Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31745 Publications
Experimental and theoretical study on the co-current two-phase downflow regime transition in open solid foam packed reactors
Möller, F.;
The main objective of this Diploma thesis was to determine the regime transition between trickling and pulsing flow for solid ceramic foams made of silicium carbid with extra silicium coating (SiSiC). Two pressure transducers were used in order to determine this transition. Additional to the experimental determination, a predictive model was developed after the idea of Grosser et al. (1988) as well as Attou and Ferschneider (2000). Therefore, bed specific parameters (specific surface area, pressure drop parameters, static liquid holdup, porosity of the bed) and fluid specific parameters (gas and liquid density and viscosity, surface tension) had to be known. Since these models were only validated for conventional FBRs with a packing of spheres, modifications have been carried out in order to fit the model to foam related parameters.
In order to describe the regime transition through the models, further experiments had been carried out. The static liquid holdup as well as the singe phase (gas phase) pressure drop were investigated and afterwards modeled though different approaches.
To obtain the influences of changing the surface tension as well as the viscosity on the regime transition, additional experiments with tergitol and glycerin were carried out.
Three different pore sizes (20 PPI, 30 PPI and 45PPI) as well as two different foam diameters (0.05m and 0.1 m) were investigated with two different spray systems. For the change of viscosity and surface tension, only foams with a diameter of 0.1m had been used.
Keywords: Solid foam packing, trickle-bed reactor, flow regime transition, relative permeability concept, static holdup
  • Diploma thesis
    TU Dresden, 2015
    Mentor: Zalucky, J., Schubert, M.
    124 Seiten

Publ.-Id: 22161 - Permalink


Neutron-capture experiment on 77Se with EXILL at ILL Grenoble
Lorenz, C.; John, R.; Massarczyk, R.; Schwengner, R.; Blanc, A.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Urban, W.; Valenta, S.; Belgya, T.;
The neutron capture reaction at 77 Se has been studied with cold neutrons in the course of the EXILL campaign at the high-flux reactor of the Institut Laue-Langevin Grenoble. A simulation of the detector array with Geant4 has been accomplished and evaluated. The detector response has been deduced and measured spectra were unfolded, which have been compared with simulations using γDex to determine strength functions.
Keywords: Neutron capture, gamma-spectroscopy

Publ.-Id: 22160 - Permalink


Investigation of dipole strength up to the neutron separation energy at γELBE
Massarczyk, R.; Schwengner, R.; Bemmerer, D.; Beyer, R.; Hannaske, R.; Junghans, A. R.; Kempe, M.; Kögler, T.; Schramm, G.; Wagner, A.;
The bremsstrahlung facility at the ELBE accelerator offers the possibility to investigate dipole strength distributions up to the neutron-separation energies with photon up to 16 MeV in energy. The facility and various results for nuclides measured during recent years are presented. One example is the study of the N = 80 nuclide 136 Ba. The other presented example is the study of the chain of xenon isotopes from N = 70 to N = 80 which aimed to investigate the influence of nuclear deformation an neutron excess on the dipole strength in the pygmy region. An overview of the analysis is given. GEANT4 simulations were performed to determine the non-nuclear background that has to be removed from the measured spectra. This opens up the possibility to take into account also the strength of unresolved transitions. Simulations of gamma-ray cascades were carried out that consider the transitions from states in the quasi-continuum and allow us to estimate their branching ratios. As a result, the photoabsorption cross sections obtained from corrected intensities of ground-state transitions are compared with theoretical predictions and results within the chain of isotopes. With the help of the measured dipole distribution it is possible to describe gamma-ray spectra following neutron capture more precisely.
Keywords: photon scattering, nuclear structure, photon strength

Publ.-Id: 22159 - Permalink


Combined study of the gamma-ray strength function of 114Cd with (n,γ) and (γ,γ’) reactions
Belgya, T.; Massarzyk, R.; Szentmiklósi, L.; Schramm, G.; Schwengner, R.; Junghans, A. R.; Wagner, A.; Grosse, E.;
Collaboration on strength function measurements and level density determinations is ongoing between the Budapest Prompt Gamma Neutron Activation Analysis and the ELBE Nuclear Physics groups within the framework of EU FP6 EFNUDAT project. The idea is to prove that good theoretical fits to the measured gamma-ray spectra collected in the (n,γ) and (γ,γ’) reactions can be carried out using common photon strength and level density functions over a wide spectral energy range from 1 to 10 MeV for the same residual nucleus. Here, preliminary results on the isotope pair of 113,114Cd are presented for which the neutron capture state in 114Cd has 1+ or 0+ spin and parity.
Keywords: electromagnetic strength function neutron capture resonance fluorescence

Publ.-Id: 22158 - Permalink


Spin decoherence processes in the S=1/2 scalene triangular cluster (Cu3(OH))
Ponomaryov, A. N.; Kim, N.; Jang, Z. H.; van Tol, J.; Koo, H.-J.; Law, J. M.; Suh, B. J.; Yoon, S.; Choi, K. Y.;
We report the synthesis and magnetic properties of the molecular cluster Cu33−OH)(μ-OH)(μ-O2Ar4F-Ph)2(py)3(OTf)2, abbreviated as (Cu3(OH)). Using magnetization, electron paramagnetic resonance and spin dimer analysis, we derive a microscopic magnetic model of (Cu3(OH)) and measure the electron T1 and T2 relaxation times. The Cu2+ ions are arranged to form a distorted triangular structure with the three different exchange coupling constants J1 = −43.5 K, J2 = −53.0 K, and J3 = −37.7 K. At T = 1.5 K T1 is of the order of 10−4 s and T2 is evaluated to be 0.26 μs. We find that the temperature dependence of 1/T1 and 1/T2 is governed by Orbach process and spin bath fluctuations, respectively. We discuss the role of spin–phonon mechanism in determining a spin decoherence time in a class of spin triangular clusters.

Publ.-Id: 22157 - Permalink


Paramagnetic moments and time effects in melt-textured NdBaCuO system with Nd422 inclusions
Dias, F. T.; Vieira, V. N.; Silva, D. L.; Wolff-Fabris, F.; Kampert, E.; Almeida, M. L.; Mesquita, F.; Hneda, M.; Roa, J. J.;
We have performed magnetic measurements in two melt-textured NdBa2Cu3O7-δ samples with Nd422 inclusions under magnetic fields from 0.05 up to 14 T, applied parallel to the ab planes. The measurements were made with a superconducting quantum interference device (SQUID) and a vibrating sample magnetometer (VSM). Paramagnetic moments could be observed during FCC (field-cooled cooling) and FCW (field-cooled warming) experiments. This effect, known as Paramagnetic Meissner Effect (PME), persisted up to 14 T and strong irreversibilities were observed among FCC and FCW experiments, revealing the presence of time effects. These time effects were confirmed by specific magnetic relaxation experiments in different cooling rates and temperatures, showing an anomalous and curious paramagnetic behavior. We explain our results based on the flux-compressed state generated within nonsuperconducting regions of the sample, such as the Nd422 inclusions dispersed into the superconducting matrix. These inclusions may produce a strong vortex pinning that stabilize the paramagnetic state, allowing the admission of extra vortices into the sample responsible for the positive moments during the relaxation experiments.

Publ.-Id: 22156 - Permalink


Electron-tunneling measurements of low-Tc single-layer Bi2+xSr2−yCuO6+δ: Evidence for a scaling disparity between superconducting and pseudogap states
Jacobs, T.; Katterwe, S. O.; Motzkau, H.; Rydh, A.; Maljuk, A.; Helm, T.; Putzke, C.; Kampert, E.; Kartsovnik, M. V.; Krasnov, V. M.;
We experimentally study intrinsic tunneling and high magnetic field (up to 65 T) transport characteristics of the single-layer cuprate Bi2+xSr2−yCuO6+δ, with a very low superconducting critical temperature Tc ≲ 4 K. It is observed that the superconducting gap, the collective bosonic mode energy, the upper critical field, and the fluctuation temperature range are scaling down with Tc, while the corresponding pseudogap characteristics remain the same as in high-Tc cuprates with 20 to 30 times higher Tc. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins.

Publ.-Id: 22155 - Permalink


Charakterisierung der Oberflächenkomplexe der Oxoanionen von Se(VI) und Tc(VII) an Mineral-Waser Grenzflächen
Foerstendorf, H.; Heim, K.; Franzen, C.; Jordan, N.;
79Se und 99Tc sind als Spaltprodukte im nuklearen Brennstoffkreislauf für die Sicherheitsanalyse eines zukünftigen Endlagers von besonderem Interesse. Eine Abschätzung der Migration dieser Elemente im Nah- und Fernfeld eines geologischen Tiefenlagers ist nur möglich auf der Basis der umfassenden Kenntnis der Wechselwirkungen der Spezies mit mineralischen Oberflächen. Insbesondere die Oxoanionen Se(VI)O42– und Tc(VII)O4 gelten auf Grund ihrer hohen Löslichkeit und negativen Ladung als besonders mobile Spezies in Aquiferen.
Die Oberflächenreaktionen von in Wasser gelösten Oxoanionen an Mineraloberflächen können mittels in situ Schwingungsspektroskopie dezidiert untersucht werden. Dabei können sowohl die Sorptions- als auch die Desorptionsreaktionen der gelösten Ionen an einer stationären mineralischen Phase in Echtzeit erfasst werden. [1–2]
Für das Selenation wurden an zwei verschiedenen Mineralphasen unterschiedliche Arten von außersphärischen Oberflächenkomplexen gefunden. Obwohl die makroskopischen Eigenschaften dieser Oberflächenkomplexe an beiden Mineralen auf eine außersphärische Anbindung (Physisorption) schließen lassen, zeigen die Infrarotspektren eine signifikant abweichende spektrale Signatur, die nur mit unterschiedlichen Molekülsymmetrien erklärt werden kann. So zeigen die Spektren je nach Mineraloberfläche, dass das Selenat mit einer leicht verzerrten – der aquatischen Spezies sehr ähnlichen – tetraedrischen bzw. mit einer bidendaten C2v Symmetrie an die Oberfläche sorbiert wird. Diese Spezies können demnach als „erweiterte“ bzw. als „klassische“ außersphärische Komplexe bezeichnet werden. [3–4]
Entsprechende Experimente mit dem isostrukturellen Tc(VII)O4-Anion zeigen, dass auch dieses Ion vorwiegend außersphärische Oberflächenkomplexe an verschiedenen Mineraloberflächen bildet. Dabei weisen die ersten Ergebnisse auf eine geringere Spezifizität des TcO4 bei der Anbindung an die verschiedenen Oberflächen hin.

[1] Foerstendorf, H. et al. (2012) J. Colloid Interface Sci. 377, 299–306. [2] Müller, K. et al. (2015) Environ. Sci. Technol. 49, 2560–2567. [3] Jordan, N. et al. (2011) Geochim. Cosmochim. Acta 75, 1519–1530. [4] Jordan, N. et al. (2013) Geochim. Cosmochim. Acta 103, 63–75.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2015 Chemie verbindet, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 22154 - Permalink


Sub-pixel resolution with a color X-ray camera
Nowak, S. H.; Bjeoumikhov, A.; von Borany, J.; Buchriegler, J.; Munnik, F.; Petric, M.; Radtke, M.; Renno, A. D.; Reinholz, U.; Scharf, O.; Wedell, R.;
The color X-ray camera SLcam® is a full-field, single photon detector providing scanning-free, energy and spatially resolved X-ray imaging. Spatial resolution is achieved with the use of polycapillary optics guiding Xray photons from small regions on a sample to distinct energy dispersive pixels on a charged-coupled device detector. Applying sub-pixel resolution, signals from individual capillary channels can be distinguished. Therefore, the SLcam® spatial resolution, which is normally limited to the pixel size of the charge-coupled device, can be improved to the size of individual polycapillary channels. In this work a new approach to a sub-pixel resolution algorithm comprising photon events also from the pixel centers is proposed. The details of the employed numerical method and several sub-pixel resolution examples are presented and discussed.

Publ.-Id: 22153 - Permalink


Analysis of mononuclear uranyl(VI) hydroxo complexes using TRLFS and PARAFAC
Drobot, B.; Bauer, A.; Steudtner, R.; Tsushima, S.; Raff, J.; Brendler, V.;
Speciation analysis of fast equilibrium processes is often challenging. Metal hydrolysis is one example of such a system. It is the basis for more complex aquatic systems and thus a deep understanding of those systems is indispensable. In the case of uranyl(VI) hydrolysis spectroscopic studies are hindered by low solubility over an wide pH range. Additionally occurrence of polynuclear complexes further complicates the system when working close to the solubility limit (e.g. 10-5 M uranyl(VI)). In a previous study we demonstrated that a combination of luminescence spectroscopic methods together with state of the art data analysis (parallel factor analysis; PARAFAC) and quantum chemical calculations is a powerful setup to gain information on that system [1]. Since uranyl(VI) has high affinities to several minerals and biopolymers systems containing trace metal concentrations have to be considered. In the present study we focus on this low concentration range (10-8 M uranyl(VI)).
We were able to extract thermodynamic constants for this system [(UO2(OH)(H2O)4+), (UO2(OH)2(H2O)3), (UO2(OH)3(H2O)2-)] using optimized data processing. Furthermore, advanced deconvolution of individual luminescence spectra demonstrates the correlation of luminescence spectroscopy and vibrational spectroscopy. Raman frequencies result from symmetrical stretching of the uranyl(VI) unit. We could show that features of individual emission spectra are separated by the same energy. Thus a further luminescence signal to chemical structure correlation is demonstrated which was missing for that system.
  • Poster
    GDCh-Wissenschaftsforum Chemie 2015, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 22152 - Permalink


Repeatability of tumor SUV quantification: the role of variable blood SUV
van den Hoff, J.; Hofheinz, F.;
kein Abstract verfügbar

Publ.-Id: 22151 - Permalink


Novel (pyrazolyl)benzenesulfonamides with a nitric oxide-releasing moiety as selective cyclooxygenase-2 inhibitors
Bechmann, N.; Kniess, T.; Köckerling, M.; Pigorsch, A.; Steinbach, J.; Pietzsch, J.;
Inhibition of cyclooxygenase-2 (COX-2) is a promising anti-inflammatory therapeutic strategy, but longterm medication with COX-2-inhibitors (coxibs) may be associated with adverse cardiovascular effects. Functionalization of existing lead structures with nitric oxide (NO)-releasing moieties is an auspicious approach to minimize these effects. In this regard, an organic nitrate (–O–NO2) substituent was introduced at a (pyrazolyl)benzenesulfonamide lead structure. The novel NO-coxibs selectively inhibited COX-2 in a low micromolar range (IC50(COX-2): 0.22–1.27 lM) and are supposed to be promising antiinflammatory compounds with, in parallel, positive effects on vascular homeostasis.
Keywords: Anti-inflammatory therapy; Cardiovascular side effects; Celecoxib; Direct/indirect NO coupling; Griess assay; Organic nitrate

Publ.-Id: 22150 - Permalink


Rational design of dual peptides targeting ghrelin and Y2 receptors to regulate food intake and body weight
Kilian, T. M.; Klöting, N.; Bergmann, R.; Els-Heindl, S.; Babilon, S.; Clément-Ziza, M.; Zhang, Y.; Beck-Sickinger, A. G.; Chollet, C.;
Ghrelin and Y2 receptors play a central role in appetite regulation inducing opposite effects. The Y2 receptor induces satiety, while the ghrelin receptor promotes hunger and weight gain. However, the food regulating system is tightly controlled by interconnected pathways where redundancies can lead to poor efficacy and drug tolerance when addressing a single molecule. We developed a multitarget strategy to synthesize dual peptides simultaneously inhibiting the ghrelin receptor and stimulating the Y2 receptor. Dual peptides showed dual activity in vitro, and one compound induced a slight diminution of food intake in a rodent model of obesity. In addition, stability studies in rats revealed different behaviors between the dual peptide and its corresponding monomers. The Y2 receptor agonist was unstable in blood, while the dual peptide showed an intermediate stability compared to that of the highly stable ghrelin receptor inverse agonist.

Publ.-Id: 22149 - Permalink


On the relation between Kaiser-Bessel blob and tube of response based modelling of the system matrix in iterative PET image reconstruction
Lougovski, A.; Hofheinz, F.; Maus, J.; Schramm, G.; van den Hoff, J.;
We investigate the question of how the blob approach is related to tube of response based modelling of the system matrix. In our model, the tube of response (TOR) is approximated as a cylinder with constant density (TOR-CD) and the cubic voxels are replaced by spheres. Here we investigate a modification of the TOR model that makes it effectively equivalent to the blob model, which models the intersection of lines of response (LORs) with radially variant basis functions ('blobs') replacing the cubic voxels. Implications of the achieved equivalence regarding the necessity of final resampling in blob-based reconstructions are considered. We extended TOR-CD to a variable density tube model (TOR-VD) that yields a weighting function (defining all system matrix elements) which is essentially identical to that of the blob model. The variable density of TOR-VD was modelled by a Gaussian and a Kaiser-Bessel function, respectively. The free parameters of both model functions were determined by fitting the corresponding weighting function to the weighting function of the blob model. TOR-CD and the best-fitting TOR-VD were compared to the blob model with a final resampling step (BLOB-RS) and without resampling (BLOB-NRS) in phantom studies. For three different contrast ratios and two different voxel sizes, resolution noise curves were generated. TOR-VD and BLOB-NRS lead to nearly identical images for all investigated contrast ratios and voxel sizes. Both models showed strong Gibbs artefacts at 4 mm voxel size, while at 2 mm voxel size there were no Gibbs artefacts visible.
The spatial resolution was similar to the resolution with TOR-CD in all cases. The resampling step removed most of the Gibbs artefacts and reduced the noise level but also degraded the spatial resolution substantially. We conclude that the blob model can be considered just as a special case of a TOR-based reconstruction. The latter approach provides a more natural description of the detection process and allows for modifications that are not readily representable within the blob framework.

Publ.-Id: 22148 - Permalink


Positron-Annihilation Lifetime Spectroscopy using Electron Bremsstrahlung
Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Fritz, F.; Kempe, M.; Krause-Rehberg, R.;
A new type of an intense source of positrons for materials research has been set up at the superconducting electron linear. The source employs hard X-rays from electron-bremsstrahlung production generating energetic electron-positron pairs inside the sample under investigation. CW-operation allows performing experiments with significantly reduced pile-up artefacts in the detectors compared to pulsed mode operation in conventional accelerators. The high-resolution timing of the accelerator with bunch lengths below 10 ps full width at half maximum (FWHM) allows positron annihilation lifetime spectroscopy (PALS) measurements with high time resolution. A single-component annihilation lifetime of Kapton has been measured as (381.3 ± 0.3) ps. Employing segmented detectors for the detection of both annihilation photons allows for the first time to perform a 4D tomographic reconstruction of the annihilation sites including the annihilation lifetime.
Keywords: positrons materials research ELBE linac superconducting tomography

Publ.-Id: 22147 - Permalink


Response of Multi-Strip Multi-gap Resistive Plate Chamber
Datta, U.; Chakraborty, S.; Rahaman, A.; Basu, P.; Basu, J.; Bemmerer, D.; Boretzky, K.; Elekes, Z.; Kempe, M.; Münzenberg, G.; Simon, H.; Sobiella, M.; Stach, D.; Wagner, A.; Yakorev, D.;
A prototype of Multi-strip Multi-gap Resistive Plate chamber (MMRPC) with active area 40 cm x 20 cm has been developed at SINP, Kolkata. Detailed response of the developed detector was studied with the pulsed electron beam from ELBE at Helmholtz-Zentrum Dresden-Rossendorf. In this report the response of SINP developed MMRPC with different controlling parameters is described in details. The obtained time resolution of the detector after slew correction was 91.5 +- 3 ps. Position resolution measured along x and across y the strip was 2.8+-0.6 cm and 0.58 cm, respectively. The measured absolute efficiency of the detector for minimum ionizing particle like electron was 95.8+-1.3 %. Better timing resolution of the detector can be achieved by restricting the events to a single strip. The response of the detector was mainly in avalanche mode but a few percentage of streamer mode response was also observed. A comparison of the response of these two modes with trigger rate was studied.
Keywords: Multi-strip Multi-gap Resistive Plate chamber (MMRPC) ELBE

Publ.-Id: 22146 - Permalink


Combined phase distribution and particle velocity measurement in spout fluidized beds by ultrafast X-ray computed tomography
Bieberle, M.; Barthel, F.;
The spout fluidized bed is a very successful combination of spouted and fluidized bed, which is most interesting for processing particles with larger or varying diameter. However, the more complex hydrodynamics of the combined configuration is yet not fully understood. Here, we propose the application of ultrafast X-ray computed tomography (CT), which has proven to be a valuable measurement technique for the analysis of highly dynamic processes, for example multiphase flows. It is able to resolve material distributions with up to 8,000 frames per second and a spatial resolution down to 1 mm. Especially for opaque systems, such as fluidized beds, ultrafast X-ray CT can reveal details, which are not recoverable by e.g. optical measurement techniques. Besides the recovering of the dynamic phase distribution, determining local particle velocities is essential to understand the complex flow in fluidized beds. As we will demonstrate here for the first time, this is possible via a dual-plane ultrafast X-ray CT by using suitable marker particles. In this article, the methodology for determining particle velocities under highly dynamic conditions within a cylindrical spout fluidized bed is presented. Complementary analysis techniques for different flow conditions have been combined to increase confidence in the velocity data.
Keywords: velocity, spout fluidized bed, ultrafast, X-ray, computed tomography

