Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34122 Publications

Scanning near-field infrared micro-spectroscopy on buried InAs quantum dots

Jacob, R.; Fehrenbacher, M.; Winnerl, S.; Bhattacharyya, J.; Schneider, H.; Helm, M.; von Ribbeck, H.-G.; Eng, L. M.; Atkinson, P.; Rastelli, A.; Schmidt, O. G.

Providing an optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) turned out to be a capable technique to investigate the optical properties of perovskites, buried semiconductors and single quantum dots. Thereby, the line-width of the observed resonances (5 - 8 meV) is significantly smaller than the inhomogeneously broadened line-width of other spectroscopic measurements.
Using a scattering-type-SNOM (s-SNOM) combined with a tunable free-electron laser (FEL) light source we investigated the electronic structure of single InAs quantum dots, capped under a 70 nm thick GaAs layer. Spectroscopic near-field scans clearly identified two inter-sublevel transitions within the quantum dots at 85 meV and 120 meV, contrasting from the surrounding medium. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowed mapping the 3D distribution of such buried quantum dots.

Keywords: Spectroscopy on single quantum dots; self-assembled quantum dots; near-field microscopy; intersublevel transitions

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 25.-30.03.2012, Berlin, Deutschland

Publ.-Id: 17579

Hochskalierende Partikelsimulationen auf GPGPU-Clustern

Burau, H.; Bussmann, M.; Hübl, A.; Juckeland, G.; Schmitt, F.; Widera, R.

PIConGPU ist ein Particle-in-Cell (PIC) Code fur Grakprozessoren (GPUs). Der Particle-in-Cell Algorithmus ist ein zentraler Algorithmus in der Plasmaphysik. Er erlaubt die Dynamik eines Plasmas, die Bewegung der Elektronen und Ionen, auf Basis der Maxwell-Gleichungen voll relativistisch zu beschreiben.
Das PIConGPU Projekt integriert die 3D-Physiksimulation, eine Online-Visualisierung zur interaktiven Auswertung sowie eine einfache Parametrisierung der Simulationsläufe. Die Umsetzung erfolgte so generisch, dass PIConGPU auch als Grundlage fur weitere GPU-Simulationen dienen kann. Um komplexe physikalische Probleme simulieren zu können ist die Skalierbarkeit auf massiv-parallele GPU-Cluster ausgelegt.

Keywords: particle-in-cell; PIConGPU; CUDA; GPGPU; HPC; laser-plasma; numerics

  • Poster
    OUTPUT.DD 2012, 10.07.2012, Dresden, Deutschland

Publ.-Id: 17578

Physics verification tests on a 3 dimensional GPU-driven PIC-code (PIConGPU 3D)

Hübl, A.; Steiniger, K.; Pausch, R.; Widera, R.; Debus, A.; Burau, H.; Köhler, A.; Irman, A.; Bussmann, M.

We present the validation of the key physics features of PIConGPU according to known physical scenarios. For this, we evaluate the evolution of position and energy errors for analytically known particle trajectories and the numerical dispersion of a Gaussian wavepacket over time.
Furthermore, we present a new approximation within the particle push step.
This allows for a comparison of the established CPU/FORTRAN code ILLUMINATION with the GPU/C++ code PIConGPU for selected physical test cases in laser-electron acceleration.

Keywords: particle-in-cell; PIConGPU; CUDA; GPGPU; laser-electron acceleration; laser-plasma interaction; underdense plasma; numerics; HPC; cluster

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity 2nd Dresden Exchange on Laser-Plasma Interaction Theory ENLITE, 16.-20.04.2012, Dresden, Deutschland

Publ.-Id: 17577

Comparison of a new simple system for high depth resolution RBS with the magnetic spectrometer

Munnik, F.; Hanf, D.; Wilhelm, R. A.; von Borany, J.; Lange, H.

With decreasing layer thicknesses e.g. in semi-conductor devices, there is a strong need for increasing depth resolution in analytical methods used for the determination of elemental depth profiles. Standard RBS using Si detectors has a depth resolution of about 5 – 15 nm mainly depending on incidence angle and energy resolution. The traditional and high-tech solution is to use a magnetic spectrometer or a time-of-flight system to improve the energy resolution of the detector and thus the depth resolution.
At HZDR, a Browne-Buechner type magnetic spectrometer is available for high depth resolution measu¬rements with sub-nm depth resolution in a near-surface region  5 nm. However, such a system is expensive and requires complicated operation. In addi¬tion, the small energy window of the magnetic spectrometer limits the measurement to one element and about 10 nm depth range. Currently we are implementing a low-tech detection system that uses improvements in amplifiers and cooling to improve the energy resolution of standard semiconductor detectors to sub-10 keV values. The capabilities of such a system are described and compared to the magnetic spectrometer.

  • Lecture (Conference)
    Workshop Ionenstrahlphysik, 10.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17576

Nanostructures created in SiO2 surface: A comparison between the impingement by slow highly charged ions and by swift heavy ions

El-Said, A. S.

Swift heavy ions (SHI) of MeV–GeV energy lead to the creation of nanometric surface structures as well as modifications in the bulk along the ion penetration depth. Recently, similar surface modifications have been observed for the impact of individual slow highly charged ions (HCI). Non-amorphizable ionic-halide single crystals, like KBr, CaF2 and BaF2, are considered as the most intensively studied materials after irradiation with HCI.
In this contribution we study the creation of surface nanostructures in an amorphizable material, namely SiO2 quartz after irradiation with slow highly charged Xe ions from the Electron Beam Ion Trap at Helmholtz Zentrum Dresden-Rossendorf and swift xenon ions from Universal Linear Accelerator at GSI in Darmstadt. After irradiation at room temperature, the crystals were investigated by scanning force microscopy. For both SHI and HCI, the created nanostructures exhibit the shape of hillocks. Moreover UV–VIS spectroscopy was performed to identify the defects created by ion irradiation at high fluence. The results are discussed in terms of the creation mechanisms driven by the dependence on both potential and kinetic energies of the ions.

Keywords: SiO2; Surface nanostructures; Highly charged ions; Swift heavy ions

Publ.-Id: 17575

Remarks on Scientific Poetry

Brauer, G.

Some personal remarks on scientific poetry in general are presented together with a little poetry collection, in particular about the positron and its fate.

Keywords: poetry; positron; positron annihilation; Higgs boson

  • Book chapter
    B.N. Ganguly, G. Brauer: Near Surface Depth Profiling by Mono-energetic Positrons, Switzerland: Trans Tech Publishers, 2012, 978-3-03785-524-9, 3-6
    DOI: 10.4028/


Publ.-Id: 17574

Status and new trends in FIB processing

Bischoff, L.

In the last decade focused ion beams (FIB) became an irrecoverable instrument in research and industry. Sample preparation, local ion implantation and ion analysis are the main application topics. Most of the systems are equipped with a gallium liquid metal ion source (LMIS). But, modern trends in nanotechnology require more extended properties like variable ion species, non-contaminating milling at higher rates or higher lateral resolution in the field of ion microscopy.
In this contribution the status and application of new source concepts including prototypes will be reviewed in particular high current gas sources (ECR, ICP) for effective high rate milling, ion trap sources providing highly charged ions or used for SIMS applications as well as gas field ion sources for high resolution ion microscopy in the sub-nm range. Furthermore the use of alloy liquid metal ion sources and its characterization for mass separated FIB systems and ToF-SIMS applications will be presented.
New trends and prospective developments in FIB instrumentation will be discussed.

Keywords: Focused Ion Beam; Liquid Metal (Alloy) Ion Source; FIB SIMS

  • Lecture (Conference)
    Workshop Ionenstrahlphysik 2012, 10.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17573

Messung von Geschwindigkeitsfeldern in Flüssigmetallen mit der Ultraschall-Doppler Methode

Eckert, S.; Gerbeth, G.

Der Mangel an kommerziell verfügbarer Messtechnik zum Einsatz in heißen, nichtransparenten Fluiden erschwert Strömungsmessungen in einer Reihe von technologischen Prozessen, in denen Flüssigmetalle oder Halbleiterschmelzen eine wichtige Rolle spielen. Ultraschall-methoden erscheinen für derartige Anwendungen äußerst attraktiv, da sie in der Lage sind, quantitative Messdaten aus opaken Schmelzen zu liefern. Dieser Artikel gibt einen Überblick über internationale Forschungsaktivitäten der letzten 3 Jahrzehnte, die auf eine Nutzung dieser Methode für Strömungsmessungen in Metallschmelzen abzielen.

Keywords: flow measurements; ultrasound Doppler method; liquid metals; magnetohydrodynamics

Publ.-Id: 17572

Inspired by nature: Novel biosensors based on an assembly of self-assembling S-layer proteins, aptamers and fluorescence dyes

Weinert, U.; Pollmann, K.; Strehlitz, B.; Raff, J.

The detection of pharmaceuticals in drinking water and food becomes of increasing relevance. Currently there are only few methods available allowing their reliable detection. These methods are mostly highly complicated and time consuming. Therefore, new techniques are required which enable a fast and easy detection of traces of pharmaceuticals. Biosensors based on natural self-organising biomolecules may provide new approaches for a highly specific detection of pharmaceuticals.

Aim of the presented project is the development of such a sensory layer. Our sensory device consists of S layer proteins, aptamers and fluorescence dyes. The S layer proteins serve as binding matrix, aptamers are used as receptors and fluorescence dyes represent our transducer system.
S layer proteins are structural proteins found in numerous bacteria and almost all archaea. They are able to self-assemble in aqueous solutions and on surfaces forming highly ordered crystalline structure with different symmetries. The proteins expose many COOH and NH2-groups that can be modified and functionalized. Aptamers are short DNA or RNA oligonucleotides which are able to reversibly bind specific analytes due to their 3D-structure. For the optical signal of our sensory layer we use two fluorescence dyes which are able to perform a fluorescence resonance energy transfer (FRET).
This effect is very sensitive and is affected by its environment. In our assembly, fluorescence dyes and aptamers are very close to each other. It is expected that a binding of an analyte to the aptamer will also affect FRET.

Our experiments prove a FRET between two fluorescence dyes linked to S layer proteins in solution and on a surface. In addition, the Anti-Thrombin-aptamer, used as model aptamer, was successfully coupled to S-layer proteins without losing its function. These results provide the basis for the intended sensor concept.

Keywords: FRET; S-layer proteins; sensory layer; aptamers

  • Poster
    bio-inspired Materials, 20.-23.03.2012, Potsdam, Deutschland

Publ.-Id: 17571

Selective liquid-liquid extraction of Sr-85 with modified calixarenes

Poetsch, M.; Mansel, A.; Schnorr, R.; Haupt, S.; Kersting, B.

Sr-90 is a long-lived radionuclide (T(1/2) = 28.6 a), produced as a by-product in nuclear power plants. Due to its chemically similarity to calcium, it follows the food chain from environment (e.g. aquatic systems and soil) to fauna and human in case of release in the biosphere. Strontium can be, as well as calcium, incorporated in bones. Stable isotopes of strontium might not be harmful, but radioactive strontium can lead to bone disorders and diseases, including leukaemia[1].
Calixarenes and their functionalised derivatives are research subjects in the development of extracting agents, transporters, stationary phases[2] or biosensors. We used modified calixarenes, including derivatives having carbonyl binding sites, for the extraction of strontium[3] by means of a liquid-liquid extraction in a chloroform / water system. As a simulated contamination solution with Sr-90, the aqueous strontium phase was traced using the short-lived radionuclide Sr-85 (T(1/2) = 64.9 d), which was produced and purified at the in-house 18 MeV-cyclotron[4].
Under alkaline conditions, strontium extraction yields of >(90±4)% were obtained. Furthermore, the impact of inorganic and organic impurities, competing ions like sodium, calcium, acetate or tartaric acid, to the extraction performance was studied. The used carboxy-modified calixarenes are highly potent and selective extracting agents towards strontium, under conditions near to nature (e.g. synthetic groundwater).

The authors gratefully thank the German Federal Ministry of Education and Research (BMBF) for financial support of this study (project no. 02NUK014).

[1] Wallova, G., N. Kandler, and G. Wallner, Monitoring of radionuclides in soil and bone samples from Austria. Journal of Environmental Radioactivity, 2012. 107(0): p. 44-50.
[2] Wendel, V., Neuartige Wirt-Gast-Komplexe basierend auf Cycloheptatrienbausteinen, Mathematisch-Naturwissenschaftliche Fakultät I 1998, Humboldt-Universität zu Berlin: Berlin.
[3] Casnati, A., et al., New Efficient Calixarene Amide Ionophores for the Selective Removal of Strontium Ion from Nuclear Waste: Synthesis, Complexation, and Extraction Properties. J. Am. Chem. Soc., 2001. 123: p. 12182-12190.
[4] Mansel, A., et al., Production of Sr-85 at a 18 MeV-cyclotron and purification for geochemical investigations, 2012. (submitted)

Keywords: calixarene; radio strontium; liquid-liquid extraction

  • Poster
    EuCheMS International Conference on Nuclear and Radiochemistry (NRC-8), 16.-21.09.2012, Como, Italia

Publ.-Id: 17570

Developing sensory layers as combination of S-layer proteins, aptamers and fluorescence dyes

Weinert, U.; Strehlitz, B.; Pollmann, K.; Raff, J.

In recent years detection of pharmaceuticals in drinking water and food becomes increasing relevance. Nevertheless, most recently used methods are complex and time consuming. Thus, new solutions are required allowing a fast and their reliable detection of pharmaceuticals.

Therefore we are developing sensory layers which are able to specifically detect small amounts of pharmaceuticals. This sensory device will consist of surface(S)-layer proteins, aptamers and fluorescence dyes.
S-layer proteins are structural proteins found in numerous bacteria and archaea. They have the ability to self assembly in aqueous solutions and on surfaces building highly ordered paracrystalline structures. On the surface of such a layer different functional groups are available which can be modified without the loss of its paracrystalline structure. Hence S-layer proteins are useful binding blocks for the defined arrangement of aptamers and fluorescence on an area of a few nanometers. Thereby aptamers serve as receptor for specific analytes and two fluorescence dyes allowing a FRET a signal transducer system.

In first experiments we coupled the model aptamer, Anti-thrombin-aptamer, on S-layer proteins and proved its functionality after being linked to the protein. Furthermore we modified S-layer proteins with a FRET pair containing a green and red fluorescence dye and succeed to detect a FRET between those S-layer linked fluorescence dyes.

In subsequent work we will assemble the components, aptamers and fluorescence dyes, on the S layer proteins. The aptamer will bind the specific analyte. It is supposed that the binding will affect the fluorescence dyes and disturb FRET due to their close proximity to each other. As a result a sensory layer is created which uses the high specifity of aptamers in combination with the sensitivity of fluorescence dyes, thus enabling the easy and reliable detection of analytes by an optical signal.

