Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

31828 Publications
Complexation and Adsorption of [152Eu]Eu to Superplasticizers and Bentonite at Variable Salt Concentrations
Becker, M.; Lippold, H.;
The preferred method for the storage of spent nuclear fuel (HLW) is the disposal in deep geological formations. The repository will consist not only of the geological barrier but also of an engineered barrier and has to isolate the waste for at least 106 years from the biosphere [1]. In this barrier, several materials like concrete or bentonite are effective in retention of radionuclides. In modern concrete, several additives are used to improve the properties of the cement paste. Superplasticizers of the polycarboxylateether (PCE)-family are widely used for this purpose [2]. These organic materials might have an influence on the mobility of radionuclides. Hence, it is necessary to study their complexation and adsorption behaviour with radionuclides, cement-phases like C-S-H and buffer materials like bentonite considering a possible leaching of PCE from cement in consequence of water influx. In this study, the complexation and adsorption behaviour of the superplasticizer MasterGlenium® 51 was investigated by means of the radionuclide 152Eu, which is an analogue for trivalent actinides such as Cm(III) or Am(III), at a fixed pH and variable salt concentrations (NaCl, CaCl2). Complexation constant and loading capacity for the PCE with [152Eu]Eu were determined on the basis of the Langmuir isotherm equation as well as of the charge neutralisation model [3]. Furthermore the adsorption behaviour of [152Eu]Eu to bentonite with and without MasterGlenium51® in the presence of different background electrolytes was studied.
Keywords: Adsorption Complexation Superplasticizer
  • Poster
    2nd Petrus-OPERA Conference on Radioactive Waste Management and Geological Disposal, 27.06.-01.07.2016, Delft, Niederlande

Publ.-Id: 23858 - Permalink


Physical realization of a quantum spin liquid based on a complex frustration mechanism
Balz, C.; Lake, B.; Reuther, J.; Luetkens, H.; Schönemann, R.; Herrmannsdörfer, T.; Singh, Y.; Nazmul Islam, A. T. M.; Wheeler, E. M.; Rodriguez-Rivera, J. A.; Guidi, T.; Simeoni, G. G.; Baines, C.; Ryll, H.;
Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. In the case of magnets with isotropic interactions, spin-liquid behaviour is sought in simple lattices with antiferromagnetic interactions that favour antiparallel alignments of the magnetic moments and are incompatible with the lattice geometries. Despite an extensive search, experimental realizations remain very few. Here we investigate the novel, unexplored magnet Ca10Cr7O28, which has a complex Hamiltonian consisting of several different isotropic interactions and where the ferromagnetic couplings are stronger than the antiferromagnetic ones. We show both experimentally and theoretically that it displays all the features expected of a quantum spin liquid. Thus spin-liquid behaviour in isotropic magnets is not restricted to the simple idealized models currently investigated, but can be compatible with complex structures and ferromagnetic interactions.

Publ.-Id: 23857 - 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.;
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

Publ.-Id: 23856 - Permalink


Mg and Cs2Te photocathodes in ELBE SRF-gun
Xiang, R.; Teichert, J.;
For the accelerator-based light sources and the electron colliders, the development of photo injectors has become a key technology. Especially for the superconducing radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. The “perfect” photocathodes require four important aspects: high efficiency, long life time, small transverse emittance and prompt time response.
To use Metallic photocathodes for ELBE SRF Gun is the primary choice to prevent the contamination of the SC cavity. In this contribution, we will report the investigation of magnesium (Mg) cathode in ELBE SRF gun, including the laser cleaning treatment and the measurement on quantum efficiency, Schottkey effect, dark current and damage threshold. From our experience, Mg cathode can reach high QE of 0.1% and produce up to 300 pC bunch charge in SRF gun, which is suitable for the applications with medium beam current.
However, semiconductor photocathodes in the SRF gun-I gave out very positive results. For high bunch charge and high current application, Cs2Te photocathode will be applied in the SRF gun-II soon in 2016.
Keywords: Mg, Cs2Te, photocathode, SRF-gun
  • Invited lecture (Conferences)
    European Workshop on Photocathodes for Particle Accelerator Applications, 06.-08.06.2016, Daresbury, United Kingdom

Publ.-Id: 23855 - Permalink


Metallic Photocathodes as an Alternative to Semiconductor Cathodes for SRF Photo-injectors
Xiang, R.; Teichert, J.;
We report the Status of Mg and Cu Photocathodes used in the HZDR SRF Photo-injector.
Keywords: metallic photocathode, Mg, SRF gun, Quantum efficiency
  • Lecture (Conference)
    Matter and Technology 2nd Annual Meeting, 08.-10.03.2016, Karlsruhe, Germany

Publ.-Id: 23854 - Permalink


Qualification of CFD-models for multiphase flows in medium and large scale industrial applications
Lucas, D.;
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

Publ.-Id: 23853 - Permalink


BEMER electromagnetic field therapy reduces cancer cell radioresistance by enhanced ROS formation and induced DNA damage
Storch, K.; Dickreuter, E.; Artati, A.; Adamski, J.; Cordes, N.;
Each year more than 450,000 Germans are expected to be diagnosed with cancer subsequently receiving standard multimodal therapies including surgery, chemotherapy and radiotherapy. On top, molecular-targeted agents are increasingly administered. Owing to intrinsic and acquired resistance to these therapeutic approaches, both a better molecular understanding of tumor biology and an intensive consideration of alternative and complementary therapeutic support are warranted and open up broader and novel possibilities for therapy personalization. Particularly the latter is clearly underpinned by the increasing utilization of non-invasive complementary and alternative medicine by the population. One intensively investigated approach is the application of low-dose electromagnetic fields (EMF) to modulate cellular processes. A particular system is the BEMER therapy as a Physical Vascular Therapy for which a normalization of the microcirculation has evidently been demonstrated by a unique EMF pattern. Open remained whether this EMF pattern impacts on cancer cell survival upon treatment with radiotherapy, chemotherapy and the molecular-targeted agent Cetuximab inhibiting the epidermal growth factor receptor. Using more physiological, three-dimensional, matrix-based cell culture models and cancer cell lines originating from lung, head and neck, colorectal and pancreas, we show significant changes in distinct intermediates of the glycolysis and tricarboxylic acid cycle pathways and enhanced cancer cell radiosensitization associated with increased DNA double strand break numbers and higher levels of reactive oxygen species upon BEMER treatment relative to controls. Intriguingly, exposure of cells to the BEMER EMF pattern failed to result in sensitization to chemotherapy and Cetuximab. Further studies are necessary to better understand the mechanisms underlying the cellular alterations induced by the specific BEMER EMF pattern and clarify the application areas for human disease.
Keywords: Magnetic field therapy, radiotherapy, cancer, ROS

Publ.-Id: 23852 - 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.;
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.

Downloads:

Publ.-Id: 23851 - Permalink


Methoden zur Charakterisierung und Optimierung von Belebungsbecken
Reinecke, S. F.; Hampel, U.;
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

Publ.-Id: 23850 - Permalink


Strömungsfolgende Sensorpartikel zur Charakterisierung von Bioreaktoren
Reinecke, S.; Hampel, U.;
Die Kenntnis der in Bioreaktoren und speziell in großen Behältern, wie Biogasfermentern, Belebtschlammbecken und Hefefermentern, ablaufenden hydrodynamischen und biochemischen Prozesse ist begrenzt. Der Zugang für Messtechnik ist durch die Behälter und die rauen mechanischen und chemischen Umgebungsbedingungen stark eingeschränkt. Daher sind bekannte bildgebende Messverfahren zur Strömungscharakterisierung, wie Hochgeschwindigkeitsvideometrie, Particle Image Velocimetry (PIV) und Prozesstomografie, nicht anwendbar.
Zur räumlichen Erfassung der Prozessparameter in Bioreaktoren wurde am HZDR das Konzept instrumentierter, strömungsfolgender Sensorpartikel entwickelt [1,2]. Die Sensorpartikel werden als auftriebsneutrale Strömungsfolger eingesetzt und erfassen dabei kontinuierlich Prozessparameter. Nach der Rückgewinnung der Sensorpartikel aus dem Prozess werden die Daten ausgewertet. Die Sensorpartikel bestehen aus robusten Kapseln, welche mit einer integrierten Messelektronik und einer mechanischen Auftriebseinheit ausgestattet sind (siehe Abb. 1). Das Systemkonzept berücksichtigt derzeit miniaturisierte Sensoren für die Umgebungstemperatur, die Eintauchtiefe als Funktion des hydrostatischen Drucks, die Beschleunigung, die Drehrate und das Magnetfeld. Das Konzept ist zudem offen für die Einbindung ergänzender miniaturisierter Messfühler, wie z.B. für pH-Wert und Gelöst-Sauerstoff. Eine Auftriebseinheit erlaubt zum einen die automatisierte Tarierung der Sensorpartikel im ruhenden Prozessmedium und weiterhin eine erleichterte Rückgewinnung der Sensorpartikel von der Flüssigkeitsoberfläche nach Beendigung der Messung [3].
Die Sensorpartikel wurden bereits unter realen Bedingungen von Biogasfermentern getestet und es wurden erste Strömungsanalysen erstellt [2,4]. Ein weiteres aktuelles Anwendungsfeld der Sensorpartikel sind Kläranlagen und speziell Belebtschlammbecken zur biologischen Abwasserreinigung. Erste Tests mit Sensorpartikeln wurden bereits durchgeführt (siehe Abb. 2). Der Beitrag stellt neben dem Konzept der Sensorpartikel deren Anwendungsmöglichkeiten in Bioreaktoren und damit verbundene technische Herausforderungen vor.
  • Lecture (Conference)
    AHMT 2016 – XXX. Messtechnisches Symposium des Arbeitskreises der Hochschullehrer für Messtechnik, 15.-16.09.2016, Hannover, Deutschland
  • Contribution to proceedings
    XXX. Messtechnische Symposium des Arbeitskreises der Hochschullehrer für Messtechnik, 15.-16.09.2016, Hannover, Deutschland
    Tagungsband XXX. Messtechnisches Symposium 2016, Oldenburg: De Gruyter, 978-3-11-049487-7, 19-27

Publ.-Id: 23849 - Permalink


Tomographic Interrogation of Gas-Liquid Flows in Inclined Risers
Lokman, A. A.; Escrig, E.; Reinecke, S.; Hewakandamby, B. N.; Azzopardi, B. J.;
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

Publ.-Id: 23848 - Permalink


Dipole strength in 80Se for s process and nuclear transmutation of 79Se
Makinaga, A.; Massarczyk, R.; Beard, M.; Schwengner, R.; Otsu, H.; Al-Abdullah, T.; Anders, M.; Bemmerer, D.; Hannaske, R.; John, R.; Junghans, A. R.; Müller, S. E.; Röder, M.; Schmidt, K.; Wagner, A.;
The dipole strength distribution of 80Se was studied in a photon-scattering experiment using bremsstrahlung produced with an electron beam of energy 11.5 MeV at the linear accelerator ELBE. We identified 180 gamma transitions up to an energy of 9.6 MeV, and analyzed the strength in the quasicontinuum of the spectrum. Simulations of statistical gamma-ray cascades were performed to estimate intensities of inelastic transitions, and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section below the neutron-separation energy derived in this way was combined with the photoabsorption cross section obtained from an earlier (gamma, n) experiment and used as an input for the calculation of 79 Se(n, gamma) reaction rates on the basis of the statistical reaction model.
Keywords: Nuclear structure, statistical reactions, gamma spectroscopy, photon scattering, nuclear resonance fluorescence, photoabsorption cross section, gamma-ray strength function.

