Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

31742 Publications
Ultra-high-speed X-ray imaging of laser driven processes using synchrotron light
Grenzer, J.; Rack, A.; Olbinado, M. P.; de Resseguier, T.; Danilewsky, A.; Kraus, D.; Cowan, T.;
Time-resolved in-situ or/and in-operando X-ray experiments open a very direct, natural way to study the formation and transformation of materials during relevant technological processes. High-brilliance, fs-pulsed X-rays generated by XFels demonstrate the highest temporal and spatial resolutions, but the maximum X-ray energy is currently limited to ~25 keV. Despite the possibility to illuminate macroscopic objects with large beams (~100mm2) synchrotron light sources produce X-rays pulses with much lower temporal resolution (~100ps), spatial coherence and brilliance but are able to reach X-ray energies higher than achieved at current FELs. MHz pulse repetition rates (ESRF:up to 5.6MHz in the 16 bunch mode) are characteristic to synchrotrons, allowing transient processes to be tracked using ultra-high-speed image acquisition systems with multiple frames, that are even able to visualize transient processes that are stochastic or a-periodic.
Here, we report on an in-situ real time investigation into high-power (>1J), ns single-pulsed (Nd:YAG, = 532 nm; pulse length ~10 ns) laser-driven irradiation processes leading either to surface ablation, crack propagation or shock generation [1] studied by a combined diffraction-direct-space-imaging experiment exploiting the single bunch structure. Whereas macroscopic changes (i.e. density changes or cracks) in bulk materials can be quite easily deduced from X-ray phase contrast imaging, information probing changes at the lattice level can be obtained using diffraction imaging.
As an example is in the figure shown such a combined experiment [2]: The first laser shot of an in-situ real-time laser hole-drilling experiment into a 0.50 mm thick Si (001) single crystalline wafer that was carried out for about 120sec. The sample was placed by about 45° with respect to the laser and the X-ray beam. Both beams intersect horizontally at the same height at an angle of 90° at the rotation center of the sample. The laser light was directed to the sample using a focusing lens. The synchronization of the cameras with laser and X-ray pulses are described in [1]. The X-ray beam fully illuminates the 10×10 mm2 wafer. The diffraction angle was tuned so that the Si (333) reflection in transmission geometry was recorded by the diffraction imaging detector.
Keywords: X-ray imaging laser
  • Lecture (Conference)
    XTOP 2018. XIV Biennial Conference of High Resolution X-ray Diffraction and Imaging, 03.-07.09.2018, Bari, Italy

Publ.-Id: 28414 - Permalink


Heterogeneous modeling approach for gas-limited reactions in an inclined rotating fixed bed reactor with stratified flow
Timaeus, R.; Schubert, M.; Hampel, U.;
Mass transfer limitations in multiphase reactions are a widespread phenomenon in reaction engineering. Particularly in trickle bed reactors, space-time yield is limited due to the low accessibility of the gaseous educts to the solid catalyst. The inclined rotating fixed bed reactor is a new intensification strategy for trickle bed reactors to circumvent this bottleneck. The superposition of reactor inclination and rotation results in a stratified flow, which causes wetting intermittency of the catalytic fixed bed with alternatingly unhindered access of gas and liquid educts to the catalyst. The conversion for the α-methylstyrene hydrogenation has been doubled with the new reactor concept compared to the trickle bed operation, which highlights the potential of the process intensification strategy [1].
Within a DFG-funded project, a feasible model approach for the prediction of the space-time yield of the process intensification strategy is developed. In order to identify the most beneficial process windows and proper design parameters, a reactor model framework consisting of a two-phase Eulerian-Eulerian model and a heterogeneous continuum model to describe the hydrodynamics and to capture mass transfer and reaction phenomena, respectively, is proposed. In this contribution, the heterogeneous one-dimensional continuum model accounting for intraparticle gradients with time-dependent Neumann boundary conditions at particle scale is implemented. While the catalyst wetting intermittency leads to dynamic species concentrations at the particle scale, the species concentrations of the liquid bulk phase are stationary. Coupling of the different scales is realized by a two-way approach, using the species concentrations on each scale. The implemented model is applied for simulation studies considering the hydrogenation of α-methylstyrene to cumene in order to investigate the influence of period length via reactor rotation velocity and the wetting/draining cycle via flow stratification defined as split on the space-time yield.
Keywords: Inclined rotating fixed bed reactor, process intensification, modeling
  • Poster
    Jahrestreffen Reaktionstechnik 2018, 07.05.2018, Würzburg, Deutschland

Publ.-Id: 28413 - Permalink


Formation and evolution of porosity pattern in a potential host rock
Bollermann, T.;
The major goal of the iCross project is to link experimental results and reactive transport modelling across scale to get a fundamental understanding of processes in the multi barrier system of a potential nuclear waste repository. This poster shows how the mapping of surface topography via vertical scanning interferometer results in quantitative information about the surface reactivity. Furthermore, it highlights how Positron emission tomography can be used to characterize transport patterns in geomaterials.
Keywords: iCross, analysis of surface reactivity, positron emission tomography
  • Poster
    KompOst Doktorandenseminar 2018, 13.12.2018, Zittau, Deutschland

Publ.-Id: 28412 - Permalink


Materials science: in-situ, in-operando, time-resolved
Grenzer, J.; Bähtz, C.; Rack, A.;
The development of new materials is today closely related to the “creation” of new functional nano structures. Structural investigations are the key to establish a connection between the functional and structural properties generating these functions. This knowledge makes it possible to design new materials with precisely predetermined properties. The function of nano structures is not only determined by their internal structure, but in large part by their morphology and surface properties.


Time-resolved in-situ or/and in-operando X-ray experiments open a very direct, natural way to study the formation and transformation of materials during the relevant technological processes. The talk will build a bridge from classical material science problems, like the formation of 3-dimensional Germanium nano crystal arrays embedded in a dielectric matrix using synchrotron radiation, or the crystallization process during a rapid thermal annealing (RTA) of an amorphous GeSn thin film using a laboratory setup, to experiments exploiting a µsec-time resolution and even behind that.

For example, material processing by laser beams is a widely used technology in industry. Many applications, like the fabrication of thin solar cells, require a large area processing in short times with a limited heat exposure. Therefore time resolved studies of laser driven processes are again of great scientific interest. If thousand of frames are needed to follow the materials evolution on an atomic level the regular bunch structure of a synchrotron source turns out to be an ideal probe to sense changes in the morphology and crystal structure during and after a laser-sample(target) interaction.
Keywords: in-situ, time-resolved, synchrotron
  • Invited lecture (Conferences)
    EPDIC16 – The 16th European Powder Diffraction Conference, 01.-04.07.2018, Edinburgh, GB
  • Lecture (others)
    Materials science: in-situ, in-operando, time-resolved, 08.11.2018, Prag, CZ

Publ.-Id: 28411 - Permalink


Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by SAXS using XFELs
Kluge, T.; Rödel, M.; Metzkes-Ng, J.; Pelka, A.; Laso Garcia, A.; Rehwald, M.; Prencipe, I.; Galtier, E.; Lee, H. J.; Glenzer, S.; Zeil, K.; Schramm, U.; Cowan, T. E.;
Nanometer probing of ultrahigh intensity ultrashort pulse laser interaction with solid density plasmas, by SAXS using XFELs
  • Lecture (Conference)
    EUCALL Joint Foresight Topical Workshop: Theory and Simulation of Photon-Matter Interaction, 01.-05.07.2018, Szeged, Ungarn
    DOI: 10.5281/zenodo.1308068

Publ.-Id: 28410 - Permalink


3D Local Manipulation of the Metal-Insulator Transition Behavior in VO2 Thin Film by Defect-Induced Lattice Engineering
Jia, Q.; Grenzer, J.; He, H.; Anwand, W.; Ji, Y.; Yuan, Y.; Huang, K.; You, T.; Yu, W.; Ren, W.; Chen, X.; Liu, M.; Facsko, S.; Wang, X.; Ou, X.;
The ability to manipulate the metal-insulator transition (MIT) of metal oxides is of critical importance for fundamental investigations of electron correlations and practical implementations of power efficient tunable electrical and optical devices. Most of the existing techniques including chemical doping and epitaxial strain modification can only modify the global transition temperature, while the capability to locally manipulate MIT is still lacking for developing highly integrated functional devices. Here, lattice engineering induced by the energetic noble gas ion allowing a 3D local manipulation of the MIT in VO2 films is demonstrated and a spatial resolution laterally within the micrometer scale is reached. Ion-induced open volume defects efficiently modify the lattice constants of VO2 and consequently reduce the MIT temperature continuously from 341 to 275 K. According to a density functional theory calculation, the effect of lattice constant variation reduces the phase change energy barrier and therefore triggers the MIT at a much lower temperature. VO2 films with multiple transitions in both in-plane and out-of-plane dimensions can be achieved by implantation through a shadow mask or multienergy implantation. Based on this method, temperature-controlled VO2 metasurface structure is demonstrated by tuning only locally the MIT behavior on the VO2 surfaces.
Keywords: Metal–insulator transition VO2

Publ.-Id: 28409 - Permalink


Laser-driven ion acceleration at the Draco PW laser
Obst, L.ORC; Bernert, C.; Brack, F.; Branco, J.; Bussmann, M.; Cowan, T. E.; Garten, M.; Gaus, L.; Huebl, A.; Kluge, T.; Kraft, S. D.; Kroll, F.; Metzkes-Ng, J.; Rehwald, M.; Schlenvoigt, H.; Schramm, U.; Ziegler, T.; Zeil, K.
Presentation of past and ongoing campaigns aimed at the efficient generation of high energy proton beams at the Draco PW laser facility of Helmholtz-Zentrum Dresden - Rossendorf (HZDR).
  • Lecture (Conference)
    High-field laser-plasma interaction EPS DPP satellite workshop, 14.07.2018, Dolní Břežany, Tschechische Republik

Publ.-Id: 28408 - Permalink


Stress control of tensile-strained In1-xGaxP nanomechanical string resonators
Bueckle, M.; Hauber, V. C.; Cole, G. D.; Gaertner, C.; Zeimer, U.; Grenzer, J.; Weig, E. M.;
We investigate the mechanical properties of freely suspended nanostrings fabricated from tensilestressed, crystalline In1-xGaxP. The intrinsic strain arises during epitaxial growth as a consequence of the lattice mismatch between the thin film and the substrate, and is confirmed by x-ray diffraction measurements. The flexural eigenfrequencies of the nanomechanical string resonators reveal an orientation dependent stress with a maximum value of 650 MPa. The angular dependence is explained by a combination of anisotropic Young's modulus and a change of elastic properties caused by defects. As a function of the crystal orientation, a stress variation of up to 50% is observed. This enables fine tuning of the tensile stress for any given Ga content x, which implies interesting prospects for the study of high Q nanomechanical systems.
Keywords: nanomechanical string resonators

Publ.-Id: 28407 - Permalink


Advances in indirect detector systems for ultra high-speed hard X-ray imaging with synchrotron light
Olbinado, M. P.; Grenzer, J.; Pradel, P.; de Resseguier, T.; Vagovic, P.; Zdora, M.-C.; Guzenko, V. A.; David, C.; Rack, A.;
We report on indirect X-ray detector systems for various full-field, ultra high-speed X-ray imaging methodologies, such as X-ray phase-contrast radiography, diffraction topography, grating interferometry and speckle-based imaging performed at the hard X-ray imaging beamline ID19 of the European Synchrotron - ESRF. Our work highlights the versatility of indirect X-ray detectors to multiple goals such as single synchrotron pulse isolation, multiple-frame recording up to millions frames per second, high efficiency, and high spatial resolution. Besides the technical advancements, potential applications are briefly introduced and discussed.
Keywords: Inspection with x-rays; X-ray detectors; X-ray diffraction detectors

Publ.-Id: 28406 - Permalink


Einfluss der Rohrleitungsführung auf die Strömungsmorphologie in Feedleitungen von Destillationskolonnen
Döß, A.ORC; Schubert, M.; Hampel, U.; Mehringer, C.; Geipel, C. Keywords: Strömungsmorphologie, Feedleitung, Distillation, Gittersensor, TERESA
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik 2019, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 28405 - Permalink


MVT deposits
Gutzmer, J.;
This presentation provides an overview of current concepts of MVT deposit formation. As an in-depth case study, MVT-style deposits in South Africa are used to illustrate variations to the common theme.
  • Invited lecture (Conferences)
    16th Freiberg Short Course in Economic Geology, 02.-06.12.2018, Freiberg, Germany

Publ.-Id: 28404 - Permalink


An introduction to the thematic issue on “Ore deposits in the Variscan basement of Central Europe”
Gutzmer, J.; Markl, G.;
Much of the basement geology of Central Europe is characterized by volcanosedimentary successions of Late Precambrian and Early Paleozoic age that have been variably deformed and metamorphosed during the Variscan orogeny, followed by the intrusion of voluminous granites. The Variscan orogen records the closure of the Rheic ocean and the collision of Laurussia with Gondwana to form the Supercontinent Pangaea, and occurred as a series of protracted geotectonic events providing a suitable framework for the formation of a diverse range of ore deposits.

It comes as no surprise that the Variscan basement is host to most significant ore deposits of Central Europe. These ore deposits did not only provide the raw materials needed for industrial development in the past, but their mining yielded the need for scientific research and technological innovation. This need was also expressed by the publication of the world’s first textbook dedicated to economic geology as a distinct subdiscipline of the geosciences (Cotta 1855).

Industrial exploitation of most ore deposits of the Variscan basement in Central Europe ceased towards the end of the 20th century, typically due to subdued metal prices, but not motivated by a lack of mineral resources. Yet, following the demise of the mining sector there was the prevailing perception that Central Europe had little to offer for future exploration. This erroneous perception has seen a surprising reversal in the last decade. Renewed exploration interest is attributable not only to higher commodity prices but also to the realization of the significant geostrategic risk of highly industrialized countries to be entirely dependent on raw materials imports (EU 2008).

Publ.-Id: 28402 - Permalink


Recovery of REEs, Zr(+Hf), Mn and Nb by H2SO4 leaching of eudialyte concentrate
Balinski, A.; Atanasova, P.; Wiche, O.; Kelly, N.; Reuter, M. A.; Scharf, C.;
In this study three hydrometallurgical methods are described for leaching of a eudialyte concentrate with H2SO4: (i) direct leaching, (ii) fast leaching and (iii) water leaching of dehydrated acid/concentrate mixture. It is demonstrated how to obtain a silica free solution, how parameter variations impact the properties of precipitated silica and which processes lead to losses of valuable components during leaching. Furthermore, the acid solubility of gangue minerals in the concentrate is analyzed and the resulting consequences in terms of leach solution contamination and acid consumption are discussed. The best result in terms of the average yield of value components (REEs, Zr(+Hf), Mn and Nb) of 86 % is obtained by direct leaching under mild conditions (cH2SO4=1 mol/L; TL=60 °C). However, released silicic acid does not precipitate and aggregates at pulp density ϱPD,L=100 kg/m3 by gelling. Fast leaching allows the efficient removal of silica at high solid-liquid ratios in the pre-treatment stage. Due to mass transfer limitations, high efficiency stirrers are crucial for achieving high yields in short reaction times. Dehydration of the acid/concentrate mixture before water leaching can be a good alternative if well-defined amount of acid is used; however, high energy input is needed.
Keywords: eudialyte concentrate, silicate raw materials, aggregation of polysilicic acid, kinetic inhibition, gelling, leaching, mass transfer limitations, rare earth elements, zirconium, hafnium, niobium, manganese.