Keywords: S-layer proteins; FRET; aptamers; sensory layer

  • Poster
    Nanofair 2012, 12.-13.06.2012, Dresden, Deutschland

Publ.-Id: 17569

Ion-beam mixing in crystalline and amorphous germanium isotope multilayers

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

Self-atom mixing induced by Gallium (Ga) implantation in crystalline and amorphous germanium (Ge) is investigated using an isotopic multilayer structure of alternating 73Ge and natGe layers grown by molecular beam epitaxy. The distribution of the implanted Ga atoms and ion-beam induced depth-dependent mixing was determined by means of the secondary ion mass spectroscopy (SIMS). The position and form of the implanted Ga peak is very similar in the amorphous and crystalline Ge and can be reproduced accurately by computer simulations based on binary collision approximation (BCA), whereas the ion-beam induced self-atom mixing strongly depends on the state of the Ge structure. The data from SIMS-measurements reveal a stronger mixing in the crystalline than in the amorphous Ge. Atomistic simulation based on BCA can reproduce the experimental data only if unphysically low displacement energies are assumed. The low displacement energies deduced within the BCA approach are confirmed by experiments with mixing induced by silicon implantation. The disparity observed in the ion-beam mixing efficiency of crystalline and amophous Ge indicates different dominant mixing mechanisms. We propose that self-atom mixing in crystalline Ge is mainly controlled by radiation enhanced diffusion during the early stage of mixing before the crystalline structure turns into an amorpous state, whereas in an already amoprhous state self-atom mixing is mediated by cooperative diffusion events.

Keywords: ion-beam mixing; Si; Ge; isotope multilayers

  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 25.-30.03.2012, Berlin, Deutschland

Publ.-Id: 17568

Ion-beam mixing in crystalline and amorphous Si und Ge

Radek, M.; Bracht, H.; Posselt, M.; Schmidt, B.; Bougeard, D.; Haller, E. E.; Itoh, K.

Molecular dynamics simulations using Stillinger-Weber-type interatomic potentials were performed in order to investigate ion-beam mixing by 400 eV self-ion implantation at different fluences and temperatures. In general the magnitude of mixing in an amorphous structure was found to be higher than in its crystalline counterpart. This supports the results of earlier calculations (K. Nordlund et al., J. Appl. Phys. 83 (1998) 1238). The trends observed in our simulations are compared to our experimental results on ion beam mixing in crystalline and amorphous isotopically modulated Si and Ge multilayer structures.

Keywords: ion-beam mixing; Si; Ge; molecular dynamics

  • Poster
    11th International Conference on Computer Simulation of Radiation Effects in Solids, 24.-29.06.2012, Santa Fe, USA

Publ.-Id: 17567

Experimental investigations of slurry bubble column using ultra-fast electron beam x-ray tomography

Rabha, S.; Schubert, M.; Wagner, M.; Lucas, D.; Hampel, U.

The hydrodynamic flow behaviour of the gas phase in a slurry bubble column was investigated using ultra-fast electron beam X-ray tomography, which provides images at temporal resolution of 7000fps and spatial resolution of 1 mm. Bubble coalesces and breakup regime was observed with the addition of wettable solids particles. The effect of solid volumetric concentration (0 ≤ Cs ≤ 0.36) on the radial distribution of gas holdup in a slurry bubble column was established at different scanning heights (30, 60, 95 cm) and at different superficial gas velocity (0.02 ≤ UG ≤ 0.05 m/s).

Keywords: Slurry bubble column; gas hold-up; solid concentration; X-ray tomography

  • Invited lecture (Conferences)
    International Symposium on Chemical Reaction Engineering, 02.-05.09.2012, Masstricht, The Netherlands

Publ.-Id: 17566

Configurational contributions to the free energy of embedded nanoclusters

Posselt, M.; Al-Motasem, A. T.

Nanostructure evolution is a common phenomenon occurring during ion and neutron irradiation as well as during thermal treatment. It is characterized by diffusion and reaction processes that can cause the formation of embedded nanoclusters which often leads to a modification of the materials properties. Multiscale modeling can substantially contribute to a better understanding of nanostructure evolution. Atomic-scale molecular dynamics and kinetic Monte Carlo simulations are applicable on relatively small length and time scales whereas coarse-grained methods such as object kinetic Monte Carlo simulations and rate theory can be used on scales more easily accessible by experiments. The latter methods need a number of input parameters. One of the most important is the free binding energy of a monomer to a cluster which can be hardly obtained by experimental investigations but can be provided by atomistic simulations. The fundamental quantity that must be determined is the free formation energy of the clusters which consists not only of the formation energy but also of vibrational and configurational contributions. The focus of the present work is on the evaluation of the configurational part of the free formation energy. The simple example of coherent Cu nanoclusters in bcc-Fe is considered. First, at T=0 the most stable cluster configurations are determined by Metropolis Monte Carlo simulations and their formation and binding energies are calculated. Second, a modified Wang-Landau Monte Carlo method is employed in order to determine the contribution of all possible geometrical configurations of nanoclusters to the free formation energy. Finally, the total and monomer free binding energies are calculated. It is shown that even at moderate temperatures such as 600 K the configurational contributions to the free formation energy cannot be neglected. The calculation scheme applied in this work can be extended to other types of embedded nanoclusters in solids. The presented method should be especially important for nanoclusters with relatively low formation energies. Further investigations are required in order to estimate the vibrational contribution to the free formation energy and to perform a comparison with the configurational part.

Keywords: nanoclusters; free energy; configurational contributions

  • Poster
    11th International Conference on Computer Simulation of Radiation Effects in Solids, 24.-29.06.2012, Santa Fe, USA

Publ.-Id: 17565

Chemical Processes of Galvanized Steel Corrosion in the Post-LOCA Phase of a PWR and the Prevention of Sump Screen Clogging

Hoffmann, W.; Kryk, H.

The Emergency Core Coolant System has to remove the decay heat in case of a Loss of Coolant Accident (LOCA). Sump strainers are mounted at the pump inlets to retain particles and fibrous insulation material during recirculation. However, fiber fragments, debris or corrosion products could initiate a critical head loss on strainers. Problems of insulation materials NUKON® (fiberglas) or CalSil and aluminum may appear if containment spray systems using alkaline additives are installed. In such cases, dissolution / precipitation reactions resulting from insulation materials were observed, which increase the risk of sump screen blockage. In German NPPs, there are no containments spray systems, and insulation consists of more resistant materials like mineral wool (rock wool) and stainless steel. However, large scale experiments from AREVA have shown that sump screen clogging may be initiated by boric acid containing leakage jets directed towards galvanized containment internals.
The down-scaled test facility KorrVA was designed for generic corrosion investigations of galvanized steel under post-LOCA conditions. About 90 experiments were carried out with galvanized steel gratings and galvanized steel coupons in boric acid media in order to determine corrosion mechanisms depending on different experimental conditions like temperature, water chemistry and hydrodynamic conditions (flow impact, simulated by different nozzles). Changes of the chemical composition of the circulating media were determined by chemical analysis and general parameters such as conductivity and pH were measured. Galvanized samples and fiber beds were examined after each experiment by means of photographic methods, light-microscopy and different kinds of chemical analysis.
The chemical analyses of the deposits on fiber beds showed that the clogging is predominantly caused by the corrosion products of iron and lower amounts of zinc compounds. Thus, the corrosion of galvanized steel in boric acid is explained by a mechanism starting at the surface with fast Zn dissolution but without formation of solid corrosion products. The Zn corrosion is mainly influenced by pH and concentration of zinc ions in the coolant. Since boric acid/borate acts as a buffer system, the pH value increases faster at the beginning and reaches up to 6.8 in case of sufficient solved Zn, generated by corrosion. A local (flow induced) corrosion occurs if a fast liquid flow strikes the top face of a horizontal galvanized coupon. Precondition for this process is a sufficiently low pH of solution in connection with a high hydrodynamic impact of the liquid flow on the corroding surface.
For a limited period, the risk of strainer clogging due to formation of corrosion products of galvanized steel may be reduced by an additional amount of submerged Zn or changing the coolant chemistry by alkaline additions. These two possibilities were investigated by test series using galvanized steel coupons. The addition of borax seems to be the most effective method to reduce the corrosion rate and the risk of sump screen clogging.
The results were validated with galvanized gratings in a further test series since the flow conditions of a liquid jet on flat coupons significantly differ from those on gratings. Three different regions of corrosion attack were noticed on these real samples contributing to the increase of solved Zn. But the Zn dissolution should be limited since it may lead to undesired secondary effects by deposition of sparingly soluble borate salts depending on coolant temperature.

Keywords: LOCA; zinc; corrosion; sump screen clogging; PWR

  • Poster
    NPC2012, Nuclear Plant Chemistry Conference, 24.-27.09.2012, Paris, Frankreich
  • Contribution to proceedings
    NPC2012, Nuclear Plant Chemistry Conference, 24.-27.09.2012, Paris, Frankreich

Publ.-Id: 17564

Reaktionsaufklärung der Partialoxidation von Isobutan zu tert.-Butylhydroperoxid (TBHP)

Willms, T.; Hampel, U.; Kryk, H.

Die Aufgaben des Arbeitspaketes 2.5 des Projektes „Energieeffiziente chemische Mehrphasenprozesse“ werden kurz vorgestellt. Das Potential der Energieeffizienzverbesserung der Oxidation von Iso-butan mit Sauerstoff zu tert.-Butylhydroperoxid wird angesichts der Technologie mikrostrukturierter Reaktoren evaluiert. Ein vereinfachter Mechanismus der Reaktion wird angegeben. Darauf aufbauend wird das weitere Vorgehen zur Reaktionsaufklärung im Rahmen des Projekts skizziert, sowie die Verknüpfungen des Arbeitspaketes 2.5 mit anderen Arbeitspaketen aufgezeigt.

  • Lecture (others)
    Universitätsinternes Kick-off-Meeting zur Helmholtz-Energie-Allianz "Energieeffiziente chemische Mehrphasenprozesse", 13.07.2012, Dresden, Deutschland

Publ.-Id: 17563

CFD modeling of graphite dust transport, deposition and resuspension with OpenFOAM

Lecrivain, G.; Hampel, U.

In a high temperature pebble-bed reactor, carbonaceous dust is conveyed by the cooling carrier phase and eventually deposits in the primary circuit of the reactor. The numerical dispersion and deposition of Lagrangian aerosol particles in a turbulent flow is here investigated. The flow field is simulated using a Reynolds-averaged Navier-Stokes method. A Langevin equation is implemented to reproduce the turbulent dispersion of particles. Results of the deposition experiments in a vertical and horizontal square duct flow show good agreement with recently published experimental data.

Keywords: Turbulent square duct flow; aerosol particles; particle dispersion; particle deposition; numerical experiment; CFD

  • Lecture (Conference)
    THINS Workshop Thermal-Hydraulics of Innovative Nuclear Systems, 06.-08.02.2012, Ljubljana, Slovenia

Publ.-Id: 17561

Defect characterization of ion-implanted Fe-Cr alloys using Positron Doppler Broadening Spectroscopy

Butterling, M.; Anwand, W.; Bergner, F.; Cowan, T. E.; Heinze, C.; Ulbricht, A.; Wagner, A.; Krause-Rehberg, R.

Depth resolved positron Doppler broadening spectroscopy was used to investigate the effect of neutron irradiation (simulated by self-implantation with Fe ions) on the defect structure of Fe-Cr alloys with different Cr content (2.5at% - 12at%). Different defect situations depending on the Cr content were found for the alloys.

Keywords: Fe-Cr alloys; Positron Annihilation Spectroscopy; ion implantation induced damage

  • Lecture (Conference)
    Workshop Ionenstrahlphysik 2012, 09.-11.07.2012, Augsburg, Deutschland

Publ.-Id: 17560

Experiments on the deposition and resuspension of nuclear aerosol particles

Barth, T.

In this presentation the state of the ongoing gas/graphite transport experiments is presented. In the frame of the EU projects THINS and ARCHER two small-scale test facilities were designed to study the particle transport in complex geometries. Background motivation is the carbonaceous dust issue in the primary circuit of the High Temperature Reactor. It is a safety issue to explore the deposition and resuspension behaviour of such graphite particles to assess the transport behaviour during loss of coolant accidents. The first facility is called Gas Particle Loop and it is used to study the particle deposition and resuspension behaviour in a turbulent square duct flow field. The turbulent flow field was recorded using a Particle Image Velocimetry system. Furthermore, single particle as well as multilayer particle deposition and resuspension experiments were conducted to generate a data basis for the understanding of the particle transport behaviour. The second facility is called Pebble Bed Loop was specially design to generate a particle laden turbulent flow through a pebble bed. The test section is designed to fit into a Positron Emission Tomography (PET) scanner situated at the Reactive Transport Division in Leipzig. The time and space resolved formation of the particles was recorded by means of this PET scanner. The data presented can be used for CFD code development.

Keywords: High Temperature Reactor; aerosol particle; deposition; resuspension; Particle Image Velocimetry; Positron Emission Tomography

  • Lecture (Conference)
    Doktorandenseminar KOMPOST, 08.12.2011, Zittau, Deutschland

Publ.-Id: 17559

Measurement techniques and experimental investigations for multiphase flows

Hampel, U.

The presentation is a short-course lecture that introduced the current state of the art in multiphase flow measurement techniques. Sensors and measurement techniques, which are intoduced are: electrical and optical needle probes, wire-mesh sensors and tomography techniques. Beside the physical measuring and sensor construction principles the presentation addresses the topic of data processing for multiphase flow measurements.

Keywords: multiphase flow measurment; multiphase flow sensors

  • Invited lecture (Conferences)
    10th Multiphase Flow Conference and Short Course: Simulation, Experiment and Application, 12.-14.06.2012, Dresden, Germany
  • Invited lecture (Conferences)
    11th Multiphase Flow Conference and Short Course, 26.-28.11.2013, Dresden, Germany
  • Invited lecture (Conferences)
    12th Multiphase Flow Conference and Short Course, 25.-27.11.2014, Dresden, Germany
  • Invited lecture (Conferences)
    13th Multiphase Flow Conference and Short Course, 24.-26.11.2015, Dresden, Germany
  • Invited lecture (Conferences)
    14th Multiphase Flow Conference and Short Course, 07.-09.11.2016, Dresden, Germany
  • Invited lecture (Conferences)
    15th Multiphase Flow Workshop - Short Course and Conference, 14.-17.11.2017, Dresden, Deutschland
  • Invited lecture (Conferences)
    16th Multiphase Flow Workshop - Short Course and Conference, 13.-16.11.2018, Dresden, Deutschland

Publ.-Id: 17558

Structural characterization of ZnO thin films grown on various substrates by pulsed laser deposition

Novotny, M.; Cizek, J.; Kuzel, R.; Bulir, J.; Lancok, J.; Connolly, J.; Mccarthy, E.; Krishnamurthy, S.; Mosnier, J.-P.; Anwand, W.; Brauer, G.

