Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32628 Publications
Thermal-hydraulic insights during a main steam line break in a generic PWR KONVOI reactor with ATHLET 3.1A
Diaz Pescador, E.; Schäfer, F.; Kliem, S.ORC
The present paper gathers the main insights obtained during the numerical simulation of a 10 % main steam line break (MSLB) in a generic German PWR KONVOI reactor with the thermal-hydraulic system code ATHLET 3.1 A. The contents of this paper are focused first on the transient thermal-hydraulic calculation during affected steam generator (SG) 1 boil-off and subsequently on the multidimensional fluid mixing study of the overcooled water stream and the coolant in the reactor pressure vessel. With this aim, the boundary conditions from the test PKL G3.1, carried out at the PKL test facility in the framework of the OECD/PKL-II project, are implemented in the simulation over the plant nominal parameters from the KONVOI reactor. The thermal-hydraulic and fluid mixing results obtained in the simulations are qualitatively assessed against suitable experimental data from the PKL and ROCOM test facilities, showing a good agreement between simulation and test behaviour.

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  • Secondary publication expected from 01.10.2020

Permalink: https://www.hzdr.de/publications/Publ-30096
Publ.-Id: 30096


Definition of geochemical domains in a chromite mine, Bushveld Complex, South Africa
Bachmann, K.; Menzel, P.; Tolosana Delgado, R.; Gutzmer, J.ORC
The Lower and Middle Group chromitites of the Bushveld Complex are the source of a very large portion of the global chrome supply. Yet, the effectiveness of chromite beneficiation circuits is highly sensitive to mineralogical and textural variations in feed composition. The use of geochemical proxies, based on data acquired routinely during the exploration and mining process may provide a cost- and time-efficient alternative to more time-consuming and expensive mineralogical analyses. Such an approach is presented in this study, which focuses on the LG-6, LG-6A, MG-1 and MG-2 chromitite seams at the Thaba mine located on the western limb of the Bushveld Complex. According to a sound statistical assessment, the chromitites of the Thaba mine area can be subdivided into three distinct domains, domains that constitute the suitable fundament for a geometallurgical model. Accordingly, a least altered (orthomagmatic) domain is distinguished from a supergene altered domain and a domain affected by widespread hydrothermal alteration. The latter domain occurs below the depth of modern weathering, but in obvious proximity to faults and around a prominent dunite pipe. The orthomagmatic domain is represented by ores least affected by post-magmatic alteration processes. This domain occupies the centre of fault blocks below the extent of modern weathering.
  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30081
Publ.-Id: 30081


Lower Group and Middle Group chromitites of the Bushveld Complex – the effect of weathering on the distribution of platinum-group elements
Junge, M.; Bachmann, K.; Oberthür, T.; Groshev, N. Y.;
The Bushveld Complex in South African contains vast resources of Cr, PGE and V. Currently, the Merensky Reef, the Platreef and the UG-2 chromitite seam are the major mining targets for PGE, although chromitites of the Lower Group (LG) and Middle Group (MG) may also contain concentrations up to several ppm PGE.
In a suite of chromitite samples from the Thaba Mine in the western Bushveld Complex it was shown that Pt concentrations in weathered chromitite seams (LG-6 to MG-4) generally exceed those of Pd. However, differences are observed by comparing individual chromitite seams as total PGE concentrations of weathered chromitites from the LG-6 to MG-4 range between 760 and 1300 ppb. Elevated concentrations of Pt and Pd are also present in hanging and footwalls of chromitite seams (median 333 ppb Pt). The PPGE (Rh, Pt, Pd) contents of weathered ores are generally lower than those of the pristine ores. The IPGE (Os, Ir, Ru) are very similar in both pristine and weathered ores. Particularly, Ru concentration are in the same range as the pristine ores.
Platinum concentrations increase from LG-6 to MG-4, whereas Pd remains at near-constant levels, resulting in a strong increase of the Pt/Pd ratio from 2.2 to 15.3. Platinum, largely remains within the chromitite seams and is only locally mobilized within the chromitites and their surrounding hanging and footwalls, whereas a large proportion of the Pd is leached out. Weathering causes mobilization of Pt and Pd out of the chromitites, locally into the hanging and footwall. The general decrease (in particular of Pd) can also be observed by comparing the average Pt/Pd ratio of pristine chromitites from the Thaba Mine. The IPGE are generally less affected by weathering processes which may be explained by the fact that laurite [(Ru,Os,Ir)S2] commonly occurs as inclusions in chromite, and PGM incorporated in chromite are largely unaffected by weathering processes.
  • Contribution to proceedings
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-30080
Publ.-Id: 30080


Platinum-group elements in weathered Lower Group and Middle Group chromitites of the Bushveld Complex
Junge, M.; Bachmann, K.; Oberthür, T.;
All major sources of economically important platinum-group elements (PGE) are associated with sulfides and chromite in mafic-ultramafic rocks. The Bushveld Complex in South Africa is the largest PGE deposit worldwide. Chromitites of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex hold PGE contents of a few ppm. However, these chromitites are mainly mined for chromium only and extraction of PGE as a by-product is limited. Surface weathering in the area of the Bushveld Complex is up to 50 m down from surface. Attempts to recover Pt and Pd from these weathered ores lead to recoveries of <30 %, despite that Pt and Pd concentrations are similar in pristine and weathered ores. The recovery of PGE from near-surface chromitites of the LG and MG would increase the resource efficiency of current mining operations.. Therefore, an efficient utilization of these ores requires geochemical and mineralogical characterization of the PGE within these ores and the development of novel approaches of mineral beneficiation.
  • Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-30079
Publ.-Id: 30079


High energy ion beams as a powerful tool for the analysis of the elemental composition of thin layers
Munnik, F.ORC Keywords: Ion Beam Analysis
  • Lecture (others)
    Kolloquium am Ferdinand-Braun-Institut, Berlin, 29.11.2019, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-30076
Publ.-Id: 30076


Volume quantification in interphase voxels of ore minerals using 3D imaging
Da Assuncao Godinho, J. R.; Kern, M.ORC; Renno, A.ORC; Gutzmer, J.ORC
This contribution presents and validates a new method to correct for the main limitations of volume quantification using X-ray computed tomography: limited spatial resolution and lack of mineralogical classification. The volume of a phase of interest (cassiterite, SnO2) is calculated using the intensity of voxels at interphases, which are typically the regions of main uncertainty in 3D imaging. Instead of traditional segmentation methods that define boundaries between phases, our method considers interphases as regions that can be several voxels across. The method is validated using a feedback loop between 2D scanning electron microscopy-based image analysis and bulk chemical analysis where the advantages of each technique are used to correct for the limitations of another. The percent of cassiterite derived from our method are within 10% deviation from those measured by scanning electron microscopy-based image analysis and bulk chemical analysis, when the P50 of the particle size distribution is at least 5 times the voxel size of the scan, which is a better agreement than results derived from other segmentation methods. Therefore, our method reduces the uncertainty of volume quantification and lowers the limit of grain sizes for which volumes can be reliably measured using computed tomography. The reduced uncertainty and bias can contribute to broadening the application of 3D imaging to mineral engineering as complementary to well established techniques.
Keywords: Partial volume effect Computed tomography Mineral processing Raw materials X-ray imaging Geometallurgy

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  • Secondary publication expected from 01.12.2020

Permalink: https://www.hzdr.de/publications/Publ-30075
Publ.-Id: 30075


Structural, magnetic and magnetocaloric properties of NdPrFe14B and its hydrides
Tereshina, I.; Kaminskaya, T.; Ivanov, L.; Politova, G.; Drulis, H.; Gorbunov, D.; Paukov, M.; Tereshina-Chitrova, E.; Andreev, A.;
A systematic study of the influence of interstitial hydrogen on the structure, morphology of surface, magnetic and magnetothermal properties in multicomponent (Nd0.5Pr0.5)2Fe14BHx (x = 0; 2.7; 4.3) are reported. Partial substitution of Pr for Nd allows a decrease of the spin-reorientation transition temperature from 135 K for Nd2Fe14B to 73 K for (Nd0.5Pr0.5)2Fe14B. Hydrides (Nd0.5Pr0.5)2Fe14BHx crystallize in a tetragonal crystal structure (space group P42/mnm) of the Nd2Fe14B-type. Both lattice constants and unit cell volume increase upon hydrogen absorption. It was also found that the surface of the hydrogenated sample was very severely damaged by the introduction of hydrogen. Magnetic studies of both initial compound and the hydrides were performed on bulk and powder samples in static and pulsed magnetic fields up to 14 and 58 T, respectively. Hydrogenation has a significant effect on magnetic properties of a multicomponent alloy (Nd0.5Pr0.5)2Fe14B: Curie temperature and saturation magnetization increase, while temperature of SRT decreases (TSRT = 63 K for (Nd0.5Pr0.5)2Fe14BHx with x = 2.7 and 4.3). The magnetocaloric effect (MCE) in the range of spin-reorientation transition also decreases significantly. We analyzed magnetic properties of (Nd0.5Pr0.5)2Fe14BHx and compare them with that of Nd2Fe14BHx. Magnetic phase diagrams are constructed.

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Permalink: https://www.hzdr.de/publications/Publ-30068
Publ.-Id: 30068


Evidence of one-dimensional magnetic heat transport in the triangular-lattice antiferromagnet Cs2CuCl4
Schulze, E.; Arsenijevic, S.; Opherden, L.ORC; Ponomaryov, O.; Wosnitza, J.; Ono, T.; Tanaka, H.; Zvyagin, S.ORC
We report on low-temperature heat-transport properties of the spin-1/2 triangular-lattice antiferromagnet Cs2CuCl4. Broad maxima in the thermal conductivity along the three principal axes, observed at about 5 K, are interpreted in terms of the Debye model, including the phonon umklapp scattering. For thermal transport along the b axis, we found a pronounced field-dependent anomaly, close to the transition into the three-dimensional long-range-ordered state. No such anomalies were found for the transport along the a and c directions.We argue that this anisotropic behavior is related to an additional heat-transport channel through magnetic excitations, that can best propagate along the direction of the largest exchange interaction. In addition, peculiarities of the heat transport of Cs2CuCl4 in magnetic fields up to the saturation field and above are discussed.

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Permalink: https://www.hzdr.de/publications/Publ-30067
Publ.-Id: 30067


Diffusion and Interaction of In and As Implanted into SiO2 Films
Tyschenko, I. E.; Voelskow, M.; Mikhaylov, A. N.; Tetelbaum, D. I.;
By means of Rutherford backscattering spectrometry, electron microscopy, and energy-dispersive X-ray spectroscopy, the distribution and interaction of In and As atoms implanted into thermally grown SiO2 films to concentrations of about 1.5 at % are studied in relation to the temperature of subsequent annealing in nitrogen vapors in the range of T = 800–1100°C. It is found that annealing at T = 800–900°C results in the segregation of As atoms at a depth corresponding to the As+-ion range and in the formation of As nanoclusters that serve as sinks for In atoms. An increase in the annealing temperature to 1100°C yields the segregation of In atoms at the surface of SiO2 with the simultaneous enhanced diffusion of As atoms. The corresponding diffusion coefficient is DAs = 3.2 × 10–14 cm2 s–1.
Keywords: As, diffusion, In, ion implantation, silicon oxide

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Permalink: https://www.hzdr.de/publications/Publ-30063
Publ.-Id: 30063


Studies on the interaction of plant cells with U(VI) and Eu(III) and on stress-induced metabolite release
Jessat, J.;
Uranium(VI) and Europium(III) can interact with Brassica napus suspension cell cultures. This can lead to bioassociation (immobilisation of metals due to the cell metabolism), which is discussed in more detail here. Heavy metal stress can also lead to the formation of protective metabolites by the plant cells, whose complex formation behaviour with U(VI) has been investigated.
Keywords: canola, plants, uranium, europium, metabolites, WiN, Women in Nuclear, bioassociation, heavy metal, plant cells, suspension cell cultures
  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30056
Publ.-Id: 30056


Critical behavior of intercalated quasi-van der Waals ferromagnet Fe0.26TaS2
Zhang, C.; Yuan, Y.; Wang, M.ORC; Li, P.; Zhang, J.; Wen, Y.; Zhou, S.ORC; Zhang, X. X.
In the present work, single-crystalline quasi-van der Waals ferromagnet Fe0.26TaS2 was successfully synthesized with Fe atoms intercalated at ordered positions between TaS2 layers. Its critical behavior was systematically studied by measuring the magnetization around ferromagnetic to paramagnetic phase transition temperature, TC∼100.7K, under different magnetic fields. The critical exponent β for the spontaneous magnetization below TC, γ for the inverse initial susceptibility above TC, and δ for the magnetic isotherm at TC were determined with modified Arrott plots, the Kouvel-Fisher method, the Widom scaling law, and critical isotherm analysis, and found to be the following values: β=0.459(6),γ=1.205(11), and δ=3.69(1). The obtained critical exponents are self-consistent and follow the scaling equation, indicating the reliability and intrinsicality of these parameters. A close analysis within the framework of renormalization group theory reveals that the spin coupling inside Fe0.26TaS2 crystal is of the three-dimensional Heisenberg ({d:n}={3:3}) type with long-range magnetic interaction and that the exchange interaction decays with distance as J(r)∼r-4.71
Keywords: quasi-van der Waals ferromagnet,critical behavior,three-dimensional Heisenberg

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Permalink: https://www.hzdr.de/publications/Publ-30054
Publ.-Id: 30054


Bio-Fishing for Rare Earth Recycling
Lederer, F.ORC
Rare earth elements (REE) are a group of seventeen elements consisting of scandium, yttrium as well as what are known as lanthanides. These elements are found only in a few regions worldwide in quantities worth mining. REEs are considered key components in the high-tech industry and are utilized, for example, in wind turbines, smartphones and energy-saving lamps.
  • G.I.T. Laboratory Journal 23(2019)5, 30-31

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Permalink: https://www.hzdr.de/publications/Publ-30051
Publ.-Id: 30051


Wie uns die Biologie beim Recycling von Elektroschrott hilft
Lederer, F.ORC
Gold, Kupfer, Palladium und Seltene Erden sind wichtige Bestandteile von Smartphones und anderen Geräten unseres täglichen Lebens. Jedes dieser Metalle erfüllt ganz gezielt Aufgaben im Gerät und ist daraus nicht wegzudenken. Ihre Gewinnung aus den Bergbauminen dieser Erde ist häufig mit enormen Schäden für Mensch und Natur verbunden. Die Verwendung von recycelten Metallen bietet dazu eine deutlich umweltfreundlichere Alternative. Da die Metalle aber in sehr kleinen Mengen und fein verteilt im Gerät verbaut sind, ist ihr Recycling häufig nicht wirtschaftlich. Hier können neue biologische Recyclingwege Abhilfe leisten. Forscher des Helmholtz Instituts Freiberg für Ressourcentechnologie arbeiten an der Entwicklung von Metallspezifischen Antikörpern, welche gezielt ein Wertmetall nach dem anderen auch in kleinsten Konzentrationen in Form von Bioangeln aus einem Metallgemisch herausfischen können.
Keywords: Recycling, Elektroschrott, Bioangeln
  • Lecture (others)
    Campus Talks - Forschung auf den Punkt gebracht, 19.11.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30047
Publ.-Id: 30047


Metallgewinnung durch Mikrobiologie - Biologisch assistierte Prozesse in der Rohstofftechnologie
Lederer, F.ORC
Präsentation der Arbeiten der Abteilung Biotechnologie des Helmholtz Institut Freiberg für Ressourcentechnologie sowie der Arbeiten der Nachwuchsforschergruppe BioKollekt
Keywords: Biokollektoren, Peptide, Recycling
  • Lecture (others)
    Institutskolloquium, 25.09.2019, Waldheim, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30046
Publ.-Id: 30046


BioKollekt - A biobased material recycling process promotes circular economy
Lederer, F.ORC; Pollmann, K.ORC
Recycling high-value products is a pivotal part of a circular economy. Current high-tech products contain a highly complex mixture of elements in low concentrations. Elements in these mixtures usually possess similar chemical and physical properties, which poses technical difficulties when considering a potential recycling process. Currently, only 22% terbium, 1% cerium and 1% lanthanum used in electronic devices like fluorescent light bulbs is recycled.1 A large proportion of these precious elements is lost. There is a need for novel techniques to be developed in order to recycle elements that are in low concentrations and in a complex matrix. Junior research group BioKollekt has begun the design and development of highly selective bio-based collector materials for a more sustainable recycling process of these elements. Biological peptide structures were identified in a highly competitive process for their selectivity and affinity for the fluorescent phosphor lanthanum phosphate doped with cerium and terbium (LAP). LAP-selective binding peptides coupled to a carrier material could be used in the future as separation tools for the selective recycling of LAP from lamp phosphors of fluorescent light bulbs. The BioKollekt approach uses LAP as a “proof of principle” to show the efficiency of biocollector materials. Figure 1 demonstrates the BioKollekt concept. The identification of highly selective biomolecules for preferred target materials (step 1) has been already achieved. In the second step, carrier materials (e.g. hydrophobic beads) will be functionalized with material binding-selective peptides. Biocollectors will interact selectively with their target material in a separation process (step 3-4). Finally, the target material and biocollector will be recycled and reused (step 5). The talk will present the BioKollekt concept and its achievements.
Keywords: Recycling, Peptides, Fluorescent Phosphor, Lanthanum
  • Invited lecture (Conferences)
    European Congress and Exhibition on Advanced Matertials and Processes (EUROMAT 2019), 01.-05.09.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-30044
Publ.-Id: 30044


