Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35179 Publications

Development of Laser-Driven Proton Beam Therapy

Karsch, L.; Beyreuther, E.; Enghardt, W.; Gotz, M.; Hermannsdörfer, T.; Krause, M.; Masood, U.; Pawelke, J.; Sauerbrey, R.; Schramm, U.; Schürer, M.; Baumann, M.

no abstract available

Publ.-Id: 23692

Design and implementation of a robust and cost-effective double-scattering system at a horizontal proton beamline

Helmbrecht, S.; Baumann, M.; Fiedler, F.; Enghardt, W.; Krause, M.; Lühr, A.

With an increasing number of proton therapy facilities coming into operation, also the interest for research at proton beams increases. Though many centers provide beam at an experimental room, some of these rooms do not feature a device for radiation field shaping, a so called nozzle.
Therefore, a robust, mobile, and cost-effective double-scattering system for horizontal proton beamlines has been designed and implemented.

Materials and methods:
The nozzle is based on the double scattering technique. Two lead scatterers, an aluminum ridge-filter and two brass collimators were optimized in a simulation study to form a laterally homogeneous 10 cm x 10 cm field with a spread-out Bragg-peak (SOBP).
The parts were mainly manufactured using 3D printing techniques and the system was set up at the experimental beamline of the University Proton Therapy Dresden (UPTD).
Measurements of the radiation field were carried out using a water phantom.

High levels of dose homogeneity were found in lateral (dose variation ΔD < ±2%) as well as in beam direction (ΔD < ±3% in the SOBP). The system has already been used for radiobiology and physical experiments.

The presented setup allows for creating clinically realistic extended radiation fields at fixed horizontal proton beamlines and is ready to use for internal and external users.
The excellent performance combined with the simplistic design let it appear as a valuable option for proton therapy centers intending to foster their experimental portfolio.

Keywords: radiation field formation; radiobiology; ion beam therapy; proton therapy; cancer


Publ.-Id: 23691

Reducing in-core zinc borate precipitation after LOCA in pressurized water reactors

Kryk, H.; Harm, U.; Hampel, U.

During the sump recirculation phase after loss-of-coolant accidents (LOCAs) in pressurized water reactors (PWRs), coolant spilling from the leak in the primary cooling circuit is collected in the reactor sump and recirculated to the reactor core by residual-heat removal pumps as part of the emergency core cooling system (ECCS).
Lab-scale studies within previous research projects have shown that the long-term contact of the boric acid containing coolant with hot-dip galvanized steel containment internals may cause corrosion of the corresponding materials influencing the cooling water chemistry due to dissolution of the zinc coat. Generic experimental investigations regarding the solubility of Zn corrosion products in boric acid solutions resulted in a decreasing solubility with increasing temperature. Thus, precipitation of solid corrosion products (zinc borates) cannot be ruled out if zinc containing coolant is heated up due to its recirculation into hot zones.
Consequently, generic corrosion experiments were carried out in a lab-scale corrosion test facility aiming at the development and test of water-chemical measures to prevent zinc corrosion and zinc borate precipitation in boric acid containing coolants.
The experimental results showed a decreasing corrosion rate with increasing pH value of the coolant. Thus, the risk of zinc borate precipitation can be reduced by addition of alkalizing media to the coolant after a LOCA. However, by adding of a moderate amount of alkalizing media to enhance the coolant pH into the neutral region, the zinc borate precipitation rate can be reduced only to about one third but not fully prevented. Extensive suppression of zinc corrosion and zinc borate precipitation is only achievable from a coolant pH of 7.5 resulting in a lithium concentration of 125 ppm if LiOH is used as alkalizing additive. Furthermore, foaming of the coolant cannot be ruled out if the coolant pH is increased into the slightly alkaline region.

Keywords: pressurized water reactor; loss-of-coolant accidents; corrosion; zinc; zinc borate; downstream effects

  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Germany
  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Germany
    Proceedings 47th Annual Meeting on Nuclear Technology, Berlin: INFORUM Verlags- und Verwaltungsgesellschaft mbH, 978-3-926956-97-2

Publ.-Id: 23690

Bit-Vectorized GPU Implementation of a Stochastic Cellular Automaton Model for Surface Growth

Kelling, J.; Ódor, G.; Gemming, S.

Stochastic surface growth models aid in studying properties of universality classes like the Kardar--Parisi--Zhang class. High precision results obtained from large scale computational studies can be transferred to many physical systems. Many properties, such as roughening and some two-time functions can be studied using stochastic cellular automaton (SCA) variants of stochastic models. Here we present a highly efficient SCA implementation of a surface growth model capable of simulating billions of lattice sites on a single GPU. We also provide insight into cases requiring arbitrary random probabilities which are not accessible through bit-vectorization.

Keywords: Surface Growth; Kardar-Parisi-Zhang; GPU; Monte-Carlo; Stochastic Cellular Automaton

  • Contribution to proceedings
    20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016, 30.06.-02.07.2016, Budapest, Ungarn
    Proceedings of the 20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016: IEEE
    DOI: 10.1109/INES.2016.7555127
  • Lecture (Conference)
    20th Jubilee IEEE International Conference on Intelligent Engineering Systems 2016: IEEE, 30.06.-02.07.2016, Budapest, Ungarn
  • Contribution to WWW

Publ.-Id: 23689

The Sorption Processes of U(VI) onto SiO2 in the Presence of Phosphate: from Binary Surface Species to Precipitation

Comarmond, M. J.; Steudtner, R.; Stockmann, M.; Heim, K.; Müller, K.; Brendler, V.; Payne, T. E.; Foerstendorf, H.

The ternary system containing aqueous U(VI), aqueous phosphate and solid SiO2 was comprehensively investigated using a batch sorption technique, in situ attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and Surface Complexation Modeling (SCM). The batch sorption studies on silica gel (10 g/L) in the pH range 2.5 to 5 showed no significant increase in U(VI) uptake in the presence of phosphate at equimolar concentration of 20 µM, but significant increase in U(VI) uptake was observed for higher phosphate concentrations. In situ infrared and luminescence spectroscopic studies evidence the formation of two binary U(VI) surface species in the absence of phosphate, whereas after prolonged sorption in the presence of phosphate, the formation of a surface precipitate, most likely an autunite-like phase, is strongly suggested. From SCM, excellent fitting results were obtained exclusively considering two binary uranyl surface species and the formation of a solid uranyl phosphate phase. The results of this study indicate that the sorption of U(VI) on SiO2 in the presence of inorganic phosphate initially involves binary surface-sorption species and evolves towards surface precipitation.


Publ.-Id: 23688

Coordination polymers of tetravalent neptunium with aromatic polycarboxylate ligands

Martin, N.; März, J.; Henry, N.; Volkringer, C.; Ikeda-Ohno, A.; Hennig, C.; Loiseau, T.

Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with O- or N-donor ligands. In the particular case of actinides, previous literatures mainly have reported the synthesis of solid networks bearing U(VI) or Th(IV). Trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of actinides (An), the tetravalent state has been investigated most actively and large polynuclear oxo-clusters have been isolated for U1,2 or Pu3. In contrast, there is very few data concerning Np(IV) compounds. In 2012, Takao et al.4 reported the presence of a hexanuclear cluster of Np(IV) in an aqueous solution, which is the only polyoxo cluster reported for Np(IV) thus far. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids or organic pollutants (e.g. phthalates). In the present work, we studied the crystallization of Np(IV) with various aromatic polycarboxylate ligands in different solvents and analyzed their crystal structures. In water, an infinite chain of Np2O2(H2O)2(1,2-bdc)2 were isolated in the presence of phthalate. This compound crystallizes as aggregates of orange plates, whereas the analogue compound with uranium is obtained as green crystals. With mellitic acid the oxidation of Np(IV) to Np(V) was observed and led to large green plates. Single-crystal XRD analysis revealed layers of {NpO7H2O0-2} units linked to each other via trans-dioxo neptunyl bonds. Similar coordination environments have been observed in the other neptunium(V) compounds5.
The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear unit of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure. The corresponding structures revealed for the first time the isolation of the hexanuclear cluster An6O8 with Np(IV). These clusters are linked by the ligand creating tetrahedral and octahedral voids in the structure.

Keywords: actinides; neptunium; carboxylates; metal-organic complex; metal-organic framework; polymers; structure characterisation

  • Lecture (Conference)
    Plutonium Futures 2016, 18.-22.09.2016, Baden-Baden, Germany

Publ.-Id: 23687

Tunable Picosecond Laser Pulses via the Contrast of Two Reverse Saturable Absorption Phases in a Waveguide Platform

Tan, Y.; Chen, L.; Wang, D.; Chen, Y.; Akhmadaliev, S.; Zhou, S.; Hong, M.; Chen, F.

How to enhance the optical nonlinearity of saturable absorption materials is an important question to improve the functionality of various applications ranging from the high power laser to photonic computational devices. We demonstrate the saturable absorption (SA) of VO2 film attributed to the large difference of optical nonlinearities between the two states of the phase-transition materials (VO2). Such VO2 film demonstrated significantly improved performance with saturation intensity higher than other existing ultrathin saturable absorbers by 3 orders due to its unique nonlinear optical mechanisms in the ultrafast phase change process. Owing to this feature, a Q-switched pulsed laser was fabricated in a waveguide platform, which is the first time to achieve picosecond pulse duration and maintain high peak power. Furthermore, the emission of this VO2 waveguide laser can be flexibly switched between the continuous-wave (CW) and pulsed operation regimes by tuning the temperature of the VO2 film, which enables VO2-based miniature laser devices with unique and versatile functions.

Publ.-Id: 23686

Zwitterionic polymer-coated ultrasmall superparamagnetic iron oxide nanoparticles with low protein interaction and high biocompatibility

Pombo-García, K.; Weiss, S.; Zarschler, K.; Ang, C.-S.; Hübner, R.; Pufe, J.; Meister, S.; Seidel, J.; Pietzsch, J.; Spiccia, L.; Stephan, H.; Graham, B.

We report the synthesis and detailed in vitro evaluation of zwitterionic ultrasmall superparamagnetic iron oxide NPs (USPIONs) comprised of oleic acid/oleyl alcohol-stabilized magnetite particles (5 nm core diameter) coated with an amphiphilic zwitterionic polymer, poly(maleic anhydride-alt-1-decene) substituted with 3-(dimethylamino)propylamine (PMAL). These particles display a near-neutral zeta potential at pH ≥ 7 and possess high colloidal stability, maintaining a hydrodynamic diameter of ca. 15–20 nm over a wide range of pHs (4–10) and ionic strength (up to 1 M NaCl). They exhibit very low levels of nonspecific protein binding upon exposure to serum, and negligible uptake by phagocytic and non-phagocytic hepatocarcinoma cells, which suggests that they may be able to resist rapid accumulation in the liver and spleen, a common in vivo fate for NPs. The PMAL-USPIONs exhibit very low cytotoxicity and do not elicit an inflammatory response or display hemolytic activity in vitro. Minimal nonspecific uptake by either cancerous or non-cancerous cell lines was observed, an important precondition to achieve highly selective targeting upon further functionalization with an active targeting agent (e.g., antibody or peptide). Overall, this study establishes the considerable potential of PMALUSPIONs as a platform for the future development of “stealth” NP-based imaging and/or therapeutic agents.

Keywords: Iron oxide nanoparticles; zwitterionic coatings; protein corona; macrophages; proteomics


Publ.-Id: 23685

Highlights on metallic photocathodes used in SRF gun

Xiang, R.; Arnold, A.; Michel, P.; Murcek, P.; Teichert, J.; Lu, P.; Vennekate, H.

For the accelerator-based light sources and the electron colliders, the development of photoinjectors has become a key technology. Especially for the superconducting radio frequency cavity based injector (SRF Gun), the searching for better photocathodes is always a principal technical challenge. To use metallic photocathodes for ELBE SRF Gun is the primary choice to prevent cavity contamination. In this contribution, we will report the investigation of Magnesium (Mg) in ELBE SRF gun, including laser cleaning treatment and the measurement on quantum efficiency, Schottky effect, dark current and damage threshold.

Keywords: SRF gun; photocathode; metallic cathode; magnesium

  • Poster
    the Seventh International Particle Accelerator Conference (IPAC’16), 08.-13.05.2016, Busan, Korea
  • Open Access Logo Contribution to proceedings
    the Seventh International Particle Accelerator Conference (IPAC’16), 08.-13.05.2016, Busan, Korea

Publ.-Id: 23684

Wire-mesh Sensors: Recent Developments and Applications

Schleicher, E.; Tschofen, M.; Kipping, R.; Hampel, U.

Wire-mesh sensors (WMS) are today well established measurement tools to obtain both temporally and spatially highly resolved structural information as well as averaged phase fraction and phase fraction distribution data in air-water and steam-water two-phase flow experiments. Those data, with a spatial resolution of down to 0.5 mm and frame rates up to 10,000 frames per second are suitable to validate CFD code developments. During the last decade, the technology has widely spread in research laboratories all over the world and has been more and more developed towards a turnkey machine for researchers. In this work we summarize the most recent developments in hardware for high temperature and high pressure applications, new electronics with integrated void fraction calculations and flow pattern identification for industrial applications and latest software developments for data analysis and visualization.

A big issue for the application of wire-mesh sensor technology to high pressure high temperature facilities is the complicated pressure-proven and temperature-resistant insulated support and feedthrough of the measuring electrodes. Our new development facilitates a compact metallic body with flanges on both sides with a slot in sensor unit consisting of ceramic insulators and a stainless steel frame. The feedthrough of the wires is realized by commercially available multiple feedthrough fittings.

The most common and proved codes for WMS data analysis have been capsulated in our wire-mesh sensor data processing FrameWork. The tool has got a new, user friendly graphical interface and allows the implementation of new algorithms by the end user. The resulting data and profiles can be visualized within the software and a batch processing tool allows automated “over the weekend” jobs.

The wire-mesh sensor technology so far is a scientific tool for researchers. The huge amount of data, several gigabytes for one measurement of a couple of seconds, has to be stored and processed offline later on. For industrial applications, the users need online data on liquid/gas holdups and flow pattern in the pipelines. An industrial type of wire-mesh sensor electronics has been developed based on an FPGA (field programmable gate array) microcontroller calculating the frame averaged void fraction instantaneously and moreover identifying the flow pattern based on statistical values of the last 10 seconds from the two-phase flow using Fuzzy clustering algorithm.

Keywords: Industrial Process Tomography; Two-Phase Flow Measurement; Wire-Mesh Sensor

  • Contribution to proceedings
    SWINTH-2016, Specialist Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics, 15.-17.06.2016, Livorno, Italy
    Proceedings of SWINTH-2016
  • Lecture (Conference)
    SWINTH-2016, Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics, 15.-17.06.2016, Livorno, Italia

Publ.-Id: 23683

X-ray radioscopy as a powerful tool for visualization of liquid metal bubbly flows

Roshchupkina, O.; Shevchenko, N.; Strumpf, E.; Hoppe, D.; Eckert, S.

Many technical applications in metallurgy and the quality of continuous casting rely on liquid metal two-phase flows. Injection of the Argon gas became an integral part of continuous casting since it prevents clogging of the casting nozzle and also separates alumina particles from the melt. On the other hand, injection of gas has many side effects as for example induction of highly turbulent complex two-phase flows. There exist many numerical simulations and water models, but due to large differences in physical properties between water and liquid metals water models and experiments cannot be fully extended to liquid metals. Therefore, direct investigation and understanding of liquid metal two-phase flows became critical. In the present work we demonstrate that X-ray radiography can be used as a powerful tool for the visualization of liquid metal two-phase flows. Here we present an experimental study of ascending bubble chains over a wide range of gas flow rates in GaInSn alloy at room temperature. We report on differences in bubble release frequency, shape, size, velocity etc. and additionally compare with experiments in water. The efficiency of the corresponding measurement technique is primarily validated in water experiments.

* The research is supported by the German Helmholtz Association in form of the Helmholtz-Alliance “LIMTECH”.

Keywords: X-ray radiography; two-phase flows; GaInSn; water

  • Lecture (Conference)
    9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy

Publ.-Id: 23682

Topologically stable magnetization states on a spherical shell: curvature stabilized skyrmion

Kravchuk, V. P.; Rößler, U. K.; Volkov, O. M.; Sheka, D. D.; van den Brink, J.; Makarov, D.; Fangohr, H.; Gaididei, Y.

Topologically stable structures, e.g. vortices in a wide variety of matter, skyrmions in ferro- and antiferromagnets, hedgehog point defects in liquid crystals and ferromagnets, are characterized by integer valued topological quantum numbers. In this context the closed surfaces are a prominent subject of study, because they realize a link between fundamental mathematical theorems and real physical systems. Here we perform a topological analysis of equilibrium magnetization states for a thin spherical shell with easy-normal anisotropy. Skyrmion solutions are found for a range of parameters. These magnetic skyrmions on a spherical shell have two principal differences compared to the planar case: (i) they become topologically trivial, and (ii) can be stabilized by curvature effects only, also when Dzyaloshinskii-Moriya interactions are absent. Due to its specific topological nature a skyrmion on a spherical shell can be simply induced by an uniform external magnetic field.

Keywords: Dzyaloshinskii-Moriya interaction; skyrmion; curvature induced effects

Publ.-Id: 23681

Purely Antiferromagnetic Magnetoelectric Random Access Memory

Kosub, T.; Kopte, M.; Hühne, R.; Appel, P.; Shields, B.; Maletinsky, P.; Hübner, R.; Liedke, M. O.; Fassbender, J.; Schmidt, O. G.; Makarov, D.

Magnetic random access memory schemes employing magnetoelectric coupling to write binary information promise outstanding energy-efficiency. We propose and realize purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) that offers a remarkable 50 times lower writing threshold compared to ferromagnet-based counterparts, is robust against magnetic disturbances and exhibits no ferromagnetic hysteresis losses. Using the magnetoelectric antiferromagnet Cr2O3, we realize reliable isothermal switching via gate voltage pulses and all-electric read-back at room temperature. As no ferromagnetic component is present in the system, the writing magnetic field does not need to be pulsed and removed for read-out allowing permanent magnets to be used. Based on our prototypes of these novel systems, we construct a comprehensive model of the magnetoelectric selection mechanism in thin films of magnetoelectric antiferromagnets. We identify that growth induced effects lead to emergent ferrimagnetism, which interferes with the linear magnetoelectric effect. After pinpointing lattice misfit as the likely origin, we provide routes to enhance or mitigate this emergent ferrimagnetism as desired. AF-MERAM cells are a general concept for antiferromagnetic spintronics and not limited to memory applications.

Keywords: Magnetoelectric Random Access Memory; Antiferromagnets; anomalous Hall magnetometry; zero-Offset Hall

Publ.-Id: 23680

Synthesis, Morphological, and Electro-optical Characterizations of Metal/Semiconductor Nanowire Heterostructures

Glaser, M.; Kitzler, A.; Johannes, A.; Prucnal, S.; Potts, H.; Conesa-Boj, S.; Filipovic, L.; Kosina, H.; Skorupa, W.; Bertagnolli, E.; Ronning, C.; Fontcuberta I. Morral, A.; Lugstein, A.