ZnO thin films were grown by pulsed laser deposition on three different substrates: sapphire (0 0 0 1), MgO (1 0 0) and fused silica (FS). The structure and morphology of the films were characterized by x-ray diffraction and scanning electron microscopy and defect studies were carried out using slow positron implantation spectroscopy (SPIS). Films deposited on all substrates studied in this work exhibit the wurtzite ZnO structure and are characterized by an average crystallite size of 20-100 nm. However, strong differences in the microstructure of films deposited on various substrates were found. The ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit local epitaxy, i.e. a well-defined relation between film crystallites and the substrate. Domains with different orientation relationships with the substrate were found in both films. On the other hand, the film deposited on the FS substrate exhibits fibre texture with random lateral orientation of crystallites. Extremely high compressive in-plane stress of sigma similar to 14 GPa was determined in the film deposited on the MgO substrate, while the film deposited on sapphire is virtually stress-free, and the film deposited on the FS substrate exhibits a tensile in-plane stress of sigma similar to 0.9 GPa. SPIS investigations revealed that the concentration of open-volume defects in the ZnO films is substantially higher than that in a bulk ZnO single crystal. Moreover, the ZnO films deposited on MgO and sapphire single-crystalline substrates exhibit a significantly higher density of defects than the film deposited on the amorphous FS substrate.

Publ.-Id: 17557

WP4.1.3 Gas/graphite transport experiments

Barth, T.; Lehmann, A.; Preuß, J.; Reiche, M.

In this presentation the state of the ongoing gas/graphite transport experiments is presented. In the frame of the EU THINS project a small-scale test facility was designed to study the particle transport in turbulent duct flows. Background motivation is the carbonaceous dust issue in the primary circuit of the High Temperature Reactor. It is a safety issue to explore the deposition and resuspension behaviour of such graphite particles to assess the transport behaviour during loss of coolant accidents. The turbulent flow field was recorded using a Particle IImage Velocimetry system. Furthermore, single particle as well as multilayer particle deposition and resuspension experiments were conducted to generate a data basis for the understanding of the particle transport behaviour. This data basis can be used for CFD code development.

Keywords: High Temperature Reactor; carbonaceous dust; turbulent flow; deposition; resuspension

  • Lecture (Conference)
    THINS – Cluster workshop, 06.-09.02.2012, Ljubljana, Slowenien

Publ.-Id: 17556

Bubble size and radial gas hold-up distributions in a slurry bubble column using ultrafast electron beam X-ray tomography

Rabha, S.; Schubert, M.; Wagner, M.; Lucas, D.; Hampel, U.

Gas hold-up and bubble size distribution in a slurry bubble column (SBC) were measured using the advanced non-invasive ultrafast electron beam X-ray tomography technique. Experiments have been performed in a cylindrical column (DT = 0.07 m) with air and water as the gas and liquid phase and spherical glass particles (dP = 100 µm) as solids. The effects of solids concentration (0 ≤ Cs ≤ 0.36) and superficial gas velocity (0.02 ≤ UG ≤ 0.05 m/s) on the flow structure, radial gas hold-up profile and approximate bubble size distribution at different column heights in a SBC were studied. Bubble coalescence regime was observed with addition of solid particles, however, at higher solids concentrations, larger bubble slugs were found to break-up. The approximate bubble size distribution and radial gas hold-up was found to be dependent on UG and Cs. The average bubble diameter calculated from the approximate bubble size distribution was increasing with increase of UG. The average gas hold-up was calculated as a function of UG and agrees satisfactorily with previously published findings. The average gas hold-up was also predicted as a function of Cs and agrees well for low Cs and disagrees for high Cs with findings of previous literature.

Keywords: Slurry bubble column; gas hold-up; bubble size distribution; ultrafast electron beam X-ray tomography

Publ.-Id: 17555

Helmholtz-Energie-Allianz Energieeffiziente Chemische Mehrphasenprozesse

Hampel, U.

Der Vortrag stellt die neue Helmholtz-Energie-Allianz Energieeffiziente Chemische Mehrphasenprozesse vor.

  • Lecture (others)
    HZDR Klausurtagung, 28.07.2012, Bad Schandau, Germany

Publ.-Id: 17554

Experimentelle Studien und CFD-Simulation der Thermofluiddynamik bei kaltstrangseitiger Notkühleinspeisung (TOPFLOW-PTS)

Hampel, U.; Apanasevich, P.; Beyer, M.; Lucas, D.

Bei Kühlmittelverluststörfällen in Kernreaktoren wird die Kernkühlung unter anderem durch Notkühleinspeisung (emergency core cooling, ECC) in den kalten oder heißen Strang des Primärkreislaufs unterstützt. Hierbei wird zusätzliches Kühlmittel aus Notkühlreservoirs in die mit dem Reaktordruckbehälter (RDB) verbundenen Hauptkühlmittelleitungen eingespeist. Ein sicherheitsrelevantes Problem dieser Maßnahme sind thermomechanische Belastungen der Reaktordruckbehälterwand durch plötzliche Abkühlung. Das stark unterkühlte Notkühlwasser vermischt sich in der Hauptkühlmittelleitung mit dem dort stehenden Sattwasser, dessen Höhe in der Leitung durch den aktuellen RDB-Füllstand und dessen Sättigungstemperatur durch den aktuellen Systemdruck gegeben sind. Das in den Ringraum des RDB einströmende Wasser kann bei unzureichender Vermischung eine plötzliche Abkühlung der Reaktordruckbehälterwand (Thermoschock) unterhalb des Leitungsstutzens mit dem Risiko einer Rissbildung bewirken. Das Risiko eines Behälterversages hängt damit einerseits vom aktuellen strukturmechanischen Zustand der Behälterwand ab, andererseits von den die Vermischung bestimmen thermohydraulischen Phänomenen in der Hauptkühlmittelleitung. Letztere umfassen die durch die Strömungsdynamik bestimmte thermische Vermischung (Jet-Form, Turbulenz, Dampfblasenmitriss) sowie den Wärmetransport durch Kondensation am ECC-Strahl und an der Wasseroberfläche und hängen von einer Vielzahl von Parametern, wie dem ECC-Massenstrom, der ECC-Unterkühlung, dem aktuellen Systemdruck (Sättigungstemperatur) und der Höhe der Wasservorlage in der Hauptkühlmittelleitung ab.
Im Rahmen eines seit 2006 laufenden Konsortialprojektes der Partner HZDR, EDF France, AREVA NP France, IRSN, CEA, PSI Switzerland und ETH Zürich werden an der TOPFLOW-Anlage parametrische experimentelle Untersuchungen zu dem oben beschriebenen Thema durchgeführt. Ziel ist die Bereitstellung hochaufgelöster Experimentaldaten für die Ertüchtigung von CFD-Codes, die unter anderem in den europäischen Projekten NURESIM, NURISP und NURESAFE entwickelt werden. Der Vortrag gibt einen Überblick über das Projekt und seine Zielsetzungen, über den Versuchsstand und seine Instrumentierung sowie über das bisherige Experimentalprogramm, ausgewählte experimentelle Ergebnisse sowie CFD-Simulationsrechnungen.

Keywords: pressurized thermal shock

  • Lecture (others)
    Institutsseminar, 21.06.2012, Dresden, Germany

Publ.-Id: 17553

Dust deposition and remobilisation in a pebble bed - description of the test facility

Barth, T.; Hampel, U.

The presentation gives an overview over the ongoing project activities of HZDR in the ARCHER EU project. An air-particle test loop GPLoop has been setup in the HDZR laboratory and was equipped with various measurement systems. The purpose is the study of graphite dust deposition and remobilization in a pebble bed heap. Studies will be done with positron emission tomography.

Keywords: high temperature gas cooled reactor; graphite dust; particle transport; positron emission tomography

  • Lecture (Conference)
    ARCHER Project Meeting, 6.3.2012, Jülich, Germany

Publ.-Id: 17552

The TOPFLOW PTS project status report

Hampel, U.; Beyer, M.

The presentation describes the actual status of the TOPFLOW-PTS consortial project on thermal hydraulics of pressurized thermal shock.

  • Lecture (others)
    The TOPFLOW PTS Steering Committee Meeting, 16.02.2012, Paris, France
  • Lecture (others)
    The TOPFLOW PTS Steering Committee Meeting, 17.07.2012, Dresden, Germany

Publ.-Id: 17551

Condensation in Horizontal Heat Exchanger Tubes

Leyer, S.; Zacharias, T.; Maisberger, F.; Lamm, M.; Vallee, C.; Beyer, M.; Hampel, U.

Many innovative reactor concepts for Generation III nuclear power plants use passive safety equipment for residual heat removal. These systems use two phase natural circulation. Heat transfer to the coolant results in a density difference providing the driving head for the required mass flow. By balancing the pressure drop the system finds its operational mode. Therefore the systems depend on a strong link between heat transfer and pressure drop determining the mass flow through the system. In order to be able to analyze these kind of systems with the help of state of the art computer codes the implemented numerical models for heat transfer, pressure drop or two phase flow structure must be able to predict the system performance in a wide parameter range. Goal of the program is to optimize the numerical models and therefore the performance of computer codes analyzing passive systems. Within the project the heat transfer capacity of a heat exchanger tube will be investigated. Therefore the tube will be equipped with detectors, both temperature and pressure, in several directions perpendicular to the tube axis to be able to resolve the angular heat transfer. In parallel the flow structure of a two phase flow inside and along the tube will be detected with the help of x-ray tomography. The water cooling outside of the tube will be realized by forced convection. It will be possible to combine the flow structure measurement with an angular resolved heat transfer for a wide parameter range. The test rig is set up at the TOPLFOW facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), so that it will be possible to vary the pressure between 5 and 70 bar. The steam mass content will be varied between 0 and 100 percent. The results will be compared to the large scaled Emergency Condenser Tests performed at the INKA test facility in Karlstein (Germany). The paper will explain the test setup and the status of the project will be presented.

Keywords: emergency condenser; passive safety systems; steam condensation

  • Lecture (Conference)
    2012 International Congress on the Advances in Nuclear Power Plants, 24.-28.06.2012, Chicago, USA
  • Contribution to proceedings
    2012 International Congress on the Advances of Nuclear Power Plants, 24.-28.06.2012, Chicago, USA
    Conference Proceedings, Paper No. 12334

Publ.-Id: 17550

Experiments at TOPFLOW and ROCOM

Hampel, U.; Kliem, S.; Lucas, D.; Beyer, M.

The presentation introduces to activities at HZDR, which are related to thermal hydraulics safety concerns of Gen II and GEN-III nuclear reactors. We show examples of thermal hydraulic studies conducted at the TOPFLOW facility, which comprises two-phase pipe flow experiments, condensation experiments, pressurized thermal shock experiments, counter-current flow experiments, and boiling experiments. The ROCOM facility was created to study mixing and boron dilution in a 1:5 scaled-down PWR model. Both facilities, though serving different purposes and working in different parameter ranges, are equipped with most sophisticated measurement techniques and contribute to the answers on many thermal hydraulic phenomena occurring in today’s light water reactor systems.

Keywords: experimental fluid dynamics; nuclear thermal hydraulics

  • Invited lecture (Conferences)
    SILENCE Foundation Meeting, 05.-06.07.2012, Pisa, Italy

Publ.-Id: 17549

Radiation based tomography for multiphase flow

Hampel, U.

Multiphase flows are widely found in many fields of science, engineering, and industry. Examples are mineral oil processing, chemical reaction engineering, and nuclear thermal hydraulics. Measurement and visualisation of multiphase flows is therefore of high scientific and engineering relevance. In particular the development and validation of multiphase CFD models requires measurement data from flow scenarios with high spatial and temporal resolution.
Since multiphase flows are complex in space and time, high-resolution imaging modalities are needed as measurement tools. Unfortunately, multiphase flow research made only partial benefit from the recent tremendous progress in optical, laser and ultrasound based measurement techniques, because of the opaqueness of such flows for light and sound. Especially radiation based tomographic methods are therefore being considered as the key technology for multiphase flow visualisation. However, to date only few methods are suited because of the stringent requirements for high spatial and temporal resolution. In particular, methods are sought, which can visualize multiphase flow in complex geometries, within vessels with opaque walls and inserts, such as chemical reactors, heat exchangers or fuel rod assemblies, but also porous media of fixed bed reactors or rock samples. The presentation now will give an introduction to the recent progress in radiation based tomographic imaging techniques for multiphase flow measurement and discuss their particular role with respect to CFD code development.

Keywords: multiphase flow measurement techniques; tomography

  • Invited lecture (Conferences)
    7th OpenFOAM® Workshop, 25.-28.06.2012, Darmstadt, Germany

Publ.-Id: 17548

Ultrafast tomography for multiphase flow

Hampel, U.

The presentation gives an overview over state-of-the art ultrafast and high resolution tomographic imaging methods for multiphase flows. In particular the presentation elucidates recent developments in wire mesh sensor imaging, high resolution gamma ray tomography for process vessels and ultrafast X-ray tomography for real time flow studies. Sensor and hardware issues will be addressed along with problems and solutions for massive 3D image data processing and flow parameter extraction.

Keywords: multi phase flow; flow measurement; process tomography

  • Invited lecture (Conferences)
    6th International Symposium on Process Tomography, 26.-28.03.2012, Capetown, South Africa

Publ.-Id: 17547

Advanced imaging techniques for multiphase flows

Hampel, U.

Multiphase flows are widely found in different fields of science, engineering, and industry. Examples are mineral oil processing, chemical reaction engineering, and nuclear thermal hydraulics. Measurement and visualisation of multiphase flows is therefore of high scientific and engineering relevance. In particular the development of multiphase CFD codes requires measurement data from flow scenarios with high spatial and temporal resolution, in order to develop and validate physics based models for momentum, heat and mass transfer. If information about phase distributions, interfacial area structure, velocity and species concentration fields in flows are required, high-resolution imaging modalities are needed as measurement tools. However, yet there is no universal measurement or imaging modality for multiphase flow. Traditional visualisation tools, such as high-speed camera imaging and ultrasound measurements fail in multiphase systems due to the nonlinear propagation and attenuation of the signal carriers, e.g. light and sound waves. Especially radiation based tomographic methods are therefore being considered as the key technology for multiphase flow visualisation. However, to date only few methods are suited because of the stringent requirements for high spatial and temporal resolution. In particular, methods are sought, which can visualize multiphase flow in complex geometries, often with opaque walls and inserts, such as chemical reactor vessels, heat exchangers or nuclear fuel rod assemblies, but also porous media of fixed bed reactors or rock samples. The presentation introduces two novel imaging modalities, namely wire mesh sensors and ultrafast X-ray tomography and their use in two-phase flow measurement in complex flow domain geometries. It will be shown how gas-liquid and gas-solid flows can be visualized in in pipes, columns, fixed bed packings and flow channels with inserts. The presentation shows results of dedicated flow studies and introduces data analysis methods for extraction of quantitative flow parameters.