Distinct defect appearance in Gd implanted polar and nonpolar ZnO surfaces in connection to ion channeling effect
Jagerová, A.; Malinský, P.; Mikšová, R.; Nekvindová, P.; Cajzl, J.; Akhmadaliev, S.; Holý, V.; Macková, A.;
(0001) c-plane, (11-20) a-plane, and m-plane (10-10) ZnO bulk crystals were implanted with 400-keV Gd+ ions using fluences of 5 × 1014, 1 × 1015, 2.5 × 1015, and 5 × 1015 cm-2. Structural changes during the implantation and subsequent annealing were characterized by Rutherford backscattering spectrometry in channeling mode (RBS-C); the angular dependence of the backscattered ions (angular scans) in c-, a-, and m-plane ZnO was realized to get insight into structural modification and dopant position in various crystallographic orientations. X-ray diffraction (XRD) with mapping in reciprocal space was also used for introduced defect identification. Defect-accumulation depth profiles exhibited differences for c-, a-, and m-plane ZnO, with the a-plane showing significantly lower accumulated disorder in the deeper layer in Zn-sublattice, accompanied by the preservation of ion channeling phenomena in a-plane ZnO. Enlargement of the main lattice parameter was evidenced, after the implantation, in all orientations. The highest was evidenced in a-plane ZnO. The local compressive deformation was seen with XRD analysis in polar (c-plane) ZnO, and the tensile deformation was observed in nonpolar ZnO (a-plane and m-plane orientations) being in agreement with RBS-C results. Raman spectroscopy showed distinct structural modification in various ZnO orientations simultaneously with identification of the disordered structure in O-sublattice. Nonpolar ZnO showed a significant increase in disorder in O-sublattice exhibited by E2(high) disappearance and enhancement of A1(LO) and E1(LO) phonons connected partially to oxygen vibrational modes. The lowering of the E2(low) phonon mode and shift to the lower wavenumbers was observed in c-plane ZnO connected to Zn-sublattice disordering. Such observations are in agreement with He ion channeling, showing channeling effect preservation with only slight Gd dopant position modification in a-plane ZnO and the more progressive diminishing of channels with subsequent Gd movement to random position with the growing ion fluence and after the annealing in c-plane and m-plane ZnO.
Keywords: doped c-, a- plane and m-plane ZnO; damage accumulation asymmetry; rare-earth ion implantation; RBS channelling; damage-depth profiling
  • Open Access Logo Journal of Vacuum Science & Technology A 37(2019), 061406
    Online First (2019) DOI: 10.1116/1.5125320

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Permalink: https://www.hzdr.de/publications/Publ-30043
Publ.-Id: 30043


Multiconfigurational calculations of ground and excited states of actinide complexes
Kloditz, R.ORC; Patzschke, M.ORC; Stumpf, T.
Multiconfigurational wavefunction based methods are the state of the art methods to quantitatively compute excited state energies and transition moments for heavy element systems where the inclusion of electron correlation and relativistic effects is crucial. Since the advent of these methods, e.g. the complete active-space self-consistent field (CASSCF) method and the density-matrix renormalization group (DMRG) method, it is possible to accurately interpret and predict the UV-Vis spectra of these heavy element systems.
In this talk the CASSCF and DMRG methods are introduced and used to simulate the UV-Vis spectrum of the Uranium-bissalen complex. The active space is set up and varied to accurately describe the wavefunction. CASPT2 and RASSI are used to obtain quantitative results for excited state energies and transition moments.
Keywords: CASSCF, DMRG, Actinides, Excited states, Correlation
  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Thomas Heine (TU Dresden), 26.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30035
Publ.-Id: 30035


Revealing the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands
Kloditz, R.ORC; Radoske, T.ORC; Patzschke, M.ORC; Stumpf, T.
The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.
Keywords: DFT, QTAIM, DMRG, Actinides, Quantum chemistry, Bonding
  • Poster
    European Summerschool of Quantum Chemistry, 08.-21.09.2019, Palermo, Italien
  • Poster
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30034
Publ.-Id: 30034


Insights into the excited states of 5f systems: Protactinium and Uranium
Kloditz, R.ORC; Patzschke, M.ORC; Stumpf, T.
The calculation of the excited states of actinide systems is a challenging task because of the delicate influence of electron correlation and relativistic effects. Density functional theory is not applicable for obtaining quantitative results, hence multiconfigurational wavefunction based methods have to be used. State of the art is a combination of spinfree CASSCF and CASPT2/NEVPT2 and a following inclusion of spin-orbit coupling.
This talk presents quantitative excited state energy calculations of simple Protactinium and Uranium systems in comparison with qualitative group-theoretical considerations.
Keywords: CASSCF, Actinides, Excited states, Group theory
  • Invited lecture (Conferences)
    Arbeitsgruppenseminar des AK Markus Reiher (ETH Zürich), 10.07.2019, Zürich, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-30033
Publ.-Id: 30033


Analysis of the metal-ligand bonding character in tetravalent f-element complexes with Schiff-base ligands
Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.;
The contribution of the f-orbitals to chemical bonding leads to the rich chemistry of the actinides. This is in contrast to the lanthanides, where it is known that this contribution is less important. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands reflecting natural binding motifs.
This study compares the different bonding behavior of tetravalent actinides and lanthanides with the Schiff base salen by means of real-space bonding analysis. Our approach makes use of the quantum theory of atoms in molecules (QTAIM), non-covalent interaction (NCI) analysis and density differences complemented by natural population analysis (NPA). Especially the local properties at the bond critical points, for instance charge, density, ellipticity and others, can be used to characterize a bond’s order, strength, and covalent contribution.
First results reveal a strong interaction of the actinides, i.e. Th to Pu, with the oxygen of salen characterized by a high electron density concentration between the atoms. In contrast, the interaction between the actinides and the nitrogen of salen is much weaker. The delocalization index, density and Laplacian reveal a significant increase of covalency for Pa to Pu compared to Th and Ce being an indicator of the contribution of the f-electrons. Tetravalent Ce as a lanthanide analogue of Th is expected to show a similar bonding behavior, but, surprisingly, this is not the case for all investigated bonding properties.
This detailed analysis of the electronic properties of actinide compounds will help to improve understanding of their behavior in the environment as well as in technical processes and leads to the possibility to predict properties of unknown complexes.
Keywords: Actinides, DFT, QTAIM, bonding, covalency, quantum chemistry
  • Poster
    Molecular Quantum Mechanics, 30.06.-05.07.2019, Heidelberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30032
Publ.-Id: 30032


NORM research and strategy at the HZDR, Germany
Arnold, T.;
The presentation gives an overview of the NORM research at the HZDR
Keywords: NORM, radioecology, uranium, research, strategy
  • Invited lecture (Conferences)
    Cores Symposium on Radon and NORM – regulatory aspects, scientific achievements and research needs, 03.-04.09.2019, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-30025
Publ.-Id: 30025


CFD simulation of multiphase flow in evaporators
Schlottke, J.; Kühnel, W.; Porombka, P.; Lucas, D.ORC
Inside evaporators of air-conditioning systems, uneven mass flow distribution of refrigerant leads to a loss of efficiency and finally a reduction of comfort in passenger compartments. The distribution is influenced by the flow field and two-phase distribution (flow pattern) in various elements, comprising developing and developed two-phase flow in straight and angled ducts, headers, flat tubes and the connection between these.
This talk presents on-going efforts to predict this type of flow with CFD.
In a first step, extensive experimental investigations on generic geometries are done using advanced measurement techniques. This data are then used to develop and validate numerical models capable of reproducing the relevant physics.
Important two-phase phenomena are: multiple regimes (continuous-disperse + separated flow), wall films, stripping/impingement, particle size distribution, two-phase heat transfer, boiling/condensation. In a final step, the developed modeling strategy is applied to real evaporators.
In comparing simulation results to experimental data, we find both good agreement as well as discrepancies which confirm that there is still more work on developing appropriate models to do.
Keywords: evaporator, CFD, flow distribution, air-conditioning systems, Euler-Euler method
  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30024
Publ.-Id: 30024


The Inverse Trans Influence in a novel Uranium(IV)bis(carbene) Complex
Köhler, L.; Patzschke, M.ORC; März, J.ORC; Stumpf, T.
The trans influence is an extensively investigated electronic concept in transition metal chemistry. It can be defined as the extent to which a bond in trans position to a ligand L is weakened.[1,2] In contrast, f-block elements exhibit an opposite effect, meaning a bond shortening and thus strengthening can be observed in the trans position to a strongly donating ligand. This is established as the inverse trans influence (ITI),[3–5] and is commonly assumed to be most prominent for actinides in high oxidation states.
A novel UIVbis(carbene) complex [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) was synthesized by salt metathesis from UCl4 in the presence of iPrImHCl and TMSA. In the complex, the U centre is surrounded by two carbenes, three chloro- and one TMSA-ligand. The U–Cl bond in trans position to the TMSA is slightly shorter (0.01 Å) compared to the other U–Cl bonds, indicating an TMSA-induced ITI. However, this change is very small. For comparison, a structural optimization based on the SC-XRD data of 1 was carried out using tetravalent tungsten as a d-block analogue, because of its similar ionic radius to UIV. Tungsten’s transition metal behaviour should result in a trans influence. In the WIVbis(carbene) complex 2, the W–Cl bond trans to the TMSA ligand is indeed 0.05 Å longer than the other W–Cl bonds. This large change expresses the existence of a strong trans influence in 2 and hence ITI in 1.
References:
[1] A. Pidcock, R. E. Richards, L. M. Venanzi, J. Chem. Soc. Inorg. Phys. Theor. 1966, 0, 1707–1710.
[2] T. G. Appleton, H. C. Clark, L. E. Manzer, Coord. Chem. Rev. 1973, 10, 335–422.
[3] R. G. Denning, J. Phys. Chem. A 2007, 111, 4125–4143.
[4] H. S. La Pierre, K. Meyer, Inorg. Chem. 2013, 52, 529–539.
[5] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
Keywords: uranium carbene complex, inverse trans influence, ITI, tungsten carbene complex
  • Lecture (Conference)
    Tagung Gesellschaft Deutscher Chemiker, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30023
Publ.-Id: 30023


Actinid-Komplexe mit N-heterocyclischen Carbenen
Köhler, L.; Patzschke, M.ORC; März, J.ORC; Stumpf, T.
The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅](L¹H)₂ 2 (TMSI = NSiMe₃−) were synthesized from UIV starting material in the presence of iPrIm. In the case of 1 the metal center is surrounded by three chloro-, two carbene and one TMSA ligand, whereas 2 exhibits five chloro- and one TMSI ligand, thus generating an dianion, whose charge is compensated by the protonated carbene. In 1, the U–Cl bond, located trans to the TMSA ligand, is remarkably shorter (0.02 Å) than the other U–Cl bonds. This indicates the existence of an ITI, induced by TMSA. Based on the higher valent UV cation and stronger donating TMSI ligand, a similar or stronger effect should also be observed in 2. Surprisingly, this could not be confirmed by the experimental data. The U–Cl bond lying trans to the TMSI ligand is not the shortest U–Cl bond (2.68 Å compared to 2.66 Å for U–Cl1/2), but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.
Keywords: carbenes, inverse trans influence, ITI, uranium(V) complex
  • Invited lecture (Conferences)
    Finale der WiN Preisverleihung, 11.10.2019, Karlstein/Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30022
Publ.-Id: 30022


The Inverse Trans Influence in U(IV/V) complexes
Köhler, L.; Patzschke, M.ORC; März, J.ORC; Stumpf, T.
The inverse trans influence (ITI) is an effect well-known to occur in high valent U(V/VI) complexes. It appears as a shortening of the M–L bond in trans position to a strongly donating ligand. The effect can be explained by electron density donation from the strong ligand to the metal center, which fills up the electron hole formed through electron density transfer from semi-core 6p to vacant 5f orbitals.[1,2] This results in the observed contraction and strengthening of the bond trans to the donating ligand.
To compare the ITI in UIV and UV complexes, the U compounds [UIV(L¹)₂(TMSA)Cl₃] 1 (L¹ = iPr₂Im, TMSA = (N(SiMe₃)₂)−) and [UV(TMSI)Cl₅](L¹H)₂ 2 (TMSI = NSiMe₃−) were synthesized from UIVstarting material in the presence of iPrIm. In the case of 1 the metal center is surrounded by three chloro-, two carbene and one TMSA ligand, whereas 2 exhibits five chloro- and one TMSI ligand, thus generating an dianion, whose charge is compensated by the protonated carbene. In 1, the U–Cl bond, located trans to the TMSA ligand, is remarkably shorter (0.02 Å) than the other U–Cl bonds. This indicates the existence of an ITI, induced by TMSA. Based on the higher valent UV cation and stronger donating TMSI ligand, a similar or stronger effect should also be observed in 2. Surprisingly, this could not be confirmed by the experimental data. The U–Cl bond lying trans to the TMSI ligand is not the shortest U–Cl bond (2.68 Å compared to 2.66 Å for U–Cl1/2), but is in the same range as the other chloro ligands. The absence of a notable ITI can be attributed to intermolecular interactions in the crystal structure of 2. Structure optimization of the molecular UV complex dianion by DFT yield a U–Cl5 bond length of 2.55 Å, shorter than any other U–Cl bond by 0.02 Å. The difference between experiment and theory results from a great number of electrostatic interactions and hydrogen bonding between the complex dianion and the carbene counterions in 2. Similar intermolecular interactions are not present in the crystal structure of 1, which is why the ITI could be observed for this compound.
The results demonstrate that the ITI affects complex structures for both, UIV and UV compounds, but additional effects, such as the intermolecular network observed in the structure of 2 can surpass its relatively small structural contribution.

References
[1] M. Gregson, E. Lu, D. P. Mills, F. Tuna, E. J. L. McInnes, C. Hennig, A. C. Scheinost, J. McMaster, W. Lewis, A. J. Blake, et al., Nat. Commun. 2017, 8, 14137.
[2] B. Kosog, H. S. La Pierre, F. W. Heinemann, S. T. Liddle, K. Meyer, J. Am. Chem. Soc. 2012, 134, 5284–5289.
Keywords: inverse trans influence, ITI, uranium(V), carbenes,
  • Lecture (Conference)
    Journées des Actinides, 14.-18.04.2019, Erice, Italien

Permalink: https://www.hzdr.de/publications/Publ-30021
Publ.-Id: 30021


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures
Eibl, M.ORC; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.
The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.
  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30019
Publ.-Id: 30019


Trivalent Lanthanide and Actinide Incorporation into Zirconium(IV) Oxide – Spectroscopic Investigations of Defect Fluorite Structures
Eibl, M.ORC; Shaw, S.; Hennig, C.; Morris, K.; Stumpf, T.; Huittinen, N. M.
The incorporation of trivalent lanthanides and actinides into zirconia (ZrO₂) was studied using PXRD and spectroscopic methods (EXAFS, TRLFS). In highly doped cubic zirconia three Eu(III) incorporation species could be found using TRLFS. A surface associated species with an excitation maximum of 578.1 nm and two bulk incorporation species with excitation maxima at 579.0 and 579.7 nm were found.
  • Lecture (Conference)
    17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere., 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-30018
Publ.-Id: 30018


CFD simulation of flashing phenomena
Liao, Y.;
Due to its relevance for technical applications, experimental and theoretical investigation on flashing flows through nozzles and tubes has gained great attention. Most of them have focused on area-averaged quantities such as mass flow rate and pressure drop, while little attention has been paid to the internal flow structure and interfacial exchanging processes. More recently, computational fluid dynamics is frequently utilized to explore the phase distribution in the flashing flows. Various gas-liquid mixture or two-fluid models have been proposed in the literature. However, knowledge on the non-equilibrium effects, interphase transfer as well as bubble dynamics under different flashing conditions is still insufficient, and a general and precise definition of the problem in numerical simulations remains a challenge. A broad consensus on the numerical methods for flashing flows is not available. Guidelines for selecting an appropriate model are desirable, which is, however, not an easy task due to the complex physics and lack of insights. The talk is focused on the elucidation of important interfacial processes such as interfacial area density, interfacial heat transfer, bubble nucleation, coalescence and breakup as well as available modelling approaches. Numerical simulations for various flashing scenarios, i.e. converging-diverging flow, pipe-blowdown, natural circulation loop and pressure release transient, are presented. The influence of chosen numerical methods is discussed, especially the mixture model versus two-fluid ones and mono-disperse versus poly-disperse approaches. Progresses towards developing a general framework for modelling of complex gas-liquid flows are demonstrated.
Keywords: Flashing flow, Numerical simulation, Phase change, Mono-disperse approach, Poly-disperse approach
  • Lecture (Conference)
    17th Multiphase Flow Conference & Short Course, 11.-15.11.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30016
Publ.-Id: 30016


Synthesis and Characterization of Tri- and Tetravalent Actinide Amidinates
Fichter, S.ORC
Tri- and tetravalent actinide amidinates have been synthesized and characterized in solid state and in solution.
  • Lecture (others)
    FENABIUM Projekttreffen, 12.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30014
Publ.-Id: 30014


A Flow Pattern Adaptive Multi-field Two-fluid Concept for Turbulent Two-phase Flows
Schlegel, F.; Meller, R.; Lehnigk, R.; Hänsch, S.; Tekavčič, M.;
Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby a broad range of flow morphologies and different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multi-fluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research, including a state-of-the-art IT concept. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfil the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled either by an isotropic (Strubelj and Tiselj, 2011) or by an anisotropic drag. In both cases, the immensely strong phase coupling requires an adapted numerical method. State and evolution of bubble size distribution in disperse phase context is solved with either class or moment methods.
The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.
  • Poster
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30012
Publ.-Id: 30012


On non drag interfacial force and thermal phase change modelling of reactingEulerFoam
Peltola, J.; Pättikangas, T.; Bainbridge, W.; Lehnigk, R.; Schlegel, F.;
The reactingEulerFoam framework included in OpenFOAM releases since 3.0.0 provides a highly flexible platform for the modelling of multiphase flows. Extensive selection of interfacial force models is provided along with alternate turbulence models. The thermal phase change capability [1,2] was first introduced in OpenFOAM 3.0.1 [3] and has since been extended and refined in subsequent releases.
The current OpenFOAM 7 release features include support for non-equilibrium wall boiling, n-phase thermal phase change and for bubble diameter modelling algebraic, IATE and inhomogeneous class method models are supported.The present simulations have been carried out with the OpenFOAM Foundation development release [4]. The goal is to aid those that intend to use the publicly available reactingEulerFoam by providing a summary of the models and demonstrations of a few modelling details by expanding upon tutorials recently added to the OpenFOAM Foundation development line.
DEDALE experiments [5] are used as a reference for the non-drag interfacial force modelling.
Subcooled nucleate boiling simulation results with different models combinations are compared to the DEBORA experiments [6,7]. Finally, a more complex direct contact condensation simulation of SEF-POOL test facility [8] is presented and results are compared to the experiment.

