold of this process, the energy flux from the decay of the directly excited mode must overcome the internal losses of the secondary modes. The resulting scattering processes obey certain selection rules which result in the two output frequencies to be distinct from one another. Moreover, three-magnon scattering of the directly excited mode into multiple pairs of secondary modes is possible. However, typically one of these scattering channels has a lower threshold than the others which leads to this channel being activated first and limiting the energy flux in the other possible “silent” channels. Here, we show that three-magnon scattering in such a system can be stimulated below the usual instability threshold by additionaly pumping one of the secondary modes. This is achieved by coupling the magnetic vortex to an adjacent magnonic wave guide. The response to the stimulation is instantaneous and can be used to activate the silent three-magnon channels, as well.
Keywords: nonlinear, magnon, vortex, magnetism, magnonics
  • Lecture (Conference)
    Magnonics 2019, 28.07.-01.08.2019, Carovigno, Italien

Permalink: https://www.hzdr.de/publications/Publ-29716
Publ.-Id: 29716


Liquid metal battery research activities at HZDR

Weier, T.; Horstmann, G. M.ORC; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.
Liquid metal batteries are promising candidates for low-cost, large-scale stationary electricity storage. Different systems investigated at HZDR are discussed with a focus on fluid dynamic phenomena like interfacial wave interactions, mass transfer, and electro-vortex flows.
Keywords: liquid metal batteries, mass transfer, electro-vortex flows
  • Invited lecture (Conferences)
    Institutskolloquium Institut für Thermo- und Fluiddynamik TU Ilmenau, 12.09.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29715
Publ.-Id: 29715


Anisotropic temperature-field phase diagram of single crystalline β-Li2IrO3: Magnetization, specific heat, and 7Li NMR study

Majumder, M.; Freund, F.; Dey, T.; Prinz-Zwick, M.; Büttgen, N.; Scurschii, I.; Jesche, A.; Tsirlin, A. A.; Gegenwart, P.
Detailed magnetization, specific heat, and 7Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyperhoneycomb Kitaev magnet β-Li2IrO3 are reported. At high temperatures, anisotropy of the magnetization is reflected by the different Curie-Weiss temperatures for different field directions, in agreement with the combination of a ferromagnetic Kitaev interaction (K) and a negative off-diagonal anisotropy (Γ) as two leading terms in the spin Hamiltonian. At low temperatures, magnetic fields applied along a or c have only a weak effect on the system and reduce the Néel temperature from 38 K at 0 T to about 35.5 K at 14 T, with no field-induced transitions observed up to 58 T on a powder sample. In contrast, the field applied along b causes a drastic reduction in the TN that vanishes around Hc = 2.8 T, giving way to a crossover toward a quantum paramagnetic state. Li NMR measurements in this field-induced state reveal a gradual line broadening and a continuous evolution of the line shift with temperature, suggesting the development of local magnetic fields. The spin-lattice relaxation rate shows a peak around the crossover temperature 40 K and follows power-law behavior below this temperature.

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Permalink: https://www.hzdr.de/publications/Publ-29713
Publ.-Id: 29713


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