Keywords: multiphase flow; flow measurement

  • Invited lecture (Conferences)
    ITUN Seminar, 31.5.12, Freiberg, Germany
  • Invited lecture (Conferences)
    36th Tulsa University Separation Technology Projects Advisory Board Meeting, 15.5.2012, Tulsa, USA
  • Invited lecture (Conferences)
    Brazilian Multiphase Flow Week 2012 (EBECEM), 07.-11.05.2012, Curitiba, Brazil
  • Invited lecture (Conferences)
    Petrobras Multiphase Flow Meeting, 11.05.2012, Rio de Janeiro, Brazil
  • Invited lecture (Conferences)
    Multiphase Flow & Flow Assurance Program Meeting, 14.05.2012, San Antonio, USA
  • Invited lecture (Conferences)
    Chevron Multiphase Flow Meeting, 17.05.2012, Houston, USA

Publ.-Id: 17546

Strong paramagnetism of Gold nanoparticles deposited on a Sulfolobus acidocaldarius S-layer

Bartolome, J.; Bartolome, F.; Garcia, L. M.; Figueroa, A. I.; Repolles, A.; Martinez, M. J.; Luis, F.; Magen, C.; Selenska-Pobell, S.; Pobell, F.; Reitz, T.; Schönemann, T.; Herrmannsdörfer, T.; Merroun, M.; Geissler, A.; Wilhelm, F.; Rogalev, A.

Magnetic properties of Au nanoparticles deposited on an archaeal S-layer are reported. XMCD and SQUID magnetometries demonstrate that the particles are strongly paramagnetic, without any indication of magnetic blocking down to 16 mK. The average magnetic moment per particle is 2.36(7) mkB. This contribution originates at the particles Au 5d band, in which an increased number of holes with respect to the bulk value is observed. The magnetic moment per Au atom is 25 times larger than any measured in other Au nanoparticles or any other configurations up to date.

Keywords: Au nanoparticles; archaeal S-layer; XMCD; SQUID; paramagnetism

Publ.-Id: 17545

Feasibility study for MeV electron beam tomography

Hampel, U.; Bärtling, Y.; Hoppe, D.; Kuksanov, N.; Fadeev, S.; Salimov, R.

Electron beam tomography is a promising imaging modality for the study of fast technical processes. But for many technical objects of interest X-rays of several hundreds of keV energy are required to achieve sufficient material penetration. In this article we report on a feasibility study for fast electron beam computed tomography with a 1 MeV electron beam. The experimental setup comprises an electrostatic accelerator with beam optics, transmission target, and a single X-ray detector. We employed an inverse fan-beam tomography approach with radiographic projections being generated from the linearly moving X-ray source. Angular projections were obtained by rotating the object.

Keywords: electron beam tomography; ultrafast tomography

Publ.-Id: 17544

Capacitance wire-mesh sensor applied for the visualization of three-phase gas-liquid-liquid flows

Da Silva, M. J.; Hampel, U.

This short communication describes the application of a capacitance wire-mesh sensor for the investigation of a simulated gas-liquid-liquid three-phase flow in a laboratory setup. Experiments with air, silicone oil and water are performed first in static and second in dynamic conditions. The capacitance mesh sensor is capable of generatinge images of the cross-sectional distribution of relative permittivity values, which in turn is an indication to the phases present in the multiphase mixture. Initial tests show that the sensor is a valuable tool to investigate such three-phase flows, which are very common in the oil industry.

Keywords: wire mesh sensor; three phase flow; multiphase flow; flow measurement

Publ.-Id: 17543

Development of high-rate MRPCs for high resolution time-of-flight systems

Wang, J.; Wang, Y.; Gonzalez-Diaz, D.; Chen, H.; Fan, X.; Li, Y.; Cheng, J.; Kaspar, M.; Kotte, R.; Laso Garcia, A.; Naumann, L.; Stach, D.; Wendisch, C.; Wüstenfeld, J.

We show how the high charged-particle fluxes (1-20 kHz/cm²) expected over the 150 m² large time-of-flight wall of the future Compressed Baryonic Matter experiment (CBM) at FAIR can be realistically handled with Multi-gap Resistive Plate Chambers (MRPCs). This crucial 100-fold increase of the chamber rate capability, as compared to that of standard MRPCs presently employed in experiments resorting to sub-100 ps timing, has been achieved thanks to the development of a new type of low-resistive doped glass. Following the encouraging results previously obtained with small counters, two types of modules (active area: ~150 cm²) have been built at Tsinghua University with the new material. The measurements conveyed in this work, obtained with a quasi-minimum ionizing electron beam, prove their suitability as the building blocks of the present hadron-identification concept of the CBM experiment. Namely, they provide a time resolution better than 80 ps and an efficiency above 90% at particle fluxes of 50 kHz/cm², being at the core of a modular concept that is easily scalable. Recent measurements of the electrical and mechanical properties of this new material, together with its long-term behavior, are shortly summarized.

Publ.-Id: 17542

Production and purification of 56Co at the Leipzig cyclotron

Mansel, A.; Franke, K.

60Co (T1/2 = 5.27 a) is one of the most used radionuclide for sterilization of medical equipment, as a radiation source for medical radiotherapy, industrial radiography and food irradiation due to the high gamma-energy of 1.33 MeV. In case of release in the geosphere, e.g. soil and aquatic systems, the migration behaviour of cobalt is not well understood. For geochemical investigations, e.g. migration and adsorption studies in soil and rock formations, the short-lived isotope 56Co (T1/2 = 77 d) can be used.
We produced 56Co at a recently installed 18 MeV-cyclotron by using the nuclear reaction 56Fe(p,n)56Co.[1] The target was prepared by pressing metallic iron powder into an aluminium plate and cover it with an aluminium foil. After the irradiation with 11 MeV protons for 1 h at a current of 25 µA, the iron was dissolved with a mixture of concentrated HCl and concentrated H2O2.[2] The separation of 56Co from the target material was done by liquid-liquid extraction with methyl-tert-butylether (MTBE) from 5.2 M HCl.[3] Alternatively, an anionic exchange with DOWEX 1x8 as a column material can be used.[4] Due to the shorter separation time the liquid-liquid extraction is preferred. The radiochemical yield was 82% ± 6%. The activity concentration in the 56Co stock solution was ~4.5 MBq / ml.

[1] Jenkins, I. L., Wain, A. G., (1970) J. Inorg. Nucl. Chem. 32(5) 1419-1425.
[2] Lagunas-Solar, M. C., Jungerman, J. A., (1979) Int. J. Appl. Radiat. Isot. 30(1) 25-32.
[3] V. Wiskamp, S. Zenker, (1997), Eisenextraktion mit tertiärem Butylmethylether. CLB 48 (Beilage Memory) 22.
[4] Kraus, K. A., Moore, G. E., (1953) J. Am. Chem. Soc. 75(6) 1460-1462.

  • Lecture (Conference)
    NRC 8 - International Conference on Nuclear and Radiochemistry, 16.-21.09.2012, Como, Italy

Publ.-Id: 17541

Dose-Controlled Radiobiological Experiments with Laser Accelerated Proton Pulses as a Prerequisite for Radiation Therapy

Schramm, U.

  • Invited lecture (Conferences)
    EPS / ICPP - 39th European Physical Society Conference on Plasma Physics / 16th International Congress on Plasma Physics, 02.-06.07.2012, Stockholm, Sweden

Publ.-Id: 17540

Synthesis, Characterization and Evaluation of Radiometal-Containing Peptide Nucleic Acids

Stephan, H.; Förster, C.; Gasser, G.

As described in Chapter, peptide nucleic acids (PNAs) have very attractive properties, which include, among them, high selectivity towards DNA/RNA recognition. It is therefore not surprising that their potential in nuclear medicine and biology to explore in vitro and in vivo processes has also been investigated. The high thermal and radiolytic stability as well as resistance toward nuclease/protease degradation of these bioconjugates offers new opportunities in this field of research, which could, potentially, lead to a transformation of the whole scope of diagnostically and therapeutically relevant radionuclides. Importantly, as demonstrated in Chapter with metal complexes, PNAs can be synthetically modified allowing their intrinsic physico-chemical properties to be significantly modulated. For example, the attachment of appropriate spacer elements and specific building blocks, such as targeting units, to both the C- and N-terminus of PNAs allows a broad variation of the pharmacologic properties of PNA bioconjugates, hence enabling the development of application-orientated probes for imaging of gene expression. Furthermore, the high metabolic resistance of these non-natural oligonucleotides makes them interesting for therapeutic applications. In this book chapter, we report on the current developments towards the preparation of radiometal-containing PNA constructs and summarize the protocols for labeling these oligonucleotides with 99mTc, 111In, 64Cu, 90Y and 177Lu.

Keywords: Peptide Nucleic Acid (PNA); Radiometal Complexes; Bifunctional Chelating Agents; Molecular Imaging; Endoradionuclide Therapy

  • Book chapter
    P. E. Nielsen, D. H. Appella: Peptide Nucleic Acids: Methods and Protocols, 2nd ed., Series: Methods in Molecular Biology, Vol. 1050, New York: Springer, Humana Press, 2014, 978-1627035521, 37-54

Publ.-Id: 17539

Polyoxometalates as versatile enzyme inhibitors

Stephan, H.; Müller, C. E.

Polynuclear metal compounds may have considerable potential as metallic drugs. The most prominent representatives are polyoxometalates (POMs) which have been investigated since the last third of the 19th century. In addition to applications in catalysis, separation, analysis, and as electron-dense imaging agents, some of these substances have been shown to exhibit biological activity in vitro as well as in vivo ranging from anti-cancer, antibiotic, and antiviral to anti-diabetic effects.
Polyoxometalates represent a diverse ensemble of nanostructures with an almost infinite variability of chemical, physical and biological properties. The size of typical covalent bridged cluster compounds is in the range from 1 to 3 nm. The attachment of special surface groups on the periphery of cluster compounds may result in self-assembled non-covalent organized structures larger than 5 nm which are characteristic for bio-molecules, such as enzymes. Cells of mammalian organisms are typically 10 to 30 µm. However, sub-cellular organelle dimensions are smaller and range in sub-µm sizes. This comparison of size dimension illustrates that polymetalates are small enough to allow the cell membrane to be penetrated without too much interference. Evidently, some types of polyoxometalates are able to be transported into cells, particularly into mitochondria. However, many of such polyanions are only slightly taken up by cells, obviously caused by negatively charged membranes.
On the way to explore the biological activity of polynuclear cluster compounds, we recently recognised POMs as a new class of potent enzyme inhibitors. Certain polyanionic complexes are able to inhibit extracellular E-NTPDases (ecto-nucleoside triphosphate diphosphohydrolases) that are surface-located nucleotide-hydrolyzing enzymes involved in the regulation of signaling cascades by activating P2 (nucleotide) receptors.
We want to present a brief overview about the potential of POMs as E-NTPDase inhibitors and P2 receptor antagonists.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17538

Look-Locker Acquisition for Estimation of partial volume fractions in ASL Data

Petr, J.; Schramm, G.; Hofheinz, F.; Langner, J.; Steinbach, J.; van den Hoff, J.

Due to the relatively low spatial resolution, arterial spin labeling (ASL) images are strongly affected by partial volume effects (PVE). This can make the qualitative analysis of ASL images difficult and it also significantly decreases the accuracy of cerebral blood flow (CBF) quantification. The PVE can be corrected for by using gray matter (GM) and white matter (WM) tissue segmentation of high-resolution T1-weighted images as proposed by Asllani et al1. The main drawback of this method is the need for precise knowledge of the partial volume ratios. However, the segmentation of T1-weighted images is very difficult at the border of GM and WM. Moreover, ASL images contain susceptibility induced deformations typical for EPI images and thus a correct registration with T1-weighted images is not always possible. Hence, the PVE correction using segmented T1-weighted images can introduce artifacts. In this study, we analyze an alternative method to obtain the partial volume ratios through the longitudinal magnetization relaxation times obtained from a Look-Locker sampling acquired in a multiple inversion time (TI) ASL sequence.

  • Contribution to proceedings
    ISMRM 20th Annual Meeting, 05.-11.05.2012, Melbourne, Australia
    2012 Annual Meeting Proceedings, 2001
  • Poster
    ISMRM 20th Annual Meeting, 05.-11.05.2012, Melbourne, Australia

Publ.-Id: 17537

Validierung eines Gammatomographen zur Bestimmung der Phasenanteilsverteilung in einem geneigt rotierenden Festbettreaktor

Arlit, M.

Das Institut für Fluiddynamik im Helmholtz-Zentrum Dresden-Rossendorf (HZDR) beschäftigt sich unter anderem mit der Untersuchung mehrphasiger verfahrenstechnischer Prozesse sowie der Entwicklung und Charakterisierung neuer effizienter Mehrphasenkontaktapparate und -reaktoren.
Ein solches neuartiges Konzept stellt der geneigt rotierende Festbettreaktor dar. Im Gegensatz zum zeitlich-periodischen Reaktorbetrieb erfolgt die Prozessintensivierung hier durch Aufprägung einer örtlichen Periodizität unter ansonsten stationären Betriebsbedingungen. Aus dieser veränderten Betriebsweise ergeben sich durch die Wahl von Reaktorneigung und Reaktordrehzahl zusätzliche Freiheitsgrade bei der Strömungsführung und damit zur Beeinflussung der Reaktorleistung.
Im Rahmen der Diplomarbeit ist ein tomographisches Messsystem für die Ermittlung von Phasenanteilen zu validieren. Weiterhin ist der Einfluss von Reaktorneigung und –drehzahl auf die Verteilung der Phasenanteile und den Druckverlust bei ausgewählten Gas- und Flüssigkeitsdurchsätzen zu untersuchen und mit dem etablierten Rieselbettreaktor zu vergleichen.

Keywords: Fixed bed reactor; Liquid Holdup; Phase Distribution; Inclination; Rotation; Gamma-ray Tomography

  • Diploma thesis
    TU Dresden, 2012
    130 Seiten

Publ.-Id: 17536

High specific activity 61Cu via 64Zn(p,α)61Cu reaction at low proton energies

Thieme, S.; Walther, M.; Preusche, S.; Rajander, J.; Pietzsch, H.-J.; Solin, O.; Steinbach, J.

The PET radionuclide 61Cu is accessible through several nuclear reactions. Besides the common production route via 61Ni(p,n)61Cu the 64Zn(p,α)61Cu reaction offers some advantages. Especially the comparatively cheap enriched 64Zn makes this process economical. For fast product purification and recycling of target material an ion exchanger cascade was developed. In addition a separation technique with a copper selective resin was tested. 61Cu with specific activities up to 1000 GBq/µmol was produced with these methods.