In this letter, we demonstrate the formation of unique Ga/GaAs/Si nanowire heterostructures, which were successfully implemented in nanoscale light-emitting devices with visible room temperature electroluminescence. Based on our recent approach for the integration of InAs/Si heterostructures into Si nanowires by ion implantation and flash lamp annealing, we developed a routine that has proven to be suitable for the monolithic integration of GaAs nanocrystallite segments into the core of silicon nanowires. The formation of a Ga segment adjacent to longer GaAs nanocrystallites resulted in Schottky-diode-like I/V characteristics with distinct electroluminescence originating from the GaAs nanocrystallite for the nanowire device operated in the reverse breakdown regime.
The observed electroluminescence was ascribed to radiative band-to-band recombinations resulting in distinct emission peaks and a low contribution due to intraband transition, which were also observed under forward bias. Simulations of the obtained nanowire heterostructure confirmed the proposed impact ionization process responsible for hot carrier luminescence. This approach may enable a new route for on-chip photonic devices used for light emission or detection purposes.

Keywords: Nanowires; flash lamp annealing; ion implantation; GaAs; Si; liquid phase epitaxy

Publ.-Id: 23679

The effect of millisecond flash lamp annealing on electrical and structural properties of ZnO:Al/Si structures

Lindberg, P. F.; Lipp Bregolin, F.; Wiesenhütter, K.; Wiesenhütter, U.; Riise, H. N.; Vines, L.; Prucnal, S.; Skorupa, W.; Svensson, B. G.; Monakhov, E. V.

The effect of millisecond flash lamp annealing (FLA) on aluminum doped ZnO (AZO) films and their interface with Si have been studied. The AZO films were deposited by magnetron sputtering on Si (100) substrates. The electrical and structural properties of the film and AZO/Si structures were characterized by current–voltage, capacitance–voltage, and deep level transient spectroscopy measurements, X-ray diffraction, and secondary ion mass spectrometry. The resistivity of the AZO film is reduced to a close to state-of-the-art value of 2x10-4Ohmcm after FLA for 3ms with an average energy density of 29 J/cm2. In addition, most of the interfacial defects energy levels are simultaneously annealed out, except for one persisting shallow level, tentatively assigned to the vacancy-oxygen complex in Si, which was not affected by FLA. Subsequent to the FLA, the samples were treated in N2 or forming gas (FG) (N2/H2, 90/10%mole) ambient at 200–500 C. The latter samples maintained the low resistivity achieved after the FLA, but not the former ones. The interfacial defect level persisting after the FLA is removed by the FG treatment, concurrently as another level emerges at ~0.18 eV below the conduction band. The electrical data of the AZO films are discussed in term of point defects controlling the resistivity, and it is argued that the FLA promotes formation of electrically neutral clusters of Zink vacancies (VZn’s) rather than passivating/compensating complexes between the Al donors and VZn’s.

Keywords: AZO; flash lamp annealing; magnetron sputtering; doping

Publ.-Id: 23678

Narrow-band tunable terahertz emission from ferrimagnetic Mn3-xGa thin films

Awari, N.; Kovalev, S.; Fowley, C.; Rode, K.; Gallardo, R. A.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B.; Yildrim, O.; Lindner, J.; Fassbender, J.; Coey, J. M. D.; Deac, A. M.; Gensch, M.

Narrow-band terahertz emission from coherently excited spin precession in metallic Mn3-xGa Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition making this type of metallic films a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is potentially a sensitive probe of magnetic properties of ultra-thin films.

Keywords: THz emission; ferrimagnets; spin excitations

Publ.-Id: 23677

NeptuniumV retention by siderite under anoxic conditions: Precipitation of NpO2–like nanoparticles and of NpIV pentacarbonate

Scheinost, A. C.; Steudtner, R.; Hübner, R.; Weiss, S.; Bok, F.

The NpV retention by siderite, an FeII carbonate mineral with relevance for the near-field of high-level radioactive waste repositories, was investigated under anoxic conditions. Batch sorption experiments show that siderite has a high affinity for aqueous NpVO2+ across pH 7 to 13 as expressed by solid-water distribution coefficients, log Rd, >5, similar to the log Rd determined for the (solely) tetravalent actinide Th on calcite, suggesting reduction of NpV to NpIV by siderite. Np L3-edge X-ray absorption near edge (XANES) spectroscopy conducted in a pH range typical for siderite-containing host rocks (7 - 8), confirmed the tetravalent Np oxidation state. Extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed a local structure in line with NpO2–like nanoparticles with diameter < 1 nm, a result further corroborated by high-resolution transmission electron microscopy (HRTEM). The low solubility of these NpO2–like nanoparticles (10-9 M), along with their negligible surface charge at neutral pH conditions which favors particle aggregation, suggest an efficient retention of Np in the near-field of radioactive waste repositories. When NpV was added to ferrous carbonate solution, the subsequent precipitation of siderite did not lead to a structural incorporation of NpIV by siderite, but caused precipitation of a NpIV pentacarbonate phase.

Keywords: neptunium; siderite; carbonate; radioactive waste respository; XAFS; XANES


Publ.-Id: 23676

Speciation of tetravalent uranium with inorganic ligands in aqueous solution investigated by UV/vis and time-resolved laser-fluorescence measurements.

Lehmann, S.; Steudtner, R.; Brendler, V.

This work is focused on uranium as the major component of spent nuclear fuel. For safety assessment of a future repository it is important to predict the environmental behavior of uranium in diluted to highly saline aquifer systems. Currently most reports are related to the hexavalent oxidation state which is stable under oxidizing conditions. However, reducing conditions are expected in the near field of high level nuclear waste repository after sealing the repository. Therefore, the major purpose of this study is to improve the knowledge of the physico-chemical properties of the tetravalent uranium and to provide thermodynamic data to enable a better prediction of speciation and solubility limits under reducing conditions.
The aim of this study is to examine the potential of U(IV) fluorescence for speciation studies. Kirishima et al. described in 2004 for the first time the luminescence spectra of the free U(IV) ion [1, 2]. Since then, only a few studies on U(IV) fluorescence properties have been published [3, 4]. However, spectroscopic data of U(IV) are necessary to provide a basic understanding of the U(IV) speciation under environmental conditions. We used in our study a combination of UV/vis spectroscopy with long path flow cell and time-resolved laser-induced fluorescence spectroscopy (TRLFS).
First, a U(IV) stock solution was produced by reduction in an electrochemical cell and was monitored by UV/vis spectroscopy. The residual content of U(VI) was determined by TRLFS to be lower than 1%. After that, we studied the aqueous speciation in presence of various inorganic ligands (ClO4–, Cl–, SO42–, PO43–, CO32–). To perform TRLFS measurements of U(IV) a laser system employing a Nd/YAG driven OPO system as excitation source with λexc = 245 nm were installed including a cryogenic unit for measurements at liquid nitrogen temperature (77 K). We detected the luminescence of the free U(IV) ion in acidic aqueous solution at room temperature (rt) and in frozen state at 77 K. At rt we observe the typical fluorescence properties of U(IV) with the peak maxima at 321, 410 and 523 nm and a fluorescence decay time of 2.6 ± 0.3 ns in perchloric and chloric acid. The detection limit of 10–5 M at rt was determined. By using cryo-TRLFS at 77 K the detection limit was lowered to 5x10–6 M and the fluorescence lifetime increases up to 148.4 ± 6.5 ns. The spectroscopic results are in good agreement with earlier reports for rt [3] and cryo measurements [2]. In contrast to U(VI), which is often quenched by chloride, a well resolved luminescence spectrum of U(IV) was obtained in 0.1 as well as in 1 M HCl.
The potential of U(IV) fluorescence for speciation analysis was assessed in this study. With our setup we could study aqueous U(IV) systems with concentrations lower than 10–5 M and this corresponds to uranium concentrations occurring in the environment [5, 6].

[1] A. Kirishima, Chem. Commun., 2003, (7), 910-911.
[2] A. Kirishima, Radiochim. Acta, 2004, 92, 705-710.
[3] S. Lehmann, J. Radioanal. Nucl. Chem., 2010 283(2), 395-401.
[4] N. Aoyagi, N., J. Radioanal. Nucl. Chem., 2015, 303(2), 1095-1098.
[5] T. Arnold, Geochim. Cosmochim. Acta, 2011, 75(8), 2200-221.
[6] G. Bernhard, J. Alloys Compd., 1998, 271, 201-205.

Keywords: tetravalent uranium; aqueous solution; fluorescence; speciation

  • Lecture (Conference)
    Ninth International Conference on Nuclear and Radiochemistry - NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Publ.-Id: 23675

Redox Stability of Uranium in High Ionic Strength Media: An Electrochemical and Spectroscopic Study

Lehmann, S.; Bok, F.; Ikeda-Ohno, A.; Muñoz, A. G.

Knowledge of redox behavior of uranium in concentrated solutions of the hexary oceanic salt system is essential for the transport modeling of radioactive nuclides in repositories for the long-term disposal of radioactive wastes in rock salt formations. Especially critical is the behavior of the couple U(IV)/U(VI) in the surrounding high ionic strength saline milieu, which regulates the release of mobile U(VI) species at given redox conditions defined by the presence of trace oxygen. The redox potential (Eredox) and the solubility in brines in particular implicate the activity of the different ligand- and hydroxo-complexes (ai): Eredox = f(mi, ai, βj), where βj is the complexation constant. Thus, the prediction of transport behavior of uranium at given chemical environments needs appropriate complexation and thermodynamic models assuming the ionic activities beyond the limited Debye-Hückel theory. This latter is supplied by the Pitzer formulation [1], where deviations from the limit Debye-Hückel behavior are given by specific interaction parameters among the constituting ionic species, which have to be determined experimentally.
The kinetics of the electrochemical reduction and oxidation reactions was studied in a three-electrodes type cell using a Au working electrode, Pt wire counter electrode and a Ag/AgCl in3 M KCl reference electrode. Experiments were performed under an oxygen-free atmosphere in a glove-box. Cyclic voltammetry (CV) and normal pulse voltammetry (NPV) were applied to investigate the influence of chloride concentrations in the kinetics parameters, such as reaction rate, k, and the diffusion coefficient in solutions containing U(VI) or U(IV) in HCl solutions from 0.1 to 1.3 M. The solution speciation of uranium was investigated by UV/vis absorption spectroscopy.
Reference: [1] K.S. Pitzer in Activity coefficients in electrolyte solutions, Ch.3, CRC Press, Boca Raton, Florida, 1991.

Keywords: uranium; saline solutions; electrochemistry; redox behaviour; Pitzer

  • Lecture (Conference)
    PRIME 2016 - Pacific rim meeting on electrochemical and solid-state science, 02.-07.10.2016, Honolulu, Hawaii, USA

Publ.-Id: 23674

Self-Assembled Magnetite Mesocrystalline Films: Towards Structural Evolution from 2D to 3D Superlattices

Brunner, J.; Baburin, I. A.; Sturm, S.; Kvashnina, K.; Rossberg, A.; Pietsch, T.; Andreev, S.; Sturm, E.; Cölfen, H.

This study describes synthesis and detailed characterization of 2D and 3D mesocrystalline films produced by self-assembly of iron oxide (magnetite) truncated nanocubes. The orientational relations between nanocrystals within the superlattice are examined and atomistic models for a detailed description of the structures of the 2D and 3D mesocrystals are introduced. The most efficient space filling within the 3D superstructure is achieved by changing the orientational order of the nanoparticles and following the “bump-tohollow” packing principle. These data provide a fundamental understanding of a mesocrystal formation mechanism and their structural evolution. Structure, composition and magnetic properties of the synthesised nanoparticles are also characterized.

Keywords: magnetite; nanoparticle; self-assembly; mesocrystal; particle films

Publ.-Id: 23673

Complexation studies of modified calix[4]arenes with uranium in non-aqueous solution

Bauer, A.; Schmeide, K.; März, J.; Jäschke, A.; Glasneck, F.; Kersting, B.

The actinide uranium, well known from nuclear power cycle, plays also a role in rare earth production. The rare earth ores contain, apart from various other components, the actinides uranium and thorium occur as undesired constituents. To facilitate the production of rare earth elements, uranium and thorium have to be removed. Due to their modifiable selectivity and solubility calix[n]arenes are interesting compounds for the extraction of actinides and lanthanides. The chalice-like macrocyclic molecules consist of para-substituted phenolic units. The para-substitution determines the solubility of the molecule and the hydroxyl groups serve either directly as complexation site or can be further functionalized to adjust the selectivity of the calix[n]arene.
Several calix[4]arenes with affinity towards actinides or lanthanides are available. These are to be applied to eliminate uranium (IV)/(VI) and thorium from ore concentrates and subsequently, to separate lanthanides. The separation method based on liquid-liquid extraction utilizing the calix[4]arenes. Thereby metal calix[4]arene complexes are formed in the organic phase. For better process understanding we investigated the mechanisms of uranium interaction with the synthesized calix[4]arenes by UV-Vis spectroscopy, TRLFS, isothermal titration calorimetry, single crystal XRD and extraction experiments. The calix[4]arene modified with 8-hydroxychinolin derivatives called L1 is one of the new calix[4]arenes. It achieves a U(VI) extraction yield between 90 to 100 % in the pH range of 4 to 9. It possesses two potential binding sites for U(VI). Stoichiometry determination by the Job´s Plot from UV-Vis data indicates a ligand to metal ratio of 1:2 (Fig. 1). The calix[4]arene-L1 complex absorbs at 280 nm. During spectrophotometric titration of L1 with U(VI) in acetonitrile the absorption maximum decreases and new peaks at 318, 360 and 525 nm occur. Luminescence signals of L1 and uranyl nitrate in acetonitrile are weakened by complex formation. First microcalorimetric measurements confirm the binding of two metal ions by L1. All measurements in solution were carried out at 25°C. In addition to the UV-Vis spectroscopy and isothermal titration calorimetry, the capillary electrophoresis is to be used for determining stability constants.
Whereas in solution a stoichiometry of 1:2 is obviously preferred, the single crystal XRD analysis reveals a formation of a 1:1 U(VI)-L1 complex (Fig. 2). Thereby the hexavalent uranyl ion is coordinated by the singly deprotonated ligand via a N2O2 donor set. The charge is compensated by an additional coordinated nitrate ion. To complete the structure information of the formed U(VI)-L1 complex in solution mass spectrometric and NMR measurements as well as theoretical studies are currently performed. In addition, for better understanding the complexation properties of L1 the interaction with U(IV) and Th(IV) is studied.

Keywords: SE-FLECX; calix[4]arene; uranium; solvent extraction; complexation studies; rare earth production

  • Poster
    The 9th Conference on Nuclear and Radiochemistry – NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Publ.-Id: 23671

Removal of Nickel Impurities from Recycled Mg-Al Alloys by Precipitation of Intermetallic Compounds

Duwe, S.; Scharf, C.; Ditze, A.

The primary production of pure magnesium and its alloys is highly energy intensive and expensive.
Thus, their recycling is necessary considering energy saving and metal content. Magnesium postconsumer scrap often is contaminated with copper, nickel and iron resulting from aluminium alloy adherences, nickel platings and steel. Especially nickel is detrimental to the corrosion properties of magnesium alloys. To produce secondary magnesium alloys nickel impurities have to be removed to obtain appropriate corrosion resistance. In this case no traditional metallurgical refining process is applicable because nickel is nobler than magnesium. It has been found that the refining can be done by a combined addition of aluminium and zirconium to remove nickel by formation of high melting intermetallic compounds and hence their precipitation. The aim of the investigation is to determine and verify the amounts of zirconium and aluminium which are necessary to reach the low nickel content of 10 ppm (high purity quality). However, the mutual solubilities of nickel and zirconium in aluminium containing magnesium alloys are unknown. Therefore, the solubility isotherms of this system at 720 °C were experimentally investigated by adding nickel to magnesium melts with different aluminium contents (5 and 8 mass.-%). Subsequently aluminium and zirconium have been added to remove the nickel. At the near equilibrium state samples have been taken from the melt and analysed for the components. Furthermore, the formed intermetallic aluminium-nickelzirconium compounds have to be determined for identification by chemical analysis and EDX. Besides the solubility isotherms for the system are calculated using a thermodynamic model.

Keywords: Magnesium scrap; recycling; nickel removal; intermetallic compound

  • Open Access Logo Contribution to proceedings
    EMC 2013 - European Metallurgical Conference, 23.-26.06.2013, Weimar, Deutschland: GDMB Verlag GmbH, 978-3-940276-50-6, 597-604

Publ.-Id: 23670

Structural modification of Ga+ and N+ ion implanted ta-C films

Berova, M.; Sandulov, M.; Tsvetkova, T.; Karashanova, D.; Boettger, R.; Bischoff, L.

Thin-film samples (d ~ 40 nm) of tetrahedral amorphous carbon (ta-C) deposited by filtered cathodic vacuum arc (FCVA) were implanted with Ga+ at ion energy E = 20 keV and ion fluences D = 3×10^14÷3×10^15 cm-2 and N+ with the same energy and a dose D = 3×1014 cm-2. The Ga+ ion beam induced a structural modification of the implanted material. This resulted in a considerable change of its structural properties, manifested as the formation of a new phase under non-equilibrium conditions, which could be accompanied by considerable changes in the ta-C films optical properties. The N+ implantation also resulted in a modification of the surface structure. These effects were explored using transmission (TEM) and scanning (SEM) electron microscopy.

Keywords: ta-C; ion implantation

Publ.-Id: 23669

Atomic transport during solid-phase epitaxial recrystallization of amorphous germanium

Radek, M.; Bracht, H.; Johnson, B. C.; Mccallum, J. C.; Posselt, M.; Liedke, B.

We report experimental studies on atomic mixing of matrix atoms during solid-phase epitaxy (SPE). For this purpose isotopically enriched germanium (Ge) multilayer structures were amorphized by Ge ion implantation up to a depth of 1.5 um. Recrystallization of the amorphous structure was performed at temperatures between 350°C and 450°C. By means of secondary-ion-mass-spectrometry (SIMS) the concentration-depth profiles of the Ge isotope before and after the SPE process were determined. Analyses of the experimental depth profiles reveal an upper limit of 0.5 nm for the displacement length of the Ge matrix atoms induced by the SPE process. This small displacement length confirms theoretical models and atomistic simulations of SPE, indicating that the SPE mechanism consists of bond-switching with nearest-neighbours at the amorphous-crystalline (a/c) interface.

Keywords: Solid-phase epitaxial recrystallization; germanium; atom transport

  • Lecture (Conference)
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Publ.-Id: 23668

Investigation of ion-beam mixing in silicon at temperatures below 500°C and the role of mobile extended defects

Radek, M.; Bracht, H.; Posselt, M.; Liedke, B.

