Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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

31745 Publications
Laser cooling of stored relativistic ion beams with large momentum spreads using a laser system with a wide scanning range
Wen, W.; Winters, D.; Beck, T.; Rein, B.; Walther, T.; Tichelmann, S.; Birkl, G.; Sanchez-Alarcon, R.; Ullmann, J.; Lochmann, M.; Nörtershäuser, W.; Clark, C.; Kozhuharov, C.; Kühl, T.; Sanjari, S.; Litvinov, Y.; Giacomini, T.; Steck, M.; Dimopoulou, C.; Nolden, F.; Stöhlker, T.; Yang, J.; Zhang, D.; Ma, X.; Seltmann, M.; Siebold, M.; Schramm, U.; Bussmann, M.;
New results on laser cooling of stored, bunched, relativistic ion beams are presented. For the first time it has been possible to cool an ion beam with large momentum spread without initial electron cooling or scanning of the bunching frequency by using a single cw laser system.
Keywords: laser cooling, ion beams, relativistic, cw laser, scanning, broadband

Publ.-Id: 20791 - Permalink


Cooling of Bunched Relativistic Ion Beams using a CW Laser with a Frequency Scanning Range Greater than the Bucket Acceptance
Bussmann, M. H.; Schramm, U.; Seltmann, M.; Siebold, M.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y. A.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sanchez Alarcon, R. M.; Sanjari, M. S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Winters, D. F. A.; Ma, X.; Wen, W. Q.; Zhang, D.;
With new, all solid-state cw laser sources cooling of relativistic ion beams with a large momentum spread has become possible. We present results on laser cooling of relativistic C3+ ion beams at the Experimental Storage Ring at GSI. In the experiment we used a frequency-quadrupled external-cavity diode laser for scanning over a relative ion momentum spread of dp/p ~ 10-5. We could show that laser cooling with such a system is almost independent of beam current and that the momentum spread reached for various bunching harmonics, bucket depths and beam currents always was found to be comparable to the resolution of the resonant Schottky pickup at ESR. We further found a decrease in Schottky power with decreasing momentum spread and that cooling times were only limited by the scanning time of the laser. The laser cooling technique presented here is of great interest for future heavy ion storage rings as it allows to address ion beams with an initially large momentum spread, thus not requiring initial electron cooling.
Keywords: laser cooling, ion beams, relativistic, esr, fair
  • Poster
    5th International Particle Accelerator Conference, 15.-20.06.2014, Dresden, Deutschland

Publ.-Id: 20790 - Permalink


Cooling Relativistic Ion Beams of initially large Momentum Spread with a fast scanning cw Laser System
Bussmann, M.; Winters, D.; Wen, W.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sánchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Zhang, D.; Loeser, M.; Seltmann, M.; Siebold, M.; Schramm, U.;
We present new results from a recent experiment on laser cooling of relativistic bunched ion beams at the Experimental Storage Ring at GSI. Our results show laser cooling with a single solid-state cw laser system with a laser frequency scanning range larger than the bucket acceptance. This technique is of great importance for future storage ring facilities such as FAIR and HIAF, as it allows for all-optical beam cooling of initially hot ion beams without the need for pre-electron cooling or stochastic cooling.
Keywords: laser cooling, ion beams, relativistic, esr, fair
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion AMOP (SAMOP), 17.-21.03.2014, Berlin, Deutschland

Publ.-Id: 20789 - Permalink


Laser Cooling of Relativistic Ion Beams with Large Momentum Spreads
Bussmann, M.; Winters, D.; Wen, W.; Dimopoulou, C.; Giacomini, T.; Kozhuharov, C.; Kühl, T.; Litvinov, Y.; Lochmann, M.; Nörtershäuser, W.; Nolden, F.; Sánchez, R.; Sanjari, S.; Steck, M.; Stöhlker, T.; Ullmann, J.; Beck, T.; Birkl, G.; Rein, B.; Tichelmann, S.; Walther, T.; Ma, X.; Zhang, D.; Loeser, M.; Seltmann, M.; Siebold, M.; Schramm, U.;
We present new results from a recent experiment on laser cooling of relativistic bunched ion beams at the Experimental Storage Ring at GSI. Our results show laser cooling with a single solid-state cw laser system with a laser frequency scanning range larger than the bucket acceptance. This technique is of great importance for future storage ring facilities such as FAIR and HIRFL, as it allows for all-optical beam cooling of initially hot ion beams without the need for pre-electron cooling.
Keywords: laser cooling, ion beams, relativistic, esr, fair
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM), 30.03.-04.04.2014, Dresden, Deutschland

Publ.-Id: 20788 - Permalink


The Helmholtz Beamline at XFEL - Probing solid density laser-plasma physics with XFELs on the femtosecond scale
Bussmann, M.; Kluge, T.; Huang, L.; Cowan, T. E.;
We show that probing the ionization evolution and plasma dynamics in high power laser interaction with matter on the femtosecond and nanometer scale is in reach with state of the art X-ray lasers at facilities such as LCLS, SACLA and the European XFEL.
We have conducted particle-in-cell simulations including radiative and collisional atomic processes to generate absolute predictions for synthetic scattering images using SAXS and RCXDI techniques. We could show that plasma dynamics from the target front side and bulk can be distinguished and plasma instabilities identified and their development could be temporarily involved. Inclduing atomic physics models from SCFly we could furthermore show that the temporal evolution of the ionization dynamics can be probed by resonant scattering.
Keywords: xfel, hibef, helmholtz beamline, scattering, x-ray, laser, plasma, imaging, simulation
  • Lecture (Conference)
    Strongly Coupled Coulomb Systems, 27.07.-01.08.2014, Santa Fe, NM, United States of America

Publ.-Id: 20787 - Permalink


Direct measurement of the magnetic anisotropy field in Mn-Ga and Mn-Co-Ga Heusler films
Fowley, C.; Ouardi, S.; Kubota, T.; Oguz, Y.; Neudert, A.; Lenz, K.; Sluka, V.; Lindner, J.; Law, J. M.; Mizukami, S.; Fecher, G. H.; Felser, C.; Deac, A. M.;
The static and dynamic properties of tetragonally distorted Mn–Ga based alloys were investigated. Static magnetic properties are determined in magnetic fields up to 6.5 T using SQUID magnetometry. For the pure Mn1.6Ga film, the saturation magnetisation is 0.36 MA/m and the coercivity is 0.29 T. Partial substitution of Mn by Co results in Mn2.6Co0.3Ga1.1. The saturation magnetisation of those films drops to 0.2 MA/m and the coercivity is increased to 1 T. Time-resolved magneto-optical Kerr effect (TR-MOKE) is used to probe the high-frequency dynamics of Mn–Ga. The ferromagnetic resonance frequency extrapolated to zero-field is found to be 125 GHz with a Gilbert damping, $\alpha$, of 0.019. The anisotropy field is determined from both SQUID and TR-MOKE to be 4.5 T, corresponding to an effective anisotropy density of 0.81 MJ/m3. Given the large anisotropy field of the Mn2.6Co0.3Ga1.1 film, pulsed magnetic fields up to 60 T are used to determine the field strength required to saturate the film in the plane. For this, the extraordinary Hall effect was employed as a probe of the local magnetisation. By integrating the reconstructed in–plane magnetisation curve, the effective anisotropy energy density for Mn2.6Co0.3Ga1.1 is determined to be 1.23 MJ/m3.
Keywords: Heusler alloys, Mn-Ga, Hall Effect, Time resolved MOKE, magneto-optics, magnetotransport, high magnetic fields, anisotropy, perpendicular magnetic anisotropy.

Publ.-Id: 20786 - Permalink


The influence of current collectors on Tayler instability and electro-vortex flows in liquid metal batteries
Weber, N.; Galindo, V.; Priede, J.; Stefani, F.; Weier, T.;
The Tayler instability is a kink-type flow instability which occurs when the electrical current through a conducting fluid exceeds a certain critical value. Originally studied in the astrophysical context, the instability was recently shown to be also a limiting factor for the upward scalability of liquid metal batteries. In this paper, we continue our efforts to simulate this instability for liquid metals within the framework of an integro-differential equation approach. The original solver is enhanced by multi-domain support with Dirichlet-Neumann partitioning for the static boundaries. Particular focus is laid on the detailed influence of the axial electrical boundary conditions on the characteristic features of the Tayler instability, and, secondly, on the occurrence of electro-vortex flows and their relevance for okliquid metal batteries.
Keywords: liquid metal battery, simulation, OpenFOAM, magnetohydrodynamics, Tayler instability, electro-vortex flow

Publ.-Id: 20785 - Permalink


Plasma-based nanotechnology against corrosion of organ pipes
Pelic, B.; Skorupa, W.;
Experiments have been undertaken to explore the improvement of aqueous corrosion of Cu-Zn, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-20Zn alloy (namely brass) is strongly enhanced by traces of acid vapors (from wooden parts and glue) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.
Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), corrosion of organ pipes, Cu-Zn alloys, PbSn alloys
  • Invited lecture (Conferences)
    Final conference of the EU research project ''EU-PANNA'', 04.09.2014, Berlin, Germany

Publ.-Id: 20782 - Permalink


Investigation of the interactions between selected bacteria and selenium oxyanions
Luthardt, P.; Fischer, S.; Fischer, S.; Vogel, M.; Steudtner, R.; Henle, T.;
The microbial reduction of soluble selenium cations into its insoluble elemental form presents a unique opportunity to decontaminate industrial waste. We tested two strains of Bacillus sp. (JG-B5T, JG-B41) isolated from a uranium mining waste pile in Johanngeorgenstadt (Saxony) for their potential capacity to reduce selenium. A third species (Shewanella oneidensis) with a known reduction capacity is used as reference organism.
The microbial behavior of the bacteria under the influence of sodium selenite and selenate was observed. This included recording growth curves, pH alteration and changes in redox potential. The bacteria displayed differential growth when confronted with 2.5 mM selenite (Fig. 1) and selenate compared to controls. The content of the water soluble oxyanions was analyzed in the supernatant using inductively coupled plasma optical emission spectrometry. All selected strains have the ability to reduce selenite, whereas a reaction with selenate was not observed.
In addition we have observed and characterized the extracellular matrix focused on organic acids via High Performance Liquid Chromatography during the trial period. So far, the results indicate that two of the selected strains rely on different mechanisms.
The produced particles (Fig. 2) were isolated from the bacterial matrix and analyzed with Scanning electron microscopy with energy dispersive X-ray spectroscopy, by Raman spectroscopy, and Dynamic Light Scattering. With that we can determine their particle size, the type of bonding involved and their elemental compositions. The Raman spectra have already given indications for Se8-ring formation. X-ray analyses will reveal if other elements, like sulfur, are incorporated.After investigating the interaction of the selected strains with selenium in a defined medium, we will perform trials with real wastewater to test and validate our laboratory results under industrial conditions.
Reactions between selenium and microorganisms can significantly influence its transport behavior in the bio- and geosphere. Furthermore these metalloid-bacteria interactions can be used for various biotechnological applications.
Keywords: Selenium, Microbial Reduction, Shewanella oneidensis, Bacillus, Selenite, Selenate
  • Poster
    Selen2014 - Selenium in geological, hydrological and biological systems, 13.-14.10.2014, Karlsruhe, Deutschland

Publ.-Id: 20781 - Permalink


Convenient recycling and reuse of bombarded [18O]H2O for the production and the application of [18F]F
Rötering, S.; Franke, K.; Zessin, J.; Brust, P.; Füchtner, F.; Fischer, S.; Steinbach, J.;
The limited availability and the increasing demands of [18O]H2O force the reuse of bombarded [18O]H2O for the production of [18F]F at least for the purposes of research. Therefore inorganic and organic contaminants have to be removed from the [18O]water. We present a simple and effective method of [18O]water purification including oxidation and distillation. The obtained recycled [18O]water has comparable properties to unused [18O]water. This was confirmed by a detailed comparison of produced radionuclides and their activities and the application of [18F]F in standardised radiotracer synthesis.
Keywords: purification of used [18O]water; recycling and reuse; production of [18F]fluoride; radiosynthesis; analysis methods

Publ.-Id: 20780 - Permalink


Photoemission studies of niobium and lead photocathodes using picosecond UV laser
Xiang, R.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Barday, R.;
We present the results of our investigations on superconducting photocathodes for supercondcuting rf injectors. Bulk niobium and lead film on niobium have been considered as the best candidates. The quantum efficiency (QE) at room temperature has been measured with 258 nm UV laser pulses of 14 ps duration. A QE of 10-4 has been obtained for the lead film. In order to improve the photoemission yield of niobium, new treatment methods, like Cs-activation and implantation with alkali metals, have been applied and the results are reported.
Keywords: photocathode, niobium, lead, quantum efficiency (QE)
  • Open Access LogoContribution to proceedings
    the 36th International Free Electron Laser Conference (FEL 2014), 25.-29.08.2014, Basel, Switzerland
    Proceedings of FEL2014
  • Poster
    the 36th International Free Electron Laser Conference (FEL 2014), 25.-29.08.2014, Basel, Switzerland

Publ.-Id: 20779 - Permalink


The challenges of regional geochemistry to compositional data analysis from a methodological viewpoint
van den Boogaart, K. G.; Tolosana-Delgado, R.;
Regional Geochemistry is an important tool for the detect on of geopotenials (e.g. deposits) and risks (e.g. polution sources) and is an important source of geological insight on large scale. It is mainly concerned with geochemical data, which is inherently compositional. Modern compositional data analysis (CoDa) provides a lot of tools like distribution models, transforms, graphics, compositional geostatistics, imputation, compositional regression and linear models, outlier detection and robustness. However it does not yet provide tools for typical tasks in regional geochemistry, which among others are: maps of single components, anomaly detection and background definition, dealing with below detection limit, dealing with spatially varying geology and land use, working with surveys with too many components to explore all pairwise log ratios, calibration of instruments, collocated compositions, etc.. Ideally CoDa methods should be superior to classical statistical methods for geochemical data and it should thus be possible to simply replace the statistical methods in state-of-the-art geochemical practice by corresponding CoDa tools.The aim of the talk is to give a systematic account of how and why this is not yet occuring. For instance, single components maps are considered a key information in geochemistry, but spurious according to the doctrine of the Aitchison simplex. The compositional alternative would be to work with pairwise log ratios. However such compositional tools have other drawbacks, like e.g. too many pairs, mixing of different information on and no standard literature on their interpretation. Anomaly detection and spa! al factors are not yet sufficiently developed in the methodology research on CoDa. O$ en the application on of standard CoDa tools generates practical problems, like e.g. the identification of anomalies in a multivariate compositon will show a multitude of kinds of anomalies and we are confronted with many different sources and reasons for their occurrence. Par! ally CoDa methods need to be developed for tasks specific to geochemistry, and partly geochemists need to to develop a new thinking for interpreting the results of CoDa methods.From this systematic analysis we have deduced a set of key issues:
• The composition as a whole holds too much information at once. We need efficient methods to extract informative summaries with respect to geochemical tasks. This includes developing readable CoDa graphics and summaries for more than 30 components and multiple layers.
• The single component is understood in a completely different way by geochemists and CoDa-statistians. It is necessary to generate a joint view of this problem and then solve it.
• Enabling CoDa methods for below detection limit and measurement error issues including taylored callibration on for the needs of regional geochemistry.
• High level key publications of the proper use of compositional methods in a regional geochemistry context as reference for future geochemical publications.
• Specialized CoDa based so$ ware for geochemistry powerful enough to replace the existing tools.
Keywords: geochemical exploration, CODA, anomaly detection
  • Lecture (Conference)
    GeoMap Workshop, 17.06.-20.09.2014, Olomouc, Česká republika
  • Contribution to proceedings
    Geomap Workshop, 17.-20.6.2014, Olmouc, Česká republika
    GeoMap Workshop Proceedings, Oulmouc: Univerzita Palackého in Olomouc, 978-80-244-4149-8, 14-15

Downloads:

Publ.-Id: 20778 - Permalink


New Insight into the Photochemical Reaction Mechanism of Uranyl Citrate by Combining NMR Experiment and DFT Calculation
Tsushima, S.; Kretzschmar, J.; Steudtner, R.;
A sound understanding of the major reaction mechanisms is crucial to handle uranium containing waste appropriately. This means both the synthesis of unique compounds and the treatment of uranium occurring in or released into the environment. In an environmental context, uranium occurs in two main redox states: mobile U(VI) and immobile U(IV).
Due to both its model character in U(VI) complexation by chelating polycarboxylates and the citrate being a ubiquitous occurring ligand, particularly being important in the citric acid cycle in vivo, the uranyl citrate system itself [1–4] and also its photoreaction [5,6] is already repeatedly investigated, but still not fully understood.
This investigation provides not only further insight into the U(VI)-citrate complexation, but also a better understanding of the (photo-)redox chemistry of uranium in general.
Here we want to present the reaction pathway of the U(VI) citrate complex photooxidation to its degradation products ketoglutaric acid, acetoacetic acid and acetone with concomitant CO2 formation by several decarboxylation steps and the formation of U(IV). The oxidation state of the latter is indicated by NMR showing 1H chemical shifts > 50 ppm and proven by UV-vis. Moreover, the yielded U(IV) appears as soluble complexes of citrate and its degradation products. The identity of the formed compounds was experimentally proven by one- and twodimensional NMR methods and confirmed by DFT calculations.
The photoreaction starts by irradiating the sample with light from a simple light source such as the sun or a commercial mercury lamp. Interestingly, the initial chemical alteration starts by a single electron transfer from a citrate molecule, being hydrogen bonded to the fifth remaining coordination site not occupied by U(VI)–coordinating citrate. Most likely the intermediate, i.e., not observable U(V) disproportionates fast to U(VI) and the aforementioned U(IV).