Publ.-Id: 17535

Absorption saturation in optically pumped graphene

Winzer, T.; Knorr, A.; Mittendorff, M.; Winnerl, S.; Sun, D.; Norris, T. B.; Helm, M.; Malic, E.

We investigate the saturation of the optical absorption in graphene induced by ultrafast optical pulses. Within a microscopic theory, we study the momentum-, angle-, and time-resolved interplay of anisotropic excitation, carrier-carrier and carrier-phonon scattering and its influence on the saturation of absorption and transmission as a function of the input intensity. In agreement with recent experiments, we observe a linear regime for the intensity-dependence of the transmission at low pump fluences and a nonlinear saturation in the high excitation regime. Applying 10 fs-pulses we obtain a saturation fluence of approximately 6.5mJ/cm2. We demonstrate how the interplay of Pauli-blocking and intensity-dependent relaxation determines the saturation behavior.

Publ.-Id: 17534

1550 nm ErAs:In(Al)GaAs Large Area Photoconductive Emitters

Preu, S.; Mittendorff, M.; Lu, H.; Weber, H. B.; Winnerl, S.; Gossard, A. C.

We report on high power Terahertz emission from ErAs-enhanced InAlAs-InGaAs superlattices for operation at 1550 nm. ErAs clusters act as ecient recombination centers. The optical power is distributed among a large, microstructured area in order to reduce the local optical intensity. A THz field strength of 0.7 V/cm (1 V/cm peak-to-peak) at 100 mW average optical power has been obtained, with emission up to about 4 THz in air, limited by the detection crystal used in the system.

Publ.-Id: 17533

Relaxation dynamics in epitaxial graphene investigated in the whole infrared spectral range

Winnerl, S.; Göttfert, F.; Mittendorff, M.; Schneider, H.; Helm, M.; Orlita, M.; Potemski, M.; Winzer, T.; Knorr, A.; Malic, E.; Sprinkle, M.; Berger, C.; de Heer, W. A.

As a gapless material with linear dispersion graphene is of great interest for the infrared spectral range. In this study we investigate the carrier relaxation dynamics of graphene in a wide spectral range from the near to the far-infrared, covering more than two orders of magnitude in photon energy.
The samples for this study are epitaxially grown graphene layers on the carbon-terminated face of SiC, which behave essentially like a stack of electronically uncoupled layers. In the near infrared (NIR) spectral range (photon energy 0.41 eV – 1.5 eV) degenerate and two-color experiments were performed. In the mid (MIR) and far infrared (FIR) range (photon energy 10 meV – 250 meV) degenerate pump-experiments were carried out employing the free-electron laser FELBE as a source.
In the NIR range pump-induced transmission was observed in two-color experiments with both red and blue shifted probe radiation. The signals in case of the blue shifted probe are evidence for a hot carrier distribution. The thermalization process is beyond the temporal resolution of our experiment (~ 100 fs in the near infrared). The observed decay times are in the range of 2 – 4 ps. In the MIR range we observe a significant increase of the relaxation time as the photon energy is decreased to values below the optical phonon energy (~200 meV). These experiments are complemented by microscopic theory based on the density matrix formalism [1]. The theory reflects the trends seen in the experiment well. It reveals the contribution of Coulomb scattering as well as the role of both optical and acoustic phonons in the observed dynamics.
In the FIR range an unexpected change from enhanced transmission to enhanced absorption is found (cf. Fig. 1). It is caused by an interplay of interband and intraband processes. For photon energies above twice the value of the Fermi energy, bleaching of interband transitions results in pump-induced transmission. For smaller photon energies, however, interband transitions are not possible. Here intraband transitions cause a heating of the carrier distribution, which is responsible for the intraband absorption.

  • Poster
    International Conference on Superlattices, Nanostructures and Nanodevices, 22.-27.07.2012, Dresden, Deutschland

Publ.-Id: 17532

Graphene excited with short infrared pulses: fundamental aspects and application perspectives

Winnerl, S.

Detailed knowledge of the ultrafast carrier dynamics is of crucial importance for the development of novel electronic and optoelectronic devices. Graphene, a gapless semiconductor, is very attractive for broadband photonic and optoelectronic applications. We performed pump-probe experiments on graphene samples in a wide spectral range from the near-infrared to the terahertz region (wavelength 0.8 µm – 120 µm). We show results on the relaxation dynamics and identify the main relaxation channels, namely optical phonons, intraband carrier-carrier scattering, and Auger-type processes [1]. Furthermore the saturation behaviour of the signals is investigated. This is important with respect to graphene-based saturable absorbers. Here we find that the intensity required for full beaching of graphene decreases by three orders of magnitude, when the pump wavelength is increased from 5 µm to 40 µm. Finally we present a fast graphene-based terahertz detector, which can be operated at room temperature.
This work was carried out in collaboration with M. Mittendorff, F. Göttfert, H. Schneider, and M. Helm from the Helmholtz-Zentrum Dresden Rossendorf, M. Orlita and M. Potemski from LNCMI-CNRS Grenoble. Modelling based on microscopic theory was performed by T. Winzer, E. Malic, and A. Knorr at the TU Berlin, sample growth by M. Sprinkle, C. Berger, and W.A. de Heer from the Georgia Institute of Technology, Atlanta. We acknowledge support by the German Science Foundation (DFG) in the framework of the priority program “Graphene”.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

  • Invited lecture (Conferences)
    7th International Conference on Surfaces, Coatings and Nanostructured Materials, 18.-21.09.2012, Prague, Czech Republic

Publ.-Id: 17531

Intersublevel spectroscopy on single InAs-quantum dots by terahertz near-field microscopy

Jacob, R.; Winnerl, S.; Fehrenbacher, M.; Bhattacharyya, J.; Schneider, H.; Wenzel, M. T.; von Ribbeck, H.-G.; Eng, L. M.; Atkinson, P.; Schmidt, O. G.; Helm, M.

Using scattering-type near-field infrared microscopy in combination with a free-electron laser, intersublevel transitions in buried single InAs quantum dots are investigated. The experiments are performed at room temperature on doped self-assembled quantum dots capped with a 70 nm GaAs layer. Clear near-field contrast of single dots is observed when the photon energy of the incident beam matches intersublevel transition energies, namely the p-d and s-d transition of conduction band electrons confined in the dots. The observed room-temperature linewidth of 5 – 8 meV of these resonances in the mid-infrared range is significantly below the inhomogeneously broadened spectral lines of quantum dot ensembles. The experiment highlights the strength of near-field micro-spectroscopy by demonstrating signals from bound-to-bound transitions of single electrons in a probe volume of the order of (100 nm)^3.

Publ.-Id: 17530

Cyclammonopropionic acid- a promising chelating system for radiocopper isotopes

Kubeil, M.; Peschel, L.; Stephan, H.; Steinbach, J.

A wide variety of radiometal-chelating bioconjugates have been studied intensively to design effective radiopharmaceuticals for diagnostic and therapeutic purposes. Azamacrocycles offer an enormous potential to achieve highly stable radiometal complexes and allow the covalent attachment of targeting and/or fluorescence units at the ligand skeleton. In this context, 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid (TETA) is quite often used for the development of copper-based target-specific radiopharmaceuticals, although demetallation and transchelation occur in biological systems. In contrast, radiolabeling of propionic acid analogues has not been reported so far.
An appropriate building block to form very stable complexes with copper(II) is N-mono-(2-(carboxy)ethyl)-1,4,8,11-tetraazacyclotetradecane (Cyclammonopropionic acid, CMPA) which permits the formation of stable radiocopper complexes as well as a facile approach to obtain peptide multimers. An improved pharmaceutical targeting might be utilized due to the multimeric peptide functionalization of the chelating agent. The Epidermal-Growth-Factor-Receptor (EGFR), which is overexpressed on a multitude of tumors, has been chosen as target system to be studied.
Herein, we want to report about coupling reactions of the model dipeptide H-(L)-Leu-(L)-Ala-OH, which is a part of an EGFR-specific peptide, with the cyclammonopropionic acid skeleton. Radiolabeling of CMPA-peptide conjugates with copper-64 indicate high in vitro stability of the complexes formed. So far, this promising behavior may pave the way to develop attractive candidates for radiopharmaceutical applications.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17529

Relaxation dynamics in graphene

Winnerl, S.

The peculiar properties of graphene, most importantly its gapless, linear band structure, give rise to exciting phenomena such as constant optical absorption over a wide range of photon energies and an unusual quantum Hall effect. Furthermore graphene is considered as an interesting material for electronic and optoelectronic applications. A good understanding of the relaxation dynamics is essential both for fundamental research and applications.
After an introduction into graphene research, I will present our results of pump-probe experiments in the mid- and far-infrared spectral range (photon energy 245 meV – 10 meV). We identify the role of optical phonons in the relaxation dynamics and discuss contributions from Auger-type processes and acoustic phonons. Furthermore an interesting change in sign of the pump-probe signal is observed at low photon energies (20 – 30 meV), which can be explained by an interplay of intraband and interband absorption processes [1]. In the second part of the talk I will focus on the relaxation dynamics in Landau-quantized graphene. Since the Landau levels (LLs) in graphene are not equidistant but scale with both the square root of the LL index and the square root of the magnetic field, optical pumping of individual LL-transitions is possible. Here we focus on the LL-1 → LL0 and LL0 → LL1 transitions, which exhibit equal transition energies but can be distinguished by applying either right-handed or left-handed circularly polarized light. Employing all four combinations of pumping and probing with right-handed and left-handed circularly polarized light, respectively, results in complex pump-probe signals: They involve fast and slow components, which exhibit either positive or negative signs. The relaxation dynamics in this regime can be understood by attributing the fast components to Auger-type processes and the slower components to phonon-mediated energy relaxation.
[1] S. Winnerl, M. Orlita, P. Plochocka, P. Kossacki, M. Potemski, T. Winzer, E. Malic, A. Knorr, M. Sprinkle, C. Berger, W. A. de Heer, H. Schneider, and M. Helm, Phys. Rev. Lett. 107, 237401 (2011).

  • Lecture (others)
    Seminar der Arbeitsgruppe Prof. Wiek, 06.07.2012, Bochum, Deutschland

Publ.-Id: 17528

Charakterisierung der Bindungseigenschaften rheniumhaltiger Clusterverbindungen gegenüber Dendrimeren

Kuhlmann, M.

kein Abstract verfügbar

  • Diploma thesis
    TU Dresden, Fakultät Mathematik und Naturwissenschaften, Fachrichtung Chemie und Lebensmittelchemie, 2009
    74 Seiten

Publ.-Id: 17527

The FELBE user facility

Seidel, W.; Winnerl, S.; Bhattacharyya, J.; Teich, M.; Fehrenbacher, M.; Drachenko, O.; Schneider, H.; Helm, M.; Bauer, C.; Gensch, M.; Schurig, R.; Lehnert, U.; Michel, P.

The FELBE user facility located at the Helmholtz-Zentrum Dresden-Rossendorf operates two free-electron lasers (FELs). Here we discuss the basic parameters of the FELs and the experimental opportunities at the facility. The FELs are based on the superconducting electron linear accelerator ELBE, which provides short (picosecond) electron bunches with energies up to 35 MeV at a 13 MHz repetition rate. The two FELs of FELBE (FELBE stands for FEL@ELBE) are equipped with two undulators, one for the mid-infrared spectral range (wavelengths 4 – 22 μm) and one for the far-infrared or THz range (wavelengths 20 – 250 μm). The key feature which distinguishes FELBE from other FEL user facilities is the possibility of “quasi cw” operation (meaning a continuous train of pulses, also called micropulses), made possible by the superconducting accelerator cavities. The FEL thus provides picosecond optical pulses at a repetition rate of 13 MHz. In this mode, the average power can reach up to 30 W (depending on the wavelength) corresponding to more than 1 μJ pulse energy. Additionally FELBE can be operated in a macrobunch mode and, via pulse-picking, a 1 kHz mode. The two FELs can be synchronized to a number of tabletop femtosecond and picosecond lasers, enabling two-color experiments from the near-infrared to the THz frequency range. The main techniques at FELBE are pump-probe spectroscopy [1-3] and time-resolved photoluminescence [4]. Furthermore there is a lab devoted to near-field microscopy [5,6]. Spectroscopy with FELBE radiation is also possible in pulsed high magnetic fields up to 70 T (150 ms magnetic pulse duration) [7,8]. FELBE is operated as a user facility, i.e., scientists from other institutions are invited to submit short research proposals and apply for beamtime.
[1] D. Stehr et al., Appl. Phys. Lett. 92, 051104 (2008).
[2] E.A. Zibik, et al., Nature Mat. 8, 803 (2009).
[3] S. Winnerl et al., Phys. Rev. Lett. 107, 237401 (2011).
[4] J. Bhattacharyya et al., Rev. Sci. Instr. 82, 103107 (2011).
[5] S.C. Kehr et al., Phys. Rev. Lett. 100, 256403 (2008).
[6] S.C. Kehr et al., Nature Comm. 2, 249 (2011).
[7] S. A. Zvyagin, et al, Rev. Sci. Instr. 80, 073102 (2009).
[8] O. Drachenko et al., Phys. Rev. B 79, 245207 (2011).

  • Poster
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17526

Biofunctionalisation and 64Cu-labeling of pyridine-containing TACN ligands for specific targeting of EGF-receptor

Hesse, J.; Viehweger, K.; Stephan, H.; Steinbach, J.

The application of radiolabeled peptides in biomedicine is increasing rapidly and offers excellent prospects for the development of target-specific tumor imaging agents. In this perspective, the incorporation of the positron-emitting radionuclide 64CuII into ligand-peptide conjugates would permit the use of positron emitting tomography (PET) for tumor identification. An important requirement is that the resulting radiocopper-ligand complex is both kinetically and thermodynamically stable in vivo. We have developed a ligand scaffold based on bis(2-pyridylmethyl)triazacyclononane (DMPTACN) that forms very stable CuII complexes [1]. This structure allows for the introduction of linker groups, such as carboxylic acids, maleimide or isothiocyanate, thereby facilitating coupling of targeting molecules.
Among many characteristic targets of cancer tissue, the epidermal growth factor receptor (EGFR) is one of the most important mediators involved in the development of highly malignant tumors. This surface receptor is overexpressed in several tumor entities. The altered expression of EGFR during tumor growth, invasion, and metastasis present an interesting molecular target for tumor diagnosis and therapy.
Meanwhile, some specific peptides are identified capable of recognition EGFR-rich cancer tissue. Among these, the hexapeptide D4 (Leu-Ala-Arg-Leu-Leu-Thr) has been described [2]. We want to present the synthesis of a DMPTACN-peptide conjugate, applying thiourea coupling of the hexapeptide D4 by a DMPTACN isothiocyanate derivative. Radiochemical and radiopharmacological properties will be reported. In vitro binding characteristics of the [64Cu]CuII-labeled DMPTACN-peptide conjugate in EGFR overexpressing cancer cells ( FaDu, A431) using an immunoprecipitation protocol point to specific interactions.