Publ.-Id: 22142 - Permalink


Coulomb Dissociation Experiment of P-27
Marganiec, J.; Beceiro-Novo, S.; Typel, S.; Wimmer, C.; Alvarez-Pol, H.; Aumann, T.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Cortina Gil, D.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Plag, R.; Prokopowicz, W.; Rodriguez Tajes, C.; Rossi, D.; Simon, H.; Stanoiu, M.; Stroth, J.; Sümmerer, K.; Wagner, A.; Wamers, F.; Weick, H.;
The 26Si(p;gamma)27P reaction, which might play an important role in the rp process, was studied by the Coulomb Dissociation method. The experiment was performed at GSI, Darmstadt. A secondary 27P ion beam of 500 MeV/nucleon was directed onto a Pb target. From this experiment, the Coulomb Dissociation cross section will be deduced and then converted to the photoabsorption cross section, and the radiative-capture cross section. Also information on the structure of 27P will be obtained. The analysis is in progress.
Keywords: Coulom dissociation radiative-capture radioactive beams

Publ.-Id: 22141 - Permalink


Depth-resolved slow positron beam analysis of ECR proton and argon implanted graphite and boron nitride system
Ganguly, B. N.; Menon, R.; Yalagoud, N. P.; Bandyopadhyay, S. K.; Anwand, W.; Brauer, G.;
Layered materials and sp2 hybridized structures like graphite and hexagonal-boron nitride (h-BN) have been subjected to electron cyclotron resonance (ECR) ion beam implantation of proton and argon ions at different fluences and studied primarily employing slow positron beam technique using positron annihilation Doppler broadening spectroscopy (DBS). The results show remarkable structural perturbation effects in the implantation areas around the depth of 200–300 nm from the top surface, in both the systems but with glaring differences in the trends of the line shape analysis in terms of S and W parameters. Due to proton and argon ion implantation, structurally damaged lattice with open volume defects exists in graphite. But, for both the ion implantations at the high fluence, profound clustering effect of the respective atoms within the interstitial space are evident in h-BN. The structural effects of both graphite and h-BN lattice after the said implantation have been studied and corroborated through grazing incidence X-ray diffraction (GI-Xray) method and Raman scattering spectroscopy as complementary analytical techniques.
Keywords: BN, graphite, grazing incidence X-ray diffraction, positron beams, Raman spectroscopy, slow positrons

Publ.-Id: 22140 - Permalink


How radio-ecological research helps to develop innovative nanobiomaterials
Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.;
The presentation introduces the Institute of Resource Ecology and the Helmholtz Institute Freiberg for Resource Technology and provides an insight into the work of the Biotechnology Group.
Keywords: radio-ecology, resource technology, nano-biotechnology
  • Lecture (others)
    Arbeitskreisseminar Technische Chemie, 03.07.2015, Paderborn, Deutschland

Publ.-Id: 22139 - Permalink


Investigating hadronic resonances in pp interactions with HADES
Przygoda, W.; Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, K.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc3, H.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.;
In this paper we report on the investigation of baryonic resonance production in proton-proton collisions at the kinetic energies of 1.25 GeV and 3.5 GeV, based on data measured with HADES. Exclusive channels npπ+ and ppπ0 as well as ppe+e− were studied simultaneously in the framework of a one-boson exchange model. The resonance cross sections were determined from the one-pion channels for Δ(1232) and N(1440) (1.25 GeV) as well as further Δ and N* resonances up to 2 GeV/c2 for the 3.5 GeV data. The data at 1.25 GeV energy were also analysed within the framework of the partial wave analysis together with the set of several other measurements at lower energies. The obtained solutions provided the evolution of resonance production with the beam energy, showing a sizeable non-resonant contribution but with still dominating contribution of Δ(1232)P33. In the case of 3.5 GeV data, the study of the ppe+e− channel gave the insight on the Dalitz decays of the baryon resonances and, in particular, on the electromagnetic transition form-factors in the time-like region. We show that the assumption of a constant electromagnetic transition form-factors leads to underestimation of the yield in the dielectron invariant mass spectrum below the vector mesons pole. On the other hand, a comparison with various transport models shows the important role of intermediate ρ production, though with a large model dependency. The exclusive channels analysis done by the HADES collaboration provides new stringent restrictions on the parameterizations used in the models.

Publ.-Id: 22138 - Permalink


Specific binding biomolecules
Raff, J.; Weinert, U.; Matys, S.; Vogel, M.; Suhr, M.; Günther, T.; Hofinger, J.; Drobot, B.; Lehmann, F.; Kutschke, S.; Pollmann, K.;
During evolution nature has evolved different kinds of specific binding macro-molecules being crucial for cell metabolism and their interaction with the environment. Most important examples therefore are proteins and nucleic acids. But beside biogenic molecules, specific proteins and nucleic acids can also be selected by doing an in vitro evolution using large molecule libraries. In this way specific ligands for various targets can be obtained allowing the development of new materials for different industrial applications.
Keywords: Sepcific binding, proteins, peptides, aptamers
  • Invited lecture (Conferences)
    Professur-Seminar Biomaterialien, 01.07.2015, Dresden, Deutschland

Publ.-Id: 22137 - Permalink


Developed turbulence and nonlinear amplification of magnetic fields in laboratory and astrophysical plasmas
Meinecke, J.; Tzeferacos, P.; Bell, A.; Bingham, R.; Clarke, R.; Churazov, E.; Crowston, R.; Doyle, H.; Drake, R. P.; Heathcote, R.; Koenig, M.; Kuramitsu, Y.; Kuranz, C.; Lee, D.; Macdonald, M.; Murphy, C.; Notley, M.; Park, H.-S.; Pelka, A.; Ravasio, A.; Reville, B.; Sakawa, Y.; Wan, W.; Woolsey, N.; Yurchak, R.; Miniati, F.; Schekochihin, A.; Lamb, D.; Gregori, G.;
The visible matter in the universe is turbulent and magnetized. Turbulence in galaxy clusters is produced by mergers and by jets of the central galaxies and believed responsible for the amplification of magnetic fields. We report on experiments looking at the collision of two laser-produced plasma clouds, mimicking, in the laboratory, a cluster merger event. By measuring the spectrum of the density fluctuations, we infer developed, Kolmogorov-like turbulence. From spectral line broadening, we estimate a level of turbulence consistent with turbulent heating balancing radiative cooling, as it likely does in galaxy clusters. We show that the magnetic field is amplified by turbulent motions, reaching a nonlinear regime that is a precursor to turbulent dynamo. Thus, our experiment provides a promising platform for understanding the structure of turbulence and the amplification of magnetic fields in the universe.
Keywords: galaxy clusters, laboratory analogues, lasers, magnetic fields, turbulence
  • Proceedings of the National Academy of Sciences of the United States of America 112(2015)27, 8211-8215
    DOI: 10.1073/pnas.1502079112

Publ.-Id: 22136 - Permalink


Retention of trivalent Actinides by structural Incorporation
Schmidt, M.; Peschel, S.; Hofmann, S.; Walther, C.; Bosbach, D.; Stumpf, T.;
The incorporation of radionuclides into a host mineral’s crystal structure is a particularly efficient means of retention, due to the fact that the incorporated radionuclide is removed from the water path. The process is relevant, both, naturally occurring under repository conditions[1], and as a technical means for the sequestration of actinide waste streams. Consequently, it is of utmost importance to understand the processes leading up to the incorporation, as well as the structural properties of the formed solid solution at the molecular level[2].
We will give an overview on the incorporation of trivalent actinides and lanthanides into Ca- and Ln-bearing mineral phases of technical and geochemical relevance. The minor actinides dominate the radiotoxicity in a nuclear waste storage site over hundreds of thousands of years. For Am and Cm the trivalent oxidation states is the only relevant oxidation in aqueous solutions, and even Pu may be present as Pu(III) under reducing repository conditions. The trivalent actinides have ionic radii closely matched to their lanthanides homologues as well as calcium, making mineral phases with these host cations ideal matrices for the incorporation of the trivalent minor actinides.
To identify and characterize actinides in solid solutions at the trace concentration level, we make use of time-resolved laser fluorescence spectroscopy (TRLFS). TRLFS allows for speciation of Cm(III) at concentrations below 10-9 mol/L, or 1 ppm in the solid state. Cm TRLFS can be complemented by experiments with Eu(III), which, while less sensitive, are more sensitive to changes in the local coordination geometry of the fluorescent probe.
An overview will be given on the characterization of solid solutions of secondary phases relevant under repository conditions. We will compare a phase formed close to equilibrium (calcite) with a metastable phase undergoing a phase transition (vaterite[3]), as well as a phase from high-temperature synthesis (powellite[4]). The effect of various reaction parameters on the reactions, and their implications for the stability of the formed solid solutions, and hence the retention of the radionuclides will be discussed.
[1] T. Stumpf and Th. Fanghänel, J. Colloid Interf. Sci. 249, 119 (2002).
[2] H. Geckeis, et al., Chem. Rev. 113, 1016 (2013).
[3] M. Schmidt, et al., J. Colloid Interf. Sci. 351, 50 (2010).
[4] M. Schmidt, et al., Dalton Trans. 42, 8387 (2013).
Keywords: acitnides, solid solutions, TRLFS, calcite
  • Poster
    MIGRATION 2015: 15th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 13.-18.09.2015, Santa Fe, USA

Publ.-Id: 22135 - Permalink


Recycling of magnesium chips
Ohmann, S.; Ditze, A.; Scharf, C.;
Magnesium chips were processed by means of re-melting. An important requirement of re-melting the chips is the removal of oil and moisture. The results show that using acetone in a soxhlet as an organic solvent is a more efficient method to obtain good results compared to vacuum distillation with a rotational evaporator. The subsequent re-melting has been successfully performed without the addition of flux between temperatures of 580 °C and 600°C. At this temperature range, the exothermic reaction of magnesium with the oxygen present in the surrounding atmosphere was avoided. Results show that more than 95 % of the magnesium chips were able to be recovered as metal. Experiments were performed at different scales to obtain production parameters for the recycling process. Larger particle size of magnesium chips were able to be faster remelted than the smaller ones. In the case of added lime for oil removal, the yield of recovered magnesium was lower due to the reaction towards magnesium foam. The ability of re-melting at low temperatures without the need for flux demonstrates the possibility of recovering virtually all of the metal from the chips.
Keywords: Magnesium, Chips, Recycling, Remelting, Analysis
  • Contribution to proceedings
    European Metallurgical Conference, 14.-17.06.2015, Düsseldorf, Germany
    EMC 2015 Volume 1: GDMB Verlag GmbH, 978-3-940276-61-2, 429-442

Publ.-Id: 22134 - Permalink


Understanding Cu mobilisation from Kupfershale leaching: [64Cu]CuS: Ligand identification, kinetic rates and modelling Preliminary Results.
Lippmann-Pipke, J.; Barthen, R.; Gründig, M.; Karimzadeh, L.; Schössler, C.; Mansel, A.; Grenzer, J.; Scholz, A.; Bischoff, L.; Schymura, S.; Kulenkampff, J.; Franke, K.; Lippold, H.;
Es ist kein Abstract vorhanden.
  • Poster
    General Meeting 3, Ecometals, 23.-24.06.2015, Halle/Saale, Deutschland

Publ.-Id: 22133 - Permalink


Liquid phase epitaxy of binary III-V nanocrystals in thin Si layers triggered by ion implantation and flash lamp annealing
Wutzler, R.; Rebohle, L.; Prucnal, S.; Bregolin, F.; Hübner, R.; Voelskow, M.; Helm, M.; Skorupa, W.;
The integration of III-V compound semiconductors in Si is a crucial step towards faster and smaller devices in future technologies. In this work, we investigate the formation process of III-V compound semiconductor nanocrystals, namely, GaAs, GaSb, and InP, by ion implantation and sub-second flash lamp annealing in a SiO2/Si/SiO2 layer stack on Si grown by plasma-enhanced chemical vapor deposition. Raman spectroscopy, Rutherford Backscattering spectrometry, and transmission electron microscopy were performed to identify the structural and optical properties of these structures. Raman spectra of the nanocomposites show typical phonon modes of the compound semiconductors. The formation process of the III-V compounds is found to be based on liquid phase epitaxy, and the model is extended to the case of an amorphous matrix without an epitaxial template from a Si substrate. It is shown that the particular segregation and diffusion coefficients of the implanted group-III and group-V ions in molten Si significantly determine the final appearance of the nanostructure and thus their suitability for potential applications.
Keywords: ion implantation, flash lamp annealing, III-V integration into silicon, nanostructure, liquid phase epitaxy, compound semiconductor

Publ.-Id: 22132 - Permalink


Flash-Enhanced Atomic Layer Deposition: Basics, Opportunities, Review, and Principal Studies on the Flash-Enhanced Growth of Thin Films
Henke, T.; Knaut, M.; Hossbach, C.; Geidel, M.; Rebohle, L.; Albert, M.; Skorupa, W.; Bartha, J.;
Within this work, flash lamp annealing (FLA) is utilized to thermally enhance the film growth in atomic layer deposition (ALD). First, the basic principles of this flash-enhanced ALD (FEALD) are presented in detail, the technology is reviewed and classified. Thereafter, results of our studies on the FEALD of aluminum-based and ruthenium thin films are presented. These depositions were realized by periodically flashing on a substrate during the precursor exposure. In both cases, the film growth is induced by the flash heating and the processes exhibit typical ALD characteristics such as layer-by-layer growth and growth rates smaller than one angstrom/cycle. The obtained relations between process parameters and film growth parameters are discussed with the main focus on the impact of the FLA-caused temperature profile on the film growth.

Similar, substrate-dependent growth rates are attributed to the different optical characteristics of the applied substrates. Regarding the ruthenium deposition, a single-source process was realized. It was also successfully applied to significantly enhance the nucleation behavior in order to overcome substrate-inhibited film growth. Besides, this work addresses technical challenges for the practical realization of this film deposition method and demonstrates the potential of this technology to extend the capabilities of thermal ALD.
Keywords: flash lamp annealing, atomic layer deposition

Publ.-Id: 22131 - Permalink


Uranyl(VI) hydrolysis studied by luminescence spectroscopy
Drobot, B.; Steudtner, R.; Raff, J.; Brendler, V.; Geipel, G.; Tsushima, S.;
Speciation constitutes the basis for actinide complexation studies. These systems can be very complex and challenging especially because of the polynuclear species. An advanced combination of theoretical and experimental methods is proposed here. Continuous wave (CW) and time-resolved laser-induced fluorescence spectroscopy (TRLFS) data of uranyl(VI) hydrolysis were analyzed using parallel factor analysis (PARAFAC). Distribution patterns of five major species were thereby derived under a fixed uranyl concentration (10-5) over a wide pH range from 2 to 11. UV (180 nm to 370 nm) excitation spectra were extracted for individual species. Time-dependent density functional theory (TD-DFT) calculations revealed ligand excitation (water, hydroxo, oxo) in this region and ligand-to-metal charge transfer (LMCT) responsible for luminescence. Thus excitation in the UV is extreme ligand sensitive and highly specific. Combining findings from PARAFAC and DFT the [UO2(H2O)5]2+ cation (aquo complex, 1:0) and four hydroxo complexes (1:1, 3:5, 3:7 and 1:3) were identified. Refined structural and thermodynamical data of uranyl(VI) hydrolysis is thus acquired.
  • Poster
    Second Joint Student Workshop on f-Element Chemistry, 09.-10.06.2015, Karlsruhe, Deutschland

Publ.-Id: 22130 - Permalink


Mikoskopische Lithiumverteilung in Pfadfinder-Mineralien
Neri, G.; Gernhäuser, R.; Lichtinger, J.; Renno, A. D.; Rugel, G.; Kudejova, P.; Revay, S.; Winkler, S.; Seiler, D.; Bendel, M.; Keywords: FRM II, Prompte Neutronenaktivierung, Lithium
  • Poster
    Tag der Physikerinnen, 23.06.2015, Garching, Deutschland

Publ.-Id: 22129 - Permalink


Flow regime transition in open-cell solid foam packed reactors: Adaption of the relative permeability concept and experimental validation
Zalucky, J.; Möller, F.; Schubert, M.; Hampel, U.;
The trickle-to-pulse flow regime transition in silicon-infiltrated silicon carbide (SiSiC) foam packed fixed bed reactors has been investigated. Based on the film stability concepts of Grosser et al.1 (DOI: 10.1002/aic.690341111) as well as Attou and Ferschneider2 (DOI: 10.1016/S0009-2509(99)00344-9), two predictive models have been adapted to foams’ specific geometric parameters. To account for the different nature of solid foams and their interactions with various fluids, the fixed bed characteristics (specific surface area and bed porosity) and fluid specific parameters (gas and liquid density, liquid viscosity, surface tension) have been incorporated in the model. Ergun parameters and static liquid holdup which are required for the modelling of the prevailing tractive forces were determined experimentally.
The modelling results were compared to regime transition measurements performed for SiSiC solid foams with different linear pore densities (20, 30 and 45 PPI), for different reactor diameters (50 and 100 mm) and initial liquid distributors (spray cone nozzle and multipoint distributor) as well as liquids with various physicochemical properties (water, Tergitol®, 50% glycerin) under ambient operating conditions. Compared to conventional random fixed bed reactors, the onset of pulsing in solid foam packed fixed beds is significantly shifted towards larger liquid and gas fluxes allowing high throughputs in the trickle regime. Moreover, the homogeneity of initial liquid distribution strongly affects the trickle-to-pulse flow transition.
Keywords: Solid foam packing, trickle-bed reactor, flow regime transition, relative permeability concept, static holdup

Publ.-Id: 22128 - Permalink


Mineralogical investigations of agates from Cordón de Lila, Chile
Richter, S.; Götze, J.; Niemeyer, H.; Möckel, R.;
In the present study a first found of agates in Chile is reported from the Cordón de Lila region in northern Chile. The agates occur as veins and lenses in altered Permian volcanic rocks. The rock composition is rhyodacitic/dacitic consisting of a fine-grained K-feldspar-quartz groundmass with phenocrysts of plagioclase (An50-60) and pyroxene (augite). The volcanic host rocks show strong features of alteration and brecciation.
Results of XRD, polarizing microscopy and cathodoluminescence (CL) microscopy and spectroscopy point to a late- to postvolcanic formation of the agates by hydrothermal fluids and SiO2 which was released during the alteration of unstable minerals and volcanic glass. Strongly varying agate micro-textures and the appearance of euhedral quartz crystals with μm-sized growth lamellae (so called Bambauer quartz) indicate fluctuations in the physico-chemical conditions (SiO2 concentration, pH) during alteration and agate formation. Another indication for the alteration processes is the occurrence of secondary calcite in the agate-bearing rocks.

Publ.-Id: 22127 - Permalink


XAS and XMCD studies of magnetic properties modifications of Pt/Co/Au and Pt/Co/Pt trilayers induced by Ga+ ions irradiation
Mazalski, P.; Sveklo, I.; Kurant, Z.; Ollefs, K.; Rogalev, A.; Wilhelm, F.; Fassbender, J.ORC; Baczewski, L.; Wawro, A.; Maziewski, A.
Magnetic and magneto-optical properties of Pt/Co/Au and Pt/Co/Pt trilayers subjected to 30 keV Ga+ ion irradiation are compared. In two-dimensional maps of these properties as a function of cobalt thickness and ion fluence, two branches with perpendicular magnetic anisotropy (PMA) for Pt/Co/Pt trilayers are well distinguished. The replacement of the Pt capping layer with Au results in the two branches still being visible but the in-plane anisotropy for the low-fluence branch is suppressed whereas the high-fluence branch displays PMA. The X-ray absorption spectra and X-ray magnetic circular dichroism (XMCD) spectra are discussed and compared with non-irradiated reference samples. The changes of their shapes and peak amplitude, particularly for the high-fluence branch, are related to the modifications of the local environment of Co(Pt) atoms and the etching effects induced by ion irradiation. Additionally, in irradiated trilayers the XMCD measurements at the Pt L-2,L-3-edge reveal an increase of the magnetic moment induced in Pt atoms.