References

[1] Peltola, J., & Pättikangas, T.J.H. Development and validation of a boiling model for OpenFOAM multiphase solver. CFD4NRS-4 Conference Proceedings, Daejeon, Korea, paper 59, (2012).
[2] Peltola, J., Pättikangas, T., Bainbridge, W., Lehnigk, R., Schlegel, F., On development and validation of subcooled nucleate boiling models for OpenFOAM Foundation release. NURETH-18 Conference Proceedings, Portland, Oregon, United States (2019).
[3] OpenFOAM Foundation, “OpenFOAM 3.0.1,” http://openfoam.org/version/3.0.1/ (2015).
[4] OpenFOAM Foundation, “OpenFOAM-dev,” https://openfoam.org/version/dev/ (2014-2019).
[5] Grossetete, C., Experimental investigation and numerical simulations of void profile development in a vertical cylindrical pipe (No. EDF--96-NB-00120). Electricite de France (EDF), (1995).
[6] E. Manon, Contribution à l’anayse et à la modélisation locale des écoulements boillants sous-saturésdans les conditions des Réacteurs à Eau sous Pression, PhD thesis, Ecole Centrale Paris (2000).
[7] J. Garnier, E. Manon, G. Cubizolles, “Local measurements on flow boiling of refrigerant 12 in avertical tube”, Multiphase Science and Technology, pp. 1-111 (2001).
[8] M. Puustinen, J. Laine, A. Räsänen, E. Kotro, and K. Tielinen, “Characterizing tests in SEF-POOLfacility,” Technical Report, Lappeenranta University of Technology, Nuclear Engineering, INSTAB3/2017 (2017).
  • Lecture (Conference)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30011
Publ.-Id: 30011


Flexible development framework for the Euler Euler approach
Schlegel, F.; Greenshields, C.;
The presentation gives a detailed insight into the OpenFOAM Developments for Euler-Euler simulations at HZDR, i.p. the multi-field two-fluid model approach, LES simulations, stratified flow simulations, entrainment modelling and more. Furthermore, the successfull development strategy and co-working with the OpenFOAM Foundation is explained.
Keywords: Euler-Euler, OpenFOAM, Numerical Simulation, Entrainment, Gentop, Stratified Flow
  • Invited lecture (Conferences)
    17th Multiphase Flow Conference and Short Course, 11.-15.11.2019, Dresden, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-30010
Publ.-Id: 30010


X2 benchmark specification dataset
Bilodid, Y.ORC

The X2 VVER-1000 benchmark specification dataset.

Keywords: VVER-1000, X2 benchmark
Related publications
X2 VVER-1000 benchmark revision: fresh HZP core state and … (Id 29992) is supplemented by this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-11-27
    DOI: 10.14278/rodare.199
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30009
Publ.-Id: 30009


AER working group D meeting on VVER safety analysis - report of the 2019 meeting
Kliem, S.ORC
The AER Working Group D on VVER reactor safety analysis held its 28th meeting in Garching, Germany, during the period 26-27 June, 2019. The meeting was hosted by GRS Garching and was held in conjunction with the second workshop on multi-physics MPMV-2 and the first workshop on the ROSTOV-2 benchmark. Altogether 20 participants from eleven AER member organizations and seven guests attended the meeting of the working group D. The co-ordinator of the working group, Mr. S. Kliem, served as the chairperson of the meeting.

The meeting started with a general information exchange about the recent activities in the participating organizations.

The given 12 presentations and the discussions can be attributed to the following topics:

• Safety analyses methods and results
• Code development and benchmarking
• Future activities

A list of the participants and a list of the handouts distributed at the meeting are attached to the report. The corresponding PDF-files of the handouts can be obtained from the chairperson.
  • Contribution to proceedings
    29th Symposium of AER on VVER Reactor Physics and Reactor Safety, 14.-18.10.2019, Mochovce, Slovakia
    Proceedings of the 29th Symposium of AER on VVER Reactor Physics and Reactor Safety, Budapest: Kiadja az EK, 9789637351327, 325-330

Permalink: https://www.hzdr.de/publications/Publ-30008
Publ.-Id: 30008


Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development
Hildebrand, H.; Schymura, S.; Franke, K.; Fischer, C.ORC
The aim of the present report was to obtain an overview of current strategies and methods for the detection of (manufactured) nanomaterials (NMs) in the environmental compartments surface water, soil, sediment, air, biota and sewage sludge. Based on this several recommendations for future needs of action in the short to long term are derived in order to establish a standardized detection of NMs in the environment that is necessary in order to check the pollution in the environment, to check whether or not potential risk management measures take the intended effect and to validate NM release models with real data.
A literature review was performed using predominantly “Web of Science” and screening for literature, such as review articles summarising the state of the art of NM detection techniques for environmental samples. More than 160 scientific publications were evaluated concerning NM detection methods. Results of the literature survey clearly show that a combination of detection techniques is necessary in order to detect and identify NMs, and to differentiate between natural NMs and manufactured NMs. The crucial step is accurate sample preparation for the selected detection method which means in most cases complete removal of the (disturbing) matrix and transfer of the NM in appropriate media for measurement. So far field studies in terms of detection of unknown amounts of unspecific engineered NMs in natural samples are rare and only existing for a few compartments, mainly surface waters.
Hence, it is concluded that the need of action is focused on the development, standardization and validation of existing methods in a combinatory approach.
Keywords: technische Nanomaterialien, manufactured nanomaterials Detektion, detection Umwelt, Environment
  • Open Access Logo Other report
    Desssau-Roßlau: Umweltbundesamt, 2019
    63 Seiten

Permalink: https://www.hzdr.de/publications/Publ-30005
Publ.-Id: 30005


Tracking in magnetic fields
Müller, S.ORC
Tracking in magnetic fields with the FLUKA radiation transport and reaction code
Keywords: FLUKA, radiation transport
  • Lecture (others)
    5th Advanced FLUKA course, 18.-22.11.2019, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-29995
Publ.-Id: 29995


FLAIR:Geometries
Müller, S.ORC
Usage of the FLAIR Geometry-Editor
(Lecture given at the 5th Advanced FLUKA Course at NEA, Paris)
Keywords: FLUKA, FLAIR
  • Lecture (others)
    5th FLUKA Advanced Course, 18.-22.11.2019, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-29994
Publ.-Id: 29994


Non-quenching photoluminescence emission up to at least 865 K upon near-UV excitation in a single crystal of orange-red emitting SmPO4
Sharma, S.ORC; Beyer, J.ORC; Gloaguen, R.ORC; Heitmann, J.
The adjustment of photoluminescence emission spectrum and an enhancement in the thermal stability of red/orange-red emitting phosphors is an important issue for the whole lighting industry. Herein, we present our results on the luminescence spectroscopy of a single crystal sample of SmPO4 exhibiting a prominent orange-red emission at 597 nm, along with a charge-transfer absorption (O2− → Sm3+) around 200 nm. We study the temperature dependence of emission spectra in SmPO4 for excitations at 365 and 455 nm, to mimic experimental conditions for phosphor converted light emitting diodes, to show that the sample has a non-quenching photoluminescence emission up to at least 865 K for an excitation at 365 nm, and ∼865 K for an excitation at wavelength, 455 nm. The thermal stability of SmPO4 was found to be much higher than its structural analogue, EuPO4, which is also an orange-red emission phosphor, but possesses a thermal quenching temperature of 710 K (exc. 365 nm), and 735 K (exc. 455 nm). The extraordinary thermal stability of SmPO4 is a result of the energy transfer from deep defects to the Sm3+ ions at high temperatures. The color purity of SmPO4 (65%) was found to be slightly lower than the EuPO4 sample (70%), at room temperature. The results suggests that the rare earth orthophosphate, SmPO4, has a large potential for near-UV excited phosphor converted solid state lighting devices.
Keywords: SmPO4, photoluminescence, thermal quenching, lighting.

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Permalink: https://www.hzdr.de/publications/Publ-29993
Publ.-Id: 29993


Uranium(VI) complexation with aqueous silicates in the acidic to alkaline pH-range
Lösch, H.; Tits, J.; Marques-Fernandes, M.; Baeyens, B.; Krüger, S.; Chiorescu, I.; Stumpf, T.; Huittinen, N. M.;
An important parameter for the safety assessment of radioactive waste repositories is the prediction and modelling of aqueous complex formation reactions between actinides (An) and common dissolved inorganic or organic ligands.Alteration processes at the contact zone between the backfill material, bentonite, or the clay host rock and the cementitious materials of the geotechnical barrier will lead to high silicate concentrations in the groundwater, which may strongly influence the aqueous speciation of actinides[1]. A detailed knowledge of the An–silicate complex formation is therefore very important. In the present study, we have investigated the U(VI)-complexation in with aqueous silicates using two approaches: 1) Time-resolved laser-induced luminescence spectroscopy(TRLFS) in the acidic pH-range (pH 3.5)was used to determine the in-situU(VI) speciation in dependency of temperature(1-25°C)and silicon concentration, 2) the Schubert method was used to acquire the U(VI)-silicate complexation constant and stoichiometryin the alkaline pH-range where no literature data for U(VI)-silicates currently exists. For the TRLFS studythe uranium concentration was fixed at 5×10-6Mwith an ionic strength of 0.2 M (NaClO4),while the silicon concentration was varied between 3×10-4and1.5×10-3M. In the absence of silicate the 1:1 U-hydroxo complex was found to play a significant role in the U-speciationin the acidic pH-range. With increasing silicon concentration an increase of the luminescence intensity and a bathochromic shift of the emission spectra couldbe observed. Based on the peak deconvolution the free component spectra of U-hydroxo and U-silicate complexeswere extracted. The following slope analysis resulted in aslope close to 1 for all temperatures, confirming the formation of the UO2OSi(OH)3+complex at pH 3.5. The temperature dependent measurements enabledthe determination of the thermodynamicparameters ΔrH0=46.3kJ∙mol-1and ΔrS0=154.1J∙K-1∙mol-1. For the Schubert method, the U(VI) sorption distribution coefficient Rdon ZrO2was determined by LSC-measurements as a function of the ligand concentration and the pH in the alkaline pH range. By plotting the Rd-values as a function of the ligand concentration, information about the number of involved ligands in the U(VI)-silicate complex could be obtained. When further plotting the fitting constant (obtained from the Rd-plot) as a function of log[H+], the number of protons involved in the complexation reaction and the conditional complexation constant could be determined. With the obtained stoichiometry, two possible complexes could be proposed in the alkaline pH-range.DFT-calculations supportedthe formation of the UO2(OH)2OSi(OH)3complex.References:[1]D. Savage, Mineral. Mag., 2011, 75
  • Lecture (Conference)
    Gesellschaft Deutscher Chemiker, Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29988
Publ.-Id: 29988


Uranium(VI) complexation with aqueous silicates in the acidic to alkaline pH-range
Lösch, H.; Tits, J.; Marques-Fernandes, M.; Baeyens, B.; Chiorescu, I.; Krüger, S.; Stumpf, T.; Huittinen, N. M.;
An important parameter for the safety assessment of radioactive waste repositories is the prediction and modelling of aqueous complex formation reactions between actinides (An) and common dissolved inorganic or organic ligands. Alteration processes at the contact zone between the backfill material, bentonite, or the clay host rock and the cementitious materials of the geotechnical barrier will lead to high silicate concentrations in the groundwater, which may strongly influence the aqueous speciation of actinides such as uranium, which is stable in the hexavalent oxidation state under oxidizing conditions. [1]. A detailed knowledge of the U(VI) –silicate complex formation is therefore very important.
Depending on the used host rock and backfill material, the pH of the groundwater will be in the neutral to alkaline range. However, in this pH-range, reliable thermodynamic data for aqueous An(VI) - silicate complexes are scarce. In the acidic pH-range, only the 1:1 An(VI)-Si complex, i.e. An(VI)O2OSiOH3+, has been determined for U(VI), Np(VI), and Pu(VI), and the complex formation constants differ by almost two orders of magnitude (Table 1) [2].
Table 1: Complex formation constants for An(VI)-Si complexes [2].
An logK0
U(VI) -1,86
Np(VI) -2,61
Pu(VI) -3,65

In the alkaline pH-range (pH ~8), Yusov et al. [3] postulated the formation of either a ternary Pu-OH-Si complex: (PuO2(H2O)3(OH)OSi(OH)3) with the H3SiO4- ligand or a binary Pu-Si complex (PuO2(H2O)3O2Si(OH)2) with H2SiO42-. For other hexavalent actinides, no complexes in the alkaline pH-range have been reported, however, in analogy with Pu(VI), comparable complexes should also exist for U(VI) and Np(VI).
This contribution reports on a study of the U(VI) complexation with silicate in the pH range between 3.4 and 11.5. Two approaches were used: 1) Time-resolved laser-induced luminescence spectroscopy (TRLS) was applied to determine the in situ U(VI) speciation in U(VI) solutions with various silicate concentrations and various pH. 2) U(VI)-silicate complexation constants and complex stoichiometries were determined using Schubert’s method. For the TRLFS measurements, a U(VI) concentration of 5×10-6 M (pH = 3.5) or 1×10-7 M (pH = 9) was used, while the silicon concentration was varied between 3×10-4 and 1.5×10-3 M. To determine the thermodynamic parameters ΔrH0 and ΔrS0, temperature dependent measurements were performed in the range from 1°C to 25°C. The ionic strength was fixed with NaClO4 at 0.2 M. The Schubert method allows determination of complex stoichiometry and complexation constant by measuring the solid/liquid distribution ratio (Rd value) for the U(VI) sorption on a solid phase in absence and in the presence of increasing concentrations of silicate. Here, monoclinic ZrO2 was used as a solid phase. The U(VI) concentration in the experiments was 1×10-7 M and silicate concentrations were varied between 5×10-5 and 5×10-3 M, at pH values ranging from 6.0 to 11.5 at an ionic strength of 0.1 M NaCl. LSC measurements of the 233U activity were used to determine the U(VI) concentration in solution.
In the absence of aqueous silicates, the 1:1 uranium hydrolysis species UO2OH+ plays a significant role in the speciation starting from a pH of 3.5. Therefore, this species has to be taken into account in the speciation. Figure 1 shows the luminescence spectra with increasing Si-concentration at different temperatures. The obtained spectra show a bathochromic shift and an increase in the luminescence intensity with increasing silicate concentration. Based on peak deconvolution, the pure component spectra of the UO2OSi(OH)3+ and UO2OH+ complex were extracted. The species distributions were calculated by a least-square fit method. The following slope analysis resulted in a slope close to 1 for all temperatures, confirming the formation of a UO2OSi(OH)3+ complex at pH 3.5. The obtained complexation constants were corrected to standard conditions using the Davies equation. The obtained stability constant at 25°C is significantly higher than the literature values due to the consideration of the hydroxo complex and the solubility limit of the aqueous silicates [2]. A van’t Hoff plot was used to extract the reaction enthalpy and entropy, which were found to be ΔrH0 = 46.3 kJ∙mol-1 and ΔrS0 = 154.1 J∙K-1∙mol-1.

Figure 1: Emission spectra of the U-Si complexation at pH 3.5 with varying [Si] between 3×10-4 and 1.5×10-3 M, [U] = 5×10-6 M, fixed [NaClO4] = 0.2 M, in the temperature range between 1°C to 25°C.
For the Schubert method, the U(VI) sorption distribution coefficient Rd on ZrO2 was determined by LSC-measurements as a function of the ligand concentration and the pH in the alkaline pH range. By plotting the Rd-values as a function of the ligand concentration, information about the number of involved ligands in the U(VI)-silicate complex could be obtained. When further plotting the fitting constant (obtained from the Rd-plot) as a function of corrected pH, the number of protons involved in the complexation reaction and the conditional complexation constant could be determined. With the obtained stoichiometry, two possible complexes could be proposed in the alkaline pH-range, (i) UO2(OH)O2Si(OH)2- or (ii) UO2(OH)2OSi(OH)3-. DFT-calculations support the formation of the second complex with a corrected stability constant of logK0 = -16.30.


[1] D. Savage, Mineral. Mag.,2011, 75, 2401-2418.
[2] R. Guillaumont et al., Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, 2003, NEA-TBD.
[3] A. B. Yusov, A. M. Fedoseev, Russ. J. Coord. Chem., 2003, 29, 625-634.
  • Lecture (Conference)
    17th International Conference on the Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere, 15.-20.09.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29987
Publ.-Id: 29987


The capability of Ansys CFX to predict the mixing phenomena in ROCOM test facility
Boumaza, M.; Höhne, T.ORC; Mohammedi, B.; Dizene, R.
This work consists of a Computational Fluid Dynamics (CFD) modeling of a reference experiment on boron dilution in the Rossendorf coolant mixing Model (ROCOM) as part of a coordinated research project of the International Atomic Energy Agency, namely, “Application of numerical codes of fluid dynamics to the design of nuclear power plants”. This coordinated project aims to address the application of CFD codes to the process of optimizing the design of nuclear power plants related to pressurized water reactors and to evaluate the performance and predictive capabilities of these codes and to contribute to their validation. In this context, a three-dimensional numerical simulation study was carried out using CFD code ANSYS CFX v14.5, to study the boron mixing phenomenon at the core inlet and the downcomer of the ROCOM test facility. The phenomenon of experimental mixing occurs by the injection of a tracer (sodium chloride) into one of the loops of the ROCOM installation mainly containing demineralized water in its primary circuit. The concentration field of the tracer is measured and simulated at the entrance of the heart and in the lowering. The SST-kω turbulence model used in this study could reasonably predict the distribution of the injected tracer in measurement locations within the test facility. The results of this numerical simulation were compared to the Benchmark data provided by the ROCOM experimental facility of the Helmholtz-Zentrum Dresden-Rossendorf Institute.
Keywords: Boron dilution CFD codes Mixing

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Towards Optimal Bubble Generation for Biological Wastewater Treatment
Mohseni, E.ORC; Reinecke, S. F.; Hampel, U.
Gas bubble dispersion determines the efficiency of the aeration process in biological wastewater treatment plants (WWTP). The purpose of aeration is to provide an aerobic environment for microbial degradation of organic matters. This is an expensive procedure, which is responsible for the largest share of energy bill in the whole WWTP in the range from 45% to 75% [1]. The state of the art of aerators, which are currently in use at the activated sludge facilities, is the rubber membrane diffusers. These diffusers offer relatively low standard oxygen transfer efficiency (SOTE) in the range of 40% to 60% [2]. Several factors affect the SOTE, e.g. the gas holdup, bubble size, bubble residence time, and the apparent viscosity [3]. Among these parameters, the bubble size is of a great importance, since it directly influences the gas holdup and the bubble residence time. Moreover, the bubble size determines the surface area to volume ratio, which affects the volumetric oxygen transfer coefficient k_L a and the oxygen transfer rate OTR. To specify the oxygen transfer, one needs to know the mass transfer coefficient from a gas bubble as a function of its diameter and accurate information on the terminal bubble rising velocity. Accordingly, Motarjemi and Jameson have measured the initial bubble size required to achieve 95% transfer of available oxygen from an air bubble as a function of the depth of the basin [3].
To achieve the optimal bubble size, it is important to know the relation between the initial bubble volume and other influential parameters, e.g. the gas flow rate, orifice diameter, gas reservoir volume, and physical properties of both phases. Since 1960, many authors have tried to calculate the initial bubble volume. The majority of these models divide the bubble formation into two stages, namely the growing stage and the elongation stage through a neck. Each stage can be solved either by its corresponding force balance, or by empirical assumptions related to the moment of bubble detachment. Although these models are quite reliable in low flow rates, by increasing the gas flow rate, they diverge. Latter is due to the fact that, the assumptions, which are used to close the equations in each stage, do not take into account the variation in the detachment condition at different bubbling regimes.By increasing the gas flow rate, the bubble surface moves more dynamic and the influence of the gas momentum force is more pronounced. In this case, the final bubble is a product of multiple coalescence of smaller bubbles right above the orifice. Moreover, the three-phase contact of the gas phase, the liquid phase, and the solid phase during the bubble formation is generally a dynamic procedure. However, in most of the models this measure is assumed to be a constant value.