Publ.-Id: 28400 - Permalink


Bioangeln zum Recycling Seltener Erden Selektive Trennung von Mineralen durch Phagen-gebundene Peptide
Lederer, F. L.;
Selten-Erd-Elemente (SEE) sind 17 verschiedene Elemente (Scandium, Yttrium sowie die sog. Lanthanoide), die weltweit in nur wenigen Regionen in abbauwürdigen Mengen zu finden sind. SEE gelten als Schlüsselkomponenten der Hightech-Industrie und werden unter anderem in Windturbinen, Smartphones und Energiesparlampen eingesetzt.
Keywords: SEE, Phage Surface Display
  • GIT Laborfachzeitschrift 69(2019)2, 27-29

Publ.-Id: 28399 - Permalink


X-ray and neutron imaging studies on particle-laden liquid metal flow
Lappan, T.; Eckert, S.;
In metallurgy, the achievement of inclusion cleanliness is a major challenge for the production of high-performance structural and functional metallic materials like aluminium alloys and steels. Ladle treat-ment of molten metal by gas injection has been employed for a long time as the processing stage is mainly responsible for the control of non-metallic inclusions in metal alloys. In these ladles, inclusion are separated by the combination of settling down and floating up. Since bigger inclusion aggregates are eliminated more easily, agglomeration is supposed to play an essential role. In case of the floata-tion process, the probabilities of collision as well as attachment between gas bubbles and solid in-clusions is strongly dependent on their sizes.
This work is focussed on the visualization of three-phase particle-laden liquid metal flow in model experiments, applying 2D X-ray and neutron transmission imaging. Low-melting gallium-based alloys are employed for the imaging studies at room temperature. Modell particles containing tungsten and gadolinium are used due to their excellent attenuation characteristics for polychromatic X-ray and thermal neutrons, respectively. Injection of inert argon gas drives the liquid metal flow in a rectangular shaped vessel having a gap size of up to 20 mm. For both X-ray and neutron imaging, the time-resolved measurements are performed by means of a scintillation screen in combination with a sCMOS camera. The captured trajectories of rising millimetre-sized gas bubbles and submillimetre-sized solid particles, carried by the bubbly liquid metal flow, are analysed regarding bubble - particle and particle - particle interactions.
Keywords: X-ray transmission imaging; neutron transmission imaging; inclusions; liquid metal
  • Lecture (Conference)
    Materials Science and Engineering Congress 2018 (MSE 2018), 26.-28.09.2018, Darmstadt, Deutschland

Publ.-Id: 28398 - Permalink


Scanning Transmission Ion Detection in the Helium Ion Microscope
Serralta, E.ORC; Klingner, N.ORC; Hlawacek, G.ORC
The helium ion microscope has already proven its value for high-resolution imaging, composition analysis, nanofabrication, and material modification. However, imaging in transmission mode remains not fully explored. Mass-thickness contrast has been studied using a conversion plate below the specimen and collecting secondary electrons with an ET detector. Changing from bright to dark field regime was demonstrated using an annular microchannel plate and changing the acceptance angle by adjusting the distance between the sensor and the sample. Channeling and diffraction phenomena provide information about the crystal structure and can be recorded by a position-sensitive detector. In this report, we present our approach to explore this imaging mode, the challenges and main figures of merit. Our test setup with a position-sensitive detector will be shown, and simulations of the contrast mechanism will be presented.
  • Poster
    2nd international HeFIB conference on Helium and emerging Focused Ion Beams, 11.-13.06.2018, Dresden, Deutschland

Publ.-Id: 28397 - Permalink


Application of marine amphiphilic siderophores in froth flotation process
Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.;
Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process. The hydrophilic part, carrying hydroxamate groups is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested, that siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubbles and avoid additional chemicals and further working steps for making the target mineral particles hydrophobic. The aim of this study is to show the usage of amphiphilic siderophores in froth flotation process in different scales and with different minerals.
  • Lecture (others)
    UCT Biohydrometallurgy meeting, 19.06.2018, Cape Town, South Africa

Publ.-Id: 28396 - Permalink


Enhanced photoresponses of an optically driven VO₂-based terahertz wave modulator near percolation threshold
Zhai, Z.-H.; Zhu, H.-F.; Shi, Q.; Chen, S.-C.; Li, J.; Li, Z.-R.; Schneider, H.; Zhu, L.-G.;
We proposed and demonstrated a method to enhance photoresponses in the timescale from nanoseconds to microseconds of an all optically driven VO₂-based terahertz (THz) wave modulator by driving the initial VO₂ close to percolation threshold (via externally heating the initial VO₂ thin film near insulator-to-metal transition temperature). We experimentally realized 10-fold, 3-fold, and 3-fold improvement of photosensitivity, photoresponsivity, and optical modulation bandwidth of the VO₂-based THz wave modulator, respectively. Percolation theory, along with the macroscopic conductivity response, was used to explain the mechanism for photomodulation response enhancement. The enhanced photomodulation response is promising especially for optical modulators and photodetectors. This approach is also compatible with other optimization methods and can be further used to enhance other VO₂-based optoelectronic devices.
Keywords: Vanadiumdioxide, terahertz modulator

Downloads:

Publ.-Id: 28395 - Permalink


Thermodynamic and structural studies on the Ln(III)/An(III) malate complexation
Taube, F.; Drobot, B.; Roßberg, A.; Foerstendorf, H.ORC; Acker, M.; Patzschke, M.; Trumm, M.; Taut, S.; Stumpf, T.
The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi−method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (logβ0, ΔrH0m,2, ΔrS0m, ΔrG0m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X–ray absorption fine structure spectroscopy complemented with quantum-mechanical ab–initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV–Vis, laser fluorescence and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal:malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding logβ10 and logβ20 of about 6 and 9, respectively. The respective complexation enthalpies ΔrH0m,1 and ΔrH0m,2 showed average values of 5 kJ·mol−1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f–/ 5f–element homology.

Publ.-Id: 28394 - Permalink


Ln(III)/An(III) Retention on CSH Phases and the Influence of Malate
Taube, F.; Roßberg, A.; Acker, M.; Foerstendorf, H.; Taut, S.; Stumpf, T.;
Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...
  • Lecture (Conference)
    4th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 06.-09.11.2018, Nice, France

Publ.-Id: 28393 - Permalink


Am3+ Malate Sorption on CSH Phases
Taube, F.; Acker, M.; Roßberg, A.; Taut, S.; Stumpf, T.;
Concrete widely serves as an engineering barrier and for waste conditioning in nuclear waste re-positories. Organic additives like poly(hydroxyl)carboxylates are commonly used for tuning the physico-chemical and mechanical properties of fresh concrete. In the worst-case scenario of wa-ter intrusion into the waste repository, the concrete may degrade, so that the soluble organic ad-ditives will be leached out and may form stable radionuclide (RN) complexes. Consequently, for a long-term risk assessment in nuclear waste repositories, the interactions of RNs with cement additives and CSH phases (main phase of cement) must be known. Americium(III) is one of the RN that will determine the radiotoxicity of a waste repository for a long time. As a model com-pound for cement additives malic acid (α-hydroxydicarboxylic acid) was chosen...
  • Poster
    2nd Workshop on Calcium-Silicate Hydrates Containing Aluminium: C-A-S-H II, 23.-24.04.2018, Dübendorf, Schweiz

Publ.-Id: 28391 - Permalink


Lithium Ion Beams from Liquid Metal Alloy Ion Sources
Pilz, W.; Mazarov, P.; Klingner, N.; Bauerdick, S.; Bischoff, L.;
In recent years Focused Ion Beam (FIB) processing has been developed into a well-established and promising technique in nearly all fields of nanotechnology for patterning and prototyping on the µm-scale and below. Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the FIB application fields beside all other source concepts. The need of light elements like Li was investigated using various alloys. A promising candidate is a Ga35Bi60Li5 based LMAIS which is introduced in more detail and operates stable for more than 1000 µAh. It enables high resolution imaging and patterning using Li and sample modification using Ga or heavy polyatomic Bi clusters, all coming from one ion source.
Keywords: Focused Ion Beam, Liquid Metal Alloy Ion Source, Li ions
  • Open Access LogoJournal of Vacuum Science & Technology B 37(2019)2, 021802-1-021802-4
    DOI: 10.1116/1.5086271

Downloads:

Publ.-Id: 28390 - Permalink


Is hydroxypyridonate 3,4,3‐LI(1,2‐HOPO) a good competitor of fetuin for uranyl metabolism?
Younes, A.; Creff, G.; Beccia, M. R.; Moisy, P.; Roques, J.; Aupiais, J.; Hennig, C.; Solari, P. L.; Den Auwer, C.; Vitaud, C.;
Uranium is widespread in the environment, resulting both from natural occurrences and anthropogenic activities. Its toxicity is mainly chemical rather than radiological. In the blood it is transported as uranyl UO22+ cation and forms complexes with small ligands like carbonates and with some proteins. From there it reaches the skeleton, its main target organ for accumu lation. Fetuin is a serum protein involved in biomineralization processes which was demonstrated to be the main UO22+‐binder in vitro. Fetuin’s life cycle ends in bone. It is thus suspected to be a key protagonist of U accumulation in this organ. Up to now, there has been no effective treatment for the removal of U from the body and studies devoted to the interactions involving chelating agents with both UO22+ and its protein targets are lacking. The present work aims at studying the potential role of the 3,4,3‐LI(1,2‐HOPO) as a promising chelating agent in competition with fetuin. The apparent affinity constant of the 3,4,3‐LI(1,2‐HOPO) was first determined, giving evidence for its very high affinity similarity to that of fetuin. Chromatography experiments, aimed at identifying the complexes formed and quantify their UO22+ content, and spectroscopic structural investigations (XAS) were carried out, demonstrating that the 3,4,3‐LI(1,2‐HOPO) inhibits/limits the formation of fetuin‐uranyl complexes in stoichiometric conditions. But surprisingly, possible ternary complexes stable enough to remain present after the process, were identified for sub stoichiometric conditions of HOPO versus fetuin. These results contribute to the understanding of the mechanisms accounting for U residual accumulation despite the chelation therapy after internal contamination.

Publ.-Id: 28389 - Permalink


Compositional Data Analysis - Mineral Chemistry
Frenzel, M.ORC
Short introduction to general principles for the statistical analysis of mineral chemistry data.
  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 09.10.2018, Freiberg, Deutschland

Publ.-Id: 28388 - Permalink


Compositional Data Analysis - General Principles
Frenzel, M.ORC
Any data measured (or reported) in terms of proportions of a whole is called ‘compositional’. Virtually all geochemical data falls under this category. Because such data has a number of special properties, specific procedures are required for its statistical analysis. Generally, it cannot be meaningfully analyzed by methods designed for the analysis of multivariate Gaussian data, such as the standard regression analysis still used by many geologists.

This lecture is intended to give a brief overview of the most important mathematical characteristics of compositional data, and what consequences these have for the statistical analysis of such data. It will provide the theoretical foundations for the next lecture(s) in which the specific problems associated to the analysis of mineral chemistry data (lecture 2) and hierarchical data structures (lecture 3) will be considered in somewhat more detail. These later two lectures are intended as more practical guides to actual data analysis.
  • Lecture (others)
    Forschungsseminar Lagerstättenlehre, 18.09.2018, Freiberg, Deutschland

Publ.-Id: 28387 - Permalink


Field-Driven Hopping Transport of Oxygen Vacancies in Memristive Oxide Switches with Interface-Mediated Resistive Switching
Du, N.; Manjunath, N.; Li, Y.; Menzel, S.; Linn, E.; Waser, R.; You, T.; Burger, D.; Skorupa, I.; Walczyk, D.; Walczyk, C.; Schmidt, O. G.; Schmidt, H.;
We investigate the hopping transport of positively charged mobile oxygen vacancies V(o)(+)in electroforming-free bipolar memristive BiFeO3 switches by conducting impedance spectroscopy and quasistatic state-test measurements. We demonstrate that BiFeO3 switches with mobile oxygen vacancies (V-o(+)) and fixed substitutional Ti4+ donors on Fe3+ lattice sites close to the bottom electrode have a rectifying top electrode with an unflexible barrier height and a rectifying and/or nonrectifying bottom electrode with a flexible barrier height. The field-driven hopping transport of the oxygen vacancies determines the recon- figuration of the flexible barrier and the dynamics of the resistive switching. Average activation energies of 0.53 eV for trapping and of 0.31 eV for the release of oxygen vacancies by the Ti4+ donors during application of the SET and RESET excitation pulses are extracted, respectively. The larger activation energy during SET is experimentally verified by impedance spectroscopy measurements and evidences the local enhancement of the electrostatic potential profile at the bottom electrode due to the Ti4+ donors on Fe3+ lattice sites.
Keywords: BIFEO3; KINETICS; CONDUCTIVITY; TEMPERATURES; ELECTRODES; FILMS

Publ.-Id: 28384 - Permalink


A Novel Statistical Insight to Selection of the Best flotation Kinetic Model
Hassanzadeh, A.; Cagirici, S.; Ozturk, Z.;
Many flotation kinetics models have been studied in the literature. Their applicability was extensively investigated and argued in detail. However, model selection criteria were not adequately discussed from the statistical points of view. In this investigation, the kinetic behavior of a complex copper sulfide ore was studied in a mechanical Denver flotation cell focusing on flotation kinetics of chalcopyrite, pyrite and molybdenite. Different flotation kinetics models including nine common empirical models and four mathematical models namely Hill, Chapman (Sigmodial function), single rectangular (Hyperbola equation) and exponential were applied to the experimental data. In addition to assessment of the goodness of fit criterion for each model, a factor of model complexity was considered using information criteria (IC) (i.e. Bayesian information (BIC), low of iterated logarithm (LILC) and Akaike information (AIC) indices). The obtained results showed that the IC indices could simply manifest the best-fitted model to the experimental data. Whereas, the coefficient of determination values (R2) were relatively same for all models. By taking the R2 and model complexity criteria into account, the exponential model was chosen as the best representative mathematical model to demonstrate chalcopyrite kinetic behavior. However, Chapman model was selected as the best one for the flotation of pyrite and molybdenite. In case of the common first-order flotation kinetics models, fast and slow flotation kinetic model (Kelsall) was reasonably fitted the best to the given data of chalcopyrite. However, the gas/solid kinetics adsorption model was chosen as the best-fitted one for pyrite and molybdenite. Furthermore, it was found that mathematical models represent better results in association with flotation kinetic behavior of chalcopyrite, pyrite and molybdenite due to the consideration of more parameters in modeling. Finally, it was concluded that the IC indices must be applied to the process of model selection due to consideration of goodness of fit, complexity of a model and model consistency.
Keywords: Flotation kinetics model, information criteria (IC), modeling, Akaike information criterion (AIC)
  • Contribution to proceedings
    XXIX International Mineral Processing Conference (IMPC), 15.09.-21.12.2018, Moscow, Russia
    A Novel Statistical Insight to Selection of the Best flotation Kinetic Model

