Publication database - Helmholtz-Zentrum Dresden-Rossendorf

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26100 Publications
Covellite CuS as a matrix for “invisible” gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals
Tagirov, B. R.; Trigub, A. L.; Kvashnina, K. O.; Shiryaev, A. A.; Chareev, D. A.; Nickolsky, M. S.; Abramova, V. D.; Kovalchuk, E. V.
Abstract: Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in “invisible” (or ”refractory”) state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu-Fe-S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the “invisible” Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3 wt.% of Au in the “invisible” state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2)) ∼ 0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450 °C, whereas further temperature increase to 500 °C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼ 0.3 for both positions of Cu. This result is confirmed by theoretical analysis of electron density performed using quantum theory of atoms in molecules (QTAIM). Modeling of the Au L3 edge EXAFS/XANES spectra showed that Au in covellite exists in the form of the isomorphous solid solution formed by substitution for Cu atoms in triangular coordination with the Me-S distance in the first coordination shell increased by 0.18 Å relative to the pure CuS structure. The “formal” oxidation state of Au in covellite is +1. The Bader partial atomic charge for Au in covellite is lower than the charge of Cu (+0.2 e vs. +0.5 e) indicating that the degree of covalency for the Au-bearing covellite is higher than that of pure CuS. The analysis of electronic density of states shows that this structural position of Au results in strong interactions between hybridized Au s,p,d, S p, and Cu p,d orbitals. Such chemical bonding of Au to S and Cu can result in the formation of Au-bearing solid solution with other minerals in the Cu-Fe-S system. Registration No. 23953 - Permalink

Curvilinear magnetism
Makarov, D.
Abstract: Extending planar two-dimensional structures into the three-dimensional space has become a general trend in electronics, photonics, plasmonics and magnetics. In magnetism, a consequence of the curvilinear geometry is the appearance of novel curvature-driven effects including magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. These theoretical predictions and the application potential of 3D-shaped magnetic objects will be presented in this talk.
Keywords: curved magnetic thin films, magnetic caps
  • Invited lecture (Conferences)
    META2016: The 7th International Conference on Metamaterials, Photonic Crystals and Plasmonics, 25.-28.07.2016, Malaga, Spain
Registration No. 23952 - Permalink

Introducing a novel method for fast and accurate estimation and compensation of beam deflection in MR-integrated proton therapy
Schellhammer, S. M.; Hoffmann, A. L.
Abstract: Proton therapy is highly sensitive to anatomical variations due to steep dose gradients in proximity of the Bragg peak (BP). Magnetic resonance imaging (MRI) is a promising candidate to enable real-time tracking of such variations during treatment delivery with high spatial, temporal and contrast resolution and without ionizing radiation exposure. However, an MRI magnetic field applied during irradiation deflects the proton beam from its intended trajectory.
We present a numerical method for fast and accurate quantification and compensation of this effect. As compared to existing approaches, it features fewer approximations than analytical models and a strongly reduced computation time compared to Monte Carlo simulations. We use it to reconstruct the trajectory of a monoenergetic proton beam of energy E0 traversing a water phantom behind a 25 cm air gap inside a virtual MRI bore with a uniform transverse magnetic flux density B. We study the dislocation of the BP as function of E0 and B and introduce an optimization method to compensate for it.
The magnitude of BP dislocation ranges from 2 cm for E0=60 MeV and B=0.5 T up to 26 cm for E0=250 MeV and B=3.0 T. A unique solution exists for repositioning the BP by beam incidence angle and energy adjustment.
The predicted magnetic-field induced BP dislocation complies with results obtained by Monte Carlo methods and the model is more versatile than analytical methods. The proposed optimization of beam incidence angle and energy effectively repositions the BP to its intended location.

Keywords: proton therapy, image-guided radiotherapy, IGPT, magnetic resonance imaging, MR guidance, beam trajectory prediction
  • Poster
    55th Annual Conference of the Particle Therapy Co-operative Group (PTCOG 55), 22.-28.05.2016, Praha, Ceska republika
  • Poster
    10th HZDR PhD seminar, 02.-04.11.2015, Altenberg, Deutschland
  • Poster
    National Center for Radiation Oncology, 2nd Scientific Retreat, 14.-16.04.2016, Dresden, Deutschland
Registration No. 23950 - Permalink

Characterisation of nano-particulate powder pellets
Garbe-Schönberg, D.; Renno, A. D.; Leißner, T.; Müller, S.; Nordstad, S.
Abstract: Matrix-matched reference materials are urgently needed for calibration and validation of (micro-)analytical data. It is desirable that these materials can be analyzed by different analytical techniques like LA-ICP-MS, LIBS, μ-XRF, EPMA, PIXE, SIMS etc. accomplishing a better definition of elemental and isotopic composition of materials and also allowing for systematic studies on elemental fractionation. Nano-particulate powder pellets have now been produced from a large variety of materials and shown to be of excellent homogeneity and cohesiveness enabling accurate and high precision determination of elemental composition by LA-ICP-MS with RSD <1-5% even at high spatial resolution with <32μm spot size (Garbe-Schönberg and Müller 2014). Here we present new data on particle size and surface roughness being quality criteria for micro-analytical techniques using electron (EPMA) or ion beams (PIXE, SIMS). We demonstrate homogeneity within and between pellets, and significantly improved accuracy after matrix-matched calibration with nano-pellets is shown for granite AC-E as an example. Meanwhile, nano-pellets are succesfully used also for LA-based Rb-Sr age determination (Karlsson et al., EWLA 2016) and Li-B isotopic studies (LeRoex et al., 2015) and were analysed by EPMA and LIBS.
Keywords: Reference Material, Nano-particulate powder pellets, homogeneity
  • Poster
    European Workshop on Laser Ablation, 12.-15.07.2016, Ljubljana, Slovenien
Registration No. 23949 - Permalink

Experimental x-ray ghost imaging
Pelliccia, D.; Rack, A.; Scheel, M.; Cantelli, V.; Paganin, D. M.
Abstract: We report an experimental proof of principle for ghost imaging in the hard x-ray energy range. We used a synchrotron x-ray beam that was split using a thin crystal in Laue diffraction geometry. With an ultra-fast imaging camera, we were able to image x-rays generated by isolated electron bunches. At this time scale, the shot noise of the synchrotron emission process is measurable as speckles, leading to speckle correlation between the two beams. The integrated transmitted intensity from a sample located in the first beam was correlated with the spatially resolved intensity measured on the second, empty, beam to retrieve the shadow of the sample. The demonstration of ghost imaging with hard x-rays may open the way to protocols to reduce radiation damage in medical imaging and in non-destructive structural characterization using Free Electron Lasers.
Keywords: Ghost imaging, optics, X-ray

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Registration No. 23939 - Permalink

Euler-Euler Simulation und Modellvalidierung einer Blasensäule
Krauß, M.
Abstract: Die Anwendung von Methoden der CFD („Computational fluid dynamics“) für Scale-up und Intensivierung verfahrenstechnischer Prozesse bietet die Möglichkeit, energie- und ressourceneffiziente Lösungen zu identifizieren, deren Untersuchung mit konventionellen halb-empirischen Methoden kostspielig und langwierig wäre.
Eine solche Simulation im großtechnischen Maßstab ist im Rahmen der Euler-Euler Beschreibung möglich, in der Prozesse auf der Skala einzelner Blasen modelliert werden.
Ein solches Schließungsmodell für Hydrodynamik und Stofftransport in Blasenströmungen wird am HZDR entwickelt. Ziel dieser Entwicklung ist, ein vorhersagetaugliches Modell zu etablieren, das für einen breiten Bereich von Anwendungsbedingungen validiert ist.
Zu diesem Zweck werden Simulationsrechnungen mit experimentellen Daten verglichen, die zunehmend komplexere Geometrien und Effekte einbeziehen. Auf Basis der jeweils erzielten Übereinstimmung werden Modellerweiterungen und -verbesserungen vorgenommen. Im Rahmen der Belegarbeit soll eine mit Wasser befüllte, von Luft bzw. Kohlenstoffdioxid durchströmte, zylinderförmige Blasensäule mit einem Innendurchmesser von 142 mm untersucht werden.

Keywords: Blasensäule, Euler-Euler Modell, CFD-Simulation, Modellvalidierung
  • Study thesis
    TU Dresden, 2016
    Mentor: Dr. Roland Rzehak (HZDR), Prof. Rüdiger Lange (TU-Dresden)
    94 Seiten
Registration No. 23935 - Permalink

Effect of compression on the electronic, optical and transport properties of MoS2/graphene-based junctions
Ghorbani-Asl, M.; Bristowe, P. D.; Koziol, K.; Heine, T.; Kuc, A.
Abstract: Electronic, optical and transport properties of the MoS2/graphene heterostructure have been investigated as function of applied uniaxial compression normal to the interface plane using first principles calculations and a non-equilibrium Green’s function approach. The results show that a small compressive load (∼1 GPa) can open up the band gap (∼12 meV), reduce the optical absorption coefficient (∼7%), redshift the absorption spectrum, and create non-Ohmic I–V characteristics that depend on the magnitude of applied bias. This suggests that graphene/MoS2 heterostructure can be suitable for electromechanical and photomechanical devices where the electronic, optical and transport properties can be tuned by an appropriate application of bias and mechanical deformations.
Keywords: MoS2/graphene heterojunction, interlayer compression, transport properties, NEGF, DFT

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Registration No. 23934 - Permalink

Electron-beam induced transformations of layered tin dichalcogenides
Sutter, E.; Huang, Y.; Komsa, H.-P.; Ghorbani-Asl, M.; Krasheninnikov, A. V.; Sutter, P.
Abstract: By combining high-resolution transmission electron microscopy and associated analytical methods with first-principles calculations, we study the behavior of layered tin dichalcogenides under electron beam irradiation. We demonstrate that the controllable removal of chalcogen atoms due to electron irradiation, at both room and elevated temperatures, gives rise to transformations in the atomic structure of Sn−S and Sn−Se systems so that new phases with different properties can be induced. In particular, rhombohedral layered SnS2 and SnSe2 can be transformed via electron beam induced loss of chalcogen atoms into highly anisotropic orthorhombic layered SnS and SnSe. A striking dependence of the layer orientation of the resulting SnS parallel to the layers of ultrathin SnS2 starting material, but slanted for transformations of thicker few-layer SnS2is rationalized by a transformation pathway in which vacancies group into ordered S-vacancy lines, which convert via a Sn2S3 intermediate to SnS. Absence of a stable Sn2Se3 intermediate precludes this pathway for the selenides, hence SnSe2 always transforms into basal plane oriented SnSe. Our results provide microscopic insights into the transformation mechanism and show how irradiation can be used to tune the properties of layered tin chalcogenides for applications in electronics, catalysis, or energy storage.
Keywords: two-dimensional materials, defects, electron irradiation, structural transformation, sulfide, selenide

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Registration No. 23932 - Permalink

Surprising effects of electron-electron scattering in graphene revealed by THz pump-probe spectroscopy
Helm, M.; König-Otto, J. C.; Mittendorff, M.; Pashkin, A.; Schneider, H.; Winnerl, S.; Wendler, F.; Winzer, T.; Malic, E.; Knorr, A.
Abstract: Electron-electron scattering in graphene gives rise to some unexpected behavior in the electron dynamics, as observed by THz pump-probe measurements.
When excited with a near-infrared femtosecond laser pulse, the pump-probe signal depends on the angle between the linear polarization of the pump and the probe pulse, which is due to preferential excitation of electrons perpendicular to the laser electric field. This indicates an anisotropic distribution function in momentum space that is preserved by electron-electron scattering, since it mainly occurs collinearly along the Dirac cone. Only after 150 fs the distribution function is rendered isotropic through optical-phonon scattering. The effect is even more pronounced when exciting at small photon energies (88 meV), below the optical-phonon energy: In this case the anisotropic distribution function survives for as long as 5 ps, when it is finally thermalized by non-collinear Coulomb scattering. These results challenge the common view of ultrafast thermalization by electron-electron scattering.
When a magnetic field is applied to graphene, Landau levels are formed that can be selectively excited by circular-polarized radiation. In a pump-probe experiment, exciting and probing all possible transitions between the n=-1, n=0 and n=+1 Landau levels in slightly n-type graphene, we observe an unexpected sign reversal of the n=0 →1 probe signal when pumping the -1→0 transition. This directly reflects the fact that the n=0 Landau level is depleted by electron-electron Auger-type scattering, even though it is optically pumped at the same time.
Both effects can be quantitatively reproduced by a microscopic calculation based on the graphene Bloch equations, and shed new light on the possibility of infrared and THz devices based on hot carriers in graphene.

Keywords: THz, graphene, free electron laser, pump-probe spectroscopy
  • Invited lecture (Conferences)
    International Workshop on Terahertz Science, Nanotechnologies and Applications, 16.-22.07.2016, Erice, Italy
Registration No. 23927 - Permalink

Synthesis and evaluation of a 18F-labeled 4-phenylpiperidine-4-carbonitrile radioligand for σ1 receptor imaging
Ye, J.; Wang, X.; Deuther-Conrad, W.; Zhang, J.; Li, J.; Zhang, X.; Wang, L.; Steinbach, J.; Brust, P.; Jia, H.
Abstract: We report the design and synthesis of several 4-phenylpiperidine-4-carbonitrile derivatives as σ1 receptor ligands. In vitro radioligand competition binding assays showed that all the ligands exhibited low nanomolar affinity for σ1 receptors (Ki(σ1) = 1.22–2.14 nM) and extremely high subtype selectivity (Ki(σ2) = 830–1710 nM; Ki(σ2)/Ki(σ1) = 680–887). [18F]9 was prepared in 42–46% isolated radiochemical yield, with a radiochemical purity of >99% by HPLC analysis after purification, via nucleophilic 18F- substitution of the corresponding tosylate precursor. Biodistribution studies in mice demonstrated high initial brain uptakes and high brain-to-blood ratios. Administration of SA4503 or haloperidol 5 min prior to injection of [18F]9 significantly reduced the accumulation of radiotracers in organs known to contain σ1 receptors. Two radioactive metabolites were observed in the brain at 30 min after radiotracer injection. [18F]9 may serve as a lead compound to develop suitable radiotracers for σ1 receptor imaging with positron emission tomography.
Keywords: fluorine-18; σ1 receptor; positron emission tomography; 4-phenylpiperidine-4-carbonitrile derivatives; molecular probe Registration No. 23925 - Permalink

Corrosion of hot-dip galvanized containment installations – A potential cause for thermal-hydraulic effects after LOCA in PWR?
Kryk, H.; Harm, U.; Hampel, U.
Abstract: During the sump recirculation phase after loss-of-coolant accidents (LOCA) in pressurized water reactors (PWR), coolant spilling out of the leak in the primary cooling circuit is collected in the reactor sump and recirculated to the reactor core by residual-heat removal pumps as part of the emergency core cooling system (ECCS). The contact of the coolant with several forms of debris may influence the sump strainer clogging behavior as well as the cooling water chemistry. Damage to fibrous insulation materials located near to the leak may compromise the operation of the ECCS, if insulation fibers are transported to the strainers. Furthermore, the long-term contact of the boric acid containing coolant with hot-dip galvanized containment internals (e.g. grating treads, supporting grids of sump strainers) may cause corrosion of the corresponding materials.
Generic investigations regarding the influence of such corrosion processes on strainer clogging as well as on the coolant chemistry and possible resulting in-core effects are subject of joint research projects of the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), TU Dresden (TUD) and Zittau-Görlitz University of Applied Sciences (HSZG). Lab-scale experiments at HZDR and TUD are focused on elucidation of physico-chemical corrosion and precipitation processes as well as resulting clogging effects.
Results of generic experiments in a lab-scale corrosion test facility, representing the ECCS operation in a simplified manner, suggest that there is a multi-stage corrosion process. The first stage comprises dissolution of the zinc layer in the coolant forming zinc ions and in turn affecting the coolant chemistry. During the second stage, the base material (steel) corrodes forming insoluble corrosion particles, which can subsequently lead to accelerated clogging of fiber-laden strainers within a few hours. The main influences on corrosion were identified as impact of the coolant jet onto the corroding surface, water chemistry and zinc surface / coolant volume ratio.
Furthermore, retrograde solubility of zinc corrosion products in boric acid containing coolants with increasing temperature was observed. Thus, formation and deposition of solid corrosion products cannot be ruled out if zinc containing coolant is heated up during its recirculation into hot downstream components (e.g. hot-spots in core). Corrosion experiments, which included formation of corrosion products at a heated cladding tube, proved that zinc, dissolved in the coolant at low sump temperatures, turns into solid deposits of zinc borates when contacting heated zircaloy surfaces. Due to alternating heating and cooling of the coolant during sump recirculation operation, a cycle of zinc corrosion and zinc borate precipitation may be initiated, which may eventually influence the thermal hydraulics in downstream components during the post-LOCA stage. The results obtained at lab-scale were confirmed by corresponding experiments in semi-technical test facilities of the project partner HSZG.
Based on the experimental results, water chemical measures were tested to reduce corrosion and/or zinc borate precipitation effects. Additionally, joint research projects have been established by the TUD and the HSZG dealing with local effects of corrosion, corrosion product precipitation and the interplay thereof at LOCA-specific conditions.
The investigations have been supported by the German Federal Ministry for Economic Affairs and Energy under contract nos. 1501363, 1501430, 1501467 and 1501496.

Keywords: loss-of-coolant accident, LOCA, pressurized water reactor, PWR, sump strainer clogging, chemical effects, corrosion, zinc borate
  • Lecture (Conference)
    ICONE 24 – International Conference on Nuclear Engineering, 26.-30.06.2016, Charlotte, USA
Registration No. 23918 - Permalink

Optimisation of the bioleaching of REE from FP with chemoorgano-heterotrophic microorganisms.
Hopfe, S.; Kutschke, S.; Pollmann, K.
Abstract: Rare earth elements (REE) are used in mostly all new technologies and until now, there is nearly no recycling of REE containing end-of-life products [1]. Furthermore, only poor information is available regarding interactions of microorganisms with REE and there are almost no studies describing the bioleaching of REE. However, it can be assumed that microorganisms play an important role in the biogeochemistry of REE. This study investigates the potential of organic acid and metal binding molecules producing microbes to extract REE from technical waste.
During recycling of energy-saving bulbs fluorescent phosphor (FP) is collected as a distinct fraction. It contains about 10% REE-oxides bound in the hardly water-soluble triband dyes as oxides, phosphates, aluminates and silicates [2]. Previous experiments showed, that the chemoorgano-heterotrophic, organic acid producing micrrooganisms Yarrowia lipolytica, Komatogateiibacter xylinus and Lactobacillus casei as well as the mixed culture Kombucha are in principle suitable for the bioleaching of REE from FP. In this presentation the solubilisation process is investigated regarding the leaching metabolites and optimised with respect to maximal REE release. Thereto, the results are transferred from shake flasks to bioreactor and the media were adjusted. Furthermore, the influence of metal binding molecules like siderophores was tested.
It could be shown, that bioleaching is a potential alternative to technical leaching approaches, even though, the leaching efficiency is still low. This provides the basis for the development of an eco-friendly alternative to the currently applied methods.