Publ.-Id: 22126 - Permalink


P1317 - Vorrichtung und Verfahren zur Gewinnung von 2- und 3-wertigen Metallionen aus primären und sekundären Rohstoffen mit Hilfe von mikrobiellen Metaboliten
Gutzmer, J.; Kutschke, S.; Pollmann, K.; Raff, J.;
Die vorliegende Erfindung betrifft eine Vorrichtung und ein Verfahren zur Gewinnung von Metallen aus primären und sekundären Rohstoffen, basierend auf der Nutzung von organischen Säuren und anderen mikrobiellen Metaboliten.
Die Gewinnung von 2- und/oder 3-wertigen Metallionen erfolgt aus primären und/oder sekundären Rohstoffen, erfolgt mittels einer Vorrichtung mit zwei Kompartimenten. Das erste Kompartiment enthält ein heterogenes Gemisch aus einem oder mehreren primären und/oder sekundären Rohstoffen mit einer wässrigen Lösung. Das zweite Kompartiment ist vom ersten Kompartiment durch eine Membran abgetrennt und enthält Mikroorganismen oder einen Kulturüberstand oder einen oder mehrere Komplexbildner.
  • Patent
    DE102013226042 - Offenlegung 18.06.2015, Nachanmeldung: WO, EP

Publ.-Id: 22125 - Permalink


Kinematic dynamos resulting from the interaction of high permeability material and flows of liquid sodium
Giesecke, A.; Stefani, F.;
We perform numerical simulations of the dynamo effect driven by various flow fields of a conducting liquid interacting with "magnetic material" characterized by a large relative permeability. The examinations are motivated by the key role of soft iron impellers for the Von-Kármán-Sodium (VKS) dynamo [1] and by the repeatedly expressed idea to make use of Oxide Dispersion Strengthened (ODS) ferritic/martensitic alloys in the core of a fast reactor which may exhibit a permeability much larger than one [2].

The results of our simulations that consider a localized distribution with finite permeability clearly differ from computations using simplyfying pseudo-vacuum boundary conditions (vanishing tangential field conditions) in order to mimic the impact of infinite permeability. Our kinematic simulations of an axisymmetric model of the VKS dynamo show a close connection between the exclusive occurrence of dynamo action in the presence of soft iron impellers and the observed axisymmetry of the magnetic field [3]. We qualitatively explain this effect by paramagnetic pumping at the fluid-disk interface and propose a simplified analytical model that quantitatively reproduces numerical results. In order to fully explain the observation of growing magnetic fields in the VKS dynamo we resort to mean-field dynamo theory [4] in terms of an α-effect caused by helical outflows between adjacent blades attached to the impeller disks.

In order to examine the properties of the α- and β-effect (which is closely related to the turbulent diffusivity) under influence of magnetic material [5] we use an idealized helical flow field (a modified Roberts flow). We compute the mean-field coefficients using the test-field method [6] and proof that the corresponding mean-field models are indeed capable to reproduce growth-rates and principle field structure of the fully resolved model by requiring much less computational efforts.

Further remarkable results are the observed reduction of the critical magnetic Reynolds number by roughly 30 percent independently of configuration or flow geometry when the permeability is sufficiently large. However, this universality is not reflected in the behavior of the mean-field coefficients. In particular, the β-effect strongly depends on the geometry and the permeability. A striking feature is the occurrence of negative β which has previously been observed in simulations [7] and, more recently, in experiments [8].

Our results for the mean-field coefficients allow the development of dynamo models for nearly arbitrary systems of various sizes consisting of a large number of helical small scale flow cells embedded into some large flow structure.


[1]Monchaux, R. et al., Phys. Rev. Lett. 98 (2007), 044502
[2]Dubuisson, P., de Carlan, Y., Garat, V. and Blat, M., J. Nucl. Mater. 428 (2012), 6–12
[3]Giesecke, A. et al., New J. Phys. 14 (2012), 053005
[4]Krause, F. and Rädler, K.-H. Mean-field Magnetohydrodynamics and dynamo theory, Pergamon Press 1980
[5]Giesecke, A. et al., New J. Phys. 16 (2014), 073034
[6]Schrinner, M. et al., Astron. Nachr. 326 (2005), 245-249
[7]Rädler, K.-H. and Brandenburg, A., Phys. Rev. E 67 (2003), 026401
[8]Frick, P., Noskov, V., Denisov, S. and Stepanov ,R., Phys. Rev. Lett. 105 (2010), 184502
Keywords: dynamo
  • Lecture (Conference)
    Russian Conference on Magnetohydrodynamics, 22.-25.06.2015, Perm, Russia

Publ.-Id: 22124 - Permalink


Influence of calcium on the uranium(VI) interaction with mineral surfaces
Richter, C.; Brendler, V.; Steudtner, R.; Drobot, B.;
Many minerals have a strong tendency to sorb ions from the surrounding environment. An understanding of this process allows a realistic prediction of distribution and transport of the elements in nature. In case of uranium this is of high importance with respect to former mining sites or envisaged deposits. In this work, sorption of uranium(VI) onto orthoclase and muscovite, representing important components (feldspars and micas) of the earth crust, was investigated in absence and presence of calcium under aerobic conditions.
Batch experiments with both minerals were performed as triplicates in 0.01 M NaClO4 in the pH range of 5 to 8, with solid-to-liquid ratios of 1/20 and 1/80 g/mL, uranium concentrations of 10-5 and 10-6 M, with and without 1.5×10-3 M Ca. Furthermore time-resolved laser-induced fluorescence spectroscopy (TRLFS) was performed at batch samples with orthoclase (pH 4 to 9, with 10-5 M U and 1.5×10-3 M Ca). There, the aquatic solutions as well as the mineral suspensions were investigated as described in [1].
Uranium sorption shows its maximum at circumneutral pH values. At pH ≥ 8 in presence of calcium a reduced uranium(VI) sorption was observed which is due to the formation of the non-sorbing neutral Ca2UO2(CO3)3 complex. The evaluation of the spectroscopic results by Parallel factor analysis (PARAFAC) indicates the formation of three surface species. In detail the sorption of U(VI) onto orthoclase indicate two surface species. Based on the peak positions given in [2] they can be attributed to the formation of ≡SiO2UO20 and ≡SiO2UO2OHCO33– surface complexes. In presence of Ca2+ the ≡SiO2UO2OHCO33– surface complex disappears and instead the ≡SiO2UO2OH– surface complex also given in [2] can be observed. It occurs at lower pH values than the carbonate complex and shows different peak positions of the fluorescence bands.
The results improve the basis for a mechanistic modeling of the U(VI) sorption onto orthoclase and muscovite, which is important for long-term safety analysis of nuclear waste repositories.
With regard to the U(VI) sorption onto mica and feldspars not only the binary systems have to be understood because in natural systems many more components are present. For calcium this work already showed a significant influence on the speciation and thus on the potential transport of U(VI). But many other elements leached from surrounding minerals or contained in the groundwater may affect the overall sorption, too. Thus future work has to focus on more complex systems representing natural conditions as well as on the generation of surface complexation parameters for predictions of the U(VI) speciation.
  • Poster
    GDCh Wissenschaftsforum 2015, 30.08.-02.09.2015, Dresden, Deutschland

Publ.-Id: 22123 - Permalink


Numerical Modelling of the FCC Regenerator Reactor Based on Shrinkage Reaction Rate Model
Azizi, S.; Schubert, M.;
Fluid catalytic cracking (FCC) reactors are applied to convert gas oils and residues to lighter, higher-value products. Circulating fluidized bed technologies are used in modern FCC units, where cracking reactions take place in the riser with co-current upflow of the vaporized gasoil feed and the catalyst. After the disengagement from the product gas, the catalyst needs to be regenerated to compensate the deactivation due to coke deposition. The deactivation of the FCC catalyst can occur already in a few seconds and regeneration of the deactivated catalyst plays an important role for the yield of the FCC unit. For an effective regeneration, burning of deposited coke in the fluidized bed solves the early decay time of the catalysts. During the process the heavy hydrocarbons deposit on the catalyst, which subsequently block the active sites. To restore the activity, deposited hydrocarbons are oxidized with air in the regenerator reactor. The performance of the regenerator as well as its coupling with the cracking reactor are important to reach a high overall yield in the FCC unit. Usually, Geldart-A particles are used as catalyst in the FCC reactors. As the aeration rate of the FCC catalyst is low and the particles are cohesive, big bubbles are formed, channeling occurs and fluidization is often nonhomogeneous, which makes the hydrodynamic modeling a challenge. The clustering behavior of the fluidizing gas also increases the complexity of the reactor design. The complicated hydrodynamic behavior of gas phase and solid particles is a critical point to model coupled heat and mass transfer phenomena inside the fluidized reactors. The aim of the work is to develop an Eulerian-Eulerian numerical model for the FCC regenerator reactor operated as a fluidized bed based on the kinetic theory of granular flows to consider the clustering effect of the FCC catalysts in the regeneration process. In addition, the model shall consider the impact of the shrinkage of the deposited coke on FCC catalyst regeneration time, product yield, and temperature history of the regenerator reactor.
Keywords: Numerical Modeling, Two-Fluid Model, Fluidized Bed Reactor, Hydrodynamics, FCC Catalyst Regeneration.
  • Lecture (Conference)
    12th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York, USA

Publ.-Id: 22122 - Permalink


The Breakup and Coalescence of Bubbles Considering Interphase Turbulence Transfer in Bubbly Flows
Azizi, S.; Lau, Y. M.; Schubert, M.;
The ability to accurately predict the bubble size distribution in bubble column reactors is a requirement for any process design as well as for scale-up. The bubble size distribution depends mainly on the magnitude of bubble breakup and coalescence. Several breakup and coalescence models have been developed assuming different driving mechanisms, such as turbulence dissipation and shear rate of the liquid phase. The proposed breakup and coalescence models contain turbulence contributions in breakup and coalescence of the bubbles and also the relative velocity of the bubbles. The realistic expressionfor the mentioned terms is missing for the implementation of the breakup and coalescence models due to poor knowledge on the turbulence behavior of the bubbly flows. Here, bubble-liquid turbulence interactions of the bubbly flows are considered to predictparticipating turbulence energy in breakup and also relative velocity of the bubbles at coalescence of the bubbles.
Keywords: Breakup and Coalescence, Bubbly Flows, Numerical Modeling, Turbulence, Bubbles Fluctuation
  • Poster
    12th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York, USA

Publ.-Id: 22121 - Permalink


Pyrolysis of Biomass Particles Using Circulating Fluidized Bed reactor with Heat loop of the Heat Carrier Particles
Salar, A.;
Conversion of biomass into fuel and chemicals is currently receiving a great deal of attention because of the reduction of greenhouse gas emissions and national energy security and sustainability. The design of the pyrolysis process is important to reach higher bio-oil products and a key factor to produce higher bio-oil than char, is supplying high heat transfer rate to the biomass particles (fast pyrolysis) and fast removal of the volatiles. Although fluidized bed reactors provide higher heat transfer than conventional pyrolysis reactors, the heat transfer is limited by the convection at particle surface and conduction inside particle. The added inert particles to the fluidized bed improve heat transfer rate and fluidization properties of the biomass to reach desired fluidization velocity and good mixing of the particles. In this work, instead of using heated wall, performance of a circulating fluidized bed reactor with the heating loop of inert particles at the circulation path is investigated for pyrolysis of biomass.
Keywords: Numerical Modeling, Algae Biomass, Flash pyrolysis, Fluidized Bed Reactor, Heat Carrier Particles, Heat Transfer
  • Lecture (Conference)
    12th International Conference on Gas-Liquid & Gas-Liquid-Solid Reactor Engineering (GLS12), 28.06.-01.07.2015, New York, USA

Publ.-Id: 22120 - Permalink


Methods to increase the metabolic stability of 18F-radiotracers
Kuchar, M.; Mamat, C.;
The majority of pharmaceuticals and other organic compounds including radiotracers that are considered foreign to the body undergo metabolic changes in vivo. Most of these compounds are metabolic degraded by a system of enzymes of low substrate specificity requirement which is present mainly in the liver but drug metabolism may also take place in the kidneys or other organs. Thus, radiotracers and all other pharmaceuticals are faced with enormous challenges to maintain their stability in vivo implicating a high requirement on their structure. Often in practice, such biologically active molecules with manifested properties are found in vitro but these results could not be confirmed in vivo due to an increased metabolism within minutes. Many pharmacologically and biologically interesting compounds fail for further application due to their lack of stability.
One of the most important issues of radiotracers development based on fluorine-18 is the stability in vitro and in vivo. Sometimes, the metabolism of 18F-radiotracers goes along with the cleavage of the F-C bond and with the rejection of [18F]fluoride mostly combined with high background and accumulation in the skeleton. This review deals with the impact of radiodefluorination and with approaches to stabilize the F-C bond to avoid the cleavage between fluorine and carbon.

Publ.-Id: 22119 - Permalink


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.;
A novel, promising strategy for cancer diagnosis and therapy is the use of a pretargeting approach. For this purpose, the non-natural DNA/RNA analogues Peptide Nucleic Acids (PNAs) are ideal candidates as in vivo recognition units due to their high metabolic stability and lack of unspecific accumulation. In the pretargeting approach, an unlabeled, highly specific antibody-PNA conjugate has sufficient time to target a tumor before administration of a small fast-clearing radiolabeled complementary PNA that hybridizes with the antibody-PNA conjugate at the tumor site. Herein, we report the first successful application of this multistep process using a PNA-modified epidermal growth factor receptor (EGFR) specific antibody (Cetuximab) and a complementary 99mTc-labeled PNA. In vivo studies on tumor bearing mice demonstrated a rapid and efficient in vivo hybridization of the radiolabeled PNA with the antibody-PNA conjugate. Decisively, a high specific tumor accumulation was observed with a tumor-to-muscle ratio of >8, resulting in a clear visualization of the tumor by single photon emission computed tomography (SPECT).

Publ.-Id: 22118 - Permalink


Optimizing a stepwise fractionation chain in mineral processing or metallurgy
Tolosana-Delgado, R.; van den Boogaart, K. G.; Konsulke, S.; Scholz, A.; Matos Camacho, S.; Christesen, C.; Rudolph, M.; Scharf, C.;
This paper presents a framework of optimization of design and operation of a chain of identical cells or operator units that splits a raw input stream into two streams, increasing their total monetary value. This can be seen as a simplified conceptualization of several mineral processing or metallurgical techniques, where a cell itself badly separates the stream, hence its repeated operation seems appropriate. The solution is based on standard theory of linear differential equations. Uncertainty in the composition of the feed can be accounted for by Monte Carlo techniques.
  • Contribution to proceedings
    Annual Conference of the International Association of Mathematical Geosciences, 07.-10.09.2015, Freiberg, Deutschland
    Proceedings of the Annual Conference of the International Association of Mathematical Geosciences, 978-3-00-050337-5

Publ.-Id: 22117 - Permalink


Geostatistical Fisher discriminant analysis
Tolosana-Delgado, R.; Mckinley, J.; van den Boogaart, K. G.;
A geostatistical version of the classical Fisher rule (linear discriminant analysis) is presented. This method is applicable when a large dataset of multivariate observations is available within a domain split in several known subdomains, and it assumes that the variograms (or covariance functions) are comparable between subdomains, which only differ in the mean values of the available variables. The method consists on finding the eigen-decomposition of the matrix inv(W) B, where W is the matrix of sills of all direct- and cross-variograms, and B is the covariance matrix of the vectors of weighted means within each subdomain, obtained by generalized least squares. The method is used to map peat blanket occurrence in Northern Ireland, with data from the Tellus survey, which requires a minimal change to the general recipe: to use compositionally-compliant variogram tools and models, and work with log-ratio transformed data.
  • Contribution to proceedings
    Annual Conference of the International Association of Mathematical Geosciences, 07.-10.09.2015, Freiberg, Deutschland
    Proceedings of the Annual Conference of the International Association of Mathematical Geosciences, 978-3-00-050337-5

Publ.-Id: 22116 - Permalink


Influence of oxygen impurities on growth morphology, structure and mechanical properties of Ti‐Al‐N thin films
Riedl, H.; Koller, C. M.; Munnik, F.; Hutter, H.; Mendez Martin, F.; Rachbauer, R.; Kolozsvári, S.; Bartosik, M.; Mayrhofer, P. H.;
Unintended impurities, such as oxygen, can significantly influence the growth morphology, structure, and mechanical properties of many materials. Therefore, we study the origin and impact of oxygen impurities (between ~ 0.3 and 1.3 at.%) on sputtered Ti1‐xAlxN thin films by using targets with three different oxygen impurity levels and modifying the deposition conditions such as the base pressure. The oxygen impurity content of our coatings was always (by around ≥ 0.1 at.%) above that of the target used. Detailed atom probe tomography as well as secondary ion mass spectroscopy indicate a homogeneous distribution of the oxygen impurities across our face centred cubic structured Ti0.50Al0.50N coatings. Except for higher oxygen levels at the interface to the substrate, which is more pronounced when the target is not sputter‐cleaned prior to the deposition, and at the coating surface, there are no detectable oxygen variations at the grain or column boundaries. Based on our results we can conclude that the growth orientation of our coatings changes from random (for the cleanest coatings with ~ 0.3 at.% O) to pronounced 111 (for the coatings with the highest oxygen content of ~ 1.3 at.% O) with increasing oxygen impurity content. Thereby, also the coherently diffracting crystallite sizes increase from around 35 to 100 nm, the growth morphology changes from dense columnar grains to more open, porous columnar grains, and thus the hardness decreases from around 35 to 20 GPa.
Our study highlights the importance of well‐defined deposition conditions and high quality targets for developing high quality thin films.
Keywords: Ti‐Al‐N; Oxygen impurities; ERDA; SIMS; Texture; Grain Size; Hardness

Publ.-Id: 22115 - Permalink


Tomographic investigations on the effects of gas entrainment on centrifugal pumps
Schäfer, T.;
High-resolution gamma-ray computed tomography (HireCT) was applied to clarify the two phase flow distribution inside the impeller wheel of a running pump. Thus, the accumulated gas holdup inside the impeller of an industrial centrifugal pump was investigated and analysed, depending on the suction side gas volume fraction and type of two phase flow regime. Using time-averaging rotation-synchronized tomographic imaging technique, effects on the conveying performance of the centrifugal pump could be clarified. The obtained results contributes to a better understanding of the flow behavior and its effects inside the impeller of a centrifugal pump, which is running under two phase flow conditions due to gas entrainment. Moreover, the results can help to develop improved pump designs to avoid loss of conveying performance due to gas entrainment.
Keywords: centrifugal pump, gas entrainment, two-phase flow, advanced gamma-ray computed tomography, phase fraction visualization
  • Contribution to proceedings
    46th Annual Meeting on Nuclear Technology (AMNT), 05.-07.05.2015, Berlin, Deutschland
    Proceedings of 46th Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology (AMNT), 05.-07.05.2015, Berlin, Deutschland

Publ.-Id: 22114 - Permalink


Untersuchung von Zweiphasenströmungen in einer Kreiselpumpe mittels tomographischer Bildgebungsverfahren
Schäfer, T.; Neumann, M.; Bieberle, A.; Hampel, U.;
Zentrifugalpumpen sind sehr weitverbreitet und werden in vielfältiger Weise unter anderem in der Prozessindustrie oder im Kraftwerksbereich eingesetzt. Beispielweise nutzt man Kreiselpumpen in Raffinerien als Speisepumpen oder in Kraftwerken als Umwälzpumpen in Kühlkreisläufen. Erfolgt der Einsatz auch in sicherheitsrelevanten Bereichen, wie z.B. in der Reaktornotkühlung von Kernkraftwerken, muss unbedingt ein störungsfreier und zuverlässiger Betrieb gewährleistet werden. Obwohl diese Pumpen einfach aufgebaut sind, bieten sie eine Reihe von Vorteilen, wie zum Beispiel hohe Effizienz bei geringem Energieverbrauch, ruhiger und kontinuierlicher Förderstrom und hohe Haltbarkeit und Beständigkeit. Es ist bekannt, dass sowohl Gaseintrag als auch Dampfbildung durch Kavitation schädlich und kritisch für den Betrieb von Kreiselpumpen sind, welche eigentlich für den einphasigen Betrieb ausgelegt sind. Gaseintrag kann beispielsweise in Situationen entstehen, wo Flüssigkeiten aus Reservoirs mit einem zu niedrigen Füllstand gefördert werden. Hier können sich als Konsequenz aus der unzureichenden Überdeckung des Pumpenansaugstutzens und der Anwesenheit von Initialwirbeln an der Flüssigkeitsoberfläche Hohlwirbel ausprägen. Derartige Situationen sind insbesondere in Kernkraftwerken, wo beispielsweise Notkühlmittel aus einem Reservoir wie der Kondensationskammer gefördert wird, unbedingt zu vermeiden. Der Gaseintrag führt zu einer verminderten Förderleistung der Pumpe, bis hin zum vollständigen Zusammenbruch der Förderrate. Außerdem kann vorhandenes Gas in Pumpen unter anderem zum Verlust der Kühlung der Lager und der Gleitringdichtung führen, was zu einer früheren Abnutzung bis hin zum Versagen der Pumpe führt. Auch starke Vibrationen welche ebenfalls zur Schädigung der Lager beitragen, sowie Abnutzungserscheinungen an den Laufradschaufeln können eintreten. Die vorgestellte Arbeit leistet mit quantitativen Messungen, Visualisierungen und Analysen der Gas-Flüssigkeits-Phasenverteilungen innerhalb des Laufrades und des umgebenden Pumpengehäuses einer fördernden Kreiselpumpe einen Beitrag zum fundamentalen Verständnis der Auswirkungen von Gaseintrag in Zentrifugalpumpen.
Keywords: Kreiselpumpe, Gaseintrag, Zweiphasenströmung, erweiterte Gammastrahlen-Computertomographie, Visualisierung der Phasenanteile, centrifugal pump, gas entrainment, two-phase flow, advanced gamma-ray computed tomography, phase fraction visualization
  • Invited lecture (Conferences)
    2. Projektstatusgespräch zur BMBF-geförderten Nuklearen Sicherheitsforschung, 25.-26.03.2015, Dresden, Deutschland