Publ.-Id: 28383 - Permalink


On the surface wettability heterogeneities in fine particle separation technologies - inverse Gas Chromatography investigations and interface interaction studies
Rudolph, M.; Sygusch, J.;
Fine particle separation is a challenging task and relies on a proper understanding of interfacial properties. In our research the focus lies on the process of flotation, which is a heterocoagulation separation method for fine particles in aqueous dispersions (size range approx. 5 µm < x <200 µm). It has been used in large extent for several decades and with billions of tons of particles processed per annum in the mining industry to separate valuable mineral particles from worthless ones. The main principle of separation is the particles' differences in wettability. This wettability is influenced by controlled selective adsorption of amphiphilic molecules rendering most typically the valuable containing minerals hydrophobic. Usually the particle property "wettability" is being quantified with a water contact angle. However, this value is not only difficult to assess for particles but furthermore through Young's equation a function of the surface free energy, which is a complex parameter as a result of various interatomic/intermolecular interactions. Using iGC we show how to characterize these complex wettability properties of particles assessing the heterogeneity of disperse and acid base specific surface free energies. These complex values are used in accordance to an approach by van Oss to formulate a new wettability parameter for flotation which is the specific free energy of interaction between a particle and a gas bubble immersed in water. We are presenting the general approach and results from various mineral collector systems and give insights to the boundary conditions and the general calculation scheme. In a recent trial we show the predictive power of the results. Furthermore we show how iGC can be put in context to other interaction investigations using flotability, contact angle measurements and colloidal probe atomic force microscopy.
  • Invited lecture (Conferences)
    1st European Symposium on Sorption Science, 05.-07.09.2018, Wien, Österreich

Publ.-Id: 28381 - Permalink


The Effect of Tin on the Formation and Properties of Pt/MgAl(Sn)Ox Catalysts for Dehydrogenation of Alkanes
Belskaya, O. B.; Stepanova, L. N.; Nizovskii, A. I.; Kalinkin, A. V.; Erenburg, S. B.; Trubina, S. V.; Kvashnina, K. O.; Leont’Eva, N. N.; Gulyaeva, T. I.; Trenikhin, M. V.; Bukhtiyarov, V. I.; Likholobov, V. A.;
The MgAl(Sn) layered double hydroxides (LDH) with the atomic ratios Mg/(Al+Sn) = 3 and Sn/(Sn+Al) = 0, 0.002, 0.005, 0.01, 0.05, 0.1, 0.3, 0.5, 0.7, 1.0 were synthesized and the ratio Sn/(Sn+Al) ≤ 0.1 was shown to provide the formation of systems with uniform phase composition. Mixed oxides derived from LDH retain the high specific surface area of 150-200 m2/g and the basic properties when some aluminium atoms are replaced with tin. It was found that the Sn-containing mixed oxides are able to restore the layered structure during rehydration and intercalate the anion precursors of platinum into the interlayer space of the formed LDH.
The emerging platinum sites initiate the reduction of tin at temperatures below 723 K. TEM, EXAFS and XPS studies demonstrated that tin introduction in the support increases the dispersion of supported platinum. An extreme dependence of the activity of Pt/MgAl(Sn)Ox catalysts in propane and n-decane dehydrogenation on the tin content in the support was revealed. The active catalysts are characterized by the phase and elemental uniformity of the support, highly disperse state of Pt(0), and the absence of a noticeable amount of reduced tin and bimetallic particles.

Downloads:

  • Secondary publication expected from 05.12.2019

Publ.-Id: 28380 - Permalink


An investigation of the recovery and kinetics during the flotation of residual petroleum coke in lime calcination exhaust tailings
Vaziri Hassas, B.; Guven, O.; Hassanzadeh, A.;
Flotation is one of the feasible separation methods suggested for recovery of petroleum coke from the tailings of lime calcination furnaces. In this study, analyses of ash content and calorific value of petroleum coke in lime calcination tailings were used to measure its floatability and product quality. In addition, seven most common flotation kinetics models were fitted to the obtained experimentalm data. Based on the maximum recovery, minimum ash content, and maximum calorific value of the flotation products, optimum dosages for collector (kerosene) and frother (MIBC) were found 30 g/t and 60 g/t, respectively. Regarding the flotation kinetic modeling and the obtained sum of squared errors (SSEs), Agar and Klimpell models were found to have the best and the poorest fits to the experimental data, respectively. Finally, it was concluded that new statistical concepts such as information criteria (IC) and non-linear generalized least squares estimation (NLGLSE) must be applied to the process of model selection owing to consideration of goodness of fit, complexity of a model and model consistency.
Keywords: Reagent optimization; flotation rate constant; flotation kinetic model; petroleum coke

Publ.-Id: 28379 - Permalink


Explaining metal zonation at the Lisheen deposit
Frenzel, M.ORC; Burisch, M.; Röhner, M.; Gilbert, S.; Cook, N. J.; Ciobanu, C. C.; Güven, J.; Gutzmer, J.
  • Lecture (others)
    16th Freiberg Shortcourse in Economic Geology - "Zinc Deposits", 04.12.2018, Freiberg, Deutschland

Publ.-Id: 28378 - Permalink


Stratified and Segregated Flow Modelling - AIAD 2018
Höhne, T.;
Today: Limits in simulating stratified & segregated two phase flow
Algebraic Interfacial Area Density Model (AIAD)
Free Surface Drag
Turbulence Damping
Sub-grid wave turbulence (SWT)
Verification and Validation is going on – more experimental data are required for the validation
Keywords: AIAD, Free Surface Drag, Sub-grid wave turbulence (SWT)
  • Lecture (Conference)
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application", 13.-16.11.2018, Dresden, Deutschland
  • Contribution to proceedings
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application, 13.-16.11.2018, Dresden, Deutschland
  • Poster
    16th Short Course “Multiphase Flow: Simulation,Experiment and Application, 13.-16.11.2018, Dresden, Deutschland

Publ.-Id: 28377 - Permalink


Spin-Wave Modes in Transition from a Thin Film to a Full Magnonic Crystal
Langer, M.; Gallardo, R. A.ORC; Schneider, T.; Stienen, S.; Roldán-Molina, A.; Yuan, Y.; Lenz, K.ORC; Lindner, J.; Landeros, P.ORC; Fassbender, J.ORC
Surface-modulated magnonic crystals are the natural link between continuous films with sinusoidal spin-wave eigenmodes and one-dimensional magnonic crystals composed of individual nanowires. Nevertheless, the transformation process of the spin-wave modes in this transition remains yet unclear. Here, spin-wave modes in their entire transition from a flat film to a ‘full’ (one-dimensional) magnonic crystal are studied by ferromagnetic resonance (FMR) and micromagnetic simulations. For this purpose, the surface of a pre-patterned thin permalloy film was sequentially ion milled resulting in hybrid structures, referred to as surface-modulated magnonic crystals, with increasing modulation depth. After each step, FMR measurements were carried out in backward-volume and Damon-Eshbach geometry. The evolution of each spin-wave resonance is studied together with the corresponding mode profile obtained by micromagnetic simulations. Simple rules describing the transition of the modes from the film to the modes of the full magnonic crystal are provided unraveling the complexity of spin-wave states in these hybrid systems.
Keywords: spin waves, ferromagnetic resonance, magnonic crystals, band structure, magnonics, thin films, magnetism

Downloads:

Publ.-Id: 28375 - Permalink


Functionalized DNA Origami Structures for Molecular Electronics
Bayrak, T.; Helmi, S.; Ye, J.; Martinez-Reyes, A.; Samano-Tirado, E.; Seidel, R.; Erbe, A.;
The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance. The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Poster
    IHRS NanoNET Annual Workshop, 05.-07.09.2018, Bad Gottleuba, Germany

Publ.-Id: 28372 - Permalink


Functionalized DNA Origami Nanostructures for Molecular Electronics
Bayrak, T.; Ye, J.; Helmi, S.; Martinez-Reyes, A.; Samano, E.; Seidel, R.; Erbe, A.;
The DNA origami method provides a programmable bottom-up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance . The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Poster
    CECAM/Psi-k research conference: BioMolecular Electronics (BIOMOLECTRO), 27.-31.08.2018, Madrid, Spain

Publ.-Id: 28371 - Permalink


Functionalized DNA Origami Nanostructures for Molecular Electronics
Bayrak, T.; Ye, J.; Helmi, S.; Martinez-Reyes, A.; Samano, E.; Seidel, R.; Erbe, A.;
The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nanoelectronics and nanophotonics device fabrications.
This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanoMOLDS are used for the fabrication of nanoelectronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanoMOLDS and create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanoMOLD based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires showed metallic conductance. The other two wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Poster
    13th HZDR PhD Seminar, 05.-07.11.2018, Usti nad Labem, Czech Republic

Publ.-Id: 28370 - Permalink


Electrical transport study as a function of temperature on a C-shape gold nanowire templated by a DNA origami
Bayrak, T.; Martinez-Reyes, A.; Ruiz-Arce, D.; Kelling, J.; Samano, E.; Erbe, A.;
Small DNA origami templates 90 nm x 70 nm DNA origami nanosheets with three functionalized sides holding a total of eight capture strands for decoration with gold nanoparticles were fabricated. Electroless gold growth is applied to selectively grow the gold nanoparticles until they merge into continuous nanowires. Finally, this work demonstrates the application of shape-controlled C-shaped gold wires as precisely tailored metal contacts to single, isolated nanowires to better understand the charge transport characteristics at different temperatures.
  • Lecture (Conference)
    DNA Mitteldeutschland, 24.05.2018, Leibniz IPHT Jena, Germany

Publ.-Id: 28369 - Permalink


DNA Origami templated assembly of metallic nanowires
Bayrak, T.; Erbe, A.;
The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds1,2 and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance.1 The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Lecture (Conference)
    PhD Seminar HZDR, 07.05.2018, Dresden, Germany

Publ.-Id: 28368 - Permalink


DNA origami sheet based C-shaped conducting nanowires
Bayrak, T.; Martinez-Reyes, A.; Ruiz-Arce, D.; Kelling, J.; Samano, E.; Erbe, A.;
Small DNA origami templates 90 nm x 70 nm DNA origami nanosheets with three functionalized sides holding a total of eight capture strands for decoration with gold nanoparticles were fabricated. Electroless gold growth is applied to selectively grow the gold nanoparticles until they merge into continuous nanowires. Finally, this work demonstrates the application of shape-controlled C-shaped gold wires as precisely tailored metal contacts to single, isolated nanowires to better understand the charge transport characteristics at different temperatures.
  • Lecture (Conference)
    BAC Retreat, 25.06.2018, Rathen, Germany

Publ.-Id: 28367 - Permalink


Functionalized DNA Origami Nanostructures for Molecular Electronics
Bayrak, T.; Helmi, S.; Ye, J.; Kelling, J.; Schönherr, T.; Erbe, A.; Seidel, R.;
The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nanoelectronics and nanophotonics device fabrications.
This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanoMOLDS are used for the fabrication of nanoelectronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanoMOLDS and create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanoMOLD based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires showed metallic conductance. The other two wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Poster
    DPG Meeting Berlin, 11.-16.03.2018, Berlin, Germany

Publ.-Id: 28366 - Permalink


Functionalized DNA Origami Nanostructures for Molecular Electronics
Bayrak, T.; Helmi, S.; Ye, J.; Martinez-Reyes, A.; Samano-Tirado, E.; Seidel, R.; Erbe, A.;
The DNA origami method provides a programmable bottom up approach for creating nanostructures of any desired shape, which can be used as scaffolds for nano-electronics and nano-photonics device fabrications. This technique enables the precise positioning of metallic and semiconducting nanoparticles along the DNA nanostructures. In this study, DNA origami nanomolds1,2 and nanosheets are used for the fabrication of nano-electronic devices. To this end, electroless gold deposition is used to grow the AuNPs within the DNA origami nanomolds and nanosheets create eventually continues nanowires. In order to contact the fabricated nanostructues electrically, a method using electron-beam lithography was developed. The DNA origami nanomold and nanosheet based metallic wires were electrically characterized from room temperature down to 4.2K.
Temperature-dependent characterizations for four wires exhibiting different conductance at RT were performed in order to understand the dominant conductance mechanisms from RT to 4.2K. Two of these nanowires based on nanomold structure showed metallic conductance.1 The other wires deviated from pure metallic behavior and they showed thermionic, hopping and tunneling charge transport mechanism.
  • Lecture (Conference)
    3rd Functional DNA Nanotechnology Workshop, 06.-08.06.2018, Rome, Italy

Publ.-Id: 28364 - Permalink


Thermal dependence of large scale freckle defect formation
Kao, A.; Shevchenko, N.; Alexandrakis, M.; Krastins, I.; Eckert, S.; Pericleous, K.;
The fundamental mechanisms governing macroscopic freckle defect formation during directional solidification are studied experimentally in a Hele-Shaw cell for a low melting point Ga-25wt.%In alloy, and modelled numerically in 3D using a microscopic parallelised Cellular Automata lattice Boltzmann method. The size and distribution of freckles (long solute channels, or chimneys) is shown to be strongly dependent on the thermal profile of the casting, with flat, concave and convex isotherms being considered. For the flat isotherm case, no large-scale freckles form, while for concave or convex isotherms large freckles appear but in different locations. The freckle formation mechanism is as expected buoyancy-driven, but the chimney stability, its long-term endurance and its location, are shown to depend critically on the detailed convective transport through the inter-dendritic region. Flow is generated by curved isopleths of solute concentration. As solute density is different from that of the bulk fluid, gravity causes ‘uphill´ or ‘downhill’ lateral flow from the sample centre to the edges through the mush, feeding the freckle. An excellent agreement is obtained between the numerical model and real-time x-ray observations of a solidifying sample under strictly controlled temperature conditions.
Keywords: Freckle defect formation, Ga-In alloy, Convective transport

Downloads:

  • Secondary publication expected from 22.04.2020

Publ.-Id: 28363 - Permalink


Organische Chemie XV - Stereoselektive Reaktionen, Naturstoffsynthese, Syntheseplanung - Retrosynthese
Mamat, C.;
Im ersten Teil dieses letzten Studienheftes wollen wir uns mit Reaktionen vertraut machen, bei denen aus einer prochiralen Verbindung selektiv chirale Verbindung gebildet wird, bei der ausschließlich eines der beiden Stereoisomere mit Chiralitätszentrum entsteht. Aus den Studienheften davor wissen wir schon, dass aus nichtchiralen Verbindungen mit prochiralem Zentrum meist Racemate entstehen. Faktoren, die zu einer Bevorzugung eines der beiden Stereoisomere führen, werden wir uns genau anschauen.
Im zweiten Teil wollen wir uns mit Retrosynthese und Syntheseplanung beschäftigen. Ausgehend von teils komplizierten Molekülen und Strukturen werden Sie sehen, wie durch eine gedankliche „Rückwärtsreaktion“ (Zerlegung in Bestandteile) ein Syntheseplan erstellt werden kann. Dazu wird das Zielmolekül immer weiter in seine Bestandteile, also hypotetische Ausgangsstoffe, zerlegt.
Keywords: Wittig-Reaktion, Walden-Umkehr, Auxiliar, Zerlegung, Totalsynthese
  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    44 Seiten