[1] R. Bramley, W. F. Reynolds, I. Feldman, J. Am. Chem. Soc. 1965, 87, 3329–3332.
[2] E. Ohyoshi, J. Oda, A. Ohyoshi, Bull. Chem. Soc. Jap. 1975, 48, 227–229.
[3] S. P. Pasilis and J. E. Pemberton, Inorg. Chem. 2003, 42, 6793–6800.
[4] A. Günther, R. Steudtner, K. Schmeide, G. Bernhard, Radiochim. Acta 2011, 99, 535–541.
[5] H. D. Burrows and T. J. Kemp, Chem. Soc. Rev. 1974, 3, 139–165.
[6] A. J. Francis and C. J. Dodge, DAE-BRNS Biennial Symposium on Emerging Trends in Separation Science and Technology (SESTEC) 2008 (BNL-80322-2008-CP).
Keywords: uranium, citrate, photoreaction, reaction mechanism, NMR spectroscopy, DFT calculation
  • Poster
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden-Rossendorf, Deutschland

Publ.-Id: 20777 - Permalink


Nuclear Magnetic Resonance Spectroscopy in Ln/An Research
Kretzschmar, J.; Schott, J.; Tsushima, S.; Barkleit, A.; Paasch, S.; Brunner, E.; Scholz, G.; Brendler, V.;
Since signal separation by lanthanide shift reagents [1,2] has been replaced by elaborate pulse sequences and high-field spectrometers, lanthanides have advanced from auxiliaries to real objects of interest, also as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Here we want to report on interactions and structures of the Ln(III) (La3+, Eu3+ and, where applicable, Y3+) with selected systems, i.e., L-lactate [3], inorganic (poly)borates [4] and organoborates [5]. Small organic molecules such as lactate are important as model molecules and potential complexing agents found throughout the biosphere. Borates are ubiquitous in nature. In the context of nuclear waste disposal they occur in remarkable amounts in salt formations being potential host rocks for nuclear waste repositories, but also in boron containing cooling water or borosilicate glass coquilles for spent nuclear fuel. Organoborates are considered due to possible reaction of the former compounds and, additionally, suggested as analogues to model the interaction between Ln/An and borates in general.
Among several possible structures, infrared (IR) and NMR measurements, supported by density functional theory (DFT) calculation, revealed that lactate forms Ln(III) (and Am3+) complexes with both the carboxyl and hydroxyl group involved. Polyborates, i.e., triborate and pentaborate form soluble weak aqueous Ln(III) complexes prior to precipitation as amorphous white solids, whereas condensation to higher polyborates can be excluded. Two signals in both the 89Y and the 11B NMR spectra probably arise from two coordination sites, which may reflect the polyborate species found in the supernatant solution. The organoborates formed by the reaction of boric acid and, e.g., lactate or salicylate also possess a tetra-coordinated boron atom [BO4], considered as the responsible site for Ln(III) interaction in inorganic (poly)borates. Since the (poly)borate/boric acid equilibrium is strongly concentration and pH dependent, their replacement by organic analogues allows investigations at both lower total boron concentrations and pH values.

[1] Hinckley, C. C. J. Am. Chem. Soc. 1969, 91, 5160–5162.
[2] Gansow, O. A.; Willcott, M. R.; Lenkinski, R. E. J. Am. Chem. Soc. 1971, 93, 4295–4297.
[3] Barkleit, A.; Kretzschmar, J.; Tsushima, S.; Acker, M. Dalton Trans. 2014, 43, 11221–11232.
[4] Schott, J.; Kretzschmar, J.; Acker, M.; Eidner, S.; Kumke, M. U.; Drobot, B.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T. Dalton Trans. 2014, 43, 11516–11528.
[5] Schott, J; Kretzschmar, J; Acker, M.; Tsushima, S.; Barkleit, A.; Taut, S.; Brendler, V.; Stumpf, T., Dalton Trans., in preparation.
Keywords: lanthanides, actinides, lanthanum, europium, yttrium, phosphorylated amino acid, boric acid, polyborate, NMR spectroscopy
  • Lecture (Conference)
    Advanced Techniques in Actinide Spectroscopy 2014 (ATAS 2014), 03.-07.11.2014, Dresden-Rossendorf, Deutschland

Publ.-Id: 20776 - Permalink


The 40Ca(α,γ)44Ti reaction studied by in-beam γ-spectroscopy and activation
Schmidt, K.; Akhmadaliev, S.; Anders, M.; Bemmerer, D.; Boretzky, K.; Caciolli, A.; Dietz, M.; Elekes, Z.; Fülöp, Z.; Gyürky, G.; Hannaske, R.; Junghans, A. R.; Marta, M.; Menzel, M.-L.; Schwengner, R.; Szücs, T.; Takács, M. P.; Wagner, A.; Wagner, L.; Yakorev, D.; Zuber, K.;
The radioactive nuclide 44Ti is believed to be produced in the α-rich freezeout preceding supernova explosions. The γ-rays from its decay have been observed in space-based γ-observatories for the Cassiopeia A and recently also SN 1987A supernova remnants. The rates of the nuclear reactions governing the production and destruction of 44Ti should therefore be known with high precision. Over the last years there have been various studies of the 40Ca(α,γ)44Ti reaction, which is dominating the 44Ti production in supernovae.
Using the α-beam of the 3-MV Tandetron at Dresden, the strengths of 40Ca(α,γ)44Ti resonance triplet at 4.5 MeV laboratory α-energy has been studied by in-beam γ-spectroscopy and activation. In addition, preliminary results of resonance strengths between 3.5 and 3.8 MeV will be presented.
The irradiated samples have been analyzed in the underground laboratory Dresden Felsenkeller. The target stoichiometry has been determined by nuclear reactions and by elastic recoil detection analysis (ERDA), whereby the strength of the Ep = 1.842 MeV resonance in the 40Ca(p,γ)41Sc reaction could be restudied.
Keywords: titanium-44, capture reaction, nuclear astrophysiscs
  • Poster
    Nuclei in the Cosmos XIII 2014, 07.-11.07.2014, Debrecen, Hungary
  • Poster
    Fifteenth International Symposium on Capture Gamma-Ray Spectroscopy and Related Topics, 25.-29.08.2014, Dresden, Deutschland

Publ.-Id: 20775 - Permalink


Primo – Projekterfahrungen im Helmholtz-Zentrum Dresden-Rossendorf
Reschke, E.;
Primo ist eines der am meisten eingesetzten Discovery-Systeme weltweit. Im Helmholtz-Zentrum Dresden-Rossendorf entschied man sich für den Einsatz von Primo Total Care (https://www.hzdr.de/primo) Im Bericht werden die Projekterfahrungen dargestellt, von der Entscheidungsfindung bis zur Akzeptanz durch die Nutzer. Insbesondere werden die erfahrenen Vor- und Nachteile der Total Care-Installation dargestellt.
Keywords: Discovery system, Primo Total Care
  • Invited lecture (Conferences)
    Jahrestagung des AK Bibliotheken der Leibnitz-Gemeinschaft, 10.-12.09.2014, Bonn, Deutschland

Publ.-Id: 20774 - Permalink


Measuring at relevant concentrations - radiolabelling as a versatile tool for sensitive nanoparticle detection
Schymura, S.; Hildebrand, H.; Dalmiglio, M.; Holzwarth, U.; Gibson, N.; Franke, K.;
The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories, a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as geological formations or ground water is nearly impossible using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabelling, which may be of crucial value in enabling such research.
We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, Silica and TiO2 nanoparticles. The labelling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labelling utilizing the recoil of a nuclear reaction to introduce a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [7Be]MWCNT, [7Be]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations.
  • Poster
    International Conference on Safe production and use of nanomaterials, Nanosafe 2014, 18.-20.11.2014, Grenoble, France

Publ.-Id: 20773 - Permalink


Environmental mobility of carbon nanotubes
Schymura, S.; Kulenkampff, J.; Franke, K.; Lippmann-Pipke, J.;
The environmental mobility of nanoparticles is a key factor for the risk assessment of nanoparticle release into the environment. If the environmental conditions render the nanoparticles mobile, a risk beyond the very near field of the actual release has to be taken into account. However, the lack of suitable detection methods constitutes a severe setback for studies of these effects, especially in the low concentration range environmentally relevant and with a considerable background of the same element. This is particularly significant for the study of carbon based nanoparticles such as carbon nanotubes, as carbon-containing water constituents such as humic or fulvic acids are ubiquitous in many ground and surface waters.
We present the results of our studies using carbon nanotubes labelled with radioactive iodine isotopes, e.g. 124I, 125I, 131I. This allowed us to detect carbon nanotubes in the ng/L range, even against a background of mg/L of fulvic or humic acids. Experiments were conducted to investigate the transport behaviour of carbon nanotubes in dependence of the carbon nanotube type, their modification, the geomatrix material and grain size, and the water composition regarding the presence of natural organic matter and electrolytes. The radiolabelling enabled working with a typical amount of about 100 ng carbon nanotubes per experiment. Experiments using different surfactants allowed the distinguishing between different removal mechanisms.
Moreover, the labelling of carbon nanotubes with 124I, a positron emitter, allowed the use of positron emission tomography (PET) to record 4D data (3 spatial dimension plus time) of nanotube transport inside a column.
  • Lecture (Conference)
    International Conference on Safe production and use of nanomaterials, Nanosafe 2014, 18.-20.11.2014, Grenoble, France

Publ.-Id: 20772 - Permalink


Die Bibliothek als Open Access-Kompetenzzentrum in einer außeruniversitären Forschungseinrichtung
Reschke, E.;
Open Access zu publizieren, ist noch nicht selbstverständlich für WissenschaftlerInnen in den außeruniversitären Forschungsgemeinschaften. Neue Publikationsmöglichkeiten erfordern neue, prozessbegleitende Services. Der Aufbau eines Open Access Kompetenzzentrums in der Bibliothek ist ein bereits erfolgreicher Weg, die WissenschaftlerInnen umfassend zu informieren und zu unterstützen. Welche Leistungen erbringt das Kompetenzzentrum und wie erwirbt es die notwendige Kompetenz? Im Fallbeispiel 2 soll dargestellt werden, welche administrativen Bereiche das Thema Open Access tangiert, wie diese Bereiche zusammenarbeiten und wie sich dieses Netz für seine Aufgaben qualifiziert.
Keywords: Open Access, Library management
  • Invited lecture (Conferences)
    Open-Access-Tage 2014, 29.-30.09.2014, Köln, Deutschland

Publ.-Id: 20771 - Permalink


Adenosine activates brown adipose tissue and recruits beige adipocytes via A2A receptors
Gnad, T.; Scheibler, S.; von Kügelgen, I.; Scheele, C.; Kilic, A.; Glöde, A.; Hoffmann, L.; Reverte, L.; Horn, P.; Mutlu, S.; El-Tayeb, A.; Kranz, M.; Deuther-Conrad, W.; Brust, P.; Lidell, M.; Betz, M.; Enerbäck, S.; Schrader, J.; Yegutkin, G.; Mueller, C.; Pfeifer, A.;
Brown adipose tissue (BAT) is specialised in energy expenditure making it a potential target for anti-obesity therapies. Following cold-exposure, BAT is activated by the sympathetic nervous system with concomitant release of catecholamines and activation of β-adrenergic receptors. Because BAT therapies based on cold-exposure or β-adrenergic agonists are clinically not feasible, alternative strategies must be explored. Purinergic co-transmission might be involved in sympathetic control of BAT and previous studies reported inhibitory effects of the purinergic transmitter adenosine in BAT from hamster or rat. However, the role of adenosine in human BAT is unknown. Here we show that adenosine activates human and murine brown adipocytes at low nanomolar concentrations. Adenosine is released in BAT during stimulation of sympathetic nerves as well as from brown adipocytes. The adenosine A2A receptor is the most abundant adenosine receptor in human and murine BAT. Pharmacological blockade or genetic loss of A2A2A agonists significantly increases energy expenditure. Moreover, pharmacological stimulation of A2A2A receptor into white fat induces brown-like cells - so called beige adipocytes. Importantly, mice fed a high-fat diet and treated with an A2A agonist are leaner with improved glucose tolerance. Taken together, we demonstrate that adenosine/A2A signalling plays an unexpected physiological role in sympathetic BAT activation and protects mice from diet-induced obesity - findings that reveal new possibilities for developing novel obesity therapies.

Publ.-Id: 20769 - Permalink


Project NanoTrack - Untersuchung des Lebenszyklus von Nanopartikeln anhand von [45Ti]TiO2 und [105Ag] Ag0
Franke, K.; Hildebrand, H.; Schymura, S.; Keywords: NanoTrack Lebenszyklus Nanopartikeln Ti-45 TiO2 Ag-105 Ag0
  • Invited lecture (Conferences)
    27th Meeting of the DECHEMA/VCI-Working Party „Responsible Production and Use of Nanomaterials“, 04.09.2014, Frankfurt am Main, Deutschland

Publ.-Id: 20768 - Permalink


Range assessment in particle therapy based on prompt γ-ray timing measurements
Golnik, C.; Hueso-González, F.; Müller, A.; Dendooven, P.; Enghardt, W.; Fiedler, F.; Kormoll, T.; Roemer, K.; Petzoldt, J.; Wagner, A.; Pausch, G.;
Proton and ion beams open up new vistas for the curative treatment of tumors, but adequate technologies for monitoring the compliance of dose delivery with treatment plans in real time are still missing. Range assessment, meaning the monitoring of therapy-particle ranges in tissue during dose delivery (treatment), is a continuous challenge considered a key for tapping the full potential of particle therapies. In this context the paper introduces an unconventional concept of range assessment by prompt-gamma timing (PGT), which is based on an elementary physical effect not considered so far: therapy particles penetrating tissue move very fast, but still need a finite transit time—about 1–2 ns in case of protons with a 5–20 cm range—from entering the patient’s body until stopping in the target volume. The transit time increases with the particle range. This causes measurable effects in PGT spectra, usable for range verification. The concept was verified by proton irradiation experiments at the AGOR cyclotron, KVICART, University of Groningen. Based on the presented kinematical relations, we describe model calculations that very precisely reproduce the experimental results. As the clinical treatment conditions entail measurement constraints (e.g. limited treatment time), we propose a setup, based on clinical irradiation conditions, capable of determining proton range deviations within a few seconds of irradiation, thus allowing for a fast safety survey. Range variations of 2 mm are expected to be clearly detectable.
Keywords: particle therapy, range assessment, prompt gamma, timing spectroscopy

Publ.-Id: 20767 - Permalink


Characterisation of graphite by automated mineral liberation analysis
Sandmann, D.; Haser, S.; Gutzmer, J.;
The beneficiation of graphite is very costly and energy intensive and can necessitate multiple processing steps, often including flotation. Products have to satisfy very stringent quality criteria. To decrease beneficiation costs, a careful characterisation of feed and concentrate materials is needed. This study elucidates the additional benefit of methods of automated SEM-based image analysis, such as mineral liberation analysis (MLA), in addition to ‘traditional’ methods [optical microscopy and X-ray powder diffraction (XRD)] for the analyses of graphite raw materials and processing products. Owing to the physical and chemical properties of the mineral graphite, samples require delicate sample preparation as well as particular backscattered electron (BSE) imaging calibration for automated image analysis. These are illustrated in this study. The results illustrate that SEM-based image analysis of graphite feeds and concentrates can provide accurate and reliable information for the graphite beneficiation process. This applies to both mineralogical characteristics and process relevant parameters.
Keywords: Graphite, Beneficiation, SEM-based image analysis, Modal mineralogy, Mineral association, Liberation, MLA

Publ.-Id: 20766 - Permalink


Fate and transport of engineered nanoparticles along the exposure pathway wastewater - sludge - plant
Hildebrand, H.; Schymura, S.; Schneider, P.; Lange, T.; Ziegler, K.; Franke, K.;
The potential risks accompanying the rising use of nanotechnology are in dire need of a careful assessment. Wastewater treatment plants (WWTP) are in a key position for managing the potential risks of nanoparticles (NP) load in urban and industrial wastewater. They have to deal with the specific conditions of NP polluted wastewater and have to tackle the task of removing NP from the purified water to guarantee maximum safety of the WWTP effluent for the environment and humans. At the same time, WWTPs can potentially act as sources of NP release through the secondary uses of WWT sludge in agriculture and landscaping.
The recently started project “nanoSuppe” aims on the development of a conclusive picture of NP behaviour in WWTPs and their further fate in potential sludge uses up to the possible reintroduction in the food chain by uptake in plants. To reach this goal a strong international consortium from WWTPs, related industries, governmental agencies and research centres is formed. The project is focused on engineered NPs such as TiO2, CeO2, multiwalled carbon nanotubes (MWCNT) and quantum dots which might reach wastewater treatment plants e.g. through the use of consumer products (such as sunscreen) or industrial processes.
The research strategy is comprised of a thorough characterization of NPs in WWTPs from lab to field scale, including the development of predictive models of the exposure and the impact on society and environment. In this context, typical scenarios of municipal and industrial wastewater treatment technologies are evaluated and their impact on the fate of NPs with various degradation and modification levels is investigated. Furthermore, the bioavailability and the possible introduction of NPs into the food chain from the agricultural use of sewage sludge (typical used as fertilizer or for landscaping) is investigated by studying the NP extractability from soils and sediments as the crucial parameter for environmental mobility and transport of NPs and the uptake in and toxicity to various agricultural plants such as cultivated radish.
For evaluation of the transport and behaviour of NPs in highly complex media such as wastewater, sludge or plants, a reliable and sensitive detection method is the crucial parameter. Therefore, radiolabeling strategies for the NPs under study are developed. The use of radiolabeled NPs ensures identification, localisation and quantification of NPs even under the anticipated low environmentally relevant concentrations despite the highly complex media (waste water, sludge, soil, plant) and background levels of natural NPs, colloids or substances of the same elemental composition. For MWCNTs, detection in environments with a high carbon background can be realised.
Within this presentation, research strategies, project partners and first results from the collaborative project “nanoSuppe” are presented and open for discussion.
Keywords: Nanoparticles, Transport, Wastewater treatment, Radiolabeling
  • Poster
    NanoSafe 2014, 18.-20.11.2014, Grenoble, France

Publ.-Id: 20765 - Permalink


Investigation of the life cycle of titania NPs using radiolabeling techniques for highly sensitive NP detection
Hildebrand, H.; Franke, K.; Schymura, S.; Freyer, A.; Bilz, E.; Mehnert, R.; Mai, E.; Isaacson, C.; Schug, H.; Schirmer, K.; Ammann, A.; Sigg, L.;
Production and application of TiO2-containing nanocomposites such as functional surface coatings have significantly increased in recent years. These coatings are used in a wide field of applications ranging from self-cleaning and scratch resistant surfaces to biocidal coatings. Therefore, knowledge about potential nanoparticle (NP) release due to aging or abrasion of these coatings is essential for safe application of these materials.
Radiolabeling of the NPs provides a method to sensitively detect NPs and is feasible for qualitative and quantitative fate and effects determination. With this detection method, evaluation of NPs fate during aging and abrasion of nanocomposites, estimation of release rates, transport of NPs in the environment and up-take and effects with organisms can be readily quantified.
The joint research project NanoTrack used model surface coatings in an acrylate-based formulation containing TiO2 NPs (d = 21 nm, P25, Evonik Industries). Coatings were produced by application of 25 µm thick nanocomposite layers on a substrate followed by curing and later weathered under standard laboratory test conditions. Due to the low resistivity of this model system, the organic matrix of the surface coating was severely degraded and NPs were partly released. Scanning electron microscopy showed that mostly aggregates and agglomerates of NPs were released and only a small fraction of primary NPs can be expected to be discharged. For industrial nanocomposites (realistic case), the same weathering procedure resulted in release of only small amounts of TiO2-NPs. Nevertheless, radioactivity detection methods proved this release.
Current studies on the environmental fate and effects of nanoparticles are limited by the inability to detect and quantify nanoparticles in complex environmental test systems and radiolabeling nanoparticles may provide a solution to this limitation. Isotopic labeling was developed using a low-temperature diffusive method of radionuclides implementation resulting in [44Ti]TiO2. Chemical composition, particle size distributions and morphology of the radiolabeled NPs remained unaltered compared to the original material. Additionally, [48V]TiO2, which was produced via proton irradiation of TiO2 NPs (Abbas et al., 2010), was applied within the test systems.
For getting knowledge about transport of TiO2, interactions of relevant concentrations of these NPs with environmental media (such as humic acids or natural sediments) were studied. Results show that depending on geochemical conditions, transport of TiO2 in groundwater sediments can be expected, especially in presence of humic acids which act as natural stabilisers for the NPs.
Another important aspect is the ecotoxicological impact of the released NPs. As TiO2 NP aggregate and sediment from the water column, exposure of benthic organisms to TiO2 NP is expected. Exposure of [48V]TiO2 NP to the nematode Plectus aquatilis resulted in bioconcentration of the [48V]TiO2 NPs by the nematode, which indicates that transport of TiO2 NPs up the food chain is possible.
The integrated examination of NPs in surface coatings in terms of production, aging and abrasion, NP release and their fate and transport in the environment provides a data base for risk assessment and validation or possibly adaptation of new nanocomposite production.