Implantation of germanium (Ge), gallium (Ga), or arsenic (As) ions into crystalline and preamorphized isotopically enriched silicon (Si) multilayer structures at temperatures between 20°C and 500°C was performed to study the mechanisms contributing to atomic mixing. Secondary-ion-mass-spectrometry (SIMS) was applied to determine the concentration-depth profiles of the Si isotopes after ion implantation. In contrast to Ge multilayer structures [1] a radiation enhanced self-diffusion (RESD), as well as a dopant dependence of RESD is observed in Si. The contribution of cascade mixing (thermal spike mixing) to the overall atomic mixing is estimated by means of molecular dynamics simulations leaving the contribution due to RESD. Continuum theoretical calculations reveals that the magnitude of RESD can not be described by the diffusion of isolated native defects in supersaturation. Instead RESD is successfully modelled assuming highly mobile di-interstials that form during annealing of the implantation damage.
[1] M. Radek et al.: Temperature dependence of ion-beam induced atomic mixing in germanium isotope structures, Appl. Phys. Lett. 115, 023506 (2015)

Keywords: Ion-beam mixing; silicon isotope multilayers

  • Lecture (Conference)
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Publ.-Id: 23667

Self-diffusion in amorphous silicon: An experimental and theoretical study

Kirschbaum, J.; Teuber, T.; Radek, M.; Bracht, H.; Posselt, M.; Bougeard, D.

Amorphous silicon (a-Si) is a widely used material, especially for solar cells and thin-film-transistors. Measuring the self-diffusion coefficient of a-Si is experimentally demanding since recrystallization during diffusion annealing must be suppressed. We used Si on insulator (SOI) structures to stabilize the amorphous state during annealing. Isotopically enriched Si multilayers with a thickness per layer of about 10 nm were grown by means of molecular beam epitaxy on top of SOI wafers. Subsequently the whole top crystalline Si layer was amorphized by means of Si ion implantation. Before and after annealing the distribution of the Si isotopes within the isotope structure was measured with SIMS. The observed broadening suggests a significantly higher self-diffusion in the amorphous compared to the crystalline state. Molecular dynamics simulations are employed to gain information about the mechanism of self-diffusion. We used an adjusted Stillinger-Weber potential, as the original Stillinger-Weber parametrization for Si overestimates the mobility of the matrix atoms. The parameters were chosen to simulate the experimentally observed diffusion in a-Si. The coordination numbers and radial-distribution-function were analyzed to confirm the assumption of bond switching as the dominant mechanism of self-diffusion.

Keywords: amorphous silicon; diffusion

  • Poster
    E-MRS Spring Meeting, Symposium K: Group IV semiconductors materials research - growth, characterization and applications to electronics and spintronics, 02.-06.05.2016, Lille, France

Publ.-Id: 23666

Fractional Quantum Hall States in a Ge Quantum Well

Mironov, O. A.; D'Ambrumenil, N.; Dobbie, A.; Leadley, D. R.; Suslov, A. V.; Green, E.

Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We analyze the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long-range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarized Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required.

Publ.-Id: 23665

From Describing to Prescribing Parallelism: Translating the SPEC ACCEL OpenACC Suite to OpenMP Target Directives

Juckeland, G.; Hernandez, O.; Jacob, A. C.; Neilson, D.; Vergara Larrea, V. G.; Wienke, S.; Chandrasekaran, S.; Grund, A.; Henschel, R.; Müller, M. S.; Perminov, M.; Shelepugin, P.; Whitney, B.; Joubert, W.; Wang, B.; Kumaran, K.; SPEC High Performance Group (HPG), Email: – Website:; Bobyr, A.

Current and next generation HPC systems will exploit accelerators and self-hosting devices within their compute nodes to accelerate applications. This comes at a time when programmer productivity and the ability to produce portable code has been recognized as a major concern. One of the goals of OpenMP and OpenACC is to allow the user to specify parallelism via directives so that compilers can generate device specific code and optimizations. However, the challenge of porting codes becomes more complex because of the different types of parallelism and memory hierarchies available on different architectures.
In this paper we discuss our experience with porting the SPEC ACCEL benchmarks from OpenACC to OpenMP 4.5 using a performance portable style that lets the compiler make platform-specific decisions to achieve performance. The SPEC ACCEL OpenMP benchmarks were tested on different platforms including Xeon Phi, GPUs and CPU cores. We also discuss some performance-portable best practices that help expose more parallelism in the codes in a portable style. We believe that this expe rience can help the community and compiler vendors understand how users plan to write OpenMP 4.5 applications in a performance portable

Keywords: SPEC; SPEC ACCEL; OpenMP; OpenACC; Offloading

  • Contribution to proceedings
    Workshop on Performance Portable Programming Models for Accelerators (P^3MA), 23.06.2016, Frankfurt (Main), Deutschland
    Lecture Notes on Computer Science (LNCS) - Volume 9934: High Performance Computing ISC High Performance 2016 International Workshops, ExaComm, E-MuCoCoS, HPC-IODC, IXPUG, IWOPH, P^3MA, VHPC, WOPSSS, Frankfurt, Germany, June 19–23, 2016: Springer, 978-3-319-46078-9, 470-488
    DOI: 10.1007/978-3-319-46079-6_33

Publ.-Id: 23664

Cryogel-Supported Stem Cell Factory for Customized Sustained Release of Bispecific Antibodies for Cancer Immunotherapy

Aliperta, R.; Welzel, P. B.; Bergmann, R.; Freudenberg, R.; Berndt, N.; Feldmann, A.; Arndt, C.; Koristka, S.; Stanzione, M.; Cartellieri, M.; Ehninger, A.; Ehninger, G.; Werner, C.; Pietzsch, J.; Steinbach, J.; Bornhäuser, M.; Bachmann, M.

Combining stem cells with biomaterial scaffolds provides a promising strategy for the development of drug delivery systems. Here we propose an innovative immunotherapeutic organoid by housing human mesenchymal stromal cells (MSCs), gene-modified for the secretion of an anti-CD33-anti-CD3 bispecific antibody (bsAb), in a small biocompatible star-shaped poly(ethylene glycol)-heparin cryogel scaffold as a transplantable and low invasive therapeutic machinery for the treatment of acute myeloid leukemia (AML). The macroporous biohybrid cryogel platform displays effectiveness in supporting proliferation and survival of bsAb-releasing-MSCs overtime in vitro and in vivo, avoiding cell loss and ensuring a constant release of sustained and detectable levels of bsAb capable of triggering T-cell-mediated anti-tumor responses and a rapid regression of CD33+ AML blasts. This therapeutic device results as a promising and safe alternative to the continuous administration of short-lived immunoagents and paves the way for effective bsAb-based therapeutic strategies for future tumor treatments.

Keywords: starPEG-heparin cryogel; Mesenchymal stromal cells; Bispecific antibody; Cancer immunotherapy

Publ.-Id: 23663

Tos-Nos-Mos: Synthesis of different aryl sulfonate precursors for the radiosynthesis of the alpha7 nicotinic acetylcholine receptor radioligand [18F]NS14490

Rötering, S.; Scheunemann, M.; Günther, R.; Löser, R.; Hiller, A.; Peters, D.; Brust, P.; Fischer, S.; Steinbach, J.

Radiopharmacological investigations of [18F]NS14490 have proven that this radiotracer could be a potential PETradiotracer for imaging of alpha7 nicotinic acetylcholine receptor particularly with regard to vulnerable plaques of diseased vessels. For further optimisation of the previously automated one-pot radiosynthesis of [18F]NS14490 using a tosylate precursor, precursors with other leaving groups (nosylate and mosylate) were synthesized and compared with the tosylate with respect to their reactivities towards [18F]fluoride. The use of these different precursors resulted in comparable labelling yields of [18F]NS14490. A novel mosylate precursor was synthesized and evaluated, which has revealed a higher stability during a storage period of five months compared to the corresponding tosylate and nosylate.

Keywords: Alpha7 nAChR ligand; PET; Synthesis of precursor; Reactivity of precursor; Tosylate; Nosylate; Mosylate

Publ.-Id: 23661

Extracellular S100A4 affects endothelial cell integrity and stimulates transmigratory behavior of human A375 melanoma cells

Herwig, N.; Belter, B.; Pietzsch, J.

High extracellular S100A4 level proves a specific characteristic of some cancer cases, including malignant melanoma. Concerning the latter, extracellular S100A4 in an autocrine manner was shown to promote prometastatic activation of A375 cells by interaction with the receptor for advanced glycation endproducts (RAGE). We hypothesized that interaction of extracellular S100A4 with RAGE in a paracrine manner will affect endothelial cell (EC) integrity thus further promoting melanoma metastasis. We investigated the influence of recombinant and cell (A375)-derived S100A4 on RAGE and junction protein expression, and EC (hCMEC/D3) integrity by measuring transendothelial electrical resistance (TEER). RAGE was upregulated by recombinant S100A4. Decrease of TEER and diminished expression of both occludin and VE-cadherin revealed the loss of EC integrity. Transmigration of transgenic A375 cells (A375-hS100A4/A375-hRAGE) through the EC monolayer was significantly higher compared to wild-type A375 cells, and was substantially decreased by sRAGE. An additional pilot study in mice, intracardially injected with A375-hS100A4 or A375-hRAGE cells, showed lower survival rates and a higher incidence of metastases compared to wild-type A375 cells. Tumor development was mostly located in the brain, bones, and ovaries. These findings provide further evidence on extracellular S100A4 as paracrine mediator of prometastatic endothelial dysfunction involving its interaction with RAGE.

Keywords: hCMEC/D3; prometastatic endothelial dysfunction; receptor for advanced glycation endproducts (RAGE); soluble RAGE (sRAGE); S100 proteins; transendothelial electrical resistance (TEER)


Publ.-Id: 23660

Electrochemical behavior of nanocrystalline Ta/TaN multilayer on 316L stainless steel: Novel bipolar plates for proton exchange membrane fuel-cells

Alishahi, M.; Mahboubi, F.; Mousavi Khoie, S. M.; Aparicio, M.; Hübner, R.; Soldera, F.; Gago, R.

Insufficient corrosion resistance and surface conductivity are two main issues that plague large-scale application of stainless steel (SS) bipolar plates in proton exchange membrane fuel cells (PEMFCs). This study explores the use of nanocrystalline Ta/TaN multilayer coatings to improve the electrical and electrochemical performance of polished 316L SS bipolar plates. The multilayer coatings have been deposited by (reactive) magnetron sputtering and characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The electrochemical behavior of bare and coated substrates has been evaluated in simulated PEMFC working environments by potentiodynamic and potentiostatic polarization tests at ambient temperature and 80 °C. The results show that the Ta/TaN multilayer coating increases the polarization resistance of 316L SS by about 30 and 104 times at ambient and elevated temperatures, respectively. The interfacial contact resistance (ICR) shows a low value of 12 µOhm cm-2 before the potentiostatic test. This ICR is significantly lower than for the bare substrate and remains mostly unchanged after potentiostatic polarization for 14 h. In addition, the high contact angle (92 °) with water for coated substrates indicates a hydrophobic character, which can improve the water management within the cell in PEMFC stacks.

Keywords: PEMFC; Bipolar plate; Magnetron sputtering; Multilayer coating; Interfacial contact resistance; Corrosion

  • Journal of Power Sources 322(2016), 1-9

Publ.-Id: 23659

Tailoring the magnetic anisotropy of (Ga,Mn)(As,P) by ion irradiation

Yuan, Y.; Rushforth, A.; Sawicki, M.; Dietl, T.; Helm, M.; Zhou, S.

The rich phenomena in the magnetic anisotropy of diluted ferromagnetic semiconductors (DFS) have opened new concepts for spintronics beyond conventional electronic logic devices [1]. As an example, the magnetic anisotropy of (Ga,Mn)(As,P) can be changed from in-plane to out-of-plane by low temperature annealing [2, 3]. In this work, we demonstrate another flexible approach to tune the magnetic anisotropy by He+ ion irradiation, which is a well-developed chip-technology. For the as-prepared (Ga,Mn)(As,P), the low-temperature long-time annealing suppresses the compensation from Mn interstitials, resulting in a higher carrier concentration and the switching of the magnetic easy axis from the in-plane [100] to the out-of-plane [001] direction [3]. By He+ irradiation, we can turn the magnetic easy axis gradually back to the out-of-plane direction. Therefore, ion irradiation combined with low-temperature long-time annealing boosts the prospects of flexible tailoring of the magnetic anisotropy of DFS material, allowing for the development of new concepts for spintronic devices.

[1] T. Dietl et al., Rev. Mod. Phys. 86, 187-251 (2014).
[2] M. Sawicki et al., Phys. Rev. B 70, 245325 (2004).
[3] A. Casiraghi et al., Appl. Phys. Lett. 97, 122504 (2010).

  • Poster
    EMRS 2016 Spring, 02.-06.05.2016, Lille, France

Publ.-Id: 23658

Pulsed laser melting: A versatile approach for the preparation of dilute ferromagnetic semiconductors

Yuan, Y.; Helm, M.; Zhou, S.

Mn doped III-V dilute ferromagnetic semiconductors (DFS) are of great interest in recent decades due to their potential for spintronics [1]. However, the low solid solubility of Mn in III-V semiconductors prohibits the common equilibrium preparation process. For long time, the low-temperature molecule beam epitaxy (LT-MBE) has been the only method to obtain DFS. The technical challenges in LT-MBE result in the fact that GaMnAs (and its alloys with low concentration of phosphorus or indium) is the only available DFS.
In our work, making the full use of ion implantation combined with pulsed laser melting, we have extended the family of Mn doped III-V DFSs. All specimens exhibit the epitaxial structure and pronounced uniaxial magnetic anisotropy. Particularly, we have prepared InMnAs with both high Curie temperature and perpendicular magnetic anisotropy, which is difficult to prepare by LT-MBE due to many n-type defects [3], as well as GaMnP [4] and InMnP [5] which have only been prepared by ion implantation up to now. When compared with LT-MBE, this approach combining ion implantation and pulsed laser melting brightens the future of III-Mn-V DFS by two aspects: (1) Its efficiency and reproducibility make the possibility of the large-scale production in industry; (2) The introduction of new materials (GaMnP and InMnP) provides a more complete platform for understanding the DFS family.

[1]. T. Dietl et al., Rev. Mod. Phys., 86, 187-251 (2014)
[2]. D. Bürger et al., Phys. Rev. B, 81, 115202 (2010)
[3]. Y. Yuan et al., J. Phys. D: Appl. Phys. 48, 235002 (2015)
[4].Y. Yuan et al., IEEE Trans. Mag. 50, 2401304 (2014)
[5]. M. Khalid et al., Phys. Rev. B, 89, 121301(R) (2014)

  • Lecture (Conference)
    EMRS 2016 Spring Meeting, 02.-06.05.2016, Lille, France

Publ.-Id: 23657

Numerical simulation of mass transfer and convection near a hydrogen bubble during water electrolysis in a magnetic field

Mutschke, G.; Fröhlich, J.; Yang, X.; Eckert, K.; Karnbach, F.; Uhlemann, M.; Baczyzmalski, D.; Cierpka, C.

Hydrogen produced from wind or solar power could be used easily for storing energy also at large scale, thus allowing to bridge the gap between supply and demand of renewable energy with respect to time and place. When splitting water by electrolysis, a deeper look at local phenomena near single bubbles at the electrode might be helpful to improve our understanding of the process. In the recent literature, magnetic fields are discussed with respect to the bubble departure, thereby possibly influencing the efficiency of the process [1-6].
The contribution will present numerical simulations resolving in detail local phenomena near a single hydrogen bubble at the cathode during the electrolysis of water. The modeling is supported by data of recent experiments on hydrogen single bubbles evolving at a platinum micro-electrode. The results will provide insight into the local and temporal behavior of electrolyte convection, species concentration and mass transfer during electrolysis. Furthermore, the influence of the Lorentz force caused by vertical magnetic fields will be discussed in detail.
[1] X. Yang et al., Langmuir 31 (2015) 8184-8193.
[2] D. Fernandez et al., Langmuir 30 (2014) 13065-13074.
[3] H. Liu et al., J. Electroanal. Chem. 754 (2015) 22-29.
[4] H. Liu et al., Can. J. Chem. Eng. 94 (2016) 192-199.
[5] D. Baczyzmalski et al., Exp. Fluids 56 (2015) 162ff.
[6] J. Koza et al., Electrochem. Comm. 10 (2009) 425-429.

Keywords: electrolysis; hydrogen evolution; magnetic field; Lorentz force; convection; mass transfer

  • Poster
    67th Annual Meeting of the International Society of ELectrochemistry, 21.-26.08.2016, Den Haag, Niederlande
  • Lecture (Conference)
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia
  • Contribution to proceedings
    10th PAMIR International Conference on Fundamental and Applied MHD, 20.-24.06.2016, Cagliari (Sardinia), Italia
    Proceedings of the 10th PAMIR International Conference on FUndamental and Applied MHD, 978-88-90551-93-2, 97-101
  • Open Access Logo Magnetohydrodynamics 53(2017)1, 193-199


Publ.-Id: 23656

PET/CT during degradation processes at the cement-clay interface and derivation of process parameters

Kulenkampff, J.; Mäder, U.; Gründig, M.; Eichelbaum, S.; Lippmann-Pipke, J.

Observation of degradation processes is complicated by the heterogeneous nature of the process. Better process understanding requires methods for both monitoring the fate of chemical species (mobile phase) and structural alterations (stationary phase). In the past decade, we empowered positron emission tomography (PET) for quantitative transport visualization in geological media – GeoPET. It has an unrivalled sensitivity and robustness for quantitative, non-destructive, spatio-temporal concentration measurements cPET(x,y,z,t). CT adds structural information.

  • Poster
    1st Annual Workshop of the CEBAMA project, 11.-13.05.2016, Barcelona, Spanien
  • Open Access Logo Contribution to proceedings
    1st Annual Workshop of the CEBAMA project, 11.-13.05.2016, Barcelona, Spanien
    Proceedings of the First Annual Workshop of the HORIZON 2020 CEBAMA Project KIT scientific reports 7734, Karlsruhe: KIT Scientific Publishing, 978-3-7315-0660-7, 113-119
    DOI: 10.5445/KSP/1000068889

Publ.-Id: 23655

Multiscale Self-Assembly of Silicon Quantum Dots into an Anisotropic Three-Dimensional Random Network

Ilday, S.; Ilday, F. O.; Hübner, R.; Prosa, T. J.; Martin, I.; Nogay, G.; Kabacelik, I.; Mics, Z.; Bonn, M.; Turchinovich, D.; Toffoli, H.; Toffoli, D.; Friedrich, D.; Schmidt, B.; Heinig, K.-H.; Turan, R.