Publ.-Id: 28362 - Permalink


Organische Chemie XIV - Metallorganische Verbindungen und Übergangsmetallkatalyse
Mamat, C.;
Elementorganische Verbindungen sind uns schon ganz am Anfang dieses Studiums seit dem ersten Studienheft über den Weg gelaufen. Bisher haben wir uns auf Substanzen beschränkt, die Hauptgruppenmetalle wie Magnesium, Natrium oder Lithium beinhalten. Denken Sie dabei zum Beispiel an die Aldol-Reaktion. Aber auch ein typisches Nebengruppenelement, nämlich das Zink, haben wir uns angeschaut.
Für Sie ist wichtig zu wissen, welche Bindungsverhältnisse in diesen metallorganischen Verbindungen vorherrschen. Das betrifft insbesondere die Umpolung der Bindung des Kohlenstoffs, wenn er an Metallen gebunden ist im Vergleich zur Bindung von elektronegativeren Elementen, wie den Halogenen, Stickstoff, Sauerstoff oder auch Schwefel. Damit soll klarwerden, dass dieses Kohlenstoffatom dann carbanionisch reagiert.
Keywords: Grignard, Kreutzkupplung, Metallorganyle, Komplexe, Katalysatoren
  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0045 Seiten

Publ.-Id: 28361 - Permalink


Organische Chemie XIII - Umlagerungen und Elektrocyclische Reaktionen
Mamat, C.;
Das Ziel des ersten Teils dieses Studienheftes besteht darin, ein Gefühl beziehungsweise Verständnis von Nebenreaktionen zu bekommen, die beispielsweise bei nucleophilen Substitutionsreaktionen oder Additionen und Eliminierungen auftreten. Diese Nebenreaktionen sind meist Umlagerungen, haben teilweise ihren eigenen Mechanismus und führen vielfach zu unerwarteten Produkten, wie wir schon in der Vergangenheit sehen konnten. Wir werden uns intensiv damit beschäftigen, ob und wie diese Umlagerungen beeinflusst werden können und welche Varianten es gibt.
Des Weiteren werden wir schauen, welche weiteren Umlagerungen existieren und welche Produkte zu erwarten sind. Am Ende werden wir einen Blick auf elektrocyclische Reaktionen werfen und sehen, dass durch deren Übergangszustände und Zwischenstufen stereoselektiv Produkte gebildet werden.
Keywords: Wasserstoffwanderung, Alkylgruppenwanderung, Claisen-Reaktion,Cope-Reaktion, Abbaureaktionen
  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0043 Seiten

Publ.-Id: 28360 - Permalink


Organische Chemie XII - Stereoisomerie
Mamat, C.;
Nachdem wir uns in der Organischen Chemie I in der Hauptsache mit Stoffklassen, funktionellen Gruppen und wichtigen Reaktionen beschäftigt haben und in der Organischen Chemie II die Reaktionsmechanismen genau beleuchteten, wollen wir uns im dritten Teil mit speziellen Themen der organischen Chemie beschäftigen. In diesem Studienheft wollen wir uns einzig und allein mit der Anordnung der Atome in Molekülen und den damit verbundenen Besonderheiten dieser Moleküle beschäftigen. Doch warum brauchen wir das ganze Wissen über den exakten Aufbau der Moleküle? Es ist speziell für die Pharmazie und Biochemie von grundlegender Bedeutung, genau zu wissen, wie Moleküle aufgebaut sind. Denn mit exakt der gleichen Summenformel, selbst mit gleicher Aneinanderreihung der Atome können unterschiedliche Wirkungen auftreten.
Deshalb werden wir noch einmal genau beleuchten, was Isomere sind und welche Arten es gibt. Dann werden wir uns die Auswirkungen anschauen, die vier unterschiedliche Substituenten an einem Kohlenstoffatom haben. Wichtig ist, dass Sie verstehen, dass unterschiedliche Stoffe oder Verbindungen da sind, wenn Sie die Stellung (Anordnung) der Substituenten im Molekül „vertauschen“. Zudem sollten Sie mit dem Begriff Stereoisomerie sicher umgehen können und wissen, was für Isomere da existieren und was das für Folgen auf die Reaktivität des Moleküls hat. Darauf aufbauend finden wir Moleküle, in denen mehr als ein Chiralitätszentrum existiert. Welche Auswirkungen das auf die Eigenschaften des Moleküls hat, werden wir am Schluss sehen.
Keywords: Isomere, Enantiomere, prochiral, Chiralität
  • Book (Authorship)
    Heidelberg: Springer Verlag, 2018
    0039 Seiten

Publ.-Id: 28359 - Permalink


Symmetry Breaking of Azimuthal Magnetorotational Instability Caused by Thermal Boundary Conditions
Seilmayer, M.; Stefani, F.;
The first evidence of azimuthal magnetorotaional instability was given some years ago by Seilmayer et al. (2014). A Taylor Couette Setup, filled with liquid metal, was exposed to magnetic field Bφ ~ r^ -1. The necessary current was supplied by a large frame of copper rods which caused a residual m=1 field disturbance. This imperfection caused a stationary dominant background flow. Since then, several changes took place to circumvent external asymmetries and influences. The main improvement was the symmetric current return path which eliminates the m=1 background flow and reduces stray fields. Now the AMRI wave is mainly located at the top of the cylinder, which is surprising since the theoretical prediction allows a symmetric wave with m=±1 configuration. However, the wave component from below is missing. Recent work indicate that thermal convection could be a possible source of symmetry breaking. We present experimental results which give evidence to the strong dependency on thermal boundary conditions which affect AMRI action in the volume.
Keywords: AMRI, MRI, Taylor Couette, magnetorotational instability
  • Poster
    MHD Days and GDRI Dynamo Meeting, 26.-28.11.2018, Dresden, Deutschland

Publ.-Id: 28358 - Permalink


Thallium pollution in China and removal technologies for waters: A review
Liu, J.; Luo, X.; Sun, Y.; Tsang, D. C. W.; Qi, J.; Zhang, W.; Li, N.; Yin, M.; Wang, J.; Lippold, H.; Chen, Y.; Sheng, G.;
Thallium (Tl) is a typical toxic metal, which poses a great threat to human health through drinking water and the food chain (biomagnification). China has rich Tl-bearing mineral resources, which have been extensively explored and utilized, leading to release of large amounts of Tl into the environment. However, research on Tl pollution and removal techniques is relatively limited, because Tl has not been listed within the scope of environmental monitoring in China for several decades. This paper reviewed Tl pollution in wastewater arising from various industries in China, as well as the latest available methods for treating Tl-containing industrial wastewater, in order to give an outlook on effective technologies for controlling Tl pollution. Conventional physical and chemical treatment technologies are efficient at removing trace amounts of Tl, but it proved to be difficult to achieve the stringent environmental standard (≤0.1–5 μg/L) cost-effectively. Adsorption by using newly developed nanomaterials, and metal oxide modified polymer materials and microbial fuel cells are highly promising and expected to become next-generation technologies for remediation of Tl pollution. With the potential for greater Tl contamination in the environment under accelerated growth of industrialization, researches based on lab-scale implementation of such promising treatment technologies should be further expanded to pilot and industrial scale, ensuring environmental protection and the safety of drinking water for sustainable development. Comprehensive insights into experiences of Tl pollution in China and in-depth perspectives on new frontier technologies of Tl removal from wastewaters will also benefit other nations/regions worldwide, which are susceptible to high exposure to Tl likewise.
Keywords: Thallium pollution; Industrial wastewater treatment; Anthropogenic source; Nanomaterials

Publ.-Id: 28357 - Permalink


Fine grinding characteristics of a cassiterite-bearing skarn ore
Buchmann, M.; Leißner, T.; Kern, M.; Schach, E.; Tolosana-Delgado, R.; Rudolph, M.; Gutzmer, J.; Peuker, U. A.;
The grinding characteristic of a cassiterite-bearing skarn ore was investigated for the fine particle size range using an agitated ball mill. The applicability of Mineral Liberation Analyzer was investigated for the fine particle range. The appropriate liberation of cassiterite was determined with the help of tangible parameters such as the degree and coefficient of liberation and grade-recovery diagrams. The liberation of cassiterite was found to be in a satisfying range for downstream upgrading. A more etailed analysis of the liberation characteristics of the potential valuables together with a better understanding of the breakage characteristics of the gangue minerals will help to optimize the operation of the subsequent upgrading process. Therefore, the breakage behavior of the most important gangue minerals was analyzed. The effect of selectivity in breakage for the different minerals became visible.
A clear spreading for the mineral recovery versus size class indicated a mineral specific accumulation during milling. These trends lead to the assumption that the separation of the minerals into different particle size classes can be optimized by applying a specific energy input.
  • Contribution to proceedings
    European Mineral Processing and Recycling Congress (EMPRC) 2018, 22.06.2018, Essen, Germany

Publ.-Id: 28355 - Permalink


Evaluation of Magnetic Separation Efficiency on a Cassiterite-Bearing Skarn Ore by Means of Integrative SEM-Based Image and XRF–XRD Data Analysis
Buchmann, M.; Schach, E.; Tolosana-Delgado, R.; Leißner, T.; Astoveza, J.; Kern, M.; Möckel, R.; Ebert, D.; Rudolph, M.; van den Boogaart, K. G.;
Image analysis data obtained from scanning electron microscopy provided data for a detailed evaluation of the separation efficiency for various processes involving the beneficiation of particulate materials. A dry magnetic separation by a drum type magnetic separator served as a case study to visualize effects of processing of a skarn ore with a high content of cassiterite as ore mineral (~4 wt%). For this material, iron oxides and silicates are the main gangue mineral groups. Based on the obtained data, partition curves were generated with the help of local regression.
From the partition curves, the separation efficiency was evaluated and the relevant particle properties deduced. A detailed analysis of the bias of the quantitative mineralogical data is presented. This bias was monitored and further analyzed in detail. Thorough analysis of feed and products of magnetic separation enabled identification of the most important factors that control losses of cassiterite to the magnetic product, namely the association with iron oxides and particle sizes below ~40 µm.
The introduced methodology is a general approach applicable for the optimization of different separation processes and is not limited to the presented case study.
Keywords: SEM-based image analysis; MLA (Mineral Liberation Analyzer); magnetic separation; cassiterite; partition curve; local regression

Publ.-Id: 28354 - Permalink


The inherent link between ore formation and geometallurgy as documented by complex tin mineralization at the Hämmerlein deposit (Erzgebirge, Germany)
Kern, M.; Kästner, J.; Tolosana-Delgado, R.; Jeske, T.; Gutzmer, J.;
A comprehensive quantitative mineralogical study on the Hämmerlein tin deposit in the Erzgebirge, Germany, not only yields insights into the genesis of Sn mineralization but also provides also important clues for beneficiation. The lithological units of the skarn and greisen deposit show significant differences in modal mineralogy and Sn deportment. These systematic differences are attributed to several stages of ore formation. Of greatest significance is a paragenetically late cassiterite-chlorite-fluorite-sulfide assemblage. This assemblage replaces pre-existing skarn lithologies and also forms stockwork mineralization in greisen-type ores developed at the expense of mica schist that surrounds the skarn. The co-genetic formation of the cassiterite-chlorite-fluorite-sulfide assemblage is captured by the mineral association parameter—a parameter that can be easily quantified from data acquired during automated mineralogy studies. To document the preferred mineral association, a ratio is introduced that illustrates how closely cassiterite—the only Sn mineral of economic relevance—is associated with chlorite, fluorite, and sulfides. This socalled MAMA ratio illustrates the strongly preferred association between cassiterite and chlorite. The results also illustrate that the abundance of rock-forming chlorite may be used as a proxy for the abundance of the much less common cassiterite. This proxy is well-suited to sort ore from poorly mineralized/unmineralized rock fragments early during the beneficiation process. Such separation may well be achieved by using a short wave infrared detector that is already deployed in commercially available sorting equipment. The case study illustrates the inherent link between the processes responsible for ore genesis, the definition of geometallurgical domains, and the selection of suitable beneficiation strategies.

Publ.-Id: 28351 - Permalink


Synthese von deuterierten Oxocortisolderivaten
Hocke, V.;
Ziel dieser Masterarbeit war die Synthese der Steroidderivate 18-Oxocortisol (8a) und dessen deuteriertes Analogon 1,2-2H2-18-Oxocortisol (8b). Die Darstellung erfolgte ausgehend vom strukturell ähnlichen Prednisolon (1). Dazu mussten zunächst orthogonale Schutzgruppen eingeführt werden, um selektiv Modifizierungen an der Steroidstruktur vornehmen zu können. Im Anschluss musste die 18-Methylgruppe funktionalisiert werden um die Einführung der Aldehydfunktion zu ermöglichen. Nach der darauffolgenden Entschützung sollte Derivat 7 erhalten werden, das sich von 8a und 8b lediglich in der C=C-Doppelbindung zwischen den Kohlenstoffatomen C-1 und C-2 unterschiedet und durch selektive Hydrierung oder Deuterierung dieser zu den Zielverbindungen umgesetzt werden kann.
Keywords: 18-Oxocortisol, Deuterium
  • Master thesis
    HTW Dresden, 2018
    Mentor: Dr. habil. Constantin Mamat
    0063 Seiten

Publ.-Id: 28348 - Permalink


Process Analytical Techniques
Hampel, U.;
The lecture gives an introduction to modern process analytical techniques in the industry and research.
Keywords: process analytical techniques
  • Invited lecture (Conferences)
    TOMOCON 1st Summer School, 26.-28.09.2018, Lublin, Poland