Publ.-Id: 22113 - Permalink


Liquid Metal Ultrasound Velocimetry in a High Current Environment
Starace, M.; Weber, N.; Seilmayer, M.; Weier, T.; Stefani, F.; Eckert, S.;
Ultrasound Doppler velocimetry is an important tool for the characterization of liquid metal flows, including those caused by magnetohydrodynamic instabilities. Here we consider the Tayler Instability (TI), which is driven by a high current flowing through the system. This can entail a great deal of electromagnetic noise, which must be decoupled from the signal produced by ultrasound scatterers within the liquid metal. In the experiment described herein, two ultrasound transducers encased within a copper electrode are in contact with a cylindrical liquid GaInSn column. Currents in the order of several kA produced by a switching-mode power supply flow through the electrode and the liquid GaInSn, resulting in the TI, which causes vortices with vertical velocity components in the range of several mm/s to appear. Noise produced by the power supply was significantly reduced by adding film capacitors and toroidal cores, including a common-mode choke to the circuit. Electromagnetic interference was further reduced by adding toroidal and split cores to the coaxial cables connecting the ultrasound transducers to the velocimeter, with the latter drawing power through an isolating transformer. These precautions permitted the retrieval of reliable velocity data, which generally agree with previously conducted B_z-measurements.
Keywords: Liquid metals, magnetohydrodynamics, Tayler Instability, noise suppression
  • Open Access LogoContribution to proceedings
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 27.-29.08.2014, Strasbourg, France
    Proceedings of the 9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Straßburg, Frankreich: iCUBE, Ubertone, 161-164
  • Lecture (Conference)
    9th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 27.-29.08.2014, Strasbourg, France

Downloads:

Publ.-Id: 22112 - Permalink


Synthesis and First Evaluation of [18F]Fluorocyano- and [18F]Fluoronitroquinoxalinedione as Putative AMPA Receptor Antagonists
Olma, S.; Ermert, J.; Sihver, W.; Coenen, H.-H.;
Derivatives of quinoxalinedione (QX) were chosen as chemical lead for the development of new radioligands of the AMPA receptor, since there are several examples of QX-derivatives with high affinity. The radiosyntheses of the new compounds 6-[18F]fluoro-7-nitro-QX ([18F]FNQX) and 7-[18F]fluoro-6-cyano-QX ([18F]FCQX) with radiochemical yields of 8 ± 2 and 3 ± 2 %, respectively, as well as the evaluation of their binding properties to the AMPA-receptor were performed. A comparison of the Ki-values of the new QX-derivatives FCQX and FNQX with mono-substituted cyanoand nitro-QX shows negligibly small differences of affinity (within the range of 1.4 to 5 µM), but exhibits a tenfold lower affinity than derivatives with two electron withdrawing groups like the 7-cyano-6-nitro-compound CNQX and the 6,7- dinitro compound DNQX. Thus, with respect to the low affinity and a high non-specific binding with in vitro and ex vivo autoradiographic studies, the new compounds do not lend themselves for in vivo imaging.
Keywords: AMPA receptor, fluorine-18, glutamate receptor, positron emission tomography, quinoxalinedione, radiofluorination.

Publ.-Id: 22111 - Permalink


Ultrasound Velocimetry in High Current Driven Liquid Metal Flow
Starace, M.; Weber, N.; Seilmayer, M.; Kasprzyk, C.; Stefani, F.; Weier, T.; Eckert, S.;
The understanding of magnetohydrodynamic phenomena in liquid metals relies heavily on measurement techniques such as ultrasound Doppler velocimetry that can be used to characterize flow patterns within them. The Tayler instability (TI), as well as electro-vortex flow (EVF) in a liquid GaInSn column whose top and bottom are bounded by copper current collectors connected to a switching mode power supply are considered here. The TI is driven by currents above a critical value of 2.7 kA and results in a number of vortices with vertical velocity components of the order of several mm s^−1 , whereas EVF is caused by inhomogeneities in the current density from the current collectors. Ultrasound transducers embedded within the top current collector are in direct contact with the liquid metal. At the high currents required to investigate the TI such a configuration is problematic, because the electromagnetic noise the transducers are exposed to greatly overshadows the signal from ultrasound echoes, if left unchecked. The noise generated by the power supply was significantly damped with the addition of toroidal cores and film capacitors to the current circuit. Moreover, coiling the coaxial cables connecting the transducers to the velocimeter around ring and split cores reduced the noise further. The velocimeter itself drew power through an isolation transformer and was thus prevented from being disturbed by ground loops. Reliable velocity data could be obtained from the experiment after these measures were taken and will be discussed here.
  • Poster
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows (MTLM2015), 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 22110 - Permalink


Nichtinvasive Zustandsüberwachung von Kernreaktoren zur Detektion von Füllstandsänderungen und Deformationen des Kerns
Hampel, U.; Brachem, C.; Lange, C.; Kratzsch, A.; Schmidt, S.; Fiß, D.; Härtel, S.; Konheiser, J.;
Der Vortrag stell das laufende BMBF-Vorhaben "Nichtinvasive Zustandsüberwachung von Kernreaktoren zur Detektion von Füllstandsänderungen und Deformationen des Kerns" vor. Berichtet wird über den Hintergrund des Vorhabens, Zielstellungen im Rahmen der Reaktorsicherheitsforschung und Nachwuchsförderung in der Kerntechnik sowie über aktuelle Projektergebnisse.
Keywords: Nuclear Safety, Reactor Safety, Reactor Monitoring, Monte-Carlo Simulation
  • Invited lecture (Conferences)
    Projektstatusgespräch zu BMBF-geförderten FuE-Arbeiten auf dem Gebiet der Nuklearen Sicherheits- und Entsorgungsforschung sowie Strahlenforschung, 25.03.2015, Dresden, Deutschland

Publ.-Id: 22109 - Permalink


Numerische Untersuchungen zur Strömungsdynamik von Flüssigmetallbatterien
Kasprzyk, C.;
Due to global shortage of fossil fuels, the well known danger of nuclear-energy and the growing threats of climate change the interest in a full switch to renewable based energy-supply is still growing.
The fluctuating and unpredictable character of the power gained from renewable energy-sources, especially sun and wind, is an important fact when considering a turnaround in energy-policy. Therefore, the use of effective storage-technologies is unavoidable to ensure a stable energy-supply.
A promising candidate for cheap electro-chemical storage is the liquid-metal-battery. Coming up from a stable density-stratification of a molten salt in between an alkali metal and an alloy the battery is easy to assemble because of its fully liquid content.
The entirely liquid configuration allows the application of high current densities. By exceeding a critical total current value the so-called Tayler-instability could force a fluid movement in the cell. The instability can cause a mixing or in worst case a short-circuit of the electrodes. An experimental proof of the Tayler-instability shows also a characteristic velocity distribution below the critical current value.
Aim of the present work is a numerical analysis investigating the sub-critical fluid movement.
Possible causes are natural convection as a result of Joule heating or electro-vortex-flow induced by inhomogeneous current density distribution. Central parts of the investigation are the creation of a consistent model including the model validation and the application of the generated setup on the experimental case. An adapted in-house OpenFOAM version for the prediction of magnetohydrodynamics is available.
In a last step a multiphase system, made of a realistic material selection under the influence of electro-vortex-flow, is studied.
Each part of the study is concluded with a summary of the findings.
Keywords: Liquid Metal Battery, Electro-Vortex Flow, OpenFOAM, Rayleigh-Benard, Multiphase-Flow
  • Diploma thesis
    TU Dresden, 2015
    Mentor: Prof. Fröhlich, Martin Niemann, Tom Weier
    89 Seiten

Publ.-Id: 22108 - Permalink


Toward polarized antiprotons: Machine development for spin-filtering experiments
Weidemann, C.; Rathmann, F.; Stein, H.; Lorentz, B.; Bagdasarian, Z.; Barion, L.; Barsov, S.; Bechstedt, U.; Bertelli, S.; Chiladze, D.; Ciullo, G.; Contalbrigo, M.; Dymov, S.; Engels, R.; Gaisser, M.; Gebel, R.; Goslawski, P.; Grigoriev, K.; Guidoboni, G.; Kacharava, A.; Kamerdzhiev, V.; Khoukaz, A.; Kulikov, A.; Lehrach, A.; Lenisa, P.; Lomidze, N.; Macharashvili, G.; Maier, R.; Martin, S.; Mchedlishvili, D.; Meyer, H.; Merzliakov, S.; Mielke, M.; Mikirtychiants, M.; Mikirtychiants, S.; Nass, A.; Nikolaev, N.; Oellers, D.; Papenbrock, M.; Pesce, A.; Prasuhn, D.; Retzlaff, M.; Schleichert, R.; Schroer, D.; Seyfarth, H.; Soltner, H.; Statera, M.; Steffens, E.; Stockhorst, H.; Stroher, H.; Tabidze, M.; Tagliente, G.; Engblom, P.; Trusov, S.; Valdau, Y.; Vasiliev, A.; Wustner, P.;
The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3 MeV in COSY. The implementation of a low-β insertion made it possible to achieve beam lifetimes of τb=8000  s in the presence of a dense polarized hydrogen storage-cell target of areal density dt=(5.5±0.2)×1013  atoms/cm2. The developed techniques can be directly applied to antiproton machines and allow the determination of the spin-dependent p¯p cross sections via spin filtering.

Publ.-Id: 22107 - Permalink


Analysing powers and spin correlations in deuteron–proton charge exchange at 726 MeV
Dymov, S.; Azaryan, T.; Bagdasarian, Z.; Barsov, S.; Carbonell, J.; Chiladze, D.; Engels, R.; Gebel, R.; Grigoryev, K.; Hartmann, M.; Kacharava, A.; Khoukaz, A.; Komarov, V.; Kulessa, P.; Kulikov, A.; Kurbatov, V.; Lomidze, N.; Lorentz, B.; Macharashvili, G.; Mchedlishvili, D.; Merzliakov, S.; Mielke, M.; Mikirtychyants, M.; Mikirtychyants, S.; Nioradze, M.; Ohm, H.; Prasuhn, D.; Rathmann, F.; Serdyuk, V.; Seyfarth, H.; Shmakova, V.; Stroeher, H.; Tabidze, M.; Trusov, S.; Tsirkov, D.; Uzikov, Y.; Valdau, Y.; Weidemann, C.; Wilkin, C.;
The charge exchange of vector polarised deuterons on a polarised hydrogen target has been studied in a high statistics experiment at the COSY-ANKE facility at a deuteron beam energy of Td=726 MeV. By selecting two fast protons at low relative energy Epp, the measured analysing powers and spin correlations are sensitive to interference terms between specific neutron–proton charge-exchange amplitudes at a neutron kinetic energy of Tn≈1/2 Td=363 MeV. An impulse approximation calculation, which takes into account corrections due to the angular distribution in the diproton, describes reasonably the dependence of the data on both Epp and the momentum transfer. This lends broad support to the current neutron–proton partial wave solution that was used in the estimation.

Publ.-Id: 22106 - Permalink


Preclinical small animal PET/MRI for radiopharmaceutical dosimetry
Kranz, M.; Sattler, B.; Patt, M.; Deuther-Conrad, W.; Fischer, S.; Smits, R.; Hoepping, A.; Sabri, O.; Brust, P.;
Aim
To assess the radiation risk after injection of new PET radiotracers small animal PET/MRI provides the essential whole body biodistribution data for image based dosimetry (ibD). In this study, we investigate ((S)-(-)# and (R)-(+)##-[18F]fluspidine, a PET radioligand for neuroimaging of σ1 receptors in mice. Organ doses (OD) and the effective dose (ED) were determined using PET/MR ibD to assess the radiation risk to humans. The results will be compared to those previously acquired for (-)-*and (+)-** [18F]flubatine , to proof the concept of small animal PET/MRI for incorporation dosimetry to assess the radiation exposure to humans by radiopharmaceuticals.

Materials and methods
Six female CD1 mice (weight: 30.9±1.3 g) were injected i.v. with 13.2±3.0 MBq (#, n=3) or 12.6±1.4 MBq (##, n=3), respectively. A dynamic 2 h animal PET/MRI protocol was performed (MEDISO nanoScan®, Hungary). All relevant organs were defined by volumes of interest. Time- and mass-scales were adapted to the human anatomy; exponential curves were fitted to the time-activity-data (%ID/organ). The ODs were computed using the adult male model with OLINDA and the ED using tissue weighting factors (ICRP103). The results were compared to previously acquired data of post mortem biodistribution (PMB) studies in mice for (-)-[18F]flubatine (n=27, Ø28.2 g) and [18F]fluspidine (n=28#/n=22##, Ø29.6 g).

Results
The excreting organs (kidneys, liver and urinary bladder) received the highest ODs. Subsequently, these organs provide the largest contribution to the ED. The overall radiation risk to humans based on animal biodistribution data acquired with ibD would be 12.9# and 14.0## (16.7#; 18.4## based on PMB). Comparable results were estimated for [18F]flubatine: 12.5*(PMB), 12.1**.

Conclusion
ibD of [18F]fluspidine reveals major differences between the two enantiomers. The tracer with higher affinity and slower kinetics (##) causes a higher radiation exposure than its enantiomeric counterpart (#) both in ibD and PMB. Furthermore, the ibD shows lower ED values compared to the PMB due to the intrinsic methodological differences. Small animal ibB is feasible and its reliability needs to be further investigated and confirmed.
  • Poster
    Annual Congress of the European Association of Nuclear Medicine - EANM 2015, 09.-14.10.2015, Hamburg, Deutschland
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 42(2015), 347-348

Publ.-Id: 22105 - Permalink


Biodistribution, cellular localization, and in vivo tolerability of S-35-labeled antiinflammatory dendritic polyglycerol sulfate amine
Holzhausen, C.; Groger, D.; Mundhenk, L.; Donat, C. K.; Schnorr, J.; Haag, R.; Gruber, A. D.;
Antiinflammatory dendritic polyglycerol sulfate (dPGS) holds great potential in the treatment and imaging of inflammatory processes. Here, we studied its biokinetic behavior, biodistribution, target cells, and in vivo toxicology. Following intravenous or subcutaneous application of (35)sulfur-labeled dPGS amine with a molecular weight of 10.05 kDa and a hydrodynamic diameter of 5.7 +/- 1.5 nm to mice, tissues were collected at specific time points (2, 15 min; 1, 24 h; 5, 21 days) and analyzed by liquid scintillation counting, autoradiography, radioluminography, and light microscopic autoradiography. The blood half-life of dPGS amine was 12 days. The major route of elimination was via the bile and feces.
Elimination via the kidney and urine was only initially observed after i.v., but not after s.c. injection. Regardless of the administration mode, liver and spleen were late target organs where dPGS amine accumulated in phagocytic cells. Despite bioaccumulation, toxicological histopathology failed to identify any adverse effects at any time and in any tissues examined suggesting a high in vivo biocompatibility and encouraging future investigation for biomedical applications.

Publ.-Id: 22104 - Permalink


Felsenkeller shallow-underground accelerator laboratory for nuclear astrophysics (at p-process workshop)
Szücs, T.;
A very low background level is a key requirement for low-energy nuclear astrophysics experiments. A series of detailed high energy (E> 3 MeV) laboratory gamma-background study with escape-suppressed HPGe detectors has been performed at the surface of the Earth [1,2], at shallow underground (110 m w. e.) in the Felsenkeller laboratory in Dresden, Germany [2,3], at medium deep underground (400 m w. e.) in the Reiche Zeche mine in Freiberg, Germany [3], and at deep underground (3800 m w. e.) in LNGS in Gran Sasso, Italy [1]. The data show that already a shallow underground site has sufficiently low gamma-background for many nuclear astrophysics studies when an additional active shield is used to veto the remaining muon flux [2,3].
Benefiting from these low background conditions, a used 5 MV Pelletron tandem accelerator with external high-current sputter ion source for hydrogen and carbon beams is currently being refurbished for installation in Felsenkeller [4]. Installation of an additional radio-frequency ion source on the high voltage terminal is under way. The ions will be injected into the acceleration tube by an electrostatic deflector, thus the tandem mode of operation will be kept. With the RF-source up to 100A alpha beam is foreseen. Similarly high proton current either from the external or the internal source will be available. In addition, also a large, well-shielded HPGe detector for offline counting will be included in the new laboratory, enabling activation experiments.

The Felsenkeller accelerator will be used in part for in-house research by HZDR and TU Dresden, aiming for complementarity with the LUNA-MV project and science program. In addition, external users from any field of science will be highly welcome at Felsenkeller. Users are to be selected based on the recommendations of an independent group of outside advisers judging the scientific merits of the proposals.
Owing to the high current of the 5 MV Pelletron and the low laboratory background, the Felsenkeller laboratory may be suited to study p-process related nuclear reactions.

In addition to the detailed introduction of the new Felsenkeller accelerator laboratory, the talk will flash the recent status of the KADoNiS-p database [5].

- Supported by the Helmholtz Association (HGF) through the Nuclear Astrophysics Virtual Institute (NAVI, HGF VH-VI-417)

[1] T. Szücs et al., Eur. Phys. J. A 44, (2010) 513
[2] T. Szücs et al., Eur. Phys. J. A 48, (2012) 8
[3] T. Szücs et al., Eur. Phys. J. A 51, (2015) 33
[4] D. Bemmerer et al., Procc. of Sciences NIC XIII, (2015) 044
[5] T.Szücs et al., Nucl. Data Sheets 120, (2014) 191
http://www.kadonis.org/pprocess/
Keywords: Felsenkeller, Underground, accelerator, nuclear astrophysics
  • Lecture (Conference)
    p-process workshop 2015: status and outlook, 10.-13.06.2015, Limassol, Cyprus

Publ.-Id: 22103 - Permalink


Active Site Mapping of Human Cathepsin F with Dipeptide Nitrile Inhibitors
Schmitz, J.; Furtmann, N.; Ponert, M.; Frizler, M.; Löser, R.; Bartz, U.; Bajorath, J.; Gütschow, M.;
The cleavage of the invariant chain is the key event in the trafficking pathway of major histocompatibility complex class II. Cathepsin S constitutes the major processing enzyme of the invariant chain, but cathepsin F acts in macrophages as its functional synergist which is as potent as cathepsin S in invariant chain cleavage. Dedicated low molecular weight inhibitors for cathepsin F have not been developed so far. An active site mapping with 52 dipeptide nitriles, reacting as covalent-reversible inhibitors, was performed to draw structureactivity relationships for the non-primed binding region of human cathepsin F. In a stepwise process, new compounds with optimized fragment combinations were designed and synthesized. These dipeptide nitriles were evaluated on human cysteine cathepsins F, B, L, K and S. Compounds 10 (N-(4-phenylbenzoyl)-leucyl-glycine nitrile) and 12 (N-(4-phenylbenzoyl)-leucyl-methionine nitrile) were potent inhibitors of human cathepsin F with Ki values less than 10 nM. With all dipeptide nitriles from our study, a 3D activity landscape was generated to visualize structure-activity relationships for this
series of cathepsin F inhibitors.