[1] European Commission (2014) On the review of the list of critical raw materials for the EU and the implementation of the Raw Materials Initiative, Brüssel. [2] Haucke et al. (2011) Verfahren zur Rückgewinnung seltener Erden aus Leuchtstofflampen, Osram AG.
  • Poster
    Annual Conference 2016 of the Association for General and Applied Microbiology (VAAM), 13.-16.03.2016, Jena, Deutschland
Registration No. 23916 - Permalink

Magnetic Excitations in Spin-1/2 Triangular-lattice Antiferromagnets: High-field ESR studies
Zvyagin, S.
Abstract: es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    Lehrstuhl-Seminar (Seminar zur Statistischen Physik) an der Bergischen Universität Wuppertal, 23.06.2016, Wuppertal, Deutschland
Registration No. 23915 - Permalink

Operational Experience of SRF Gun II
Arnold, A.; Teichert, J.; Xiang, R.
Abstract: In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and a new cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time. With the improved parameters first user experiments of the superconducting CW accelerator ELBE are to be served, that benefit from an increased average beam current at a given repetition rate of some hundred kHz. Although the cavity performance stays behind its specifications (Ecath~12 MV/m), beam commissioning is underway. In this contribution we will report on our operational experiences of the first two years of SRF gun II.
Keywords: SRF gun, photo electron source, injector, ELBE, superconducting RF
  • Lecture (others)
    HOPE / SINEMP Projekttreffen im Rahmen BMBF Verbundforschungsinitiative, 21.-22.06.2016, Darmstadt, Deutschland
Registration No. 23914 - Permalink

Probing Ionization and Buried Layer Plasma Physics Driven by Optical High Power Lasers using XFELs
Huang, L. G.; Prencipe, I.; Kluge, T.; Cowan, T.
Abstract: In the presentation, the fundamental plasma physics driven by high power lasers on bulk electron heating,solid target and ion heating is discussed. Probing the relative dynamics using XFELs is also presented.
Keywords: Heating,Ionization,XFEL,high power lasers
  • Lecture (Conference)
    The 1st Asia-Pacific User Meeting for HIBEF at European XFEL, 23.-24.06.2016, Shanghai, China
Registration No. 23913 - Permalink

Numerical adiabatic potentials of orthorhombic Jahn-Teller effects retrieved from ultrasound attenuation experiments. Application to the SrF2:Cr crystal
Zhevstovskikh, I. V.; Bersuker, I. B.; Gudkov, V. V.; Averkiev, N. S.; Sarychev, M. N.; Zherlitsyn, S.; Yasin, S.; Shakurov, G. S.; Ulanov, V. A.; Surikov, V. T.
Abstract: A methodology is worked out to retrieve the numerical values of all the main parameters of the sixdimensional adiabatic potential energy surface (APES) of a polyatomic system with a quadratic T-term Jahn-Teller effect (JTE) from the ultrasound experiments. The method is based on a verified assumption that ultrasound attenuation and speed encounter anomalies when the direction of propagation and polarization of its wave of strain coincides with the characteristic directions of symmetry breaking in the JTE. For the SrF2:Cr crystal, employed as a basic example, we observed anomaly peaks in the temperature dependence of attenuation of ultrasound at frequencies of 50-160 MHz in the temperature interval of 40-60 K for the wave propagating along the [110] direction, for both the longitudinal and the shear modes, the latter with two polarizations along the [001] and [11-0] axes, respectively. We show that these anomalies are due to the ultrasound Relaxation by the system of non-interacting Cr2+ JT centers with orthorhombic local distortions. The interpretation of the experimental findings is based on the T2g - (eg+t2g) JTE problem including the linear and the quadratic terms of vibronic interactions in the Hamiltonian and the same-symmetry modes reduced to one interaction mode. Combining the experimental results with a theoretical analysis, we show that on the complicated six-dimensional APES of this system with three tetragonal, four trigonal, and six orthorhombic extrema points, the latter are global minima, while the former are saddle points, and we estimate numerically all the main parameters of this surface, including the linear and quadratic vibronic coupling constants, the primary force constants, the coordinates of all the extrema points and their energies, the energy barrier between the orthorhombic minima, and the tunneling splitting of the ground vibrational states. To our knowledge, such a based-on-experimental-data numerical reconstruction of the APES of a JTE problem in the five-dimensional space of all active tetragonal and trigonal displacements has not been reported before. Registration No. 23911 - Permalink

Robust range prediction for arbitrary tissue mixtures based on dual-energy CT
Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.
Abstract: The treatment planning of proton or ion radiation therapy is affected by uncertainties arising from the heuristic conversion of computed tomography (CT) images to stopping-power ratio (SPR) maps. In this work, we present how these uncertainties can potentially be reduced by the use of dual-energy CT (DECT), via a physics-based SPR prediction. According to the Bethe formula, the SPR is the product of the electron density and the stopping number relative to water. The latter ranges between 0.96 and 1.02 for human tissue at a therapeutic beam energy of 200 MeV/u and depends on the mean excitation energy (I-value).
As a first step, the relative electron density can be directly determined from DECT images in a universal and robust procedure, based on a simple assumption for the cross section parameterization. Secondly, we propose to infer the relative stopping number from the relative photon absorption cross section obtained from DECT scans - instead of using an effective atomic number as a proxy for the I-value, which has previously been suggested in literature. Our choice of variables makes a proper treatment of tissue mixtures possible, which inevitably occur in patient CT images, and allows for a convenient definition of the uncertainties.
A calculation-based analysis of tabulated body tissues and tissue base components - such as water, lipid, carbohydrates and protein - suggests a maximum uncertainty below one percent for arbitrary mixtures of human tissue. We performed first experiments, combining particle range measurements with DECT scans, to validate our method of stopping-number prediction.

Keywords: dual-energy CT, proton therapy, ion-beam therapy
  • Poster
    55th Annual Conference of the Particle Therapy Co-operative Group (PTCOG), 22.-28.05.2016, Prag, Czech Republic
Registration No. 23909 - Permalink

Numerical simulations for the precession dynamo experiment in the framework of the DRESDYN project
Giesecke, A.; Stefani, F.
Abstract: In a next generation dynamo experiment currently under development at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) a fluid flow of liquid sodium, solely driven by precession, will be considered as a possible source for magnetic field generation.

I will present results from hydrodynamic simulations of a precession driven flow in cylindrical geometry. In a second step, the velocity fields obtained from the hydrodynamic simulations have been applied to a kinematic solver for the magnetic induction equation in order to determine whether a precession driven flow will be capable to drive a dynamo at experimental conditions.

It turns out that excitation of dynamo action in a precessing cylinder at moderate precession rates is difficult, and future dynamo simulations are required in more extreme parameter regimes where a more complex fluid flow is observed in water experiments which is supposed to be beneficial for dynamo action.

Keywords: Dynamo Precession Magnetohydrodynamics Geodynamo DRESDYN
  • Lecture (Conference)
    European GDR Meeting 20016, 27.06.-01.07.2016, Barcelona, Spain
Registration No. 23908 - Permalink

Frustrated magnets in high magnetic fields—selected examples
Wosnitza, J.; Zvyagin, S. A.; Zherlitsyn, S.
Abstract: An indispensable parameter to study strongly correlated electron systems is the magnetic field. Application of high magnetic fields allows the investigation, modification and control of different states of matter. Specifically for magnetic materials experimental tools applied in such fields are essential for understanding their fundamental properties. Here, we focus on selected high-field studies of frustrated magnetic materials that have been shown to host a broad range of fascinating new and exotic phases. We will give brief insights into the influence of geometrical frustration on the critical behavior of triangular-lattice antiferromagnets, the accurate determination of exchange constants in the high-field saturated state by use of electron spin resonance measurements, and the coupling of magnetic degrees of freedom to the lattice evidenced by ultrasound experiments. The latter technique as well allowed new, partially metastable phases in strong magnetic fields to be revealed. Registration No. 23905 - Permalink

Magnetic properties of HoFe6Al6H hydride: A single-crystal study
Andreev, A. V.; Pelevin, I. A.; Sebek, J.; Tereshina, E. A.; Gorbunov, D. I.; Drulis, H.; Tereshina, I. S.
Abstract: Crystal structure and magnetic properties were studied on a single crystal of HoFe6Al6H and compared with those of the parent HoFe6Al compound with a tetragonal crystal structure of the ThMn126Al6 is a ferrimagnet with exact compensation of the Ho and Fe sublattices magnetizations at low temperatures. Both the hydride and the parent compound display a high magnetic anisotropy of the easy-plane type, a noticeable anisotropy exists also within the easy plane with the [110] axis as the easy magnetization direction. The hydrogenation increases slightly (from 10 to 10.45 µB) the magnetic moment of the Fe sublattice as a result of volume expansion. It leads to a decompensation of the Fe and Ho sublattices and HoFe6Al6H has a spontaneous moment 0.45 µB/f.u. The enhancement of the Fe-Fe intra-sublattice exchange interaction results in a higher Curie temperature (TC) value, 350 K in the hydride as compared to 315 K of HoFe6Al6. The Ho-Fe inter-sublattice interaction is also enhanced in the hydride. The molecular field Hmol created on Ho Ions by Fe sublattice is 38 T in HoFe6Al6 and 48 T in HoFe6Al6H. The inter-sublattice exchange constant nHoFe is 3.8 T/µB and 4.6 T/µB, respectively. High-field measurements confirm the enhancement of the Ho-Fe exchange interaction in the hydride found from the temperature dependence of magnetization.

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Registration No. 23904 - Permalink

A study of the reprocessing of fine and ultrafine cassiterite from gravity tailing residues by using various flotation techniques
Leistner, T.; Embrechts, M.; Leissner, T.; Chehreh Chelgani, S.; Osbahr, I.; Möckel, R.; Peuker, U. A.; Rudolph, M.
Abstract: This study investigates the reprocessing of once disposed tin tailings from a historic German tin operation through different surface properties based processing techniques. Froth flotation and agglomeration flotation, by using commercially available cassiterite collectors from Clariant, were chosen as processing techniques. Isooctane as a nonpolar oil was used to promote the collection of ultrafine (-10 µm) cassiterite by selective agglomeration, and thus, size enlargement. Results indicate that by using sulfosuccinamates as a collector, around 80% of the fine (-50 µm) to very fine (-20 µm) cassiterite can be recovered (representing ~50% of the total cassiterite in the tailings sample). Agglomeration flotation experiments showed inferior results for recovering the ultrafine cassiterite (for feed fractions in the -25 µm size range). Oil/froth interaction and increased pulp ion content are considered as the main contributing causes.
Keywords: Tailings, Reprocessing, Cassiterite, Flotation, Ultrafine, Oil-assisted flotation

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Registration No. 23900 - Permalink

Solid state spectroscopy with THz free electron lasers
Helm, M.
Abstract: Some applications of infrared and THz free electron lasers in solid state spectroscopy are discussed. In particular, nonlinear experiments on semiconductor quantum well excitons and pump-probe studies on carrier relaxation in graphene are presented.
Keywords: free electron laser, infrared, terahertz, quantum well, graphene
  • Invited lecture (Conferences)
    Laser Optics 2016, 27.06.-01.07.2016, St. Petersburg, Russland
Registration No. 23898 - Permalink

Transitions in a Magnetized Quasi-laminar Spherical Couette Flow
Kasprzyk, C.; Kaplan, E.; Seilmayer, M.; Stefani, F.
Abstract: First results from a new magnetized spherical Couette experiment are presented.
For a line in the Re-Ha instability diagram with constant Reynolds Number Re = 1000 and increasing Hartmann number Ha we study the liquid metal movement in a spherical gap under the influence of a vertical magnetic field.
The resulting flow structures are inspected with comprehensive ultrasound technique.
Increasing the magnetic field strength until Ha = 60, we observe the equatorially anti-symmetric jet instability with azimuthal wave number m = 3 at low Ha.
At intermediate Ha, no dominant m is identifiable.
At high Ha, an unstable, equatorially symmetric state with various transitions between different azimuthal modes becomes visible.
Our observations are in agreement with numerical linear instability analysis.

Keywords: Magnetized spherical Couette flow, Instabilities
  • Contribution to proceedings
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
    Proceedings of the 10th PAMIR International Conference Fundamental and Applied MHD, 9788890551932, 547-551
  • Lecture (Conference)
    10th PAMIR International Conference Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italy
Registration No. 23894 - Permalink

Influence of magnetic fields on the behavior of single hydrogen bubbles generated via water electrolysis
Karnbach, F.; Uhlemann, M.; Yang, X.; Eckert, K.; Baczyzmalski, D.; Cierpka, C.; Mutschke, G.; Gebert, A.
Abstract: Hydrogen production via water electrolysis is an established method for energy storage the efficiency of which is limited by the gas bubbles blocking the electrode surface during the process. The application of a magnetic field can be a promising solution for an increased bubble detachment due to the Lorentz force induced electrolyte convection. Therefore single hydrogen bubbles offer a nice possibility for a detailed analysis of the underlying mechanisms. To analyze the impact of the magnetic field single hydrogen bubbles were produced potentiostatically at different potentials via electrolysis of sulfuric acid at a Pt microelectrode (Ø 100 μm) with a magnetic field superimposed in two different field configurations to the electrode surface for varying magnetic field strengths. The bubble behavior was visualized by a CCD camera and the electrolyte flow analyzed via Particle Image Velocimetry and Astigmatism Particle Tracking Velocimetry. Significant changes in the current signal were obtained (Fig. 1), depending on field orientation and strength, and are discussed due to the impact of the Lorentz force induced flow around the bubble, which possibly also influences the mass transfer in the vicinity of the bubble surface. If the magnetic field is applied parallel, a different bubble behavior is observed in comparison to a perpendicular applied magnetic field what may result in a higher efficiency.
Keywords: electrochemistry, electrolysis, renewable energy, hydrogen production, water splitting, magnetic field, Lorentz force, particle tracking velocimetry
  • Poster
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia
Registration No. 23892 - Permalink

Test Software
Henrion, K.
Abstract: Alles Test Registration No. 23889 - Permalink

Comparative evaluation of SUV, tumor-to-blood standard uptake ratio (SUR), and dual time point measurements for assessment of the metabolic uptake rate in FDG PET
Hofheinz, F.; van den Hoff, J.; Steffen, I. G.; Lougovski, A.; Ego, K.; Amthauer, H.; Apostolova, I.
Abstract: Background

We have demonstrated recently that the tumor-to-blood standard uptake ratio (SUR) is superior to tumor standardized uptake value (SUV) as a surrogate of the metabolic uptake rate K m of fluorodeoxyglucose (FDG), overcoming several of the known shortcomings of the SUV approach: excellent linear correlation of SUR and K m from Patlak analysis was found using dynamic imaging of liver metastases. However, due to the perfectly standardized uptake period used for SUR determination and the comparatively short uptake period, these results are not automatically valid and applicable for clinical whole-body examinations in which the uptake periods (T) are distinctly longer and can vary considerably. Therefore, the aim of this work was to investigate the correlation between SUR derived from clinical static whole-body scans and K m-surrogate derived from dual time point (DTP) measurements.

Methods

DTP 18F-FDG PET/CT was performed in 90 consecutive patients with histologically proven non-small cell lung cancer (NSCLC). In the PET images, the primary tumor was delineated with an adaptive threshold method. For determination of the blood SUV, an aorta region of interest (ROI) was delineated manually in the attenuation CT and transferred to the PET image. Blood SUV was computed as the mean value of the aorta ROI. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values from the early time point of each DTP measurement were scan time corrected to 75 min postinjection (SURtc). As surrogate of K m, we used the SUR(T) slope, K slope, derived from DTP measurements since it is proportional to the latter under the given circumstances. The correlation of SUV and SURtc with K slope was investigated. The prognostic value of SUV, SURtc, and K slope for overall survival (OS) and progression-free survival (PFS) was investigated with univariate Cox regression in a homogeneous subgroup (N=31) treated with primary chemoradiation.


Results

Correlation analysis revealed for both, SUV and SURtc, a clear linear correlation with K slope (P<0.001). Correlation SUR vs. K slope was considerably stronger than correlation SUV vs. K slope (R 2=0.92 and R 2=0.69, respectively, P<0.001). Univariate Cox regression revealed SURtc and K slope as significant prognostic factors for PFS (hazard ratio (HR) =3.4/ P=0.017 and HR =4.3/ P=0.020, respectively). For SUV, no significant effect was found. None of the investigated parameters was prognostic for OS.

Conclusions

Scan-time-corrected SUR is a significantly better surrogate of tumor FDG metabolism in clinical whole-body PET compared to SUV. The very high linear correlation of SUR and DTP-derived K slope (which is proportional to actual K m) implies that for histologically proven malignant lesions, FDG-DTP does not provide added value in comparison to the SUR approach in NSCLC.