Publ.-Id: 28347 - Permalink


High-Resolution Flow Measurement Techniques for the Generation of Validation Data in Nuclear Thermal Hydraulics Experiments
Hampel, U.;
The past years have seen a tremendous increase in computational power and hence a trend to employ more and more advanced numerical tools for the analysis of nuclear thermal hydraulics. Primary applications are accident analyses as well as safety assessment for new reactor systems and prominent directions are 3D computational multiphase fluid dynamics, coupled codes, and advanced BEPU analyses. While years ago it was believed that one day such tools may be able to replace experiments fully or in part, it is meanwhile commonly accepted, that a focus must be given on validation experiments for single effect problems and that such validation experiments should be preferably at original system t/h conditions to account for difficult upscaling conditions, and that such experiments need new instrumentation in order to get CFD grade data. The latter means field quantities of phase fraction, velocity and temperature at high spatial and temporal resolution.
The lecture gives an in-depth overview over novel field measuring techniques for nuclear thermal hydraulics experiments. We will briefly touch the field of distributed sensors for phase fraction, temperature and velocity and then dive into the field of advanced imaging techniques. We will discuss the application of well-known imaging techniques, such as high speed videometry, PIV and IR thermography and then come to computed tomography techniques, which are very useful to study multiphase problems. The methodological description of the basic physics and technology will be accompanied by application examples in nuclear safety research being pursued at the TOPFLOW facility at Helmholtz-Zentrum Dresden-Rossendorf.
Keywords: Flow measurement, multiphase flow, reactor safety, nuclear thermal hydraulics, tomography
  • Invited lecture (Conferences)
    The Frédéric Joliot / Otto Hahn Summer School on Nuclear Reactors "Maximizing the Benefits of Experiments for the Simulation, Design and Analysis of Reactors", 22.-31.08.2018, Aix en Provence, Frankreich

Publ.-Id: 28346 - Permalink


Recent developments and future trends in tomographic imaging for multiphase flows
Hampel, U.;
The presentation gives a overview over recent activities in the field of tomographic imaging for multiphase flows.
Keywords: Multiphase flow, imaging techniques, process tomography
  • Invited lecture (Conferences)
    International Workshop on Multiphase Flow Imaging and Measurement, 13.-14.08.2018, Tianjin, China

Publ.-Id: 28345 - Permalink


TOMOCON: A Marie Skłodowska-Curie European Training Network on Tomography-based Control in Industrial Processes
Hampel, U.; Wondrak, T.; Fjeld, M.; Mudde, R.; Portela, L. M.; Kenjeres, S.; Legendre, D.; Link, G.; Koiranen, T.; Hlava, J.; Babout, L.; Jackowska-Strumiłło, L.; Soleimani, M.; Vauhkonen, M.; Lähivaara, T.; Rymarczyk, T.; Trepte, M.; Voutilainen, A.; Rodriguez, M.; Bos, J.; Betz, S.; Hysky, J.; Pennerstorfer, P.; Goldammer, M.; Matten, C.; Hoffmann, R.; Gingras, J.-P.; van der Plas, D.; Veenstra, P.; Nurmi, J.; Pudack, C.; Da Silva, M. J.;
The European Doctoral Training Network “Smart Tomographic Sensors for Advanced Industrial Process Control (TOMOCON)” gathers academic and industrial partners from different sectors with the mission to develop new fundamentals and technological solutions of advanced industrial control by tomographic sensors. It has received funding by the EU under the Marie Skłodowska-Curie scheme as an Innovative Training Network. It runs from September 2018 to August 2022 with 15 Early Stage Researchers, who are working as PhD students in 10 different European academic institutions. Within their research projects the doctoral students receive an extensive training in various fields of engineering and natural sciences being carried out in the frame of so called secondments at different industrial and academic partners as well as via three dedicated Summer Schools. The network is further supported by an Advisory Board with members from leading institutions in the field of process tomography.
Keywords: Marie Skłodowska-Curie Innovative Training Network, Process Tomography, Process Control, Process Modelling, Doctoral Education and Training
  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
  • Open Access LogoContribution to proceedings
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
    Proceeding of the 9th World Congress on Industrial Process Tomography

Publ.-Id: 28344 - Permalink


Leaching of U(VI) and Cm(III) doped calcium (aluminum) silicate hydrate gel (C-(A)-S-H) and tobermorite in saline brines
Wolter, J. M.; Schmeide, K.; Huittinen, N.; Bok, F.; Weiss, S.; Brendler, V.; Stumpf, T.;
To evaluate the retention potential of concrete inside a nuclear waste repository for actinides under saline and hyperalkaline conditions, leaching experiments with actinide doped cementitious phases were performed in repository-relevant brines. Therefore, U(VI) and Cm(III) doped calcium silicate hydrate (C-S-H) phases with different calcium-to-silicon (C/S) ratios (1.0−2.0) were synthesized directly in presence of either U(VI) or Cm(III) and characterized by time-resolved laser-induced luminescence spectroscopy (TRLFS), infrared (IR) spectroscopy, powder X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM). The time-dependent release of Ca, Si, U or Cm from CSH phases into brines that contained either 2.5 M NaCl, 2.5 M NaCl/0.02 M Na₂;SO₄, 2.5 M NaCl/0.02 M NaHCO₃ or 0.02 M NaHCO₃ for U(VI) doped CSH phases or 2.5 M NaCl/0.02 M NaHCO₃ or 0.02 M NaHCO₃ for Cm(III) doped CSH phases was monitored in batch leaching experiments for 30 to 60 days. Subsequently, leaching induced changes of the C-S-H structure and of the U(VI) or Cm(III) coordination environment were investigated with TRLFS, IR spectroscopy and XRD. Results indicated that the U(VI) retention by C-S-H phases is maintained in the presence of NaCl rich solutions due to the formation of uranophane [1]. The presence of carbonate in saline leaching solutions increased the U(VI) mobility due to formation of Ca₂UO₂(CO₃)₃(aq) at moderate alkaline pH values [1]. Furthermore, an influence of the secondary CaCO₃ phases calcite, vaterite and aragonite was detected. Calcite contributed to the U(VI) retention which was shown with TRLFS [1]. The binding study of Cm(III) incorporated into C-S-H gel revealed at least two Cm(III) species: (i) Cm(III) substituted against Ca2+ from the C-S-H interlayer and (ii) Cm(III) incorporated in the polyhedral CaO plane of the C-S-H structure. Additionally, a luminescence line narrowing effect was observed indicating variations of the local surrounding of Cm(III) in C-S-H gel. Leaching experiments showed that Cm(III) is not mobilized by carbonate but becomes partially incorporated into secondary CaCO₃ phases. Recently, we started to investigate the Al and U(VI) incorporation into C-S-H phases at different Al/Si ratios (0.025−0.2) and synthesis temperatures (25°C or 200°C). The obtained phases were investigated with ² ⁷Al NMR, TRLFS, XRD and Raman microscopy. First results indicated an influence of the Al starting material and synthesis temperature on the Al incorporation.
Keywords: C-S-H, Aluminum, TRLFS, XRD, Raman, IR, Leaching, Saline, Carbonate
  • Contribution to proceedings
    5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions, 25.-27.03.2019, Karlsruhe, Deutschland
    Proceedings of the 5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions
  • Poster
    5th International Workshop on Mechanisms and Modelling of Waste/Cement interactions, 25.-27.03.2019, Karlsruhe, Deutschland

Publ.-Id: 28342 - Permalink


Lattice relaxation effects of the spin-ice Dy2Ti2O7
Stoeter, T.; Nomura, T.; Granovsky, S.; Doerr, M.; Petrenko, O. A.; Balakrishnan, G.; Zherlitsyn, S.; Wosnitza, J.;
Dy2Ti2O and Ho2Ti2O7 have attracted enormous scientific interest because of the unusual spin-ice ground state and exotic excitations – magnetic monopoles. In this work, we investigated how the lattice reacted to the change of the monopole density from the spin-ice through the Kagome ice to the saturated monopole phase and whether the very slow monopole dynamics predicted in theory were also detectable in lattice effects. We have performed magnetostriction and thermal-expansion measurements with a capacitive dilatometer on Dy2Ti2O7 at temperatures down to 0.28 K to explore the lattice effects in the different regimes: Indeed, we have observed a field-dependent lattice anomaly and have found lattice relaxation effects which could be related to previously proposed monopole dynamics. This research has been supported by the DFG within project C01 of SFB 1143.
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28341 - Permalink


Magnetic ground state of the cubic perovskite Ba3NiNb2O9
Yamamoto, S.; Aslan Cansever, G.; Gottschall, T.; Uhlarz, M.; Blum, C. G. F.; Wolter-Giraud, A.; Aswartham, S.; Wurmehl, S.; Herrmannsdörfer, T.; Seiro, S.;
We investigated the magnetic spin-1 perovskite Ba3NiNb2O9 by means of complex ac susceptibility measurements at extreme sample conditions. Ba3NiNb2O9 with cubic perovskite structure (Pm-3m) has a random occupation of Nb(66 %)/Ni(33 %) at the center of the cubic perovskite unit cell. Different from the isostoichiometric sister compound, Ba3NiNb2O9 with P-3m1 structure which shows both uud-spin configuration and multiferroicity, the magnetic properties of the investigated system have not been studied below 2 K yet. For our single crystals, we observe a spin freezing transition at around 0.7 K. Furthermore, the peak of 𝜒’ is suppressed by applying an external dc field of 200 mT and 𝜒” shows a sudden onset near the freezing temperature.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28340 - Permalink


Thermal and thermal-Hall conductivity study of SrCu2(BO3)2
Arsenijevic, S.; Dabkowska, H.; Gaulin, B.; Stern, R.; Wosnitza, J.;
We present measurements of the thermal and the thermal-Hall conductivity as a function of temperature and magnetic field in the twodimensional dimer spin system SrCu2(BO3)2. The thermal conductivity in zero magnetic field shows a pronounced peak around 4 K which is ascribed to a spin-gap opening. The low-temperature maximum is strongly suppressed by the application of magnetic field. This result implies that the majority of heat is conducted by phonons which interact with the magnetic excitations. Furthermore, a theoretical study predicted a strong thermal Hall signature due to anisotropies originating from the Dzyaloshinskii-Moriya interactions which lead to a topological character of triplon excitations [1]. Our detailed experimental investigation did not reveal such effect disproving the existence of topological transitions in the triplon band structure.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28339 - Permalink


Inverted hysteresis within the antiferromagnetic all-in-allout state of the pyrochlore Nd2Hf2O7
Opherden, L.; Bilitewski, T.; Hornung, J.; Herrmannsdörfer, T.; Samartzis, A.; Islam, A. T. M. N.; Anand, V. K.; Lake, B.; Moessner, R.; Wosnitza, J.;
We report the observation of an anisotropic and inverted hysteresis loop in the antiferromagnetic all-in-all-out ordered phase of Nd2Hf2O7 having a negative remnant magnetization. The hysteresis emerges once exceeding a characteristic magnetic-field strength 𝐻(𝑇) below the Neél temperature. The very unusual appearance of a negative remnant magnetization is observed for a field parallel to the [111] and [110] direction. However, for field parallel to [001] no hysteresis can be seen. For this orientation the projection of the field onto all four local spin directions is equal and, hence, both realizations of the all-in-all-out state gaining equal Zeeman energy through a canting of their spins. We show further, that the underlying all-in-all-out phase is established in Nd2Hf2O7 for temperatures below 𝑇𝑁 = 0.48 K and persists up to fields of 0.27 T. We account for the inverted hysteresis in terms of a theory of uncompensated domain-wall spins of spherical Domains forming inside a fully polarized single-domain state.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28338 - Permalink


Electronic structure of the B20 compound CrGe
Klotz, J.; Götze, K.; Bruin, J.; Geibel, C.; Weber, K.; Schmidt, M.; Rosner, H.; Wosnitza, J.;
CrGe is a nonmagnetic transition-metal germanide with the B20 noncentrosymmetric cubic structure. In contrast, the isostructural MnGe and FeGe both show a helical spin order. We present dHvA-effect data on CrGe that were obtained employing capacitive torque Magnetometers in a 18 T/30 mK and a 33 T/340 mK system. In combination with our fplo calculations, we provide a detailed picture of the Fermisurface topology of CrGe. Furthermore, by comparing the calculated band structures of CrGe and MnGe, we discuss possible reasons for the absence of magnetic order in CrGe. Finally, our calculations indicate that substituting Ge by As or Sn will not lead to magnetic order.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28337 - Permalink


Reversibility of minor hysteresis loops in magnetocaloric Heusler alloys
Gottschall, T.; Stern-Taulats, E.; Manosa, L.; Planes, A.; Skokov, K. P.; Gutfleisch, O.; Skourski, Y.; Wosnitza, J.;
The unavoidable existence of thermal hysteresis in these magnetocaloric materials is one of the central challenges limiting their implementation in cooling devices. Transforming the material in minor loops of the thermal hysteresis, however, allows achieving significant reversible effects even when the hysteresis is relatively large. In this work, we focus on the magnetocaloric properties of Heusler alloys under cycling. We compare thermometric measurements of the adiabatic temperature change in low magnetic fields and pulsed field experiments with calorimetric measurements of the isothermal entropy change when moving in minor hysteresis loops driven by magnetic fields [1, 2].
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berline, Deutschland

Publ.-Id: 28336 - Permalink


Exploring the Quantum Limit of Weyl semimetal candidates
Förster, T.; Klotz, J.; Wosnitza, J.; Shekhar, C.; Yan, B.; Felser, C.;
Non-centrosymmetric transition-metal mono-pnictides such as NbAs, NbP and TaAs attracted a lot of attention because their bandstructures show linear non-degenerate band crossings, dubbed Weyl nodes [1,2]. Additionally, for certain magnetic-field orientations, the highest de Haas-van Alphen frequencies observed are smaller than 50 T. For that reason, all bands are expected to be in the quantum limit at fields easily reachable by pulsed magnetic fields. Thus, these semimetals constitute an ideal playground to study the quantum limit by electric transport and magnetic-torque measurements. Our first results for NbP show an unexpected linear increase in magnetic-torque measurements. In our contribution we show the results of our magnetic-torque measurements on NbP, NbAs, TaP and TaAs in pulsed fields up to 70 T.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28335 - Permalink


NMR of the two-dimensional 𝑆 = 1/2 Heisenberg antiferromagnet CuPOF
Dmytriieva, D.; Zhang, Z. T.; Uhlarz, M.; Landee, C. P.; Wosnitza, J.; Kühne, M.;
The metal-organic compound [Cu(pz)2(2-OHpy)2](PF6)2 (CuPOF) is a molecular-based analog of the two-dimensional quantum 𝑆 = 1/2 Heisenberg antiferromagnet (2D QHAF) with well-isolated Cu(pz) layers and a very low 𝑘𝐵𝑇𝑁/𝐽 = 0.21 ratio (𝐽/𝑘𝐵 = 6.8 K, 𝑇𝑁 = 1.38 K). We present a focus study of the low-temperature phase transition to long-range order performed via 1H and 31P nuclear magnetic resonance (NMR), as well as high-field magnetometry. A low-temperature Minimum of the temperature-dependent local and uniform magnetizations at 𝑇𝑚𝑖𝑛 indicates a presence of the magnetic order. Within the ordered state, a splitting of the 1H NMR spectra reveals commensurate AF order, presumably of checkerboard type. The phase transition, manifested as a sharp maximum of the temperature-dependent 31P nuclear spin-lattice relaxation rate 1/𝑇1, occurs at temperatures slightly lower than 𝑇𝑚𝑖𝑛, indicating an easy-plane anisotropy as well as a crossover between isotropic and XY behavior.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28334 - Permalink