Publ.-Id: 22102 - Permalink


Cysteine cathepsins: their role in tumor progression and recent trends in the development of imaging probes
Löser, R.; Pietzsch, J.;
Papain-like cysteine proteases bear an enormous potential as drug discovery targets for both infectious and systemic human diseases. The considerable progress in this field over the last two decades has also raised interest in the visualization of these enzymes in their native context, especially with regard to tumor imaging.
After a short introduction to structure and general functions of human cysteine cathepsins, we highlight their importance for drug discovery and development and provide a critical update on the current state of knowledge towards their involvement in tumor progression, with a special emphasis on their role in therapy response. In accordance with a radiopharmaceutical point of view, the main focus of this review article will be the discussion of recently developed fluorescence and radiotracer-based imaging agents together with related molecular probes.
Keywords: Cancer, Carcinogenesis, extracellular enzymes, Fluorescence-based probes, Lysosomal cysteine proteases, metastasis, Molecular Imaging, radiotracers

Publ.-Id: 22101 - Permalink


Measuring techniques for experimental investigations and monitoring of liquid metal flows
Eckert, S.; Wondrak, T.; Franke, S.; Gundrum, T.; Ratajczak, M.; Stefani, F.; Gerbeth, G.;
The safe and reliable operation of liquid metal systems requires corresponding measuring systems and control units, both for the liquid metal single-phase flow as well as for bubble-laden liquid metal two-phase flows. Moreover, significant research effort is permanently focused on the optimization of technologies and facilities for materials processing such as smelting, refining and casting of metals and alloys. The main objectives are an improvement of the final product quality, an enhancement of the process efficiency and an economical consumption of resources and energy. Further developments of processes involving metallic melts require a better, detailed knowledge about the flow structure and the transport properties of the flow. Numerical simulations could provide a better understanding of the complex flow behavior, but, experimental data are indispensable with respect to a validation of the respective CFD codes. The determination of flow quantities in liquid metals is considerably impeded by the special material properties. Powerful optical methods as used for measurements in transparent liquids are obviously not applicable in molten metals. Further serious restrictions arise from the high temperature or the chemical reactivity of the melt. As a consequence there is a very constrained choice of commercially available techniques to measure the velocity structure of fluid flows at elevated temperatures.
The presentation reports on established methods and new developments in the field of measuring techniques for liquid metal flows. This review is focused on measurements of the flow rate and the local velocity field as well as on the characterization of liquid metal two-phase flows and solidifying melts. During the last two decades considerable effort was spent by miscellaneous researcher groups to provide new solutions for measurements of flow fields in liquid metals. The presentation intends to summarize different approaches and attempts to account on perspectives, particularly in view of some recent developments.
Keywords: liquid metal, flow measurements, ultrasound Doppler method, inductive flow tomography
  • Invited lecture (Conferences)
    Heavy Metal Summer School, 15.-19.06.2015, Mol, Belgium

Publ.-Id: 22100 - Permalink


Flexible Antigen-Specific Redirection of Human Regulatory T Cells Via a Novel Universal Chimeric Antigen Receptor System
Koristka, S.; Cartellieri, M.; Feldmann, A.; Arndt, C.; Loff, S.; Michalk, I.; Aliperta, R.; von Bonin, M.; Bornhäuser, M.; Ehninger, A.; Ehninger, G.; Bachmann, M. P.;
Based on compelling evidence from a vast number of in vitro and in vivostudies, Tregs have become an attractive cell population to treat or even prevent auto- and alloimmunity including Graft-versus-Host disease (GvHD). However, several safety concerns still exist as for example the risk of global immunosuppression using polyclonal Tregs. In fact, experiments in mice showed that adoptive transfer or induction of antigen-specific Tregs is more potent regarding suppression of pathogenic immune responses when compared to polyclonal Treg populations. Unfortunately, the isolation and expansion of naturally occurring antigen-specific Tregs is technically difficult, labour-intensive, and time-consuming. An attractive way to overcome these limitations and to endow polyclonal Treg populations with a desired antigen-specificity is their engraftment with chimeric antigen receptors (CARs). In this context, CAR-modification represents a promising approach to redirect polyclonal Tregs in an antigen-specific manner to suppress ongoing self-destructive immune responses at the site of inflammation.

Nevertheless, until now redirection of CAR-engineered T cells is limited to a single target antigen, restricting this approach to an unflexible monospecific therapy. Therefore, we developed a more flexible universal CAR (UCAR) platform that allows redirection of T cells to an in principal unrestricted number of surface antigens. T cells are engrafted with UCARs that bind to a small peptide epitope derived from a human nuclear protein. Cross-linkage to target cells is mediated by independent target modules that provide antigen-specificity and comprise the peptide epitope recognized by the UCAR. In order to target different tissue antigens, the target modules can easily be exchanged. Thereby, once established, the treatment strategy can easily be applied to various auto- and alloimmune diseases.

At present, the CD45RA+ population is the Treg subset of choice for a clinical application as these cells have the highest capacity to maintain phenotypic and functional Treg properties upon prolonged ex vivo expansion. Here we show that highly pure, sorted CD4+CD25+CD127lowCD45RA+ Tregs can be genetically manipulated using lentiviral gene transfer, resulting in approximately 70 % of UCAR-expressing Treg cells. The transduction procedure itself did not affect the phenotype of UCAR-engineered Tregs as it was similar to non-transduced wildtype cells. Both Treg populations presevered FOXP3 expression even after prolonged in vitro cultivation (> 95 % FOXP3+). Upon incubation with antigen-positive target cells and a respective target module UCAR-engineered Tregs upregulate the activation markers CD69 and LAP demonstrating that the cells can be restimulated antigen-specifically. Most importantly, UCAR-engrafted Tregs were functionally activated upon antigen encounter, demonstrated by suppression of proliferation and expansion of cocultured autologous T effector cells.

Taken together, our results pave the way towards an application of UCAR technology for a site-specific recruitment of CAR-modified Tregs into inflamed tissues aiming at re-establishing immune homeostasis. Due to its high flexibility UCAR-engrafted Tregs can easily and universally be used for treatment of various autoimmune diseases or GvHD just by exchanging the tissue-specific target modules.

Disclosures Cartellieri: Cellex Patient Treatment GmbH: Employment. Ehninger: GEMoaB GmbH: Employment, Patents & Royalties. Ehninger: GEMoaB GmbH: Consultancy, Patents & Royalties. Bachmann: GEMoaB GmbH: Consultancy, Patents & Royalties.
  • Abstract in refereed journal
    BLOOD 124(2014)21, 3494
  • Poster
    56th ASH Annual Meeting, 06.-09.12.2014, San Francisco, USA

Publ.-Id: 22099 - Permalink


Copper(II) cyclam complexes with N-propionic acid pendant arms
Kubeil, M.; Zarschler, K.; Pietzsch, J.; Kraus, W.; Comba, P.; Stephan, H.;
Four cyclam (1,4,8,11-tetraazacyclotetradecane) ligands with different number of N-substituted propionic acid groups lead to penta-coordinated copper(II) complexes adopting trans-I configuration (4+1 geometry), i.e. the complexes have dx2−y2 ground state with significant rhombic distortion. From the structural data (X-ray, electron paramagnetic resonance, UV/vis, infrared), it appears that with increasing substitution of the secondary amines of the macrocyclic ring with propionic acid groups the distortion from square-pyramidal to trigonal-bipyramidal rises, and this is expected to lead to relatively low complex stabilities. This is confirmed by in vitro studies using superoxide dismutase (SOD) and human serum challenge experiments as well as by biodistribution data with the 64Cu-labelled ligands. 64Cu-labelled cyclam monopropionic and dipropionic acid show high in vitro and in vivo stability at which the latter provides a comparable biodistribution profile as 64Cu-TETA (1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid).

Publ.-Id: 22098 - Permalink


Synthesis and characterization of novel fluorescent sigma-2 receptor ligands
Ye, J.; Deuther-Conrad, W.; Steinbach, J.; Brust, P.; Jia, H.;
Sigam-2 (σ2) receptors are overexpressed in a variety of human and rodent tumors and play a pivotal role in cancer biology. Furthermore, it has proved to be a unique biomarker of cell proliferation in solid tumors. With the aim of providing more potent and reliable tools to investigate the σ2 receptor biology, we report herein on the synthesis and characterization of novel fluorescent σ2 receptor ligands designed via an integrated approach by using N-(4-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)butyl)-2-(2- [18F]fluoroethoxy)-5-methylbenzamide ([18F]ISO-1, the only σ2 receptor radioligand used in clinical trials up to date) as the lead compound.
All the synthesized compounds possess the pharmacophore (6,7-dimethoxy-1,2,3,4-tetrahdyroxyisoquinoline) and a fluorophore directly connected via various carbon linkers as shown in Figure 1. The clog P values were calculated by On-line Lipophilicity in Virtual Computational Chemistry Laboratory as shown in Table 1 (compounds 2-5 vs SW116 and SW120, the clog P 4.24–5.05 vs 6.74 and 7.29). We measured the excitation/emission wavelength, the quantum yields (QY) and the absorbance in phosphate-buffered saline (PBS). The emission maxima of these compounds are about 450 nm. High QYs were observed for compounds 2–5 with 5.95%, 8.11%, 7.52% and 5.48%, respectively.
The affinities of ligands for the σ2 and σ1 receptors were determined with radioligand competition experiments. [3H]DTG in the presence of 10 μM dextrallorphan was used for the σ2 receptors and (+)-[3H]pentazocine for σ1 receptors. The results are presented in Table 1. In general, the fluorescent compounds preferred to bind to σ2 receptors. Compounds 2–5, containing a barbituric acid moiety as electron acceptor, possessed high affinity (10.9–22.3 nM) and subtype selectivity for σ2 receptors (Ki1)/Ki2) = 14–57).
In conclusion, fluorescent σ2 receptor ligands with high affinity and subtype selectivity have been developed and warrant further evaluation.
  • Lecture (Conference)
    World Molecular Imaging Congress 2015, 02.-05.09.2015, Hawaii, USA

Publ.-Id: 22097 - Permalink


Novel indole-based sigma-2 receptor ligands: synthesis, structure–affinity relationship and antiproliferative activity
Xie, F.; Kniess, T.; Neuber, C.; Deuther-Conrad, W.; Mamat, C.; Liebermann, B. P.; Liu, B.; Mach, R. H.; Brust, P.; Steinbach, J.; Pietzsch, J.; Jia, H.;
We report the synthesis and biological evaluation of a series of indole-based σ2 receptor ligands derived from siramesine. In vitro competition binding assays showed that these analogues possessed high to moderate affinity and selectivity for σ2 receptors. Structure–affinity relationship analyses of these indole-based σ2 receptor ligands were performed. In the 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, 1a and 1b displayed significant and comparable antiproliferative activity in DU145, MCF7 and C6 cells to siramesine. In cell cycle analyses, compounds 1a, 1b and siramesine were found to induce a G1 phase cell cycle arrest in DU145 cells using flow cytometry. The combination of 5,6-dimethoxyisoindoline scaffold and N-(4-fluorophenyl)indole moiety was identified as a new σ2 receptor ligand deserving further investigation as an antitumor agent.

Publ.-Id: 22096 - Permalink


Two surface plasmon decay of plasma oscillations
Kluge, T.; Metzkes, J.; Zeil, K.; Bussmann, M.; Schramm, U.; Cowan, T. E.;
The interaction of ultra-intense lasers with solid foils can be used to accelerate ions to high energies well exceeding 60MeV [Gaillard et al., Phys. Plasmas 18, 056710 (2011)]. The non-linear relativistic motion of electrons in the intense laser radiation leads to their acceleration and later to the acceleration of ions. Ions can be accelerated from the front surface, the foil interior region, and the foil rear surface (target normal sheath acceleration (TNSA), most widely used), or the foil may be accelerated as a whole if sufficiently thin (radiation pressure acceleration). Here, we focus on the most widely used mechanism for laser ion-acceleration of TNSA. Starting from perfectly flat foils, we show by simulations how electron filamentation at or inside the solid leads to spatial modulations in the ions. The exact dynamics depend very sensitively on the chosen initial parameters which has a tremendous effect on electron dynamics. In the case of step-like density gradients, we find evidence that suggests a two-surface-plasmon decay of plasma oscillations triggering a Raileigh-Taylor-like instability.

Publ.-Id: 22095 - Permalink


The origin and crust/mantle mass balance of Central Andean ignimbrite magmatism constrained by oxygen and strontium isotopes and erupted volumes
Freymuth, H.; Brandmeier, M.; Wörner, G.;
Volcanism during the Neogene in the Central Volcanic Zone (CVZ) of the Andes produced 1) stratovolcanoes, 2) rhyodacitic to rhyolitic ignimbrites which reach volumes of generally less than 300 km3 and 3) large volume monotonous dacitic ignimbrites of up to several thousand cubic kilometres. We present models for the origin of these magma types using O and Sr isotopes to, constrain crust/mantle proportions for the large volume ignimbrites and explore the relationship to the evolution of the Andean crust.
Oxygen isotope ratios were measured on phenocrysts in order to avoid the effects of secondary alteration. Our results show a complete overlap in the Sr-O isotope compositions of lavas from stratovolcanoes and low-volume rhyolitic ignimbrites as well as older (>9 Ma) large-volume dacitic ignimbrites. This suggests that the mass balance of crustal and mantle components are largely similar. By contrast, younger (<10 Ma) large-volume dacitic ignimbrites from the southern portion of the Central Andes have distinctly more radiogenic Sr and heavier O isotopes and thus contrast with older dacitic ignimbrites in northernmost Chile and southern Peru.
Results of assimilation and fractional crystallization (AFC) models show that the largest chemical changes occur in the lower crust where magmas acquire a base-level geochemical signature that is later modified by middle to upper crustal AFC. Using geospatial analysis we estimated the volume of these ignimbrite deposits throughout the Central Andes during the Neogene and examined the spatiotemporal pattern of so- called "ignimbrite flare-ups". We observe a N-S migration of maximum ages of the onset of large volume "ignimbrite pulses" through time: Major pulses occurred at 19-24 Ma (e.g. Oxaya, Nazca Group), 13-14 Ma (e.g. Huaylillas and Altos de Pica ignimbrites), <10 Ma (Altiplano and Puna ignimbrites). Such "flare-ups" represent magmatic production rates of 25 to >70 km3 Ma-1 km-1 (assuming plutonic:volcanic ratios of 1:5) which are additional to, but within the order of, the arc background magmatic flux. Comparing our results to average shortening rates observed in the Andes, we observe a "lag-time" with large-volume eruptions occurring after accelerated shortening. A similar delay exists between the ignimbrite pulses and the subduction of the Juan-Fernandez ridge. This is consistent with the idea that large-volume ignimbrite eruptions occurred in the wake of the N-S passage of the ridge after slab steepening has allowed hot asthenospheric mantle to ascend into and cause the melting of the mantle wedge.
In our model, the older large-volume dacitic ignimbrites in the northern part of the CVZ have lower (15 to 37 %) crustal contributions because they were produced at times when the Central Andean crust was thinner and colder, and large-scale melting in the middle crust could not be achieved. Younger ignimbrite flare-ups further south (< 10 Ma, > 22°S) formed with a significantly higher crustal contribution (22 to 68 %) because at that time the Andean crust was thicker and hotter and, therefore primed for more extensive crustal melting. The rhyolitic lower-volume ignimbrites are more equally distributed in the Central Volcanic Zone (CVZ) in time and space and are produced by mechanisms similar to those operating below large stratovolcanoes, but at times of higher melt fluxes from the mantle wedge.

Publ.-Id: 22094 - Permalink


Solidification of pure aluminium affected by a pulsed electrical field and electromagnetic stirring
Zhang, Y.; Räbiger, D.; Eckert, S.;
Pure aluminium (99.997 up to 99.9999 wt % Al) has been solidified under the influence of both electric current pulses and a traveling magnetic field for electromagnetic melt stirring. The electric current was applied by means of two parallel electrodes immersed into the melt through the free surface. In contradistinction to well-known investigations in solute-rich alloys or recently published studies for pure aluminium we did not find a grain refinement effect owing to the melt treatment here. It becomes obvious that a slight contamination of the basic raw material by an impure processing during melt preparation has a dramatic influence on the grain structure.
Keywords: Solidification; Metals and alloys; Pure aluminium; Grain refinement; Electric Current Pulses (ECP); Electromagnetic stirring

Publ.-Id: 22093 - Permalink


Reichweiteverifikation bei der Protonentherapie mit einer Prompt-Gamma-Schlitzkamera – Auf dem Weg zur klinischen Anwendung
Priegnitz, M.; Barczyk, S.; Golnik, C.; Janssens, G.; Smeets, J.; Vander Stappen, F.; Clementel, E.; Hotoiu, L.; de Xivry, J. O.; Baumann, M.; Enghardt, W.; Fiedler, F.; Krause, M.; Prieels, D.; Pausch, G.; Richter, C.;
In der Radioonkologie gewinnt die Bestrahlung mit Protonen zunehmend an Bedeutung. Um die vorteilhaften strahlenphysikalischen Eigenschaften jedoch voll ausschöpfen zu können, ist eine Verifizierung der Protonenreichweite notwendig. Hierfür gibt es verschiedene Ansätze, wobei das Prompt Gamma Imaging (PGI) eine vielversprechende Methode ist. Eine Schlitzkamera, welche eine mögliche technische Realisierung für das PGI darstellt, ermöglicht die tiefenaufgelöste Messung von protoneninduzierten Prompt-Gamma-Emissionen und erlaubt Aussagen über die tatsächliche Reichweite der applizierten Protonen. An der Universitätsprotonentherapie Dresden (UPTD) wird in naher Zukunft eine klinische Studie zur Nutzung einer solchen Schlitzkamera im Patientenbetrieb beginnen. Hierfür erfolgen gegenwärtig die Vorbereitung der klinischen Implementierung sowie die systematische Charakterisierung des Kamerasystems.
  • Lecture (Conference)
    46. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 09.-12.09.2015, Marburg, Deutschland
  • Contribution to proceedings
    46. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 09.-12.09.2015, Marburg, Deutschland
    DGMP 2015 - 46. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik - Abstractband, 978-3-9816508-8-4, 286-287

Publ.-Id: 22092 - Permalink


Melanoma targeting with [99mTcN(PNP3)]-labeled α-MSH peptide analogs: Preliminary studies
Gao, F.; Carta, D.; Salvarese, N.; Sihver, W.; Pietzsch, H.-J.; Biondi, B.; Ruzza, P.; Refosco, F.; Bolzati, C.;
Objectives: The purpose of this study was to examine the effect of cyclization on the biological profiles of [99mTcN(PNP3)]-labeled α-MSH analogs.
Methods: The linear peptide H-Cys-Ahx-bAla-Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2 (NAP-NS1) (1) and a corresponding lactam bridge-cyclized peptide, H-Cys-Ahx-bAla3-c[Lys4-Glu-His-D-Phe-Arg-Trp-Glu10]-Arg11-Pro-Val-NH2 (NAP-NS2) (2), were synthesized, characterized by ESI-MS, and their melanocortin-1 receptor (MC1R) binding affinity was determined in B16F10 melanoma cells. In vitro stability and pharmacological parameters of [99mTc(N)(NAP-NS1)(PNP3)]+ (1a) and [99mTc(N)(NAP-NS2)(PNP3)]+ (2a) were assessed. Challenges with an excess of glutathione and cysteine and LogD values were also investigated. Furthermore, 1a and 2a were applied to study in vivo stability and the pharmacokinetic profiles on healthy rats.
Results: 1a and 2a were obtained in high yield (RCY > 90%). LogD values demonstrated the hydrophilic nature of the radiolabeled peptides: -1.43 for 1a; - 2.09 for 2a. No significant variations in RCPs of both the complexes were observed. Both complexes showed high stability after incubation in human and rat sera as well as in rat liver homogenate. A fast degradation of 2a was detected in kidneys homogenate. 1a retained a high receptor affinity (Kd: 7.1±0.5 nM). Biodistribution of 1a displayed a favorable pharmacokinetic profile with fast blood clearance and elimination from normal tissues. Rapid renal excretion of 1a was observed due to the high hydrophilic character. The pharmacokinetic profile of 2a was reflected in reduction of the blood clearance and the elimination from the other organs; especially the kidneys showed restraint elimination.
Conclusions: Compared with the linear peptide 1, cyclization affected the pharmacological properties of 2 negatively by reducing its stability, its binding affinity to MC1Rs (Ki: 0.9±0.3 nM for 1; 7.1±2.4 nM for 2) and decreasing the overall excretion rate of the corresponding [99mTcN(PNP3)]-labeled peptide from the body. Thus, only the linear labeled peptide 1a will be considered for further investigations in tumor bearing mice.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S359
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22091 - Permalink


(Radio)pharmacological characterization of novel α-MSH derivatives
Gao, F.; Sihver, W.; Bergmann, R.; Haase-Kohn, C.; Steinbach, J.; Carta, D.; Bolzati, C.; Calderan, A.; Pietzsch, J.; Pietzsch, H.-J.;
Objectives: Melanocortin-1 receptor (MC1R) is well known to be overexpressed in melanoma. Thus, it has been a great interest in targeting this receptor for diagnosis of human metastasized melanoma. We aimed at investigating
(radio)pharmacological properties of novel derivatives of the α-melanocyte-stimulating hormone (α-MSH) and selecting most promising candidates for further studies in melanoma models in vivo.
Methods: Linear and cyclic α-MSH derivatives (NAP-NS1(1), NOTA-NAP-NS1(2), natCu-NOTA-NAP-NS1(3), NAP-NS2(4), NOTA-NAP-NS2(5), natCu-NOTA-NAP-NS2(6), DPA-NAP-NS1(7) and Re-tricarbonyl-DPA-NAPNS1(8)) were investigated in competition assays in both murine B16F10 and human MeWo cells. In vitro stabilities of [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 were tested in phosphate buffer (pH=7.4) and human serum at 37°C for 1h and 24h. Transchelation and octanol/water partition coefficients of radiolabeled peptides were also investigated. Additionally, [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 with high radiochemical purities and specific activities were applied in saturation assays and kinetic studies.
Results: Linear α-MSH derivatives (1, 2, 3, 7 and 8) showed higher affinities on both murine and human cells than cyclic α-MSH derivatives (4, 5, 6). Linking the chelator to the peptide and coordinating the chelator-peptide with
natCu or Re were accompanied by some loss of affinity. [64Cu]Cu-2, [64Cu]Cu-5 and 99mTc-tricarbonyl-7 were stable in phosphate buffer and serum at 37°C after incubation for 1h and 24h. No transchelation of radiolabeled peptides was observed in cysteine and histidine challenge experiments. LogD values suggested that [64Cu]Cu-2 (-2.30±0.01) and [64Cu]Cu-5 (-3.39±0.04) had higher hydrophilicity than 99mTc-tricarbonyl-7 (-0.43±0.01). Saturation studies in both cell lines resulted in Kd values (nM) in the lower nanomolar ranges for [64Cu]Cu-2 (B16F10: 1.7±0.2; MeWo: 2.6±0.5) and 99mTc-tricarbonyl-7 (B16F10: 6.0±0.5; MeWo: 4.5±0.8). But Bmax (fmol/mg protein) of [64Cu]Cu-2 on murine and human cells (B16F10: 46.6±3.9; MeWo: 16.6±1.6) was notably lower than that of 99mTc-tricarbonyl-7 (B16F10: 403.5±46.1; MeWo: 50.3±6.4). Kinetic study of [64Cu]Cu-2 in murine cells showed rapid cellular association and dissociation in vitro.
Conclusions: [64Cu]Cu-2 showed high stability, hydrophilicity, binding affinities and rapid cellular association and dissociation in vitro, which made it promising for further investigations in melanoma models.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S345
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22090 - Permalink