Downloads:

Publ.-Id: 23847 - Permalink


Untersuchung der Hydrodynamik von ovalen Biogasreaktoren mit instrumentierten Strömungsfolgern
Reinecke, S. F.; Hampel, U.;
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

Publ.-Id: 23846 - Permalink


Instrumented flow-following sensor particles with magnetic position detection and buoyancy control
Reinecke, S. F.; Hampel, U.;
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

Downloads:

Publ.-Id: 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.;
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

Publ.-Id: 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.;
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.

Downloads:

Publ.-Id: 23843 - Permalink


Confined catalytic Janus swimmers in a crowded channel: geometry-driven rectification transients and directional locking
Yu, H.; Kopach, A.; Misko, V. R.; Vasylenko, A. A.; Makarov, D.; Marchesoni, F.; Nori, F.; Baraban, L.; Cuniberti, G.;
Self-propelled Janus particles, acting as microscopic vehicles, have the potential of performing complex tasks on a microscopic scale, suitable, e.g., for environmental applications, on-chip chemical information processing or in vivo drug delivery. Development of these smart nano-devices requires a better understanding of how synthetic swimmers move in crowded and confined environments that mimic actual biosystems,e.g.network of blood vessels. Here the dynamics of self-propelled Janus particles interactingwith catalytically passive silica beads in a narrow channel isstudied both experimentally and through numerical simulations. Upon varying the area density of thesilica beads and the width of the channel, active transport reveals a number of intriguing properties, which range from distinct bulk and boundary-free diffusivity at low densities, to directional “locking” and channel “unclogging” at higher densities, whereby a Janus swimmer is capable of transporting large clusters of passive particles.
Keywords: Janus particles motors, microswimmers, microfluidic channel, catalytic propulsion

Publ.-Id: 23842 - Permalink


Development of interatomic potential for bcc FeCrNi and its validation
Bonny, G.; Bakaev, A.; Olsson, P.; Domain, C.; Zhurkin, E. E.; Posselt, M.;
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

Publ.-Id: 23841 - Permalink


Radiation-induced segregation in FeNiCr model alloys
Bakaev, A.; Posselt, M.; Terentyev, D.; Bonny, G.; Zhurkin, E. E.;
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

Publ.-Id: 23840 - Permalink


Spatially-resolved sorption studies of Eu(III) on granite surface with time-resolved laser fluorescence microscopy (TRLFM)
Zesewitz, K.; Schmidt, M.;
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

Publ.-Id: 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.;
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

Publ.-Id: 23837 - Permalink


Frequency- and Amplitude Modulation of Spin-Wave Signals emitted from Topological Spin Textures
Wintz, S.; Finizio, S.; Schultheiss, K.; Liersch, V.; Kilibarda, F.; Warnatz, T.; Suszka, A. K.; Warnicke, P.; Wohlhüter, P.; Erbe, A.; Lindner, J.; Fassbender, J.ORC; Raabe, J.
The investigation of spin-wave phenomena, dubbed magnonics, is an important branch of present magnetism research. This is in particular the case since spin waves are seen as promising signal carriers for future spintronic information and communication technology devices. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths (striplines or point-contacts) or to generate such spin waves parametrically by a spatially uniform double-frequency microwave signal. Recently, however, a new mechanism for the local excitation of spin waves has been found, which overcomes the lower wavelength limit given by the minimum patterning size. This method utilizes the translation of layered topological magnetic defects, i.e. the gyration of coupled spin vortex cores to generate propagating spin waves. In the present contribution we will show that a system similar to the one used in can be exploited to excite spin-wave signals with frequency- and amplitude modulation. With respect to a certain high-frequency spin-wave carrier signal, frequency and amplitude were periodically modulated encoding a lower frequency information signal. The resulting spin-wave dynamics was directly imaged by means of time-resolved scanning transmission x-ray microscopy. By demonstrating a very high agility for the vortex core based spin-wave generation mechanism, our findings further underline the potential applicability of this concept.
  • Poster
    61st Annual Conference on Magnetism and Magnetic Materials, 31.10.-04.11.2016, New Orleans, USA

Publ.-Id: 23836 - 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.;
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

Publ.-Id: 23835 - Permalink


Uranium Redox Transformations after U(VI) Coprecipitation with Magnetite Nanoparticles
Pidchenko, I.; Kvashnina, K. O.; Yokosawa, T.; Finck, N.; Schild, D.; Polly, R.; Bohnert, E.; Rossberg, A.; Göttlicher, J.; Dardenne, K.; Rothe, J.; Schäfer, T.; Geckeis, H.; Vitova, T.;
Uranium redox states and speciation in magnetite nanoparticles co-precipitated with U(VI) for uranium loadings varying from 1,000 to 10,000 ppm are investigated by X-ray absorption spectroscopy (XAS). It is demonstrated that the U M4 high energy resolution X-ray absorption near edge structure (HR-XANES) method is capable to clearly characterize U(IV), U(V) and U(VI) existing simultaneously in the same sample. The contributions of the three different uranium redox states present in the samples are quantified with the iterative transformation factor analysis (ITFA) method. U(V) incorporated in octahedral magnetite sites remains stable over 226 days under ambient conditions as unambiguously shown for the magnetite nanoparticles containing 1,000 ppm uranium. U L3 XAS and transmission electron microscopy (TEM) studies reveal that initially precipitated U(VI) phases recrystallize to non-stoichiometric UO2+x nanoclusters within 147 days when stored under anoxic conditions. XAS results are supported by density functional theory (DFT) calculations. Further characterization of the samples include powder X-ray diffraction (pXRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).
Keywords: Uranium, actinides, redox state, magnetite, HR-XANES

Downloads:

Publ.-Id: 23834 - 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.;
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

Publ.-Id: 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.;
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

Publ.-Id: 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.;
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.

Publ.-Id: 23830 - Permalink


General switching voltages for magnetic tunnel junctions with in-plane and/or perpendicular-to-plane anisotropy free layers
Bernert, K.; Sluka, V.; Fowley, C.; Lindner, J.; Deac, A. M.; Fassbender, J.ORC
We analytically calculate the switching voltages for MgO-based magnetic tunnel junctions for the generalized case where the free layer has two generic “intrinsic” fields oriented along orthogonal directions. The magnetization of the reference layer and the applied field are assumed to be parallel to one of the two intrinsic field axis. Both the in-plane and the field-like spin-torque terms are taken into account, with the field-like torque assumed to have a quadratic dependence on the applied voltage and to favour the antiparallel state [1]. The switching voltages thus determined can be particularized for different geometries by replacing the two generic intrinsic field terms with the appropriate expressions for the anisotropy and demagnetizing fields, according to the specific free and reference layer configuration considered. The results are consistent with numerical integration of the Landau-Lifshitz-Gilbert equation with the relevant spin-torque terms.
For in-plane MgO-based magnetic tunnel junctions, one of the two intrinsic fields of the free layer corresponds to the (negative) demagnetizing field, which pulls the magnetization of the free layer towards the film plane. The orthogonal intrinsic field component is the easy-axis anisotropy, parallel to the current polarization and the external field direction. We demonstrate that in this configuration the quadratic dependence of the field-like torque on the applied voltage can cause back-hopping (a somewhat obscure behaviour characteristic to tunnel junctions, whereby reliable switching to the desired state is achieved for applied voltages of the order of the critical voltage, but a larger applied bias induces a telegraph-noise behaviour [2, 3]). For perpendicular anisotropy tunnel junctions without in-plane shape anisotropy, the only intrinsic field present in the free layer is parallel the effective anisotropy, parallel to the reference layer direction. In this case, we find that neither back-hopping, nor spin-transfer driven steady stare precession are expected, as evidenced by experimental results [4]. Finally, if an in-plane shape anisotropy is considered in addition to the effective perpendicular anisotropy, a variety of canted states are predicted [5].
REFERENCES
[1] C. Heiliger and M. Stiles, Ab Initio Studies of the Spin-Transfer Torque in Magnetic Tunnel Junctions, Phys. Rev. Lett. 100, 186805 (2008).
[2] J. Z. Sun, , M. C. Gaidis, G. Hu, E. J. O’Sullivan, S. L. Brown, J. J. Nowak, P. L. Trouilloud and D. C. Worledge, High-bias backhopping in nanosecond time-domain spin-torque switches of MgO-based magnetic tunnel junctions, J. Appl. Phys. 105, 07D109 (2009).
[3] T. Min, J. Z. Sun, R. Beach, D. Tang and P. Wang, Back-hopping after spin torque transfer induced magnetization switching in magnetic tunneling junction cells, J. Appl. Phys. 105, 07D126 (2009).
[4] J.J. Nowak, R. P. Robertazzi, J. Z. Sun, G. Hu, David W. Abraham, P. L. Trouilloud, S. Brown, M. C. Gaidis, E. J. O’Sullivan, W. J. Gallagher, and D. C. Worledge, Demonstration of Ultralow Bit Error Rates for Spin-Torque Magnetic Random-Access Memory With Perpendicular Magnetic Anisotropy, IEEE Magn. Lett. 2, 3000204 (2011).
[5] K. Bernert, V. Sluka, C. Fowley, J. Lindner, J. Fassbender and A. M. Deac, Phase diagrams of MgO magnetic tunnel junctions including the perpendicular spin-transfer torque in different geometries, Phys. Rev. B 89, 134415 (2014).
Keywords: spin-transfer torque, magnetic tunnel junctions
  • Invited lecture (Conferences)
    New Horizons for Memory Storage: Advancing Non-volatile Memory with Atomistic Simulations, 29.06.-01.07.2016, Dublin, Ireland

Publ.-Id: 23829 - Permalink


An outlook on the rare earth elements mining industry
Barakos, G.; Mischo, H.; Gutzmer, J.;
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:

Publ.-Id: 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.;
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.
  • Open Access LogoContribution to proceedings
    SME Annual Meeting 2016, 21.-24.02.2016, Phoenix, United States of America
    SME Annual Meeting 2016, Phoenix, USA: SME

Publ.-Id: 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.;
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.
  • Open Access LogoContribution 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

Publ.-Id: 23826 - Permalink


Strategic evaluations and mining process optimization towards a strong global ree supply chain
Barakos, G.; Gutzmer, J.; Mischo, H.;
Rare earth elements (REE) have turned from an inconspicuous group of raw materials to critical commodities in the last decade. The insatiable and continuously growing demand for rare earths combined with their small and opaque market has resulted in a global exploration boom that has led to the delineation of extensive resources on every continent. Nevertheless, the special boundary conditions that govern the REE industry require second thoughts and careful evaluations when it comes to the potential exploitation of such resources. Past mistakes, with respect to environmental impacts and uncertain investments, have resulted in an overall uncertainty whether the mining and beneficiation of rare earth elements can be a viable industry in a free market context. This paper attempts to record the erroneous practices of the past and use them as guidelines to strengthen the global REE supply-chain. Moreover, the paper focuses on the assessments that need to be made in order to optimize the mining process and reinforce the growth prospects of the market. An overall assessment tool for the mineability of rare earth deposits is also used to consolidate these evaluations and answer the question, if REE mining can be sustainable.
Keywords: Rare earth elements Global supply chain Mining optimization Mining sustainability

Publ.-Id: 23825 - 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. J.; Belderbos, J. S. A.; Dieleman, E. M. T.; Rossi, M.; Rasch, C. R. N.; Damhuis, R. A. M.; Houben, R. M. A.; Troost, E. G. C.;
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

Publ.-Id: 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.;
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.