Keywords: PET FDG Tumor-to-blood ratio SUR Registration No. 23888 - Permalink

Subsecond thermal processing for the advancement of thin layers and functional coatings
Skorupa, W.
Abstract: This talk reviews the advances that subsecond thermal processing in the millisecond range using xenon-filled flash lamps (FLA) brings to the processing of the most advanced thin layer and coating materials, thus enabling the fabrication of novel electronic structures and materials. It will be demonstrated how such developments can translate into important practical applications leading to a wide range of technological benefits. An important issue of our work was the formation and characterization of semiconductor materials and coatings for the green energy advancement. Regarding photovoltaic applications, we dealt with the ion beam doping and thermal processing of PV silicon demonstrating using FLA a distinct improvement of the minority carrier diffusion length compared to rapid thermal processing and furnace treatments. Moreover, we engineered the hydrogen content in photovoltaic silicon in correlation to the phosphorus doping using plasma immersion ion implantation and FLA. Recently, we demonstrated also FLA driven boron and phosphorus in-diffusion from surface coatings. Further, we prepared coarse grained dendritic crystal structures in thin silicon films on silicon dioxide to show that the addition of carbon prevents the agglomeration of the molten silicon films and largely influences the crystallisation process. Finally the strongly developing field of large area electronics is represented by reporting on our activities in regard to transparent conductive oxide (TCO) and copper paste coatings.
Keywords: subsecond thermal processing, flash lamp annealing, ion implantation, photovoltaics, transparent conductive oxide, copper paste,
  • Invited lecture (Conferences)
    SVC (Society of Vacuum Coaters) 59th Annual Technical Conference (TechCon), 09.-13.05.2016, Indianapolis, IN, USA
Registration No. 23885 - Permalink

Range prediction for tissue mixtures based on dual-energy CT
Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.
Abstract: The use of dual-energy CT (DECT) potentially decreases range uncertainties in proton and ion therapy treatment planning via determination of the involved physical target quantities. For eventual clinical application, the correct treatment of tissue mixtures and heterogeneities is an essential feature, as they naturally occur within a patient’s CT. Here, we present how existing methods for DECT-based ion-range prediction can be modified in order to incorporate proper mixing behavior on several structural levels. Our approach is based on the factorization of the stopping-power ratio into the relative electron density and the relative stopping number. The latter is confined for tissue between about 0.95 and 1.02 at a therapeutic beam energy of 200 MeV/u and depends on the I-value. We show that convenient mixing and averaging properties arise by relating the relative stopping number to the relative cross section obtained by DECT. From this, a maximum uncertainty of the stopping-power ratio prediction below 1% is suggested for arbitrary mixtures of human body tissues.
Keywords: proton and ion radiation therapy, treatment planning, computed tomography, volume averaging Registration No. 23880 - Permalink

Clinical implementation of dual-energy CT for proton treatment planning to reduce CT-based range uncertainties
Wohlfahrt, P.; Möhler, C.; Baumann, M.; Enghardt, W.; Krause, M.; Greilich, S.; Richter, C.
Abstract: Purpose/Objective:
Particle treatment planning is particularly afflicted by CT-based range uncertainties. A clinical application of dual-energy CT (DECT) provides additional tissue information to potentially achieve more precise range predictions compared to single-energy CT (SECT). Therefore, the clinical implementation of DECT was aimed to be reached in this study.

Materials/Methods:
To define an optimal DECT protocol (Siemens Somatom Definition AS: 80/140kVp, kernel D34), CT scan settings were experimentally analyzed concerning beam hardening, image quality and influence on the heuristic conversion of CT numbers into stopping-power ratios (SPRs) per look-up table (HLUT) using phantoms consisting of tissues and tissue surrogates. Differences in range prediction and dose distribution between SECT and pseudo-monoenergetic CT datasets (MonoCT), derived by a weighted sum of both DECT scans, were quantified for phantoms and patients.

Results:
For treatment planning a DECT-based MonoCT of 79 keV is optimal, since CT-based HLUT uncertainties can be reduced (Figure 1). Dose distributions planned on SECT and MonoCT datasets reveal mean range deviations of 0.3mm, gamma passing rates (1%,1mm) greater than 99.9% and no clinically relevant changes in dose-volume histograms. Therefore, DECT was clinically implemented for patients treated with protons. 70 planning and 400 control DECT scans of overall 90 patients were acquired until January 2016.

Conclusions:
More precise range predictions and a wider diagnostic variety are feasible with DECT-based MonoCTs. Further improvements are expected from a direct, patient-specific, non-heuristic SPR determination. To quantify their possible benefits, first investigations of intra- and interpatient variations were performed on the still growing patient database.

Keywords: dual-energy CT, proton therapy
  • Poster
    PTCOG - annual conference, 23.-28.05.2016, Prag, Czech Republic
Registration No. 23879 - Permalink

Dual-energy CT for range prediction in proton and ion therapy
Möhler, C.; Wohlfahrt, P.; Richter, C.; Jäkel, O.; Greilich, S.
Abstract: Purpose/Objective:
Proton and ion therapy require accurate prediction of particle ranges in tissue. In current clinical practice, computed tomography (CT) images are voxel-wise converted to ion-stopping power ratio maps using direct heuristic relations. The general validity of these approaches is, however, limited due to the different physical regimes of photon and ion interaction. Using a more sophisticated method based on dual-energy CT (DECT), which provides access to the physical quantities influencing photon attenuation, Hünemohr et al. (2014) reported an improved ion-range prediction for homogeneous tissue surrogates. Here, we present a major modification of the latter method, enabling a proper treatment of heterogeneities and mixtures on several structural levels, which represent a crucial feature of the realistic clinical situation.

Material and Methods:
We treat the stopping-power ratio as the product of the electron density relative to water and a correction factor that implicitly involves the logarithmic dependence on the mean excitation energy (I-value). The relative electron density, being an important parameter in both photon and ion energy loss, can be derived directly from DECT scans using a universal and robust method. The correction factor, however, has to be determined with an empirical method. For this purpose, we propose to use the information from CT images that is complementary to the relative electron density, i.e. the electronic photon absorption cross section relative to water. Using the attenuation sum rule and Bragg’s additivity rule, the relative cross sections and correction factors were calculated for single elements, tissue base materials like water, lipid, etc. and tabulated real tissues.

Results:
For a therapeutic beam energy of 200 MeV/u, the correction factor varies between 1.15 and 0.70 for single elements with atomic numbers between 1 and 100. Building up compounds from a certain number of elements, a maximum spread of possible values for the correction factor can be quoted for a given relative cross section, due to the mathematical structure of the variable space. In practice, this could be used as an uncertainty estimate for a given calibration. The accessible variable space is drastically reduced by admitting only tissue base materials such as water, lipids and hydroxylapatite. The space is further reduced by admitting only mixtures of real tissue materials. For human tissue, the correction factor is thus limited overall to a small range around one (0.96 - 1.02).

Conclusions:
With the definition of the correction factor in the stopping-power ratio prediction and its relation to the relative cross section, a mathematically rigorous treatment of tissue mixtures was made possible. Such mixtures influence CT imaging of patients e.g. in the form of volume averaging in a CT voxel. This thorough treatment of mixtures, like the one presented here, is thus essential for the clinical applicability of DECT-based ion-range prediction.

Keywords: dual-energy CT, proton therapy
  • Poster
    ESTRO 35 - annual meeting, 29.04.-03.05.2016, Turin, Italy
Registration No. 23878 - Permalink

Trapping of hydrogen and helium at dislocations in tungsten: an ab initio study
Bakaev, A.; Grigorev, P.; Terentyev, D.; Bakaeva, A.; Zhurkin, E. E.; Posselt, M.
Abstract: Retention of plasma gas components such as hydrogen (H) isotopes and helium (He) is one of the limiting factors in selection of plasma facing materials for future thermonuclear fusion devices. Tungsten (W) is one of the promising candidates for such materials and was chosen for the divertor armor for International Thermonuclear Experimental Reactor (ITER) and the first wall material for the design of the demonstrational fusion power plant - DEMO. For the analytical estimation of accumulation of H/He components in tungsten, it is important to understand the relevant physical mechanisms of their trapping in the material and thoroughly parameterize them numerically.
Experiments involving high flux plasma exposures of tungsten at temperature below 500 K conclude on significant amount of retained hydrogen, which unlike helium, does not agglomerate in the form of clusters in the bulk defect-free material. The observed hydrogen isotope trapping and deep diffusion is conventionally attributed to the trapping at the natural lattice defects such as dislocations and grain boundaries.
Computational assessment of trapping strength and capacity of the dislocations is the subject of this work. Here the electronic structure calculations using density functional theory (DFT) are done to evaluate the affinity of hydrogen and helium to the screw and edge dislocations. For this, we calculate the interaction energy map around the dislocation core for hydrogen and helium atoms. The energetically favorable positions are rationalized on the basis of charge density distribution and local stress concentraion. The results obtained help to refine the input parameters of the macro-scale models of retention of plasma components, such as mean field rate theory methods.
The additional molecular statics simulations are also performed to analyze whether the contempory atomistic models using the recently developed interatomic potentials for W-H-He system can grasp adequately the interaction of H and He with dislocations.

Keywords: H and He in W, trapping at dislocation, DFT
  • Lecture (Conference)
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK
Registration No. 23877 - Permalink

Operation and sound field of an ultrasonic biplane-array
Hipp, R.; Gommlich, A.; Joneit, D.; Schubert, F.; Heuer, H.
Abstract: For ultrasonic non-destructive testing several types of transducers are available based on single-channel or multi-channel technology. Transducers with more than two individual elements are usually called arrays. These arrays can differ in geometry and arrangement of their individual elements, e.g. linear, matrix and annular geometry. The advantage of arrays in contrast to single element transducers is the ability to tilt and focus the sound beam to a desired region inside the specimen. The biplane phased array is a new possibility in NDE for combining the advantages of linear phased arrays, regarding low costs and high compatibility to existing phased array electronics with the goal of matrix arrays to get signal information from the evaluated specimen in all three dimensions. The biplane array consists of a piezoelectric sensor with a conventional line electrode structure on the top and a second perpendicular line electrode structure rotated by 90° on the bottom side of the piezo layer. By using appropriate excitation and control techniques the biplane array is able to perform a conventional sector scan in two spatial directions. Moreover it is also possible to excite or receive with one single element or a choice of adjacent elements which allows flexible 3-D reconstruction techniques. All these features go along with significantly less technological effort compared to 2-D matrix arrays where each single element needs to be electrically connected and a large number of individual channels needs to supported by the used ultrasonic hardware. The paper describes and visualizes the operation of a biplane array by calculating its spatio-temporal sound field. The numerical simulations are performed by the CEFIT-PSS technique, a powerful combination of the axisymmetric Elastodynamic Finite Integration Technique (EFIT) with transient Point Source Synthesis (PSS).
Keywords: sound field simulation, biplane-array, cefit, pss
  • Contribution to proceedings
    19th World Conference on Non-Destructive Testing 2016, 13.-17.06.2016, München, Deutschland

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Registration No. 23876 - Permalink

Kinetic Monte Carlo simulation of irradiation-induced nanostructure evolution in Oxide Dispersion Strengthened Fe alloys
Liedke, B.; Posselt, M.; Murali, D.; Claisse, A.; Olsson, P.
Abstract: Rigid-lattice Kinetic Monte Carlo simulations are performed in order to investigate the modification of Y-Ti-O nanoclusters during irradiation, at selected temperatures, doses and dose rates. The simulations use input parameters for the atomic interactions and the migration barriers obtained by DFT calculations as well as data on representative examples of the cascade debris determined by Molecular Dynamics. Before irradiation the nanostructure is prepared by performing thermal relaxation of a system with randomly distributed Y, Ti, O atoms, and vacancies. The concentration of Y, Ti, and O is chosen according to the common 14 YWT ODS alloy and both low and high vacancy contents are considered. The nanostructures obtained in the preparation step were used subsequently in KMC simulations of irradiation. The results demonstrate the competition between ballistic effects leading to the dissolution and the growth of the clusters. While the former effect dominates at high doses and low temperatures the latter prevails at low doses and high temperatures. On the other hand, the nanoclusters formed in the preparation step show a very high stability under irradiation within the temperature and dose range relevant for the application of ODS alloys in advanced nuclear reactors. The findings of this work are consistent with the results of experimental studies of ion and neutron irradiation of ODS alloys.
Keywords: Oxide Dispersion Strengthened (ODS) Fe alloys, Kinetic Monte Carlo simulation, Irradiation
  • Lecture (Conference)
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK
Registration No. 23875 - Permalink

First-principles-based calculation of self- and solute diffusion in bcc-Fe
Posselt, M.; Abdou, J.; Murali, D.; Liedke, B.
Abstract: DFT calculations were performed in order to study self-diffusion as well as oxygen and titanium diffusion in bcc Fe. It is commonly accepted that self-diffusion proceeds via the exchange of a Fe atom with a vacancy. The octahedral interstitial site is the most stable position of oxygen in bcc Fe. Therefore, it is assumed that O diffuses via the interstitial mechanism, i.e. an O atom moves from one octahedral site to the other. As for other substitutional solutes in bcc Fe, in the case of Ti the vacancy mechanism is considered. The migration barriers occurring in all these processes were calculated using the Nudged Elastic Band method. The corresponding attempt frequencies were obtained from the difference between the vibrational contribution to the free energy of the related equilibrium and saddle point configurations. While in the case of self- and O-diffusion only one saddle point and one attempt frequency are relevant, several barriers and frequencies must be determined to consider Ti diffusion by the vacancy mechanism. Different models were used to obtain the diffusion coefficient of Ti: (i) the original nine-frequency model [1], (ii) a modified nine-frequency model [2], and (iii) the Self-Consistent Mean Field model [3]. The comparison between the calculated self-, O-, and Ti-diffusion coefficients with experimental data shows significant differences. This is mainly due to fact that electron and magnon excitations were neglected in the calculations, whereas the phonon excitations were taken into account via the vibrational free energy. Under the assumption that electron excitations are small different phenomenological models are applied to consider the magnon excitations, which decrease the spontaneous magnetization of bcc Fe with increasing temperature. Choosing suitable model parameters a good agreement with measurements is obtained for self- and Ti-diffusion. On the other hand, the agreement with the few existing experimental data on O diffusion is poor. Possible reasons for this are discussed.

[1] A. D. Le Claire, in Physical chemistry: an advanced treatise, edited by H. Eyring
(Academic Press, New York, 1970).
[2] L. Messina, M. Nastar, T. Garnier, C. Domain, P. Olsson, Phys. Rev. B 90, 104203 (2014)
[3] M. Nastar, Philos. Mag. 85, 3767 (2005).

Keywords: Self- and solute diffusion, bcc-Fe, DFT
  • Poster
    13th International Conference on Computer Simulation of Radiation Effects in Solids (COSIRES 2016), 19.-24.06.2016, Loughborough, UK
Registration No. 23873 - Permalink

On determination off focal laws for linear phased array probes as to the active and passive element size
Gommlich, A.; Schubert, F.
Abstract: Ultrasonic linear phased array probes consist of several single transducer elements. By exciting each single element at a particular time wave fronts can be tilted, focused or both combined. The required set of time delays is called ''focal law''. Hence, the shape of the resulting wave front depends significantly on focal law calculation. The typical single transducer element in linear phased array probes has a rectangle shape with a width-to-length-ratio of approximately 0.1 to 0.5. The width of the short side is called ''active aperture size'', the larger one is called ''passive aperture size''. In state of the art calculations of the focal laws only the pitch between the single elements is considered and the elements are approximated by a point source in the centre of their aperture. Therefore, the real dimensions of the elements - both the active and the passive dimension - have no further influence. Moreover the wave propagation process itself is modelled by geometrical acoustics.
The numerical CEFIT (Cylindrical Elastodynamic Finite Integration Technique) in combination with transient PSS (Point Source Synthesis) enables flexible and fast simulation of 4-D spatio-temporal sound fields in homogeneous and layered half spaces, espectively. Thereby all wave physical effects like diffraction, scattering and mode conversion will be considered. The calculations with different geometrical parameters for the probes show that both the active as well as the passive aperture size influence the time and frequency characteristic of the signal in the focal point. Based on the focal laws calculated with and without respect to the aperture size, sound fields were simulated for selected focal points. The results were qualitatively and quantitatively compared whereby the differences between both methods are distinguishable. It becomes evident that geometrical focus and acoustical focus are different. The feasibility of corrections for the focal laws with respect to time and frequency characteristics in the focal point as well as the improvement of resolution will be discussed. The results further allow an estimation of the optimal width-tolength-ratio for single transducer elements of linear phased arrays.

Keywords: focal law, phased array, sound field simulation, cefit, pss
  • Contribution to proceedings
    19th World Conference on Non-Destructive Testing 2016, 13.-17.06.2016, München, Deutschland

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Registration No. 23872 - Permalink

Tuning pattern symmetry by choosing the substrate in reverse epitaxy
Engler, M.; Ou, X.; Facsko, S.
Abstract: Ion beam erosion of solid surfaces is long known to yield regular surface morphologies, like periodic ripples or hexagonal dot patterns. At room temperature, semiconductors are amorphized by the ion beam. Pattern formation under these conditions has been studied extensively in the last decades.

Ion beam erosion above a material dependent dynamic recrystallization temperature allows the formation of crystalline nano scale patterns on semiconductor surfaces. At these elevated temperature pattern formation is driven by diffusion of vacancies created by sputtering of atoms. Anisotropic diffusion on the surface and diffusion barriers across step edges lead to the formation of pattern reflecting the symmetry of the irradiated surface. We will discuss how the surface symmetry determines the pattern symmetry.