In the current study, we investigate the bubble formation from a submerged orifice at different bubbling regimes. To track the three-contact phase point inside and above the orifice, we use an optical setup with a matched refractive index of the solid and the liquid phase. Consequently, we are able to follow the three-phase contact point even inside of the orifice. To mimic the bubble formation in water, we keep the dimensionless Reynolds number constant. The bubble formation is recorded with a high-speed camera with a maximum spatial resolution of 2 μm and a temporal resolution of up to 25 μs.
The gas flow rate is set via a mass flow controller. We cover the full range of bubbling regimes, from the quasi-static to the chaotic regime. Similar to Badam et al., the change in the map of the bubbling regime is reported according to the dimensionless Froude and Bond number [4]. By increasing the gas flow rate, we track the progressive bubble volume and the trajectory of the bubble’s center of mass using an in-house bubble tracking algorithm. Latter enables us to report the change in the distance of the bubble’s center of mass to the orifice surface, until one instant before the bubble pinch-off, and correlate it to its corresponding bubbling regime. By implementing these detachment conditions, we develop a model to estimate the final bubble volume. Finally, using this model we are able to estimate the appropriate operating parameters, e.g. the gas flow rate, and the orifice diameter, in order to achieve the optimal bubble size for enhanced aeration efficiency.


References
1. Zimmerman, W.B., V. Tesař, and H.H. Bandulasena, Towards energy efficient nanobubble generation with fluidic oscillation. Current Opinion in Colloid & Interface Science, 2011. 16(4): p. 350-356.
2. Wang, L.K., N.K. Shammas, and Y.-T. Hung, Advanced biological treatment processes. Vol. 9. 2010: Springer Science & Business Media.
3. Motarjemi, M. and G. Jameson, Mass transfer from very small bubbles—the optimum bubble size for aeration. Chemical Engineering Science, 1978. 33(11): p. 1415-1423.
4. Badam, V., V. Buwa, and F. Durst, Experimental investigations of regimes of bubble formation on submerged orifices under constant flow condition. The Canadian Journal of Chemical Engineering, 2007. 85(3): p. 257-267.
Keywords: Bubble Formation; Aeration; Activated Sludge; Oxygen Mass Transfer; Bubbling Regime
  • Contribution to proceedings
    14th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-14), 30.05.-03.06.2019, Guilin, China

Permalink: https://www.hzdr.de/publications/Publ-29982
Publ.-Id: 29982


ExploreASL: an image processing pipeline for multi-center ASL perfusion MRI studies
Mutsaerts, H. J.; Petr, J.ORC; Groot, P. F.; Vandemaele, P.; Ingala, S.; Robertson, A. D.; Vaclavu, L.; Groote, I.; Kuijf, H.; Zelaya, F.; O'Daly, O.; Hilal, S.; Wink, A. M.; Kant, I.; Caan, M.; Morgan, C.; de Bresser, J.; Lysvik, E.; Schrantee, A.; Bjornebekk, A.; Clement, P.; Shirzadi, Z.; Kuijer, J.; Anazodo, U.; Pajkrt, D.; Richard, E.; Bokkers, R.; Reneman, L.; Masellis, M.; Guenther, M.; Macintosh, B.; Achten, E.; Chappell, M.; van Osch, M.; Golay, X.; Thomas, D.; de Vita, E.; Bjornerud, A.; Nederveen, A.; Hendrikse, J.; Asllani, I.; Barkhof, F.
Arterial spin labeling (ASL) has undergone significant development since its inception, with a focus on improving standardization and reproducibility of its acquisition and quantification. In a community-wide effort towards robust and reproducible clinical ASL image processing, we developed the software package ExploreASL, allowing standardized analyses across centers and scanners. The procedures used in ExploreASL capitalize on published image processing advancements and address the challenges of multi-center datasets with scanner-specific processing and artifact reduction to limit patient exclusion. ExploreASL is self-contained, written in MATLAB and based on Statistical Parameter Mapping (SPM) and runs on multiple operating systems. The toolbox adheres to previously defined international standards for data structure, provenance, and best analysis practice. ExploreASL was iteratively refined and tested in the analysis of >10,000 ASL scans using different pulse-sequences in a variety of clinical populations, resulting in four processing modules: Import, Structural, ASL, and Population that perform tasks, respectively, for data curation, structural and ASL image processing and quality control, and finally preparing the results for statistical analyses on both single-subject and group level. We illustrate ExploreASL processing results from three cohorts: perinatally HIV-infected children, healthy adults, and elderly at risk for neurodegenerative disease. We show the reproducibility for each cohort when processed at different centers with different operating systems and MATLAB versions, and its effects on the quantification of gray matter cerebral blood flow. ExploreASL facilitates the standardization of image processing and quality control, allowing the pooling of cohorts to increase statistical power and discover between-group perfusion differences. Ultimately, this workflow may advance ASL for wider adoption in clinical studies, trials, and practice.

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Publ.-Id: 29980


ASL-BIDS, the brain imaging data structure extension for arterial spin labeling
Clement, P.; Castellaro, M.; Okell, T.; Thomas, D.; Gorgolewski, C.; Appelhoff, S.; Petr, J.ORC; Chappell, M.; Mutsaerts, H.-J.
Purpose/Introduction: The Brain Imaging Data Structure (BIDS) is a recently developed data storage standard, that meets the need for a structured manner to organize imaging data in the age of big datasets and data sharing (https://bids.neuroimaging.io). 1 This abstract presents a BIDS extension for ASL, which only supports ASL approaches as recommended in the ASL acquisition consensus paper, and several M0 calibration approaches. 2

Subjects and Methods: A group of ASL experts initiated this extension by defining several concepts and preparing a first draft. This draft was shared online from May 2017 until March 2019 with the international ASL community, and several teleconference and face-to-face meetings were organised. Per BIDS convention, existing BIDS fields were reused for the ASL-BIDS extension if possible. The BIDS fields names were based on the NEMA ASL DICOM fields, where possible. Additionally, three example datasets were collected 3
and efforts were initiated to adapt existing ASL analysis tools and the BIDS validator for ASL-BIDS compatibility.

Results: Six concepts were defined to allow a uniform yet flexible ASL-BIDS specification. First, it was decided to focus solely on the implementation of the ASL approaches discussed in the ASL consensus paper: single- and multi-delay, pulsed, continuous, and pseudo-continuous ASL. 5 Second, the BIDS-structure consists of two mandatory files and several optional files (Fig. 1). Third, it is obligatory to keep the ASL time series in the original acquisition order in a 4D NIfTI file, including any M0, if it was part of the original ASL
time series. If an M0 image was acquired separately, it should be stored as a separate NIfTI file. The ASL-context BIDS field explains the content of each volume in the ASL time series. Fourth, the derivative images DeltaM and CBF are considered to be raw images if the ASL-sequence or vendor only provided derivative images, lacking raw data. This principle follows the prioritization shown in Fig. 2. Fifth, all ASL data need to be stored in at least 32 bit floating point, without any scale slopes. Some vendor implementations store scaled ASL data to increase the precision of the stored data within the traditional 12 bit DICOM files. It is the responsibility of the DICOM to BIDS conversion to apply any existing scale slopes. Sixth, it is recommended to specify as much information as labeling as possible: the exact location of the labeling plane and the labeling efficiency.

Discussion/Conclusion: The current ASL-BIDS extension is restricted to the ASL approaches recommended by the consensus paper. 1 With the current development of more advanced ASL approaches, such as time-encoded and velocity-selective ASL, the ASL-BIDS may be extended for these technique. Also, a derivatives extension for ASL is anticipated.
  • Poster
    ESMRMB 2019, 36th Annual Scientific Meeting, 05.10.2019, Rotterdam, Netherlands
  • Abstract in refereed journal
    Magnetic Resonance Materials in Physics, Biology and Medicine 32(2019)Suppl 1, S147-S148
    DOI: 10.1007/s10334-019-00754-2

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Publ.-Id: 29979


Multi-modal evaluation of haemodynamic impairments within individual watershed areas reveals increased sensitivity in unilateral carotid artery stenosis
Kaczmarz, S.; Göttler, J.; Petr, J.ORC; Hansen, M. B.; Kufer, J.; Zimmer, C.; Mouridsen, K.; Hyder, F.; Preibisch, C.
Purpose/Introduction: Internal carotid-artery stenosis (ICAS) is a major public health issue and causes complex haemodynamic impairments. 1–3 However, influences of microvascular effects remain poorly understood. Furthermore, increased sensitivity for regional pathophysiological changes is required to detect early disease stages.
The aim of our study was therefore to establish a multi-modal MRI protocol allowing deeper insights into the pathology. Furthermore, we hypothesize to be most sensitive to ICAS-impairments within individual watershed areas (iWSAs), which were proposed to be most vulnerable to haemodynamic compromise. 4

Subjects and Methods: Fifty-nine participants (29 unilateral ICAS-patients, age = 70.1 ± 4.8y and 30 age-matched healthy controls [HC]) underwent MRI on a Philips 3T Ingenia. The imaging protocol yielded oxygenation, perfusion and microvascular biomarkers which are summarized in Fig. 1. Additionally, iWSA’s were defined for each participant. 4 Mean haemodynamic parameter values were compared within each hemisphere of ICAS-patients vs. HC and inside vs. outside iWSAs (Fig. 2A, B) in GM and WM.

Results: Exemplary data of an ICAS-patient is shown in Fig. 2. On group-level, significant lateralisation of CBF, CVR, rCBV, CTH and OEC were found in ICAS, while rOEF was not lateralized (Fig. 3). Lateralisation was significantly enhanced inside iWSAs compared to outside of iWSAs for CBF and CVR, with a strong trend for rCBV—and strongest in WM of iWSAs (t test, p \ 0.05). OEC and CTH were indeed lateralized, but not different inside vs. outside iWSAs (Fig. 3). All HC parameters were symmetrical (data not shown).
Discussion/Conclusion: We successfully applied the proposed multimodal MRI-protocol and demonstrated its sensitivity to haemodynamic impairments in ICAS. Specificity was affirmed by symmetrical HC results. Individual parameter lateralisation in ICAS excellently agrees with the literature. Decreased CVR along with increased rCBV indicates chronic vasodilation. 1 Pronounced effects in WM-iWSA fit with the different blood supply in GM/WM. Ipsi-laterally decreased CBF, symmetrical rOEF 2 and increased CTH also coincide with recent studies 3 . The DCBF vs. DrOEF mismatch could relate to variable oxygen diffusivity 8 —potentially moderated by CTH 3, 9 . Interestingly, CTH and OEC lateralisation were iWSA-location independent, which matches previous findings. 10 These complimentary information of TTP and CTH about macrovascular effects, respectively microvascular flow 3 are highly promising to gain deeper insights into the pathology. And as initially hypothesized, evaluation within iWSA significantly increased the sensitivity to
CBF, CVR and rCBV impairments and allows to detect even subtle changes.
  • Lecture (Conference)
    ESMRMB 2019, 36th Annual Scientific Meeting, 05.10.2019, Rotterdam, Netherlands
  • Abstract in refereed journal
    Magnetic Resonance Materials in Physics, Biology and Medicine 32(2019)Suppl 1, S352-S353
    DOI: 10.1007/s10334-019-00755-1

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  • Secondary publication expected from 24.09.2020

Permalink: https://www.hzdr.de/publications/Publ-29978
Publ.-Id: 29978


Multi-modality perfusion imaging in gliomas: quantitative and visual comparison between ASL, DSC, and [15O]H20 PET
Petr, J.ORC; Verburg, N.; Koopman, T.; Kuijer, J. P.; Barkhof, F.; van den Hoff, J.ORC; Boellaard, R.; de Witt Hamer, P. C.; Mutsaerts, H. J.
Purpose/Introduction
Glioma vascularization and perfusion are important factors for tumor diagnostics. Dynamic Susceptibility Contrast (DSC) provides a proxy of perfusion by measuring mean transit time and blood volume and is sensitive to blood-brain-barrier breakdown. Arterial spin labeling (ASL) measures true tissue perfusion and can thus provide complementary information to DSC that may aid in tumor grading and in imaging the treatment response to, e.g., antiangiogenic drugs. Agreement of ASL and PET was shown in volunteers 1 .
However, ASL can also partly show intravascular signal making ASL imaging of tumors challenging especially in the presence of vascular shunting. We compared ASL and DSC to the gold-standard for perfusion, [ 15 O]H 2 0 PET, to understand their limits as a surrogate of true regional perfusion.

Subjects and Methods
As part of the FRONTIER study, 8 glioma patients underwent multiple biopsies before scanning using Philips 3T Achieva MR and Gemini PET-CT 2 . PET (10min, 370 MBq of [ 15 O]H 2 0, simultaneous arterial blood sampling), ASL (pCASL 2D EPI, post-labeling delay and labeling duration 1800ms, 3x3x5 mm 3 ), DSC (TR 1.9s, TE 30ms, 1.7x2.4x3.6mm 3 , preloaded contrast) images were acquired. Cerebral blood flow (CBF) was quantified for ASL with ExploreASL, for DSC with Olea Sphere 3.0 with AIF obtained manually from MCA 3 . CBF images were aligned to PET and downsampled 6x6x6mm 3 resolution. Mean and voxel-wise CBF was compared between modalities in tumors and in contralateral-hemisphere gray matter (GM). Absolute and relative CBF (divided by subject’s mean whole-hemisphere contralateral GM CBF) were assessed.

Results
Mean hemispheric and voxelwise GM CBF values in the contralateral hemisphere were compared before and after normalization to global GM mean. For relative CBF, we observed a linear relationship between modalities in the tumor maximum values. Voxelwise analysis shows good agreement of PET and ASL for CBF ratio<1.5. For higher values ASL overestimated CBF, however, the relation was monotonic. DSC and ASL differed due to ASL overestimation in shunting vessels or low DSC signal in non-enhancing
gliomas.

Discussion/Conclusion
CBF normalization to contralateral GM improves the agreement of ASL and PET in tumors, after which a linear relationship in tumor-maximum was observed between all three modalities. The voxel-wise analysis, however, showed that ASL overestimates CBF in the presence of vascular shunting offering a different type of contrast than perfusion. We also observed increased CBF in both PET and ASL in non-enhancing tumors where CBF was underestimated by DSC. ASL presents a viable alternative to DSC with a monotonic relation to PET CBF, can present complementary information to DSC and thus warrants further research in its utility for glioma assessment.
  • Lecture (Conference)
    ESMRMB 2019, 36th Annual Scientific Meeting, 05.10.2019, Rotterdam, Netherlands

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Glioma MR Imaging 2.0: a new European Cooperation in Science & Technology (COST) Action
Clement, P.; Hirschler, L.; Jančálek, R.; Keil, V.; Maumet, C.; Petr, J.ORC; Smits, M.; Zhao, M.; Warnert, E. A. H.
Purpose/Introduction
In Europe, 50,000 new cases of primary glioma occur each year, and this number is expected to rise with the aging population 1 . Established international consortia are putting tremendous research efforts into a better understanding of glioma pathology and improved treatment strategies. Magnetic resonance imaging (MRI) only has a minor role in these research efforts, despite being a widely available medical imaging modality and whilst advanced MRI techniques are emerging with great potential for improved characterisation of
glioma. To exploit advanced MRI to the fullest, two issues need to be solved: (1) The scattered research landscape in which advanced MRI is being developed for glioma imaging. (2) The limited presence of advanced MRI research in established consortia for clinical work and research in glioma. To solve these issues, we have recently formed Glioma MR Imaging 2.0 (GliMR), an international consortium funded by the European Cooperation in Science & Technology (COST) 2 . In the coming 4 years, GliMR will establish an
international network of experts in glioma research, patient organisations, and data and MR imaging scientists that aims to progress development and application of MRI for improved decision making in diagnosis, patient monitoring, and assessment of treatment response in clinical trials and practice.

Subjects and Methods
GliMR starts as a network of 37 proposers spread across 22 countries world-wide (Figure 1). There are 5 working groups (WGs) (Figure 2) that will ensure we will reach the Research Coordination and Capacity Building Objectives of the network (Table 1) via the organisation of meetings, workshops, and training schools. Additionally, individual researchers and clinicians can apply for funds to go on Short Term Scientific Missions (STSMs) and gain experience by working in a different hospital/lab abroad. The network will be open to new members and participation for all those interested is highly encouraged.

Results
GliMR will lead to an international network operating at the forefront of glioma imaging diagnostics. It will result into recommendations and open-access software tools for advanced MRI assessment of glioma, the creation of multi-site, cross-border data sets on glioma imaging, and strengthened connections between all stakeholders in glioma diagnostics. GliMR will facilitate further understanding of glioma pathophysiology, scientific breakthroughs in novel therapies and improve personalised patient management, ultimately
increasing the quality of life of patients diagnosed with glioma.