Publ.-Id: 23823 - Permalink


[Melanoma brain metastases : Treatment options]. [Hirnmetastasen des malignen Melanoms].
Rauschenberg, R.; Tabatabai, G.; Troost, E. G. C.; Garzarolli, M.; Beissert, S.; Meier, F.;
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

Publ.-Id: 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.;
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

Publ.-Id: 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.;
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

Publ.-Id: 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. C.; Bons, J.; Menheere, P.; Lambin, P.; Oberije, C.;
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

Publ.-Id: 23819 - Permalink


Improved Killing of AML Blasts By Dual-Targeting of CD123 and CD33 Via Unitarg a Novel Antibody-Based Modular T Cell Retargeting System
Arndt, C.; Feldmann, A.; Koristka, S.; Cartellieri, M.; von Bonin, M.; Ehninger, A.; Bornhäuser, M.; Ehninger, G.; Bachmann, M. P.;
Acute myeloid leukemia (AML) is a hematologic malignancy of the myeloid line with high prevalence in older patients. As complete eradication of metastatic cancer cells is often not achieved by standard therapies, alternative treatment modalities are urgently needed.
In recent years, bispecific antibodies (bsAbs) and chimeric antigen receptors (CARs) emerged as promising candidates for an antigen-specific cancer immunotherapy. Both bsAbs and CARs are able to redirect T cells for efficient tumor cell lysis. Nevertheless, the development of a novel TAA specific bsAb or a CAR is a long lasting process. Therefore, we recently introduced a novel antibody-based modular platform (UniTARG) that can be rapidly and easily adapted for redirection of T cells to any TAA in both a bsAb or CAR related manner. The modular UniTARG system distributes the effector arm (the anti-CD3 domain or CAR) and the anti-TAA binding domain to two separate molecules: (I) an exchangeable target module (TM) comprising an anti-TAA binding moiety and a short peptide epitope (E5B9), and (II) a universal effector unit. The effector systems represent either a bsAb with specificity for CD3 and a peptide epitope (E5B9) termed UniMAB or a CAR directed to the E5B9 epitope (UniCAR). Thus, TMs can form a complex with the respective effector system that facilitates the cross-linkage of tumor and T cells similar to conventional bsAbs or CARs. For redirection of T cells to any kind of TAA only the binding moiety of the TM has to be adapted what saves costs and time. To increase tumor specificity and to reduce the risk of tumor escape variants, the modular UniTARG system further offers the possibility to apply simultaneously different monospecific or even bispecific TMs recognizing two TAAs.

For proof of concept of a dual targeting using the UniTARG system we selected as TAA on AML blasts the molecules CD33 and CD123. They represent promising target antigens as they are overexpressed on both rapidly proliferating terminal AML blasts and leukemic stem cells which might be responsible for disease relapse after initial chemotherapy. Thus, we generated an anti-CD123 TM and anti-CD33 TM that can be applied within the modular system for single-targeting or that can be combined for dual-targeting of AML blasts. By fusion of the anti-CD123 and anti-CD33 domains via the E5B9 epitope a bispecific TM was further constructed. As revealed by cytotoxicity assays with CD33+CD123+ AML cell lines, the novel mono- and bispecific TMs can be easily applied to the modular systems to trigger highly potent tumor cell lysis at low E:T ratios and picomolar Ab concentrations. By using the dual-targeting approach we can show that lysis of CD123+CD33+ AML blasts can be considerably improved in comparison to the mono-specific strategy.

Overall, due to the ease and cost-effectiveness of development the UniTARG platform technology represents a promising tool in the field of both bsAbs and CARs with the advantage of simultaneous or consecutive dual or even multispecific targeting. This approach might additionally improve anti-tumor activity by increasing tumor specificity and diminishing off-target effects.
  • BLOOD 126(2015), 2565

Downloads:

Publ.-Id: 23818 - Permalink


„Qualifizierung von CFD-Programmen für Fragestellungen der Reaktorsicherheit“
Höhne, T.;
The last decade has seen an increasing use of three-dimensional CFD codes to predict steady state and transient flows in nuclear reactors because a number of important phenomena such as pressurized thermal shocks, coolant mixing, and thermal striping cannot be predicted by traditional one-dimensional system codes with the required accuracy and spatial resolution.
The nuclear industry now also recognizes that CFD codes have reached the desired level of maturity (at least for single-phase applications) for them to be used as part of the Nuclear Power Plant (NPP) design process, and it is the objective the research and development teams to assess the current capabilities of such codes in this regard, and contribute to the technology advance in respect to their verification and validation. CFD is already well-established in addressing certain safety issues in NPPs, as reported and discussed at various international workshops. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations. In parallel, it remains an overriding necessity to benchmark the performance of the CFD codes, and for this experimental databases need to be established, first for separate-effect tests but especially for full-size integral tests.
In order to validate the CFD Code ANSYS CFX for reactor safety relevant flow phenomena it is essential to use the UPTF experiments, since they are full scale tests. All other separate effect test rigs and test facilities like ROCOM (Höhne, 2000) are scaled. Scaling parameters of flow conditions are one of the still open topics for the use of CFD codes in nuclear reactor safety. Three UPTF tests were selected and post-test calculation were performed. The major focus was analyzing the qualitative flow behavior.
Keywords: AIAD, CFD, CCFL, UPTF
  • Article, self-published (no contribution to HZDR-Annual report)
    Helmholtz-Zentrum Rossendorf 2016
    1
    44 Seiten

Publ.-Id: 23817 - 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.;
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

Publ.-Id: 23816 - Permalink


Profiling Performance of hybrid applications with Score-P and Vampir
Juckeland, G.; Dietrich, R.;
OpenACC aims at providing a relatively easy and straightforward way to describe parallelism for exploitation on platforms with hardware accelerators. It is by design also an approach for porting legacy HPC applications to this novel architecture. Especially such legacy applications, but also newly developed applications that require more resources than a single node can offer, use MPI for inter-node communication and coarse work distribution, thus, becoming so-called hybrid applications. It is also possible to combine OpenACC with OpenMP on the host side to utilize all resources of a compute node or to even use all three levels of parallelism concurrently. Tuning application performance for one parallelization paradigm is challenging, adding the second or third level of parallelism introduces a whole new layer of potential performance problems from the interaction of all parallelization paradigms. It is, however, possible to extend the previously mentioned profile-guided development to also cover this usage scenario.
Profiling tools from compiler or accelerator vendors are usually limited to the scheme the product address, e.g. only OpenACC or CUDA/OpenCL activity. Almost all vendor tools cannot record MPI activity leaving the programmer in the dark how well hybrid applications perform over all used levels of parallelism. Research based performance tools cover this gap. HPCtoolkit, Tau, and Score-P are the most prominent ones that also offer hardware accelerator support. Out of the three Score-P is the one that covers the most parallelization paradigms, can record the most concurrent activity and, as a result, can provide the most complete performance picture even for very complex applications. Therefore, Score-P will be used as the example performance recording tool for this chapter. The other tools can provide similar results. Vampir will be use for visualizing the performance data since it is by far the most capable trace visualizer and profile generator.
  • Book chapter
    Farber, Rob: OpenACC - Parallel Programming with OpenACC, Amsterdam: Elsevier, 2016, 978-0-12-410397-9, 55-68

Publ.-Id: 23815 - Permalink


Reshaping on demand
Makarov, D.;
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

Publ.-Id: 23814 - Permalink


Bunch arrival-time monitoring for laser particle accelerators and Thomson scattering x-ray sources.
Krämer, J.; Kuntzsch, M.; Zarini, O.; Köhler, A.; Lehnert, U.; Michel, P.; Irman, A.; Schramm, U.; Couperus, J. P.;
The ELBE center of high power radiation sources at Helmholtz-Zentrum Dresden-Rossendorf combines a superconducting CW linear accelerator with Terawatt- and Petawatt- level laser sources. Key experiments rely on precise timing and synchronization between the different radiation pulses. An online single shot monitoring system has been set up in order to measure the timing between the high-power Ti:Sa laser DRACO and electron bunches generated by the conventional SRF accelerator. This turnkey timing system is suitable for timing control of Thomson scattering x-ray sources and external injection of electron bunches into a laser wakefield accelerator. It uses a broadband RF pickup to acquire a probe of the particle bunch’s electric field and modulates a fraction of the high power laser pulse in a fast electro-optical modulator. The amplitude modulation gives a direct measure for the timing between both beams. Using this setup a resolution of <200 fs RMS has been demonstrated. The contribution will show the prototype, first measurement results and will discuss future modification in order to improve the resolution of the system.
Keywords: ELBE BAM arrival time diagnostic Thomson
  • Poster
    International Beam Instrumentation Conference IBIC, 11.-15.09.2016, Barcelona, Spain
  • Open Access LogoContribution to proceedings
    International Beam Instrumentation Conference IBIC, 11.-15.09.2016, Barcelona, Spain

Publ.-Id: 23813 - Permalink


Role of solvents in the electronic transport properties of single-molecule junctions
Luka-Guth, K.; Hambsch, S.; Bloch, A.; Ehrenreich, P.; Briechle, B. M.; Kilibarda, F.; Sendler, T.; Sysoiev, D.; Huhn, T.; Erbe, A.; Scheer, E.;
We report on an experimental study of the charge transport through tunnel gaps formed by adjustable gold electrodes immersed into different solvents which are commonly used in the field of molecular electronics (ethanol, toluene, mesitylene, 1,2,4-trichlorobenzene, isopropanol, toluene/tetrahydrofuran mixtures) for the study of single-molecule contacts of functional molecules. We present measurements of the conductance as a function of gap width, conductance histograms as well as current-voltage characteristics of narrow gaps and discuss them in terms of the Simmons model, which is the standard model for describing transport via tunnel barriers, and the resonant single-level model, often applied to single-molecule junctions. One of our conclusions is that stable junctions may form from solvents as well and that both conductance-distance traces and current-voltage characteristics have to be studied to distinguish between contacts of solvent molecules and of molecules under study.
Keywords: mechanically controllable break junction, polar solvent, molecular electronics, electrochemical environment, single-molecule junctions

Publ.-Id: 23812 - Permalink


Radiolabelling of nanoparticles for the use in environmental fate studies in waste water treatment and beyond
Schymura, S.; Fricke, T.; Hildebrand, H.; Franke, K.;
Radiolabeling is a strong tool for the research of nanoparticle fate in the environment as it allows sensitive detection at very low concentrations. We introduced radiolabels into commerical TiO2, CeO2 and multi-wall carbon nanotubes using various cyclotron and non-cyclotron techniques. The so-labelled nanoparticles can be used in fate studies of nanoparticle beahavior in waste water treatment and their possible uptake into plants.
Keywords: Radiomarkierung, radiolabelling Nanopartikel, nanoparticles Zyklotron, Cyclotron
  • Lecture (Conference)
    CYCLEUR 2016, 23.-24.06.2016, Bern, Schweiz