Abbas et al. (2010) J Nanopart Res 12:2435-2443.
Keywords: Titania, Radiolabeling, Nanoparticles
  • Lecture (Conference)
    NanoSafe 2014, 18.-20.11.2014, Grenoble, France

Publ.-Id: 20764 - Permalink


Tuning perpendicular anisotropy gradient in Co/Pd multilayers by ion irradiation
Greene, P. K.; Osten, J.; Lenz, K.; Fassbender, J.ORC; Jenkins, C.; Arenholz, E.; Endo, T.; Iwata, N.; Liu, K.
The tunability of Ar+ ion irradiation of Co/Pd multilayers has been employed to create depthdependent perpendicular anisotropy gradients. By adjusting the Arþ kinetic energy and fluence, the depth and lateral density of the local structural modification are controlled. First-order reversal curve analysis through X-ray magnetic circular dichroism and conventional magnetometry studies shows that the local structural damage weakens the perpendicular anisotropy near the surface, leading to a magnetization tilting towards the in-plane direction. The ion irradiation method is complementary to and may be used in conjunction with, other synthesis approaches to maximize the anisotropy gradient.
Keywords: perpendicular anisotropy gradient ion irradiation Co\Pd multilayer

Publ.-Id: 20763 - Permalink


A luminescence line-narrowing spectroscopic study of the uranium(VI) interaction with cementitious materials and titanium dioxide
Tits, J.; Walther, C.; Stumpf, T.; Macé, N.; Wieland, E.;
The aim of this work is to assess the processes controlling of UO22+ sorption in calcium silicate hydrates (C-S-H phases) and in hardened cement paste (HCP). This is of particular importance for the assessment of the mobility of this radionuclide in a deep geological repository for low and intermediate level radioactive waste (L/ILW) as this kind of waste is often solidified with cement prior to storage. Broadband luminescence spectroscopy and luminescence line-narrowing spectroscopy were used to study the sorption of UO22+ with TiO2, synthetic C-S-H phases and hardened cement paste (HCP). Broadband luminescence spectra suffered from strong inhomogeneous line broadening resulting from a strongly disordered UO22+ bonding environment. This problem was largely overcome by using luminescence line-narrowing spectroscopy. This technique allowed the unambiguous identification of three different types of UO22+ sorbed species on C-S-H phases and HCP. Comparison with spectra of UO22+ doped TiO2 allowed assignment of these species to a surface complex, an incorporated species and an uranate-like surface precipitate.
Keywords: Uranium, Luminescence-line-narrowing spectroscopy, C-S-H, cement, sorption, incorporation

Publ.-Id: 20762 - Permalink


Spectroscopic investigation in high magnetic fields of the dilute nitride GaAsN
Eßer, F.; Drachenko, O.; Schneider, H.; Patanè, A.; Hopkinson, M.; Helm, M.;
As a member of the dilute nitride family, GaAsN is a highly interesting material system for many application purposes such as LEDs, lasers, solar cells, and infrared photodetectors because of the tuning possibility of these devices by the variation of the nitrogen content. An accurate description of this new material system involves the knowledge of the band structure and in particular the effective mass. Motivated by the inconsistency of previous results (e.g. [1, 2]), which can be traced down to the particular investigation method, we use several spectroscopy techniques in a series of GaAsN epilayers with 0.1 - 1 % of nitrogen. Cyclotron resonance spectroscopy, being the most direct method, reveals that the cyclotron resonance frequency is not significantly affected by the nitrogen doping and thus the effective mass. Magneto-photoluminescence, on the other hand, stems from several transitions, which are not resolved spectrally, but identified in time-resolved measurements. We discuss the different behaviour of these transitions in magnetic fields up to 7 T (static) and 41 T (pulsed). We find that the diamagnetic shift of the electron-to-carbon impurity transition cannot be always applied reliably to determine the electron effective mass. However, this method has been employed frequently in previous studies, which may explain the contradictory values reported in the literature.

[1] K. Alberi et al. Phys. Rev. Lett. 110, 156405 (2013)
[2] F. Masia et al Phys. Rev. B 73, 073201 (2006)
Keywords: Dilute nitride, GaAsN, effective mass, cyclotron resonance, magneto-photoluminescence, pulsed magnetic field
  • Lecture (Conference)
    International conference on the physics of semiconductors, 10.-15.08.2014, Austin, TX, USA

Publ.-Id: 20761 - Permalink


The Evidence of Quasi-Free Positronium State in GiPS-AMOC Spectra of Glycerol
Zvezhinskiy, D.; Butterling, M.; Wagner, A.; Krause-Rehberg, R.; Stepanov, S. V.;
We present the results of processing of age-momentum correlation spectra that were measured for glycerol by the gamma-induced positron spectroscopy facility. Our research has shown that the shape of experimental s(t) curve cannot be explained without introduction of the intermediate state of positronium (Ps), called quasi-free Ps. This state yields the wide Doppler line near zero lifetimes. We discuss the possible properties of this intermediate Ps state from the viewpoint of developed model. The amount of annihilation events produced by quasi-free Ps is estimated to be less than 5% of total annihilations. In the proposed model, quasi-free Ps serves as a precursor for trapped Ps of para- and ortho-states.
Keywords: Positron Annihilation Spectroscopy, Bremsstrahlung, Positronium

Publ.-Id: 20760 - Permalink


Phase transitions of anisotropic and exchange origins in TmFe5Al7
Gorbunov, D. I.; Yasin, S.; Andreev, A. V.; Mushnikov, N. V.; Rosenfeld, E. V.; Skourski, Y.; Zherlitsyn, S.; Wosnitza, J.;
Magnetization and sound propagation reveal a number of unusual spontaneous and field-induced transformations in ferrimagnetic TmFe5Al7 (TC = 193 K). The rare-earth sublattice was found to provide a uniaxial magnetic anisotropy, whereas the iron sublattice favors an easy-plane anisotropy. A competition between them results in a first-order spin-reorientation transition at 64 K as the magnetic moments rotate from the c axis to the basal plane of a tetragonal structure. The transition is preceded by a first-order magnetization process of type II along the hard axis. Remarkably, the intersublattice Tm-Fe exchange interaction is weakened at the spin-reorientation transition. Concomitantly, the spontaneous magnetic moment disappears, and the ferrimagnetic state changes to antiferromagnetic. With increasing temperature, the strength of the Tm-Fe exchange is recovered, and the ferrimagnetism is restored at 82 K through another first-order phase transformation. Below 40 K, a first-order field-induced transition occurs for a magnetic field applied along the easy [001] axis. It reflects a rotation of the magnetic moments towards the forced ferromagnetic state observed above 30 T. Along the hard [100] axis the ferromagnetic saturation is not reached even at 60 T.

Publ.-Id: 20757 - Permalink


Observation of anisotropic exchange in a spin ladder by ESR
Čižmár, E.; Ozerov, M.; Krämer, K. W.; Rüegg, C.; Zvyagin, S. A.;
We report on high resolution X-band electron spin resonance (ESR) spectroscopy studies of the spinladder material (C5H12N)2CuBr4. Our experiments provide a direct evidence for the presence of anisotropy in (C5H12N)2CuBr4 in contrast to a fully isotropic spin-ladder model employed for this system previously. Low-temperature angular dependence of ESR transitions is analyzed employing a simple spin-1/2 dimer model with the symmetric anisotropic exchange interaction.

Publ.-Id: 20756 - Permalink


Uranyl sorption onto birnessite: A surface complexation modeling and EXAFS study
Rihs, S.; Gaillard, C.; Reich, T.; Kohler, S. J.;
This work investigates the mechanism of the uranyl interaction with birnessite, one of themost common layertype MnO2 mineral at the Earth's surface, by coupling macroscopic (surface complexation experiments) andmicroscopic (EXAFSmeasurements) approaches. The sorption of uranyl on synthetic hexagonal birnessite, the lowpH birnessite form, was studied under various conditions of pH (3–6), electrolyte backgrounds (0.1 M NaClO4, NaNO3 and Na2CO3), and solid/liquid ratios (from0.27 to 4.5 g/L). Sorption isotherms exhibit a complex form indicative of at least two types of sorption sites. EXAFS data reveal the presence of two equatorial O shells at ca. 2.32 Å and 2.46 Å for all the samples, and a Mn shell at ca. 3.38 Å in the low-pH (≤5) samples only. No U–U pair was detected, despite the presence of polynuclear dissolved species in some of the samples.
From the combination of the sorption isotherms and EXAFS results, a structural model for the sorption of uranyl onto hexagonal birnessite is proposed, in which two energetically different sites are involved. At low pH (≤5) a bidentate edge-sharing complex with Mn octahedra of the mineral edges can be inferred, whereas bidentate corner-sharing and/or monodentate complexation to layer vacancies would most likely describe EXAFS features of higher pH samples. A diffuse double layermodel of surface complexationwas developed for describing within the same framework the uranyl sorption against pH, involving both high-affinity (Mn octahedra edge) and lowaffinity (above layer vacancies) sites.
The comparison of the uranyl sorption onto hexagonal birnessite and various related environmental minerals shows that the affinity of uranyl for birnessite largely exceeds the sorption observed on montmorillonite and zeolite and turns out to be comparable to iron oxides, confirming the potential role of phyllomanganates to the control of uranyl mobility in post-oxic acidic environments.
Keywords: EXAFS U birnessite

Publ.-Id: 20755 - Permalink


Pathways for abiotic reduction in the FeS/Se(IV) and FeS2/Se(IV) systems
Breynaert, E.; Wangermez, W.; Dom, D.; Scheinost, A. C.; Parac-Vogt, T. N.; Kirschhock, C. E. A.; Maes, A.;
The geochemical behaviour and bio-availability of selenium have an unexpectedly intricate impact on modern society. While selenium is an essential micronutrient for many living organisms, the window between deficiency and toxicity is very narrow (0.04 ppm ; essential; 0.04 – 0.1 ppm beneficial; 3 ppm toxic). Due to its similarity to sulphur, it is commonly encountered in subsurface deposits such as coal and uranium, phosphate and sulphidic transitionmetal ores. The release of selenium to the environment is closely associated with the economic exploitation of such deposits. Because of its significant contribution to long-term radiation exposure, 79Se is considered as one of the important isotopes in the inventory of the long-lived radioactive waste produced by nuclear industry. In view of redox properties and abundant occurence in reducing soils and sediments, iron sulphides play an important role in the availability of mobile inorganic selenium in the environment.
While previous studies have demonstrated the formation of FeSe and Se0 upon reduction of Se(IV) with respectively iron monsulphides and iron disulphides, the mechanistic pathways explaining the different outcome are missing.
Combination of published results in a wide range of relevant systems [1-5] with new spectroscopic information (XAS and NMR spectroscopy) obtained for specifically synthesized key intermediates allows to rationalise all previous observations. These results allow to outline the different pathways and demonstrate how the intermediary selenium, sulphur and selenosulphur species determine the final outcome of the reactions.
[1] Scheinost et al (2008), ES&T, 42, 1984–1989
[2] Breynaert et al (2008), ES&T, 42, 3595–3601
[3] Scheinost et al (2008), J. Contam. Hydrol., 102, 228-245
[4] Breynaert et al (2010), ES&T, 44, 6649–6655
[5] Kang et al (2011), ES&T, 45, 2704–2710
Keywords: selenium EXAFS NMR nuclear waste
  • Lecture (Conference)
    Goldschmidt2014, 08.-13.06.2014, Sacramento, USA

Publ.-Id: 20754 - Permalink


Retention of selenium by cementitious materials under oxidizing and reducing conditions
Rojo, H.; Tits, J.; Scheinost, A. C.; Wieland, E.;
79Se is an important redox-sensitive, dose-determining radionuclide in low and intermediate level radioactive waste repositories [1]. In this type of repository, cementitious materials play a crucial role as barrier for radionuclide migration from the near-field into the host rock. In current sorption databases for the cementitious near-field, only sorption data for Se(IV/VI) have been considered. Robust sorption measurements and a sufficiently detailed mechanistic understanding of the retention of the reduced Se species in a cementitious environment are lacking [2].
The objective of this work is to investigate the immobilisation of Se under the reducing conditions existing in a cement-based repository (-230mV < Eh < -750 mV). Under these conditions, Se(IV) and Se(-II) are the dominating redox states. Note that the selenium sorption behaviour is largely controlled by its oxidation state. Under oxidizing conditions, Se forms the oxyanions SeIVO32- and SeVIO42-. Generally, the adsorption of these oxyanions is expected to be very weak based on the assumption that surface complexation onto negatively charged surfaces solids, such as calcium-silicate-hydrates (C-S-H) in cement paste, is the dominating sorption mechanism [2]. Under reducing conditions, and in an alkaline environment with pH values ranging between 10 < pH < 14, Se is present either as Se(0) or as Se(-II). While Se(0) is controlled by solubility limitation, the sorption behavior of Se(-II) is largely unknown in cementitious environments.
Se(IV) and Se(-II) sorption kinetic studies have been carried out on various synthetic cement components, such as calcium silicate hydrates (C-S-H) and hydrated calcium aluminates (AFm), the principal host phases for radionuclides in hydrated cement. XANES studies allowed characterizing the redox state of selenium in the samples under alkaline conditions.
The sorption tests revealed that the uptake of Se(IV) by C-S-H phases is much stronger than expected. Furthermore, Rd values for Se(IV) on various AFm phases are correlated with their interlayer spacing. The sorption of Se(-II) on the different cementitious materials that are currently being investigated was found to be lower than the sorption of Se(IV).

References
[1] NAGRA (2002). Nagra Technical Report NTB 02-05, Nagra, Wettingen, Switzerland
[2] E. Wieland, L.R. Van Loon (2003). PSI Bericht 03-06, Paul Scherrer Institut, Villigen, Switzerland and Nagra Technical Report NTB 02-20, Nagra, Wettingen, Switzerland.
Keywords: selenium XANES cement nuclear waste
  • Poster
    Selen2014, 13.-14.10.2014, Karlsruhe, Germany

Publ.-Id: 20753 - Permalink


High Pressure Phase Transition of Coffinite, USiO4
Bauer, J. D.; Labs, S.; Weiss, S.; Bayarjargal, L.; Morgenroth, W.; Milman, V.; Perlov, A.; Curtius, H.; Bosbach, D.; Zänker, H.; Winkler, B.;
Synchrotron powder diffraction patterns and Raman spectra of synthetic coffinite, USiO4, were collected for pressures up to 35 GPa and are complemented with DFT+Ubased calculations. USiO4 undergoes a first order phase transition from zircon-type (space group I41/amd) to scheelite-type structure (space group I41/a) at 15GPa and ambient temperature. Contrary to earlier reports, the data indicate that this transition is completely reversible upon pressure release. Bulk moduli were obtained from the p−V data for the zircon-type and scheelite-type USiO4 phase. For zircon-type USiO4 the value for B = 186(5)GPa, while for the scheelite-type phase B = 204(9)GPa, where the latter is significantly lower than a value proposed earlier (B = 274(16) GPa1). Lattice dynamical calculations point towards a Γ-point soft mode triggering the pressure-induced phase transition.
Keywords: Coffinite, Raman spectroscopy, phase transformation, scheelite structure, high pressure

Publ.-Id: 20752 - Permalink


A radically new suggestion about the electrodynamics of water: Can the pH index and the Debye relaxation be of a common origin?
Volkov, A. A.; Artemov, V. G.; Pronin, A. V.;
The structure of pure water is commonly viewed as an openwork matrix of hydrogen-bonded H2O molecules with a Debye relaxation dynamics. The matrix is filled with free ions of low concentration, which makes water a weak electrolyte with pH = 7. Traditionally, the Debye relaxation is considered having no relevance to the dc water conductivity (or the pH index): while the Debye relaxation is caused by the dynamics of intact H2O molecules, the dc conductivity, in contrast, is due to self-dissociation of H2O into H3O+ and OH- ions. Here, we consider a microscopic mechanism, which could unify the Debye and the dc dynamics, namely the Brownian-like motion of strongly interacting ions. The model comprehensively describes the low-energy electrodynamics of water (up to 1011Hz) giving however an unexpected outcome: water behaves as if it had far more free ions than the standard model assumes. High concentration of counter charges results in a polarization structure of water. We recognize full well that such a radical model is contrary to many years of research on the dynamics, thermodynamics, and dielectric properties of water; but the results seem logically consistent and may prove stimulating.

Publ.-Id: 20751 - Permalink


Multiband transport and nonmetallic low-temperature state of K0.50Na0.24Fe1.52Se2
Ryu, H.; Wolff-Fabris, F.; Warren, J. B.; Uhlarz, M.; Wosnitza, J.; Petrovic, C.;
We report evidence for multiband transport and an insulating low-temperature normal state in superconducting K0.50Na0.24Fe1.52Se2 with Tc approximate to 20 K. The temperature-dependent upper critical field Hc2 is well described by a two-band BCS model. The normal-state resistance, accessible at low temperatures only in pulsed magnetic fields, shows an insulating logarithmic temperature dependence as T -> 0 after superconductivity is suppressed. This is similar as for high-Tc copper oxides and granular type-I superconductors, suggesting that the superconductor-insulator transition observed in high magnetic fields is related to intrinsic nanoscale phase separation.