Discussion/Conclusion
We would like to thank all proposers and our advisors for their input to the proposal. Special thanks go to the EORTC, GLASS, INCF, PanCare Society, Gold Standard Phantoms, Medical Software Solutions, Mediri, and Quantib for endorsing GliMR.
  • Lecture (Conference)
    ESMRMB 2019, 36th Annual Scientific Meeting, 05.10.2019, Rotterdam, Netherlands

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Publ.-Id: 29976


Anforderungen an Materialien zur definierten Immobilisierung von Biomolekülen und Zellen
Raff, J.ORC
In dem Vortag wird der aktuelle Stand der Forschungen zur Funktionalisierung von Oberflächen am HZDR vorgestellt und daraus entsprechende Anforderungen an Materialien zur definierten Immobilisierung von Molekülen und Zellen abgeleitet.
Keywords: Immobilisierung, Funktionalisierung, Mikroskopie
  • Invited lecture (Conferences)
    PolCarr-Innovationsforum, 28.-29.03.2019, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29974
Publ.-Id: 29974


Spatially-resolved speciation of Eu(III) and Cm(III) on granite surfaces
Demnitz, M.; Molodtsov, K.; Bollermann, T.; Schymura, S.; Schierz, A.; Schmidt, M.ORC
The search for a suitable site for a nuclear waste repository in Germany requires linking molecular scale information with the large scale of the repository. Here, we present a novel approach to bridge the gap from the molecular to the millimeter scale.
We complement well-known surface investigation techniques such as Raman microscopy, interferometry and autoradiography with μTRLFS. This newly developed technique allows the investigation of luminescent radionuclides, such as Cm(III) and its chemical homologue Eu(III), on the surface of crystalline rocks with complex mineral composition. The combination of multiple surface investigation techniques allows to draw a correlation between surface mineralogy, topography, radionuclide speciation and the resulting retention behavior.
In an initial μTRLFS study using natural granite from Eibenstock, Germany, it was found that uptake strength, capacity, and homogeneity vary from mineral to mineral. For example, Eu(III) on feldspars adsorbed relatively weakly but in large amounts, whereas only minor sorption was observed on quartz, but with a high sorption strength. In addition, distinct sorption behavior was found on some mineral grain boundaries.[1]
To obtain a more comprehensive picture, granitic drill core samples were obtained from across Europe, from which thin section samples were prepared for μTRLFS experiments. The sorption of Eu(III) and Cm(III) onto these samples was conducted using solutions with defined ionic strength, metal concentration and pH.
We will discuss the speciation differences between varying mineral phases one each rock, as well as differences between the characteristic crystalline rocks from diverse locations and the potential impact of the radionuclide speciation on their migration properties in the geosphere. Additionally the results will be compared to single phase studies from literature to evaluate the validity of an additive component mixing approach.
Keywords: sorption, granite, europium, curium, spatial, resolution
  • Lecture (Conference)
    Goldschmidt Barcelona 2019, 18.-23.08.2019, Barcelona, Spanien
  • Lecture (Conference)
    GDCh Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Deutschland

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Publ.-Id: 29973


Hemodynamic impairments in asymptomatic unilateral carotid artery stenosis are most pronounced within individual watershed areas
Kaczmarz, S.; Petr, J.ORC; Hansen, M. B.; Hock, A.; Kufer, J.; Mouridsen, K.; Zimmer, C.; Hyder, F.; Preibisch, C.; Göttler, J.
Background: Watershed areas are most susceptible for ischemia in patients with high-grade internal carotid artery stenosis (ICAS) [1]. Thorough investigation of the currently not well understood hemodynamic impairments is important to improve treatment guidelines. [2] Here, we propose a multimodal-MRI protocol to better characterise hemodynamic impairments in asymptomatic ICAS with increased sensitivity within individual watershed areas (iWSA).
Methods: Twenty-nine asymptomatic, unilateral ICAS patients (age = 70.1 ± 4.8y), and 30 age-matched healthy controls (age = 70.3 ± 7.3y) underwent 3T-MRI. Imaging yielded maps of cerebrovascular reactivity (CVR) [3], cerebral blood flow (CBF) [4], relative oxygen extraction fraction (rOEF), [5] relative cerebral blood volume (rCBV), capillary transit-time heterogeneity (CTH), and oxygen extraction capacity (OEC) [6] (Fig. 1). Based on DSC-derived time-to-peak (TTP) maps, iWSAs were defined for each participant (Fig. 2a) [7]. Mean hemodynamic parameter values within each hemisphere were compared between ICAS-patients vs. HC and inside vs. outside iWSAs (Fig. 2a, b) within GM and WM.
Result: We found significant lateralisation of CBF, CVR, rCBV, CTH, and OEC for ICAS-patients (all p < 0.05), whereas no significant rOEF lateralisation was found (Fig. 2). Inside iWSAs, lateralisation was enhanced for CBF and CVR (p < 0.05), with a strong trend for rCBV.
Overall, lateralisation was stronger within WM than GM (Fig. 2I).
Contrary, OEC and CTH were indeed lateralised, but comparable inside vs. outside iWSAs (Fig. 2I). For HC, all parameters were symmetrical between hemispheres (data not shown).
Discussion: Observed impairments of CBF, CVR, and CBV are in line with recent studies [8]. As proposed, CBF and CVR impairments are specifically pronounced within iWSAs (Fig. 2I). Interestingly, CTH and OEC were lateralized, however not specifically changed within iWSAs, indicating an independently impaired hemodynamic mechanism.
Conclusion: CBF and CVR reductions may be indicative of the severity of hemodynamic changes within iWSAs, and thus future stroke risk. CTH and OEC impairments are independent of iWSA locations.
  • Lecture (Conference)
    54. Jahrestagung der Deutschen Gesellschaft für Neuroradiologie e.V., 09.10.2019, Frankfurt, Germany

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Publ.-Id: 29972


Recovery of cerebrovascular reactivity after treatment of asymptomatic carotid artery stenosis is assessable by non-invasive breath-hold fMRI within global watershed areas
Kaczmarz, S.; Petr, J.ORC; Sollmann, N.; Hock, A.; Zimmer, C.; Hyder, F.; Preibisch, C.; Göttler, J.
Background: Treatment of asymptomatic internal carotid artery stenosis (ICAS) patients remains still controversial [1]. Hemodynamic biomarkers such as the cerebrovascular reactivity (CVR) are promising to identify patients who benefit from revascularization precedures [2–4]. However, commonly employed methods are invasive acetazolamide or complicated gas applications [2–6]. The aim of our study was therefore to measure CVR recovery in ICAS-patients after treatment by easily-applicable breath-hold fMRI (BH-fMRI) with increased sensitivity by evaluation within global watershed areas (gWSAs) [7].
Methods: Thirty-three participants (16 asymptomatic, unilateral ICAS-patients, age = 71.4 ± 5.8y, and 17 healthy controls [HC], age = 70.8 ± 5.3y, see Fig. 1) underwent MRI on a 3T Philips Ingenia.
All participants were scanned twice, patients before and at least three months after treatment, HC at similar follow-up delays. BH-fMRI comprised five breath-holds à 15s each; CVR-maps were calculated by data-driven analysis [8] (Fig. 2a, b). Lateralization of CVR was calculated in GM of gWSAs between hemispheres for each participant (Fig. 2c).
Result: Exemplary ICAS-patient’s data shows impaired CVR before treatment, which recovered after treatment (Fig. 1A,B). On group level, CVR was significantly impaired ipsilateral to the stenosis before treatment (Fig. 3a, t-test, p = 0.0038). After treatment, CVR significantly recovered (2-sample t-test, p = 0.0495) resulting in symmetrical CVR between hemispheres (t-test, p = 0.25). HC data was symmetrical between hemispheres (Fig. 3b, p > 0.60).
Discussion: BH-fMRI based evaluation within gWSAs was sensitive to CVR impairments in asymptomatic ICAS, indicating chronic vasodilation [5]. Specificity was affirmed by symmetrical HC results. Consistent with current literature, CVR recovered after ICAS-treatment [4–7], demonstrating improved hemodynamic status.
Conclusion: We successfully analyzed CVR recovery after ICAS treatment by easily applicable, tolerable and non-invasive BH-fMRI within clinically feasible scan times. This technique could potentially improve future treatment decisions.
  • Lecture (Conference)
    54. Jahrestagung der Deutschen Gesellschaft für Neuroradiologie e.V., 09.10.2019, Frankfurt, Germany

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Publ.-Id: 29971


Tuning the metal-insulator transition in epitaxial SrVO3 films by uniaxial strain
Wang, C.ORC; Zhang, H.; Deepak, K.; Chen, C.; Fouchet, A.; Duan, J.; Hilliard, D.; Kentsch, U.; Chen, D.; Zeng, M.; Gao, X.; Zeng, Y.-J.; Helm, M.; Prellier, W.; Zhou, S.ORC
Understanding of the metal-insulator transition (MIT) in correlated transition-metal oxides is a fascinating topic in condensed matter physics and a precise control of such transitions plays a key role in developing novel electronic devices. Here we report an effective tuning of the MIT in epitaxial SrVO3 (SVO) films by expanding the out-of-plane lattice constant without changing in-plane lattice parameters, through helium ion irradiation. Upon increase of the ion fluence, we observe a MIT with a crossover from metallic to insulating state in SVO films. A combination of transport and magnetoresistance measurements in SVO at low temperatures reveals that the observed MIT is mainly ascribed to electron-electron interactions rather than disorder-induced localization. Moreover, these results are well supported by the combination of density functional theory and dynamical mean field theory (DFT+DMFT) calculations, further confirming the decrease of the bandwidth and the enhanced electron-electron interactions resulting from the expansion of out-of-plane lattice constant. These findings provide insights into the understanding of MIT in correlated oxides and perspectives for the design of unexpected functional devices based on strongly correlated electrons.
Keywords: Oxide thin film, Strain engineering, Metal-insulator transition, Lattice distortion, Correlated electrons

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Publ.-Id: 29969


Confirmation of the prognostic value of pretherapeutic tumor SUR and MTV in patients with esophageal squamous cell carcinoma
Hofheinz, F.ORC; Li, Y.; Steffen, I.; Lin, Q.; Lili, C.; Hua, W.; van den Hoff, J.ORC; Zschaeck, S.
Purpose

The prognosis for patients with inoperable esophageal carcinoma is still poor and the reliability of individual therapy outcome prediction based on clinical parameters is not convincing. In a recent publication, we were able to show that PET can provide independent prognostic information in such a patient group and that the tumor-to-blood standard uptake ratio (SUR) can improve the prognostic value of tracer uptake values. The present investigation addresses the question of whether the distinctly improved prognostic value of SUR can be confirmed in a similar patient group that was examined and treated at a different site.
Methods

18F-FDG PET/CT was performed in 147 consecutive patients (115 male, 32 female, mean age: 62 years) with newly diagnosed esophageal squamous cell carcinoma prior to definitive radiochemotherapy. In the PET images, the metabolic active volume (MTV) of the primary tumor was delineated with an adaptive threshold method. For the resulting ROIs, SUVmax and total lesion glycolysis (TLG = MTV × SUVmean) were computed. The blood SUV was determined by manually delineating the aorta in the low-dose CT. SUR values were computed as ratio of tumor SUV and blood SUV. Univariate Cox regression and Kaplan–Meier analysis with respect to overall survival (OS), distant-metastases-free survival (DM), and locoregional control (LRC) was performed. Additionally, a multivariate Cox regression including clinically relevant parameters was performed.
Results

Univariate Cox regression revealed MTV, TLG, and SURmax as significant prognostic factors for OS. MTV as well as TLG were significant prognostic factors for LRC while SURmax showed only a trend for significance. None of the PET parameters was prognostic for DM. In univariate analysis, SUVmax was not prognostic for any of the investigated clinical endpoints. In multivariate analysis (T-stage, N-stage, MTV, and SURmax), MTV was an independent prognostic factor for OS and showed a trend for significance for LRC. SURmax was not an independent predictor for OS or LRC. When including the PET parameters separately in multivariate analysis, MTV as well as SURmax were prognostic factors for OS indicating that SURmax is independent from the clinical parameters but not from MTV. In addition, MTV was an independent prognostic factor for LRC in this separate analysis.
Conclusions

Our study revealed a clearly improved prognostic value of tumor SUR compared to tumor SUV and confirms our previously published findings regarding OS. Furthermore, SUR delivers prognostic information beyond that provided by the clinical parameters alone, but does not add prognostic information beyond that provided by MTV in this patient group. Therefore, our results suggest that pretherapeutic MTV is the parameter of choice for PET-based risk stratification in the considered setting but further investigations are necessary to demonstrate that this suggestion is correct.
Keywords: PET Esophageal cancer Definitive radiochemotherapy SUV SUR

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Publ.-Id: 29968


HZDR Data Management Strategy — Meeting at Leibniz Institute of Polymer Research Dresden (IPF)
Knodel, O.ORC; Gruber, T.ORC; Müller, S.ORC
Top-Level Architecture of the proposed HZDR Data Management Strategy with an example experiment
Keywords: data management
  • Open Access Logo Invited lecture (Conferences)
    Meeting at Leibniz Institute of Polymer Research Dresden (IPF), 15.11.2019, Dresden, Germany

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Publ.-Id: 29967


Validation of an independent prognostic value of the asphericity of F18-fluorodeoxyglucose (FDG) uptake in non-small cell lung cancer (NSCLC) patients undergoing treatment in curative intent
Rogasch, J.; Furth, C.; Chibolela, C.; Hofheinz, F.ORC; Ochsenreither, S.; Rückert, J.; Neudecker, J.; Böhmer, D.; Laffert, M.; Amthauer, H.; Frost, N.
Background

In patients with non-small cell lung cancer (NSCLC), asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) has shown prognostic significance. This study aimed at validation in an independent, sufficiently large cohort.
Patients and Methods

Retrospective study in 311 NSCLC patients undergoing FDG-PET/CT before curatively intended treatment (always including surgery). 140 patients had UICC stage I, 78 stage II, and 93 stage III (adenocarcinoma [ADC]:153; squamous cell carcinoma [SCC]:141). Primary tumor MTV was delineated with semiautomated background-adapted threshold relative to SUVmax. Cox regression (PFS/OS) for PET (MTV, ASP, SUVmax), clinical (T/N descriptor, UICC stages), histological and treatment variables (Rx/1 vs. R0 resection, chemotherapy/radiotherapy yes/no).
Results

Events (progression/relapse) occurred in 167/311 patients, 137 died (median survivor follow-up, 37 months). In multivariable Cox regression for OS, ASP>33.3% (HR, 1.58 [1.04-2.39]), male sex (1.84), age (1.04 per year), EGOG≥2 vs. 0/1 (2.68), stage II vs. I (1.96), and Rx/1 vs. R0 resection (2.1) were significant. Among separate UICC stages, ASP only predicted OS in stage II (optimal, >19.5%; median OS, 33 vs. 59 months). Regarding PFS, ASP>21.2%, male sex, EGOG≥2, stage II vs. I, and Rx/1 resection were prognostic. ASP remained prognostic in stage II (optimal, >19.5%; PFS, 12 vs. 47 months). Log-rank test for ASP was significant at any cut-off ≥18% (OS) or from 9-59% (PFS).
Conclusion

ASP was validated as prognostic factor for PFS and OS in patients with NSCLC and curative treatment intent, especially stage II. High ASP in stage II could imply intensified treatment or intensified follow-up.
Keywords: Prognosis survival FDG-PET metabolic tumor volume quantification

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Permalink: https://www.hzdr.de/publications/Publ-29966
Publ.-Id: 29966


Time reversal and quantum Loschmidt echo in optical lattices
Schützhold, R.; Szpak, N.;
A quantum Loschmidt echo (also referred to as quantum time mirror) corresponds to an effective time inversion after which the quantum wave function reverses its previous time evolution and eventually reaches its initial distribution again. We propose a comparably simple protocol for such an effective time reversal for ultra-cold atoms in optical lattices which should be easier to realize experimentally than previous proposals.
Keywords: Quantum Physics; Quantum Gases

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Permalink: https://www.hzdr.de/publications/Publ-29961
Publ.-Id: 29961


Reply to comment on "Interaction of a BEC with a gravitational wave"
Schützhold, R.;
This reply contains a brief response to the comment by R. Howl, D. Rätzel, and I. Fuentes [arXiv:1811.10306]
Keywords: Quantum Physics, General Relativity and Quantum Cosmology

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Permalink: https://www.hzdr.de/publications/Publ-29960
Publ.-Id: 29960


Quantum simulation of spontaneous pair creation in 2D optical lattices
Schützhold, R.; Klar, L.; Szpak, N.;
One of the fundamental predictions of Quantum Electrodynamics (QED) is the spontaneous creation of particle--antiparticle pairs from vacuum in presence of a very strong electric field. Under these extreme conditions a strongly bound state can fetch an otherwise unobservable electron from the Dirac sea, leaving behind a hole representing a positron. Although generally known for many decades, the effect has not yet been demonstrated experimentally. We propose an analogue model of the quantum Dirac field, realized by ultra--cold fermionic atoms in an optical lattice, aiming at an experimental simulation of this intriguing non--perturbative phenomenon. Numerical simulations demonstrate the effect of spontaneous pair creation in the optical analogue system, in qualitative agreement with QED: in the adiabatic regime the vacuum can be destabilized only by supercritical fields exceeding a critical threshold.
Keywords: Quantum Physics, Quantum Gases

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Permalink: https://www.hzdr.de/publications/Publ-29959
Publ.-Id: 29959


Phonon Pair Creation by Inflating Quantum Fluctuations in an Ion Trap
Schützhold, R.; Wittemer, M.; Hakelberg, F.; Kiefer, P.; Schröder, J.-P.; Warring, U.; Schaetz, T.; Fey, C.;
Quantum theory predicts intriguing dynamics during drastic changes of external conditions. We switch the trapping field of two ions sufficiently fast to tear apart quantum fluctuations, i.e., create pairs of phonons and, thereby, squeeze the ions’ motional state. This process can be interpreted as an experimental analog to cosmological particle creation and is accompanied by the formation of spatial entanglement. Hence, our platform allows one to study the causal connections of squeezing, pair creation, and entanglement and might permit one to cross-fertilize between concepts in cosmology and applications of quantum information processing.
Keywords: Inflation, Quantum Information with trapped Ions, Quantum simulation

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Permalink: https://www.hzdr.de/publications/Publ-29958
Publ.-Id: 29958


Relaxation dynamics in a Hubbard dimer coupled to fermionic baths: phenomenological description and its microscopic foundation
Schützhold, R.; Kleinherbers, E.; Szpak, N.; König, J.;
We study relaxation dynamics in a strongly-interacting two-site Fermi-Hubbard model that is induced by fermionic baths. To derive the proper form of the Lindblad operators that enter an effective description of the system-bath coupling in different temperature regimes, we employ a diagrammatic real-time technique for the reduced density matrix. An improvement on the commonly-used secular approximation, referred to as coherent approximation, is presented. We analyze the spectrum of relaxation rates and identify different time scales that are involved in the equilibration of the Hubbard dimer after a quantum quench.