Multiscale self-assembly is ubiquitous in nature but its deliberate use to synthesize multifunctional three-dimensional materials remains rare, partly due to the notoriously difficult problem of controlling topology from atomic to macroscopic scales to obtain intended material properties. Here, we propose a simple, modular, noncolloidal methodology that is based on exploiting universality in stochastic growth dynamics and driving the growth process under far-from-equilibrium conditions toward a preplanned structure. As proof of principle, we demonstrate a confined-butconnected solid structure, comprising an anisotropic random network of silicon quantum-dots that hierarchically self-assembles from the atomic to the microscopic scales. First, quantum-dots form to subsequently interconnect without inflating their diameters to form a random network, and this network then grows in a preferential direction to form undulated and branching nanowire-like structures. This specific topology simultaneously achieves two scale-dependent features, which were previously thought to be mutually exclusive: good electrical conduction on the microscale and a bandgap tunable over a range of energies on the nanoscale.

Keywords: Si; random network; hierarchical; multiscale; self-assembly; stochastic deposition

  • Nano Letters 16(2016), 1942-1948

Publ.-Id: 23654

Investigation of single bubbles and bubble chains in liquid metal under the influence of magnetic fields

Strumpf, E.; Eckert, S.

Two-phase flows play an important role in industrial applications, such as the continuous casting of steel. Here, inert gas is injected into the beginning of the submerged entry nozzle to avoid nozzle clogging as well as to catch impurities within the melt and to transport them to the free surface, away from the solidification front. Furthermore electromagnetic brakes are used with the aim to dampen the highly turbulent flow and to reduce high velocities in the liquid metal. Although a vast number of simulations and experiments of bubbly flows in water exist, such investigations in liquid metal still lack quantity. However, liquid metal experiments are unavoidable for a correct modelling of such special cases, like the influence of magnetic fields on the flow or the two-phase flow behavior. In the present study the ascents of single bubbles and of bubble chains in a liquid metal are investigated. For this purpose a benchmark experiment is set up, a cuboid vessel of the dimensions 144 x 144 x 12 mm³, which is filled with eutectic alloy GaInSn. A transversal magnetic field up to 1.1 T is imposed to this vessel. Ultrasound Doppler Velocimetry (UDV) is used to map the flow in the continuous phase of bubble chain regimes as well as the ascent velocity of single bubbles.

Keywords: liquid metal; single bubble; bubble chain; magnetic field; ultrasound

  • Lecture (Conference)
    International Conference on Multiphase Flow (ICMF 2016), 22.-27.05.2016, Firenze, Italia

Publ.-Id: 23653

Magnetic vortex cores as tunable spin wave emitters

Wintz, S.; Tyberkevych, V.; Weigand, M.; Raabe, J.; Lindner, J.; Erbe, A.; Slavin, A.; Fassbender, J.

The use of spin waves as information carriers in spintronic devices can substantially reduce energy losses by eliminating the ohmic heating associated with electron transport. Yet, the excitation of short-wavelength spin waves in nanoscale magnetic systems remains a significant challenge. Here, we propose a method for their coherent generation in a heterostructure composed of antiferromagnetically coupled magnetic layers. The driven dynamics of naturally formed nanosized stacked pairs of magnetic vortex cores is used to achieve this aim. The resulting spin-wave propagation is directly imaged by time-resolved scanning transmission X-ray microscopy. We show that the dipole-exchange spin waves excited in this system have a linear, non-reciprocal dispersion and that their wavelength can be tuned by changing the driving frequency.

Keywords: magnetism spinwaves magnonics vortex

Publ.-Id: 23652

Defect studies of Mg films deposited on various substrates

Hruška, P.; Čížek, J.; Anwand, W.; Bulíř, J.; Drahokoupil, J.; Stráská, J.; Melikhova, O.; Procházka, I.; Lančok, J.

In the present work the structure of Mg films deposited by RF magnetron sputtering was characterized using variable energy positron annihilation spectroscopy combined with scanning electron microscopy and X-ray diffraction. The effect of deposition parameters, namely temperature, type of substrate and deposition rate, on the microstructure was examined. All Mg films studied grow with the basal (0001) plane parallel with the substrate and exhibit only negligible in-plane stress. Films deposited at room temperature are characterized by nanocrystalline structure with high volume fraction of grain boundaries. and positrons are preferentially trapped in open volume defects present at grain boundaries. In these films positrons are trapped predominantly in open-volume defects present at grain boundaries. With increasing deposition temperature the mean grain size increases and the volume fraction of grain boundaries decreases. Hence, in Mg films prepared at elevated temperatures positrons are trapped mainly at misfit dislocations compensating different atomic spacing in the films and the substrate. Moreover, it was found that slow deposition rate leads to higher density of defects compared to fast deposition rate. By annealing of Mg film with thin 20 nm Pd over-layer at 300°C for 1 hour Pd layer is mixed with Mg film forming a Mg-Pd compound. The Mg-Pd phase likely contains structural open-volume defects which trap positrons.

Keywords: defect studies; Mg films; positron annihilation

Publ.-Id: 23651

Ferromagnetism in 5f-band metamagnet UCoAl induced by Os doping

Andreev, A. V.; Shirasaki, K.; Sebek, J.; Vejprovova, J.; Gorbunov, D. I.; Havela, L.; Danis, S.; Yamamura, T.

UCoAl is a 5f-band metamagnet with a uniquely low paramagnetic-to-ferromagnetic transition field, 0.7 T, extremely sensitive to any perturbation such as elemental substitution. Here, we study variations of magnetic properties in the UCoAl-UOsAl system on single- and polycrystalline samples with different concentration of Os. We found that osmium can substitute Co in UCoAl up to 20%, while preserving the ZrNiAl structure type. Pure UOsAl was identified as a hexagonal Laves phase, MgZn2 type. It is a weak Pauli paramagnet. Even a 2%-substitution of Os for Co in the 5f band metamagnet stabilizes ferromagnetism with the Curie temperature TC = 26 K and uranium magnetic moment µ = 0.4 µB and shifts the critical metamagnetic field to zero. Higher Os concentrations enhance both TC and µ. All magnetic response is concentrated into the c-axis; the susceptibility for magnetic field perpendicular to c is low and practically temperature-independent. Our study reflects the decisive role of the 5f-5d hybridization in the magnetism of the UCoAl-UOsAl system. This work completes the study of the alloying of UCoAl with late transition metals and indicates that the non-magnetic phase exhibiting band metamagnetism is very limited in the concentration range.

Publ.-Id: 23650

Evaluation of covalence in An(III)- and Ln(III)-complexes by NMR Spectroscopy

Adam, C.; Kaden, P.; Beele, B. B.; Geist, A.; Müllich, U.; Panak, P. J.

Partitioning and transmutation (P&T) facilitates a reduction of the long-term radiotoxicity and heat load of spent nuclear fuel by separation of the actinides and subsequent conversion into shorter-lived or stable nuclides. A chemically demanding key step in this process is the separation of the trivalent actinides from fission lanthanides. This can be achieved by liquid-liquid extraction using highly selective extraction agents, such as nPrBTP (1) or C5-BPP (2). These have high separation factors (>100) for trivalent americium over europium. However, the molecular origin of their selectivity is largely unclear.
NMR spectroscopy on paramagnetic samples allows a separation of the observed paramagnetic shift into a part due to transferred electron spin density (Fermi contact shift, FCS) and a part due to dipolar coupling of electron and nuclear spin (Pseudo contact shift, PCS). Evaluation of the FCS thus allows an assessment of the share of covalence in the metal-ligand bond of the N-donor complexes. Several methods that enable the separation of the shift contributions have been proposed in literature. So-called “model free methods” that do not require structural models of the complexes appear most promising.
We will present and compare the results of different temperature-dependent and temperature-independent model-free methods for complexes of both ligands. The merits, but also the limitations of currently available methods will be discussed in detail. Furthermore, we will evaluate the applicability of temperature-dependent methods for shift separation of Am(III) complexes and give a qualitative assessment on covalence in the bonding of these complexes.

Keywords: NMR Spectroscopy; Separation; Partitioning Ligands; Bonding

  • Poster
    ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles, 05.-10.06.2016, Montpellier, Frankreich

Publ.-Id: 23649

Comparative NMR Study of nPrBTP and iPrBTP Complexes

Adam, C.; Rohde, V.; Müllich, U.; Kaden, P.; Geist, A.; Panak, P. J.

Partitioning and transmutation (P&T) is a strategy for reducing the long-term radiotoxicity and heat load of spent nuclear fuel by separating actinides from the used fuel and converting them into shorterlived or stable products. A key step in this process is the separation of the trivalent actinides from lanthanides, which can be achieved by liquid-liquid extraction using selective N-donor extracting ligands, such as alkylated bis-triazinyl pyridines (BTP). These have high separation factors (>100) for trivalent americium over europium. However, little is known about the molecular origin of their selectivity.
The aliphatic side chains of BTP ligands influence the stability against radiation and hydrolysis, the solubility, but also the selectivity and extraction behaviour. While nPrBTP (1) has been thoroughly studied over the past years, only few data are available for its isomer iPrBTP (2). TRLFS studies showed that the stability constants for the Eu(III) complex are almost three orders of magnitude higher than for nPrBTP, while the increase for Cm(III) complexes is less pronounced.
This result prompted us to investigate Ln(III) and the Am(III) complexes by NMR spectroscopy, which offers insight into the metal-ligand bond properties. For the NMR studies, iPrBTP with 15N isotope labelling of the nitrogen atoms in the pyrazole moiety was synthesized. We will show a comparison of the bonding properties in complexes of (1) and (2) and discuss the share of covalence in the bonding. Furthermore, the implications for the mechanism of complex formation with ligand (2) will be evaluated.

Keywords: NMR Spectroscopy; Separation; Partitioning Ligands; Bonding

  • Lecture (Conference)
    ATALANTE 2016 – Nuclear Chemistry for Sustainable Fuel Cycles, 05.-10.06.2016, Montpellier, Frankreich

Publ.-Id: 23648

Comparative NMR study of nPrBTP and iPrBTP

Adam, C.; Rohde, V.; Müllich, U.; Kaden, P.; Geist, A.; Panak, P. J.; Geckeis, H.

Bistriazinyl-pyridine type ligands are important extracting agents for separating trivalent actinide ions from trivalent lanthanides. The alkyl substituents on the lateral triazine rings have a significant effect on the stability of the ligand against hydrolysis and radiolysis. Furthermore they influence solubility, extraction behaviour and selectivity. TRLFS and extraction studies suggest differences in complexation and extraction behaviour of BTP ligands bearing iso-propyl or n-propyl substituents, respectively. As NMR studies allow insight into the metal-ligand bonding, we conducted NMR studies on a range of 15N-labelled nPrBTP and iPrBTP complexes. Our results show that no strong change in the metal-ligand bonding occurs, thus excluding electronic reasons for differences in complexation behaviour, extraction kinetics and selectivity. This supports mechanistic reasons for the observed differences.

Keywords: NMR Spectroscopy; Bonding; Extraction; BTP; An(III)/Ln(III) separation

  • Open Access Logo Contribution to proceedings
    Comparative NMR study of nPrBTP and iPrBTP, 05.-10.06.2016, Montpellier, Frankreich
    Procedia Chemistry
    DOI: 10.1016/j.proche.2016.10.006


Publ.-Id: 23647

Guided-wave second harmonics in Nd:YCOB ridge waveguides produced by combination of carbon ion irradiation and precise diamond blade dicing

Li, R.; Nie, W.; Shang, Z.; Cheng, C.; Akhmadaliev, S.; Zhou, S.; Lu, Q.; Chen, F.

We report on the fabrication of Nd:YCa4O(BO3)3 (Nd:YCOB) ridge waveguides by combining carbon ion irradiation and precise diamond blade dicing. The guiding and spectroscopic properties of the planar as well as ridge waveguides are investigated. The second harmonic generation (SHG) at 532 nm has been realized through the waveguide structures. With nearly the same input power, the maximum average output powers are 0.56 mW and 0.62 mW, and the maximum conversion efficiencies reach 0.3%W−1 and 0.5%W−1, for planar and ridge waveguides, respectively.

Keywords: Optical waveguides; Nd:YCOB crystal; Second harmonic generation

Publ.-Id: 23646

Universality of (2+1)-dimensional restricted solid-on-solid models

Kelling, J.; Ódor, G.; Gemming, S.

Extensive dynamical simulations of Restricted Solid on Solid models in D=2+1 dimensions have been done using parallel multisurface algorithms implemented on graphics cards. Numerical evidence is presented that these models exhibit KPZ surface growth scaling, irrespective of the step heights N. We show that by increasing N the corrections to scaling increase, thus smaller step sized models describe better the asymptotic, long wave scaling behavior.

Related publications


Publ.-Id: 23645

A possible new origin of long absorption tail in Nd-doped yttrium aluminum garnet induced by 15 MeV gold-ion irradiation and heat treatment

Amekura, H.; Akhmadaliev, S.; Zhou, S.; Chen, F.

When ion irradiation introduces point-defects in semiconductors/insulators, discrete energy levels can be introduced in the bandgap, and then optical transitions whose energies are lower than the bandgap become possible. The electronic transitions between the discrete level and the continuous host band are observed as a continuous tail starting from the fundamental edge. This is the well-known mechanism of the absorption tail close to the band-edge observed in many semiconductors/insulators. In this paper, we propose another mechanism for the absorption tail, which is probably active in Nd-doped yttrium aluminum garnet (Nd:YAG) after ion irradiation and annealing. A Nd:YAG bulk crystal was irradiated with 15 MeV Au5+ ions to a fluence of 8 × 1014 ions/cm2. The irradiation generates an amorphous layer of ∼3 μm thick with refractive index reduction of Δn = −0.03. Thermal annealing at 1000 °C induces recrystallization to randomly aligned small crystalline grains. Simultaneously, an extraordinarily long absorption tail appeared in the optical spectrum covering from 0.24 to ∼2 μm without fringes. The origin of the tail is discussed based on two models: (i) conventional electronic transitions between defect levels and YAG host band and (ii) enhanced light scattering by randomly aligned small grains.

Publ.-Id: 23644

Structure and X-ray diagnostics in non-equilibrium warm dense matter

Vorberger, J.; Chapman, D. A.

We present a quantum theory for the dynamic structure factors in non-equilibrium, non-ideal, two-component warm dense matter. This general framework allows the derivation of expressions for the local field corrections in non-equilibrium. Based on a perturbation expansion of the non-equilibrium polarization function in terms of the interaction strength and taking the Wigner function as input quantity, we calculate the dynamic structure for a variety of typical scenarios and demonstrate typical effects. Example situations include laser heated matter or shock produced warm dense matter.
We provide a generalized Chihara decomposition of the total dynamic electron structure factor. The formula features the free electrons, the non-equilibrium ion structure, the generalized non-equilibrium screening cloud and an additional term arising due to not invoking the Born-Oppenheimer approximation. This puts the theory of x-ray scattering in non-equilibrium on a sound theoretical basis and makes x-ray scattering a possible diagnostics for non-equilibrium warm dense matter on all time scales, in particular on femtosecond electronic time scales.
We give examples for the expected x-ray scattering signals in laser heated systems and in two-temperature systems. We discuss the possibility to resolve temperature relaxation using x-ray scattering and point out possible problems in the current models used for the description of such relaxation processes.

Keywords: x-ray scattering; warm dense matter; dynamic structure factor; exchange; correlations

  • Poster
    HEDLA 2016, 16.-20.05.2016, Menlo Park, USA

Publ.-Id: 23643

Time structure influence on the radiobiological response to MeV electron beams

Beyreuther, E.; Gotz, M.; Karsch, L.; Lessmann, E.; Schürer, M.; Pawelke, J.

No abstract available

Publ.-Id: 23642

Status of the Development of a Novel Compact Proton Therapy Gantry System Based on Pulsed Magnets for Laser-driven Beams

Masood, U.; Baumann, M.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Pawelke, J.

Proton acceleration on m scale via high intensity laser has become a compelling alternative to conventional accelerators and gained interests for its potential to reduce size and costs for proton therapy (PT) facilities. Next generation petawatt lasers promise laser-driven protons (LDP) with therapeutic energies. But, in contrast to conventionally accelerated quasi-continuous mono-energetic pencil beams with about 30 Gy/sec dose rate, LDP beams have diverse properties, i.e. ultra-intense pico-sec bunches with up to 1010 Gy/sec dose rate, large energy spread and divergence, and with only up to 10 Hz repetition rate. These properties make it challenging to adapt LDP beams directly for medical applications. The presented work is an ongoing joint translational research project of several institutions aiming to establish laser-driven PT. We will present the recent progress in design concepts and the status of the development.

In addition to laser accelerator development, LDP beams demand radiobiological characterization and new solutions for beam transport and dose delivery. Laser-based technology for low energy LDP beams has been established for cell and small animal irradiation using a fixed beamline and is being utilized for systematic extreme dose rate radiobiological studies. For translation towards patient irradiation a highly compact 360° isocentric proton gantry system was designed based on light-weight iron-less high-field pulsed magnets. The gantry is integrated with beam control, energy selection and a novel dose delivery system, capable to magnetically control the beam spot size and to scan the beam for advanced irradiation schemes. A 3D TPS has been adapted and used to demonstrate clinical functionality of our system. For its realization, key high-field pulsed magnets are being developed.

Radiobiologically, so far no overall difference is observed for laser-driven ultra-high dose rates compared to conventional PT beams. Our double achromatic gantry system is about 3 times smaller than conventional PT gantries. The new dose delivery system can simultaneously widens the beam size (Ø 1-20 cm) and scan 10x20 cm2 field size, for the most efficient dose delivery. High quality clinical treatment plans can be provided with such beams. For the gantry realization a pulsed 40 T solenoid for particle capture and a 10 T compact iron-less 50° sector magnet were successfully tested. A pulsed 120 T/m gradient quadrupole is being manufactured.
Our compact, light-weight gantry could provide an optimized solution for the laser-driven PT. The tests of pulsed gantry magnets are being continued. Our new conventional PT facility is additionally equipped with a petawatt laser laboratory and an experimental bunker. This will allow testing for clinical applicability of LDP systems side-by-side with conventional therapeutic proton beams as reference.

This project was supported by German BMBF grant (03Z1N511 and 03Z1O511).