Synthesis, 18F-labeling and radiopharmacological characterization of a claudin-targeting peptide
Löser, R.; Bader, M.; Kuchar, M.; Wodtke, R.; Bergmann, R.; Lenk, J.; Haase-Kohn, C.; Pufe, J.; Steinbach, J.; Pietzsch, J.;
Objectives: The cell surface receptor claudin-4 (Cld-4) is upregulated in various tumors and represents a promising target for both diagnosis and treatment of solid tumors of epithelial origin [1]. A suitable ligand to address Cld-4 in vivo seems to be the C-terminal fragment of the Clostridium perfringens enterotoxin cCPE(290-319) (1; Figure 1) [2].
Methods: 1 and N-terminally modified (fluorobenzoylated and FITC-conjugated) as well as other analogs were synthesized by microwave-assisted solid-phase peptide synthesis (SPPS). Their affinity to a protein construct containing both extracellular loops of Cld-4 was studied by surface plasmon resonance (SPR). Labeling of 1 with fluorine-18 was achieved on solid phase using [18F]SFB and 4-[18F]fluorobenzoyl chloride as 18F-acylating agents [3]. The stability of the resulting radiotracer was evaluated in different physiological media. Its cell binding was investigated using the HT29, A375 and A431 tumor cell lines. The in vivo behavior of 18F-labeled 1 was studied in NMRI nu/nu mice and Wistar rats by dynamic PET imaging and radiometabolite analyses, respectively. Furthermore, the binding of FITC-conjugated 1 was investigated by fluorescence microscopy.
Results: Among several approaches tried, sequential SPPS using three pseudoproline-dipeptide building blocks revealed as the most efficient one to afford 1 and its derivatives. Their affinities to the Cld-4 mimicking construct are in the low micromolar range. 18F-labeling was most advantageous when [18F]SFB was reacted with resin-bound 1 containing an N-terminal aminohexanoic spacer. The resulting radiotracer was sufficiently stable in cell supernatants and plasma. Its cell binding was time-dependent and higher to the Cld-4-positive A375 and A431 compared to the negative HT29 line. Results of confocal microscopy using FITC-1 and A431 cells are in accordance with these findings. 18F-labeled 1 is subject to substantial liver uptake and rapid metabolic degradation in vivo.
Conclusions: The synthesis and 18F-labeling of 1 was successfully established. Its binding to Cld-4 in vitro and in cellulo has been demonstrated. Initial radiopharmacological studies suggest the limited suitability of this peptide in its current form to target Cld-4 in vivo.
References
[1] Neese A, et al (2012) Arch. Biochem. Biophys. 524, 64–70.
[2] Ling J, et al (2008) J. Biol. Chem. 283, 30585–30595.
[3] Kuchar M, et al (2012) Amino Acids 43, 1431-1443.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S205
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22089 - Permalink


Targeting lysyl oxidase for molecular imaging in breast cancer
Wuest, M.; Kuchar, M.; Sharma, S. K.; Richter, S.; Wankg, M.; Vos, L.; Mackey, J. R.; Wuest, F.; Löser, R.;
Objectives: Lysyl oxidase (LOX, EC 1.4.3.13) and its family members LOX-like 1-4 are copper-dependent matrixmodifying enzymes [1]. The expression of LOX is elevated in many human cancers, including breast cancer and correlates with tissue hypoxia. The enzyme plays a critical role in breast cancer metastasis [2]. The goal of the current study was to target LOX with fluorescent and radiolabeled oligopeptides to visualize LOX in preclinical models of breast cancer.
Methods: mRNA expression of all 5 LOX family members was analyzed by gene expression microarray analysis on samples from 176 breast cancer patients. The peptidic substrate GGGDPKGGGGG was selected to target LOX [3]. The peptide was labeled with either FITC for confocal microscopy experiments or with the positron emitter fluorine-18 for molecular imaging in vivo using positron emission tomography (PET) (Figure 1). The preclinical breast cancer models utilized were the murine breast cancer cell line EMT-6 and xenografts of MCF-7 and MDAMB-231.
Results: Immunofluorescence with a LOX-specific antibody confirmed that LOX protein expression is enhanced in hypoxic EMT-6 cells. FITC-labeled oligopeptide binds to several cell compartments of EMT6 cells under hypoxic conditions. After injection of 18F-labeled oligopeptide, radioactivity uptake was visible in all three breast cancer models in vivo with SUV5min values of: 0.70±0.07 (n=3) in EMT-6, 0.57±0.01 (n=3) in MCF-7 and 0.68 (n=2) in MDA-MB-231. The following continuous washout of radioactivity led to SUV60min values of: 0.18±0.03 (n=3) in EMT-6, 0.14±0.02 (n=3) in MCF-7 and 0.13 (n=2) in MDA-MB-231. Tumor uptake was reduced by pre-dosing with the irreversible LOX inhibitor BAPN 4 h and 24 h prior to injection of the radiotracer.
Conclusions: These data support further investigations towards the development of LOX-binding peptides as molecular probes for imaging of LOX expression in breast cancer.
Acknowledgements: The access to the Alberta Cancer Foundation-supported CBCF Tumor Bank is well appreciated.
References
[1] Payne SL, et al (2007) J. Cell. Biochem.101, 1338-54.
[2] Erler JT, et al (2006) Nature 440, 1222-6.
[3] Nagan N and Kagan HM (1994) J. Biol. Chem. 269, 22366-71.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S204
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22088 - Permalink


Fast 18F-fluoroethylation without azeotropic drying in the radiosynthesis of cyclooxygenase-2 inhibitors
Kniess, T.; Laube, M.; Pietzsch, J.; Steinbach, J.;
Objectives: 18F-Fluoroethylation is a basic approach in PET labeling chemistry and 2-[18F]fluoroethyl tosylate ([18F]FETs) is one of the mostly used agents. Usual protocols with [18F]FETs are covering the azeotropic drying of [18F]fluoride, nucleophilic substitution, purification and 18F-fluoroethylation within 60-90 min synthesis time. We developed a fast 18F-fluoroethylation avoiding azeotropic drying to yield e.g. 18F-fluoroethylated cyclooxygenase-2 (COX-2) inhibitors within 25 min.
Methods: Our approach is based on the finding that [18F]fluoride trapped on SAX cartridges can be completely eluted by a mixture of K222/K2CO3/acetonitrile/2% water and is bsufficiently reactive for 18F-labeling. [1,2] [18F]Fluoride, trapped on the SAX cartridge is eluted with 0.7 mL K222/K2CO3/acetonitrile/H2O into a vial containing 20 μmol bis-tosylate precursor. The vial is heated 10 min at 100°C, than 20 μmol hydroxyl precursor and 40 μmol Cs2CO3 dissolved in 0.5 mL DMF are added. Additional heating for 10 min at 110°C yields the 18Ffluoroethylated COX-2 radiotracers, by almost complete consumption of [18F]FETs. We used three different precursors to build COX-2 inhibitors (Fig) as model compounds to elucidate 18F-fluoroethylation.
Results: By elution of the SAX cartridge (46 mg) with K222/K2CO3/acetonitrile/H2O (42 μmol, 21 μmol, 679 μL, 21 μL) the adsorbed activity could be tranferred nearly quantitatively (93-95%). [18F]FETs was formed in 79-88% rcy as confirmed by radio-TLC. Subsequent 18F-fluoroethylation of the corresponding hydroxyl precursors resulted in yields of 77-92% (n=7) in case of the cyclopentene (1), 54-65% (n=3) for the pyrazolo[1,5-b]pyridazine (2), and 44-70% (n=3) for the indomethacine (3).
Conclusions: The [18F]KF/K222/K2CO3/H2O complex, formed without azeotropic drying is highly reactive to form [18F]FETs in yields up to 88%. Hence the reaction time can be shortened resulting in fast 18F-fluoethylations with total radiochemical yields up to 92% as exemplified for three radiolabeled COX-2 inhibitors.
References
[1] Wessmann S.H. et al., Nuklearmedizin, 2012, 51, 1-8
[2] Kolb H.C. et al., J.Label.Compd.Radiopharm.,2011, 54, S518
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S169
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22087 - Permalink


18F-Radiolabeling of Second Generation EphB4 Inhibitors Based on Bis-anilinopyrimidines
Mamat, C.; Wiemer, J.; Mosch, B.; Pietzsch, J.; Steinbach, J.;
Objectives: Ephrins and its Eph receptors are dysregulated in several human tumor entities including malignant melanoma. In this regard, the EphB4/ephrinB2 system seems to play a major role in melanoma angiogenesis [1].
Thus,we developed a fluorine-18-containing peptide [2] extracellularly binding to EphB4 and a small 18F-labeled molecule which intracellularly binds to the EphB4 kinase domain with high affinity [3] in the past. However, the results showed low binding/uptake in A375EphB4 melanoma cells in vitro and in vivo. Therfore, a “second generation” lead structure based on bis-anilinopyrimidines (IC50 = 1.3 nM) [4] was chosen for novel EphB4-targeted radioligands.
Methods: The lead compound is based on two substructures (part A and B) which were synthesized independently. Two positions of the original inhibitor for the best position of the radiolabel were figured out using docking studies. Based on this, references 2 and 4 as well as precursors 1 and 3 were obtained. In order to introduce [18F]fluoride by ring opening, precursors 1 and 3 were prepared as azetidinium mesylates and lead to high RCYs.
The radiolabeling was done in anhydrous acetonitrile for 30 min at 100°C. Afterwards, the EOE protecting group, which is mandatory for the successful introduction, was cleaved under acidic conditions. The subsequent purification should be easy done by cartridges due to the ionic nature of the precursors [5].
Results: Interestingly, radiofluorination of the first precursor 1 did not lead to the desired tracer [18F]2. The delocalization of the positive charge over both aromatic rings might be the reason for this result. On the other hand, radiofluorination of diazaspirononane precursor 3 was successful and gives the desired [18F]4 in a radiochemical yield of 34% (n.d.c.) and high purity (>95%).
Conclusions: [18F]4 as novel potential EphB4-targeted radioligand based on the bis-anilinopyrimidine scaffold has been successfully synthesized and radiolabeled. Ongoing work is focused on the alternative preparation of radiotracer [18F]2 and on the biological evaluation of both radiotracers to be a suitable target for diagnostic applications.
References
[1] Mosch, B. et al. (2010), J. Oncol., DOI: 10.1155/2010/135285,
[2] Pretze, M., et al. (2013) ChemMedChem, 8, 935–945,
[3] Mamat, C., et al. (2012) ChemMedChem, 7, 1991–3002,
[4] Bardelle, C., et al. (2010) Bioorg. Med. Chem. Lett., 20, 6242–6245,
[5] Grosse-Gehling, P., et al. (2011) Radiochim. Acta 99, 365–373
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S166
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22086 - Permalink


18F-Labeling and Radiopharmacological Evaluation of Novel Purinedione Multi-Eph Inhibitors
Mamat, C.; Pretze, M.; Neuber, C.; Mosch, B.; Steinbach, J.; Pietzsch, J.;
Objectives: The overexpression of various Eph receptors in tumors provokes the recent interest in highly affine inhibitors as attractive leads for the development of new targeted radioligands to image cancer [1]. Selective Ephtyrosine
kinase inhibitors based on the purinedione skeleton have been explored in the past as potential probes for imaging of EphB4 [2] and a SNEW peptide for EphB2 [3]. However up to now, there is still no optimal radiotracer
available. Herein, we report the synthesis, radiofluorination and biological evaluation of two novel purinedione derivatives as potential multi Eph inhibitor radioligands.
Methods: Based on known positions for affinity-related interactions of the lead structure with the receptor [4] two positions are favorable for the labeling with fluorine-18. Two precursors 1 and 3 as well as their reference compounds 2 and 4 were prepared. The radiolabeling was done in dry ACN at 100°C for 30 min. First cell association studies were performed using various Eph expressing melanoma cells (A375wt/mock, A375EphB4,
A375EphB6, A375EphB4) and Eph-negative controls (HL-60).
Results: After labeling, both tracers [18F]2 and [18F]4 were obtained in 10 – 15 % RCY (n.d.c.) after HPLC separation (RCP: > 95%). Cell experiments in vitro revealed a substantial cell association of both [18F]2 and [18F]4 ranging from 40 to 50 %ID/mg protein at 120 min in all cell lines used. The lack of any significant difference between wild type, recombinant and control cells is indicative for cell association of, as expected, low selectivity, but also of low specificity. The latter is consistent with the observation that preincubation with 100 μM of nonradioactive compound did not result in substantial inhibition of cell association.
Conclusions: [18F]2 and [18F]4 were synthesized successfully and first in vitro experiments were accomplished showing substantial cell association for both tracers in various melanoma cells. However, the cell experiments revealed data on specificity of purinedione derivatives that are contradictory to data from literature [4]. These observations will be elucidated in ongoing studies.
Acknowledgements
References
[1] Mosch, B. et al. (2010), J. Oncol., DOI: 10.1155/2010/135285;
[2] Mamat, C. et al. (2012), ChemMedChem, 7, 1991–2003;
[3] Pretze, M., et al. (2013) ChemMedChem, 8, 935–945; [4] Lafleur, K. et al.
(2009) J. Med. Chem., 52, 6433–6446.
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S165
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22085 - Permalink


First-in-human PET quantification study of cerebral α4β2* nicotinic acetylcholine receptors using the novel specific radioligand (−)-[18F]Flubatine
Sabri, O.; Becker, G.-A.; Meyer, P. M.; Hesse, S.; Wilke, S.; Graef, S.; Patt, M.; Luthardt, J.; Wagenknecht, G.; Hoepping, A.; Smits, R.; Franke, A.; Sattler, B.; Habermann, B.; Neuhaus, P.; Fischer, S.; Tiepolt, S.; Deuther-Conrad, W.; Barthel, H.; Schönknecht, P.; Brust, P.;
α4β2* nicotinic receptors (α4β2* nAChRs) could provide a biomarker in neuropsychiatric disorders (e.g., Alzheimer's and Parkinson's diseases, depressive disorders, and nicotine addiction). However, there is a lack of α4β2* nAChR specific PET radioligands with kinetics fast enough to enable quantification of nAChR within a reasonable time frame. Following on from promising preclinical results, the aim of the present study was to evaluate for the first time in humans the novel PET radioligand (−)-[18F]Flubatine, formerly known as (−)-[18F]NCFHEB, as a tool for α4β2* nAChR imaging and in vivo quantification.
Dynamic PET emission recordings lasting 270 min were acquired on an ECAT EXACT HR+ scanner in 12 healthy male non-smoking subjects (71.0 ± 5.0 years) following the intravenous injection of 353.7 ± 9.4 MBq of (−)-[18F]Flubatine. Individual magnetic resonance imaging (MRI) was performed for co-registration. PET frames were motion-corrected, before the kinetics in 29 brain regions were characterized using 1- and 2-tissue compartment models (1TCM, 2TCM). Given the low amounts of metabolite present in plasma, we tested arterial input functions with and without metabolite corrections. In addition, pixel-based graphical analysis (Logan plot) was used. The model's goodness of fit, with and without metabolite correction was assessed by Akaike's information criterion. Model parameters of interest were the total distribution volume VT (mL/cm3), and the binding potential BPND relative to the corpus callosum, which served as a reference region.
The tracer proved to have high stability in vivo,with 90% of the plasma radioactivity remaining as untransformed parent compound at 90 min, fast brain kinetics with rapid uptake and equilibration between free and receptor bound tracer. Adequate fits of brain TACs were obtained with the 1TCM. VT could be reliably estimated within 90 min for all regions investigated, and within 30 min for low-binding regions such as the cerebral cortex.
The rank order of VT by region corresponded well with the known distribution of α4β2* receptors (VT [thalamus] 27.4±3.8, VT [putamen] 12.7±0.9, VT [frontal cortex] 10.0±0.8, and VT [corpus callosum] 6.3±0.8). The BPND, which is a parameter of α4β2* nAChR availability, was 3.41±0.79 for the thalamus, 1.04±0.25 for the putamen and 0.61 ± 0.23 for the frontal cortex, indicating high specific tracer binding. Use of the arterial input function without metabolite correction resulted in a 10% underestimation in VT, and was without important biasing effects on BPND.
Keywords: (−)-[18F]Flubatine [(−)-[18F]NCFHEB] PET α4β2* nicotinic acetylcholine receptors Human brain Kinetic modeling

Publ.-Id: 22084 - Permalink


Radiosynthesis of [18F]cabozantinib and [18F]fluoroethyl-sunitinib: two RTK-inhibitors of VEGFR-2
Schwebe, M.; Bergmann, R.; Steinbach, J.; Pietzsch, J.; Kniess, T.;
Objectives: Radiolabeled inhibitors of the angiokinase VEGFR-2 might be suitable probes for monitoring induction of angiogenesis and anti-angiogenic therapy response in vivo with PET. [1,2]. We selected two VEGFR-2 inhibitors, cabozantinib (IC50, 0.03 nM) and sunitinib (IC50, 9.0 nM), both bearing a fluorine substituent, as lead structures for 18F-radiolabeled PET tracers.
Methods: [18F]Cabozantinib is synthesized by a 3-step radiosynthesis with final condensation of 4-[18F]fluoroaniline with an acyl chloride precursor. 4-[18F]Fluoroaniline is formed by substitution of 1,4-dinitrobenzene with [18F]fluoride, subsequent reduction of the intermediate 4-[18F]fluoro-nitrobenzene with Pd/C and NaBH4. Since [18F]sunitinib is not accessible via direct nucleophilic 18F-substitution, we developed the 5-fluoroethylated derivative (IC50, 9 nM) as well the corresponding radiolabeled analogue.
Results: 4-[18F]fluoroaniline was obtained in >60% rcy starting from [18F]fluoride after SPE purification. [18F]Cabozantinib was formed by reaction of 4-[18F]fluoroaniline with 10 mg of acyl precursor in THF at rt in >90% rcy. HPLC purification delivered [18F]cabozantinib in 95% purity and specific activity >20 GBq/μmol. Reaction of the methanesulfonyl-substituted sunitinib precursor with [18F]fluoride resulted in 8% 18F-incorporation. HPLC purification yielded [18F]fluoroethyl-sunitinib in 100 MBq scale. First in vitro investigations on VEGFR-2 expressing human A 2058 melanoma cell line showed cellular uptake of [18F]cabozantinib up to 790±100 %ID/mg protein at 60 min that could be significantly blocked by 46±3% by its non-radioactive counterpart (10 μM). For [18F]fluoroethyl-sunitinib the uptake reached 340±48 %ID/mg protein at 60 min. Stability tests in rat blood over 60 min revealed almost no metabolism for both radiotracers.
Conclusions: With the reliable radiosynthesis of [18F]cabozantinib and [18F]fluoroethyl-sunitinib two radiolabeled VEGFR-2 inhibitors with nano- and sub-nanomolar affinity and high in vivo stability are available.
Acknowledgements
References [1] Slobbe P. et al (2012) Drug Discov. Today, 17, 1175-1187
[2] Kniess T. (2012) Curr Pharm Des, 18, 2867-2874
  • Poster
    21st Internation Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S159
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22083 - Permalink