Keywords: reverse epitaxy ion beam pattern pattern formation semiconductor
  • Lecture (Conference)
    80. Jahrestagung der DPG und DPG-Frühjahrstagung, 06.-11.03.2016, Regensburg, Deutschland
Registration No. 23868 - Permalink

Time-Resolved Two Million Year Old Supernova Activity Discovered in the Earth’s Microfossil Record
Bishop, S.; Ludwig, P.; Egli, R.; Chernenko, V.; Deveva, B.; Faestermann, T.; Famulok, N.; Fimiani, L.; Gomez, J.; Hain, K.; Korschinek, G.; Hanzlik, M.; Merchel, S.; Rugel, G.
Abstract: Massive stars (M≥M⊙), which terminate their evolution as core collapse supernovae, are theoretically predicted to eject >10−5M⊙ of the radioisotope 60Fe (t1/2=2.6 Ma). If such an event occurs sufficiently close to our solar system, traces of the supernova debris could be deposited on Earth. Herein, we report a time-resolved 60Fe signal residing, at least partially, in a biogenic reservoir. Using accelerator mass spectrometry, this signal was found through the direct detection of live 60Fe atoms contained within secondary iron-oxides, among which are magnetofossils; the fossilized chains of magnetite crystals produced by magnetotactic bacteria. The magnetofossils were chemically extracted from two Pacific Ocean sediment drill cores. Our results show that the 60Fe signal onset occurs around 2.6−2.8 Ma, near the lower Pleistocene boundary, terminates around 1.7 Ma, and peaks at about 2.2 Ma.
Keywords: accelerator mass spectrometry, AMS
  • Invited lecture (Conferences)
    2016 Carpathian Summer School of Physics, Romania: http://cssp16.nipne.ro/, 26.06.-09.07.2016, Sinaia, Romania
Registration No. 23867 - Permalink

Validation of the surveillance concepts and trend curves by the investigation of decommissioned RPVs
Viehrig, H.-W.; Altstadt, E.; Houska, M.; Valo, M.
Abstract: The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald NPP representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The paper presents test results measured on trepans taken from the multilayer beltline welding seam SN0.1.4. and forged base metal ring 0.3.1. located in the reactor core region of the Unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The characterisation of the irradiation response is based on the measurement of the hardness, the yield stress, the Master Curve reference temperature, T0, and the Charpy-V transition temperature through the thickness of multi-layer beltline welding seam SN0.1.4 and the forged base metal ring 0.3.1.
For the beltline welding seam we observed a large variation in the through thickness T0 values. The T0 values measured with the T-S-oriented Charpy size SE(B) specimens cut from different thickness locations of the multilayer beltline welding seam strongly depend on the intrinsic weld bead structure along the crack tip. In general, the fracture toughness values at cleavage failure, KJc-1T, measured on SE(B) specimens from beltline welding seam follow the Master Curve description, but more than the expected number lie outside the curves for 2 % and 98 % fracture probability. In this case the test standard ASTM E1921 indicates the investigated multi-layer weld metal as not uniform. The multi modal Master Curve based approach describes the temperature dependence of the specimen size adjusted KJc-1T values well.
The KJc values measured on L-S oriented Charpy size SE(B) specimens from defined thickness locations of the forged base metal ring 0.3.1. strongly scatter. The progression of the T0 values through the thickness lies in the range from 121 °C to 130 °C and indicate no irradiation induced embrittlement within the through the thickness fluence range from 5.38 to 1.20 ∙ 1019 n/cm2 (E > 0.5 MeV). The application of the multi modal extension [Wallin 2004, Viehrig 2006, Scibetta 2010] on the summarised dataset does essentially improve the situation. More than allowed 2% of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2% fracture probability. The reason for the occurrence of very low KJc values is seen in intergranular planes detected on the fractured surfaces of the specimens. The application of modified MC based evaluation methods indicates the material as non-homogeneous.
The investigation show that Master Curve, T0, and Charpy-V, TT47J, based ductile-to-brittle transition temperature progressions through the thickness of the multi-layer welding seam and the forged base metal ring of the decommissioned Greifswald WWER-440 first generation RPV do not correspond to the forecast according to the current Russian code.

Keywords: reactor pressure vessel, multi-layer welding seam, forged base metal ring, neutron irradiation, hardness, tensile strength, fracture toughness, Master Curve approach, Charpy-V
  • Lecture (Conference)
    Workshop on Nuclear Reactor Pressure Vessel Surveillance Programs, 28.-29.06.2016, Chicago, USA
Registration No. 23866 - Permalink

Protective effects of 2,3-diaryl-substituted indole-based cyclooxygenase-2 inhibitors on oxidative modification of human low density lipoproteins in vitro
Pietzsch, J.; Laube, M.; Bechmann, N.; Pietzsch, F.-J.; Kniess, T.
Abstract: It has been suggested that 2,3-diaryl-substituted indole-based

cyclooxygenase-2 (COX-2) inhibitors (2,3-diaryl-indole coxibs) do not only appear as potent anti-inflammatory agents but also show the ability to scavenge reactive oxygen species (ROS). This led to the hypothesis that 2,3-diaryl-indole coxibs also may act as potent inhibitors of oxidative modification of low-density lipoprotein (LDL), which is considered a key factor in atherogenesis. The aim of this study was to explore i) the reactivity of a series of new synthesized 2,3-diaryl-indoles with several well characterized LDL oxidation systems and ii) subsequent effects on an inflammatory/atherogenic microenvironment. The results demonstrate that under the present experimental conditions 2,3-diaryl-indoles showed potent ROS scavenging activity and were able to markedly inhibit LDL oxidation. Subsequently, this led to a substantial decrease of modified LDL uptake by scavenger receptors in THP-1 macrophages in vitro and in rats in vivo. Moreover, modified LDL-mediated monocyte/neutrophil adhesion to endothelial cells, macrophage NF kappa B activation, as well as macrophage and endothelial cell cytokine release was diminished in vitro. The reduction of modified LDL-induced atherogenic effects by antioxidant 2,3-diaryl-indole coxibs may widen the therapeutic window of COX-2 targeted treatment.

Keywords: Antioxidants, atherogenesis, selective cyclooxygenase-2 (COX-2) inhibitors (coxibs), inflammation, lipid peroxidation, protein oxidation, radical scavenger, reactive oxygen species (ROS) Registration No. 23861 - Permalink

Visualization of trace-element zoning in apatite using BSE and CL imaging and EPMA and particle-induced X-ray/gamma-ray emission mapping
Gros, K.; Słaby, E.; Förster, H.-J.; Michalak, P. P.; Munnik, F.; Götze, J.; Rhede, D.
Abstract: In this paper, zonation patterns of trace elements in apatite were visualized using four analytical techniques, namely back-scattered electrons (BSE) and cathodoluminescence (CL) imaging and electron probe micro-analysis (EPMA) and micro-proton-induced X-ray/gamma-ray emission (μPIXE/μPIGE) mapping. Each method demonstrates the in-grain compositional variations in a slightly different way. Both BSE and CL provide qualitative data, and the internal textures are displayed in most detail. Additionally, CL points to specific elements enriched in certain growth zones. Qualitative EPMA maps show detailed zonation patterns for specific elements (with high spatial resolution), which are in general correspondence with the patterns observed in BSE and CL images. The µPIXE/µPIGE maps are fully quantitative and the detection limits are relatively low compared to EPMA mapping. In present spot measurements µPIXE demonstrates lower detection limits than EPMA, however, the latter could be considerably improved by extending the acquisition times. There is no significant overlap of REE (rare earth elements) peaks in the acquired µPIXE energy spectra, however, when multiple REEs are present with sufficiently high concentrations, peak deconvolution may pose some difficulties. Spatial resolution of µPIXE/µPIGE images is not sufficiently high to reflect minor textural features, which also result from the greater interaction depth of the proton beam. However, major growth zones are distinguishable. Even though each method has their advantages and limitations, when applied together, they provide an almost complete characterization of compositional variability in trace-element-bearing minerals.
Keywords: trace-element zoning, apatite, BSE, CL, EPMA, µPIXE/µPIGE

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Registration No. 23856 - Permalink

Qualification of CFD-models for multiphase flows in medium and large scale industrial applications
Lucas, D.
Abstract: Multiphase flows are frequently applied in industrial processes as e.g. in chemical engineering, oil industries or power plants. Reliable predictions of the flow characteristics such as local concentration of species, interfacial area density or heat transfer in gas-liquid flows can contribute to an optimization of the design of corresponding apparatuses and processes. Computational Fluid Dynamics (CFD) in principle allows the simulation of such flows and provides local flow characteristics. While it is frequently used for industrial problems in case of single phase flows it is not yet mature for two-phase flows. The reason is the complex gas-liquid interface. For medium and large scale flow domains it is not feasible to resolve all details of this interface. Averaging procedures have to be applied and in most cases the so-called two- or multi-fluid approach is used. It assumes interpenetrating phases and the information on the interface gets lost by these averaging procedures. This information has to be added to the basic balance equations by so-called closure models. The development and validation of such models is done at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) to obtain tools for reliable predictions of multiphase flow characteristics in medium and large industrial scales.
One difficulty for the model development and validation results from the fact that we still have a lack of knowledge on local phenomena which determine the two-phase flow characteristics and which should be considered in the closure models. Experimental data with high resolution in space and time are required. To get such information on the gas-liquid interface new innovative measuring techniques as wire-mesh sensors and ultrafast X-ray tomography were developed at Helmholtz-Zentrum Dresden – Rossendorf (HZDR) and extensively used to establish comprehensive databases. The corresponding experiments were conducted at the TOPFLOW-facility of HZDR. It can be operated for air-water and steam-water flows with a pressure up to 7 MPa and the corresponding saturation temperature of 286 °C. An electrical steam generator with a power of 4 MW is able provide up to 1.5 kg steam per second.
In this lecture the strategy of the CFD-model development and validation for multiphase flows is presented. This includes the corresponding experimental work and development of innovative measuring techniques.

Keywords: CFD, two-phase flow, TOPFLOW
  • Invited lecture (Conferences)
    Lecture series of the Energy Department of Politecnico die Milano, 15.06.2016, Milano, Italy
Registration No. 23853 - Permalink

Radiation-Hard Ceramic Resistive Plate Chambers for Forward TOF and T0 Systems
Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kiselev, S.; Kotte, R.; Laso Garcia, A.; Malkevich, D.; Naumann, L.; Nedosekin, A.; Plotnikov, V.; Stach, D.; Sultanov, R.; Voloshin, K.
Abstract: Resistive Plate Chambers with ceramic electrodes are the main candidates to be used in precise multi-channel timing systems operating in high-radiation conditions. We report the latest R&D results on these detectors aimed to meet the requirements of the forward T0 counter at the CBM experiment. RPC design, gas mixture, limits on the bulk resistivity of ceramic electrodes, efficiency, time resolution, counting rate capabilities and ageing test results are presented. Registration No. 23851 - Permalink

Methoden zur Charakterisierung und Optimierung von Belebungsbecken
Reinecke, S. F.; Hampel, U.
Abstract: Für den Großteil der in Deutschland betriebenen Kläranlagen übersteigt die aufgewendete Energie zur Durchmischung und Belüftung des Abwassers oftmals den tatsächlich notwendigen Energiebedarf. Dies wird oft durch eine nicht-optimale Auslegung bzw. Anordnung der Begasungs- und Dispergierorgane im Belebtschlammbecken hervorgerufen. Im Vortrag werden die am HZDR durchgeführten Forschungsvorhaben zur Effizienzsteigerung von Abwasseraufbereitungsanlagen vorgestellt.
  • Lecture (Conference)
    25. Lehrer-Obmann-Tag der Kläranlagen- und Kanal-Nachbarschaften, 15.-16.03.2016, Dresden, Deutschland
Registration No. 23850 - Permalink

Tomographic Interrogation of Gas-Liquid Flows in Inclined Risers
Lokman, A. A.; Escrig, E.; Reinecke, S.; Hewakandamby, B. N.; Azzopardi, B. J.
Abstract: Measurements have been made with Electrical Capacitance Tomography (ECT) and a Wire Mesh Sensor (WMS) using air-silicone
oil (viscosity 5 mPa s) on a 67 mm diameter pipe. The experiments were carried out in a facility at Nottingham University different
inclinations. The cross-sectional distribution of gas fraction is obtained from the WMS and from the ECT the latter after post -
processing. The combined data is used to provide information on the size, frequency and velocity of large bubbles (Taylor bubbles
and spherical cap bubbles) and how they are influenced by the phase flow rates and the pipe inclinations. The boundary for spherical
cap bubbles is identified. In addition, WMS output presents the results for a radial void fraction, as well as bubble size distribution, in
particular that gives the percentage of void fraction in relation to bubble diameter. It is concluded that moving from horizontal to
inclined to vertical, there is an increase in the percentage of smaller bubbles. There are also large diameter bubbles forming for all the
inclinations. The cross-section averaged void fraction and its variation in time were measured. Taylor bubble frequency increases
with increasing of liquid flow rate and inclination angle of the pipe

Keywords: wire mesh sensor, electrical capacitance tomography, two phase flow, inclined riser
  • Contribution to proceedings
    ICMF-2016 - 9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien
    Proceedings of ICMF-2016
  • Lecture (Conference)
    ICMF-2016 - 9th International Conference on Multiphase Flow, 22.-27.05.2016, Florenz, Italien
Registration No. 23848 - Permalink

Untersuchung der Hydrodynamik von ovalen Biogasreaktoren mit instrumentierten Strömungsfolgern
Reinecke, S. F.; Hampel, U.
Abstract: Zur Untersuchung der ablaufenden Prozesse in großen Behältern, wie z. B. Biogasfermentern, Bioreaktoren und Belebtschlammbecken, wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Diese Daten werden nach der Rückgewinnung der Sensorpartikel aus dem Prozess einem computergestützten Analysesystem zur Verfügung gestellt. Die erweiterten Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit zur Tarierung und Rückgewinnung ausgestattet sind (Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung und das Magnetfeld und offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z.B. für pH-Wert und Gelöst-Sauerstoff.
Zur Erweiterung der Positionserfassung wurde die Detektion eines festen Positionsmarkers mit den Sensorpartikeln realisiert. Als Positionsmarker wird eine eigens entwickelte Tauschspule eingesetzt, deren kodiertes Anregungssignal über das entstehende Magnetfeld von den vorbeiströmenden Sensorpartikeln empfangen wird.
Die Sensorpartikel mit magnetischer Positionsdetektion wurden erstmals in einer hydrodynamischen Studie von drei Fermentern mit ovalen Behältergeometrien genutzt . Die Fermenter haben ein Füllvolumen von 1,5 m³, 2 m³ und 32 m³ und wurden mit je zwei horizontalen Rührwerken bei zwei Umfangsgeschwindigkeiten (5,5 m/s und 6,7m/s) in einer Xanthan-Lösung (5 g/L) betrieben (Abb. 2).
Mit der Positionsdetektion im Scheitelpunkt der Fermenter wurden die Zirkulationszeitverteilungen der Fluidelemente bestimmt (Abb. 3). Dies lässt Aussagen über das Mischverhalten in den Behältern zu. In Kombination mit den extrahierten vertikalen Aufenthaltsprofilen der Sensorpartikel erfolgt ein Vergleich der drei Fermenter.
  • Poster
    Jahrestreffen Reaktionstechnik 2016 zusammen mit der Fachgruppe Mischvorgänge, 02.-04.05.2016, Würzburg, Deutschland
Registration No. 23846 - Permalink

Instrumented flow-following sensor particles with magnetic position detection and buoyancy control
Reinecke, S. F.; Hampel, U.
Abstract: A concept for buoyancy control and magnetic position detection has been developed for the improvement of instrumented flow-following sensor particles. The sensor particles are used for investigation of hydrodynamic and biochemical processes in large-scale vessels such as biogas fermenters, bioreactors and aerated sludge basins. Neutral buoyancy of the sensor particles is required for tracing of the fluid flows. Buoyancy control is performed by adjustment of the sensor particles’ volume, which is altered by an integrated piston. A miniaturized linear actuator, namely a stepper motor with linear transmission, is operated by a microcontroller to drive the piston. The buoyancy control unit enables accurate automated taring of the sensor particles in the stagnant process fluid to achieve neutral buoyancy. Therefore, the measured vertical position of the sensor particle as a function of the hydrostatic pressure is used as feedback. It has an incremental density change of 0.0136 % as compared to water and a residual drift velocity of approximately 3.6 × 10−3 m s−1. Furthermore, a minimum density of 926 kg m−3 can be set by full extension of the piston, which allows floating of the sensor particles after a defined event, namely critical charge of battery, full data storage or the end of a fixed time cycle. Thus, recovery of the sensor particles can proceed easily from the fluid level. The sensor particles with a buoyancy control unit are tested for depths up to 15 m. Also, detection of a local magnetic position marker by the sensor particles has been implemented to enhance movement tracking. It was tested in a lab-scale biogas digester and was used for estimation of the liquid circulation time distribution and Peclét number to describe the macro-flow.
Keywords: Flow follower, sensor particle, autonomous sensor, position detection, buoyancy

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Registration No. 23845 - Permalink

In-situ study of high temperature stability and optical properties of aluminum-titanium oxynitride thin films
Heras, I.; Guillén, E.; Wenisch, R.; Krause, M.; Escobar-Galindo, R.
Abstract: Aluminum-titanium oxynitride AlTiO(x)N(y) thin films were investigated in order to understand the influence of the oxygen/nitrogen ratio on the optical properties and their failure mechanisms at high temperatures. The optical properties of oxynitride thin films as well as their high temperature stability showed a wide range of different responses according the oxygen/nitrogen ratio and the deposition pressure. AlTiO(x)N(y) thin films were deposited by cathodic vacuum arc and characterized at different temperatures to follow the temperature dependence of the composition and the optical constants. The samples were heated in vacuum from room temperature up to 800°C inside a multi-chamber cluster tool and the analysis of the thin films was carried out in-situ without intermittent sample exposure to air. Ellipsometry and Rutherford backscattering spectrometry (RBS) results showed the influence of the as-deposited oxygen content in the sample with the inward diffusion of oxygen into the coating and therefore oxidation resistance at high temperatures. Likewise, ex-situ annealing in air was performed to compare the results observed when exposed to ambient conditions. The low emittance properties of AlTiO(x)N(y) enabled in-situ RBS analysis at temperatures higher than 750°C. No significant changes of the optical properties and composition were found when heating in vacuum demonstrating excellent stability at high temperatures.
Keywords: solar-selective coatings, concentrated solar power, in situ RBS, cluster tool
  • Lecture (Conference)
    EMRS 2016 Spring Meeting, 02.-06.05.2016, Lille, Frankreich
Registration No. 23844 - Permalink

High-field paramagnetic Meissner effect up to 14 T in melt-textured YBa2Cu3O7–δ
Dias, F. T.; Vieira, V. N.; Wolff-Fabris, F.; Kampert, E.; Gouvea, C. P.; Campos, A. P. C.; Archanjo, B. S.; Schaf, J.; Obradors, X.; Puig, T.
Abstract: We have performed magnetization experiments in a melt-textured YBa2Cu3O7-δ (Y123) sample with Y2BaCuO5 (Y211) inclusions, under magnetic fields up to 14 T applied parallel or perpendicular to the ab plane. Magnetic anisotropy and paramagnetic moments were observed in both FC (field-cooling) and FCW (field-cooled warming) procedures and these features correspond to the so-called High-Field Paramagnetic Meissner Effect (HFPME). The HFPME effect increases monotonically as the magnetic field rises and a strong paramagnetic relaxation, toward increasing paramagnetic moment was additionally observed as a function of time. Microscopy analysis revealed a complex and correlated microstructure of the Y211 particles. These correlated defects are well known to cause strong flux pinning. Our results suggest a scenario of strong flux compression within weak or non-superconducting regions of the samples, developed as a consequence of the Meissner effect and assisted by strong flux pinning by the Y211 particles. This scenario is observed up to 14 T and clearly persists beyond. Registration No. 23843 - Permalink