Keywords: Proton Therapy; Gantry; Pulsed Magnets; Laser acceleration

  • Poster
    ASTRO 2016 Annual Meeting, 25.-28.09.2016, Boston, USA
  • Abstract in refereed journal
    International Journal of Radiation Oncology Biology Physics 96(2016)2, E612
    DOI: 10.1016/j.ijrobp.2016.06.2162

Publ.-Id: 23641

Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

Thies, R.; Heinz, A.; Adachi, T.; Aksyutina, Y.; Alcantara-Núñes, J.; Altstadt, S.; Alvarez-Pol, H.; Ashwood, N.; Aumann, T.; Avdeichikov, V.; Barr, M.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boretzky, K.; Borge, M. J. G.; Burgunder, G.; Camaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkäll, J.; Chakraborty, S.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Crespo, R.; Datta, U.; Díaz Fernández, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estradé, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Freudenberger, M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Göbel, K.; Golubev, P.; Gonzalez Diaz, D.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Henriques, A.; Holl, M.; Ickert, G.; Ignatov, A.; Jakobsson, B.; Johansson, H. T.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Knöbel, R.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lepyoshkina, O.; Lindberg, S.; Machado, J.; Marganiec, J.; Maroussov, V.; Mostazo, M.; Movsesyan, A.; Najafi, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Prochazka, A.; Rahaman, A.; Rastrepina, G.; Reifarth, R.; Ribeiro, G.; Ricciardi, M. V.; Rigollet, C.; Riisager, K.; Röder, M.; Rossi, D.; Sanchez Del Rio, J.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Stoica, V.; Streicher, B.; Taylor, J. T.; Tengblad, O.; Terashima, S.; Togano, Y.; Uberseder, E.; van de Walle, J.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M. V.; Zilges, A.; Zuber, K.

Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions.
Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes.
Method: We have measured projectile fragments from C10,12−18 and B10−15 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations.
Results: One-proton removal cross sections with different final neutron numbers (1pxn) for relativistic C10,12−18 and B10−15 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well.
Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study.

Keywords: nuclear fragmentation fission radioactive ion beam facilities C10 C12−18 B10−15 isotope


Publ.-Id: 23640

Remote Sensing-Based Exploration of Structurally-Related Mineralizations around Mount Isa, Queensland, Australia

Jakob, S.; Gloaguen, R.; Laukamp, C.

Hyperspectral imaging is a powerful tool for mineral mapping and increasingly used in poorly-accessible areas. It only requires a limited amount of validation sample points, but can fail to discriminate spectrally-similar features. In this manuscript, we show that we improve the identification of interesting targets by including geomorphological data in the spectral mapping scheme. We jointly use geomorphic and spectral features to locate gossanous ironstone ridges as an indicator for possible Pb-Zn-Ag-mineralization and provide an application around Mount Isa and George Fisher/Hilton mine, Queensland, Australia. We combine hyperspectral HyMap data using mixture tuned matched filtering with topographical indices, such as maximum curvature and the topographical position index. As it is often the case with structurally-controlled mineralization, the amount of training sites is limited, and supervised classification methods cannot be implemented. Therefore, we implement expert knowledge in a decision tree to take advantage of the relationship between mineralization, alteration and structure. Optimized rock sampling and spectral measurements provided data for validation. We are able to map sets of gossanous ridges with a minimum of validation points, not only within the Mount Isa mining area itself, but also outside the commonly-accepted host rocks. The ridges are parallel to north-south trending geomorphological features and probably associated with the Paroo fault zone. Similarities between the ridges were confirmed by field observations, spectral measurements and a qualitative rock sample analysis. We identified new mineralized ridges that we could subsequently attribute to a poorly-known and sub-economic deposit known as the Mount Novit Pb-Zn-deposit.

Keywords: HyMap; hyperspectral; mineral mapping; geomorphological features; alteration mapping

Publ.-Id: 23639

JRQ and JPA irradiated and annealed reactor pressure vessel steels studied by positron annihilation

Slugen, V.; Gokhman, O.; Pecko, S.; Sojak, S.; Bergner, F.

The paper is focused on a comprehensive study of JRQ and JPA reactor pressure vessel steels from the positron annihilation lifetime spectroscopy (PALS) point of view. Based on our more than 20 years’ experience with characterization of irradiated reactor steels, we confirmed that defects after irradiation start to grow and/or merge into bigger clusters. Experimental results shown that JPA steel is more sensitive to the creation of irradiation-induced defects than JRQ steel. It is most probably due to high copper content (0.29 wt.% in JPA) and copper precipitation has a major impact on neutron-induced defect creation at the beginning of the irradiation. Based on current PALS results, no large vacancy clusters were formed during irradiation, which could cause dangerous embrittlement concerning operation safety of nuclear power plant. The combined PALS, small angle neutron scattering and atomic probe tomography studies support the model for JRQ and JPA steels describing the structure of irradiationinduced clusters as agglomerations of vacancy clusters (consisting of 2–6 vacancies each) and are separated from each other by a distribution of atoms.

Keywords: Nuclear materials; positron annihilation spectroscopy; RPV steel; irradiation; ion beam implantation

Publ.-Id: 23638

Interaction of radio-metals with microorganisms

Raff, J.; Vogel, M.; Günther, A.; Drobot, B.; Schmoock, C.; Moll, H.; Börnick, H.; Worch, E.; Stumpf, T.

Metals interact in various ways with living organisms. This affects first of all the behavior of the metals in the environment as different metal species differ in their mobility in the geo- and the biosphere as well as in their bioavailability. Conversely, metals are essential for the vitality of cells. Many metals are an integral part of one or more enzymes involved in metabolic and biochemical processes. Beside essential metals there are also toxic and radioactive metals that can seriously damage an organism at least at higher concentrations. Figure 1 shows possible interaction mechanisms between microorganisms and radio-metals.
Furthermore, radio-metals may damage or even destroy cells by radiation. The latter excites or ionizes atoms or molecules causing the formation of radicals, changes of biomolecules or even the breakage of chemical bonds. But also for this kind of damage microorganisms have successfully developed effective strategies. Different spectroscopic methods and electron microscopy reveal that different groups of organisms such as bacteria, algae and fungi, differ in their interaction with radio-metals.
In case of bacterial uranium mining waste pile isolates belonging to the genera Lysinibacillus and Bacillus it was demonstrated that so-called S-layer proteins, forming a latticed protein envelope on many bacteria and almost all archaea, are able to effectively scavenge reactive oxygen species (ROS). The latter can be formed by either radiolysis of water or the Fenton reaction. These ROS react with tyrosine side chains of the proteins forming bityrosines and thereby causing an intramolecular crosslinking. Furthermore, these S-layers possess different functional groups on their surface such as carboxyl, hydroxyl, amino, phosphate, sulfoxide and sulfate groups. These groups mediate selective binding of different metals including uranyl(VI) [2]. As most S-layer proteins are also calcium binding proteins, these S-layers additionally possess at least two different Ca binding sites binding trivalent actinides such as Cm(III) with high affinity [3]. In case of the alga Chlorella vulgaris U(VI) concentrations up to 5 µM are bound via carboxyl and phosphate groups being located on the cell surface. This process is followed by desorption in which probably the secretion of complexing bio-ligands is involved [4]. At higher uranium concentrations of 100 µM the alga will die and no desorption can be observed. In comparison to this alga, the fungus Schizophyllum commune interacts with moderate concentrations of uranium (4.2 µM) via organic phosphates. At higher U(VI) concentrations (420 µM) the fungus stays alive and accumulates uranium additionally inside the cell by forming inorganic uranyl phosphates [5]. Due to their high uranium resistance and high accumulation rates different fungi were selected to be further investigated regarding their application potential for a fungal-based concept for the reliable immobilization of released radionuclides within the so called BioVeStRa project.

[1] Lloyd J.R. and Macaskie L. E. (2002), In Interactions of Microorganisms with Radionuclides, Ed. Keith-Roach & Livens, Elsevier, 313-342,
[2] Merroun M.L. et al. (2005), Appl. Environ. Microbiol. 71(9), 5532-5543.
[3] Moll H. et al. (2011), Curium(III) complexation with surface-layer (S-layer) proteins from a uranium mining waste pile isolate. Poster at Migration 2011, 18.-23.09.2011, Beijing, PR China.
[4] Vogel M. et al. (2010), Sci. Total Environ. 409, 384-395.
[5] Günther A. et al. (2014), Biometals 27,775-785.

Keywords: radionuclides; microorganism; interaction

  • Poster
    Ninth International Conference on Nuclear and Radiochemistry – NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Publ.-Id: 23637

Pulsed-power high-field magnets for laser-driven proton therapy gantry systems

Karsch, L.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Kroll, F.; Masood, U.; Schramm, U.; Schürer, M.; Pawelke, J.

please ask the authors

  • Lecture (Conference)
    EAPPC with BEAMS and MEGAGAUSS 2016, 18.-22.09.2016, Estoril, Portugal

Publ.-Id: 23636

Ionization chamber collection efficiency in pulsed radiation fields of high pulse dose

Gotz, M.; Karsch, L.; Pawelke, J.

please ask the authors

  • Poster
    AAPM 58th Annual Meeting, 31.07.-04.08.2016, Washington, DC, USA
  • Abstract in refereed journal
    Medical Physics 43(2016)6, 3316
    DOI: 10.1118/1.4955543

Publ.-Id: 23635

Entwicklung kompakter, gepulster Elektro-Dipolmagnete für die laserbasierte Protonentherapie

Schürer, M.; Herrmannsdörfer, T.; Karsch, L.; Kroll, F.; Masood, U.; Pawelke, J.

no abstract is available

  • Lecture (Conference)
    Entwerfen Entwickeln Erleben – EEE2016, 30.06.-01.07.2016, Dresden, Deutschland
  • Contribution to proceedings
    Entwerfen Entwickeln Erleben – EEE2016, 30.06.-01.07.2016, Dresden, Deutschland
    Entwickeln - Entwerfen - Erleben 2016: Beiträge zur virtuellen Produktentwicklung und Konstruktionstechnik, Dresden: Verlag der Wissenschaften GmbH, TUDpress, 978-3-95908-062-0, 91-96


Publ.-Id: 23634

Preparation of in vivo radiobiological characterization of laser-driven proton beams

Karsch, L.; Baumann, M.; Beyreuther, E.; Brüchner, K.; Gotz, M.; Krause, M.; Leßmann, E.; Schmidt, M.; Schramm, U.; Schürer, M.; Pawelke, J.

please ask the authors

  • Poster
    Annual ARR Meeting, 27.-29.06.2016, Leicester, Great Britain

Publ.-Id: 23633

A compact proton therapy facility concept for pulsed beams from high power laser accelerators

Masood, U.; Baumann, M.; Enghardt, W.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Pawelke, J.

please ask the authors

  • Poster
    55th Annual Conference of the PTCOG, 22.-28.05.2016, Prague, Czech Republic
  • Open Access Logo Abstract in refereed journal
    International Journal of Particle Therapy 3(2016)1, 160
    DOI: 10.14338/IJPT.16-PTCOG-1.1

Publ.-Id: 23632

Novel Approach to utilize Proton Beams from High Power Laser Accelerators for Therapy

Masood, U.; Baumann, M.; Cowan, T. E.; Enghardt, W.; Herrmannsdörfer, T.; Hofmann, K. M.; Karsch, L.; Kroll, F.; Schramm, U.; Schürer, M.; Wilkens, J. J.; Pawelke, J.

please ask the authors

  • Poster
    7th International Particle Accelerator Conference (IPAC), 08.-13.05.2016, Busan, South Korea
  • Contribution to proceedings
    7th International Particle Accelerator Conference (IPAC), 08.-13.05.2016, Busan, South Korea
    Proceedings of IPAC2016, 978-3-95450-147-2, 1-3

Publ.-Id: 23631

In-vivo Simulation of the Relative Biological Effectiveness in Proton Therapy Using a Monte Carlo Method

Oesten, H.; Loeck, S.; Helmbrecht, S.; Tillner, F.; Wohlfahrt, P.; Schuemann, J.; Luehr, A.

urpose: In proton therapy, the relative biological effectiveness (RBE) – compared with conventional photon therapy – is routinely set to 1.1. However, experimental in vitro studies indicate evidence for the variability of the RBE. To clarify the impact on patient treatment, investigation of the RBE in a preclinical case study should be performed.
Methods: The Monte Carlo software TOPAS was used to simulate the radiation field of an irradiation setup at the experimental beamline of the proton therapy facility (OncoRay) in Dresden, Germany. Simulations were performed on cone beam CT-data of a xenogeneous mouse with an orthotopic lung carcinoma obtained by an in-house developed small animal image-guided radiotherapy device. A homogeneous physical fraction dose of 1.8Gy was prescribed for the contoured tumor volume. Simulated dose and linear energy transfer distributions were used to estimate RBE values in the mouse based on an RBE model by Wedenberg et al. To characterize radiation sensitivity of normal and tumor tissue, α/β-ratios were taken from the literature for NB1RGB (10.1Gy) and human squamous lung cancer (6.2Gy) cell lines, respectively.
Results: Good dose coverage of the target volume was achieved with a spread-out Bragg peak (SOBP). The contra-lateral lung was completely spared from receiving radiation. An increase in RBE towards the distal end of the SOBP from 1.07 to 1.35 and from 1.05 to 1.3 was observed when considering normal tissue and tumor, respectively, with the highest RBE values located distal to the target volume.
Conclusion: Modeled RBE values simulated on cone beam CT-data for experimental preclinical proton therapy varied with tissue type and depth in a mouse and differed therefore from a constant value of 1.1. Further translational work will include, first, conducting preclinical experiments and, second, analogous RBE studies in patients using experimentally verified simulation settings for our clinically used patient-specific beam conforming technique.

Keywords: proton therapy; cancer; hadron therapy; RBE; radiobiology; lung cancer; orthotopic tumor model; Monte Carlo; TOPAS

  • Contribution to proceedings
    AAPM Annual Meeting, 31.07.-04.08.2016, Washington, DC, USA
    Medical Physics 43, 3621
    DOI: 10.1118/1.4956868

Publ.-Id: 23630

The specific sorption of Np(V) on the corundum (α-Al2O3) surface in the presence of trivalent lanthanides Eu(III) and Gd(III): a batch sorption and XAS study

Virtanen, S.; Bok, F.; Ikeda-Ohno, A.; Rossberg, A.; Lützenkirchen, J.; Rabung, T.; Lehto, J.; Huittinen, N.

The sorption of pentavalent neptunium, Np(V), on corundum (α-Al2O3) was investigated in the absence and presence of trivalent europium or gadolinium as competing element under CO2-free conditions. The objective of this study was to investigate how a trivalent metal ion with a higher charge than that of the neptunyl ion would affect the sorption of Np(V) when allowed to adsorb on the mineral surface before the addition of Np(V). Batch sorption experiments conducted as a function of pH (pH-edges) and as a function of Np(V) concentration (isotherms) in the absence and presence of 1×10-5 M Eu(III) showed no sign of Eu being able to block Np sorption sites. Surface complexation modelling using the diffuse double layer model was employed to the batch data to obtain surface complexation constants for the formed Np(V) complexes on corundum. To account for potential changes occurring in the coordination environment of the neptunium ion in the presence of a trivalent lanthanide, X-ray absorption spectroscopic (XAS) studies of samples containing only Np(V) or Np(V) and Gd(III) were conducted. The XAS-measurements reveal the presence of a bidentate Np(V) edgesharing complex on the corundum surface in the absence of Gd(III). In the presence of Gd(III) our Np(V) EXAFS data show a contraction of the Np-Al distance together with the formation of an additional peak that is not resolved in the absence of the competing metal. These differences might point toward a change in the Np(V) surface configuration on corundum when Gd(III) is added to the sample before Np(V).

Keywords: Np(V); Eu(III); Gd(III); sorption competition; batch sorption; EXAFS

Publ.-Id: 23628

Completing the nuclear reaction puzzle of the nucleosynthesis of 92Mo

Tveten, G. M.; Spyrou, A.; Schwengner, R.; Naqvi, F.; Larsen, A. C.; Eriksen, T. K.; Bellogarrote, F. L.; Bernstein, L. A.; Bleuel, D. L.; Crespo-Campo, L.; Guttormsen, M.; Giacoppo, F.; Görgen, A.; Hagen, T. W.; Hadynska-Klek, K.; Klintefjord, M.; Meyer, B. S.; Nyhus, H. T.; Renstrom, T.; Rose, S. J.; Sahin, E.; Siem, S.; Tornyi, T. G.

One of the greatest questions for modern physics to address is how elements heavier than iron are created in extreme, astrophysical environments. A particularly challenging part of that question is the description of the so-called p-nuclei, which are believed to be mainly produced in some types of supernovae.
In this work, we present for the first time measurements on the nuclear level density and average strength function of 92 Mo. State-of-the-art p-process calculations systematically underestimate the observed solar abundance. Our data provide stringent constraints on the 91 Nb(p,gamma92 Mo reaction rate, which is the last unmeasured reaction in the nucleosynthesis puzzle of 92 Mo. Based on our results, we conclude that the 92 Mo abundance anomaly is not due to the nuclear physics input.

Keywords: P-nuclei; p-process; nucleosynthesis; solar abundance; strength function; reaction rate

Publ.-Id: 23627

Comprehensive UV/vis and Infrared Studies of Light-induced Carbon Monoxide Release From Ruthenium(II) Complexes

Kubeil, M.; Vernooij, R. R.; Wood, B. R.; Stephan, H.; Graham, B.; Spiccia, L.

The use of carbon monoxide as a therapeutic agent has been demonstrated in pre-clinical trials, with CO-releasing molecules (CORMs) exhibiting anti-inflammatory, anti-proliferative, anti-apoptotic, anti-oxidative and vasodilatory effects. Organometallic compounds that can release CO in a highly controlled fashion under physiological conditions have therefore become a major field of scientific and medical research. Light-induced activation of CORMs is a controlled CO release approach that has received considerable attention. However, despite the number of photo-CORMs reported in the literature, their utility has been limited because excitation into the UV region results in low tissue penetrability and direct damage to healthy tissue. The challenge to extend the excitation wavelength further into the visible region of the electromagnetic spectrum has led us to explore the application of ruthenium(II) -carbonyl complexes as photo-CORMs.
Herein, we report the synthesis of ruthenium(II)-carbonyl complexes (Figure 1) functionalized with bidentate polypyridyl ligands and investigate the mechanism of CO release (before and after light-activation) using a combination of spectral techniques (UV/Vis, FTIR and Raman spectroscopy). The photo-induced CO-release kinetics of the Ru(II)-photo-CORMs, as well as the identity of the intermediates and photo-activated products, will be presented. These results have important implications in guiding the design of new photo-CORMs activated by visible light.

  • Lecture (Conference)
    27th International Conference on Organometallic Chemistry (ICOMC), 17.-22.07.2016, Melbourne, Australia

Publ.-Id: 23626

Experimental investigations on a common centrifugal pump operating under gas entrainment conditions

Schäfer, T.; Neumann, M.; Bieberle, A.; Hampel, U.

This paper presents an experimental study on the effects of additional gas entrainment in centrifugal pumps designed for conveying liquid phases only. The pump performance has been evaluated for several gas entrainment conditions, and for various operational settings of the pump, such as its alignment and the rotational speed of the impeller. As a main performance indicator the impact of entrained gas on the hydraulic power of the pump has been analyzed using experimental data. Additionally, high-resolution gamma-ray computed tomography (HireCT) operated in time-averaged rotation-synchronized scanning mode has been applied to quantify local phase fraction distributions inside the rapidly rotating pump impeller. Based on these quantitative tomographic measurements, gas holdup profiles along selected streamlines have been calculated and gas accumulation areas inside the impeller chambers have been visualized. Thus, various internally accumulated gas holdup patterns have been identified and, eventually, associated with characteristic pump performance behaviors. Moreover, the tomographic measuring method allowed an enhanced gas holdup analysis in specified pump compartments. As a result, the related specific gas and liquid phase holdup profiles have been evaluated.