Publ.-Id: 23811 - Permalink


First experience using a MTCAMicroTCA.4-based LLRF-controller driving the SSPA-based high power RF system at ELBE.
Kuntzsch, M.; Rutkowski, I.; Hierholzer, M.; Grzegrzółka, M.; Rybaniec, R.; Schmidt, C.; Hoffmann, M.; Büttig, H.; Schurig, R.;
The ELBE center for high power radiation sources is operating a superconducting RF accelerator in CW mode. Since 2012 solid state amplifiers are used to drive the accelerating structures at ELBE. New experiments which are in preparation need a better temporal resolution and therefore a higher beam stability. Since 2013 a test series has been performed to evaluate a MicroTCA.4-based digital LLRF (low level RF) system foreseen to replace the analogue controllers. The contribution gives an overview of the setup, reports first performance results and discusses challenges and experience gained during commissioning.
Keywords: ELBE SSPA high power RF LLRF
  • Poster
    Continuous Wave and High Average Power RF Workshop, 21.-24.06.2016, Grenoble, France

Publ.-Id: 23810 - Permalink


The molecular switching mechanism at the conserved D(E)RY motif in class-A GPCRs
Sandoval, A.; Eichler, S.; Madathil, S.; Reeves, P. J.; Fahmy, K.; Boeckmann, R. A.;
The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the photoreceptor rhodopsin, this is accompanied by proton uptake at Glu134 in the class-conserved E(D)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed here by molecular dynamics (MD) simulations on TM3 model peptides in a DOPC bilayer. We show that protonation of the conserved glutamic acid alters its side chain rotamer preferences and stabilizes the C-terminal helical structure. Both factors contribute to the rise of the side chain pKa (> 6) and to reduced polarity around the TM3 C-terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved FTIR spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu134- and Gln134-containing opsin mutants and demonstrates that the E(D)RY motif is a hydrated microdomain. 25 The function of the E(D)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface.
Keywords: infrared fluorescence membrane protein hydration

Downloads:

Publ.-Id: 23809 - Permalink


Measuring techniques for experimental investigations and monitoring of liquid metal flows
Ratajczak, M.; Wondrak, T.; Klotsche, K.; Zürner, T.; Martin, R.; Stefani, F.; Gundrum, T.; Franke, S.; Räbiger, D.; Eckert, S.;
Flow measurements in hot liquid metals using the ultrasound Doppler method (UDV)
Contactless Inductive Flow Tomography
  • Invited lecture (Conferences)
    SCK CEN Heavy Metal Summer School 2016, 13.-17.06.2016, Mol, Belgium

Publ.-Id: 23808 - 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.;
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

Publ.-Id: 23807 - Permalink


Excitonic mobility edge and ultra-short photoluminescence decay time in n-type GaAsN
Eßer, F.; Winnerl, S.; Patanè, A.; Helm, M.; Schneider, H.;
We use time-resolved photoluminescence (PL) spectroscopy to study the recombination dynamics in Si-doped GaAsN semiconductor alloys with a nitrogen content up to 0.2%. The PL decay is predominantly monoexponential and exhibits a strong energy dispersion. We find ultra-short decay times on the high-energy side and long decay times on the low-energy side of the photoluminescence spectrum. This asymmetry can be explained by the existence of an additional non-radiative energy transfer channel and is consistent with previous studies on intrinsic GaAsN epilayers. However, the determined maximum decay times of GaAsN:Si are significantly reduced in comparison to undoped GaAsN. The determined excitonic mobility edge energy constantly decreases with increasing N content, in agreement with the two-level band anticrossing model.
Keywords: dilute nitride, mobility edge, recombination dynamics, time-resolved photoluminescence

Downloads:

Publ.-Id: 23806 - 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.;
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
  • Lecture (others)
    Fachgespräches des Fachbereichs Strahlenschutz des VKTA, 23.11.2016, Dresden, Deutschland
  • Lecture (others)
    Institutsseminar des Instituts für Kern- und Teilchenphysik der TU-Dresden, 29.06.2017, Dresden, Deutschland

Publ.-Id: 23805 - Permalink


P1219 - Funktionalised silicon nanoparticles
Stephan, H.ORC; Bergmann, R.; Ruffani, A.; de Cola, L.
The present invention is related to silicon nanoparticles, a pharmaceutical composition comprising silicon nanoparticles, a method for synthesis of the silicon nanoparticles and their use for in vivo diagnostics, visualization of drug delivery or staining of cells, biological processes or pathways. The silicon nanoparticles are characterised that they comprise a silicon core of a size of 1 to 10 nm and are terminated with allylamine or poly(allylamine) comprising up to 10 allylamine groups.
  • Patent
    WO2013087734 - Offenlegung 20.06.2013, Nachanmeldungen: CN, EP, US

Publ.-Id: 23804 - Permalink


Systematic XAS study on the reduction and uptake of Tc by magnetite and mackinawite
Yalcintas, E.; Scheinost, A. C.; Gaona, X.; Altmaier, M.;
The mechanisms for the reduction and uptake of Tc by magnetite (Fe3O4) and mackinawite (FeS) are investigated using XAS techniques (XANES, EXAFS), in combination with thermodynamic calculations of the Tc/Fe systems and accurate characterization of the solution properties (pHm, pe, [Tc]). Batch sorption experiments were performed in the presence of freshly prepared magnetite and mackinawite in 0.1 M NaCl solutions with varying [Tc(VII)]0 (2·10–5 – 2·10–4 M) and loading of Tc (400–900 ppm ). XANES confirms the complete reduction of Tc(VII) to Tc(IV) in all investigated systems, as predicted by experimental (pHm + pe) measurements and thermodynamic calculations. Two Tc pure endmember species are identified by EXAFS in the magnetite system, corresponding to fully incorporated Tc in the magnetite structure and (likely) to a Tc-Tc dimeric structure with triple-bonding to the magnetite {111} faces. The latter endmember is favoured at higher [Tc], whereas incorporation prevails at low [Tc] and less alkaline pH conditions. The key role of pH in the uptake mechanism is interpreted in terms of magnetite solubility, with higher [Fe] and greater recrystallization rates occurring with decreasing pH values. A TcS2-like phase prevails in all investigated mackinawite systems, although the contribution of up to  20% of TcO2xH2O(s) (likely as surface precipitate) is observed for the highest investigated loadings (900 ppm). These results provide key inputs for an accurate mechanistic interpretation of the Tc uptake by magnetite and mackinawite, so far controversially discussed in the literature, and represent a very relevant contribution in the context of nuclear waste disposal.
Keywords: Tc nuclear waste XAS XAFS XANES magnetite mackinawite

Publ.-Id: 23803 - Permalink


Phosphorene under electron beam: from monolayer to one-dimensional chains
Vierimaa, V. V.; Krasheninnikov, A. V.; Komsa, H.-P.;
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

Publ.-Id: 23802 - Permalink


Biologische Laugung von Kupfer aus Kupferschiefer
Kostudis, S.; Bachmann, K.; Kutsche, S.; Pollmann, K.; Gutzmer, J.;
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

Publ.-Id: 23801 - Permalink


Resource Analytics:An introduction into automated mineralogy and application on REE
Birtel, S.;
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

Publ.-Id: 23800 - Permalink


How to use a MLA correctly
Birtel, S.; Tolosana Delgado, R.; Bachmann, K.; Heinig, T.; Gutzmer, J.; Matos Camacho, S.; van den Boogaart, K. G.;
SEM-based image analysis (aka Automated Mineralogy) has become a standard method not only in mineral processing but also for petrological studies, e.g., for the determination of modal mineralogy, search for rare phases, or for fabric parameters such as grain size and mineral association. A very small aliquot (the surface of a polished epoxy block prepared from a few grams of ground material or the surface of a polished thin section) are used during analysis. All caution is needed to assure that this small aliquot is representative of the sample material to be examined – and that it yields the information of particular interest, e.g., the abundance and microfabric relations of rare phases such as PGEs or Au.
SEM-based image analysis is performed on surfaces, i.e. observations are obtained on two-dimensional surfaces, whereas the relevant attributes all related to the properties of three dimensional mineral grains/particles/rock volumes. For grain mounts, the appearance of a grain on the analyzed surface is controlled by the behavior of the grain during sample preparation and depends on grain size, shape and density of phases. Cutting effects usually cause an underestimation of grain size for isotropic grains, whereas phases forming grains with a shape preferred orientation (e.g. mica) may be over- or underestimated depending on the plane chosen for analysis. This causes also bias in modal mineralogy, grain size and shape or mineral association and liberation. At best, measurements can be precise but not accurate with reference to the entire sample.
To evaluate these effects, a systematic study was performed on grain mounts of a mineralogically rather simple greisen from the Erzgebirge (Germany), mainly constituted by zinnwaldite mica, topaz and quartz, i.e minerals with different density, mineral grain size and shape. Eight values of the ratio solid load/resin and analyses of two cutting planes (xy and xz) were performed, having 16 MLA measurements. Apparent modal mineralogy compositions were statistically compared, using bootstrapping techniques to estimate their uncertainty. Results showed a significant and constant difference of the topaz proportion between xy and xz measurements, as well as a significant systematic reduction in the ratio zinnwaldite/quartz with increasing solid load/resin ratio on xy measurements, a bias absent from xz measurements. In conclusion, sample preparation biases can be reduced by measuring on transverse planes (xz) or reducing the amount of resin added to the sample. For a first time the error in analyzing modal mineralogy was quantified. Other biases remain, like e.g. stereological distortion in estimating 3D quantities from 2D measurements. Such challenges are left for further research.
  • Poster
    Gordon Conference Geochemistry of Mineral Deposits, 19.-24.06.2016, Les Diablerets,, Switzerland

Publ.-Id: 23799 - 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.;
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

Downloads:

Publ.-Id: 23798 - Permalink


Radio-labelled nanomaterials for cancer diagnostics and treatment
Stephan, H.ORC
The field of nanomedicine offers excellent prospects for the development of new non-invasive strategies for the diagnosis and therapy of cancer. A major advantage of nanomaterials (NMs) is their potential to be used as non-invasive diagnostic tools. By combining multiple modalities into a single probe, higher sensitivity can be achieved, leading to deeper insights into different in vitro and in vivo processes. Despite the significant progress that has been made in the field of NMs-based cancer diagnostics, our overall understanding of their pharmacokinetics (adsorption, uptake, distribution, metabolism and excretion) is still limited. Detailed investigations of the physicochemical properties and physiological behavior of NMs in biological environments are required to be better able to understand, predict and control their biodistribution.
  • Invited lecture (Conferences)
    ICARO Kick-off Meeting, 10.06.2016, Sestri Levante (Genua), Italy

Publ.-Id: 23796 - Permalink


Hydroxyquinoline-Calix[4]arene-Conjugates as Ligands for Polynuclear Lanthanide Complexes: Preparation, Characterization, and Properties of a Dinuclear Eu(III) complex
Jäschke, A.; Kischel, M.; Mansel, A.; Kersting, B.;
The synthesis of a calixarene-based N4O4 donor ligand H6L, in which two 8-hydroxyquinoline-2-carbaldehyde units are appended via hydrazone-carbonylmethoxy linkages in a 1,3-arrangement to the lower rim of tert-butyl-calix[4]arene, and its coordination properties towards Eu(III) are described. The reaction of H6L with Eu(NO3)3.6H2O produces a dinuclear complex [Eu2(H3L)2] (4). The Eu(III) ions in 4 are well-separated from each other (d > 8 Å) each being coordinated by two tetradentate hydroxyquinoline-2-carbaldehyde-hydrazone substituents from two triply deprotonated molecules (H3L)3- in a dodecahedral geometry. As a consequence there are no exchange interactions between the Eu(III) ions, and the magnetic properties are solely associated with thermal population of excited (7F1-7F6) terms. The spin-orbit coupling constant lambda is 325.2(4) cm-1. Moreover, the ligand H6L was found to extract Eu(III) and Tb(III) at pH 7-8 from aqueous solution, as established by radiotracing using the short-lived radionuclides 160Tb and 152Eu.
Keywords: Polynuclear Complex; 8-Hydroxyquinoline; Calix[4]arene; Europium; Extraction

Publ.-Id: 23795 - Permalink


P1407 - Verfahren zur Hydrophilisierung von Metalloxid-Nanopartikeln
Hunoldt, S.; Stephan, H.;
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

Publ.-Id: 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.;
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.