Exploring the magnetic phase diagram of a metal-organic S = 1 triangular spin system.
Chattopadhyay, S.; Herrmannsdörfer, T.; Kanungo, S.; Zvyagin, S.; Uhlarz, M.; Manna, K.; Schnelle, W.; Sannigrahi, J.; Wosnitza, J.; Patra, R.;
We report on magnetic properties of a novel metal-organic S = 1 antiferromagnetic triangular spin compound with isolated Ni2+ triangles entitled as BHAP-Ni3. Specific heat measurements reflect an onset of magnetic correlation at low temperatures without any long-range order down to 300 mK, indicating the presence of an unusual magnetic ground state. ESR measurements performed at 1.5 K advocate this ground state to be a gapped one. Field-dependent magnetization measured on the single crystal shows anisotropic behavior with field applied parallel and perpendicular to the triangle plane. However, a clear plateau-like region is seen in both directions above 8 T which corresponds to half of the fully polarized value of Ni2+ moment. The presence of such half-magnetization plateau is quite unusual in the family of triangular magnets. High-field magnetization measurements using pulsed magnet show another field-induced plateau above 30 T corresponding to the fully polarized state of S = 1 triangles.
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28333 - Permalink


High-field ESR studies of the honeycomb-lattice material 𝛼-RuCl3
Ponomaryov, A. N.; Schulze, E.; Wosnitza, J.; Lampen-Kelley, P.; Banerjee, A.; Yan, J. Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Kolezhuk, A. K.; Zvyagin, S.;
We present high-field electron spin resonance (ESR) studies of the honeycomb-lattice material 𝛼-RuCl3, a prime candidate to exhibit Kitaev physics. Two modes of antiferromagnetic resonance were detected in the zigzag ordered phase, with magnetic field applied in the 𝑎𝑏 plane. A very rich excitation spectrum was observed in the field-induced Quantum paramagnetic phase. The obtained data are compared with results of recent numerical calculations, strongly suggesting a very unconventional multiparticle character of the spin dynamics in 𝛼-RuCl3. The frequency-field diagram of the lowest-energy ESR mode is found consistent with the behavior of the field-induced energy gap, revealed by thermodynamic measurements. This work was supported by DFG (project ZV 6/2-2).
  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 28332 - Permalink


Magnetoelastic phenomena in antiferromagnetic uranium intermetallics: The UAu2Si2 case
Valiska, M.; Saito, H.; Yanagisawa, T.; Tabata, C.; Amitsuka, H.; Uhlirova, K.; Prokleska, J.; Proschek, P.; Valenta, J.; Misek, M.; Gorbunov, D. I.; Wosnitza, J.; Sechovsky, V.;
Thermal expansion, magnetostriction, and magnetization measurements under magnetic field and hydrostatic pressure were performed on a UAu2Si2 single crystal. They revealed a large anisotropy of magnetoelastic properties manifested by prominent length changes, leading to a collapse of the unit-cell volume accompanied by breaking the fourfold symmetry (similar to that in URu2Si2 in the hidden-order state) in the antiferromagnetic state as consequences of strong magnetoelastic coupling. The magnetostriction curves measured at higher temperatures confirm a bulk character of the 50K weak ferromagnetic phase. The large positive pressure change of the ordering temperature predicted from Ehrenfest relation contradicts the more than an order of magnitude smaller pressure dependence observed by the magnetization and specific heat measured under hydrostatic pressure. A comprehensive magnetic phase diagram of UAu2Si2 in magnetic field applied along the c axis is presented. The ground-state antiferromagnetic phase is suppressed by a field-induced metamagnetic transition that changes its character from second to first order at the tricritical point

Publ.-Id: 28330 - Permalink


Chronic low dose ethanol induces an aggressive metastatic phenotype in TRAMP mice, which is counteracted by parthenolide
Morel, K.; Ormsby, R.; Solly, E.; Tran, L.; Sweeney, C.; Klebe, S.; Cordes, N.; Sykes, P.;
Despite advances in prostate cancer therapy, dissemination and growth of metastases results in shortened survival. Here we examined the potential anti-cancer effect of the NF-B inhibitor parthenolide (PTL) and its water soluble analogue dimethylaminoparthenolide (DMAPT) on tumour progression and metastasis in the TRansgenic Adenocarcinoma of the Mouse Prostate (TRAMP) model of prostate cancer. Six-week-old male TRAMP mice received PTL (40mg/kg in 10% ethanol/saline), DMAPT (100mg/kg in sterile water), or vehicle controls by oral gavage thrice weekly until palpable tumour formation. DMAPT treatment slowed normal tumour development in TRAMP mice, extending the time-to-palpable prostate tumour by 20%. PTL did not slow overall tumour development, while the ethanol/saline vehicle used to administer PTL unexpectedly induced an aggressive metastatic tumour phenotype. Chronic ethanol/saline vehicle upregulated expression of NF-B, MMP2, integrin 1, collagen IV, and laminin, and induced vascular basement membrane degradation in primary prostate tumours, as well as increased metastatic spread to the lung and liver. All of these changes were largely prevented by co-administration with PTL. DMAPT (in water) reduced metastasis to below that of water-control. These data suggest that DMAPT has the potential to be used as a cancer preventive and anti-metastatic therapy for prostate cancer. Although low levels of ethanol consumption have not been shown to strongly correlate with prostate cancer epidemiology, these results would support a potential effect of chronic low dose ethanol on metastasis and the TRAMP model provides a useful system in which to further explore the mechanisms involved.
Keywords: Parthenolide; DMAPT; Metastasis; TRAMP; Prostate cancer; Ethanol

Publ.-Id: 28329 - Permalink


Investigations on potential methods for the long-term monitoring of the state of fuel elements in dry storage casks
Hampel, U.; Kratzsch, A.; Rachamin, R.; Wagner, M.; Schmidt, S.; Fiß, D.; Reinicke, S.;
Extended dry storage of spent nuclear fuel is a relevant issue in many countries operating nuclear power plants. Beside regulatory and security aspects there are questions with respect to the long-term integrity of the spent fuel as this is of relevance for final transportation and reloading to final waste repository casks. Within the frame of the BMWi project DCS-MONITOR, we investigate the potentials of different methods for non-intrusive monitoring of dry cask storage containers with spent nuclear fuel. These are thermography, radiation-based methods, and acoustic methods. For all of them we study the sensitivity and cross-sensitivity with respect to defined changes in the nuclear fuel distribution inside the containers. The analyses are mainly based on numerical simulations but also include some dedicated experimental studies.
Keywords: extended storagy, spent fuel, monitoring
  • Kerntechnik 83(2018)6, 513-522
    DOI: 10.3139/124.110949
  • Lecture (Conference)
    2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 06.-08.06.2018, Garching, Deutschland
  • Contribution to proceedings
    2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel, 06.-08.06.2018, Garching, Germany
    Proceedings of 2nd Workshop on Safety of Extended Dry Storage of Spent Nuclear Fuel

Downloads:

  • Secondary publication expected from 31.12.2019

Publ.-Id: 28328 - Permalink


Effect of neutron flux on the microstructure of irradiated RPV steels
Ulbricht, A.; Bergner, F.;
This invited talk about the effect of neutron flux on the microstructure of irradiated RPV steels was given to the participants of a Training School in the Framework of the European project SOTERIA.
Keywords: Pressure vessel steels, neutron irradiation, neutron flux, microstructure
  • Invited lecture (Conferences)
    International SOTERIA Training School, 03.07.-07.09.2018, Valencia, Spain

Publ.-Id: 28327 - Permalink


Metallische Verbundwerkstoffe mit funktionellen Eigenschaften
Weissgärber, T.; Schubert, T.; Hutsch, T.; Hilger, I.; Bergner, F.; Kieback, B.;
Der Vortrag umfasst Aspekte der Herstellung, Mikrostruktur, Eigenschaften und Anwendung von pulvermetallurgisch hergestellten Werkstoffen. Als Beispielsysteme werden ODS-Fe-Cr-Legierungen, Verbundwerkstoffe für die Elektronikkühlung und Aluminiumverbundwerkstoffe betrachtet.
Keywords: ODS Legierungen
  • Invited lecture (Conferences)
    7. Dresdner Werkstoffsymposium 2018, 06.-07.12.2018, Dresden, Deutschland

Publ.-Id: 28326 - Permalink


Machbarkeitsstudie zur MRT-integrierten Protonentherapie: Strahlablenkung, Sekundärteilchen und Bildqualität
Schellhammer, S. M.ORC; Gantz, S.; Lühr, A.; Pawelke, J.; Karsch, L.; Smeets, J.; Quets, S.; Burigo, L. N.; Oborn, B.; Bussmann, M.; Hoffmann, A. L.
Einleitung
Ungefähr 50% der Krebspatienten werden durch Strahlentherapie behandelt, und die Protonentherapie (PT) bietet hier aufgrund der begrenzten Eindringtiefe und des steilen Dosismaximums eine sehr gezielte Behandlungsform mit potentiell reduzierten Nebenwirkungen. Die Treffgenauigkeit der Protonentherapie kann jedoch durch Bewegungen und anatomische Veränderungen während der Therapie stark kompromittiert werden. Eine gleichzeitige Bildgebung mittels Echtzeit-Magnetresonanztomographie (MRT) wäre deshalb ideal. Bis heute existieren jedoch keine kombinierten Systeme für MRT und PT. Ziele dieser Studie waren die erste Integration eines MR-Scanners in eine PT-Strahlführung, die experimentelle Verifizierung der Ablenkung des Strahls und der Sekundärteilchen im Magnetfled des MRT-Scanners, die Überprüfung der Machbarkeit einer gleichzeitigen MR-Bildgebung und Bestrahlung, und die Kontrolle der MR-Bildqualität mit und ohne Strahleinfluss.

Material & Methoden
Ein offener MR-Scanner mit einem vertikalen Magnetfeld von 0.22 T (MRJ2200, Paramed Medical Systems SpA) wurde an einer strahldüsenlosen horizontalen Strahlführung (Ion Beam Applications SA) installiert, und durch einen kompakten Faraday-Käfig von Hochfrequenz-Interferenzen abgeschirmt (Abb. 1). Die Strahlablenkung und der Einfluss des Magnets auf die Sekundärteilchen im Strahl wurden mithilfe an einem PMMA-Phantom befestigter radiochromischer Filme (EBT3, Ashland) in einem 1 T Magneten gemessen und mit Monte-Carlo-simulationsbasierten Vorhersagen verglichen. Zur Überprüfung der MR-Bildgebung wurden anatomische MR-Bilder eines Probanden bei ausgeschalteter Strahlführung sowie MR-Bilder eines Gewebephantoms und eines dedizierten Bildqualitätsphantoms mit und ohne Strahleinfluss (bei 125 MeV und 5 nA) aufgenommen.

Ergebnisse
Die gemessene Ablenkung des Strahls sowie lokale Dosiserhöhung durch Sekundärteilchen im Magnetfeld waren gering (< 1 cm bzw. 2%) und zeigten sehr gute Übereinstimmung mit simulationsbasierten Vorhersagen. Die MR-Aufnahmen (Abb. 2) zeigten die für den verwendeten Scanner übliche Bildqualität. Es wurde keine Veränderung der Bildqualität durch die Strahlführungsmagneten und den Protonenstrahl beobachtet, jedoch eine gleichförmige, korrigierbare Bildverschiebung (< 1 mm) in Frequenzkodierrichtung.

Diskussion
Die Integration eines offenen MR-Scanners in den experimentellen Strahlengang einer Protonentherapie-Anlage war erfolgreich. Die Einflüsse des Magnetfelds des MRT-Scanners auf den Strahl sind vorhersagbar und eine gleichzeitige MR-Bildgebung und Bestrahlung ohne Bildverzerrung ist möglich. Dies rechtfertigt die Entwicklung eines ersten Prototyps für die MRT-integrierte Protonentherapie.
  • Poster
    1. Deutscher KrebsForschungsKongress (DKFK) | 1st German Cancer Research Congress (GCRC), 04.-05.02.2019, Heidelberg, Deutschland

Publ.-Id: 28323 - Permalink


Including anatomical variations in robust optimization for head and neck proton therapy can reduce the need of adaptation
Cubillos-Mesías, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.ORC
Background and purpose: Classical robust optimization considers uncertainties in patient setup and particle range. However, anatomical changes occurring during the treatment are neglected. Our aim was to compare classical robust optimization (cRO) with anatomical robust optimization (aRO), to quantify the influence of anatomical variations during the treatment course, and to assess the need of adaptation.
Materials and methods: Planning CT and weekly control CTs (cCTs) from 20 head and neck patients were analysed. Three intensity-modulated proton therapy (IMPT) plans were compared: conventional PTV-based plan; cRO, using solely the planning CT, and aRO, including additionally the first 2 cCTs in the optimization. Weekly and total cumulative doses, considering anatomical variations during the treatment, were calculated and compared with the nominal plans.
Results: Nominal plans fulfilled clinical specifications for target coverage (D98% ≥ 95% of prescribed dose). The PTV-based and cRO approaches were not sufficient to account for anatomical changes during the treatment in 10 and 5 patients, respectively, resulting in the need of plan adaptation. With the aRO approach, in all except one patient the target coverage was conserved, and no adaptations were necessary.
Conclusion: In 25% of the investigated cases, classical robust optimization is not sufficient to account for anatomical changes during the treatment. Adding additional information of random anatomical variations in the optimization improves plan robustness.
Keywords: Robust optimization; head and neck cancer; proton therapy; treatment planning; anatomical variations; dose accumulation; plan adaptation

Downloads:

  • Secondary publication expected from 31.12.2019

Publ.-Id: 28322 - Permalink


McSAFE - High Performance Monte Carlo methods for safety demonstration
Vocka, R.; Sanchez, V.; Mercatali, L.; Malvagi, F.; Smith, P.; Dufek, J.; Seidl, M.; Milisdorfer, L.; Leppänen, J.; Hoogenboom, E.; Kliem, S.ORC; van Uffelen, P.; Kerkar, N.
The main objective of the McSAFE project is the development of the Monte Carlo based multiphysics coupled methodologies for reactor analysis and safety investigations of different reactor systems. Key-research areas are e.g. advanced depletion methods, optimal coupling of MC-codes to thermalhydraulic solvers, time-dependent Monte Carlo and methods and algorithms for massively parallel simulations. The project has started in September 2017 under the coordination of KIT. Among the other partners are European research institutes and technical support organizations (VTT, JRC, CEA, HZDR, NRI, KTH,WOOD), electricity providers (CEZ, PreussenElektra) and consultants (DNC). The software developed within the project should allow for the high precision evaluation of core safety parameters and will be applicable also to VVER reactor types.
  • Contribution to proceedings
    28. Symposium of AER, 08.-12.10.2018, Olomouc, Czech Republic
    Proceedings of the 28. Symposium of AER, Budapest: MTA EK, 9789637351303, 237-238

Publ.-Id: 28321 - Permalink


Synthesis, Receptor Affinity, and Antiallodynic Activity of Spirocyclic σ Receptor Ligands with Exocyclic Amino Moiety
Bergkemper, M.; Kronenberg, E.; Thum, S.; Börgel, F.; Daniliuc, C.; Schepmann, D.; Nieto, F. R.; Brust, P.; Reinoso, R. F.; Alvarez, I.; Wünsch, B.;
In order to detect novel σ receptor ligands, the rigit spiro [[2]benzopyran-1,1'-cyclohexan]-4'-one was connected with amino moieties derived from σ2 receptor preferring lead compounds resulting in mixtures of trans- and cis-configured amines 6, 18, and 27. In a four step synthesis the methyl acetals 6 were converted into fluoroethyl derivatives 13 and 30. The most promising σ2 receptor ligand is the methyl acetal 6a bearing a 2,4-dimethylbenzylamino moiety. The fluoroethyl derivatives 13c and 13d reveal high σ1 affinity but moderate selectivity over the σ2 subtype. In mice 13c and 13d showed antiallodynic activity that is stronger than that of the reference σ1 antagonist BD-1063 (34). Since the antiallodynic activity of 13c could only be partially reversed by the σ1 agonist PRE-084 (35), it is postulated that a second mechanism contributes to its overall antiallodynic effect. In contrast, the antiallodynic effect of its diastereomer 13d can be totally explained by a σ1 antagonism.