Development of interatomic potential for bcc FeCrNi and its validation
Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.
Abstract: Potential:
Vac-Ni dragging possible
DFT logic substitutional configs reproduced
Most stable interstitial configs reproduced
Defect free Monte Carlo simulations:
Cr and Ni precipitate as separate fractions
Cr precipitation is independent of Ni content (<2%Ni)
Ni precipitation is enhanced by Cr

Keywords: FeCrNi alloy, interatomic potential
  • Lecture (Conference)
    8th N-FAME Workshop on modelling and modelling-oriented experiments in Fe alloys for nuclear applications, 13.-14.06.2016, Brussels, Belgium
Registration No. 23841 - Permalink

Radiation-induced segregation in FeNiCr model alloys
Bakaev, A.; Posselt, M.; Terentyev, D.; Bonny, G.; Zhurkin, E. E.
Abstract: Defect-free FeNiCr alloys:
No influence of Ni on Cr solubility, limited effect of Cr on Ni at 2%Ni : ↗100 K
Ni and Cr precipitate as separate fractions. Ni forms B2 FeNi clusters with {100} facets while the Cr atoms form pure Cr clusters with {110} facets
FeNiCr alloys with dislocation loops:
No mixing of Ni and Cr precipitates: Ni moves to compressive regions, Cr - tensile regions
Dislocation loops stabilize by 100-200 K Ni clusters only at Ni content in the alloy >=0.5%
Ni decreases significantly the segregation of Cr, cancelling the segregation or causing the depletion at Ni>=1%
Cr decreases the segregation of Ni at ½<111> loops for low Ni (0.25%) alloys, strongly enhances the Ni segregation at <100> loops for high Ni (2%) at T < 800 K due to Cr depletion
Enrichment values for Cr and Ni at ½<111 > loops at T = 600 K are consistent with experiments:
small ½<111> loops can serve as nucleus for NiCr(Si/P)-rich clusters

Keywords: FeCrNi alloys, radiation-induced segregation, Metropolis Monte Carlo simulation
  • Lecture (Conference)
    8th N-FAME Workshop on modelling and modelling-oriented experiments in Fe alloys for nuclear applications, 13.-14.06.2016, Brussels, Belgium
Registration No. 23840 - Permalink

Spatially-resolved sorption studies of Eu(III) on granite surface with time-resolved laser fluorescence microscopy (TRLFM)
Zesewitz, K.; Schmidt, M.
Abstract: The finding of an appropriate long-term repository for high-level nuclear waste is a highly relevant topic. To that end, it is required to research the interaction of occurring radionuclides with mineral phases contained in possible host rocks and construction materials. On a time scale of up to a million years, especially the scenario of a water intrusion into the repository and thus dissolution of radionuclides has to be considered. To investigate the sorption behavior of actinides and lanthanides, time-resolved laser fluorescence spectroscopy (TRLFS) is a widely used method, because of its trace concentration sensitivity and capability to distinguish multiple species in complex systems. On one hand this method gives the spectral information of the emitted fluorescence light, which allows determining the symmetry and the grade of complexation of the sorbed Ln/Ac. On the other hand the lifetimes of the excited electron states provide information about the surrounding quenchers, mainly water. Typically, TRLFS investigations will focus on the interaction of an actinide with one relevant mineral phase. For a real rock formation, e.g. granite, sorption will however be a competitive process involving multiple mineral phases at the same time.
In this study a new method called time-resolved laser fluorescence microscopy (TRLFM) is introduced, which will add a spatial dimension to TRLFS. By doing so, it is possible to separate the multi-phase system into discrete single-phase systems and therefore to make a step beyond model systems by researching, for example whole natural granite rock with TRLFS. Because of its advantageous fluorescence properties we use europium as an analogue for the trivalent actinides americium and curium. Sorption experiments with Eu(III) on granite under different solution conditions, regarding metal concentration and pH will be presented. These samples are excited by a focused pulsed laser beam at a wavelength of 394 nm, and scanned through the laser’s focal point by an XYZ-Stage with a resolution in the micrometer range. The sample is subsequently mapped by Raman-Microscopy to distinguish the different phases and the TRLFM data is then compared to the combination of Raman-data with TRLFS data of the single phases.
First results show that the different sorption behavior of the single phases can be resolved by this method. Lifetimes and emission spectra have been measured for quartz, feldspar and mica phases on granite plates, which evidence that the spatial resolution is sufficient to distinguish mineral grains in natural granite. XRD and XFA are done for the samples to determine all possible constituents. Partial maps of the europium distribution and speciation are presented together with phase identification by Raman microscopy and a comparison to optical microscopy images.

Keywords: TRLFS, granite, TRLFM, europium, speciation
  • Lecture (Conference)
    3rd International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 07.-10.11.2016, EMSL, Richland, Washington, USA
Registration No. 23839 - Permalink

Coulomb dissociation of 27P at 500 MeV/u
Marganiec, J.; Beceiro Novo, S.; Typel, S.; Langer, C.; Wimmer, C.; Alvarez-Pol, H.; Aumann, T.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Cortina-Gil, D.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y. A.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Rodriguez Tajes, C.; Rossi, D. M.; Simon, H.; Stanoiu, M.; Stroth, J.; Sümmerer, K.; Wagner, A.; Wamers, F.; Weick, H.; Wiescher, M.
Abstract: The proton-capture reaction 26Si(p,γ)27P was studied via Coulomb dissociation (CD) of 27P at an incident energy of about 500 MeV / u. The three lowest-lying resonances in 27P have been populated and their resonance strengths have been measured. In addition, a nonresonant direct-capture component was clearly identified and its astrophysical S factor measured. The experimental results are compared to Monte Carlo simulations of the CD process using a semiclassical model. Our thermonuclear reaction rates show good agreement with the rates from a recent compilation. With respect to the nuclear structure of 27P we have found evidence for a negative-parity intruder state at 2.88-MeV excitation energy.
Keywords: proton capture radioactive beam thermonuclear Registration No. 23837 - Permalink

Band structure modification in silicon hyperdoped with tellurium for optoelectronics
Wang, M.; Liu, F.; Yuan, Y.; Prucna, S.; Berencen, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption exhibited by these materials, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped Si layers have been fabricated by ion implantation followed by either millisecond range flash lamp annealing (FLA) or nanosecond range pulsed-laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted Si by both FLA and PLM. From the transport measurements, the conductivity increases with increasing tellurium concentration and the high tellurium concentration samples show a finite conductivity if temperature tends to zero. This indicates that the high concentration doping of tellurium induces an insulator-to-metal transition in silicon although tellurium introduces a deep donor in Si. Moreover, the ellipsometry measurements show that the band gap narrows with increasing doping concentration, which could enable silicon-based optoelectronics in the infrared spectral range.

[1] Kim, T. G., et al., Appl. Phys. Lett. 88, 241902 (2006)
[2] Tabbal, M., et al., Appl. Phys. A 98, 589–594 (2010)
[3] Umezu, I., et al., J. Appl. Phys. 113, 213501 (2013)

Keywords: Hyperdoping silicon, Flash lamp annealing, Pulsed-laser melting, Band structure modification
  • Lecture (Conference)
    The 2016 E-MRS Spring Meeting, 02.-06.05.2016, Lille, France
Registration No. 23835 - Permalink

Tellurium hyperdoped Si: Flash lamp annealing vs. Pulsed laser melting
Wang, M.; Liu, F.; Yuan, Y.; Prucna, S.; Berencen, Y.; Rebohle, L.; Skorupa, W.; Helm, M.; Zhou, S.
Abstract: Chalcogen-hyperdoped silicon has been a topic of great interesting due to its potential properties of sub-band gap optical and optoelectronic [1-3]. Tellurium hyperdoped Si was fabricated by the ion-implantation with different doses ranging from 1.09×1015 to 1.25×1016 atom/cm2 followed by two ultra-short annealing processing: flash lamp annealing (FLA) and pulsed laser melting (PLM). The structural properties of Te doped Si were characterized by Rutherford backscattering spectrometry / Channeling and Raman scattering. The Raman results show the high quality recrystallization of tellurium implanted Si by both FLA and PLM. In addition the Electrical properties of Tellurium hyperdoping silicon were measured by using a commercial Lakeshore Hall System. The differentiation of conductivity occurs with increasing tellurium concentration, which indicated that upon high concentration doping the insulator-metal transition was observed in tellurium doped Si. Moreover the carrier concentration and Hall mobilities measured at 300 K for different FLA and PLM samples with increasing tellurium concentration were measured. The PLM samples generally have a larger carrier concentration than the FLA samples, the mobility is around 2 times smaller.
Keywords: Hyperdoped Si, Ion-implantation, Flash lamp annealing, Pulsed laser melting
  • Lecture (Conference)
    80. Jahrestagung der DPG und DPG-Frühjahrstagung (80th Annual Conference of the DPG and DPG Spring Meeting), 06.-11.03.2016, Universität Regensburg, Regensburg, Germany
Registration No. 23833 - Permalink

Dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses
Huang, L. G.; Kluge, T.; Cowan, T. E.
Abstract: The dynamics of bulk heating and ionization is investigated both in simulations and theory, which determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. During laser-plasma interactions, the solid density plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A portion of the electrons with relativistic kinetic energy goes through the solid density plasma and transfers energy into the bulk electrons, which results in bulk electron heating. The bulk electron heating is finally translated into the processes of bulk collisional ionization inside the solid target. A simple model based on the Ohmic heating mechanism indicates that the local and temporal profile of bulk return current is essential to determine the temporal evolution of bulk electron temperature. A series of particle-in-cell simulations showing the local heating model is robust in the cases of target with a preplasma and without a preplasma. Predicting the bulk electron heating is then benefit for understanding the collisional ionization dynamics inside the solid targets. The connection of the heating and ionization inside the solid target is further studied using Thomas-Fermi model.
Keywords: bulk heating, ionization, local, temporal,Ohmic heating, return current Registration No. 23832 - Permalink

Putaminal dopamine turnover in de novo Parkinson disease predicts later motor complications
Loehle, M.; Mende, J.; Wolz, M.; Beuthien-Baumann, B.; Oehme, L.; van den Hoff, J.; Kotzerke, J.; Reichmann, H.; Storch, A.
Abstract: Objective: To investigate the predictive value of striatal dopamine turnover in patients with de novo Parkinson disease (PD) for the onset of later motor complications.

Methods: This retrospective, observer-blinded cohort study followed up 31 patients with early PD who completed quantitative 18F-dopa PET imaging to measure striatal 18F-dopa uptake (Kocc) and effective distribution volume ratio (EDVR) as the inverse of dopamine turnover prior to antiparkinsonian treatment. The onset of wearing-off and dyskinesias was determined based on blinded clinical assessments and patient records. The predictive value of baseline PET measures for motor complications was evaluated using Cox proportional hazard models.

Results: During a mean follow-up time of 6.8 years, 18 (58.1%) patients developed wearing-off, 11 (35.5%) dyskinesia, and 20 (64.5%) any motor complication. Patients with dyskinesia and any motor complication showed lower baseline EDVR (higher dopamine turnover) in the putamen than those without dyskinesias and any motor complication, with differences most markedly present in the posterior putamen. Baseline EDVR in the whole and the posterior putamen predicted development of motor complications with an increasing risk with lower EDVR (higher dopamine turnover), whereas EDVR in other regions and Kocc did not correlate with motor complications. Correspondingly, Kaplan-Meier curves showed reduced survival from motor complications in patients with lower baseline EDVR (higher dopamine turnover) in the posterior putamen with ongoing levodopa treatment and disease duration.

Conclusions: Elevated putaminal dopamine turnover in de novo PD is associated with an increased risk for later motor complications and comprises a disease-intrinsic predisposing factor for their development.
Registration No. 23830 - Permalink

An outlook on the rare earth elements mining industry
Barakos, G.; Mischo, H.; Gutzmer, J.
Abstract: How learning from the mistakes of the past can contribute to building a strong global rare earth elements supply chain
  • Other report
    Carlton Victoria, Australia: The Australasian Institute of Mining and Metallurgy, 2016

Downloads:

Registration No. 23828 - Permalink

Legislation; Challenges and Policy Strategies: In search for a regulatory framework for sustainable development in the Rare Earths mining industry
Barakos, G.; Mischo, H.; Gutzmer, J.
Abstract: One of the major issues that the Rare Earth Elements Mining Industry has to deal with is the legislation vacuum that exists in many countries around the world. Among these, are countries which have long history and tradition in mining. In many cases the lack of direct legislation for REE mine management as well as for other potentially polluting industries can be a barrier to sustainable development. Moreover, the case of lax legislation in China has led to environmental pollution problems and extended smuggling of rare earth elements.
This paper looks into the current regulatory status on the mining of REEs, identifies the loopholes and suggests some elements for a new global legislation framework for sustainable development in the REE mining industry. The setting of this regulatory framework will be in line with the present and future challenges of the rare earths market as well as with the policy strategies that are defined internationally. The aim of such a legislative framework will be to strengthen the global rare earth elements supply chain, appease social concerns and ensure the preservation and conservation of the environment.
  • Contribution to proceedings
    SME Annual Meeting 2016, 21.-24.02.2016, Phoenix, United States of America
    SME Annual Meeting 2016, Phoenix, USA: SME
Registration No. 23827 - Permalink

Status Quo and Future Evaluations of Global Rare Earth Mining (with Respect to Special Rare Earth Element-industry Criteria)
Barakos, G.; Mischo, H.; Gutzmer, J.
Abstract: The continuously growing demand for rare earth elements (REEs), in combination with the crisis of 2009 and the price spike of 2011, has initiated a treasure hunt for rare earth deposits all over the world in recent years. Since then, commodity prices have declined and are now quite stable, yet the world is still dependent on China’s dominance of the market and its export policies. Exploration is unremitting and numerous resources of potential interest have already been revealed in many countries; however, proceeding to mining operations is not that simple, especially when it comes to the exploitation of rare earth deposits. Evaluating the feasibility of a mining project is always a unique, sensitive and rather complex process that depends on multiple criteria. This paper focuses on clarifying the present and future global situation in the development of respective deposits and on identifying rare earth-specific criteria that influence the overall feasibility assessments of any potential (especially underground) mining projects. Environmental impacts, legislation issues and the presence of radioactive pollutants are some of the notable boundary conditions that govern rare earth mining operations and need to be taken into consideration. Furthermore, the balance problem between the supply and demand of the different REEs can determine decisively whether a deposit of specific REEs is economically exploitable. For this reason, evaluations are made regarding the future strategies to be enacted in order for the rest of the world to detach itself from this situation. The ultimate goal of these evaluations is for them to be incorporated in an overall assessment tool for rare earth underground mining procedures that will be implemented in real case studies to determine their sustainability.
  • Contribution to proceedings
    Third International Future Mining Conference, 04.-06.11.2015, Sydney, Australia
    Third International Future Mining Conference, Carlton Victoria, Australia: The Australasian Institute of Mining and Metallurg, 978 1 925100 40 2
Registration No. 23826 - Permalink

Improved progression free survival for patients with diabetes and locally advanced non-small cell lung cancer (NSCLC) using metformin during concurrent chemoradiotherapy.
Wink, K. C.; Belderbos, J. S.; Dieleman, E. M.; Rossi, M.; Rasch, C. R.; Damhuis, R. A.; Houben, R. M.; Troost, E. G.
Abstract: BACKGROUND AND PURPOSE:

The aim was to investigate whether the use of metformin during concurrent chemoradiotherapy (cCRT) for locally advanced non-small cell lung cancer (NSCLC) improved treatment outcome.
MATERIAL AND METHODS:

A total of 682 patients were included in this retrospective cohort study (59 metformin users, 623 control patients). All received cCRT in one of three participating radiation oncology departments in the Netherlands between January 2008 and January 2013. Primary endpoint was locoregional recurrence free survival (LRFS), secondary endpoints were overall survival (OS), progression-free survival (PFS) and distant metastasis free survival (DMFS).
RESULTS:

No significant differences in LRFS or OS were found. Metformin use was associated with an improved DMFS (74% versus 53% at 2years; p=0.01) and PFS (58% versus 37% at 2years and a median PFS of 41months versus 15months; p=0.01). In a multivariate cox-regression analysis, the use of metformin was a statistically significant independent variable for DMFS and PFS (p=0.02 and 0.03).
CONCLUSIONS:

Metformin use during cCRT is associated with an improved DMFS and PFS for locally advanced NSCLC patients, suggesting that metformin may be a valuable treatment addition in these patients. Evidently, our results merit to be verified in a prospective trial.