Publ.-Id: 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.;
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

Publ.-Id: 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.;
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

Publ.-Id: 23791 - Permalink


P1512 - Gittersensor-System zum Charakterisieren einer Fluidströmung
Schleicher, E.; Tschofen, M.; Pietruske, H.;
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, Nachanmeldungen: WO

Publ.-Id: 23790 - Permalink


P1501 - Anordnung zum Erfassen der Strömungsgeschwindigkeit einer Fluidströmung in einem Strömungsquerschnitt
Hampel, U.;
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

Publ.-Id: 23789 - Permalink


P1411 - Anordnung und Verfahren zur Dispersionsmessung sowie Mehrphasenapparat mit einer solchen Anordnung
Hampel, U.;
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

Publ.-Id: 23788 - Permalink


P1408 - Photochemische Entfernung von Uran(VI)-Verbindungen aus mit Uran(VI)-verschmutzten Flüssigkeiten
Fahmy, K.; Tsushima, S.; Attia, E.;
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

Publ.-Id: 23787 - Permalink


Das Ende der letzten Eiszeit – 10Be Expositionsdatierung im Aaretal, Schweiz
Zech, R.; Wüthrich, L.; Morabito, E. G.; Gnägi, C.; Zech, J.; Veit, H.; Merchel, S.;
Während der Eiszeiten sind wiederholt die Gletscher aus den Alpen bis weit in das Schweizer Mittelland vorgestossen. Genaues Ausmass und Zeitpunkt sind selbst für die letzte Vergletscherung umstritten. Publizierte 10Be Expositionsalter von Findlingen auf dem Niederbippstadium des Rhone-Aare-Gletschers dokumentieren scheinbar den maximalen Vorstoss während der letzten Vergletscherung vor ca. 24 ka. Allerdings ist die Bodenentwicklung auf dem Niederbippstadium deutlich fortgeschrittener (Entkalkungstiefen von 3 bis 4 m) als die Bodenentwicklung auf dem Bern- und Gurtenstadium mit vermuteten Altern von ca. 18 – 20 ka (Entkalkungstiefen dort <1,5 m).
Wir haben mehrere Findlinge auf dem Bern- und Gurtenstadium beprobt und ihre 10Be Expositionsalter bestimmt. Die ältesten drei von sechs Findlingen vom Bernstadium liefern Expositionsalter um ca. 18 ka und dokumentieren den Gletscherstand des Aaregletschers kurz vor dem endgültigen und raschen Zerfall der Vorlandgletscher am Ende der letzten Eiszeit. Zwei von fünf Findlingen vom Gurtenstadium haben Expositionsalter um 20 ka und zeigen, dass der Aaregletscher zu diesem Zeitpunkt noch sehr viel grösser war. Auf beiden Stadien gibt es deutlich “zu junge” Expositionsalter, die höchstwahrscheinlich mit Erosion, geomorphologischer Instabilität, und menschlicher Aktivität erklärt werden müssen.
Es kann bisher nicht vollständig ausgeschlossen werden, dass die Expositionsalter des Niederbippstadium ebenfalls “zu jung” sind. Dann liesse sich die Bodenentwicklung auf dem Niederbippstadium problemslos erklären. Dokumentieren die Expositionsalter tatsächlich den maximalen Gletschervorstoss vor 24 ka, muss davon ausgegangen werden, dass die mächtige Entkalkung und Tonverlagerung dort in wenigen tausend Jahren, und vor allem unter glazialen Bedingungen stattgefunden hat. Weitere Findlinge sind daher im Moment in Bearbeitung, um den Zeitpunkt der maximalen, letztglazialen Vergletscherung zu klären.
Keywords: AMS, cosmogenic nuclide, moraine
  • Lecture (Conference)
    Jahrestagung Deutscher Arbeitskreis für Geomorphologie 2016, 06.-08.10.2016, Jena, Deutschland

Publ.-Id: 23785 - Permalink


The constancy of the galactic cosmic rays: The contribution of cosmogenic noble gases and radionuclides in iron meteorites
Smith, T.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.; Scharf, A.;
Introduction: The temporal constancy of galactic cosmic rays (GCRs) over the last few billion years is an important and long-standing question in meteorite research. Over the years, meteorites have been intensely studied to answer this question [1]. While travelling in space, meteoroids are exposed to GCRs and the nuclear interactions produce (among others) stable (noble gases) and radioactive cosmogenic nuclides. Being interested in the long-term variation of the GCRs, we study iron meteorites because they typically have cosmic ray exposure (CRE) ages in the range of a few million years (Ma) and – for some – even up to 2 Ga [2]. It has been demonstrated previously that periodic GCR flux variations can induce peaks in CRE age histograms, which is due to the fact that during periods of high fluency the “apparent” time seems to run faster and vice-versa. Therefore, setting up a consistent exposure age histogram and then searching for periodic peaks would make it possible to study GCR flux variations.
Experimental methods: We measured the isotopic concentrations of He, Ne, and Ar by noble gas mass spectrometry at the University of Bern following procedures described earlier [3,4]. Analyses of the cosmogenic radionuclides 10Be, 26Al, 36Cl, and 41Ca have been performed at the DREsden Accelerator Mass Spectrometry facility (DREAMS, [5]) using chemical separation procedures described in [6].
Results: In total 55 iron meteorite samples, predominantly of class IIIAB, have been selected and investigated for their cosmogenic nuclide contents. The CRE ages have been calculated using the 36Cl-36Ar dating scheme [1]. However, doing so we had to correct 36Cl for radioactive decay on Earth, i.e., we had to determine the terrestrial age for each studied meteorite. To avoid problems with 10Be and 26Al production from inhomogeneously distributed sulfur- and phosphorous-bearing minerals, we use the 41Ca-36Cl system to determine terrestrial ages instead of e.g. 10Be-36Cl system. Doing so we use updated Monte-Carlo calculations, e.g., [3], instead of the classical semiempirical approaches [7]. Up to now, noble gases have been measured in 35 samples and radionuclides in 48 samples. The calculated CRE ages range between ~5 and ~700 Ma, which is in the range expected for iron meteorites [2,8]. So far, no features can be observed in the CRE ages histogram. Additional noble gas and radionuclide measurements are ongoing, which will increase the statistics and will help to study possible long-term variations in the GCR intensities over the last few billion years.
References: [1] Lavielle B. et al. 1999. Earth Planetary and Science Letters 170:93–104. [2] Wieler R. et al. 2013. Space Science Reviews 176:351-363. [3] Ammon K. et al. 2009. Meteoritics and Planetary Science 44:485-503. [4] Ammon K. et al. 2011. Meteoritics and Planetary Science 46:785-792. [5] Rugel G. et al. 2016. Nuclear Instruments and Methods in Physics B 370:94-100. [6] Merchel S. and Herpers U. 1999. Radiochimica Acta 84:215-219. [7] Welten, K. et al. 2001. Abstract in 31st Lunar and Planetary Science Conference. [8] Eugster O. et al. 2006. Meteorites and the Early Solar System II, Part IX: 829-851.
Acknowledgments: The authors would like to thank the following museums and colleagues for their precious contribution to this study: D. Cook (ETH Zürich), the Ege University Observatory Research and Application Center, Turkey, L. Ferrière and F. Brandstätter (Naturhistorisches Museum Wien), P. Heck (The Field Museum, Chicago), A. Muszyński (Department of Mineralogy and Petrology, Poznań), I. Nicklin (Royal Ontario Museum), P. Rochette (CEREGE, Aix-Marseille Université), C. Smith (Natural History Museum London), and J. Zipfel (Senckenberg Naturmuseum Frankfurt). This work is supported by the Swiss National Science Foundation (SNF).
Keywords: AMS, cosmogenic nuclide, cosmic rays
  • Lecture (Conference)
    79th Annual Meeting of the Meteoritical Society, 07.-12.08.2016, Berlin, Deutschland

Publ.-Id: 23784 - Permalink


Preatmospheric size and terrestrial age of the Twannberg meteorite (IIG)
Smith, T.; Leya, I.; Hofmann, B.; Merchel, S.; Rugel, G.; Pavetich, S.; Scharf, A.;
Introduction: The main mass of the Twannberg meteorite (15.9 kg) has been found 1984 in the Canton of Bern, Switzerland. The Twannberg meteorite belongs to the IIG group, which comprises so far only six members and which is characterized by large amounts of schreibersite (Fe,Ni)3P and a low nickel content of 5% only [1]. Twannberg is so far the largest meteorite found in Switzerland. Recent research campaigns have increased the amount of recovered material yielding to a total mass of ~70 kg in ~550 individual pieces.
In this study, we analyzed 17 individual samples and calculated their cosmic ray exposure (CRE) age using cosmogenic noble gases and radionuclides. We applied updated Monte-Carlo model calculations to determine (i) the preatmospheric size, (ii) the cosmic ray exposure age, and (ii), especially, the terrestrial age of Twannberg to better understand its relation to the last glaciation event in Europe [1].
Experimental methods: The isotopic concentrations for He, Ne, and Ar have been measured by noble gas mass spectrometry at the University of Bern following procedures described earlier [2,3]. Analyses of the cosmogenic radionuclides (i.e., 10Be, 26Al, 36Cl, and 41Ca) have been performed at the DREsden Accelerator Mass Spectrometry facility (DREAMS, [4]) using procedures described in [5].
Results: In total, 17 samples have been analyzed for noble gas concentrations; seven of them have also been investigated for their cosmogenic radionuclide contents. We observe a wide range of noble gas and radionuclide concentrations of more than one order of magnitude among the different samples. The noble gas and radionuclide concentrations linearly correlate, demonstrating the reliability of the analysis despite low concentrations. Combining the data with improved model calculations indicate a preatmospheric radius of up to 10 m. Considering an average density of about 8 g/cm3 and assuming a spherical object, the preatmospheric mass of Twannberg was most likely larger than 33000 tons.
The CRE age for Twannberg, which has been determined using the 36Cl-36Ar method [6], is 236±50 Ma, which is in the range of typical CRE ages for iron meteorites [7] and which is in good agreement with the adopted age of 230±50 Ma found previously [1]. More importantly, the mean terrestrial age based on 41Ca-36Cl systematics and up-dated Monte-Carlo calculations is 165±58 ka. The age therefore indicates that Twannberg most likely fell during the second last glaciation (~185-130 ka), or even during one of the two last (~130-115 ka) or (~225-185 ka) interglacials. Research campaigns in the field are still ongoing and we hope for a further recoveries of Twannberg material.
References: [1] Hofmann B. et al. 2009. Meteoritics and Planetary Science 44:187-199. [2] Ammon K. et al. 2008. Meteoritics and Planetary Science 43:685-699. [3] Ammon K. et al. 2011. Meteoritics and Planetary Science 46:785-792. [4] Rugel G. et al. 2016. Nuclear Instruments and Methods in Physics B 370:94-100. [5] Merchel S. and Herpers U. 1999. Radiochimica Acta 84:215-219. [6] Lavielle B. et al. 1999. Earth and Planetary Science Letters 170:93-104. [7] Eugster O. 2003. Chemie der Erde-Geochemistry 63:3-30.
Acknowlegments: This study heavily relies on samples collected in a great effort by a joint group of meteorite enthusiasts and scientists. We particularly thank for the collaboration and samples: Marc Jost, Manuel Eggimann, Hannes Weiss, Sergey Vasiliev, Andreas Koppelt, Ernst Wyler, Gino Bernasconi, Marcel Häuselmann, and Edwin Gnos. This work is supported by the Swiss National Science Foundation (SNF).
Keywords: AMS, cosmogenic nuclide, meteorite
  • Poster
    79th Annual Meeting of the Meteoritical Society, 07.-12.08.2016, Berlin, Deutschland