Keywords: centrifugal pump; gas entrainment; two-phase flow; gas holdup; gamma-ray computed tomography


Publ.-Id: 23625

Commissioning of a Compton Camera for particle beam range monitoring

Thirolf, P. G.; Aldawood, S.; Böhmer, M.; Bortfeldt, J.; Castelhano, I.; Dedes, G.; Enghardt, W.; Fiedler, F.; Gernhäuser, R.; Golnik, C.; Helmbrecht, S.; Hueso-González, F.; Kolff, H. V. D.; Kormoll, T.; Lang, C.; Liprandi, S.; Maier, L.; Marinšek, T.; Miani, A.; Pausch, G.; Petzoldt, J.; Pocevicius, M.; Römer, K.; Schaart, D. R.; Valencia-Lozano, I.; Parodi, K.

A Compton camera prototype for the position-sensitive detection of prompt γ rays from nuclear reactions between proton (or ion) beams and organic targets is being commissioned in Garching. The detector system is designed to allow for reconstructing the γ-source position from the Compton scattering kinematics of the primary photon as well as from tracking the Compton-scattered electron trajectory. The camera consists of a monolithic LaBr3(Ce) scintillation absorber crystal, read out by a 256-fold segmented multi-anode PMT and preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The detector system has been calibrated and characterized in the laboratory as well as at different accelerator facilities, including clinical proton beams. Results from online commissioning runs will be presented, demonstrating excellent agreement between experimental prompt-γ spectra and Monte-Carlo simulations. Particular effort was dedicated to characterize the spatial resolution achievable with the monolithic LaBr 3 (Ce) scintillator when targeting the primary photon interaction position. Intense, tightly collimated 137Cs and 60Co sources were used for 2D irradiation scans as prerequisite for studying the performance of the “k-Nearest Neighbour”-algorithm developed in Delft and extending its applicability into the energy range beyond 511 keV. Systematic results of the monolithic scintillator’s spatial resolution will be presented as a function of the k-NN parameters (e.g. events per irradiation position) and the PMT segmentation, resulting in the realization of the presently optimum spatial resolution (3.8(2) mm @1.3 MeV) already for a reduced PMT segmentation (8x8). An outline of ongoing and planned further experimental activities and upgrade plans will be presented.
This work is supported by the DFG Cluster of Excellence MAP (Munich-Centre for Advanced Photonics).

Keywords: in-vivo dosimetry; prompt gamma; proton therapy; ion beam therapy; compton camera; cancer; radiooncology; imaging

  • Contribution to proceedings
    2016 IEEE Nuclear Science Symposium and Medical Imaging Conference (IEEE NSS/MIC), 29.10.-06.11.2016, Strasbourg, France

Publ.-Id: 23623

The inhibitory potency of polyoxometalates at P2X receptors

Spanier, C.; Abdelrahman, A.; Tang, J.; Hausmann, R.; Kortz, U.; Schmalzin, G.; Stephan, H.; Wang, W.; Müller, C. E.

P2X receptors are trimeric ligand-gated ion channels activated by ATP and permeable for cations such as Na+, K+ and Ca2+. Seven different subunits exist, assembled as homo- or heterotrimers of various stoichiometry.1 Polyoxometalates (POMs) are polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+). This class of inorganic metal cluster compounds exhibits great variability with respect to shape, size, charge and composition.2 POMs bear several negative charges and in this respect resemble ATP, which binds to P2X receptors in its negatively charged state. We previously found that certain POMs can inhibit ATP-hydrolyzing ectonucleotidases.2-4 In the present study we investigated whether tungsten-containing POMs can interact with P2X receptors. A series of POMs was investigated for their ability to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X receptor subtypes. Several POMs were found to be highly potent inhibitors of P2X receptors exhibiting low nanomolar potency. PEGylation of POMs to increase their metabolic stability was tolerated by the receptors. Structure-activity relationships at P2X receptor subtypes differed from those observed for ecto¬nucleotidases. The majority of POMs were found to be non-cytotoxic at pharmacologically active concentrations.

  • Poster
    Frontiers in Medicinal Chemistry (FiMC) Meeting 2016, 13.-16.03.2016, Bonn, Deutschland

Publ.-Id: 23622

Experimental and Theoretical Investigation of the Collection Efficiency of Air-Filled Ionization Chambers in Pulsed Radiation Fields of High Pulse Dose

Gotz, M.; Karsch, L.; Pawelke, J.

Ionization chambers are used in physical radiation research and are the most important dosimeters in radiation therapy. In this contribution an investigation of the collection efficiency by experiments and theoretical description is presented. The collection efficiency was measured for a plane-parallel advanced Markus ionization chamber (PTW 34045, 1 mm electrode spacing, 300 V nominal voltage), a chamber often used in clinical practice. The measurements were performed for collection voltages of 100 V and 300 V by irradiation with a pulsed electron beam of varied pulse dose up to approximately 600 mGy (0.8 nC liberated charge). These results are compared to existing descriptions of the collection efficiency and our own model based on a numeric solution by Euler method of a differential equation system modelling the processes within the chamber.
While the existing models accurately describe the collection efficiency at the lower collection voltage (100 V) they fail to reproduce the experimentally observed behavior at the higher collection voltage (300 V) particularly at high pulse doses. In contrast, our own numeric solution reproduces the collection efficiency at all tested voltages and pulse doses. This illustrates the importance of considering additional effects such as electric shielding by the liberated charges and field strength dependent attachment of electrons which are not considered in the existing models. Subsequently, the developed more accurate numeric solution might provide a valuable tool for future investigations.

  • Poster
    Nuclear Science Symposium & Medical Imaging Conference, 29.10.-06.11.2016, Strasbourg, France

Publ.-Id: 23621

Small, but hitting the target – towards novel nanoparticle platforms for diagnostic cancer imaging

Zarschler, K.

For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
The presented work focusses on the epidermal growth factor receptor (EGFR) acting as a model receptor, since it is overexpressed and/or deregulated in a variety of solid tumours. Thus, bioconjugation of EGFR-specific single-domain antibodies (sdAbs) to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signalling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. The results show that sdAb-functionalised nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.

  • Lecture (others)
    Eingeladener Vortrag am Institut für Chemie der Universität Zürich, Schweiz, 29.01.2015, Zürich, Schweiz

Publ.-Id: 23620

Small, but hitting the target – towards novel nanoparticle platforms for diagnostic cancer imaging

Zarschler, K.

For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
The presented work focusses on the epidermal growth factor receptor (EGFR) acting as a model receptor, since it is overexpressed and/or deregulated in a variety of solid tumours. Thus, bioconjugation of EGFR-specific single-domain antibodies (sdAbs) to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signalling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. The results show that sdAb-functionalised nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.

  • Lecture (others)
    Eingeladener Vortrag am Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Australia, 27.11.2014, Melbourne, Australien

Publ.-Id: 23619

Specific nanoparticle targeting of the EGF-receptor using single-domain antibodies

Zarschler, K.; Rocks, L.; Mahon, E.; Prapainop, K.; Stephan, H.; Dawson, K. A.

For effective localization of functionalized nanoparticles at diseased tissues such as solid tumors or metastases through biorecognition, appropriate targeting vectors directed against selected tumor biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
In the presented work we analyze the specific nanoparticle targeting capabilities of a small camelid single-domain antibody (sdAb), representing a potential recognition agent for the epidermal growth factor receptor (EGFR).

Bioconjugation of EGFR-specific sdAbs to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signaling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum.

Results and Discussion
The results show that sdAb-functionalized nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentrations. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realized in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.

  • Lecture (Conference)
    ICONAN 2016 - International Conference on Nanomedicine and Nanobiotechnology 2016, 28.-30.09.2016, Paris, Frankreich

Publ.-Id: 23618

Gastric Bypass Surgery Recruits a Gut – Striatal Dopamine Pathway to Reduce Fat Appetite in Obese Rats

Hankir, M. K.; Seyfried, F.; Hintschich, C. A.; Diep, T. A.; Kleberg, K.; Kranz, M.; Deuther-Conrad, W.; Tellez, L. A.; Rullmann, M.; Patt, M.; Teichert, S.; Sabri, O.; Brust, P.; Hansen, H. S.; de Araujo, I. E.; Krügel, U.; Fenske, W. K.

Roux-en-Y gastric bypass (RYGB) surgery produces well-documented improvements in maladaptive feeding behaviors, yet the underlying mechanisms remain ill-defined. As recognized mediators of fat intake, we evaluated the functional requirement of gut lipid-sensing and striatal dopamine signaling on healthier fat appetite after RYGB. We found that surgical rerouting of intestinal fat passage mobilized jejunal/ileal production of the dietary fat-derived molecule oleoylethanolamide (OEA). Vagal afferents link intestinal OEA signaling to nigrostriatal function. RYGB-treatment increased in vivo dorsal striatal dopamine release and dopamine-1-receptor density under conditions of high-fat meal consumption independently of bodyweight. Moreover, blocking OEA, vagal and dorsal striatal dopamine signaling all reversed the beneficial effects of surgery on fat appetite. Our findings suggest that RYGB re-sensitizes gut lipid-sensing to modify brain reward circuits compromised in obesity.

Publ.-Id: 23617

In vivo demonstration of an active tumor pretargeting approach with peptide nucleic acid bioconjugates as complementary system

Leonidova, A.; Foerster, C.; Zarschler, K.; Schubert, M.; Pietzsch, H.-J.; Steinbach, J.; Bergmann, R.; Metzler-Nolte, N.; Stephan, H.; Gasser, G.

The ability of early-stage diagnosis of tumor malignancies and personalized treatment ultimately relies on the availability of highly tumor-affine compounds with purposeful pharmacological profile. Although monoclonal antibodies (mAbs) specifically bind to tumor-associated epitopes, the conventional concept of directly radiolabeled tumor-specific mAb has several drawbacks most prominently the prolonged radiation exposure of non-cancerous tissue. However, the concept of tumor pretargeting allows for the rational use of long-circulating high-affinity mAbs for non-invasive cancer radioimmunodetection and therapy. Our work describes a successful tumor pretargeting utilizing an EGFR-specific mAb and peptide nucleic acid (PNA) derivatives as the complementary system for specific radionuclide delivery to pretargeted tumor tissue.

After chemical synthesis, purification and detailed characterization of the individual components including antibody-PNA conjugates and different PNA oligomers, biodistribution studies were carried out using healthy Wistar rats. Finally, the pretargeting approach was evaluated in murine A431 tumor xenografts by single photon emission computed tomography.

After optimizing the pharmacokinetic properties of PNA oligomers and investigating their hybridization properties, we elaborated a versatile conjugation protocol based on coupling a cysteine-functionalized PNA oligomer to a maleimido-functionalized mAb. The in vivo studies demonstrated a rapid and efficient accumulation of activity at the tumor site with a tumor-to-muscle ratio of > 8 and clearly distinguishable tumor visualization.

This successful tumor pretargeting study has demonstrated the high potential of this concept by applying radiolabeled complementary PNA strands as an alternative in vivo recognition and radionuclide transporting system. The next step involves the translation of these results to the application of therapeutic relevant radionuclides.

  • Lecture (Conference)
    NuklearMedizin 2016 - 54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin e.V., 20.-23.04.2016, Dresden, Deutschland

Publ.-Id: 23616

Single-domain antibodies for specific nanoparticle targeting of the EGF-receptor

Zarschler, K.

For effective localization of functionalized nanoparticles at diseased tissues such as solid tumours or metastases through biorecognition, appropriate targeting vectors directed against selected tumour biomarkers are a key prerequisite. The diversity of such vector molecules ranges from proteins, including antibodies and fragments thereof, through aptamers and glycans to short peptides and small molecules.
The presented work focusses on the epidermal growth factor receptor (EGFR) acting as a model receptor, since it is overexpressed and/or deregulated in a variety of solid tumours. Thus, bioconjugation of EGFR-specific single-domain antibodies (sdAbs) to different nanomaterials and characterization of sdAb-conjugates covering in vitro cancer cell imaging, cell proliferation as well as EGFR phosphorylation and signalling are described. The specificity of the sdAb-conjugates is investigated by way of receptor RNA silencing techniques with increasing complexity in vitro by introducing increasing concentrations of human or bovine serum. The results show that sdAb-functionalised nanomaterials can effectively target the EGFR, even in more complex bovine and human serum conditions where targeting specificity is largely conserved for increasing serum concentration. For highly affine targeting ligands such as sdAbs, targeting a receptor such as EGFR with low serum competitor abundance, receptor recognition function can still be partially realised in complex conditions. Moreover, sdAb-mediated biorecognition of EGFR is not restricted to particular nanomaterials, but was observed to work efficiently in combination with a variety of materials.

  • Invited lecture (Conferences)
    Scientific Symposium "Targeting tumor angiogenesis with antibody-based technologies", 08.06.2015, Madrid, Spanien

Publ.-Id: 23615

Diagnostic and therapeutic targeting of EGF-receptor positive cancer cells using single-domain antibodies

Zarschler, K.

Single-domain antibodies (sdAbs) provide several advantages over classical antibodies and fragments thereof. Due to their small size and strict monomeric appearance combined with other important properties such as high solubility and stability as well as high specificity and affinity for the respective antigen, these proteins have been identified as attractive targeting moieties for molecular imaging and drug delivery. Furthermore, sdAbs are easily engineered into bivalent and bispecific constructs by genetic in-frame joining of two identical or two different sdAbs, respectively. This results in increased antigen binding through avidity effects and in enhanced construct specificity by simultaneous interaction with two different antigens, respectively.
In addition to intrinsic agonistic or antagonistic effects on their target, sdAbs appear to be ideally suited to create novel tailored derivatives equipped with innovative effector functions. The chemical or genetic linkage of sdAbs to accessory effector moieties such as toxins and enzymes results in a new class of target-specific anticancer therapeutics. Thereby, the sdAb guides the effector moiety to the diseased tissue, where it carries out its particular function.
Herein the application of radiolabelled epidermal growth factor receptor (EGFR) specific sdAbs as in vivo molecular imaging tracers as well as their intrinsic antagonistic effects on tumor cells will be described. Furthermore, the construction and characterisation of sdAb-based therapeutics will be exemplified. Thus, this contribution sheds light on the future application of sdAb derivatives in the field of cancer diagnosis and therapy.

  • Lecture (Conference)
    PACHIFICHEM 2015, 15.-20.12.2015, Honolulu, USA

Publ.-Id: 23614

Ultra-fast Thermal Processing

Rebohle, L.; Schumann, T.; Prucnal, S.; Skorupa, W.

Thermal processing in the subsecond range comprises modern, non-equilibrium annealing techniques which allow various material modifications at the surface without affecting the bulk. Flash lamp annealing (FLA) is one of the most diverse methods of short time annealing with applications ranging from the classical field of semiconductor doping to the treatment of polymers and flexible substrates. The presentation focuses on several FLA aspects which are especially important for thin film applications. In detail, it briefly introduces to the technological background, deals with the broad subject of temperature distributions and addresses constraints and other process issues like thermal stress or homogeneity. Finally, an overview of the various applications of FLA is given.

Keywords: flash lamp annealing; pulsed light sintering; semiconductors

  • Invited lecture (Conferences)
    The International Conference on Coatings on Glass and Plastics, 12.-16.06.2016, Braunschweig, Deutschland

Publ.-Id: 23613

Subsecond thermal processing with flash lamps: equipment and modelling issues

Schumann, T.; Rebohle, L.; Skorupa, W.

This contribution presents an overview of the complex technical aspects of flash-lamp-annealing-tools for thermal processing in the millisecond range used at the Helmholtz Research Center Dresden-Rossendorf (HZDR). It outlines that Flash Lamp Annealing (FLA) is established as a high-performance alternative to Rapid Thermal Annealing and Furnace Annealing when it comes to treatment of the most advanced thin layer and coating materials, thus enabling the fabrication of novel electronic structures and materials classes. It shows the unique variety of parameters the HZDR is able to provide for applications ranging from annealing of implanted Si and Ge, transparent conductive oxides, photovoltaic materials, silver and copper inks on various non-metal substrates to exceptional applications (roof tiles, watchcases). It explains, how crucial parameters, such as emission spectrum, energy density, and preheat temperature are monitored to provide a reliable reproducibility. Modelling aspects regarding temperature distribution and heat transport within the millisecond range will also be addressed. Furthermore, a summary will be given of characteristic features of our tools to convey the diversity of the fields of application and the enormous range of possible research.

Keywords: flash lamp annealing

  • Poster
    The International Conference on Coatings on Glass and Plastics, 12.-16.06.2016, Braunschweig, Deutschland

Publ.-Id: 23612

Flash lamp annealing for low-cost transparent conducting oxide layers

Rebohle, L.; Mathey, A.; Prucnal, S.; Wiesenhütter, K.; Vines, L.; Lindberg, P.; Svensson, B.; Bregolin, F. L.; Skorupa, W.

Aluminum-doped zinc oxide (AZO) is one of the most promising transparent conductive oxide material which is characterized by low resistivity, high transparency and most of all, by low cost of fabrication. AZO thin-films were deposited on p-type Si wafers via r.f. magnetron sputtering either at room temperature or at 400 °C followed by a thermal treatment in the millisecond range using flash lamp annealing (FLA). It is shown that FLA enhances the electrical activation of Al and minimizes secondary phase formation during post-deposition annealing. In addition, the optoelectronic and microstructural properties of the FLA treated samples are independent on the deposition temperature. As FLA is a cost-effective, easily scalable high-throughput technology, these results opens the possibility for a further, desirable cost reduction of the overall fabrication process.

Keywords: flash lamp annealing; doping; zinc oxide; transparent conducting oxide

  • Poster
    The International Conference on Coatings on Glass and Plastics, 12.-16.06.2016, Braunschweig, Deutschland

Publ.-Id: 23611

X-ray spectroscopic study of the chemical state of “invisible” Au in synthetic minerals in the Fe-As-S system

Trigub, A. L.; Tagirov, B. R.; Kvashnina, K. O.; Chareev, D. A.; Nickolsky, M. S.; Shiryaev, A. A.; Baranova, N. N.; Mokhov, E. V. Kovalchuk A. V.