Downloads:

  • Secondary publication expected from 12.10.2019

Publ.-Id: 28319 - Permalink


The Serial Interface Package -- v2.0
Seilmayer, M.ORC
The 'serial' package as an extension to the programming language R enables reading and writing binary and ASCII data to RS232/RS422/RS485 or any other virtual serial interfaces of the computer.
Keywords: serial interface, RS232, RS422, RS485, R
  • Software in external data repository
    Publication year 2018
    Programming language: R
    System requirements: Windows, Mac, Unix
    License: GPL-2
    Hosted on r-project.org: Link to location

Publ.-Id: 28318 - Permalink


Characterization and beneficiation of pyrolyzed black mass from lithium ion batteries
Vanderbruggen, A.; Gilbricht, S.; Möckel, R.; Rudolph, M.;
The lithium-ion battery (LiB) market is growing rapidly. Consequently, LiB wastes will increase in the future and LiB components such as Co, Li, but also graphite, are forecast to be critical materials. These critical materials are contained in the black mass produced by LiBs recycling. This original research focuses on graphite beneficiation from cathode lithium metal oxides by flotation. Detailed characterization of the pyrolyzed black mass (inculding MLA, XRF and XRD) shows that the graphite particles are fully liberated from the copper foils, and the organic layer PVDF is removed. Batch flotation shows that pretreatment, such as attritioning, improves process efficiency while preserving the shape of spheriodized graphite. Concentrate impurities mainly comprise fine particles from cathode active materials, which can be removed with desliming and flotation cleaner stages. As an outlook, this reasearch is expected to bring about an innovative and useful process for the recycling industry.
Keywords: Attritionning, black mass, characterization, flotation, graphite, mineral liberation analysis (MLA), pre-treatment, recycling, spent lithium ion battery, surface analysis
  • Poster
    Minerals Engineering International (MEI) conference: Process Mineralogy '18, 19.-21.11.2018, Cape Town, South Africa

Publ.-Id: 28316 - Permalink


Serpent solution of the X2 VVER-1000 benchmark fresh core experiments
Bilodid, Y.; Fridman, E.;
The X2 VVER-1000 benchmark describes first 4 fuel cycles of the Khmelnitsky NPP 2nd unit with VVER-1000 reactor as well as some operational transients. The benchmark specifications contain description of the reactor core material, geometry and operational history supplemented by measured operational data and startup experiments. In this work, the hot zero power experiments conducted during the fresh core startup are modelled with the Serpent-2 Monte Carlo code. The numerical results are validated against the available measured core data. The calculated and measured values of a critical boron concentration, temperature reactivity effect, and control rod worth are in a very good agreement while the deviations lay within the measurement uncertainties. Since the power distribution was not measured at the hot zero power state, the obtained Serpent solution could be used as a reference for a deterministic codes verification.
Keywords: X2 benchmark, VVER-1000, Serpent
  • Contribution to proceedings
    PHYSOR 2018: Reactor Physics Paving The Way Towards More Efficient Systems, 22.-26.04.2018, Cancun, Mexico, 1982-1989

Publ.-Id: 28315 - Permalink


Doping issues in silicon nanowires by ion implantation and flash lamp annealing
Berencen, Y.; Prucnal, S.; Wang, M.; Rebohle, L.; Helm, M.; Zhou, S.; Skorupa, W.;
Semiconducting nanowires (NWs) hold promises for functional nanoscale devices. Although several applications have been demonstrated in the areas of electronics, photonics and sensing, the doping of NWs remains challenging. Ion implantation is a standard doping method in top-down semiconductor industry, which offers precise control over the areal dose and depth profile as well as allows for the doping of all elements of the periodic table even beyond their equilibrium solid solubility. Yet its major disadvantage is the concurrent material damage. A subsequent annealing process is commonly used for the healing of implant damage and the electrical activation of dopants. This step, however, might lead to the out-diffusion of dopants and eventually the degradation of NWs because of the low thermal stability caused by the large surface–area-to-volume ratio.

In this work, we report on non-equilibrium processing (flash lamps) for controlled doping of drop-casted Si/SiO2 core/shell NWs with shallow- and deep-level dopants below and above their equilibrium solid solubility. The approach lies on the implantation of either shallow-level dopants, such as B and P, or deep-level dopants like Se followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to intermediate-band Si/SiO2 core/shell NWs that have room-temperature sub-band gap photoresponse when configured as a photoconductor device [1]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual NWs at different depth along the NW core.
[1] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 1800101
Keywords: doping, nanowires, semiconductor, silicon, ion implantation, flash lamp annealing
  • Lecture (Conference)
    22nd International Conference on Ion Implantation Technology, 16.-21.09.2018, Würzburg, Deutschland

Publ.-Id: 28313 - Permalink


Advanced doping issues using nonequilibrium processing
Skorupa, W.; Rebohle, L.; Prucnal, S.; Berencen, Y.; Zhou, S.; Helm, M.;
In this talk I will introduce with a short view on the background of the transistor invention as a key element driving the topic of semiconductor doping. After that I will discuss examples of advanced doping including ion beam based and other methods: doping and alloying of germanium, hyperdoping of silicon, doping from deposited layers, doping of silicon nanowires, doping from deposited layers. In all cases the experiments were performed in correlation to nonequilibrium thermal processing using flash lamps in the millisecond time range.
Keywords: semiconductor doping, ion beam based methods, flash lamp annealing
  • Lecture (others)
    Eingeladener Seminarvortrag an der Marie-Curie-Universität Lublin/Polen, 11.10.2018, Lublin, Polen

Publ.-Id: 28311 - Permalink


Dataset on characterization, ion irradiation and nanoindentation of ODS Fe14Cr-based alloys
Bergner, F.;

The dataset comprises raw data of the nanoindentation tests and processed data on the ion irradiations and irradiation-induced hardness changes. File formats are excel, word, origin and ascii.


Related publications
Nanoindentation of single- (Fe) and dual-beam (Fe and He) … (Id 28308) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-12-04
    DOI: 10.14278/rodare.72

Downloads:

Publ.-Id: 28310 - Permalink


Bonding and stability analysis of tetravalent f-element complexes with mixed N-, O-donor ligands
Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.;
The contribution of the f-orbitals leads to a very rich chemistry of the f-elements[1] where it is known that this contribution is less important for lanthanides. Of special interest is the influence of these orbitals on the bonding character of actinides and lanthanides with organic ligands re- flecting natural bonding motifs.
This study shows the different bonding behaviour of tetravalent f-elements with Schiff bases, like salen (see Fig. 1) and derivatives, by means of real-space bonding analysis. This includes the popular quantum theory of atoms in molecules (QTAIM), plots of the non-covalent inter- actions (NCI)[2] and density differences complemented by natural population analysis (NPA). Thermodynamic calculations on the stability of these complexes are presented. The obtained results are a direct consequence of the different interaction strengths of the f-elements.
First studies 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 inter- action between the actinides and the nitrogen of salen is much weaker.
By acquiring knowledge about the different behaviours of bonding and complexation it is possi- ble to understand the chemical properties of the f-elements and predict yet unknown complexes.
Keywords: Bonding analysis, Theoretical Chemistry, DFT, QTAIM, Actinides
  • Poster
    Symposium on Theoretical Chemistry, 17.-20.09.2018, Halle, Deutschland

Publ.-Id: 28309 - Permalink


Nanoindentation of single- (Fe) and dual-beam (Fe and He) ion-irradiated ODS Fe-14Cr-based alloys: Effect of the initial microstructure on irradiation-induced hardening
Heintze, C.; Hilger, I.; Bergner, F.ORC; Weissgärber, T.; Kieback, B.
Although the view that nm-sized oxide particles modify and essentially improve the irradiation resistance of Fe-Cr-based alloys is widely accepted, the correctness of this view has only been demonstrated in singular cases. An extension of the field of considered microstructures, irradiation conditions, and measures of irradiation resistance is required. The present study is focused on nanostructured ferritic Fe-14%Cr-based alloys, with and without the addition of 0.6 wt% Y2O3, produced via mechanical alloying and consolidation by spark plasma sintering. The materials were exposed to single-beam (Fe) and dual-beam (Fe+He) ion irradiations at room temperature. The initial microstructures were characterized, bimodal grain size distributions were observed and nanoindentation was applied to measure irradiation hardening for fine-grained and coarse-grained areas separately. We have found that grain size governs irradiation hardening for single-beam irradiation, while oxide nanoparticles play a dominant role for dual-beam irradiations. This sheds a light on the role of particle-matrix interfaces on helium management.
Keywords: Nanostructured ferritic alloys, oxide dispersion strengthening, ion irradiation, dual-beam irradiation, helium, nanoindentation, irradiation hardening
Related publications
Dataset on characterization, ion irradiation and … (Id 28310) HZDR-primary research data are used by this publication

Downloads:

  • Secondary publication expected from 04.03.2020

Publ.-Id: 28308 - Permalink


Bonding and stability analysis of tetravalent actinide and lanthanide complexes with N,O-donor ligands
Kloditz, R.; Radoske, T.; Patzschke, M.; Stumpf, T.;
The contribution of the f-orbitals leads to a very rich chemistry of the f-elements[1] where it is known that this contribution is less important for lanthanides. 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 shows the different bonding behaviour of tetravalent actinide and lanthanide complexes with Schiff bases, like salen (see Fig. 1) and derivatives, by means of real-space bonding analysis. This includes the popular quantum theory of atoms in molecules (QTAIM), plots of the non-covalent interactions (NCI)[2] and density differences complemented by natural population analysis (NPA). Thermodynamic calculations on the stability of these complexes are done being a direct consequence of the different interaction strengths of the f-elements.
First studies 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.
By acquiring knowledge about the different behaviours of bonding and complexation it is possible to understand the chemical properties of the f-elements and predict yet unknown complexes.
Keywords: Bonding, Salen, Actinides, theoretical chemistry, DFT, QTAIM
  • Lecture (Conference)
    International Symposium on Nano and Supramolecular Chemistry, 09.-12.07.2018, Dresden, Deutschland

Publ.-Id: 28307 - Permalink


The Study and Development of Pulsed High-field Magnets for Application in Laser-plasma Physics
Kroll, F.;
The thesis at hand addresses design, characterization and experimental testing of pulsed high-field magnets for utilization in the field of laser-plasma physics. The central task was to establish a technology platform that allows to manipulate laser-driven ion sources in a way that the accelerated ions can be used in complex application studies, e.g. radiobiological cell or tumor irradiation.

Laser-driven ion acceleration in the regime of target normal sheath acceleration (TNSA) offers the unique opportunity to accelerate particles to kinetic energies of few 10MeV on the micrometer scale. The generated bunches are short, intense, show broad exponentially decaying energy spectra and high divergence. In order to efficiently use the generated particles, it is crucial to gain control over their divergence directly after their production. For most applications it additionally is favorable to reduce the energy spread of the beam. This work shows that the developed pulsed high-field magnets, so-called solenoids (cylindrical magnets), can efficiently capture, transport and focus laser-accelerated protons. The chromaticity of the magnetic lens thereby provides for energy selection.

Three prototype solenoids, adapted to fit different application scenarios, and associated current pulse drivers have been developed. The magnets generate fields of several 10 T. Pulse durations are of the order of one millisecond and thus the fields can be considered as quasi-static for laser-plasma interaction processes taking place on the ps- to ns-scale. Their high field strength in combination with abandoning magnetic cores make the solenoids compact and light-weight.

The presented experiments focus on a solenoid magnet designed for the capture of divergent laser-driven ion beams. They have been carried out at the 6MV tandetron accelerator and the laser acceleration source Draco of Helmholtz-Zentrum Dresden – Rossendorf as well as at the PHELIX laser of GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt. The results show that the developed technology platform breaks ground for a variety of practical applications of laser ion acceleration. It is shown that laser-driven ion beams can be efficiently injected into conventional accelerator structures to allow for phase space modulation. Furthermore, first practical studies on medical beam guidance systems are presented. Hence, the developed magnets allow to investigate feasibility and potential of the frequently proposed laser-based ion beam therapy of tumor diseases. The pulsed high-field magnets bring us one step closer to the realization of this ambitious endeavor, as they pave the way for compact and efficient beam guidance toward the patient but also, in the phase of translational research, allow to study the radiobiological properties of the novel particle source. In this context, worldwide first irradiation studies with laser-accelerated protons on volumetric tumors in the mouse model have been prepared and their feasibility studied, identifying already met radiobiological criteria and hurdles yet to overcome.
Keywords: Pulsed magnets, high-field magnets, beam transport, laser-acceleration, laser acceleration, TNSA, laser particle acceleration, laser-radiooncology
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-094 2018

Downloads:

Publ.-Id: 28306 - Permalink


Photo-induced THz response of VO2 under high pressures
Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.ORC
We apply ultrafast optical pump – THz probe spectroscopy in order to investigate the nature of the high pressure metallic state of VO2 single crystal. The pump excitation was performed using near-infrared pulses at the wavelength of 800 nm. The probe pulses with a frequency of 30 THz were generated by difference frequency mixing and focused on the sample mounted inside a diamond anvil pressure cell. Using the probe photon energy far below the bandgap of VO2 we were able to explore the response of free charge carriers near the Fermi level.
  • Lecture (Conference)
    Non-equilibrium Dynamics of Condensed Matter in the Time Domain, 03.-06.09.2018, Kerkrade, Netherlands