Publ.-Id: 23783 - Permalink


Can Morasko and Mundrabilla help reconstructing production rates and nuclear reaction cross-section for light cosmogenic nuclides?
Merchel, S.; Smith, T.; Leya, I.; Pavetich, S.; Rugel, G.; Scharf, A.; Muszynski, A.;
Introduction: The reconstruction of pre-atmospheric sizes and exposure and terrestrial ages of meteorites including shielding depths of individual samples has advanced in the last decades. Technical developments in noble gas and accelerator mass spectrometry (AMS) led to cosmogenic nuclide data of higher accuracy. Additionally, progress in Monte-Carlo calculations [1] seems to produce more reliable interpretation of the experimental data than earlier “classical” semiempirical approaches. However, some problems regarding both experimental data and calculations are persistent. One of these is the production of lighter nuclides such as 10Be, 21,22Ne, and 26Al from inhomogeneously distributed sulfur- and phosphorus-rich inclusions or from trace elements in iron meteorites or metal phases of stony-iron meteorites. As we lately experienced again, the uselessness of 26Al and 21,22Ne for deciphering the history of a newly discovered iron meteorite, i.e. Gebel Kamil [2], we follow an approach to measure cosmogenic nuclides in schreibersite and troilite inclusions from iron meteorites compared to bulk metal to get more quantitative insights into these difficulties. First, samples from Morasko and Mundrabilla (metal, troilite, schreibersite) were investigated.
Experimental: Lighter stable nuclides of He, Ne, and Ar have been measured by noble gas mass spectrometry at the University of Bern [3], radionuclides (10Be, 26Al, 36Cl, and 41Ca) at the DREsden Accelerator Mass Spectrometry facility (DREAMS) [4,5] after radiochemical separation [6].
Results and discussion: Data of 36Cl and 36Ar of the metal yield to partially consistent exposure ages, i.e. (247 ± 26) Ma for Mundrabilla (compared to (350 ± 90) Ma [7]) and (210 ± 22) Ma for Morasko (compared to (130 ± 15) Ma [8]). Our Morasko exposure age is validated by the corresponding troilite analyses giving an age of (246 ± 49) Ma proving the 36Cl-36Ar-system not being influenced by contributions from sulfur within uncertainties. All our ages are based on three to four individual 36Cl-36Ar-analysis.
Terrestrial ages based on the 41Ca-36Cl-system should be the most reliable and least influenced by S- and P-abundances. Data of Morasko was indistinguishable from saturation activities, thus, confirming the young terrestrial age of 5 ka determined by earlier luminescence-dating of the corresponding crater [9]. However, high 41Ca/36Cl of 1.5 and 2.9 for troilite and metal fractions of Mundrabilla, respectively, do not allow calculating a reasonable terrestrial age pointing to unexplained discrepancies in either the AMS measurements or Monte-Carlo calculations for shielded samples. Further work is needed.
As expected, 26Al is most severely influenced by S- and P-abundances. In Mundrabilla 26Al (mean of four individual samples each; standard deviation) is as high as (4.618 ± 0.071) dpm/kgtroilite compared to neighboring metal fractions (0.1635 ± 0.010) dpm/kgmetal, resulting in 26Al/10Be-ratios of 20.8 (troilite) compared to 0.9 (metal). Same observations (mean of three samples each; standard deviation) can be made for 26Al in Morasko: (7.36 ± 0.18) dpm/kgtroilite vs. (0.2399 ± 0.0063) dpm/kgmetal with 26Al/10Be of 19.4 (troilite) and 0.8 (metal). A single analysis of Morasko schreibersite produced intermediate 26Al-data of (3.286 ± 0.081) dpm/kgschreibersite resulting in 26Al/10Be of ~1.6.
Conclusions and outlook: It has been clearly shown that even traces of troilite influence the 26Al-concentration. It seems obvious that careful sample inspection under a binocular is essential to overcome the most severe influences by S- and P-inclusions. However, the determination of S and P in aliquots of each metal sample is analytical challenging and mean bulk values might not be representative for the individual sample. Nevertheless, we are aiming at deciphering thick-target production rates and cross-sections for 10Be, 21,22Ne, and 26Al - from S and P - from this first data and future analyses to include them into Monte-Carlo calculations for later use.
References: [1] Ammon K. et al. 2009. Meteoritics and Planetary Science 44:485-503. [2] Ott U. et al. 2014. Meteoritics and Planetary Science 49:1365-1374. [3] Ammon K. et al. 2008. Meteoritics and Planetary Science 43:685-699. [4] Akhmadaliev et al. 2013. Nuclear Instruments and Methods in Physic B 294:5-10. [5] Rugel G. et al. 2016. Nuclear Instruments and Methods in Physics B 370:94-100. [6] Merchel S. and Herpers U. 1999. Radiochimica Acta 84:215-219. [7] Maruoka T. and Matsuda J. 2011. Chemical Geology 175:751-756. [8] Hutzler A. 2015. PhD thesis, Aix-Marseille Université. [9] Stankowski W.T.J. et al. 2007. Geochronometria 28:25-29.
Acknowledgements: We thank the operators of the ion beam centre and further colleagues at HZDR, especially René Ziegenrücker, for help in performing AMS measurements at DREAMS. We are grateful to Jutta Zipfel from Senckenberg Forschungsinstitut und Naturmuseum Frankfurt for putting precious Mundrabilla samples at our disposal.
Keywords: AMS, cosmogenic nuclide
  • Lecture (Conference)
    79th Annual Meeting of the Meteoritical Society, 07.-12.08.2016, Berlin, Deutschland

Publ.-Id: 23782 - Permalink


New insights in preservation of meteorites in hot deserts: The oldest hot desert meteorite collection
Hutzler, A.; Rochette, P.; Bourlès, D.; Gattacceca, J.; Merchel, S.; Jull, A. J. T.; Valenzuela, M.;
With a meteorite concentration up to 170 meteorites over 10 g per km² [1], the Central Depression of the Ataca-ma Desert is an exceptional field for recovery of meteorites. Without clear evidence of physical concentration, and based on models calculating the falling rate of meteorites on Earth at 80 meteorites (>10 g) Ma-1 km² [2], the time needed to reach such a density is in the order of million years.
To test this hypothesis, a random subset of 25 chondrites from Chilean dense collection areas (DCA) were first 14C-dated. Over 67% of them are beyond the C-14 dating limit, namely ~40 ka. This led us to conclude that longer half-lived cosmogenic nuclides are better-suited to study this collection.
A random subset of 24 ordinary chondrites was chosen from the 213 meteorites of the El Médano collection (El Médano and Caleta el Cobre DCAs). Their terrestrial ages were calculated using cosmogenic nuclide concentrations. For comparison, we also present the terrestrial ages calculated for 10 Chilean iron meteorites (4 from this study, 6 from the literature [3]).
Cosmogenic nuclides (10Be, 26Al, 36Cl and 41Ca) were extracted from iron fractions of chondrites and from iron meteorites following [4]. Their concentrations were measured at the French 5 MV AMS national facility ASTER (CEREGE, France) [5]. Terrestrial ages have been calculated using three different methods: Tterr 36Cl/10Be, Tterr 36Cl/41Ca and Tterr 36Cl [6][7].
The terrestrial ages of the El Médano collection meteorites are distributed between 35 ka and 1 Ma (36Cl /41Ca method), with an unweighted average of (0.41±0.26) Ma. Terrestrial ages of the Chilean iron meteorites range be-tween 0 and 2.7 Ma, with an unweighted average at (0.43±0.43) Ma. This distribution highlights significantly older terrestrial ages than those related to other hot desert collections. It is comparable to the age spectrum for DCAs from Antarctica, such as Allan Hills. According to these results, it is possible for a meteorite collection to be preserved for over 1 Ma in a hot desert environment, providing the environment shows long-standing hyperarid conditions. In view of its exceptional old age, the El Medano meteorite collection offers the possibility to study the meteorite flux to Earth on the million years time scale.
References: [1] Hutzler A. et al. 2016. Meteoritics & Planetary Science 51:468-482. [2] Halliday, I. et al. 1989. Meteoritics 24:87-122 [3] Koblitz J. 2005. Metbase, version 7.1. [4] Hutzler A. 2015. PhD Thesis, Aix-Marseille-University. [5] Arnold et al. 2010. Physics Research B 268:1954-1959.[6] Leya I. and Masarik J. 2009. Meteoritics & Planetary Science 44, 1061-1086. [7] Nishiizumi K. et al. 1989. Earth and Planetary Science Letter 93:299-313.
Keywords: AMS, terrestrial age
  • Poster
    79th Annual Meeting of the Meteoritical Society, 07.-12.08.2016, Berlin, Deutschland

Publ.-Id: 23781 - 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.;
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

Downloads:

Publ.-Id: 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.;
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

Downloads:

Publ.-Id: 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.;
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

Publ.-Id: 23777 - Permalink


Velocity Measurement For Two-Phase Flows Based On Ultrafast X-ray Tomography
Barthel, F.; Bieberle, M.; Hoppe, D.; Banowski, M.; Hampel, U.;
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

Publ.-Id: 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.;
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

Downloads:

  • Secondary publication expected

Publ.-Id: 23775 - Permalink


Remote sensing exploration of Nb-Ta-LREE-enriched carbonatite (Epembe/Namibia)
Zimmermann, R.; Brandmeier, M.; Andreani, L.; Mhopjeni, K.; Gloaguen, R.;
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

Publ.-Id: 23774 - Permalink


Direct measurements of the magnetocaloric effect in pulsed magnetic fields
Skourski, Y.;
es hat kein Abstract vorgelegen
  • Invited lecture (Conferences)
    European Campus Card Conference (ECCA) 2016, 22.-24.05.2016, Wroclaw, Polen