Minerals of the Fe-As-S system are ubiquitous components of Au ores in many deposits of hydrothermal origin, including world-class volcanogenic massive sulfide, low-temperature epithermal and mesothermal ones. The “invisible” (or refractory) form of Au is present in all types of hydrothermal ores and in many cases predominates. Knowledge of the “invisible” Au chemical state (local atomic environment/structural position, electronic structure and oxidation state) is a fundamental problem crucial for understanding conditions of the ore formation, is necessary for physical-chemical modeling of hydrothermal Au mineralization, and will help to create more efficient technologies of ore concentration and Au extraction. We report investigation of the “invisible” Au chemical state in synthetic analogues of natural minerals: pyrite (FeS2), arsenopyrite (FeAsS), and löllingite (FeAs2). The compounds were synthesized using hydrothermal (pyrite) and salt flux techniques (all the minerals) and studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode in combination with first-principles quantum chemical calculations. The concentration of the “invisible” Au in the synthesized löllingite (800±300 ppm) was much higher compared to arsenopyrite (23±14 ppm), whereas the lowest Au content with zonal Au concentration profiles was observed in crystals of salt flux pyrite. The concentration of Au in the hydrothermal pyrite (40-90 ppm) is independent on sulfur fugacity and probably reflects the maximum Au solubility at the experimental P/T parameters (450 °C, 1 kbar). It is shown that Au replaces Fe in structure of löllingite, arsenopyrite, and hydrothermal pyrite. The nearest-neighbors Au-ligand distance increases by 0.14 Å (pyrite), 0.16 Å (löllingite), and 0.23 (As), 0.13 (S) Å for arsenopyrite relative to Fe-ligand distance in pure compounds. Distortion of the local atomic structure around the Au is negatively correlated with the distance and disappears at r > ~4 Å. The chemically bound Au is stable only in hydrothermal pyrite, whereas the pyrite synthesized in the absence of hydrothermal fluid contains only Au°. Heating (metamorphism) of hydrothermal pyrite results in decomposition of the chemically bound Au with formation of Au° nuggets which coarsen with temperature. Depending on chemical composition of the host mineral Au can play a role either of cation or anion: the Bader atomic partial charges of Au decrease in the order of pyrite (+0.4 e) > arsenopyrite (0) > löllingite (-0.4 e). Our results suggest that other noble metals (platinum group elements, Ag) can form the chemically bound refractory admixture in base metal sulfides/chalcogenides. The chemical state, as well as the concentration, of this form of noble metals can differ depending on the composition of the host mineral and the ore history.

Keywords: invisible gold; pyrite; arsenopyrite; löllingite; synthetic minerals; X-ray absorption spectroscopy; atomic charges


Publ.-Id: 23610

Microbial Influence on Bentonite-Transformation

Matschiavelli, N.; Steglich, J.; Arnold, T.; Cherkouk, A.

Bentonites are clay silicates consisting mostly of montmorillonite. Due to their mineral composition, bentonites are characterized by a high swelling capacity and low hydraulic conductivity. Therefore, Bentonite is a promising raw material for serving as a natural clay barrier for the disposal of highly radioactive waste. To address the question, whether and to which extend microbial activity affects the respective parameters, selected bentonites can be supplied with a pore water solution and afterwards incubated for short- and long-term analyses at different temperatures in order to simulate the evolution of microbial activity and the resulting impact on Bentonite-transformation. For characterization the respective Bentonite samples will be analyzed considering their geochemistry, molecular biology and mineralogy – three divisions that influence each other directly. We expect that the obtained results could reveal variations in microbial diversity and a correlation with changes of geochemical parameters which could affect the composition and solubility of minerals, and furthermore the beneficial properties of bentonite. The gained information can be further used to indicate a trend in bentonite transformation, which is a prerequisite for evaluating the influence of prokaryotes on safety-relevant processes and properties in radioactive waste repositories.

  • Contribution to proceedings
    MIND Project Annual Meeting, 03.-04.05.2016, Granada, Spain
  • Lecture (Conference)
    MIND Project Annual Meeting, 03.-04.05.2016, Granada, Spain
  • Poster
    MIND Project Annual Meeting, 03.-04.05.2016, Granada, Spain

Publ.-Id: 23609

Clinical Validation of a New Digital Spectrometer System for Range Verification in Proton Therapy

Werner, T.; Petzoldt, J.; Hueso-González, F.; Berthold, J.; Rinscheid, A.; Enghardt, W.; Pausch, G.

Particle therapy is a promising technique for cancer treatment because of the characteristic dose deposition of protons in matter. As an alternative method to conventional photon therapy, it allows a precise irradiation of the tumor volume in the patient body, while sparing healthy, radiosensitive organs.
However, body modifications during the treatment period hinder the precise positioning of the Bragg peak in the target volume, and thus limits the accuracy of proton therapy.
These uncertainties and the lack of a suitable monitoring system, which should control the range in vivo and real-time during the irradiation, make it necessary to establish broad safety margins around the irradiated volume in the patient body. This decreases the effectiveness of the therapy and reduces the benefits compared to conventional photon therapy. To counteract this, many solutions for a clinically applicable system for online range verification are under discussion. One approach is the Prompt Gamma Timing (PGT) method. The energy-resolved timing spectra of the detected photons encode the range information of the primary protons and allow a real time range verification [1]. The concept of PGT was developed and tested in first experiments, which confirm that PGT is a promising method for range assessment [2]. Especially the simplicity of the concept according to the experimental implementation justifies a further development with special focus on clinical applications.

  • Lecture (Conference)
    IEEE Nuclear Science Symposium and Medical Imaging Conference, 29.10.-06.11.2016, Strasbourg, France

Publ.-Id: 23608

Field-Induced Magnonic Liquid in the 3D Spin-Dimerized Antiferromagnet Sr3Cr2O8

Wang, Z.; Quintero-Castro, D. L.; Zherlitsyn, S.; Yasin, S.; Skourski, Y.; Islam, A. T. M. N.; Lake, B.; Deisenhofer, J.; Loidl, A.

We report on ultrasound and magnetization studies in three-dimensional, spin-dimerized Sr3Cr2O8 as a function of temperature and external magnetic field up to 61 T. It is well established [A. A. Aczel et al., Phys. Rev. Lett. 103, 207203 (2009)] that this system exhibits a magnonic-superfluid phase between 30 and 60 T and below 8 K. By mapping ultrasound and magnetization anomalies as a function of magnetic field and temperature we establish that this superfluid phase is embedded in a domelike phase regime of a hightemperature magnonic liquid extending up to 18 K. Compared to thermodynamic results, our study indicates that the magnonic liquid could be characterized by an Ising-like order but has lost the coherence of the transverse components.

Publ.-Id: 23607

Characterization of a fast timing and energy spectroscopy system for real-time range verification in particle therapy

Rinscheid, A.; Berthold, J.; Enghardt, W.; Golnik, C.; Fiedler, F.; Hueso-González, F.; Kormoll, T.; Petzoldt, J.; Römer, K.; Werner, T.; Wolf, A.; Reichert, D.; Pausch, G.

A compact high-throughput gamma-ray timing and energy spectrometry systems has been characterized with respect to time and energy resolution at detector loads up to 1.5 Mcps by using 0.1-12.5 MeV bremsstrahlung and a common radioactive source. The detection system, developed for range assessment in particle therapy based on the Prompt Gamma-Ray Timing (PGT) technique, consist of a commercial ⌀2”×1” or ⌀2”×2” CeBr 3 scintillation detector with photomultiplier readout (Scionix), coupled to a digital plug-on spectrometer (U100) by Target Systemelektronik. The excellent time structure of the bremsstrahlung beam at ELBE (HZDR) allowed measuring the system time resolution simultaneously for 0.1-12 MeV photons. Also, the beam current and thus the detector load could be varied in a wide range. The energy resolution was determined in parallel with a 60 Co-source attached to the detector. Source and bremsstrahlung photons were separated by means of cuts in the timing spectra measured against the accelerator RF. The detection system could demonstrate a time resolution of < 260 ps (FWHM) for energies above 3 MeV with the smaller crystal, and an energy resolution of < 3.7% at 1.173 MeV for both crystals, up to detector loads of 1.4 Mcps and a corresponding system throughput of ~ 600 kcps. This fits well with the design goals of the detection system. Corresponding units shall be used for measuring PGT spectra during patients treatments with proton beams, in order to verify the proton beam range for single beam spots in Pencil Beam Scanning (PBS) mode. Range verification is considered a key for reducing margins and for improving precision and health outcome of particle therapy.

  • Lecture (Conference)
    2016 IEEE Nuclear Science Symposium and Medical Imaging Conference, 29.10.-06.11.2016, Strasbourg, France

Publ.-Id: 23606

Ultraschall zur Bestimmung von Partikelbewegungen in flüssigem Metall

Hoppe, D.; Strumpf, E.

In flüssigem Metall schwebende Partikel können Echos von Ultraschall verursachen. Aus solchen Echos wird versucht, die entlang der Schallausbreitung vorkommenden Partikelbewegungen zu rekonstruieren. Konkret sind damit die Positionen gemeint, welche die Partikel vertikal oberhalb des Schallwandlers als Funktionen der Zeit einnehmen. Anhand solcher Funktionen soll dann auf Strömungsvorgänge im flüssigen Metall geschlossen werden.

Keywords: Flüssigmetall; Ultraschall; Partikelbewegungen

Publ.-Id: 23605

Use of Target Capsules for Radiolabeling of Platinum Nanoparticles with a Modified Nirta® Solid Target Station (Cyclone 18/9)

Franke, K.

The increased use of nanoparticles (NP) in technical processes and consumer products requires a comprehensive and thorough nanosafety research. Challenging is the sensitive and selective detection of NP in different environments. Here radiolabeling offers a unique tool for even in situ detection of NP for nanosafety studies. Often radiotracers are introduced into NP via the NP synthesis process. Highest activity concentrations are achievable. However, this strategy requires careful characterization of the synthesized NP to allow a comparison with the commercially available NP. Mostly there is very little detailed knowledge about the commercial synthesis process. The direct activation of NP can overcome this limitation. In this study we present the use of a Cyclone 18/9 for the activation of 10 nm Pt-NP. The activation yields into the NP labeling with Au radionuclides.

Keywords: Platinum nanoparticles; Cyclotron; Radiolabeling; Targetry; Gold radioisotopes

  • Lecture (Conference)
    16th International Workshop on Targetry and Target Chemistry (WTTC16), 29.08.-01.09.2016, Santa Fe, USA

Publ.-Id: 23604

Measurement of the 92,93,94,100Mo(γ,n) reactions by Coulomb Dissociation

Göbel, K.; Adrich, P.; Altstadt, S.; Alvarez-Pol, H.; Aksouh, F.; Aumann, T.; Babilon, M.; Behr, K.-H.; Benlliure, J.; Berg, T.; Böhmer, M.; Boretzky, K.; Brünle, A.; Beyer, R.; Casarejos, E.; Chartier, M.; Cortina-Gil, D.; Chatillon, A.; Pramanik, U. D.; Deveaux, L.; Elvers, M.; Elze, T. W.; Emling, H.; Erhard, M.; Ershova, O.; Fernandez-Dominguez, B.; Geissel, H.; Górska, M.; Heftrich, T.; Heil, M.; Hellstroem, M.; Ickert, G.; Johansson, H.; Junghans, A. R.; Käppeler, F.; Kiselev, O.; Klimkiewicz, A.; Kratz, J. V.; Kulessa, R.; Kurz, N.; Labiche, M.; Langer, C.; Bleis, T. L.; Lemmon, R.; Lindenberg, K.; Litvinov, Y. A.; Maierbeck, P.; Movsesyan, A.; Müller, S.; Nilsson, T.; Nociforo, C.; Paar, N.; Palit, R.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Reifarth, R.; Rossi, D. M.; Schnorrenberger, L.; Simon, H.; Sonnabend, K.; Sümmerer, K.; Surówka, G.; Vretenar, D.; Wagner, A.; Walter, S.; Waluś, W.; Wamers, F.; Weick, H.; Weig, M.; Winckler, N.; Winkler, M.; Zilges, A.

The Coulomb Dissociation (CD) cross sections of the stable isotopes 92,94,100 Mo , of the unstable isotope 93 Mo were measured at the L, /R 3 B setup at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Experimental data on these isotopes may help to explain the problem of the underproduction of 92,94 Mo , 96,98 Ru in the models of p-process nucleosynthesis. The CD cross sections obtained for the stable Mo isotopes are in good agreement with experiments performed with real photons, thus validating the method of Coulomb Dissociation. The result for the reaction 93 Mo(γ,n) is especially important since the corresponding cross section has not been measured before. A preliminary integral Coulomb Dissociation cross section of the 94 Mo(γ,n) reaction is presented. Further analysis will complete the experimental database for the (γ,n) production chain of the p-isotopes of molybdenum.

  • Open Access Logo Contribution to proceedings
    Nuclear Physics in Astrophysics VI (NPA6), 19.-24.05.2013, Lisboa, Portugal
    Journal of Physics: Conference Series 665, London: IOPscience, 012034
    DOI: 10.1088/1742-6596/665/1/012034

Publ.-Id: 23603

Radiation dosimetry of the α4β2 nicotinic receptor ligand (+)-[18F]Flubatine, comparing preclinical PET/MRI and PET/CT to first-in-human PET/CT results

Kranz, M.; Sattler, B.; Tiepolt, S.; Wilke, S.; Deuther-Conrad, W.; Donat, C.; Fischer, S.; Patt, M.; Schildan, A.; Patt, J.; Smits, R.; Hoepping, A.; Steinbach, J.; Sabri, O.; Brust, P.

Background: Both enantiomers of [18F]flubatine are promising radioligands for neuroimaging of α4β2 nicotinic acetylcholine receptors with positron emission tomography (PET) exhibiting promising pharmacokinetics which makes them attractive for different clinical questions. Ina previous preclinical study, the main advantage of (+)-[18F]flubatine compared to (-)-[18F]flubatine was its higher binding affinity suggesting that (+)-[18F]flubatine might be able to detect also slight reductions of α4β2 nAChRs and could be more sensitive than (-)-[18F]flubatine in early stages of Alzheimer's disease. To support the clinical translation, we investigated a fully image-based internal dosimetry approach for (+)-[18F]flubatine, coparing mouse data collected on a preclinical PET/MR system to piglet and first-in-human data acquired on a clinical PET/CT system. Time-activity curves (TACs) were obtained from the three species, the animal data extrapolated to human scale, exponentially fitted and the organ doses (OD), and the effective dose (ED) calculated with OLINDA.

Results: The excreting organs (urinary bladder, kidneys, and liver) receive the highest organ doses in all species. Hence, a renal/hepatobiliary excretion pathway can be assumed. In addition, the ED conversion factors of 12.1 µSv/MBq (mice), 14.3 µSv/MBq (piglets) and 23.0 µSv/MBq (humans) were calculated which are well within the order of magnitude as known from other 18F-labeled radiotracers.

Conclusion: Although both enantiomers of [18F]flubatine] exhibit different binding kinetics in the brain due to the respective affinities, the effective dose revealed no enantiomer-specific differences among the investigated species. The preclinical dosimetry and biodistribution of (+)-[18F]flubatine was shown and the feasibility of a dose assessment based on image data acquired on a small animal PET/MR and a clinical PET/CT was demonstrated. Additionally, the first-in-human study confirmed the tolerability of the radiation risk of (+)-[18F]flubatine imaging which is well within the range as caused by other 18F-labeled tracers. However, as shown in previous studies, the ED in humans is underestimated by up to 50 % using preclinical imaging for internal dosimetry. This fact needs to be considered when applying for first-in-human studies based on preclinical biokinetic data scaled to human anatomy.

Keywords: Image-based internal dosimetry; (+)-[18F]flubatine; Preclinical hybrid PET/MRI; OLINDA/EXM; Dosimetry; Nicotinic receptors; Radiation safaty

Publ.-Id: 23602

THEREDA, the thermodynamic reference database for a nuclear waste disposal in Germany

Bok, F.; Moog, H. C.; Altmaier, M.; Voigt, W.; Thoenen, T.

The disposal of nuclear waste including the assessment of long-term safety is still an open question in Germany. In addition to the still pending decision about the repository host rock (salt, granite, or clay) the basic necessity of a consistent and obligatory thermodynamic reference database persists. Such a database is essential to assess potential failure scenarios accurately and to make well-founded predictions about the long-term safety. Specific challenges are comprehensive datasets covering also high temperatures and salinities. Against this background, available databases do not suffice and are limited in their use, partly because of high restrictions and resulting incompleteness of reactions. Other databases rely on heterogeneous and therefore inconsistent data leading to incorrect model calculations. Due to these deficiencies THEREDA, a joint project of institutions leading in the field of safety research for nuclear waste disposal in Germany and Switzerland, was started in 2006.
THEREDA contains a relational databank whose structure has been designed in a way that promotes the internal consistency of thermodynamic data. Data considered cover the needs of Gibbs Energy Minimizers (ChemApp) and Law-of-Mass-Action programs (Geochemist’s Workbench, EQ3/6, PHREEQC) alike. Parameters for a variety of models describing interactions in mixed phases are included. Namely the Pitzer parameters to describe activity coefficients of hydrated ions and molecules are considered. Both thermodynamic and interaction parameters can be described by temperature functions.
THEREDA offers evaluated thermodynamic data for many compounds (solid phases, aqueous species, or constituents of the gaseous phase) of elements relevant according to the present state of research. In particular, all oxidation states expected for disposal site conditions are covered.
Ready-to-use parameter files are created from the databank in a variety of formats (generic ASCII type, and formats required by the geochemical speciation codes) and offered to the users. They are also used for internal test calculations – one essential element of the quality assurance scheme. The results are documented and provided to the users.
THEREDA is accessible via internet through This is not only a portal to the database, but shall also serve as an information and discussion platform on issues concerning the database. Thus we are confident to generate helpful feedback from the anticipated user community.

Keywords: THEREDA; Modelling; Solubility; Pitzer; Thermodynamic; Database

  • Poster
    17 International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP17), 24.-29.07.2016, Geneva, Schweiz

Publ.-Id: 23600

Oxygen solubility modelling in water and brines

Bok, F.; Moog, Helge C.

Dissolved molecular oxygen influences the chemistry of various redox reactions in the aqueous solution e.g. corrosion processes, microbial activity or the immobilisation of radionuclides. In the presence of dissolved oxygen, the poorly soluble (hydro)oxides of reduced actinides, e.g. U(OH)₄(am), PuO₂(am/cr) get oxidized and these elements become more soluble in water. Furthermore, the activity of dissolved oxygen is used as redox parameter in common geochemical codes (i.e. Geochemist’s Workbench®). Thus, the correct prediction of the O₂ solubility in water and saline solutions is necessary for the correct modelling of redox processes in water and in brines especially.
For reasons of consistency, the few existing sets of O₂-ion interaction coefficients for the Pitzer model cannot be used in combination with the THEREDA Pitzer model for the oceanic salt system and would result in wrong gas solubility calculation’s results. Therefore, a new and consistent set of solubility parameters was deduced using published O₂ solubility data in water and binary and ternary salt solutions from ~100 literature references.
First a critical review of the published data on oxygen solubility in water and salt solutions has been performed. Using these data, the temperature function of the O₂ Henry’s constant could be obtained valid for the temperature range 273–618 K. Then a consistent set of Pitzer interaction coefficients including its temperature function’s parameters was deduced for the calculation of the amount of dissolved oxygen in aqueous solution and brines. All parameters have been determined using the geochemical speciation software PHREEQC coupled with the parameter estimation software UCODE-2005.
A self-consistent set of Pitzer interaction coefficients for the description of oxygen solubility in binary and some ternary salt solutions could be obtained for the system Na⁺, K⁺, H⁺, Ca²⁺, Mg²⁺ / Cl⁻, SO₄²⁻, CO₃²⁻, PO₄³⁻, OH⁻ - H₂O(l). For the chloride and the sulphate subsystems, temperature function parameters could be obtained to describe the temperature dependency of the O₂ solubility in these salt solutions.