An attractive method for radiolabeling antibodies with Tc-99m
Wunderlich, G.; Naumann, A.; Schubert, M.; Pietzsch, H.-J.;
Objectives: Radiolabeled Cetuximab (C225, Ab) is an attractive tool for tumor targeting and delivering of particles for therapy or imaging applications of EGFR positive tumors. The labeling of Ab with radionuclides requires suitable chelating agents for a stable binding of the radionuclides. Well known is the Ab labeling with In-111 (imaging) and Y-90 (therapy). The aim of the present study was to develop a sufficient radiolabeling technique of this Ab with Tc-99m for SPECT imaging. A second label with a fluorescent dye (Alexa 488) enables to track the uptake of the compound with fluorescent microscopy.
Methods: NOTA (2,2',2''-(1,4,7-triazonane-1,4,7-triyl)triacetic-acid) was linked to C225 and labeled with the [Tc-99m]Tc(H2O)3(CO)3 complex that was made by a standard tricarbonylkit preparation [1]. For preparation of [Tc-99m]Tc(CO)3-NOTA-C225-Alexa(488) (figure 1) and [Tc-99m]Tc(CO)3-NOTA-C225 1 nM of the modified antibody was incubated with up to 1 GBq [Tc-99m]Tc(H2O)3(CO)3 complex and was shaken for 2 h at 40°C. The product was isolated by gelfiltration and tested for yield and stability with ITLC (Silica gel impregnated glass fiber sheets, Varian) in 5% acetic acid. The cell membrane binding and cell uptake of the compound was detected with Cetuximab receptor positive A431 cells and Cetuximab negative MDA cells. For comparison the pure NOTA ligand and unmodified Cetuximab were labeled with [Tc-99m]Tc(H2O)3(CO)3.
Results: NOTA-C225-Alexa(488), NOTA-C225 and NOTA ligand were successfully labeled with [Tc-99m]Tc(H2O)3(CO)3. Sufficient radiolabeling of Cetuximab was achieved and determined by ITLC. Yields: [Tc-99m]Tc-NOTA-C225-Alexa(488) 25-30% and [Tc-99m]Tc-NOTA-C225 50-60%. After purification the labeled compound is stable in cell culture medium and phosphate buffered saline to 24 h with a release of about 20%. Maximum membrane uptake at A431cells is determined after 1 h followed by a partly internalization into the cells. The affinity constant was found Kd = 3.71 nM and Bmax = 35 nM. Already after 1 h the localisation of NOTAC225-Alexa(488) is visualized with fluorescence microscope at cell membrane.
Conclusions: NOTA-Cetuximab can be radiolabeled with Tc-99m which is an interesting approach for SPECT studies in Nuclear Medicine besides the Ab labeling with Ga-68 or Cu-64.
Acknowledgements
References [1] Alberto, R. et al. (1998) J. Am. Chem. Soc., 120, 7987-7988.
  • Poster
    21st Internatioonal Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S105
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22082 - Permalink


Potential labeling strategies with NCA 197(m)Hg
Walther, M.; Wang, C.; Bergmann, R.; Pietzsch, H.-J.; Steinbach, J.;
Objectives: The decay properties of both nuclear isomers, like convenient half life 197mHg (T1/2 = 23.8 h, Eγ 133.98 keV, 33.5%) and 197Hg (T1/2 = 64.14 h, Eγ 77.4 keV, 18.7%), low energy gamma radiations for imaging and numerous Auger- and conversion electrons useful for therapy combined with unique chemical and physical properties of mercury and its compounds represent the motivation for this project. The no carrier added (NCA) radionuclide 197(m)Hg is accessible in sufficient quantity and quality for radiopharmaceutical research by irradiation of gold with protons using a cyclotron [1]. As the following logical step after examination of the production feasibility, the search for a suitable labeling tool was intensified.
Methods: Three different approaches to prepare a stable labeling unit at NCA level with 197(m)Hg were studied. The reactivity of the mercury(II) ions towards sulfur containing ligands (a), solvomercuration of alkenes (b) and electrophilic aromatic substitution (c) were investigated in this context. Prepared characteristic representatives of all three groups are shown in Figure 1.
Results: For all studied reactions the desired 197(m)Hg labeled compounds were detected. The mercury thiolate complexe (a) and the product of solvomercuration (b) show low stability in the presence of competing thiol ligands and therefore the suitability for radiopharmaceutical applications is not given. In contrast, diphenylmercury (c) as the simplest representative for symmetric diarylmercury compounds shows high stability against competing
ligands.
Conclusions: As a basis for the development of a convenient labeling method different kinds of mercury compounds were prepared and characterized at NCA level. After nuclide production this was the required succeeding part of the evaluation of the cyclotron-based NCA 197(m)Hg regarding their suitability for diagnostics and therapy of tumors. First promising results of investigations concerning the development of mercury compounds stable in vivo will be reported.

References: [1] Walther, M., Preusche, S., Bartel, S., Wunderlich, G., Freudenberg, R., Steinbach, J., Pietzsch, H.-J., Theranostic mercury: 197(m)Hg with high specific activity for imaging and therapy (2014) Appl. Radiat. Isot. submitted
  • Poster
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S99
    DOI: 10.1002/jlcr.3302_2

Publ.-Id: 22081 - Permalink


68Ga-DATATOC: Synthesis, radiolabeling and first in vivo studies
Waldron, B.; Seemann, J.; Sinnes, J.-P.; Bergmann, R.; Nagel, J.; Rösch, F.;
Objectives: 68 Ga-DOTATOC is currently used as standard for diagnostic imaging of neuroendocrine tumors (NETs) and its metastases. Radiolabeling can be performed manually and automated at 95 °C. In order to approach application of 68 Ga following a kit-type procedure, a DATA-based chelator (6-Amino-1,4-diazepine-triacetate) was used as it has shown to radiolabel under very mild conditions. Conjugation with TOC may enable radiolabeling of the peptide at room temperature.
Methods: DATATOC was synthesized in a seven step synthesis. Radiolabeling with 68 Ga was performed manually at room temperature and stability was assessed in human serum. An automated setup was also examined, using the Modular-Lab eazy (Eckert & Ziegler, Berlin, Germany). First in vivo studies using MPC-mCherry tumor bearing mice were performed and compared with 68 Ga-DOTATATE.
Results: Radiolabeling was performed at room temperature using N2 solution, NaOAc-buffer and 14 nmol DATATOC. Within 3 min a RCY of 96.3 ± 1.2 % was obtained. Stability was tested in human serum over a period
of 2 h (Δ = 1.3 %). Automated labeling with 23 nmol precursor achieved quantitative complexation of 68 Ga (> 99 %). In vivo PET/CT-studies with 68Ga-DATATOC indicate a high specific uptake in the tumor region after 10 min (SUV of 3.73 ± 1.49). In a blocking study with OC, the SUV in the tumor was reduced to 0.45 ± 0.15. In addition, 68 Ga-DATATOC showed high stability in mouse plasma with 93.7 % of the tracer remaining intact after 120 min. Compared to 68 Ga-DOTATATE a faster renal excretion of the tracer was observed.
Conclusions: DATATOC can be labeled with 68 Ga in a manual or automated setup rapidly at room temperature, offering significant advantages over similar DOTA-based derivatives. Because of quantitative labeling yields, product purification is unnecessary. Furthermore, first in vivo studies confirm excellent targeting and excretion characteristics for the novel tracer. With the perspective towards a kit-type formulation, the superior characteristics
of this new compound pave the way for a new generation of 68 Ga radiopharmaceuticals.
  • Lecture (Conference)
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S15
    DOI: 10.1002/jlcr.3302_1

Publ.-Id: 22080 - Permalink


A novel pretargeting system based on complementary L-oligonucleotides
Schubert, M.; Foerster, C.; Bergmann, R.; Sihver, W.; Vonhoff, S.; Klussmann, S.; Bethge, L.; Walther, M.; Pietzsch, J.; Pietzsch, H.-J.; Steinbach, J.;
Objectives: High metabolic stability, low immunogenicity and negligible specificity for naturally binding partners are predominant characteristics of L-configured oligonucleotides. These advantages predestine this substance class
for its use in pretargeted radioimmunotherapy as in vivo recognition system between a tumor-specific antibody and a radiolabeled chelate. We evaluated this new pretargeting system consisting of 64Cu labeled NOTA-L-DNA-10kDa-PEG and c-L-DNA modified Cetuximab (C225) in vitro and in vivo.
Methods: C225 was functionalized with NOTA, maleimide moieties and thiol-bearing c-L-DNA. Competition studies were carried out against 64Cu labeled standard NOTA3-C225 in FaDu and A431-cell lysates. In vitro pretargeting studies were done in intact FaDu and A431 cells. PET and biodistribution studies were performed both in FaDu and A431 tumor bearing mice by intravenous injection of 4 nmol NOTA3-C225-(c-L-DNA)1,5 and 1 nmol [64Cu]Cu-NOTA-L-DNA-10kDa-PEG 24 h later.
Results: We synthesized two Cetuximab derivatives with 1.5 and respective 5 c-L-DNA molecules per antibody. Competition assays showed that affinities are not affected as a result of conjugation with NOTA and c-L-DNA.
PET studies injecting only [64Cu]Cu-NOTA3-C225-(c-L-DNA)1.5 revealed that a pretargeting interval of 24 h is the best compromise between tumor accumulation, blood background as well as liver uptake. Biodistribution in pretargeted A431 tumor mice is characterized by decreased tumor uptake (see figure). Internalization of antibody within waiting period is the obvious reason and could be confirmed by cellular uptake studies. After 24 h over 2/3 of surface bound antibody was internalized.
Conclusions: The present pretargeting concept shows high potential for further preclinical studies. Use of a noninternalizing antibody is necessary to enhance both tumor uptake and tumor to background ratios.
  • Lecture (Conference)
    21st International Symposium on Radiopharmaceutical Sciences (ISRS), 26.-31.05.2015, Columbia/Missouri, USA
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 58(2015), S14
    DOI: 10.1002/jlcr.3302_1

Publ.-Id: 22079 - Permalink


An Image Reconstruction Framework and Camera Prototype Aimed for Compton Imaging for In-vivo Dosimetry of Therapeutic Ion Beams
Schoene, S.; Enghardt, W.; Fiedler, F.; Golnik, C.; Pausch, G.; Rohling, H.; Kormoll, T.;
Prompt gamma-ray imaging in hadron therapy is a novel approach for range verification. Due to the high energy of prompt gamma-rays emitted during therapeutic irradiation in the order of MeV, Compton imaging is a feasible method. In this work, an imaging prototype together with a data handling and an image reconstruction framework are presented. Data and reconstructed images from laboratory measurements are shown and evaluated. A spatial resolution of 7 mm in a distance of 7 cm has been achieved. More importantly, current limitations were identified for further work. It has been shown that an assumption on the unknown initial photon energy can considerably improve the imaging result.
Keywords: Compton camera, dosimetry, dose monitoring, Compton camera imaging, hadron therapy, cadmium zinc telluride, image reconstruction, system matrix

Publ.-Id: 22078 - Permalink


Evidence of a distinct Permian thermal event by EMP-Th-Pb-monazite ages in metapelites of the polymetamorphic Austroalpine basement
Schulz, B.; Zimmermann, R.; Krenn, E.;
During the Alpine orogeny, the Austroalpine basement complex of the Eastern Alps was thrusted upon the Penninic ophiolites and the European basement, now exposed in the Tauern and Engadine tectonic windows. The Austroalpine basement underwent a polymetamor- phic evolution since the Early Paleozoic. An Ordovi- cian-Silurian event, the Devonian-Carboniferous Var- iscan orogeny, as well as the Cretaceous and Tertiary Alpine orogenic periods have been recognised in many parts. Although a wealth of radiometric data on these events exist, a distinct Permian metamorphic episode has not yet been established. Corresponding mica cool- ing ages were considered as Variscan-to-Alpine “mixed ages” in this polymetamorphic frame. However, the intrusion of Permian pegmatites between 270-250 Ma is an important marker of the tectonic and magmatic activity (Schuster et al. 2001).

The Permian pegmatites can be traced from the Ortler- Campo basement through the basement to the south of the Tauern Window toward the East into the Saualpe and Koralpe units. The electron microprobe (EMP) Th-U-Pb monazite dating method (Montel et al. 1996) has been applied to the garnet-bearing metapelitic host rocks of these Permian pegmatites. In the Saualpe, the Permian pegmatites were strongly deformed during the eclogite-facies Cretaceous event. In the metapelitic host rocks, the Permian monazites have the largest grain sizes and abundance. They are often character- ised by spectacular coronas of apatite and allanite of a partial decomposition.

In the Schobergruppe and the Defereggen Alps to the south of the Tauern Window, the Permian monazites are a less prominent population, but clearly distinct from the Carboniferous monazites (Krenn et al. 2012). The characteristic coronas around the Permian mona- zites are lacking. Permian monazites occur mainly in a zone with fibrolitic sillimanite and andalusite in the vicinity of the pegmatites.

The Oetztal-Stubai basement to the W of the Tauern Window is characterised by a Cretaceous metamor- phic overprint. Permian pegmatites have not yet been reported. The monazite Th-U-Pb EMP ages in the Sellrain area and in the central Oetztal valley (Umhau- sen, Sölden) in the northern vicinity of the Cretaceous metamorphic zone are mostly Carboniferous. They are interpreted to be related to a Variscan amphibolite- to-eclogite-facies garnet crystallisation (Rode et al. 2012). Recent investigations in the Stubai valley re- vealed garnet metapelites with exclusively Permian monazites. These monazites are often surrounded and partly replaced by coronas of apatite and allanite. The mineral-chemical properties and the special character of the dating method allow the conclusion that the Permian monazites represent a distinct crystallisation event at low pressures, apparently in an occasional association to the pegmatites.

References

Krenn, E., Schulz, B. & Finger, F. (2012): Three generations of monazite in Austroalpine basement rocks to the south of the Tauern Window – evidences for Variscan, Permian and Alpine metamorphism. – Swiss Journal of Geosci- ences, 105, DOI 10.1007/s00015-012-0104-6.

Montel, J.-M., Foret, S., Veschambre, M., Nicollet, C. & Provost, A. (1996): A fast, reliable, inexpensive in-situ dating technique: Electron microprobe ages on monazite. – Chem. Geol., 131: 37-53.

Rode, S., Rösel, D. & Schulz, B. (2012): Constraints on the Variscan P-T evolution by EMP Th-U-Pb monazite dat- ing in the polymetamorphic Austroalpine Oetztal-Stubai basement (Eastern Alps). – Z. Dt. Ges. Geowiss. 163: 43- 67; Stuttgart.

Schuster, R., Scharbert, S., Abart, R. & Frank, W. (2001): Permo-Triassic extension and related HT/LP metamor- phism in the Austroalpine - Southalpine realm. – Mitt. Ges. Geol. Bergbaustud. Österr., 45: 111-141; Wien.
  • Poster
    GeoFrankfurt 2014, 21.-24.09.2014, Frankfurt/Main, Deutschland

Publ.-Id: 22077 - Permalink


Numerical Simulation of the Copper Slag Cleaning Process
Yang, H.; Wolters, J.; Pischke, P.; Solters, H.; Fröhlich, J.; Eckert, S.;
Slags from smelting of copper still contains up to 20 % of copper inclusions, which can to some extend be recovered by a special cleaning process. The long-term goal of the authors is to use numerical MHD to simulate the complex slag cleaning process in detail and to optimize it. The paper presents preliminary results on simplified test cases and configurations.
It turned out when simulating the copper droplets in the slag by a discrete phase model, the pure stochastic parcel collision algorithm in FLUENT failed to provide mesh-independent and precise results for inter-droplets collisions and coalescence. Therefore, a new hybrid collision algorithm and the updated coalescence regimes were implemented in FLUENT. Several benchmark tests were reported in order to demonstrate the significant differences between the two algorithms and the main advantages of the new hybrid algorithm for simulations on the slag cleaning process.
Keywords: EM stirring, collision model, copper slag cleaning, MHD
  • Poster
    8th International Conference on Electromagnetic Processing of Materials (EPM), 12.-16.10.2015, Cannes, France
  • Contribution to proceedings
    8th International Conference on Electromagnetic Processing of Materials (EPM), 12.-16.10.2015, Cannes, France, 978-2-9553861-0-1, 255-258

Publ.-Id: 22076 - Permalink


Simulation of the Gamma Radiation Distribution Emitted from a PWR Core under Severe Accident-Like Conditions
Brachem, C.; Schmidt, S.; Konheiser, J.; Hampel, U.;
Using a generic model of a pressurized water reactor, we have defined a set of severe accident-like reactor states depicting various degrees of coolant level decrease and core degradation. We then computed the gamma radiation distribution which would occur outside the reactor pressure vessel in each of the previously defined states using stationary Monte Carlo simulations. This is done in an effort to understand if it is possible to detect the occurrence of certain phenomena from outside the RPV and to eventually develop a system for state detection.
Keywords: accident, Monte Carlo simulation, gamma radiation
  • Lecture (Conference)
    46th Annual Meeting on Nuclear Technology, 05.-07.05.2015, Berlin, Germany

Publ.-Id: 22075 - Permalink


Feasibility assessment of the once-through Thorium fuel cycle for the PTVM LWR concept
Rachamin, R.; Fridman, E.; Galperin, A.;
This paper investigates the feasibility of a once-through thorium fuel cycle for the novel reactor-design concept named the pressure tube light water reactor with variable moderator control (PTVM LWR). The PTVM LWR operates in a “breed & burn” mode, which makes it an attractive system for utilizing thorium fuel in a once-through mode. The “breed & burn” mode can emphasize the in-situ generation as well as incineration of 233U, which are the basic foundations of the once-through thorium fuel cycle. The PTVM LWR concept makes use of a seed-blanket geometry, whereby the core is divided into separated regions of thorium-based fuel channel assemblies (blanket) and low-enriched uranium (LEU) based fuel channel assemblies (seed). A novel fuel in-core management scheme based on two separate fuel flow routes (i.e., seed route and blanket route) is proposed and analyzed. Neutronic performance analysis indicates that the proposed novel fuel in-core management scheme has the potential to utilize both LEU- and thorium- based fuel in an efficient manner. The once-through thorium cycle, presented and discussed in this paper, provide interesting research leads and can serve as a bridge between current LEU-based fuel cycles and a thorium fuel cycle based on recycling of 233U.
Keywords: pressure tube reactor, “breed & burn”, moderator variation, seed-blanket geometry, once-through thorium fuel cycle

Publ.-Id: 22074 - Permalink


A single-strand annealing protein clamps DNA to detect and secure homology
Ander, M.; Subramaniam, S.; Fahmy, K.; Stewart, F.; Schäffer, E.;
Repair of DNA breaks by single-strand annealing (SSA) is a major mechanism for the maintenance of genomic integrity. SSA is promoted by proteins (SSAPs) like eukaryotic RAD52 and lambda phage Redß that use a short single-stranded region to find sequence identity and initiate homologous recombination. However, it is unclear how SSAPs detect homology and catalyze annealing. Using single-molecule experiments, we provide evidence that homology is recognized by Redß monomers that weakly hold single DNA strands together. Once annealing begins, dimerization of Redß clamps the double-stranded region and nucleates nucleoprotein filament growth. In this manner, DNA clamping ensures and secures a successful search for DNA sequence homology. The clamp is characterized by a structural change of Redß and a remarkable stability against force up to 200 pN. Our findings not only present a detailed explanation for SSAP action but also identify the DNA clamp as a very stable, non-covalent, DNA-protein interaction.
Keywords: DNA repair; homologous recombination; single strand annealing; conformational proofreading; DNA mechanics; single molecule biophysics; optical tweezers; fluorescence correlation spectroscopy; circular dichroism; recombineering

Publ.-Id: 22073 - Permalink


RMF-driven spin-up flow in a rectangular cavity
Galindo, V.; Nauber, R.; Franke, S.; Räbiger, D.; Czarske, J.; Eckert, S.;
Numerical simulations of a liquid metal flow and corresponding velocity measurements using a dual plane, two-component ultrasound array Doppler velocimeter were carried out in a rectangular cavity with an aspect ratio of unity. The liquid metal (GaInSn) was suddenly exposed to an azimuthal body force generated by a rotating magnetic field (RMF). The measurements show a similar flow structure compared to the case of the RMF-driven flow in a cylindrical container, in particular the so-called initial adjustment phase followed by an inertial phase which is dominated by inertial oscillations of the secondary flow. The transition from the steady double vortex structure of the secondary flow to an oscillating regime was detected at a magnetic Taylor number of T a > 3 × 10^5.
Keywords: Liquid metals, rotating magnetic field, spin-up
  • Contribution to proceedings
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes sur Mer, France
    EPM 2015 8th International Conference on Electromagnetic Processing of Materials, St. Martin d'Héres: SIMAPLaboratory, 978-2-9553861-0-1, 227-230
  • Lecture (Conference)
    8th International Conference on Electromagnetic Processing of Materials, 12.-16.10.2015, Cannes sur Mer, France