Publ.-Id: 23773 - Permalink


BMBF-Verbundprojekt SAVE: Sicherheitsrelevante Analyse des Verhaltens von Armaturen, Kreiselpumpen und Einlaufgeometrien unter Berücksichtigung störfallbedingter Belastungen
Szeliga, N.; Bezecny, D.; Richter, S.; Hoffmann, M.; Schlüter, M.; Schäfer, T.; Hampel, U.; Blömeling, F.; Lawall, R.; Hamberger, M.; Walberer, A.;
In Leichtwasserreaktoren sind Not- und Nachkühlsysteme vorhanden, die auch bei einem Kühlmittelverluststörfall zu jedem Zeitpunkt die im Kern erzeugte Nachzerfallsleistung über einen längeren Zeitraum abführen müssen. Dazu muss die für die Abfuhr der Nachwärme erforderliche Menge Wasser zur Verfügung stehen. Die Not- und Nachkühlsysteme müssen derart betrieben werden, dass ihre Funktion weder durch Einschränkungen des hydraulischen Verhaltens noch durch mechanische Probleme beeinträchtigt wird. Insbesondere Gasmitriss durch luftziehende Hohlwirbel, Dralleintrag sowie Kavitation können zu einer Störung oder sogar zu einem Ausfall des Not- oder Nachkühlsystems führen. Das Ziel des Verbundprojektes SAVE ist die Bereitstellung von verbesserten bzw. neuen Berechnungsgleichungen sowie von Auslegungsempfehlungen zur Vermeidung von Gasmitriss in Pumpenzuläufen. Da sich ein Gasmitriss nicht immer konstruktiv ausschließen lässt, erfolgt darüber hinaus die Beschreibung des Gasmitrisses in Pumpenzuläufen und des hieraus resultierenden Einflusses auf Kreiselpumpen und Armaturen. Hierfür werden experimentelle Messungen an groß- und kleindimensionierten Anlagenkomponenten durchgeführt und durch dreidimensionale Strömungssimulationen (CFD) ergänzt. Die Ergebnisse der Untersuchungen dienen der Aufstellung und Validierung theoretischer Modelle, die durch physikalisch begründete Ansätze an reale Prozesse angepasst werden können. Die experimentelle und theoretische Analyse ist für die Ermittlung von Gültigkeitsbereichen und Skalierungsansätzen sowie für die Gewährleistung der Übertragbarkeit auf andere Stoffsysteme und Betriebsbedingungen unerlässlich. Dies wiederum ermöglicht eine Übertragung der Erkenntnisse über die nukleare Sicherheitsforschung hinaus auf andere Forschungsbereiche.
  • Lecture (Conference)
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland
  • Book chapter
    in: Kraftwerkstechnik 2016, Freiberg: Saxonia Standortentwicklungs- und -verwaltungsgese, 2016, ISBN 978-3-934409-69-9

Publ.-Id: 23772 - Permalink


Experimentelle Untersuchung von Armaturen und Kreiselpumpen unter störfallbedingten Belastungen
Schäfer, T.; Szeliga, N.; Bezecny, D.; Richter, S.; Hoffmann, M.; Blömeling, F.; Lawall, R.; Hamberger, M.; Walberer, A.; Schlüter, M.; Hampel, U.;
In Kraftwerken ist der zuverlässige Betrieb von Pumpen und Armaturen eine Grundvoraussetzung für einen effizienten und sicheren Betrieb. Beispielsweise sind in Kernkraftwerken mit Leichtwasserreaktoren Not- und Nachkühlsysteme vorhanden, die auch bei einem Kühlmittelverluststörfall zu jedem Zeitpunkt die im Kern erzeugte Nachzerfallsleistung über einen längeren Zeitraum abführen müssen. Im Rahmen des Verbundprojektes SAVE wird das Verhalten von Pumpen und Armaturen in Leichtwasserreaktoranlagen unter kritischen Betriebsbedingungen untersucht. Ein Schwerpunkt bildet dabei die Problematik des Gasmitrisses durch Hohlwirbelbildung in Pumpenzulaufbecken sowie die Auswirkung von Luftmitriss auf das Betriebsverhalten der Komponenten. Dazu wurden umfangreiche experimentelle Studien an Einlaufbeckengeometrien, Kreiselpumpen und Armaturen durchgeführt und durch numerische Simulationen begleitet. Ziel ist die experimentelle Validierung bzw. Weiterentwicklung von Modellen zur Auslegung von Einlaufgeometrien sowie zur Festlegung sicherer Einlaufüberdeckungen. Die Ergebnisse können für die Auslegung, Optimierung, Nachrechnung sowie Prüfung von Zulauf- und Armaturgeometrien genutzt werden. Einer der Schwerpunkte liegt hierbei auf der Erfassung von Maßstabseffekten, wofür Untersuchungen in verschiedenen Größenordnungen durchgeführt wurden. Die Arbeiten umfassen u.a. die experimentelle Untersuchung der Hohlwirbelbildung im Pumpenansaugbecken sowie der Auswirkungen des daraus resultierenden Luftmitrisses auf nachfolgende Systemkomponenten wie Kreiselpumpen und Armaturen, die tomographische Untersuchung und Visualisierung der Gas-Flüssigkeitsverteilungen im Inneren von Kreiselpumpen und Armaturen sowie die experimentelle Untersuchung von nuklearen Armaturen in verschiedenen Stresstests, so zum Beispiel unter erhöhten seismischen Belastungen. Begleitet werden die experimentellen Untersuchungen von numerischen Simulationen, wobei die experimentell erzielten Ergebnisse in eine verbesserte Modellbildung einfließen.
Keywords: Kreiselpumpen, Armaturen, störfallbedingte Belastungen, Hohlwirbelbildung, Gaseintrag
  • Poster
    48. Kraftwerkstechnisches Kolloquium, 18.-19.10.2016, Dresden, Deutschland

Publ.-Id: 23771 - 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.;
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

Publ.-Id: 23770 - Permalink


Are established glioblastoma models suitable to mirror the radiobiology of patient tumors?
Dietrich, A.; Jakob, A.; von Neubeck, C.; Fursov, A.; Tillner, F.; Baumann, M.; Krause, M.; Bütof, R.;
Introduction: Suitable in vivo modelling of Glioblastoma multiforme (GBM) is essential for developing new radio-oncological treatment strategies. On the translational axis from bench to bedside, it is important to have a model which closely reflects the clinical situation. However, it is also essential to investigate clinically relevant endpoints and use models which are reasonable regarding costs and feasible regarding statistically necessary animal numbers. Established cell lines are comprehensively characterized and can be efficiently engrafted in large cohorts of animals. In this project, a panel of five human GBM cell lines (U 87 MG, U 251 MG, A7, LN 229, HGL21) is characterized after subcutaneous and orthotopic xenograft transplantation (take rate, radiosensitivity, histology, putative stem cell markers (SM)) to investigate their potential as suitable GBM models.

Methods: Limiting dilution assays were performed using subcutaneous injection of decreasing cell numbers. Intrinsic radiosensitivity and effectiveness of combined Radiochemotherapy was studied by irradiation of subcutaneous tumors with different dose levels. Take dose 50% (TD50) and tumor control dose 50% (TCD50) were calculated. For orthotopic transplantation, mCherry- or luciferase-positive cell variants were used. Intracranial transplantation was performed with a stereotactic frame. Tumor growth was assessed weekly via optical imaging and contrast-enhanced magnetic resonance imaging. After excision, tumors were analysed histologically (Haematoxylin/Eosin, SM).

Results: Both, TD50 and TCD50 values are low for the five GBM models. One of four investigated models showed no signs of orthotopic tumor growth. Two models grew within 30-60 days to end size but the histological phenotype showed weak analogy to GBM patients. Stem cell marker heterogeneity was high between the models and also differed between the orthotopic and heterotopic transplantation site (e.g. Nestin positivity in U-87 MG ortho: 100%, hetero: ~80%).

Conclusion: The low TD50 values indicate high amounts of cancer initiating cells. However, the surprisingly low TCD50 values are in contrast to the remarkable radioresistance of GBM in patients. Additionally, no investigated model shows a GBM-like histology after orthotopic transplantation. Although xenograft models from established cell lines of other entities very closely mirror the clinical situation, this remains questionable for GBM.
  • Lecture (Conference)
    19th Annual Meeting of the Society for Biological Radiation Research - GBS, 26.-28.09.2016, Erlangen, Deutschland

Publ.-Id: 23769 - Permalink


Experimental study of centrifugal pumps under gas entrainment conditions
Schäfer, T.; Neumann, M.; Bieberle, A.; Hampel, U.;
The effects of gas entrainment in centrifugal pumps have been experimentally investigated. Depending on different gas entrainment conditions, the impact on the hydraulic power of the pump has been analyzed and the influence of the pump installation position has been disclosed. Additionally, high-resolution gamma-ray computed tomography (HireCT), operated in time-averaged rotation-synchronized scanning mode, has been used to resolve and quantify the local gas/liquid phase fraction distribution inside the operating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation inside the impeller chambers has been visualized.
Keywords: centrifugal pump, gas entrainment, two-phase flow, gas holdup, gamma-ray computed tomography
  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology (AMNT47), 10.-12.05.2016, Hamburg, Deutschland
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology (AMNT47), 10.-12.05.2016, Hamburg, Deutschland
    Proceedings of 47th Annual Meeting on Nuclear Technology (AMNT47)

Publ.-Id: 23768 - Permalink


Advanced imaging techniques for multiphase flow analysis in industrial and scientific applications
Schäfer, T.;
survey lecture on recent imaging techniques developed at HZDR focused on industrial and scientific applications
Keywords: process tomography, gamma-ray CT, ultrafast X-ray Ct, wire mesh sensor, process microscope
  • Lecture (others)
    Strategiegespräch Fa. Bitzer, 24.02.2016, Schkeuditz, Deutschland

Publ.-Id: 23767 - Permalink


Large magnetoresistance of insulating silicon films with superconducting nanoprecipitates
Heera, V.; Fiedler, J.; Skorupa, W.;
We report on large negative and positive magnetoresistance in inhomogeneous, insulating Si:Ga films below a critical temperature of about 7 K. The magnetoresistance effect exceeds 300% at temperatures below 3Kand fields of 8T. The comparison of the transport properties of superconducting samples with that of insulating ones reveals that the large magnetoresistance is associated with the appearance of local superconductivity. A simple phenomenological model based on localized Cooper pairs and hopping quasiparticles is able to describe the temperature and magnetic field dependence of the sheet resistance of such films.
Keywords: insulating silicon films, superconducting nanoprecipitates, Ga doping, low temperature magnetoresistance, transport model

Publ.-Id: 23765 - Permalink


Carbon nanotubes in low molar mass liquid crystals
Schymura, S.; Park, J. H.; Dierking, I.; Scalia, G.;
Carbon nanotubes constitute a highly anisotropic form of carbon with outstanding mechanical, thermal end electrical properties. Their dispersion and organization are important but challenging issues and this chapter describes the advantages of using thermotropic liquid crystals as host for nanotube dispersion and ordering.
Keywords: Kohlenstoff-Nanoröhrchen/ carbon nanotube Flüssigkristall/ liquid crystal
  • Book chapter
    Lagerwall, Jan P.F., Scalia, Giusy: Liquid Crystals with Nano and Microparticles, London: World Scientific, 2016, 603-630
    DOI: 10.1142/9789814619264_0017

Publ.-Id: 23764 - Permalink


Bipolar resistive switching in YMnO3/Nb:SrTiO3 pn-heterojunctions
Bogusz, A.; Bürger, D.; Skorupa, I.; Schmidt, O. G.; Schmidt, H.;
Resistively switching oxides are promising materials for use in electronic applications such as nonvolatile memories, logic gates, and artificial synapses. This work presents the bipolar resistive switching (BRS) in YMnO3/Nb:SrTiO3 pn-heterojunctions. A thermally driven electroforming process is required prior to the observed BRS. Results indicate that the BRS in YMnO3/Nb:SrTiO3 originates from the combined effects of charge trapping and detrapping processes along with the electro-migration of charged point defects in the depletion layer of the pn-heterojunction. It is shown that the built-in voltage of the pn-heterojunctions can be tuned by the oxygen partial pressure during growth of the YMnO3 thin film and impacts the working parameters of the resistively switching cell. This study provides a guideline for material engineering of bipolar resistive switches based on pn-heterojunctions.
Keywords: YMnO₃, Nb:SrTiO₃, bipolar resistive switching, pn-heterojunction, forward current, reverse current