Publ.-Id: 20750 - Permalink


Nonmetallic low-temperature normal state of K0.7Fe1.46Se1.85Te0.15
Wang, K.; Ryu, H.; Kampert, E.; Uhlarz, M.; Warren, J.; Wosnitza, J.; Petrovic, C.;
The normal-state in-plane resistivity below the zero-field superconducting transition temperature Tc and the upper critical field μ0Hc2 (T) was measured by suppressing superconductivity in pulsed magnetic fields for K0.70Fe1.46Se1.85Te0.15. The normal-state resistivity ρab is found to increase logarithmically with decreasing temperature as (T/Tc) → 0. Similar to granular metals, our results suggest that a superconductor-insulator transition below zero-field Tc may be induced in high magnetic fields. This is related to the intrinsic real-space phase-separated states common to all inhomogeneous superconductors.

Publ.-Id: 20749 - Permalink


Controlling Magnetic Order and Quantum Disorder in Molecule-Based Magnets
Lancaster, T.; Goddard, P. A.; Blundell, S. J.; Foronda, F. R.; Ghannadzadeh, S.; Moeller, J. S.; Baker, P. J.; Pratt, F. L.; Baines, C.; Huang, L.; Wosnitza, J.; Mcdonald, R. D.; Modic, K. A.; Singleton, J.; Topping, C. V.; Beale, T. A. W.; Xiao, F.; Schlueter, J. A.; Barton, A. M.; Cabrera, R. D.; Carreiro, K. E.; Tran, H. E.; Manson, J. L.;
We investigate the structural and magnetic properties of two molecule-based magnets synthesized from the same starting components. Their different structural motifs promote contrasting exchange pathways and consequently lead to markedly different magnetic ground states. Through examination of their structural and magnetic properties we show that [Cu(pyz)(H2O)(gly)2](ClO4)2 may be considered a quasi-one-dimensional quantum Heisenberg antiferromagnet whereas the related compound [Cu(pyz)(gly)](ClO4), which is formed from dimers of antiferromagnetically interacting Cu2+ spins, remains disordered down to at least 0.03 K in zero field but shows a field-temperature Phase diagram reminiscent of that seen in materials showing a Bose-Einstein condensation of magnons.

Publ.-Id: 20748 - Permalink


Evolution of the Pauli spin-paramagnetic effect on the upper critical fields of single-crystalline KxFe2-ySe2-zSz
Wolff-Fabris, F.; Lei, H.; Wosnitza, J.; Petrovic, C.;
We have studied the temperature dependence of the upper critical fields µ0Hc2 of KxFe2-ySe2-zSz single crystals up to 60 T. The µ0Hc2 for H parallel to ab and H parallel to c decrease with increasing sulfur content. The detailed analysis using Werthamer-Helfand-Hohenberg theory including the Pauli spin-paramagnetic effect shows that µ0Hc2 for H parallel to ab is dominated by the spin-paramagnetic effect, which diminishes with higher S content, whereas µ0Hc2 for H parallel to c shows a linear temperature dependence with an upturn at high fields. The latter observation can be ascribed to multiband effects that become weaker for higher S content. This results in an enhanced anisotropy of µ0Hc2 for high S content due to the different trends of the spin-paramagnetic and multiband effect for H parallel to ab and H parallel to c, respectively.

Publ.-Id: 20747 - Permalink


DEM-Based Analysis of Interactions between Tectonics and Landscapes in the Ore Mountains and Eger Rift (East Germany and NW Czech Republic)
Andreani, L.; Stanek, K. P.; Gloaguen, R.; Krentz, O.; Domínguez-González, L.;
Tectonics modify the base-level of rivers and result in the progressive erosion of landscapes. We propose here a new method to classify landscapes according to their erosional stages. This method is based on the combination of two DEM-based geomorphic indices: the hypsometric integral, which highlights elevated surfaces, and surface roughness, which increases with the topographic elevation and the incision by the drainage network. The combination of these two indices allows one to produce a map of erosional discontinuities that can be easily compared with the known structural framework. In addition, this method can be easily implemented (e.g., in MATLAB) and provides a quick way to analyze regional-scale landscapes. We propose here an example of a region where this approach becomes extremely valuable: the Ore Mountains and adjacent regions. The lack of young stratigraphic markers prevents a detailed analysis of recent fault activity. However, discontinuities in mapped geomorphic indices coupled to the analysis of river longitudinal profiles suggest a tight relationship between erosional discontinuities and main tectonic lineaments.
Keywords: Eger Rift; Ore Mountains (Erzgebirge); geomorphic indices; tectonics; Germany (Saxony); Czech Republic

Publ.-Id: 20746 - Permalink


Fermi-surface topology of the iron pnictide LaFe2P2
Blackburn, S.; Prevost, B.; Bartkowiak, M.; Ignatchik, O.; Polyakov, A.; Foerster, T.; Cote, M.; Seyfarth, G.; Capan, C.; Fisk, Z.; Goodrich, R. G.; Sheikin, I.; Rosner, H.; Bianchi, A. D.; Wosnitza, J.;
We report on a comprehensive de Haas-van Alphen (dHvA) study of the iron pnictide LaFe2P2. Our extensive density-functional band-structure calculations can well explain the measured angular-dependent dHvA frequencies. As salient feature, we observe only one quasi-two-dimensional Fermi-surface sheet; i.e., a hole-like Fermi-surface cylinder around Gamma, essential for s+/- pairing, is missing. In spite of considerable mass enhancements due to many-body effects, LaFe2P2 shows no superconductivity. This is likely caused by the absence of any nesting between electron and hole bands.

Publ.-Id: 20745 - Permalink


Optical study of superconducting Pr2CuOx with x similar or equal to 4
Chanda, G.; Lobo, R. P. S. M.; Schachinger, E.; Wosnitza, J.; Naito, M.; Pronin, A. V.;
Superconducting Pr2CuOx, x similar or equal to 4 (PCO), films with T' structure and a Tc of 27 K have been investigated by various optical methods in a wide frequency (7 - 55 000 cm-1) and temperature (2 - 300 K) range. The optical spectra do not reveal any indication of a normal-state gap formation. A Drude-like peak centered at zero frequency dominates the optical conductivity below 150 K. At higher temperatures, it shifts to finite frequencies. The detailed analysis of the low-frequency conductivity reveals that the Drude peak and a far-infrared (FIR) peak centered at about 300 cm-1 persist at all temperatures. The FIR-peak spectral weight is found to grow at the expense of the Drude spectral weight with increasing temperature. The temperature dependence of the penetration depth follows a behavior typical for d-wave superconductors. The absolute value of the penetration depth for zero temperature is 1.6 mu m, indicating a rather low density of the superconducting condensate.

Publ.-Id: 20744 - Permalink


Neutron and EPR study of Cu(tn)Cl2 - A two-dimensional spatially anisotropic triangular-lattice antiferromagnet
Tarasenko, R.; Orendáčová, A.; Čižmár, E.; Mataš, S.; Orendáč, M.; Zeleňák, V.; Pavlík, V.; Siemensmeyer, K.; Zvyagin, S. E.; Wosnitza, J.; Feher, A.;
We have studied the temperature dependence of the lattice parameters and the influence of spin anisotropy on the electron paramagnetic spectra of Cu(tn)Cl2, an S = 1/2 quasi-two-dimensional spatially-anisotropic triangular-lattice Heisenberg antiferromagnet. The variation of the resonance fields with temperature reflects the presence of an easy-plane exchange anisotropy with Jz/Jx,y < 1 and g-factor anisotropy, gz/gx,y > 1.

Publ.-Id: 20743 - Permalink


Ultrasonic investigations of the spin ices Dy2Ti2O7 and Ho2Ti2O7 in and out of equilibrium
Erfanifam, S.; Zherlitsyn, S.; Yasin, S.; Skourski, Y.; Wosnitza, J.; Zvyagin, A. A.; Mcclarty, P.; Moessner, R.; Balakrishnan, G.; Petrenko, O. A.;
We report ultrasound studies of spin-lattice and single-ion effects in the spin-ice materials Dy2Ti2O7 (DTO) and Ho2Ti2O7 (HTO) across a broad field range up to 60 T, covering phase transformations, interactions with low-energy magnetic excitations, and single-ion effects. In particular, a sharp dip observed in the sound attenuation in DTO at the gas-liquid transition of the magnetic monopoles is explained based on an approach involving negative relaxation processes. Furthermore, quasiperiodic peaks in the acoustic properties of DTO due to nonequilibrium processes are found to be strongly affected by macroscopic thermal-coupling conditions: the thermal runaway observed in previous studies in DTO can be suppressed altogether by immersing the sample in liquid helium. Crystal-electric-field effects having a higher energy scale lead to a renormalization of the sound velocity and sound attenuation at very high magnetic fields. We analyze our observations using an approach based on an analysis of exchange-striction couplings and single-ion effects.

Publ.-Id: 20742 - Permalink


Observation of spatially modulated laser-driven proton beams from micrometer thick targets
Zeil, K.; Metzkes, J.; Kroll, F.; Obst, L.; Kraft, S.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Sauerbrey, R.; Schramm, U.;
The advent of a new generation of high repetition rate Petawatt (PW) laser systems in combination with recent experimentally achieved proton energies of up to 45 MeV from ultra-short pulse (~ 50 fs) facilities is expected to strongly advance the application of laser-plasma based accelerators for ions, e.g. in medicine. In our presentation, we report on the experimental observation of spatially modulated proton beams emitted from micrometer thick targets which were irradiated with ultrashort (30 fs) laser pulses of a peak intensity of 5•1020W/cm2. The net-like proton beam modulations were recorded using stacks of radio-chromic films and the investigation of different target systems for a laser energy range of 0.9 to 2.9 J revealed a clear dependence on laser energy and target thickness for the onset and strength of the modulations. Numerical simulations suggest that intensity-dependent instabilities in the laser-produced plasma at the target front side lead to electron beam break-up or filamentation, then serving as the source of the observed proton beam modulations.
We propose that these results on laser intensity dependent plasma instabilities may have implications for the scaling of present acceleration mechanisms, such as target normal sheath acceleration, to higher proton energies and hence higher laser powers. Furthermore a brief overview of the recent laser and target area upgrade for laser-driven ion acceleration experiments at the HZDR will be given.
  • Lecture (Conference)
    16th Advanced Accelerator Concepts Workshop (AAC 2014), 13.-18.07.2014, San Jose, United States of America

Publ.-Id: 20741 - Permalink


Laser ion acceleration at HZDR
Zeil, K.; Metzkes, J.; Kroll, F.; Obst, L.; Kraft, S.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Sauerbrey, R.; Schramm, U.;
The talk gives an introduction into the laser-ion acceleration program at HZDR.
  • Lecture (Conference)
    3rd Topical Workshop on Novel Acceleration Techniques (LA3NET), 27.-30.04.2014, Dresden, Deutschland

Publ.-Id: 20740 - Permalink


Robust energy enhancement of ultrashort pulse laser accelerated protons from reduced mass targets
Zeil, K.; Metzkes, J.; Kluge, T.; Bussmann, M.; Cowan, T. E.; Kraft, S. D.; Sauerbrey, R.; Schmidt, B.; Zier, M.; Schramm, U.;
This paper reports on a systematic investigation of the ultrashort pulse laser driven acceleration of protons from thin targets of finite size, so-called reduced mass targets (RMTs). Reproducible series of targets, manufactured with lithographic techniques, and varying in size, thickness, and mounting geometry, were irradiated with ultrashort (30 fs) laser pulses of intensities of about 8 × 1020 Wcm−2. A robust maximum energy enhancement of almost a factor of two was found when comparing gold RMTs to reference irradiations of plain gold foils of the same thickness. Furthermore, a change of the thickness of these targets has less influence on the measured maximum proton energy when compared to standard foils, which, based on detailed particle-in-cell simulations, can be explained by the influence of the RMT geometry on the electron sheath. The performance gain was, however, restricted to lateral target sizes of greater than 50μm, which can be attributed to edge and mounting structure influences.

Publ.-Id: 20739 - Permalink


13,14B(n,γ) via Coulomb Dissociation for Nucleosynthesis towards the r-Process
Altstadt, S.; Adachi, T.; Aksyutina, Y.; Alcantara, J.; Alvarez-Pol, H.; Ashwood, N.; Atar, L.; Aumann, T.; Avdeichikov, V.; Barr, M.; Beceiro, S.; Bemmerer, D.; et al.;
Radioactive beams of 14,15B produced by fragmentation of a primary 40Ar beam were directed onto a Pb target to investigate the neutron breakup within the Coulomb field. The experiment was performed at the LAND/R3B setup. Preliminary results for the Coulomb dissociation cross sections as well as for the astrophysically interesting inverse reactions, 13,14B(n,γ), are presented.

Publ.-Id: 20738 - Permalink


Microstructural and mechanical characterisation of ODS ferritic alloys produced by mechanical alloying and spark plasma sintering
Hernández-Mayoral, M.; Serrano, M.; Oñorbe, E.; García-Junceda, A.; Hilger, I.; Kloeden, B.; Weissgaerber, T.; Ulbricht, A.; Bergner, F.; Radiguet, B.; Etienne, A.; Shariq, A.; Dewhurst, C. D.;
Powders with basic composition Fe-14Cr-2W-0.4Ti were mechanically alloyed (MA) with Y2O3 in a planetary ball mill under two different rotation speeds. Consolidation of the as-milled powders was performed by spark plasma sintering (SPS). As-milled powders showed a highly deformed microstructure with elongated nanometric grains, around 50nm and different nanoclusters were found depending upon the rotational speed that produces different stages on the nanoclusters evolution. In the case of SPS materials, grain growth occurred during the SPS process and it was possible to observe the influence of the MA parameters, with larger and more homogeneously distributed grains at the higher speed. The mechanical behavior of the SPS compacts was evaluated by tensile and small punch testing also showing the influence of the MA parameters in the material behavior.
Keywords: FeCr ODS alloys; Mechanical alloying; Spark plasma sintering; Nanostructured materials; Yttria; Microstructure; Tensile and small punch tests

Publ.-Id: 20737 - Permalink


β-Diketiminate Rare Earth Borohydride Complexes: Synthesis, Structure, and Catalytic Activity in the Ring-Opening Polymerization of epsilon-Caprolactone and Trimethylene Carbonate
Schmid, M.; Guillaume, S. M.; Roesky, P. W.;
The synthesis of a series of divalent and trivalent β-diketiminate borohydrides [(dipp)2NacNacLn(BH4)(THF)2] ((dipp)2NacNac = (2,6-C6H3iPr2)NC(Me)CHC(Me)N(2,6-C6H3iPr2); Ln = Sm, Eu, Yb) and [(dipp)2NacNacLn(BH4)2(THF)] (Ln = Sc, Sm, Dy, Yb, Lu) is reported. All compounds were obtained by salt metathesis in THF from [(dipp)2NacNacK] and the corresponding homoleptic divalent and trivalent borohydrides [Ln(BH4)2(THF)2] (Ln = Sm, Eu, Yb), [Sc(BH4)3(THF)2], and [Ln(BH4)3(THF)3] (Ln = Sm, Dy, Yb, Lu), respectively. The complexes were fully characterized and their solid state structures were established by single crystal X-ray diffraction. In both the divalent and trivalent compounds, the BH4 groups coordinate in a κ3(H) mode to the metal. Only in the lutetium complex [(dipp)2NacNacLu(BH4)2(THF)] does one BH4 group coordinate in a κ3(H) mode, whereas the other one coordinates as κ2(H). This kind of mixed κ23(H) coordination mode is rare. The application of the divalent and trivalent compounds as initiators in the ring-opening polymerization (ROP) of ε-caprolactone (CL) and trimethylene carbonate (TMC) was investigated. All complexes afforded a generally well-controlled ROP of both of these cyclic esters. High molar mass poly(ε-caprolactone)diols (Mn,NMR < 92 700 g/mol, ÐM = 1.51) and α-hydroxy,ω-formate telechelic poly(trimethylene carbonate)s (Mn,NMR < 16 000 g/mol, ÐM = 1.59) were thus synthesized under mild operating conditions.

Publ.-Id: 20736 - Permalink


Studie zur Partitionierung und Transmutation (P&T) hochradioaktiver Abfälle Stand der Grundlagen- und technologischen Forschung
Merk, B.; Glivici-Cotruţă, V.;
Das, dem Teilprojekt zu Grunde liegende, Gesamtprojekt gliederte sich in zwei Module: In Modul A (Förderung durch das BMWi, Federführung durch KIT) und Modul B (Förderung durch das BMBF, Federführung durch acatech). Projektpartner im Modul A waren DBE TECHNOLOGY GmbH, die Gesellschaft für Anlagen- und Reaktorsicherheit mbH (GRS), das Helmholtz-Zentrum Dresden-Rossendorf (HZDR), das Karlsruher Institut für Technologie (KIT) und die Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen zusammen mit dem Forschungszentrum Jülich (FZJ). Modul B wurde vom Zentrum für Interdisziplinäre Risiko- und Innovationsforschung der Universität Stuttgart (ZIRIUS) bearbeitet. Die Gesamtkoordination der beidem Module erfolgte durch die Deutsche Akademie der Technikwissenschaften (acatech). Auf Grundlage einer Analyse der wissenschaftlich-technischen Aspekte durch Modul A wurden die gesellschaftlichen Implikationen bewertet und daraus in Modul B Kommunikations- und Handlungsempfehlungen für die zukünftige Positionierung von P&T formuliert.
Im, vom HZDR koordinierten, Teilprojekt „Stand der Grundlagen- und technologischen Forschung“ wird eine Übersicht über den genannten Bereich gegeben. Eingeführt wird das Thema mit einer Kurzbeschreibung möglicher Reaktorsysteme für die Transmutation. Danach wird der Entwicklungsstand der Spezialbereiche Trennchemie, Sicherheitstechnologie, Beschleunigertechnologie Flüssigmetalltechnologie, Entwicklung von Spallationstargets, Transmutationsbrennstoffen und Werkstoffkonzepten sowie Konditionierung von Abfällen, beschrieben. Dies wird ergänzt durch Spezifika von Transmutationsanlagen beginnend bei physikalischen Grundlagen und Kerndesigns, über Reaktorphysik von Transmutationsanlagen, Simulationstools und die Entwicklung von Safety Approaches. Im Anschluss wird der Stand existierender Bestrahlungseinrichtungen mit schnellem Spektrum beschrieben. Nachfolgend werden basierend auf dem derzeitigen Stand von F&E die offenen Fragen und Forschungslücken in den einzelnen Teilbereichen – Wiederaufbereitung und Konditionierung, Beschleuniger und Spallationstarget, Reaktor – zusammengestellt und sowohl eine Strategie, als auch ein Fahrplan zur Schließung der Technology Gaps entwickelt.
Zusätzlich werden die Hauptbeiträge, des HZDR zur Gesamtstudie beschrieben. Dies sind insbesondere die Beschreibungen der Möglichkeiten und Grenzen von P&T, die Herausforderungen an Bestrahlungseinrichtungen zur Transmutation und deren Effektivität, sowie Sicherheitsmerkmale beschleuniger-getriebener unterkritischer Systeme inclusive grundlegender Störfallbetrachtungen und Sicherheitscharakteristik.