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Permalink: https://www.hzdr.de/publications/Publ-29957
Publ.-Id: 29957


On the Use of Statistical Entropy Analysis as Assessment Parameter for the Comparison of Lithium-Ion Battery Recycling Processes
Velázquez-Martinez, O.; van den Boogaart, K. G.ORC; Lundström, M.; Santasalo-Aarnio, A.; Reuter, M.ORC; Serna-Guerrero, R.
The principle of the circular economy is to reintroduce end-of-life materials back into the economic cycle. While reintroduction processes, for example, recycling or refurbishing, undoubtedly support this objective, they inevitably present material losses or generation of undesired by-products. Balancing losses and recoveries into a single and logical assessment has now become a major concern. The present work broadens the use of relative statistical entropy and material flow analysis to assess the recycling processes of two lithium-ion batteries previously published in the literature. Process simulation software, that is, HSC Sim®, was employed to evaluate with a high level of accuracy the performance of such recycling processes. Hereby, this methodology introduces an entropic association between the quality of final recoveries and the pre-processing stages, that is, shredding, grinding, and separation, by a parameter based on information theory. The results demonstrate that the pre-processing stages have a significant impact on the entropy value obtained at the final stages, reflecting the losses of materials into waste and side streams. In this manner, it is demonstrated how a pre-processing system capable of separating a wider number of components is advantageous, even when the final quality of refined products in two different processes is comparable. Additionally, it is possible to observe where the process becomes redundant, that is, where processing of material does not result in a significant concentration in order to take corrective actions on the process. The present work demonstrates how material flow analysis combined with statistical entropy can be used as a parameter upon which the performance of multiple recycling processes can be objectively compared from a material-centric perspective.
Keywords: material flow analysis; relative statistical entropy; circular economy; lithium-ion batteries; LIB recycling; process simulation

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Permalink: https://www.hzdr.de/publications/Publ-29948
Publ.-Id: 29948


The energy needed to concentrate minerals from common rocks: the case of copper ore
Palacios, J.-L.; Abadias Llamas, A.; Valero, A.; Valero, A.; Reuter, M.ORC
A way to assess today's mineral patrimony is to evaluate how much mining energy is saved today because of having concentrated mines instead of finding the minerals dispersed throughout the crust. This can be assessed through the so-called exergy replacement costs (ERC), which are a measure of the exergy required to extract and concentrate minerals from barerock. Previous studies evaluated such exergy using a theoretical approach. In this paper, from a mineral processing point-of-view through a model developed with HSC Chemistry 9.4.1, we calculated the energy needed to concentrate copper from common rocks at average crustal concentrations. In the model, current state-of-the-art technologies for copper concentration were considered. The results were then compared to the theoretical value obtained before for the ERC of copper and helped to update it. The updated ERC value is of one order of magnitude greater than the original one. This difference in magnitude enhances, even more, the issue of ore grade decline in terms of the associated spiraling energy required for mining. It also reveals the importance of valuing properly the mineral heritage of nations and the effort that should be placed for increasing secondary metal production.
Keywords: Copper Mining energy Ore grade decline Thanatia Exergy replacement cost

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Permalink: https://www.hzdr.de/publications/Publ-29947
Publ.-Id: 29947


Producing metals from common rock: the case of gold
Palacios, J.-L.; Abadias Llamas, A.; Valero, A.; Valero, A.; Reuter, M.ORC
The depletion of the mineral capital is a topic of concern because the worldwide demand for minerals is rapidly increasing. Moreover, since the energy consumption increases as ore grades decline, there is growing stress on energy resources and the environment associated with mining activities. The energy costs associated with the exhaustion of mineral deposits is ruled by the entropy law through a negative logarithmic pattern, in which as the ore grade tends to zero, the energy tends to infinity. This study analyzes through a model developed in HSC Chemistry software, the energy that would be required to produce gold from common bare rock. In this way, we evaluate the maximum energy consumption with current technologies, to obtain gold at the final ore grade, i.e., when all mineral deposits were completely exhausted until reaching crustal concentration. The final theoretical concentration of gold is assumed to be that of the model of Thanatia, which is a resource exhausted Earth with the most abundant minerals found at crustal concentrations. The results are then compared to theoretical values obtained in previous studies for gold and serve to update with a more accurate methodology, the so-called thermodynamic rarity of minerals, as a way to assess the avoided mining energy for having minerals con- centrated in mines and not dispersed throughout the crust. This then serves to assess the mineral capital and its degradation velocity from a thermodynamic point of view.
Keywords: Mineral processing Gold Crust Thanatia Exergy replacement cost Thermodynamic rarity

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  • Secondary publication expected from 24.04.2020

Permalink: https://www.hzdr.de/publications/Publ-29946
Publ.-Id: 29946


The importance of viscous and interfacial forces in the hydrodynamics of the Top-Submerged-Lance furnace
Obiso, D.; Kriebitzsch, S.; Reuter, M.ORC; Meyer, B.
The purpose of this work is to focus on the hydrodynamics of a Top-Submerged-Lance (TSL) smelting furnace, understanding how liquid properties and operational parameters act on key factors of a TSL process, such as splashing, mixing, mass transfer area, and bubble development. A deep knowledge of all those aspects is needed since they all influence the smelting reaction rates; hence the efficiency of the reactor. The characterization and scaling of the TSL gas injection are commonly based on the modified Froude number, the ratio of dynamic and gravitational forces. Detailed literature research reveals a potential weakness of this approach, since it does not consider the effects of viscosity and surface tension. To investigate this question an extensive parametric study was performed applying computational fluid dynamics to cold and non-reactive flows, which provided a broad overview of the physics of the flow. The analysis was performed on fluid dynamic properties (liquid density, liquid viscosity, surface tension) and operational variables (gas volume flow, lance immersion depth). The coupled Level Set—Volume of Fluid model, available in the commercial solver ANSYS FluentÒ, was used to resolve the gas–liquid interface in the multiphase flow. The results of the work underscore the significance of the viscous and interfacial forces for gas injection in smelting slags, confirming the incompleteness of applying only the Froude number to describe such flows.

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Permalink: https://www.hzdr.de/publications/Publ-29942
Publ.-Id: 29942


A Critical Review of Lithium-Ion Battery Recycling Processes from a Circular Economy Perspective
Velázquez-Martínez, J. V.; Santasalo-Aarnio, A.; Reuter, M.ORC; Serna-Guerrero, R.
Lithium-ion batteries (LIBs) are currently one of the most important electrochemical energy storage devices, powering electronic mobile devices and electric vehicles alike. However, there is a remarkable difference between their rate of production and rate of recycling. At the end of their lifecycle, only a limited number of LIBs undergo any recycling treatment, with the majority go to landfills or being hoarded in households. Further losses of LIB components occur because the the state-of-the-art LIB recycling processes are limited to components with high economic value, e.g., Co, Cu, Fe, and Al. With the increasing popularity of concepts such as “circular economy” (CE), new LIB recycling systems have been proposed that target a wider spectrum of compounds, thus reducing the environmental impact associated with LIB production. This review work presents a discussion of the current practices and some of the most promising emerging technologies for recycling LIBs. While other authoritative reviews have focused on the description of recycling processes, the aim of the present was is to offer an analysis of recycling technologies from a CE perspective. Consequently, the discussion is based on the ability of each technology to recover every component in LIBs. The gathered data depicted a direct relationship between process complexity and the variety and usability of the recovered fractions. Indeed, only processes employing a combination of mechanical processing, and hydro- and pyrometallurgical steps seemed able to obtain materials suitable for LIB (re)manufacture. On the other hand, processes relying on pyrometallurgical steps are robust, but only capable of recovering metallic components.
Keywords: circular economy; recycling processes; lithium-ion battery

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Permalink: https://www.hzdr.de/publications/Publ-29941
Publ.-Id: 29941


The simulation-based analysis of the resource efficiency of the circular economy – the enabling role of metallurgical infrastructure
Bartie, N. J.; Abadias Llamas, A.; Heibeck, M.; Fröhling, M.; Reuter, M.ORC
Process metallurgy is a key enabler and the heart of the Circular Economy (CE). This paper shows the state-of-the-art approach to understanding the resource efficiency of very large-scale CE systems. Process simulation permits system-wide exergy analysis also linked to environmental footprinting. It is shown that digital twins of large CE systems can be created and their resource efficiencies quantified. This approach provides the basis for detailed estimation of financial expenditures as well as high-impact CE system innovation. The cadmium telluride (CdTe) photovoltaic technology life cycle, which brings several metal infrastructures into play, is studied. The results show that considerable work remains to optimise the CdTe system. Low exergy efficiencies resulting specifically from energy-intensive processes highlight areas with the greatest renewables-based improvement potential. This detail sheds light on the true performance of the CE and the inconvenient truth that it cannot be fully realised but only driven to its thermodynamic limits.
Keywords: Circular economy; exergy; life cycle assessment; metallurgy; photovoltaics; resource efficiency; sustainability; digital twin

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Permalink: https://www.hzdr.de/publications/Publ-29940
Publ.-Id: 29940


Case study of bilayered spin-1/2 square lattice compound VO(HCOO)2 · (H2O)
Guchhait, S.; Arjun, U.; Anjana, P. K.; Sahoo, M.; Thirumurugan, A.; Medhi, A.; Scurschii, I.; Koo, B.; Sichelschmidt, J.; Schmidt, B.; Baenitz, M.; Nath, R.;
We present the synthesis and a detailed investigation of structural and magnetic properties of polycrystalline VO(HCOO)2 · (H2O) by means of x-ray diffraction, magnetic susceptibility, high-field magnetization, heat capacity, and electron-spin-resonance measurements. The compound crystallizes in an orthorhombic structure with space group Pcca. The crystal lattice features distorted VO6 octahedra connected via HCOO linkers (formate anions), forming a two-dimensional square lattice network with a bilayered structure. Analysis of magnetic susceptibility, high-field magnetization, and heat capacity data in terms of the frustrated square lattice model unambiguously establish the quasi-two-dimensional nature of the compound with nearest-neighbor interaction J1/kB ≃ 11.7 K and next-nearest-neighbor interaction J2/k ≃ 0.02 K. A Néel antiferromagnetic ordering sets in at TN ≃ 1.1 K. The ratio θCW/TN ≃ 10.9 reflects excellent two-dimensionality of the spin-lattice in the compound. A strong in-plane anisotropy is inferred from the linear increase of TN with magnetic field, consistent with the structural data.

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Permalink: https://www.hzdr.de/publications/Publ-29936
Publ.-Id: 29936


One- and three-dimensional quantum phase transitions and anisotropy in Rb2CuMo3O12
Hayashida, S.; Blosser, D.; Povarov, K. Y.; Yan, Z.; Gvasaliya, S.; Ponomaryov, O.; Zvyagin, S.ORC; Zheludev, A.
Single crystal samples of the frustrated quasi-one-dimensional quantum magnet Rb2Cu2Mo3O12 are investigated by magnetic, thermodynamic, and electron spin resonance (ESR) measurements. Quantum Phase transitions between the gapped, magnetically ordered, and fully saturated phases are observed. Surprisingly, the former has a distinctive three-dimensional character, while the latter is dominated by one-dimensional Quantum spin fluctuations. The entire H-T phase diagram is mapped out and found to be substantially anisotropic. In particular, the lower critical fields differ by over 50% depending on the direction of applied field, while the upper ones are almost isotropic, as is the magnetization above saturation. The ESR spectra are strongly dependent on field orientation and point to a helical structure with a rigidly defined spin rotation plane.

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Permalink: https://www.hzdr.de/publications/Publ-29933
Publ.-Id: 29933


Halophilic bacteria as potential pyrite bio-depressants in Cu-Mo bioflotation
Luque Consuegra, G.ORC; Kutschke, S.ORC; Rudolph, M.ORC; Pollmann, K.ORC
Five halophilic bacteria have been studied as potential pyrite biodepressants. Microflotation experiments, as well as hydrophobicity and adhesion experiments were performed in order to assess the potential of these bacteria in the sulfide flotation process. It was shown that bacteria with hydrophobic properties in the Microbial Adhesion To Hydrocarbons (MATH) test adhere to pyrite and that Halomonas boliviensis and Halomonas sp. adhere to chalcopyrite in artificial sea water medium. Selective pyrite biodepression was greatly enhanced in the presence of Halobacillus sp. and Halomonas sp., and Halomonas boliviensis whilst chalcopyrite flotation was unaffected and in fact, enhanced by Halobacillus sp., Marinobacter spp. and Marinococcus sp. showing that the potential of this family of bacteria is yet to be untapped and could be an interesting development in sulfide bioflotation/biodepression processes.
Keywords: Halophilic bacteria, bioflotation, biodepression, pyrite, chalcopyrite, biobeneficiation

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Permalink: https://www.hzdr.de/publications/Publ-29931
Publ.-Id: 29931


Effect of background electrolyte composition on the formation of Th(IV) nanoparticles on mica (001)
Neumann, J.; Qiu, C.; Hellebrandt, S.; Eng, P.; Skanthakumar, S.; Steppert, M.; Soderholm, L.; Stumpf, T.; Schmidt, M.ORC
Actinides are known to form nanoparticles (NP), which may enhance[1] or decrease radionuclide mobility in the environment. Understanding these processes on the molecular level is therefore of particular interest for a reliable safety assessment for nuclear waste repositories. Previous results showed a strong and unusual influence of the background electrolyte composition on Th sorption on the mica (001) basal plane based on surface x-ray diffraction (SXD) data. Uptake was shown to be significantly lower (~0.04 Th/AUC; AUC = 46.72 Ų, the area of the mica (001) unit cell) for NaClO4 solution compared to NaCl (0.4 Th/AUC). An exceptional high coverage was detected for LiClO4 (4.9 Th/AUC) and surprisingly intermediate sorption occurs for KClO4 (~0.1 Th/AUC) under otherwise identical solution conditions.[2,3] The measured Th coverage from LiClO4 medium far exceeds the amount needed for surface charge compensation (0.25 Th/AUC), which suggests the formation of Th NP.[3] The mechanism of the reaction remains unclear, for instance whether the reaction occurs at the interface or in solution and if anion and cation effect occur independently. We applied SXD as well as electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) and in situ atomic force microscopy (AFM) to address these questions. ESI-TOF-MS measurements show no NP formation or other electrolyte influence in solution over a broad concentration range of Th in all media, which proofs the processes happen on the mica surface. From Cl- media higher coverages are found for LiCl (8.8 Th/AUC) and KCl (3.6 Th/AUC) compared to Na (0.4 Th/AUC), confirming the trend observed with perchlorates. All samples with Cl- electrolytes show higher coverages than the corresponding ClO4- samples, which confirms two independent effects for the electrolyte cation and anion. In situ AFM images show the Th-NP to have a variable lateral size and a height of a few nanometers. For higher Th(IV) concentrations the formation of Th-nanochains is observed. In the suggested mechanism the formation of Th NP occurs on the mica surface in a first step and the particles move along the surface in a second step to form band like structures of up to several hundred nanometer length. Formation of Thnanochains occurs at lower Th concentrations in the presence of LiCl (0.5 mM) compared to NaCl (1 mM). The findings suggest that the electrolyte cation influences oligomerization at the mineral-water-interface.
References:
[1] A. Kersting, Nature, 1999, 397, 56-59.
[2] M. Schmidt, Geochim. Et Cosmochim. Acta. 2015, 165, 280-293.
[3] M. Schmidt, Geochim. Et Cosmochim. Acta. 2012, 88, 66-76.
Keywords: Sorption, Thorium, Nanoparticles, Surface X-ray Diffraction, Background Electrolyte
  • Poster
    GDCh Fachgruppentagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29930
Publ.-Id: 29930


Radionuclide sorption in heterogeneous systems: Form model mineral oxides to complex rock
Schierz, A.; Stockmann, M.; Jordan, N.; Foerstendorf, H.; Steudtner, R.; Bok, F.; Brendler, V.;
The fate of radionuclides in natural rocks is governed by their sorption reactions onto heterogeneous systems. Fundamental process understanding of the retardation mechanisms is crucial in the long-term safety assessment of nuclear waste repositories.
The “Component Additivity” (CA) approach is widely used to model radionuclide sorption onto rocks or soils in a realistic manner. This bottom up approach is based on the principle that the sorption in a complex material is determined by competitive sorption effects from the individual minerals. In the context of repository safety assessment the CA approach is used in the smart Kd concept, which is developed for complex geochemical transport models to describe the radionuclide migration in the far-field of a repository more realistically [1].
In this work, batch sorption experiments of radionuclides, e.g. Np(V) and U(VI) onto mixtures of different mineral oxides, such as iron oxides, silicium dioxide, manganese oxides were performed varying the ratio of mineral oxides, solid-liquid-ratios and geochemical conditions. Vibrational (IR) and luminescence spectroscopy (TRLFS) were performed to identify sorbed species and to gain mechanistic understanding of the radionuclide sorption processes. Surface complexation parameters (such as surface protolysis and complex formation constants) of single minerals and mixtures thereof were derived, namely from titration and batch sorption experiments.
Finally, the experimental results were compared with results obtained from sorption predictions to verify the robustness and applicability of the CA approach. Based on the results obtained, estimations on the applicability of the CA approach for radionuclide sorption processes are presented.
  • Poster
    GDCh, Jahrestagung der Fachgruppe Nuklearchemie 2019, 25.-27.09.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29929
Publ.-Id: 29929


Radionuclide sorption in heterogeneous systems: From model mineral oxides to complex rocks
Schierz, A.; Stockmann, M.; Jordan, N.; Foerstendorf, H.; Steudtner, R.; Bok, F.; Brendler, V.;
The fate of radionuclides in natural rocks is governed by their sorption reactions onto heterogeneous systems. Fundamental process understanding of the retardation mechanisms is crucial in the long-term safety assessment of nuclear waste repositories.
The “Component Additivity” (CA) approach is widely used to model radionuclide sorption onto rocks or soils in a realistic manner. This bottom-up approach is based on the principle that the sorption in a complex material is determined by competitive sorption effects from the individual minerals. In the context of repository safety assessment the CA approach is used in the smart Kd-concept, which is developed for complex geochemical transport models to describe the radionuclide migration in the far-field of a repository more realistically [1].
In this work, batch sorption experiments of radionuclides, e.g. Np(V) and U(VI) onto mixtures of different mineral oxides, such as iron oxides, silicium dioxide, manganese oxides were performed varying the ratio of mineral oxides, solid-liquid-ratios and geochemical conditions. Vibrational (IR) and luminescence spectroscopy (TRLFS) were performed to identify sorbed species and to gain mechanistic understanding of the radionuclide sorption processes. Surface complexation parameters (such as surface protolysis and complex formation constants) of single minerals and mixtures thereof were derived, namely from titration and batch sorption experiments.
Finally, the experimental results were compared with results obtained from sorption predictions to verify the robustness and applicability of the CA approach. Based on the results obtained, a first estimation on the applicability of the CA approach for radionuclide sorption processes is presented.
[1] Stockmann et al. (2017), Chemosphere 187, 277-285.
Keywords: Sorption
  • Poster
    Goldschmidt2019, 18.-23.08.2019, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-29928
Publ.-Id: 29928