[1] G. Gasser, L. Tjioe, B. Graham, M. J. Belousoff, S. Juran, M. Walther, J.-U. Künstler, R. Bergmann, H. Stephan, L. Spiccia, Bioconjugate Chem. 2008, 9, 719-730.
[2] S. Song, D. Liu, J. Peng, H. Deng, Y. Guo, L. X. Xu, A. D. Miller, Y. Xu, FASEB J. 2009, 23, 1396–1404.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17525

Semiconductor quantum structures in high THz fields

Winnerl, S.

Electronic resonances in semiconductor quantum structures such as quantum wells and quantum dots are often accompanied by nonlinear phenomena. The intense, spectrally narrow radiation of a free-electron laser (FEL) is ideally suited for studying these nonlinear effects. We briefly discuss effects that can be treated in a perturbative way, such as the appearance of THz-sidebands around near-infrared absorption lines of quantum wells and quantum dots. Mainly we focus on an effect, which is beyond the perturbative description, namely the Autler-Townes splitting of excitonic absorption lines. Photogenerated electrons and holes in semiconductors form excitons, which exhibit a hydrogen-like energy spectrum. Due to the presence of the crystal lattice, however, the energy is scaled to the meV range. Excitation with intense THz pulses from an FEL "dresses" the excitonic states and leads to a splitting of energy levels. This splitting can be observed by probing the samples's transmission with broadband near-infrared radiation. While the main features, such as the dependence of the peak position on the THZ intensity, can be explained by a simple two-level model, other observations such as the relative strength of the peaks require more complex modelling. The mauin results presented here were obtained by M. Wagner, D. Stehr, H. Schneider and M. Helm on a sample grown by A. M. Andrews, S. Schartner, and G. Strasser.

  • Invited lecture (Conferences)
    503th Wilhelm and Else Heraeus Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17524

Dose controlled irradiation of cancer cells with laser accelerated proton pulses

Zeil, K.; Baumann, M.; Beyreuther, E.; Burris-Mog, T.; Cowan, T. E.; Enghardt, W.; Karsch, L.; Kraft, S. D.; Laschinsky, L.; Metzkes, J.; Naumburger, D.; Oppelt, M.; Richter, C.; Sauerbrey, R.; Schürer, M.; Schramm, U.; Pawelke, J.

Proton beams are a promising tool for the improvement of radiotherapy of cancer, and compact laserdriven proton radiation (LDPR) is discussed as an alternative to established large-scale technology acilitating wider clinical use. Yet, clinical use of LDPR requires substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies. Here, we present the first dose-controlled direct comparison of the radiobiological effectiveness of intense proton pulses from a laser-driven accelerator with conventionally generated continuous proton beams, demonstrating a first milestone in translational research. Controlled dose delivery, precisely online and offline monitored for each out of *4,000 pulses, resulted in an unprecedented relative dose uncertainty of below 10 %, using approaches scalable to the next translational step toward radiotherapy application.

Publ.-Id: 17523

Synthesis and cytotoxicity of pyridine and quinoline oxorhenium(V) complexes with tridentate (NS2, S-3)/monodentate (s) coordination

Segal, I.; Zablotskaya, A.; Kniess, T.; Shestakova, I.

New oxorhenium complexes with tridentate 3-thia- and 3-methylazapentane-1,5-dithiolate and monodentate pyridine and quinoline derivatives have been synthesized. As a result of investigation of biological activity a high cytotoxicity was found for the synthesized complexes in relation to tumor cells. The specificity of the 2-pyridylthiolato[3-(N-methyl)azapentane-1,5-dithiolato]oxorhenium(V) cytotoxic action towards cells of mouse hepatoma MG-22A on a background of low acute toxicity was established.

Keywords: oxorhenium(V) complexes; pyridine; quinoline; rhenium; cytotoxicity

Publ.-Id: 17522

Ultrafast relaxation dynamics close to the Dirac point in graphene

Winnerl, S.; Malic, E.

The relaxation dynmics in graphene is studied in the mid- and far-infrared spectral range.

  • Poster
    International Workshop on THz dynamics in carbon based nanostructures, 05.-07.03.2012, Dresden, Deutschland

Publ.-Id: 17521

Modularisierung der Geometrieinformation einer C++/Qt-basierten iterativen Bildrekonstruktion in der Positronen-Emissions-Tomographie

Domula, S.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule für Technik und Wirtschaft Dresden, 2012
    78 Seiten

Publ.-Id: 17520

Improved composit targets for small scale Cu-64 production comparing Au- and Pt-foils as Ni-64 backing

Walther, M.; Preusche, S.; Füchtner, F.; Pietzsch, H.-J.; Steinbach, J.

Advantages of a stacked assembly of target support components for 64Cu production via 64Ni(p,n)64Cu reaction were reported recently.1 The present work shows the applicability of these composit targets for beam currents up to 22 µA. Gold and platinum foils were evaluated as 64Ni backing. The effective specific activity (ESA) and specific activity (SA) were determined by TETA titration at room temperature and at 80 °C and compared with additional copper quantification results via stripping voltammetric trace analysis (VA).

  • Lecture (Conference)
    14th International Workshop on Targetry and Target Chemistry (WTTC14), 26.-29.08.2012, Playa del Carmen, Mexico
  • Contribution to proceedings
    14th International Workshop on Targetry and Target Chemistry, 26.-29.08.2012, Playa del Carmen, Mexico
    AIP Conference Proceedings Vol. 1509: American Institute of Physics, 978-0-7354-1127-2, 81-83
    DOI: 10.1063/1.4773945

Publ.-Id: 17519

Ultrafast relaxation dynamics close to the Dirac point in graphene

Winnerl, S.; Malic, E.

The relaxation dynamics at low photon energies (10 meV - 300 meV) is studied experimentally. Comparison with mcroscopic theory allows us to identify teh role of carrier-carrier scattering and scattering by optical and acoustic phonons.

  • Poster
    1st Workshop of the Priority Programme Graphene, 04.-08.12.2011, Rothenfels, Deutschland

Publ.-Id: 17518

Four years experience in operation and maintenance of the [18F]F2 proton target at the Rossendorf Cyclone® 18/9 cyclotron

Preusche, S.; Füchtner, F.; Steinbach, J.

Experience in operation of the [18F]F2-p target to achieve stable and sufficient activity yields and reaction yields for [18F]FDOPA preparations are summarized. Hints for maintenance are given.

  • Lecture (Conference)
    The eigth workshop of the "CYCLONE 18/9 + 10/5 USER COMMUNITY", 09.-13.10.2010, Coimbra, Portugal

Publ.-Id: 17517

Strahlenschutz im PET-Zentrum Dresden-Rossendorf - Überblick -

Preusche, S.; Füchtner, F.; Zessin, J.; Beuthien-Baumann, B.; Bergmann, R.; Walther, M.

kein Abstract verfügbar

  • Lecture (others)
    Strahlenschutz-Kolloqium, VKTA, 02.09.2010, Rossendorf, Deutschland

Publ.-Id: 17516

Transport von Kohlenstoffnanoröhrchen in Umweltsystemen

Schymura, S.

Einführung in den Transport von Kohlenstoffnanoröhrchen in Umweltsystemen

Keywords: carbon nanotubes; transport

  • Communication & Media Relations
    Poster & Handout (Lange Nacht der Wissenschaft) 29.06.2012
    1 Seiten

Publ.-Id: 17515

Three years experience in operation and maintenance of the [18F]F2 proton target at the Rossendorf Cyclone® 18/9 cyclotron

Preusche, S.; Füchtner, F.; Steinbach, J.

An increasing demand of radiopharmaceuticals based on electrophilic reaction with [18F]F2 gas (for instance [18F]FDOPA) led to an upgrade of the IBA [18F]F2 gas target system in summer 2007. The more than 10 years operated [18F]F2 deuteron target [20Ne(p,α)18F] was not able to meet the increasing requirements in terms of activity anymore and was thus replaced by an IBA [18F]F2 proton gas target [18O(p,n)18F] based on the so-called “double-shot” ‘irradiation method by R.J. Nickles [1]. The upgrade itself was done by IBA.
We run the Cyclone® 18/9 cyclotron in routine operation for more than 14 years. One of the specific features of the Rossendorf PET Center is the Radionuclide transport system (RATS) [2], 500 m in length that bridges the distance from the cyclotron to the radiopharmaceutical laboratories. The activity at the end of bombardment (EOB) is calculated taking in account the transfer time and experimental data of activity losses (about 30%) in the transfer tube [2].

  • Lecture (Conference)
    WTTC13 - 13th International Workshop on Targetry and Target Chemistry, 25.-28.06.2010, Risoe, Denmark
  • Poster
    WTTC13 - 13th International Workshop on Targetry and Target Chemistry, 25.-28.06.2010, Risoe, Denmark

Publ.-Id: 17514

Entwicklung maleinimidhaltiger, bifunktioneller Markierungsbausteine auf der Basis von 1,4,7-Triazacyclononanliganden

Fähnemann, S.

kein Abstract verfügbar

  • Master thesis
    Hochschule für Technik und Wirtschaft Fachbereich Maschinenbau/Verfahrenstechnik Studiengang Chemie, 2008
    75 Seiten

Publ.-Id: 17513

Radiometallmarkierung und kolloid-chemische Charakterisierung von magnetischen Nanopartikeln

Fähnemann, S.

kein Abstract verfügbar

  • Diploma thesis
    Hochschule für Technik und Wirtschaft Fachbereich Maschinenbau/Verfahrenstechnik Studiengang Chemie, 2007
    70 Seiten

Publ.-Id: 17512

Enhanced ion heating induced by collisional shocks generated by an ultra-short intense laser pulse interacting on a heterogeneous solid target

Huang, L. G.; Bussmann, M.; Kluge, T.; Ramakrishna, B.; Cowan, T. E.

To achieve above keV ion temperatures, we propose a method to deposit enough energy of an ultra-short intense laser pulse into a multilayer solid target by creating an ion shock wave. In the scenario studied the bulk ions are heated efficiently when the shock wave is created inside the target and propagates through the target. To study the feasibility of this scheme a heterogeneous solid target with of CD-Al-CD multi-layer structure is studied using Particle-in-Cell (PIC) simulations. These simulations give insight into the dynamics of the shock generation by an ultra-short intense laser pulse (~100fs, 10^20W/cm2). The simulations show that shock waves are created in the interfaces of the CD-Al layer. Deuteron temperatures in the keV range are observed after the shock. Such high ion temperatures may be benefitial for neutron production via D-D fusion reactions.

Keywords: Laser plasma physics; ion heating; kev temperature

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity, 16.-20.04.2012, Dresden, Germany

Publ.-Id: 17511

A Critical Review on Multiscale Material Database Requirement for Accurate Three-Dimensional IC Simulation Input

Yeap, K.-B.; Röllig, M.; Hübner, R.; Gall, M.; Sukharev, V.; Zschech, E.

Material behavior and properties at different scales, from nanometers to millimeters, are the input data needed for a model-based design-for-manufacturing approach of 3-D through-silicon-via (TSV) stacked ICs. In particular, mechanical and thermomechanical material data have to be used as input for physics-based modeling and simulation of stress-induced phenomena in 3-D stacks. Both package-and wafer-level properties, including their interaction, have to be considered. This paper reviews the thermomechanical and mechanical properties of several structures: time-dependent properties of solder materials (millimeter and micrometer scales), microstructure-dependent properties of Cu TSVs (micrometer scale), and process-dependent properties of ultralow-k materials in on-chip interconnect stacks (10-nm scale). To minimize the keep-out zone for active devices in the stress-affected surrounding of TSVs, while maintaining the device performance during 3-D TSV stacking of ICs, highly accurate material data are needed as input for the thermomechanical stress simulation. A similar strategy is supposed to be developed for a model-based design-for-reliability approach of 3-D TSV stacked ICs.

Keywords: Device performance; material database; multiscale simulation; through-silicon via (TSV); 3-D integration

Publ.-Id: 17510

Radiolabelling of engineered nanoparticles for environmental particle tracing - HZDR – Cyclotron facility – Radionuclide production

Franke, K.; Hildebrand, H.; Schymura, S.

Radiolabelling of engineered nanoparticles for environmental particle tracing --> Presentation of the radionuclide production at the HZDR - cyclotron facility in Leipzig together with yields and stability of different radiolabelling strategies for nanoparticles

  • Lecture (Conference)
    JRC-QNano-seminar, 15.06.2012, Ispra, Italia

Publ.-Id: 17509

Untersuchung des Lebenszyklus von TiO2- und Ag0-Nanopartikeln - NanoTRACK

Franke, K.

Untersuchung des Lebenszyklus von TiO2 - und Ag0 - Nanopartikeln mithilfe Radiotracern. Radionuklidherstellung, Markierungsausbeuten, Markierungsstabilität und erste Ergebnisse zur Partikelfreisetzung aus Lacksystemen werden vorgestellt.

  • Lecture (Conference)
    2. Clustertreffen der Fördermaßnahmen NanoCare und NanoNature, 13.-14.03.2012, Frankfurt /Main, Deutschland

Publ.-Id: 17508

CNT-Modification and radiolabelling at the HZDR

Schymura, S.; Hildebrand, H.; Franke, K.

Presentation of results on microwave-assisted carbon nanotube modification and iodine radiolabelling

Keywords: carbon nanotubes; modification; radiolabelling

  • Lecture (others)
    Seminar at the JRC-cyclotron facility within the Qnano project: "Be-7 Recoil labelling of multi-wall carbon nanotubes", 04.-15.06.2012, Ispra, Italien

Publ.-Id: 17507

Rapid carbon nanotube modification and radiolabelling for particle tracing applications

Schymura, S.; Franke, K.; Lippmann-Pipke, J.

Presentation of results on carbon nanotube modification via microwave-assisted oxidation and iodine radiolabelling of carbon nanotubes for particle tracing applications

Keywords: carbon nanotubes; radiolabelling; modification

  • Poster
    2. NanoNature Clustertreffen, 12.-14.03.2012, Frankfurt, Deutschland

Publ.-Id: 17506

Eu3+ in NMR spectroscopy – a helpful tool in tracking binding sites

Kretzschmar, J.; Barkleit, A.; Brendler, V.