Publ.-Id: 28305 - Permalink


Photoinduced non-thermal insulator-to-metal transition in NbO2 epitaxial thin films
Rana, R.; Klopf, M. J.; Grenzer, J.; Schneider, H.; Helm, M.; Pashkin, A.ORC
Ultrafast insulator-to-metal transition in the correlated oxides such as vanadium dioxide (VO2) has been extensively explored for rich physics and potential applications. In this regard, its isovalent counterpart niobium dioxide (NbO2) with considerably higher transition temperature (Tc = 1080 K) can be envisaged as a potential candidate. We have performed time-resolved optical pump – terahertz (THz) probe measurements on NbO2 epitaxial thin at room temperature.
The onset of the THz conductivity is followed by an exponential decay on a timescale of 400 fs. The photoinduced change in THz transmission at later delay times exhibits excitation threshold of 17.5 mJ/cm2. Notably, in contrast to VO2, the pump energy required for the switching into a metastable metallic state is smaller than the energy necessary for heating NbO2 up to Tc providing a strong evidence for the non-thermal character of the photoinduced insulator-to-metal transition in this system. The transient optical conductivity in the metastable state can be modelled using the Drude model confirming its metallic character.
  • Lecture (Conference)
    DPG-Frühjahrstagung 2018, 11.-16.03.2018, Berlin, Germany

Publ.-Id: 28304 - Permalink


Electron dynamics in InxGa1-xAs shells around GaAs nanowires probed by terahertz spectroscopy
Fotev, I.; Balaghi, L.; Schmidt, J.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, A.ORC
We present the electrical properties of GaAs/InxGa1-xAs core/shell nanowires measured by ultrafast optical pump - terahertz probe spectroscopy.
This contactless technique was used to measure the photoconductivity of nanowires with shell compositions of x = 0.20, 0.30 and 0.44. The results were fitted with the model of localized surface plasmon in a cylinder in order to obtain electron mobilities, concentrations and lifetimes in the InxGa1-xAs NW shells.
The estimated lifetimes are about 80 - 100 ps and the electron mobility reaches 3700 cm2/Vs at room temperature. This makes GaAs/InGaAs nanowires good candidates for the near-future realization of InGaAs based high-electronmobility transistor.
Keywords: GaAs nanowires, terahertz spectroscopy, ultrafast dynamics, electron mobility, plasmon, carrier lifetime

Publ.-Id: 28302 - Permalink


Nonthermal nature of photo-induced insulator-to-metal transition in NbO2
Rana, R.; Klopf, J. M.; Grenzer, J.; Schneider, H.; Helm, M.; Pashkin, A.;
We study the photo-induced metallization process in niobium dioxide NbO2. This compound undergoes the thermal insulator-to-metal transition at the remarkably high temperature of 1080 K. Our optical pump ¬– terahertz probe measurements reveal the ultrafast switching of the film on a sub-picosecond timescale and the formation of a metastable metallic phase when the incident pump fluence exceeds the threshold of ~10 mJ/cm2. Remarkably, this threshold value corresponds to the deposited energy which is capable of heating NbO2 only up to 790 K, thus, evidencing the non-thermal character of the photo-induced insulator-to-metal transition. We also observe an enhanced formation of the metallic phase above the second threshold of ~17.5 mJ/cm2 which corresponds to the onset of the thermal switching. The transient optical conductivity in the metastable phase can be modeled using the Drude-Smith model confirming its metallic character. The present observation of non-thermal transition in NbO2 can serve as an important test bed for understanding photo-induced phenomena in strongly correlated oxides.
Keywords: metal-insulator transition, pump-probe spectroscopy, transition metal oxides

Downloads:

Publ.-Id: 28301 - Permalink


Optical Pump – THz Probe Response of VO2 under High Pressure
Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.;
We present the ultrafast THz response of VO2 under high pressures. A clear anomaly is observed around 8 GPa indicating a pressure-induced phase transition. Our observations can be interpreted in terms of a bandwidth-controlled Mott-Hubbard transition.
Keywords: metal-insulator transition, high pressure, VO2, pump-probe spectroscopy
  • Open Access LogoContribution to proceedings
    XXI International Conference on Ultrafast Phenomena, 15.-20.07.2018, Hamburg, Deutschland
    Proceedings of Ultrafast Phenomena XXI, 91944 Les Ulis cedex A - France: EDP Sciences Web of Conferences
    DOI: 10.1051/epjconf/201920504003

Publ.-Id: 28300 - Permalink


Optical Pump – THz Probe Response of VO2 under High Pressure
Braun, J. M.; Schneider, H.; Helm, M.; Mirek, R.; Boatner, L. A.; Marvel, R. E.; Haglund, R. F.; Pashkin, A.ORC
We present the ultrafast THz response of VO2 under high pressures. Pump-probe signals and a photoexcitation threshold are detected even in a metallic state. Our observations can be described as a pressure-driven Mott-Hubbard transition.
Keywords: vanadium dioxide, high pressure, pump-probe spectroscopy
  • Lecture (Conference)
    XXI. International Conference on Ultrafast Phenomena, 15.-20.07.2018, Hamburg, Deutschland

Publ.-Id: 28299 - Permalink


Freie Software in der Wissenschaft: Prototypen, Reproduzierbarkeit, Infrastruktur
Huebl, A.ORC
Beitrag zur Ringvorlesung der FSFW im Wintersemester 2018 an der HTW, TU Dresden und Bürgeruniversität.
Keywords: open science, open source, open infrastructure, open data
  • Lecture (others)
    Ringvorlesung WS2018: Freie Software und Freies Wissen als Beruf, 27.11.2018, Dresden, Germany
    DOI: 10.5281/zenodo.1884442

Publ.-Id: 28298 - Permalink


Measurement of torsional and sloshing modes in Rayleigh-Bénard convection using contactless inductive flow tomography
Wondrak, T.; Stefani, F.; Galindo, V.; Eckert, S.;
Flows driven by temperature differences play an important role in geo- and astrophysics as well as in many metallurgical applications. The dynamics of the large scale circulation (LSC) of Rayleigh-Bénard (RB) convection include azimuthal reorientations, cessations, torsional and sloshing modes. In this presentation we will show that the contactless inductive flow tomography (CIFT) is able to visualise these features. This will be shown using numerical simulations as well as measurements at a small model filled with GaInSn.
Keywords: contactless inductive flow tomography, liquid metal, flow measurement, Rayleigh-Bénard convection
  • Lecture (Conference)
    MHD Days and GDRI Dynamo Meeting, 26.-28.11.2018, Dresden, Deutschland

Publ.-Id: 28297 - Permalink


AER Working Group Meeting on VVER safety analysis - report of the 2018 meeting
Kliem, S.ORC
The AER Working Group D on VVER reactor safety analysis held its 27th meeting in Rossendorf, Germany, during the period 12-13 June, 2018. The meeting was hosted by Helmholtz-Zentrum Dresden-Rossendorf. Altogether 19 participants from nine AER member organizations 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 13 presentations and the discussions can be attributed to the following topics:
• Safety analyses methods and results
• Code development and benchmarking
• Severe accident analyses
• Future activities
The Working Group decided to include also in future the severe accident analyses into the scope of the 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
    28. Symposium of AER, 08.-12.10.2018, Olomouc, Czech Republic
    Proceedings of the 28. Symposium of AER, Budapest: MTA EK Budapest, 9789637351303, 665-671
  • Lecture (Conference)
    28. Symposium of AER, 08.-12.10.2018, Olomouc, Czech Republic

Publ.-Id: 28295 - Permalink


Aerosol particle deposition and resuspension in turbulent air channel flows
Lecrivain, G.; Hampel, U.;
The deposition of aerosol graphite particles in a turbulent channel flow obstructed with periodic steps is here investigated et experimentally at Reynolds number Re = 8,000. Particles in the size range d = 1...100µm deposit non-uniformly on the various wall surfaces and eventually form a fairly thick layer of dust. The build-up of the dust layer affects the air flow which in turn affects the deposition rate of the conveyed particles. To numerically reproduce the growth of the dust layer an interdisciplinary study involving the dynamic coupling of fluid simulation, Lagrangian particles, mesh deformation and granular bed is carried out. The numerical results compare well with the experimental data.
  • Invited lecture (Conferences)
    Workshop on particle resuspension, 04.09.2018, Nice, France

Publ.-Id: 28294 - Permalink


Numerical Models for the DRESDYN Precession Dynamo Experiment
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.;
More than 100 years ago, Henri Poincare in his pioneering study showed that the inviscid base flow in a precessing spheroid is described by a constant vorticity solution, the spin-over mode. Since then there have been repeated discussions whether the geodynamo is driven (or at least influenced) by precession. More recently, precession has also been considered as an important mechanism for the explanation of the ancient lunar dynamo.

Experiments with precessing fluids in cylindrical and in spherical geometry showed that precession indeed is an efficient mechanism to drive substantial flows even on the laboratory scale without making use of propellers or pumps. A precession dynamo experiment is currently under construction within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which a precession driven flow of liquid sodium will be used to drive dynamo action.

In the present study we address related numerical and experimental examinations in order to identify parameter regions where the onset of magnetic field excitation will be possible. Preliminary kinematic dynamo models using a prescribed flow field from hydrodynamic simulations, exhibit magnetic field excitation at critical magnetic Reynolds numbers around Rm_c ≈ 430, which is well within the range of the planned liquid sodium experiment. Our results show that large scale inertial modes excited by precission are able to excite dynamo action when their structure is sufficient complex, i.e. the forcing is sufficient strong.

More advanced models that take into account the container's finite conductivity show that boundary conditions may play an important role, but the critical magnetic Reynolds number will still be achievable in the planned experiment. Finally, we discuss the role of turbulent flow fluctuations for the occurrence of dynamo action.
Keywords: Dynamo, DRESDYN
  • Poster
    AGU Fall Meeting 2018, 09.-14.12.2018, Washington DC, USA
  • Open Access LogoContribution to proceedings
    AGU Fall Meeting 2018, 09.-14.12.2018, Washington DC, USA

Publ.-Id: 28293 - Permalink


Numerical simulations for the DRESDYN precession dynamo
Giesecke, A.; Vogt, T.; Gundrum, T.; Stefani, F.;
More than 100 years ago, Henri Poincar{\'e} in his pioneering study showed that the inviscid base flow in a precessing spheroid is described by a constant vorticity solution, the spin-over mode. Since then there have been repeated discussions whether the geodynamo is driven (or at least influenced) by precession. More recently, precession has also been considered as an important mechanism for the explanation of the ancient lunar dynamo.

Experiments with precessing fluids in cylindrical and in spherical geometry showed that precession indeed is an efficient mechanism to drive substantial flows even on the laboratory scale without making use of propellers or pumps. A precession dynamo experiment is currently under construction within the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in which a precession driven flow of liquid sodium will be used to drive dynamo action.

Here we address related numerical and experimental examinations in order to identify parameter regions where the onset of magnetic field excitation will be possible. Preliminary kinematic dynamo models using a prescribed flow field from hydrodynamic simulations, exhibit magnetic field excitation at critical magnetic Reynolds numbers around ${\rm{Rm}}_{\rm{c}} \approx 430$, which is well within the range of the planned liquid sodium experiment. Our results show that large scale inertial modes excited by precession are able to excite dynamo action when their structure is sufficiently complex, i.e. the forcing is sufficiently strong.
More advanced models that take into account the container's finite conductivity show that boundary conditions may play an important role, but the critical magnetic Reynolds number will still be achievable in the planned experiment.
Keywords: Dynamo, DRESDYN
  • Lecture (Conference)
    MHD Days 2018, 26.-29.11.2018, Dresden, Germany

Publ.-Id: 28292 - Permalink


Kopplung von CFD, Elektrochemie und Elektrodynamik am Beispiel Flüssigmetallbatterie
Weber, N.; Personnettaz, P.; Weier, T.;
Flüssigmetallbatterien (FMB) werden seit etwa 10 Jahren als preisgünstige stationäre Speicher für die Energiewende diskutiert. Der Aufbau aus zwei flüssigen Metallen, welche nur durch eine dünne Salzschmelze getrennt sind, erlaubt extreme Stromdichten und eine potentiell sehr hohe Lebensdauer. Für einen optimalen Wirkungsgrad muss die Salzschicht möglichst dünn sein – ohne jedoch einen Kurzschluss zuzulassen. Weiterhin ist effektiver Massetransport durch Konvektion von zentraler Bedeutung.

Im ersten Teil des Vortrags soll Aufbau und Funktionsweise einer FMB kurz erklärt werden. Anschließend werden verschiedene physikalische Phänomene an Hand von OpenFOAM-Simulationen diskutiert (thermische und solutale Konvektion, magnetohydrodynamische Instabilitäten, Elektrochemie, Stromverteilung in der Zelle). Im letzten Teil des Vortrags wird auf die Kopplung von CFD mit Elektrodynamik sowie von Massetransport mit der Potential- und Stromverteilung detailiert eingegangen.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppe Computational Fluid Dynamics mit OpenFOAM Workshop, 19.03.2019, Frankfurt, Deutschland

Publ.-Id: 28291 - Permalink


Antihypertensive drug classes, not blood pressure, are associated with cerebral perfusion. Results from the PREvention of Dementia by Intensive VAscular care (PREDIVA) study
van Dalen, J.; Mutsaerts, H.; Petr, J.; van Charante, M. E.; van Gool, W.; Nederveen, A.; Richard, E.;
Background: Constant cerebral blood flow (CBF) is fundamental to cerebral function. With aging and chronic hypertension, arteriolar damage may disrupt the CBF autoregulatory capacity. This might cause CBF to fluctuate with blood pressure (BP) levels, low BP and antihypertensive medication (AHM), potentially evoking hypoperfusion. We investigated the cross-sectional and longitudinal relations of BP and AHM with cerebral perfusion using arterial spin labeling (ASL).
Methods: In 186 community-dwelling individuals with hypertension (77±3 years, 53% female), 125 (67%) with 3-year follow-up (Figure 1), we assessed grey matter (GM) and white matter (WM) CBF (ml/100g/min) and the spatial coefficient of variation (CoV; SD CBF/mean CBF). Cross-sectional associations were assessed combining baseline and follow-up data using mixed models, longitudinal associations using linear regression assessing change, adjusted for baseline. We additionally adjusted for age, sex, AHM, stroke and parenchymal fraction.
Results: Cross-sectionally, higher diastolic BP was associated with lower GM and WM CBF (Table 1). AHM were associated with lower GM CBF and higher spatial CoV. Since calcium channel blockers (CCB) and angiotensin receptor blockers (ARB) in our main study were specifically associated with lower dementia risk compared to other AHM, we assessed these separately. Other AHM were associated with lower GM and WM CBF, while CCBs and ARBs were not. There were no correlations between BP change and perfusion changes (Table 2). We observed no J-shaped relationships.
Discussion: We found no evidence for any direct relation between BP and cerebral perfusion. Possibly, higher diastolic BP was associated with lower CBF by being a marker of more severe long-standing hypertension evoking vascular damage. Our finding that ARBs and CCBs are relatively protective of CBF compared to other AHM is consistent with findings of a protective effect of these AHM classes on dementia incidence, and could influence future treatment.
  • Contribution to proceedings
    VasCog 2018 - The 9th International Conference of The International Society of Vascular Behavioural and Congnitive Disorders, 14.11.2018, Hong-Kong, China
  • Poster
    VasCog 2018 - The 9th International Conference of The International Society of Vascular Behavioural and Congnitive Disorders, 14.11.2018, Hong-Kong, China

Publ.-Id: 28289 - Permalink


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262]