Dr. Bruno Merk wirkte zusätzlich, sowohl in Modul B als Fachmann für Transmutation als auch bei der Erstellung der acatech POSITION als fachlicher Berater mit.

Abstract
The main project, where this sub project contributed to, has been structured into two modules: module A (funded by the federal ministry of economics, managed by KIT) and module B (funded by the federal ministry of education and research, managed by acatech). Partners in module A were DBE TECHNOLOGY GmbH, the Gesellschaft für Anlagen- und Reaktorsicherheit mbH (GRS), the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), the Karlsruher Institute of Technology (KIT) and the Rheinisch-Westfälische Technische Hochschule (RWTH) Aachen, in co-operation with the Forschungszentrum Jülich (FZJ). Modul B has been executed by the Zentrum für Interdisziplinäre Risiko- und Innovationsforschung der Universität Stuttgart (ZIRIUS). The overall coordination has been carried out by the Deutsche Akademie der Technikwissenschaften (acatech). The social implications have been evaluated in module B based on the analysis of the scientific and technological aspects in module A. Recommendations for communication and actions to be taken for the future positioning of P&T have been developed.
In the project part, coordinated by HZDR – status of R&D – an overview on the whole topic P&T is given. The topic is opened by a short description of reactor systems possible for transmutation. In the following the R&D status of separation technologies, safety technology, accelerator technology, liquid metal technology, spallation target development, transmutation fuel and structural material development, as well as waste conditioning is described. The topic is completed by the specifics of transmutation systems, the basic physics and core designs, the reactor physics, the simulation tools and the development of Safety Approaches. Additionally, the status of existing irradiation facilities with fast neutron spectrum is described. Based on the current R&D status, the research and technology gaps in the topics: separation and conditioning, accelerator and spallation target, and reactor are characterized and a strategy as well as a roadmap for closing these gaps has been developed.
In addition the major contributions of HZDR to the main project are described. The major parts are the description of the potential and the limits of P&T, the requirements and challenges for transmutation systems and the related efficiency, as well as the safety features of accelerator driven subcritical systems including the transient behavior and the safety characteristics.

Dr. Bruno Merk additionally contributed to module B as specialist for transmutation and acted as scientific advisor for the preparation of the acatech POSITION.
Keywords: Partitioning, Transmutation, Nuclear Technology, Nuclear Reactors
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-052 2014

Downloads:

Publ.-Id: 20735 - Permalink


Assessment of the diagnostic performance of 18F-FDG-PET/CT for detection and characterization of solid renal malignancies.
Nakhoda, Z.; Torigian, D. A.; Saboury, B.; Hofheinz, F.; Alavi, A.;
To evaluate the sensitivity of the positron emission tomography (PET) portion of fluorine-18 fluorodeoxyglucose- PET-computerized tomography (18F-FDG-PET/CT) to detect solid malignant renal masses, and to assess for metabolic differences based on histopathological type. Nineteen subjects with 25 known solid malignant renal masses who underwent 18F-FDG-PET/CT were retrospectively evaluated. Qualitative analysis of the PET portion only of 18F-FDG-PET/CT examinations to assess visual detection of renal masses was initially performed in blinded fashion. Subsequently, measurements of standardized uptake value (SUV) and lesion-to-background ratios were performed for all masses and compared between histopathological types. Of 25 solid malignant renal masses, 18 were renal cell carcinoma (RCC), 3 were renal lymphoma, and 4 were metastases. Twenty-two of 25 were detectable, and all were correctly spatially localized. Fifteen of 22 detectable lesions were exophytic in configuration. The three non-detectable masses were non-exophytic RCC's with average diameter of 2.0cm. Fifteen of 18 of RCC were detectable, whereas all renal lymphomas and metastases were detectable. None of the metabolic parameters were statistically significant between RCC and renal lymphoma. However, all metabolic parameters were statistically significantly greater for renal metastases compared to RCC and renal lymphoma, and for clear cell RCC compared to papillary RCC. In conclusion, the PET portion of 18F-FDG-PET/CT had a sensitivity of 88% for detection of solid malignant renal lesions in patients with known renal malignancy, and reveals differences in metabolic activity based on histopathological type, which may be useful for purposes of individualized medicine. Further studies are required for more in depth assessment of these preliminary observations.
  • Open Access LogoHellenic Journal of Nuclear Medicine 16(2013), 19-24

Publ.-Id: 20734 - Permalink


Predictive value of asphericity of pretherapeutic FDG uptake in NSCLC
Apostolova, I.; Steffen, I.; Rogasch, J.; Furth, C.; Buchert, R.; Hofheinz, F.; Amthauer, H.;
Objectives: FDG-PET/CT has become the standard for staging of local tumor extent, mediastinal lymph node involvement and distant metastatic disease in patients with non-small-cell lung cancer (NSCLC). However, its role for prognosis is less clear. The aim of the present study was to evaluate the prognostic value of a novel quantitative measure for the spatial heterogeneity of FDG uptake, the asphericity (ASP).

Methods: FDG-PET/CT had been performed in 68 patients (65.5±8.8y) with newly diagnosed NSCLC prior to treatment. PET images of the primary tumor were segmented using the ROVER 3D segmentation tool based on thresholding at the volume-reproducible intensity threshold after subtraction of local background. ASP defined as the deviation of the tumor's shape from sphere shape was computed. Kaplan-Meier analysis with respect to progression-free (PFS) and overall survival (OS) was performed for localization (central vs. peripheral), SUVmax, metabolically active tumor volume (MTV), total lesion glycolysis (TLG) and ASP. OS and PFS curves were separated by the median value and compared by log-rank tests.

Results: 38 patients experienced tumor progression or recurrence after a median interval of 6.2 months (range 1.4-23.7). 28 patients died after a median interval of 7.1 months (0.4-19.4). The localization of the tumor was a predictor of both PFS (p=0.04, 2-year PFS 58% vs 45% for peripheral vs central localization) and OS (p=0.02, 2-year OS 57% vs 33%). ASP was the only PET-based parameter with prognostic value for PFS (p=0.005): the probability of 2-year PFS decreased from 60 % in the patients with low ASP to 47 % in the patients with high ASP. None of the PET-based parameters was predictive for OS.

Conclusions: The asphericity of the pretherapeutic FDG-uptake provides more power for the prediction of PFS in NCSLC than conventional quantitative measures including SUVmax, MTV and TLG.
  • Lecture (Conference)
    Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2014, 07.-11.06.2014, St. Louis, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 55(2014)Suppl. 1, 125
  • Lecture (Conference)
    Annual Congress of the European Association of Nuclear Medicine (EANM), 18.-22.10.2014, Gothenburg, Sweden
  • Abstract in refereed journal
    European Journal of Nuclear Medicine and Molecular Imaging 41(2014), S268
    DOI: 10.1007/s00259-014-2901-9

Publ.-Id: 20733 - Permalink


Dynamic Ga-68 DOTATOC PET for segregation of tumor perfusion from somatostatin receptor expression on neuroendocrine tumor (NET)
Steffen, I.; Hofheinz, F.; Pavel, M.; Brenner, W.; Prasad, V.;
Objectives: To generate quantitative parameters from dynamic Ga-68 DOTATOC PET (PET) as new markers for tumor perfusion and somatostatin receptor expression on gastroenteropancreatic NET.

Methods: PET was performed in 8 patients (pts) Images were acquired in list mode for 15 minutes after i.v. bolus injection. 63 regions of interests (spleen/adrenals, n=21; normal liver tissue, n=8; primary tumor/metastases (mets); n=34) were evaluated to generate k1, k2, k3, k4 and the fractional blood volume (fbv) using a reversable two compartment model.

Results: Mets in pts with proliferation rate (Ki67) 5-20% showed (n=12) significant higher k1, k2, k3, k4 (all p<0.01) compared to pts with lower Ki67 (<5%) (n=22) but significantly lower fbv (p<0.05). In liver (not receptor-specific uptake), k2 was signficantly higher (p<0.05) than in mets (median, 0.50 vs 0.23). SUVmax in mets showed significant correlations with k1 (rho, 0.37; p<0.001) und fbv (rho, 0.51; p<0.01) but not with k3. SUVmax in spleen/adrenal glands (receptor-specific uptake) correlated significantly with k3 (rho, 0.51; p<0.05).

Conclusions: These preliminary results, within its limitations (low pts number) suggests that dynamic Ga-68 DOTATOC PET enables segregation of tumor perfusion (fbv) from receptor specific binding (k1) in mets. Both parameters, fbv and k1, are primarily correlated to SUVmax in mets. The internalization of receptor ligand (Ga-68 DOTATOC) complexes (k3) appears to be mainly responsible for specific uptake in spleen and adrenal glands, while in normal liver a significantly higher washout of the ligand (k2) was observed which is in line with non-specific peptide uptake due to peptide metabolism in the liver. Moreover, mets in pts with higher Ki67 showed higher receptor ligand dynamics as denoted by higher k1-4 values.
  • Abstract in refereed journal
    Journal of Nuclear Medicine 55(2014)Suppl. 1, 558
  • Lecture (Conference)
    Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2014, 07.-11.06.2014, St. Louis, USA

Publ.-Id: 20732 - Permalink


Asphericity of pretherapeutic tumour FDG uptake provides independent prognostic value in head-and-neck cancer
Apostolova, I.; Steffen, I. G.; Wedel, F.; Lougovski, A.; Marnitz, S.; Derlin, T.; Amthauer, H.; Buchert, R.; Hofheinz, F.; Brenner, W.;
Objective:
To propose a novel measure, namely the ‘asphericity’ (ASP), of spatial irregularity of FDG uptake in the primary tumour as a prognostic marker in head-and-neck cancer.

Methods:
PET/CT was performed in 52 patients (first presentation, n = 36; recurrence, n = 16). The primary tumour was segmented based on thresholding at the volume-reproducible intensity threshold after subtraction of the local background. ASP was used to characterise the deviation of the tumour’s shape from sphere symmetry. Tumour stage, tumour localisation, lymph node metastases, distant metastases, SUVmax, SUVmean, metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were also considered. The association of overall (OAS) and progression-free survival (PFS) with these parameters was analysed.

Results:
Cox regression revealed high SUVmax [hazard ratio (HR) = 4.4/7.4], MTV (HR = 4.6/5.7), TLG (HR = 4.8/8.9) and ASP (HR = 7.8/7.4) as significant predictors with respect to PFS/OAS in case of first tumour manifestation. The combination of high MTV and ASP showed very high HRs of 22.7 for PFS and 13.2 for OAS. In case of recurrence, MTV (HR = 3.7) and the combination of MTV/ASP (HR = 4.2) were significant predictors of PFS.

Conclusions:
ASP of pretherapeutic FDG uptake in the primary tumour improves the prediction of tumour progression in head-and-neck cancer at first tumour presentation.
Keywords: Head-and-neck cancer; Prognosis; FDG PET; Heterogeneity; Asphericity

Publ.-Id: 20731 - Permalink


Near-field resonance shifts of ferroelectric barium titanate domains upon low-temperature phase transition
Döring, J.; von Ribbeck, H.-G.; Fehrenbacher, M.; Kehr, S. C.; Eng, L. M.;
Scattering scanning near-field optical microscopy (s-SNOM) has been established as an excellent tool to probe domains in ferroelectric crystals at room temperature. Here, we apply the s-SNOM possibilities to quantify low-temperature phase transitions in barium titanate single crystals by both temperature-dependent resonance spectroscopy and domain distribution imaging. The orthorhombic-to-tetragonal structural phase transition at 263 K manifests in a change of the spatial arrangement of ferroelectric domains as probed with a tunable free-electron laser. More intriguingly, the domain distribution unravels non-favored domain configurations upon sample recovery to room temperature as explainable by increased sample disorder. Ferroelectric domains and topographic influences are clearly deconvolved even at low temperatures, since complementing our s-SNOM nano-spectroscopy with piezoresponse force microscopy and topographic imaging using one and the same atomic force microscope and tip.

Publ.-Id: 20730 - Permalink


Rates of river incision across the main tectonic units of the Pamir identified using optically stimulated luminescence dating of fluvial terraces
Fuchs, M. C.; Gloaguen, R.; Krbetschek, M.; Szulc, A.;
Calculated incision rates along the Panj, the main river of the Pamir, are used to investigate any influence by tectonics or climate on the architecture of the river. The depositional ages of Panj River terraces were calculated using optically stimulated luminescence (OSL) dating of terrace sand. Fluvial incision rates were generated by integrating the terrace depositional ages with accurate kinematic GPS measurements of terrace heights above the modern Panj. We investigated 16 terraces along the Panj at the western Pamir margin and one terrace from the Vakhsh River to the north of the Pamir. The results reveal brief periods of fluvial deposition over the past 26 kyr. The oldest Panj terrace depositional ages coincide with early MIS 2 and MIS 2/1 glaciations on the Pamir Plateau. Younger terrace ages have no apparent link with glacial cycles. Terraces with varying heights above the modern Panj at different localities yielded similar depositional ages. This suggests that local conditions have determined fluvial incision rates. Combining all of the terrace measurements, the average incision rate of the Panj over the last 26 kyr has been similar to 5.6 mm/yr. A high mean incision rate of similar to 7.3 mm/yr was calculated from terraces where the Panj has cut a steep-sided valley through the Shakhdara dome. Significantly lower incision rates (similar to 2-3 mm/yr) were calculated from terraces where the Panj flows along the southern boundaries of the Shakhdara and Yazgulom domes. At those localities, graded segments of the Panj River profile and increased valley widths are indicative of local base levels. Downstream of the Yazgulom dome, river incision rates are generally lower (similar to 4-5 mm/yr) than the Panj average.
However, there is one exception where higher incision rates (similar to 6 mm/yr) were calculated upstream of the Darvaz Fault Zone, a major tectonic feature that forms the western boundary of the Pamir. The Vakhsh River terrace to the north of the Pamir yielded a lower incision rate (similar to 3 mm/yr) compared to the Panj average. Variation in incision rates along the Panj does not correspond to changes in rock type or river catchment area. Instead, incision rates appear to have been primarily influenced by river capture across the southern and central metamorphic domes of the Pamir. Wherever the Panj cuts these domes it displays a convex river profile. The combination of localized river profile convexity and changes in incision rates across the Pamir domes indicates that the dome boundaries have been active recently.

Publ.-Id: 20729 - Permalink


Seismotectonics of the Pamir
Schurr, B.; Ratschbacher, L.; Sippl, C.; Gloaguen, R.; Yuan, X.; Mechie, J.;
Based on a 2 year seismic record from a local network, we characterize the deformation of the seismogenic crust of the Pamir in the northwestern part of the India-Asia collision zone. We located more than 6000 upper crustal earthquakes in a regional 3-D velocity model. For 132 of these events, we determined source mechanisms, mostly through full waveform moment tensor inversion of locally and regionally recorded seismograms. We also produced a new and comprehensive neotectonic map of the Pamir, which we relate to the seismic deformation. Along Pamir's northern margin, where GPS measurements show significant shortening, we find thrust and dextral strike-slip faulting along west to northwest trending planes, indicating slip partitioning between northward thrusting and westward extrusion. An active, north-northeast trending, sinistral transtensional fault system dissects the Pamir's interior, connecting the lakes Karakul and Sarez, and extends by distributed faulting into the Hindu Kush of Afghanistan. East of this lineament, the Pamir moves northward en bloc, showing little seismicity and internal deformation. The western Pamir exhibits a higher amount of seismic deformation; sinistral strike-slip faulting on northeast trending or conjugate planes and normal faulting indicate east-west extension and north-south shortening. We explain this deformation pattern by the gravitational collapse of the western Pamir Plateau margin and the lateral extrusion of Pamir rocks into the Tajik-Afghan depression, where it causes thin-skinned shortening of basin sediments above an evaporitic décollement. Superposition of Pamir's bulk northward movement and collapse and westward extrusion of its western flank causes the gradual change of surface velocity orientations from north-northwest to due west observed by GPS geodesy. The distributed shear deformation of the western Pamir and the activation of the Sarez-Karakul fault system may ultimately be caused by the northeastward propagation of India's western transform margin into Asia, thereby linking deformation in the Pamir all the way to the Chaman fault in the south in Afghanistan.
Keywords: Pamir; seismotectonics; India-Asia collision; seismicity; moment tensors

Publ.-Id: 20728 - Permalink


Improving the Estimation of Above Ground Biomass Using Dual Polarimetric PALSAR and ETM+ Data in the Hyrcanian Mountain Forest (Iran)
Attarchi, S.; Gloaguen, R.;
The objective of this study is to develop models based on both optical and L-band Synthetic Aperture Radar (SAR) data for above ground dry biomass (hereafter AGB) estimation in mountain forests. We chose the site of the Loveh forest, a part of the Hyrcanian forest for which previous attempts to estimate AGB have proven difficult. Uncorrected ETM+ data allow a relatively poor AGB estimation, because topography can hinder AGB estimation in mountain terrain. Therefore, we focused on the use of atmospherically and topographically corrected multispectral Landsat ETM+ and Advanced Land-Observing Satellite/Phased Array L-band Synthetic Aperture Radar (ALOS/PALSAR) to estimate forest AGB. We then evaluated 11 different multiple linear regression models using different combinations of corrected spectral and PolSAR bands and their derived features. The use of corrected ETM+ spectral bands and GLCM textures improves AGB estimation significantly (adjusted R2 = 0.59; RMSE = 31.5 Mg/ha). Adding SAR backscattering coefficients as well as PolSAR features and textures increase substantially the accuracy of AGB estimation (adjusted R2 = 0.76; RMSE = 25.04 Mg/ha). Our results confirm that topographically and atmospherically corrected data are indispensable for the estimation of mountain forest’s physical properties. We also demonstrate that only the joint use of PolSAR and multispectral data allows a good estimation of AGB in those regions.
Keywords: Landsat7/ETM+; ALOS/PALSAR; L-band; above ground biomass (AGB); DBH; linear multiple regression; topographic effects; Hyrcanian mountainous forest; Iran