Lanthanides have become a useful tool in NMR spectroscopy within the last 40 years. Due to their paramagnetic properties they can be utilized as probes to determine the binding sites of biologically or environmentally relevant organic molecules as they cause significant line broadenings and / or paramagnetic induced shifts [1-3].
Actual research deals with the interactions, thermodynamic and kinetic behaviour of actinides and biomolecules. Lanthanides can easily be used as inactive analogues for trivalent actinides in consequence of their similar chemistry.
Glutathione is a high concentrated intracellular reducing agent, playing a major role in detoxification processes. Important targets are electrophiles such as heavy metal ions. With its high natural abundance, different functional groups and reducing ability, this tripeptide provides outstanding characteristics for actinide complexation research and, furthermore by its small size it is well suited as a model molecule in NMR spectroscopy.
1H-NMR signals are shifted and broadened by the paramagnetic induced shift of the Eu3+ with their 4f6 electron configuration. These interactions between nuclear spins and electron unpaired spins exhibit a strong distance dependency. The closer the binding site, the bigger the shift of the signals.
From these findings, it can be derived that the carboxylate group of the glutamate residue is the most potential binding site at pH 2.9. According to the aqueous speciation, the glycine carboxylic acid group is only partially deprotonated and therefore less involved in complexation. The thiol group does not interact with the metal ion.

Acknowledgement: We thank Dr. Erica Brendler, Technische Universität Bergakademie Freiberg, for providing the possibility to acquire 2D-NMR spectra.

[1] C. C. Hinckley, J. Am. Chem. Soc. 1969, 91, 5160-5162.
[2] O. A. Gansow, M. R. Willcott, R. E. Lenkinski, J. Am. Chem. Soc. 1971, 93, 4295-4297.
[3] I. Bertini, C. Luchinat, G. Parigi, Solution NMR of paramagnetic molecules, Vol. 2, in: Current methods in inorganic chemistry, Elsevier, Amsterdam, 2001.

Keywords: Advanced Techniques in Actinide Spectroscopy (ATAS); Eu3+; glutathione; NMR spectroscopy

  • Lecture (Conference)
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17505

Electromagnetic fields and electron dynamics in Traveling-wave Thomson scattering

Steiniger, K.; Debus, A.; Pausch, R.; Widera, R.; Bussmann, M.; Sauerbrey, R.

The Traveling-wave Thomson scattering (TWTS) scheme is a novel high-yield Thomson scattering geometry using ultrashort laser pulses with tilted pulse fronts. Combined with relativistic electron bunches this can be utilized as an optical undulator or as an optically driven free electron laser for generation of high-brightness, narrow bandwidth X-Ray pulses. In order to examine the wave-optical propagation of these TWTS pulses we developed an analytical formalism to calculate the electrical field of a spatio-temporal distorted laser pulse which has been diffracted at a grating of arbitrary periodicity function. This allows for numerical analysis of a TWTS laser pulse in terms of its envelope and dispersion properties. We use this to investigate the applicability of the scheme as an optical undulator and free electron laser.

Keywords: travelling wave; thomson scattering; x-ray; laser pulse; vls grating

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity - ENLITE 12, 16.04.-20.07.2012, Dresden, Deutschland

Publ.-Id: 17504

Quantitative accuracy of attenuation correction in the Philips Ingenuity TF whole-body PET/MR system A direct comparison with transmission-based attenuation correction

Schramm, G.; Langner, J.; Hofheinz, F.; Petr, J.; Beuthien-Baumann, B.; Platzek, I.; Steinbach, J.; Kotzerke, J.; van den Hoff, J.

Objective: Evaluation of the quantitative accuracy of MR-based atten- uation correction (MRAC) in the Philips Ingenuity TF whole-body PET/MR.

Materials and methods: In 13 patients, PET emission data from the PET/MR were reconstructed using two different methods for attenuation correction. In the first reconstruction the vendor-provided standard MRAC was used. In the second reconstruction, a coregistered transmission-based attenuation map from a second immediately preceding investigation with a stand-alone Siemens ECAT EXACT HR+ PET scanner was used (TRAC). The two attenuation maps were compared regarding occurrence of segmentation artifacts in the MRAC procedure.
Standard uptake values (SUVs) of multiple VOIs (liver, cerebellum, hot focal structures at various locations in the trunk) were compared between both reconstructed data sets. Furthermore, a voxel-wise intensity correlation analysis of both data sets in the lung and trunk was performed.

Results: VOI averaged SUV differences between MRAC and TRAC were as follows (relative differences, mean ± standard deviation): (+12 ± 6)% cerebellum, (−4 ± 9% liver, (−2 ± 11)% hot focal structures. The fitted slopes of the voxel-wise correlations in the lung and trunk were 0.87 ± 0.17 and 0.95 ± 0.10 with averaged adjusted R2 -values of 0.96 and 0.98, respectively. These figures include two instances with partially erroneous lung segmentation due to artifacts in the underlying MR images.

Conclusion: The MR-based attenuation correction implemented on the Philips Ingenuity PET/MR provides reasonable quantitative accuracy. On average, deviations from TRAC-based results are small (on the order of 10% or below) across the trunk, but due to interindividual variability of the segmentation quality, deviations of more than 20% can occur.
Future improvement of the segmentation quality would help to increase the quantitation accuracy further and to reduce the inter-subject variability.

Publ.-Id: 17503

Simulation of electro-magnetic emissions in laser-particle interactions

Pausch, R.; Debus, A.; Widera, R.; Bussmann, M.; Schramm, U.

Modern laser-plasma simulations are able to model complex plasma processes. However, since particle dynamics within a plasma are usually not directly accessible to experiments, there is interest to compare experimental results with Particle-In-Cell (PIC) simulations.
One way to accomplish this task is to simulate the electro-magnetic emissions from both relativistic and sub-relativistic plasma electrons.
Here we present a newly developed software for spectral analysis of laser-plasma phenomena and for simulating novel light sources. Moreover, a GPU based code was developed to work directly within PIConGPU.

Keywords: laser-plasma simulations; electro-magnetic emission; spectral analysis; laser-plasma phenomena; novel light sources; PIConGPU

  • Poster
    International Workshop on Laser-Plasma Interaction at Ultra-High Intensity 2nd Dresden Exchange on Laser-Plasma Interaction Theory ENLITE, 16.-20.04.2012, Dresden, Germany

Publ.-Id: 17502

18F-labelled CCR1-receptor antagonist is not suitable for imaging of Alzheimer's disease

Beuthien-Baumann, B.; Holthoff, V.; Mäding, P.; Bergmann, R.; Pawelke, B.; Holl, G.; von Kummer, R.; Kotzerke, J.; van den Hoff, J.

Diagnosis of Alzheimer’s disease (AD) with positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) relies on typical alterations of brain glucose metabolism which are, however, not disease specific. Amyloid-β imaging has not entered clinical routine yet. Post mortem histological specimen of brain tissue from AD patients revealed enhanced expression of the chemotactic cytocine receptor 1 (CCR1). Participants, methods: CCR1-antagonist ZK811460 was labeled with fluorine-18 to explore its possible use as specific diagnostic tool in AD. Tracer characterization comprising PET imaging of brain and metabolite analysis was performed in AD patients and controls.
Results: Neither qualitative evaluation nor quantitative compartment analysis of PET data did show any enhanced binding of the 18F-labeled CCR1-antagonist in the brain of AD patients or controls.
Conclusion: 18F-ZK811460 did not fulfill the expectation as diagnostic tracer in PET imaging of AD.

Keywords: Alzheimer’s disease; Positron emission tomography; CCR1 receptor antagonist

Publ.-Id: 17501

Assessment of low-dose radiotoxicity in microorganisms using calorimetric metabolic monitoring

Obeid, M.

At this project the effects of low doses of radionuclides and heavy metals on the metabolic activity of microorganisms was assessed, using the state of the art Thermal Activity monitor microcalorimeter, TAM(III), as a novel monitoring tool in this study. Therefore, the toxicity was measured as the metabolic response for these low doses reflected by bacterial growth thermograms. The bacterial strain used in this project, Paenibacillus sp. JG-TB8, was isolated from a soil sample of the uranium mining waste pile “Haberland” (Johanngeorgenstadt, Saxony, Germany) by Thomas Reitz [4]. This bacterial strain was exposed to different concentrations in the range of micromolar of Eu(III) and U(VI) salts. Thetoxicity of europium chloride (Eu(III)Cl3) as a heavy metal was reflected by the thermogram as a decrement of its maximal heat flow. In contrast, the effect of the uranium salts was more complicated. It showed a strong dependence on temperature and pH. Correlation of the degree of toxicity with concentration of the uranium salt was observed strongly at 30 °C in R2A medium, while it showed more constructive effect related to the usage of uranium as energetic source for the metabolic activity of the PB at 20°C. The mentioned thermograms showed that the general toxic effect of uranium is present but does not scale systematically with the applied concentrations. The data reveal that the thermal signature of a contaminant is unique for each concentration.

Keywords: calorimetry; radionuclide; europium; uranium

  • Master thesis
    Technische Universität Dresden, 2011
    100 Seiten

Publ.-Id: 17500

Use of targeted therapy for refractory ALK-positive anaplastic large cell lymphoma as a bridging strategy prior to allogeneic transplantation

Ordemann, R.; Stöhlmacher, J.; Beuthien-Baumann, B.; Platzek, I.; van den Hoff, J.; Kroschinsky, F.; Middeke, J. M.; Platzbecker, U.; Zietz, C.; Bornhäuser, M.; Ehninger, G.

Letter to the editor - kein Abstract verfügbar

Publ.-Id: 17499

Spektroskopische Untersuchungen zur Struktur und Funktion der Kupfer-ATPase CopB von E.Hirae

Groß, M.

The aim of this study is to investigate the structure and function of P-type-ATPases. Enterococcus hirae is a gram-positive lactic acid bacterium with two copper ATPases CopA and CopB. They show sequence similarity to known P-type-ATPases. The monovalent copper exporting ATPase CopB is a central regulator for copper homeostasis in E. hirae which shows 39 % sequence similarity to the sarcoplamic reticulum calcium ATPase SERCA1a of rabbit hind leg muscle (Oryctolagus cuniculus). SERCA1a undergoes large conformational changes of cytoplasmatic and transmembrane domains to translocate ions. Despite some former work, the transport of copper and the biochemical properties of the ATPase, however, has to be analyzed and the observation of hydrolytic activities has to be pursued. During thesis work the functional status of conformational states was studied by spectroscopy work on metal and nucleotide binding. The ability of nonionic detergents to stabilize the membrane-bound enzymes was used to work in lipid analogue environment, whereby the effect of light scattering of lipid systems is prevented. I have investigated the secondary structure of purified CopB in the absence and presence of the non-hydrolyzable ATP analogs ATPgS, mantATP and silver (a redox inert Cu+ analog) using circular dichroism spectroscopy. Binding of metals unfolds the protein, whereas ATP analogs partially elliminate this effect. ATPgS and silver form an optically active complex. Negative and positive CD peaks appear, at 257 nm and 277 nm, respectively, at a ratio of 1:3 of Ag:ATPgS corresponding to the predominant species ATPgS3Ag4. CopB competes with complex formation by binding both ATPgS and silver. To my knowledge this is the first description of such a complex. It is used in this work as a possible high sensitive realtime ATPase monitor. This assay could ultimately be exploited to determine binding affinities of nucleotide, silver and CopB in enzyme assays in real time. In the present work it is used to determine binding affinitiy of CopB to ATPgS. In addition to check the influence of the binding of ATP analogs and silver on stability of CopB, the protein was denaturated in the absence and presence of ATPgS, mantATP, ADP and silver. Whereas ATPgS and mantATP stabilize CopB, the same nucleotide-CopB complex is destabilized by silver. This evidences a strong negative coupling between the nucleotide and metal binding site as an important output of my work.

Keywords: copper; ATPase; CopA; CopB; circular dichroism; unfolding

  • Diploma thesis
    TU Dresden, 2011
    90 Seiten

Publ.-Id: 17498

New Bispidine-Derivatives for dual-modality imaging

Fähnemann, S.; Walther, M.; Stephan, H.; Kraus, W.; Emmerling, F.; Steinbach, J.

The diagnostic evaluation and treatment of complex diseases, like cancer, is very difficult using only standing alone methods with their individual limitations. To overcome these restrictions, a combination of different imaging modalities will be conceivable. The radionuclide based positron emission tomography (PET) and single photon emission computed tomography (SPECT) are useful for functional imaging. To obtain anatomical information, computer tomography (CT) and magnetic resonance imaging (MRI) can be used, whereas fluorescence-based optical imaging finds application in surgery guidance. [1]

Extensive research effort has shown, that 3,7-diazabicyclo[3.3.1]nonane-derivatives (bispidines) built up thermodynamic and kinetic very stable complexes with copper(II) ions (logK = 16.28) [2]. Different functional groups of the backbone (hydroxyl and carboxyl groups) provide the opportunity for simultaneous attachment of dyes and biomolecules (e. g. peptides, proteins, antibodies) as vector molecules. After that functionalization, the complexation of radioactive copper isotopes (61Cu, 64Cu, 67Cu) allows visualization of cancer tissue with PET and radiotherapy.

The hydroxyl group at C9 was functionalized using nitrophenyl chloroformate for active ester generation. Therefore, a fluorescence label could be coupled to the bispidine by urethane bond formation.

We will report about the versatility of bispidines as compounds to realize different functionalities in one molecule. The synthesis and characterization of such derivatives, and radiolabeling experiments with the PET-radionuclide 64Cu will be discussed.

[1] Kuil, J., Velders, A. H., van Leeuwen, F. W. B.; Bioconjugate Chem. 2010, 21, 1709-1719.
[2] Juran, S., Walther, M., Stephan, H., Bergmann, R., Steinbach, J., Kraus, W., Emmerling, F., Comba, P.; Bioconjugate Chem. 2009, 20, 347-359.

  • Lecture (Conference)
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republik

Publ.-Id: 17497

The impact of the bispidine structure on the stability of their Cu(II) complexes

Hunoldt, S.; Comba, P.; Morgen, M.; Steinbach, J.; Stephan, H.

Rigid bispidine (3,7-diazabicyclo[3.3.1]nonane) derivatives have been shown to form stable complexes, particularly with first row transition metal ions [1]. The variable number, type and position of donor groups provide a variety of tailor-made coordination sites for specific metal ions. Furthermore, the bispidine skeleton opens suitable pathways to introduce biomolecules, which are important in view of the pharmaceutical targeting of such complexes. Due to these interesting features, bispidines are predestined as attractive bifunctional chelating agents for the development of target-specific copper-based radiopharmaceuticals. In this perspective, a hexadentate bispidine ligand consisting of pyridine units in the positions C-2, C-4, N-3, and N-7 was conjugated to the tumour-seeking peptide bombesin. The 64Cu-labeled bioconjugate is accumulated in human prostate tumors to allow clear visualization of the tumor tissue [2].
In order to optimize the radiopharmaceutical behavior, further bispidine ligands have been developed with different denticity (tetra-, penta, hexadentate) with pyridine and/or methoxypyridine donor groups and with the possibility to introduce functionalities, such as targeting units and fluorescence labels in view of pharmaceutical targeting as well as dual labeling (PET and optical imaging).
These ligands and the important properties of their CuII complexes, e. g. stabilities, exchange kinetics and partition coefficients (64Cu: octanol/water) will be reported.