Effect of Background Electrolyte Composition on the Interfacial Formation of Th(IV) Nanoparticles
Neumann, J.; Qiu, C.; Hellebrandt, S.; Eng, P.; Skanthakumar, S.; Steppert, M.; Soderholm, L.; Stumpf, T.; Schmidt, M.;
Understanding actinide nanoparticle (NP) formation and its influence on their mobility in ecosystems is essential for the reliable safety assessment of nuclear waste repositories. Previous surface x-ray diffraction (SXD) results showed a strong and unusual influence of the background electrolyte composition on Th sorption on the mica (001) basal plane.
Uptake was shown to be significantly lower (0.04 Th/AUC; AUC = 46.72 Å2, area of mica (001) unit cell) for NaClO4 solution compared to NaCl (0.4 Th/AUC). An exceptionally high coverage was detected for LiClO4 (4.9 Th/AUC), which far exceeds the amount needed for surface charge compensation (0.25 Th/AUC), suggesting the formation of Th-NP. However, it remained unclear, if the reaction occurs at the interface or in solution and if anion and cation effect occur independently. We applied SXD as well as electrospray-ionization time-offlight mass spectrometry (ESI-TOF-MS) and in situ AFM to address these questions. ESI-TOF-MS measurements show no influence on solution speciation, indicating the processes happen on the mica surface. In all media, only monomers are observed. From Cl- media higher coverages are found for LiCl (8.8 Th/AUC) and KCl (3.6 Th/AUC) compared to NaCl (0.4 Th/AUC), confirming the trend observed with perchlorates and the occurrence of two independent effects for the electrolyte cation and anion. In situ AFM images show the Th-NP to have variable lateral size and a height of a few nanometers. For higher Th(IV) concentrations the formation of Th nanochains is observed. In the suggested mechanism the formation of Th-NP occurs on the mica surface. In a first step, Th is adsorbed on the surface, where large local concentrations lead to the formation of Th-NP in some media. These particles move along the surface in a second step to form band-like structures of up to several hundred nanometer length.
Keywords: Sorption, Thorium, Nanoparticles, Surface X-ray Diffraction, Background electrolyte
  • Lecture (Conference)
    Goldschmidt Konferenz 2019, 18.-23.08.2019, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-29927
Publ.-Id: 29927


Determination of electron effective mass in InN by cyclotron resonance spectroscopy
Fang, X.; Zheng, F.; Drachenko, O.; Zhou, S.ORC; Zheng, X.; Chen, Z.; Wang, P.; Ge, W.; Shen, B.; Feng, J.; Wang, X.
We report the determination of electron effective mass in InN by using cyclotron resonance (CR) spectroscopy. To avoid the influence of sapphire substrate on CR measurements, InN epilayer with low residual electron concentration of 5 × 1017 cm−3 was grown on silicon substrate. Together with analyzing the effect of non-parabolic band structure, we derive that the isotropy c-plane electron effective mass of InN epilayer is 0.050±0.002 m0 and 0.058±0.002 m0 at temperatures of 4.2 and 50 K, respectively, which is in good agreement with our theoretical predication of the effective mass near the Γ point.
Keywords: Cyclotron resonance spectroscopy, Effective mass, InN

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Permalink: https://www.hzdr.de/publications/Publ-29918
Publ.-Id: 29918


Two types of axisymmetric helical magnetorotational instability in rotating flows with positive shear
Mamatsashvili, G.; Stefani, F.ORC; Hollerbach, R.; Rüdiger, G.
We reveal and investigate a type of linear axisymmetric helical magnetorotational instability which is capable of destabilizing viscous and resistive rotational flows with radially increasing angular velocity, or positive shear. This instability is double-diffusive by nature and is different from the more familiar helical magnetorotational instability, operating at positive shear above the Liu limit, in that it works instead for a wide range of the positive shear when (i) a combination of axial and azimuthal magnetic fields is applied and (ii) the magnetic Prandtl number is not too close to unity. We study this instability first with radially local Wentzel-Kramers-Brillouin (WKB) analysis, deriving the scaling properties of its growth rate with respect to Hartmann, Reynolds, and magnetic Prandtl numbers. Then we confirm its existence using a global stability analysis of the magnetized flow confined between two rotating coaxial cylinders with purely conducting or insulating boundaries and compare the results with those of the local analysis. From an experimental point of view, we also demonstrate the presence of this instability in a magnetized viscous and resistive Taylor-Couette flow with positive shear for such values of the flow parameters, which can be realized in upcoming experiments at the DRESDYN facility. Finally, this instability might have implications for the dynamics of the equatorial parts of the solar tachocline and dynamo action there, since the above two necessary conditions for the instability to take place are satisfied in this region. Our global stability calculations for the tachocline-like configuration, representing a thin rotating cylindrical layer with the appropriate boundary conditions—conducting inner and insulating outer cylinders—and the values of the flow parameters, indicate that it can indeed arise in this case with a characteristic growth time comparable to the solar cycle period.

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Permalink: https://www.hzdr.de/publications/Publ-29917
Publ.-Id: 29917


Hierarchy of double-time correlations
Queißer, F.; Schützhold, R.;
The hierarchy of correlations is an analytical approximation method which allows us to study non-equilibrium phenomena in strongly interacting quantum many-body systems on lattices in higher dimensions. So far, this method was restricted to equal-time correlators ⟨A ^ μ (t)B ^ ν (t)⟩ . In this work, we generalize this method to double-time correlators ⟨A ^ μ (t)B ^ ν (t ′ )⟩ , which allows us to study effective light cones and Green functions and to incorporate finite initial temperatures.

Permalink: https://www.hzdr.de/publications/Publ-29916
Publ.-Id: 29916


Boltzmann relaxation dynamics of strongly interacting spinless fermions on a lattice
Queißer, F.; Schützhold, R.; Schreiber, S.; Kratzer, P.;
Motivated by the recent interest in non-equilibrium phenomena in quantum many-body systems, we study strongly interacting fermions on a lattice by deriving and numerically solving quantum Boltzmann equations that describe their relaxation to thermodynamic equilibrium.The derivation is carried out by inspecting the hierarchy of correlations within the framework of the 1/Z-expansion. Applying the Markov approximation, we obtain the dynamic equations for the distribution functions. Interestingly, we find that in the strong-coupling limit, collisions between particles and holes dominate over particle-particle and hole-hole collisions -- in stark contrast to weakly interacting systems. As a consequence, our numerical simulations show that the relaxation time scales strongly depend on the type of excitations (particles or holes or both) that are initially present.

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Permalink: https://www.hzdr.de/publications/Publ-29915
Publ.-Id: 29915


Environment induced pre-thermalization in the Mott-Hubbard model
Queißer, F.; Schützhold, R.;
Via the hierarchy of correlations, we study the strongly interacting Fermi-Hubbard model in the Mott insulator state and couple it to a Markovian environment which constantly monitors the particle numbers \hat n_\mu^\uparrow and \hat n_\mu^\downarrow for each lattice site \mu. As expected, the environment induces an imaginary part \gamma (i.e., decay rate) of the quasi-particle frequencies \omega_{\mathbf{k}}\to\omega_{\mathbf{k}}-i\gamma and tends to diminish the correlations between lattice sites. Surprisingly, the environment does also steer the state of the system on intermediate time scales \mathcal{O}(1/\gamma) to a pre-thermalized state very similar to a quantum quench (i.e., suddenly switching on the hopping rate J). Full thermalization occurs via local on-site heating and takes much longer.

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Permalink: https://www.hzdr.de/publications/Publ-29912
Publ.-Id: 29912


Dynamically assisted nuclear fusion
Queißer, F.; Schützhold, R.;
We consider deuterium-tritium fusion as a generic example for general fusion reactions. For initial kinetic energies in the keV regime, the reaction rate is exponentially suppressed due to the Coulomb barrier between the nuclei, which is overcome by tunneling. Here, we study whether the tunneling probability could be enhanced by an additional electromagnetic field, such as an x-ray free electron laser (XFEL). We find that the XFEL frequencies and field strengths required for this dynamical assistance mechanism should come within reach of present-day or near-future technology.

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Permalink: https://www.hzdr.de/publications/Publ-29909
Publ.-Id: 29909


Antibacterial activity of selenium nanoparticles studied by calorimetry, flow cytometry and electron microscopy
Schäfer, S.; Fahmy, K.; Merroun, M. L.;
Nanoparticles (NPs) are of growing interest for various applications due to their unique properties, such as elevated surface-to-volume-ratio and variability of composition surface features and charge. Moreover, certain metal NPs possess antimicrobial activity and are therefore considered as an alternative to common antibiotics to overcome the recently emerging issue of bacterial resistance against common antibiotics [1].
Silver (Ag) NPs are well-studied concerning their antimicrobial activity and already applied in medicine and household products. However, cellular interaction mechanisms and consequent toxicity are not entirely elucidated. It is proposed, that NPs either interact with the cell membrane via intermolecular interactions, such as charge-charge interactions or intracellular accumulation. Once interacting with the cell extra- or intracellularly, NPs release reactive oxygen species and metal ions, which subsequently damage the cell membrane and affect enzymatic activity, ultimately leading to cell death. [1]
Besides AgNPs, selenium (Se) NPs exhibit prominent antimicrobial activity, without being studied into more detail [2,3]. In our approach, gram-positive and gram-negative bacterial strains are chosen their putatively differing response to the metal NPs based on differing cell wall compositions. Calorimetric studies of differentially-coated Se NPs exhibited a decrease in growth rate of the bacterial model strains, indicating their antimicrobial activity. To further investigate the cytotoxicity, the influence on reactive oxygen species and enzymatic activity, fluorescence-based flow cytometry is being performed. Furthermore, electron microscopy is exploited to localize the NPs and to elucidate putative metal ion release.

References:
[1] Brandelli et al. (2017) Springer Int Publ 337-363.
[2] Piacenza et al. (2017) Microb Biotechnol 10, 804-818.
[3] Srivastava & Mukhopadhyay (2015) Bioprocess Biosyst Eng 38, 1723-1730.
  • Open Access Logo Lecture (Conference)
    Goldschmidt Conference, 18.-23.08.2019, Barcelona, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29907
Publ.-Id: 29907


Antibacterial activity of selenium nanoparticles studied by calorimetry, flow cytometry and electron microscopy
Schäfer, S.; Fahmy, K.; Merroun, M. L.;
Nanoparticles are of growing interest for various applications due to their unique properties, such as elevated surface-to-volume-ratio and variability of material, surface features, and charge. Therefore, they are applied in industry as catalysts and are investigated concerning their feasibility in drug delivery [1]. Moreover, certain metal nanoparticles possess antimicrobial activity and are therefore considered as an alternative to common antibiotics [2]. Especially due to increasing bacterial resistance against common antibiotics and the lack of the development of novel ones, metal nanoparticles attracted interest in biomedical research.
Silver nanoparticles are well-studied concerning their antimicrobial activity and already applied in medicine and household products. However, cellular interaction mechanisms and consequent toxicity are not entirely elucidated. It is proposed, that nanoparticles either interact with the cell membrane via intermolecular interactions, such as charge-charge interactions or penetrate it. Thus, the size and charge of the nanoparticles are the main properties to influence interaction and antimicrobial activity. Once interacting with the cell extra- or intracellularly, nanoparticles release reactive oxygen species and metal ions, which subsequently damage the cell membrane and affect enzymatic activity, consequently leading to cell death. [2]
Besides silver nanoparticles, selenium nanoparticles exhibit prominent antimicrobial activity, without being studied into more detail [3,4]. In our approach, gram-positive (Lysinibacillus sphaericus) and gram-negative (Stenotrophomonas bentonitica) bacterial strains are chosen due to their different cell wall composition and their putatively differing response to the metal nanoparticles. Calorimetric studies of BSA- and Chitosan-coated selenium nanoparticles exhibited a decrease in growth rate of the bacterial model strains, indicating their antimicrobial activity. To further investigate the cytotoxicity, influence of reactive oxygen species and enzymatic activity, the bacterial model strains are incubated with selenium nanoparticles with different surface coatings and charges and studied via fluorescence-based flow cytometry. Furthermore, electron microscopy is performed to characterize interaction mechanisms, to localize the nanoparticles and to elucidate putative metal ion release.

References:
[1] Faraji, A. H. & Wipf, P. Nanoparticles in cellular drug delivery. Bioorganic Med. Chem. 17, 2950–2962 (2009).
[2] Brandelli, A., Ritter, A. C. & Veras, F. F. in Metal Nanoparticles in Pharma 337–363 (Springer International Publishing, 2017). doi:10.1007/978-3-319-63790-7_1
[3] Piacenza, E. et al. Antimicrobial activity of biogenically produced spherical Se-nanomaterials embedded in organic material against Pseudomonas aeruginosa and Staphylococcus aureus strains on hydroxyapatite-coated surfaces. Microb. Biotechnol. 10, 804–818 (2017).
[4] Srivastava, N. & Mukhopadhyay, M. Green synthesis and structural characterization of selenium nanoparticles and assessment of their antimicrobial property. Bioprocess Biosyst. Eng. 38, 1723–1730 (2015).
  • Open Access Logo Lecture (Conference)
    Congreso Nacional de Microbiología, 01.-05.07.2019, Málaga, Spain

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Permalink: https://www.hzdr.de/publications/Publ-29906
Publ.-Id: 29906


Comparison of Static and Dynamic 18F-FDG PET/CT for Quantification of Pulmonary Inflammation in Acute Lung Injury
Braune, A.; Hofheinz, F.ORC; Bluth, T.; Kiss, T.; Wittenstein, J.; Scharffenberg, M.; Kotzerke, J.; Gama De Abreu, M.
PET imaging with 18F-FDG followed by mathematic modeling of the pulmonary uptake rate (Ki) is the gold standard for assessment of pulmonary inflammation in experimental studies of acute respiratory distress syndrome (ARDS). However, dynamic PET requires long imaging and allows the assessment of only 1 cranio-caudal field of view (∼15 cm). We investigated whether static 18F-FDG PET/CT and analysis of SUV or standardized uptake ratios (SURstat, uptake time-corrected ratio of 18F-FDG concentration in lung tissue and blood plasma) might be an alternative to dynamic 18F-FDG PET/CT and Patlak analysis for quantification of pulmonary inflammation in experimental ARDS.

Methods: ARDS was induced by saline lung lavage followed by injurious mechanical ventilation in 14 anesthetized pigs (29.5-40.0 kg). PET/CT imaging sequences were acquired before and after 24 h of mechanical ventilation. Ki and the apparent volume of distribution were calculated from dynamic 18F-FDG PET/CT scans using the Patlak analysis. Static 18F-FDG PET/CT scans were obtained immediately after dynamic PET/CT and used for calculations of SUV and SURstat Mean Ki values of the whole imaged field of view and of 5 ventro-dorsal lung regions were compared with corresponding SUV and SURstat values, respectively, by means of linear regression and concordance analysis. The variability of the 18F-FDG concentration in blood plasma (arterial input function) was analyzed.

Results: Both for the whole imaged field of view and ventro-dorsal subregions, Ki was linearly correlated with SURstat (r2 ≥ 0.84), whereas Ki-SUV correlations were worse (r2 ≤ 0.75). The arterial input function exhibited an essentially invariant shape across all animals and time points and can be described by an inverse power law. Compared with Ki, SURstat and SUV tracked the same direction of change in regional lung inflammation in 98.6% and 84.3% of measurements, respectively.


Conclusion: The Ki-SURstat correlations were considerably stronger than the Ki-SUV correlations. The good Ki-SURstat correlations suggest that static 18F-FDG PET/CT and SURstat analysis provides an alternative to dynamic 18F-FDG PET/CT and Patlak analysis, allowing the assessment of inflammation of whole lungs, repeated measurements within the period of 18F-FDG decay, and faster data acquisition. © 2019 by the Society of Nuclear Medicine and Molecular Imaging.
Keywords: Animal Imaging Image Processing PET/CT Radiotracer Tissue Kinetics Respiratory 18-F-FDG positron emission tomography pulmonary inflammation standard uptake value tumor-to-blood standard uptake ratio (SUR)

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Permalink: https://www.hzdr.de/publications/Publ-29904
Publ.-Id: 29904


Metal deportment and ore variability of the Bolcana porphyry Au–Cu system (Apuseni Mts, Romania) – Implications for ore processing
Blannin, R.; Tusa, L.; Birtel, S.; Gutzmer, J.ORC; Gilbricht, S.; Ivascanu, P.
The maiden resource estimate for the Bolcana gold-copper porphyry defines 381 Mt at 0.53 g/t gold and 0.18% copper. The early stage of exploration provides the perfect opportunity for the application of geometallurgical studies, to enable optimisation of future mine and plant operations. Quantitative mineralogy and microfabric characterisation of crushed material and thin sections from seven 40 m drill core intervals were accomplished by Scanning Electron Microscopy based Mineral Liberation Analysis, complemented by X-ray Powder Diffraction. The mineralogy of the studied samples is highly variable, depending on lithology, mineralisation and alteration. The main Cu-bearing mineral is chalcopyrite, predominantly occurring in B and C veins. At shallow depths, secondary bornite and covellite form rims around chalcopyrite. Primary bornite occurs at greater depths in the system. Native gold grains are typically <10 μm and hosted by chalcopyrite or, to a lesser extent, pyrite. Electron Probe Microanalysis on four samples determined that gold concentrations in solid solution in selected sulphide minerals are <100 ppm. Copper and associated gold should be recoverable by flotation of chalcopyrite. The recovery of free gold and gold associated with pyrite may require additional processing steps.
  • Open Access Logo Lecture (Conference)
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.08.2019, Glasgow, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29903
Publ.-Id: 29903


Metal deportment and ore variability of the Bolcana porphyry Au–Cu system (Apuseni Mts, Romania) – Implications for ore processing
Blannin, R.; Tusa, L.; Birtel, S.; Gutzmer, J.ORC; Gilbricht, S.; Ivascanu, P.
The maiden resource estimate for the Bolcana gold-copper porphyry defines 381 Mt at 0.53 g/t gold and 0.18% copper. The early stage of exploration provides the perfect opportunity for the application of geometallurgical studies, to enable optimisation of future mine and plant operations. Quantitative mineralogy and microfabric characterisation of crushed material and thin sections from seven 40 m drill core intervals were accomplished by Scanning Electron Microscopy based Mineral Liberation Analysis, complemented by X-ray Powder Diffraction. The mineralogy of the studied samples is highly variable, depending on lithology, mineralisation and alteration. The main Cu-bearing mineral is chalcopyrite, predominantly occurring in B and C veins. At shallow depths, secondary bornite and covellite form rims around chalcopyrite. Primary bornite occurs at greater depths in the system. Native gold grains are typically <10 μm and hosted by chalcopyrite or, to a lesser extent, pyrite. Electron Probe Microanalysis on four samples determined that gold concentrations in solid solution in selected sulphide minerals are <100 ppm. Copper and associated gold should be recoverable by flotation of chalcopyrite. The recovery of free gold and gold associated with pyrite may require additional processing steps.
  • Open Access Logo Contribution to proceedings
    15th Biennial Meeting of the Society for Geology Applied to Mineral Deposits, 27.-30.08.2019, Glasgow, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-29902
Publ.-Id: 29902


Antiferromagnetic domain wall control via surface spin flop in fully tunable synthetic antiferromagnets with perpendicular magnetic anisotropy
Böhm, B.; Fallarino, L.ORC; Pohl, D.; Rellinghaus, B.; Nielsch, K.; Kiselev, N. S.; Hellwig, O.
Antiferromagnetic (AF) domain walls have recently attracted revived attention, not only in the emerging field of AF spintronics, but also more specifically for offering fast domain wall velocities and dynamic excitations up to the terahertz frequency regime. Here, we introduce an approach to nucleate and stabilize an AF domain wall in a synthetic antiferromagnet (SAF). We present experimental and micromagnetic studies of the magnetization reversal in [(Co/Pt)X-1/Co/Ir]N-1(Co/Pt)X SAFs, where interface-induced perpendicular magnetic anisotropy (PMA) and AF interlayer exchange coupling (IEC) are completely controlled via the individual layer thicknesses within the multilayer stack. By combining strong PMA with even stronger AF-IEC, the SAF reveals a collective response to an external magnetic field applied normal to the surface, and we stabilize the characteristic surface spin-flop (SSF) state for an even number N of AF-coupled (Co/Pt)X-1/Co multilayer blocks. In the SSF state our system provides a well-controlled and fully tunable vertical AF domain wall, easy to integrate as no single-crystal substrates are required and with uniform two-dimensional magnetization in the film plane for further functionalization options, such as lateral patterning via lithography.