Keywords: Chemotherapy; Diabetes; Metformin; NSCLC; Radiotherapy Registration No. 23824 - Permalink

An Epigenetic Reprogramming Strategy to Resensitize Radioresistant Prostate Cancer Cells.
Peitzsch, C.; Cojoc, M.; Hein, L.; Kurth, I.; Mäbert, K.; Trautmann, F.; Klink, B.; Schröck, E.; Wirth, M. P.; Krause, M.; Stakhovsky, E. A.; Telegeev, G. D.; Novotny, V.; Toma, M.; Muders, M.; Baretton, G. B.; Frame, F. M.; Maitland, N. J.; Baumann, M.; Dubrovska, A.
Abstract: Radiotherapy is a mainstay of curative prostate cancer treatment, but risks of recurrence after treatment remain significant in locally advanced disease. Given that tumor relapse can be attributed to a population of cancer stem cells (CSC) that survives radiotherapy, analysis of this cell population might illuminate tactics to personalize treatment. However, this direction remains challenging given the plastic nature of prostate cancers following treatment. We show here that irradiating prostate cancer cells stimulates a durable upregulation of stem cell markers that epigenetically reprogram these cells. In both tumorigenic and radioresistant cell populations, a phenotypic switch occurred during a course of radiotherapy that was associated with stable genetic and epigenetic changes. Specifically, we found that irradiation triggered histone H3 methylation at the promoter of the CSC marker aldehyde dehydrogenase 1A1 (ALDH1A1), stimulating its gene transcription. Inhibiting this methylation event triggered apoptosis, promoted radiosensitization, and hindered tumorigenicity of radioresistant prostate cancer cells. Overall, our results suggest that epigenetic therapies may restore the cytotoxic effects of irradiation in radioresistant CSC populations. Cancer Res; 76(9); 2637-51. ©2016 AACR. Registration No. 23823 - Permalink

[Melanoma brain metastases : Treatment options]. [Hirnmetastasen des malignen Melanoms].
Rauschenberg, R.; Tabatabai, G.; Troost, E. G.; Garzarolli, M.; Beissert, S.; Meier, F.
Abstract: Hirnmetastasen treten bei der Mehrheit der Patienten mit metastasiertem Melanom auf und sind die häufigste Todesursache. Bis vor Kurzem war die Lokaltherapie die einzige Option für die Kontrolle von Hirnmetastasen. Inzwischen stehen wirksame systemische Therapieoptionen zur Verfügung. Bei Verdacht auf Hirnmetastasen sind eine Staging-Diagnostik mit Craniale Magnetresonanztomographie (cMRT) sowie eine neurologische Untersuchung indiziert. Für die Therapieplanung sollten prognostische Faktoren wie Anzahl und Symptomatik der zerebralen Metastasen, der LDH- und S100-Wert im Serum, die extrazerebrale Metastasierung sowie der ECOG (Eastern Cooperative Oncology Group)-Status einbezogen werden. Die Therapieentscheidung bzw. -durchführung sollte interdisziplinär bzw. multimodal erfolgen. Bei singulären Hirnmetastasen sind die neurochirurgische Resektion und die stereotaktische Radiatio etabliert. Das Behandlungsspektrum hat sich durch die Neuzulassung von wirksamen Immuntherapien (CTLA-4- und PD-1-Antikörper) sowie zielgerichteten Therapien (BRAF-und MEK-Inhibitoren) erheblich erweitert. Die palliative Ganzhirnradiatio wird bei multiplen symptomatischen Hirnmetastasen eingesetzt, wobei bisher kein signifikanter Vorteil für das Gesamtüberleben gezeigt werden konnte. Bei erhöhtem intrakraniellem Druck und epileptischen Anfällen sind Kortikosteroide und Antikonvulsiva indiziert. In aktuellen klinischen Studien werden für Melanompatienten mit Hirnmetastasen neue Therapieoptionen wie PD-1-Antikörper, Ipilimumab plus Nivolumab, BRAF-Inhibitoren plus MEK-Inhibitoren sowie stereotaktische Radiatio in Kombination mit Immuntherapie bzw. zielgerichteter Therapie untersucht.
Keywords: Resektion Radiatio Systemtherapie BRAF-Inhibitor Immuntherapie Registration No. 23822 - Permalink

Efficacy of Beta1 Integrin and EGFR Targeting in Sphere-Forming Human Head and Neck Cancer Cells.
Zscheppang, K.; Kurth, I.; Wachtel, N.; Dubrovska, A.; Kunz-Schughart, L. A.; Cordes, N.
Abstract: BACKGROUND:

Resistance to radiotherapy continues to be a limiting factor in the treatment of cancer including head and neck squamous cell carcinoma (HNSCC). Simultaneous targeting of β1 integrin and EGFR was shown to have a higher radiosensitizing potential than mono-targeting in the majority of tested HNSCC cancer models. As tumor-initiating cells (TIC) are thought to play a key role for therapy resistance and recurrence and can be enriched in sphere forming conditions, this study investigated the efficacy of β1 integrin/EGFR targeting without and in combination with X-ray irradiation on the behavior of sphere-forming cells (SFC).
METHODS:

HNSCC cell lines (UTSCC15, UTSCC5, Cal33, SAS) were injected subcutaneously into nude mice for tumor up-take and plated for primary and secondary sphere formation under non-adhesive conditions which is thought to reflect the enrichment of SFC and their self-renewal capacity, respectively. Treatment was accomplished by inhibitory antibodies for β1 integrin (AIIB2) and EGFR (Cetuximab) as well as X-ray irradiation (2 - 6 Gy single doses). Further, flow cytometry for TIC marker expression and cell cycling as well as Western blotting for DNA repair protein expression and phosphorylation were employed.
RESULTS:

We found higher primary and secondary sphere forming capacity of SAS cells relative to other HNSCC cell lines, which was in line with the tumor up-take rates of SAS versus UTSCC15 cells. AIIB2 and Cetuximab administration had minor cytotoxic and no radiosensitizing effects on SFC. Intriguingly, secondary SAS spheres, representing the fraction of surviving SFC upon passaging, showed greatly enhanced radiosensitivity compared to primary spheres. Intriguingly, neither AIIB2 nor Cetuximab significantly altered basal sphere forming capacity and radiosensitivity. While an increased accumulation of G0/G1 phase cells was observable in secondary SAS spheres, DNA double strand break repair indicated no difference on the basis of significantly enhanced ATM and Chk2 dephosphorylation upon irradiation.
CONCLUSIONS:

In the HNSCC model, sphere-forming conditions select for cells, which are unsusceptible to both anti-β1 integrin and anti-EGFR inhibitory antibodies. With regard to primary and secondary sphere formation, our data suggest that both of these SFC fractions express distinct survival strategies independent from β1 integrin and EGFR and that future work is warranted to better understand SFC survival and enrichment before and after treatment to untangle the underlying mechanisms for identifying novel, druggable cancer targets in SFC.

Keywords: EGFR.; Sphere formation; beta1 integrin; head and neck squamous cell carcinoma; radiosensitivity Registration No. 23821 - Permalink

Comparative analysis of transcriptomics based hypoxia signatures in head- and neck squamous cell carcinoma.
Tawk, B.; Schwager, C.; Deffaa, O.; Dyckhoff, G.; Warta, R.; Linge, A.; Krause, M.; Weichert, W.; Baumann, M.; Herold-Mende, C.; Debus, J.; Abdollahi, A.
Abstract: BACKGROUND AND PURPOSE:

Hypoxia renders tumors resistant to radiotherapy. However, the paucity of sensitive and reliable methods for detection of tumor hypoxia limits the translation of novel therapy strategies targeting this well-known resistance factor. We sought to investigate the ability of three previously discovered transcriptomics based hypoxia signatures to identify hypoxic tumors and consequently discriminate between patients with poor- vs. good prognosis.
MATERIAL AND METHODS:

Three different hypoxia gene signatures developed by Toustrup et al., Eustace et al. and Lendahl et al. were evaluated in an independent cohort consisting of 302 patients with head and neck squamous cell carcinoma (HNSCC). Clinical data as well as genome-wide RNA-sequencing based gene expression data were retrieved from The Cancer Genome Atlas (TCGA). Clustering and statistical analysis were performed using Statistical Utilities for Microarray and Omics data (SUMO) software package.
RESULTS:

The 15 gene hypoxia signature developed by Toustrup et al. as well as the 30 gene signature by Lendahl et al. successfully discriminated between HNSCC patients with poor vs. good prognosis. The 26 gene signature developed by Eustace et al. was prognostic in HNSCC patients treated with radiotherapy. The best prognostic value was achieved when a consensus cohort of patients was assigned, i.e., low- or high- degree of tumor hypoxia was found, by all three signatures. Interestingly, the number of signature genes could be successfully reduced to the only common gene across all three signatures, i.e., P4HA1, encoding prolyl-4-hydroxylase, alpha polypeptide I.
CONCLUSIONS:

This is the first independent proof for the feasibility of hypoxia gene expression signatures as a prognostic tool in HNSCC patients.

Keywords: Gene signatures; Head and neck squamous cell carcinoma; Hypoxia; Transcriptomics Registration No. 23820 - Permalink

Prognostic value of blood-biomarkers related to hypoxia, inflammation, immune response and tumour load in non-small cell lung cancer - A survival model with external validation.
Carvalho, S.; Troost, E. G.; Bons, J.; Menheere, P.; Lambin, P.; Oberije, C.
Abstract: AIM:

Improve the prognostic prediction of clinical variables for non-small cell lung cancer (NSCLC), by selecting from blood-biomarkers, non-invasively describing hypoxia, inflammation and tumour load.
METHODS:

Model development and validation included 182 and 181 inoperable stage I-IIIB NSCLC patients treated radically with radiotherapy (55.2%) or chemo-radiotherapy (44.8%). Least absolute shrinkage and selection operator (LASSO), selected from blood-biomarkers related to hypoxia [osteopontin (OPN) and carbonic anhydrase IX (CA-IX)], inflammation [interleukin-6 (IL-6), IL-8, and C-reactive protein (CRP)], and tumour load [carcinoembryonic antigen (CEA), and cytokeratin fragment 21-1 (Cyfra 21-1)]. Sequent model extension selected from alpha-2-macroglobulin (α2M), serum interleukin-2 receptor (sIL2r), toll-like receptor 4 (TLR4), and vascular endothelial growth factor (VEGF). Discrimination was reported by concordance-index.
RESULTS:

OPN and Cyfra 21-1 (hazard ratios of 3.3 and 1.7) significantly improved a clinical model comprising gender, World Health Organization performance-status, forced expiratory volume in 1s, number of positive lymph node stations, and gross tumour volume, from a concordance-index of 0.66 to 0.70 (validation=0.62 and 0.66). Extension of the validated model yielded a concordance-index of 0.67, including α2M, sIL2r and VEGF (hazard ratios of 4.6, 3.1, and 1.4).
CONCLUSION:

Improvement of a clinical model including hypoxia and tumour load blood-biomarkers was validated. New immunological markers were associated with overall survival. Data and models can be found at www.cancerdata.org (http://dx.doi.org/10.17195/candat.2016.04.1) and www.predictcancer.org.

Keywords: Blood-biomarkers; NSCLC; Prognostic model Registration No. 23819 - Permalink

Bioassociation of uranium on halophilic archaea analyzed with microscopic and spectroscopic methods
Bader, M.; Müller, K.; Foerstendorf, H.; Schmidt, M.; Musat, N.; Stumpf, T.; Cherkouk, A.
Abstract: Salt rock is one potential host rock formation for the final disposal of radioactive waste in Germany. Next to geochemical and physical parameters in salt rock indigenous microorganisms have to be taken into account for the safety performance of the deep geological repository. The halophilic archaeon Halobacterium noricense DSM-15987 is indigenous in salt rock and was originally isolated from a salt mine in Austria [1]. This extreme halophilic archaeon was used to study its interactions with uranium. ICP-MS analyses of the supernatant were performed to document the bioassociation kinetic of uranium to cells of Hbt. noricense, which showed a so far unknown behavior. More detailed information about the formed complexes were gained by using different spectroscopic and microscopic methods. All experiments with Hbt. noricense have to be performed at 3 M NaCl which leads to a limited selection of methods or makes their application complicated. Hence, different approaches to generate samples for electron microscopy have been performed and will be the focus of the talk. For example preparation steps like fixation as well as washing steps to get rid of the salt have been varied to obtain SEM and TEM samples which are unaffected by the preparation steps. The used electron microscopic methods have been a useful tool for various reasons. First, by using SEM coupled with EDX a localization of uranium was possible. Second, changes in cell agglomeration as well as uranium bioassociation over time were visible supporting the so far unknown multi-stage bioassociation process. In combination with spectroscopic tools like infrared spectroscopy and laser fluorescence spectroscopy the applied microscopic methods were essential for a better understanding of the bioassociation process of uranium to cells of the halophilic archaeon.
  • Lecture (others)
    Open ProVIS Meetings, 16.06.2016, Leipzig, Deutschland
Registration No. 23816 - Permalink

Reshaping on demand
Makarov, D.
Abstract: The emergent field of flexible magneto-electronics is reviewed with respect to its application potential for e-mobility, personal appliances and medicine.
Keywords: shapeable magnetoelectronics Registration No. 23814 - Permalink

New insights into the petrogenesis of the Jameson Range layered intrusion and associated Fe-Ti-P-V-PGE-Au mineralisation, West Musgrave Province, Western Australia
Karykowski, B. T.; Polito, P. A.; Maier, W. D.; Gutzmer, J.; Krause, J.
Abstract: The Mesoproterozoic Jameson Range intrusion forms part of the Giles Complex, Musgrave Province, Western Australia. It is predominantly mafic in composition comprising olivine-bearing gabbroic lithologies with variable amounts of magnetite and ilmenite. Lithologies containing more than 50 vol% magnetite and ilmenite are classified as magnetitites. The Jameson Range hosts several of these magnetitites forming laterally extensive layers, which can be traced for at least 19 km as continuous magnetic anomalies. Similar occurrences of magnetitites are known from the upper parts of other layered intrusions, such as the Bushveld Complex. In addition, the intrusion hosts several P-rich zones, one of which is at least 59 m in thickness containing 1.0 wt% P2O5. The P-rich zones are not directly associated with the magnetitites, but they mostly occur slightly above them. The mineral chemistry of the Jameson Range cumulates is relatively evolved with olivine compositions ranging from Fo44 to Fo60 and plagioclase compositions varying between An56 and An59. The Mg# (100 × Mg / (Mg + Fe)) of ortho- and clinopyroxene ranges from 60 to 61 and from 70 to 75, respectively. Magnetite compositions are characterised by low TiO2 concentrations varying from 0.39 to 3.04 wt% representing near end-member magnetite with up to 1.2 wt% Cr and 1.3 wt% V, respectively. The basal magnetite layer reaches up to 68.8 wt% Fe2O3(t) and 24.2 wt% TiO2, and it is also markedly enriched in Cu (up to 0.3 wt% Cu), V (up to 1.05 wt% V2O5) and platinum-group elements (PGE) (up to 2 ppm Pt + Pd). Sulphide minerals comprising bornite, chalcopyrite and minor pentlandite occur finely disseminated in the magnetitite and account for the elevated base metal and PGE concentrations. Modelling indicates that the PGE mineralisation was formed at very high R factors of up to 100,000, which is typical for PGE reefs in layered intrusions. Whole rock geochemical and mineralogical data of the magnetite layers and their host rocks further allow for a refinement of current formation models of layered igneous sequences. Several lines of evidence suggest that the magnetite layers formed in response to primarily density-controlled mineral sorting within crystal slurries, although the grain size also affects the sorting process.
Keywords: Giles Complex; Layered intrusion; Magnetite layers; Musgrave Province; Platinum-group elements Registration No. 23807 - Permalink

Secondary Neutron Fields During Modern Cancer Treatments -- Simulation and Measurement of the Secondary Radiation Field at the University Proton Therapy Dresden (UPTD)
Lutz, B.; Reginatto, M.; Zboril, M.; Swanson, R.; Enghardt, W.; Fiedler, F.
Abstract: Particle therapy is a strongly growing field in cancer therapy. More than 60 treatment centres are currently operating worldwide and the total number will reach more than 90 by 2017(1). The majority of the centres uses protons to treat patients.

With the increasing importance of particle therapy, the development of application-specific monitoring systems has received a significant boost. On the one side, there are the radio-protection questions like the secondary dose to patients or to radio-sensitive equipment. On the other side, there are the methods that intend to verify the correct application of the treatment dose, during or short after the treatment, like prompt-gamma-imaging or -timing, or PET. For both groups of measurements, a good understanding of the secondary radiation field is crucial.

The greatest challenge in determining the secondary radiation field comes from neutrons. The spectra of the neutrons, generated by protons of therapeutic energies, extend far beyond the specification of most commercially available dosimeters. Additionally, the generated neutron fields are spatially non-uniform and in case of passive field formation strongly dependent on the operational setting. Combined with the very limited spatial and spectral resolution of the available neutron detectors, many details of the field cannot be experimentally resolved. Therefore, a dependable measurement of the neutron field requires a detailed simulation of the neutron generation in the treatment system.

The talk gives an overview of the passive proton field formation used at the University Proton Therapy Dresden. The challenges in modelling and measuring the resulting neutron fields are discussed. The current status of the simulation model is presented. The predicted neutron fields are also compared to first experimental measurements with a neutron REM meter and an extended Bonner sphere spectrometer.

(1) Particle Therapy Co-Operative Group (PTCOG), www.ptcog.ch

Keywords: neutron simulation neutron experiment UPTD
  • Lecture (others)
    lunch seminar University of Michigan, 15.06.2016, Ann Arbor, USA
Registration No. 23805 - Permalink

Phosphorene under electron beam: from monolayer to one-dimensional chains
Vierimaa, V. V.; Krasheninnikov, A. V.; Komsa, H.-P.
Abstract: Phosphorene, a single sheet of black phosphorus, is an elemental two-dimensional material with unique properties and potential applications in semiconductor technology. While few-layer flakes of the material have been characterized using transmission electron microscopy, very little is known about its response to electron irradiation, which may be particularly important in the context of top-down engineering of phosphorus nanostructures using a focused electron beam. Here, using first-principles simulations, we study the production of defects in a single phosphorene sheet under impacts of energetic electrons. By employing the McKinley–Feshbach formalism and accounting for the thermal motion of atoms, we assess the cross section for atom displacement as a function of electron energy. We further investigate the ener- getics and dynamics of point defects and the stability of ribbons and edges under an electron beam. Finally, we show that P atomic chains should be surprisingly stable, and their atomic structure is not linear giving rise to the absence of a gap in the electronic spectrum.
Keywords: Phosphorene, 2D materials, first-principles simulations, defect, irradiation

Downloads:

Registration No. 23802 - Permalink

Biologische Laugung von Kupfer aus Kupferschiefer
Kostudis, S.; Bachmann, K.; Kutsche, S.; Pollmann, K.; Gutzmer, J.
Abstract: Die Kupferschiefervorkommen Mitteleuropas stellen eine anspruchsvolle lokale Ressource von Basismetallen wie Kupfer, aber auch strategischen Elementen wie Gallium oder Molybdän dar. Um diese Wertstoffe aus dem Kupferschiefer umweltfreundlich und effizient zu gewinnen, werden biotechnologische Laugungsverfahren untersucht. Die klassische Biolaugung, die säureliebende Mikroorganismen verwendet, stößt beim Kupferschiefer aufgrund hoher Karbonatgehalte von bis zu 18 % (Material aus Polkowice, Polen)an ihre Grenzen, da der optimale mikrobielle pH-Bereich um pH 2 überschritten wird. Daher werden alternative Verfahren getestet; so beispielsweise die Produktion organischer Säuren wie Glutamin- oder Zitronensäure durch Mikroorganismen. Hier wurden mithilfe von Schimmelpilzen bereits gute Kupferausbeuten aus Material des Kupferschiefertyps erzielt. Allerdings konnte in eigenen Arbeiten gezeigt werden, dass bei der Verwendung organischer Säuren die Laugungseffektivität im neutralen pH-Bereich höher ist als im schwach sauren Milieu. Daher stellt der Beitrag Ergebnisse zur Biolaugung von Kupfer aus Kupferschiefer im neutralen pH-Bereich vor. Dabei werden sowohl geochemische als auch mineralogische Daten präsentiert.
  • Poster
    Jahrestagung Aufbereitung und Recycling, 11.-12.11.2015, Freiberg, Deutschland
Registration No. 23801 - Permalink

Resource Analytics:An introduction into automated mineralogy and application on REE
Birtel, S.
Abstract: An introduction into automated mineralogy and application on REE is an oral contribution to the Ist Workshop Goiano de Terras Raras in Catalo, Brasil which was oraginzed by the universidad de federal de Goias within the 'fact finding' Mission for a CLIENT II proposal. The workshop itself had ca 300 participants including the German and Brasilian delegations. The presentation is about the analytical facilites at HIF in particular MLA analytics, some technical background on MLA and case studies to demonstrate the application of MLA to specific challenges in ore and processiong product characterisation with focus on REE elements
  • Invited lecture (Conferences)
    Ist Workshop Goiano de Terras Raras, 23.-25.05.2016, Catalao, Brazil
Registration No. 23800 - Permalink

Zinc corrosion after loss-of-coolant accidents in pressurized water reactors - Thermo- and Fluid-dynamic effects
Seeliger, A.; Alt, S.; Kästner, W.; Renger, S.; Kryk, H.; Harm, U.
Abstract: Within the framework of the German reactor safety research, generic experimental investigations were carried out aiming at thermal-hydraulic consequences of physicochemical mechanisms, caused by dissolution of zinc in boric acid during corrosion processes at hot-dip galvanized surfaces of containment internals at lower coolant temperatures and the subsequent precipitation of solid zinc borates in PWR core regions of higher temperature. This constellation can occur during sump recirculation operation of ECCS after LOCA. Hot-dip galvanized components, which are installed inside a PWR containment, may act as zinc sources. Getting in contact with boric acid coolant, zinc at their surfaces is released into coolant in form of ions due to corrosion processes. As a long-term behavior resp. over a time period of several days, metal layers of zinc and zinc alloys can dissolve extensively.
First fundamental studies at laboratory scale were done at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Their experimental results were picked up for the definition of boundary conditions for experiments at semi-technical scale at the University of Applied Sciences Zittau/Görlitz (HSZG). Electrical heating rods with zircaloy cladding tubes have been used as fuel rod simulators.
As near-plant core components, a 3x3 configuration of heating rods (HRC) and a shortened, partially heatable PWR fuel assembly dummy were applied into cooling circuits. The HRC module include segments of spacers for a suitable representation of a heating channel geometry. Formations of different solid zinc compounds (mainly borates) were observed at heatable zircaloy surfaces and characterized in detail for heating-up to several coolant temperatures. As a strict consequence of their proven influence on heat removal and coolant flow behavior in the PWR core, preventive water-chemical methods were defined and tested.