Publ.-Id: 20727 - Permalink


Classifying Complex Mountainous Forests with L-Band SAR and Landsat Data Integration: A Comparison among Different Machine Learning Methods in the Hyrcanian Forest
Attarchi, S.; Gloaguen, R.;
Forest environment classification in mountain regions based on single-sensor remote sensing approaches is hindered by forest complexity and topographic effects. Temperate broadleaf forests in western Asia such as the Hyrcanian forest in northern Iran have already suffered from intense anthropogenic activities. In those regions, forests mainly extend in rough terrain and comprise different stand structures, which are difficult to discriminate. This paper explores the joint analysis of Landsat7/ETM+, L-band SAR and their derived parameters and the effect of terrain corrections to overcome the challenges of discriminating forest stand age classes in mountain regions. We also verified the performances of three machine learning methods which have recently shown promising results using multisource data; support vector machines (SVM), neural networks (NN), random forest (RF) and one traditional classifier (i.e., maximum likelihood classification (MLC)) as a benchmark. The non-topographically corrected ETM+ data failed to differentiate among different forest stand age classes (average classification accuracy (OA) = 65%). This confirms the need to reduce relief effects prior data classification in mountain regions. SAR backscattering alone cannot properly differentiate among different forest stand age classes (OA = 62%). However, textures and PolSAR features are very efficient for the separation of forest classes (OA = 82%). The highest classification accuracy was achieved by the joint usage of SAR and ETM+ (OA = 86%).
However, this shows a slight improvement compared to the ETM+ classification (OA = 84%). The machine learning classifiers proved t o be more robust and accurate compared to MLC. SVM and RF statistically produced better classification results than NN in the exploitation of the considered multi-source data.
Keywords: Landsat; ALOS/PALSAR; L-band; maximum likelihood classification; support vector machines; neural networks; random forest; topographic effects; Hyrcanian mountainous forest; Iran

Publ.-Id: 20726 - Permalink


Improving Lithological Mapping by SVM Classification of Spectral and Morphological Features: The Discovery of a New Chromite Body in the Mawat Ophiolite Complex (Kurdistan, NE Iraq)
Othman, A. A.; Gloaguen, R.;
The mineral ore potential of many mountainous regions of the world, like the Kurdistan region of Iraq, remains unexplored. For logistical and sometimes political reasons, these areas are difficult to map using traditional methods. We highlight the improvement in remote sensing geological mapping that arises from the integration of geomorphic features in classifications. The Mawat Ophiolite Complex (MOC) is located in the NE of Iraq and is known for its mineral deposits. The aims of this study are: (I) to refine the existing lithological map of the MOC; (II) to identify the best discriminatory datasets for lithological classification, including geomorphic features and textures; and (III) to identify potential locations with high concentrations of chromite. We performed a Support Vector Machine (SVM) classification method to allow the joint use of geomorphic features, textures and multispectral data of the Advanced Space-borne Thermal Emission and Reflection radiometer (ASTER) satellite. The updated map allowed the identification of a new mafic body and a substantial improvement of the geometry of the known lithological units. The use of geomorphic features allowed for the increase of the overall accuracy from 73% to 79.3%. In addition, we detected chromite occurrences within the ophiolite by applying Spectral Angle Mapping (SAM) technique. We identified two new locations having high concentrations of chromite and verified one of these promising areas in the field. This new body covers ~0.3 km2 and has coarsely crystalline chromite within dunite host rock. The chromium (Cr2O3) concentration is ~8.46%. The SAM and SVM methods applied on ASTER satellite data show that these can be used as a powerful tool to explore ore deposits and to further improve lithological mapping in mountainous semi-arid regions
Keywords: Zagros; Mawat; ophiolite; chromite; SVM; SAM; ASTER; remote sensing; GIS

Publ.-Id: 20725 - Permalink


Molekulare Bildgebung des Sigma1-Rezeptors: Von der Idee bis zur klinischen Anwendung
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    Symposium "Translationale Radiochemie", 20.09.2014, Mannheim, Deutschland

Publ.-Id: 20723 - Permalink


Microorganisms in potential host rocks for geological disposal of nuclear waste and their interactions with radionuclides
Cherkouk, A.; Liebe, M.; Lütke, L.; Moll, H.; Stumpf, T.;
The long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the oxidation state, speciation and therefore the mobility of radionuclides as well as gas generation or canister corrosion. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g., clay, salt) and if these microorganisms can influence the performance of a repository.
Microbial diversity in potential host rocks for geological disposal of nuclear waste was analyzed by culture-independent molecular biological methods (e.g., 16S rRNA gene retrieval) as well as enrichment and isolation of indigenous microbes.
Among other isolates, a Paenibacillus strain, as a representative of Firmicutes, was recovered in R2A media under anaerobic conditions from Opalinus clay from the Mont Terri in Switzerland. Accumulation experiments and potentiometric titrations showed a strong interaction of Paenibacillus sp. cells with U(VI) within a broad pH range (3-7) [1].
Additionally, the interactions of the halophilic archaeal strain Halobacterium noricense DSM 15987, a salt rock representative reference strain, with U(VI) at high ionic strength was investigated. After 48 h the cells were still alive at uranium concentrations up to 60 μM, which demonstrates that Halobacterium noricense can tolerate uranium concentrations up to this level. The formed uranium sorption species were examined with time-resolved laser-induced fluorescence spectroscopy (TRLFS).
The results about the microbial communities present in potential host rocks for nuclear waste repositories and their interactions with radionuclides contribute to the safety assessment of a prospective nuclear waste repository.
  • Poster
    Key topics on deep geological disposal, 24.-26.09.2014, Köln, Deutschland

Publ.-Id: 20722 - Permalink


Growth of separated individual SWCNTs from metal:matrix templates
Melkhanova, S.; Kunze, T.; Haluska, M.; Hübner, R.; Keller, A.; Gemming, S.; Krause, M.;
Metal: matrix templates deposited by physical vapor deposition (PVD) were used to grow separated, individual single-walled carbon nanotubes (SWCNTs). The templates are thin films of 2 nm thickness, where the metal is either segregated as nanoparticles (NPs) or diluted in the matrix. The upper limit of the NP diameter was confined by the film thickness. The function of the matrix is to prevent the metal particle from coalescence during nanotube growth by chemical vapor deposition. SEM, TEM, AFM, and Raman mapping were used for template and carbon nanotube characterization. SWCNTs with a narrow, monomodal diameter distribution are obtained from templates with NPs of 2 nm diameter. About 50 % of the SWCNTs detected by Raman mapping have a diameter between 1.3 nm and 1.5 nm. Smaller SWCNT diameters down to 0.8 nm are obtained from templates where the metal is diluted in the matrix. For these templates a bimodal SWCNT diameter distribution was observed. The two maxima of the CNT diameter distribution were found at about 0.8 nm to 1.0 nm and at about 1.2 nm to 1.4 nm, respectively. The CNTs are in their majority separated each from other.
Keywords: Nanocomposites, Carbon Nanotubes, SEM, TEM, AFM, Raman
  • Poster
    XXVIII. International Winterschool on Electronic Properties of Novel Materials, 08.-15.03.2014, Kirchberg, Österreich

Publ.-Id: 20721 - Permalink


Periacetabular bone metabolism following hip revision surgery. PET-based evaluation of allograft osteointegration.
Bernstein, P.; Beuthien-Baumann, B.; Kotzerke, J.; Hofheinz, F.; Zessin, J.; Stiehler, M.; Günther, K.-P.;
The treatment of loosened total hip replacement (THR) acetabular components may require the management of severe bone defects. Although being applied for decades, there is only limited scientific data about the osteointegration of cancellous bone allografts (CBA) and other void fillers. Monitoring of periprosthetic bone regeneration could possibly help to optimize this process thereby reducing late failure rates. The aim of this study was to show osteometabolic changes in periprosthetic CBA after THR revision with the use of sodium-[18F]-fluoride (NaF) and positron emission tomography (PET). Patients, methods: Twelve patients undergoing THR revision with the use of CBA were prospectively enrolled in the study. Nine patients completed all necessary examinations and were included in the evaluation. The temporal pattern of osteointegration was assessed via NaF-PET at one (PET1) and six weeks (PET2) after surgery. CBA, tantalum implants, supraacetabular regions ipsilateral and contralateral, and parasymphyseal pubic bones were delineated as volumes of interest (VOI) in postop CT scans, which were then merged with the PET data. Results: In comparison to the contralateral supraacetabular reference bone, a significant 1.5-fold increase of osteometabolic activity from PET1 to PET2 was seen in the CBA region. Also, the ipsilateral supraacetabular host bone showed a higher NaF-influx in week 6, compared to the first postoperative week. The supraacetabular site exhibited a significantly 1.8- to 2-fold higher influx and uptake than bone regions in non-operated sites. Tantalum implants had a low NaF influx at both time points investigated.

Conclusion: Using NaF-PET osteometabolic changes of CBA and implant-bone-interfaces can be monitored. Applying this method we demonstrated early periprosthetic temporal bone regeneration patterns in THR cup revision patients.
Keywords: Allograft; NaF-PET, bone metabolism; endoprothesis; acetabular

Publ.-Id: 20720 - Permalink


Zwitterionic-Coated "Stealth" Nanoparticles for Biomedical Applications: Recent Advances in Countering Biomolecular Corona Formation and Uptake by the Mononuclear Phagocyte System
Pombo Garcia, K.; Zarschler, K.; Barbaro, L.; Barreto, J. A.; O'Malley, W.; Spiccia, L.; Stephan, H.; Graham, B.;
Nanoparticles represent highly promising platforms for the development of imaging and therapeutic agents, including those that can either be detected via more than one imaging technique (multi-modal imaging agents) or used for both diagnosis and therapy (theranostics). A major obstacle to their medical application and translation to the clinic, however, is the fact that many accumulate in the liver and spleen as a result of opsonization and scavenging by the mononuclear phagocyte system. This focused Review summarizes recent efforts to develop zwitterionic-coatings to counter this issue and render nanoparticles more biocompatible. Such coatings have been found to greatly reduce the rate and/or extent of non-specific adsorption of proteins and lipids to the nanoparticle surface, thereby inhibiting production of the "biomolecular corona" that is proposed to be a universal feature of nanoparticles within a biological environment. Additionally, in vivo studies have demonstrated that larger-sized nanoparticles with a zwitterionic coating have extended circulatory lifetimes, while those with hydrodynamic diameters of <= 5 nm exhibit small-molecule-like pharmacokinetics, remaining sufficiently small to pass through the fenestrae and slit pores during glomerular filtration within the kidneys, and enabling efficient excretion via the urine. The larger particles represent ideal candidates for use as blood pool imaging agents, whilst the small ones provide a highly promising platform for the future development of theranostics with reduced side effect profiles and superior dose delivery and image contrast capabilities.

Publ.-Id: 20719 - Permalink


Development of Radiotracers for Neuroimaging with PET: Challenges and Problems.
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    5th INBR International Neuroscience Conference 2014, Satellite Meeting on Neuroimaging – the PET Experience, 01.08.2014, Owerri, Nigeria

Publ.-Id: 20717 - Permalink


Introduction into Autoradiography and Radioligand Binding Assays.
Brust, P.;
Es ist kein Abstract vorhanden.
  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), Advanced school on Improving Neuroscience Research in the Third World, 28.-31.07.2014, Owerri, Nigeria

Publ.-Id: 20716 - Permalink


Nonlinear PT−symmetric plaquettes --- and beyond
Günther, U.; Kevrekidis, P.; Li, K.; Malomed, B.;
Nonlinear 2-dimensional PT-symmetric plaquettes of various types are considered. A technique is developed to obtain explicit matrix representations for the parity (P) and for the time-reversal (T) operators starting from initially heuristically designed gain-loss setups of general 2D-type. The threshold behavior of the corresponding linear sub-systems is analyzed near PT-phase transition points in parameter space, the concrete type of exceptional point is established and the analytical construction of stationary solutions for the nonlinear setups is made explicit. The presentation is based on common work with Panayotis Kevrekidis, Kai Li and Boris Malomed [J. Phys. A 45, 444021 (2012)]. Next possible steps of technical extensions towards higher-dimensional soliton setups and required integrability tests via the search for Lax pairs of Zakharov-Shabat and Fordy-Kulish type are briefly sketched.
Keywords: PT symmetry, nonlinear 2-dimensional plaquettes, parity operator, time reversal operator, PT phase transition, exceptional point, Lax pair
  • Invited lecture (Conferences)
    SIAM Conference on Nonlinear Waves and Coherent Structures (SIAM-NW14), Churchill College, University of Cambridge, 11.-14.08.2014, Cambridge, United Kingdom

Publ.-Id: 20715 - Permalink


Hydrothermal carbonate chimneys from a continental rift (Afar Rift): Mineralogy, geochemistry, and mode of formation
Dekov, V. M.; Egueh, N. M.; Kamenov, G. D.; Bayon, G.; Lalonde, S. V.; Schmidt, M.; Liebetrau, V.; Munnik, F.; Fouquet, Y.; Tanimizu, M.; Awaleh, M. O.; Guirreh, I.; Le Gall, B.;
Carbonate chimney-like structures up to 60 m high are scattered or arranged in rows at the shores of a desiccating hypersaline and alkaline lake from a continental rift setting (Lake Abhé, Afar Rift, Djibouti). The chimneys apparently formed sub-aqueously in the lake water body at a higher water level than observed today. Alternating calcite and low-Mg calcite + silica concentric layers compose the chimney structures. Mineralogical and geochemical investigations of the chimneys, lake water, and hot spring (hydrothermal) fluids suggest that the chimneys are a result of rapid carbonate precipitation during the mixing of hydrothermal fluids with lake water. In contrast to hot spring fluid, lake water is enriched in HREE and possesses a pronounced positive Ce anomaly, features that are preserved in the carbonate chimney layers. Mixing calculations based on Sr- isotope and concentration data indicate a hydrothermal fluid contribution of ~45 % in the chimney interior, which decreases to ~4 % in the external chimney layer. Sr in the hydrothermal fluids is predominantly leached from the underlying volcanic rocks, whereas the lake’s Sr budget is dominated by riverine input. Considering the fluid mixing ratios calculated by Sr-data, the measured C and O isotope compositions indicate that chimney carbonates precipitated at temperatures between 14°C (internal part) and 22°C (external part) with a carbon source that was most likely atmospheric.
The low-Mg calcite layers, including the outermost layer, appear to have enhanced signals of lake water inheritance based on elevated concentrations of immobile elements, ΣREE, and Sr and Ca isotope compositions. Ca-isotope data reveal that internal chimney layers formed by non-equilibrium calcite precipitation with a predominantly hydrothermal Ca source. The external low-Mg calcite layer received Ca contributions from both hydrothermal fluid and lake water, with the latter being the dominant Ca source. Highly positive δ44/40Ca of lake water likely reflects non-equilibrium Ca-carbonate precipitation during lake water evaporation with resulting 44Ca enrichment of residual lake water. The strong degree of 44Ca enrichment may point towards multiple lake drying and Ca-reservoir depletion events. Coupled C-O-Ca-isotope data of the sampled carbonate chimney suggest late-stage (low-temperature) hydrothermal carbonate chimney formation during strongly evaporative lake conditions at the time of low-Mg calcite precipitation. U-Th age dating suggests the chimneys formed no earlier than 0.82 kyr BP (0.28 ± 0.54).
Keywords: carbonate; chimney; continental rift; H-C-O-Ca-Sr-Nd-Pb-Th-U-isotopes; hydrothermalism

Publ.-Id: 20714 - Permalink


Entwicklung, Synthese und F-18-Markierung von fluoralkylierten Triazinderivaten zur bildgebenden Darstellung der Phosphodiesterase 2A mittels PET
Schröder, S.; Wenzel, B.; Kranz, M.; Egerland, U.; Teodoro, R.; Deuther-Conrad, W.; Fischer, S.; Höfgen, N.; Steinbach, J.; Brust, P.;
Ziel:
Phosphodiesterasen (PDE) hydrolysieren die zyklischen Nucleotide cAMP und/oder cGMP. PDE-Inhibitoren verzögern den Abbau dieser sekundären Botenstoffe und beeinflussen physiologische Prozesse. Die PDE2A zeigt eine hohe, spezifische Expression im Gehirn sowie in bestimmten Tumoren und ist vermutlich an der Pathophysiologie entsprechender Erkrankungen beteiligt. Ziel ist die Darstellung eines F-18-Radioliganden für die Bildgebung der PDE2A mittels PET.

Methodik:
Ausgehend von der Leitstruktur TA1 wurden neue Fluoralkyl-Derivate TA2-4 entwickelt
(Abb. 1). Für potentielle PDE2A-Inhibitoren ist neben der Affinität v. a. die Selektivität zwischen der PDE2A und der PDE10A aufgrund ähnlicher Verteilungsmuster entscheidend.
Abb. 1
Zu den Derivaten TA3/4 wurden Tosylat-Präkursoren für einstufige F-18-Markierungen synthetisiert, wobei folgend der Radioligand [F-18]TA3 vorgestellt wird.
Die F-18-Fluorierung erfolgte in Acetonitril bei 80°C in 15 Minuten. [F-18]TA3 wurde mittels semi-präparativer HPLC isoliert, über eine Sep-Pak® C18 Kartusche gereinigt und in 0,9%iger NaCl-Lösung formuliert. Die Analytik des Endproduktes erfolgte mittels Radio-DC und -HPLC. Für in-vitro-Autoradiographien wurden sagittale Rattenhirnschnitte mit 1 MBq [F-18]TA3 für 60 Minuten bei Raumtemperatur inkubiert.

Ergebnisse:
[F-18]TA3 wurde mit einer Markierungsausbeute von 75,4 ± 4,9%, einer radiochemischen Ausbeute von 57,2 ± 0,4%, einer spezifischen Aktivität von 60,4 ± 11,6 GBq/µmol (EOS) und einer radiochemischen Reinheit von ≥ 99,5% synthetisiert.
Entsprechend dem PDE2A-Verteilungsmuster zeigten erste in-vitro-Autoradiographien eine hohe und spezifische Anreicherung von [F-18]TA3 im Cortex und Striatum (Abb. 2).