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Publ.-Id: 29901


Unveiling Electronic Properties in Metal−Phthalocyanine-Based Pyrazine-Linked Conjugated Two-Dimensional Covalent Organic Frameworks
Mingchao, W.; Marco, B.; Wang, M.ORC; Hung-Hsuan, L.; Bishnu, P. B.; Xiaocang, H.; Silvia, P.; Eike, B.ORC; Pan, L.ORC; Mingwei, C.ORC; Mischa, B.ORC; Heine, T.ORC; Zhou, S.ORC; Enrique, C.; Renhao, D.ORC; Xinliang, F.ORC
π-Conjugated two-dimensional covalent organic frameworks (2D COFs) are emerging as a novel class of electroactive materials for (opto)electronic and chemiresistive sensing applications. However, understanding the intricate interplay between chemistry, structure, and conductivity in π-conjugated 2D COFs remains elusive. Here, we report a detailed characterization for the electronic properties of two novel samples consisting of Zn− and Cu−phthalocyaninebased pyrazine-linked 2D COFs. These 2D COFs are synthesized by condensation of metal−phthalocyanine (M =Zn and Cu) and pyrene derivatives. The obtained polycrystalline-layered COFs are p-type semiconductors both with a band gap of ∼1.2 eV. A record device-relevant mobility up to ∼5 cm2/(V s) is resolved in the dc limit, which represents a lower threshold induced by charge carrier localization at crystalline grain boundaries. Hall effect measurements (dc limit) and terahertz (THz) spectroscopy (ac limit) in combination with density functional theory (DFT) calculations demonstrate that varying metal center from Cu to Zn in the phthalocyanine moiety has a negligible effect in the conductivity (∼5 × 10−7 S/cm), charge carrier density (∼1012 cm−3), charge carrier scattering rate (∼3 × 1013 s−1), and effective mass (∼2.3m0) of majority carriers (holes). Notably, charge carrier transport is found to be anisotropic, with hole mobilities being practically null in-plane and finite out-of-plane for these 2D COFs.

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Permalink: https://www.hzdr.de/publications/Publ-29900
Publ.-Id: 29900


Nonsaturating extreme magnetoresistance and large electronic magnetostriction in LuAs
Juraszek, J.; Bochenek, L.; Rudenko, A.; Hosen, M. M.; Daszkiewicz, M.; Wang, Z.; Wosnitza, J.; Henkie, Z.; Samsel-Czekala, M.; Neupane, M.;
In the known topological semimetals, conventional charge carriers exist in addition to relativistic quasiparticles, and thus a disentangling of their conduction properties remains challenging. Here, we address an unsaturated extreme magnetoresistance (XMR) with a marked deviation from the semiclassical B2 behavior that is commonly credited to the presence of topologically protected electronic states. For the topologically trivial semimetal LuAs, we observe a nonsaturating XMR with a nonquadratic magnetic-field dependence gained up to nearly 60 T. Remarkably, this diamagnetic material exhibits a very large magnetostriction that provides solid evidence for a field-dependent variation of electron and hole concentrations. We show that an underlying strain-induced change in the charge-carrier densities can give rise to an unsaturated XMR even in a moderately imbalanced semimetal. Our finding is of importance as well for topological semimetals in which the number of conventional charge carriers can be continuously altered with increasing field, and hence some of their high-field properties may not necessarily reflect the presence of massless quasiparticles.

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Permalink: https://www.hzdr.de/publications/Publ-29899
Publ.-Id: 29899


Bose-Einstein condensation of triplons close to the quantum critical point in the quasi-one-dimensional spin-1/2 antiferromagnet NaVOPO4
Mukharjee, P. K.; Ranjith, K. M.; Koo, B.; Sichelschmidt, J.; Baenitz, M.; Scurschii, I.; Inagaki, Y.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.;
Structural and magnetic properties of a quasi-one-dimensional spin-½ compound NaVOPO4 are explored by x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, electron spin resonance, and 31P nuclear magnetic resonance measurements, as well as complementary ab initio calculations. Whereas magnetic susceptibility of NaVOPO4 may be compatible with the gapless uniform spin chain model, detailed examination of the crystal structure reveals a weak alternation of the exchange couplings with the alternation ratio α 󠆪≃ 0.98 and the ensuing zero-field spin gap Δ0/kB ≃ 2.4 K directly probed by field-dependent magnetization measurements. No long-range order is observed down to 50 mK in zero field. However, applied fields above the critical field Hc1 ≃ 1.6 T give rise to a magnetic ordering transition with the phase boundary TN ∝ (H – Hc1) 1/φ, where φ ≃ 1.8 is close to the value expected for Bose-Einstein condensation of triplons.With its weak alternation of the exchange couplings and small spin gap, NaVOPO4 lies close to the quantum critical point.

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Permalink: https://www.hzdr.de/publications/Publ-29898
Publ.-Id: 29898


Model Experiments for Flow Phenomena in Crystal Growth
Dadzis, K.; Pätzold, O.; Gerbeth, G.;
The concept of a physical model experiment is introduced and discussed in the context of melt and gas flows in bulk crystal growth processes. Such experiments allow one to "extract" selected physical phenomena from the full complexity of a real crystal growth process and “transfer” them to material systems with an easier access for experimental measurements. Model experiments for the main techniques of melt growth are summarized in a literature review, and the applicability of the results to real crystal growth systems is analyzed. Recent examples of model experiments for melt and gas flows in Czochralski growth of silicon are used to demonstrate the state of the art and show the potential of such experiments to improve the understanding of complex multi-physical multi-scale phenomena occurring in every crystal growth process. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords: crystal growth, melt flows, model experiments, numerical simulation

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Permalink: https://www.hzdr.de/publications/Publ-29894
Publ.-Id: 29894


Magnetocaloric effect and spin-strain coupling in the spin-nematic state of LiCuVO4
Gen, M.; Nomura, T.; Gorbunov, D.; Yasin, S.; Cong, P. T.; Dong, C.; Kohama, Y.; Green, E. L.; Law, J. M.; Henriques, M. S.; Wosnitza, J.; Zvyagin, A. A.; Cheranovskii, V. O.; Kremer, R. K.; Zherlitsyn, S.ORC
We report on the magnetocaloric effect and ultrasound studies of the frustrated quasi-one-dimensional spin-1/2 compound LiCuVO4, evidencing a spin-nematic state. The magnetic Grüneisen parameter diverges at the transition to the spin-nematic phase, μ0Hc3 ≈ 40 T, showing quantum criticality accompanied by entropy accumulation. The observed high-field anomalies in the acoustic properties clearly evidence a strong involvement of the lattice in the spin dynamics. The theoretical approach, based on exchange-striction coupling with dipolar and quadrupolar contributions, suggests that the spin-dipole-strain and quadrupole-strain interactions govern the
spin-nematicity in LiCuVO4.

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Permalink: https://www.hzdr.de/publications/Publ-29892
Publ.-Id: 29892


Fermi surface of LaFe2P2—a detailed density functional study
Förster, T.; Kraft, I.; Sheikin, I.; Bianchi, A. D.; Wosnitza, J.; Rosner, H.;
Angular-dependent de Haas-van Alphen measurements allow the mapping of Fermi surfaces in great detail with high accuracy. Density functional electronic-structure calculations can be carried out with high precision, but depend crucially on the used structural information and the applied calculational approximations. We report in a detailed study the sensitivity of the calculated electronic band structure of the 122 compound LaFe2P2 on (i) the exact P position in the unit cell, parametrized by a so-called z parameter, and on (ii) the treatment of the La 4f states. Depending on the chosen exchange and correlation-potential approximation, the calculated z parameter varies slightly and corresponding small but distinctive differences in the calculated band structure and Fermi-surface topology appear. Similarly, topology changes appear when the energy of the mostly unoccupied La 4f states is corrected regarding their experimentally observed position. The calculated results are compared to experimental de Haas-van Alphen data. Our findings show a high sensitivity of the calculated band structure on the pnictide z position and the need for an accurate experimental determination of this parameter at low temperatures, and a particular need for a sophisticated treatment of the La 4f states. Thus, this is not only crucial for the special case of LaFe2P2 studied here, but of importance for the precise determination of the band structure of related 122 materials and La containing compounds in general.

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  • Secondary publication expected from 18.10.2020

Permalink: https://www.hzdr.de/publications/Publ-29891
Publ.-Id: 29891


The Helmholtz Innovation Lab for ultra-short time annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC; Skorupa, W.
Der Vortrag stellt das Helmholtz Innovation Lab für Ultrakurzzeitausheilung vor. Im zweiten Teil werden experimentelle Ergebnisse bei der Kristallisation von dünnen amorphen Halbleiterschichten (Si, Ge, NiGe) mittels magnetron sputtering und Blitzlampenausheilung diskutiert.
Keywords: Helmholtz Innovation Lab, flash lamp annealung, ultra-short time annealing, magnetron sputtering, nickel germanide
  • Lecture (Conference)
    43. Nutzertreffen Heißprozesse und RTP, 23.10.2019, Stuttgart, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29890
Publ.-Id: 29890


Crystallization of thin Si, Ge and NiGe films on SiO2 by flash lamp annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Schumann, T.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC; Skorupa, W.
There is a broad palette of applications for thin Si and Ge films ranging from photovoltaics over various microelectronic devices to sensor applications. Both amorphous and polycrystalline thin films are of interest for thin film photovoltaics, and thin film poly-Si transistors are the heart piece for driving LCDs and OLEDs [1]. In addition, the ability to deposit SiO2 and Si layers in an alternating order and to process them allows to extend the device density without further downscaling [2]. Amorphous thin film deposition methods are the most cost-effective ones, the subsequent crystallization is the most critical process step with regard to microstructure, defect density, and electrical properties.

Potentially, flash lamp annealing (FLA) is a very suitable method due to the short process time, the qualification for temperature-sensible substrates and the possibility to take advantage of non-equilibrium crystallization modes [3]. In this work thin amorphous Si and Ge films have been deposited on SiO2 by DC-magnetron sputtering and crystallized by in-situ FLA in a new FLA sputter tool recently installed by the Rovak GmbH at HZDR (Fig. 1). The in-situ-processing suppresses the influence of surface oxidation effects after deposition prior to FLA. In order to investigate the crystallization behaviour, the thin films have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements. Based on these results and in combination with temperature simulations, a model for the crystallization of thin amorphous Si and Ge films is derived.
Keywords: flah lamp annealing; magnetron sputtering, nickel germanide, crystallization
  • Lecture (Conference)
    Gettering and Defect Engineering in Semiconductor Technology 2019, 22.-27.09.2019, Zeuthen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29888
Publ.-Id: 29888


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a semi-circular constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29886) has this publication as part
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29885) is a supplement to this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29882) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) is a supplement to this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.195
    License: CC-BY-NC-4.0
    Embargo: 30.06.2020

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Permalink: https://www.hzdr.de/publications/Publ-29887
Publ.-Id: 29887


Hydrodynamic experimental benchmark data of bubbly two-phase pipe flow around a ring-shaped constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY provide valueable data of the gas phase dynamics with high temporal and spatial resolution.

The provided data set contains the entire results of the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. 

An additional info.txt file provides all required information (e.g. nomenclature or binary file structure) and is, thus, necessary for interpretation of the experimental data.

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; flow constriction; experimental benchmark data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is part of this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29885) has this publication as part
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29882) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) has this publication as part
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-12-01
    DOI: 10.14278/rodare.197
    License: CC-BY-NC-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29886
Publ.-Id: 29886


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a semi-circular constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L30 that uses a semi-circular flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is supplemented by this publication
Hydrodynamic experimental benchmark data of bubbly … (Id 29886) is part of this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29882) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) has this publication as part
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) is a supplement to this publication
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.137
    License: CC-BY-NC-4.0
    Embargo: 30.06.2020

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Permalink: https://www.hzdr.de/publications/Publ-29885
Publ.-Id: 29885


Structural, Magnetocaloric, and Critical Behavior of La0.5Ca0.5Mn1−xVxO3 Manganites Prepared by High-Energy Ball Milling
Mansouri, M.; Fallarino, L.ORC; M'Nassri, R.; Cheikhrouhou-Koubaa, W.; Cheikhrouhou, A.
The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model.
Keywords: Critical exponents, High-energy ball milling, Magnetocaloric effect, Manganites

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Permalink: https://www.hzdr.de/publications/Publ-29884
Publ.-Id: 29884


The formation of Ni germanides by magnetron sputtering and flash lamp annealing
Rebohle, L.ORC; Begeza, V.; Garcia Munoz, A.; Neubert, M.; Xie, Y.; Prucnal, S.; Grenzer, J.; Hübner, R.; Zhou, S.ORC
Silicides have been widely used for CMOS devices in order to provide a stable Ohmic contact with a low contact resistivity. With the integration of Ge on Si the focus also shifted to germanides as a low resistivity contact material. In addition, ferromagnetic germanides may serve as spin injector materials for Ge-based spintronic devices. Usually, germanides have been fabricated by furnace or rapid thermal annealing in literature.

In this contribution we investigate the formation process of Ni germanides using a combination of magnetron sputtering and flash lamp annealing (FLA). Three different types of Ge served as a substrate for the deposition of the transition metal: amorphous Ge made by magnetron-sputtering on a SiO2-Si substrate, polycrystalline Ge made by magnetron-sputtering followed by FLA, and monocrystalline Ge in the form of a (100) Ge wafer. After metal deposition samples are in-situ annealed by FLA without breaking the vacuum, which triggers the formation of germanides and prevents a possible, but unwanted oxidation. In order to investigate the crystallization behavior, the structures have been characterized by Raman spectroscopy, X-ray diffraction, ellipsometry, current-voltage and Hall effect measurements.
Keywords: flash lamp annealing; magnetron sputtering; nickel germanide
  • Lecture (Conference)
    EMRS 2019 Fall Meeting, 16.-19.09.2019, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-29883
Publ.-Id: 29883


Ultrafast X-ray tomography image data of bubbly two-phase pipe flow around a ring-shaped constriction
Neumann-Kipping, M.ORC; Hampel, U.ORC

For the investigation of bubbly two-phase flow, which should serve as a future benchmark experiment for CFD code validation, an experimental study has been conducted at the Transient Two-Phase Flow (TOPFLOW) facility at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) using ultrafast electron beam X-ray tomography (UFXRAY). In this study, flow constrictions were installed into a DN50 pipe to create a generic three-dimensional flow field as an advanced test case for CFD codes. UFXRAY CT scans were performed in dual-imaging mode and 9 imaging planes for 15 s with a temporal resolution of 1.0 kHz and 2.5 kHz to provide valuable data of the gas phase dynamics.

The provided data set contains tomographic image data for the experimental series L32 that uses a ring-shaped flow constriction with a blockage ratio of 0.5. Here, all image stacks for a given operating point are stored in a single HDF5 file with a spatial resolution of 0.5 mm/pixel (Images are stacked as time series). Further attributes (e.g. reconstruction parameters) are available for each image stack and are accessible e.g. using Matlab or Octave. The relative distance of the each respective scanning position is defined in an additional info.txt. 

Keywords: ultrafast X-ray computed tomography; bubbly two-phase flow; three-dimensional flow field; two-phase pipe flow; tomographic image data
Related publications
Hydrodynamic experimental benchmark data of bubbly … (Id 29887) is part of this publication
Hydrodynamic experimental benchmark data of bubbly … (Id 29886) is supplemented by this publication
Ultrafast X-ray tomography image data of bubbly two-phase … (Id 29885) is part of this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29354) is a supplement to this publication
Ultrafast X-ray tomography raw-data of bubbly two-phase … (Id 29353) has this publication as part
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-08-01
    DOI: 10.14278/rodare.139
    License: CC-BY-NC-4.0
    Embargo: 30.06.2020

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29882
Publ.-Id: 29882


Measurement of f orbital hybridization in rare earths through electric dipole-octupole interference in X-ray Absorption Spectroscopy
Juhin, A.; Collins, S. P.; Joly, Y.; Diaz-Lopez, M.; Kvashnina, K.ORC; Glatzel, P.; Brouder, C.; de Groot, F.
This work provides a direct route to measure the degree of hybridization of f states in rare earths. The interference between electric dipole and octupole transitions is measured at the L1 edge of Gd in Gd3Ga5O12 using X-ray Natural Linear Dichroism (XNLD) and high energy resolution fluorescence detection. The Gd 4f-6p admixture is quantiffed through the integral of the dipole-octupole XNLD using a new sum rule easily applicable to experimental data. The mixing of the Gd valence states with the O ligand orbitals, calculated from first-principles, reveals that despite their localized character, the Gd 4f orbitals mix with the O 2p and 2s orbitals with an antibonding and bonding character, respectively.

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Permalink: https://www.hzdr.de/publications/Publ-29881
Publ.-Id: 29881


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