Publ.-Id: 23763 - Permalink


Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system
Ishikawa, T.; Sakawa, Y.; Morita, T.; Yamaura, Y.; Kuramitsu, Y.; Moritak, T.; Sano, T.; Shimoda, R.; Tomita, K.; Uchino, K.; Matsukiyo, S.; Mizuta, A.; Ohnishi, N.; Crowston, R.; Woolsey, N.; Doyle, H.; Gregori, G.; Koenig, M.; Michaut, C.; Pelka, A.; Yuan, D.; Li, Y.; Zhang, K.; Zhong, J.; Wang, F.; Takabe, H.;
We present first measurements of spectrally resolved x-rays scattered from cryogenic hydrogen jets in the single photon counting limit. The 120 Hz capabilities of the LCLS, together with a novel hydrogen jet design, allow for the ability to record a near background free spectrum. Such high-dynamic-range x-ray scattering measurements enable a platform to study ultra-fast, laser-driven, heating dynamics of hydrogen plasmas. This measurement has been achieved using two Highly Annealed Pyrolytic Graphite (HAPG) crystal spectrometers to spectrally resolve 5.5 keV x-rays elastically and inelastically scattered from cryogenic hydrogen and focused on to Cornell-SLAC Pixel Array Detectors (CSPAD).
Keywords: x-ray scattering, x-ray lasers, hydrogen

Publ.-Id: 23762 - Permalink


The peculiar chemistry of the nuclear fuel-sodium coolant interaction
Smith, A. L.; Raison, P. E.; Y. Colle, J.; Colineau, E.; Griveau, J.-C.; Hen, A.; Beneš, O.; Guéneau, C.; Martin, P.; Prieur, D.; Martel, L.; Magnani, N.; Caciuffo, R.; Sanchez, J. P.; Charpentier, T.; Scheinost, A. C.; Hennig, C.; Kvashnina, K.; Suard, E.; Wallez, G.; Cheetham, A. K.; Konings, R. J. M.;
In the event of a clad breach in Sodium-cooled Fast Reactors (SFRs), the metallic sodium coolant will enter the pin and react with the (U, Pu, Np)O2 fuel. The reaction products are numerous, but there is still little knowledge of their structural and thermodynamic properties. Under the oxygen potential conditions of the reactor, pentavalent Na3U1-xPuxO4 is expected to form, but its structure was the subject of controversy until now. This compound was shown in the 1980s to be of lower density and lower thermal conductivity than the fuel, leading to local swelling and creation of hot spots. Such a situation can induce further cladding failure and result in a contamination of the primary coolant with highly radioactive fission products.

In this work, we have revisited the crystal structure of the Na3MO4 (M=U,Np,Pu) reaction product. Surprisingly, the structure of the sodium uranate differs from the one observed with neptunium and plutonium. In addition, this phase can accommodate excess sodium on the uranium site, with subsequent charge compensation from U(V) to U(VI), which was not previously foreseen. By contrast, the sodium neptunate and plutonate remain pentavalent.

Temperature and oxygen potential are the two fundamental parameters that control the chemistry of the interaction. Assessing the margin to the safe operation of SFRs requires a thorough knowledge of the actinide cation valence state in the reaction products, and a complete thermodynamic description of the system. The valence state was determined in the Na-M-O (M=U,Np,Pu) ternary phases using XANES and Mössbauer spectroscopy, covering a wide range of oxidation states, namely (IV) to (VII). Coupling experimental thermodynamic investigations with thermodynamic modelling assessments using the CALPHAD method, we have calculated the phase equilibria in the Na-U-O system, and derived the oxygen potential threshold required within the fuel (and sodium coolant) to form the sodium uranate ternary phases.
Keywords: Sodium-cooled nuclear reactor safety uranium sodium uranate EXAFS XANES Moessbauer
  • Invited lecture (Conferences)
    NuMat2016: The Nuclear Materials Conference, 07.-10.11.2016, Montpellier, France

Publ.-Id: 23761 - Permalink


Polymer and cluster chemistry of tetravalent cerium (Ce(IV)) in aqueous solutions
Ikeda-Ohno, A.;
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

Publ.-Id: 23760 - Permalink


Viren als Nützlinge - Biologie hilft beim Recycling
Lederer, F.;
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

Publ.-Id: 23759 - Permalink


Fluid Dynamics in a Bubble Column: New Experiments and Simulations
Rzehak, R.; Krauß, M.; Kováts, P.; Zähringer, K.;
Bubble columns are a common type of multiphase reactors used in many chemical engineering applications. Optimization and scale-up of bubble column processes is a complex task that can greatly benefit from multiphase CFD simulations. Calculations on industrial scales become feasible by the Euler-Euler two-fluid model, but suitable closure relations describing interfacial exchange processes are needed for practical application. Concerning pure fluid dynamics of dispersed gas-liquid multiphase flow an ongoing effort has led to a validated set of closures that is applicable under a rather broad range of conditions. The availability of new experimental data with large spatial and temporal resolution and high accuracy for a comprehensive set of observables and a range of different conditions provides the opportunity for further testing of this model. In this way the reliability of the obtained predictions is continually increased.
Keywords: bubble-columns, CFD simulation, Euler Euler two fluid model, shadowgraphy, PIV, model validation

Downloads:

Publ.-Id: 23757 - Permalink


Structural and kinetic considerations for the application of the traceless Staudinger ligation to future 18F radiolabeling using XRD and 19F-NMR
Köckerling, M.; Mamat, C.;
A 4-fluorobenzoate-functionalized phosphane was synthesized and reacted with different azides using the traceless Staudinger ligation as a representative sample reaction for future radiolabeling purposes with short-lived radionuclides like fluorine-18. For this purpose, the reaction rate was evaluated at different temperatures. The effect of starting material concentrations and the influence of the steric effect coming from the applied azides were investigated. 19F NMR was used to determine the reaction half-live (τ1/2) and the reaction rate constant (kobs) of this ligation under mild reaction conditions in a water–acetonitrile mixture. Furthermore, the phosphane key compound 1 (orthorhombic, space group Pna21, a = 18.6363(9), b = 8.3589(4), c = 18.5480(9) Å, V = 2889.4(2) Å3, Z = 8, Dobs = 1.277 g/cm3), which acts as starting material for all subsequent syntheses, and the fluorine-containing phosphane 3 (monoclinic, space group P21/c, a = 8.321(2), b = 16.160(4), c = 14.940(4) Å, β = 99.51(1)°, V = 1981.4(8) Å3, Z = 4, Dobs = 1.342 g/cm3) were analyzed by single-crystal XRD.
Keywords: Click – bioorthogonal – building blocks – kinetics

Downloads:

Publ.-Id: 23756 - Permalink


Statistical Analysis of the Early Phase of SBO Accident for PWR
Kozmenkov, Y.; Jobst, M.; Kliem, S.; Schaefer, F.; Wilhelm, P.;
A statistical approach is used to analyse the early phase of station blackout accident for generic German PWR with the best estimate system code ATHLET-CD as a computation tool. The analysis is mainly focused on the timescale uncertainties of the accident events which can be detected at the plant. The developed input deck allows variations of all input uncertainty parameters relevant to the case. The list of identified and quantified input uncertainties includes 30 parameters related to the simulated physical phenomena/processes. Time uncertainties of main events as well as the major contributors to these uncertainties are defined. A linear regression analysis is used for predicting times of future events from detected times of occurred/past events. The presented statistical approach could be helpful for assessing and improving existing or elaborating additional emergency operating procedures aimed to prevent severe damage of reactor core.
Keywords: Pressurized water reactor, best estimate simulation, station blackout, accident management measures, statistical approach, timescale uncertainties of events, sensitivity analysis, linear regression, prediction intervals.

Publ.-Id: 23754 - Permalink


Uranium contaminated drinking water linked to leukaemia – revisiting a case study from South Africa taking alternative exposure pathways into account
Winde, F.; Erasmus, E.; Geipel, G.;
The paper presents results of a follow-up to an earlier study which established a geospatial link between naturally elevated uranium (U) levels in borehole water and haematological abnormalities in local residents serving as a proxy for leukaemia prevalent in the area. While the original study focussed on drinking water only, this paper also explores alternative exposure pathways including the inhalation of dust and the food chain.
U-levels in grass and tissue of sheep generally reflect U-levels in nearby borehole water and exceed background concentrations by 20 to nearly 500 times. U-levels in sheep tissue increase with age of the animal. Wool showed the highest U-concentration followed by other non-consumable tissue such as hooves, teeth and bones. Lower levels occur in edible parts such as meat and inner organs. The U-deposition rate in wool is several orders of magnitudes higher than in bone as a known target organ. Wool is an easy-to-sample noninvasive bioindicator for U-levels in meat. Depending on the original water content, dried samples show up to 5 times higher U-levels than identical fresh material.
Contaminated drinking water is the main exposure pathway for farm residents resulting in U-uptake rates exceeding the WHO’s tolerable daily intake (TDI) limit by up to 900%. This is somewhat mitigated by the fact that U-speciation is dominated by a neutral calcium-uranyl-carbonate complex of relatively low toxicity. Commercially available household filters are able to significantly reduce U-levels in well water and are thus recommended as a short-term intervention. Based on average consumption rates sheep meat, as local staple food, accounts for 34% of the TDI for U. Indoor levels of radon should be monitored, too, since it is linked to both, U and leukaemia. With elevated U-levels being present in other geological formations across South Africa boreholes in these areas should be surveyed.
Keywords: uranium, groundwater, sheep, leukaemia, food chain

Publ.-Id: 23753 - 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.;
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

Publ.-Id: 23752 - Permalink


Investigations on viscous couplings using time-averaged rotation-synchronized gamma-ray computed tomography
Bieberle, A.; Schlottke, J.; Kühnel, W.; Hampel, U.;
For controlled transfer of high torques in devices, like engine fans and/or four wheel drives, viscous couplings are frequently used. Torque transfer is realized in viscous couplings by a working fluid, mainly responsible for the transfer quality, i.e. efficiency and operating range as well as stability. Unfortunately, investigations at rapidly rotating couplings is challenging since they consist of dense material, e.g. aluminum, have no optical access and the work area is composed of ring channels being significantly smaller than on millimeter. Thus, the high-resolution computed tomography measurement system (HireCT) is used for contactless liquid investigations in an industrial viscous coupling operated under various authentic operation scenarios. Despite the limited spatial resolution of approximately 2 mm and a measuring interval of approximately 900 s sharp liquid phase distributions could be provided in both primary disc and housing side of the coupling from a single CT scan. Here, the so called time-averaged rotation synchronized CT scanning mode is applied, where the acquired projection data stream are synchronized and averaged corresponding to the rotational position of the couplings’ parts. Therefore, zero crossing signals from the primary and secondary side are simultaneously acquired. The reconstructed data comprises the cross-section of the coupling and liquid distribution correspondingly.
Keywords: gamma-ray computed tomography, viscous coupling
  • Contribution to proceedings
    8th World Congress On Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien
  • Lecture (Conference)
    8th World Congress On Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brasilien

Publ.-Id: 23751 - Permalink


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263]