Abb. 2
Schlussfolgerungen:
Die Ergebnisse zu [F-18]TA3 zeigen, dass ein neuartiger und hochaffiner PDE2A-Radioligand erfolgreich dargestellt werden kann. Die Radiosynthese von [F-18]TA4 wird derzeit bearbeitet. Die Charakterisierung dieser F-18-Alkyl-Derivate mittels TierPET/MR, Autoradiographie und Studien zum Metabolismus ist geplant.
  • Lecture (Conference)
    AGRR2014 - 22. Jahrestagung der Arbeitsgemeinschaft Radiochemie/Radiopharmazie, 11.-13.09.2014, Mainz, Deutschland

Publ.-Id: 20713 - Permalink


Spectroscopic study on uranyl carboxylate complexes formed at the surface layer of Sulfolobus acidocaldarius
Reitz, T.; Rossberg, A.; Barkleit, A.; Steudtner, R.; Selenska-Pobell, S.; Merroun, M. L.;
The complexation of U(VI) at the proteinaceous surface layer (S-Layer) of the archaeal strain Sulfolobus acidocaldarius was investigated over a pH range from pH 1.5 to 6 at the molecular scale using time-resolved laser-induced fluorescence spectroscopy (TRLFS) and U LIII-edge extended X-ray absorption fine structure (EXAFS). The S-layer, which represents the interface between the cell and its environment, is very stable against high temperatures, proteases, and detergents. This allowed the isolation and purification of S-layer ghosts (=empty cells) that maintain the size and shape of the cells. In contrast to many other cell envelope compounds the studied S-layer is not phosphorylated, which enabled the investigation of uranyl carboxylate complexes, which are usually masked by uranyl phosphate complexes. We demonstrated that at highly acidic conditions (pH 1.5 to 3) no uranium was bound by the S layer. In contrast to that, at moderate acidic pH conditions (pH 4.5 and 6) a complexation of U(VI) at the S layer via deprotonated carboxylic groups was stimulated. Titration studies revealed dissociation constants for the carboxylic groups of glutamic and aspartic acid residues of pKa = 4.78 and 6.31. The uranyl carboxylate complexes formed at the S-layer did not show luminescence properties at room temperature, but only under cryogenic conditions. The obtained luminescence maxima are similar to those of uranyl acetate. EXAFS spectroscopy demonstrated that U(VI) in these complexes is mainly coordinated to carbon in a bidentate binding mode. The elucidation of the molecular structure of these complexes was facilitated by the absence of phosphate groups in the studied S-layer protein.
Keywords: Sulfolobus acidocaldarius, S-Layer, Uranium, Interactions, uranyl carboxylate complexes, XANES, EXAFS, TRLFS

Publ.-Id: 20712 - Permalink


Decrease of U(VI) immobilization capability of the facultative anaerobic strain Paenibacillus sp. JG TB8 under anoxic conditions due to strongly reduced phosphatase activity.
Reitz, T.; Rossberg, A.; Barkleit, A.; Selenska-Pobell, S.; Merroun, M. L.;
Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization.
Keywords: Paenibacillus, Uranium, Biomineralization, XAS, TRLFS, TEM, Phosphatase activity

Publ.-Id: 20711 - Permalink


Neuroimaging the PET experience
Brust, P.;
Positron Emission Tomography (PET) is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide that is routinely used in radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109,8 min. The administration of such radiotracers into the brain provides images of transport, metaboic and neurotransmission processes on the molecular level. After a short introduction into the principles of PET this talk will mainly focus on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as discussed in this talk provides molecular probes which are not only useful for imaging of human brain diseases. They allow also molecular neuroreceptor imaging studies in various small-animal models of disease including genetically engineerd animals. Futhermore, they provide a powerful tool for in vivo pharmacology during the process of preclinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the phramacokinetics and pharmacodynamics of drugs in vivo.
  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Publ.-Id: 20710 - Permalink


Plasma based nanotechnology against corrosion of CuZn and TiAl alloys.
Pelic, B.; Bregolin, F. L.; Prucnal, S.; Yankov, R.; Skorupa, W.;
Experiments have been undertaken to explore the improvement of the aqueous corrosion and high temperature oxidation of CuZn and TiAl, respectively, by applying plasma immersion ion implantation (PI3).
The atmospheric corrosion of the tongues within the reed pipes which consist of a Cu-Zn alloy (namely brass) is strongly enhanced by traces of VOC (acetic acid vapors) and also the alloy’s instability caused by dezincification. A significant improvement in corrosion resistance has been achieved by applying a 30 nm aluminum oxide film using pulsed laser deposition (PLD) and implanting nitrogen ions into the near surface and the interface regions. In the case of γ-TiAl alloys which exhibit poor oxidation resistance, despite their good mechanical properties at elevated temperatures, this limits the replacement of the nowadays used heavy components made of Ni-alloys. A significant improvement in high temperature oxidation resistance of TiAl alloys (up to 900 °C) has been achieved by implanting fluorine ions (1017 cm-2) at 30 keV into the alloy’s subsurface using PI3 process. A TiAl alloy modified in this way has been shown to acquire a stable, adherent and highly protective alumina scale (Al2O3) under high temperature oxidation in air. The influence of the implanted N+ into CuZn and F+ into TiAl samples on the corrosion process has been investigated. For the sample evaluation, different characterization methods including scanning electron microscope with energy dispersive X-ray spectroscopy (SEM / EDX), Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS), Elastic recoil detection analysis (ERDA), and Dektak stylus profiling have been applied to determine the chemical composition, the elemental depth profiles, roughness and defect formation of the samples before and after exposure.
Keywords: Plasma immersion ion implantation (PI3), Pulsed laser deposition (PLD), corrosion of reed organ pipes, CuZn alloys, TiAl alloys, oxidation protection.
  • Lecture (Conference)
    ION 2014 X-th INTERNATIONAL CONFERENCE on Ion Implantation and Other Applications of Ions and Electrons, 23.-26.06.2014, Kazimierz Dolny, Poland

Publ.-Id: 20709 - Permalink


Importance of the blood-brain barrier for neuroimaging studies
Brust, P.;
The blood-brain barrier (BBB) is a control system to preserve homeostasis in the nervous system, facilitating the entry of necessary metabolites, but blocking the entry or facilitating the removal of unnecessary metabolites or toxic substances. For any solute the efficacy of the exclusion or transport is determined by the morphological and functional characteristics of the brain capillaries and by the biochemical and biophysical characteristics of the solute. This applies also for radiotracers which are used for brain imaging. Several transport routes across the BBB exist. Therfore, the transport of radiotracers depends on the functional status of the brain endothelium. Studies were performed to investigate the expression and function of various transport systems at the BBB, such as ABC transporters, aquaporins, glucose, amino acid, choline and serotonin transporters. The influence of drugs, hormones and brain development on transport processes has been explored. Our main findins are: (1) The brain uptake of certain 99m/99Tc-labelled radiotracers is reduced by the presence of drug efflux transporters, e.g: P-glycoprotein. (2) Peptide hormones selectively alter the water permeability and the transport of neutral amino acids at the BBB. (3) The BBB transport of neutral amino acids decreases during development. (4) The transport of basic drugs from blood to brain is partly mediated by the BBB choline transporter. (5) The transport of the PET radiotracer [11C]McN5652 is mediated by the serotonin transporter at the BBB but of no relevance for human PET studies. It is concluded that the transport of radiotracers across the BBB does not solely depend on the lipophilicity of the compounds. Active and regulated efflux systems need to be considered. For many radiotracers specific transport systems exist, which underlie developmental changes and physiological regulation. Nutrient transporter, e. g. for glucose, amino acids and choline, are of special importance.
  • Invited lecture (Conferences)
    5th Biennial Inernational Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Publ.-Id: 20708 - Permalink


Molecular Imaging of Neurodegeneration
Brust, P.;
Molecular imaging (MI) originated from the field of radiopharmacology due to the need to better understand the fundamental molecular pathways inside organisms in a noninvasive manner. It emerged in the early twenty-first century as a discipline at the intersection of molecular biology and in vivo imaging and enables the visualization of the cellular function and the follow-up of the molecular process in living organisms without perturbing them. Basic requirements for MI are probes whose concentration and/or spectral properties are altered by the specific biological process under investigation technology to monitor these probes in living organisms and to reconstruct images from their distribution patterns. Positron Emission Tomography (PET) ist the most sensitive molecular imaging tool and a well-established method for neuroimaging of neurodegeneration such as Alzheimer's disease (AD). An ideal PET biomarker for AD should allow a reliable estimation of disease risk and rate of disease progression long before first symptoms are clinically diagnosed. The main pathologic processes of AD, deposition of beta-amyloid, hyperphosphorylated tau protein, degeneration of cholinergic and other neurons, precede clinical symptoms by years providing potential targets for the identification of individuals at risk for AD. In the last few years, several PET tracers targeting beta-amyloid in AD have been developed. The suitability of these PET radiopharmaceuticals to differentiate AD patients and patients with mild cognitive impairment (MCI) from control subjects has been demonstrated and will be discussed. However beta-amyloid deposition has been found in about 20% of normal elderly subjects.
  • Invited lecture (Conferences)
    5th Biennial International Neuroscience Conference (INBR2014), 28.-31.07.2014, Owerri, Nigeria

Publ.-Id: 20707 - Permalink


Systematic analysis on the achievable accuracy of PT-PET through automated evaluation techniques
Helmbrecht, S.; Kuess, P.; Birkfellner, W.; Enghardt, W.; Stützer, K.; Georg, D.; Fiedler, F.;
Introduction: Particle Therapy - Positron Emission Tomography (PT-PET) is currently the only clinically applied method for in vivo verication of ion-beam radiotherapy during or close in time to the treatment.
Since a direct deduction of the delivered dose from the measured activity is not feasible, images are compared to a reference distribution. The achievable accuracy of two image analysis approaches was investigated by means of reproducible phantom benchmark tests. This is an objective method that exclude patient related factors of influence.
Material and Methods: Two types of phantoms were designed to produce well dened deviations in the activity distributions. Pure range dierences were simulated using the rst phantom type while the other emulated cavity structures. The phantoms were irradiated with 12C-ions. PT-PET measurements were performed by means of a camera system installed at the beamline. Dierent measurement time scenarios were investigated, assuming a PET scanner directly at the irradiation site or placed within the treatment room.
The images were analyzed by means of the Pearson Correlation Coecient (PCC) and a range calculation algorithm combined with a dedicated cavity lling detection method.
Results: Range dierences could be measured with an error of less than 2 mm. The range comparison algorithm yielded slightly better results than the PCC method. The lling of a cavity structure could be safely detected if its inner diameter was at least 5 mm.
Conclusion: Both approaches evaluate the PT-PET data in an objective way and deliver promising results for in-beam and in-room PET for clinical realistic dose rates.

Publ.-Id: 20706 - Permalink


Leaching of copper from Kupferschiefer by organic acid and heterotrophic bacteria
Kostudis, S.; Bachmann, K.; Kutschke, S.; Pollmann, K.; Gutzmer, J.;
Polymetallic Cu-Ag ores of the Central European Kupferschiefer deposits are one of the most important sources of Cu in Europe. Because the ores are typically complex and often exceptionally fine-grained the development of efficient alternatives to conventional beneficiation strategies are an important target of current research. Biomining – the use of biological components for metal extraction - may offer solutions that are both efficient and environmentally benign. As conventional bioleaching with acidophilic microorganisms is impeded by the high carbonate content of the Kupferschiefer ores, heterotrophic microorganisms and glutamic acid are investigated as a possible alternative in the present study. The focus of this investigation is solely on the recovery of copper from the Kupferschiefer sensu strictu. Bioleaching experiments were carried out using such material from the Polkowice Mine in Poland. This material is marked by high grade (3.8 wt% Cu), complex ore mineralogy (chalcocite, bornite, chalcopyrite and covellite in significant quantity) and a gangue mineralogy that is rich in carbonate, organic carbon and clay minerals that together form a very fine-grained matrix. (Bio)-leaching experiments yield best results when glutamic acid alone is used – reaching Cu recoveries up to 44 %. Recoveries are consistently lower in experiments in which glutamic acids and microbiological metabolites are both present. The leaching of chalcocite renders the greatest contribution to the Cu recovered to the leach solution in all experiments. It can be concluded that glutamic acid solubilise copper efficiently from Kupferschiefer, mainly from chalcocite.
Keywords: sulphide ores, bacteria, bioleaching, liberation analysis, ore mineralogy
  • Minerals Engineering (2015)

Publ.-Id: 20705 - Permalink


Determination of Uranium (VI)-Speciation in Natural Occurring Waters by Time-resolved Laser-induced Fluorescence Spectroscopy
Baumann, N.; Geipel, G.;
Method of Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS) is explained, and illustrated with U(VI) measuring results gained from surface water and soil water samples originated from the area of the former uranium mining heap "Gessenhalde" close to Ronneburg in Eastern Thuringia. Comparative former TRLFS measuring results gained from several uranium mining tailing waters and from further water samples are shown.
  • Invited lecture (Conferences)
    Special lecture at the Department of Applied Radiation and Isotopes, Faculty of Science, Kasetsart University, 27.08.2014, Bangkok, Thailand

Publ.-Id: 20704 - Permalink


Speciation of uranyl(VI) using combined theoretical and luminescence spectroscopic methods
Drobot, B.; Tsushima, S.; Steudtner, R.; Raff, J.;
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.
  • Lecture (others)
    PSI meeting, 25.08.2014, Villigen, Schweiz

Publ.-Id: 20703 - Permalink


Geobiotechnologie: „Grüne“ Technologie zur Metallgewinnung?
Pollmann, K.;
Perspektiven der Geobiotechnologie
  • Invited lecture (Conferences)
    Seminar zum Stipendienprogramm der Deutschen Bundesstiftung Umwelt, 02.09.2014, Ostritz/Kloster Marienthal, Deutschland

Publ.-Id: 20702 - Permalink


Biologische Bausteine für Materialien der Zukunft
Drobot, B.;
Auf der Suche nach umwelt- und ressourcenschonenden industriellen Prozessen richtet sich der Fokus zunehmend auf die Biologie. Unzählige Organsimen haben im Laufe der Evolution vielfältige Mechanismen entwickelt, die sowohl spezifisch als auch effizient sind. Damit reicht der potentielle Anwendungsbereich von antimikrobiellen Oberflächen über Filtration bis hin zu hochempfindlichen Sensoren.
  • Lecture (others)
    Tage der Wissenschaften, 02.07.2014, Radebeul, Deutschland

Publ.-Id: 20701 - Permalink


Polyoxometalates as potent inhibitors of P2X receptors
Spanier, C.; Stephan, H.; Kortz, U.; Haider, A.; Hausmann, R.; Abdelrahman, A.; Müller, C. E.;
P2X receptors are trimeric ion channels that are activated by ATP and are permeable for the cations Na+, K+ and Ca2+. Seven different subunits exist, which are assembled as homo- or heterotrimers of various stoichiometry.1,2 Polyoxometalates (POMs) are discrete, polynuclear metal-oxo anions of early transition metals in high oxidation states (e. g. W6+, Mo6+, V5+), comprising edge- and corner-shared MO6 octahedra. They exhibit enormous flexibility with respect to shape, size, composition and charge.3 POMs are relatively large molecules (> 1 nm) and bear several negative charges. In this respect they bear similarity to ATP, which binds to P2X2 and P2X4 in its tetraanionic form (ATP4-) and to P2X1 and P2X3 possibly also in its dianionic state as a Mg2+ complex (MgATP2-).4 We previously found that certain POMs can inhibit alkaline phosphatase5 and ectonucleotidases,6, 7 enzymes that are capable of hydrolyzing nucleotides such as ATP and ADP. In the present study we investigated whether POMs can interact with P2X receptors. A series of POMs was investigated for their effects to inhibit ATP-induced calcium influx in recombinant 1321N1 astrocytoma cells stably transfected with P2X1, P2X2, P2X3, P2X4 or P2X7 receptors. Several POMs were found to be highly potent inhibitors of P2X receptors with potency in the low nanomolar range. The compounds were found to be non-cytotoxic at pharmacologically active concentrations, whereas some POMs showed cytotoxic effects in an MTT assay at concentrations typically higher than 1 µM.


1 Young, MT (2010), Trends Biochem. Sci. 35: 83-90
2 Torres, GE, Egan, TM, Voigt, MM (1999), J Biol. Chem. 274: 6653-6659
3 Hasenknopf, B (2005), Front Biosci. 10: 275-28
4 Li, M, Silberberg, SD, Swartz, KJ (2013), Proc. Natl. Acad. Sci. USA: 110: E3455-E3463
5 Raza, R, Matin, A, Sarwar, S, Barsukova-Stuckart, M, Ibrahim, M, Kortz, U, Iqbal, J (2012), Dalton Trans. 41: 14329-14336
6 Müller, CE, Iqbal, J, Baqi, Y, Zimmermann, H, Röllich, A, Stephan, H (2006), Bioorg. Med. Chem. Lett. 16: 5943-5947
7 Stephan, H, Kubeil, M, Emmerling, F, Müller, CE (2013), Eur. J. Inorg. Chem. 1585-1594
  • Poster
    Purines International Conference on Nucleotides Nucleosides and Nucleobases, 23.-27.07.2014, Bonn, Deutschland
  • Open Access LogoAbstract in refereed journal
    Purinergic Signalling 10(2014), 779-780
    DOI: 10.1007/s11302-014-9430-7

Publ.-Id: 20700 - Permalink


Bioleaching of Kupferschiefer blackshale – A review including perspectives of the Ecometals project
Kutschke, S.; Guézennec, A.-G.; Hedrich, S.; Schippers, A.; Borg, G.; Kamradt, A.; Gouin, J.; Giebner, F.; Schopf, S.; Schlömann, M.; Rahfeld, A.; Gutzmer, J.; D’Hugues, P.; Pollmann, K.; Dirlich, S.; Bodénan, F.;
In Europe, most of the primary copper resources that possess a high or moderate amount of metals, have a reasonable accessibility and are easy to process are exhausted. In this context, low grade and complex ores as well as old waste deposits related to past mining activities are receiving increasing attention. For an economic exploitation of such ores and resources, with quite different mineral matrix, new and efficient methods need to be developed. Bioleaching is a reliable and promising option .
Among the different kinds of copper mineralisation that can be found in Europe, sulphidic Kupferschiefer deposits have been explored and exploited for years in Germany and Poland. They are Europe’s largest copper reserve with more than 60 Mill. tons of Cu, and contain additional associated metals such as Ag, Pb, Zn and possibly other high-value metals. Kupferschiefer deposits are currently under exploitation in Poland, but process operations are more and more penalised by the significant amounts of organic matter and arsenic present in this type of ores. Therefore bioleaching is more and more considered as a credible alternative to the pyrometallurgical technology which may no longer be feasible in future given the concentrate chemistry.
In this context, this paper provides an overview of the previous work on the geology, mineralogy, and (bio)processing of the Kupferschiefer. It will also present new opportunities and challenges related to the development of innovative methods for metal recovery by means of biotechnology.
Generally, bioleaching of Kupferschiefer is influenced by the mineralogical nature of sulphides and organic matter contained in the ores. For example, recalcitrance of chalcopyrite during leaching is a major limitation of biohydrometallurgy applied to copper ores in general and blackshales in particular. Organic matter, moreover, causes also flotation problems. However, the organic materials especially the metallorganic compounds containing platinum group (PGE) or rare earth elements (REE) may make processing of Kupferschiefer economically interesting.
The first works dealing with Kupferschiefer bioleaching in Europe date back more than three decades, and were pursued again beginning of the 21st century in the European Bioshale project. This project demonstrated the overall efficiency of continuous stirred tank reactors (CSTR) bioleaching of a blackshale concentrate with an extraction rate above 90 %. Nevertheless, two possible improvement paths were identified: reducing the tank size or improving chalcopyrite dissolution affecting the operation efficiency. These challenges were then further addressed in ProMine project opening new perspectives for bioleaching of Kupferschiefer ores which will be dealt with in the French-German project Ecometals.
Keywords: copper, blackshale, chalcopyrite, organic matter, bioleaching

Publ.-Id: 20699 - Permalink


Potential mapping from geochemical surveys using a Cox process
Tolosana-Delgado, R.; van den Boogaart, K. G.; Schaeben, H.;
Punctual occurrence phenomena are often modeled as Poisson point processes, sometimes with an inhomogeneous, unknown intensity, that is desired to be estimated from some covariables. Within this setting, we study the case in which the covariables form a regionalized geochemical composition of stream sediments, and the known punctual occurrences are existing mineral deposits, not collocated with the available explanatory data. This is modeled by assuming a two-layer stochastic process, where the observed Poisson log-intensity is taken as a balanced log-linear function of the geochemical composition of stream sediments, which coefficients must be estimated. Estimation is possible through a pseudolikelihood device based on generalized loglinear models, though the result intensity function appears to be valid only up to arbitrary scaling and addition of constants.
  • Contribution to proceedings
    GeoENV 2014 - 10th Conference on Geostatistics for Environmental Applications, 09.-11.07.2014, Paris, France
    Proceedings of geoENV 2014

Publ.-Id: 20698 - Permalink


Applications in Compositional Data Analysis
Tolosana-Delgado, R.; van den Boogaart, K. G.;
Compositional data occur in all fields of science: from politics to materials engineering, from biomedical sciences to geochemistry. In all these fields, variables representing the relative contribution of some parts forming a whole are routinely acquired. Actually, compositions form their own scale, essentially characterized by their intrinsic multivariate nature and the closure to constant sum to 100%. Statistical techniques used with these data must then conform to that scale.