Keywords: loss-of-coolant accident, LOCA, pressurized water reactor, PWR, zinc, corrosion, zinc borate, boric acid, reactor safety research, downstream effects Registration No. 23798 - Permalink

P1407 - Verfahren zur Hydrophilisierung von Metalloxid-Nanopartikeln
Hunoldt, S.; Stephan, H.
Abstract: Die vorliegende Erfindung betrifft ein Verfahren zur Hydrophilisierung von Metalloxid-Nanopartikeln durch eine gezielte Modifizierung der Gitterplätze und die Verwendung dieser, wobei das Verfahren zur Herstellung oberflächenhydrophilisierter Metalloxid-Nanopartikel die folgenden Schritte umfasst:
a. Aktivierung von hydrophoben Metalloxid-Nanopartikel in einem organischen Lösungsmittel, durch Zugabe einer organophilen Base,
b. Zugabe eines aktiven C1-6-Alkans, aufweisend eine Funktionalität,
c. Abtrennung des Niederschlags und Überführung in eine wässrige Lösung,
wobei die kovalente Anbindung in (b) über ein Kohlenstoffatom der C1-6-Alkylgruppe des aktiven C1-6-Alkans an den Nanopartikel-eigenen, die Oberflächengitterplätze der Metalloxid-Nanopartikel besetzenden, Sauerstoff erfolgt.
  • Patent
    DE102014218355 - Offenlegung 17.03.2016
Registration No. 23794 - Permalink

Underground nuclear astrophysics: Why and how
Best, A.; Caciolli, A.; Fulop, Z.; Gyurky, G.; Laubenstein, M.; Napolitani, E.; Rigato, V.; Roca, V.; Szucs, T.
Abstract: The goal of nuclear astrophysics is to measure cross-sections of nuclear physics reactions of interest in astrophysics. At stars temperatures, these cross-sections are very low due to the suppression of the Coulomb barrier. Cosmic-ray-induced background can seriously limit the determination of reaction cross-sections at energies relevant to astrophysical processes and experimental setups should be arranged in order to improve the signal-to-noise ratio. Placing experiments in underground sites, however, reduces this background opening the way towards ultra low cross-section determination. LUNA (Laboratory for Underground Nuclear Astrophysics) was pioneer in this sense. Two accelerators were mounted at the INFN National Laboratories of Gran Sasso (LNGS) allowing to study nuclear reactions close to stellar energies. A summary of the relevant technology used, including accelerators, target production and characterisation, and background treatment is given. Registration No. 23793 - Permalink

P1508 - Complementary resistance switch,contact-connected polycrystalline piezo-orferroelectric thin-film layer,method for encrypting a bit sequence
Schmidt, H.; Bürger, D.; Du, N.; Manjunath, N.; Skorupa, I.; You, T.
Abstract: Gemäß verschiedenen Ausführungsformen kann ein komplementärer Widerstandsschalter aufweisen: zwei äußere Kontakte (T1, T2 ), zwischen denen zwei piezo- oder ferroelektrische Schichten (11a und 11b) liegen, die durch einen inneren gemeinsamen Kontakt voneinander getrennt sind, dadurch gekennzeichnet, dass mindestens ein Bereich der piezo- oder ferroelektrischen Schicht (11a und 11b) mindestens einmal derart modifiziert ist, dass in der piezo- oder ferroelektrischen Schicht (11a und 11b) jeweils zwischen dem inneren Kontakt und dem zugehörigen äußeren Kontakt ein Bereich (11') der Dicke (d ') entsteht, weicher mindestens zusätzlich in einem Bereich (11") der Dicke (d") modifiziert sein kann, wobei a) die äußeren Kontakte Oberflächenkontakte (Sa) und (Sb) und der innere Kontakt ein gemeinsamer zugehöriger Gegenkontakt (O) oder die äußeren Kontakte Gegenkontakte (Oa) und (Ob) und der innere Kontakt ein gemeinsamer zugehöriger Oberflächenkontakt (S) sind, b) die Oberflächenkontakte (S), (Sa) und (Sb) gleichrichtend und die Gegenkontakte (O) bzw. (Oa) und (Ob) nicht-gleichrichtend sind, c) sich die modifizierten Bereiche in der piezo- oder ferroelektrischen Schicht (11a und 11b) an den Oberflächenkontakten (S) bzw. (Sa) und (Sb) ausbilden, d) die piezo- oder ferroelektrische Schichten (11, 11', 11") verschiedene verspannungsabhängige strukturelle Phasen mit unterschiedlicher Bandlücke und/oder unterschiedlicher Polarisationsladung aufweisen, und e) die elektrische Leitfähigkeit der piezo- oder ferroelektrischen Schichten (11, 11', 11") unterschiedlich ist.
  • Patent
    US20150358151 - Offenlegung 10.12.2015
Registration No. 23792 - Permalink

P1507 - Komplementärer Widerstandsschalter, kontaktierte Polykristalline piezo- oder ferroelektrische Dünnschicht, Verfahren zum Verschlüsseln einer Bitfolge
Schmidt, H.; Bürger, D.; Du, N.; Manjunath, N.; Skorupa, I.; You, T.
Abstract: Gemäß verschiedenen Ausführungsformen kann ein komplementärer Widerstandsschalter aufweisen: zwei äußere Kontakte (T1, T2 ), zwischen denen zwei piezo- oder ferroelektrische Schichten (11a und 11b) liegen, die durch einen inneren gemeinsamen Kontakt voneinander getrennt sind, dadurch gekennzeichnet, dass mindestens ein Bereich der piezo- oder ferroelektrischen Schicht (11a und 11b) mindestens einmal derart modifiziert ist, dass in der piezo- oder ferroelektrischen Schicht (11a und 11b) jeweils zwischen dem inneren Kontakt und dem zugehörigen äußeren Kontakt ein Bereich (11') der Dicke (d ') entsteht, weicher mindestens zusätzlich in einem Bereich (11") der Dicke (d") modifiziert sein kann, wobei a) die äußeren Kontakte Oberflächenkontakte (Sa) und (Sb) und der innere Kontakt ein gemeinsamer zugehöriger Gegenkontakt (O) oder die äußeren Kontakte Gegenkontakte (Oa) und (Ob) und der innere Kontakt ein gemeinsamer zugehöriger Oberflächenkontakt (S) sind, b) die Oberflächenkontakte (S), (Sa) und (Sb) gleichrichtend und die Gegenkontakte (O) bzw. (Oa) und (Ob) nicht-gleichrichtend sind, c) sich die modifizierten Bereiche in der piezo- oder ferroelektrischen Schicht (11a und 11b) an den Oberflächenkontakten (S) bzw. (Sa) und (Sb) ausbilden, d) die piezo- oder ferroelektrische Schichten (11, 11', 11") verschiedene verspannungsabhängige strukturelle Phasen mit unterschiedlicher Bandlücke und/oder unterschiedlicher Polarisationsladung aufweisen, und e) die elektrische Leitfähigkeit der piezo- oder ferroelektrischen Schichten (11, 11', 11") unterschiedlich ist.
  • Patent
    EP2917946 - Offenlegung 16.09.2015
Registration No. 23791 - Permalink

P1512 - Gittersensor-System zum Charakterisieren einer Fluidströmung
Schleicher, E.; Tschofen, M.; Pietruske, H.
Abstract: Die Erfindung betrifft ein Gittersensor-System zum Charakterisieren einer Fluidströmung, aufweisend einen Sensoreinschub mit einem Gittersensorelement und eine Strömungsführung mit einer Einlass-Leitung, einer Auslass-Leitung und einer dazwischen angeordneten Einschubaufnahme zum Aufnehmen des Sensoreinschubes, wobei von der Strömungsführung ein geradliniger Strömungsweg gebildet ist, und wobei die Einschubaufnahme derart ausgebildet ist, dass der Sensoreinschub entlang einer quer zu dem Strömungsweg verlaufenden Einschubrichtung in die Einschubaufnahme einschiebbar ist.
  • Patent
    DE102015117084 - Erteilung 19.05.2016
Registration No. 23790 - Permalink

P1501 - Anordnung zum Erfassen der Strömungsgeschwindigkeit einer Fluidströmung in einem Strömungsquerschnitt
Hampel, U.
Abstract: Die Erfindung betrifft eine Anordnung zum Erfassen der Strömungsgeschwindigkeit einer Fluidströmung in einem Strömungsquerschnitt, aufweisend ein Sensorelement, eine Spannungsbeaufschlagungs-Einrichtung und eine Auswerteeinrichtung, wobei das Sensorelement mehrere unter Ausbildung von Kreuzungspunkten gitterartig angeordnete Elektroden und Gegenelektroden mit dazwischen angeordneten schwingfähigen Körpern aufweist, wobei die Spannungsbeaufschlagungs-Einrichtung zum Anlegen einer elektrischen Spannung zwischen die Elektrode und die Gegenelektrode der einzelnen Kreuzungspunkte ausgebildet ist, sodass das dadurch hervorgerufene elektrische Feld bei in die Fluidströmung eingebrachtem Sensorelement durch die strömungsinduzierte Schwingung der schwingfähigen Körper variiert wird, und wobei die Auswerteeinrichtung zum Ermitteln der lokalen Strömungsgeschwindigkeiten an den einzelnen Kreuzungspunkten mittels Auswertens der zugehörigen Feldvariation ausgebildet ist.
  • Patent
    DE102015100213 - Erteilung 25.05.2016
Registration No. 23789 - Permalink

P1411 - Anordnung und Verfahren zur Dispersionsmessung sowie Mehrphasenapparat mit einer solchen Anordnung
Hampel, U.
Abstract: Die Erfindung betrifft eine Anordnung und ein Verfahren zur Dispersionsmessung sowie einen Mehrphasenapparat mit einer solchen Anordnung, wobei die Anordnung zum Ermitteln der Dispersion einer dispersen ersten Phase beim Durchlaufen eines Strömungsweges innerhalb einer kontinuierlichen zweiten Phase vorgesehen ist und zum Durchführen folgender Schritte ausgebildet ist: Zuführen eines Stoffstromes der ersten Phase in die zweite Phase an einer Zuführposition zur Ausbildung eines Gemischs mit der ersten Phase und der zweiten Phase, wobei der Stoffstrom der ersten Phase mit einem vorgegebenen Zuführstrom-Zeitverlauf moduliert wird; Erfassen eines zeitlichen Verlaufs eines Messsignals, das den Gehalt der ersten Phase in dem Gemisch an einer stromabwärts der Zuführposition angeordneten Messposition repräsentiert, als Messsignal-Zeitverlauf; und Charakterisieren der Dispersion der ersten Phase basierend auf dem Messsignal-Zeitverlauf.
  • Patent
    DE102014118649 - Erteilung 24.12.2015
Registration No. 23788 - Permalink

P1408 - Photochemische Entfernung von Uran(VI)-Verbindungen aus mit Uran(VI)-verschmutzten Flüssigkeiten
Fahmy, K.; Tsushima, S.; Attia, E.
Abstract: Die Erfindung betrifft ein Verfahren zur Abtrennung von Uran(VI)-Verbindungen aus Uran(VI)-Verbindungen-haltigen Flüssigkeiten mit den Verfahrensschritten herstellen einer Suspension, enthaltend eine Mikrostruktur, aufweisend mindestens ein Flavonoid und mindestens eine amphiphile Substanz, zugeben der Uran(VI)-Verbindungen-haltigen Flüssigkeit zu der Mikrostruktur, wobei eine einen Flavonoid-Uran(VI)-Komplexes, wobei mindestens eine Uran-Spezies mit einer Oxidationsstufe kleiner sechs gebildet wird und entfernen der Uran-Spezies aus der Suspension.
  • Patent
    DE102014225951 - Erteilung 04.02.2016
Registration No. 23787 - Permalink

Investigation of Acidithiobacillus ferrooxidans in pure and mixed-species culture for bioleaching of Theisen sludge from former copper smelting
Klink, C.; Eisen, S.; Daus, B.; Heim, J.; Schlömann, M.; Schopf, S.
Abstract: Aims: The aim of this study was to investigate the potential of bioleaching for the treatment of an environmentally hazardous waste, a blast-furnace flue dust designated Theisen sludge.
Methods and Results: Bioleaching of Theisen sludge was investigated at acidic conditions with Acidithiobacillus ferrooxidans in pure and mixed-species culture with Acidiphilium. In shaking-flask experiments, bioleaching parameters (pH, redox potential, zinc extraction from ZnS, ferrous- and ferric-iron concentration) were controlled regularly. The analysis of the dissolved metals showed that 70% zinc and 45% copper were extracted. Investigations regarding the arsenic and antimony species were performed. When iron ions were lacking, animonate (Sb(V)) and total arsenic concentration were highest in solution. The bioleaching approach was scaled up in stirred-tank bioreactors resulting in higher leaching efficiency of valuable trace elements. Concentrations of dissolved antimony were approx. 23 times, and of cobalt, germanium, and rhenium three times higher in comparison to shaking-flask experiments, when considering the difference in solid load of Theisen sludge.
Conclusions: The extraction of base and trace metals from Theisen sludge, despite of its high content of heavy metals and organic compounds, was
feasible with iron-oxidizing acidophilic bacteria. In stirred-tank bioreactors, the mixed-species culture performed better.
Significance and Impact of the Study: To the best of our knowledge, this study is the first providing an appropriate biological technology for the treatment of Theisen sludge to win valuable elements.