Publ.-Id: 22072 - Permalink


Combined PET/MR: The Real Work Has Just Started. Summary Report of the Third International Workshop on PET/MR Imaging; February 17-21, 2014, Tubingen, Germany
Bailey, D. L.; Antoch, G.; Bartenstein, P.; Barthel, H.; Beer, A. J.; Bisdas, S.; Bluemke, D. A.; Boellaard, R.; Claussen, C. D.; Franzius, C.; Hacker, M.; Hricak, H.; La Fougere, C.; Guckel, B.; Nekolla, S. G.; Pichler, B. J.; Purz, S.; Quick, H. H.; Sabri, O.; Sattler, B.; Schafer, J.; Schmidt, H.; van den Hoff, J.; Voss, S.; Weber, W.; Wehrl, H. F.; Beyer, T.;
This paper summarises the proceedings and discussions at the third annual workshop held in Tubingen, Germany, dedicated to the advancement of the technical, scientific and clinical applications of combined PET/MRI systems in humans. Two days of basic scientific and technical instructions with "hands-on" tutorials were followed by 3 days of invited presentations from active researchers in this and associated fields augmented by round-table discussions and dialogue boards with specific themes. These included the use of PET/MRI in paediatric oncology and in adult neurology, oncology and cardiology, the development of multi-parametric analyses, and efforts to standardise PET/MRI examinations to allow pooling of data for evaluating the technology. A poll taken on the final day demonstrated that over 50 % of those present felt that while PET/MRI technology underwent an inevitable slump after its much-anticipated initial launch, it was now entering a period of slow, progressive development, with new key applications emerging. In particular, researchers are focusing on exploiting the complementary nature of the physiological (PET) and biochemical (MRI/MRS) data within the morphological framework (MRI) that these devices can provide. Much of the discussion was summed up on the final day when one speaker commented on the state of PET/MRI: "the real work has just started".
Keywords: Hybrid imaging, Molecular imaging, PET/CT, PET/MRI, PET, MRI, Quantification, Attenuation correction, Oncology, Paediatric oncology, Neurology, Cardiology

Publ.-Id: 22071 - Permalink


The association of tumor-to-background ratios and SUVmax deviations related to point spread function and time-of-flight F18-FDG-PET/CT reconstruction in colorectal liver metastases
Rogasch, J. M. M.; Steffen, I. G.; Hofheinz, F.; Großer, O. S.; Furth, C.; Mohnike, K.; Hass, P.; Walke, M.; Apostolova, I.; Amthauer, H.;
Methods: Fifteen patients (f, 6; m, 9; median age, 59 years; range, 32 to 72 years) with 28 liver metastases were included retrospectively. FDG-PET/CT imaging (median activity, 237 MBq; range, 231 to 252 MBq; median uptake, 61 min; range, 55 to 67 min) was performed on a Siemens Biograph mCT 64 followed by image reconstruction using 3D-ordered subset expectation maximization (3D-OSEM) or 3D-OSEM with PSF modeling - both with and without TOF information. Differences in SUVmax were analyzed using the Friedman test and Wilcoxon test for paired non-parametric data. The correlation of inter-method differences with the lesions’ TBR was studied using Spearman’s rank correlation coefficient (rho). Differences between lesions with low (<4.8) and high (>4.8) TBR were analyzed using the Mann-Whitney U test (TBR measured with 3D-OSEM; binarized by its median).
Background: The maximum standardized uptake value (SUVmax) is a common clinical parameter for quantification in F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), but it is influenced by image reconstruction. The aim of this study was to analyze the association of SUVmax deviations related to point spread function (PSF) and time-of-flight (TOF) reconstruction with tumor-to-background ratios (TBR) in colorectal liver metastases (CRLM).
Results: There was a significant correlation of the lesions’ TBR with relative SUVmax differences related to PSF (PSF + TOF vs. 3D-OSEM + TOF, rho = 0.61; PSF vs. 3D-OSEM, rho = 0.52) or TOF (PSF + TOF vs. PSF, rho = −0.58; 3D-OSEM + TOF vs. 3D-OSEM, rho = −0.61). Accordingly, PSF algorithms only showed higher SUVmax than non-PSF algorithms in lesions with a high TBR (median differences at low/high TBR, +2.6%/+9.1% [PSF + TOF vs. 3D-OSEM + TOF]; +0.7%/+6.4% [PSF vs. 3D-OSEM]). TOF integration also led to higher SUVmax but mainly at low TBR (low/high TBR, +10.4%/+1.8% [PSF + TOF vs. PSF]; +8.6%/−0.1% [3D-OSEM + TOF vs. 3D-OSEM]).
Conclusions: Both PSF and TOF reconstruction resulted in a substantial alteration of SUVmax in CRLM. TOF provided the highest SUVmax increase in low-contrast lesions while - vice versa - PSF showed the most relevant increase in high-contrast lesions. Thus, one should be aware that quantitative analyses of lesions with varying TBR, e.g., in radiotherapy or follow-up studies, may be mainly affected by either PSF or TOF reconstruction, respectively.
Keywords: Colorectal liver metastases; F18-FDG-PET/CT; PSF; Reconstruction algorithm; SUVmax; Target volume definition; TOF; Tumor-to-background ratio

Publ.-Id: 22070 - Permalink


Cutting-edge analytics at DREAMS: Cool application stuff using tandem accelerators
Merchel, S.; Pavetich, S.; Rugel, G.; Ziegenrücker, R.; DREAMS-Users; DREAMS-Friends;
The DREsden Accelerator Mass Spectrometry facility (DREAMS) is in routine operation since autumn 2011 [1, Figure 1].

Figure 1. DREAMS incl. planned Time-of-Flight (ToF) and SIMS connection for TEAMS/Super-SIMS.

Here, long-lived so-called cosmogenic radionuclides such as 10Be, 26Al, 36Cl, 41Ca and 129I can be quantified at the 10-14 (radionuclide/stable nuclide) level. Applications are performed within interdisciplinary cooperations with users from universities and research centres. Hence, research is focussed on topics from e.g. astrophysics [2], climate, cosmochemistry [3,4], geomorphology [5-7], hydrogeology and nuclear decommissioning [8].

To keep DREAMS a state-of-the-art facility in-house research such as the development of a low cross-contamination and memory-effect ion source [9], a high-current ion source and expansion to stable nuclides with (Super-Secondary Ion Mass Spectrometry (SIMS)) or without spatial resolution (Trace Element AMS = TEAMS) is performed. This kind of technology development is partially based on our own research interests, but also driven by the steadily increasing demands of our users.

Quality assurance incl. the use of primary or traceable standards and dedicated AMS chemistry labs accessible for users make DREAMS especially attractive for experienced cosmogenic nuclide researchers but even more for newcomers. Thus, training on the job e.g. in the chemistry labs is an essential tool of our “mission” to widen the fields of AMS applications and user communities.

Ackn.: Operators, S. Akhmadaliev, S. Enamorado Baez & A. Renno for help; DFG/DAAD for funding.

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. Phys. Res. B 2013, 294, 5. [2] J. Feige et al., EPJ Web of Conferences 2013, 63, 03003. [3] U. Ott et al., Meteorit. Planet. Sci. 2014, 49, 1365. [4] J. Llorca, et al., Meteorit. Planet. Sci. 2013, 48, 493. [5] M.C. Fuchs et al., Earth Surf. Dynam. Discuss. 2015, 3, 83. [6] K. Hahne et al., System Erde. GFZ-Journal 2013, 3 (2), 44. [7] R. Zech et al., Palaeogeography, Palaeoclimatology, Palaeoecology 2013, 369, 253. [8] D. Hampe et al., J. Radioanal. Nucl. Chem. 2013, 296, 617. [9] S. Pavetich et al., Nucl. Instr. Meth. Phys. Res. B 2014, 329, 22.
Keywords: accelerator mass spectrometry, radionuclide
  • Poster
    Workshop für Ionenstrahlen und Nanostrukturen 2015, 22.-24.07.2015, Heidelberg, Deutschland

Publ.-Id: 22069 - Permalink


The first four years of DREAMS: Sweet dreams or nightmares?
Merchel, S.; Pavetich, S.; Rugel, G.; Ziegenrücker, R.; DREAMS-Users; DREAMS-Friends;
The DREsden Accelerator Mass Spectrometry facility (DREAMS) is in routine operation since autumn 2011 [1, Figure 1].

Figure 1. DREAMS incl. planned Time-of-Flight (ToF) and SIMS connection for TEAMS/Super-SIMS.

Here, long-lived so-called cosmogenic radionuclides such as 10Be, 26Al, 36Cl, 41Ca and 129I can be quantified at the 10-14 (radionuclide/stable nuclide) level. Applications are performed within interdisciplinary cooperations with users from universities and research centres. Hence, research is focussed on topics from e.g. astrophysics [2], climate, cosmochemistry [3,4], geomorphology [5-7], hydrogeology and nuclear decommissioning [8].

To keep DREAMS a state-of-the-art facility in-house research such as the development of a low cross-contamination and memory-effect ion source [9], a high-current ion source and expansion to stable nuclides with (Super-Secondary Ion Mass Spectrometry (SIMS)) or without spatial resolution (Trace Element AMS = TEAMS) is performed. This kind of technology development is partially based on our own research interests, but also driven by the steadily increasing demands of our users.

Quality assurance incl. the use of primary or traceable standards and dedicated AMS chemistry labs accessible for users make DREAMS especially attractive for experienced cosmogenic nuclide researchers but even more for newcomers. Thus, training on the job e.g. in the chemistry labs is an essential tool of our “mission” to widen the fields of AMS applications and user communities.

Ackn.: Operators, S. Akhmadaliev, S. Enamorado Baez & A. Renno for help; DFG/DAAD for funding.

[1] S. Akhmadaliev et al., Nucl. Instr. Meth. Phys. Res. B 2013, 294, 5. [2] J. Feige et al., EPJ Web of Conferences 2013, 63, 03003. [3] U. Ott et al., Meteorit. Planet. Sci. 2014, 49, 1365. [4] J. Llorca, et al., Meteorit. Planet. Sci. 2013, 48, 493. [5] M.C. Fuchs et al., Earth Surf. Dynam. Discuss. 2015, 3, 83. [6] K. Hahne et al., System Erde. GFZ-Journal 2013, 3 (2), 44. [7] R. Zech et al., Palaeogeography, Palaeoclimatology, Palaeoecology 2013, 369, 253. [8] D. Hampe et al., J. Radioanal. Nucl. Chem. 2013, 296, 617. [9] S. Pavetich et al., Nucl. Instr. Meth. Phys. Res. B 2014, 329, 22.
Keywords: accelerator mass spectrometry, radionuclide
  • Lecture (others)
    Oberseminar des II. Physikalischen Institutes, Universität Göttingen., 03.07.2015, Göttingen, Deutschland

Publ.-Id: 22068 - Permalink


A Droplet Entrainment Model for Horizontal Flows
Höhne, T.;
For heat and mass transfer processes in two-phase flow systems an understanding of the conditions leading to entrainment of a liquid surface film by a gas flow is of considerable practical importance.
Keywords: Entrainment model, AIAD, CFX, multiphase flow
  • Invited lecture (Conferences)
    ANSYS Conference & 33. CADFEM Users‘ Meeting 2015, 25.06.2015, Bremen, Deutschland
  • Contribution to proceedings
    ANSYS Conference & 33. CADFEM Users´ Meeting 2015, 24.-26.6.2015, Bremen, Deutschland
    CD-ROM

Publ.-Id: 22067 - Permalink


Photon emission rates near the critical point in the linear sigma model
Wunderlich, F.; Kämpfer, B.;
Employing the linear sigma model, the effective masses of quasi-particle excitations are found to exhibit significant variations within the phase diagram, which has a critical point at non-zero chemical potential, where a first-order phase transition sets in.
Soft-photon emission rates in lowest order display, for selected channels, a sensible dependence on the effective masses of the involved excitations and let us argue that they could map out the phase diagram.
Keywords: linear sigma model, QCD, phase diagram, photon emission, effective theory, critical point
  • Open Access LogoContribution to proceedings
    9th International Workshop on Critical Point and Onset of Deconfinement, 17.-21.11.2014, Bielefeld, Deutschland
    Proceedings of Science (CPOD2014) 027: Scuola Internazionale Superiore di Studi Avanzati

Publ.-Id: 22066 - Permalink


Ultrasound Doppler measurements in liquid metal two-phase flows
Vogt, T.; Zhang, C.; Strumpf, E.; Eckert, S.; Gerbeth, G.;
Because of the ability to work in opaque fluids and to deliver complete velocity profiles in real time the Ultrasound Doppler Velocimetry (UDV) can be considered as an attractive technique to obtain velocity data from liquid metal flows. This paper presents several examples for UDV measurements in liquid metal two-phase flows. The measuring technique shows the capability to detect both the bubble and the liquid velocity simultaneously. The probability density function of the recorded velocity data was examined to the signals arising from the liquid and the gaseous phase. Multiple reflections of the ultrasonic beam occurring between the gas bubbles at higher gas flow rates may complicate a precise discrimination between both phase velocities. An iterative threshold method was applied to obtain accurate velocity profiles by identifying and excluding artifacts in the signal. Nevertheless, the signal quality deteriorates significantly with increasing gas flow rate.
Bubble-driven flows play a prominent role in many industrial facilities and processes. In metallurgical applications gas bubbles are injected into furnaces, ladles or similar melt containing transfer vessels in order to homogenize the melt and their physical and chemical properties. On the other hand, uncontrolled entrainment of cover gas into the liquid metal in the casting process causes a worsening of the mechanical properties of the casting products. In the field of nuclear engineering, gas entrainment into the coolant is one of the essential safety issues in the design of innovative liquid metal-cooled fast reactors. Model experiments using low-melting metal alloys can be considered as an effective tool to gain a better understanding of the complex character of liquid metal two-phase flows. In this paper, we present exemplary measurements performed at various experimental configurations concerning the behaviour of single bubbles and bubble plumes under the influence of AC and DC magnetic fields and a visualization of gas entrainment at the free surface of a liquid metal.
  • Lecture (Conference)
    3rd International Workshop on Measuring Techniques for Liquid Metal Flows, 15.-17.04.2015, Dresden, Deutschland

Publ.-Id: 22065 - Permalink


Detection of gas entrainment into liquid metals
Vogt, T.; Boden, S.; Andruszkiewicz, A.; Eckert, K.; Eckert, S.; Gerbeth, G.;
Entrainment of cover gas into the liquid metal coolant is one of the principal safety issues in the design of innovative liquid metal-cooled fast reactors. We present generic experimental studies of this phenomenon in low-melting metals. Ultrasonic and X-ray diagnostic tools were considered for a visualization of gas entrainment at the free surface of the melt. Laboratory experiments were conducted using the eutectic alloy GaInSn, which is liquid at room temperature. Vortex-activated entrainment of air at the free surface of a rotating flow was revealed by ultrasonic techniques. X-ray radioscopy was used to visualize the behavior of argon bubbles inside a slit geometry. The measurements reveal distinct differences between water and GaInSn, especially with respect to the process of bubble formation and the coalescence and breakup of bubbles. Our results emphasize the importance of liquid metal experiments which are able to provide a suitable data base for numerical code validation.

Publ.-Id: 22064 - Permalink


Development of highly potent phosphodiesterase 10A (PDE10A) inhibitors: Synthesis and in vitro evaluation of 1,8-dipyridyl- and 1-pyridinol-substituted imidazo[1,5-a]quinoxalines
Wagner, S.; Scheunemann, M.; Dipper, K.; Egerland, U.; Hoefgen, N.; Steinbach, J.; Brust, P.;
Herein we report the synthesis of fluorinated inhibitors of phosphodiesterase 10A (PDE10A) which can be used potentially as lead structure for the development of a F-18 labeled PDE10A imaging agent for positron emission tomography. Fluorine is located in the ortho-postion of pyridine to enable the introduction of F-18 into an appropriate labeling precursor by nucleophilic aromatic substitution for a possible radiosynthesis. 2-Fluoropyridines are introduced by a Suzuki coupling at different positions of the molecule. The reference compounds, 1,8-dipyridylimidazo[1,5-a]quinoxalines and 1-pyridylimidazo[1,5-a]quinoxalines, show inhibitory potencies down to the subnanomolar range and selectivity factors greater than 50. 1,8-Dipyridylimidazo[1,5-a]quinoxalines are more potent inhibitors than 1-pyridylimidazo[1,5-a]quinoxalines. Using 2-fluoro-3-pyridyl as residue gave the most potent inhibitors 11A (IC50 = 0.12 nM), 11B (IC50 = 0.048 nM) and 23 (IC50 = 0.037 nM).
Keywords: PDE10A inhibitor, Imidazo[1,5-a]quinoxalines, PDE10A imaging agent

Publ.-Id: 22063 - Permalink


Interactions between a halophilic archaeon and uranium regarding the final disposal of radioactive waste in salt rock
Bader, M.; Drobot, B.; Müller, K.; Stumpf, T.; Cherkouk, A.;
Regarding the deposit of radioactive waste in a deep geological formation, salt rock is one possibility in Germany. The archaeon Halobacterium noricense was chosen to study the interactions between a halophilic microorganism and uranium. Biosorption experiments showed that this microorganism is able to bind uranium effectively and that the presence of uranium provokes a reaction from the cells. By the use of spectroscopic methods a coordination of uranium to cellular carboxyl and phosphate groups was proven.
  • Poster
    Petrus PhD Conference 2015, Radioative waste management and disposal., 22.-26.06.2015, Nancy, Frankreich
  • Lecture (Conference)
    Petrus PhD Conference 2015, Radioactive waste management and disposal, 22.-26.06.2015, Nancy, Frankreich

Publ.-Id: 22062 - Permalink


Stoichiometry variation for the atomic layer deposition of SrxTiyOz from Sr((Pr3Cp)-Pr-i)(2), Ti[N(CH3)(2)](4) and H2O
Rentrop, S.; Abendroth, B.; Walter, J.; Rensberg, J.; Muenchgesang, W.; Strohmeyer, R.; Stoecker, H.; Ronning, C.; Gemming, S.; Meyer, D. C.;
The atomic layer deposition (ALD) of stoichiometric SrTiO3 as well as layers with either Sr or Ti excess from the commercial precursors Bis(tri-isopropylcyclopentadienyl)-strontium Sr((Pr3Cp)-Pr-i)(2),

Tetrakis-(dimethylamido)titanium(IV) Ti[N(CH3)(2)](4) and H2O on a commercial ALD system is demonstrated. The influence of the stoichiometry on the optical layer properties was investigated.

Spectroscopic ellipsometry shows that all SrxTiyOz layers are transparent up to the optical gap energy, which amounts to 3.87 eV for stoichiometric SrTiO3. A direct correlation between the Sr content, optical properties, layer density and the growth per cycle value was determined. X-ray photoelectron spectroscopy after Ar ion cluster sputtering indicates that the layers are free of carbon. After ex situ annealing under atmospheric conditions we observed a change in microstructure from amorphous to polycrystalline starting at 545 degrees C by atomic force microscopy and grazing incidence X-ray diffraction.
Electrical I-V measurements show very small leakage currents confirming the insulating character of the SrxTiyOz layers.

Publ.-Id: 22061 - Permalink


Nature and distribution of PGE mineralisation in gabbroic rocks of the Lusatian Block, Saxony, Germany
Sandmann, D.; Gutzmer, J.;
We have employed quantitative automated mineralogy using a mineral liberation analyser to assess samples of gabbroic dykes of the Lusatian Block. These mafic dykes contain platinum-group elements - locally enriched with Cu and Ni sulphides up to subeconomic concentrations of 0.4 ppm (4PGE+Au). In this study we analysed about 100 polished thin sections and polished blocks with both a mapping method and a search mode for bright phases in BSE images (sparse phase liberation analysis).
The aim of the study was to obtain information regarding the occurrence of platinum-group minerals (PGM) and their relationship to base metal sulphides (BMS). Mineral groups found by sparse phase liberation analysis include several PGE-bearing and non-PGE-bearing tellurides, Pd bismuthides and antimonides, Pt arsenide as well as native gold and native bismuth. Mineral grain sizes of these trace minerals are in general below 10 mu m. The results of the mineral association evaluation show that pyrrhotite is the main host for tellurides, native metals and platinum-group minerals. However, several other minerals show also a high degree of association with the PGM, most notably Ni-Co sulpharsenides, chalcopyrite, hydrothermal feldspar and chlorite. By using quantitative automated mineralogy we can clearly demonstrate that low-alteration, low-BMS gabbroic dyke samples contain no or only small amounts of PGM, whereas intense-alteration, high-BMS gabbroic dyke samples have elevated PGM contents. Furthermore, we show that for PGE concentrations <1 ppm MLA analyses of just one polished thin section per sample show limitations with respect to the representativity of results for calculated element concentration, due to a combination of different limiting factors. Mineral liberation analysis reveals that PGM are much more widespread and abundant in the studied area compared to the results of previous careful light microscopic investigations and single grain electron probe microanalysis that resulted only in very few and isolated PGM grains to be identified.
Keywords: gabbroic dykes of the Lusatian Block, PGM, BMS

Publ.-Id: 22058 - Permalink


Direct determination of the electron effective mass of GaAsN by terahertz cyclotron resonance spectroscopy
Eßer, F.; Drachenko, O.; Patanè, A.; Ozerov, M.; Winnerl, S.; Schneider, H.; Helm, M.;
We use cyclotron resonance THz-spectroscopy in pulsed magnetic fields up to 63 T to measure the electron effective mass in Si-doped GaAsN semiconductor alloys with nitrogen content up to 0.2%. This technique directly probes the transport properties of the N-modified conduction band, particularly the electron effective mass, which has been discussed controversially in the experimental and theoretical literature. We report a slight increase of the electron effective mass and nonparabolicity with Ncontent for different photon energies in agreement with the two-level band anticrossing model calculations. Furthermore, we show a pronounced electron mobility drop with increasing N-content.
Keywords: GaAsN, effective mass, cyclotron resonance spectroscopy, III-N-V alloy

Publ.-Id: 22057 - Permalink


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