This contribution presents a comprehensive summary of how to adapt the most common statistical techniques, based on the principle of working on coordinates within the log-ratio approach. In application of this principle, data are represented in an one-to-one set of logratios of the original components, the scores are analysed with classical multivariate tools, and results are eventually back-transformed for interpretation. In particular, this contribution explores the uses of cluster analysis, principal components and linear regression to explain the natural variability on several data sets from the Earth sciences.
Keywords: biplot ; PCA ; linear model ; geochemical survey ; clr ; ilr
  • Lecture (Conference)
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA

Publ.-Id: 20697 - Permalink


Spatial Analysis of Compositional Data
Pawlowsky-Glahn, V.; Tolosana-Delgado, R.; van den Boogaart, K. G.;
Spurious correlation is known to be a problem in statistics since Pearson's early warnings in 1897. The same problems arise in spatial statistics: bias towards negative values and non-zero cross-covariances and cross-covariograms; singular matrices of intrinsic co-dispersion; co-kriged regionalised vectors of proportions that do not satisfy the constant sum constraint. A way out is to use log-ratio transformations: the spatial structure can be described in terms of direct variograms of each possible pairwise logratio; variation-variograms can be estimated even in case of missing components; they can be modelled with standard tools; both the data and the spatial structure model can be expressed in isometric logratio coordinates, and standard co-kriging techniques can be applied to obtain interpolated logratios. These can be back-transformed to compositions, delivering interpolated maps of each component that satisfy the required constraints. Moreover, the result does not depend on which logratio transformation was used for the computations. This approach and its potentialities is illustrated with a data set of soil geochemistry.
Keywords: Aitchison geometry of the simplex ; co-kriging ; compositional data ; spurious spatial covariance ; variation-variogram
  • Lecture (Conference)
    Joint Statistical Meeting, 02.-07.08.2014, Boston, USA

Publ.-Id: 20696 - Permalink


Multi-functional bispidine derivatives as versatile imaging agents
Stephan, H.; Coma, P.;
The development of multi-functional complexing agents for radiometal nuclides with a view of nuclear medical application represents a fast developing field of intensive research [1]. A requirement for ligands in this field is fast complexation kinetics and high complex stabilities with specific radiometal ions and ligands which are easy to functionalize with several different groups for linking to biological vectors, nanoparticles and/or fluorescence molecules.

Ligands based on 3,7-diazabicyclo[3.3.1]nonane (bispidine) form very stable transition metal complexes [2]. Due to the formation of thermodynamically and kinetically stable CuII complexes, pentadentate and hexadentate bispidines are very well suited for in vivo application, i.e. for tumor imaging (64CuII) using positron emission tomography (PET) and tumor therapy (64CuII, 67CuII) [3, 4]. The bispidine scaffold has various sites for functionalization that permit the introduction of biomolecules for pharmaceutical targeting and fluorescent units for optical imaging (see Figure 1).

Several bispidine ligands have been developed in order to improve the radiopharmaceutical behavior as well as possibilities for further beneficial functionalization. These ligands and the important properties of their CuII complexes, e.g., stabilities, ligand exchange kinetics, serum stability, partition coefficients ([64Cu]Cu-bispidine: n-octanol/water) and biodistribution studies 64Cu-labeled bispidines will be reported.

References
1. C. S. Cutler, M. H. Hemmkens, N. Sisay, S. Markai-Huclier. S. S. Jurisson, Chem. Rev. 113, 858 (2013).
2. P. Comba, M. Kerscher, W. Schiek, Prog. Inorg. Chem. 55, 613 (2007).
3. S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem. 20, 347, (2009).
4. P. Comba, S. Hunoldt, M. Morgen, J. Pietzsch, H. Stephan, H. Wadepohl, Inorg. Chem. 52, 8131 (2013).
  • Lecture (Conference)
    5th EuCheMS Chemistry Congress, 31.08.-04.09.2014, Istanbul, Turkey

Publ.-Id: 20695 - Permalink


Single-domain antibodies as targeting moieties for nanomaterial-based cancer imaging
Zarschler, K.; Zscheppang, K.; Cordes, N.; Stephan, H.; Steinbach, J.;
ken Abstract verfügbar
  • Poster
    DKTK Retreat 2014, 12.-13.05.2014, Heidelberg, Deutschland

Publ.-Id: 20694 - Permalink


Ultrasmall silicon nanoparticles: preparation strategies and bioapplications
Licciardello, N.; Hsu, C.-W.; Prasetyanto, E. A.; Hunoldt, S.; Viehweger, K.; Stephan, H.; de Cola, L.;
The use of nanoparticles in multimodal bio-imaging is attracting increasing interest, but toxicity and accumulation in organs still limit their in vivo applications. Silicon nanoparticles (Si NPs) are very promising in this respect as their size, 1.5 - 4 nm, can allow body excretion. In addition Si NPs are photo- and chemical stable, possess bright tunable luminescence and can be covalently functionalized with desired molecules. Indeed several techniques have been described to obtain Si NPs [1-3] with different sizes and bearing various functional groups.
Here we report on some optimized wet chemistry techniques to prepare ultrasmall (< 5 nm) Si NPs and, in particular, the focus is on microemulsion methods and hydrothermal synthesis. The obtained Si NPs can bear different functional groups, allowing a wide spectrum of subsequent conjugations. Once functionalized and purified, Si NPs were characterized by HR-TEM and IR spectroscopy, and their photophysical properties were investigated. Reactivity and properties of the NPs obtained by various methods will be compared and the results of in vitro and in vivo experiments will be shown to demonstrate the great potentialities of such ultrasmall Si NPs.
This work was financially supported by Helmholtz Virtual Institute “Nano-Tracking”, Agreement No. VH-VI-421

1. J. H. Warner et al., Angew. Chem. Int. Ed. 2005, 44, 4550 –4554
2. M. Rosso-Vasic et al., Small, 2008, 4, 1835–1841
3. Y. Zhong et al., J. Am. Chem. Soc., 2013, 135, 8350-8356
  • Lecture (Conference)
    E-MRS Spring Meeting, 26.-30.05.2014, Lille, France

Publ.-Id: 20693 - Permalink


Morphological transformations of top electrodes on YMnO3 caused by filamentary resistive switching in the oxide matrix
Bogusz, A.; Blaschke, D.; Skorupa, I.; Bürger, D.; Schmidt, O. G.; Schmidt, H.;
Unipolar resistive switching in YMnO3 with large-scale bottom and small-scale top electrodes is analyzed in detail by tracking the morphological transformations of the top electrodes induced by applied writing voltages. Micro-scale digital images are taken after each subsequent quasi-static current-voltage sweep. Current mapping after electrical investigations indicates a shift in the conductivity at the localized areas of the morphologically transformed top electrodes. Those changes are assigned to the heat induced structural and compositional changes within YMnO3 which lead to the formation and rupture of conductive filaments observed as unipolar resistive switching. Presented results underline the importance of Joule heating in the fostering of resistive switching and its adverse impact on the device endurance.
Keywords: resistive switching, Joule heating, morphological changes of electrode, multiferroic YMnO₃
  • Lecture (Conference)
    3rd International Conference on Material Science and Engineering Technology (ICMSET 2014), 24.-26.10.2014, Beijing, China
  • Advanced Materials Research 1101(2015), 120-123
    DOI: 10.4028/www.scientific.net/AMR.1101.120

Publ.-Id: 20692 - Permalink


Transport in Nanoelectronic Systems
Grebing, J.; Deb, D.; Grube, M.; Trommer, J.; Teshome, B.; Sendler, T.; Wieser, M.; Helm, M.; Weber, W.; Keller, A.; Erbe, A.;
Microelectronics today is still based on the silicon technology it has been employing for the past 40 years even though it has been highly optimised and iteratively refined. Yet, it will come to a point where new concepts will be needed when “More Moore” has been extended to its ultimate limits. This is why there is a high interest in researching different approaches, e.g., with added functionality (“More-than-Moore”) [1] or even completely different concepts going “beyond Moore” like molecular electronics.

In the first part of this paper we present recent work on the top-down fabrication of silicon nano wire field effect transistors (FET) with two gates allowing not only for the control of the current through the device as it is done in a conventional FET but also to switch between the conduction mechanism, i.e., p- or n-type behaviour. It has been demonstrated previously that this kind of device can be used to build circuits [2,3]. However, we want to extend the principle from single nano wire devices to complex integrated circuits.

The second part will then go “beyond Moore” to illustrate results from our research on two challenges in the field of molecular electronics: Joining bottom-up with top-down techniques to form electrical contacts to nano objects on the one hand. We employ ion beam treatment of the substrate to form a preferential alignment for DNA templated wires. These will ultimately be used for DNA templated quantum dot transistors. On the other hand we will present a single molecular switch sensitive to light in the UV/VIS regime [4].

[1] ITRS “More-than-Moore” White Paper (2010) – http://www.itrs.net/papers.html
[2] A. Heinzig et al., Nano Lett. 12 (1) 119–124 (2012)
[3] T. Mikolajick et al., Phys. Status Solidi Rapid Res. Lett. 7 (10), 793–799
[4] Y. Kim et al., Nano Lett. 12 (7) 3736–3742 (2012)
Keywords: nanoelectronics, DNA template, nanowire, molecular electronics
  • Invited lecture (Conferences)
    9. Silicon Saxony Day, 03.07.2014, Dresden, Deutschland

Publ.-Id: 20691 - Permalink


HASEonGPU - An Open-Source ASE code for calculating the gain in high power laser media on GPU clusters
Zenker, E.; Eckert, C.; Albach, D.; Bussmann, M.; Debus, A.;
We present an adaptive Monte Carlo approach for computing the amplified spontaneous emission (ASE) flux in large size laser gain media pumped by pulsed lasers. Computations are based on a GPU algorithm with large speedup compared to previously existing solutions, capable of simulating the upcoming generation of high-power laser systems.
Keywords: GPU, MPI, Monte Carlo, laser, ASE flux, CUDA, HPC, parallel, gain media, high-power laser systems
  • Poster
    16th Advanced Accelerator Concepts Workshop, 13.-18.07.2014, San Jose, USA

Publ.-Id: 20690 - Permalink


An adaptive, load-balanced MPI/GPU-Code for calculating the gain in High Power Laser media
Zenker, E.; Eckert, C.; Albach, D.; Bussmann, M.;
We present an adaptive Monte Carlo approach for computing the amplified spontaneous emission (ASE) flux in a laser medium pumped by pulsed lasers. For high energy laser systems with large apertures sufficient spatial resolution requires high computational power. We have developed an adaptive multi-node GPU algorithm with load balancing that shows close to perfect strong scaling that allows for large speedups compared to previously existing CPU implementations. This code will allow to calculate the ASE flux in large size gain media as they will be used in the upcoming generation of high-power laser systems.
Keywords: CUDA, MPI, Monte Carlo, ASE flux, HPC, Cluster, laser, parallel, GPU
  • Lecture (Conference)
    Workshop Programming of Heterogeneous Systems in Physics, 14.-15.07.2014, Jena, Deutschland

Publ.-Id: 20689 - Permalink


Spectroscopic investigation of the complexation of trivalent actinides/lanthanides in body fluids
Wilke, C.; Barkleit, A.; Stumpf, T.;
The lanthanide and actinide elements are exogenous metals, which have no essential role in normal biochemistry. Through different processes these heavy metals can be potentially released into the environment where they can be incorporated into the food chain. There are executed Laser-Fluorescence measurements to possible complexes of Eu(III) in body fluids of the human gastrointestinal tract.
Keywords: trivalent lanthanides/actinides, TRLFS, body fluids
  • Poster
    Wilhelm and Else Heraeus Physics School on "Ionizing Radiation and Protection of Man", 10.-22.08.2014, Bad Honnef, Deutschland
  • Poster
    Aufbereitung von Wasserproben und Nachweis von Radionukliden in Wasserproben, 25.-27.11.2014, KIT, Karlsruhe, Deutschland
  • Lecture (others)
    Workshop zum Verbund "Transfer von Radionukliden in aquatischen Ökosystemen", 20.-21.04.2015, Bremen, Deutschland
  • Poster
    GDCh-Wissenschaftsforum Chemie 2015 Chemie verbindet, 30.08.-02.09.2015, Dresden, Deutschland
  • Lecture (others)
    10th HZDR PhD Seminar, 02.-04.11.2015, Altenberg, Deutschland
  • Lecture (others)
    2. Workshop TransAqua zum Thema „Verhalten von Radionukliden im Wasserpfad“, 16.-17.11.2015, Jena, Deutschland

Publ.-Id: 20688 - Permalink


Do microorganisms help to clean up uranium polluted waters?
Gerber, U.; Krawczyk-Bärsch, E.; Arnold, T.; Stumpf, T.;
The well examined uranium mining waste piles Königstein (Germany) is heavily polluted with uranium and also other toxic metals. Despite it is a reservoir for a high diversity of microorganisms that have evolved special strategies to survive in these extreme environments. Microorganisms are the beginning of the food chain and therefor the transfer of bound uranium along this food chain could rise to a serious threat to human health. The aim of the study should be to characterize the quantitative and structural interactions of different microorganisms with uranium in environmental concentrations and pH ranges. Bodo saltans a eukaryotic flagellate and it´s feeder bacterium Acidovorax facilis should be the representatives of this biodiversity.
Keywords: uranium, microorganisms, sorption
  • Poster
    WE-Heraeus Physics School in Ionizing Radiation and Protection of Man, 10.-22.08.2014, Bad Honnef, Deutschland

Publ.-Id: 20687 - Permalink


Contactless inductive flow tomography: brief history and recent developments in its application to continuous casting
Ratajczak, M.; Gundrum, T.; Stefani, F.; Wondrak, T.;
The contactless inductive flow tomography (CIFT) aims at reconstructing the velocity field of electrically conducting fluids, with special focus on applications in metallurgy and crystal growth technologies The method relies on the induction of secondary magnetic fields if the moving fluid is exposed to a primary magnetic field. The theoretical foundation of the method is delineated, and some early experiments on the reconstruction of the three-dimensional flow in a cylinder are sketched. Then, the recent efforts to apply CIFT to various model problems in connection with the continuous casting of steel are summarized.

Publ.-Id: 20686 - Permalink


P1401WO-Komplementärer Widerstandsschalter, Kontaktierte Polykristalline Piezo- oder Ferroelektrische Dünnschicht, Verfahren zum Verschlüsseln einer Bitfolge
Schmdit, H.; Kolitsch, A.; Manjunath, N.; Ou, X.; Shuai, Y.; Skorupa, I.; You, T.; Bürger, D.; Du, N.;
Gemäß verschiedenen Ausführungsformen kann ein komplementärer Widerstandsschalter aufweisen: zwei äußere Kontakte (T1, T2 ), zwischen denen zwei piezo- oder ferroelektrische Schichten (11a und 11b) liegen, die durch einen inneren gemeinsamen Kontakt voneinander getrennt sind, dadurch gekennzeichnet, dass mindestens ein Bereich der piezo- oder ferroelektrischen Schicht (11a und 11b) mindestens einmal derart modifiziert ist, dass in der piezo- oder ferroelektrischen Schicht (11a und 11b) jeweils zwischen dem inneren Kontakt und dem zugehörigen äußeren Kontakt ein Bereich (11') der Dicke (d ') entsteht, weicher mindestens zusätzlich in einem Bereich (11") der Dicke (d") modifiziert sein kann, wobei a) die äußeren Kontakte Oberflächenkontakte (Sa) und (Sb) und der innere Kontakt ein gemeinsamer zugehöriger Gegenkontakt (O) oder die äußeren Kontakte Gegenkontakte (Oa) und (Ob) und der innere Kontakt ein gemeinsamer zugehöriger Oberflächenkontakt (S) sind, b) die Oberflächenkontakte (S), (Sa) und (Sb) gleichrichtend und die Gegenkontakte (O) bzw. (Oa) und (Ob) nicht-gleichrichtend sind, c) sich die modifizierten Bereiche in der piezo- oder ferroelektrischen Schicht (11a und 11b) an den Oberflächenkontakten (S) bzw. (Sa) und (Sb) ausbilden, d) die piezo- oder ferroelektrische Schichten (11, 11', 11") verschiedene verspannungsabhängige strukturelle Phasen mit unterschiedlicher Bandlücke und/oder unterschiedlicher Polarisationsladung aufweisen, und e) die elektrische Leitfähigkeit der piezo- oder ferroelektrischen Schichten (11, 11', 11") unterschiedlich ist.
  • Patent
    PCT/EP2014/050829 - Offenlegung: 14.07.2014;

Publ.-Id: 20685 - Permalink


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