Keywords: acidophilic bacteria, bioleaching of valuable trace elements, stirred-tank bioreactors, Theisen sludge, toxic organic compounds

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Registration No. 23780 - Permalink

Optical ridge waveguides in Nd:LGS crystal produced by combination of swift C5+ ion irradiation and precise diamond blade dicing
Cheng, Y.; Lv, J.; Akhmadaliev, S.; Zhou, S.; Chen, F.
Abstract: We report on the fabrication of optical ridge waveguides in Nd:LGS crystal by using combination of swift C5+ ion irradiation and precise diamond blade dicing. The ridge structures support guidance both at 632.8 nm and 1064 nm wavelength along the TE and TM polarizations. The lowest propagation losses of the ridge waveguide for the TM mode are ~1.6 dB/cm at 632.8 nm and ~1.2 dB/cm at 1064 nm, respectively. The investigation of micro-fluorescence spectra and micro-Raman spectra indicates that the Nd3+ luminescence features have been well preserved and the microstructure of the waveguide region has no significant change after C5+ ion irradiation.
Keywords: Optical waveguide; Nd:LGS crystal; Ion irradiation; Diamond blade dicing Registration No. 23779 - Permalink

Hydrogen release from irradiated elastomers measured by Nuclear Reaction Analysis
Jagielski, J.; Ostaszewska, U.; Bielinski, D.; Grambole, D.; Romaniec, M.; Jozwik, I.; Kozinski, R.; Kosinska, A.
Abstract: Ion irradiation appears as an interesting method of modification of elastomers, especially friction and wear properties. Main structural effect caused by heavy ions is a massive loss of hydrogen from the surface layer leading to its smoothening and shrinking. The paper presents the results of hydrogen release from various elastomers upon irradiation with H+, He+ and Ar+ studied by using Nuclear Reaction Analysis (NRA) method. The analysis of the experimental data indicates that the hydrogen release is controlled by inelastic collisions between ions and target electrons. The last part of the study was focused on preliminary analysis of mechanical properties of irradiated rubbers
Keywords: Ion implantation; Elastomers; Ion beam analysis; Hydrogen release Registration No. 23777 - Permalink

Velocity Measurement For Two-Phase Flows Based On Ultrafast X-ray Tomography
Barthel, F.; Bieberle, M.; Hoppe, D.; Banowski, M.; Hampel, U.
Abstract: The ultrafast electron beam X-ray tomography scanner ROFEX is used for the investigation of multiphase flows. Its functional principle allows us to obtain sequences of cross-sectional flow images, which shows local attenuation properties of the flow. Hence, the X-ray CT images mainly reveal the shape and interfaces of flow constituents, such as gas, liquid and solids via their X-ray contrast. It is, however, more difficult to obtain velocity information from multi phase flows. In this article we discuss different methods to extract information on the velocities of particles or interfaces as well as for continuous phase. For disperse phase velocity measurement, e.g. ingas–liquidorgas–solids flows, we employ cross-correlation based techniques using two imaging planes. Apart from the standard cross-correlation technique we developed a method and algorithm, which is capable to identify identical bubbles in the two planes giving us a unique Lagrangian particle-related velocity information. Eventually we give an example of velocity measurement in the continuous liquid phase using an X-ray contrast agent.
Keywords: Ultrafast X-raytomography Velocity measurement Cross-correlation ROFEX Registration No. 23776 - Permalink

Anomalous Hall Effect in Polycrystalline MnxSi1–x (x ≈ 0.5) Films with the Self-Organized Distribution of Crystallites over Their Shapes and Sizes
Chernoglazov, K. Y.; Nikolaev, S. N.; Rylkov, V. V.; Semisalova, A. S.; Zenkevich, A. V.; Tugushev, V. V.; Vasil’Ev, A. L.; Chesnokov, Y. M.; Pashaev, E. M.; Matveev, Y. A.; Granovskii, A. B.; Novodvorskii, O. A.; Vedeneev, A. S.; Bugaev, A. S.; Drachenko, O.; Zhou, S.
Abstract: The structural, transport, and magnetic characteristics of polycrystalline MnxSi1 – x (x ≈ 0.51–0.52) films grown by pulsed laser deposition onto Al2O3(0001) substrates when the low-energy components are deposited owing to collisions with the atoms of the buffer gas have been studied in the “shadow” geometry. The magnetization of these films is determined by two ferromagnetic phases—the high-temperature phase with the Curie temperature TC ≈ 370 K and the low-temperature one with TC ≈ 46 K. The anomalous Hall effect changes sign from positive to negative with a decrease in temperature. The sign change occurs in the temperature range of 30–50 K; the specific value of this temperature depends on the thickness of the MnxSi1–x film. The results can be interpreted in terms of the structural self-organization related to the formation of two layers in the course of film growth. These layers have nearly the same chemical composition but significantly differ in the shapes and sizes of crystallites. This leads to a drastic difference in the values of TC and in the value and the sign of the anomalous Hall effect for such layers.
Keywords: SiMn alloys, room-temperature ferromagnetism, PLD, anomalous Hall effect Registration No. 23775 - Permalink

Remote sensing exploration of Nb-Ta-LREE-enriched carbonatite (Epembe/Namibia)
Zimmermann, R.; Brandmeier, M.; Andreani, L.; Mhopjeni, K.; Gloaguen, R.
Corresponding author: Zimmermann, Robert Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology
Abstract: On the example of the Epembe carbonatite-hosted Nb-Ta-LREE deposit we showcase the use of hyperspectral reflectance data and geomorphic indicators to improve the remote sensing exploration of structurally controlled critical raw material deposits. It further demonstrates how exploration can benefit from a combination of expert knowledge and remotely sensed relief as well as imaging data. In a first stage, multi-source remote sensing data feed lithological mapping based on \textit{kohonen} Self-Organizing maps. We show that morphological indices such as Topographic Position Index, and spatial coordinates are crucial parameters to improve the accuracy of carbonate classification by 10%. The resulting lithological map shows the spatial distribution of the ridge forming carbonatite dyke, the fenitization zone, syenite plugs and mafic intrusions. In a second step, the internal zones of the carbonatite complex were identified using multi-range spectral feature fitting (MRSFF) algorithm and a specific decision tree. This approach allowed detecting potential enrichment zones characterized by an abundance of fluorapatite and pyroxene as well as dolomite-carbonatite (beforsite). Cross validation of the mineral map with field observations and radiometric data confirm the accuracy of the proposed method.
Keywords: Carbonatite; REE; Self-Organizing Maps; Decision Tree; Spectral Feature Fitting; Geomorphology; Namibia; HyMap; SRTM Registration No. 23774 - Permalink

Direct measurements of the magnetocaloric effect in pulsed magnetic fields
Skourski, Y.
Abstract: es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    European Campus Card Conference (ECCA) 2016, 22.-24.05.2016, Wroclaw, Polen
Registration No. 23773 - Permalink

Precise image-guided irradiation of small animals: a flexible non-profit platform
Tillner, F.; Thute, P.; Löck, S.; Dietrich, A.; Fursov, A.; Haase, R.; Lukas, M.; Rimarzig, B.; Sobiella, M.; Krause, M.; Baumann, M.; Bütof, R.; Enghardt, W.
Abstract: Preclinical in-vivo studies using small animals are essential to develop new therapeutic options in radiation oncology. Of particular interest are orthotopic tumour models, which better reflect the clinical situation in terms of growth patterns and microenvironmental parameters of the tumour as well as the interplay of tumours with the surrounding normal tissues. Such orthotopic models increase the technical demands and the complexity of preclinical studies as local irradiation with therapeutically relevant doses requires image-guided target localisation and accurate beam application. Moreover, advanced imaging techniques are needed for monitoring treatment outcome. We present a novel Small Animal Image-Guided Radiation Therapy (SAIGRT) system, which allows for precise and accurate, conformal irradiation and X-ray imaging of small animals. High accuracy is achieved by its robust construction, the precise movement of its components and a fast high-resolution flat-panel detector. Field forming and X-ray imaging is accomplished close to the animal resulting in a small penumbra and a high image quality. Feasibility for irradiating orthotopic models has been proven using lung tumour and glioblastoma models in mice. The SAIGRT system provides a flexible, non-profit academic research platform which can be adapted to specific experimental needs and therefore enables systematic preclinical trials in multicentre research networks.
Keywords: translational cancer research, small animal research platform, image-guided radiotherapy (IGRT), cone beam computed tomography (CBCT), orthotopic tumour models, precision irradiation, X-ray dosimetry

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Registration No. 23770 - Permalink

Polymer and cluster chemistry of tetravalent cerium (Ce(IV)) in aqueous solutions
Ikeda-Ohno, A.
Abstract: Because of their high charge density, the aqueous chemistry of f-elements (i.e. lanthanides and actinides) with lower valences (e.g. tri- and tetravalent) is predominantly controlled by strong hydrolysis producing a variety of hydroxide species. Interestingly enough, this strong hydrolysis often induces the intrinsic formation of polymer and nano-sized cluster complexes which are stable even in aqueous solutions. This talk will provide a recent overview of the hydrolysis-induced polymer/cluster formation of tetravalent f-elements, with a special focus on tetravalent cerium (Ce(IV)), primarily from the viewpoint of structural chemistry, as well as the associated characterisation techniques (e.g. X-ray absorption spectroscopy or X-ray scattering).
Keywords: f-elements / hydrolysis / cerium / tetravalent / characterisation / X-ray / polymer / cluster
  • Invited lecture (Conferences)
    UMR Internal Colloquium, 25.07.2016, UMR, Université de Lille, France
Registration No. 23760 - Permalink

Viren als Nützlinge - Biologie hilft beim Recycling
Lederer, F.
Abstract: Populärwissenschaftlicher Beitrag unter Vorstellung der Phage Surface Display Methode und aktuellen Forschungsergebnissen im MinePep Projekt
Keywords: Phage surface display, Peptide, Seltene Erden, Lanthanphosphat
  • Lecture (others)
    Tag des offenen Labors am HZDR, 28.05.2016, Dresden, Deutschland
Registration No. 23759 - Permalink

Modelling of Oxide Dispersion Strengthened Fe alloys with Kinetic Monte Carlo simulation supported by DFT calculations
Liedke, B.; Posselt, M.; Murali, D.; Claisse, A.; Olsson, P.
Abstract: Oxide Dispersion Strengthened (ODS) steels are considered as one of the most promising candidates for structural materials in next generation nuclear fusion reactors and future nuclear fission reactors [1]. The ODS materials consist of a ferritic or ferritic/martensitic Fe-Cr matrix filled with yttria-based oxide particles and is fabricated during mechanical alloying and hot consolidation processes. It is well known that their extraordinary properties such as high-temperature creep strength as well as high dose ion/neutron irradiation resistance are due to formation of small Y-Ti-O clusters with a size of few nanometers. Besides their significant effect on reduction of dislocations and grain-boundaries mobility, the nanoclusters also act as traps for point defects like vacancies, interstitials and helium, which may be typically generated in a nuclear reactor. It is still under debate what the formation mechanisms of the nanoclusters are and why they prove such high temperature and radiation damage stability.
Experimental methods typically applied to investigate the issues stated above cannot fully reflect the atomic-scale of the nanoclusters, as well as the mechanisms related to their formation, evolution and destruction upon radiation damage. Therefore, atomistic computer experiments can significantly contribute to a general understanding.
In this work, kinetic Monte Carlo (KMC) technique is applied to study evolution of Y-Ti-O nanoclusters in a bcc-Fe and FeCr matrix. Starting from a uniform distribution of O, Y, Ti atoms in the matrix at first a stationary state is produced by high temperature annealing. Such a state is characterized by a certain population of Y-Ti-O nanoclusters. Then vacancies and interstitials are introduced in order to simulate ion and neutron irradiation taking into account realistic conditions, and the evolution of the nanostructure is studied. The parameters for the atomic interactions used in KMC were obtained recently by first-principle Density-Functional-Theory calculations and applied in Metropolis Monte Carlo simulations on energetics, structure and composition of the Y-Ti-O nanoclusters [2].
1. G. R. Odette, M. J. Alinger, B. D. Wirth, Annu. Rev. Mater. Res. 38, 471 (2008)
2. M. Posselt, D. Murali, B. K. Panigrahi, Modelling Simul. Mater. Sci. Eng. 22, 085003 (2014)

Keywords: ODS alloys, DFT, KMC, atomistic modelling, radiation damage
  • Lecture (Conference)
    3rd ODISSEUS Workshop, 19.-20.04.2016, HZDR, Germany
Registration No. 23752 - Permalink

Recent progress at the LUNA 400 kV underground accelerator
Bemmerer, D.
Abstract: The experimental study of radiative capture reactions directly at the energies of relevance for astrophysics requires long experiments with low counting rate. This type of study has greatly bene ted in recent years from the ultra-low gamma-ray background level underground, in the INFN Gran Sasso laboratory, Italy. There, the LUNA 400kV accelerator has enabled a rich research program. The 2 H(alpha,gamma)6 Li reaction has been studied for the first time in the Big Bang energy region. Very recently, three resonances have been observed for the first time in the 22 Ne(p,gamma)23 Na reaction, directly at energies relevant for the hot- bottom burning process in asymptotic giant branch stars. Studies on other hydrogen burning reactions on 17,18O and 23Na are ongoing, with promising preliminary results. The group report will show an overview of recent progress and discuss future perspectives, in particular on the future LUNA experiment on the Big Bang 2H(p,gamma)3He reaction.
Keywords: Nuclear Astrophysics underground LUNA Big Bang nucleosynthesis hydrogen burning NeNa cycle
  • Lecture (Conference)
    Frühjahrstagung 2016 der Deutschen Physikalischen Gesellschaft, 14.-18.03.2016, Darmstadt, Deutschland
Registration No. 23749 - Permalink

Felsenkeller shallow-underground 5 MV accelerator for nuclear astrophysics, status and outlook
Bemmerer, D.
Abstract: Felsenkeller shallow-underground 5 MV accelerator for nuclear astrophysics, status and outlook is discussed as of February 2016, with a view also on potential European collaborations.
Keywords: Nuclear Astrophysics Underground Nuclear Astrophysics Helium burning Solar fusion Felsenkeller
  • Invited lecture (Conferences)
    2nd Workshop on Nuclear Astrophysics at the Canfranc Underground Laboratory, 29.02.-01.03.2016, Canfranc Estacion, Spanien
  • Lecture (Conference)
    German-Japanese minisymposium on hot topics in particle and nuclear physics, 12.05.2016, Dresden, Deutschland
Registration No. 23748 - Permalink

Progress of the Felsenkeller shallow-underground 5 MV accelerator for nuclear astrophysics early 2016
Bemmerer, D.
Abstract: The progress of the Felsenkeller shallow-underground 5 MV accelerator for nuclear astrophysics is reviewed, as of early 2016
Keywords: Felsenkeller Nuclear Astrophysics Underground nuclear astrophysics low-background measurements solar fusion helium burning
  • Lecture (Conference)
    NAVI Physics Days, 18.01.2016, Darmstadt, Deutschland
Registration No. 23747 - Permalink

Towards SiPM readout for the NeuLAND large plastic scintillator
Bemmerer, D.
Abstract: Towards SiPM readout for the NeuLAND large plastic scintillator
Keywords: R3B NeuLAND neutron time of flight picosecond timing ELBE scintillator silicon photomultiplier
  • Invited lecture (Conferences)
    Fraunhofer IMS workshop on CMOS SiPM technology, 26.11.2015, Duisburg, Deutschland
Registration No. 23746 - Permalink

The copper spoil heap Knappenberg, Austria, as a model for metal habitats - Vegetation, substrate and contamination
Adlassnig, W.; Weiss, Y. S.; Sassmann, S.; Steinhauser, G.; Hofhansl, F.; Baumann, N.; Lichtscheidl, I. K.; Lang, I.
Abstract: Historic mining in the Eastern Alps has left us with a legacy of numerous spoil heaps hosting specific, metal tolerant vegetation. Such habitats are characterized by elevated concentrations of toxic elements but also by high irradiation, a poorly developed substrate or extreme pH of the soil. This study investigates the distribution of vascular plants, mosses and lichens on a copper spoil heap on the ore bearing Knappenberg formed by Prebichl Layers and Werfener Schist in Lower Austria. It serves as a model for discriminating between various ecological traits and their effects on vegetation.Five distinct clusters were distinguished: (1) The bare, metal rich Central Spoil Heap was only colonised by highly resistant specialists. (2) The Northern and (3) Southern Peripheries contained less copper; the contrasting vegetation was best explained by the different microclimate. (4) A forest over acidic bedrock hosted a vegetation overlapping with the periphery of the spoil heap. (5) A forest over calcareous bedrock was similar to the spoil heap with regard to pH and humus content but hosted a vegetation differing strongly to all other habitats.Among the multiple toxic elements at the spoil heap, only Cu seems to exert a crucial influence on the vegetation pattern. Besides metal concentrations, irradiation, humidity, humus, pH and grain size distribution are important for the establishment of a metal tolerant vegetation. The difference between the species poor Northern and the diverse Southern Periphery can be explained by the microclimate rather than by the substrate. All plant species penetrating from the forest into the periphery of the spoil heap originate from the acidic but not from the calcareous bedrock.
Keywords: Copper pollution; Metal tolerance; Metallophytes; Mine residues; Ore minerals Registration No. 23745 - Permalink

Ultra-sensitive γ-ray spectroscopy set-up for investigating primordial lithium problem
Gervino, G.; Gustavino, C.; Trezzi, D.; Aliotta, M.; Anders, M.; Boeltzig, A.; Bemmerer, D.; Best, A.; Broggini, C.; Bruno, C.; Caciolli, A.; Cavanna, F.; Corvisiero, P.; Davinson, T.; Depalo, R.; Dileva, A.; Elekes, Z.; Ferraro, F.; Formicola, A.; Fülöp, Z.; Guglielmetti, A.; Gyürky, G.; Imbriani, G.; Junker, M.; Menegazzo, R.; Prati, P.; Scott, D. A.; Straniero, O.; Szücs, T.
Abstract: To precisely determine BBN 6Li production, the cross-section of the nuclear reaction 2H(α, γ)6Li must be directly measured within the astrophysical energy range of 30–400 keV. This measure requires an ultra- low γ-ray background in the experimental set-up. We have realized the conditions matching these very strict requirements at LUNA, the deep underground accelerator laboratory active in the INFN Gran Sasso National Laboratory (LNGS), Italy: the γ-ray spectrometer background has been reduced down to reach unmatched low levels, comparable to the good ones experienced in dedicated off-line underground ultra low γ counting rate. We present and discuss the γ-ray background reduction reached in the HpGe spectrometer, where most of the remaining γ-ray background seen in the spectra are coming from the energetic deuterons scattered in the gas target by the α beam. Thanks to the low neutron environmental background at LUNA, the effect of this weak flux of 2–3 MeV neutrons on HpGe detectors has been studied in details and the results are presented and discussed.
Keywords: Gamma spectroscopy Underground Physics Lithium problem Registration No. 23743 - Permalink

Coordination chemistry of tetravalent actinides
März, J.
Abstract: Against the background of nuclear waste disposal, the interactions between actinides and organic complexation agents were studied. Actinides show a variety of different oxidation states, but in case of a deep disposal, the tetravalent species can be predominant in the environment. We synthesised An(IV) chlorides and iodides as actinide starting materials and studied organic ligand systems ranging from pure oxygen to pure nitrogen donors. Some first isostructural actinide complexes were determined by single crystal X-ray diffraction and spectroscopic techniques showing the typical shortening of the donor-acinide bonds across the actinide series.
Keywords: Tetravalent actinides Coordination chemistry
  • Invited lecture (Conferences)
    8th International Workshop on „Coordination Chemistry of Metals with Medical Relevance and Supramolecular Building Blocks“, 26.-27.05.2016, Berlin, Deutschland
Registration No. 23742 - Permalink

Cosmic Background Measurements at a Proposed Underground Laboratory by the REGARD Muontomograph
Oláh, L.; Surányi, G.; Barnaföldi, G. G.; Bemmerer, D.; Hamar, G.; Melegh, H. G.; Varga, D.
Abstract: A portable cosmic particle tracking detector has been developed by the REGARD group with angular resolution of 10 mrad. The Close Cathode Chamber-based tracking system is optimized for environmental and geophysical applications with its weight of 15 kg and size of 51 cm × 43 cm × 32 cm. Our aim was to determine the cosmic background at the site of the proposed accelerator and experimental facilities at an approximate 50 meter depth in Felsenkeller, Dresden, Germany. Here, we present our high-precision muon flux measurements, which have been performed during 44 days in one of the tunnels. Angular acceptance of our mapping covered full 2π solid angle of the upper hemisphere. The maximum flux value is found to be below 2.5 m^{-2}sr^{-1}s^{-1}.
Keywords: Felsenkeller Nuclear Astrophysics Muon flux

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Registration No. 23741 - Permalink
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