Keywords: Saline solutions; Redox; Oxygen; Pitzer; Solubility

  • Lecture (Conference)
    17 International Symposium on Solubility Phenomena and Related Equilibrium Processes (ISSP17), 24.-29.07.2016, Geneva, Schweiz

Publ.-Id: 23599

Application of solvent extraction to environmental science - Identification of radioactive contaminants in surface water

Ikeda-Ohno, A.

Solvent extraction is a very traditional but still a very versatile technique with a variety of applications. This presentation will focus on the application of solvent extraction particularly to the environmental science associated with radioactive contamination.

Keywords: Solvent extraction; separation; surface water; environmental science; speciation; actinides; radionuclides; radioactive contamination

  • Invited lecture (Conferences)
    Interdisciplinary German-Japanese Symposium iJaDe2016 - 2nd German-Japanese Microsymposium "Solvent Extraction: From Fundamentals to Applications", 10.05.2016, Dresden, Germany

Publ.-Id: 23598

High Conductivity in Molecularly p-doped Diketopyrrolopyrrole–Based Polymer: the Impact of a High Dopant Strength and Good Structural Order

Karpov, Y.; Erdmann, T.; Raguzin, I.; Al-Hussein, M.; Binner, M.; Lappan, U.; Stamm, M.; Gerasimov, K. L.; Beryozkina, T.; Bakulev, V.; Anokhin, D. V.; Ivanov, D. A.; Günther, F.; Gemming, S.; Seifert, G.; Voit, B.; Kiriy, A.

[3]-Radialene-based dopant CN6-CP studied herein, with its reduction potential of +0.8 vs Fc/Fc+ and LUMO level of -5.88 eV, is the strongest molecular p-dopant reported in open literature so far. The efficient p-doping of the donor-acceptor copolymer PDPP(6-DO)2TT having the HOMO level of -5.5 eV was achieved which confirmed by UV-vis-IR spectroscopy studies and DFT calculations. Films of PDPP(6-DO)2TT doped by CN6-CP exhibit electrical conductivities up to 50 S/cm which is one of the highest conductivity for molecularly doped semiconducting polymers. The high conductivity is attributed to a good structural order in the doped polymer as confirmed by x-ray scattering studiesdue and its high doping level. CN6-CP shows a relatively good thermal stability up to 280°C and it withstands sublimation in vacuum which makes it potentially suitable for the doping of small semiconducting molecules processed by vacuum evaporation techniques. The superior electron affinity of CN6-CP significantly broadens the range of semiconductors that can be used in devices in the p-doped state.

Keywords: p-dopant; conjugated polymer; electrical conductivity; organic electronics

Publ.-Id: 23597

Hopping Based Charge Transfer in Diketopyrrolopyrrole Based Donor-Acceptor Polymers: A Theoretical Study

Günther, F.; Gemming, S.; Seifert, G.

Diketopyrrolopyrrole (DPP) based materials have recently been considered as promising candidates for novel organic electronics.
In this article, we report an investigation on intermolecular charge transfer between DPP based polymers.

We use Marcus transfer theory and evaluate the required quantities, the reorganization energy and the coupling, by density functional-based tight binding (DFTB) calculations.
Since the coupling is dependent on the stacking geometry we employ an energy-weighted statistical approach to derive a single quantity, which can been entered in the Marcus formula.
This value contains the variation of the coupling when the stacking conformation is changed.
The application of this method, as we implement it in this study, does not require a detailed analysis of the energy landscape, but samples over large number of stacking possibilities on a regular, but very dense grid into account.
These average values can been used to analyze isomeric effects such as the orientation of units, the influence of the molecular structure as functionalization, or the importance of stacking properties as parallel and anti-parallel stacking.
The obtained results show that enhanced charge carrier mobilities can be achieved when specific molecular configurations are considered rather than by working with a set of random orientations.

Keywords: Diketopyrrolopyrrole; Hopping; Electronic Transfer; Marcus theory; density functional based tight binding

Publ.-Id: 23596

Lutetium Fine Silicate (LFS): A new scintillator for range-verification applications in oncology

Roemer, K.; Pausch, G.; Bemmerer, D.; Fahmy, K.; Golnik, C.; Hueso-Gonzalez, F.; Iltzsche, M.; Lutz, B.; Petzoldt, J.; Weinberger, D.; Fiedler, F.

Proton therapy facilities are built all around the world for optimized cancer treatments. In order to fully exploit the advantages of this therapy, a proton range verification is mandatory. The most promising advances use either the positron emission tomography (PT-PET) approach or the prompt gamma emissions caused by nuclear reactions (by means of passive collimation, Compton cameras or prompt gamma timing). Gamma ray detectors in this field face unique requirements: Good properties with respect to energy, time and spatial resolution even when operated with high counting rates in rather high background environments.
Lutetium Fine Silicate (LFS) is a novel scintillation material which is especially designed for PET applications. Thus, in this work, the characteristics of LFS are determined for energy ranges which match the requirements of the prompt gamma ray monitors (i.e. up to 8 MeV). The usage of different photodetectors (i.e. PMT or Silicon-based read-out), depending on the particular application, is discussed.

Keywords: Scintillator; Photodetector; Proton range monitor

  • Lecture (Conference)
    2016 IEEE NSS/MIC, 29.10.-06.11.2016, Strasbourg, France
  • Poster
    2016 IEEE NSS/MIC, 30.10.-05.11.2016, Strassbourg, France

Publ.-Id: 23595

Determination of stability constants of selected U(VI) flavonol complexes by absorption and emission spectroscopy

Günther, A.; Geipel, G.

Flavonols are polyphenol compounds, which belong to the class of flavonoids. They are produced by plants and can be segregated by the root into the soil. Flavonols can bind metals, e.g. Co, Fe, Ni, Al, Zn and Pb due to the presence of the carbonyl group on the gamma-pyranone ring and the hydroxyl groups as substituents in different positions of the whole organic molecule. The interactions of these polyphenols with radioactive metals have been studied very rare up to now. In this work first results of spectroscopic investigations of the U(VI) complexation by flavonols with several number of hydroxyl groups and glycosidic substituent are presented and discussed. The flavonols and their U(VI) complexes have specific absorption bands and emission signals in the UV-Vis range, which were used for the calculation of deprotonation constants of organic ligands and of the stability constants of the formed U(VI) flavonol complexes in methanolic solution.

Keywords: Flavonol; Uran(VI); complexation; absorption; emission

  • Poster
    Biometals, 10.-15.07.2016, Dresden, Germany

Publ.-Id: 23594

Mobilisation of metals from Kupferschiefer sensu strictu in neutral to alkaline environment using bulk and biotechnologically produced organic acids

Kostudis, S.; Kutschke, S.; Pollmann, K.

The European Kupferschiefer deposits constitute a challenging local resource of a broad spectrum of metals such as copper, manganese, molybdenum, silver and zinc. In order to exploit them both efficiently and environmentally benignly, biotechnological leaching approaches are investigated. Commonly used acidophilic bioleaching is limited by high carbonate content of up to 18 % resulting in an increased pH value of more than 2. Hence, alternative processes such as neutral leaching are tested. Experiments were aiming at metal solubilisation using glutamic and citric acid as bulk chemicals, as well as biotechnologically produced citric acid. Subsequently, mobilisation of Cu, Mn, Mo, Co, Zn, Ga, Ag, Au, Ni and Pt has been reported. Results show that mostly the use of organic acids in neutral to alkaline pH range performs better in metal solubilisation than in acidic milieu.

Keywords: Kupferschiefer; black shale; leaching; organic acid; copper; trace metals; mobilisation

  • Contribution to proceedings
    Biohydrometallurgy '16, 20.-22.06.2016, Falmouth, United Kingdom
    Proceedings of Biohydrometallurgy '16

Publ.-Id: 23593

OECD PKL3 Project - Final Report on the ROCOM Tests

Kliem, S.; Franz, R.

In the frame of the OECD PKL 3 Project three groups of experiments have been conducted at the HZDR coolant mixing test facility ROCOM.
The first series concerned the influence of the coolant mixing in the reactor pressure vessel on the Natural Circulation Interruption (NCI). For that purpose boundary conditions (mass flow rates and temperatures in the individual loops at the inlet of the RPV) have been derived for subsequent tests in the ROCOM test facility on coolant mixing inside the pressure vessel. The ROCOM tests were designed to address the fluid/fluid mixing of hot and cold water in the RPV downcomer and in the lower plenum and the temperature distribution at the core inlet. A series of three quasi-stationary experiments was carried out. Boundary conditions were taken from the PKLIII test H4.1 (Schoen, 2014).
The second test series was dedicated to the investigation of the mixing of unborated coolant which is injected into the reactor pressure vessel in the late phase of an accident. It is assumed that the standard sources of the emergency core cooling water are not available. Unborated water is injected to ensure the core cooling. Due to the injection of unborated water, an occurrence of re-criticality in the shut-down reactor is threatening. This possible re-criticality depends in a dominant manner on the mixing of the injected water with the high-borated coolant in the reactor pressure vessel. The ROCOM experiments provided an insight into the mixing and therefore allow drawing corresponding conclusions.
The last series (consisting of one experiment) was on the investigation of the thermal-hydraulic behavior inside the RPV during the ECC-injection from ACCU into the cold leg of loop 1. It is based on the PKLIII test H3.1, which objective was to explore the effectiveness of ECC-injections from ACCU to restore operating conditions of RHRS during the core heat-up phase. The test H3.1 addressed the failure of RHRS under cold shut-down condition with open RCS (RPV closure head removed). Experimental results at the RPV inlet from the PKLIII test H3.1 Run 1 Phase C were used as boundary conditions for the corresponding ROCOM test.
Altogether six ROCOM tests have been conducted within the OECD PKL3 Project.
The current report describes the results of all tests.

  • Article, self-published (no contribution to HZDR-Annual report)
    Forschungszentrum Rossendorf 2016
    118 Seiten
    ISSN: 2191-8708, eISSN: 2191-8716

Publ.-Id: 23591

Reduction of Uranium(VI) by isolated, anaerobic microorganisms from the flooding water of the former uranium mine Königstein (Saxony/Germany)

Gerber, U.; Krawczyk-Bärsch, E.; Scheinost, A. C.; Arnold, T.

The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation. The under-ground is flooded in a controlled way, and the flooding water is cleaned up in an elaborate waste water treat-ment plant. Despite high uranium concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity as detected by culture-independent methods [1]. Microorganisms are known to interact with metals and radionuclides in different ways [2]. As a result, microorganisms can change the chemical behavior of metals and radionuclides. Anaerobic bacteria which are able to gain energy from the reduction of several metals are known to change the redox state of radionuclides. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the insoluble U(IV) [3]. For that reason, these anaerobic living bacteria are able to use U(VI) as energy source. Genomic sequence analysis of the flooding water of Königstein revealed the presence of such anaerobic SRB. By culture dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were then incubated with 10 mM glycerol using the flooding water as background solution. The uranium concentration was about 13 mg/L. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. After four and six weeks of incubation, the cells were separated from the incubation medium by centrifugation and then analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. By Iterative Target-Factor Analysis (ITFA) we determined that
100 % of U(VI) was reduced to U(IV). Simultaneously, investigations of the supernatant with UV-vis resulted in the same findings. The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).


1. Zirnstein, I., Charakterisierung der mikrobiellen Biozönose im sauren Grubenwasser des ehemaligen Uranbergwerks Königstein, Institut für Ressourcenökologie, Dissertation, 2015, TU Dresden: Dresden.
2. Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
3. Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.

Keywords: Uranium; Reduction; Bioremediation; Sulfate-reducing bacteria

  • Lecture (Conference)
    10th International Biometals Symposium, 10.-15.07.2016, Dresden, Deutschland

Publ.-Id: 23590

Evidence of uranium uptake in Acidovorax facilis cells by TRLFS and EF-TEM/EELS

Krawczyk-Bärsch, E.; Gerber, U.; Steudtner, R.

For bioremediation of uranium contaminated environments from activities such as uranium mining and uranium processing, microorganisms could be important due to their ability to immobilize radionuclides and heavy met-als. Since the main public concern is the possibility of radionuclide escaping and migrating into groundwater, there is an intense interest in the development of effective remediation methods. The aim is to improve biore-mediation strategies, based on a better understanding of binding mechanisms on the molecular level.

For our studies we used Acidovorax facilis (formerly Pseudomonas facilis), an aerobic Gram-negative Betapro-teobacteria, which is commonly found in soil. Experiments were performed in batch cultures under aerobic con-ditions at 25 °C using nutrient broth. The cells were grown to an optical density (OD600) of around 1.5. For U(VI) biosorption experiments the cultures were washed 2 times with tap water and then resuspended in tap water. After that UO2(NO3)2 was added to the solution to achieve an initial uranium concentration of 0.05 and 0.1 M, respectively, at a neutral pH range. The duration of the sorption experiments were limited to 48 h. As a re-sponse to uranium stress Acidovorax f. were forming extracellular polymeric substances (EPS) resulting in the formation of cell agglomerates. For separating the EPS from the bacteria, the cell agglomerates were ultra-centrifuged (40.000 x g) for 2 h at 10 °C. The cell pellet was used for time-resolved laser fluorescence spectros-copy (TRLFS). The U(VI) luminescence at 274 K was measured after excitation with laser pulses at 266 nm and with an average pulse energy of 300 μJ. The emitted fluorescence light of the cell pellet was recorded using an iHR550 spectrograph and an ICCD camera in the 370 – 670-nm wavelength range by averaging 100 laser pulses and using a gate of 2000 µs. The measured emission spectrum of the pellet is characterized by five emission bands. Their peak maxima were observed at 481.2, 497.8, 519.5, 544.1 and 569.3 nm ± 0.5 nm. In addition, the spectra of the Uranyl-complexes of lipopolysaccharide (R−O−PO3−UO2) and peptidoglycan (R−COO−UO2) were used for comparison. The reference spectra display band positions at 481.5, 498.1, 519.6, 542.9 and 567.5 nm for pH 4 [1] as well as 481.6, 498.1, 518.0, 539.0 and 566.0 nm for pH 4 [2], respectively. They show only a small deviation from those observed in our studies with the best agreement by those of the Uranyl-lipopolysaccharide-complex. Hence, it can be concluded that phosphoryl groups may be the main binding sites for uranyl, located in the lipopolysaccharide Acidovorax f. cells. But, at this moment it is not clear if it is bound on carboxylic functionality groups either.

Acidovorax f. cells were prepared for Energy-filtered transmission electron microscopy (EF-TEM) and electron energy-loss spectroscopy (EELS) by following the routine embedding protocol as described in [3]. The results provide microscopically and spectroscopically evidence of Uranium sorbed at the outer membrane of Acidovorax f. cells by showing high electron density and U ionization intensity peaks. The results support the TRLFS measurements and contribute to a better understanding of the binding mechanisms of U(VI) on Acidovorax f. cells.

[1] Barkleit, A. et al. (2008) Dalton Transaction, 2879–2886.
[2] Barkleit, A. et al. (2009) Dalton Transaction, 5379–5385.
[3] Lünsdorf, H. et al. (2001) Methods in Enzymology 331, 317–331.

Keywords: Uranium; TRLFS; Acidovorax facilis; TEM-EELS

  • Poster
    BioMetals 2016, 10th International Biometals Symposium, 10.-15.07.2016, Dresden, Germany

Publ.-Id: 23589

U(VI) reduction by anaerobic microorganisms isolated from the flooding water of the former uranium mine Königstein (Saxony)

Gerber, U.; Röder, G.; Krawczyk-Bärsch, E.; Arnold, T.; Scheinost, A. C.

The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation. The underground is flooded in a controlled way, and the flooding water is cleaned up in a dedicated waste water treatment plant. Despite high U concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity as detected by culture-independent methods. Microorganisms are known to interact with metals and radionuclides in different ways [1]. Anaerobic bacteria which are able to gain energy from the reduction of several metals, are known to change the redox state of metals and radionuclides. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the less soluble U(IV) [2]. Genomic sequence analysis of the flooding water revealed the presence of such anaerobic SRB. By culture-dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were incubated with 10 mM glycerol using the flooding water as background medium. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. After four and six weeks of incubation, the cells were separated from the incubation medium by centrifugation and than analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. By Iterative Target-Factor Analysis (ITFA) we determined that 100 % of U(VI) was reduced to U(IV). Simultaneously, investigations of the supernatant with UV-vis resulted in the same findings. The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).

1. Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
2. Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.

Keywords: Uranium; Reduction; Sulfate-reducing bacteria; Bioremediation

  • Lecture (others)
    5. Workshop - TransAqua, 06.-07.04.2016, Dresden, Deutschland

Publ.-Id: 23587

Speciation studies of Rn/Ln with selected degradation products of organic LILW – New spectroscopic insights into the uranyl-acetate system –

Brinkmann, H.; Moll, H.; Arnold, T.

Organic polymers (e.g. cellulose, PVC, bitumen) present in low and intermediate level wastes (LILW) are exposed to ionizing radiation, alkaline pH, and organic degrading microorganisms. This may lead to the formation of smaller, water soluble organic compounds, affecting amongst others the chemical behavior and mobility of radionuclides (RN). In the worst case complexation will lead to an increased mobility and a decreased retention of RN in the barriers of a nuclear waste disposal. Therefore, the characterization of RN complexes with degradation products is necessary for the assessment of the safety and the long-term performance of a nuclear waste repository.
The presentation will give an overview of our planned activities in cooperation with our partners (UNIMAN, SCK·CEN, and UGR) to contribute to task 1.2 of WP 1. Here our focus and expertise lies on the application of different modern spectroscopic tools to directly characterize the speciation of Rn/Ln with organic degradation products and/or with selected microbes, to underpin the findings from UNIMAN and SCK·CEN. Current results obtained by TRLFS, cryo-TRLFS, and UV-vis giving new insights into the uranyl-acetate system will be presented.

Keywords: Uranium; Acetate; TRLFS; UV-vis; MIND

  • Lecture (others)
    MIND Project Annual Meeting 2016, 02.-04.05.2016, Granada, Spain

Publ.-Id: 23586

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