[1] P. Comba, M. Kerscher, W. Schiek, Progr. Inorg. Chem. 2008, 55, 613-704.
[2] S. Juran, M. Walther, H. Stephan, R. Bergmann, J. Steinbach, W. Kraus, F. Emmerling, P. Comba, Bioconjugate Chem. 2009, 20, 347-359.

Keywords: bispidine; copper(II); radiolabeling

  • Poster
    4th EuCheMS Chemistry Congress, 26.-30.08.2012, Prague, Czech Republic

Publ.-Id: 17496

Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

Joseph, C.; van Loon, L. R.; Jakob, A.; Steudtner, R.; Schmeide, K.; Sachs, S.; Bernhard, G.

The diffusion of U(VI) (c0 = 1×10-6 M) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10 mg/L) at two different temperatures (25 °C, 60 °C) under anaerobic conditions. As background electrolyte a synthetic Opalinus Clay pore water (pH 7.6, I = 0.36 M) was used. The diffusion-accessible porosity, ε, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25 °C as well as at 60 °C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60 °C indicate the contributions of two different humic acid particle size fractions (< 1 kD and 10-100 kD). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the three months duration of the U(VI) diffusion experiments. At 60 °C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60 °C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60 °C. An increase of Kd from 0.025 ± 0.003 m3/kg at 25 °C to 0.25 ± 0.05 m3/kg for U(VI)colloidal at 60 °C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60 °C, a preliminary activation energy for the diffusion of U(VI) through Opalinus Clay of 10 kJ/mol was calculated. The observed increased Kd and De values for U(VI)aqueous at 60 °C compensated each other to almost equal values of the apparent diffusion coefficient Da at 25 and 60 °C. Hence, the migration of U(VI) through OPA was not significantly influenced by the investigated higher temperature of 60 °C.

Keywords: uranium(VI); diffusion; Opalinus Clay; humic acid; temperature; LIFS; SEM-EDX; PCS

Publ.-Id: 17495

Investigation of the life cycle of nanoparticles by means of radiolabelling – NanoTRACK

Hildebrand, H.; Franke, K.

Presentation of current activities and results from the NanoTrack project, especially results from radiolabelling of Ag(0) and TiO2 nanoparticles

Keywords: radiolabelling Ag(0) TiO2 nanoparticles

  • Poster
    2. Clustertreffen NanoCare/NanoNature, 13.-14.03.2012, Frankfurt, Deutschland

Publ.-Id: 17494

Radiolabelling of commercial Ag0 and TiO2 nanoparticles with 110mAg and 44/45Ti for life-cycle studies and results from the QNANO research stay at JRC

Hildebrand, H.; Schymura, S.; Franke, K.

Presentation of the current research activivities concerning the radiolabelling of Ag(0) and TiO2 nanoparticles within the NanoTrack project at HZDR and first results from the QNANO research stay at the Joint Research Center in Ispra, Italy

Keywords: radiolabelling of nanoparticles

  • Lecture (others)
    QNANO seminar within the QNANO research stay at JRC in Ispra, Italy, 15.06.2012, Ispra, Italia

Publ.-Id: 17493

Multi edge X-ray absorption spectroscopy of thorium, neptunium and plutonium hexacyanoferrate compounds

Dumas, T.; Charbonnel, M. C.; Charushnikova, I. A.; Conradson, S. D.; Fillaux, C.; Hennig, C.; Moisy, P.; Petit, S.; Scheinost, A. C.; Shuh, D. K.; Tyliszczak, T.; Den Auwer, C.

Although transition metal cyano bimetallic compounds have been well known for decades for their interesting optical and magnetic properties, reports on actinide hexacyanoferrate compounds are scarce. For instance, a thorough structural description is still lacking. Another question is the possible covalency or charge transfer effects in these materials that are known to foster electron delocalization with a large variety of transition metal cations. In this paper, new members of the actinide(IV) hexacyanoferrates have been synthesized with Th, Np and Pu. This is the first review of thorium to plutonium hexacyanoferrate compounds since the early investigations during the Manhattan Project some 70 years ago. We have carried out an extensive structural characterization using powder X-ray Diffraction (XRD), X-ray Absorption Spectroscopy (XAS) and X-ray microscopy for the plutonium adduct. The crystallographic space group of microcrystalline Th, Np and Pu hexacyanoferrate compounds appears to be very similar to that of the early lanthanide adducts, suggesting that the tetravalent actinides are arranged in a tricapped trigonal prismatic polyhedron of coordination number 9, in which the actinide atom is bonded to six nitrogen atoms and to three water molecules. Further combined analysis of the iron K-edge and actinide LIII-edge EXAFS data and XRD data provided the basis for a threedimensional molecular model. Structural data in terms of actinide–ligand bond lengths have been compared to those reported for the parent lanthanide(III) compounds, confirming the structural similarities. In addition, two new structures with the thorium cation have been obtained and described using single-crystal XRD: (H5O2)[Th(DMF)5(H2O)]2[Fe(CN)6]3 and [Th(DMF)4(H2O)3][Fe(CN)6](NO3)2H2O. This structural description of the Th, Np and Pu hexacyanoferrate system will be followed by a semi-quantitative electronic description of the actinide–cyano bond using NEXAFS data analysis in a coming paper.

Keywords: XAFS; Th; Np; Pu

Publ.-Id: 17492

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) of aqueous Am(III) complexes at ambient and elevated temperature

Barkleit, A.; Acker, M.; Geipel, G.; Bernhard, G.

Time-resolved laser-induced fluorescence spectroscopy (TRLFS) has been extensively used as a sensi-tive and selective technique to analyze actinide complexation with inorganic and organic ligands in trace metal concentrations. However, the application of TRLFS onto Am(III) complexation systems was up to now limited because of the much lower luminescence intensity and much shorter lifetime of Am(III) in comparison to U(VI) or Cm(III).
We investigated the complexation behavior of Am(III) complexes with lactate (Lac) and substituted benzoic acids like pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid, BTC) at ambient and ele-vated temperatures with TRLFS.
Using the emission of the 5D1-7F1 transition at around 691 nm, spectral data like luminescence life-times, luminescence maxima and complex stability constants were calculated. Temperature dependent stability constants were determined to estimate thermodynamic data (reaction enthalpy, reaction en-tropy).
The Am(III) aquo ion shows at pH 4-6 a luminescence lifetime of 23 ns, corresponding to approxi-mately 9 coordinating water molecules. Complexation with BTC shows no change of the excitation and emission maximum but an increase of the luminescence intensity and lifetime. The luminescence lifetime was prolonged to 27 ns, corresponding to 8 remaining water molecules in the first coordina-tion shell. This indicates an exchange of 1 water molecule with 1 coordination site of the ligand, re-sulting in an Am-BTC 1:1 complex [1]. In contrast, complexation with lactate causes a red shift of the excitation wavelength of Am(III) (Fig. 1), resulting in a red shift of the luminescence emission maxi-mum of about 5 nm. The luminescence lifetime is prolonged up to 37 ns which corresponds to 5-6 re-maining water molecules. This indicates an exchange of about 3-4 water molecules with coordination sites of ligand molecules which implies the formation of 1:1, 1:2 and 1:3 complexes. The stability con-stants increase slightly with rising temperature which is consistent with an endothermic complexation reaction.

  • Contribution to proceedings
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland
    Wissenschaftlich-Technische Berichte HZDR-027: Helmholtz-Zentrum Dresden-Rossendorf, ISSN 2191-8708, 41
  • Poster
    International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 05.-07.11.2012, Dresden, Deutschland

Publ.-Id: 17491

Interfacial heat and mass tansfer models

Krepper, E.; Scheuerer, G.

The lesson 4 of the "Short Course on Multiphase Flow Modelling" deals with the simulation of mass and energy exchange between the phases based on the two fluid model approach. After the basic principles the lesson describes the simulation of subcooled boiling and the simulation of cavitation processes.

Keywords: CFD; Two fluid model; heat transfer; mass transfer; boiling; cavitation

  • Lecture (Conference)
    10th HZDR & ANSYS Short Course and Workshop "Multiphase Flow - Simulation, Experiment and Applications", 12.-14.6.2012, Dresden, Deutschland

Publ.-Id: 17490

Annihilation Lifetime Spectroscopy using Positrons from Bremsstrahlung Production

Wagner, A.; Anwand, W.; Butterling, M.; Cowan, T. E.; Fiedler, F.; Kempe, M.; Krause-Rehberg, R.

A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [1] at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.

Keywords: pulsed positron source; positron annihilation lifetime spectroscopy; age-momentum correlation; bulk sample; fluids; gases; biological samples; bremsstrahlung; superconducting LINAC

  • Book chapter
    B.N. Ganguly, G. Brauer:: Near Surface Depth Profiling of Solids by Mono-energetic Positrons, Zurich, Switzerland: TransTech Publications Ltd, 2012, 978-3-03785-524-9, 41-52
    DOI: 10.4028/


Publ.-Id: 17489

Control of fluid flow using electromagnetic body forces

Albrecht, T.; Weier, T.; Gerbeth, G.

In many engineering applications, the way natural fluid flows behave leaves some room for improvement. While geometric optimizations, such as streamlined shapes, require no additional energy input, they might not always be possible, feasible, or sufficient.

Another option is active flow control, where a suitable actuator more or less directly alters flow structures. Of the variety of such devices proposed for flow control applications, we focus on Lorentz force actuators. They consist of (permanent) magnets and electrodes, generating a body force near the wall it is attached to. The momentum added to the flow is linearly driven by an electric current.

The actuator can be applied to prevent transition from laminar to turbulent flow, a process that would otherwise lead to a rapid increase in drag. Its linear response is also advantageous when suppressing flow separation at inclined airfoils to prevent the loss of lift. The talk will cover both applications, and include numerical as well as experimental results.

Keywords: Lorentz force actuator; flow control; DNS; PIV

  • Invited lecture (Conferences)
    CE Seminar, 03.05.2012, Darmstadt, Deutschland

Publ.-Id: 17488

Dose contributions due to radiation scattered by air (skyshine) in the case of x-ray machines

Sahre, P.; Kaden, M.; Schönmuth, T.; Pawelke, J.; Naumann, B.; Reichelt, U.

Radiation transport simulations had to be done in preparation of operation of the X-ray tube ISOVOLT 320 kV/13mA in a special laboratory. At first simulation was done without shielding the roof of the laboratory, showing a dose rate maximum of more than 100 mSv/h. This dose rate results in a skyshine dose rate of at most 2 lSv/h in the surrounding of the building without shielding the roof. For similar geometries the skyshine is negligible for dose rates at the unshielded roof of less than 3 mSv/h (exclusion area).

  • Kerntechnik 77(2012)3, 191

Publ.-Id: 17487

Ion Acceleration in Ultra-Intense Laser-Matter Interactions, and Applications in Radiation Oncology

Cowan, T.

  • Invited lecture (Conferences)
    Kolloquium, 09.05.2012, Chemnitz, Deutschland

Publ.-Id: 17486

Beschleunigung der Beschleunigung: Lasergetriebene Strahlungsquellen und ihre Anwendungen

Cowan, T.

  • Invited lecture (Conferences)
    ZIH Colloquium, 26.04.2012, Dresden, Deutschland

Publ.-Id: 17485

The Helmholtz Beamlines at the European XFEL and FAIR

Cowan, T.

  • Invited lecture (Conferences)
    Joint IZEST – Helmholtz Beamlines Workshop 2012, 23.-25.04.2012, Darmstadt, Deutschland

Publ.-Id: 17484

Applications of laser-matter interaction at ultra-high intensity

Cowan, T.

  • Invited lecture (Conferences)
    Workshop on Laser-Plasma Interaction at Ultra-High Intensity ENLITE – 2nd Dresden Exchange oN Laser-plasma Interaction ThEory, 16.-20.04.2012, Dresden, Deutschland

Publ.-Id: 17483

Comparison of PIV-based methods for airfoil loads evaluation

Albrecht, T.; Del Campo, V.; Weier, T.; Gerbeth, G.

We compare the accuracy achievable with different methods of calculating time-averaged airfoil loads if the surrounding velocity field is known, e.g., from Particle Image Velocimetry. These methods require integration over a control volume enclosing the body. For separated flow around an inclined flat plate at Re=10^4, we investigate the effect of varying the control volume. Some methods yield excellent results for both lift and drag.
Preliminary results for a corresponding experiment indicate that the calculated lift coincides well with direct force measurements, whereas agreement for the drag can be considered fair.
Implementation of the methods was validated using a circular cylinder flow at Re=200.

Keywords: PIV; DNS; airfoil loads; lift; drag

  • Contribution to proceedings
    16th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 09.-12.07.2012, Lisboa, Portugal
    Proceedings of the 16th International Symposium on Applications of Laser Techniques to Fluid Mechanics

Publ.-Id: 17482

Science with high-power lasers at the European XFEL

Cowan, T.

  • Invited lecture (Conferences)
    503. WE-Heraeus-Seminar Free-Electron Lasers: from Fundamentals to Applications, 10.-13.04.2012, Bad Honnef, Deutschland

Publ.-Id: 17481

Einfluss von Mikroorganismen auf die Geochemie des Bergwerkes/Wassers - Königstein

Zirnstein, I.

Mikroorganismen in ehemaligen Uran Bergwerken leben meist unter extremen Bedingungen, wie auch in der ehemaligen Mine Königstein. Dort müssen die Mikroben einem saurem pH Wert (2,7), hohen Konzentrationen an Sulfationen, Eisenionen und Uran standhalten. Nachdem die Schächte unter tage weitestgehend geflutet wurden, sind die Bedingungen noch selektierender, da Sauerstoff im Wasser fehlt und keine organische Kohlenstoffquelle vorhanden ist. Der Vergleich der Mikroorganismen in der Grube vor der Flutung und nachher zeigt, dass sich die veränderten Bedingungen auf die Biodiversität auswirken. Vor der Flutung waren in den Schächten neben Bakterien auch zahlreiche Eukaryonten vorhanden. Diese konnten bisher im Flutungswasser nicht nachgewiesen werden.

Keywords: biofilms; uranium mine; biodiversity

  • Lecture (others)
    Fortschritt der Forschungsarbeiten, 23.03.2012, Chemnitz, Deutschland

Publ.-Id: 17480

Helmholtz Beamline at European XFEL Status & Next Steps

Cowan, T.

  • Lecture (Conference)
    Peak Brightness Collaboration @ XFEL Users Meeting, 26.01.2012, Hamburg, Deutschland

Publ.-Id: 17479

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